Unix/Linux Go Back    


RedHat 9 (Linux i386) - man page for gcc (redhat section 1)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


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] infile...

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

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 pre-
       processor 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 lan-
       guage, you can use that option with all supported languages.

       The gcc program accepts options and file names as operands.  Many options have multi-let-
       ter names; therefore multiple single-letter options may not be grouped: -dr is very dif-
       ferent 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, -fforce-mem,
       -fstrength-reduce, -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	-pipe  -pass-exit-codes  -x language -v  -###  --help  --tar-
	   get-help  --version

       C Language Options
	   -ansi  -std=standard  -aux-info filename -fno-asm  -fno-builtin -fno-builtin-function
	   -fhosted  -ffreestanding -trigraphs	-no-integrated-cpp  -traditional  -tradi-
	   tional-cpp -fallow-single-precision	-fcond-mismatch -fsigned-bitfields  -fsigned-char
	   -funsigned-bitfields  -funsigned-char -fwritable-strings

       C++ Language Options
	   -fno-access-control	-fcheck-new  -fconserve-space -fno-const-strings  -fdol-
	   lars-in-identifiers -fno-elide-constructors -fno-enforce-eh-specs  -fexternal-tem-
	   plates -falt-external-templates -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  -fper-
	   missive -frepo  -fno-rtti  -fstats  -ftemplate-depth-n -fuse-cxa-atexit  -fvtable-gc
	   -fno-weak  -nostdinc++ -fno-default-inline -Wabi -Wctor-dtor-privacy -Wnon-vir-
	   tual-dtor  -Wreorder -Weffc++  -Wno-deprecated -Wno-non-template-friend
	   -Wold-style-cast -Woverloaded-virtual  -Wno-pmf-conversions -Wsign-promo  -Wsynth

       Objective-C Language Options
	   -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime  -gen-decls -Wno-pro-
	   tocol  -Wselector

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

       Warning Options
	   -fsyntax-only  -pedantic  -pedantic-errors -w  -W  -Wall -Waggregate-return
	   -Wcast-align  -Wcast-qual  -Wchar-subscripts  -Wcomment -Wconversion  -Wno-depre-
	   cated-declarations -Wdisabled-optimization  -Wdiv-by-zero  -Werror -Wfloat-equal
	   -Wformat  -Wformat=2 -Wformat-nonliteral  -Wformat-security -Wimplicit  -Wimplicit-int
	   -Wimplicit-function-declaration -Werror-implicit-function-declaration -Wimport  -Win-
	   line -Wlarger-than-len  -Wlong-long -Wmain  -Wmissing-braces -Wmissing-for-
	   mat-attribute  -Wmissing-noreturn -Wmultichar  -Wno-format-extra-args  -Wno-format-y2k
	   -Wno-import	-Wpacked  -Wpadded -Wparentheses  -Wpointer-arith  -Wredundant-decls
	   -Wreturn-type  -Wsequence-point  -Wshadow -Wsign-compare  -Wswitch  -Wsystem-headers
	   -Wtrigraphs	-Wundef  -Wuninitialized -Wunknown-pragmas  -Wunreachable-code -Wunused
	   -Wunused-function  -Wunused-label  -Wunused-parameter -Wunused-value  -Wunused-vari-
	   able  -Wwrite-strings

       C-only Warning Options
	   -Wbad-function-cast	-Wmissing-declarations -Wmissing-prototypes  -Wnested-externs
	   -Wstrict-prototypes	-Wtraditional

       Debugging Options
	   -dletters  -dumpspecs  -dumpmachine	-dumpversion -fdump-unnumbered -fdump-transla-
	   tion-unit[-n] -fdump-class-hierarchy[-n] -fdump-tree-original[-n] -fdump-tree-opti-
	   mized[-n] -fdump-tree-inlined[-n] -fmem-report  -fpretend-float -fprofile-arcs
	   -fsched-verbose=n -ftest-coverage  -ftime-report -g	-glevel  -gcoff  -gdwarf
	   -gdwarf-1  -gdwarf-1+  -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 -fbounds-check
	   -fbranch-probabilities  -fcaller-saves -fcprop-registers -fcse-follow-jumps
	   -fcse-skip-blocks  -fdata-sections -fdelayed-branch	-fdelete-null-pointer-checks
	   -fexpensive-optimizations  -ffast-math  -ffloat-store -fforce-addr  -fforce-mem
	   -ffunction-sections -fgcse  -fgcse-lm  -fgcse-sm -finline-functions	-finline-limit=n
	   -fkeep-inline-functions -fkeep-static-consts  -fmerge-constants  -fmerge-all-constants
	   -fmove-all-movables	-fno-branch-count-reg -fno-default-inline  -fno-defer-pop
	   -fno-function-cse  -fno-guess-branch-probability -fno-inline  -fno-math-errno
	   -fno-peephole  -fno-peephole2 -funsafe-math-optimizations -fno-trapping-math
	   -fomit-frame-pointer  -foptimize-register-move -foptimize-sibling-calls
	   -fprefetch-loop-arrays -freduce-all-givs -fregmove  -frename-registers -fre-
	   run-cse-after-loop  -frerun-loop-opt -fschedule-insns  -fschedule-insns2
	   -fno-sched-interblock  -fno-sched-spec -fsched-spec-load  -fsched-spec-load-dangerous
	   -fsingle-precision-constant	-fssa -fssa-ccp -fssa-dce -fstrength-reduce
	   -fstrict-aliasing  -fthread-jumps -ftrapv -funroll-all-loops  -funroll-loops --param
	   name=value -O  -O0  -O1  -O2  -O3  -Os

       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 -iwith-
	   prefixbefore dir  -isystem dir -M  -MM  -MF	-MG  -MP  -MQ  -MT  -nostdinc  -P  -remap
	   -trigraphs  -undef  -Umacro	-Wp,option

       Assembler Option
	   -Wa,option

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

       Directory Options
	   -Bprefix  -Idir  -I-  -Ldir	-specs=file

       Target Options
	   -b machine  -V version

       Machine Dependent Options
	   M680x0 Options

	   -m68000  -m68020  -m68020-40  -m68020-60  -m68030  -m68040 -m68060  -mcpu32	-m5200
	   -m68881  -mbitfield	-mc68000  -mc68020 -mfpa  -mnobitfield	-mrtd  -mshort
	   -msoft-float  -mpcrel -malign-int  -mstrict-align

	   M68hc1x Options

	   -m6811  -m6812  -m68hc11  -m68hc12 -mauto-incdec  -mshort  -msoft-reg-count=count

	   VAX Options

	   -mg	-mgnu  -munix

	   SPARC Options

	   -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -m32  -m64 -mapp-regs  -mbro-
	   ken-saverestore  -mcypress -mfaster-structs	-mflat -mfpu  -mhard-float
	   -mhard-quad-float -mimpure-text  -mlive-g0  -mno-app-regs -mno-faster-structs
	   -mno-flat  -mno-fpu -mno-impure-text  -mno-stack-bias  -mno-unaligned-doubles
	   -msoft-float  -msoft-quad-float  -msparclite  -mstack-bias -msupersparc
	   -munaligned-doubles	-mv8

	   Convex Options

	   -mc1  -mc2  -mc32  -mc34  -mc38 -margcount  -mnoargcount -mlong32  -mlong64
	   -mvolatile-cache  -mvolatile-nocache

	   AMD29K Options

	   -m29000  -m29050  -mbw  -mnbw  -mdw	-mndw -mlarge  -mnormal  -msmall -mkernel-regis-
	   ters  -mno-reuse-arg-regs -mno-stack-check  -mno-storem-bug -mreuse-arg-regs
	   -msoft-float  -mstack-check -mstorem-bug  -muser-registers

	   ARM Options

	   -mapcs-frame  -mno-apcs-frame -mapcs-26  -mapcs-32 -mapcs-stack-check
	   -mno-apcs-stack-check -mapcs-float  -mno-apcs-float -mapcs-reentrant  -mno-apcs-reen-
	   trant -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian  -mwords-lit-
	   tle-endian -malignment-traps  -mno-alignment-traps -msoft-float  -mhard-float  -mfpe
	   -mthumb-interwork  -mno-thumb-interwork -mcpu=name  -march=name  -mfpe=name -mstruc-
	   ture-size-boundary=n -mbsd -mxopen  -mno-symrename -mabort-on-noreturn -mlong-calls
	   -mno-long-calls -msingle-pic-base  -mno-single-pic-base -mpic-register=reg
	   -mnop-fun-dllimport -mpoke-function-name -mthumb  -marm -mtpcs-frame
	   -mtpcs-leaf-frame -mcaller-super-interworking  -mcallee-super-interworking

	   MN10200 Options

	   -mrelax

	   MN10300 Options

	   -mmult-bug  -mno-mult-bug -mam33  -mno-am33 -mno-crt0  -mrelax

	   M32R/D Options

	   -m32rx -m32r -mcode-model=model-type  -msdata=sdata-type -G num

	   M88K Options

	   -m88000  -m88100  -m88110  -mbig-pic -mcheck-zero-division  -mhandle-large-shift
	   -midentify-revision	-mno-check-zero-division -mno-ocs-debug-info
	   -mno-ocs-frame-position -mno-optimize-arg-area  -mno-serialize-volatile -mno-under-
	   scores  -mocs-debug-info -mocs-frame-position  -moptimize-arg-area -mserial-
	   ize-volatile  -mshort-data-num  -msvr3 -msvr4  -mtrap-large-shift  -muse-div-instruc-
	   tion -mversion-03.00  -mwarn-passed-structs

	   RS/6000 and PowerPC Options

	   -mcpu=cpu-type -mtune=cpu-type -mpower  -mno-power  -mpower2  -mno-power2 -mpowerpc
	   -mpowerpc64	-mno-powerpc -maltivec -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt
	   -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mnew-mnemonics  -mold-mnemonics -mfull-toc
	   -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64	-m32  -mxl-call  -mno-xl-call
	   -mpe -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
	   -mcall-aix -mcall-sysv -mcall-netbsd -maix-struct-return -msvr4-struct-return
	   -mabi=altivec -mabi=no-altivec -mprototype  -mno-prototype -msim  -mmvme  -mads
	   -myellowknife  -memb -msdata -msdata=opt  -mvxworks -G num -pthread

	   RT Options

	   -mcall-lib-mul  -mfp-arg-in-fpregs  -mfp-arg-in-gregs -mfull-fp-blocks
	   -mhc-struct-return  -min-line-mul -mminimum-fp-blocks  -mnohc-struct-return

	   MIPS Options

	   -mabicalls -march=cpu-type -mtune=cpu=type -mcpu=cpu-type -membedded-data
	   -muninit-const-in-rodata -membedded-pic  -mfp32  -mfp64  -mfused-madd  -mno-fused-madd
	   -mgas  -mgp32  -mgp64 -mgpopt  -mhalf-pic  -mhard-float  -mint64  -mips1 -mips2
	   -mips3  -mips4  -mlong64  -mlong32  -mlong-calls  -mmemcpy -mmips-as  -mmips-tfile
	   -mno-abicalls -mno-embedded-data  -mno-uninit-const-in-rodata -mno-embedded-pic
	   -mno-gpopt  -mno-long-calls -mno-memcpy  -mno-mips-tfile  -mno-rnames  -mno-stats
	   -mrnames  -msoft-float -m4650  -msingle-float  -mmad -mstats  -EL  -EB  -G num  -nocpp
	   -mabi=32  -mabi=n32	-mabi=64  -mabi=eabi -mfix7000	-mno-crt0 -mflush-func=func
	   -mno-flush-func

	   i386 and x86-64 Options

	   -mcpu=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-dou-
	   ble -mpreferred-stack-boundary=num -mmmx  -msse -msse2 -m3dnow -mthreads
	   -mno-align-stringops  -minline-all-stringops -mpush-args  -maccumulate-outgoing-args
	   -m128bit-long-double -m96bit-long-double  -mregparm=num  -momit-leaf-frame-pointer
	   -mno-red-zone -mcmodel=code-model -m32 -m64

	   HPPA Options

	   -march=architecture-type -mbig-switch  -mdisable-fpregs  -mdisable-indexing
	   -mfast-indirect-calls  -mgas  -mjump-in-delay -mlong-load-store  -mno-big-switch
	   -mno-disable-fpregs -mno-disable-indexing  -mno-fast-indirect-calls	-mno-gas
	   -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime  -mno-soft-float
	   -mno-space-regs  -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0
	   -mportable-runtime -mschedule=cpu-type  -mspace-regs

	   Intel 960 Options

	   -mcpu-type  -masm-compat  -mclean-linkage -mcode-align  -mcomplex-addr  -mleaf-proce-
	   dures -mic-compat  -mic2.0-compat  -mic3.0-compat -mintel-asm  -mno-clean-linkage
	   -mno-code-align -mno-complex-addr  -mno-leaf-procedures -mno-old-align
	   -mno-strict-align  -mno-tail-call -mnumerics  -mold-align  -msoft-float
	   -mstrict-align -mtail-call

	   DEC Alpha Options

	   -mno-fp-regs  -msoft-float  -malpha-as  -mgas -mieee  -mieee-with-inexact  -mieee-con-
	   formant -mfp-trap-mode=mode	-mfp-rounding-mode=mode -mtrap-precision=mode
	   -mbuild-constants -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
	   -mfloat-vax	-mfloat-ieee -mexplicit-relocs	-msmall-data  -mlarge-data -mmem-
	   ory-latency=time

	   DEC Alpha/VMS Options

	   -mvms-return-codes

	   Clipper Options

	   -mc300  -mc400

	   H8/300 Options

	   -mrelax  -mh  -ms  -mint32  -malign-300

	   SH Options

	   -m1	-m2  -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single  -m4 -m5-64media
	   -m5-64media-nofpu -m5-32media -m5-32media-nofpu -m5-compact -m5-compact-nofpu -mb  -ml
	   -mdalign  -mrelax -mbigtable  -mfmovd  -mhitachi  -mnomacsave -mieee  -misize  -mpad-
	   struct  -mspace -mprefergot	-musermode

	   System V Options

	   -Qy	-Qn  -YP,paths	-Ym,dir

	   ARC Options

	   -EB	-EL -mmangle-cpu  -mcpu=cpu  -mtext=text-section -mdata=data-section  -mro-
	   data=readonly-data-section

	   TMS320C3x/C4x Options

	   -mcpu=cpu  -mbig  -msmall  -mregparm  -mmemparm -mfast-fix  -mmpyi  -mbk  -mti
	   -mdp-isr-reload -mrpts=count  -mrptb  -mdb  -mloop-unsigned -mparallel-insns  -mparal-
	   lel-mpy  -mpreserve-float

	   V850 Options

	   -mlong-calls  -mno-long-calls  -mep	-mno-ep -mprolog-function  -mno-prolog-function
	   -mspace -mtda=n  -msda=n  -mzda=n -mv850  -mbig-switch

	   NS32K Options

	   -m32032  -m32332  -m32532  -m32081  -m32381 -mmult-add  -mnomult-add  -msoft-float
	   -mrtd  -mnortd -mregparam  -mnoregparam  -msb  -mnosb -mbitfield  -mnobitfield
	   -mhimem  -mnohimem

	   AVR Options

	   -mmcu=mcu  -msize  -minit-stack=n  -mno-interrupts -mcall-prologues	-mno-tablejump
	   -mtiny-stack

	   MCore Options

	   -mhardlit  -mno-hardlit  -mdiv  -mno-div  -mrelax-immediates -mno-relax-immediates
	   -mwide-bitfields  -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions  -mcall-
	   graph-data -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes  -mno-lsim -mlit-
	   tle-endian  -mbig-endian  -m210  -m340  -mstack-increment

	   MMIX Options

	   -mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu -mabi=mmixware -mzero-extend
	   -mknuthdiv -mtoplevel-symbols -melf -mbranch-predict -mno-branch-predict
	   -mbase-addresses -mno-base-addresses

	   IA-64 Options

	   -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld  -mno-pic -mvolatile-asm-stop
	   -mb-step  -mregister-names  -mno-sdata -mconstant-gp  -mauto-pic  -min-
	   line-divide-min-latency -minline-divide-max-throughput  -mno-dwarf2-asm
	   -mfixed-range=register-range

	   D30V Options

	   -mextmem  -mextmemory  -monchip  -mno-asm-optimize -masm-optimize -mbranch-cost=n
	   -mcond-exec=n

	   S/390 and zSeries Options

	   -mhard-float  -msoft-float  -mbackchain  -mno-backchain -msmall-exec  -mno-small-exec
	   -mmvcle -mno-mvcle -m64 -m31 -mdebug -mno-debug

	   CRIS Options

	   -mcpu=cpu -march=cpu -mtune=cpu -mmax-stack-frame=n -melinux-stacksize=n -metrax4
	   -metrax100 -mpdebug -mcc-init -mno-side-effects -mstack-align -mdata-align
	   -mconst-align -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt -melf
	   -maout -melinux -mlinux -sim -sim2

	   PDP-11 Options

	   -mfpu  -msoft-float	-mac0  -mno-ac0  -m40  -m45  -m10 -mbcopy  -mbcopy-builtin
	   -mint32  -mno-int16 -mint16	-mno-int32  -mfloat32  -mno-float64 -mfloat64
	   -mno-float32  -mabshi  -mno-abshi -mbranch-expensive  -mbranch-cheap -msplit
	   -mno-split  -munix-asm  -mdec-asm

	   Xstormy16 Options

	   -msim

	   Xtensa Options

	   -mbig-endian -mlittle-endian -mdensity -mno-density -mmac16 -mno-mac16 -mmul16
	   -mno-mul16 -mmul32 -mno-mul32 -mnsa -mno-nsa -mminmax -mno-minmax -msext -mno-sext
	   -mbooleans -mno-booleans -mhard-float -msoft-float -mfused-madd -mno-fused-madd -mse-
	   rialize-volatile -mno-serialize-volatile -mtext-section-literals -mno-text-sec-
	   tion-literals -mtarget-align -mno-target-align -mlongcalls -mno-longcalls

       Code Generation Options
	   -fcall-saved-reg  -fcall-used-reg -ffixed-reg -fexceptions -fnon-call-exceptions
	   -funwind-tables -fasynchronous-unwind-tables -finhibit-size-directive  -finstru-
	   ment-functions -fno-common  -fno-ident  -fno-gnu-linker -fpcc-struct-return	-fpic
	   -fPIC -freg-struct-return  -fshared-data  -fshort-enums -fshort-double  -fshort-wchar
	   -fvolatile -fvolatile-global  -fvolatile-static -fverbose-asm  -fpack-struct
	   -fstack-check -fstack-limit-register=reg  -fstack-limit-symbol=sym -fargument-alias
	   -fargument-noalias -fargument-noalias-global  -fleading-underscore -ftls-model=model

       Options Controlling the Kind of Output

       Compilation can involve up to four stages: preprocessing, compilation proper, assembly and
       linking, always in that order.  The first three stages apply to an individual source file,
       and end by producing an object file; 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 library libobjc.a to make
	   an Objective-C program work.

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

       file.h
	   C header file (not to be compiled or linked).

       file.cc
       file.cp
       file.cxx
       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.f
       file.for
       file.FOR
	   Fortran source code which should not be preprocessed.

