cppcheck/man/manual.docbook

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<book>
  <bookinfo>
    <title>Cppcheck 1.73</title>

    <date>2015-09-09</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. Instead,
    Cppcheck 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>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 recursively 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. 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 <filename class="directory">src/a</filename> and
      <filename class="directory">src/b</filename> are then checked.</para>

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

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

    <section>
      <title>Include paths</title>

      <para>To add an include path, use <parameter
      class="command">-I</parameter>, followed by the path.</para>

      <para>Cppcheck's preprocessor basically handles includes like any other
      preprocessor. However, while other preprocessors stop working when they
      encounter a missing header, cppcheck will just print an information
      message and continues parsing the code.</para>

      <para>The purpose of this behaviour is that cppcheck is meant to work
      without necessarily seeing the entire code. Actually, it is recommended
      to not give all include paths. While it is useful for cppcheck to see
      the declaration of a class when checking the implementation of its
      members, passing standard library headers is highly discouraged because
      it will result in worse results and longer checking time. For such
      cases, .cfg files (see below) are the better way to provide information
      about the implementation of functions and types to cppcheck.</para>
    </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. These suggestions
            are only based on common knowledge. It is not certain you'll get
            any measurable difference in speed by fixing these
            messages.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>portability</term>

          <listitem>
            <para>portability warnings. 64-bit portability. code might work
            different on different compilers. etc.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>information</term>

          <listitem>
            <para>Configuration problems. The recommendation is to only enable
            these during configuration.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

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

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

      <programlisting># 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 performance messages
cppcheck --enable=warning,performance 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</programlisting>

      <para>Please note that <literal>--enable=unusedFunction</literal> should
      only be used when the whole program is scanned. Therefore,
      <literal>--enable=all</literal> 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.</para>

      <section>
        <title>Inconclusive checks</title>

        <para>By default Cppcheck only writes error messages if it is certain.
        With <parameter class="command">--inconclusive</parameter> error
        messages will also be written when the analysis is
        inconclusive.</para>

        <programlisting>cppcheck --inconclusive path</programlisting>

        <para>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.</para>
      </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>The option <literal>-j</literal> 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:</para>

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

      <para>Please note that this will disable unusedFunction checking.</para>
    </section>

    <section>
      <title>Platform</title>

      <para>You should use a platform configuration that match your
      target.</para>

      <para>By default Cppcheck uses native platform configuration that works
      well if your code is compiled and executed locally.</para>

      <para>Cppcheck has builtin configurations for <literal>unix</literal>
      and <literal>windows</literal> targets. You can easily use these with
      the <literal>--platform</literal> command line flag.</para>

      <para>You can also create your own custom platform configuration in a
      xml file. Here is an example:</para>

      <programlisting>&lt;?xml version="1"?&gt;
&lt;platform&gt;
  &lt;char_bit&gt;8&lt;/char_bit&gt;
  &lt;default-sign&gt;signed&lt;/default-sign&gt;
  &lt;sizeof&gt;
    &lt;short&gt;2&lt;/short&gt;
    &lt;int&gt;4&lt;/int&gt;
    &lt;long&gt;4&lt;/long&gt;
    &lt;long-long&gt;8&lt;/long-long&gt;
    &lt;float&gt;4&lt;/float&gt;
    &lt;double&gt;8&lt;/double&gt;
    &lt;long-double&gt;12&lt;/long-double&gt;
    &lt;pointer&gt;4&lt;/pointer&gt;
    &lt;size_t&gt;4&lt;/size_t&gt;
    &lt;wchar_t&gt;2&lt;/wchar_t&gt;
  &lt;/sizeof&gt;
&lt;/platform&gt;</programlisting>
    </section>
  </chapter>

  <chapter id="preprocessor-configurations">
    <title>Preprocessor configurations</title>

    <para>By default Cppcheck will check all preprocessor configurations
    (except those that have #error in them).</para>

    <para>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 <literal>--force</literal> or
    <literal><literal>--max-configs</literal></literal> to override the number
    of configurations.</para>

    <programlisting># 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</programlisting>

    <para>Another useful flag might be -U. It undefines a symbol. Example
    usage:</para>

    <programlisting>cppcheck -UX file.c</programlisting>

    <para>That will mean that X is not defined. Cppcheck will not check what
    happens when X is defined.</para>
  </chapter>

