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IAR C/C++ Development
Guide
Compiling and linking

for Advanced RISC Machines Ltd’s
ARM® Cores

DARM-4

COPYRIGHT NOTICE
Copyright © 1999–2009 IAR Systems AB.
No part of this document may be reproduced without the prior written consent of IAR
Systems AB. The software described in this document is furnished under a license and
may only be used or copied in accordance with the terms of such a license.

DISCLAIMER
The information in this document is subject to change without notice and does not
represent a commitment on any part of IAR Systems. While the information contained
herein is assumed to be accurate, IAR Systems assumes no responsibility for any errors
or omissions.
In no event shall IAR Systems, its employees, its contractors, or the authors of this
document be liable for special, direct, indirect, or consequential damage, losses, costs,
charges, claims, demands, claim for lost profits, fees, or expenses of any nature or kind.

TRADEMARKS
IAR Systems, IAR Embedded Workbench, C-SPY, visualSTATE, From Idea To Target,
IAR KickStart Kit, IAR PowerPac, IAR YellowSuite, IAR Advanced Development Kit,
IAR, and the IAR Systems logotype are trademarks or registered trademarks owned by
IAR Systems AB. J-Link is a trademark licensed to IAR Systems AB.
Microsoft and Windows are registered trademarks of Microsoft Corporation.
ARM, Thumb, and Cortex are registered trademarks of Advanced RISC Machines Ltd.
All other product names are trademarks or registered trademarks of their respective
owners.

EDITION NOTICE
Fourth edition: June 2009
Part number: DARM-4
This guide applies to version 5.4x of IAR Embedded Workbench® for ARM.
The IAR C/C++ Development Guide for ARM® replaces all versions of the ARM IAR
C/C++ Compiler Reference Guide and the IAR Linker and Library Tools Reference
Guide.
Internal reference: R10, 5.5.x, ISUD.

DARM-4

Brief contents
Tables

.................................................................................................................. xxvii

Preface

................................................................................................................. xxix

Part 1. Using the build tools
Introduction to the IAR build tools

..................................................... 1

.......................................................... 3

Developing embedded applications ........................................................... 9
Data storage
Functions

...................................................................................................... 25

............................................................................................................... 29

Linking using ILINK

........................................................................................ 39

Linking your application

................................................................................ 47

The DLIB runtime environment
Assembler language interface
Using C++

.............................................................. 61

................................................................... 91

.......................................................................................................... 107

Application-related considerations

....................................................... 115

Efficient coding for embedded applications

Part 2. Reference information
External interface details
Compiler options
Linker options

...................................... 127

........................................... 145

............................................................................ 147

........................................................................................... 155

.................................................................................................. 189

Data representation

...................................................................................... 209

Compiler extensions

.................................................................................... 221

Extended keywords

....................................................................................... 233

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Pragma directives ............................................................................................ 245
Intrinsic functions

........................................................................................... 259

The preprocessor ........................................................................................... 283
Library functions

............................................................................................. 289

The linker configuration file

...................................................................... 297

Section reference ............................................................................................ 319
IAR utilities

........................................................................................................ 323

Implementation-defined behavior
Glossary
Index

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.......................................................... 349

.............................................................................................................. 361

..................................................................................................................... 377

Contents
Tables

.................................................................................................................. xxvii

Preface

................................................................................................................. xxix

Who should read this guide ............................................................ xxix
How to use this guide ....................................................................... xxix
What this guide contains ................................................................. xxx
Other documentation ........................................................................ xxxi
Further reading ...............................................................................xxxii

Document conventions ...................................................................xxxiii
Typographic conventions ..............................................................xxxiii
Naming conventions ..................................................................... xxxiv

Part 1. Using the build tools
Introduction to the IAR build tools

..................................................... 1

.......................................................... 3

The IAR build tools—an overview ..................................................... 3
IAR C/C++ Compiler ........................................................................... 3
IAR Assembler ..................................................................................... 4
The IAR ILINK Linker ........................................................................ 4
Specific ELF tools ................................................................................ 4
External tools ....................................................................................... 4

IAR language overview ........................................................................... 5
Device support ........................................................................................... 5
Supported ARM devices ...................................................................... 5
Preconfigured support files .................................................................. 6
Examples for getting started ................................................................ 6

Special support for embedded systems .......................................... 6
Extended keywords .............................................................................. 6
Pragma directives ................................................................................. 7
Predefined symbols .............................................................................. 7
Special function types .......................................................................... 7
Accessing low-level features ............................................................... 7

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Developing embedded applications ........................................................... 9
Developing embedded software using IAR build tools ............ 9
Mapping of internal and external memory ........................................... 9
Communication with peripheral units ................................................ 10
Event handling ................................................................................... 10
System startup .................................................................................... 10
Real-time operating systems .............................................................. 10
Interoperability with other build tools ............................................... 11

The build process—an overview ...................................................... 11
The translation process ....................................................................... 11
The linking process ............................................................................ 12
After linking ....................................................................................... 14

Application execution—an overview ............................................. 14
The initialization phase ...................................................................... 15
The execution phase ........................................................................... 19
The termination phase ........................................................................ 19

Basic project configuration ................................................................. 19
Processor configuration ...................................................................... 20
Optimization for speed and size ......................................................... 21
Runtime environment ......................................................................... 22

Data storage

...................................................................................................... 25

Introduction ............................................................................................. 25
Different ways to store data ............................................................... 25

Auto variables—on the stack ............................................................ 26
The stack ............................................................................................ 26

Dynamic memory on the heap ........................................................ 27

Functions

............................................................................................................... 29

Function-related extensions .............................................................. 29
ARM and Thumb code ........................................................................ 29
Execution in RAM ................................................................................... 30

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Primitives for interrupts, concurrency, and OS-related
programming ............................................................................................ 30
Interrupt functions ............................................................................. 31
Installing exception functions ............................................................ 31
Interrupts and fast interrupts .............................................................. 32
Nested interrupts ................................................................................ 33
Software interrupts ............................................................................. 34
Interrupt operations ............................................................................ 35
Interrupts for ARM Cortex-M ............................................................ 36
C++ and special function types ......................................................... 36

Linking using ILINK

........................................................................................ 39

Linking—an overview ............................................................................ 39
Modules and sections ............................................................................ 40
The linking process ................................................................................ 41
Placing code and data—the linker configuration file .............. 42
A simple example of a configuration file ........................................... 43

Initialization at system startup ......................................................... 45
The initialization process ................................................................... 46

Linking your application

................................................................................ 47

Linking considerations .......................................................................... 47
Choosing a linker configuration file .................................................. 47
Defining your own memory areas ...................................................... 48
Placing sections .................................................................................. 49
Reserving space in RAM ................................................................... 51
Keeping modules ................................................................................ 51
Keeping symbols and sections ........................................................... 52
Application startup ............................................................................. 52
Setting up the stack ............................................................................ 52
Setting up the heap ............................................................................. 52
Setting up the atexit limit ................................................................... 53
Changing the default initialization ..................................................... 53
Interaction between ILINK and the application ................................. 56
Standard library handling ................................................................... 57

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Producing other output formats than ELF/DWARF .......................... 57
Veneers ............................................................................................... 57

Hints for troubleshooting .................................................................. 57
Relocation errors ................................................................................ 58

The DLIB runtime environment

.............................................................. 61

Introduction to the runtime environment .................................. 61
Runtime environment functionality ................................................... 61
Library selection ................................................................................ 62
Situations that require library building .............................................. 63
Library configurations ....................................................................... 63
Low-level interface for debug support ............................................... 64

Using a prebuilt library ........................................................................ 64
Groups of library files ........................................................................ 65
Customizing a prebuilt library without rebuilding ............................ 66

Choosing formatters for printf and scanf ..................................... 67
Choosing printf formatter ................................................................... 67
Choosing scanf formatter .................................................................. 68

Overriding library modules ............................................................... 69
Building and using a customized library ....................................... 71
Setting up a library project ................................................................. 71
Modifying the library functionality .................................................... 71
Using a customized library ................................................................ 72

System startup and termination ...................................................... 72
System startup .................................................................................... 72
System termination ............................................................................ 75

Customizing system initialization ................................................... 76
__low_level_init ............................................................................... 76
Modifying the file cstartup.s ............................................................. 77

Standard streams for input and output ........................................ 77
Implementing low-level character input and output .......................... 77

Configuration symbols for printf and scanf ................................. 79
Customizing formatting capabilities .................................................. 80

File input and output ............................................................................. 80

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Locale ........................................................................................................... 81
Locale support in prebuilt libraries .................................................... 81
Customizing the locale support .......................................................... 82
Changing locales at runtime .............................................................. 83

Environment interaction ..................................................................... 83
The getenv function ........................................................................... 84
The system function ........................................................................... 84

Signal and raise ........................................................................................ 84
Time ............................................................................................................. 85
Strtod ........................................................................................................... 85
Assert ........................................................................................................... 85
Atexit ........................................................................................................... 86
C-SPY runtime interface .................................................................... 86
Low-level debugger runtime interface ............................................... 86
The debugger terminal I/O window ................................................... 87

Checking module consistency ........................................................... 87
Runtime model attributes ................................................................... 88
Using runtime model attributes .......................................................... 88

Assembler language interface

................................................................... 91

Mixing C and assembler ....................................................................... 91
Intrinsic functions .............................................................................. 91
Mixing C and assembler modules ...................................................... 92
Inline assembler ................................................................................ 93

Calling assembler routines from C ................................................. 94
Creating skeleton code ....................................................................... 94
Compiling the code ............................................................................ 95

Calling assembler routines from C++ ............................................ 96
Calling convention .................................................................................. 97
Function declarations ........................................................................ 98
Using C linkage in C++ source code ................................................. 98
Preserved versus scratch registers ...................................................... 98
Function entrance .............................................................................. 99
Function exit ................................................................................... 101

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Examples .......................................................................................... 102

Call frame information ....................................................................... 103
CFI directives ................................................................................... 103
Creating assembler source with CFI support ................................... 104

Using C++

.......................................................................................................... 107

Overview .................................................................................................. 107
Standard Embedded C++ ................................................................. 107
Extended Embedded C++ ................................................................ 108
Enabling C++ support ...................................................................... 108

Feature descriptions ............................................................................ 109
Classes .............................................................................................. 109
Function types .................................................................................. 110
Templates ........................................................................................ 110
Variants of cast operators ................................................................. 111
Mutable ............................................................................................ 111
Namespace ...................................................................................... 111
The STD namespace ........................................................................ 111
Pointer to member functions ............................................................ 111
Using interrupts and EC++ destructors ............................................ 112

C++ language extensions ................................................................... 112

Application-related considerations

....................................................... 115

Output format considerations ........................................................ 115
Stack considerations ........................................................................... 115
Stack size considerations ................................................................. 116
Aligning the stack ............................................................................ 116
Exception stacks ............................................................................... 116

Heap considerations ............................................................................ 117
Interaction between the tools and your application ............. 117
Checksum calculation ......................................................................... 119
Calculating a checksum ................................................................... 120
Adding a checksum function to your source code ........................... 121
Things to remember ......................................................................... 122
C-SPY considerations ...................................................................... 122

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AEABI compliance ............................................................................... 123
Linking AEABI compliant modules using the IAR ILINK Linker . 124
Linking AEABI compliant modules using a linker from a different vendor .................................................................................................... 124
Enabling AEABI compliance in the compiler ................................. 124

Efficient coding for embedded applications

...................................... 127

Selecting data types ............................................................................. 127
Using efficient data types ................................................................. 127
Floating-point types ......................................................................... 128
Alignment of elements in a structure ............................................... 129
Anonymous structs and unions ........................................................ 129

Controlling data and function placement in memory .......... 131
Data placement at an absolute location ............................................ 132
Data and function placement in sections .......................................... 133

Controlling compiler optimizations ............................................. 134
Scope for performed optimizations .................................................. 134
Optimization levels .......................................................................... 135
Speed versus size ............................................................................. 136
Fine-tuning enabled transformations ............................................... 136

Facilitating good code generation ................................................. 139
Writing optimization-friendly source code ...................................... 139
Saving stack space and RAM memory ............................................ 140
Function prototypes .......................................................................... 140
Integer types and bit negation .......................................................... 141
Protecting simultaneously accessed variables .................................. 141
Accessing special function registers ................................................ 142
Passing values between C and assembler objects ............................ 143
Non-initialized variables .................................................................. 143

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Part 2. Reference information
External interface details

........................................... 145

............................................................................ 147

Invocation syntax ................................................................................. 147
Compiler invocation syntax ............................................................. 147
ILINK invocation syntax ................................................................. 147
Passing options ................................................................................. 148
Environment variables ..................................................................... 148

Include file search procedure .......................................................... 149
Compiler output ................................................................................... 150
ILINK output .......................................................................................... 151
Diagnostics .............................................................................................. 152
Message format for the compiler ..................................................... 152
Message format for the linker .......................................................... 152
Severity levels .................................................................................. 153
Setting the severity level .................................................................. 153
Internal error .................................................................................... 154

Compiler options

........................................................................................... 155

Options syntax ....................................................................................... 155
Types of options ............................................................................... 155
Rules for specifying parameters ....................................................... 155

Summary of compiler options ........................................................ 158
Descriptions of options ...................................................................... 160
--aapcs .............................................................................................. 161
--aeabi ............................................................................................... 161
--align_sp_on_irq ............................................................................. 161
--arm ................................................................................................. 162
--char_is_signed ............................................................................... 162
--cpu ................................................................................................. 162
--cpu_mode ...................................................................................... 163
-D ..................................................................................................... 164
--debug, -r ......................................................................................... 164
--dependencies ................................................................................. 165

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--diag_error ...................................................................................... 166
--diag_remark ................................................................................... 166
--diag_suppress ................................................................................ 167
--diag_warning ................................................................................. 167
--diagnostics_tables .......................................................................... 167
--discard_unused_publics ................................................................. 168
--dlib_config .................................................................................... 168
-e ...................................................................................................... 169
--ec++ ............................................................................................... 169
--eec++ ............................................................................................. 169
--enable_hardware_workaround ...................................................... 170
--enable_multibytes .......................................................................... 170
--endian ............................................................................................ 170
--enum_is_int ................................................................................... 171
--error_limit ...................................................................................... 171
-f ....................................................................................................... 171
--fpu .................................................................................................. 172
--header_context ............................................................................... 172
-I ....................................................................................................... 173
--interwork ....................................................................................... 173
-l ....................................................................................................... 173
--legacy ............................................................................................. 174
--mfc ................................................................................................. 175
--migration_preprocessor_extensions .............................................. 175
--no_clustering ................................................................................. 176
--no_code_motion ............................................................................ 176
--no_const_align ............................................................................... 176
--no_cse ............................................................................................ 177
--no_fragments ................................................................................. 177
--no_guard_calls ............................................................................... 177
--no_inline ........................................................................................ 178
--no_path_in_file_macros ................................................................ 178
--no_scheduling ................................................................................ 178
--no_tbaa .......................................................................................... 179

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--no_typedefs_in_diagnostics .......................................................... 179
--no_unaligned_access ..................................................................... 180
--no_unroll ....................................................................................... 180
--no_warnings .................................................................................. 181
--no_wrap_diagnostics ..................................................................... 181
-O ..................................................................................................... 181
-o, --output ....................................................................................... 182
--only_stdout .................................................................................... 182
--output, -o ....................................................................................... 183
--predef_macros ............................................................................... 183
--preinclude ...................................................................................... 183
--preprocess ...................................................................................... 184
--public_equ ..................................................................................... 184
-r, --debug ......................................................................................... 185
--remarks .......................................................................................... 185
--require_prototypes ......................................................................... 185
--section ............................................................................................ 186
--separate_cluster_for_initialized_variables .................................... 186
--silent .............................................................................................. 187
--strict_ansi ....................................................................................... 187
--thumb ............................................................................................. 187
--use_unix_directory_separators ...................................................... 188
--warnings_affect_exit_code ............................................................ 188
--warnings_are_errors ...................................................................... 188

Linker options

.................................................................................................. 189

Summary of linker options ............................................................... 189
Descriptions of options ...................................................................... 191
--BE8 ................................................................................................ 191
--BE32 .............................................................................................. 191
--config ............................................................................................. 192
--config_def ...................................................................................... 192
--cpp_init_routine ............................................................................. 193
--cpu ................................................................................................. 193

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--define_symbol ............................................................................... 193
--diag_error ...................................................................................... 194
--diag_remark ................................................................................... 194
--diag_suppress ................................................................................ 195
--diag_warning ................................................................................. 195
--diagnostics_tables .......................................................................... 196
--entry ............................................................................................... 196
--error_limit ...................................................................................... 196
--export_builtin_config .................................................................... 197
-f ....................................................................................................... 197
--force_output ................................................................................... 197
--image_input ................................................................................... 198
--keep ............................................................................................... 198
--log .................................................................................................. 199
--log_file ........................................................................................... 199
--mangled_names_in_messages ....................................................... 199
--map ................................................................................................ 200
--no_fragments ................................................................................. 200
--no_library_search .......................................................................... 201
--no_locals ........................................................................................ 201
--no_remove ..................................................................................... 201
--no_veneers ..................................................................................... 202
--no_warnings .................................................................................. 202
--no_wrap_diagnostics ..................................................................... 202
-o, --output ....................................................................................... 202
--only_stdout .................................................................................... 203
--ose_load_module ........................................................................... 203
--output, -o ....................................................................................... 203
--pi_veneers ...................................................................................... 204
--place_holder .................................................................................. 204
--redirect ........................................................................................... 205
--remarks .......................................................................................... 205
--semihosting .................................................................................... 205
--silent .............................................................................................. 206

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--strip ................................................................................................ 206
--warnings_affect_exit_code ............................................................ 206
--warnings_are_errors ...................................................................... 206

Data representation

...................................................................................... 209

Alignment ................................................................................................ 209
Alignment on the ARM core ........................................................... 209

Byte order ................................................................................................ 210
Basic data types .................................................................................... 210
Integer types ..................................................................................... 210
Floating-point types ........................................................................ 213

Pointer types .......................................................................................... 215
Function pointers .............................................................................. 215
Data pointers .................................................................................... 215
Casting ............................................................................................. 215

Structure types ..................................................................................... 216
Alignment ......................................................................................... 216
General layout ................................................................................. 216
Packed structure types ..................................................................... 217

Type qualifiers ........................................................................................ 218
Declaring objects volatile ................................................................ 218
Declaring objects const .................................................................... 219

Data types in C++ ................................................................................. 219

Compiler extensions

.................................................................................... 221

Compiler extensions overview ....................................................... 221
Enabling language extensions .......................................................... 222

C language extensions ........................................................................ 222
Important language extensions ......................................................... 222
Useful language extensions .............................................................. 224
Minor language extensions .............................................................. 228

Extended keywords

....................................................................................... 233

General syntax rules for extended keywords ........................... 233
Type attributes .................................................................................. 233

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Object attributes .............................................................................. 235

Summary of extended keywords ................................................... 236
Descriptions of extended keywords ............................................. 237
__arm ............................................................................................... 237
__big_endian .................................................................................... 237
__fiq ................................................................................................. 237
__interwork ...................................................................................... 238
__intrinsic ........................................................................................ 238
__irq ................................................................................................. 238
__little_endian ................................................................................. 238
__nested ........................................................................................... 239
__no_init .......................................................................................... 239
__noreturn ........................................................................................ 239
__packed .......................................................................................... 240
__ramfunc ........................................................................................ 240
__root ............................................................................................... 241
__swi ................................................................................................ 241
__task ............................................................................................... 242
__thumb ........................................................................................... 243
__weak ............................................................................................. 243

Pragma directives ............................................................................................ 245
Summary of pragma directives ...................................................... 245
Descriptions of pragma directives ................................................ 246
bitfields ............................................................................................. 246
data_alignment ................................................................................. 247
diag_default ...................................................................................... 248
diag_error ......................................................................................... 248
diag_remark ..................................................................................... 248
diag_suppress ................................................................................... 249
diag_warning .................................................................................... 249
include_alias ..................................................................................... 249
inline ................................................................................................. 250
language ........................................................................................... 251

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location ............................................................................................. 251
message ............................................................................................ 252
object_attribute ................................................................................. 252
optimize ............................................................................................ 252
pack ................................................................................................. 253
__printf_args .................................................................................... 254
required ............................................................................................ 254
rtmodel ............................................................................................. 255
__scanf_args .................................................................................... 256
section .............................................................................................. 256
swi_number ...................................................................................... 257
type_attribute ................................................................................... 257
weak ................................................................................................. 258

Intrinsic functions

........................................................................................... 259

Summary of intrinsic functions ....................................................... 259
Descriptions of intrinsic functions ................................................. 262
__CLZ .............................................................................................. 262
__disable_fiq .................................................................................... 262
__disable_interrupt .......................................................................... 263
__disable_irq .................................................................................... 263
__DMB ............................................................................................ 263
__DSB .............................................................................................. 263
__enable_fiq .................................................................................... 264
__enable_interrupt ........................................................................... 264
__enable_irq .................................................................................... 264
__get_BASEPRI .............................................................................. 264
__get_CONTROL ............................................................................ 264
__get_CPSR ..................................................................................... 265
__get_FAULTMASK ...................................................................... 265
__get_interrupt_state ....................................................................... 265
__get_PRIMASK ............................................................................. 265
__ISB ............................................................................................... 266
__LDC ............................................................................................. 266

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__LDCL ........................................................................................... 266
__LDC2 ........................................................................................... 266
__LDC2L ......................................................................................... 266
__LDC_noidx .................................................................................. 266
__LDCL_noidx ................................................................................ 266
__LDC2_noidx ................................................................................ 266
__LDC2L_noidx .............................................................................. 266
__LDREX ........................................................................................ 267
__MCR ............................................................................................ 267
__MRC ............................................................................................ 268
__no_operation ................................................................................ 268
__QADD .......................................................................................... 268
__QADD8 ........................................................................................ 268
__QADD16 ...................................................................................... 269
__QASX .......................................................................................... 269
__QDADD ....................................................................................... 269
__QDOUBLE .................................................................................. 269
__QDSUB ........................................................................................ 270
__QFlag ........................................................................................... 270
__QSUB ........................................................................................... 270
__QSUB8 ......................................................................................... 270
__QSUB16 ....................................................................................... 270
__QSAX .......................................................................................... 271
__REV ............................................................................................. 271
__REVSH ........................................................................................ 271
__SADD8 ........................................................................................ 271
__SADD16 ...................................................................................... 271
__SASX ........................................................................................... 272
__SEL .............................................................................................. 272
__set_BASEPRI .............................................................................. 272
__set_CONTROL ............................................................................ 272
__set_CPSR ..................................................................................... 273
__set_FAULTMASK ...................................................................... 273
__set_interrupt_state ........................................................................ 273

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__set_PRIMASK ............................................................................. 273
__SHADD8 ...................................................................................... 273
__SHADD16 .................................................................................... 274
__SHASX ........................................................................................ 274
__SHSUB8 ...................................................................................... 274
__SHSUB16 .................................................................................... 274
__SHSAX ........................................................................................ 274
__SMUL .......................................................................................... 275
__SSUB8 ......................................................................................... 275
__SSUB16 ....................................................................................... 275
__SSAX ........................................................................................... 275
__STC .............................................................................................. 276
__STCL ............................................................................................ 276
__STC2 ............................................................................................ 276
__STC2L .......................................................................................... 276
__STC_noidx ................................................................................... 276
__STCL_noidx ................................................................................ 276
__STC2_noidx ................................................................................. 276
__STC2L_noidx .............................................................................. 276
__STREX ......................................................................................... 277
__SWP ............................................................................................. 277
__SWPB .......................................................................................... 277
__UADD8 ........................................................................................ 277
__UADD16 ...................................................................................... 277
__UASX .......................................................................................... 278
__UHADD8 ..................................................................................... 278
__UHADD16 ................................................................................... 278
__UHASX ........................................................................................ 278
__UHSAX ........................................................................................ 278
__UHSUB8 ...................................................................................... 279
__UHSUB16 .................................................................................... 279
__UQADD8 ..................................................................................... 279
__UQADD16 ................................................................................... 279
__UQASX ........................................................................................ 280

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__UQSUB8 ...................................................................................... 280
__UQSUB16 .................................................................................... 280
__UQSAX ........................................................................................ 280
__USAX .......................................................................................... 280
__USUB8 ......................................................................................... 281
__USUB16 ....................................................................................... 281

The preprocessor ........................................................................................... 283
Overview of the preprocessor ........................................................ 283
Descriptions of predefined preprocessor symbols ................. 284
__TID__ .......................................................................................... 286

Descriptions of miscellaneous preprocessor extensions ..... 287
NDEBUG ......................................................................................... 287
_Pragma() ......................................................................................... 287
#warning message ............................................................................ 288
__VA_ARGS__ ............................................................................... 288

Library functions

............................................................................................. 289

Introduction ............................................................................................ 289
Header files ...................................................................................... 289
Library object files ........................................................................... 289
Reentrancy ....................................................................................... 290

IAR DLIB Library .................................................................................. 290
C header files ................................................................................... 291
C++ header files ............................................................................... 292
Library functions as intrinsic functions ........................................... 294
Added C functionality ...................................................................... 294

The linker configuration file

...................................................................... 297

Overview .................................................................................................. 297
Defining memories and regions ..................................................... 298
Define memory directive ................................................................. 298
Define region directive ..................................................................... 299

Regions ...................................................................................................... 299
Region literal .................................................................................... 299

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Region expression ............................................................................ 301
Empty region .................................................................................... 302

Section handling .................................................................................... 302
Define block directive ...................................................................... 303
Define overlay directive ................................................................... 304
Initialize directive ............................................................................ 305
Do not initialize directive ................................................................. 308
Keep directive .................................................................................. 309
Place at directive .............................................................................. 309
Place in directive .............................................................................. 310

Section selection ................................................................................... 311
Section-selectors .............................................................................. 311
Extended-selectors ........................................................................... 313

Using symbols, expressions, and numbers ................................ 313
Define symbol directive ................................................................... 314
Export directive ................................................................................ 315
Expressions ...................................................................................... 315
Numbers ........................................................................................... 316

Structural configuration .................................................................... 317
If directive ........................................................................................ 317
Include directive ............................................................................... 318

Section reference ............................................................................................ 319
Summary of sections ......................................................................... 319
Descriptions of sections and blocks .............................................. 320
.bss .................................................................................................... 320
CSTACK .......................................................................................... 320
.cstart ................................................................................................ 321
.data .................................................................................................. 321
.data_init ........................................................................................... 321
.difunct ............................................................................................. 321
HEAP ............................................................................................... 321
.iar.dynexit ....................................................................................... 321
.intvec ............................................................................................... 322

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Contents

IRQ_STACK .................................................................................... 322
.noinit ............................................................................................... 322
.rodata ............................................................................................... 322
.text ................................................................................................... 322

IAR utilities

........................................................................................................ 323

The IAR Archive Tool—iarchive .................................................... 323
Invocation syntax ............................................................................. 323
Summary of iarchive commands ...................................................... 324
Summary of iarchive options ........................................................... 325
Descriptions of command line options ............................................. 325
-f ....................................................................................................... 325
--create ............................................................................................. 325
--delete, -d ........................................................................................ 326
--extract, -x ....................................................................................... 326
-o ...................................................................................................... 327
--replace, -r ....................................................................................... 327
--silent, -S ......................................................................................... 327
--toc, -t .............................................................................................. 328
--symbols .......................................................................................... 328
--verbose, -V .................................................................................... 328
Diagnostic messages ........................................................................ 329

The IAR ELF Tool—ielftool .............................................................. 330
Invocation syntax ............................................................................. 330
Summary of ielftool options ............................................................ 331
Descriptions of options .................................................................... 331
--bin .................................................................................................. 332
--checksum ....................................................................................... 332
--fill .................................................................................................. 333
--ihex ................................................................................................ 334
--silent .............................................................................................. 334
--simple ............................................................................................ 334
--srec ................................................................................................. 334
--srec-len .......................................................................................... 335

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--srec-s3only ..................................................................................... 335
--strip ................................................................................................ 335
--verbose ........................................................................................... 335

The IAR ELF Dumper for ARM—ielfdumparm ..................... 336
Invocation syntax ............................................................................. 336
Summary of ielfdumparm options ................................................... 336
Descriptions of options .................................................................... 337
--all ................................................................................................... 337
-o, --output ....................................................................................... 337
--section, -s ....................................................................................... 338
--raw ................................................................................................. 338

The IAR ELF Object Tool—iobjmanip ........................................ 338
Invocation syntax ............................................................................. 339
Summary of iobjmanip options ........................................................ 339
Descriptions of command line options ............................................. 339
-f ....................................................................................................... 340
--remove_section .............................................................................. 340
--rename_section .............................................................................. 340
--rename_symbol ............................................................................. 341
--strip ................................................................................................ 341
Diagnostic messages ........................................................................ 341

The IAR Absolute Symbol Exporter—isymexport ................ 343
Invocation syntax ............................................................................. 343
Summary of isymexport options ...................................................... 344
Descriptions of options .................................................................... 344
--edit ................................................................................................. 344
Steering files .................................................................................... 345
Show directive .................................................................................. 345
Hide directive ................................................................................... 346
Rename directive .............................................................................. 346
Diagnostic messages ........................................................................ 347

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Contents

Implementation-defined behavior

.......................................................... 349

Descriptions of implementation-defined behavior ................ 349
Translation ....................................................................................... 349
Environment ..................................................................................... 350
Identifiers ......................................................................................... 350
Characters ......................................................................................... 350
Integers ............................................................................................. 352
Floating point ................................................................................... 352
Arrays and pointers .......................................................................... 353
Registers ........................................................................................... 353
Structures, unions, enumerations, and bitfields ............................... 353
Qualifiers .......................................................................................... 354
Declarators ....................................................................................... 354
Statements ........................................................................................ 354
Preprocessing directives ................................................................... 354
IAR DLIB Library functions ............................................................ 356

Glossary
Index

.............................................................................................................. 361

..................................................................................................................... 377

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Tables
1: Typographic conventions used in this guide .................................................... xxxiii
2: Naming conventions used in this guide ........................................................... xxxiv
3: Command line options for specifying library and dependency files ..................... 23
4: Sections holding initialized data ........................................................................... 45
5: Description of a relocation error ........................................................................... 58
6: Library configurations ........................................................................................... 63
7: Customizable items ............................................................................................... 66
8: Formatters for printf .............................................................................................. 68
9: Formatters for scanf .............................................................................................. 69
10: Descriptions of printf configuration symbols ..................................................... 79
11: Descriptions of scanf configuration symbols ...................................................... 80
12: Low-level I/O files .............................................................................................. 81
13: Functions with special meanings when linked with debug info ......................... 86
14: Example of runtime model attributes .................................................................. 88
15: Registers used for passing parameters .............................................................. 100
16: Registers used for returning values ................................................................... 101
17: Call frame information resources defined in a names block ............................. 104
18: Exception stacks ................................................................................................ 116
19: Compiler optimization levels ............................................................................ 135
20: Compiler environment variables ....................................................................... 148
21: ILINK environment variables ........................................................................... 149
22: Error return codes .............................................................................................. 151
23: Compiler options summary ............................................................................... 158
24: Linker options summary ................................................................................... 189
25: Integer types ...................................................................................................... 210
26: Floating-point types .......................................................................................... 213
27: Section operators and their symbols ................................................................. 224
28: Extended keywords summary ........................................................................... 236
29: Pragma directives summary .............................................................................. 245
30: Intrinsic functions summary .............................................................................. 259
31: Predefined symbols ........................................................................................... 284

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32: Values for specifying different CPU core families in __TID__ ....................... 286
33: Traditional standard C header files—DLIB ...................................................... 291
34: Embedded C++ header files .............................................................................. 292
35: Additional Embedded C++ header files—DLIB ............................................... 292
36: Standard template library header files ............................................................... 293
37: New standard C header files—DLIB ................................................................ 293
38: Section summary ............................................................................................... 319
39: iarchive parameters ........................................................................................... 324
40: iarchive commands summary ............................................................................ 324
41: iarchive options summary ................................................................................. 325
42: ielftool parameters ............................................................................................. 331
43: ielftool options summary ................................................................................... 331
44: ielfdumparm parameters .................................................................................... 336
45: ielfdumparm options summary ......................................................................... 336
46: iobjmanip parameters ........................................................................................ 339
47: iobjmanip options summary .............................................................................. 339
48: ielftool parameters ............................................................................................. 344
49: isymexport options summary ............................................................................ 344
50: Message returned by strerror()—IAR DLIB library ......................................... 359

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Preface
Welcome to the IAR C/C++ Development Guide for ARM®. The purpose of
this guide is to provide you with detailed reference information that can help
you to use the build tools to best suit your application requirements. This
guide also gives you suggestions on coding techniques so that you can develop
applications with maximum efficiency.

Who should read this guide
Read this guide if you plan to develop an application using the C or C++ language for
the ARM core and need detailed reference information on how to use the build tools.
You should have working knowledge of:
●

The architecture and instruction set of the ARM core. Refer to the documentation
from Advanced RISC Machines Ltd for information about the ARM core

●

The C or C++ programming language

●

Application development for embedded systems

●

The operating system of your host computer.

How to use this guide
When you start using the IAR C/C++ compiler and linker for ARM, you should read
Part 1. Using the build tools in this guide.
When you are familiar with the compiler and linker and have already configured your
project, you can focus more on Part 2. Reference information.
If you are new to using the IAR Systems build tools, we recommend that you first study
the IAR Embedded Workbench® IDE User Guide for ARM®. This guide contains a
product overview, tutorials that can help you get started, conceptual and user
information about the IDE and the IAR C-SPY® Debugger, and corresponding
reference information.

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What this guide contains

What this guide contains
Below is a brief outline and summary of the chapters in this guide.

Part 1. Using the build tools
●

Introduction to the IAR build tools gives an introduction to the IAR build tools,
which includes an overview of the tools, the programming languages, the available
device support, and extensions provided for supporting specific features of the
ARM core.

●

Developing embedded applications gives the information you need to get started
developing your embedded software using the IAR build tools.

●

Data storage describes how to store data in memory.

●

Functions gives a brief overview of function-related extensions—mechanisms for
controlling functions—and describes some of these mechanisms in more detail.

●

Linking using ILINK describes the linking process using the IAR ILINK Linker and
the related concepts.

●

Linking your application lists aspects that you must consider when linking your
application, including using ILINK options and tailoring the linker configuration
file.

●

The DLIB runtime environment describes the DLIB runtime environment in which
an application executes. It covers how you can modify it by setting options,
overriding default library modules, or building your own library. The chapter also
describes system initialization introducing the file cstartup, how to use modules
for locale, and file I/O.

●

Assembler language interface contains information required when parts of an
application are written in assembler language. This includes the calling convention.

●

Using C++ gives an overview of the two levels of C++ support: The
industry-standard EC++ and IAR Extended EC++.

●

Application-related considerations discusses a selected range of application issues
related to using the compiler and linker.

●

Efficient coding for embedded applications gives hints about how to write code that
compiles to efficient code for an embedded application.

Part 2. Reference information
●

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External interface details provides reference information about how the compiler
and linker interact with their environment—the invocation syntax, methods for
passing options to the compiler and linker, environment variables, the include file
search procedure, and the different types of compiler and linker output. The chapter
also describes how the diagnostic system works.

Preface

●

Compiler options explains how to set options, gives a summary of the options, and
contains detailed reference information for each compiler option.

●

Linker options gives a summary of the options, and contains detailed reference
information for each linker option.

●

Data representation describes the available data types, pointers, and structure types.
This chapter also gives information about type and object attributes.

●

Compiler extensions gives a brief overview of the compiler extensions to the
ISO/ANSI C standard. More specifically the chapter describes the available C
language extensions.

●

Extended keywords gives reference information about each of the ARM-specific
keywords that are extensions to the standard C/C++ language.

●

Pragma directives gives reference information about the pragma directives.

●

Intrinsic functions gives reference information about functions to use for accessing
ARM-specific low-level features.

●

The preprocessor gives a brief overview of the preprocessor, including reference
information about the different preprocessor directives, symbols, and other related
information.

●

Library functions gives an introduction to the C or C++ library functions, and
summarizes the header files.

●

The linker configuration file describes the purpose of the linker configuration file
and describes its contents.

●

Section reference gives reference information about the use of sections.

●

IAR utilities describes the IAR utilities that handle the ELF and DWARF object
formats.

●

Implementation-defined behavior describes how the compiler handles the
implementation-defined areas of the C language standard.

Glossary
The glossary contains definitions of programming terms.

Other documentation
The complete set of IAR Systems development tools for the ARM core is described in
a series of guides. For information about:
●

Using the IDE and the IAR C-SPY Debugger®, refer to the IAR Embedded
Workbench® IDE User Guide for ARM®

●

Programming for the ARM IAR Assembler, refer to the ARM® IAR Assembler
Reference Guide

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Other documentation

●

Using the IAR DLIB Library functions, refer to the online help system

●

Porting application code and projects created with a previous IAR Embedded
Workbench for ARM, refer to the ARM® IAR Embedded Workbench® Migration
Guide

●

Using the MISRA-C:1998 rules or the MISRA-C:2004 rules, refer to the IAR
Embedded Workbench® MISRA C:1998 Reference Guide or the IAR Embedded
Workbench® MISRA C:2004 Reference Guide, respectively.

All of these guides are delivered in hypertext PDF or HTML format on the installation
media. Some of them are also delivered as printed books.

FURTHER READING
These books might be of interest to you when using the IAR Systems development tools:
●

Seal, David, and David Jagger. ARM Architecture Reference Manual.
Addison-Wesley.

●

Barr, Michael, and Andy Oram, ed. Programming Embedded Systems in C and
C++. O’Reilly & Associates.

●

Furber, Steve, ARM System-on-Chip Architecture. Addison-Wesley.

●

Harbison, Samuel P. and Guy L. Steele (contributor). C: A Reference Manual.
Prentice Hall.

●

Kernighan, Brian W. and Dennis M. Ritchie. The C Programming Language.
Prentice Hall. [The later editions describe the ANSI C standard.]

●

Labrosse, Jean J. Embedded Systems Building Blocks: Complete and Ready-To-Use
Modules in C. R&D Books.

●

Lippman, Stanley B. and Josée Lajoie. C++ Primer. Addison-Wesley.

●

Mann, Bernhard. C für Mikrocontroller. Franzis-Verlag. [Written in German.]

●

Sloss, Andrew N. et al, ARM System Developer's Guide: Designing and Optimizing
System Software. Morgan Kaufmann.

●

Stroustrup, Bjarne. The C++ Programming Language. Addison-Wesley.

We recommend that you visit these web sites:

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●

The Advanced RISC Machines Ltd web site, www.arm.com, contains information
and news about the ARM cores, as well as information about the ARM Embedded
Application Binary Interface (AEABI).

●

The IAR Systems web site, www.iar.com, holds application notes and other
product information.

●

The web site www.SevensAndNines.com, maintained by IAR Systems, provides
an online user community and resource site for ARM developers.

Preface

●

Finally, the Embedded C++ Technical Committee web site,
www.caravan.net/ec2plus, contains information about the Embedded C++
standard.

Document conventions
When, in this text, we refer to the programming language C, the text also applies to C++,
unless otherwise stated.
When referring to a directory in your product installation, for example arm\doc, the full
path to the location is assumed, for example c:\Program Files\IAR
Systems\Embedded Workbench 5.n\arm\doc.

TYPOGRAPHIC CONVENTIONS
This guide uses the following typographic conventions:
Style

Used for

computer

• Source code examples and file paths.
• Text on the command line.
• Binary, hexadecimal, and octal numbers.

parameter

A placeholder for an actual value used as a parameter, for example
filename.h where filename represents the name of the file.

[option]

An optional part of a command, where [] is part of the described
syntax.

{option}

A mandatory part of a command, where {} is part of the described
syntax.

[option]

An optional part of a command.

a|b|c

Alternatives in a command.

{a|b|c}

A mandatory part of a command with alternatives.

bold

Names of menus, menu commands, buttons, and dialog boxes that
appear on the screen.

italic

• A cross-reference within this guide or to another guide.
• Emphasis.

…

An ellipsis indicates that the previous item can be repeated an arbitrary
number of times.
Identifies instructions specific to the IAR Embedded Workbench® IDE
interface.
Identifies instructions specific to the command line interface.

Table 1: Typographic conventions used in this guide

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Document conventions

Style

Used for

Identifies helpful tips and programming hints.
Identifies warnings.
Table 1: Typographic conventions used in this guide (Continued)

NAMING CONVENTIONS
The following naming conventions are used for the products and tools from IAR
Systems® referred to in this guide:
Brand name

IAR Embedded Workbench® for ARM

IAR Embedded Workbench®

IAR Embedded Workbench® IDE for ARM

the IDE

IAR C-SPY® Debugger for ARM

C-SPY, the debugger

IAR C-SPY® Simulator

the simulator

IAR C/C++ Compiler™ for ARM

the compiler

IAR Assembler™ for ARM

the assembler

IAR ILINK™ Linker

ILINK, the linker

IAR DLIB Library™

the DLIB library

Table 2: Naming conventions used in this guide

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Generic term

Part 1. Using the build
tools
This part of the IAR C/C++ Development Guide for ARM® includes these
chapters:
●

Introduction to the IAR build tools

●

Developing embedded applications

●

Data storage

●

Functions

●

Linking using ILINK

●

Linking your application

●

The DLIB runtime environment

●

Assembler language interface

●

Using C++

●

Application-related considerations

●

Efficient coding for embedded applications.

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Introduction to the IAR
build tools
This chapter gives an introduction to the IAR build tools for the ARM core,
which means you will get an overview of:
●

The IAR build tools—the build interfaces, compiler, assembler, and linker

●

The programming languages

●

The available device support

●

The extensions provided by the IAR C/C++ Compiler for ARM to support
specific features of the ARM core.

The IAR build tools—an overview
In the IAR product installation you can find a set of tools, code examples, and user
documentation, all suitable for developing software for ARM-based embedded
applications. The tools allow you to develop your application in C, C++, or in assembler
language.
For a more detailed product overview, see the IAR Embedded Workbench® IDE User
Guide for ARM®. There you can also read about the debugger.
IAR Embedded Workbench® is a very powerful Integrated Development Environment
(IDE) that allows you to develop and manage complete embedded application projects.
It provides an easy-to-learn and highly efficient development environment with
maximum code inheritance capabilities, comprehensive and specific target support. IAR
Embedded Workbench promotes a useful working methodology, and thus a significant
reduction of the development time.
The compiler, assembler, and linker can also be run from a command line environment,
if you want to use them as external tools in an already established project environment.

IAR C/C++ COMPILER
The IAR C/C++ Compiler for ARM is a state-of-the-art compiler that offers the
standard features of the C and C++ languages, plus extensions designed to take
advantage of the ARM-specific facilities.

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The IAR build tools—an overview

IAR ASSEMBLER
The IAR Assembler for ARM is a powerful relocating macro assembler with a
versatile set of directives and expression operators. The assembler features a built-in
C language preprocessor and supports conditional assembly.
The IAR Assembler for ARM uses the same mnemonics and operand syntax as the
Advanced RISC Machines Ltd ARM Assembler, which simplifies the migration of
existing code. For detailed information, see the ARM® IAR Assembler Reference Guide.

THE IAR ILINK LINKER
The IAR ILINK Linker is a powerful, flexible software tool for use in the development
of embedded controller applications. It is equally well suited for linking small,
single-file, absolute assembler programs as it is for linking large, relocatable input,
multi-module, C/C++, or mixed C/C++ and assembler programs.

SPECIFIC ELF TOOLS
Because ILINK both uses and produces industry-standard ELF and DWARF as object
format, additional IAR utilities that handle these formats can be used:
●

The IAR Archive Tool—iarchive—creates and manipulates a library (archive) of
several ELF object files

●

The IAR ELF Tool—ielftool—performs various transformations on an ELF
executable image (such as, fill, checksum, format conversion etc)

●

The IAR ARM ELF Dumper—ielfdumparm—creates a text representation of the
contents of an ELF relocatable or executable image

●

The IAR ELF Object Tool—iobjmanip—is used for performing low-level
manipulation of ELF object files

●

The IAR Absolute Symbol Exporter—isymexport—exports absolute symbols
from a ROM image file, so that they can be used when linking an add-on
application.

Note: These ELF utilities are well-suited for object files produced by the tools from
IAR Systems. Thus, we recommend using them instead of the GNU binary utilities.

EXTERNAL TOOLS
For information about how to extend the tool chain in the IDE, see the IAR Embedded
Workbench® IDE User Guide for ARM®.

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Introduction to the IAR build tools

IAR language overview
There are two high-level programming languages you can use with the IAR C/C++
Compiler for ARM:
●

C, the most widely used high-level programming language in the embedded
systems industry. Using the IAR C/C++ Compiler for ARM, you can build
freestanding applications that follow the standard ISO 9899:1990. This standard is
commonly known as ANSI C.

●

C++, a modern object-oriented programming language with a full-featured library
well suited for modular programming. IAR Systems supports two levels of the
C++ language:
●

Embedded C++ (EC++), a subset of the C++ programming standard, which is
intended for embedded systems programming. It is defined by an industry
consortium, the Embedded C++ Technical committee. See the chapter Using
C++.

●

IAR Extended Embedded C++, with additional features such as full template
support, multiple inheritance, namespace support, the new cast operators, as well
as the Standard Template Library (STL).

Each of the supported languages can be used in strict or relaxed mode, or relaxed with
IAR extensions enabled. The strict mode adheres to the standard, whereas the relaxed
mode allows some deviations from the standard. For more details, see the chapter
Compiler extensions.
For information about how the compiler handles the implementation-defined areas of
the C language, see the chapter Implementation-defined behavior.
It is also possible to implement parts of the application, or the whole application, in
assembler language. See the ARM® IAR Assembler Reference Guide.
For more information about the Embedded C++ language and Extended Embedded
C++, see the chapter Using C++.

Device support
To get a smooth start with your product development, the IAR product installation
comes with wide range of device-specific support.

SUPPORTED ARM DEVICES
The IAR C/C++ Compiler for ARM supports several different ARM cores and devices
based on the instruction sets version 4, 5, 6, 6M, and 7. The object code that the compiler

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5

Special support for embedded systems

generates is not always binary compatible between the cores. Therefore it is crucial to
specify a processor option to the compiler. The default core is ARM7TDMI.

PRECONFIGURED SUPPORT FILES
The IAR product installation contains a vast amount of preconfigured files for
supporting different devices.

Header files for I/O
Standard peripheral units are defined in device-specific I/O header files with the
filename extension h. The product package supplies I/O files for all devices that are
available at the time of the product release. You can find these files in the
arm\inc\ directory. Make sure to include the appropriate include file in your
application source files. If you need additional I/O header files, they can be created using
one of the provided ones as a template. For detailed information about the header file
format, see EWARM_HeaderFormat.pdf located in the arm\doc\ directory.

Device description files
The debugger handles several of the device-specific requirements, such as definitions of
peripheral registers and groups of these, by using device description files. These files are
located in the arm\inc directory and they have the filename extension ddf. To read
more about these files, see the IAR Embedded Workbench® IDE User Guide for ARM®
and EWARM_DDFFormat.pdf located in the arm\doc\ directory.

EXAMPLES FOR GETTING STARTED
The arm\examples directory contains several hundreds of examples of working
applications to give you a smooth start with your development. The complexity of the
examples ranges from simple LED blink to USB mass storage controllers. There are
examples provided for most of the supported devices.

Special support for embedded systems
This section briefly describes the extensions provided by the compiler to support
specific features of the ARM core.

EXTENDED KEYWORDS
The compiler provides a set of keywords that can be used for configuring how the code
is generated. For example, there are keywords for declaring special function types.
By default, language extensions are enabled in the IDE.

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Introduction to the IAR build tools

The command line option -e makes the extended keywords available, and reserves them
so that they cannot be used as variable names. See, -e, page 169 for additional
information.
For detailed descriptions of the extended keywords, see the chapter Extended keywords.

PRAGMA DIRECTIVES
The pragma directives control the behavior of the compiler, for example how it allocates
memory, whether it allows extended keywords, and whether it issues warning messages.
The pragma directives are always enabled in the compiler. They are consistent with
ISO/ANSI C, and are very useful when you want to make sure that the source code is
portable.
For detailed descriptions of the pragma directives, see the chapter Pragma directives.

PREDEFINED SYMBOLS
With the predefined preprocessor symbols, you can inspect your compile-time
environment, for example the CPU mode and time of compilation.
For detailed descriptions of the predefined symbols, see the chapter The preprocessor.

SPECIAL FUNCTION TYPES
The special hardware features of the ARM core are supported by the compiler’s special
function types: software interrupts, interrupts, and fast interrupts. You can write a
complete application without having to write any of these functions in assembler
language.
For detailed information, see Primitives for interrupts, concurrency, and OS-related
programming, page 30.

ACCESSING LOW-LEVEL FEATURES
For hardware-related parts of your application, accessing low-level features is essential.
The compiler supports several ways of doing this: intrinsic functions, mixing C and
assembler modules, and inline assembler. For information about the different methods,
see Mixing C and assembler, page 91.

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Special support for embedded systems

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Developing embedded
applications
This chapter provides the information you need to get started developing your
embedded software for the ARM core using the IAR build tools.
First, you will get an overview of the tasks related to embedded software
development, followed by an overview of the build process, including the steps
involved for compiling and linking an application.
Next, the program flow of an executing application is described.
Finally, you will get an overview of the basic settings needed for a project.

Developing embedded software using IAR build tools
Typically, embedded software written for a dedicated microcontroller is designed as an
endless loop waiting for some external events to happen. The software is located in
ROM and executes on reset. You must consider several hardware and software factors
when you write this kind of software.

MAPPING OF INTERNAL AND EXTERNAL MEMORY
Embedded systems typically contain various types of memory, such as on-chip RAM,
external DRAM or SRAM, ROM, EEPROM, or flash memory.
As an embedded software developer, you must understand the features of the different
memory types. For example, on-chip RAM is often faster than other types of memories,
and variables that are accessed often would in time-critical applications benefit from
being placed here. Conversely, some configuration data might be accessed seldom but
must maintain their value after power off, so they should be saved in EEPROM or flash
memory.
For efficient memory usage, the compiler provides several mechanisms for controlling
placement of functions and data objects in memory. For an overview see Controlling
data and function placement in memory, page 131. The linker places sections of code in
memory according to the directives you specify in the linker configuration file, see
Placing code and data—the linker configuration file, page 42.

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Developing embedded software using IAR build tools

COMMUNICATION WITH PERIPHERAL UNITS
If external devices are connected to the microcontroller, you might need to initialize and
control the signalling interface, for example by using chip select pins, and detect and
handle external interrupt signals. Typically, this must be initialized and controlled at
runtime. The normal way to do this is to use special function registers, or SFRs. These
are typically available at dedicated addresses, containing bits that control the chip
configuration.
Standard peripheral units are defined in device-specific I/O header files with the
filename extension h. See Device support, page 5. For an example, see Accessing special
function registers, page 142.

EVENT HANDLING
In embedded systems, using interrupts is a method for handling external events
immediately; for example, detecting that a button was pressed. In general, when an
interrupt occurs in the code, the core simply stops executing the code it runs, and starts
executing an interrupt routine instead.
The compiler supports the following processor exception types: interrupts, software
interrupts, and fast interrupts, which means that you can write your interrupt routines in
C, see Interrupt functions, page 31.

SYSTEM STARTUP
In all embedded systems, system startup code is executed to initialize the system—both
the hardware and the software system—before the main function of the application is
called. The CPU imposes this by starting execution from a fixed memory address.
As an embedded software developer, you must ensure that the startup code is located at
the dedicated memory addresses, or can be accessed using a pointer from the vector
table. This means that startup code and the initial vector table must be placed in
non-volatile memory, such as ROM, EPROM, or flash.
A C/C++ application further needs to initialize all global variables. This initialization is
handled by the linker and the system startup code in conjunction. For more information,
see Application execution—an overview, page 14.

REAL-TIME OPERATING SYSTEMS
In many cases, the embedded application is the only software running in the system.
However, using an RTOS has some advantages.
For example, the timing of high-priority tasks is not affected by other parts of the
program which are executed in lower priority tasks. This typically makes a program

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more deterministic and can reduce power consumption by using the CPU efficiently and
putting the CPU in a lower-power state when idle.
Using an RTOS can make your program easier to read and maintain, and in many cases
smaller as well. Application code can be cleanly separated in tasks which are truly
independent of each other. This makes teamwork easier, as the development work can
be easily split into separate tasks which are handled by one developer or a group of
developers.
Finally, using an RTOS reduces the hardware dependence and creates a clean interface
to the application, making it easier to port the program to different target hardware.

INTEROPERABILITY WITH OTHER BUILD TOOLS
The IAR compiler and linker provide support for AEABI, the Embedded Application
Binary Interface for ARM. For more information about this interface specification,
see the www.arm.com web site.
The advantage of this interface is the interoperability between vendors supporting it;
an application can be built up of libraries of object files produced by different vendors
and linked with a linker from any vendor, as long as they adhere to the AEABI
standard.
AEABI specifies full compatibility for C and C++ object code, and for the C library. The
AEABI does not include specifications for the C++ library.
For more information about the AEABI support in the IAR build tools, see AEABI
compliance, page 123.
The ARM IAR build tools version 5.xx are not fully compatible with earlier versions of
the product, see the ARM® IAR Embedded Workbench® Migration Guide for more
information.

The build process—an overview
This section gives an overview of the build process; how the various build
tools—compiler, assembler, and linker—fit together, going from source code to an
executable image.
To get familiar with the process in practice, you should run one or more of the tutorials
available in the IAR Embedded Workbench® IDE User Guide for ARM®.

THE TRANSLATION PROCESS
There are two tools in the IDE that translate application source files to intermediary
object files. The IAR C/C++ Compiler and the IAR relocatable assembler. Both produce

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The build process—an overview

relocatable object files in the industry-standard format ELF, including the DWARF
format for debug information.
Note: The compiler can also be used for translating C/C++ source code into assembler
source code. If required, you can modify the assembler source code which then can be
assembled into object code. For more information about the IAR Assembler, see the
ARM® IAR Assembler Reference Guide.
This illustration shows the translation process:

Figure 1: The build process before linking

After the translation, you can choose to pack any number of modules into an archive, or
in other words, a library. The important reason you should use libraries is that each
module in a library is conditionally linked in the application, or in other words, is only
included in the application if the module is used directly or indirectly by a module
supplied as an object file. Optionally, you can create a library; then use the IAR utility
iarchive.

THE LINKING PROCESS
The relocatable modules, in object files and libraries, produced by the IAR compiler and
assembler cannot be executed as is. To become an executable application, they must be
linked.
Note: Modules produced by a toolset from another vendor can be included in the build
as well. Be aware that this also might require a compiler utility library from the same
vendor.

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The IAR ILINK Linker (ilinkarm.exe) is used for building the final application.
Normally, ILINK requires the following information as input:
●

Several object files and possibly certain libraries

●

A program start label (set by default)

●

The linker configuration file that describes placement of code and data in the
memory of the target system.

This illustration shows the linking process:

Figure 2: The linking process

Note: The standard C/C++ library contains support routines for the compiler, and the
implementation of the C/C++ standard library functions.
During the linking, ILINK might produce error messages and logging messages on
stdout and stderr. The log messages are useful for understanding why an application
was linked the way it was, for example, why a module was included or a section
removed.
For an in-depth description of the procedure performed by ILINK, see The linking
process, page 41.

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Application execution—an overview

AFTER LINKING
The IAR ILINK Linker produces an absolute object file in ELF format that contains the
executable image. After linking, the produced absolute executable image can be used
for:
●

Loading into the IAR C-SPY Debugger or any other external debugger that reads
ELF and DWARF.

●

Programming to a flash/PROM using a flash/PROM programmer. Before this is
possible, the actual bytes in the image must be converted into the standard Motorola
32-bit S-record format or the Intel Hex-32 format. For this, use ielftool, see The
IAR ELF Tool—ielftool, page 330.

This illustration shows the possible uses of the absolute output ELF/DWARF file:

Figure 3: Possible uses of the absolute output ELF/DWARF file

Application execution—an overview
This section gives an overview of the execution of an embedded application divided into
three phases, the:

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●

Initialization phase

●

Execution phase

●

Termination phase.

Developing embedded applications

THE INITIALIZATION PHASE
Initialization is executed when an application is started (the CPU is reset) but before the
main function is entered. The initialization phase can for simplicity be divided into:
●

Hardware initialization, which generally at least initializes the stack pointer.
The hardware initialization is typically performed in the system startup code
cstartup.s and if required, by an extra low-level routine that you provide. It might
include resetting/starting the rest of the hardware, setting up the CPU, etc, in
preparation for the software C/C++ system initialization.

●

Software C/C++ system initialization
Typically, this includes assuring that every global (statically linked) C/C++ symbol
receives its proper initialization value before the main function is called.

●

Application initialization
This depends entirely on your application. Typically, it can include setting up an
RTOS kernel and starting initial tasks for an RTOS-driven application. For a
bare-bone application, it can include setting up various interrupts, initializing
communication, initializing devices, etc.

For a ROM/flash-based system, constants and functions are already placed in ROM. All
symbols placed in RAM must be initialized before the main function is called. The
linker has already divided the available RAM into different areas for variables, stack,
heap, etc.

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Application execution—an overview

The following sequence of illustrations gives a simplified overview of the different
stages of the initialization.

1 When an application is started, the system startup code first performs hardware
initialization, such as initialization of the stack pointer to point at the end of the
predefined stack area:

Figure 4: Initializing hardware

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2 Then, memories that should be zero-initialized are cleared, in other words, filled with
zeros:

Figure 5: Zero-initializing variables

Typically, this is data referred to as zero-initialized data; variables declared as, for
example, int i = 0;

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Application execution—an overview

3 For initialized data, data declared, for example, like int i = 6; the initializers are
copied from ROM to RAM:

Figure 6: Initializing variables

4 Finally, the main function is called:

Figure 7: Calling main

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For a detailed description about each stage, see System startup and termination, page 72.
For more details about initialization of data, see Initialization at system startup, page 45.

THE EXECUTION PHASE
The software of an embedded application is typically implemented as a loop which is
either interrupt-driven or uses polling for controlling external interaction or internal
events. For an interrupt-driven system, the interrupts are typically initialized at the
beginning of the main function.
In a system with real-time behavior and where responsiveness is critical, a multi-task
system might be required. This means that your application software should be
complemented with a real-time operating system. In this case, the RTOS and the
different tasks must also be initialized at the beginning of the main function.

THE TERMINATION PHASE
Typically, the execution of an embedded application should never end. If it does, you
must define a proper end behavior.
To terminate an application in a controlled way, either call one of the standard C library
functions exit, _Exit, or abort, or return from main. If you return from main, the
exit function is executed, which means that C++ destructors for static and global
variables are called (C++ only) and all open files are closed.
Of course, in case of incorrect program logic, the application might terminate in an
uncontrolled and abnormal way—a system crash.
To read more about this, see System termination, page 75.

Basic project configuration
In the command line interface, this line compiles the source file myfile.c into the
object file myfile.o using the default settings:
iccarm myfile.c

On the command line, this line can be used for starting ILINK:
ilinkarm myfile.o myfile2.o -o a.out --config my_configfile.icf

In this example, myfile.o and myfile2.o are object files, and my_configfile.icf
is the linker configuration file. The option -o specifies the name of the output file.
Note: By default, the label where the application starts is __iar_program_start.
You can use the --entry command line option to change this.

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Basic project configuration

However, you must specify some additional options. This section gives an overview of
the basic settings for the project setup that are needed to make the compiler and linker
generate the best code for the ARM device you are using. You can specify the options
either from the command line interface or in the IDE.
You need settings for:
●

Processor configuration, that is processor variant, CPU mode, interworking, VFP
and floating-point arithmetic, and byte order

●

Optimization settings

●

Runtime environment

●

Customizing the ILINK configuration, see the chapter Linking your application

●

AEBI compliance, see AEABI compliance, page 123.

In addition to these settings, many other options and settings can fine-tune the result
even further. For details about how to set options and for a list of all available options,
see the chapters Compiler options, Linker options, and the IAR Embedded Workbench®
IDE User Guide for ARM®, respectively.

PROCESSOR CONFIGURATION
To make the compiler generate optimum code, you should configure it for the ARM core
you are using.

Processor variant
The IAR C/C++ Compiler for ARM supports several different ARM cores and devices
based on the instruction sets version 4, 5, 6, and 7. All supported cores support Thumb
instructions and 64-bit multiply instructions. The object code that the compiler
generates is not always binary compatible between the cores. Therefore it is crucial to
specify a processor option to the compiler. The default core is ARM7TDMI.
See the IAR Embedded Workbench® IDE User Guide for ARM® for information about
setting the Processor variant option in the IDE.
Use the --cpu option to specify the ARM core; see --cpu, page 162 for syntax
information.

CPU mode
The IAR C/C++ Compiler for ARM supports two CPU modes: ARM and Thumb.
All functions and function pointers will compile in the mode that you specify, except
those explicitly declared __arm or __thumb.
See the IAR Embedded Workbench® IDE User Guide for ARM® for information about
setting the Processor variant or Chip option in the IDE.

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Use the --arm or --thumb option to specify the CPU mode for your project; see --arm,
page 162 and --thumb, page 187, for syntax information.

Interworking
When code is compiled with the --interwork option, ARM and Thumb code can be
freely mixed. Interworking functions can be called from both ARM and Thumb code.
Interworking is default for devices based on the instruction sets version 5, 6, and 7, or
when using the --aeabi compiler option.
See the IAR Embedded Workbench® IDE User Guide for ARM® for information about
setting the Generate interwork code option in the IDE.
Use the --interwork option to specify interworking capabilities for your project; see
--interwork, page 173, for syntax information.

VFP and floating-point arithmetic
If you are using an ARM core that contains a Vector Floating Point (VFP) coprocessor,
you can use the --fpu option to generate code that carries out floating-point operations
utilizing the coprocessor, instead of using the software floating-point library routines.
See the IAR Embedded Workbench® IDE User Guide for ARM® for information about
setting the FPU option in the IDE.
Use the --fpu option to use the coprocessor for floating-point operations; see --fpu,
page 172, for syntax information.

Byte order
The IAR C/EC++ Compiler for ARM supports the big-endian and little-endian byte
order. All user and library modules in your application must use the same byte order.
See the IAR Embedded Workbench® IDE User Guide for ARM® for information about
setting the Endian mode option in the IDE.
Use the --endian option to specify the byte order for your project; see --endian, page
170, for syntax information.

OPTIMIZATION FOR SPEED AND SIZE
The compiler is a state-of-the-art compiler with an optimizer that performs, among other
things, dead-code elimination, constant propagation, inlining, common subexpression
elimination, static clustering, instruction scheduling, and precision reduction. It also
performs loop optimizations, such as unrolling and induction variable elimination.
You can decide between several optimization levels and for the highest level you can
choose between different optimization goals—size, speed, or balanced. Most

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Basic project configuration

optimizations will make the application both smaller and faster. However, when this is
not the case, the compiler uses the selected optimization goal to decide how to perform
the optimization.
The optimization level and goal can be specified for the entire application, for individual
files, and for individual functions. In addition, some individual optimizations, such as
function inlining, can be disabled.
For details about compiler optimizations and for more information about efficient
coding techniques, see the chapter Efficient coding for embedded applications.

RUNTIME ENVIRONMENT
To create the required runtime environment you should choose a runtime library and set
library options. You might also need to override certain library modules with your own
customized versions.
The runtime library provided is the IAR DLIB Library, which supports ISO/ANSI C and
C++. This library also supports floating-point numbers in IEEE 754 format and it can
be configured to include different levels of support for locale, file descriptors, multibyte
characters, etc.
The runtime library you choose can be one of the prebuilt libraries, or a library that you
customized and built yourself. The IDE provides a library project template that you can
use for building your own library version. This gives you full control of the runtime
environment. If your project only contains assembler source code, you do not need to
choose a runtime library.
Note: Some tailoring might be required, for example to meet hardware requirements.
For detailed information about the runtime environment, see the chapter The DLIB
runtime environment.
The way you set up a runtime environment and locate all the related files differs
depending on which build interface you are using—the IDE or the command line.

Setting up for the runtime environment in the IDE
The library is automatically chosen by the linker according to the settings you made in
Project>Options>General Options, on the pages Library Configuration, Library
Options, and Library Usage.
Note that for the DLIB library there are different configurations—Normal and
Full—which include different levels of support for locale, file descriptors, multibyte
characters, et cetera. See Library configurations, page 63, for more information.

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Based on which library configuration you choose and your other project settings, the
correct library file is used automatically. For the device-specific include files, a correct
include path is set up.

Setting up for the runtime environment from the command line
Use these command line options to explicitly specify the library and the dependency
files:
Command line

Description

-I arm\inc

Specifies the include path to device-specific I/O definition
files.

--dlib_config
C:\...\configfile.h

Specifies the library configuration file, either
DLib_Config_Normal.h or
DLib_Config_Full.h

Table 3: Command line options for specifying library and dependency files

Normally, it is not needed to specify a library file explicitly, as ILINK automatically uses
the correct library file.
For a list of all prebuilt library object files for the IAR DLIB Library, see Using a
prebuilt library, page 64. Here you also get information about how the object files
correspond to the dependent project options, and the corresponding configuration files.
Make sure to use the object file that matches your other project options.

Setting library and runtime environment options
You can set certain options to reduce the library and runtime environment size:
●

The formatters used by the functions printf, scanf, and their variants, see
Choosing formatters for printf and scanf, page 67.

●

The size of the stack and the heap, see Setting up the stack, page 52, and Setting up
the heap, page 52, respectively.

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Data storage
This chapter gives a brief introduction to the memory layout of the ARM core
and the fundamental ways data can be stored in memory: on the stack, in static
(global) memory, or in heap memory. Finally, detailed information about data
storage on the stack and the heap is provided.

Introduction
An ARM core can address 4 Gbytes of continuous memory, ranging from 0x00000000
to 0xFFFFFFFF. Different types of physical memory can be placed in the memory range.
A typical application will have both read-only memory (ROM) and read/write memory
(RAM). In addition, some parts of the memory range contain processor control registers
and peripheral units.

DIFFERENT WAYS TO STORE DATA
In a typical application, data can be stored in memory in three different ways:
●

Auto variables.
All variables that are local to a function, except those declared static, are stored on
the stack. These variables can be used as long as the function executes. When the
function returns to its caller, the memory space is no longer valid.

●

Global variables and local variables declared static.
In this case, the memory is allocated once and for all. The word static in this context
means that the amount of memory allocated for this kind of variables does not change
while the application is running. The ARM core has one single address space and the
compiler supports full memory addressing.

●

Dynamically allocated data.
An application can allocate data on the heap, where the data remains valid until it is
explicitly released back to the system by the application. This type of memory is
useful when the number of objects is not known until the application executes. Note
that there are potential risks connected with using dynamically allocated data in
systems with a limited amount of memory, or systems that are expected to run for a
long time. For more information, see Dynamic memory on the heap, page 27.

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Auto variables—on the stack

Auto variables—on the stack
Variables that are defined inside a function—and not declared static—are named auto
variables by the C standard. A few of these variables are placed in processor registers;
the rest are placed on the stack. From a semantic point of view, this is equivalent. The
main differences are that accessing registers is faster, and that less memory is required
compared to when variables are located on the stack.
Auto variables can only live as long as the function executes; when the function returns,
the memory allocated on the stack is released.

THE STACK
The stack can contain:
●

Local variables and parameters not stored in registers

●

Temporary results of expressions

●

The return value of a function (unless it is passed in registers)

●

Processor state during interrupts

●

Processor registers that should be restored before the function returns (callee-save
registers).

The stack is a fixed block of memory, divided into two parts. The first part contains
allocated memory used by the function that called the current function, and the function
that called it, etc. The second part contains free memory that can be allocated. The
borderline between the two areas is called the top of stack and is represented by the stack
pointer, which is a dedicated processor register. Memory is allocated on the stack by
moving the stack pointer.
A function should never refer to the memory in the area of the stack that contains free
memory. The reason is that if an interrupt occurs, the called interrupt function can
allocate, modify, and—of course—deallocate memory on the stack.

Advantages
The main advantage of the stack is that functions in different parts of the program can
use the same memory space to store their data. Unlike a heap, a stack will never become
fragmented or suffer from memory leaks.
It is possible for a function to call itself—a recursive function—and each invocation can
store its own data on the stack.

Potential problems
The way the stack works makes it impossible to store data that is supposed to live after
the function returns. The following function demonstrates a common programming

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mistake. It returns a pointer to the variable x, a variable that ceases to exist when the
function returns.
int *MyFunction()
{
int x;
/* Do something here. */
return &x; /* Incorrect */
}

Another problem is the risk of running out of stack. This will happen when one function
calls another, which in turn calls a third, etc., and the sum of the stack usage of each
function is larger than the size of the stack. The risk is higher if large data objects are
stored on the stack, or when recursive functions—functions that call themselves either
directly or indirectly—are used.

Dynamic memory on the heap
Memory for objects allocated on the heap will live until the objects are explicitly
released. This type of memory storage is very useful for applications where the amount
of data is not known until runtime.
In C, memory is allocated using the standard library function malloc, or one of the
related functions calloc and realloc. The memory is released again using free.
In C++, a special keyword, new, allocates memory and runs constructors. Memory
allocated with new must be released using the keyword delete.

Potential problems
Applications that are using heap-allocated objects must be designed very carefully,
because it is easy to end up in a situation where it is not possible to allocate objects on
the heap.
The heap can become exhausted if your application uses too much memory. It can also
become full if memory that no longer is in use was not released.
For each allocated memory block, a few bytes of data for administrative purposes is
required. For applications that allocate a large number of small blocks, this
administrative overhead can be substantial.
There is also the matter of fragmentation; this means a heap where small sections of free
memory is separated by memory used by allocated objects. It is not possible to allocate
a new object if no piece of free memory is large enough for the object, even though the
sum of the sizes of the free memory exceeds the size of the object.

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Dynamic memory on the heap

Unfortunately, fragmentation tends to increase as memory is allocated and released. For
this reason, applications that are designed to run for a long time should try to avoid using
memory allocated on the heap.

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Functions
This chapter contains information about functions. It gives a brief overview of
function-related extensions—mechanisms for controlling functions—and
describes some of these mechanisms in more detail.

Function-related extensions
In addition to the ISO/ANSI C standard, the compiler provides several extensions for
writing functions in C. Using these, you can:
●

Generate code for the different CPU modes ARM and Thumb

●

Make functions execute in RAM

●

Use primitives for interrupts, concurrency, and OS-related programming

●

Facilitate function optimization

●

Access hardware features.

The compiler uses compiler options, extended keywords, pragma directives, and
intrinsic functions to support this.
For more information about optimizations, see Efficient coding for embedded
applications, page 127. For information about the available intrinsic functions for
accessing hardware operations, see the chapter Intrinsic functions.

ARM and Thumb code
The IAR C/C++ Compiler for ARM can generate code for either the 32-bit ARM, or the
16-bit Thumb or Thumb2 instruction set. Use the --cpu_mode option, alternatively the
--arm or --thumb options, to specify which instruction set should be used for your
project. For individual functions, it is possible to override the project setting by using
the extended keywords __arm and __thumb. You can freely mix ARM and thumb code
in the same application, as long as the code is interworking.
When performing function calls, the compiler always attempts to generate the most
efficient assembler language instruction or instruction sequence available. As a result, 4
Gbytes of continuous memory in the range 0x0-0xFFFFFFFF can be used for placing
code. There is a limit of 4 Mbytes per code module.
The size of all code pointers is 4 bytes. There are restrictions to implicit and explicit
casts from code pointers to data pointers or integer types or vice versa. For further
information about the restrictions, see Pointer types, page 215.

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Execution in RAM

In the chapter Assembler language interface, the generated code is studied in more detail
in the description of calling C functions from assembler language and vice versa.