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

       file.r
	   Fortran source code which must be preprocessed with a RATFOR preprocessor (not
	   included with GCC).

       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 renam-
	   ing 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.

       file.S
	   Assembler code which must be preprocessed.

       other
	   An object file to be fed straight into linking.  Any file name with no recognized suf-
	   fix 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	cpp-output
		   c++	c++-cpp-output
		   objective-c	objc-cpp-output
		   assembler  assembler-with-cpp
		   ada
		   f77	f77-cpp-input  ratfor
		   java

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

       -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.

       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.

	   Since only one output file can be specified, it does not make sense to use -o when
	   compiling more than one input file, unless you are producing an executable file as
	   output.

	   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, and all prepro-
	   cessed C source on standard output.

       -v  Print (on standard error output) the commands executed to run the stages of compila-
	   tion.  Also print the version number of the compiler driver program and of the pre-
	   processor 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.

       --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 -W 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.

       Compiling C++ Programs

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

       However, C++ programs often require class libraries as well as a compiler that understands
       the C++ language---and under some circumstances, you might want to compile programs from
       standard input, or otherwise without a suffix that flags them as C++ programs.  g++ is a
       program that calls GCC with the default language set to C++, and automatically specifies
       linking against the C++ library.  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++
       and Objective-C) that the compiler accepts:

       -ansi
	   In C mode, support all ISO C89 programs.  In C++ mode, remove GNU extensions that con-
	   flict with ISO C++.

	   This turns off certain features of GCC that are incompatible with ISO C89 (when com-
	   piling 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 // com-
	   ments as well as the "inline" keyword.

	   The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__" con-
	   tinue 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 compi-
	   lations 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 compil-
	   ing C.  A value for this option must be provided; possible values are

	   c89
	   iso9899:1990
	       ISO C89 (same as -ansi).

	   iso9899:199409
	       ISO C89 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-3.1/c99status.html> for more information.  The names c9x
	       and iso9899:199x are deprecated.

	   gnu89
	       Default, ISO C89 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.

	   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 C89 but are in the specified version (for
	   example, // comments and the "inline" keyword in ISO C99) are not disabled.

       -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 unproto-
	   typed (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.

       -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 (C and Objective-C only)
	   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 effi-
	   ciently; 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 C++, -fno-builtin is always in effect.  The -fbuiltin option has no effect.  There-
	   fore, in C++, the only way to get the optimization benefits of built-in functions is
	   to call the function using the __builtin_ prefix.  The GNU C++ Standard Library uses
	   built-in functions to implement many functions (like "std::strchr"), so that you auto-
	   matically get efficient code.

	   With the -fno-builtin-function option, not available when compiling C++, 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 ker-
	   nel.  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.

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

       -no-integrated-cpp
	   Invoke the external cpp during compilation.	The default is to use the integrated cpp
	   (internal cpp).  This option also allows a user-supplied cpp via the -B option.  This
	   flag is applicable in both C and C++ modes.

	   We do not guarantee to retain this option in future, and we may change its semantics.

       -traditional
	   Attempt to support some aspects of traditional C compilers.	Specifically:

	   o   All "extern" declarations take effect globally even if they are written inside of
	       a function definition.  This includes implicit declarations of functions.

	   o   The newer keywords "typeof", "inline", "signed", "const" and "volatile" are not
	       recognized.  (You can still use the alternative keywords such as "__typeof__",
	       "__inline__", and so on.)

	   o   Comparisons between pointers and integers are always allowed.

	   o   Integer types "unsigned short" and "unsigned char" promote to "unsigned int".

	   o   Out-of-range floating point literals are not an error.

	   o   Certain constructs which ISO regards as a single invalid preprocessing number,
	       such as 0xe-0xd, are treated as expressions instead.

	   o   String ``constants'' are not necessarily constant; they are stored in writable
	       space, and identical looking constants are allocated separately.  (This is the
	       same as the effect of -fwritable-strings.)

	   o   All automatic variables not declared "register" are preserved by "longjmp".  Ordi-
	       narily, GNU C follows ISO C: automatic variables not declared "volatile" may be
	       clobbered.

	   o   The character escape sequences \x and \a evaluate as the literal characters x and
	       a respectively.	Without -traditional, \x is a prefix for the hexadecimal repre-
	       sentation of a character, and \a produces a bell.

	   This option is deprecated and may be removed.

	   You may wish to use -fno-builtin as well as -traditional if your program uses names
	   that are normally GNU C built-in functions for other purposes of its own.

	   You cannot use -traditional if you include any header files that rely on ISO C fea-
	   tures.  Some vendors are starting to ship systems with ISO C header files and you can-
	   not use -traditional on such systems to compile files that include any system headers.

	   The -traditional option also enables -traditional-cpp.

       -traditional-cpp
	   Attempt to support some aspects of traditional C preprocessors.  See the GNU CPP man-
	   ual 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++.

       -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 -fun-
	   signed-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.

	   However, when -traditional is used, bit-fields are all unsigned no matter what.

       -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.
	   The option -traditional also has this effect.

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

       -fallow-single-precision
	   Do not promote single precision math operations to double precision, even when compil-
	   ing with -traditional.

	   Traditional K&R C promotes all floating point operations to double precision, regard-
	   less of the sizes of the operands.	On the architecture for which you are compiling,
	   single precision may be faster than double precision.   If you must use -traditional,
	   but want to use single precision operations when the operands are single precision,
	   use this option.   This option has no effect when compiling with ISO or GNU C conven-
	   tions (the default).

       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:

       -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.  The current Working Paper requires that "operator new"
	   never return a null pointer, so this check is normally unnecessary.

	   An alternative to using this option is to specify that your "operator new" does not
	   throw any exceptions; if you declare it throw(), G++ will check the return value.  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.

       -fno-const-strings
	   Give string constants type "char *" instead of type "const char *".	By default, G++
	   uses type "const char *" as required by the standard.  Even if you use
	   -fno-const-strings, you cannot actually modify the value of a string constant, unless
	   you also use -fwritable-strings.

	   This option might be removed in a future release of G++.  For maximum portability, you
	   should structure your code so that it works with string constants that have type
	   "const char *".

       -fdollars-in-identifiers
	   Accept $ in identifiers.  You can also explicitly prohibit use of $ with the option
	   -fno-dollars-in-identifiers.  (GNU C allows $ by default on most target systems, but
	   there are a few exceptions.)  Traditional C allowed the character $ to form part of
	   identifiers.  However, ISO C and C++ forbid $ in identifiers.

       -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 check for violation of exception specifications at runtime.  This option vio-
	   lates the C++ standard, but may be useful for reducing code size in production builds,
	   much like defining NDEBUG.  The compiler will still optimize based on the exception
	   specifications.

       -fexternal-templates
	   Cause #pragma interface and implementation to apply to template instantiation; tem-
	   plate instances are emitted or not according to the location of the template defini-
	   tion.

	   This option is deprecated.

       -falt-external-templates
	   Similar to -fexternal-templates, but template instances are emitted or not according
	   to the place where they are first instantiated.

	   This option is deprecated.

       -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 behav-
	   ior.

       -fno-gnu-keywords
	   Do not recognize "typeof" as a keyword, so that code can use this word as an identi-
	   fier.  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 get-
	   ting 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 func-
	   tions.

       -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.  Cur-
	   rently, the only such diagnostic issued by G++ is the one for a name having multiple
	   meanings within a class.

       -fpermissive
	   Downgrade messages about nonconformant code from errors to warnings.  By default, G++
	   effectively sets -pedantic-errors without -pedantic; this option reverses that.  This
	   behavior and this option are superseded by -pedantic, which works as it does for GNU
	   C.

       -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.

       -fstats
	   Emit statistics about front-end processing at the end of the compilation.  This infor-
	   mation 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 tem-
	   plate 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.

       -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 stan-
	   dards-compliant handling of static destructors, but will only work if your C library
	   supports "__cxa_atexit".

       -fvtable-gc
	   Emit special relocations for vtables and virtual function references so that the
	   linker can identify unused virtual functions and zero out vtable slots that refer to
	   them.  This is most useful with -ffunction-sections and -Wl,--gc-sections, in order to
	   also discard the functions themselves.

	   This optimization requires GNU as and GNU ld.  Not all systems support this option.
	   -Wl,--gc-sections is ignored without -static.

       -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 incompat-
	   ible 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 incompatibilites 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 pad-
	       ding 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 compil-
	       ers 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.

       -Wctor-dtor-privacy (C++ only)
	   Warn when a class seems unusable, because all the constructors or destructors in a
	   class are private and the class has no friends or public static member functions.

       -Wnon-virtual-dtor (C++ only)
	   Warn when a class declares a non-virtual destructor that should probably be virtual,
	   because it looks like the class will be used polymorphically.

       -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) { }
		   };

	   Here the compiler will warn that the member initializers for i and j will be rear-
	   ranged to match the declaration order of the members.

       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.

	   and about violations of the following style guidelines from Scott Meyers' More Effec-
	   tive C++ book:

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

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

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

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

       -Wno-non-template-friend (C++ only)
	   Disable warnings when non-templatized friend functions are declared within a template.
	   With 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-tem-
	   plate-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-tem-
	   plate-friend which keeps the conformant compiler code but disables the helpful warn-
	   ing.

       -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 (static_cast, reinterpret_cast, and const_cast) are less vulnera-
	   ble to unintended effects, and much easier to grep for.

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

		   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 enumeral 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.

       -Wsynth (C++ only)
	   Warn when G++'s synthesis behavior does not match that of cfront.  For instance:

		   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 Dialect

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

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

       In this example, only -fgnu-runtime is an option meant only for Objective-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 Objective-C programs:

       -fconstant-string-class=class-name
	   Use class-name as the name of the class to instantiate for each literal string speci-
	   fied with the syntax "@"..."".  The default class name is "NXConstantString".

       -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.

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

       -Wno-protocol
	   Do not warn if methods required by a protocol are not implemented in the class adopt-
	   ing it.

       -Wselector
	   Warn if a selector has multiple methods of different types defined.

       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.

       Options to Request or Suppress Warnings

       Warnings are diagnostic messages that report constructions which are not inherently erro-
       neous 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 fur-
       ther, language-specific options also refer to @ref{C++ Dialect Options} and @ref{Objec-
       tive-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.

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

       -Wcomment
	   Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a Back-
	   slash-Newline appears in a // comment.

       -Wformat
	   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 speci-
	   fied 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.

	   The formats are checked against the format features supported by GNU libc version 2.2.
	   These include all ISO C89 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).

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

       -Wno-format-y2k
	   If -Wformat is specified, do not 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 $ oper-
	   and 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.

       -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".

       -Wformat-security
	   If -Wformat is specified, also warn about uses of format functions that represent pos-
	   sible 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 -Wfor-
	   mat-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.

       -Wimplicit-int
	   Warn when a declaration does not specify a type.

       -Wimplicit-function-declaration
       -Werror-implicit-function-declaration
	   Give a warning (or error) whenever a function is used before being declared.

       -Wimplicit
	   Same as -Wimplicit-int and -Wimplicit-function-declaration.

       -Wmain
	   Warn if the type of main is suspicious.  main should be a function with external link-
	   age, returning int, taking either zero arguments, two, or three arguments of appropri-
	   ate types.

       -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 brack-
	   eted.

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

       -Wparentheses
	   Warn if parentheses are omitted in certain contexts, such as when there is an assign-
	   ment in a context where a truth value is expected, or when operators are nested whose
	   precedence people often get confused about.

	   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 illus-
	   trated 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 ();
		       }
		   }

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

	   The C standard defines the order in which expressions in a 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 evalu-
	   ation of its arguments and the expression denoting the called function), and in cer-
	   tain 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 com-
	   mittee 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 standard specifies 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 implementa-
	   tion 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 present implementation of this option only works for C programs.  A future imple-
	   mentation may also work for C++ programs.

	   The C 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 our readings page, at
	   <http://gcc.gnu.org/readings.html>.

       -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++, 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.

       -Wswitch
	   Warn whenever a "switch" statement has an index of enumeral 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 pro-
	   voke 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).

       -Wunused-function
	   Warn whenever a static function is declared but not defined or a non\-inline static
	   function is unused.

       -Wunused-label
	   Warn whenever a label is declared but not used.

	   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

	   To suppress this warning use the unused attribute.

       -Wunused-value
	   Warn whenever a statement computes a result that is explicitly not used.

	   To suppress this warning cast the expression to void.

       -Wunused
	   All all the above -Wunused options combined.

	   In order to get a warning about an unused function parameter, you must either specify
	   -W -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 don't specify -O, you
	   simply won't get these warnings.

	   These warnings occur only for variables that are candidates for register allocation.
	   Therefore, they do not occur for a variable that is declared "volatile", or whose
	   address is taken, or whose size is other than 1, 2, 4 or 8 bytes.  Also, they do not
	   occur for structures, unions or arrays, even when they are in registers.

	   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 rea-
	   sons 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 compila-
	   tion.

	   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".

       -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:

       -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 sys-
	   tem header files.  This is not the case if the warnings were only enabled by the -Wall
	   command line option.

       -Wall
	   All of the above -W options combined.  This enables all the warnings about construc-
	   tions that some users consider questionable, and that are easy to avoid (or modify to
	   prevent the warning), even in conjunction with macros.

       -Wdiv-by-zero
	   Warn about compile-time integer division by zero.  This is default.	To inhibit the
	   warning messages, use -Wno-div-by-zero.  Floating point division by zero is not warned
	   about, as it can be a legitimate way of obtaining infinities and NaNs.

       -Wmultichar
	   Warn if a multicharacter constant ('FOOF') is used.	This is default.  To inhibit the
	   warning messages, use -Wno-multichar.  Usually they indicate a typo in the user's
	   code, as they have implementation-defined values, and should not be used in portable
	   code.

       -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.

       The following -W... options are not implied by -Wall.  Some of them warn about construc-
       tions 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.

       -W  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 func-
	       tion 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   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.

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

	   o   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.
	       (But don't warn about the GNU extension of "volatile void" return types.  That
	       extension will be warned about if -pedantic is specified.)

	   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-com-
	       pare is also specified.)

	   o   An aggregate has a partly bracketed initializer.  For example, the following code
	       would evoke such a warning, because braces are missing around the initializer for
	       "x.h":

		       struct s { int f, g; };
		       struct t { struct s h; int i; };
		       struct t x = { 1, 2, 3 };

	   o   An aggregate has an initializer which does not initialize all members.  For exam-
	       ple, the following code would cause such a warning, because "x.h" would be implic-
	       itly initialized to zero:

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

       -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 con-
	   sider floating-point values as approximations to infinitely precise real numbers.  If
	   you are doing this, then you need to compute (by analysing 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.

       -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 tradi-
	       tional 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 pre-
	       processors would only consider a line to be a directive if the # appeared in col-
	       umn 1 on the line.  Therefore -Wtraditional warns about directives that tradi-
	       tional 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 suf-
	       fixes 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 nor-
	       mally 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.

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

       -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.

       -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 *".

       -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 com-
	   piling C++, warn about the deprecated conversion from string constants to "char *".
	   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 decla-
	   rations 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 signed-
	   ness 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".

       -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 -W; to get the other warnings of -W without this warning, use -W -Wno-sign-compare.

       -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.)

       -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 declara-
	   tion which specifies the argument types.)

       -Wmissing-prototypes (C only)
	   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
	   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 func-
	   tions that are not declared in header files.

       -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
	   If -Wformat is enabled, also warn about functions which might be candidates for "for-
	   mat" attributes.  Note these are only possible candidates, not absolute ones.  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.  This
	   option has no effect unless -Wformat is enabled (possibly by -Wall).

       -Wno-deprecated-declarations
	   Do not warn about uses of functions, variables, and types marked as deprecated by
	   using the "deprecated" attribute.  (@pxref{Function Attributes}, @pxref{Variable
	   Attributes}, @pxref{Type Attributes}.)

       -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 struc-
	   ture 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 circum-
	   stances 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 unreach-
	   able 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.

       -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.

       -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.

       -Werror
	   Make all warnings into errors.

       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).  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+,
	   -gstabs, -gxcoff+, -gxcoff, -gdwarf-1+, -gdwarf-1, or -gvms (see below).

	   Unlike most other C compilers, 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 sup-
	   ported), 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.

       -gstabs+
	   Produce debugging information in stabs format (if that is supported), using GNU exten-
	   sions 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.

       -gcoff
	   Produce debugging information in COFF format (if that is supported).  This is the for-
	   mat used by SDB on most System V systems prior to System V Release 4.

       -gxcoff
	   Produce debugging information in XCOFF format (if that is supported).  This is the
	   format used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
	   Produce debugging information in XCOFF format (if that is supported), using GNU exten-
	   sions 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, and may cause
	   assemblers other than the GNU assembler (GAS) to fail with an error.

       -gdwarf
	   Produce debugging information in DWARF version 1 format (if that is supported).  This
	   is the format used by SDB on most System V Release 4 systems.

       -gdwarf+
	   Produce debugging information in DWARF version 1 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.

       -gvms
	   Produce debugging information in VMS debug format (if that is supported).  This is the
	   format used by DEBUG on VMS systems.

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

	   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.

	   Note that in order to avoid confusion between DWARF1 debug level 2, and DWARF2, nei-
	   ther -gdwarf nor -gdwarf-2 accept a concatenated debug level.  Instead use an addi-
	   tional -glevel option to change the debug level for DWARF1 or DWARF2.

       -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 sta-
	   tistics 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.

       -fprofile-arcs
	   Instrument arcs during compilation to generate coverage data or for profile-directed
	   block ordering.  During execution the program records how many times each branch is
	   executed and how many times it is taken.  When the compiled program exits it saves
	   this data to a file called sourcename.da for each source file.

	   For profile-directed block ordering, compile the program with -fprofile-arcs plus
	   optimization and code generation options, generate the arc profile information by run-
	   ning the program on a selected workload, and then compile the program again with the
	   same optimization and code generation options plus -fbranch-probabilities.

	   The other use of -fprofile-arcs is for use with "gcov", when it is used with the
	   -ftest-coverage option.

	   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 span-
	   ning 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
	   Create data files for the gcov code-coverage utility.  The data file names begin with
	   the name of your source file:

	   sourcename.bb
	       A mapping from basic blocks to line numbers, which "gcov" uses to associate basic
	       block execution counts with line numbers.

	   sourcename.bbg
	       A list of all arcs in the program flow graph.  This allows "gcov" to reconstruct
	       the program flow graph, so that it can compute all basic block and arc execution
	       counts from the information in the "sourcename.da" file.

	   Use -ftest-coverage with -fprofile-arcs; the latter option adds instrumentation to the
	   program, which then writes execution counts to another data file:

	   sourcename.da
	       Runtime arc execution counts, used in conjunction with the arc information in the
	       file "sourcename.bbg".

	   Coverage data will map better to the source files if -ftest-coverage is used without
	   optimization.

