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4 .TH "CLANG" "1" "Dec 24, 2017" "6" "Clang"
6 clang \- the Clang C, C++, and Objective-C compiler
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36 \fBclang\fP [\fIoptions\fP] \fIfilename ...\fP
39 \fBclang\fP is a C, C++, and Objective\-C compiler which encompasses
40 preprocessing, parsing, optimization, code generation, assembly, and linking.
41 Depending on which high\-level mode setting is passed, Clang will stop before
42 doing a full link. While Clang is highly integrated, it is important to
43 understand the stages of compilation, to understand how to invoke it. These
48 The clang executable is actually a small driver which controls the overall
49 execution of other tools such as the compiler, assembler and linker.
50 Typically you do not need to interact with the driver, but you
51 transparently use it to run the other tools.
54 This stage handles tokenization of the input source file, macro expansion,
55 #include expansion and handling of other preprocessor directives. The
56 output of this stage is typically called a ".i" (for C), ".ii" (for C++),
57 ".mi" (for Objective\-C), or ".mii" (for Objective\-C++) file.
59 .B Parsing and Semantic Analysis
60 This stage parses the input file, translating preprocessor tokens into a
61 parse tree. Once in the form of a parse tree, it applies semantic
62 analysis to compute types for expressions as well and determine whether
63 the code is well formed. This stage is responsible for generating most of
64 the compiler warnings as well as parse errors. The output of this stage is
65 an "Abstract Syntax Tree" (AST).
67 .B Code Generation and Optimization
68 This stage translates an AST into low\-level intermediate code (known as
69 "LLVM IR") and ultimately to machine code. This phase is responsible for
70 optimizing the generated code and handling target\-specific code generation.
71 The output of this stage is typically called a ".s" file or "assembly" file.
73 Clang also supports the use of an integrated assembler, in which the code
74 generator produces object files directly. This avoids the overhead of
75 generating the ".s" file and of calling the target assembler.
78 This stage runs the target assembler to translate the output of the
79 compiler into a target object file. The output of this stage is typically
80 called a ".o" file or "object" file.
83 This stage runs the target linker to merge multiple object files into an
84 executable or dynamic library. The output of this stage is typically called
85 an "a.out", ".dylib" or ".so" file.
88 \fBClang Static Analyzer\fP
90 The Clang Static Analyzer is a tool that scans source code to try to find bugs
91 through code analysis. This tool uses many parts of Clang and is built into
92 the same driver. Please see <\fI\%http://clang\-analyzer.llvm.org\fP> for more details
93 on how to use the static analyzer.
95 .SS Stage Selection Options
99 Run the preprocessor stage.
104 Run the preprocessor, parser and type checking stages.
109 Run the previous stages as well as LLVM generation and optimization stages
110 and target\-specific code generation, producing an assembly file.
115 Run all of the above, plus the assembler, generating a target ".o" object file.
119 .B no stage selection option
120 If no stage selection option is specified, all stages above are run, and the
121 linker is run to combine the results into an executable or shared library.
123 .SS Language Selection and Mode Options
127 Treat subsequent input files as having type language.
132 Specify the language standard to compile for.
136 .B \-stdlib=<library>
137 Specify the C++ standard library to use; supported options are libstdc++ and
138 libc++. If not specified, platform default will be used.
143 Specify the compiler runtime library to use; supported options are libgcc and
144 compiler\-rt. If not specified, platform default will be used.
154 Treat source input files as Objective\-C and Object\-C++ inputs respectively.
164 Indicate that the file should be compiled for a freestanding, not a hosted,
170 Disable special handling and optimizations of builtin functions like
171 \fBstrlen()\fP and \fBmalloc()\fP\&.
176 Indicate that math functions should be treated as updating \fBerrno\fP\&.
180 .B \-fpascal\-strings
181 Enable support for Pascal\-style strings with "\epfoo".
186 Enable support for Microsoft extensions.
191 Set _MSC_VER. Defaults to 1300 on Windows. Not set otherwise.
195 .B \-fborland\-extensions
196 Enable support for Borland extensions.
200 .B \-fwritable\-strings
201 Make all string literals default to writable. This disables uniquing of
202 strings and other optimizations.
206 .B \-flax\-vector\-conversions
207 Allow loose type checking rules for implicit vector conversions.
212 Enable the "Blocks" language feature.
216 .B \-fobjc\-abi\-version=version
217 Select the Objective\-C ABI version to use. Available versions are 1 (legacy
218 "fragile" ABI), 2 (non\-fragile ABI 1), and 3 (non\-fragile ABI 2).
