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5<title>Clang Compiler User's Manual</title>
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16<!--#include virtual="../menu.html.incl"-->
17
18<div id="content">
19
20<h1>Clang Compiler User's Manual</h1>
21
22<ul>
23<li><a href="#intro">Introduction</a>
24 <ul>
25 <li><a href="#terminology">Terminology</a></li>
26 <li><a href="#basicusage">Basic Usage</a></li>
27 </ul>
28</li>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]29<li><a href="#commandline">Command Line Options</a>
30 <ul>
31 <li><a href="#cl_diagnostics">Options to Control Error and Warning
32 Messages</a></li>
Chad Rosierb211a4b2012-02-22 19:14:46 +0000[diff] [blame]33 <li><a href="#cl_crash_diagnostics">Options to Control Clang Crash
34 Diagnostics</a></li>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]35 </ul>
36</li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]37<li><a href="#general_features">Language and Target-Independent Features</a>
38 <ul>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]39 <li><a href="#diagnostics">Controlling Errors and Warnings</a>
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]40 <ul>
41 <li><a href="#diagnostics_display">Controlling How Clang Displays Diagnostics</a></li>
42 <li><a href="#diagnostics_mappings">Diagnostic Mappings</a></li>
Chris Lattner67db8cd2010-05-30 23:42:51 +0000[diff] [blame]43 <li><a href="#diagnostics_categories">Diagnostic Categories</a></li>
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]44 <li><a href="#diagnostics_commandline">Controlling Diagnostics via Command Line Flags</a></li>
45 <li><a href="#diagnostics_pragmas">Controlling Diagnostics via Pragmas</a></li>
Richard Smithf122a132012-06-13 20:27:03 +0000[diff] [blame]46 <li><a href="#diagnostics_systemheader">Controlling Diagnostics in System Headers</a></li>
Ted Kremenekf391fa72011-08-18 01:17:05 +0000[diff] [blame]47 <li><a href="#diagnostics_enable_everything">Enabling All Warnings</a></li>
Ted Kremenek2fb11eb2010-08-24 18:12:35 +0000[diff] [blame]48 <li><a href="#analyzer_diagnositics">Controlling Static Analyzer Diagnostics</a></li>
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]49 </ul>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]50 </li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]51 <li><a href="#precompiledheaders">Precompiled Headers</a></li>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]52 <li><a href="#codegen">Controlling Code Generation</a></li>
Alexey Samsonov5ab52492012-05-30 06:55:10 +0000[diff] [blame]53 <li><a href="#debuginfosize">Controlling Size of Debug Information</a></li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]54 </ul>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]55</li>
56<li><a href="#c">C Language Features</a>
57 <ul>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]58 <li><a href="#c_ext">Extensions supported by clang</a></li>
59 <li><a href="#c_modes">Differences between various standard modes</a></li>
60 <li><a href="#c_unimpl_gcc">GCC extensions not implemented yet</a></li>
61 <li><a href="#c_unsupp_gcc">Intentionally unsupported GCC extensions</a></li>
62 <li><a href="#c_ms">Microsoft extensions</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]63 </ul>
64</li>
Richard Smithbdb10182011-11-21 20:54:59 +0000[diff] [blame]65<li><a href="#cxx">C++ Language Features</a>
66 <ul>
67 <li><a href="#cxx_implimits">Controlling implementation limits</a></li>
68 </ul>
69</li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]70<li><a href="#target_features">Target-Specific Features and Limitations</a>
71 <ul>
72 <li><a href="#target_arch">CPU Architectures Features and Limitations</a>
73 <ul>
74 <li><a href="#target_arch_x86">X86</a></li>
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]75 <li><a href="#target_arch_arm">ARM</a></li>
76 <li><a href="#target_arch_other">Other platforms</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]77 </ul>
78 </li>
79 <li><a href="#target_os">Operating System Features and Limitations</a>
80 <ul>
81 <li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li>
82 <li>Linux, etc.</li>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]83 <li><a href="#target_os_win32">Windows</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]84 </ul>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]85 </li>
86 </ul>
87</li>
88</ul>
89
90
91<!-- ======================================================================= -->
92<h2 id="intro">Introduction</h2>
93<!-- ======================================================================= -->
94
95<p>The Clang Compiler is an open-source compiler for the C family of programming
96languages, aiming to be the best in class implementation of these languages.
97Clang builds on the LLVM optimizer and code generator, allowing it to provide
98high-quality optimization and code generation support for many targets. For
99more general information, please see the <a href="http://clang.llvm.org">Clang
100Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p>
101
102<p>This document describes important notes about using Clang as a compiler for
103an end-user, documenting the supported features, command line options, etc. If
104you are interested in using Clang to build a tool that processes code, please
105see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are
Michael J. Spencer8275fc02012-02-12 09:11:39 +0000[diff] [blame]106interested in the <a href="http://clang-analyzer.llvm.org">Clang
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]107Static Analyzer</a>, please see its web page.</p>
108
109<p>Clang is designed to support the C family of programming languages, which
110includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a
111href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many
112dialects of those. For language-specific information, please see the
113corresponding language specific section:</p>
114
115<ul>
116<li><a href="#c">C Language</a>: K&amp;R C, ANSI C89, ISO C90, ISO C94
117 (C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li>
118<li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus
119 variants depending on base language.</li>
Richard Smithbdb10182011-11-21 20:54:59 +0000[diff] [blame]120<li><a href="#cxx">C++ Language</a></li>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]121<li><a href="#objcxx">Objective C++ Language</a></li>
122</ul>
123
124<p>In addition to these base languages and their dialects, Clang supports a
125broad variety of language extensions, which are documented in the corresponding
126language section. These extensions are provided to be compatible with the GCC,
127Microsoft, and other popular compilers as well as to improve functionality
128through Clang-specific features. The Clang driver and language features are
129intentionally designed to be as compatible with the GNU GCC compiler as
130reasonably possible, easing migration from GCC to Clang. In most cases, code
131"just works".</p>
132
133<p>In addition to language specific features, Clang has a variety of features
134that depend on what CPU architecture or operating system is being compiled for.
Douglas Gregorcd5a5052009-11-09 15:15:41 +0000[diff] [blame]135Please see the <a href="#target_features">Target-Specific Features and
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]136Limitations</a> section for more details.</p>
137
138<p>The rest of the introduction introduces some basic <a
139href="#terminology">compiler terminology</a> that is used throughout this manual
140and contains a basic <a href="#basicusage">introduction to using Clang</a>
141as a command line compiler.</p>
142
143<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
144<h3 id="terminology">Terminology</h3>
145<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
146
147<p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic,
148 optimizer</p>
149
150<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
151<h3 id="basicusage">Basic Usage</h3>
152<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
153
154<p>Intro to how to use a C compiler for newbies.</p>
155<p>
156compile + link
157
158compile then link
159
160debug info
161
162enabling optimizations
163
164picking a language to use, defaults to C99 by default. Autosenses based on
165extension.
166
167using a makefile
168</p>
169
170
171<!-- ======================================================================= -->
172<h2 id="commandline">Command Line Options</h2>
173<!-- ======================================================================= -->
174
175<p>
176This section is generally an index into other sections. It does not go into
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]177depth on the ones that are covered by other sections. However, the first part
178introduces the language selection and other high level options like -c, -g, etc.
