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18 <h1>Clang Compiler User's Manual</h1>
21 <li><a href="#intro">Introduction</a>
23 <li><a href="#terminology">Terminology</a></li>
24 <li><a href="#basicusage">Basic Usage</a></li>
27 <li><a href="#commandline">Command Line Options</a>
29 <li><a href="#cl_diagnostics">Options to Control Error and Warning
33 <li><a href="#general_features">Language and Target-Independent Features</a>
35 <li><a href="#diagnostics">Controlling Errors and Warnings</a></li>
36 <li><a href="#precompiledheaders">Precompiled Headers</a></li>
39 <li><a href="#c">C Language Features</a>
41 <li><a href="#c_ext">Extensions supported by clang</a></li>
42 <li><a href="#c_modes">Differences between various standard modes</a></li>
43 <li><a href="#c_unimpl_gcc">GCC extensions not implemented yet</a></li>
44 <li><a href="#c_unsupp_gcc">Intentionally unsupported GCC extensions</a></li>
45 <li><a href="#c_ms">Microsoft extensions</a></li>
48 <li><a href="#objc">Objective-C Language Features</a>
50 <li><a href="#objc_incompatibilities">Intentional Incompatibilities with
54 <li><a href="#cxx">C++ Language Features</a>
59 <li><a href="#objcxx">Objective C++ Language Features</a>
64 <li><a href="#target_features">Target-Specific Features and Limitations</a>
66 <li><a href="#target_arch">CPU Architectures Features and Limitations</a>
68 <li><a href="#target_arch_x86">X86</a></li>
73 <li><a href="#target_os">Operating System Features and Limitations</a>
75 <li><a href="#target_os_darwin">Darwin (Mac OS/X)</a></li>
85 <!-- ======================================================================= -->
86 <h2 id="intro">Introduction</h2>
87 <!-- ======================================================================= -->
89 <p>The Clang Compiler is an open-source compiler for the C family of programming
90 languages, aiming to be the best in class implementation of these languages.
91 Clang builds on the LLVM optimizer and code generator, allowing it to provide
92 high-quality optimization and code generation support for many targets. For
93 more general information, please see the <a href="http://clang.llvm.org">Clang
94 Web Site</a> or the <a href="http://llvm.org">LLVM Web Site</a>.</p>
96 <p>This document describes important notes about using Clang as a compiler for
97 an end-user, documenting the supported features, command line options, etc. If
98 you are interested in using Clang to build a tool that processes code, please
99 see <a href="InternalsManual.html">the Clang Internals Manual</a>. If you are
100 interested in the <a href="http://clang.llvm.org/StaticAnalysis.html">Clang
101 Static Analyzer</a>, please see its web page.</p>
103 <p>Clang is designed to support the C family of programming languages, which
104 includes <a href="#c">C</a>, <a href="#objc">Objective-C</a>, <a
105 href="#cxx">C++</a>, and <a href="#objcxx">Objective-C++</a> as well as many
106 dialects of those. For language-specific information, please see the
107 corresponding language specific section:</p>
110 <li><a href="#c">C Language</a>: K&R C, ANSI C89, ISO C90, ISO C94
111 (C89+AMD1), ISO C99 (+TC1, TC2, TC3). </li>
112 <li><a href="#objc">Objective-C Language</a>: ObjC 1, ObjC 2, ObjC 2.1, plus
113 variants depending on base language.</li>
114 <li><a href="#cxx">C++ Language Features</a></li>
115 <li><a href="#objcxx">Objective C++ Language</a></li>
118 <p>In addition to these base languages and their dialects, Clang supports a
119 broad variety of language extensions, which are documented in the corresponding
120 language section. These extensions are provided to be compatible with the GCC,
121 Microsoft, and other popular compilers as well as to improve functionality
122 through Clang-specific features. The Clang driver and language features are
123 intentionally designed to be as compatible with the GNU GCC compiler as
124 reasonably possible, easing migration from GCC to Clang. In most cases, code
127 <p>In addition to language specific features, Clang has a variety of features
128 that depend on what CPU architecture or operating system is being compiled for.
