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gcc



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.

           grated-cpp  -traditional  -traditional-cpp -fal­
           low-single-precision  -fcond-mismatch -fsigned-bit­
           fields  -fsigned-char -funsigned-bitfields  -fun­
           signed-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
           -frandom-seed=n -fsched-verbose=n -ftest-coverage
           -ftime-report -g  -glevel  -gcoff  -gdwarf  -gdwarf-1
           -gdwarf-1+  -gdwarf-2 -ggdb  -gstabs  -gstabs+  -gvms
           -gxcoff  -gxcoff+ -p  -pg  -print-file-name=library
           -print-libgcc-file-name -print-multi-directory
           -print-multi-lib -print-prog-name=program
           -print-search-dirs  -Q -save-temps  -time

       Optimization Options
           -falign-functions=n  -falign-jumps=n -falign-labels=n
           -falign-loops=n -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
           -fvrp -fstrength-reduce  -fstrict-aliasing  -ftracer
           -fthread-jumps -funroll-all-loops  -funroll-loops
           --param name=value -O  -O0  -O1  -O2  -O3  -Os

       Preprocessor Options
           -$  -Aquestion=answer -A-question[=answer] -C  -dD
           -dI  -dM  -dN -Dmacro[=defn]  -E  -H -idirafter dir
           -include file  -imacros file -iprefix file  -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  -nodefault­
           bitfield  -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  -mbro­
           ken-saverestore  -mcypress -mfaster-structs  -mflat
           -mfpu  -mhard-float  -mhard-quad-float -mimpure-text
           -mlittle-endian  -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 -m32rx  -m32r  -mcode-model=model-type
           -msdata=sdata-type  -G num

           M88K Options -m88000  -m88100  -m88110  -mbig-pic
           -mcheck-zero-division  -mhandle-large-shift -miden­
           tify-revision  -mno-check-zero-division
           -mno-ocs-debug-info  -mno-ocs-frame-position
           -mno-optimize-arg-area  -mno-serialize-volatile
           -mno-underscores  -mocs-debug-info -mocs-frame-posi­
           tion  -moptimize-arg-area -mserialize-volatile
           -mshort-data-num  -msvr3 -msvr4  -mtrap-large-shift
           -muse-div-instruction -mversion-03.00
           -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlit­
           tle-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 -mproto­
           type  -mno-prototype -msim  -mmvme  -mads  -myel­
           lowknife  -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

           MIPS Options -mabicalls  -march=cpu-type
           -mtune=cpu=type -mcpu=cpu-type  -membedded-data
           -muninit-const-in-rodata -membedded-pic  -mfp32
           -mfp64  -mfused-madd  -mno-fused-madd -mgas  -mgp32
           -mgp64 -mgpopt  -mhalf-pic  -mhard-float  -mint64
           -mips1 -mips2  -mips3  -mips4  -mlong64  -mlong32
           -mlong-calls  -mmemcpy -mmips-as  -mmips-tfile
           -mno-abicalls -mno-embedded-data
           -mno-uninit-const-in-rodata -mno-embedded-pic
           -mno-gpopt  -mno-long-calls -mno-memcpy
           -mno-mips-tfile  -mno-rnames  -mno-stats -mrnames
           -msoft-float -m4650  -msingle-float  -mmad -mstats
           -EL  -EB  -G num  -nocpp -mabi=32  -mabi=n32  -mabi=64
           -mabi=eabi -mfix7000  -mno-crt0  -mflush-func=func
           -mno-flush-func -mbranch-likely  -mno-branch-likely
           rect-calls  -mgas  -mgnu-ld  -mhp-ld -mjump-in-delay
           -mlinker-opt  -mlong-calls -mlong-load-store
           -mno-big-switch  -mno-disable-fpregs -mno-dis­
           able-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 -nolibdld  -static
           -threads

           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-proce­
           dures -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  -mal­
           pha-as  -mgas -mieee  -mieee-with-inexact  -mieee-con­
           formant -mfp-trap-mode=mode  -mfp-rounding-mode=mode
           -mtrap-precision=mode  -mbuild-constants -mcpu=cpu-
           type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
           -mfloat-vax  -mfloat-ieee -mexplicit-relocs
           -msmall-data  -mlarge-data -mmemory-latency=time

           DEC Alpha/VMS Options -mvms-return-codes

           H8/300 Options -mrelax  -mh  -ms  -mn  -mint32
           -malign-300

           SH Options -m1  -m2  -m3  -m3e -m4-nofpu  -m4-sin­
           gle-only  -m4-single  -m4 -m5-64media
           -m5-64media-nofpu -m5-32media  -m5-32media-nofpu
           -m5-compact  -m5-compact-nofpu -mb  -ml  -mdalign
           -mrelax -mbigtable  -mfmovd  -mhitachi  -mnomacsave
           -mieee  -misize  -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  -mro­
           data=readonly-data-section

           TMS320C3x/C4x Options -mcpu=cpu  -mbig  -msmall
           -mregparm  -mmemparm -mfast-fix  -mmpyi  -mbk  -mti
           -mdp-isr-reload -mrpts=count  -mrptb  -mdb
           -mloop-unsigned -mparallel-insns  -mparallel-mpy
           -mpreserve-float
           -mtiny-stack

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
           -mrelax-immediates -mno-relax-immediates  -mwide-bit­
           fields  -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  -mtoplevel-symbols -melf  -mbranch-predict
           -mno-branch-predict  -mbase-addresses
           -mno-base-addresses  -msingle-exit  -mno-single-exit

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as
           -mgnu-ld  -mno-pic -mvolatile-asm-stop  -mb-step
           -mregister-names  -mno-sdata -mconstant-gp  -mauto-pic
           -minline-float-divide-min-latency -min­
           line-float-divide-max-throughput -min­
           line-int-divide-min-latency -min­
           line-int-divide-max-throughput  -mno-dwarf2-asm
           -mfixed-range=register-range

           D30V Options -mextmem  -mextmemory  -monchip
           -mno-asm-optimize -masm-optimize  -mbranch-cost=n
           -mcond-exec=n

           S/390 and zSeries Options -march=cpu-type -mtune=cpu-
           type -mhard-float  -msoft-float  -mbackchain
           -mno-backchain -msmall-exec  -mno-small-exec  -mmvcle
           -mno-mvcle -m64  -m31  -mesa -mzarch -mdebug
           -mno-debug

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

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0
           -m40  -m45  -m10 -mbcopy  -mbcopy-builtin  -mint32
           -mno-int16 -mint16  -mno-int32  -mfloat32
           -mno-float64 -mfloat64  -mno-float32  -mabshi
           -mno-abshi -mbranch-expensive  -mbranch-cheap -msplit
           -mno-split  -munix-asm  -mdec-asm

           Xstormy16 Options -msim

           Xtensa Options -mbig-endian  -mlittle-endian -mdensity
           -mcond-move  -mno-cond-move -mscc  -mno-scc
           -mcond-exec  -mno-cond-exec  -mvliw-branch
           -mno-vliw-branch -mmulti-cond-exec
           -mno-multi-cond-exec  -mnested-cond-exec
           -mno-nested-cond-exec  -mtomcat-stats -mcpu=cpu

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fex­
           ceptions -fnon-call-exceptions  -funwind-tables
           -fasynchronous-unwind-tables -finhibit-size-directive
           -finstrument-functions -fno-common  -fno-ident
           -fno-gnu-linker -fpcc-struct-return  -fpic  -fPIC
           -freg-struct-return  -fshared-data  -fshort-enums
           -fshort-double  -fshort-wchar  -fvolatile
           -fvolatile-global  -fvolatile-static -fverbose-asm
           -fpack-struct  -fstack-check -fstack-limit-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
       file.FOR
           Fortran source code which should not be preprocessed.

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

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

       file.ads
           Ada source code file which contains a library unit
           declaration (a declaration of a package, subprogram,
           or generic, or a generic instantiation), or a library
           unit 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

           error produced by any phase that returned an error
           indication.

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

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

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

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

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

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

           Input files that don't require compilation are
           ignored.

