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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
20 codebases.</p>
21 <ul>
22 <li><a href="#docs">Developer Documentation</a></li>
23 <li><a href="#debugging">Debugging</a></li>
24 <li><a href="#testing">Testing</a></li>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]25 <ul>
26 <li><a href="#testingNonWindows">Testing on Unix-like Systems</a></li>
27 <li><a href="#testingWindows">Testing using Visual Studio on Windows</a></li>
28 </ul>
29 <li><a href="#patches">Creating Patch Files</a></li>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]30 <li><a href="#irgen">LLVM IR Generation</a></li>
31 </ul>
32
33 <!--=====================================================================-->
34 <h2 id="docs">Developer Documentation</h2>
35 <!--=====================================================================-->
36
37 <p>Both Clang and LLVM use doxygen to provide API documentation. Their
38 respective web pages (generated nightly) are here:</p>
39 <ul>
40 <li><a href="http://clang.llvm.org/doxygen">Clang</a></li>
41 <li><a href="http://llvm.org/doxygen">LLVM</a></li>
42 </ul>
43
44 <p>For work on the LLVM IR generation, the LLVM assembly language
45 <a href="http://llvm.org/docs/LangRef.html">reference manual</a> is
46 also useful.</p>
47
48 <!--=====================================================================-->
49 <h2 id="debugging">Debugging</h2>
50 <!--=====================================================================-->
51
52 <p>Inspecting data structures in a debugger:</p>
53 <ul>
54 <li>Many LLVM and Clang data structures provide
55 a <tt>dump()</tt> method which will print a description of the
56 data structure to <tt>stderr</tt>.</li>
57 <li>The <a href="docs/InternalsManual.html#QualType"><tt>QualType</tt></a>
58 structure is used pervasively. This is a simple value class for
59 wrapping types with qualifiers; you can use
60 the <tt>isConstQualified()</tt>, for example, to get one of the
61 qualifiers, and the <tt>getTypePtr()</tt> method to get the
62 wrapped <tt>Type*</tt> which you can then dump.</li>
63 </ul>
64
65 <!--=====================================================================-->
66 <h2 id="testing">Testing</h2>
67 <!--=====================================================================-->
68
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]69 <p><i>[Note: The test running mechanism is currently under revision, so the
70 following might change shortly.]</i></p>
71
72 <!--=====================================================================-->
73 <h3 id="testingNonWindows">Testing on Unix-like Systems</h3>
74 <!--=====================================================================-->
75
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]76 <p>Clang includes a basic regression suite in the tree which can be
77 run with <tt>make test</tt> from the top-level clang directory, or
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]78 just <tt>make</tt> in the <em>test</em> sub-directory.
79 <tt>make VERBOSE=1</tt> can be used to show more detail
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]80 about what is being run.</p>
81
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]82 <p>The tests primarily consist of a test runner script running the compiler
83 under test on individual test files grouped in the directories under the
84 test directory. The individual test files include comments at the
85 beginning indicating the Clang compile options to use, to be read
86 by the test runner. Embedded comments also can do things like telling
87 the test runner that an error is expected at the current line.
88 Any output files produced by the test will be placed under
89 a created Output directory.</p>
90
91 <p>During the run of <tt>make test</tt>, the terminal output will
92 display a line similar to the following:</p>
93
94 <ul><tt>--- Running clang tests for i686-pc-linux-gnu ---</tt></ul>
95
96 <p>followed by a line continually overwritten with the current test
97 file being compiled, and an overall completion percentage.</p>
98
99 <p>After the <tt>make test</tt> run completes, the absence of any
100 <tt>Failing Tests (count):</tt> message indicates that no tests
101 failed unexpectedly. If any tests did fail, the
102 <tt>Failing Tests (count):</tt> message will be followed by a list
103 of the test source file paths that failed. For example:</p>
104
105 <tt><pre>
106 Failing Tests (3):
107 /home/john/llvm/tools/clang/test/SemaCXX/member-name-lookup.cpp
108 /home/john/llvm/tools/clang/test/SemaCXX/namespace-alias.cpp
109 /home/john/llvm/tools/clang/test/SemaCXX/using-directive.cpp
110 </pre></tt>
111
112 <p>If you used the <tt>make VERBOSE=1</tt> option, the terminal
113 output will reflect the error messages from the compiler and
114 test runner.</p>
115
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]116 <p>The regression suite can also be run with Valgrind by running
117 <tt>make test VG=1</tt> in the top-level clang directory.</p>
118
119 <p>For more intensive changes, running
120 the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM
121 Test Suite</a> with clang is recommended. Currently the best way to
122 override LLVMGCC, as in: <tt>make LLVMGCC="ccc -std=gnu89"
123 TEST=nightly report</tt> (make sure ccc is in your PATH or use the
124 full path).</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]125
126 <!--=====================================================================-->
127 <h3 id="testingWindows">Testing using Visual Studio on Windows</h3>
128 <!--=====================================================================-->
129
130 <p>The cmake build tool is set up to create Visual Studio project files
131 for running the tests, "clang-test" being the root.
132 Unfortunately, the test runner scripts presently don't work on Windows.
133 This will be fixed during the test runner revision in progress.</p>
134
135 <p>Note that the current and coming revised test runner is based on
136 Python, which must be installed. Find Python at:
137 <a href="http://www.python.org/download">http://www.python.org/download</a>.
138 Download the latest stable version (2.6.2 at the time of this writing).</p>
139
140 <!--=====================================================================-->
141 <h2 id="patches">Creating Patch Files</h2>
142 <!--=====================================================================-->
143
144 <p>To return changes to the Clang team, unless you have checkin
145 privileges, the prefered way is to send patch files to the
146 cfe-commits mailing list, with an explanation of what the patch is for.
147 Or, if you have questions, or want to have a wider discussion of what
148 you are doing, such as if you are new to Clang development, you can use
149 the cfe-dev mailing list also.
150 </p>
151
152 <p>To create these patch files, change directory
153 to the llvm/tools/clang root and run:</p>
154
155 <ul><tt>svn diff (relative path) >(patch file name)</tt></ul>
156
157 <p>For example, for getting the diffs of all of clang:</p>
158
159 <ul><tt>svn diff . >~/mypatchfile.patch</tt></ul>
160
161 <p>For example, for getting the diffs of a single file:</p>
162
163 <ul><tt>svn diff lib/Parse/ParseDeclCXX.cpp >~/ParseDeclCXX.patch</tt></ul>
164
165 <p>Note that the paths embedded in the patch depend on where you run it,
166 so changing directory to the llvm/tools/clang directory is recommended.</p>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]167
168 <!--=====================================================================-->
169 <h2 id="irgen">LLVM IR Generation</h2>
170 <!--=====================================================================-->
171
172 <p>The LLVM IR generation part of clang handles conversion of the
173 AST nodes output by the Sema module to the LLVM Intermediate
174 Representation (IR). Historically, this was referred to as
175 "codegen", and the Clang code for this lives
176 in <tt>lib/CodeGen</tt>.</p>
177
178 <p>The output is most easily inspected using the <tt>-emit-llvm</tt>
179 option to clang (possibly in conjunction with <tt>-o -</tt>). You
180 can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file
181 which can be processed by the suite of LLVM tools
182 like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM
183 <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a>
184 for more information.</p>
185
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