cppcheck/man/manual.docbook

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<book>
  <bookinfo>
    <title>Cppcheck 1.47</title>

    <date>2011-02-06</date>
  </bookinfo>

  <chapter>
    <title>Introduction</title>

    <para>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.</para>

    <para>Supported code and platforms:</para>

    <itemizedlist>
      <listitem>
        <para>You can check non-standard code that includes various compiler
        extensions, inline assembly code, etc.</para>
      </listitem>

      <listitem>
        <para>Cppcheck should be compilable by any C++ compiler that handles
        the latest C++ standard.</para>
      </listitem>

      <listitem>
        <para>Cppcheck should work on any platform that has sufficient CPU and
        memory.</para>
      </listitem>
    </itemizedlist>

    <para>Accuracy</para>

    <para>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.</para>

    <para>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.</para>
  </chapter>

  <chapter>
    <title>Getting started</title>

    <section>
      <title>First test</title>

      <para>Here is a simple code</para>

      <programlisting>int main()
{
    char a[10];
    a[10] = 0;
    return 0;
}</programlisting>

      <para>If you save that into <filename>file1.c</filename> and
      execute:</para>

      <programlisting>cppcheck file1.c</programlisting>

      <para>The output from cppcheck will then be:</para>

      <programlisting>Checking file1.c...
[file1.c:4]: (error) Array 'a[10]' index 10 out of bounds</programlisting>
    </section>

    <section>
      <title>Checking all files in a folder</title>

      <para>Normally a program has many source files. And you want to check
      them all. Cppcheck can check all source files in a directory:</para>

      <programlisting>cppcheck path</programlisting>

      <para>If "path" is a folder then cppcheck will check all source files in
      this folder.</para>

      <programlisting>Checking path/file1.cpp...
1/2 files checked 50% done
Checking path/file2.cpp...
2/2 files checked 100% done</programlisting>
    </section>

    <section>
      <title>Excluding a file or folder from checking</title>

      <para>To exclude a file or folder, there are two options.</para>

      <para>The first option is to only provide the paths and files you want
      to check.</para>

      <programlisting>cppcheck src/a src/b</programlisting>

      <para>All files under "src/a" and "src/b" are then checked.</para>

      <para>The second option is to use <literal>-i</literal>, with it you
      specify files/paths to ignore. With this command no files in "src/c" are
      checked:</para>

      <programlisting>cppcheck -isrc/c src</programlisting>
    </section>

    <section>
      <title>Severities</title>

      <para>The possible severities for messages are:</para>

      <variablelist>
        <varlistentry>
          <term>error</term>

          <listitem>
            <para>used when bugs are found</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>warning</term>

          <listitem>
            <para>suggestions about defensive programming to prevent
            bugs</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>style</term>

          <listitem>
            <para>stylistic issues related to code cleanup (unused functions,
            redundant code, constness, and such)</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>performance</term>

          <listitem>
            <para>suggestions for making the code faster</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>information</term>

          <listitem>
            <para>Informational messages that might be interesting. Ignore
            these messages unless you really agree.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <remark>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.</remark>
    </section>

    <section>
      <title>Enable messages</title>

      <para>By default only <literal>error</literal> messages are shown.
      Through the <literal>--enable</literal> command more checks can be
      enabled.</para>

      <section>
        <title>Stylistic issues</title>

        <para>With <literal>--enable=style</literal> you enable most
        <literal>warning</literal>, <literal>style</literal> and
        <literal>performance</literal> messages.</para>

        <para>Here is a simple code example:</para>

        <programlisting>void f(int x)
{
    int i;
    if (x == 0)
    {
        i = 0;
    }
}</programlisting>

        <para>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:</para>

        <programlisting>cppcheck --enable=style file3.c</programlisting>

        <para>The output from Cppcheck is now:</para>

        <para><programlisting>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</programlisting></para>
      </section>

      <section>
        <title>Unused functions</title>

        <para>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.</para>

        <programlisting>cppcheck --enable=unusedFunction path</programlisting>
      </section>

      <section>
        <title>Enable all checks</title>

        <para>To enable all checks your can use the
        <literal>--enable=all</literal> flag:</para>

        <programlisting>cppcheck --enable=all path</programlisting>
      </section>
    </section>

