Cppcheck 1.672014-09-28IntroductionCppcheck 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.AccuracyPlease 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.Getting startedFirst testHere is a simple codeint main()
{
char a[10];
a[10] = 0;
return 0;
}If you save that into file1.c and
execute:cppcheck file1.cThe output from cppcheck will then be:Checking file1.c...
[file1.c:4]: (error) Array 'a[10]' index 10 out of boundsChecking all files in a folderNormally a program has many source files. And you want to check
them all. Cppcheck can check all source files in a directory:cppcheck pathIf "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% doneExcluding a file or folder from checkingTo exclude a file or folder, there are two options.The first option is to only provide the paths and files you want
to check.cppcheck src/a src/bAll 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 srcSeveritiesThe possible severities for messages are:errorused when bugs are foundwarningsuggestions about defensive programming to prevent
bugsstylestylistic issues related to code cleanup (unused functions,
redundant code, constness, and such)performanceSuggestions for making the code faster. These suggestions
are only based on common knowledge. It is not certain you'll get
any measurable difference in speed by fixing these
messages.portabilityportability warnings. 64-bit portability. code might work
different on different compilers. etc.informationInformational messages about checking problems.Enable messagesBy default only error
messages are shown. Through the --enable command more checks can be
enabled.# enable warning messages
cppcheck --enable=warning file.c
# enable performance messages
cppcheck --enable=performance file.c
# enable information messages
cppcheck --enable=information file.c
# For historical reasons, --enable=style enables warning, performance,
# portability and style messages. These are all reported as "style" when
# using the old xml format.
cppcheck --enable=style file.c
# enable warning and information messages
cppcheck --enable=warning,information file.c
# enable unusedFunction checking. This is not enabled by --enable=style
# because it doesn't work well on libraries.
cppcheck --enable=unusedFunction file.c
# enable all messages
cppcheck --enable=allPlease note that --enable=unusedFunction should
only be used when the whole program is scanned. And therefore
--enable=all should also only be used when the whole
program is scanned. The reason is that the unusedFunction checking will
warn if a function is not called. There will be noise if function calls
are not seen.Inconclusive checksBy default Cppcheck only writes error messages if it is certain.
With --inconclusive error
messages will also be written when the analysis is
inconclusive.cppcheck --inconclusive pathThis can of course cause false warnings, it might be reported
that there are bugs even though there are not. Only use this command
if false warnings are acceptable.Saving results in fileMany 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.txtMultithreaded checkingThe 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 pathPreprocessor configurationsBy default Cppcheck will check all preprocessor configurations
(except those that have #error in them).You can use -D to change this. When you use -D, cppcheck will by
default only check the given configuration and nothing else. This is how
compilers work. But you can use --force or
--max-configs to override the number
of configurations.# check all configurations
cppcheck file.c
# only check the configuration A
cppcheck -DA file.c
# check all configurations when macro A is defined
cppcheck -DA --force file.cAnother useful flag might be -U. It undefines a symbol. Example
usage:cppcheck -UX file.cThat will mean that X is not defined. Cppcheck will not check what
happens when X is defined.XML outputCppcheck can generate the output in XML format.
There is an old XML format (version 1) and a new
XML format (version 2). Please use the new version if
you can.The old version is kept for backwards compatibility only. It will
not be changed. But it will likely be removed someday. Use
--xml to enable this format.The new version fixes a few problems with the old format. The new
format will probably be updated in future versions of cppcheck with new
attributes and elements. A sample command to check a file and output
errors in the new XML format:cppcheck --xml-version=2 file1.cppHere
is a sample version 2 report:<?xml version="1.0" encoding="UTF-8"?>
<results version="2">
<cppcheck version="1.66">
<errors>
<error id="someError" severity="error" msg="short error text"
verbose="long error text" inconclusive="true">
<location file="file.c" line="1"/>
</error>
</errors>
</results>The <error> elementEach error is reported in a <error>
element. Attributes:idid of error. These are always valid symbolnames.severityeither: error,
warning, style,
performance, portability or
informationmsgthe error message in short formatverbosethe error message in long format.inconclusiveThis attribute is only used when the message is
inconclusive.The <location> elementAll locations related to an error is listed with
<location> elements. The primary location is
listed first.Attributes:filefilename. Both relative and absolute paths are
possiblelinea numbermsgthis attribute doesn't exist yet. But in the future we may
add a short message for each location.Reformatting the outputIf 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.cppThis 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: kTo get gcc compatible output you can use --template=gcc:cppcheck --template=gcc gui/test.cppThe 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: kYou can write your own pattern (for example a comma-separated
format):cppcheck --template="{file},{line},{severity},{id},{message}" gui/test.cppThe 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: kThe following format specifiers are supported:callstackcallstack - if availablefilefilenameidmessage idlineline numbermessageverbose message textseverityseverityThe escape sequences \b (backspace), \n (newline), \r (formfeed) and
\t (horizontal tab) are supported.SuppressionsIf you want to filter out certain errors you can suppress
these.Suppressing a certain error typeYou 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.Command line suppressionThe --suppress= command
line option is used to specify suppressions on the command line.
