Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / clang / 74976f231130b843f555a8f73df18ffb4d89639e / . / docs / UsersManual.html
blob: 22d44ceea1552723329ec0fa31c89de6158b6758 [file] [log] [blame]
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]3<html>
4<head>
5<title>Clang Compiler User's Manual</title>
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]6<link type="text/css" rel="stylesheet" href="../menu.css">
7<link type="text/css" rel="stylesheet" href="../content.css">
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]8<style type="text/css">
9td {
10 vertical-align: top;
11}
12</style>
13</head>
14<body>
15
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>
190<p><b>-Wfoo</b>: Enable warning foo</p>
191<p><b>-Wno-foo</b>: Disable warning foo</p>
192<p><b>-w</b>: Disable all warnings.</p>
193<p><b>-pedantic</b>: Warn on language extensions.</p>
194<p><b>-pedantic-errors</b>: Error on language extensions.</p>
195<p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p>
196
Chris Lattner0f0c9632010-04-07 20:49:23 +0000[diff] [blame]197<p><b>-ferror-limit=123</b>: Stop emitting diagnostics after 123 errors have
198 been produced. The default is 20, and the error limit can be disabled with
199 -ferror-limit=0.</p>
200
Douglas Gregor575cf372010-04-20 07:18:24 +0000[diff] [blame]201<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>
202
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]203<!-- ================================================= -->
204<h4 id="cl_diag_formatting">Formatting of Diagnostics</h4>
205<!-- ================================================= -->
206
207<p>Clang aims to produce beautiful diagnostics by default, particularly for new
208users that first come to Clang. However, different people have different
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]209preferences, and sometimes Clang is driven by another program that wants to
210parse simple and consistent output, not a person. For these cases, Clang
211provides a wide range of options to control the exact output format of the
212diagnostics that it generates.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]213
214<dl>
215
216<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
217<dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in
218diagnostic.</dt>
219<dd>This option, which defaults to on, controls whether or not Clang prints the
220column number of a diagnostic. For example, when this is enabled, Clang will
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]221print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]222
223<pre>
224 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
225 #endif bad
226 ^
227 //
228</pre>
229
230<p>When this is disabled, Clang will print "test.c:28: warning..." with no
231column number.</p>
Jordan Rose6f977c32012-07-16 20:52:12 +0000[diff] [blame]232
233<p>The printed column numbers count bytes from the beginning of the line; take
234care if your source contains multibyte characters.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]235</dd>
236
237<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
238<dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print
239source file/line/column information in diagnostic.</dt>
240<dd>This option, which defaults to on, controls whether or not Clang prints the
241filename, line number and column number of a diagnostic. For example,
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]242when this is enabled, Clang will print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]243
244<pre>
245 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
246 #endif bad
247 ^
248 //
249</pre>
250
251<p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p>
252</dd>
253
254<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
255<dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source
256line and ranges from source code in diagnostic.</dt>
257<dd>This option, which defaults to on, controls whether or not Clang prints the
258source line, source ranges, and caret when emitting a diagnostic. For example,
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]259when this is enabled, Clang will print something like:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]260
261<pre>
262 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
263 #endif bad
264 ^
265 //
266</pre>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]267</dd>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]268<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]269<dt id="opt_fcolor_diagnostics"><b>-f[no-]color-diagnostics</b>: </dt>
270<dd>This option, which defaults to on when a color-capable terminal is
271 detected, controls whether or not Clang prints diagnostics in color.
272 When this option is enabled, Clang will use colors to highlight
273 specific parts of the diagnostic, e.g.,
Chris Lattner4e1c53d2011-01-24 03:47:34 +0000[diff] [blame]274 <pre>
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]275 <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]276 #endif bad
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]277 <span style="color:green">^</span>
278 <span style="color:green">//</span>
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]279</pre>
Chris Lattner4e1c53d2011-01-24 03:47:34 +0000[diff] [blame]280
281<p>When this is disabled, Clang will just print:</p>
282
283<pre>
284 test.c:2:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
285 #endif bad
286 ^
287 //
288</pre>
289</dd>
Douglas Gregore8d44dd2010-07-09 16:31:58 +0000[diff] [blame]290<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Douglas Gregorc9471b02011-05-21 17:07:29 +0000[diff] [blame]291<dt id="opt_fdiagnostics-format"><b>-fdiagnostics-format=clang/msvc/vi</b>:
292Changes diagnostic output format to better match IDEs and command line tools.</dt>
293<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:
294
295 <dl>
296 <dt><b>clang</b> (default)</dt>
297 <dd>
298 <pre>t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
299 </dd>
300
301 <dt><b>msvc</b></dt>
302 <dd>
303 <pre>t.c(3,11) : warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
304 </dd>
305
306 <dt><b>vi</b></dt>
307 <dd>
308 <pre>t.c +3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre>
309 </dd>
310 </dl>
311</dd>
312
313<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Argyrios Kyrtzidis477aab62011-05-25 05:05:01 +0000[diff] [blame]314<dt id="opt_fdiagnostics-show-name"><b>-f[no-]diagnostics-show-name</b>:
315Enable the display of the diagnostic name.</dt>
316<dd>This option, which defaults to off, controls whether or not
Benjamin Kramer665a8dc2012-01-15 15:26:07 +0000[diff] [blame]317Clang prints the associated name.<p></p></dd>
Argyrios Kyrtzidis477aab62011-05-25 05:05:01 +0000[diff] [blame]318<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]319<dt id="opt_fdiagnostics-show-option"><b>-f[no-]diagnostics-show-option</b>:
320Enable <tt>[-Woption]</tt> information in diagnostic line.</dt>
321<dd>This option, which defaults to on,
322controls whether or not Clang prints the associated <A
323href="#cl_diag_warning_groups">warning group</a> option name when outputting
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]324a warning diagnostic. For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]325
326<pre>
327 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
328 #endif bad
329 ^
330 //
331</pre>
332
333<p>Passing <b>-fno-diagnostics-show-option</b> will prevent Clang from printing
334the [<a href="#opt_Wextra-tokens">-Wextra-tokens</a>] information in the
335diagnostic. This information tells you the flag needed to enable or disable the
336diagnostic, either from the command line or through <a
337href="#pragma_GCC_diagnostic">#pragma GCC diagnostic</a>.</dd>
338
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]339<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
340<dt id="opt_fdiagnostics-show-category"><b>-fdiagnostics-show-category=none/id/name</b>:
341Enable printing category information in diagnostic line.</dt>
342<dd>This option, which defaults to "none",
343controls whether or not Clang prints the category associated with a diagnostic
344when emitting it. Each diagnostic may or many not have an associated category,
345if it has one, it is listed in the diagnostic categorization field of the
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]346diagnostic line (in the []'s).
