## 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, com
           pilation, assembly and linking.  The ``overall options''
           allow you to stop this process at an intermediate stage.
           For example, the -c option says not to run the linker.
           Then the output consists of object files output by the
           assembler.

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

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

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

           You can mix options and other arguments.  For the most
           part, the order you use doesn't matter.  Order does matter
           when you use several options of the same kind; for exam
           ple, 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.

               -traditional-cpp -fallow-single-precision  -fcond-mis
               match -fsigned-bitfields  -fsigned-char -fun
               signed-bitfields  -funsigned-char -fwritable-strings

           C++ Language Options
               -fabi-version=n -fno-access-control  -fcheck-new
               -fconserve-space -fno-const-strings  -fdol
               lars-in-identifiers -fno-elide-constructors
               -fno-enforce-eh-specs  -fexternal-templates
               -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-opera
               tor-names -fno-optional-diags  -fpermissive -frepo
               -fno-rtti  -fstats  -ftemplate-depth-n
               -fuse-cxa-atexit  -fvtable-gc  -fno-weak  -nostdinc++
               -fno-default-inline -Wabi -Wctor-dtor-privacy
               -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wno-depre
               cated -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-protocol  -Wselector
               -Wundeclared-selector

           Language Independent Options
               -fmessage-length=n -fdiagnostics-show-loca
               tion=[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
               -Wno-div-by-zero  -Werror -Wfloat-equal  -Wformat
               -Wformat=2 -Wformat-nonliteral  -Wformat-security
               -Wimplicit  -Wimplicit-int -Wimplicit-function-decla
               ration -Werror-implicit-function-declaration -Wimport
               -Winline -Wno-endif-labels -Wlarger-than-len
               -Wlong-long -Wmain  -Wmissing-braces -Wmissing-for
               mat-attribute  -Wmissing-noreturn -Wno-multichar
               -Wno-format-extra-args  -Wno-format-y2k -Wno-import
               -Wnonnull  -Wpacked  -Wpadded -Wparentheses
               -Wpointer-arith  -Wredundant-decls -Wreturn-type
               -Wsequence-point  -Wshadow -Wsign-compare
               -Wstrict-aliasing -Wswitch  -Wswitch-default
               -Wswitch-enum -Wsystem-headers -Wtrigraphs  -Wundef
               -Wuninitialized -Wunknown-pragmas  -Wunreachable-code
               -Wunused  -Wunused-function  -Wunused-label
               -Wunused-parameter -Wunused-value  -Wunused-variable
               -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 -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
               -floop-optimize -fcrossjumping -fif-conversion
               -fif-conversion2 -finline-functions  -finline-limit=n
               -fkeep-inline-functions -fkeep-static-consts
               -fmerge-constants  -fmerge-all-constants
               -fmove-all-movables  -fnew-ra  -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 -fun
               safe-math-optimizations -ffinite-math-only -fno-trap
               ping-math -fno-zero-initialized-in-bss
               -fomit-frame-pointer  -foptimize-register-move -fopti
               mize-sibling-calls  -fprefetch-loop-arrays -fre
               duce-all-givs -fregmove  -frename-registers -fre
               order-blocks -freorder-functions -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  -fsignaling-nans -fsin
               gle-precision-constant  -fssa -fssa-ccp -fssa-dce
               -fstrength-reduce  -fstrict-aliasing  -ftracer
               -fthread-jumps -funroll-all-loops  -funroll-loops
               -fweb --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  -iwithpre
               fix dir -iwithprefixbefore dir  -isystem dir -M  -MM
               -MF  -MG  -MP  -MQ  -MT  -nostdinc  -P  -remap -tri
               graphs  -undef  -Umacro  -Wp,option

           Assembler Option
               -Wa,option

           Linker Options
                object-file-name  -llibrary -nostartfiles  -node
               faultlibs  -nostdlib -s  -static  -static-libgcc
               -mc68000  -mc68020 -mfpa  -mnobitfield  -mrtd  -mshort
               -msoft-float  -mpcrel -malign-int  -mstrict-align

               M68hc1x Options

               -m6811  -m6812  -m68hc11  -m68hc12  -m68hcs12
               -mauto-incdec  -minmax  -mlong-calls  -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  -mbroken-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-dou
               bles -msoft-float  -msoft-quad-float  -msparclite
               -mstack-bias -msupersparc  -munaligned-doubles  -mv8

               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-reentrant
               -msched-prolog  -mno-sched-prolog -mlittle-endian
               -mbig-endian  -mwords-little-endian -malignment-traps
               -mno-alignment-traps -msoft-float  -mhard-float  -mfpe
               -mthumb-interwork  -mno-thumb-interwork -mcpu=name
               -march=name  -mfpe=name -mstructure-size-boundary=n
               -mabort-on-noreturn -mlong-calls  -mno-long-calls
               -msingle-pic-base  -mno-single-pic-base -mpic-regis
               ter=reg -mnop-fun-dllimport -mpoke-function-name
               -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame
               -mcaller-super-interworking  -mcallee-super-interwork
               ing

               MN10200 Options

               -mrelax

               MN10300 Options

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

               M32R/D Options

               -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-gfx
               opt -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-relocat
               able-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 -mabi=spe -mabi=no-spe
               -misel=yes -misel=no -mprototype  -mno-prototype -msim
               -mmvme  -mads  -myellowknife  -memb -msdata
               -msdata=opt  -mvxworks -mwindiss -G num -pthread

               Darwin Options

               -all_load -allowable_client -arch -arch_errors_fatal
               -arch_only -bind_at_load -bundle -bundle_loader
               -client_name -compatibility_version -current_version
               -dependency-file -dylib_file -dylinker_install_name
               -dynamic -dynamiclib -exported_symbols_list -filelist
               -flat_namespace -force_cpusubtype_ALL
               -force_flat_namespace -headerpad_max_install_names
               -image_base -init -install_name -keep_private_externs
               -multi_module -multiply_defined -multi
               ply_defined_unused -noall_load -nomultidefs -noprebind
               -noseglinkedit -pagezero_size -prebind -pre
               bind_all_twolevel_modules -private_bundle
               -read_only_relocs -sectalign -sectobjectsymbols -why
               load -seg1addr -sectcreate -sectobjectsymbols -sec
               torder -seg_addr_table -seg_addr_table_filename
               -seglinkedit -segprot -segs_read_only_addr
               -segs_read_write_addr -single_module -static
               -sub_library -sub_umbrella -twolevel_namespace
               -umbrella -undefined -unexported_symbols_list
               -weak_reference_mismatches -whatsloaded

               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
               -mstats  -EL  -EB  -G num  -nocpp -mabi=32  -mabi=n32
               -mabi=64  -mabi=eabi -mfix7000  -mno-crt0
               -mflush-func=func -mno-flush-func -mbranch-likely
               -mno-branch-likely

               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-double -mpreferred-stack-boundary=num -mmmx
               -msse -msse2 -m3dnow -mthreads  -mno-align-stringops
               -minline-all-stringops -mpush-args  -maccumulate-out
               going-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  -mdis
               able-fpregs  -mdisable-indexing -mfast-indirect-calls
               -mgas  -mgnu-ld -mhp-ld -mjump-in-delay -mlinker-opt
               -mlong-calls -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
               -msio -mwsio

               Intel 960 Options

               -mcpu-type  -masm-compat  -mclean-linkage -mcode-align
               -mcomplex-addr  -mleaf-procedures -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-conformant
               -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 -mmemory-latency=time

               DEC Alpha/VMS Options
               -mpadstruct  -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  -mrodata=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 -mparal
               lel-insns  -mparallel-mpy  -mpreserve-float

               V850 Options

               -mlong-calls  -mno-long-calls  -mep  -mno-ep -mpro
               log-function  -mno-prolog-function  -mspace -mtda=n
               -msda=n  -mzda=n -mapp-regs -mno-app-regs -mdis
               able-callt -mno-disable-callt -mv850e -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  -mre
               lax-immediates -mno-relax-immediates  -mwide-bitfields
               -mno-wide-bitfields -m4byte-functions
               -mno-4byte-functions  -mcallgraph-data -mno-call
               graph-data  -mslow-bytes  -mno-slow-bytes  -mno-lsim
               -mlittle-endian  -mbig-endian  -m210  -m340
               -mstack-increment

               MMIX Options

               -mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon
               -mabi=gnu -mabi=mmixware -mzero-extend -mknuthdiv

               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-pro
               logue-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 -mserial
               ize-volatile -mno-serialize-volatile -mtext-sec
               tion-literals -mno-text-section-literals -mtar
               get-align -mno-target-align -mlongcalls -mno-longcalls

               FRV Options

               -mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 -mhard-float
               -msoft-float -malloc-cc -mfixed-cc -mdword -mno-dword
               -mdouble -mno-double -mmedia -mno-media -mmuladd
               -mno-muladd -mlibrary-pic -macc-4 -macc-8 -mpack
               -mno-pack -mno-eflags -mcond-move -mno-cond-move -mscc
               -fpack-struct  -fstack-check -fstack-limit-regis
               ter=reg  -fstack-limit-symbol=sym -fargument-alias
               -fargument-noalias -fargument-noalias-global  -flead
               ing-underscore -ftls-model=model -ftrapv
               -fbounds-check

           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 prepro
               cessed.

           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
               declaration (a declaration of a package, subprogram,
               or generic, or a generic instantiation), or a library
               unit renaming declaration (a package, generic, or sub
               program 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 suffix is treated this
               way.

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

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

                       c  c-header  cpp-output
                       c++  c++-cpp-output
                       objective-c  objc-cpp-output
                       assembler  assembler-with-cpp
                       ada
                       f77  f77-cpp-input  ratfor
                       java
                       treelang

           -x none
               Turn off any specification of a language, so that sub
               sequent files are handled according 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
               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 prepro
               cessed source code, which is sent to the standard out
               put.

               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 exe
               cutable file in a.out, the object file for source.suf
               fix in source.o, its assembler file in source.s, and
               all preprocessed C source on standard output.

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

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

           -pipe
               ated 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 compiles them as C++ programs even if you call the
           compiler the same way as for compiling C programs (usually
           with the name gcc).

           However, 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 pro
           grams 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 auto
           matically 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 pro
           grams in any language; or command-line options meaningful
           for C and related languages; or options that are meaning
           ful only for C++ programs.

           Options Controlling C Dialect

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

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

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

               The macro "__STRICT_ANSI__" is predefined when the
               -ansi option is used.  Some header files may notice
               this macro and refrain from declaring certain func
               tions 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 cur
               rently only supported when compiling C or C++.  A
               value for this option must be provided; possible val
               ues are

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

               iso9899:199409
                   ISO C90 as modified in amendment 1.

               c99
               c9x
               iso9899:1999
               iso9899:199x
                   ISO C99.  Note that this standard is not yet fully
                   supported; see <http://gcc.gnu.org/gcc-3.3/c99sta
                   tus.html> for more information.  The names c9x and
                   iso9899:199x are deprecated.

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

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

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

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

               for all functions declared and/or defined in a trans
               lation unit, including those in header files.  This
               option is silently ignored in any language other than
               C.

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

           -fno-asm
               Do not recognize "asm", "inline" or "typeof" as a key
               word, 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 key
               word in ISO C99.

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

               GCC normally generates special code to handle certain
               built-in functions more efficiently; for instance,
               calls to "alloca" may become single instructions that
               adjust the stack directly, and calls to "memcpy" may
               become inline copy loops.  The resulting code is often
               both smaller and faster, but since the function calls
               no longer appear as such, you cannot set a breakpoint
               on those calls, nor can you change the behavior of the
               functions by linking with a different library.

               With the -fno-builtin-function option only the built-
               in function function is disabled.  function must not
               begin with __builtin_.  If a function is named this is
               not built-in in this version of GCC, this option is
               ignored.  There is no corresponding -fbuiltin-function
               option; if you wish to enable built-in functions

           -ffreestanding
               Assert that compilation takes place in a freestanding
               environment.  This implies -fno-builtin.  A freestand
               ing 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 ker
               nel.  This is equivalent to -fno-hosted.