       -dletters
	   Says to make debugging dumps during compilation at times specified by letters.  This
	   is used for debugging the compiler.	The file names for most of the dumps are made by
	   appending a pass number and a word to the source file name (e.g.  foo.c.00.rtl or
	   foo.c.01.sibling).  Here are the possible letters for use in letters, and their mean-
	   ings:

	   A   Annotate the assembler output with miscellaneous debugging information.

	   b   Dump after computing branch probabilities, to file.14.bp.

	   B   Dump after block reordering, to file.29.bbro.

	   c   Dump after instruction combination, to the file file.16.combine.

	   C   Dump after the first if conversion, to the file file.17.ce.

	   d   Dump after delayed branch scheduling, to file.31.dbr.

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

	   e   Dump after SSA optimizations, to file.04.ssa and file.07.ussa.

	   E   Dump after the second if conversion, to file.26.ce2.

	   f   Dump after life analysis, to file.15.life.

	   F   Dump after purging "ADDRESSOF" codes, to file.09.addressof.

	   g   Dump after global register allocation, to file.21.greg.

	   h   Dump after finalization of EH handling code, to file.02.eh.

	   k   Dump after reg-to-stack conversion, to file.28.stack.

	   o   Dump after post-reload optimizations, to file.22.postreload.

	   G   Dump after GCSE, to file.10.gcse.

	   i   Dump after sibling call optimizations, to file.01.sibling.

	   j   Dump after the first jump optimization, to file.03.jump.

	   k   Dump after conversion from registers to stack, to file.32.stack.

	   l   Dump after local register allocation, to file.20.lreg.

	   L   Dump after loop optimization, to file.11.loop.

	   M   Dump after performing the machine dependent reorganisation pass, to file.30.mach.

	   n   Dump after register renumbering, to file.25.rnreg.

	   N   Dump after the register move pass, to file.18.regmove.

	   r   Dump after RTL generation, to file.00.rtl.

	   R   Dump after the second scheduling pass, to file.27.sched2.

	   s   Dump after CSE (including the jump optimization that sometimes follows CSE), to
	       file.08.cse.

	   S   Dump after the first scheduling pass, to file.19.sched.

	   t   Dump after the second CSE pass (including the jump optimization that sometimes
	       follows CSE), to file.12.cse2.

	   w   Dump after the second flow pass, to file.23.flow2.

	   X   Dump after SSA dead code elimination, to file.06.ssadce.

	   z   Dump after the peephole pass, to file.24.peephole2.

	   a   Produce all the dumps listed above.

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

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

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

	   v   For each of the other indicated dump files (except for file.00.rtl), dump a repre-
	       sentation of the control flow graph suitable for viewing with VCG to
	       file.pass.vcg.

	   x   Just generate RTL for a function instead of compiling it.  Usually used with r.

	   y   Dump debugging information during parsing, to standard error.

       -fdump-unnumbered
	   When doing debugging dumps (see -d option above), suppress instruction numbers and
	   line number note 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 and C++ only)
       -fdump-translation-unit-options (C and 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-tree-switch (C++ only)
       -fdump-tree-switch-options (C++ only)
	   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.

	   all Turn on all options.

	   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.

       -fsched-verbose=n
	   On targets that use instruction scheduling, this option controls the amount of debug-
	   ging 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 infor-
	   mation 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.

       -fpretend-float
	   When running a cross-compiler, pretend that the target machine uses the same floating
	   point format as the host machine.  This causes incorrect output of the actual floating
	   constants, but the actual instruction sequence will probably be the same as GCC would
	   make when running on the target machine.

       -save-temps
	   Store the usual ``temporary'' intermediate files permanently; place them in the cur-
	   rent 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 inte-
	   grated preprocessor.

       -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.

       -print-file-name=library
	   Print the full absolute name of the library file library that would be used when link-
	   ing---and don't do anything else.  With this option, GCC does not compile or link any-
	   thing; 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 environ-
	   ment 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.)

       Options That Control Optimization

       These options control various sorts of optimizations:

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

	   Without -O, 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.

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

       -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 func-
	   tion 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 optional optimizations except for loop unrolling, function inlining,
	   and register renaming.  It also turns on the -fforce-mem option on all machines and
	   frame pointer elimination on machines where doing so does not interfere with debug-
	   ging.

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

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also turns on
	   the -finline-functions and -frename-registers options.

       -O0 Do not optimize.

       -Os Optimize for size.  -Os enables all -O2 optimizations that do not typically increase
	   code size.  It also performs further optimizations designed to reduce code size.

	   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 posi-
       tive 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.

       -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 perti-
	   nent intermediate computations into variables.

       -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.

       -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 subexpres-
	   sions.  When they are not common subexpressions, instruction combination should elimi-
	   nate the separate register-load.  The -O2 option turns on this option.

       -fforce-addr
	   Force memory address constants to be copied into registers before doing arithmetic on
	   them.  This may produce better code just as -fforce-mem may.

       -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 call-
	   ing sequence automatically handles the frame pointer and nothing is saved by pretend-
	   ing it doesn't exist.  The machine-description macro "FRAME_POINTER_REQUIRED" controls
	   whether a target machine supports this flag.

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

       -ftrapv
	   This option generates traps for signed overflow on addition, subtraction, multiplica-
	   tion operations.

       -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.

       -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 (ie
	   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 count-
	   ing 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++.

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

       -fkeep-inline-functions
	   Even if all calls to a given function are integrated, and the function is declared
	   "static", nevertheless output a separate run-time callable version of the function.
	   This switch does not affect "extern inline" functions.

       -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.

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

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

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

	   This option implies -fmerge-constants.  In addition to -fmerge-constants this consid-
	   ers e.g. even constant initialized arrays or initialized constant variables with inte-
	   gral 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.

       -fno-branch-count-reg
	   Do not use ``decrement and branch'' instructions on a count register, but instead gen-
	   erate 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.

       -fno-function-cse
	   Do not put function addresses in registers; make each instruction that calls a con-
	   stant 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.

       -ffast-math
	   Sets -fno-math-errno, -funsafe-math-optimizations, and -fno-trapping-math.

	   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 incor-
	   rect 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 instruc-
	   tion, 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.

	   This option should never be turned on by any -O option since it can result in incor-
	   rect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications for math functions.

	   The default is -fmath-errno.

       -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 incor-
	   rect 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.

       -fno-trapping-math
	   Compile code assuming that floating-point operations cannot generate user-visible
	   traps.  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 incor-
	   rect output for programs which depend on an exact implementation of IEEE or ISO
	   rules/specifications for math functions.

	   The default is -ftrapping-math.

       -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 currenly only supported by the
	   Java and Fortran 77 front-ends, where this option defaults to true and false respec-
	   tively.

       The following options control specific optimizations.  The -O2 option turns on all of
       these optimizations except -funroll-loops and -funroll-all-loops.  On most machines, the
       -O option turns on the -fthread-jumps and -fdelayed-branch options, but specific machines
       may handle it differently.

       You can use the following flags in the rare cases when ``fine-tuning'' of optimizations to
       be performed is desired.

       Not all of the optimizations performed by GCC have -f options to control them.

       -fstrength-reduce
	   Perform the optimizations of loop strength reduction and elimination of iteration
	   variables.

       -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 redi-
	   rected 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.

       -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.

       -fcse-skip-blocks
	   This is similar to -fcse-follow-jumps, but causes CSE to follow jumps which condition-
	   ally 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".

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

       -frerun-loop-opt
	   Run the loop optimizer twice.

       -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 bet-
	   ter runtime performance if you disable the global common subexpression elmination pass
	   by adding -fno-gcse to the command line.

       -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 con-
	   taining a load/store sequence to be changed to a load outside the loop, and a
	   copy/store within the loop.

       -fgcse-sm
	   When -fgcse-sm is enabled, A store motion pass is run after global common subexpres-
	   sion 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.

       -fdelete-null-pointer-checks
	   Use global dataflow analysis to identify and eliminate useless checks for null point-
	   ers.  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.

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

       -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 espe-
	   cially helpful on machines with two-operand instructions.  GCC enables this optimiza-
	   tion by default with -O2 or higher.

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

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

       -fschedule-insns
	   If supported for the target machine, attempt to reorder instructions to eliminate exe-
	   cution 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.

       -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.

       -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 sched-
	   uling 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 sched-
	   uling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -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.  HPPA processors running HP-UX and
	   Sparc processors running Solaris 2 have linkers with such optimizations.  Other sys-
	   tems using the ELF object format as well as 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 exe-
	   cutable 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.

       -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 other-
	   wise be produced.

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

	   For all machines, optimization level 2 and higher enables this flag by default.

       -funroll-loops
	   Unroll loops whose number of iterations can be determined at compile time or upon
	   entry to the loop.  -funroll-loops implies both -fstrength-reduce and -fre-
	   run-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,

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

       -fmove-all-movables
	   Forces all invariant computations in loops to be moved outside the loop.

       -freduce-all-givs
	   Forces all general-induction variables in loops to be strength-reduced.

	   Note: When compiling programs written in Fortran, -fmove-all-movables and -fre-
	   duce-all-givs are enabled by default when you use the optimizer.

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

	   These two options are intended to be removed someday, once they have helped determine
	   the efficacy of various approaches to improving loop optimizations.

	   Please let us (<gcc@gcc.gnu.org> and <fortran@gnu.org>) know how use of these options
	   affects the performance of your production code.  We're very interested in code that
	   runs slower when these options are enabled.

       -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.

       -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.da for each source file  The informa-
	   tion 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 compila-
	   tions.

	   With -fbranch-probabilities, GCC puts a REG_EXEC_COUNT note on the first instruction
	   of each basic block, and 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.

       -fno-guess-branch-probability
	   Do not guess branch probabilities using a randomized model.

	   Sometimes gcc will opt to use a randomized model to guess branch probabilities, when
	   none are available from either profiling feedback (-fprofile-arcs) or
	   __builtin_expect.  This means that different runs of the compiler on the same program
	   may produce different object code.

	   In a hard real-time system, people don't want different runs of the compiler to pro-
	   duce code that has different behavior; minimizing non-determinism is of paramount
	   import.  This switch allows users to reduce non-determinism, possibly at the expense
	   of inferior optimization.

       -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 writ-
	   ten 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".

       -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 bound-
	   ary, 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, use a machine-dependent default.

       -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.

	   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, use a machine-dependent default which is very likely to be 1,
	   meaning no alignment.

       -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 exe-
	   cution of the dummy operations.

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

       -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.

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

       -fssa
	   Perform optimizations in static single assignment form.  Each function's flow graph is
	   translated into SSA form, optimizations are performed, and the flow graph is trans-
	   lated back from SSA form.  Users should not specify this option, since it is not yet
	   ready for production use.

       -fssa-ccp
	   Perform Sparse Conditional Constant Propagation in SSA form.  Requires -fssa.  Like
	   -fssa, this is an experimental feature.

       -fssa-dce
	   Perform aggressive dead-code elimination in SSA form.  Requires -fssa.  Like -fssa,
	   this is an experimental feature.

       -fsingle-precision-constant
	   Treat floating point constant as single precision constant instead of implicitly con-
	   verting it to double precision constant.

       -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.  It can, however, make debugging impossible, since variables will
	   no longer stay in a ``home register''.

       -fno-cprop-registers
	   After register allocation and post-register allocation instruction splitting, we per-
	   form a copy-propagation pass to try to reduce scheduling dependencies and occasionally
	   eliminate the copy.

       --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.

	   In each case, the value is an integer.  The allowable choices for name are given in
	   the following table:

	   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 com-
	       pile 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 com-
	       pile 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 per-
	       form 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.

	   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
	       If an function contains more than this many instructions, it will not be inlined.
	       This option is precisely equivalent to -finline-limit.

       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 unsuit-
       able for actual compilation.

       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 possi-
       ble you should avoid using -Wp and let the driver handle the options instead.

       -D name
	   Predefine name as a macro, with definition 1.

       -D name=definition
	   Predefine name as a macro, with definition definition.  There are no restrictions on
	   the contents of definition, but 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 charac-
	   ters 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 macros.  The common 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.

	   It is dangerous to specify a standard system include directory in an -I option.  This
	   defeats the special treatment of system headers .  It can also defeat the repairs to
	   buggy system headers which GCC makes when it is installed.

       -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 and -Wtrigraphs.  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 back-
	   slash-newline appears in a // comment.  (Both forms have the same effect.)

       -Wtrigraphs
	   Warn if any trigraphs are encountered.  This option used to take effect only if -tri-
	   graphs was also specified, but now works independently.  Warnings are not given for
	   trigraphs within comments, as they do not affect the meaning of the program.

       -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.

       -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 \-new-
	   line.  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_OUT-
	   PUT.  Debug output will still be sent to the regular output stream as normal.

	   Passing -M to the driver implies -E.

       -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 direc-
	   tive 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
	   @anchor{-MF} 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.

       -MG When used with -M or -MM, -MG says to treat missing header files as generated files
	   and assume they live in the same directory as the source file.  It suppresses prepro-
	   cessed output, as a missing header file is ordinarily an error.

	   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 deter-
	   mines 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 @pxref{-MF}), but if used without -E, each -o is under-
	   stood 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.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
	   Specify the source language: C, 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, 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 lan-
	   guage 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 only knows about
	   the standards for C; other language standards will 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.

       -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"".

       -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 appro-
	   priate) 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 rep-
	   resents 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.

	   Use of these options is discouraged.

       -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.

       -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 com-
	   ments, so that you can pass a file preprocessed with -C to the compiler without prob-
	   lems.  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.

       -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 pre-
	   ferred 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.

       -A- Cancel all predefined assertions and all assertions preceding it on the command line.
	   Also, undefine all predefined macros and all macros preceding it on the command line.
	   (This is a historical wart and may change in the future.)

       -dCHARS
	   CHARS is a sequence of one or more of the following characters, and must not be pre-
	   ceded 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.

	   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 #.

       -gcc
	   Define the macros __GNUC__, __GNUC_MINOR__ and __GNUC_PATCHLEVEL__.	These are defined
	   automatically when you use gcc -E; you can turn them off in that case with -no-gcc.

       -traditional
	   Try to imitate the behavior of old-fashioned C, as opposed to ISO C.

       -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 tri-
	   graphs, 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.

       -$  Forbid the use of $ in identifiers.	The C standard allows implementations to define
	   extra characters that can appear in identifiers.  By default GNU CPP permits $, a com-
	   mon extension.

       -h
       --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.

       -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.

       Options for Linking

       These options come into play when the compiler links object files into an executable out-
       put file.  They are meaningless if the compiler is not doing a link step.

       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 sur-
	   rounds 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 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, and memcpy
	   for System V (and ISO C) environments or to bcopy and bzero for BSD environments.
	   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, and memcpy for System V (and ISO C) environments
	   or to bcopy and bzero for BSD environments.	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 spec-
	   ify -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.)

       -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.

       -shared
	   Produce a shared object which can then be linked with other objects to form an exe-
	   cutable.  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]

       -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 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 ver-
	   sion 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 unre-
	   solved 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 defini-
	   tions, you must write -Xlinker -assert -Xlinker definitions.  It does not work to
	   write -Xlinker "-assert definitions", because this passes the entire string as a sin-
	   gle 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 addi-
	   tional 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 ver-
	   sion, since these directories are searched before the system header file directories.
	   However, you should not use this option to add directories that contain vendor-sup-
	   plied 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 direc-
	   tories 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 inadvertantly changed.  If you really need to
	   change the search order for system directories, use the -nostdinc and/or -isystem
	   options.

       -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 directo-
	   ries 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 cur-
	   rent 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.

       -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-lib/.  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 com-
	   mand line, and they are processed in order, from left to right.

       Specifying Target Machine and Compiler Version

       By default, GCC compiles code for the same type of machine that you are using.  However,
       it can also be installed as a cross-compiler, to compile for some other type of machine.
       In fact, several different configurations of GCC, for different target machines, can be
       installed side by side.	Then you specify which one to use with the -b option.

       In addition, older and newer versions of GCC can be installed side by side.  One of them
       (probably the newest) will be the default, but you may sometimes wish to use another.

       -b machine
	   The argument machine specifies the target machine for compilation.  This is useful
	   when you have installed GCC as a cross-compiler.

	   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 i386v, meaning to compile for an 80386 running System V, then you would
	   specify -b i386v to run that cross compiler.

	   When you do not specify -b, it normally means to compile for the same type of machine
	   that you are using.

       -V version
	   The argument version specifies which version of GCC to run.	This is useful when mul-
	   tiple versions are installed.  For example, version might be 2.0, meaning to run GCC
	   version 2.0.

	   The default version, when you do not specify -V, is the last version of GCC that you
	   installed.

       The -b and -V options actually work by controlling part of the file name used for the exe-
       cutable files and libraries used for compilation.  A given version of GCC, for a given
       target machine, is normally kept in the directory /usr/local/lib/gcc-lib/machine/version.

       Thus, sites can customize the effect of -b or -V either by changing the names of these
       directories or adding alternate names (or symbolic links).  If in directory
       /usr/local/lib/gcc-lib/ the file 80386 is a link to the file i386v, then -b 80386 becomes
       an alias for -b i386v.

       In one respect, the -b or -V do not completely change to a different compiler: the top-
       level driver program gcc that you originally invoked continues to run and invoke the other
       executables (preprocessor, compiler per se, assembler and linker) that do the real work.
       However, since no real work is done in the driver program, it usually does not matter that
       the driver program in use is not the one for the specified target.  It is common for the
       interface to the other executables to change incompatibly between compiler versions, so
       unless the version specified is very close to that of the driver (for example, -V 3.0 with
       a driver program from GCC version 3.0.1), use of -V may not work; for example, using -V
       2.95.2 will not work with a driver program from GCC 3.0.

       The only way that the driver program depends on the target machine is in the parsing and
       handling of special machine-specific options.  However, this is controlled by a file which
       is found, along with the other executables, in the directory for the specified version and
       target machine.	As a result, a single installed driver program adapts to any specified
       target machine, and sufficiently similar compiler versions.

       The driver program executable does control one significant thing, however: the default
       version and target machine.  Therefore, you can install different instances of the driver
       program, compiled for different targets or versions, under different names.

       For example, if the driver for version 2.0 is installed as ogcc and that for version 2.1
       is installed as gcc, then the command gcc will use version 2.1 by default, while ogcc will
       use 2.0 by default.  However, you can choose either version with either command with the
       -V option.

       Hardware Models and Configurations

       Earlier we discussed the standard option -b which chooses among different installed com-
       pilers 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 com-
       pile 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.

       These options are defined by the macro "TARGET_SWITCHES" in the machine description.  The
       default for the options is also defined by that macro, which enables you to change the
       defaults.

       M680x0 Options

       These are the -m options defined for the 68000 series.  The default values for these
       options depends on which style of 68000 was selected when the compiler was configured; the
       defaults for the most common choices are given below.

       -m68000
       -mc68000
	   Generate output for a 68000.  This is the default when the compiler is configured for
	   68000-based systems.

	   Use this option for microcontrollers with a 68000 or EC000 core, including the 68008,
	   68302, 68306, 68307, 68322, 68328 and 68356.

       -m68020
       -mc68020
	   Generate output for a 68020.  This is the default when the compiler is configured for
	   68020-based systems.