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]347
348<p>For example, a format string warning will produce these three renditions
349based on the setting of this option:</p>
350
351<pre>
352 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat]
353 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,1</b>]
354 t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,Format String</b>]
355</pre>
356
357<p>This category can be used by clients that want to group diagnostics by
358category, so it should be a high level category. We want dozens of these, not
359hundreds or thousands of them.</p>
360</dd>
361
362
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]363
364<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
365<dt id="opt_fdiagnostics-fixit-info"><b>-f[no-]diagnostics-fixit-info</b>:
366Enable "FixIt" information in the diagnostics output.</dt>
367<dd>This option, which defaults to on, controls whether or not Clang prints the
368information on how to fix a specific diagnostic underneath it when it knows.
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]369For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]370
371<pre>
372 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
373 #endif bad
374 ^
375 //
376</pre>
377
378<p>Passing <b>-fno-diagnostics-fixit-info</b> will prevent Clang from printing
379the "//" line at the end of the message. This information is useful for users
380who may not understand what is wrong, but can be confusing for machine
381parsing.</p>
382</dd>
383
384<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]385<dt id="opt_fdiagnostics-print-source-range-info">
386<b>-f[no-]diagnostics-print-source-range-info</b>:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]387Print machine parsable information about source ranges.</dt>
388<dd>This option, which defaults to off, controls whether or not Clang prints
389information about source ranges in a machine parsable format after the
390file/line/column number information. The information is a simple sequence of
391brace enclosed ranges, where each range lists the start and end line/column
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]392locations. For example, in this output:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]393
394<pre>
395exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
396 P = (P-42) + Gamma*4;
397 ~~~~~~ ^ ~~~~~~~
398</pre>
399
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]400<p>The {}'s are generated by -fdiagnostics-print-source-range-info.</p>
Jordan Rose6f977c32012-07-16 20:52:12 +0000[diff] [blame]401
402<p>The printed column numbers count bytes from the beginning of the line; take
403care if your source contains multibyte characters.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]404</dd>
405
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]406<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
407<dt id="opt_fdiagnostics-parseable-fixits">
408<b>-fdiagnostics-parseable-fixits</b>:
409Print Fix-Its in a machine parseable form.</dt>
410<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>
411
412<pre>
Douglas Gregorbf5e09d2010-08-20 03:17:33 +0000[diff] [blame]413 fix-it:"t.cpp":{7:25-7:29}:"Gamma"
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]414</pre>
415
NAKAMURA Takumi44626362011-04-05 00:57:02 +0000[diff] [blame]416<p>The range printed is a half-open range, so in this example the characters at
417column 25 up to but not including column 29 on line 7 in t.cpp should be
418replaced with the string &quot;Gamma&quot;. Either the range or the replacement
419string may be empty (representing strict insertions and strict erasures,
420respectively). Both the file name and the insertion string escape backslash (as
421&quot;\\&quot;), tabs (as &quot;\t&quot;), newlines (as &quot;\n&quot;), double
422quotes(as &quot;\&quot;&quot;) and non-printable characters (as octal
423&quot;\xxx&quot;).</p>
Jordan Rose6f977c32012-07-16 20:52:12 +0000[diff] [blame]424
425<p>The printed column numbers count bytes from the beginning of the line; take
426care if your source contains multibyte characters.</p>
Douglas Gregor4786c152010-08-19 20:24:43 +0000[diff] [blame]427</dd>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]428
Richard Trieue59331a2012-06-27 02:00:20 +0000[diff] [blame]429<dt id="opt_fno-elide-type">
430<b>-fno-elide-type</b>:
431Turns off elision in template type printing.</td>
432<dd><p>The default for template type printing is to elide as many template
433arguments as possible, removing those which are the same in both template types,
434leaving only the differences. Adding this flag will print all the template
435arguments. If supported by the terminal, highlighting will still appear on
436differing arguments.</p>
437
438Default:
439<pre>
440t.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;
441</pre>
442-fno-elide-type:
443<pre>
444t.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;
445</pre>
446</dd>
447
448<dt id="opt_fdiagnostics-show-template-tree">
449<b>-fdiagnostics-show-template-tree</b>:
450Template type diffing prints a text tree.</td>
451<dd><p>For diffing large templated types, this option will cause Clang to
452display the templates as an indented text tree, one argument per line, with
453differences marked inline. This is compatible with -fno-elide-type.</p>
454
455Default:
456<pre>
457t.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;
458</pre>
459-fdiagnostics-show-template-tree
460<pre>
461t.cc:4:5: <span class="note">note</span>: candidate function not viable: no known conversion for 1st argument;
462 vector&lt;
463 map&lt;
464 [...],
465 map&lt;
466 [<span class="template-highlight">float</span> != <span class="template-highlight">float</span>],
467 [...]&gt;&gt;&gt;
468</pre>
469</dd>
470
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]471</dl>
472
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]473
474
475<!-- ===================================================== -->
476<h4 id="cl_diag_warning_groups">Individual Warning Groups</h4>
477<!-- ===================================================== -->
478
479<p>TODO: Generate this from tblgen. Define one anchor per warning group.</p>
480
481
482<dl>
483
484
485<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
486<dt id="opt_Wextra-tokens"><b>-Wextra-tokens</b>: Warn about excess tokens at
487 the end of a preprocessor directive.</dt>
488<dd>This option, which defaults to on, enables warnings about extra tokens at
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]489the end of preprocessor directives. For example:
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]490
491<pre>
492 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
493 #endif bad
494 ^
495</pre>
496
497<p>These extra tokens are not strictly conforming, and are usually best handled
498by commenting them out.</p>
499
500<p>This option is also enabled by <a href="">-Wfoo</a>, <a href="">-Wbar</a>,
501 and <a href="">-Wbaz</a>.</p>
502</dd>
503
Jeffrey Yasskin21d07e42010-06-05 01:39:57 +0000[diff] [blame]504<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
505<dt id="opt_Wambiguous-member-template"><b>-Wambiguous-member-template</b>:
506Warn about unqualified uses of a member template whose name resolves
507to another template at the location of the use.</dt>
508<dd>This option, which defaults to on, enables a warning in the
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]509following code:
Jeffrey Yasskin21d07e42010-06-05 01:39:57 +0000[diff] [blame]510
511<pre>
512template&lt;typename T> struct set{};
513template&lt;typename T> struct trait { typedef const T& type; };
514struct Value {
515 template&lt;typename T> void set(typename trait&lt;T>::type value) {}
516};
517void foo() {
518 Value v;
519 v.set&lt;double>(3.2);
520}
521</pre>
522
523<p>C++ [basic.lookup.classref] requires this to be an error, but,
524because it's hard to work around, Clang downgrades it to a warning as
525an extension.</p>
526</dd>
527
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]528<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
529<dt id="opt_Wbind-to-temporary-copy"><b>-Wbind-to-temporary-copy</b>: Warn about
530an unusable copy constructor when binding a reference to a temporary.</dt>
531<dd>This option, which defaults to on, enables warnings about binding a
532reference to a temporary when the temporary doesn't have a usable copy
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]533constructor. For example:
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]534
535<pre>
536 struct NonCopyable {
537 NonCopyable();
538 private:
539 NonCopyable(const NonCopyable&);
540 };
541 void foo(const NonCopyable&);
542 void bar() {
David Blaikie5090e9f2011-10-18 05:49:30 +0000[diff] [blame]543 foo(NonCopyable()); // Disallowed in C++98; allowed in C++11.
