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GCC(1)					       GNU					   GCC(1)

NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
	   [-g] [-pg] [-Olevel]
	   [-Wwarn...] [-pedantic]
	   [-Idir...] [-Ldir...]
	   [-Dmacro[=defn]...] [-Umacro]
	   [-foption...] [-mmachine-option...]
	   [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the remainder.  g++ accepts
       mostly the same options as gcc.

       In Apple's version of GCC, both cc and gcc are actually symbolic links to a compiler named
       like gcc-version.  Similarly, c++ and g++ are links to a compiler named like g++-version.

       Note that Apple's GCC includes a number of extensions to standard GCC (flagged below with
       "APPLE ONLY"), and that not all generic GCC options are available or supported on Darwin /
       Mac OS X.  In particular, Apple does not currently support the compilation of Fortran,
       Ada, or Java, although there are third parties who have made these work.

DESCRIPTION
       When you invoke GCC, it normally does preprocessing, compilation, assembly and linking.
       The "overall options" allow you to stop this process at an intermediate stage.  For
       example, the -c option says not to run the linker.  Then the output consists of object
       files output by the assembler.

       Other options are passed on to one stage of processing.	Some options control the
       preprocessor and others the compiler itself.  Yet other options control the assembler and
       linker; most of these are not documented here, since you rarely need to use any of them.

       Most of the command line options that you can use with GCC are useful for C programs; when
       an option is only useful with another language (usually C++), the explanation says so
       explicitly.  If the description for a particular option does not mention a source
       language, you can use that option with all supported languages.

       The gcc program accepts options and file names as operands.  Many options have multi-
       letter names; therefore multiple single-letter options may not be grouped: -dr is very
       different from -d -r.

       You can mix options and other arguments.  For the most part, the order you use doesn't
       matter.	Order does matter when you use several options of the same kind; for example, if
       you specify -L more than once, the directories are searched in the order specified.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both positive and negative
       forms; the negative form of -ffoo would be -fno-foo.  This manual documents only one of
       these two forms, whichever one is not the default.

OPTIONS
       Option Summary

       Here is a summary of all the options, grouped by type.  Explanations are in the following
       sections.

       Overall Options
	   -c  -S  -E  -o file	-combine -pipe	-pass-exit-codes -ObjC (APPLE ONLY) -ObjC++
	   (APPLE ONLY) -arch arch (APPLE ONLY) -Xarch_arch option (APPLE ONLY)
	   -fsave-repository=file -x language  -v  -###  --help  --target-help	--version @file

       C Language Options
	   -ansi  -std=standard  -fgnu89-inline -aux-info filename -faltivec (APPLE ONLY)
	   -fasm-blocks (APPLE ONLY) -fno-asm  -fno-builtin  -fno-builtin-function -fhosted
	   -ffreestanding -fopenmp -fms-extensions -trigraphs  -no-integrated-cpp  -traditional
	   -traditional-cpp -fallow-single-precision  -fcond-mismatch -flax-vector-conversions
	   -fconstant-cfstrings (APPLE ONLY) -fnon-lvalue-assign (APPLE ONLY)
	   -fno-nested-functions -fpch-preprocess (APPLE ONLY) -fsigned-bitfields  -fsigned-char
	   -Wno-#warnings (APPLE ONLY) -Wextra-tokens (APPLE ONLY) -Wnewline-eof (APPLE ONLY)
	   -Wno-altivec-long-deprecated (APPLE ONLY) -fglobal-alloc-prefer-bytes (APPLE ONLY)
	   -fno-global-alloc-prefer-bytes (APPLE ONLY) -funsigned-bitfields  -funsigned-char
	   -fwritable-strings

       C++ Language Options
	   -fabi-version=n  -fno-access-control  -fcheck-new -fconserve-space  -ffriend-injection
	   -fno-elide-constructors -fno-enforce-eh-specs -ffor-scope  -fno-for-scope
	   -fno-gnu-keywords -fno-implicit-templates -fno-implicit-inline-templates
	   -fno-implement-inlines  -fms-extensions -fno-nonansi-builtins  -fno-operator-names
	   -fno-optional-diags	-fpermissive -frepo  -fno-rtti	-fstats  -ftemplate-depth-n
	   -fno-threadsafe-statics -fuse-cxa-atexit  -fno-weak	-nostdinc++ -fno-default-inline
	   -fvisibility-inlines-hidden -fvisibility-ms-compat -Wabi  -Wctor-dtor-privacy
	   -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wno-deprecated  -Wstrict-null-sentinel
	   -Wno-non-template-friend  -Wold-style-cast -Woverloaded-virtual  -Wno-pmf-conversions
	   -Wsign-promo

       Objective-C and Objective-C++ Language Options
	   -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime -fno-nil-receivers
	   -fobjc-call-cxx-cdtors -fobjc-direct-dispatch -fobjc-sjlj-exceptions -fobjc-gc
	   -freplace-objc-classes -fzero-link -gen-decls -Wassign-intercept -Wno-protocol
	   -Wselector -Wno-property-assign-default -Wstrict-selector-match -Wundeclared-selector

       Language Independent Options
	   -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
	   -fdiagnostics-show-option

       Warning Options
	   -fsyntax-only  -pedantic  -pedantic-errors -w  -Wextra  -Wall  -Waddress
	   -Waggregate-return -Wno-attributes -Wc++-compat -Wcast-align  -Wcast-qual
	   -Wchar-subscripts  -Wcomment -Wconversion  -Wno-deprecated-declarations
	   -Wdisabled-optimization  -Wno-div-by-zero  -Wno-endif-labels -Werror  -Werror=*
	   -Werror-implicit-function-declaration -Wfatal-errors  -Wfloat-equal	-Wno-format
	   -Wformat=2 -Wno-format-extra-args -Wformat-nonliteral -Wno-format-security
	   -Wformat-y2k -Wglobal-constructors -Wimplicit  -Wimplicit-function-declaration
	   -Wimplicit-int -Wimport  -Wno-import  -Winit-self  -Winline -Wno-int-to-pointer-cast
	   -Wno-invalid-offsetof  -Winvalid-pch -Wlarger-than-len  -Wunsafe-loop-optimizations
	   -Wlong-long -Wmain  -Wmissing-braces  -Wmissing-field-initializers
	   -Wmissing-format-attribute  -Wmissing-include-dirs -Wmissing-noreturn
	   -Wmissing-prototypes -Wmost (APPLE ONLY) -Wno-multichar  -Wnonnull  -Wno-overflow
	   -Woverlength-strings  -Wpacked  -Wpadded -Wparentheses  -Wpointer-arith
	   -Wno-pointer-to-int-cast -Wredundant-decls -Wreturn-type  -Wsequence-point  -Wshadow
	   -Wsign-compare  -Wstack-protector -Wstrict-aliasing -Wstrict-aliasing=2
	   -Wstrict-overflow -Wstrict-overflow=n -Wswitch  -Wswitch-default  -Wswitch-enum
	   -Wsystem-headers  -Wtrigraphs  -Wundef  -Wuninitialized -Wunknown-pragmas
	   -Wno-pragmas -Wunreachable-code -Wunused  -Wunused-function	-Wunused-label
	   -Wunused-parameter -Wunused-value  -Wunused-variable  -Wvariadic-macros
	   -Wvolatile-register-var  -Wwrite-strings

       C-only Warning Options
	   -Wbad-function-cast	-Wmissing-declarations -Wnested-externs  -Wold-style-definition
	   -Wstrict-prototypes	-Wtraditional -Wdeclaration-after-statement -Wno-discard-qual
	   -Wno-pointer-sign

       Debugging Options
	   -dletters  -dumpspecs  -dumpmachine	-dumpversion -fdump-noaddr -fdump-unnumbered
	   -fdump-translation-unit[-n] -fdump-class-hierarchy[-n] -fdump-ipa-all
	   -fdump-ipa-cgraph -fdump-tree-all -fdump-tree-original[-n] -fdump-tree-optimized[-n]
	   -fdump-tree-inlined[-n] -fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias
	   -fdump-tree-ch -fdump-tree-ssa[-n] -fdump-tree-pre[-n] -fdump-tree-ccp[-n]
	   -fdump-tree-dce[-n] -fdump-tree-gimple[-raw] -fdump-tree-mudflap[-n]
	   -fdump-tree-dom[-n] -fdump-tree-dse[-n] -fdump-tree-phiopt[-n]
	   -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n] -fdump-tree-nrv -fdump-tree-vect
	   -fdump-tree-sink -fdump-tree-sra[-n] -fdump-tree-salias -fdump-tree-fre[-n]
	   -fdump-tree-vrp[-n] -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n]
	   -flimit-debug-info -feliminate-dwarf2-dups -feliminate-unused-debug-types
	   -feliminate-unused-debug-symbols -femit-class-debug-always -fmem-report -fopt-diary
	   -fprofile-arcs -frandom-seed=string -fsched-verbose=n -ftest-coverage  -ftime-report
	   -fvar-tracking -g  -glevel  -gcoff -gdwarf-2 -ggdb  -gstabs	-gstabs+  -gvms  -gxcoff
	   -gxcoff+ -p	-pg  -print-file-name=library  -print-libgcc-file-name
	   -print-multi-directory  -print-multi-lib -print-prog-name=program  -print-search-dirs
	   -Q -save-temps  -time

       Optimization Options
	   -falign-functions=n	-falign-jumps=n -falign-labels=n  -falign-loops=n
	   -falign-loops-max-skip=n -falign-jumps-max-skip=n -fbounds-check -fmudflap -fmudflapth
	   -fmudflapir -fbranch-probabilities -fprofile-values -fvpt
	   -fbranch-target-load-optimize -fbranch-target-load-optimize2 -fbtr-bb-exclusive
	   -fcaller-saves  -fcprop-registers  -fcreate-profile -fcse-follow-jumps
	   -fcse-skip-blocks  -fcx-limited-range  -fdata-sections -fdelayed-branch
	   -fdelete-null-pointer-checks -fearly-inlining -fexpensive-optimizations  -ffast-math
	   -ffloat-store -fforce-addr  -ffunction-sections -fgcse  -fgcse-lm  -fgcse-sm
	   -fgcse-las  -fgcse-after-reload -fcrossjumping  -fif-conversion  -fif-conversion2
	   -finline-functions  -finline-functions-called-once -finline-limit=n
	   -fkeep-inline-functions -fkeep-static-consts -flocal-alloc (APPLE ONLY)
	   -fmerge-constants  -fmerge-all-constants -fmodulo-sched -fno-branch-count-reg
	   -fno-default-inline	-fno-defer-pop -fmove-loop-invariants -fno-function-cse
	   -fno-guess-branch-probability -fno-inline  -fno-math-errno  -fno-peephole
	   -fno-peephole2 -funsafe-math-optimizations  -funsafe-loop-optimizations
	   -ffinite-math-only -fno-toplevel-reorder -fno-trapping-math
	   -fno-zero-initialized-in-bss -mstackrealign -fomit-frame-pointer
	   -foptimize-register-move -foptimize-sibling-calls  -fprefetch-loop-arrays
	   -fprofile-generate -fprofile-use -fregmove  -frename-registers -freorder-blocks
	   -freorder-blocks-and-partition -freorder-functions -frerun-cse-after-loop
	   -frounding-math -frtl-abstract-sequences -fschedule-insns  -fschedule-insns2
	   -fno-sched-interblock  -fno-sched-spec  -fsched-spec-load -fsched-spec-load-dangerous
	   -fsched-stalled-insns=n -fsched-stalled-insns-dep=n -fsched2-use-superblocks
	   -fsched2-use-traces -fsee -freschedule-modulo-scheduled-loops -fsection-anchors
	   -fsignaling-nans  -fsingle-precision-constant -fstack-protector  -fstack-protector-all
	   -fstrict-aliasing  -fstrict-overflow  -ftracer  -fthread-jumps -funroll-all-loops
	   -funroll-loops  -fpeel-loops -fsplit-ivs-in-unroller -funswitch-loops
	   -fvariable-expansion-in-unroller -ftree-pre	-ftree-ccp  -ftree-dce
	   -ftree-loop-optimize -ftree-loop-linear -ftree-loop-im -ftree-loop-ivcanon -fivopts
	   -ftree-dominator-opts -ftree-dse -ftree-copyrename -ftree-sink -ftree-ch -ftree-sra
	   -ftree-ter -ftree-lrs -ftree-fre -ftree-vectorize -ftree-vect-loop-version
	   -ftree-salias -fuse-profile -fipa-pta -fweb -ftree-copy-prop -ftree-store-ccp
	   -ftree-store-copy-prop -fwhole-program --param name=value -O  -O0  -O1  -O2	-O3  -Os
	   -Oz (APPLE ONLY) -fast (APPLE ONLY)

       Preprocessor Options
	   -Aquestion=answer -A-question[=answer] -C  -dD  -dI	-dM  -dN -Dmacro[=defn]  -E  -H
	   -idirafter dir -include file  -imacros file -iprefix file  -iwithprefix dir
	   -iwithprefixbefore dir  -isystem dir -imultilib dir -isysroot dir -iwithsysroot (APPLE
	   ONLY) dir -M  -MM  -MF  -MG	-MP  -MQ  -MT  -nostdinc -P  -fworking-directory  -remap
	   -trigraphs  -undef  -Umacro	-Wp,option -Xpreprocessor option

       Assembler Option
	   -Wa,option  -Xassembler option

       Linker Options
	   object-file-name  -llibrary -nostartfiles  -nodefaultlibs  -nostdlib -pie -rdynamic -s
	   -static  -static-libgcc  -shared  -shared-libgcc  -symbolic -Wl,option  -Xlinker
	   option -u symbol

       Directory Options
	   -Bprefix  -Idir  -iquotedir	-Ldir -specs=file  -I- --sysroot=dir

       Target Options
	   -V version  -b machine

       Machine Dependent Options
	   ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name -mapcs-stack-check
	   -mno-apcs-stack-check -mapcs-float  -mno-apcs-float -mapcs-reentrant
	   -mno-apcs-reentrant -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian
	   -mwords-little-endian -mfloat-abi=name  -msoft-float  -mhard-float  -mfpe
	   -mthumb-interwork  -mno-thumb-interwork -mcpu=name  -march=name  -mfpu=name
	   -mstructure-size-boundary=n -mabort-on-noreturn -mlong-calls  -mno-long-calls
	   -msingle-pic-base  -mno-single-pic-base -mpic-register=reg -mnop-fun-dllimport
	   -mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns -mpoke-function-name -mthumb
	   -marm -mtpcs-frame  -mtpcs-leaf-frame -mcaller-super-interworking
	   -mcallee-super-interworking -mtp=name -mms-bitfields -mno-ms-bitfields

	   CRX Options -mmac -mpush-args

	   Darwin Options -all_load  -allowable_client	-arch  -arch_errors_fatal -arch_only
	   -bind_at_load  -bundle  -bundle_loader -client_name	-compatibility_version
	   -current_version -dead_strip -dependency-file  -dylib_file  -dylinker_install_name
	   -dynamic  -dynamiclib  -exported_symbols_list -filelist  -flat_namespace
	   -force_cpusubtype_ALL -force_flat_namespace	-headerpad_max_install_names -iframework
	   -image_base	-init  -install_name  -keep_private_externs -multi_module
	   -multiply_defined  -multiply_defined_unused -noall_load
	   -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs  -noprebind
	   -noseglinkedit -pagezero_size  -prebind  -prebind_all_twolevel_modules -private_bundle
	   -read_only_relocs  -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
	   -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr -segs_read_write_addr
	   -seg_addr_table  -seg_addr_table_filename  -seglinkedit -segprot  -segs_read_only_addr
	   -segs_read_write_addr -single_module  -static  -sub_library	-sub_umbrella
	   -twolevel_namespace	-umbrella  -undefined -unexported_symbols_list
	   -weak_reference_mismatches -whatsloaded -F -gused -gfull -mmacosx-version-min=version
	   -miphoneos-version-min=version -mpascal-strings (APPLE ONLY) -mkernel -mone-byte-bool
	   -Xarch_arch

	   i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type -mfpmath=unit -masm=dialect
	   -mno-fancy-math-387 -mno-fp-ret-in-387  -msoft-float  -msvr3-shlib -mno-wide-multiply
	   -mrtd  -malign-double -mpreferred-stack-boundary=num -mmmx  -msse  -msse2 -msse3
	   -mssse3 -msse4.1 -msse4.2 -msse4 -msse4a -mthreads  -mno-align-stringops
	   -minline-all-stringops -mpush-args  -maccumulate-outgoing-args  -m128bit-long-double
	   -m96bit-long-double	-mregparm=num  -msseregparm -mstackrealign
	   -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs -mcmodel=code-model
	   -m32  -m64 -mlarge-data-threshold=num -mms-bitfields -mno-ms-bitfields

	   PowerPC Options See RS/6000 and PowerPC Options.

	   RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mpower  -mno-power
	   -mpower2  -mno-power2 -mpowerpc  -mpowerpc64  -mno-powerpc -maltivec  -mno-altivec
	   -mpim-altivec -mno-pim-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
	   -mno-powerpc-gfxopt -mmfcrf	-mno-mfcrf  -mpopcntb  -mno-popcntb  -mfprnd  -mno-fprnd
	   -mnew-mnemonics  -mold-mnemonics -mfull-toc	 -mminimal-toc	-mno-fp-in-toc
	   -mno-sum-in-toc -m64  -m32  -mxl-compat  -mno-xl-compat  -mpe -malign-power
	   -malign-natural -msoft-float  -mhard-float  -mmultiple  -mno-multiple -mstring
	   -mno-string	-mupdate  -mno-update -mfused-madd  -mno-fused-madd  -mbit-align
	   -mno-bit-align -mstrict-align  -mno-strict-align  -mrelocatable -mno-relocatable
	   -mrelocatable-lib  -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian
	   -mbig  -mbig-endian -mdynamic-no-pic  -maltivec  -mswdiv
	   -mprioritize-restricted-insns=priority -msched-costly-dep=dependence_type
	   -minsert-sched-nops=scheme -mcall-sysv  -mcall-netbsd -maix-struct-return
	   -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt -misel -mno-isel -misel=yes
	   -misel=no -mspe -mno-spe -mspe=yes  -mspe=no -mvrsave -mno-vrsave -mmulhw -mno-mulhw
	   -mdlmzb -mno-dlmzb -mfloat-gprs=yes	-mfloat-gprs=no -mfloat-gprs=single
	   -mfloat-gprs=double -mprototype  -mno-prototype -msim  -mmvme  -mads  -myellowknife
	   -memb  -msdata -msdata=opt  -mvxworks  -mwindiss  -G num  -pthread -mms-bitfields
	   -mno-ms-bitfields

       Code Generation Options
	   -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions -fnon-call-exceptions
	   -funwind-tables -fasynchronous-unwind-tables -finhibit-size-directive
	   -finstrument-functions -fno-common  -fno-ident -fpcc-struct-return  -fpic  -fPIC -fpie
	   -fPIE -fno-jump-tables -freg-struct-return  -fshort-enums -fshort-double
	   -fshort-wchar -fverbose-asm	-fpack-struct[=n]  -fstack-check
	   -fstack-limit-register=reg  -fstack-limit-symbol=sym -fargument-alias
	   -fargument-noalias -fargument-noalias-global  -fargument-noalias-anything
	   -fleading-underscore  -ftls-model=model -fwrapv  -fbounds-check -fvisibility

       Options Controlling the Kind of Output

       Compilation can involve up to four stages: preprocessing, compilation proper, assembly and
       linking, always in that order.  GCC is capable of preprocessing and compiling several
       files either into several assembler input files, or into one assembler input file; then
       each assembler input file produces an object file, and linking combines all the object
       files (those newly compiled, and those specified as input) into an executable file.

       For any given input file, the file name suffix determines what kind of compilation is
       done:

       file.c
	   C source code which must be preprocessed.

       file.i
	   C source code which should not be preprocessed.

       file.ii
	   C++ source code which should not be preprocessed.

       file.m
	   Objective-C source code.  Note that you must link with the libobjc library to make an
	   Objective-C program work.

       file.mi
	   Objective-C source code which should not be preprocessed.

       file.mm
       file.M
	   Objective-C++ source code.  Note that you must link with the libobjc library to make
	   an Objective-C++ program work.  Note that .M refers to a literal capital M.

       file.mii
	   Objective-C++ source code which should not be preprocessed.

       file.h
	   C, C++, Objective-C or Objective-C++ header file to be turned into a precompiled
	   header.

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
	   C++ source code which must be preprocessed.	Note that in .cxx, the last two letters
	   must both be literally x.  Likewise, .C refers to a literal capital C.

       file.hh
       file.H
	   C++ header file to be turned into a precompiled header.

       file.f
       file.for
       file.FOR
	   Fixed form Fortran source code which should not be preprocessed.

       file.F
       file.fpp
       file.FPP
	   Fixed form Fortran source code which must be preprocessed (with the traditional
	   preprocessor).

       file.f90
       file.f95
	   Free form Fortran source code which should not be preprocessed.

       file.F90
       file.F95
	   Free form Fortran source code which must be preprocessed (with the traditional
	   preprocessor).

       file.ads
	   Ada source code file which contains a library unit declaration (a declaration of a
	   package, subprogram, or generic, or a generic instantiation), or a library unit
	   renaming declaration (a package, generic, or subprogram renaming declaration).  Such
	   files are also called specs.

       file.adb
	   Ada source code file containing a library unit body (a subprogram or package body).
	   Such files are also called bodies.

       file.s
	   Assembler code.  Apple's version of GCC runs the preprocessor on these files as well
	   as those ending in .S.

       file.S
	   Assembler code which must be preprocessed.

       other
	   An object file to be fed straight into linking.  Any file name with no recognized
	   suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
	   Specify explicitly the language for the following input files (rather than letting the
	   compiler choose a default based on the file name suffix).  This option applies to all
	   following input files until the next -x option.  Possible values for language are:

		   c  c-header	c-cpp-output
		   c++	c++-header  c++-cpp-output
		   objective-c	objective-c-header  objective-c-cpp-output
		   objective-c++ objective-c++-header objective-c++-cpp-output
		   assembler  assembler-with-cpp
		   ada
		   f95	f95-cpp-input
		   java
		   treelang

       -x none
	   Turn off any specification of a language, so that subsequent files are handled
	   according to their file name suffixes (as they are if -x has not been used at all).

       -ObjC
       -ObjC++
	   These are similar in effect to -x objective-c and -x objective-c++, but affect only
	   the choice of compiler for files already identified as source files.  (APPLE ONLY)

       -arch arch
	   Compile for the specified target architecture arch.	The allowable values are i386,
	   x86_64, ppc and ppc64.  Multiple options work, and direct the compiler to produce
	   "universal" binaries including object code for each architecture specified with -arch.
	   This option only works if assembler and libraries are available for each architecture
	   specified.  (APPLE ONLY)

       -Xarch_arch option
	   Apply option to the command line for architecture arch.  This is useful for specifying
	   an option that should only apply to one architecture when building a "universal"
	   binary.  (APPLE ONLY)

       -fsave-repository=file
	   Save debug info in separate object file.  This is available only while building PCH in
	   -gfull mode.

       -pass-exit-codes
	   Normally the gcc program will exit with the code of 1 if any phase of the compiler
	   returns a non-success return code.  If you specify -pass-exit-codes, the gcc program
	   will instead return with numerically highest error produced by any phase that returned
	   an error indication.  The C, C++, and Fortran frontends return 4, if an internal
	   compiler error is encountered.

       If you only want some of the stages of compilation, you can use -x (or filename suffixes)
       to tell gcc where to start, and one of the options -c, -S, or -E to say where gcc is to
       stop.  Note that some combinations (for example, -x cpp-output -E) instruct gcc to do
       nothing at all.

       -c  Compile or assemble the source files, but do not link.  The linking stage simply is
	   not done.  The ultimate output is in the form of an object file for each source file.

	   By default, the object file name for a source file is made by replacing the suffix .c,
	   .i, .s, etc., with .o.

	   Unrecognized input files, not requiring compilation or assembly, are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The output is in the
	   form of an assembler code file for each non-assembler input file specified.

	   By default, the assembler file name for a source file is made by replacing the suffix
	   .c, .i, etc., with .s.

	   Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.	The output is in
	   the form of preprocessed source code, which is sent to the standard output.

	   Input files which don't require preprocessing are ignored.

       -o file
	   Place output in file file.  This applies regardless to whatever sort of output is
	   being produced, whether it be an executable file, an object file, an assembler file or
	   preprocessed C code.

	   If -o is not specified, the default is to put an executable file in a.out, the object
	   file for source.suffix in source.o, its assembler file in source.s, a precompiled
	   header file in source.suffix.gch, and all preprocessed C source on standard output.

       -v  Print (on standard error output) the commands executed to run the stages of
	   compilation.  Also print the version number of the compiler driver program and of the
	   preprocessor and the compiler proper.

       -###
	   Like -v except the commands are not executed and all command arguments are quoted.
	   This is useful for shell scripts to capture the driver-generated command lines.

       -pipe
	   Use pipes rather than temporary files for communication between the various stages of
	   compilation.  This fails to work on some systems where the assembler is unable to read
	   from a pipe; but the GNU assembler has no trouble.

       -combine
	   If you are compiling multiple source files, this option tells the driver to pass all
	   the source files to the compiler at once (for those languages for which the compiler
	   can handle this).  This will allow intermodule analysis (IMA) to be performed by the
	   compiler.  Currently the only language for which this is supported is C.  If you pass
	   source files for multiple languages to the driver, using this option, the driver will
	   invoke the compiler(s) that support IMA once each, passing each compiler all the
	   source files appropriate for it.  For those languages that do not support IMA this
	   option will be ignored, and the compiler will be invoked once for each source file in
	   that language.  If you use this option in conjunction with -save-temps, the compiler
	   will generate multiple pre-processed files (one for each source file), but only one
	   (combined) .o or .s file.

       --help
	   Print (on the standard output) a description of the command line options understood by
	   gcc.  If the -v option is also specified then --help will also be passed on to the
	   various processes invoked by gcc, so that they can display the command line options
	   they accept.  If the -Wextra option is also specified then command line options which
	   have no documentation associated with them will also be displayed.

       --target-help
	   Print (on the standard output) a description of target specific command line options
	   for each tool.

       --version
	   Display the version number and copyrights of the invoked GCC.

       @file
	   Read command-line options from file.  The options read are inserted in place of the
	   original @file option.  If file does not exist, or cannot be read, then the option
	   will be treated literally, and not removed.

	   Options in file are separated by whitespace.  A whitespace character may be included
	   in an option by surrounding the entire option in either single or double quotes.  Any
	   character (including a backslash) may be included by prefixing the character to be
	   included with a backslash.  The file may itself contain additional @file options; any
	   such options will be processed recursively.

       Compiling C++ Programs

       C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP, .c++, .cp, or
       .cxx; C++ header files often use .hh or .H; and preprocessed C++ files use the suffix .ii.
       GCC recognizes files with these names and compiles them as C++ programs even if you call
       the compiler the same way as for compiling C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program that calls GCC and
       treats .c, .h and .i files as C++ source files instead of C source files unless -x is
       used, and automatically specifies linking against the C++ library.  This program is also
       useful when precompiling a C header file with a .h extension for use in C++ compilations.
       On many systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same command-line options that
       you use for compiling programs in any language; or command-line options meaningful for C
       and related languages; or options that are meaningful only for C++ programs.

       Options Controlling C Dialect

       The following options control the dialect of C (or languages derived from C, such as C++,
       Objective-C and Objective-C++) that the compiler accepts:

       -ansi
	   In C mode, support all ISO C90 programs.  In C++ mode, remove GNU extensions that
	   conflict with ISO C++.

	   This turns off certain features of GCC that are incompatible with ISO C90 (when
	   compiling C code), or of standard C++ (when compiling C++ code), such as the "asm" and
	   "typeof" keywords, and predefined macros such as "unix" and "vax" that identify the
	   type of system you are using.  It also enables the undesirable and rarely used ISO
	   trigraph feature.  For the C compiler, it disables recognition of C++ style //
	   comments as well as the "inline" keyword.

	   The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__"
	   continue to work despite -ansi.  You would not want to use them in an ISO C program,
	   of course, but it is useful to put them in header files that might be included in
	   compilations done with -ansi.  Alternate predefined macros such as "__unix__" and
	   "__vax__" are also available, with or without -ansi.

	   The -ansi option does not cause non-ISO programs to be rejected gratuitously.  For
	   that, -pedantic is required in addition to -ansi.

	   The macro "__STRICT_ANSI__" is predefined when the -ansi option is used.  Some header
	   files may notice this macro and refrain from declaring certain functions or defining
	   certain macros that the ISO standard doesn't call for; this is to avoid interfering
	   with any programs that might use these names for other things.

	   Functions which would normally be built in but do not have semantics defined by ISO C
	   (such as "alloca" and "ffs") are not built-in functions with -ansi is used.

       -std=
	   Determine the language standard.  This option is currently only supported when
	   compiling C or C++.	A value for this option must be provided; possible values are

	   c89
	   iso9899:1990
	       ISO C90 (same as -ansi).

	   iso9899:199409
	       ISO C90 as modified in amendment 1.

	   c99
	   c9x
	   iso9899:1999
	   iso9899:199x
	       ISO C99.  Note that this standard is not yet fully supported; see
	       <http://gcc.gnu.org/gcc-4.2/c99status.html> for more information.  The names c9x
	       and iso9899:199x are deprecated.

	   gnu89
	       Default, ISO C90 plus GNU extensions (including some C99 features).

	   gnu99
	   gnu9x
	       ISO C99 plus GNU extensions.  When ISO C99 is fully implemented in GCC, this will
	       become the default.  The name gnu9x is deprecated.

	   c++98
	       The 1998 ISO C++ standard plus amendments.

	   gnu++98
	       The same as -std=c++98 plus GNU extensions.  This is the default for C++ code.

	   Even when this option is not specified, you can still use some of the features of
	   newer standards in so far as they do not conflict with previous C standards.  For
	   example, you may use "__restrict__" even when -std=c99 is not specified.

	   The -std options specifying some version of ISO C have the same effects as -ansi,
	   except that features that were not in ISO C90 but are in the specified version (for
	   example, // comments and the "inline" keyword in ISO C99) are not disabled.

       -fgnu89-inline
	   The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline"
	   functions when in C99 mode.
	     Using this option is roughly equivalent to adding the "gnu_inline" function
	   attribute to all inline functions.

	   This option is accepted by GCC versions 4.1.3 and up.  In GCC versions /* APPLE LOCAL
	   extern inline */ prior to 4.3 (4.2 for Apple's gcc), C99 inline semantics are not
	   supported, and thus this option is effectively assumed to be present regardless of
	   whether or not it is specified; the only effect of specifying it explicitly is to
	   disable warnings about using inline functions in C99 mode.  Likewise, the option
	   -fno-gnu89-inline is not supported in versions of /* APPLE LOCAL extern inline */ GCC
	   before 4.3 (4.2 for Apple's gcc).  It is supported only in C99 or gnu99 mode, not in
	   C89 or gnu89 mode.

	   The preprocesor macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be used to
	   check which semantics are in effect for "inline" functions.

       -aux-info filename
	   Output to the given filename prototyped declarations for all functions declared and/or
	   defined in a translation unit, including those in header files.  This option is
	   silently ignored in any language other than C.

	   Besides declarations, the file indicates, in comments, the origin of each declaration
	   (source file and line), whether the declaration was implicit, prototyped or
	   unprototyped (I, N for new or O for old, respectively, in the first character after
	   the line number and the colon), and whether it came from a declaration or a definition
	   (C or F, respectively, in the following character).	In the case of function
	   definitions, a K&R-style list of arguments followed by their declarations is also
	   provided, inside comments, after the declaration.

       -faltivec
	   This flag is provided for compatibility with Metrowerks CodeWarrior and MrC compilers
	   as well as previous Apple versions of GCC.  It causes the -mpim-altivec option to be
	   turned on.

       -fasm-blocks
	   Enable the use of blocks and entire functions of assembly code within a C or C++ file.
	   The syntax follows that used in CodeWarrior. (APPLE ONLY)

       -fno-asm
	   Do not recognize "asm", "inline" or "typeof" as a keyword, so that code can use these
	   words as identifiers.  You can use the keywords "__asm__", "__inline__" and
	   "__typeof__" instead.  -ansi implies -fno-asm.

	   In C++, this switch only affects the "typeof" keyword, since "asm" and "inline" are
	   standard keywords.  You may want to use the -fno-gnu-keywords flag instead, which has
	   the same effect.  In C99 mode (-std=c99 or -std=gnu99), this switch only affects the
	   "asm" and "typeof" keywords, since "inline" is a standard keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
	   Don't recognize built-in functions that do not begin with __builtin_ as prefix.

	   GCC normally generates special code to handle certain built-in functions more
	   efficiently; for instance, calls to "alloca" may become single instructions that
	   adjust the stack directly, and calls to "memcpy" may become inline copy loops.  The
	   resulting code is often both smaller and faster, but since the function calls no
	   longer appear as such, you cannot set a breakpoint on those calls, nor can you change
	   the behavior of the functions by linking with a different library.  In addition, when
	   a function is recognized as a built-in function, GCC may use information about that
	   function to warn about problems with calls to that function, or to generate more
	   efficient code, even if the resulting code still contains calls to that function.  For
	   example, warnings are given with -Wformat for bad calls to "printf", when "printf" is
	   built in, and "strlen" is known not to modify global memory.

	   With the -fno-builtin-function option only the built-in function function is disabled.
	   function must not begin with __builtin_.  If a function is named this is not built-in
	   in this version of GCC, this option is ignored.  There is no corresponding
	   -fbuiltin-function option; if you wish to enable built-in functions selectively when
	   using -fno-builtin or -ffreestanding, you may define macros such as:

		   #define abs(n)	   __builtin_abs ((n))
		   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fhosted
	   Assert that compilation takes place in a hosted environment.  This implies -fbuiltin.
	   A hosted environment is one in which the entire standard library is available, and in
	   which "main" has a return type of "int".  Examples are nearly everything except a
	   kernel.  This is equivalent to -fno-freestanding.

       -ffreestanding
	   Assert that compilation takes place in a freestanding environment.  This implies
	   -fno-builtin.  A freestanding environment is one in which the standard library may not
	   exist, and program startup may not necessarily be at "main".  The most obvious example
	   is an OS kernel.  This is equivalent to -fno-hosted.

       -fopenmp
	   Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran.
	   When -fopenmp is specified, the compiler generates parallel code according to the
	   OpenMP Application Program Interface v2.5 <http://www.openmp.org/>.

       -fms-extensions
	   Accept some non-standard constructs used in Microsoft header files.

	   Some cases of unnamed fields in structures and unions are only accepted with this
	   option.

       -trigraphs
	   Support ISO C trigraphs.  The -ansi option (and -std options for strict ISO C
	   conformance) implies -trigraphs.

       -no-integrated-cpp
	   Performs a compilation in two passes: preprocessing and compiling.  This option allows
	   a user supplied "cc1", "cc1plus", or "cc1obj" via the -B option.  The user supplied
	   compilation step can then add in an additional preprocessing step after normal
	   preprocessing but before compiling.	The default is to use the integrated cpp
	   (internal cpp)

	   The semantics of this option will change if "cc1", "cc1plus", and "cc1obj" are merged.

       -traditional
       -traditional-cpp
	   Formerly, these options caused GCC to attempt to emulate a pre-standard C compiler.
	   They are now only supported with the -E switch.  The preprocessor continues to support
	   a pre-standard mode.  See the GNU CPP manual for details.

       -fcond-mismatch
	   Allow conditional expressions with mismatched types in the second and third arguments.
	   The value of such an expression is void.  This option is not supported for C++.

       -fno-nested-functions
	   Disable nested functions.  This option is not supported for C++ or Objective-C++.  On
	   Darwin, nested functions are disabled by default.

       -fpch-preprocess
	   Enable PCH processing even when -E or -save-temps is used.

       -fnon-lvalue-assign
	   C and C++ forbid the use of casts and conditional expressions as lvalues, e.g.:

		   float *p, q, r;
		   ((int *)p)++;
		   (cond ? q : r) = 3.0;

	   As a transitional measure, the Apple version of GCC 4.0 allows casts and conditional
	   expressions to be used as lvalues in certain situations.  This is accomplished via the
	   -fnon-lvalue-assign switch, which is on by default.	Whenever an lvalue cast or an
	   lvalue conditional expression is encountered, the compiler will issue a deprecation
	   warning and then rewrite the expression as follows:

		   (type)expr		     ---becomes--->	 *(type *)&expr
		   cond ? expr1 : expr2      ---becomes--->	 *(cond ? &expr1 : &expr2)

	   To disallow lvalue casts and lvalue conditional expressions altogether, specify
	   -fno-non-lvalue-assign; lvalue casts and lvalue conditional expressions will be
	   disallowed in future versions of Apple's GCC.

       -flax-vector-conversions
	   Allow implicit conversions between vectors with differing numbers of elements and/or
	   incompatible element types.	This option should not be used for new code.

       -funsigned-char
	   Let the type "char" be unsigned, like "unsigned char".

	   Each kind of machine has a default for what "char" should be.  It is either like
	   "unsigned char" by default or like "signed char" by default.

	   Ideally, a portable program should always use "signed char" or "unsigned char" when it
	   depends on the signedness of an object.  But many programs have been written to use
	   plain "char" and expect it to be signed, or expect it to be unsigned, depending on the
	   machines they were written for.  This option, and its inverse, let you make such a
	   program work with the opposite default.

	   The type "char" is always a distinct type from each of "signed char" or "unsigned
	   char", even though its behavior is always just like one of those two.

       -fsigned-char
	   Let the type "char" be signed, like "signed char".

	   Note that this is equivalent to -fno-unsigned-char, which is the negative form of
	   -funsigned-char.  Likewise, the option -fno-signed-char is equivalent to
	   -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
	   These options control whether a bit-field is signed or unsigned, when the declaration
	   does not use either "signed" or "unsigned".	By default, such a bit-field is signed,
	   because this is consistent: the basic integer types such as "int" are signed types.