Example:cppcheck --suppress=memleak:src/file1.cpp src/Listing suppressions in a fileYou 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
uninitvarNote that you may add empty lines and comments in the
suppressions file.You can use the suppressions file like this:cppcheck --suppressions suppressions.txt src/Inline suppressionsSuppressions 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 boundsTo 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.cLibrary configurationWhen external libraries are used, such as windows/posix/gtk/qt/etc,
Cppcheck doesn't know how the external functions
behave. Cppcheck then fails to detect various problems
such as leaks, buffer overflows, possible null pointer dereferences, etc.
But this can be fixed with configuration files.If you create a configuration file for a popular library, we would
appreciate if you upload it to us.Using your own custom .cfg fileYou can create and use your own .cfg files for your
projects.The command line cppcheck will try to load custom .cfg files from
the working path - execute cppcheck from the path where the .cfg files
are.The cppcheck GUI will try to load custom .cfg files from the
project file path. The custom .cfg files should be shown in the
Edit Project File dialog that you open from the
File menu.Memory/resource leaksHere is an example program:void test()
{
HPEN pen = CreatePen(PS_SOLID, 1, RGB(255,0,0));
}The code example above has a resource leak -
CreatePen() is a windows function that creates a pen.
However Cppcheck doesn't assume that return values from functions must
be freed. There is no error message:# cppcheck pen1.c
Checking pen1.c...If you provide a windows configuration file then
Cppcheck detects the bug:# cppcheck --library=windows.cfg pen1.c
Checking pen1.c...
[pen1.c:3]: (error) Resource leak: penHere is a minimal windows.cfg file:<?xml version="1.0"?>
<def>
<resource>
<alloc>CreatePen</alloc>
<dealloc>DeleteObject</dealloc>
</resource>
</def>Function argument: Uninitialized memoryHere is an example program:void test()
{
char buffer1[1024];
char buffer2[1024];
CopyMemory(buffer1, buffer2, 1024);
}The bug here is that buffer2 is uninitialized. The second argument
for CopyMemory needs to be initialized. However
Cppcheck assumes that it is fine to pass
uninitialized variables to functions:# cppcheck uninit.c
Checking uninit.c...If you provide a windows configuration file then Cppcheck detects
the bug:# cppcheck --library=windows.cfg uninit.c
Checking uninit.c...
[uninit.c:5]: (error) Uninitialized variable: buffer2Here is the minimal windows.cfg:<?xml version="1.0"?>
<def>
<function name="CopyMemory">
<arg nr="2">
<not-uninit/>
</arg>
</function>
</def>Function Argument: Null pointersCppcheck assumes it's ok to pass NULL pointers to functions. Here
is an example program:void test()
{
CopyMemory(NULL, NULL, 1024);
}The MSDN documentation is not clear if that is ok or not. But
let's assume it's bad. Cppcheck assumes that it's ok to pass NULL to
functions so no error is reported:# cppcheck null.c
Checking null.c...If you provide a windows configuration file then
Cppcheck detects the bug:cppcheck --library=windows.cfg null.c
Checking null.c...
[null.c:3]: (error) Null pointer dereferenceHere is a minimal windows.cfg file:<?xml version="1.0"?>
<def>
<function name="CopyMemory">
<arg nr="1">
<not-null/>
</arg>
</function>
</def>Function Argument: Format stringYou can define that a function takes a format string.
Example:void test()
{
do_something("%i %i\n", 1024);
}No error is reported for that:# cppcheck formatstring.c
Checking formatstring.c...A configuration file can be created that says that the string is a
format string. For instance:<?xml version="1.0"?>
<def>
<function name="do_something">
<arg nr="1">
<formatstr/>
</arg>
</function>
</def>Now Cppcheck will report an error:cppcheck --library=test.cfg formatstring.c
Checking formatstring.c...
[formatstring.c:3]: (error) do_something format string requires 2 parameters but only 1 is given.Function Argument: Value rangeThe valid values can be defined. Imagine:void test()
{
do_something(1024);
}No error is reported for that:# cppcheck valuerange.c
Checking valuerange.c...A configuration file can be created that says that 1024 is out of
bounds. For instance:<?xml version="1.0"?>
<def>
<function name="do_something">
<arg nr="1">
<valid>0-1023</valid>
</arg>
</function>
</def>Now Cppcheck will report an error:cppcheck --library=test.cfg range.c
Checking range.c...
[range.c:3]: (error) Invalid do_something() argument nr 1. The value is 1024 but the valid values are '0-1023'.noreturnCppcheck doesn't assume that functions always return. Here is an
example code:void test(int x)
{
int data, buffer[1024];
if (x == 1)
data = 123;
else
ZeroMemory(buffer, sizeof(buffer));
buffer[0] = data; // <- error: data is uninitialized if x is not 1
}In theory, if ZeroMemory terminates the program
then there is no bug. Cppcheck therefore reports no error:# cppcheck noreturn.c
Checking noreturn.c...However if you use --check-library and
--enable=information you'll get this:# cppcheck --check-library --enable=information noreturn.c
Checking noreturn.c...