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]179</p>
180
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]181
182<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
183<h3 id="cl_diagnostics">Options to Control Error and Warning Messages</h3>
184<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
185
186<p><b>-Werror</b>: Turn warnings into errors.</p>
187<p><b>-Werror=foo</b>: Turn warning "foo" into an error.</p>
188<p><b>-Wno-error=foo</b>: Turn warning "foo" into an warning even if -Werror is
189 specified.</p>
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]190<p><b>-Wfoo</b>: Enable warning "foo".</p>
191<p><b>-Wno-foo</b>: Disable warning "foo".</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]192<p><b>-w</b>: Disable all warnings.</p>
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]193<p><b>-Weverything</b>: <a href="#diagnostics_enable_everything">Enable <b>all</b> warnings.</a></p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]194<p><b>-pedantic</b>: Warn on language extensions.</p>
195<p><b>-pedantic-errors</b>: Error on language extensions.</p>
196<p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p>
197
Chris Lattner0f0c9632010-04-07 20:49:23 +0000[diff] [blame]198<p><b>-ferror-limit=123</b>: Stop emitting diagnostics after 123 errors have
199 been produced. The default is 20, and the error limit can be disabled with
200 -ferror-limit=0.</p>
201
Douglas Gregor575cf372010-04-20 07:18:24 +0000[diff] [blame]202<p><b>-ftemplate-backtrace-limit=123</b>: Only emit up to 123 template instantiation notes within the template instantiation backtrace for a single warning or error. The default is 10, and the limit can be disabled with -ftemplate-backtrace-limit=0.</p>
203
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]204<!-- ================================================= -->
205<h4 id="cl_diag_formatting">Formatting of Diagnostics</h4>
206<!-- ================================================= -->
207
208<p>Clang aims to produce beautiful diagnostics by default, particularly for new
209users that first come to Clang. However, different people have different
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]210preferences, and sometimes Clang is driven by another program that wants to
211parse simple and consistent output, not a person. For these cases, Clang
212provides a wide range of options to control the exact output format of the
213diagnostics that it generates.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]214
215<dl>
216
217<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
218<dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in
219diagnostic.</dt>
220<dd>This option, which defaults to on, controls whether or not Clang prints the
221column number of a diagnostic. For example, when this is enabled, Clang will
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]222print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]223
224<pre>
225 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
226 #endif bad
227 ^
228 //
229</pre>
230
231<p>When this is disabled, Clang will print "test.c:28: warning..." with no
232column number.</p>
233</dd>
234
235<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
236<dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print
237source file/line/column information in diagnostic.</dt>
238<dd>This option, which defaults to on, controls whether or not Clang prints the
239filename, line number and column number of a diagnostic. For example,
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]240when this is enabled, Clang will print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]241
242<pre>
243 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
244 #endif bad
245 ^
246 //
247</pre>
248
249<p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p>
250</dd>
251
252<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
253<dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source
254line and ranges from source code in diagnostic.</dt>
255<dd>This option, which defaults to on, controls whether or not Clang prints the
256source line, source ranges, and caret when emitting a diagnostic. For example,
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]257when this is enabled, Clang will print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]258
259<pre>
260 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
261 #endif bad
262 ^
263 //
264</pre>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]265</dd>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]266<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]267<dt id="opt_fcolor_diagnostics"><b>-f[no-]color-diagnostics</b>: </dt>
268<dd>This option, which defaults to on when a color-capable terminal is
269 detected, controls whether or not Clang prints diagnostics in color.
270 When this option is enabled, Clang will use colors to highlight
271 specific parts of the diagnostic, e.g.,
Chris Lattner4e1c53d2011-01-24 03:47:34 +0000[diff] [blame]272 <pre>
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]273 <b><span style="color:black">test.c:28:8: <span style="color:magenta">warning</span>: extra tokens at end of #endif directive [-Wextra-tokens]</span></b>
Chris Lattner4e1c53d2011-01-24 03:47:34 +0000[diff] [blame]274 #endif bad
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]275 <span style="color:green">^</span>
276 <span style="color:green">//</span>
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]277</pre>
Chris Lattner4e1c53d2011-01-24 03:47:34 +0000[diff] [blame]278
279<p>When this is disabled, Clang will just print:</p>
280
281<pre>
282 test.c:2:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
283 #endif bad
284 ^
285 //
286</pre>
287</dd>
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]288<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Douglas Gregorc9471b02011-05-21 17:07:29 +0000[diff] [blame]289<dt id="opt_fdiagnostics-format"><b>-fdiagnostics-format=clang/msvc/vi</b>:
290Changes diagnostic output format to better match IDEs and command line tools.</dt>
291<dd>This option controls the output format of the filename, line number, and column printed in diagnostic messages. The options, and their affect on formatting a simple conversion diagnostic, follow:
292
293 <dl>
294 <dt><b>clang</b> (default)</dt>
295 <dd>
296 <pre>t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
297 </dd>
298
299 <dt><b>msvc</b></dt>
300 <dd>
301 <pre>t.c(3,11) : warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
302 </dd>
303
304 <dt><b>vi</b></dt>
305 <dd>
306 <pre>t.c +3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
307 </dd>
308 </dl>
309</dd>
310
311<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Argyrios Kyrtzidis477aab62011-05-25 05:05:01 +0000[diff] [blame]312<dt id="opt_fdiagnostics-show-name"><b>-f[no-]diagnostics-show-name</b>:
313Enable the display of the diagnostic name.</dt>
314<dd>This option, which defaults to off, controls whether or not
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]315Clang prints the associated name.<p></p></dd>
Argyrios Kyrtzidis477aab62011-05-25 05:05:01 +0000[diff] [blame]316<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]317<dt id="opt_fdiagnostics-show-option"><b>-f[no-]diagnostics-show-option</b>:
318Enable <tt>[-Woption]</tt> information in diagnostic line.</dt>
319<dd>This option, which defaults to on,
320controls whether or not Clang prints the associated <A
321href="#cl_diag_warning_groups">warning group</a> option name when outputting
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]322a warning diagnostic. For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]323
324<pre>
325 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
326 #endif bad
327 ^
328 //
329</pre>
330
331<p>Passing <b>-fno-diagnostics-show-option</b> will prevent Clang from printing
332the [<a href="#opt_Wextra-tokens">-Wextra-tokens</a>] information in the
333diagnostic. This information tells you the flag needed to enable or disable the
334diagnostic, either from the command line or through <a
335href="#pragma_GCC_diagnostic">#pragma GCC diagnostic</a>.</dd>
336
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]337<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
338<dt id="opt_fdiagnostics-show-category"><b>-fdiagnostics-show-category=none/id/name</b>:
339Enable printing category information in diagnostic line.</dt>
340<dd>This option, which defaults to "none",
341controls whether or not Clang prints the category associated with a diagnostic
342when emitting it. Each diagnostic may or many not have an associated category,
343if it has one, it is listed in the diagnostic categorization field of the
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]344diagnostic line (in the []'s).
