MirOS Manual: mgcc(1)


GCC(1)                         GNU                         GCC(1)

NAME

     gcc - GNU project C compiler

SYNOPSIS

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

     Only the most useful options are listed here; see below for
     the remainder.

DESCRIPTION

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

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

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

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

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

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

gcc-3.4.6                  2014-04-02                           1

GCC(1)                         GNU                         GCC(1)

OPTIONS

     Option Summary

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

     Overall Options
         -c  -S  -E  -o file  -pipe  -pass-exit-codes -x language
         -v  -###  --help  --target-help  --version

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

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

     Objective-C Language Options
         -fconstant-string-class=class-name -fgnu-runtime
         -fnext-runtime -fno-nil-receivers -fobjc-exceptions
         -freplace-objc-classes -fzero-link -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  -Wextra
         -Wall  -Waggregate-return -Wbounded -Wcast-align
         -Wcast-qual  -Wchar-subscripts  -Wcomment -Wconversion
         -Wno-deprecated-declarations -Wdisabled-optimization
         -Wno-div-by-zero  -Wendif-labels -Werror
         -Werror-maybe-reset
         -Werror-implicit-function-declaration -Wfloat-equal

gcc-3.4.6                  2014-04-02                           2

GCC(1)                         GNU                         GCC(1)

         -Wformat  -Wformat=2 -Wno-format-extra-args
         -Wformat-nonliteral -Wformat-security  -Wformat-y2k
         -Wimplicit  -Wimplicit-function-declaration
         -Wimplicit-int -Wimport  -Wno-import  -Winit-self  -Win-
         line -Wno-invalid-offsetof  -Winvalid-pch
         -Wlarger-than-len  -Wlong-long -Wmain  -Wmissing-braces
         -Wmissing-field-initializers -Wmissing-format-attribute
         -Wmissing-noreturn -Wno-multichar  -Wnonnull  -Wpacked
         -Wpadded -Wparentheses  -Wpointer-arith
         -Wredundant-decls -Wreturn-type  -Wsequence-point
         -Wshadow -Wsign-compare  -Wstack-larger-than-len
         -Wstack-protector  -Wstrict-aliasing -Wswitch
         -Wswitch-default  -Wswitch-enum -Wsystem-headers
         -Wtrampolines -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
         -Wold-style-definition -Wstrict-prototypes  -Wtradi-
         tional -Wdeclaration-after-statement

     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 -feliminate-unused-debug-types
         -feliminate-unused-debug-symbols -fmem-report
         -fprofile-arcs -frandom-seed=string -fsched-verbose=n
         -ftest-coverage  -ftime-report -g  -glevel  -gcoff
         -gdwarf-2 -ggdb  -gstabs  -gstabs+  -gvms  -gxcoff
         -gxcoff+ -p  -pg  -print-file-name=library
         -print-libgcc-file-name -print-multi-directory
         -print-multi-lib -print-prog-name=program
         -print-search-dirs  -Q -save-temps  -time

     Optimization Options
         -falign-functions=n  -falign-jumps=n -falign-labels=n
         -falign-loops=n -fbranch-probabilities -fprofile-values
         -fvpt -fbranch-target-load-optimize
         -fbranch-target-load-optimize2 -fcaller-saves
         -fcprop-registers -fcse-follow-jumps  -fcse-skip-blocks
         -fdata-sections -fdelayed-branch
         -fdelete-null-pointer-checks -fexpensive-optimizations
         -ffast-math  -ffloat-store -fforce-addr  -fforce-mem
         -ffunction-sections -fgcse  -fgcse-lm  -fgcse-sm
         -fgcse-las  -floop-optimize -fcrossjumping
         -fif-conversion  -fif-conversion2 -finline-functions
         -finline-limit=n  -fkeep-inline-functions

gcc-3.4.6                  2014-04-02                           3

GCC(1)                         GNU                         GCC(1)