Execution in RAM
The __ramfunc keyword makes a function execute in RAM, or in other words places
the function in a section that has read/write attributes. The function is copied from ROM
to RAM at system startup just like any initialized variable, see System startup and
termination, page 72.
The keyword is specified before the return type:
__ramfunc void foo(void);

If a function declared __ramfunc tries to access ROM, the compiler will issue a
warning.
If the whole memory area used for code and constants is disabled—for example, when
the whole flash memory is being erased—only functions and data stored in RAM may
be used. Interrupts must be disabled unless the interrupt vector and the interrupt service
routines are also stored in RAM.
String literals and other constants can be avoided by using initialized variables. For
example, the following lines:
const int myc[] = { 10, 20 };
msg("Hello");
may be rewritten to:
static int myc[] = { 10, 20 };
static char hello[] = "Hello";
msg(hello);

//
//
//
//

myc initializer in
DATA_C (ROM)
String literal in
DATA_C (ROM)

//
//
//
//

Initialized by cstartup
Initialized by cstartup
hello stored in DATA_I
(RAM)

For more details, see Initializing code—copying ROM to RAM, page 55.

Primitives for interrupts, concurrency, and OS-related programming
The IAR C/C++ Compiler for ARM provides the following primitives related to writing
interrupt functions, concurrent functions, and OS-related functions:

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●

The extended keywords __irq, __fiq, __swi, and __nested

●

The intrinsic functions __enable_interrupt, __disable_interrupt,
__get_interrupt_state, and __set_interrupt_state.

Functions

Note: ARM Cortex-M has a different interrupt mechanism than other ARM devices,
and for these devices a different set of primitives is available. For more details, see
Interrupts for ARM Cortex-M, page 36.

INTERRUPT FUNCTIONS
In embedded systems, using interrupts is a method for handling external events
immediately; for example, detecting that a button was pressed.
In general, when an interrupt occurs in the code, the core simply stops executing the
code it runs, and starts executing an interrupt routine instead. It is extremely important
that the environment of the interrupted function is restored after the interrupt is handled;
this includes the values of processor registers and the processor status register. This
makes it possible to continue the execution of the original code after the code that
handled the interrupt was executed.
The compiler supports interrupts, software interrupts, and fast interrupts. For each
interrupt type, an interrupt routine can be written.
All interrupt functions must be compiled in ARM mode; if you are using Thumb mode,
use the __arm extended keyword or the #pragma type_attribute=__arm directive
to override the default behavior.
Each interrupt routine is associated with a vector address/instruction in the exception
vector table, which is specified in the ARM cores documentation. The interrupt vector
is the address in the exception vector table. For the ARM cores, the exception vector
table starts at address 0x0.
To define an interrupt function, the __irq or the __fiq keyword can be used. For
example:
__irq __arm void IRQ_Handler(void)
{
/* Do something */
}

See the ARM cores documentation for more information about the interrupt vector
table.

INSTALLING EXCEPTION FUNCTIONS
All interrupt functions and software interrupt handlers must be installed in the vector
table. This is done in assembler language in the system startup file cstartup.s.
The default implementation of the ARM exception vector table in the standard runtime
library jumps to predefined functions that implement an infinite loop. Any exception
that occurs for an event not handled by your application will therefore be caught in the
infinite loop (B. ).

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The predefined functions are defined as weak symbols. A weak symbol is only included
by the linker as long as no duplicate symbol is found. If another symbol is defined with
the same name, it will take precedence. Your application can therefore simply define its
own exception function by just defining it using the correct name.
These exception function names are defined in cstartup.s and referred to by the
library exception vector code:
Undefined_Handler
SWI_Handler
Prefetch_Handler
Abort_Handler
IRQ_Handler
FIQ_Handler

To implement your own exception handler, define a function using the appropriate
exception function name from the list above.
For example to add an interrupt function in C, it is sufficient to define an interrupt
function named IRQ_Handler:
__irq __arm void IRQ_Handler()
{
}

An interrupt function must have C linkage, read more in Calling convention, page 97.
If you use C++, an interrupt function could look, for example, like this:
extern "C"
{
__irq __arm void IRQ_Handler(void);
}
__irq __arm void IRQ_Handler()
{
}

No other changes are needed.

INTERRUPTS AND FAST INTERRUPTS
The interrupt and fast interrupt functions are easy to handle as they do not accept
parameters or have a return value.
●

To declare an interrupt function, use the __irq extended keyword or the #pragma
type_attribute=__irq directive. For syntax information, see __irq, page 238,
and type_attribute, page 257, respectively.

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Functions

●

To declare a fast interrupt function, use the __fiq extended keyword or the
#pragma type_attribute=__fiq directive. For syntax information, see __fiq,
page 237, and type_attribute, page 257, respectively.

Note: An interrupt function (irq) and a fast interrupt function (fiq) must have a return
type of void and cannot have any parameters. A software interrupt function (swi) may
have parameters and return values. By default, only four registers, R0–R3, can be used
for parameters and only the registers R0–R1 can be used for return values.

NESTED INTERRUPTS
Interrupts are automatically disabled by the ARM core prior to entering an interrupt
handler. If an interrupt handler re-enables interrupts, calls functions, and another
interrupt occurs, then the return address of the interrupted function—stored in LR—is
overwritten when the second IRQ is taken. In addition, the contents of SPSR will be
destroyed when the second interrupt occurs. The __irq keyword itself does not save
and restore LR and SPSR. To make an interrupt handler perform the necessary steps
needed when handling nested interrupts, the keyword __nested must be used in
addition to __irq. The function prolog—function entrance sequence—that the
compiler generates for nested interrupt handlers will switch from IRQ mode to system
mode. Make sure that both the IRQ stack and system stack is set up. If you use the
default cstartup.s file, both stacks are correctly set up.
Compiler-generated interrupt handlers that allow nested interrupts are supported for
IRQ interrupts only. The FIQ interrupts are designed to be serviced quickly, which in
most cases mean that the overhead of nested interrupts would be too high.
This example shows how to use nested interrupts with the ARM vectored interrupt
controller (VIC):
__irq __nested __arm void interrupt_handler(void)
{
void (*interrupt_task)();
unsigned int vector;
vector = VICVectAddr;
// Get interrupt vector.
VICVectAddr = 0;
// Acknowledge interrupt in VIC.
interrupt_task = (void(*)())vector;
__enable_interrupt();

(*interrupt_task)();

// Allow other IRQ interrupts
to be serviced from this
point.
// Execute the task associated
with this interrupt.

}

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Note: The __nested keyword requires the processor mode to be in either User or
System mode.

SOFTWARE INTERRUPTS
Software interrupt functions are slightly more complex than other interrupt functions, in
the way that they need a software interrupt handler (a dispatcher), are invoked (called)
from running application software, and that they accept arguments and have return
values. The mechanisms for calling a software interrupt function and how the software
interrupt handler dispatches the call to the actual software interrupt function is described
here.

Calling a software interrupt function
To call a software interrupt function from your application source code, the assembler
instruction SVC #immed is used, where immed is an integer value that is referred to as
the software interrupt number—or swi_number—in this guide. The compiler provides
an easy way to implicitly generate this instruction from C/C++ source code, by using the
__swi keyword and the #pragma swi_number directive when declaring the function.
A __swi function can for example be declared like this:
#pragma swi_number=0x23
__swi int swi_function(int a, int b);

In this case, the assembler instruction SVC 0x23 will be generated where the function is
called.
Software interrupt functions follow the same calling convention regarding parameters
and return values as an ordinary function, except for the stack usage, see Calling
convention, page 97.
For more information, see __swi, page 241, and swi_number, page 257, respectively.

The software interrupt handler and functions
The interrupt handler, for example SWI_Handler works as a dispatcher for software
interrupt functions. It is invoked from the interrupt vector and is responsible for
retrieving the software interrupt number and then calling the proper software interrupt
function. The SWI_Handler must be written in assembler as there is no way to retrieve
the software interrupt number from C/C++ source code.

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The software interrupt functions
The software interrupt functions can be written in C or C++. Use the __swi keyword in
a function definition to make the compiler generate a return sequence suited for a
specific software interrupt function. The #pragma swi_number directive is not needed
in the interrupt function definition.
For more information, see __swi, page 241.

Setting up the software interrupt stack pointer
If software interrupts will be used in your application, then the software interrupt stack
pointer (SVC_STACK) must be set up and some space must be allocated for the stack. The
SVC_STACK pointer can be setup together with the other stacks in the cstartup.s file.
As an example, see the set up of the interrupt stack pointer. Relevant space for the
SVC_STACK pointer is set up in the linker configuration file, see Setting up the stack,
page 52.

INTERRUPT OPERATIONS
An interrupt function is called when an external event occurs. Normally it is called
immediately while another function is executing. When the interrupt function has
finished executing, it returns to the original function. It is imperative that the
environment of the interrupted function is restored; this includes the value of processor
registers and the processor status register.
When an interrupt occurs, the following actions are performed:
●
●
●
●
●

The operating mode is changed corresponding to the particular exception
The address of the instruction following the exception entry instruction is saved in
R14 of the new mode
The old value of the CPSR is saved in the SPSR of the new mode
Interrupt requests are disabled by setting bit 7 of the CPSR and, if the exception is a
fast interrupt, further fast interrupts are disabled by setting bit 6 of the CPSR
The PC is forced to begin executing at the relevant vector address.

For example, if an interrupt for vector 0x18 occurs, the processor will start to execute
code at address 0x18. The memory area that is used as start location for interrupts is
called the interrupt vector table. The content of the interrupt vector is normally a branch
instruction jumping to the interrupt routine.
Note: If the interrupt function enables interrupts, the special processor registers needed
to return from the interrupt routine must be assumed to be destroyed. For this reason
they must be stored by the interrupt routine to be restored before it returns. This is
handled automatically if the __nested keyword is used.

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Primitives for interrupts, concurrency, and OS-related programming

INTERRUPTS FOR ARM CORTEX-M
ARM Cortex-M has a different interrupt mechanism than previous ARM architectures,
which means the primitives provided by the compiler are also different.
On ARM Cortex-M, an interrupt service routine enters and returns in the same way as a
normal function, which means no special keywords are required. Thus, the keywords
__irq, __fiq, and __nested are not available when you compile for ARM Cortex-M.
These exception function names are defined in cstartup_M.c and cstartup_M.s.
They are referred to by the library exception vector code:
NMI_Handler
HardFault_Handler
MemManage_Handler
BusFault_Handler
UsageFault_Handler
SVC_Handler
DebugMon_Handler
PendSV_Handler
SysTick_Handler

The vector table is implemented as an array. It should always have the name
__vector_table, because cmain refers to that symbol and C-SPY looks for that
symbol when determining where the vector table is located.
The predefined exception functions are defined as weak symbols. A weak symbol is
only included by the linker as long as no duplicate symbol is found. If another symbol
is defined with the same name, it will take precedence. Your application can therefore
simply define its own exception function by just defining it using the correct name from
the list above. If you need other interrupts or other exception handlers, you must make
a copy of the cstartup_M.c or cstartup_M.s file and make the proper addition to
the vector table.
The intrinsic functions __get_CPSR and __set_CPSR are not available when you
compile for ARM Cortex-M. Instead, if you need to get or set values of these or other
registers, you can use inline assembler. For more information, see Passing values
between C and assembler objects, page 143.

C++ AND SPECIAL FUNCTION TYPES
C++ member functions can be declared using special function types, with the restriction
that interrupt member functions must be static. When a non-static member function is

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Functions

called, it must be applied to an object. When an interrupt occurs and the interrupt
function is called, there is no object available to apply the member function to.
Special function types can be used for static member functions. For example, in the
following example, the function handler is declared as an interrupt function:
class Device
{
static __irq void handler();
};

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Linking using ILINK
This chapter describes the linking process using the IAR ILINK Linker and the
related concepts—first with an overview and then in more detail.

Linking—an overview
The IAR ILINK Linker is a powerful, flexible software tool for use in the development
of embedded applications. It is equally well suited for linking small, single-file, absolute
assembler programs as it is for linking large, relocatable, multi-module, C/C++, or
mixed C/C++ and assembler programs.
ILINK combines one or more relocatable object files—produced by the IAR Systems
compiler or assembler—with selected parts of one or more object libraries to produce
an executable image in the industry-standard format Executable and Linking Format
(ELF).
ILINK will automatically load only those library modules—user libraries and standard
C or C++ library variants—that are actually needed by the application you are linking.
Further, ILINK eliminates duplicate sections and sections that are not required.
ILINK can link both ARM and Thumb code, as well as a combination of them. By
automatically inserting additional instructions (veneers), ILINK will assure that the
destination will be reached for any calls and branches, and that the processor state is
switched when required. For more details about how to generate veneers, see Veneers,
page 57.
ILINK uses a configuration file where you can specify separate locations for code and
data areas of your target system memory map. This file also supports automatic handling
of the application’s initialization phase, which means initializing global variable areas
and code areas by copying initializers and possibly decompressing them as well.
The final output produced by ILINK is an absolute object file containing the executable
image in the ELF (including DWARF for debug information) format. The file can be
downloaded to C-SPY or any other debugger that supports ELF/DWARF, or it can be
programmed into EPROM.
To handle ELF files, various tools are included. For a list of included utilities, see
Specific ELF tools, page 4.

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Modules and sections

Modules and sections
Each relocatable object file contains one module, which consists of:
●

Several sections of code or data

●

Runtime attributes specifying various types of information, for example the used
device

●

Optionally, debug information in DWARF format

●

A symbol table of all global symbols and all external symbols used.

A section is a logical entity containing a piece of data or code that should be placed at a
physical location in memory. A section can consist of several section fragments,
typically one for each variable or function (symbols). A section can be placed either in
RAM or in ROM. In a normal embedded application, sections that are placed in RAM
do not have any content, they only occupy space.
Each section has a name and a type attribute that determines the content. The type
attribute is used (together with the name) for selecting sections for the ILINK
configuration. The most commonly used attributes are:
code

Executable code

readonly

Constant variables

readwrite

Initialized variables

zeroinit

Zero-initialized variables

Note: In addition to these section types—sections that contain the code and data that
are part of your application—a final object file will contain many other types of
sections, for example sections that contain debugging information or other type of meta
information.
A section is the smallest linkable unit; but if possible, ILINK can exclude smaller
units—section fragments—from the final application. For more information, see
Keeping modules, page 51, and Keeping symbols and sections, page 52.
At compile time, data and functions are placed in different sections. At link time, one of
the most important functions of the linker is to assign execute addresses to the various
sections used by the application.
The IAR build tools have many predefined section names. See the chapter Section
reference for more details about each section.

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The linking process
The relocatable modules in object files and libraries, produced by the IAR compiler and
assembler, cannot be executed as is. To become an executable application, they must be
linked.
Note: Modules produced by a toolset from another vendor can be included in the build
as well, as long as the module is AEABI (ARM Embedded Application Binary
Interface) compliant. Be aware that this also might require a compiler utility library
from the same vendor.
The IAR ILINK Linker is used for the link process. It normally performs the following
procedure (note that some of the steps can be turned off by command line options or by
directives in the linker configuration file):
●

Determine which modules to include in the application. Modules provided in object
files are always included. A module in a library file is only included if it provides a
definition for a global symbol that is referenced from an included module.

●

Select which standard library files to use. The selection is based on attributes of the
included modules. These libraries are then used for satisfying any still outstanding
undefined symbols.

●

Determine which sections/section fragments from the included modules to include
in the application. Only those sections/section fragments that are actually needed by
the application are included. There are several ways to determine of which
sections/section fragments that are needed, for example, the __root object
attribute, the #pragma required directive, and the keep linker directive. In case
of duplicate sections, only one is included.

●

Where appropriate, arrange for the initialization of initialized variables and code in
RAM. The initialize directive causes the linker to create extra sections to
enable copying from ROM to RAM. Each section that will be initialized by copying
is divided into two sections, one for the ROM part and one for the RAM part. If
manual initialization is not used, the linker also arranges for the startup code to
perform the initialization.

●

Determine where to place each section according to the section placement directives
in the linker configuration file. Sections that are to be initialized by copying appear
twice in the matching against placement directives, once for the ROM part and once
for the RAM part, with different attributes. During the placement, the linker also
adds any required veneers to make a code reference reach its destination or to
switch CPU modes.

●

Produce an absolute object file that contains the executable image and any debug
information provided. This involves resolving symbolic references between
sections, and locating relocatable values.

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Placing code and data—the linker configuration file

●

Optionally, produce a map file that lists the result of the section placement, the
address of each global symbol, and finally, a summary of memory usage for each
module and library.

This illustration shows the linking process:

Figure 8: The linking process

During the linking, ILINK might produce error messages and logging messages on
stdout and stderr. The log messages are useful for understanding why an application
was linked as it was. For example, why a module or section (or section fragment) was
included.
Note: To see the actual content of an ELF object file, use ielfdumparm. See The IAR
ELF Dumper for ARM—ielfdumparm, page 336.

Placing code and data—the linker configuration file
The placement of sections in memory is performed by the IAR ILINK Linker. It uses the
linker configuration file where you can define how ILINK should treat each section and
how they should be placed into the available memories.
A typical linker configuration file contains definitions of:
●

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Available addressable memories

Linking using ILINK

●

Populated regions of those memories

●

How to treat input sections

●

Created sections

●

How to place sections into the available regions.

The file consists of a sequence of declarative directives. This means that the linking
process will be governed by all directives at the same time.
To use the same source code with different derivatives, just rebuild the code with the
appropriate configuration file.

A SIMPLE EXAMPLE OF A CONFIGURATION FILE
A simple configuration file can look like this:
/* The memory space denoting the maximum possible amount
of addressable memory */
define memory Mem with size = 4G;
/* Memory regions in an address space */
define region ROM = Mem:[from 0x00000 size 0x10000];
define region RAM = Mem:[from 0x20000 size 0x10000];
/* Create a stack */
define block STACK with size = 0x1000, alignment = 8 { };
/* Handle initialization */
do not initialize { section .noinit };
initialize by copy { readwrite }; /* Initialize RW sections,
exclude zero-initialized
sections */
/* Place startup code at a fixed address */
place at start of ROM { readonly section .cstartup };
/* Place code and data */
place in ROM { readonly }; /* Place constants and initializers in
ROM: .rodata and .data_init
*/
place in RAM { readwrite, /* Place .data, .bss, and .noinit */
block STACK }; /* and STACK
*/

This configuration file defines one addressable memory Mem with the maximum of
4 Gbytes of memory. Further, it defines a ROM region and a RAM region in Mem,
namely ROM and RAM. Each region has the size of 64 Kbytes.
The file then creates an empty block called STACK with a size of 4 Kbytes in which the
application stack will reside. To create a block is the basic method which you can use to

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Placing code and data—the linker configuration file

get detailed control of placement, size, etc. It can be used for grouping sections, but also
as in this example, to specify the size and placement of an area of memory.
Next, the file defines how to handle the initialization of variables, read/write type
(readwrite) sections. In this example, the initializers are placed in ROM and copied at
startup of the application to the RAM area. By default, ILINK may compress the
initializers if this appears to be advantageous.
The last part of the configuration file handles the actual placement of all the sections into
the available regions. First, the startup code—defined to reside in the read-only
(readonly) section .cstartup—is placed at the start of the ROM region, that is at
address 0x10000. Note that the part within {} is referred to as section selection and it
selects the sections for which the directive should be applied to. Then the rest of the
read-only sections are placed in the ROM region. Note that the section selection
{ readonly section .cstartup } takes precedence over the more generic section
selection { readonly }.
Finally, the read/write (readwrite) sections and the STACK block are placed in the RAM
region.
This illustration gives a schematic overview of how the application is placed in memory:

Figure 9: Application in memory

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In addition to these standard directives, a configuration file can contain directives that
define how to:
●

Map a memory that can be addressed in multiple ways

●

Handle conditional directives

●

Create symbols with values that can be used in the application

●

More in detail, select the sections a directive should be applied to

●

More in detail, initialize code and data.

For more details and examples about customizing the linker configuration file, see the
chapter Linking your application.
For reference information about the linker configuration file, see the chapter The linker
configuration file.

Initialization at system startup
In ISO/ANSI C, all static variables—variables that are allocated at a fixed memory
address—must be initialized by the runtime system to a known value at application
startup. This value is either an explicit value assigned to the variable, or if no value is
given, it is cleared to zero. In the compiler, there is one exception to this rule and that is
variables declared __no_init which are not initialized at all.
The compiler generates a specific type of section for each type of variable initialization:
Categories of

Section

Source

Section type

Zero-initialized
data

int i;

Read/write data,
zero-init

.bss

None

Zero-initialized
data

int i = 0;

Read/write data,
zero-init

.bss

None

Initialized data
(non-zero)

int i = 6;

Read/write data

.data

The initializer

Non-initialized
data

__no_init int i;

Read/write data,
zero-init

.noinit

None

Constants

const int i = 6;

Read-only data

.rodata

The constant

Code

__ramfunc void
myfunc() {}

Read/write code

.textrw

The code

declared data

name

Section content

Table 4: Sections holding initialized data

Note: Clustering of static variables might group zero-initialized variables together with
initialized data in .data.

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Initialization at system startup

For a summary of all supported sections, see the chapter Section reference.

THE INITIALIZATION PROCESS
Initialization of data is handled by ILINK and the system startup code in conjunction.
To configure the initialization of variables, you must consider these issues:
●

Sections that should be zero-initialized are handled automatically by ILINK; they
should only be placed in RAM

●

Sections that should be initialized, except for zero-initialized sections, should be
listed in an initialize directive
Normally during linking, a section that should be initialized is split in two sections,
where the original initialized section will keep the name. The contents are placed in
the new initializer section, which will keep the original name suffixed with _init.
The initializers should be placed in ROM and the initialized sections in RAM, by
means of placement directives. The most common example is the .data section that
the linker splits in .data and .data_init.

●

Sections that contains constants should not be initialized; they should only be
placed in flash/ROM

●

Sections holding __no_init declared variables should not be initialized and thus
should be listed in a do not initialize directive. They should also be placed in
RAM.

In the linker configuration file, it can look like this:
/* Handle initialization */
do not initialize { section .noinit };
initialize by copy { readwrite }; /* Initialize RW sections,
exclude zero-initialized
sections */
/* Place startup code at a fixed address */
place at start of ROM { readonly section .cstartup };
/* Place code and data */
place in ROM { readonly }; /* Place constants and initializers in
ROM: .rodata and .data_init
*/
place in RAM { readwrite, /* Place .data, .bss, and .noinit */
block STACK }; /* and STACK
*/

For detailed information and examples about how to configure the initialization, see
Linking considerations, page 47.

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Linking your application
This chapter lists aspects that you must consider when linking your application.
This includes using ILINK options and tailoring the linker configuration file.
Finally, this chapter provides some hints for troubleshooting.

Linking considerations
Before you can link your application, you must set up the configuration required by
ILINK. Typically, you must consider:
●

Defining your own memory areas

●

Placing sections

●

Keeping modules in the application

●

Keeping symbols and sections in the application

●

Application startup

●

Setting up the stack and heap

●

Setting up the atexit limit

●

Changing the default initialization

●

Symbols for controlling the application

●

Standard library handling

●

Other output formats than ELF/DWARF

●

Veneers.

CHOOSING A LINKER CONFIGURATION FILE
The config directory contains two ready-made templates for the linker configuration
file:
●

generic.icf, designed for all cores except for Cortex-M cores

●

generic_cortex.icf, designed for all Cortex-M cores

These files contain the information required by ILINK. The only change you will
normally have to make to the supplied configuration file is to customize the start and end
addresses of each region so they fit the target system memory map. If, for example, your
application uses additional external RAM, you must also add details about the external
RAM memory area.

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Linking considerations

To edit a linker configuration file, use the editor in the IDE, or any other suitable editor.
Alternatively, choose Project>Options>Linker and click the Edit button on the
Config page to open the dedicated linker configuration file editor.
Remember not to change the original template file. We recommend that you make a
copy in the working directory, and modify the copy instead. If you are using the linker
configuration file editor in the IDE, the IDE will make a copy for you.
Each project in the IDE should have a reference to one, and only one, linker
configuration file. This file can be edited, but for the majority of all projects it is
sufficient to configure the vital parameters in Project>Options>Linker>Config.

DEFINING YOUR OWN MEMORY AREAS
The default configuration file that you selected has predefined ROM and RAM regions.
This example will be used as a starting-point for all further examples in this chapter:
/* Define the addressable memory */
define memory Mem with size = 4G;
/* Define a region named ROM with start address 0 and to be 64
Kbytes large */
define region ROM = Mem:[from 0 size 0x10000];
/* Define a region named RAM with start address 0x20000 and to be
64 Kbytes large */
define region RAM = Mem:[from 0x20000 size 0x10000];

Each region definition must be tailored for the actual hardware.
To find out how much of each memory that was filled with code and data after linking,
inspect the memory summary in the map file (command line option --map).

Adding an additional region
To add an additional region, use the define region directive, for example:
/* Define a 2nd ROM region to start at address 0x80000 and to be
128 Kbytes large */
define region ROM2 = Mem:[from 0x80000 size 0x20000];

Merging different areas into one region
If the region is comprised of several areas, use a region expression to merge the different
areas into one region, for example:
/* Define the 2nd ROM region to have two areas. The first with
the start address 0x80000 and 128 Kbytes large, and the 2nd with
the start address 0xC0000 and 32 Kbytes large */

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Linking your application

define region ROM2 = Mem:[from 0x80000 size 0x20000]
| Mem:[from 0xC0000 size 0x08000];

or equivalently
define region ROM2 = Mem:[from 0x80000 to 0xC7FFF]
–Mem:[from 0xA0000 to 0xBFFFF];

Adding a region in a new memory
To add a region in a new memory, write:
/* Define a 2nd addressable memory */
define memory Mem2 with size = 64k;
/* Define a region for constants with start address 0 and 64
Kbytes large */
define region CONSTANT = Mem2:[from 0 size 0x10000];

Defining the unit size for a new memory
If the new memory is not byte-oriented (8-bits per byte) you should define what unit size
to use:
/* Define the bit addressable memory */
define memory Bit with size = 256, unitbitsize = 1;

Sharing memories
If your core can address a physical memory either by:
●

Several different addressing modes; addresses in different defined memories are
actually the same physical entity

●

Using different addresses in the same memory, for example some bits in the address
are not connected to the physical memory

the define sharing directive must be used. For example:
/* First 32 Kbytes of Mem2 are mirrored in the last 32 Kbytes */
define sharing Mem2:[from 0 size 0x8000] <=>
Mem2:[from 0x8000 size 0x8000];
/* Bit memory is mapped in the first 32 bytes of Mem2 */
define sharing Bit:[from 0 size 256] <=> Mem2:[from 0 size 32];

The sharing directive instructs ILINK to allocate contents in all connected memories if
any content is placed in one memory.

PLACING SECTIONS
The default configuration file that you selected places all predefined sections in memory,
but there are situations when you might want to modify this. For example, if you want

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to place the section that holds constant symbols in the CONSTANT region instead of in
the default place. In this case, use the place in directive, for example:
/* Place
place in
/* Place
place in

sections with readonly content in the ROM region */
ROM {readonly};
the constant symbols in the CONSTANT region */
CONSTANT {readonly section .rodata};

Note: Placing a section—used by the IAR build tools—in a different memory which
use a different way of referring to its content, will fail.
For the result of each placement directive after linking, inspect the placement summary
in the map file (the command line option --map).

Placing a section at a specific address in memory
To place a section at a specific address in memory, use the place at directive, for
example:
/* Place section .vectors at address 0 */
place at address Mem:[0] {readonly section .vectors};

Placing a section first or last in a region
To place a section first or last in a region is similar, for example:
/* Place section .vectors at start of ROM */
place at start of ROM {readonly section .vectors};

Declare and place your own sections
To declare new sections—in addition to the ones used by the IAR build tools—to hold
specific parts of your code or data, use mechanisms in the compiler and assembler. For
example:
/* Places a variable in your own section MyOwnSection. */
const int MyVariable @ "MyOwnSection" = 5;

name

createSection

/* Create a section */
section myOwnSection:CONST
/* And fill it with constant bytes */
dcb
5, 6, 7, 8
end

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To place your new section, the original place in ROM {readonly}; directive is
sufficient.
However, to place the section MyOwnSection explicitly, update the linker configuration
file with a place in directive, for example:
/* Place MyOwnSection in the ROM region */
place in ROM {readonly section MyOwnSection};

RESERVING SPACE IN RAM
Often, an application must have an empty uninitialized memory area to be used for
temporary storage, for example a heap or a stack. It is easiest to achieve this at link time.
You must create a block with a specified size and then place it in a memory.
In the linker configuration file, it can look like this:
define block TempStorage with size = 0x1000, alignment = 4 { };
place in RAM { block TempStorage };

To retrieve the start of the allocated memory from the application, the source code could
look like this:
/* Declares a section */
#pragma section = "TempStorage"
char *TempStorage()
{
/* Return start address of section TempStorage. */
return __section_begin("TempStorage");
}

KEEPING MODULES
If a module is linked as an object file, it is always kept. That is, it will contribute to the
linked application. However, if a module is part of a library, it is included only if it is
symbolically referred to from other parts of the application. This is true, even if the
library module contains a root symbol. To assure that such a library module is always
included, use iarchive to extract the module from the library, see The IAR Archive
Tool—iarchive, page 323.
For information about included and excluded modules, inspect the log file (the
command line option --log modules).
For more information about modules, see Modules and sections, page 40.

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KEEPING SYMBOLS AND SECTIONS
By default, ILINK removes any sections, section fragments, and global symbols that are
not needed by the application. To retain a symbol that does not appear to be needed—or
actually, the section fragment it is defined in—you can either use the root attribute on
the symbol in your C/C++ or assembler source code, or use the ILINK option --keep.
To retain sections based on attribute names or object names, use the directive keep in
the linker configuration file.
To prevent ILINK from excluding sections and section fragments, use the command line
options --no_remove or --no_fragments, respectively.
For information about included and excluded symbols and sections, inspect the log file
(the command line option --log sections).
For more information about the linking procedure for keeping symbols and sections, see
The linking process, page 41.

APPLICATION STARTUP
By default, the point where the application starts execution is defined by the
__iar_program_start label, which is defined to point at the start of the cstartup.s
file. The label is also communicated via ELF to any debugger that is used.
To change the start point of the application to another label, use the ILINK option
--entry; see --entry, page 196.

SETTING UP THE STACK
The size of the CSTACK block is defined in the linker configuration file. To change the
allocated amount of memory, change the block definition for CSTACK:
define block CSTACK with size = 0x2000, alignment = 8{ };
define block IRQ_STACK with size = 64, alignment = 8{ };

Specify an appropriate size for your application.
To read more about the stack, see Stack considerations, page 115.

SETTING UP THE HEAP
The size of the heap is defined in the linker configuration file as a block:
define block HEAP with size = 0x1000, alignment = 8{ };
place in RAM {block HEAP};

Specify the appropriate size for your application.

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SETTING UP THE ATEXIT LIMIT
By default, the atexit function can be called a maximum of 32 times from your
application. To either increase or decrease this number, add a line to your configuration
file. For example, to reserve room for 10 calls instead, write:
define symbol __iar_maximum_atexit_calls = 10;

CHANGING THE DEFAULT INITIALIZATION
By default, memory initialization is performed during application startup. ILINK sets
up the initialization process and chooses a suitable packing method. If the default
initialization process does not suit your application and you want more precise control
over the initialization process, these alternatives are available:
●

Choosing the packing algorithm

●

Overriding the default copy-initialize function

●

Manual initialization

●

Initializing code—copying ROM to RAM.

For information about the performed initializations, inspect the log file (the command
line option --log initialization).

Choosing packing algorithm
To override the default packing algorithm, write for example:
initialize by copy with packing = lzw { readwrite };

To read more about the available packing algorithms, see Initialize directive, page 305.

Overriding default copy-initialize function
To override the default function that copies the initializers to the RAM memory, supply
the copy routine parameter to the initialize by copy directive. Your function will
be called at program start as many times as needed. This can be useful when special code
is required for the copy.
This example shows how it can look in the linker configuration file:
/* Initialize special sections */
initialize by copy with packing = none, copy routine =
myInitializers { section .special };
place in RAM { section .special };
place in ROM { section .special_init };

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Your routine should look like this:
void myInitializers(char *dst,
char const *src,
unsigned long size);

See the system startup code for an exact type definition.

Manual initialization
The initialize manually directive lets you take complete control over initialization.
For each involved section, ILINK creates an extra section that contains the initialization
data, but makes no arrangements for the actual copying. This directive is, for example,
useful for overlays:
/* Sections MYOVERLAY1 and MYOVERLAY2 will be overlaid in
MyOverlay */
define overlay MyOverlay { section MYOVERLAY1 };
define overlay MyOverlay { section MYOVERLAY2 };
/* Split the overlay sections but without initialization during
system startup */
initialize manually { section MYOVERLAY* };
/* Place the initializer sections in a block each */
define block MyOverlay1InRom { section MYOVERLAY1_init };
define block MyOverlay2InRom { section MYOVERLAY2_init };
/* Place the overlay and the initializers for it */
place in RAM { overlay MyOverlay };
place in ROM { block MyOverlay1InRom, block MyOverlay2InRom };

The application can then start a specific overlay by copying, as in this case, ROM to
RAM:
#include 

/* Declare the sections. */
#pragma section = "MyOverlay"
#pragma section = "MyOverlay1InRom"

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/* Function that switches in image 1 into the overlay. */
void SwitchToOverlay1()
{
char *targetAddr
= __section_begin("MyOverlay");
char *sourceAddr
= __section_begin("MyOverlay1InRom");
char *sourceAddrEnd = __section_end("MyOverlay1InRom");
int size = sourceAddrEnd - sourceAddr;
memcpy(targetAddr, sourceAddrEnd, size);
}

Initializing code—copying ROM to RAM
Sometimes, an application copies pieces of code from flash/ROM to RAM. This can be
easily achieved by ILINK for whole code regions. However, for individual functions, the
__ramfunc keyword can be used, see Execution in RAM, page 30
List the code sections that should be initialized in an initialize directive and then
place the initializer and initialized sections in ROM and RAM, respectively.
In the linker configuration file, it can look like this:
/* Split the RAMCODE section into a readonly and a readwrite
section */
initialize by copy { section RAMCODE };
/* Place both in a block */
define block RamCode { section RAMCODE }
define block RamCodeInit { section RAMCODE_init };
/* Place them in ROM and RAM */
place in ROM { block RamCodeInit };
place in RAM { block RamCode };

The block definitions makes it possible to refer to the start and end of the blocks from
the application.
For more examples, see Interaction between the tools and your application, page 117.

Running all code from RAM
If you want to copy the entire application from ROM to RAM at program startup, use
the initilize by copy directive, for example:
initialize by copy { readonly, readwrite }

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The readwrite pattern will match all statically initialized variables and arrange for
them to be initialized at startup. The readonly pattern will do the same for all read-only
code and data, except for code and data needed for the initialization.
To reduce the ROM space that is needed, it might be useful to compress the data with
one of the available packing algorithms. For example,
initialize by copy { readonly, readwrite } with packing lzw

To read more about the available compression algorithms, see Initialize directive, page
305.
Because the function __low_level_init, if present, is called before initialization, it,
and anything it needs, will not be copied from ROM to RAM either. In some
circumstances—for example, if the ROM contents are no longer available to the
program after startup—you might need to avoid using the same functions during startup
and in the rest of the code.
If anything else should not be copied, include it in an except clause. This can apply to,
for example, the interrupt vector table.
It is also recommended to exclude the C++ dynamic initialization table from being
copied to RAM, as it is typically only read once and then never referenced again. For
example, like this:
initialize by copy { readonly, readwrite }
except { section .intvec,
/* Don’t copy
interrupt table */
section .init_array } /* Don’t copy
C++ init table */

INTERACTION BETWEEN ILINK AND THE APPLICATION
ILINK provides the command line options --config_def and --define_symbol to
define symbols which can be used for controlling the application. You can also use
symbols to represent the start and end of a continuous memory area that is defined in the
linker configuration file. For more details, see Interaction between the tools and your
application, page 117.
To change a reference to one symbol to another symbol, use the ILINK command line
option --redirect. This is useful, for example, to redirect a reference from a
non-implemented function to a stub function, or to choose one of several different
implementations of a certain function, for example, how to choose the DLIB formatter
for the standard library functions printf and scanf.
The compiler generates mangled names to represent complex C/C++ symbols. If you
want to refer to these symbols from assembler source code, you must use the mangled
names.

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For information about the addresses and sizes of all global (statically linked) symbols,
inspect the entry list in the map file (the command line option --map).
For more information, see Interaction between the tools and your application, page 117.

STANDARD LIBRARY HANDLING
By default, ILINK determines automatically which variant of the standard library to
include during linking. The decision is based on the sum of the runtime attributes
available in each object file and the library options passed to ILINK.
To disable the automatic inclusion of the library, use the option
--no_library_search. In this case, you must explicitly specify every library file to
be included. For information about available library files, see Using a prebuilt library,
page 64.

PRODUCING OTHER OUTPUT FORMATS THAN ELF/DWARF
ILINK can only produce an output file in the ELF/DWARF format. To convert that
format into a format suitable for programming PROM/flash, use ielftool.

VENEERS
The ARM cores need to use veneers on two occasions:
●

When calling an ARM function from Thumb mode or vice versa; the veneer then
changes the state of the microprocessor. If the core supports the BLX instruction, a
veneer is not needed for changing modes.

●

When calling a function that it cannot normally reach; the veneer introduces code
which makes the call successfully reach the destination.

Code for veneers can be inserted between any caller and called function. As a result, the
R12 register must be treated as a scratch register at function calls, including functions
written in assembler. This also applies to jumps.
For more information, see --no_veneers, page 202.

Hints for troubleshooting
ILINK has several features that can help you manage code and data placement correctly,
for example:
●

Messages at link time, for examples when a relocation error occurs

●

The --log option that makes ILINK log information to stdout, which can be
useful to understand why an executable image became the way it is, see --log, page
199

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●

The --map option that makes ILINK produce a memory map file, which contains
the result of the linker configuration file, see --map, page 200.

RELOCATION ERRORS
For each instruction that cannot be relocated correctly, ILINK will generate a relocation
error. This can occur for instructions where the target is out of reach or is of an
incompatible type, or for many other reasons.
A relocation error produced by ILINK can look like this:
Error[Lp002]: relocation failed: out of range or illegal value
Kind
:
R_XXX_YYY[0x1]
Location :
0x40000448
"myfunc" + 0x2c
Module: somecode.o
Section: 7 (.text)
Offset: 0x2c
Destination: 0x9000000c
"read"
Module: read.o(iolib.a)
Section: 6 (.text)
Offset: 0x0

The message entries are described in this table:
Message entry

Description

Kind

The relocation directive that failed. The directive depends on the
instruction used.

Location

The location where the problem occurred, described with the following
details:
• The instruction address, expressed both as a hexadecimal value and as
a label with an offset. In this example, 0x40000448 and
"myfunc" + 0x2c.
• The module, and the file. In this example, the
module somecode.o.
• The section number and section name. In this example, section number
7 with the name .text.
• The offset, specified in number of bytes, in the section. In this example,
0x2c.

Table 5: Description of a relocation error

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Message entry

Description

Destination

The target of the instruction, described with the following details:
• The instruction address, expressed both as a hexadecimal value and as
a label with an offset. In this example, 0x9000000c and
"read" (thus, no offset).
• The module, and when applicable the library. In this example, the
module read.o and the library iolib.a.
• The section number and section name. In this example, section number
6 with the name .text.
• The offset, specified in number of bytes, in the section. In this example,
0x0.

Table 5: Description of a relocation error (Continued)

Possible solutions
In this case, the distance from the instruction in getchar to __read is too long for the
branch instruction.
Possible solutions include ensuring that the two .text sections are allocated closer to
each other or using some other calling mechanism that can reach the required distance.
It is also possible that the referring function tried to refer to the wrong target and that
this caused the range error.
Different range errors have different solutions. Usually, the solution is a variant of the
ones presented above, in other words modifying either the code or the section
placement.

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The DLIB runtime
environment
This chapter describes the runtime environment in which an application
executes. In particular, the chapter covers the DLIB runtime library and how
you can modify it—setting options, overriding default library modules, or
building your own library—to optimize it for your application.
The chapter also covers system initialization and termination; how an
application can control what happens before the function main is called, and
how you can customize the initialization.
The chapter then describes how to configure functionality like locale and file
I/O, how to get C-SPY® runtime support, and how to prevent incompatible
modules from being linked together.

Introduction to the runtime environment
The runtime environment is the environment in which your application executes. The
runtime environment depends on the target hardware, the software environment, and the
application code. The IAR DLIB runtime environment can be used as is together with
the debugger. However, to be able to run the application on hardware, you must adapt
the runtime environment.
This section gives an overview of:
●

The runtime environment and its components

●

Library selection.

For information about AEABI compliance, see AEABI compliance, page 123.

RUNTIME ENVIRONMENT FUNCTIONALITY
The runtime environment supports ISO/ANSI C and C++ including the standard
template library. The runtime environment consists of the runtime library, which
contains the functions defined by these standards, and include files that define the library
interface.

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Introduction to the runtime environment

The runtime library is delivered both as prebuilt libraries and (depending on your
product package) as source files, and you can find them in the product subdirectories
arm\lib and arm\src\lib, respectively.
The runtime environment also consists of a part with specific support for the target
system, which includes:
●

Support for hardware features:
●

Direct access to low-level processor operations by means of intrinsic functions,
such as functions for register handling

●

Peripheral unit registers and interrupt definitions in include files

●

The Vector Floating Point (VFP) coprocessor.

●

Runtime environment support, that is, startup and exit code and low-level interface
to some library functions.

●

Special compiler support for some functions, for instance functions for
floating-point arithmetics.

The runtime environment support and the size of the heap must be tailored for the
specific hardware and application requirements.
For further information about the library, see the chapter Library functions.

LIBRARY SELECTION
To configure the most code-efficient runtime environment, you must determine your
application and hardware requirements. The more functionality you need, the larger
your code will become.
IAR Embedded Workbench comes with a set of prebuilt runtime libraries. To get the
required runtime environment, you can customize it by:
●

Setting library options, for example, for choosing scanf input and printf output
formatters, and for specifying the size of the stack and the heap

●

Overriding certain library functions, for example cstartup.s, with your own
customized versions

●

Choosing the level of support for certain standard library functionality, for example,
locale, file descriptors, and multibyte characters, by choosing a library
configuration: normal or full.

You can also make your own library configuration, but that requires that you rebuild the
library. This allows you to get full control of the runtime environment.
Note: Your application project must be able to locate the library, include files, and the
library configuration file. ILINK will automatically choose a prebuilt library suitable for
the application.

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SITUATIONS THAT REQUIRE LIBRARY BUILDING
Building a customized library is complex. Therefore, consider carefully whether it is
really necessary.
You must build your own library when:
●

There is no prebuilt library for the required combination of compiler options or
hardware support

●

You want to define your own library configuration with support for locale, file
descriptors, multibyte characters, et cetera.

For information about how to build a customized library, see Building and using a
customized library, page 71.

LIBRARY CONFIGURATIONS
It is possible to configure the level of support for, for example, locale, file descriptors,
multibyte characters. The runtime library configuration is defined in the library
configuration file. It contains information about what functionality is part of the runtime
environment. The configuration file is used for tailoring a build of a runtime library, and
tailoring the system header files used when compiling your application. The less
functionality you need in the runtime environment, the smaller it is.
These DLIB library configurations are available:
Library configuration

Description

Normal DLIB

No locale interface, C locale, no file descriptor support, no multibyte
characters in printf and scanf, and no hexadecimal floating-point
numbers in strtod.

Full DLIB

Full locale interface, C locale, file descriptor support, multibyte
characters in printf and scanf, and hexadecimal floating-point
numbers in strtod.

Table 6: Library configurations

You can also define your own configurations, which means that you must modify the
configuration file. Note that the library configuration file describes how a library was
built and thus cannot be changed unless you rebuild the library. For further information,
see Building and using a customized library, page 71.
The prebuilt libraries are based on the default configurations, see Using a prebuilt
library, page 64. There is also a ready-made library project template that you can use if
you want to rebuild the runtime library.

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LOW-LEVEL INTERFACE FOR DEBUG SUPPORT
If your application uses the DLIB low-level interface (see C-SPY runtime interface,
page 86), you must implement support for the parts used by the application. However,
if you must debug your application before this is implemented, you can temporarily use
the semihosted debug support also provided as a library.
The low-level debugger runtime interface provided by DLIB is compatible with the
semihosting interface provided by ARM Limited. The interface is implemented by a set
of SVC (SuperVisor Call) instructions that generate exceptions from program control.
The application invokes the appropriate semihosting call and the debugger then handles
the exception. The debugger provides the required communication with the host
computer.
If you build your application project with the ILINK option Semihosted
(--semihosting) or IAR breakpoint (--semihosting=iar_breakpoint), certain
functions in the library are replaced by functions that communicate with the debugger.
To set linker options for debug support in the IDE, choose Project>Options and select
the General Options category. On the Library configuration page, select the
Semihosted option or the IAR breakpoint option.

Using a prebuilt library
The prebuilt runtime libraries are configured for different combinations of features:
●

Architecture

●

CPU mode

●

Interworking

●

Library configuration—Normal or Full

●

Floating-point implementation.

In the IDE, the linker will include the correct library object file and library configuration
file based on the options you select. See the IAR Embedded Workbench® IDE User
Guide for ARM® for additional information.
If you build your application from the command line, you must specify the library
configuration file for the compiler, either DLib_Config_Full.h or
DLib_Config_Normal.h, for example:
--dlib_config C:\...\DLib_Config_Normal.h

You can find the library object files and the library configuration files in the subdirectory
arm\lib\, and the library configuration files in the arm\inc directory.

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GROUPS OF LIBRARY FILES
The libraries are delivered in three groups of library functions:
●

C/C++ standard library functions
These are the functions defined by the ISO/ANSI C/C++ standard, for example
functions like printf and scanf.

●

Runtime support functions
These are functions for system startup, initialization, floating-point arithmetics, ABI
support, and some of the functions part of the ISO/ANSI C/C++ standard.

●

Debug support functions
These are functions for debug support for the semihosting interface.

Library filename syntax
The names of the libraries are constructed by the following constituents:
●

 is the name of the architecture. It can be one of 4t, 5E, 6M, or 7M

for the ARM architectures v4T, v5TE, v6M, or v7M, respectively. Libraries built for
the v5TE architecture are also used for the v6 architecture.
●

 is one of t or a, for Thumb and ARM, respectively.

●

 is one of l or b, for little-endian and big-endian, respectively.

●

 is _ when the library is compiled without VFP support,
that is, software implementation compliant to AAPCS. It is s when the library is
compiled with VFP support and compliant to AAPCS/STD. It is v when compiled
with VFP support and using VFP registers in function calls; this is not AEABI
compliant. The supported version of VFP is v1 when architecture is 4t and v2 when
architecture is 5E.

●

 is i when the library contains interworking code, otherwise it is
_.
 is one of n or f for normal and full, respectively.
 is one of s, b or i, for the SWI/SVC mechanism, the BKPT

●
●

mechanism, and the IAR-specific breakpoint mechanism, respectively. For more
information, see --semihosting, page 205.

Library files for C/C++ standard library functions
The names of the library files are constructed in the following way:
dl_
.a

which more specifically means
dl<4t|5E|6M|7M>_<_|s|v>.a

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Library files for runtime support functions
The names of the library files are constructed in the following way:
rt_.a

which more specifically means
rt<4t|5E|6M|7M>_<_|s|v>.a

Library files for debug support functions
The names of the library files are constructed in the following way:
sh_.a

which more specifically means
sh_.a

CUSTOMIZING A PREBUILT LIBRARY WITHOUT REBUILDING
The prebuilt libraries delivered with the compiler can be used as is. However, it is
possible to customize parts of a library without rebuilding it. There are two different
methods:
●

●

Setting options for:
●

Formatters used by printf and scanf

●

The sizes of the heap and the stack

Overriding library modules with your own customized versions.

These items can be customized:
Items that can be customized

Formatters for printf and scanf

Choosing formatters for printf and scanf, page 67

Startup and termination code

System startup and termination, page 72

Low-level input and output

Standard streams for input and output, page 77

File input and output

File input and output, page 80

Low-level environment functions

Environment interaction, page 83

Low-level signal functions

Signal and raise, page 84

Low-level time functions

Time, page 85

Table 7: Customizable items

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Described in

The DLIB runtime environment

Items that can be customized

Described in

Size of heaps, stacks, and sections

Stack considerations, page 115
Heap considerations, page 117
Placing code and data—the linker configuration file,
page 42

Table 7: Customizable items (Continued)

For a description about how to override library modules, see Overriding library
modules, page 69.

Choosing formatters for printf and scanf
To override the default formatter for all the printf- and scanf-related functions,
except for wprintf and wscanf variants, you simply set the appropriate library
options. This section describes the different options available.
Note: If you rebuild the library, it is possible to optimize these functions even further,
see Configuration symbols for printf and scanf, page 79.

CHOOSING PRINTF FORMATTER
The printf function uses a formatter called _Printf. The default version is quite
large, and provides facilities not required in many embedded applications. To reduce the
memory consumption, three smaller, alternative versions are also provided in the
standard C/EC++ library.

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Choosing formatters for printf and scanf

This table summarizes the capabilities of the different formatters:
Formatting capabilities

_PrintfFull _PrintfLarge

Basic specifiers c, d, i, o, p, s, u, X, Yes
x, and %

_PrintfSmall

_PrintfTiny

Yes

Yes

Yes

Multibyte support

†

†

†

No

Floating-point specifiers a, and A

Yes

No

No

No

Floating-point specifiers e, E, f, F, g, Yes
and G

Yes

No

No

Conversion specifier n

Yes

Yes

No

No

Format flag space, +, -, #, and 0

Yes

Yes

Yes

No

Length modifiers h, l, L, s, t, and Z Yes

Yes

Yes

No

Field width and precision, including * Yes

Yes

Yes

No

long long support

Yes

No

No

Yes

Table 8: Formatters for printf
†

Depends on the library configuration that is used.

For information about how to fine-tune the formatting capabilities even further, see
Configuration symbols for printf and scanf, page 79.

Specifying the print formatter in the IDE
To use any other formatter than the default (Full), choose Project>Options and select
the General Options category. Select the appropriate option on the Library options
page.

Specifying printf formatter from the command line
To use any other formatter than the default (_PrintfFull), add one of these ILINK
command line options:
--redirect _Printf=_PrintfLarge
--redirect _Printf=_PrintfSmall
--redirect _Printf=_PrintfTiny

CHOOSING SCANF FORMATTER
In a similar way to the printf function, scanf uses a common formatter, called
_Scanf. The default version is very large, and provides facilities that are not required
in many embedded applications. To reduce the memory consumption, two smaller,
alternative versions are also provided in the standard C/C++ library.

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This table summarizes the capabilities of the different formatters:
Formatting capabilities

_ScanfFull

_ScanfLarge

_ScanfSmall

Basic specifiers c, d, i, o, p, s, u, X,
x, and %

Yes

Yes

Yes

Multibyte support

†

†

†

Floating-point specifiers a, and A

Yes

No

No

Floating-point specifiers e, E, f, F, g, Yes
and G

No

No

Conversion specifier n

Yes

No

No

Scan set [ and ]

Yes

Yes

No

Assignment suppressing *

Yes

Yes

No

long long support

Yes

No

No

Table 9: Formatters for scanf
†

Depends on the library configuration that is used.

For information about how to fine-tune the formatting capabilities even further, see
Configuration symbols for printf and scanf, page 79.

Specifying scanf formatter in the IDE
To use any other formatter than the default (Full), choose Project>Options and select
the General Options category. Select the appropriate option on the Library options
page.

Specifying scanf formatter from the command line
To use any other variant than the default (_ScanfFull), add one of these ILINK
command line options:
--redirect _Scanf=_ScanfLarge
--redirect _Scanf=_PrintfSmall

Overriding library modules
The library contains modules which you probably need to override with your own
customized modules, for example functions for character-based I/O and cstartup.
This can be done without rebuilding the entire library. This section describes the
procedure for including your version of the module in the application project build
process. The library files that you can override with your own versions are located in the
arm\src\lib directory.

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Overriding library modules

Note: If you override a default I/O library module with your own module, C-SPY
support for the module is turned off. For example, if you replace the module __write
with your own version, the C-SPY Terminal I/O window will not be supported.

Overriding library modules using the IDE
This procedure is applicable to any source file in the library, which means that
library_module.c in this example can be any module in the library.

1 Copy the appropriate library_module.c file to your project directory.
2 Make the required additions to the file (or create your own routine, using the default
file as a model).

3 Add the customized file to your project.
4 Rebuild your project.
Overriding library modules from the command line
This procedure is applicable to any source file in the library, which means that
library_module.c in this example can be any module in the library.

1 Copy the appropriate library_module.c to your project directory.
2 Make the required additions to the file (or create your own routine, using the default
file as a model), and make sure that it has the same module name as the original
module. The easiest way to achieve this is to save the new file under the same name as
the original file.

3 Compile the modified file using the same options as for the rest of the project:
iccarm library_module.c

This creates a replacement object module file named library_module.o.

4 Add library_module.o to the ILINK command line, either directly or by using an
extended linker command file, for example:
ilinkarm library_module.o

Make sure that library_module.o is placed before the library on the command line.
This ensures that your module is used instead of the one in the library.
Run ILINK to rebuild your application.
This will use your version of library_module.o, instead of the one in the library. For
information about the ILINK options, see the chapter Linker options.

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Building and using a customized library
In some situations, see Situations that require library building, page 63, it is necessary
to rebuild the C/C++ standard library. In those cases you must:
●

Set up a library project

●

Make the required library modifications

●

Build your customized library

●

Finally, make sure your application project will use the customized library.

Note: To build IAR Embedded Workbench projects from the command line, use the
IAR Command Line Build Utility (iarbuild.exe). However, no make or batch files
for building the library from the command line are provided.
For information about the build process and the IAR Command Line Build Utility, see
the IAR Embedded Workbench® IDE User Guide for ARM®.

SETTING UP A LIBRARY PROJECT
The IDE provides a library project template which can be used for customizing the
runtime environment configuration. This library template has Full library configuration,
see Table 6, Library configurations, page 63.
In the IDE, modify the generic options in the created library project to suit your
application, see Basic project configuration, page 19.
Note: There is one important restriction on setting options. If you set an option on file
level (file level override), no options on higher levels that operate on files will affect that
file.

MODIFYING THE LIBRARY FUNCTIONALITY
You must modify the library configuration file and build your own library if you want
to modify support for, for example, locale, file descriptors, and multibyte characters.
This will include or exclude certain parts of the runtime environment.
The library functionality is determined by a set of configuration symbols. The default
values of these symbols are defined in the file DLib_Defaults.h. This read-only file
describes the configuration possibilities. In addition, your library must have its own
library configuration file based on either DLib_Config_Normal.h or
DLib_Config_Full.h, which sets up that specific library with the required library
configuration. For more information, see Table 7, Customizable items, page 66.
The library configuration file is used for tailoring a build of the runtime library, and for
tailoring the system header files.

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System startup and termination

Modifying the library configuration file
In your library project, open the file DLib_Config_Normal.h or
DLib_Config_Full.h, depending on your library, make a copy of the file and
customize it by setting the values of the configuration symbols according to the
application requirements.
When you are finished, build your library project with the appropriate project options.

USING A CUSTOMIZED LIBRARY
After you build your library, you must make sure to use it in your application project.
In the IDE you must do these steps:

1 Choose Project>Options and click the Library Configuration tab in the General
Options category.

2 Choose Custom DLIB from the Library drop-down menu.
3 In the Configuration file text box, locate your library configuration file.
4 Click the Library tab, also in the Linker category. Use the Additional libraries text
box to locate your library file.

System startup and termination
This section describes the runtime environment actions performed during startup and
termination of your application.
The code for handling startup and termination is located in the source files
cstartup.s, cmain.s, cexit.s, and low_level_init.c or low_level_init.s
located in the arm\src\lib directory.
For Cortex-M, one of the following files is used instead of cstartup.s:
thumb\cstartup_M.s or thumb\cstartup_M.c

For information about how to customize the system startup code, see Customizing
system initialization, page 76.

SYSTEM STARTUP
During system startup, an initialization sequence is executed before the main function
is entered. This sequence performs initializations required for the target hardware and
the C/C++ environment.

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For the hardware initialization, it looks like this:

Figure 10: Target hardware initialization phase
●

When the CPU is reset it will jump to the program entry label
__iar_program_start in the system startup code.

●

Exception stack pointers are initialized to the end of each corresponding section

●

The stack pointer is initialized to the end of the CSTACK block

●

The function __low_level_init is called if you defined it, giving the application
a chance to perform early initializations.

Note: For Cortex-M devices, the second bullet in the above list is not valid. The first
and the third bullets are handled slightly differently. At reset, a Cortex-M CPU
initializes PC and SP from the vector table (__vector_table), which is defined in the
cstartup_M.c file.

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System startup and termination

For the C/C++ initialization, it looks like this:

Figure 11: C/C++ initialization phase
●

Static and global variables are initialized. That is, zero-initialized variables are
cleared and the values of other initialized variables are copied from ROM to RAM
memory. This step is skipped if __low_level_init returns zero. For more details,
see Initialization at system startup, page 45

●

Static C++ objects are constructed

●

The main function is called, which starts the application.

For an overview of the initialization phase, see Application execution—an overview,
page 14.

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SYSTEM TERMINATION
This illustration shows the different ways an embedded application can terminate in a
controlled way:

Figure 12: System termination phase

An application can terminate normally in two different ways:
●

Return from the main function

●

Call the exit function.

As the ISO/ANSI C standard states that the two methods should be equivalent, the
system startup code calls the exit function if main returns. The parameter passed to the
exit function is the return value of main.
The default exit function is written in C. It calls a small assembler function _exit that
will perform these operations:
●

Call functions registered to be executed when the application ends. This includes
C++ destructors for static and global variables, and functions registered with the
standard C function atexit

●

Close all open files

●

Call __exit

●

When __exit is reached, stop the system.

An application can also exit by calling the abort or the _Exit function. The abort
function just calls __exit to halt the system, and does not perform any type of cleanup.
The _Exit function is equivalent to the abort function, except for the fact that _Exit
takes an argument for passing exit status information.

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Customizing system initialization

If you want your application to do anything extra at exit, for example resetting the
system, you can write your own implementation of the __exit(int) function.

C-SPY interface to system termination
If your project is linked with the semihosted interface, the normal __exit and abort
functions are replaced with special ones. C-SPY will then recognize when those
functions are called and can take appropriate actions to simulate program termination.
For more information, see C-SPY runtime interface, page 86.

Customizing system initialization
It is likely that you need to customize the code for system initialization. For example,
your application might need to initialize memory-mapped special function registers
(SFRs), or omit the default initialization of data sections performed by cstartup.
You can do this by providing a customized version of the routine __low_level_init,
which is called from cmain.s before the data sections are initialized. Modifying the file
cstartup directly should be avoided.
The code for handling system startup is located in the source files cstartup.s and
low_level_init.c, located in the arm\src\lib directory.
Note: Normally, you do not need to customize either of the files cmain.s or cexit.s.
If you intend to rebuild the library, the source files are available in the template library
project, see Building and using a customized library, page 71.
Note: Regardless of whether you modify the routine __low_level_init or the file
cstartup.s, you do not have to rebuild the library.

__LOW_LEVEL_INIT
Two skeleton low-level initialization files are supplied with the product: a C source file,
low_level_init.c and an alternative assembler source file, low_level_init.s.
The latter is part of the prebuilt runtime environment. The only limitation using the C
source version is that static initialized variables cannot be used within the file, as
variable initialization has not been performed at this point.
The value returned by __low_level_init determines whether or not data sections
should be initialized by the system startup code. If the function returns 0, the data
sections will not be initialized.

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MODIFYING THE FILE CSTARTUP.S
As noted earlier, you should not modify the file cstartup.s if a customized version of
__low_level_init is enough for your needs. However, if you do need to modify the
file cstartup.s, we recommend that you follow the general procedure for creating a
modified copy of the file and adding it to your project, see Overriding library modules,
page 69.
Note that you must make sure that the linker uses the start label used in your version of
cstartup.s. For information about how to change the start label used by the linker, see

--entry, page 196.
For Cortex-M, you must create a modified copy of cstartup_M.s or cstartup_M.c
to use interrupts or other exception handlers.

Standard streams for input and output
Standard communication channels (streams) are defined in stdio.h. If any of these
streams are used by your application, for example by the functions printf and scanf,
you must customize the low-level functionality to suit your hardware.
There are primitive I/O functions, which are the fundamental functions through which
C and C++ performs all character-based I/O. For any character-based I/O to be available,
you must provide definitions for these functions using whatever facilities the hardware
environment provides.

IMPLEMENTING LOW-LEVEL CHARACTER INPUT AND
OUTPUT
To implement low-level functionality of the stdin and stdout streams, you must write
the functions __read and __write, respectively. You can find template source code for
these functions in the arm\src\lib directory.
If you intend to rebuild the library, the source files are available in the template library
project, see Building and using a customized library, page 71. Note that customizing the
low-level routines for input and output does not require you to rebuild the library.
Note: If you write your own variants of __read or __write, special considerations
for the C-SPY runtime interface are needed, see C-SPY runtime interface, page 86.

Example of using __write
The code in this example uses memory-mapped I/O to write to an LCD display:
#include 
__no_init volatile unsigned char lcdIO @ 0x1000;

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Standard streams for input and output

size_t __write(int handle,
const unsigned char *buf,
size_t bufSize)
{
size_t nChars = 0;
/* Check for the command to flush all handles */
if (handle == -1)
{
return 0;
}
/* Check for stdout and stderr
(only necessary if FILE descriptors are enabled.) */
if (handle != 1 && handle != 2)
{
return -1;
}
for (/* Empty */; bufSize > 0; --bufSize)
{
lcdIO = *buf;
++buf;
++nChars;
}
return nChars;
}

Note: A call to __write where buf has the value NULL is a command to flush the
handle. When the handle is -1, all streams should be flushed.

Example of using __read
The code in this example uses memory-mapped I/O to read from a keyboard:
#include 
__no_init volatile unsigned char kbIO @ 0x1000;
size_t __read(int handle,
unsigned char *buf,
size_t bufSize)
{
size_t nChars = 0;
/* Check for stdin

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(only necessary if FILE descriptors are enabled) */
if (handle != 0)
{
return -1;
}
for (/*Empty*/; bufSize > 0; --bufSize)
{
unsigned char c = kbIO;
if (c == 0)
break;
*buf++ = c;
++nChars;
}
return nChars;
}

For information about the @ operator, see Controlling data and function placement in
memory, page 131.

Configuration symbols for printf and scanf
When you set up your application project, you typically need to consider what printf
and scanf formatting capabilities your application requires, see Choosing formatters
for printf and scanf, page 67.
If the provided formatters do not meet your requirements, you can customize the full
formatters. However, that means you must rebuild the runtime library.
The default behavior of the printf and scanf formatters are defined by configuration
symbols in the file DLib_Defaults.h.
These configuration symbols determine what capabilities the function printf should
have:
Printf configuration symbols

Includes support for

_DLIB_PRINTF_MULTIBYTE

Multibyte characters

_DLIB_PRINTF_LONG_LONG

Long long (ll qualifier)

_DLIB_PRINTF_SPECIFIER_FLOAT

Floating-point numbers

_DLIB_PRINTF_SPECIFIER_A

Hexadecimal floating-point numbers

_DLIB_PRINTF_SPECIFIER_N

Output count (%n)

Table 10: Descriptions of printf configuration symbols

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File input and output

Printf configuration symbols

Includes support for

_DLIB_PRINTF_QUALIFIERS

Qualifiers h, l, L, v, t, and z

_DLIB_PRINTF_FLAGS

Flags -, +, #, and 0

_DLIB_PRINTF_WIDTH_AND_PRECISION

Width and precision

_DLIB_PRINTF_CHAR_BY_CHAR

Output char by char or buffered

Table 10: Descriptions of printf configuration symbols (Continued)

When you build a library, these configurations determine what capabilities the function
scanf should have:
Scanf configuration symbols

Includes support for

_DLIB_SCANF_MULTIBYTE

Multibyte characters

_DLIB_SCANF_LONG_LONG

Long long (ll qualifier)

_DLIB_SCANF_SPECIFIER_FLOAT

Floating-point numbers

_DLIB_SCANF_SPECIFIER_N

Output count (%n)

_DLIB_SCANF_QUALIFIERS

Qualifiers h, j, l, t, z, and L

_DLIB_SCANF_SCANSET

Scanset ([*])

_DLIB_SCANF_WIDTH

Width

_DLIB_SCANF_ASSIGNMENT_SUPPRESSING Assignment suppressing ([*])
Table 11: Descriptions of scanf configuration symbols

CUSTOMIZING FORMATTING CAPABILITIES
To customize the formatting capabilities, you must set up a library project, see Building
and using a customized library, page 71. Define the configuration symbols according to
your application requirements.

File input and output
The library contains a large number of powerful functions for file I/O operations. If you
use any of these functions, you must customize them to suit your hardware. To simplify
adaptation to specific hardware, all I/O functions call a small set of primitive functions,
each designed to accomplish one particular task; for example, __open opens a file, and
__write outputs characters.
Note that file I/O capability in the library is only supported by libraries with full library
configuration, see Library configurations, page 63. In other words, file I/O is supported
when the configuration symbol __DLIB_FILE_DESCRIPTOR is enabled. If not enabled,
functions taking a FILE * argument cannot be used.

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Template code for these I/O files are included in the product:
I/O function

File

Description

__close

close.c

Closes a file.

__lseek

lseek.c

Sets the file position indicator.

__open

open.c

Opens a file.

__read

read.c

Reads a character buffer.

__write

write.c

Writes a character buffer.

remove

remove.c

Removes a file.

rename

rename.c

Renames a file.

Table 12: Low-level I/O files

The primitive functions identify I/O streams, such as an open file, with a file descriptor
that is a unique integer. The I/O streams normally associated with stdin, stdout, and
stderr have the file descriptors 0, 1, and 2, respectively.
Note: If you link your library with I/O debugging support, C-SPY variants of the
low-level I/O functions are linked for interaction with C-SPY. For more information,
see Low-level interface for debug support, page 64.

Locale
Locale is a part of the C language that allows language- and country-specific settings for
several areas, such as currency symbols, date and time, and multibyte character
encoding.
Depending on what runtime library you are using you get different level of locale
support. However, the more locale support, the larger your code will get. It is therefore
necessary to consider what level of support your application needs.
The DLIB library can be used in two main modes:
●

With locale interface, which makes it possible to switch between different locales
during runtime

●

Without locale interface, where one selected locale is hardwired into the
application.

LOCALE SUPPORT IN PREBUILT LIBRARIES
The level of locale support in the prebuilt libraries depends on the library configuration.
●

All prebuilt libraries support the C locale only

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Locale

●

All libraries with full library configuration have support for the locale interface. For
prebuilt libraries with locale interface, it is by default only supported to switch
multibyte character encoding during runtime.

●

Libraries with normal library configuration do not have support for the locale
interface.

If your application requires a different locale support, you must rebuild the library.

CUSTOMIZING THE LOCALE SUPPORT
If you decide to rebuild the library, you can choose between these locales:
●

The standard C locale

●

The POSIX locale

●

A wide range of European locales.

Locale configuration symbols
The configuration symbol _DLIB_FULL_LOCALE_SUPPORT, which is defined in the
library configuration file, determines whether a library has support for a locale interface
or not. The locale configuration symbols _LOCALE_USE_LANG_REGION and
_ENCODING_USE_ENCODING define all the supported locales and encodings:
#define
#define
#define
#define
#define

_DLIB_FULL_LOCALE_SUPPORT 1
_LOCALE_USE_C
/* C locale */
_LOCALE_USE_EN_US
/* American English */
_LOCALE_USE_EN_GB
/* British English */
_LOCALE_USE_SV_SE
/* Swedish in Sweden */

See DLib_Defaults.h for a list of supported locale and encoding settings.
If you want to customize the locale support, you simply define the locale configuration
symbols required by your application. For more information, see Building and using a
customized library, page 71.
Note: If you use multibyte characters in your C or assembler source code, make sure
that you select the correct locale symbol (the local host locale).

Building a library without support for locale interface
The locale interface is not included if the configuration symbol
_DLIB_FULL_LOCALE_SUPPORT is set to 0 (zero). This means that a hardwired locale
is used—by default the standard C locale—but you can choose one of the supported
locale configuration symbols. The setlocale function is not available and can
therefore not be used for changing locales at runtime.

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Building a library with support for locale interface
Support for the locale interface is obtained if the configuration symbol
_DLIB_FULL_LOCALE_SUPPORT is set to 1. By default, the standard C locale is used,
but you can define as many configuration symbols as required. Because the setlocale
function will be available in your application, it will be possible to switch locales at
runtime.

CHANGING LOCALES AT RUNTIME
The standard library function setlocale is used for selecting the appropriate portion
of the application’s locale when the application is running.
The setlocale function takes two arguments. The first one is a locale category that is
constructed after the pattern LC_CATEGORY. The second argument is a string that
describes the locale. It can either be a string previously returned by setlocale, or it
can be a string constructed after the pattern:
lang_REGION

or
lang_REGION.encoding

The lang part specifies the language code, and the REGION part specifies a region
qualifier, and encoding specifies the multibyte character encoding that should be used.
The lang_REGION part matches the _LOCALE_USE_LANG_REGION preprocessor
symbols that can be specified in the library configuration file.

Example
This example sets the locale configuration symbols to Swedish to be used in Finland and
UTF8 multibyte character encoding:
setlocale (LC_ALL, "sv_FI.Utf8");

Environment interaction
According to the C standard, your application can interact with the environment using
the functions getenv and system.
Note: The putenv function is not required by the standard, and the library does not
provide an implementation of it.

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Signal and raise

THE GETENV FUNCTION
The getenv function searches the string, pointed to by the global variable __environ,
for the key that was passed as argument. If the key is found, the value of it is returned,
otherwise 0 (zero) is returned. By default, the string is empty.
To create or edit keys in the string, you must create a sequence of null terminated strings
where each string has the format:
key=value\0

End the string with an extra null character (if you use a C string, this is added
automatically). Assign the created sequence of strings to the __environ variable.
For example:
const char MyEnv[] = ”Key=Value\0Key2=Value2\0”;
__environ = MyEnv;

If you need a more sophisticated environment variable handling, you should implement
your own getenv, and possibly putenv function. This does not require that you rebuild
the library. You can find source templates in the files getenv.c and environ.c in the
arm\src\lib directory. For information about overriding default library modules, see
Overriding library modules, page 69.

THE SYSTEM FUNCTION
If you need to use the system function, you must implement it yourself. The system
function available in the library simply returns -1.
If you decide to rebuild the library, you can find source templates in the library project
template. For further information, see Building and using a customized library, page 71.
Note: If you link your application with support for I/O debugging, the functions
getenv and system are replaced by C-SPY variants. For further information, see

Low-level interface for debug support, page 64.

Signal and raise
Default implementations of the functions signal and raise are available. If these
functions do not provide the functionality that you need, you can implement your own
versions.
This does not require that you rebuild the library. You can find source templates in the
files signal.c and raise.c in the arm\src\lib directory. For information about
overriding default library modules, see Overriding library modules, page 69.

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If you decide to rebuild the library, you can find source templates in the library project
template. For further information, see Building and using a customized library, page 71.

Time
To make the time and date functions work, you must implement the three functions
clock, time, and __getzone.
This does not require that you rebuild the library. You can find source templates in the
files clock.c and time.c, and getzone.c in the arm\src\lib directory. For
information about overriding default library modules, see Overriding library modules,
page 69.
If you decide to rebuild the library, you can find source templates in the library project
template. For further information, see Building and using a customized library, page 71.
The default implementation of __getzone specifies UTC as the time zone.
Note: If you link your application with support for I/O debugging, the functions clock
and time are replaced by C-SPY variants that return the host clock and time
respectively. For further information, see C-SPY runtime interface, page 86.