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]345
346<p>For example, a format string warning will produce these three renditions
347based on the setting of this option:</p>
348
349<pre>
350 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat]
351 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,1</b>]
352 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,Format String</b>]
353</pre>
354
355<p>This category can be used by clients that want to group diagnostics by
356category, so it should be a high level category. We want dozens of these, not
357hundreds or thousands of them.</p>
358</dd>
359
360
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]361
362<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
363<dt id="opt_fdiagnostics-fixit-info"><b>-f[no-]diagnostics-fixit-info</b>:
364Enable "FixIt" information in the diagnostics output.</dt>
365<dd>This option, which defaults to on, controls whether or not Clang prints the
366information on how to fix a specific diagnostic underneath it when it knows.
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]367For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]368
369<pre>
370 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
371 #endif bad
372 ^
373 //
374</pre>
375
376<p>Passing <b>-fno-diagnostics-fixit-info</b> will prevent Clang from printing
377the "//" line at the end of the message. This information is useful for users
378who may not understand what is wrong, but can be confusing for machine
379parsing.</p>
380</dd>
381
382<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]383<dt id="opt_fdiagnostics-print-source-range-info">
384<b>-f[no-]diagnostics-print-source-range-info</b>:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]385Print machine parsable information about source ranges.</dt>
386<dd>This option, which defaults to off, controls whether or not Clang prints
387information about source ranges in a machine parsable format after the
388file/line/column number information. The information is a simple sequence of
389brace enclosed ranges, where each range lists the start and end line/column
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]390locations. For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]391
392<pre>
393exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
394 P = (P-42) + Gamma*4;
395 ~~~~~~ ^ ~~~~~~~
396</pre>
397
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]398<p>The {}'s are generated by -fdiagnostics-print-source-range-info.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]399</dd>
400
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]401<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
402<dt id="opt_fdiagnostics-parseable-fixits">
403<b>-fdiagnostics-parseable-fixits</b>:
404Print Fix-Its in a machine parseable form.</dt>
405<dd><p>This option makes Clang print available Fix-Its in a machine parseable format at the end of diagnostics. The following example illustrates the format:</p>
406
407<pre>
Douglas Gregorbf5e09d2010-08-20 03:17:33 +0000[diff] [blame]408 fix-it:"t.cpp":{7:25-7:29}:"Gamma"
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]409</pre>
410
NAKAMURA Takumi44626362011-04-05 00:57:02 +0000[diff] [blame]411<p>The range printed is a half-open range, so in this example the characters at
412column 25 up to but not including column 29 on line 7 in t.cpp should be
413replaced with the string &quot;Gamma&quot;. Either the range or the replacement
414string may be empty (representing strict insertions and strict erasures,
415respectively). Both the file name and the insertion string escape backslash (as
416&quot;\\&quot;), tabs (as &quot;\t&quot;), newlines (as &quot;\n&quot;), double
417quotes(as &quot;\&quot;&quot;) and non-printable characters (as octal
418&quot;\xxx&quot;).</p>
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]419</dd>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]420
Richard Trieue59331a2012-06-27 02:00:20 +0000[diff] [blame]421<dt id="opt_fno-elide-type">
422<b>-fno-elide-type</b>:
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]423Turns off elision in template type printing.</dt>
Richard Trieue59331a2012-06-27 02:00:20 +0000[diff] [blame]424<dd><p>The default for template type printing is to elide as many template
425arguments as possible, removing those which are the same in both template types,
426leaving only the differences. Adding this flag will print all the template
427arguments. If supported by the terminal, highlighting will still appear on
428differing arguments.</p>
429
430Default:
431<pre>
432t.cc:4:5: <span class="note">note</span>: candidate function not viable: no known conversion from 'vector&lt;map&lt;[...], map&lt;<span class="template-highlight">float</span>, [...]&gt;&gt;&gt;' to 'vector&lt;map&lt;[...], map&lt;<span class="template-highlight">double</span>, [...]&gt;&gt;&gt;' for 1st argument;
433</pre>
434-fno-elide-type:
435<pre>
436t.cc:4:5: <span class="note">note</span>: candidate function not viable: no known conversion from 'vector&lt;map&lt;int, map&lt;<span class="template-highlight">float</span>, int&gt;&gt;&gt;' to 'vector&lt;map&lt;int, map&lt;<span class="template-highlight">double</span>, int&gt;&gt;&gt;' for 1st argument;
437</pre>
438</dd>
439
440<dt id="opt_fdiagnostics-show-template-tree">
441<b>-fdiagnostics-show-template-tree</b>:
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]442Template type diffing prints a text tree.</dt>
Richard Trieue59331a2012-06-27 02:00:20 +0000[diff] [blame]443<dd><p>For diffing large templated types, this option will cause Clang to
444display the templates as an indented text tree, one argument per line, with
445differences marked inline. This is compatible with -fno-elide-type.</p>
446
447Default:
448<pre>
449t.cc:4:5: <span class="note">note</span>: candidate function not viable: no known conversion from 'vector&lt;map&lt;[...], map&lt;<span class="template-highlight">float</span>, [...]&gt;&gt;&gt;' to 'vector&lt;map&lt;[...], map&lt;<span class="template-highlight">double</span>, [...]&gt;&gt;&gt;' for 1st argument;
450</pre>
451-fdiagnostics-show-template-tree
452<pre>
453t.cc:4:5: <span class="note">note</span>: candidate function not viable: no known conversion for 1st argument;
454 vector&lt;
455 map&lt;
456 [...],
457 map&lt;
458 [<span class="template-highlight">float</span> != <span class="template-highlight">float</span>],
459 [...]&gt;&gt;&gt;
460</pre>
461</dd>
462
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]463</dl>
464
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]465
466
467<!-- ===================================================== -->
468<h4 id="cl_diag_warning_groups">Individual Warning Groups</h4>
469<!-- ===================================================== -->
470
471<p>TODO: Generate this from tblgen. Define one anchor per warning group.</p>
472
473
474<dl>
475
476
477<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
478<dt id="opt_Wextra-tokens"><b>-Wextra-tokens</b>: Warn about excess tokens at
479 the end of a preprocessor directive.</dt>
480<dd>This option, which defaults to on, enables warnings about extra tokens at
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]481the end of preprocessor directives. For example:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]482
483<pre>
484 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
485 #endif bad
486 ^
487</pre>
488
489<p>These extra tokens are not strictly conforming, and are usually best handled
490by commenting them out.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]491</dd>
492
Jeffrey Yasskin21d07e42010-06-05 01:39:57 +0000[diff] [blame]493<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
494<dt id="opt_Wambiguous-member-template"><b>-Wambiguous-member-template</b>:
495Warn about unqualified uses of a member template whose name resolves
496to another template at the location of the use.</dt>
497<dd>This option, which defaults to on, enables a warning in the
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]498following code:
Jeffrey Yasskin21d07e42010-06-05 01:39:57 +0000[diff] [blame]499
500<pre>
501template&lt;typename T> struct set{};
502template&lt;typename T> struct trait { typedef const T& type; };
503struct Value {
504 template&lt;typename T> void set(typename trait&lt;T>::type value) {}
505};
506void foo() {
507 Value v;
508 v.set&lt;double>(3.2);
509}
510</pre>
511
512<p>C++ [basic.lookup.classref] requires this to be an error, but,
513because it's hard to work around, Clang downgrades it to a warning as
514an extension.</p>
515</dd>
516
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]517<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
518<dt id="opt_Wbind-to-temporary-copy"><b>-Wbind-to-temporary-copy</b>: Warn about
519an unusable copy constructor when binding a reference to a temporary.</dt>
520<dd>This option, which defaults to on, enables warnings about binding a
521reference to a temporary when the temporary doesn't have a usable copy
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]522constructor. For example:
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]523
524<pre>
525 struct NonCopyable {
526 NonCopyable();
527 private:
528 NonCopyable(const NonCopyable&);
529 };
530 void foo(const NonCopyable&);
531 void bar() {
David Blaikie5090e9f2011-10-18 05:49:30 +0000[diff] [blame]532 foo(NonCopyable()); // Disallowed in C++98; allowed in C++11.
