Cppcheck Manual
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Cppcheck 1.53
Cppcheck 1.53
Table of Contents
1. Introduction............................................................................................................................................1
2. Getting started .......................................................................................................................................2
2.1. First test.......................................................................................................................................2
2.2. Checking all files in a folder .......................................................................................................2
2.3. Excluding a file or folder from checking ....................................................................................2
2.4. Severities .....................................................................................................................................3
2.5. Enable messages .........................................................................................................................3
2.5.1. Stylistic issues ................................................................................................................3
2.5.2. Unused functions ............................................................................................................4
2.5.3. Enable all checks ............................................................................................................4
2.6. Saving results in file ....................................................................................................................4
2.7. Multithreaded checking...............................................................................................................5
3. Preprocessor configurations..................................................................................................................6
4. XML output............................................................................................................................................7
5. Reformatting the output........................................................................................................................8
6. Suppressions ...........................................................................................................................................9
6.1. Suppressing a certain error type..................................................................................................9
6.1.1. Command line suppression.............................................................................................9
6.1.2. Listing suppressions in a file ..........................................................................................9
6.2. Inline suppressions ....................................................................................................................10
7. Leaks .....................................................................................................................................................11
7.1. User-defined allocation/deallocation functions.........................................................................11
8. Exception safety ...................................................................................................................................13
9. HTML report .......................................................................................................................................14
10. Graphical user interface....................................................................................................................15
10.1. Introduction .............................................................................................................................15
10.2. Check source code ..................................................................................................................15
10.3. Inspecting results.....................................................................................................................15
10.4. Settings....................................................................................................................................15
10.5. Project files..............................................................................................................................15
iii
Chapter 1. Introduction
Cppcheck is an analysis tool for C/C++ code. Unlike C/C++ compilers and many other analysis tools, it
doesn’t detect syntax errors. Cppcheck only detects the types of bugs that the compilers normally fail to
detect. The goal is no false positives.
Supported code and platforms:
•
You can check non-standard code that includes various compiler extensions, inline assembly code, etc.
•
Cppcheck should be compilable by any C++ compiler that handles the latest C++ standard.
•
Cppcheck should work on any platform that has sufficient CPU and memory.
Accuracy
Please understand that there are limits of Cppcheck. Cppcheck is rarely wrong about reported errors. But
there are many bugs that it doesn’t detect.
You will find more bugs in your software by testing your software carefully, than by using Cppcheck.
You will find more bugs in your software by instrumenting your software, than by using Cppcheck. But
Cppcheck can still detect some of the bugs that you miss when testing and instrumenting your software.
1
Chapter 2. Getting started
2.1. First test
Here is a simple code
int main()
{
char a[10];
a[10] = 0;
return 0;
}
If you save that into file1.c and execute:
cppcheck file1.c
The output from cppcheck will then be:
Checking file1.c...
[file1.c:4]: (error) Array ’a[10]’ index 10 out of bounds
2.2. Checking all files in a folder
Normally a program has many source files. And you want to check them all. Cppcheck can check all
source files in a directory:
cppcheck path
If "path" is a folder then cppcheck will check all source files in this folder.
Checking path/file1.cpp...
1/2 files checked 50% done
Checking path/file2.cpp...
2/2 files checked 100% done
2.3. Excluding a file or folder from checking
To exclude a file or folder, there are two options.
2
Chapter 2. Getting started
The first option is to only provide the paths and files you want to check.
cppcheck src/a src/b
All files under src/a and src/b are then checked.
The second option is to use -i, with it you specify files/paths to ignore. With this command no files in
src/c are checked:
cppcheck -isrc/c src
2.4. Severities
The possible severities for messages are:
error
used when bugs are found
warning
suggestions about defensive programming to prevent bugs
style
stylistic issues related to code cleanup (unused functions, redundant code, constness, and such)
performance
suggestions for making the code faster
portability
portability warnings. 64-bit portability. code might work different on different compilers. etc.
information
Informational messages that might be interesting. Ignore these messages unless you really agree.
* The performance messages are based on ’common knowledge’. It is not certain that fixing performance messages will make any
measurable difference in speed. Fixing performance messages generally doesn’t make your code more readable.
2.5. Enable messages
By default only error messages are shown. Through the --enable command more checks can be
enabled.
3
Chapter 2. Getting started
2.5.1. Stylistic issues
With --enable=style you enable most warning , style and performance messages.