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

    <para>Cppcheck can generate output in <literal>XML</literal> format. There
    is an old <literal>XML</literal> format (version 1) and a new
    <literal>XML</literal> format (version 2). Please use the new version if
    you can.</para>

    <para>The old version is kept for backwards compatibility only. It will
    not be changed, but it will likely be removed someday. Use
    <parameter>--xml</parameter> to enable this format.</para>

    <para>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 <literal>XML</literal> format:</para>

    <programlisting>cppcheck --xml-version=2 file1.cpp</programlisting>

    <para>Here is a sample version 2 report:</para>

    <programlisting>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;results version="2"&gt;
  &lt;cppcheck version="1.66"&gt;
  &lt;errors&gt;
    &lt;error id="someError" severity="error" msg="short error text"
           verbose="long error text" inconclusive="true" cwe="312"&gt;
      &lt;location file="file.c" line="1"/&gt;
    &lt;/error&gt;
  &lt;/errors&gt;
&lt;/results&gt;</programlisting>

    <section>
      <title>The &lt;error&gt; element</title>

      <para>Each error is reported in a <literal>&lt;error&gt;</literal>
      element. Attributes:</para>

      <variablelist>
        <varlistentry>
          <term><sgmltag class="attribute">id</sgmltag></term>

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

        <varlistentry>
          <term><sgmltag class="attribute">severity</sgmltag></term>

          <listitem>
            <para>either: <literal>error</literal>,
            <literal>warning</literal>, <literal>style</literal>,
            <literal>performance</literal>, <literal>portability</literal> or
            <literal>information</literal></para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><sgmltag class="attribute">msg</sgmltag></term>

          <listitem>
            <para>the error message in short format</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><sgmltag>verbose</sgmltag></term>

          <listitem>
            <para>the error message in long format.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><sgmltag>inconclusive</sgmltag></term>

          <listitem>
            <para>This attribute is only used when the message is
            inconclusive.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><sgmltag>cwe</sgmltag></term>

          <listitem>
            <para>CWE ID for message. This attribute is only used when the CWE
            ID for the message is known.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section>
      <title>The &lt;location&gt; element</title>

      <para>All locations related to an error is listed with
      <literal>&lt;location&gt;</literal> elements. The primary location is
      listed first.</para>

      <para>Attributes:</para>

      <variablelist>
        <varlistentry>
          <term><sgmltag class="attribute">file</sgmltag></term>

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

        <varlistentry>
          <term><sgmltag class="attribute">line</sgmltag></term>

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

        <varlistentry>
          <term><sgmltag>msg</sgmltag></term>

          <listitem>
            <para>this attribute doesn't exist yet. But in the future we may
            add a short message for each location.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
  </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 <parameter
    class="command">--template=vs</parameter>:</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 <parameter
    class="command">--template=gcc</parameter>:</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>The following format specifiers are supported:</para>

    <variablelist>
      <varlistentry>
        <term>callstack</term>

        <listitem>
          <para>callstack - if available</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>file</term>

        <listitem>
          <para>filename</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>id</term>

        <listitem>
          <para>message id</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>line</term>

        <listitem>
          <para>line number</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>message</term>

        <listitem>
          <para>verbose message text</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>severity</term>

        <listitem>
		<para>a type/rank of message</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>The escape sequences \b (backspace), \n (newline), \r (formfeed) and
    \t (horizontal tab) are supported.</para>
  </chapter>

  <chapter>
    <title>Suppressions</title>

    <para>If you want to filter out certain errors you can suppress
    these.</para>

    <section>
      <title>Suppressing a certain error type</title>

      <para>You can suppress certain types of errors. The format for such a
      suppression is one of:</para>

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

      <para>The <replaceable>error id</replaceable> is the id that you want to
      suppress. The easiest way to get it is to use the <parameter
      class="command">--xml</parameter> command line flag. Copy and paste the
      <replaceable>id</replaceable> string from the XML output. This may be
      <literal>*</literal> to suppress all warnings (for a specified file or
      files).</para>

      <para>The <replaceable>filename</replaceable> may include the wildcard
      characters <literal>*</literal> or <literal>?</literal>, which match any
      sequence of characters or any single character respectively. It is
      recommended that you use "/" as path separator on all operating
      systems.</para>