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]533 }
534</pre>
535<pre>
536 struct NonCopyable2 {
537 NonCopyable2();
538 NonCopyable2(NonCopyable2&);
539 };
540 void foo(const NonCopyable2&);
541 void bar() {
David Blaikie5090e9f2011-10-18 05:49:30 +0000[diff] [blame]542 foo(NonCopyable2()); // Disallowed in C++98; allowed in C++11.
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]543 }
544</pre>
545
546<p>Note that if <tt>NonCopyable2::NonCopyable2()</tt> has a default
547argument whose instantiation produces a compile error, that error will
548still be a hard error in C++98 mode even if this warning is turned
549off.</p>
550
551</dd>
552
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]553</dl>
554
Chad Rosiercd376a12012-02-22 20:26:10 +0000[diff] [blame]555<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
556<h3 id="cl_crash_diagnostics">Options to Control Clang Crash Diagnostics</h3>
557<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
558
559<p>As unbelievable as it may sound, Clang does crash from time to time.
560Generally, this only occurs to those living on the
561<a href="http://llvm.org/releases/download.html#svn">bleeding edge</a>. Clang
562goes to great lengths to assist you in filing a bug report. Specifically, Clang
563generates preprocessed source file(s) and associated run script(s) upon a
564crash. These files should be attached to a bug report to ease reproducibility
565of the failure. Below are the command line options to control the crash
566diagnostics.
567</p>
568
569<p><b>-fno-crash-diagnostics</b>: Disable auto-generation of preprocessed
570source files during a clang crash.</p>
571
572<p>The -fno-crash-diagnostics flag can be helpful for speeding the process of
573generating a delta reduced test case.</p>
574
575
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]576<!-- ======================================================================= -->
577<h2 id="general_features">Language and Target-Independent Features</h2>
578<!-- ======================================================================= -->
579
580
581<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
582<h3 id="diagnostics">Controlling Errors and Warnings</h3>
583<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
584
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]585<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]586emit errors and warning messages, and how they are displayed to the console.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]587
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]588<h4 id="diagnostics_display">Controlling How Clang Displays Diagnostics</h4>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]589
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]590<p>When Clang emits a diagnostic, it includes rich information in the output,
591and gives you fine-grain control over which information is printed. Clang has
592the ability to print this information, and these are the options that control
593it:</p>
594
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]595<ol>
596<li>A file/line/column indicator that shows exactly where the diagnostic occurs
597 in your code [<a href="#opt_fshow-column">-fshow-column</a>, <a
598 href="#opt_fshow-source-location">-fshow-source-location</a>].</li>
599<li>A categorization of the diagnostic as a note, warning, error, or fatal
600 error.</li>
601<li>A text string that describes what the problem is.</li>
602<li>An option that indicates how to control the diagnostic (for diagnostics that
603 support it) [<a
604 href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li>
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]605<li>A <a href="#diagnostics_categories">high-level category</a> for the
606 diagnostic for clients that want to group diagnostics by class (for
607 diagnostics that support it) [<a
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]608 href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a>].</li>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]609<li>The line of source code that the issue occurs on, along with a caret and
610 ranges that indicate the important locations [<a
611 href="opt_fcaret-diagnostics">-fcaret-diagnostics</a>].</li>
612<li>"FixIt" information, which is a concise explanation of how to fix the
613 problem (when Clang is certain it knows) [<a
614 href="opt_fdiagnostics-fixit-info">-fdiagnostics-fixit-info</a>].</li>
615<li>A machine-parsable representation of the ranges involved (off by
616 default) [<a
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]617 href="opt_fdiagnostics-print-source-range-info">-fdiagnostics-print-source-range-info</a>].</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]618</ol>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]619
620<p>For more information please see <a href="#cl_diag_formatting">Formatting of
621Diagnostics</a>.</p>
622
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]623
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]624<h4 id="diagnostics_mappings">Diagnostic Mappings</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]625
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]626<p>All diagnostics are mapped into one of these 5 classes:</p>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]627
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]628<ul>
629<li>Ignored</li>
630<li>Note</li>
631<li>Warning</li>
632<li>Error</li>
633<li>Fatal</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]634</ul>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]635
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]636<h4 id="diagnostics_categories">Diagnostic Categories</h4>
637
638<p>Though not shown by default, diagnostics may each be associated with a
639 high-level category. This category is intended to make it possible to triage
640 builds that produce a large number of errors or warnings in a grouped way.
641</p>
642
643<p>Categories are not shown by default, but they can be turned on with the
644<a href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a> option.
645When set to "<tt>name</tt>", the category is printed textually in the diagnostic
646output. When it is set to "<tt>id</tt>", a category number is printed. The
647mapping of category names to category id's can be obtained by running '<tt>clang
648 --print-diagnostic-categories</tt>'.
649</p>
650
651<h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line
652 Flags</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]653
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]654<p>TODO: -W flags, -pedantic, etc</p>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]655
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]656<h4 id="diagnostics_pragmas">Controlling Diagnostics via Pragmas</h4>
657
658<p>Clang can also control what diagnostics are enabled through the use of
659pragmas in the source code. This is useful for turning off specific warnings
660in a section of source code. Clang supports GCC's pragma for compatibility
661with existing source code, as well as several extensions. </p>
662
663<p>The pragma may control any warning that can be used from the command line.
664Warnings may be set to ignored, warning, error, or fatal. The following
665example code will tell Clang or GCC to ignore the -Wall warnings:</p>
666
667<pre>
668#pragma GCC diagnostic ignored "-Wall"
669</pre>
670
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]671<p>In addition to all of the functionality provided by GCC's pragma, Clang
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]672also allows you to push and pop the current warning state. This is particularly
673useful when writing a header file that will be compiled by other people, because
674you don't know what warning flags they build with.</p>
675
676<p>In the below example
677-Wmultichar is ignored for only a single line of code, after which the
678diagnostics return to whatever state had previously existed.</p>
679
680<pre>
681#pragma clang diagnostic push
682#pragma clang diagnostic ignored "-Wmultichar"
683
684char b = 'df'; // no warning.