       -E  Stop after the preprocessing stage; do not run the
           compiler proper.  The output is in the form of 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

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

       --help
           Print (on the standard output) a description of the
           command line options understood by gcc.  If the -v
           option is also specified then --help will also be
           passed on to the various processes invoked by gcc, so
           that they can display the command line options they
           accept.  If the -W option is also specified then com­
           mand line options which have no documentation associ­
           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
           piler, it disables recognition of C++ style // com­
           ments as well as the "inline" keyword.

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

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

           The macro "__STRICT_ANSI__" is predefined when the
           -ansi option is used.  Some header files may notice
           this macro and refrain from declaring certain 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

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

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

       -aux-info filename
           Output to the given filename prototyped declarations
           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
           option; if you wish to enable built-in functions
           selectively when using -fno-builtin or -ffreestanding,
           you may define macros such as:

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

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

       -ffreestanding
           Assert that compilation takes place in a freestanding
           environment.  This implies -fno-builtin.  A 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.

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

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

       -traditional
       -traditional-cpp
           Formerly, these options caused GCC to attempt to 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.

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

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

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

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

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or
           unsigned, when the declaration does not use either
           "signed" or "unsigned".  By default, such a bit-field
           is signed, because this is consistent: the basic 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.
       -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.  This check is normally unnecessary because the
           C++ standard specifies that "operator new" will only
           return 0 if it is declared tthhrrooww(()), in which case the
           compiler will always check the return value even with­
           out this option.  In all other cases, when "operator
           new" has a non-empty exception specification, memory
           exhaustion is signalled by throwing "std::bad_alloc".
           See also new (nothrow).

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

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

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

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

       -fdollars-in-identifiers
           Accept $ in identifiers.  You can also explicitly 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
           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.

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

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

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

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

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline
           templates, either.  The default is to handle inlines
           differently so that compiles with and without 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
           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
           -pedantic-errors without -pedantic; this option
           reverses that.  This behavior and this option are
           superseded by -pedantic, which works as it does for
           GNU C.

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

       -fno-rtti
           Disable generation of information about every class
           with virtual functions for use by the C++ runtime type
           identification features (dynamic_cast and typeid).  If
           you don't use those parts of the language, you can
           save some space by using this flag.  Note that 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".

           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
       tion options have meanings only for C++ programs:

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

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

           You should rewrite your code to avoid these warnings
           if you are concerned about the fact that code 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.
               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".

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

                       struct A {};

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

                       struct C : public B, public A {};

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

           *   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 that class are private,
           and it has neither friends nor public static member
           functions.  This warning is enabled by default.

       -Wnon-virtual-dtor (C++ only)

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

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

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

           *   Item 11:  Define a copy constructor and an assign­
               ment operator for classes with dynamically allo­
               cated memory.

           *   Item 12:  Prefer initialization to assignment in
               constructors.

           *   Item 14:  Make destructors virtual in base
               classes.

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

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

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

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

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

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

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

       -Wno-non-template-friend (C++ only)
           Disable warnings when non-templatized friend functions
           are declared within a template.  Since the advent of
           explicit template specification support in G++, if the
           name of the friend is an unqualified-id (i.e., friend
           foo(int)), the C++ language specification demands that
           the friend declare or define an ordinary, nontemplate
           function.  (Section 14.5.3).  Before G++ implemented
           explicit specification, unqualified-ids could be
           less vulnerable to unintended effects and much easier
           to search 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();
                   };

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

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

                   B* b;
                   b->f();

           will fail to compile.

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

       -Wsign-promo (C++ only)
           Warn when overload resolution chooses a promotion from
           unsigned or enumeral type to a signed type, over a
           conversion to an unsigned type of the same size.  Pre­
           vious 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 =.

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

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

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

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

       -Wselector
           Warn if multiple methods of different types for the
           same selector are found during compilation.  The check
           is performed on the list of methods in the final stage
           of compilation.  Additionally, a check is performed
           for each selector appearing in a "@selector(...)"
           expression, and a corresponding method for that selec­
           tor 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

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

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

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

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

       Options to Request or Suppress Warnings

       Warnings are diagnostic messages that report constructions
       which are not inherently 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}.

           required version of ISO C).  However, without this
           option, certain GNU extensions and traditional C and
           C++ features are supported as well.  With this option,
           they are rejected.

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

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

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

           Where the standard specified with -std represents a
           GNU extended dialect of C, such as gnu89 or gnu99,
           there is a corresponding base standard, the version of
           ISO C on which the GNU extended dialect is based.
           Warnings from -pedantic are given where they are
           required by the base standard.  (It would not make
           sense for such warnings to be given only for features
           not in the specified GNU C dialect, since by 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
           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
           standard).

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

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

       -Wno-format-y2k
           If -Wformat is specified, do not warn about "strftime"
           formats which may yield only a two-digit year.

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

           Where the unused arguments lie between used arguments
           that are specified with $ 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
           -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.

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

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

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

       -Wimplicit
           Same as -Wimplicit-int and -Wimplicit-function-decla­
           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:

           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 ();
                         else
                           bar ();
                       }
                   }

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

           The C standard defines the order in which expressions
           in a C program are evaluated in terms of sequence
           points, which represent a partial ordering between the
           execution of parts of the program: those executed
           before the sequence point, and those executed after
           it.  These occur after the evaluation of a full
           expression (one which is not part of a larger 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
           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
           return-type is not "void".

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

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

       -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.


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

           These warnings are possible only in optimizing compi­
           lation, because they require data flow information
           that is computed only when optimizing.  If you don't
           specify -O, you simply won't get these warnings.

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

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

           These warnings are made optional because GCC is not
           smart enough to see all the 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;

                   }

           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.

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

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

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

       -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

           *   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
               first things in a declaration.  According to the C
               Standard, this usage is obsolescent.

           *   The return type of a function has a type qualifier
               such as "const".  Such a type qualifier has no
               effect, since the value returned by a function is
               not an lvalue.  (But don't warn about the GNU
               extension of "volatile void" return types.  That
               extension will be warned about if -pedantic is
               specified.)

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

           *   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 };

           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
           ent problem).  In particular, instead of testing for
           equality, you would check to see whether the two val­
           ues have ranges that overlap; and this is done with
           the relational operators, so equality comparisons are
           probably mistaken.

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

           *   Macro parameters that appear within string liter­
               als in the macro body.  In traditional C macro
               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.

           *   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.

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

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

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

           *   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
           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
           where integers can only be accessed at two- or four-
           byte boundaries.

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

       -Wconversion
           Warn if a prototype causes a type conversion that is
           different from what would happen to the same argument
           in the absence of a prototype.  This includes 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
           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 (C only)
           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
           candidates, not absolute ones.  Care should be taken
           to manually verify functions actually do not ever
           return before adding the "noreturn" attribute, other­
           wise subtle code generation bugs could be introduced.
           You will not get a warning for "main" in hosted C
           environments.

       -Wmissing-format-attribute
           If -Wformat is enabled, also warn about functions
           which might be candidates for "format" attributes.
           Note these are only possible candidates, not absolute
           ones.  GCC will guess that "format" attributes might
           be appropriate for any function that calls a function
           like "vprintf" or "vscanf", but this might not always
           be the case, and some functions for which "format"
           attributes are appropriate may not be detected.  This
           option has no effect unless -Wformat is enabled (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
                   };

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

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

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

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

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

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

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

           This option is not made part of -Wall because in a
           debugging version of a program there is often 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.  Even with this option, the com­
           piler will not warn about failures to inline functions
           declared in system headers.

           The compiler uses a variety of heuristics to determine

       -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).

           Unlike most other C compilers, GCC allows you to use
           -g with -O.  The shortcuts taken by optimized code may
           occasionally produce surprising results: some vari­
           ables you declared may not exist at all; flow of con­
           trol may briefly move where you did not expect it;
           some statements may not be executed because they com­
           pute constant results or their values were already at
           hand; some statements may execute in different places
           because they were moved out of loops.

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

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

       -ggdb
           Produce debugging information for use by GDB.  This
           means to use the most expressive format available
           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.

       -gdwarf+
           Produce debugging information in DWARF version 1 for­
           mat (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.