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]544 }
545</pre>
546<pre>
547 struct NonCopyable2 {
548 NonCopyable2();
549 NonCopyable2(NonCopyable2&);
550 };
551 void foo(const NonCopyable2&);
552 void bar() {
David Blaikie5090e9f2011-10-18 05:49:30 +0000[diff] [blame]553 foo(NonCopyable2()); // Disallowed in C++98; allowed in C++11.
Jeffrey Yasskin57d12fd2010-06-07 15:58:05 +0000[diff] [blame]554 }
555</pre>
556
557<p>Note that if <tt>NonCopyable2::NonCopyable2()</tt> has a default
558argument whose instantiation produces a compile error, that error will
559still be a hard error in C++98 mode even if this warning is turned
560off.</p>
561
562</dd>
563
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]564</dl>
565
Chad Rosiercd376a12012-02-22 20:26:10 +0000[diff] [blame]566<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
567<h3 id="cl_crash_diagnostics">Options to Control Clang Crash Diagnostics</h3>
568<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
569
570<p>As unbelievable as it may sound, Clang does crash from time to time.
571Generally, this only occurs to those living on the
572<a href="http://llvm.org/releases/download.html#svn">bleeding edge</a>. Clang
573goes to great lengths to assist you in filing a bug report. Specifically, Clang
574generates preprocessed source file(s) and associated run script(s) upon a
575crash. These files should be attached to a bug report to ease reproducibility
576of the failure. Below are the command line options to control the crash
577diagnostics.
578</p>
579
580<p><b>-fno-crash-diagnostics</b>: Disable auto-generation of preprocessed
581source files during a clang crash.</p>
582
583<p>The -fno-crash-diagnostics flag can be helpful for speeding the process of
584generating a delta reduced test case.</p>
585
586
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]587<!-- ======================================================================= -->
588<h2 id="general_features">Language and Target-Independent Features</h2>
589<!-- ======================================================================= -->
590
591
592<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
593<h3 id="diagnostics">Controlling Errors and Warnings</h3>
594<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
595
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]596<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]597emit errors and warning messages, and how they are displayed to the console.</p>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]598
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]599<h4 id="diagnostics_display">Controlling How Clang Displays Diagnostics</h4>
Chris Lattner65a795b2009-04-20 06:00:23 +0000[diff] [blame]600
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]601<p>When Clang emits a diagnostic, it includes rich information in the output,
602and gives you fine-grain control over which information is printed. Clang has
603the ability to print this information, and these are the options that control
604it:</p>
605
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]606<ol>
607<li>A file/line/column indicator that shows exactly where the diagnostic occurs
608 in your code [<a href="#opt_fshow-column">-fshow-column</a>, <a
609 href="#opt_fshow-source-location">-fshow-source-location</a>].</li>
610<li>A categorization of the diagnostic as a note, warning, error, or fatal
611 error.</li>
612<li>A text string that describes what the problem is.</li>
613<li>An option that indicates how to control the diagnostic (for diagnostics that
614 support it) [<a
615 href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li>
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]616<li>A <a href="#diagnostics_categories">high-level category</a> for the
617 diagnostic for clients that want to group diagnostics by class (for
618 diagnostics that support it) [<a
Chris Lattner28a43a42010-05-05 01:35:28 +0000[diff] [blame]619 href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a>].</li>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]620<li>The line of source code that the issue occurs on, along with a caret and
621 ranges that indicate the important locations [<a
622 href="opt_fcaret-diagnostics">-fcaret-diagnostics</a>].</li>
623<li>"FixIt" information, which is a concise explanation of how to fix the
624 problem (when Clang is certain it knows) [<a
625 href="opt_fdiagnostics-fixit-info">-fdiagnostics-fixit-info</a>].</li>
626<li>A machine-parsable representation of the ranges involved (off by
627 default) [<a
Chris Lattner2a9cc232009-04-21 05:35:32 +0000[diff] [blame]628 href="opt_fdiagnostics-print-source-range-info">-fdiagnostics-print-source-range-info</a>].</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]629</ol>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]630
631<p>For more information please see <a href="#cl_diag_formatting">Formatting of
632Diagnostics</a>.</p>
633
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]634
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]635<h4 id="diagnostics_mappings">Diagnostic Mappings</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]636
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]637<p>All diagnostics are mapped into one of these 5 classes:</p>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]638
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]639<ul>
640<li>Ignored</li>
641<li>Note</li>
642<li>Warning</li>
643<li>Error</li>
644<li>Fatal</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]645</ul>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]646
Chris Lattner3f145382010-05-24 21:35:18 +0000[diff] [blame]647<h4 id="diagnostics_categories">Diagnostic Categories</h4>
648
649<p>Though not shown by default, diagnostics may each be associated with a
650 high-level category. This category is intended to make it possible to triage
651 builds that produce a large number of errors or warnings in a grouped way.
