1 =pod 2 3 =head1 NAME 4 5 clang - the Clang C, C++, and Objective-C compiler 6 7 =head1 SYNOPSIS 8 9 B<clang> [B<-c>|B<-S>|B<-E>] B<-std=>I<standard> B<-g> 10 [B<-O0>|B<-O1>|B<-O2>|B<-Os>|B<-O3>|B<-O4>] 11 B<-W>I<warnings...> B<-pedantic> 12 B<-I>I<dir...> B<-L>I<dir...> 13 B<-D>I<macro[=defn]> 14 B<-f>I<feature-option...> 15 B<-m>I<machine-option...> 16 B<-o> I<output-file> 17 B<-stdlib=>I<library> 18 I<input-filenames> 19 20 =head1 DESCRIPTION 21 22 B<clang> is a C, C++, and Objective-C compiler which encompasses preprocessing, 23 parsing, optimization, code generation, assembly, and linking. Depending on 24 which high-level mode setting is passed, Clang will stop before doing a full 25 link. While Clang is highly integrated, it is important to understand the 26 stages of compilation, to understand how to invoke it. These stages are: 27 28 =over 29 30 =item B<Driver> 31 32 The B<clang> executable is actually a small driver which controls the overall 33 execution of other tools such as the compiler, assembler and linker. Typically 34 you do not need to interact with the driver, but you transparently use it to run 35 the other tools. 36 37 =item B<Preprocessing> 38 39 This stage handles tokenization of the input source file, macro expansion, 40 #include expansion and handling of other preprocessor directives. The output of 41 this stage is typically called a ".i" (for C), ".ii" (for C++), ".mi" (for 42 Objective-C) , or ".mii" (for Objective-C++) file. 43 44 =item B<Parsing and Semantic Analysis> 45 46 This stage parses the input file, translating preprocessor tokens into a parse 47 tree. Once in the form of a parser tree, it applies semantic analysis to compute 48 types for expressions as well and determine whether the code is well formed. This 49 stage is responsible for generating most of the compiler warnings as well as 50 parse errors. The output of this stage is an "Abstract Syntax Tree" (AST). 51 52 =item B<Code Generation and Optimization> 53 54 This stage translates an AST into low-level intermediate code (known as "LLVM 55 IR") and ultimately to machine code. This phase is responsible for optimizing 56 the generated code and handling target-specific code generation. The output of 57 this stage is typically called a ".s" file or "assembly" file. 58 59 Clang also supports the use of an integrated assembler, in which the code 60 generator produces object files directly. This avoids the overhead of generating 61 the ".s" file and of calling the target assembler. 62 63 =item B<Assembler> 64 65 This stage runs the target assembler to translate the output of the compiler 66 into a target object file. The output of this stage is typically called a ".o" 67 file or "object" file. 68 69 =item B<Linker> 70 71 This stage runs the target linker to merge multiple object files into an 72 executable or dynamic library. The output of this stage is typically called an 73 "a.out", ".dylib" or ".so" file. 74 75 =back 76 77 The Clang compiler supports a large number of options to control each of these 78 stages. In addition to compilation of code, Clang also supports other tools: 79 80 B<Clang Static Analyzer> 81 82 The Clang Static Analyzer is a tool that scans source code to try to find bugs 83 through code analysis. This tool uses many parts of Clang and is built into the 84 same driver. 85 86 87 =head1 OPTIONS 88 89 =head2 Stage Selection Options 90 91 =over 92 93 =item B<-E> 94 95 Run the preprocessor stage. 96 97 =item B<-fsyntax-only> 98 99 Run the preprocessor, parser and type checking stages. 100 101 =item B<-S> 102 103 Run the previous stages as well as LLVM generation and optimization stages and 104 target-specific code generation, producing an assembly file. 105 106 =item B<-c> 107 108 Run all of the above, plus the assembler, generating a target ".o" object file. 109 110 =item B<no stage selection option> 111 112 If no stage selection option is specified, all stages above are run, and the 113 linker is run to combine the results into an executable or shared library. 