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Writing rules: minor tweaks

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Daniel Marjamäki 2010-12-05 21:50:17 +01:00
parent cdcd3c4a8f
commit 55e12659ff
1 changed files with 19 additions and 22 deletions
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41
man/writing-rules.docbook
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@ -118,48 +118,50 @@
<section> <section>
<title>Regular expressions</title> <title>Regular expressions</title>
<para>Simple rules can be defined through regular expressions. Cppcheck <para>Simple rules can be defined through regular expressions.</para>
uses PCRE to handle regular expressions.</para>
<para>Cppcheck uses the <literal>PCRE</literal> library to handle regular
expressions. <literal>PCRE</literal> stands for "Perl Compatible Regular
Expressions". The homepage for <literal>PCRE</literal> is
<literal>http://www.pcre.org</literal>.</para>
<section> <section>
<title>Creating regular expression</title> <title>Creating the regular expression</title>
<para>Let's create a regular expression that checks for:</para> <para>Let's create a regular expression that checks for:</para>
<programlisting>if (p) <programlisting>if (p)
free(p);</programlisting> free(p);</programlisting>
<para>The condition is often redundant, on most implementations it is <para>For such code the condition is often redundant, on most
valid to free a NULL pointer.</para> implementations it is valid to free a NULL pointer.</para>
<para>The regular expression must match the simplified code. Create a <para>The regular expression must be written for the simplified code. To
source file that has the bad code:</para> see what the simplified code looks like you can create a source file
with some code:</para>
<programlisting>void f() { <programlisting>void f() {
if (p) if (p)
free(p); free(p);
}</programlisting> }</programlisting>
<para>To see the simplified code you can use <literal>cppcheck <para>Save that code as <literal>dealloc.cpp</literal> and use
--rule=".+" dealloc.cpp</literal>:</para> <literal>cppcheck --rule=".+" dealloc.cpp</literal>:</para>
<programlisting>$ ./cppcheck --rule=".+" dealloc.cpp <programlisting>$ ./cppcheck --rule=".+" dealloc.cpp
Checking dealloc.cpp... Checking dealloc.cpp...
[dealloc.cpp:1]: (style) found ' void f ( ) { if ( p ) { free ( p ) ; } }'</programlisting> [dealloc.cpp:1]: (style) found ' void f ( ) { if ( p ) { free ( p ) ; } }'</programlisting>
<para>In short, the simplified code is:</para> <para>From that output we can see that the simplified code is:</para>
<programlisting> void f ( ) { if ( p ) { free ( p ) ; } }</programlisting> <programlisting> void f ( ) { if ( p ) { free ( p ) ; } }</programlisting>
<para>Now that the simplified code is known we can create a regular <para>Now that we know how the simplified code looks for a simple test
expression:</para> case, we can create a regular expression:</para>
<programlisting>$ cppcheck --rule="if \( p \) { free \( p \) ; }" dealloc.cpp <programlisting>$ cppcheck --rule="if \( p \) { free \( p \) ; }" dealloc.cpp
Checking dealloc.cpp... Checking dealloc.cpp...
[dealloc.cpp:2]: (style) found 'if ( p ) { free ( p ) ; }'</programlisting> [dealloc.cpp:2]: (style) found 'if ( p ) { free ( p ) ; }'</programlisting>
<para>Feel free to improve the pattern. Above, the pointer name must be
"p" to get a match.</para>
</section> </section>
<section> <section>
@ -169,12 +171,11 @@ Checking dealloc.cpp...
<itemizedlist> <itemizedlist>
<listitem> <listitem>
<para>a pattern to search for.</para> <para>a pattern to search for</para>
</listitem> </listitem>
<listitem> <listitem>
<para>an error message that is reported when pattern is found - this <para>an error message that is reported when pattern is found</para>
is optional, if none is given a default message is written.</para>
</listitem> </listitem>
</itemizedlist> </itemizedlist>
@ -190,10 +191,6 @@ Checking dealloc.cpp...
&lt;/message&gt; &lt;/message&gt;
&lt;/rule&gt;</programlisting> &lt;/rule&gt;</programlisting>
<para>The <literal>message</literal>, <literal>id</literal>,
<literal>severity</literal> and <literal>summary</literal> elements are
optional. But highly recommended.</para>
<para>If you save that xml data in <literal>dealloc.rule</literal> you <para>If you save that xml data in <literal>dealloc.rule</literal> you
can test this rule:</para> can test this rule:</para>