       -m68881
	   Generate output containing 68881 instructions for floating point.  This is the default
	   for most 68020 systems unless --nfp was specified when the compiler was configured.

       -m68030
	   Generate output for a 68030.  This is the default when the compiler is configured for
	   68030-based systems.

       -m68040
	   Generate output for a 68040.  This is the default when the compiler is configured for
	   68040-based systems.

	   This option inhibits the use of 68881/68882 instructions that have to be emulated by
	   software on the 68040.  Use this option if your 68040 does not have code to emulate
	   those instructions.

       -m68060
	   Generate output for a 68060.  This is the default when the compiler is configured for
	   68060-based systems.

	   This option inhibits the use of 68020 and 68881/68882 instructions that have to be
	   emulated by software on the 68060.  Use this option if your 68060 does not have code
	   to emulate those instructions.

       -mcpu32
	   Generate output for a CPU32.  This is the default when the compiler is configured for
	   CPU32-based systems.

	   Use this option for microcontrollers with a CPU32 or CPU32+ core, including the 68330,
	   68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360.

       -m5200
	   Generate output for a 520X ``coldfire'' family cpu.	This is the default when the com-
	   piler is configured for 520X-based systems.

	   Use this option for microcontroller with a 5200 core, including the MCF5202, MCF5203,
	   MCF5204 and MCF5202.

       -m68020-40
	   Generate output for a 68040, without using any of the new instructions.  This results
	   in code which can run relatively efficiently on either a 68020/68881 or a 68030 or a
	   68040.  The generated code does use the 68881 instructions that are emulated on the
	   68040.

       -m68020-60
	   Generate output for a 68060, without using any of the new instructions.  This results
	   in code which can run relatively efficiently on either a 68020/68881 or a 68030 or a
	   68040.  The generated code does use the 68881 instructions that are emulated on the
	   68060.

       -mfpa
	   Generate output containing Sun FPA instructions for floating point.

       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries are not available for all m68k targets.  Normally the facilities of the
	   machine's usual C compiler are used, but this can't be done directly in cross-compila-
	   tion.  You must make your own arrangements to provide suitable library functions for
	   cross-compilation.  The embedded targets m68k-*-aout and m68k-*-coff do provide soft-
	   ware floating point support.

       -mshort
	   Consider type "int" to be 16 bits wide, like "short int".

       -mnobitfield
	   Do not use the bit-field instructions.  The -m68000, -mcpu32 and -m5200 options imply
	   -mnobitfield.

       -mbitfield
	   Do use the bit-field instructions.  The -m68020 option implies -mbitfield.  This is
	   the default if you use a configuration designed for a 68020.

       -mrtd
	   Use a different function-calling convention, in which functions that take a fixed num-
	   ber of arguments return with the "rtd" instruction, which pops their arguments while
	   returning.  This saves one instruction in the caller since there is no need to pop the
	   arguments there.

	   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 num-
	   bers 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.)

	   The "rtd" instruction is supported by the 68010, 68020, 68030, 68040, 68060 and CPU32
	   processors, but not by the 68000 or 5200.

       -malign-int
       -mno-align-int
	   Control whether GCC aligns "int", "long", "long long", "float", "double", and "long
	   double" variables on a 32-bit boundary (-malign-int) or a 16-bit boundary
	   (-mno-align-int).  Aligning variables on 32-bit boundaries produces code that runs
	   somewhat faster on processors with 32-bit busses at the expense of more memory.

	   Warning: if you use the -malign-int switch, GCC will align structures containing the
	   above types	differently than most published application binary interface specifica-
	   tions for the m68k.

       -mpcrel
	   Use the pc-relative addressing mode of the 68000 directly, instead of using a global
	   offset table.  At present, this option implies -fpic, allowing at most a 16-bit offset
	   for pc-relative addressing.	-fPIC is not presently supported with -mpcrel, though
	   this could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
	   Do not (do) assume that unaligned memory references will be handled by the system.

       M68hc1x Options

       These are the -m options defined for the 68hc11 and 68hc12 microcontrollers.  The default
       values for these options depends on which style of microcontroller was selected when the
       compiler was configured; the defaults for the most common choices are given below.

       -m6811
       -m68hc11
	   Generate output for a 68HC11.  This is the default when the compiler is configured for
	   68HC11-based systems.

       -m6812
       -m68hc12
	   Generate output for a 68HC12.  This is the default when the compiler is configured for
	   68HC12-based systems.

       -mauto-incdec
	   Enable the use of 68HC12 pre and post auto-increment and auto-decrement addressing
	   modes.

       -mshort
	   Consider type "int" to be 16 bits wide, like "short int".

       -msoft-reg-count=count
	   Specify the number of pseudo-soft registers which are used for the code generation.
	   The maximum number is 32.  Using more pseudo-soft register may or may not result in
	   better code depending on the program.  The default is 4 for 68HC11 and 2 for 68HC12.

       VAX Options

       These -m options are defined for the VAX:

       -munix
	   Do not output certain jump instructions ("aobleq" and so on) that the Unix assembler
	   for the VAX cannot handle across long ranges.

       -mgnu
	   Do output those jump instructions, on the assumption that you will assemble with the
	   GNU assembler.

       -mg Output code for g-format floating point numbers instead of d-format.

       SPARC Options

       These -m switches are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
	   Specify -mapp-regs to generate output using the global registers 2 through 4, which
	   the SPARC SVR4 ABI reserves for applications.  This is the default.

	   To be fully SVR4 ABI compliant at the cost of some performance loss, specify
	   -mno-app-regs.  You should compile libraries and system software with this option.

       -mfpu
       -mhard-float
	   Generate output containing floating point instructions.  This is the default.

       -mno-fpu
       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries are not available for all SPARC targets.  Normally the facilities of the
	   machine's usual C compiler are used, but this cannot be done directly in cross-compi-
	   lation.  You must make your own arrangements to provide suitable library functions for
	   cross-compilation.  The embedded targets sparc-*-aout and sparclite-*-* do provide
	   software floating point support.

	   -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.

       -mhard-quad-float
	   Generate output containing quad-word (long double) floating point instructions.

       -msoft-quad-float
	   Generate output containing library calls for quad-word (long double) floating point
	   instructions.  The functions called are those specified in the SPARC ABI.  This is the
	   default.

	   As of this writing, there are no sparc implementations that have hardware support for
	   the quad-word floating point instructions.  They all invoke a trap handler for one of
	   these instructions, and then the trap handler emulates the effect of the instruction.
	   Because of the trap handler overhead, this is much slower than calling the ABI library
	   routines.  Thus the -msoft-quad-float option is the default.

       -mno-flat
       -mflat
	   With -mflat, the compiler does not generate save/restore instructions and will use a
	   ``flat'' or single register window calling convention.  This model uses %i7 as the
	   frame pointer and is compatible with the normal register window model.  Code from
	   either may be intermixed.  The local registers and the input registers (0--5) are
	   still treated as ``call saved'' registers and will be saved on the stack as necessary.

	   With -mno-flat (the default), the compiler emits save/restore instructions (except for
	   leaf functions) and is the normal mode of operation.

       -mno-unaligned-doubles
       -munaligned-doubles
	   Assume that doubles have 8 byte alignment.  This is the default.

	   With -munaligned-doubles, GCC assumes that doubles have 8 byte alignment only if they
	   are contained in another type, or if they have an absolute address.	Otherwise, it
	   assumes they have 4 byte alignment.	Specifying this option avoids some rare compati-
	   bility problems with code generated by other compilers.  It is not the default because
	   it results in a performance loss, especially for floating point code.

       -mno-faster-structs
       -mfaster-structs
	   With -mfaster-structs, the compiler assumes that structures should have 8 byte align-
	   ment.  This enables the use of pairs of "ldd" and "std" instructions for copies in
	   structure assignment, in place of twice as many "ld" and "st" pairs.  However, the use
	   of this changed alignment directly violates the Sparc ABI.  Thus, it's intended only
	   for use on targets where the developer acknowledges that their resulting code will not
	   be directly in line with the rules of the ABI.

       -mv8
       -msparclite
	   These two options select variations on the SPARC architecture.

	   By default (unless specifically configured for the Fujitsu SPARClite), GCC generates
	   code for the v7 variant of the SPARC architecture.

	   -mv8 will give you SPARC v8 code.  The only difference from v7 code is that the com-
	   piler emits the integer multiply and integer divide instructions which exist in SPARC
	   v8 but not in SPARC v7.

	   -msparclite will give you SPARClite code.  This adds the integer multiply, integer
	   divide step and scan ("ffs") instructions which exist in SPARClite but not in SPARC
	   v7.

	   These options are deprecated and will be deleted in a future GCC release.  They have
	   been replaced with -mcpu=xxx.

       -mcypress
       -msupersparc
	   These two options select the processor for which the code is optimized.

	   With -mcypress (the default), the compiler optimizes code for the Cypress CY7C602
	   chip, as used in the SparcStation/SparcServer 3xx series.  This is also appropriate
	   for the older SparcStation 1, 2, IPX etc.

	   With -msupersparc the compiler optimizes code for the SuperSparc cpu, as used in the
	   SparcStation 10, 1000 and 2000 series.  This flag also enables use of the full SPARC
	   v8 instruction set.

	   These options are deprecated and will be deleted in a future GCC release.  They have
	   been replaced with -mcpu=xxx.

       -mcpu=cpu_type
	   Set the instruction set, register set, and instruction scheduling parameters for
	   machine type cpu_type.  Supported values for cpu_type are v7, cypress, v8, supersparc,
	   sparclite, hypersparc, sparclite86x, f930, f934, sparclet, tsc701, v9, and ultrasparc.

	   Default instruction scheduling parameters are used for values that select an architec-
	   ture and not an implementation.  These are v7, v8, sparclite, sparclet, v9.

	   Here is a list of each supported architecture and their supported implementations.

		       v7:	       cypress
		       v8:	       supersparc, hypersparc
		       sparclite:      f930, f934, sparclite86x
		       sparclet:       tsc701
		       v9:	       ultrasparc

       -mtune=cpu_type
	   Set the instruction scheduling parameters for machine type cpu_type, but do not set
	   the instruction set or register set that the option -mcpu=cpu_type would.

	   The same values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the only use-
	   ful values are those that select a particular cpu implementation.  Those are cypress,
	   supersparc, hypersparc, f930, f934, sparclite86x, tsc701, and ultrasparc.

       These -m switches are supported in addition to the above on the SPARCLET processor.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.

       -mlive-g0
	   Treat register %g0 as a normal register.  GCC will continue to clobber it as necessary
	   but will not assume it always reads as 0.

       -mbroken-saverestore
	   Generate code that does not use non-trivial forms of the "save" and "restore" instruc-
	   tions.  Early versions of the SPARCLET processor do not correctly handle "save" and
	   "restore" instructions used with arguments.	They correctly handle them used without
	   arguments.  A "save" instruction used without arguments increments the current window
	   pointer but does not allocate a new stack frame.  It is assumed that the window over-
	   flow trap handler will properly handle this case as will interrupt handlers.

       These -m switches are supported in addition to the above on SPARC V9 processors in 64-bit
       environments.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.

       -m32
       -m64
	   Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,
	   long and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and
	   pointer to 64 bits.

       -mcmodel=medlow
	   Generate code for the Medium/Low code model: the program must be linked in the low 32
	   bits of the address space.  Pointers are 64 bits.  Programs can be statically or
	   dynamically linked.

       -mcmodel=medmid
	   Generate code for the Medium/Middle code model: the program must be linked in the low
	   44 bits of the address space, the text segment must be less than 2G bytes, and data
	   segment must be within 2G of the text segment.  Pointers are 64 bits.

       -mcmodel=medany
	   Generate code for the Medium/Anywhere code model: the program may be linked anywhere
	   in the address space, the text segment must be less than 2G bytes, and data segment
	   must be within 2G of the text segment.  Pointers are 64 bits.

       -mcmodel=embmedany
	   Generate code for the Medium/Anywhere code model for embedded systems: assume a 32-bit
	   text and a 32-bit data segment, both starting anywhere (determined at link time).
	   Register %g4 points to the base of the data segment.  Pointers are still 64 bits.
	   Programs are statically linked, PIC is not supported.

       -mstack-bias
       -mno-stack-bias
	   With -mstack-bias, GCC assumes that the stack pointer, and frame pointer if present,
	   are offset by -2047 which must be added back when making stack frame references.  Oth-
	   erwise, assume no such offset is present.

       Convex Options

       These -m options are defined for Convex:

       -mc1
	   Generate output for C1.  The code will run on any Convex machine.  The preprocessor
	   symbol "__convex__c1__" is defined.

       -mc2
	   Generate output for C2.  Uses instructions not available on C1.  Scheduling and other
	   optimizations are chosen for max performance on C2.	The preprocessor symbol "__con-
	   vex_c2__" is defined.

       -mc32
	   Generate output for C32xx.  Uses instructions not available on C1.  Scheduling and
	   other optimizations are chosen for max performance on C32.  The preprocessor symbol
	   "__convex_c32__" is defined.

       -mc34
	   Generate output for C34xx.  Uses instructions not available on C1.  Scheduling and
	   other optimizations are chosen for max performance on C34.  The preprocessor symbol
	   "__convex_c34__" is defined.

       -mc38
	   Generate output for C38xx.  Uses instructions not available on C1.  Scheduling and
	   other optimizations are chosen for max performance on C38.  The preprocessor symbol
	   "__convex_c38__" is defined.

       -margcount
	   Generate code which puts an argument count in the word preceding each argument list.
	   This is compatible with regular CC, and a few programs may need the argument count
	   word.  GDB and other source-level debuggers do not need it; this info is in the symbol
	   table.

       -mnoargcount
	   Omit the argument count word.  This is the default.

       -mvolatile-cache
	   Allow volatile references to be cached.  This is the default.

       -mvolatile-nocache
	   Volatile references bypass the data cache, going all the way to memory.  This is only
	   needed for multi-processor code that does not use standard synchronization instruc-
	   tions.  Making non-volatile references to volatile locations will not necessarily
	   work.

       -mlong32
	   Type long is 32 bits, the same as type int.	This is the default.

       -mlong64
	   Type long is 64 bits, the same as type long long.  This option is useless, because no
	   library support exists for it.

       AMD29K Options

       These -m options are defined for the AMD Am29000:

       -mdw
	   Generate code that assumes the "DW" bit is set, i.e., that byte and halfword opera-
	   tions are directly supported by the hardware.  This is the default.

       -mndw
	   Generate code that assumes the "DW" bit is not set.

       -mbw
	   Generate code that assumes the system supports byte and halfword write operations.
	   This is the default.

       -mnbw
	   Generate code that assumes the systems does not support byte and halfword write opera-
	   tions.  -mnbw implies -mndw.

       -msmall
	   Use a small memory model that assumes that all function addresses are either within a
	   single 256 KB segment or at an absolute address of less than 256k.  This allows the
	   "call" instruction to be used instead of a "const", "consth", "calli" sequence.

       -mnormal
	   Use the normal memory model: Generate "call" instructions only when calling functions
	   in the same file and "calli" instructions otherwise.  This works if each file occupies
	   less than 256 KB but allows the entire executable to be larger than 256 KB.	This is
	   the default.

       -mlarge
	   Always use "calli" instructions.  Specify this option if you expect a single file to
	   compile into more than 256 KB of code.

       -m29050
	   Generate code for the Am29050.

       -m29000
	   Generate code for the Am29000.  This is the default.

       -mkernel-registers
	   Generate references to registers "gr64-gr95" instead of to registers "gr96-gr127".
	   This option can be used when compiling kernel code that wants a set of global regis-
	   ters disjoint from that used by user-mode code.

	   Note that when this option is used, register names in -f flags must use the normal,
	   user-mode, names.

       -muser-registers
	   Use the normal set of global registers, "gr96-gr127".  This is the default.

       -mstack-check
       -mno-stack-check
	   Insert (or do not insert) a call to "__msp_check" after each stack adjustment.  This
	   is often used for kernel code.

       -mstorem-bug
       -mno-storem-bug
	   -mstorem-bug handles 29k processors which cannot handle the separation of a mtsrim
	   insn and a storem instruction (most 29000 chips to date, but not the 29050).

       -mno-reuse-arg-regs
       -mreuse-arg-regs
	   -mno-reuse-arg-regs tells the compiler to only use incoming argument registers for
	   copying out arguments.  This helps detect calling a function with fewer arguments than
	   it was declared with.

       -mno-impure-text
       -mimpure-text
	   -mimpure-text, used in addition to -shared, tells the compiler to not pass -assert
	   pure-text to the linker when linking a shared object.

       -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 com-
	   piler 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.

       -mno-multm
	   Do not generate multm or multmu instructions.  This is useful for some embedded sys-
	   tems which do not have trap handlers for these instructions.

       ARM Options

       These -m options are defined for Advanced RISC Machines (ARM) architectures:

       -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-26
	   Generate code for a processor running with a 26-bit program counter, and conforming to
	   the function calling standards for the APCS 26-bit option.  This option replaces the
	   -m2 and -m3 options of previous releases of the compiler.

       -mapcs-32
	   Generate code for a processor running with a 32-bit program counter, and conforming to
	   the function calling standards for the APCS 32-bit option.  This option replaces the
	   -m6 option of previous releases of the compiler.

       -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 pro-
	   gram.  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 func-
	   tions 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-compi-
	   lation.  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.

       -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 com-
	   patibility with code for big-endian ARM processors generated by versions of the com-
	   piler prior to 2.8.

       -malignment-traps
	   Generate code that will not trap if the MMU has alignment traps enabled.  On ARM
	   architectures prior to ARMv4, there were no instructions to access half-word objects
	   stored in memory.  However, when reading from memory a feature of the ARM architecture
	   allows a word load to be used, even if the address is unaligned, and the processor
	   core will rotate the data as it is being loaded.  This option tells the compiler that
	   such misaligned accesses will cause a MMU trap and that it should instead synthesise
	   the access as a series of byte accesses.  The compiler can still use word accesses to
	   load half-word data if it knows that the address is aligned to a word boundary.

	   This option is ignored when compiling for ARM architecture 4 or later, since these
	   processors have instructions to directly access half-word objects in memory.

       -mno-alignment-traps
	   Generate code that assumes that the MMU will not trap unaligned accesses.  This pro-
	   duces better code when the target instruction set does not have half-word memory oper-
	   ations (i.e. implementations prior to ARMv4).

	   Note that you cannot use this option to access unaligned word objects, since the pro-
	   cessor will only fetch one 32-bit aligned object from memory.

	   The default setting for most targets is -mno-alignment-traps, since this produces bet-
	   ter code when there are no half-word memory instructions available.

       -mshort-load-bytes
       -mno-short-load-words
	   These are deprecated aliases for -malignment-traps.

       -mno-short-load-bytes
       -mshort-load-words
	   This are deprecated aliases for -mno-alignment-traps.

       -mbsd
	   This option only applies to RISC iX.  Emulate the native BSD-mode compiler.	This is
	   the default if -ansi is not specified.

       -mxopen
	   This option only applies to RISC iX.  Emulate the native X/Open-mode compiler.

