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<title>pycparser v2.07</title>
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<div class="document" id="pycparser-v2-07">
<h1 class="title">pycparser v2.07</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<col class="docinfo-content" />
<tbody valign="top">
<tr><th class="docinfo-name">Author:</th>
<td><a class="first reference external" href="http://eli.thegreenplace.net">Eli Bendersky</a></td></tr>
</tbody>
</table>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="auto-toc simple">
<li><a class="reference internal" href="#introduction" id="id1">1&nbsp;&nbsp;&nbsp;Introduction</a><ul class="auto-toc">
<li><a class="reference internal" href="#what-is-pycparser" id="id2">1.1&nbsp;&nbsp;&nbsp;What is pycparser?</a></li>
<li><a class="reference internal" href="#what-is-it-good-for" id="id3">1.2&nbsp;&nbsp;&nbsp;What is it good for?</a></li>
<li><a class="reference internal" href="#which-version-of-c-does-pycparser-support" id="id4">1.3&nbsp;&nbsp;&nbsp;Which version of C does pycparser support?</a></li>
<li><a class="reference internal" href="#what-grammar-does-pycparser-follow" id="id5">1.4&nbsp;&nbsp;&nbsp;What grammar does pycparser follow?</a></li>
<li><a class="reference internal" href="#how-is-pycparser-licensed" id="id6">1.5&nbsp;&nbsp;&nbsp;How is pycparser licensed?</a></li>
<li><a class="reference internal" href="#contact-details" id="id7">1.6&nbsp;&nbsp;&nbsp;Contact details</a></li>
</ul>
</li>
<li><a class="reference internal" href="#installing" id="id8">2&nbsp;&nbsp;&nbsp;Installing</a><ul class="auto-toc">
<li><a class="reference internal" href="#prerequisites" id="id9">2.1&nbsp;&nbsp;&nbsp;Prerequisites</a></li>
<li><a class="reference internal" href="#installation-process" id="id10">2.2&nbsp;&nbsp;&nbsp;Installation process</a></li>
<li><a class="reference internal" href="#known-problems" id="id11">2.3&nbsp;&nbsp;&nbsp;Known problems</a></li>
</ul>
</li>
<li><a class="reference internal" href="#using" id="id12">3&nbsp;&nbsp;&nbsp;Using</a><ul class="auto-toc">
<li><a class="reference internal" href="#interaction-with-the-c-preprocessor" id="id13">3.1&nbsp;&nbsp;&nbsp;Interaction with the C preprocessor</a></li>
<li><a class="reference internal" href="#what-about-the-standard-c-library-headers" id="id14">3.2&nbsp;&nbsp;&nbsp;What about the standard C library headers?</a></li>
<li><a class="reference internal" href="#basic-usage" id="id15">3.3&nbsp;&nbsp;&nbsp;Basic usage</a></li>
<li><a class="reference internal" href="#advanced-usage" id="id16">3.4&nbsp;&nbsp;&nbsp;Advanced usage</a></li>
</ul>
</li>
<li><a class="reference internal" href="#modifying" id="id17">4&nbsp;&nbsp;&nbsp;Modifying</a></li>
<li><a class="reference internal" href="#package-contents" id="id18">5&nbsp;&nbsp;&nbsp;Package contents</a></li>
<li><a class="reference internal" href="#contributors" id="id19">6&nbsp;&nbsp;&nbsp;Contributors</a></li>
</ul>
</div>
<div class="section" id="introduction">
<h1>1&nbsp;&nbsp;&nbsp;Introduction</h1>
<div class="section" id="what-is-pycparser">
<h2>1.1&nbsp;&nbsp;&nbsp;What is pycparser?</h2>
<p><tt class="docutils literal">pycparser</tt> is a parser for the C language, written in pure Python. It is a module designed to be easily integrated into applications that need to parse C source code.</p>
</div>
<div class="section" id="what-is-it-good-for">
<h2>1.2&nbsp;&nbsp;&nbsp;What is it good for?</h2>
<p>Anything that needs C code to be parsed. The following are some uses for <tt class="docutils literal">pycparser</tt>, taken from real user reports:</p>
<ul class="simple">
<li>C code obfuscator</li>
<li>Front-end for various specialized C compilers</li>
<li>Static code checker</li>
<li>Automatic unit-test discovery</li>
<li>Adding specialized extensions to the C language</li>
</ul>
<p><tt class="docutils literal">pycparser</tt> is unique in the sense that it's written in pure Python - a very high level language that's easy to experiment with and tweak. To people familiar with Lex and Yacc, <tt class="docutils literal">pycparser</tt>'s code will be simple to understand.</p>
</div>
<div class="section" id="which-version-of-c-does-pycparser-support">
<h2>1.3&nbsp;&nbsp;&nbsp;Which version of C does pycparser support?</h2>
<p><tt class="docutils literal">pycparser</tt> aims to support the full C99 language (according to the standard ISO/IEC 9899). This is a new feature in the version 2.x series - earlier versions only supported C89. For more information on the change, read <a class="reference external" href="http://code.google.com/p/pycparser/wiki/C99support">this wiki page</a>.</p>
