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Coding_Conventions.html
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<title>Firm - Coding Conventions</title>
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<div class="layout-document">
<h1>Coding Conventions</h1>
<div id="preamble">
<div class="sectionbody">
<div class="paragraph"><p>This document summarizes lib<span class="algo"><span class="algo">Firm</span></span> coding style conventions.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_indentation_and_formatting">Indentation and formatting</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="title">Example</div>
<div class="content"><div class="highlight"><pre><span class="n">ir_node</span> <span class="o">*</span><span class="nf">maybe_create</span><span class="p">(</span><span class="kt">int</span> <span class="n">a</span><span class="p">,</span> <span class="kt">int</span> <span class="n">b</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">z</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">a</span> <span class="o">+</span> <span class="n">b</span> <span class="o"><</span> <span class="mi">10</span><span class="p">)</span> <span class="p">{</span>
<span class="n">z</span> <span class="o">=</span> <span class="n">create_node</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">b</span><span class="p">);</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="n">do_something</span><span class="p">();</span>
<span class="p">}</span>
<span class="k">return</span> <span class="n">z</span><span class="p">;</span>
<span class="p">}</span>
</pre></div></div></div>
<div class="ulist"><ul>
<li>
<p>
function and variable names are all in lowercase; words are separated with an underscore <em>_</em>
</p>
</li>
<li>
<p>
the star from pointer declarations is put next to the name to be declared (Wrong: ir_node* foo; Right: ir_node *foo;)
</p>
</li>
<li>
<p>
opening curly braces for functions start on a new line
</p>
</li>
<li>
<p>
opening curly braces for if, while, etc. start on the same line!
</p>
</li>
<li>
<p>
in a call there is no space between the function name and the braces for the arguments
</p>
</li>
<li>
<p>
there is a space between builtin keywords (if, while, switch, for) and the following opening braces.
</p>
</li>
<li>
<p>
return is not a function call. So no braces around the return value
</p>
</li>
<li>
<p>
Try to keep lines shorter than 80 characters (breaking this rule is tolerated)
</p>
</li>
<li>
<p>
Don’t break message strings between 2 lines. (so you can grep for messages in the source)
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_indentation">Indentation</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
Indentation at the beginning of the line is done with tabs.
</p>
</li>
<li>
<p>
Indentation to match certain points in the previous line is done with spaces (see next part)
</p>
</li>
</ul></div>
<div class="listingblock">
<div class="title">Indentation Example (using <T> to show tabs)</div>
<div class="content"><div class="highlight"><pre><span class="kt">void</span> <span class="nf">func</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
<span class="p">{</span>
<span class="o"><</span><span class="n">T</span><span class="o">></span><span class="k">if</span> <span class="p">(</span><span class="n">bla</span> <span class="o"><</span> <span class="mi">20</span> <span class="o">&&</span> <span class="n">foobar_bar</span><span class="p">(</span><span class="n">long_variable_name</span><span class="p">)</span> <span class="o">||</span> <span class="n">another_long_thingy</span>
<span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="o">&&</span> <span class="n">this_was_a_long_condition</span><span class="p">)</span> <span class="p">{</span>
<span class="o"><</span><span class="n">T</span><span class="o">><</span><span class="n">T</span><span class="o">></span><span class="n">print</span><span class="p">();</span>
<span class="o"><</span><span class="n">T</span><span class="o">><</span><span class="n">T</span><span class="o">></span><span class="n">foobar</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">b</span><span class="p">,</span> <span class="n">more_long_stuff_here</span><span class="p">,</span>
<span class="o"><</span><span class="n">T</span><span class="o">><</span><span class="n">T</span><span class="o">></span> <span class="n">and_this_is</span> <span class="o">+</span> <span class="n">another</span> <span class="o">*</span> <span class="p">(</span><span class="n">longish</span> <span class="o">-</span> <span class="n">argument</span><span class="p">);</span>
<span class="o"><</span><span class="n">T</span><span class="o">></span><span class="p">}</span>
<span class="p">}</span>
</pre></div></div></div>
<div class="paragraph"><p>This style allows different people to set tab to different sizes and still get nice layout. Most firm developers tend to set tab to 4 spaces though.</p></div>
<div class="ulist"><ul>
<li>
<p>
Case labels should not get extra indentation. Correct example:
</p>
</li>
</ul></div>
<div class="listingblock">
<div class="content"><div class="highlight"><pre><span class="k">switch</span> <span class="p">(</span><span class="n">foo</span><span class="p">)</span> <span class="p">{</span>
<span class="k">case</span> <span class="nl">BLA_ENUM_VAL</span><span class="p">:</span>
<span class="n">FooBar</span><span class="p">();</span>
<span class="k">break</span><span class="p">;</span>
<span class="k">default</span><span class="o">:</span>
<span class="k">break</span><span class="p">;</span>
<span class="p">}</span>
</pre></div></div></div>
</div>
</div>
<div class="sect1">
<h2 id="_documentation">Documentation</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
All functions in the public API (= stuff in the headers in libfirm/include) must have at least a short doxygen documentation
</p>
</li>
<li>
<p>
Documentation for functions should be put in the header (except of course static functions which are only in the C file)
</p>
</li>
<li>
<p>
Each file must have an @brief doxygen comment describing the intention/purpose of the file (except public headers with a detailed description in a @defgroup)
</p>
</li>
<li>
<p>
Each file must have an @author doxygen comment so that we can easily see who has written what code.