           This option is deprecated.

       -gdwarf-2
           Produce debugging information in DWARF version 2 for­
           mat (if that is supported).  This is the format used
           by DBX on IRIX 6.

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

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

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

       -fprofile-arcs
           Instrument arcs during compilation to generate cover­
           age data or for profile-directed block ordering.  Dur­
           ing execution the program records how many times each
           branch is executed and how many times it is taken.
           When the compiled program exits it saves this data to
           a file called auxname.da for each source file.  aux­
           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
           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
               with the arc information in the file auxname.bbg.

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

       -dletters
           Says to make debugging dumps during compilation at
           times specified by letters.  This is used for debug­
           ging the compiler.  The file names for most of the
           dumps are made by appending a pass number and a word
           to the dumpname. dumpname is generated from the name
           of the output file, if explicitly specified and it is
           not an executable, otherwise it is the basename of the
           source file. In both cases any suffix is removed (e.g.
           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.

           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 control and data flow analysis, to
               file.14.cfg.  Also 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.

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

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

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

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

           k   Dump after conversion from registers to stack, to
               file.31.stack.

           l   Dump after local register allocation, to
               file.23.lreg.

           L   Dump after loop optimization, to file.12.loop.

           M   Dump after performing the machine dependent reor­
               ganization pass, to file.33.mach.

           n   Dump after register renumbering, to file.28.rnreg.

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

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

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

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


           V   Dump after value range propagation, to
               file.11.vrp.

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

           W   Dump after SSA conditional constant propagation,
               to file.05.ssaccp.

           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
               standard error.

           Z   Dump after web construction pass, to file.10.web.

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

       -fdump-translation-unit (C and C++ only)
       -fdump-translation-unit-options (C and C++ only)
           Dump a representation of the tree structure for the
           entire translation unit to a file.  The file name is

       -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.

       -frandom-seed=string
           This option provides a seed that GCC uses when it
           would otherwise use random numbers.  At present, this
           is used to generate certain symbol names that have to
           be different in every compiled file.

           The string should be different for every file you com­
           pile.

       -fsched-verbose=n
           On targets that use instruction scheduling, this
           option controls the amount of debugging output the
           scheduler prints.  This information is written to
           standard error, unless -dS or -dR is specified, in
           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.

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

           This is useful when you use -nostdlib or -nodefault­
           libs but you do want to link with libgcc.a.  You can
           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
           fer-pop -fmerge-constants -fthread-jumps -floop-opti­
           mize -fcrossjumping -fif-conversion -fif-conversion2
           -fvrp -fdelayed-branch -fguess-branch-probability
           -fcprop-registers

           -O also turns on -fomit-frame-pointer on machines
           -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
           because they are defined inside the class scope (C++
           only).  Otherwise, when you specify -O, member func­
           tions defined inside class scope are compiled inline
           by default; i.e., you don't need to add inline in
           front of the member function name.

           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
           right.

           Enabled at level -O3.

       -finline-limit=n
           By default, gcc limits the size of functions that can

           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-auto
             is set to I<n>/2.
            @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
           Attempt to merge identical constants (string constants
           and floating point constants) across compilation
           units.

           This option is the default for optimized compilation
           if the assembler and linker support it.  Use
           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
           Perform optimizations where we check to see if a jump
           branches to a location where another comparison sub­
           sumed by the first is found.  If so, the first branch
           is redirected to either the destination of the second
           branch or a point immediately following it, depending
           on whether the condition is known to be true or false.
           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
           load/store sequence can be changed to a load before
           the loop and a store after the loop.

           Enabled by default when gcse is enabled.

       -floop-optimize

       -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.

       -fvrp
           Find out which range is a value of a register in.  If
           the register may have no value in some block the block
           is unreachable and is deleted.  For example a "printf"
           call in following code may be deleted:

                   if (i < 0)
                   {
                     if (i > 5)
                       printf ("foo");
                   }

           Enabled at levels -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
           reorder instructions to exploit instruction slots
           available after delayed branch instructions.

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

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

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

       -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
           outside the loop.

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

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

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

           These two options are intended to be removed someday,
           once they have helped determine the efficacy of 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
           to reduce number of taken branches and improve code
           locality. This is implemented by using special subsec­
           tions "text.hot" for most frequently executed func­
           tions and "text.unlikely" for unlikely executed func­
           tions.  Reordering is done by the linker so object
           file format must support named sections and linker
           must place them in a reasonable way.

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

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

       -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;

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

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

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

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

           Enabled at levels -O2, -O3.

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

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

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

           If n is not specified or is zero, use a machine-depen­
           dent 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.

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

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

           dent default.

           Enabled at levels -O2, -O3.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code
           by making use of registers left over after register
           allocation.  This optimization will most benefit pro­
           cessors with lots of registers.  It can, however, make
           debugging impossible, since variables will no longer
           stay in a ``home register''.

       -fweb
           Constructs webs as commonly used for register alloca­
           tion purposes and assign each web individual pseudo
           register.  This allows our register allocation pass to
           operate on pseudos directly, but also strengthens sev­
           eral other optimization passes, such as CSE, loop
           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.

       -fno-math-errno
           Do not set ERRNO after calling math functions that are
           executed with a single instruction, e.g., sqrt.  A
           program that relies on IEEE exceptions for math error
           handling may want to use this flag for speed while
           maintaining IEEE arithmetic compatibility.

           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 -fmath-errno.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that
           (a) assume that arguments and results are valid and
           (b) may violate IEEE or ANSI standards.  When used at
           link-time, it may include libraries or startup files
           that change the default FPU control word or other 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
           PORT_SNAN__" to be defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently
           guarantee to disable all GCC optimizations that affect
           signaling NaN behavior.

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

       The following options control optimizations that may
       improve performance, but are not enabled by any -O
       options.  This section includes experimental options that
       may produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs,
           you can compile it a second time using -fbranch-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.

           Disabled at level -Os.

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section
           in the output file if the target supports arbitrary
           sections.  The name of the function or the name of the
           data item determines the section's name in the output
           file.

           Use these options on systems where the linker can per­
           form optimizations to improve locality of reference in
           the instruction space.  Most systems using the ELF
           object format and SPARC processors running Solaris 2
           have linkers with such optimizations.  AIX may have
           these optimizations in the future.

           Only use these options when there are significant 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.

               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
               a block with valid live register information.
               Increasing this arbitrarily chosen value means
               more aggressive optimization, increasing the com­
               pile time.  This parameter should be removed when
               the delay slot code is rewritten to maintain the
               control-flow graph.

           max-gcse-memory
               The approximate maximum amount of memory that will
               be allocated in order to perform the global common
               subexpression elimination optimization.  If more
               memory than specified is required, the optimiza­
               tion will not be done.

           max-gcse-passes
               The maximum number of passes of GCSE to run.

           max-pending-list-length
               The maximum number of pending dependencies
               scheduling will allow before flushing the current
               state and starting over.  Large functions with few
               branches or calls can create excessively large
               lists which needlessly consume memory and
               resources.

           max-inline-insns-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
               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.

           min-inline-insns
               The repeated inlining is throttled more and more
               by the linear function after exceeding the limit.
               To avoid too much throttling, a minimum for this
               function is specified here to allow repeated
               inlining for very small functions even when a lot
               of repeated inlining already has been done.  The
               default value is 130.

           max-inline-insns-rtl
               For languages that use the RTL inliner (this hap­
               pens at a later stage than tree inlining), you can
               set the maximum allowable size (counted in RTL
               instructions) for the RTL inliner with this param­
               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
               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
               more conservative (higher) in order to make tracer
               effective.

           ggc-min-expand
               GCC uses a garbage collector to manage its own
               memory allocation.  This parameter specifies the
               minimum percentage by which the garbage collec­
               tor's heap should be allowed to expand between
               collections.  Tuning this may improve compilation
               speed; it has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper
               bound of 100% when RAM >= 1GB.  If "getrlimit" is
               available, the notion of "RAM" is the smallest of
               actual RAM, 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

       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=definition
           Predefine name as a macro, with definition definition.
           There are no restrictions on the contents of defini­
           tion, but if you are invoking the preprocessor from a
           shell or shell-like program you may need to use the
           shell's quoting syntax to protect characters such as
           spaces that have a meaning in the shell syntax.

