avr-gcc (1)





NAME

       gcc - GNU project C and C++ compiler


SYNOPSIS

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

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


DESCRIPTION

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

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

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

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

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

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


OPTIONS

       Option Summary

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

       Overall Options
           strings

       C++ Language Options
           -fabi-version=n  -fno-access-control  -fcheck-new -fconserve-space
           -fno-const-strings  -fdollars-in-identifiers -fno-elide-construc-
           tors -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-operator-names
           -fno-optional-diags  -fpermissive -frepo  -fno-rtti  -fstats
           -ftemplate-depth-n -fuse-cxa-atexit  -fvtable-gc  -fno-weak  -nost-
           dinc++ -fno-default-inline  -Wabi  -Wctor-dtor-privacy -Wnon-vir-
           tual-dtor  -Wreorder -Weffc++  -Wno-deprecated -Wno-non-template-
           friend  -Wold-style-cast -Woverloaded-virtual  -Wno-pmf-conversions
           -Wsign-promo  -Wsynth

       Objective-C Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
           -gen-decls -Wno-protocol  -Wselector  -Wundeclared-selector

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

       Warning Options
           -fsyntax-only  -pedantic  -pedantic-errors -w  -W  -Wall  -Waggre-
           gate-return -Wcast-align  -Wcast-qual  -Wchar-subscripts  -Wcomment
           -Wconversion  -Wno-deprecated-declarations -Wdisabled-optimization
           -Wno-div-by-zero  -Werror -Wfloat-equal  -Wformat  -Wformat=2
           -Wformat-nonliteral  -Wformat-security -Wimplicit  -Wimplicit-int
           -Wimplicit-function-declaration -Werror-implicit-function-declara-
           tion -Wimport  -Winline  -Wno-endif-labels -Wlarger-than-len
           -Wlong-long -Wmain  -Wmissing-braces -Wmissing-format-attribute
           -Wmissing-noreturn -Wno-multichar  -Wno-format-extra-args  -Wno-
           format-y2k -Wno-import  -Wnonnull  -Wpacked  -Wpadded -Wparentheses
           -Wpointer-arith  -Wredundant-decls -Wreturn-type  -Wsequence-point
           -Wshadow -Wsign-compare  -Wstrict-aliasing -Wswitch  -Wswitch-
           default  -Wswitch-enum -Wsystem-headers  -Wtrigraphs  -Wundef
           -Wuninitialized -Wunknown-pragmas  -Wunreachable-code -Wunused
           -Wunused-function  -Wunused-label  -Wunused-parameter -Wunused-
           value  -Wunused-variable  -Wwrite-strings

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

       Debugging Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -fdump-unnumbered
           -fdump-translation-unit[-n] -fdump-class-hierarchy[-n] -fdump-tree-
           original[-n] -fdump-tree-optimized[-n] -fdump-tree-inlined[-n]
           -feliminate-dwarf2-dups  -fmem-report -fprofile-arcs  -fsched-ver-
           bose=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
           -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 -funsafe-math-optimiza-
           tions  -ffinite-math-only -fno-trapping-math  -fno-zero-initial-
           ized-in-bss -fomit-frame-pointer  -foptimize-register-move -fopti-
           mize-sibling-calls  -fprefetch-loop-arrays -freduce-all-givs
           -fregmove  -frename-registers -freorder-blocks  -freorder-functions
           -frerun-cse-after-loop  -frerun-loop-opt -fschedule-insns  -fsched-
           ule-insns2 -fno-sched-interblock  -fno-sched-spec  -fsched-spec-
           load -fsched-spec-load-dangerous  -fsignaling-nans -fsingle-preci-
           sion-constant  -fssa  -fssa-ccp  -fssa-dce -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  -iwithprefix 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  -nodefaultlibs  -nost-
           dlib -s  -static  -static-libgcc  -shared  -shared-libgcc  -sym-
           bolic -Wl,option  -Xlinker option -u symbol

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

       Target Options
           -V version  -b machine

       Machine Dependent Options
           M680x0 Options -m68000  -m68020  -m68020-40  -m68020-60  -m68030
           -m68040 -m68060  -mcpu32  -m5200  -m68881  -mbitfield  -mc68000
           -mc68020 -mfpa  -mnobitfield  -mrtd  -mshort  -msoft-float  -mpcrel
           -malign-int  -mstrict-align

           M68hc1x Options -m6811  -m6812  -m68hc11  -m68hc12  -m68hcs12
           -mauto-incdec  -minmax  -mlong-calls  -mshort -msoft-reg-
           count=count

           VAX Options -mg  -mgnu  -munix

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -m32  -m64 -mapp-regs  -mbroken-saverestore  -mcypress -mfaster-
           structs  -mflat -mfpu  -mhard-float  -mhard-quad-float -mimpure-
           text  -mlive-g0  -mno-app-regs -mno-faster-structs  -mno-flat
           -mno-fpu -mno-impure-text  -mno-stack-bias  -mno-unaligned-doubles
           -msoft-float  -msoft-quad-float  -msparclite  -mstack-bias -msuper-
           sparc  -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-

           MN10200 Options -mrelax

           MN10300 Options -mmult-bug  -mno-mult-bug -mam33  -mno-am33 -mno-
           crt0  -mrelax

           M32R/D Options -m32rx  -m32r  -mcode-model=model-type
           -msdata=sdata-type  -G num

           M88K Options -m88000  -m88100  -m88110  -mbig-pic -mcheck-zero-
           division  -mhandle-large-shift -midentify-revision  -mno-check-
           zero-division -mno-ocs-debug-info  -mno-ocs-frame-position -mno-
           optimize-arg-area  -mno-serialize-volatile -mno-underscores  -mocs-
           debug-info -mocs-frame-position  -moptimize-arg-area -mserialize-
           volatile  -mshort-data-num  -msvr3 -msvr4  -mtrap-large-shift
           -muse-div-instruction -mversion-03.00  -mwarn-passed-structs

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mpower
           -mno-power  -mpower2  -mno-power2 -mpowerpc  -mpowerpc64  -mno-pow-
           erpc -maltivec  -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt
           -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mnew-mnemonics  -mold-
           mnemonics -mfull-toc   -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-
           toc -m64  -m32  -mxl-call  -mno-xl-call  -mpe -msoft-float  -mhard-
           float  -mmultiple  -mno-multiple -mstring  -mno-string  -mupdate
           -mno-update -mfused-madd  -mno-fused-madd  -mbit-align  -mno-bit-
           align -mstrict-align  -mno-strict-align  -mrelocatable -mno-relo-
           catable  -mrelocatable-lib  -mno-relocatable-lib -mtoc  -mno-toc
           -mlittle  -mlittle-endian  -mbig  -mbig-endian -mcall-aix  -mcall-
           sysv  -mcall-netbsd -maix-struct-return  -msvr4-struct-return
           -mabi=altivec  -mabi=no-altivec -mabi=spe  -mabi=no-spe -misel=yes
           -misel=no -mprototype  -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 -compatibil-
           ity_version -current_version -dependency-file -dylib_file
           -dylinker_install_name -dynamic -dynamiclib -exported_symbols_list
           -filelist -flat_namespace -force_cpusubtype_ALL -force_flat_names-
           pace -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 -prebind_all_twolevel_mod-
           ules -private_bundle -read_only_relocs -sectalign -sectobjectsym-
           bols -whyload -seg1addr -sectcreate -sectobjectsymbols -sectorder
           -seg_addr_table -seg_addr_table_filename -seglinkedit -segprot
           -segs_read_only_addr -segs_read_write_addr -single_module -static
           -sub_library -sub_umbrella -twolevel_namespace -umbrella -undefined
           -unexported_symbols_list -weak_reference_mismatches -whatsloaded

           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
           -mfix7000  -mno-crt0  -mflush-func=func  -mno-flush-func -mbranch-
           likely  -mno-branch-likely

           i386 and x86-64 Options -mcpu=cpu-type  -march=cpu-type -mfp-
           math=unit  -masm=dialect  -mno-fancy-math-387 -mno-fp-ret-in-387
           -msoft-float  -msvr3-shlib -mno-wide-multiply  -mrtd  -malign-dou-
           ble -mpreferred-stack-boundary=num -mmmx  -msse  -msse2  -m3dnow
           -mthreads  -mno-align-stringops  -minline-all-stringops -mpush-args
           -maccumulate-outgoing-args  -m128bit-long-double -m96bit-long-dou-
           ble  -mregparm=num  -momit-leaf-frame-pointer -mno-red-zone
           -mcmodel=code-model -m32  -m64

           HPPA Options -march=architecture-type -mbig-switch  -mdisable-
           fpregs  -mdisable-indexing -mfast-indirect-calls  -mgas  -mgnu-ld
           -mhp-ld -mjump-in-delay  -mlinker-opt  -mlong-calls -mlong-load-
           store  -mno-big-switch  -mno-disable-fpregs -mno-disable-indexing
           -mno-fast-indirect-calls  -mno-gas -mno-jump-in-delay  -mno-long-
           load-store -mno-portable-runtime  -mno-soft-float -mno-space-regs
           -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0
           -mportable-runtime -mschedule=cpu-type  -mspace-regs  -msio  -mwsio
           -nolibdld  -static  -threads

           Intel 960 Options -mcpu-type  -masm-compat  -mclean-linkage -mcode-
           align  -mcomplex-addr  -mleaf-procedures -mic-compat  -mic2.0-com-
           pat  -mic3.0-compat -mintel-asm  -mno-clean-linkage  -mno-code-
           align -mno-complex-addr  -mno-leaf-procedures -mno-old-align  -mno-
           strict-align  -mno-tail-call -mnumerics  -mold-align  -msoft-float
           -mstrict-align -mtail-call

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

           DEC Alpha/VMS Options -mvms-return-codes

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

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

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           ARC Options -EB  -EL -mmangle-cpu  -mcpu=cpu  -mtext=text-section
           -mdata=data-section  -mrodata=readonly-data-section

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

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep -mprolog-
           AVR Options -mmcu=mcu  -msize  -minit-stack=n  -mno-interrupts
           -mcall-prologues  -mno-tablejump  -mtiny-stack

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div  -mrelax-
           immediates -mno-relax-immediates  -mwide-bitfields  -mno-wide-bit-
           fields -m4byte-functions  -mno-4byte-functions  -mcallgraph-data
           -mno-callgraph-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
           -minline-float-divide-max-throughput -minline-int-divide-min-
           latency -minline-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 -mhard-float  -msoft-float  -mbackchain
           -mno-backchain -msmall-exec  -mno-small-exec  -mmvcle  -mno-mvcle
           -m64  -m31  -mdebug  -mno-debug

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

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

           Xstormy16 Options -msim

           Xtensa Options -mbig-endian  -mlittle-endian -mdensity  -mno-den-
           sity -mmac16  -mno-mac16 -mmul16  -mno-mul16 -mmul32  -mno-mul32
           -mnsa  -mno-nsa -mminmax  -mno-minmax -msext  -mno-sext -mbooleans
           -mno-booleans -mhard-float  -msoft-float -mfused-madd  -mno-fused-
           madd -mserialize-volatile  -mno-serialize-volatile -mtext-section-
           literals  -mno-text-section-literals -mtarget-align  -mno-target-
           align -mlongcalls  -mno-longcalls

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
           -msoft-float  -malloc-cc  -mfixed-cc -mdword  -mno-dword  -mdouble
           -mno-double -mmedia  -mno-media  -mmuladd  -mno-muladd  -mlibrary-
           pic -macc-4  -macc-8  -mpack  -mno-pack  -mno-eflags -mcond-move
           -mno-cond-move -mscc  -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
           ter=reg  -fstack-limit-symbol=sym -fargument-alias  -fargument-
           noalias -fargument-noalias-global  -fleading-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 com-
       piled, and those specified as input) into an executable file.

