Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 1 | <html> |
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| 3 | <title>Clang Compiler User's Manual</title> |
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| 14 | <!--#include virtual="../menu.html.incl"--> |
| 15 | |
| 16 | <div id="content"> |
| 17 | |
| 18 | <h1>Clang Compiler User's Manual</h1> |
| 19 | |
| 20 | <ul> |
| 21 | <li><a href="#intro">Introduction</a> |
| 22 | <ul> |
| 23 | <li><a href="#terminology">Terminology</a></li> |
| 24 | <li><a href="#basicusage">Basic Usage</a></li> |
| 25 | </ul> |
| 26 | </li> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 27 | <li><a href="#commandline">Command Line Options</a> |
| 28 | <ul> |
| 29 | <li><a href="#cl_diagnostics">Options to Control Error and Warning |
| 30 | Messages</a></li> |
| 31 | </ul> |
| 32 | </li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 33 | <li><a href="#general_features">Language and Target-Independent Features</a> |
| 34 | <ul> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 35 | <li><a href="#diagnostics">Controlling Errors and Warnings</a> |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 36 | <ul> |
| 37 | <li><a href="#diagnostics_display">Controlling How Clang Displays Diagnostics</a></li> |
| 38 | <li><a href="#diagnostics_mappings">Diagnostic Mappings</a></li> |
Chris Lattner | 67db8cd | 2010-05-30 23:42:51 +0000 | [diff] [blame] | 39 | <li><a href="#diagnostics_categories">Diagnostic Categories</a></li> |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 40 | <li><a href="#diagnostics_commandline">Controlling Diagnostics via Command Line Flags</a></li> |
| 41 | <li><a href="#diagnostics_pragmas">Controlling Diagnostics via Pragmas</a></li> |
Ted Kremenek | f391fa7 | 2011-08-18 01:17:05 +0000 | [diff] [blame] | 42 | <li><a href="#diagnostics_enable_everything">Enabling All Warnings</a></li> |
Ted Kremenek | 2fb11eb | 2010-08-24 18:12:35 +0000 | [diff] [blame] | 43 | <li><a href="#analyzer_diagnositics">Controlling Static Analyzer Diagnostics</a></li> |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 44 | </ul> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 45 | </li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 46 | <li><a href="#precompiledheaders">Precompiled Headers</a></li> |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 47 | <li><a href="#codegen">Controlling Code Generation</a></li> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 48 | </ul> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 49 | </li> |
| 50 | <li><a href="#c">C Language Features</a> |
| 51 | <ul> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 52 | <li><a href="#c_ext">Extensions supported by clang</a></li> |
| 53 | <li><a href="#c_modes">Differences between various standard modes</a></li> |
| 54 | <li><a href="#c_unimpl_gcc">GCC extensions not implemented yet</a></li> |
| 55 | <li><a href="#c_unsupp_gcc">Intentionally unsupported GCC extensions</a></li> |
| 56 | <li><a href="#c_ms">Microsoft extensions</a></li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 57 | </ul> |
| 58 | </li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 59 | <li><a href="#target_features">Target-Specific Features and Limitations</a> |
| 60 | <ul> |
| 61 | <li><a href="#target_arch">CPU Architectures Features and Limitations</a> |
| 62 | <ul> |
| 63 | <li><a href="#target_arch_x86">X86</a></li> |
Eli Friedman | 3b658d3 | 2009-06-08 05:12:39 +0000 | [diff] [blame] | 64 | <li><a href="#target_arch_arm">ARM</a></li> |
| 65 | <li><a href="#target_arch_other">Other platforms</a></li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 66 | </ul> |
| 67 | </li> |
| 68 | <li><a href="#target_os">Operating System Features and Limitations</a> |
| 69 | <ul> |
| 70 | <li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li> |
| 71 | <li>Linux, etc.</li> |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 72 | <li><a href="#target_os_win32">Windows</a></li> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 73 | </ul> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 74 | </li> |
| 75 | </ul> |
| 76 | </li> |
| 77 | </ul> |
| 78 | |
| 79 | |
| 80 | <!-- ======================================================================= --> |
| 81 | <h2 id="intro">Introduction</h2> |
| 82 | <!-- ======================================================================= --> |
| 83 | |
| 84 | <p>The Clang Compiler is an open-source compiler for the C family of programming |
| 85 | languages, aiming to be the best in class implementation of these languages. |
| 86 | Clang builds on the LLVM optimizer and code generator, allowing it to provide |
| 87 | high-quality optimization and code generation support for many targets. For |
| 88 | more general information, please see the <a href="http://clang.llvm.org">Clang |
| 89 | Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p> |
| 90 | |
| 91 | <p>This document describes important notes about using Clang as a compiler for |
| 92 | an end-user, documenting the supported features, command line options, etc. If |
| 93 | you are interested in using Clang to build a tool that processes code, please |
| 94 | see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are |
| 95 | interested in the <a href="http://clang.llvm.org/StaticAnalysis.html">Clang |
| 96 | Static Analyzer</a>, please see its web page.</p> |
| 97 | |
| 98 | <p>Clang is designed to support the C family of programming languages, which |
| 99 | includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a |
| 100 | href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many |
| 101 | dialects of those. For language-specific information, please see the |
| 102 | corresponding language specific section:</p> |
| 103 | |
| 104 | <ul> |
| 105 | <li><a href="#c">C Language</a>: K&R C, ANSI C89, ISO C90, ISO C94 |
| 106 | (C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li> |
| 107 | <li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus |
| 108 | variants depending on base language.</li> |
| 109 | <li><a href="#cxx">C++ Language Features</a></li> |
| 110 | <li><a href="#objcxx">Objective C++ Language</a></li> |
| 111 | </ul> |
| 112 | |
| 113 | <p>In addition to these base languages and their dialects, Clang supports a |
| 114 | broad variety of language extensions, which are documented in the corresponding |
| 115 | language section. These extensions are provided to be compatible with the GCC, |
| 116 | Microsoft, and other popular compilers as well as to improve functionality |
| 117 | through Clang-specific features. The Clang driver and language features are |
| 118 | intentionally designed to be as compatible with the GNU GCC compiler as |
| 119 | reasonably possible, easing migration from GCC to Clang. In most cases, code |
| 120 | "just works".</p> |
| 121 | |
| 122 | <p>In addition to language specific features, Clang has a variety of features |
| 123 | that depend on what CPU architecture or operating system is being compiled for. |
Douglas Gregor | cd5a505 | 2009-11-09 15:15:41 +0000 | [diff] [blame] | 124 | Please see the <a href="#target_features">Target-Specific Features and |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 125 | Limitations</a> section for more details.</p> |
| 126 | |
| 127 | <p>The rest of the introduction introduces some basic <a |
| 128 | href="#terminology">compiler terminology</a> that is used throughout this manual |
| 129 | and contains a basic <a href="#basicusage">introduction to using Clang</a> |
| 130 | as a command line compiler.</p> |
| 131 | |
| 132 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 133 | <h3 id="terminology">Terminology</h3> |
| 134 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 135 | |
| 136 | <p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic, |
| 137 | optimizer</p> |
| 138 | |
| 139 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 140 | <h3 id="basicusage">Basic Usage</h3> |
| 141 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 142 | |
| 143 | <p>Intro to how to use a C compiler for newbies.</p> |
| 144 | <p> |
| 145 | compile + link |
| 146 | |
| 147 | compile then link |
| 148 | |
| 149 | debug info |
| 150 | |
| 151 | enabling optimizations |
| 152 | |
| 153 | picking a language to use, defaults to C99 by default. Autosenses based on |
| 154 | extension. |
| 155 | |
| 156 | using a makefile |
| 157 | </p> |
| 158 | |
| 159 | |
| 160 | <!-- ======================================================================= --> |