685
686#pragma clang diagnostic pop
687</pre>
688
689<p>The push and pop pragmas will save and restore the full diagnostic state of
690the compiler, regardless of how it was set. That means that it is possible to
691use push and pop around GCC compatible diagnostics and Clang will push and pop
692them appropriately, while GCC will ignore the pushes and pops as unknown
693pragmas. It should be noted that while Clang supports the GCC pragma, Clang and
694GCC do not support the exact same set of warnings, so even when using GCC
695compatible #pragmas there is no guarantee that they will have identical behaviour
696on both compilers. </p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]697
Richard Smithf122a132012-06-13 20:27:03 +0000[diff] [blame]698<h4 id="diagnostics_systemheader">Controlling Diagnostics in System Headers</h4>
699
700<p>Warnings are suppressed when they occur in system headers. By default, an
701included file is treated as a system header if it is found in an include path
702specified by <tt>-isystem</tt>, but this can be overridden in several ways.</p>
703
704<p>The <tt>system_header</tt> pragma can be used to mark the current file as
705being a system header. No warnings will be produced from the location of the
706pragma onwards within the same file.</p>
707
708<pre>
709char a = 'xy'; // warning
710
711#pragma clang system_header
712
713char b = 'ab'; // no warning
714</pre>
715
716<p>The <tt>-isystem-prefix</tt> and <tt>-ino-system-prefix</tt> command-line
717arguments can be used to override whether subsets of an include path are treated
718as system headers. When the name in a <tt>#include</tt> directive is found
719within a header search path and starts with a system prefix, the header is
720treated as a system header. The last prefix on the command-line which matches
721the specified header name takes precedence. For instance:</p>
722
723<pre>
724clang -Ifoo -isystem bar -isystem-prefix x/ -ino-system-prefix x/y/
725</pre>
726
727<p>Here, <tt>#include "x/a.h"</tt> is treated as including a system header, even
728if the header is found in <tt>foo</tt>, and <tt>#include "x/y/b.h"</tt> is
729treated as not including a system header, even if the header is found in
730<tt>bar</tt>.
731</p>
732
733<p>A <tt>#include</tt> directive which finds a file relative to the current
734directory is treated as including a system header if the including file is
735treated as a system header.</p>
736
Ted Kremenekf391fa72011-08-18 01:17:05 +0000[diff] [blame]737<h4 id="diagnostics_enable_everything">Enabling All Warnings</h4>
738
739<p>In addition to the traditional <tt>-W</tt> flags, one can enable <b>all</b>
740 warnings by passing <tt>-Weverything</tt>.
741 This works as expected with <tt>-Werror</tt>,
742 and also includes the warnings from <tt>-pedantic</tt>.</p>
743
744<p>Note that when combined with <tt>-w</tt> (which disables all warnings), that
745 flag wins.</p>
746
Ted Kremenek2fb11eb2010-08-24 18:12:35 +0000[diff] [blame]747<h4 id="analyzer_diagnositics">Controlling Static Analyzer Diagnostics</h4>
748
749<p>While not strictly part of the compiler, the diagnostics from Clang's <a
750href="http://clang-analyzer.llvm.org">static analyzer</a> can also be influenced
Anna Zaks843f0e82012-06-16 00:30:21 +0000[diff] [blame]751by the user via changes to the source code. See the avaliable
752<a href = "http://clang-analyzer.llvm.org/annotations.html" >annotations</a> and
753the analyzer's
754<a href= "http://clang-analyzer.llvm.org/faq.html#exclude_code" >FAQ page</a> for
755more information.
Ted Kremenek2fb11eb2010-08-24 18:12:35 +0000[diff] [blame]756
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]757<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
758<h3 id="precompiledheaders">Precompiled Headers</h3>
759<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
760
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]761<p><a href="http://en.wikipedia.org/wiki/Precompiled_header">Precompiled
762headers</a> are a general approach employed by many compilers to reduce
763compilation time. The underlying motivation of the approach is that it is
764common for the same (and often large) header files to be included by
765multiple source files. Consequently, compile times can often be greatly improved
766by caching some of the (redundant) work done by a compiler to process headers.
767Precompiled header files, which represent one of many ways to implement
768this optimization, are literally files that represent an on-disk cache that
769contains the vital information necessary to reduce some of the work
770needed to process a corresponding header file. While details of precompiled
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]771headers vary between compilers, precompiled headers have been shown to be
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]772highly effective at speeding up program compilation on systems with very large
773system headers (e.g., Mac OS/X).</p>
774
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]775<h4>Generating a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]776
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]777<p>To generate a PCH file using Clang, one invokes Clang with
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]778the <b><tt>-x <i>&lt;language&gt;</i>-header</tt></b> option. This mirrors the
779interface in GCC for generating PCH files:</p>
780
781<pre>
782 $ gcc -x c-header test.h -o test.h.gch
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]783 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]784</pre>
785
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]786<h4>Using a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]787
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]788<p>A PCH file can then be used as a prefix header when a
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]789<b><tt>-include</tt></b> option is passed to <tt>clang</tt>:</p>
790
791<pre>
792 $ clang -include test.h test.c -o test
793</pre>
794
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]795<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]796is 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]797will be processed from the PCH file. Otherwise, Clang falls back to
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]798directly processing the content of <tt>test.h</tt>. This mirrors the behavior of
799GCC.</p>
800
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]801<p><b>NOTE:</b> Clang does <em>not</em> automatically use PCH files
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]802for headers that are directly included within a source file. For example:</p>
803
804<pre>
Chris Lattnere42ec542009-06-13 20:35:58 +0000[diff] [blame]805 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]806 $ cat test.c
807 #include "test.h"
808 $ clang test.c -o test
809</pre>
810
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]811<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]812<tt>test.h</tt> since <tt>test.h</tt> was included directly in the source file
813and not specified on the command line using <tt>-include</tt>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]814
Douglas Gregore650c8c2009-07-07 00:12:59 +0000[diff] [blame]815<h4>Relocatable PCH Files</h4>
816<p>It is sometimes necessary to build a precompiled header from headers that
817are not yet in their final, installed locations. For example, one might build a
818precompiled header within the build tree that is then meant to be installed
819alongside the headers. Clang permits the creation of "relocatable" precompiled
820headers, which are built with a given path (into the build directory) and can
821later be used from an installed location.</p>
822
823<p>To build a relocatable precompiled header, place your headers into a
824subdirectory whose structure mimics the installed location. For example, if you
825want to build a precompiled header for the header <code>mylib.h</code> that
826will be installed into <code>/usr/include</code>, create a subdirectory
827<code>build/usr/include</code> and place the header <code>mylib.h</code> into
828that subdirectory. If <code>mylib.h</code> depends on other headers, then
829they can be stored within <code>build/usr/include</code> in a way that mimics
830the installed location.</p>
831
832<p>Building a relocatable precompiled header requires two additional arguments.
