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16<div id="content">
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>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]27<li><a href="#commandline">Command Line Options</a>
28 <ul>
29 <li><a href="#cl_diagnostics">Options to Control Error and Warning
30 Messages</a></li>
31 </ul>
32</li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]33<li><a href="#general_features">Language and Target-Independent Features</a>
34 <ul>
35 <li><a href="#diagnostics">Controlling Errors and Warnings</a></li>
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]36 <ul>
37 <li><a href="#diagnostics_display">Controlling How Clang Displays Diagnostics</a></li>
38 <li><a href="#diagnostics_mappings">Diagnostic Mappings</a></li>
39 <li><a href="#diagnostics_commandline">Controlling Diagnostics via Command Line Flags</a></li>
40 <li><a href="#diagnostics_pragmas">Controlling Diagnostics via Pragmas</a></li>
41 </ul>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]42 <li><a href="#precompiledheaders">Precompiled Headers</a></li>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]43 <li><a href="#codegen">Controlling Code Generation</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]44 </ul>
45</li>
46<li><a href="#c">C Language Features</a>
47 <ul>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]48 <li><a href="#c_ext">Extensions supported by clang</a></li>
49 <li><a href="#c_modes">Differences between various standard modes</a></li>
50 <li><a href="#c_unimpl_gcc">GCC extensions not implemented yet</a></li>
51 <li><a href="#c_unsupp_gcc">Intentionally unsupported GCC extensions</a></li>
52 <li><a href="#c_ms">Microsoft extensions</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]53 </ul>
54</li>
55<li><a href="#objc">Objective-C Language Features</a>
56 <ul>
57 <li><a href="#objc_incompatibilities">Intentional Incompatibilities with
58 GCC</a></li>
59 </ul>
60</li>
61<li><a href="#cxx">C++ Language Features</a>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]62</li>
63<li><a href="#objcxx">Objective C++ Language Features</a>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]64</li>
65<li><a href="#target_features">Target-Specific Features and Limitations</a>
66 <ul>
67 <li><a href="#target_arch">CPU Architectures Features and Limitations</a>
68 <ul>
69 <li><a href="#target_arch_x86">X86</a></li>
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]70 <li><a href="#target_arch_arm">ARM</a></li>
71 <li><a href="#target_arch_other">Other platforms</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]72 </ul>
73 </li>
74 <li><a href="#target_os">Operating System Features and Limitations</a>
75 <ul>
76 <li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li>
77 <li>Linux, etc.</li>
78 </ul>
79
80 </li>
81 </ul>
82</li>
83</ul>
84
85
86<!-- ======================================================================= -->
87<h2 id="intro">Introduction</h2>
88<!-- ======================================================================= -->
89
90<p>The Clang Compiler is an open-source compiler for the C family of programming
91languages, aiming to be the best in class implementation of these languages.
92Clang builds on the LLVM optimizer and code generator, allowing it to provide
93high-quality optimization and code generation support for many targets. For
94more general information, please see the <a href="http://clang.llvm.org">Clang
95Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p>
96
97<p>This document describes important notes about using Clang as a compiler for
98an end-user, documenting the supported features, command line options, etc. If
99you are interested in using Clang to build a tool that processes code, please
100see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are
101interested in the <a href="http://clang.llvm.org/StaticAnalysis.html">Clang
102Static Analyzer</a>, please see its web page.</p>
103
104<p>Clang is designed to support the C family of programming languages, which
105includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a
106href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many
107dialects of those. For language-specific information, please see the
108corresponding language specific section:</p>
109
110<ul>
111<li><a href="#c">C Language</a>: K&amp;R C, ANSI C89, ISO C90, ISO C94
112 (C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li>
113<li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus
114 variants depending on base language.</li>
115<li><a href="#cxx">C++ Language Features</a></li>
116<li><a href="#objcxx">Objective C++ Language</a></li>
117</ul>
118
119<p>In addition to these base languages and their dialects, Clang supports a
120broad variety of language extensions, which are documented in the corresponding
121language section. These extensions are provided to be compatible with the GCC,
122Microsoft, and other popular compilers as well as to improve functionality
123through Clang-specific features. The Clang driver and language features are
124intentionally designed to be as compatible with the GNU GCC compiler as
125reasonably possible, easing migration from GCC to Clang. In most cases, code
126"just works".</p>
127
128<p>In addition to language specific features, Clang has a variety of features
129that depend on what CPU architecture or operating system is being compiled for.