Strtod
The function strtod does not accept hexadecimal floating-point strings in libraries
with the normal library configuration. To make a library do so, you must rebuild the
library, see Building and using a customized library, page 71. Enable the configuration
symbol _DLIB_STRTOD_HEX_FLOAT in the library configuration file.

Assert
If you linked your application with support for runtime debugging, an assert will print a
message on stdout. If this is not the behavior you require, you must add the source file
xreportassert.c to your application project. The __ReportAssert function
generates the assert notification. You can find template code in the arm\src\lib
directory. For further information, see Building and using a customized library, page 71.
To turn off assertions, you must define the symbol NDEBUG.
In the IDE, this symbol NDEBUG is by default defined in a Release project and not
defined in a Debug project. If you build from the command line, you must explicitly
define the symbol according to your needs. See NDEBUG, page 287.

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Atexit

Atexit
The linker allocates a static memory area for atexit function calls. By default, the
number of calls to the atexit function are limited to 32 bytes. To change this limit, see
Setting up the atexit limit, page 53.

C-SPY runtime interface
To include support for runtime and I/O debugging, you must link your application with
the option Semihosted or IAR breakpoint, see Low-level interface for debug support,
page 64.
In this case, special debugger variants of these library functions are linked to the
application:
Function

Description

abort

C-SPY notifies that the application has called abort

clock

Returns the clock on the host computer

__close

Closes the associated host file on the host computer

__exit

C-SPY notifies that the end of the application was reached

__open

Opens a file on the host computer

__read

stdin, stdout, and stderr will be directed to the Terminal I/O
window; all other files will read the associated host file

remove

Writes a message to the Debug Log window and returns -1

rename

Writes a message to the Debug Log window and returns -1

_ReportAssert

Handles failed asserts

__seek

Seeks in the associated host file on the host computer

system

Writes a message to the Debug Log window and returns -1

time

Returns the time on the host computer

__write

stdin, stdout, and stderr will be directed to the Terminal I/O
window, all other files will write to the associated host file

Table 13: Functions with special meanings when linked with debug info

LOW-LEVEL DEBUGGER RUNTIME INTERFACE
The low-level debugger runtime interface is used for communication between the
application being debugged and the debugger itself. The debugger provides runtime
services to the application via this interface; services that allow capabilities like file and
terminal I/O to be performed on the host computer.

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The DLIB runtime environment

These capabilities can be valuable during the early development of an application, for
example in an application using file I/O before any flash file system I/O drivers are
implemented. Or, if you need to debug constructions in your application that use stdin
and stdout without the actual hardware device for input and output being available.
Another debugging purpose can be to produce debug trace printouts.

THE DEBUGGER TERMINAL I/O WINDOW
To make the Terminal I/O window available, the application must be linked with support
for I/O debugging, see Low-level interface for debug support, page 64. This means that
when the functions __read or __write are called to perform I/O operations on the
streams stdin, stdout, or stderr, data will be sent to or read from the C-SPY
Terminal I/O window.
Note: The Terminal I/O window is not opened automatically just because __read or
__write is called; you must open it manually.
See the IAR Embedded Workbench® IDE User Guide for ARM® for more information
about the Terminal I/O window.

Speeding up terminal output
On some systems, terminal output might be slow because the host computer and the
target hardware must communicate for each character.
For this reason, a replacement for the __write function called __write_buffered is
included in the DLIB library. This module buffers the output and sends it to the debugger
one line at a time, speeding up the output. Note that this function uses about 80 bytes of
RAM memory.
To use this feature you can either choose Project>Options>Linker>Output and select
the option Buffered terminal output in the IDE, or add this to the linker command line:
--redirect __write=__write_buffered

Checking module consistency
This section introduces the concept of runtime model attributes, a mechanism that you
can use to ensure that modules are built using compatible settings.
When developing an application, it is important to ensure that incompatible modules are
not used together. For example, if you have a UART that can run in two modes, you can
specify a runtime model attribute, for example uart. For each mode, specify a value,
for example mode1 and mode2. Declare this in each module that assumes that the UART
is in a particular mode.

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Checking module consistency

The tools provided by IAR Systems use a set of predefined runtime model attributes to
automatically ensure module consistency.

RUNTIME MODEL ATTRIBUTES
A runtime attribute is a pair constituted of a named key and its corresponding value. In
general, two modules can only be linked together if they have the same value for each
key that they both define.
There is one exception: if the value of an attribute is *, then that attribute matches any
value. The reason for this is that you can specify this in a module to show that you have
considered a consistency property, and this ensures that the module does not rely on that
property.
Note: For IAR predefined runtime model attributes, the linker uses several ways of
checking them.
Example
In this table, the object files could (but do not have to) define the two runtime attributes
color and taste:
Object file

Color

Taste

file1

blue

not defined

file2

red

not defined

file3

red

*

file4

red

spicy

file5

red

lean

Table 14: Example of runtime model attributes

In this case, file1 cannot be linked with any of the other files, since the runtime
attribute color does not match. Also, file4 and file5 cannot be linked together,
because the taste runtime attribute does not match.
On the other hand, file2 and file3 can be linked with each other, and with either
file4 or file5, but not with both.

USING RUNTIME MODEL ATTRIBUTES
To ensure module consistency with other object files, use the #pragma rtmodel
directive to specify runtime model attributes in your C/C++ source code. For example:
#pragma rtmodel="uart", "mode1"

For detailed syntax information, see rtmodel, page 255.

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The DLIB runtime environment

You can also use the rtmodel assembler directive to specify runtime model attributes
in your assembler source code. For example:
rtmodel "color", "red"

For detailed syntax information, see the ARM® IAR Assembler Reference Guide.
At link time, the IAR ILINK Linker checks module consistency by ensuring that
modules with conflicting runtime attributes will not be used together. If conflicts are
detected, an error is issued.

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Assembler language
interface
When you develop an application for an embedded system, there might be
situations where you will find it necessary to write parts of the code in
assembler, for example when using mechanisms in the ARM core that require
precise timing and special instruction sequences.
This chapter describes the available methods for this and some C alternatives,
with their advantages and disadvantages. It also describes how to write
functions in assembler language that work together with an application written
in C or C++.
Finally, the chapter covers how functions are called, and how you can
implement support for call frame information in your assembler routines for
use in the C-SPY® Call Stack window.

Mixing C and assembler
The IAR C/C++ Compiler for ARM provides several ways to access low-level
resources:
●

Modules written entirely in assembler

●

Intrinsic functions (the C alternative)

●

Inline assembler.

It might be tempting to use simple inline assembler. However, you should carefully
choose which method to use.

INTRINSIC FUNCTIONS
The compiler provides a few predefined functions that allow direct access to low-level
processor operations without having to use the assembler language. These functions are
known as intrinsic functions. They can be very useful in, for example, time-critical
routines.

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An intrinsic function looks like a normal function call, but it is really a built-in function
that the compiler recognizes. The intrinsic functions compile into inline code, either as
a single instruction, or as a short sequence of instructions.
The advantage of an intrinsic function compared to using inline assembler is that the
compiler has all necessary information to interface the sequence properly with register
allocation and variables. The compiler also knows how to optimize functions with such
sequences; something the compiler is unable to do with inline assembler sequences. The
result is that you get the desired sequence properly integrated in your code, and that the
compiler can optimize the result.
For detailed information about the available intrinsic functions, see the chapter Intrinsic
functions.

MIXING C AND ASSEMBLER MODULES
It is possible to write parts of your application in assembler and mix them with your C
or C++ modules. This gives several benefits compared to using inline assembler:
●

The function call mechanism is well-defined

●

The code will be easy to read

●

The optimizer can work with the C or C++ functions.

This causes some overhead in the form of a function call and return instruction
sequences, and the compiler will regard some registers as scratch registers. However, the
compiler will also assume that all scratch registers are destroyed by an inline assembler
instruction. In many cases, the overhead of the extra instructions can be removed by the
optimizer.
An important advantage is that you will have a well-defined interface between what the
compiler produces and what you write in assembler. When using inline assembler, you
will not have any guarantees that your inline assembler lines do not interfere with the
compiler generated code.
When an application is written partly in assembler language and partly in C or C++, you
are faced with several questions:

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●

How should the assembler code be written so that it can be called from C?

●

Where does the assembler code find its parameters, and how is the return value
passed back to the caller?

●

How should assembler code call functions written in C?

●

How are global C variables accessed from code written in assembler language?

●

Why does not the debugger display the call stack when assembler code is being
debugged?

Assembler language interface

The first issue is discussed in the section Calling assembler routines from C, page 94.
The following two are covered in the section Calling convention, page 97.
The section Inline assembler, page 93, covers how to use inline assembler, but it also
shows how data in memory is accessed.
The answer to the final question is that the call stack can be displayed when you run
assembler code in the debugger. However, the debugger requires information about the
call frame, which must be supplied as annotations in the assembler source file. For more
information, see Call frame information, page 103.
The recommended method for mixing C or C++ and assembler modules is described in
Calling assembler routines from C, page 94, and Calling assembler routines from C++,
page 96, respectively.

INLINE ASSEMBLER
It is possible to insert assembler code directly into a C or C++ function. The asm
keyword inserts the supplied assembler statement in-line, see Inline assembler, page 225
for reference information. The following example demonstrates the use of the asm
keyword. This example also shows the risks of using inline assembler.
bool flag;
void foo()
{
while (!flag)
{
asm("
ldr r2,[pc,#0]
"
b .+8
"
DCD flag
"
ldr r3,[pc,#0]
"
b .+8
"
DCD PIND
"
ldr r0,[r3]
"
str r0,[r2]");
}
}

\n"
\n"
\n"
\n"
\n"
\n"
\n"

/*
/*
/*
/*
/*
/*
/*
/*

r2 = address of flag
jump over constant
address of flag
r3 = address of PIND
jump over constant
address of PIND
r0 = PIND
flag = r0

*/
*/
*/
*/
*/
*/
*/
*/

In this example, the assignment of flag is not noticed by the compiler, which means the
surrounding code cannot be expected to rely on the inline assembler statement.
The inline assembler instruction will simply be inserted at the given location in the
program flow. The consequences or side-effects the insertion might have on the
surrounding code are not taken into consideration. If, for example, registers or memory
locations are altered, they might have to be restored within the sequence of inline
assembler instructions for the rest of the code to work properly.

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Calling assembler routines from C

Inline assembler sequences have no well-defined interface with the surrounding code
generated from your C or C++ code. This makes the inline assembler code fragile, and
will possibly also become a maintenance problem if you upgrade the compiler in the
future. There are also several limitations to using inline assembler:
●

The compiler’s various optimizations will disregard any effects of the inline
sequences, which will not be optimized at all

●

In general, assembler directives will cause errors or have no meaning. Data
definition directives will however work as expected

●

Alignment cannot be controlled; this means, for example, that DC32 directives
might be misaligned

●

Auto variables cannot be accessed

●

Alternative register names, mnemonics, and operators are not supported; read more
about the -j assembler option in the ARM® IAR Assembler Reference Guide.

Inline assembler is therefore often best avoided. If no suitable intrinsic function is
available, we recommend that you use modules written in assembler language instead
of inline assembler, because the function call to an assembler routine normally causes
less performance reduction.

Calling assembler routines from C
An assembler routine that will be called from C must:
●

Conform to the calling convention

●

Have a PUBLIC entry-point label

●

Be declared as external before any call, to allow type checking and optional
promotion of parameters, as in these examples:
extern int foo(void);

or
extern int foo(int i, int j);

One way of fulfilling these requirements is to create skeleton code in C, compile it, and
study the assembler list file.

CREATING SKELETON CODE
The recommended way to create an assembler language routine with the correct
interface is to start with an assembler language source file created by the C compiler.
Note that you must create skeleton code for each function prototype.
The following example shows how to create skeleton code to which you can easily add
the functional body of the routine. The skeleton source code only needs to declare the

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variables required and perform simple accesses to them. In this example, the assembler
routine takes an int and a char, and then returns an int:
extern int gInt;
extern char gChar;
int Func(int arg1, char arg2)
{
int locInt = arg1;
gInt = arg1;
gChar = arg2;
return locInt;
}
int main()
{
int locInt = gInt;
gInt = Func(locInt, gChar);
return 0;
}

Note: In this example we use a low optimization level when compiling the code to
show local and global variable access. If a higher level of optimization is used, the
required references to local variables could be removed during the optimization. The
actual function declaration is not changed by the optimization level.

COMPILING THE CODE
In the IDE, specify list options on file level. Select the file in the workspace window.
Then choose Project>Options. In the C/C++ Compiler category, select Override
inherited settings. On the List page, deselect Output list file, and instead select the
Output assembler file option and its suboption Include source. Also, be sure to specify
a low level of optimization.
Use these options to compile the skeleton code:
iccarm skeleton.c -lA .

The -lA option creates an assembler language output file including C or C++ source
lines as assembler comments. The . (period) specifies that the assembler file should be
named in the same way as the C or C++ module (skeleton), but with the filename
extension s. Also remember to specify a low level of optimization, and -e for enabling
language extensions.
The result is the assembler source output file skeleton.s.
Note: The -lA option creates a list file containing call frame information (CFI)
directives, which can be useful if you intend to study these directives and how they are

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Calling assembler routines from C++

used. If you only want to study the calling convention, you can exclude the CFI
directives from the list file. In the IDE, choose Project>Options>C/C++
Compiler>List and deselect the suboption Include call frame information.
On the command line, use the option -lB instead of -lA. Note that CFI information
must be included in the source code to make the C-SPY Call Stack window work.

The output file
The output file contains the following important information:
●

The calling convention

●

The return values

●

The global variables

●

The function parameters

●

How to create space on the stack (auto variables)

●

Call frame information (CFI).

The CFI directives describe the call frame information needed by the Call Stack window
in the debugger. For more information, see Call frame information, page 103.

Calling assembler routines from C++
The C calling convention does not apply to C++ functions. Most importantly, a function
name is not sufficient to identify a C++ function. The scope and the type of the function
are also required to guarantee type-safe linkage, and to resolve overloading.
Another difference is that non-static member functions get an extra, hidden argument,
the this pointer.
However, when using C linkage, the calling convention conforms to the C calling
convention. An assembler routine can therefore be called from C++ when declared in
this manner:
extern "C"
{
int MyRoutine(int);
}

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Assembler language interface

The following example shows how to achieve the equivalent to a non-static member
function, which means that the implicit this pointer must be made explicit. It is also
possible to “wrap” the call to the assembler routine in a member function. Use an inline
member function to remove the overhead of the extra call—this assumes that function
inlining is enabled:
class MyClass;
extern "C"
{
void DoIt(MyClass *ptr, int arg);
}
class MyClass
{
public:
inline void DoIt(int arg)
{
::DoIt(this, arg);
}
};

Calling convention
A calling convention is the way a function in a program calls another function. The
compiler handles this automatically, but, if a function is written in assembler language,
you must know where and how its parameters can be found, how to return to the program
location from where it was called, and how to return the resulting value.
It is also important to know which registers an assembler-level routine must preserve. If
the program preserves too many registers, the program might be ineffective. If it
preserves too few registers, the result would be an incorrect program.
This section describes the calling conventions used by the compiler. These items are
examined:
●

Choosing a calling convention

●

Function declarations

●

C and C++ linkage

●

Preserved versus scratch registers

●

Function entrance

●

Function exit

●

Return address handling.

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Calling convention

At the end of the section, some examples are shown to describe the calling convention
in practice.
Unless otherwise noted, the calling convention used by the compiler adheres to AAPCS,
a part of AEABI; see AEABI compliance, page 123.

FUNCTION DECLARATIONS
In C, a function must be declared in order for the compiler to know how to call it. A
declaration could look as follows:
int MyFunction(int first, char * second);

This means that the function takes two parameters: an integer and a pointer to a
character. The function returns a value, an integer.
In the general case, this is the only knowledge that the compiler has about a function.
Therefore, it must be able to deduce the calling convention from this information.

USING C LINKAGE IN C++ SOURCE CODE
In C++, a function can have either C or C++ linkage. To call assembler routines from
C++, it is easiest if you make the C++ function have C linkage.
This is an example of a declaration of a function with C linkage:
extern "C"
{
int F(int);
}

It is often practical to share header files between C and C++. This is an example of a
declaration that declares a function with C linkage in both C and C++:
#ifdef __cplusplus
extern "C"
{
#endif
int F(int);
#ifdef __cplusplus
}
#endif

PRESERVED VERSUS SCRATCH REGISTERS
The general ARM CPU registers are divided into three separate sets, which are
described in this section.

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Scratch registers
Any function is permitted to destroy the contents of a scratch register. If a function needs
the register value after a call to another function, it must store it during the call, for
example on the stack.
Any of the registers R0 to R3, and R12, can be used as a scratch register by the function.
Note that R12 is a scratch register also when calling between assembler functions only
because of automatically inserted instructions for veneers.

Preserved registers
Preserved registers, on the other hand, are preserved across function calls. The called
function can use the register for other purposes, but must save the value before using the
register and restore it at the exit of the function.
The registers R4 through to R11 are preserved registers. They are preserved by the called
function.

Special registers
For some registers, you must consider certain prerequisites:
●

The stack pointer register, R13/SP, must at all times point to or below the last
element on the stack. In the eventuality of an interrupt, everything below the point
the stack pointer points to, can be destroyed. At function entry and exit, the stack
pointer must be 8-byte aligned. In the function, the stack pointer must always be
word aligned. At exit, SP must have the same value as it had at the entry.

●

The register R15/PC is dedicated for the Program Counter.

●

The link register, R14/LR, holds the return address at the entrance of the function.

FUNCTION ENTRANCE
Parameters can be passed to a function using one of two basic methods: in registers or
on the stack. It is much more efficient to use registers than to take a detour via memory,
so the calling convention is designed to use registers as much as possible. Only a limited
number of registers can be used for passing parameters; when no more registers are
available, the remaining parameters are passed on the stack. These exceptions to the
rules apply:
●

Interrupt functions cannot take any parameters, except software interrupt functions
that accept parameters and have return values

●

Software interrupt functions cannot use the stack in the same way as ordinary
functions. When an SVC instruction is executed, the processor switches to
supervisor mode where the supervisor stack is used. Arguments can therefore not be

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passed on the stack if your application is not running in supervisor mode previous to
the interrupt.

Hidden parameters
In addition to the parameters visible in a function declaration and definition, there can
be hidden parameters:
●

If the function returns a structure larger than 32 bits, the memory location where the
structure is to be stored is passed as an extra parameter. Notice that it is always
treated as the first parameter.

●

If the function is a non-static C++ member function, then the this pointer is passed
as the first parameter (but placed after the return structure pointer, if there is one).
For more information, see Calling assembler routines from C++, page 96.

Register parameters
The registers available for passing parameters are R0–R3:
Parameters

Passed in registers

Scalar and floating-point values no larger than 32 bits, and Passed using the first free register:
single-precision (32-bits) floating-point values
R0–R3
long long and double-precision (64-bit) values

Passed in first available register pair:
R0:R1, or R2:R3

Table 15: Registers used for passing parameters

The assignment of registers to parameters is a straightforward process. Traversing the
parameters from left to right, the first parameter is assigned to the available register or
registers. Should there be no more available registers, the parameter is passed on the
stack in reverse order.
When functions that have parameters smaller than 32 bits are called, the values are sign
or zero extended to ensure that the unused bits have consistent values. Whether the
values will be sign or zero extended depends on their type—signed or unsigned.

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Stack parameters and layout
Stack parameters are stored in memory, starting at the location pointed to by the stack
pointer. Below the stack pointer (towards low memory) there is free space that the called
function can use. The first stack parameter is stored at the location pointed to by the
stack pointer. The next one is stored at the next location on the stack that is divisible by
four, etc. It is the responsibility of the caller to clean the stack after the called function
has returned.

Figure 13: Storing stack parameters in memory

The stack should be aligned to 8 at function entry.

FUNCTION EXIT
A function can return a value to the function or program that called it, or it can have the
return type void.
The return value of a function, if any, can be scalar (such as integers and pointers),
floating-point, or a structure.

Registers used for returning values
The registers available for returning values are R0 and R0:R1.
Return values

Passed in register/register pair

Scalar and structure return values no larger than 32 bits,
and single-precision (32-bit) floating-point return values

R0

The memory address of a structure return value larger
than 32 bits

R0

long long and double-precision (64-bit) return values

R0:R1

Table 16: Registers used for returning values

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If the returned value is smaller than 32 bits, the value is sign- or zero-extended to 32 bits.

Stack layout at function exit
It is the responsibility of the caller to clean the stack after the called function has
returned.

Return address handling
A function written in assembler language should, when finished, return to the caller by
jumping to the address pointed to by the register LR.
At function entry, non-scratch registers and the LR register can be pushed with one
instruction. At function exit, all these registers can be popped with one instruction. The
return address can be popped directly to PC.
The following example shows what this can look like:
PUSH
.
.
.
POP

{R4-R6,LR}

{R4-R6,PC}

/* Function entry. */

/* Function exit. */

EXAMPLES
The following section shows a series of declaration examples and the corresponding
calling conventions. The complexity of the examples increases toward the end.
Example 1
Assume this function declaration:
int add1(int);

This function takes one parameter in the register R0, and the return value is passed back
to its caller in the register R0.
This assembler routine is compatible with the declaration; it will return a value that is
one number higher than the value of its parameter:
add1:
ADDS
BX

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R0,R0,#+0x1
BX,LR

Assembler language interface

Example 2
This example shows how structures are passed on the stack. Assume these declarations:
struct MyStruct
{
int a,b,c,d,e;
};
int MyFunction(struct MyStruct x, int y);

The values of the structure members a, b, c, and d are passed in registers R0-R3. The
last structure member e and the integer parameter y are passed on the stack. The calling
function must reserve eight bytes on the top of the stack and copy the contents of the two
stack parameters to that location. The return value is passed back to its caller in the
register R0.

Call frame information
When you debug an application using C-SPY, you can view the call stack, that is, the
chain of functions that called the current function. To make this possible, the compiler
supplies debug information that describes the layout of the call frame, in particular
information about where the return address is stored.
If you want the call stack to be available when debugging a routine written in assembler
language, you must supply equivalent debug information in your assembler source using
the assembler directive CFI. This directive is described in detail in the ARM® IAR
Assembler Reference Guide.

CFI DIRECTIVES
The CFI directives provide C-SPY with information about the state of the calling
function(s). Most important of this is the return address, and the value of the stack
pointer at the entry of the function or assembler routine. Given this information, C-SPY
can reconstruct the state for the calling function, and thereby unwind the stack.
A full description about the calling convention might require extensive call frame
information. In many cases, a more limited approach will suffice.
When describing the call frame information, the following three components must be
present:
●

A names block describing the available resources to be tracked

●

A common block corresponding to the calling convention

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Call frame information

●

A data block describing the changes that are performed on the call frame. This
typically includes information about when the stack pointer is changed, and when
permanent registers are stored or restored on the stack.

This table lists all the resources defined in the names block used by the compiler:
Resource

Description

CFA R13

The call frames of the stack

R0–R12

Processor general-purpose 32-bit registers

R13

Stack pointer, SP

R14

Link register, LR

S0–S31

Vector Floating Point (VFP) 32-bit coprocessor registers

CPSR

Current program status register

SPSR

Saved program status register

Table 17: Call frame information resources defined in a names block

CREATING ASSEMBLER SOURCE WITH CFI SUPPORT
The recommended way to create an assembler language routine that handles call frame
information correctly is to start with an assembler language source file created by the
compiler.

1 Start with suitable C source code, for example:
int F(int);
int cfiExample(int i)
{
return i + F(i);
}

2 Compile the C source code, and make sure to create a list file that contains call frame
information—the CFI directives.
On the command line, use the option -lA.
In the IDE, choose Project>Options>C/C++ Compiler>List and make sure the
suboption Include call frame information is selected.
For the source code in this example, the list file looks like this:
NAME cfiexample
EXTERN F
PUBLIC cfiExample

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CFI Names cfiNames0
CFI StackFrame CFA R13 DATA
CFI Resource R0:32, R1:32, R2:32, R3:32, R4:32, R5:32,
R6:32, R7:32
CFI Resource R8:32, R9:32, R10:32, R11:32, R12:32,
R13:32, R14:32
CFI EndNames cfiNames0
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI
CFI

Common cfiCommon0 Using cfiNames0
CodeAlign 4
DataAlign 4
ReturnAddress R14 CODE
CFA R13+0
R0 Undefined
R1 Undefined
R2 Undefined
R3 Undefined
R4 SameValue
R5 SameValue
R6 SameValue
R7 SameValue
R8 SameValue
R9 SameValue
R10 SameValue
R11 SameValue
R12 Undefined
R14 SameValue
EndCommon cfiCommon0

SECTION `.text`:CODE:NOROOT(2)
CFI Block cfiBlock0 Using cfiCommon0
CFI Function cfiExample
ARM
cfiExample:
PUSH
{R4,LR}
CFI R14 Frame(CFA, -4)
CFI R4 Frame(CFA, -8)
CFI CFA R13+8
MOVS
R4,R0
MOVS
R0,R4
BL
F
ADDS
R0,R0,R4
POP
{R4,LR}
CFI R4 SameValue
CFI R14 SameValue
CFI CFA R13+0

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Call frame information

BX
LR
CFI EndBlock cfiBlock0

;; return

END

Note: The header file cfiCommon.i contains the macros CFI_NAME_BLOCK,
CFI_COMMON_ARM, and CFI_COMMON_Thumb which declare a typical names block and
two typical common blocks. These macros declare several resources, both concrete and
virtual.

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Using C++
IAR Systems supports two levels of the C++ language: The industry-standard
Embedded C++ and IAR Extended Embedded C++. They are described in this
chapter.

Overview
Embedded C++ is a subset of the C++ programming language which is intended for
embedded systems programming. It was defined by an industry consortium, the
Embedded C++ Technical Committee. Performance and portability are particularly
important in embedded systems development, which was considered when defining the
language.

STANDARD EMBEDDED C++
The following C++ features are supported:
●

Classes, which are user-defined types that incorporate both data structure and
behavior; the essential feature of inheritance allows data structure and behavior to
be shared among classes

●

Polymorphism, which means that an operation can behave differently on different
classes, is provided by virtual functions

●

Overloading of operators and function names, which allows several operators or
functions with the same name, provided that their argument lists are sufficiently
different

●

Type-safe memory management using the operators new and delete

●

Inline functions, which are indicated as particularly suitable for inline expansion.

C++ features that are excluded are those that introduce overhead in execution time or
code size that are beyond the control of the programmer. Also excluded are late
additions to the ISO/ANSI C++ standard. This is because they represent potential
portability problems, due to that few development tools support the standard. Embedded
C++ thus offers a subset of C++ which is efficient and fully supported by existing
development tools.
Standard Embedded C++ lacks these features of C++:
●

Templates

●

Multiple and virtual inheritance

●

Exception handling

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Overview

●

Runtime type information

●

New cast syntax (the operators dynamic_cast, static_cast,
reinterpret_cast, and const_cast)

●

Namespaces

●

The mutable attribute.

The exclusion of these language features makes the runtime library significantly more
efficient. The Embedded C++ library furthermore differs from the full C++ library in
that:
●

The standard template library (STL) is excluded

●

Streams, strings, and complex numbers are supported without the use of templates

●

Library features which relate to exception handling and runtime type information
(the headers except, stdexcept, and typeinfo) are excluded.

Note: The library is not in the std namespace, because Embedded C++ does not
support namespaces.

EXTENDED EMBEDDED C++
IAR Systems’ Extended EC++ is a slightly larger subset of C++ which adds these
features to the standard EC++:
●

Full template support

●

Multiple and virtual inheritance

●

Namespace support

●

The mutable attribute

●

The cast operators static_cast, const_cast, and reinterpret_cast.

All these added features conform to the C++ standard.
To support Extended EC++, this product includes a version of the standard template
library (STL), in other words, the C++ standard chapters utilities, containers, iterators,
algorithms, and some numerics. This STL is tailored for use with the Extended EC++
language, which means no exceptions, no multiple inheritance, and no support for
runtime type information (rtti). Moreover, the library is not in the std namespace.
Note: A module compiled with Extended EC++ enabled is fully link-compatible with
a module compiled without Extended EC++ enabled.

ENABLING C++ SUPPORT
In the compiler, the default language is C. To be able to compile files written in
Embedded C++, you must use the --ec++ compiler option. See --ec++, page 169.

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Using C++

To take advantage of Extended Embedded C++ features in your source code, you must
use the --eec++ compiler option. See --eec++, page 169.
To set the equivalent option in the IDE, choose Project>Options>C/C++
Compiler>Language.

Feature descriptions
When you write C++ source code for the IAR C/C++ Compiler for ARM, you must be
aware of some benefits and some possible quirks when mixing C++ features—such as
classes, and class members—with IAR language extensions, such as IAR-specific
attributes.

CLASSES
A class type class and struct in C++ can have static and non-static data members,
and static and non-static function members. The non-static function members can be
further divided into virtual function members, non-virtual function members,
constructors, and destructors. For the static data members, static function members, and
non-static non-virtual function members the same rules apply as for statically linked
symbols outside of a class. In other words, they can have any applicable IAR-specific
type and object attribute.
The non-static virtual function members can have any applicable IAR-specific type and
object attribute as long as a pointer to the member function can be implicitly converted
to the default function pointer type. The constructors, destructors, and non-static data
members cannot have any IAR attributes.
The location operator @ can be used on static data members and on any type of function
members.
For further information about attributes, see Type qualifiers, page 218.
Example
class MyClass
{
public:
// Locate a static variable at address 60
static __no_init int mI @ 60;
// A static Thumb function
static __thumb void f();
// A Thumb function
__thumb void g();

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Feature descriptions

// Interworking assumed
virtual __thumb void th()
// Interworking assumed
virtual __arm void ah();
// Locate a virtual function into SPECIAL
virtual void M() const volatile @ "SPECIAL";
};

FUNCTION TYPES
A function type with extern "C" linkage is compatible with a function that has C++
linkage.
Example
extern "C"
{
typedef void (*FpC)(void);
}
typedef void (*FpCpp)(void);

// A C function typedef

// A C++ function typedef

FpC F1;
FpCpp F2;
void MyF(FpC);
void MyG()
{
MyF(F1);
MyF(F2);
}

// Always works
// FpCpp is compatible with FpC

TEMPLATES
Extended EC++ supports templates according to the C++ standard, except for the
support of the export keyword. The implementation uses a two-phase lookup which
means that the keyword typename must be inserted wherever needed. Furthermore, at
each use of a template, the definitions of all possible templates must be visible. This
means that the definitions of all templates must be in include files or in the actual source
file.

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Using C++

The standard template library
The STL (standard template library) delivered with the product is tailored for Extended
EC++, as described in Extended Embedded C++, page 108.

STL and the IAR C-SPY® Debugger
C-SPY has built-in display support for the STL containers. The logical structure of
containers is presented in the watch views in a comprehensive way that is easy to
understand and follow.
To read more about displaying STL containers in the C-SPY debugger, see the IAR
Embedded Workbench® IDE User Guide for ARM®.

VARIANTS OF CAST OPERATORS
In Extended EC++ these additional variants of C++ cast operators can be used:
const_cast(from)
static_cast(from)
reinterpret_cast(from)

MUTABLE
The mutable attribute is supported in Extended EC++. A mutable symbol can be
changed even though the whole class object is const.

NAMESPACE
The namespace feature is only supported in Extended EC++. This means that you can
use namespaces to partition your code. Note, however, that the library itself is not placed
in the std namespace.

THE STD NAMESPACE
The std namespace is not used in either standard EC++ or in Extended EC++. If you
have code that refers to symbols in the std namespace, simply define std as nothing;
for example:
#define std

You must make sure that identifiers in your application do not interfere with identifiers
in the runtime library.

POINTER TO MEMBER FUNCTIONS
A pointer to a member function can only contain a default function pointer, or a function
pointer that can implicitly be casted to a default function pointer. To use a pointer to a

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C++ language extensions

member function, make sure that all functions that should be pointed to reside in the
default memory or a memory contained in the default memory.
Example
class X
{
public:
__interwork void aF();
};
void (__interwork

X::*ap)() = &X::af;

USING INTERRUPTS AND EC++ DESTRUCTORS
If interrupts are enabled and the interrupt functions use static class objects that need to
be destroyed (using destructors), there might be problems if the interrupt occur during
or after application exits. If an interrupt occurs after the static class object was destroyed,
the application will not work properly.
To avoid this, make sure that interrupts are disabled when returning from main or when
calling exit or abort. To do this, call the intrinsic function __disable_interrupt.

C++ language extensions
When you use the compiler in C++ mode and enable IAR language extensions, the
following C++ language extensions are available in the compiler:
●

In a friend declaration of a class, the class keyword can be omitted, for example:
class B;
class A
{
friend B;

//Possible when using IAR language
//extensions
friend class B; //According to standard

};
●

Constants of a scalar type can be defined within classes, for example:
class A
{
const int mSize = 10; //Possible when using IAR language
//extensions
int mArr[mSize];
};

According to the standard, initialized static data members should be used instead.

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Using C++

●

In the declaration of a class member, a qualified name can be used, for example:
struct A
{
int A::F(); // Possible when using IAR language extensions
int G();
// According to standard
};

●

It is permitted to use an implicit type conversion between a pointer to a function
with C linkage (extern "C") and a pointer to a function with C++ linkage
(extern "C++"), for example:
extern "C" void F(); // Function with C linkage
void (*PF)()
// PF points to a function with C++ linkage
= &F; // Implicit conversion of function pointer.

According to the standard, the pointer must be explicitly converted.
●

If the second or third operands in a construction that contains the ? operator are
string literals or wide string literals (which in C++ are constants), the operands can
be implicitly converted to char * or wchar_t *, for example:
bool X;
char *P1 = X ? "abc" : "def";

//Possible when using IAR
//language extensions
char const *P2 = X ? "abc" : "def"; //According to standard
●

Default arguments can be specified for function parameters not only in the top-level
function declaration, which is according to the standard, but also in typedef
declarations, in pointer-to-function function declarations, and in pointer-to-member
function declarations.

●

In a function that contains a non-static local variable and a class that contains a
non-evaluated expression (for example a sizeof expression), the expression can
reference the non-static local variable. However, a warning is issued.

Note: If you use any of these constructions without first enabling language extensions,
errors are issued.

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C++ language extensions

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Application-related
considerations
This chapter discusses a selected range of application issues related to
developing your embedded application.
Typically, this chapter highlights issues that are not specifically related to only
the compiler or the linker.

Output format considerations
The linker produces an absolute executable image in the ELF/DWARF object file
format.
You can use the IAR ELF Tool—ielftool— to convert an absolute ELF image to a
format more suitable for loading directly to memory, or burning to a PROM or flash
memory etc.
ielftool can produce these output formats:
●

Plain binary

●

Motorola S-records

●

Intel hex.

Note: ielftool can also be used for other types of transformations, such as filling and
calculating checksums in the absolute image.
The source code for ielftool is provided in the arm/src directory. For more
information about ielftool, see The IAR ELF Tool—ielftool, page 330.

Stack considerations
The stack is used by functions to store variables and other information that is used
locally by functions, as described in the chapter Data storage. It is a continuous block
of memory pointed to by the processor stack pointer register SP.
The data section used for holding the stack is called CSTACK. The system startup code
initializes the stack pointer to the end of the stack.

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Stack considerations

STACK SIZE CONSIDERATIONS
The compiler uses the internal data stack, CSTACK, for a variety of user application
operations, and the required stack size depends heavily on the details of these
operations. If the given stack size is too large, RAM will be wasted. If the given stack
size is too small, two things can happen, depending on where in memory you located
your stack. Both alternatives are likely to result in application failure. Either variable
storage will be overwritten, leading to undefined behavior, or the stack will fall outside
of the memory area, leading to an abnormal termination of your application. Because
the second alternative is easier to detect, you should consider placing your stack so that
it grows toward the end of the memory.
For more information about the stack size, see Setting up the stack, page 52, and Saving
stack space and RAM memory, page 140.

ALIGNING THE STACK
You must make sure that the stack of your application is 8-byte aligned, because this is
expected by some parts of the runtime library.
For more information about aligning the stack, see Calling convention, page 97 and
more specifically Special registers, page 99 and Stack parameters and layout, page 101.

EXCEPTION STACKS
The ARM architecture supports five exception modes which are entered when different
exceptions occur. Each exception mode has its own stack to avoid corrupting the
System/User mode stack.
The table shows proposed stack names for the various exception stacks, but any name
can be used:

Processor mode

Proposed stack section
name

Supervisor

SVC_STACK

Operating system stack.

IRQ

IRQ_STACK

Stack for general-purpose (IRQ) interrupt
handlers.

FIQ

FIQ_STACK

Stack for high-speed (FIQ) interrupt handlers.

Undefined

UND_STACK

Stack for undefined instruction interrupts.
Supports software emulation of hardware
coprocessors and instruction set extensions.

Abort

ABT_STACK

Stack for instruction fetch and data access
memory abort interrupt handlers.

Table 18: Exception stacks

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Description

Application-related considerations

For each processor mode where a stack is needed, a separate stack pointer must be
initialized in your startup code, and section placement should be done in the linker
configuration file. The IRQ and FIQ stacks are the only exception stacks which are
preconfigured in the supplied cstartup.s and lnkarm.icf files, but other exception
stacks can easily be added.
Cortex-M does not have individual exception stacks. By default, all exception stacks are
placed in the CSTACK section.
To view any of these stacks in the Stack window available in the IDE, these
preconfigured section names must be used instead of user-defined section names.

Heap considerations
The heap contains dynamic data allocated by use of the C function malloc (or one of
its relatives) or the C++ operator new.
If your application uses dynamic memory allocation, you should be familiar with:
●

Linker sections used for the heap

●

Allocating the heap size, see Setting up the heap, page 52.

The memory allocated to the heap is placed in the section HEAP, which is only included
in the application if dynamic memory allocation is actually used.

Heap size and standard I/O
If you excluded FILE descriptors from the DLIB runtime environment, as in the normal
configuration, there are no input and output buffers at all. Otherwise, as in the full
configuration, be aware that the size of the input and output buffers is set to 512 bytes
in the stdio library header file. If the heap is too small, I/O will not be buffered, which
is considerably slower than when I/O is buffered. If you execute the application using
the simulator driver of the IAR C-SPY® Debugger, you are not likely to notice the speed
penalty, but it is quite noticeable when the application runs on an ARM core. If you use
the standard I/O library, you should set the heap size to a value which accommodates the
needs of the standard I/O buffer.

Interaction between the tools and your application
The linking process and the application can interact symbolically in four ways:
●

Creating a symbol by using the ILINK command line option --define_symbol.
ILINK will create a public absolute constant symbol that the application can use as
a label, as a size, as setup for a debugger, et cetera.

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Interaction between the tools and your application

●

Creating an exported configuration symbol by using the command line option
--config_def or the configuration directive define symbol, and exporting the
symbol using the export symbol directive. ILINK will create a public absolute
constant symbol that the application can use as a label, as a size, as setup for a
debugger, etc.
One advantage of this symbol definition is that this symbol can also be used in
expressions in the configuration file, for example to control the placement of sections
into memory ranges.

●

Using the compiler operators __section_begin, __section_end, or
__section_size, or the assembler operators SFB, SFE, or SIZEOF on a named
section or block. These operators provide access to the start address, end address,
and size of a contiguous sequence of sections with the same name, or of a linker
block specified in the linker configuration file.

●

The command line option --entry informs ILINK about the start label of the
application. It is used by ILINK as a root symbol and to inform the debugger where
to start execution.

The following lines illustrate how to use these mechanisms. Add these options to your
command line:
--define_symbol NrOfElements=10
--config_def HeapSize=1024

The linker configuration file can look like this:
define memory Mem with size = 4G;
define region ROM = Mem:[from 0x00000 size 0x10000];
define region RAM = Mem:[from 0x20000 size 0x10000];
/* Export of symbol */
export symbol HeapSize;
/* Setup a heap area witha size defined by an ILINK option */
define block MyHEAP with size = HeapSize, alignment = 8 {};
place in RAM { block MyHEAP };

Add these lines to your application source code:
#include 
/* Use symbol defined by ILINK option to dynamically allocate
an array of elements with specified size */
extern char NrOfElements;

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Application-related considerations

typedef long Elements;
Elements *GetElementArray()
{
return malloc(sizeof(Elements) * (int)& NrOfElements);
}
/* Use a symbol defined by ILINK option, a symbol that in the
configuration file was made available to the application */
extern char HeapSize;
/* Declares the section that contains our heap */
#pragma section = "MyHEAP"
char *MyHeap()
{
/* First get start of statically allocated section */
char *p = __section_begin("MyHEAP");
/* then we zero it, using the imported size */
for (int i = 0; i < (int)& HeapSize; ++i)
{
p[i] = 0;
}
return p;
}

Checksum calculation
The IAR ELF Tool—ielftool—fills specific ranges of memory with a pattern and
then calculates a checksum for those ranges. The calculated checksum replaces the value
of an existing symbol in the input ELF image. The application can then verify that the
ranges did not change.
To use checksumming to verify the integrity of your application, you must:
●

Reserve a place, with an associated name and size, for the checksum calculated by
ielftool

●

Choose a checksum algorithm, set up ielftool for it, and include source code for
the algorithm in your application

●

Decide what memory ranges to verify and set up both ielftool and the source
code for it in your application source code.

Note: To set up ielftool in the IDE, choose Project>Options>Linker>Checksum.

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Checksum calculation

CALCULATING A CHECKSUM
In this example, a checksum is calculated for ROM memory at 0x8002 up to 0x8FFF
and the 2-byte calculated checksum is placed at 0x8000.

Creating a place for the calculated checksum
You can create a place for the calculated checksum in two ways; by creating a global
C/C++ or assembler constant symbol with a proper size, residing in a specific section
(in this example .checksum), or by using the linker option --place_holder.
For example, to create a 2-byte space for the symbol __checksum in the section
.checksum, with alignment 4:
--place_holder __checksum,2,.checksum,4

To place the .checksum section, you must modify the linker configuration file. It can
look like this (note the handling of the block CHECKSUM):
define memory Mem with size = 4G;
define region ROM_region = Mem:[from 0x8000 to 0x80000000 - 1];
define region RAM_region = Mem:[from 0x80000000 to 0x100000000 -2 ];
initialize by copy { rw };
do not initialize { section .noinit };
define
define
define
define

block
block
block
block

HEAP
CSTACK
IRQ_STACK
FIQ_STACK

with
with
with
with

alignment
alignment
alignment
alignment

=
=
=
=

8,
8,
8,
8,

size
size
size
size

=
=
=
=

16M
16K
16K
16K

{};
{};
{};
{};

define block CHECKSUM
{ ro section .checksum };
place at address Mem:0x0 { ro section .intvec};
place in ROM_region { ro, first block CHECKSUM };
place in RAM_region { rw, block HEAP, block CSTACK, block
IRQ_STACK, block FIQ_STACK };

Running ielftool
To calculate the checksum, run ielftool:
ielftool --fill=0x00;0x8000–0x8FFF
--checksum=__checksum:2,crc16;0x8000–0x8FFF sourceFile.out
destinationFile.out

To calculate a checksum you also must define a fill operation. In this example, the fill
pattern 0x0 is used. The checksum algorithm used is crc16.

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Application-related considerations

Note that ielftool needs an unstripped input ELF image. If you use the --strip
linker option, remove it and use the --strip ielftool option instead.

ADDING A CHECKSUM FUNCTION TO YOUR SOURCE CODE
To check the value of the ielftool generated checksum, it must be compared with a
checksum that your application calculated. This means that you must add a function for
checksum calculation (that uses the same algorithm as ielftool) to your application
source code. Your application must also include a call to this function.

A function for checksum calculation
This function—a slow variant but with small memory footprint—uses the crc16
algorithm:
unsigned short slow_crc16(unsigned short sum,
unsigned char *p,
unsigned int len)
{
while (len--)
{
int i;
unsigned char byte = *(p++);
for (i = 0; i < 8; ++i)
{
unsigned long oSum = sum;
sum <<= 1;
if (byte & 0x80)
sum |= 1;
if (oSum & 0x8000)
sum ^= 0x1021;
byte <<= 1;
}
}
return sum;
}

You can find the source code for the checksum algorithms in the arm\src\linker
directory of your product installation.

Checksum calculation
This code gives an example of how the checksum can be calculated:
/* Start and end of the checksum range */
unsigned long ChecksumStart = 0x8000+2;
unsigned long ChecksumEnd
= 0x8FFF;

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Checksum calculation

/* The checksum calculated by ielftool
* (note that it lies on address 0x8000)
*/
extern unsigned short const __checksum;

void TestChecksum()
{
unsigned short calc = 0;
unsigned char zeros[2] = {0, 0};
/* Run the checksum algorithm */
calc = slow_crc16(0,
(unsigned char *) ChecksumStart,
(ChecksumEnd - ChecksumStart+1));
/* Rotate out the answer */
calc = slow_crc16(calc, zeros, 2);
/* Test the checksum */
if (calc != __checksum)
{
abort();
/* Failure */
}
}

THINGS TO REMEMBER
When calculating a checksum, you must remember that:
●

The checksum must be calculated from the lowest to the highest address for every
memory range

●

Each memory range must be verified in the same order as defined

●

It is OK to have several ranges for one checksum

●

If several checksums are used, you should place them in sections with unique names
and use unique symbol names

●

If a slow function is used, you must make a final call to the checksum calculation
with as many bytes (with the value 0x00) as there are bytes in the checksum.

For more information, see also The IAR ELF Tool—ielftool, page 330.

C-SPY CONSIDERATIONS
By default, a symbol that you have allocated in memory by using the linker option
--place_holder is considered by C-SPY to be of the type int. If the size of the

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Application-related considerations

checksum is less than four bytes, you can change the display format of the checksum
symbol to match its size.
In the C-SPY Watch window, select the symbol and choose Show As from the context
menu. Choose the display format that matches the size of the checksum symbol.

AEABI compliance
The IAR build tools for ARM support the Embedded Application Binary Interface for
ARM, AEABI, defined by ARM Limited. This interface is based on the Intel IA64 ABI
interface. The advantage of adhering to AEABI is that any such module can be linked
with any other AEABI compliant module, even modules produced by tools provided by
other vendors.
The IAR build tools for ARM support the following parts of the AEABI:
AAPCS

Procedure Call Standard for the ARM architecture

CPPABI

C++ ABI for the ARM architecture (EC++ parts only)

AAELF

ELF for the ARM architecture

AADWARF

DWARF for the ARM architecture

RTABI

Runtime ABI for the ARM architecture

CLIBABI

C library ABI for the ARM architecture

The IAR build tools only support a bare metal platform, that is a ROM-based system
that lacks an explicit operating system.
Note that:
●

The AEABI is specified for C89 only

●

The IAR build tools only support using the default and C locales

●

The AEABI does not specify C++ library compatibility

●

The IAR build tools do not support the use of exceptions and rtti

●

Neither the size of an enum or of wchar_t is constant in the AEABI.

If AEABI compliance is enabled, almost all optimizations performed in the system
header files are turned off, and certain preprocessor constants become real constant
variables instead.

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AEABI compliance

LINKING AEABI COMPLIANT MODULES USING THE IAR ILINK
LINKER
When building an application using the IAR ILINK Linker, the following types of
modules can be combined:
●

Modules produced using IAR build tools, both AEABI compliant modules as well
as modules that are not AEABI compliant

●

AEABI compliant modules produced using build tools from another vendor.

Note: To link a module produced by a compiler from another vendor, extra support
libraries from that vendor might be required.
The IAR ILINK Linker automatically chooses the appropriate standard C/C++ libraries
to use based on attributes from the object files. Imported object files might not have all
these attributes. Therefore, you might need to help ILINK choose the standard library
by verifying one or more of the following details:
●

The used cpu by specifying the --cpu linker option

●

If full I/O is needed; make sure to link with a Full library configuration in the
standard library

●

Explicitly specify runtime library file(s), possibly in combination with the
--no_library_search linker option.

LINKING AEABI COMPLIANT MODULES USING A LINKER
FROM A DIFFERENT VENDOR
If you have a module produced using the IAR C/C++ Compiler and you plan to link that
module using a linker from a different vendor, that module must be AEABI compliant,
see Enabling AEABI compliance in the compiler, page 124.
In addition, if that module uses any of the IAR-specific compiler extensions, you must
make sure that those features are also supported by the tools from the other vendor. Note
specifically:
●

Support for the following extensions must be verified: #pragma pack, __no_init,
__root, and __ramfunc

●

The following extensions are harmless to use: #pragma location/@, __arm,
__thumb, __swi, __irq, __fiq, and __nested.

ENABLING AEABI COMPLIANCE IN THE COMPILER
You can enable AEABI compliance in the compiler by setting the --aeabi option.
In the IDE, use the Project>Options>C/C++ Compiler>Extra Options page to
specify the --aeabi option.

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On the command line, use the option --aeabi to enable AEABI support in the
compiler.
Alternatively, to enable support for AEABI for a specific system header file, you must
define the preprocessor symbol _AEABI_PORTABILITY_LEVEL to non-zero prior to
including a system header file, and make sure that the symbol AEABI_PORTABLE is set
to non-zero after the inclusion of the header file:
#define _AEABI_PORTABILITY_LEVEL 1
#undef _AEABI_PORTABLE
#include 
#ifndef _AEABI_PORTABLE
#error "header.h not AEABI compatible"
#endif

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Efficient coding for
embedded applications
For embedded systems, the size of the generated code and data is very
important, because using smaller external memory or on-chip memory can
significantly decrease the cost and power consumption of a system.
The topics discussed are:
●

Selecting data types

●

Controlling data and function placement in memory

●

Controlling compiler optimizations

●

Facilitating good code generation.

As a part of this, the chapter also demonstrates some of the more common
mistakes and how to avoid them, and gives a catalog of good coding
techniques.

Selecting data types
For efficient treatment of data, you should consider the data types used and the most
efficient placement of the variables.

USING EFFICIENT DATA TYPES
The data types you use should be considered carefully, because this can have a large
impact on code size and code speed.
●

Use int or long instead of char or short whenever possible, to avoid sign
extension or zero extension. In particular, loop indexes should always be int or
long to minimize code generation. Also, in Thumb mode, accesses through the
stack pointer (SP) is restricted to 32-bit data types, which further emphasizes the
benefits of using one of these data types.

●

Use unsigned data types, unless your application really requires signed values.

●

Be aware of the costs of using 64-bit data types, such as double and long long.

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●

Bitfields and packed structures generate large and slow code.

●

Using floating-point types on a microprocessor without a math coprocessor is very
inefficient, both in terms of code size and execution speed.

●

Declaring a pointer to const data tells the calling function that the data pointed to
will not change, which opens for better optimizations.

For details about representation of supported data types, pointers, and structures types,
see the chapter Data representation.

FLOATING-POINT TYPES
Using floating-point types on a microprocessor without a math coprocessor is very
inefficient, both in terms of code size and execution speed. Thus, you should consider
replacing code that uses floating-point operations with code that uses integers, because
these are more efficient.
The compiler supports two floating-point formats—32 and 64 bits. The 32-bit
floating-point type float is more efficient in terms of code size and execution speed.
However, the 64-bit format double supports higher precision and larger numbers.
In the compiler, the floating-point type float always uses the 32-bit format, and the
type double always uses the 64-bit format. The format used by the double
floating-point type depends on the setting of the --double compiler option.
Unless the application requires the extra precision that 64-bit floating-point numbers
give, we recommend using 32-bit floating-point numbers instead.
By default, a floating-point constant in the source code is treated as being of the type
double. This can cause innocent-looking expressions to be evaluated in double
precision. In the example below a is converted from a float to a double, the double
constant 1.0 is added and the result is converted back to a float:
float Test(float a)
{
return a + 1.0;
}

To treat a floating-point constant as a float rather than as a double, add the suffix f
to it, for example:
float Test(float a)
{
return a + 1.0f;
}

For more information about floating-point types, see Floating-point types, page 213.

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ALIGNMENT OF ELEMENTS IN A STRUCTURE
The ARM core requires that data in memory must be aligned. Each element in a
structure must be aligned according to its specified type requirements. This means that
the compiler might need to insert pad bytes to keep the alignment correct.
There are two reasons why this can be considered a problem:
●

Due to external demands; for example, network communication protocols are
usually specified in terms of data types with no padding in between

●

You need to save data memory.

For information about alignment requirements, see Alignment, page 209.
There are two ways to solve the problem:
●

Use the #pragma pack directive or the __packed data type attribute for a tighter
layout of the structure. The drawback is that each access to an unaligned element in
the structure will use more code.

●

Write your own customized functions for packing and unpacking structures. This is
a more portable way, which will not produce any more code apart from your
functions. The drawback is the need for two views on the structure data—packed
and unpacked.

For further details about the #pragma pack directive, see pack, page 253.

ANONYMOUS STRUCTS AND UNIONS
When a structure or union is declared without a name, it becomes anonymous. The effect
is that its members will only be seen in the surrounding scope.
Anonymous structures are part of the C++ language; however, they are not part of the C
standard. In the IAR C/C++ Compiler for ARM they can be used in C if language
extensions are enabled.
In the IDE, language extensions are enabled by default.
Use the -e compiler option to enable language extensions. See -e, page 169, for
additional information.

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Example
In this example, the members in the anonymous union can be accessed, in function f,
without explicitly specifying the union name:
struct S
{
char mTag;
union
{
long mL;
float mF;
};
} St;
void F(void)
{
St.mL = 5;
}

The member names must be unique in the surrounding scope. Having an anonymous
struct or union at file scope, as a global, external, or static variable is also allowed.
This could for instance be used for declaring I/O registers, as in this example:
__no_init volatile
union
{
unsigned char IOPORT;
struct
{
unsigned char Way: 1;
unsigned char Out: 1;
};
} @ 0x1000;

/* Here the variables are used*/
void Test(void)
{
IOPORT = 0;
Way = 1;
Out = 1;
}

This declares an I/O register byte IOPORT at address 0. The I/O register has 2 bits
declared, Way and Out. Note that both the inner structure and the outer union are
anonymous.

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Anonymous structures and unions are implemented in terms of objects named after the
first field, with a prefix _A_ to place the name in the implementation part of the
namespace. In this example, the anonymous union will be implemented through an
object named _A_IOPORT.

Controlling data and function placement in memory
The compiler provides different mechanisms for controlling placement of functions and
data objects in memory. To use memory efficiently, you should be familiar with these
mechanisms to know which one is best suited for different situations. You can use:
●

The @ operator and the #pragma location directive for absolute placement
Use the @ operator or the #pragma location directive to place individual global and
static variables at absolute addresses. The variables must be declared __no_init.
This is useful for individual data objects that must be located at a fixed address, for
example variables with external requirements. Note that it is not possible to use this
notation for absolute placement of individual functions.

●

The @ operator and the #pragma location directive for section placement
Use the @ operator or the #pragma location directive to place groups of functions
or global and static variables in named sections, without having explicit control of
each object. The sections can, for example, be placed in specific areas of memory, or
initialized or copied in controlled ways using the section begin and end operators.
This is also useful if you want an interface between separately linked units, for
example an application project and a boot loader project. Use named sections when
absolute control over the placement of individual variables is not needed, or not
useful.

●

The --section option
Use the --section option to place functions and/or data objects in named sections,
which is useful, for example, if you want to direct them to different fast or slow
memories. To read more about the --section option, see --section, page 186.

At compile time, data and functions are placed in different sections as described in
Modules and sections, page 40. At link time, one of the most important functions of the
linker is to assign load addresses to the various sections used by the application. All
sections, except for the sections holding absolute located data, are automatically
allocated to memory according to the specifications in the linker configuration file, as
described in Placing code and data—the linker configuration file, page 42.

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DATA PLACEMENT AT AN ABSOLUTE LOCATION
The @ operator, alternatively the #pragma location directive, can be used for placing
global and static variables at absolute addresses. The variables must be declared using
one of these combinations of keywords:
●

__no_init

●

__no_init and const (without initializers).

To place a variable at an absolute address, the argument to the @ operator and the
#pragma location directive should be a literal number, representing the actual
address. The absolute location must fulfill the alignment requirement for the variable
that should be located.
Note: A variable placed in an absolute location should be defined in an include file, to
be included in every module that uses the variable. An unused definition in a module
will be ignored. A normal extern declaration—one that does not use an absolute
placement directive—can refer to a variable at an absolute address; however,
optimizations based on the knowledge of the absolute address cannot be performed.

Examples
In this example, a __no_init declared variable is placed at an absolute address. This
is useful for interfacing between multiple processes, applications, etc:
__no_init volatile char alpha @ 0x1000;/* OK */

This example contains a const declared object which is not initialized. The object is
placed in ROM. This is useful for configuration parameters, which are accessible from
an external interface.
#pragma location=0x1004
__no_init const int beta;

/* OK */

The actual value must be set by other means. The typical use is for configurations where
the values are loaded to ROM separately, or for special function registers that are
read-only.
These examples show incorrect usage:
int delta @ 0x100C;

/* Error, not __no_init */

__no_init int epsilon @ 0x1011;

/* Error, misaligned. */

C++ considerations
In C++, module scoped const variables are static (module local), whereas in C they are
global. This means that each module that declares a certain const variable will contain

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a separate variable with this name. If you link an application with several such modules
all containing (via a header file), for instance, the declaration:
volatile const __no_init int x @ 0x100;

/* Bad in C++ */

the linker will report that more than one variable is located at address 0x100.
To avoid this problem and make the process the same in C and C++, you should declare
these variables extern, for example:
/* The extern keyword makes x public. */
extern volatile const __no_init int x @ 0x100;

Note: C++ static member variables can be placed at an absolute address just like any
other static variable.

DATA AND FUNCTION PLACEMENT IN SECTIONS
The following methods can be used for placing data or functions in named sections other
than default:
●

The @ operator, alternatively the #pragma location directive, can be used for
placing individual variables or individual functions in named sections. The named
section can either be a predefined section, or a user-defined section.

●

The --section option can be used for placing variables and functions, which are
parts of the whole compilation unit, in named sections.

C++ static member variables can be placed in named sections just like any other static
variable.
If you use your own sections, in addition to the predefined sections, the sections must
also be defined in the linker configuration file.
Note: Take care when explicitly placing a variable or function in a predefined section
other than the one used by default. This is useful in some situations, but incorrect
placement can result in anything from error messages during compilation and linking to
a malfunctioning application. Carefully consider the circumstances; there might be strict
requirements on the declaration and use of the function or variable.
The location of the sections can be controlled from the linker configuration file.
For more information about sections, see the chapter Section reference.

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Examples of placing variables in named sections
In the following three examples, a data object is placed in a user-defined section.
__no_init int alpha @ "NOINIT";

/* OK */

#pragma location="CONSTANTS"
const int beta;

/* OK */

Examples of placing functions in named sections
void f(void) @ "FUNCTIONS";
void g(void) @ "FUNCTIONS"
{
}
#pragma location="FUNCTIONS"
void h(void);

Controlling compiler optimizations
The compiler performs many transformations on your application to generate the best
possible code. Examples of such transformations are storing values in registers instead
of memory, removing superfluous code, reordering computations in a more efficient
order, and replacing arithmetic operations by cheaper operations.
The linker should also be considered an integral part of the compilation system, because
some optimizations are performed by the linker. For instance, all unused functions and
variables are removed and not included in the final output.

SCOPE FOR PERFORMED OPTIMIZATIONS
You can decide whether optimizations should be performed on your whole application
or on individual files. By default, the same types of optimizations are used for an entire
project, but you should consider using different optimization settings for individual files.
For example, put code that must execute very quickly into a separate file and compile it
for minimal execution time, and the rest of the code for minimal code size. This will give
a small program, which is still fast enough where it matters.
You can also exclude individual functions from the performed optimizations. The
#pragma optimize directive allows you to either lower the optimization level, or
specify another type of optimization to be performed. Refer to optimize, page 252, for
information about the pragma directive.

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Multi-file compilation units
In addition to applying different optimizations to different source files or even functions,
you can also decide what a compilation unit consists of—one or several source code
files.
By default, a compilation unit consists of one source file, but you can also use multi-file
compilation to make several source files in a compilation unit. The advantage is that
interprocedural optimizations such as inlining and cross jump have more source code to
work on. Ideally, the whole application should be compiled as one compilation unit.
However, for large applications this is not practical because of resource restrictions on
the host computer. For more information, see --mfc, page 175.
If the whole application is compiled as one compilation unit, it is very useful to make
the compiler also discard unused public functions and variables before the
interprocedural optimizations are performed. Doing this limits the scope of the
optimizations to functions and variables that are actually used. For more information,
see --discard_unused_publics, page 168.

OPTIMIZATION LEVELS
The compiler supports different levels of optimizations. This table lists optimizations
that are typically performed on each level:
Optimization level

Description

None (Best debug support)

Variables live through their entire scope

Low

Same as above but variables only live for as long as they are
needed, not necessarily through their entire scope

Medium

Same as above, and:
Live-dead analysis and optimization
Dead code elimination
Redundant label elimination
Redundant branch elimination
Code hoisting
Peephole optimization
Some register content analysis and optimization
Static clustering
Common subexpression elimination

Table 19: Compiler optimization levels

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Optimization level

Description

High (Maximum optimization)

Same as above, and:
Instruction scheduling
Cross jumping
Advanced register content analysis and optimization
Loop unrolling
Function inlining
Code motion
Type-based alias analysis

Table 19: Compiler optimization levels (Continued)

Note: Some of the performed optimizations can be individually enabled or disabled.
For more information about these, see Fine-tuning enabled transformations, page 136.
A high level of optimization might result in increased compile time, and will most likely
also make debugging more difficult, because it is less clear how the generated code
relates to the source code. For example, at the low, medium, and high optimization
levels, variables do not live through their entire scope, which means processor registers
used for storing variables can be reused immediately after they were last used. Due to
this, the C-SPY Watch window might not be able to display the value of the variable
throughout its scope. At any time, if you experience difficulties when debugging your
code, try lowering the optimization level.

SPEED VERSUS SIZE
At the high optimization level, the compiler balances between size and speed
optimizations. However, it is possible to fine-tune the optimizations explicitly for either
size or speed. They only differ in what thresholds that are used; speed will trade size for
speed, whereas size will trade speed for size. Note that one optimization sometimes
enables other optimizations to be performed, and an application might in some cases
become smaller even when optimizing for speed rather than size.

FINE-TUNING ENABLED TRANSFORMATIONS
At each optimization level you can disable some of the transformations individually. To
disable a transformation, use either the appropriate option, for instance the command
line option --no_inline, alternatively its equivalent in the IDE Function inlining, or
the #pragma optimize directive. These transformations can be disabled individually:

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●

Common subexpression elimination

●

Loop unrolling

●

Function inlining

●

Code motion

●

Type-based alias analysis

Efficient coding for embedded applications

●

Static clustering

●

Instruction scheduling.

Common subexpression elimination
Redundant re-evaluation of common subexpressions is by default eliminated at
optimization levels Medium and High. This optimization normally reduces both code
size and execution time. However, the resulting code might be difficult to debug.
Note: This option has no effect at optimization levels None and Low.
To read more about the command line option, see --no_cse, page 177.

Loop unrolling
It is possible to duplicate the loop body of a small loop, whose number of iterations can
be determined at compile time, to reduce the loop overhead.
This optimization, which can be performed at optimization level High, normally
reduces execution time, but increases code size. The resulting code might also be
difficult to debug.
The compiler heuristically decides which loops to unroll. Different heuristics are used
when optimizing for speed, size, or when balancing between size and speed.
Note: This option has no effect at optimization levels None, Low, and Medium.
To read more about the command line option, see --no_unroll, page 180.

Function inlining
Function inlining means that a simple function, whose definition is known at compile
time, is integrated into the body of its caller to eliminate the overhead of the call. This
optimization, which is performed at optimization level High, normally reduces
execution time, but increases code size. The resulting code might also be difficult to
debug.
The compiler decides which functions to inline. Different heuristics are used when
optimizing for speed, size, or when balancing between size and speed.
Note: This option has no effect at optimization levels None, Low, and Medium.
To read more about the command line option, see --no_inline, page 178.

Code motion
Evaluation of loop-invariant expressions and common subexpressions are moved to
avoid redundant re-evaluation. This optimization, which is performed at optimization

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level High, normally reduces code size and execution time. The resulting code might
however be difficult to debug.
Note: This option has no effect at optimization levels None, and Low.

Type-based alias analysis
When two or more pointers reference the same memory location, these pointers are said
to be aliases for each other. The existence of aliases makes optimization more difficult
because it is not necessarily known at compile time whether a particular value is being
changed.
Type-based alias analysis optimization assumes that all accesses to an object are
performed using its declared type or as a char type. This assumption lets the compiler
detect whether pointers can reference the same memory location or not.
Type-based alias analysis is performed at optimization level High. For ISO/ANSI
standard-conforming C or C++ application code, this optimization can reduce code size
and execution time. However, non-standard-conforming C or C++ code might result in
the compiler producing code that leads to unexpected behavior. Therefore, it is possible
to turn this optimization off.
Note: This option has no effect at optimization levels None, Low, and Medium.
To read more about the command line option, see --no_tbaa, page 179.
Example
short F(short *p1, long *p2)
{
*p2 = 0;
*p1 = 1;
return *p2;
}

With type-based alias analysis, it is assumed that a write access to the short pointed to
by p1 cannot affect the long value that p2 points to. Thus, it is known at compile time
that this function returns 0. However, in non-standard-conforming C or C++ code these
pointers could overlap each other by being part of the same union. If you use explicit
casts, you can also force pointers of different pointer types to point to the same memory
location.

Static clustering
When static clustering is enabled, static and global variables that are defined within the
same module are arranged so that variables that are accessed in the same function are
stored close to each other. This makes it possible for the compiler to use the same base
pointer for several accesses.

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Note: This option has no effect at optimization levels None and Low.

Instruction scheduling
The compiler features an instruction scheduler to increase the performance of the
generated code. To achieve that goal, the scheduler rearranges the instructions to
minimize the number of pipeline stalls emanating from resource conflicts within the
microprocessor. Note that not all cores benefit from scheduling.
Note: This option has no effect at optimization levels None, Low and Medium.

Facilitating good code generation
This section contains hints on how to help the compiler generate good code, for
example:
●

Using efficient addressing modes

●

Helping the compiler optimize

●

Generating more useful error message.

WRITING OPTIMIZATION-FRIENDLY SOURCE CODE
The following is a list of programming techniques that will, when followed, enable the
compiler to better optimize the application.
●

Local variables—auto variables and parameters—are preferred over static or global
variables. The reason is that the optimizer must assume, for example, that called
functions can modify non-local variables. When the life spans for local variables
end, the previously occupied memory can then be reused. Globally declared
variables will occupy data memory during the whole program execution.

●

Avoid taking the address of local variables using the & operator. This is inefficient
for two main reasons. First, the variable must be placed in memory, and thus cannot
be placed in a processor register. This results in larger and slower code. Second, the
optimizer can no longer assume that the local variable is unaffected over function
calls.

●

Module-local variables—variables that are declared static—are preferred over
global variables. Also avoid taking the address of frequently accessed static
variables.

●

The compiler is capable of inlining functions. This means that instead of calling a
function, the compiler inserts the content of the function at the location where the
function was called. The result is a faster, but often larger, application. Also,
inlining might enable further optimizations. The compiler often inlines small
functions declared static. The use of the #pragma inline directive and the C++

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keyword inline gives you fine-grained control, and it is the preferred method
compared to the traditional way of using preprocessor macros. Too much inlining
can decrease performance due to the limited number of registers. This feature can be
disabled using the --no_inline command line option; see --no_inline, page 178.
●

Avoid using inline assembler. Instead, try writing the code in C or C++, use intrinsic
functions, or write a separate module in assembler language. For more details, see
Mixing C and assembler, page 91.

SAVING STACK SPACE AND RAM MEMORY
The following is a list of programming techniques that will, when followed, save
memory and stack space:
●

If stack space is limited, avoid long call chains and recursive functions.

●

Avoid using large non-scalar types, such as structures, as parameters or return type.
To save stack space, you should instead pass them as pointers or, in C++, as
references.

FUNCTION PROTOTYPES
It is possible to declare and define functions using one of two different styles:
●

Prototyped

●

Kernighan & Ritchie C (K&R C)

Both styles are included in the C standard; however, it is recommended to use the
prototyped style, since it makes it easier for the compiler to find problems in the code.
Using the prototyped style will also make it possible to generate more efficient code,
since type promotion (implicit casting) is not needed. The K&R style is only supported
for compatibility reasons.
To make the compiler verify that all functions have proper prototypes, use the compiler
option Require prototypes (--require_prototypes).

Prototyped style
In prototyped function declarations, the type for each parameter must be specified.
int Test(char, int); /* Declaration */
int Test(char ch, int i) /* Definition */
{
return i + ch;
}

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Kernighan & Ritchie style
In K&R style—traditional pre-ISO/ANSI C—it is not possible to declare a function
prototyped. Instead, an empty parameter list is used in the function declaration. Also,
the definition looks different.
For example:
int Test();

/* Declaration */

int Test(ch, i) /* Definition */
char ch;
int i;
{
return i + ch;
}

INTEGER TYPES AND BIT NEGATION
In some situations, the rules for integer types and their conversion lead to possibly
confusing behavior. Things to look out for are assignments or conditionals (test
expressions) involving types with different size, and logical operations, especially bit
negation. Here, types also includes types of constants.
In some cases there might be warnings (for example, for constant conditional or
pointless comparison), in others just a different result than what is expected. Under
certain circumstances the compiler might warn only at higher optimizations, for
example, if the compiler relies on optimizations to identify some instances of constant
conditionals. In this example an 8-bit character, a 32-bit integer, and two’s complement
is assumed:
void F1(unsigned char c1)
{
if (c1 == ~0x80)
;
}

Here, the test is always false. On the right hand side, 0x80 is 0x00000080, and
~0x00000080 becomes 0xFFFFFF7F. On the left hand side, c1 is an 8-bit unsigned
character, so it cannot be larger than 255. It also cannot be negative, which means that
the integral promoted value can never have the topmost 24 bits set.

PROTECTING SIMULTANEOUSLY ACCESSED VARIABLES
Variables that are accessed asynchronously, for example by interrupt routines or by code
executing in separate threads, must be properly marked and have adequate protection.
The only exception to this is a variable that is always read-only.

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To mark a variable properly, use the volatile keyword. This informs the compiler,
among other things, that the variable can be changed from other threads. The compiler
will then avoid optimizing on the variable (for example, keeping track of the variable in
registers), will not delay writes to it, and be careful accessing the variable only the
number of times given in the source code. To read more about the volatile type
qualifier, see Declaring objects volatile, page 218.

ACCESSING SPECIAL FUNCTION REGISTERS
Specific header files for several ARM devices are included in the IAR product
installation. The header files are named iodevice.h and define the processor-specific
special function registers (SFRs).
Note: Each header file contains one section used by the compiler, and one section used
by the assembler.
SFRs with bitfields are declared in the header file. This example is from
ioks32c5000a.h:
/* system configuration
typedef struct {
__REG32 se
:1;
__REG32 ce
:1;
__REG32 we
:1;
__REG32 cm
:2;
__REG32 isbp
:10;
__REG32 srbbp
:10;
__REG32
:6;
} __syscfg_bits;

register */
/* stall enable, must be 0 */
/* cache enable */
/* cache mode */
/* internal SRAM base pointer */
/* special register bank base pointer */

__IO_REG32_BIT(__SYSCFG,0x03FF0000,__READ_WRITE,__syscfg_bits);

By including the appropriate include file into the user code it is possible to access either
the whole register or any individual bit (or bitfields) from C code as follows:
/* whole register access */
__SYSCFG = 0x12345678;
/* Bitfield accesses */
__SYSCFG_bit.we = 1;
__SYSCFG_bit.cm = 3;

You can also use the header files as templates when you create new header files for other
ARM devices. For details about the @ operator, see Controlling data and function
placement in memory, page 131.