| 161 | <h2 id="commandline">Command Line Options</h2> |
| 162 | <!-- ======================================================================= --> |
| 163 | |
| 164 | <p> |
| 165 | This section is generally an index into other sections. It does not go into |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 166 | depth on the ones that are covered by other sections. However, the first part |
| 167 | introduces the language selection and other high level options like -c, -g, etc. |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 168 | </p> |
| 169 | |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 170 | |
| 171 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 172 | <h3 id="cl_diagnostics">Options to Control Error and Warning Messages</h3> |
| 173 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 174 | |
| 175 | <p><b>-Werror</b>: Turn warnings into errors.</p> |
| 176 | <p><b>-Werror=foo</b>: Turn warning "foo" into an error.</p> |
| 177 | <p><b>-Wno-error=foo</b>: Turn warning "foo" into an warning even if -Werror is |
| 178 | specified.</p> |
| 179 | <p><b>-Wfoo</b>: Enable warning foo</p> |
| 180 | <p><b>-Wno-foo</b>: Disable warning foo</p> |
| 181 | <p><b>-w</b>: Disable all warnings.</p> |
| 182 | <p><b>-pedantic</b>: Warn on language extensions.</p> |
| 183 | <p><b>-pedantic-errors</b>: Error on language extensions.</p> |
| 184 | <p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p> |
| 185 | |
Chris Lattner | 0f0c963 | 2010-04-07 20:49:23 +0000 | [diff] [blame] | 186 | <p><b>-ferror-limit=123</b>: Stop emitting diagnostics after 123 errors have |
| 187 | been produced. The default is 20, and the error limit can be disabled with |
| 188 | -ferror-limit=0.</p> |
| 189 | |
Douglas Gregor | 575cf37 | 2010-04-20 07:18:24 +0000 | [diff] [blame] | 190 | <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> |
| 191 | |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 192 | <!-- ================================================= --> |
| 193 | <h4 id="cl_diag_formatting">Formatting of Diagnostics</h4> |
| 194 | <!-- ================================================= --> |
| 195 | |
| 196 | <p>Clang aims to produce beautiful diagnostics by default, particularly for new |
| 197 | users that first come to Clang. However, different people have different |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 198 | preferences, and sometimes Clang is driven by another program that wants to |
| 199 | parse simple and consistent output, not a person. For these cases, Clang |
| 200 | provides a wide range of options to control the exact output format of the |
| 201 | diagnostics that it generates.</p> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 202 | |
| 203 | <dl> |
| 204 | |
| 205 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 206 | <dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in |
| 207 | diagnostic.</dt> |
| 208 | <dd>This option, which defaults to on, controls whether or not Clang prints the |
| 209 | column number of a diagnostic. For example, when this is enabled, Clang will |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 210 | print something like: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 211 | |
| 212 | <pre> |
| 213 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 214 | #endif bad |
| 215 | ^ |
| 216 | // |
| 217 | </pre> |
| 218 | |
| 219 | <p>When this is disabled, Clang will print "test.c:28: warning..." with no |
| 220 | column number.</p> |
| 221 | </dd> |
| 222 | |
| 223 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 224 | <dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print |
| 225 | source file/line/column information in diagnostic.</dt> |
| 226 | <dd>This option, which defaults to on, controls whether or not Clang prints the |
| 227 | filename, line number and column number of a diagnostic. For example, |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 228 | when this is enabled, Clang will print something like: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 229 | |
| 230 | <pre> |
| 231 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 232 | #endif bad |
| 233 | ^ |
| 234 | // |
| 235 | </pre> |
| 236 | |
| 237 | <p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p> |
| 238 | </dd> |
| 239 | |
| 240 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 241 | <dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source |
| 242 | line and ranges from source code in diagnostic.</dt> |
| 243 | <dd>This option, which defaults to on, controls whether or not Clang prints the |
| 244 | source line, source ranges, and caret when emitting a diagnostic. For example, |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 245 | when this is enabled, Clang will print something like: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 246 | |
| 247 | <pre> |
| 248 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 249 | #endif bad |
| 250 | ^ |
| 251 | // |
| 252 | </pre> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 253 | </dd> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 254 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
Douglas Gregor | e8d44dd | 2010-07-09 16:31:58 +0000 | [diff] [blame] | 255 | <dt id="opt_fcolor_diagnostics"><b>-f[no-]color-diagnostics</b>: </dt> |
| 256 | <dd>This option, which defaults to on when a color-capable terminal is |
| 257 | detected, controls whether or not Clang prints diagnostics in color. |
| 258 | When this option is enabled, Clang will use colors to highlight |
| 259 | specific parts of the diagnostic, e.g., |
Chris Lattner | 4e1c53d | 2011-01-24 03:47:34 +0000 | [diff] [blame] | 260 | <pre> |
| 261 | <b><font color="black">test.c:28:8: <font color="magenta">warning</font>: extra tokens at end of #endif directive [-Wextra-tokens]</font></b> |
| 262 | #endif bad |
| 263 | <font color="green">^</font> |
| 264 | <font color="green">//</font> |
Douglas Gregor | e8d44dd | 2010-07-09 16:31:58 +0000 | [diff] [blame] | 265 | </pre> |
Chris Lattner | 4e1c53d | 2011-01-24 03:47:34 +0000 | [diff] [blame] | 266 | |
| 267 | <p>When this is disabled, Clang will just print:</p> |
| 268 | |
| 269 | <pre> |
| 270 | test.c:2:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 271 | #endif bad |
| 272 | ^ |
| 273 | // |
| 274 | </pre> |
| 275 | </dd> |
Douglas Gregor | e8d44dd | 2010-07-09 16:31:58 +0000 | [diff] [blame] | 276 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
Douglas Gregor | c9471b0 | 2011-05-21 17:07:29 +0000 | [diff] [blame] | 277 | <dt id="opt_fdiagnostics-format"><b>-fdiagnostics-format=clang/msvc/vi</b>: |
| 278 | Changes diagnostic output format to better match IDEs and command line tools.</dt> |
| 279 | <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: |
| 280 | |
| 281 | <dl> |
| 282 | <dt><b>clang</b> (default)</dt> |
| 283 | <dd> |
| 284 | <pre>t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre> |
| 285 | </dd> |
| 286 | |
| 287 | <dt><b>msvc</b></dt> |
| 288 | <dd> |
| 289 | <pre>t.c(3,11) : warning: conversion specifies type 'char *' but the argument has type 'int'</pre> |
| 290 | </dd> |
| 291 | |
| 292 | <dt><b>vi</b></dt> |
| 293 | <dd> |
| 294 | <pre>t.c +3:11: warning: conversion specifies type 'char *' but the argument has type 'int'</pre> |
| 295 | </dd> |
| 296 | </dl> |
| 297 | </dd> |
| 298 | |
| 299 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
Argyrios Kyrtzidis | 477aab6 | 2011-05-25 05:05:01 +0000 | [diff] [blame] | 300 | <dt id="opt_fdiagnostics-show-name"><b>-f[no-]diagnostics-show-name</b>: |
| 301 | Enable the display of the diagnostic name.</dt> |
| 302 | <dd>This option, which defaults to off, controls whether or not |
| 303 | Clang prints the associated name.</dd> |
| 304 | <br> |
| 305 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 306 | <dt id="opt_fdiagnostics-show-option"><b>-f[no-]diagnostics-show-option</b>: |
| 307 | Enable <tt>[-Woption]</tt> information in diagnostic line.</dt> |
| 308 | <dd>This option, which defaults to on, |
| 309 | controls whether or not Clang prints the associated <A |
| 310 | href="#cl_diag_warning_groups">warning group</a> option name when outputting |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 311 | a warning diagnostic. For example, in this output: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 312 | |
| 313 | <pre> |
| 314 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 315 | #endif bad |
| 316 | ^ |
| 317 | // |
| 318 | </pre> |
| 319 | |