[noreturn.c:7]: (information) --check-library: Function ZeroMemory() should have <noreturn> configuration
If a proper windows.cfg is provided, the bug is
detected:# cppcheck --library=windows.cfg noreturn.c
Checking noreturn.c...
[noreturn.c:8]: (error) Uninitialized variable: dataHere is a minimal windows.cfg file:<?xml version="1.0"?>
<def>
<function name="ZeroMemory">
<noreturn>false</noreturn>
</function>
</def>use-retvalPer default, cppcheck assumes that ignoring the return value of a function is ok:bool test(const char* a, const char* b)
{
strcmp(a, b); // <- bug: The call of strcmp does not have side-effects, but the return value is ignored.
return true;
}In case strcmp has side effects, such as assigning the result to one of the parameters passed to it, nothing bad would happen:# cppcheck useretval.c
Checking useretval.c...If a proper lib.cfg is provided, the bug is
detected:# cppcheck --library=lib.cfg --enable=warning useretval.c
Checking useretval.c...
[noreturn.c:3]: (warning) Return value of function strcmp() is not used.Here is a minimal lib.cfg file:<?xml version="1.0"?>
<def>
<function name="strcmp">
<use-retval/>
</function>
</def>Example configuration for strcpy()The proper configuration for the standard strcpy() function would
be: <function name="strcpy">
<leak-ignore/>
<noreturn>false</noreturn>
<arg nr="1">
<not-null/>
</arg>
<arg nr="2">
<not-null/>
<not-uninit/>
</arg>
</function>The <leak-ignore/> tells Cppcheck to
ignore this function call in the leaks checking. Passing allocated
memory to this function won't mean it will be deallocated.The <noreturn> tells Cppcheck if this
function returns or not.The first argument that the function takes is a pointer. It must
not be a null pointer, therefore <not-null> is
used.The second argument the function takes is a pointer. It must not
be null. And it must point at initialized data. Using
<not-null> and
<not-uninit> is correct.Specifications for all argumentsSpecifying -1 as the argument number is going
to apply a check to all arguments of that function. The specifications
for individual arguments override this setting.RulesYou can define custom rules using regular expressions.These rules can not perform sophisticated analysis of the code. But
they give you an easy way to check for various simple patterns in the
code.To get started writing rules, see the related articles here:http://sourceforge.net/projects/cppcheck/files/Articles/The file format for rules is:<?xml version="1.0"?>
<rule>
<tokenlist>LIST</tokenlist>
<pattern>PATTERN</pattern>
<message>
<id>ID</id>
<severity>SEVERITY</severity>
<summary>SUMMARY</summary>
</message>
</rule>CDATA can be used to include characters in a pattern that might interfere with XML:<![CDATA[some<strange>pattern]]><tokenlist>The <tokenlist> element is optional. With
this element you can control what tokens are checked. The
LIST can be either define,
raw, normal or
simple.defineused to check #define preprocessor statements.rawused to check the preprocessor output.normalused to check the normal token list.
There are some simplifications.simpleused to check the simple token list. All simplifications are
used. Most Cppcheck checks use the simple token list.If there is no <tokenlist> element then
simple is used automatically.<pattern>The PATTERN is the
PCRE-compatible regular expression that will be
executed.<id>The ID specify the user-defined message id.<severity>The SEVERITY must be one of the
Cppcheck severities: information,
performance, portability,
style, warning, or
error.<summary>Optional. The summary for the message. If no summary is given, the
matching tokens is written.Cppcheck extensions with PythonUsing dump files it is possible to write Cppcheck extensions with
for instance Python.The cppcheckdata.py module
(http://github.com/danmar/cppcheck/blob/master/tools/cppcheckdata.py)
allows you to load such dump file. It contains
Token/Variable/ValueFlow.Value/Scope
classes that are similar to the C++ classes in
Cppcheck-core. The doxygen information for the
C++ classes should be somewhat useful for Python
developers also.Simple checker: Division by zeroHere is a simple checker:import cppcheckdata
data = cppcheckdata.parsedump('1.c.dump')
for token in data.tokenlist:
if token.str == '/' or token.str == '%':
# Get denominator (2nd operand)
den = token.astOperand2
# Can denominator be zero?
if den.getValue(0):
print '[' + token.file + ':' + str(token.linenr) + '] Division by zero'Example usage:cppcheck --dump 1.c
python divzero.pyLicensingThe dump file is just a xml file, so it is an open interface
without restrictions. You can use it in any way you need.The cppcheckdata.py is also free to use. No
matter if your project is open source or closed source. Use it for any
purpose.HTML reportYou 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 -hThe output screen says:Usage: cppcheck-htmlreport [options]
Options:
-h, --help show this help message and exit
--file=FILE 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=.Graphical user interfaceIntroductionA Cppcheck GUI is available.The main screen is shown immediately when the GUI is
started.Check source codeUse the Check menu.Inspecting resultsThe 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.SettingsThe language can be changed at any time by using the
Language menu.More settings are available in EditPreferences.Project filesThe project files are used to store project specific settings.
These settings are:include folderspreprocessor definesAs 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.