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Efficient coding for embedded applications

PASSING VALUES BETWEEN C AND ASSEMBLER OBJECTS
The following example shows how you in your C source code can use inline assembler
to set and get values from a special purpose register:
#pragma diag_suppress=Pe940
#pragma optimize=no_inline
static unsigned long get_APSR( void )
{
/* On function exit,
function return value should be present in R0 */
asm( "MRS R0, APSR" );
}
#pragma diag_default=Pe940
#pragma optimize=no_inline
static void set_APSR( unsigned long value)
{
/* On function entry, the first parameter is found in R0 */
asm( "MSR APSR, R0" );
}

The general purpose register R0 is used for getting and setting the value of the special
purpose register APSR. As the functions only contain inline assembler, the compiler will
not interfere with the register usage. The register R0 is always used for return values. The
first parameter is always passed in R0 if the type is 32 bits or smaller.
The same method can be used also for accessing other special purpose registers and
specific instructions.
To read more about the risks of using inline assembler, see Inline assembler, page 93.
For reference information about using inline assembler, see Inline assembler, page 225.
Note: Before you use inline assembler, see if you can use an intrinsic function instead.
See Summary of intrinsic functions, page 259.

NON-INITIALIZED VARIABLES
Normally, the runtime environment will initialize all global and static variables when the
application is started.
The compiler supports the declaration of variables that will not be initialized, using the
__no_init type modifier. They can be specified either as a keyword or using the
#pragma object_attribute directive. The compiler places such variables in a
separate section
For __no_init, the const keyword implies that an object is read-only, rather than that
the object is stored in read-only memory. It is not possible to give a __no_init object
an initial value.

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Facilitating good code generation

Variables declared using the __no_init keyword could, for example, be large input
buffers or mapped to special RAM that keeps its content even when the application is
turned off.
For information about the __no_init keyword, see page 239. Note that to use this
keyword, language extensions must be enabled; see -e, page 169. For information about
the #pragma object_attribute, see page 252.

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Part 2. Reference
information
This part of the IAR C/C++ Development Guide for ARM® contains these
chapters:
●

External interface details

●

Compiler options

●

Linker options

●

Data representation

●

Compiler extensions

●

Extended keywords

●

Pragma directives

●

Intrinsic functions

●

The preprocessor

●

Library functions

●

The linker configuration file

●

Section reference

●

IAR utilities

●

Implementation-defined behavior.

145

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External interface details
This chapter provides reference information about how the compiler and
linker interact with their environment. The chapter briefly lists and describes
the invocation syntax, methods for passing options to the tools, environment
variables, the include file search procedure, and finally the different types of
compiler and linker output.

Invocation syntax
You can use the compiler and linker either from the IDE or from the command line.
Refer to the IAR Embedded Workbench® IDE User Guide for ARM® for information
about using the build tools from the IDE.

COMPILER INVOCATION SYNTAX
The invocation syntax for the compiler is:
iccarm [options] [sourcefile] [options]

For example, when compiling the source file prog.c, use this command to generate an
object file with debug information:
iccarm prog.c --debug

The source file can be a C or C++ file, typically with the filename extension c or cpp,
respectively. If no filename extension is specified, the file to be compiled must have the
extension c.
Generally, the order of options on the command line, both relative to each other and to
the source filename, is not significant. There is, however, one exception: when you use
the -I option, the directories are searched in the same order that they are specified on the
command line.
If you run the compiler from the command line without any arguments, the compiler
version number and all available options including brief descriptions are directed to
stdout and displayed on the screen.

ILINK INVOCATION SYNTAX
The invocation syntax for ILINK is:
ilinkarm [arguments]

Each argument is either a command-line option, an object file, or a library.

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Invocation syntax

For example, when linking the object file prog.o, use this command:
ilinkarm prog.o --config configfile

If no filename extension is specified for the linker configuration file, the configuration
file must have the extension icf.
Generally, the order of arguments on the command line is not significant. There is,
however, one exception: when you supply several libraries, the libraries are searched in
the same order that they are specified on the command line. The default libraries are
always searched last.
The output executable image will be placed in a file named a.out, unless the -o option
is used.
If you run ILINK from the command line without any arguments, the ILINK version
number and all available options including brief descriptions are directed to stdout and
displayed on the screen.

PASSING OPTIONS
There are three different ways of passing options to the compiler and to ILINK:
●

Directly from the command line
Specify the options on the command line after the iccarm or ilinkarm commands;
see Invocation syntax, page 147.

●

Via environment variables
The compiler and linker automatically append the value of the environment variables
to every command line; see Environment variables, page 148.

●

Via a text file, using the -f option; see -f, page 171.

For general guidelines for the option syntax, an options summary, and a detailed
description of each option, see the Compiler options chapter.

ENVIRONMENT VARIABLES
These environment variables can be used with the compiler:
Environment variable Description

C_INCLUDE

Specifies directories to search for include files; for example:
C_INCLUDE=c:\program files\iar systems\embedded
workbench 5.n\arm\inc;c:\headers

QCCARM

Specifies command line options; for example: QCCARM=-lA asm.lst

Table 20: Compiler environment variables

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External interface details

This environment variable can be used with ILINK:
Environment variable

Description

ILINKARM_CMD_LINE

Specifies command line options; for example:
ILINKARM_CMD_LINE=--config full.icf
--silent

Table 21: ILINK environment variables

Include file search procedure
This is a detailed description of the compiler’s #include file search procedure:
●

If the name of the #include file is an absolute path, that file is opened.

●

If the compiler encounters the name of an #include file in angle brackets, such as:
#include 

it searches these directories for the file to include:
1 The directories specified with the -I option, in the order that they were
specified, see -I, page 173.
2 The directories specified using the C_INCLUDE environment variable, if any, see
Environment variables, page 148.
●

If the compiler encounters the name of an #include file in double quotes, for
example:
#include "vars.h"

it searches the directory of the source file in which the #include statement occurs,
and then performs the same sequence as for angle-bracketed filenames.
If there are nested #include files, the compiler starts searching the directory of the
file that was last included, iterating upwards for each included file, searching the
source file directory last. For example:
src.c in directory dir\src
#include "src.h"
...
src.h in directory dir\include
#include "config.h"
...

When dir\exe is the current directory, use this command for compilation:
iccarm ..\src\src.c -I..\include -I..\debugconfig

Then the following directories are searched in the order listed below for the file
config.h, which in this example is located in the dir\debugconfig directory:
dir\include

Current file is src.h.

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Compiler output

dir\src

File including current file (src.c).

dir\include

As specified with the first -I option.

dir\debugconfig

As specified with the second -I option.

Use angle brackets for standard header files, like stdio.h, and double quotes for files
that are part of your application.

Compiler output
The compiler can produce the following output:
●

A linkable object file
The object files produced by the compiler use the industry-standard format ELF. By
default, the object file has the filename extension o.

●

Optional list files
Various kinds of list files can be specified using the compiler option -l, see -l, page
173. By default, these files will have the filename extension lst.

●

Optional preprocessor output files
A preprocessor output file is produced when you use the --preprocess option; by
default, the file will have the filename extension i.

●

Diagnostic messages
Diagnostic messages are directed to the standard error stream and displayed on the
screen, and printed in an optional list file. To read more about diagnostic messages,
see Diagnostics, page 152.

●

Error return codes
These codes provide status information to the operating system which can be tested
in a batch file, see Error return codes, page 151.

●

Size information
Information about the generated amount of bytes for functions and data for each
memory is directed to the standard output stream and displayed on the screen. Some
of the bytes might be reported as shared.
Shared objects are functions or data objects that are shared between modules. If any
of these occur in more than one module, only one copy is retained. For example, in
some cases inline functions are not inlined, which means that they are marked as
shared, because only one instance of each function will be included in the final
application. This mechanism is sometimes also used for compiler-generated code or
data not directly associated with a particular function or variable, and when only one
instance is required in the final application.

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Error return codes
The compiler and linker return status information to the operating system that can be
tested in a batch file.
These command line error codes are supported:
Code

Description

0

Compilation or linking successful, but there might have been warnings.

1

Warnings were produced and the option --warnings_affect_exit_code was
used.

2

Errors occurred.

3

Fatal errors occurred, making the tool abort.

4

Internal errors occurred, making the tool abort.

Table 22: Error return codes

ILINK output
ILINK can produce the following output:
●

An absolute executable image
The final output produced by the IAR ILINK Linker is an absolute object file
containing the executable image that can be put into an EPROM, downloaded to a
hardware emulator, or executed on your PC using the IAR C-SPY Debugger
Simulator. By default, the file has the filename extension out. The output format is
always in ELF, which optionally includes debug information in the DWARF format.

●

Optional logging information
During operation, ILINK logs its decisions on stdout, and optionally to a file. For
example, if a library is searched, whether a required symbol is found in a library
module, or whether a module will be part of the output. Timing information for each
ILINK subsystem is also logged.

●

Optional map files
A linker map file—containing summaries of linkage, runtime attributes, memory,
and placement, as well as an entry list— can be generated by the ILINK option
--map, see --map, page 200. By default, the map file has the filename extension map.

●

Diagnostic messages
Diagnostic messages are directed to stderr and displayed on the screen, as well as
printed in the optional map file. To read more about diagnostic messages, see
Diagnostics, page 152.

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Diagnostics

●

Error return codes
ILINK returns status information to the operating system which can be tested in a
batch file, see Error return codes, page 151.

●

Size information about used memory and amount of time
Information about the generated amount of bytes for functions and data for each
memory is directed to stdout and displayed on the screen.

Diagnostics
This section describes the format of the diagnostic messages and explains how
diagnostic messages are divided into different levels of severity.

MESSAGE FORMAT FOR THE COMPILER
All diagnostic messages are issued as complete, self-explanatory messages. A typical
diagnostic message from the compiler is produced in the form:
filename,linenumber

level[tag]: message

with these elements:
filename

The name of the source file in which the issue was encountered

linenumber

The line number at which the compiler detected the issue

level

The level of seriousness of the issue

tag

A unique tag that identifies the diagnostic message

message

An explanation, possibly several lines long

Diagnostic messages are displayed on the screen, as well as printed in the optional list
file.
Use the option --diagnostics_tables to list all possible compiler diagnostic
messages.

MESSAGE FORMAT FOR THE LINKER
All diagnostic messages are issued as complete, self-explanatory messages. A typical
diagnostic message from ILINK is produced in the form:
level[tag]: message

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with these elements:
level

The level of seriousness of the issue

tag

A unique tag that identifies the diagnostic message

message

An explanation, possibly several lines long

Diagnostic messages are displayed on the screen, as well as printed in the optional map
file.
Use the option --diagnostics_tables to list all possible linker diagnostic messages.

SEVERITY LEVELS
The diagnostic messages are divided into different levels of severity:

Remark
A diagnostic message that is produced when the compiler or linker finds a construct that
can possibly lead to erroneous behavior in the generated code. Remarks are by default
not issued, but can be enabled, see --remarks, page 185.

Warning
A diagnostic message that is produced when the compiler or linker finds a problem
which is of concern, but not so severe as to prevent the completion of compilation or
linking. Warnings can be disabled by use of the command line option --no_warnings,
see page 181.

Error
A diagnostic message that is produced when the compiler or linker finds a serious error.
An error will produce a non-zero exit code.

Fatal error
A diagnostic message that is produced when the compiler finds a condition that not only
prevents code generation, but which makes further processing pointless. After the
message is issued, compilation terminates. A fatal error will produce a non-zero exit
code.

SETTING THE SEVERITY LEVEL
The diagnostic messages can be suppressed or the severity level can be changed for all
diagnostics messages, except for fatal errors and some of the regular errors.

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Diagnostics

See Summary of compiler options, page 158, for a description of the compiler options
that are available for setting severity levels.
For the compiler see also the chapter Pragma directives, for a description of the pragma
directives that are available for setting severity levels.

INTERNAL ERROR
An internal error is a diagnostic message that signals that there was a serious and
unexpected failure due to a fault in the compiler or linker. It is produced using this form:
Internal error: message

where message is an explanatory message. If internal errors occur, they should be
reported to your software distributor or IAR Systems Technical Support. Include enough
information to reproduce the problem, typically:

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●

The product name

●

The version number of the compiler or of ILINK, which can be seen in the header of
the list or map files generated by the compiler or by ILINK, respectively

●

Your license number

●

The exact internal error message text

●

The files involved of the application that generated the internal error

●

A list of the options that were used when the internal error occurred.

Compiler options
This chapter describes the syntax of compiler options and the general syntax
rules for specifying option parameters, and gives detailed reference
information about each option.

Options syntax
Compiler options are parameters you can specify to change the default behavior of the
compiler. You can specify options from the command line—which is described in more
detail in this section—and from within the IDE.
Refer to the IAR Embedded Workbench® IDE User Guide for ARM® for information
about the compiler options available in the IDE and how to set them.

TYPES OF OPTIONS
There are two types of names for command line options, short names and long names.
Some options have both.
●

A short option name consists of one character, and it can have parameters. You
specify it with a single dash, for example -e

●

A long option name consists of one or several words joined by underscores, and it
can have parameters. You specify it with double dashes, for example
--char_is_signed.

For information about the different methods for passing options, see Passing options,
page 148.

RULES FOR SPECIFYING PARAMETERS
There are some general syntax rules for specifying option parameters. First, the rules
depending on whether the parameter is optional or mandatory, and whether the option
has a short or a long name, are described. Then, the rules for specifying filenames and
directories are listed. Finally, the remaining rules are listed.

Rules for optional parameters
For options with a short name and an optional parameter, any parameter should be
specified without a preceding space, for example:
-O or -Oh

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Options syntax

For options with a long name and an optional parameter, any parameter should be
specified with a preceding equal sign (=), for example:
--misrac2004=n

Rules for mandatory parameters
For options with a short name and a mandatory parameter, the parameter can be
specified either with or without a preceding space, for example:
-I..\src or -I ..\src\

For options with a long name and a mandatory parameter, the parameter can be specified
either with a preceding equal sign (=) or with a preceding space, for example:
--diagnostics_tables=MyDiagnostics.lst

or
--diagnostics_tables MyDiagnostics.lst

Rules for options with both optional and mandatory parameters
For options taking both optional and mandatory parameters, the rules for specifying the
parameters are:
●

For short options, optional parameters are specified without a preceding space

●

For long options, optional parameters are specified with a preceding equal sign (=)

●

For short and long options, mandatory parameters are specified with a preceding
space.

For example, a short option with an optional parameter followed by a mandatory
parameter:
-lA MyList.lst

For example, a long option with an optional parameter followed by a mandatory
parameter:
--preprocess=n PreprocOutput.lst

Rules for specifying a filename or directory as parameters
These rules apply for options taking a filename or directory as parameters:
●

Options that take a filename as a parameter can optionally also take a path. The path
can be relative or absolute. For example, to generate a listing to the file List.lst
in the directory ..\listings\:
iccarm prog.c -l ..\listings\List.lst

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Compiler options

●

For options that take a filename as the destination for output, the parameter can be
specified as a path without a specified filename. The compiler stores the output in
that directory, in a file with an extension according to the option. The filename will
be the same as the name of the compiled source file, unless a different name was
specified with the option -o, in which case that name is used. For example:
iccarm prog.c -l ..\listings\

The produced list file will have the default name ..\listings\prog.lst
●

The current directory is specified with a period (.). For example:
iccarm prog.c -l .

●

/ can be used instead of \ as the directory delimiter.

●

By specifying -, input files and output files can be redirected to the standard input
and output stream, respectively. For example:
iccarm prog.c -l -

Additional rules
These rules also apply:
●

When an option takes a parameter, the parameter cannot start with a dash (-)
followed by another character. Instead, you can prefix the parameter with two
dashes; this example will create a list file called -r:
iccarm prog.c -l ---r

●

For options that accept multiple arguments of the same type, the arguments can be
provided as a comma-separated list (without a space), for example:
--diag_warning=Be0001,Be0002

Alternatively, the option can be repeated for each argument, for example:
--diag_warning=Be0001
--diag_warning=Be0002

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Summary of compiler options

Summary of compiler options
This table summarizes the compiler command line options:
Command line option

Description

--aapcs

Specifies the calling convention

--aeabi

Enables AEABI-compliant code generation

--align_sp_on_irq

Generates code to align SP on entry to __irq
functions

--arm

Sets the default function mode to ARM

--char_is_signed

Treats char as signed

--cpu

Specifies a processor variant

--cpu_mode

Selects the default mode for functions

-D

Defines preprocessor symbols

--debug

Generates debug information

--dependencies

Lists file dependencies

--diag_error

Treats these as errors

--diag_remark

Treats these as remarks

--diag_suppress

Suppresses these diagnostics

--diag_warning

Treats these as warnings

--diagnostics_tables

Lists all diagnostic messages

--discard_unused_publics

Discards unused public symbols

--dlib_config

Determines the library configuration file

-e

Enables language extensions

--ec++

Enables Embedded C++ syntax

--eec++

Enables Extended Embedded C++ syntax

--enable_hardware_workaround

Enables a specific hardware workaround

--enable_multibytes

Enables support for multibyte characters in source
files

--endian

Specifies the byte order of the generated code and
data

--enum_is_int

Sets the minimum size on enumeration types

--error_limit

Specifies the allowed number of errors before
compilation stops

-f

Extends the command line

Table 23: Compiler options summary

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Compiler options

Command line option

Description

--fpu

Selects the type of floating-point unit

--header_context

Lists all referred source files and header files

-I

Specifies include file path

--interwork

Generates interworking code

-l

Creates a list file

--legacy

Generates object code linkable with older tool
chains

--mfc

Enables multi file compilation

--migration_preprocessor
_extensions

Extends the preprocessor

--misrac1998

Enables error messages specific to MISRA-C:1998.
See the IAR Embedded Workbench® MISRA C:1998
Reference Guide.

--misrac2004

Enables error messages specific to MISRA-C:2004.
See the IAR Embedded Workbench® MISRA C:2004
Reference Guide.

--misrac_verbose

Enables verbose logging of MISRA C checking. See
the IAR Embedded Workbench® MISRA C:1998
Reference Guide or the IAR Embedded Workbench®
MISRA C:2004 Reference Guide.

--no_clustering

Disables static clustering optimizations

--no_code_motion

Disables code motion optimization

--no_const_align

Disables the alignment optimization for constants.

--no_cse

Disables common subexpression elimination

--no_fragments

Disables section fragment handling

--no_guard_calls

Disables guard calls for static initializers

--no_inline

Disables function inlining

--no_path_in_file_macros

Removes the path from the return value of the
symbols __FILE__ and __BASE_FILE__

--no_scheduling

Disables the instruction scheduler

--no_tbaa

Disables type-based alias analysis

--no_typedefs_in_diagnostics

Disables the use of typedef names in diagnostics

--no_unaligned_access

Avoids unaligned accesses

--no_unroll

Disables loop unrolling

Table 23: Compiler options summary (Continued)

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Descriptions of options

Command line option

Description

--no_warnings

Disables all warnings

--no_wrap_diagnostics

Disables wrapping of diagnostic messages

-O

Sets the optimization level

-o

Sets the object filename

--only_stdout

Uses standard output only

--output

Sets the object filename

--predef_macros

Lists the predefined symbols.

--preinclude

Includes an include file before reading the source
file

--preprocess

Generates preprocessor output

--public_equ

Defines a global named assembler label

-r

Generates debug information

--remarks

Enables remarks

--require_prototypes

Verifies that functions are declared before they are
defined

--section

Changes a section name

--separate_cluster_for_
initialized_variables

Separates initialized and non-initialized variables

--silent

Sets silent operation

--strict_ansi

Checks for strict compliance with ISO/ANSI C

--thumb

Sets default function mode to Thumb

--use_unix_directory_
separators

Uses / as directory separator in paths

--warnings_affect_exit_code

Warnings affects exit code

--warnings_are_errors

Warnings are treated as errors

Table 23: Compiler options summary (Continued)

Descriptions of options
The following section gives detailed reference information about each compiler option.
Note that if you use the options page Extra Options to specify specific command line
options, the IDE does not perform an instant check for consistency problems like
conflicting options, duplication of options, or use of irrelevant options.

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Compiler options

--aapcs
Syntax

--aapcs={std|vfp}

Parameters

Description

std

Processor registers are used for floating-point parameters and
return values in function calls according to standard AAPCS. std is
the default when the --aeabi compiler option is used or the
software FPU is selected. Note that this calling convention enables
guard calls.

vfp

VFP registers are used for floating-point parameters and return
values. The generated code is not compatible with AEABI code.
vfp is the default when a VFP is selected and --aeabi is not
used.

Use this option to specify the calling convention.
Project>Options>C/C++ Compiler>Extra Options.

--aeabi
Syntax

--aeabi

Description

Use this option to generate AEABI compliant object code.

See also

AEABI compliance, page 123 and --no_guard_calls, page 177.
Project>Options>C/C++ Compiler>Extra Options.

--align_sp_on_irq
Syntax

--align_sp_on_irq

Description

Use this option to align the stack pointer (SP) on entry to __irq declared functions.

See also

__irq, page 238.
Project>Options>C/C++ Compiler>Extra Options.

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Descriptions of options

--arm
Syntax

--arm

Description

Use this option to set default function mode to ARM. This setting must be the same for
all files included in a program, unless they are interworking.
Note: This option has the same effect as the --cpu_mode=arm option.

See also

--interwork, page 173 and __interwork, page 238.
Project>Options>General Options>Target>Processor mode>Arm

--char_is_signed
Syntax

--char_is_signed

Description

By default, the compiler interprets the char type as unsigned. Use this option to make
the compiler interpret the char type as signed instead. This can be useful when you, for
example, want to maintain compatibility with another compiler.
Note: The runtime library is compiled without the --char_is_signed option. If you
use this option, you might get type mismatch warnings from the linker, because the
library uses unsigned char.
Project>Options>C/C++ Compiler>Language>Plain ‘char’ is

--cpu
Syntax

--cpu=core

Parameters
core

Description

Use this option to select the processor variant for which the code is to be generated. The
default is ARM7TDMI. The following cores and processor macrocells are recognized:
●
●
●
●
●
●
●

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Specifies a specific processor variant

ARM7TDMI
ARM7TDMI-S
ARM710T
ARM720T
ARM740T
ARM7EJ-S
ARM9TDMI

Compiler options

●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
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●

*

See also

ARM920T
ARM922T
ARM940T
ARM9E
ARM9E-S
ARM926EJ-S
ARM946E-S
ARM966E-S
ARM968E-S
ARM10E
ARM1020E
ARM1022E
ARM1026EJ-S
ARM1136J
ARM1136J-S
ARM1136JF
ARM1136JF-S
ARM1176J
ARM1176J-S
ARM1176JF
ARM1176JF-S
Cortex-M0
Cortex-M1
Cortex-Ms1*
Cortex-M3
Cortex-R4
XScale
XScale-IR7.

Cortex-M1 with Operating System extension.

Processor variant, page 20.
Project>Options>General Options>Target>Processor configuration

--cpu_mode
Syntax

--cpu_mode={arm|a|thumb|t}

Parameters

Description

arm, a (default)

Selects the arm mode as the default mode for functions

thumb, t

Selects the thumb mode as the default mode for functions

Use this option to select the default mode for functions. This setting must be the same
for all files included in a program, unless they are interworking.

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See also

--interwork, page 173 and __interwork, page 238.
Project>Options>General Options>Target>Processor mode

-D
Syntax

-D symbol[=value]

Parameters

Description

symbol

The name of the preprocessor symbol

value

The value of the preprocessor symbol

Use this option to define a preprocessor symbol. If no value is specified, 1 is used. This
option can be used one or more times on the command line.
The option -D has the same effect as a #define statement at the top of the source file:
-Dsymbol

is equivalent to:
#define symbol 1

To get the equivalence of:
#define FOO

specify the = sign but nothing after, for example:
-DFOO=

Project>Options>C/C++ Compiler>Preprocessor>Defined symbols

--debug, -r
Syntax

--debug
-r

Description

Use the --debug or -r option to make the compiler include information in the object
modules required by the IAR C-SPY® Debugger and other symbolic debuggers.
Note: Including debug information will make the object files larger than otherwise.
Project>Options>C/C++ Compiler>Output>Generate debug information

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--dependencies
Syntax

--dependencies[=[i|m]] {filename|directory}

Parameters
i (default)

Lists only the names of files

m

Lists in makefile style

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.
Description

Use this option to make the compiler list all source and header files opened by the
compilation into a file with the default filename extension i.

Example

If --dependencies or --dependencies=i is used, the name of each opened source
file, including the full path, if available, is output on a separate line. For example:
c:\iar\product\include\stdio.h
d:\myproject\include\foo.h

If --dependencies=m is used, the output uses makefile style. For each source file, one
line containing a makefile dependency rule is produced. Each line consists of the name
of the object file, a colon, a space, and the name of a source file. For example:
foo.o: c:\iar\product\include\stdio.h
foo.o: d:\myproject\include\foo.h

An example of using --dependencies with a popular make utility, such as gmake
(GNU make):

1 Set up the rule for compiling files to be something like:
%.o : %.c
$(ICC) $(ICCFLAGS) $< --dependencies=m $*.d

That is, in addition to producing an object file, the command also produces a
dependency file in makefile style (in this example, using the extension .d).

2 Include all the dependency files in the makefile using, for example:
-include $(sources:.c=.d)

Because of the dash (-) it works the first time, when the .d files do not yet exist.
This option is not available in the IDE.

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--diag_error
Syntax

--diag_error=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe117

Use this option to reclassify certain diagnostic messages as errors. An error indicates a
violation of the C or C++ language rules, of such severity that object code will not be
generated. The exit code will be non-zero. This option may be used more than once on
the command line.
Project>Options>C/C++ Compiler>Diagnostics>Treat these as errors

--diag_remark
Syntax

--diag_remark=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe177

Use this option to reclassify certain diagnostic messages as remarks. A remark is the
least severe type of diagnostic message and indicates a source code construction that
may cause strange behavior in the generated code. This option may be used more than
once on the command line.
Note: By default, remarks are not displayed; use the --remarks option to display
them.
Project>Options>C/C++ Compiler>Diagnostics>Treat these as remarks

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--diag_suppress
Syntax

--diag_suppress=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe117

Use this option to suppress certain diagnostic messages. These messages will not be
displayed. This option may be used more than once on the command line.
Project>Options>C/C++ Compiler>Diagnostics>Suppress these diagnostics

--diag_warning
Syntax

--diag_warning=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe826

Use this option to reclassify certain diagnostic messages as warnings. A warning
indicates an error or omission that is of concern, but which will not cause the compiler
to stop before compilation is completed. This option may be used more than once on the
command line.
Project>Options>C/C++ Compiler>Diagnostics>Treat these as warnings

--diagnostics_tables
Syntax

--diagnostics_tables {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

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Description

Use this option to list all possible diagnostic messages in a named file. This can be
convenient, for example, if you have used a pragma directive to suppress or change the
severity level of any diagnostic messages, but forgot to document why.
This option cannot be given together with other options.
This option is not available in the IDE.

--discard_unused_publics
Syntax

--discard_unused_publics

Description

Use this option to discard unused public functions and variables from the compilation
unit. This enhances interprocedural optimizations such as inlining, cross call, and cross
jump by limiting their scope to public functions and variables that are actually used.
This option is only useful when all source files are compiled as one unit, which means
that the --mfc compiler option is used.
Note: Do not use this option only on parts of the application, as necessary symbols
might be removed from the generated output.

See also

--mfc, page 175 and Multi-file compilation units, page 135.
Project>Options>C/C++ Compiler>Discard unused publics

--dlib_config
Syntax

--dlib_config filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Each runtime library has a corresponding library configuration file. Use this option to
specify the library configuration file for the compiler. Make sure that you specify a
configuration file that corresponds to the library you are using.
All prebuilt runtime libraries are delivered with corresponding configuration files. You
can find the library object files and the library configuration files in the directory
arm\lib. For examples and a list of prebuilt runtime libraries, see Using a prebuilt
library, page 64.

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If you build your own customized runtime library, you should also create a
corresponding customized library configuration file, which must be specified to the
compiler. For more information, see Building and using a customized library, page 71.
To set related options, choose:
Project>Options>General Options>Library Configuration

-e
Syntax

-e

Description

In the command line version of the compiler, language extensions are disabled by
default. If you use language extensions such as extended keywords and anonymous
structs and unions in your source code, you must use this option to enable them.
Note: The -e option and the --strict_ansi option cannot be used at the same time.

See also

The chapter Compiler extensions.
Project>Options>C/C++ Compiler>Language>Allow IAR extensions
Note: By default, this option is enabled in the IDE.

--ec++
Syntax

--ec++

Description

In the compiler, the default language is C. If you use Embedded C++, you must use this
option to set the language the compiler uses to Embedded C++.
Project>Options>C/C++ Compiler>Language>Embedded C++

--eec++
Syntax

--eec++

Description

In the compiler, the default language is C. If you take advantage of Extended Embedded
C++ features like namespaces or the standard template library in your source code, you
must use this option to set the language the compiler uses to Extended Embedded C++.

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See also

Extended Embedded C++, page 108.
Project>Options>C/C++ Compiler>Language>Extended Embedded C++

--enable_hardware_workaround
Syntax

--enable_hardware_workaround=waid[,waid[...]]

Parameters
waid

The ID number of the workaround to enable. For a list of available
workarounds to enable, see the release notes.

Description

Use this option to make the compiler generate a workaround for a specific hardware
problem.

See also

The release notes for a list of available parameters.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--enable_multibytes
Syntax

--enable_multibytes

Description

By default, multibyte characters cannot be used in C or C++ source code. Use this option
to make multibyte characters in the source code be interpreted according to the host
computer’s default setting for multibyte support.
Multibyte characters are allowed in C and C++ style comments, in string literals, and in
character constants. They are transferred untouched to the generated code.
Project>Options>C/C++ Compiler>Language>Enable multibyte support

--endian
Syntax

--endian={big|b|little|l}

Parameters

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big, b

Specifies big endian as the default byte order

little, l (default)

Specifies little endian as the default byte order

Compiler options

Description

Use this option to specify the byte order of the generated code and data. By default, the
compiler generates code in little-endian byte order.

See also

Byte order, page 21, Byte order, page 210, --BE8, page 191, and --BE32, page 191.
Project>Options>General Options>Target>Endian mode

--enum_is_int
Syntax

--enum_is_int

Description

Use this option to force the size of all enumeration types to be at least 4 bytes.
Note: This option will not consider the fact that an enum type can be larger than an
integer type.

See also

The enum type, page 211.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--error_limit
Syntax

--error_limit=n

Parameters
n

Description

The number of errors before the compiler stops the compilation. n
must be a positive integer; 0 indicates no limit.

Use the --error_limit option to specify the number of errors allowed before the
compiler stops the compilation. By default, 100 errors are allowed.
This option is not available in the IDE.

-f
Syntax

-f filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

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Descriptions

Use this option to make the compiler read command line options from the named file,
with the default filename extension xcl.
In the command file, you format the items exactly as if they were on the command line
itself, except that you may use multiple lines, because the newline character acts just as
a space or tab character.
Both C and C++ style comments are allowed in the file. Double quotes behave in the
same way as in the Microsoft Windows command line environment.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--fpu
Syntax

--fpu={VFPv1|VFPv2|VFP9-S|none}

Parameters
VFPv1

For a vector floating-point unit conforming to the architecture
VFPv1.

VFPv2

For a system that implements a VFP unit conforming to the
architecture VFPv2.

VFP9-S

VFP9-S is an implementation of the VFPv2 architecture that can be
used with the ARM9E family of CPU cores. Selecting the VFP9-S
coprocessor is therefore identical to selecting the VFPv2
architecture.

none (default)

The software floating-point library is used.

Description

Use this option to generate code that carries out floating-point operations using a Vector
Floating Point (VFP) coprocessor. By selecting a VFP coprocessor, you will override the
use of the software floating-point library for all supported floating-point operations.

See also

VFP and floating-point arithmetic, page 21.
Project>Options>General Options>Target>FPU

--header_context
Syntax

--header_context

Description

Occasionally, to find the cause of a problem it is necessary to know which header file
that was included from which source line. Use this option to list, for each diagnostic

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message, not only the source position of the problem, but also the entire include stack at
that point.
This option is not available in the IDE.

-I
Syntax

-I path

Parameters
path

The search path for #include files

Description

Use this option to specify the search paths for #include files. This option can be used
more than once on the command line.

See also

Include file search procedure, page 149.
Project>Options>C/C++ Compiler>Preprocessor>Additional include directories

--interwork
Syntax

--interwork

Description

Use this option to generate interworking code.
In code compiled with this option, functions will by default be of the type interwork. It
will be possible to mix files compiled as arm and thumb (using the --cpu_mode option)
as long as they are all compiled with the --interwork option.
Note: Source code compiled for an ARM architecture v5 or higher, or AEABI
compliance is interworking by default.
Project>Options>General Options>Target>Generate interwork code

-l
Syntax

-l[a|A|b|B|c|C|D][N][H] {filename|directory}

Parameters
a (default)

Assembler list file

A

Assembler list file with C or C++ source as comments

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b

Basic assembler list file. This file has the same contents as a list file
produced with -la, except that no extra compiler-generated
information (runtime model attributes, call frame information, frame
size information) is included *

B

Basic assembler list file. This file has the same contents as a list file
produced with -lA, except that no extra compiler generated
information (runtime model attributes, call frame information, frame
size information) is included *

c

C or C++ list file

C (default)

C or C++ list file with assembler source as comments

D

C or C++ list file with assembler source as comments, but without
instruction offsets and hexadecimal byte values

N

No diagnostics in file

H

Include source lines from header files in output. Without this
option, only source lines from the primary source file are included

* This makes the list file less useful as input to the assembler, but more useful for reading by a
human.

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.
Description

Use this option to generate an assembler or C/C++ listing to a file. Note that this option
can be used one or more times on the command line.
To set related options, choose:
Project>Options>C/C++ Compiler>List

--legacy
Syntax

--legacy={mode}

Parameters
RVCT3.0

Description

Generates object code linkable with the linker in RVCT3.0. Use this
mode together with the --aeabi option to export code that
should be linked with the linker in RVCT3.0.

Use this option to generate code compatible with older tool chains.
Project>Options>C/C++ Compiler>Extra Options.

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--mfc
Syntax

--mfc

Description

Use this option to enable multi-file compilation. This means that the compiler compiles
one or several source files specified on the command line as one unit, which makes
interprocedural optimizations such as inlining, cross call, and cross jump possible.
Note: The compiler will generate one object file per input source code file, where the
first object file contains all relevant data and the other ones are empty. If you want only
the first file to be produced, use the -o compiler option and specify a certain output file.

Example

iccarm myfile1.c myfile2.c myfile3.c --mfc

See also

--discard_unused_publics, page 168, -o, --output, page 182, and Multi-file compilation
units, page 135.
Project>Options>C/C++ Compiler>Multi-file compilation

--migration_preprocessor_extensions
Syntax

--migration_preprocessor_extensions

Description

If you need to migrate code from an earlier IAR Systems C or C/C++ compiler, you
might want to use this option. Use this option to use the following in preprocessor
expressions:
●

Floating-point expressions

●

Basic type names and sizeof

●

All symbol names (including typedefs and variables).

Note: If you use this option, not only will the compiler accept code that does not
conform to the ISO/ANSI C standard, but it will also reject some code that does conform
to the standard.
Important! Do not depend on these extensions in newly written code, because support
for them might be removed in future compiler versions.
Project>Options>C/C++ Compiler>Language>Enable IAR migration
preprocessor extensions

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--no_clustering
Syntax

--no_clustering

Description

Use this option to disable static clustering optimizations. When static clustering is
enabled, static and global variables are arranged so that variables that are accessed in the
same function are stored close to each other. This makes it possible for the compiler to
use the same base pointer for several accesses. These optimizations, which are
performed at optimization levels Medium and High, normally reduce code size and
execution time.
Note: This option has no effect at optimization levels below Medium.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Static clustering

--no_code_motion
Syntax

--no_code_motion

Description

Use this option to disable code motion optimizations. These optimizations, which are
performed at the optimization levels Medium and High, normally reduce code size and
execution time. However, the resulting code might be difficult to debug.
Note: This option has no effect at optimization levels below Medium.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Code motion

--no_const_align
Syntax

--no_const_align

Description

By default, the compiler uses alignment 4 for objects with a size of 4 bytes or more. Use
this option to make the compiler align const objects based on the alignment of their
type.
For example, a string literal will get alignment 1, because it is an array with elements of
the type const char which has alignment 1. Using this option might save ROM space,
possibly at the expense of processing speed.

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See also

Alignment, page 209.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--no_cse
Syntax

--no_cse

Description

Use this option to disable common subexpression elimination. At the optimization
levels Medium and High, the compiler avoids calculating the same expression more than
once. This optimization normally reduces both code size and execution time. However,
the resulting code might be difficult to debug.
Note: This option has no effect at optimization levels below Medium.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Common subexpression elimination

--no_fragments
Syntax

--no_fragments

Description

Use this option to disable section fragment handling. Normally, the toolset uses IAR
proprietary information for transferring section fragment information to the linker. The
linker uses this information to remove unused code and data, and thus further minimize
the size of the executable image. The effect of using this option in the compiler is smaller
object size.

See also

Keeping symbols and sections, page 52.
To set this option, use Project>Options>C/C++ Compiler>Extra Options

--no_guard_calls
Syntax

--no_guard_calls

Description

If the --aeabi compiler option is used, the compiler produces extra library calls that
guard the initialization of static variables in file scope. These library calls are only
meaningful in an OS environment where you must make sure that these variables are not
initialized by another concurrent process at the same time.
Use this option to remove these library calls.

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Note: To be AEABI compliant, this option must not be used.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--no_inline
Syntax

--no_inline

Description

Use this option to disable function inlining. Function inlining means that a simple
function, whose definition is known at compile time, is integrated into the body of its
caller to eliminate the overhead of the call.
This optimization, which is performed at optimization level High, normally reduces
execution time and increases code size. The resulting code might also be difficult to
debug.
The compiler heuristically decides which functions to inline. Different heuristics are
used when optimizing for speed than for size.
Note: This option has no effect at optimization levels below High.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Function inlining

--no_path_in_file_macros
Syntax

--no_path_in_file_macros

Description

Use this option to exclude the path from the return value of the predefined preprocessor
symbols __FILE__ and __BASE_FILE__.

See also

Descriptions of predefined preprocessor symbols, page 284.
This option is not available in the IDE.

--no_scheduling
Syntax

--no_scheduling

Description

Use this option to disable the instruction scheduler. The compiler features an instruction
scheduler to increase the performance of the generated code. To achieve that goal, the
scheduler rearranges the instructions to minimize the number of pipeline stalls

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emanating from resource conflicts within the microprocessor. This optimization, which
is performed at optimization level High, normally reduce execution time. However, the
resulting code might be difficult to debug.
Note: This option has no effect at optimization levels below High.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Instruction scheduling

--no_tbaa
Syntax

--no_tbaa

Description

Use this option to disable type-based alias analysis. When this options is not used, the
compiler is free to assume that objects are only accessed through the declared type or
through unsigned char.

See also

Type-based alias analysis, page 138.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Type-based alias analysis

--no_typedefs_in_diagnostics
Syntax

--no_typedefs_in_diagnostics

Description

Use this option to disable the use of typedef names in diagnostics. Normally, when a
type is mentioned in a message from the compiler, most commonly in a diagnostic
message of some kind, the typedef names that were used in the original declaration are
used whenever they make the resulting text shorter.

Example

typedef int (*MyPtr)(char const *);
MyPtr p = "foo";

will give an error message like this:
Error[Pe144]: a value of type "char *" cannot be used to
initialize an entity of type "MyPtr"

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If the --no_typedefs_in_diagnostics option is used, the error message will be like
this:
Error[Pe144]: a value of type "char *" cannot be used to
initialize an entity of type "int (*)(char const *)"

To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--no_unaligned_access
Syntax

--no_unaligned_access

Description

Use this option to make the compiler avoid unaligned accesses. Data accesses are
usually performed aligned for improved performance. However, some accesses, most
notably when reading from or writing to packed data structures, may be unaligned.
When using this option, all such accesses will be performed using a smaller data size to
avoid any unaligned accesses. This option is only useful for ARMv6 architectures and
higher.

See also

--interwork, page 173 and __interwork, page 238.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--no_unroll
Syntax

--no_unroll

Description

Use this option to disable loop unrolling. The code body of a small loop, whose number
of iterations can be determined at compile time, is duplicated to reduce the loop
overhead.
For small loops, the overhead required to perform the looping can be large compared
with the work performed in the loop body.
The loop unrolling optimization duplicates the body several times, reducing the loop
overhead. The unrolled body also opens up for other optimization opportunities.
This optimization, which is performed at optimization level High, normally reduces
execution time, but increases code size. The resulting code might also be difficult to
debug.
The compiler heuristically decides which loops to unroll. Different heuristics are used
when optimizing for speed and size.

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Note: This option has no effect at optimization levels below High.
Project>Options>C/C++ Compiler>Optimizations>Enable
transformations>Loop unrolling

--no_warnings
Syntax

--no_warnings

Description

By default, the compiler issues warning messages. Use this option to disable all warning
messages.
This option is not available in the IDE.

--no_wrap_diagnostics
Syntax

--no_wrap_diagnostics

Description

By default, long lines in diagnostic messages are broken into several lines to make the
message easier to read. Use this option to disable line wrapping of diagnostic messages.
This option is not available in the IDE.

-O
Syntax

-O[n|l|m|h|hs|hz]

Parameters
n

None* (Best debug support)

l (default)

Low*

m

Medium

h

High, balanced

hs

High, favoring speed

hz

High, favoring size

*The most important difference between None and Low is that at None, all non-static variables
will live during their entire scope.

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Description

Use this option to set the optimization level to be used by the compiler when optimizing
the code. If no optimization option is specified, the optimization level Low is used by
default. If only -O is used without any parameter, the optimization level High balanced
is used.
A low level of optimization makes it relatively easy to follow the program flow in the
debugger, and, conversely, a high level of optimization makes it relatively hard.

See also

Controlling compiler optimizations, page 134.
Project>Options>C/C++ Compiler>Optimizations

-o, --output
Syntax

-o {filename|directory}
--output {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Description

By default, the object code output produced by the compiler is located in a file with the
same name as the source file, but with the extension o. Use this option to explicitly
specify a different output filename for the object code output.
This option is not available in the IDE.

--only_stdout
Syntax

--only_stdout

Description

Use this option to make the compiler use the standard output stream (stdout) also for
messages that are normally directed to the error output stream (stderr).
This option is not available in the IDE.

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--output, -o
Syntax

--output {filename|directory}
-o {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Description

By default, the object code output produced by the compiler is located in a file with the
same name as the source file, but with the extension o. Use this option to explicitly
specify a different output filename for the object code output.
This option is not available in the IDE.

--predef_macros
Syntax

--predef_macros {filename|directory}

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Use this option to list the predefined symbols. When using this option, make sure to also
use the same options as for the rest of your project.
If a filename is specified, the compiler stores the output in that file. If a directory is
specified, the compiler stores the output in that directory, in a file with the predef
filename extension.
Note that this option requires that you specify a source file on the command line.
This option is not available in the IDE.

--preinclude
Syntax

--preinclude includefile

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

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Descriptions of options

Description

Use this option to make the compiler include the specified include file before it starts to
read the source file. This is useful if you want to change something in the source code
for the entire application, for instance if you want to define a new symbol.
Project>Options>C/C++ Compiler>Preprocessor>Preinclude file

--preprocess
Syntax

--preprocess[=[c][n][l]] {filename|directory}

Parameters
c

Preserve comments

n

Preprocess only

l

Generate #line directives

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.
Description

Use this option to generate preprocessed output to a named file.
Project>Options>C/C++ Compiler>Preprocessor>Preprocessor output to file

--public_equ
Syntax

--public_equ symbol[=value]

Parameters

Description

symbol

The name of the assembler symbol to be defined

value

An optional value of the defined assembler symbol

This option is equivalent to defining a label in assembler language using the EQU
directive and exporting it using the PUBLIC directive. This option can be used more than
once on the command line.
This option is not available in the IDE.

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Compiler options

-r, --debug
Syntax

-r
--debug

Description

Use the -r or the --debug option to make the compiler include information in the
object modules required by the IAR C-SPY Debugger and other symbolic debuggers.
Note: Including debug information will make the object files larger than otherwise.
Project>Options>C/C++ Compiler>Output>Generate debug information

--remarks
Syntax

--remarks

Description

The least severe diagnostic messages are called remarks. A remark indicates a source
code construct that may cause strange behavior in the generated code. By default, the
compiler does not generate remarks. Use this option to make the compiler generate
remarks.

See also

Severity levels, page 153.
Project>Options>C/C++ Compiler>Diagnostics>Enable remarks

--require_prototypes
Syntax

--require_prototypes

Description

Use this option to force the compiler to verify that all functions have proper prototypes.
Using this option means that code containing any of the following will generate an error:
●

A function call of a function with no declaration, or with a Kernighan & Ritchie
C declaration

●

A function definition of a public function with no previous prototype declaration

●

An indirect function call through a function pointer with a type that does not include
a prototype.

Note: This option only applies to functions in the C standard library.
Project>Options>C/C++ Compiler>Language>Require prototypes

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Descriptions of options

--section
Syntax

--section OldName=NewName

Description

The compiler places functions and data objects into named sections which are referred
to by the IAR ILINK Linker. Use this option to change the name of the section OldName
to NewName.
This is useful if you want to place your code or data in different address ranges and you
find the @ notation, alternatively the #pragma location directive, insufficient. Note
that any changes to the section names require corresponding modifications in the linker
configuration file.

Example

To place functions in the section MyText, use:
--section .text=MyText

See also

For information about the different methods for controlling placement of data and code,
see Controlling data and function placement in memory, page 131.
Project>Options>C/C++ Compiler>Output>Code section name

--separate_cluster_for_initialized_variables
Syntax

--separate_cluster_for_initialized_variables

Description

Use this option to separate initialized and non-initialized variables when using variable
clustering. This might reduce the number of bytes in the ROM area which are needed
for data initialization, but it might lead to larger code.
This option can be useful if you want to have your own data initialization routine, but
want the IAR tools to arrange for the zero-initialized variables.

See also

Manual initialization, page 54 and Initialize directive, page 305.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

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Compiler options

--silent
Syntax

--silent

Description

By default, the compiler issues introductory messages and a final statistics report. Use
this option to make the compiler operate without sending these messages to the standard
output stream (normally the screen).
This option does not affect the display of error and warning messages.
This option is not available in the IDE.

--strict_ansi
Syntax

--strict_ansi

Description

By default, the compiler accepts a relaxed superset of ISO/ANSI C/C++, see Minor
language extensions, page 228. Use this option to ensure that the program conforms to
the ISO/ANSI C/C++ standard.
Note: The -e option and the --strict_ansi option cannot be used at the same time.
Project>Options>C/C++ Compiler>Language>Language conformances>Strict
ISO/ANSI

--thumb
Syntax

--thumb

Description

Use this option to set default function mode to Thumb. This setting must be the same for
all files included in a program, unless they are interworking.
Note: This option has the same effect as the --cpu_mode=thumb option.

See also

--interwork, page 173 and __interwork, page 238.
Project>Options>General Options>Target>Processor mode>Arm

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Descriptions of options

--use_unix_directory_separators
Syntax

--use_unix_directory_separators

Description

Use this option to make DWARF debug information use / (instead of \) as directory
separators in paths.
This option can be useful if you have a debugger that requires directory separators in
UNIX style.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--warnings_affect_exit_code
Syntax

--warnings_affect_exit_code

Description

By default, the exit code is not affected by warnings, because only errors produce a
non-zero exit code. With this option, warnings will also generate a non-zero exit code.
This option is not available in the IDE.

--warnings_are_errors
Syntax

--warnings_are_errors

Description

Use this option to make the compiler treat all warnings as errors. If the compiler
encounters an error, no object code is generated. Warnings that have been changed into
remarks are not treated as errors.
Note: Any diagnostic messages that have been reclassified as warnings by the option
--diag_warning or the #pragma diag_warning directive will also be treated as
errors when --warnings_are_errors is used.

See also

--diag_warning, page 225.
Project>Options>C/C++ Compiler>Diagnostics>Treat all warnings as errors

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Linker options
This chapter gives detailed reference information about each linker option.
For general syntax rules, see Options syntax, page 155.

Summary of linker options
This table summarizes the linker options:
Command line option

Description

--BE8

Uses the big-endian format BE8

--BE32

Uses the big-endian format BE32

--config

Specifies the linker configuration file to be used by
the linker

--config_def

Defines symbols for the configuration file

--cpp_init_routine

Specifies a user-defined C++ dynamic initialization
routine

--cpu

Specifies a processor variant

--define_symbol

Defines symbols that can be used by the application

--diag_error

Treats these message tags as errors

--diag_remark

Treats these message tags as remarks

--diag_suppress

Suppresses these diagnostic messages

--diag_warning

Treats these message tags as warnings

--diagnostics_tables

Lists all diagnostic messages

--entry

Treats the symbol as a root symbol and as the start
of the application

--error_limit

Specifies the allowed number of errors before
compilation stops

--export_builtin_config

Produces an icf file for the default configuration

-f

Extends the command line

--force_output

Produces an output file even if errors occurred

--image_input

Puts an image file in a section

--keep

Forces a symbol to be included in the application

--log

Enables log output for selected topics

Table 24: Linker options summary

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Summary of linker options

Command line option

Description

--log_file

Directs the log to a file

--mangled_names_in_messages

Adds mangled names in messages

--map

Produces a map file

--misrac1998

Enables error messages specific to MISRA-C:1998.
See the IAR Embedded Workbench® MISRA C:1998
Reference Guide.

--misrac2004

Enables error messages specific to MISRA-C:2004.
See the IAR Embedded Workbench® MISRA C:2004
Reference Guide.

--misrac_verbose

Enables verbose logging of MISRA C checking. See
the IAR Embedded Workbench® MISRA C:1998
Reference Guide and the IAR Embedded Workbench®
MISRA C:2004 Reference Guide.

--no_fragments

Disables section fragment handling

--no_library_search

Disables automatic runtime library search

--no_locals

Removes local symbols from the ELF executable
image.

--no_remove

Disables removal of unused sections

--no_veneers

Disables generation of veneers

--no_warnings

Disables generation of warnings

--no_wrap_diagnostics

Does not wrap long lines in diagnostic messages

-o

Sets the object filename

--only_stdout

Uses standard output only

--ose_load_module

Produces an OSE load module image

--output

Sets the object filename

--pi_veneers

Generates position independent veneers.

--place_holder

Reserve a place in ROM to be filled by some other
tool, for example a checksum calculated by
ielftool.

--redirect

Redirects a reference to a symbol to another
symbol

--remarks

Enables remarks

--semihosting

Links with debug interface

--silent

Sets silent operation

Table 24: Linker options summary (Continued)

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Linker options

Command line option

Description

--strip

Removes debug information from the executable
image

--warnings_are_errors

Warnings are treated as errors

--warnings_affect_exit_code

Warnings affects exit code

Table 24: Linker options summary (Continued)

Descriptions of options
The following section gives detailed reference information about each compiler and
linker option.
Note that if you use the options page Extra Options to specify specific command line
options, the IDE does not perform an instant check for consistency problems like
conflicting options, duplication of options, or use of irrelevant options.

--BE8
Syntax

--BE8

Description

Use this option to specify the Byte Invariant Addressing mode.
This means that the linker reverses the byte order of the instructions, resulting in
little-endian code and big-endian data. This is the default byte addressing mode for
ARMv6 big-endian images. This is the only mode available for ARM v6M and ARM
v7 with big-endian images.
Byte Invariant Addressing mode is only available on ARM processors that support
ARMv6, ARM v6M, and ARM v7.

See also

Byte order, page 21, Byte order, page 210, --BE32, page 191, and --endian, page 170.
Project>Options>General Options>Target>Endian mode

--BE32
Syntax

--BE32

Description

Use this option to specify the legacy big-endian mode.

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Descriptions of options

This produces big-endian code and data. This is the only byte-addressing mode for all
big-endian images prior to ARMv6. This mode is also available for ARM v6 with
big-endian, but not for ARM v6M or ARM v7.
See also

Byte order, page 21, Byte order, page 210, --BE8, page 191, and --endian, page 170.
Project>Options>General Options>Target>Endian mode

--config
Syntax

--config filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Use this option to specify the configuration file to be used by the linker (the default
filename extension is icf). If no configuration file is specified, a default configuration
is used. This option can only be used once on the command line.

See also

The chapter The linker configuration file.
Project>Options>Linker>Config>Linker configuration file

--config_def
Syntax

--config_def symbol[=constant_value]

Parameters
symbol

The name of the symbol to be used in the configuration file. By
default, the value 0 (zero) is used.

constant_value

The constant value of the configuration symbol.

Description

Use this option to define a constant configuration symbol to be used in the configuration
file. This option has the same effect as the define symbol directive in the linker
configuration file. This option can be used more that once on the command line.

See also

--define_symbol, page 193 and Interaction between ILINK and the application, page 56.
Project>Options>Linker>Config>Defined symbols for configuration file

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Linker options

--cpp_init_routine
Syntax

--cpp_init_routine routine

Parameters
routine

Description

A user-defined C++ dynamic initialization routine.

When using the IAR C/C++ compiler and the standard library, C++ dynamic
initialization is handled automatically. In other cases you might need to use this option.
If any sections with the section type INIT_ARRAY or PREINIT_ARRAY are included in
your application, the C++ dynamic initialization routine is considered to be needed. By
default, this routine is named __iar_cstart_call_ctors and is called by the startup
code in the standard library. Use this option if you are not using the standard library and
require another routine to handle these section types.
To set this option, use Project>Options>Linker>Extra Options.

--cpu
Syntax

--cpu=core

Parameters
core

Specifies a specific processor variant

Description

Use this option to select the processor variant for which the code is to be generated. The
default is ARM7TDMI.

See also

--cpu, page 162 for a list of recognized cores and processor macrocells.
Project>Options>General Options>Target>Processor configuration

--define_symbol
Syntax

--define_symbol symbol[=constant_value]

Parameters
symbol

The name of the constant symbol that can be used by the
application. By default, the value 0 (zero) is used.

constant_value

The constant value of the symbol.

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Descriptions of options

Description

Use this option to define a constant symbol that can be used by your application. If no
value is specified, 0 is used. This option can be used more than once on the command
line. Note that his option is different from the define symbol directive.

See also

--config_def, page 192 and Interaction between ILINK and the application, page 56.
Project>Options>Linker>#define>Defined symbols

--diag_error
Syntax

--diag_error=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe117

Use this option to reclassify certain diagnostic messages as errors. An error indicates a
violation of the C or C++ language rules, of such severity that a violation of the linking
rules of such severity that an executable image will not be generated. The exit code will
be non-zero. This option may be used more than once on the command line.
Project>Options>Linker>Diagnostics>Treat these as errors

--diag_remark
Syntax

--diag_remark=tag[,tag,...]

Parameters
tag

Description

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The number of a diagnostic message, for example the message
number Pe177

Use this option to reclassify certain diagnostic messages as remarks. A remark is the
least severe type of diagnostic message and indicates a construction that may cause
strange behavior in the executable image. This option may be used more than once on
the command line.

Linker options

Note: By default, remarks are not displayed; use the --remarks option to display
them.
Project>Options>Linker>Diagnostics>Treat these as remarks

--diag_suppress
Syntax

--diag_suppress=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe117

Use this option to suppress certain diagnostic messages. These messages will not be
displayed. This option may be used more than once on the command line.
Project>Options>Linker>Diagnostics>Suppress these diagnostics

--diag_warning
Syntax

--diag_warning=tag[,tag,...]

Parameters
tag

Description

The number of a diagnostic message, for example the message
number Pe826

Use this option to reclassify certain diagnostic messages as warnings. A warning
indicates an error or omission that is of concern, but which will not cause the linker to
stop before linking is completed. This option may be used more than once on the
command line.
Project>Options>Linker>Diagnostics>Treat these as warnings

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Descriptions of options

--diagnostics_tables
Syntax

--diagnostics_tables {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Description

Use this option to list all possible diagnostic messages in a named file.
This option cannot be given together with other options.
This option is not available in the IDE.

--entry
Syntax

--entry symbol

Parameters
symbol

Description

The name of the symbol to be treated as a root symbol and start
label

Use this option to make a symbol be treated as a root symbol and the start label of the
application. This is useful for loaders. If this option is not used, the default start symbol
is __iar_program_start. A root symbol is kept whether or not it is referenced from
the rest of the application, provided its module is included. A module in an object file is
always included and a module part of a library is only included if needed.
Project>Options>Linker>Library>Override default program entry

--error_limit
Syntax

--error_limit=n

Parameters
n

Description

The number of errors before the linker stops linking. n must be a
positive integer; 0 indicates no limit.

Use the --error_limit option to specify the number of errors allowed before the
linker stops the linking. By default, 100 errors are allowed.
This option is not available in the IDE.

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Linker options

--export_builtin_config
Syntax

--export_builtin_config filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Exports the configuration used by default to a file.
This option is not available in the IDE.

-f
Syntax

-f filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Descriptions

Use this option to make the linker read command line options from the named file, with
the default filename extension xcl.
In the command file, you format the items exactly as if they were on the command line
itself, except that you may use multiple lines, because the newline character acts just as
a space or tab character.
Both C and C++ style comments are allowed in the file. Double quotes behave in the
same way as in the Microsoft Windows command line environment.
To set this option, use Project>Options>Linker>Extra Options.

--force_output
Syntax

--force_output

Description

Use this option to produce an output executable image regardless of any linking errors.
To set this option, use Project>Options>Linker>Extra Options

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Descriptions of options

--image_input
Syntax

--image_input filename [symbol,[section[,alignment]]]

Parameters

Description

filename

The pure binary file containing the raw image you want to link

symbol

The symbol which the binary data can be referenced with.

section

The section where the binary data will be placed; default is .text.

alignment

The alignment of the section; default is 1.

Use this option to link pure binary files in addition to the ordinary input files. The file’s
entire contents are placed in the section, which means it can only contain pure binary
data.
The section where the contents of the filename file are placed, is only included if the
symbol symbol is required by your application. Use the --keep option if you want to
force a reference to the section.

Example

--image_input bootstrap.abs,Bootstrap,CSTARTUPCODE,4

The contents of the pure binary file bootstrap.abs are placed in the section
CSTARTUPCODE. The section where the contents are placed is 4-byte aligned and will
only be included if your application (or the command line option --keep) includes a
reference to the symbol Bootstrap.
See also

--keep, page 198.
Project>Options>Linker>Input>Raw binary image

--keep
Syntax

--keep symbol

Parameters
symbol

Description

The name of the symbol to be treated as a root symbol

Normally, the linker keeps a symbol only if it is needed by your application. Use this
option to make a symbol always be included in the final application.
Project>Options>Linker>Input>Keep symbols

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Linker options

--log
Syntax

--log topic,topic,...

Parameters
initialization

Log initialization decisions

modules

Log module selections

sections

Log section selections

Description

Use this option to make the linker log information to stdout. The log information can
be useful for understanding why an executable image became the way it is.

See also

--log_file, page 199.
Project>Options>Linker>List>Generate log

--log_file
Syntax

--log_file filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Use this option to direct the log output to the specified file.

See also

--log, page 199.
Project>Options>Linker>List>Generate log

--mangled_names_in_messages
Syntax

--mangled_names_in_messages

Descriptions

Use this option to produce both mangled and unmangled names for C/C++ symbols in
messages. Mangling is a technique used for mapping a complex C name or a C++ name
(for example, for overloading) into a simple name. For example, void h(int, char)
becomes _Z1hic.
This option is not available in the IDE.

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--map
Syntax

--map {filename|directory}

Description

Use this option to produce a linker memory map file. The map file has the default
filename extension map. The map file contains:
●

Linking summary in the map file header which lists the version of the linker, the
current date and time, and the command line that was used.

●

Runtime attribute summary which lists AEABI attributes and IAR-specific runtime
attributes.

●

Placement summary which lists each section/block in address order, sorted by
placement directives.

●

Initialization table layout which lists the data ranges, packing methods, and
compression ratios.

●

Module summary which lists contributions from each module to the image, sorted
by directory and library.

●

Entry list which lists all public and some local symbols in alphabetical order,
indicating which module they came from.

●

Some of the bytes might be reported as shared.
Shared objects are functions or data objects that are shared between modules. If any
of these occur in more than one module, only one copy is retained. For example, in
some cases inline functions are not inlined, which means that they are marked as
shared, because only one instance of each function will be included in the final
application. This mechanism is sometimes also used for compiler-generated code or
data not directly associated with a particular function or variable, and when only one
instance is required in the final application.

This option can only be used once on the command line.
Project>Options>Linker>List>Generate linker map file

--no_fragments
Syntax

--no_fragments

Description

Use this option to disable section fragment handling. Normally, the toolset uses IAR
proprietary information for transferring section fragment information to the linker. The
linker uses this information to remove unused code and data, and thus further minimize
the size of the executable image.

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Linker options

See also

Keeping symbols and sections, page 52.
To set this option, use Project>Options>Linker>Extra Options

--no_library_search
Syntax

--no_library_search

Description

Use this option to disable the automatic runtime library search. This option turns off the
automatic inclusion of the correct standard libraries. This is useful, for example, if the
application needs a user-built standard library, etc.
Project>Options>Linker>Library>Automatic runtime library selection

--no_locals
Syntax

--no_locals

Description

Use this option to remove local symbols from the ELF executable image.
Note: This option does not remove any local symbols from the DWARF information
in the executable image.
Project>Options>Linker>Output

--no_remove
Syntax

--no_remove

Description

When this option is used, unused sections are not removed. In other words, each module
that is included in the executable image contains all its original sections.

See also

Keeping symbols and sections, page 52.
To set this option, use Project>Options>Linker>Extra Options

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Descriptions of options

--no_veneers
Syntax

--no_veneers

Description

Use this option to disable the insertion of veneers even though the executable image
needs it. In this case, the linker will generate a relocation error for each reference that
needs a veneer.

See also

Veneers, page 57.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--no_warnings
Syntax

--no_warnings

Description

By default, the linker issues warning messages. Use this option to disable all warning
messages.
This option is not available in the IDE.

--no_wrap_diagnostics
Syntax

--no_wrap_diagnostics

Description

By default, long lines in diagnostic messages are broken into several lines to make the
message easier to read. Use this option to disable line wrapping of diagnostic messages.
This option is not available in the IDE.

-o, --output
Syntax

-o {filename|directory}
--output {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

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Linker options

Description

By default, the object executable image produced by the linker is located in a file with
the name a.out. Use this option to explicitly specify a different output filename, which
by default will have the filename extension out.
Project>Options>Linker>Output>Output file

--only_stdout
Syntax

--only_stdout

Description

Use this option to make the linker use the standard output stream (stdout) also for
messages that are normally directed to the error output stream (stderr).
This option is not available in the IDE.

--ose_load_module
Syntax

--ose_load_module

Description

By default, the linker generates a ROMable executable image. Use this option to
generate an executable image in the OSE load module image format instead.
Project>Options>Linker>Output

--output, -o
Syntax

--output {filename|directory}
-o {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Description

By default, the object executable image produced by the linker is located in a file with
the name a.out. Use this option to explicitly specify a different output filename, which
by default will have the filename extension out.
Project>Options>Linker>Output>Output file

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Descriptions of options

--pi_veneers
Syntax

--pi_veneers

Description

Use this option to make the linker generate position-independent veneers. Note that this
type of veneers is bigger and slower than normal veneers.

See also

Veneers, page 57.
To set this option, use Project>Options>C/C++ Compiler>Extra Options.

--place_holder
Syntax

--place_holder symbol[,size[,section[,alignment]]]

Parameters

Description

symbol

The name of the symbol to create

size

Size in ROM; by default 4 bytes

section

Section name to use; by default .text

alignment

Alignment of section; by default 1

Use this option to reserve a place in ROM to be filled by some other tool, for example a
checksum calculated by ielftool. Each use of this linker option results in a section
with the specified name, size, and alignment. The symbol can be used by your
application to refer to the section.
Note: Like any other section, sections created by the --place_holder option will
only be included in your application if the section appears to be needed. The --keep
linker option, or the keep linker directive can be used for forcing such section to be
included.

See also

IAR utilities, page 323.
To set this option, use Project>Options>Linker>Extra Options

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Linker options

--redirect
Syntax

--redirect from_symbol=to_symbol

Parameters

Description

from_symbol

The name of the source symbol

to_symbol

The name of the destination symbol

Use this option to change a reference from one symbol to another symbol.
To set this option, use Project>Options>Linker>Extra Options

--remarks
Syntax

--remarks

Description

The least severe diagnostic messages are called remarks. A remark indicates a source
code construct that may cause strange behavior in the generated code. By default, the
linker does not generate remarks. Use this option to make the linker generate remarks.

See also

Severity levels, page 153.
Project>Options>Linker>Diagnostics>Enable remarks

--semihosting
Syntax

--semihosting[=iar_breakpoint]

Parameters
iar_breakpoint

The IAR-specific mechanism can be used when debugging
applications that use SWI/SVC extensively.

Description

Use this option to include the debug interface—breakpoint mechanism—in the output
image. If no parameter is specified, the SWI/SVC mechanism is included for
ARM7/9/11, and the BKPT mechanism is included for Cortex-M.

See also

Low-level interface for debug support, page 64.
Project>Options>General Options>Library Configuration>Semihosted

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--silent
Syntax

--silent

Description

By default, the linker issues introductory messages and a final statistics report. Use this
option to make the linker operate without sending these messages to the standard output
stream (normally the screen).
This option does not affect the display of error and warning messages.
This option is not available in the IDE.

--strip
Syntax

--strip

Description

By default, the linker retains the debug information from the input object files in the
output executable image. Use this option to remove that information.
To set related options, choose:
Project>Options>Linker>Output>Include debug information in output

--warnings_affect_exit_code
Syntax

--warnings_affect_exit_code

Description

By default, the exit code is not affected by warnings, because only errors produce a
non-zero exit code. With this option, warnings will also generate a non-zero exit code.
This option is not available in the IDE.

--warnings_are_errors
Syntax

--warnings_are_errors

Description

Use this option to make the linker treat all warnings as errors. If the linker encounters
an error, no executable image is generated. Warnings that have been changed into
remarks are not treated as errors.

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Linker options

Note: Any diagnostic messages that have been reclassified as warnings by the option
--diag_warning directive will also be treated as errors when
--warnings_are_errors is used.
See also

--diag_warning, page 195 and --diag_warning, page 167.
Project>Options>Linker>Diagnostics>Treat all warnings as errors

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Data representation
This chapter describes the data types, pointers, and structure types supported
by the compiler.
See the chapter Efficient coding for embedded applications for information about
which data types and pointers provide the most efficient code for your
application.

Alignment
Every C data object has an alignment that controls how the object can be stored in
memory. Should an object have an alignment of, for example, 4, it must be stored on an
address that is divisible by 4.
The reason for the concept of alignment is that some processors have hardware
limitations for how the memory can be accessed.
Assume that a processor can read 4 bytes of memory using one instruction, but only
when the memory read is placed on an address divisible by 4. Then, 4-byte objects, such
as long integers, will have alignment 4.
Another processor might only be able to read 2 bytes at a time; in that environment, the
alignment for a 4-byte long integer might be 2.
A structure type will have the same alignment as the structure member with the most
strict alignment. To decrease the alignment requirements on the structure and its
members, use #pragma pack or the __packed data type attribute.
All data types must have a size that is a multiple of their alignment. Otherwise, only the
first element of an array would be guaranteed to be placed in accordance with the
alignment requirements. This means that the compiler might add pad bytes at the end of
the structure. For more information about pad bytes, see Packed structure types, page
217.
Note that with the #pragma data_alignment directive you can increase the alignment
demands on specific variables.

ALIGNMENT ON THE ARM CORE
The alignment of a data object controls how it can be stored in memory. The reason for
using alignment is that the ARM core can access 4-byte objects more efficiently only
when the object is stored at an address divisible by 4.

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Objects with alignment 4 must be stored at an address divisible by 4, while objects with
alignment 2 must be stored at addresses divisible by 2.
The compiler ensures this by assigning an alignment to every data type, ensuring that
the ARM core will be able to read the data.

Byte order
The ARM core stores data in either little-endian or big-endian byte order. To specify the
byte order, use the --endian compiler option; see --endian, page 170.
In the little-endian byte order, which is default, the least significant byte is stored at the
lowest address in memory. The most significant byte is stored at the highest address.
In the big-endian byte order, the most significant byte is stored at the lowest address in
memory. The least significant byte is stored at the highest address. If you use the
big-endian byte order, it might be necessary to use the
#pragma bitfields=reversed directive to be compatible with code for other
compilers and I/O register definitions of some devices, see Bitfields, page 212.
Note: There are two variants of the big-endian mode, BE8 and BE32, which you
specify at link time. In BE8 data is big-endian and code is little-endian. In BE32 both
data and code are big-endian. In architectures before v6, the BE32 endian mode is used,
and after v6 the BE8 mode is used. In the v6 (ARM11) architecture, both big-endian
modes are supported.

Basic data types
The compiler supports both all ISO/ANSI C basic data types and some additional types.

INTEGER TYPES
This table gives the size and range of each integer data type:
Data type

Size

Range

Alignment

bool

8 bits

0 to 1

1

char

8 bits

0 to 255

1

signed char

8 bits

-128 to 127

1

unsigned char

8 bits

0 to 255

1

signed short

16 bits

-32768 to 32767

2

unsigned short

16 bits

0 to 65535

2

Table 25: Integer types

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Data type

Size

Range

Alignment

signed int

32 bits

-231 to 231-1

4

unsigned int

32 bits

0 to 232-1

4

31

31

to 2 -1

signed long

32 bits

-2

unsigned long

32 bits

0 to 232-1
63

to

4

263-1

signed long long

64 bits

-2

unsigned long long

64 bits

0 to 264-1

4

8
8

Table 25: Integer types (Continued)

Signed variables are represented using the two’s complement form.

Bool
The bool data type is supported by default in the C++ language. If you have enabled
language extensions, the bool type can also be used in C source code if you include the
file stdbool.h. This will also enable the boolean values false and true.

The enum type
The compiler will use the smallest type required to hold enum constants, preferring
signed rather than unsigned.
When IAR Systems language extensions are enabled, and in C++, the enum constants
and types can also be of the type long, unsigned long, long long, or unsigned
long long.
To make the compiler use a larger type than it would automatically use, define an enum
constant with a large enough value. For example:
/* Disables usage of the char type for enum */
enum Cards{Spade1, Spade2,
DontUseChar=257};

Read also about the compiler option --enum_is_int, page 171.

The char type
The char type is by default unsigned in the compiler, but the --char_is_signed
compiler option allows you to make it signed. Note, however, that the library is compiled
with the char type as unsigned.

The wchar_t type
The wchar_t data type is an integer type whose range of values can represent distinct
codes for all members of the largest extended character set specified among the
supported locals.

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The wchar_t data type is supported by default in the C++ language. To use the
wchar_t type also in C source code, you must include the file stddef.h from the
runtime library.