           If you wish to define a function-like macro on the
           command line, write its argument list with surrounding
           parentheses before the equals sign (if any).  Paren­
           theses are meaningful to most shells, so you will need
           to quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are
           given on the command line.  All -imacros file and
           -include file options are processed after all -D and
           -U options.

       -U name
           Cancel any previous definition of name, either built
           in or provided with a -D option.

       -undef
           Do not predefine any system-specific or GCC-specific
           macros.  The standard predefined macros remain
           defined.

       -I dir
           Add the directory dir to the list of directories to be
           searched for header files.  Directories named by -I
           are searched before the standard system include 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
           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 certain constructs that behave differently
           in traditional and ISO C.  Also warn about ISO C con­
           structs that have no traditional C equivalent, and
           problematic constructs which should be avoided.

       -Wimport
           Warn the first time #import is used.

       -Wundef
           Warn whenever an identifier which is not a macro is
           encountered in an #if directive, outside of defined.
           Such identifiers are replaced with zero.

       -Wunused-macros
           Warn about macros defined in the main file that are
           unused.  A macro is used if it is expanded or tested
           for existence at least once.  The preprocessor will
           also warn if the macro has not been used at the time
           it is redefined or undefined.

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

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

                   #if defined the_macro_causing_the_warning
                   #endif

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

                   #if FOO

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

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

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

       -pedantic-errors
           Issue all the mandatory diagnostics, and make all
           mandatory diagnostics into errors.  This includes
           mandatory diagnostics that GCC issues without -pedan­
           tic but treats as warnings.

       -M  Instead of outputting the result of preprocessing,
           output a rule suitable for make describing the depen­
           dencies of the main source file.  The preprocessor
           outputs one make rule containing the object file name
           for that source file, a colon, and the names of all
           the included files, including those coming from
           -include or -imacros command line options.

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

           This option does not suppress the preprocessor's debug
           output, such as -dM.  To avoid mixing such debug 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
           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
           each dependency other than the main file, causing each
           to depend on nothing.  These dummy rules work around
           errors make gives if you remove header files without
           updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency
           generation.  By default CPP takes the name of the main
           input file, including any path, deletes any file 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
           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
           extensions for C++ and assembly are also recognized.
           If cpp does not recognize the extension, it will treat
           the file as C; this is the most generic mode.

           Note: Previous versions of cpp accepted a -lang option
           which selected both the language and the standards
           conformance level.  This option has been removed,
           because it conflicts with the -l option.

       -std=standard
       -ansi
           Specify the standard to which the code should conform.
           Currently CPP knows about C and C++ standards; others
           may be added in the future.

           standard may be one of:

           "iso9899:1990"
           "c89"
               The ISO C standard from 1990.  c89 is the 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"
           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.

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

       -include file
           Process file as if "#include "file"" appeared as the
           first line of the primary source file.  However, the
           first directory searched for file is the preproces­
           sor's working directory instead of the directory con­
           taining the main source file.  If not found there, it
           is searched for in the remainder of the "#include
           "..."" search chain as normal.

           If multiple -include options are given, the files are
           included in the order they appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced
           by scanning file is thrown away.  Macros it defines
           remain defined.  This allows you to acquire all the
           macros from a header without also processing its 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 /.

           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
           enizer for the front ends.

           -fpreprocessed is implicit if the input file has one
           of the extensions .i, .ii or .mi.  These are the
           extensions that GCC uses for preprocessed files cre­
           ated by -save-temps.

       -ftabstop=width
           Set the distance between tab stops.  This helps the
           preprocessor report correct column numbers in warnings
           or errors, even if tabs appear on the line.  If the
           value is less than 1 or greater than 100, the option
           is ignored.  The default is 8.

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

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

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

       -dCHARS
           CHARS is a sequence of one or more of the following
           characters, and must not be preceded by a space.
           Other characters are interpreted by the compiler
           proper, or reserved for future versions of GCC, and so
           are silently ignored.  If you specify characters whose
           behavior conflicts, the result is undefined.

           M   Instead of the normal output, generate a list of
               #define directives for all the macros defined dur­
               put file.

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

           I   Output #include directives in addition to the
               result of preprocessing.

       -P  Inhibit generation of linemarkers in the output from
           the preprocessor.  This might be useful when running
           the preprocessor on something that is not C code, and
           will be sent to a program which might be confused by
           the linemarkers.

       -C  Do not discard comments.  All comments are passed
           through to the output file, except for comments in
           processed directives, which are deleted along with the
           directive.

           You should be prepared for side effects when using -C;
           it causes the preprocessor to treat comments as tokens
           in their own right.  For example, comments appearing
           at the start of what would be a directive line have
           the effect of turning that line into an ordinary
           source line, since the first token on the line is no
           longer a #.

       -CC Do not discard comments, including during macro 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.

       -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
           instead of preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at
           the beginning of execution, and report the final form
           of the include path.

       -H  Print the name of each header file used, in addition
           to other normal activities.  Each name is indented to
           show how deep in the #include stack it is.

       -version
       --version
           Print out GNU CPP's version number.  With one dash,
           proceed to preprocess as normal.  With two dashes,
           exit immediately.

       Passing Options to the Assembler

       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option
           contains commas, it is split into multiple options at
           the commas.

       Options for Linking

       These options come into play when the compiler links
       object files into an executable 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.)


           Normally the files found this way are library
           files---archive files whose members are object files.
           The linker handles an archive file by scanning through
           it for members which define symbols that have so far
           been referenced but not defined.  But if the file that
           is found is an ordinary object file, it is linked in
           the usual fashion.  The only difference between using
           an -l option and specifying a file name is that -l
           surrounds library with lib and .a and searches several
           directories.

       -lobjc
           You need this special case of the -l option in order
           to link an Objective-C 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

       -shared
           Produce a shared object which can then be linked with
           other objects to form an executable.  Not all systems
           support this option.  For predictable results, you
           must also specify the same set of options that were
           used to generate code (-fpic, -fPIC, or model subop­
           tions) when you specify this option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library,
           these options force the use of either the shared or
           static version respectively.  If no shared version of
           libgcc was built when the compiler was configured,
           these options have no effect.

           There are several situations in which an application
           should use the shared libgcc instead of the static
           version.  The most common of these is when the 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
           definitions.  It does not work to write -Xlinker
           "-assert definitions", because this passes the entire
           string as a single argument, which is not what the
           linker expects.

       -Wl,option
           Pass option as an option to the linker.  If option
           contains commas, it is split into multiple options at
           the commas.

       -u symbol
           Pretend the symbol symbol is undefined, to force link­
           ing of library modules to define it.  You can use -u
           multiple times with different symbols to force loading
           of additional library modules.

       Options for Directory Search

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

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

           If a standard system include directory, or a directory
           specified with -isystem, is also specified with -I,
           the -I option will be ignored.  The directory will
           still be searched but as a system directory at its
           normal position in the system include chain.  This is
           to ensure that GCC's procedure to fix buggy system
           headers and the ordering for the include_next 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.)

       -Ldir
           Add directory dir to the list of directories to be
           searched for -l.

       -Bprefix
           This option specifies where to find the executables,
           libraries, include files, and data files of the com­
           piler itself.

           The compiler driver program runs one or more of the
           subprograms cpp, cc1, as and ld.  It tries prefix as a
           prefix for each program it tries to run, both with and
           without machine/version/.

           For each subprogram to be run, the compiler driver
           first tries the -B prefix, if any.  If that name is
           not found, or if -B was not specified, the driver
           tries two standard prefixes, which are /usr/lib/gcc/
           and /usr/local/lib/gcc-lib/.  If neither of those
           results in a file name that is found, the unmodified
           program name is searched for using the directories
           specified in your PATH environment variable.

           The compiler will check to see if the path provided by
           the -B refers to a directory, and if necessary it will
           add a directory separator character at the end of the
           path.