       -mno-symrename
	   This option only applies to RISC iX.  Do not run the assembler post-processor, symre-
	   name, after code has been assembled.  Normally it is necessary to modify some of the
	   standard symbols in preparation for linking with the RISC iX C library; this option
	   suppresses this pass.  The post-processor is never run when the compiler is built for
	   cross-compilation.

       -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, arm8, strongarm, strongarm110, strongarm1100, arm8,
	   arm810, arm9, arm9e, arm920, arm920t, arm940t, arm9tdmi, arm10tdmi, arm1020t, xscale.

       -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 implementa-
	   tions 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 deter-
	   mine 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.

       -mfpe=number
       -mfp=number
	   This specifies the version of the floating point emulation available on the target.
	   Permissible values are 2 and 3.  -mfp= is a synonym for -mfpe=, for compatibility with
	   older versions of GCC.

       -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 and 32.  The default value
	   varies for different toolchains.  For the COFF targeted toolchain the default value is
	   8.  Specifying the larger number can produce faster, more efficient code, but can also
	   increase the size of the program.  The two values are potentially incompatible.  Code
	   compiled with one value cannot necessarily expect to work with code or libraries com-
	   piled with the other 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 func-
	   tion 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 defi-
	   nitions, functions with the long-call attribute or the section attribute, and func-
	   tions 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 gen-
	   erates 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.

       -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 func-
	   tions.)  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.

       MN10200 Options

       These -m options are defined for Matsushita MN10200 architectures:

       -mrelax
	   Indicate to the linker that it should perform a relaxation optimization pass to
	   shorten branches, calls and absolute memory addresses.  This option only has an effect
	   when used on the command line for the final link step.

	   This option makes symbolic debugging impossible.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
	   Generate code to avoid bugs in the multiply instructions for the MN10300 processors.
	   This is the default.

       -mno-mult-bug
	   Do not generate code to avoid bugs in the multiply instructions for the MN10300 pro-
	   cessors.

       -mam33
	   Generate code which uses features specific to the AM33 processor.

       -mno-am33
	   Do not generate code which uses features specific to the AM33 processor.  This is the
	   default.

       -mno-crt0
	   Do not link in the C run-time initialization object file.

       -mrelax
	   Indicate to the linker that it should perform a relaxation optimization pass to
	   shorten branches, calls and absolute memory addresses.  This option only has an effect
	   when used on the command line for the final link step.

	   This option makes symbolic debugging impossible.

       M32R/D Options

       These -m options are defined for Mitsubishi M32R/D architectures:

       -m32rx
	   Generate code for the M32R/X.

       -m32r
	   Generate code for the M32R.	This is the default.

       -mcode-model=small
	   Assume all objects live in the lower 16MB of memory (so that their addresses can be
	   loaded with the "ld24" instruction), and assume all subroutines are reachable with the
	   "bl" instruction.  This is the default.

	   The addressability of a particular object can be set with the "model" attribute.

       -mcode-model=medium
	   Assume objects may be anywhere in the 32-bit address space (the compiler will generate
	   "seth/add3" instructions to load their addresses), and assume all subroutines are
	   reachable with the "bl" instruction.

       -mcode-model=large
	   Assume objects may be anywhere in the 32-bit address space (the compiler will generate
	   "seth/add3" instructions to load their addresses), and assume subroutines may not be
	   reachable with the "bl" instruction (the compiler will generate the much slower
	   "seth/add3/jl" instruction sequence).

       -msdata=none
	   Disable use of the small data area.	Variables will be put into one of .data, bss, or
	   .rodata (unless the "section" attribute has been specified).  This is the default.

	   The small data area consists of sections .sdata and .sbss.  Objects may be explicitly
	   put in the small data area with the "section" attribute using one of these sections.

       -msdata=sdata
	   Put small global and static data in the small data area, but do not generate special
	   code to reference them.

       -msdata=use
	   Put small global and static data in the small data area, and generate special instruc-
	   tions to reference them.

       -G num
	   Put global and static objects less than or equal to num bytes into the small data or
	   bss sections instead of the normal data or bss sections.  The default value of num is
	   8.  The -msdata option must be set to one of sdata or use for this option to have any
	   effect.

	   All modules should be compiled with the same -G num value.  Compiling with different
	   values of num may or may not work; if it doesn't the linker will give an error mes-
	   sage---incorrect code will not be generated.

       M88K Options

       These -m options are defined for Motorola 88k architectures:

       -m88000
	   Generate code that works well on both the m88100 and the m88110.

       -m88100
	   Generate code that works best for the m88100, but that also runs on the m88110.

       -m88110
	   Generate code that works best for the m88110, and may not run on the m88100.

       -mbig-pic
	   Obsolete option to be removed from the next revision.  Use -fPIC.

       -midentify-revision
	   Include an "ident" directive in the assembler output recording the source file name,
	   compiler name and version, timestamp, and compilation flags used.

       -mno-underscores
	   In assembler output, emit symbol names without adding an underscore character at the
	   beginning of each name.  The default is to use an underscore as prefix on each name.

       -mocs-debug-info
       -mno-ocs-debug-info
	   Include (or omit) additional debugging information (about registers used in each stack
	   frame) as specified in the 88open Object Compatibility Standard, ``OCS''.  This extra
	   information allows debugging of code that has had the frame pointer eliminated.  The
	   default for DG/UX, SVr4, and Delta 88 SVr3.2 is to include this information; other 88k
	   configurations omit this information by default.

       -mocs-frame-position
	   When emitting COFF debugging information for automatic variables and parameters stored
	   on the stack, use the offset from the canonical frame address, which is the stack
	   pointer (register 31) on entry to the function.  The DG/UX, SVr4, Delta88 SVr3.2, and
	   BCS configurations use -mocs-frame-position; other 88k configurations have the default
	   -mno-ocs-frame-position.

       -mno-ocs-frame-position
	   When emitting COFF debugging information for automatic variables and parameters stored
	   on the stack, use the offset from the frame pointer register (register 30).	When this
	   option is in effect, the frame pointer is not eliminated when debugging information is
	   selected by the -g switch.

       -moptimize-arg-area
	   Save space by reorganizing the stack frame.	This option generates code that does not
	   agree with the 88open specifications, but uses less memory.

       -mno-optimize-arg-area
	   Do not reorganize the stack frame to save space.  This is the default.  The generated
	   conforms to the specification, but uses more memory.

       -mshort-data-num
	   Generate smaller data references by making them relative to "r0", which allows loading
	   a value using a single instruction (rather than the usual two).  You control which
	   data references are affected by specifying num with this option.  For example, if you
	   specify -mshort-data-512, then the data references affected are those involving dis-
	   placements of less than 512 bytes.  -mshort-data-num is not effective for num greater
	   than 64k.

       -mserialize-volatile
       -mno-serialize-volatile
	   Do, or don't, generate code to guarantee sequential consistency of volatile memory
	   references.	By default, consistency is guaranteed.

	   The order of memory references made by the MC88110 processor does not always match the
	   order of the instructions requesting those references.  In particular, a load instruc-
	   tion may execute before a preceding store instruction.  Such reordering violates
	   sequential consistency of volatile memory references, when there are multiple proces-
	   sors.   When consistency must be guaranteed, GCC generates special instructions, as
	   needed, to force execution in the proper order.

	   The MC88100 processor does not reorder memory references and so always provides
	   sequential consistency.  However, by default, GCC generates the special instructions
	   to guarantee consistency even when you use -m88100, so that the code may be run on an
	   MC88110 processor.  If you intend to run your code only on the MC88100 processor, you
	   may use -mno-serialize-volatile.

	   The extra code generated to guarantee consistency may affect the performance of your
	   application.  If you know that you can safely forgo this guarantee, you may use
	   -mno-serialize-volatile.

       -msvr4
       -msvr3
	   Turn on (-msvr4) or off (-msvr3) compiler extensions related to System V release 4
	   (SVr4).  This controls the following:

	   1.  Which variant of the assembler syntax to emit.

	   2.  -msvr4 makes the C preprocessor recognize #pragma weak that is used on System V
	       release 4.

	   3.  -msvr4 makes GCC issue additional declaration directives used in SVr4.

	   -msvr4 is the default for the m88k-motorola-sysv4 and m88k-dg-dgux m88k configura-
	   tions.  -msvr3 is the default for all other m88k configurations.

       -mversion-03.00
	   This option is obsolete, and is ignored.

       -mno-check-zero-division
       -mcheck-zero-division
	   Do, or don't, generate code to guarantee that integer division by zero will be
	   detected.  By default, detection is guaranteed.

	   Some models of the MC88100 processor fail to trap upon integer division by zero under
	   certain conditions.	By default, when compiling code that might be run on such a pro-
	   cessor, GCC generates code that explicitly checks for zero-valued divisors and traps
	   with exception number 503 when one is detected.  Use of -mno-check-zero-division sup-
	   presses such checking for code generated to run on an MC88100 processor.

	   GCC assumes that the MC88110 processor correctly detects all instances of integer
	   division by zero.  When -m88110 is specified, no explicit checks for zero-valued divi-
	   sors are generated, and both -mcheck-zero-division and -mno-check-zero-division are
	   ignored.

       -muse-div-instruction
	   Use the div instruction for signed integer division on the MC88100 processor.  By
	   default, the div instruction is not used.

	   On the MC88100 processor the signed integer division instruction div) traps to the
	   operating system on a negative operand.  The operating system transparently completes
	   the operation, but at a large cost in execution time.  By default, when compiling code
	   that might be run on an MC88100 processor, GCC emulates signed integer division using
	   the unsigned integer division instruction divu), thereby avoiding the large penalty of
	   a trap to the operating system.  Such emulation has its own, smaller, execution cost
	   in both time and space.  To the extent that your code's important signed integer divi-
	   sion operations are performed on two nonnegative operands, it may be desirable to use
	   the div instruction directly.

	   On the MC88110 processor the div instruction (also known as the divs instruction) pro-
	   cesses negative operands without trapping to the operating system.  When -m88110 is
	   specified, -muse-div-instruction is ignored, and the div instruction is used for
	   signed integer division.

	   Note that the result of dividing "INT_MIN" by -1 is undefined.  In particular, the
	   behavior of such a division with and without -muse-div-instruction may differ.

       -mtrap-large-shift
       -mhandle-large-shift
	   Include code to detect bit-shifts of more than 31 bits; respectively, trap such shifts
	   or emit code to handle them properly.  By default GCC makes no special provision for
	   large bit shifts.

       -mwarn-passed-structs
	   Warn when a function passes a struct as an argument or result.  Structure-passing con-
	   ventions have changed during the evolution of the C language, and are often the source
	   of portability problems.  By default, GCC issues no such warning.

       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
	   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 Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and the IBM 4xx 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 support-
	   ing 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 recom-
	   mend 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 -mpow-
	   erpc and also allows GCC to use the optional PowerPC architecture instructions in the
	   General Purpose group, including floating-point square root.  Specifying -mpow-
	   erpc-gfxopt implies -mpowerpc and also allows GCC to use the optional PowerPC archi-
	   tecture instructions in the Graphics group, including floating-point select.

	   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 rios, rios1,
	   rsc, rios2, rs64a, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400, 7450, 750,
	   power, power2, powerpc, 403, 505, 801, 821, 823, and 860 and common.

	   -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 other -m options as follows:

	   common
	       -mno-power, -mno-powerc

	   power
	   power2
	   rios1
	   rios2
	   rsc -mpower, -mno-powerpc, -mno-new-mnemonics

	   powerpc
	   rs64a
	   602
	   603
	   603e
	   604
	   620
	   630
	   740
	   7400
	   7450
	   750
	   505 -mno-power, -mpowerpc, -mnew-mnemonics

	   601 -mpower, -mpowerpc, -mnew-mnemonics

	   403
	   821
	   860 -mno-power, -mpowerpc, -mnew-mnemonics, -msoft-float

       -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.

       -maltivec
       -mno-altivec
	   These switches enable or disable the use of built-in functions that allow access to
	   the AltiVec instruction set.  You may also need to set -mabi=altivec to adjust the
	   current ABI with AltiVec ABI enhancements.

       -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 exe-
	   cutable 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 con-
	   stants 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-call
       -mno-xl-call
	   On AIX, pass floating-point arguments to prototyped functions beyond the register save
	   area (RSA) on the stack in addition to argument FPRs.  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.
	   AIX 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 AIX
	   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 sys-
	   tem 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.

       -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.

       -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 instruc-
	   tions 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 instruc-
	   tions 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.

       -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 mod-
	   ule, all objects linked together must be compiled with -mrelocatable or -mrelocat-
	   able-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 -mrelocat-
	   able-lib can be linked with either modules compiled without -mrelocatable and -mrelo-
	   catable-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.

       -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 pow-
	   erpc-*-eabiaix.

       -mcall-sysv-eabi
	   Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
	   Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aix
	   On System V.4 and embedded PowerPC systems compile code using calling conventions that
	   are similar to those used on AIX.  This is the default if you configured GCC using
	   powerpc-*-eabiaix.

       -mcall-solaris
	   On System V.4 and embedded PowerPC systems compile code for the Solaris operating sys-
	   tem.

       -mcall-linux
	   On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU sys-
	   tem.

       -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 sys-
	   tem.

       -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=altivec
	   Extend the current ABI with AltiVec ABI extensions.	This does not change the default
	   ABI, instead it adds the AltiVec ABI extensions to the current ABI.

       -mabi=no-altivec
	   Disable AltiVec ABI extensions for the current ABI.

       -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 reg-
	   isters 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 pow-
	   erpc-*-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.

       -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 Applica-
	   tions Binary Interface (eabi) which is a set of modifications to the System V.4 speci-
	   fications.  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 config-
	   ured 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 incom-
	   patible 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 and static data in the
	   .sdata section.  Put small uninitialized global and static 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.

       -pthread
	   Adds support for multithreading with the pthreads library.  This option sets flags for
	   both the preprocessor and linker.

       IBM RT Options

       These -m options are defined for the IBM RT PC:

       -min-line-mul
	   Use an in-line code sequence for integer multiplies.  This is the default.

       -mcall-lib-mul
	   Call "lmul$$" for integer multiples.

       -mfull-fp-blocks
	   Generate full-size floating point data blocks, including the minimum amount of scratch
	   space recommended by IBM.  This is the default.

       -mminimum-fp-blocks
	   Do not include extra scratch space in floating point data blocks.  This results in
	   smaller code, but slower execution, since scratch space must be allocated dynamically.

       -mfp-arg-in-fpregs
	   Use a calling sequence incompatible with the IBM calling convention in which floating
	   point arguments are passed in floating point registers.  Note that "varargs.h" and
	   "stdarg.h" will not work with floating point operands if this option is specified.

       -mfp-arg-in-gregs
	   Use the normal calling convention for floating point arguments.  This is the default.

       -mhc-struct-return
	   Return structures of more than one word in memory, rather than in a register.  This
	   provides compatibility with the MetaWare HighC (hc) compiler.  Use the option
	   -fpcc-struct-return for compatibility with the Portable C Compiler (pcc).

       -mnohc-struct-return
	   Return some structures of more than one word in registers, when convenient.	This is
	   the default.  For compatibility with the IBM-supplied compilers, use the option
	   -fpcc-struct-return or the option -mhc-struct-return.

       MIPS Options

       These -m options are defined for the MIPS family of computers:

       -march=cpu-type
	   Assume the defaults for the machine type cpu-type when generating instructions.  The
	   choices for cpu-type are  r2000, r3000, r3900, r4000, r4100, r4300, r4400, r4600,
	   r4650, r5000, r6000, r8000, and orion.  Additionally, the r2000, r3000, r4000, r5000,
	   and r6000 can be abbreviated as r2k (or r2K), r3k, etc.

       -mtune=cpu-type
	   Assume the defaults for the machine type cpu-type when scheduling instructions.  The
	   choices for cpu-type are r2000, r3000, r3900, r4000, r4100, r4300, r4400, r4600,
	   r4650, r5000, r6000, r8000, and orion.  Additionally, the r2000, r3000, r4000, r5000,
	   and r6000 can be abbreviated as r2k (or r2K), r3k, etc.  While picking a specific cpu-
	   type will schedule things appropriately for that particular chip, the compiler will
	   not generate any code that does not meet level 1 of the MIPS ISA (instruction set
	   architecture) without a -mipsX or -mabi switch being used.

       -mcpu=cpu-type
	   This is identical to specifying both -march and -mtune.

       -mips1
	   Issue instructions from level 1 of the MIPS ISA.  This is the default.  r3000 is the
	   default cpu-type at this ISA level.

       -mips2
	   Issue instructions from level 2 of the MIPS ISA (branch likely, square root instruc-
	   tions).  r6000 is the default cpu-type at this ISA level.

       -mips3
	   Issue instructions from level 3 of the MIPS ISA (64-bit instructions).  r4000 is the
	   default cpu-type at this ISA level.

       -mips4
	   Issue instructions from level 4 of the MIPS ISA (conditional move, prefetch, enhanced
	   FPU instructions).  r8000 is the default cpu-type at this ISA level.

       -mfp32
	   Assume that 32 32-bit floating point registers are available.  This is the default.

       -mfp64
	   Assume that 32 64-bit floating point registers are available.  This is the default
	   when the -mips3 option is used.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating point multiply and accumulate
	   instructions, when they are available.  These instructions are generated by default if
	   they are available, but this may be undesirable if the extra precision causes problems
	   or on certain chips in the mode where denormals are rounded to zero where denormals
	   generated by multiply and accumulate instructions cause exceptions anyway.

       -mgp32
	   Assume that 32 32-bit general purpose registers are available.  This is the default.

       -mgp64
	   Assume that 32 64-bit general purpose registers are available.  This is the default
	   when the -mips3 option is used.

       -mint64
	   Force int and long types to be 64 bits wide.  See -mlong32 for an explanation of the
	   default, and the width of pointers.

       -mlong64
	   Force long types to be 64 bits wide.  See -mlong32 for an explanation of the default,
	   and the width of pointers.

       -mlong32
	   Force long, int, and pointer types to be 32 bits wide.

	   If none of -mlong32, -mlong64, or -mint64 are set, the size of ints, longs, and point-
	   ers depends on the ABI and ISA chosen.  For -mabi=32, and -mabi=n32, ints and longs
	   are 32 bits wide.  For -mabi=64, ints are 32 bits, and longs are 64 bits wide.  For
	   -mabi=eabi and either -mips1 or -mips2, ints and longs are 32 bits wide.  For
	   -mabi=eabi and higher ISAs, ints are 32 bits, and longs are 64 bits wide.  The width
	   of pointer types is the smaller of the width of longs or the width of general purpose
	   registers (which in turn depends on the ISA).

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
	   Generate code for the indicated ABI.  The default instruction level is -mips1 for 32,
	   -mips3 for n32, and -mips4 otherwise.  Conversely, with -mips1 or -mips2, the default
	   ABI is 32; otherwise, the default ABI is 64.

       -mmips-as
	   Generate code for the MIPS assembler, and invoke mips-tfile to add normal debug infor-
	   mation.  This is the default for all platforms except for the OSF/1 reference plat-
	   form, using the OSF/rose object format.  If the either of the -gstabs or -gstabs+
	   switches are used, the mips-tfile program will encapsulate the stabs within MIPS
	   ECOFF.