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

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

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

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

           -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
               is signed, because this is consistent: the basic inte
               ger types such as "int" are signed types.

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

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

           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 lan
           guage 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 lan
           guage supported by GCC.

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

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

               The default is version 1.

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

               An alternative to using this option is to specify that
               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 pro
               hibit use of $ with the option -fno-dollars-in-identi
               fiers.  (GNU C allows $ by default on most target sys
               tems, 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 cre
               ating 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 violates 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; template instances are emitted
               or not according to the location of the template defi
               nition.

               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.
               style code that would otherwise be invalid, or have
               different behavior.

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

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

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

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

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

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

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

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

           -fpermissive
               Downgrade messages about nonconformant code from
               errors to warnings.  By default, G++ effectively sets
               save some space by using this flag.  Note that excep
               tion 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 information is generally
               only useful to the G++ development team.

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

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

           -fvtable-gc
               Emit special relocations for vtables and virtual func
               tion 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 direc
               tories 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 genera
               about, even though G++ is generating incompatible
               code.  There may also be cases where warnings are
               emitted even though the code that is generated will be
               compatible.

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

               The known incompatibilities at this point include:

               ·   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 com
                   pilers to layout "B" identically.

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

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

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

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

                           union U { int i : 4096; };

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

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

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

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

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

                   Instantiations of these templates may be mangled
                   incorrectly.

           -Wctor-dtor-privacy (C++ only)
               Warn when a class seems unusable, because all the con
               structors or destructors in a class are private and
               the class has no friends or public static member func
               tions.  This warning is enabled by default.

           -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.  This warning
               is enabled by -Wall.

           -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 initializ
               ers for i and j will be rearranged to match the decla
               ration order of the members.  This warning is enabled
               by -Wall.

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

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

                   must return an object.

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

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

               ·   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 tem
               platized function.  Because this non-conforming behav
               ior is no longer the default behavior for G++,
               -Wnon-template-friend allows the compiler to check
               existing code for potential trouble spots, and is on
               by default.  This new compiler behavior can be turned
               off with -Wno-non-template-friend which keeps the con
               formant 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 vulnerable to unintended effects, and much easier
               to grep for.

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

                       struct A {
                         virtual void f();
                       };

               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 con
               version to an unsigned type of the same size.  Previ
               ous versions of G++ would try to preserve unsigned
               ness, 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
           language your program is in.  For example, you might com
           pile 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 specified with the syntax
               "@"..."".  The default class name is "NXCon
               stantString".

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

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

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

           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

           -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 erroneous but which are risky or
           suggest there may have been an error.

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

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

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

           -pedantic
               Issue all the warnings demanded by strict ISO C and
               ISO C++; reject all programs that use forbidden exten
               sions, 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 prop
               erly 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.
               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 defini
               tion 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 programmers often forget
               that this type is signed on some machines.

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

           -Wformat
               Check calls to "printf" and "scanf", etc., to make
               sure that the arguments supplied have types appropri
               ate to the format string specified, and that the con
               versions specified in the format string make sense.
               This includes standard functions, and others specified
               by format attributes, in the "printf", "scanf", "strf
               time" 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 C90 and C99 features, as well as features from the
               Single Unix Specification and some BSD and GNU exten
               sions.  Other library implementations may not support
               all these features; GCC does not support warning about
               features that go beyond a particular library's limita
               tions.  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
               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 $ operand number specifica
               tions, normally warnings are still given, since the
               implementation could not know what type to pass to
               "va_arg" to skip the unused arguments.  However, in
               the case of "scanf" formats, this option will suppress
               the warning if the unused arguments are all pointers,
               since the Single Unix Specification says that such
               unused arguments are allowed.

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

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

           -Wformat-security
               If -Wformat is specified, also warn about uses of for
               mat functions that represent possible security prob
               lems.  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 con
               tains %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 -Wfor
               mat-nonliteral -Wformat-security.

           -Wnonnull
               Enable warning about passing a null pointer for argu
               ments marked as requiring a non-null value by the
               "nonnull" function attribute.
               ration.

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

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

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

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

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

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

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

                       {
                         if (a)
                           {
                             if (b)
                               foo ();

               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 expres
               sion), after the evaluation of the first operand of a
               "&&", "||", "? :" or "," (comma) operator, before a
               function is called (but after the evaluation of its
               arguments and the expression denoting the called func
               tion), and in certain other places.  Other than as
               expressed by the sequence point rules, the order of
               evaluation of subexpressions of an expression is not
               specified.  All these rules describe only a partial
               order rather than a total order, since, for example,
               if two functions are called within one expression with
               no sequence point between them, the order in which the
               functions are called is not specified.  However, the
               standards committee have ruled that function calls do
               not overlap.

               It is not specified when between sequence points modi
               fications to the values of objects take effect.  Pro
               grams 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 evalua
               tion of an expression.  Furthermore, the prior value
               shall be read only to determine the value to be
               stored.''.  If a program breaks these rules, the
               results on any particular implementation are entirely
               unpredictable.

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

               The present implementation of this option only works
               for C programs.  A future implementation 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 dis
               cussions 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

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

           -Wswitch-enum
               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.  "case" labels
               outside the enumeration range also provoke warnings
               when this option is used.

           -Wtrigraphs
               Warn if any trigraphs are encountered that might
               change the meaning of the program (trigraphs within
               comments are not warned about).

           -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 the above -Wunused options combined.

               In order to get a warning about an unused function
               parameter, you must either specify -W -Wunused or sep
               arately specify -Wunused-parameter.

           -Wuninitialized
               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 reasons why the code might
               be correct despite appearing to have an error.  Here
               is one example of how this can happen:

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

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

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

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

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

               The compiler sees only the calls to "setjmp".  It can
               not 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.

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

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

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

           -W  Print extra warning messages for these events:

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

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

               ·   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.

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

               ·   A comparison like x<=y<=z appears; this is equiva
                   lent to (x<=y ? 1 : 0) <= z, which is a different
                   interpretation from that of ordinary mathematical
                   notation.

               ·   Storage-class specifiers like "static" are not the
               ·   A comparison between signed and unsigned values
                   could produce an incorrect result when the signed
                   value is converted to unsigned.  (But don't warn
                   if -Wno-sign-compare is also specified.)

               ·   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 };

               ·   An aggregate has an initializer which does not
                   initialize all members.  For example, the follow
                   ing code would cause such a warning, because "x.h"
                   would be implicitly initialized to zero:

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

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

           -Wsystem-headers
               Print warning messages for constructs found in system
               header files.  Warnings from system headers are nor
               mally 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 head
               ers---for that, -Wunknown-pragmas must also be used.

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

               The idea behind this is that sometimes it is conve
               nient (for the programmer) to consider floating-point
               values as approximations to infinitely precise real
               numbers.  If you are doing this, then you need to com
               pute (by analyzing the code, or in some other way) the
               maximum or likely maximum error that the computation
               introduces, and allow for it when performing compar
               isons (and when producing output, but that's a differ
                   replacement takes place within string literals,
                   but does not in ISO C.

               ·   In traditional C, some preprocessor directives did
                   not exist.  Traditional preprocessors would only
                   consider a line to be a directive if the #
                   appeared in column 1 on the line.  Therefore
                   -Wtraditional warns about directives that 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 indent
                   ing them.  Some traditional implementations would
                   not recognize #elif, so it suggests avoiding it
                   altogether.

               ·   A function-like macro that appears without argu
                   ments.

               ·   The unary plus operator.

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

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

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

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

               ·   The ISO type of an integer constant has a differ
                   ent 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 val
                   ues, which typically represent bit patterns, are
                   not warned about.

               ·   Usage of ISO string concatenation is detected.

               ·   Initialization of automatic aggregates.
                   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.

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

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

           -Wendif-labels
               Warn whenever an #else or an #endif are followed by
               text.

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

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

           -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-match
               ing 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
               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 conver
               sions of fixed point to floating and vice versa, and
               conversions changing the width or signedness of a
               fixed point argument except when the same as the
               default promotion.

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

           -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 declaration which specifies the argument types.)

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

           -Wmissing-noreturn
               Warn about functions which might be candidates for
               attribute "noreturn".  Note these are only possible
               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 (pos
               sibly by -Wall).

           -Wno-multichar
               Do not warn if a multicharacter constant ('FOOF') is
               used.  Usually they indicate a typo in the user's
               code, as they have implementation-defined values, and
               should not be used in portable code.

           -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{Vari
               able 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 mis
               aligned even though "struct bar" does not itself have
               the packed attribute:

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

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

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

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

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

               This option is not made part of -Wall because in a
               debugging version of a program there is often substan
               tial code which checks correct functioning of the pro
               gram and is, hopefully, unreachable because the pro
               gram 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 debug
           ging either your program or GCC:

           -g  Produce debugging information in the operating sys
               tem'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).

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

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

           -gstabs
               Produce debugging information in stabs format (if that
               is supported), without GDB extensions.  This is the
               format used by DBX on most BSD systems.  On MIPS,
               Alpha and System V Release 4 systems this option pro
               duces 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 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.

           -gcoff
               Produce debugging information in COFF format (if that
               is supported).  This is the format 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 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, and may cause assemblers other than
               the GNU assembler (GAS) to fail with an error.

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

               This option is deprecated.

           -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 mak
               ing backtraces in parts of the program that you don't
               plan to debug.  This includes descriptions of func
               tions 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 debug
               gers support macro expansion when you use -g3.

               Note that in order to avoid confusion between DWARF1
               debug level 2, and DWARF2, neither -gdwarf nor
               -gdwarf-2 accept a concatenated debug level.  Instead
               use an additional -glevel option to change the debug
               level for DWARF1 or DWARF2.

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

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

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

           -ftime-report
               name is generated from the name of the output file, if
               explicitly specified and it is not the final exe
               cutable, otherwise it is the basename of the source
               file. In both cases any suffix is removed (e.g.
               foo.da for input file dir/foo.c, or dir/foo.da for
               output file specified as -o dir/foo.o).

               For profile-directed block ordering, compile the pro
               gram with -fprofile-arcs plus optimization and code
               generation options, generate the arc profile informa
               tion by running the program on a selected workload,
               and then compile the program again with the same opti
               mization 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 span
               ning tree for the graph.  Only arcs that are not on
               the spanning tree have to be instrumented: the com
               piler 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.
               See -fprofile-arcs option above for a description of
               auxname.

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

               auxname.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
                   auxname.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:

               auxname.da
                   Runtime arc execution counts, used in conjunction

               foo.00.rtl or foo.01.sibling).  Here are the possible
               letters for use in letters, and their meanings:

               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.32.bbro.

               c   Dump after instruction combination, to the file
                   file.19.combine.

               C   Dump after the first if conversion, to the file
                   file.15.ce1.

               d   Dump after delayed branch scheduling, to
                   file.34.dbr.

               D   Dump all macro definitions, at the end of prepro
                   cessing, 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.29.ce3.

               f   Dump after life analysis, to file.18.life.

               F   Dump after purging "ADDRESSOF" codes, to
                   file.10.addressof.

               g   Dump after global register allocation, to
                   file.24.greg.

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

               k   Dump after reg-to-stack conversion, to
                   file.31.stack.

               o   Dump after post-reload optimizations, to
                   file.25.postreload.

               G   Dump after GCSE, to file.11.gcse.

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

               j   Dump after the first jump optimization, to

               N   Dump after the register move pass, to file.21.reg
                   move.

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

               R   Dump after the second scheduling pass, to
                   file.30.sched2.

               s   Dump after CSE (including the jump optimization
                   that sometimes follows CSE), to file.09.cse.

               S   Dump after the first scheduling pass, to
                   file.22.sched.

               t   Dump after the second CSE pass (including the jump
                   optimization that sometimes follows CSE), to
                   file.17.cse2.

               u   Dump after null pointer elimination pass to
                   file.08.null.

               w   Dump after the second flow pass, to file.26.flow2.

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

               z   Dump after the peephole pass, to file.27.peep
                   hole2.

               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 indi
                   cating which pattern and alternative 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 anno
                   tation.

