clang(1)



CLANG(1)                             Clang                            CLANG(1)

NAME
       clang - the Clang C, C++, and Objective-C compiler

SYNOPSIS
       clang [options] filename

DESCRIPTION
       clang  is  a C, C++, and Objective-C compiler which encompasses prepro-
       cessing, parsing, optimization, code generation, assembly, and linking.
       Depending  on  which high-level mode setting is passed, Clang will stop
       before doing a full link.  While Clang is highly integrated, it is  im-
       portant  to  understand the stages of compilation, to understand how to
       invoke it.  These stages are:

       Driver The clang executable is actually a small driver  which  controls
              the  overall  execution of other tools such as the compiler, as-
              sembler and linker.  Typically you do not need to interact  with
              the driver, but you transparently use it to run the other tools.

       Preprocessing
              This  stage handles tokenization of the input source file, macro
              expansion, #include expansion and handling of other preprocessor
              directives.  The output of this stage is typically called a ".i"
              (for C), ".ii" (for C++), ".mi"  (for  Objective-C),  or  ".mii"
              (for Objective-C++) file.

       Parsing and Semantic Analysis
              This  stage  parses the input file, translating preprocessor to-
              kens into a parse tree.  Once in the form of a  parse  tree,  it
              applies  semantic  analysis  to compute types for expressions as
              well and determine whether the code is well formed.  This  stage
              is  responsible  for generating most of the compiler warnings as
              well as parse errors. The output of this stage is  an  "Abstract
              Syntax Tree" (AST).

       Code Generation and Optimization
              This  stage  translates  an AST into low-level intermediate code
              (known as "LLVM IR") and ultimately to machine code.  This phase
              is  responsible  for  optimizing the generated code and handling
              target-specific code generation.  The output of  this  stage  is
              typically called a ".s" file or "assembly" file.

              Clang also supports the use of an integrated assembler, in which
              the code generator produces object files directly.  This  avoids
              the overhead of generating the ".s" file and of calling the tar-
              get assembler.

       Assembler
              This stage runs the target assembler to translate the output  of
              the compiler into a target object file. The output of this stage
              is typically called a ".o" file or "object" file.

       Linker This stage runs the target linker to merge multiple object files
              into  an executable or dynamic library. The output of this stage
              is typically called an "a.out", ".dylib" or ".so" file.

       Clang Static Analyzer

       The Clang Static Analyzer is a tool that scans source code  to  try  to
       find  bugs  through  code analysis.  This tool uses many parts of Clang
       and   is   built   into   the   same    driver.     Please    see    <-
       http://clang-analyzer.llvm.org>  for  more  details  on  how to use the
       static analyzer.

OPTIONS
   Stage Selection Options
       -E     Run the preprocessor stage.

       -fsyntax-only
              Run the preprocessor, parser and type checking stages.

       -S     Run the previous stages as well as LLVM generation and optimiza-
              tion  stages  and  target-specific code generation, producing an
              assembly file.

       -c     Run all of the above, plus the assembler,  generating  a  target
              ".o" object file.

       no stage selection option
              If  no stage selection option is specified, all stages above are
              run, and the linker is run to combine the results into  an  exe-
              cutable or shared library.

   Language Selection and Mode Options
       -x <language>
              Treat subsequent input files as having type language.

       -std=<standard>
              Specify the language standard to compile for.

              Supported values for the C language are:
                 c89
                 c90
                 iso9899:1990

                     ISO C 1990
                 iso9899:199409

                     ISO C 1990 with amendment 1
                 gnu89
                 gnu90

                     ISO C 1990 with GNU extensions
                 c99
                 iso9899:1999

                     ISO C 1999
                 gnu99

                     ISO C 1999 with GNU extensions
                 c11
                 iso9899:2011

                     ISO C 2011
                 gnu11

                     ISO C 2011 with GNU extensions
                 c17
                 iso9899:2017

                     ISO C 2017
                 gnu17

                     ISO C 2017 with GNU extensions

              The  default  C language standard is gnu11, except on PS4, where
              it is gnu99.