129 Please see the <a href="target_features">Target-Specific Features and
130 Limitations</a> section for more details.</p>
132 <p>The rest of the introduction introduces some basic <a
133 href="#terminology">compiler terminology</a> that is used throughout this manual
134 and contains a basic <a href="#basicusage">introduction to using Clang</a>
135 as a command line compiler.</p>
137 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
138 <h3 id="terminology">Terminology</h3>
139 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
141 <p>Front end, parser, backend, preprocessor, undefined behavior, diagnostic,
144 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
145 <h3 id="basicusage">Basic Usage</h3>
146 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
148 <p>Intro to how to use a C compiler for newbies.</p>
156 enabling optimizations
158 picking a language to use, defaults to C99 by default. Autosenses based on
165 <!-- ======================================================================= -->
166 <h2 id="commandline">Command Line Options</h2>
167 <!-- ======================================================================= -->
170 This section is generally an index into other sections. It does not go into
171 depth on the ones that are covered by other sections. However, the first part
172 introduces the language selection and other high level options like -c, -g, etc.
176 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
177 <h3 id="cl_diagnostics">Options to Control Error and Warning Messages</h3>
178 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
180 <p><b>-Werror</b>: Turn warnings into errors.</p>
181 <p><b>-Werror=foo</b>: Turn warning "foo" into an error.</p>
182 <p><b>-Wno-error=foo</b>: Turn warning "foo" into an warning even if -Werror is
184 <p><b>-Wfoo</b>: Enable warning foo</p>
185 <p><b>-Wno-foo</b>: Disable warning foo</p>
186 <p><b>-w</b>: Disable all warnings.</p>
187 <p><b>-pedantic</b>: Warn on language extensions.</p>
188 <p><b>-pedantic-errors</b>: Error on language extensions.</p>
189 <p><b>-Wsystem-headers</b>: Enable warnings from system headers.</p>
191 <!-- ================================================= -->
192 <h4 id="cl_diag_formatting">Formatting of Diagnostics</h4>
193 <!-- ================================================= -->
195 <p>Clang aims to produce beautiful diagnostics by default, particularly for new
196 users that first come to Clang. However, different people have different
197 preferences, and sometimes Clang is driven by another program that wants to
198 parse simple and consistent output, not a person. For these cases, Clang
199 provides a wide range of options to control the exact output format of the
200 diagnostics that it generates.</p>
204 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
205 <dt id="opt_fshow-column"><b>-f[no-]show-column</b>: Print column number in
207 <dd>This option, which defaults to on, controls whether or not Clang prints the
208 column number of a diagnostic. For example, when this is enabled, Clang will
209 print something like:</p>
212 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
218 <p>When this is disabled, Clang will print "test.c:28: warning..." with no
222 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
223 <dt id="opt_fshow-source-location"><b>-f[no-]show-source-location</b>: Print
224 source file/line/column information in diagnostic.</dt>
225 <dd>This option, which defaults to on, controls whether or not Clang prints the
226 filename, line number and column number of a diagnostic. For example,
227 when this is enabled, Clang will print something like:</p>
230 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
236 <p>When this is disabled, Clang will not print the "test.c:28:8: " part.</p>
239 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
240 <dt id="opt_fcaret-diagnostics"><b>-f[no-]caret-diagnostics</b>: Print source
241 line and ranges from source code in diagnostic.</dt>
242 <dd>This option, which defaults to on, controls whether or not Clang prints the
243 source line, source ranges, and caret when emitting a diagnostic. For example,
244 when this is enabled, Clang will print something like:</p>
247 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
253 <p>When this is disabled, Clang will just print:</p>
256 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
261 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
262 <dt id="opt_fdiagnostics-show-option"><b>-f[no-]diagnostics-show-option</b>:
263 Enable <tt>[-Woption]</tt> information in diagnostic line.</dt>
264 <dd>This option, which defaults to on,
265 controls whether or not Clang prints the associated <A
266 href="#cl_diag_warning_groups">warning group</a> option name when outputting
267 a warning diagnostic. For example, in this output:</p>
270 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
276 <p>Passing <b>-fno-diagnostics-show-option</b> will prevent Clang from printing
277 the [<a href="#opt_Wextra-tokens">-Wextra-tokens</a>] information in the
278 diagnostic. This information tells you the flag needed to enable or disable the
279 diagnostic, either from the command line or through <a
280 href="#pragma_GCC_diagnostic">#pragma GCC diagnostic</a>.</dd>
283 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
284 <dt id="opt_fdiagnostics-fixit-info"><b>-f[no-]diagnostics-fixit-info</b>:
285 Enable "FixIt" information in the diagnostics output.</dt>
286 <dd>This option, which defaults to on, controls whether or not Clang prints the
287 information on how to fix a specific diagnostic underneath it when it knows.
