616 lines
18 KiB
XML
616 lines
18 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"/usr/share/xml/docbook/schema/dtd/4.4/docbookx.dtd">
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<book>
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<bookinfo>
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<title>Cppcheck 1.48</title>
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<date>2011-02-06</date>
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</bookinfo>
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<chapter>
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<title>Introduction</title>
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<para>Cppcheck is an analysis tool for C/C++ code. Unlike C/C++ compilers
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and many other analysis tools, it doesn't detect syntax errors. Cppcheck
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only detects the types of bugs that the compilers normally fail to detect.
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The goal is no false positives.</para>
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<para>Supported code and platforms:</para>
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<itemizedlist>
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<listitem>
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<para>You can check non-standard code that includes various compiler
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extensions, inline assembly code, etc.</para>
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</listitem>
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<listitem>
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<para>Cppcheck should be compilable by any C++ compiler that handles
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the latest C++ standard.</para>
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</listitem>
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<listitem>
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<para>Cppcheck should work on any platform that has sufficient CPU and
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memory.</para>
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</listitem>
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</itemizedlist>
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<para>Accuracy</para>
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<para>Please understand that there are limits of Cppcheck. Cppcheck is
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rarely wrong about reported errors. But there are many bugs that it
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doesn't detect.</para>
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<para>You will find more bugs in your software by testing your software
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carefully, than by using Cppcheck. You will find more bugs in your
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software by instrumenting your software, than by using Cppcheck. But
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Cppcheck can still detect some of the bugs that you miss when testing and
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instrumenting your software.</para>
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</chapter>
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<chapter>
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<title>Getting started</title>
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<section>
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<title>First test</title>
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<para>Here is a simple code</para>
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<programlisting>int main()
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{
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char a[10];
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a[10] = 0;
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return 0;
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}</programlisting>
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<para>If you save that into <filename>file1.c</filename> and
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execute:</para>
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<programlisting>cppcheck file1.c</programlisting>
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<para>The output from cppcheck will then be:</para>
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<programlisting>Checking file1.c...
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[file1.c:4]: (error) Array 'a[10]' index 10 out of bounds</programlisting>
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</section>
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<section>
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<title>Checking all files in a folder</title>
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<para>Normally a program has many source files. And you want to check
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them all. Cppcheck can check all source files in a directory:</para>
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<programlisting>cppcheck path</programlisting>
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<para>If "path" is a folder then cppcheck will check all source files in
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this folder.</para>
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<programlisting>Checking path/file1.cpp...
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1/2 files checked 50% done
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Checking path/file2.cpp...
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2/2 files checked 100% done</programlisting>
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</section>
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<section>
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<title>Excluding a file or folder from checking</title>
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<para>To exclude a file or folder, there are two options.</para>
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<para>The first option is to only provide the paths and files you want
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to check.</para>
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<programlisting>cppcheck src/a src/b</programlisting>
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<para>All files under "src/a" and "src/b" are then checked.</para>
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<para>The second option is to use <literal>-i</literal>, with it you
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specify files/paths to ignore. With this command no files in "src/c" are
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checked:</para>
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<programlisting>cppcheck -isrc/c src</programlisting>
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</section>
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<section>
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<title>Severities</title>
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<para>The possible severities for messages are:</para>
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<variablelist>
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<varlistentry>
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<term>error</term>
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<listitem>
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<para>used when bugs are found</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>warning</term>
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<listitem>
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<para>suggestions about defensive programming to prevent
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bugs</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>style</term>
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<listitem>
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<para>stylistic issues related to code cleanup (unused functions,
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redundant code, constness, and such)</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>performance</term>
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<listitem>
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<para>suggestions for making the code faster</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>information</term>
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<listitem>
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<para>Informational messages that might be interesting. Ignore
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these messages unless you really agree.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<remark>The performance messages are based on 'common knowledge'. It is
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not certain that fixing performance messages will make any measurable
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difference in speed. Fixing performance messages generally doesn't make
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your code more readable.</remark>
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</section>
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<section>
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<title>Enable messages</title>
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<para>By default only <literal>error</literal> messages are shown.
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Through the <literal>--enable</literal> command more checks can be
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enabled.</para>
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<section>
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<title>Stylistic issues</title>
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<para>With <literal>--enable=style</literal> you enable most
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<literal>warning</literal>, <literal>style</literal> and
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<literal>performance</literal> messages.</para>
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<para>Here is a simple code example:</para>
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<programlisting>void f(int x)
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{
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int i;
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if (x == 0)
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{
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i = 0;
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}
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}</programlisting>
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<para>There are no bugs in that code so Cppcheck won't report anything
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by default. To enable the stylistic messages, use the --enable=style
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command:</para>
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<programlisting>cppcheck --enable=style file3.c</programlisting>
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<para>The output from Cppcheck is now:</para>
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<para><programlisting>Checking file3.c...
