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Writing rules: rewrote the chapter about writing rule files

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Daniel Marjamäki 2010-12-05 09:36:13 +01:00
parent c20b8831ee
commit eaea572683
1 changed files with 64 additions and 17 deletions
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man/writing-rules.docbook
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@ -120,32 +120,79 @@
<para>Simple rules can be defined through regular expressions.</para>
<para>A rule consist of:</para>
<section>
<title>Creating regular expression</title>
<itemizedlist>
<listitem>
<para>a pattern to search for.</para>
</listitem>
<para>Let's create a regular expression that checks for:</para>
<listitem>
<para>an error message that is reported when pattern is found</para>
</listitem>
</itemizedlist>
<programlisting>if (p)
free(p);</programlisting>
<para>Here is a simple example:</para>
<para>The condition is often redundant, it is valid to free a NULL
pointer.</para>
<programlisting>&lt;?xml version="1.0"?&gt;
<para>It is important to write the regular expression so it matches the
simplified code. Create a source file that has the bad code:</para>
<programlisting>void f() {
if (p) free(p);
}</programlisting>
<para>I intentionally put the whole pattern on a single line. The
simplified code is written on a single line of code.</para>
<para>To see the simplified code I use <literal>cppcheck --debug
file.cpp</literal>.</para>
<programlisting>##file dealloc.cpp
1: void f ( ) {
2: if ( p ) { free ( p ) ; }
3: }</programlisting>
<para>I save that in a file <literal>test.txt</literal>.</para>
<para>Now we can use <literal>grep</literal> to develop a regular
expression.</para>
<programlisting>grep "if [(] p [)] { free [(] p [)] ; }" test.txt</programlisting>
<para>Feel free to improve the pattern.</para>
</section>
<section>
<title>Create rule file</title>
<para>A rule consist of:</para>
<itemizedlist>
<listitem>
<para>a pattern to search for.</para>
</listitem>
<listitem>
<para>an optional error message that is reported when pattern is
found</para>
</listitem>
</itemizedlist>
<para>Here is a simple example:</para>
<programlisting>&lt;?xml version="1.0"?&gt;
&lt;rule version="1"&gt;
&lt;pattern&gt;/ 0&lt;/pattern&gt;
&lt;pattern&gt;if [(] p [)] { free [(] p [)] ; }&lt;/pattern&gt;
&lt;message&gt;
&lt;id&gt;divbyzero&lt;/id&gt;
&lt;severity&gt;error&lt;/severity&gt;
&lt;summary&gt;Division by zero&lt;/summary&gt;
&lt;id&gt;redundantCondition&lt;/id&gt;
&lt;severity&gt;style&lt;/severity&gt;
&lt;summary&gt;Redundant condition. It is valid to free a NULL pointer.&lt;/summary&gt;
&lt;/message&gt;
&lt;/rule&gt;</programlisting>
<para></para>
<para>The <literal>message</literal>, <literal>id</literal>,
<literal>severity</literal> and <literal>summary</literal> elements are
optional. If they are not written default values are used.</para>
<para></para>
<para>Now you can test this rule. Use the <literal>cppcheck
--rule-file=dealloc.rule test.cpp</literal> command.</para>
</section>
</section>
</article>