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.

Chapter 2. Getting started

int main()
{
    char a[10];
    a[10] = 0;
    return 0;
}

cppcheck file1.c

Checking file1.c...
[file1.c:4]: (error) Array 'a[10]' index 10 out of bounds

cppcheck path

Checking path/file1.cpp...
1/2 files checked 50% done
Checking path/file2.cpp...
2/2 files checked 100% done

cppcheck src/a src/b

void f(int x)
{
    int i;
    if (x == 0)
    {
        i = 0;
    }
}

cppcheck --enable=style file3.c

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

cppcheck --enable=unusedFunction path

cppcheck --enable=all path

cppcheck file1.c 2> err.txt

cppcheck -j 4 path

Chapter 3. Preprocessor configurations

By default Cppcheck will check all preprocessor configurations (except those that have #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

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:

<?xml version="1.0"?>
<results>
  <error file="file1.cpp" line="123" id="someError"
               severity="error" msg="some error text"/>
</results>

Attributes:

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

Chapter 6. Suppressions

If you want to filter out certain errors you can suppress these. First you need to create a suppressions file. The format is:

[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.

Here is an example:

memleak:file1.cpp
exceptNew:file1.cpp
uninitvar

You can then use the suppressions file:

cppcheck --suppressions suppressions.txt src/

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.

void foo(int x)
{
    void *f = CreateFred();
    if (x == 1)
        return;
    DestroyFred(f);
}

cppcheck --enable=possibleError fred1.cpp

void *CreateFred()
{
    return malloc(100);
}

void DestroyFred(void *p)
{
    free(p);
}

cppcheck --append=fred.cpp fred1.cpp

Checking fred1.cpp...
[fred1.cpp:5]: (error) Memory leak: f

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

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      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=.

Chapter 10. Graphical user interface