| 320 | <p>Passing <b>-fno-diagnostics-show-option</b> will prevent Clang from printing |
| 321 | the [<a href="#opt_Wextra-tokens">-Wextra-tokens</a>] information in the |
| 322 | diagnostic. This information tells you the flag needed to enable or disable the |
| 323 | diagnostic, either from the command line or through <a |
| 324 | href="#pragma_GCC_diagnostic">#pragma GCC diagnostic</a>.</dd> |
| 325 | |
Chris Lattner | 28a43a4 | 2010-05-05 01:35:28 +0000 | [diff] [blame] | 326 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 327 | <dt id="opt_fdiagnostics-show-category"><b>-fdiagnostics-show-category=none/id/name</b>: |
| 328 | Enable printing category information in diagnostic line.</dt> |
| 329 | <dd>This option, which defaults to "none", |
| 330 | controls whether or not Clang prints the category associated with a diagnostic |
| 331 | when emitting it. Each diagnostic may or many not have an associated category, |
| 332 | if it has one, it is listed in the diagnostic categorization field of the |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 333 | diagnostic line (in the []'s). |
Chris Lattner | 28a43a4 | 2010-05-05 01:35:28 +0000 | [diff] [blame] | 334 | |
| 335 | <p>For example, a format string warning will produce these three renditions |
| 336 | based on the setting of this option:</p> |
| 337 | |
| 338 | <pre> |
| 339 | t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat] |
| 340 | t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,1</b>] |
| 341 | t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat<b>,Format String</b>] |
| 342 | </pre> |
| 343 | |
| 344 | <p>This category can be used by clients that want to group diagnostics by |
| 345 | category, so it should be a high level category. We want dozens of these, not |
| 346 | hundreds or thousands of them.</p> |
| 347 | </dd> |
| 348 | |
| 349 | |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 350 | |
| 351 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 352 | <dt id="opt_fdiagnostics-fixit-info"><b>-f[no-]diagnostics-fixit-info</b>: |
| 353 | Enable "FixIt" information in the diagnostics output.</dt> |
| 354 | <dd>This option, which defaults to on, controls whether or not Clang prints the |
| 355 | information on how to fix a specific diagnostic underneath it when it knows. |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 356 | For example, in this output: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 357 | |
| 358 | <pre> |
| 359 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 360 | #endif bad |
| 361 | ^ |
| 362 | // |
| 363 | </pre> |
| 364 | |
| 365 | <p>Passing <b>-fno-diagnostics-fixit-info</b> will prevent Clang from printing |
| 366 | the "//" line at the end of the message. This information is useful for users |
| 367 | who may not understand what is wrong, but can be confusing for machine |
| 368 | parsing.</p> |
| 369 | </dd> |
| 370 | |
| 371 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
Chris Lattner | 2a9cc23 | 2009-04-21 05:35:32 +0000 | [diff] [blame] | 372 | <dt id="opt_fdiagnostics-print-source-range-info"> |
| 373 | <b>-f[no-]diagnostics-print-source-range-info</b>: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 374 | Print machine parsable information about source ranges.</dt> |
| 375 | <dd>This option, which defaults to off, controls whether or not Clang prints |
| 376 | information about source ranges in a machine parsable format after the |
| 377 | file/line/column number information. The information is a simple sequence of |
| 378 | brace enclosed ranges, where each range lists the start and end line/column |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 379 | locations. For example, in this output: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 380 | |
| 381 | <pre> |
| 382 | exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float') |
| 383 | P = (P-42) + Gamma*4; |
| 384 | ~~~~~~ ^ ~~~~~~~ |
| 385 | </pre> |
| 386 | |
Chris Lattner | 2a9cc23 | 2009-04-21 05:35:32 +0000 | [diff] [blame] | 387 | <p>The {}'s are generated by -fdiagnostics-print-source-range-info.</p> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 388 | </dd> |
| 389 | |
Douglas Gregor | 4786c15 | 2010-08-19 20:24:43 +0000 | [diff] [blame] | 390 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 391 | <dt id="opt_fdiagnostics-parseable-fixits"> |
| 392 | <b>-fdiagnostics-parseable-fixits</b>: |
| 393 | Print Fix-Its in a machine parseable form.</dt> |
| 394 | <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> |
| 395 | |
| 396 | <pre> |
Douglas Gregor | bf5e09d | 2010-08-20 03:17:33 +0000 | [diff] [blame] | 397 | fix-it:"t.cpp":{7:25-7:29}:"Gamma" |
Douglas Gregor | 4786c15 | 2010-08-19 20:24:43 +0000 | [diff] [blame] | 398 | </pre> |
| 399 | |
NAKAMURA Takumi | 4462636 | 2011-04-05 00:57:02 +0000 | [diff] [blame] | 400 | <p>The range printed is a half-open range, so in this example the characters at |
| 401 | column 25 up to but not including column 29 on line 7 in t.cpp should be |
| 402 | replaced with the string "Gamma". Either the range or the replacement |
| 403 | string may be empty (representing strict insertions and strict erasures, |
| 404 | respectively). Both the file name and the insertion string escape backslash (as |
| 405 | "\\"), tabs (as "\t"), newlines (as "\n"), double |
| 406 | quotes(as "\"") and non-printable characters (as octal |
| 407 | "\xxx").</p> |
Douglas Gregor | 4786c15 | 2010-08-19 20:24:43 +0000 | [diff] [blame] | 408 | </dd> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 409 | |
| 410 | </dl> |
| 411 | |
| 412 | |
| 413 | |
| 414 | |
| 415 | <!-- ===================================================== --> |
| 416 | <h4 id="cl_diag_warning_groups">Individual Warning Groups</h4> |
| 417 | <!-- ===================================================== --> |
| 418 | |
| 419 | <p>TODO: Generate this from tblgen. Define one anchor per warning group.</p> |
| 420 | |
| 421 | |
| 422 | <dl> |
| 423 | |
| 424 | |
| 425 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 426 | <dt id="opt_Wextra-tokens"><b>-Wextra-tokens</b>: Warn about excess tokens at |
| 427 | the end of a preprocessor directive.</dt> |
| 428 | <dd>This option, which defaults to on, enables warnings about extra tokens at |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 429 | the end of preprocessor directives. For example: |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 430 | |
| 431 | <pre> |
| 432 | test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens] |
| 433 | #endif bad |
| 434 | ^ |
| 435 | </pre> |
| 436 | |
| 437 | <p>These extra tokens are not strictly conforming, and are usually best handled |
| 438 | by commenting them out.</p> |
| 439 | |
| 440 | <p>This option is also enabled by <a href="">-Wfoo</a>, <a href="">-Wbar</a>, |
| 441 | and <a href="">-Wbaz</a>.</p> |
| 442 | </dd> |
| 443 | |
Jeffrey Yasskin | 21d07e4 | 2010-06-05 01:39:57 +0000 | [diff] [blame] | 444 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 445 | <dt id="opt_Wambiguous-member-template"><b>-Wambiguous-member-template</b>: |
| 446 | Warn about unqualified uses of a member template whose name resolves |
| 447 | to another template at the location of the use.</dt> |
| 448 | <dd>This option, which defaults to on, enables a warning in the |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 449 | following code: |
Jeffrey Yasskin | 21d07e4 | 2010-06-05 01:39:57 +0000 | [diff] [blame] | 450 | |
| 451 | <pre> |
| 452 | template<typename T> struct set{}; |
| 453 | template<typename T> struct trait { typedef const T& type; }; |
| 454 | struct Value { |
| 455 | template<typename T> void set(typename trait<T>::type value) {} |
| 456 | }; |
| 457 | void foo() { |
| 458 | Value v; |
| 459 | v.set<double>(3.2); |
| 460 | } |
| 461 | </pre> |
| 462 | |
| 463 | <p>C++ [basic.lookup.classref] requires this to be an error, but, |
| 464 | because it's hard to work around, Clang downgrades it to a warning as |
| 465 | an extension.</p> |
| 466 | </dd> |
| 467 | |
Jeffrey Yasskin | 57d12fd | 2010-06-07 15:58:05 +0000 | [diff] [blame] | 468 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
| 469 | <dt id="opt_Wbind-to-temporary-copy"><b>-Wbind-to-temporary-copy</b>: Warn about |
| 470 | an unusable copy constructor when binding a reference to a temporary.</dt> |
| 471 | <dd>This option, which defaults to on, enables warnings about binding a |
| 472 | reference to a temporary when the temporary doesn't have a usable copy |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 473 | constructor. For example: |