652</p>
653
654<p>Categories are not shown by default, but they can be turned on with the
655<a href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a> option.
656When set to "<tt>name</tt>", the category is printed textually in the diagnostic
657output. When it is set to "<tt>id</tt>", a category number is printed. The
658mapping of category names to category id's can be obtained by running '<tt>clang
659 --print-diagnostic-categories</tt>'.
660</p>
661
662<h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line
663 Flags</h4>
Chris Lattner8217f4e2009-04-20 06:26:18 +0000[diff] [blame]664
665<p>-W flags, -pedantic, etc</p>
666
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]667<h4 id="diagnostics_pragmas">Controlling Diagnostics via Pragmas</h4>
668
669<p>Clang can also control what diagnostics are enabled through the use of
670pragmas in the source code. This is useful for turning off specific warnings
671in a section of source code. Clang supports GCC's pragma for compatibility
672with existing source code, as well as several extensions. </p>
673
674<p>The pragma may control any warning that can be used from the command line.
675Warnings may be set to ignored, warning, error, or fatal. The following
676example code will tell Clang or GCC to ignore the -Wall warnings:</p>
677
678<pre>
679#pragma GCC diagnostic ignored "-Wall"
680</pre>
681
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]682<p>In addition to all of the functionality provided by GCC's pragma, Clang
Chris Lattner3401cf82009-07-12 21:22:10 +0000[diff] [blame]683also allows you to push and pop the current warning state. This is particularly
684useful when writing a header file that will be compiled by other people, because
685you don't know what warning flags they build with.</p>
686
687<p>In the below example
688-Wmultichar is ignored for only a single line of code, after which the
689diagnostics return to whatever state had previously existed.</p>
690
691<pre>
692#pragma clang diagnostic push
693#pragma clang diagnostic ignored "-Wmultichar"
694
695char b = 'df'; // no warning.
696
697#pragma clang diagnostic pop
698</pre>
699
700<p>The push and pop pragmas will save and restore the full diagnostic state of
701the compiler, regardless of how it was set. That means that it is possible to
702use push and pop around GCC compatible diagnostics and Clang will push and pop
703them appropriately, while GCC will ignore the pushes and pops as unknown
704pragmas. It should be noted that while Clang supports the GCC pragma, Clang and
705GCC do not support the exact same set of warnings, so even when using GCC
706compatible #pragmas there is no guarantee that they will have identical behaviour
707on both compilers. </p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]708
Richard Smithf122a132012-06-13 20:27:03 +0000[diff] [blame]709<h4 id="diagnostics_systemheader">Controlling Diagnostics in System Headers</h4>
710
711<p>Warnings are suppressed when they occur in system headers. By default, an
712included file is treated as a system header if it is found in an include path
713specified by <tt>-isystem</tt>, but this can be overridden in several ways.</p>
714
715<p>The <tt>system_header</tt> pragma can be used to mark the current file as
716being a system header. No warnings will be produced from the location of the
717pragma onwards within the same file.</p>
718
719<pre>
720char a = 'xy'; // warning
721
722#pragma clang system_header
723
724char b = 'ab'; // no warning
725</pre>
726
727<p>The <tt>-isystem-prefix</tt> and <tt>-ino-system-prefix</tt> command-line
728arguments can be used to override whether subsets of an include path are treated
729as system headers. When the name in a <tt>#include</tt> directive is found
730within a header search path and starts with a system prefix, the header is
731treated as a system header. The last prefix on the command-line which matches
732the specified header name takes precedence. For instance:</p>
733
734<pre>
735clang -Ifoo -isystem bar -isystem-prefix x/ -ino-system-prefix x/y/
736</pre>
737
738<p>Here, <tt>#include "x/a.h"</tt> is treated as including a system header, even
739if the header is found in <tt>foo</tt>, and <tt>#include "x/y/b.h"</tt> is
740treated as not including a system header, even if the header is found in
741<tt>bar</tt>.
742</p>
743
744<p>A <tt>#include</tt> directive which finds a file relative to the current
745directory is treated as including a system header if the including file is
746treated as a system header.</p>
747
Ted Kremenekf391fa72011-08-18 01:17:05 +0000[diff] [blame]748<h4 id="diagnostics_enable_everything">Enabling All Warnings</h4>
749
750<p>In addition to the traditional <tt>-W</tt> flags, one can enable <b>all</b>
751 warnings by passing <tt>-Weverything</tt>.
752 This works as expected with <tt>-Werror</tt>,
753 and also includes the warnings from <tt>-pedantic</tt>.</p>
754
755<p>Note that when combined with <tt>-w</tt> (which disables all warnings), that
756 flag wins.</p>
757
Ted Kremenek2fb11eb2010-08-24 18:12:35 +0000[diff] [blame]758<h4 id="analyzer_diagnositics">Controlling Static Analyzer Diagnostics</h4>
759
760<p>While not strictly part of the compiler, the diagnostics from Clang's <a
761href="http://clang-analyzer.llvm.org">static analyzer</a> can also be influenced
Anna Zaks843f0e82012-06-16 00:30:21 +0000[diff] [blame]762by the user via changes to the source code. See the avaliable
763<a href = "http://clang-analyzer.llvm.org/annotations.html" >annotations</a> and
764the analyzer's
765<a href= "http://clang-analyzer.llvm.org/faq.html#exclude_code" >FAQ page</a> for
766more information.
Ted Kremenek2fb11eb2010-08-24 18:12:35 +0000[diff] [blame]767</ul>
768
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]769<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
770<h3 id="precompiledheaders">Precompiled Headers</h3>
771<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
772
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]773<p><a href="http://en.wikipedia.org/wiki/Precompiled_header">Precompiled
774headers</a> are a general approach employed by many compilers to reduce
775compilation time. The underlying motivation of the approach is that it is
776common for the same (and often large) header files to be included by
777multiple source files. Consequently, compile times can often be greatly improved
778by caching some of the (redundant) work done by a compiler to process headers.