833First, pass the <code>--relocatable-pch</code> flag to indicate that the
834resulting PCH file should be relocatable. Second, pass
835<code>-isysroot /path/to/build</code>, which makes all includes for your
836library relative to the build directory. For example:</p>
837
838<pre>
839 # clang -x c-header --relocatable-pch -isysroot /path/to/build /path/to/build/mylib.h mylib.h.pch
840</pre>
841
842<p>When loading the relocatable PCH file, the various headers used in the PCH
843file are found from the system header root. For example, <code>mylib.h</code>
844can be found in <code>/usr/include/mylib.h</code>. If the headers are installed
845in some other system root, the <code>-isysroot</code> option can be used provide
846a different system root from which the headers will be based. For example,
847<code>-isysroot /Developer/SDKs/MacOSX10.4u.sdk</code> will look for
848<code>mylib.h</code> in
849<code>/Developer/SDKs/MacOSX10.4u.sdk/usr/include/mylib.h</code>.</p>
850
851<p>Relocatable precompiled headers are intended to be used in a limited number
852of cases where the compilation environment is tightly controlled and the
853precompiled header cannot be generated after headers have been installed.
854Relocatable precompiled headers also have some performance impact, because
855the difference in location between the header locations at PCH build time vs.
856at the time of PCH use requires one of the PCH optimizations,
857<code>stat()</code> caching, to be disabled. However, this change is only
858likely to affect PCH files that reference a large number of headers.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]859
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]860<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
861<h3 id="codegen">Controlling Code Generation</h3>
862<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
863
864<p>Clang provides a number of ways to control code generation. The options are listed below.</p>
865
866<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]867<dl>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]868<dt id="opt_fcatch-undefined-behavior"><b>-fcatch-undefined-behavior</b>: Turn
869on runtime code generation to check for undefined behavior.</dt>
870
871<dd>This option, which defaults to off, controls whether or not Clang
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]872adds runtime checks for undefined runtime behavior. If a check fails,
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]873<tt>__builtin_trap()</tt> is used to indicate failure.
874The checks are:
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]875<ul>
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]876<li>Subscripting where the static type of one operand is a variable
Mike Stump88b2a172009-12-16 03:25:12 +0000[diff] [blame]877 which is decayed from an array type and the other operand is
878 greater than the size of the array or less than zero.</li>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]879<li>Shift operators where the amount shifted is greater or equal to the
880 promoted bit-width of the left-hand-side or less than zero.</li>
Mike Stump8f6a3ed2009-12-16 03:18:14 +0000[diff] [blame]881<li>If control flow reaches __builtin_unreachable.
882<li>When llvm implements more __builtin_object_size support, reads and
883 writes for objects that __builtin_object_size indicates we aren't
884 accessing valid memory. Bit-fields and vectors are not yet checked.
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]885</ul>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]886</dd>
887
Kostya Serebryany48a8cd92012-03-01 23:14:19 +0000[diff] [blame]888<dt id="opt_faddress-sanitizer"><b>-f[no-]address-sanitizer</b>:
889Turn on <a href="AddressSanitizer.html">AddressSanitizer</a>,
890a memory error detector.
891
892<dt id="opt_fthread-sanitizer"><b>-f[no-]thread-sanitizer</b>:
893Turn on ThreadSanitizer, an <em>experimental</em> data race detector.
894Not ready for widespread use.
895
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]896<dt id="opt_fno-assume-sane-operator-new"><b>-fno-assume-sane-operator-new</b>:
897Don't assume that the C++'s new operator is sane.</dt>
Nuno Lopesb23f20d2009-12-17 10:15:49 +0000[diff] [blame]898<dd>This option tells the compiler to do not assume that C++'s global new
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]899operator will always return a pointer that does not
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]900alias any other pointer when the function returns.</dd>
Evan Chengfda026b2011-04-08 22:18:01 +0000[diff] [blame]901
Evan Cheng4cf4b592011-04-08 22:34:21 +0000[diff] [blame]902<dt id="opt_ftrap-function"><b>-ftrap-function=[name]</b>: Instruct code
Evan Chengfda026b2011-04-08 22:18:01 +0000[diff] [blame]903generator to emit a function call to the specified function name for
904<tt>__builtin_trap()</tt>.</dt>
905
906<dd>LLVM code generator translates <tt>__builtin_trap()</tt> to a trap
907instruction if it is supported by the target ISA. Otherwise, the builtin is
908translated into a call to <tt>abort</tt>. If this option is set, then the code
909generator will always lower the builtin to a call to the specified function
910regardless of whether the target ISA has a trap instruction. This option is
Chris Lattner02e266b2011-04-08 22:58:43 +0000[diff] [blame]911useful for environments (e.g. deeply embedded) where a trap cannot be properly
912handled, or when some custom behavior is desired.</dd>
Hans Wennborg7bf9d9b2012-07-13 12:47:15 +0000[diff] [blame]913
914<dt id="opt_ftls-model"><b>-ftls-model=[model]</b>: Select which TLS model to
915use.</dt>
916<dd>Valid values are: <tt>global-dynamic</tt>, <tt>local-dynamic</tt>,
917<tt>initial-exec</tt> and <tt>local-exec</tt>. The default value is
918<tt>global-dynamic</tt>. The compiler may use a different model if the selected
919model is not supported by the target, or if a more efficient model can be used.
920The TLS model can be overridden per variable using the <tt>tls_model</tt>
921attribute.
922</dd>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]923</dl>
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]924
Alexey Samsonov5ab52492012-05-30 06:55:10 +0000[diff] [blame]925<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
926<h3 id="debuginfosize">Controlling Size of Debug Information</h3>
927<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
928
929<p>Debug info kind generated by Clang can be set by one of the flags listed
930below. If multiple flags are present, the last one is used.</p>
931
932<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
933<dl>
934<dt id="opt_g0"><b>-g0</b>: Don't generate any debug info (default).
935
936<dt id="opt_gline-tables-only"><b>-gline-tables-only</b>:
937Generate line number tables only.
938<dd>
939This kind of debug info allows to obtain stack traces with function
940names, file names and line numbers (by such tools as
941gdb or addr2line). It doesn't contain any other data (e.g.
942description of local variables or function parameters).
943</dd>
944
945<dt id="opt_g"><b>-g</b>: Generate complete debug info.
946</dl>
947
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]948<!-- ======================================================================= -->
949<h2 id="c">C Language Features</h2>
950<!-- ======================================================================= -->
951
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]952<p>The support for standard C in clang is feature-complete except for the C99
953floating-point pragmas.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]954
955<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]956<h3 id="c_ext">Extensions supported by clang</h3>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]957<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
958
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]959<p>See <a href="LanguageExtensions.html">clang language extensions</a>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]960
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]961<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
962<h3 id="c_modes">Differences between various standard modes</h3>
963<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]964
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]965<p>clang supports the -std option, which changes what language mode clang uses.
966The supported modes for C are c89, gnu89, c94, c99, gnu99 and various aliases
967for those modes. If no -std option is specified, clang defaults to gnu99 mode.