         -fkeep-static-consts  -fmerge-constants
         -fmerge-all-constants -fmove-all-movables  -fnew-ra
         -fno-branch-count-reg -fno-default-inline
         -fno-defer-pop -fno-function-cse
         -fno-guess-branch-probability -fno-inline
         -fno-math-errno  -fno-peephole  -fno-peephole2
         -funsafe-math-optimizations  -ffinite-math-only
         -fno-trapping-math  -fno-zero-initialized-in-bss
         -fomit-frame-pointer  -foptimize-register-move
         -foptimize-sibling-calls  -fprefetch-loop-arrays
         -fprofile-generate -fprofile-use -freduce-all-givs
         -fregmove  -frename-registers -freorder-blocks
         -freorder-functions -frerun-cse-after-loop
         -frerun-loop-opt -frounding-math -fschedule-insns
         -fschedule-insns2 -fno-sched-interblock  -fno-sched-spec
         -fsched-spec-load -fsched-spec-load-dangerous
         -fsched-stalled-insns=n -sched-stalled-insns-dep=n
         -fsched2-use-superblocks -fsched2-use-traces
         -fsignaling-nans -fsingle-precision-constant
         -fstrength-reduce  -fstrict-aliasing  -ftracer
         -fthread-jumps -funroll-all-loops  -funroll-loops
         -fpeel-loops -funswitch-loops  -fold-unroll-loops
         -fold-unroll-all-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 -iwithpre-
         fixbefore dir  -isystem dir -M  -MM  -MF  -MG  -MP  -MQ
         -MT  -nostdinc -P  -fworking-directory  -remap -tri-
         graphs  -undef  -Umacro  -Wp,option -Xpreprocessor
         option

     Assembler Option
         -Wa,option  -Xassembler option

     Linker Options
         object-file-name  -llibrary -nostartfiles  -node-
         faultlibs  -nostdlib -pie -s  -static  -static-libgcc
         -shared  -shared-libgcc  -symbolic -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

gcc-3.4.6                  2014-04-02                           4

GCC(1)                         GNU                         GCC(1)

         -mbitfield  -mc68000  -mc68020 -mnobitfield  -mrtd
         -mshort  -msoft-float  -mpcrel -malign-int
         -mstrict-align  -msep-data  -mno-sep-data
         -mshared-library-id=n  -mid-shared-library
         -mno-id-shared-library

         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
         -mno-app-regs -mfaster-structs  -mno-faster-structs
         -mflat  -mno-flat  -mfpu  -mno-fpu -mhard-float
         -msoft-float -mhard-quad-float  -msoft-quad-float
         -mimpure-text  -mno-impure-text  -mlittle-endian
         -mstack-bias  -mno-stack-bias -munaligned-doubles
         -mno-unaligned-doubles -mv8plus  -mno-v8plus  -mvis
         -mno-vis -mcypress  -mf930  -mf934 -msparclite  -msuper-
         sparc  -mv8 -threads -pthreads

         ARM Options -mapcs-frame  -mno-apcs-frame -mapcs-26
         -mapcs-32 -mapcs-stack-check  -mno-apcs-stack-check
         -mapcs-float  -mno-apcs-float -mapcs-reentrant
         -mno-apcs-reentrant -msched-prolog  -mno-sched-prolog
         -mlittle-endian  -mbig-endian  -mwords-little-endian
         -malignment-traps  -mno-alignment-traps -msoft-float
         -mhard-float  -mfpe -mthumb-interwork
         -mno-thumb-interwork -mcpu=name  -march=name  -mfpe=name
         -mstructure-size-boundary=n -mabort-on-noreturn
         -mlong-calls  -mno-long-calls -msingle-pic-base
         -mno-single-pic-base -mpic-register=reg
         -mnop-fun-dllimport -mcirrus-fix-invalid-insns
         -mno-cirrus-fix-invalid-insns -mpoke-function-name
         -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame
         -mcaller-super-interworking  -mcallee-super-interworking

         MN10300 Options -mmult-bug  -mno-mult-bug -mam33
         -mno-am33 -mam33-2  -mno-am33-2 -mno-crt0  -mrelax

         M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops
         -mno-align-loops -missue-rate=number
         -mbranch-cost=number -mmodel=code-size-model-type
         -msdata=sdata-type -mno-flush-func -mflush-func=name
         -mno-flush-trap -mflush-trap=number -G num

         RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-
         type -mpower  -mno-power  -mpower2  -mno-power2
         -mpowerpc  -mpowerpc64  -mno-powerpc -maltivec
         -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt

gcc-3.4.6                  2014-04-02                           5

GCC(1)                         GNU                         GCC(1)

         -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mnew-mnemonics
         -mold-mnemonics -mfull-toc   -mminimal-toc
         -mno-fp-in-toc  -mno-sum-in-toc -m64  -m32  -mxl-compat
         -mno-xl-compat  -mpe -malign-power  -malign-natural
         -msoft-float  -mhard-float  -mmultiple  -mno-multiple
         -mstring  -mno-string  -mupdate  -mno-update
         -mfused-madd  -mno-fused-madd  -mbit-align
         -mno-bit-align -mstrict-align  -mno-strict-align
         -mrelocatable -mno-relocatable  -mrelocatable-lib
         -mno-relocatable-lib -mtoc  -mno-toc  -mlittle
         -mlittle-endian  -mbig  -mbig-endian -mdynamic-no-pic
         -mprioritize-restricted-insns=priority
         -msched-costly-dep=dependence_type
         -minsert-sched-nops=scheme -mcall-sysv  -mcall-netbsd
         -maix-struct-return  -msvr4-struct-return -mabi=altivec
         -mabi=no-altivec -mabi=spe  -mabi=no-spe -misel=yes
         -misel=no -mspe=yes  -mspe=no -mfloat-gprs=yes
         -mfloat-gprs=no -mprototype  -mno-prototype -msim
         -mmvme  -mads  -myellowknife  -memb  -msdata -msdata=opt
         -mvxworks  -mwindiss  -G num  -pthread

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

         MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1
         -mips2  -mips3  -mips4  -mips32  -mips32r2  -mips64
         -mips16  -mno-mips16  -mabi=abi  -mabicalls
         -mno-abicalls -mxgot  -mno-xgot  -membedded-pic
         -mno-embedded-pic -mgp32  -mgp64  -mfp32  -mfp64
         -mhard-float  -msoft-float -msingle-float
         -mdouble-float  -mint64  -mlong64  -mlong32 -Gnum
         -membedded-data  -mno-embedded-data
         -muninit-const-in-rodata  -mno-uninit-const-in-rodata

gcc-3.4.6                  2014-04-02                           6

GCC(1)                         GNU                         GCC(1)

         -msplit-addresses  -mno-split-addresses
         -mexplicit-relocs  -mno-explicit-relocs -mrnames
         -mno-rnames -mcheck-zero-division
         -mno-check-zero-division -mmemcpy  -mno-memcpy
         -mlong-calls  -mno-long-calls -mmad  -mno-mad
         -mfused-madd  -mno-fused-madd  -nocpp -mfix-sb1
         -mno-fix-sb1  -mflush-func=func -mno-flush-func
         -mbranch-likely  -mno-branch-likely

         i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type
         -mfpmath=unit -masm=dialect  -mno-fancy-math-387
         -mno-fp-ret-in-387  -msoft-float  -msvr3-shlib
         -mno-wide-multiply  -mrtd  -malign-double
         -mpreferred-stack-boundary=num -mmmx  -msse  -msse2
         -msse3 -m3dnow -mthreads  -mno-align-stringops
         -minline-all-stringops -mpush-args
         -maccumulate-outgoing-args  -m128bit-long-double
         -m96bit-long-double  -mregparm=num
         -momit-leaf-frame-pointer -mno-red-zone
         -mno-tls-direct-seg-refs -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-compat
         -mic3.0-compat -mintel-asm  -mno-clean-linkage
         -mno-code-align -mno-complex-addr  -mno-leaf-procedures
         -mno-old-align  -mno-strict-align  -mno-tail-call
         -mnumerics  -mold-align  -msoft-float  -mstrict-align
         -mtail-call

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

         DEC Alpha/VMS Options -mvms-return-codes

gcc-3.4.6                  2014-04-02                           7

GCC(1)                         GNU                         GCC(1)