222 .B \-fobjc\-nonfragile\-abi\-version=<version>
223 Select the Objective\-C non\-fragile ABI version to use by default. This will
224 only be used as the Objective\-C ABI when the non\-fragile ABI is enabled
225 (either via \fI\%\-fobjc\-nonfragile\-abi\fP, or because it is the platform
230 .B \-fobjc\-nonfragile\-abi, \-fno\-objc\-nonfragile\-abi
231 Enable use of the Objective\-C non\-fragile ABI. On platforms for which this is
232 the default ABI, it can be disabled with \fI\%\-fno\-objc\-nonfragile\-abi\fP\&.
234 .SS Target Selection Options
236 Clang fully supports cross compilation as an inherent part of its design.
237 Depending on how your version of Clang is configured, it may have support for a
238 number of cross compilers, or may only support a native target.
241 .B \-arch <architecture>
242 Specify the architecture to build for.
246 .B \-mmacosx\-version\-min=<version>
247 When building for Mac OS X, specify the minimum version supported by your
252 .B \-miphoneos\-version\-min
253 When building for iPhone OS, specify the minimum version supported by your
259 Specify that Clang should generate code for a specific processor family
260 member and later. For example, if you specify \-march=i486, the compiler is
261 allowed to generate instructions that are valid on i486 and later processors,
262 but which may not exist on earlier ones.
264 .SS Code Generation Options
267 .B \-O0, \-O1, \-O2, \-O3, \-Ofast, \-Os, \-Oz, \-Og, \-O, \-O4
268 Specify which optimization level to use:
271 \fI\%\-O0\fP Means "no optimization": this level compiles the fastest and
272 generates the most debuggable code.
274 \fI\%\-O1\fP Somewhere between \fI\%\-O0\fP and \fI\%\-O2\fP\&.
276 \fI\%\-O2\fP Moderate level of optimization which enables most
279 \fI\%\-O3\fP Like \fI\%\-O2\fP, except that it enables optimizations that
280 take longer to perform or that may generate larger code (in an attempt to
281 make the program run faster).
283 \fI\%\-Ofast\fP Enables all the optimizations from \fI\%\-O3\fP along
284 with other aggressive optimizations that may violate strict compliance with
287 \fI\%\-Os\fP Like \fI\%\-O2\fP with extra optimizations to reduce code
290 \fI\%\-Oz\fP Like \fI\%\-Os\fP (and thus \fI\%\-O2\fP), but reduces code
293 \fI\%\-Og\fP Like \fI\%\-O1\fP\&. In future versions, this option might
294 disable different optimizations in order to improve debuggability.
296 \fI\%\-O\fP Equivalent to \fI\%\-O2\fP\&.
298 \fI\%\-O4\fP and higher
301 Currently equivalent to \fI\%\-O3\fP
309 .B \-g, \-gline\-tables\-only, \-gmodules
310 Control debug information output. Note that Clang debug information works
311 best at \fI\%\-O0\fP\&. When more than one option starting with \fI\-g\fP is
312 specified, the last one wins:
315 \fB\-g\fP Generate debug information.
317 \fB\-gline\-tables\-only\fP Generate only line table debug information. This
318 allows for symbolicated backtraces with inlining information, but does not
319 include any information about variables, their locations or types.
321 \fI\%\-gmodules\fP Generate debug information that contains external
322 references to types defined in Clang modules or precompiled headers instead
323 of emitting redundant debug type information into every object file. This
324 option transparently switches the Clang module format to object file
325 containers that hold the Clang module together with the debug information.
326 When compiling a program that uses Clang modules or precompiled headers,
327 this option produces complete debug information with faster compile
328 times and much smaller object files.
330 This option should not be used when building static libraries for
331 distribution to other machines because the debug info will contain
332 references to the module cache on the machine the object files in the
333 library were built on.
339 .B \-fstandalone\-debug \-fno\-standalone\-debug
340 Clang supports a number of optimizations to reduce the size of debug
341 information in the binary. They work based on the assumption that the
342 debug type information can be spread out over multiple compilation units.
343 For instance, Clang will not emit type definitions for types that are not
344 needed by a module and could be replaced with a forward declaration.
345 Further, Clang will only emit type info for a dynamic C++ class in the
346 module that contains the vtable for the class.
348 The \fB\-fstandalone\-debug\fP option turns off these optimizations.
349 This is useful when working with 3rd\-party libraries that don\(aqt come with
350 debug information. This is the default on Darwin. Note that Clang will
351 never emit type information for types that are not referenced at all by the
357 Enable generation of unwind information. This allows exceptions to be thrown
358 through Clang compiled stack frames. This is on by default in x86\-64.
363 Generate code to catch integer overflow errors. Signed integer overflow is
364 undefined in C. With this flag, extra code is generated to detect this and
365 abort when it happens.
370 This flag sets the default visibility level.
374 .B \-fcommon, \-fno\-common
375 This flag specifies that variables without initializers get common linkage.
376 It can be disabled with \fI\%\-fno\-common\fP\&.
380 .B \-ftls\-model=<model>
381 Set the default thread\-local storage (TLS) model to use for thread\-local
382 variables. Valid values are: "global\-dynamic", "local\-dynamic",
383 "initial\-exec" and "local\-exec". The default is "global\-dynamic". The default
384 model can be overridden with the tls_model attribute. The compiler will try
385 to choose a more efficient model if possible.