114 115 =item B<--analyze> 116 117 Run the Clang Static Analyzer. 118 119 =back 120 121 122 123 =head2 Language Selection and Mode Options 124 125 =over 126 127 =item B<-x> I<language> 128 129 Treat subsequent input files as having type I<language>. 130 131 =item B<-std>=I<language> 132 133 Specify the language standard to compile for. 134 135 =item B<-stdlib>=I<language> 136 137 Specify the C++ standard library to use; supported options are libstdc++ and 138 libc++. 139 140 =item B<-ansi> 141 142 Same as B<-std=c89>. 143 144 =item B<-ObjC++> 145 146 Treat source input files as Objective-C++ inputs. 147 148 =item B<-ObjC> 149 150 Treat source input files as Objective-C inputs. 151 152 =item B<-trigraphs> 153 154 Enable trigraphs. 155 156 =item B<-ffreestanding> 157 158 Indicate that the file should be compiled for a freestanding, not a hosted, 159 environment. 160 161 =item B<-fno-builtin> 162 163 Disable special handling and optimizations of builtin functions like strlen and 164 malloc. 165 166 =item B<-fmath-errno> 167 168 Indicate that math functions should be treated as updating errno. 169 170 =item B<-fpascal-strings> 171 172 Enable support for Pascal-style strings with "\pfoo". 173 174 =item B<-fms-extensions> 175 176 Enable support for Microsoft extensions. 177 178 =item B<-fmsc-version=> 179 180 Set _MSC_VER. Defaults to 1300 on Windows. Not set otherwise. 181 182 =item B<-fborland-extensions> 183 184 Enable support for Borland extensions. 185 186 =item B<-fwritable-strings> 187 188 Make all string literals default to writable. This disables uniquing of 189 strings and other optimizations. 190 191 =item B<-flax-vector-conversions> 192 193 Allow loose type checking rules for implicit vector conversions. 194 195 =item B<-fblocks> 196 197 Enable the "Blocks" language feature. 198 199 =item B<-fobjc-gc-only> 200 201 Indicate that Objective-C code should be compiled in GC-only mode, which only 202 works when Objective-C Garbage Collection is enabled. 203 204 =item B<-fobjc-gc> 205 206 Indicate that Objective-C code should be compiled in hybrid-GC mode, which works 207 with both GC and non-GC mode. 208 209 =item B<-fobjc-abi-version>=I<version> 210 211 Select the Objective-C ABI version to use. Available versions are 1 (legacy 212 "fragile" ABI), 2 (non-fragile ABI 1), and 3 (non-fragile ABI 2). 213 214 =item B<-fobjc-nonfragile-abi-version>=I<version> 215 216 Select the Objective-C non-fragile ABI version to use by default. This will only 217 be used as the Objective-C ABI when the non-fragile ABI is enabled (either via 218 -fobjc-nonfragile-abi, or because it is the platform default). 219 220 =item B<-fobjc-nonfragile-abi> 221 222 Enable use of the Objective-C non-fragile ABI. On platforms for which this is 223 the default ABI, it can be disabled with B<-fno-objc-nonfragile-abi>. 224 225 =back 226 227 228 229 =head2 Target Selection Options 230 231 Clang fully supports cross compilation as an inherent part of its design. 232 Depending on how your version of Clang is configured, it may have support for 233 a number of cross compilers, or may only support a native target. 234 235 =over 236 237 =item B<-arch> I<architecture> 238 239 Specify the architecture to build for. 240 241 =item B<-mmacosx-version-min>=I<version> 242 243 When building for Mac OS/X, specify the minimum version supported by your 244 application. 245 246 =item B<-miphoneos-version-min> 247 248 When building for iPhone OS, specify the minimum version supported by your 249 application. 