       -fconstant-cfstrings
	   Enable the automatic creation of a CoreFoundation-type constant string whenever a
	   special builtin "__builtin__CFStringMakeConstantString" is called on a literal string.
	   (APPLE ONLY)

       -Wnonportable-cfstrings
	   Warn if constant CFString objects contain non-portable characters (default behavior)

       -fglobal-alloc-prefer-bytes
       -fno-global-alloc-prefer-bytes
	   For the x86_32 architecture, prefer byte or short values to word values during global
	   register allocation.  Some of the registers on this target can't be used with values
	   smaller than a 32-bit word; allocating these values earlier increases the chance they
	   will get a byte-capable (or short-capable) register.  Ignored for other targets.
	   Defaults on with global register allocation ("-Os", "-O2", or "-O3").  (APPLE ONLY)

       -fwritable-strings
	   Store string constants in the writable data segment and don't uniquize them.  This is
	   for compatibility with old programs which assume they can write into string constants.

	   Writing into string constants is a very bad idea; "constants" should be constant.

	   This option is deprecated.

       Options Controlling C++ Dialect

       This section describes the command-line options that are only meaningful for C++ programs;
       but you can also use most of the GNU compiler options regardless of what language your
       program is in.  For example, you might compile a file "firstClass.C" like this:

	       g++ -g -frepo -O -c firstClass.C

       In this example, only -frepo is an option meant only for C++ programs; you can use the
       other options with any language supported by GCC.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
	   Use version n of the C++ ABI.  Version 2 is the version of the C++ ABI that first
	   appeared in G++ 3.4.  Version 1 is the version of the C++ ABI that first appeared in
	   G++ 3.2.  Version 0 will always be the version that conforms most closely to the C++
	   ABI specification.  Therefore, the ABI obtained using version 0 will change as ABI
	   bugs are fixed.

	   The default is version 2.

       -fno-access-control
	   Turn off all access checking.  This switch is mainly useful for working around bugs in
	   the access control code.

       -fcheck-new
	   Check that the pointer returned by "operator new" is non-null before attempting to
	   modify the storage allocated.  This check is normally unnecessary because the C++
	   standard specifies that "operator new" will only return 0 if it is declared throw(),
	   in which case the compiler will always check the return value even without this
	   option.  In all other cases, when "operator new" has a non-empty exception
	   specification, memory exhaustion is signalled by throwing "std::bad_alloc".	See also
	   new (nothrow).

       -fconserve-space
	   Put uninitialized or runtime-initialized global variables into the common segment, as
	   C does.  This saves space in the executable at the cost of not diagnosing duplicate
	   definitions.  If you compile with this flag and your program mysteriously crashes
	   after "main()" has completed, you may have an object that is being destroyed twice
	   because two definitions were merged.

	   This option is no longer useful on most targets, now that support has been added for
	   putting variables into BSS without making them common.

       -ffriend-injection
	   Inject friend functions into the enclosing namespace, so that they are visible outside
	   the scope of the class in which they are declared.  Friend functions were documented
	   to work this way in the old Annotated C++ Reference Manual, and versions of G++ before
	   4.1 always worked that way.	However, in ISO C++ a friend function which is not
	   declared in an enclosing scope can only be found using argument dependent lookup.
	   This option causes friends to be injected as they were in earlier releases.

	   This option is for compatibility, and may be removed in a future release of G++.

       -fno-elide-constructors
	   The C++ standard allows an implementation to omit creating a temporary which is only
	   used to initialize another object of the same type.	Specifying this option disables
	   that optimization, and forces G++ to call the copy constructor in all cases.

       -fno-enforce-eh-specs
	   Don't generate code to check for violation of exception specifications at runtime.
	   This option violates the C++ standard, but may be useful for reducing code size in
	   production builds, much like defining NDEBUG.  This does not give user code permission
	   to throw exceptions in violation of the exception specifications; the compiler will
	   still optimize based on the specifications, so throwing an unexpected exception will
	   result in undefined behavior.

       -ffor-scope
       -fno-for-scope
	   If -ffor-scope is specified, the scope of variables declared in a for-init-statement
	   is limited to the for loop itself, as specified by the C++ standard.  If
	   -fno-for-scope is specified, the scope of variables declared in a for-init-statement
	   extends to the end of the enclosing scope, as was the case in old versions of G++, and
	   other (traditional) implementations of C++.

	   The default if neither flag is given to follow the standard, but to allow and give a
	   warning for old-style code that would otherwise be invalid, or have different
	   behavior.

       -fno-gnu-keywords
	   Do not recognize "typeof" as a keyword, so that code can use this word as an
	   identifier.	You can use the keyword "__typeof__" instead.  -ansi implies
	   -fno-gnu-keywords.

       -fno-implicit-templates
	   Never emit code for non-inline templates which are instantiated implicitly (i.e. by
	   use); only emit code for explicit instantiations.

       -fno-implicit-inline-templates
	   Don't emit code for implicit instantiations of inline templates, either.  The default
	   is to handle inlines differently so that compiles with and without optimization will
	   need the same set of explicit instantiations.

       -fno-implement-inlines
	   To save space, do not emit out-of-line copies of inline functions controlled by
	   #pragma implementation.  This will cause linker errors if these functions are not
	   inlined everywhere they are called.

       -fms-extensions
	   Disable pedantic warnings about constructs used in MFC, such as implicit int and
	   getting a pointer to member function via non-standard syntax.

       -fno-nonansi-builtins
	   Disable built-in declarations of functions that are not mandated by ANSI/ISO C.  These
	   include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other related
	   functions.

       -fno-operator-names
	   Do not treat the operator name keywords "and", "bitand", "bitor", "compl", "not", "or"
	   and "xor" as synonyms as keywords.

       -fno-optional-diags
	   Disable diagnostics that the standard says a compiler does not need to issue.
	   Currently, the only such diagnostic issued by G++ is the one for a name having
	   multiple meanings within a class.

       -fpermissive
	   Downgrade some diagnostics about nonconformant code from errors to warnings.  Thus,
	   using -fpermissive will allow some nonconforming code to compile.

       -frepo
	   Enable automatic template instantiation at link time.  This option also implies
	   -fno-implicit-templates.

       -fno-rtti
	   Disable generation of information about every class with virtual functions for use by
	   the C++ runtime type identification features (dynamic_cast and typeid).  If you don't
	   use those parts of the language, you can save some space by using this flag.  Note
	   that exception handling uses the same information, but it will generate it as needed.
	   The dynamic_cast operator can still be used for casts that do not require runtime type
	   information, i.e. casts to "void *" or to unambiguous base classes.

       -fstats
	   Emit statistics about front-end processing at the end of the compilation.  This
	   information is generally only useful to the G++ development team.

       -ftemplate-depth-n
	   Set the maximum instantiation depth for template classes to n.  A limit on the
	   template instantiation depth is needed to detect endless recursions during template
	   class instantiation.  ANSI/ISO C++ conforming programs must not rely on a maximum
	   depth greater than 17.

       -fno-threadsafe-statics
	   Do not emit the extra code to use the routines specified in the C++ ABI for thread-
	   safe initialization of local statics.  You can use this option to reduce code size
	   slightly in code that doesn't need to be thread-safe.

       -fuse-cxa-atexit
	   Register destructors for objects with static storage duration with the "__cxa_atexit"
	   function rather than the "atexit" function.	This option is required for fully
	   standards-compliant handling of static destructors, but will only work if your C
	   library supports "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
	   Don't use the "__cxa_get_exception_ptr" runtime routine.  This will cause
	   "std::uncaught_exception" to be incorrect, but is necessary if the runtime routine is
	   not available.

       -fvisibility-inlines-hidden
	   This switch declares that the user does not attempt to compare pointers to inline
	   methods where the addresses of the two functions were taken in different shared
	   objects.

	   The effect of this is that GCC may, effectively, mark inline methods with
	   "__attribute__ ((visibility ("hidden")))" so that they do not appear in the export
	   table of a DSO and do not require a PLT indirection when used within the DSO.
	   Enabling this option can have a dramatic effect on load and link times of a DSO as it
	   massively reduces the size of the dynamic export table when the library makes heavy
	   use of templates.

	   The behaviour of this switch is not quite the same as marking the methods as hidden
	   directly, because it does not affect static variables local to the function or cause
	   the compiler to deduce that the function is defined in only one shared object.

	   You may mark a method as having a visibility explicitly to negate the effect of the
	   switch for that method.  For example, if you do want to compare pointers to a
	   particular inline method, you might mark it as having default visibility.  Marking the
	   enclosing class with explicit visibility will have no effect.

	   Explicitly instantiated inline methods are unaffected by this option as their linkage
	   might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
	   This flag attempts to use visibility settings to make GCC's C++ linkage model
	   compatible with that of Microsoft Visual Studio.

	   The flag makes these changes to GCC's linkage model:

	   1. It sets the default visibility to 'hidden', like -fvisibility=hidden.  2. Types,
	   but not their members, are not hidden by default.  3. The One Definition Rule is
	   relaxed for types without explicit visibility specifications which are defined in more
	   than one different shared object: those declarations are permitted if they would have
	   been permitted when this option was not used.

	   This option is discouraged, rather, it is preferable for types to be explicitly
	   exported as desired on a per-class basis.  Unfortunately because Visual Studio can't
	   compare two different hidden types as unequal for the purposes of type_info and
	   exception handling, users are able to write code that relies upon this behavior.

	   Among the consequences of these changes are that static data members of the same type
	   with the same name but defined in different shared objects will be different, so
	   changing one will not change the other; and that pointers to function members defined
	   in different shared objects will not compare equal.	When this flag is given, it is a
	   violation of the ODR to define types with the same name differently.

       -fno-weak
	   Do not use weak symbol support, even if it is provided by the linker.  By default, G++
	   will use weak symbols if they are available.  This option exists only for testing, and
	   should not be used by end-users; it will result in inferior code and has no benefits.
	   This option may be removed in a future release of G++.

       -nostdinc++
	   Do not search for header files in the standard directories specific to C++, but do
	   still search the other standard directories.  (This option is used when building the
	   C++ library.)

       In addition, these optimization, warning, and code generation options have meanings only
       for C++ programs:

       -fno-default-inline
	   Do not assume inline for functions defined inside a class scope.
	     Note that these functions will have linkage like inline functions; they just won't
	   be inlined by default.

       -Wabi (C++ only)
	   Warn when G++ generates code that is probably not compatible with the vendor-neutral
	   C++ ABI.  Although an effort has been made to warn about all such cases, there are
	   probably some cases that are not warned about, even though G++ is generating
	   incompatible code.  There may also be cases where warnings are emitted even though the
	   code that is generated will be compatible.

	   You should rewrite your code to avoid these warnings if you are concerned about the
	   fact that code generated by G++ may not be binary compatible with code generated by
	   other compilers.

	   The known incompatibilities at this point include:

	   o   Incorrect handling of tail-padding for bit-fields.  G++ may attempt to pack data
	       into the same byte as a base class.  For example:

		       struct A { virtual void f(); int f1 : 1; };
		       struct B : public A { int f2 : 1; };

	       In this case, G++ will place "B::f2" into the same byte as"A::f1"; other compilers
	       will not.  You can avoid this problem by explicitly padding "A" so that its size
	       is a multiple of the byte size on your platform; that will cause G++ and other
	       compilers to layout "B" identically.

	   o   Incorrect handling of tail-padding for virtual bases.  G++ does not use tail
	       padding when laying out virtual bases.  For example:

		       struct A { virtual void f(); char c1; };
		       struct B { B(); char c2; };
		       struct C : public A, public virtual B {};

	       In this case, G++ will not place "B" into the tail-padding for "A"; other
	       compilers will.	You can avoid this problem by explicitly padding "A" so that its
	       size is a multiple of its alignment (ignoring virtual base classes); that will
	       cause G++ and other compilers to layout "C" identically.

	   o   Incorrect handling of bit-fields with declared widths greater than that of their
	       underlying types, when the bit-fields appear in a union.  For example:

		       union U { int i : 4096; };

	       Assuming that an "int" does not have 4096 bits, G++ will make the union too small
	       by the number of bits in an "int".

	   o   Empty classes can be placed at incorrect offsets.  For example:

		       struct A {};

		       struct B {
			 A a;
			 virtual void f ();
		       };

		       struct C : public B, public A {};

	       G++ will place the "A" base class of "C" at a nonzero offset; it should be placed
	       at offset zero.	G++ mistakenly believes that the "A" data member of "B" is
	       already at offset zero.

	   o   Names of template functions whose types involve "typename" or template template
	       parameters can be mangled incorrectly.

		       template <typename Q>
		       void f(typename Q::X) {}

		       template <template <typename> class Q>
		       void f(typename Q<int>::X) {}

	       Instantiations of these templates may be mangled incorrectly.

       -Wctor-dtor-privacy (C++ only)
	   Warn when a class seems unusable because all the constructors or destructors in that
	   class are private, and it has neither friends nor public static member functions.

       -Wnon-virtual-dtor (C++ only)
	   Warn when a class appears to be polymorphic, thereby requiring a virtual destructor,
	   yet it declares a non-virtual one.  This warning is also enabled if -Weffc++ is
	   specified.

       -Wreorder (C++ only)
	   Warn when the order of member initializers given in the code does not match the order
	   in which they must be executed.  For instance:

		   struct A {
		     int i;
		     int j;
		     A(): j (0), i (1) { }
		   };

	   The compiler will rearrange the member initializers for i and j to match the
	   declaration order of the members, emitting a warning to that effect.  This warning is
	   enabled by -Wall.

       The following -W... options are not affected by -Wall.

       -Weffc++ (C++ only)
	   Warn about violations of the following style guidelines from Scott Meyers' Effective
	   C++ book:

	   o   Item 11:  Define a copy constructor and an assignment operator for classes with
	       dynamically allocated memory.

	   o   Item 12:  Prefer initialization to assignment in constructors.

	   o   Item 14:  Make destructors virtual in base classes.

	   o   Item 15:  Have "operator=" return a reference to *this.

	   o   Item 23:  Don't try to return a reference when you must return an object.

	   Also warn about violations of the following style guidelines from Scott Meyers' More
	   Effective C++ book:

	   o   Item 6:	Distinguish between prefix and postfix forms of increment and decrement
	       operators.

	   o   Item 7:	Never overload "&&", "||", or ",".

	   When selecting this option, be aware that the standard library headers do not obey all
	   of these guidelines; use grep -v to filter out those warnings.

       -Wno-deprecated (C++ only)
	   Do not warn about usage of deprecated features.

       -Wstrict-null-sentinel (C++ only)
	   Warn also about the use of an uncasted "NULL" as sentinel.  When compiling only with
	   GCC this is a valid sentinel, as "NULL" is defined to "__null".  Although it is a null
	   pointer constant not a null pointer, it is guaranteed to of the same size as a
	   pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend (C++ only)
	   Disable warnings when non-templatized friend functions are declared within a template.
	   Since the advent of explicit template specification support in G++, if the name of the
	   friend is an unqualified-id (i.e., friend foo(int)), the C++ language specification
	   demands that the friend declare or define an ordinary, nontemplate function.  (Section
	   14.5.3).  Before G++ implemented explicit specification, unqualified-ids could be
	   interpreted as a particular specialization of a templatized function.  Because this
	   non-conforming behavior is no longer the default behavior for G++,
	   -Wnon-template-friend allows the compiler to check existing code for potential trouble
	   spots and is on by default.	This new compiler behavior can be turned off with
	   -Wno-non-template-friend which keeps the conformant compiler code but disables the
	   helpful warning.

       -Wold-style-cast (C++ only)
	   Warn if an old-style (C-style) cast to a non-void type is used within a C++ program.
	   The new-style casts (dynamic_cast, static_cast, reinterpret_cast, and const_cast) are
	   less vulnerable to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ only)
	   Warn when a function declaration hides virtual functions from a base class.	For
	   example, in:

		   struct A {
		     virtual void f();
		   };

		   struct B: public A {
		     void f(int);
		   };

	   the "A" class version of "f" is hidden in "B", and code like:

		   B* b;
		   b->f();

	   will fail to compile.

       -Wno-pmf-conversions (C++ only)
	   Disable the diagnostic for converting a bound pointer to member function to a plain
	   pointer.

       -Wsign-promo (C++ only)
	   Warn when overload resolution chooses a promotion from unsigned or enumerated type to
	   a signed type, over a conversion to an unsigned type of the same size.  Previous
	   versions of G++ would try to preserve unsignedness, but the standard mandates the
	   current behavior.

		   struct A {
		     operator int ();
		     A& operator = (int);
		   };

		   main ()
		   {
		     A a,b;
		     a = b;
		   }

	   In this example, G++ will synthesize a default A& operator = (const A&);, while cfront
	   will use the user-defined operator =.

       Options Controlling Objective-C and Objective-C++ Dialects

       (NOTE: This manual does not describe the Objective-C and Objective-C++ languages
       themselves.  See

       This section describes the command-line options that are only meaningful for Objective-C
       and Objective-C++ programs, but you can also use most of the language-independent GNU
       compiler options.  For example, you might compile a file "some_class.m" like this:

	       gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C and Objective-C++
       programs; you can use the other options with any language supported by GCC.

       Note that since Objective-C is an extension of the C language, Objective-C compilations
       may also use options specific to the C front-end (e.g., -Wtraditional).	Similarly,
       Objective-C++ compilations may use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and Objective-C++
       programs:

       -fconstant-string-class=class-name
	   Use class-name as the name of the class to instantiate for each literal string
	   specified with the syntax "@"..."".	The default class name is "NXConstantString" if
	   the GNU runtime is being used, and "NSConstantString" if the NeXT runtime is being
	   used (see below).  The -fconstant-cfstrings option, if also present, will override the
	   -fconstant-string-class setting and cause "@"..."" literals to be laid out as constant
	   CoreFoundation strings.

       -fgnu-runtime
	   Generate object code compatible with the standard GNU Objective-C runtime.  This is
	   the default for most types of systems.

       -fnext-runtime
	   Generate output compatible with the NeXT runtime.  This is the default for NeXT-based
	   systems, including Darwin and Mac OS X.  The macro "__NEXT_RUNTIME__" is predefined if
	   (and only if) this option is used.

       -fno-nil-receivers
	   Assume that all Objective-C message dispatches (e.g., "[receiver message:arg]") in
	   this translation unit ensure that the receiver is not "nil".  This allows for more
	   efficient entry points in the runtime to be used.  Currently, this option is only
	   available in conjunction with the NeXT runtime on Mac OS X 10.3 and later.

       -fobjc-call-cxx-cdtors
	   For each Objective-C class, check if any of its instance variables is a C++ object
	   with a non-trivial default constructor.  If so, synthesize a special "- (id)
	   .cxx_construct" instance method that will run non-trivial default constructors on any
	   such instance variables, in order, and then return "self".  Similarly, check if any
	   instance variable is a C++ object with a non-trivial destructor, and if so, synthesize
	   a special "- (void) .cxx_destruct" method that will run all such default destructors,
	   in reverse order.

	   The "- (id) .cxx_construct" and/or "- (void) .cxx_destruct" methods thusly generated
	   will only operate on instance variables declared in the current Objective-C class, and
	   not those inherited from superclasses.  It is the responsibility of the Objective-C
	   runtime to invoke all such methods in an object's inheritance hierarchy.  The "- (id)
	   .cxx_construct" methods will be invoked by the runtime immediately after a new object
	   instance is allocated; the "- (void) .cxx_destruct" methods will be invoked
	   immediately before the runtime deallocates an object instance.

	   As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has support for
	   invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
	   Allow fast jumps to the message dispatcher.	On Darwin this is accomplished via the
	   comm page.

       -fobjc-sjlj-exceptions
	   Enable syntactic support for structured exception handling in Objective-C, similar to
	   what is offered by C++ and Java.  This option is unavailable in conjunction with the
	   NeXT runtime on Mac OS X 10.2 and earlier.  This option is on by default with the NeXT
	   runtime.

		     @try {
		       ...
			  @throw expr;
		       ...
		     }
		     @catch (AnObjCClass *exc) {
		       ...
			 @throw expr;
		       ...
			 @throw;
		       ...
		     }
		     @catch (AnotherClass *exc) {
		       ...
		     }
		     @catch (id allOthers) {
		       ...
		     }
		     @finally {
		       ...
			 @throw expr;
		       ...
		     }

	   The @throw statement may appear anywhere in an Objective-C or Objective-C++ program;
	   when used inside of a @catch block, the @throw may appear without an argument (as
	   shown above), in which case the object caught by the @catch will be rethrown.

	   Note that only (pointers to) Objective-C objects may be thrown and caught using this
	   scheme.  When an object is thrown, it will be caught by the nearest @catch clause
	   capable of handling objects of that type, analogously to how "catch" blocks work in
	   C++ and Java.  A "@catch(id ...)" clause (as shown above) may also be provided to
	   catch any and all Objective-C exceptions not caught by previous @catch clauses (if
	   any).

	   The @finally clause, if present, will be executed upon exit from the immediately
	   preceding "@try ... @catch" section.  This will happen regardless of whether any
	   exceptions are thrown, caught or rethrown inside the "@try ... @catch" section,
	   analogously to the behavior of the "finally" clause in Java.

	   There are several caveats to using the new exception mechanism:

	   o   Although currently designed to be binary compatible with "NS_HANDLER"-style idioms
	       provided by the "NSException" class, the new exceptions can only be used on Mac OS
	       X 10.3 (Panther) and later systems, due to additional functionality needed in the
	       (NeXT) Objective-C runtime.

	   o   As mentioned above, the new exceptions do not support handling types other than
	       Objective-C objects.   Furthermore, when used from Objective-C++, the Objective-C
	       exception model does not interoperate with C++ exceptions at this time.	This
	       means you cannot @throw an exception from Objective-C and "catch" it in C++, or
	       vice versa (i.e., "throw ... @catch").

	   The -fobjc-sjlj-exceptions switch also enables the use of synchronization blocks for
	   thread-safe execution:

		     @synchronized (ObjCClass *guard) {
		       ...
		     }

	   Upon entering the @synchronized block, a thread of execution shall first check whether
	   a lock has been placed on the corresponding "guard" object by another thread.  If it
	   has, the current thread shall wait until the other thread relinquishes its lock.  Once
	   "guard" becomes available, the current thread will place its own lock on it, execute
	   the code contained in the @synchronized block, and finally relinquish the lock
	   (thereby making "guard" available to other threads).

	   Unlike Java, Objective-C does not allow for entire methods to be marked @synchronized.
	   Note that throwing exceptions out of @synchronized blocks is allowed, and will cause
	   the guarding object to be unlocked properly.

       -fobjc-gc
	   Enable garbage collection (GC) in Objective-C and Objective-C++ programs.  The
	   resulting binary requires additional runtime support which is present on Mac OS X
	   Version 10.5 (Leopard) and later.  All Objective-C objects are presumed to be garbage
	   collected. To aid in this effort, compiler implements assignments of Objective-C
	   object pointers via runtime support functions. These functions work correctly in non-
	   GC environments as well, in case this code is used as part of a library.  Assignments
	   of objects into instance variables of other objects are intercepted, so are
	   assignments to global object variables. In general, assignments through pointers to
	   objects are intercepted. Additionally, assignments of objects as fields within
	   structures are intercepted.

	   In addition, other pointer variables may be marked with the __strong storage class
	   modifier to indicate to the compiler that these assignments need to use the assignment
	   runtime functions as well, allowing the memory referenced by these pointers to be
	   allocated from the collector. A __weak storage class modifier for pointers is also
	   introduced to indicate a zero-ing weak reference. This is permitted only for instance
	   variables of an object or globals.  The compiler arranges for all reads as well as
	   writes to these variables to occur via runtime support functions.  Under garbage
	   collection these variables are not consulted when determining what is not garbage and
	   they are set to nil (zero) if the memory they reference is deemed garbage and is
	   collected.

		     __strong void *p;	// assignments to 'p' will have runtime support calls
		     int *q;		// assignments to 'q' ordinarly will not
		       ...
		     (__strong int *)q = 0;   // this assignment will call a runtime support function

	   Conversely, the "__weak" type qualifier may be used to call weak runtime functions.

		     __weak id q;      // assignments to 'q' will have the '__weak' semantics
		     id p;	       // assignments to 'p' will have the "__strong' semantics
		       ...
		     (__weak id)p = 0;	 // Fall back to '__weak' semantics in this assignment.

       -fobjc-gc-only
	   Use this option to indicate that the Objective-C program supports garbage collection
	   (GC) only - that is, it does not contain retain/release logic.  This flag implies
	   -fobjc-gc as well. With this flag, framework is marked as not honoring retain/release.

       -freplace-objc-classes
	   Emit a special marker instructing ld(1) not to statically link in the resulting object
	   file, and allow dyld(1) to load it in at run time instead.  This is used in
	   conjunction with the Fix-and-Continue debugging mode, where the object file in
	   question may be recompiled and dynamically reloaded in the course of program
	   execution, without the need to restart the program itself.  Currently, Fix-and-
	   Continue functionality is only available in conjunction with the NeXT runtime on Mac
	   OS X 10.3 and later.

       -fzero-link
	   When compiling for the NeXT runtime, the compiler ordinarily replaces calls to
	   "objc_getClass("...")" (when the name of the class is known at compile time) with
	   static class references that get initialized at load time, which improves run-time
	   performance.  Specifying the -fzero-link flag suppresses this behavior and causes
	   calls to "objc_getClass("...")"  to be retained.  This is useful in Zero-Link
	   debugging mode, since it allows for individual class implementations to be modified
	   during program execution.

       -gen-decls
	   Dump interface declarations for all classes seen in the source file to a file named
	   sourcename.decl.

       -Wassign-intercept
	   Warn whenever an Objective-C assignment is being intercepted by the garbage collector.

       -Wno-protocol
	   If a class is declared to implement a protocol, a warning is issued for every method
	   in the protocol that is not implemented by the class.  The default behavior is to
	   issue a warning for every method not explicitly implemented in the class, even if a
	   method implementation is inherited from the superclass.  If you use the -Wno-protocol
	   option, then methods inherited from the superclass are considered to be implemented,
	   and no warning is issued for them.

       -Wselector
	   Warn if multiple methods of different types for the same selector are found during
	   compilation.  The check is performed on the list of methods in the final stage of
	   compilation.  Additionally, a check is performed for each selector appearing in a
	   "@selector(...)"  expression, and a corresponding method for that selector has been
	   found during compilation.  Because these checks scan the method table only at the end
	   of compilation, these warnings are not produced if the final stage of compilation is
	   not reached, for example because an error is found during compilation, or because the
	   -fsyntax-only option is being used.

       -Wproperty-assign-default
	   Warn if no "assign", "retain", or "copy" attribute is specified on a property of
	   pointer to object type. Property is then assumed to be "assign" by default.

       -Wdirect-ivar-access
	   Warn if ivar of pointer to object type is directly accessed in non-gc mode, instead of
	   using property syntax access.

       -Wstrict-selector-match
	   Warn if multiple methods with differing argument and/or return types are found for a
	   given selector when attempting to send a message using this selector to a receiver of
	   type "id" or "Class".  When this flag is off (which is the default behavior), the
	   compiler will omit such warnings if any differences found are confined to types which
	   share the same size and alignment.

       -Wundeclared-selector
	   Warn if a "@selector(...)" expression referring to an undeclared selector is found.	A
	   selector is considered undeclared if no method with that name has been declared before
	   the "@selector(...)" expression, either explicitly in an @interface or @protocol
	   declaration, or implicitly in an @implementation section.  This option always performs
	   its checks as soon as a "@selector(...)" expression is found, while -Wselector only
	   performs its checks in the final stage of compilation.  This also enforces the coding
	   style convention that methods and selectors must be declared before being used.

       -print-objc-runtime-info
	   Generate C header describing the largest structure that is passed by value, if any.

       Options to Control Diagnostic Messages Formatting

       Traditionally, diagnostic messages have been formatted irrespective of the output device's
       aspect (e.g. its width, ...).  The options described below can be used to control the
       diagnostic messages formatting algorithm, e.g. how many characters per line, how often
       source location information should be reported.	Right now, only the C++ front end can
       honor these options.  However it is expected, in the near future, that the remaining front
       ends would be able to digest them correctly.

       -fmessage-length=n
	   Try to format error messages so that they fit on lines of about n characters.  The
	   default is 72 characters for g++ and 0 for the rest of the front ends supported by
	   GCC.  If n is zero, then no line-wrapping will be done; each error message will appear
	   on a single line.

       -fdiagnostics-show-location=once
	   Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
	   emit once source location information; that is, in case the message is too long to fit
	   on a single physical line and has to be wrapped, the source location won't be emitted
	   (as prefix) again, over and over, in subsequent continuation lines.	This is the
	   default behavior.

       -fdiagnostics-show-location=every-line
	   Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
	   emit the same source location information (as prefix) for physical lines that result
	   from the process of breaking a message which is too long to fit on a single line.

       -fdiagnostics-show-option
	   This option instructs the diagnostic machinery to add text to each diagnostic emitted,
	   which indicates which command line option directly controls that diagnostic, when such
	   an option is known to the diagnostic machinery.

       Options to Request or Suppress Warnings

       Warnings are diagnostic messages that report constructions which are not inherently
       erroneous but which are risky or suggest there may have been an error.

       You can request many specific warnings with options beginning -W, for example -Wimplicit
       to request warnings on implicit declarations.  Each of these specific warning options also
       has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit.
       This manual lists only one of the two forms, whichever is not the default.

       The following options control the amount and kinds of warnings produced by GCC; for
       further, language-specific options also refer to C++ Dialect Options and Objective-C and
       Objective-C++ Dialect Options.

       -fsyntax-only
	   Check the code for syntax errors, but don't do anything beyond that.

       -pedantic
	   Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that
	   use forbidden extensions, and some other programs that do not follow ISO C and ISO
	   C++.  For ISO C, follows the version of the ISO C standard specified by any -std
	   option used.

	   Valid ISO C and ISO C++ programs should compile properly with or without this option
	   (though a rare few will require -ansi or a -std option specifying the required version
	   of ISO C).  However, without this option, certain GNU extensions and traditional C and
	   C++ features are supported as well.	With this option, they are rejected.

	   -pedantic does not cause warning messages for use of the alternate keywords whose
	   names begin and end with __.  Pedantic warnings are also disabled in the expression
	   that follows "__extension__".  However, only system header files should use these
	   escape routes; application programs should avoid them.

	   Some users try to use -pedantic to check programs for strict ISO C conformance.  They
	   soon find that it does not do quite what they want: it finds some non-ISO practices,
	   but not all---only those for which ISO C requires a diagnostic, and some others for
	   which diagnostics have been added.

	   A feature to report any failure to conform to ISO C might be useful in some instances,
	   but would require considerable additional work and would be quite different from
	   -pedantic.  We don't have plans to support such a feature in the near future.

	   Where the standard specified with -std represents a GNU extended dialect of C, such as
	   gnu89 or gnu99, there is a corresponding base standard, the version of ISO C on which
	   the GNU extended dialect is based.  Warnings from -pedantic are given where they are
	   required by the base standard.  (It would not make sense for such warnings to be given
	   only for features not in the specified GNU C dialect, since by definition the GNU
	   dialects of C include all features the compiler supports with the given option, and
	   there would be nothing to warn about.)

       -pedantic-errors
	   Like -pedantic, except that errors are produced rather than warnings.

       -w  Inhibit all warning messages.

       -Wno-import
	   Inhibit warning messages about the use of #import.

       -Wno-#warnings
	   Inhibit warning messages issued by #warning.

       -Wextra-tokens
	   Warn about extra tokens at the end of prepreprocessor directives.  (APPLE ONLY)

       -Wnewline-eof
	   Warn about files missing a newline at the end of the file.  (APPLE ONLY)

       -Wno-altivec-long-deprecated
	   Do not warn about the use of the deprecated 'long' keyword in AltiVec data types.
	   (APPLE ONLY)

       -Wchar-subscripts
	   Warn if an array subscript has type "char".	This is a common cause of error, as
	   programmers often forget that this type is signed on some machines.	This warning is
	   enabled by -Wall.

       -Wcomment
	   Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
	   Backslash-Newline appears in a // comment.  This warning is enabled by -Wall.

       -Wfatal-errors
	   This option causes the compiler to abort compilation on the first error occurred
	   rather than trying to keep going and printing further error messages.

       -Wno-format
	   Check calls to "printf" and "scanf", etc., to make sure that the arguments supplied
	   have types appropriate to the format string specified, and that the conversions
	   specified in the format string make sense.  This includes standard functions, and
	   others specified by format attributes, in the "printf", "scanf", "strftime" and
	   "strfmon" (an X/Open extension, not in the C standard) families (or other target-
	   specific families).	Which functions are checked without format attributes having been
	   specified depends on the standard version selected, and such checks of functions
	   without the attribute specified are disabled by -ffreestanding or -fno-builtin.

	   The formats are checked against the format features supported by GNU libc version 2.2.
	   These include all ISO C90 and C99 features, as well as features from the Single Unix
	   Specification and some BSD and GNU extensions.  Other library implementations may not
	   support all these features; GCC does not support warning about features that go beyond
	   a particular library's limitations.	However, if -pedantic is used with -Wformat,
	   warnings will be given about format features not in the selected standard version (but
	   not for "strfmon" formats, since those are not in any version of the C standard).

	   Since -Wformat also checks for null format arguments for several functions, -Wformat
	   also implies -Wnonnull.

	   -Wformat is included in -Wall.  For more control over some aspects of format checking,
	   the options -Wformat-y2k, -Wno-format-extra-args, -Wno-format-zero-length,
	   -Wformat-nonliteral, -Wformat-security, and -Wformat=2 are available, but are not
	   included in -Wall.

       -Wformat-y2k
	   If -Wformat is specified, also warn about "strftime" formats which may yield only a
	   two-digit year.

       -Wno-format-extra-args
	   If -Wformat is specified, do not warn about excess arguments to a "printf" or "scanf"
	   format function.  The C standard specifies that such arguments are ignored.

	   Where the unused arguments lie between used arguments that are specified with $
	   operand number specifications, normally warnings are still given, since the
	   implementation could not know what type to pass to "va_arg" to skip the unused
	   arguments.  However, in the case of "scanf" formats, this option will suppress the
	   warning if the unused arguments are all pointers, since the Single Unix Specification
	   says that such unused arguments are allowed.

       -Wno-format-zero-length
	   If -Wformat is specified, do not warn about zero-length formats.  The C standard
	   specifies that zero-length formats are allowed.

       -Wformat-nonliteral
	   If -Wformat is specified, also warn if the format string is not a string literal and
	   so cannot be checked, unless the format function takes its format arguments as a
	   "va_list".

       -Wno-format-security
	   If -Wformat is specified, also warn about uses of format functions that represent
	   possible security problems.	At present, this warns about calls to "printf" and
	   "scanf" functions where the format string is not a string literal and there are no
	   format arguments, as in "printf (foo);".  This may be a security hole if the format
	   string came from untrusted input and contains %n.  (This is currently a subset of what
	   -Wformat-nonliteral warns about, but in future warnings may be added to
	   -Wformat-security that are not included in -Wformat-nonliteral.)

       -Wformat=2
	   Enable -Wformat plus format checks not included in -Wformat.  Currently equivalent to
	   -Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k.

       -Wnonnull
	   Warn about passing a null pointer for arguments marked as requiring a non-null value
	   by the "nonnull" function attribute.

	   -Wnonnull is included in -Wall and -Wformat.  It can be disabled with the -Wno-nonnull
	   option.

       -Wglobal-constructors
	   Warn about namespace scope data that requires construction or destruction, or
	   functions that use the constructor attribute or the destructor attribute.
	   Additionally warn if the Objective-C GNU runtime is used to initialize various
	   metadata.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
	   Warn about uninitialized variables which are initialized with themselves.  Note this
	   option can only be used with the -Wuninitialized option, which in turn only works with
	   -O1 and above.

	   For example, GCC will warn about "i" being uninitialized in the following snippet only
	   when -Winit-self has been specified:

		   int f()
		   {
		     int i = i;
		     return i;
		   }

       -Wimplicit-int
	   Warn when a declaration does not specify a type.  This warning is enabled by -Wall.

       -Wimplicit-function-declaration
       -Werror-implicit-function-declaration
	   Give a warning (or error) whenever a function is used before being declared.  The form
	   -Wno-error-implicit-function-declaration is not supported.  This warning is enabled by
	   -Wall (as a warning, not an error).

       -Wimplicit
	   Same as -Wimplicit-int and -Wimplicit-function-declaration.	This warning is enabled
	   by -Wall.

       -Wmain
	   Warn if the type of main is suspicious.  main should be a function with external
	   linkage, returning int, taking either zero arguments, two, or three arguments of
	   appropriate types.  This warning is enabled by -Wall.

       -Wmissing-braces
	   Warn if an aggregate or union initializer is not fully bracketed.  In the following
	   example, the initializer for a is not fully bracketed, but that for b is fully
	   bracketed.

		   int a[2][2] = { 0, 1, 2, 3 };
		   int b[2][2] = { { 0, 1 }, { 2, 3 } };

	   This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
	   Warn if a user-supplied include directory does not exist.

       -Wparentheses
	   Warn if parentheses are omitted in certain contexts, such as when there is an
	   assignment in a context where a truth value is expected, or when operators are nested
	   whose precedence people often get confused about.  Only the warning for an assignment
	   used as a truth value is supported when compiling C++; the other warnings are only
	   supported when compiling C.

	   Also warn if a comparison like x<=y<=z appears; this is equivalent to (x<=y ? 1 : 0)
	   <= z, which is a different interpretation from that of ordinary mathematical notation.

	   Also warn about constructions where there may be confusion to which "if" statement an
	   "else" branch belongs.  Here is an example of such a case:

		   {
		     if (a)
		       if (b)
			 foo ();
		     else
		       bar ();
		   }

	   In C, every "else" branch belongs to the innermost possible "if" statement, which in
	   this example is "if (b)".  This is often not what the programmer expected, as
	   illustrated in the above example by indentation the programmer chose.  When there is
	   the potential for this confusion, GCC will issue a warning when this flag is
	   specified.  To eliminate the warning, add explicit braces around the innermost "if"
	   statement so there is no way the "else" could belong to the enclosing "if".	The
	   resulting code would look like this:

		   {
		     if (a)
		       {
			 if (b)
			   foo ();
			 else
			   bar ();
		       }
		   }

	   This warning is enabled by -Wall.