Bitfields
In ISO/ANSI C, int, signed int, and unsigned int can be used as the base type for
integer bitfields. It is implementation defined whether the type specified by int is the
same as signed int or unsigned int. In the IAR C/C++ Compiler for ARM, bitfields
specified as int are treated as unsigned int. Furthermore, any integer type can be
used as the base type when language extensions are enabled. Bitfields in expressions
will have the same data type as the integer base type.
The compiler places bitfield members based on the byte order mode that is used. By
default in little-endian mode, the compiler places bitfield members from the least
significant to the most significant bit in the container type. And by default in big-endian
mode, the compiler places bitfield members from the most significant to the least
significant bit in the container type. A bitfield is assigned to the last available container
of its base type which has enough unassigned bits to contain the entire bitfield. This
means that bitfield containers can overlap other structure members as long as the order
of the fields in the structure is preserved, for example in big-endian mode:
struct example
{
char a;
short b : 10;
int
c : 6;
};

Here the first declaration creates an unsigned character which is allocated to bits 24
through 31. The second declaration creates a signed short integer member of size 10 bits.
This member is allocated to bits 15 through 6 as it will not fit in the remaining 8 bits of
the first short integer container. The last bitfield member declared is placed in the bits 0
through 5. If seen as a 32-bit value, the structure looks like this in memory:

Figure 14: Layout of bitfield members in big-endian mode

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Use the directive #pragma bitfields=disjoint_types to force the bitfield
containers to be disjoint, or in other words, not to overlap. The layout of the above
example structure would then become:

Figure 15: Layout of bitfield members forced to be disjoint in big-endian mode

Use the directive #pragma bitfields=reversed_disjoint_types to place the
bitfield members from the least significant bit to the most significant bit in
non-overlapping storage containers.

FLOATING-POINT TYPES
In the IAR C/C++ Compiler for ARM, floating-point values are represented in standard
IEEE 754 format. The sizes for the different floating-point types are:
Type

Size

Range (+/-)

Decimals

Exponent

Mantissa

float

32 bits

±1.18E-38 to ±3.40E+38

7

8 bits

23 bits

double

64 bits

±2.23E-308 to ±1.79E+308

15

11 bits

52 bits

long
double

64 bits

±2.23E-308 to ±1.79E+308

15

11 bits

52 bits

Table 26: Floating-point types

For Cortex-M0 and Cortex-M1, the compiler does not support subnormal numbers. All
operations that should produce subnormal numbers will instead generate zero. For
information about the representation of subnormal numbers for other cores, see
Representation of special floating-point numbers, page 214.
Exception flags according to the IEEE 754 standard are not supported. The alignment
for the float type is 4, and for the long double type it is 8.

32-bit floating-point format
The representation of a 32-bit floating-point number as an integer is:
31 30
23 22
S
Exponent

0
Mantissa

The exponent is 8 bits, and the mantissa is 23 bits.

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The value of the number is:
(-1)S * 2(Exponent-127) * 1.Mantissa

The range of the number is:
±1.18E-38 to ±3.40E+38

The precision of the float operators (+, -, *, and /) is approximately 7 decimal digits.

64-bit floating-point format
The representation of a 64-bit floating-point number as an integer is:
63 62
52 51
S
Exponent

0
Mantissa

The exponent is 11 bits, and the mantissa is 52 bits.
The value of the number is:
(-1)S * 2(Exponent-1023) * 1.Mantissa

The range of the number is:
±2.23E-308 to ±1.79E+308

The precision of the float operators (+, -, *, and /) is approximately 15 decimal digits.

Representation of special floating-point numbers
This list describes the representation of special floating-point numbers:
●

Zero is represented by zero mantissa and exponent. The sign bit signifies positive or
negative zero.

●

Infinity is represented by setting the exponent to the highest value and the mantissa
to zero. The sign bit signifies positive or negative infinity.

●

Not a number (NaN) is represented by setting the exponent to the highest positive
value and at least one bit set in the 20 most significant bits of the mantissa.
Remaining bits are zero.

●

Subnormal numbers are used for representing values smaller than what can be
represented by normal values. The drawback is that the precision will decrease with
smaller values. The exponent is set to 0 to signify that the number is denormalized,
even though the number is treated as if the exponent was 1. Unlike normal numbers,
denormalized numbers do not have an implicit 1 as the most significant bit (the
MSB) of the mantissa. The value of a denormalized number is:
(-1)S * 2(1-BIAS) * 0.Mantissa

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where BIAS is 127 and 1023 for 32-bit and 64-bit floating-point values, respectively.

Pointer types
The compiler has two basic types of pointers: function pointers and data pointers.

FUNCTION POINTERS
The size of function pointers is always 32 bits and the range is 0x0–0xFFFFFFFF.
When function pointer types are declared, attributes are inserted before the * sign, for
example:
typedef void (__thumb __interwork * IntHandler) (void);

This can be rewritten using #pragma directives:
#pragma type_attribute=__thumb __interwork
typedef void IntHandler_function(void);
typedef IntHandler_function *IntHandler;

DATA POINTERS
There is one data pointer available. Its size is 32 bits and the range is 0x0–0xFFFFFFFF.

CASTING
Casts between pointers have these characteristics:
●

Casting a value of an integer type to a pointer of a smaller type is performed by
truncation

●

Casting a value of an unsigned integer type to a pointer of a larger type is performed
by zero extension

●

Casting a value of a signed integer type to a pointer of a larger type is performed by
sign extension

●

Casting a pointer type to a smaller integer type is performed by truncation

●

Casting a pointer type to a larger integer type is performed by zero extension

●

Casting a data pointer to a function pointer and vice versa is illegal

●

Casting a function pointer to an integer type gives an undefined result

size_t
size_t is the unsigned integer type required to hold the maximum size of an object. In
the IAR C/C++ Compiler for ARM, the size of size_t is 32 bits.

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Structure types

ptrdiff_t
ptrdiff_t is the type of the signed integer required to hold the difference between two

pointers to elements of the same array. In the IAR C/C++ Compiler for ARM, the size
of ptrdiff_t is 32 bits.

intptr_t
intptr_t is a signed integer type large enough to contain a void *. In the IAR C/C++
Compiler for ARM, the size of intptr_t is 32 bits.

uintptr_t
uintptr_t is equivalent to intptr_t, with the exception that it is unsigned.

Structure types
The members of a struct are stored sequentially in the order in which they are
declared: the first member has the lowest memory address.

ALIGNMENT
The struct and union types have the same alignment as the member with the highest
alignment requirement. The size of a struct is also adjusted to allow arrays of aligned
structure objects.

GENERAL LAYOUT
Members of a struct are always allocated in the order specified in the declaration.
Each member is placed in the struct according to the specified alignment (offsets).
Example
struct First
{
char c;
short s;
} s;

This diagram shows the layout in memory:

Figure 16: Structure layout

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The alignment of the structure is 2 bytes, and a pad byte must be inserted to give
short s the correct alignment.

PACKED STRUCTURE TYPES
The __packed data type attribute or the #pragma pack directive is used for relaxing
the alignment requirements of the members of a structure. This changes the layout of the
structure. The members are placed in the same order as when declared, but there might
be less pad space between members.
Note that accessing an object that is not correctly aligned requires code that is both
larger and slower. If such structure members are accessed many times, it is usually better
to construct the correct values in a struct that is not packed, and access this struct
instead.
Special care is also needed when creating and using pointers to misaligned members.
For direct access to misaligned members in a packed struct, the compiler will emit the
correct (but slower and larger) code when needed. However, when a misaligned member
is accessed through a pointer to the member, the normal (smaller and faster) code is
used. In the general case, this will not work.
Example
This example declares a packed structure:
#pragma pack(1)
struct S
{
char c;
short s;
};
#pragma pack()

In this example, the structure S has this memory layout:

Figure 17: Packed structure layout

This example declares a new non-packed structure, S2, that contains the structure s
declared in the previous example:
struct S2
{
struct S s;
long l;
};

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Type qualifiers

S2 has this memory layout

Figure 18: Packed structure layout

The structure S will use the memory layout, size, and alignment described in the
previous example. The alignment of the member l is 4, which means that alignment of
the structure S2 will become 2.
For more information, see Alignment of elements in a structure, page 129.

Type qualifiers
According to the ISO/ANSI C standard, volatile and const are type qualifiers.

DECLARING OBJECTS VOLATILE
There are three main reasons for declaring an object volatile:
●

Shared access; the object is shared between several tasks in a multitasking
environment

●

Trigger access; as for a memory-mapped SFR where the fact that an access occurs
has an effect

●

Modified access; where the contents of the object can change in ways not known to
the compiler.

Definition of access to volatile objects
The ISO/ANSI standard defines an abstract machine, which governs the behavior of
accesses to volatile declared objects. In general and in accordance to the abstract
machine, the compiler:
●

Considers each read and write access to an object declared volatile as an access

●

The unit for the access is either the entire object or, for accesses to an element in a
composite object—such as an array, struct, class, or union—the element. For
example:
char volatile a;
a = 5;
/* A write access */
a += 6; /* First a read then a write access */

●

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An access to a bitfield is treated as an access to the underlying type.

Data representation

However, these rules are not detailed enough to handle the hardware-related
requirements. The rules specific to the IAR C/C++ Compiler for ARM are described
below.

Rules for accesses
In the IAR C/C++ Compiler for ARM, accesses to volatile declared objects are
subject to these rules:
●

All accesses are preserved

●

All accesses are complete, that is, the whole object is accessed

●

All accesses are performed in the same order as given in the abstract machine

●

All accesses are atomic, that is, they cannot be interrupted.

The compiler adheres to these rules for accesses to all 8-, 16-, and 32-bit scalar types,
except for accesses to unaligned 16- and 32-bit fields in packed structures.
For all other object types, only the rule that states that all accesses are preserved applies.

DECLARING OBJECTS CONST
The const type qualifier is used for indicating that a data object, accessed directly or
via a pointer, is non-writable. A pointer to const declared data can point to both
constant and non-constant objects. It is good programming practice to use const
declared pointers whenever possible because this improves the compiler’s possibilities
to optimize the generated code and reduces the risk of application failure due to
erroneously modified data.
Static and global objects declared const are allocated in ROM.
In C++, objects that require runtime initialization cannot be placed in ROM.

Data types in C++
In C++, all plain C data types are represented in the same way as described earlier in this
chapter. However, if any Embedded C++ features are used for a type, no assumptions
can be made concerning the data representation. This means, for example, that it is not
supported to write assembler code that accesses class members.

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Compiler extensions
This chapter gives a brief overview of the compiler extensions to the
ISO/ANSI C standard. All extensions can also be used for the C++
programming language. More specifically the chapter describes the available C
language extensions.

Compiler extensions overview
The compiler offers the standard features of ISO/ANSI C and a wide set of extensions,
ranging from features specifically tailored for efficient programming in the embedded
industry to the relaxation of some minor standards issues.
You can find the extensions available as:
●

C/C++ language extensions
For a summary of available language extensions, see C language extensions, page
222. For reference information about the extended keywords, see the chapter
Extended keywords. For information about C++, the two levels of support for the
language, and C++ language extensions; see the chapter Using C++.

●

Pragma directives
The #pragma directive is defined by the ISO/ANSI C standard and is a mechanism
for using vendor-specific extensions in a controlled way to make sure that the source
code is still portable.
The compiler provides a set of predefined pragma directives, which can be used for
controlling the behavior of the compiler, for example how it allocates memory,
whether it allows extended keywords, and whether it outputs warning messages.
Most pragma directives are preprocessed, which means that macros are substituted
in a pragma directive. The pragma directives are always enabled in the compiler. For
several of them there is also a corresponding C/C++ language extension. For a list of
available pragma directives, see the chapter Pragma directives.

●

Preprocessor extensions
The preprocessor of the compiler adheres to the ISO/ANSI standard. The compiler
also makes several preprocessor-related extensions available to you. For more
information, see the chapter The preprocessor.

●

Intrinsic functions
The intrinsic functions provide direct access to low-level processor operations and
can be very useful in, for example, time-critical routines. The intrinsic functions
compile into inline code, either as a single instruction or as a short sequence of

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C language extensions

instructions. To read more about using intrinsic functions, see Mixing C and
assembler, page 91. For a list of available functions, see the chapter Intrinsic
functions.
●

Library functions
The IAR DLIB Library provides most of the important C and C++ library definitions
that apply to embedded systems. The library also provides some extensions, partly
taken from the C99 standard. For more information, see IAR DLIB Library, page 290.

Note: Any use of these extensions, except for the pragma directives, makes your
application inconsistent with the ISO/ANSI C standard.

ENABLING LANGUAGE EXTENSIONS
In the IDE, language extensions are enabled by default.
For information about how to enable and disable language extensions from the
command line, see the compiler options -e, page 169, and --strict_ansi, page 187.

C language extensions
This section gives a brief overview of the C language extensions available in the
compiler. The compiler provides a wide set of extensions, so to help you to find the
extensions required by your application, the extensions are grouped according to their
expected usefulness. In short, this means:
●

Important language extensions—extensions specifically tailored for efficient
embedded programming, typically to meet memory restrictions

●

Useful language extensions—features considered useful and typically taken from
related standards, such as C99 and C++

●

Minor language extensions, that is, the relaxation of some minor standards issues
and also some useful but minor syntax extensions.

IMPORTANT LANGUAGE EXTENSIONS
The following language extensions available both in the C and the C++ programming
languages are well suited for embedded systems programming:
●

Type attributes, and object attributes
For information about the related concepts, the general syntax rules, and for
reference information, see the chapter Extended keywords.

●

Placement at an absolute address or in a named section
The @ operator or the directive #pragma location can be used for placing global
and static variables at absolute addresses, or placing a variable or function in a named

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section. For more information about using these primitives, see Controlling data and
function placement in memory, page 131, and location, page 251.
●

Alignment
Each data type has its own alignment, for more details, see Alignment, page 209. If
you want to change the alignment, the __packed data type attribute, and the
#pragma pack and #pragma data_alignment directives are available. If you
want to use the alignment of an object, use the __ALIGNOF__() operator.
The __ALIGNOF__ operator is used for accessing the alignment of an object. It takes
one of two forms:
●

__ALIGNOF__ (type)

●

__ALIGNOF__ (expression)

In the second form, the expression is not evaluated.
●

Anonymous structs and unions
C++ includes a feature named anonymous unions. The compiler allows a similar
feature for both structs and unions in the C programming language. For more
information, see Anonymous structs and unions, page 129.

●

Bitfields and non-standard types
In ISO/ANSI C, a bitfield must be of type int or unsigned int. Using IAR
Systems language extensions, any integer type or enumeration can be used. The
advantage is that the struct will sometimes be smaller. This matches G.5.8 in the
appendix of the ISO standard, ISO Portability Issues. For more information, see
Bitfields, page 212.

Dedicated section operators
The compiler supports for these built-in section operators: __section_begin,
__section_end, and __section_size.
These operators behave syntactically as if declared like this:
void * __section_begin(char const * section)
void * __section_end(char const * section)
size_t * __section_size(char const * section)

These operators can be used on named sections or on named blocks defined in the linker
configuration file.
The __section_begin operator returns the address of the first byte of the named
section or block.
The __section_end operator returns the address of the first byte after the named
section or block.
The __section_size operator returns the size of the named section or block in bytes.

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Note: The aliases __segment_begin/__sfb, __segment_end/__sfe, and
__segment_size/__sfs can also be used.
When using the @ operator or the #pragma location directive to place a data object or
a function in a user-defined section, or when using named blocks in the linker
configuration file, the section operators can be used for getting the start and end of the
memory range where the sections or blocks were placed.
The named section must be a string literal and section must have been declared
earlier with the #pragma section directive. The type of the __section_begin
operator is a pointer to void. Note that you must enable language extensions to use these
operators.
The operators are implemented in terms of symbols with dedicated names, and will
appear in the linker map file under these names:
.

Operator

Symbol

__section_begin(sec)

sec$$Base

__section_end(sec)

sec$$Limit

__section_size(sec)

sec$$Length

Table 27: Section operators and their symbols

Note that the linker will not necessarily place sections with the same name contiguously
when these operators are not used. Using one of these operators (or the equivalent
symbols) will cause the linker to behave as if the sections were in a named block. This
is to assure that the sections are placed contiguously, so that the operators can be
assigned meaningful values. If this is in conflict with the section placement as specified
in the linker configuration file, the linker will issue an error.
Example
In this example, the type of the __section_begin operator is void *.
#pragma section="MYSECTION"
...
section_start_address = __section_begin("MYSECTION");

See also section, page 256, and location, page 251.

USEFUL LANGUAGE EXTENSIONS
This section lists and briefly describes useful extensions, that is, useful features typically
taken from related standards, such as C99 and C++:

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●

Inline functions
The #pragma inline directive, alternatively the inline keyword, advises the
compiler that the function whose declaration follows immediately after the directive
should be inlined. This is similar to the C++ keyword inline. For more information,
see inline, page 250.

●

Mixing declarations and statements
It is possible to mix declarations and statements within the same scope. This feature
is part of the C99 standard and C++.

●

Declaration in for loops
It is possible to have a declaration in the initialization expression of a for loop, for
example:
for (int i = 0; i < 10; ++i)
{
/* Do something here. */
}

This feature is part of the C99 standard and C++.
●

The bool data type
To use the bool type in C source code, you must include the file stdbool.h. This
feature is part of the C99 standard and C++. (The bool data type is supported by
default in C++.)

●

C++ style comments
C++ style comments are accepted. A C++ style comment starts with the character
sequence // and continues to the end of the line. For example:
// The length of the bar, in centimeters.
int length;

This feature is copied from the C99 standard and C++.

Inline assembler
Inline assembler can be used for inserting assembler instructions in the generated
function. This feature is part of the C99 standard and C++.
The asm and __asm extended keywords both insert an assembler instruction. However,
when compiling C source code, the asm keyword is not available when the option
--strict_ansi is used. The __asm keyword is always available.
Note: Not all assembler directives or operators can be inserted using this keyword.
The syntax is:
asm ("string");

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C language extensions

The string can be a valid assembler instruction or a data definition assembler directive,
but not a comment. You can write several consecutive inline assembler instructions, for
example:
asm ("Label:
"

nop\n"
b Label");

where \n (new line) separates each new assembler instruction. Note that you can define
and use local labels in inline assembler instructions.
For more information about inline assembler, see Mixing C and assembler, page 91.

Compound literals
To create compound literals you can use this syntax:
/* Create a pointer to an anonymous array */
int *p = (int []) {1, 2, 3};
/* Create a pointer to an anonymous structX */
structX *px = &(structX) {5, 6, 7};

Note:
●

A compound literal can be modified unless it is declared const

●

Compound literals are not supported in Embedded C++ and Extended EC++.

●

This feature is part of the C99 standard.

Incomplete arrays at end of structs
The last element of a struct can be an incomplete array. This is useful for allocating a
chunk of memory that contains both the structure and a fixed number of elements of the
array. The number of elements can vary between allocations.
This feature is part of the C99 standard.
Note: The array cannot be the only member of the struct. If that was the case, then
the size of the struct would be zero, which is not allowed in ISO/ANSI C.
Example
struct str
{
char a;
unsigned long b[];
};

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struct str * GetAStr(int size)
{
return malloc(sizeof(struct str) +
sizeof(unsigned long) * size);
}
void UseStr(struct str * s)
{
s->b[10] = 0;
}

The incomplete array will be aligned in the structure just like any other member of the
structure. For more information about structure alignment, see Structure types, page
216.

Hexadecimal floating-point constants
Floating-point constants can be given in hexadecimal style. The syntax is
0xMANTp{+|-}EXP, where MANT is the mantissa in hexadecimal digits, including an
optional . (decimal point), and EXP is the exponent with decimal digits, representing an
exponent of 2. This feature is part of the C99 standard.
Examples
0x1p0 is 1
0xA.8p2 is 10.5*22

Designated initializers in structures and arrays
Any initialization of either a structure (struct or union) or an array can have a
designation. A designation consists of one or more designators followed by an
initializer. A designator for a structure is specified as .elementname and for an array
[constant index expression]. Using designated initializers is not supported in
C++.

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Examples
This definition shows a struct and its initialization using designators:
struct
{
int i;
int j;
int k;
int l;
short array[10];
} u =
{
.l = 6,
.j = 6,
8,
.array[7] = 2,
.array[3] = 2,
5,
.k = 4
};

/*
/*
/*
/*
/*
/*
/*

initialize l to 6 */
initialize j to 6 */
initialize k to 8 */
initialize element 7 to 2 */
initialize element 3 to 2 */
array[4] = 5 */
reinitialize k to 4 */

Note that a designator specifies the destination element of the initialization. Note also
that if one element is initialized more than once, it is the last initialization that will be
used.
To initialize an element in a union other than the first, do like this:
union
{
int i;
float f;
} y = {.f = 5.0};

To set the size of an array by initializing the last element, do like this:
char array[] = {[10] = 'a'};

MINOR LANGUAGE EXTENSIONS
This section lists and briefly describes minor extensions, that is, the relaxation of some
standards issues and also some useful but minor syntax extensions:
●

Arrays of incomplete types
An array can have an incomplete struct, union, or enum type as its element type.
The types must be completed before the array is used (if it is), or by the end of the
compilation unit (if it is not).

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Compiler extensions

●

Forward declaration of enum types
The IAR Systems language extensions allow that you first declare the name of an
enum and later resolve it by specifying the brace-enclosed list.

●

Missing semicolon at end of struct or union specifier
A warning is issued if the semicolon at the end of a struct or union specifier is
missing.

●

Null and void
In operations on pointers, a pointer to void is always implicitly converted to another
type if necessary, and a null pointer constant is always implicitly converted to a null
pointer of the right type if necessary. In ISO/ANSI C, some operators allow such
things, while others do not allow them.

●

Casting pointers to integers in static initializers
In an initializer, a pointer constant value can be cast to an integral type if the integral
type is large enough to contain it. For more information about casting pointers, see
Casting, page 215.

●

Taking the address of a register variable
In ISO/ANSI C, it is illegal to take the address of a variable specified as a register
variable. The compiler allows this, but a warning is issued.

●

Duplicated size and sign specifiers
Should the size or sign specifiers be duplicated (for example, short short or
unsigned unsigned), an error is issued.

●

long float means double

The type long float is accepted as a synonym for double.
●

Repeated typedef declarations
Redeclarations of typedef that occur in the same scope are allowed, but a warning
is issued.

●

Mixing pointer types
Assignment and pointer difference is allowed between pointers to types that are
interchangeable but not identical; for example, unsigned char * and char *. This
includes pointers to integral types of the same size. A warning is issued.
Assignment of a string constant to a pointer to any kind of character is allowed, and
no warning is issued.

●

Non-top level const
Assignment of pointers is allowed in cases where the destination type has added type
qualifiers that are not at the top level (for example, int ** to int const **).
Comparing and taking the difference of such pointers is also allowed.

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C language extensions

●

Non-lvalue arrays
A non-lvalue array expression is converted to a pointer to the first element of the
array when it is used.

●

Comments at the end of preprocessor directives
This extension, which makes it legal to place text after preprocessor directives, is
enabled, unless strict ISO/ANSI mode is used. The purpose of this language
extension is to support compilation of legacy code; we do not recommend that you
write new code in this fashion.

●

An extra comma at the end of enum lists
Placing an extra comma is allowed at the end of an enum list. In strict ISO/ANSI
mode, a warning is issued.

●

A label preceding a }
In ISO/ANSI C, a label must be followed by at least one statement. Therefore, it is
illegal to place the label at the end of a block. The compiler issues a warning.

Note: This also applies to the labels of switch statements.
●

Empty declarations
An empty declaration (a semicolon by itself) is allowed, but a remark is issued
(provided that remarks are enabled).

●

Single-value initialization
ISO/ANSI C requires that all initializer expressions of static arrays, structs, and
unions are enclosed in braces.
Single-value initializers are allowed to appear without braces, but a warning is
issued. The compiler accepts this expression:
struct str
{
int a;
} x = 10;

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Compiler extensions

●

Declarations in other scopes
External and static declarations in other scopes are visible. In the following example,
the variable y can be used at the end of the function, even though it should only be
visible in the body of the if statement. A warning is issued.
int test(int x)
{
if (x)
{
extern int y;
y = 1;
}
return y;
}

●

Expanding function names into strings with the function as context
Use any of the symbols __func__ or __FUNCTION__ inside a function body to
make the symbol expand into a string, with the function name as context. Use the
symbol __PRETTY_FUNCTION__ to also include the parameter types and return
type. The result might, for example, look like this if you use the
__PRETTY_FUNCTION__ symbol:
"void func(char)"

These symbols are useful for assertions and other trace utilities and they require that
language extensions are enabled, see -e, page 169.

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Extended keywords
This chapter describes the extended keywords that support specific features
of the ARM core and the general syntax rules for the keywords. Finally the
chapter gives a detailed description of each keyword.

General syntax rules for extended keywords
To understand the syntax rules for the extended keywords, it is important to be familiar
with some related concepts.
The compiler provides a set of attributes that can be used on functions or data objects to
support specific features of the ARM core. There are two types of attributes—type
attributes and object attributes:
●

Type attributes affect the external functionality of the data object or function

●

Object attributes affect the internal functionality of the data object or function.

The syntax for the keywords differs slightly depending on whether it is a type attribute
or an object attribute, and whether it is applied to a data object or a function.
For detailed information about each attribute, see Descriptions of extended keywords,
page 237.
Note: The extended keywords are only available when language extensions are enabled
in the compiler.
In the IDE, language extensions are enabled by default.
Use the -e compiler option to enable language extensions. See -e, page 169 for
additional information.

TYPE ATTRIBUTES
Type attributes define how a function is called, or how a data object is accessed. This
means that if you use a type attribute, it must be specified both when a function or data
object is defined and when it is declared.
You can either place the type attributes directly in your source code, or use the pragma
directive #pragma type_attribute.
These general type attributes are available:
●

Function type attributes affect how the function should be called: __arm, __fiq,
__interwork, __irq, __swi, __task, and __thumb

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General syntax rules for extended keywords

●

Data type attributes: __big_endian, const, __little_endian, __packed, and
volatile

You can specify as many type attributes as required for each level of pointer indirection.
To read more about the type qualifiers const and volatile, see Type qualifiers, page
218.

Syntax for type attributes used on data objects
In general, type attributes for data objects follow the same syntax as the type qualifiers
const and volatile.
The following declaration assigns the __little_endian type attribute to the variables
i and j; in other words, the variable i and j will be accessed with little endian byte
order. The variables k and l behave in the same way:
__little_endian int i, j;
int __little_endian k, l;

Note that the attribute affects both identifiers.
This declaration of i and j is equivalent with the previous one:
#pragma type_attribute=__little_endian
int i, j;

The advantage of using pragma directives for specifying keywords is that it offers you a
method to make sure that the source code is portable.

Syntax for type attributes on data pointers
The syntax for declaring pointers using type attributes follows the same syntax as the
type qualifiers const and volatile:
int __little_endian * p;

The int object will be accessed in little endian byte order.

int * __little_endian p;

The pointer will be accessed in little endian byte order.

__little_endian int * p;

The pointer will be accessed in little endian byte order.

Syntax for type attributes on functions
The syntax for using type attributes on functions differs slightly from the syntax of type
attributes on data objects. For functions, the attribute must be placed either in front of
the return type, or in parentheses, for example:
__irq __arm void my_handler(void);

or

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void (__irq __arm my_handler)(void);

This declaration of my_handler is equivalent with the previous one:
#pragma type_attribute=__irq __arm
void my_handler(void);

OBJECT ATTRIBUTES
Object attributes affect the internal functionality of functions and data objects, but not
how the function is called or how the data is accessed. This means that an object attribute
does not need to be present in the declaration of an object.
These object attributes are available:
●

Object attributes that can be used for variables: __no_init

●

Object attributes that can be used for functions and variables: location, @,
__root, and __weak,

●

Object attributes that can be used for functions: __intrinsic, __nested,
__noreturn, and __ramfunc.

You can specify as many object attributes as required for a specific function or data
object.
For more information about location and @, see Controlling data and function
placement in memory, page 131.

Syntax for object attributes
The object attribute must be placed in front of the type. For example, to place myarray
in memory that is not initialized at startup:
__no_init int myarray[10];

The #pragma object_attribute directive can also be used. This declaration is
equivalent to the previous one:
#pragma object_attribute=__no_init
int myarray[10];

Note: Object attributes cannot be used in combination with the typedef keyword.

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Summary of extended keywords

Summary of extended keywords
This table summarizes the extended keywords:
Extended keyword

Description

__arm

Makes a function execute in ARM mode

__big_endian

Declares a variable to use the big endian byte order

__fiq

Declares a fast interrupt function

__interwork

Declares a function to be callable from both ARM and
Thumb mode

__intrinsic

Reserved for compiler internal use only

__irq

Declares an interrupt function

__little_endian

Declares a variable to use the little endian byte order

__nested

Allows an __irq declared interrupt function to be nested,
that is, interruptible by the same type of interrupt

__no_init

Supports non-volatile memory

__noreturn

Informs the compiler that the function will not return

__packed

Decreases data type alignment to 1

__ramfunc

Makes a function execute in RAM

__root

Ensures that a function or variable is included in the object
code even if unused

__swi

Declares a software interrupt function

__task

Relaxes the rules for preserving registers

__thumb

Makes a function execute in Thumb mode

__weak

Declares a symbol to be externally weakly linked

Table 28: Extended keywords summary

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Descriptions of extended keywords
These sections give detailed information about each extended keyword.

__arm
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

The __arm keyword makes a function execute in ARM mode. An __arm declared
function can, unless it is also declared __interwork, only be called from functions that
also execute in ARM mode.
A function declared __arm cannot be declared __thumb.
Note: Non-interwork ARM functions cannot be called from Thumb mode.

Example

__arm int func1(void);

See also

__interwork, page 238.

__big_endian
Syntax

Follows the generic syntax rules for type attributes that can be used on data objects, see
Type attributes, page 233.

Description

The __big_endian keyword is used for accessing a variable that is stored in the
big-endian byte order regardless of what byte order the rest of the application uses. The
__big_endian keyword is available when you compile for ARMv6 or higher.

Example

__big_endian long my_variable;

See also

__little_endian, page 238.

Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

The __fiq keyword declares a fast interrupt function. All interrupt functions must be
compiled in ARM mode. A function declared __fiq does not accept parameters and
does not have a return value.

__fiq

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Descriptions of extended keywords

Example

__fiq __arm void interrupt_function(void);

__interwork
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

A function declared __interwork can be called from functions executing in either
ARM or Thumb mode.
Note: By default, functions are interwork when the --interwork compiler option is
used, and when the --cpu option is used and it specifies a core where interwork is
default.

Example

typedef void (__thumb __interwork *IntHandler)(void);

__intrinsic
Description

The __intrinsic keyword is reserved for compiler internal use only.

__irq
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

The __irq keyword declares an interrupt function. All interrupt functions must be
compiled in ARM mode. A function declared __irq does not accept parameters and
does not have a return value.

Example

__irq __arm void interrupt_function(void);

__little_endian
Syntax

Follows the generic syntax rules for type attributes that can be used on data objects, see
Type attributes, page 233.

Description

The __little_endian keyword is used for accessing a variable that is stored in the
little-endian byte order regardless of what byte order the rest of the application uses. The
__little_endian keyword is available when you compile for ARMv6 or higher.

Example

__little_endian long my_variable;

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Extended keywords

See also

__big_endian, page 237.

__nested
Syntax

Follows the generic syntax rules for object attributes that can be used on functions, see
Object attributes, page 235.

Description

The __nested keyword modifies the enter and exit code of an interrupt function to
allow for nested interrupts. This allows interrupts to be enabled, which means new
interrupts can be served inside an interrupt function, without overwriting the SPSR and
return address in R14. Nested interrupts are only supported for __irq declared
functions.
Note: The __nested keyword requires the processor mode to be in either User or
System mode.

Example

__irq __nested __arm void interrupt_handler(void);

See also

Nested interrupts, page 33.

__no_init
Syntax

Follows the generic syntax rules for object attributes, see Object attributes, page 235.

Description

Use the __no_init keyword to place a data object in non-volatile memory. This means
that the initialization of the variable, for example at system startup, is suppressed.

Example

__no_init int myarray[10];

See also

Do not initialize directive, page 308.

__noreturn
Syntax

Follows the generic syntax rules for object attributes, see Object attributes, page 235.

Description

The __noreturn keyword can be used on a function to inform the compiler that the
function will not return. If you use this keyword on such functions, the compiler can
optimize more efficiently. Examples of functions that do not return are abort and exit.

Example

__noreturn void terminate(void);

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__packed
Syntax

Follows the generic syntax rules for type attributes that can be used on data, see Type
attributes, page 233.

Description

Use the __packed keyword to decrease the data type alignment to 1. __packed can be
used for two purposes:
●

When used with a struct or union type definition, the maximum alignment of
members of that struct or union is set to 1, to eliminate any gaps between the
members. The type of each members also receives the __packed type attribute.

●

When used with any other type, the resulting type is the same as the type without
the __packed type attribute, but with an alignment of 1. Types that already have an
alignment of 1 are not affected by the __packed type attribute.

A normal pointer can be implicitly converted to a pointer to __packed, but the reverse
conversion requires a cast.
Note: Accessing data types at other alignments than their natural alignment can result
in code that is significantly larger and slower.
Example

See also

__packed struct X {char ch; int i;};
/* No pad bytes
void foo (struct X * xp)
/* No need for __packed here
{
int * p1
= &xp->1;/* Error:"int *">"int __packed *"
int __packed * p2 = &xp->i;
/* OK
char * p2
= &xp->ch;
/* OK, char not affected
}

*/
*/
*/
*/
*/

pack, page 253.

__ramfunc
Syntax

Follows the generic syntax rules for object attributes, see Object attributes, page 235.

Description

The __ramfunc keyword makes a function execute in RAM. Two code sections will be
created: one for the RAM execution, and one for the ROM initialization.
If a function declared __ramfunc tries to access ROM, the compiler will issue a
warning. This behavior is intended to simplify the creation of upgrade routines, for
instance, rewriting parts of flash memory. If this is not why you have declared the
function __ramfunc, you may safely ignore or disable these warnings.
Functions declared __ramfunc are by default stored in the section named CODE_I.

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Extended keywords

Example

__ramfunc int FlashPage(char * data, char * page);

See also

To read more about __ramfunc declared functions in relation to breakpoints, see the
IAR Embedded Workbench® IDE User Guide for ARM®.

__root
Syntax

Follows the generic syntax rules for object attributes, see Object attributes, page 235.

Description

A function or variable with the __root attribute is kept whether or not it is referenced
from the rest of the application, provided its module is included. Program modules are
always included and library modules are only included if needed.

Example

__root int myarray[10];

See also

To read more about root symbols and how they are kept, see the .

__swi
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

The __swi keyword declares a software interrupt function. It inserts an SVC (formerly
SWI) instruction and the specified software interrupt number to make a proper function
call. A function declared __swi accepts arguments and returns values. The __swi
keyword makes the compiler generate the correct return sequence for a specific software
interrupt function. Software interrupt functions follow the same calling convention
regarding parameters and return values as an ordinary function, except for the stack
usage.
The __swi keyword also expects a software interrupt number which is specified with
the #pragma swi_number=number directive. The swi_number is used as an
argument to the generated assembler SWC instruction, and can be used by the SVC
interrupt handler, for example SWI_Handler, to select one software interrupt function
in a system containing several such functions. Note that the software interrupt number
should only be specified in the function declaration—typically, in a header file that you
include in the source code file that calls the interrupt function—not in the function
definition.
Note: All interrupt functions must be compiled in ARM mode, except for Cortex-M.
Use either the __arm keyword or the #pragma type_attribute=__arm directive to
alter the default behavior if needed.

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Descriptions of extended keywords

Example

To declare your software interrupt function, typically in a header file, write for example
like this:
#pragma swi_number=0x23
__swi int swi0x23_function(int a, int b);
...

To call the function:
...
int x = swi0x23_function(1, 2);

/* Will be replaced by SVC 0x23,
hence the linker will
never try to locate
swi0x23_function */

...

Somewhere in your application source code, you define your software interrupt
function:
...
__swi __arm int the_actual_swi0x23_function(int a, int b)
{
...
return 42;
}

See also

Software interrupts, page 34 and Calling convention, page 97.

__task
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

This keyword allows functions to relax the rules for preserving registers. Typically, the
keyword is used on the start function for a task in an RTOS.
By default, functions save the contents of used preserved registers on the stack upon
entry, and restore them at exit. Functions that are declared __task do not save all
registers, and therefore require less stack space.
Because a function declared __task can corrupt registers that are needed by the calling
function, you should only use __task on functions that do not return or call such a
function from assembler code.
The function main can be declared __task, unless it is explicitly called from the
application. In real-time applications with more than one task, the root function of each
task can be declared __task.

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Extended keywords

Example

__task void my_handler(void);

__thumb
Syntax

Follows the generic syntax rules for type attributes that can be used on functions, see
Type attributes, page 233.

Description

The __thumb keyword makes a function execute in Thumb mode. Unless the function
is also declared __interwork, the function declared __thumb can only be called from
functions that also execute in Thumb mode.
A function declared __thumb cannot be declared __arm.
Note: Non-interwork Thumb functions cannot be called from ARM mode.

Example

__thumb int func2(void);

See also

__interwork, page 238.

__weak
Syntax

Follows the generic syntax rules for object attributes, see Object attributes, page 235.

Description

Using the __weak object attribute on an external declaration of a symbol makes all
references to that symbol in the module weak.
Using the __weak object attribute on a public definition of a symbol makes that
definition a weak definition.
The linker will not include a module from a library solely to satisfy weak references to
a symbol, nor will the lack of a definition for a weak reference result in an error. If no
definition is included, the address of the object will be zero.
When linking, a symbol can have any number of weak definitions, and at most one
non-weak definition. If the symbol is needed, and there is a non-weak definition, this
definition will be used. If there is no non-weak definition, one of the weak definitions
will be used.

Example

extern __weak int foo; /* A weak reference */
__weak void bar(void); /* A weak definition */
{
/* Increment foo if it was included */
if (&foo != 0)
++foo;

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Descriptions of extended keywords

}

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Pragma directives
This chapter describes the pragma directives of the compiler.
The #pragma directive is defined by the ISO/ANSI C standard and is a
mechanism for using vendor-specific extensions in a controlled way to make
sure that the source code is still portable.
The pragma directives control the behavior of the compiler, for example how
it allocates memory for variables and functions, whether it allows extended
keywords, and whether it outputs warning messages.
The pragma directives are always enabled in the compiler.

Summary of pragma directives
This table lists the pragma directives of the compiler that can be used either with the
#pragma preprocessor directive or the _Pragma() preprocessor operator:
Pragma directive

Description

bitfields

Controls the order of bitfield members

data_alignment

Gives a variable a higher (more strict) alignment

diag_default

Changes the severity level of diagnostic messages

diag_error

Changes the severity level of diagnostic messages

diag_remark

Changes the severity level of diagnostic messages

diag_suppress

Suppresses diagnostic messages

diag_warning

Changes the severity level of diagnostic messages

include_alias

Specifies an alias for an include file

inline

Inlines a function

language

Controls the IAR Systems language extensions

location

Specifies the absolute address of a variable, or places groups
of functions or variables in named sections

message

Prints a message

object_attribute

Changes the definition of a variable or a function

optimize

Specifies the type and level of an optimization

Table 29: Pragma directives summary

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Descriptions of pragma directives

Pragma directive

Description

pack

Specifies the alignment of structures and union members

__printf_args

Verifies that a function with a printf-style format string is
called with the correct arguments

required

Ensures that a symbol that is needed by another symbol is
included in the linked output

rtmodel

Adds a runtime model attribute to the module

__scanf_args

Verifies that a function with a scanf-style format string is
called with the correct arguments

section

Declares a section name to be used by intrinsic functions

swi_number

Sets the interrupt number of a software interrupt function

type_attribute

Changes the declaration and definitions of a variable or
function

weak

Makes a definition a weak definition, or creates a weak alias
for a function or a variable

Table 29: Pragma directives summary (Continued)

Note: For portability reasons, the pragma directives alignment, baseaddr,
codeseg, constseg, dataseg, function, memory, and warnings are recognized
but will give a diagnostic message. It is important to be aware of this if you need to port
existing code that contains any of those pragma directives. See also Recognized pragma
directives (6.8.6), page 355.

Descriptions of pragma directives
This section gives detailed information about each pragma directive.

bitfields
Syntax

#pragma bitfields=disjoint_types|joined_types|
reversed_disjoint_types|reversed|default}

Parameters
disjoint_types

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Bitfield members are placed from the least significant bit to
the most significant bit in the container type. Storage
containers of bitfields with different base types will not
overlap.

Pragma directives

joined_types

Bitfield members are placed depending on the byte order.
Storage containers of bitfields will overlap other structure
members. For more details, see Bitfields, page 212.

reversed_disjoint_types Bitfield members are placed from the most significant bit to
the least significant bit in the container type. Storage
containers of bitfields with different base types will not
overlap.
reversed

This is an alias for reversed_disjoint_types.

default

Restores to default layout of bitfield members. The default
behavior for the compiler is joined_types.

Description

Use this pragma directive to control the layout of bitfield members.

Example

#pragma bitfields=disjoint_types
/* Structure that uses disjoint types. */
{
unsigned char error :1;
unsigned char size :4;
unsigned short code :10;
}
#pragma bitfields=default /* Restores to default setting. */

See also

Bitfields, page 212.

data_alignment
Syntax

#pragma data_alignment=expression

Parameters
expression

Description

A constant which must be a power of two (1, 2, 4, etc.).

Use this pragma directive to give a variable a higher (more strict) alignment of the start
address than it would otherwise have. This directive can be used on variables with static
and automatic storage duration.
When you use this directive on variables with automatic storage duration, there is an
upper limit on the allowed alignment for each function, determined by the calling
convention used.
Note: Normally, the size of a variable is a multiple of its alignment. The
data_alignment directive only affects the alignment of the variable’s start address,

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Descriptions of pragma directives

and not its size, and can thus be used for creating situations where the size is not a
multiple of the alignment.

diag_default
Syntax

#pragma diag_default=tag[,tag,...]

Parameters
tag

The number of a diagnostic message, for example the message
number Pe117.

Description

Use this pragma directive to change the severity level back to the default, or to the
severity level defined on the command line by any of the options --diag_error,
--diag_remark, --diag_suppress, or --diag_warnings, for the diagnostic
messages specified with the tags.

See also

Diagnostics, page 152.

diag_error
Syntax

#pragma diag_error=tag[,tag,...]

Parameters
tag

The number of a diagnostic message, for example the message
number Pe117.

Description

Use this pragma directive to change the severity level to error for the specified
diagnostics.

See also

Diagnostics, page 152.

diag_remark
Syntax

#pragma diag_remark=tag[,tag,...]

Parameters
tag

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The number of a diagnostic message, for example the message
number Pe177.

Pragma directives

Description

Use this pragma directive to change the severity level to remark for the specified
diagnostic messages.

See also

Diagnostics, page 152.

diag_suppress
Syntax

#pragma diag_suppress=tag[,tag,...]

Parameters
tag

The number of a diagnostic message, for example the message
number Pe117.

Description

Use this pragma directive to suppress the specified diagnostic messages.

See also

Diagnostics, page 152.

diag_warning
Syntax

#pragma diag_warning=tag[,tag,...]

Parameters
tag

The number of a diagnostic message, for example the message
number Pe826.

Description

Use this pragma directive to change the severity level to warning for the specified
diagnostic messages.

See also

Diagnostics, page 152.

include_alias
Syntax

#pragma include_alias ("orig_header" , "subst_header")
#pragma include_alias ( , )

Parameters
orig_header

The name of a header file for which you want to create an alias.

subst_header

The alias for the original header file.

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Description

Use this pragma directive to provide an alias for a header file. This is useful for
substituting one header file with another, and for specifying an absolute path to a relative
file.
This pragma directive must appear before the corresponding #include directives and
subst_header must match its corresponding #include directive exactly.

Example

#pragma include_alias ( , )
#include 

This example will substitute the relative file stdio.h with a counterpart located
according to the specified path.
See also

Include file search procedure, page 149.

inline
Syntax

#pragma inline[=forced]

Parameters
forced

Description

Disables the compiler’s heuristics and forces inlining.

Use this pragma directive to advise the compiler that the function whose declaration
follows immediately after the directive should be inlined—that is, expanded into the
body of the calling function. Whether the inlining actually occurs is subject to the
compiler’s heuristics.
This is similar to the C++ keyword inline, but has the advantage of being available in
C code.
Specifying #pragma inline=forced disables the compiler’s heuristics and forces
inlining. If the inlining fails for some reason, for example if it cannot be used with the
function type in question (like printf), an error message is emitted.
Note: Because specifying #pragma inline=forced disables the compiler’s
heuristics, including the inlining heuristics, the function declared immediately after the
directive will not be inlined on optimization levels None or Low. No error or warning
message will be emitted.

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Pragma directives

language
Syntax

#pragma language={extended|default}

Parameters

Description

extended

Turns on the IAR Systems language extensions and turns off the
--strict_ansi command line option.

default

Uses the language settings specified by compiler options.

Use this pragma directive to enable the compiler language extensions or for using the
language settings specified on the command line.

location
Syntax

#pragma location={address|NAME}

Parameters
address

The absolute address of the global or static variable for which you
want an absolute location.

NAME

A user-defined section name; cannot be a section name predefined
for use by the compiler and linker.

Description

Use this pragma directive to specify the location—the absolute address—of the global
or static variable whose declaration follows the pragma directive. The variable must be
declared either __no_init or const. Alternatively, the directive can take a string
specifying a section for placing either a variable or a function whose declaration follows
the pragma directive.

Example

#pragma location=0xFFFF0400
__no_init volatile char PORT1; /* PORT1 is located at address
0xFFFF0400 */
#pragma location="foo"
char PORT1; /* PORT1 is located in section foo */
/* A better way is to use a corresponding mechanism */
#define FLASH _Pragma("location=\"FLASH\"")
...
FLASH int i; /* i is placed in the FLASH section */

See also

Controlling data and function placement in memory, page 131.

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message
Syntax

#pragma message(message)

Parameters
message

The message that you want to direct to the standard output stream.

Description

Use this pragma directive to make the compiler print a message to the standard output
stream when the file is compiled.

Example:

#ifdef TESTING
#pragma message("Testing")
#endif

object_attribute
Syntax

#pragma object_attribute=object_attribute[,object_attribute,...]

Parameters

For a list of object attributes that can be used with this pragma directive, see Object
attributes, page 235.

Description

Use this pragma directive to declare a variable or a function with an object attribute. This
directive affects the definition of the identifier that follows immediately after the
directive. The object is modified, not its type. Unlike the directive #pragma
type_attribute that specifies the storing and accessing of a variable or function, it is
not necessary to specify an object attribute in declarations.

Example

#pragma object_attribute=__no_init
char bar;

See also

General syntax rules for extended keywords, page 233.

optimize
Syntax

#pragma optimize=param[ param...]

Parameters

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balanced|size|speed

Optimizes balanced between speed and size,
optimizes for size, or optimizes for speed

none|low|medium|high

Specifies the level of optimization

no_code_motion

Turns off code motion

Pragma directives

Description

no_cse

Turns off common subexpression elimination

no_inline

Turns off function inlining

no_tbaa

Turns off type-based alias analysis

no_unroll

Turns off loop unrolling

no_scheduling

Turns off instruction scheduling

Use this pragma directive to decrease the optimization level, or to turn off some specific
optimizations. This pragma directive only affects the function that follows immediately
after the directive.
The parameters speed, size, and balanced only have effect on the high optimization
level and only one of them can be used as it is not possible to optimize for speed and size
at the same time. It is also not possible to use preprocessor macros embedded in this
pragma directive. Any such macro will not be expanded by the preprocessor.
Note: If you use the #pragma optimize directive to specify an optimization level that
is higher than the optimization level you specify using a compiler option, the pragma
directive is ignored.

Example

#pragma optimize=speed
int small_and_used_often()
{
...
}
#pragma optimize=size no_inline
int big_and_seldom_used()
{
...
}

pack
Syntax

#pragma pack(n)
#pragma pack()
#pragma pack({push|pop}[,name] [,n])

Parameters
n

Sets an optional structure alignment; one of: 1, 2, 4, 8, or 16

Empty list

Restores the structure alignment to default

push

Sets a temporary structure alignment

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Description

pop

Restores the structure alignment from a temporarily pushed alignment

name

An optional pushed or popped alignment label

Use this pragma directive to specify the maximum alignment of struct and union
members.
The #pragma pack directive affects declarations of structures following the pragma
directive to the next #pragma pack or end of file.
Note: This can result in significantly larger and slower code when accessing members
of the structure.

See also

Structure types, page 216 and __packed, page 240.

__printf_args
Syntax

#pragma __printf_args

Description

Use this pragma directive on a function with a printf-style format string. For any call to
that function, the compiler verifies that the argument to each conversion specifier (for
example %d) is syntactically correct.

Example

#pragma __printf_args
int printf(char const *,...);

/* Function call */
printf("%d",x); /* Compiler checks that x is an integer */

required
Syntax

#pragma required=symbol

Parameters
symbol

Description

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Any statically linked function or variable.

Use this pragma directive to ensure that a symbol which is needed by a second symbol
is included in the linked output. The directive must be placed immediately before the
second symbol.

Pragma directives

Use the directive if the requirement for a symbol is not otherwise visible in the
application, for example if a variable is only referenced indirectly through the section it
resides in.
Example

const char copyright[] = "Copyright by me";
#pragma required=copyright
int main()
{
/* Do something here. */
}

Even if the copyright string is not used by the application, it will still be included by the
linker and available in the output.

rtmodel
Syntax

#pragma rtmodel="key","value"

Parameters

Description

"key"

A text string that specifies the runtime model attribute.

"value"

A text string that specifies the value of the runtime model attribute.
Using the special value * is equivalent to not defining the attribute at
all.

Use this pragma directive to add a runtime model attribute to a module, which can be
used by the linker to check consistency between modules.
This pragma directive is useful for enforcing consistency between modules. All modules
that are linked together and define the same runtime attribute key must have the same
value for the corresponding key, or the special value *. It can, however, be useful to state
explicitly that the module can handle any runtime model.
A module can have several runtime model definitions.
Note: The predefined compiler runtime model attributes start with a double underscore.
To avoid confusion, this style must not be used in the user-defined attributes.

Example

#pragma rtmodel="I2C","ENABLED"

The linker will generate an error if a module that contains this definition is linked with
a module that does not have the corresponding runtime model attributes defined.
See also

Checking module consistency, page 87.

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__scanf_args
Syntax

#pragma __scanf_args

Description

Use this pragma directive on a function with a scanf-style format string. For any call to
that function, the compiler verifies that the argument to each conversion specifier (for
example %d) is syntactically correct.

Example

#pragma __scanf_args
int printf(char const *,...);

/* Function call */
scanf("%d",x); /* Compiler checks that x is an integer */

section
Syntax

#pragma section="NAME" [align]

alias
#pragma segment="NAME" [align]

Parameters
align

Specifies an alignment for the section. The value must be a constant
integer expression to the power of two.

Use this pragma directive to define a section name that can be used by the section
operators __section_begin, __section_end, and __section_size. All section
declarations for a specific section must have the same memory type attribute and
alignment.

Example

#pragma section="MYSECTION" 4

See also

Dedicated section operators, page 223. For more information about sections, see the
chapter Linking your application.

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The name of the section or segment

Description

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NAME

Pragma directives

swi_number
Syntax

#pragma swi_number=number

Parameters
number

The software interrupt number

Description

Use this pragma directive together with the __swi extended keyword. It is used as an
argument to the generated SWC assembler instruction, and is used for selecting one
software interrupt function in a system containing several such functions.

Example

#pragma swi_number=17

See also

Software interrupts, page 34.

type_attribute
Syntax

#pragma type_attribute=type_attribute[,type_attribute,...]

Parameters

For a list of type attributes that can be used with this pragma directive, see Type
attributes, page 233.

Description

Use this pragma directive to specify IAR-specific type attributes, which are not part of
the ISO/ANSI C language standard. Note however, that a given type attribute might not
be applicable to all kind of objects.
This directive affects the declaration of the identifier, the next variable, or the next
function that follows immediately after the pragma directive.

Example

In this example, thumb-mode code is generated for the function foo:
#pragma type_attribute=__thumb
void foo(void)
{
}

This declaration, which uses extended keywords, is equivalent:
__thumb void foo(void);
{
}

See also

See the chapter Extended keywords for more details.

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weak
Syntax

#pragma weak symbol1={symbol2}

Parameters

Description

Example

symbol1

A function or variable with external linkage.

symbol2

A defined function or variable.

This pragma directive can be used in one of two ways:
●

To make the definition of a function or variable with external linkage a weak
definition. The __weak attribute can also be used for this purpose.

●

To create a weak alias for another function or variable. You can make more than one
alias for the same function or variable.

To make the definition of foo a weak definition, write:
#pragma weak foo

To make NMI_Handler a weak alias for Default_Handler, write:
#pragma weak NMI_Handler=Default_Handler

If NMI_Handler is not defined elsewhere in the program, all references to
NMI_Handler will refer to Default_Handler.
See also

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__weak, page 243.

Intrinsic functions
This chapter gives reference information about the intrinsic functions, a
predefined set of functions available in the compiler.
The intrinsic functions provide direct access to low-level processor operations
and can be very useful in, for example, time-critical routines. The intrinsic
functions compile into inline code, either as a single instruction or as a short
sequence of instructions.

Summary of intrinsic functions
To use intrinsic functions in an application, include the header file intrinsics.h.
Note that the intrinsic function names start with double underscores, for example:
__disable_interrupt

This table summarizes the intrinsic functions:
Intrinsic function

Description

__CLZ

Inserts a CLZ instruction

__disable_fiq

Disables fast interrupt requests (fiq)

__disable_interrupt

Disables interrupts

__disable_irq

Disables interrupt requests (irq)

__DMB

Inserts a DMB instruction

__DSB

Inserts a DSB instruction

__enable_fiq

Enables fast interrupt requests (fiq)

__enable_interrupt

Enables interrupts

__enable_irq

Enables interrupt requests (irq)

__get_BASEPRI

Returns the value of the Cortex-M3 BASEPRI register

__get_CONTROL

Returns the value of the Cortex-M CONTROL register

__get_CPSR

Returns the value of the ARM CPSR (Current Program
Status Register)

__get_FAULTMASK

Returns the value of the Cortex-M3 FAULTMASK register

__get_interrupt_state

Returns the interrupt state

Table 30: Intrinsic functions summary

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Summary of intrinsic functions

Intrinsic function

Description

__get_PRIMASK

Returns the value of the Cortex-M PRIMASK register

__ISB

Inserts a ISB instruction

__LDC

Inserts the coprocessor load instruction LDC

__LDCL

Inserts the coprocessor load instruction LDCL

__LDC2

Inserts the coprocessor load instruction LDC2

__LDC2L

Inserts the coprocessor load instruction LDC2L

__LDC_noidx

Inserts the coprocessor load instruction LDC

__LDCL_noidx

Inserts the coprocessor load instruction LDCL

__LDC2_noidx

Inserts the coprocessor load instruction LDC2

__LDC2L_noidx

Inserts the coprocessor load instruction LDC2L

__LDREX

Inserts an LDREX instruction

__MCR

Inserts the coprocessor write instruction MCR

__MRC

Inserts the coprocessor read instruction MRC

__no_operation

Inserts a NOP instruction

__QADD

Inserts a QADD instruction

__QADD8

Inserts a QADD8 instruction

__QADD16

Inserts a QADD16 instruction

__QASX

Inserts a QASX instruction

__QDADD

Inserts a QDADD instruction

__QDOUBLE

Inserts a QADD instruction

__QDSUB

Inserts a QDSUB instruction

__QFlag

Returns the Q flag that indicates if overflow/saturation has
occurred

__QSUB

Inserts a QSUB instruction

__QSUB8

Inserts a QSUB8 instruction

__QSUB16

Inserts a QSUB16 instruction

__QSAX

Inserts a QSAX instruction

__REV

Inserts a REV instruction

__REVSH

Inserts a REVSH instruction

__SADD8

Inserts a SADD8 instruction

__SADD16

Inserts a SADD16 instruction

__SASX

Inserts a SASX instruction

Table 30: Intrinsic functions summary (Continued)

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Intrinsic functions

Intrinsic function

Description

__SEL

Inserts a SEL instruction

__set_BASEPRI

Sets the value of the Cortex-M3 BASEPRI register

__set_CONTROL

Sets the value of the Cortex-M CONTROL register

__set_CPSR

Sets the value of the ARM CPSR (Current Program Status
Register)

__set_FAULTMASK

Sets the value of the Cortex-M3 FAULTMASK register

__set_interrupt_state

Restores the interrupt state

__set_PRIMASK

Sets the value of the Cortex-M PRIMASK register

__SHADD8

Inserts a SHADD8 instruction

__SHADD16

Inserts a SHADD16 instruction

__SHASX

Inserts a SHASX instruction

__SHSUB8

Inserts a SHSUB8 instruction

__SHSUB16

Inserts a SHSUB16 instruction

__SHSAX

Inserts a SHSAX instruction

__SMUL

Inserts a signed 16-bit multiplication

__SSUB8

Inserts a SSUB8 instruction

__SSUB16

Inserts a SSUB16 instruction

__SSAX

Inserts a SSAX instruction

__STC

Inserts the coprocessor store instruction STC

__STCL

Inserts the coprocessor store instruction STCL

__STC2

Inserts the coprocessor store instruction STC2

__STC2L

Inserts the coprocessor store instruction STC2L

__STC_noidx

Inserts the coprocessor store instruction STC

__STCL_noidx

Inserts the coprocessor store instruction STCL

__STC2_noidx

Inserts the coprocessor store instruction STC2

__STC2L_noidx

Inserts the coprocessor store instruction STC2L

__STREX

Inserts a STREX instruction

__SWP

Inserts an SWP instruction

__SWPB

Inserts an SWPB instruction

__UADD8

Inserts a UADD8 instruction

__UADD16

Inserts a UADD16 instruction

__UASX

Inserts a UASX instruction

Table 30: Intrinsic functions summary (Continued)

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Descriptions of intrinsic functions

Intrinsic function

Description

__UHADD8

Inserts a UHADD8 instruction

__UHADD16

Inserts a UHADD16 instruction

__UHASX

Inserts a UHASX instruction

__UHSAX

Inserts a UHSAX instruction

__UHSUB8

Inserts a UHSUB8 instruction

__UHSUB16

Inserts a UHSUB16 instruction

__UQADD8

Inserts a UQADD8 instruction

__UQADD16

Inserts a UQADD16 instruction

__UQASX

Inserts a UQASX instruction

__UQSUB8

Inserts a UQSUB8 instruction

__UQSUB16

Inserts a UQSUB16 instruction

__UQSAX

Inserts a UQSAX instruction

__USAX

Inserts a USAX instruction

__USUB8

Inserts a USUB8 instruction

__USUB16

Inserts a USUB16 instruction

Table 30: Intrinsic functions summary (Continued)

Descriptions of intrinsic functions
This section gives reference information about each intrinsic function.

__CLZ
Syntax

unsigned char __CLZ(unsigned long);

Description

Inserts a CLZ instruction.
This intrinsic function requires an ARM v5 architecture or higher for ARM mode, and
ARM v6T2 or higher for Thumb mode.

__disable_fiq
Syntax

void __disable_fiq(void);

Description

Disables fast interrupt requests (fiq).

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Intrinsic functions

This intrinsic function can only be used in privileged mode and is not available for
Cortex-M devices.

__disable_interrupt
Syntax

void __disable_interrupt(void);

Description

Disables interrupts. For Cortex-M devices, it raises the execution priority level to 0 by
setting the priority mask bit, PRIMASK. For other devices, it disables interrupt requests
(irq) and fast interrupt requests (fiq).
This intrinsic function can only be used in privileged mode.

__disable_irq
Syntax

void __disable_irq(void);

Description

Disables interrupt requests (irq).
This intrinsic function can only be used in privileged mode and is not available for
Cortex-M devices.

__DMB
Syntax

void __DMB(void);

Description

Inserts a DMB instruction. This intrinsic function requires an ARM v7 architecture or
higher.

__DSB
Syntax

void __DSB(void);

Description

Inserts a DSB instruction. This intrinsic function requires an ARM v7 architecture or
higher.

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__enable_fiq
Syntax

void __enable_fiq(void);

Description

Enables fast interrupt requests (fiq).
This intrinsic function can only be used in privileged mode, and it is not available for
Cortex-M devices.

__enable_interrupt
Syntax

void __enable_interrupt(void);

Description

Enables interrupts. For Cortex-M devices, it resets the execution priority level to default
by clearing the priority mask bit, PRIMASK. For other devices, it enables interrupt
requests (irq) and fast interrupt requests (fiq).
This intrinsic function can only be used in privileged mode.

__enable_irq
Syntax

void __enable_irq(void);

Description

Enables interrupt requests (irq).
This intrinsic function can only be used in privileged mode, and it is not available for
Cortex-M devices.

__get_BASEPRI
Syntax

unsigned long __get_BASEPRI(void);

Description

Returns the value of the BASEPRI register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M3 device.

__get_CONTROL
Syntax

unsigned long __get_CONTROL(void);

Description

Returns the value of the CONTROL register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M device.

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Intrinsic functions

__get_CPSR
Syntax

unsigned long __get_CPSR(void);

Description

Returns the value of the ARM CPSR (Current Program Status Register). This intrinsic
function can only be used in privileged mode, is not available for Cortex-M devices, and
it requires ARM mode.

__get_FAULTMASK
Syntax

unsigned long __get_FAULTMASK(void);

Description

Returns the value of the FAULTMASK register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M3 device.

__get_interrupt_state
Syntax

__istate_t __get_interrupt_state(void);

Description

Returns the global interrupt state. The return value can be used as an argument to the
__set_interrupt_state intrinsic function, which will restore the interrupt state.
This intrinsic function can only be used in privileged mode, and cannot be used when
using the --aeabi compiler option.

Example

__istate_t s = __get_interrupt_state();
__disable_interrupt();
/* Do something here. */
__set_interrupt_state(s);

The advantage of using this sequence of code compared to using
__disable_interrupt and __enable_interrupt is that the code in this example
will not enable any interrupts disabled before the call of __get_interrupt_state.

__get_PRIMASK
Syntax

unsigned long __get_PRIMASK(void);

Description

Returns the value of the PRIMASK register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M device.

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Descriptions of intrinsic functions

__ISB
Syntax

void __ISB(void);

Description

Inserts a ISB instruction. This intrinsic function requires an ARM v7 architecture or
higher.

__LDC
__LDCL
__LDC2
__LDC2L
Syntax

void __nnn(__ul coproc, __ul CRn, __ul const *src);

where nnn can be one of LDC, LDCL, LDC2, or LDC2L.
Parameters

Description

coproc

The coprocessor number 0..15.

CRn

The coprocessor register to load.

src

A pointer to the data to load.

Inserts the coprocessor load instruction LDC—or one of its variants—which means that
a value will be loaded into a coprocessor register. The parameters coproc and CRn will
be encoded in the instruction and must therefore be constants.

__LDC_noidx
__LDCL_noidx
__LDC2_noidx
__LDC2L_noidx
Syntax

void __nnn_noidx(__ul coproc, __ul CRn, __ul const *src, __ul
option);

where nnn can be one of LDC, LDCL, LDC2, or LDC2L.
Parameters

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coproc

The coprocessor number 0..15.

CRn

The coprocessor register to load.

src

A pointer to the data to load.

Intrinsic functions

option

Description

Additional coprocessor option 0..255.

Inserts the coprocessor load instruction LDC, or one of its variants. A value will be
loaded into a coprocessor register. The parameters coproc, CRn, and option will be
encoded in the instruction and must therefore be constants.

__LDREX
Syntax

unsigned long __LDREX(unsigned long *);

Description

Inserts an LDREX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v6T2 or higher for Thumb mode.

__MCR
Syntax

void __MCR(__ul coproc, __ul opcode_1, __ul src, __ul CRn, __ul
CRm, __ul opcode_2);

Parameters

Description

coproc

The coprocessor number 0..15.

opcode_1

Coprocessor-specific operation code.

src

The value to be written to the coprocessor.

CRn

The coprocessor register to write to.

CRm

Additional coprocessor register; set to zero if not used.

opcode_2

Additional coprocessor-specific operation code; set to zero if not used.

Inserts a coprocessor write instruction (MCR). A value will be written to a coprocessor
register. The parameters coproc, opcode_1, CRn, CRm, and opcode_2 will be encoded
in the MCR instruction operation code and must therefore be constants.
This intrinsic function requires either ARM mode, or an ARM v6T2 or higher for
Thumb mode.

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__MRC
Syntax

unsigned long __MRC(__ul coproc, __ul opcode_1, __ul CRn, __ul
CRm, __ul opcode_2);

Parameters

Description

coproc

The coprocessor number 0..15.

opcode_1

Coprocessor-specific operation code.

CRn

The coprocessor register to write to.

CRm

Additional coprocessor register; set to zero if not used.

opcode_2

Additional coprocessor-specific operation code; set to zero if not used.

Inserts a coprocessor read instruction (MRC). Returns the value of the specified
coprocessor register. The parameters coproc, opcode_1, CRn, CRm, and opcode_2 will
be encoded in the MRC instruction operation code and must therefore be constants.
This intrinsic function requires either ARM mode, or an ARM v6T2 or higher for
Thumb mode.

__no_operation
Syntax

void __no_operation(void);

Description

Inserts a NOP instruction.

__QADD
Syntax

signed long __QADD(signed long, signed long);

Description

Inserts a QADD instruction.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QADD8
Syntax

unsigned long __QADD8(unsigned long, unsigned long);

Description

Inserts a QADD8 instruction.

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Intrinsic functions

This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QADD16
Syntax

unsigned long __QADD16(unsigned long, unsigned long);

Description

Inserts a QADD16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QASX
Syntax

unsigned long __QASX(unsigned long, unsigned long);

Description

Inserts a QASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QDADD
Syntax

signed long __QDADD(signed long, signed long);

Description

Inserts a QDADD instruction.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QDOUBLE
Syntax

signed long __QDOUBLE(signed long);

Description

Inserts an instruction QADD Rd,Rs,Rs for a source register Rs, and a destination register
Rd.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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__QDSUB
Syntax

signed long __QDSUB(signed long, signed long);

Description

Inserts a QDSUB instruction.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QFlag
Syntax

int __QFlag(void);

Description

Returns the Q flag that indicates if overflow/saturation has occurred.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QSUB
Syntax

signed long __QSUB(signed long, signed long);

Description

Inserts a QSUB instruction.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QSUB8
Syntax

unsigned long __QSUB8(unsigned long, unsigned long);

Description

Inserts a QSUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QSUB16
Syntax

unsigned long __QSUB16(unsigned long, unsigned long);

Description

Inserts a QSUB16 instruction.

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Intrinsic functions

This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__QSAX
Syntax

unsigned long __QSAX(unsigned long, unsigned long);

Description

Inserts a QSAX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__REV
Syntax

unsigned long __REV(unsigned long);

Description

Inserts a REV instruction. This intrinsic function requires an ARM v6 architecture or
higher.

__REVSH
Syntax

signed long __REVSH(short);

Description

Inserts a REVSH instruction. This intrinsic function requires an ARM v6 architecture or
higher.

__SADD8
Syntax

unsigned long __SADD8(unsigned long, unsigned long);

Description

Inserts a SADD8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SADD16
Syntax

unsigned long __SADD16(unsigned long, unsigned long);

Description

Inserts a SADD16 instruction.

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This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SASX
Syntax

unsigned long __SASX(unsigned long, unsigned long);

Description

Inserts a SASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SEL
Syntax

unsigned long __SEL(unsigned long, unsigned long);

Description

Inserts a SEL instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__set_BASEPRI
Syntax

void __set_BASEPRI(unsigned long);

Description

Sets the value of the BASEPRI register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M3 device.

__set_CONTROL
Syntax

void __set_CONTROL(unsigned long);

Description

Sets the value of the CONTROL register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M device.

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Intrinsic functions

__set_CPSR
Syntax

void __set_CPSR(unsigned long);

Description

Sets the value of the ARM CPSR (Current Program Status Register). Only the control
field is changed (bits 0-7). This intrinsic function can only be used in privileged mode,
is not available for Cortex-M devices, and it requires ARM mode.

__set_FAULTMASK
Syntax

void __set_FAULTMASK(unsigned long);

Description

Sets the value of the FAULTMASK register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M3 device.

__set_interrupt_state
Syntax

void __set_interrupt_state(__istate_t);

Descriptions

Restores the interrupt state to a value previously returned by the
__get_interrupt_state function.
For information about the __istate_t type, see __get_interrupt_state, page 265.

__set_PRIMASK
Syntax

void __set_PRIMASK(unsigned long);

Description

Sets the value of the PRIMASK register. This intrinsic function can only be used in
privileged mode and it requires a Cortex-M device.

__SHADD8
Syntax

unsigned long __SHADD8(unsigned long, unsigned long);

Description

Inserts a SHADD8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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__SHADD16
Syntax

unsigned long __SHADD16(unsigned long, unsigned long);

Description

Inserts a SHADD16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SHASX
Syntax

unsigned long __SHASX(unsigned long, unsigned long);

Description

Inserts a SHASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SHSUB8
Syntax

unsigned long __SHSUB8(unsigned long, unsigned long);

Description

Inserts a SHSUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SHSUB16
Syntax

unsigned long __SHSUB16(unsigned long, unsigned long);

Description

Inserts a SHSUB16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SHSAX
Syntax

unsigned long __SHSAX(unsigned long, unsigned long);

Description

Inserts a SHSAX instruction.

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Intrinsic functions

This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SMUL
Syntax

signed long __SMUL(signed short, signed short);

Description

Inserts a signed 16-bit multiplication.
This intrinsic function requires an ARM v5E architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SSUB8
Syntax

unsigned long __SSUB8(unsigned long, unsigned long);

Description

Inserts a SSUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SSUB16
Syntax

unsigned long __SSUB16(unsigned long, unsigned long);

Description

Inserts a SSUB16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__SSAX
Syntax

unsigned long __SSAX(unsigned long, unsigned long);

Description

Inserts a SSAX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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__STC
__STCL
__STC2
__STC2L
Syntax

void __nnn(__ul coproc, __ul CRn, __ul const *dst);

where nnn can be one of STC, STCL, STC2, or STC2L.
Parameters

Description

coproc

The coprocessor number 0..15.

CRn

The coprocessor register to load.

dst

A pointer to the destination.

Inserts the coprocessor store instruction STC—or one of its variants—which means that
the value of the specified coprocessor register will be written to a memory location. The
parameters coproc and CRn will be encoded in the instruction and must therefore be
constants.

__STC_noidx
__STCL_noidx
__STC2_noidx
__STC2L_noidx
Syntax

void __nnn_noidx(__ul coproc, __ul CRn, __ul const *dst, __ul
option);

where nnn can be one of STC, STCL, STC2, or STC2L.
Parameters

Description

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coproc

The coprocessor number 0..15.

CRn

The coprocessor register to load.

dst

A pointer to the destination.

option

Additional coprocessor option 0..255.

Inserts the coprocessor store instruction STC—or one of its variants—which means that
the value of the specified coprocessor register will be written to a memory location. The
parameters coproc, CRn, and option will be encoded in the instruction and must
therefore be constants.

Intrinsic functions

__STREX
Syntax

unsigned long __STREX(unsigned long, unsigned long *);

Description

Inserts a STREX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v6T2 or higher for Thumb mode.

__SWP
Syntax

unsigned long __SWP(unsigned long, unsigned long *);

Description

Inserts an SWP instruction. This intrinsic function requires ARM mode.

__SWPB
Syntax

char __SWPB(unsigned char, unsigned char *);

Description

Inserts an SWPB instruction. This intrinsic function requires ARM mode.

__UADD8
Syntax

unsigned long __UADD8(unsigned long, unsigned long);

Description

Inserts a UADD8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UADD16
Syntax

unsigned long __UADD16(unsigned long, unsigned long);

Description

Inserts a UADD16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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__UASX
Syntax

unsigned long __UASX(unsigned long, unsigned long);

Description

Inserts a UASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHADD8
Syntax

unsigned long __UHADD8(unsigned long, unsigned long);

Description

Inserts a UHADD8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHADD16
Syntax

unsigned long __UHADD16(unsigned long, unsigned long);

Description

Inserts a UHADD16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHASX
Syntax

unsigned long __UHASX(unsigned long, unsigned long);

Description

Inserts a UHASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHSAX
Syntax

unsigned long __UHSAX(unsigned long, unsigned long);

Description

Inserts a UHSAX instruction.