      <section>
        <title>Command line suppression</title>

        <para>The <parameter class="command">--suppress=</parameter> command
        line option is used to specify suppressions on the command line.
        Example:</para>

        <programlisting>cppcheck --suppress=memleak:src/file1.cpp src/</programlisting>
      </section>

      <section>
        <title>Listing suppressions in a file</title>

        <para>You can create a suppressions file. Example:</para>

        <programlisting>// 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</programlisting>

        <para>Note that you may add empty lines and comments in the
        suppressions file.</para>

        <para>You can use the suppressions file like this:</para>

        <programlisting>cppcheck --suppressions-list=suppressions.txt src/</programlisting>
      </section>
    </section>

    <section>
      <title>Inline suppressions</title>

      <para>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.</para>

      <para>This code will normally generate an error message:</para>

      <programlisting>void f() {
    char arr[5];
    arr[10] = 0;
}</programlisting>

      <para>The output is:</para>

      <programlisting># cppcheck test.c
Checking test.c...
[test.c:3]: (error) Array 'arr[5]' index 10 out of bounds</programlisting>

      <para>To suppress the error message, a comment can be added:</para>

      <programlisting>void f() {
    char arr[5];

    // cppcheck-suppress arrayIndexOutOfBounds
    arr[10] = 0;
}</programlisting>

      <para>Now the --inline-suppr flag can be used to suppress the warning.
      No error is reported when invoking cppcheck this way:</para>

      <programlisting>cppcheck --inline-suppr test.c</programlisting>
    </section>
  </chapter>

  <chapter>
    <title>Library configuration</title>

    <para>When external libraries are used, such as windows/posix/gtk/qt/etc,
    <literal>Cppcheck</literal> doesn't know how the external functions
    behave. <literal>Cppcheck</literal> then fails to detect various problems
    such as leaks, buffer overflows, possible null pointer dereferences, etc.
    But this can be fixed with configuration files.</para>

    <para>If you create a configuration file for a popular library, we would
    appreciate if you upload it to us.</para>

    <section>
      <title>Using your own custom .cfg file</title>

      <para>You can create and use your own .cfg files for your projects. Use
      <literal>--check-library</literal> and
      <literal>--enable=information</literal> to get hints about what you
      should configure.</para>

      <para>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.</para>

      <para>The cppcheck GUI will try to load custom .cfg files from the
      project file path. The custom .cfg files should be shown in the
      <literal>Edit Project File</literal> dialog that you open from the
      <literal>File</literal> menu.</para>
    </section>

    <section>
      <title>Memory/resource leaks</title>

      <para>Cppcheck has configurable checking for leaks.</para>

      <section>
        <title>alloc and dealloc</title>

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

        <para><programlisting>void test()
{
    HPEN pen = CreatePen(PS_SOLID, 1, RGB(255,0,0));
}</programlisting></para>

        <para>The code example above has a resource leak -
        <literal>CreatePen()</literal> 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:</para>

        <programlisting># cppcheck pen1.c
Checking pen1.c...</programlisting>

        <para>If you provide a windows configuration file then
        <literal>Cppcheck</literal> detects the bug:</para>

        <programlisting># cppcheck --library=windows.cfg pen1.c
Checking pen1.c...
[pen1.c:3]: (error) Resource leak: pen</programlisting>

        <para>Here is a minimal <literal>windows.cfg</literal> file:</para>

        <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;resource&gt;
    &lt;alloc&gt;CreatePen&lt;/alloc&gt;
    &lt;dealloc&gt;DeleteObject&lt;/dealloc&gt;
  &lt;/resource&gt;
&lt;/def&gt;</programlisting>
      </section>

      <section>
        <title>leak-ignore and use</title>

        <para>Often the allocated pointer is passed to functions.
        Example:</para>

        <programlisting>void test()
{
    char *p = malloc(100);
    dostuff(p);
}</programlisting>

        <para>If Cppcheck doesn't know what <literal>dostuff</literal> does,
        without configuration it will assume that <literal>dostuff</literal>
        takes care of the memory so there is no memory leak.</para>

        <para>To specify that <literal>dostuff</literal> doesn't take care of
        the memory in any way, use <literal>leak-ignore</literal>:</para>

        <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="dostuff"&gt;
    &lt;leak-ignore/&gt;
    &lt;arg nr="1"/&gt;
    &lt;arg nr="2"/&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>