389 .B \-flto, \-flto=full, \-flto=thin, \-emit\-llvm
390 Generate output files in LLVM formats, suitable for link time optimization.
391 When used with \fI\%\-S\fP this generates LLVM intermediate language
392 assembly files, otherwise this generates LLVM bitcode format object files
393 (which may be passed to the linker depending on the stage selection options).
395 The default for \fI\%\-flto\fP is "full", in which the
396 LLVM bitcode is suitable for monolithic Link Time Optimization (LTO), where
397 the linker merges all such modules into a single combined module for
398 optimization. With "thin", ThinLTO
399 compilation is invoked instead.
405 Print (but do not run) the commands to run for this compilation.
410 Display available options.
414 .B \-Qunused\-arguments
415 Do not emit any warnings for unused driver arguments.
420 Pass the comma separated arguments in args to the assembler.
425 Pass the comma separated arguments in args to the linker.
430 Pass the comma separated arguments in args to the preprocessor.
435 Pass arg to the static analyzer.
439 .B \-Xassembler <arg>
440 Pass arg to the assembler.
445 Pass arg to the linker.
449 .B \-Xpreprocessor <arg>
450 Pass arg to the preprocessor.
455 Write output to file.
459 .B \-print\-file\-name=<file>
460 Print the full library path of file.
464 .B \-print\-libgcc\-file\-name
465 Print the library path for the currently used compiler runtime library
466 ("libgcc.a" or "libclang_rt.builtins.*.a").
470 .B \-print\-prog\-name=<name>
471 Print the full program path of name.
475 .B \-print\-search\-dirs
476 Print the paths used for finding libraries and programs.
481 Save intermediate compilation results.
485 .B \-save\-stats, \-save\-stats=cwd, \-save\-stats=obj
486 Save internal code generation (LLVM) statistics to a file in the current
487 directory (\fI\%\-save\-stats\fP/"\-save\-stats=cwd") or the directory
488 of the output file ("\-save\-state=obj").
492 .B \-integrated\-as, \-no\-integrated\-as
493 Used to enable and disable, respectively, the use of the integrated
494 assembler. Whether the integrated assembler is on by default is target
500 Time individual commands.
505 Print timing summary of each stage of compilation.
510 Show commands to run and use verbose output.
512 .SS Diagnostics Options
515 .B \-fshow\-column, \-fshow\-source\-location, \-fcaret\-diagnostics, \-fdiagnostics\-fixit\-info, \-fdiagnostics\-parseable\-fixits, \-fdiagnostics\-print\-source\-range\-info, \-fprint\-source\-range\-info, \-fdiagnostics\-show\-option, \-fmessage\-length
516 These options control how Clang prints out information about diagnostics
517 (errors and warnings). Please see the Clang User\(aqs Manual for more information.
519 .SS Preprocessor Options
522 .B \-D<macroname>=<value>
523 Adds an implicit #define into the predefines buffer which is read before the
524 source file is preprocessed.
529 Adds an implicit #undef into the predefines buffer which is read before the
530 source file is preprocessed.
534 .B \-include <filename>
535 Adds an implicit #include into the predefines buffer which is read before the
536 source file is preprocessed.
541 Add the specified directory to the search path for include files.
546 Add the specified directory to the search path for framework include files.
551 Do not search the standard system directories or compiler builtin directories
557 Do not search the standard system directories for include files, but do
558 search compiler builtin include directories.
563 Do not search clang\(aqs builtin directory for include files.
569 These environment variables are checked, in order, for the location to write
570 temporary files used during the compilation process.
575 If this environment variable is present, it is treated as a delimited list of
576 paths to be added to the default system include path list. The delimiter is
577 the platform dependent delimiter, as used in the PATH environment variable.
579 Empty components in the environment variable are ignored.
583 .B C_INCLUDE_PATH, OBJC_INCLUDE_PATH, CPLUS_INCLUDE_PATH, OBJCPLUS_INCLUDE_PATH
584 These environment variables specify additional paths, as for \fI\%CPATH\fP, which are
585 only used when processing the appropriate language.
589 .B MACOSX_DEPLOYMENT_TARGET
590 If \fI\%\-mmacosx\-version\-min\fP is unspecified, the default deployment
591 target is read from this environment variable. This option only affects
596 To report bugs, please visit <\fI\%http://llvm.org/bugs/\fP>. Most bug reports should
597 include preprocessed source files (use the \fI\%\-E\fP option) and the full
598 output of the compiler, along with information to reproduce.
601 \fBas(1)\fP, \fBld(1)\fP
603 Maintained by the Clang / LLVM Team (<http://clang.llvm.org>)
605 2007-2017, The Clang Team
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