288 For example, in this output:</p>
291 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
297 <p>Passing <b>-fno-diagnostics-fixit-info</b> will prevent Clang from printing
298 the "//" line at the end of the message. This information is useful for users
299 who may not understand what is wrong, but can be confusing for machine
303 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
304 <dt id="opt_fdiagnostics-print-source-range-info">
305 <b>-f[no-]diagnostics-print-source-range-info</b>:
306 Print machine parsable information about source ranges.</dt>
307 <dd>This option, which defaults to off, controls whether or not Clang prints
308 information about source ranges in a machine parsable format after the
309 file/line/column number information. The information is a simple sequence of
310 brace enclosed ranges, where each range lists the start and end line/column
311 locations. For example, in this output:</p>
314 exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
315 P = (P-42) + Gamma*4;
319 <p>The {}'s are generated by -fdiagnostics-print-source-range-info.</p>
328 <!-- ===================================================== -->
329 <h4 id="cl_diag_warning_groups">Individual Warning Groups</h4>
330 <!-- ===================================================== -->
332 <p>TODO: Generate this from tblgen. Define one anchor per warning group.</p>
338 <!-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -->
339 <dt id="opt_Wextra-tokens"><b>-Wextra-tokens</b>: Warn about excess tokens at
340 the end of a preprocessor directive.</dt>
341 <dd>This option, which defaults to on, enables warnings about extra tokens at
342 the end of preprocessor directives. For example:</p>
345 test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
350 <p>These extra tokens are not strictly conforming, and are usually best handled
351 by commenting them out.</p>
353 <p>This option is also enabled by <a href="">-Wfoo</a>, <a href="">-Wbar</a>,
354 and <a href="">-Wbaz</a>.</p>
359 <!-- ======================================================================= -->
360 <h2 id="general_features">Language and Target-Independent Features</h2>
361 <!-- ======================================================================= -->
364 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
365 <h3 id="diagnostics">Controlling Errors and Warnings</h3>
366 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
368 <p>Clang provides a number of ways to control which code constructs cause it to
369 emit errors and warning messages, and how they are displayed to the console.</p>
371 <h4>Controlling How Clang Displays Diagnostics</h4>
373 <p>When Clang emits a diagnostic, it includes rich information in the output,
374 and gives you fine-grain control over which information is printed. Clang has
375 the ability to print this information, and these are the options that control
380 <li>A file/line/column indicator that shows exactly where the diagnostic occurs
381 in your code [<a href="#opt_fshow-column">-fshow-column</a>, <a
382 href="#opt_fshow-source-location">-fshow-source-location</a>].</li>
383 <li>A categorization of the diagnostic as a note, warning, error, or fatal
385 <li>A text string that describes what the problem is.</li>
386 <li>An option that indicates how to control the diagnostic (for diagnostics that
388 href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li>
389 <li>The line of source code that the issue occurs on, along with a caret and
390 ranges that indicate the important locations [<a
391 href="opt_fcaret-diagnostics">-fcaret-diagnostics</a>].</li>
392 <li>"FixIt" information, which is a concise explanation of how to fix the
393 problem (when Clang is certain it knows) [<a
394 href="opt_fdiagnostics-fixit-info">-fdiagnostics-fixit-info</a>].</li>