<p><tt class="docutils literal">pycparser</tt> doesn't support any GCC extensions. See the <a class="reference external" href="http://code.google.com/p/pycparser/wiki/FAQ">FAQ</a> for more details.</p>
</div>
<div class="section" id="what-grammar-does-pycparser-follow">
<h2>1.4&nbsp;&nbsp;&nbsp;What grammar does pycparser follow?</h2>
<p><tt class="docutils literal">pycparser</tt> very closely follows the C grammar provided in the end of the C99 standard document</p>
</div>
<div class="section" id="how-is-pycparser-licensed">
<h2>1.5&nbsp;&nbsp;&nbsp;How is pycparser licensed?</h2>
<p><a class="reference external" href="http://www.opensource.org/licenses/bsd-license.php">New BSD License</a></p>
</div>
<div class="section" id="contact-details">
<h2>1.6&nbsp;&nbsp;&nbsp;Contact details</h2>
<p>Drop me an email to <a class="reference external" href="mailto:eliben&#64;gmail.com">eliben&#64;gmail.com</a> for any questions regarding <tt class="docutils literal">pycparser</tt>. For reporting problems with <tt class="docutils literal">pycparser</tt> or submitting feature requests, the best way is to open an issue on the <a class="reference external" href="http://code.google.com/p/pycparser/">pycparser page at Google Code</a>.</p>
</div>
</div>
<div class="section" id="installing">
<h1>2&nbsp;&nbsp;&nbsp;Installing</h1>
<div class="section" id="prerequisites">
<h2>2.1&nbsp;&nbsp;&nbsp;Prerequisites</h2>
<ul class="simple">
<li><tt class="docutils literal">pycparser</tt> was tested on Python 2.6, 2.7 and 3.2, on both Linux and Windows. It should work on any later version (in both the 2.x and 3.x lines) as well.</li>
<li><tt class="docutils literal">pycparser</tt> uses the PLY module for the actual lexer and parser construction. Install PLY from <a class="reference external" href="http://www.dabeaz.com/ply/">its website</a>.</li>
</ul>
</div>
<div class="section" id="installation-process">
<h2>2.2&nbsp;&nbsp;&nbsp;Installation process</h2>
<p>Installing <tt class="docutils literal">pycparser</tt> is very simple. Once you download it from its <a class="reference external" href="http://code.google.com/p/pycparser/">website</a> and unzip the package, you just have to execute the standard <tt class="docutils literal">python setup.py install</tt>. The setup script will then place the <tt class="docutils literal">pycparser</tt> module into <tt class="docutils literal"><span class="pre">site-packages</span></tt> in your Python's installation library.</p>
<p>Alternatively, since <tt class="docutils literal">pycparser</tt> is listed in the <a class="reference external" href="http://pypi.python.org/pypi/pycparser">Python Package Index</a> (PyPI), you can install it using your favorite Python packaging/distribution tool, for example with:</p>
<pre class="literal-block">
&gt; pip install pycparser
</pre>
<p>It's recommended to run <tt class="docutils literal">_build_tables.py</tt> in the <tt class="docutils literal">pycparser</tt> code directory after installation to make sure the parsing tables of PLY are pre-generated. This can make your code run faster.</p>
</div>
<div class="section" id="known-problems">
<h2>2.3&nbsp;&nbsp;&nbsp;Known problems</h2>
<ul class="simple">
<li>Some users who've installed a new version of <tt class="docutils literal">pycparser</tt> over an existing version ran into a problem using the newly installed library. This has to do with parse tables staying around as <tt class="docutils literal">.pyc</tt> files from the older version. If you see unexplained errors from <tt class="docutils literal">pycparser</tt> after an upgrade, remove it (by deleting the <tt class="docutils literal">pycparser</tt> directory in your Python's <tt class="docutils literal"><span class="pre">site-packages</span></tt>, or wherever you installed it) and install again.</li>
</ul>
</div>
</div>
<div class="section" id="using">
<h1>3&nbsp;&nbsp;&nbsp;Using</h1>
<div class="section" id="interaction-with-the-c-preprocessor">
<h2>3.1&nbsp;&nbsp;&nbsp;Interaction with the C preprocessor</h2>
<p>In order to be compilable, C code must be preprocessed by the C preprocessor - <tt class="docutils literal">cpp</tt>. <tt class="docutils literal">cpp</tt> handles preprocessing directives like <tt class="docutils literal">#include</tt> and <tt class="docutils literal">#define</tt>, removes comments, and does other minor tasks that prepare the C code for compilation.</p>
<p>For all but the most trivial snippets of C code, <tt class="docutils literal">pycparser</tt>, like a C compiler, must receive preprocessed C code in order to function correctly. If you import the top-level <tt class="docutils literal">parse_file</tt> function from the <tt class="docutils literal">pycparser</tt> package, it will interact with <tt class="docutils literal">cpp</tt> for you, as long as it's in your PATH, or you provide a path to it.</p>