Jeffrey Yasskin | 57d12fd | 2010-06-07 15:58:05 +0000 | [diff] [blame] | 474 | |
| 475 | <pre> |
| 476 | struct NonCopyable { |
| 477 | NonCopyable(); |
| 478 | private: |
| 479 | NonCopyable(const NonCopyable&); |
| 480 | }; |
| 481 | void foo(const NonCopyable&); |
| 482 | void bar() { |
| 483 | foo(NonCopyable()); // Disallowed in C++98; allowed in C++0x. |
| 484 | } |
| 485 | </pre> |
| 486 | <pre> |
| 487 | struct NonCopyable2 { |
| 488 | NonCopyable2(); |
| 489 | NonCopyable2(NonCopyable2&); |
| 490 | }; |
| 491 | void foo(const NonCopyable2&); |
| 492 | void bar() { |
| 493 | foo(NonCopyable2()); // Disallowed in C++98; allowed in C++0x. |
| 494 | } |
| 495 | </pre> |
| 496 | |
| 497 | <p>Note that if <tt>NonCopyable2::NonCopyable2()</tt> has a default |
| 498 | argument whose instantiation produces a compile error, that error will |
| 499 | still be a hard error in C++98 mode even if this warning is turned |
| 500 | off.</p> |
| 501 | |
| 502 | </dd> |
| 503 | |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 504 | </dl> |
| 505 | |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 506 | <!-- ======================================================================= --> |
| 507 | <h2 id="general_features">Language and Target-Independent Features</h2> |
| 508 | <!-- ======================================================================= --> |
| 509 | |
| 510 | |
| 511 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 512 | <h3 id="diagnostics">Controlling Errors and Warnings</h3> |
| 513 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 514 | |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 515 | <p>Clang provides a number of ways to control which code constructs cause it to |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 516 | emit errors and warning messages, and how they are displayed to the console.</p> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 517 | |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 518 | <h4 id="diagnostics_display">Controlling How Clang Displays Diagnostics</h4> |
Chris Lattner | 65a795b | 2009-04-20 06:00:23 +0000 | [diff] [blame] | 519 | |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 520 | <p>When Clang emits a diagnostic, it includes rich information in the output, |
| 521 | and gives you fine-grain control over which information is printed. Clang has |
| 522 | the ability to print this information, and these are the options that control |
| 523 | it:</p> |
| 524 | |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 525 | <ol> |
| 526 | <li>A file/line/column indicator that shows exactly where the diagnostic occurs |
| 527 | in your code [<a href="#opt_fshow-column">-fshow-column</a>, <a |
| 528 | href="#opt_fshow-source-location">-fshow-source-location</a>].</li> |
| 529 | <li>A categorization of the diagnostic as a note, warning, error, or fatal |
| 530 | error.</li> |
| 531 | <li>A text string that describes what the problem is.</li> |
Argyrios Kyrtzidis | 477aab6 | 2011-05-25 05:05:01 +0000 | [diff] [blame] | 532 | <li>An option that indicates whether to print the diagnostic name [<a |
| 533 | href="#opt_fdiagnostics-show-name">-fdiagnostics-show-name</a>].</li> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 534 | <li>An option that indicates how to control the diagnostic (for diagnostics that |
| 535 | support it) [<a |
| 536 | href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li> |
Chris Lattner | 3f14538 | 2010-05-24 21:35:18 +0000 | [diff] [blame] | 537 | <li>A <a href="#diagnostics_categories">high-level category</a> for the |
| 538 | diagnostic for clients that want to group diagnostics by class (for |
| 539 | diagnostics that support it) [<a |
Chris Lattner | 28a43a4 | 2010-05-05 01:35:28 +0000 | [diff] [blame] | 540 | href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a>].</li> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 541 | <li>The line of source code that the issue occurs on, along with a caret and |
| 542 | ranges that indicate the important locations [<a |
| 543 | href="opt_fcaret-diagnostics">-fcaret-diagnostics</a>].</li> |
| 544 | <li>"FixIt" information, which is a concise explanation of how to fix the |
| 545 | problem (when Clang is certain it knows) [<a |
| 546 | href="opt_fdiagnostics-fixit-info">-fdiagnostics-fixit-info</a>].</li> |
| 547 | <li>A machine-parsable representation of the ranges involved (off by |
| 548 | default) [<a |
Chris Lattner | 2a9cc23 | 2009-04-21 05:35:32 +0000 | [diff] [blame] | 549 | href="opt_fdiagnostics-print-source-range-info">-fdiagnostics-print-source-range-info</a>].</li> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 550 | </ol> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 551 | |
| 552 | <p>For more information please see <a href="#cl_diag_formatting">Formatting of |
| 553 | Diagnostics</a>.</p> |
| 554 | |
Chris Lattner | 3f14538 | 2010-05-24 21:35:18 +0000 | [diff] [blame] | 555 | |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 556 | <h4 id="diagnostics_mappings">Diagnostic Mappings</h4> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 557 | |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 558 | <p>All diagnostics are mapped into one of these 5 classes:</p> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 559 | |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 560 | <ul> |
| 561 | <li>Ignored</li> |
| 562 | <li>Note</li> |
| 563 | <li>Warning</li> |
| 564 | <li>Error</li> |
| 565 | <li>Fatal</li> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 566 | </ul> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 567 | |
Chris Lattner | 3f14538 | 2010-05-24 21:35:18 +0000 | [diff] [blame] | 568 | <h4 id="diagnostics_categories">Diagnostic Categories</h4> |
| 569 | |
| 570 | <p>Though not shown by default, diagnostics may each be associated with a |
| 571 | high-level category. This category is intended to make it possible to triage |
| 572 | builds that produce a large number of errors or warnings in a grouped way. |
| 573 | </p> |
| 574 | |
| 575 | <p>Categories are not shown by default, but they can be turned on with the |
| 576 | <a href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a> option. |
| 577 | When set to "<tt>name</tt>", the category is printed textually in the diagnostic |
| 578 | output. When it is set to "<tt>id</tt>", a category number is printed. The |
| 579 | mapping of category names to category id's can be obtained by running '<tt>clang |
| 580 | --print-diagnostic-categories</tt>'. |
| 581 | </p> |
| 582 | |
| 583 | <h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line |
| 584 | Flags</h4> |
Chris Lattner | 8217f4e | 2009-04-20 06:26:18 +0000 | [diff] [blame] | 585 | |
| 586 | <p>-W flags, -pedantic, etc</p> |
| 587 | |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 588 | <h4 id="diagnostics_pragmas">Controlling Diagnostics via Pragmas</h4> |
| 589 | |
| 590 | <p>Clang can also control what diagnostics are enabled through the use of |
| 591 | pragmas in the source code. This is useful for turning off specific warnings |
| 592 | in a section of source code. Clang supports GCC's pragma for compatibility |
| 593 | with existing source code, as well as several extensions. </p> |
| 594 | |
| 595 | <p>The pragma may control any warning that can be used from the command line. |
| 596 | Warnings may be set to ignored, warning, error, or fatal. The following |
| 597 | example code will tell Clang or GCC to ignore the -Wall warnings:</p> |
| 598 | |
| 599 | <pre> |
| 600 | #pragma GCC diagnostic ignored "-Wall" |
| 601 | </pre> |
| 602 | |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 603 | <p>In addition to all of the functionality provided by GCC's pragma, Clang |
Chris Lattner | 3401cf8 | 2009-07-12 21:22:10 +0000 | [diff] [blame] | 604 | also allows you to push and pop the current warning state. This is particularly |
| 605 | useful when writing a header file that will be compiled by other people, because |
| 606 | you don't know what warning flags they build with.</p> |
| 607 | |
| 608 | <p>In the below example |
| 609 | -Wmultichar is ignored for only a single line of code, after which the |
| 610 | diagnostics return to whatever state had previously existed.</p> |
| 611 | |
| 612 | <pre> |
| 613 | #pragma clang diagnostic push |
| 614 | #pragma clang diagnostic ignored "-Wmultichar" |
| 615 | |
| 616 | char b = 'df'; // no warning. |
| 617 | |
| 618 | #pragma clang diagnostic pop |