779Precompiled header files, which represent one of many ways to implement
780this optimization, are literally files that represent an on-disk cache that
781contains the vital information necessary to reduce some of the work
782needed to process a corresponding header file. While details of precompiled
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]783headers vary between compilers, precompiled headers have been shown to be
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]784highly effective at speeding up program compilation on systems with very large
785system headers (e.g., Mac OS/X).</p>
786
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]787<h4>Generating a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]788
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]789<p>To generate a PCH file using Clang, one invokes Clang with
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]790the <b><tt>-x <i>&lt;language&gt;</i>-header</tt></b> option. This mirrors the
791interface in GCC for generating PCH files:</p>
792
793<pre>
794 $ gcc -x c-header test.h -o test.h.gch
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]795 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]796</pre>
797
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]798<h4>Using a PCH File</h4>
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]799
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]800<p>A PCH file can then be used as a prefix header when a
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]801<b><tt>-include</tt></b> option is passed to <tt>clang</tt>:</p>
802
803<pre>
804 $ clang -include test.h test.c -o test
805</pre>
806
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]807<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]808is 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]809will be processed from the PCH file. Otherwise, Clang falls back to
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]810directly processing the content of <tt>test.h</tt>. This mirrors the behavior of
811GCC.</p>
812
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]813<p><b>NOTE:</b> Clang does <em>not</em> automatically use PCH files
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]814for headers that are directly included within a source file. For example:</p>
815
816<pre>
Chris Lattnere42ec542009-06-13 20:35:58 +0000[diff] [blame]817 $ clang -x c-header test.h -o test.h.pch
Chris Lattner5c3074f2009-04-20 04:37:38 +0000[diff] [blame]818 $ cat test.c
819 #include "test.h"
820 $ clang test.c -o test
821</pre>
822
Douglas Gregorf4d59532009-06-03 22:37:00 +0000[diff] [blame]823<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]824<tt>test.h</tt> since <tt>test.h</tt> was included directly in the source file
825and not specified on the command line using <tt>-include</tt>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]826
Douglas Gregore650c8c2009-07-07 00:12:59 +0000[diff] [blame]827<h4>Relocatable PCH Files</h4>
828<p>It is sometimes necessary to build a precompiled header from headers that
829are not yet in their final, installed locations. For example, one might build a
830precompiled header within the build tree that is then meant to be installed
831alongside the headers. Clang permits the creation of "relocatable" precompiled
832headers, which are built with a given path (into the build directory) and can
833later be used from an installed location.</p>
834
835<p>To build a relocatable precompiled header, place your headers into a
836subdirectory whose structure mimics the installed location. For example, if you
837want to build a precompiled header for the header <code>mylib.h</code> that
838will be installed into <code>/usr/include</code>, create a subdirectory
839<code>build/usr/include</code> and place the header <code>mylib.h</code> into
840that subdirectory. If <code>mylib.h</code> depends on other headers, then
841they can be stored within <code>build/usr/include</code> in a way that mimics
842the installed location.</p>
843
844<p>Building a relocatable precompiled header requires two additional arguments.
845First, pass the <code>--relocatable-pch</code> flag to indicate that the
846resulting PCH file should be relocatable. Second, pass
847<code>-isysroot /path/to/build</code>, which makes all includes for your
848library relative to the build directory. For example:</p>
849
850<pre>
851 # clang -x c-header --relocatable-pch -isysroot /path/to/build /path/to/build/mylib.h mylib.h.pch
852</pre>
853
854<p>When loading the relocatable PCH file, the various headers used in the PCH
855file are found from the system header root. For example, <code>mylib.h</code>
856can be found in <code>/usr/include/mylib.h</code>. If the headers are installed
857in some other system root, the <code>-isysroot</code> option can be used provide
858a different system root from which the headers will be based. For example,
859<code>-isysroot /Developer/SDKs/MacOSX10.4u.sdk</code> will look for
860<code>mylib.h</code> in
861<code>/Developer/SDKs/MacOSX10.4u.sdk/usr/include/mylib.h</code>.</p>
862
863<p>Relocatable precompiled headers are intended to be used in a limited number
864of cases where the compilation environment is tightly controlled and the
865precompiled header cannot be generated after headers have been installed.
866Relocatable precompiled headers also have some performance impact, because
867the difference in location between the header locations at PCH build time vs.
868at the time of PCH use requires one of the PCH optimizations,
869<code>stat()</code> caching, to be disabled. However, this change is only
870likely to affect PCH files that reference a large number of headers.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]871
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]872<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
873<h3 id="codegen">Controlling Code Generation</h3>
874<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
875
876<p>Clang provides a number of ways to control code generation. The options are listed below.</p>
877
878<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]879<dl>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]880<dt id="opt_fcatch-undefined-behavior"><b>-fcatch-undefined-behavior</b>: Turn
881on runtime code generation to check for undefined behavior.</dt>
882
883<dd>This option, which defaults to off, controls whether or not Clang
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]884adds runtime checks for undefined runtime behavior. If a check fails,
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]885<tt>__builtin_trap()</tt> is used to indicate failure.
886The checks are:
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]887<ul>
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]888<li>Subscripting where the static type of one operand is a variable
Mike Stump88b2a172009-12-16 03:25:12 +0000[diff] [blame]889 which is decayed from an array type and the other operand is
890 greater than the size of the array or less than zero.</li>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]891<li>Shift operators where the amount shifted is greater or equal to the
892 promoted bit-width of the left-hand-side or less than zero.</li>
Mike Stump8f6a3ed2009-12-16 03:18:14 +0000[diff] [blame]893<li>If control flow reaches __builtin_unreachable.
894<li>When llvm implements more __builtin_object_size support, reads and
895 writes for objects that __builtin_object_size indicates we aren't
896 accessing valid memory. Bit-fields and vectors are not yet checked.
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]897</ul>
Mike Stump53664ca2009-12-14 23:53:10 +0000[diff] [blame]898</dd>
899
Kostya Serebryany48a8cd92012-03-01 23:14:19 +0000[diff] [blame]900<dt id="opt_faddress-sanitizer"><b>-f[no-]address-sanitizer</b>:
901Turn on <a href="AddressSanitizer.html">AddressSanitizer</a>,
902a memory error detector.
