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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
Daniel Dunbar12e57bc2009-08-06 16:47:53 +0000[diff] [blame]122 override LLVMGCC, as in: <tt>make LLVMGCC="clang -std=gnu89"
123 TEST=nightly report</tt> (make sure <tt>clang</tt> is in your PATH or use the
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]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
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]130 <p>The Clang test suite can be run from either Visual Studio or
131 the command line.</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]132
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]133 <p>Note that the test runner is based on
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]134 Python, which must be installed. Find Python at:
135 <a href="http://www.python.org/download">http://www.python.org/download</a>.
136 Download the latest stable version (2.6.2 at the time of this writing).</p>
Chris Lattner357f7ce2009-08-20 06:17:11 +0000[diff] [blame]137
138 <p>The GnuWin32 tools are also necessary for running the tests.
139 (Note that the grep from MSYS or Cygwin doesn't work with the tests
140 because of embedded double-quotes in the search strings. The GNU
141 grep does work in this case.)
142 Get them from <a href="http://getgnuwin32.sourceforge.net">
143 http://getgnuwin32.sourceforge.net</a>.</p>
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]144
145 <p>The cmake build tool is set up to create Visual Studio project files
146 for running the tests, "clang-test" being the root. Therefore, to
147 run the test from Visual Studio, right-click the clang-test project
148 and select "Build".</p>
149
150 <p>To run all the tests from the command line, execute a command like
151 the following:</p>
152
153 <tt>
154 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
155 (path to llvm)/llvm/tools/clang/test
156 </tt>
157
158 <p>To run a single test:</p>
159
160 <tt>
161 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
162 (path to llvm)/llvm/tools/clang/test/(dir)/(test)
163 </tt>
164
165 <p>For example:</p>
166
167 <tt>
168 python C:/Tools/llvm/utils/lit/lit.py -sv --no-progress-bar
169 C:/Tools/llvm/tools/clang/test/Sema/wchar.c
170 </tt>
171
172 <p>The -sv option above tells the runner to show the test output if
173 any tests failed, to help you determine the cause of failure.</p>
174
175 <p>Note that a few tests currently fail on Windows. We are working to
176 correct this. Therefore your output might look something like this:</p>
177
178<tt><pre>lit.py: lit.cfg:152: note: using clang: 'C:/Tools/llvm/bin/Debug\\clang.EXE'
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]179-- Testing: 1723 tests, 2 threads --
180FAIL: Clang::(test path) (659 of 1723)
181******************** TEST 'Clang::(test path)' FAILED ********************
182Script:
183 (commands run)
184Command Output (stdout):
185 (output here)
186Command Output (stderr):
187 (output here)
188********************
189Testing Time: 83.66s
190********************
191Failing Tests (1):
192 Clang::(test path)
193 Expected Passes : 1704
194 Expected Failures : 18
195 Unexpected Failures: 1
196</pre></tt>
197
198 <p>The last statistic, "Unexpected Failures", is the important one.</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]199
200 <!--=====================================================================-->
201 <h2 id="patches">Creating Patch Files</h2>
202 <!--=====================================================================-->
203
204 <p>To return changes to the Clang team, unless you have checkin
205 privileges, the prefered way is to send patch files to the
206 cfe-commits mailing list, with an explanation of what the patch is for.
207 Or, if you have questions, or want to have a wider discussion of what
208 you are doing, such as if you are new to Clang development, you can use
209 the cfe-dev mailing list also.
210 </p>
211
212 <p>To create these patch files, change directory
213 to the llvm/tools/clang root and run:</p>
214
215 <ul><tt>svn diff (relative path) >(patch file name)</tt></ul>
216
217 <p>For example, for getting the diffs of all of clang:</p>
218
219 <ul><tt>svn diff . >~/mypatchfile.patch</tt></ul>
220
221 <p>For example, for getting the diffs of a single file:</p>
222
223 <ul><tt>svn diff lib/Parse/ParseDeclCXX.cpp >~/ParseDeclCXX.patch</tt></ul>
224
225 <p>Note that the paths embedded in the patch depend on where you run it,
226 so changing directory to the llvm/tools/clang directory is recommended.</p>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]227
228 <!--=====================================================================-->
229 <h2 id="irgen">LLVM IR Generation</h2>
230 <!--=====================================================================-->
231
232 <p>The LLVM IR generation part of clang handles conversion of the
233 AST nodes output by the Sema module to the LLVM Intermediate
234 Representation (IR). Historically, this was referred to as
235 "codegen", and the Clang code for this lives
236 in <tt>lib/CodeGen</tt>.</p>
237
238 <p>The output is most easily inspected using the <tt>-emit-llvm</tt>
239 option to clang (possibly in conjunction with <tt>-o -</tt>). You
240 can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file
241 which can be processed by the suite of LLVM tools
242 like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM
243 <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a>
244 for more information.</p>
245
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