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_c99">C99</h2>
<div class="sectionbody">
<div class="paragraph"><p>While alot of firm code has been written for C89, we do use C99 now. Use it:</p></div>
<div class="ulist"><ul>
<li>
<p>
Use the bool type from stdbool.h .
</p>
</li>
<li>
<p>
Move declarations as close as possible to their first assignment.
</p>
</li>
<li>
<p>
But as we don’t want to force our users to use C99 we keep the public API free of C99. So no bool type in the public headers.
</p>
</li>
</ul></div>
<div class="listingblock">
<div class="title">Bad</div>
<div class="content"><div class="highlight"><pre><span class="kt">void</span> <span class="nf">bad_example</span><span class="p">(</span><span class="n">ir_node</span> <span class="o">*</span><span class="n">arg0</span><span class="p">,</span> <span class="kt">int</span> <span class="n">swap_directions</span><span class="p">)</span>
<span class="p">{</span>
<span class="kt">int</span> <span class="n">arity</span><span class="p">;</span>
<span class="kt">int</span> <span class="n">i</span><span class="p">;</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">n</span><span class="p">,</span> <span class="o">*</span><span class="n">left</span><span class="p">,</span> <span class="o">*</span><span class="n">right</span><span class="p">;</span>
<span class="n">arity</span> <span class="o">=</span> <span class="n">get_irn_arity</span><span class="p">(</span><span class="n">arg0</span><span class="p">);</span>
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">arity</span><span class="p">;</span> <span class="o">++</span><span class="n">i</span><span class="p">)</span> <span class="p">{</span>
<span class="n">n</span> <span class="o">=</span> <span class="n">get_irn_n</span><span class="p">(</span><span class="n">arg0</span><span class="p">,</span> <span class="n">i</span><span class="p">);</span>
<span class="n">left</span> <span class="o">=</span> <span class="n">get_binop_left</span><span class="p">(</span><span class="n">n</span><span class="p">);</span>
<span class="n">right</span> <span class="o">=</span> <span class="n">get_binop_right</span><span class="p">(</span><span class="n">n</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">swap_directions</span><span class="p">)</span> <span class="p">{</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">tmp</span> <span class="o">=</span> <span class="n">left</span><span class="p">;</span>
<span class="n">left</span> <span class="o">=</span> <span class="n">right</span><span class="p">;</span>
<span class="n">right</span> <span class="o">=</span> <span class="n">tmp</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">do_something</span><span class="p">(</span><span class="n">left</span><span class="p">,</span> <span class="n">right</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div></div></div>
<div class="listingblock">
<div class="title">Good</div>
<div class="content"><div class="highlight"><pre><span class="kt">void</span> <span class="nf">good_example</span><span class="p">(</span><span class="n">ir_node</span> <span class="o">*</span><span class="n">arg0</span><span class="p">,</span> <span class="kt">bool</span> <span class="n">swap_directions</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">for</span> <span class="p">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">arity</span> <span class="o">=</span> <span class="n">get_irn_arity</span><span class="p">(</span><span class="n">arg0</span><span class="p">);</span> <span class="n">i</span> <span class="o"><</span> <span class="n">arity</span><span class="p">;</span> <span class="o">++</span><span class="n">i</span><span class="p">)</span> <span class="p">{</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">n</span> <span class="o">=</span> <span class="n">get_irn_n</span><span class="p">(</span><span class="n">arg0</span><span class="p">,</span> <span class="n">i</span><span class="p">);</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">left</span> <span class="o">=</span> <span class="n">get_binop_left</span><span class="p">(</span><span class="n">n</span><span class="p">);</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">right</span> <span class="o">=</span> <span class="n">get_binop_right</span><span class="p">(</span><span class="n">n</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">swap_directions</span><span class="p">)</span> <span class="p">{</span>
<span class="n">ir_node</span> <span class="o">*</span><span class="n">tmp</span> <span class="o">=</span> <span class="n">left</span><span class="p">;</span>
<span class="n">left</span> <span class="o">=</span> <span class="n">right</span><span class="p">;</span>
<span class="n">right</span> <span class="o">=</span> <span class="n">tmp</span><span class="p">;</span>
<span class="p">}</span>
<span class="n">do_something</span><span class="p">(</span><span class="n">left</span><span class="p">,</span> <span class="n">right</span><span class="p">);</span>
<span class="p">}</span>
<span class="cm">/* even better in this case: foreach_irn_in(arg0, i, n) { ... } */</span>
<span class="p">}</span>
</pre></div></div></div>
</div>
</div>
<div class="sect1">
<h2 id="_tips_amp_tricks">Tips & Tricks</h2>
<div class="sectionbody">
<div class="ulist"><ul>
<li>
<p>
<a href="Subclassing">Subclassing</a>
</p>
</li>
<li>
<p>
Allocate memory with the macros from <a class="external text" href="http://pp.ipd.kit.edu/git/libfirm/tree/include/libfirm/adt/xmalloc.h">xmalloc.h</a> to be more robust against type errors.