           -B prefixes that effectively specify directory names
           also apply to libraries in the linker, because the
           compiler translates these options into -L options for
           the linker.  They also apply to includes files in the
           preprocessor, because the compiler translates these
           options into -isystem options for the preprocessor.
           In this case, the compiler appends include to the 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.

       nient, so GCC provides options that will switch to another
       cross-compiler or version.

       -b machine
           The argument machine specifies the target machine for
           compilation.

           The value to use for machine is the same as was speci­
           fied as the machine type when configuring GCC as a
           cross-compiler.  For example, if a cross-compiler was
           configured with configure i386v, meaning to compile
           for an 80386 running System V, then you would specify
           -b i386v to run that cross compiler.

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

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

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

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

           This option inhibits the use of 68881/68882 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
           Generate output containing library calls for floating
           point.  Warning: the requisite libraries are not
           available for all m68k targets.  Normally the facili­
           ties 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.  The embedded
           targets m68k-*-aout and m68k-*-coff do provide soft­
           ware floating point support.

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

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

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

       -mrtd
           Use a different function-calling convention, in which
           functions that take a fixed 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",
           directly, instead of using a global offset table.  At
           present, this option implies -fpic, allowing at most a
           16-bit offset for pc-relative addressing.  -fPIC is
           not presently supported with -mpcrel, though this
           could be supported for 68020 and higher processors.

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

       M68hc1x Options

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

       -m6811
       -m68hc11
           Generate output for a 68HC11.  This is the default
           when the compiler is configured for 68HC11-based 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
           Do not output certain jump instructions ("aobleq" and
           so on) that the Unix assembler for the VAX cannot han­
           dle across long ranges.

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

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

       SPARC Options

       These -m switches are supported on the SPARC:

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

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

       -mfpu
       -mhard-float
           Generate output containing floating point 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)
           calling the ABI library routines.  Thus the
           -msoft-quad-float option is the default.

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

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

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

           With -munaligned-doubles, GCC assumes that doubles
           have 8 byte alignment only if they are contained in
           another type, or if they have an absolute address.
           Otherwise, it assumes they have 4 byte alignment.
           Specifying this option avoids some rare 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.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the
           compiler to not pass -z text to the linker when link­
           ing a shared object.  Using this option, you can link
           position-dependent code into a shared object.

           -mimpure-text suppresses the ``relocations remain
           against allocatable but non-writable sections'' linker
           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.

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

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

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

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

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction
           scheduling parameters for machine type cpu_type.  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

           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
           the "save" and "restore" instructions.  Early versions
           of the SPARCLET processor do not correctly handle
           "save" and "restore" instructions used with arguments.
           They correctly handle them used without arguments.  A
           "save" instruction used without arguments increments
           the current window pointer but does not allocate a new
           stack frame.  It is assumed that the window overflow
           trap handler will properly handle this case as will
           interrupt handlers.

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

       -mlittle-endian
           Generate code for a processor running in little-endian
           mode. It is only available for a few configurations
           and most notably not on Solaris.

       -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
           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
           Procedure Call Standard for all functions, even if
           this is not strictly necessary for correct execution
           of the code.  Specifying -fomit-frame-pointer with
           this option will cause the stack frames not to be gen­
           erated for leaf functions.  The default is
           -mno-apcs-frame.

       -mapcs
           This is a synonym for -mapcs-frame.

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

       -mapcs-32
           Generate code for a processor running with a 32-bit
           program counter, and conforming to the function 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
           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
           tions.

       -mbig-endian
           Generate code for a processor running in big-endian
           mode; the default is to compile code for a little-
           endian processor.

       -mwords-little-endian
           This option only applies when generating code for big-
           endian processors.  Generate code for a little-endian
           word order but a big-endian byte order.  That is, a
           byte order of the form 32107654.  Note: this option
           should only be used if you require compatibility with
           code for big-endian ARM processors generated by ver­
           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.
           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,
           arm710c, arm7100, arm7500, arm7500fe, arm7tdmi, arm8,
           strongarm, strongarm110, strongarm1100, arm8, arm810,
           arm9, arm9e, arm920, arm920t, arm940t, arm9tdmi,
           arm10tdmi, arm1020t, xscale.

       -mtune=name
           This option is very similar to the -mcpu= option,
           except that instead of specifying the actual target
           processor type, and hence restricting which instruc­
           tions can be used, it specifies that GCC should tune
           the performance of the code as if the target were of
           the type specified in this option, but still choosing
           the instructions that it will generate based on the
           cpu specified by a -mcpu= option.  For some ARM imple­
           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
           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
           #pragma no_long_calls directive and functions whose
           definitions have already been compiled within the cur­
           rent compilation unit, will not be turned into long
           calls.  The exception to this rule is that weak func­
           tion definitions, functions with the long-call
           attribute or the section attribute, and functions that
           are within the scope of a #pragma long_calls direc­
           tive, will always be turned into long calls.

           This feature is not enabled by default.  Specifying
           -mno-long-calls will restore the default behavior, as
           will placing the function calls within the scope of a
           #pragma long_calls_off directive.  Note these switches
           have no effect on how the compiler generates code to
           handle function calls via function pointers.

       -mnop-fun-dllimport
           Disable support for the "dllimport" attribute.

       -msingle-pic-base
           Treat the register used for PIC addressing as
           read-only, rather than loading it in the prologue for
           each function.  The run-time system is responsible for
           initializing this register with an appropriate value
           before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.
           The default is R10 unless stack-checking is enabled,
           when R9 is used.

       -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:
                            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.
           (A leaf function is one that does not call any other
           functions.)  The default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file
           being compiled an ARM instruction set header which
           switches to Thumb mode before executing the rest of
           the function.  This allows these functions to be
           called from non-interworking code.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual
           functions) to execute correctly regardless of whether
           the target code has been compiled for interworking or
           not.  There is a small overhead in the cost of 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.

           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.

       M32R/D Options

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

       -m32rx
           Generate code for the M32R/X.

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

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

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

       -mcode-model=medium
           Assume objects may be anywhere in the 32-bit address
           space (the compiler will generate "seth/add3" 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
           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.

       M88K Options

       These -m options are defined for Motorola 88k architec­
       tures:

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

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

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

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

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

       -mno-underscores
           In assembler output, emit symbol names without adding

       -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.

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

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

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

           The order of memory references made by the MC88110
           processor does not always match the order of the
           instructions requesting those references.  In 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
           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.

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

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

           GCC assumes that the MC88110 processor correctly
           detects all instances of integer division by zero.
           When -m88110 is specified, no explicit checks for
           zero-valued 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
           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
           the source of portability problems.  By default, GCC
           issues no such warning.

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and Pow­
       erPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-powerpc
       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
           GCC supports two related instruction set architectures
           for the RS/6000 and PowerPC.  The POWER instruction
           set are those instructions supported by the rios chip
           set used in the original RS/6000 systems and the 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
           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
           will use only the instructions in the common subset of
           both architectures plus some special AIX common-mode
           calls, and will not use the MQ register.  Specifying
           both -mpower and -mpowerpc permits GCC to use any
           instruction from either architecture and to allow use
           of the MQ register; specify this for the Motorola
           MPC601.

       -mnew-mnemonics
       -mold-mnemonics
           Select which mnemonics to use in the generated assem­
           bler code.  With -mnew-mnemonics, GCC uses the assem­
           bler mnemonics defined for the PowerPC architecture.
           With -mold-mnemonics it uses the assembler mnemonics
           defined for the POWER architecture.  Instructions
           defined in only one architecture have only one
           mnemonic; GCC uses that mnemonic irrespective of which
           of these options is specified.

