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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    <-
       https://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 gnu17, 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. Note that it is assumed that a	 free-
	      standing	environment will additionally provide memcpy, memmove,
	      memset and memcmp	implementations, as these are needed for effi-
	      cient codegen for	many programs.

       -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,	      -flax-vector-conversions=<kind>,
       -fno-lax-vector-conversions
	      Allow loose type checking	rules for implicit vector conversions.
	      Possible values of <kind>:

	      o	none: allow no implicit	conversions between vectors

	      o	integer: allow implicit	bitcasts between  integer  vectors  of
		the same overall bit-width

	      o	all:  allow  implicit bitcasts between any vectors of the same
		overall	bit-width

	      <kind> defaults to integer if unspecified.

       -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.

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

       -mmacosx-version-min=<version>
	      When building for	macOS, specify the minimum  version  supported
	      by your application.

       -miphoneos-version-min
	      When  building  for  iPhone OS, specify the minimum version sup-
	      ported by	your application.

       --print-supported-cpus
	      Print out	a list of supported processors for  the	 given	target
	      (specified  through  --target=<architecture> or -arch <architec-
	      ture>). If no target is specified,  the  system  default	target
	      will be used.

       -mcpu=?,	-mtune=?
	      Acts as an alias for --print-supported-cpus.

       -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 -O1.

		 -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.

       -feliminate-unused-debug-types
	      By  default, Clang does not emit type information	for types that
	      are defined but not used in a program. To	retain the debug  info
	      for  these  unused types,	the negation -fno-eliminate-unused-de-
	      bug-types	can be used.

       -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.

	      NOTE:
		 On Darwin, when using -flto along with	-g and	compiling  and
		 linking  in  separate	steps,	you also need to pass -Wl,-ob-
		 ject_path_lto,<lto-filename>.o	at the	linking	 step  to  in-
		 struct	 the  ld64  linker  not	to delete the temporary	object
		 file generated	during Link Time Optimization  (this  flag  is
		 automatically	passed	to  the	linker by Clang	if compilation
		 and linking are done in a single step). This allows debugging
		 the  executable  as well as generating	the .dSYM bundle using
		 dsymutil(1).

   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.

       MACOSX_DEPLOYMENT_TARGET
	      If  -mmacosx-version-min	is unspecified,	the default deployment
	      target is	read from this environment variable. This option  only
	      affects Darwin targets.

BUGS
       To  report  bugs,  please visit <https://bugs.llvm.org/>.  Most bug re-
       ports 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
       2007-2021, The Clang Team

12				  2021-06-07			      CLANG(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | BUGS | SEE ALSO | AUTHOR | COPYRIGHT

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