              Supported values for the C++ language are:
                 c++98
                 c++03

                     ISO C++ 1998 with amendments
                 gnu++98
                 gnu++03

                     ISO C++ 1998 with amendments and GNU extensions
                 c++11

                     ISO C++ 2011 with amendments
                 gnu++11

                     ISO C++ 2011 with amendments and GNU extensions
                 c++14

                     ISO C++ 2014 with amendments
                 gnu++14

                     ISO C++ 2014 with amendments and GNU extensions
                 c++17

                     ISO C++ 2017 with amendments
                 gnu++17

                     ISO C++ 2017 with amendments and GNU extensions
                 c++2a

                     Working draft for ISO C++ 2020
                 gnu++2a

                     Working draft for ISO C++ 2020 with GNU extensions

              The default C++ language standard is gnu++14.

              Supported values for the OpenCL language are:
                 cl1.0

                     OpenCL 1.0
                 cl1.1

                     OpenCL 1.1
                 cl1.2

                     OpenCL 1.2
                 cl2.0

                     OpenCL 2.0

              The default OpenCL language standard is cl1.0.

              Supported values for the CUDA language are:
                 cuda

                     NVIDIA CUDA(tm)

       -stdlib=<library>
              Specify the C++ standard library to use; supported  options  are
              libstdc++ and libc++. If not specified, platform default will be
              used.

       -rtlib=<library>
              Specify the compiler runtime library to use;  supported  options
              are  libgcc  and compiler-rt. If not specified, platform default
              will be used.

       -ansi  Same as -std=c89.

       -ObjC, -ObjC++
              Treat source input files as Objective-C  and  Object-C++  inputs
              respectively.

       -trigraphs
              Enable trigraphs.

       -ffreestanding
              Indicate  that  the  file should be compiled for a freestanding,
              not a hosted, environment.

       -fno-builtin
              Disable special handling and optimizations of builtin  functions
              like strlen() and malloc().

       -fmath-errno
              Indicate  that  math functions should be treated as updating er-
              rno.

       -fpascal-strings
              Enable support for Pascal-style strings with "\pfoo".

       -fms-extensions
              Enable support for Microsoft extensions.

       -fmsc-version=
              Set _MSC_VER. Defaults to 1300 on Windows. Not set otherwise.

       -fborland-extensions
              Enable support for Borland extensions.

       -fwritable-strings
              Make all string literals default  to  writable.   This  disables
              uniquing of strings and other optimizations.

       -flax-vector-conversions
              Allow loose type checking rules for implicit vector conversions.

       -fblocks
              Enable the "Blocks" language feature.

       -fobjc-abi-version=version
              Select  the  Objective-C  ABI version to use. Available versions
              are 1 (legacy "fragile" ABI),  2  (non-fragile  ABI  1),  and  3
              (non-fragile ABI 2).

       -fobjc-nonfragile-abi-version=<version>
              Select  the  Objective-C  non-fragile  ABI version to use by de-
              fault. This will only be used as the Objective-C  ABI  when  the
              non-fragile ABI is enabled (either via -fobjc-nonfragile-abi, or
              because it is the platform default).

       -fobjc-nonfragile-abi, -fno-objc-nonfragile-abi
              Enable use of the Objective-C non-fragile ABI. On platforms  for
              which  this  is  the  default  ABI,  it  can  be  disabled  with
              -fno-objc-nonfragile-abi.

   Target Selection Options
       Clang fully supports cross compilation as an inherent part of  its  de-
       sign.   Depending  on  how  your version of Clang is configured, it may
       have support for a number of cross compilers, or may only support a na-
       tive target.

       -target <architecture>
              Specify the architecture to build for.

       -march=<cpu>
              Specify that Clang should generate code for a specific processor
              family  member  and  later.   For  example,   if   you   specify
              -march=i486,  the  compiler  is allowed to generate instructions
              that are valid on i486 and later processors, but which  may  not
              exist on earlier ones.

   Code Generation Options
       -O0, -O1, -O2, -O3, -Ofast, -Os, -Oz, -Og, -O, -O4
              Specify which optimization level to use:
                 -O0  Means "no optimization": this level compiles the fastest
                 and generates the most debuggable code.