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

       file.c
           C source code which must be preprocessed.

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

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

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

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

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

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

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

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

       file.r
           Fortran source code which must be preprocessed with a RATFOR pre-

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

       file.s
           Assembler code.

       file.S
           Assembler code which must be preprocessed.

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

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

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

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

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

       -pass-exit-codes
           Normally the gcc program will exit with the code of 1 if any phase
           of the compiler returns a non-success return code.  If you specify
           -pass-exit-codes, the gcc program will instead return with numeri-
           cally highest error produced by any phase that returned an error
           indication.

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

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

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

           Unrecognized input files, not requiring compilation or assembly,
           Input files that don't require compilation are ignored.

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

           Input files which don't require preprocessing are ignored.

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

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

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

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

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

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

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

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

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

       Compiling C++ Programs

       C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
       .c++, .cp, or .cxx; preprocessed C++ files use the suffix .ii.  GCC
       recognizes files with these names and compiles them as C++ programs
       also installed with the name c++.

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

       Options Controlling C Dialect

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

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

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

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

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

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

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

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

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

           iso9899:199409
               ISO C90 as modified in amendment 1.

               Default, ISO C90 plus GNU extensions (including some C99 fea-
               tures).

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

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

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

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

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

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

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

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

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

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with
           different library.

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

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

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

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

       -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 -trigraphs.

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

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

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

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second
           and third arguments.  The value of such an expression is void.
           This option is not supported for C++.
           "unsigned char" when it depends on the signedness of an object.
           But many programs have been written to use plain "char" and expect
           it to be signed, or expect it to be unsigned, depending on the
           machines they were written for.  This option, and its inverse, let
           you make such a program work with the opposite default.

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

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

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

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

       -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 meaning-
       ful for C++ programs; but you can also use most of the GNU compiler
       options regardless of what language your program is in.  For example,
       you might compile a file "firstClass.C" like this:

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

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

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

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

           The default is version 1.

           case the compiler will always check the return value even without
           this option.  In all other cases, when "operator new" has a non-
           empty exception specification, memory exhaustion is signalled by
           throwing "std::bad_alloc".  See also new (nothrow).

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

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

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

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

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

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

       -fno-enforce-eh-specs
           Don't check for violation of exception specifications at runtime.
           This option violates the C++ standard, but may be useful for reduc-
           ing code size in production builds, much like defining NDEBUG.  The
           compiler will still optimize based on the exception specifications.

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

           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.
           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 instantia-
           tions.

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

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

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

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

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

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

       -fpermissive
           Downgrade messages about nonconformant code from errors to warn-
           ings.  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

       -fstats
           Emit statistics about front-end processing at the end of the compi-
           lation.  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 end-
           less 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 destructors, but will only work if your C library supports
           "__cxa_atexit".

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

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

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

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

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

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

       -Wabi (C++ only)
           Warn when G++ generates code that is probably not compatible with
           the vendor-neutral C++ ABI.  Although an effort has been made to
           warn about all such cases, there are probably some cases that are
           not warned about, even though G++ is generating incompatible code.
           There may also be cases where warnings are emitted even though the
           code that is generated will be compatible.
               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 prob-
               lem by explicitly padding "A" so that its size is a multiple of
               the byte size on your platform; that will cause G++ and other
               compilers to layout "B" identically.

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

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

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

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

                       union U { int i : 4096; };

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

              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) {}

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

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

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

           Here the compiler will warn that the member initializers for i and
           j will be rearranged to match the declaration order of the members.
           This warning is enabled by -Wall.

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

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

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

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

              Item 6:  Distinguish between prefix and postfix forms of incre-
               ment and decrement operators.

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

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

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

       -Wno-non-template-friend (C++ only)
           Disable warnings when non-templatized friend functions are declared
           within a template.  With the advent of explicit template specifica-
           tion support in G++, if the name of the friend is an unqualified-id
           (i.e., friend foo(int)), the C++ language specification demands

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

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

                   struct A {
                     virtual void f();
                   };

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

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

                   B* b;
                   b->f();

           will fail to compile.

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

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

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

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

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

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

       Options Controlling Objective-C Dialect

       This section describes the command-line options that are only meaning-

       Here is a list of options that are only for compiling Objective-C pro-
       grams:

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

       -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 implemen-
           tation is inherited from the superclass.  If you use the "-Wno-pro-
           tocol" option, then methods inherited from the superclass are con-
           sidered to be implemented, and no warning is issued for them.

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

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

       Options to Control Diagnostic Messages Formatting

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

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

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

       Options to Request or Suppress Warnings

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

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

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

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

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

           Valid ISO C and ISO C++ programs should compile properly with or
           without this option (though a rare few will require -ansi or a -std
           option specifying the required version of ISO C).  However, without
           this option, certain GNU extensions and traditional C and C++ fea-
           tures 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__".  How-
           A feature to report any failure to conform to ISO C might be useful
           in some instances, but would require considerable additional work
           and would be quite different from -pedantic.  We don't have plans
           to support such a feature in the near future.

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

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

       -w  Inhibit all warning messages.

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

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

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

       -Wformat
           Check calls to "printf" and "scanf", etc., to make sure that the
           arguments supplied have types appropriate to the format string
           specified, and that the conversions specified in the format string
           make sense.  This includes standard functions, and others specified
           by format attributes, in the "printf", "scanf", "strftime" and
           "strfmon" (an X/Open extension, not in the C standard) families.

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

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

           -Wformat is included in -Wall.  For more control over some aspects
           of format checking, the options -Wno-format-y2k, -Wno-format-extra-
           "printf" or "scanf" format function.  The C standard specifies that
           such arguments are ignored.

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

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

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

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

       -Wformat=2
           Enable -Wformat plus format checks not included in -Wformat.  Cur-
           rently equivalent to -Wformat -Wformat-nonliteral -Wformat-secu-
           rity.

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

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

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

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

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

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

       -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 confusion to which
           "if" statement an "else" branch belongs.  Here is an example of
           such a case:

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

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

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

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

           The C standard defines the order in which expressions in a C pro-
           gram are evaluated in terms of sequence points, which represent a
           partial ordering between the execution of parts of the program:
           those executed before the sequence point, and those executed after
           it.  These occur after the evaluation of a full expression (one
           which is not part of a larger expression), after the evaluation of
           the first operand of a "&&", "||", "? :" or "," (comma) operator,
           before a function is called (but after the evaluation of its argu-
           ments and the expression denoting the called function), and in cer-
           tain other places.  Other than as expressed by the sequence point
           rules, the order of evaluation of subexpressions of an expression
           is not specified.  All these rules describe only a partial order
           ``Between the previous and next sequence point an object shall have
           its stored value modified at most once by the evaluation of an
           expression.  Furthermore, the prior value shall be read only to
           determine the value to be stored.''.  If a program breaks these
           rules, the results on any particular implementation are entirely
           unpredictable.

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

           The present implementation of this option only works for C pro-
           grams.  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 sub-
           tle cases.  Links to discussions of the problem, including proposed
           formal definitions, may be found on our readings page, at
           <http://gcc.gnu.org/readings.html>.

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

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

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

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

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

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

       -Wunused-variable
           Warn whenever a local variable or non-constant static variable is
           unused aside from its declaration

           To suppress this warning use the unused attribute.

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

           To suppress this warning cast the expression to void.

       -Wunused
           All the above -Wunused options combined.

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

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

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

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

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

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

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

           If the value of "y" is always 1, 2 or 3, then "x" is always ini-
           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 pos-
           sible only in optimizing compilation.

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

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

       -Wunknown-pragmas
           Warn when a #pragma directive is encountered which is not under-
           stood 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 warn-
           ings 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 question-
       able, but which occasionally you might wish to check for; others warn
       about constructions that are necessary or hard to avoid in some cases,
       and there is no simple way to modify the code to suppress the warning.

       -W  Print extra warning messages for these events:

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

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

               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 exten-
               sion will be warned about if -pedantic is specified.)

              If -Wall or -Wunused is also specified, warn about unused argu-
               ments.

              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 speci-
               fied.)

              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 following code would cause such a
               warning, because "x.h" would be implicitly initialized to zero:

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

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

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

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

           The idea behind this is that sometimes it is convenient (for the
           programmer) to consider floating-point values as approximations to

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

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

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

              A function-like macro that appears without arguments.

              The unary plus operator.

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

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

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

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

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

              Usage of ISO string concatenation is detected.

              Initialization of automatic aggregates.

              Identifier conflicts with labels.  Traditional C lacks a sepa-
               rate 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.

              Use of ISO C style function definitions.  This warning inten-
               tionally 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 exten-
               sion and thus not relevant to traditional C compatibility.

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

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

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

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

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

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

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

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

       -Wwrite-strings
           When compiling C, give string constants the type "const
           char[length]" so that copying the address of one into a non-"const"
           "char *" pointer will get a warning; when 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 care-
           ful about using "const" in declarations and prototypes.  Otherwise,
           it will just be a nuisance; this is why we did not make -Wall
           request these warnings.

       -Wconversion
           Warn if a prototype causes a type conversion that is different from
           what would happen to the same argument in the absence of a proto-

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could
           produce an incorrect result when the signed value is converted to
           unsigned.  This warning is enabled by -W, and by -Wall in C++ only.

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

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

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

       -Wmissing-declarations
           Warn if a global function is defined without a previous declara-
           tion.  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 "nore-
           turn".  Note these are only possible candidates, not absolute ones.
           Care should be taken to manually verify functions actually do not
           ever return before adding the "noreturn" attribute, otherwise sub-
           tle 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 func-
           tion like "vprintf" or "vscanf", but this might not always be the
           case, and some functions for which "format" attributes are appro-
           priate may not be detected.  This option has no effect unless
           -Wformat is enabled (possibly 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 implementa-
           tion-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{Variable Attributes}, @pxref{Type Attributes}.)

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

       -Wpadded
           Warn if padding is included in a structure, either to align an ele-
           ment 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 proce-
           dure 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 ver-
           sion of a program there is often substantial code which checks cor-
           rect functioning of the program and is, hopefully, unreachable
           because the program does work.  Another common use of unreachable
           code is to provide behavior which is selectable at compile-time.

       -Winline
           Warn if a function can not be inlined and it was declared as
           inline.

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

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning
           does not generally indicate that there is anything wrong with your
           code; it merely indicates that GCC's optimizers were unable to han-
           dle the code effectively.  Often, the problem is that your code is

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

       -g  Produce debugging information in the operating system's native for-
           mat (stabs, COFF, XCOFF, or DWARF).  GDB can work with this debug-
           ging 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 con-
           trol 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 sur-
           prising results: some variables you declared may not exist at all;
           flow of control may briefly move where you did not expect it; some
           statements may not be executed because they compute constant
           results or their values were already at hand; some statements may
           execute in different places because they were moved out of loops.