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Intrinsic functions

This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHSUB8
Syntax

unsigned long __UHSUB8(unsigned long, unsigned long);

Description

Inserts a UHSUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UHSUB16
Syntax

unsigned long __UHSUB16(unsigned long, unsigned long);

Description

Inserts a UHSUB16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UQADD8
Syntax

unsigned long __UQADD8(unsigned long, unsigned long);

Description

Inserts a UQADD8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UQADD16
Syntax

unsigned long __UQADD16(unsigned long, unsigned long);

Description

Inserts a UQADD16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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__UQASX
Syntax

unsigned long __UQASX(unsigned long, unsigned long);

Description

Inserts a UQASX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UQSUB8
Syntax

unsigned long __UQSUB8(unsigned long, unsigned long);

Description

Inserts a UQSUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UQSUB16
Syntax

unsigned long __UQSUB16(unsigned long, unsigned long);

Description

Inserts a UQSUB16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__UQSAX
Syntax

unsigned long __UQSAX(unsigned long, unsigned long);

Description

Inserts a UQSAX instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__USAX
Syntax

unsigned long __USAX(unsigned long, unsigned long);

Description

Inserts a USAX instruction.

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Intrinsic functions

This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__USUB8
Syntax

unsigned long __USUB8(unsigned long, unsigned long);

Description

Inserts a USUB8 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

__USUB16
Syntax

unsigned long __USUB16(unsigned long, unsigned long);

Description

Inserts a USUB16 instruction.
This intrinsic function requires an ARM v6 architecture or higher for ARM mode, and
ARM v7 with profile A or R for Thumb mode.

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Descriptions of intrinsic functions

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The preprocessor
This chapter gives a brief overview of the preprocessor, including reference
information about the different preprocessor directives, symbols, and other
related information.

Overview of the preprocessor
The preprocessor of the IAR C/C++ Compiler for ARM adheres to the ISO/ANSI
standard. The compiler also makes these preprocessor-related features available to you:
●

Predefined preprocessor symbols
These symbols allow you to inspect the compile-time environment, for example the
time and date of compilation. For details, see Descriptions of predefined
preprocessor symbols, page 284.

●

User-defined preprocessor symbols defined using a compiler option
In addition to defining your own preprocessor symbols using the #define directive,
you can also use the option -D, see -D, page 164.

●

Preprocessor extensions
There are several preprocessor extensions, for example many pragma directives; for
more information, see the chapter Pragma directives in this guide. Read also about
the corresponding _Pragma operator and the other extensions related to the
preprocessor, see Descriptions of miscellaneous preprocessor extensions, page 287.

●

Preprocessor output
Use the option --preprocess to direct preprocessor output to a named file, see
--preprocess, page 184.

Some parts listed by the ISO/ANSI standard are implementation-defined, for example
the character set used in the preprocessor directives and inclusion of bracketed and
quoted filenames. To read more about this, see Preprocessing directives, page 354.

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Descriptions of predefined preprocessor symbols

Descriptions of predefined preprocessor symbols
This table describes the predefined preprocessor symbols:
Predefined symbol

Identifies

__BASE_FILE__

A string that identifies the name of the base source file (that is,
not the header file), being compiled. See also __FILE__, page
284, and --no_path_in_file_macros, page 178.

__BUILD_NUMBER__

A unique integer that identifies the build number of the
compiler currently in use.

__CORE__

An integer that identifies the processor architecture in use.
The symbol reflects the --cpu option and is defined to
__ARM4M__, __ARM4TM__, __ARM5__, __ARM5E__,
__ARM6__, __ARM6M__, __ARM6SM__, __ARM7M__, or
__ARM7R__. These symbolic names can be used when
testing the __CORE__ symbol.

__ARMVFP__

An integer that reflects the --fpu option and is defined to 1
for VFPv1 and 2 for VFPv2. If VFP code generation is disabled
(default), the symbol will be undefined.

__cplusplus

An integer which is defined when the compiler runs in any of
the C++ modes, otherwise it is undefined. When defined, its
value is 199711L. This symbol can be used with #ifdef to
detect whether the compiler accepts C++ code. It is
particularly useful when creating header files that are to be
shared by C and C++ code.*

__CPU_MODE__

An integer that reflects the selected CPU mode and is defined
to 1 for Thumb and 2 for ARM.

__DATE__

A string that identifies the date of compilation, which is
returned in the form "Mmm dd yyyy", for example "Oct 30
2008". *

__embedded_cplusplus

An integer which is defined to 1 when the compiler runs in
any of the C++ modes, otherwise the symbol is undefined.
This symbol can be used with #ifdef to detect whether the
compiler accepts C++ code. It is particularly useful when
creating header files that are to be shared by C and C++
code.*

__FILE__

A string that identifies the name of the file being compiled,
which can be both the base source file and any included
header file. See also __BASE_FILE__, page 284, and
--no_path_in_file_macros, page 178.*

Table 31: Predefined symbols

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The preprocessor

Predefined symbol

Identifies

__func__

A string that identifies the name of the function in which the
symbol is used. This is useful for assertions and other trace
utilities. The symbol requires that language extensions are
enabled, see -e, page 169. See also __PRETTY_FUNCTION__,
page 285.

__FUNCTION__

A string that identifies the name of the function in which the
symbol is used. This is useful for assertions and other trace
utilities. The symbol requires that language extensions are
enabled, see -e, page 169. See also __PRETTY_FUNCTION__,
page 285.

__IAR_SYSTEMS_ICC__

An integer that identifies the IAR compiler platform. The
current value is 7. Note that the number could be higher in a
future version of the product. This symbol can be tested with
#ifdef to detect whether the code was compiled by a
compiler from IAR Systems.

__ICCARM__

An integer that is set to 1 when the code is compiled with the
IAR C/C++ Compiler for ARM, and otherwise to 0.

__LINE__

An integer that identifies the current source line number of
the file being compiled, which can be both the base source file
and any included header file.*

__LITTLE_ENDIAN__

An integer that reflects the --endian option and is defined
to 1 when the byte order is little-endian. The symbol is
defined to 0 when the byte order is big-endian.

__PRETTY_FUNCTION__

A string that identifies the function name, including parameter
types and return type, of the function in which the symbol is
used, for example "void func(char)". This symbol is
useful for assertions and other trace utilities. The symbol
requires that language extensions are enabled, see -e, page
169. See also __func__, page 285.

__STDC__

An integer that is set to 1, which means the compiler adheres
to the ISO/ANSI C standard. This symbol can be tested with
#ifdef to detect whether the compiler in use adheres to
ISO/ANSI C.*

__STDC_VERSION__

An integer that identifies the version of ISO/ANSI C standard
in use. The symbols expands to 199409L. This symbol does
not apply in EC++ mode.*

__TIME__

A string that identifies the time of compilation in the form
"hh:mm:ss".*

Table 31: Predefined symbols (Continued)

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Descriptions of predefined preprocessor symbols

Predefined symbol

Identifies

__VER__

An integer that identifies the version number of the IAR
compiler in use. For example, version 5.11.3 is returned as
5011003.

Table 31: Predefined symbols (Continued)
*

This symbol is required by the ISO/ANSI standard.

__TID__
Description

Target identifier for the IAR C/C++ Compiler for ARM. Expands to the target identifier
which contains the following parts:
●

A one-bit intrinsic flag (i) which is reserved for use by IAR

●

A target identifier (t) unique for each IAR compiler. For the ARM compiler, the
target identifier is 79

●

A value (c) reserved for specifying different CPU core families. The value is
derived from the setting of the --cpu option:

Value

CPU core family

0

Unspecified

1

ARM7TDMI

2

ARM9TDMI

3

ARM9E

4

ARM10E

5

ARM11

6

Cortex–M3

7

Cortex–M0 or Cortex–M1

8

Cortex–R4

Table 32: Values for specifying different CPU core families in __TID__

The __TID__value is constructed as:
((i << 15) | (t << 8) | (c << 4))

You can extract the values as follows:

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i = (__TID__ >> 15) & 0x01;

/* intrinsic flag */

t = (__TID__ >> 8) & 0x7F;

/* target identifier */

c = (__TID__ >> 4) & 0x0F;

/* cpu core family */

The preprocessor

To find the value of the target identifier for the current compiler, execute:
printf("%ld",(__TID__ >> 8) & 0x7F)

Note: Because coding may change or functionality may be entirely removed in future
versions, the use of __TID__ is not recommended. We recommend that you use the
symbols __ICCARM__ and __CORE__ instead.

Descriptions of miscellaneous preprocessor extensions
This section gives reference information about the preprocessor extensions that are
available in addition to the predefined symbols, pragma directives, and ISO/ANSI
directives.

NDEBUG
Description

This preprocessor symbol determines whether any assert macros you have written in
your application shall be included or not in the built application.
If this symbol is not defined, all assert macros are evaluated. If the symbol is defined,
all assert macros are excluded from the compilation. In other words, if the symbol is:
●

defined, the assert code will not be included

●

not defined, the assert code will be included

This means that if you write any assert code and build your application, you should
define this symbol to exclude the assert code from the final application.
Note that the assert macro is defined in the assert.h standard include file.
See also

Assert, page 85.
In the IDE, the NDEBUG symbol is automatically defined if you build your application in
the Release build configuration.

_Pragma()
Syntax

_Pragma("string")

where string follows the syntax of the corresponding pragma directive.
Description

This preprocessor operator is part of the C99 standard and can be used, for example, in
defines and is equivalent to the #pragma directive.
Note: The -e option—enable language extensions—does not have to be specified.

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Descriptions of miscellaneous preprocessor extensions

Example

#if NO_OPTIMIZE
#define NOOPT _Pragma("optimize=none")
#else
#define NOOPT
#endif

See also

See the chapter Pragma directives.

#warning message
Syntax

#warning message

where message can be any string.
Description

Use this preprocessor directive to produce messages. Typically, this is useful for
assertions and other trace utilities, similar to the way the ISO/ANSI standard #error
directive is used.

__VA_ARGS__
Syntax

#define P(...)
__VA_ARGS__
#define P(x, y, ...)
x + y + __VA_ARGS__
__VA_ARGS__ will contain all variadic arguments concatenated, including the

separating commas.
Description

Variadic macros are the preprocessor macro equivalents of printf style functions.
__VA_ARGS__ is part of the C99 standard.

Example

#if DEBUG
#define DEBUG_TRACE(S, ...) printf(S, __VA_ARGS__)
#else
#define DEBUG_TRACE(S, ...)
#endif
/* Place your own code here */
DEBUG_TRACE("The value is:%d\n",value);

will result in:
printf("The value is:%d\n",value);

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Library functions
This chapter gives an introduction to the C and C++ library functions. It also
lists the header files used for accessing library definitions.
For detailed reference information about the library functions, see the online
help system.

Introduction
The compiler comes with the IAR DLIB Library, a complete ISO/ANSI C and C++
library. This library also supports floating-point numbers in IEEE 754 format and it can
be configured to include different levels of support for locale, file descriptors, multibyte
characters, et cetera.
For additional information, see the chapter The DLIB runtime environment.
For detailed information about the library functions, see the online documentation
supplied with the product. There is also keyword reference information for the DLIB
library functions. To obtain reference information for a function, select the function
name in the editor window and press F1.
For additional information about library functions, see the chapter
Implementation-defined behavior in this guide.

HEADER FILES
Your application program gains access to library definitions through header files, which
it incorporates using the #include directive. The definitions are divided into several
different header files, each covering a particular functional area, letting you include just
those that are required.
It is essential to include the appropriate header file before making any reference to its
definitions. Failure to do so can cause the call to fail during execution, or generate error
or warning messages at compile time or link time.

LIBRARY OBJECT FILES
Most of the library definitions can be used without modification, that is, directly from
the library object files that are supplied with the product. For information about how to
choose a runtime library, see Basic project configuration, page 19. The linker will
include only those routines that are required—directly or indirectly—by your
application.

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REENTRANCY
A function that can be simultaneously invoked in the main application and in any
number of interrupts is reentrant. A library function that uses statically allocated data is
therefore not reentrant.
Most parts of the DLIB library are reentrant, but these functions and parts are not
reentrant because they need static data:
●

Heap functions—malloc, free, realloc, calloc, and the C++ operators new
and delete

●

Time functions—asctime, localtime, gmtime, mktime

●

Multibyte functions—mbrlen, mbrtowc, mbsrtowc, wcrtomb, wcsrtomb,
wctomb

●

The miscellaneous functions setlocale, rand, atexit, strerror, strtok

●

Functions that use files in some way. This includes printf, scanf, getchar, and
putchar. The functions sprintf and sscanf are not included.

Some functions also share the same storage for errno. These functions are not
reentrant, since an errno value resulting from one of these functions can be destroyed
by a subsequent use of the function before it is read. Among these functions are:
exp, exp10, ldexp, log, log10, pow, sqrt, acos, asin, atan2,
cosh, sinh, strtod, strtol, strtoul

Remedies for this are:
●

Do not use non-reentrant functions in interrupt service routines

●

Guard calls to a non-reentrant function by a mutex, or a secure region, etc.

IAR DLIB Library
The IAR DLIB Library provides most of the important C and C++ library definitions
that apply to embedded systems. These are of the following types:
●

Adherence to a free-standing implementation of the ISO/ANSI standard for the
programming language C. For additional information, see the chapter
Implementation-defined behaviour in this guide.

●

Standard C library definitions, for user programs.

●

Embedded C++ library definitions, for user programs.

●

CSTARTUP, the module containing the start-up code. It is described in the chapter

●

Runtime support libraries; for example low-level floating-point routines.

The DLIB runtime environment in this guide.

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Library functions

●

Intrinsic functions, allowing low-level use of ARM features. See the chapter
Intrinsic functions for more information.

In addition, the IAR DLIB Library includes some added C functionality, partly taken
from the C99 standard, see Added C functionality, page 294.

C HEADER FILES
This section lists the header files specific to the DLIB library C definitions. Header files
may additionally contain target-specific definitions; these are documented in the chapter
Compiler extensions.
The following table lists the C header files:
Header file

Usage

assert.h

Enforcing assertions when functions execute

ctype.h

Classifying characters

errno.h

Testing error codes reported by library functions

float.h

Testing floating-point type properties

inttypes.h

Defining formatters for all types defined in stdint.h

iso646.h

Using Amendment 1—iso646.h standard header

limits.h

Testing integer type properties

locale.h

Adapting to different cultural conventions

math.h

Computing common mathematical functions

setjmp.h

Executing non-local goto statements

signal.h

Controlling various exceptional conditions

stdarg.h

Accessing a varying number of arguments

stdbool.h

Adds support for the bool data type in C.

stddef.h

Defining several useful types and macros

stdint.h

Providing integer characteristics

stdio.h

Performing input and output

stdlib.h

Performing a variety of operations

string.h

Manipulating several kinds of strings

time.h

Converting between various time and date formats

wchar.h

Support for wide characters

wctype.h

Classifying wide characters

Table 33: Traditional standard C header files—DLIB

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C++ HEADER FILES
This section lists the C++ header files.

Embedded C++
The following table lists the Embedded C++ header files:
Header file

Usage

complex

Defining a class that supports complex arithmetic

exception

Defining several functions that control exception handling

fstream

Defining several I/O stream classes that manipulate external files

iomanip

Declaring several I/O stream manipulators that take an argument

ios

Defining the class that serves as the base for many I/O streams classes

iosfwd

Declaring several I/O stream classes before they are necessarily defined

iostream

Declaring the I/O stream objects that manipulate the standard streams

istream

Defining the class that performs extractions

new

Declaring several functions that allocate and free storage

ostream

Defining the class that performs insertions

sstream

Defining several I/O stream classes that manipulate string containers

stdexcept

Defining several classes useful for reporting exceptions

streambuf

Defining classes that buffer I/O stream operations

string

Defining a class that implements a string container

strstream

Defining several I/O stream classes that manipulate in-memory character
sequences

Table 34: Embedded C++ header files

The following table lists additional C++ header files:
Header file

Usage

fstream.h

Defining several I/O stream classes that manipulate external files

iomanip.h

Declaring several I/O stream manipulators that take an argument

iostream.h

Declaring the I/O stream objects that manipulate the standard streams

new.h

Declaring several functions that allocate and free storage

Table 35: Additional Embedded C++ header files—DLIB

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Library functions

Extended Embedded C++ standard template library
The following table lists the Extended EC++ standard template library (STL) header
files:
Header file

Description

algorithm

Defines several common operations on sequences

deque

A deque sequence container

functional

Defines several function objects

hash_map

A map associative container, based on a hash algorithm

hash_set

A set associative container, based on a hash algorithm

iterator

Defines common iterators, and operations on iterators

list

A doubly-linked list sequence container

map

A map associative container

memory

Defines facilities for managing memory

numeric

Performs generalized numeric operations on sequences

queue

A queue sequence container

set

A set associative container

slist

A singly-linked list sequence container

stack

A stack sequence container

utility

Defines several utility components

vector

A vector sequence container

Table 36: Standard template library header files

Using standard C libraries in C++
The C++ library works in conjunction with 15 of the header files from the standard C
library, sometimes with small alterations. The header files come in two forms—new and
traditional—for example, cassert and assert.h.
The following table shows the new header files:
Header file

Usage

cassert

Enforcing assertions when functions execute

cctype

Classifying characters

cerrno

Testing error codes reported by library functions

cfloat

Testing floating-point type properties

cinttypes

Defining formatters for all types defined in stdint.h

Table 37: New standard C header files—DLIB

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Header file

Usage

climits

Testing integer type properties

clocale

Adapting to different cultural conventions

cmath

Computing common mathematical functions

csetjmp

Executing non-local goto statements

csignal

Controlling various exceptional conditions

cstdarg

Accessing a varying number of arguments

cstdbool

Adds support for the bool data type in C.

cstddef

Defining several useful types and macros

cstdint

Providing integer characteristics

cstdio

Performing input and output

cstdlib

Performing a variety of operations

cstring

Manipulating several kinds of strings

ctime

Converting between various time and date formats

cwchar

Support for wide characters

cwctype

Classifying wide characters

Table 37: New standard C header files—DLIB (Continued)

LIBRARY FUNCTIONS AS INTRINSIC FUNCTIONS
Certain C library functions will under some circumstances be handled as intrinsic
functions and will generate inline code instead of an ordinary function call, for example
memcpy, memset, and strcat.

ADDED C FUNCTIONALITY
The IAR DLIB Library includes some added C functionality, partly taken from the C99
standard.
The following include files provide these features:

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●

ctype.h

●

inttypes.h

●

math.h

●

stdbool.h

●

stdint.h

●

stdio.h

●

stdlib.h

●

wchar.h

Library functions

●

wctype.h

ctype.h
In ctype.h, the C99 function isblank is defined.

inttypes.h
This include file defines the formatters for all types defined in stdint.h to be used by
the functions printf, scanf, and all their variants.

math.h
In math.h all functions exist in a float variant and a long double variant, suffixed
by f and l respectively. For example, sinf and sinl.
The following C99 macro symbols are defined:
HUGE_VALF, HUGE_VALL, INFINITY, NAN, FP_INFINITE, FP_NAN, FP_NORMAL,
FP_SUBNORMAL, FP_ZERO, MATH_ERRNO, MATH_ERREXCEPT, math_errhandling.

The following C99 macro functions are defined:
fpclassify, signbit, isfinite, isinf, isnan, isnormal, isgreater, isless,
islessequal, islessgreater, isunordered.

The following C99 type definitions are added:
float_t, double_t.

stdbool.h
This include file makes the bool type available if the Allow IAR extensions (-e) option
is used.

stdint.h
This include file provides integer characteristics.

stdio.h
In stdio.h, the following C99 functions are defined:
vscanf, vfscanf, vsscanf, vsnprintf, snprintf

The functions printf, scanf, and all their variants have added functionality from the
C99 standard. For reference information about these functions, see the library reference
available from the Help menu.

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The following functions providing I/O functionality for libraries built without FILE
support are defined:
__write_array Corresponds to fwrite on stdout.
__ungetchar

Corresponds to ungetc on stdout.

__gets

Corresponds to fgets on stdin.

stdlib.h
In stdlib.h, the following C99 functions are defined:
_Exit, llabs, lldiv, strtoll, strtoull, atoll, strtof, strtold.

The function strtod has added functionality from the C99 standard. For reference
information about this functions, see the library reference available from the Help
menu.
The __qsortbbl function is defined; it provides sorting using a bubble sort algorithm.
This is useful for applications that have a limited stack.

wchar.h
In wchar.h, the following C99 functions are defined:
vfwscanf, vswscanf, vwscanf, wcstof, wcstolb.

wctype.h
In wctype.h, the C99 function iswblank is defined.

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The linker configuration
file
This chapter describes the purpose of the linker configuration file and
describes its contents.
To read this chapter you must be familiar with the concept of sections, see
Modules and sections, page 40.

Overview
To link and locate an application in memory according to your requirements, ILINK
needs information about how to handle sections and how to place them into the available
memory regions. In other words, ILINK needs a configuration, passed to it by means of
the linker configuration file.
This file consists of a sequence of directives and typically, provides facilities for:
●

Defining available addressable memories
giving the linker information about the maximum size of possible addresses and
defining the available physical memory, as well as dealing with memories that can be
addressed in different ways.

●

Defining the regions of the available memories that are populated with ROM or
RAM
giving the start and end address for each region.

●

Section groups
dealing with how to group sections into blocks and overlays depending on the section
requirements.

●

Defining how to handle initialization of the application
giving information about which sections that are to be initialized, and how that
initialization should be made.

●

Memory allocation
defining where—in what memory region—each set of sections should be placed.

●

Using symbols, expressions, and numbers
expressing addresses and sizes, etc, in the other configuration directives. The
symbols can also be used in the application itself.

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Defining memories and regions

●

Structural configuration
meaning that you can include or exclude directives depending on a condition, and to
split the configuration file into several different files.

Comments can be written either as C comments (/*...*/) or as C++ comments
(//...).

Defining memories and regions
ILINK needs information about the available memory spaces, or more specifically it
needs information about:
●

The maximum size of possible addressable memories
The define memory directive defines a memory space with a given size, which is
the maximum possible amount of addressable memory, not necessarily physically
available. See Define memory directive, page 298.

●

Available physical memory
The define region directive defines a region in the available memories in which
specific sections of application code and sections of application data can be placed.
See Define region directive, page 299.
A region consists of one or several memory ranges. A range is a continuous sequence
of bytes in a memory and several ranges can be expressed by using region
expressions. See Region expression, page 301.

Define memory directive
Syntax

define memory

[ name ] with size = size_expr [ ,unit-size ];

where unit-size is one of:
unitbitsize = bitsize_expr
unitbytesize = bytesize_expr

and where expr is an expression, see Expressions, page 315.
Parameters

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size_expr

Specifies how many units the memory space contains; always
counted from address zero.

bitsize_expr

Specifies how many bits each unit contains.

bytesize_expr

Specifies how many bytes each unit contains. Each byte
contains 8 bits.

The linker configuration file

Description

The define memory directive defines a memory space with a given size, which is the
maximum possible amount of addressable memory, not necessarily physically available.
This sets the limits for the possible addresses to be used in the linker configuration file.
For many microcontrollers, one memory space is sufficient. However, some
microcontrollers require two or more. For example, a Harvard architecture usually
requires two different memory spaces, one for code and one for data. If only one
memory is defined, the memory name is optional. If no unit-size is given, the unit
contains 8 bits.

Example

/* Declare the memory space Mem of four Gigabytes */
define memory Mem with size = 4G;

Define region directive
Syntax

define region name = region-expr;

where region-expr is a region expression, see also Regions, page 299.
Parameters
name

The name of the region.

Description

The define region directive defines a region in which specific sections of code and
sections of data can be placed. A region consists of one or several memory ranges, where
each memory range consists of a continuous sequence of bytes in a specific memory.
Several ranges can be combined by using region expressions. Note that those ranges do
not need to be consecutive or even in the same memory.

Example

/* Define the 0x10000-byte code region ROM located at address
0x10000 in memory Mem */
define region ROM = Mem:[from 0x10000 size 0x10000];

Regions
A region is s a set of non-overlapping memory ranges. A region expression is built up
out of region literals and set operations (union, intersection, and difference) on regions.

Region literal
Syntax

[ memory-name: ][from expr { to expr | size expr }
[ repeat expr [ displacement expr ]]]

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Regions

where expr is an expression, see Expressions, page 315.
Parameters

Description

memory-name

The name of the memory space in which the region literal will be
located. If there is only one memory, the name is optional.

from

The start address of the memory range (inclusive).

to

The end address of the memory range (inclusive).

size

The size of the memory range.

repeat

Defines several ranges in the same memory for the region literal.

displacement

Displacement from the previous range start in the repeat sequence.
Default displacement is the same value as the range size.

A region literal consists of one memory range. When you define a range, the memory it
resides in, a start address, and a size must be specified. The range size can be stated
explicitly by specifying a size, or implicitly by specifying the final address of the range.
The final address is included in the range and a zero-sized range will only contain an
address. A range can span over the address zero and the range can even be expressed by
unsigned values, because it is known where the memory wraps.
The repeat parameter will create a region literal that contains several ranges, one for
each repeat. This is useful for banked or far regions.

Example

/* The 5-byte size range spans over the address zero */
Mem:[from -2 to 2]
/* The 512-byte size range spans over zero, in a 64-Kbyte memory
*/
Mem:[from 0xFF00 to 0xFF]
/* Defining several ranges in the same memory, a repeating
literal */
Mem:[from 0 size 0x100 repeat 3 displacement 0x1000]
/* Resulting
Mem:[from
Mem:[from
Mem:[from
*/

See also

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in a region containing:
0 size 0x100]
0x1000 size 0x100]
0x2000 size 0x100]

Define region directive, page 299, and Region expression, page 301.

The linker configuration file

Region expression
Syntax

region-operand
| region-expr | region-operand
| region-expr - region-operand
| region-expr & region-operand

where region-operand is one of:
( region-expr )
region-name
region-literal
empty-region

where region-name is a region, see Define region directive, page 299
where region-literal is a region literal, see Region literal, page 299
and where empty-region is an empty region, see Empty region, page 302.
Description

Normally, a region consists of one memory range, which means a region literal is
sufficient to express it. When a region contains several ranges, possibly in different
memories, it is instead necessary to use a region expression to express it. Region
expressions are actually set expressions on sets of memory ranges.
To create region expressions, three operators are available: union (|), intersection (&),
and difference (-). These operators work as in set theory. For example, if you have the
sets A and B, then the result of the operators would be:

Example

●

A | B: all elements in either set A or set B

●

A & B: all elements in both set A and B

●

A - B: all elements in set A but not in B.

/* Resulting in a range starting at 1000 and ending at 2FFF, in
memory Mem */
Mem:[from 0x1000 to 0x1FFF] | Mem:[from 0x1500 to 0x2FFF]
/* Resulting in a range starting at 1500 and ending at 1FFF, in
memory Mem */
Mem:[from 0x1000 to 0x1FFF] & Mem:[from 0x1500 to 0x2FFF]
/* Resulting in a range starting at 1000 and ending at 14FF, in
memory Mem */
Mem:[from 0x1000 to 0x1FFF] - Mem:[from 0x1500 to 0x2FFF]

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Section handling

/* Resulting in two ranges. The first starting at 1000 and ending
at 1FFF, the second starting at 2501 and ending at 2FFF.
Both located in memory Mem */
Mem:[from 0x1000 to 0x2FFF] - Mem:[from 0x2000 to 0x24FF]

Empty region
Syntax

[ ]

Description

The empty region does not contain any memory ranges. If the empty region is used in a
placement directive that actually is used for placing one or more sections, ILINK will
issue an error.

Example

define region Code = Mem:[from 0 size 0x10000];
if (Banked) {
define region Bank = Mem:[from 0x8000 size 0x1000];
} else {
define region Bank = [];
}
define region NonBanked = Code - Bank;
/* Depending on the Banked symbol, the NonBanked region is either
one range with 0x10000 bytes, or two ranges with 0x8000 and
0x7000 bytes, respectively. */

See also

Region expression, page 301.

Section handling
Section handling describes how ILINK should handle the sections of the execution
image, which means:
●

Placing sections in regions
The place at and place into directives place sets of sections with similar
attributes into previously defined regions. See Place at directive, page 309 and Place
in directive, page 310.

●

Making sets of sections with special requirements
The block directive makes it possible to create empty sections with specific sizes
and alignments, sequentially sorted sections of different types, etc.
The overlay directive makes it possible to create an area of memory that can
contain several overlay images. See Define block directive, page 303, and Define
overlay directive, page 304.

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The linker configuration file

●

Initializing the application
The directives initialize and do not initialize control how the application
should be started. With these directives, the application can initialize global symbols
at startup, and copy pieces of code. The initializers can be stored in several ways, for
example they can be compressed. See Initialize directive, page 305 and Do not
initialize directive, page 308.

●

Keeping removed sections
The keep directive retains sections even though they are not referred to by the rest
of the application, which means it is equivalent to the root concept in the assembler
and compiler. See Keep directive, page 309.

Define block directive
Syntax

define block name
[ with param, param...
{
extended-selectors
}
[except
{
section_selectors
}];

]

where param can be one of:
size = expr
maximum size = expr
alignment = expr
fixed order

and where the rest of the directive selects sections to include in the block, see Section
selection, page 311.
Parameters
name

The name of the defined block.

size

Customizes the size of the block. By default, the size of a block is
the sum of its parts dependent of its contents.

maximum size

Specifies an upper limit for the size of the block. An error is
generated if the sections in the block do not fit.

alignment

Specifies a minimum alignment for the block. If any section in the
block has a higher alignment than the minimum alignment, the block
will have that alignment.

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Section handling

fixed order

Places sections in fixed order; if not specified, the order of the
sections will be arbitrary.

Description

The block directive defines a named set of sections. By defining a block you can create
empty blocks of bytes that can be used, for example as stacks or heaps. Another use for
the directive is to group certain types of sections, consecutive or non-consecutive. A
third example of use for the directive is to group sections into one memory area to access
the start and end of that area from the application.

Example

/* Create a 0x1000-byte block for the heap */
define block HEAP with size = 0x1000, alignment = 8 { };

See also

Interaction between the tools and your application, page 117. See Define overlay
directive, page 304 for an accessing example.

Define overlay directive
Syntax

define overlay name [ with param, param...
{
extended-selectors;
}
[except
{
section_selectors
}];

]

For information about extended selectors and except clauses, see Section selection, page
311.
Parameters

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name

The name of the overlay.

size

Customizes the size of the overlay. By default, the size of a overlay is
the sum of its parts dependent of its contents.

maximum size

Specifies an upper limit for the size of the overlay. An error is
generated if the sections in the overlay do not fit.

alignment

Specifies a minimum alignment for the overlay. If any section in the
overlay has a higher alignment than the minimum alignment, the
overlay will have that alignment.

fixed order

Places sections in fixed order; if not specified, the order of the
sections will be arbitrary.

The linker configuration file

Description

The overlay directive defines a named set of sections. In contrast to the block
directive, the overlay directive can define the same name several times. Each definition
will then be grouped in memory at the same place as all other definitions of the same
name. This creates an overlaid memory area, which can be useful for an application that
has several independent sub-applications.
Place each sub-application image in ROM and reserve a RAM overlay area that can hold
all sub-applications. To execute a sub-application, first copy it from ROM to the RAM
overlay. Note that ILINK does not help you with managing interdependent overlay
definitions, apart from generating a diagnostic message for any reference from one
overlay to another overlay.
The size of an overlay will be the same size as the largest definition of that overlay name
and the alignment requirements will be the same as for the definition with the highest
alignment requirements.
Note: Sections that were overlaid must be split into a RAM and a ROM part and you
must take care of all the copying needed.

See also

Manual initialization, page 54.

Initialize directive
Syntax

initialize { by copy | manually
[ with param, param... ]
{
section-selectors
}
[except
{
section_selectors
}];

}

where param is one of:
packing =

{ none | zeros | packbits | bwt | lzw | auto |
smallest }

copy routine = functionname

and where the rest of the directive selects sections to include in the block. See Section
selection, page 311.
Parameters
by copy

Splits the section into sections for initializers and initialized data,
and handles the initialization at application startup automatically.

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Section handling

manually

Splits the section into sections for initializers and initialized data.
The initialization at application startup is not handled automatically.

packing

Specifies how to handle the initializers. Choose between:

copy routine

Description

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none

Disables compression of the selected
section contents. This is the default method
for initialize manually.

zeros

Compresses sequential bytes with the value
zero.

packbits

Compresses with the PackBits algorithm.
This method generates good results for data
with many consecutive bytes of the same
value.

bwt

Compresses with the Burrows-Wheeler
algorithm. This method improves the
packbits method by transforming blocks
of data before they are compressed.

lzw

Compresses with the Lempel-Ziv-Welch
algorithm. This method uses a dictionary to
store byte patterns in the data.

auto

Similar to smallest, but ILINK chooses
between none and packbits. This is the
default method for initialize by
copy.

smallest

ILINK estimates the resulting size using each
packing method (except for auto), and
then chooses the packing method that
produces the smallest estimated size. Note
that the size of the decompressor is also
included.

Uses your own initialization routine instead of the default routine. It
will be automatically called at the application startup.

The initialize directive splits the initialization section into one section holding the
initializers and another section holding the initialized data. You can choose whether the
initialization at startup should be handled automatically (initialize by copy) or
whether you should handle it yourself (initialize manually).

The linker configuration file

When you use the packing method auto (default for initialize by copy) or
smallest, ILINK will automatically choose an appropriate packing algorithm for the
initializers and automatically revert it at the initialization process when the application
starts. To override this, specify a different packing method. Use the copy routine
parameter to override the method for copying the initializers. The --log
initialization option shows how ILINK decided which packing algorithm to use.
When initializers are compressed, a decompressor is automatically added to the image.
The decompressors for bwt and lzw use significantly more execution time and RAM
than zeros and packbits. Approximately 9 Kbytes of stack space is needed for bwt
and 3.5 Kbytes for lzw.
When initializers are compressed, the exact size of the compressed initializers is
unknown until the exact content of the uncompressed data is known. If this data contains
other addresses, and some of these addresses are dependent on the size of the
compressed initializers, the linker fails with error Lp017. To avoid this, place
compressed initializers last, or in a memory region together with sections whose
addresses do not need to be known.
Optionally, ILINK will also produce a table that an initialization function in the system
startup code uses for copying the section contents from the initializer sections to the
corresponding original sections. Normally, the section content is initialized variables.
Zero-initialized sections are not affected by the initialize directive.
Sections that must execute before the initialization finishes are not affected by the
initialize by copy directive. This includes the __low_level_init function and

anything it references.
Anything reachable from the program entry label is considered needed for initialization
unless reached via a section fragment with a label starting with __iar_init$$done.
The --log sections option can be used for creating a log of this process (in addition
to the more general process of marking section fragments to be included in the
application).
The initialize directive can be used for copying other things as well, for example
copying executable code from slow ROM to fast RAM. For another example, see Define
overlay directive, page 304.
Example

/* Copy all read-write sections automatically from ROM to RAM at
program start */
initialize by copy { rw };
place in RAM { rw };
place in ROM { ro };

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Section handling

/* Initialize special sections (initializers placed in flash) */
initialize by copy with packing = none, copy routine =
my_initializers { section .special };
place in RAM { section .special };
place in ROM { section .special_init };

See also

Initialization at system startup, page 45, and Do not initialize directive, page 308.

Do not initialize directive
Syntax

do not initialize
{
section-selectors
}
[except
{
section-selectors
}];

For information about extended selectors and except clauses, see Section selection, page
311.
Description

The do not initialize directive specifies the sections that should not be initialized
by the system startup code. The directive can only be used on zeroinit sections.
The compiler keyword __no_init places variables into sections that must be handled
by a do not initialize directive.

Example

/* Do not initialize read-write sections whose name ends with
_noinit at program start */
do not initialize { rw section .*_noinit };
place in RAM { rw section .*_noinit };

See also

Initialization at system startup, page 45, and Initialize directive, page 305.

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The linker configuration file

Keep directive
Syntax

keep
{
section-selectors
}
[except
{
section-selectors
}];

For information about extended selectors and except clauses, see Section selection, page
311.
Description

The keep directive specifies that all selected sections should be kept in the executable
image, even if there are no references to the sections.

Example

keep { section .keep* } except {section .keep};

Place at directive
Syntax

[ "name": ]
place at { address [ memory: ] expr | start of region_expr |
end of region_expr }
{
extended-selectors
}
[except
{
section-selectors
}];

For information about extended selectors and except clauses, see Section selection, page
311.
Parameters
memory: expr

A specific address in a specific memory. The address must be
available in the supplied memory defined by the define
memory directive. The memory specifier is optional if there is
only one memory.

start of region_expr A region expression. The start of the region is used.
end of region_expr

A region expression. The end of the region is used.

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Section handling

Description

The place at directive places sections and blocks either at a specific address or, at the
beginning or the end of a region. The same address cannot be used for two different
place at directives. It is also not possible to use an empty region in a place at
directive. If placed in a region, the sections and blocks will be placed before any other
sections or blocks placed in the same region with a place in directive.
The sections and blocks will be placed in the region in an arbitrary order. To specify a
specific order, use the block directive.
The name, if specified, is used in the map file and in some log messages.

Example

/* Place the read-only section .startup at the beginning of the
code_region */
"START": place at start of ROM { readonly section .startup };

See also

Place in directive, page 310.

Place in directive
Syntax

[ "name": ]
place in region-expr
{
extended-selectors
}
[{
section-selectors
}];

where region-expr is a region expression, see also Regions, page 299.
and where the rest of the directive selects sections to include in the block. See Section
selection, page 311.
Description

The place in directive places sections and blocks in a specific region. The sections and
blocks will be placed in the region in an arbitrary order.
To specify a specific order, use the block directive. The region can have several ranges.
The name, if specified, is used in the map file and in some log messages.

Example

/* Place the read-only sections in the code_region */
"ROM": place in ROM { readonly };

See also

Place at directive, page 309.

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The linker configuration file

Section selection
The purpose of section selection is to specify—by means of section selectors and except
clauses—the sections that an ILINK directive should be applied to. All sections that
match one or more of the section selectors will be selected, and none of the sections
selectors in the except clause, if any. Each section selector can match sections on section
attributes, section name, and object or library name.
Some directives provide functionality that requires more detailed selection capabilities,
for example directives that can be applied on both sections and blocks. In this case, the
extended-selectors are used.

Section-selectors
Syntax

{

[ section-selector ][, section-selector...] }

where section-selector is:

[ section-attribute ][ section sectionname ]
[object {module | filename} ]
where section-attribute is:

[ ro [ code | data ] | rw [ code | data ] | zi ]
and where ro, rw, and zi also can be readonly, readwrite, and zeroinit,
respectively.
Parameters
ro or readonly

Read-only sections.

rw or readwrite

Read/write sections.

zi or zeroinit

Zero-initialized sections. These sections should be initialized with
zeros during system startup.

code

Sections that contain code.

data

Sections that contain data.

sectionname

The section name. Two wildcards are allowed:
? matches any single character
* matches zero or more characters.

module

A name in the form objectname(libraryname). Sections
from object modules where both the object name and the library
name match their respective patterns are selected. An empty library
name pattern selects only sections from object files.

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Section selection

filename

Description

The name of an object file, a library, or an object in a library. Two
wildcards are allowed:
? matches any single character
* matches zero or more characters.

A section selector selects all sections that match the section attribute, section name, and
the name of the object, where object is an object file, a library, or an object in a library.
It is only possible to omit one or two of the three conditions. If the section attribute is
omitted, any section will be selected, without restrictions on the section attribute.
If the section name part or the object name part is omitted, sections will be selected
without restrictions on the section name or object name, respectively.
It is also possible to use only { } without any section selectors, which can be useful
when defining blocks.
Note that a section selector with narrower scope has higher priority than a more generic
section selector.

Example

{ rw }

/* Selects all read-write sections */

{ section .mydata* }
/* Selects only .mydata* sections */
/* Selects .mydata* sections available in the object special.o */
{ section .mydata* object special.o }

Assuming a section in an object named foo.o in a library named lib.a, any of these
selectors will select that section:
object
object
object
object

See also

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foo.o(lib.a)
f*(lib*)
foo.o
lib.a

Initialize directive, page 305, Do not initialize directive, page 308, and Keep directive,
page 309.

The linker configuration file

Extended-selectors
Syntax

{

[ extended-selector ][, extended-selector...] }

where extended-selector is:

[ first | last ]{ section-selector |
block name [ inline-block-def ]|
overlay name }
where inline-block-def is:

[ block-params ] extended-selectors
Parameters
first

Places the selected name first in the region, block, or overlay.

last

Places the selected name last in the region, block, or overlay.

block

The name of the block.

overlay

The name of the overlay.

Description

In addition to what the section-selector does, extended-selector provides
functionality for placing blocks or overlays first or last in a set of sections, a block, or
an overlay. It is also possible to create an inline definition of a block. This means that
you can get more precise control over section placement.

Example

define block First { section .first }; /* Define a block holding
the section .first */
define block Table { first block First }; /* Define a block where
the first is placed
first */

or, equivalently using an inline definition of the block First:
define block Table { first block First { section .first }};

See also

Define block directive, page 303, Define overlay directive, page 304, and Place at
directive, page 309.

Using symbols, expressions, and numbers
In the linker configuration file, you can also:
●

Define and export symbols
The define symbol directive defines a symbol with a specified value that can be
used in expressions in the configuration file. The symbol can also be exported to be

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Using symbols, expressions, and numbers

used by the application or the debugger. See Define symbol directive, page 314, and
Export directive, page 315.
●

Use expressions and numbers
In the linker configuration file, expressions and numbers are used for specifying
addresses, sizes, et cetera. See Expressions, page 315.

Define symbol directive
Syntax

define

[ exported ] symbol name = expr;

Parameters

Description

exported

Exports the symbol to be usable by the executable image.

name

The name of the symbol.

expr

The symbol value.

The define symbol directive defines a symbol with a specified value. The symbol can
then be used in expressions in the configuration file. The symbols defined in this way
work exactly like the symbols defined with the option --config_def outside of the
configuration file.
The define exported symbol variant of this directive is a shortcut for using the
directive define symbol in combination with the export symbol directive. On the
command line this would require both a --config_def option and a
--define_symbol option to achieve the same effect.
Note:
Symbols that are either prefixed by _X, where X is a capital letter, or that contain
__ (double underscore) are reserved for toolset vendors.

/* Define the symbol my_symbol with the value 4 */
define symbol my_symbol = 4;

See also

Export directive, page 315 and Interaction between ILINK and the application, page 56.

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A symbol cannot be redefined

●

Example

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●

The linker configuration file

Export directive
Syntax

export symbol name;

Parameters
name

The name of the symbol.

Description

The export directive defines a symbol to be exported, so that it can be used both from
the executable image and from a global label. The application, or the debugger, can then
refer to it for setup purposes etc.

Example

/* Define the symbol my_symbol to be exported */
export symbol my_symbol;

Expressions
Syntax

An expression is built up of the following constituents:
expression binop expression
unop expression
expression ? expression : expression
(expression)
number
symbol
func-operator

where binop is one of these binary operators:
+, -, *, /, %, <<, >>, <, >, ==, !=, &, ^, |, &&, ||

where unop is one of this unary operators:
+, -, !, ~

where number is a number, see Numbers, page 316
where symbol is a defined symbol, see Define symbol directive, page 314 and
--config_def, page 192
and where func-operator is one of these function-like operators:
minimum(expr,expr)

Returns the smallest of the two parameters.

maximum(expr,expr)

Returns the largest of the two parameters.

isempty(r)

Returns True if the region is empty, otherwise False.

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Using symbols, expressions, and numbers

isdefinedsymbol(expr-symbol)Returns True if the expression symbol is defined,
otherwise False.
start(r)

Returns the lowest address in the region.

end(r)

Returns the highest address in the region.

size(r)

Returns the size of the complete region.

where expr is an expression, and r is a region expression, see Region expression, page
301.
Description

In the linker configuration file, an expression is a 65-bit value with the range -2^64 to
2^64. The expression syntax closely follows C syntax with some minor exceptions.
There are no assignments, casts, pre- or post-operations, and no address operations (*,
&, [], ->, and .). Some operations that extract a value from a region expression, etc, use
a syntax resembling that of a function call. A boolean expression returns 0 (false) or 1
(true).

Numbers
Syntax

nr [nr-suffix]

where nr is either a decimal number or a hexadecimal number (0x... or 0X...).
and where nr-suffix is one of:
K
M
G
T
P

=
=
=
=
=

(1
(1
(1
(1
(1

<<
<<
<<
<<
<<

10)
20)
30)
40)
50)

1024 */
1048576 */
1073741824 */
1099511627776 */
1125899906842624 */

A number can be expressed either by normal C means or by suffixing it with a set of
useful suffixes, which provides a compact way of specifying numbers.

Example

1024 is the same as 0x400, which is the same as 1K.

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Kilo
Mega
Giga
Tera
Peta

Description

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/*
/*
/*
/*
/*

The linker configuration file

Structural configuration
The structural directives provide means for creating structure within the configuration,
such as:
●

Conditional inclusion
An if directive includes or excludes other directives depending on a condition,
which makes it possible to have directives for several different memory
configurations in the same file. See If directive, page 317.

●

Dividing the linker configuration file into several different files
The include directive makes it possible to divide the configuration file into several
logically distinct files. See Include directive, page 318.

If directive
Syntax

if (expr) {
directives
[ } else if (expr) {
directives ]
[ } else {
directives ]
}

where expr is an expression, see Expressions, page 315.
Parameters
directives

Description

Any ILINK directive.

An if directive includes or excludes other directives depending on a condition, which
makes it possible to have directives for several different memory configurations, for
example both a banked and non-banked memory configuration, in the same file.
The directives inside an if part, else if part, or an else part are syntax checked and
processed regardless of whether the conditional expression was true or false, but only
the directives in the part where the conditional expression was true, or the else part if
none of the conditions were true, will have any effect outside the if directive. The if
directives can be nested.

Example

See Empty region, page 302.

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Structural configuration

Include directive
Syntax

include filename;

Parameters
filename

Description

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A string literal where both / and \ can be used as the directory
delimiter.

The include directive makes it possible to divide the configuration file into several
logically distinct files. For instance, files that you need to change often and files that you
seldom edit.

Section reference
The compiler places code and data into sections. Based on a configuration
specified in the linker configuration file, ILINK places sections in memory.
This chapter lists all predefined sections and blocks that are available for the
IAR build tools for ARM, and gives detailed reference information about each
section.
For more information about sections, see the chapter Modules and sections,
page 40.

Summary of sections
This table lists the sections and blocks that are used by the IAR build tools:
Section

Description

.bss

Holds zero-initialized static and global variables.

CSTACK

Holds the stack used by C or C++ programs.

.cstart

Holds the startup code.

.data

Holds static and global initialized variables, including the initializers.

.data_init

Holds initializers for.data sections.

.difunct

Holds pointers to code, typically C++ constructors, that should be
executed by the system startup code before main is called.

HEAP

Holds the heap used for dynamically allocated data.

.iar.dynexit

Holds the atexit table.

.intvec

Holds the reset and interrupt vectors.

IRQ_STACK

Holds the stack for interrupt requests, IRQ, and exceptions.

.noinit

Holds __no_init static and global variables.

.rodata

Holds constant data.

.text

Holds the program code.

Table 38: Section summary

In addition to the ELF sections used for your application, the tools use a number of other
ELF sections for a variety of purposes:

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Descriptions of sections and blocks

●

Sections starting with .debug generally contain debug information in the DWARF
format

●

Sections starting with .iar.debug contain supplemental debug information in an
IAR format

●

The section .comment contains the tools and command lines used for building the
file

●

Sections starting with .rel or .rela contain ELF relocation information

●

The section .symtab contains the symbol table for a file

●

The section .strtab contains the names of the symbol in the symbol table

●

The section .shstrtab contains the names of the sections.

Descriptions of sections and blocks
This section gives reference information about each section, where the:
●

Description describes what type of content the section is holding and, where
required, how the section is treated by the linker

●

Memory placement describes memory placement restrictions.

For information about how to allocate sections in memory by modifying the linker
configuration file, see the Placing code and data—the linker configuration file, page 42.

.bss
Description

Holds zero-initialized static and global variables.

Memory placement

This section can be placed anywhere in memory.

CSTACK
Description

Block that holds the internal data stack.

Memory placement

This block can be placed anywhere in memory.

See also

Setting up the stack, page 52.

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Section reference

.cstart
Description

Holds the startup code.

Memory placement

This section can be placed anywhere in memory.

Description

Holds static and global initialized variables inlcuding initializers.

Memory placement

This section can be placed anywhere in memory.

.data

.data_init
Description

Holds initializers for .data sections. This section is created by the linker.

Memory placement

This section can be placed anywhere in memory.

.difunct
Description

Holds the dynamic initialization vector used by C++.

Memory placement

This section can be placed anywhere in memory.

HEAP
Description

Holds the heap used for dynamically allocated data, in other words data allocated by
malloc and free, and in C++, new and delete.

Memory placement

This section can be placed anywhere in memory.

See also

Setting up the heap, page 52.

.iar.dynexit
Description

Holds the table of calls to be made at exit.

Memory placement

This section can be placed anywhere in memory.

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Descriptions of sections and blocks

See also

Setting up the atexit limit, page 53.

.intvec
Description

Holds the reset vector and exception vectors which contain branch instructions to
cstartup, interrupt service routines etc.

Memory placement

Must be placed at address range 0x00 to 0x3F.

IRQ_STACK
Description

Holds the stack which is used when servicing IRQ exceptions. Other stacks may be
added as needed for servicing other exception types: FIQ, SVC, ABT, and UND. The
cstartup.s file must be modified to initialize the exception stack pointers used.
Note: This section is not used when compiling for Cortex-M.

Memory placement

This section can be placed anywhere in memory.

See also

Exception stacks, page 116.

.noinit
Description

Holds static and global __no_init variables.

Memory placement

This section can be placed anywhere in memory.

.rodata
Description

Holds constant data. This can include constant variables, string and aggregate literals,
etc.

Memory placement

This section can be placed anywhere in memory.

Description

Holds program code, except the code for system initialization.

Memory placement

This section can be placed anywhere in memory.

.text

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IAR utilities
This chapter describes the IAR command line utilities that are available:
●

The IAR Archive Tool—iarchive—creates and manipulates a library (an
archive) of several ELF object files

●

The IAR ELF Tool—ielftool—performs various transformations on an ELF
executable image (such as fill, checksum, format conversions, etc)

●

The IAR ELF Dumper for ARM—ielfdumparm—creates a text
representation of the contents of an ELF relocatable or executable image

●

The IAR ELF Object Tool—iobjmanip—is used for performing low-level
manipulation of ELF object files

●

The IAR Absolute Symbol Exporter—isymexport—exports absolute
symbols from a ROM image file, so that they can be used when you link an
add-on application.

The IAR Archive Tool—iarchive
The IAR Archive Tool, iarchive, can create a library (an archive) file from several
ELF object files. You can also use iarchaive to manipulate ELF libraries.
A library file contains several relocatable ELF object modules, each of which can be
independently used by a linker. In contrast with object modules specified directly to the
linker, each module in a library is only included if it is needed.
For information about how to build a library in the IDE, see the IAR Embedded
Workbench® IDE User Guide for ARM®.

INVOCATION SYNTAX
The invocation syntax for the archive builder is:
iarchive parameters

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The IAR Archive Tool—iarchive

Parameters
The parameters are:
Parameter

Description

command

Command line options that define an operation to be performed. Such
an option must be specified before the name of the library file.

libraryfile

The library file to be operated on.

objectfile1 ...
objectfileN

The object file(s) that the specified command operates on.

options

Command line options that define actions to be performed. These
options can be placed anywhere on the command line.

Table 39: iarchive parameters

Examples
This example creates a library file called mylibrary.a from the source object files
module1.o, module.2.o, and module3.o:
iarchive mylibrary.a module1.o module2.o module3.o.

This example lists the contents of mylibrary.a:
iarchive --toc mylibrary.a

This example replaces module3.o in the library with the content in the module3.o file
and appends module4.o to mylibrary.a:
iarchive --replace mylibrary.a module3.o module4.o

SUMMARY OF IARCHIVE COMMANDS
This table summarizes the iarchive commands:
Command line option

Description

--create

Creates a library that contains the listed object files.

--delete, -d

Deletes the listed object files from the library.

--extract, -x

Extracts the listed object files from the library.

--replace, -r

Replaces or appends the listed object files to the library.

--symbols

Lists all symbols defined by files in the library.

--toc, -t

Lists all files in the library.

Table 40: iarchive commands summary

For more detailed descriptions, see Descriptions of command line options, page 325.

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IAR utilities

SUMMARY OF IARCHIVE OPTIONS
This table summarizes the iarchive options:
Command line option

Description

-f

Extends the command line.

-o

Specifies the library file.

--silent, -S

Sets silent operation.

--verbose, -V

Reports all performed operations.

Table 41: iarchive options summary

DESCRIPTIONS OF COMMAND LINE OPTIONS
This section gives detailed reference information about each iarchive command line
option.

-f
Syntax

-f filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Use this option to make iarchive read command line options from the named file, with
the default filename extension xcl.
In the command file, you format the items exactly as if they were on the command line
itself, except that you can use multiple lines, because the newline character acts just as
a space or tab character.
Both C and C++ style comments are allowed in the file. Double quotes behave in the
same way as in the Microsoft Windows command line environment.

--create
Syntax

--create libraryfile objectfile1 ... objectfileN

Parameters
libraryfile

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

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The IAR Archive Tool—iarchive

objectfile1 ... The object file(s) to build the library from.
objectfileN

Description

Use this command to build a new library from a set of object files (modules). The object
files are added to the library in the exact order that they are specified on the command
line.
If no command is specified on the command line, --create is used by default.

--delete, -d
Syntax

--delete libraryfile objectfile1 ... objectfileN
-d libraryfile objectfile1 ... objectfileN

Parameters
libraryfile

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

objectfile1 ... The object file(s) that the command operates on.
objectfileN

Description

Use this command to remove object files (modules) from an existing library. All object
files that are specified on the command line will be removed from the library.

--extract, -x
Syntax

--extract libraryfile [objectfile1 ... objectfileN]
-x libraryfile [objectfile1 ... objectfileN]

Parameters
libraryfile

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

objectfile1 ... The object file(s) that the command operates on.
objectfileN

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IAR utilities

Description

Use this command to extract object files (modules) from an existing library. If a list of
object files is specified, only these files are extracted. If a list of object files is not
specified, all object files in the library are extracted.

Syntax

-o libraryfile

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

By default, iarchive assumes that the first argument after the iarchive command is
the name of the destination library. Use this option to explicitly specify a different
filename for the library.

-o

--replace, -r
Syntax

--replace libraryfile objectfile1 ... objectfileN
-r libraryfile objectfile1 ... objectfileN

Parameters
libraryfile

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

objectfile1 ... The object file(s) that the command operates on.
objectfileN

Description

Use this command to replace or add object files (modules) to an existing library. The
object files specified on the command line either replace existing object files in the
library (if they have the same name) or are appended to the library.

--silent, -S
Syntax

--silent
-S

Description

Use this option to make iarchive operate without sending any messages to the
standard output stream.

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By default, iarchive sends various messages via the standard output stream. You can
use this option to prevent this. iarchive sends error and warning messages to the error
output stream, so they are displayed regardless of this setting.

--toc, -t
Syntax

--toc libraryfile
-t libraryfile

Parameters
libraryfile

Description

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

Use this command to list the names of all object files (modules) in a specified library.
In silent mode (--silent), this command performs basic syntax checks on the library
file, and displays only errors and warnings.

--symbols
Syntax

--symbols libraryfile

Parameters
libraryfile

Description

The library file that the command operates on. For information about
specifying a filename, see Rules for specifying a filename or directory as
parameters, page 156.

Use this command to list all external symbols that are defined by any object file
(module) in the specified library, together with the name of the object file (module) that
defines it.
In silent mode (--silent), this command performs symbol table-related syntax checks
on the library file and displays only errors and warnings.

--verbose, -V
Syntax

--verbose
-V

Description

Use this option to make iarchive report which operations it performs, in addition to
giving diagnostic messages.

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DIAGNOSTIC MESSAGES
This section lists the messages produced by iarchive:

La001: could not open file filename
iarchive failed to open an object file.

La002: illegal path pathname
The path pathname is not a valid path.

La006: too many parameters to cmd command
A list of object modules was specified as parameters to a command that only accepts a
single library file.

La007: too few parameters to cmd command
A command that takes a list of object modules was issued without the expected modules.

La008: lib is not a library file
The library file did not pass a basic syntax check. Most likely the file is not the intended
library file.

La009: lib has no symbol table
The library file does not contain the expected symbol information. The reason might be
that the file is not the intended library file, or that it does not contain any ELF object
modules.

La010: no library parameter given
The tool could not identify which library file to operate on. The reason might be that a
library file has not been specified.

La011: file file already exists
The file could not be created because a file with the same name already exists.

La013: file confusions, lib given as both library and object
The library file was also mentioned in the list of object modules.

La014: module module not present in archive lib
The specified object module could not be found in the archive.

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La015: internal error
The invocation triggered an unexpected error in iarchive.

Ms003: could not open file filename for writing
iarchive failed to open the archive file for writing. Make sure that it is not write

protected.

Ms004: problem writing to file filename
An error occurred while writing to file filename. A possible reason for this is that the
volume is full.

Ms005: problem closing file filename
An error occurred while closing the file filename.

The IAR ELF Tool—ielftool
The IAR ELF Tool, ielftool, can generate a checksum on specific ranges of
memories. This checksum can be compared with a checksum calculated on your
application.
The source code for ielftool and a Microsoft VisualStudio 2005 template project are
available in the arm\src\elfutils directory. If you have specific requirements for
how the checksum should be generated or requirements for format conversion, you can
modify the source code accordingly.

INVOCATION SYNTAX
The invocation syntax for the IAR ELF Tool is:
ielftool [options] inputfile outputfile [options]

The ielftool tool will first process all the fill options, then it will process all the
checksum options (from left to right).

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Parameters
The parameters are:
Parameter

Description

inputfile

An absolute ELF executable image produced by the ILINK linker.

options

Any of the available command line options, see Summary of ielftool
options, page 331.

outputfile

An absolute ELF executable image.

Table 42: ielftool parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Example
This example fills a memory range with 0xFF and then calculates a checksum on the
same range:
ielftool my_input.out my_output.out --fill 0xFF;0–0xFF
--checksum __checksum:4,crc32;0–0xFF

SUMMARY OF IELFTOOL OPTIONS
This table summarizes the ielftool command line options:
Command line option

Description

--bin

Sets the format of the output file to binary.

--checksum

Generates a checksum.

--fill

Specifies fill requirements.

--ihex

Sets the format of the output file to linear Intel hex.

--silent

Sets silent operation.

--simple

Sets the format of the output file to Simple code.

--srec

Sets the format of the output file to Motorola S-records.

--srec-len

Restricts the number of data bytes in each S-record.

--srec-s3only

Restricts the S-record output to contain only a subset of records.

--strip

Removes debug information.

--verbose

Prints all performed operations.

Table 43: ielftool options summary

DESCRIPTIONS OF OPTIONS
This section gives detailed reference information about each ielftool option.

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--bin
Syntax

--bin

Description

Sets the format of the output file to binary.
To set related options, choose:
Project>Options>Output converter

--checksum
Syntax

--checksum {symbol[+offset]|address}:size,algorithm[:flags]
[,start];range[;range...]

Parameters

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symbol

The name of the symbol where the checksum value should be stored.
Note that it must exist in the symbol table in the input ELF file.

offset

An offset to the symbol.

address

The absolute address where the checksum value should be stored.

size

The number of bytes in the checksum: 1, 2, or 4; must not be larger
than the size of the checksum symbol.

algorithm

The checksum algorithm used, one of:
• sum, a byte-wise calculated arithmetic sum. The result is truncated to
8 bits.
• sum8wide, a byte-wise calculated arithmetic sum. The result is
truncated to the size of the symbol.
• sum32, a word-wise (32 bits) calculated arithmetic sum
• crc16, CRC16 (generating polynomial 0x11021); used by default
• crc32, CRC32 (generating polynomial 0x104C11DB7)
• crc=n, CRC with a generating polynomial of n.

flags

1 specifies one's complement and 2 specifies two's complement. m
reverses the order of the bits within each byte when calculating the
checksum. For example, 2m.

start

By default, the initial value of the checksum is 0. If necessary, use start
to supply a different initial value.

range

The address range on which the checksum should be calculated.
Hexadecimal and decimal notation is allowed (for example,
0x8002–0x8FFF).

IAR utilities

Description

Use this option to calculate a checksum with the specified algorithm for the specified
ranges. The checksum will then replace the original value in symbol. A new absolute
symbol will be generated; with the symbol name suffixed with _value containing the
calculated checksum. This symbol can be used for accessing the checksum value later
when needed, for example during debugging.
If the --checksum option is used more than once on the command line, the options are
evaluated from left to right. If a checksum is calculated for a symbol that is specified in
a later evaluated --checksum option, an error is issued.
To set related options, choose:
Project>Options>Linker>Checksum

--fill
Syntax

--fill pattern;range[;range...]

Parameters

Description

range

Specifies the address range for the fill. Hexadecimal and decimal
notation is allowed (for example, 0x8002–0x8FFF). Note that each
address must be 4-byte aligned.

pattern

A hexadecimal string with the 0x prefix (for example, 0xEF)
interpreted as a sequence of bytes, where each pair of digits
corresponds to one byte (for example 0x123456, for the sequence of
bytes 0x12, 0x34, and 0x56). This sequence is repeated over the fill
area. If the length of the fill pattern is greater than 1 byte, it is repeated
as if it started at address 0.

Use this option to fill all gaps in one or more ranges with a pattern, which can be either
an expression or a hexadecimal string. The contents will be calculated as if the fill
pattern was repeatedly filled from the start address until the end address is passed, and
then the real contents will overwrite that pattern.
If the --fill option is used more than once on the command line, the fill ranges cannot
overlap each other.
To set related options, choose:
Project>Options>Linker>Checksum

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--ihex
Syntax

--ihex

Description

Sets the format of the output file to linear Intel hex.
To set related options, choose:
Project>Options>Linker>Output converter

--silent
Syntax

--silent

Description

Causes ielftool to operate without sending any messages to the standard output
stream.
By default, ielftool sends various messages via the standard output stream. You can
use this option to prevent this. ielftool sends error and warning messages to the error
output stream, so they are displayed regardless of this setting.
This option is not available in the IDE.

--simple
Syntax

--simple

Description

Sets the format of the output file to Simple code.
To set related options, choose:
Project>Options>Output converter

--srec
Syntax

--srec

Description

Sets the format of the output file to Motorola S-records.
To set related options, choose:
Project>Options>Output converter

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--srec-len
Syntax

--srec-len=length

Parameters
length

Description

The number of data bytes in each S-record.

Restricts the number of data bytes in each S-record. This option can be used in
combination with the --srec option.
This option is not available in the IDE.

--srec-s3only
Syntax

--srec-s3only

Description

Restricts the S-record output to contain only a subset of records, that is S3 and S7
records. This option can be used in combination with the --srec option.
This option is not available in the IDE.

--strip
Syntax

--strip

Description

Removes debug information from the ELF output file. Note that ielftool needs an
unstripped input ELF image. If you use the --strip option in the linker, remove it and
use the --strip option in ielftool instead.
To set related options, choose:
Project>Options>Linker>Output>Include debug information in output

--verbose
Syntax

--verbose

Description

Use this option to make ielftool report which operations it performs, in addition to
giving diagnostic messages.
This option is not available in the IDE because this setting is always enabled.

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The IAR ELF Dumper for ARM—ielfdumparm

The IAR ELF Dumper for ARM—ielfdumparm
The IAR ELF Dumper for ARM, ielfdumparm, can be used for creating a text
representation of the contents of a relocatable or absolute ELF file.
ielfdumparm can be used in one of three ways:
●

To produce a listing of the general properties of the input file and the ELF segments
and ELF sections it contains. This is the default behavior when no command line
options are used.

●

To also include a textual representation of the contents of each ELF section in the
input file. To specify this behavior, use the command line option --all.

●

To produce a textual representation of selected ELF sections from the input file. To
specify this behavior, use the command line option --section.

INVOCATION SYNTAX
The invocation syntax for ielfdumparm is:
ielfdumparm filename

Note: ielfdumparm is a command line tool which is not primarily intended to be used
in the IDE.

Parameters
The parameters are:
Parameter

Description

filename

An ELF relocatable or executable file to use as input.

Table 44: ielfdumparm parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

SUMMARY OF IELFDUMPARM OPTIONS
This table summarizes the ielfdumparm command line options:
Command line option

Description

--all

Generates output for all input sections regardless of their names or
numbers.

-o

Specifies an output file.

Table 45: ielfdumparm options summary

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Command line option

Description

--raw

Uses the generic hexadecimal/ASCII output format for the contents of
any selected section, instead of any dedicated output format for that
section.

--section/-s

Generates output for selected input sections.

Table 45: ielfdumparm options summary (Continued)

DESCRIPTIONS OF OPTIONS
This section gives detailed reference information about each ielfdumparm option.

--all
Syntax

--all

Description

Use this option to include the contents of all ELF sections in the output, in addition to
the general properties of the input file. Sections are output in index order, except that
each relocation section is output immediately after the section it holds relocations for.
By default, no section contents are included in the output.

-o, --output
Syntax

-o {filename|directory}
--output {filename|directory}

Parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Description

By default, output from the dumper is directed to the console. Use this option to direct
the output to a file instead.
If you specify a directory, the output file will be named the same as the input file, only
with an extra id extension.

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The IAR ELF Object Tool—iobjmanip

--section, -s
Syntax

--section section_number|section_name[,...]
--s section_number|section_name[,...]

Parameters

Description

section_number

The number of the section to be dumped.

section_name

The name of the section to be dumped.

Use this option to dump the contents of a section with the specified number, or any
section with the specified name. If a relocation section is associated with a selected
section, its contents are output as well.
If you use this option, the general properties of the input file will not be included in the
output.
You can specify multiple section numbers or names by separating them with commas,
or by using this option more than once.
By default, no section contents are included in the output.

Example

-s 3,17
-s .debug_frame,42

/* Sections #3 and #17
/* Any sections named .debug_frame and
also section #42 */

--raw
Syntax

--raw

Description

By default, many ELF sections will be dumped using a text format specific to a
particular kind of section. Use this option to dump each selected ELF section using the
generic text format.
The generic text format dumps each byte in the section in hexadecimal format, and
where appropriate, as ASCII text.

The IAR ELF Object Tool—iobjmanip
Use the IAR ELF Object Tool, iobjmanip, to perform low-level manipulation of ELF
object files.

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INVOCATION SYNTAX
The invocation syntax for the IAR ELF Object Tool is:
iobjmanip options inputfile outputfile

Parameters
The parameters are:
Parameter

Description

options

Command line options that define actions to be performed. These
options can be placed anywhere on the command line. At least one of
the options must be specified.

inputfile

A relocatable ELF object file.

outputfile

A relocatable ELF object file with all the requested operations applied.

Table 46: iobjmanip parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

Examples
This example renames the section .example in input.o to .example2 and stores the
result in output.o:
iobjmanip --rename_section .example=.example2 input.o output.o

SUMMARY OF IOBJMANIP OPTIONS
This table summarizes the iobjmanip options:
Command line option

Description

-f

Extends the command line.

--remove_section

Removes a section.

--rename_section

Renames a section.

--rename_symbol

Renames a symbol.

--strip

Removes debug information.

Table 47: iobjmanip options summary

DESCRIPTIONS OF COMMAND LINE OPTIONS
This section gives detailed reference information about each iobjmanip command line
option.

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-f
Syntax

-f filename

Parameters

For information about specifying a filename, see Rules for specifying a filename or
directory as parameters, page 156.

Description

Use this option to make iobjmanip read command line options from the named file,
with the default filename extension xcl.
In the command file, you format the items exactly as if they were on the command line
itself, except that you can use multiple lines, because the newline character acts just as
a space or tab character.
Both C and C++ style comments are allowed in the file. Double quotes behave in the
same way as in the Microsoft Windows command line environment.

--remove_section
Syntax

--remove_section {section|number}

Parameters

Description

section

The section—or sections, if there are more than one section with the
same name—to be removed.

number

The number of the section to be removed. Section numbers can be
obtained from an object dump created using ielfdumparm.

Use this option to make iobjmanip omit the specified section when generating the
output file.

--rename_section
Syntax

--rename_section {oldname|oldnumber}=newname

Parameters

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oldname

The section—or sections, if there are more than one section with the
same name—to be renamed.

oldnumber

The number of the section to be renamed. Section numbers can be
obtained from an object dump created using ielfdumparm.

newname

The new name of the section.

IAR utilities

Description

Use this option to make iobjmanip rename the specified section when generating the
output file.

--rename_symbol
Syntax

--rename_symbol oldname =newname

Parameters

Description

oldname

The symbol to be renamed.

newname

The new name of the symbol.

Use this option to make iobjmanip rename the specified symbol when generating the
output file.

--strip
Syntax

--strip

Description

Use this option to remove all sections containing debug information before writing the
output file.
To set related options, choose:
Project>Options>Linker>Output>Include debug information in output

DIAGNOSTIC MESSAGES
This section lists the messages produced by iobjmanip:

Lm001: No operation given
None of the command line parameters specified an operation to perform.

Lm002: Expected nr1 parameters but got nr2
Too few or too many parameters. Check invocation syntax for iobjmanip and for the
used command line options.

Lm003: Invalid section/symbol renaming pattern pattern
The pattern does not define a valid renaming operation.

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Lm004: Could not open file filename
iobjmanip failed to open the input file.

Lm005: ELF format error msg
The input file is not a valid ELF object file.

Lm006: Unsupported section type nr
The object file contains a section that iobjmanip cannot handle. This section will be
ignored when generating the output file.

Lm007: Unknown section type nr
iobjmanip encountered an unrecognized section. iobjmanip will try to copy the
content as is.

Lm008: Symbol symbol has unsupported format
iobjmanip encountered a symbol that cannot be handled. iobjmanip will ignore this
symbol when generating the output file.

Lm009: Group type nr not supported
iobjmanip only supports groups of type GRP_COMDAT. If any other group type is

encountered, the result is undefined.

Lm010: Unsupported ELF feature in file: msg
The input file uses a feature that iobjmanip does not support.

Lm011: Unsupported ELF file type
The input file is not a relocatable object file.

Lm012: Ambiguous rename for section/symbol name (alt1 and alt2)
An ambiguity was detected while renaming a section or symbol. One of the alternatives
will be used.

Lm013: Section name1 removed due to transitive dependency on
name2
A section was removed as it depends on an explicitly removed section.

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Lm014: File has no section with index nr
A section index, used as a parameter to --remove_section or --rename_section,
did not refer to a section in the input file.

Ms003: could not open file filename for writing
iobjmanip failed to open the output file for writing. Make sure that it is not write

protected.

Ms004: problem writing to file filename
An error occurred while writing to file filename. A possible reason for this is that the
volume is full.

Ms005: problem closing file filename
An error occurred while closing the file filename.

The IAR Absolute Symbol Exporter—isymexport
The IAR Absolute Symbol Exporter, isymexport, can export absolute symbols from a
ROM image file, so that they can be used when you link an add-on application.