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

         SH Options -m1  -m2  -m2e  -m3  -m3e -m4-nofpu
         -m4-single-only  -m4-single  -m4 -m5-64media
         -m5-64media-nofpu -m5-32media  -m5-32media-nofpu
         -m5-compact  -m5-compact-nofpu -mb  -ml  -mdalign  -mre-
         lax -mbigtable  -mfmovd  -mhitachi  -mnomacsave -mieee
         -misize  -mpadstruct  -mspace -mprefergot  -musermode

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

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

         TMS320C3x/C4x Options -mcpu=cpu  -mbig  -msmall  -mreg-
         parm  -mmemparm -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-function  -mno-prolog-function  -mspace
         -mtda=n  -msda=n  -mzda=n -mapp-regs  -mno-app-regs
         -mdisable-callt  -mno-disable-callt -mv850e1 -mv850e
         -mv850  -mbig-switch

         NS32K Options -m32032  -m32332  -m32532  -m32081
         -m32381 -mmult-add  -mnomult-add  -msoft-float  -mrtd
         -mnortd -mregparam  -mnoregparam  -msb  -mnosb -mbit-
         field  -mnobitfield  -mhimem  -mnohimem

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

         MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
         -mrelax-immediates -mno-relax-immediates
         -mwide-bitfields  -mno-wide-bitfields -m4byte-functions
         -mno-4byte-functions  -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

gcc-3.4.6                  2014-04-02                           8

GCC(1)                         GNU                         GCC(1)

         -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
         -minline-sqrt-min-latency -minline-sqrt-max-throughput
         -mno-dwarf2-asm -mearly-stop-bits
         -mfixed-range=register-range -mtls-size=tls-size
         -mtune=cpu-type -mt -pthread -milp32 -mlp64

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

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

         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
         -mmul-bug-workaround  -mno-mul-bug-workaround

         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 -mconst16 -mno-const16 -mfused-madd
         -mno-fused-madd -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

gcc-3.4.6                  2014-04-02                           9

GCC(1)                         GNU                         GCC(1)

         -mcpu=cpu

     Code Generation Options
         -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexcep-
         tions -fnon-call-exceptions  -funwind-tables
         -fasynchronous-unwind-tables -finhibit-size-directive
         -finstrument-functions -fno-common  -fident  -fno-ident
         -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE
         -freg-struct-return  -fshared-data  -fshort-enums
         -fshort-double  -fshort-wchar -fverbose-asm
         -fpack-struct  -fstack-check -fstack-limit-register=reg
         -fstack-limit-symbol=sym -fstack-protector
         -fstack-protector-all -fargument-alias
         -fargument-noalias -fargument-noalias-global
         -fleading-underscore -ftls-model=model -ftrampolines
         -ftrapv  -fwrapv  -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.  GCC is capable of preprocessing and compiling
     several files either into several assembler input files, or
     into one assembler input file; then each assembler input
     file produces an object file, and linking combines all the
     object files (those newly compiled, and those specified as
     input) into an executable file.

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

     file.c
         C source code which must be preprocessed.

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

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

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

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

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

gcc-3.4.6                  2014-04-02                          10

GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

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

     file.s
         Assembler code.

     file.S
         Assembler code which must be preprocessed.

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

gcc-3.4.6                  2014-04-02                          11

GCC(1)                         GNU                         GCC(1)

     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++-header  c++-cpp-output
                 objective-c  objective-c-header  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 subse-
         quent files are handled according to their file name
         suffixes (as they are if -x has not been used at all).

     -pass-exit-codes
         Normally the gcc program will exit with the code of 1 if
         any phase of the compiler returns a non-success return
         code.  If you specify -pass-exit-codes, the gcc program
         will instead return with numerically highest error pro-
         duced 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 out-
         put is in the form of an object file for each source
         file.

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

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

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

gcc-3.4.6                  2014-04-02                          12

GCC(1)                         GNU                         GCC(1)

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

         Input files that don't require compilation are ignored.

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

         Input files which don't require preprocessing are
         ignored.

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

         If you specify -o when compiling more than one input
         file, or you are producing an executable file as output,
         all the source files on the command line will be com-
         piled at once.

         If -o is not specified, the default is to put an execut-
         able 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 ver-
         sion number of the compiler driver program and of the
         preprocessor and the compiler proper.