Douglas Gregorcd5a5052009-11-09 15:15:41 +0000[diff] [blame]130Please see the <a href="#target_features">Target-Specific Features and
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]131Limitations</a> section for more details.</p>
132
133<p>The rest of the introduction introduces some basic <a
134href="#terminology">compiler terminology</a> that is used throughout this manual
135and contains a basic <a href="#basicusage">introduction to using Clang</a>
136as a command line compiler.</p>
137
138<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
139<h3 id="terminology">Terminology</h3>
140<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
141
142<p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic,
143 optimizer</p>
144
145<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
146<h3 id="basicusage">Basic Usage</h3>
147<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
148
149<p>Intro to how to use a C compiler for newbies.</p>
150<p>
151compile + link
152
153compile then link
154
155debug info
156
157enabling optimizations
158
159picking a language to use, defaults to C99 by default. Autosenses based on
160extension.
161
162using a makefile
163</p>
164
165
166<!-- ======================================================================= -->
167<h2 id="commandline">Command Line Options</h2>
168<!-- ======================================================================= -->
169
170<p>
171This section is generally an index into other sections. It does not go into
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]172depth on the ones that are covered by other sections. However, the first part
173introduces the language selection and other high level options like -c, -g, etc.
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]174</p>
175
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]176
177<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
178<h3 id="cl_diagnostics">Options to Control Error and Warning Messages</h3>
179<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
180
181<p><b>-Werror</b>: Turn warnings into errors.</p>
182<p><b>-Werror=foo</b>: Turn warning "foo" into an error.</p>
183<p><b>-Wno-error=foo</b>: Turn warning "foo" into an warning even if -Werror is
184 specified.</p>
185<p><b>-Wfoo</b>: Enable warning foo</p>
186<p><b>-Wno-foo</b>: Disable warning foo</p>
187<p><b>-w</b>: Disable all warnings.</p>
188<p><b>-pedantic</b>: Warn on language extensions.</p>
189<p><b>-pedantic-errors</b>: Error on language extensions.</p>
190<p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p>
191
Chris Lattner0f0c9632010-04-07 20:49:23 +0000[diff] [blame^]192<p><b>-ferror-limit=123</b>: Stop emitting diagnostics after 123 errors have
193 been produced. The default is 20, and the error limit can be disabled with
194 -ferror-limit=0.</p>
195
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]196<!-- ================================================= -->
197<h4 id="cl_diag_formatting">Formatting of Diagnostics</h4>
198<!-- ================================================= -->
199
200<p>Clang aims to produce beautiful diagnostics by default, particularly for new
201users that first come to Clang. However, different people have different
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]202preferences, and sometimes Clang is driven by another program that wants to
203parse simple and consistent output, not a person. For these cases, Clang
204provides a wide range of options to control the exact output format of the
205diagnostics that it generates.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]206
207<dl>
208
209<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
210<dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in
211diagnostic.</dt>
212<dd>This option, which defaults to on, controls whether or not Clang prints the
213column number of a diagnostic. For example, when this is enabled, Clang will
214print something like:</p>
215
216<pre>
217 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
218 #endif bad
219 ^
220 //
221</pre>
222
223<p>When this is disabled, Clang will print "test.c:28: warning..." with no
224column number.</p>
225</dd>
226
227<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
228<dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print
229source file/line/column information in diagnostic.</dt>
230<dd>This option, which defaults to on, controls whether or not Clang prints the
231filename, line number and column number of a diagnostic. For example,
232when this is enabled, Clang will print something like:</p>
233
234<pre>
235 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
236 #endif bad
237 ^
238 //
239</pre>
240
241<p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p>
242</dd>
243
244<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
245<dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source
246line and ranges from source code in diagnostic.</dt>
247<dd>This option, which defaults to on, controls whether or not Clang prints the
248source line, source ranges, and caret when emitting a diagnostic. For example,
249when this is enabled, Clang will print something like:</p>
250
251<pre>
252 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
253 #endif bad
254 ^
255 //
256</pre>
257
258<p>When this is disabled, Clang will just print:</p>
259
260<pre>
261 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
262</pre>
263
264</dd>
265
266<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
267<dt id="opt_fdiagnostics-show-option"><b>-f[no-]diagnostics-show-option</b>:
268Enable <tt>[-Woption]</tt> information in diagnostic line.</dt>
269<dd>This option, which defaults to on,
270controls whether or not Clang prints the associated <A
271href="#cl_diag_warning_groups">warning group</a> option name when outputting
272a warning diagnostic. For example, in this output:</p>
273
274<pre>
275 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
276 #endif bad
277 ^
278 //
279</pre>
280
281<p>Passing <b>-fno-diagnostics-show-option</b> will prevent Clang from printing
282the [<a href="#opt_Wextra-tokens">-Wextra-tokens</a>] information in the
283diagnostic. This information tells you the flag needed to enable or disable the
284diagnostic, either from the command line or through <a
285href="#pragma_GCC_diagnostic">#pragma GCC diagnostic</a>.</dd>
286
287
288<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
289<dt id="opt_fdiagnostics-fixit-info"><b>-f[no-]diagnostics-fixit-info</b>:
290Enable "FixIt" information in the diagnostics output.</dt>
291<dd>This option, which defaults to on, controls whether or not Clang prints the
292information on how to fix a specific diagnostic underneath it when it knows.