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[file3.c:3]: (style) Variable 'i' is assigned a value that is never used
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[file3.c:3]: (style) The scope of the variable i can be reduced</programlisting></para>
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</section>
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<section>
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<title>Unused functions</title>
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<para>This check will try to find unused functions. It is best to use
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this when the whole program is checked, so that all usages is seen by
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cppcheck.</para>
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<programlisting>cppcheck --enable=unusedFunction path</programlisting>
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</section>
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<section>
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<title>Enable all checks</title>
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<para>To enable all checks your can use the
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<literal>--enable=all</literal> flag:</para>
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<programlisting>cppcheck --enable=all path</programlisting>
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</section>
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</section>
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<section>
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<title>Saving results in file</title>
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<para>Many times you will want to save the results in a file. You can
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use the normal shell redirection for piping error output to a
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file.</para>
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<programlisting>cppcheck file1.c 2> err.txt</programlisting>
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</section>
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<section>
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<title>Multithreaded checking</title>
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<para>To use 4 threads to check the files in a folder:</para>
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<programlisting>cppcheck -j 4 path</programlisting>
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</section>
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</chapter>
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<chapter>
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<title>Preprocessor configurations</title>
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<para>By default Cppcheck will check all preprocessor configurations
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(except those that has #error in them). This is the recommended
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behaviour.</para>
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<para>But if you want to manually limit the checking you can do so with
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<literal>-D</literal>.</para>
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<para>Beware that only the macros, which are given here and the macros
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defined in source files and known header files are considered. That
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excludes all the macros defined in some system header files, which are by
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default not examined by cppcheck.</para>
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<para>The usage: if you, for example, want to limit the checking so the
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only configuration to check should be "DEBUG=1;__cplusplus" then something
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like this can be used:</para>
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<programlisting>cppcheck -DDEBUG=1 -D__cplusplus path</programlisting>
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</chapter>
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<chapter>
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<title>XML output</title>
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<para>Cppcheck can generate the output in XML format.</para>
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<para>Use the --xml flag when you execute cppcheck:</para>
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<programlisting>cppcheck --xml file1.cpp</programlisting>
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<para>The XML format is:</para>
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<programlisting><?xml version="1.0"?>
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<results>
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<error file="file1.cpp" line="123" id="someError"
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severity="error" msg="some error text"/>
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</results></programlisting>
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<para>Attributes:</para>
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<variablelist>
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<varlistentry>
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<term>file</term>
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<listitem>
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<para>filename. Both relative and absolute paths are possible</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>line</term>
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<listitem>
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<para>a number</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>id</term>
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<listitem>
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<para>id of error. These are always valid symbolnames.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>severity</term>
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<listitem>
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<para>either <literal>error</literal> or <literal>style</literal>.
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<literal>warning</literal> and <literal>performance</literal> are
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saved as <literal>style</literal>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>msg</term>
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<listitem>
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<para>the error message</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</chapter>
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<chapter>
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<title>Reformatting the output</title>
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<para>If you want to reformat the output so it looks different you can use
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templates.</para>
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<para>To get Visual Studio compatible output you can use "--template
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vs":</para>
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<programlisting>cppcheck --template vs gui/test.cpp</programlisting>
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<para>This output will look like this:</para>
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<programlisting>Checking gui/test.cpp...
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gui/test.cpp(31): error: Memory leak: b
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gui/test.cpp(16): error: Mismatching allocation and deallocation: k</programlisting>
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<para>To get gcc compatible output you can use "--template gcc":</para>
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<programlisting>cppcheck --template gcc gui/test.cpp</programlisting>
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<para>The output will look like this:</para>
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<programlisting>Checking gui/test.cpp...
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gui/test.cpp:31: error: Memory leak: b
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gui/test.cpp:16: error: Mismatching allocation and deallocation: k</programlisting>
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<para>You can write your own pattern (for example a comma-separated
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format):</para>
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<programlisting>cppcheck --template "{file},{line},{severity},{id},{message}" gui/test.cpp</programlisting>
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<para>The output will look like this:</para>
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<programlisting>Checking gui/test.cpp...
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gui/test.cpp,31,error,memleak,Memory leak: b
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gui/test.cpp,16,error,mismatchAllocDealloc,Mismatching allocation and deallocation: k</programlisting>
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<para></para>
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</chapter>
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<chapter>
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<title>Suppressions</title>
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<para>If you want to filter out certain errors you can suppress these.
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The <literal>--suppress=</literal> command line option is used to specify
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suppressions on the command line. The format is one of:</para>
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<programlisting>[error id]:[filename]:[line]
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[error id]:[filename2]
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[error id]</programlisting>
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<para>The <literal>error id</literal> is the id that you want to suppress.