903
904<dt id="opt_fthread-sanitizer"><b>-f[no-]thread-sanitizer</b>:
905Turn on ThreadSanitizer, an <em>experimental</em> data race detector.
906Not ready for widespread use.
907
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]908<dt id="opt_fno-assume-sane-operator-new"><b>-fno-assume-sane-operator-new</b>:
909Don't assume that the C++'s new operator is sane.</dt>
Nuno Lopesb23f20d2009-12-17 10:15:49 +0000[diff] [blame]910<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]911operator will always return a pointer that does not
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]912alias any other pointer when the function returns.</dd>
Evan Chengfda026b2011-04-08 22:18:01 +0000[diff] [blame]913
Evan Cheng4cf4b592011-04-08 22:34:21 +0000[diff] [blame]914<dt id="opt_ftrap-function"><b>-ftrap-function=[name]</b>: Instruct code
Evan Chengfda026b2011-04-08 22:18:01 +0000[diff] [blame]915generator to emit a function call to the specified function name for
916<tt>__builtin_trap()</tt>.</dt>
917
918<dd>LLVM code generator translates <tt>__builtin_trap()</tt> to a trap
919instruction if it is supported by the target ISA. Otherwise, the builtin is
920translated into a call to <tt>abort</tt>. If this option is set, then the code
921generator will always lower the builtin to a call to the specified function
922regardless of whether the target ISA has a trap instruction. This option is
Chris Lattner02e266b2011-04-08 22:58:43 +0000[diff] [blame]923useful for environments (e.g. deeply embedded) where a trap cannot be properly
924handled, or when some custom behavior is desired.</dd>
Hans Wennborg7bf9d9b2012-07-13 12:47:15 +0000[diff] [blame]925
926<dt id="opt_ftls-model"><b>-ftls-model=[model]</b>: Select which TLS model to
927use.</dt>
928<dd>Valid values are: <tt>global-dynamic</tt>, <tt>local-dynamic</tt>,
929<tt>initial-exec</tt> and <tt>local-exec</tt>. The default value is
930<tt>global-dynamic</tt>. The compiler may use a different model if the selected
931model is not supported by the target, or if a more efficient model can be used.
932The TLS model can be overridden per variable using the <tt>tls_model</tt>
933attribute.
934</dd>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]935</dl>
Nuno Lopesaa526242009-12-17 10:00:52 +0000[diff] [blame]936
Alexey Samsonov5ab52492012-05-30 06:55:10 +0000[diff] [blame]937<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
938<h3 id="debuginfosize">Controlling Size of Debug Information</h3>
939<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
940
941<p>Debug info kind generated by Clang can be set by one of the flags listed
942below. If multiple flags are present, the last one is used.</p>
943
944<!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
945<dl>
946<dt id="opt_g0"><b>-g0</b>: Don't generate any debug info (default).
947
948<dt id="opt_gline-tables-only"><b>-gline-tables-only</b>:
949Generate line number tables only.
950<dd>
951This kind of debug info allows to obtain stack traces with function
952names, file names and line numbers (by such tools as
953gdb or addr2line). It doesn't contain any other data (e.g.
954description of local variables or function parameters).
955</dd>
956
957<dt id="opt_g"><b>-g</b>: Generate complete debug info.
958</dl>
959
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]960<!-- ======================================================================= -->
961<h2 id="c">C Language Features</h2>
962<!-- ======================================================================= -->
963
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]964<p>The support for standard C in clang is feature-complete except for the C99
965floating-point pragmas.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]966
967<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]968<h3 id="c_ext">Extensions supported by clang</h3>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]969<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
970
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]971<p>See <a href="LanguageExtensions.html">clang language extensions</a>.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]972
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]973<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
974<h3 id="c_modes">Differences between various standard modes</h3>
975<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]976
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]977<p>clang supports the -std option, which changes what language mode clang uses.
978The supported modes for C are c89, gnu89, c94, c99, gnu99 and various aliases
979for those modes. If no -std option is specified, clang defaults to gnu99 mode.
980</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]981
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]982<p>Differences between all c* and gnu* modes:</p>
983<ul>
984<li>c* modes define "__STRICT_ANSI__".</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]985<li>Target-specific defines not prefixed by underscores, like "linux", are
986defined in gnu* modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]987<li>Trigraphs default to being off in gnu* modes; they can be enabled by the
988-trigraphs option.</li>
989<li>The parser recognizes "asm" and "typeof" as keywords in gnu* modes; the
990variants "__asm__" and "__typeof__" are recognized in all modes.</li>
Eli Friedmanb0ac5452009-05-16 23:17:30 +0000[diff] [blame]991<li>The Apple "blocks" extension is recognized by default in gnu* modes
992on some platforms; it can be enabled in any mode with the "-fblocks"
993option.</li>
Chris Lattner741be6a2011-06-15 00:41:40 +0000[diff] [blame]994<li>Arrays that are VLA's according to the standard, but which can be constant
995 folded by the frontend are treated as fixed size arrays. This occurs for
996 things like "int X[(1, 2)];", which is technically a VLA. c* modes are
997 strictly compliant and treat these as VLAs.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]998</ul>
999
1000<p>Differences between *89 and *99 modes:</p>
1001<ul>
1002<li>The *99 modes default to implementing "inline" as specified in C99, while
1003the *89 modes implement the GNU version. This can be overridden for individual
1004functions with the __gnu_inline__ attribute.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]1005<li>Digraphs are not recognized in c89 mode.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1006<li>The scope of names defined inside a "for", "if", "switch", "while", or "do"
1007statement is different. (example: "if ((struct x {int x;}*)0) {}".)</li>
1008<li>__STDC_VERSION__ is not defined in *89 modes.</li>
Eli Friedman26fa0ed2009-05-27 23:02:57 +0000[diff] [blame]1009<li>"inline" is not recognized as a keyword in c89 mode.</li>
1010<li>"restrict" is not recognized as a keyword in *89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1011<li>Commas are allowed in integer constant expressions in *99 modes.</li>
1012<li>Arrays which are not lvalues are not implicitly promoted to pointers in
1013*89 modes.</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1014<li>Some warnings are different.</li>
1015</ul>
1016
1017<p>c94 mode is identical to c89 mode except that digraphs are enabled in
1018c94 mode (FIXME: And __STDC_VERSION__ should be defined!).</p>
1019
1020<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1021<h3 id="c_unimpl_gcc">GCC extensions not implemented yet</h3>
1022<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1023
1024<p>clang tries to be compatible with gcc as much as possible, but some gcc
1025extensions are not implemented yet:</p>
1026
1027<ul>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1028
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1029<li>clang does not support #pragma weak
Eli Friedman4da92552009-06-02 08:21:31 +0000[diff] [blame]1030(<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]1031the uses described in the bug, this is likely to be implemented at some
1032point, at least partially.</li>
1033
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1034<li>clang does not support decimal floating point types (_Decimal32 and
1035friends) or fixed-point types (_Fract and friends); nobody has expressed
1036interest in these features yet, so it's hard to say when they will be
1037implemented.</li>
1038
1039<li>clang does not support nested functions; this is a complex feature which
1040is infrequently used, so it is unlikely to be implemented anytime soon.</li>
1041
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1042<li>clang does not support global register variables, this is unlikely
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1043to be implemented soon because it requires additional LLVM backend support.