293For example, in this output:</p>
294
295<pre>
296 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
297 #endif bad
298 ^
299 //
300</pre>
301
302<p>Passing <b>-fno-diagnostics-fixit-info</b> will prevent Clang from printing
303the "//" line at the end of the message. This information is useful for users
304who may not understand what is wrong, but can be confusing for machine
305parsing.</p>
306</dd>
307
308<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]309<dt id="opt_fdiagnostics-print-source-range-info">
310<b>-f[no-]diagnostics-print-source-range-info</b>:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]311Print machine parsable information about source ranges.</dt>
312<dd>This option, which defaults to off, controls whether or not Clang prints
313information about source ranges in a machine parsable format after the
314file/line/column number information. The information is a simple sequence of
315brace enclosed ranges, where each range lists the start and end line/column
316locations. For example, in this output:</p>
317
318<pre>
319exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
320 P = (P-42) + Gamma*4;
321 ~~~~~~ ^ ~~~~~~~
322</pre>
323
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]324<p>The {}'s are generated by -fdiagnostics-print-source-range-info.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]325</dd>
326
327
328</dl>
329
330
331
332
333<!-- ===================================================== -->
334<h4 id="cl_diag_warning_groups">Individual Warning Groups</h4>
335<!-- ===================================================== -->
336
337<p>TODO: Generate this from tblgen. Define one anchor per warning group.</p>
338
339
340<dl>
341
342
343<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
344<dt id="opt_Wextra-tokens"><b>-Wextra-tokens</b>: Warn about excess tokens at
345 the end of a preprocessor directive.</dt>
346<dd>This option, which defaults to on, enables warnings about extra tokens at
347the end of preprocessor directives. For example:</p>
348
349<pre>
350 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
351 #endif bad
352 ^
353</pre>
354
355<p>These extra tokens are not strictly conforming, and are usually best handled
356by commenting them out.</p>
357
358<p>This option is also enabled by <a href="">-Wfoo</a>, <a href="">-Wbar</a>,
359 and <a href="">-Wbaz</a>.</p>
360</dd>
361
362</dl>
363
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]364<!-- ======================================================================= -->
365<h2 id="general_features">Language and Target-Independent Features</h2>
366<!-- ======================================================================= -->
367
368
369<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
370<h3 id="diagnostics">Controlling Errors and Warnings</h3>
371<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
372
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]373<p>Clang provides a number of ways to control which code constructs cause it to
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]374emit errors and warning messages, and how they are displayed to the console.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]375
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]376<h4 id="diagnostics_display">Controlling How Clang Displays Diagnostics</h4>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]377
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]378<p>When Clang emits a diagnostic, it includes rich information in the output,
379and gives you fine-grain control over which information is printed. Clang has
380the ability to print this information, and these are the options that control
381it:</p>
382
383<p>
384<ol>
385<li>A file/line/column indicator that shows exactly where the diagnostic occurs
386 in your code [<a href="#opt_fshow-column">-fshow-column</a>, <a
387 href="#opt_fshow-source-location">-fshow-source-location</a>].</li>
388<li>A categorization of the diagnostic as a note, warning, error, or fatal
389 error.</li>
390<li>A text string that describes what the problem is.</li>
391<li>An option that indicates how to control the diagnostic (for diagnostics that
392 support it) [<a
393 href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li>
394<li>The line of source code that the issue occurs on, along with a caret and
395 ranges that indicate the important locations [<a
396 href="opt_fcaret-diagnostics">-fcaret-diagnostics</a>].</li>
397<li>"FixIt" information, which is a concise explanation of how to fix the
398 problem (when Clang is certain it knows) [<a
399 href="opt_fdiagnostics-fixit-info">-fdiagnostics-fixit-info</a>].</li>
400<li>A machine-parsable representation of the ranges involved (off by
401 default) [<a
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]402 href="opt_fdiagnostics-print-source-range-info">-fdiagnostics-print-source-range-info</a>].</li>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]403</ol></p>
404
405<p>For more information please see <a href="#cl_diag_formatting">Formatting of
406Diagnostics</a>.</p>
407
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]408<h4 id="diagnostics_mappings">Diagnostic Mappings</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]409
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]410<p>All diagnostics are mapped into one of these 5 classes:</p>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]411
412<p>
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]413<ul>
414<li>Ignored</li>
415<li>Note</li>
416<li>Warning</li>
417<li>Error</li>
418<li>Fatal</li>
419</ul></p>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]420
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]421<h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line Flags</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]422
423<p>-W flags, -pedantic, etc</p>
424
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]425<h4 id="diagnostics_pragmas">Controlling Diagnostics via Pragmas</h4>
426
427<p>Clang can also control what diagnostics are enabled through the use of
428pragmas in the source code. This is useful for turning off specific warnings
429in a section of source code. Clang supports GCC's pragma for compatibility
430with existing source code, as well as several extensions. </p>
431
432<p>The pragma may control any warning that can be used from the command line.