| 619 | </pre> |
| 620 | |
| 621 | <p>The push and pop pragmas will save and restore the full diagnostic state of |
| 622 | the compiler, regardless of how it was set. That means that it is possible to |
| 623 | use push and pop around GCC compatible diagnostics and Clang will push and pop |
| 624 | them appropriately, while GCC will ignore the pushes and pops as unknown |
| 625 | pragmas. It should be noted that while Clang supports the GCC pragma, Clang and |
| 626 | GCC do not support the exact same set of warnings, so even when using GCC |
| 627 | compatible #pragmas there is no guarantee that they will have identical behaviour |
| 628 | on both compilers. </p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 629 | |
Ted Kremenek | f391fa7 | 2011-08-18 01:17:05 +0000 | [diff] [blame] | 630 | <h4 id="diagnostics_enable_everything">Enabling All Warnings</h4> |
| 631 | |
| 632 | <p>In addition to the traditional <tt>-W</tt> flags, one can enable <b>all</b> |
| 633 | warnings by passing <tt>-Weverything</tt>. |
| 634 | This works as expected with <tt>-Werror</tt>, |
| 635 | and also includes the warnings from <tt>-pedantic</tt>.</p> |
| 636 | |
| 637 | <p>Note that when combined with <tt>-w</tt> (which disables all warnings), that |
| 638 | flag wins.</p> |
| 639 | |
Ted Kremenek | 2fb11eb | 2010-08-24 18:12:35 +0000 | [diff] [blame] | 640 | <h4 id="analyzer_diagnositics">Controlling Static Analyzer Diagnostics</h4> |
| 641 | |
| 642 | <p>While not strictly part of the compiler, the diagnostics from Clang's <a |
| 643 | href="http://clang-analyzer.llvm.org">static analyzer</a> can also be influenced |
| 644 | by the user via changes to the source code. This can be done in two ways: |
| 645 | |
| 646 | <ul> |
| 647 | |
| 648 | <li id="analyzer_annotations"><b>Annotations</b>: The static analyzer recognizes various GCC-style |
| 649 | attributes (e.g., <tt>__attribute__((nonnull)))</tt>) that can either suppress |
| 650 | static analyzer warnings or teach the analyzer about code invariants which |
| 651 | enable it to find more bugs. While many of these attributes are standard GCC |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 652 | attributes, additional ones have been added to Clang to specifically support the |
Ted Kremenek | 2fb11eb | 2010-08-24 18:12:35 +0000 | [diff] [blame] | 653 | static analyzer. Detailed information on these annotations can be found in the |
| 654 | <a href="http://clang-analyzer.llvm.org/annotations.html">analyzer's |
| 655 | documentation</a>.</li> |
| 656 | |
| 657 | <li><b><tt>__clang_analyzer__</tt></b>: When the static analyzer is using Clang |
| 658 | to parse source files, it implicitly defines the preprocessor macro |
| 659 | <tt>__clang_analyzer__</tt>. While discouraged, code can use this macro to |
| 660 | selectively exclude code the analyzer examines. Here is an example: |
| 661 | |
| 662 | <pre> |
| 663 | #ifndef __clang_analyzer__ |
| 664 | // Code not to be analyzed |
| 665 | #endif |
| 666 | </pre> |
| 667 | |
| 668 | In general, this usage is discouraged. Instead, we prefer that users file bugs |
| 669 | against the analyzer when it flags false positives. There is also active |
| 670 | discussion of allowing users in the future to selectively silence specific |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 671 | analyzer warnings (some of which can already be done using <a |
Ted Kremenek | 2fb11eb | 2010-08-24 18:12:35 +0000 | [diff] [blame] | 672 | href="analyzer_annotations">annotations</a>).</li> |
| 673 | |
| 674 | </ul> |
| 675 | |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 676 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 677 | <h3 id="precompiledheaders">Precompiled Headers</h3> |
| 678 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 679 | |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 680 | <p><a href="http://en.wikipedia.org/wiki/Precompiled_header">Precompiled |
| 681 | headers</a> are a general approach employed by many compilers to reduce |
| 682 | compilation time. The underlying motivation of the approach is that it is |
| 683 | common for the same (and often large) header files to be included by |
| 684 | multiple source files. Consequently, compile times can often be greatly improved |
| 685 | by caching some of the (redundant) work done by a compiler to process headers. |
| 686 | Precompiled header files, which represent one of many ways to implement |
| 687 | this optimization, are literally files that represent an on-disk cache that |
| 688 | contains the vital information necessary to reduce some of the work |
| 689 | needed to process a corresponding header file. While details of precompiled |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 690 | headers vary between compilers, precompiled headers have been shown to be |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 691 | highly effective at speeding up program compilation on systems with very large |
| 692 | system headers (e.g., Mac OS/X).</p> |
| 693 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 694 | <h4>Generating a PCH File</h4> |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 695 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 696 | <p>To generate a PCH file using Clang, one invokes Clang with |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 697 | the <b><tt>-x <i><language></i>-header</tt></b> option. This mirrors the |
| 698 | interface in GCC for generating PCH files:</p> |
| 699 | |
| 700 | <pre> |
| 701 | $ gcc -x c-header test.h -o test.h.gch |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 702 | $ clang -x c-header test.h -o test.h.pch |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 703 | </pre> |
| 704 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 705 | <h4>Using a PCH File</h4> |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 706 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 707 | <p>A PCH file can then be used as a prefix header when a |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 708 | <b><tt>-include</tt></b> option is passed to <tt>clang</tt>:</p> |
| 709 | |
| 710 | <pre> |
| 711 | $ clang -include test.h test.c -o test |
| 712 | </pre> |
| 713 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 714 | <p>The <tt>clang</tt> driver will first check if a PCH file for <tt>test.h</tt> |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 715 | is available; if so, the contents of <tt>test.h</tt> (and the files it includes) |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 716 | will be processed from the PCH file. Otherwise, Clang falls back to |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 717 | directly processing the content of <tt>test.h</tt>. This mirrors the behavior of |
| 718 | GCC.</p> |
| 719 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 720 | <p><b>NOTE:</b> Clang does <em>not</em> automatically use PCH files |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 721 | for headers that are directly included within a source file. For example:</p> |
| 722 | |
| 723 | <pre> |
Chris Lattner | e42ec54 | 2009-06-13 20:35:58 +0000 | [diff] [blame] | 724 | $ clang -x c-header test.h -o test.h.pch |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 725 | $ cat test.c |
| 726 | #include "test.h" |
| 727 | $ clang test.c -o test |
| 728 | </pre> |
| 729 | |
Douglas Gregor | f4d5953 | 2009-06-03 22:37:00 +0000 | [diff] [blame] | 730 | <p>In this example, <tt>clang</tt> will not automatically use the PCH file for |
Chris Lattner | 5c3074f | 2009-04-20 04:37:38 +0000 | [diff] [blame] | 731 | <tt>test.h</tt> since <tt>test.h</tt> was included directly in the source file |
| 732 | and not specified on the command line using <tt>-include</tt>.</p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 733 | |
Douglas Gregor | e650c8c | 2009-07-07 00:12:59 +0000 | [diff] [blame] | 734 | <h4>Relocatable PCH Files</h4> |
| 735 | <p>It is sometimes necessary to build a precompiled header from headers that |
| 736 | are not yet in their final, installed locations. For example, one might build a |
| 737 | precompiled header within the build tree that is then meant to be installed |
| 738 | alongside the headers. Clang permits the creation of "relocatable" precompiled |
| 739 | headers, which are built with a given path (into the build directory) and can |
| 740 | later be used from an installed location.</p> |
| 741 | |
| 742 | <p>To build a relocatable precompiled header, place your headers into a |