                 -O1 Somewhere between -O0 and -O2.

                 -O2 Moderate level of optimization which enables  most  opti-
                 mizations.

                 -O3  Like -O2, except that it enables optimizations that take
                 longer to perform or that may generate larger code (in an at-
                 tempt to make the program run faster).

                 -Ofast  Enables  all  the  optimizations  from -O3 along with
                 other aggressive optimizations that may violate  strict  com-
                 pliance with language standards.

                 -Os Like -O2 with extra optimizations to reduce code size.

                 -Oz Like -Os (and thus -O2), but reduces code size further.

                 -Og  Like  -O1. In future versions, this option might disable
                 different optimizations in order to improve debuggability.

                 -O Equivalent to -O2.

                 -O4 and higher
                     Currently equivalent to -O3

       -g, -gline-tables-only, -gmodules
              Control debug information output.  Note that Clang debug  infor-
              mation  works  best  at -O0.  When more than one option starting
              with -g is specified, the last one wins:
                 -g Generate debug information.

                 -gline-tables-only Generate only line  table  debug  informa-
                 tion.  This  allows for symbolicated backtraces with inlining
                 information, but does not include any information about vari-
                 ables, their locations or types.

                 -gmodules  Generate  debug information that contains external
                 references to types defined in Clang modules  or  precompiled
                 headers  instead of emitting redundant debug type information
                 into every object file.  This option  transparently  switches
                 the  Clang  module format to object file containers that hold
                 the Clang module together with the debug  information.   When
                 compiling  a  program  that uses Clang modules or precompiled
                 headers, this option produces complete debug information with
                 faster compile times and much smaller object files.

                 This option should not be used when building static libraries
                 for distribution to other machines  because  the  debug  info
                 will  contain  references  to the module cache on the machine
                 the object files in the library were built on.

       -fstandalone-debug -fno-standalone-debug
              Clang supports a number of optimizations to reduce the  size  of
              debug  information in the binary. They work based on the assump-
              tion that the debug type information can be spread out over mul-
              tiple compilation units.  For instance, Clang will not emit type
              definitions for types that are not needed by a module and  could
              be  replaced  with  a  forward declaration.  Further, Clang will
              only emit type info for a dynamic C++ class in the  module  that
              contains the vtable for the class.

              The  -fstandalone-debug  option  turns  off these optimizations.
              This is useful when working with 3rd-party libraries that  don't
              come  with  debug  information.   This is the default on Darwin.
              Note that Clang will never emit type information for types  that
              are not referenced at all by the program.

       -fexceptions
              Enable  generation of unwind information. This allows exceptions
              to be thrown through Clang compiled stack frames.  This is on by
              default in x86-64.

       -ftrapv
              Generate  code to catch integer overflow errors.  Signed integer
              overflow is undefined in C. With this flag, extra code is gener-
              ated to detect this and abort when it happens.

       -fvisibility
              This flag sets the default visibility level.

       -fcommon, -fno-common
              This flag specifies that variables without initializers get com-
              mon linkage.  It can be disabled with -fno-common.

       -ftls-model=<model>
              Set the default thread-local storage  (TLS)  model  to  use  for
              thread-local variables. Valid values are: "global-dynamic", "lo-
              cal-dynamic", "initial-exec" and "local-exec".  The  default  is
              "global-dynamic".  The  default model can be overridden with the
              tls_model attribute. The compiler will try to choose a more  ef-
              ficient model if possible.

       -flto, -flto=full, -flto=thin, -emit-llvm
              Generate  output  files  in LLVM formats, suitable for link time
              optimization.  When used with -S this generates LLVM  intermedi-
              ate  language assembly files, otherwise this generates LLVM bit-
              code format object files (which may be passed to the linker  de-
              pending on the stage selection options).

              The  default  for  -flto is "full", in which the LLVM bitcode is
              suitable for monolithic Link Time Optimization (LTO), where  the
              linker merges all such modules into a single combined module for
              optimization. With "thin", ThinLTO compilation  is  invoked  in-
              stead.

   Driver Options
       -###   Print (but do not run) the commands to run for this compilation.