       -mgas
	   Generate code for the GNU assembler.  This is the default on the OSF/1 reference plat-
	   form, using the OSF/rose object format.  Also, this is the default if the configure
	   option --with-gnu-as is used.

       -msplit-addresses
       -mno-split-addresses
	   Generate code to load the high and low parts of address constants separately.  This
	   allows GCC to optimize away redundant loads of the high order bits of addresses.  This
	   optimization requires GNU as and GNU ld.  This optimization is enabled by default for
	   some embedded targets where GNU as and GNU ld are standard.

       -mrnames
       -mno-rnames
	   The -mrnames switch says to output code using the MIPS software names for the regis-
	   ters, instead of the hardware names (ie, a0 instead of $4).	The only known assembler
	   that supports this option is the Algorithmics assembler.

       -mgpopt
       -mno-gpopt
	   The -mgpopt switch says to write all of the data declarations before the instructions
	   in the text section, this allows the MIPS assembler to generate one word memory refer-
	   ences instead of using two words for short global or static data items.  This is on by
	   default if optimization is selected.

       -mstats
       -mno-stats
	   For each non-inline function processed, the -mstats switch causes the compiler to emit
	   one line to the standard error file to print statistics about the program (number of
	   registers saved, stack size, etc.).

       -mmemcpy
       -mno-memcpy
	   The -mmemcpy switch makes all block moves call the appropriate string function (memcpy
	   or bcopy) instead of possibly generating inline code.

       -mmips-tfile
       -mno-mips-tfile
	   The -mno-mips-tfile switch causes the compiler not postprocess the object file with
	   the mips-tfile program, after the MIPS assembler has generated it to add debug sup-
	   port.  If mips-tfile is not run, then no local variables will be available to the
	   debugger.  In addition, stage2 and stage3 objects will have the temporary file names
	   passed to the assembler embedded in the object file, which means the objects will not
	   compare the same.  The -mno-mips-tfile switch should only be used when there are bugs
	   in the mips-tfile program that prevents compilation.

       -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 com-
	   piler 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.

       -mhard-float
	   Generate output containing floating point instructions.  This is the default if you
	   use the unmodified sources.

       -mabicalls
       -mno-abicalls
	   Emit (or do not emit) the pseudo operations .abicalls, .cpload, and .cprestore that
	   some System V.4 ports use for position independent code.

       -mlong-calls
       -mno-long-calls
	   Do all calls with the JALR instruction, which requires loading up a function's address
	   into a register before the call.  You need to use this switch, if you call outside of
	   the current 512 megabyte segment to functions that are not through pointers.

       -mhalf-pic
       -mno-half-pic
	   Put pointers to extern references into the data section and load them up, rather than
	   put the references in the text section.

       -membedded-pic
       -mno-embedded-pic
	   Generate PIC code suitable for some embedded systems.  All calls are made using PC
	   relative address, and all data is addressed using the $gp register.	No more than
	   65536 bytes of global data may be used.  This requires GNU as and GNU ld which do most
	   of the work.  This currently only works on targets which use ECOFF; it does not work
	   with ELF.

       -membedded-data
       -mno-embedded-data
	   Allocate variables to the read-only data section first if possible, then next in the
	   small data section if possible, otherwise in data.  This gives slightly slower code
	   than the default, but reduces the amount of RAM required when executing, and thus may
	   be preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
	   When used together with -membedded-data, it will always store uninitialized const
	   variables in the read-only data section.

       -msingle-float
       -mdouble-float
	   The -msingle-float switch tells gcc to assume that the floating point coprocessor only
	   supports single precision operations, as on the r4650 chip.	The -mdouble-float switch
	   permits gcc to use double precision operations.  This is the default.

       -mmad
       -mno-mad
	   Permit use of the mad, madu and mul instructions, as on the r4650 chip.

       -m4650
	   Turns on -msingle-float, -mmad, and, at least for now, -mcpu=r4650.

       -mips16
       -mno-mips16
	   Enable 16-bit instructions.

       -mentry
	   Use the entry and exit pseudo ops.  This option can only be used with -mips16.

       -EL Compile code for the processor in little endian mode.  The requisite libraries are
	   assumed to exist.

       -EB Compile code for the processor in big endian mode.  The requisite libraries are
	   assumed to exist.

       -G num
	   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.	This allows the assembler to emit
	   one word memory reference instructions based on the global pointer (gp or $28),
	   instead of the normal two words used.  By default, num is 8 when the MIPS assembler is
	   used, and 0 when the GNU assembler is used.	The -G num switch is also passed to the
	   assembler and linker.  All modules should be compiled with the same -G num value.

       -nocpp
	   Tell the MIPS assembler to not run its preprocessor over user assembler files (with a
	   .s suffix) when assembling them.

       -mfix7000
	   Pass an option to gas which will cause nops to be inserted if the read of the destina-
	   tion register of an mfhi or mflo instruction occurs in the following two instructions.

       -no-crt0
	   Do not include the default crt0.

       -mflush-func=func
       -mno-flush-func
	   Specifies the function to call to flush the I and D caches, or to not call any such
	   function.  If called, the function must take the same arguments as the common
	   "_flush_func()", that is, the address of the memory range for which the cache is being
	   flushed, the size of the memory range, and the number 3 (to flush both caches).  The
	   default depends on the target gcc was configured for, but commonly is either
	   _flush_func or __cpu_flush.

       These options are defined by the macro "TARGET_SWITCHES" in the machine description.  The
       default for the options is also defined by that macro, which enables you to change the
       defaults.

       Intel 386 and AMD x86-64 Options

       These -m options are defined for the i386 and x86-64 family of computers:

       -mcpu=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 i386, i486, i586,
	   i686, pentium, pentium-mmx, pentiumpro, pentium2, pentium3, pentium4, k6, k6-2, k6-3,
	   athlon, athlon-tbird, athlon-4, athlon-xp and athlon-mp.

	   While picking a specific cpu-type will schedule things appropriately for that particu-
	   lar chip, the compiler will not generate any code that does not run on the i386 with-
	   out the -march=cpu-type option being used.  i586 is equivalent to pentium and i686 is
	   equivalent to pentiumpro.  k6 and athlon are the AMD chips as opposed to the Intel
	   ones.

       -march=cpu-type
	   Generate instructions for the machine type cpu-type.  The choices for cpu-type are the
	   same as for -mcpu.  Moreover, specifying -march=cpu-type implies -mcpu=cpu-type.

       -m386
       -m486
       -mpentium
       -mpentiumpro
	   These options are synonyms for -mcpu=i386, -mcpu=i486, -mcpu=pentium, and -mcpu=pen-
	   tiumpro 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 emu-
	       lated otherwise.  Code compiled with this option will run almost everywhere.  The
	       temporary results are computed in 80bit precesion 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 pre-
	       cision arithmetics is still done using 387.  Later version, present only in Pen-
	       tium4 and the future AMD x86-64 chips supports double precision arithmetics too.

	       For i387 you need to use -march=cpu-type, -msse or -msse2 switches to enable SSE
	       extensions and make this option effective.  For x86-64 compiler, these extensions
	       are enabled by default.

	       The resulting code should be considerably faster in 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 x86-64 compiler.

	   sse,387
	       Attempt to utilize both instruction sets at once.  This effectivly 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 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).

       -mieee-fp
       -mno-ieee-fp
	   Control whether or not the compiler uses IEEE floating point comparisons.  These han-
	   dle 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 com-
	   piler 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 regis-
	   ters 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 indi-
	   cates 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.

	   Warning: if you use the -malign-double switch, structures containing the above types
	   will be aligned differently than the published application binary interface specifica-
	   tions for the 386 and will not be binary compatible with structures in code compiled
	   without that switch.

       -m128bit-long-double
	   Control the size of "long double" type. i386 application binary interface specify the
	   size to be 12 bytes, while modern architectures (Pentium and newer) prefer "long dou-
	   ble" aligned to 8 or 16 byte boundary.  This is impossible to reach with 12 byte long
	   doubles in the array accesses.

	   Warning: if you use the -m128bit-long-double switch, the structures and arrays con-
	   taining "long double" will change their size as well as function calling convention
	   for function taking "long double" will be modified.

       -m96bit-long-double
	   Set the size of "long double" to 96 bits as required by the i386 application binary
	   interface.  This is the default.

       -msvr3-shlib
       -mno-svr3-shlib
	   Control whether GCC places uninitialized local variables into the "bss" or "data" seg-
	   ments.  -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 num-
	   ber 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 num-
	   bers 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 regis-
	   ters 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.

       -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),
	   except when optimizing for code size (-Os), in which case the default is the minimum
	   correct alignment (4 bytes for x86, and 8 bytes for x86-64).

	   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 penal-
	   ties.  On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" suffers
	   similar penalties 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 com-
	   piled 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 oper-
	   ating system kernels, may want to reduce the preferred alignment to -mpre-
	   ferred-stack-boundary=2.

       -mmmx
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -m3dnow
       -mno-3dnow
	   These switches enable or disable the use of built-in functions that allow direct
	   access to the MMX, SSE and 3Dnow extensions of the instruction set.

	   To have SSE/SSE2 instructions generated automatically from floating-point code, see
	   -mfpmath=sse.

       -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 com-
	   puted in the function prologue.  This is faster on most modern CPUs because of reduced
	   dependencies, improved scheduling and reduced stack usage when preferred stack bound-
	   ary 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 don'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.

       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.

       -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 tempo-
	   rary 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 stati-
	   cally 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 sup-
	   ported 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.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
	   Generate code for the specified architecture.  The choices for architecture-type are
	   1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA 2.0 processors.  Refer to
	   /usr/lib/sched.models on an HP-UX system to determine the proper architecture option
	   for your machine.  Code compiled for lower numbered architectures will run on higher
	   numbered architectures, but not the other way around.

	   PA 2.0 support currently requires gas snapshot 19990413 or later.  The next release of
	   binutils (current is 2.9.1) will probably contain PA 2.0 support.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
	   Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only if the assem-
	   bler/linker complain about out of range branches within a switch table.

       -mjump-in-delay
	   Fill delay slots of function calls with unconditional jump instructions by modifying
	   the return pointer for the function call to be the target of the conditional jump.

       -mdisable-fpregs
	   Prevent floating point registers from being used in any manner.  This is necessary for
	   compiling kernels which perform lazy context switching of floating point registers.
	   If you use this option and attempt to perform floating point operations, the compiler
	   will abort.

       -mdisable-indexing
	   Prevent the compiler from using indexing address modes.  This avoids some rather
	   obscure problems when compiling MIG generated code under MACH.

       -mno-space-regs
	   Generate code that assumes the target has no space registers.  This allows GCC to gen-
	   erate faster indirect calls and use unscaled index address modes.

	   Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
	   Generate code that assumes calls never cross space boundaries.  This allows GCC to
	   emit code which performs faster indirect calls.

	   This option will not work in the presence of shared libraries or nested functions.

       -mlong-load-store
	   Generate 3-instruction load and store sequences as sometimes required by the HP-UX 10
	   linker.  This is equivalent to the +k option to the HP compilers.

       -mportable-runtime
	   Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
	   Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
	   Schedule code according to the constraints for the machine type cpu-type.  The choices
	   for cpu-type are 700 7100, 7100LC, 7200, and 8000.  Refer to /usr/lib/sched.models on
	   an HP-UX system to determine the proper scheduling option for your machine.

       -mlinker-opt
	   Enable the optimization pass in the HPUX linker.  Note this makes symbolic debugging
	   impossible.	It also triggers a bug in the HPUX 8 and HPUX 9 linkers in which they
	   give bogus error messages when linking some programs.

       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries are not available for all HPPA targets.  Normally the facilities of the
	   machine's usual C compiler are used, but this cannot be done directly in cross-compi-
	   lation.  You must make your own arrangements to provide suitable library functions for
	   cross-compilation.  The embedded target hppa1.1-*-pro does provide software floating
	   point support.

	   -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.

       Intel 960 Options

       These -m options are defined for the Intel 960 implementations:

       -mcpu-type
	   Assume the defaults for the machine type cpu-type for some of the other options,
	   including instruction scheduling, floating point support, and addressing modes.  The
	   choices for cpu-type are ka, kb, mc, ca, cf, sa, and sb.  The default is kb.

       -mnumerics
       -msoft-float
	   The -mnumerics option indicates that the processor does support floating-point
	   instructions.  The -msoft-float option indicates that floating-point support should
	   not be assumed.

       -mleaf-procedures
       -mno-leaf-procedures
	   Do (or do not) attempt to alter leaf procedures to be callable with the "bal" instruc-
	   tion as well as "call".  This will result in more efficient code for explicit calls
	   when the "bal" instruction can be substituted by the assembler or linker, but less
	   efficient code in other cases, such as calls via function pointers, or using a linker
	   that doesn't support this optimization.

       -mtail-call
       -mno-tail-call
	   Do (or do not) make additional attempts (beyond those of the machine-independent por-
	   tions of the compiler) to optimize tail-recursive calls into branches.  You may not
	   want to do this because the detection of cases where this is not valid is not totally
	   complete.  The default is -mno-tail-call.

       -mcomplex-addr
       -mno-complex-addr
	   Assume (or do not assume) that the use of a complex addressing mode is a win on this
	   implementation of the i960.	Complex addressing modes may not be worthwhile on the
	   K-series, but they definitely are on the C-series.  The default is currently -mcom-
	   plex-addr for all processors except the CB and CC.

       -mcode-align
       -mno-code-align
	   Align code to 8-byte boundaries for faster fetching (or don't bother).  Currently
	   turned on by default for C-series implementations only.

       -mic-compat
       -mic2.0-compat
       -mic3.0-compat
	   Enable compatibility with iC960 v2.0 or v3.0.

       -masm-compat
       -mintel-asm
	   Enable compatibility with the iC960 assembler.

       -mstrict-align
       -mno-strict-align
	   Do not permit (do permit) unaligned accesses.

       -mold-align
	   Enable structure-alignment compatibility with Intel's gcc release version 1.3 (based
	   on gcc 1.37).  This option implies -mstrict-align.

       -mlong-double-64
	   Implement type long double as 64-bit floating point numbers.  Without the option long
	   double is implemented by 80-bit floating point numbers.  The only reason we have it
	   because there is no 128-bit long double support in fp-bit.c yet.  So it is only useful
	   for people using soft-float targets.  Otherwise, we should recommend against use of
	   it.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
	   Use (do not use) the hardware floating-point instructions for floating-point opera-
	   tions.  When -msoft-float is specified, functions in libgcc.a will be used to perform
	   floating-point operations.  Unless they are replaced by routines that emulate the
	   floating-point operations, or compiled in such a way as to call such emulations rou-
	   tines, these routines will issue floating-point operations.	 If you are compiling for
	   an Alpha without floating-point operations, you must ensure that the library is built
	   so as not to call them.

	   Note that Alpha implementations without floating-point operations are required to have
	   floating-point registers.

       -mfp-reg
       -mno-fp-regs
	   Generate code that uses (does not use) the floating-point register set.  -mno-fp-regs
	   implies -msoft-float.  If the floating-point register set is not used, floating point
	   operands are passed in integer registers as if they were integers and floating-point
	   results are passed in $0 instead of $f0.  This is a non-standard calling sequence, so
	   any function with a floating-point argument or return value called by code compiled
	   with -mno-fp-regs must also be compiled with that option.

	   A typical use of this option is building a kernel that does not use, and hence need
	   not save and restore, any floating-point registers.

       -mieee
	   The Alpha architecture implements floating-point hardware optimized for maximum per-
	   formance.  It is mostly compliant with the IEEE floating point standard.  However, for
	   full compliance, software assistance is required.  This option generates code fully
	   IEEE compliant code except that the inexact-flag is not maintained (see below).  If
	   this option is turned on, the preprocessor macro "_IEEE_FP" is defined during compila-
	   tion.  The resulting code is less efficient but is able to correctly support denormal-
	   ized numbers and exceptional IEEE values such as not-a-number and plus/minus infinity.
	   Other Alpha compilers call this option -ieee_with_no_inexact.

       -mieee-with-inexact
	   This is like -mieee except the generated code also maintains the IEEE inexact-flag.
	   Turning on this option causes the generated code to implement fully-compliant IEEE
	   math.  In addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
	   On some Alpha implementations the resulting code may execute significantly slower than
	   the code generated by default.  Since there is very little code that depends on the
	   inexact-flag, you should normally not specify this option.  Other Alpha compilers call
	   this option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
	   This option controls what floating-point related traps are enabled.	Other Alpha com-
	   pilers call this option -fptm trap-mode.  The trap mode can be set to one of four val-
	   ues:

	   n   This is the default (normal) setting.  The only traps that are enabled are the
	       ones that cannot be disabled in software (e.g., division by zero trap).

	   u   In addition to the traps enabled by n, underflow traps are enabled as well.

	   su  Like su, but the instructions are marked to be safe for software completion (see
	       Alpha architecture manual for details).

	   sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
	   Selects the IEEE rounding mode.  Other Alpha compilers call this option -fprm round-
	   ing-mode.  The rounding-mode can be one of:

	   n   Normal IEEE rounding mode.  Floating point numbers are rounded towards the nearest
	       machine number or towards the even machine number in case of a tie.

	   m   Round towards minus infinity.

	   c   Chopped rounding mode.  Floating point numbers are rounded towards zero.

	   d   Dynamic rounding mode.  A field in the floating point control register (fpcr, see
	       Alpha architecture reference manual) controls the rounding mode in effect.  The C
	       library initializes this register for rounding towards plus infinity.  Thus,
	       unless your program modifies the fpcr, d corresponds to round towards plus infin-
	       ity.

       -mtrap-precision=trap-precision
	   In the Alpha architecture, floating point traps are imprecise.  This means without
	   software assistance it is impossible to recover from a floating trap and program exe-
	   cution normally needs to be terminated.  GCC can generate code that can assist operat-
	   ing system trap handlers in determining the exact location that caused a floating
	   point trap.	Depending on the requirements of an application, different levels of pre-
	   cisions can be selected:

	   p   Program precision.  This option is the default and means a trap handler can only
	       identify which program caused a floating point exception.

	   f   Function precision.  The trap handler can determine the function that caused a
	       floating point exception.

	   i   Instruction precision.  The trap handler can determine the exact instruction that
	       caused a floating point exception.

	   Other Alpha compilers provide the equivalent options called -scope_safe and -resump-
	   tion_safe.

       -mieee-conformant
	   This option marks the generated code as IEEE conformant.  You must not use this option
	   unless you also specify -mtrap-precision=i and either -mfp-trap-mode=su or
	   -mfp-trap-mode=sui.	Its only effect is to emit the line .eflag 48 in the function
	   prologue of the generated assembly file.  Under DEC Unix, this has the effect that
	   IEEE-conformant math library routines will be linked in.

       -mbuild-constants
	   Normally GCC examines a 32- or 64-bit integer constant to see if it can construct it
	   from smaller constants in two or three instructions.  If it cannot, it will output the
	   constant as a literal and generate code to load it from the data segment at runtime.

	   Use this option to require GCC to construct all integer constants using code, even if
	   it takes more instructions (the maximum is six).