<p>On the vast majority of Linux systems, <tt class="docutils literal">cpp</tt> is installed and is in the PATH. If you're on Windows and don't have <tt class="docutils literal">cpp</tt> somewhere, you can use the one provided in the <tt class="docutils literal">utils</tt> directory in <tt class="docutils literal">pycparser</tt>'s distribution. This <tt class="docutils literal">cpp</tt> executable was compiled from the <a class="reference external" href="http://www.cs.princeton.edu/software/lcc/">LCC distribution</a>, and is provided under LCC's license terms.</p>
</div>
<div class="section" id="what-about-the-standard-c-library-headers">
<h2>3.2&nbsp;&nbsp;&nbsp;What about the standard C library headers?</h2>
<p>C code almost always includes various header files from the standard C library, like <tt class="docutils literal">stdio.h</tt>. While, with some effort, <tt class="docutils literal">pycparser</tt> can be made to parse the standard headers from any C compiler, it's much simpler to use the provided &quot;fake&quot; standard  includes in <tt class="docutils literal">utils/fake_libc_include</tt>. These are standard C header files that contain only the bare necessities to allow valid parsing of the files that use them. As a bonus, since they're minimal, it can significantly improve the performance of parsing C files.</p>
<p>See the <tt class="docutils literal">using_cpp_libc.py</tt> example for more details.</p>
</div>
<div class="section" id="basic-usage">
<h2>3.3&nbsp;&nbsp;&nbsp;Basic usage</h2>
<p>Take a look at the <tt class="docutils literal">examples</tt> directory of the distribution for a few examples of using <tt class="docutils literal">pycparser</tt>. These should be enough to get you started.</p>
</div>
<div class="section" id="advanced-usage">
<h2>3.4&nbsp;&nbsp;&nbsp;Advanced usage</h2>
<p>The public interface of <tt class="docutils literal">pycparser</tt> is well documented with comments in <tt class="docutils literal">pycparser/c_parser.py</tt>. For a detailed overview of the various AST nodes created by the parser, see <tt class="docutils literal">pycparser/_c_ast.cfg</tt>.</p>
<p>There's also a <a class="reference external" href="http://code.google.com/p/pycparser/wiki/FAQ">FAQ available here</a>. In any case, you can always drop me an <a class="reference external" href="mailto:eliben&#64;gmail.com">email</a> for help.</p>
</div>
</div>
<div class="section" id="modifying">
<h1>4&nbsp;&nbsp;&nbsp;Modifying</h1>
<p>There are a few points to keep in mind when modifying <tt class="docutils literal">pycparser</tt>:</p>
<ul class="simple">
<li>The code for <tt class="docutils literal">pycparser</tt>'s AST nodes is automatically generated from a configuration file - <tt class="docutils literal">_c_ast.cfg</tt>, by <tt class="docutils literal">_ast_gen.py</tt>. If you modify the AST configuration, make sure to re-generate the code.</li>
<li>Make sure you understand the optimized mode of <tt class="docutils literal">pycparser</tt> - for that you must read the docstring in the constructor of the <tt class="docutils literal">CParser</tt> class. For development you should create the parser without optimizations, so that it will regenerate the Yacc and Lex tables when you change the grammar.</li>
</ul>
</div>
<div class="section" id="package-contents">
<h1>5&nbsp;&nbsp;&nbsp;Package contents</h1>
<p>Once you unzip the <tt class="docutils literal">pycparser</tt> package, you'll see the following files and directories:</p>
<dl class="docutils">
<dt>README.txt/html:</dt>
<dd>This README file.</dd>
<dt>setup.py:</dt>
<dd>Installation script</dd>
<dt>examples/:</dt>
<dd>A directory with some examples of using <tt class="docutils literal">pycparser</tt></dd>
<dt>pycparser/:</dt>
<dd>The <tt class="docutils literal">pycparser</tt> module source code.</dd>
<dt>tests/:</dt>
<dd>Unit tests.</dd>
<dt>utils/cpp.exe:</dt>
<dd>A Windows executable of the C pre-processor suitable for working with pycparser</dd>
<dt>utils/fake_libc_include:</dt>
<dd>Minimal standard C library include files that should allow to parse any C code.</dd>
<dt>utils/internal/:</dt>
<dd>Internal utilities for my own use. You probably don't need them.</dd>
</dl>
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<div class="section" id="contributors">
<h1>6&nbsp;&nbsp;&nbsp;Contributors</h1>
<p>Some people have contributed to <tt class="docutils literal">pycparser</tt> by opening issues on bugs they've found and/or submitting patches. The list of contributors is at <a class="reference external" href="http://code.google.com/p/pycparser/wiki/Contributors">this pycparser Wiki page</a>.</p>
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