433Warnings may be set to ignored, warning, error, or fatal. The following
434example code will tell Clang or GCC to ignore the -Wall warnings:</p>
435
436<pre>
437#pragma GCC diagnostic ignored "-Wall"
438</pre>
439
440<p>In addition to all of the functionality of provided by GCC's pragma, Clang
441also allows you to push and pop the current warning state. This is particularly
442useful when writing a header file that will be compiled by other people, because
443you don't know what warning flags they build with.</p>
444
445<p>In the below example
446-Wmultichar is ignored for only a single line of code, after which the
447diagnostics return to whatever state had previously existed.</p>
448
449<pre>
450#pragma clang diagnostic push
451#pragma clang diagnostic ignored "-Wmultichar"
452
453char b = 'df'; // no warning.
454
455#pragma clang diagnostic pop
456</pre>
457
458<p>The push and pop pragmas will save and restore the full diagnostic state of
459the compiler, regardless of how it was set. That means that it is possible to
460use push and pop around GCC compatible diagnostics and Clang will push and pop
461them appropriately, while GCC will ignore the pushes and pops as unknown
462pragmas. It should be noted that while Clang supports the GCC pragma, Clang and
463GCC do not support the exact same set of warnings, so even when using GCC
464compatible #pragmas there is no guarantee that they will have identical behaviour
465on both compilers. </p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]466
467<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
468<h3 id="precompiledheaders">Precompiled Headers</h3>
469<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
470
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]471<p><a href="http://en.wikipedia.org/wiki/Precompiled_header">Precompiled
472headers</a> are a general approach employed by many compilers to reduce
473compilation time. The underlying motivation of the approach is that it is
474common for the same (and often large) header files to be included by
475multiple source files. Consequently, compile times can often be greatly improved
476by caching some of the (redundant) work done by a compiler to process headers.