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

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

               y   Dump debugging information during parsing, to
               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 suf
               fix 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 meaning
               ful will be ignored. The following options are avail
               able

               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.

               list information and unit/insn info.  For n greater
               than two, it includes RTL at abort point, control-flow
               and regions info.  And for n over four, -fsched-ver
               bose also includes dependence info.

           -save-temps
               Store the usual ``temporary'' intermediate files per
               manently; place them in the current directory and name
               them based on the source file.  Thus, compiling foo.c
               with -c -save-temps would produce files foo.i and
               foo.s, as well as foo.o.  This creates a preprocessed
               foo.i output file even though the compiler now nor
               mally uses an integrated 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 linking---and don't do
               anything else.  With this option, GCC does not compile
               or link anything; it just prints the file name.

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

           -print-multi-lib
               Print the mapping from multilib directory names to
               compiler switches that enable them.  The directory
               name is separated from the switches by ;, and each
               switch starts with an @} instead of the @samp{-, with
               out spaces between multiple switches.  This is sup
               posed to ease shell-processing.

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

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

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

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

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

           Options That Control Optimization

           These options control various sorts of optimizations.

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

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

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

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

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

               -O turns on the following optimization flags: -fde

               -O2 turns on all optimization flags specified by -O.
               It also turns on the following optimization flags:
               -fforce-mem -foptimize-sibling-calls -fstrength-reduce
               -fcse-follow-jumps  -fcse-skip-blocks -fre
               run-cse-after-loop  -frerun-loop-opt -fgcse
               -fgcse-lm   -fgcse-sm -fdelete-null-pointer-checks
               -fexpensive-optimizations -fregmove -fschedule-insns
               -fschedule-insns2 -fsched-interblock -fsched-spec
               -fcaller-saves -fpeephole2 -freorder-blocks  -fre
               order-functions -fstrict-aliasing -falign-functions
               -falign-jumps -falign-loops  -falign-labels

               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-func
               tions, -fweb, -funit-at-a-time, -ftracer,
               -funswitch-loops and -frename-registers options.

           -O0 Do not optimize.  This is the default.

           -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.

               -Os disables the following optimization flags:
               -falign-functions  -falign-jumps  -falign-loops
               -falign-labels  -freorder-blocks
               -fprefetch-loop-arrays

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

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

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

           -fno-default-inline
               Do not make member functions inline by default merely

           -fforce-mem
               Force memory operands to be copied into registers
               before doing arithmetic on them.  This produces better
               code by making all memory references potential common
               subexpressions.  When they are not common subexpres
               sions, instruction combination should eliminate the
               separate register-load.

               Enabled at levels -O2, -O3, -Os.

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

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

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

               Enabled at levels -O, -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

           -fno-inline
               Don't pay attention to the "inline" keyword.  Normally
               this option is used to keep the compiler from expand
               ing 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
               lation time and memory consumption.  Decreasing usu
               ally makes the compilation faster and less code will
               be inlined (which presumably means slower programs).
               This option is particularly useful for programs that
               use inlining heavily such as those based on recursive
               templates with C++.

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

                @item max-inline-insns
                 is set to I<n>.
                @item max-inline-insns-single
                 is set to I<n>/2.
                @item max-inline-insns-single-auto
                 is set to I<n>*2/5.
                @item min-inline-insns
                 is set to 130 or I<n>/4, whichever is smaller.
                @item max-inline-insns-rtl
                 is set to I<n>.

               Using -finline-limit=600 thus results in the default
               settings for these parameters.  See below for a docu
               mentation of the individual parameters controlling
               inlining.

               Note: pseudo instruction represents, in this particu
               lar context, an abstract measurement 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 optimiza
               tion 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 refer
               enced, regardless of whether or not optimization is
               turned on, use the -fno-keep-static-consts option.

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

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

               The default is -fbranch-count-reg, enabled when
               -fstrength-reduce is enabled.

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

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

               The default is -ffunction-cse

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

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

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

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

               Enabled at levels -O2, -O3, -Os.

           -fthread-jumps
               CSE will follow the jump when the condition tested is
               false.

               Enabled at levels -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

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

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

               Enabled at levels -O2, -O3, -Os.

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

               Enabled by default when gcse is enabled.

           -fgcse-sm
               When -fgcse-sm is enabled, A store motion pass is run
               after global common subexpression elimination.  This
               pass will attempt to move stores out of loops.  When
               used in conjunction with -fgcse-lm, loops containing a
               Perform cross-jumping transformation. This transforma
               tion unifies equivalent code and save code size. The
               resulting code may or may not perform better than
               without cross-jumping.

               Enabled at levels -O, -O2, -O3, -Os.

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

               Enabled at levels -O, -O2, -O3, -Os.

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

               Enabled at levels -O, -O2, -O3, -Os.

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

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

               Enabled at levels -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

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

               Note -fregmove and -foptimize-register-move are the
               to required data being unavailable.  This helps
               machines that have slow floating point or memory load
               instructions by allowing other instructions to be
               issued until the result of the load or floating point
               instruction is required.

               Enabled at levels -O2, -O3, -Os.

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

               Enabled at levels -O2, -O3, -Os.

           -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 instruc
               tions.  This is normally enabled by default when
               scheduling before register allocation, i.e.  with
               -fschedule-insns or at -O2 or higher.

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

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

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

               This option is always enabled by default on certain
               machines, usually those which have no call-preserved
               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 vari
               ous approaches to improving loop optimizations.

               Please let us (<gcc@gcc.gnu.org> and <for
               tran@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-peep
               hole2 is in how they are implemented in the compiler;
               some targets use one, some use the other, a few use
               both.

               -fpeephole is enabled by default.  -fpeephole2 enabled
               at levels -O2, -O3, -Os.

           -fbranch-probabilities
           -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 differ
               ent runs of the compiler to produce code that has dif
               ferent behavior; minimizing non-determinism is of
               paramount import.  This switch allows users to reduce
               non-determinism, possibly at the expense of inferior
               optimization.

               The default is -fguess-branch-probability at levels
               -O, -O2, -O3, -Os.

           -freorder-blocks
               Reorder basic blocks in the compiled function in order
               to reduce number of taken branches and improve code
               Also profile feedback must be available in to make
               this option effective.  See -fprofile-arcs for
               details.

               Enabled at levels -O2, -O3, -Os.

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

               Pay special attention to code like this:

                       union a_union {
                         int i;
                         double d;
                       };

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

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

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

               Every language that wishes to perform language-spe
               cific 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 func
               tion "c_get_alias_set".
               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.

               Enabled at levels -O2, -O3.

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

               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.

               Enabled at levels -O2, -O3.

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

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

               Enabled at levels -O2, -O3.

           -falign-jumps
           -falign-jumps=n
               Align branch targets to a power-of-two boundary, for
               branch targets where the targets can only be reached
               by jumping, skipping up to n bytes like -falign-func
               tions.  In this case, no dummy operations need be exe
               cuted.

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

               Enabled at levels -O2, -O3.

               optimizer and trivial dead code remover.  It can, how
               ever, make debugging impossible, since variables will
               no longer stay in a ``home register''.

               Enabled at levels -O3.

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

               Disabled at levels -O, -O2, -O3, -Os.

           The following options control compiler behavior regarding
           floating point arithmetic.  These options trade off
           between speed and correctness.  All must be specifically
           enabled.

           -ffloat-store
               Do not store floating point variables in registers,
               and inhibit other options that might change whether a
               floating point value is taken from a register or mem
               ory.

               This option prevents undesirable excess precision on
               machines such as the 68000 where the floating regis
               ters (of the 68881) keep more precision than a "dou
               ble" is supposed to have.  Similarly for the x86
               architecture.  For most programs, the excess precision
               does only good, but a few programs rely on the precise
               definition of IEEE floating point.  Use -ffloat-store
               for such programs, after modifying them to store all
               pertinent intermediate computations into variables.

           -ffast-math
               Sets -fno-math-errno, -funsafe-math-optimizations,
               -fno-trapping-math, -ffinite-math-only and -fno-sig
               naling-nans.

               This option causes the preprocessor macro
               "__FAST_MATH__" to be defined.

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

           -fno-math-errno
               Do not set ERRNO after calling math functions that are
               executed with a single instruction, e.g., sqrt.  A
               program that relies on IEEE exceptions for math error
               link-time, it may include libraries or startup files
               that change the default FPU control word or other sim
               ilar optimizations.

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

               The default is -fno-unsafe-math-optimizations.

           -ffinite-math-only
               Allow optimizations for floating-point arithmetic that
               assume that arguments and results are not NaNs or
               +-Infs.

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

               The default is -fno-finite-math-only.

           -fno-trapping-math
               Compile code assuming that floating-point operations
               cannot generate user-visible traps.  These traps
               include division by zero, overflow, underflow, inexact
               result and invalid operation.  This option implies
               -fno-signaling-nans.  Setting this option may allow
               faster code if one relies on ``non-stop'' IEEE arith
               metic, for example.

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

               The default is -ftrapping-math.

           -fsignaling-nans
               Compile code assuming that IEEE signaling NaNs may
               generate user-visible traps during floating-point
               operations.  Setting this option disables optimiza
               tions that may change the number of exceptions visible
               with signaling NaNs.  This option implies -ftrap
               ping-math.

               This option causes the preprocessor macro "__SUP
               PORT_SNAN__" to be defined.

               The default is -fno-signaling-nans.

           -fbranch-probabilities
               After running a program compiled with -fprofile-arcs,
               you can compile it a second time using -fbranch-proba
               bilities, to improve optimizations based on the number
               of times each branch was taken.  When the program com
               piled with -fprofile-arcs exits it saves arc execution
               counts to a file called sourcename.da for each source
               file  The information in this data file is very depen
               dent on the structure of the generated code, so you
               must use the same source code and the same optimiza
               tion options for both compilations.

               With -fbranch-probabilities, GCC puts a REG_BR_PROB
               note on each JUMP_INSN and CALL_INSN.  These can be
               used to improve optimization.  Currently, they are
               only used in one place: in reorg.c, instead of guess
               ing which path a branch is mostly to take, the
               REG_BR_PROB values are used to exactly determine which
               path is taken more often.

           -fnew-ra
               Use a graph coloring register allocator.  Currently
               this option is meant for testing, so we are interested
               to hear about miscompilations with -fnew-ra.

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

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

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

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

               Disabled at level -Os.

           -ffunction-sections

               Only use these options when there are significant ben
               efits from doing so.  When you specify these options,
               the assembler and linker will create larger object and
               executable files and will also be slower.  You will
               not be able to use "gprof" on all systems if you spec
               ify this option and you may have problems with debug
               ging if you specify both this option and -g.

           -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 translated 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 experi
               mental feature.

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

           --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 compile time increase
                   with probably small improvement in executable run
                   time.

               max-delay-slot-live-search
                   When trying to fill delay slots, the maximum num
                   ber of instructions to consider when searching for

               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-single
                   Several parameters control the tree inliner used
                   in gcc.  This number sets the maximum number of
                   instructions (counted in gcc's internal represen
                   tation) in a single function that the tree inliner
                   will consider for inlining.  This only affects
                   functions declared inline and methods implemented
                   in a class declaration (C++).  The default value
                   is 300.

               max-inline-insns-auto
                   When you use -finline-functions (included in -O3),
                   a lot of functions that would otherwise not be
                   considered for inlining by the compiler will be
                   investigated.  To those functions, a different
                   (more restrictive) limit compared to functions
                   declared inline can be applied.  The default value
                   is 240.

               max-inline-insns
                   The tree inliner does decrease the allowable size
                   for single functions to be inlined after we
                   already inlined the number of instructions given
                   here by repeated inlining.  This number should be
                   a factor of two or more larger than the single
                   function limit.  Higher numbers result in better
                   runtime performance, but incur higher compile-time
                   resource (CPU time, memory) requirements and
                   result in larger binaries.  Very high values are
                   not advisable, as too large binaries may adversely
                   affect runtime performance.  The default value is
                   600.

               max-inline-slope
                   After exceeding the maximum number of inlined
                   instructions by repeated inlining, a linear func
                   tion is used to decrease the allowable size for
                   single functions.  The slope of that function is
                   the negative reciprocal of the number specified
                   here.  The default value is 32.

                   eter.  The default value is 600.

               max-unrolled-insns
                   The maximum number of instructions that a loop
                   should have if that loop is unrolled, and if the
                   loop is unrolled, it determines how many times the
                   loop code is unrolled.

               hot-bb-count-fraction
                   Select fraction of the maximal count of repeti
                   tions of basic block in program given basic block
                   needs to have to be considered hot.

               hot-bb-frequency-fraction
                   Select fraction of the maximal frequency of execu
                   tions of basic block in function given basic block
                   needs to have to be considered hot

               tracer-dynamic-coverage
               tracer-dynamic-coverage-feedback
                   This value is used to limit superblock formation
                   once the given percentage of executed instructions
                   is covered.  This limits unnecessary code size
                   expansion.