	   You would typically use this option to build a shared library dynamic loader.  Itself
	   a shared library, it must relocate itself in memory before it can find the variables
	   and constants in its own data segment.

       -malpha-as
       -mgas
	   Select whether to generate code to be assembled by the vendor-supplied assembler
	   (-malpha-as) or by the GNU assembler -mgas.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
	   Indicate whether GCC should generate code to use the optional BWX, CIX, FIX and MAX
	   instruction sets.  The default is to use the instruction sets supported by the CPU
	   type specified via -mcpu= option or that of the CPU on which GCC was built if none was
	   specified.

       -mfloat-vax
       -mfloat-ieee
	   Generate code that uses (does not use) VAX F and G floating point arithmetic instead
	   of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Older Alpha assemblers provided no way to generate symbol relocations except via
	   assembler macros.  Use of these macros does not allow optimial instruction scheduling.
	   GNU binutils as of version 2.12 supports a new syntax that allows the compiler to
	   explicitly mark which relocations should apply to which instructions.  This option is
	   mostly useful for debugging, as GCC detects the capabilities of the assembler when it
	   is built and sets the default accordingly.

       -msmall-data
       -mlarge-data
	   When -mexplicit-relocs is in effect, static data is accessed via gp-relative reloca-
	   tions.  When -msmall-data is used, objects 8 bytes long or smaller are placed in a
	   small data area (the ".sdata" and ".sbss" sections) and are accessed via 16-bit relo-
	   cations off of the $gp register.  This limits the size of the small data area to 64KB,
	   but allows the variables to be directly accessed via a single instruction.

	   The default is -mlarge-data.  With this option the data area is limited to just below
	   2GB.  Programs that require more than 2GB of data must use "malloc" or "mmap" to allo-
	   cate the data in the heap instead of in the program's data segment.

	   When generating code for shared libraries, -fpic implies -msmall-data and -fPIC
	   implies -mlarge-data.

       -mcpu=cpu_type
	   Set the instruction set and instruction scheduling parameters for machine type
	   cpu_type.  You can specify either the EV style name or the corresponding chip number.
	   GCC supports scheduling parameters for the EV4, EV5 and EV6 family of processors and
	   will choose the default values for the instruction set from the processor you specify.
	   If you do not specify a processor type, GCC will default to the processor on which the
	   compiler was built.

	   Supported values for cpu_type are

	   ev4
	   ev45
	   21064
	       Schedules as an EV4 and has no instruction set extensions.

	   ev5
	   21164
	       Schedules as an EV5 and has no instruction set extensions.

	   ev56
	   21164a
	       Schedules as an EV5 and supports the BWX extension.

	   pca56
	   21164pc
	   21164PC
	       Schedules as an EV5 and supports the BWX and MAX extensions.

	   ev6
	   21264
	       Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.

	   ev67
	   21264a
	       Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.

       -mtune=cpu_type
	   Set only the instruction scheduling parameters for machine type cpu_type.  The
	   instruction set is not changed.

       -mmemory-latency=time
	   Sets the latency the scheduler should assume for typical memory references as seen by
	   the application.  This number is highly dependent on the memory access patterns used
	   by the application and the size of the external cache on the machine.

	   Valid options for time are

	   number
	       A decimal number representing clock cycles.

	   L1
	   L2
	   L3
	   main
	       The compiler contains estimates of the number of clock cycles for ``typical'' EV4
	       & EV5 hardware for the Level 1, 2 & 3 caches (also called Dcache, Scache, and
	       Bcache), as well as to main memory.  Note that L3 is only valid for EV5.

       DEC Alpha/VMS Options

       These -m options are defined for the DEC Alpha/VMS implementations:

       -mvms-return-codes
	   Return VMS condition codes from main.  The default is to return POSIX style condition
	   (e.g. error) codes.

       Clipper Options

       These -m options are defined for the Clipper implementations:

       -mc300
	   Produce code for a C300 Clipper processor.  This is the default.

       -mc400
	   Produce code for a C400 Clipper processor, i.e. use floating point registers f8--f15.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
	   Shorten some address references at link time, when possible; uses the linker option
	   -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8/S.

       -ms2600
	   Generate code for the H8/S2600.  This switch must be used with -ms.

       -mint32
	   Make "int" data 32 bits by default.

       -malign-300
	   On the H8/300H and H8/S, use the same alignment rules as for the H8/300.  The default
	   for the H8/300H and H8/S is to align longs and floats on 4 byte boundaries.
	   -malign-300 causes them to be aligned on 2 byte boundaries.	This option has no effect
	   on the H8/300.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m3 Generate code for the SH3.

       -m3e
	   Generate code for the SH3e.

       -m4-nofpu
	   Generate code for the SH4 without a floating-point unit.

       -m4-single-only
	   Generate code for the SH4 with a floating-point unit that only supports single-preci-
	   sion arithmetic.

       -m4-single
	   Generate code for the SH4 assuming the floating-point unit is in single-precision mode
	   by default.

       -m4 Generate code for the SH4.

       -mb Compile code for the processor in big endian mode.

       -ml Compile code for the processor in little endian mode.

       -mdalign
	   Align doubles at 64-bit boundaries.	Note that this changes the calling conventions,
	   and thus some functions from the standard C library will not work unless you recompile
	   it first with -mdalign.

       -mrelax
	   Shorten some address references at link time, when possible; uses the linker option
	   -relax.

       -mbigtable
	   Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       -mfmovd
	   Enable the use of the instruction "fmovd".

       -mhitachi
	   Comply with the calling conventions defined by Hitachi.

       -mnomacsave
	   Mark the "MAC" register as call-clobbered, even if -mhitachi is given.

       -mieee
	   Increase IEEE-compliance of floating-point code.

       -misize
	   Dump instruction size and location in the assembly code.

       -mpadstruct
	   This option is deprecated.  It pads structures to multiple of 4 bytes, which is incom-
	   patible with the SH ABI.

       -mspace
	   Optimize for space instead of speed.  Implied by -Os.

       -mprefergot
	   When generating position-independent code, emit function calls using the Global Offset
	   Table instead of the Procedure Linkage Table.

       -musermode
	   Generate a library function call to invalidate instruction cache entries, after fixing
	   up a trampoline.  This library function call doesn't assume it can write to the whole
	   memory address space.  This is the default when the target is "sh-*-linux*".

       Options for System V

       These additional options are available on System V Release 4 for compatibility with other
       compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or -shared be used instead.

       -Qy Identify the versions of each tool used by the compiler, in a ".ident" assembler
	   directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is the default).

       -YP,dirs
	   Search the directories dirs, and no others, for libraries specified with -l.

       -Ym,dir
	   Look in the directory dir to find the M4 preprocessor.  The assembler uses this
	   option.

       TMS320C3x/C4x Options

       These -m options are defined for TMS320C3x/C4x implementations:

       -mcpu=cpu_type
	   Set the instruction set, register set, and instruction scheduling parameters for
	   machine type cpu_type.  Supported values for cpu_type are c30, c31, c32, c40, and c44.
	   The default is c40 to generate code for the TMS320C40.

       -mbig-memory
       -mbig
       -msmall-memory
       -msmall
	   Generates code for the big or small memory model.  The small memory model assumed that
	   all data fits into one 64K word page.  At run-time the data page (DP) register must be
	   set to point to the 64K page containing the .bss and .data program sections.  The big
	   memory model is the default and requires reloading of the DP register for every direct
	   memory access.

       -mbk
       -mno-bk
	   Allow (disallow) allocation of general integer operands into the block count register
	   BK.

       -mdb
       -mno-db
	   Enable (disable) generation of code using decrement and branch, DBcond(D), instruc-
	   tions.  This is enabled by default for the C4x.  To be on the safe side, this is dis-
	   abled for the C3x, since the maximum iteration count on the C3x is 2^{23 + 1} (but who
	   iterates loops more than 2^{23} times on the C3x?).	Note that GCC will try to reverse
	   a loop so that it can utilise the decrement and branch instruction, but will give up
	   if there is more than one memory reference in the loop.  Thus a loop where the loop
	   counter is decremented can generate slightly more efficient code, in cases where the
	   RPTB instruction cannot be utilised.

       -mdp-isr-reload
       -mparanoid
	   Force the DP register to be saved on entry to an interrupt service routine (ISR),
	   reloaded to point to the data section, and restored on exit from the ISR.  This should
	   not be required unless someone has violated the small memory model by modifying the DP
	   register, say within an object library.

       -mmpyi
       -mno-mpyi
	   For the C3x use the 24-bit MPYI instruction for integer multiplies instead of a
	   library call to guarantee 32-bit results.  Note that if one of the operands is a con-
	   stant, then the multiplication will be performed using shifts and adds.  If the -mmpyi
	   option is not specified for the C3x, then squaring operations are performed inline
	   instead of a library call.

       -mfast-fix
       -mno-fast-fix
	   The C3x/C4x FIX instruction to convert a floating point value to an integer value
	   chooses the nearest integer less than or equal to the floating point value rather than
	   to the nearest integer.  Thus if the floating point number is negative, the result
	   will be incorrectly truncated an additional code is necessary to detect and correct
	   this case.  This option can be used to disable generation of the additional code
	   required to correct the result.

       -mrptb
       -mno-rptb
	   Enable (disable) generation of repeat block sequences using the RPTB instruction for
	   zero overhead looping.  The RPTB construct is only used for innermost loops that do
	   not call functions or jump across the loop boundaries.  There is no advantage having
	   nested RPTB loops due to the overhead required to save and restore the RC, RS, and RE
	   registers.  This is enabled by default with -O2.

       -mrpts=count
       -mno-rpts
	   Enable (disable) the use of the single instruction repeat instruction RPTS.	If a
	   repeat block contains a single instruction, and the loop count can be guaranteed to be
	   less than the value count, GCC will emit a RPTS instruction instead of a RPTB.  If no
	   value is specified, then a RPTS will be emitted even if the loop count cannot be
	   determined at compile time.	Note that the repeated instruction following RPTS does
	   not have to be reloaded from memory each iteration, thus freeing up the CPU buses for
	   operands.  However, since interrupts are blocked by this instruction, it is disabled
	   by default.

       -mloop-unsigned
       -mno-loop-unsigned
	   The maximum iteration count when using RPTS and RPTB (and DB on the C40) is 2^{31 + 1}
	   since these instructions test if the iteration count is negative to terminate the
	   loop.  If the iteration count is unsigned there is a possibility than the 2^{31 + 1}
	   maximum iteration count may be exceeded.  This switch allows an unsigned iteration
	   count.

       -mti
	   Try to emit an assembler syntax that the TI assembler (asm30) is happy with.  This
	   also enforces compatibility with the API employed by the TI C3x C compiler.	For exam-
	   ple, long doubles are passed as structures rather than in floating point registers.

       -mregparm
       -mmemparm
	   Generate code that uses registers (stack) for passing arguments to functions.  By
	   default, arguments are passed in registers where possible rather than by pushing argu-
	   ments on to the stack.

       -mparallel-insns
       -mno-parallel-insns
	   Allow the generation of parallel instructions.  This is enabled by default with -O2.

       -mparallel-mpy
       -mno-parallel-mpy
	   Allow the generation of MPY||ADD and MPY||SUB parallel instructions, provided -mparal-
	   lel-insns is also specified.  These instructions have tight register constraints which
	   can pessimize the code generation of large functions.

       V850 Options

       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
	   Treat all calls as being far away (near).  If calls are assumed to be far away, the
	   compiler will always load the functions address up into a register, and call indirect
	   through the pointer.

       -mno-ep
       -mep
	   Do not optimize (do optimize) basic blocks that use the same index pointer 4 or more
	   times to copy pointer into the "ep" register, and use the shorter "sld" and "sst"
	   instructions.  The -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
	   Do not use (do use) external functions to save and restore registers at the prolog and
	   epilog of a function.  The external functions are slower, but use less code space if
	   more than one function saves the same number of registers.  The -mprolog-function
	   option is on by default if you optimize.

       -mspace
	   Try to make the code as small as possible.  At present, this just turns on the -mep
	   and -mprolog-function options.

       -mtda=n
	   Put static or global variables whose size is n bytes or less into the tiny data area
	   that register "ep" points to.  The tiny data area can hold up to 256 bytes in total
	   (128 bytes for byte references).

       -msda=n
	   Put static or global variables whose size is n bytes or less into the small data area
	   that register "gp" points to.  The small data area can hold up to 64 kilobytes.

       -mzda=n
	   Put static or global variables whose size is n bytes or less into the first 32 kilo-
	   bytes of memory.

       -mv850
	   Specify that the target processor is the V850.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only if the assem-
	   bler/linker complain about out of range branches within a switch table.

       ARC Options

       These options are defined for ARC implementations:

       -EL Compile code for little endian mode.  This is the default.

       -EB Compile code for big endian mode.

       -mmangle-cpu
	   Prepend the name of the cpu to all public symbol names.  In multiple-processor sys-
	   tems, there are many ARC variants with different instruction and register set charac-
	   teristics.  This flag prevents code compiled for one cpu to be linked with code com-
	   piled for another.  No facility exists for handling variants that are ``almost identi-
	   cal''.  This is an all or nothing option.

       -mcpu=cpu
	   Compile code for ARC variant cpu.  Which variants are supported depend on the configu-
	   ration.  All variants support -mcpu=base, this is the default.

       -mtext=text-section
       -mdata=data-section
       -mrodata=readonly-data-section
	   Put functions, data, and readonly data in text-section, data-section, and readonly-
	   data-section respectively by default.  This can be overridden with the "section"
	   attribute.

       NS32K Options

       These are the -m options defined for the 32000 series.  The default values for these
       options depends on which style of 32000 was selected when the compiler was configured; the
       defaults for the most common choices are given below.

       -m32032
       -m32032
	   Generate output for a 32032.  This is the default when the compiler is configured for
	   32032 and 32016 based systems.

       -m32332
       -m32332
	   Generate output for a 32332.  This is the default when the compiler is configured for
	   32332-based systems.

       -m32532
       -m32532
	   Generate output for a 32532.  This is the default when the compiler is configured for
	   32532-based systems.

       -m32081
	   Generate output containing 32081 instructions for floating point.  This is the default
	   for all systems.

       -m32381
	   Generate output containing 32381 instructions for floating point.  This also implies
	   -m32081.  The 32381 is only compatible with the 32332 and 32532 cpus.  This is the
	   default for the pc532-netbsd configuration.

       -mmulti-add
	   Try and generate multiply-add floating point instructions "polyF" and "dotF".  This
	   option is only available if the -m32381 option is in effect.  Using these instructions
	   requires changes to register allocation which generally has a negative impact on per-
	   formance.  This option should only be enabled when compiling code particularly likely
	   to make heavy use of multiply-add instructions.

       -mnomulti-add
	   Do not try and generate multiply-add floating point instructions "polyF" and "dotF".
	   This is the default on all platforms.

       -msoft-float
	   Generate output containing library calls for floating point.  Warning: the requisite
	   libraries may not be available.

       -mnobitfield
	   Do not use the bit-field instructions.  On some machines it is faster to use shifting
	   and masking operations.  This is the default for the pc532.

       -mbitfield
	   Do use the bit-field instructions.  This is the default for all platforms except the
	   pc532.

       -mrtd
	   Use a different function-calling convention, in which functions that take a fixed num-
	   ber of arguments return pop their arguments on return with the "ret" instruction.

	   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 num-
	   bers 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.)

	   This option takes its name from the 680x0 "rtd" instruction.

       -mregparam
	   Use a different function-calling convention where the first two arguments are passed
	   in registers.

	   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.

       -mnoregparam
	   Do not pass any arguments in registers.  This is the default for all targets.

       -msb
	   It is OK to use the sb as an index register which is always loaded with zero.  This is
	   the default for the pc532-netbsd target.

       -mnosb
	   The sb register is not available for use or has not been initialized to zero by the
	   run time system.  This is the default for all targets except the pc532-netbsd.  It is
	   also implied whenever -mhimem or -fpic is set.

       -mhimem
	   Many ns32000 series addressing modes use displacements of up to 512MB.  If an address
	   is above 512MB then displacements from zero can not be used.  This option causes code
	   to be generated which can be loaded above 512MB.  This may be useful for operating
	   systems or ROM code.

       -mnohimem
	   Assume code will be loaded in the first 512MB of virtual address space.  This is the
	   default for all platforms.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
	   Specify ATMEL AVR instruction set or MCU type.

	   Instruction set avr1 is for the minimal AVR core, not supported by the C compiler,
	   only for assembler programs (MCU types: at90s1200, attiny10, attiny11, attiny12,
	   attiny15, attiny28).

	   Instruction set avr2 (default) is for the classic AVR core with up to 8K program mem-
	   ory space (MCU types: at90s2313, at90s2323, attiny22, at90s2333, at90s2343, at90s4414,
	   at90s4433, at90s4434, at90s8515, at90c8534, at90s8535).

	   Instruction set avr3 is for the classic AVR core with up to 128K program memory space
	   (MCU types: atmega103, atmega603, at43usb320, at76c711).

	   Instruction set avr4 is for the enhanced AVR core with up to 8K program memory space
	   (MCU types: atmega8, atmega83, atmega85).

	   Instruction set avr5 is for the enhanced AVR core with up to 128K program memory space
	   (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323, atmega64, atmega128,
	   at43usb355, at94k).

       -msize
	   Output instruction sizes to the asm file.

       -minit-stack=N
	   Specify the initial stack address, which may be a symbol or numeric value, __stack is
	   the default.

       -mno-interrupts
	   Generated code is not compatible with hardware interrupts.  Code size will be smaller.

       -mcall-prologues
	   Functions prologues/epilogues expanded as call to appropriate subroutines.  Code size
	   will be smaller.

       -mno-tablejump
	   Do not generate tablejump insns which sometimes increase code size.

       -mtiny-stack
	   Change only the low 8 bits of the stack pointer.

       MCore Options

       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mhardlit
       -mno-hardlit
	   Inline constants into the code stream if it can be done in two instructions or less.

       -mdiv
       -mdiv
       -mno-div
	   Use the divide instruction.	(Enabled by default).

       -mrelax-immediate
       -mrelax-immediate
       -mno-relax-immediate
	   Allow arbitrary sized immediates in bit operations.

       -mwide-bitfields
       -mwide-bitfields
       -mno-wide-bitfields
	   Always treat bit-fields as int-sized.

       -m4byte-functions
       -m4byte-functions
       -mno-4byte-functions
	   Force all functions to be aligned to a four byte boundary.

       -mcallgraph-data
       -mcallgraph-data
       -mno-callgraph-data
	   Emit callgraph information.

       -mslow-bytes
       -mslow-bytes
       -mno-slow-bytes
	   Prefer word access when reading byte quantities.

       -mlittle-endian
       -mlittle-endian
       -mbig-endian
	   Generate code for a little endian target.

       -m210
       -m210
       -m340
	   Generate code for the 210 processor.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
	   Generate code for a big endian target.  This is the default for HPUX.

       -mlittle-endian
	   Generate code for a little endian target.  This is the default for AIX5 and Linux.

       -mgnu-as
       -mno-gnu-as
	   Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
	   Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
	   Generate code that does not use a global pointer register.  The result is not position
	   independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
	   Generate (or don't) a stop bit immediately before and after volatile asm statements.