250 251 252 =item B<-march>=I<cpu> 253 254 Specify that Clang should generate code for a specific processor family member 255 and later. For example, if you specify -march=i486, the compiler is allowed to 256 generate instructions that are valid on i486 and later processors, but which 257 may not exist on earlier ones. 258 259 =back 260 261 262 =head2 Code Generation Options 263 264 =over 265 266 =item B<-O0> B<-O1> B<-O2> B<-Os> B<-O3> B<-O4> 267 268 Specify which optimization level to use. B<-O0> means "no optimization": this 269 level compiles the fastest and generates the most debuggable code. B<-O2> is a 270 moderate level of optimization which enables most optimizations. B<-Os> is like 271 B<-O2> with extra optimizations to reduce code size. B<-O3> is like B<-O2>, 272 except that it enables optimizations that take longer to perform or that may 273 generate larger code (in an attempt to make the program run faster). On 274 supported platforms, B<-O4> enables link-time optimization; object files are 275 stored in the LLVM bitcode file format and whole program optimization is done at 276 link time. B<-O1> is somewhere between B<-O0> and B<-O2>. 277 278 =item B<-g> 279 280 Generate debug information. Note that Clang debug information works best at 281 B<-O0>. At higher optimization levels, only line number information is 282 currently available. 283 284 =item B<-fexceptions> 285 286 Enable generation of unwind information, this allows exceptions to be thrown 287 through Clang compiled stack frames. This is on by default in x86-64. 288 289 =item B<-ftrapv> 290 291 Generate code to catch integer overflow errors. Signed integer overflow is 292 undefined in C, with this flag, extra code is generated to detect this and abort 293 when it happens. 294 295 296 =item B<-fvisibility> 297 298 This flag sets the default visibility level. 299 300 =item B<-fcommon> 301 302 This flag specifies that variables without initializers get common linkage. It 303 can be disabled with B<-fno-common>. 304 305 =item B<-ftls-model> 306 307 Set the default thread-local storage (TLS) model to use for thread-local 308 variables. Valid values are: "global-dynamic", "local-dynamic", "initial-exec" 309 and "local-exec". The default is "global-dynamic". The default model can be 310 overridden with the tls_model attribute. The compiler will try to choose a more 311 efficient model if possible. 312 313 =item B<-flto> B<-emit-llvm> 314 315 Generate output files in LLVM formats, suitable for link time optimization. When 316 used with B<-S> this generates LLVM intermediate language assembly files, 317 otherwise this generates LLVM bitcode format object files (which may be passed 318 to the linker depending on the stage selection options). 319 320 =cut 321 322 ##=item B<-fnext-runtime> B<-fobjc-nonfragile-abi> B<-fgnu-runtime> 323 ##These options specify which Objective-C runtime the code generator should 324 ##target. FIXME: we don't want people poking these generally. 325 326 =pod 327 328 =back 329 330 331 =head2 Driver Options 332 333 =over 334 335 =item B<-###> 336 337 Print the commands to run for this compilation. 338 339 =item B<--help> 340 341 Display available options. 342 343 =item B<-Qunused-arguments> 344 345 Don't emit warning for unused driver arguments. 346 347 =item B<-Wa,>I<args> 348 349 Pass the comma separated arguments in I<args> to the assembler. 350 351 =item B<-Wl,>I<args> 352 353 Pass the comma separated arguments in I<args> to the linker. 354 355 =item B<-Wp,>I<args> 356 357 Pass the comma separated arguments in I<args> to the preprocessor. 358 359 =item B<-Xanalyzer> I<arg> 360 361 Pass I<arg> to the static analyzer. 362 363 =item B<-Xassembler> I<arg> 364 365 Pass I<arg> to the assembler. 366 367 =item B<-Xlinker> I<arg> 368 369 Pass I<arg> to the linker. 370 371 =item B<-Xpreprocessor> I<arg> 372 373 Pass I<arg> to the preprocessor. 374 375 =item B<-o> I<file> 376 377 Write output to I<file>. 378 379 =item B<-print-file-name>=I<file> 380 381 Print the full library path of I<file>. 382 383 =item B<-print-libgcc-file-name> 384 385 Print the library path for "libgcc.a". 386 387 =item B<-print-prog-name>=I<name> 388 389 Print the full program path of I<name>. 390 391 =item B<-print-search-dirs> 392 393 Print the paths used for finding libraries and programs. 394 395 =item B<-save-temps> 396 397 Save intermediate compilation results. 398 399 =item B<-integrated-as> B<-no-integrated-as> 400 401 Used to enable and disable, respectively, the use of the integrated 402 assembler. Whether the integrated assembler is on by default is target 403 dependent. 