968</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]969
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]970<p>Differences between all c* and gnu* modes:</p>
971<ul>
972<li>c* modes define "__STRICT_ANSI__".</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]973<li>Target-specific defines not prefixed by underscores, like "linux", are
974defined in gnu* modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]975<li>Trigraphs default to being off in gnu* modes; they can be enabled by the
976-trigraphs option.</li>
977<li>The parser recognizes "asm" and "typeof" as keywords in gnu* modes; the
978variants "__asm__" and "__typeof__" are recognized in all modes.</li>
Eli Friedmanb0ac5452009-05-16 23:17:30 +0000[diff] [blame]979<li>The Apple "blocks" extension is recognized by default in gnu* modes
980on some platforms; it can be enabled in any mode with the "-fblocks"
981option.</li>
Chris Lattner741be6a2011-06-15 00:41:40 +0000[diff] [blame]982<li>Arrays that are VLA's according to the standard, but which can be constant
983 folded by the frontend are treated as fixed size arrays. This occurs for
984 things like "int X[(1, 2)];", which is technically a VLA. c* modes are
985 strictly compliant and treat these as VLAs.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]986</ul>
987
988<p>Differences between *89 and *99 modes:</p>
989<ul>
990<li>The *99 modes default to implementing "inline" as specified in C99, while
991the *89 modes implement the GNU version. This can be overridden for individual
992functions with the __gnu_inline__ attribute.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]993<li>Digraphs are not recognized in c89 mode.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]994<li>The scope of names defined inside a "for", "if", "switch", "while", or "do"
995statement is different. (example: "if ((struct x {int x;}*)0) {}".)</li>
996<li>__STDC_VERSION__ is not defined in *89 modes.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]997<li>"inline" is not recognized as a keyword in c89 mode.</li>
998<li>"restrict" is not recognized as a keyword in *89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]999<li>Commas are allowed in integer constant expressions in *99 modes.</li>
1000<li>Arrays which are not lvalues are not implicitly promoted to pointers in
1001*89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1002<li>Some warnings are different.</li>
1003</ul>
1004
1005<p>c94 mode is identical to c89 mode except that digraphs are enabled in
1006c94 mode (FIXME: And __STDC_VERSION__ should be defined!).</p>
1007
1008<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1009<h3 id="c_unimpl_gcc">GCC extensions not implemented yet</h3>
1010<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1011
1012<p>clang tries to be compatible with gcc as much as possible, but some gcc
1013extensions are not implemented yet:</p>
1014
1015<ul>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1016
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1017<li>clang does not support #pragma weak
Eli Friedman4da92552009-06-02 08:21:31 +0000[diff] [blame]1018(<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]1019the uses described in the bug, this is likely to be implemented at some
1020point, at least partially.</li>
1021
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1022<li>clang does not support decimal floating point types (_Decimal32 and
1023friends) or fixed-point types (_Fract and friends); nobody has expressed
1024interest in these features yet, so it's hard to say when they will be
1025implemented.</li>
1026
1027<li>clang does not support nested functions; this is a complex feature which
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]1028is infrequently used, so it is unlikely to be implemented anytime soon. In C++11
1029it can be emulated by assigning lambda functions to local variables, e.g:
1030<pre>
1031 auto const local_function = [&](int parameter) {
1032 // Do something
1033 };
1034 ...
1035 local_function(1);
1036</pre>
1037</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1038
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]1039<li>clang does not support global register variables; this is unlikely
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1040to be implemented soon because it requires additional LLVM backend support.
1041</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1042
1043<li>clang does not support static initialization of flexible array
1044members. This appears to be a rarely used extension, but could be
1045implemented pending user demand.</li>
1046
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1047<li>clang does not support __builtin_va_arg_pack/__builtin_va_arg_pack_len.
1048This is used rarely, but in some potentially interesting places, like the
1049glibc headers, so it may be implemented pending user demand. Note that
1050because clang pretends to be like GCC 4.2, and this extension was introduced
1051in 4.3, the glibc headers will not try to use this extension with clang at
1052the moment.</li>
1053
1054<li>clang does not support the gcc extension for forward-declaring function
Dmitri Gribenko1dfb72f2012-07-17 18:51:47 +0000[diff] [blame]1055parameters; this has not shown up in any real-world code yet, though, so it
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1056might never be implemented.</li>
1057
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1058</ul>
1059
1060<p>This is not a complete list; if you find an unsupported extension
1061missing from this list, please send an e-mail to cfe-dev. This list
1062currently excludes C++; see <a href="#cxx">C++ Language Features</a>.
1063Also, this list does not include bugs in mostly-implemented features; please
1064see 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">
1065bug tracker</a> for known existing bugs (FIXME: Is there a section for
1066bug-reporting guidelines somewhere?).</p>
1067
1068<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1069<h3 id="c_unsupp_gcc">Intentionally unsupported GCC extensions</h3>
1070<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1071
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]1072<ul>
1073
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]1074<li>clang does not support the gcc extension that allows variable-length arrays
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]1075in structures. This is for a few reasons: one, it is tricky
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1076to implement, two, the extension is completely undocumented, and three, the
Chris Lattnerb9d511c2010-10-28 02:20:32 +0000[diff] [blame]1077extension appears to be rarely used. Note that clang <em>does</em> support
1078flexible array members (arrays with a zero or unspecified size at the end of
1079a structure).</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1080
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1081<li>clang does not have an equivalent to gcc's "fold"; this means that
1082clang doesn't accept some constructs gcc might accept in contexts where a
Eli Friedman248f9732011-06-13 23:12:01 +0000[diff] [blame]1083constant expression is required, like "x-x" where x is a variable.</li>
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1084
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1085<li>clang does not support __builtin_apply and friends; this extension is
1086extremely obscure and difficult to implement reliably.</li>
1087
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]1088</ul>
1089
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1090<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1091<h3 id="c_ms">Microsoft extensions</h3>
1092<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1093
1094<p>clang has some experimental support for extensions from
1095Microsoft Visual C++; to enable it, use the -fms-extensions command-line
Eli Friedmana1821b52009-06-08 06:21:03 +0000[diff] [blame]1096option. This is the default for Windows targets. Note that the
1097support is incomplete; enabling Microsoft extensions will silently drop
1098certain constructs (including __declspec and Microsoft-style asm statements).
