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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>
Daniel Dunbar79bba502010-01-22 02:04:46 +0000[diff] [blame]22 <li><a href="#style">Coding Standards</a></li>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]23 <li><a href="#docs">Developer Documentation</a></li>
24 <li><a href="#debugging">Debugging</a></li>
25 <li><a href="#testing">Testing</a></li>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]26 <ul>
27 <li><a href="#testingNonWindows">Testing on Unix-like Systems</a></li>
28 <li><a href="#testingWindows">Testing using Visual Studio on Windows</a></li>
Dawn Perchik217a3452010-09-03 17:01:13 +0000[diff] [blame^]29 <li><a href="#testingCommands">Testing on the Command Line</a></li>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]30 </ul>
31 <li><a href="#patches">Creating Patch Files</a></li>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]32 <li><a href="#irgen">LLVM IR Generation</a></li>
33 </ul>
34
35 <!--=====================================================================-->
Daniel Dunbar79bba502010-01-22 02:04:46 +0000[diff] [blame]36 <h2 id="docs">Coding Standards</h2>
37 <!--=====================================================================-->
38
39 <p>Clang follows the
40 LLVM <a href="http://llvm.org/docs/CodingStandards.html">Coding
41 Standards</a>. When submitting patches, please take care to follow these standards
42 and to match the style of the code to that present in Clang (for example, in
43 terms of indentation, bracing, and statement spacing).</p>
44
45 <p>Clang has a few additional coding standards:</p>
46 <ul>
47 <li><i>cstdio is forbidden</i>: library code should not output diagnostics
48 or other information using <tt>cstdio</tt>; debugging routines should
49 use <tt>llvm::errs()</tt>. Other uses of <tt>cstdio</tt> impose behavior
50 upon clients and block integrating Clang as a library. Libraries should
51 support <tt>raw_ostream</tt> based interfaces for textual
52 output. See <a href="http://llvm.org/docs/CodingStandards.html#ll_raw_ostream">Coding
53 Standards</a>.</li>
54 </ul>
55
56 <!--=====================================================================-->
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]57 <h2 id="docs">Developer Documentation</h2>
58 <!--=====================================================================-->
59
60 <p>Both Clang and LLVM use doxygen to provide API documentation. Their
61 respective web pages (generated nightly) are here:</p>
62 <ul>
63 <li><a href="http://clang.llvm.org/doxygen">Clang</a></li>
64 <li><a href="http://llvm.org/doxygen">LLVM</a></li>
65 </ul>
66
67 <p>For work on the LLVM IR generation, the LLVM assembly language
68 <a href="http://llvm.org/docs/LangRef.html">reference manual</a> is
69 also useful.</p>
70
71 <!--=====================================================================-->
72 <h2 id="debugging">Debugging</h2>
73 <!--=====================================================================-->
74
75 <p>Inspecting data structures in a debugger:</p>
76 <ul>
77 <li>Many LLVM and Clang data structures provide
78 a <tt>dump()</tt> method which will print a description of the
79 data structure to <tt>stderr</tt>.</li>
80 <li>The <a href="docs/InternalsManual.html#QualType"><tt>QualType</tt></a>
81 structure is used pervasively. This is a simple value class for
82 wrapping types with qualifiers; you can use
83 the <tt>isConstQualified()</tt>, for example, to get one of the
84 qualifiers, and the <tt>getTypePtr()</tt> method to get the
85 wrapped <tt>Type*</tt> which you can then dump.</li>
86 </ul>
87
88 <!--=====================================================================-->
89 <h2 id="testing">Testing</h2>
90 <!--=====================================================================-->
91
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]92 <p><i>[Note: The test running mechanism is currently under revision, so the
93 following might change shortly.]</i></p>
94
95 <!--=====================================================================-->
96 <h3 id="testingNonWindows">Testing on Unix-like Systems</h3>
97 <!--=====================================================================-->
98
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]99 <p>Clang includes a basic regression suite in the tree which can be
100 run with <tt>make test</tt> from the top-level clang directory, or
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]101 just <tt>make</tt> in the <em>test</em> sub-directory.
102 <tt>make VERBOSE=1</tt> can be used to show more detail
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]103 about what is being run.</p>
104
Daniel Dunbardf293782010-06-10 17:01:45 +0000[diff] [blame]105 <p>If you built LLVM and Clang using CMake, the test suite can be run
106 with <tt>make clang-test</tt> from the top-level LLVM directory.</p>
107
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]108 <p>The tests primarily consist of a test runner script running the compiler
109 under test on individual test files grouped in the directories under the
110 test directory. The individual test files include comments at the
111 beginning indicating the Clang compile options to use, to be read
112 by the test runner. Embedded comments also can do things like telling
113 the test runner that an error is expected at the current line.