    <section>
      <title>Saving results in file</title>

      <para>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.</para>

      <programlisting>cppcheck file1.c 2&gt; err.txt</programlisting>
    </section>

    <section>
      <title>Multithreaded checking</title>

      <para>To use 4 threads to check the files in a folder:</para>

      <programlisting>cppcheck -j 4 path</programlisting>
    </section>
  </chapter>

  <chapter>
    <title>Preprocessor configurations</title>

    <para>By default Cppcheck will check all preprocessor configurations
    (except those that has #error in them). This is the recommended
    behaviour.</para>

    <para>But if you want to manually limit the checking you can do so with
    <literal>-D</literal>.</para>

    <para>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.</para>

    <para>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:</para>

    <programlisting>cppcheck -DDEBUG=1 -D__cplusplus path</programlisting>
  </chapter>

  <chapter>
    <title>XML output</title>

    <para>Cppcheck can generate the output in XML format.</para>

    <para>Use the --xml flag when you execute cppcheck:</para>

    <programlisting>cppcheck --xml file1.cpp</programlisting>

    <para>The XML format is:</para>

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

    <para>Attributes:</para>

    <variablelist>
      <varlistentry>
        <term>file</term>

        <listitem>
          <para>filename. Both relative and absolute paths are possible</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>line</term>

        <listitem>
          <para>a number</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>id</term>

        <listitem>
          <para>id of error. These are always valid symbolnames.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>severity</term>

        <listitem>
          <para>either <literal>error</literal> or <literal>style</literal>.
          <literal>warning</literal> and <literal>performance</literal> are
          saved as <literal>style</literal>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>msg</term>

        <listitem>
          <para>the error message</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Reformatting the output</title>

    <para>If you want to reformat the output so it looks different you can use
    templates.</para>

    <para>To get Visual Studio compatible output you can use "--template
    vs":</para>

    <programlisting>cppcheck --template vs gui/test.cpp</programlisting>

    <para>This output will look like this:</para>

    <programlisting>Checking gui/test.cpp...
gui/test.cpp(31): error: Memory leak: b
gui/test.cpp(16): error: Mismatching allocation and deallocation: k</programlisting>

    <para>To get gcc compatible output you can use "--template gcc":</para>

    <programlisting>cppcheck --template gcc gui/test.cpp</programlisting>

    <para>The output will look like this:</para>

    <programlisting>Checking gui/test.cpp...
gui/test.cpp:31: error: Memory leak: b
gui/test.cpp:16: error: Mismatching allocation and deallocation: k</programlisting>

    <para>You can write your own pattern (for example a comma-separated
    format):</para>

    <programlisting>cppcheck --template "{file},{line},{severity},{id},{message}" gui/test.cpp</programlisting>

    <para>The output will look like this:</para>

    <programlisting>Checking gui/test.cpp...
gui/test.cpp,31,error,memleak,Memory leak: b
gui/test.cpp,16,error,mismatchAllocDealloc,Mismatching allocation and deallocation: k</programlisting>

    <para></para>
  </chapter>

  <chapter>
    <title>Suppressions</title>

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

    <programlisting>[error id]:[filename]:[line]
[error id]:[filename2]
[error id]</programlisting>

    <para>The <literal>error id</literal> is the id that you want to suppress.
    The easiest way to get it is to use the <literal>--xml</literal> command
    line flag. Copy and paste the <literal>id</literal> string from the XML
    output.</para>

    <para>Here is an example:</para>

    <programlisting>memleak:file1.cpp
exceptNew:file1.cpp
uninitvar</programlisting>

    <para>You can then use the suppressions file:</para>

    <programlisting>cppcheck --suppressions suppressions.txt src/</programlisting>

    <para></para>
  </chapter>

  <chapter>
    <title>Leaks</title>

    <para>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.</para>

    <section>
      <title>User-defined allocation/deallocation functions</title>

      <para><literal>Cppcheck</literal> understands many common allocation and
      deallocation functions. But not all.</para>

      <para>Here is example code that might leak memory or resources:</para>

      <para><programlisting>void foo(int x)
{
    void *f = CreateFred();
    if (x == 1)
        return;
    DestroyFred(f);
}</programlisting></para>