       --help Display available options.

       -Qunused-arguments
              Do not emit any warnings for unused driver arguments.

       -Wa,<args>
              Pass the comma separated arguments in args to the assembler.

       -Wl,<args>
              Pass the comma separated arguments in args to the linker.

       -Wp,<args>
              Pass the comma separated arguments in args to the preprocessor.

       -Xanalyzer <arg>
              Pass arg to the static analyzer.

       -Xassembler <arg>
              Pass arg to the assembler.

       -Xlinker <arg>
              Pass arg to the linker.

       -Xpreprocessor <arg>
              Pass arg to the preprocessor.

       -o <file>
              Write output to file.

       -print-file-name=<file>
              Print the full library path of file.

       -print-libgcc-file-name
              Print  the  library path for the currently used compiler runtime
              library ("libgcc.a" or "libclang_rt.builtins.*.a").

       -print-prog-name=<name>
              Print the full program path of name.

       -print-search-dirs
              Print the paths used for finding libraries and programs.

       -save-temps
              Save intermediate compilation results.

       -save-stats, -save-stats=cwd, -save-stats=obj
              Save internal code generation (LLVM) statistics to a file in the
              current  directory (-save-stats/"-save-stats=cwd") or the direc-
              tory of the output file ("-save-state=obj").

       -integrated-as, -no-integrated-as
              Used to enable and disable, respectively, the use of  the  inte-
              grated  assembler. Whether the integrated assembler is on by de-
              fault is target dependent.

       -time  Time individual commands.

       -ftime-report
              Print timing summary of each stage of compilation.

       -v     Show commands to run and use verbose output.

   Diagnostics Options
       -fshow-column, -fshow-source-location, -fcaret-diagnostics,  -fdiagnos-
       tics-fixit-info,       -fdiagnostics-parseable-fixits,       -fdiagnos-
       tics-print-source-range-info,   -fprint-source-range-info,   -fdiagnos-
       tics-show-option, -fmessage-length
              These options control how Clang prints out information about di-
              agnostics (errors and warnings). Please  see  the  Clang  User's
              Manual for more information.

   Preprocessor Options
       -D<macroname>=<value>
              Adds  an  implicit  #define  into the predefines buffer which is
              read before the source file is preprocessed.

       -U<macroname>
              Adds an implicit #undef into the predefines buffer which is read
              before the source file is preprocessed.

       -include <filename>
              Adds  an  implicit  #include into the predefines buffer which is
              read before the source file is preprocessed.

       -I<directory>
              Add the specified directory  to  the  search  path  for  include
              files.

       -F<directory>
              Add the specified directory to the search path for framework in-
              clude files.

       -nostdinc
              Do not  search  the  standard  system  directories  or  compiler
              builtin directories for include files.

       -nostdlibinc
              Do not search the standard system directories for include files,
              but do search compiler builtin include directories.

       -nobuiltininc
              Do not search clang's builtin directory for include files.

ENVIRONMENT
       TMPDIR, TEMP, TMP
              These environment variables are checked, in order, for the loca-
              tion  to  write  temporary  files  used  during  the compilation
              process.

       CPATH  If this environment variable is present, it is treated as a  de-
              limited  list of paths to be added to the default system include
              path list. The delimiter is the platform dependent delimiter, as
              used in the PATH environment variable.

              Empty components in the environment variable are ignored.

       C_INCLUDE_PATH,   OBJC_INCLUDE_PATH,  CPLUS_INCLUDE_PATH,  OBJCPLUS_IN-
       CLUDE_PATH
              These environment variables specify  additional  paths,  as  for
              CPATH,  which are only used when processing the appropriate lan-
              guage.

BUGS
       To report bugs, please visit <http://llvm.org/bugs/>.  Most bug reports
       should  include  preprocessed  source files (use the -E option) and the
       full output of the compiler, along with information to reproduce.

SEE ALSO
       as(1), ld(1)

AUTHOR
       Maintained by the Clang / LLVM Team (<http://clang.llvm.org>)

COPYRIGHT
       2007-2019, The Clang Team

7                                Feb 03, 2019                         CLANG(1)

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