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The easiest way to get it is to use the <literal>--xml</literal> command
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line flag. Copy and paste the <literal>id</literal> string from the XML
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output. This may be * to suppress all warnings (for a specified file or
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files).</para>
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<para>The <literal>filename</literal> may include the wildcard characters
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* or ?, which match any sequence of characters or any single character
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respectively.</para>
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<programlisting>cppcheck --suppress=memleak:file1.cpp src/</programlisting>
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<para>If you have more than a couple of suppressions, create a suppressions
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file with one line per suppression as above.</para>
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<para>Here is an example:</para>
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<programlisting>memleak:file1.cpp
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exceptNew:file1.cpp
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uninitvar</programlisting>
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<para>You can then use the suppressions file:</para>
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<programlisting>cppcheck --suppressions suppressions.txt src/</programlisting>
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<para></para>
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</chapter>
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<chapter>
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<title>Leaks</title>
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<para>Looking for memory leaks and resource leaks is a key feature of
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Cppcheck. Cppcheck can detect many common mistakes by default. But through
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some tweaking you can improve the checking.</para>
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<section>
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<title>User-defined allocation/deallocation functions</title>
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<para><literal>Cppcheck</literal> understands many common allocation and
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deallocation functions. But not all.</para>
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<para>Here is example code that might leak memory or resources:</para>
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<para><programlisting>void foo(int x)
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{
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void *f = CreateFred();
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if (x == 1)
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return;
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DestroyFred(f);
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}</programlisting></para>
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<para>If you analyse that with Cppcheck it won't find any leaks:</para>
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<programlisting>cppcheck --enable=possibleError fred1.cpp</programlisting>
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<para>You can add some custom leaks checking by providing simple
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implementations for the allocation and deallocation functions. Write
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this in a separate file:</para>
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<programlisting>void *CreateFred()
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{
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return malloc(100);
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}
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void DestroyFred(void *p)
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{
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free(p);
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}</programlisting>
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<para>When Cppcheck see this it understands that CreateFred will return
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allocated memory and that DestroyFred will deallocate memory.</para>
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<para>Now, execute <literal>Cppcheck</literal> this way:</para>
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<programlisting>cppcheck --append=fred.cpp fred1.cpp</programlisting>
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<para>The output from cppcheck is:</para>
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<programlisting>Checking fred1.cpp...
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[fred1.cpp:5]: (error) Memory leak: f</programlisting>
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</section>
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</chapter>
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<chapter>
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<title>Exception safety</title>
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<para>Cppcheck has a few checks that ensure that you don't break the basic
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guarantee of exception safety. It doesn't have any checks for the strong
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guarantee yet.</para>
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<para>Example:</para>
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<programlisting>Fred::Fred() : a(new int[20]), b(new int[20])
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{
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}</programlisting>
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<para>By default cppcheck will not detect any problems in that
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code.</para>
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<para>To enable the exception safety checking you can use
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<literal>--enable</literal>:</para>
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<programlisting>cppcheck --enable=exceptNew --enable=exceptRealloc fred.cpp</programlisting>
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<para>The output will be:</para>
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<programlisting>[fred.cpp:3]: (style) Upon exception there is memory leak: a</programlisting>
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<para>If an exception occurs when <literal>b</literal> is allocated,
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<literal>a</literal> will leak.</para>
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<para>Here is another example:</para>
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<programlisting>int *p;
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int a(int sz)
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{
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delete [] p;
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if (sz <= 0)
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throw std::runtime_error("size <= 0");
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p = new int[sz];
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}</programlisting>
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<para>Check that with Cppcheck:</para>
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<programlisting>cppcheck --enable=exceptNew --enable=exceptRealloc except2.cpp</programlisting>
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<para>The output from Cppcheck is:</para>
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<programlisting>[except2.cpp:7]: (error) Throwing exception in invalid state, p points at deallocated memory</programlisting>
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</chapter>
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<chapter>
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<title>HTML report</title>
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<para>You can convert the XML output from cppcheck into a HTML report.
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You'll need Python and the pygments module
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(<uri>http://pygments.org/</uri>) for this to work. In the Cppcheck source
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tree there is a folder "htmlreport" that contains a script that transforms
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a Cppcheck XML file into HTML output.</para>
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<para>This command generates the help screen:</para>
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<para><programlisting>htmlreport/cppcheck-htmlreport -h</programlisting></para>
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<para>The output screen says:</para>
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<para><programlisting>Usage: cppcheck-htmlreport [options]
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Options:
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-h, --help show this help message and exit
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--file=FILE The cppcheck xml output file to read defects from.
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Default is reading from stdin.
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--report-dir=REPORT_DIR
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The directory where the html report content is written.
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--source-dir=SOURCE_DIR
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Base directory where source code files can be found.</programlisting></para>
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<para>An example usage:</para>
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<programlisting>./cppcheck gui/test.cpp --xml 2> err.xml
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htmlreport/cppcheck-htmlreport --file=err.xml --report-dir=test1 --source-dir=.</programlisting>
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</chapter>
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<chapter>
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<title>Graphical user interface</title>
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<section>
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<title>Introduction</title>
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<para>A Cppcheck GUI is available.</para>
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|
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<para>The main screen is shown immediately when the GUI is
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started.</para>
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</section>
|
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<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>><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>
|