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14 <!--*********************************************************************-->
15 <h1>Hacking on Clang</h1>
16 <!--*********************************************************************-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]17
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]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>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]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>
29 <li><a href="#testingCommands">Testing on the Command Line</a></li>
30 </ul>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]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>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]34
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]35 <!--=====================================================================-->
Daniel Dunbar79bba502010-01-22 02:04:46 +0000[diff] [blame]36 <h2 id="docs">Coding Standards</h2>
37 <!--=====================================================================-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]38
Daniel Dunbar79bba502010-01-22 02:04:46 +0000[diff] [blame]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 <!--=====================================================================-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]59
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]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>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]66
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]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 <!--=====================================================================-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]74
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]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>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]87
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]88 <!--=====================================================================-->
Douglas Gregor3ef1ad22011-07-27 05:22:46 +0000[diff] [blame]89 <h3 id="debuggingVisualStudio">Debugging using Visual Studio</h3>
90 <!--=====================================================================-->
91
92 <p>The file <tt>utils/clangVisualizers.txt</tt> provides debugger visualizers that make debugging
93 of more complex data types much easier.</p>
94 <p>There are two ways to install them:</p>
95
96 <ul>
97 <li>Put the path to <tt>clangVisualizers.txt</tt> in the environment variable called
98 <tt>_vcee_autoexp</tt>. This method should work for Visual Studio 2008 and above.
99 </li>
100 <li>Edit your local <tt>autoexp.dat</tt> (make sure you make a backup first!),
101 located in <tt>Visual Studio Directory\Common7\Packages\Debugger</tt> and append
102 the contents of <tt>clangVisuailzers.txt</tt> to it. This method should work for
Chandler Carruth245a5382011-11-16 19:29:07 +0000[diff] [blame]103 Visual Studio 2008 and above.
Douglas Gregor3ef1ad22011-07-27 05:22:46 +0000[diff] [blame]104 </li>
105 </ul>
106
107 <p><i>[Note: To disable the visualizer for any specific variable, type
108 <tt>variable_name,!</tt> inside the watch window.]</i></p>
109
110 <!--=====================================================================-->
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]111 <h2 id="testing">Testing</h2>
112 <!--=====================================================================-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]113
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]114 <p><i>[Note: The test running mechanism is currently under revision, so the
115 following might change shortly.]</i></p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]116
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]117 <!--=====================================================================-->
118 <h3 id="testingNonWindows">Testing on Unix-like Systems</h3>
119 <!--=====================================================================-->
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]120
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]121 <p>Clang includes a basic regression suite in the tree which can be
122 run with <tt>make test</tt> from the top-level clang directory, or
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]123 just <tt>make</tt> in the <em>test</em> sub-directory.
124 <tt>make VERBOSE=1</tt> can be used to show more detail
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]125 about what is being run.</p>
126
Daniel Dunbardf293782010-06-10 17:01:45 +0000[diff] [blame]127 <p>If you built LLVM and Clang using CMake, the test suite can be run
128 with <tt>make clang-test</tt> from the top-level LLVM directory.</p>
129
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]130 <p>The tests primarily consist of a test runner script running the compiler
131 under test on individual test files grouped in the directories under the
132 test directory. The individual test files include comments at the
133 beginning indicating the Clang compile options to use, to be read
134 by the test runner. Embedded comments also can do things like telling
135 the test runner that an error is expected at the current line.
136 Any output files produced by the test will be placed under
137 a created Output directory.</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]138
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]139 <p>During the run of <tt>make test</tt>, the terminal output will
140 display a line similar to the following:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]141
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]142 <ul><tt>--- Running clang tests for i686-pc-linux-gnu ---</tt></ul>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]143
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]144 <p>followed by a line continually overwritten with the current test
145 file being compiled, and an overall completion percentage.</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]146
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]147 <p>After the <tt>make test</tt> run completes, the absence of any
148 <tt>Failing Tests (count):</tt> message indicates that no tests
149 failed unexpectedly. If any tests did fail, the
150 <tt>Failing Tests (count):</tt> message will be followed by a list
151 of the test source file paths that failed. For example:</p>
152
153 <tt><pre>
154 Failing Tests (3):
155 /home/john/llvm/tools/clang/test/SemaCXX/member-name-lookup.cpp
156 /home/john/llvm/tools/clang/test/SemaCXX/namespace-alias.cpp
157 /home/john/llvm/tools/clang/test/SemaCXX/using-directive.cpp
158 </pre></tt>
159
160 <p>If you used the <tt>make VERBOSE=1</tt> option, the terminal
161 output will reflect the error messages from the compiler and
162 test runner.</p>
163
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]164 <p>The regression suite can also be run with Valgrind by running
165 <tt>make test VG=1</tt> in the top-level clang directory.</p>
166
167 <p>For more intensive changes, running
168 the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM
169 Test Suite</a> with clang is recommended. Currently the best way to
Daniel Dunbar12e57bc2009-08-06 16:47:53 +0000[diff] [blame]170 override LLVMGCC, as in: <tt>make LLVMGCC="clang -std=gnu89"
171 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]172 full path).</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]173
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]174 <!--=====================================================================-->
175 <h3 id="testingWindows">Testing using Visual Studio on Windows</h3>
176 <!--=====================================================================-->
177
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]178 <p>The Clang test suite can be run from either Visual Studio or
179 the command line.</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]180
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]181 <p>Note that the test runner is based on
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]182 Python, which must be installed. Find Python at:
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]183 <a href="http://www.python.org/download/">http://www.python.org/download/</a>.
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]184 Download the latest stable version (2.6.2 at the time of this writing).</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]185
Chris Lattner357f7ce2009-08-20 06:17:11 +0000[diff] [blame]186 <p>The GnuWin32 tools are also necessary for running the tests.