395 <li>A machine-parsable representation of the ranges involved (off by
397 href="opt_fdiagnostics-print-source-range-info">-fdiagnostics-print-source-range-info</a>].</li>
400 <p>For more information please see <a href="#cl_diag_formatting">Formatting of
403 <h4>Controlling Which Diagnostics Clang Generates</h4>
405 <p>mappings: ignore, note, warning, error, fatal</p>
408 The two major classes are control from the command line and control via pragmas
412 <p>-W flags, -pedantic, etc</p>
414 <p>pragma GCC diagnostic</p>
416 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
417 <h3 id="precompiledheaders">Precompiled Headers</h3>
418 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
420 <p><a href="http://en.wikipedia.org/wiki/Precompiled_header">Precompiled
421 headers</a> are a general approach employed by many compilers to reduce
422 compilation time. The underlying motivation of the approach is that it is
423 common for the same (and often large) header files to be included by
424 multiple source files. Consequently, compile times can often be greatly improved
425 by caching some of the (redundant) work done by a compiler to process headers.
426 Precompiled header files, which represent one of many ways to implement
427 this optimization, are literally files that represent an on-disk cache that
428 contains the vital information necessary to reduce some of the work
429 needed to process a corresponding header file. While details of precompiled
430 headers vary between compilers, precompiled headers have been shown to be a
431 highly effective at speeding up program compilation on systems with very large
432 system headers (e.g., Mac OS/X).</p>
434 <h4>Generating a PCH File</h4>
436 <p>To generate a PCH file using Clang, one invokes Clang with
437 the <b><tt>-x <i><language></i>-header</tt></b> option. This mirrors the
438 interface in GCC for generating PCH files:</p>
441 $ gcc -x c-header test.h -o test.h.gch
442 $ clang -x c-header test.h -o test.h.pch
445 <h4>Using a PCH File</h4>
447 <p>A PCH file can then be used as a prefix header when a
448 <b><tt>-include</tt></b> option is passed to <tt>clang</tt>:</p>
451 $ clang -include test.h test.c -o test
454 <p>The <tt>clang</tt> driver will first check if a PCH file for <tt>test.h</tt>
455 is available; if so, the contents of <tt>test.h</tt> (and the files it includes)
456 will be processed from the PCH file. Otherwise, Clang falls back to
457 directly processing the content of <tt>test.h</tt>. This mirrors the behavior of
460 <p><b>NOTE:</b> Clang does <em>not</em> automatically use PCH files
461 for headers that are directly included within a source file. For example:</p>
464 $ clang -x c-header test.h -o test.h.cth
467 $ clang test.c -o test
470 <p>In this example, <tt>clang</tt> will not automatically use the PCH file for
471 <tt>test.h</tt> since <tt>test.h</tt> was included directly in the source file
472 and not specified on the command line using <tt>-include</tt>.</p>
475 <!-- ======================================================================= -->
476 <h2 id="c">C Language Features</h2>
477 <!-- ======================================================================= -->
479 <p>The support for standard C in clang is feature-complete except for the C99
480 floating-point pragmas.</p>
482 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
483 <h3 id="c_ext">Extensions supported by clang</h3>
484 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
486 <p>See <a href="LanguageExtensions.html">clang language extensions</a>.</p>
488 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
489 <h3 id="c_modes">Differences between various standard modes</h3>
490 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
492 <p>clang supports the -std option, which changes what language mode clang uses.