477Precompiled header files, which represent one of many ways to implement
478this optimization, are literally files that represent an on-disk cache that
479contains the vital information necessary to reduce some of the work
480needed to process a corresponding header file. While details of precompiled
481headers vary between compilers, precompiled headers have been shown to be a
482highly effective at speeding up program compilation on systems with very large
483system headers (e.g., Mac OS/X).</p>
484
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]485<h4>Generating a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]486
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]487<p>To generate a PCH file using Clang, one invokes Clang with
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]488the <b><tt>-x <i>&lt;language&gt;</i>-header</tt></b> option. This mirrors the
489interface in GCC for generating PCH files:</p>
490
491<pre>
492 $ gcc -x c-header test.h -o test.h.gch
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]493 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]494</pre>
495
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]496<h4>Using a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]497
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]498<p>A PCH file can then be used as a prefix header when a
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]499<b><tt>-include</tt></b> option is passed to <tt>clang</tt>:</p>
500
501<pre>
502 $ clang -include test.h test.c -o test
503</pre>
504
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]505<p>The <tt>clang</tt> driver will first check if a PCH file for <tt>test.h</tt>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]506is available; if so, the contents of <tt>test.h</tt> (and the files it includes)
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]507will be processed from the PCH file. Otherwise, Clang falls back to
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]508directly processing the content of <tt>test.h</tt>. This mirrors the behavior of
509GCC.</p>
510
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]511<p><b>NOTE:</b> Clang does <em>not</em> automatically use PCH files
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]512for headers that are directly included within a source file. For example:</p>
513
514<pre>
Chris Lattnere42ec542009-06-13 20:35:58 +0000[diff] [blame]515 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]516 $ cat test.c
517 #include "test.h"
518 $ clang test.c -o test
519</pre>
520
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]521<p>In this example, <tt>clang</tt> will not automatically use the PCH file for
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]522<tt>test.h</tt> since <tt>test.h</tt> was included directly in the source file
523and not specified on the command line using <tt>-include</tt>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]524
Douglas Gregore650c8c2009-07-07 00:12:59 +0000[diff] [blame]525<h4>Relocatable PCH Files</h4>
526<p>It is sometimes necessary to build a precompiled header from headers that
527are not yet in their final, installed locations. For example, one might build a
528precompiled header within the build tree that is then meant to be installed
529alongside the headers. Clang permits the creation of "relocatable" precompiled
530headers, which are built with a given path (into the build directory) and can
531later be used from an installed location.</p>
532
533<p>To build a relocatable precompiled header, place your headers into a
534subdirectory whose structure mimics the installed location. For example, if you
535want to build a precompiled header for the header <code>mylib.h</code> that
536will be installed into <code>/usr/include</code>, create a subdirectory
537<code>build/usr/include</code> and place the header <code>mylib.h</code> into
538that subdirectory. If <code>mylib.h</code> depends on other headers, then
539they can be stored within <code>build/usr/include</code> in a way that mimics
540the installed location.</p>
541
542<p>Building a relocatable precompiled header requires two additional arguments.
543First, pass the <code>--relocatable-pch</code> flag to indicate that the
544resulting PCH file should be relocatable. Second, pass
545<code>-isysroot /path/to/build</code>, which makes all includes for your
546library relative to the build directory. For example:</p>
547
548<pre>
549 # clang -x c-header --relocatable-pch -isysroot /path/to/build /path/to/build/mylib.h mylib.h.pch
550</pre>
551
552<p>When loading the relocatable PCH file, the various headers used in the PCH
553file are found from the system header root. For example, <code>mylib.h</code>
554can be found in <code>/usr/include/mylib.h</code>. If the headers are installed
555in some other system root, the <code>-isysroot</code> option can be used provide
556a different system root from which the headers will be based. For example,
557<code>-isysroot /Developer/SDKs/MacOSX10.4u.sdk</code> will look for
558<code>mylib.h</code> in
559<code>/Developer/SDKs/MacOSX10.4u.sdk/usr/include/mylib.h</code>.</p>
560
561<p>Relocatable precompiled headers are intended to be used in a limited number
562of cases where the compilation environment is tightly controlled and the
563precompiled header cannot be generated after headers have been installed.
564Relocatable precompiled headers also have some performance impact, because
565the difference in location between the header locations at PCH build time vs.
566at the time of PCH use requires one of the PCH optimizations,
567<code>stat()</code> caching, to be disabled. However, this change is only
568likely to affect PCH files that reference a large number of headers.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]569
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]570<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
571<h3 id="codegen">Controlling Code Generation</h3>
572<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
573
574<p>Clang provides a number of ways to control code generation. The options are listed below.</p>
575
576<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
577<dt id="opt_fcatch-undefined-behavior"><b>-fcatch-undefined-behavior</b>: Turn
578on runtime code generation to check for undefined behavior.</dt>
579
580<dd>This option, which defaults to off, controls whether or not Clang
581adds runtime checks for undefined runtime behavior. If the check fails,
582<tt>__builtin_trap()</tt> is used to indicate failure.
583The checks are:
584<p>
Mike Stump88b2a172009-12-16 03:25:12 +0000[diff] [blame]585<li>Subscripting where the static type of one operand is variable
586 which is decayed from an array type and the other operand is
587 greater than the size of the array or less than zero.</li>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]588<li>Shift operators where the amount shifted is greater or equal to the
589 promoted bit-width of the left-hand-side or less than zero.</li>
Mike Stump8f6a3ed2009-12-16 03:18:14 +0000[diff] [blame]590<li>If control flow reaches __builtin_unreachable.
591<li>When llvm implements more __builtin_object_size support, reads and
592 writes for objects that __builtin_object_size indicates we aren't
593 accessing valid memory. Bit-fields and vectors are not yet checked.