| 743 | subdirectory whose structure mimics the installed location. For example, if you |
| 744 | want to build a precompiled header for the header <code>mylib.h</code> that |
| 745 | will be installed into <code>/usr/include</code>, create a subdirectory |
| 746 | <code>build/usr/include</code> and place the header <code>mylib.h</code> into |
| 747 | that subdirectory. If <code>mylib.h</code> depends on other headers, then |
| 748 | they can be stored within <code>build/usr/include</code> in a way that mimics |
| 749 | the installed location.</p> |
| 750 | |
| 751 | <p>Building a relocatable precompiled header requires two additional arguments. |
| 752 | First, pass the <code>--relocatable-pch</code> flag to indicate that the |
| 753 | resulting PCH file should be relocatable. Second, pass |
| 754 | <code>-isysroot /path/to/build</code>, which makes all includes for your |
| 755 | library relative to the build directory. For example:</p> |
| 756 | |
| 757 | <pre> |
| 758 | # clang -x c-header --relocatable-pch -isysroot /path/to/build /path/to/build/mylib.h mylib.h.pch |
| 759 | </pre> |
| 760 | |
| 761 | <p>When loading the relocatable PCH file, the various headers used in the PCH |
| 762 | file are found from the system header root. For example, <code>mylib.h</code> |
| 763 | can be found in <code>/usr/include/mylib.h</code>. If the headers are installed |
| 764 | in some other system root, the <code>-isysroot</code> option can be used provide |
| 765 | a different system root from which the headers will be based. For example, |
| 766 | <code>-isysroot /Developer/SDKs/MacOSX10.4u.sdk</code> will look for |
| 767 | <code>mylib.h</code> in |
| 768 | <code>/Developer/SDKs/MacOSX10.4u.sdk/usr/include/mylib.h</code>.</p> |
| 769 | |
| 770 | <p>Relocatable precompiled headers are intended to be used in a limited number |
| 771 | of cases where the compilation environment is tightly controlled and the |
| 772 | precompiled header cannot be generated after headers have been installed. |
| 773 | Relocatable precompiled headers also have some performance impact, because |
| 774 | the difference in location between the header locations at PCH build time vs. |
| 775 | at the time of PCH use requires one of the PCH optimizations, |
| 776 | <code>stat()</code> caching, to be disabled. However, this change is only |
| 777 | likely to affect PCH files that reference a large number of headers.</p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 778 | |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 779 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 780 | <h3 id="codegen">Controlling Code Generation</h3> |
| 781 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 782 | |
| 783 | <p>Clang provides a number of ways to control code generation. The options are listed below.</p> |
| 784 | |
| 785 | <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 786 | <dl> |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 787 | <dt id="opt_fcatch-undefined-behavior"><b>-fcatch-undefined-behavior</b>: Turn |
| 788 | on runtime code generation to check for undefined behavior.</dt> |
| 789 | |
| 790 | <dd>This option, which defaults to off, controls whether or not Clang |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 791 | adds runtime checks for undefined runtime behavior. If a check fails, |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 792 | <tt>__builtin_trap()</tt> is used to indicate failure. |
| 793 | The checks are: |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 794 | <ul> |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 795 | <li>Subscripting where the static type of one operand is a variable |
Mike Stump | 88b2a17 | 2009-12-16 03:25:12 +0000 | [diff] [blame] | 796 | which is decayed from an array type and the other operand is |
| 797 | greater than the size of the array or less than zero.</li> |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 798 | <li>Shift operators where the amount shifted is greater or equal to the |
| 799 | promoted bit-width of the left-hand-side or less than zero.</li> |
Mike Stump | 8f6a3ed | 2009-12-16 03:18:14 +0000 | [diff] [blame] | 800 | <li>If control flow reaches __builtin_unreachable. |
| 801 | <li>When llvm implements more __builtin_object_size support, reads and |
| 802 | writes for objects that __builtin_object_size indicates we aren't |
| 803 | accessing valid memory. Bit-fields and vectors are not yet checked. |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 804 | </ul> |
Mike Stump | 53664ca | 2009-12-14 23:53:10 +0000 | [diff] [blame] | 805 | </dd> |
| 806 | |
Nuno Lopes | aa52624 | 2009-12-17 10:00:52 +0000 | [diff] [blame] | 807 | <dt id="opt_fno-assume-sane-operator-new"><b>-fno-assume-sane-operator-new</b>: |
| 808 | Don't assume that the C++'s new operator is sane.</dt> |
Nuno Lopes | b23f20d | 2009-12-17 10:15:49 +0000 | [diff] [blame] | 809 | <dd>This option tells the compiler to do not assume that C++'s global new |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 810 | operator will always return a pointer that does not |
Nuno Lopes | aa52624 | 2009-12-17 10:00:52 +0000 | [diff] [blame] | 811 | alias any other pointer when the function returns.</dd> |
Evan Cheng | fda026b | 2011-04-08 22:18:01 +0000 | [diff] [blame] | 812 | |
Evan Cheng | 4cf4b59 | 2011-04-08 22:34:21 +0000 | [diff] [blame] | 813 | <dt id="opt_ftrap-function"><b>-ftrap-function=[name]</b>: Instruct code |
Evan Cheng | fda026b | 2011-04-08 22:18:01 +0000 | [diff] [blame] | 814 | generator to emit a function call to the specified function name for |
| 815 | <tt>__builtin_trap()</tt>.</dt> |
| 816 | |
| 817 | <dd>LLVM code generator translates <tt>__builtin_trap()</tt> to a trap |
| 818 | instruction if it is supported by the target ISA. Otherwise, the builtin is |
| 819 | translated into a call to <tt>abort</tt>. If this option is set, then the code |
| 820 | generator will always lower the builtin to a call to the specified function |
| 821 | regardless of whether the target ISA has a trap instruction. This option is |
Chris Lattner | 02e266b | 2011-04-08 22:58:43 +0000 | [diff] [blame] | 822 | useful for environments (e.g. deeply embedded) where a trap cannot be properly |
| 823 | handled, or when some custom behavior is desired.</dd> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 824 | </dl> |
Nuno Lopes | aa52624 | 2009-12-17 10:00:52 +0000 | [diff] [blame] | 825 | |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 826 | <!-- ======================================================================= --> |
| 827 | <h2 id="c">C Language Features</h2> |
| 828 | <!-- ======================================================================= --> |
| 829 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 830 | <p>The support for standard C in clang is feature-complete except for the C99 |
| 831 | floating-point pragmas.</p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 832 | |
| 833 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 834 | <h3 id="c_ext">Extensions supported by clang</h3> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 835 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 836 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 837 | <p>See <a href="LanguageExtensions.html">clang language extensions</a>.</p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 838 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 839 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 840 | <h3 id="c_modes">Differences between various standard modes</h3> |
| 841 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 842 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 843 | <p>clang supports the -std option, which changes what language mode clang uses. |
| 844 | The supported modes for C are c89, gnu89, c94, c99, gnu99 and various aliases |
| 845 | for those modes. If no -std option is specified, clang defaults to gnu99 mode. |
| 846 | </p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 847 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 848 | <p>Differences between all c* and gnu* modes:</p> |
| 849 | <ul> |
| 850 | <li>c* modes define "__STRICT_ANSI__".</li> |
Eli Friedman | 26fa0ed | 2009-05-27 23:02:57 +0000 | [diff] [blame] | 851 | <li>Target-specific defines not prefixed by underscores, like "linux", are |
| 852 | defined in gnu* modes.</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 853 | <li>Trigraphs default to being off in gnu* modes; they can be enabled by the |