Here is a simple code example:
void f(int x)
{
int i;
if (x == 0)
{
i = 0;
}
}
There are no bugs in that code so Cppcheck won’t report anything by default. To enable the stylistic
messages, use the --enable=style command:
cppcheck --enable=style file3.c
The output from Cppcheck is now:
Checking file3.c...
[file3.c:3]: (style) Variable ’i’ is assigned a value that is never used
[file3.c:3]: (style) The scope of the variable i can be reduced
2.5.2. Unused functions
This check will try to find unused functions. It is best to use this when the whole program is checked, so
that all usages is seen by cppcheck.
cppcheck --enable=unusedFunction path
2.5.3. Enable all checks
To enable all checks your can use the --enable=all flag:
cppcheck --enable=all path
4
Chapter 2. Getting started
2.6. Saving results in file
Many times you will want to save the results in a file. You can use the normal shell redirection for piping
error output to a file.
cppcheck file1.c 2> err.txt
2.7. Multithreaded checking
The command line client can only use threads in posix environments. But it is the goal to be able to use
threads on all platforms.
The option -j is used to specify the number of threads you want to use. For example, to use 4 threads to
check the files in a folder:
cppcheck -j 4 path
5
Chapter 3. Preprocessor configurations
By default Cppcheck will check all preprocessor configurations (except those that has #error in them).
This is the recommended behaviour.
But if you want to manually limit the checking you can do so with -D .
Beware that only the macros, which are given here and the macros defined in source files and known
header files are considered. That excludes all the macros defined in some system header files, which are
by default not examined by Cppcheck.
The usage: if you, for example, want to limit the checking so the only configuration to check should be
DEBUG=1;__cplusplus then something like this can be used:
cppcheck -DDEBUG=1 -D__cplusplus path
6
Chapter 4. XML output
Cppcheck can generate the output in XML format.
Use the --xml flag when you execute cppcheck:
cppcheck --xml file1.cpp
The XML format is:
Attributes:
file
filename. Both relative and absolute paths are possible
line
a number
id
id of error. These are always valid symbolnames.
severity
either error or style.
warning and performance are saved as style.
msg
the error message
7
Chapter 5. Reformatting the output
If you want to reformat the output so it looks different you can use templates.
To get Visual Studio compatible output you can use --template=vs:
cppcheck --template=vs gui/test.cpp
This output will look like this:
Checking gui/test.cpp...
gui/test.cpp(31): error: Memory leak: b
gui/test.cpp(16): error: Mismatching allocation and deallocation: k
To get gcc compatible output you can use --template=gcc:
cppcheck --template=gcc gui/test.cpp
The output will look like this:
Checking gui/test.cpp...
gui/test.cpp:31: error: Memory leak: b
gui/test.cpp:16: error: Mismatching allocation and deallocation: k
You can write your own pattern (for example a comma-separated format):
cppcheck --template="{file},{line},{severity},{id},{message}" gui/test.cpp
The output will look like this:
Checking gui/test.cpp...
gui/test.cpp,31,error,memleak,Memory leak: b
gui/test.cpp,16,error,mismatchAllocDealloc,Mismatching allocation and deallocation: k
8
Chapter 6. Suppressions
If you want to filter out certain errors you can suppress these.
6.1. Suppressing a certain error type
You can suppress certain types of errors. The format for such a suppression is one of:
[error id]:[filename]:[line]
[error id]:[filename2]
[error id]
The error id is the id that you want to suppress. The easiest way to get it is to use the --xml
command line flag. Copy and paste the id string from the XML output. This may be * to suppress all
warnings (for a specified file or files).
The filename may include the wildcard characters * or ?, which match any sequence of characters or
any single character respectively. It is recommended that you use "/" as path separator on all operating
systems.
6.1.1. Command line suppression
The --suppress= command line option is used to specify suppressions on the command line. Example:
cppcheck --suppress=memleak:src/file1.cpp src/
6.1.2. Listing suppressions in a file
You can create a suppressions file. Example:
// suppress memleak and exceptNew errors in the file src/file1.cpp
memleak:src/file1.cpp
exceptNew:src/file1.cpp
// suppress all uninitvar errors in all files
uninitvar
Note that you may add empty lines and comments in the suppressions file.
You can use the suppressions file like this:
9
Chapter 6. Suppressions
cppcheck --suppressions suppressions.txt src/
6.2. Inline suppressions
Suppressions can also be added directly in the code by adding comments that contain special keywords.
Before adding such comments, consider that the code readability is sacrificed a little.