114 Any output files produced by the test will be placed under
115 a created Output directory.</p>
116
117 <p>During the run of <tt>make test</tt>, the terminal output will
118 display a line similar to the following:</p>
119
120 <ul><tt>--- Running clang tests for i686-pc-linux-gnu ---</tt></ul>
121
122 <p>followed by a line continually overwritten with the current test
123 file being compiled, and an overall completion percentage.</p>
124
125 <p>After the <tt>make test</tt> run completes, the absence of any
126 <tt>Failing Tests (count):</tt> message indicates that no tests
127 failed unexpectedly. If any tests did fail, the
128 <tt>Failing Tests (count):</tt> message will be followed by a list
129 of the test source file paths that failed. For example:</p>
130
131 <tt><pre>
132 Failing Tests (3):
133 /home/john/llvm/tools/clang/test/SemaCXX/member-name-lookup.cpp
134 /home/john/llvm/tools/clang/test/SemaCXX/namespace-alias.cpp
135 /home/john/llvm/tools/clang/test/SemaCXX/using-directive.cpp
136 </pre></tt>
137
138 <p>If you used the <tt>make VERBOSE=1</tt> option, the terminal
139 output will reflect the error messages from the compiler and
140 test runner.</p>
141
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]142 <p>The regression suite can also be run with Valgrind by running
143 <tt>make test VG=1</tt> in the top-level clang directory.</p>
144
145 <p>For more intensive changes, running
146 the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM
147 Test Suite</a> with clang is recommended. Currently the best way to
Daniel Dunbar12e57bc2009-08-06 16:47:53 +0000[diff] [blame]148 override LLVMGCC, as in: <tt>make LLVMGCC="clang -std=gnu89"
149 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]150 full path).</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]151
152 <!--=====================================================================-->
153 <h3 id="testingWindows">Testing using Visual Studio on Windows</h3>
154 <!--=====================================================================-->
155
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]156 <p>The Clang test suite can be run from either Visual Studio or
157 the command line.</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]158
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]159 <p>Note that the test runner is based on
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]160 Python, which must be installed. Find Python at:
161 <a href="http://www.python.org/download">http://www.python.org/download</a>.
162 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]163
164 <p>The GnuWin32 tools are also necessary for running the tests.
165 (Note that the grep from MSYS or Cygwin doesn't work with the tests
166 because of embedded double-quotes in the search strings. The GNU
167 grep does work in this case.)
168 Get them from <a href="http://getgnuwin32.sourceforge.net">
169 http://getgnuwin32.sourceforge.net</a>.</p>
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]170
171 <p>The cmake build tool is set up to create Visual Studio project files
172 for running the tests, "clang-test" being the root. Therefore, to
173 run the test from Visual Studio, right-click the clang-test project
174 and select "Build".</p>
175
Dawn Perchik217a3452010-09-03 17:01:13 +0000[diff] [blame^]176 <!--=====================================================================-->
177 <h3 id="testingCommands">Testing on the Command Line</h3>
178 <!--=====================================================================-->
179
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]180 <p>To run all the tests from the command line, execute a command like
181 the following:</p>
182
183 <tt>
184 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
185 (path to llvm)/llvm/tools/clang/test
186 </tt>
187
188 <p>To run a single test:</p>
189
190 <tt>
191 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
192 (path to llvm)/llvm/tools/clang/test/(dir)/(test)
193 </tt>
194
195 <p>For example:</p>
196
197 <tt>
198 python C:/Tools/llvm/utils/lit/lit.py -sv --no-progress-bar
199 C:/Tools/llvm/tools/clang/test/Sema/wchar.c
200 </tt>
201
202 <p>The -sv option above tells the runner to show the test output if
203 any tests failed, to help you determine the cause of failure.</p>
204
205 <p>Note that a few tests currently fail on Windows. We are working to
206 correct this. Therefore your output might look something like this:</p>
207
208<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]209-- Testing: 1723 tests, 2 threads --
210FAIL: Clang::(test path) (659 of 1723)
211******************** TEST 'Clang::(test path)' FAILED ********************
212Script:
213 (commands run)
214Command Output (stdout):
215 (output here)
216Command Output (stderr):
217 (output here)
218********************
219Testing Time: 83.66s
220********************
221Failing Tests (1):
222 Clang::(test path)
223 Expected Passes : 1704
224 Expected Failures : 18
225 Unexpected Failures: 1
226</pre></tt>
227
228 <p>The last statistic, "Unexpected Failures", is the important one.</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]229
230 <!--=====================================================================-->
231 <h2 id="patches">Creating Patch Files</h2>
232 <!--=====================================================================-->
233
234 <p>To return changes to the Clang team, unless you have checkin
235 privileges, the prefered way is to send patch files to the
236 cfe-commits mailing list, with an explanation of what the patch is for.
237 Or, if you have questions, or want to have a wider discussion of what
238 you are doing, such as if you are new to Clang development, you can use
239 the cfe-dev mailing list also.
240 </p>
241
242 <p>To create these patch files, change directory
243 to the llvm/tools/clang root and run:</p>
244
245 <ul><tt>svn diff (relative path) >(patch file name)</tt></ul>
246
247 <p>For example, for getting the diffs of all of clang:</p>
248
249 <ul><tt>svn diff . >~/mypatchfile.patch</tt></ul>
250
251 <p>For example, for getting the diffs of a single file:</p>
252
253 <ul><tt>svn diff lib/Parse/ParseDeclCXX.cpp >~/ParseDeclCXX.patch</tt></ul>
254
255 <p>Note that the paths embedded in the patch depend on where you run it,
256 so changing directory to the llvm/tools/clang directory is recommended.</p>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]257
258 <!--=====================================================================-->
259 <h2 id="irgen">LLVM IR Generation</h2>
260 <!--=====================================================================-->
261
262 <p>The LLVM IR generation part of clang handles conversion of the
263 AST nodes output by the Sema module to the LLVM Intermediate
264 Representation (IR). Historically, this was referred to as
265 "codegen", and the Clang code for this lives
266 in <tt>lib/CodeGen</tt>.</p>
267
268 <p>The output is most easily inspected using the <tt>-emit-llvm</tt>
269 option to clang (possibly in conjunction with <tt>-o -</tt>). You
270 can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file
271 which can be processed by the suite of LLVM tools
272 like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM
273 <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a>
274 for more information.</p>
275
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