       -mb-step
	   Generate code that works around Itanium B step errata.

       -mregister-names
       -mno-register-names
	   Generate (or don't) in, loc, and out register names for the stacked registers.  This
	   may make assembler output more readable.

       -mno-sdata
       -msdata
	   Disable (or enable) optimizations that use the small data section.  This may be useful
	   for working around optimizer bugs.

       -mconstant-gp
	   Generate code that uses a single constant global pointer value.  This is useful when
	   compiling kernel code.

       -mauto-pic
	   Generate code that is self-relocatable.  This implies -mconstant-gp.  This is useful
	   when compiling firmware code.

       -minline-divide-min-latency
	   Generate code for inline divides using the minimum latency algorithm.

       -minline-divide-max-throughput
	   Generate code for inline divides using the maximum throughput algorithm.

       -mno-dwarf2-asm
       -mdwarf2-asm
	   Don't (or do) generate assembler code for the DWARF2 line number debugging info.  This
	   may be useful when not using the GNU assembler.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.	A fixed register
	   is one that the register allocator can not use.  This is useful when compiling kernel
	   code.  A register range is specified as two registers separated by a dash.  Multiple
	   register ranges can be specified separated by a comma.

       D30V Options

       These -m options are defined for D30V implementations:

       -mextmem
	   Link the .text, .data, .bss, .strings, .rodata, .rodata1, .data1 sections into exter-
	   nal memory, which starts at location 0x80000000.

       -mextmemory
	   Same as the -mextmem switch.

       -monchip
	   Link the .text section into onchip text memory, which starts at location 0x0.  Also
	   link .data, .bss, .strings, .rodata, .rodata1, .data1 sections into onchip data mem-
	   ory, which starts at location 0x20000000.

       -mno-asm-optimize
       -masm-optimize
	   Disable (enable) passing -O to the assembler when optimizing.  The assembler uses the
	   -O option to automatically parallelize adjacent short instructions where possible.

       -mbranch-cost=n
	   Increase the internal costs of branches to n.  Higher costs means that the compiler
	   will issue more instructions to avoid doing a branch.  The default is 2.

       -mcond-exec=n
	   Specify the maximum number of conditionally executed instructions that replace a
	   branch.  The default is 4.

       S/390 and zSeries Options

       These are the -m options defined for the S/390 and zSeries architecture.

       -mhard-float
       -msoft-float
	   Use (do not use) the hardware floating-point instructions and registers for floating-
	   point operations.  When -msoft-float is specified, functions in libgcc.a will be used
	   to perform floating-point operations.  When -mhard-float is specified, the compiler
	   generates IEEE floating-point instructions.	This is the default.

       -mbackchain
       -mno-backchain
	   Generate (or do not generate) code which maintains an explicit backchain within the
	   stack frame that points to the caller's frame.  This is currently needed to allow
	   debugging.  The default is to generate the backchain.

       -msmall-exec
       -mno-small-exec
	   Generate (or do not generate) code using the "bras" instruction to do subroutine
	   calls.  This only works reliably if the total executable size does not exceed 64k.
	   The default is to use the "basr" instruction instead, which does not have this limita-
	   tion.

       -m64
       -m31
	   When -m31 is specified, generate code compliant to the Linux for S/390 ABI.	When -m64
	   is specified, generate code compliant to the Linux for zSeries ABI.	This allows GCC
	   in particular to generate 64-bit instructions.  For the s390 targets, the default is
	   -m31, while the s390x targets default to -m64.

       -mmvcle
       -mno-mvcle
	   Generate (or do not generate) code using the "mvcle" instruction to perform block
	   moves.  When -mno-mvcle is specifed, use a "mvc" loop instead.  This is the default.

       -mdebug
       -mno-debug
	   Print (or do not print) additional debug information when compiling.  The default is
	   to not print debug information.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
	   Generate code for the specified architecture.  The choices for architecture-type are
	   v3, v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.  Default is v0
	   except for cris-axis-linux-gnu, where the default is v10.

       -mtune=architecture-type
	   Tune to architecture-type everything applicable about the generated code, except for
	   the ABI and the set of available instructions.  The choices for architecture-type are
	   the same as for -march=architecture-type.

       -mmax-stack-frame=n
	   Warn when the stack frame of a function exceeds n bytes.

       -melinux-stacksize=n
	   Only available with the cris-axis-aout target.  Arranges for indications in the pro-
	   gram to the kernel loader that the stack of the program should be set to n bytes.

       -metrax4
       -metrax100
	   The options -metrax4 and -metrax100 are synonyms for -march=v3 and -march=v8 respec-
	   tively.

       -mpdebug
	   Enable CRIS-specific verbose debug-related information in the assembly code.  This
	   option also has the effect to turn off the #NO_APP formatted-code indicator to the
	   assembler at the beginning of the assembly file.

       -mcc-init
	   Do not use condition-code results from previous instruction; always emit compare and
	   test instructions before use of condition codes.

       -mno-side-effects
	   Do not emit instructions with side-effects in addressing modes other than post-incre-
	   ment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
	   These options (no-options) arranges (eliminate arrangements) for the stack-frame,
	   individual data and constants to be aligned for the maximum single data access size
	   for the chosen CPU model.  The default is to arrange for 32-bit alignment.  ABI
	   details such as structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
	   Similar to the stack- data- and const-align options above, these options arrange for
	   stack-frame, writable data and constants to all be 32-bit, 16-bit or 8-bit aligned.
	   The default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
	   With -mno-prologue-epilogue, the normal function prologue and epilogue that sets up
	   the stack-frame are omitted and no return instructions or return sequences are gener-
	   ated in the code.  Use this option only together with visual inspection of the com-
	   piled code: no warnings or errors are generated when call-saved registers must be
	   saved, or storage for local variable needs to be allocated.

       -mno-gotplt
       -mgotplt
	   With -fpic and -fPIC, don't generate (do generate) instruction sequences that load
	   addresses for functions from the PLT part of the GOT rather than (traditional on other
	   architectures) calls to the PLT.  The default is -mgotplt.

       -maout
	   Legacy no-op option only recognized with the cris-axis-aout target.

       -melf
	   Legacy no-op option only recognized with the cris-axis-elf and cris-axis-linux-gnu
	   targets.

       -melinux
	   Only recognized with the cris-axis-aout target, where it selects a GNU/linux-like mul-
	   tilib, include files and instruction set for -march=v8.

       -mlinux
	   Legacy no-op option only recognized with the cris-axis-linux-gnu target.

       -sim
	   This option, recognized for the cris-axis-aout and cris-axis-elf arranges to link with
	   input-output functions from a simulator library.  Code, initialized data and zero-ini-
	   tialized data are allocated consecutively.

       -sim2
	   Like -sim, but pass linker options to locate initialized data at 0x40000000 and zero-
	   initialized data at 0x80000000.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
	   Specify that intrinsic library functions are being compiled, passing all values in
	   registers, no matter the size.

       -mepsilon
       -mno-epsilon
	   Generate floating-point comparison instructions that compare with respect to the "rE"
	   epsilon register.

       -mabi=mmixware
       -mabi=gnu
	   Generate code that passes function parameters and return values that (in the called
	   function) are seen as registers $0 and up, as opposed to the GNU ABI which uses global
	   registers $231 and up.

       -mzero-extend
       -mno-zero-extend
	   When reading data from memory in sizes shorter than 64 bits, use (do not use) zero-
	   extending load instructions by default, rather than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
	   Make the result of a division yielding a remainder have the same sign as the divisor.
	   With the default, -mno-knuthdiv, the sign of the remainder follows the sign of the
	   dividend.  Both methods are arithmetically valid, the latter being almost exclusively
	   used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
	   Prepend (do not prepend) a : to all global symbols, so the assembly code can be used
	   with the "PREFIX" assembly directive.

       -melf
	   Generate an executable in the ELF format, rather than the default mmo format used by
	   the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
	   Use (do not use) the probable-branch instructions, when static branch prediction indi-
	   cates a probable branch.

       -mbase-addresses
       -mno-base-addresses
	   Generate (do not generate) code that uses base addresses.  Using a base address auto-
	   matically generates a request (handled by the assembler and the linker) for a constant
	   to be set up in a global register.  The register is used for one or more base address
	   requests within the range 0 to 255 from the value held in the register.  The generally
	   leads to short and fast code, but the number of different data items that can be
	   addressed is limited.  This means that a program that uses lots of static data may
	   require -mno-base-addresses.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
	   Use hardware FPP floating point.  This is the default.  (FIS floating point on the
	   PDP-11/40 is not supported.)

       -msoft-float
	   Do not use hardware floating point.

       -mac0
	   Return floating-point results in ac0 (fr0 in Unix assembler syntax).

       -mno-ac0
	   Return floating-point results in memory.  This is the default.

       -m40
	   Generate code for a PDP-11/40.

       -m45
	   Generate code for a PDP-11/45.  This is the default.

       -m10
	   Generate code for a PDP-11/10.

       -mbcopy-builtin
	   Use inline "movstrhi" patterns for copying memory.  This is the default.

       -mbcopy
	   Do not use inline "movstrhi" patterns for copying memory.

       -mint16
       -mno-int32
	   Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
	   Use 32-bit "int".

       -mfloat64
       -mno-float32
	   Use 64-bit "float".	This is the default.

       -mfloat32
       -mno-float64
	   Use 32-bit "float".

       -mabshi
	   Use "abshi2" pattern.  This is the default.

       -mno-abshi
	   Do not use "abshi2" pattern.

       -mbranch-expensive
	   Pretend that branches are expensive.  This is for experimenting with code generation
	   only.

       -mbranch-cheap
	   Do not pretend that branches are expensive.	This is the default.

       -msplit
	   Generate code for a system with split I&D.

       -mno-split
	   Generate code for a system without split I&D.  This is the default.

       -munix-asm
	   Use Unix assembler syntax.  This is the default when configured for pdp11-*-bsd.

       -mdec-asm
	   Use DEC assembler syntax.  This is the default when configured for any PDP-11 target
	   other than pdp11-*-bsd.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
	   Choose startup files and linker script suitable for the simulator.

       Xtensa Options

       The Xtensa architecture is designed to support many different configurations.  The com-
       piler's default options can be set to match a particular Xtensa configuration by copying a
       configuration file into the GCC sources when building GCC.  The options below may be used
       to override the default options.

       -mbig-endian
       -mlittle-endian
	   Specify big-endian or little-endian byte ordering for the target Xtensa processor.

       -mdensity
       -mno-density
	   Enable or disable use of the optional Xtensa code density instructions.

       -mmac16
       -mno-mac16
	   Enable or disable use of the Xtensa MAC16 option.  When enabled, GCC will generate
	   MAC16 instructions from standard C code, with the limitation that it will use neither
	   the MR register file nor any instruction that operates on the MR registers.	When this
	   option is disabled, GCC will translate 16-bit multiply/accumulate operations to a com-
	   bination of core instructions and library calls, depending on whether any other multi-
	   plier options are enabled.

       -mmul16
       -mno-mul16
	   Enable or disable use of the 16-bit integer multiplier option.  When enabled, the com-
	   piler will generate 16-bit multiply instructions for multiplications of 16 bits or
	   smaller in standard C code.	When this option is disabled, the compiler will either
	   use 32-bit multiply or MAC16 instructions if they are available or generate library
	   calls to perform the multiply operations using shifts and adds.

       -mmul32
       -mno-mul32
	   Enable or disable use of the 32-bit integer multiplier option.  When enabled, the com-
	   piler will generate 32-bit multiply instructions for multiplications of 32 bits or
	   smaller in standard C code.	When this option is disabled, the compiler will generate
	   library calls to perform the multiply operations using either shifts and adds or
	   16-bit multiply instructions if they are available.

       -mnsa
       -mno-nsa
	   Enable or disable use of the optional normalization shift amount ("NSA") instructions
	   to implement the built-in "ffs" function.

       -mminmax
       -mno-minmax
	   Enable or disable use of the optional minimum and maximum value instructions.

       -msext
       -mno-sext
	   Enable or disable use of the optional sign extend ("SEXT") instruction.

       -mbooleans
       -mno-booleans
	   Enable or disable support for the boolean register file used by Xtensa coprocessors.
	   This is not typically useful by itself but may be required for other options that make
	   use of the boolean registers (e.g., the floating-point option).

       -mhard-float
       -msoft-float
	   Enable or disable use of the floating-point option.	When enabled, GCC generates
	   floating-point instructions for 32-bit "float" operations.  When this option is dis-
	   abled, GCC generates library calls to emulate 32-bit floating-point operations using
	   integer instructions.  Regardless of this option, 64-bit "double" operations are
	   always emulated with calls to library functions.

       -mfused-madd
       -mno-fused-madd
	   Enable or disable use of fused multiply/add and multiply/subtract instructions in the
	   floating-point option.  This has no effect if the floating-point option is not also
	   enabled.  Disabling fused multiply/add and multiply/subtract instructions forces the
	   compiler to use separate instructions for the multiply and add/subtract operations.
	   This may be desirable in some cases where strict IEEE 754-compliant results are
	   required: the fused multiply add/subtract instructions do not round the intermediate
	   result, thereby producing results with more bits of precision than specified by the
	   IEEE standard.  Disabling fused multiply add/subtract instructions also ensures that
	   the program output is not sensitive to the compiler's ability to combine multiply and
	   add/subtract operations.

       -mserialize-volatile
       -mno-serialize-volatile
	   When this option is enabled, GCC inserts "MEMW" instructions before "volatile" memory
	   references to guarantee sequential consistency.  The default is -mserialize-volatile.
	   Use -mno-serialize-volatile to omit the "MEMW" instructions.

       -mtext-section-literals
       -mno-text-section-literals
	   Control the treatment of literal pools.  The default is -mno-text-section-literals,
	   which places literals in a separate section in the output file.  This allows the lit-
	   eral pool to be placed in a data RAM/ROM, and it also allows the linker to combine
	   literal pools from separate object files to remove redundant literals and improve code
	   size.  With -mtext-section-literals, the literals are interspersed in the text section
	   in order to keep them as close as possible to their references.  This may be necessary
	   for large assembly files.

       -mtarget-align
       -mno-target-align
	   When this option is enabled, GCC instructs the assembler to automatically align
	   instructions to reduce branch penalties at the expense of some code density.  The
	   assembler attempts to widen density instructions to align branch targets and the
	   instructions following call instructions.  If there are not enough preceding safe den-
	   sity instructions to align a target, no widening will be performed.	The default is
	   -mtarget-align.  These options do not affect the treatment of auto-aligned instruc-
	   tions like "LOOP", which the assembler will always align, either by widening density
	   instructions or by inserting no-op instructions.

       -mlongcalls
       -mno-longcalls
	   When this option is enabled, GCC instructs the assembler to translate direct calls to
	   indirect calls unless it can determine that the target of a direct call is in the
	   range allowed by the call instruction.  This translation typically occurs for calls to
	   functions in other source files.  Specifically, the assembler translates a direct
	   "CALL" instruction into an "L32R" followed by a "CALLX" instruction.  The default is
	   -mno-longcalls.  This option should be used in programs where the call target can
	   potentially be out of range.  This option is implemented in the assembler, not the
	   compiler, so the assembly code generated by GCC will still show direct call instruc-
	   tions---look at the disassembled object code to see the actual instructions.  Note
	   that the assembler will use an indirect call for every cross-file call, not just those
	   that really will be out of range.

       Options for Code Generation Conventions

       These machine-independent options control the interface conventions used in code genera-
       tion.

       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.

       -fexceptions
	   Enable exception handling.  Generates extra code needed to propagate exceptions.  For
	   some targets, this implies GCC will generate frame unwind information for all func-
	   tions, 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 lan-
	   guages like C++ which normally require exception handling, and disable it for lan-
	   guages 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 han-
	   dlers 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 asyn-
	   chronous 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 con-
	   figuration 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 com-
	   piler.  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 com-
	   patible 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 com-
	   patible 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 com-
	   patible with code generated without that switch.  Use it to conform to a non-default
	   application binary interface.

       -fshared-data
	   Requests that the data and non-"const" variables of this compilation be shared data
	   rather than private data.  The distinction makes sense only on certain operating sys-
	   tems, where shared data is shared between processes running the same program, while
	   private data exists in one copy per process.

       -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.

       -fno-gnu-linker
	   Do not output global initializations (such as C++ constructors and destructors) in the
	   form used by the GNU linker (on systems where the GNU linker is the standard method of
	   handling them).  Use this option when you want to use a non-GNU linker, which also
	   requires using the collect2 program to make sure the system linker includes construc-
	   tors and destructors.  (collect2 is included in the GCC distribution.)  For systems
	   which must use collect2, the compiler driver gcc is configured to do this automati-
	   cally.

       -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 read-
	   able.  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 use-
	   ful when comparing two assembler files.

       -fvolatile
	   Consider all memory references through pointers to be volatile.

       -fvolatile-global
	   Consider all memory references to extern and global data items to be volatile.  GCC
	   does not consider static data items to be volatile because of this switch.

       -fvolatile-static
	   Consider all memory references to static data to be volatile.

       -fpic
	   Generate position-independent code (PIC) suitable for use in a shared library, if sup-
	   ported 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 pro-
	   gram starts (the dynamic loader is not part of GCC; it is part of the operating sys-
	   tem).  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 16k on the m88k, 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 cer-
	   tain 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.

       -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, m88k, and the Sparc.

	   Position-independent code requires special support, and therefore works only on cer-
	   tain machines.

       -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 com-
	   piled 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
	   Pack all structure members together without holes.

	   Warning: the -fpack-struct switch causes GCC to generate code that is not binary com-
	   patible with code generated without that switch.  Additionally, it makes the code sub-
	   optimial.  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 expan-
	   sion 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 pro-
	   filing 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 over-
	   flow 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 sys-
	   tem 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 spe-
	   cial 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,--def-
	   sym,__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
	   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.

	   Each language will automatically use whatever option is required by the language stan-
	   dard.  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".

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_UK for English in the United Kingdom.

	   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 mes-
	   sages.

	   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 subpro-
	   grams 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-lib/ 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-lib (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 stan-
	   dard 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 recog-
	   nized:

	   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.

       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_SEPARA-
	   TOR", is target-dependent and determined at GCC build time.	For 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.  The environment variable
	   is used regardless of which language is being preprocessed.

	   The remaining environment variables apply only when preprocessing the particular lan-
	   guage 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.

       DEPENDENCIES_OUTPUT
	   @anchor{DEPENDENCIES_OUTPUT} If this variable is set, its value specifies how to out-
	   put dependencies for Make based on the non-system header files processed by the com-
	   piler.  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 the environment variable DEPENDENCIES_OUTPUT, 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
       For instructions on reporting bugs, see <http://gcc.gnu.org/bugs.html>.	Use of the gccbug
       script to report bugs is recommended.

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), g77(1), as(1), ld(1), gdb(1), adb(1),
       dbx(1), sdb(1) and the Info entries for gcc, cpp, g77, 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 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 1.1 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-3.2.2				    2003-02-25					   GCC(1)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 05:51 AM.