493 The supported modes for C are c89, gnu89, c94, c99, gnu99 and various aliases
494 for those modes. If no -std option is specified, clang defaults to gnu99 mode.
497 <p>Differences between all c* and gnu* modes:</p>
499 <li>c* modes define "__STRICT_ANSI__".</li>
500 <li>Target-specific defines not prefixed by underscores, like "linux", are
501 defined in gnu* modes.</li>
502 <li>Trigraphs default to being off in gnu* modes; they can be enabled by the
503 -trigraphs option.</li>
504 <li>The parser recognizes "asm" and "typeof" as keywords in gnu* modes; the
505 variants "__asm__" and "__typeof__" are recognized in all modes.</li>
506 <li>The Apple "blocks" extension is recognized by default in gnu* modes
507 on some platforms; it can be enabled in any mode with the "-fblocks"
509 <li>Some warnings are different.</li>
512 <p>Differences between *89 and *99 modes:</p>
514 <li>The *99 modes default to implementing "inline" as specified in C99, while
515 the *89 modes implement the GNU version. This can be overridden for individual
516 functions with the __gnu_inline__ attribute.</li>
517 <li>Digraphs are not recognized in c89 mode.</li>
518 <li>The scope of names defined inside a "for", "if", "switch", "while", or "do"
519 statement is different. (example: "if ((struct x {int x;}*)0) {}".)</li>
520 <li>__STDC_VERSION__ is not defined in *89 modes.</li>
521 <li>"inline" is not recognized as a keyword in c89 mode.</li>
522 <li>"restrict" is not recognized as a keyword in *89 modes.</li>
523 <li>Commas are allowed in integer constant expressions in *99 modes.</li>
524 <li>Arrays which are not lvalues are not implicitly promoted to pointers in
526 <li>Some warnings are different.</li>
529 <p>c94 mode is identical to c89 mode except that digraphs are enabled in
530 c94 mode (FIXME: And __STDC_VERSION__ should be defined!).</p>
532 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
533 <h3 id="c_unimpl_gcc">GCC extensions not implemented yet</h3>
534 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
536 <p>clang tries to be compatible with gcc as much as possible, but some gcc
537 extensions are not implemented yet:</p>
540 <li>clang does not support __label__
541 (<a href="http://llvm.org/bugs/show_bug.cgi?id=3429">bug 3429</a>). This is
542 a relatively small feature, so it is likely to be implemented relatively
545 <li>clang does not support attributes on function pointers
546 (<a href="http://llvm.org/bugs/show_bug.cgi?id=2461">bug 2461</a>). This is
547 a relatively important feature, so it is likely to be implemented relatively
550 <li>clang does not support #pragma weak
551 (<a href="http://llvm.org/bugs/show_bug.cgi?id=3679">bug 3679</a>). Due to
552 the uses described in the bug, this is likely to be implemented at some
553 point, at least partially.</li>
555 <li>clang does not support #pragma align
556 (<a href="http://llvm.org/bugs/show_bug.cgi?id=3811">bug 3811</a>). This is a
557 relatively small feature, so it is likely to be implemented relatively
560 <li>clang does not support code generation for local variables pinned to
561 registers (<a href="http://llvm.org/bugs/show_bug.cgi?id=3933">bug 3933</a>).
562 This is a relatively small feature, so it is likely to be implemented
563 relatively soon.</li>
565 <li>clang does not support decimal floating point types (_Decimal32 and
566 friends) or fixed-point types (_Fract and friends); nobody has expressed
567 interest in these features yet, so it's hard to say when they will be
570 <li>clang does not support nested functions; this is a complex feature which
571 is infrequently used, so it is unlikely to be implemented anytime soon.</li>
573 <li>clang does not support __builtin_apply and friends; this extension requires
574 complex code generator support that does not currently exist in LLVM, and there
575 is very little demand, so it is unlikely to be implemented anytime soon.</li>
577 <li>clang does not support global register variables, this is unlikely
578 to be implemented soon.</li>
580 <li>clang does not support static initialization of flexible array
581 members. This appears to be a rarely used extension, but could be
582 implemented pending user demand.</li>
586 <p>This is not a complete list; if you find an unsupported extension
587 missing from this list, please send an e-mail to cfe-dev. This list
588 currently excludes C++; see <a href="#cxx">C++ Language Features</a>.