       -Wsequence-point
	   Warn about code that may have undefined semantics because of violations of sequence
	   point rules in the C and C++ standards.

	   The C and C++ standards defines the order in which expressions in a C/C++ program are
	   evaluated in terms of sequence points, which represent a partial ordering between the
	   execution of parts of the program: those executed before the sequence point, and those
	   executed after it.  These occur after the evaluation of a full expression (one which
	   is not part of a larger expression), after the evaluation of the first operand of a
	   "&&", "||", "? :" or "," (comma) operator, before a function is called (but after the
	   evaluation of its arguments and the expression denoting the called function), and in
	   certain other places.  Other than as expressed by the sequence point rules, the order
	   of evaluation of subexpressions of an expression is not specified.  All these rules
	   describe only a partial order rather than a total order, since, for example, if two
	   functions are called within one expression with no sequence point between them, the
	   order in which the functions are called is not specified.  However, the standards
	   committee have ruled that function calls do not overlap.

	   It is not specified when between sequence points modifications to the values of
	   objects take effect.  Programs whose behavior depends on this have undefined behavior;
	   the C and C++ standards specify that "Between the previous and next sequence point an
	   object shall have its stored value modified at most once by the evaluation of an
	   expression.	Furthermore, the prior value shall be read only to determine the value to
	   be stored.".  If a program breaks these rules, the results on any particular
	   implementation are entirely unpredictable.

	   Examples of code with undefined behavior are "a = a++;", "a[n] = b[n++]" and "a[i++] =
	   i;".  Some more complicated cases are not diagnosed by this option, and it may give an
	   occasional false positive result, but in general it has been found fairly effective at
	   detecting this sort of problem in programs.

	   The standard is worded confusingly, therefore there is some debate over the precise
	   meaning of the sequence point rules in subtle cases.  Links to discussions of the
	   problem, including proposed formal definitions, may be found on the GCC readings page,
	   at <http://gcc.gnu.org/readings.html>.

	   This warning is enabled by -Wall for C and C++.

       -Wreturn-type
	   Warn whenever a function is defined with a return-type that defaults to "int".  Also
	   warn about any "return" statement with no return-value in a function whose return-type
	   is not "void".

	   For C, also warn if the return type of a function has a type qualifier such as
	   "const".  Such a type qualifier has no effect, since the value returned by a function
	   is not an lvalue.  ISO C prohibits qualified "void" return types on function
	   definitions, so such return types always receive a warning even without this option.

	   For C++, a function without return type always produces a diagnostic message, even
	   when -Wno-return-type is specified.	The only exceptions are main and functions
	   defined in system headers.

	   This warning is enabled by -Wall.

       -Wswitch
	   Warn whenever a "switch" statement has an index of enumerated type and lacks a "case"
	   for one or more of the named codes of that enumeration.  (The presence of a "default"
	   label prevents this warning.)  "case" labels outside the enumeration range also
	   provoke warnings when this option is used.  This warning is enabled by -Wall.

       -Wswitch-default
	   Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
	   Warn whenever a "switch" statement has an index of enumerated type and lacks a "case"
	   for one or more of the named codes of that enumeration.  "case" labels outside the
	   enumeration range also provoke warnings when this option is used.

       -Wtrigraphs
	   Warn if any trigraphs are encountered that might change the meaning of the program
	   (trigraphs within comments are not warned about).  This warning is enabled by -Wall.

       -Wunused-function
	   Warn whenever a static function is declared but not defined or a non-inline static
	   function is unused.	This warning is enabled by -Wall.

       -Wunused-label
	   Warn whenever a label is declared but not used.  This warning is enabled by -Wall.

	   To suppress this warning use the unused attribute.

       -Wunused-parameter
	   Warn whenever a function parameter is unused aside from its declaration.

	   To suppress this warning use the unused attribute.

       -Wunused-variable
	   Warn whenever a local variable or non-constant static variable is unused aside from
	   its declaration.  This warning is enabled by -Wall.

	   To suppress this warning use the unused attribute.

       -Wunused-value
	   Warn whenever a statement computes a result that is explicitly not used.  This warning
	   is enabled by -Wall.

	   To suppress this warning cast the expression to void.

       -Wunused
	   All the above -Wunused options combined.

	   In order to get a warning about an unused function parameter, you must either specify
	   -Wextra -Wunused (note that -Wall implies -Wunused), or separately specify
	   -Wunused-parameter.

       -Wuninitialized
	   Warn if an automatic variable is used without first being initialized or if a variable
	   may be clobbered by a "setjmp" call.

	   These warnings are possible only in optimizing compilation, because they require data
	   flow information that is computed only when optimizing.  If you do not specify -O, you
	   will not get these warnings. Instead, GCC will issue a warning about -Wuninitialized
	   requiring -O.

	   If you want to warn about code which uses the uninitialized value of the variable in
	   its own initializer, use the -Winit-self option.

	   These warnings occur for individual uninitialized or clobbered elements of structure,
	   union or array variables as well as for variables which are uninitialized or clobbered
	   as a whole.	They do not occur for variables or elements declared "volatile".  Because
	   these warnings depend on optimization, the exact variables or elements for which there
	   are warnings will depend on the precise optimization options and version of GCC used.

	   Note that there may be no warning about a variable that is used only to compute a
	   value that itself is never used, because such computations may be deleted by data flow
	   analysis before the warnings are printed.

	   These warnings are made optional because GCC is not smart enough to see all the
	   reasons why the code might be correct despite appearing to have an error.  Here is one
	   example of how this can happen:

		   {
		     int x;
		     switch (y)
		       {
		       case 1: x = 1;
			 break;
		       case 2: x = 4;
			 break;
		       case 3: x = 5;
		       }
		     foo (x);
		   }

	   If the value of "y" is always 1, 2 or 3, then "x" is always initialized, but GCC
	   doesn't know this.  Here is another common case:

		   {
		     int save_y;
		     if (change_y) save_y = y, y = new_y;
		     ...
		     if (change_y) y = save_y;
		   }

	   This has no bug because "save_y" is used only if it is set.

	   This option also warns when a non-volatile automatic variable might be changed by a
	   call to "longjmp".  These warnings as well are possible only in optimizing
	   compilation.

	   The compiler sees only the calls to "setjmp".  It cannot know where "longjmp" will be
	   called; in fact, a signal handler could call it at any point in the code.  As a
	   result, you may get a warning even when there is in fact no problem because "longjmp"
	   cannot in fact be called at the place which would cause a problem.

	   Some spurious warnings can be avoided if you declare all the functions you use that
	   never return as "noreturn".

	   This warning is enabled by -Wall.

       -Wunknown-pragmas
	   Warn when a #pragma directive is encountered which is not understood by GCC.  If this
	   command line option is used, warnings will even be issued for unknown pragmas in
	   system header files.  This is not the case if the warnings were only enabled by the
	   -Wall command line option.

       -Wno-pragmas
	   Do not warn about misuses of pragmas, such as incorrect parameters, invalid syntax, or
	   conflicts between pragmas.  See also -Wunknown-pragmas.

       -Wstrict-aliasing
	   This option is only active when -fstrict-aliasing is active.  It warns about code
	   which might break the strict aliasing rules that the compiler is using for
	   optimization.  The warning does not catch all cases, but does attempt to catch the
	   more common pitfalls.  It is included in -Wall.

       -Wstrict-aliasing=2
	   This option is only active when -fstrict-aliasing is active.  It warns about code
	   which might break the strict aliasing rules that the compiler is using for
	   optimization.  This warning catches more cases than -Wstrict-aliasing, but it will
	   also give a warning for some ambiguous cases that are safe.

       -Wstrict-overflow
       -Wstrict-overflow=n
	   This option is only active when -fstrict-overflow is active.  It warns about cases
	   where the compiler optimizes based on the assumption that signed overflow does not
	   occur.  Note that it does not warn about all cases where the code might overflow: it
	   only warns about cases where the compiler implements some optimization.  Thus this
	   warning depends on the optimization level.

	   An optimization which assumes that signed overflow does not occur is perfectly safe if
	   the values of the variables involved are such that overflow never does, in fact,
	   occur.  Therefore this warning can easily give a false positive: a warning about code
	   which is not actually a problem.  To help focus on important issues, several warning
	   levels are defined.	No warnings are issued for the use of undefined signed overflow
	   when estimating how many iterations a loop will require, in particular when
	   determining whether a loop will be executed at all.

	   -Wstrict-overflow=1
	       Warn about cases which are both questionable and easy to avoid.	For example: "x +
	       1 > x"; with -fstrict-overflow, the compiler will simplify this to 1.  This level
	       of -Wstrict-overflow is enabled by -Wall; higher levels are not, and must be
	       explicitly requested.

	   -Wstrict-overflow=2
	       Also warn about other cases where a comparison is simplified to a constant.  For
	       example: "abs (x) >= 0".  This can only be simplified when -fstrict-overflow is in
	       effect, because "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero.
	       -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2.

	   -Wstrict-overflow=3
	       Also warn about other cases where a comparison is simplified.  For example: "x + 1
	       > 1" will be simplified to "x > 0".

	   -Wstrict-overflow=4
	       Also warn about other simplifications not covered by the above cases.  For
	       example: "(x * 10) / 5" will be simplified to "x * 2".

	   -Wstrict-overflow=5
	       Also warn about cases where the compiler reduces the magnitude of a constant
	       involved in a comparison.  For example: "x + 2 > y" will be simplified to "x + 1
	       >= y".  This is reported only at the highest warning level because this
	       simplification applies to many comparisons, so this warning level will give a very
	       large number of false positives.

       -Wall
	   All of the above -W options combined.  This enables all the warnings about
	   constructions that some users consider questionable, and that are easy to avoid (or
	   modify to prevent the warning), even in conjunction with macros.  This also enables
	   some language-specific warnings described in C++ Dialect Options and Objective-C and
	   Objective-C++ Dialect Options.

       -Wmost
	   This is equivalent to -Wall -Wno-parentheses.  (APPLE ONLY)

       The following -W... options are not implied by -Wall.  Some of them warn about
       constructions that users generally do not consider questionable, but which occasionally
       you might wish to check for; others warn about constructions that are necessary or hard to
       avoid in some cases, and there is no simple way to modify the code to suppress the
       warning.

       -Wextra
	   (This option used to be called -W.  The older name is still supported, but the newer
	   name is more descriptive.)  Print extra warning messages for these events:

	   o   A function can return either with or without a value.  (Falling off the end of the
	       function body is considered returning without a value.)	For example, this
	       function would evoke such a warning:

		       foo (a)
		       {
			 if (a > 0)
			   return a;
		       }

	   o   An expression-statement or the left-hand side of a comma expression contains no
	       side effects.  To suppress the warning, cast the unused expression to void.  For
	       example, an expression such as x[i,j] will cause a warning, but x[(void)i,j] will
	       not.

	   o   An unsigned value is compared against zero with < or >=.

	   o   Storage-class specifiers like "static" are not the first things in a declaration.
	       According to the C Standard, this usage is obsolescent.

	   o   If -Wall or -Wunused is also specified, warn about unused arguments.

	   o   A comparison between signed and unsigned values could produce an incorrect result
	       when the signed value is converted to unsigned.	(But don't warn if
	       -Wno-sign-compare is also specified.)

	   o   An aggregate has an initializer which does not initialize all members.  This
	       warning can be independently controlled by -Wmissing-field-initializers.

	   o   An initialized field without side effects is overridden when using designated
	       initializers.  This warning can be independently controlled by -Woverride-init.

	   o   A function parameter is declared without a type specifier in K&R-style functions:

		       void foo(bar) { }

	   o   An empty body occurs in an if or else statement.

	   o   (C++ only) An empty body occurs in a while or for statement with no whitespacing
	       before the semicolon. This warning can be independently controlled by
	       -Wempty-body.

	   o   A pointer is compared against integer zero with <, <=, >, or >=.

	   o   A variable might be changed by longjmp or vfork.

	   o   (C++ only) An enumerator and a non-enumerator both appear in a conditional
	       expression.

	   o   (C++ only) A non-static reference or non-static const member appears in a class
	       without constructors.

	   o   (C++ only) Ambiguous virtual bases.

	   o   (C++ only) Subscripting an array which has been declared register.

	   o   (C++ only) Taking the address of a variable which has been declared register.

	   o   (C++ only) A base class is not initialized in a derived class' copy constructor.

       -Wno-div-by-zero
	   Do not warn about compile-time integer division by zero.  Floating point division by
	   zero is not warned about, as it can be a legitimate way of obtaining infinities and
	   NaNs.

       -Wsystem-headers
	   Print warning messages for constructs found in system header files.	Warnings from
	   system headers are normally suppressed, on the assumption that they usually do not
	   indicate real problems and would only make the compiler output harder to read.  Using
	   this command line option tells GCC to emit warnings from system headers as if they
	   occurred in user code.  However, note that using -Wall in conjunction with this option
	   will not warn about unknown pragmas in system headers---for that, -Wunknown-pragmas
	   must also be used.

       -Wfloat-equal
	   Warn if floating point values are used in equality comparisons.

	   The idea behind this is that sometimes it is convenient (for the programmer) to
	   consider floating-point values as approximations to infinitely precise real numbers.
	   If you are doing this, then you need to compute (by analyzing the code, or in some
	   other way) the maximum or likely maximum error that the computation introduces, and
	   allow for it when performing comparisons (and when producing output, but that's a
	   different problem).	In particular, instead of testing for equality, you would check
	   to see whether the two values have ranges that overlap; and this is done with the
	   relational operators, so equality comparisons are probably mistaken.

       -Wfour-char-constants
	   Warn about four char constants, e.g. OSType 'APPL'.	This warning is disabled by
	   default.

       -Wtraditional (C only)
	   Warn about certain constructs that behave differently in traditional and ISO C.  Also
	   warn about ISO C constructs that have no traditional C equivalent, and/or problematic
	   constructs which should be avoided.

	   o   Macro parameters that appear within string literals in the macro body.  In
	       traditional C macro replacement takes place within string literals, but does not
	       in ISO C.

	   o   In traditional C, some preprocessor directives did not exist.  Traditional
	       preprocessors would only consider a line to be a directive if the # appeared in
	       column 1 on the line.  Therefore -Wtraditional warns about directives that
	       traditional C understands but would ignore because the # does not appear as the
	       first character on the line.  It also suggests you hide directives like #pragma
	       not understood by traditional C by indenting them.  Some traditional
	       implementations would not recognize #elif, so it suggests avoiding it altogether.

	   o   A function-like macro that appears without arguments.

	   o   The unary plus operator.

	   o   The U integer constant suffix, or the F or L floating point constant suffixes.
	       (Traditional C does support the L suffix on integer constants.)	Note, these
	       suffixes appear in macros defined in the system headers of most modern systems,
	       e.g. the _MIN/_MAX macros in "<limits.h>".  Use of these macros in user code might
	       normally lead to spurious warnings, however GCC's integrated preprocessor has
	       enough context to avoid warning in these cases.

	   o   A function declared external in one block and then used after the end of the
	       block.

	   o   A "switch" statement has an operand of type "long".

	   o   A non-"static" function declaration follows a "static" one.  This construct is not
	       accepted by some traditional C compilers.

	   o   The ISO type of an integer constant has a different width or signedness from its
	       traditional type.  This warning is only issued if the base of the constant is ten.
	       I.e. hexadecimal or octal values, which typically represent bit patterns, are not
	       warned about.

	   o   Usage of ISO string concatenation is detected.

	   o   Initialization of automatic aggregates.

	   o   Identifier conflicts with labels.  Traditional C lacks a separate namespace for
	       labels.

	   o   Initialization of unions.  If the initializer is zero, the warning is omitted.
	       This is done under the assumption that the zero initializer in user code appears
	       conditioned on e.g. "__STDC__" to avoid missing initializer warnings and relies on
	       default initialization to zero in the traditional C case.

	   o   Conversions by prototypes between fixed/floating point values and vice versa.  The
	       absence of these prototypes when compiling with traditional C would cause serious
	       problems.  This is a subset of the possible conversion warnings, for the full set
	       use -Wconversion.

	   o   Use of ISO C style function definitions.  This warning intentionally is not issued
	       for prototype declarations or variadic functions because these ISO C features will
	       appear in your code when using libiberty's traditional C compatibility macros,
	       "PARAMS" and "VPARAMS".	This warning is also bypassed for nested functions
	       because that feature is already a GCC extension and thus not relevant to
	       traditional C compatibility.

       -Wdeclaration-after-statement (C only)
	   Warn when a declaration is found after a statement in a block.  This construct, known
	   from C++, was introduced with ISO C99 and is by default allowed in GCC.  It is not
	   supported by ISO C90 and was not supported by GCC versions before GCC 3.0.

       -Wno-discard-qual
	   This flag allows user to suppress warning that is issued when qualification is
	   discarded in situations like, initialization, assignment and argument passing.

       -Wundef
	   Warn if an undefined identifier is evaluated in an #if directive.

       -Wno-endif-labels
	   Do not warn whenever an #else or an #endif are followed by text.

       -Wshadow
	   Warn whenever a local variable shadows another local variable, parameter or global
	   variable or whenever a built-in function is shadowed.

       -Wlarger-than-len
	   Warn whenever an object of larger than len bytes is defined.

       -Wunsafe-loop-optimizations
	   Warn if the loop cannot be optimized because the compiler could not assume anything on
	   the bounds of the loop indices.  With -funsafe-loop-optimizations warn if the compiler
	   made such assumptions.

       -Wpointer-arith
	   Warn about anything that depends on the "size of" a function type or of "void".  GNU C
	   assigns these types a size of 1, for convenience in calculations with "void *"
	   pointers and pointers to functions.

       -Wbad-function-cast (C only)
	   Warn whenever a function call is cast to a non-matching type.  For example, warn if
	   "int malloc()" is cast to "anything *".

       -Wc++-compat
	   Warn about ISO C constructs that are outside of the common subset of ISO C and ISO
	   C++, e.g. request for implicit conversion from "void *" to a pointer to non-"void"
	   type.

       -Wcast-qual
	   Warn whenever a pointer is cast so as to remove a type qualifier from the target type.
	   For example, warn if a "const char *" is cast to an ordinary "char *".

       -Wcast-align
	   Warn whenever a pointer is cast such that the required alignment of the target is
	   increased.  For example, warn if a "char *" is cast to an "int *" on machines where
	   integers can only be accessed at two- or four-byte boundaries.

       -Wwrite-strings
	   When compiling C, give string constants the type "const char[length]" so that copying
	   the address of one into a non-"const" "char *" pointer will get a warning; when
	   compiling C++, warn about the deprecated conversion from string literals to "char *".
	   This warning, by default, is enabled for C++ programs.  These warnings will help you
	   find at compile time code that can try to write into a string constant, but only if
	   you have been very careful about using "const" in declarations and prototypes.
	   Otherwise, it will just be a nuisance; this is why we did not make -Wall request these
	   warnings.

       -Wconversion
	   Warn if a prototype causes a type conversion that is different from what would happen
	   to the same argument in the absence of a prototype.	This includes conversions of
	   fixed point to floating and vice versa, and conversions changing the width or
	   signedness of a fixed point argument except when the same as the default promotion.

	   Also, warn if a negative integer constant expression is implicitly converted to an
	   unsigned type.  For example, warn about the assignment "x = -1" if "x" is unsigned.
	   But do not warn about explicit casts like "(unsigned) -1".

       -Wshorten-64-to-32
	   Warn if a value is implicitly converted from a 64 bit type to a 32 bit type.

       -Wempty-body
	   Warn if an empty body occurs in an if or else statement.  Additionally, in C++, warn
	   when an empty body occurs in a while or for statement with no whitespacing before the
	   semicolon.  This warning is also enabled by -Wextra.

       -Wsign-compare
	   Warn when a comparison between signed and unsigned values could produce an incorrect
	   result when the signed value is converted to unsigned.  This warning is also enabled
	   by -Wextra; to get the other warnings of -Wextra without this warning, use -Wextra
	   -Wno-sign-compare.

       -Waddress
	   Warn about suspicious uses of memory addresses. These include using the address of a
	   function in a conditional expression, such as "void func(void); if (func)", and
	   comparisons against the memory address of a string literal, such as "if (x == "abc")".
	   Such uses typically indicate a programmer error: the address of a function always
	   evaluates to true, so their use in a conditional usually indicate that the programmer
	   forgot the parentheses in a function call; and comparisons against string literals
	   result in unspecified behavior and are not portable in C, so they usually indicate
	   that the programmer intended to use "strcmp".  This warning is enabled by -Wall.

       -Waggregate-return
	   Warn if any functions that return structures or unions are defined or called.  (In
	   languages where you can return an array, this also elicits a warning.)

       -Wno-attributes
	   Do not warn if an unexpected "__attribute__" is used, such as unrecognized attributes,
	   function attributes applied to variables, etc.  This will not stop errors for
	   incorrect use of supported attributes.

       -Wstrict-prototypes (C only)
	   Warn if a function is declared or defined without specifying the argument types.  (An
	   old-style function definition is permitted without a warning if preceded by a
	   declaration which specifies the argument types.)

       -Wold-style-definition (C only)
	   Warn if an old-style function definition is used.  A warning is given even if there is
	   a previous prototype.

       -Wmissing-prototypes
	   Warn if a global function is defined without a previous prototype declaration.  This
	   warning is issued even if the definition itself provides a prototype.  The aim is to
	   detect global functions that fail to be declared in header files.

       -Wmissing-declarations (C only)
	   Warn if a global function is defined without a previous declaration.  Do so even if
	   the definition itself provides a prototype.	Use this option to detect global
	   functions that are not declared in header files.

       -Wmissing-field-initializers
	   Warn if a structure's initializer has some fields missing.  For example, the following
	   code would cause such a warning, because "x.h" is implicitly zero:

		   struct s { int f, g, h; };
		   struct s x = { 3, 4 };

	   This option does not warn about designated initializers, so the following modification
	   would not trigger a warning:

		   struct s { int f, g, h; };
		   struct s x = { .f = 3, .g = 4 };

	   This warning is included in -Wextra.  To get other -Wextra warnings without this one,
	   use -Wextra -Wno-missing-field-initializers.

       -Wmissing-noreturn
	   Warn about functions which might be candidates for attribute "noreturn".  Note these
	   are only possible candidates, not absolute ones.  Care should be taken to manually
	   verify functions actually do not ever return before adding the "noreturn" attribute,
	   otherwise subtle code generation bugs could be introduced.  You will not get a warning
	   for "main" in hosted C environments.

       -Wmissing-format-attribute
	   Warn about function pointers which might be candidates for "format" attributes.  Note
	   these are only possible candidates, not absolute ones.  GCC will guess that function
	   pointers with "format" attributes that are used in assignment, initialization,
	   parameter passing or return statements should have a corresponding "format" attribute
	   in the resulting type.  I.e. the left-hand side of the assignment or initialization,
	   the type of the parameter variable, or the return type of the containing function
	   respectively should also have a "format" attribute to avoid the warning.

	   GCC will also warn about function definitions which might be candidates for "format"
	   attributes.	Again, these are only possible candidates.  GCC will guess that "format"
	   attributes might be appropriate for any function that calls a function like "vprintf"
	   or "vscanf", but this might not always be the case, and some functions for which
	   "format" attributes are appropriate may not be detected.

       -Wno-multichar
	   Do not warn if a multicharacter constant ('FOO') is used.  Usually they indicate a
	   typo in the user's code, as they have implementation-defined values, and should not be
	   used in portable code.  This flag does not control warning for a constant with four
	   characters, use -Wfour-char-constants instead.

       -Wnormalized=<none|id|nfc|nfkc>
	   In ISO C and ISO C++, two identifiers are different if they are different sequences of
	   characters.	However, sometimes when characters outside the basic ASCII character set
	   are used, you can have two different character sequences that look the same.  To avoid
	   confusion, the ISO 10646 standard sets out some normalization rules which when applied
	   ensure that two sequences that look the same are turned into the same sequence.  GCC
	   can warn you if you are using identifiers which have not been normalized; this option
	   controls that warning.

	   There are four levels of warning that GCC supports.	The default is -Wnormalized=nfc,
	   which warns about any identifier which is not in the ISO 10646 "C" normalized form,
	   NFC.  NFC is the recommended form for most uses.

	   Unfortunately, there are some characters which ISO C and ISO C++ allow in identifiers
	   that when turned into NFC aren't allowable as identifiers.  That is, there's no way to
	   use these symbols in portable ISO C or C++ and have all your identifiers in NFC.
	   -Wnormalized=id suppresses the warning for these characters.  It is hoped that future
	   versions of the standards involved will correct this, which is why this option is not
	   the default.

	   You can switch the warning off for all characters by writing -Wnormalized=none.  You
	   would only want to do this if you were using some other normalization scheme (like
	   "D"), because otherwise you can easily create bugs that are literally impossible to
	   see.

	   Some characters in ISO 10646 have distinct meanings but look identical in some fonts
	   or display methodologies, especially once formatting has been applied.  For instance
	   "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N", will display just like a regular "n"
	   which has been placed in a superscript.  ISO 10646 defines the NFKC normalization
	   scheme to convert all these into a standard form as well, and GCC will warn if your
	   code is not in NFKC if you use -Wnormalized=nfkc.  This warning is comparable to
	   warning about every identifier that contains the letter O because it might be confused
	   with the digit 0, and so is not the default, but may be useful as a local coding
	   convention if the programming environment is unable to be fixed to display these
	   characters distinctly.

       -Wno-deprecated-declarations
	   Do not warn about uses of functions, variables, and types marked as deprecated by
	   using the "deprecated" attribute.

       -Wno-overflow
	   Do not warn about compile-time overflow in constant expressions.

       -Woverride-init
	   Warn if an initialized field without side effects is overridden when using designated
	   initializers.

	   This warning is included in -Wextra.  To get other -Wextra warnings without this one,
	   use -Wextra -Wno-override-init.

       -Wpacked
	   Warn if a structure is given the packed attribute, but the packed attribute has no
	   effect on the layout or size of the structure.  Such structures may be mis-aligned for
	   little benefit.  For instance, in this code, the variable "f.x" in "struct bar" will
	   be misaligned even though "struct bar" does not itself have the packed attribute:

		   struct foo {
		     int x;
		     char a, b, c, d;
		   } __attribute__((packed));
		   struct bar {
		     char z;
		     struct foo f;
		   };

       -Wpadded
	   Warn if padding is included in a structure, either to align an element of the
	   structure or to align the whole structure.  Sometimes when this happens it is possible
	   to rearrange the fields of the structure to reduce the padding and so make the
	   structure smaller.

       -Wredundant-decls
	   Warn if anything is declared more than once in the same scope, even in cases where
	   multiple declaration is valid and changes nothing.

       -Wnested-externs (C only)
	   Warn if an "extern" declaration is encountered within a function.

       -Wunreachable-code
	   Warn if the compiler detects that code will never be executed.

	   This option is intended to warn when the compiler detects that at least a whole line
	   of source code will never be executed, because some condition is never satisfied or
	   because it is after a procedure that never returns.

	   It is possible for this option to produce a warning even though there are
	   circumstances under which part of the affected line can be executed, so care should be
	   taken when removing apparently-unreachable code.

	   For instance, when a function is inlined, a warning may mean that the line is
	   unreachable in only one inlined copy of the function.

	   This option is not made part of -Wall because in a debugging version of a program
	   there is often substantial code which checks correct functioning of the program and
	   is, hopefully, unreachable because the program does work.  Another common use of
	   unreachable code is to provide behavior which is selectable at compile-time.

       -Winline
	   Warn if a function can not be inlined and it was declared as inline.  Even with this
	   option, the compiler will not warn about failures to inline functions declared in
	   system headers.

	   The compiler uses a variety of heuristics to determine whether or not to inline a
	   function.  For example, the compiler takes into account the size of the function being
	   inlined and the amount of inlining that has already been done in the current function.
	   Therefore, seemingly insignificant changes in the source program can cause the
	   warnings produced by -Winline to appear or disappear.

       -Wno-invalid-offsetof (C++ only)
	   Suppress warnings from applying the offsetof macro to a non-POD type.  According to
	   the 1998 ISO C++ standard, applying offsetof to a non-POD type is undefined.  In
	   existing C++ implementations, however, offsetof typically gives meaningful results
	   even when applied to certain kinds of non-POD types. (Such as a simple struct that
	   fails to be a POD type only by virtue of having a constructor.)  This flag is for
	   users who are aware that they are writing nonportable code and who have deliberately
	   chosen to ignore the warning about it.

	   The restrictions on offsetof may be relaxed in a future version of the C++ standard.

       -Wno-int-to-pointer-cast (C only)
	   Suppress warnings from casts to pointer type of an integer of a different size.

       -Wno-pointer-to-int-cast (C only)
	   Suppress warnings from casts from a pointer to an integer type of a different size.

       -Winvalid-pch
	   Warn if a precompiled header is found in the search path but can't be used.

       -Wlong-long
	   Warn if long long type is used.  This is default.  To inhibit the warning messages,
	   use -Wno-long-long.	Flags -Wlong-long and -Wno-long-long are taken into account only
	   when -pedantic flag is used.

       -Wvariadic-macros
	   Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU alternate syntax
	   when in pedantic ISO C99 mode.  This is default.  To inhibit the warning messages, use
	   -Wno-variadic-macros.

       -Wvolatile-register-var
	   Warn if a register variable is declared volatile.  The volatile modifier does not
	   inhibit all optimizations that may eliminate reads and/or writes to register
	   variables.

       -Wdisabled-optimization
	   Warn if a requested optimization pass is disabled.  This warning does not generally
	   indicate that there is anything wrong with your code; it merely indicates that GCC's
	   optimizers were unable to handle the code effectively.  Often, the problem is that
	   your code is too big or too complex; GCC will refuse to optimize programs when the
	   optimization itself is likely to take inordinate amounts of time.

       -Wpointer-sign
	   Warn for pointer argument passing or assignment with different signedness.  This
	   option is only supported for C and Objective-C.  It is implied by -Wall and by
	   -pedantic, which can be disabled with -Wno-pointer-sign.

       -Werror
	   Make all warnings into errors.

       -Werror=
	   Make the specified warning into an errors.  The specifier for a warning is appended,
	   for example -Werror=switch turns the warnings controlled by -Wswitch into errors.
	   This switch takes a negative form, to be used to negate -Werror for specific warnings,
	   for example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror
	   is in effect.  You can use the -fdiagnostics-show-option option to have each
	   controllable warning amended with the option which controls it, to determine what to
	   use with this option.

	   Note that specifying -Werror=foo automatically implies -Wfoo.  However, -Wno-error=foo
	   does not imply anything.

       -Wstack-protector
	   This option is only active when -fstack-protector is active.  It warns about functions
	   that will not be protected against stack smashing.

       -Woverlength-strings
	   Warn about string constants which are longer than the "minimum maximum" length
	   specified in the C standard.  Modern compilers generally allow string constants which
	   are much longer than the standard's minimum limit, but very portable programs should
	   avoid using longer strings.

	   The limit applies after string constant concatenation, and does not count the trailing
	   NUL.  In C89, the limit was 509 characters; in C99, it was raised to 4095.  C++98 does
	   not specify a normative minimum maximum, so we do not diagnose overlength strings in
	   C++.

	   This option is implied by -pedantic, and can be disabled with -Wno-overlength-strings.

       Options for Debugging Your Program or GCC

       GCC has various special options that are used for debugging either your program or GCC:

       -g  Produce debugging information in the operating system's native format (stabs, COFF,
	   XCOFF, or DWARF 2).	GDB can work with this debugging information.

	   On most systems that use stabs format, -g enables use of extra debugging information
	   that only GDB can use; this extra information makes debugging work better in GDB but
	   will probably make other debuggers crash or refuse to read the program.  If you want
	   to control for certain whether to generate the extra information, use -gstabs+ or
	   -gstabs (see below).

	   GCC allows you to use -g with -O.  The shortcuts taken by optimized code may
	   occasionally produce surprising results: some variables you declared may not exist at
	   all; flow of control may briefly move where you did not expect it; some statements may
	   not be executed because they compute constant results or their values were already at
	   hand; some statements may execute in different places because they were moved out of
	   loops.

	   Nevertheless it proves possible to debug optimized output.  This makes it reasonable
	   to use the optimizer for programs that might have bugs.

	   The following options are useful when GCC is generated with the capability for more
	   than one debugging format.

       -ggdb
	   Produce debugging information for use by GDB.  This means to use the most expressive
	   format available (DWARF 2, stabs, or the native format if neither of those are
	   supported), including GDB extensions if at all possible.

       -gstabs
	   Produce debugging information in stabs format (if that is supported), without GDB
	   extensions.	This is the format used by DBX on most BSD systems.  On MIPS, Alpha and
	   System V Release 4 systems this option produces stabs debugging output which is not
	   understood by DBX or SDB.  On System V Release 4 systems this option requires the GNU
	   assembler.

       -flimit-debug-info
	   Limit debug information produced to reduce size of debug binary.

       -feliminate-unused-debug-symbols
	   Produce debugging information in stabs format (if that is supported), for only symbols
	   that are actually used.

       -femit-class-debug-always
	   Instead of emitting debugging information for a C++ class in only one object file,
	   emit it in all object files using the class.  This option should be used only with
	   debuggers that are unable to handle the way GCC normally emits debugging information
	   for classes because using this option will increase the size of debugging information
	   by as much as a factor of two.

       -gstabs+
	   Produce debugging information in stabs format (if that is supported), using GNU
	   extensions understood only by the GNU debugger (GDB).  The use of these extensions is
	   likely to make other debuggers crash or refuse to read the program.

       -gdwarf-2
	   Produce debugging information in DWARF version 2 format (if that is supported).  This
	   is the format used by DBX on IRIX 6.  With this option, GCC uses features of DWARF
	   version 3 when they are useful; version 3 is upward compatible with version 2, but may
	   still cause problems for older debuggers.

	   (Other debug formats, such as -gcoff, are not supported in Darwin or Mac OS X.)

       -glevel
       -ggdblevel
       -gstabslevel
	   Request debugging information and also use level to specify how much information.  The
	   default level is 2.

	   Level 0 produces no debug information at all.  Thus, -g0 negates -g.

	   Level 1 produces minimal information, enough for making backtraces in parts of the
	   program that you don't plan to debug.  This includes descriptions of functions and
	   external variables, but no information about local variables and no line numbers.

	   Level 3 includes extra information, such as all the macro definitions present in the
	   program.  Some debuggers support macro expansion when you use -g3.

	   -gdwarf-2 does not accept a concatenated debug level, because GCC used to support an
	   option -gdwarf that meant to generate debug information in version 1 of the DWARF
	   format (which is very different from version 2), and it would have been too confusing.
	   That debug format is long obsolete, but the option cannot be changed now.  Instead use
	   an additional -glevel option to change the debug level for DWARF2.

       -feliminate-dwarf2-dups
	   Compress DWARF2 debugging information by eliminating duplicated information about each
	   symbol.  This option only makes sense when generating DWARF2 debugging information
	   with -gdwarf-2.

       -p  Generate extra code to write profile information suitable for the analysis program
	   prof.  You must use this option when compiling the source files you want data about,
	   and you must also use it when linking.

       -pg Generate extra code to write profile information suitable for the analysis program
	   gprof.  You must use this option when compiling the source files you want data about,
	   and you must also use it when linking.

       -Q  Makes the compiler print out each function name as it is compiled, and print some
	   statistics about each pass when it finishes.

       -ftime-report
	   Makes the compiler print some statistics about the time consumed by each pass when it
	   finishes.

       -fmem-report
	   Makes the compiler print some statistics about permanent memory allocation when it
	   finishes.

       -fopt-diary
	   Enable optimization diary entries using DWARF encoding. This option does nothing
	   unless gdwarf-2 is specified.

       -fprofile-arcs
	   Add code so that program flow arcs are instrumented.  During execution the program
	   records how many times each branch and call is executed and how many times it is taken
	   or returns.	When the compiled program exits it saves this data to a file called
	   auxname.gcda for each source file.  The data may be used for profile-directed
	   optimizations (-fbranch-probabilities), or for test coverage analysis
	   (-ftest-coverage).  Each object file's auxname is generated from the name of the
	   output file, if explicitly specified and it is not the final executable, otherwise it
	   is the basename of the source file.	In both cases any suffix is removed (e.g.
	   foo.gcda for input file dir/foo.c, or dir/foo.gcda for output file specified as -o
	   dir/foo.o).

       --coverage
	   This option is used to compile and link code instrumented for coverage analysis.  The
	   option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov
	   (when linking).  See the documentation for those options for more details.

	   o   Compile the source files with -fprofile-arcs plus optimization and code generation
	       options.  For test coverage analysis, use the additional -ftest-coverage option.
	       You do not need to profile every source file in a program.

	   o   Link your object files with -lgcov or -fprofile-arcs (the latter implies the
	       former).

	   o   Run the program on a representative workload to generate the arc profile
	       information.  This may be repeated any number of times.	You can run concurrent
	       instances of your program, and provided that the file system supports locking, the
	       data files will be correctly updated.  Also "fork" calls are detected and
	       correctly handled (double counting will not happen).

	   o   For profile-directed optimizations, compile the source files again with the same
	       optimization and code generation options plus -fbranch-probabilities.

	   o   For test coverage analysis, use gcov to produce human readable information from
	       the .gcno and .gcda files.  Refer to the gcov documentation for further
	       information.

	   With -fprofile-arcs, for each function of your program GCC creates a program flow
	   graph, then finds a spanning tree for the graph.  Only arcs that are not on the
	   spanning tree have to be instrumented: the compiler adds code to count the number of
	   times that these arcs are executed.	When an arc is the only exit or only entrance to
	   a block, the instrumentation code can be added to the block; otherwise, a new basic
	   block must be created to hold the instrumentation code.

       -ftest-coverage
	   Produce a notes file that the gcov code-coverage utility can use to show program
	   coverage.  Each source file's note file is called auxname.gcno.  Refer to the
	   -fprofile-arcs option above for a description of auxname and instructions on how to
	   generate test coverage data.  Coverage data will match the source files more closely,
	   if you do not optimize.