                   The tracer-dynamic-coverage-feedback is used only
                   when profile feedback is available.  The real pro
                   files (as opposed to statically estimated ones)
                   are much less balanced allowing the threshold to
                   be larger value.

               tracer-max-code-growth
                   Stop tail duplication once code growth has reached
                   given percentage.  This is rather hokey argument,
                   as most of the duplicates will be eliminated later
                   in cross jumping, so it may be set to much higher
                   values than is the desired code growth.

               tracer-min-branch-ratio
                   Stop reverse growth when the reverse probability
                   of best edge is less than this threshold (in per
                   cent).

               tracer-min-branch-ratio
               tracer-min-branch-ratio-feedback
                   Stop forward growth if the best edge do have prob
                   ability lower than this threshold.

                   Similarly to tracer-dynamic-coverage two values
                   are present, one for compilation for profile feed
                   back and one for compilation without.  The value
                   for compilation with profile feedback needs to be
                   available, the notion of "RAM" is the smallest of
                   actual RAM, RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS.
                   If GCC is not able to calculate RAM on a particu
                   lar platform, the lower bound of 30% is used.
                   Setting this parameter and ggc-min-heapsize to
                   zero causes a full collection to occur at every
                   opportunity.  This is extremely slow, but can be
                   useful for debugging.

               ggc-min-heapsize
                   Minimum size of the garbage collector's heap
                   before it begins bothering to collect garbage.
                   The first collection occurs after the heap expands
                   by ggc-min-expand% beyond ggc-min-heapsize.
                   Again, tuning this may improve compilation speed,
                   and has no effect on code generation.

                   The default is RAM/8, with a lower bound of 4096
                   (four megabytes) and an upper bound of 131072 (128
                   megabytes).  If "getrlimit" is available, the
                   notion of "RAM" is the smallest of actual RAM,
                   RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS.  If GCC is
                   not able to calculate RAM on a particular plat
                   form, the lower bound is used.  Setting this
                   parameter very large effectively disables garbage
                   collection.  Setting this parameter and ggc-min-
                   expand to zero causes a full collection to occur
                   at every opportunity.

           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 prepro
           cessing.  Some of these options make sense only together
           with -E because they cause the preprocessor output to be
           unsuitable 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, trans
           lated or interpreted by the compiler driver before being
           passed to the preprocessor, and -Wp forcibly bypasses this
           phase.  The preprocessor's direct interface is undocu
           mented and subject to change, so whenever possible 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(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 com
               mon 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 direc
               tories.  If the directory dir is a standard system
               include directory, the option is ignored to ensure
               that the default search order for system directories
               and the special treatment of system headers are not
               defeated .

           -o file
               Write output to file.  This is the same as specifying
               file as the second non-option argument to cpp.  gcc
               has a different interpretation of a second non-option
               argument, so you must use -o to specify the output
               file.

           -Wall
               Turns on all optional warnings which are desirable for
               normal code.  At present this is -Wcomment and -Wtri
               graphs.  Note that many of the preprocessor's warnings
               are on by default and have no options to control them.

           -Wcomment
           -Wcomments
               Warn whenever a comment-start sequence /* appears in a
               /* comment, or whenever a backslash-newline appears in
               a // comment.  (Both forms have the same effect.)

           -Wtrigraphs
               Warn if any trigraphs are encountered.  This option
               used to take effect only if -trigraphs was also speci
               fied, 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 macros defined in the main file that are
               unused.  A macro is used if it is expanded or tested
               for existence at least once.  The preprocessor will
               also warn if the macro has not been used at the time
               it is redefined or undefined.

               Built-in macros, macros defined on the command line,
               and macros defined in include files are not warned
               about.

               Note: If a macro is actually used, but only used in
               skipped conditional blocks, then CPP will report it as
               unused.  To avoid the warning in such a case, you
               might improve the scope of the macro's definition by,
               for example, moving it into the first skipped block.
               Alternatively, you could provide a dummy use with
               something like:

                       #if defined the_macro_causing_the_warning
                       #endif

           -Wendif-labels
               Warn whenever an #else or an #endif are followed by
               text.  This usually happens in code of the form

                       #if FOO
                       ...
                       #else FOO
                       ...
                       #endif FOO

               The second and third "FOO" should be in comments, but
               often are not in older programs.  This warning is on
               by default.

           -Werror
               Make all warnings into hard errors.  Source code which
               triggers warnings will be rejected.

           -Wsystem-headers
               Issue warnings for code in system headers.  These are
               normally unhelpful in finding bugs in your own code,
               therefore suppressed.  If you are responsible for the
               system library, you may want to see them.

           -w  Suppress all warnings, including those which GNU CPP
               issues by default.

           -pedantic
               Issue all the mandatory diagnostics listed in the C
               standard.  Some of them are left out by default, since
               they trigger frequently on harmless code.

               Unless specified explicitly (with -MT or -MQ), the
               object file name consists of the basename of the
               source file with any suffix replaced with object file
               suffix.  If there are many included files then the
               rule is split into several lines using \-newline.  The
               rule has no commands.

               This option does not suppress the preprocessor's debug
               output, such as -dM.  To avoid mixing such debug out
               put with the dependency rules you should explicitly
               specify the dependency output file with -MF, or use an
               environment variable like DEPENDENCIES_OUTPUT.  Debug
               output will still be sent to the regular output stream
               as normal.

               Passing -M to the driver implies -E, and suppresses
               warnings with an implicit -w.

           -MM Like -M but do not mention header files that are found
               in system header directories, nor header files that
               are included, directly or indirectly, from such a
               header.

               This implies that the choice of angle brackets or dou
               ble quotes in an #include directive does not in itself
               determine whether that header will appear in -MM
               dependency output.  This is a slight change in seman
               tics 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 In conjunction with an option such as -M requesting
               dependency generation, -MG assumes missing header
               files are generated files and adds them to the depen
               dency list without raising an error.  The dependency
               filename is taken directly from the "#include" direc
               tive without prepending any path.  -MG also suppresses
               preprocessed output, as a missing header file renders
               this useless.

               This feature is used in automatic updating of make
               files.

           -MP This option instructs CPP to add a phony target for
               input file, including any path, deletes any file suf
               fix such as .c, and appends the platform's usual
               object suffix.  The result is the target.

               An -MT option will set the target to be exactly the
               string you specify.  If you want multiple targets, you
               can specify them as a single argument to -MT, or use
               multiple -MT options.

               For example, -MT '$(objpfx)foo.o' might give

                       $(objpfx)foo.o: foo.c

           -MQ target
               Same as -MT, but it quotes any characters which are
               special to Make.  -MQ '$(objpfx)foo.o' gives

                       $$(objpfx)foo.o: foo.c

               The default target is automatically quoted, as if it
               were given with -MQ.

           -MD -MD is equivalent to -M -MF file, except that -E is
               not implied.  The driver determines file based on
               whether an -o option is given.  If it is, the driver
               uses its argument but with a suffix of .d, otherwise
               it take the basename of the input file and applies a
               .d suffix.

               If -MD is used in conjunction with -E, any -o switch
               is understood to specify the dependency output file
               (but @pxref{-MF}), but if used without -E, each -o is
               understood to specify a target object file.

               Since -E is not implied, -MD can be used to generate a
               dependency output file as a side-effect of the compi
               lation 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 con
               formance 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

               standard may be one of:

               "iso9899:1990"
               "c89"
                   The ISO C standard from 1990.  c89 is the custom
                   ary shorthand for this version of the standard.

                   The -ansi option is equivalent to -std=c89.

               "iso9899:199409"
                   The 1990 C standard, as amended in 1994.

               "iso9899:1999"
               "c99"
               "iso9899:199x"
               "c9x"
                   The revised ISO C standard, published in December
                   1999.  Before publication, this was known as C9X.

               "gnu89"
                   The 1990 C standard plus GNU extensions.  This is
                   the default.

               "gnu99"
               "gnu9x"
                   The 1999 C standard plus GNU extensions.

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

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

           -I- Split the include path.  Any directories specified
               with -I options before -I- are searched only for head
               ers requested with "#include "file""; they are not
               searched for "#include <file>".  If additional direc
               tories are specified with -I options after the -I-,
               those directories are searched for all #include direc
               tives.

               In addition, -I- inhibits the use of the directory of
               the current file directory as the first search direc
               tory 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 appropriate) are searched.
               "..."" 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 dec
               larations.

               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 -iwithpre
               fix options.  If the prefix represents a directory,
               you should include the final /.

           -iwithprefix dir
           -iwithprefixbefore dir
               Append dir to the prefix specified previously with
               -iprefix, and add the resulting directory to the
               include search path.  -iwithprefixbefore puts it in
               the same place -I would; -iwithprefix puts it where
               -idirafter would.

               Use of these options is discouraged.

           -isystem dir
               Search dir for header files, after all directories
               specified by -I but before the standard system direc
               tories.  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 problems.  In this mode the
               integrated preprocessor is little more than a tok

           -fno-show-column
               Do not print column numbers in diagnostics.  This may
               be necessary if diagnostics are being scanned by a
               program that does not understand the column numbers,
               such as dejagnu.

           -A predicate=answer
               Make an assertion with the predicate predicate and
               answer answer.  This form is preferred to the older
               form -A predicate(answer), which is still supported,
               because it does not use shell special characters.

           -A -predicate=answer
               Cancel an assertion with the predicate predicate and
               answer answer.

           -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 preceded by a space.
               Other characters are interpreted by the compiler
               proper, or reserved for future versions of GCC, and so
               are silently ignored.  If you specify characters whose
               behavior conflicts, the result is undefined.

               M   Instead of the normal output, generate a list of
                   #define directives for all the macros defined dur
                   ing the execution of the preprocessor, including
                   predefined macros.  This gives you a way of find
                   ing 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 preprocess
                   ing.  Both kinds of output go to the standard out
                   put file.

               N   Like D, but emit only the macro names, not their
                   expansions.

               I   Output #include directives in addition to the
               it causes the preprocessor to treat comments as tokens
               in their own right.  For example, comments appearing
               at the start of what would be a directive line have
               the effect of turning that line into an ordinary
               source line, since the first token on the line is no
               longer a #.

           -CC Do not discard comments, including during macro expan
               sion.  This is like -C, except that comments contained
               within macros are also passed through to the output
               file where the macro is expanded.

               In addition to the side-effects of the -C option, the
               -CC option causes all C++-style comments inside a
               macro to be converted to C-style comments.  This is to
               prevent later use of that macro from inadvertently
               commenting out the remainder of the source line.

               The -CC option is generally used to support lint com
               ments.

           -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-cpp
               Try to imitate the behavior of old-fashioned C prepro
               cessors, as opposed to ISO C preprocessors.

           -trigraphs
               Process trigraph sequences.  These are three-character
               sequences, all starting with ??, that are defined by
               ISO C to stand for single characters.  For example,
               ??/ stands for \, so '??/n' is a character constant
               for a newline.  By default, GCC ignores trigraphs, but
               in standard-conforming modes it converts them.  See
               the -std and -ansi options.

               The nine trigraphs and their replacements are

                       Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                       Replacement:      [    ]    {    }    #    \    ^    |    ~

           -remap
               Enable special code to work around file systems which
               only permit very short file names, such as MS-DOS.

           --help
           --target-help
               Print text describing all the command line options
               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 output 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 con
               tents.)  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 rec
               ommended.)