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

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

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

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

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

       -gcoff
           Produce debugging information in COFF format (if that is sup-
           ported).  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 sup-

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

           This option is deprecated.

       -gdwarf+
           Produce debugging information in DWARF version 1 format (if that is
           supported), using GNU extensions understood only by the GNU debug-
           ger (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 format (if that is
           supported).  This is the format used by DBX on IRIX 6.

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

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

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

           Level 3 includes extra information, such as all the macro defini-
           tions present in the program.  Some debuggers support macro expan-
           sion 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 suitable for the
           analysis program prof.  You must use this option when compiling the
           source files you want data about, and you must also use it when
           linking.

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

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

       -fprofile-arcs
           Instrument arcs during compilation to generate coverage data or for
           profile-directed block ordering.  During execution the program
           records how many times each branch is executed and how many times
           it is taken.  When the compiled program exits it saves this data to
           a file called auxname.da for each source file.  auxname is gener-
           ated from the name of the output file, if explicitly specified and
           it is not the final executable, otherwise it is the basename of the
           source file. In both cases any suffix is removed (e.g.  foo.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 program with
           -fprofile-arcs plus optimization and code generation options, gen-
           erate the arc profile information by running the program on a
           selected workload, and then compile the program again with the same
           optimization and code generation options plus -fbranch-probabili-
           ties.

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

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

       -ftest-coverage
           Create data files for the gcov code-coverage utility.  See -fpro-
           file-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
           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.

           B   Dump after block reordering, to file.32.bbro.

           c   Dump after instruction combination, to the file file.19.com-
               bine.

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

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

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

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

           E   Dump after the second if conversion, to file.29.ce3.

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

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

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

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

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

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

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

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

           j   Dump after the first jump optimization, to 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 reorganization
               pass, to file.33.mach.

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

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

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

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

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

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

           z   Dump after the peephole pass, to file.27.peephole2.

           a   Produce all the dumps listed above.

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

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

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

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

           x   Just generate RTL for a function instead of compiling it.  Usu-
               ally used with r.

           y   Dump debugging information during parsing, to standard error.

       -fdump-unnumbered
           When doing debugging dumps (see -d option above), suppress instruc-
           tion numbers and line number note output.  This makes it more fea-
           sible 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 transla-
           tion unit to a file.  The file name is made by appending .tu to the
           source file name.  If the -options form is used, options controls
           the details of the dump as described for the -fdump-tree options.

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

       -fdump-tree-switch (C++ only)
           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 environ-
               ment.

           slim
               Inhibit dumping of members of a scope or body of a function
               merely because that scope has been reached. Only dump such
               items when they are directly reachable by some other path.

           all Turn on all options.

           The following tree dumps are possible:

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

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

           inlined
               Dump after function inlining, to file.inlined.

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

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

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

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

       -print-multi-lib
           Print the mapping from multilib directory names to compiler
           switches that enable them.  The directory name is separated from
           the switches by ;, and each switch starts with an @} instead of the
           @samp{-, without spaces between multiple switches.  This is 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 -nodefaultlibs but you do
           want to link with libgcc.a.  You can do

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

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

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

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

       -dumpversion
           Print the compiler version (for example, 3.0)---and don't do any-
           thing 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 produce the expected results.
       Statements are independent: if you stop the program with a breakpoint
       between statements, you can then assign a new value to any variable or

       -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 com-
           pilation time.

           -O turns on the following optimization flags: -fdefer-pop -fmerge-
           constants -fthread-jumps -floop-optimize -fcrossjumping -fif-con-
           version -fif-conversion2 -fdelayed-branch -fguess-branch-
           probability -fcprop-registers

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

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

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

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

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2
           and also turns on the -finline-functions 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 optimiza-
           tions 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
           are defined inside the class scope (C++ only).  Otherwise, when you
           specify -O, member functions defined inside class scope are com-
           piled inline by default; i.e., you don't need to add inline in
           front of the member function name.

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

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

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

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

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

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

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

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

       -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 expanding any functions inline.
           Note that if you are not optimizing, no functions can be expanded
           inline.

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

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

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

            @table @gcctabopt
            @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>.
            @end table

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

           Note: pseudo instruction represents, in this particular context, an
           abstract measurement of function's size.  In no way, 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 func-
           tion is declared "static", nevertheless output a separate run-time
           callable version of the function.  This switch does not affect
           "extern inline" functions.

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

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

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

           This option is the default for optimized compilation if the assem-
           stants this considers e.g. even constant initialized arrays or ini-
           tialized constant variables with integral or floating point types.
           Languages like C or C++ require each non-automatic variable to have
           distinct location, so using this option will result in non-conform-
           ing behavior.

       -fno-branch-count-reg
           Do not use ``decrement and branch'' instructions on a count regis-
           ter, 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 programs explic-
           itly rely on variables going to the data section.  E.g., so that
           the resulting executable can find the beginning of that section
           and/or make assumptions based on that.

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

       -fstrength-reduce
           Perform the optimizations of loop strength reduction and elimina-
           tion 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 subsumed by the first is found.
           If so, the first branch is redirected to either the destination of
           the second branch or a point immediately following it, depending on
           whether the condition is known to be true or false.

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

       -fcse-follow-jumps
           In common subexpression elimination, scan through jump instructions
           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 exten-
           sion, you may get better runtime performance if you disable the
           global common subexpression elimination pass by adding -fno-gcse to
           the command line.

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

       -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
           Perform loop optimizations: move constant expressions out of loops,
           simplify exit test conditions and optionally do strength-reduction
           and loop unrolling as well.

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

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

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

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

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

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

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

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

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

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

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

           Note -fregmove and -foptimize-register-move are the same optimiza-
           tion.

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

       -fdelayed-branch
           If supported for the target machine, attempt to reorder instruc-
           tions 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 instruc-
           tions 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.

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

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

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

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

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

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

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

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

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

           Note: When compiling programs written in Fortran, -fmove-all-mov-
           ables 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 various approaches to improv-
           ing loop optimizations.

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

       -fno-peephole
       -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 feed-
           back (-fprofile-arcs) or __builtin_expect.  This means that differ-
           ent runs of the compiler on the same program may produce different
           object code.

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

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

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

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

       -freorder-functions
           Reorder basic blocks in the compiled function in order to reduce
           number of taken branches and improve code locality. This is imple-
           mented by using special subsections "text.hot" for most frequently
           executed functions 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 applica-
           ble to the language being compiled.  For C (and C++), this
           activates optimizations based on the type of expressions.  In par-
           ticular, 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() {

           work as expected.  However, this code might not:

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

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

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

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

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

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

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

           Enabled at levels -O2, -O3.

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

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

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

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
           Align loops to a power-of-two boundary, skipping up to n bytes like
           -falign-functions.  The hope is that the loop will be executed many
           times, which will make up for any execution of the dummy opera-
           tions.
           bytes like -falign-functions.  In this case, no dummy operations
           need be executed.

           If n is not specified, use a machine-dependent 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 optimiza-
           tion will most benefit processors with lots of registers.  It can,
           however, 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 correct-
       ness.  All must be specifically enabled.

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

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

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

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

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

       -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

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

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

           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 gener-
           ate user-visible traps.  These traps include division by zero,
           overflow, underflow, inexact result and invalid operation.  This
           option implies -fno-signaling-nans.  Setting this option may allow
           faster code if one relies on ``non-stop'' IEEE arithmetic, for
           example.

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

           The default is -ftrapping-math.

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

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

           The default is -fno-signaling-nans.

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

       -fsingle-precision-constant
           Treat floating point constant as single precision constant instead
           of implicitly converting it to double precision constant.
           When the program compiled 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 dependent on the
           structure of the generated code, so you must use the same source
           code and the same optimization options for both compilations.

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

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

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

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

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

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

           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 perform optimiza-
           tions to improve locality of reference in the instruction space.
           Most systems using the ELF object format and SPARC processors run-
           ning Solaris 2 have linkers with such optimizations.  AIX may have
           these optimizations in the future.

           Only use these options when there are significant benefits from
           doing so.  When you specify these options, the assembler and linker
           Users should not specify this option, since it is not yet ready for
           production use.

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

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

       --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 func-
           tions that contain more that a certain number of instructions.  You
           can control some of these constants on the command-line using the
           --param option.

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

           max-crossjump-edges
               The maximum number of incoming edges to consider for crossjump-
               ing.  The algorithm used by -fcrossjumping is O(N^2) in the
               number of edges incoming to each block.  Increasing values mean
               more aggressive optimization, making the compile time increase
               with probably small improvement in executable size.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking for
               an instruction to fill a delay slot.  If more than this arbi-
               trary 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 exe-
               cutable run time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of instruc-
               tions to consider when searching for a block with valid live
               register information.  Increasing this arbitrarily chosen value
               means more aggressive optimization, increasing the compile
               time.  This parameter should be removed when the delay slot
               code is rewritten to maintain the control-flow graph.

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

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

           max-pending-list-length
               The maximum number of pending dependencies scheduling will
               allow before flushing the current state and starting over.
               functions declared inline and methods implemented in a class
               declaration (C++).  The default value is 300.

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of
               functions that would otherwise not be considered for inlining
               by the compiler will be investigated.  To those functions, a
               different (more restrictive) limit compared to functions
               declared inline can be applied.  The default value is 300.

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

           max-inline-slope
               After exceeding the maximum number of inlined instructions by
               repeated inlining, a linear function is used to decrease the
               allowable size for single functions.  The slope of that func-
               tion 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 throt-
               tling, 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 happens at a later
               stage than tree inlining), you can set the maximum allowable
               size (counted in RTL instructions) for the RTL inliner with
               this parameter.  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 deter-
               mines how many times the loop code is unrolled.

           hot-bb-count-fraction
               Select fraction of the maximal count of repetitions of basic
               block in program given basic block needs to have to be consid-
               ered hot.

           hot-bb-frequency-fraction
               Select fraction of the maximal frequency of executions of basic
               block in function given basic block needs to have to be consid-
               ered hot

               threshold to be larger value.

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

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

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

               Similarly to tracer-dynamic-coverage two values are present,
               one for compilation for profile feedback and one for compila-
               tion 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 alloca-
               tion.  This parameter specifies the minimum percentage by which
               the garbage collector's heap should be allowed to expand
               between collections.  Tuning this may improve compilation
               speed; it has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of
               100% when RAM >= 1GB.  If "getrlimit" is available, the notion
               of "RAM" is the smallest of actual RAM, RLIMIT_RSS, RLIMIT_DATA
               and RLIMIT_AS.  If GCC is not able to calculate RAM on a par-
               ticular 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-heap-
               size.  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 platform, the
               lower bound is used.  Setting this parameter very large effec-
               tively disables garbage collection.  Setting this parameter and
               ggc-min-expand to zero causes a full collection to occur at
               every opportunity.

       Options Controlling the Preprocessor
       directly through to the preprocessor.  If option contains commas, it is
       split into multiple options at the commas.  However, many options are
       modified, translated or interpreted by the compiler driver before being
       passed to the preprocessor, and -Wp forcibly bypasses this phase.  The
       preprocessor's direct interface is undocumented and subject to change,
       so whenever possible you should avoid using -Wp and let the driver han-
       dle the options instead.