      <para>If you analyse that with Cppcheck it won't find any leaks:</para>

      <programlisting>cppcheck --enable=possibleError fred1.cpp</programlisting>

      <para>You can add some custom leaks checking by providing simple
      implementations for the allocation and deallocation functions. Write
      this in a separate file:</para>

      <programlisting>void *CreateFred()
{
    return malloc(100);
}

void DestroyFred(void *p)
{
    free(p);
}</programlisting>

      <para>When Cppcheck see this it understands that CreateFred will return
      allocated memory and that DestroyFred will deallocate memory.</para>

      <para>Now, execute <literal>Cppcheck</literal> this way:</para>

      <programlisting>cppcheck --append=fred.cpp fred1.cpp</programlisting>

      <para>The output from cppcheck is:</para>

      <programlisting>Checking fred1.cpp...
[fred1.cpp:5]: (error) Memory leak: f</programlisting>
    </section>
  </chapter>

  <chapter>
    <title>Exception safety</title>

    <para>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.</para>

    <para>Example:</para>

    <programlisting>Fred::Fred() : a(new int[20]), b(new int[20])
{
}</programlisting>

    <para>By default cppcheck will not detect any problems in that
    code.</para>

    <para>To enable the exception safety checking you can use
    <literal>--enable</literal>:</para>

    <programlisting>cppcheck --enable=exceptNew --enable=exceptRealloc fred.cpp</programlisting>

    <para>The output will be:</para>

    <programlisting>[fred.cpp:3]: (style) Upon exception there is memory leak: a</programlisting>

    <para>If an exception occurs when <literal>b</literal> is allocated,
    <literal>a</literal> will leak.</para>

    <para>Here is another example:</para>

    <programlisting>int *p;

int a(int sz)
{
    delete [] p;
    if (sz &lt;= 0)
        throw std::runtime_error("size &lt;= 0");
    p = new int[sz];
}</programlisting>

    <para>Check that with Cppcheck:</para>

    <programlisting>cppcheck --enable=exceptNew --enable=exceptRealloc except2.cpp</programlisting>

    <para>The output from Cppcheck is:</para>

    <programlisting>[except2.cpp:7]: (error) Throwing exception in invalid state, p points at deallocated memory</programlisting>
  </chapter>

  <chapter>
    <title>HTML report</title>

    <para>You can convert the XML output from cppcheck into a HTML report.
    You'll need Python and the pygments module
    (<uri>http://pygments.org/</uri>) 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.</para>

    <para>This command generates the help screen:</para>

    <para><programlisting>htmlreport/cppcheck-htmlreport -h</programlisting></para>

    <para>The output screen says:</para>

    <para><programlisting>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.</programlisting></para>

    <para>An example usage:</para>

    <programlisting>./cppcheck gui/test.cpp --xml 2&gt; err.xml
htmlreport/cppcheck-htmlreport --file=err.xml --report-dir=test1 --source-dir=.</programlisting>
  </chapter>

  <chapter>
    <title>Graphical user interface</title>

    <section>
      <title>Introduction</title>

      <para>A Cppcheck GUI is available.</para>

      <para>The main screen is shown immediately when the GUI is
      started.</para>
    </section>

    <section>
      <title>Check source code</title>

      <para>Use the <literal>Check</literal> menu.</para>
    </section>

    <section>
      <title>Inspecting results</title>

      <para>The results are shown in a list.</para>

      <para>You can show/hide certain types of messages through the
      <literal>View</literal> menu.</para>

      <para>Results can be saved to an XML file that can later be opened. See
      <literal>Save results to file</literal> and <literal>Open
      XML</literal>.</para>
    </section>

    <section>
      <title>Settings</title>

      <para>The language can be changed at any time by using the
      <literal>Language</literal> menu.</para>

      <para>More settings are available in
      <literal>Edit</literal>&gt;<literal>Preferences</literal>.</para>
    </section>

    <section>
      <title>Project files</title>

      <para>The project files are used to store project specific settings.
      These settings are:</para>

      <itemizedlist>
        <listitem>
          <para>include folders</para>
        </listitem>

        <listitem>
          <para>preprocessor defines</para>
        </listitem>
      </itemizedlist>

      <para>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.</para>

      <para>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.</para>
    </section>
  </chapter>
</book>