| 854 | -trigraphs option.</li> |
| 855 | <li>The parser recognizes "asm" and "typeof" as keywords in gnu* modes; the |
| 856 | variants "__asm__" and "__typeof__" are recognized in all modes.</li> |
Eli Friedman | b0ac545 | 2009-05-16 23:17:30 +0000 | [diff] [blame] | 857 | <li>The Apple "blocks" extension is recognized by default in gnu* modes |
| 858 | on some platforms; it can be enabled in any mode with the "-fblocks" |
| 859 | option.</li> |
Chris Lattner | 741be6a | 2011-06-15 00:41:40 +0000 | [diff] [blame] | 860 | <li>Arrays that are VLA's according to the standard, but which can be constant |
| 861 | folded by the frontend are treated as fixed size arrays. This occurs for |
| 862 | things like "int X[(1, 2)];", which is technically a VLA. c* modes are |
| 863 | strictly compliant and treat these as VLAs.</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 864 | </ul> |
| 865 | |
| 866 | <p>Differences between *89 and *99 modes:</p> |
| 867 | <ul> |
| 868 | <li>The *99 modes default to implementing "inline" as specified in C99, while |
| 869 | the *89 modes implement the GNU version. This can be overridden for individual |
| 870 | functions with the __gnu_inline__ attribute.</li> |
Eli Friedman | 26fa0ed | 2009-05-27 23:02:57 +0000 | [diff] [blame] | 871 | <li>Digraphs are not recognized in c89 mode.</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 872 | <li>The scope of names defined inside a "for", "if", "switch", "while", or "do" |
| 873 | statement is different. (example: "if ((struct x {int x;}*)0) {}".)</li> |
| 874 | <li>__STDC_VERSION__ is not defined in *89 modes.</li> |
Eli Friedman | 26fa0ed | 2009-05-27 23:02:57 +0000 | [diff] [blame] | 875 | <li>"inline" is not recognized as a keyword in c89 mode.</li> |
| 876 | <li>"restrict" is not recognized as a keyword in *89 modes.</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 877 | <li>Commas are allowed in integer constant expressions in *99 modes.</li> |
| 878 | <li>Arrays which are not lvalues are not implicitly promoted to pointers in |
| 879 | *89 modes.</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 880 | <li>Some warnings are different.</li> |
| 881 | </ul> |
| 882 | |
| 883 | <p>c94 mode is identical to c89 mode except that digraphs are enabled in |
| 884 | c94 mode (FIXME: And __STDC_VERSION__ should be defined!).</p> |
| 885 | |
| 886 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 887 | <h3 id="c_unimpl_gcc">GCC extensions not implemented yet</h3> |
| 888 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 889 | |
| 890 | <p>clang tries to be compatible with gcc as much as possible, but some gcc |
| 891 | extensions are not implemented yet:</p> |
| 892 | |
| 893 | <ul> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 894 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 895 | <li>clang does not support #pragma weak |
Eli Friedman | 4da9255 | 2009-06-02 08:21:31 +0000 | [diff] [blame] | 896 | (<a href="http://llvm.org/bugs/show_bug.cgi?id=3679">bug 3679</a>). Due to |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 897 | the uses described in the bug, this is likely to be implemented at some |
| 898 | point, at least partially.</li> |
| 899 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 900 | <li>clang does not support decimal floating point types (_Decimal32 and |
| 901 | friends) or fixed-point types (_Fract and friends); nobody has expressed |
| 902 | interest in these features yet, so it's hard to say when they will be |
| 903 | implemented.</li> |
| 904 | |
| 905 | <li>clang does not support nested functions; this is a complex feature which |
| 906 | is infrequently used, so it is unlikely to be implemented anytime soon.</li> |
| 907 | |
Daniel Dunbar | 05fa629 | 2009-05-12 23:12:07 +0000 | [diff] [blame] | 908 | <li>clang does not support global register variables, this is unlikely |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 909 | to be implemented soon because it requires additional LLVM backend support. |
| 910 | </li> |
Daniel Dunbar | 05fa629 | 2009-05-12 23:12:07 +0000 | [diff] [blame] | 911 | |
| 912 | <li>clang does not support static initialization of flexible array |
| 913 | members. This appears to be a rarely used extension, but could be |
| 914 | implemented pending user demand.</li> |
| 915 | |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 916 | <li>clang does not support __builtin_va_arg_pack/__builtin_va_arg_pack_len. |
| 917 | This is used rarely, but in some potentially interesting places, like the |
| 918 | glibc headers, so it may be implemented pending user demand. Note that |
| 919 | because clang pretends to be like GCC 4.2, and this extension was introduced |
| 920 | in 4.3, the glibc headers will not try to use this extension with clang at |
| 921 | the moment.</li> |
| 922 | |
| 923 | <li>clang does not support the gcc extension for forward-declaring function |
| 924 | parameters; this has not showed up in any real-world code yet, though, so it |
| 925 | might never be implemented.</li> |
| 926 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 927 | </ul> |
| 928 | |
| 929 | <p>This is not a complete list; if you find an unsupported extension |
| 930 | missing from this list, please send an e-mail to cfe-dev. This list |
| 931 | currently excludes C++; see <a href="#cxx">C++ Language Features</a>. |
| 932 | Also, this list does not include bugs in mostly-implemented features; please |
| 933 | see 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"> |
| 934 | bug tracker</a> for known existing bugs (FIXME: Is there a section for |
| 935 | bug-reporting guidelines somewhere?).</p> |
| 936 | |
| 937 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 938 | <h3 id="c_unsupp_gcc">Intentionally unsupported GCC extensions</h3> |
| 939 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 940 | |
Eli Friedman | 0b32600 | 2009-06-12 20:11:05 +0000 | [diff] [blame] | 941 | <ul> |
| 942 | |
Eli Friedman | 2f3fca0 | 2009-06-12 20:08:48 +0000 | [diff] [blame] | 943 | <li>clang does not support the gcc extension that allows variable-length arrays |
Chris Lattner | d462b6a | 2011-01-24 03:47:59 +0000 | [diff] [blame] | 944 | in structures. This is for a few reasons: one, it is tricky |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 945 | to implement, two, the extension is completely undocumented, and three, the |
Chris Lattner | b9d511c | 2010-10-28 02:20:32 +0000 | [diff] [blame] | 946 | extension appears to be rarely used. Note that clang <em>does</em> support |
| 947 | flexible array members (arrays with a zero or unspecified size at the end of |
| 948 | a structure).</li> |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 949 | |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 950 | <li>clang does not have an equivalent to gcc's "fold"; this means that |
| 951 | clang doesn't accept some constructs gcc might accept in contexts where a |
Eli Friedman | 248f973 | 2011-06-13 23:12:01 +0000 | [diff] [blame] | 952 | constant expression is required, like "x-x" where x is a variable.</li> |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 953 | |
Eli Friedman | 2f3fca0 | 2009-06-12 20:08:48 +0000 | [diff] [blame] | 954 | <li>clang does not support multiple alternative constraints in inline asm; this |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 955 | is an extremely obscure feature which would be complicated to implement |
Eli Friedman | 2f3fca0 | 2009-06-12 20:08:48 +0000 | [diff] [blame] | 956 | correctly.</li> |
Eli Friedman | ca130bd | 2009-06-12 20:04:25 +0000 | [diff] [blame] | 957 | |
| 958 | <li>clang does not support __builtin_apply and friends; this extension is |
| 959 | extremely obscure and difficult to implement reliably.</li> |
| 960 | |
Eli Friedman | 0b32600 | 2009-06-12 20:11:05 +0000 | [diff] [blame] | 961 | </ul> |
| 962 | |
Eli Friedman | 660a5ac | 2009-04-28 18:48:34 +0000 | [diff] [blame] | 963 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 964 | <h3 id="c_ms">Microsoft extensions</h3> |
| 965 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 966 | |
| 967 | <p>clang has some experimental support for extensions from |
| 968 | Microsoft Visual C++; to enable it, use the -fms-extensions command-line |
Eli Friedman | a1821b5 | 2009-06-08 06:21:03 +0000 | [diff] [blame] | 969 | option. This is the default for Windows targets. Note that the |
| 970 | support is incomplete; enabling Microsoft extensions will silently drop |