        <para>If instead <literal>dostuff</literal> takes care of the memory
        then this can be configured with:</para>

        <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;memory&gt;
    &lt;alloc&gt;malloc&lt;/alloc&gt;
    &lt;dealloc&gt;free&lt;/dealloc&gt;
    &lt;use&gt;dostuff&lt;/use&gt;
  &lt;/memory&gt;
&lt;/def&gt;</programlisting>

        <para>The <literal><literal>&lt;use&gt;</literal></literal>
        configuration has no logical purpose. You will get the same warnings
        without it. Use it to silence <literal>--check-library</literal>
        information messages.</para>
      </section>
    </section>

    <section>
      <title>Function argument: Uninitialized memory</title>

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

      <programlisting>void test()
{
    char buffer1[1024];
    char buffer2[1024];
    CopyMemory(buffer1, buffer2, 1024);
}</programlisting>

      <para>The bug here is that buffer2 is uninitialized. The second argument
      for CopyMemory needs to be initialized. However
      <literal>Cppcheck</literal> assumes that it is fine to pass
      uninitialized variables to functions:</para>

      <programlisting># cppcheck uninit.c 
Checking uninit.c...</programlisting>

      <para>If you provide a windows configuration file then Cppcheck detects
      the bug:</para>

      <programlisting># cppcheck --library=windows.cfg uninit.c 
Checking uninit.c...
[uninit.c:5]: (error) Uninitialized variable: buffer2</programlisting>

      <para>Here is the minimal <literal>windows.cfg</literal>:</para>

      <para><programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="CopyMemory"&gt;
    &lt;arg nr="1"/&gt;
    &lt;arg nr="2"&gt;
      &lt;not-uninit/&gt;
    &lt;/arg&gt;
    &lt;arg nr="3"/&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting></para>
    </section>

    <section>
      <title>Function Argument: Null pointers</title>

      <para>Cppcheck assumes it's ok to pass NULL pointers to functions. Here
      is an example program:</para>

      <programlisting>void test()
{
    CopyMemory(NULL, NULL, 1024);
}</programlisting>

      <para>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:</para>

      <programlisting># cppcheck null.c 
Checking null.c...</programlisting>

      <para>If you provide a windows configuration file then
      <literal>Cppcheck</literal> detects the bug:</para>

      <programlisting>cppcheck --library=windows.cfg null.c 
Checking null.c...
[null.c:3]: (error) Null pointer dereference</programlisting>

      <para>Here is a minimal <literal>windows.cfg</literal> file:</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="CopyMemory"&gt;
    &lt;arg nr="1"&gt;
      &lt;not-null/&gt;
    &lt;/arg&gt;
    &lt;arg nr="2"/&gt;
    &lt;arg nr="3"/&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>
    </section>

    <section>
      <title>Function Argument: Format string</title>

      <para>You can define that a function takes a format string.
      Example:</para>

      <programlisting>void test()
{
    do_something("%i %i\n", 1024);
}</programlisting>

      <para>No error is reported for that:</para>

      <programlisting># cppcheck formatstring.c 
Checking formatstring.c...</programlisting>

      <para>A configuration file can be created that says that the string is a
      format string. For instance:</para>

      <para><programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="do_something"&gt;
    &lt;formatstr type="printf"/&gt;
    &lt;arg nr="1"&gt;
      &lt;formatstr/&gt;
    &lt;/arg&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>Now Cppcheck will report an error:</para>

      <programlisting>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.</programlisting>

      <para>The <literal>type</literal> attribute can be either:</para>

      <itemizedlist>
        <listitem>
          <para>printf - format string follows the printf rules</para>
        </listitem>

        <listitem>
          <para>scanf - format string follows the scanf rules</para>
        </listitem>
      </itemizedlist>
    </section>

    <section>
      <title>Function Argument: Value range</title>

      <para>The valid values can be defined. Imagine:</para>

      <programlisting>void test()
{
    do_something(1024);
}</programlisting>

      <para>No error is reported for that:</para>

      <programlisting># cppcheck valuerange.c 
Checking valuerange.c...</programlisting>

      <para>A configuration file can be created that says that 1024 is out of
      bounds. For instance:</para>

      <para><programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="do_something"&gt;
    &lt;arg nr="1"&gt;
      &lt;valid&gt;0:1023&lt;/valid&gt;
    &lt;/arg&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>Now Cppcheck will report an error:</para>