1099</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1100
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1101<p>clang has a -fms-compatibility flag that makes clang accept enough
1102invalid C++ to be able to parse most Microsoft headers. This flag is enabled by
1103default for Windows targets.</p>
1104
1105<p>-fdelayed-template-parsing lets clang delay all template instantiation until
1106the end of a translation unit. This flag is enabled by default for Windows
1107targets.</p>
1108
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1109<ul>
Douglas Gregord3b227d2010-12-14 16:21:49 +0000[diff] [blame]1110<li>clang allows setting _MSC_VER with -fmsc-version=. It defaults to 1300 which
Michael J. Spencerdae4ac42010-10-21 05:21:48 +0000[diff] [blame]1111is the same as Visual C/C++ 2003. Any number is supported and can greatly affect
1112what Windows SDK and c++stdlib headers clang can compile. This option will be
1113removed when clang supports the full set of MS extensions required for these
1114headers.</li>
1115
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1116<li>clang does not support the Microsoft extension where anonymous
Daniel Dunbar869e0542009-05-13 00:23:53 +0000[diff] [blame]1117record members can be declared using user defined typedefs.</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1118
Daniel Dunbar9375ed12009-05-13 21:40:49 +0000[diff] [blame]1119<li>clang supports the Microsoft "#pragma pack" feature for
1120controlling record layout. GCC also contains support for this feature,
1121however where MSVC and GCC are incompatible clang follows the MSVC
1122definition.</li>
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1123
1124<li>clang defaults to C++11 for Windows targets.</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1125</ul>
Daniel Dunbar9375ed12009-05-13 21:40:49 +0000[diff] [blame]1126
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1127<!-- ======================================================================= -->
Richard Smithbdb10182011-11-21 20:54:59 +0000[diff] [blame]1128<h2 id="cxx">C++ Language Features</h2>
1129<!-- ======================================================================= -->
1130
1131<p>clang fully implements all of standard C++98 except for exported templates
1132(which were removed in C++11), and
1133<a href="http://clang.llvm.org/cxx_status.html">many C++11 features</a> are also
1134implemented.</p>
1135
1136<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1137<h3 id="cxx_implimits">Controlling implementation limits</h3>
1138<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1139
1140<p><b>-fconstexpr-depth=N</b>: Sets the limit for recursive constexpr function
1141invocations to N. The default is 512.</p>
1142
1143<p><b>-ftemplate-depth=N</b>: Sets the limit for recursively nested template
1144instantiations to N. The default is 1024.</p>
1145
1146<!-- ======================================================================= -->
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1147<h2 id="target_features">Target-Specific Features and Limitations</h2>
1148<!-- ======================================================================= -->
1149
1150
1151<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1152<h3 id="target_arch">CPU Architectures Features and Limitations</h3>
1153<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1154
1155<!-- ======================== -->
1156<h4 id="target_arch_x86">X86</h4>
1157<!-- ======================== -->
Daniel Dunbarbcaf7aa2010-09-19 19:26:59 +0000[diff] [blame]1158
1159<p>The support for X86 (both 32-bit and 64-bit) is considered stable on Darwin
1160(Mac OS/X), Linux, FreeBSD, and Dragonfly BSD: it has been tested to correctly
1161compile many large C, C++, Objective-C, and Objective-C++ codebases.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1162
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1163<p>On x86_64-mingw32, passing i128(by value) is incompatible to Microsoft x64
1164calling conversion. You might need to tweak WinX86_64ABIInfo::classify()
1165in lib/CodeGen/TargetInfo.cpp.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1166
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1167<!-- ======================== -->
1168<h4 id="target_arch_arm">ARM</h4>
1169<!-- ======================== -->
Daniel Dunbarbcaf7aa2010-09-19 19:26:59 +0000[diff] [blame]1170
1171<p>The support for ARM (specifically ARMv6 and ARMv7) is considered stable on
1172Darwin (iOS): it has been tested to correctly compile many large C, C++,
Bob Wilson4ea8dfa2011-01-10 17:55:14 +0000[diff] [blame]1173Objective-C, and Objective-C++ codebases. Clang only supports a limited number
1174of ARM architectures. It does not yet fully support ARMv5, for example.</p>
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1175
1176<!-- ======================== -->
1177<h4 id="target_arch_other">Other platforms</h4>
1178<!-- ======================== -->
1179clang currently contains some support for PPC and Sparc; however, significant
1180pieces of code generation are still missing, and they haven't undergone
1181significant testing.
1182
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1183<p>clang contains limited support for the MSP430 embedded processor, but both
1184the clang support and the LLVM backend support are highly experimental.
1185
1186<p>Other platforms are completely unsupported at the moment. Adding the
1187minimal support needed for parsing and semantic analysis on a new platform
1188is quite easy; see lib/Basic/Targets.cpp in the clang source tree. This level
1189of support is also sufficient for conversion to LLVM IR for simple programs.
1190Proper support for conversion to LLVM IR requires adding code to
1191lib/CodeGen/CGCall.cpp at the moment; this is likely to change soon, though.
1192Generating assembly requires a suitable LLVM backend.
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1193
1194<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1195<h3 id="target_os">Operating System Features and Limitations</h3>
1196<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1197
1198<!-- ======================================= -->
1199<h4 id="target_os_darwin">Darwin (Mac OS/X)</h4>
1200<!-- ======================================= -->
1201
Chris Lattner396663b2012-05-04 21:11:08 +0000[diff] [blame]1202<p>None</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1203
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1204<!-- ======================================= -->
1205<h4 id="target_os_win32">Windows</h4>
1206<!-- ======================================= -->
1207
1208<p>Experimental supports are on Cygming.</p>
1209
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1210<p>See also <a href="#c_ms">Microsoft Extensions</a>.</p>
1211
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1212<h5>Cygwin</h5>
1213
1214<p>Clang works on Cygwin-1.7.</p>
1215
1216<h5>MinGW32</h5>
1217
1218<p>Clang works on some mingw32 distributions.
1219Clang assumes directories as below;</p>
1220
1221<ul>
1222<li><tt>C:/mingw/include</tt></li>
1223<li><tt>C:/mingw/lib</tt></li>
1224<li><tt>C:/mingw/lib/gcc/mingw32/4.[3-5].0/include/c++</tt></li>
1225</ul>
1226
NAKAMURA Takumi0e53df62011-11-17 07:54:13 +0000[diff] [blame]1227<p>On MSYS, a few tests might fail.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1228
1229<h5>MinGW-w64</h5>
1230
Douglas Gregordad879a2011-08-30 00:40:12 +0000[diff] [blame]1231<p>For 32-bit (i686-w64-mingw32), and 64-bit (x86_64-w64-mingw32), Clang assumes as below;<p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1232
1233<ul>
Douglas Gregordad879a2011-08-30 00:40:12 +0000[diff] [blame]1234<li><tt>GCC versions 4.5.0 to 4.5.3, 4.6.0 to 4.6.2, or 4.7.0 (for the C++ header search path)</tt></li>
1235<li><tt>some_directory/bin/gcc.exe</tt></li>
1236<li><tt>some_directory/bin/clang.exe</tt></li>
1237<li><tt>some_directory/bin/clang++.exe</tt></li>
1238<li><tt>some_directory/bin/../include/c++/GCC_version</tt></li>
1239<li><tt>some_directory/bin/../include/c++/GCC_version/x86_64-w64-mingw32</tt></li>
1240<li><tt>some_directory/bin/../include/c++/GCC_version/i686-w64-mingw32</tt></li>
1241<li><tt>some_directory/bin/../include/c++/GCC_version/backward</tt></li>
1242<li><tt>some_directory/bin/../x86_64-w64-mingw32/include</tt></li>
1243<li><tt>some_directory/bin/../i686-w64-mingw32/include</tt></li>
1244<li><tt>some_directory/bin/../include</tt></li>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1245</ul>
1246
David Blaikiea9639622012-04-19 17:21:46 +0000[diff] [blame]1247<p>This directory layout is standard for any toolchain you will find on the official <a href="http://mingw-w64.sourceforge.net">MinGW-w64 website</a>.
Douglas Gregordad879a2011-08-30 00:40:12 +0000[diff] [blame]1248
1249<p>Clang expects the GCC executable &quot;gcc.exe&quot; compiled for i686-w64-mingw32 (or x86_64-w64-mingw32) to be present on PATH.</p>
1250
1251<p><a href="http://llvm.org/bugs/show_bug.cgi?id=9072">Some tests might fail</a>
1252on x86_64-w64-mingw32.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1253
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1254</div>
1255</body>
1256</html>