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3<title>Clang Compiler User's Manual</title>
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17
18<h1>Clang Compiler User's Manual</h1>
19
20<ul>
21<li><a href="#intro">Introduction</a>
22 <ul>
23 <li><a href="#terminology">Terminology</a></li>
24 <li><a href="#basicusage">Basic Usage</a></li>
25 </ul>
26</li>
27<li><a href="#commandline">Command Line Options</a></li>
28<li><a href="#general_features">Language and Target-Independent Features</a>
29 <ul>
30 <li><a href="#diagnostics">Controlling Errors and Warnings</a></li>
31 <li><a href="#precompiledheaders">Precompiled Headers</a></li>
32 </ul>
33</li>
34<li><a href="#c">C Language Features</a>
35 <ul>
36<!-- <li><a href="#pragmas">Pragmas Supported</a></li> -->
37 <li><a href="#c_extensions">C Extensions Supported</a></li>
38 <li><a href="#c_incompatibilities">Intentional Incompatibilities with
39 GCC</a></li>
40 </ul>
41</li>
42<li><a href="#objc">Objective-C Language Features</a>
43 <ul>
44 <li><a href="#objc_incompatibilities">Intentional Incompatibilities with
45 GCC</a></li>
46 </ul>
47</li>
48<li><a href="#cxx">C++ Language Features</a>
49 <ul>
50 <li>...</li>
51 </ul>
52</li>
53<li><a href="#objcxx">Objective C++ Language Features</a>
54 <ul>
55 <li>...</li>
56 </ul>
57</li>
58<li><a href="#target_features">Target-Specific Features and Limitations</a>
59 <ul>
60 <li><a href="#target_arch">CPU Architectures Features and Limitations</a>
61 <ul>
62 <li><a href="#target_arch_x86">X86</a></li>
63 <li>PPC</li>
64 <li>ARM</li>
65 </ul>
66 </li>
67 <li><a href="#target_os">Operating System Features and Limitations</a>
68 <ul>
69 <li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li>
70 <li>Linux, etc.</li>
71 </ul>
72
73 </li>
74 </ul>
75</li>
76</ul>
77
78
79<!-- ======================================================================= -->
80<h2 id="intro">Introduction</h2>
81<!-- ======================================================================= -->
82
83<p>The Clang Compiler is an open-source compiler for the C family of programming
84languages, aiming to be the best in class implementation of these languages.
85Clang builds on the LLVM optimizer and code generator, allowing it to provide
86high-quality optimization and code generation support for many targets. For
87more general information, please see the <a href="http://clang.llvm.org">Clang
88Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p>
89
90<p>This document describes important notes about using Clang as a compiler for
91an end-user, documenting the supported features, command line options, etc. If
92you are interested in using Clang to build a tool that processes code, please
93see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are
94interested in the <a href="http://clang.llvm.org/StaticAnalysis.html">Clang
95Static Analyzer</a>, please see its web page.</p>
96
97<p>Clang is designed to support the C family of programming languages, which
98includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a
99href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many
100dialects of those. For language-specific information, please see the
101corresponding language specific section:</p>
102
103<ul>
104<li><a href="#c">C Language</a>: K&amp;R C, ANSI C89, ISO C90, ISO C94
105 (C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li>
106<li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus
107 variants depending on base language.</li>
108<li><a href="#cxx">C++ Language Features</a></li>
109<li><a href="#objcxx">Objective C++ Language</a></li>
110</ul>
111
112<p>In addition to these base languages and their dialects, Clang supports a
113broad variety of language extensions, which are documented in the corresponding
114language section. These extensions are provided to be compatible with the GCC,
115Microsoft, and other popular compilers as well as to improve functionality
116through Clang-specific features. The Clang driver and language features are
117intentionally designed to be as compatible with the GNU GCC compiler as
118reasonably possible, easing migration from GCC to Clang. In most cases, code
119"just works".</p>
120
121<p>In addition to language specific features, Clang has a variety of features
122that depend on what CPU architecture or operating system is being compiled for.
123Please see the <a href="target_features">Target-Specific Features and
124Limitations</a> section for more details.</p>
125
126<p>The rest of the introduction introduces some basic <a
127href="#terminology">compiler terminology</a> that is used throughout this manual
128and contains a basic <a href="#basicusage">introduction to using Clang</a>
129as a command line compiler.</p>
130
131<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
132<h3 id="terminology">Terminology</h3>
133<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
134
135<p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic,
136 optimizer</p>
137
138<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
139<h3 id="basicusage">Basic Usage</h3>
140<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
141
142<p>Intro to how to use a C compiler for newbies.</p>
143<p>
144compile + link
145
146compile then link
147
148debug info
149
150enabling optimizations
151
152picking a language to use, defaults to C99 by default. Autosenses based on
153extension.
154
155using a makefile
156</p>
157
158
159<!-- ======================================================================= -->
160<h2 id="commandline">Command Line Options</h2>
161<!-- ======================================================================= -->
162
163<p>
164This section is generally an index into other sections. It does not go into
165depth on most. However, the first part introduces the language selection and
166other high level options like -c, -g, etc.
167</p>
168
169<!-- ======================================================================= -->
170<h2 id="general_features">Language and Target-Independent Features</h2>
171<!-- ======================================================================= -->
172
173
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175<h3 id="diagnostics">Controlling Errors and Warnings</h3>
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178
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183
184
185<!-- ======================================================================= -->
186<h2 id="c">C Language Features</h2>
187<!-- ======================================================================= -->
188
189
190<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
191<h3 id="c_incompatibilities">Intentional Incompatibilities with GCC</h3>
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193
194<p>No VLAs in structs.</p>
195
196
197
198
199<!-- ======================================================================= -->
200<h2 id="objc">Objective-C Language Features</h2>
201<!-- ======================================================================= -->
202
203
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205<h3 id="objc_incompatibilities">Intentional Incompatibilities with GCC</h3>
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207
208<p>No cast of super, no lvalue casts.</p>
209
210
211
212<!-- ======================================================================= -->
213<h2 id="cxx">C++ Language Features</h2>
214<!-- ======================================================================= -->
215
216<p>At this point, Clang C++ is not generally useful. However, Clang C++ support
217is under active development and is progressing rapidly. Please see the <a
218href="http://clang.llvm.org/cxx_status.html">C++ Status</a> page for details or
219ask on the mailing list about how you can help.</p>
220
221<p>Note that the clang driver will refuse to even try to use clang to compile
222C++ code unless you pass the <tt>-ccc-clang-cxx</tt> option to the driver. If
223you really want to play with Clang's C++ support, please pass that flag. </p>
224
225<!-- ======================================================================= -->
226<h2 id="objcxx">Objective C++ Language Features</h2>
227<!-- ======================================================================= -->
228
229<p>At this point, Clang C++ support is not generally useful (and therefore,
230neither is Objective-C++). Please see the <a href="#cxx">C++ section</a> for
231more information.</p>
232
233<!-- ======================================================================= -->
234<h2 id="target_features">Target-Specific Features and Limitations</h2>
235<!-- ======================================================================= -->
236
237
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239<h3 id="target_arch">CPU Architectures Features and Limitations</h3>
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241
242<!-- ======================== -->
243<h4 id="target_arch_x86">X86</h4>
244<!-- ======================== -->
245
246
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248<h3 id="target_os">Operating System Features and Limitations</h3>
249<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
250
251<!-- ======================================= -->
252<h4 id="target_os_darwin">Darwin (Mac OS/X)</h4>
253<!-- ======================================= -->
254
255<p>No __thread support, 64-bit ObjC support requires SL tools.</p>
256
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