1044</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1045
1046<li>clang does not support static initialization of flexible array
1047members. This appears to be a rarely used extension, but could be
1048implemented pending user demand.</li>
1049
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1050<li>clang does not support __builtin_va_arg_pack/__builtin_va_arg_pack_len.
1051This is used rarely, but in some potentially interesting places, like the
1052glibc headers, so it may be implemented pending user demand. Note that
1053because clang pretends to be like GCC 4.2, and this extension was introduced
1054in 4.3, the glibc headers will not try to use this extension with clang at
1055the moment.</li>
1056
1057<li>clang does not support the gcc extension for forward-declaring function
1058parameters; this has not showed up in any real-world code yet, though, so it
1059might never be implemented.</li>
1060
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1061</ul>
1062
1063<p>This is not a complete list; if you find an unsupported extension
1064missing from this list, please send an e-mail to cfe-dev. This list
1065currently excludes C++; see <a href="#cxx">C++ Language Features</a>.
1066Also, this list does not include bugs in mostly-implemented features; please
1067see 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">
1068bug tracker</a> for known existing bugs (FIXME: Is there a section for
1069bug-reporting guidelines somewhere?).</p>
1070
1071<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1072<h3 id="c_unsupp_gcc">Intentionally unsupported GCC extensions</h3>
1073<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1074
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]1075<ul>
1076
Eli Friedman2f3fca02009-06-12 20:08:48 +0000[diff] [blame]1077<li>clang does not support the gcc extension that allows variable-length arrays
Chris Lattnerd462b6a2011-01-24 03:47:59 +0000[diff] [blame]1078in structures. This is for a few reasons: one, it is tricky
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1079to implement, two, the extension is completely undocumented, and three, the
Chris Lattnerb9d511c2010-10-28 02:20:32 +0000[diff] [blame]1080extension appears to be rarely used. Note that clang <em>does</em> support
1081flexible array members (arrays with a zero or unspecified size at the end of
1082a structure).</li>
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1083
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1084<li>clang does not have an equivalent to gcc's "fold"; this means that
1085clang doesn't accept some constructs gcc might accept in contexts where a
Eli Friedman248f9732011-06-13 23:12:01 +0000[diff] [blame]1086constant expression is required, like "x-x" where x is a variable.</li>
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1087
Eli Friedmanca130bd2009-06-12 20:04:25 +0000[diff] [blame]1088<li>clang does not support __builtin_apply and friends; this extension is
1089extremely obscure and difficult to implement reliably.</li>
1090
Eli Friedman0b326002009-06-12 20:11:05 +0000[diff] [blame]1091</ul>
1092
Eli Friedman660a5ac2009-04-28 18:48:34 +0000[diff] [blame]1093<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1094<h3 id="c_ms">Microsoft extensions</h3>
1095<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1096
1097<p>clang has some experimental support for extensions from
1098Microsoft Visual C++; to enable it, use the -fms-extensions command-line
Eli Friedmana1821b52009-06-08 06:21:03 +0000[diff] [blame]1099option. This is the default for Windows targets. Note that the
1100support is incomplete; enabling Microsoft extensions will silently drop
1101certain constructs (including __declspec and Microsoft-style asm statements).
1102</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1103
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1104<p>clang has a -fms-compatibility flag that makes clang accept enough
1105invalid C++ to be able to parse most Microsoft headers. This flag is enabled by
1106default for Windows targets.</p>
1107
1108<p>-fdelayed-template-parsing lets clang delay all template instantiation until
1109the end of a translation unit. This flag is enabled by default for Windows
1110targets.</p>
1111
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1112<ul>
Douglas Gregord3b227d2010-12-14 16:21:49 +0000[diff] [blame]1113<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]1114is the same as Visual C/C++ 2003. Any number is supported and can greatly affect
1115what Windows SDK and c++stdlib headers clang can compile. This option will be
1116removed when clang supports the full set of MS extensions required for these
1117headers.</li>
1118
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1119<li>clang does not support the Microsoft extension where anonymous
Daniel Dunbar869e0542009-05-13 00:23:53 +0000[diff] [blame]1120record members can be declared using user defined typedefs.</li>
Daniel Dunbar05fa6292009-05-12 23:12:07 +0000[diff] [blame]1121
Daniel Dunbar9375ed12009-05-13 21:40:49 +0000[diff] [blame]1122<li>clang supports the Microsoft "#pragma pack" feature for
1123controlling record layout. GCC also contains support for this feature,
1124however where MSVC and GCC are incompatible clang follows the MSVC
1125definition.</li>
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1126
1127<li>clang defaults to C++11 for Windows targets.</li>
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1128</ul>
Daniel Dunbar9375ed12009-05-13 21:40:49 +0000[diff] [blame]1129
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1130<!-- ======================================================================= -->
Richard Smithbdb10182011-11-21 20:54:59 +0000[diff] [blame]1131<h2 id="cxx">C++ Language Features</h2>
1132<!-- ======================================================================= -->
1133
1134<p>clang fully implements all of standard C++98 except for exported templates
1135(which were removed in C++11), and
1136<a href="http://clang.llvm.org/cxx_status.html">many C++11 features</a> are also
1137implemented.</p>
1138
1139<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1140<h3 id="cxx_implimits">Controlling implementation limits</h3>
1141<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1142