589 Also, this list does not include bugs in mostly-implemented features; please
590 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">
591 bug tracker</a> for known existing bugs (FIXME: Is there a section for
592 bug-reporting guidelines somewhere?).</p>
594 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
595 <h3 id="c_unsupp_gcc">Intentionally unsupported GCC extensions</h3>
596 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
598 <p>clang does not support the gcc extension that allows variable-length arrays
599 in structures. This is for a few of reasons: one, it is tricky
600 to implement, two, the extension is completely undocumented, and three, the
601 extension appears to be very rarely used.</p>
603 <p>clang does not support duplicate definitions of a function where one is
604 inline. This complicates clients of the AST which normally can expect there is
605 at most one definition for each function. Source code using this feature should
606 be changed to define the inline and out-of-line definitions in separate
607 translation units.</p>
609 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
610 <h3 id="c_ms">Microsoft extensions</h3>
611 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
613 <p>clang has some experimental support for extensions from
614 Microsoft Visual C++; to enable it, use the -fms-extensions command-line
615 option. Eventually, this will be the default for Windows targets.
616 These extensions are not anywhere near complete, so please do not
617 file bugs; patches are welcome, though.</p>
619 <li>clang does not support the Microsoft extension where anonymous
620 record members can be declared using user defined typedefs.</li>
622 <li>clang supports the Microsoft "#pragma pack" feature for
623 controlling record layout. GCC also contains support for this feature,
624 however where MSVC and GCC are incompatible clang follows the MSVC
627 <!-- ======================================================================= -->
628 <h2 id="objc">Objective-C Language Features</h2>
629 <!-- ======================================================================= -->
632 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
633 <h3 id="objc_incompatibilities">Intentional Incompatibilities with GCC</h3>
634 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
636 <p>No cast of super, no lvalue casts.</p>
640 <!-- ======================================================================= -->
641 <h2 id="cxx">C++ Language Features</h2>
642 <!-- ======================================================================= -->
644 <p>At this point, Clang C++ is not generally useful. However, Clang C++ support
645 is under active development and is progressing rapidly. Please see the <a
646 href="http://clang.llvm.org/cxx_status.html">C++ Status</a> page for details or
647 ask on the mailing list about how you can help.</p>
649 <p>Note that the clang driver will refuse to even try to use clang to compile
650 C++ code unless you pass the <tt>-ccc-clang-cxx</tt> option to the driver. If
651 you really want to play with Clang's C++ support, please pass that flag. </p>
653 <!-- ======================================================================= -->
654 <h2 id="objcxx">Objective C++ Language Features</h2>
655 <!-- ======================================================================= -->
657 <p>At this point, Clang C++ support is not generally useful (and therefore,
658 neither is Objective-C++). Please see the <a href="#cxx">C++ section</a> for
659 more information.</p>
661 <!-- ======================================================================= -->
662 <h2 id="target_features">Target-Specific Features and Limitations</h2>
663 <!-- ======================================================================= -->
666 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
667 <h3 id="target_arch">CPU Architectures Features and Limitations</h3>
668 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
670 <!-- ======================== -->
671 <h4 id="target_arch_x86">X86</h4>
672 <!-- ======================== -->
675 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
676 <h3 id="target_os">Operating System Features and Limitations</h3>
677 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
679 <!-- ======================================= -->
680 <h4 id="target_os_darwin">Darwin (Mac OS/X)</h4>
681 <!-- ======================================= -->
683 <p>No __thread support, 64-bit ObjC support requires SL tools.</p>