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

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

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

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

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

       -undef
           Do not predefine any system-specific macros.  The common predefined
           macros remain defined.

       -I dir
           Add the directory dir to the list of directories to be searched for
           header files.  Directories named by -I are searched before the
           standard system include directories.  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 spe-
           cial treatment of system headers are not defeated .

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

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

       -Wcomment
           as they do not affect the meaning of the program.

       -Wtraditional
           Warn about certain constructs that behave differently in tradi-
           tional and ISO C.  Also warn about ISO C constructs that have no
           traditional C equivalent, and problematic constructs which should
           be avoided.

       -Wimport
           Warn the first time #import is used.

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

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

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

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

                   #if defined the_macro_causing_the_warning
                   #endif

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

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

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

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

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

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

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

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

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

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

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

           This implies that the choice of angle brackets or double quotes in
           an #include directive does not in itself determine whether that
           header will appear in -MM dependency output.  This is a slight
           change in semantics from GCC versions 3.0 and earlier.

       -MF file
           @anchor{-MF} When used with -M or -MM, specifies a file to write
           the dependencies to.  If no -MF switch is given the preprocessor
           sends the rules to the same place it would have sent preprocessed
           output.

           When used with the driver options -MD or -MMD, -MF overrides the
           default dependency output file.

       -MG In conjunction with an option such as -M requesting dependency gen-
           eration, -MG assumes missing header files are generated files and
           adds them to the dependency list without raising an error.  The
           dependency filename is taken directly from the "#include" directive
           without prepending any path.  -MG also suppresses preprocessed out-
           put, as a missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency
           other than the main file, causing each to depend on nothing.  These

       -MT target
           Change the target of the rule emitted by dependency generation.  By
           default CPP takes the name of the main input file, including any
           path, deletes any file suffix such as .c, and appends the plat-
           form's usual object suffix.  The result is the target.

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

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

                   $(objpfx)foo.o: foo.c

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

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

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

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

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

           Since -E is not implied, -MD can be used to generate a dependency
           output file as a side-effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system -header
           files.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
           Specify the source language: C, C++, Objective-C, or assembly.
           This has nothing to do with standards conformance or extensions; it
           merely selects which base syntax to expect.  If you give none of
           these options, cpp will deduce the language from the extension of
           the source file: .c, .cc, .m, or .S.  Some other common extensions
           for C++ and assembly are also recognized.  If cpp does not recog-
           nize 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

           standard may be one of:

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

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

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

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

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

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

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

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

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

           In addition, -I- inhibits the use of the directory of the current
           file directory as the first search directory for "#include "file"".

       -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 direc-
           tories, but do still search the other standard directories.  (This
           option is used when building the C++ library.)

       -include file
           Process file as if "#include "file"" appeared as the first line of
           the primary source file.  However, the first directory searched for
           file is the preprocessor's working directory instead of the direc-
           file is thrown away.  Macros it defines remain defined.  This
           allows you to acquire all the macros from a header without also
           processing its declarations.

           All files specified by -imacros are processed before all files
           specified by -include.

       -idirafter dir
           Search dir for header files, but do it after all directories speci-
           fied with -I and the standard system directories have been
           exhausted.  dir is treated as a system include directory.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.
           If the prefix represents a directory, you should include the final
           /.

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

           Use of these options is discouraged.

       -isystem dir
           Search dir for header files, after all directories specified by -I
           but before the standard system directories.  Mark it as a system
           directory, so that it gets the same special treatment as is applied
           to the standard system directories.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been
           preprocessed.  This suppresses things like macro expansion, tri-
           graph 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 com-
           piler without problems.  In this mode the integrated preprocessor
           is little more than a tokenizer for the front ends.

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

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

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

       -A predicate=answer
           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 direc-
               tives for all the macros defined during the execution of the
               preprocessor, including predefined macros.  This gives you a
               way of finding out what is predefined in your version of the
               preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               will show all the predefined macros.

           D   Like M except in two respects: it does not include the prede-
               fined macros, and it outputs both the #define directives and
               the result of preprocessing.  Both kinds of output go to the
               standard output file.

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

           I   Output #include directives in addition to the result of prepro-
               cessing.

       -P  Inhibit generation of linemarkers in the output from the preproces-
           sor.  This might be useful when running the preprocessor on some-
           thing 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 ordi-
           nary source line, since the first token on the line is no longer a
           #.

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

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

           The -CC option is generally used to support lint comments.

       -gcc
           Define the macros __GNUC__, __GNUC_MINOR__ and __GNUC_PATCHLEVEL__.
           These are defined automatically when you use gcc -E; you can turn
           them off in that case with -no-gcc.
           ter constant for a newline.  By default, GCC ignores trigraphs, but
           in standard-conforming modes it converts them.  See the -std and
           -ansi options.

           The nine trigraphs and their replacements are

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

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

       --help
       --target-help
           Print text describing all the command line options instead of pre-
           processing 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 nor-
           mal 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 pre-
           process 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 com-
           mas, 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
           contents.)  If linking is done, these object files are used as
           input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and
           object file names should not be used as arguments.

           after file foo.o but before bar.o.  If bar.o refers to functions in
           z, those functions may not be loaded.

           The linker searches a standard list of directories for the library,
           which is actually a file named liblibrary.a.  The linker then uses
           this file as if it had been specified precisely by name.

           The directories searched include several standard system directo-
           ries plus any that you specify with -L.

           Normally the files found this way are library files---archive files
           whose members are object files.  The linker handles an archive file
           by scanning through it for members which define symbols that have
           so far been referenced but not defined.  But if the file that is
           found is an ordinary object file, it is linked in the usual fash-
           ion.  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 normally, unless -nostdlib or
           -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the
           libraries you specify will be passed to the linker.  The standard
           startup files are used normally, unless -nostartfiles is used.  The
           compiler may generate calls to memcmp, memset, and memcpy for Sys-
           tem V (and ISO C) environments or to bcopy and bzero for BSD envi-
           ronments.  These entries are usually resolved by entries in libc.
           These entry points should be supplied through some other mechanism
           when this option is specified.

       -nostdlib
           Do not use the standard system startup files or libraries when
           linking.  No startup files and only the libraries you specify will
           be passed to the linker.  The compiler may generate calls to mem-
           cmp, 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 -nodefault-
           libs is libgcc.a, a library of internal subroutines that GCC uses
           to overcome shortcomings of particular machines, or special needs
           for some languages.

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

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

       -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 con-
           figured, these options have no effect.

           There are several situations in which an application should use the
           shared libgcc instead of the static version.  The most common of
           these is when the application wishes to throw and catch exceptions
           across different shared libraries.  In that case, each of the
           libraries as well as the application itself should use the shared
           libgcc.

           Therefore, the G++ and GCJ drivers automatically add -shared-libgcc
           whenever you build a shared library or a main executable, because
           C++ and Java programs typically use exceptions, so this is the
           right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you
           may find that they will not always be linked with the shared
           libgcc.  If GCC finds, at its configuration time, that you have a
           GNU linker that does not support option --eh-frame-hdr, it will
           link the shared version of libgcc into shared libraries by default.
           Otherwise, it will take advantage of the linker and optimize away
           the linking with the shared version of libgcc, linking with the
           static version of libgcc by default.  This allows exceptions to
           propagate through such shared libraries, without incurring reloca-
           tion costs at library load time.

           However, if a library or main executable is supposed to throw or
           catch exceptions, you must link it using the G++ or GCJ driver, as
           appropriate for the languages used in the program, or using the
           option -shared-libgcc, such that it is linked with the shared
           libgcc.

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

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

           If you want to pass an option that takes an argument, you must use
           -Xlinker twice, once for the option and once for the argument.  For
           example, to pass -assert definitions, you must write -Xlinker
           Pretend the symbol symbol is undefined, to force linking of library
           modules to define it.  You can use -u multiple times with different
           symbols to force loading of additional library modules.

       Options for Directory Search

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

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

           If a standard system include directory, or a directory specified
           with -isystem, is also specified with -I, the -I option will be
           ignored.  The directory will still be searched but as a system
           directory at its normal position in the system include chain.  This
           is to ensure that GCC's procedure to fix buggy system headers and
           the ordering for the include_next directive are not inadvertently
           changed.  If you really need to change the search order for system
           directories, use the -nostdinc and/or -isystem options.

       -I- Any directories you specify with -I options before the -I- option
           are searched only for the case of #include "file"; they are not
           searched for #include <file>.

           If additional directories are specified with -I options after the
           -I-, these directories are searched for all #include directives.
           (Ordinarily all -I directories are used this way.)

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

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

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

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

           The compiler driver program runs one or more of the subprograms
           cpp, cc1, as and ld.  It tries prefix as a prefix for each program
           it tries to run, both with and without machine/version/.
           The compiler will check to see if the path provided by the -B
           refers to a directory, and if necessary it will add a directory
           separator character at the end of the path.

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

           The run-time support file libgcc.a can also be searched for using
           the -B prefix, if needed.  If it is not found there, the two stan-
           dard prefixes above are tried, and that is all.  The file is left
           out of the link if it is not found by those means.

           Another way to specify a prefix much like the -B prefix is to use
           the environment variable GCC_EXEC_PREFIX.

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

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

       Specifying Target Machine and Compiler Version

       The usual way to run GCC is to run the executable called gcc, or
       <machine>-gcc when cross-compiling, or <machine>-gcc-<version> to run a
       version other than the one that was installed last.  Sometimes this is
       inconvenient, so GCC provides options that will switch to another
       cross-compiler or version.

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

           The value to use for machine is the same as was specified as the
           machine type when configuring GCC as a cross-compiler.  For exam-
           ple, if a cross-compiler was configured with configure i386v, mean-
           ing to compile for an 80386 running System V, then you would spec-
           ify -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, ver-
           sion might be 2.0, meaning to run GCC version 2.0.

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

       or none.  A single installed version of the compiler can compile for
       any model or configuration, according to the options specified.

       Some configurations of the compiler also support additional special
       options, usually for compatibility with other compilers on the same
       platform.

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

       M680x0 Options

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

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

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

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

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

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

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

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

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

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

       -mcpu32
           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 instruc-
           tions.  This results in code which can run relatively efficiently
           on either a 68020/68881 or a 68030 or a 68040.  The generated code
           does use the 68881 instructions that are emulated on the 68040.

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

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

       -msoft-float
           Generate output containing library calls for floating point.  Warn-
           ing: the requisite libraries are not available for all m68k tar-
           gets.  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.  The embedded targets m68k-*-aout
           and m68k-*-coff do provide software 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 com-
           piled with the Unix compiler.

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

           In addition, seriously incorrect code will result if you call a
           "double", and "long double" variables on a 32-bit boundary
           (-malign-int) or a 16-bit boundary (-mno-align-int).  Aligning
           variables on 32-bit boundaries produces code that runs somewhat
           faster on processors with 32-bit busses at the expense of more mem-
           ory.

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

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

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

       M68hc1x Options

       These are the -m options defined for the 68hc11 and 68hc12 microcon-
       trollers.  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 com-
           piler is configured for 68HC11-based systems.