               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 spec
               ified.  Thus, foo.o -lz bar.o searches library z after
               file foo.o but before bar.o.  If bar.o refers to func
               tions 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 libli
               brary.a.  The linker then uses this file as if it had
               been specified precisely by name.

               The directories searched include several standard sys
               tem directories plus any that you specify with -L.
               to link an Objective-C program.

           -nostartfiles
               Do not use the standard system startup files when
               linking.  The standard system libraries are used nor
               mally, 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 gener
               ate 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 sup
               plied 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 lan
               guages.

               In most cases, you need libgcc.a even when you want to
               avoid other standard libraries.  In other words, when
               you specify -nostdlib or -nodefaultlibs you should
               usually specify -lgcc as well.  This ensures that you
               have no unresolved references to internal GCC library
               subroutines.  (For example, __main, used to ensure C++
               constructors will be called.)

           -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.

               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 appli
               cation 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 typi
               cally 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
               version of libgcc, linking with the static version of
               libgcc by default.  This allows exceptions to propa
               gate 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 lan
               guages used in the program, or using the option
               -shared-libgcc, such that it is linked with the shared
               libgcc.

           -symbolic
               Bind references to global symbols when building a
               shared object.  Warn about any unresolved references
               (unless overridden by the link editor option -Xlinker
               -z -Xlinker defs).  Only a few systems support this
               option.

           -Xlinker option
               Pass option as an option to the linker.  You can use
               this to supply system-specific linker options which
               GCC does not know how to recognize.

               If you want to pass an option that takes an argument,
               you must use -Xlinker twice, once for the option and
               once for the argument.  For example, to pass -assert
               definitions, you must write -Xlinker -assert -Xlinker
               of additional library modules.

           Options for Directory Search

           These options specify directories to search for header
           files, for libraries and for parts of the compiler:

           -Idir
               Add the directory dir to the head of the list of
               directories to be searched for header files.  This can
               be used to override a system header file, substituting
               your own version, since these directories are searched
               before the system header file directories.  However,
               you should not use this option to add directories that
               contain vendor-supplied system header files (use
               -isystem for that).  If you use more than one -I
               option, the directories are scanned in left-to-right
               order; the standard system directories come after.

               If a standard system include directory, or a directory
               specified with -isystem, is also specified with -I,
               the -I option will be ignored.  The directory will
               still be searched but as a system directory at its
               normal position in the system include chain.  This is
               to ensure that GCC's procedure to fix buggy system
               headers and the ordering for the include_next direc
               tive are not inadvertently changed.  If you really
               need to change the search order for system directo
               ries, 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 directories are searched
               for all #include directives.  (Ordinarily all -I
               directories are used this way.)

               In addition, the -I- option inhibits the use of the
               current directory (where the current input file came
               from) as the first search directory for #include
               "file".  There is no way to override this effect of
               -I-.  With -I. you can specify searching the directory
               which was current when the compiler was invoked.  That
               is not exactly the same as what the preprocessor does
               by default, but it is often satisfactory.

               -I- does not inhibit the use of the standard system
               directories for header files.  Thus, -I- and -nostdinc
               are independent.

               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 pre
               fix.

               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 pre
               fix is to use the environment variable GCC_EXEC_PRE
               FIX.

               As a special kludge, if the path provided by -B is
               [dir/]stageN/, where N is a number in the range 0 to
               9, then it will be replaced by [dir/]include.  This is
               to help with boot-strapping the compiler.

           -specs=file
               Process file after the compiler reads in the standard
               specs file, in order to override the defaults that the
               gcc driver program uses when determining what switches
               to pass to cc1, cc1plus, as, ld, etc.  More than one
               -specs=file can be specified on the command line, and
               they are processed in order, from left to right.

           Specifying Target Machine and Compiler Version

           The usual way to run GCC is to run the executable called
           gcc, or <machine>-gcc when cross-compiling, or
           <machine>-gcc-<version> to run a version other than the
           one that was installed last.  Sometimes this is inconve
           -V version
               The argument version specifies which version of GCC to
               run.  This is useful when multiple versions are
               installed.  For example, version might be 2.0, meaning
               to run GCC version 2.0.

           The -V and -b options work by running the
           <machine>-gcc-<version> executable, so there's no real
           reason to use them if you can just run that directly.

           Hardware Models and Configurations

           Earlier we discussed the standard option -b which chooses
           among different installed compilers for completely differ
           ent target machines, such as VAX vs. 68000 vs. 80386.

           In addition, each of these target machine types can have
           its own special options, starting with -m, to choose among
           various hardware models or configurations---for example,
           68010 vs 68020, floating coprocessor or none.  A single
           installed version of the compiler can compile for any
           model or configuration, according to the options speci
           fied.

           Some configurations of the compiler also support addi
           tional 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 config
           ured; 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 68040.  This is the default when
               the compiler is configured for 68040-based systems.

               This option inhibits the use of 68881/68882 instruc
               tions 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 compiler 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
           -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 number 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 com
               piler.

               Also, you must provide function prototypes for all
               functions that take variable numbers of arguments
               (including "printf"); otherwise incorrect code will be
               generated for calls to those functions.

               In addition, seriously incorrect code will result if
               you call a function with too many arguments.  (Nor
               mally, 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 bound
               aries produces code that runs somewhat faster on pro
               cessors with 32-bit busses at the expense of more mem
               ory.

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

           -mpcrel
               Use the pc-relative addressing mode of the 68000

           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 sys
               tems.

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

           -m68S12
           -m68hcs12
               Generate output for a 68HCS12.

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

           -minmax
           -nominmax
               Enable the use of 68HC12 min and max instructions.

           -mlong-calls
           -mno-long-calls
               Treat all calls as being far away (near).  If calls
               are assumed to be far away, the compiler will use the
               "call" instruction to call a function and the "rtc"
               instruction for returning.

           -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

           -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 instruc
               tions.  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 facili
               ties of the machine's usual C compiler are used, but
               this cannot be done directly in cross-compilation.
               You must make your own arrangements to provide suit
               able 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 com
               pile all of a program with this option.  In particu
               lar, 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 func
               tions 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 han
               dler emulates the effect of the instruction.  Because
               of the trap handler overhead, this is much slower than
               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 compatibility
               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 alignment.  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 compiler 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.
               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.  Sup
               ported values for cpu_type are v7, cypress, v8, super
               sparc, sparclite, hypersparc, sparclite86x, f930,
               f934, sparclet, tsc701, v9, ultrasparc, and ultra
               sparc3.

               Default instruction scheduling parameters are used for
               values that select an architecture and not an imple
               mentation.  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, ultrasparc3

           -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 useful values are those
               that select a particular cpu implementation.  Those
               are cypress, supersparc, hypersparc, f930, f934, spar
               clite86x, tsc701, ultrasparc, and ultrasparc3.

           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
               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 pro
               gram must be linked in the low 32 bits of the address
               space.  Pointers are 64 bits.  Programs can be stati
               cally 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.  Point
               ers 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 ref
               erences.  Otherwise, assume no such offset is present.

           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
               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 call
               ing 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 program.  The default is -mno-thumb-interwork,
               since slightly larger code is generated when
               -mthumb-interwork is specified.

           -mno-sched-prolog
               Prevent the reordering of instructions in the function
               prolog, or the merging of those instruction with the
               instructions in the function's body.  This means that
               all functions will start with a recognizable set of
               instructions (or in fact one of a choice from a small
               set of different function prologues), and this infor
               mation 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 instruc
               tions.  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 facili
               ties of the machine's usual C compiler are used, but
               this cannot be done directly in cross-compilation.
               You must make your own arrangements to provide suit
               able library functions for cross-compilation.

               -msoft-float changes the calling convention in the
               output file; therefore, it is only useful if you com
               pile all of a program with this option.  In particu
               lar, 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 configura
               sions of the compiler prior to 2.8.

           -malignment-traps
               Generate code that will not trap if the MMU has align
               ment 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 mis
               aligned accesses will cause a MMU trap and that it
               should instead synthesize 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 archi
               tecture 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 produces better code when
               the target instruction set does not have half-word
               memory operations (i.e. implementations prior to
               ARMv4).

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

               The default setting for most targets is -mno-align
               ment-traps, since this produces better 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.

           -mcpu=name
               This specifies the name of the target ARM processor.
               GCC uses this name to determine what kind of instruc
               tions it can emit when generating assembly code.  Per
               missible names are: arm2, arm250, arm3, arm6, arm60,
               arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm,
               arm7di, arm7dmi, arm70, arm700, arm700i, arm710,
               mentations better performance can be obtained by using
               this option.

           -march=name
               This specifies the name of the target ARM architec
               ture.  GCC uses this name to determine what kind of
               instructions it can emit when generating assembly
               code.  This option can be used in conjunction with or
               instead of the -mcpu= option.  Permissible names are:
               armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5,
               armv5t, armv5te.

           -mfpe=number
           -mfp=number
               This specifies the version of the floating point emu
               lation available on the target.  Permissible values
               are 2 and 3.  -mfp= is a synonym for -mfpe=, for com
               patibility 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 compiled 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 function into a register
               and then performing a subroutine call on this regis
               ter.  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
               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 gener
               ated 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 func
               tions.  (A leaf function is one that does not call any
               other functions.)  The default is -mno-tpcs-frame.

           -mtpcs-leaf-frame
               Generate a stack frame that is compliant with the
               Thumb Procedure Call Standard for all leaf functions.
               not.  There is a small overhead in the cost of execut
               ing a function pointer if this option is enabled.

           MN10200 Options

           These -m options are defined for Matsushita MN10200 archi
           tectures:

           -mrelax
               Indicate to the linker that it should perform a relax
               ation 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 archi
           tectures:

           -mmult-bug
               Generate code to avoid bugs in the multiply instruc
               tions 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 processors.

           -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 relax
               ation 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.

               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" instruc
               tions to load their addresses), and assume all subrou
               tines 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" instruc
               tions 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 instructions 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 message---incorrect code will not be generated.

           -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 ver
               sion, 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 speci
               fied in the 88open Object Compatibility Standard,
               ``OCS''.  This extra information allows debugging of
               code that has had the frame pointer eliminated.  The
               default for 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 SVr4 and 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.

               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 particu
               lar, a load instruction may execute before a preceding
               store instruction.  Such reordering violates sequen
               tial consistency of volatile memory references, when
               there are multiple processors.   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 refer
               ences 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-serial
               ize-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 con
               figuration.  -msvr3 is the default for all other m88k
               configurations.

           -mversion-03.00
               This option is obsolete, and is ignored.
               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 divisors 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 instruc
               tion 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 execu
               tion 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 division 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) processes 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 conventions have changed
               during the evolution of the C language, and are often

           -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 Pow
               erPC 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.  How
               ever there is a large common subset of instructions
               supported by both.  An MQ register is included in pro
               cessors supporting the POWER architecture.

               You use these options to specify which instructions
               are available on the processor you are using.  The
               default value of these options is determined when con
               figuring GCC.  Specifying the -mcpu=cpu_type overrides
               the specification of these options.  We recommend you
               use the -mcpu=cpu_type option rather than the options
               listed above.

               The -mpower option allows GCC to generate instructions
               that are found only in the POWER architecture and to
               use the MQ register.  Specifying -mpower2 implies
               -power and also allows GCC to generate instructions
               that are present in the POWER2 architecture but not
               the original POWER architecture.

               The -mpowerpc option allows GCC to generate instruc
               tions that are found only in the 32-bit subset of the
               PowerPC architecture.  Specifying -mpowerpc-gpopt
               implies -mpowerpc and also allows GCC to use the
               optional PowerPC architecture instructions in the Gen
               eral Purpose group, including floating-point square
               root.  Specifying -mpowerpc-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
               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 some
               times 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 instruc
               tions 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 pur
               poses.

               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-powerpc

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

               powerpc

               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 speci
               fied, 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.

           -mabi=spe
               Extend the current ABI with SPE ABI extensions.  This
               does not change the default ABI, instead it adds the
               SPE ABI extensions to the current ABI.

           -mabi=no-spe
               Disable Booke SPE ABI extensions for the current ABI.