INVOCATION SYNTAX
The invocation syntax for the IAR Absolute Symbol Exporter is:
isymexport [options] inputfile outputfile [options]

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The IAR Absolute Symbol Exporter—isymexport

Parameters
The parameters are:
Parameter

Description

inputfile

A ROM image in the form of an executable ELF file (output from
linking).

options

Any of the available command line options, see Summary of isymexport
options, page 344.

outputfile

A relocatable ELF file that can be used as input to linking, and which
contains all or a selection of the absolute symbols in the input file. The
output file contains only the symbols, not the actual code or data
sections. A steering file can be used to control which symbols that are
included, and also to rename some of the symbols if that is desired.

Table 48: ielftool parameters

For information about specifying a filename or a directory, see Rules for specifying a
filename or directory as parameters, page 156.

SUMMARY OF ISYMEXPORT OPTIONS
This table summarizes the isymexport command line options:
Command line option

Description

--edit

Specifies a steering file.

-f

Extends the command line; for more information, see -f, page 171.

Table 49: isymexport options summary

DESCRIPTIONS OF OPTIONS
This section gives detailed reference information about each isymexport option.

--edit
Syntax

--edit steering_file

Description

Use this option to specify a steering file to control what symbols that are included in the
isymexport output file, and also to rename some of the symbols if that is desired.

See also

Steering files, page 345.

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STEERING FILES
A steering file can be used for controlling which symbols that are included, and also to
rename some of the symbols if that is desired. In the file, you can use show and hide
directives to select which public symbols from the input file that are to be included in
the output file. rename directives can be used for changing the names of symbols in the
input file.

Syntax
The following syntax rules apply:
●

Each directive is specified on a separate line.

●

C comments (/*...*/) and C++ comments (//...) can be used.

●

Patterns can contain wildcard characters that match more than one possible
character in a symbol name.

●

The * character matches any sequence of zero or more characters in a symbol name.

●

The ? character matches any single character in a symbol name.

Example
rename xxx_* as YYY_* /*Change symbol prefix from xxx_ to YYY_ */
show YYY_*
/* Export all symbols from YYY package */
hide *_internal
/* But do not export internal symbols */
show zzz?
/* Export zzza, but not zzzaaa */
hide zzzx
/* But do not export zzzx */

Show directive
Syntax

show pattern

Parameters
pattern

A pattern to match against a symbol name.

Description

A symbol with a name that matches the pattern will be included in the output file unless
this is overridden by a later hide directive.

Example

/* Include all public symbols ending in _pub. */
show *_pub

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Hide directive
Syntax

hide pattern

Parameters
pattern

A pattern to match against a symbol name.

Description

A symbol with a name that matches the pattern will not be included in the output file
unless this is overridden by a later show directive.

Example

/* Do not include public symbols ending in _sys. */
hide *_sys

Rename directive
Syntax

rename pattern1 pattern2

Parameters

Description

pattern1

A pattern used for finding symbols to be renamed. The pattern can
contain no more than one * or ? wildcard character.

pattern2

A pattern used for the new name for a symbol. If the pattern contains a
wildcard character, it must be of the same kind as in pattern1.

Use this directive to rename symbols from the output file to the input file. No exported
symbol is allowed to match more than one rename pattern.
rename directives can be placed anywhere in the steering file, but they are executed
before any show and hide directives. Thus, if a symbol will be renamed, all show and
hide directives in the steering file must refer to the new name.

If the name of a symbol matches a pattern1 pattern that contains no wildcard
characters, the symbol will be renamed pattern2 in the output file.
If the name of a symbol matches a pattern1 pattern that contains a wildcard character,
the symbol will be renamed pattern2 in the output file, with part of the name matching
the wildcard character preserved.
Example

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/* xxx_start will be renamed Y_start_X in the output file,
xxx_stop will be renamed Y_stop_X in the output file. */
rename xxx_* Y_*_X

IAR utilities

DIAGNOSTIC MESSAGES
This section lists the messages produced by isymexport:

Es001: could not open file filename
isymexport failed to open the specified file.

Es002: illegal path pathname
The path pathname is not a valid path.

Es003: format error: message
A problem occurred while reading the input file.

Es004: no input file
No input file was specified.

Es005: no output file
An input file, but no output file was specified.

Es006: too many input files
More than two files were specified.

Es007: input file is not an ELF executable
The input file is not an ELF executable file.

Es008: unknown directive: directive
The specified directive in the steering file is not recognized.

Es009: unexpected end of file
The steering file ended when more input was required.

Es010: unexpected end of line
A line in the steering file ended before the directive was complete.

Es011: unexpected text after end of directive
There is more text on the same line after the end of a steering file directive.

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Es012: expected text
The specified text was not present in the steering file, but must be present for the
directive to be correct.

Es013: pattern can contain at most one * or ?
Each pattern in the current directive can contain at most one * or one ? wildcard
character.

Es014: rename patterns have different wildcards
Both patterns in the current directive must contain exactly the same kind of wildcard.
That is, both must either contain:
●

No wildcards

●

Exactly one *

●

Exactly one ?

This error occurs if the patterns are not the same in this regard.

Es014: ambiguous pattern match: symbol matches more than one
rename pattern
A symbol in the input file matches more than one rename pattern.

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Implementation-defined
behavior
This chapter describes how the compiler handles the implementation-defined
areas of the C language.
ISO 9899:1990, the International Organization for Standardization standard Programming Languages - C (revision and redesign of ANSI X3.159-1989,
American National Standard), changed by the ISO Amendment 1:1994,
Technical Corrigendum 1, and Technical Corrigendum 2, contains an appendix
called Portability Issues. The ISO appendix lists areas of the C language that ISO
leaves open to each particular implementation.
Note: The compiler adheres to a freestanding implementation of the ISO
standard for the C programming language. This means that parts of a standard
library can be excluded in the implementation.

Descriptions of implementation-defined behavior
This section follows the same order as the ISO appendix. Each item covered includes
references to the ISO chapter and section (in parenthesis) that explains the
implementation-defined behavior.

Translation
Diagnostics (5.1.1.3)
Diagnostics are produced in the form:
filename,linenumber level[tag]: message

where filename is the name of the source file in which the error was encountered,
linenumber is the line number at which the compiler detected the error, level is the
level of seriousness of the message (remark, warning, error, or fatal error), tag is a
unique tag that identifies the message, and message is an explanatory message, possibly
several lines.

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Descriptions of implementation-defined behavior

Environment
Arguments to main (5.1.2.2.2.1)
The function called at program startup is called main. No prototype was declared for
main, and the only definition supported for main is:
int main(void)

To change this behavior for the IAR DLIB runtime environment, see Customizing
system initialization, page 76.

Interactive devices (5.1.2.3)
The streams stdin and stdout are treated as interactive devices.

Identifiers
Significant characters without external linkage (6.1.2)
The number of significant initial characters in an identifier without external linkage is
200.

Significant characters with external linkage (6.1.2)
The number of significant initial characters in an identifier with external linkage is 200.

Case distinctions are significant (6.1.2)
Identifiers with external linkage are treated as case-sensitive.

Characters
Source and execution character sets (5.2.1)
The source character set is the set of legal characters that can appear in source files. The
default source character set is the standard ASCII character set. However, if you use the
command line option --enable_multibytes, the source character set will be the host
computer’s default character set.
The execution character set is the set of legal characters that can appear in the execution
environment. The default execution character set is the standard ASCII character set.
However, if you use the command line option --enable_multibytes, the execution
character set will be the host computer’s default character set. The IAR DLIB Library
needs a multibyte character scanner to support a multibyte execution character set.

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Implementation-defined behavior

See Locale, page 81.

Bits per character in execution character set (5.2.4.2.1)
The number of bits in a character is represented by the manifest constant CHAR_BIT. The
standard include file limits.h defines CHAR_BIT as 8.

Mapping of characters (6.1.3.4)
The mapping of members of the source character set (in character and string literals) to
members of the execution character set is made in a one-to-one way. In other words, the
same representation value is used for each member in the character sets except for the
escape sequences listed in the ISO standard.

Unrepresented character constants (6.1.3.4)
The value of an integer character constant that contains a character or escape sequence
not represented in the basic execution character set or in the extended character set for
a wide character constant generates a diagnostic message, and will be truncated to fit the
execution character set.

Character constant with more than one character (6.1.3.4)
An integer character constant that contains more than one character will be treated as an
integer constant. The value will be calculated by treating the leftmost character as the
most significant character, and the rightmost character as the least significant character,
in an integer constant. A diagnostic message will be issued if the value cannot be
represented in an integer constant.
A wide character constant that contains more than one multibyte character generates a
diagnostic message.

Converting multibyte characters (6.1.3.4)
The only locale supported—that is, the only locale supplied with the IAR C/C++
Compiler—is the ‘C’ locale. If you use the command line option
--enable_multibytes, the IAR DLIB Library will support multibyte characters if
you add a locale with multibyte support or a multibyte character scanner to the library.
See Locale, page 81.

Range of 'plain' char (6.2.1.1)
A ‘plain’ char has the same range as an unsigned char.

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Integers
Range of integer values (6.1.2.5)
The representation of integer values are in the two's complement form. The most
significant bit holds the sign; 1 for negative, 0 for positive and zero.
See Basic data types, page 210, for information about the ranges for the different integer
types.

Demotion of integers (6.2.1.2)
Converting an integer to a shorter signed integer is made by truncation. If the value
cannot be represented when converting an unsigned integer to a signed integer of equal
length, the bit-pattern remains the same. In other words, a large enough value will be
converted into a negative value.

Signed bitwise operations (6.3)
Bitwise operations on signed integers work the same way as bitwise operations on
unsigned integers; in other words, the sign-bit will be treated as any other bit.

Sign of the remainder on integer division (6.3.5)
The sign of the remainder on integer division is the same as the sign of the dividend.

Negative valued signed right shifts (6.3.7)
The result of a right-shift of a negative-valued signed integral type preserves the sign-bit.
For example, shifting 0xFF00 down one step yields 0xFF80.

Floating point
Representation of floating-point values (6.1.2.5)
The representation and sets of the various floating-point numbers adheres to IEEE
854–1987. A typical floating-point number is built up of a sign-bit (s), a biased
exponent (e), and a mantissa (m).
See Floating-point types, page 213, for information about the ranges and sizes for the
different floating-point types: float and double.

Converting integer values to floating-point values (6.2.1.3)
When an integral number is cast to a floating-point value that cannot exactly represent
the value, the value is rounded (up or down) to the nearest suitable value.

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Demoting floating-point values (6.2.1.4)
When a floating-point value is converted to a floating-point value of narrower type that
cannot exactly represent the value, the value is rounded (up or down) to the nearest
suitable value.

Arrays and pointers
size_t (6.3.3.4, 7.1.1)
See size_t, page 215, for information about size_t.

Conversion from/to pointers (6.3.4)
See Casting, page 215, for information about casting of data pointers and function
pointers.

ptrdiff_t (6.3.6, 7.1.1)
See ptrdiff_t, page 216, for information about the ptrdiff_t.

Registers
Honoring the register keyword (6.5.1)
User requests for register variables are not honored.

Structures, unions, enumerations, and bitfields
Improper access to a union (6.3.2.3)
If a union gets its value stored through a member and is then accessed using a member
of a different type, the result is solely dependent on the internal storage of the first
member.

Padding and alignment of structure members (6.5.2.1)
See the section Basic data types, page 210, for information about the alignment
requirement for data objects.

Sign of 'plain' bitfields (6.5.2.1)
A 'plain' int bitfield is treated as a unsigned int bitfield. All integer types are allowed
as bitfields.

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Allocation order of bitfields within a unit (6.5.2.1)
Bitfields are allocated within an integer from least-significant to most-significant bit.

Can bitfields straddle a storage-unit boundary (6.5.2.1)
Bitfields can straddle a storage-unit boundary for the chosen bitfield integer type.

Integer type chosen to represent enumeration types (6.5.2.2)
The chosen integer type for a specific enumeration type depends on the enumeration
constants defined for the enumeration type. The chosen integer type is the smallest
possible.

Qualifiers
Access to volatile objects (6.5.3)
Any reference to an object with volatile qualified type is an access.

Declarators
Maximum numbers of declarators (6.5.4)
The number of declarators is not limited. The number is limited only by the available
memory.

Statements
Maximum number of case statements (6.6.4.2)
The number of case statements (case values) in a switch statement is not limited. The
number is limited only by the available memory.

Preprocessing directives
Character constants and conditional inclusion (6.8.1)
The character set used in the preprocessor directives is the same as the execution
character set. The preprocessor recognizes negative character values if a 'plain' character
is treated as a signed character.

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Including bracketed filenames (6.8.2)
For file specifications enclosed in angle brackets, the preprocessor does not search
directories of the parent files. A parent file is the file that contains the #include
directive. Instead, it begins by searching for the file in the directories specified on the
compiler command line.

Including quoted filenames (6.8.2)
For file specifications enclosed in quotes, the preprocessor directory search begins with
the directories of the parent file, then proceeds through the directories of any
grandparent files. Thus, searching begins relative to the directory containing the source
file currently being processed. If there is no grandparent file and the file is not found,
the search continues as if the filename was enclosed in angle brackets.

Character sequences (6.8.2)
Preprocessor directives use the source character set, except for escape sequences. Thus,
to specify a path for an include file, use only one backslash:
#include "mydirectory\myfile"

Within source code, two backslashes are necessary:
file = fopen("mydirectory\\myfile","rt");

Recognized pragma directives (6.8.6)
In addition to the pragma directives described in the chapter Pragma directives, the
following directives are recognized and will have an indeterminate effect:
alignment
baseaddr
basic_template_matching
building_runtime
can_instantiate
codeseg
cspy_support
define_type_info
do_not_instantiate
early_dynamic_initialization
function
hdrstop
important_typedef
instantiate

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keep_definition
memory
module_name
no_pch
once
__printf_args
public_equ
__scanf_args
STDC
system_include
vector
warnings

Default __DATE__ and __TIME__ (6.8.8)
The definitions for __TIME__ and __DATE__ are always available.

IAR DLIB Library functions
The information in this section is valid only if the runtime library configuration you have
chosen supports file descriptors. See the chapter The DLIB runtime environment for
more information about runtime library configurations.

NULL macro (7.1.6)
The NULL macro is defined to 0.

Diagnostic printed by the assert function (7.2)
The assert() function prints:
filename:linenr expression -- assertion failed

when the parameter evaluates to zero.

Domain errors (7.5.1)
NaN (Not a Number) will be returned by the mathematic functions on domain errors.

Underflow of floating-point values sets errno to ERANGE (7.5.1)
The mathematics functions set the integer expression errno to ERANGE (a macro in
errno.h) on underflow range errors.

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fmod() functionality (7.5.6.4)
If the second argument to fmod() is zero, the function returns NaN; errno is set to
EDOM.

signal() (7.7.1.1)
The signal part of the library is not supported.
Note: Low-level interface functions exist in the library, but will not perform anything.
Use the template source code to implement application-specific signal handling. See
Signal and raise, page 84.

Terminating newline character (7.9.2)
stdout stream functions recognize either newline or end of file (EOF) as the

terminating character for a line.

Blank lines (7.9.2)
Space characters written to the stdout stream immediately before a newline character
are preserved. There is no way to read the line through the stdin stream that was
written through the stdout stream.

Null characters appended to data written to binary streams (7.9.2)
No null characters are appended to data written to binary streams.

Files (7.9.3)
Whether a write operation on a text stream causes the associated file to be truncated
beyond that point, depends on the application-specific implementation of the low-level
file routines. See File input and output, page 80.

remove() (7.9.4.1)
The effect of a remove operation on an open file depends on the application-specific
implementation of the low-level file routines. See File input and output, page 80.

rename() (7.9.4.2)
The effect of renaming a file to an already existing filename depends on the
application-specific implementation of the low-level file routines. See File input and
output, page 80.

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%p in printf() (7.9.6.1)
The argument to a %p conversion specifier, print pointer, to printf() is treated as
having the type void *. The value will be printed as a hexadecimal number, similar to
using the %x conversion specifier.

%p in scanf() (7.9.6.2)
The %p conversion specifier, scan pointer, to scanf() reads a hexadecimal number and
converts it into a value with the type void *.

Reading ranges in scanf() (7.9.6.2)
A - (dash) character is always treated as a range symbol.

File position errors (7.9.9.1, 7.9.9.4)
On file position errors, the functions fgetpos and ftell store EFPOS in errno.

Message generated by perror() (7.9.10.4)
The generated message is:
usersuppliedprefix:errormessage

Allocating zero bytes of memory (7.10.3)
The calloc(), malloc(), and realloc() functions accept zero as an argument.
Memory will be allocated, a valid pointer to that memory is returned, and the memory
block can be modified later by realloc.

Behavior of abort() (7.10.4.1)
The abort() function does not flush stream buffers, and it does not handle files,
because this is an unsupported feature.

Behavior of exit() (7.10.4.3)
The argument passed to the exit function will be the return value returned by the main
function to cstartup.

Environment (7.10.4.4)
The set of available environment names and the method for altering the environment list
is described in Environment interaction, page 83.

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Implementation-defined behavior

system() (7.10.4.5)
How the command processor works depends on how you have implemented the system
function. See Environment interaction, page 83.

Message returned by strerror() (7.11.6.2)
The messages returned by strerror() depending on the argument is:
Argument

Message

EZERO

no error

EDOM

domain error

ERANGE

range error

EFPOS

file positioning error

EILSEQ

multi-byte encoding error

<0 || >99

unknown error

all others

error nnn

Table 50: Message returned by strerror()—IAR DLIB library

The time zone (7.12.1)
The local time zone and daylight savings time implementation is described in Time, page
85.

clock() (7.12.2.1)
From where the system clock starts counting depends on how you have implemented the
clock function. See Time, page 85.

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Glossary

Glossary
This is a general glossary for terms relevant to embedded
systems programming. Some of the terms do not apply to the
IAR Embedded Workbench® version that you are using.

A
Absolute location
A specific memory address for an object specified in the
source code, as opposed to the object being assigned a location
by the IAR ILINK Linker.
Address expression
An expression which has an address as its value.
AEABI
Embedded Application Binary Interface for ARM, defined by
ARM Limited.
Application
The program developed by the user of the IAR Systems toolkit
and which will be run as an embedded application on a target
processor.
Ar
The GNU binary utility for creating, modifying, and extracting
from archives, that is, libraries. See also Iarchive.
Architecture
A term used by computer designers to designate the structure
of complex information-processing systems. It includes the
kinds of instructions and data used, the memory organization
and addressing, and the methods by which the system is
implemented. The two main architecture types used in
processor design are Harvard architecture and von Neumann
architecture.
Archive
See Library.
Assembler directives
The set of commands that control how the assembler operates.

Assembler options
Parameters you can specify to change the default behavior of
the assembler.
Assembler language
A machine-specific set of mnemonics used to specify
operations to the target processor and input or output registers
or data areas. Assembler language might sometimes be
preferred over C/C++ to save memory or to enhance the
execution speed of the application.
Attributes
See Section attributes.
Auto variables
The term refers to the fact that each time the function in which
the variable is declared is called, a new instance of the variable
is created automatically. This can be compared with the
behavior of local variables in systems using static overlay,
where a local variable only exists in one instance, even if the
function is called recursively. Also called local variables.
Compare Register variables.

B
Backtrace
Information that allows the IAR C-SPY® Debugger to show,
without any runtime penalty, the complete stack of function
calls wherever the program counter is, provided that the code
comes from compiled C functions.
Bank
See Memory bank.
Bank switching
Switching between different sets of memory banks. This
software technique increases a computer's usable memory by
allowing different pieces of memory to occupy the same
address space.
Banked code
Code that is distributed over several banks of memory. Each
function must reside in only one bank.

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Banked data
Data that is distributed over several banks of memory. Each
data object must fit inside one memory bank.
Banked memory
Has multiple storage locations for the same address. See also
Memory bank.
Bank-switching routines
Code that selects a memory bank.
Batch files
A text file containing operating system commands which are
executed by the command line interpreter. In Unix, this is
called a “shell script” because it is the Unix shell which
includes the command line interpreter. Batch files can be used
as a simple way to combine existing commands into new
commands.
Bitfield
A group of bits considered as a unit.
Block, in linker configuration file
A continuous piece of code or data. It is either built up of
blocks, overlays, and sections or it is empty. A block has a
name, and the start and end address of the block can be referred
to from the application. It can have attributes such as a
maximum size, a specific size, or a minimum alignment. The
contents can have a specific order or not.
Breakpoint
1. Code breakpoint. A point in a program that, when reached,
triggers some special behavior useful to the process of
debugging. Generally, breakpoints are used for stopping
program execution or dumping the values of some or all of the
program variables. Breakpoints can be part of the program
itself, or they can be set by the programmer as part of an
interactive session with a debugging tool for scrutinizing the
program's execution.
2. Data breakpoint. A point in memory that, when accessed,
triggers some special behavior useful to the process of
debugging. Generally, data breakpoints are used to stop
program execution when an address location is accessed either
by a read operation or a write operation.

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3. Immediate breakpoint. A point in memory that, when
accessed, trigger some special behavior useful in the process of
debugging. Immediate breakpoints are generally used for
halting the program execution in the middle of a memory
access instruction (before or after the actual memory access
depending on the access type) while performing some
user-specified action. The execution is then resumed. This
feature is only available in the simulator version of C-SPY.

C
Calling convention
A calling convention describes the way one function in a
program calls another function. This includes how register
parameters are handled, how the return value is returned, and
which registers that will be preserved by the called function.
The compiler handles this automatically for all C and C++
functions. All code written in assembler language must
conform to the rules in the calling convention to be callable
from C or C++, or to be able to call C and C++ functions. The
C calling convention and the C++ calling conventions are not
necessarily the same.
Cheap
As in cheap memory access. A cheap memory access either
requires few cycles to perform, or few bytes of code to
implement. A cheap memory access is said to have a low cost.
See Memory access cost.
Checksum
A computed value which depends on the ROM content of the
whole or parts of the application, and which is stored along
with the application to detect corruption of the data. The
checksum is produced by the linker to be verified with the
application. Several algorithms are supported. Compare CRC
(cyclic redundancy checking).
Code banking
See Banked code.

Glossary

Code model
The code model controls how code is generated for an
application. Typically, the code model controls behavior such
as how functions are called and in which code section
functions will be located. All object files of an application
must be compiled using the same code model.
Code pointers
A code pointer is a function pointer. As many cores allow
several different methods of calling a function, compilers for
embedded systems usually provide the users with the ability to
use all these methods.
Do not confuse code pointers with data pointers.
Code sections
Read-only sections that contain code. See also Section.
Compilation unit
See Translation unit.
Compiler options
Parameters you can specify to change the default behavior of
the compiler.
Configuration
See ILINK configuration, and Linker configuration file.
Cost
See Memory access cost.
CRC (cyclic redundancy checking)
A number derived from, and stored with, a block of data to
detect corruption. A CRC is based on polynomials and is a
more advanced way of detecting errors than a simple
arithmetic checksum. Compare Checksum.
C-SPY options
Parameters you can specify to change the default behavior of
the IAR C-SPY Debugger.
Cstartup
Code that sets up the system before the application starts
executing.

C-style preprocessor
A preprocessor is either a stand-alone application or an
integrated part of a compiler, that performs preprocessing of
the input stream before the actual compilation occurs. A
C-style preprocessor follows the rules set up in the ANSI
specification of the C language and implements commands
like #define, #if, and #include, which are used to handle
textual macro substitution, conditional compilation, and
inclusion of other files.

D
Data banking
See Banked data.
Data model
The data model specifies the default memory type. This means
that the data model typically controls one or more of the
following: The method used and the code generated to access
static and global variables, dynamically allocated data, and the
runtime stack. It also controls the default pointer type and in
which data sections static and global variables will be located.
A project can only use one data model at a time, and the same
model must be used by all user modules and all library
modules in the project.
Data pointers
Many cores have different addressing modes to access
different memory types or address spaces. Compilers for
embedded systems usually have a set of different data pointer
types so they can access the available memory efficiently.
Data representation
How different data types are laid out in memory and what
value ranges they represent.
Declaration
A specification to the compiler that an object, a variable or
function, exists. The object itself must be defined in exactly
one translation unit (source file). An object must either be
declared or defined before it is used. Normally an object that is
used in many files is defined in one source file. A declaration
is normally placed in a header file that is included by the files
that use the object.

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For example:
/* Variable "a" exists somewhere. Function
"b" takes two int parameters and returns an
int. */
extern int a;
int b(int, int);

Definition
The variable or function itself. Only one definition can exist
for each variable or function in an application. See also
Tentative definition.
For example:
int a;
int b(int x, int y)
{
return x + y;
}

Demangling
To restore a mangled name to the more common C/C++ name.
See also Mangling.
Derivative
One of two or more processor variants in a series or family of
microprocessors or microcontrollers.
Device description file
A file used by C-SPY that contains various device-specific
information such as I/O registers (SFR) definitions, interrupt
vectors, and control register definitions.
Device driver
Software that provides a high-level programming interface to
a particular peripheral device.
Digital signal processor (DSP)
A device that is similar to a microprocessor, except that the
internal CPU is optimized for use in applications involving
discrete-time signal processing. In addition to standard
microprocessor instructions, digital signal processors usually
support a set of complex instructions to perform common
signal-processing computations quickly.

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Disassembly window
A C-SPY window that shows the memory contents
disassembled as machine instructions, interspersed with the
corresponding C source code (if available).
DWARF
An industry-standard debugging format which supports source
level debugging. This is the format used by the IAR ILINK
Linker for representing debug information in an object.
Dynamic initialization
Variables in a program written in C are initialized during the
initial phase of execution, before the main function is called.
These variables are always initialized with a static value,
which is determined either at compile time or at link time. This
is called static initialization. In C++, variables might require
initialization to be performed by executing code, for example,
running the constructor of global objects, or performing
dynamic memory allocation.
Dynamic memory allocation
There are two main strategies for storing variables: statically at
link time, or dynamically at runtime. Dynamic memory
allocation is often performed from the heap and it is the size of
the heap that determines how much memory that can be used
for dynamic objects and variables. The advantage of dynamic
memory allocation is that several variables or objects that are
not active at the same time can be stored in the same memory,
thus reducing the memory requirements of an application. See
also Heap memory.
Dynamic object
An object that is allocated, created, destroyed, and released at
runtime. Dynamic objects are almost always stored in memory
that is dynamically allocated. Compare Static object.

E
EEPROM
Electrically Erasable, Programmable Read-Only Memory. A
type of ROM that can be erased electronically, and then be
re-programmed.

Glossary

ELF
Executable and Linking Format, an industry-standard object
file format. This is the format used by the IAR ILINK Linker.
The debug information is formatted using DWARF.
EPROM
Erasable, Programmable Read-Only Memory. A type of ROM
that can be erased by exposing it to ultraviolet light, and then
be re-programmed.
Embedded C++
A subset of the C++ programming language, which is intended
for embedded systems programming. The fact that
performance and portability are particularly important in
embedded systems development was considered when
defining the language.
Embedded system
A combination of hardware and software, designed for a
specific purpose. Embedded systems are often part of a larger
system or product.
Emulator
An emulator is a hardware device that performs emulation of
one or more derivatives of a processor family. An emulator can
often be used instead of the actual core and connects directly
to the printed circuit board—where the core would have been
connected—via a connecting device. An emulator always
behaves exactly as the processor it emulates, and is used when
debugging requires all systems actuators, or when debugging
device drivers.
Enea OSE Load module format
A specific ELF format that is loadable by the OSE operating
system. See also ELF.
Enumeration
A type which includes in its definition an exhaustive list of
possible values for variables of that type. Common examples
include Boolean, which takes values from the list [true, false],
and day-of-week which takes values [Sunday, Monday,
Tuesday, Wednesday, Thursday, Friday, Saturday].
Enumerated types are a feature of typed languages, including
C and Ada.

Characters, (fixed-size) integers, and even floating-point types
might be (but are not usually) considered to be (large)
enumerated types.
Executable image
Contains the executable image; the result of linking several
relocatable object files and libraries. The file format used for
an object file is ELF with embedded DWARF for debug
information.
Exceptions
An exception is an interrupt initiated by the processor
hardware, or hardware that is tightly coupled with the
processor, for instance, a memory management unit (MMU).
The exception signals a violation of the rules of the
architecture (access to protected memory), or an extreme error
condition (division by zero).
Do not confuse this use of the word exception with the term
exception used in the C++ language (but not in Embedded
C++).
Expensive
As in expensive memory access. An expensive memory access
either requires many cycles to perform, or many bytes of code
to implement. An expensive memory access is said to have a
high cost. See Memory access cost.
Extended keywords
Non-standard keywords in C and C++. These usually control
the definition and declaration of objects (that is, data and
functions). See also Keywords.

F
Filling
How to fill up bytes—with a specific fill pattern—that exists
between the sections in an executable image. These bytes exist
because of the alignment demands on the sections.

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Format specifiers
Used to specify the format of strings sent by library functions
such as printf. In the following example, the function call
contains one format string with one format specifier, %c, that
prints the value of a as a single ASCII character:

Host
The computer that communicates with the target processor.
The term is used to distinguish the computer on which the
debugger is running from the core the embedded application
you develop runs on.

printf("a = %c", a);

I

G
General options
Parameters you can specify to change the default behavior of
all tools that are included in the IDE.
Generic pointers
Pointers that have the ability to point to all different memory
types in, for example, a core based on the Harvard architecture.

H
Harvard architecture
A core based on the Harvard architecture has separate data and
instruction buses. This allows execution to occur in parallel.
As an instruction is being fetched, the current instruction is
executing on the data bus. Once the current instruction is
complete, the next instruction is ready to go. This theoretically
allows for much faster execution than a von Neumann
architecture, but adds some silicon complexity. Compare von
Neumann architecture.
Heap memory
The heap is a pool of memory in a system that is reserved for
dynamic memory allocation. An application can request parts
of the heap for its own use; once memory is allocated from the
heap it remains valid until it is explicitly released back to the
heap by the application. This type of memory is useful when
the number of objects is not known until the application
executes. Note that this type of memory is risky to use in
systems with a limited amount of memory or systems that are
expected to run for a very long time.
Heap size
Total size of memory that can be dynamically allocated.

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Iarchive
The IAR Systems utility for creating archives, that is, libraries.
Iarchive is delivered with IAR Embedded Workbench.
IDE (integrated development environment)
A programming environment with all necessary tools
integrated into one single application.
Ielfdumparm
The IAR Systems utility for creating a text representation of
the contents of ELF relocatable or executable image.
Ielftool
The IAR Systems utility for performing various
transformations on an ELF executable image, such as fill,
checksum, and format conversion.
ILINK
The IAR ILINK Linker which produces absolute output in the
ELF/DWARF format.
ILINK configuration
The definition of available physical memories and the
placement of sections—pieces of code and data—into those
memories. ILINK requires a configuration to build an
executable image.
Image
See Executable image.
Include file
A text file which is included into a source file. This is often
done by the preprocessor.

Glossary

Initialization setup in linker configuration file
Defines how to initialize RAM sections with their initializers.
Normally, only non-constant non-noinit variables are
initialized but, for example, pieces of code can be initialized as
well.

Interrupts are asynchronous events that suspend normal
processing and temporarily divert the flow of control through
an “interrupt handler” routine. Interrupts can be caused by both
hardware (I/O, timer, machine check) and software
(supervisor, system call or trap instruction). Compare Trap.

Initialized sections
Read-write sections that should be initialized with specific
values at startup. See also Section.

Intrinsic
An adjective describing native compiler objects, properties,
events, and methods.

Inline assembler
Assembler language code that is inserted directly between C
statements.

Intrinsic functions
1. Function calls that are directly expanded into specific
sequences of machine code. 2. Functions called by the
compiler for internal purposes (that is, floating point
arithmetic etc.).

Inlining
An optimization that replaces function calls with the body of
the called function. This optimization increases the execution
speed and can even reduce the size of the generated code.
Instruction mnemonics
A word or acronym used in assembler language to represent a
machine instruction. Different processors have different
instruction sets and therefore use a different set of mnemonics
to represent them, such as, ADD, BR (branch), BLT (branch if
less than), MOVE, LDR (load register).
Interrupt vector
A small piece of code that will be executed, or a pointer that
points to code that will be executed when an interrupt occurs.
Interrupt vector table
A table containing interrupt vectors, indexed by interrupt type.
This table contains the processor's mapping between interrupts
and interrupt service routines and must be initialized by the
programmer.
Interrupts
In embedded systems, the use of interrupts is a method of
detecting external events immediately, for example a timer
overflow or the pressing of a button.

Iobjmanip
The IAR Systems utility for performing low-level
manipulation of ELF object files.

K
Key bindings
Key shortcuts for menu commands used in the IDE.
Keywords
A fixed set of symbols built into the syntax of a programming
language. All keywords used in a language are reserved—they
cannot be used as identifiers (in other words, user-defined
objects such as variables or procedures). See also Extended
keywords.

L
L-value
A value that can be found on the left side of an assignment and
thus be changed. This includes plain variables and
de-referenced pointers. Expressions like (x + 10) cannot be
assigned a new value and are therefore not L-values.
Language extensions
Target-specific extensions to the C language.

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Library
See Runtime library.
Library configuration file
A file that contains a configuration of the runtime library. The
file contains information about what functionality is part of the
runtime environment. The file is used for tailoring a build of a
runtime library. See also Runtime library.
Linker configuration file
A file that contains a configuration used by ILINK when
building an executable image. See also ILINK configuration.

3. C-SPY macros are programs that you can write to enhance
the functionality of C-SPY. A typical application of C-SPY
macros is to associate them with breakpoints; when such a
breakpoint is hit, the macro is run and can for example be used
to simulate peripheral devices, to evaluate complex conditions,
or to output a trace.

Local variable
See Auto variables.

The C-SPY macro language is like a simple dialect of C, but is
less strict with types.

Location counter
See Program location counter (PLC).

Mailbox
A mailbox in an RTOS is a point of communication between
two or more tasks. One task can send messages to another task
by placing the message in the mailbox of the other task.
Mailboxes are also known as message queues or message
ports.

Logical address
See Virtual address (logical address).

M
MAC (Multiply and accumulate)
A special instruction, or on-chip device, that performs a
multiplication together with an addition. This is very useful
when performing signal processing where many filters and
transforms have the form:

The accumulator of the MAC usually has a higher precision
(more bits) than normal registers. See also Digital signal
processor (DSP).
Macro
1. Assembler macros are user-defined sets of assembler lines
that can be expanded later in the source file by referring to the
given macro name. Parameters will be substituted if referred
to.

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2. C macro. A text substitution mechanism used during
preprocessing of source files. Macros are defined using the
#define preprocessing directive. The replacement text of
each macro is then substituted for any occurrences of the
macro name in the rest of the translation unit.

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Mangling
Mangling is a technique used for mapping a complex C/C++
name into a simple name. Both mangled and unmangled
names can be produced for C/C++ symbols in ILINK
messages.
Memory, in linker configuration file
A physical memory. The number of units it contains and how
many bits a unit consists of, are defined in the linker
configuration file. The memory is always addressable from
0x0 to size -1.
Memory access cost
The cost of a memory access can be in clock cycles, or in the
number of bytes of code needed to perform the access. A
memory which requires large instructions or many instructions
is said to have a higher access cost than a memory which can
be accessed with few, or small instructions.
Memory area
A region of the memory.

Glossary

Memory bank
The smallest unit of continuous memory in banked memory.
One memory bank at a time is visible in a core’s physical
address space.
Memory map
A map of the different memory areas available to the core.
Memory model
Specifies the memory hierarchy and how much memory the
system can handle. Your application must use only one
memory model at a time, and the same model must be used by
all user modules and all library modules.
Microcontroller
A microprocessor on a single integrated circuit intended to
operate as an embedded system. In addition to a CPU, a
microcontroller typically includes small amounts of RAM,
PROM, timers, and I/O ports.
Microprocessor
A CPU contained on one (or a few) integrated circuits. A
single-chip microprocessor can include other components
such as memory, memory management, caches, floating-point
unit, I/O ports and timers. Such devices are also known as
microcontrollers.
Multi-file compilation
A technique which means that the compiler compiles several
source files as one compilation unit, which enables for
interprocedural optimizations such as inlining, cross call, and
cross jump on multiple source files in a compilation unit.
Module
An object. An object file contains a module and library
contains one or more objects. The basic unit of linking. A
module contains definitions for symbols (exports) and
references to external symbols (imports). When you compile
C/C++, each translation unit produces one module.

N
Nested interrupts
A system where an interrupt can be interrupted by another
interrupt is said to have nested interrupts.
Non-banked memory
Has a single storage location for each memory address in a
core’s physical address space.
Non-initialized memory
Memory that can contain any value at reset, or in the case of a
soft reset, can remember the value it had before the reset.
No-init sections
Read-write sections that should not be initialized at startup.
See also Section.
Non-volatile storage
Memory devices such as battery-backed RAM, ROM,
magnetic tape and magnetic disks that can retain data when
electric power is shut off. Compare Volatile storage.
NOP
No operation. This is an instruction that does not do anything,
but is used to create a delay. In pipelined architectures, the NOP
instruction can be used for synchronizing the pipeline. See also
Pipeline.

O
Objcopy
A GNU binary utility for converting an absolute object file in
ELF format into an absolute object file, for example the format
Motorola-std or Intel-std. See also Ielftool.
Object
An object file or a library member.
Object file, absolute
See Executable image.

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Object file, relocatable
The result of compiling or assembling a source file. The file
format used for an object file is ELF with embedded DWARF
for debug information.

Placement, in linker configuration file
How to place blocks, overlays, and sections into a region. It
determines how pieces of code and data are actually placed in
the available physical memory.

Operator
A symbol used as a function, with infix syntax if it has two
arguments (+, for example) or prefix syntax if it has only one
(for instance, bitwise negation, ~). Many languages use
operators for built-in functions such as arithmetic and logic.

Pointer
An object that contains an address to another object of a
specified type.

Operator precedence
Each operator has a precedence number assigned to it that
determines the order in which the operator and its operands are
evaluated. The highest precedence operators are evaluated
first. Use parentheses to group operators and operands to
control the order in which the expressions are evaluated.
Output image
The resulting application after linking. This term is equivalent
to executable image, which is the term used in the IAR
Systems user documentation.
Overlay, in linker configuration file
Like a block, but it contains several overlaid entities, each built
up of blocks, overlays, and sections. The size of an overlay is
determined by its largest constituent.

P
Parameter passing
See Calling convention.
Peripheral unit
A hardware component other than the processor, for example
memory or an I/O device.
Pipeline
A structure that consists of a sequence of stages through which
a computation flows. New operations can be initiated at the
start of the pipeline even though other operations are already
in progress through the pipeline.

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#pragma
During compilation of a C/C++ program, the #pragma
preprocessing directive causes the compiler to behave in an
implementation-defined manner. This can include, for
example, producing output on the console, changing the
declaration of a subsequent object, changing the optimization
level, or enabling/disabling language extensions.
Pre-emptive multitasking
An RTOS task is allowed to run until a higher priority process
is activated. The higher priority task might become active as
the result of an interrupt. The term preemptive indicates that
although a task is allotted to run a given length of time (a
timeslice), it might lose the processor at any time. Each time
an interrupt occurs, the task scheduler looks for the highest
priority task that is active and switches to that task. If the
located task is different from the task that was executing before
the interrupt, the previous task is suspended at the point of
interruption.
Compare Round Robin.
Preprocessing directives
A set of directives that are executed before the parsing of the
actual code is started.
Preprocessor
See C-style preprocessor.
Processor variant
The different chip setups that the compiler supports. See
Derivative.
Program counter (PC)
A special processor register that is used to address instructions.
Compare Program location counter (PLC).

Glossary

Program location counter (PLC)
Used in the IAR Assembler to denote the code address of the
current instruction. The PLC is represented by a special symbol
(typically $) that can be used in arithmetic expressions. Also
called simply location counter (LC).
PROM
Programmable Read-Only Memory. A type of ROM that can
be programmed only once.

Real-time system
A computer system whose processes are time-sensitive.
Compare Real-time operating system (RTOS).
Region, in linker configuration file
A set of non-overlapping ranges. The ranges can lie in one or
more memories. Blocks, overlays, and sections are placed into
regions in the linker configuration file.

Project
The user application development project.

Region expression, in linker configuration file
A region built up from region literals, regions, and the common
set operations possible in the linker configuration file.

Project options
General options that apply to an entire project, for example the
target processor that the application will run on.

Region literal, in linker configuration file
A literal that defines a set of one or more non-overlapping
ranges in a memory.

Q

Register constant
A register constant is a value that is loaded into a dedicated
processor register when the system is initialized. The compiler
can then generate code that assumes that the constants are
present in the dedicated registers.

Qualifiers
See Type qualifiers.

R
Range, in linker configuration file
A range of consecutive addresses in a memory. A region is
built up of ranges.
R-value
A value that can be found on the right side of an assignment.
This is just a plain value. See also L-value.
Read-only sections
Sections that contain code or constants. See also Section.
Real-time operating system (RTOS)
An operating system which guarantees the latency between an
interrupt being triggered and the interrupt handler starting, and
how tasks are scheduled. An RTOS is typically much smaller
than a normal desktop operating system. Compare Real-time
system.

Register
A small on-chip memory unit, usually just one or a few bytes
in size, which is particularly efficient to access and therefore
often reserved as a temporary storage area during program
execution.
Register locking
Register locking means that the compiler can be instructed that
some processor registers shall not be used during normal code
generation. This is useful in many situations. For example,
some parts of a system might be written in assembler language
to gain speed. These parts might be given dedicated processor
registers. Or the register might be used by an operating system,
or by other third-party software.
Register variables
Typically, register variables are local variables that are placed
in registers instead of on the (stack) frame of the function.
Register variables are much more efficient than other variables
because they do not require memory accesses, so the compiler
can use shorter/faster instructions when working with them.
See also Auto variables.

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Relay
A synonym to veneer, see Veneer.

S

Relocatable sections
Sections that have no fixed location in memory before linking.

Saturation arithmetics
Most, if not all, C and C++ implementations use mod–2N
2-complement-based arithmetics where an overflow wraps the
value in the value domain, that is, (127 + 1) = -128. Saturation
arithmetics, on the other hand, does not allow wrapping in the
value domain, for instance, (127 + 1) = 127, if 127 is the upper
limit. Saturation arithmetics is often used in signal processing,
where an overflow condition would have been fatal if value
wrapping had been allowed.

Reset
A reset is a restart from the initial state of a system. A reset can
originate from hardware (hard reset), or from software (soft
reset). A hard reset can usually not be distinguished from the
power-on condition, which a soft reset can be.
ROM-monitor
A piece of embedded software designed specifically for use as
a debugging tool. It resides in the ROM of the evaluation board
chip and communicates with a debugger via a serial port or
network connection. The ROM-monitor provides a set of
primitive commands to view and modify memory locations
and registers, create and remove breakpoints, and execute your
application. The debugger combines these primitives to fulfill
higher-level requests like program download and single-step.
Round Robin
Task scheduling in an operating system, where all tasks have
the same priority level and are executed in turn, one after the
other. Compare Pre-emptive multitasking.

Scheduler
The part of an RTOS that performs task-switching. It is also
responsible for selecting which task that should be allowed to
run. Many scheduling algorithms exist, but most of them are
either based on static scheduling (performed at compile-time),
or on dynamic scheduling (where the actual choice of which
task to run next is taken at runtime, depending on the state of
the system at the time of the task-switch). Most real-time
systems use static scheduling, because it makes it possible to
prove that the system will not violate the real-time
requirements.

RTOS
See Real-time operating system (RTOS).

Scope
The section of an application where a function or a variable can
be referenced by name. The scope of an item can be limited to
file, function, or block.

Runtime library
A collection of relocatable object files that will be included in
the executable image only if referred to from an object file, in
other words conditionally linked.

Section
An entity that either contains data or text. Typically, one or
more variables, or functions. A section is the smallest linkable
unit.

Runtime model attributes
A mechanism that is designed to prevent modules that are not
compatible to be linked into an application. ILINK uses the
runtime model attributes when automatically choosing library
to verify that the correct one is used.

Section attributes
Each section has a name and an attribute. The attribute defines
what a section contains, that is, if the section content is
read-only, read/write, code, data, etc.
Section fragment
A part of a section, typically a variable or a function.

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Glossary

Section selection
In the linker configuration file, defining a set of sections by
using section selectors. A section belongs to the most
restrictive section selector if it can be part of more than one
selection. Three different selectors can be used individually or
in conjunction to select the set of sections: section attribute
(selecting by the section content), section name (selecting by
the section name), and object name (selecting from a specific
object).

Side effect
An expression in C or C++ is said to have a side-effect if it
changes the state of the system. Examples are assignments to
a variable, or using a variable with the post-increment operator.
The C and C++ standards state that a variable that is subject to
a side-effect should not be used more that once in an
expression. As an example, this statement violates that rule:

Semaphore
A semaphore is a type of flag that is used for guaranteeing
exclusive access to resources. The resource can be a hardware
port, a configuration memory, or a set of variables. If several
tasks must access the same resource, the parts of the code (the
critical sections) that access the resource must be made
exclusive for every task. This is done by obtaining the
semaphore that protects that resource, thus blocking all other
tasks from it. If another task wishes to use the resource, it also
must obtain the semaphore. If the semaphore is already in use,
the second task must wait until the semaphore is released.
After the semaphore is released, the second task is allowed to
execute and can obtain the semaphore for its own exclusive
access.

Signal
Signals provide event-based communication between tasks. A
task can wait for one or more signals from other tasks. Once a
task receives a signal it waits for, execution continues. A task
in an RTOS that waits for a signal does not use any processing
time, which allows other tasks to execute.

Severity level
The level of seriousness of the diagnostic response from the
assembler, compiler, or debugger, when it notices that
something is wrong. Typical severity levels are remarks,
warnings, errors, and fatal errors. A remark just points to a
possible problem, while a fatal error means that the
programming tool exits without finishing.

*d++ = *d;

Simulator
A debugging tool that runs on the host and behaves as similar
to the target processor as possible. A simulator is used to debug
the application when the hardware is unavailable, or not
needed for proper debugging. A simulator is usually not
connected to any physical peripheral devices. A simulated
processor is often slower, or even much slower, than the real
hardware.
Single stepping
Executing one instruction or one C statement at a time in the
debugger.
Skeleton code
An incomplete code framework that allows the user to
specialize the code.

Sharing
A physical memory that can be addressed in several ways;
defined in the linker configuration file.

Special function register (SFR)
A register that is used to read and write to the hardware
components of the core.

Short addressing
Many cores have special addressing modes for efficient access
to internal RAM and memory mapped I/O. Short addressing is
therefore provided as an extended feature by many compilers
for embedded systems. See also Data pointers.

Stack frames
Data structures containing data objects like preserved
registers, local variables, and other data objects that must be
stored temporary for a particular scope (usually a function).

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Earlier compilers usually had a fixed size and layout on a stack
frame throughout a complete function, while modern
compilers might have a very dynamic layout and size that can
change anywhere and anytime in a function.
Standard libraries
The C and C++ library functions as specified by the C and C++
standard, and support routines for the compiler, like
floating-point routines.
Statically allocated memory
This kind of memory is allocated once and for all at link-time,
and remains valid all through the execution of the application.
Variables that are either global or declared static are
allocated this way.
Static object
An object whose memory is allocated at link-time and is
created during system startup (or at first use). Compare
Dynamic object.
Static overlay
Instead of using a dynamic allocation scheme for parameters
and auto variables, the linker allocates space for parameters
and auto variables at link time. This generates a worst-case
scenario of stack usage, but might be preferable for small chips
with expensive stack access or no stack access at all.
Structure value
A collecting names for structs and unions. A struct is a
collection of data object placed sequentially in memory
(possibly with pad bytes between them). A union is a
collection of data sharing the same memory location.
Symbol
1. A name that represents a register, an absolute value, or a
memory address (relative or absolute).
2. A configuration symbol that can be referred to from the
executable image. The symbol is defined to be used in the
linker configuration file and it has a constant value.
Symbolic location
A location that uses a symbolic name because the exact
address is unknown.

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T
Target
1. An architecture. 2. A piece of hardware. The particular
embedded system you are developing the application for. The
term is usually used to distinguish the system from the host
system.
Task (thread)
A task is an execution thread in a system. Systems that contain
many tasks that execute in parallel are called multitasking
systems. Because a processor only executes one instruction
stream at the time, most systems implement some sort of
task-switch mechanism (often called context switch) so that all
tasks get their share of processing time. The process of
determining which task that should be allowed to run next is
called scheduling. Two common scheduling methods are
Pre-emptive multitasking and Round Robin.
Tentative definition
A variable that can be defined in multiple files, provided that
the definition is identical and that it is an absolute variable.
Terminal I/O
A simulated terminal window in C-SPY.
Timeslice
The (longest) time an RTOS allows a task to run without
running the task-scheduling algorithm. A task might be
allowed to execute during several consecutive timeslices
before being switched out. A task might also not be allowed to
use its entire time slice, for example if, in a preemptive system,
a higher priority task is activated by an interrupt.
Timer
A peripheral that counts independent of the program
execution.
Translation unit
A source file together with all the header files and source files
included via the preprocessor directive #include, except for
the lines skipped by conditional preprocessor directives such
as #if and #ifdef.

Glossary

Trap
A trap is an interrupt initiated by inserting a special instruction
into the instruction stream. Many systems use traps to call
operating system functions. Another name for trap is software
interrupt.
Type qualifiers
In standard C/C++, const or volatile. IAR Systems
compilers usually add target-specific type qualifiers for
memory and other type attributes.

U
UBROF (Universal Binary Relocatable Object
Format)
File format produced by some of the IAR Systems
programming tools, however, not by these tools.

V
Value expressions, in linker configuration file
A constant number that can be built up out of expressions that
has a syntax similar to C expressions.
Veneer
A small piece of code that is inserted as a springboard between
caller and callee when:
• There is a mismatch in mode, for example ARM and Thumb
• The call instruction does not reach its destination.
Virtual address (logical address)
An address that must be translated by the compiler, linker or
the runtime system into a physical memory address before it is
used. The virtual address is the address seen by the application,
which can be different from the address seen by other parts of
the system.

Volatile storage
Data stored in a volatile storage device is not retained when the
power to the device is turned off. To preserve data during a
power-down cycle, you should store it in non-volatile storage.
This should not be confused with the C keyword volatile.
Compare Non-volatile storage.
von Neumann architecture
A computer architecture where both instructions and data are
transferred over a common data channel. Compare Harvard
architecture.

W
Watchpoints
Watchpoints keep track of the values of C variables or
expressions in the C-SPY Watch window as the application is
being executed.

X
XLINK
The IAR XLINK Linker which uses the UBROF output
format.

Z
Zero-initialized sections
Sections that should be initialized to zero at startup. See also
Section.
Zero-overhead loop
A loop in which the loop condition, including branching back
to the beginning of the loop, does not take any time at all. This
is usually implemented as a special hardware feature of the
processor and is not available in all architectures.

Virtual space
An IAR Embedded Workbench Editor feature which allows
you to place the insertion point outside of the area where there
are actual characters.

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Zone
Different processors have widely differing memory
architectures. Zone is the term C-SPY uses for a named
memory area. For example, on processors with separately
addressable code and data memory there would be at least two
zones. A processor with an intricate banked memory scheme
might have several zones.

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Index

Index
A
--aapcs (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 161
ABI, AEABI and IA64 . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
abort
implementation-defined behavior (DLIB) . . . . . . . . . . 358
system termination (DLIB) . . . . . . . . . . . . . . . . . . . . . . 75
Abort_Handler (exception function) . . . . . . . . . . . . . . . . . . 32
absolute location
data, placing at (@) . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
language support for . . . . . . . . . . . . . . . . . . . . . . . . . . 222
#pragma location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
address expression, definition of . . . . . . . . . . . . . . . . . . . . 361
AEABI
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
support for in IAR build tools . . . . . . . . . . . . . . . . . . . 123
--aeabi (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 161
_AEABI_PORTABILITY_LEVEL (preprocessor
symbol) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
_AEABI_PORTABLE (preprocessor symbol) . . . . . . . . . 125
algorithm (STL header file) . . . . . . . . . . . . . . . . . . . . . . . 293
alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
forcing stricter (#pragma data_alignment) . . . . . . . . . . 247
in structures (#pragma pack) . . . . . . . . . . . . . . . . . . . . 254
in structures, causing problems . . . . . . . . . . . . . . . . . . 129
of an object (__ALIGNOF__) . . . . . . . . . . . . . . . . . . . 223
of data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
restrictions for inline assembler . . . . . . . . . . . . . . . . . . . 94
alignment (pragma directive) . . . . . . . . . . . . . . . . . . . . . . 355
__ALIGNOF__ (operator) . . . . . . . . . . . . . . . . . . . . . . . . 223
--align_sp_on_irq (compiler option) . . . . . . . . . . . . . . . . . 161
--all (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
anonymous structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
anonymous symbols, creating . . . . . . . . . . . . . . . . . . . . . . 226
application
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
startup and termination (DLIB) . . . . . . . . . . . . . . . . . . . 72

architecture
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
more information about . . . . . . . . . . . . . . . . . . . . . . . xxix
of ARM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
archive, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
ARM
and Thumb code, overview . . . . . . . . . . . . . . . . . . . . . . 29
CPU mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
memory layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
supported devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
--arm (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . 162
__arm (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 237
__ARMVFP__ (predefined symbol) . . . . . . . . . . . . . . . . . 284
__ARM4M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM4TM__ (predefined symbol) . . . . . . . . . . . . . . . . 284
__ARM5__ (predefined symbol) . . . . . . . . . . . . . . . . . . . 284
__ARM5E__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM6__ (predefined symbol) . . . . . . . . . . . . . . . . . . . 284
__ARM6M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM6SM__ (predefined symbol). . . . . . . . . . . . . . . . . 284
__ARM7M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM7R__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
arrays
designated initializers in . . . . . . . . . . . . . . . . . . . . . . . 227
implementation-defined behavior. . . . . . . . . . . . . . . . . 353
incomplete at end of structs . . . . . . . . . . . . . . . . . . . . . 226
non-lvalue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
of incomplete types . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
single-value initialization . . . . . . . . . . . . . . . . . . . . . . . 230
ar, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
asm, __asm (language extension) . . . . . . . . . . . . . . . . . . . 225
assembler code
calling from C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
calling from C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
inserting inline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
assembler directives
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
for call frame information . . . . . . . . . . . . . . . . . . . . . . 103
using in inline assembler code . . . . . . . . . . . . . . . . . . . . 94

377

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assembler instructions
inserting inline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
assembler labels, making public (--public_equ) . . . . . . . . 184
assembler language interface . . . . . . . . . . . . . . . . . . . . . . . 91
calling convention. See assembler code
assembler language, definition of . . . . . . . . . . . . . . . . . . . 361
assembler list file, generating . . . . . . . . . . . . . . . . . . . . . . 173
assembler options, definition of . . . . . . . . . . . . . . . . . . . . 361
assembler output file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
assembler, inline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
asserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
implementation-defined behavior of, (DLIB) . . . . . . . . 356
including in application . . . . . . . . . . . . . . . . . . . . . . . . 287
assert.h (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
atexit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
reserving space for calls . . . . . . . . . . . . . . . . . . . . . . . . . 53
atexit limit, setting up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
atoll, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
attributes
object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
attributes on sections, definition of . . . . . . . . . . . . . . . . . . 372
auto variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
at function entrance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
programming hints for efficient code . . . . . . . . . . . . . . 139
using in inline assembler code . . . . . . . . . . . . . . . . . . . . 94
auto, packing algorithm for initializers . . . . . . . . . . . . . . . 306

B
backtrace information
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
backtrace information See call frame information
bank switching, definition of. . . . . . . . . . . . . . . . . . . . . . . 361
banked code, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 361
banked data, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 362
banked memory, definition of . . . . . . . . . . . . . . . . . . . . . . 362
bank-switching routines, definition of. . . . . . . . . . . . . . . . 362
Barr, Michael . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii

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baseaddr (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . 355
__BASE_FILE__ (predefined symbol) . . . . . . . . . . . . . . . 284
basic type names, using in preprocessor expressions
(--migration_preprocessor_extensions) . . . . . . . . . . . . . . . 175
basic_template_matching (pragma directive) . . . . . . . . . . 355
batch files
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
error return codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
none for building library from command line . . . . . . . . 71
--BE8 (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
--BE32 (linker option). . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
big-endian (byte order) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
__big_endian (extended keyword) . . . . . . . . . . . . . . . . . . 237
--bin (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
binary streams (DLIB) . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
bit negation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
bitfields
data representation of . . . . . . . . . . . . . . . . . . . . . . . . . . 212
hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
implementation-defined behavior of . . . . . . . . . . . . . . 353
non-standard types in . . . . . . . . . . . . . . . . . . . . . . . . . . 223
bitfields (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 246
bitfield, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Block, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
bold style, in this guide . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
bool (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
adding support for in DLIB . . . . . . . . . . . . . . . . . 291, 294
making available in C code . . . . . . . . . . . . . . . . . . . . . 295
breakpoints, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 362
bubble sort function, defined in stdlib.h . . . . . . . . . . . . . . 296
building_runtime (pragma directive) . . . . . . . . . . . . . . . . . 355
__BUILD_NUMBER__ (predefined symbol) . . . . . . . . . 284
Burrows-Wheeler algorithm, for packing initializers . . . . 306
BusFault_Handler (exception function) . . . . . . . . . . . . . . . 36
bwt, packing algorithm for initializers . . . . . . . . . . . . . . . 306
byte order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
identifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
specifying (--endian) . . . . . . . . . . . . . . . . . . . . . . . . . . 170

Index

C
C and C++ linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
C/C++ calling convention. See calling convention
C header files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
call frame information . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
in assembler list file . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
in assembler list file (-lA) . . . . . . . . . . . . . . . . . . . . . . 174
call stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
callee-save registers, stored on stack . . . . . . . . . . . . . . . . . . 26
calling convention
C++, requiring C linkage . . . . . . . . . . . . . . . . . . . . . . . . 96
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
in compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
calloc (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
See also heap
implementation-defined behavior of (DLIB) . . . . . . . . 358
can_instantiate (pragma directive) . . . . . . . . . . . . . . . . . . 355
cassert (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 293
cast operators
in Extended EC++ . . . . . . . . . . . . . . . . . . . . . . . . 108, 111
missing from Embedded C++ . . . . . . . . . . . . . . . . . . . 108
casting
of pointers and integers . . . . . . . . . . . . . . . . . . . . . . . . 215
pointers to integers, language extension . . . . . . . . . . . . 229
cctype (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 293
cerrno (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 293
cexit (system termination code)
in DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
CFI (assembler directive) . . . . . . . . . . . . . . . . . . . . . . . . . 103
cfiCommon.i (CFI header example file) . . . . . . . . . . . . . . 106
CFI_COMMON_ARM (CFI macro) . . . . . . . . . . . . . . . . 106
CFI_COMMON_Thumb (CFI macro) . . . . . . . . . . . . . . . 106
CFI_NAME_BLOCK (CFI macro). . . . . . . . . . . . . . . . . . 106
cfloat (DLIB header file). . . . . . . . . . . . . . . . . . . . . . . . . . 293
char (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
changing default representation (--char_is_signed) . . . 162
signed and unsigned . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
characters, implementation-defined behavior of . . . . . . . . 350

character-based I/O
in DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
overriding in runtime library . . . . . . . . . . . . . . . . . . . . . 69
--char_is_signed (compiler option) . . . . . . . . . . . . . . . . . . 162
cheap memory access, definition of . . . . . . . . . . . . . . . . . 362
checksum
calculation of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
display format in C-SPY for symbol . . . . . . . . . . . . . . 122
--checksum (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . 332
cinttypes (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . 293
classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
climits (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 294
clocale (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 294
clock (DLIB library function),
implementation-defined behavior of . . . . . . . . . . . . . . . . . 359
clock.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
__close (DLIB library function) . . . . . . . . . . . . . . . . . . . . . 81
clustering (compiler transformation) . . . . . . . . . . . . . . . . . 138
disabling (--no_clustering) . . . . . . . . . . . . . . . . . . . . . . 176
__CLZ (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 262
cmain (system initialization code)
in DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
cmath (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 294
code
ARM and Thumb, overview. . . . . . . . . . . . . . . . . . . . . . 29
banked, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 361
interruption of execution . . . . . . . . . . . . . . . . . . . . . . . . 31
skeleton, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 373
code model, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 363
code motion (compiler transformation) . . . . . . . . . . . . . . . 137
disabling (--no_code_motion) . . . . . . . . . . . . . . . . . . . 176
code pointers, definition of . . . . . . . . . . . . . . . . . . . . . . . . 363
code sections, definition of . . . . . . . . . . . . . . . . . . . . . . . . 363
codeseg (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 355
command line options
part of compiler invocation syntax . . . . . . . . . . . . . . . . 147
part of linker invocation syntax . . . . . . . . . . . . . . . . . . 147
passing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
See also compiler options

379

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See also linker options
typographic convention . . . . . . . . . . . . . . . . . . . . . . xxxiii
command prompt icon, in this guide . . . . . . . . . . . . . . . xxxiii
commands, iarchive.
.comment (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . 320
comments
after preprocessor directives. . . . . . . . . . . . . . . . . . . . . 230
C++ style, using in C code . . . . . . . . . . . . . . . . . . . . . . 225
common block (call frame information) . . . . . . . . . . . . . . 103
common subexpr elimination (compiler transformation) . 137
disabling (--no_cse) . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
compilation date
exact time of (__TIME__) . . . . . . . . . . . . . . . . . . . . . . 285
identifying (__DATE__) . . . . . . . . . . . . . . . . . . . . . . . 284
compiler
environment variables . . . . . . . . . . . . . . . . . . . . . . . . . 148
invocation syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
output from . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
compiler listing, generating (-l). . . . . . . . . . . . . . . . . . . . . 173
compiler object file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
including debug information in (--debug, -r) . . . . . . . . 164
output from compiler . . . . . . . . . . . . . . . . . . . . . . . . . . 150
compiler optimization levels . . . . . . . . . . . . . . . . . . . . . . . 135
compiler options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
passing to compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
reading from file (-f) . . . . . . . . . . . . . . . . . . . . . . . . . . 171
specifying parameters . . . . . . . . . . . . . . . . . . . . . . . . . 157
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
for creating skeleton code . . . . . . . . . . . . . . . . . . . . . . . 95
instruction scheduling . . . . . . . . . . . . . . . . . . . . . . . . . 139
--warnings_affect_exit_code . . . . . . . . . . . . . . . . . . . . 151
compiler platform, identifying . . . . . . . . . . . . . . . . . . . . . 285
compiler transformations . . . . . . . . . . . . . . . . . . . . . . . . . 134
compiler version number . . . . . . . . . . . . . . . . . . . . . . . . . 286
compiling
from the command line . . . . . . . . . . . . . . . . . . . . . . . . . 19
syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

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complex numbers, supported in Embedded C++ . . . . . . . . 108
complex (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
compound literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
computer style, typographic convention . . . . . . . . . . . . xxxiii
--config (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
--config_def (linker option). . . . . . . . . . . . . . . . . . . . . . . . 192
configuration
basic project settings . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
__low_level_init . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
configuration file for linker
See also linker configuration file
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
configuration symbols
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
for file input and output . . . . . . . . . . . . . . . . . . . . . . . . . 80
for locale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
for printf and scanf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
for strtod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
in library configuration files . . . . . . . . . . . . . . . . . . . . . . 71
in linker configuration files . . . . . . . . . . . . . . . . . . . . . 314
specifying for linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
consistency, module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
const
declaring objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
non-top level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
const_cast (cast operator) . . . . . . . . . . . . . . . . . . . . . . . . . 108
contents, of this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxx
conventions, used in this guide . . . . . . . . . . . . . . . . . . . xxxiii
copyright notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
__CORE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 284
core
identifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
selecting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Cortex
special considerations for interrupt functions . . . . . . . . . 36
support for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
cost. See memory access cost
__cplusplus (predefined symbol) . . . . . . . . . . . . . . . . . . . 284
--cpp_init_routine (linker option) . . . . . . . . . . . . . . . . . . . 193

Index

--cpu (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
--cpu (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
CPU modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
specifying on command line . . . . . . . . . . . . . . . . . . . . 162
CPU variant, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 364
CPU, specifying on command line . . . . . . . . . . . . . . . . . . 193
__CPU_MODE__ (predefined symbol) . . . . . . . . . . . . . . 284
--cpu_mode (compiler option) . . . . . . . . . . . . . . . . . . . . . 163
CRC, definition of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
--create (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 325
csetjmp (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 294
csignal (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 294
cspy_support (pragma directive) . . . . . . . . . . . . . . . . . . . . 355
CSTACK (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
See also stack
.cstart (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
cstartup (system startup code)
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
overriding in runtime library . . . . . . . . . . . . . . . . . . . . . 69
cstartup.s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
cstdarg (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 294
cstdbool (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . 294
cstddef (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . 294
cstdio (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 294
cstdlib (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 294
cstring (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . 294
ctime (DLIB header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 294
ctype.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
added C functionality . . . . . . . . . . . . . . . . . . . . . . . . . . 295
cwctype.h (library header file) . . . . . . . . . . . . . . . . . . . . . 294
C++
See also Embedded C++ and Extended Embedded C++
absolute location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
calling convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
features excluded from EC++ . . . . . . . . . . . . . . . . . . . 107
header files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
language extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

special function types. . . . . . . . . . . . . . . . . . . . . . . . . . . 36
static member variables . . . . . . . . . . . . . . . . . . . . . . . . 133
support for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
C++ terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
C++-style comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
C-SPY
interface to system termination . . . . . . . . . . . . . . . . . . . 76
STL container support . . . . . . . . . . . . . . . . . . . . . . . . . 111
C-SPY options, definition of . . . . . . . . . . . . . . . . . . . . . . . 363
C-style preprocessor, definition of . . . . . . . . . . . . . . . . . . 363
C_INCLUDE (environment variable) . . . . . . . . . . . . 148–149
C99 standard, added functionality from . . . . . . . . . . . . . . 294

D
-D (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
-d (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
data
alignment of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
different ways of storing . . . . . . . . . . . . . . . . . . . . . . . . 25
located, declaring extern . . . . . . . . . . . . . . . . . . . . . . . 132
placing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131, 186, 319
at absolute location . . . . . . . . . . . . . . . . . . . . . . . . . 132
representation of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
data block (call frame information) . . . . . . . . . . . . . . . . . . 104
data model, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 363
data pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
data representation, definition of . . . . . . . . . . . . . . . . . . . . 363
data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
floating point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
in C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
integers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
data_alignment (pragma directive) . . . . . . . . . . . . . . . . . . 247
__DATE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 284
date (library function), configuring support for . . . . . . . . . . 85
DC32 (assembler directive). . . . . . . . . . . . . . . . . . . . . . . . . 94
--debug (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 164

381

DARM-4

debug information, including in object file . . . . . . . . 164, 185
.debug (ELF section). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
debugger, low-level interface . . . . . . . . . . . . . . . . . . . . . . . 86
DebugMon_Handler (exception function). . . . . . . . . . . . . . 36
declarations
empty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
in for loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Kernighan & Ritchie . . . . . . . . . . . . . . . . . . . . . . . . . . 141
of functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
declarations and statements, mixing . . . . . . . . . . . . . . . . . 225
declaration, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 363
declarators, implementation-defined behavior . . . . . . . . . 354
define block (linker directive) . . . . . . . . . . . . . . . . . . . . . . 303
define overlay (linker directive) . . . . . . . . . . . . . . . . . . . . 304
define symbol (linker directive) . . . . . . . . . . . . . . . . . . . . 314
--define_symbol (linker option) . . . . . . . . . . . . . . . . . . . . 193
define_type_info (pragma directive) . . . . . . . . . . . . . . . . . 355
definition, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
--delete (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 326
delete (keyword) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
demangling, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 364
denormalized numbers. See subnormal numbers
--dependencies (compiler option) . . . . . . . . . . . . . . . . . . . 165
deque (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 293
derivative, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
destructors and interrupts, using . . . . . . . . . . . . . . . . . . . . 112
device description files
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
preconfigured . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
device driver, definition of . . . . . . . . . . . . . . . . . . . . . . . . 364
diagnostic messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
classifying as compilation errors . . . . . . . . . . . . . . . . . 166
classifying as compilation remarks . . . . . . . . . . . . . . . 166
classifying as compiler warnings . . . . . . . . . . . . . . . . . 167
classifying as errors . . . . . . . . . . . . . . . . . . . . . . . 177, 200
classifying as linker warnings . . . . . . . . . . . . . . . . . . . 195
classifying as linking errors . . . . . . . . . . . . . . . . . . . . . 194
classifying as linking remarks . . . . . . . . . . . . . . . . . . . 194
disabling compiler warnings . . . . . . . . . . . . . . . . . . . . 181

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disabling linker warnings . . . . . . . . . . . . . . . . . . . . . . . 202
disabling wrapping of in compiler . . . . . . . . . . . . . . . . 181
disabling wrapping of in linker . . . . . . . . . . . . . . . . . . 202
enabling compiler remarks . . . . . . . . . . . . . . . . . . . . . . 185
enabling linker remarks . . . . . . . . . . . . . . . . . . . . . . . . 205
listing all used by compiler . . . . . . . . . . . . . . . . . . . . . 167
listing all used by linker . . . . . . . . . . . . . . . . . . . . . . . . 196
suppressing in compiler . . . . . . . . . . . . . . . . . . . . . . . . 167
suppressing in linker . . . . . . . . . . . . . . . . . . . . . . . . . . 195
diagnostics
iarchive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
iobjmanip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
isymexport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
--diagnostics_tables (compiler option) . . . . . . . . . . . . . . . 167
--diagnostics_tables (linker option) . . . . . . . . . . . . . . . . . . 196
diag_default (pragma directive) . . . . . . . . . . . . . . . . . . . . 248
--diag_error (compiler option) . . . . . . . . . . . . . . . . . . . . . 166
--diag_error (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 194
--no_fragments (compiler option) . . . . . . . . . . . . . . . . . . . 177
--no_fragments (linker option) . . . . . . . . . . . . . . . . . . . . . 200
diag_error (pragma directive) . . . . . . . . . . . . . . . . . . . . . . 248
--diag_remark (compiler option) . . . . . . . . . . . . . . . . . . . . 166
--diag_remark (linker option) . . . . . . . . . . . . . . . . . . . . . . 194
diag_remark (pragma directive) . . . . . . . . . . . . . . . . . . . . 248
--diag_suppress (compiler option) . . . . . . . . . . . . . . . . . . 167
--diag_suppress (linker option) . . . . . . . . . . . . . . . . . . . . . 195
diag_suppress (pragma directive) . . . . . . . . . . . . . . . . . . . 249
--diag_warning (compiler option) . . . . . . . . . . . . . . . . . . . 167
--diag_warning (linker option) . . . . . . . . . . . . . . . . . . . . . 195
diag_warning (pragma directive) . . . . . . . . . . . . . . . . . . . 249
DIFUNCT (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
digital signal processor, definition of . . . . . . . . . . . . . . . . 364
directives
pragma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 245
to the linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
directory, specifying as parameter . . . . . . . . . . . . . . . . . . . 156
__disable_fiq (intrinsic function) . . . . . . . . . . . . . . . . . . . 262
__disable_interrupt (intrinsic function) . . . . . . . . . . . . . . . 263
__disable_irq (intrinsic function) . . . . . . . . . . . . . . . . . . . 263