       -dletters
       -fdump-rtl-pass
	   Says to make debugging dumps during compilation at times specified by letters.    This
	   is used for debugging the RTL-based passes of the compiler.	The file names for most
	   of the dumps are made by appending a pass number and a word to the dumpname.  dumpname
	   is generated from the name of the output file, if explicitly specified and it is not
	   an executable, otherwise it is the basename of the source file. These switches may
	   have different effects when -E is used for preprocessing.

	   Most debug dumps can be enabled either passing a letter to the -d option, or with a
	   long -fdump-rtl switch; here are the possible letters for use in letters and pass, and
	   their meanings:

	   -dA Annotate the assembler output with miscellaneous debugging information.

	   -dB
	   -fdump-rtl-bbro
	       Dump after block reordering, to file.148r.bbro.

	   -dc
	   -fdump-rtl-combine
	       Dump after instruction combination, to the file file.129r.combine.

	   -dC
	   -fdump-rtl-ce1
	   -fdump-rtl-ce2
	       -dC and -fdump-rtl-ce1 enable dumping after the first if conversion, to the file
	       file.117r.ce1.  -dC and -fdump-rtl-ce2 enable dumping after the second if
	       conversion, to the file file.130r.ce2.

	   -dd
	   -fdump-rtl-btl
	   -fdump-rtl-dbr
	       -dd and -fdump-rtl-btl enable dumping after branch target load optimization, to
	       file.31.btl.  -dd and -fdump-rtl-dbr enable dumping after delayed branch
	       scheduling, to file.36.dbr.

	   -dD Dump all macro definitions, at the end of preprocessing, in addition to normal
	       output.

	   -dE
	   -fdump-rtl-ce3
	       Dump after the third if conversion, to file.146r.ce3.

	   -df
	   -fdump-rtl-cfg
	   -fdump-rtl-life
	       -df and -fdump-rtl-cfg enable dumping after control and data flow analysis, to
	       file.116r.cfg.  -df and -fdump-rtl-cfg enable dumping dump after life analysis, to
	       file.128r.life1 and file.135r.life2.

	   -dg
	   -fdump-rtl-greg
	       Dump after global register allocation, to file.139r.greg.

	   -dG
	   -fdump-rtl-gcse
	   -fdump-rtl-bypass
	       -dG and -fdump-rtl-gcse enable dumping after GCSE, to file.114r.gcse.  -dG and
	       -fdump-rtl-bypass enable dumping after jump bypassing and control flow
	       optimizations, to file.115r.bypass.

	   -dh
	   -fdump-rtl-eh
	       Dump after finalization of EH handling code, to file.02.eh.

	   -di
	   -fdump-rtl-sibling
	       Dump after sibling call optimizations, to file.106r.sibling.

	   -dj
	   -fdump-rtl-jump
	       Dump after the first jump optimization, to file.112r.jump.

	   -dk
	   -fdump-rtl-stack
	       Dump after conversion from registers to stack, to file.152r.stack.

	   -dl
	   -fdump-rtl-lreg
	       Dump after local register allocation, to file.138r.lreg.

	   -dL
	   -fdump-rtl-loop2
	       -dL and -fdump-rtl-loop2 enable dumping after the loop optimization pass, to
	       file.119r.loop2, file.120r.loop2_init, file.121r.loop2_invariant, and
	       file.125r.loop2_done.

	   -dm
	   -fdump-rtl-sms
	       Dump after modulo scheduling, to file.136r.sms.

	   -dM
	   -fdump-rtl-mach
	       Dump after performing the machine dependent reorganization pass, to file.155r.mach
	       if that pass exists.

	   -dn
	   -fdump-rtl-rnreg
	       Dump after register renumbering, to file.147r.rnreg.

	   -dN
	   -fdump-rtl-regmove
	       Dump after the register move pass, to file.132r.regmove.

	   -do
	   -fdump-rtl-postreload
	       Dump after post-reload optimizations, to file.24.postreload.

	   -dr
	   -fdump-rtl-expand
	       Dump after RTL generation, to file.104r.expand.

	   -dR
	   -fdump-rtl-sched2
	       Dump after the second scheduling pass, to file.150r.sched2.

	   -ds
	   -fdump-rtl-cse
	       Dump after CSE (including the jump optimization that sometimes follows CSE), to
	       file.113r.cse.

	   -dS
	   -fdump-rtl-sched
	       Dump after the first scheduling pass, to file.21.sched.

	   -dt
	   -fdump-rtl-cse2
	       Dump after the second CSE pass (including the jump optimization that sometimes
	       follows CSE), to file.127r.cse2.

	   -dT
	   -fdump-rtl-tracer
	       Dump after running tracer, to file.118r.tracer.

	   -dV
	   -fdump-rtl-vpt
	   -fdump-rtl-vartrack
	       -dV and -fdump-rtl-vpt enable dumping after the value profile transformations, to
	       file.10.vpt.  -dV and -fdump-rtl-vartrack enable dumping after variable tracking,
	       to file.154r.vartrack.

	   -dw
	   -fdump-rtl-flow2
	       Dump after the second flow pass, to file.142r.flow2.

	   -dz
	   -fdump-rtl-peephole2
	       Dump after the peephole pass, to file.145r.peephole2.

	   -dZ
	   -fdump-rtl-web
	       Dump after live range splitting, to file.126r.web.

	   -da
	   -fdump-rtl-all
	       Produce all the dumps listed above.

	   -dH Produce a core dump whenever an error occurs.

	   -dm Print statistics on memory usage, at the end of the run, to standard error.

	   -dp Annotate the assembler output with a comment indicating which pattern and
	       alternative was used.  The length of each instruction is also printed.

	   -dP Dump the RTL in the assembler output as a comment before each instruction.  Also
	       turns on -dp annotation.

	   -dv For each of the other indicated dump files (either with -d or -fdump-rtl-pass),
	       dump a representation of the control flow graph suitable for viewing with VCG to
	       file.pass.vcg.

	   -dx Just generate RTL for a function instead of compiling it.  Usually used with r
	       (-fdump-rtl-expand).

	   -dy Dump debugging information during parsing, to standard error.

       -fdump-noaddr
	   When doing debugging dumps (see -d option above), suppress address output.  This makes
	   it more feasible to use diff on debugging dumps for compiler invocations with
	   different compiler binaries and/or different text / bss / data / heap / stack / dso
	   start locations.

       -fdump-unnumbered
	   When doing debugging dumps (see -d option above), suppress instruction numbers, line
	   number note and address output.  This makes it more feasible to use diff on debugging
	   dumps for compiler invocations with different options, in particular with and without
	   -g.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
	   Dump a representation of the tree structure for the entire translation unit to a file.
	   The file name is made by appending .tu to the source file name.  If the -options form
	   is used, options controls the details of the dump as described for the -fdump-tree
	   options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
	   Dump a representation of each class's hierarchy and virtual function table layout to a
	   file.  The file name is made by appending .class to the source file name.  If the
	   -options form is used, options controls the details of the dump as described for the
	   -fdump-tree options.

       -fdump-ipa-switch
	   Control the dumping at various stages of inter-procedural analysis language tree to a
	   file.  The file name is generated by appending a switch specific suffix to the source
	   file name.  The following dumps are possible:

	   all Enables all inter-procedural analysis dumps; currently the only produced dump is
	       the cgraph dump.

	   cgraph
	       Dumps information about call-graph optimization, unused function removal, and
	       inlining decisions.

       -fdump-tree-switch
       -fdump-tree-switch-options
	   Control the dumping at various stages of processing the intermediate language tree to
	   a file.  The file name is generated by appending a switch specific suffix to the
	   source file name.  If the -options form is used, options is a list of - separated
	   options that control the details of the dump.  Not all options are applicable to all
	   dumps, those which are not meaningful will be ignored.  The following options are
	   available

	   address
	       Print the address of each node.	Usually this is not meaningful as it changes
	       according to the environment and source file.  Its primary use is for tying up a
	       dump file with a debug environment.

	   slim
	       Inhibit dumping of members of a scope or body of a function merely because that
	       scope has been reached.	Only dump such items when they are directly reachable by
	       some other path.  When dumping pretty-printed trees, this option inhibits dumping
	       the bodies of control structures.

	   raw Print a raw representation of the tree.	By default, trees are pretty-printed into
	       a C-like representation.

	   details
	       Enable more detailed dumps (not honored by every dump option).

	   stats
	       Enable dumping various statistics about the pass (not honored by every dump
	       option).

	   blocks
	       Enable showing basic block boundaries (disabled in raw dumps).

	   vops
	       Enable showing virtual operands for every statement.

	   lineno
	       Enable showing line numbers for statements.

	   uid Enable showing the unique ID ("DECL_UID") for each variable.

	   all Turn on all options, except raw, slim and lineno.

	   The following tree dumps are possible:

	   original
	       Dump before any tree based optimization, to file.original.

	   optimized
	       Dump after all tree based optimization, to file.optimized.

	   inlined
	       Dump after function inlining, to file.inlined.

	   gimple
	       Dump each function before and after the gimplification pass to a file.  The file
	       name is made by appending .gimple to the source file name.

	   cfg Dump the control flow graph of each function to a file.	The file name is made by
	       appending .cfg to the source file name.

	   vcg Dump the control flow graph of each function to a file in VCG format.  The file
	       name is made by appending .vcg to the source file name.	Note that if the file
	       contains more than one function, the generated file cannot be used directly by
	       VCG.  You will need to cut and paste each function's graph into its own separate
	       file first.

	   ch  Dump each function after copying loop headers.  The file name is made by appending
	       .ch to the source file name.

	   ssa Dump SSA related information to a file.	The file name is made by appending .ssa
	       to the source file name.

	   salias
	       Dump structure aliasing variable information to a file.	This file name is made by
	       appending .salias to the source file name.

	   alias
	       Dump aliasing information for each function.  The file name is made by appending
	       .alias to the source file name.

	   ccp Dump each function after CCP.  The file name is made by appending .ccp to the
	       source file name.

	   storeccp
	       Dump each function after STORE-CCP.  The file name is made by appending .storeccp
	       to the source file name.

	   pre Dump trees after partial redundancy elimination.  The file name is made by
	       appending .pre to the source file name.

	   fre Dump trees after full redundancy elimination.  The file name is made by appending
	       .fre to the source file name.

	   copyprop
	       Dump trees after copy propagation.  The file name is made by appending .copyprop
	       to the source file name.

	   store_copyprop
	       Dump trees after store copy-propagation.  The file name is made by appending
	       .store_copyprop to the source file name.

	   dce Dump each function after dead code elimination.	The file name is made by
	       appending .dce to the source file name.

	   mudflap
	       Dump each function after adding mudflap instrumentation.  The file name is made by
	       appending .mudflap to the source file name.

	   sra Dump each function after performing scalar replacement of aggregates.  The file
	       name is made by appending .sra to the source file name.

	   sink
	       Dump each function after performing code sinking.  The file name is made by
	       appending .sink to the source file name.

	   dom Dump each function after applying dominator tree optimizations.	The file name is
	       made by appending .dom to the source file name.

	   dse Dump each function after applying dead store elimination.  The file name is made
	       by appending .dse to the source file name.

	   phiopt
	       Dump each function after optimizing PHI nodes into straightline code.  The file
	       name is made by appending .phiopt to the source file name.

	   forwprop
	       Dump each function after forward propagating single use variables.  The file name
	       is made by appending .forwprop to the source file name.

	   copyrename
	       Dump each function after applying the copy rename optimization.	The file name is
	       made by appending .copyrename to the source file name.

	   nrv Dump each function after applying the named return value optimization on generic
	       trees.  The file name is made by appending .nrv to the source file name.

	   vect
	       Dump each function after applying vectorization of loops.  The file name is made
	       by appending .vect to the source file name.

	   vrp Dump each function after Value Range Propagation (VRP).	The file name is made by
	       appending .vrp to the source file name.

	   all Enable all the available tree dumps with the flags provided in this option.

       -ftree-vectorizer-verbose=n
	   This option controls the amount of debugging output the vectorizer prints.  This
	   information is written to standard error, unless -fdump-tree-all or -fdump-tree-vect
	   is specified, in which case it is output to the usual dump listing file, .vect.  For
	   n=0 no diagnostic information is reported.  If n=1 the vectorizer reports each loop
	   that got vectorized, and the total number of loops that got vectorized.  If n=2 the
	   vectorizer also reports non-vectorized loops that passed the first analysis phase
	   (vect_analyze_loop_form) - i.e. countable, inner-most, single-bb, single-entry/exit
	   loops.  This is the same verbosity level that -fdump-tree-vect-stats uses.  Higher
	   verbosity levels mean either more information dumped for each reported loop, or same
	   amount of information reported for more loops: If n=3, alignment related information
	   is added to the reports.  If n=4, data-references related information (e.g. memory
	   dependences, memory access-patterns) is added to the reports.  If n=5, the vectorizer
	   reports also non-vectorized inner-most loops that did not pass the first analysis
	   phase (i.e. may not be countable, or may have complicated control-flow).  If n=6, the
	   vectorizer reports also non-vectorized nested loops.  For n=7, all the information the
	   vectorizer generates during its analysis and transformation is reported.  This is the
	   same verbosity level that -fdump-tree-vect-details uses.

       -frandom-seed=string
	   This option provides a seed that GCC uses when it would otherwise use random numbers.
	   It is used to generate certain symbol names that have to be different in every
	   compiled file.  It is also used to place unique stamps in coverage data files and the
	   object files that produce them.  You can use the -frandom-seed option to produce
	   reproducibly identical object files.

	   The string should be different for every file you compile.

       -fsched-verbose=n
	   On targets that use instruction scheduling, this option controls the amount of
	   debugging output the scheduler prints.  This information is written to standard error,
	   unless -dS or -dR is specified, in which case it is output to the usual dump listing
	   file, .sched or .sched2 respectively.  However for n greater than nine, the output is
	   always printed to standard error.

	   For n greater than zero, -fsched-verbose outputs the same information as -dRS.  For n
	   greater than one, it also output basic block probabilities, detailed ready list
	   information and unit/insn info.  For n greater than two, it includes RTL at abort
	   point, control-flow and regions info.  And for n over four, -fsched-verbose also
	   includes dependence info.

       -save-temps
	   Store the usual "temporary" intermediate files permanently; place them in the current
	   directory and name them based on the source file.  Thus, compiling foo.c with -c
	   -save-temps would produce files foo.i and foo.s, as well as foo.o.  This creates a
	   preprocessed foo.i output file even though the compiler now normally uses an
	   integrated preprocessor.

	   When used in combination with the -x command line option, -save-temps is sensible
	   enough to avoid over writing an input source file with the same extension as an
	   intermediate file.  The corresponding intermediate file may be obtained by renaming
	   the source file before using -save-temps.

       -time
	   Report the CPU time taken by each subprocess in the compilation sequence.  For C
	   source files, this is the compiler proper and assembler (plus the linker if linking is
	   done).  The output looks like this:

		   # cc1 0.12 0.01
		   # as 0.00 0.01

	   The first number on each line is the "user time", that is time spent executing the
	   program itself.  The second number is "system time", time spent executing operating
	   system routines on behalf of the program.  Both numbers are in seconds.

       -fvar-tracking
	   Run variable tracking pass.	It computes where variables are stored at each position
	   in code.  Better debugging information is then generated (if the debugging information
	   format supports this information).

	   It is enabled by default when compiling with optimization (-Os, -O, -O2, -Oz (APPLE
	   ONLY), ...), debugging information (-g) and the debug info format supports it.

       -print-file-name=library
	   Print the full absolute name of the library file library that would be used when
	   linking---and don't do anything else.  With this option, GCC does not compile or link
	   anything; it just prints the file name.

       -print-multi-directory
	   Print the directory name corresponding to the multilib selected by any other switches
	   present in the command line.  This directory is supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
	   Print the mapping from multilib directory names to compiler switches that enable them.
	   The directory name is separated from the switches by ;, and each switch starts with an
	   @} instead of the @samp{-, without spaces between multiple switches.  This is supposed
	   to ease shell-processing.

       -print-prog-name=program
	   Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
	   Same as -print-file-name=libgcc.a.

	   This is useful when you use -nostdlib or -nodefaultlibs but you do want to link with
	   libgcc.a.  You can do

		   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
	   Print the name of the configured installation directory and a list of program and
	   library directories gcc will search---and don't do anything else.

	   This is useful when gcc prints the error message installation problem, cannot exec
	   cpp0: No such file or directory.  To resolve this you either need to put cpp0 and the
	   other compiler components where gcc expects to find them, or you can set the
	   environment variable GCC_EXEC_PREFIX to the directory where you installed them.  Don't
	   forget the trailing /.

       -dumpmachine
	   Print the compiler's target machine (for example, i686-pc-linux-gnu)---and don't do
	   anything else.

       -dumpversion
	   Print the compiler version (for example, 3.0)---and don't do anything else.

       -dumpspecs
	   Print the compiler's built-in specs---and don't do anything else.  (This is used when
	   GCC itself is being built.)

       -feliminate-unused-debug-types
	   Normally, when producing DWARF2 output, GCC will emit debugging information for all
	   types declared in a compilation unit, regardless of whether or not they are actually
	   used in that compilation unit.  Sometimes this is useful, such as if, in the debugger,
	   you want to cast a value to a type that is not actually used in your program (but is
	   declared).  More often, however, this results in a significant amount of wasted space.
	   With this option, GCC will avoid producing debug symbol output for types that are
	   nowhere used in the source file being compiled.

       Options That Control Optimization

       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the cost of compilation
       and to make debugging produce the expected results.  Statements are independent: if you
       stop the program with a breakpoint between statements, you can then assign a new value to
       any variable or change the program counter to any other statement in the function and get
       exactly the results you would expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve the performance and/or
       code size at the expense of compilation time and possibly the ability to debug the
       program.

       The compiler performs optimization based on the knowledge it has of the program.
       Optimization levels -O and above, in particular, enable unit-at-a-time mode, which allows
       the compiler to consider information gained from later functions in the file when
       compiling a function.  Compiling multiple files at once to a single output file in unit-
       at-a-time mode allows the compiler to use information gained from all of the files when
       compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only optimizations that have a
       flag are listed.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot more memory for
	   a large function.

	   With -O, the compiler tries to reduce code size and execution time, without performing
	   any optimizations that take a great deal of compilation time.

	   -O turns on the following optimization flags: -fdefer-pop -fdelayed-branch
	   -fguess-branch-probability -fcprop-registers -fif-conversion -fif-conversion2
	   -ftree-ccp -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-ter -ftree-lrs
	   -ftree-sra -ftree-copyrename -ftree-fre -ftree-ch -funit-at-a-time -fmerge-constants

	   -O also turns on -fomit-frame-pointer on machines where doing so does not interfere
	   with debugging.

       -O2 Optimize even more.	GCC performs nearly all supported optimizations that do not
	   involve a space-speed tradeoff.  The compiler does not perform loop unrolling or
	   function inlining when you specify -O2.  As compared to -O, this option increases both
	   compilation time and the performance of the generated code.

	   -O2 turns on all optimization flags specified by -O.  It also turns on the following
	   optimization flags: -fthread-jumps -fcrossjumping -foptimize-sibling-calls
	   -fcse-follow-jumps  -fcse-skip-blocks -fgcse  -fgcse-lm -fexpensive-optimizations
	   -frerun-cse-after-loop -fcaller-saves -fpeephole2 -fschedule-insns  -fschedule-insns2
	   -fsched-interblock  -fsched-spec -fregmove -fstrict-aliasing -fstrict-overflow
	   -fdelete-null-pointer-checks -freorder-blocks  -freorder-functions -falign-functions
	   -falign-jumps -falign-loops	-falign-labels -ftree-vrp -ftree-pre

	   Please note the warning under -fgcse about invoking -O2 on programs that use computed
	   gotos.

	   -O2 doesn't turn on -ftree-vrp for the Ada compiler.  This option must be explicitly
	   specified on the command line to be enabled for the Ada compiler.

	   In Apple's version of GCC, -fstrict-aliasing, -freorder-blocks, and -fsched-interblock
	   are disabled by default when optimizing.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also turns on
	   the -finline-functions, -funswitch-loops and -fgcse-after-reload options.

       -O0 Do not optimize.  This is the default.

       -fast
	   Optimize for maximum performance. -fast changes the overall optimization strategy of
	   GCC in order to produce the fastest possible running code for PPC7450 and G5
	   architectures. By default, -fast optimizes for G5. Programs optimized for G5 will not
	   run on PPC7450. To optimize for PPC7450, add -mcpu=7450 on command line.

	   -fast currently enables the following optimization flags (for G5 and PPC7450).  These
	   flags may change in the future.  You cannot override any of these options if you use
	   -fast except by setting -mcpu=7450 (or -fPIC, see below).

	   -O3 -falign-loops-max-skip=15 -falign-jumps-max-skip=15 -falign-loops=16
	   -falign-jumps=16 -falign-functions=16 -malign-natural (except when -fastf is
	   specified) -ffast-math -fstrict-aliasing -funroll-loops -ftree-loop-linear
	   -ftree-loop-memset -mcpu=G5 -mpowerpc-gpopt -mtune=G5  (unless -mtune=G4 is
	   specified).	-fsched-interblock -fgcse-sm -mpowerpc64

	   To build shared libraries with -fast, specify -fPIC on the command line as -fast turns
	   on -mdynamic-no-pic otherwise.

	   Important notes: -ffast-math results in code that is not necessarily IEEE-compliant.
	   -fstrict-aliasing is highly likely to break non-standard-compliant programs.
	   -malign-natural only works properly if the entire program is compiled with it, and
	   none of the standard headers/libraries contain any code that changes alignment when
	   this option is used.

	   On Intel target, -fast currently enables the following optimization flags:

	   -O3 -fomit-frame-pointer -fstrict-aliasing -momit-leaf-frame-pointer -fno-tree-pre
	   -falign-loops

	   All choices of flags enabled by -fast are subject to change without notice.

       -Os Optimize for size, but not at the expense of speed.	-Os enables all -O2 optimizations
	   that do not typically increase code size.  However, instructions are chosen for best
	   performance, regardless of size.  To optimize solely for size on Darwin, use -Oz
	   (APPLE ONLY).

	   The following options are set for -O2, but are disabled under -Os: -falign-functions
	   -falign-jumps  -falign-loops -falign-labels	-freorder-blocks
	   -freorder-blocks-and-partition -fprefetch-loop-arrays  -ftree-vect-loop-version

	   When optimizing with -Os or -Oz (APPLE ONLY) on Darwin, any function up to 30
	   "estimated insns" in size will be considered for inlining.  When compiling C and
	   Objective-C sourcefiles with -Os or -Oz on Darwin, functions explictly marked with the
	   "inline" keyword up to 450 "estimated insns" in size will be considered for inlining.
	   When compiling for Apple POWERPC targets, -Os and -Oz (APPLE ONLY) disable use of the
	   string instructions even though they would usually be smaller, because the kernel
	   can't emulate them correctly in some rare cases.  This behavior is not portable to any
	   other gcc environment, and will not affect most programs at all.  If you really want
	   the string instructions, use -mstring.

       -Oz (APPLE ONLY) Optimize for size, regardless of performance.  -Oz enables the same
	   optimization flags that -Os uses, but -Oz also enables other optimizations intended
	   solely to reduce code size.	In particular, instructions that encode into fewer bytes
	   are preferred over longer instructions that execute in fewer cycles.  -Oz on Darwin is
	   very similar to -Os in FSF distributions of GCC.  -Oz employs the same inlining limits
	   and avoids string instructions just like -Os.

	   If you use multiple -O options, with or without level numbers, the last such option is
	   the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags have both
       positive and negative forms; the negative form of -ffoo would be -fno-foo.  In the table
       below, only one of the forms is listed---the one you typically will use.  You can figure
       out the other form by either removing no- or adding it.

       The following options control specific optimizations.  They are either activated by -O
       options or are related to ones that are.  You can use the following flags in the rare
       cases when "fine-tuning" of optimizations to be performed is desired.

       -fno-default-inline
	   Do not make member functions inline by default merely because they are defined inside
	   the class scope (C++ only).	Otherwise, when you specify -O, member functions defined
	   inside class scope are compiled inline by default; i.e., you don't need to add inline
	   in front of the member function name.

       -fno-defer-pop
	   Always pop the arguments to each function call as soon as that function returns.  For
	   machines which must pop arguments after a function call, the compiler normally lets
	   arguments accumulate on the stack for several function calls and pops them all at
	   once.

	   Disabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fforce-mem
	   Force memory operands to be copied into registers before doing arithmetic on them.
	   This produces better code by making all memory references potential common
	   subexpressions.  When they are not common subexpressions, instruction combination
	   should eliminate the separate register-load. This option is now a nop and will be
	   removed in 4.3.

       -fforce-addr
	   Force memory address constants to be copied into registers before doing arithmetic on
	   them.

       -fomit-frame-pointer
	   Don't keep the frame pointer in a register for functions that don't need one.  This
	   avoids the instructions to save, set up and restore frame pointers; it also makes an
	   extra register available in many functions.	It also makes debugging impossible on
	   some machines.

	   On some machines, such as the VAX, this flag has no effect, because the standard
	   calling sequence automatically handles the frame pointer and nothing is saved by
	   pretending it doesn't exist.  The machine-description macro "FRAME_POINTER_REQUIRED"
	   controls whether a target machine supports this flag.

	   Enabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -foptimize-sibling-calls
	   Optimize sibling and tail recursive calls.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fno-inline
	   Don't pay attention to the "inline" keyword.  Normally this option is used to keep the
	   compiler from expanding any functions inline.  Note that if you are not optimizing, no
	   functions can be expanded inline.

       -finline-functions
	   Integrate all simple functions into their callers.  The compiler heuristically decides
	   which functions are simple enough to be worth integrating in this way.

	   If all calls to a given function are integrated, and the function is declared
	   "static", then the function is normally not output as assembler code in its own right.

	   Enabled at level -O3.

       -finline-functions-called-once
	   Consider all "static" functions called once for inlining into their caller even if
	   they are not marked "inline".  If a call to a given function is integrated, then the
	   function is not output as assembler code in its own right.

	   Enabled if -funit-at-a-time is enabled.

       -fearly-inlining
	   Inline functions marked by "always_inline" and functions whose body seems smaller than
	   the function call overhead early before doing -fprofile-generate instrumentation and
	   real inlining pass.	Doing so makes profiling significantly cheaper and usually
	   inlining faster on programs having large chains of nested wrapper functions.

	   Enabled by default.

       -finline-limit=n
	   By default, GCC limits the size of functions that can be inlined.  This flag allows
	   the control of this limit for functions that are explicitly marked as inline (i.e.,
	   marked with the inline keyword or defined within the class definition in c++).  n is
	   the size of functions that can be inlined in number of pseudo instructions (not
	   counting parameter handling).  The default value of n is 600.  Increasing this value
	   can result in more inlined code at the cost of compilation time and memory
	   consumption.  Decreasing usually makes the compilation faster and less code will be
	   inlined (which presumably means slower programs).  This option is particularly useful
	   for programs that use inlining heavily such as those based on recursive templates with
	   C++.

	   Inlining is actually controlled by a number of parameters, which may be specified
	   individually by using --param name=value.  The -finline-limit=n option sets some of
	   these parameters as follows:

	   max-inline-insns-single
		is set to I<n>/2.

	   max-inline-insns-auto
		is set to I<n>/2.

	   min-inline-insns
		is set to 130 or I<n>/4, whichever is smaller.

	   max-inline-insns-rtl
		is set to I<n>.

	   See below for a documentation of the individual parameters controlling inlining.

	   Note: pseudo instruction represents, in this particular context, an abstract
	   measurement of function's size.  In no way does it represent a count of assembly
	   instructions and as such its exact meaning might change from one release to an
	   another.

       -fkeep-inline-functions
	   In C, emit "static" functions that are declared "inline" into the object file, even if
	   the function has been inlined into all of its callers.  This switch does not affect
	   functions using the "extern inline" extension in GNU C.  In C++, emit any and all
	   inline functions into the object file.

       -fkeep-static-consts
	   Emit variables declared "static const" when optimization isn't turned on, even if the
	   variables aren't referenced.

	   GCC enables this option by default.	If you want to force the compiler to check if the
	   variable was referenced, regardless of whether or not optimization is turned on, use
	   the -fno-keep-static-consts option.

       -flocal-alloc
	   (APPLE ONLY) Enable the local (intra-basic-block) register allocator.

	   GCC enables this option by default.	If you want to force the compiler to supress
	   register allocation within a basic block, use the -fno-local-alloc option.  This
	   option cannot be disabled with -O0, for correctness reasons.

       -fmerge-constants
	   Attempt to merge identical constants (string constants and floating point constants)
	   across compilation units.

	   This option is the default for optimized compilation if the assembler and linker
	   support it.	Use -fno-merge-constants to inhibit this behavior.

	   Enabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fmerge-all-constants
	   Attempt to merge identical constants and identical variables.

	   This option implies -fmerge-constants.  In addition to -fmerge-constants this
	   considers e.g. even constant initialized arrays or initialized constant variables with
	   integral or floating point types.  Languages like C or C++ require each non-automatic
	   variable to have distinct location, so using this option will result in non-conforming
	   behavior.

       -fmodulo-sched
	   Perform swing modulo scheduling immediately before the first scheduling pass.  This
	   pass looks at innermost loops and reorders their instructions by overlapping different
	   iterations.

       -fno-branch-count-reg
	   Do not use "decrement and branch" instructions on a count register, but instead
	   generate a sequence of instructions that decrement a register, compare it against
	   zero, then branch based upon the result.  This option is only meaningful on
	   architectures that support such instructions, which include x86, PowerPC, IA-64 and
	   S/390.

	   The default is -fbranch-count-reg.

       -fno-function-cse
	   Do not put function addresses in registers; make each instruction that calls a
	   constant function contain the function's address explicitly.

	   This option results in less efficient code, but some strange hacks that alter the
	   assembler output may be confused by the optimizations performed when this option is
	   not used.

	   The default is -ffunction-cse

       -fno-zero-initialized-in-bss
	   If the target supports a BSS section, GCC by default puts variables that are
	   initialized to zero into BSS.  This can save space in the resulting code.

	   This option turns off this behavior because some programs explicitly rely on variables
	   going to the data section.  E.g., so that the resulting executable can find the
	   beginning of that section and/or make assumptions based on that.

	   The default is -fzero-initialized-in-bss.

       -fbounds-check
	   For front-ends that support it, generate additional code to check that indices used to
	   access arrays are within the declared range.  This is currently only supported by the
	   Java and Fortran front-ends, where this option defaults to true and false
	   respectively.

       -fmudflap -fmudflapth -fmudflapir
	   For front-ends that support it (C and C++), instrument all risky pointer/array
	   dereferencing operations, some standard library string/heap functions, and some other
	   associated constructs with range/validity tests.  Modules so instrumented should be
	   immune to buffer overflows, invalid heap use, and some other classes of C/C++
	   programming errors.	The instrumentation relies on a separate runtime library
	   (libmudflap), which will be linked into a program if -fmudflap is given at link time.
	   Run-time behavior of the instrumented program is controlled by the MUDFLAP_OPTIONS
	   environment variable.  See "env MUDFLAP_OPTIONS=-help a.out" for its options.

	   Use -fmudflapth instead of -fmudflap to compile and to link if your program is multi-
	   threaded.  Use -fmudflapir, in addition to -fmudflap or -fmudflapth, if
	   instrumentation should ignore pointer reads.  This produces less instrumentation (and
	   therefore faster execution) and still provides some protection against outright memory
	   corrupting writes, but allows erroneously read data to propagate within a program.

       -fthread-jumps
	   Perform optimizations where we check to see if a jump branches to a location where
	   another comparison subsumed by the first is found.  If so, the first branch is
	   redirected to either the destination of the second branch or a point immediately
	   following it, depending on whether the condition is known to be true or false.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fcse-follow-jumps
	   In common subexpression elimination, scan through jump instructions when the target of
	   the jump is not reached by any other path.  For example, when CSE encounters an "if"
	   statement with an "else" clause, CSE will follow the jump when the condition tested is
	   false.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fcse-skip-blocks
	   This is similar to -fcse-follow-jumps, but causes CSE to follow jumps which
	   conditionally skip over blocks.  When CSE encounters a simple "if" statement with no
	   else clause, -fcse-skip-blocks causes CSE to follow the jump around the body of the
	   "if".

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -frerun-cse-after-loop
	   Re-run common subexpression elimination after loop optimizations has been performed.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fgcse
	   Perform a global common subexpression elimination pass.  This pass also performs
	   global constant and copy propagation.

	   Note: When compiling a program using computed gotos, a GCC extension, you may get
	   better runtime performance if you disable the global common subexpression elimination
	   pass by adding -fno-gcse to the command line.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fgcse-lm
	   When -fgcse-lm is enabled, global common subexpression elimination will attempt to
	   move loads which are only killed by stores into themselves.	This allows a loop
	   containing a load/store sequence to be changed to a load outside the loop, and a
	   copy/store within the loop.

	   Enabled by default when gcse is enabled.

       -fgcse-sm
	   When -fgcse-sm is enabled, a store motion pass is run after global common
	   subexpression elimination.  This pass will attempt to move stores out of loops.  When
	   used in conjunction with -fgcse-lm, loops containing a load/store sequence can be
	   changed to a load before the loop and a store after the loop.

	   Not enabled at any optimization level.

       -fgcse-las
	   When -fgcse-las is enabled, the global common subexpression elimination pass
	   eliminates redundant loads that come after stores to the same memory location (both
	   partial and full redundancies).

	   Not enabled at any optimization level.

       -fgcse-after-reload
	   When -fgcse-after-reload is enabled, a redundant load elimination pass is performed
	   after reload.  The purpose of this pass is to cleanup redundant spilling.

       -funsafe-loop-optimizations
	   If given, the loop optimizer will assume that loop indices do not overflow, and that
	   the loops with nontrivial exit condition are not infinite.  This enables a wider range
	   of loop optimizations even if the loop optimizer itself cannot prove that these
	   assumptions are valid.  Using -Wunsafe-loop-optimizations, the compiler will warn you
	   if it finds this kind of loop.

       -fcrossjumping
	   Perform cross-jumping transformation.  This transformation unifies equivalent code and
	   save code size.  The resulting code may or may not perform better than without cross-
	   jumping.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fif-conversion
	   Attempt to transform conditional jumps into branch-less equivalents.  This include use
	   of conditional moves, min, max, set flags and abs instructions, and some tricks doable
	   by standard arithmetics.  The use of conditional execution on chips where it is
	   available is controlled by "if-conversion2".

	   Enabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fif-conversion2
	   Use conditional execution (where available) to transform conditional jumps into
	   branch-less equivalents.

	   Enabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fdelete-null-pointer-checks
	   Use global dataflow analysis to identify and eliminate useless checks for null
	   pointers.  The compiler assumes that dereferencing a null pointer would have halted
	   the program.  If a pointer is checked after it has already been dereferenced, it
	   cannot be null.

	   In some environments, this assumption is not true, and programs can safely dereference
	   null pointers.  Use -fno-delete-null-pointer-checks to disable this optimization for
	   programs which depend on that behavior.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fexpensive-optimizations
	   Perform a number of minor optimizations that are relatively expensive.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -foptimize-register-move
       -fregmove
	   Attempt to reassign register numbers in move instructions and as operands of other
	   simple instructions in order to maximize the amount of register tying.  This is
	   especially helpful on machines with two-operand instructions.

	   Note -fregmove and -foptimize-register-move are the same optimization.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fdelayed-branch
	   If supported for the target machine, attempt to reorder instructions to exploit
	   instruction slots available after delayed branch instructions.

	   Enabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fschedule-insns
	   If supported for the target machine, attempt to reorder instructions to eliminate
	   execution stalls due to required data being unavailable.  This helps machines that
	   have slow floating point or memory load instructions by allowing other instructions to
	   be issued until the result of the load or floating point instruction is required.

	   Enabled at levels -O2, -O3, -Os, -Oz for PPC targets; ignored for x86 targets (APPLE
	   ONLY).

       -fschedule-insns2
	   Similar to -fschedule-insns, but requests an additional pass of instruction scheduling
	   after register allocation has been done.  This is especially useful on machines with a
	   relatively small number of registers and where memory load instructions take more than
	   one cycle.

	   Enabled at levels -O2, -O3, -Os, -Oz for PPC targets; ignored for x86 targets (APPLE
	   ONLY).

       -fno-sched-interblock
	   Don't schedule instructions across basic blocks.  This is normally enabled by default
	   when scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or
	   higher.

       -fno-sched-spec
	   Don't allow speculative motion of non-load instructions.  This is normally enabled by
	   default when scheduling before register allocation, i.e.  with -fschedule-insns or at
	   -O2 or higher.

       -fsched-spec-load
	   Allow speculative motion of some load instructions.	This only makes sense when
	   scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
	   Allow speculative motion of more load instructions.	This only makes sense when
	   scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns=n
	   Define how many insns (if any) can be moved prematurely from the queue of stalled
	   insns into the ready list, during the second scheduling pass.

       -fsched-stalled-insns-dep=n
	   Define how many insn groups (cycles) will be examined for a dependency on a stalled
	   insn that is candidate for premature removal from the queue of stalled insns.  Has an
	   effect only during the second scheduling pass, and only if -fsched-stalled-insns is
	   used and its value is not zero.

       -fsched2-use-superblocks
	   When scheduling after register allocation, do use superblock scheduling algorithm.
	   Superblock scheduling allows motion across basic block boundaries resulting on faster
	   schedules.  This option is experimental, as not all machine descriptions used by GCC
	   model the CPU closely enough to avoid unreliable results from the algorithm.

	   This only makes sense when scheduling after register allocation, i.e. with
	   -fschedule-insns2 or at -O2 or higher.

       -fsched2-use-traces
	   Use -fsched2-use-superblocks algorithm when scheduling after register allocation and
	   additionally perform code duplication in order to increase the size of superblocks
	   using tracer pass.  See -ftracer for details on trace formation.

	   This mode should produce faster but significantly longer programs.  Also without
	   -fbranch-probabilities the traces constructed may not match the reality and hurt the
	   performance.  This only makes sense when scheduling after register allocation, i.e.
	   with -fschedule-insns2 or at -O2 or higher.

       -fsee
	   Eliminates redundant extension instructions and move the non redundant ones to optimal
	   placement using LCM.