1143<p><b>-fconstexpr-depth=N</b>: Sets the limit for recursive constexpr function
1144invocations to N. The default is 512.</p>
1145
1146<p><b>-ftemplate-depth=N</b>: Sets the limit for recursively nested template
1147instantiations to N. The default is 1024.</p>
1148
1149<!-- ======================================================================= -->
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1150<h2 id="target_features">Target-Specific Features and Limitations</h2>
1151<!-- ======================================================================= -->
1152
1153
1154<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1155<h3 id="target_arch">CPU Architectures Features and Limitations</h3>
1156<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1157
1158<!-- ======================== -->
1159<h4 id="target_arch_x86">X86</h4>
1160<!-- ======================== -->
Daniel Dunbarbcaf7aa2010-09-19 19:26:59 +0000[diff] [blame]1161
1162<p>The support for X86 (both 32-bit and 64-bit) is considered stable on Darwin
1163(Mac OS/X), Linux, FreeBSD, and Dragonfly BSD: it has been tested to correctly
1164compile many large C, C++, Objective-C, and Objective-C++ codebases.</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1165
NAKAMURA Takumiddf68ff2011-04-05 04:31:31 +0000[diff] [blame]1166<p>On x86_64-mingw32, passing i128(by value) is incompatible to Microsoft x64
1167calling conversion. You might need to tweak WinX86_64ABIInfo::classify()
1168in lib/CodeGen/TargetInfo.cpp.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1169
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1170<!-- ======================== -->
1171<h4 id="target_arch_arm">ARM</h4>
1172<!-- ======================== -->
Daniel Dunbarbcaf7aa2010-09-19 19:26:59 +0000[diff] [blame]1173
1174<p>The support for ARM (specifically ARMv6 and ARMv7) is considered stable on
1175Darwin (iOS): it has been tested to correctly compile many large C, C++,
Bob Wilson4ea8dfa2011-01-10 17:55:14 +0000[diff] [blame]1176Objective-C, and Objective-C++ codebases. Clang only supports a limited number
1177of ARM architectures. It does not yet fully support ARMv5, for example.</p>
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1178
1179<!-- ======================== -->
1180<h4 id="target_arch_other">Other platforms</h4>
1181<!-- ======================== -->
1182clang currently contains some support for PPC and Sparc; however, significant
1183pieces of code generation are still missing, and they haven't undergone
1184significant testing.
1185
Eli Friedman3b658d32009-06-08 05:12:39 +0000[diff] [blame]1186<p>clang contains limited support for the MSP430 embedded processor, but both
1187the clang support and the LLVM backend support are highly experimental.
1188
1189<p>Other platforms are completely unsupported at the moment. Adding the
1190minimal support needed for parsing and semantic analysis on a new platform
1191is quite easy; see lib/Basic/Targets.cpp in the clang source tree. This level
1192of support is also sufficient for conversion to LLVM IR for simple programs.
1193Proper support for conversion to LLVM IR requires adding code to
1194lib/CodeGen/CGCall.cpp at the moment; this is likely to change soon, though.
1195Generating assembly requires a suitable LLVM backend.
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1196
1197<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1198<h3 id="target_os">Operating System Features and Limitations</h3>
1199<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
1200
1201<!-- ======================================= -->
1202<h4 id="target_os_darwin">Darwin (Mac OS/X)</h4>
1203<!-- ======================================= -->
1204
Chris Lattner396663b2012-05-04 21:11:08 +0000[diff] [blame]1205<p>None</p>
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1206
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1207<!-- ======================================= -->
1208<h4 id="target_os_win32">Windows</h4>
1209<!-- ======================================= -->
1210
1211<p>Experimental supports are on Cygming.</p>
1212
Nico Weberd4047b32012-07-11 16:56:28 +0000[diff] [blame]1213<p>See also <a href="#c_ms">Microsoft Extensions</a>.</p>
1214
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1215<h5>Cygwin</h5>
1216
1217<p>Clang works on Cygwin-1.7.</p>
1218
1219<h5>MinGW32</h5>
1220
1221<p>Clang works on some mingw32 distributions.
1222Clang assumes directories as below;</p>
1223
1224<ul>
1225<li><tt>C:/mingw/include</tt></li>
1226<li><tt>C:/mingw/lib</tt></li>
1227<li><tt>C:/mingw/lib/gcc/mingw32/4.[3-5].0/include/c++</tt></li>
1228</ul>
1229
NAKAMURA Takumi0e53df62011-11-17 07:54:13 +0000[diff] [blame]1230<p>On MSYS, a few tests might fail.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1231
1232<h5>MinGW-w64</h5>
1233
Douglas Gregordad879a2011-08-30 00:40:12 +0000[diff] [blame]1234<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]1235
1236<ul>
Douglas Gregordad879a2011-08-30 00:40:12 +0000[diff] [blame]1237<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>
1238<li><tt>some_directory/bin/gcc.exe</tt></li>
1239<li><tt>some_directory/bin/clang.exe</tt></li>
1240<li><tt>some_directory/bin/clang++.exe</tt></li>
1241<li><tt>some_directory/bin/../include/c++/GCC_version</tt></li>
1242<li><tt>some_directory/bin/../include/c++/GCC_version/x86_64-w64-mingw32</tt></li>
1243<li><tt>some_directory/bin/../include/c++/GCC_version/i686-w64-mingw32</tt></li>
1244<li><tt>some_directory/bin/../include/c++/GCC_version/backward</tt></li>
1245<li><tt>some_directory/bin/../x86_64-w64-mingw32/include</tt></li>
1246<li><tt>some_directory/bin/../i686-w64-mingw32/include</tt></li>
1247<li><tt>some_directory/bin/../include</tt></li>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1248</ul>
1249
David Blaikiea9639622012-04-19 17:21:46 +0000[diff] [blame]1250<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]1251
1252<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>
1253
1254<p><a href="http://llvm.org/bugs/show_bug.cgi?id=9072">Some tests might fail</a>
1255on x86_64-w64-mingw32.</p>
NAKAMURA Takumia75fdb22011-04-04 15:02:41 +0000[diff] [blame]1256
Chris Lattnercf17d9d2009-04-20 04:23:09 +0000[diff] [blame]1257</div>
1258</body>
1259</html>