           -misel=yes/no
           -misel
               This switch enables or disables the generation of ISEL
               instructions.

           -mfull-toc
           -mno-fp-in-toc
           -mno-sum-in-toc
           -mminimal-toc
               Modify generation of the TOC (Table Of Contents),
               which is created for every executable file.  The
               -mfull-toc option is selected by default.  In that
               case, GCC will allocate at least one TOC entry for
               each unique non-automatic variable reference in your
               program.  GCC will also place floating-point constants
               in the TOC.  However, only 16,384 entries are avail
               able 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
               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 system must have PE installed in the stan
               dard 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 multi
               These instructions are generated by default on POWER
               systems, and not generated on PowerPC systems.  Do not
               use -mstring on little endian PowerPC systems, since
               those instructions do not work when the processor is
               in little endian mode.  The exceptions are PPC740 and
               PPC750 which permit the instructions usage in little
               endian mode.

           -mupdate
           -mno-update
               Generate code that uses (does not use) the load or
               store instructions that update the base register to
               the address of the calculated memory location.  These
               instructions are generated by default.  If you use
               -mno-update, there is a small window between the time
               that the stack pointer is updated and the address of
               the previous frame is stored, which means code that
               walks the stack frame across interrupts or signals may
               get corrupted data.

           -mfused-madd
           -mno-fused-madd
               Generate code that uses (does not use) the floating
               point multiply and accumulate instructions.  These
               instructions are generated by default if hardware
               floating is used.

           -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 han
               dled by the system.

           -mrelocatable
           -mno-relocatable
               On embedded PowerPC systems generate code that allows
               (does not allow) the program to be relocated to a dif
               ferent address at runtime.  If you use -mrelocatable
               on any module, all objects linked together must be
               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 config
               ured GCC using powerpc-*-eabiaix.

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

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

           -mcall-gnu
               On System V.4 and embedded PowerPC systems compile
               code for the Hurd-based GNU system.

           -mcall-netbsd
               On System V.4 and embedded PowerPC systems compile
               code for the NetBSD operating system.

               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 registers in case the function
               takes a variable arguments.  With -mprototype, only
               calls to prototyped variable argument functions will
               set or clear the bit.

           -msim
               On embedded PowerPC systems, assume that the startup
               module is called sim-crt0.o and that the standard C
               libraries are libsim.a and libc.a.  This is the
               default for powerpc-*-eabisim.  configurations.

           -mmvme
               On embedded PowerPC systems, assume that the startup
               module is called crt0.o and the standard C libraries
               are libmvme.a and libc.a.

           -mads
               On embedded PowerPC systems, assume that the startup
               module is called crt0.o and the standard C libraries
               are libads.a and libc.a.

           -myellowknife
               On embedded PowerPC systems, assume that the startup
               module is called crt0.o and the standard C libraries
               are libyk.a and libc.a.

           -mvxworks
               On System V.4 and embedded PowerPC systems, specify
               that you are compiling for a VxWorks system.

           -mwindiss
               Specify that you are compiling for the WindISS simula
               tion environment.

           -memb
               On embedded PowerPC systems, set the PPC_EMB bit in
               the ELF flags header to indicate that eabi extended
               relocations are used.

           -meabi
           -mno-eabi
               On System V.4 and embedded PowerPC systems do (do not)

           -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, other
               wise 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 com
               piled 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
               do this, as can the GNU linker for PowerPC/64.  It is
               planned to add this feature to the GNU linker for
               32-bit PowerPC systems as well.

               In the future, we may cause GCC to ignore all longcall
               specifications when the linker is known to generate
               glue.

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

           Darwin Options

           -all_load
               Loads all members of static archive libraries.  See
               man ld(1) for more information.

           -arch_errors_fatal
               Cause the errors having to do with files that have the
               wrong architecture to be fatal.

           -bind_at_load
               Causes the output file to be marked such that the
               dynamic linker will bind all undefined references when
               the file is loaded or launched.

           -bundle
               Produce a Mach-o bundle format file.  See man ld(1)
               for more information.

           -bundle_loader executable
               This specifies the executable that will be loading the
               build output file being linked. See man ld(1) for more
               information.

           -allowable_client  client_name
           -arch_only
           -client_name
           -compatibility_version
           -current_version
           -dependency-file
           -dylib_file
           -dylinker_install_name
           -dynamic
           -dynamiclib
           -exported_symbols_list
           -filelist
           -flat_namespace
           -force_cpusubtype_ALL
           -force_flat_namespace
           -prebind_all_twolevel_modules
           -private_bundle
           -read_only_relocs
           -sectalign
           -sectobjectsymbols
           -whyload
           -seg1addr
           -sectcreate
           -sectobjectsymbols
           -sectorder
           -seg_addr_table
           -seg_addr_table_filename
           -seglinkedit
           -segprot
           -segs_read_only_addr
           -segs_read_write_addr
           -single_module
           -static
           -sub_library
           -sub_umbrella
           -twolevel_namespace
           -umbrella
           -undefined
           -unexported_symbols_list
           -weak_reference_mismatches
           -whatsloaded
               This options are available for Darwin linker. Darwin
               linker man page describes them in detail.

           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, includ
               ing 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
               option -fpcc-struct-return for compatibility with the
               Portable C Compiler (pcc).

           -mnohc-struct-return
               Return some structures of more than one word in regis
               ters, when convenient.  This is the default.  For com
               patibility 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 com
           puters:

           -march=arch
               Generate code that will run on arch, which can be the
               name of a generic MIPS ISA, or the name of a particu
               lar processor.  The ISA names are: mips1, mips2,
               mips3, mips4, mips32 and mips64.  The processor names
               are: r2000, r3000, r3900, r4000, vr4100, vr4300,
               r4400, r4600, r4650, vr5000, r6000, r8000, 4kc, 4kp,
               5kc, 20kc, orion, and sb1.  The special value from-abi
               selects the most compatible architecture for the
               selected ABI (that is, mips1 for 32-bit ABIs and mips3
               for 64-bit ABIs).

               In processor names, a final 000 can be abbreviated as
               k (for example, -march=r2k).  Prefixes are optional,
               and vr may be written r.

               GCC defines two macros based on the value of this
               option.  The first is _MIPS_ARCH, which gives the name
               of target architecture, as a string.  The second has
               the form _MIPS_ARCH_foo, where foo is the capitalized
               value of _MIPS_ARCH.  For example, -march=r2000 will
               set _MIPS_ARCH to "r2000" and define the macro
               _MIPS_ARCH_R2000.

               Note that the _MIPS_ARCH macro uses the processor
               names given above.  In other words, it will have the
               full prefix and will not abbreviate 000 as k.  In the
               case of from-abi, the macro names the resolved archi
               tecture (either "mips1" or "mips3").  It names the
               default architecture when no -march option is given.

           -mtune=arch
               Optimize for arch.  Among other things, this option
               controls the way instructions are scheduled, and the
               perceived cost of arithmetic operations.  The list of
               arch values is the same as for -march.

               Equivalent to -march=mips2.

           -mips3
               Equivalent to -march=mips3.

           -mips4
               Equivalent to -march=mips4.

           -mips32
               Equivalent to -march=mips32.

           -mips64
               Equivalent to -march=mips64.

           -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 unde
               sirable 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.

           -mfp32
               Assume that floating point registers are 32 bits wide.

           -mfp64
               Assume that floating point registers are 64 bits wide.

           -mgp32
               Assume that general purpose registers are 32 bits
               wide.

           -mgp64
               Assume that general purpose registers are 64 bits
               wide.

           -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 point
               ers.

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

               Note that there are two embedded ABIs: -mabi=eabi
               selects the one defined by Cygnus while -meabi=meabi
               selects the one defined by MIPS.  Both these ABIs have
               32-bit and 64-bit variants.  Normally, GCC will gener
               ate 64-bit code when you select a 64-bit architecture,
               but you can use -mgp32 to get 32-bit code instead.

           -mmips-as
               Generate code for the MIPS assembler, and invoke mips-
               tfile to add normal debug information.  This is the
               default for all platforms except for the OSF/1 refer
               ence platform, 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 platform, 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 registers, instead of the hard
               ware names (ie, a0 instead of $4).  The only known
               assembler that supports this option is the Algorith
               mics assembler.

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

           -mstats
           -mno-stats
               postprocess the object file with the mips-tfile pro
               gram, after the MIPS assembler has generated it to add
               debug support.  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 tem
               porary file names passed to the assembler embedded in
               the object file, which means the objects will not com
               pare 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 compiler are used, but this can't be done
               directly in cross-compilation.  You must make your own
               arrangements to provide suitable library functions for
               cross-compilation.

           -mhard-float
               Generate output containing floating point instruc
               tions.  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 func
               tions that are not through pointers.

           -mhalf-pic
           -mno-half-pic
               Put pointers to extern references into the data sec
               tion 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.
               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 preci
               sion operations, as on the r4650 chip.  The -mdou
               ble-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 instruc
               tions 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.

               mon "_flush_func()", that is, the address of the mem
               ory 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.

           -mbranch-likely
           -mno-branch-likely
               Enable or disable use of Branch Likely instructions,
               regardless of the default for the selected architec
               ture.  By default, Branch Likely instructions may be
               generated if they are supported by the selected archi
               tecture.  An exception is for the MIPS32 and MIPS64
               architectures and processors which implement those
               architectures; for those, Branch Likely instructions
               will not be generated by default because the MIPS32
               and MIPS64 architectures specifically deprecate their
               use.

           Intel 386 and AMD x86-64 Options

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

           -mcpu=cpu-type
               Tune to cpu-type everything applicable about the gen
               erated code, except for the ABI and the set of avail
               able 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, athlon-mp,
               winchip-c6, winchip2 and c3.

               While picking a specific cpu-type will schedule things
               appropriately for that particular chip, the compiler
               will not generate any code that does not run on the
               i386 without the -march=cpu-type option being used.
               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
                   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 sup
                   ports only single precision arithmetics, thus the
                   double and extended precision arithmetics is still
                   done using 387.  Later version, present only in
                   Pentium4 and the future AMD x86-64 chips supports
                   double precision arithmetics too.

                   For 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 effectively double the amount of available
                   registers and on chips with separate execution
                   units for 387 and SSE the execution resources too.
                   Use this option with care, as it is still experi
                   mental, because gcc register allocator does not
                   model separate functional units well resulting in
                   instable performance.

           -masm=dialect
               Output asm instructions using selected dialect. Sup
               ported 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 handle correctly the case
               where the result of a comparison is unordered.

           -msoft-float
               Generate output containing library calls for floating
               point.  Warning: the requisite libraries are not part

               The usual calling convention has functions return val
               ues of types "float" and "double" in an FPU register,
               even if there is no FPU.  The idea is that the operat
               ing system should emulate an FPU.

               The option -mno-fp-ret-in-387 causes such values to be
               returned in ordinary CPU registers instead.

           -mno-fancy-math-387
               Some 387 emulators do not support the "sin", "cos" and
               "sqrt" instructions for the 387.  Specify this option
               to avoid generating those instructions.  This option
               is the default on FreeBSD, OpenBSD and NetBSD.  This
               option is overridden when -march indicates that the
               target cpu will always have an FPU and so the instruc
               tion 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, struc
               tures containing the above types will be aligned dif
               ferently than the published application binary inter
               face specifications 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 applica
               tion binary interface specify the size to be 12 bytes,
               while modern architectures (Pentium and newer) prefer
               "long double" 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 containing "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
               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 com
               piler.

               Also, you must provide function prototypes for all
               functions that take variable numbers of arguments
               (including "printf"); otherwise incorrect code will be
               generated for calls to those functions.

               In addition, seriously incorrect code will result if
               you call a function with too many arguments.  (Nor
               mally, extra arguments are harmlessly ignored.)

           -mregparm=num
               Control how many registers are used to pass integer
               arguments.  By default, no registers are used to pass
               arguments, and at most 3 registers can be used.  You
               can control this behavior for a specific function by
               using the function attribute regparm.

               Warning: if you use this switch, and num is nonzero,
               then you must build all modules with the same value,
               including any libraries.  This includes the system
               libraries and startup modules.