       -freschedule-modulo-scheduled-loops
	   The modulo scheduling comes before the traditional scheduling, if a loop was modulo
	   scheduled we may want to prevent the later scheduling passes from changing its
	   schedule, we use this option to control that.

       -fcaller-saves
	   Enable values to be allocated in registers that will be clobbered by function calls,
	   by emitting extra instructions to save and restore the registers around such calls.
	   Such allocation is done only when it seems to result in better code than would
	   otherwise be produced.

	   This option is always enabled by default on certain machines, usually those which have
	   no call-preserved registers to use instead.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -ftree-pre
	   Perform Partial Redundancy Elimination (PRE) on trees.  This flag is enabled by
	   default at -O2 and -O3.

       -ftree-fre
	   Perform Full Redundancy Elimination (FRE) on trees.	The difference between FRE and
	   PRE is that FRE only considers expressions that are computed on all paths leading to
	   the redundant computation.  This analysis faster than PRE, though it exposes fewer
	   redundancies.  This flag is enabled by default at -O and higher.

       -ftree-copy-prop
	   Perform copy propagation on trees.  This pass eliminates unnecessary copy operations.
	   This flag is enabled by default at -O and higher.

       -ftree-store-copy-prop
	   Perform copy propagation of memory loads and stores.  This pass eliminates unnecessary
	   copy operations in memory references (structures, global variables, arrays, etc).
	   This flag is enabled by default at -O2 and higher.

       -ftree-salias
	   Perform structural alias analysis on trees.	This flag is enabled by default at -O and
	   higher.

       -fipa-pta
	   Perform interprocedural pointer analysis.

       -ftree-sink
	   Perform forward store motion  on trees.  This flag is enabled by default at -O and
	   higher.

       -ftree-ccp
	   Perform sparse conditional constant propagation (CCP) on trees.  This pass only
	   operates on local scalar variables and is enabled by default at -O and higher.

       -ftree-store-ccp
	   Perform sparse conditional constant propagation (CCP) on trees.  This pass operates on
	   both local scalar variables and memory stores and loads (global variables, structures,
	   arrays, etc).  This flag is enabled by default at -O2 and higher.

       -ftree-dce
	   Perform dead code elimination (DCE) on trees.  This flag is enabled by default at -O
	   and higher.

       -ftree-dominator-opts
	   Perform a variety of simple scalar cleanups (constant/copy propagation, redundancy
	   elimination, range propagation and expression simplification) based on a dominator
	   tree traversal.  This also performs jump threading (to reduce jumps to jumps). This
	   flag is enabled by default at -O and higher.

       -ftree-ch
	   Perform loop header copying on trees.  This is beneficial since it increases
	   effectiveness of code motion optimizations.	It also saves one jump.  This flag is
	   enabled by default at -O and higher.  It is not enabled for -Os or -Oz (APPLE ONLY),
	   since it usually increases code size.

       -ftree-loop-optimize
	   Perform loop optimizations on trees.  This flag is enabled by default at -O and
	   higher.

       -ftree-loop-linear
	   Perform linear loop transformations on tree.  This flag can improve cache performance
	   and allow further loop optimizations to take place.	This flag is known to have bugs
	   that cause incorrect code to be generated in some rare cases. Note this flag is
	   included in -fast.

       -ftree-loop-im
	   Perform loop invariant motion on trees.  This pass moves only invariants that would be
	   hard to handle at RTL level (function calls, operations that expand to nontrivial
	   sequences of insns).  With -funswitch-loops it also moves operands of conditions that
	   are invariant out of the loop, so that we can use just trivial invariantness analysis
	   in loop unswitching.  The pass also includes store motion.

       -ftree-loop-ivcanon
	   Create a canonical counter for number of iterations in the loop for that determining
	   number of iterations requires complicated analysis.	Later optimizations then may
	   determine the number easily.  Useful especially in connection with unrolling.

       -fivopts
	   Perform induction variable optimizations (strength reduction, induction variable
	   merging and induction variable elimination) on trees.

       -ftree-sra
	   Perform scalar replacement of aggregates.  This pass replaces structure references
	   with scalars to prevent committing structures to memory too early.  This flag is
	   enabled by default at -O and higher.

       -ftree-copyrename
	   Perform copy renaming on trees.  This pass attempts to rename compiler temporaries to
	   other variables at copy locations, usually resulting in variable names which more
	   closely resemble the original variables.  This flag is enabled by default at -O and
	   higher.

       -ftree-ter
	   Perform temporary expression replacement during the SSA->normal phase.  Single
	   use/single def temporaries are replaced at their use location with their defining
	   expression.	This results in non-GIMPLE code, but gives the expanders much more
	   complex trees to work on resulting in better RTL generation.  This is enabled by
	   default at -O and higher.

       -ftree-lrs
	   Perform live range splitting during the SSA->normal phase.  Distinct live ranges of a
	   variable are split into unique variables, allowing for better optimization later.
	   This is enabled by default at -O and higher.

       -ftree-vectorize
	   Perform loop vectorization on trees.

	   In Apple's version of GCC, -fstrict-aliasing is enabled by default when loop
	   vectorization is enabled. See -fstrict-aliasing document for more information.

       -ftree-vect-loop-version
	   Perform loop versioning when doing loop vectorization on trees.  When a loop appears
	   to be vectorizable except that data alignment or data dependence cannot be determined
	   at compile time then vectorized and non-vectorized versions of the loop are generated
	   along with runtime checks for alignment or dependence to control which version is
	   executed.  This option is enabled by default except at level -Os where it is disabled.

       -ftree-vrp
	   Perform Value Range Propagation on trees.  This is similar to the constant propagation
	   pass, but instead of values, ranges of values are propagated.  This allows the
	   optimizers to remove unnecessary range checks like array bound checks and null pointer
	   checks.  This is enabled by default at -O2 and higher.  Null pointer check elimination
	   is only done if -fdelete-null-pointer-checks is enabled.

       -ftracer
	   Perform tail duplication to enlarge superblock size.  This transformation simplifies
	   the control flow of the function allowing other optimizations to do better job.

       -funroll-loops
	   Unroll loops whose number of iterations can be determined at compile time or upon
	   entry to the loop.  -funroll-loops implies -frerun-cse-after-loop.  This option makes
	   code larger, and may or may not make it run faster.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations is uncertain when the loop is
	   entered.  This usually makes programs run more slowly.  -funroll-all-loops implies the
	   same options as -funroll-loops,

       -fsplit-ivs-in-unroller
	   Enables expressing of values of induction variables in later iterations of the
	   unrolled loop using the value in the first iteration.  This breaks long dependency
	   chains, thus improving efficiency of the scheduling passes.

	   Combination of -fweb and CSE is often sufficient to obtain the same effect.	However
	   in cases the loop body is more complicated than a single basic block, this is not
	   reliable.  It also does not work at all on some of the architectures due to
	   restrictions in the CSE pass.

	   This optimization is enabled by default.

       -fvariable-expansion-in-unroller
	   With this option, the compiler will create multiple copies of some local variables
	   when unrolling a loop which can result in superior code.

       -fprefetch-loop-arrays
	   If supported by the target machine, generate instructions to prefetch memory to
	   improve the performance of loops that access large arrays.

	   This option may generate better or worse code; results are highly dependent on the
	   structure of loops within the source code.

	   Disabled at levels -Os and -Oz (APPLE ONLY).

       -fno-peephole
       -fno-peephole2
	   Disable any machine-specific peephole optimizations.  The difference between
	   -fno-peephole and -fno-peephole2 is in how they are implemented in the compiler; some
	   targets use one, some use the other, a few use both.

	   -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2, -O3, -Os, -Oz
	   (APPLE ONLY).

       -fno-guess-branch-probability
	   Do not guess branch probabilities using heuristics.

	   GCC will use heuristics to guess branch probabilities if they are not provided by
	   profiling feedback (-fprofile-arcs).  These heuristics are based on the control flow
	   graph.  If some branch probabilities are specified by __builtin_expect, then the
	   heuristics will be used to guess branch probabilities for the rest of the control flow
	   graph, taking the __builtin_expect info into account.  The interactions between the
	   heuristics and __builtin_expect can be complex, and in some cases, it may be useful to
	   disable the heuristics so that the effects of __builtin_expect are easier to
	   understand.

	   The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os, -Oz (APPLE
	   ONLY).

       -freorder-blocks
	   Reorder basic blocks in the compiled function in order to reduce number of taken
	   branches and improve code locality.

	   Enabled at levels -O2, -O3.

       -freorder-blocks-and-partition
	   In addition to reordering basic blocks in the compiled function, in order to reduce
	   number of taken branches, partitions hot and cold basic blocks into separate sections
	   of the assembly and .o files, to improve paging and cache locality performance.

	   This optimization is automatically turned off in the presence of exception handling,
	   for linkonce sections, for functions with a user-defined section attribute and on any
	   architecture that does not support named sections.

       -freorder-functions
	   Reorder functions in the object file in order to improve code locality.  This is
	   implemented by using special subsections ".text.hot" for most frequently executed
	   functions and ".text.unlikely" for unlikely executed functions.  Reordering is done by
	   the linker so object file format must support named sections and linker must place
	   them in a reasonable way.

	   Also profile feedback must be available in to make this option effective.  See
	   -fprofile-arcs for details.

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fstrict-aliasing
	   Allows the compiler to assume the strictest aliasing rules applicable to the language
	   being compiled.  For C (and C++), this activates optimizations based on the type of
	   expressions.  In particular, an object of one type is assumed never to reside at the
	   same address as an object of a different type, unless the types are almost the same.
	   For example, an "unsigned int" can alias an "int", but not a "void*" or a "double".	A
	   character type may alias any other type.

	   Pay special attention to code like this:

		   union a_union {
		     int i;
		     double d;
		   };

		   int f() {
		     a_union t;
		     t.d = 3.0;
		     return t.i;
		   }

	   The practice of reading from a different union member than the one most recently
	   written to (called "type-punning") is common.  Even with -fstrict-aliasing, type-
	   punning is allowed, provided the memory is accessed through the union type.	So, the
	   code above will work as expected.  However, this code might not:

		   int f() {
		     a_union t;
		     int* ip;
		     t.d = 3.0;
		     ip = &t.i;
		     return *ip;
		   }

	   Every language that wishes to perform language-specific alias analysis should define a
	   function that computes, given an "tree" node, an alias set for the node.  Nodes in
	   different alias sets are not allowed to alias.  For an example, see the C front-end
	   function "c_get_alias_set".

	   Enabled at levels -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fstrict-overflow
	   Allow the compiler to assume strict signed overflow rules, depending on the language
	   being compiled.  For C (and C++) this means that overflow when doing arithmetic with
	   signed numbers is undefined, which means that the compiler may assume that it will not
	   happen.  This permits various optimizations.  For example, the compiler will assume
	   that an expression like "i + 10 > i" will always be true for signed "i".  This
	   assumption is only valid if signed overflow is undefined, as the expression is false
	   if "i + 10" overflows when using twos complement arithmetic.  When this option is in
	   effect any attempt to determine whether an operation on signed numbers will overflow
	   must be written carefully to not actually involve overflow.

	   See also the -fwrapv option.  Using -fwrapv means that signed overflow is fully
	   defined: it wraps.  When -fwrapv is used, there is no difference between
	   -fstrict-overflow and -fno-strict-overflow.	With -fwrapv certain types of overflow
	   are permitted.  For example, if the compiler gets an overflow when doing arithmetic on
	   constants, the overflowed value can still be used with -fwrapv, but not otherwise.

	   The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
	   Align the start of functions to the next power-of-two greater than n, skipping up to n
	   bytes.  For instance, -falign-functions=32 aligns functions to the next 32-byte
	   boundary, but -falign-functions=24 would align to the next 32-byte boundary only if
	   this can be done by skipping 23 bytes or less.

	   -fno-align-functions and -falign-functions=1 are equivalent and mean that functions
	   will not be aligned.

	   Some assemblers only support this flag when n is a power of two; in that case, it is
	   rounded up.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
	   Align all branch targets to a power-of-two boundary, skipping up to n bytes like
	   -falign-functions.  This option can easily make code slower, because it must insert
	   dummy operations for when the branch target is reached in the usual flow of the code.

	   -fno-align-labels and -falign-labels=1 are equivalent and mean that labels will not be
	   aligned.

	   If -falign-loops or -falign-jumps are applicable and are greater than this value, then
	   their values are used instead.

	   If n is not specified or is zero, use a machine-dependent default which is very likely
	   to be 1, meaning no alignment.

	   Enabled at levels -O2, -O3.

       -falign-loops-max-skip
       -falign-loops-max-skip=n
	   Align loops to a power-of-two boundary, but do not skip more than n bytes to do so.

       -falign-loops
       -falign-loops=n
	   Align loops to a power-of-two boundary, skipping up to n bytes like -falign-functions.
	   The hope is that the loop will be executed many times, which will make up for any
	   execution of the dummy operations.

	   -fno-align-loops and -falign-loops=1 are equivalent and mean that loops will not be
	   aligned.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
	   Align branch targets to a power-of-two boundary, for branch targets where the targets
	   can only be reached by jumping, skipping up to n bytes like -falign-functions.  In
	   this case, no dummy operations need be executed.

       -falign-jumps-max-skip
       -falign-jumps-max-skip=n
	   Align branch targets to a power-of-two boundary, but do not skip more than n bytes to
	   do so.

	   -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops will not be
	   aligned.

	   If n is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -funit-at-a-time
	   Parse the whole compilation unit before starting to produce code.  This allows some
	   extra optimizations to take place but consumes more memory (in general).  There are
	   some compatibility issues with unit-at-a-time mode:

	   o   enabling unit-at-a-time mode may change the order in which functions, variables,
	       and top-level "asm" statements are emitted, and will likely break code relying on
	       some particular ordering.  The majority of such top-level "asm" statements,
	       though, can be replaced by "section" attributes.  The fno-toplevel-reorder option
	       may be used to keep the ordering used in the input file, at the cost of some
	       optimizations.

	   o   unit-at-a-time mode removes unreferenced static variables and functions.  This may
	       result in undefined references when an "asm" statement refers directly to
	       variables or functions that are otherwise unused.  In that case either the
	       variable/function shall be listed as an operand of the "asm" statement operand or,
	       in the case of top-level "asm" statements the attribute "used" shall be used on
	       the declaration.

	   o   Static functions now can use non-standard passing conventions that may break "asm"
	       statements calling functions directly.  Again, attribute "used" will prevent this
	       behavior.

	   As a temporary workaround, -fno-unit-at-a-time can be used, but this scheme may not be
	   supported by future releases of GCC.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fno-toplevel-reorder
	   Do not reorder top-level functions, variables, and "asm" statements.  Output them in
	   the same order that they appear in the input file.  When this option is used,
	   unreferenced static variables will not be removed.  This option is intended to support
	   existing code which relies on a particular ordering.  For new code, it is better to
	   use attributes.

       -fweb
	   Constructs webs as commonly used for register allocation purposes and assign each web
	   individual pseudo register.	This allows the register allocation pass to operate on
	   pseudos directly, but also strengthens several other optimization passes, such as CSE,
	   loop optimizer and trivial dead code remover.  It can, however, make debugging
	   impossible, since variables will no longer stay in a "home register".

	   Enabled by default with -funroll-loops.

       -fwhole-program
	   Assume that the current compilation unit represents whole program being compiled.  All
	   public functions and variables with the exception of "main" and those merged by
	   attribute "externally_visible" become static functions and in a affect gets more
	   aggressively optimized by interprocedural optimizers.  While this option is equivalent
	   to proper use of "static" keyword for programs consisting of single file, in
	   combination with option --combine this flag can be used to compile most of smaller
	   scale C programs since the functions and variables become local for the whole combined
	   compilation unit, not for the single source file itself.

       -fno-cprop-registers
	   After register allocation and post-register allocation instruction splitting, we
	   perform a copy-propagation pass to try to reduce scheduling dependencies and
	   occasionally eliminate the copy.

	   Disabled at levels -O, -O2, -O3, -Os, -Oz (APPLE ONLY).

       -fprofile-generate
	   Enable options usually used for instrumenting application to produce profile useful
	   for later recompilation with profile feedback based optimization.  You must use
	   -fprofile-generate both when compiling and when linking your program.

	   The following options are enabled: "-fprofile-arcs", "-fprofile-values", "-fvpt".

       -fprofile-use
	   Enable profile feedback directed optimizations, and optimizations generally profitable
	   only with profile feedback available.

	   The following options are enabled: "-fbranch-probabilities", "-fvpt",
	   "-funroll-loops", "-fpeel-loops", "-ftracer"

       The following options control compiler behavior regarding floating point arithmetic.
       These options trade off between speed and correctness.  All must be specifically enabled.

       -ffloat-store
	   Do not store floating point variables in registers, and inhibit other options that
	   might change whether a floating point value is taken from a register or memory.

	   This option prevents undesirable excess precision on machines such as the 68000 where
	   the floating registers (of the 68881) keep more precision than a "double" is supposed
	   to have.  Similarly for the x86 architecture.  For most programs, the excess precision
	   does only good, but a few programs rely on the precise definition of IEEE floating
	   point.  Use -ffloat-store for such programs, after modifying them to store all
	   pertinent intermediate computations into variables.

       -ffast-math
	   Sets -fno-math-errno, -funsafe-math-optimizations, -fno-trapping-math,
	   -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans and fcx-limited-range.

	   This option causes the preprocessor macro "__FAST_MATH__" to be defined.

	   This option should never be turned on by any -O option since it can result in
	   incorrect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications for math functions.

       -fno-math-errno
	   Do not set ERRNO after calling math functions that are executed with a single
	   instruction, e.g., sqrt.  A program that relies on IEEE exceptions for math error
	   handling may want to use this flag for speed while maintaining IEEE arithmetic
	   compatibility.

	   (APPLE ONLY) The Darwin math libraries never set errno, so there is no point in having
	   the compiler generate code that assumes they might.	Therefore, the default is
	   -fno-math-errno on Darwin.

	   On Darwin systems, the math library never sets "errno".  There is therefore no reason
	   for the compiler to consider the possibility that it might, and -fno-math-errno is the
	   default.

       -funsafe-math-optimizations
	   Allow optimizations for floating-point arithmetic that (a) assume that arguments and
	   results are valid and (b) may violate IEEE or ANSI standards.  When used at link-time,
	   it may include libraries or startup files that change the default FPU control word or
	   other similar optimizations.

	   This option should never be turned on by any -O option since it can result in
	   incorrect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications for math functions.

	   The default is -fno-unsafe-math-optimizations.

       -ffinite-math-only
	   Allow optimizations for floating-point arithmetic that assume that arguments and
	   results are not NaNs or +-Infs.

	   This option should never be turned on by any -O option since it can result in
	   incorrect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications.

	   The default is -fno-finite-math-only.

       -fno-trapping-math
	   Compile code assuming that floating-point operations cannot generate user-visible
	   traps.  These traps include division by zero, overflow, underflow, inexact result and
	   invalid operation.  This option implies -fno-signaling-nans.  Setting this option may
	   allow faster code if one relies on "non-stop" IEEE arithmetic, for example.

	   This option should never be turned on by any -O option since it can result in
	   incorrect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications for math functions.

	   The default is -ftrapping-math.

       -frounding-math
	   Disable transformations and optimizations that assume default floating point rounding
	   behavior.  This is round-to-zero for all floating point to integer conversions, and
	   round-to-nearest for all other arithmetic truncations.  This option should be
	   specified for programs that change the FP rounding mode dynamically, or that may be
	   executed with a non-default rounding mode.  This option disables constant folding of
	   floating point expressions at compile-time (which may be affected by rounding mode)
	   and arithmetic transformations that are unsafe in the presence of sign-dependent
	   rounding modes.

	   The default is -fno-rounding-math.

	   This option is experimental and does not currently guarantee to disable all GCC
	   optimizations that are affected by rounding mode.  Future versions of GCC may provide
	   finer control of this setting using C99's "FENV_ACCESS" pragma.  This command line
	   option will be used to specify the default state for "FENV_ACCESS".

       -frtl-abstract-sequences
	   It is a size optimization method. This option is to find identical sequences of code,
	   which can be turned into pseudo-procedures  and then  replace  all  occurrences with
	   calls to  the  newly created subroutine. It is kind of an opposite of
	   -finline-functions.	This optimization runs at RTL level.

       -fsignaling-nans
	   Compile code assuming that IEEE signaling NaNs may generate user-visible traps during
	   floating-point operations.  Setting this option disables optimizations that may change
	   the number of exceptions visible with signaling NaNs.  This option implies
	   -ftrapping-math.

	   This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined.

	   The default is -fno-signaling-nans.

	   This option is experimental and does not currently guarantee to disable all GCC
	   optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
	   Treat floating point constant as single precision constant instead of implicitly
	   converting it to double precision constant.

       -fcx-limited-range
       -fno-cx-limited-range
	   When enabled, this option states that a range reduction step is not needed when
	   performing complex division.  The default is -fno-cx-limited-range, but is enabled by
	   -ffast-math.

	   This option controls the default setting of the ISO C99 "CX_LIMITED_RANGE" pragma.
	   Nevertheless, the option applies to all languages.

       The following options control optimizations that may improve performance, but are not
       enabled by any -O options.  This section includes experimental options that may produce
       broken code.

       -fbranch-probabilities
	   After running a program compiled with -fprofile-arcs, you can compile it a second time
	   using -fbranch-probabilities, to improve optimizations based on the number of times
	   each branch was taken.  When the program compiled with -fprofile-arcs exits it saves
	   arc execution counts to a file called sourcename.gcda for each source file  The
	   information in this data file is very dependent on the structure of the generated
	   code, so you must use the same source code and the same optimization options for both
	   compilations.

	   With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and
	   CALL_INSN.  These can be used to improve optimization.  Currently, they are only used
	   in one place: in reorg.c, instead of guessing which path a branch is mostly to take,
	   the REG_BR_PROB values are used to exactly determine which path is taken more often.

       -fprofile-values
	   If combined with -fprofile-arcs, it adds code so that some data about values of
	   expressions in the program is gathered.

	   With -fbranch-probabilities, it reads back the data gathered from profiling values of
	   expressions and adds REG_VALUE_PROFILE notes to instructions for their later usage in
	   optimizations.

	   Enabled with -fprofile-generate and -fprofile-use.

       -fvpt
	   If combined with -fprofile-arcs, it instructs the compiler to add a code to gather
	   information about values of expressions.

	   With -fbranch-probabilities, it reads back the data gathered and actually performs the
	   optimizations based on them.  Currently the optimizations include specialization of
	   division operation using the knowledge about the value of the denominator.

       -frename-registers
	   Attempt to avoid false dependencies in scheduled code by making use of registers left
	   over after register allocation.  This optimization will most benefit processors with
	   lots of registers.  Depending on the debug information format adopted by the target,
	   however, it can make debugging impossible, since variables will no longer stay in a
	   "home register".

	   Enabled by default with -funroll-loops.

       -ftracer
	   Perform tail duplication to enlarge superblock size.  This transformation simplifies
	   the control flow of the function allowing other optimizations to do better job.

	   Enabled with -fprofile-use.

       -funroll-loops
	   Unroll loops whose number of iterations can be determined at compile time or upon
	   entry to the loop.  -funroll-loops implies -frerun-cse-after-loop, -fweb and
	   -frename-registers.	It also turns on complete loop peeling (i.e. complete removal of
	   loops with small constant number of iterations).  This option makes code larger, and
	   may or may not make it run faster.

	   Enabled with -fprofile-use.

       -funroll-all-loops
	   Unroll all loops, even if their number of iterations is uncertain when the loop is
	   entered.  This usually makes programs run more slowly.  -funroll-all-loops implies the
	   same options as -funroll-loops.

       -fpeel-loops
	   Peels the loops for that there is enough information that they do not roll much (from
	   profile feedback).  It also turns on complete loop peeling (i.e. complete removal of
	   loops with small constant number of iterations).

	   Enabled with -fprofile-use.

       -fmove-loop-invariants
	   Enables the loop invariant motion pass in the RTL loop optimizer.  Enabled at level
	   -O1

       -funswitch-loops
	   Move branches with loop invariant conditions out of the loop, with duplicates of the
	   loop on both branches (modified according to result of the condition).

       -ffunction-sections
       -fdata-sections
	   Place each function or data item into its own section in the output file if the target
	   supports arbitrary sections.  The name of the function or the name of the data item
	   determines the section's name in the output file.

	   Use these options on systems where the linker can perform optimizations to improve
	   locality of reference in the instruction space.  Most systems using the ELF object
	   format and SPARC processors running Solaris 2 have linkers with such optimizations.
	   AIX may have these optimizations in the future.

	   Only use these options when there are significant benefits from doing so.  When you
	   specify these options, the assembler and linker will create larger object and
	   executable files and will also be slower.  You will not be able to use "gprof" on all
	   systems if you specify this option and you may have problems with debugging if you
	   specify both this option and -g.

       -fbranch-target-load-optimize
	   Perform branch target register load optimization before prologue / epilogue threading.
	   The use of target registers can typically be exposed only during reload, thus hoisting
	   loads out of loops and doing inter-block scheduling needs a separate optimization
	   pass.

       -fbranch-target-load-optimize2
	   Perform branch target register load optimization after prologue / epilogue threading.

       -fbtr-bb-exclusive
	   When performing branch target register load optimization, don't reuse branch target
	   registers in within any basic block.

       -fstack-protector
	   Emit extra code to check for buffer overflows, such as stack smashing attacks.  This
	   is done by adding a guard variable to functions with vulnerable objects.  This
	   includes functions that call alloca, and functions with buffers larger than 8 bytes.
	   The guards are initialized when a function is entered and then checked when the
	   function exits.  If a guard check fails, an error message is printed and the program
	   exits.

       -fstack-protector-all
	   Like -fstack-protector except that all functions are protected.

       -fsection-anchors
	   Try to reduce the number of symbolic address calculations by using shared "anchor"
	   symbols to address nearby objects.  This transformation can help to reduce the number
	   of GOT entries and GOT accesses on some targets.

	   For example, the implementation of the following function "foo":

		   static int a, b, c;
		   int foo (void) { return a + b + c; }

	   would usually calculate the addresses of all three variables, but if you compile it
	   with -fsection-anchors, it will access the variables from a common anchor point
	   instead.  The effect is similar to the following pseudocode (which isn't valid C):

		   int foo (void)
		   {
		     register int *xr = &x;
		     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
		   }

	   Not all targets support this option.

       --param name=value
	   In some places, GCC uses various constants to control the amount of optimization that
	   is done.  For example, GCC will not inline functions that contain more that a certain
	   number of instructions.  You can control some of these constants on the command-line
	   using the --param option.

	   The names of specific parameters, and the meaning of the values, are tied to the
	   internals of the compiler, and are subject to change without notice in future
	   releases.

	   In each case, the value is an integer.  The allowable choices for name are given in
	   the following table:

	   salias-max-implicit-fields
	       The maximum number of fields in a variable without direct structure accesses for
	       which structure aliasing will consider trying to track each field.  The default is
	       5

	   salias-max-array-elements
	       The maximum number of elements an array can have and its elements still be tracked
	       individually by structure aliasing. The default is 4

	   sra-max-structure-size
	       The maximum structure size, in bytes, at which the scalar replacement of
	       aggregates (SRA) optimization will perform block copies.  The default value, 0,
	       implies that GCC will select the most appropriate size itself.

	   sra-field-structure-ratio
	       The threshold ratio (as a percentage) between instantiated fields and the complete
	       structure size.	We say that if the ratio of the number of bytes in instantiated
	       fields to the number of bytes in the complete structure exceeds this parameter,
	       then block copies are not used.	The default is 75.

	   max-crossjump-edges
	       The maximum number of incoming edges to consider for crossjumping.  The algorithm
	       used by -fcrossjumping is O(N^2) in the number of edges incoming to each block.
	       Increasing values mean more aggressive optimization, making the compile time
	       increase with probably small improvement in executable size.

	   min-crossjump-insns
	       The minimum number of instructions which must be matched at the end of two blocks
	       before crossjumping will be performed on them.  This value is ignored in the case
	       where all instructions in the block being crossjumped from are matched.	The
	       default value is 5.

	   max-grow-copy-bb-insns
	       The maximum code size expansion factor when copying basic blocks instead of
	       jumping.  The expansion is relative to a jump instruction.  The default value is
	       8.

	   max-goto-duplication-insns
	       The maximum number of instructions to duplicate to a block that jumps to a
	       computed goto.  To avoid O(N^2) behavior in a number of passes, GCC factors
	       computed gotos early in the compilation process, and unfactors them as late as
	       possible.  Only computed jumps at the end of a basic blocks with no more than max-
	       goto-duplication-insns are unfactored.  The default value is 8.

	   max-delay-slot-insn-search
	       The maximum number of instructions to consider when looking for an instruction to
	       fill a delay slot.  If more than this arbitrary number of instructions is
	       searched, the time savings from filling the delay slot will be minimal so stop
	       searching.  Increasing values mean more aggressive optimization, making the
	       compile time increase with probably small improvement in executable run time.

	   max-delay-slot-live-search
	       When trying to fill delay slots, the maximum number of instructions to consider
	       when searching for a block with valid live register information.  Increasing this
	       arbitrarily chosen value means more aggressive optimization, increasing the
	       compile time.  This parameter should be removed when the delay slot code is
	       rewritten to maintain the control-flow graph.

	   max-gcse-memory
	       The approximate maximum amount of memory that will be allocated in order to
	       perform the global common subexpression elimination optimization.  If more memory
	       than specified is required, the optimization will not be done.

	   max-gcse-passes
	       The maximum number of passes of GCSE to run.  The default is 1.

	   max-pending-list-length
	       The maximum number of pending dependencies scheduling will allow before flushing
	       the current state and starting over.  Large functions with few branches or calls
	       can create excessively large lists which needlessly consume memory and resources.

	   max-inline-insns-single
	       Several parameters control the tree inliner used in gcc.  This number sets the
	       maximum number of instructions (counted in GCC's internal representation) in a
	       single function that the tree inliner will consider for inlining.  This only
	       affects functions declared inline and methods implemented in a class declaration
	       (C++).  The default value is 450.

	   max-inline-insns-auto
	       When you use -finline-functions (included in -O3), a lot of functions that would
	       otherwise not be considered for inlining by the compiler will be investigated.  To
	       those functions, a different (more restrictive) limit compared to functions
	       declared inline can be applied.	The default value is 90.

	   large-function-insns
	       The limit specifying really large functions.  For functions larger than this limit
	       after inlining inlining is constrained by --param large-function-growth.  This
	       parameter is useful primarily to avoid extreme compilation time caused by non-
	       linear algorithms used by the backend.  This parameter is ignored when
	       -funit-at-a-time is not used.  The default value is 2700.

	   large-function-growth
	       Specifies maximal growth of large function caused by inlining in percents.  This
	       parameter is ignored when -funit-at-a-time is not used.	The default value is 100
	       which limits large function growth to 2.0 times the original size.

	   large-unit-insns
	       The limit specifying large translation unit.  Growth caused by inlining of units
	       larger than this limit is limited by --param inline-unit-growth.  For small units
	       this might be too tight (consider unit consisting of function A that is inline and
	       B that just calls A three time.	If B is small relative to A, the growth of unit
	       is 300\% and yet such inlining is very sane.  For very large units consisting of
	       small inlininable functions however the overall unit growth limit is needed to
	       avoid exponential explosion of code size.  Thus for smaller units, the size is
	       increased to --param large-unit-insns before applying --param inline-unit-growth.
	       The default is 10000

	   inline-unit-growth
	       Specifies maximal overall growth of the compilation unit caused by inlining.  This
	       parameter is ignored when -funit-at-a-time is not used.	The default value is 50
	       which limits unit growth to 1.5 times the original size.

	   max-inline-insns-recursive
	   max-inline-insns-recursive-auto
	       Specifies maximum number of instructions out-of-line copy of self recursive inline
	       function can grow into by performing recursive inlining.

	       For functions declared inline --param max-inline-insns-recursive is taken into
	       account.  For function not declared inline, recursive inlining happens only when
	       -finline-functions (included in -O3) is enabled and --param max-inline-insns-
	       recursive-auto is used.	The default value is 450.

	   max-inline-recursive-depth
	   max-inline-recursive-depth-auto
	       Specifies maximum recursion depth used by the recursive inlining.

	       For functions declared inline --param max-inline-recursive-depth is taken into
	       account.  For function not declared inline, recursive inlining happens only when
	       -finline-functions (included in -O3) is enabled and --param max-inline-recursive-
	       depth-auto is used.  The default value is 450.

	   min-inline-recursive-probability
	       Recursive inlining is profitable only for function having deep recursion in
	       average and can hurt for function having little recursion depth by increasing the
	       prologue size or complexity of function body to other optimizers.

	       When profile feedback is available (see -fprofile-generate) the actual recursion
	       depth can be guessed from probability that function will recurse via given call
	       expression.  This parameter limits inlining only to call expression whose
	       probability exceeds given threshold (in percents).  The default value is 10.

	   inline-call-cost
	       Specify cost of call instruction relative to simple arithmetics operations (having
	       cost of 1).  Increasing this cost disqualifies inlining of non-leaf functions and
	       at the same time increases size of leaf function that is believed to reduce
	       function size by being inlined.	In effect it increases amount of inlining for
	       code having large abstraction penalty (many functions that just pass the arguments
	       to other functions) and decrease inlining for code with low abstraction penalty.
	       The default value is 16.

	   max-unrolled-insns
	       The maximum number of instructions that a loop should have if that loop is
	       unrolled, and if the loop is unrolled, it determines how many times the loop code
	       is unrolled.

	   max-average-unrolled-insns
	       The maximum number of instructions biased by probabilities of their execution that
	       a loop should have if that loop is unrolled, and if the loop is unrolled, it
	       determines how many times the loop code is unrolled.

	   max-unroll-times
	       The maximum number of unrollings of a single loop.

	   max-peeled-insns
	       The maximum number of instructions that a loop should have if that loop is peeled,
	       and if the loop is peeled, it determines how many times the loop code is peeled.

	   max-peel-times
	       The maximum number of peelings of a single loop.

	   max-completely-peeled-insns
	       The maximum number of insns of a completely peeled loop.

	   max-completely-peel-times
	       The maximum number of iterations of a loop to be suitable for complete peeling.

	   max-unswitch-insns
	       The maximum number of insns of an unswitched loop.

	   max-unswitch-level
	       The maximum number of branches unswitched in a single loop.

	   lim-expensive
	       The minimum cost of an expensive expression in the loop invariant motion.

	   iv-consider-all-candidates-bound
	       Bound on number of candidates for induction variables below that all candidates
	       are considered for each use in induction variable optimizations.  Only the most
	       relevant candidates are considered if there are more candidates, to avoid
	       quadratic time complexity.

	   iv-max-considered-uses
	       The induction variable optimizations give up on loops that contain more induction
	       variable uses.

	   iv-always-prune-cand-set-bound
	       If number of candidates in the set is smaller than this value, we always try to
	       remove unnecessary ivs from the set during its optimization when a new iv is added
	       to the set.

	   scev-max-expr-size
	       Bound on size of expressions used in the scalar evolutions analyzer.  Large
	       expressions slow the analyzer.

	   vect-max-version-checks
	       The maximum number of runtime checks that can be performed when doing loop
	       versioning in the vectorizer.  See option ftree-vect-loop-version for more
	       information.

	   max-iterations-to-track
	       The maximum number of iterations of a loop the brute force algorithm for analysis
	       of # of iterations of the loop tries to evaluate.

	   hot-bb-count-fraction
	       Select fraction of the maximal count of repetitions of basic block in program
	       given basic block needs to have to be considered hot.

	   hot-bb-frequency-fraction
	       Select fraction of the maximal frequency of executions of basic block in function
	       given basic block needs to have to be considered hot

	   max-predicted-iterations
	       The maximum number of loop iterations we predict statically.  This is useful in
	       cases where function contain single loop with known bound and other loop with
	       unknown.  We predict the known number of iterations correctly, while the unknown
	       number of iterations average to roughly 10.  This means that the loop without
	       bounds would appear artificially cold relative to the other one.

	   tracer-dynamic-coverage
	   tracer-dynamic-coverage-feedback
	       This value is used to limit superblock formation once the given percentage of
	       executed instructions is covered.  This limits unnecessary code size expansion.

	       The tracer-dynamic-coverage-feedback is used only when profile feedback is
	       available.  The real profiles (as opposed to statically estimated ones) are much
	       less balanced allowing the threshold to be larger value.

	   tracer-max-code-growth
	       Stop tail duplication once code growth has reached given percentage.  This is
	       rather hokey argument, as most of the duplicates will be eliminated later in cross
	       jumping, so it may be set to much higher values than is the desired code growth.

	   tracer-min-branch-ratio
	       Stop reverse growth when the reverse probability of best edge is less than this
	       threshold (in percent).

	   tracer-min-branch-ratio
	   tracer-min-branch-ratio-feedback
	       Stop forward growth if the best edge do have probability lower than this
	       threshold.

	       Similarly to tracer-dynamic-coverage two values are present, one for compilation
	       for profile feedback and one for compilation without.  The value for compilation
	       with profile feedback needs to be more conservative (higher) in order to make
	       tracer effective.

	   max-cse-path-length
	       Maximum number of basic blocks on path that cse considers.  The default is 10.

	   max-cse-insns
	       The maximum instructions CSE process before flushing. The default is 1000.

	   global-var-threshold
	       Counts the number of function calls (n) and the number of call-clobbered variables
	       (v).  If nxv is larger than this limit, a single artificial variable will be
	       created to represent all the call-clobbered variables at function call sites.
	       This artificial variable will then be made to alias every call-clobbered variable.
	       (done as "int * size_t" on the host machine; beware overflow).

	   max-aliased-vops
	       Maximum number of virtual operands allowed to represent aliases before triggering
	       the alias grouping heuristic.  Alias grouping reduces compile times and memory
	       consumption needed for aliasing at the expense of precision loss in alias
	       information.

	   ggc-min-expand
	       GCC uses a garbage collector to manage its own memory allocation.  This parameter
	       specifies the minimum percentage by which the garbage collector's heap should be
	       allowed to expand between collections.  Tuning this may improve compilation speed;
	       it has no effect on code generation.