This code will normally generate an error message:
void f() {
char arr[5];
arr[10] = 0;
}
The output is:
# cppcheck test.c
Checking test.c...
[test.c:3]: (error) Array ’arr[5]’ index 10 out of bounds
To suppress the error message, a comment can be added:
void f() {
char arr[5];
// cppcheck-suppress arrayIndexOutOfBounds
arr[10] = 0;
}
Now the --inline-suppr flag can be used to suppress the warning. No error is reported when invoking
cppcheck this way:
cppcheck --inline-suppr test.c
10
Chapter 7. Leaks
Looking for memory leaks and resource leaks is a key feature of Cppcheck. Cppcheck can detect many
common mistakes by default. But through some tweaking you can improve the checking.
7.1. User-defined allocation/deallocation functions
Cppcheck understands many common allocation and deallocation functions. But not all.
Here is example code that might leak memory or resources:
void foo(int x)
{
void *f = CreateFred();
if (x == 1)
return;
DestroyFred(f);
}
If you analyse that with Cppcheck it won’t find any leaks:
cppcheck --enable=possibleError fred1.cpp
You can add some custom leaks checking by providing simple implementations for the allocation and
deallocation functions. Write this in a separate file:
void *CreateFred()
{
return malloc(100);
}
void DestroyFred(void *p)
{
free(p);
}
When Cppcheck see this it understands that CreateFred() will return allocated memory and that
DestroyFred() will deallocate memory.
Now, execute cppcheck this way:
cppcheck --append=fred.cpp fred1.cpp
The output from cppcheck is:
11
Chapter 7. Leaks
Checking fred1.cpp...
[fred1.cpp:5]: (error) Memory leak: f
12
Chapter 8. Exception safety
Cppcheck has a few checks that ensure that you don’t break the basic guarantee of exception safety. It
doesn’t have any checks for the strong guarantee yet.
Example:
Fred::Fred() : a(new int[20]), b(new int[20])
{
}
By default Cppcheck will not detect any problems in that code.
To enable the exception safety checking you can use --enable:
cppcheck --enable=exceptNew --enable=exceptRealloc fred.cpp
The output will be:
[fred.cpp:3]: (style) Upon exception there is memory leak: a
If an exception occurs when b is allocated, a will leak.
Here is another example:
int *p;
int a(int sz)
{
delete [] p;
if (sz <= 0)
throw std::runtime_error("size <= 0");
p = new int[sz];
}
Check that with Cppcheck:
cppcheck --enable=exceptNew --enable=exceptRealloc except2.cpp
The output from Cppcheck is:
[except2.cpp:7]: (error) Throwing exception in invalid state, p points at deallocated memory
13
Chapter 9. HTML report
You can convert the XML output from cppcheck into a HTML report. You’ll need Python and the
pygments module (http://pygments.org/) for this to work. In the Cppcheck source tree there is a folder
htmlreport that contains a script that transforms a Cppcheck XML file into HTML output.
This command generates the help screen:
htmlreport/cppcheck-htmlreport -h
The output screen says:
Usage: cppcheck-htmlreport [options]
Options:
-h, --help
--file=FILE
show this help message and exit
The cppcheck xml output file to read defects from.
Default is reading from stdin.
--report-dir=REPORT_DIR
The directory where the html report content is written.
--source-dir=SOURCE_DIR
Base directory where source code files can be found.
An example usage:
./cppcheck gui/test.cpp --xml 2> err.xml
htmlreport/cppcheck-htmlreport --file=err.xml --report-dir=test1 --source-dir=.
14
Chapter 10. Graphical user interface
10.1. Introduction
A Cppcheck GUI is available.
The main screen is shown immediately when the GUI is started.
10.2. Check source code
Use the Check menu.
10.3. Inspecting results
The results are shown in a list.
You can show/hide certain types of messages through the View menu.
Results can be saved to an XML file that can later be opened. See Save results to file and Open
XML.
10.4. Settings
The language can be changed at any time by using the Language menu.
More settings are available in Edit−→Preferences.
10.5. Project files
The project files are used to store project specific settings. These settings are:
•
include folders
•
preprocessor defines
15
Chapter 10. Graphical user interface
It isn’t recommended to provide the paths to the standard C/C++ headers - Cppcheck has internal
knowledge about ANSI C/C++ and it isn’t recommended that this known functionality is redefined. But
feel free to try it.
As you can read in chapter 3 in this manual the default is that Cppcheck checks all configurations. So
only provide preprocessor defines if you want to limit the checking.
16
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