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

       -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.

       VAX Options

       These -m options are defined for the VAX:

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

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

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

       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 sys-
           tem software with this option.

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

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

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this to
           work.

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

       -msoft-quad-float
           Generate output containing library calls for quad-word (long dou-
           ble) floating point instructions.  The functions called are those

       -mno-flat
       -mflat
           With -mflat, the compiler does not generate save/restore instruc-
           tions and will use a ``flat'' or single register window calling
           convention.  This model uses %i7 as the frame pointer and is com-
           patible 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.

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

           By default (unless specifically configured for the Fujitsu SPAR-
           Clite), GCC generates code for the v7 variant of the SPARC archi-
           tecture.

           -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.


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

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

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling
           parameters for machine type cpu_type.  Supported values for
           cpu_type are v7, cypress, v8, supersparc, sparclite, hypersparc,
           sparclite86x, f930, f934, sparclet, tsc701, v9, ultrasparc, and
           ultrasparc3.

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

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

                       v7:             cypress
                       v8:             supersparc, hypersparc
                       sparclite:      f930, f934, sparclite86x
                       sparclet:       tsc701
                       v9:             ultrasparc, ultrasparc3

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

           The same values for -mcpu=cpu_type can be used for -mtune=cpu_type,
           but the only useful values are those that select a particular cpu
           implementation.  Those are cypress, supersparc, hypersparc, f930,
           f934, sparclite86x, tsc701, ultrasparc, and ultrasparc3.

       These -m switches are supported in addition to the above on the SPAR-
       CLET 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

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

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

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

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

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

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

       ARM Options

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

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure
           Call Standard for all functions, even if this is not strictly nec-
           essary 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 calling standards for the
           APCS 26-bit option.  This option replaces the -m2 and -m3 options
           of previous releases of the compiler.

           cannot be reliably used inside one program.  The default is -mno-
           thumb-interwork, since slightly larger code is generated when
           -mthumb-interwork is specified.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prolog, or
           the merging of those instruction with the instructions in the func-
           tion's body.  This means that all functions will start with a rec-
           ognizable set of instructions (or in fact one of a choice from a
           small set of different function prologues), and this information
           can be used to locate the start if functions inside an executable
           piece of code.  The default is -msched-prolog.

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

       -msoft-float
           Generate output containing library calls for floating point.  Warn-
           ing: the requisite libraries are not available for all ARM targets.
           Normally the facilities of the machine's usual C compiler are used,
           but this cannot be done directly in cross-compilation.  You must
           make your own arrangements to provide suitable library functions
           for cross-compilation.

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this to
           work.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This
           is the default for all standard configurations.

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

       -mwords-little-endian
           This option only applies when generating code for big-endian pro-
           cessors.  Generate code for a little-endian word order but a big-
           endian byte order.  That is, a byte order of the form 32107654.
           Note: this option should only be used if you require compatibility
           with code for big-endian ARM processors generated by versions of
           the compiler prior to 2.8.

       -malignment-traps
           Generate code that will not trap if the MMU has alignment traps
           enabled.  On ARM architectures prior to ARMv4, there were no
           instructions to access half-word objects stored in memory.  How-
           ever, when reading from memory a feature of the ARM architecture
           allows a word load to be used, even if the address is unaligned,
           and the processor core will rotate the data as it is being loaded.
           This option tells the compiler that such misaligned accesses will
           cause a MMU trap and that it should instead synthesize the access
           as a series of byte accesses.  The compiler can still use word
           accesses.  This produces better code when the target instruction
           set does not have half-word memory operations (i.e. implementations
           prior to ARMv4).

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

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

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

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

       -mcpu=name
           This specifies the name of the target ARM processor.  GCC uses this
           name to determine what kind of instructions it can emit when gener-
           ating assembly code.  Permissible names are: arm2, arm250, arm3,
           arm6, arm60, arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm,
           arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100,
           arm7500, arm7500fe, arm7tdmi, arm8, strongarm, strongarm110, stron-
           garm1100, arm8, arm810, arm9, arm9e, arm920, arm920t, arm940t,
           arm9tdmi, arm10tdmi, arm1020t, xscale.

       -mtune=name
           This option is very similar to the -mcpu= option, except that
           instead of specifying the actual target processor type, and hence
           restricting which instructions can be used, it specifies that GCC
           should tune the performance of the code as if the target were of
           the type specified in this option, but still choosing the instruc-
           tions that it will generate based on the cpu specified by a -mcpu=
           option.  For some ARM implementations better performance can be
           obtained by using this option.

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

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

       -mstructure-size-boundary=n
           The size of all structures and unions will be rounded up to a mul-
           tiple of the number of bits set by this option.  Permissible values

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a "noreturn"
           function.  It will be executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the
           address of the function into a register and then performing a sub-
           routine call on this register.  This switch is needed if the target
           function will lie outside of the 64 megabyte addressing range of
           the offset based version of subroutine call instruction.

           Even if this switch is enabled, not all function calls will be
           turned into long calls.  The heuristic is that static functions,
           functions which have the short-call attribute, functions that are
           inside the scope of a #pragma no_long_calls directive and functions
           whose definitions have already been compiled within the current
           compilation unit, will not be turned into long calls.  The excep-
           tion to this rule is that weak function definitions, functions with
           the long-call attribute or the section attribute, and functions
           that are within the scope of a #pragma long_calls directive, will
           always be turned into long calls.

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

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

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

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

       -mpoke-function-name
           Write the name of each function into the text section, directly
           preceding the function prologue.  The generated code is similar to
           this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4


       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all non-leaf functions.  (A leaf function is one
           that does not call any other functions.)  The default is -mno-tpcs-
           frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all leaf functions.  (A leaf function is one that
           does not call any other functions.)  The default is -mno-apcs-leaf-
           frame.

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

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

       MN10200 Options

       These -m options are defined for Matsushita MN10200 architectures:

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

           This option makes symbolic debugging impossible.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

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

       -mno-mult-bug
           Do not generate code to avoid bugs in the multiply instructions for
           the MN10300 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 pro-
           cessor.  This is the default.

       -mno-crt0

       M32R/D Options

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

       -m32rx
           Generate code for the M32R/X.

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

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

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

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

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

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

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

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

       -msdata=use
           Put small global and static data in the small data area, and gener-
           ate 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.  Compil-
           Generate code that works well on both the m88100 and the m88110.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

           1.  Which variant of the assembler syntax to emit.

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

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

           -msvr4 is the default for the m88k-motorola-sysv4 configuration.
           -msvr3 is the default for all other m88k configurations.

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

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

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

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

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

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

       -mtrap-large-shift
       -mhandle-large-shift
           Include code to detect bit-shifts of more than 31 bits; respec-
           tively, 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 PowerPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-powerpc
       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
           GCC supports two related instruction set architectures for the
           RS/6000 and PowerPC.  The POWER instruction set are those instruc-
           tions supported by the rios chip set used in the original RS/6000
           systems and the PowerPC instruction set is the architecture of the
           Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and the IBM 4xx
           microprocessors.


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

           The -mpowerpc option allows GCC to generate instructions that are
           found only in the 32-bit subset of the PowerPC architecture.  Spec-
           ifying -mpowerpc-gpopt implies -mpowerpc and also allows GCC to use
           the optional PowerPC architecture instructions in the General Pur-
           pose group, including floating-point square root.  Specifying
           -mpowerpc-gfxopt implies -mpowerpc and also allows GCC to use the
           optional PowerPC architecture instructions in the Graphics group,
           including floating-point select.

           The -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 regis-
           ter.  Specifying both -mpower and -mpowerpc permits GCC to use any
           instruction from either architecture and to allow use of the MQ
           register; specify this for the Motorola MPC601.

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

           GCC defaults to the mnemonics appropriate for the architecture in
           use.  Specifying -mcpu=cpu_type sometimes overrides the value of
           these option.  Unless you are building a cross-compiler, you should
           normally not specify either -mnew-mnemonics or -mold-mnemonics, but
           should instead accept the default.

       -mcpu=cpu_type
           Set architecture type, register usage, choice of mnemonics, and
           instruction scheduling parameters for machine type cpu_type.  Sup-
           ported values for cpu_type are rios, rios1, rsc, rios2, rs64a, 601,
           602, 603, 603e, 604, 604e, 620, 630, 740, 7400, 7450, 750, power,
           power2, powerpc, 403, 505, 801, 821, 823, and 860 and common.

           -mcpu=common selects a completely generic processor.  Code gener-
           ated under this option will run on any POWER or PowerPC processor.
           GCC will use only the instructions in the common subset of both
           architectures, and will not use the MQ register.  GCC assumes a
           generic processor model for scheduling purposes.

           -mcpu=power, -mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64 spec-
           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 specified,
           the code generated will use the architecture, registers, and
           mnemonics set by -mcpu, but the scheduling parameters set by
           -mtune.

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

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

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

       -misel=yes/no
       -misel
           default.  In that case, GCC will allocate at least one TOC entry
           for each unique non-automatic variable reference in your program.
           GCC will also place floating-point constants in the TOC.  However,
           only 16,384 entries are available in the TOC.

           If you receive a linker error message that saying you have over-
           flowed 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 cal-
           culate the sum of an address and a constant at run-time instead of
           putting that sum into the TOC.  You may specify one or both of
           these options.  Each causes GCC to produce very slightly slower and
           larger code at the expense of conserving TOC space.

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

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

       -mxl-call
       -mno-xl-call
           On AIX, pass floating-point arguments to prototyped functions
           beyond the register save area (RSA) on the stack in addition to
           argument FPRs.  The AIX calling convention was extended but not
           initially documented to handle an obscure K&R C case of calling a
           function that takes the address of its arguments with fewer argu-
           ments than declared.  AIX XL compilers access floating point argu-
           ments which do not fit in the RSA from the stack when a subroutine
           is compiled without optimization.  Because always storing floating-
           point arguments on the stack is inefficient and rarely needed, this
           option is not enabled by default and only is necessary when calling
           subroutines compiled by AIX XL compilers without optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an applica-
           tion written to use message passing with special startup code to
           enable the application to run.  The system must have PE installed
           in the standard location (/usr/lpp/ppe.poe/), or the specs file
           must be overridden with the -specs= option to specify the appropri-
           ate directory location.  The Parallel Environment does not support
           threads, so the -mpe option and the -pthread option are incompati-
           ble.

       -msoft-float
       -mhard-float
           generated on PowerPC systems.  Do not use -mmultiple on little
           endian PowerPC systems, since those instructions do not work when
           the processor is in little endian mode.  The exceptions are PPC740
           and PPC750 which permit the instructions usage in little endian
           mode.

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

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

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

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force struc-
           tures and unions that contain bit-fields to be aligned to the base
           type of the bit-field.

           For example, by default a structure containing nothing but 8
           "unsigned" bit-fields of length 1 would be aligned to a 4 byte
           boundary and have a size of 4 bytes.  By using -mno-bit-align, the
           structure would be aligned to a 1 byte boundary and be one byte in
           size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume that
           unaligned memory references will be handled by the system.

       -mrelocatable
       -mno-relocatable
           On embedded PowerPC systems generate code that allows (does not
           allow) the program to be relocated to a different address at run-
           time.  If you use -mrelocatable on any module, all objects linked
           together must be compiled with -mrelocatable or -mrelocatable-lib.