	       The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB.
	       If "getrlimit" is available, the notion of "RAM" is the smallest of actual RAM and
	       "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to calculate RAM on a particular
	       platform, the lower bound of 30% is used.  Setting this parameter and ggc-min-
	       heapsize to zero causes a full collection to occur at every opportunity.  This is
	       extremely slow, but can be useful for debugging.

	   ggc-min-heapsize
	       Minimum size of the garbage collector's heap before it begins bothering to collect
	       garbage.  The first collection occurs after the heap expands by ggc-min-expand%
	       beyond ggc-min-heapsize.  Again, tuning this may improve compilation speed, and
	       has no effect on code generation.

	       The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which tries to ensure
	       that RLIMIT_DATA or RLIMIT_AS are not exceeded, but with a lower bound of 4096
	       (four megabytes) and an upper bound of 131072 (128 megabytes).  If GCC is not able
	       to calculate RAM on a particular platform, the lower bound is used.  Setting this
	       parameter very large effectively disables garbage collection.  Setting this
	       parameter and ggc-min-expand to zero causes a full collection to occur at every
	       opportunity.

	   max-reload-search-insns
	       The maximum number of instruction reload should look backward for equivalent
	       register.  Increasing values mean more aggressive optimization, making the compile
	       time increase with probably slightly better performance.  The default value is
	       100.

	   max-cselib-memory-locations
	       The maximum number of memory locations cselib should take into account.
	       Increasing values mean more aggressive optimization, making the compile time
	       increase with probably slightly better performance.  The default value is 500.

	   max-flow-memory-locations
	       Similar as max-cselib-memory-locations but for dataflow liveness.  The default
	       value is 100.

	   reorder-blocks-duplicate
	   reorder-blocks-duplicate-feedback
	       Used by basic block reordering pass to decide whether to use unconditional branch
	       or duplicate the code on its destination.  Code is duplicated when its estimated
	       size is smaller than this value multiplied by the estimated size of unconditional
	       jump in the hot spots of the program.

	       The reorder-block-duplicate-feedback is used only when profile feedback is
	       available and may be set to higher values than reorder-block-duplicate since
	       information about the hot spots is more accurate.

	   max-sched-ready-insns
	       The maximum number of instructions ready to be issued the scheduler should
	       consider at any given time during the first scheduling pass.  Increasing values
	       mean more thorough searches, making the compilation time increase with probably
	       little benefit.	The default value is 100.

	   max-sched-region-blocks
	       The maximum number of blocks in a region to be considered for interblock
	       scheduling.  The default value is 10.

	   max-sched-region-insns
	       The maximum number of insns in a region to be considered for interblock
	       scheduling.  The default value is 100.

	   min-spec-prob
	       The minimum probability (in percents) of reaching a source block for interblock
	       speculative scheduling.	The default value is 40.

	   max-sched-extend-regions-iters
	       The maximum number of iterations through CFG to extend regions.	0 - disable
	       region extension, N - do at most N iterations.  The default value is 0.

	   max-sched-insn-conflict-delay
	       The maximum conflict delay for an insn to be considered for speculative motion.
	       The default value is 3.

	   sched-spec-prob-cutoff
	       The minimal probability of speculation success (in percents), so that speculative
	       insn will be scheduled.	The default value is 40.

	   max-last-value-rtl
	       The maximum size measured as number of RTLs that can be recorded in an expression
	       in combiner for a pseudo register as last known value of that register.	The
	       default is 10000.

	   integer-share-limit
	       Small integer constants can use a shared data structure, reducing the compiler's
	       memory usage and increasing its speed.  This sets the maximum value of a shared
	       integer constant's.  The default value is 256.

	   min-virtual-mappings
	       Specifies the minimum number of virtual mappings in the incremental SSA updater
	       that should be registered to trigger the virtual mappings heuristic defined by
	       virtual-mappings-ratio.	The default value is 100.

	   virtual-mappings-ratio
	       If the number of virtual mappings is virtual-mappings-ratio bigger than the number
	       of virtual symbols to be updated, then the incremental SSA updater switches to a
	       full update for those symbols.  The default ratio is 3.

	   ssp-buffer-size
	       The minimum size of buffers (i.e. arrays) that will receive stack smashing
	       protection when -fstack-protection is used.

	   max-jump-thread-duplication-stmts
	       Maximum number of statements allowed in a block that needs to be duplicated when
	       threading jumps.

	   max-fields-for-field-sensitive
	       Maximum number of fields in a structure we will treat in a field sensitive manner
	       during pointer analysis.

       Options Controlling the Preprocessor

       These options control the C preprocessor, which is run on each C source file before actual
       compilation.

       If you use the -E option, nothing is done except preprocessing.	Some of these options
       make sense only together with -E because they cause the preprocessor output to be
       unsuitable for actual compilation.

       -Wp,option
	   You can use -Wp,option to bypass the compiler driver and pass option directly through
	   to the preprocessor.  If option contains commas, it is split into multiple options at
	   the commas.	However, many options are modified, translated or interpreted by the
	   compiler driver before being passed to the preprocessor, and -Wp forcibly bypasses
	   this phase.	The preprocessor's direct interface is undocumented and subject to
	   change, so whenever possible you should avoid using -Wp and let the driver handle the
	   options instead.

       -Xpreprocessor option
	   Pass option as an option to the preprocessor.  You can use this to supply system-
	   specific preprocessor options which GCC does not know how to recognize.

	   If you want to pass an option that takes an argument, you must use -Xpreprocessor
	   twice, once for the option and once for the argument.

       -D name
	   Predefine name as a macro, with definition 1.

       -D name=definition
	   The contents of definition are tokenized and processed as if they appeared during
	   translation phase three in a #define directive.  In particular, the definition will be
	   truncated by embedded newline characters.

	   If you are invoking the preprocessor from a shell or shell-like program you may need
	   to use the shell's quoting syntax to protect characters such as spaces that have a
	   meaning in the shell syntax.

	   If you wish to define a function-like macro on the command line, write its argument
	   list with surrounding parentheses before the equals sign (if any).  Parentheses are
	   meaningful to most shells, so you will need to quote the option.  With sh and csh,
	   -D'name(args...)=definition' works.

	   -D and -U options are processed in the order they are given on the command line.  All
	   -imacros file and -include file options are processed after all -D and -U options.

       -U name
	   Cancel any previous definition of name, either built in or provided with a -D option.

       -undef
	   Do not predefine any system-specific or GCC-specific macros.  The standard predefined
	   macros remain defined.

       -I dir
	   Add the directory dir to the list of directories to be searched for header files.
	   Directories named by -I are searched before the standard system include directories.
	   If the directory dir is a standard system include directory, the option is ignored to
	   ensure that the default search order for system directories and the special treatment
	   of system headers are not defeated .

       -o file
	   Write output to file.  This is the same as specifying file as the second non-option
	   argument to cpp.  gcc has a different interpretation of a second non-option argument,
	   so you must use -o to specify the output file.

       -Wall
	   Turns on all optional warnings which are desirable for normal code.	At present this
	   is -Wcomment, -Wtrigraphs, -Wmultichar and a warning about integer promotion causing a
	   change of sign in "#if" expressions.  Note that many of the preprocessor's warnings
	   are on by default and have no options to control them.

       -Wcomment
       -Wcomments
	   Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
	   backslash-newline appears in a // comment.  (Both forms have the same effect.)

       -Wtrigraphs
	   Most trigraphs in comments cannot affect the meaning of the program.  However, a
	   trigraph that would form an escaped newline (??/ at the end of a line) can, by
	   changing where the comment begins or ends.  Therefore, only trigraphs that would form
	   escaped newlines produce warnings inside a comment.

	   This option is implied by -Wall.  If -Wall is not given, this option is still enabled
	   unless trigraphs are enabled.  To get trigraph conversion without warnings, but get
	   the other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wtraditional
	   Warn about certain constructs that behave differently in traditional and ISO C.  Also
	   warn about ISO C constructs that have no traditional C equivalent, and problematic
	   constructs which should be avoided.

       -Wimport
	   Warn the first time #import is used.

       -Wundef
	   Warn whenever an identifier which is not a macro is encountered in an #if directive,
	   outside of defined.	Such identifiers are replaced with zero.

       -Wunused-macros
	   Warn about macros defined in the main file that are unused.	A macro is used if it is
	   expanded or tested for existence at least once.  The preprocessor will also warn if
	   the macro has not been used at the time it is redefined or undefined.

	   Built-in macros, macros defined on the command line, and macros defined in include
	   files are not warned about.

	   Note: If a macro is actually used, but only used in skipped conditional blocks, then
	   CPP will report it as unused.  To avoid the warning in such a case, you might improve
	   the scope of the macro's definition by, for example, moving it into the first skipped
	   block.  Alternatively, you could provide a dummy use with something like:

		   #if defined the_macro_causing_the_warning
		   #endif

       -Wendif-labels
	   Warn whenever an #else or an #endif are followed by text.  This usually happens in
	   code of the form

		   #if FOO
		   ...
		   #else FOO
		   ...
		   #endif FOO

	   The second and third "FOO" should be in comments, but often are not in older programs.
	   This warning is on by default.

       -Werror
	   Make all warnings into hard errors.	Source code which triggers warnings will be
	   rejected.

       -Wsystem-headers
	   Issue warnings for code in system headers.  These are normally unhelpful in finding
	   bugs in your own code, therefore suppressed.  If you are responsible for the system
	   library, you may want to see them.

       -w  Suppress all warnings, including those which GNU CPP issues by default.

       -pedantic
	   Issue all the mandatory diagnostics listed in the C standard.  Some of them are left
	   out by default, since they trigger frequently on harmless code.

       -pedantic-errors
	   Issue all the mandatory diagnostics, and make all mandatory diagnostics into errors.
	   This includes mandatory diagnostics that GCC issues without -pedantic but treats as
	   warnings.

       -M  Instead of outputting the result of preprocessing, output a rule suitable for make
	   describing the dependencies of the main source file.  The preprocessor outputs one
	   make rule containing the object file name for that source file, a colon, and the names
	   of all the included files, including those coming from -include or -imacros command
	   line options.

	   Unless specified explicitly (with -MT or -MQ), the object file name consists of the
	   basename of the source file with any suffix replaced with object file suffix.  If
	   there are many included files then the rule is split into several lines using
	   \-newline.  The rule has no commands.

	   This option does not suppress the preprocessor's debug output, such as -dM.	To avoid
	   mixing such debug output with the dependency rules you should explicitly specify the
	   dependency output file with -MF, or use an environment variable like
	   DEPENDENCIES_OUTPUT.  Debug output will still be sent to the regular output stream as
	   normal.

	   Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

       -MM Like -M but do not mention header files that are found in system header directories,
	   nor header files that are included, directly or indirectly, from such a header.

	   This implies that the choice of angle brackets or double quotes in an #include
	   directive does not in itself determine whether that header will appear in -MM
	   dependency output.  This is a slight change in semantics from GCC versions 3.0 and
	   earlier.

       -MF file
	   When used with -M or -MM, specifies a file to write the dependencies to.  If no -MF
	   switch is given the preprocessor sends the rules to the same place it would have sent
	   preprocessed output.

	   When used with the driver options -MD or -MMD, -MF overrides the default dependency
	   output file.

       -dependency-file
	   Like -MF. (APPLE ONLY)

       -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes
	   missing header files are generated files and adds them to the dependency list without
	   raising an error.  The dependency filename is taken directly from the "#include"
	   directive without prepending any path.  -MG also suppresses preprocessed output, as a
	   missing header file renders this useless.

	   This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency other than the
	   main file, causing each to depend on nothing.  These dummy rules work around errors
	   make gives if you remove header files without updating the Makefile to match.

	   This is typical output:

		   test.o: test.c test.h

		   test.h:

       -MT target
	   Change the target of the rule emitted by dependency generation.  By default CPP takes
	   the name of the main input file, including any path, deletes any file suffix such as
	   .c, and appends the platform's usual object suffix.	The result is the target.

	   An -MT option will set the target to be exactly the string you specify.  If you want
	   multiple targets, you can specify them as a single argument to -MT, or use multiple
	   -MT options.

	   For example, -MT '$(objpfx)foo.o' might give

		   $(objpfx)foo.o: foo.c

       -MQ target
	   Same as -MT, but it quotes any characters which are special to Make.
	   -MQ '$(objpfx)foo.o' gives

		   $$(objpfx)foo.o: foo.c

	   The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The driver
	   determines file based on whether an -o option is given.  If it is, the driver uses its
	   argument but with a suffix of .d, otherwise it take the basename of the input file and
	   applies a .d suffix.

	   If -MD is used in conjunction with -E, any -o switch is understood to specify the
	   dependency output file, but if used without -E, each -o is understood to specify a
	   target object file.

	   Since -E is not implied, -MD can be used to generate a dependency output file as a
	   side-effect of the compilation process.

       -MMD
	   Like -MD except mention only user header files, not system header files.

       -fpch-deps
	   When using precompiled headers, this flag will cause the dependency-output flags to
	   also list the files from the precompiled header's dependencies.  If not specified only
	   the precompiled header would be listed and not the files that were used to create it
	   because those files are not consulted when a precompiled header is used.

       -fpch-preprocess
	   This option allows use of a precompiled header together with -E.  It inserts a special
	   "#pragma", "#pragma GCC pch_preprocess "<filename>"" in the output to mark the place
	   where the precompiled header was found, and its filename.  When -fpreprocessed is in
	   use, GCC recognizes this "#pragma" and loads the PCH.

	   This option is off by default, because the resulting preprocessed output is only
	   really suitable as input to GCC.  It is switched on by -save-temps.

	   You should not write this "#pragma" in your own code, but it is safe to edit the
	   filename if the PCH file is available in a different location.  The filename may be
	   absolute or it may be relative to GCC's current directory.

       -x c
       -x c++
       -x objective-c
       -x objective-c++
       -x assembler-with-cpp
	   Specify the source language: C, C++, Objective-C, Objective-C++, or assembly.  This
	   has nothing to do with standards conformance or extensions; it merely selects which
	   base syntax to expect.  If you give none of these options, cpp will deduce the
	   language from the extension of the source file: .c, .cc, .m, .mm, or .S.  Some other
	   common extensions for C++ and assembly are also recognized.	If cpp does not recognize
	   the extension, it will treat the file as C; this is the most generic mode.

	   Note: Previous versions of cpp accepted a -lang option which selected both the
	   language and the standards conformance level.  This option has been removed, because
	   it conflicts with the -l option.

       -std=standard
       -ansi
	   Specify the standard to which the code should conform.  Currently CPP knows about C
	   and C++ standards; others may be added in the future.

	   standard may be one of:

	   "iso9899:1990"
	   "c89"
	       The ISO C standard from 1990.  c89 is the customary shorthand for this version of
	       the standard.

	       The -ansi option is equivalent to -std=c89.

	   "iso9899:199409"
	       The 1990 C standard, as amended in 1994.

	   "iso9899:1999"
	   "c99"
	   "iso9899:199x"
	   "c9x"
	       The revised ISO C standard, published in December 1999.	Before publication, this
	       was known as C9X.

	   "gnu89"
	       The 1990 C standard plus GNU extensions.  This is the default.

	   "gnu99"
	   "gnu9x"
	       The 1999 C standard plus GNU extensions.

	   "c++98"
	       The 1998 ISO C++ standard plus amendments.

	   "gnu++98"
	       The same as -std=c++98 plus GNU extensions.  This is the default for C++ code.

       -I- Split the include path.  Any directories specified with -I options before -I- are
	   searched only for headers requested with "#include "file""; they are not searched for
	   "#include <file>".  If additional directories are specified with -I options after the
	   -I-, those directories are searched for all #include directives.

	   In addition, -I- inhibits the use of the directory of the current file directory as
	   the first search directory for "#include "file"".  This option has been deprecated.

       -nostdinc
	   Do not search the standard system directories for header files.  Only the directories
	   you have specified with -I options (and the directory of the current file, if
	   appropriate) are searched.

       -nostdinc++
	   Do not search for header files in the C++-specific standard directories, but do still
	   search the other standard directories.  (This option is used when building the C++
	   library.)

       -include file
	   Process file as if "#include "file"" appeared as the first line of the primary source
	   file.  However, the first directory searched for file is the preprocessor's working
	   directory instead of the directory containing the main source file.	If not found
	   there, it is searched for in the remainder of the "#include "..."" search chain as
	   normal.

	   If multiple -include options are given, the files are included in the order they
	   appear on the command line.

       -imacros file
	   Exactly like -include, except that any output produced by scanning file is thrown
	   away.  Macros it defines remain defined.  This allows you to acquire all the macros
	   from a header without also processing its declarations.

	   All files specified by -imacros are processed before all files specified by -include.

       -idirafter dir
	   Search dir for header files, but do it after all directories specified with -I and the
	   standard system directories have been exhausted.  dir is treated as a system include
	   directory.

       -iprefix prefix
	   Specify prefix as the prefix for subsequent -iwithprefix options.  If the prefix
	   represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
	   Append dir to the prefix specified previously with -iprefix, and add the resulting
	   directory to the include search path.  -iwithprefixbefore puts it in the same place -I
	   would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
	   This option is like the --sysroot option, but applies only to header files.	See the
	   --sysroot option for more information.

       -imultilib dir
	   Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -isystem dir
	   Search dir for header files, after all directories specified by -I but before the
	   standard system directories.  Mark it as a system directory, so that it gets the same
	   special treatment as is applied to the standard system directories.

       -iquote dir
	   Search dir only for header files requested with "#include "file""; they are not
	   searched for "#include <file>", before all directories specified by -I and before the
	   standard system directories.

       -fdollars-in-identifiers
	   Accept $ in identifiers.

       -fextended-identifiers
	   Accept universal character names in identifiers.  This option is experimental; in a
	   future version of GCC, it will be enabled by default for C99 and C++.

       -fpreprocessed
	   Indicate to the preprocessor that the input file has already been preprocessed.  This
	   suppresses things like macro expansion, trigraph conversion, escaped newline splicing,
	   and processing of most directives.  The preprocessor still recognizes and removes
	   comments, so that you can pass a file preprocessed with -C to the compiler without
	   problems.  In this mode the integrated preprocessor is little more than a tokenizer
	   for the front ends.

	   -fpreprocessed is implicit if the input file has one of the extensions .i, .ii or .mi.
	   These are the extensions that GCC uses for preprocessed files created by -save-temps.

       -ftabstop=width
	   Set the distance between tab stops.	This helps the preprocessor report correct column
	   numbers in warnings or errors, even if tabs appear on the line.  If the value is less
	   than 1 or greater than 100, the option is ignored.  The default is 8.

       -fexec-charset=charset
	   Set the execution character set, used for string and character constants.  The default
	   is UTF-8.  charset can be any encoding supported by the system's "iconv" library
	   routine.

       -fwide-exec-charset=charset
	   Set the wide execution character set, used for wide string and character constants.
	   The default is UTF-32 or UTF-16, whichever corresponds to the width of "wchar_t".  As
	   with -fexec-charset, charset can be any encoding supported by the system's "iconv"
	   library routine; however, you will have problems with encodings that do not fit
	   exactly in "wchar_t".

       -finput-charset=charset
	   Set the input character set, used for translation from the character set of the input
	   file to the source character set used by GCC.  If the locale does not specify, or GCC
	   cannot get this information from the locale, the default is UTF-8.  This can be
	   overridden by either the locale or this command line option.  Currently the command
	   line option takes precedence if there's a conflict.	charset can be any encoding
	   supported by the system's "iconv" library routine.

       -fworking-directory
	   Enable generation of linemarkers in the preprocessor output that will let the compiler
	   know the current working directory at the time of preprocessing.  When this option is
	   enabled, the preprocessor will emit, after the initial linemarker, a second linemarker
	   with the current working directory followed by two slashes.	GCC will use this
	   directory, when it's present in the preprocessed input, as the directory emitted as
	   the current working directory in some debugging information formats.  This option is
	   implicitly enabled if debugging information is enabled, but this can be inhibited with
	   the negated form -fno-working-directory.  If the -P flag is present in the command
	   line, this option has no effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
	   Do not print column numbers in diagnostics.	This may be necessary if diagnostics are
	   being scanned by a program that does not understand the column numbers, such as
	   dejagnu.

       -A predicate=answer
	   Make an assertion with the predicate predicate and answer answer.  This form is
	   preferred to the older form -A predicate(answer), which is still supported, because it
	   does not use shell special characters.

       -A -predicate=answer
	   Cancel an assertion with the predicate predicate and answer answer.

       -dCHARS
	   CHARS is a sequence of one or more of the following characters, and must not be
	   preceded by a space.  Other characters are interpreted by the compiler proper, or
	   reserved for future versions of GCC, and so are silently ignored.  If you specify
	   characters whose behavior conflicts, the result is undefined.

	   M   Instead of the normal output, generate a list of #define directives for all the
	       macros defined during the execution of the preprocessor, including predefined
	       macros.	This gives you a way of finding out what is predefined in your version of
	       the preprocessor.  Assuming you have no file foo.h, the command

		       touch foo.h; cpp -dM foo.h

	       will show all the predefined macros.

	       If you use -dM without the -E option, -dM is interpreted as a synonym for
	       -fdump-rtl-mach.

	   D   Like M except in two respects: it does not include the predefined macros, and it
	       outputs both the #define directives and the result of preprocessing.  Both kinds
	       of output go to the standard output file.

	   N   Like D, but emit only the macro names, not their expansions.

	   I   Output #include directives in addition to the result of preprocessing.

       -P  Inhibit generation of linemarkers in the output from the preprocessor.  This might be
	   useful when running the preprocessor on something that is not C code, and will be sent
	   to a program which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the output file, except
	   for comments in processed directives, which are deleted along with the directive.

	   You should be prepared for side effects when using -C; it causes the preprocessor to
	   treat comments as tokens in their own right.  For example, comments appearing at the
	   start of what would be a directive line have the effect of turning that line into an
	   ordinary source line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C, except
	   that comments contained within macros are also passed through to the output file where
	   the macro is expanded.

	   In addition to the side-effects of the -C option, the -CC option causes all C++-style
	   comments inside a macro to be converted to C-style comments.  This is to prevent later
	   use of that macro from inadvertently commenting out the remainder of the source line.

	   The -CC option is generally used to support lint comments.

       -traditional-cpp
	   Try to imitate the behavior of old-fashioned C preprocessors, as opposed to ISO C
	   preprocessors.

       -trigraphs
	   Process trigraph sequences.	These are three-character sequences, all starting with
	   ??, that are defined by ISO C to stand for single characters.  For example, ??/ stands
	   for \, so '??/n' is a character constant for a newline.  By default, GCC ignores
	   trigraphs, but in standard-conforming modes it converts them.  See the -std and -ansi
	   options.

	   The nine trigraphs and their replacements are

		   Trigraph:	   ??(	??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
		   Replacement:      [	  ]    {    }	 #    \    ^	|    ~

       -remap
	   Enable special code to work around file systems which only permit very short file
	   names, such as MS-DOS.

       --help
       --target-help
	   Print text describing all the command line options instead of preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the beginning of execution, and
	   report the final form of the include path.

       -H  Print the name of each header file used, in addition to other normal activities.  Each
	   name is indented to show how deep in the #include stack it is.  Precompiled header
	   files are also printed, even if they are found to be invalid; an invalid precompiled
	   header file is printed with ...x and a valid one with ...! .

       -version
       --version
	   Print out GNU CPP's version number.	With one dash, proceed to preprocess as normal.
	   With two dashes, exit immediately.

       Passing Options to the Assembler

       You can pass options to the assembler.

       -Wa,option
	   Pass option as an option to the assembler.  If option contains commas, it is split
	   into multiple options at the commas.

       -Xassembler option
	   Pass option as an option to the assembler.  You can use this to supply system-specific
	   assembler options which GCC does not know how to recognize.

	   If you want to pass an option that takes an argument, you must use -Xassembler twice,
	   once for the option and once for the argument.

       Options for Linking

       These options come into play when the compiler links object files into an executable
       output file.  They are meaningless if the compiler is not doing a link step.

       In addition to the options listed below, Apple's GCC also accepts and passes nearly all of
       the options defined by the linker ld and by the library tool libtool.  Common options
       include -framework, -dynamic, -bundle, -flat_namespace, and so forth.  See the ld and
       libtool man pages for further details.

       object-file-name
	   A file name that does not end in a special recognized suffix is considered to name an
	   object file or library.  (Object files are distinguished from libraries by the linker
	   according to the file contents.)  If linking is done, these object files are used as
	   input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and object file names
	   should not be used as arguments.

       -llibrary
       -l library
	   Search the library named library when linking.  (The second alternative with the
	   library as a separate argument is only for POSIX compliance and is not recommended.)

	   It makes a difference where in the command you write this option; the linker searches
	   and processes libraries and object files in the order they are specified.  Thus, foo.o
	   -lz bar.o searches library z after file foo.o but before bar.o.  If bar.o refers to
	   functions in z, those functions may not be loaded.

	   The linker searches a standard list of directories for the library, which is actually
	   a file named liblibrary.a.  The linker then uses this file as if it had been specified
	   precisely by name.

	   The directories searched include several standard system directories plus any that you
	   specify with -L.

	   Normally the files found this way are library files---archive files whose members are
	   object files.  The linker handles an archive file by scanning through it for members
	   which define symbols that have so far been referenced but not defined.  But if the
	   file that is found is an ordinary object file, it is linked in the usual fashion.  The
	   only difference between using an -l option and specifying a file name is that -l
	   surrounds library with lib and .a and searches several directories.

       -lobjc
	   You need this special case of the -l option in order to link an Objective-C or
	   Objective-C++ program.

       -nostartfiles
	   Do not use the standard system startup files when linking.  The standard system
	   libraries are used normally, unless -nostdlib or -nodefaultlibs is used.

       -nodefaultlibs
	   Do not use the standard system libraries when linking.  Only the libraries you specify
	   will be passed to the linker.  The standard startup files are used normally, unless
	   -nostartfiles is used.  The compiler may generate calls to "memcmp", "memset",
	   "memcpy" and "memmove".  These entries are usually resolved by entries in libc.  These
	   entry points should be supplied through some other mechanism when this option is
	   specified.

       -nostdlib
	   Do not use the standard system startup files or libraries when linking.  No startup
	   files and only the libraries you specify will be passed to the linker.  The compiler
	   may generate calls to "memcmp", "memset", "memcpy" and "memmove".  These entries are
	   usually resolved by entries in libc.  These entry points should be supplied through
	   some other mechanism when this option is specified.

	   One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is libgcc.a, a
	   library of internal subroutines that GCC uses to overcome shortcomings of particular
	   machines, or special needs for some languages.

	   In most cases, you need libgcc.a even when you want to avoid other standard libraries.
	   In other words, when you specify -nostdlib or -nodefaultlibs you should usually
	   specify -lgcc as well.  This ensures that you have no unresolved references to
	   internal GCC library subroutines.  (For example, __main, used to ensure C++
	   constructors will be called.)

       -pie
	   Produce a position independent executable on targets which support it.  For
	   predictable results, you must also specify the same set of options that were used to
	   generate code (-fpie, -fPIE, or model suboptions) when you specify this option.

       -rdynamic
	   Pass the flag -export-dynamic to the ELF linker, on targets that support it. This
	   instructs the linker to add all symbols, not only used ones, to the dynamic symbol
	   table. This option is needed for some uses of "dlopen" or to allow obtaining
	   backtraces from within a program.

       -s  Remove all symbol table and relocation information from the executable.

       -static
	   On systems that support dynamic linking, this prevents linking with the shared
	   libraries.  On other systems, this option has no effect.

	   This option will not work on Mac OS X unless all libraries (including libgcc.a) have
	   also been compiled with -static.  Since neither a static version of libSystem.dylib
	   nor crt0.o are provided, this option is not useful to most people.

       -shared
	   Produce a shared object which can then be linked with other objects to form an
	   executable.	Not all systems support this option.  For predictable results, you must
	   also specify the same set of options that were used to generate code (-fpic, -fPIC, or
	   model suboptions) when you specify this option.[1]

	   This option is not supported on Mac OS X.

       -shared-libgcc
       -static-libgcc
	   On systems that provide libgcc as a shared library, these options force the use of
	   either the shared or static version respectively.  If no shared version of libgcc was
	   built when the compiler was configured, these options have no effect.

	   There are several situations in which an application should use the shared libgcc
	   instead of the static version.  The most common of these is when the application
	   wishes to throw and catch exceptions across different shared libraries.  In that case,
	   each of the libraries as well as the application itself should use the shared libgcc.

	   Therefore, the G++ and GCJ drivers automatically add -shared-libgcc whenever you build
	   a shared library or a main executable, because C++ and Java programs typically use
	   exceptions, so this is the right thing to do.

	   If, instead, you use the GCC driver to create shared libraries, you may find that they
	   will not always be linked with the shared libgcc.  If GCC finds, at its configuration
	   time, that you have a non-GNU linker or a GNU linker that does not support option
	   --eh-frame-hdr, it will link the shared version of libgcc into shared libraries by
	   default.  Otherwise, it will take advantage of the linker and optimize away the
	   linking with the shared version of libgcc, linking with the static version of libgcc
	   by default.	This allows exceptions to propagate through such shared libraries,
	   without incurring relocation costs at library load time.

	   However, if a library or main executable is supposed to throw or catch exceptions, you
	   must link it using the G++ or GCJ driver, as appropriate for the languages used in the
	   program, or using the option -shared-libgcc, such that it is linked with the shared
	   libgcc.

       -symbolic
	   Bind references to global symbols when building a shared object.  Warn about any
	   unresolved references (unless overridden by the link editor option -Xlinker -z
	   -Xlinker defs).  Only a few systems support this option.

       -Xlinker option
	   Pass option as an option to the linker.  You can use this to supply system-specific
	   linker options which GCC does not know how to recognize.

	   If you want to pass an option that takes an argument, you must use -Xlinker twice,
	   once for the option and once for the argument.  For example, to pass -assert
	   definitions, you must write -Xlinker -assert -Xlinker definitions.  It does not work
	   to write -Xlinker "-assert definitions", because this passes the entire string as a
	   single argument, which is not what the linker expects.

       -Wl,option
	   Pass option as an option to the linker.  If option contains commas, it is split into
	   multiple options at the commas.

       -u symbol
	   Pretend the symbol symbol is undefined, to force linking of library modules to define
	   it.	You can use -u multiple times with different symbols to force loading of
	   additional library modules.

       Options for Directory Search

       These options specify directories to search for header files, for libraries and for parts
       of the compiler:

       -Idir
	   Add the directory dir to the head of the list of directories to be searched for header
	   files.  This can be used to override a system header file, substituting your own
	   version, since these directories are searched before the system header file
	   directories.  However, you should not use this option to add directories that contain
	   vendor-supplied system header files (use -isystem for that).  If you use more than one
	   -I option, the directories are scanned in left-to-right order; the standard system
	   directories come after.

	   If a standard system include directory, or a directory specified with -isystem, is
	   also specified with -I, the -I option will be ignored.  The directory will still be
	   searched but as a system directory at its normal position in the system include chain.
	   This is to ensure that GCC's procedure to fix buggy system headers and the ordering
	   for the include_next directive are not inadvertently changed.  If you really need to
	   change the search order for system directories, use the -nostdinc and/or -isystem
	   options.

	   The option -iwithsysroot (APPLE ONLY), if specified with an absolute path, will
	   prepend the system root directory (if applicable) to the path and add it to the
	   beginning of the system search paths.  If specified with a relative path,
	   -iwithsysroot will behave identically to -isystem.

       -iquotedir
	   Add the directory dir to the head of the list of directories to be searched for header
	   files only for the case of #include "file"; they are not searched for #include <file>,
	   otherwise just like -I.

       -Ldir
	   Add directory dir to the list of directories to be searched for -l.

       -Bprefix
	   This option specifies where to find the executables, libraries, include files, and
	   data files of the compiler itself.

	   The compiler driver program runs one or more of the subprograms cpp, cc1, as and ld.
	   It tries prefix as a prefix for each program it tries to run, both with and without
	   machine/version/.

	   For each subprogram to be run, the compiler driver first tries the -B prefix, if any.
	   If that name is not found, or if -B was not specified, the driver tries two standard
	   prefixes, which are /usr/lib/gcc/ and /usr/local/lib/gcc/.  If neither of those
	   results in a file name that is found, the unmodified program name is searched for
	   using the directories specified in your PATH environment variable.

	   The compiler will check to see if the path provided by the -B refers to a directory,
	   and if necessary it will add a directory separator character at the end of the path.

	   -B prefixes that effectively specify directory names also apply to libraries in the
	   linker, because the compiler translates these options into -L options for the linker.
	   They also apply to includes files in the preprocessor, because the compiler translates
	   these options into -isystem options for the preprocessor.  In this case, the compiler
	   appends include to the prefix.

	   The run-time support file libgcc.a can also be searched for using the -B prefix, if
	   needed.  If it is not found there, the two standard prefixes above are tried, and that
	   is all.  The file is left out of the link if it is not found by those means.

	   Another way to specify a prefix much like the -B prefix is to use the environment
	   variable GCC_EXEC_PREFIX.

	   As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a number
	   in the range 0 to 9, then it will be replaced by [dir/]include.  This is to help with
	   boot-strapping the compiler.

       -specs=file
	   Process file after the compiler reads in the standard specs file, in order to override
	   the defaults that the gcc driver program uses when determining what switches to pass
	   to cc1, cc1plus, as, ld, etc.  More than one -specs=file can be specified on the
	   command line, and they are processed in order, from left to right.

       --sysroot=dir
	   Use dir as the logical root directory for headers and libraries.  For example, if the
	   compiler would normally search for headers in /usr/include and libraries in /usr/lib,
	   it will instead search dir/usr/include and dir/usr/lib.

	   If you use both this option and the -isysroot option, then the --sysroot option will
	   apply to libraries, but the -isysroot option will apply to header files.

	   The GNU linker (beginning with version 2.16) has the necessary support for this
	   option.  If your linker does not support this option, the header file aspect of
	   --sysroot will still work, but the library aspect will not.

       -I- This option has been deprecated.  Please use -iquote instead for -I directories before
	   the -I- and remove the -I-.	Any directories you specify with -I options before the
	   -I- option are searched only for the case of #include "file"; they are not searched
	   for #include <file>.

	   If additional directories are specified with -I options after the -I-, these
	   directories are searched for all #include directives.  (Ordinarily all -I directories
	   are used this way.)

	   In addition, the -I- option inhibits the use of the current directory (where the
	   current input file came from) as the first search directory for #include "file".
	   There is no way to override this effect of -I-.  With -I. you can specify searching
	   the directory which was current when the compiler was invoked.  That is not exactly
	   the same as what the preprocessor does by default, but it is often satisfactory.

	   -I- does not inhibit the use of the standard system directories for header files.
	   Thus, -I- and -nostdinc are independent.

       Specifying Target Machine and Compiler Version

       The usual way to run GCC is to run the executable called gcc, or <machine>-gcc when cross-
       compiling, or <machine>-gcc-<version> to run a version other than the one that was
       installed last.	Sometimes this is inconvenient, so GCC provides options that will switch
       to another cross-compiler or version.

       -b machine
	   The argument machine specifies the target machine for compilation.

	   The value to use for machine is the same as was specified as the machine type when
	   configuring GCC as a cross-compiler.  For example, if a cross-compiler was configured
	   with configure arm-elf, meaning to compile for an arm processor with elf binaries,
	   then you would specify -b arm-elf to run that cross compiler.  Because there are other
	   options beginning with -b, the configuration must contain a hyphen.

       -V version
	   The argument version specifies which version of GCC to run.	This is useful when
	   multiple versions are installed.  For example, version might be 4.0, meaning to run
	   GCC version 4.0.

       The -V and -b options work by running the <machine>-gcc-<version> executable, so there's
       no real reason to use them if you can just run that directly.

       Hardware Models and Configurations

       Earlier we discussed the standard option -b which chooses among different installed
       compilers for completely different target machines, such as VAX vs. 68000 vs. 80386.

       In addition, each of these target machine types can have its own special options, starting
       with -m, to choose among various hardware models or configurations---for example, 68010 vs
       68020, floating coprocessor or none.  A single installed version of the compiler can
       compile for any model or configuration, according to the options specified.

       Some configurations of the compiler also support additional special options, usually for
       compatibility with other compilers on the same platform.

       ARM Options

       These -m options are defined for Advanced RISC Machines (ARM) architectures:

       -mabi=name
	   Generate code for the specified ABI.  Permissible values are: apcs-gnu, atpcs, aapcs,
	   aapcs-linux and iwmmxt.

       -mapcs-frame
	   Generate a stack frame that is compliant with the ARM Procedure Call Standard for all
	   functions, even if this is not strictly necessary for correct execution of the code.
	   Specifying -fomit-frame-pointer with this option will cause the stack frames not to be
	   generated for leaf functions.  The default is -mno-apcs-frame.

       -mapcs
	   This is a synonym for -mapcs-frame.

       -mapcs-stack-check
	   Generate code to check the amount of stack space available upon entry to every
	   function (that actually uses some stack space).  If there is insufficient space
	   available then either the function __rt_stkovf_split_small or __rt_stkovf_split_big
	   will be called, depending upon the amount of stack space required.  The run time
	   system is required to provide these functions.  The default is -mno-apcs-stack-check,
	   since this produces smaller code.

       -mapcs-float
	   Pass floating point arguments using the float point registers.  This is one of the
	   variants of the APCS.  This option is recommended if the target hardware has a
	   floating point unit or if a lot of floating point arithmetic is going to be performed
	   by the code.  The default is -mno-apcs-float, since integer only code is slightly
	   increased in size if -mapcs-float is used.

       -mapcs-reentrant
	   Generate reentrant, position independent code.  The default is -mno-apcs-reentrant.

       -mthumb-interwork
	   Generate code which supports calling between the ARM and Thumb instruction sets.
	   Without this option the two instruction sets cannot be reliably used inside one
	   program.  The default is -mno-thumb-interwork, since slightly larger code is generated
	   when -mthumb-interwork is specified.

       -mno-sched-prolog
	   Prevent the reordering of instructions in the function prolog, or the merging of those
	   instruction with the instructions in the function's body.  This means that all
	   functions will start with a recognizable set of instructions (or in fact one of a
	   choice from a small set of different function prologues), and this information can be
	   used to locate the start if functions inside an executable piece of code.  The default
	   is -msched-prolog.