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]594</p>
595</dd>
596
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]597<dt id="opt_fno-assume-sane-operator-new"><b>-fno-assume-sane-operator-new</b>:
598Don't assume that the C++'s new operator is sane.</dt>
Nuno Lopesb23f20d2009-12-17 10:15:49 +0000[diff] [blame]599<dd>This option tells the compiler to do not assume that C++'s global new
600operator will always return a pointer that do not
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]601alias any other pointer when the function returns.</dd>
602
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]603<!-- ======================================================================= -->
604<h2 id="c">C Language Features</h2>
605<!-- ======================================================================= -->
606
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]607<p>The support for standard C in clang is feature-complete except for the C99
608floating-point pragmas.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]609
610<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]611<h3 id="c_ext">Extensions supported by clang</h3>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]612<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
613
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]614<p>See <a href="LanguageExtensions.html">clang language extensions</a>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]615
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]616<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
617<h3 id="c_modes">Differences between various standard modes</h3>
618<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]619
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]620<p>clang supports the -std option, which changes what language mode clang uses.
621The supported modes for C are c89, gnu89, c94, c99, gnu99 and various aliases
622for those modes. If no -std option is specified, clang defaults to gnu99 mode.
623</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]624
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]625<p>Differences between all c* and gnu* modes:</p>
626<ul>
627<li>c* modes define "__STRICT_ANSI__".</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]628<li>Target-specific defines not prefixed by underscores, like "linux", are
629defined in gnu* modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]630<li>Trigraphs default to being off in gnu* modes; they can be enabled by the
631-trigraphs option.</li>
632<li>The parser recognizes "asm" and "typeof" as keywords in gnu* modes; the
633variants "__asm__" and "__typeof__" are recognized in all modes.</li>
Eli Friedmanb0ac5452009-05-16 23:17:30 +0000[diff] [blame]634<li>The Apple "blocks" extension is recognized by default in gnu* modes
635on some platforms; it can be enabled in any mode with the "-fblocks"
636option.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]637</ul>
638
639<p>Differences between *89 and *99 modes:</p>
640<ul>
641<li>The *99 modes default to implementing "inline" as specified in C99, while
642the *89 modes implement the GNU version. This can be overridden for individual
643functions with the __gnu_inline__ attribute.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]644<li>Digraphs are not recognized in c89 mode.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]645<li>The scope of names defined inside a "for", "if", "switch", "while", or "do"
646statement is different. (example: "if ((struct x {int x;}*)0) {}".)</li>
647<li>__STDC_VERSION__ is not defined in *89 modes.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]648<li>"inline" is not recognized as a keyword in c89 mode.</li>
649<li>"restrict" is not recognized as a keyword in *89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]650<li>Commas are allowed in integer constant expressions in *99 modes.</li>
651<li>Arrays which are not lvalues are not implicitly promoted to pointers in
652*89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]653<li>Some warnings are different.</li>
654</ul>
655
656<p>c94 mode is identical to c89 mode except that digraphs are enabled in
657c94 mode (FIXME: And __STDC_VERSION__ should be defined!).</p>
658
659<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
660<h3 id="c_unimpl_gcc">GCC extensions not implemented yet</h3>
661<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
662
663<p>clang tries to be compatible with gcc as much as possible, but some gcc
664extensions are not implemented yet:</p>
665
666<ul>
667<li>clang does not support __label__
668(<a href="http://llvm.org/bugs/show_bug.cgi?id=3429">bug 3429</a>). This is
669a relatively small feature, so it is likely to be implemented relatively
670soon.</li>
671
672<li>clang does not support attributes on function pointers
673(<a href="http://llvm.org/bugs/show_bug.cgi?id=2461">bug 2461</a>). This is
674a relatively important feature, so it is likely to be implemented relatively
675soon.</li>
676
677<li>clang does not support #pragma weak
Eli Friedman4da92552009-06-02 08:21:31 +0000[diff] [blame]678(<a href="http://llvm.org/bugs/show_bug.cgi?id=3679">bug 3679</a>). Due to
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]679the uses described in the bug, this is likely to be implemented at some
680point, at least partially.</li>
681
682<li>clang does not support #pragma align
Eli Friedman4da92552009-06-02 08:21:31 +0000[diff] [blame]683(<a href="http://llvm.org/bugs/show_bug.cgi?id=3811">bug 3811</a>). This is a
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]684relatively small feature, so it is likely to be implemented relatively
685soon.</li>
686
Eli Friedman4da92552009-06-02 08:21:31 +0000[diff] [blame]687<li>clang does not support code generation for local variables pinned to
688registers (<a href="http://llvm.org/bugs/show_bug.cgi?id=3933">bug 3933</a>).