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

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

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

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using call-
           ing conventions that adheres to the March 1995 draft of the System
           V Application Binary Interface, PowerPC processor supplement.  This
           is the default unless you configured GCC using powerpc-*-eabiaix.

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

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

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

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

       -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 func-
           tions will set or clear the bit.

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

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

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

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

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

       -mwindiss
           Specify that you are compiling for the WindISS simulation environ-
           ment.

       -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 initializa-
           tion 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 pow-
           erpc*-*-eabi* options.

       -msdata=eabi
       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small global and
           static data in the .sdata section, which is pointed to by register
           "r13".  Put small uninitialized global and static data in the .sbss
           section, which is adjacent to the .sdata section.  The -msdata=sysv
           option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
           On System V.4 and embedded PowerPC systems, if -meabi is used, com-
           pile code the same as -msdata=eabi, otherwise compile code the same
           as -msdata=sysv.

       -msdata-data
           On System V.4 and embedded PowerPC systems, put small global and
           static data in the .sdata section.  Put small uninitialized global
           and static data in the .sbss section.  Do not use register "r13" to
           address small data however.  This is the default behavior unless
           other -msdata options are used.

       -msdata=none
       -mno-sdata
           On embedded PowerPC systems, put all initialized global and static
           data in the .data section, and all uninitialized data in the .bss
           section.

       -G num
           On embedded PowerPC systems, put global and static items less than
           or equal to num bytes into the small data or bss sections instead
           of the normal data or bss section.  By default, num is 8.  The -G
           num switch is also passed to the linker.  All modules should be
           compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems do (do not) emit regis-
           ter names in the assembly language output using symbolic forms.

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

           Some linkers are capable of detecting out-of-range calls and gener-
           ating 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 specifica-
           tions when the linker is known to generate glue.

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

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

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

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

       -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
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           This options are available for Darwin linker. Darwin linker man
           page describes them in detail.

       IBM RT Options

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

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

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

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

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

       -mfp-arg-in-fpregs
           Use a calling sequence incompatible with the IBM calling convention
           in which floating point arguments are passed in floating point reg-
           isters.  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 compatibility with the MetaWare HighC (hc)
           compiler.  Use the option -fpcc-struct-return for compatibility
           with the Portable C Compiler (pcc).

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

       MIPS Options
           orion, and sb1.  The special value from-abi selects the most com-
           patible architecture for the selected ABI (that is, mips1 for
           32-bit ABIs and mips3 for 64-bit ABIs).

           In processor names, a final 000 can be abbreviated as k (for exam-
           ple, -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 architecture (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 arith-
           metic 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.

       -mips64
           Equivalent to -march=mips64.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating point multiply
           and accumulate instructions, when they are available.  These
           instructions are generated by default if they are available, but
           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 explana-
           tion of the default, and the width of pointers.

       -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 integer
           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 generate 64-bit code when you select a 64-bit architec-
           ture, but you can use -mgp32 to get 32-bit code instead.

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

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

       -msplit-addresses
       -mno-split-addresses
           Generate code to load the high and low parts of address constants
           separately.  This allows GCC to optimize away redundant loads of
           the high order bits of addresses.  This optimization requires GNU

       -mgpopt
       -mno-gpopt
           The -mgpopt switch says to write all of the data declarations
           before the instructions in the text section, this allows the MIPS
           assembler to generate one word memory 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 program (number of registers saved, stack
           size, etc.).

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

       -mmips-tfile
       -mno-mips-tfile
           The -mno-mips-tfile switch causes the compiler not postprocess the
           object file with the mips-tfile program, after the MIPS assembler
           has generated it to add debug 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 temporary file
           names passed to the assembler embedded in the object file, which
           means the objects will not compare the same.  The -mno-mips-tfile
           switch should only be used when there are bugs in the mips-tfile
           program that prevents compilation.

       -msoft-float
           Generate output containing library calls for floating point.  Warn-
           ing: the requisite libraries are not part of GCC.  Normally the
           facilities of the machine's usual C compiler are used, but this
           can't be done directly in cross-compilation.  You must make your
           own arrangements to provide suitable library functions for cross-
           compilation.

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

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

       -mlong-calls
       -mno-long-calls
           Do all calls with the JALR instruction, which requires loading up a
           function's address into a register before the call.  You need to
           use this switch, if you call outside of the current 512 megabyte
           Generate PIC code suitable for some embedded systems.  All calls
           are made using PC relative address, and all data is addressed using
           the $gp register.  No more than 65536 bytes of global data may be
           used.  This requires GNU as and GNU ld which do most of the work.
           This currently only works on targets which use ECOFF; it does not
           work with ELF.

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

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

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

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

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

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

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

       -EL Compile code for the processor in little endian mode.  The requi-
           site 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 refer-
           ence instructions based on the global pointer (gp or $28), instead
           of the normal two words used.  By default, num is 8 when the MIPS
           assembler is used, and 0 when the GNU assembler is used.  The -G
           num switch is also passed to the assembler and linker.  All modules
           occurs in the following two instructions.

       -no-crt0
           Do not include the default crt0.

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

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

       Intel 386 and AMD x86-64 Options

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

       -mcpu=cpu-type
           Tune to cpu-type everything applicable about the generated code,
           except for the ABI and the set of available instructions.  The
           choices for cpu-type are i386, i486, i586, i686, pentium, pentium-
           mmx, pentiumpro, pentium2, pentium3, pentium4, k6, k6-2, k6-3,
           athlon, athlon-tbird, athlon-4, athlon-xp, athlon-mp, winchip-c6,
           winchip2 and c3.

           While picking a specific cpu-type will schedule things appropri-
           ately 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=pen-
           tium, and -mcpu=pentiumpro respectively.  These synonyms are depre-
               computed in 80bit precision instead of precision specified by
               the type resulting in slightly different results compared to
               most of other chips. See -ffloat-store for more detailed
               description.

               This is the default choice for i386 compiler.

           sse Use scalar floating point instructions present in the SSE
               instruction set.  This instruction set is supported by Pentium3
               and newer chips, in the AMD line by Athlon-4, Athlon-xp and
               Athlon-mp chips.  The earlier version of SSE instruction set
               supports only single precision arithmetics, thus the double and
               extended precision arithmetics is still done using 387.  Later
               version, present only in Pentium4 and the future AMD x86-64
               chips supports double precision arithmetics too.

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

               The resulting code should be considerably faster in majority of
               cases and avoid the numerical instability problems of 387 code,
               but may break some existing code that expects temporaries to be
               80bit.

               This is the default choice for x86-64 compiler.

           sse,387
               Attempt to utilize both instruction sets at once.  This effec-
               tively double the amount of available registers and on chips
               with separate execution units for 387 and SSE the execution
               resources too.  Use this option with care, as it is still
               experimental, because gcc register allocator does not model
               separate functional units well resulting in instable perfor-
               mance.

       -masm=dialect
           Output asm instructions using selected dialect. Supported choices
           are intel or att (the default one).

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating point com-
           parisons.  These handle correctly the case where the result of a
           comparison is unordered.

       -msoft-float
           Generate output containing library calls for floating point.  Warn-
           ing: 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
           The option -mno-fp-ret-in-387 causes such values to be returned in
           ordinary CPU registers instead.

       -mno-fancy-math-387
           Some 387 emulators do not support the "sin", "cos" and "sqrt"
           instructions for the 387.  Specify this option to avoid generating
           those instructions.  This option is the default on FreeBSD, OpenBSD
           and NetBSD.  This option is overridden when -march indicates that
           the target cpu will always have an FPU and so the instruction will
           not need emulation.  As of revision 2.6.1, these instructions are
           not generated unless you also use the -funsafe-math-optimizations
           switch.

       -malign-double
       -mno-align-double
           Control whether GCC aligns "double", "long double", and "long long"
           variables on a two word boundary or a one word boundary.  Aligning
           "double" variables on a two word boundary will produce code that
           runs somewhat faster on a Pentium at the expense of more memory.

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

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

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

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

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

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

           You can specify that an individual function is called with this
           calling sequence with the function attribute stdcall.  You can also

           In addition, seriously incorrect code will result if you call a
           function with too many arguments.  (Normally, extra arguments are
           harmlessly ignored.)

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

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

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num
           byte boundary.  If -mpreferred-stack-boundary is not specified, the
           default is 4 (16 bytes or 128 bits), except when optimizing for
           code size (-Os), in which case the default is the minimum correct
           alignment (4 bytes for x86, and 8 bytes for x86-64).

           On Pentium and PentiumPro, "double" and "long double" values should
           be aligned to an 8 byte boundary (see -malign-double) or suffer
           significant run time performance 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 sensitive to stack space usage,
           such as embedded systems and operating system kernels, may want to
           reduce the preferred alignment to -mpreferred-stack-boundary=2.

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

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

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

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

       -mno-align-stringops
           Do not align destination of inlined string operations.  This switch
           reduces code size and improves performance in case the destination
           is already aligned, but gcc don't know about it.

       -minline-all-stringops
           By default GCC inlines string operations only when destination is
           known to be aligned at least to 4 byte boundary.  This enables more
           inlining, increase code size, but may improve performance of code
           that depends on fast memcpy, strlen and memset for short lengths.

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

       These -m switches are supported in addition to the above on AMD x86-64
       processors in 64-bit environments.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit envi-
           ronment sets int, long and pointer to 32 bits and generates code
           that runs on any i386 system.  The 64-bit environment sets int to
           32 bits and long and pointer to 64 bits and generates code for
           AMD's x86-64 architecture.

       -mno-red-zone
           Do not use a so called red zone for x86-64 code.  The red zone is
           mandated by the x86-64 ABI, it is a 128-byte area beyond the loca-
           tion of the stack pointer that will not be modified by signal or
           interrupt handlers and therefore can be used for temporary data
           without adjusting the stack pointer.  The flag -mno-red-zone dis-
           ables 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.

           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 computers:

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

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

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

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

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

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

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

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

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

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

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type
           cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
           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
           Enable the optimization pass in the HP-UX linker.  Note this makes
           symbolic debugging impossible.  It also triggers a bug in the HP-UX
           8 and HP-UX 9 linkers in which they give bogus error messages when
           linking some programs.

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

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this to
           work.

       -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 build-
           ing 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 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`.

       -mhp-ld
           Use HP ld specific options.  This passes -b to ld when building a

       -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 limited at 240,000 bytes.

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

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

           The types of long calls used depends on the capabilities of the
           assembler and linker, and the type of code being generated.  The
           impact on systems that support long absolute calls, and long pic
           symbol-difference or pc-relative calls should be relatively small.
           However, 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 libdld.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 version 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 necessary 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 generate 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 implementations:

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

           the "bal" instruction as well as "call".  This will result in more
           efficient code for explicit calls when the "bal" instruction can be
           substituted by the assembler or linker, but less efficient code in
           other cases, such as calls via function pointers, or using a linker
           that doesn't support this optimization.