       -mhard-float
	   Generate output containing floating point instructions.  This is the default.

       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries are not available for all ARM targets.  Normally the facilities of the
	   machine's usual C compiler are used, but this cannot be done directly in cross-
	   compilation.  You must make your own arrangements to provide suitable library
	   functions for cross-compilation.

	   -msoft-float changes the calling convention in the output file; therefore, it is only
	   useful if you compile all of a program with this option.  In particular, you need to
	   compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this
	   to work.

       -mfloat-abi=name
	   Specifies which ABI to use for floating point values.  Permissible values are: soft,
	   softfp and hard.

	   soft and hard are equivalent to -msoft-float and -mhard-float respectively.	softfp
	   allows the generation of floating point instructions, but still uses the soft-float
	   calling conventions.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.  This is the default for
	   all standard configurations.

       -mbig-endian
	   Generate code for a processor running in big-endian mode; the default is to compile
	   code for a little-endian processor.

       -mwords-little-endian
	   This option only applies when generating code for big-endian processors.  Generate
	   code for a little-endian word order but a big-endian byte order.  That is, a byte
	   order of the form 32107654.	Note: this option should only be used if you require
	   compatibility with code for big-endian ARM processors generated by versions of the
	   compiler prior to 2.8.

       -mcpu=name
	   This specifies the name of the target ARM processor.  GCC uses this name to determine
	   what kind of instructions it can emit when generating assembly code.  Permissible
	   names are: arm2, arm250, arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7m,
	   arm7d, arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100,
	   arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm8, strongarm, strongarm110,
	   strongarm1100, arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s,
	   arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s,
	   arm10e, arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp, arm1176jz-s,
	   arm1176jzf-s, xscale, iwmmxt, ep9312.

       -mtune=name
	   This option is very similar to the -mcpu= option, except that instead of specifying
	   the actual target processor type, and hence restricting which instructions can be
	   used, it specifies that GCC should tune the performance of the code as if the target
	   were of the type specified in this option, but still choosing the instructions that it
	   will generate based on the cpu specified by a -mcpu= option.  For some ARM
	   implementations better performance can be obtained by using this option.

       -march=name
	   This specifies the name of the target ARM architecture.  GCC uses this name to
	   determine what kind of instructions it can emit when generating assembly code.  This
	   option can be used in conjunction with or instead of the -mcpu= option.  Permissible
	   names are: armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5te, armv6,
	   armv6j, iwmmxt, ep9312.

       -mfpu=name
       -mfpe=number
       -mfp=number
	   This specifies what floating point hardware (or hardware emulation) is available on
	   the target.	Permissible names are: fpa, fpe2, fpe3, maverick, vfp.	-mfp and -mfpe
	   are synonyms for -mfpu=fpenumber, for compatibility with older versions of GCC.

	   If -msoft-float is specified this specifies the format of floating point values.

       -mstructure-size-boundary=n
	   The size of all structures and unions will be rounded up to a multiple of the number
	   of bits set by this option.	Permissible values are 8, 32 and 64.  The default value
	   varies for different toolchains.  For the COFF targeted toolchain the default value is
	   8.  A value of 64 is only allowed if the underlying ABI supports it.

	   Specifying the larger number can produce faster, more efficient code, but can also
	   increase the size of the program.  Different values are potentially incompatible.
	   Code compiled with one value cannot necessarily expect to work with code or libraries
	   compiled with another value, if they exchange information using structures or unions.

       -mabort-on-noreturn
	   Generate a call to the function "abort" at the end of a "noreturn" function.  It will
	   be executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls by first loading the address of the
	   function into a register and then performing a subroutine call on this register.  This
	   switch is needed if the target function will lie outside of the 64 megabyte addressing
	   range of the offset based version of subroutine call instruction.

	   Even if this switch is enabled, not all function calls will be turned into long calls.
	   The heuristic is that static functions, functions which have the short-call attribute,
	   functions that are inside the scope of a #pragma no_long_calls directive and functions
	   whose definitions have already been compiled within the current compilation unit, will
	   not be turned into long calls.  The exception to this rule is that weak function
	   definitions, functions with the long-call attribute or the section attribute, and
	   functions that are within the scope of a #pragma long_calls directive, will always be
	   turned into long calls.

	   This feature is not enabled by default.  Specifying -mno-long-calls will restore the
	   default behavior, as will placing the function calls within the scope of a #pragma
	   long_calls_off directive.  Note these switches have no effect on how the compiler
	   generates code to handle function calls via function pointers.

       -mnop-fun-dllimport
	   Disable support for the "dllimport" attribute.

       -msingle-pic-base
	   Treat the register used for PIC addressing as read-only, rather than loading it in the
	   prologue for each function.	The run-time system is responsible for initializing this
	   register with an appropriate value before execution begins.

       -mpic-register=reg
	   Specify the register to be used for PIC addressing.	The default is R10 unless stack-
	   checking is enabled, when R9 is used.

       -mcirrus-fix-invalid-insns
	   Insert NOPs into the instruction stream to in order to work around problems with
	   invalid Maverick instruction combinations.  This option is only valid if the
	   -mcpu=ep9312 option has been used to enable generation of instructions for the Cirrus
	   Maverick floating point co-processor.  This option is not enabled by default, since
	   the problem is only present in older Maverick implementations.  The default can be re-
	   enabled by use of the -mno-cirrus-fix-invalid-insns switch.

       -mpoke-function-name
	   Write the name of each function into the text section, directly preceding the function
	   prologue.  The generated code is similar to this:

			t0
			    .ascii "arm_poke_function_name", 0
			    .align
			t1
			    .word 0xff000000 + (t1 - t0)
			arm_poke_function_name
			    mov     ip, sp
			    stmfd   sp!, {fp, ip, lr, pc}
			    sub     fp, ip, #4

	   When performing a stack backtrace, code can inspect the value of "pc" stored at "fp +
	   0".	If the trace function then looks at location "pc - 12" and the top 8 bits are
	   set, then we know that there is a function name embedded immediately preceding this
	   location and has length "((pc[-3]) & 0xff000000)".

       -mthumb
	   Generate code for the 16-bit Thumb instruction set.	The default is to use the 32-bit
	   ARM instruction set.

       -mtpcs-frame
	   Generate a stack frame that is compliant with the Thumb Procedure Call Standard for
	   all non-leaf functions.  (A leaf function is one that does not call any other
	   functions.)	The default is -mno-tpcs-frame.

       -mtpcs-leaf-frame
	   Generate a stack frame that is compliant with the Thumb Procedure Call Standard for
	   all leaf functions.	(A leaf function is one that does not call any other functions.)
	   The default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
	   Gives all externally visible functions in the file being compiled an ARM instruction
	   set header which switches to Thumb mode before executing the rest of the function.
	   This allows these functions to be called from non-interworking code.

       -mcaller-super-interworking
	   Allows calls via function pointers (including virtual functions) to execute correctly
	   regardless of whether the target code has been compiled for interworking or not.
	   There is a small overhead in the cost of executing a function pointer if this option
	   is enabled.

       -mtp=name
	   Specify the access model for the thread local storage pointer.  The valid models are
	   soft, which generates calls to "__aeabi_read_tp", cp15, which fetches the thread
	   pointer from "cp15" directly (supported in the arm6k architecture), and auto, which
	   uses the best available method for the selected processor.  The default setting is
	   auto.

       -mms-bitfields
	   Set the default structure layout to be compatible with the Microsoft compiler
	   standard. This is equivalent to adding an "ms_struct" attribute to each structure and
	   union tag definition. The default is mno-ms-bitfields.

       Darwin Options

       These options are defined for all architectures running the Darwin operating system.

       FSF GCC on Darwin does not create "universal" object files; it will create an object file
       for the single architecture that it was built to target.  Apple's GCC on Darwin does
       create "universal" files if multiple -arch options are used; it does so by running the
       compiler or linker multiple times and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is determined by the
       flags that specify the ISA that GCC is targetting, like -mcpu or -march.  The
       -force_cpusubtype_ALL option can be used to override this.

       The Darwin tools vary in their behavior when presented with an ISA mismatch.  The
       assembler, as, will only permit instructions to be used that are valid for the subtype of
       the file it is generating, so you cannot put 64-bit instructions in an ppc750 object file.
       The linker for shared libraries, /usr/bin/libtool, will fail and print an error if asked
       to create a shared library with a less restrictive subtype than its input files (for
       instance, trying to put a ppc970 object file in a ppc7400 library).  The linker for
       executables, ld, will quietly give the executable the most restrictive subtype of any of
       its input files.

       -Fdir
	   Add the framework directory dir to the head of the list of directories to be searched
	   for header files.  These directories are interleaved with those specified by -I
	   options and are scanned in a left-to-right order.

	   A framework directory is a directory with frameworks in it.	A framework is a
	   directory with a "Headers" and/or "PrivateHeaders" directory contained directly in it
	   that ends in ".framework".  The name of a framework is the name of this directory
	   excluding the ".framework".	Headers associated with the framework are found in one of
	   those two directories, with "Headers" being searched first.	A subframework is a
	   framework directory that is in a framework's "Frameworks" directory.  Includes of
	   subframework headers can only appear in a header of a framework that contains the
	   subframework, or in a sibling subframework header.  Two subframeworks are siblings if
	   they occur in the same framework.  A subframework should not have the same name as a
	   framework, a warning will be issued if this is violated.  Currently a subframework
	   cannot have subframeworks, in the future, the mechanism may be extended to support
	   this.  The standard frameworks can be found in "/System/Library/Frameworks" and
	   "/Library/Frameworks".  An example include looks like "#include <Framework/header.h>",
	   where Framework denotes the name of the framework and header.h is found in the
	   "PrivateHeaders" or "Headers" directory.

       -iframeworkdir
	   Like -F except the directory is a treated as a system directory.  The main effect is
	   to not warn about constructs contained within header files found via dir.

       -gused
	   Emit debugging information for symbols that are used.  For STABS debugging format,
	   this enables -feliminate-unused-debug-symbols.  This is by default ON.

       -gfull
	   Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
	   The earliest version of MacOS X that this executable will run on is version.  Typical
	   values of version include 10.1, 10.2, and 10.3.9.

	   This value can also be set with the MACOSX_DEPLOYMENT_TARGET environment variable.  If
	   both the command-line option is specified and the environment variable is set, the
	   command-line option will take precedence.

	   If the compiler was built to use the system's headers by default, then the default for
	   this option is the system version on which the compiler is running, otherwise the
	   default is to make choices which are compatible with as many systems and code bases as
	   possible.

	   This value is not set by default for ARM targets.

       -miphoneos-version-min=version
	   The earliest version of iPhone OS that this executable will run on is version.

	   This value can also be set with the IPHONEOS_DEPLOYMENT_TARGET environment variable.
	   If both the command-line option is specified and the environment variable is set, the
	   command-line option will take precedence.

	   On ARM targets, if not specified by the command-line option or environment variable,
	   this value defaults to 2.0.

       -mkernel
	   Enable kernel development mode.  The -mkernel option sets -static, -fno-common,
	   -fno-builtin, -fno-cxa-atexit, -fno-exceptions, -fno-non-call-exceptions,
	   -fno-asynchronous-unwind-tables, -fapple-kext, -fno-weak and -fno-rtti where
	   applicable.	This mode also sets -mno-altivec, -msoft-float and -mlong-branch for
	   PowerPC targets, -mno-red-zone on x86_64, and -mlong-branch for ARM targets.  Of
	   these, only -msoft-float can be changed which is useful in a kext that wishes to use
	   the hardware floating point unit.  -dynamic can be used to override the effects of
	   -static on the assembler to enable the use of weak_import.

       -mone-byte-bool
	   Override the defaults for bool so that sizeof(bool)==1.  By default sizeof(bool) is 4
	   when compiling for Darwin/PowerPC and 1 when compiling for Darwin/x86, so this option
	   has no effect on x86.

	   Warning: The -mone-byte-bool switch causes GCC to generate code that is not binary
	   compatible with code generated without that switch.	Using this switch may require
	   recompiling all other modules in a program, including system libraries.  Use this
	   switch to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
	   Generate code suitable for fast turn around development.  Needed to enable gdb to
	   dynamically load ".o" files into already running programs.  -findirect-data and
	   -ffix-and-continue are provided for backwards compatibility.

       -fapple-kext
       -findirect-virtual-calls
       -fterminated-vtables
	   Alter vtables, destructors, and other implementation details to more closely resemble
	   the GCC 2.95 ABI for PowerPC and 32-bit i386.  This is to make kernel extensions
	   loadable by Darwin kernels, and is required to build any Darwin kernel extension.  In
	   addition, virtual calls are not made directly, instead, code is generated to always go
	   through the virtual table, as virtual tables can be patched by the kernel module
	   loader.  Vtables are altered by adding a zero word at the end of every vtable.
	   -findirect-virtual-calls and -fterminated-vtables are accepted for backwards
	   compatibility but will be removed in the future.  Additionally implies most of
	   -mkernel except for -msoft-float and -mlong-branch for PowerPC targets.  (APPLE ONLY)

       -mpascal-strings
	   Allow Pascal-style string literals to be constructed.  This option implies
	   -Wpointer-sign so that conversions between Pascal-style strings and C-style strings
	   are warned about.  (APPLE ONLY)

       -all_load
	   Loads all members of static archive libraries.  See man ld(1) for more information.

       -arch_errors_fatal
	   Cause the errors having to do with files that have the wrong architecture to be fatal.

       -bind_at_load
	   Causes the output file to be marked such that the dynamic linker will bind all
	   undefined references when the file is loaded or launched.

       -bundle
	   Produce a Mach-o bundle format file.  See man ld(1) for more information.

       -bundle_loader executable
	   This option specifies the executable that will be loading the build output file being
	   linked.  See man ld(1) for more information.

       -dynamiclib
	   When passed this option, GCC will produce a dynamic library instead of an executable
	   when linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
	   This causes GCC's output file to have the ALL subtype, instead of one controlled by
	   the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
	   These options are passed to the Darwin linker.  The Darwin linker man page describes
	   them in detail.

       Intel 386 and AMD x86-64 Options

       These -m options are defined for the i386 and x86-64 family of computers:

       -mtune=cpu-type
	   Tune to cpu-type everything applicable about the generated code, except for the ABI
	   and the set of available instructions.  The choices for cpu-type are:

	   generic
	       Produce code optimized for the most common IA32/AMD64/EM64T processors.	If you
	       know the CPU on which your code will run, then you should use the corresponding
	       -mtune option instead of -mtune=generic.  But, if you do not know exactly what CPU
	       users of your application will have, then you should use this option.

	       As new processors are deployed in the marketplace, the behavior of this option
	       will change.  Therefore, if you upgrade to a newer version of GCC, the code
	       generated option will change to reflect the processors that were most common when
	       that version of GCC was released.

	       There is no -march=generic option because -march indicates the instruction set the
	       compiler can use, and there is no generic instruction set applicable to all
	       processors.  In contrast, -mtune indicates the processor (or, in this case,
	       collection of processors) for which the code is optimized.

	   native
	       This selects the CPU to tune for at compilation time by determining the processor
	       type of the compiling machine.  Using -mtune=native will produce code optimized
	       for the local machine under the constraints of the selected instruction set.
	       Using -march=native will enable all instruction subsets supported by the local
	       machine (hence the result might not run on different machines).

	   i386
	       Original Intel's i386 CPU.

	   i486
	       Intel's i486 CPU.  (No scheduling is implemented for this chip.)

	   i586, pentium
	       Intel Pentium CPU with no MMX support.

	   pentium-mmx
	       Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.

	   pentiumpro
	       Intel PentiumPro CPU.

	   i686
	       Same as "generic", but when used as "march" option, PentiumPro instruction set
	       will be used, so the code will run on all i686 family chips.

	   pentium2
	       Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.

	   pentium3, pentium3m
	       Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set
	       support.

	   pentium-m
	       Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set
	       support.  Used by Centrino notebooks.

	   pentium4, pentium4m
	       Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.

	   prescott
	       Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction
	       set support.

	   nocona
	       Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and
	       SSE3 instruction set support.

	   core2
	       Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction
	       set support.

	   k6  AMD K6 CPU with MMX instruction set support.

	   k6-2, k6-3
	       Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support.

	   athlon, athlon-tbird
	       AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions
	       support.

	   athlon-4, athlon-xp, athlon-mp
	       Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE instruction
	       set support.

	   k8, opteron, athlon64, athlon-fx
	       AMD K8 core based CPUs with x86-64 instruction set support.  (This supersets MMX,
	       SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)

	   winchip-c6
	       IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction set
	       support.

	   winchip2
	       IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW!
	       instruction set support.

	   c3  Via C3 CPU with MMX and 3dNOW! instruction set support.	(No scheduling is
	       implemented for this chip.)

	   c3-2
	       Via C3-2 CPU with MMX and SSE instruction set support.  (No scheduling is
	       implemented for this chip.)

	   While picking a specific cpu-type will schedule things appropriately for that
	   particular chip, the compiler will not generate any code that does not run on the i386
	   without the -march=cpu-type option being used.

       -march=cpu-type
	   Generate instructions for the machine type cpu-type.  The choices for cpu-type are the
	   same as for -mtune.	Moreover, specifying -march=cpu-type implies -mtune=cpu-type.

       -mcpu=cpu-type
	   A deprecated synonym for -mtune.

       -m386
       -m486
       -mpentium
       -mpentiumpro
	   These options are synonyms for -mtune=i386, -mtune=i486, -mtune=pentium, and
	   -mtune=pentiumpro respectively.  These synonyms are deprecated.

       -mfpmath=unit
	   Generate floating point arithmetics for selected unit unit.	The choices for unit are:

	   387 Use the standard 387 floating point coprocessor present majority of chips and
	       emulated otherwise.  Code compiled with this option will run almost everywhere.
	       The temporary results are computed in 80bit precision instead of precision
	       specified by the type resulting in slightly different results compared to most of
	       other chips.  See -ffloat-store for more detailed description.

	       This is the default choice for i386 compiler.

	   sse Use scalar floating point instructions present in the SSE instruction set.  This
	       instruction set is supported by Pentium3 and newer chips, in the AMD line by
	       Athlon-4, Athlon-xp and Athlon-mp chips.  The earlier version of SSE instruction
	       set supports only single precision arithmetics, thus the double and extended
	       precision arithmetics is still done using 387.  Later version, present only in
	       Pentium4 and the future AMD x86-64 chips supports double precision arithmetics
	       too.

	       For the i386 compiler, you need to use -march=cpu-type, -msse or -msse2 switches
	       to enable SSE extensions and make this option effective.  For the x86-64 compiler,
	       these extensions are enabled by default.

	       The resulting code should be considerably faster in the majority of cases and
	       avoid the numerical instability problems of 387 code, but may break some existing
	       code that expects temporaries to be 80bit.

	       This is the default choice for the x86-64 compiler.

	   sse,387
	       Attempt to utilize both instruction sets at once.  This effectively double the
	       amount of available registers and on chips with separate execution units for 387
	       and SSE the execution resources too.  Use this option with care, as it is still
	       experimental, because the GCC register allocator does not model separate
	       functional units well resulting in instable performance.

       -masm=dialect
	   Output asm instructions using selected dialect.  Supported choices are intel or att
	   (the default one).  Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
	   Control whether or not the compiler uses IEEE floating point comparisons.  These
	   handle correctly the case where the result of a comparison is unordered.

       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries are not part of GCC.  Normally the facilities of the machine's usual C
	   compiler are used, but this can't be done directly in cross-compilation.  You must
	   make your own arrangements to provide suitable library functions for cross-
	   compilation.

	   On machines where a function returns floating point results in the 80387 register
	   stack, some floating point opcodes may be emitted even if -msoft-float is used.

       -mno-fp-ret-in-387
	   Do not use the FPU registers for return values of functions.

	   The usual calling convention has functions return values of types "float" and "double"
	   in an FPU register, even if there is no FPU.  The idea is that the operating system
	   should emulate an FPU.

	   The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU
	   registers instead.

       -mno-fancy-math-387
	   Some 387 emulators do not support the "sin", "cos" and "sqrt" instructions for the
	   387.  Specify this option to avoid generating those instructions.  This option is the
	   default on FreeBSD, OpenBSD and NetBSD.  This option is overridden when -march
	   indicates that the target cpu will always have an FPU and so the instruction will not
	   need emulation.  As of revision 2.6.1, these instructions are not generated unless you
	   also use the -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
	   Control whether GCC aligns "double", "long double", and "long long" variables on a two
	   word boundary or a one word boundary.  Aligning "double" variables on a two word
	   boundary will produce code that runs somewhat faster on a Pentium at the expense of
	   more memory.

	   On x86-64, -malign-double is enabled by default.

	   Warning: if you use the -malign-double switch, structures containing the above types
	   will be aligned differently than the published application binary interface
	   specifications for the 386 and will not be binary compatible with structures in code
	   compiled without that switch.

       -m96bit-long-double
       -m128bit-long-double
	   These switches control the size of "long double" type.  The i386 application binary
	   interface specifies the size to be 96 bits, so -m96bit-long-double is the default in
	   32 bit mode.

	   Modern architectures (Pentium and newer) would prefer "long double" to be aligned to
	   an 8 or 16 byte boundary.  In arrays or structures conforming to the ABI, this would
	   not be possible.  So specifying a -m128bit-long-double will align "long double" to a
	   16 byte boundary by padding the "long double" with an additional 32 bit zero.

	   In the x86-64 compiler, -m128bit-long-double is the default choice as its ABI
	   specifies that "long double" is to be aligned on 16 byte boundary.

	   Notice that neither of these options enable any extra precision over the x87 standard
	   of 80 bits for a "long double".

	   Warning: if you override the default value for your target ABI, the structures and
	   arrays containing "long double" variables will change their size as well as function
	   calling convention for function taking "long double" will be modified.  Hence they
	   will not be binary compatible with arrays or structures in code compiled without that
	   switch.

       -mmlarge-data-threshold=number
	   When -mcmodel=medium is specified, the data greater than threshold are placed in large
	   data section.  This value must be the same across all object linked into the binary
	   and defaults to 65535.

       -msvr3-shlib
       -mno-svr3-shlib
	   Control whether GCC places uninitialized local variables into the "bss" or "data"
	   segments.  -msvr3-shlib places them into "bss".  These options are meaningful only on
	   System V Release 3.

       -mrtd
	   Use a different function-calling convention, in which functions that take a fixed
	   number of arguments return with the "ret" num instruction, which pops their arguments
	   while returning.  This saves one instruction in the caller since there is no need to
	   pop the arguments there.

	   You can specify that an individual function is called with this calling sequence with
	   the function attribute stdcall.  You can also override the -mrtd option by using the
	   function attribute cdecl.

	   Warning: this calling convention is incompatible with the one normally used on Unix,
	   so you cannot use it if you need to call libraries compiled with the Unix compiler.

	   Also, you must provide function prototypes for all functions that take variable
	   numbers of arguments (including "printf"); otherwise incorrect code will be generated
	   for calls to those functions.

	   In addition, seriously incorrect code will result if you call a function with too many
	   arguments.  (Normally, extra arguments are harmlessly ignored.)

       -mregparm=num
	   Control how many registers are used to pass integer arguments.  By default, no
	   registers are used to pass arguments, and at most 3 registers can be used.  You can
	   control this behavior for a specific function by using the function attribute regparm.

	   Warning: if you use this switch, and num is nonzero, then you must build all modules
	   with the same value, including any libraries.  This includes the system libraries and
	   startup modules.

       -msseregparm
	   Use SSE register passing conventions for float and double arguments and return values.
	   You can control this behavior for a specific function by using the function attribute
	   sseregparm.

	   Warning: if you use this switch then you must build all modules with the same value,
	   including any libraries.  This includes the system libraries and startup modules.

       -mstackrealign
	   Realign the stack at entry.	On the Intel x86, the -mstackrealign option will generate
	   an alternate prologue and epilogue that realigns the runtime stack.	This supports
	   mixing legacy codes that keep a 4-byte aligned stack with modern codes that keep a
	   16-byte stack for SSE compatibility.  The alternate prologue and epilogue are slower
	   and bigger than the regular ones, and the alternate prologue requires an extra scratch
	   register; this lowers the number of registers available if used in conjunction with
	   the "regparm" attribute.  The -mstackrealign option is incompatible with the nested
	   function prologue; this is considered a hard error.	See also the attribute
	   "force_align_arg_pointer", applicable to individual functions.

       -mpreferred-stack-boundary=num
	   Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary.  If
	   -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128 bits).

	   On Pentium and PentiumPro, "double" and "long double" values should be aligned to an 8
	   byte boundary (see -malign-double) or suffer significant run time performance
	   penalties.  On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" may
	   not work properly if it is not 16 byte aligned.

	   To ensure proper alignment of this values on the stack, the stack boundary must be as
	   aligned as that required by any value stored on the stack.  Further, every function
	   must be generated such that it keeps the stack aligned.  Thus calling a function
	   compiled with a higher preferred stack boundary from a function compiled with a lower
	   preferred stack boundary will most likely misalign the stack.  It is recommended that
	   libraries that use callbacks always use the default setting.

	   This extra alignment does consume extra stack space, and generally increases code
	   size.  Code that is sensitive to stack space usage, such as embedded systems and
	   operating system kernels, may want to reduce the preferred alignment to
	   -mpreferred-stack-boundary=2.

       -mmmx
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -msse3
       -mno-sse3
       -mssse3
       -mno-ssse3
       -msse4.1
       -mno-sse4.1
       -msse4.2
       -mno-sse4.2
       -msse4
       -mno-sse4
       -msse4a
       -mno-sse4a
       -m3dnow
       -mno-3dnow
	   These switches enable or disable the use of instructions in the MMX, SSE, SSE2, SSE3,
	   SSSE3, 3Dnow, SSE4.1, SSE4.2, and SSE4A extended instruction sets.  These extensions
	   are also available as built-in functions: see X86 Built-in Functions, for details of
	   the functions enabled and disabled by these switches.

	   To have SSE/SSE2 instructions generated automatically from floating-point code (as
	   opposed to 387 instructions), see -mfpmath=sse.

	   These options will enable GCC to use these extended instructions in generated code,
	   even without -mfpmath=sse.  Applications which perform runtime CPU detection must
	   compile separate files for each supported architecture, using the appropriate flags.
	   In particular, the file containing the CPU detection code should be compiled without
	   these options.

       -mpush-args
       -mno-push-args
	   Use PUSH operations to store outgoing parameters.  This method is shorter and usually
	   equally fast as method using SUB/MOV operations and is enabled by default.  In some
	   cases disabling it may improve performance because of improved scheduling and reduced
	   dependencies.

       -maccumulate-outgoing-args
	   If enabled, the maximum amount of space required for outgoing arguments will be
	   computed in the function prologue.  This is faster on most modern CPUs because of
	   reduced dependencies, improved scheduling and reduced stack usage when preferred stack
	   boundary is not equal to 2.	The drawback is a notable increase in code size.  This
	   switch implies -mno-push-args.

       -mthreads
	   Support thread-safe exception handling on Mingw32.  Code that relies on thread-safe
	   exception handling must compile and link all code with the -mthreads option.  When
	   compiling, -mthreads defines -D_MT; when linking, it links in a special thread helper
	   library -lmingwthrd which cleans up per thread exception handling data.

       -mno-align-stringops
	   Do not align destination of inlined string operations.  This switch reduces code size
	   and improves performance in case the destination is already aligned, but GCC doesn't
	   know about it.

       -minline-all-stringops
	   By default GCC inlines string operations only when destination is known to be aligned
	   at least to 4 byte boundary.  This enables more inlining, increase code size, but may
	   improve performance of code that depends on fast memcpy, strlen and memset for short
	   lengths.

       -momit-leaf-frame-pointer
	   Don't keep the frame pointer in a register for leaf functions.  This avoids the
	   instructions to save, set up and restore frame pointers and makes an extra register
	   available in leaf functions.  The option -fomit-frame-pointer removes the frame
	   pointer for all functions which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
	   Controls whether TLS variables may be accessed with offsets from the TLS segment
	   register (%gs for 32-bit, %fs for 64-bit), or whether the thread base pointer must be
	   added.  Whether or not this is legal depends on the operating system, and whether it
	   maps the segment to cover the entire TLS area.

	   For systems that use GNU libc, the default is on.

       These -m switches are supported in addition to the above on AMD x86-64 processors in
       64-bit environments.

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,
	   long and pointer to 32 bits and generates code that runs on any i386 system.  The
	   64-bit environment sets int to 32 bits and long and pointer to 64 bits and generates
	   code for AMD's x86-64 architecture. For darwin only the -m64 option turns off the
	   -fno-pic and -mdynamic-no-pic options.

       -mno-red-zone
	   Do not use a so called red zone for x86-64 code.  The red zone is mandated by the
	   x86-64 ABI, it is a 128-byte area beyond the location of the stack pointer that will
	   not be modified by signal or interrupt handlers and therefore can be used for
	   temporary data without adjusting the stack pointer.	The flag -mno-red-zone disables
	   this red zone.

       -mcmodel=small
	   Generate code for the small code model: the program and its symbols must be linked in
	   the lower 2 GB of the address space.  Pointers are 64 bits.	Programs can be
	   statically or dynamically linked.  This is the default code model.

       -mcmodel=kernel
	   Generate code for the kernel code model.  The kernel runs in the negative 2 GB of the
	   address space.  This model has to be used for Linux kernel code.

       -mcmodel=medium
	   Generate code for the medium model: The program is linked in the lower 2 GB of the
	   address space but symbols can be located anywhere in the address space.  Programs can
	   be statically or dynamically linked, but building of shared libraries are not
	   supported with the medium model.

       -mcmodel=large
	   Generate code for the large model: This model makes no assumptions about addresses and
	   sizes of sections.  Currently GCC does not implement this model.

       -mms-bitfields
	   Set the default structure layout to be compatible with the Microsoft compiler
	   standard. This is equivalent to adding an "ms_struct" attribute to each structure and
	   union tag definition. The default is mno-ms-bitfields.

       PowerPC Options

       These are listed under

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-powerpc
       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mfprnd
       -mno-fprnd
	   GCC supports two related instruction set architectures for the RS/6000 and PowerPC.
	   The POWER instruction set are those instructions supported by the rios chip set used
	   in the original RS/6000 systems and the PowerPC instruction set is the architecture of
	   the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and the IBM 4xx, 6xx, and
	   follow-on microprocessors.

	   Neither architecture is a subset of the other.  However there is a large common subset
	   of instructions supported by both.  An MQ register is included in processors
	   supporting the POWER architecture.

	   You use these options to specify which instructions are available on the processor you
	   are using.  The default value of these options is determined when configuring GCC.
	   Specifying the -mcpu=cpu_type overrides the specification of these options.	We
	   recommend you use the -mcpu=cpu_type option rather than the options listed above.

	   The -mpower option allows GCC to generate instructions that are found only in the
	   POWER architecture and to use the MQ register.  Specifying -mpower2 implies -power and
	   also allows GCC to generate instructions that are present in the POWER2 architecture
	   but not the original POWER architecture.

	   The -mpowerpc option allows GCC to generate instructions that are found only in the
	   32-bit subset of the PowerPC architecture.  Specifying -mpowerpc-gpopt implies
	   -mpowerpc and also allows GCC to use the optional PowerPC architecture instructions in
	   the General Purpose group, including floating-point square root.  Specifying
	   -mpowerpc-gfxopt implies -mpowerpc and also allows GCC to use the optional PowerPC
	   architecture instructions in the Graphics group, including floating-point select.

	   The -mmfcrf option allows GCC to generate the move from condition register field
	   instruction implemented on the POWER4 processor and other processors that support the
	   PowerPC V2.01 architecture.	The -mpopcntb option allows GCC to generate the popcount
	   and double precision FP reciprocal estimate instruction implemented on the POWER5
	   processor and other processors that support the PowerPC V2.02 architecture.	The
	   -mfprnd option allows GCC to generate the FP round to integer instructions implemented
	   on the POWER5+ processor and other processors that support the PowerPC V2.03
	   architecture.

	   The -mpowerpc64 option allows GCC to generate the additional 64-bit instructions that
	   are found in the full PowerPC64 architecture and to treat GPRs as 64-bit, doubleword
	   quantities.	GCC defaults to -mno-powerpc64.

	   If you specify both -mno-power and -mno-powerpc, GCC will use only the instructions in
	   the common subset of both architectures plus some special AIX common-mode calls, and
	   will not use the MQ register.  Specifying both -mpower and -mpowerpc permits GCC to
	   use any instruction from either architecture and to allow use of the MQ register;
	   specify this for the Motorola MPC601.

       -mnew-mnemonics
       -mold-mnemonics
	   Select which mnemonics to use in the generated assembler code.  With -mnew-mnemonics,
	   GCC uses the assembler mnemonics defined for the PowerPC architecture.  With
	   -mold-mnemonics it uses the assembler mnemonics defined for the POWER architecture.
	   Instructions defined in only one architecture have only one mnemonic; GCC uses that
	   mnemonic irrespective of which of these options is specified.

	   GCC defaults to the mnemonics appropriate for the architecture in use.  Specifying
	   -mcpu=cpu_type sometimes overrides the value of these option.  Unless you are building
	   a cross-compiler, you should normally not specify either -mnew-mnemonics or
	   -mold-mnemonics, but should instead accept the default.

       -mcpu=cpu_type
	   Set architecture type, register usage, choice of mnemonics, and instruction scheduling
	   parameters for machine type cpu_type.  Supported values for cpu_type are 401, 403,
	   405, 405fp, 440, 440fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400,
	   7450, 750, 801, 821, 823, 860, 970, 8540, ec603e, G3, G4, G5, power, power2, power3,
	   power4, power5, power5+, power6, common, powerpc, powerpc64, rios, rios1, rios2, rsc,
	   and rs64.

	   -mcpu=common selects a completely generic processor.  Code generated under this option
	   will run on any POWER or PowerPC processor.	GCC will use only the instructions in the
	   common subset of both architectures, and will not use the MQ register.  GCC assumes a
	   generic processor model for scheduling purposes.

	   -mcpu=power, -mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64 specify generic POWER,
	   POWER2, pure 32-bit PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture
	   machine types, with an appropriate, generic processor model assumed for scheduling
	   purposes.

	   The other options specify a specific processor.  Code generated under those options
	   will run best on that processor, and may not run at all on others.

	   The -mcpu options automatically enable or disable the following options: -maltivec,
	   -mfprnd, -mhard-float, -mmfcrf, -mmultiple, -mnew-mnemonics, -mpopcntb, -mpower,
	   -mpower2, -mpowerpc64, -mpowerpc-gpopt, -mpowerpc-gfxopt, -mstring, -mmulhw, -mdlmzb.
	   The particular options set for any particular CPU will vary between compiler versions,
	   depending on what setting seems to produce optimal code for that CPU; it doesn't
	   necessarily reflect the actual hardware's capabilities.  If you wish to set an
	   individual option to a particular value, you may specify it after the -mcpu option,
	   like -mcpu=970 -mno-altivec.

	   On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled by the -mcpu
	   option at present because AIX does not have full support for these options.	You may
	   still enable or disable them individually if you're sure it'll work in your
	   environment.

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type cpu_type, but do not set
	   the architecture type, register usage, or choice of mnemonics, as -mcpu=cpu_type
	   would.  The same values for cpu_type are used for -mtune as for -mcpu.  If both are
	   specified, the code generated will use the architecture, registers, and mnemonics set
	   by -mcpu, but the scheduling parameters set by -mtune.

       -mswdiv
       -mno-swdiv
	   Generate code to compute division as reciprocal estimate and iterative refinement,
	   creating opportunities for increased throughput.  This feature requires: optional
	   PowerPC Graphics instruction set for single precision and FRE instruction for double
	   precision, assuming divides cannot generate user-visible traps, and the domain values
	   not include Infinities, denormals or zero denominator.

       -maltivec
       -mno-altivec
	   Generate code that uses (does not use) AltiVec instructions, and also enable the use
	   of built-in functions that allow more direct access to the AltiVec instruction set.
	   You may also need to set -mabi=altivec to adjust the current ABI with AltiVec ABI
	   enhancements.

       -mpim-altivec
       -mno-pim-altivec
	   Enable (or disable) built-in compiler support for the syntactic extensions as well as
	   operations and predicates defined in the Motorola AltiVec Technology Programming
	   Interface Manual (PIM).  This includes the recognition of "vector" and "pixel" as
	   (context-dependent) keywords, the definition of built-in functions such as "vec_add",
	   and the use of parenthesized comma expression as AltiVec literals.  Note that unlike
	   the option -maltivec, the extension does not require the inclusion of any special
	   header files; if "<altivec.h>" is included, a warning will be issued and the contents
	   of the header will be ignored.  The preprocessor shall provide an "__APPLE_ALTIVEC__"
	   manifest constant when -mpim-altivec is specified.  (APPLE ONLY)

	   In addition, the -mpim-altivec option disables the inlining of functions containing
	   AltiVec instructions into functions that do not make use of the vector unit.  Certain
	   other optimizations, such as inline vectorization of "memset" and "memcpy" calls, are
	   also disabled.  These adjustments make it possible to compile programs whose use of
	   AltiVec instructions is preceded by a run-time check for the presence of AltiVec
	   functionality, and that can therefore be made to run on G3 processors.  Note that all
	   of these optimizations may be re-enabled by supplying the -maltivec option, or an
	   -mcpu option specifying a processor that supports AltiVec instructions.

       -mvrsave
       -mno-vrsave
	   Generate VRSAVE instructions when generating AltiVec code.

       -msecure-plt
	   Generate code that allows ld and ld.so to build executables and shared libraries with
	   non-exec .plt and .got sections.  This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
	   Generate code that uses a BSS .plt section that ld.so fills in, and requires .plt and
	   .got sections that are both writable and executable.  This is a PowerPC 32-bit SYSV
	   ABI option.

       -misel
       -mno-isel
	   This switch enables or disables the generation of ISEL instructions.

       -misel=yes/no
	   This switch has been deprecated.  Use -misel and -mno-isel instead.

       -mspe
       -mno-spe
	   This switch enables or disables the generation of SPE simd instructions.