689This is a relatively small feature, so it is likely to be implemented
690relatively soon.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]691
692<li>clang does not support decimal floating point types (_Decimal32 and
693friends) or fixed-point types (_Fract and friends); nobody has expressed
694interest in these features yet, so it's hard to say when they will be
695implemented.</li>
696
697<li>clang does not support nested functions; this is a complex feature which
698is infrequently used, so it is unlikely to be implemented anytime soon.</li>
699
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]700<li>clang does not support global register variables, this is unlikely
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]701to be implemented soon because it requires additional LLVM backend support.
702</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]703
704<li>clang does not support static initialization of flexible array
705members. This appears to be a rarely used extension, but could be
706implemented pending user demand.</li>
707
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]708<li>clang does not support __builtin_va_arg_pack/__builtin_va_arg_pack_len.
709This is used rarely, but in some potentially interesting places, like the
710glibc headers, so it may be implemented pending user demand. Note that
711because clang pretends to be like GCC 4.2, and this extension was introduced
712in 4.3, the glibc headers will not try to use this extension with clang at
713the moment.</li>
714
715<li>clang does not support the gcc extension for forward-declaring function
716parameters; this has not showed up in any real-world code yet, though, so it
717might never be implemented.</li>
718
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]719</ul>
720
721<p>This is not a complete list; if you find an unsupported extension
722missing from this list, please send an e-mail to cfe-dev. This list
723currently excludes C++; see <a href="#cxx">C++ Language Features</a>.
724Also, this list does not include bugs in mostly-implemented features; please
725see the <a href="http://llvm.org/bugs/buglist.cgi?quicksearch=product%3Aclang+component%3A-New%2BBugs%2CAST%2CBasic%2CDriver%2CHeaders%2CLLVM%2BCodeGen%2Cparser%2Cpreprocessor%2CSemantic%2BAnalyzer">
726bug tracker</a> for known existing bugs (FIXME: Is there a section for
727bug-reporting guidelines somewhere?).</p>
728
729<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
730<h3 id="c_unsupp_gcc">Intentionally unsupported GCC extensions</h3>
731<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
732
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]733<ul>
734
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]735<li>clang does not support the gcc extension that allows variable-length arrays
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]736in structures. This is for a few of reasons: one, it is tricky
737to implement, two, the extension is completely undocumented, and three, the
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]738extension appears to be rarely used.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]739
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]740<li>clang does not support duplicate definitions of a function where one is
Daniel Dunbarc5f928c2009-06-04 18:37:52 +0000[diff] [blame]741inline. This complicates clients of the AST which normally can expect there is
742at most one definition for each function. Source code using this feature should
743be changed to define the inline and out-of-line definitions in separate
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]744translation units.</li>
Daniel Dunbarc5f928c2009-06-04 18:37:52 +0000[diff] [blame]745
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]746<li>clang does not have an equivalent to gcc's "fold"; this means that
747clang doesn't accept some constructs gcc might accept in contexts where a
748constant expression is required, like "x-x" where x is a variable, or calls
749to C library functions like strlen.</li>
750
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]751<li>clang does not support multiple alternative constraints in inline asm; this
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]752is an extremely obscure feature which would be complicated to implement
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]753correctly.</li>
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]754
755<li>clang does not support __builtin_apply and friends; this extension is
756extremely obscure and difficult to implement reliably.</li>
757
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]758</ul>
759
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]760<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
761<h3 id="c_ms">Microsoft extensions</h3>
762<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
763
764<p>clang has some experimental support for extensions from
765Microsoft Visual C++; to enable it, use the -fms-extensions command-line
Eli Friedmana1821b52009-06-08 06:21:03 +0000[diff] [blame]766option. This is the default for Windows targets. Note that the
767support is incomplete; enabling Microsoft extensions will silently drop
768certain constructs (including __declspec and Microsoft-style asm statements).
