2013-07-14 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.

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

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

To 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/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

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. These suggestions are only based on common knowledge. It is not certain you'll get any measurable difference in speed by fixing these messages. portability portability warnings. 64-bit portability. code might work different on different compilers. etc. information Informational messages about checking problems.

By 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=all Please 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.

By 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 path This 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.

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

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

By 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.c Another useful flag might be -U. It undefines a symbol. Example usage: cppcheck -UX file.c That will mean that X is not defined. Cppcheck will not check what happens when X is defined. Cppcheck 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="1.53"> <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>

Each error is reported in a <error> element. Attributes: id id of error. These are always valid symbolnames. severity either: error, warning, style, performance, portability or information msg the error message in short format verbose the error message in long format. inconclusive This attribute is only used when the message is inconclusive.

All locations related to an error is listed with <location> elements. The primary location is listed first. Attributes: file filename. Both relative and absolute paths are possible line a number msg this attribute doesn't exist yet. But in the future we may add a short message for each location.

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 The following format specifiers are supported: callstack callstack - if available file filename id message id line line number message verbose message text severity severity The escape sequences \b (backspace), \n (newline), \r (formfeed) and \t (horizontal tab) are supported. If you want to filter out certain errors you can suppress these.

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.

The --suppress= command line option is used to specify suppressions on the command line. Example: cppcheck --suppress=memleak:src/file1.cpp src/

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: cppcheck --suppressions suppressions.txt src/

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

You 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>

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. define used to check #define preprocessor statements. raw used to check the preprocessor output. normal used to check the normal token list. There are some simplifications. simple used 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.

The PATTERN is the PCRE-compatible regular expression that will be executed.

The ID specify the user-defined message id.

The SEVERITY must be one of the Cppcheck severities: information, performance, portability, style, warning, or error.

Optional. The summary for the message. If no summary is given, the matching tokens is written.

Cppcheck has internal knowledge about how standard C/C++ functions work. There is no internal knowledge about how all libraries and environments work, and there can't be. Cppcheck can be told how libraries and environments work by using configuration files. The idea is that users will be able to download library configuration files for all popular libraries and environments here: http://cppcheck.sourceforge.net/archive Ideally, all you need to do is choose and download the configuration files you need. The archive is not complete however. If you can't find the configuration file you need in the archive, you can wait - maybe somebody else will write it and share it. Or you can write your own configuration file (and then it's possible to share your configuration file with others). A minimal configuration file looks like this: <?xml version="1.0"?> <def> </def>

Allocation and deallocation is defined using <alloc> and <dealloc>. These are used inside inside <memory> or <resource>. Here is example code: void ok() { char *p = alloc_something(); free_something(p); } void leak() { char *p = alloc_something(); } Cppcheck doesn't normally report any errors for that: # cppcheck test.c Checking test.c... Example configuration: <?xml version="1.0"?> <def> <memory> <alloc>alloc_something</alloc> <dealloc>free_something</dealloc> </memory> </def> That tells Cppcheck that alloc_something allocates memory and that the matching deallocation function is free_something. Output from Cppcheck: # cppcheck --library=something.cfg test.c Checking test.c... [test.c:10]: (error) Memory leak: p

The <ignore> and <use> tells Cppcheck how functions uses allocated memory. Example code: void f() { char *p = alloc_something(); do_something(p); *p = 0; } If you want that the do_something function call is ignored, use <ignore>: <?xml version="1.0"?> <def> <memory> <alloc>alloc_something</alloc> <dealloc>free_something</dealloc> </memory> <ignore>do_something</ignore> </def> Running Cppcheck now: # cppcheck --library=something.cfg test.c Checking test.c... [test.c:10]: (error) Memory leak: pIf the do_something takes the allocated memory and deallocates it later, then use <use> instead: <?xml version="1.0"?> <def> <memory> <alloc>alloc_something</alloc> <dealloc>free_something</dealloc> <use>do_something</use> </memory> </def>Running Cppcheck now: # cppcheck --library=something.cfg test.c Checking test.c... Cppcheck will often assume that functions "use" allocated memory. By using <ignore> you can make Cppcheck detect more errors. By using <use>, no extra errors are detected but Cppcheck will not need to assume.

Some allocation function initialize the data, others don't. Here is a example code: void f() { char *p = alloc_something(); char c = *p; free_something(); } No error is reported: # cppcheck --library=something.cfg test.c Checking test.c... Here is a configuration that tells cppcheck that alloc_something doesn't initialize the data: <?xml version="1.0"?> <def> <memory> <alloc init="false">alloc_something</alloc> <dealloc>free_something</dealloc> </memory> </def> Now you will get this error message: # cppcheck --library=something.cfg test.c Checking test.c... [test.c:4]: (error) Memory is allocated but not initialized: p

You can define if a function parameter can be NULL or if it must be non-NULL. Example code: void do_something(char *p); void f() { do_something(NULL); } Normally no error is reported for that code. But if the do_something() parameter should be non-NULL you can use this configuration: <?xml version="1.0"?> <def> <function name="do_something"> <arg nr="1"> <not-null/> </arg> </function> </def> Now the output from cppcheck is: # cppcheck --library=something.cfg test1.c Checking test1.c... [test1.c:5]: (error) Null pointer dereference

Here is example code: void do_something(char *p); void f() { char str[10]; do_something(str); } Normally Cppcheck doesn't report any error message for that. However if the parameter must be initialized there is a problem. Here is a configuration that says that the parameter must be initialized: <?xml version="1.0"?> <def> <function name="do_something"> <arg nr="1"> <not-uninit/> </arg> </function> </def>Now the cppcheck output is: # cppcheck --library=something.cfg test1.c Checking test1.c... [test1.c:6]: (error) Uninitialized variable: str

You can define if a function is "noreturn" or not. Example code: int f(int x) { int a; if (x == 3) a = 1; else do_something(); return a; // a is uninitialized if do_something() is called and it returns } The output is: # cppcheck test.c Checking test.c... To tell Cppcheck that do_something is not a noreturn function, use such configuration: <?xml version="1.0"?> <def> <function name="do_something"> <noreturn>false</noreturn> </function> </def> Now Cppcheck will be able to detect the error: cppcheck --library=something.cfg test.c Checking test.c... [test.c:8]: (error) Uninitialized variable: a

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 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=.

A Cppcheck GUI is available. The main screen is shown immediately when the GUI is started.

Use the Check menu.

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.

The language can be changed at any time by using the Language menu. More settings are available in Edit Preferences .

The project files are used to store project specific settings. These settings are: include folders preprocessor defines 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.