       -mspe=yes/no
	   This option has been deprecated.  Use -mspe and -mno-spe instead.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
	   This switch enables or disables the generation of floating point operations on the
	   general purpose registers for architectures that support it.

	   The argument yes or single enables the use of single-precision floating point
	   operations.

	   The argument double enables the use of single and double-precision floating point
	   operations.

	   The argument no disables floating point operations on the general purpose registers.

	   This option is currently only available on the MPC854x.

       -m32
       -m64
	   Generate code for 32-bit or 64-bit environments of Darwin and SVR4 targets (including
	   GNU/Linux).	The 32-bit environment sets int, long and pointer to 32 bits and
	   generates code that runs on any PowerPC variant.  The 64-bit environment sets int to
	   32 bits and long and pointer to 64 bits, and generates code for PowerPC64, as for
	   -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
	   Modify generation of the TOC (Table Of Contents), which is created for every
	   executable file.  The -mfull-toc option is selected by default.  In that case, GCC
	   will allocate at least one TOC entry for each unique non-automatic variable reference
	   in your program.  GCC will also place floating-point constants in the TOC.  However,
	   only 16,384 entries are available in the TOC.

	   If you receive a linker error message that saying you have overflowed the available
	   TOC space, you can reduce the amount of TOC space used with the -mno-fp-in-toc and
	   -mno-sum-in-toc options.  -mno-fp-in-toc prevents GCC from putting floating-point
	   constants in the TOC and -mno-sum-in-toc forces GCC to generate code to calculate the
	   sum of an address and a constant at run-time instead of putting that sum into the TOC.
	   You may specify one or both of these options.  Each causes GCC to produce very
	   slightly slower and larger code at the expense of conserving TOC space.

	   If you still run out of space in the TOC even when you specify both of these options,
	   specify -mminimal-toc instead.  This option causes GCC to make only one TOC entry for
	   every file.	When you specify this option, GCC will produce code that is slower and
	   larger but which uses extremely little TOC space.  You may wish to use this option
	   only on files that contain less frequently executed code.

       -maix64
       -maix32
	   Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit "long" type, and
	   the infrastructure needed to support them.  Specifying -maix64 implies -mpowerpc64 and
	   -mpowerpc, while -maix32 disables the 64-bit ABI and implies -mno-powerpc64.  GCC
	   defaults to -maix32.

       -mxl-compat
       -mno-xl-compat
	   Produce code that conforms more closely to IBM XL compiler semantics when using AIX-
	   compatible ABI.  Pass floating-point arguments to prototyped functions beyond the
	   register save area (RSA) on the stack in addition to argument FPRs.	Do not assume
	   that most significant double in 128-bit long double value is properly rounded when
	   comparing values and converting to double.  Use XL symbol names for long double
	   support routines.

	   The AIX calling convention was extended but not initially documented to handle an
	   obscure K&R C case of calling a function that takes the address of its arguments with
	   fewer arguments than declared.  IBM XL compilers access floating point arguments which
	   do not fit in the RSA from the stack when a subroutine is compiled without
	   optimization.  Because always storing floating-point arguments on the stack is
	   inefficient and rarely needed, this option is not enabled by default and only is
	   necessary when calling subroutines compiled by IBM XL compilers without optimization.

       -mpe
	   Support IBM RS/6000 SP Parallel Environment (PE).  Link an application written to use
	   message passing with special startup code to enable the application to run.	The
	   system must have PE installed in the standard location (/usr/lpp/ppe.poe/), or the
	   specs file must be overridden with the -specs= option to specify the appropriate
	   directory location.	The Parallel Environment does not support threads, so the -mpe
	   option and the -pthread option are incompatible.

       -malign-natural
       -malign-power
	   On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural
	   overrides the ABI-defined alignment of larger types, such as floating-point doubles,
	   on their natural size-based boundary.  The option -malign-power instructs GCC to
	   follow the ABI-specified alignment rules.  GCC defaults to the standard alignment
	   defined in the ABI.

	   On 64-bit Darwin, natural alignment is the default, and -malign-power is not
	   supported.

       -msoft-float
       -mhard-float
	   Generate code that does not use (uses) the floating-point register set.  Software
	   floating point emulation is provided if you use the -msoft-float option, and pass the
	   option to GCC when linking.

	   (APPLE ONLY) While the -msoft-float option is supported, the libraries that do the
	   floating point emulation are not shipped on Apple PowerPCs, with the effect that the
	   emulation does not work.  However, the option may be useful for a different reason.
	   Normally the compiler can use floating point registers in contexts where you might not
	   expect it, for example, to copy data from one memory location to another.  The
	   -msoft-float option will prevent it from doing this.

       -mmultiple
       -mno-multiple
	   Generate code that uses (does not use) the load multiple word instructions and the
	   store multiple word instructions.  These instructions are generated by default on
	   POWER systems, and not generated on PowerPC systems.  Do not use -mmultiple on little
	   endian PowerPC systems, since those instructions do not work when the processor is in
	   little endian mode.	The exceptions are PPC740 and PPC750 which permit the
	   instructions usage in little endian mode.

       -mstring
       -mno-string
	   Generate code that uses (does not use) the load string instructions and the store
	   string word instructions to save multiple registers and do small block moves.  These
	   instructions are generated by default on POWER systems, and not generated on PowerPC
	   systems.  Do not use -mstring on little endian PowerPC systems, since those
	   instructions do not work when the processor is in little endian mode.  The exceptions
	   are PPC740 and PPC750 which permit the instructions usage in little endian mode.

       -mupdate
       -mno-update
	   Generate code that uses (does not use) the load or store instructions that update the
	   base register to the address of the calculated memory location.  These instructions
	   are generated by default.  If you use -mno-update, there is a small window between the
	   time that the stack pointer is updated and the address of the previous frame is
	   stored, which means code that walks the stack frame across interrupts or signals may
	   get corrupted data.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating point multiply and accumulate
	   instructions.  These instructions are generated by default if hardware floating is
	   used.

       -mmulhw
       -mno-mulhw
	   Generate code that uses (does not use) the half-word multiply and multiply-accumulate
	   instructions on the IBM 405 and 440 processors.  These instructions are generated by
	   default when targetting those processors.

       -mdlmzb
       -mno-dlmzb
	   Generate code that uses (does not use) the string-search dlmzb instruction on the IBM
	   405 and 440 processors.  This instruction is generated by default when targetting
	   those processors.

       -mno-bit-align
       -mbit-align
	   On System V.4 and embedded PowerPC systems do not (do) force structures and unions
	   that contain bit-fields to be aligned to the base type of the bit-field.

	   For example, by default a structure containing nothing but 8 "unsigned" bit-fields of
	   length 1 would be aligned to a 4 byte boundary and have a size of 4 bytes.  By using
	   -mno-bit-align, the structure would be aligned to a 1 byte boundary and be one byte in
	   size.

       -mno-strict-align
       -mstrict-align
	   On System V.4 and embedded PowerPC systems do not (do) assume that unaligned memory
	   references will be handled by the system.

       -mrelocatable
       -mno-relocatable
	   On embedded PowerPC systems generate code that allows (does not allow) the program to
	   be relocated to a different address at runtime.  If you use -mrelocatable on any
	   module, all objects linked together must be compiled with -mrelocatable or
	   -mrelocatable-lib.

       -mrelocatable-lib
       -mno-relocatable-lib
	   On embedded PowerPC systems generate code that allows (does not allow) the program to
	   be relocated to a different address at runtime.  Modules compiled with
	   -mrelocatable-lib can be linked with either modules compiled without -mrelocatable and
	   -mrelocatable-lib or with modules compiled with the -mrelocatable options.

       -mno-toc
       -mtoc
	   On System V.4 and embedded PowerPC systems do not (do) assume that register 2 contains
	   a pointer to a global area pointing to the addresses used in the program.

       -mlittle
       -mlittle-endian
	   On System V.4 and embedded PowerPC systems compile code for the processor in little
	   endian mode.  The -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
	   On System V.4 and embedded PowerPC systems compile code for the processor in big
	   endian mode.  The -mbig-endian option is the same as -mbig.

       -mdynamic-no-pic
	   On Darwin and Mac OS X systems, compile code so that it is not relocatable, but that
	   its external references are relocatable.  The resulting code is suitable for
	   applications, but not shared libraries.

       -mprioritize-restricted-insns=priority
	   This option controls the priority that is assigned to dispatch-slot restricted
	   instructions during the second scheduling pass.  The argument priority takes the value
	   0/1/2 to assign no/highest/second-highest priority to dispatch slot restricted
	   instructions.

       -msched-costly-dep=dependence_type
	   This option controls which dependences are considered costly by the target during
	   instruction scheduling.  The argument dependence_type takes one of the following
	   values: no: no dependence is costly, all: all dependences are costly,
	   true_store_to_load: a true dependence from store to load is costly, store_to_load: any
	   dependence from store to load is costly, number: any dependence which latency >=
	   number is costly.

       -minsert-sched-nops=scheme
	   This option controls which nop insertion scheme will be used during the second
	   scheduling pass.  The argument scheme takes one of the following values: no: Don't
	   insert nops.  pad: Pad with nops any dispatch group which has vacant issue slots,
	   according to the scheduler's grouping.  regroup_exact: Insert nops to force costly
	   dependent insns into separate groups.  Insert exactly as many nops as needed to force
	   an insn to a new group, according to the estimated processor grouping.  number: Insert
	   nops to force costly dependent insns into separate groups.  Insert number nops to
	   force an insn to a new group.

       -mcall-sysv
	   On System V.4 and embedded PowerPC systems compile code using calling conventions that
	   adheres to the March 1995 draft of the System V Application Binary Interface, PowerPC
	   processor supplement.  This is the default unless you configured GCC using
	   powerpc-*-eabiaix.

       -mcall-sysv-eabi
	   Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
	   Specify both -mcall-sysv and -mno-eabi options.

       -mcall-solaris
	   On System V.4 and embedded PowerPC systems compile code for the Solaris operating
	   system.

       -mcall-linux
	   On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU
	   system.

       -mcall-gnu
	   On System V.4 and embedded PowerPC systems compile code for the Hurd-based GNU system.

       -mcall-netbsd
	   On System V.4 and embedded PowerPC systems compile code for the NetBSD operating
	   system.

       -maix-struct-return
	   Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
	   Return structures smaller than 8 bytes in registers (as specified by the SVR4 ABI).

       -mabi=abi-type
	   Extend the current ABI with a particular extension, or remove such extension.  Valid
	   values are altivec, no-altivec, spe, no-spe, ibmlongdouble, ieeelongdouble.

       -mabi=spe
	   Extend the current ABI with SPE ABI extensions.  This does not change the default ABI,
	   instead it adds the SPE ABI extensions to the current ABI.

       -mabi=no-spe
	   Disable Booke SPE ABI extensions for the current ABI.

       -mabi=ibmlongdouble
	   Change the current ABI to use IBM extended precision long double.  This is a PowerPC
	   32-bit SYSV ABI option.

       -mabi=ieeelongdouble
	   Change the current ABI to use IEEE extended precision long double.  This is a PowerPC
	   32-bit Linux ABI option.

       -mprototype
       -mno-prototype
	   On System V.4 and embedded PowerPC systems assume that all calls to variable argument
	   functions are properly prototyped.  Otherwise, the compiler must insert an instruction
	   before every non prototyped call to set or clear bit 6 of the condition code register
	   (CR) to indicate whether floating point values were passed in the floating point
	   registers in case the function takes a variable arguments.  With -mprototype, only
	   calls to prototyped variable argument functions will set or clear the bit.

       -msim
	   On embedded PowerPC systems, assume that the startup module is called sim-crt0.o and
	   that the standard C libraries are libsim.a and libc.a.  This is the default for
	   powerpc-*-eabisim.  configurations.

       -mmvme
	   On embedded PowerPC systems, assume that the startup module is called crt0.o and the
	   standard C libraries are libmvme.a and libc.a.

       -mads
	   On embedded PowerPC systems, assume that the startup module is called crt0.o and the
	   standard C libraries are libads.a and libc.a.

       -myellowknife
	   On embedded PowerPC systems, assume that the startup module is called crt0.o and the
	   standard C libraries are libyk.a and libc.a.

       -mvxworks
	   On System V.4 and embedded PowerPC systems, specify that you are compiling for a
	   VxWorks system.

       -mwindiss
	   Specify that you are compiling for the WindISS simulation environment.

       -memb
	   On embedded PowerPC systems, set the PPC_EMB bit in the ELF flags header to indicate
	   that eabi extended relocations are used.

       -meabi
       -mno-eabi
	   On System V.4 and embedded PowerPC systems do (do not) adhere to the Embedded
	   Applications Binary Interface (eabi) which is a set of modifications to the System V.4
	   specifications.  Selecting -meabi means that the stack is aligned to an 8 byte
	   boundary, a function "__eabi" is called to from "main" to set up the eabi environment,
	   and the -msdata option can use both "r2" and "r13" to point to two separate small data
	   areas.  Selecting -mno-eabi means that the stack is aligned to a 16 byte boundary, do
	   not call an initialization function from "main", and the -msdata option will only use
	   "r13" to point to a single small data area.	The -meabi option is on by default if you
	   configured GCC using one of the powerpc*-*-eabi* options.

       -msdata=eabi
	   On System V.4 and embedded PowerPC systems, put small initialized "const" global and
	   static data in the .sdata2 section, which is pointed to by register "r2".  Put small
	   initialized non-"const" global and static data in the .sdata section, which is pointed
	   to by register "r13".  Put small uninitialized global and static data in the .sbss
	   section, which is adjacent to the .sdata section.  The -msdata=eabi option is
	   incompatible with the -mrelocatable option.	The -msdata=eabi option also sets the
	   -memb option.

       -msdata=sysv
	   On System V.4 and embedded PowerPC systems, put small global and static data in the
	   .sdata section, which is pointed to by register "r13".  Put small uninitialized global
	   and static data in the .sbss section, which is adjacent to the .sdata section.  The
	   -msdata=sysv option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
	   On System V.4 and embedded PowerPC systems, if -meabi is used, compile code the same
	   as -msdata=eabi, otherwise compile code the same as -msdata=sysv.

       -msdata-data
	   On System V.4 and embedded PowerPC systems, put small global data in the .sdata
	   section.  Put small uninitialized global data in the .sbss section.	Do not use
	   register "r13" to address small data however.  This is the default behavior unless
	   other -msdata options are used.

       -msdata=none
       -mno-sdata
	   On embedded PowerPC systems, put all initialized global and static data in the .data
	   section, and all uninitialized data in the .bss section.

       -G num
	   On embedded PowerPC systems, put global and static items less than or equal to num
	   bytes into the small data or bss sections instead of the normal data or bss section.
	   By default, num is 8.  The -G num switch is also passed to the linker.  All modules
	   should be compiled with the same -G num value.

       -mregnames
       -mno-regnames
	   On System V.4 and embedded PowerPC systems do (do not) emit register names in the
	   assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
       -mlong-branch
       -mno-long-branch
	   By default assume that all calls are far away so that a longer more expensive calling
	   sequence is required.  This is required for calls further than 32 megabytes
	   (33,554,432 bytes) from the current location.  A short call will be generated if the
	   compiler knows the call cannot be that far away.  This setting can be overridden by
	   the "shortcall" function attribute, or by "#pragma longcall(0)".

	   Some linkers are capable of detecting out-of-range calls and generating glue code on
	   the fly.  On these systems, long calls are unnecessary and generate slower code.  As
	   of this writing, the AIX linker can do this, as can the GNU linker for PowerPC/64.  It
	   is planned to add this feature to the GNU linker for 32-bit PowerPC systems as well.

	   On Darwin/PPC systems, "#pragma longcall" will generate "jbsr callee, L42", plus a
	   "branch island" (glue code).  The two target addresses represent the callee and the
	   "branch island".  The Darwin/PPC linker will prefer the first address and generate a
	   "bl callee" if the PPC "bl" instruction will reach the callee directly; otherwise, the
	   linker will generate "bl L42" to call the "branch island".  The "branch island" is
	   appended to the body of the calling function; it computes the full 32-bit address of
	   the callee and jumps to it.

	   On Mach-O (Darwin) systems, -mlongcall directs the compiler emit to the glue for every
	   direct call, and the Darwin linker decides whether to use or discard it.
	   -mlong-branch is a synonym for -mlongcall.

	   In the future, we may cause GCC to ignore all longcall specifications when the linker
	   is known to generate glue.

       -pthread
	   Adds support for multithreading with the pthreads library.  This option sets flags for
	   both the preprocessor and linker.

       -mms-bitfields
	   Set the default structure layout to be compatible with the Microsoft compiler
	   standard. This is equivalent to adding an "ms_struct" attribute to each structure and
	   union tag definition. The default is mno-ms-bitfields.

       Options for Code Generation Conventions

       These machine-independent options control the interface conventions used in code
       generation.

       Most of them have both positive and negative forms; the negative form of -ffoo would be
       -fno-foo.  In the table below, only one of the forms is listed---the one which is not the
       default.  You can figure out the other form by either removing no- or adding it.

       -fbounds-check
	   For front-ends that support it, generate additional code to check that indices used to
	   access arrays are within the declared range.  This is currently only supported by the
	   Java and Fortran front-ends, where this option defaults to true and false
	   respectively.

       -fwrapv
	   This option instructs the compiler to assume that signed arithmetic overflow of
	   addition, subtraction and multiplication wraps around using twos-complement
	   representation.  This flag enables some optimizations and disables others.  This
	   option is enabled by default for the Java front-end, as required by the Java language
	   specification.

       -fexceptions
	   Enable exception handling.  Generates extra code needed to propagate exceptions.  For
	   some targets, this implies GCC will generate frame unwind information for all
	   functions, which can produce significant data size overhead, although it does not
	   affect execution.  If you do not specify this option, GCC will enable it by default
	   for languages like C++ which normally require exception handling, and disable it for
	   languages like C that do not normally require it.  However, you may need to enable
	   this option when compiling C code that needs to interoperate properly with exception
	   handlers written in C++.  You may also wish to disable this option if you are
	   compiling older C++ programs that don't use exception handling.

       -fnon-call-exceptions
	   Generate code that allows trapping instructions to throw exceptions.  Note that this
	   requires platform-specific runtime support that does not exist everywhere.  Moreover,
	   it only allows trapping instructions to throw exceptions, i.e. memory references or
	   floating point instructions.  It does not allow exceptions to be thrown from arbitrary
	   signal handlers such as "SIGALRM".

       -funwind-tables
	   Similar to -fexceptions, except that it will just generate any needed static data, but
	   will not affect the generated code in any other way.  You will normally not enable
	   this option; instead, a language processor that needs this handling would enable it on
	   your behalf.

       -fasynchronous-unwind-tables
	   Generate unwind table in dwarf2 format, if supported by target machine.  The table is
	   exact at each instruction boundary, so it can be used for stack unwinding from
	   asynchronous events (such as debugger or garbage collector).

       -fpcc-struct-return
	   Return "short" "struct" and "union" values in memory like longer ones, rather than in
	   registers.  This convention is less efficient, but it has the advantage of allowing
	   intercallability between GCC-compiled files and files compiled with other compilers,
	   particularly the Portable C Compiler (pcc).

	   The precise convention for returning structures in memory depends on the target
	   configuration macros.

	   Short structures and unions are those whose size and alignment match that of some
	   integer type.

	   Warning: code compiled with the -fpcc-struct-return switch is not binary compatible
	   with code compiled with the -freg-struct-return switch.  Use it to conform to a non-
	   default application binary interface.

       -freg-struct-return
	   Return "struct" and "union" values in registers when possible.  This is more efficient
	   for small structures than -fpcc-struct-return.

	   If you specify neither -fpcc-struct-return nor -freg-struct-return, GCC defaults to
	   whichever convention is standard for the target.  If there is no standard convention,
	   GCC defaults to -fpcc-struct-return, except on targets where GCC is the principal
	   compiler.  In those cases, we can choose the standard, and we chose the more efficient
	   register return alternative.

	   Warning: code compiled with the -freg-struct-return switch is not binary compatible
	   with code compiled with the -fpcc-struct-return switch.  Use it to conform to a non-
	   default application binary interface.

       -fshort-enums
	   Allocate to an "enum" type only as many bytes as it needs for the declared range of
	   possible values.  Specifically, the "enum" type will be equivalent to the smallest
	   integer type which has enough room.

	   Warning: the -fshort-enums switch causes GCC to generate code that is not binary
	   compatible with code generated without that switch.	Use it to conform to a non-
	   default application binary interface.

       -fshort-double
	   Use the same size for "double" as for "float".

	   Warning: the -fshort-double switch causes GCC to generate code that is not binary
	   compatible with code generated without that switch.	Use it to conform to a non-
	   default application binary interface.

       -fshort-wchar
	   Override the underlying type for wchar_t to be short unsigned int instead of the
	   default for the target.  This option is useful for building programs to run under
	   WINE.

	   Warning: the -fshort-wchar switch causes GCC to generate code that is not binary
	   compatible with code generated without that switch.	Use it to conform to a non-
	   default application binary interface.

       -fno-common
	   In C, allocate even uninitialized global variables in the data section of the object
	   file, rather than generating them as common blocks.	This has the effect that if the
	   same variable is declared (without "extern") in two different compilations, you will
	   get an error when you link them.  The only reason this might be useful is if you wish
	   to verify that the program will work on other systems which always work this way.

       -fno-ident
	   Ignore the #ident directive.

       -finhibit-size-directive
	   Don't output a ".size" assembler directive, or anything else that would cause trouble
	   if the function is split in the middle, and the two halves are placed at locations far
	   apart in memory.  This option is used when compiling crtstuff.c; you should not need
	   to use it for anything else.

       -fverbose-asm
	   Put extra commentary information in the generated assembly code to make it more
	   readable.  This option is generally only of use to those who actually need to read the
	   generated assembly code (perhaps while debugging the compiler itself).

	   -fno-verbose-asm, the default, causes the extra information to be omitted and is
	   useful when comparing two assembler files.

       -fpic
	   Generate position-independent code (PIC) suitable for use in a shared library, if
	   supported for the target machine.  Such code accesses all constant addresses through a
	   global offset table (GOT).  The dynamic loader resolves the GOT entries when the
	   program starts (the dynamic loader is not part of GCC; it is part of the operating
	   system).  If the GOT size for the linked executable exceeds a machine-specific maximum
	   size, you get an error message from the linker indicating that -fpic does not work; in
	   that case, recompile with -fPIC instead.  (These maximums are 8k on the SPARC and 32k
	   on the m68k and RS/6000.  The 386 has no such limit.)

	   Position-independent code requires special support, and therefore works only on
	   certain machines.  For the 386, GCC supports PIC for System V but not for the Sun
	   386i.  Code generated for the IBM RS/6000 is always position-independent.

	   When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1.

       -fPIC
	   If supported for the target machine, emit position-independent code, suitable for
	   dynamic linking and avoiding any limit on the size of the global offset table.  This
	   option makes a difference on the m68k, PowerPC and SPARC.

	   Position-independent code requires special support, and therefore works only on
	   certain machines.

	   When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2.

	   -fPIC is the default on Darwin and Mac OS X.

       -fpie
       -fPIE
	   These options are similar to -fpic and -fPIC, but generated position independent code
	   can be only linked into executables.  Usually these options are used when -pie GCC
	   option will be used during linking.

       -fno-jump-tables
	   Do not use jump tables for switch statements even where it would be more efficient
	   than other code generation strategies.  This option is of use in conjunction with
	   -fpic or -fPIC for building code which forms part of a dynamic linker and cannot
	   reference the address of a jump table.  On some targets, jump tables do not require a
	   GOT and this option is not needed.

       -ffixed-reg
	   Treat the register named reg as a fixed register; generated code should never refer to
	   it (except perhaps as a stack pointer, frame pointer or in some other fixed role).

	   reg must be the name of a register.	The register names accepted are machine-specific
	   and are defined in the "REGISTER_NAMES" macro in the machine description macro file.

	   This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-used-reg
	   Treat the register named reg as an allocable register that is clobbered by function
	   calls.  It may be allocated for temporaries or variables that do not live across a
	   call.  Functions compiled this way will not save and restore the register reg.

	   It is an error to used this flag with the frame pointer or stack pointer.  Use of this
	   flag for other registers that have fixed pervasive roles in the machine's execution
	   model will produce disastrous results.

	   This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-saved-reg
	   Treat the register named reg as an allocable register saved by functions.  It may be
	   allocated even for temporaries or variables that live across a call.  Functions
	   compiled this way will save and restore the register reg if they use it.

	   It is an error to used this flag with the frame pointer or stack pointer.  Use of this
	   flag for other registers that have fixed pervasive roles in the machine's execution
	   model will produce disastrous results.

	   A different sort of disaster will result from the use of this flag for a register in
	   which function values may be returned.

	   This flag does not have a negative form, because it specifies a three-way choice.

       -fpack-struct[=n]
	   Without a value specified, pack all structure members together without holes.  When a
	   value is specified (which must be a small power of two), pack structure members
	   according to this value, representing the maximum alignment (that is, objects with
	   default alignment requirements larger than this will be output potentially unaligned
	   at the next fitting location.

	   Warning: the -fpack-struct switch causes GCC to generate code that is not binary
	   compatible with code generated without that switch.	Additionally, it makes the code
	   suboptimal.	Use it to conform to a non-default application binary interface.

       -finstrument-functions
	   Generate instrumentation calls for entry and exit to functions.  Just after function
	   entry and just before function exit, the following profiling functions will be called
	   with the address of the current function and its call site.	(On some platforms,
	   "__builtin_return_address" does not work beyond the current function, so the call site
	   information may not be available to the profiling functions otherwise.)

		   void __cyg_profile_func_enter (void *this_fn,
						  void *call_site);
		   void __cyg_profile_func_exit  (void *this_fn,
						  void *call_site);

	   The first argument is the address of the start of the current function, which may be
	   looked up exactly in the symbol table.

	   This instrumentation is also done for functions expanded inline in other functions.
	   The profiling calls will indicate where, conceptually, the inline function is entered
	   and exited.	This means that addressable versions of such functions must be available.
	   If all your uses of a function are expanded inline, this may mean an additional
	   expansion of code size.  If you use extern inline in your C code, an addressable
	   version of such functions must be provided.	(This is normally the case anyways, but
	   if you get lucky and the optimizer always expands the functions inline, you might have
	   gotten away without providing static copies.)

	   A function may be given the attribute "no_instrument_function", in which case this
	   instrumentation will not be done.  This can be used, for example, for the profiling
	   functions listed above, high-priority interrupt routines, and any functions from which
	   the profiling functions cannot safely be called (perhaps signal handlers, if the
	   profiling routines generate output or allocate memory).

       -fstack-check
	   Generate code to verify that you do not go beyond the boundary of the stack.  You
	   should specify this flag if you are running in an environment with multiple threads,
	   but only rarely need to specify it in a single-threaded environment since stack
	   overflow is automatically detected on nearly all systems if there is only one stack.

	   Note that this switch does not actually cause checking to be done; the operating
	   system must do that.  The switch causes generation of code to ensure that the
	   operating system sees the stack being extended.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
	   Generate code to ensure that the stack does not grow beyond a certain value, either
	   the value of a register or the address of a symbol.	If the stack would grow beyond
	   the value, a signal is raised.  For most targets, the signal is raised before the
	   stack overruns the boundary, so it is possible to catch the signal without taking
	   special precautions.

	   For instance, if the stack starts at absolute address 0x80000000 and grows downwards,
	   you can use the flags -fstack-limit-symbol=__stack_limit and
	   -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of 128KB.  Note that
	   this may only work with the GNU linker.

       -fargument-alias
       -fargument-noalias
       -fargument-noalias-global
       -fargument-noalias-anything
	   Specify the possible relationships among parameters and between parameters and global
	   data.

	   -fargument-alias specifies that arguments (parameters) may alias each other and may
	   alias global storage.-fargument-noalias specifies that arguments do not alias each
	   other, but may alias global storage.-fargument-noalias-global specifies that arguments
	   do not alias each other and do not alias global storage.  -fargument-noalias-anything
	   specifies that arguments do not alias any other storage.

	   Each language will automatically use whatever option is required by the language
	   standard.  You should not need to use these options yourself.

       -fleading-underscore
	   This option and its counterpart, -fno-leading-underscore, forcibly change the way C
	   symbols are represented in the object file.	One use is to help link with legacy
	   assembly code.

	   Warning: the -fleading-underscore switch causes GCC to generate code that is not
	   binary compatible with code generated without that switch.  Use it to conform to a
	   non-default application binary interface.  Not all targets provide complete support
	   for this switch.

       -ftls-model=model
	   Alter the thread-local storage model to be used.  The model argument should be one of
	   "global-dynamic", "local-dynamic", "initial-exec" or "local-exec".

	   The default without -fpic is "initial-exec"; with -fpic the default is
	   "global-dynamic".

       -fvisibility=default|internal|hidden|protected
	   Set the default ELF image symbol visibility to the specified option---all symbols will
	   be marked with this unless overridden within the code.  Using this feature can very
	   substantially improve linking and load times of shared object libraries, produce more
	   optimized code, provide near-perfect API export and prevent symbol clashes.	It is
	   strongly recommended that you use this in any shared objects you distribute.

	   Despite the nomenclature, "default" always means public ie; available to be linked
	   against from outside the shared object.  "protected" and "internal" are pretty useless
	   in real-world usage so the only other commonly used option will be "hidden".  The
	   default if -fvisibility isn't specified is "default", i.e., make every symbol
	   public---this causes the same behavior as previous versions of GCC.

	   A good explanation of the benefits offered by ensuring ELF symbols have the correct
	   visibility is given by "How To Write Shared Libraries" by Ulrich Drepper (which can be
	   found at <http://people.redhat.com/~drepper/>)---however a superior solution made
	   possible by this option to marking things hidden when the default is public is to make
	   the default hidden and mark things public.  This is the norm with DLL's on Windows and
	   with -fvisibility=hidden and "__attribute__ ((visibility("default")))" instead of
	   "__declspec(dllexport)" you get almost identical semantics with identical syntax.
	   This is a great boon to those working with cross-platform projects.

	   For those adding visibility support to existing code, you may find #pragma GCC
	   visibility of use.  This works by you enclosing the declarations you wish to set
	   visibility for with (for example) #pragma GCC visibility push(hidden) and #pragma GCC
	   visibility pop.  Bear in mind that symbol visibility should be viewed as part of the
	   API interface contract and thus all new code should always specify visibility when it
	   is not the default ie; declarations only for use within the local DSO should always be
	   marked explicitly as hidden as so to avoid PLT indirection overheads---making this
	   abundantly clear also aids readability and self-documentation of the code.  Note that
	   due to ISO C++ specification requirements, operator new and operator delete must
	   always be of default visibility.

	   Be aware that headers from outside your project, in particular system headers and
	   headers from any other library you use, may not be expecting to be compiled with
	   visibility other than the default.  You may need to explicitly say #pragma GCC
	   visibility push(default) before including any such headers.

	   extern declarations are not affected by -fvisibility, so a lot of code can be
	   recompiled with -fvisibility=hidden with no modifications.  However, this means that
	   calls to extern functions with no explicit visibility will use the PLT, so it is more
	   effective to use __attribute ((visibility)) and/or #pragma GCC visibility to tell the
	   compiler which extern declarations should be treated as hidden.

	   Note that -fvisibility does affect C++ vague linkage entities. This means that, for
	   instance, an exception class that will be thrown between DSOs must be explicitly
	   marked with default visibility so that the type_info nodes will be unified between the
	   DSOs.

	   An overview of these techniques, their benefits and how to use them is at
	   <http://gcc.gnu.org/wiki/Visibility>.

ENVIRONMENT
       This section describes several environment variables that affect how GCC operates.  Some
       of them work by specifying directories or prefixes to use when searching for various kinds
       of files.  Some are used to specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as -B, -I and -L.
       These take precedence over places specified using environment variables, which in turn
       take precedence over those specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
	   These environment variables control the way that GCC uses localization information
	   that allow GCC to work with different national conventions.	GCC inspects the locale
	   categories LC_CTYPE and LC_MESSAGES if it has been configured to do so.  These locale
	   categories can be set to any value supported by your installation.  A typical value is
	   en_GB.UTF-8 for English in the United Kingdom encoded in UTF-8.

	   The LC_CTYPE environment variable specifies character classification.  GCC uses it to
	   determine the character boundaries in a string; this is needed for some multibyte
	   encodings that contain quote and escape characters that would otherwise be interpreted
	   as a string end or escape.

	   The LC_MESSAGES environment variable specifies the language to use in diagnostic
	   messages.

	   If the LC_ALL environment variable is set, it overrides the value of LC_CTYPE and
	   LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES default to the value of the LANG
	   environment variable.  If none of these variables are set, GCC defaults to traditional
	   C English behavior.

       TMPDIR
	   If TMPDIR is set, it specifies the directory to use for temporary files.  GCC uses
	   temporary files to hold the output of one stage of compilation which is to be used as
	   input to the next stage: for example, the output of the preprocessor, which is the
	   input to the compiler proper.

       GCC_EXEC_PREFIX
	   If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of the
	   subprograms executed by the compiler.  No slash is added when this prefix is combined
	   with the name of a subprogram, but you can specify a prefix that ends with a slash if
	   you wish.

	   If GCC_EXEC_PREFIX is not set, GCC will attempt to figure out an appropriate prefix to
	   use based on the pathname it was invoked with.

	   If GCC cannot find the subprogram using the specified prefix, it tries looking in the
	   usual places for the subprogram.

	   The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the value of
	   "prefix" when you ran the configure script.

	   Other prefixes specified with -B take precedence over this prefix.

	   This prefix is also used for finding files such as crt0.o that are used for linking.

	   In addition, the prefix is used in an unusual way in finding the directories to search
	   for header files.  For each of the standard directories whose name normally begins
	   with /usr/local/lib/gcc (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
	   replacing that beginning with the specified prefix to produce an alternate directory
	   name.  Thus, with -Bfoo/, GCC will search foo/bar where it would normally search
	   /usr/local/lib/bar.	These alternate directories are searched first; the standard
	   directories come next.

       COMPILER_PATH
	   The value of COMPILER_PATH is a colon-separated list of directories, much like PATH.
	   GCC tries the directories thus specified when searching for subprograms, if it can't
	   find the subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
	   The value of LIBRARY_PATH is a colon-separated list of directories, much like PATH.
	   When configured as a native compiler, GCC tries the directories thus specified when
	   searching for special linker files, if it can't find them using GCC_EXEC_PREFIX.
	   Linking using GCC also uses these directories when searching for ordinary libraries
	   for the -l option (but directories specified with -L come first).

       LANG
	   This variable is used to pass locale information to the compiler.  One way in which
	   this information is used is to determine the character set to be used when character
	   literals, string literals and comments are parsed in C and C++.  When the compiler is
	   configured to allow multibyte characters, the following values for LANG are
	   recognized:

	   C-JIS
	       Recognize JIS characters.

	   C-SJIS
	       Recognize SJIS characters.

	   C-EUCJP
	       Recognize EUCJP characters.

	   If LANG is not defined, or if it has some other value, then the compiler will use
	   mblen and mbtowc as defined by the default locale to recognize and translate multibyte
	   characters.

       MACOSX_DEPLOYMENT_TARGET
       IPHONEOS_DEPLOYMENT_TARGET
	   These variables are used to set the target OS version, as described for command-line
	   options -mmacosx-version-min and -miphoneos-version-min.  Only one OS version can be
	   specified per architecture, with MACOSX_DEPLOYMENT_TARGET taking precedence on non-ARM
	   targets and IPHONEOS_DEPLOYMENT_TARGET taking precedence on ARM targets.

	   If either command-line option -mmacosx-version-min or -miphoneos-version-min is
	   specified, both of these environment variables are ignored.

       Some additional environments variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
	   Each variable's value is a list of directories separated by a special character, much
	   like PATH, in which to look for header files.  The special character,
	   "PATH_SEPARATOR", is target-dependent and determined at GCC build time.  For Microsoft
	   Windows-based targets it is a semicolon, and for almost all other targets it is a
	   colon.

	   CPATH specifies a list of directories to be searched as if specified with -I, but
	   after any paths given with -I options on the command line.  This environment variable
	   is used regardless of which language is being preprocessed.

	   The remaining environment variables apply only when preprocessing the particular
	   language indicated.	Each specifies a list of directories to be searched as if
	   specified with -isystem, but after any paths given with -isystem options on the
	   command line.

	   In all these variables, an empty element instructs the compiler to search its current
	   working directory.  Empty elements can appear at the beginning or end of a path.  For
	   instance, if the value of CPATH is ":/special/include", that has the same effect as
	   -I. -I/special/include.

       DEPENDENCIES_OUTPUT
	   If this variable is set, its value specifies how to output dependencies for Make based
	   on the non-system header files processed by the compiler.  System header files are
	   ignored in the dependency output.

	   The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules
	   are written to that file, guessing the target name from the source file name.  Or the
	   value can have the form file target, in which case the rules are written to file file
	   using target as the target name.

	   In other words, this environment variable is equivalent to combining the options -MM
	   and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
	   This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system
	   header files are not ignored, so it implies -M rather than -MM.  However, the
	   dependence on the main input file is omitted.

BUGS
       To report bugs to Apple, see <http://developer.apple.com/bugreporter>.

FOOTNOTES
       1.  On some systems, gcc -shared needs to build supplementary stub code for constructors
	   to work.  On multi-libbed systems, gcc -shared must select the correct support
	   libraries to link against.  Failing to supply the correct flags may lead to subtle
	   defects.  Supplying them in cases where they are not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1),
       sdb(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR
       See the Info entry for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
       contributors to GCC.

COPYRIGHT
       Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
       2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of
       the GNU Free Documentation License, Version 1.2 or any later version published by the Free
       Software Foundation; with the Invariant Sections being "GNU General Public License" and
       "Funding Free Software", the Front-Cover texts being (a) (see below), and with the Back-
       Cover Texts being (b) (see below).  A copy of the license is included in the gfdl(7) man
       page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover Text is:

	    You have freedom to copy and modify this GNU Manual, like GNU
	    software.  Copies published by the Free Software Foundation raise
	    funds for GNU development.

gcc-4.2.1				    2009-09-18					   GCC(1)
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