      <programlisting>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'.</programlisting>

      <para>Some example expressions you can use in the valid element:</para>

      <programlisting>0,3,5  =&gt; only values 0, 3 and 5 are valid
-10:20  =&gt;  all values between -10 and 20 are valid
:0  =&gt;  all values that are less or equal to 0 are valid
0:  =&gt;  all values that are greater or equal to 0 are valid
0,2:32  =&gt;  the value 0 and all values between 2 and 32 are valid </programlisting>
    </section>

    <section>
      <title>Function Argument: minsize</title>

      <para>Some function arguments take a buffer. With minsize you can
      configure the min size of the buffer (in bytes, not elements).
      Imagine:</para>

      <programlisting>void test()
{
    char str[5];
    do_something(str,"12345");
}</programlisting>

      <para>No error is reported for that:</para>

      <programlisting># cppcheck minsize.c 
Checking minsize.c...</programlisting>

      <para>A configuration file can for instance be created that says that
      the size of the buffer in argument 1 must be larger than the strlen of
      argument 2.For instance:</para>

      <para><programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="do_something"&gt;
    &lt;arg nr="1"&gt;
      &lt;minsize type="strlen" arg="2"/&gt;
    &lt;/arg&gt;
    &lt;arg nr="2"/&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>Now Cppcheck will report this error:</para>

      <programlisting>cppcheck --library=1.cfg minsize.c
Checking minsize.c...
[minsize.c:4]: (error) Buffer is accessed out of bounds: str
</programlisting>

      <para>There are different types of minsizes:</para>

      <variablelist>
        <varlistentry>
          <term>strlen</term>

          <listitem>
            <para>buffer size must be larger than other arguments string
            length. Example: see strcpy configuration in std.cfg</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>argvalue</term>

          <listitem>
            <para>buffer size must be larger than value in other argument.
            Example: see memset configuration in std.cfg</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>sizeof</term>

          <listitem>
            <para>buffer size must be larger than other argument buffer size.
            Example: see strncpy configuration in std.cfg</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>mul</term>

          <listitem>
            <para>buffer size must be larger than multiplication result when
            multiplying values given in two other arguments. Typically one
            argument defines the element size and another element defines the
            number of elements. Example: see fread configuration in
            std.cfg</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section>
      <title>noreturn</title>

      <para>Cppcheck doesn't assume that functions always return. Here is an
      example code:</para>

      <programlisting>void test(int x)
{
    int data, buffer[1024];
    if (x == 1)
        data = 123;
    else
        ZeroMemory(buffer, sizeof(buffer));
    buffer[0] = data;  // &lt;- error: data is uninitialized if x is not 1
}</programlisting>

      <para>In theory, if <literal>ZeroMemory</literal> terminates the program
      then there is no bug. Cppcheck therefore reports no error:</para>

      <programlisting># cppcheck noreturn.c 
Checking noreturn.c...</programlisting>

      <para>However if you use <literal>--check-library</literal> and
      <literal>--enable=information</literal> you'll get this:</para>

      <programlisting># cppcheck --check-library --enable=information noreturn.c 
Checking noreturn.c...
[noreturn.c:7]: (information) --check-library: Function ZeroMemory() should have &lt;noreturn&gt; configuration
</programlisting>

      <para>If a proper <literal>windows.cfg</literal> is provided, the bug is
      detected:</para>

      <programlisting># cppcheck --library=windows.cfg noreturn.c 
Checking noreturn.c...
[noreturn.c:8]: (error) Uninitialized variable: data</programlisting>

      <para>Here is a minimal <literal>windows.cfg</literal> file:</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="ZeroMemory"&gt;
    &lt;noreturn&gt;false&lt;/noreturn&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>
    </section>

    <section>
      <title>use-retval</title>

      <para>As long as nothing else is specified, cppcheck assumes that
      ignoring the return value of a function is ok:</para>

      <programlisting>bool test(const char* a, const char* b)
{
    strcmp(a, b);  // &lt;- bug: The call of strcmp does not have side-effects, but the return value is ignored.
    return true;
}</programlisting>

      <para>In case <literal>strcmp</literal> has side effects, such as
      assigning the result to one of the parameters passed to it, nothing bad
      would happen:</para>

      <programlisting># cppcheck useretval.c 
Checking useretval.c...</programlisting>

      <para>If a proper <literal>lib.cfg</literal> is provided, the bug is
      detected:</para>