           -mpreferred-stack-boundary=num
               Attempt to keep the stack boundary aligned to a 2
               raised to num byte boundary.  If -mpre
               ferred-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 min
               imum 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 perfor
               mance penalties.  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

           -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 per
               formance because of improved scheduling and reduced
               dependencies.

           -maccumulate-outgoing-args
               If enabled, the maximum amount of space required for
               outgoing arguments will be computed in the function
               prologue.  This is faster on most modern CPUs because
               of reduced dependencies, improved scheduling and
               reduced stack usage when preferred stack boundary is
               not equal to 2.  The drawback is a notable increase in
               code size.  This switch implies -mno-push-args.

           -mthreads
               Support thread-safe exception handling on Mingw32.
               Code that relies on thread-safe exception handling
               must compile and link all code with the -mthreads
               option.  When compiling, -mthreads defines -D_MT; when
               linking, it links in a special thread helper library
               -lmingwthrd which cleans up per thread exception han
               dling 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

           -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 han
               dlers and therefore can be used for temporary data
               without adjusting the stack pointer.  The flag
               -mno-red-zone disables this red zone.

           -mcmodel=small
               Generate code for the small code model: the program
               and its symbols must be linked in the lower 2 GB of
               the address space.  Pointers are 64 bits.  Programs
               can be statically or dynamically linked.  This is the
               default code model.

           -mcmodel=kernel
               Generate code for the kernel code model.  The kernel
               runs in the negative 2 GB of the address space.  This
               model has to be used for Linux kernel code.

           -mcmodel=medium
               Generate code for the medium model: The program is
               linked in the lower 2 GB of the address space but sym
               bols can be located anywhere in the address space.
               Programs can be statically or dynamically linked, but
               building of shared libraries are not supported with
               the medium model.

           -mcmodel=large
               Generate code for the large model: This model makes no
               assumptions about addresses and sizes of sections.
               Currently GCC does not implement this model.

           HPPA Options

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

           -march=architecture-type
               Generate code for the specified architecture.  The
               choices for architecture-type are 1.0 for PA 1.0, 1.1
               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 assembler/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 per
               form 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 generate faster indi
               rect calls and use unscaled index address modes.

               Such code is suitable for level 0 PA systems and ker
               nels.

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

               Note this makes symbolic debugging impossible.  It
               also triggers a bug in the HP-UX 8 and HP-UX 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 facili
               ties of the machine's usual C compiler are used, but
               this cannot be done directly in cross-compilation.
               You must make your own arrangements to provide suit
               able 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 com
               pile all of a program with this option.  In particu
               lar, you need to compile libgcc.a, the library that
               comes with GCC, with -msoft-float in order for this to
               work.

           -msio
               Generate the predefine, "_SIO", for server IO.  The
               default is -mwsio.  This generates the predefines,
               "__hp9000s700", "__hp9000s700__" and "_WSIO", for
               workstation IO.  These options are available under HP-
               UX and HI-UX.

           -mgnu-ld
               Use GNU ld specific options.  This passes -shared to
               ld when building a shared library.  It is the default
               when GCC is configured, explicitly or implicitly, with
               the GNU linker.  This option does not have any affect
               on which ld is called, it only changes what parameters
               are passed to that ld.  The ld that is called is
               determined by the --with-ld configure option, gcc's
               program search path, and finally by the user's PATH.
               The linker used by GCC can be printed using which `gcc
               -print-prog-name=ld`.

           -mhp-ld
               Use HP ld specific options.  This passes -b to ld when
               building a shared library and passes +Accept TypeMis
               match to ld on all links.  It is the default when GCC
               is configured, explicitly or implicitly, with the HP
               linker.  This option does not have any affect on which
               ld is called, it only changes what parameters are
               passed to that ld.  The ld that is called is deter
               mined by the --with-ld configure option, gcc's program
               search path, and finally by the user's PATH.  The

               Distances are measured from the beginning of functions
               when using the -ffunction-sections option, or when
               using the -mgas and -mno-portable-runtime options
               together under HP-UX with the SOM linker.

               It is normally not desirable to use this option as it
               will degrade performance.  However, it may be useful
               in large applications, particularly when partial link
               ing is used to build the application.

               The types of long calls used depends on the capabili
               ties of the assembler and linker, and the type of code
               being generated.  The impact on systems that support
               long absolute calls, and long pic symbol-difference or
               pc-relative calls should be relatively small.  How
               ever, an indirect call is used on 32-bit ELF systems
               in pic code and it is quite long.

           Intel 960 Options

           These -m options are defined for the Intel 960 implementa
           tions:

           -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 sup
               port should not be assumed.

           -mleaf-procedures
           -mno-leaf-procedures
               Do (or do not) attempt to alter leaf procedures to be
               callable with the "bal" instruction 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 portions of the compiler)

           -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 imple
               mented 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 implementa
           tions:

           -mno-soft-float
           -msoft-float
               Use (do not use) the hardware floating-point instruc
               tions for floating-point operations.  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 float
               ing-point operations, or compiled in such a way as to
               call such emulations routines, these routines will
               issue floating-point operations.   If you are compil
               ing for an Alpha without floating-point operations,
               you must ensure that the library is built so as not to
               call them.

               by code compiled with -mno-fp-regs must also be com
               piled 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 hard
               ware optimized for maximum performance.  It is mostly
               compliant with the IEEE floating point standard.  How
               ever, for full compliance, software assistance is
               required.  This option generates code fully IEEE com
               pliant code except that the inexact-flag is not main
               tained (see below).  If this option is turned on, the
               preprocessor macro "_IEEE_FP" is defined during compi
               lation.  The resulting code is less efficient but is
               able to correctly support denormalized 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 compilers call this option
               -fptm trap-mode.  The trap mode can be set to one of
               four values:

               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 architec
                   ture manual for details).

               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 architec
                   ture reference manual) controls the rounding mode
                   in effect.  The C library initializes this regis
                   ter for rounding towards plus infinity.  Thus,
                   unless your program modifies the fpcr, d corre
                   sponds to round towards plus infinity.

           -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 pro
               gram execution normally needs to be terminated.  GCC
               can generate code that can assist operating system
               trap handlers in determining the exact location that
               caused a floating point trap.  Depending on the
               requirements of an application, different levels of
               precisions can be selected:

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

               f   Function precision.  The trap handler can deter
                   mine 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 -resumption_safe.

           -mieee-conformant
               This option marks the generated code as IEEE confor
               mant.  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
               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 optimal 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 instruc
               tions.  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 relocations.  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 reloca
               tions off of the $gp register.  This limits the size
               of the small data area to 64KB, but allows the vari
               ables to be directly accessed via a single instruc
               tion.

               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 allocate the data in the heap instead of in
               the program's data segment.

               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 exten
                   sion.

               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 typi
               cal 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.

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

           H8/300 Options

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

           -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 H8S.

           -mn Generate code for the H8S and H8/300H in the normal
               mode.  This switch must be used either with -mh or
               -ms.

           -ms2600
               Generate code for the H8S/2600.  This switch must be
               used with -ms.

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

           -malign-300
               On the H8/300H and H8S, use the same alignment rules
               as for the H8/300.  The default for the H8/300H and
               H8S is to align longs and floats on 4 byte boundaries.
               -malign-300 causes them to be aligned on 2 byte bound
               aries.  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.

           -mdalign
               Align doubles at 64-bit boundaries.  Note that this
               changes the calling conventions, and thus some func
               tions 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 mul
               tiple of 4 bytes, which is incompatible with the SH
               ABI.

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

           -mprefergot
               When generating position-independent code, emit func
               tion 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 trampo
               line.  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*".
               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 implementa
           tions:

           -mcpu=cpu_type
               Set the instruction set, register set, and instruction
               scheduling parameters for machine type cpu_type.  Sup
               ported 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) regis
               ter 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), instructions.  This is enabled
               by default for the C4x.  To be on the safe side, this
               is disabled 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 utilize 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
               ger multiplies instead of a library call to guarantee
               32-bit results.  Note that if one of the operands is a
               constant, 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 guaran
               teed 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 dis
               abled 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 instruc
               tions test if the iteration count is negative to ter
               minate the loop.  If the iteration count is unsigned
               there is a possibility than the 2^{31 + 1} maximum
               passed in registers where possible rather than by
               pushing arguments 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 -mparallel-insns is also speci
               fied.  These instructions have tight register con
               straints 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 func
               tion.  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 pre
               sent, this just turns on the -mep and -mprolog-func
               tion options.

           -mtda=n
               Put static or global variables whose size is n bytes
               or less into the tiny data area that register "ep"
               Specify that the target processor is the V850.

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

           -mapp-regs
               This option will cause r2 and r5 to be used in the
               code generated by the compiler.  This setting is the
               default.

           -mno-app-regs
               This option will cause r2 and r5 to be treated as
               fixed registers.

           -mv850e
               Specify that the target processor is the V850E.  The
               preprocessor constant __v850e__ will be defined if
               this option is used.

               If neither -mv850 nor -mv850e are defined then a
               default target processor will be chosen and the rele
               vant __v850*__ preprocessor constant will be defined.

               The preprocessor constants __v850 and __v851__ are
               always defined, regardless of which processor variant
               is the target.

           -mdisable-callt
               This option will suppress generation of the CALLT
               instruction for the v850e flavors of the v850 archi
               tecture.  The default is -mno-disable-callt which
               allows the CALLT instruction to be used.

           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 systems, there are many
               ARC variants with different instruction and register
               set characteristics.  This flag prevents code compiled
               for one cpu to be linked with code compiled for
               another.  No facility exists for handling variants
               that are ``almost identical''.  This is an all or

           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 config
           ured; 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 configura
               tion.

           -mmulti-add
               Try and generate multiply-add floating point instruc
               tions "polyF" and "dotF".  This option is only avail
               able if the -m32381 option is in effect.  Using these
               instructions requires changes to register allocation
               which generally has a negative impact on performance.
               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
               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 number of arguments return
               pop their arguments on return with the "ret" instruc
               tion.

               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 com
               piler.

               Also, you must provide function prototypes for all
               functions that take variable numbers of arguments
               (including "printf"); otherwise incorrect code will be
               generated for calls to those functions.

               In addition, seriously incorrect code will result if
               you call a function with too many arguments.  (Nor
               mally, 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 com
               piler.

           -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
               forms.

           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 pro
               grams (MCU types: at90s1200, attiny10, attiny11,
               attiny12, attiny15, attiny28).

               Instruction set avr2 (default) is for the classic AVR
               core with up to 8K program memory 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 sym
               bol or numeric value, __stack is the default.

           -mno-interrupts
               Generated code is not compatible with hardware inter
               rupts.  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.

           -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 HP-UX.

           -mlittle-endian
               Generate code for a little endian target.  This is the
               ister.  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-float-divide-min-latency
               Generate code for inline divides of floating point
               values using the minimum latency algorithm.

           -minline-float-divide-max-throughput
               Generate code for inline divides of floating point
               values using the maximum throughput algorithm.

           -minline-int-divide-min-latency
               Generate code for inline divides of integer values
               using the minimum latency algorithm.

           -minline-int-divide-max-throughput
               Generate code for inline divides of integer values
               using the maximum throughput algorithm.

           -mno-dwarf2-asm
           -mdwarf2-asm
               Don't (or do) generate assembler code for the DWARF2

           -mextmem
               Link the .text, .data, .bss, .strings, .rodata,
               .rodata1, .data1 sections into external 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 memory, 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 auto
               matically 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 instruc
               tions 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 instruc
               tions 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
               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 instruc
               tions.  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 specified, 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 program 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 respectively.

           -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 pro
               logue and epilogue that sets up the stack-frame are
               omitted and no return instructions or return sequences
               are generated in the code.  Use this option only
               together with visual inspection of the compiled 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 func
               tions from the PLT part of the GOT rather than (tradi
               tional 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 multilib, include files
               Like -sim, but pass linker options to locate initial
               ized 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 instruc
               tions 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" assem
               bly 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
               items that can be addressed is limited.  This means
               that a program that uses lots of static data may
               require -mno-base-addresses.