           GCC defaults to the mnemonics appropriate for the
           architecture in use.  Specifying -mcpu=cpu_type 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
           -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
           rs64a
           602
           603
           603e
           604
           620
           630
           740
           7400
           7450
           750
           505 -mno-power, -mpowerpc, -mnew-mnemonics

           601 -mpower, -mpowerpc, -mnew-mnemonics

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

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine
           type cpu_type, but do not set the architecture type,
           register usage, or choice of mnemonics, as
           -mcpu=cpu_type would.  The same values for cpu_type
           are used for -mtune as for -mcpu.  If both are speci­
           fied, the code generated will use the architecture,
           registers, and mnemonics set by -mcpu, but the
           scheduling parameters set by -mtune.
           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
           -mno-fp-in-toc and -mno-sum-in-toc options.
           -mno-fp-in-toc prevents GCC from putting floating-
           point constants in the TOC and -mno-sum-in-toc forces
           GCC to generate code to calculate the sum of an
           address and a constant at run-time instead of putting
           that sum into the TOC.  You may specify one or both of
           these options.  Each causes GCC to produce very
           slightly slower and larger code at the expense of con­
           serving TOC space.

           If you still run out of space in the TOC even when you
           specify both of these options, specify -mminimal-toc
           instead.  This option causes GCC to make only one TOC
           entry for every file.  When you specify this option,
           GCC will produce code that is slower and larger but
           which uses extremely little TOC space.  You may wish
           to use this option only on files that contain less
           frequently executed code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit
           pointers, 64-bit "long" type, and the infrastructure
           needed to support them.  Specifying -maix64 implies
           -mpowerpc64 and -mpowerpc, while -maix32 disables the
           64-bit ABI and implies -mno-powerpc64.  GCC defaults
           to -maix32.

       -mxl-call
           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
           ple word instructions and the store multiple word
           instructions.  These instructions are generated by
           default on POWER systems, and not generated on PowerPC
           systems.  Do not use -mmultiple on little endian Pow­
           erPC systems, since those instructions do not work
           when the processor is in little endian mode.  The
           exceptions are PPC740 and PPC750 which permit the
           instructions usage in little endian mode.

       -mstring
       -mno-string
           Generate code that uses (does not use) the load string
           instructions and the store string word instructions to
           save multiple registers and do small block moves.
           These instructions are generated by default on POWER
           systems, and not generated on PowerPC systems.  Do not
           use -mstring on little endian PowerPC systems, since
           those instructions do not work when the processor is
           in little endian mode.  The exceptions are PPC740 and
           PPC750 which permit the instructions usage in little
           endian mode.

       -mupdate
       -mno-update
           Generate code that uses (does not use) the load or
           store instructions that update the base register to
           the address of the calculated memory location.  These
           instructions are generated by default.  If you use
           -mno-update, there is a small window between the time
           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
           compiled with -mrelocatable or -mrelocatable-lib.

       -mrelocatable-lib
       -mno-relocatable-lib
           On embedded PowerPC systems generate code that allows
           (does not allow) the program to be relocated to a dif­
           ferent address at runtime.  Modules compiled with
           -mrelocatable-lib can be linked with either modules
           compiled without -mrelocatable and -mrelocatable-lib
           or with modules compiled with the -mrelocatable
           options.

       -mno-toc
       -mtoc
           On System V.4 and embedded PowerPC systems do not (do)
           assume that register 2 contains a pointer to a global
           area pointing to the addresses used in the program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile
           code for the processor in little endian mode.  The
           -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
           On System V.4 and embedded PowerPC systems compile
           code for the processor in big endian mode.  The
           -mbig-endian option is the same as -mbig.

       -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.

       -maix-struct-return
           Return all structures in memory (as specified by the
           AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers
           (as specified by the SVR4 ABI).

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

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

       -mprototype
       -mno-prototype
           On System V.4 and embedded PowerPC systems assume that
           all calls to variable argument functions are properly
           prototyped.  Otherwise, the compiler must insert an
           instruction before every non prototyped call to set or
           clear bit 6 of the condition code register (CR) to
           indicate whether floating point values were passed in
           the floating point registers in case the function
           takes a variable arguments.  With -mprototype, only
           calls to prototyped variable argument functions will
           set or clear the bit.

           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)
           adhere to the Embedded Applications Binary Interface
           (eabi) which is a set of modifications to the System
           V.4 specifications.  Selecting -meabi means that the
           stack is aligned to an 8 byte boundary, a function
           "__eabi" is called to from "main" to set up the eabi
           environment, and the -msdata option can use both "r2"
           and "r13" to point to two separate small data areas.
           Selecting -mno-eabi means that the stack is aligned to
           a 16 byte boundary, do not call an initialization
           function from "main", and the -msdata option will only
           use "r13" to point to a single small data area.  The
           -meabi option is on by default if you configured GCC
           using one of the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put small
           initialized "const" global and static data in the
           .sdata2 section, which is pointed to by register "r2".
           Put small initialized non-"const" global and static
           data in the .sdata section, which is pointed to by
           register "r13".  Put small uninitialized global and
           static data in the .sbss section, which is adjacent to
           the .sdata section.  The -msdata=eabi option is 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
           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
           using symbolic forms.

       -mlongcall
       -mno-longcall
           Default to making all function calls via pointers, so
           that functions which reside further than 64 megabytes
           (67,108,864 bytes) from the current location can be
           called.  This setting can be overridden by the "short­
           call" function attribute, or by "#pragma longcall(0)".

           Some linkers are capable of detecting out-of-range
           calls and generating glue code on the fly.  On these
           systems, long calls are unnecessary and generate
           slower code.  As of this writing, the AIX linker can
           do this, as can the GNU linker for PowerPC/64.  It is
           planned to add this feature to the GNU linker for
           32-bit PowerPC systems as well.

           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

           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
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -seg_addr_table
       -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
           Use a calling sequence incompatible with the IBM call­
           ing convention in which floating point arguments are
           passed in floating point registers.  Note that
           "stdarg.h" will not work with floating point operands
           if this option is specified.

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

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

       -mnohc-struct-return
           Return some structures of more than one word in 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
           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.

           When this option is not used, GCC will optimize for
           the processor specified by -march.  By using -march
           and -mtune together, it is possible to generate code
           that will run on a family of processors, but optimize
           the code for one particular member of that family.

           -mtune defines the macros _MIPS_TUNE and
           _MIPS_TUNE_foo, which work in the same way as the
           -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -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.

           The default size of ints, longs and pointers depends
           on the ABI.  All the supported ABIs use 32-bit ints.
           The n64 ABI uses 64-bit longs, as does the 64-bit
           Cygnus EABI; the others use 32-bit longs.  Pointers
           are the same size as longs, or the same size as inte­
           ger registers, whichever is smaller.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
       -mabi=meabi
           Generate code for the given ABI.

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

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

       -mmips-tfile
       -mno-mips-tfile
           The -mno-mips-tfile switch causes the compiler not
           postprocess the object file with the mips-tfile 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.

       -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.
           This currently only works on targets which use ECOFF;
           it does not work with ELF.

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

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

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

       -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.

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

       -no-crt0
           Do not include the default crt0.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D
           caches, or to not call any such function.  If called,
           the function must take the same arguments as the com­
           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

       -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
           These options are synonyms for -mcpu=i386, -mcpu=i486,
           -mcpu=pentium, and -mcpu=pentiumpro respectively.
           These synonyms are deprecated.

       -mfpmath=unit
           generate floating point arithmetics for selected unit
           unit.  the choices for unit are:

           387 Use the standard 387 floating point coprocessor
               present majority of chips and emulated otherwise.
               Code compiled with this option will run almost
               everywhere.  The temporary results are computed in
               80bit precision instead of precision specified by
               the type resulting in slightly different results
               compared to most of other chips. See -ffloat-store
               for more detailed description.

               This is the default choice for i386 compiler.

           sse Use scalar floating point instructions present in
               the SSE instruction set.  This instruction set is
               supported by Pentium3 and newer chips, in the AMD
               line by Athlon-4, Athlon-xp and Athlon-mp chips.
               The earlier version of SSE instruction set sup­
               ports only single precision arithmetics, thus the
               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
           of GCC.  Normally the facilities of the machine's
           usual C compiler are used, but this can't be done
           directly in cross-compilation.  You must make your own
           arrangements to provide suitable library functions for
           cross-compilation.

           On machines where a function returns floating point
           results in the 80387 register stack, some floating
           point opcodes may be emitted even if -msoft-float is
           used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of
           functions.

           The usual calling convention has functions return 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
           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.