       -mtail-call
       -mno-tail-call
           Do (or do not) make additional attempts (beyond those of the
           machine-independent portions of the compiler) to optimize tail-
           recursive calls into branches.  You may not want to do this because
           the detection of cases where this is not valid is not totally com-
           plete.  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 implementa-
           tions 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.  With-
           out the option long double is implemented by 80-bit floating point
           numbers.  The only reason we have it because there is no 128-bit
           long double support in fp-bit.c yet.  So it is only useful for peo-
           ple using soft-float targets.  Otherwise, we should recommend
           against use of it.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:
           operations.   If you are compiling for an Alpha without floating-
           point operations, you must ensure that the library is built so as
           not to call them.

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

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

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

       -mieee
           The Alpha architecture implements floating-point hardware optimized
           for maximum performance.  It is mostly compliant with the IEEE
           floating point standard.  However, for full compliance, software
           assistance is required.  This option generates code fully IEEE com-
           pliant code except that the inexact-flag is not maintained (see
           below).  If this option is turned on, the preprocessor macro
           "_IEEE_FP" is defined during compilation.  The resulting code is
           less efficient but is able to correctly support denormalized num-
           bers 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 sig-
           nificantly slower than the code generated by default.  Since there
           is very little code that depends on the inexact-flag, you should
           normally not specify this option.  Other Alpha compilers call this
           option -ieee_with_inexact.

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

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

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

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

           m   Round towards minus infinity.

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

           d   Dynamic rounding mode.  A field in the floating point control
               register (fpcr, see Alpha architecture reference manual) con-
               trols the rounding mode in effect.  The C library initializes
               this register for rounding towards plus infinity.  Thus, unless
               your program modifies the fpcr, d corresponds to round towards
               plus 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 program 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 applica-
           tion, different levels of precisions can be selected:

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

           f   Function precision.  The trap handler can determine the func-
               tion 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 conformant.  You must
           not use this option unless you also specify -mtrap-precision=i and
           either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its only effect is
           to emit the line .eflag 48 in the function prologue of the gener-
           ated assembly file.  Under DEC Unix, this has the effect that IEEE-
           conformant math library routines will be linked in.

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

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


       -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 speci-
           fied.

       -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 reloca-
           tions 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 instructions.  This
           option is mostly useful for debugging, as GCC detects the capabili-
           ties of the assembler when it is built and sets the default accord-
           ingly.

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

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

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

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for
           machine type cpu_type.  You can specify either the EV style name or
           the corresponding chip number.  GCC supports scheduling parameters
           for the EV4, EV5 and EV6 family of processors and will choose the
           default values for the instruction set from the processor you spec-
           ify.  If you do not specify a processor type, GCC will default to
           the processor on which the compiler was built.
           21164
               Schedules as an EV5 and has no instruction set extensions.

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

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

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX exten-
               sions.

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

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

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

           Valid options for time are

           number
               A decimal number representing clock cycles.

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

       DEC Alpha/VMS Options

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

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

       H8/300 Options

       These -m options are defined for the H8/300 implementations:
       -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 boundaries.  This option has no effect on the H8/300.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

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

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only sup-
           ports 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 functions from the standard C
           library will not work unless you recompile it first with -mdalign.

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

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

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

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

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

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

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

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

       Options for System V

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

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

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

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

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

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

       TMS320C3x/C4x Options

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

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling
           parameters for machine type cpu_type.  Supported values for
           cpu_type are c30, c31, c32, c40, and c44.  The default is c40 to
           generate code for the TMS320C40.
           ory model is the default and requires reloading of the DP register
           for every direct memory access.

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

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

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

       -mmpyi
       -mno-mpyi
           For the C3x use the 24-bit MPYI instruction for integer multiplies
           instead of a library call to guarantee 32-bit results.  Note that
           if one of the operands is a 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 incor-
           rectly truncated an additional code is necessary to detect and cor-
           rect 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.

           iteration, thus freeing up the CPU buses for operands.  However,
           since interrupts are blocked by this instruction, it is disabled by
           default.

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

       -mti
           Try to emit an assembler syntax that the TI assembler (asm30) is
           happy with.  This also enforces compatibility with the API employed
           by the TI C3x C compiler.  For 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 instruc-
           tions, provided -mparallel-insns is also specified.  These instruc-
           tions have tight register constraints which can pessimize the code
           generation of large functions.

       V850 Options

       These -m options are defined for V850 implementations:

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

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

       -mno-prolog-function
       -mprolog-function
           Do not use (do use) external functions to save and restore regis-

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

       -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 relevant __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 architecture.  The default is -mno-
           disable-callt which allows the CALLT instruction to be used.

       ARC Options

       These options are defined for ARC implementations:

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

       -EB Compile code for big endian mode.

       -mmangle-cpu
           Prepend the name of the cpu to all public symbol names.  In multi-
           ple-processor systems, there are many ARC variants with different

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

       NS32K Options

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

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

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

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

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

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

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

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

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

       -mieee-compare
           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" instruction.

           This calling convention is incompatible with the one normally used
           on Unix, so you cannot use it if you need to call libraries com-
           piled with the Unix compiler.

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

           In addition, seriously incorrect code will result if you call a
           function with too many arguments.  (Normally, extra arguments are
           harmlessly ignored.)

           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 com-
           piled with the Unix compiler.

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

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

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

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

       -mnohimem
           Assume code will be loaded in the first 512MB of virtual address
           space.  This is the default for all platforms.
           the C compiler, only for assembler programs (MCU types: at90s1200,
           attiny10, attiny11, attiny12, attiny15, attiny28).

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

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

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

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

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

       MCore Options

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

       -mhardlit
       -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.

       -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.

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

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

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

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

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

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

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

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data section.

       -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 mini-
           mum latency algorithm.

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

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

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

       D30V Options

       These -m options are defined for D30V implementations:

       -mextmem
           Link the .text, .data, .bss, .strings, .rodata, .rodata1, .data1
           sections into 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 automatically parallelize adjacent
           short instructions where possible.

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

       ture.

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

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

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

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

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

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

       CRIS Options

       These options are defined specifically for the CRIS ports.

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

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated
           code, except for the ABI and the set of available instructions.
           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 addressing 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 align-
           ment.

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

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

           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 functions from a simulator
           library.  Code, initialized data and zero-initialized data are
           allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at
           0x40000000 and zero-initialized data at 0x80000000.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify that intrinsic library functions are being compiled, pass-
           ing all values in registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with
           respect to the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate code that passes function parameters and return values
           that (in the called function) are seen as registers "$0" and up, as
           opposed to the GNU ABI which uses global registers "$231" and up.

       -mzero-extend
       -mno-zero-extend
           When reading data from memory in sizes shorter than 64 bits, use
           (do not use) zero-extending load instructions by default, rather
           than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same
           sign as the divisor.  With the default, -mno-knuthdiv, the sign of
           the remainder follows the sign of the dividend.  Both methods are
           arithmetically valid, the latter being almost exclusively used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the assembly
           code can be used with the "PREFIX" assembly directive.

       -melf
           Generate an executable in the ELF format, rather than the default
           Generate (do not generate) code that uses base addresses.  Using a
           base address automatically generates a request (handled by the
           assembler and the linker) for a constant to be set up in a global
           register.  The register is used for one or more base address
           requests within the range 0 to 255 from the value held in the reg-
           ister.  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 float-
           ing point on the PDP-11/40 is not supported.)

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler syn-
           tax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.

       -mbcopy-builtin
           Use inline "movstrhi" patterns for copying memory.  This is the
           default.

       -mbcopy
           Do not use inline "movstrhi" patterns for copying memory.

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

       -mint32
       -mno-int16
           Use 32-bit "int".

           Use "abshi2" pattern.  This is the default.

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

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

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

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

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

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

       -mdec-asm
           Use DEC assembler syntax.  This is the default when configured for
           any PDP-11 target other than pdp11-*-bsd.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
           Choose startup files and linker script suitable for the simulator.

       FRV Options

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

       -mgpr-64
           Use all 64 general purpose registers.

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

       -mfpr-64
           Use all 64 floating point registers

       -mhard-float
           Use hardware instructions for floating point operations.

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

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
       -mdouble
           Use floating point double instructions.

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

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

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

       -mlibrary-pic
           Enable PIC support for building libraries

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

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

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

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

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

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

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

       -mscc
           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.

       -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 instructions.

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

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

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

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

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

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

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

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

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

       -mtomcat-stats
           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 different configu-
       rations.  The compiler's default options can be set to match a particu-
       lar Xtensa configuration by copying a configuration file into the GCC
       sources when building GCC.  The options below may be used to override
       the default options.
           tions.

       -mmac16
       -mno-mac16
           Enable or disable use of the Xtensa MAC16 option.  When enabled,
           GCC will generate MAC16 instructions from standard C code, with the
           limitation that it will use neither the MR register file nor any
           instruction that operates on the MR registers.  When this option is
           disabled, GCC will translate 16-bit multiply/accumulate operations
           to a combination of core instructions and library calls, depending
           on whether any other multiplier options are enabled.

       -mmul16
       -mno-mul16
           Enable or disable use of the 16-bit integer multiplier option.
           When enabled, the compiler will generate 16-bit multiply instruc-
           tions for multiplications of 16 bits or smaller in standard C code.
           When this option is disabled, the compiler will either use 32-bit
           multiply or MAC16 instructions if they are available or generate
           library calls to perform the multiply operations using shifts and
           adds.

       -mmul32
       -mno-mul32
           Enable or disable use of the 32-bit integer multiplier option.
           When enabled, the compiler will generate 32-bit multiply instruc-
           tions for multiplications of 32 bits or smaller in standard C code.
           When this option is disabled, the compiler will generate library
           calls to perform the multiply operations using either shifts and
           adds or 16-bit multiply instructions if they are available.

       -mnsa
       -mno-nsa
           Enable or disable use of the optional normalization shift amount
           ("NSA") instructions to implement the built-in "ffs" function.

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

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

       -mbooleans
       -mno-booleans
           Enable or disable support for the boolean register file used by
           Xtensa coprocessors.  This is not typically useful by itself but
           may be required for other options that make use of the boolean reg-
           isters (e.g., the floating-point option).

       -mhard-float
       -msoft-float
           Enable or disable use of the floating-point option.  When enabled,
           GCC generates floating-point instructions for 32-bit "float" opera-
           the floating-point option is not also enabled.  Disabling fused
           multiply/add and multiply/subtract instructions forces the compiler
           to use separate instructions for the multiply and add/subtract
           operations.  This may be desirable in some cases where strict IEEE
           754-compliant results are required: the fused multiply add/subtract
           instructions do not round the intermediate result, thereby
           producing results with more bits of precision than specified by the
           IEEE standard.  Disabling fused multiply add/subtract instructions
           also ensures that the program output is not sensitive to the com-
           piler's ability to combine multiply and add/subtract operations.

       -mserialize-volatile
       -mno-serialize-volatile
           When this option is enabled, GCC inserts "MEMW" instructions before
           "volatile" memory references to guarantee sequential consistency.
           The default is -mserialize-volatile.  Use -mno-serialize-volatile
           to omit the "MEMW" instructions.

       -mtext-section-literals
       -mno-text-section-literals
           Control the treatment of literal pools.  The default is -mno-text-
           section-literals, which places literals in a separate section in
           the output file.  This allows the literal pool to be placed in a
           data RAM/ROM, and it also allows the linker to combine literal
           pools from separate object files to remove redundant literals and
           improve code size.  With -mtext-section-literals, the literals are
           interspersed in the text section in order to keep them as close as
           possible to their references.  This may be necessary for large
           assembly files.