      <programlisting># cppcheck --library=lib.cfg --enable=warning useretval.c 
Checking useretval.c...
[noreturn.c:3]: (warning) Return value of function strcmp() is not used.</programlisting>

      <para>Here is a minimal <literal>lib.cfg</literal> file:</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;function name="strcmp"&gt;
    &lt;use-retval/&gt;
  &lt;/function&gt;
&lt;/def&gt;</programlisting>
    </section>

    <section>
      <title>define</title>

      <para>Libraries can be used to define preprocessor macros as well. For
      example:</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;define name="NULL_VALUE" value="0"/&gt;
&lt;/def&gt;</programlisting>

      <para>Each occurrence of "NULL_VALUE" in the code would then be replaced
      by "0" at preprocessor stage.</para>
    </section>

    <section>
      <title>podtype</title>

      <para>Lots of code relies on typedefs providing platform independent
      types. "podtype"-tags can be used to provide necessary information to
      cppcheck to support them. Without further information, cppcheck does not
      understand the type "uint16_t" in the following example:</para>

      <programlisting>void test() {
    uint16_t a;
}</programlisting>

      <para>No message about variable 'a' being unused is printed:</para>

      <programlisting># cppcheck --enable=style unusedvar.cpp 
Checking unusedvar.cpp...</programlisting>

      <para>If uint16_t is defined in a library as follows, the result
      improves:</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;podtype name="uint16_t" sign="u" size="2"/&gt;
&lt;/def&gt;</programlisting>

      <para>The size of the type is specified in bytes. Possible values for
      the "sign" attribute are "s" (signed) and "u" (unsigned). Both
      attributes are optional. Using this library, cppcheck prints:</para>

      <programlisting># cppcheck --library=lib.cfg --enable=style unusedvar.cpp 
Checking unusedvar.cpp...
[unusedvar.cpp:2]: (style) Unused variable: a</programlisting>
    </section>

    <section>
      <title>container</title>

      <para>A lot of C++ libraries, among those the STL itself, provide
      containers with very similar functionality. Libraries can be used to
      tell cppcheck about their behaviour. Each container needs a unique ID.
      It can optionally have a startPattern, which must be a valid
      Token::Match pattern and an endPattern that is compared to the linked
      token of the first token with such a link. The optional attribute
      "inherits" takes an ID from a previously defined container.</para>

      <para>Inside the &lt;container&gt; tag, functions can be defined inside
      of the tags &lt;size&gt;, &lt;access&gt; and &lt;other&gt; (on your
      choice). Each of them can specify an action like "resize" and/or the
      result it yields, for example "end-iterator".</para>

      <para>The following example provides a definition for std::vector, based
      on the definition of "stdContainer" (not shown):</para>

      <programlisting>&lt;?xml version="1.0"?&gt;
&lt;def&gt;
  &lt;container id="stdVector" startPattern="std :: vector &amp;lt;" inherits="stdContainer"&gt;
    &lt;size&gt;
      &lt;function name="push_back" action="push"/&gt;
      &lt;function name="pop_back" action="pop"/&gt;
    &lt;/size&gt;
    &lt;access indexOperator="array-like"&gt;
      &lt;function name="at" yields="at_index"/&gt;
      &lt;function name="front" yields="item"/&gt;
      &lt;function name="back" yields="item"/&gt;
    &lt;/access&gt;
  &lt;/container&gt;
&lt;/def&gt;</programlisting>
    </section>

    <section>
      <title>Example configuration for strcpy()</title>

      <para>The proper configuration for the standard strcpy() function would
      be:</para>

      <programlisting>  &lt;function name="strcpy"&gt;
    &lt;leak-ignore/&gt;
    &lt;noreturn&gt;false&lt;/noreturn&gt;
    &lt;arg nr="1"&gt;
      &lt;not-null/&gt;
    &lt;/arg&gt;
    &lt;arg nr="2"&gt;
      &lt;not-null/&gt;
      &lt;not-uninit/&gt;
      &lt;strz/&gt;
    &lt;/arg&gt;
  &lt;/function&gt;</programlisting>

      <para>The <literal>&lt;leak-ignore/&gt;</literal> tells Cppcheck to
      ignore this function call in the leaks checking. Passing allocated
      memory to this function won't mean it will be deallocated.</para>