       -m96bit-long-double
       -m128bit-long-double
           These switches control the size of "long double" type.
           The i386 application binary interface specifies the
           size to be 96 bits, so -m96bit-long-double is the
           default in 32 bit mode.

           Modern architectures (Pentium and newer) would prefer
           "long double" to be aligned to an 8 or 16 byte bound­
           ary.  In arrays or structures conforming to the ABI,
           this would not be possible.  So specifying a
           -m128bit-long-double will align "long double" to a 16
           byte boundary by padding the "long double" with an
           additional 32 bit zero.

           In the x86-64 compiler, -m128bit-long-double is the
           default choice as its ABI specifies that "long double"
           is to be aligned on 16 byte boundary.

           Notice that neither of these options enable any extra
           precision over the x87 standard of 80 bits for a "long
           double".

           Warning: if you override the default value for your
           target ABI, the structures and arrays containing "long
           double" will change their size as well as function
           calling convention for function taking "long double"
           will be modified.  Hence they will not be binary com­
           patible with arrays or structures in code compiled
           without that switch.

       -msvr3-shlib
       -mno-svr3-shlib
           Control whether GCC places uninitialized local vari­
           ables into the "bss" or "data" segments.  -msvr3-shlib
           places them into "bss".  These options are meaningful
           only on System V Release 3.

       -mrtd
           Use a different function-calling convention, in which
           functions that take a fixed number of arguments return
           with the "ret" num instruction, which pops their argu­
           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
           required by any value stored on the stack.  Further,
           every function must be generated such that it keeps
           the stack aligned.  Thus calling a function compiled
           with a higher preferred stack boundary from a function
           compiled with a lower preferred stack boundary will
           most likely misalign the stack.  It is recommended
           that libraries that use callbacks always use the
           default setting.

           This extra alignment does consume extra stack space,
           and generally increases code size.  Code that is sen­
           sitive to stack space usage, such as embedded systems
           and operating system kernels, may want to reduce the
           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
           boundary.  This enables more inlining, increase code
           size, but may improve performance of code that depends
           on fast memcpy, strlen and memset for short lengths.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf
           functions.  This avoids the instructions to save, set
           up and restore frame pointers and makes an extra reg­
           ister available in leaf functions.  The option
           -fomit-frame-pointer removes the frame pointer for all
           functions which might make debugging harder.

       These -m switches are supported in addition to the above
           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
           for PA 1.1, and 2.0 for PA 2.0 processors.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine
           the proper architecture option for your machine.  Code
           compiled for lower numbered architectures will run on
           higher numbered architectures, but not the other way
           around.

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

       -mpa-risc-1-0
       -mpa-risc-1-1

       -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.

       -mgas
           Enable the use of assembler directives only GAS under­
           stands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the
           machine type cpu-type.  The choices for cpu-type are
           700 7100, 7100LC, 7200, 7300 and 8000.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine
           the proper scheduling option for your machine.  The
           default scheduling is 8000.

       -mlinker-opt
           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
           linker used by GCC can be printed using which `gcc
           -print-prog-name=ld`.

       -mlong-calls
           Generate code that uses long call sequences.  This
           ensures that a call is always able to reach linker
           generated stubs.  The default is to generate long
           calls only when the distance from the call site to the
           beginning of the function or translation unit, as the
           case may be, exceeds a predefined limit set by the
           branch type being used.  The limits for normal calls
           are 7,600,000 and 240,000 bytes, respectively for the
           PA 2.0 and PA 1.X architectures.  Sibcalls are always
           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.

       -nolibdld
           Suppress the generation of link options to search lib­
           dld.sl when the -static option is specified on HP-UX
           10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a
           dependency on libdld.sl.  There isn't an archive ver­
           sion of libdld.sl.  Thus, when the -static option is
           specified, special link options are needed to resolve
           this dependency.

           On HP-UX 10 and later, the GCC driver adds the neces­
           sary options to link with libdld.sl when the -static
           option is specified.  This causes the resulting binary
           to be dynamic.  On the 64-bit port, the linkers gener­
           ate dynamic binaries by default in any case.  The
           -nolibdld option can be used to prevent the GCC driver
           from adding these link options.

       -threads
           Add support for multithreading with the dce thread
           library under HP-UX.  This option sets flags for both
           the preprocessor and linker.

       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
           where this is not valid is not totally complete.  The
           default is -mno-tail-call.

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

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

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

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

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

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

       -mlong-double-64
           Implement type long double as 64-bit floating point
           numbers.  Without the option long double is 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
           ters.

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

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

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

           m   Round towards minus infinity.

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

           d   Dynamic rounding mode.  A field in the floating
               point control register (fpcr, see Alpha 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
           Use this option to require GCC to construct all inte­
           ger constants using code, even if it takes more
           instructions (the maximum is six).

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

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

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

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

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate
           symbol relocations except via assembler macros.  Use
           of these macros does not allow 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
           implies -msmall-data and -fPIC implies -mlarge-data.

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

           Supported values for cpu_type are

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

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

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

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

       DEC Alpha/VMS Options

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

       -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:

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

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

       -m4 Generate code for the SH4.

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

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

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this
           changes the calling conventions, and thus some 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 Rene­
           sas.

       -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.

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

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

       -Qy Identify the versions of each tool used by the com­
           piler, in a ".ident" assembler directive in the out­
           put.

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

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

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

       TMS320C3x/C4x Options

       These -m options are defined for TMS320C3x/C4x 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
       -mdp-isr-reload
       -mparanoid
           Force the DP register to be saved on entry to an
           interrupt service routine (ISR), reloaded to point to
           the data section, and restored on exit from the ISR.
           This should not be required unless someone has vio­
           lated the small memory model by modifying the DP reg­
           ister, say within an object library.

       -mmpyi
       -mno-mpyi
           For the C3x use the 24-bit MPYI instruction for inte­
           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

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

       -mregparm
       -mmemparm
           Generate code that uses registers (stack) for passing
           arguments to functions.  By default, arguments are
           passed in registers where possible rather than by
           pushing 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 prologue and epilogue of a
           function.  The external functions are slower, but use

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

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

       -mv850
           Specify that the target processor is the V850.

       -mbig-switch
           Generate code suitable for big switch tables.  Use
           this option only if the 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
       -mcpu=cpu
           Compile code for ARC variant cpu.  Which variants are
           supported depend on the configuration.  All variants
           support -mcpu=base, this is the default.

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

       NS32K Options

       These are the -m options defined for the 32000 series.
       The default values for these options depends on which
       style of 32000 was selected when the compiler was 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
           available.

       -mieee-compare
       -mno-ieee-compare
           Control whether or not the compiler uses IEEE floating
           point comparisons.  These handle correctly the case
           where the result of a comparison is unordered.  Warn­
           ing: the requisite kernel support may not be avail­
           able.

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

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

       -mrtd
           Use a different function-calling convention, in which
           functions that take a fixed 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

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

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


       MCore Options

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

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

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

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

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

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

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

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

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

       -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.

       -mno-pic
           Generate code that does not use a global pointer reg­
           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.

       D30V Options

       These -m options are defined for D30V implementations:

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

       -mzarch
       -mesa
           When -mzarch is specified, generate code using the
           instructions available on z/Architecture.  When -mesa
           is specified, generate code using the instructions
           available on ESA/390. Note that -mesa is not possible
           with -m64.  When generating code compliant to the
           Linux for S/390 ABI, the default is -mesa.  When gen­
           erating code compliant to the Linux for zSeries ABI,
           the default is -mzarch.

       -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.

       -march=cpu-type
           Generate code that will run on cpu-type, which is the
           name of a system representing a certain processor
           type. Possible values for cpu-type are g5, g6, z900,
           and z990.  When generating code using the instructions
           available on z/Architecture, the default is
           -march=z900.  Otherwise, the default is -march=g5.

       -mtune=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 list of cpu-type values is the
           same as for -march.  The default is the value used for
           -march.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -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.

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

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

       -mno-side-effects
           Do not emit instructions with side-effects in address­
           ing modes other than post-increment.

       -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
           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
           and instruction set for -march=v8.