| 971 | certain constructs (including __declspec and Microsoft-style asm statements). |
| 972 | </p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 973 | |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 974 | <ul> |
Douglas Gregor | d3b227d | 2010-12-14 16:21:49 +0000 | [diff] [blame] | 975 | <li>clang allows setting _MSC_VER with -fmsc-version=. It defaults to 1300 which |
Michael J. Spencer | dae4ac4 | 2010-10-21 05:21:48 +0000 | [diff] [blame] | 976 | is the same as Visual C/C++ 2003. Any number is supported and can greatly affect |
| 977 | what Windows SDK and c++stdlib headers clang can compile. This option will be |
| 978 | removed when clang supports the full set of MS extensions required for these |
| 979 | headers.</li> |
| 980 | |
Daniel Dunbar | 05fa629 | 2009-05-12 23:12:07 +0000 | [diff] [blame] | 981 | <li>clang does not support the Microsoft extension where anonymous |
Daniel Dunbar | 869e054 | 2009-05-13 00:23:53 +0000 | [diff] [blame] | 982 | record members can be declared using user defined typedefs.</li> |
Daniel Dunbar | 05fa629 | 2009-05-12 23:12:07 +0000 | [diff] [blame] | 983 | |
Daniel Dunbar | 9375ed1 | 2009-05-13 21:40:49 +0000 | [diff] [blame] | 984 | <li>clang supports the Microsoft "#pragma pack" feature for |
| 985 | controlling record layout. GCC also contains support for this feature, |
| 986 | however where MSVC and GCC are incompatible clang follows the MSVC |
| 987 | definition.</li> |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 988 | </ul> |
Daniel Dunbar | 9375ed1 | 2009-05-13 21:40:49 +0000 | [diff] [blame] | 989 | |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 990 | <!-- ======================================================================= --> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 991 | <h2 id="target_features">Target-Specific Features and Limitations</h2> |
| 992 | <!-- ======================================================================= --> |
| 993 | |
| 994 | |
| 995 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 996 | <h3 id="target_arch">CPU Architectures Features and Limitations</h3> |
| 997 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 998 | |
| 999 | <!-- ======================== --> |
| 1000 | <h4 id="target_arch_x86">X86</h4> |
| 1001 | <!-- ======================== --> |
Daniel Dunbar | bcaf7aa | 2010-09-19 19:26:59 +0000 | [diff] [blame] | 1002 | |
| 1003 | <p>The support for X86 (both 32-bit and 64-bit) is considered stable on Darwin |
| 1004 | (Mac OS/X), Linux, FreeBSD, and Dragonfly BSD: it has been tested to correctly |
| 1005 | compile many large C, C++, Objective-C, and Objective-C++ codebases.</p> |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 1006 | |
NAKAMURA Takumi | ddf68ff | 2011-04-05 04:31:31 +0000 | [diff] [blame] | 1007 | <p>On x86_64-mingw32, passing i128(by value) is incompatible to Microsoft x64 |
| 1008 | calling conversion. You might need to tweak WinX86_64ABIInfo::classify() |
| 1009 | in lib/CodeGen/TargetInfo.cpp.</p> |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 1010 | |
Eli Friedman | 3b658d3 | 2009-06-08 05:12:39 +0000 | [diff] [blame] | 1011 | <!-- ======================== --> |
| 1012 | <h4 id="target_arch_arm">ARM</h4> |
| 1013 | <!-- ======================== --> |
Daniel Dunbar | bcaf7aa | 2010-09-19 19:26:59 +0000 | [diff] [blame] | 1014 | |
| 1015 | <p>The support for ARM (specifically ARMv6 and ARMv7) is considered stable on |
| 1016 | Darwin (iOS): it has been tested to correctly compile many large C, C++, |
Bob Wilson | 4ea8dfa | 2011-01-10 17:55:14 +0000 | [diff] [blame] | 1017 | Objective-C, and Objective-C++ codebases. Clang only supports a limited number |
| 1018 | of ARM architectures. It does not yet fully support ARMv5, for example.</p> |
Eli Friedman | 3b658d3 | 2009-06-08 05:12:39 +0000 | [diff] [blame] | 1019 | |
| 1020 | <!-- ======================== --> |
| 1021 | <h4 id="target_arch_other">Other platforms</h4> |
| 1022 | <!-- ======================== --> |
| 1023 | clang currently contains some support for PPC and Sparc; however, significant |
| 1024 | pieces of code generation are still missing, and they haven't undergone |
| 1025 | significant testing. |
| 1026 | |
Eli Friedman | 3b658d3 | 2009-06-08 05:12:39 +0000 | [diff] [blame] | 1027 | <p>clang contains limited support for the MSP430 embedded processor, but both |
| 1028 | the clang support and the LLVM backend support are highly experimental. |
| 1029 | |
| 1030 | <p>Other platforms are completely unsupported at the moment. Adding the |
| 1031 | minimal support needed for parsing and semantic analysis on a new platform |
| 1032 | is quite easy; see lib/Basic/Targets.cpp in the clang source tree. This level |
| 1033 | of support is also sufficient for conversion to LLVM IR for simple programs. |
| 1034 | Proper support for conversion to LLVM IR requires adding code to |
| 1035 | lib/CodeGen/CGCall.cpp at the moment; this is likely to change soon, though. |
| 1036 | Generating assembly requires a suitable LLVM backend. |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 1037 | |
| 1038 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 1039 | <h3 id="target_os">Operating System Features and Limitations</h3> |
| 1040 | <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| 1041 | |
| 1042 | <!-- ======================================= --> |
| 1043 | <h4 id="target_os_darwin">Darwin (Mac OS/X)</h4> |
| 1044 | <!-- ======================================= --> |
| 1045 | |
| 1046 | <p>No __thread support, 64-bit ObjC support requires SL tools.</p> |
| 1047 | |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 1048 | <!-- ======================================= --> |
| 1049 | <h4 id="target_os_win32">Windows</h4> |
| 1050 | <!-- ======================================= --> |
| 1051 | |
| 1052 | <p>Experimental supports are on Cygming.</p> |
| 1053 | |
| 1054 | <h5>Cygwin</h5> |
| 1055 | |
| 1056 | <p>Clang works on Cygwin-1.7.</p> |
| 1057 | |
| 1058 | <h5>MinGW32</h5> |
| 1059 | |
| 1060 | <p>Clang works on some mingw32 distributions. |
| 1061 | Clang assumes directories as below;</p> |
| 1062 | |
| 1063 | <ul> |
| 1064 | <li><tt>C:/mingw/include</tt></li> |
| 1065 | <li><tt>C:/mingw/lib</tt></li> |
| 1066 | <li><tt>C:/mingw/lib/gcc/mingw32/4.[3-5].0/include/c++</tt></li> |
| 1067 | </ul> |
| 1068 | |
| 1069 | <p>On MSYS, a few tests might fail. It is due to <a href="http://llvm.org/bugs/show_bug.cgi?id=8520">Bug 8520</a> and is fixed in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110314/118106.html">LLVM's r127724</a>.</p> |
| 1070 | |
| 1071 | <h5>MinGW-w64</h5> |
| 1072 | |
Douglas Gregor | dad879a | 2011-08-30 00:40:12 +0000 | [diff] [blame] | 1073 | <p>For 32-bit (i686-w64-mingw32), and 64-bit (x86_64-w64-mingw32), Clang assumes as below;<p> |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 1074 | |
| 1075 | <ul> |
Douglas Gregor | dad879a | 2011-08-30 00:40:12 +0000 | [diff] [blame] | 1076 | <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> |
| 1077 | <li><tt>some_directory/bin/gcc.exe</tt></li> |
| 1078 | <li><tt>some_directory/bin/clang.exe</tt></li> |
| 1079 | <li><tt>some_directory/bin/clang++.exe</tt></li> |
| 1080 | <li><tt>some_directory/bin/../include/c++/GCC_version</tt></li> |
| 1081 | <li><tt>some_directory/bin/../include/c++/GCC_version/x86_64-w64-mingw32</tt></li> |
| 1082 | <li><tt>some_directory/bin/../include/c++/GCC_version/i686-w64-mingw32</tt></li> |
| 1083 | <li><tt>some_directory/bin/../include/c++/GCC_version/backward</tt></li> |
| 1084 | <li><tt>some_directory/bin/../x86_64-w64-mingw32/include</tt></li> |
| 1085 | <li><tt>some_directory/bin/../i686-w64-mingw32/include</tt></li> |
| 1086 | <li><tt>some_directory/bin/../include</tt></li> |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 1087 | </ul> |
| 1088 | |
Douglas Gregor | dad879a | 2011-08-30 00:40:12 +0000 | [diff] [blame] | 1089 | <p>This directory layout is standard for any toolchain you will find on the official <a href="mingw-w64.sourceforge.net">MinGW-w64 website</a>. |
| 1090 | |
| 1091 | <p>Clang expects the GCC executable "gcc.exe" compiled for i686-w64-mingw32 (or x86_64-w64-mingw32) to be present on PATH.</p> |
| 1092 | |
| 1093 | <p><a href="http://llvm.org/bugs/show_bug.cgi?id=9072">Some tests might fail</a> |
| 1094 | on x86_64-w64-mingw32.</p> |
NAKAMURA Takumi | a75fdb2 | 2011-04-04 15:02:41 +0000 | [diff] [blame] | 1095 | |
Chris Lattner | cf17d9d | 2009-04-20 04:23:09 +0000 | [diff] [blame] | 1096 | </div> |
| 1097 | </body> |
| 1098 | </html> |