Index

Disassembly window, definition of . . . . . . . . . . . . . . . . . . 364
--discard_unused_publics (compiler option) . . . . . . . . . . . 168
disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
DLIB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 290
building customized library . . . . . . . . . . . . . . . . . . . . . . 63
configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
configuring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62, 168
reference information. See the online help system . . . . 289
runtime environment . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
--dlib_config (compiler option). . . . . . . . . . . . . . . . . . . . . 168
DLib_Config_Full.h (library configuration file) . . . . . . . . . 71
DLib_Config_Normal.h (library configuration file) . . . . . . 71
DLib_Defaults.h (library configuration file) . . . . . . . . . . . . 71
__DLIB_FILE_DESCRIPTOR (configuration symbol) . . . 80
__DMB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 263
do not initialize (linker directive) . . . . . . . . . . . . . . . . . . . 308
document conventions. . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
documentation, library . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
domain errors, implementation-defined behavior . . . . . . . 356
double (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
double_t, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 295
do_not_instantiate (pragma directive) . . . . . . . . . . . . . . . . 355
__DSB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 263
DSP. See digital signal processor
DWARF, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
dynamic initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
dynamic memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
dynamic memory allocation, definition of . . . . . . . . . . . . 364
dynamic object, definition of . . . . . . . . . . . . . . . . . . . . . . 364

E
-e (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
early_initialization (pragma directive) . . . . . . . . . . . . . . . 355
--ec++ (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . 169
EC++ header files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
--edit (isymexport option) . . . . . . . . . . . . . . . . . . . . . . . . . 344
edition, of this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

--eec++ (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 169
EEPROM, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
ELF, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Embedded C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
differences from C++ . . . . . . . . . . . . . . . . . . . . . . . . . . 107
enabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
function linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
language extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Embedded C++ Technical Committee . . . . . . . . . . . . . xxxiii
embedded systems, IAR special support for . . . . . . . . . . . . . 6
embedded system, definition of . . . . . . . . . . . . . . . . . . . . 365
__embedded_cplusplus (predefined symbol) . . . . . . . . . . 284
empty region (in linker configuration file) . . . . . . . . . . . . 302
emulator (C-SPY driver), definition of . . . . . . . . . . . . . . . 365
__enable_fiq (intrinsic function) . . . . . . . . . . . . . . . . . . . . 264
--enable_hardware_workaround (compiler option) . . . . . . 170
__enable_interrupt (intrinsic function) . . . . . . . . . . . . . . . 264
__enable_irq (intrinsic function) . . . . . . . . . . . . . . . . . . . . 264
--enable_multibytes (compiler option) . . . . . . . . . . . . . . . 170
--endian (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . 170
Enea OSE load module format, definition of . . . . . . . . . . 365
--entry (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
entry label, program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
enumerations, implementation-defined behavior. . . . . . . . 353
enumeration, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 365
enums
data representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
forward declarations of . . . . . . . . . . . . . . . . . . . . . . . . 229
--enum_is_int (compiler option) . . . . . . . . . . . . . . . . . . . . 171
environment
implementation-defined behavior. . . . . . . . . . . . . . . . . 350
runtime (DLIB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
environment variables
C_INCLUDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148–149
ILINKARM_CMD_LINE . . . . . . . . . . . . . . . . . . . . . . 149
QCCARM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
EPROM, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

383

DARM-4

EQU (assembler directive) . . . . . . . . . . . . . . . . . . . . . . . . 184
ERANGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
errno.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
error messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
classifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177, 200
classifying for compiler . . . . . . . . . . . . . . . . . . . . . . . . 166
classifying for linker . . . . . . . . . . . . . . . . . . . . . . . . . . 194
range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
error return codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
--error_limit (compiler option) . . . . . . . . . . . . . . . . . . . . . 171
--error_limit (linker option) . . . . . . . . . . . . . . . . . . . . . . . 196
exception handling, missing from Embedded C++ . . . . . . 107
exception stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
exception (library header file) . . . . . . . . . . . . . . . . . . . . . . 292
exceptions, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 365
executable image, definition of . . . . . . . . . . . . . . . . . . . . . 365
_Exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
implementation-defined behavior. . . . . . . . . . . . . . . . . 358
_exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
__exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
expensive memory access, definition of . . . . . . . . . . . . . . 365
export keyword, missing from Extended EC++ . . . . . . . . 110
export (linker directive). . . . . . . . . . . . . . . . . . . . . . . . . . . 315
--export_builtin_config (linker option) . . . . . . . . . . . . . . . 197
expressions (in linker configuration file) . . . . . . . . . . . . . . 315
extended command line file
for compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
for linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
passing options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Extended Embedded C++ . . . . . . . . . . . . . . . . . . . . . . . . . 108
enabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
standard template library (STL) . . . . . . . . . . . . . . . . . . 293
extended keywords . . . . . . . . . . . . . . . . . . . . . . . . . . 233, 323
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
enabling (-e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

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DARM-4

syntax
object attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
type attributes on data objects . . . . . . . . . . . . . . . . . 234
type attributes on data pointers . . . . . . . . . . . . . . . . 234
type attributes on functions . . . . . . . . . . . . . . . . . . . 234
extended-selectors (in linker configuration file) . . . . . . . . 313
extern "C" linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
--extract (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . 326

F
-f (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
-f (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
-f (iobjmanip option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
-f (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
fast interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
fatal error messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
fgetpos (library function), implementation-defined
behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
__FILE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . . 284
file dependencies, tracking . . . . . . . . . . . . . . . . . . . . . . . . 165
file paths, specifying for #include files . . . . . . . . . . . . . . . 173
filename
extension for device description files . . . . . . . . . . . . . . . . 6
extension for header files . . . . . . . . . . . . . . . . . . . . . . . . . 6
of object executable image . . . . . . . . . . . . . . . . . . . . . . 203
search procedure for. . . . . . . . . . . . . . . . . . . . . . . . . . . 149
specifying as parameter . . . . . . . . . . . . . . . . . . . . . . . . 156
--fill (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
filling, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
__fiq (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . . 237
FIQ_Handler (exception function) . . . . . . . . . . . . . . . . . . . 32
float (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
floating-point constants
hexadecimal notation . . . . . . . . . . . . . . . . . . . . . . . . . . 227
hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
floating-point expressions,
using in preprocessor extensions . . . . . . . . . . . . . . . . . . . . 175

Index

floating-point format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
implementation-defined behavior. . . . . . . . . . . . . . . . . 352
special cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
32-bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
64-bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
floating-point unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
float.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
float_t, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
fmod (library function),
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 357
for loops, declarations in . . . . . . . . . . . . . . . . . . . . . . . . . . 225
--force_output (linker option) . . . . . . . . . . . . . . . . . . . . . . 197
format specifiers, definition of . . . . . . . . . . . . . . . . . . . . . 366
formats
floating-point values . . . . . . . . . . . . . . . . . . . . . . . . . . 213
standard IEEE (floating point) . . . . . . . . . . . . . . . . . . . 213
fpclassify, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . 295
--fpu (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
FP_INFINITE, C99 extension . . . . . . . . . . . . . . . . . . . . . 295
FP_NAN, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 295
FP_NORMAL, C99 extension . . . . . . . . . . . . . . . . . . . . . 295
FP_SUBNORMAL, C99 extension . . . . . . . . . . . . . . . . . 295
FP_ZERO, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . 295
fragmentation, of heap memory . . . . . . . . . . . . . . . . . . . . . 27
free (library function). See also heap . . . . . . . . . . . . . . . . . 27
fstream (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
fstream.h (library header file) . . . . . . . . . . . . . . . . . . . . . . 292
ftell (library function), implementation-defined behavior . 358
Full DLIB (library configuration) . . . . . . . . . . . . . . . . . . . . 63
__func__ (predefined symbol) . . . . . . . . . . . . . . . . . 231, 285
__FUNCTION__ (predefined symbol) . . . . . . . . . . . 231, 285
function calls
calling convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
stack image after . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
function declarations, Kernighan & Ritchie . . . . . . . . . . . 141
function execution, in RAM . . . . . . . . . . . . . . . . . . . . . . . . 30
function inlining (compiler transformation) . . . . . . . . . . . 137
disabling (--no_inline) . . . . . . . . . . . . . . . . . . . . . . . . . 178
function pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

function prototypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
enforcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
function (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 355
functional (STL header file) . . . . . . . . . . . . . . . . . . . . . . . 293
functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
C++ and special function types . . . . . . . . . . . . . . . . . . . 36
declaring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98, 140
inlining. . . . . . . . . . . . . . . . . . . . . . . . . 137, 139, 225, 250
interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
intrinsic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91, 140
intrinsic, definition of. . . . . . . . . . . . . . . . . . . . . . . . . . 367
parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
placing in memory . . . . . . . . . . . . . . . . . . . . 131, 133, 186
recursive
avoiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
storing data on stack . . . . . . . . . . . . . . . . . . . . . . 26–27
reentrancy (DLIB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
related extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
return values from . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
special function types. . . . . . . . . . . . . . . . . . . . . . . . . . . 30

G
general options, definition of . . . . . . . . . . . . . . . . . . . . . . 366
generic pointers, definition of . . . . . . . . . . . . . . . . . . . . . . 366
getenv (library function), configuring support for . . . . . . . . 83
getzone (library function), configuring support for . . . . . . . 85
getzone.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
__get_BASEPRI (intrinsic function) . . . . . . . . . . . . . . . . . 264
__get_CONTROL (intrinsic function) . . . . . . . . . . . . . . . 264
__get_CPSR (intrinsic function) . . . . . . . . . . . . . . . . . . . . 265
__get_FAULTMASK (intrinsic function) . . . . . . . . . . . . . 265
__get_interrupt_state (intrinsic function) . . . . . . . . . . . . . 265
__get_PRIMASK (intrinsic function) . . . . . . . . . . . . . . . . 265
glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
GRP_COMDAT, group type . . . . . . . . . . . . . . . . . . . . . . . 342
guidelines, reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix

385

DARM-4

H

I

Harbison, Samuel P. . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
HardFault_Handler (exception function). . . . . . . . . . . . . . . 36
hardware support in compiler . . . . . . . . . . . . . . . . . . . . . . . 62
Harvard architecture, definition of . . . . . . . . . . . . . . . . . . 366
hash_map (STL header file) . . . . . . . . . . . . . . . . . . . . . . . 293
hash_set (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . 293
hdrstop (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 355
header files
C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
EC++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
special function registers . . . . . . . . . . . . . . . . . . . . . . . 142
STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
DLib_Config_Full.h. . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
DLib_Config_Normal.h . . . . . . . . . . . . . . . . . . . . . . . . . 71
DLib_Defaults.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
intrinsics.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
stdbool.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211, 291
stddef.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
--header_context (compiler option) . . . . . . . . . . . . . . . . . . 172
heap
dynamic memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
storing data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
heap memory, definition of . . . . . . . . . . . . . . . . . . . . . . . . 366
heap size
and standard I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
changing default. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
HEAP (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117, 321
hide (isymexport directive) . . . . . . . . . . . . . . . . . . . . . . . . 346
hints
for good code generation . . . . . . . . . . . . . . . . . . . . . . . 139
using efficient data types . . . . . . . . . . . . . . . . . . . . . . . 127
host, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
HUGE_VALF, C99 extension . . . . . . . . . . . . . . . . . . . . . . 295
HUGE_VALL, C99 extension. . . . . . . . . . . . . . . . . . . . . . 295

-I (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
IAR Command Line Build Utility. . . . . . . . . . . . . . . . . . . . 71
IAR Systems Technical Support . . . . . . . . . . . . . . . . . . . . 154
iarbuild.exe (utility) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
iarchive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
commands summary . . . . . . . . . . . . . . . . . . . . . . . . . . 324
options summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
.iar.debug (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.iar.dynexit (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
__IAR_SYSTEMS_ICC__ (predefined symbol) . . . . . . . 285
IA64 ABI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
__ICCARM__ (predefined symbol) . . . . . . . . . . . . . . . . . 285
icons, in this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
IDE
building a library from . . . . . . . . . . . . . . . . . . . . . . . . . . 71
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
overview of build tools. . . . . . . . . . . . . . . . . . . . . . . . . . . 3
identifiers, implementation-defined behavior . . . . . . . . . . 350
IEEE format, floating-point values . . . . . . . . . . . . . . . . . . 213
ielfdump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
options summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
ielftool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
options summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
if (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
--ihex (ielftool option). . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
ILINK
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
See linker
ILINK options. See linker options
ILINKARM_CMD_LINE (environment variable) . . . . . . 149
--image_input (linker option) . . . . . . . . . . . . . . . . . . . . . . 198
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 349
important_typedef (pragma directive) . . . . . . . . . . . . . . . . 355
include files
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
including before source files . . . . . . . . . . . . . . . . . . . . 183

IAR C/C++ Development Guide

386

Compiling and linking for ARM

DARM-4

Index

specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
include (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . . 318
include_alias (pragma directive) . . . . . . . . . . . . . . . . . . . . 249
infinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
INFINITY, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . 295
inheritance, in Embedded C++ . . . . . . . . . . . . . . . . . . . . . 107
initialization
changing default. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
dynamic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
packing algorithm for . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
single-value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
initialization in ILINK config file, definition of . . . . . . . . 367
initialize (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . 305
initialized sections, definition of . . . . . . . . . . . . . . . . . . . . 367
initializers, static . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
inline assembler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93, 225
avoiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
See also assembler language interface
inline functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
in compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
inline (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . . 250
inlining, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
instantiate (pragma directive) . . . . . . . . . . . . . . . . . . . . . . 355
instruction mnemonics, definition of. . . . . . . . . . . . . . . . . 367
instruction scheduling (compiler option). . . . . . . . . . . . . . 139
integer characteristics, adding . . . . . . . . . . . . . . . . . . . . . . 295
integers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
implementation-defined behavior. . . . . . . . . . . . . . . . . 352
intptr_t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
ptrdiff_t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
size_t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
uintptr_t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
integral promotion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Integrated Development Environment (IDE)
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
Intel hex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Intel IA64 ABI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

internal error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
interrupt functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
fast interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
in ARM Cortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
nested interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
software interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
interrupt state, restoring . . . . . . . . . . . . . . . . . . . . . . . . . . 273
interrupt vector
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
interrupt vector table
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
.intvec section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
interrupts
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
nested, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
processor state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
using with EC++ destructors . . . . . . . . . . . . . . . . . . . . 112
--interwork (compiler option) . . . . . . . . . . . . . . . . . . . . . . 173
__interwork (extended keyword) . . . . . . . . . . . . . . . . . . . 238
interworking code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
intptr_t (integer type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
__intrinsic (extended keyword) . . . . . . . . . . . . . . . . . . . . . 238
intrinsic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
intrinsics.h (header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 259
intrinsic, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
introduction
linker configuration file . . . . . . . . . . . . . . . . . . . . . . . . 297
linking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
inttypes.h (library header file) . . . . . . . . . . . . . . . . . . . . . . 291
inttypes.h, added C functionality . . . . . . . . . . . . . . . . . . . 295
.intvec (section). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
invocation syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
iobjmanip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
options summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

387

DARM-4

iomanip (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
iomanip.h (library header file) . . . . . . . . . . . . . . . . . . . . . 292
ios (library header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
iosfwd (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 292
iostream (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
iostream.h (library header file) . . . . . . . . . . . . . . . . . . . . . 292
__irq (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . . 238
IRQ_Handler (exception function) . . . . . . . . . . . . . . . . . . . 32
IRQ_STACK (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
__ISB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . . 266
isblank, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
isfinite, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
isgreater, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 295
isinf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
islessequal, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . 295
islessgreater, C99 extension . . . . . . . . . . . . . . . . . . . . . . . 295
isless, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
isnan, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
isnormal, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 295
ISO/ANSI C
compiler extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
C++ features excluded from EC++ . . . . . . . . . . . . . . . 107
specifying strict usage . . . . . . . . . . . . . . . . . . . . . . . . . 187
iso646.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
istream (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 292
isunordered, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . 295
iswblank, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 296
isymexport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
options summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
italic style, in this guide . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
iterator (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . 293
I/O debugging, support for . . . . . . . . . . . . . . . . . . . . . . . . . 86
I/O module, overriding in runtime library . . . . . . . . . . . . . . 69

K
--keep (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
keep (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
keep_definition (pragma directive) . . . . . . . . . . . . . . . . . . 356

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DARM-4

Kernighan & Ritchie function declarations . . . . . . . . . . . . 141
disallowing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Kernighan, Brian W. . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
key bindings, definition of . . . . . . . . . . . . . . . . . . . . . . . . 367
keywords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
extended, overview of . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

L
-l (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
for creating skeleton code . . . . . . . . . . . . . . . . . . . . . . . 95
labels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
assembler, making public . . . . . . . . . . . . . . . . . . . . . . . 184
__program_start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Labrosse, Jean J. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
Lajoie, Josée . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
language extensions
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Embedded C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
enabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
enabling (-e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
language overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
language (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . 251
__LDC (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 266
__LDCL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 266
__LDCL_noidx (intrinsic function) . . . . . . . . . . . . . . . . . 266
__LDC_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . . 266
__LDC2 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 266
__LDC2L (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 266
__LDC2L_noidx (intrinsic function) . . . . . . . . . . . . . . . . 266
__LDC2_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 266
__LDREX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 267
--legacy (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 174
Lempel-Ziv-Welch algorithm, for packing initializers . . . 306
libraries
building DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
runtime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Index

standard template library . . . . . . . . . . . . . . . . . . . . . . . 293
library configuration file
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
library configuration files
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
DLib_Defaults.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
for Normal and Full . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
modifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
library documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
library features, missing from Embedded C++ . . . . . . . . . 108
library functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
reference information . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
summary, DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
library header files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
library modules
introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
overriding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
library object files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
library options, setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
library project template . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
using . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
library, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
lightbulb icon, in this guide . . . . . . . . . . . . . . . . . . . . . . xxxiv
limits.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
__LINE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
linkage, C and C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
linker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
output from . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
linker configuration file
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
for placing code and data . . . . . . . . . . . . . . . . . . . . . . . . 42
in depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
selecting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
linker object executable image
specifying filename of (-o) . . . . . . . . . . . . . . . . . . . . . . 203
linker options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
reading from file (-f) . . . . . . . . . . . . . . . . . . . . . . . . . . 197
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

typographic convention . . . . . . . . . . . . . . . . . . . . . . xxxiii
linking
from the command line . . . . . . . . . . . . . . . . . . . . . . . . . 19
process for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
process for, an overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
Lippman, Stanley B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
list (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
listing, generating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
literals, compound. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
literature, recommended . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
little-endian (byte order) . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
__LITTLE_ENDIAN__ (predefined symbol) . . . . . . . . . . 285
__little_endian (extended keyword) . . . . . . . . . . . . . . . . . 238
llabs, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
lldiv, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
local variables, See auto variables
locale support
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
adding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
changing at runtime. . . . . . . . . . . . . . . . . . . . . . . . . . 83
removing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
locale.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
located data, declaring extern . . . . . . . . . . . . . . . . . . . . . . 132
location counter, definition of . . . . . . . . . . . . . . . . . . . . . . 371
location (pragma directive) . . . . . . . . . . . . . . . . . . . . 132, 251
--log (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
logical address, definition of . . . . . . . . . . . . . . . . . . . . . . . 375
--log_file (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 199
long double (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
long float (data type), synonym for double . . . . . . . . . . . . 229
loop overhead, reducing . . . . . . . . . . . . . . . . . . . . . . . . . . 180
loop unrolling (compiler transformation) . . . . . . . . . . . . . 137
disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
loop-invariant expressions. . . . . . . . . . . . . . . . . . . . . . . . . 137
low-level processor operations . . . . . . . . . . . . . . . . . 221, 259
accessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
__low_level_init . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
low_level_init.c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

389

DARM-4

low_level_init.s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
__lseek (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
lzw, packing algorithm for initializers . . . . . . . . . . . . . . . . 306
L-value, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

M
-map (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
macros
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
embedded in #pragma optimize . . . . . . . . . . . . . . . . . . 253
ERANGE (in errno.h) . . . . . . . . . . . . . . . . . . . . . . . . . 356
inclusion of assert . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
NULL, implementation-defined behavior . . . . . . . . . . 356
substituted in #pragma directives . . . . . . . . . . . . . . . . . 221
variadic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
MAC, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
mailbox (RTOS), definition of . . . . . . . . . . . . . . . . . . . . . 368
main (function), definition . . . . . . . . . . . . . . . . . . . . . . . . 350
malloc (library function)
See also heap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
implementation-defined behavior. . . . . . . . . . . . . . . . . 358
--mangled_names_in_messages (linker option) . . . . . . . . 199
mangling, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
Mann, Bernhard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
map file, producing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
map (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
math.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
math.h, added C functionality . . . . . . . . . . . . . . . . . . . . . . 295
MATH_ERREXCEPT, C99 extension . . . . . . . . . . . . . . . 295
math_errhandling, C99 extension . . . . . . . . . . . . . . . . . . . 295
MATH_ERRNO, C99 extension . . . . . . . . . . . . . . . . . . . . 295
__MCR (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 267
member functions, pointers to . . . . . . . . . . . . . . . . . . . . . . 111
MemManage_Handler (exception function) . . . . . . . . . . . . 36
memory
allocating in C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
dynamic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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heap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
non-initialized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
RAM, saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
releasing in C++. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
used by global or static variables . . . . . . . . . . . . . . . . . . 25
memory access cost, definition of . . . . . . . . . . . . . . . . . . . 368
memory area, definition of . . . . . . . . . . . . . . . . . . . . . . . . 368
memory bank, definition of . . . . . . . . . . . . . . . . . . . . . . . . 369
memory layout, ARM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
memory management, type-safe . . . . . . . . . . . . . . . . . . . . 107
memory map
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
output from linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
memory model, definition of. . . . . . . . . . . . . . . . . . . . . . . 369
memory (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 356
memory (STL header file). . . . . . . . . . . . . . . . . . . . . . . . . 293
message (pragma directive). . . . . . . . . . . . . . . . . . . . . . . . 252
messages
disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187, 206
forcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
--mfc (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . 175
microcontroller, definition of . . . . . . . . . . . . . . . . . . . . . . 369
microprocessor, definition of . . . . . . . . . . . . . . . . . . . . . . 369
--migration_preprocessor_extensions (compiler option) . . 175
--misrac_verbose (compiler option) . . . . . . . . . . . . . . . . . 159
--misrac_verbose (linker option) . . . . . . . . . . . . . . . . . . . . 190
--misrac1998 (compiler option) . . . . . . . . . . . . . . . . . . . . 159
--misrac1998 (linker option) . . . . . . . . . . . . . . . . . . . . . . . 190
--misrac2004 (compiler option) . . . . . . . . . . . . . . . . . . . . 159
--misrac2004 (linker option) . . . . . . . . . . . . . . . . . . . . . . . 190
module consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
rtmodel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
modules
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
module_name (pragma directive) . . . . . . . . . . . . . . . . . . . 356
Motorola S-records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Index

__MRC (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 268
multibyte character support . . . . . . . . . . . . . . . . . . . . . . . . 170
multiple inheritance
in Extended EC++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
missing from Embedded C++ . . . . . . . . . . . . . . . . . . . 107
missing from STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Multiply and accumulate, definition of . . . . . . . . . . . . . . . 368
multitasking, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 370
multi-file compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
mutable attribute, in Extended EC++ . . . . . . . . . . . . 108, 111

N
names block (call frame information) . . . . . . . . . . . . . . . . 103
namespace support
in Extended EC++ . . . . . . . . . . . . . . . . . . . . . . . . 108, 111
missing from Embedded C++ . . . . . . . . . . . . . . . . . . . 108
naming conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
NAN, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
NDEBUG (preprocessor symbol) . . . . . . . . . . . . . . . . . . . 287
__nested (extended keyword) . . . . . . . . . . . . . . . . . . . . . . 239
nested interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
new (keyword) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
new (library header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 292
new.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . . 292
NMI_Handler (exception function) . . . . . . . . . . . . . . . . . . . 36
non-banked memory, definition of . . . . . . . . . . . . . . . . . . 369
non-initialized memory, definition of . . . . . . . . . . . . . . . . 369
non-initialized variables, hints for . . . . . . . . . . . . . . . . . . . 143
non-scalar parameters, avoiding . . . . . . . . . . . . . . . . . . . . 140
non-volatile storage, definition of . . . . . . . . . . . . . . . . . . . 369
NOP (assembler instruction) . . . . . . . . . . . . . . . . . . . . . . . 268
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
__noreturn (extended keyword) . . . . . . . . . . . . . . . . . . . . 239
Normal DLIB (library configuration) . . . . . . . . . . . . . . . . . 63
Not a number (NaN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
no-init sections, definition of . . . . . . . . . . . . . . . . . . . . . . 369

--no_clustering (compiler option) . . . . . . . . . . . . . . . . . . . 176
--no_code_motion (compiler option) . . . . . . . . . . . . . . . . 176
--no_const_align (compiler option) . . . . . . . . . . . . . . . . . . 176
--no_cse (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . 177
--no_guard_calls (compiler option) . . . . . . . . . . . . . . . . . . 177
__no_init (extended keyword) . . . . . . . . . . . . . . . . . 143, 239
--no_inline (compiler option) . . . . . . . . . . . . . . . . . . . . . . 178
--no_library_search (linker option) . . . . . . . . . . . . . . . . . . 201
--no_locals (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 201
__no_operation (intrinsic function) . . . . . . . . . . . . . . . . . . 268
--no_path_in_file_macros (compiler option) . . . . . . . . . . . 178
no_pch (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 356
--no_remove (linker option) . . . . . . . . . . . . . . . . . . . . . . . 201
--no_scheduling (compiler option) . . . . . . . . . . . . . . . . . . 178
--no_typedefs_in_diagnostics (compiler option) . . . . . . . . 179
--no_unaligned_access (compiler option) . . . . . . . . . . . . . 180
--no_unroll (compiler option) . . . . . . . . . . . . . . . . . . . . . . 180
--no_veneer (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 202
--no_warnings (compiler option) . . . . . . . . . . . . . . . . . . . 181
--no_warnings (linker option) . . . . . . . . . . . . . . . . . . . . . . 202
--no_wrap_diagnostics (compiler option) . . . . . . . . . . . . . 181
--no_wrap_diagnostics (linker option) . . . . . . . . . . . . . . . 202
NULL (macro), implementation-defined behavior . . . . . . 356
numbers (in linker configuration file) . . . . . . . . . . . . . . . . 316
numeric (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . 293

O
-O (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
-o (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
-o (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
-o (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
-o (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
objcopy, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
objdump, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
object attributes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
object file (absolute), definition of . . . . . . . . . . . . . . . . . . 369
object file (relocatable), definition of . . . . . . . . . . . . . . . . 370

391

DARM-4

object filename
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
specifying in compiler . . . . . . . . . . . . . . . . . . . . . . . . . 182
specifying in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
object module, ose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
object, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 369–370
object_attribute (pragma directive) . . . . . . . . . . . . . . 143, 252
once (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . . 356
--only_stdout (compiler option) . . . . . . . . . . . . . . . . . . . . 182
--only_stdout (linker option) . . . . . . . . . . . . . . . . . . . . . . . 203
__open (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
operator precedence, definition of . . . . . . . . . . . . . . . . . . . 370
operators
See also @ (operator)
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
optimization
clustering, disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
code motion, disabling . . . . . . . . . . . . . . . . . . . . . . . . . 176
common sub-expression elimination, disabling . . . . . . 177
configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
function inlining, disabling (--no_inline) . . . . . . . . . . . 178
hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
loop unrolling, disabling . . . . . . . . . . . . . . . . . . . . . . . 180
scheduling, disabling . . . . . . . . . . . . . . . . . . . . . . . . . . 178
specifying (-O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
type-based alias analysis, disabling (--tbaa) . . . . . . . . . 179
using inline assembler code . . . . . . . . . . . . . . . . . . . . . . 94
using pragma directive . . . . . . . . . . . . . . . . . . . . . . . . . 252
optimization levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
optimize (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . 252
option parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
options, compiler. See compiler options
options, iarchive. See iarchive options
options, ielfdump. See ielfdump options
options, ielftool. See ielftool options
options, iobjmanip. See iobjmanip options
options, isymexport. See isymexport options

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options, linker. See linker options
Oram, Andy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
--ose_load_module (linker option) . . . . . . . . . . . . . . . . . . 203
ostream (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
output
from preprocessor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
specifying for linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
--output (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 183
--output (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
overhead, reducing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
overlay, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370

P
pack (pragma directive) . . . . . . . . . . . . . . . . . . . . . . 217, 253
packbits, packing algorithm for initializers . . . . . . . . . . . . 306
__packed (extended keyword). . . . . . . . . . . . . . . . . . . . . . 240
packed structure types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
packing, algorithms for initializers . . . . . . . . . . . . . . . . . . 306
parameters
function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
hidden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
non-scalar, avoiding . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99–100
rules for specifying a file or directory . . . . . . . . . . . . . 156
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99, 101
typographic convention . . . . . . . . . . . . . . . . . . . . . . xxxiii
part number, of this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
PendSV_Handler (exception function) . . . . . . . . . . . . . . . . 36
peripheral units, definition of . . . . . . . . . . . . . . . . . . . . . . 370
permanent registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
perror (library function),
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 358
pipeline, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
--pi_veneer (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 204
place at (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . 309
place in (linker directive) . . . . . . . . . . . . . . . . . . . . . . . . . 310

Index

placement
code and data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
in named sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
of code and data, introduction to . . . . . . . . . . . . . . . . . . 42
--place_holder (linker option) . . . . . . . . . . . . . . . . . . . . . . 204
pointer types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
pointers
casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
implementation-defined behavior. . . . . . . . . . . . . . . . . 353
polymorphism, in Embedded C++ . . . . . . . . . . . . . . . . . . 107
porting, code containing pragma directives . . . . . . . . . . . . 246
_Pragma (predefined symbol) . . . . . . . . . . . . . . . . . . . . . . 287
#pragma directive, definition of . . . . . . . . . . . . . . . . . . . . 370
pragma directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
for absolute located data . . . . . . . . . . . . . . . . . . . . . . . 132
list of all recognized . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
pack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217, 253
precedence, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 370
predefined symbols
overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
--predef_macro (compiler option) . . . . . . . . . . . . . . . . . . . 183
preemptive multitasking, definition of . . . . . . . . . . . . . . . 370
Prefetch_Handler (exception function) . . . . . . . . . . . . . . . . 32
--preinclude (compiler option) . . . . . . . . . . . . . . . . . . . . . 183
--preprocess (compiler option) . . . . . . . . . . . . . . . . . . . . . 184
preprocessor
definition of. See C-style preprocessor
output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
overview of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
preprocessor directives
comments at the end of . . . . . . . . . . . . . . . . . . . . . . . . 230
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370

implementation-defined behavior. . . . . . . . . . . . . . . . . 354
#pragma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
preprocessor extensions
compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
#warning message . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
__VA_ARGS__ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
preprocessor symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
defining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164, 193
preserved registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
__PRETTY_FUNCTION__ (predefined symbol). . . . . . . 285
primitives, for special functions . . . . . . . . . . . . . . . . . . . . . 30
print formatter, selecting . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
printf (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
choosing formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
configuration symbols . . . . . . . . . . . . . . . . . . . . . . . . . . 79
implementation-defined behavior. . . . . . . . . . . . . . . . . 358
__printf_args (pragma directive) . . . . . . . . . . . . . . . . . . . . 254
processor configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
processor operations
accessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
low-level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221, 259
processor variant, definition of . . . . . . . . . . . . . . . . . . . . . 370
program counter, definition of. . . . . . . . . . . . . . . . . . . . . . 370
program entry label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
program location counter, definition of . . . . . . . . . . . . . . . 371
programming hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
__program_start (label) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
project options, definition of . . . . . . . . . . . . . . . . . . . . . . . 371
projects
basic settings for . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
setting up for a library . . . . . . . . . . . . . . . . . . . . . . . . . . 71
PROM, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
prototypes, enforcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
ptrdiff_t (integer type). . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
PUBLIC (assembler directive) . . . . . . . . . . . . . . . . . . . . . 184
publication date, of this guide . . . . . . . . . . . . . . . . . . . . . . . . ii
--public_equ (compiler option) . . . . . . . . . . . . . . . . . . . . . 184
public_equ (pragma directive) . . . . . . . . . . . . . . . . . . . . . 356

393

DARM-4

putenv (library function), absent from DLIB . . . . . . . . . . . 83

Q
__QADD (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 268
__QADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 268
__QADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 269
__QASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 269
QCCARM (environment variable) . . . . . . . . . . . . . . . . . . 148
__QDADD (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 269
__QDOUBLE (intrinsic function) . . . . . . . . . . . . . . . . . . . 269
__QDSUB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 270
__QFlag (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 270
__QSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 271
__QSUB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 270
__QSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 270
__QSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 270
qualifiers
definition of. See type qualifiers
const and volatile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
implementation-defined behavior. . . . . . . . . . . . . . . . . 354
queue (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 293

R
-r (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
-r (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
raise (library function), configuring support for . . . . . . . . . 84
raise.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
RAM
example of declaring region . . . . . . . . . . . . . . . . . . . . . . 43
execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
initializers copied from ROM . . . . . . . . . . . . . . . . . . . . 18
running code from . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
saving memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
__ramfunc (extended keyword). . . . . . . . . . . . . . . . . . 30, 240
range errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
range, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
--raw (ielfdump option). . . . . . . . . . . . . . . . . . . . . . . . . . . 338

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__read (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
read formatter, selecting . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
reading guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix
reading, recommended . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
read-only sections, definition of . . . . . . . . . . . . . . . . . . . . 371
realloc (library function)
implementation-defined behavior. . . . . . . . . . . . . . . . . 358
See also heap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
real-time operating system, definition of. . . . . . . . . . . . . . 371
real-time system, definition of . . . . . . . . . . . . . . . . . . . . . 371
recursive functions
avoiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
storing data on stack . . . . . . . . . . . . . . . . . . . . . . . . 26–27
--redirect (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 205
reentrancy (DLIB). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
reference information, typographic convention . . . . . . . xxxiii
region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
region expression
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
in linker configuration file . . . . . . . . . . . . . . . . . . . . . . 301
region literal
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
in linker configuration file . . . . . . . . . . . . . . . . . . . . . . 299
region, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
register constant, definition of . . . . . . . . . . . . . . . . . . . . . . 371
register locking, definition of . . . . . . . . . . . . . . . . . . . . . . 371
register parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 99–100
register variables, definition of . . . . . . . . . . . . . . . . . . . . . 371
registered trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
registers
assigning to parameters . . . . . . . . . . . . . . . . . . . . . . . . 100
callee-save, stored on stack . . . . . . . . . . . . . . . . . . . . . . 26
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
implementation-defined behavior. . . . . . . . . . . . . . . . . 353
in assembler-level routines . . . . . . . . . . . . . . . . . . . . . . . 97
preserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
scratch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
reinterpret_cast (cast operator) . . . . . . . . . . . . . . . . . . . . . 108

Index

.rel (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.rela (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
relay, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
relocatable segments, definition of . . . . . . . . . . . . . . . . . . 372
relocation errors, resolving . . . . . . . . . . . . . . . . . . . . . . . . . 58
remark (diagnostic message) . . . . . . . . . . . . . . . . . . . . . . . 153
classifying for compiler . . . . . . . . . . . . . . . . . . . . . . . . 166
classifying for linker . . . . . . . . . . . . . . . . . . . . . . . . . . 194
enabling in compiler . . . . . . . . . . . . . . . . . . . . . . . . . . 185
enabling in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
--remarks (compiler option) . . . . . . . . . . . . . . . . . . . . . . . 185
--remarks (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 205
remove (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
implementation-defined behavior. . . . . . . . . . . . . . . . . 357
--remove_section (iobjmanip option) . . . . . . . . . . . . . . . . 340
rename (isymexport directive). . . . . . . . . . . . . . . . . . . . . . 346
rename (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
implementation-defined behavior. . . . . . . . . . . . . . . . . 357
--rename_section (iobjmanip option) . . . . . . . . . . . . . . . . 340
--rename_symbol (iobjmanip option) . . . . . . . . . . . . . . . . 341
--replace (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . 327
__ReportAssert (library function) . . . . . . . . . . . . . . . . . . . . 85
required (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 254
--require_prototypes (compiler option) . . . . . . . . . . . . . . . 185
reset, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
return values, from functions . . . . . . . . . . . . . . . . . . . . . . 101
__REV (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 271
__REVSH (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 271
Ritchie, Dennis M. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
ROM to RAM, copying . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
ROM-monitor, definition of . . . . . . . . . . . . . . . . . . . . . . . 372
__root (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 241
Round Robin, definition of . . . . . . . . . . . . . . . . . . . . . . . . 372
routines, time-critical . . . . . . . . . . . . . . . . . . . . . 91, 221, 259
rtmodel (assembler directive) . . . . . . . . . . . . . . . . . . . . . . . 89
rtmodel (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 255
RTOS, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
rtti support, missing from STL . . . . . . . . . . . . . . . . . . . . . 108

runtime environment
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
setting options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
runtime libraries
choosing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
choosing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
customizing without rebuilding . . . . . . . . . . . . . . . . . 66
naming convention . . . . . . . . . . . . . . . . . . . . . . . . . . 65
overriding modules in . . . . . . . . . . . . . . . . . . . . . . . . 69
runtime model attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
runtime model definitions . . . . . . . . . . . . . . . . . . . . . . . . . 255
runtime type information, missing from Embedded C++ . 108
R-value, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

S
-S (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
-s (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
__SADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 271
__SADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 271
__SASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 272
saturation arithmetics, definition of. . . . . . . . . . . . . . . . . . 372
scanf (library function)
choosing formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
configuration symbols . . . . . . . . . . . . . . . . . . . . . . . . . . 79
implementation-defined behavior. . . . . . . . . . . . . . . . . 358
__scanf_args (pragma directive) . . . . . . . . . . . . . . . . . . . . 256
scheduler (RTOS), definition of . . . . . . . . . . . . . . . . . . . . 372
scheduling (compiler transformation) . . . . . . . . . . . . . . . . 139
disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
scope, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
scratch registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
section
allocation of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

395

DARM-4

--section (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . 338
section fragment, definition of . . . . . . . . . . . . . . . . . . . . . 372
section names
declaring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
section selection, definition of . . . . . . . . . . . . . . . . . . . . . 373
section (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . 256
sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
section-selectors (in linker configuration file) . . . . . . . . . . 311
__section_begin (extended operator) . . . . . . . . . . . . . . . . 223
__section_end (extended operator) . . . . . . . . . . . . . . . . . . 223
__section_size (extended operator) . . . . . . . . . . . . . . . . . . 223
segment (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . 256
__SEL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 272
semaphores, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 373
--semihosting (linker option). . . . . . . . . . . . . . . . . . . . . . . 205
--separate_cluster_for_initialized_variables
(compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
set (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
setjmp.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
setlocale (library function) . . . . . . . . . . . . . . . . . . . . . . . . . 83
settings, basic for project configuration . . . . . . . . . . . . . . . 19
__set_BASEPRI (intrinsic function) . . . . . . . . . . . . . . . . . 272
__set_CONTROL (intrinsic function) . . . . . . . . . . . . . . . . 272
__set_CPSR (intrinsic function) . . . . . . . . . . . . . . . . . . . . 273
__set_FAULTMASK (intrinsic function) . . . . . . . . . . . . . 273
__set_interrupt_state (intrinsic function) . . . . . . . . . . . . . 273
__set_PRIMASK (intrinsic function) . . . . . . . . . . . . . . . . 273
severity level
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
of diagnostic messages . . . . . . . . . . . . . . . . . . . . . . . . . 153
of diagnostic messages, specifying . . . . . . . . . . . . . . . 153
SFR
accessing special function registers . . . . . . . . . . . . . . . 142
declaring extern special function registers . . . . . . . . . . 132
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
__SHADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 273
__SHADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 274

IAR C/C++ Development Guide

396

Compiling and linking for ARM

DARM-4

shared object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150, 200
sharing, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 373, 375
__SHASX (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 274
short addressing, definition of . . . . . . . . . . . . . . . . . . . . . . 373
short (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
show (isymexport directive) . . . . . . . . . . . . . . . . . . . . . . . 345
__SHSAX (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 274
.shstrtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
__SHSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 274
__SHSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 274
side-effect, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . 373
signal (library function)
configuring support for . . . . . . . . . . . . . . . . . . . . . . . . . 84
implementation-defined behavior. . . . . . . . . . . . . . . . . 357
signals, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
signal.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
signal.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
signbit, C99 extension. . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
signed char (data type) . . . . . . . . . . . . . . . . . . . . . . . 210–211
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
signed int (data type). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
signed long long (data type) . . . . . . . . . . . . . . . . . . . . . . . 211
signed long (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
signed short (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
--silent (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 187
--silent (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 327
--silent (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--silent (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
silent operation
specifying in compiler . . . . . . . . . . . . . . . . . . . . . . . . . 187
specifying in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
--simple (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . 334
simulator, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
64-bits (floating-point format) . . . . . . . . . . . . . . . . . . . . . 214
sizeof, using in preprocessor extensions . . . . . . . . . . . . . . 175
size_t (integer type) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
skeleton code
creating for assembler language interface . . . . . . . . . . . 94
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

Index

skeleton.s (assembler source output) . . . . . . . . . . . . . . . . . . 95
slist (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
smallest, packing algorithm for initializers . . . . . . . . . . . . 306
__SMUL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 275
snprintf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
software interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
source files, list all referred . . . . . . . . . . . . . . . . . . . . . . . . 172
special function registers (SFR) . . . . . . . . . . . . . . . . . . . . 142
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
special function types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
sprintf (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
choosing formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
--srec (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--srec-len (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . 335
--srec-s3only (ielftool option) . . . . . . . . . . . . . . . . . . . . . . 335
__SSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 275
sscanf (library function)
choosing formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
sstream (library header file) . . . . . . . . . . . . . . . . . . . . . . . 292
__SSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 275
__SSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 275
stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
advantages and problems using . . . . . . . . . . . . . . . . . . . 26
aligning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
cleaning after function return . . . . . . . . . . . . . . . . . . . . 102
contents of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
internal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
saving space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
stack frames, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 373
stack parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99, 101
stack pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
stack (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
standard error
redirecting in compiler . . . . . . . . . . . . . . . . . . . . . . . . . 182
redirecting in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

standard input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
standard libraries, definition of . . . . . . . . . . . . . . . . . . . . . 374
standard output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
specifying in compiler . . . . . . . . . . . . . . . . . . . . . . . . . 182
specifying in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
standard template library (STL)
in Extended EC++ . . . . . . . . . . . . . . . . . . . . 108, 111, 293
missing from Embedded C++ . . . . . . . . . . . . . . . . . . . 108
startup system. See system startup
statements, implementation-defined behavior . . . . . . . . . . 354
static clustering (compiler transformation) . . . . . . . . . . . . 138
static objects, definition of . . . . . . . . . . . . . . . . . . . . . . . . 374
static overlay, definition of . . . . . . . . . . . . . . . . . . . . . . . . 374
static variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
taking the address of . . . . . . . . . . . . . . . . . . . . . . . . . . 139
statically allocated memory, definition of . . . . . . . . . . . . . 374
static_cast (cast operator) . . . . . . . . . . . . . . . . . . . . . . . . . 108
__STC (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 276
__STCL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 276
__STCL_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 276
__STC_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . . 276
__STC2 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 276
__STC2L (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 276
__STC2L_noidx (intrinsic function) . . . . . . . . . . . . . . . . . 276
__STC2_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 276
std namespace, missing from EC++
and Extended EC++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
stdarg.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
stdbool.h (library header file) . . . . . . . . . . . . . . . . . . 211, 291
added C functionality . . . . . . . . . . . . . . . . . . . . . . . . . . 295
__STDC__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
STDC (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . 356
__STDC_VERSION__ (predefined symbol) . . . . . . . . . . 285
stddef.h (library header file) . . . . . . . . . . . . . . . . . . . 212, 291
stderr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81, 182, 203
stdexcept (library header file) . . . . . . . . . . . . . . . . . . . . . . 292
stdin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
implementation-defined behavior. . . . . . . . . . . . . . . . . 357
stdint.h (library header file). . . . . . . . . . . . . . . . . . . . 291, 294
stdint.h, added C functionality . . . . . . . . . . . . . . . . . . . . . 295

397

DARM-4

stdio.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
stdio.h, additional C functionality . . . . . . . . . . . . . . . . . . . 295
stdlib.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
stdlib.h, additional C functionality . . . . . . . . . . . . . . . . . . 296
stdout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81, 182, 203
implementation-defined behavior. . . . . . . . . . . . . . . . . 357
Steele, Guy L. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
steering file, input to isymexport. . . . . . . . . . . . . . . . . . . . 345
stepping, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
streambuf (library header file). . . . . . . . . . . . . . . . . . . . . . 292
streams, supported in Embedded C++. . . . . . . . . . . . . . . . 108
strerror (library function)
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 359
__STREX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 277
--strict_ansi (compiler option). . . . . . . . . . . . . . . . . . . . . . 187
string (library header file) . . . . . . . . . . . . . . . . . . . . . . . . . 292
strings, supported in Embedded C++ . . . . . . . . . . . . . . . . 108
string.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . 291
--strip (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
--strip (iobjmanip option) . . . . . . . . . . . . . . . . . . . . . . . . . 341
--strip (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Stroustrup, Bjarne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
strstream (library header file) . . . . . . . . . . . . . . . . . . . . . . 292
.strtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
strtod (library function), configuring support for . . . . . . . . 85
strtod, in stdlib.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
strtof, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
strtold, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
strtoll, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
strtoull, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
structure types
alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216–217
layout of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
packed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
structure value, definition of . . . . . . . . . . . . . . . . . . . . . . . 374
structures
aligning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
anonymous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129, 223
implementation-defined behavior. . . . . . . . . . . . . . . . . 353

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incomplete arrays as last element . . . . . . . . . . . . . . . . . 226
packing and unpacking . . . . . . . . . . . . . . . . . . . . . . . . 129
subnormal numbers . . . . . . . . . . . . . . . . . . . . . . . . . . 213–214
support, technical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
SVC #immed, for software interrupts . . . . . . . . . . . . . . . . . 34
SVC_Handler (exception function) . . . . . . . . . . . . . . . . . . . 36
__swi (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 241
SWI_Handler (exception function) . . . . . . . . . . . . . . . . . . . 32
swi_number (pragma directive) . . . . . . . . . . . . . . . . . . . . 257
__SWP (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 277
__SWPB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 277
symbol names, using in preprocessor extensions . . . . . . . 175
symbolic location, definition of . . . . . . . . . . . . . . . . . . . . 374
symbols
anonymous, creating . . . . . . . . . . . . . . . . . . . . . . . . . . 226
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
directing from one to another . . . . . . . . . . . . . . . . . . . . 205
including in output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
overview of predefined. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
preprocessor, defining . . . . . . . . . . . . . . . . . . . . . 164, 193
--symbols (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . 328
.symtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
syntax
command line options . . . . . . . . . . . . . . . . . . . . . . . . . 155
extended keywords. . . . . . . . . . . . . . . . . . . . . . . . 234–235
invoking compiler and linker . . . . . . . . . . . . . . . . . . . . 147
system startup
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
initialization phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
system termination
C-SPY interface to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
DLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
system (library function)
configuring support for . . . . . . . . . . . . . . . . . . . . . . . . . 83
implementation-defined behavior. . . . . . . . . . . . . . . . . 359
system_include (pragma directive) . . . . . . . . . . . . . . . . . . 356
SysTick_Handler (exception function) . . . . . . . . . . . . . . . . 36

Index

T
-t (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
target, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
__task (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 242
task, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
technical support, IAR Systems . . . . . . . . . . . . . . . . . . . . 154
template support
in Extended EC++ . . . . . . . . . . . . . . . . . . . . . . . . 108, 110
missing from Embedded C++ . . . . . . . . . . . . . . . . . . . 107
tentative definition, definition of . . . . . . . . . . . . . . . . . . . . 374
Terminal I/O window
making available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
terminal I/O, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 374
terminal output, speeding up . . . . . . . . . . . . . . . . . . . . . . . . 87
termination of system. See system termination
terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii, 361
32-bits (floating-point format) . . . . . . . . . . . . . . . . . . . . . 213
this (pointer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
thread, definition of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
--thumb (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 187
__thumb (extended keyword) . . . . . . . . . . . . . . . . . . . . . . 243
Thumb, CPU mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
__TID__ (predefined symbol). . . . . . . . . . . . . . . . . . . . . . 286
__TIME__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
time zone (library function)
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 359
time (library function), configuring support for . . . . . . . . . 85
timer, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
timeslice, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
time-critical routines . . . . . . . . . . . . . . . . . . . . . . 91, 221, 259
time.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
time.h (library header file) . . . . . . . . . . . . . . . . . . . . . . . . 291
tips, programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
--toc (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
tools icon, in this guide . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
transformations, compiler . . . . . . . . . . . . . . . . . . . . . . . . . 134
translation unit, definition of . . . . . . . . . . . . . . . . . . . . . . . 374

translation, implementation-defined behavior . . . . . . . . . . 349
trap, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
type attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
specifying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
type qualifiers
const and volatile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
implementation-defined behavior. . . . . . . . . . . . . . . . . 354
typedefs
excluding from diagnostics . . . . . . . . . . . . . . . . . . . . . 179
repeated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
using in preprocessor extensions . . . . . . . . . . . . . . . . . 175
type-based alias analysis (compiler transformation) . . . . . 138
disabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
type-safe memory management . . . . . . . . . . . . . . . . . . . . 107
type_attribute (pragma directive) . . . . . . . . . . . . . . . . . . . 257
typographic conventions . . . . . . . . . . . . . . . . . . . . . . . . xxxiii

U
__UADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 277
__UADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 277
__UASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 278
UBROF
definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
__UHADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 278
__UHADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 278
__UHASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 278
__UHSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 278
__UHSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 279
__UHSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 279
uintptr_t (integer type) . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
Undefined_Handler (exception function) . . . . . . . . . . . . . . 32
underflow range errors,
implementation-defined behavior . . . . . . . . . . . . . . . . . . . 356
unions
anonymous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129, 223
implementation-defined behavior. . . . . . . . . . . . . . . . . 353

399

DARM-4

unsigned char (data type) . . . . . . . . . . . . . . . . . . . . . 210–211
changing to signed char . . . . . . . . . . . . . . . . . . . . . . . . 162
unsigned int (data type) . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
unsigned long long (data type) . . . . . . . . . . . . . . . . . . . . . 211
unsigned long (data type) . . . . . . . . . . . . . . . . . . . . . . . . . 211
unsigned short (data type) . . . . . . . . . . . . . . . . . . . . . . . . . 210
__UQADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 279
__UQADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 279
__UQASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 280
__UQSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 280
__UQSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 280
__UQSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 280
UsageFault_Handler (exception function). . . . . . . . . . . . . . 36
__USAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 280
--use_unix_directory_separators (compiler option). . . . . . 188
__USUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 281
__USUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 281
utility (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 293

V
-V (iarchive option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
value expressions, definition of . . . . . . . . . . . . . . . . . . . . . 375
variables
auto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
defined inside a function . . . . . . . . . . . . . . . . . . . . . . . . 26
global
placement in memory . . . . . . . . . . . . . . . . . . . . . . . . 25
hints for choosing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
local. See auto variables
non-initialized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
placing at absolute addresses . . . . . . . . . . . . . . . . . . . . 133
placing in named sections . . . . . . . . . . . . . . . . . . . . . . 133
static
placement in memory . . . . . . . . . . . . . . . . . . . . . . . . 25
taking the address of . . . . . . . . . . . . . . . . . . . . . . . . 139
vector floating-point unit . . . . . . . . . . . . . . . . . . . . . . . . . 172
vector (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . 356
vector (STL header file) . . . . . . . . . . . . . . . . . . . . . . . . . . 293

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__vector_table, array holding vector table . . . . . . . . . . . . . 36
veneers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
__VER__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . . 286
--verbose (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . 328
--verbose (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . 335
version
IAR Embedded Workbench . . . . . . . . . . . . . . . . . . . . . . . ii
of compiler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
VFP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
vfscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
vfwscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 296
virtual address, definition of . . . . . . . . . . . . . . . . . . . . . . . 375
virtual space, definition of . . . . . . . . . . . . . . . . . . . . . . . . 375
void, pointers to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
volatile storage, definition of . . . . . . . . . . . . . . . . . . . . . . 375
volatile (keyword) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
volatile, declaring objects . . . . . . . . . . . . . . . . . . . . . . . . . 218
von Neumann architecture, definition of . . . . . . . . . . . . . . 375
vscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
vsnprintf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 295
vsscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
vswscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 296
vwscanf, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . 296

W
#warning message (preprocessor extension) . . . . . . . . . . . 288
warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
classifying in compiler . . . . . . . . . . . . . . . . . . . . . . . . . 167
classifying in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
disabling in compiler . . . . . . . . . . . . . . . . . . . . . . . . . . 181
disabling in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
exit code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
in linker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
warnings icon, in this guide . . . . . . . . . . . . . . . . . . . . . xxxiv
warnings (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . 356
--warnings_affect_exit_code (compiler option) . . . . 151, 188
--warnings_affect_exit_code (linker option) . . . . . . . . . . . 206
--warnings_are_errors (compiler option) . . . . . . . . . . . . . 188

Index

--warnings_are_errors (linker option) . . . . . . . . . . . . . . . . 206
watchpoints, definition of . . . . . . . . . . . . . . . . . . . . . . . . . 375
wchar.h (library header file) . . . . . . . . . . . . . . . . . . . 291, 294
wchar.h, added C functionality . . . . . . . . . . . . . . . . . . . . . 296
wchar_t (data type), adding support for in C . . . . . . . . . . . 211
wcstof, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
wcstolb, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
wctype.h (library header file) . . . . . . . . . . . . . . . . . . . . . . 291
wctype.h, added C functionality . . . . . . . . . . . . . . . . . . . . 296
__weak (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . 243
weak (pragma directive) . . . . . . . . . . . . . . . . . . . . . . . . . . 258
web sites, recommended . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
__write (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

X
-x (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
XLINK, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
xreportassert.c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Z
zeros, packing algorithm for initializers . . . . . . . . . . . . . . 306
zero-initialized sections, definition of . . . . . . . . . . . . . . . . 375
zero-overhead loop, definition of . . . . . . . . . . . . . . . . . . . 375
zone, definition of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

Symbols
#include files, specifying . . . . . . . . . . . . . . . . . . . . . 149, 173
#pragma directive, definition of . . . . . . . . . . . . . . . . . . . . 370
#warning message (preprocessor extension) . . . . . . . . . . . 288
-D (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
-d (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
-e (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
-f (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
-f (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
-f (iobjmanip option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

-f (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
-I (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
-l (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
for creating skeleton code . . . . . . . . . . . . . . . . . . . . . . . 95
-O (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
-o (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
-o (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
-o (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
-o (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
-r (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
-r (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
-S (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
-s (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
-t (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
-V (iarchive option). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
-x (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
--aapcs (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 161
--aeabi (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 161
--align_sp_on_irq (compiler option) . . . . . . . . . . . . . . . . . 161
--all (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
--arm (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . 162
--BE32 (linker option). . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
--BE8 (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
--bin (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
--char_is_signed (compiler option) . . . . . . . . . . . . . . . . . . 162
--checksum (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . 332
--config (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
--config_def (linker option). . . . . . . . . . . . . . . . . . . . . . . . 192
--cpp_init_routine (linker option) . . . . . . . . . . . . . . . . . . . 193
--cpu (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
--cpu (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
--cpu_mode (compiler option) . . . . . . . . . . . . . . . . . . . . . 163
--create (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 325
--debug (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 164
--define_symbol (linker option) . . . . . . . . . . . . . . . . . . . . 193
--delete (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 326
--dependencies (compiler option) . . . . . . . . . . . . . . . . . . . 165
--diagnostics_tables (compiler option) . . . . . . . . . . . . . . . 167
--diagnostics_tables (linker option) . . . . . . . . . . . . . . . . . . 196

401

DARM-4

--diag_error (compiler option) . . . . . . . . . . . . . . . . . . . . . 166
--diag_error (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 194
--diag_remark (compiler option) . . . . . . . . . . . . . . . . . . . . 166
--diag_remark (linker option) . . . . . . . . . . . . . . . . . . . . . . 194
--diag_suppress (compiler option) . . . . . . . . . . . . . . . . . . 167
--diag_suppress (linker option) . . . . . . . . . . . . . . . . . . . . . 195
--diag_warning (compiler option) . . . . . . . . . . . . . . . . . . . 167
--diag_warning (linker option) . . . . . . . . . . . . . . . . . . . . . 195
--discard_unused_publics (compiler option) . . . . . . . . . . . 168
--dlib_config (compiler option). . . . . . . . . . . . . . . . . . . . . 168
--ec++ (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . 169
--edit (isymexport option) . . . . . . . . . . . . . . . . . . . . . . . . . 344
--eec++ (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 169
--enable_hardware_workaround (compiler option) . . . . . . 170
--enable_multibytes (compiler option) . . . . . . . . . . . . . . . 170
--endian (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . 170
--entry (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
--enum_is_int (compiler option) . . . . . . . . . . . . . . . . . . . . 171
--error_limit (compiler option) . . . . . . . . . . . . . . . . . . . . . 171
--error_limit (linker option) . . . . . . . . . . . . . . . . . . . . . . . 196
--export_builtin_config (linker option) . . . . . . . . . . . . . . . 197
--extract (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . 326
--fill (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
--force_output (linker option) . . . . . . . . . . . . . . . . . . . . . . 197
--fpu (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
--header_context (compiler option) . . . . . . . . . . . . . . . . . . 172
--ihex (ielftool option). . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--image_input (linker option) . . . . . . . . . . . . . . . . . . . . . . 198
--interwork (compiler option) . . . . . . . . . . . . . . . . . . . . . . 173
--keep (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
--legacy (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 174
--log (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
--log_file (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 199
--mangled_names_in_messages (linker option) . . . . . . . . 199
--map (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
--mfc (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . . . 175
--migration_preprocessor_extensions (compiler option) . . 175
--misrac_verbose (compiler option) . . . . . . . . . . . . . . . . . 159
--misrac_verbose (linker option) . . . . . . . . . . . . . . . . . . . . 190

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DARM-4

--misrac1998 (compiler option) . . . . . . . . . . . . . . . . . . . . 159
--misrac1998 (linker option) . . . . . . . . . . . . . . . . . . . . . . . 190
--misrac2004 (compiler option) . . . . . . . . . . . . . . . . . . . . 159
--misrac2004 (linker option) . . . . . . . . . . . . . . . . . . . . . . . 190
--no_clustering (compiler option) . . . . . . . . . . . . . . . . . . . 176
--no_code_motion (compiler option) . . . . . . . . . . . . . . . . 176
--no_const_align (compiler option) . . . . . . . . . . . . . . . . . . 176
--no_cse (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . 177
--no_fragments (compiler option) . . . . . . . . . . . . . . . . . . . 177
--no_fragments (linker option) . . . . . . . . . . . . . . . . . . . . . 200
--no_guard_calls (compiler option) . . . . . . . . . . . . . . . . . . 177
--no_inline (compiler option) . . . . . . . . . . . . . . . . . . . . . . 178
--no_library_search (linker option) . . . . . . . . . . . . . . . . . . 201
--no_locals (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 201
--no_path_in_file_macros (compiler option) . . . . . . . . . . . 178
--no_remove (linker option) . . . . . . . . . . . . . . . . . . . . . . . 201
--no_scheduling (compiler option) . . . . . . . . . . . . . . . . . . 178
--no_tbaa (compiler option) . . . . . . . . . . . . . . . . . . . . . . . 179
--no_typedefs_in_diagnostics (compiler option) . . . . . . . . 179
--no_unaligned_access (compiler option) . . . . . . . . . . . . . 180
--no_unroll (compiler option) . . . . . . . . . . . . . . . . . . . . . . 180
--no_veneer (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 202
--no_warnings (compiler option) . . . . . . . . . . . . . . . . . . . 181
--no_warnings (linker option) . . . . . . . . . . . . . . . . . . . . . . 202
--no_wrap_diagnostics (compiler option) . . . . . . . . . . . . . 181
--no_wrap_diagnostics (linker option) . . . . . . . . . . . . . . . 202
--only_stdout (compiler option) . . . . . . . . . . . . . . . . . . . . 182
--only_stdout (linker option) . . . . . . . . . . . . . . . . . . . . . . . 203
--ose_load_module (linker option) . . . . . . . . . . . . . . . . . . 203
--output (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 183
--output (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
--pi_veneer (linker option) . . . . . . . . . . . . . . . . . . . . . . . . 204
--place_holder (linker option) . . . . . . . . . . . . . . . . . . . . . . 204
--predef_macro (compiler option) . . . . . . . . . . . . . . . . . . . 183
--preinclude (compiler option) . . . . . . . . . . . . . . . . . . . . . 183
--preprocess (compiler option) . . . . . . . . . . . . . . . . . . . . . 184
--raw (ielfdump] option) . . . . . . . . . . . . . . . . . . . . . . . . . . 338
--redirect (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 205
--remarks (compiler option) . . . . . . . . . . . . . . . . . . . . . . . 185

Index

--remarks (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . 205
--remove_section (iobjmanip option) . . . . . . . . . . . . . . . . 340
--rename_section (iobjmanip option) . . . . . . . . . . . . . . . . 340
--rename_symbol (iobjmanip option) . . . . . . . . . . . . . . . . 341
--replace (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . 327
--require_prototypes (compiler option) . . . . . . . . . . . . . . . 185
--section (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . 186
--section (ielfdump option) . . . . . . . . . . . . . . . . . . . . . . . . 338
--semihosting (linker option). . . . . . . . . . . . . . . . . . . . . . . 205
--separate_cluster_for_initialized_variables
(compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
--silent (compiler option) . . . . . . . . . . . . . . . . . . . . . . . . . 187
--silent (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . 327
--silent (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--silent (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
--simple (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--srec (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
--srec-len (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . 335
--srec-s3only (ielftool option) . . . . . . . . . . . . . . . . . . . . . . 335
--strict_ansi (compiler option). . . . . . . . . . . . . . . . . . . . . . 187
--strip (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
--strip (iobjmanip option) . . . . . . . . . . . . . . . . . . . . . . . . . 341
--strip (linker option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
--symbols (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . 328
--thumb (compiler option). . . . . . . . . . . . . . . . . . . . . . . . . 187
--toc (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
--use_unix_directory_separators (compiler option). . . . . . 188
--verbose (iarchive option) . . . . . . . . . . . . . . . . . . . . . . . . 328
--verbose (ielftool option) . . . . . . . . . . . . . . . . . . . . . . . . . 335
--warnings_affect_exit_code (compiler option) . . . . 151, 188
--warnings_affect_exit_code (linker option) . . . . . . . . . . . 206
--warnings_are_errors (compiler option) . . . . . . . . . . . . . 188
--warnings_are_errors (linker option) . . . . . . . . . . . . . . . . 206
.bss (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.comment (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.cstart (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
.data (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
.data_init (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
.debug (ELF section). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.iar.debug (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . 320

.iar.dynexit (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
.intvec (section). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
.memattr.text (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
.noinit (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
.rel (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.rela (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.rodata (section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
.shstrtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.strtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
.symtab (ELF section) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
@ (operator)
placing at absolute address . . . . . . . . . . . . . . . . . . . . . . 132
placing in sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
_AEABI_PORTABILITY_LEVEL (preprocessor
symbol) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
_AEABI_PORTABLE (preprocessor symbol) . . . . . . . . . 125
_Exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
_exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
_Exit, C99 extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
_Pragma (predefined symbol) . . . . . . . . . . . . . . . . . . . . . . 287
__ALIGNOF__ (operator) . . . . . . . . . . . . . . . . . . . . . . . . 223
__arm (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 237
__ARMVFP__ (predefined symbol) . . . . . . . . . . . . . . . . . 284
__ARM4M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM4TM__ (predefined symbol) . . . . . . . . . . . . . . . . 284
__ARM5E__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM5__ (predefined symbol) . . . . . . . . . . . . . . . . . . . 284
__ARM6M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM6SM__ (predefined symbol). . . . . . . . . . . . . . . . . 284
__ARM6__ (predefined symbol) . . . . . . . . . . . . . . . . . . . 284
__ARM7M__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__ARM7R__ (predefined symbol) . . . . . . . . . . . . . . . . . . 284
__asm (language extension) . . . . . . . . . . . . . . . . . . . . . . . 225
__BASE_FILE__ (predefined symbol) . . . . . . . . . . . . . . . 284
__big_endian (extended keyword) . . . . . . . . . . . . . . . . . . 237
__BUILD_NUMBER__ (predefined symbol) . . . . . . . . . 284
__close (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
__CLZ (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 262
__CORE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 284
__cplusplus (predefined symbol) . . . . . . . . . . . . . . . . . . . 284

403

DARM-4

__CPU_MODE__ (predefined symbol) . . . . . . . . . . . . . . 284
__DATE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 284
__disable_fiq (intrinsic function) . . . . . . . . . . . . . . . . . . . 262
__disable_interrupt (intrinsic function) . . . . . . . . . . . . . . . 263
__disable_irq (intrinsic function) . . . . . . . . . . . . . . . . . . . 263
__DLIB_FILE_DESCRIPTOR (configuration symbol) . . . 80
__DMB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 263
__DSB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 263
__embedded_cplusplus (predefined symbol) . . . . . . . . . . 284
__enable_fiq (intrinsic function) . . . . . . . . . . . . . . . . . . . . 264
__enable_interrupt (intrinsic function) . . . . . . . . . . . . . . . 264
__enable_irq (intrinsic function) . . . . . . . . . . . . . . . . . . . . 264
__exit (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
__FILE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . . 284
__fiq (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . . 237
__FUNCTION__ (predefined symbol) . . . . . . . . . . . 231, 285
__func__ (predefined symbol) . . . . . . . . . . . . . . . . . 231, 285
__gets, in stdio.h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
__get_BASEPRI (intrinsic function) . . . . . . . . . . . . . . . . . 264
__get_CONTROL (intrinsic function) . . . . . . . . . . . . . . . 264
__get_CPSR (intrinsic function) . . . . . . . . . . . . . . . . . . . . 265
__get_FAULTMASK (intrinsic function) . . . . . . . . . . . . . 265
__get_interrupt_state (intrinsic function) . . . . . . . . . . . . . 265
__get_PRIMASK (intrinsic function) . . . . . . . . . . . . . . . . 265
__iar_maximum_atexit_calls . . . . . . . . . . . . . . . . . . . . . . . 53
__IAR_SYSTEMS_ICC__ (predefined symbol) . . . . . . . 285
__ICCARM__ (predefined symbol) . . . . . . . . . . . . . . . . . 285
__interwork (extended keyword) . . . . . . . . . . . . . . . . . . . 238
__intrinsic (extended keyword) . . . . . . . . . . . . . . . . . . . . . 238
__irq (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . . 238
__ISB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . . 266
__LDC (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 266
__LDCL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 266
__LDCL_noidx (intrinsic function) . . . . . . . . . . . . . . . . . 266
__LDC_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . . 266
__LDC2 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 266
__LDC2L (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 266
__LDC2L_noidx (intrinsic function) . . . . . . . . . . . . . . . . 266
__LDC2_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 266

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__LDREX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 267
__LINE__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
__little_endian (extended keyword) . . . . . . . . . . . . . . . . . 238
__LITTLE_ENDIAN__ (predefined symbol) . . . . . . . . . . 285
__low_level_init . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
initialization phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
__low_level_init, customizing . . . . . . . . . . . . . . . . . . . . . . 76
__lseek (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
__MCR (intrinsic function). . . . . . . . . . . . . . . . . . . . . . . . 267
__MRC (intrinsic function). . . . . . . . . . . . . . . . . . . . . . . . 268
__nested (extended keyword) . . . . . . . . . . . . . . . . . . . . . . 239
__noreturn (extended keyword) . . . . . . . . . . . . . . . . . . . . 239
__no_init (extended keyword) . . . . . . . . . . . . . . . . . 143, 239
__no_operation (intrinsic function) . . . . . . . . . . . . . . . . . . 268
__open (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
__packed (extended keyword). . . . . . . . . . . . . . . . . . . . . . 240
__PRETTY_FUNCTION__ (predefined symbol). . . . . . . 285
__printf_args (pragma directive) . . . . . . . . . . . . . . . . 254, 356
__program_start (label) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
__QADD (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 268
__QADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 268
__QADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 269
__QASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 269
__QDADD (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 269
__QDOUBLE (intrinsic function) . . . . . . . . . . . . . . . . . . . 269
__QDSUB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 270
__QFlag (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 270
__QSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 271
__qsortbbl, C99 extension. . . . . . . . . . . . . . . . . . . . . . . . . 296
__QSUB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 270
__QSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 270
__QSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 270
__ramfunc (extended keyword). . . . . . . . . . . . . . . . . . . . . 240
executing in RAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
__read (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
__ReportAssert (library function) . . . . . . . . . . . . . . . . . . . . 85
__REV (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 271
__REVSH (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 271

Index

__root (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 241
__SADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 271
__SADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 271
__SASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 272
__scanf_args (pragma directive) . . . . . . . . . . . . . . . . 256, 356
__section_begin (extended operator) . . . . . . . . . . . . . . . . 223
__section_end (extended operator) . . . . . . . . . . . . . . . . . . 223
__section_size (extended operator) . . . . . . . . . . . . . . . . . . 223
__SEL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 272
__set_BASEPRI (intrinsic function) . . . . . . . . . . . . . . . . . 272
__set_CONTROL (intrinsic function) . . . . . . . . . . . . . . . . 272
__set_CPSR (intrinsic function) . . . . . . . . . . . . . . . . . . . . 273
__set_FAULTMASK (intrinsic function) . . . . . . . . . . . . . 273
__set_interrupt_state (intrinsic function) . . . . . . . . . . . . . 273
__set_PRIMASK (intrinsic function) . . . . . . . . . . . . . . . . 273
__SHADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 273
__SHADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 274
__SHASX (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 274
__SHSAX (intrinsic function). . . . . . . . . . . . . . . . . . . . . . 274
__SHSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 274
__SHSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 274
__SMUL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 275
__SSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 275
__SSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 275
__SSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 275
__STC (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 276
__STCL (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 276
__STCL_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 276
__STC_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . . 276
__STC2 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 276
__STC2L (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 276
__STC2L_noidx (intrinsic function) . . . . . . . . . . . . . . . . . 276
__STC2_noidx (intrinsic function) . . . . . . . . . . . . . . . . . . 276
__STDC_VERSION__ (predefined symbol) . . . . . . . . . . 285
__STDC__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
__STREX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 277
__swi (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 241
__SWP (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . . 277
__SWPB (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 277

__task (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . . 242
__thumb (extended keyword) . . . . . . . . . . . . . . . . . . . . . . 243
__TID__ (predefined symbol). . . . . . . . . . . . . . . . . . . . . . 286
__TIME__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . 285
__UADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 277
__UADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 277
__UASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 278
__UHADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 278
__UHADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 278
__UHASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 278
__UHSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 278
__UHSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 279
__ungetchar, in stdio.h . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
__UQADD8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 279
__UQADD16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 279
__UQASX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 280
__UQSAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 280
__UQSUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . 280
__UQSUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . 280
__USAX (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . . 280
__USUB8 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . . 281
__USUB16 (intrinsic function) . . . . . . . . . . . . . . . . . . . . . 281
__VA_ARGS__ (preprocessor extension) . . . . . . . . . . . . . 288
__VER__ (predefined symbol) . . . . . . . . . . . . . . . . . . . . . 286
__weak (extended keyword) . . . . . . . . . . . . . . . . . . . . . . . 243
__write (library function) . . . . . . . . . . . . . . . . . . . . . . . . . . 81
customizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
__write_array, in stdio.h . . . . . . . . . . . . . . . . . . . . . . . . . . 296
__write_buffered (DLIB library function). . . . . . . . . . . . . . 87

Numerics
32-bits (floating-point format) . . . . . . . . . . . . . . . . . . . . . 213
64-bits (floating-point format) . . . . . . . . . . . . . . . . . . . . . 214

405

DARM-4



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