       -mlinux
           Legacy no-op option only recognized with the cris-
           axis-linux-gnu target.

       -sim
           This option, recognized for the cris-axis-aout and
           cris-axis-elf arranges to link with input-output func­
           tions from a simulator library.  Code, initialized
           data and zero-initialized data are allocated consecu­
           tively.

       -sim2
           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
           -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
           Use (do not use) the probable-branch instructions,
           when static branch prediction indicates a probable
           branch.

       -mbase-addresses
       -mno-base-addresses
           Generate (do not generate) code that uses base
           addresses.  Using a base address automatically gener­
           ates a request (handled by the assembler and the
           linker) for a constant to be set up in a global regis­
           ter.  The register is used for one or more base
           address requests within the range 0 to 255 from the
           value held in the register.  The generally leads to
           short and fast code, but the number of different data
           items that can be addressed is limited.  This means
           that a program that uses lots of static data may
           require -mno-base-addresses.

       -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
           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
           Use 32-bit "int".

       -mfloat64
       -mno-float32
           Use 64-bit "float".  This is the default.

       -mfloat32
       -mno-float64
           Use 32-bit "float".

       -mabshi
           Use "abshi2" pattern.  This is the default.

       -mno-abshi
           Do not use "abshi2" pattern.

       -mbranch-expensive
           Pretend that branches are expensive.  This is for
           experimenting with code generation only.

       -mbranch-cheap
           Do not pretend that branches are expensive.  This is
           the default.

       -msplit
           Generate code for a system with split I&D.

       -mno-split
           Generate code for a system without split I&D.  This is
           the default.

       -munix-asm
           Use Unix assembler syntax.  This is the default when
           configured for pdp11-*-bsd.

       -mdec-asm
       -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.

       -msoft-float
           Use library routines for floating point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code reg­
           isters, only use "icc0" and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           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
           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
           Enable the use of conditional set instructions
           (default).

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

       -mno-scc
           Disable the use of conditional set instructions.

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

       -mcond-exec
           Enable the use of conditional execution (default).

           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.

       -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
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.
           Possible values are simple, tomcat, fr500, fr400,
           fr300, frv.

       Xtensa Options

       The Xtensa architecture is designed to support many dif­
       ferent configurations.  The compiler's default options can
       be set to match a particular Xtensa configuration by copy­
       ing a configuration file into the GCC sources when build­
       ing GCC.  The options below may be used to override the
       default options.

       -mbig-endian
       -mlittle-endian
           Specify big-endian or little-endian byte ordering for
           the target Xtensa processor.

       -mdensity
       -mno-density
           Enable or disable use of the optional Xtensa code 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

       -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.

       -mminmax
       -mno-minmax
           Enable or disable use of the optional minimum and max­
           imum value instructions.

       -msext
       -mno-sext
           Enable or disable use of the optional sign extend
           ("SEXT") instruction.

       -mbooleans
       -mno-booleans
           Enable or disable support for the boolean register
           file used by Xtensa coprocessors.  This is not typi­
           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
           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
           references.  This may be necessary for large assembly
           files.

       -mtarget-align
       -mno-target-align
           When this option is enabled, GCC instructs the assem­
           bler to automatically align instructions to reduce
           branch penalties at the expense of some code density.
           The assembler attempts to widen density instructions
           to align branch targets and the instructions following
           call instructions.  If there are not enough preceding
           safe density instructions to align a target, no widen­
           ing will be performed.  The default is -mtarget-align.
           These options do not affect the treatment of auto-
           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
           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
           tion.  If you do not specify this option, GCC will
           enable it by default for languages like C++ which nor­
           mally require exception handling, and disable it for
           languages like C that do not normally require it.
           However, you may need to enable this option when com­
           piling C code that needs to interoperate properly with
           exception handlers written in C++.  You may also wish
           to disable this option if you are compiling older C++
           programs that don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to
           throw exceptions.  Note that this requires platform-
           specific runtime support that does not exist every­
           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
           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.

           Warning: code compiled with the -freg-struct-return
           switch is not binary compatible with code compiled
           with the -fpcc-struct-return switch.  Use it to con­
           form to a non-default application binary interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it
           needs for the declared range of possible values.
           Specifically, the "enum" type will be equivalent to
           the smallest integer type which has enough room.

           Warning: the -fshort-enums switch causes GCC to 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.

       -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.

           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
           lect2 is included in the GCC distribution.)  For sys­
           tems which must use collect2, the compiler driver gcc
           is configured to do this automatically.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or any­
           thing else that would cause trouble if the function is
           split in the middle, and the two halves are placed at
           locations far apart in memory.  This option is used
           when compiling crtstuff.c; you should not need to use
           it for anything else.

       -fverbose-asm
           Put extra commentary information in the generated
           assembly code to make it more readable.  This option
           is generally only of use to those who actually need to
           read the generated assembly code (perhaps while 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.
           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,
           and therefore works only on certain machines.

       -ffixed-reg
           Treat the register named reg as a fixed register; gen­
           erated code should never refer to it (except perhaps
           as a stack pointer, frame pointer or in some other
           fixed role).

           reg must be the name of a register.  The register
           names accepted are machine-specific and are defined in
           the "REGISTER_NAMES" macro in the machine description
           macro file.

           This flag does not have a negative form, because it
           specifies a three-way choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register
           that is clobbered by function calls.  It may be 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
           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
           its call site.  (On some platforms,
           "__builtin_return_address" does not work beyond the
           current function, so the call site information may not
           be available to the profiling functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the
           current function, which may be looked up exactly in
           the symbol table.

           This instrumentation is also done for functions
           expanded inline in other functions.  The profiling
           calls will indicate where, conceptually, the inline
           function is entered and exited.  This means that
           addressable versions of such functions must be 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-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
           -fstack-limit-symbol=__stack_limit and -Wl,--def­
           sym,__stack_limit=0x7ffe0000 to enforce a stack limit
           of 128KB.  Note that this may only work with the GNU
           linker.

       -fargument-alias
       -fargument-noalias
       -fargument-noalias-global
           Specify the possible relationships among parameters
           and between parameters and global data.

           -fargument-alias specifies that arguments (parameters)
           may alias each other and may alias global stor­
           age.-fargument-noalias specifies that arguments do not
           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".

       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
           dom.

           The LC_CTYPE environment variable specifies character
           classification.  GCC uses it to determine the charac­
           ter boundaries in a string; this is needed for some
           multibyte encodings that contain quote and escape
           characters that would otherwise be interpreted as a
           string end or escape.

           The LC_MESSAGES environment variable specifies the
           language to use in diagnostic messages.

           If the LC_ALL environment variable is set, it over­
           rides the value of LC_CTYPE and LC_MESSAGES; other­
           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.

           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
           of directories, much like PATH.  GCC tries the direc­
           tories thus specified when searching for subprograms,
           if it can't find the subprograms using GCC_EXEC_PRE­
           FIX.

       LIBRARY_PATH
           The value of LIBRARY_PATH is a colon-separated list of
           directories, much like PATH.  When configured as a
           native compiler, GCC tries the directories thus speci­
           fied when searching for special linker files, if it
           can't find them using GCC_EXEC_PREFIX.  Linking using
           GCC also uses these directories when searching for
           ordinary libraries for the -l option (but directories
           specified with -L come first).

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

           C-JIS
               Recognize JIS characters.

           C-SJIS
               Recognize SJIS characters.

           C-EUCJP
               Recognize EUCJP characters.

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


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

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

           In all these variables, an empty element instructs the
           compiler to search its current working directory.
           Empty elements can appear at the beginning or end of a
           path.  For instance, if the value of CPATH is ":/spe­
           cial/include", that has the same effect as -I. -I/spe­
           cial/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to
           output dependencies for Make based on the non-system
           header files processed by the compiler.  System header
           files are ignored in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file
           name, in which case the Make rules are written to that
           file, guessing the target name from the source file
           name.  Or the value can have the form file target, in
           which case the rules are written to file file using
           target as the target name.

           In other words, this environment variable is 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


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.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.

gcc-3.3.1                   2003-09-23                     GCC(1)
  
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