</p>
</li>
<li>
<p>
Use the const modifier freely, even for non-pointers. It makes program understanding easier if you can immediately see that a variable is only assigned once.
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_tools">Tools</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_astyle">AStyle</h3>
<div class="paragraph"><p>You can use astyle to enforce some of the rules above with the following options (needs astyle 2.00):</p></div>
<div class="listingblock">
<div class="content">
<pre><code>--indent=tab=4
--style=stroustrup
--indent-cases
--indent-col1-comments
--pad-header
--pad-oper
--keep-one-line-statements
--align-pointer=name</code></pre>
</div></div>
</div>
<div class="sect2">
<h3 id="_whitespace_check">Whitespace Check</h3>
<div class="paragraph"><p>A simple python script to check at least the tab/whitespace rules:</p></div>
<div class="listingblock">
<div class="content"><div class="highlight"><pre><span class="ch">#!/usr/bin/env python</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">re</span>
<span class="n">file_list</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">:]</span>
<span class="k">for</span> <span class="n">filename</span> <span class="ow">in</span> <span class="n">file_list</span><span class="p">:</span>
<span class="nb">file</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="s2">"r"</span><span class="p">)</span>
<span class="n">num</span> <span class="o">=</span> <span class="mi">1</span>
<span class="n">lastline</span> <span class="o">=</span> <span class="bp">None</span>
<span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="nb">file</span><span class="o">.</span><span class="n">readlines</span><span class="p">():</span>
<span class="c1"># Tab characters are only allowed as very first characters on a line!</span>
<span class="k">if</span> <span class="n">re</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="s2">"[^</span><span class="se">\t</span><span class="s2">]</span><span class="se">\t</span><span class="s2">"</span><span class="p">,</span> <span class="n">line</span><span class="p">):</span>
<span class="k">print</span> <span class="s2">"</span><span class="si">%s</span><span class="s2">:</span><span class="si">%d</span><span class="s2">: tabulator not at beginning of line"</span> <span class="o">%</span> <span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">num</span><span class="p">)</span>
<span class="k">if</span> <span class="n">re</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="s2">" +$"</span><span class="p">,</span> <span class="n">line</span><span class="p">):</span>
<span class="k">print</span> <span class="s2">"</span><span class="si">%s</span><span class="s2">:</span><span class="si">%d</span><span class="s2">: trailing whitespace"</span> <span class="o">%</span> <span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">num</span><span class="p">)</span>
<span class="n">num</span> <span class="o">+=</span> <span class="mi">1</span>
<span class="n">lastline</span> <span class="o">=</span> <span class="n">line</span>
<span class="k">if</span> <span class="n">lastline</span> <span class="o">!=</span> <span class="bp">None</span> <span class="ow">and</span> <span class="n">lastline</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">:]</span> <span class="o">!=</span> <span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">:</span>
<span class="k">print</span> <span class="s2">"</span><span class="si">%s</span><span class="s2">:</span><span class="si">%d</span><span class="s2">: No newline at end of file"</span> <span class="o">%</span> <span class="p">(</span><span class="n">filename</span><span class="p">,</span> <span class="n">num</span><span class="p">)</span>
</pre></div></div></div>
</div>
<div class="sect2">
<h3 id="_emacs">Emacs</h3>
<div class="paragraph"><p>The following style spec appears to make Emacs obey the coding conventions:</p></div>
<div class="listingblock">
<div class="content"><div class="highlight"><pre><span class="p">(</span><span class="nv">c-add-style</span> <span class="s">"firm"</span>
<span class="o">'</span><span class="p">(</span><span class="s">"stroustrup"</span>
<span class="p">(</span><span class="nv">case-label</span> <span class="o">.</span> <span class="mi">0</span><span class="p">)</span>
<span class="p">(</span><span class="nv">statement-case-intro</span> <span class="o">.</span> <span class="nb">+</span><span class="p">)</span>
<span class="p">(</span><span class="nv">statement-case-open</span> <span class="o">.</span> <span class="nb">+</span><span class="p">)</span>
<span class="p">(</span><span class="nv">indent-tabs-mode</span> <span class="o">.</span> <span class="no">t</span><span class="p">)</span>
<span class="p">(</span><span class="nv">c-basic-offset</span> <span class="o">.</span> <span class="mi">4</span><span class="p">)</span>
<span class="p">(</span><span class="nv">tab-width</span> <span class="o">.</span> <span class="mi">4</span><span class="p">))</span> <span class="no">nil</span><span class="p">)</span>
</pre></div></div></div>
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