           -msingle-exit
           -mno-single-exit
               Force (do not force) generated code to have a single
               exit point in each function.

           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 sup
               ported.)

           -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 mem
               ory.

           -mint16
           -mno-int32
               Use 16-bit "int".  This is the default.

           -mint32
           -mno-int16
               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.

           FRV Options

           -mgpr-32
               Only use the first 32 general purpose registers.

           -mgpr-64
               Use all 64 general purpose registers.

           -mfpr-32
               Use only the first 32 floating point registers.

           -mfpr-64
               Use all 64 floating point registers

           -mhard-float
               Use hardware instructions for floating point opera
               tions.

               Do not use double word instructions.

           -mdouble
               Use floating point double instructions.

           -mno-double
               Do not use floating point double instructions.

           -mmedia
               Use media instructions.

           -mno-media
               Do not use media instructions.

           -mmuladd
               Use multiply and add/subtract instructions.

           -mno-muladd
               Do not use multiply and add/subtract instructions.

           -mlibrary-pic
               Enable PIC support for building libraries

           -macc-4
               Use only the first four media accumulator registers.

           -macc-8
               Use all eight media accumulator registers.

           -mpack
               Pack VLIW instructions.

           -mno-pack
               Do not pack VLIW instructions.

           -mno-eflags
               Do not mark ABI switches in e_flags.

           -mcond-move
               Enable the use of conditional-move instructions
               (default).

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mno-cond-move
               Disable the use of conditional-move instructions.

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mscc

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mno-cond-exec
               Disable the use of conditional execution.

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mvliw-branch
               Run a pass to pack branches into VLIW instructions
               (default).

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mno-vliw-branch
               Do not run a pass to pack branches into VLIW instruc
               tions.

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mmulti-cond-exec
               Enable optimization of "&&" and "||" in conditional
               execution (default).

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mno-multi-cond-exec
               Disable optimization of "&&" and "||" in conditional
               execution.

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mnested-cond-exec
               Enable nested conditional execution optimizations
               (default).

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mno-nested-cond-exec
               Disable nested conditional execution optimizations.

               This switch is mainly for debugging the compiler and
               will likely be removed in a future version.

           -mtomcat-stats
           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 den
               sity 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/accu
               mulate operations to a combination of core instruc
               tions and library calls, depending on whether any
               other multiplier options are enabled.

           -mmul16
           -mno-mul16
               Enable or disable use of the 16-bit integer multiplier
               option.  When enabled, the compiler 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 mul
               tiply or MAC16 instructions if they are available or
               generate library calls to perform the multiply opera
               tions using shifts and adds.

           -mmul32
           -mno-mul32
               Enable or disable use of the 32-bit integer multiplier
               option.  When enabled, the compiler 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.

               cally 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 instruc
               tions for 32-bit "float" operations.  When this option
               is disabled, GCC generates library calls to emulate
               32-bit floating-point operations using integer
               instructions.  Regardless of this option, 64-bit "dou
               ble" operations are always emulated with calls to
               library functions.

           -mfused-madd
           -mno-fused-madd
               Enable or disable use of fused multiply/add and multi
               ply/subtract instructions in the floating-point
               option.  This has no effect if the floating-point
               option is not also enabled.  Disabling fused multi
               ply/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 produc
               ing results with more bits of precision than specified
               by the IEEE standard.  Disabling fused multiply
               add/subtract instructions also ensures that the pro
               gram 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 literal 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 liter
               als and improve code size.  With -mtext-section-liter
               als, the literals are interspersed in the text section
               in order to keep them as close as possible to their
               aligned instructions like "LOOP", which the assembler
               will always align, either by widening density instruc
               tions or by inserting no-op instructions.

           -mlongcalls
           -mno-longcalls
               When this option is enabled, GCC instructs the assem
               bler 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 func
               tions in other source files.  Specifically, the assem
               bler translates a direct "CALL" instruction into an
               "L32R" followed by a "CALLX" instruction.  The default
               is -mno-longcalls.  This option should be used in pro
               grams 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 instructions---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 generation.

           Most of them have both positive and negative forms; the
           negative form of -ffoo would be -fno-foo.  In the table
           below, only one of the forms is listed---the one which is
           not the default.  You can figure out the other form by
           either removing no- or adding it.

           -fbounds-check
               For front-ends that support it, generate additional
               code to check that indices used to access arrays are
               within the declared range.  This is currently only
               supported by the Java and Fortran 77 front-ends, where
               this option defaults to true and false respectively.

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

           -fexceptions
               Enable exception handling.  Generates extra code
               needed to propagate exceptions.  For some targets,
               this implies GCC will generate frame unwind informa
               tion for all functions, which can produce significant
               data size overhead, although it does not affect execu
               where.  Moreover, it only allows trapping instructions
               to throw exceptions, i.e. memory references or float
               ing 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 gen
               erate any needed static data, but will not affect the
               generated code in any other way.  You will normally
               not enable this option; instead, a language processor
               that needs this handling would enable it on your
               behalf.

           -fasynchronous-unwind-tables
               Generate unwind table in dwarf2 format, if supported
               by target machine.  The table is exact at each
               instruction boundary, so it can be used for stack
               unwinding from asynchronous events (such as debugger
               or garbage collector).

           -fpcc-struct-return
               Return ``short'' "struct" and "union" values in memory
               like longer ones, rather than in registers.  This con
               vention is less efficient, but it has the advantage of
               allowing intercallability between GCC-compiled files
               and files compiled with other compilers, particularly
               the Portable C Compiler (pcc).

               The precise convention for returning structures in
               memory depends on the target configuration macros.

               Short structures and unions are those whose size and
               alignment match that of some integer type.

               Warning: code compiled with the -fpcc-struct-return
               switch is not binary compatible with code compiled
               with the -freg-struct-return switch.  Use it to con
               form 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 conven
               tion is standard for the target.  If there is no stan
               dard convention, GCC defaults to -fpcc-struct-return,
               except on targets where GCC is the principal compiler.
               In those cases, we can choose the standard, and we
               chose the more efficient register return alternative.
               erated 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 gen
               erate code that is not binary compatible with code
               generated without that switch.  Use it to conform to a
               non-default application binary interface.

           -fshort-wchar
               Override the underlying type for wchar_t to be short
               unsigned int instead of the default for the target.
               This option is useful for building programs to run
               under WINE.

               Warning: the -fshort-wchar switch causes GCC to gener
               ate code that is not binary compatible with code gen
               erated 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 systems, 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 gen
               erating 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 pro
               gram 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++ con
               structors and destructors) in the form used by the GNU
               linker (on systems where the GNU linker is the stan
               dard 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 constructors and destructors.  (col
               assembly code to make it more readable.  This option
               is generally only of use to those who actually need to
               read the generated assembly code (perhaps while debug
               ging the compiler itself).

               -fno-verbose-asm, the default, causes the extra infor
               mation to be omitted and is useful 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 supported for the target
               machine.  Such code accesses all constant addresses
               through a global offset table (GOT).  The dynamic
               loader resolves the GOT entries when the program
               starts (the dynamic loader is not part of GCC; it is
               part of the operating system).  If the GOT size for
               the linked executable exceeds a machine-specific maxi
               mum 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 certain machines.  For the
               386, GCC supports PIC for System V but not for the Sun
               386i.  Code generated for the IBM RS/6000 is always
               position-independent.

           -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,
               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 allo
               cated 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 tem
               poraries or variables that live across a call.  Func
               tions compiled this way will save and restore the reg
               ister 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 gener
               ate code that is not binary compatible with code gen
               erated without that switch.  Additionally, it makes
               the code suboptimal.  Use it to conform to a non-
               default application binary interface.

           -finstrument-functions
               Generate instrumentation calls for entry and exit to
               functions.  Just after function entry and just before
               function exit, the following profiling functions will
               be called with the address of the current function and
               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 avail
               able.  If all your uses of a function are expanded
               inline, this may mean an additional expansion of code
               size.  If you use extern inline in your C code, an
               addressable version of such functions must be pro
               vided.  (This is normally the case anyways, but if you
               get lucky and the optimizer always expands the func
               tions inline, you might have gotten away without pro
               viding static copies.)

               A function may be given the attribute "no_instru
               ment_function", in which case this instrumentation
               will not be done.  This can be used, for example, for
               the profiling functions listed above, high-priority
               interrupt routines, and any functions from which the
               profiling functions cannot safely be called (perhaps
               signal handlers, if the profiling routines generate
               output or allocate memory).

           -fstack-check
               Generate code to verify that you do not go beyond the
               boundary of the stack.  You should specify this flag
               if you are running in an environment with multiple
               threads, but only rarely need to specify it in a sin
               gle-threaded environment since stack overflow is auto
               matically detected on nearly all systems if there is
               only one stack.

               Note that this switch does not actually cause checking
               to be done; the operating system must do that.  The
               switch causes generation of code to ensure that the
               operating system sees the stack being extended.

           -fstack-limit-register=reg
           -fstack-limit-symbol=sym
           -fno-stack-limit
               Generate code to ensure that the stack does not grow
               beyond a certain value, either the value of a register
               or the address of a symbol.  If the stack would grow
               beyond the value, a signal is raised.  For most tar
               gets, the signal is raised before the stack overruns
               the boundary, so it is possible to catch the signal
               without taking special precautions.

               For instance, if the stack starts at absolute address
               0x80000000 and grows downwards, you can use the flags
               alias each other, but may alias global storage.-fargu
               ment-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 standard.  You should not
               need to use these options yourself.

           -fleading-underscore
               This option and its counterpart, -fno-leading-under
               score, forcibly change the way C symbols are repre
               sented 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 configu
           ration 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 King
               wise, LC_CTYPE and LC_MESSAGES default to the value of
               the LANG environment variable.  If none of these vari
               ables 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 out
               put of the preprocessor, which is the input to the
               compiler proper.

           GCC_EXEC_PREFIX
               If GCC_EXEC_PREFIX is set, it specifies a prefix to
               use in the names of the subprograms executed by the
               compiler.  No slash is added when this prefix is com
               bined with the name of a subprogram, but you can spec
               ify 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 pre
               fix/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 nor
               mally begins with /usr/local/lib/gcc-lib (more pre
               cisely, 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 nor
               mally search /usr/local/lib/bar.  These alternate
               directories are searched first; the standard directo
               ries come next.

           COMPILER_PATH
               The value of COMPILER_PATH is a colon-separated list

           LANG
               This variable is used to pass locale information to
               the compiler.  One way in which this information is
               used is to determine the character set to be used when
               character literals, string literals and comments are
               parsed in C and C++.  When the compiler is configured
               to allow multibyte characters, the following values
               for LANG are recognized:

               C-JIS
                   Recognize JIS characters.

               C-SJIS
                   Recognize SJIS characters.

               C-EUCJP
                   Recognize EUCJP characters.

               If LANG is not defined, or if it has some other value,
               then the compiler will use mblen and mbtowc as defined
               by the default locale to recognize and translate
               multibyte characters.

           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 sepa
               rated by a special character, much like PATH, in which
               to look for header files.  The special character,
               "PATH_SEPARATOR", is target-dependent and determined
               at GCC build time.  For Windows-based targets it is a
               semicolon, and for almost all other targets it is a
               colon.

               CPATH specifies a list of directories to be searched
               as if specified with -I, but after any paths given
               with -I options on the command line.  This environment
               variable is used regardless of which language is being
               preprocessed.

               The remaining environment variables apply only when
               preprocessing the particular language indicated.  Each
               specifies a list of directories to be searched as if
               specified with -isystem, but after any paths given
               with -isystem options on the command line.

               In all these variables, an empty element instructs the
               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 equiva
               lent to combining the options -MM and -MF, with an
               optional -MT switch too.

           SUNPRO_DEPENDENCIES
               This variable is the same as DEPENDENCIES_OUTPUT (see
               above), except that system header files are not
               ignored, so it implies -M rather than -MM.  However,
               the dependence on the main input file is omitted.

## BUGS

           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 supplemen
               tary 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.  Supply
               ing 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/online
           docs/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 Documenta
           tion License, Version 1.2 or any later version published
           by the Free Software Foundation; with the Invariant Sec
           tions 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.