769</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]770
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]771<li>clang does not support the Microsoft extension where anonymous
Daniel Dunbar869e0542009-05-13 00:23:53 +0000[diff] [blame]772record members can be declared using user defined typedefs.</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]773
Daniel Dunbar9375ed12009-05-13 21:40:49 +0000[diff] [blame]774<li>clang supports the Microsoft "#pragma pack" feature for
775controlling record layout. GCC also contains support for this feature,
776however where MSVC and GCC are incompatible clang follows the MSVC
777definition.</li>
778
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]779<!-- ======================================================================= -->
780<h2 id="objc">Objective-C Language Features</h2>
781<!-- ======================================================================= -->
782
783
784<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
785<h3 id="objc_incompatibilities">Intentional Incompatibilities with GCC</h3>
786<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
787
788<p>No cast of super, no lvalue casts.</p>
789
790
791
792<!-- ======================================================================= -->
793<h2 id="cxx">C++ Language Features</h2>
794<!-- ======================================================================= -->
795
Douglas Gregor57f1a002010-02-05 23:51:14 +0000[diff] [blame]796<p>At this point, Clang C++ is not production-quality and is not recommended for use beyond experimentation. However, Clang C++ support
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]797is under active development and is progressing rapidly. Please see the <a
798href="http://clang.llvm.org/cxx_status.html">C++ Status</a> page for details or
799ask on the mailing list about how you can help.</p>
800
Douglas Gregor57f1a002010-02-05 23:51:14 +0000[diff] [blame]801<p>Note that released Clang compilers will refuse to even try to use clang to compile C++ code unless you pass the <tt>-ccc-clang-cxx</tt> option to the driver. To turn on Clang's C++ support, please pass that flag. Clang compilers built from the Subversion trunk enable C++ support by default, and do not require the <tt>-ccc-clang-cxx</tt> flag.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]802
Rafael Espindola9b2fc952010-03-17 04:31:53 +0000[diff] [blame]803<p>Clang strives to strictly conform to the C++ standard. That means
804it will reject invalid C++ code that another compiler may accept. If
805Clang reports errors in your code, please check
806the <a href="http://clang.llvm.org/cxx_compatibility.html">C++
807Compatibility</a> page to see whether they are C++-conformance bugs
808and how you can fix them.</p>
809
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]810<!-- ======================================================================= -->
811<h2 id="objcxx">Objective C++ Language Features</h2>
812<!-- ======================================================================= -->
813
814<p>At this point, Clang C++ support is not generally useful (and therefore,
815neither is Objective-C++). Please see the <a href="#cxx">C++ section</a> for
816more information.</p>
817
818<!-- ======================================================================= -->
819<h2 id="target_features">Target-Specific Features and Limitations</h2>
820<!-- ======================================================================= -->
821
822
823<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
824<h3 id="target_arch">CPU Architectures Features and Limitations</h3>
825<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
826
827<!-- ======================== -->
828<h4 id="target_arch_x86">X86</h4>
829<!-- ======================== -->
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]830<p>The support for X86 (both 32-bit and 64-bit) is considered stable
831on Darwin (Mac OS/X), Linux, FreeBSD, and Dragonfly BSD: it has been tested to
832correctly compile large C and Objective-C codebases. (FIXME: Anything specific
833we want to say here? Possibly mention some LLVM x86 limitations?)
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]834
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]835<!-- ======================== -->
836<h4 id="target_arch_arm">ARM</h4>
837<!-- ======================== -->
838ARM support is mostly feature-complete, but still experimental; it hasn't
839undergone significant testing.
840
841<!-- ======================== -->
842<h4 id="target_arch_other">Other platforms</h4>
843<!-- ======================== -->
844clang currently contains some support for PPC and Sparc; however, significant
845pieces of code generation are still missing, and they haven't undergone
846significant testing.
847
848<p>clang contains some support for the embedded PIC16 processor
849(FIXME: I haven't been keeping track of this; what should this say?).
850
851<p>clang contains limited support for the MSP430 embedded processor, but both
852the clang support and the LLVM backend support are highly experimental.
853
854<p>Other platforms are completely unsupported at the moment. Adding the
855minimal support needed for parsing and semantic analysis on a new platform
856is quite easy; see lib/Basic/Targets.cpp in the clang source tree. This level
857of support is also sufficient for conversion to LLVM IR for simple programs.
858Proper support for conversion to LLVM IR requires adding code to
859lib/CodeGen/CGCall.cpp at the moment; this is likely to change soon, though.
860Generating assembly requires a suitable LLVM backend.
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]861
862<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
863<h3 id="target_os">Operating System Features and Limitations</h3>
864<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
865
866<!-- ======================================= -->
867<h4 id="target_os_darwin">Darwin (Mac OS/X)</h4>
868<!-- ======================================= -->
869
870<p>No __thread support, 64-bit ObjC support requires SL tools.</p>
871
872</div>
873</body>
874</html>