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14 <!--*********************************************************************-->
15 <h1>Hacking on Clang</h1>
16 <!--*********************************************************************-->
17
18 <p>This document provides some hints for how to get started hacking
19 on Clang for developers who are new to the Clang and/or LLVM
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]20 codebases.</p>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]21 <ul>
22 <li><a href="#docs">Developer Documentation</a></li>
23 <li><a href="#debugging">Debugging</a></li>
Daniel Dunbar1f6572c2008-11-18 17:56:21 +0000[diff] [blame]24 <li><a href="#testing">Testing</a></li>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]25 <li><a href="#irgen">LLVM IR Generation</a></li>
26 </ul>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]27
28 <!--=====================================================================-->
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]29 <h2 id="docs">Developer Documentation</h2>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]30 <!--=====================================================================-->
31
32 <p>Both Clang and LLVM use doxygen to provide API documentation. Their
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]33 respective web pages (generated nightly) are here:</p>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]34 <ul>
35 <li><a href="http://clang.llvm.org/doxygen">Clang</a></li>
36 <li><a href="http://llvm.org/doxygen">LLVM</a></li>
37 </ul>
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]38
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]39 <p>For work on the LLVM IR generation, the LLVM assembly language
40 <a href="http://llvm.org/docs/LangRef.html">reference manual</a> is
41 also useful.</p>
42
43 <!--=====================================================================-->
44 <h2 id="debugging">Debugging</h2>
45 <!--=====================================================================-->
46
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]47 <p>Inspecting data structures in a debugger:</p>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]48 <ul>
49 <li>Many LLVM and Clang data structures provide
50 a <tt>dump()</tt> method which will print a description of the
51 data structure to <tt>stderr</tt>.</li>
52 <li>The <a href="docs/InternalsManual.html#QualType"><tt>QualType</tt></a>
53 structure is used pervasively. This is a simple value class for
54 wrapping types with qualifiers; you can use
55 the <tt>isConstQualified()</tt>, for example, to get one of the
56 qualifiers, and the <tt>getTypePtr()</tt> method to get the
57 wrapped <tt>Type*</tt> which you can then dump.</li>
58 </ul>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]59
60 <!--=====================================================================-->
Daniel Dunbar1f6572c2008-11-18 17:56:21 +0000[diff] [blame]61 <h2 id="testing">Testing</h2>
62 <!--=====================================================================-->
63
64 <p>Clang includes a basic regression suite in the tree which can be
65 run with <tt>make test</tt> from the top-level clang directory, or
66 just <tt>make</tt> in the <em>test</em> sub-directory. <tt>make
67 report</tt> can be used after running the tests to summarize the
68 results, and <tt>make VERBOSE=1</tt> can be used to show more detail
69 about what is being run.</p>
70
71 <p>For more intensive changes, running
72 the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM
73 Test Suite</a> with clang is recommended. Currently the best way to
74 override LLVMGCC, as in: <tt>make LLVMGCC="ccc -std=gnu89"
75 TEST=nightly report</tt> (make sure ccc is in your PATH or use the
76 full path).</p>
77
78 <!--=====================================================================-->
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]79 <h2 id="irgen">LLVM IR Generation</h2>
80 <!--=====================================================================-->
81
82 <p>The LLVM IR generation part of clang handles conversion of the
83 AST nodes output by the Sema module to the LLVM Intermediate
84 Representation (IR). Historically, this was referred to as
85 "codegen", and the Clang code for this lives
86 in <tt>lib/CodeGen</tt>.</p>
87
88 <p>The output is most easily inspected using the <tt>-emit-llvm</tt>
89 option to clang (possibly in conjunction with <tt>-o -</tt>). You
90 can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file
91 which can be processed by the suite of LLVM tools
92 like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM
Daniel Dunbar2f064172008-11-13 23:01:34 +0000[diff] [blame]93 <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a>
Daniel Dunbar0d7c3f92008-11-13 22:49:41 +0000[diff] [blame]94 for more information.</p>
95
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