       -mtarget-align
       -mno-target-align
           When this option is enabled, GCC instructs the assembler to auto-
           matically align instructions to reduce branch penalties at the
           expense of some code density.  The assembler attempts to widen den-
           sity instructions to align branch targets and the instructions fol-
           lowing call instructions.  If there are not enough preceding safe
           density instructions to align a target, no widening will be per-
           formed.  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
           instructions or by inserting no-op instructions.

       -mlongcalls
       -mno-longcalls
           When this option is enabled, GCC instructs the assembler to trans-
           late 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 assembler trans-
           lates a direct "CALL" instruction into an "L32R" followed by a
           "CALLX" instruction.  The default is -mno-longcalls.  This option
           should be used in programs where the call target can potentially be
           out of range.  This option is implemented in the assembler, not the
           compiler, so the assembly code generated by GCC will still show
           direct call instructions---look at the disassembled object code to
           see the actual instructions.  Note that the assembler will use an

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

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

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

       -fexceptions
           Enable exception handling.  Generates extra code needed to propa-
           gate exceptions.  For some targets, this implies GCC will generate
           frame unwind information for all functions, which can produce sig-
           nificant data size overhead, although it does not affect execution.
           If you do not specify this option, GCC will enable it by default
           for languages like C++ which normally require exception handling,
           and disable it for languages like C that do not normally require
           it.  However, you may need to enable this option when compiling C
           code that needs to interoperate properly with exception handlers
           written in C++.  You may also wish to disable this option if you
           are compiling older C++ programs that don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw excep-
           tions.  Note that this requires platform-specific runtime support
           that does not exist everywhere.  Moreover, it only allows trapping
           instructions to throw exceptions, i.e. memory references or 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 generate any
           needed static data, but will not affect the generated code in any
           other way.  You will normally not enable this option; instead, a
           language processor that needs this handling would enable it on your
           behalf.

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

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

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

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.
           This is more efficient for small structures than -fpcc-struct-
           return.

           If you specify neither -fpcc-struct-return nor -freg-struct-return,
           GCC defaults to whichever convention is standard for the target.
           If there is no standard convention, GCC defaults to -fpcc-struct-
           return, except on targets where GCC is the principal compiler.  In
           those cases, we can choose the standard, and we chose the more
           efficient register return alternative.

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

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

           Warning: the -fshort-enums switch causes GCC to generate code that
           is not binary compatible with code generated without that switch.
           Use it to conform to a non-default application binary interface.

       -fshort-double
           Use the same size for "double" as for "float".

           Warning: the -fshort-double switch causes GCC to generate code that
           is not binary compatible with code generated without that switch.
           Use it to conform to a non-default application binary interface.

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

           Warning: the -fshort-wchar switch causes GCC to generate code that
           is not binary compatible with code generated without that switch.
           Use it to conform to a non-default application binary interface.

       -fshared-data
           Requests that the data and non-"const" variables of this compila-
           tion be shared data rather than private data.  The distinction
           makes sense only on certain operating systems, where shared data is
           shared between processes running the same program, while private
           data exists in one copy per process.

       -fno-common
           In C, allocate even uninitialized global variables in the data sec-
           tion of the object file, rather than generating them as common
           blocks.  This has the effect that if the same variable is declared
           (without "extern") in two different compilations, you will get an
           error when you link them.  The only reason this might be useful is
           if you wish to verify that the program will work on other systems
           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.  (collect2 is included in the GCC
           distribution.)  For systems 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 anything else that
           would cause trouble if the function is split in the middle, and the
           two halves are placed at locations far apart in memory.  This
           option is used when compiling crtstuff.c; you should not need to
           use it for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to
           make it more readable.  This option is generally only of use to
           those who actually need to read the generated assembly code (per-
           haps while debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be
           omitted and is useful when comparing two assembler files.

       -fvolatile
           Consider all memory references through pointers to be volatile.

       -fvolatile-global
           Consider all memory references to extern and global data items to
           be volatile.  GCC does not consider static data items to be
           volatile because of this switch.

       -fvolatile-static
           Consider all memory references to static data to be volatile.

       -fpic
           Generate position-independent code (PIC) suitable for use in a
           shared library, if supported for the target machine.  Such code
           accesses all constant addresses through a global offset table
           (GOT).  The dynamic loader resolves the GOT entries when the pro-
           gram starts (the dynamic loader is not part of GCC; it is part of
           the operating system).  If the GOT size for the linked executable
           exceeds a machine-specific maximum size, you get an error message
           from the linker indicating that -fpic does not work; in that case,
           recompile with -fPIC instead.  (These maximums are 16k on the m88k,
           8k on the SPARC, and 32k on the m68k and RS/6000.  The 386 has no
           such limit.)

           Position-independent code requires special support, and therefore
           works only on certain machines.  For the 386, GCC supports PIC for
           System V but not for the Sun 386i.  Code generated for the IBM
           RS/6000 is always position-independent.

       -fPIC
           If supported for the target machine, emit position-independent
           code, suitable for dynamic linking and avoiding any limit on the
           size of the global offset table.  This option makes a difference on
           the m68k, m88k, and the SPARC.

           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 clob-
           bered by function calls.  It may be allocated for temporaries or
           variables that do not live across a call.  Functions compiled this
           way will not save and restore the register reg.

           It is an error to used this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed per-
           vasive roles in the machine's execution model will produce disas-
           trous results.

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

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by
           functions.  It may be allocated even for temporaries or variables
           that live across a call.  Functions compiled this way will save and
           restore the register reg if they use it.

           It is an error to used this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed per-
           vasive roles in the machine's execution model will produce disas-
           trous results.

           A different sort of disaster will result from the use of this flag
           for a register in which function values may be returned.

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

       -fpack-struct
           Pack all structure members together without holes.

           Warning: the -fpack-struct switch causes GCC to generate code that
           is not binary compatible with code generated without that switch.
           Additionally, it makes the code suboptimal.  Use it to conform to a
           non-default application binary interface.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.
           Just after function entry and just before function exit, the fol-
           lowing 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 func-
           tion, so the call site information may not be available to the pro-
           filing functions otherwise.)

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

           your uses of a function are expanded inline, this may mean an addi-
           tional expansion of code size.  If you use extern inline in your C
           code, an addressable version of such functions must be provided.
           (This is normally the case anyways, but if you get lucky and the
           optimizer always expands the functions inline, you might have got-
           ten away without providing static copies.)

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

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

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

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

           For instance, if the stack starts at absolute address 0x80000000
           and grows downwards, you can use the flags -fstack-limit-sym-
           bol=__stack_limit and -Wl,--defsym,__stack_limit=0x7ffe0000 to
           enforce a stack limit of 128KB.  Note that this may only work with
           the GNU linker.

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

           -fargument-alias specifies that arguments (parameters) may alias
           each other and may alias global storage.-fargument-noalias speci-
           fies that arguments do not alias each other, but may alias global
           storage.-fargument-noalias-global specifies that arguments do not
           alias each other and do not alias global storage.

           Each language will automatically use whatever option is required by
           the language standard.  You should not need to use these options
           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 argu-
           ment should be one of "global-dynamic", "local-dynamic", "ini-
           tial-exec" or "local-exec".

           The default without -fpic is "initial-exec"; with -fpic the default
           is "global-dynamic".


ENVIRONMENT

       This section describes several environment variables that affect how
       GCC operates.  Some of them work by specifying directories or prefixes
       to use when searching for various kinds of files.  Some are used to
       specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as
       -B, -I and -L.  These take precedence over places specified using envi-
       ronment variables, which in turn take precedence over those specified
       by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
           These environment variables control the way that GCC uses localiza-
           tion 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 cate-
           gories can be set to any value supported by your installation.  A
           typical value is en_UK for English in the United Kingdom.

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

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

           If the LC_ALL environment variable is set, it overrides the value
           of LC_CTYPE and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES
           default to the value of the LANG environment variable.  If none of
           these variables are set, GCC defaults to traditional C English
           behavior.

       TMPDIR
           If TMPDIR is set, it specifies the directory to use for temporary
           files.  GCC uses temporary files to hold the output of one stage of
           compilation which is to be used as input to the next stage: for
           example, the output of the preprocessor, which is the input to the
           compiler proper.

       GCC_EXEC_PREFIX
           If GCC cannot find the subprogram using the specified prefix, it
           tries looking in the usual places for the subprogram.

           The default value of GCC_EXEC_PREFIX is prefix/lib/gcc-lib/ where
           prefix is the value of "prefix" when you ran the configure script.

           Other prefixes specified with -B take precedence over this prefix.

           This prefix is also used for finding files such as crt0.o that are
           used for linking.

           In addition, the prefix is used in an unusual way in finding the
           directories to search for header files.  For each of the standard
           directories whose name normally begins with /usr/local/lib/gcc-lib
           (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
           replacing that beginning with the specified prefix to produce an
           alternate directory name.  Thus, with -Bfoo/, GCC will search
           foo/bar where it would normally search /usr/local/lib/bar.  These
           alternate directories are searched first; the standard directories
           come next.

       COMPILER_PATH
           The value of COMPILER_PATH is a colon-separated list of directo-
           ries, much like PATH.  GCC tries the directories thus specified
           when searching for subprograms, if it can't find the subprograms
           using GCC_EXEC_PREFIX.

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

       LANG
           This variable is used to pass locale information to the compiler.
           One way in which this information is used is to determine the char-
           acter 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.

           The special character, "PATH_SEPARATOR", is target-dependent and
           determined at GCC build time.  For Windows-based targets it is a
           semicolon, and for almost all other targets it is a colon.

           CPATH specifies a list of directories to be searched as if speci-
           fied with -I, but after any paths given with -I options on the com-
           mand 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 direc-
           tories to be searched as if specified with -isystem, but after any
           paths given with -isystem options on the command line.

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

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

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

           In other words, this environment variable is equivalent to
           combining the options -MM and -MF, with an optional -MT switch too.

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


BUGS

       For instructions on reporting bugs, see <http://gcc.gnu.org/bugs.html>.
       Use of the gccbug script to report bugs is recommended.


FOOTNOTES

       1.  On some systems, gcc -shared needs to build supplementary stub code
           for constructors to work.  On multi-libbed systems, gcc -shared
           must select the correct support libraries to link against.  Failing
           to supply the correct flags may lead to subtle defects.  Supplying
           them in cases where they are not necessary is innocuous.


SEE ALSO

       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), g77(1), as(1), ld(1),
       gdb(1), adb(1), dbx(1), sdb(1) and the Info entries for gcc, cpp, g77,
       as, ld, binutils and gdb.

       under the terms of the GNU Free Documentation License, Version 1.2 or
       any later version published by the Free Software Foundation; with the
       Invariant Sections being ``GNU General Public License'' and ``Funding
       Free Software'', the Front-Cover texts being (a) (see below), and with
       the Back-Cover Texts being (b) (see below).  A copy of the license is
       included in the gfdl(7) man page.

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

            A GNU Manual

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

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

3rd Berkeley Distribution           gcc-3.3                             gcc(1)