      <para>The <literal>&lt;noreturn&gt;</literal> tells Cppcheck if this
      function returns or not.</para>

      <para>The first argument that the function takes is a pointer. It must
      not be a null pointer, therefore <literal>&lt;not-null&gt;</literal> is
      used.</para>

      <para>The second argument the function takes is a pointer. It must not
      be null. And it must point at initialized data. Using
      <literal>&lt;not-null&gt;</literal> and
      <literal>&lt;not-uninit&gt;</literal> is correct. Moreover it must point
      at a zero-terminated string so &lt;strz&gt; is also used.</para>
    </section>

    <section>
      <title>Specifications for all arguments</title>

      <para>Specifying <literal>-1</literal> as the argument number is going
      to apply a check to all arguments of that function. The specifications
      for individual arguments override this setting.</para>
    </section>
  </chapter>

  <chapter>
    <title>Rules</title>

    <para>You can define custom rules using regular expressions.</para>

    <para>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.</para>

    <para>To get started writing rules, see the related articles here:</para>

    <para><ulink
    url="http://sourceforge.net/projects/cppcheck/files/Articles/">http://sourceforge.net/projects/cppcheck/files/Articles/</ulink></para>

    <para>The file format for rules is:</para>

    <programlisting>&lt;?xml version="1.0"?&gt;
&lt;rule&gt;
  &lt;tokenlist&gt;LIST&lt;/tokenlist&gt;
  &lt;pattern&gt;PATTERN&lt;/pattern&gt;
  &lt;message&gt;
    &lt;id&gt;ID&lt;/id&gt;
    &lt;severity&gt;SEVERITY&lt;/severity&gt;
    &lt;summary&gt;SUMMARY&lt;/summary&gt;
  &lt;/message&gt;
&lt;/rule&gt;</programlisting>

    <para>CDATA can be used to include characters in a pattern that might
    interfere with XML:</para>

    <programlisting>&lt;![CDATA[some&lt;strange&gt;pattern]]&gt;</programlisting>

    <section>
      <title>&lt;tokenlist&gt;</title>

      <para>The <literal>&lt;tokenlist&gt;</literal> element is optional. With
      this element you can control what tokens are checked. The
      <literal>LIST</literal> can be either <literal>define</literal>,
      <literal>raw</literal>, <literal>normal</literal> or
      <literal>simple</literal>.</para>

      <variablelist>
        <varlistentry>
          <term>define</term>

          <listitem>
            <para>used to check #define preprocessor statements.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>raw</term>

          <listitem>
            <para>used to check the preprocessor output.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>normal</term>

          <listitem>
            <para>used to check the <literal>normal</literal> token list.
            There are some simplifications.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>simple</term>

          <listitem>
            <para>used to check the simple token list. All simplifications are
            used. Most Cppcheck checks use the simple token list.</para>
          </listitem>
        </varlistentry>
      </variablelist>

      <para>If there is no &lt;tokenlist&gt; element then
      <literal>simple</literal> is used automatically.</para>
    </section>

    <section>
      <title>&lt;pattern&gt;</title>

      <para>The <literal>PATTERN</literal> is the
      <literal>PCRE</literal>-compatible regular expression that will be
      executed.</para>
    </section>

    <section>
      <title>&lt;id&gt;</title>

      <para>The ID specify the user-defined message id.</para>
    </section>

    <section>
      <title>&lt;severity&gt;</title>

      <para>The <literal>SEVERITY</literal> must be one of the
      <literal>Cppcheck</literal> severities: <literal>information</literal>,
      <literal>performance</literal>, <literal>portability</literal>,
      <literal>style</literal>, <literal>warning</literal>, or
      <literal>error</literal>.</para>
    </section>

    <section>
      <title>&lt;summary&gt;</title>

      <para>Optional. The summary for the message. If no summary is given, the
      matching tokens is written.</para>
    </section>
  </chapter>

  <chapter>
    <title>Cppcheck addons</title>

    <para>Cppcheck addons are implemented as standalone scripts or programs.
    With Cppcheck addons, you can for instance:</para>

    <itemizedlist>
      <listitem>
        <para>add extra custom checkers that use sophisticated analysis</para>
      </listitem>