404 405 =item B<-time> 406 407 Time individual commands. 408 409 =item B<-ftime-report> 410 411 Print timing summary of each stage of compilation. 412 413 =item B<-v> 414 415 Show commands to run and use verbose output. 416 417 =back 418 419 420 =head2 Diagnostics Options 421 422 =over 423 424 =item B<-fshow-column> 425 B<-fshow-source-location> 426 B<-fcaret-diagnostics> 427 B<-fdiagnostics-fixit-info> 428 B<-fdiagnostics-parseable-fixits> 429 B<-fdiagnostics-print-source-range-info> 430 B<-fprint-source-range-info> 431 B<-fdiagnostics-show-option> 432 B<-fmessage-length> 433 434 These options control how Clang prints out information about diagnostics (errors 435 and warnings). Please see the Clang User's Manual for more information. 436 437 =back 438 439 440 =head2 Preprocessor Options 441 442 =over 443 444 =item B<-D>I<macroname=value> 445 446 Adds an implicit #define into the predefines buffer which is read before the 447 source file is preprocessed. 448 449 =item B<-U>I<macroname> 450 451 Adds an implicit #undef into the predefines buffer which is read before the 452 source file is preprocessed. 453 454 =item B<-include> I<filename> 455 456 Adds an implicit #include into the predefines buffer which is read before the 457 source file is preprocessed. 458 459 =item B<-I>I<directory> 460 461 Add the specified directory to the search path for include files. 462 463 =item B<-F>I<directory> 464 465 Add the specified directory to the search path for framework include files. 466 467 =item B<-nostdinc> 468 469 Do not search the standard system directories or compiler builtin directories 470 for include files. 471 472 =item B<-nostdlibinc> 473 474 Do not search the standard system directories for include files, but do search 475 compiler builtin include directories. 476 477 =item B<-nobuiltininc> 478 479 Do not search clang's builtin directory for include files. 480 481 =cut 482 483 ## TODO, but do we really want people using this stuff? 484 #=item B<-idirafter>I<directory> 485 #=item B<-iquote>I<directory> 486 #=item B<-isystem>I<directory> 487 #=item B<-iprefix>I<directory> 488 #=item B<-iwithprefix>I<directory> 489 #=item B<-iwithprefixbefore>I<directory> 490 #=item B<-isysroot> 491 492 =pod 493 494 495 =back 496 497 498 499 =cut 500 501 ### TODO someday. 502 #=head2 Warning Control Options 503 #=over 504 #=back 505 #=head2 Code Generation and Optimization Options 506 #=over 507 #=back 508 #=head2 Assembler Options 509 #=over 510 #=back 511 #=head2 Linker Options 512 #=over 513 #=back 514 #=head2 Static Analyzer Options 515 #=over 516 #=back 517 518 =pod 519 520 521 =head1 ENVIRONMENT 522 523 =over 524 525 =item B<TMPDIR>, B<TEMP>, B<TMP> 526 527 These environment variables are checked, in order, for the location to 528 write temporary files used during the compilation process. 529 530 =item B<CPATH> 531 532 If this environment variable is present, it is treated as a delimited 533 list of paths to be added to the default system include path list. The 534 delimiter is the platform dependent delimitor, as used in the I<PATH> 535 environment variable. 536 537 Empty components in the environment variable are ignored. 538 539 =item B<C_INCLUDE_PATH>, B<OBJC_INCLUDE_PATH>, B<CPLUS_INCLUDE_PATH>, 540 B<OBJCPLUS_INCLUDE_PATH> 541 542 These environment variables specify additional paths, as for CPATH, 543 which are only used when processing the appropriate language. 544 545 =item B<MACOSX_DEPLOYMENT_TARGET> 546 547 If -mmacosx-version-min is unspecified, the default deployment target 548 is read from this environment variable. This option only affects darwin 549 targets. 550 551 =back 552 553 =head1 BUGS 554 555 To report bugs, please visit L<http://llvm.org/bugs/>. Most bug reports should 556 include preprocessed source files (use the B<-E> option) and the full output of 557 the compiler, along with information to reproduce. 558 559 =head1 SEE ALSO 560 561 as(1), ld(1) 562 563 =head1 AUTHOR 564 565 Maintained by the Clang / LLVM Team (L<http://clang.llvm.org>). 566 567 =cut 568