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]187 Get them from <a href="http://getgnuwin32.sourceforge.net/">
NAKAMURA Takumida0f45d2011-03-18 03:21:44 +0000[diff] [blame]188 http://getgnuwin32.sourceforge.net/</a>.
189 If the environment variable <tt>%PATH%</tt> does not have GnuWin32,
190 or if other grep(s) supercedes GnuWin32 on <tt>%PATH%,</tt>
191 you should specify <tt>LLVM_LIT_TOOLS_DIR</tt>
192 to CMake explicitly.</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]193
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]194 <p>The cmake build tool is set up to create Visual Studio project files
195 for running the tests, "clang-test" being the root. Therefore, to
196 run the test from Visual Studio, right-click the clang-test project
197 and select "Build".</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]198
NAKAMURA Takumida0f45d2011-03-18 03:21:44 +0000[diff] [blame]199 <p>
200 Please see also
201 <a href="http://llvm.org/docs/GettingStartedVS.html">Getting Started
202 with the LLVM System using Microsoft Visual Studio</a> and
203 <a href="http://llvm.org/docs/CMake.html">Building LLVM with CMake</a>.
204 </p>
205
Dawn Perchik217a3452010-09-03 17:01:13 +0000[diff] [blame]206 <!--=====================================================================-->
207 <h3 id="testingCommands">Testing on the Command Line</h3>
208 <!--=====================================================================-->
209
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]210 <p>To run all the tests from the command line, execute a command like
211 the following:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]212
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]213 <tt>
214 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
215 (path to llvm)/llvm/tools/clang/test
216 </tt>
217
Douglas Gregora71ef5d2011-01-24 18:04:58 +0000[diff] [blame]218 <p>For CMake builds e.g. on Windows with Visual Studio, you will need
219 to specify your build configuration (Debug, Release, etc.) via
220 <tt>--param=build_config=(build config)</tt>.</p>
221
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]222 <p>To run a single test:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]223
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]224 <tt>
225 python (path to llvm)/llvm/utils/lit/lit.py -sv --no-progress-bar
226 (path to llvm)/llvm/tools/clang/test/(dir)/(test)
227 </tt>
228
229 <p>For example:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]230
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]231 <tt>
232 python C:/Tools/llvm/utils/lit/lit.py -sv --no-progress-bar
233 C:/Tools/llvm/tools/clang/test/Sema/wchar.c
234 </tt>
235
236 <p>The -sv option above tells the runner to show the test output if
237 any tests failed, to help you determine the cause of failure.</p>
238
Francois Pichetb2043d72010-09-11 21:16:11 +0000[diff] [blame]239 <p>Your output might look something like this:</p>
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]240
Francois Pichetb2043d72010-09-11 21:16:11 +0000[diff] [blame]241<tt><pre>lit.py: lit.cfg:152: note: using clang: 'C:/Tools/llvm/bin/Release\\clang.EXE'
242-- Testing: Testing: 2534 tests, 4 threads --
243Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
244Testing Time: 81.52s
245 Expected Passes : 2503
246 Expected Failures : 28
247 Unsupported Tests : 3
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]248</pre></tt>
John Thompson99ff8da2009-11-06 00:06:29 +0000[diff] [blame]249
Francois Pichetb2043d72010-09-11 21:16:11 +0000[diff] [blame]250 <p>The statistic, "Unexpected Failures" (not shown if all tests pass), is the important one.</p>
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]251
252 <!--=====================================================================-->
253 <h2 id="patches">Creating Patch Files</h2>
254 <!--=====================================================================-->
255
256 <p>To return changes to the Clang team, unless you have checkin
Chris Lattnerfc8f0e12011-04-15 05:22:18 +0000[diff] [blame]257 privileges, the preferred way is to send patch files to the
Douglas Gregor8b06d6b2011-11-19 19:14:26 +0000[diff] [blame]258 cfe-commits mailing list, with an explanation of what the patch is
259 for. If your patch requires a wider discussion (for example,
260 because it is an architectural change), you can use the cfe-dev
261 mailing list. </p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]262
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]263 <p>To create these patch files, change directory
264 to the llvm/tools/clang root and run:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]265
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]266 <ul><tt>svn diff (relative path) >(patch file name)</tt></ul>
267
268 <p>For example, for getting the diffs of all of clang:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]269
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]270 <ul><tt>svn diff . >~/mypatchfile.patch</tt></ul>
271
272 <p>For example, for getting the diffs of a single file:</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]273
Eli Friedmand1e1ef32009-08-03 19:42:28 +0000[diff] [blame]274 <ul><tt>svn diff lib/Parse/ParseDeclCXX.cpp >~/ParseDeclCXX.patch</tt></ul>
275
276 <p>Note that the paths embedded in the patch depend on where you run it,
277 so changing directory to the llvm/tools/clang directory is recommended.</p>
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]278
279 <!--=====================================================================-->
280 <h2 id="irgen">LLVM IR Generation</h2>
281 <!--=====================================================================-->
282
283 <p>The LLVM IR generation part of clang handles conversion of the
284 AST nodes output by the Sema module to the LLVM Intermediate
285 Representation (IR). Historically, this was referred to as
286 "codegen", and the Clang code for this lives
287 in <tt>lib/CodeGen</tt>.</p>
NAKAMURA Takumi6975d072011-03-18 03:21:38 +0000[diff] [blame]288
Cedric Venet3d658642009-02-14 20:20:19 +0000[diff] [blame]289 <p>The output is most easily inspected using the <tt>-emit-llvm</tt>
290 option to clang (possibly in conjunction with <tt>-o -</tt>). You
291 can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file
292 which can be processed by the suite of LLVM tools
293 like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM
294 <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a>
295 for more information.</p>
296
297</div>
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