      <listitem>
        <para>visualize your code</para>
      </listitem>

      <listitem>
        <para>etc</para>
      </listitem>
    </itemizedlist>

    <section>
      <title>Using Cppcheck addons</title>

      <para>Currently there are two steps to use an addon:</para>

      <orderedlist>
        <listitem>
          <para>Run Cppcheck to generate dump files</para>
        </listitem>

        <listitem>
          <para>Run the addon on the dump files</para>
        </listitem>
      </orderedlist>

      <para>The <literal>--dump</literal> flag is used to generate dump files.
      To generate a dump file for every source file in the foo/ folder:</para>

      <programlisting>cppcheck --dump foo/</programlisting>

      <para>To run a addon script on all dump files in the foo/ folder:</para>

      <programlisting>python addon.py foo/*.dump</programlisting>

      <section>
        <title>Where to find some Cppcheck addons</title>

        <para>There are a few addons that can be downloaded.</para>

        <itemizedlist>
          <listitem>
            <para>Addons provided by the Cppcheck project:
            <uri>http://github.com/danmar/cppcheck/blob/master/addons</uri></para>
          </listitem>

          <listitem>
            <para>ublinter, a project that wants to "lint" for "undefined
            behaviour": <uri>http://github.com/danmar/ublinter</uri></para>
          </listitem>
        </itemizedlist>

        <para>We would be happy to add a link to your addon here (no matter if
        it's commercial or free).</para>
      </section>
    </section>

    <section>
      <title>Writing Cppcheck addons</title>

      <para>Cppcheck generates dump files in XML format that contains:</para>

      <itemizedlist>
        <listitem>
          <para>Token list</para>
        </listitem>

        <listitem>
          <para>Syntax trees</para>
        </listitem>

        <listitem>
          <para>Symbol database (functions, classes, variables, all scopes,
          ..)</para>
        </listitem>

        <listitem>
          <para>Known values (value flow analysis)</para>
        </listitem>
      </itemizedlist>

      <para>Cppcheck can't execute addons directly. There is no direct
      interface. This means there are not much restrictions:</para>

      <itemizedlist>
        <listitem>
          <para>You can use any licensing you want for your addons</para>
        </listitem>

        <listitem>
          <para>You can use an arbitrary script/programming language to write
          addons</para>
        </listitem>

        <listitem>
          <para>The user interface and output is defined by you</para>
        </listitem>

        <listitem>
          <para>You can use addons for other use cases than generating
          warnings</para>
        </listitem>
      </itemizedlist>

      <para>For your convenience, Cppcheck provides cppcheckdata.py that you
      can use to access Cppcheck data from Python. Using this is
      optional.</para>

      <section>
        <title>Example 1 - print all tokens</title>

        <para>Script:</para>

        <programlisting>import sys
import cppcheckdata

def printtokens(data):
    for token in data.tokenlist:
        print(token.str)

for arg in sys.argv[1:]:
    printtokens(cppcheckdata.parse(arg))</programlisting>
      </section>

      <section>
        <title>Example 2 - List all functions</title>

        <para>Script:</para>

        <programlisting>import sys
import cppcheckdata

def printfunctions(data):
    for scope in data.scopes:
        if scope.type == 'Function':
            print(scope.className)

for arg in sys.argv[1:]:
    printfunctions(cppcheckdata.parse(arg))</programlisting>
      </section>

      <section>
        <title>Example 3 - List all classes</title>

        <para>Script:</para>

        <programlisting>import sys
import cppcheckdata

def printclasses(data):
    for scope in data.scopes:
        if scope.type == 'Class':
            print(scope.className)

for arg in sys.argv[1:]:
    printfunctions(cppcheckdata.parse(arg))</programlisting>
      </section>
    </section>
  </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 (<ulink
    url="http://pygments.org/">http://pygments.org/</ulink>) for this to work.
    In the Cppcheck source tree there is a folder <filename
    class="directory">htmlreport</filename> that contains a script that
    transforms a Cppcheck XML file into HTML output.</para>

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

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

    <para>The output screen says:</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>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 <guimenu>Check</guimenu> 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
      <guimenu>View</guimenu> 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
      <guimenu>Language</guimenu> menu.</para>

      <para>More settings are available in <menuchoice>
          <guimenu>Edit</guimenu>

          <guimenuitem>Preferences</guimenuitem>
        </menuchoice>.</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>As you can read in <link
      linkend="preprocessor-configurations">chapter 3</link> 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>