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

     -pipe
         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 com-
         mand line options understood by gcc.  If the -v option
         is also specified then --help will also be passed on to
         the various processes invoked by gcc, so that they can
         display the command line options they accept.  If the
         -Wextra option is also specified then command line
         options which have no documentation associated with them

gcc-3.4.6                  2014-04-02                          13

GCC(1)                         GNU                         GCC(1)

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

     However, C++ programs often require class libraries as well
     as a compiler that understands the C++ language---and under
     some circumstances, you might want to compile programs or
     header files from standard input, or otherwise without a
     suffix that flags them as C++ programs.  You might also like
     to precompile a C header file with a .h extension to be used
     in C++ compilations.  g++ is a program that calls GCC with
     the default language set to C++, and automatically specifies
     linking against the C++ library.  On many systems, g++ is
     also installed with the name c++.

     When you compile C++ programs, you may specify many of the
     same command-line options that you use for compiling pro-
     grams 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 com-
     piler 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 incompa-
         tible with ISO C90 (when compiling C code), or of stan-
         dard 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

gcc-3.4.6                  2014-04-02                          14

GCC(1)                         GNU                         GCC(1)

         used ISO trigraph feature.  For the C compiler, it dis-
         ables 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 pro-
         gram, of course, but it is useful to put them in header
         files that might be included in compilations done with
         -ansi.  Alternate predefined macros such as "__unix__"
         and "__vax__" are also available, with or without -ansi.

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

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

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

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

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

         iso9899:199409
             ISO C90 as modified in amendment 1.

         c99
         c9x
         iso9899:1999
         iso9899:199x
             ISO C99.  Note that this standard is not yet fully
             supported; see
             <http://gcc.gnu.org/gcc-3.4/c99status.html> for more
             information.  The names c9x and iso9899:199x are
             deprecated.

         gnu89
             Default, ISO C90 plus GNU extensions (including some

gcc-3.4.6                  2014-04-02                          15

GCC(1)                         GNU                         GCC(1)

             C99 features).

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

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

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

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

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

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

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

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

         In C++, this switch only affects the "typeof" keyword,

gcc-3.4.6                  2014-04-02                          16

GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

     -fhosted
         Assert that compilation takes place in a hosted environ-
         ment.  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".  Exam-
         ples 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

gcc-3.4.6                  2014-04-02                          17

GCC(1)                         GNU                         GCC(1)

         header files.

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

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

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

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

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

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

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

         Ideally, a portable program should always use "signed
         char" or "unsigned char" when it depends on the signed-
         ness 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.

gcc-3.4.6                  2014-04-02                          18

GCC(1)                         GNU                         GCC(1)

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

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

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

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

         This option is deprecated.

     Options Controlling C++ Dialect

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

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

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

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

     -fabi-version=n
         Use version n of the C++ ABI.  Version 2 is the version
         of the C++ ABI that first appeared in G++ 3.4.  Version
         1 is the version of the C++ ABI that first appeared in
         G++ 3.2.  Version 0 will always be the version that con-
         forms most closely to the C++ ABI specification.

gcc-3.4.6                  2014-04-02                          19

GCC(1)                         GNU                         GCC(1)

         Therefore, the ABI obtained using version 0 will change
         as ABI bugs are fixed.

         The default is version 2.

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

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

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

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

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

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

     -fno-elide-constructors
         The C++ standard allows an implementation to omit creat-
         ing a temporary which is only used to initialize another
         object of the same type. Specifying this option disables

gcc-3.4.6                  2014-04-02                          20

GCC(1)                         GNU                         GCC(1)

         that optimization, and forces G++ to call the copy con-
         structor in all cases.

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

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

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

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

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

     -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 diag-
         nostic issued by G++ is the one for a name having multi-
         ple meanings within a class.

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

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

     -fno-rtti
         Disable generation of information about every class with
         virtual functions for use by the C++ runtime type iden-
         tification features (dynamic_cast and typeid).  If you
         don't use those parts of the language, you can save some
         space by using this flag.  Note that exception handling
         uses the same information, but it will generate it as
         needed.

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

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

     -fuse-cxa-atexit
         Register destructors for objects with static storage
         duration with the "__cxa_atexit" function rather than
         the "atexit" function. This option is required for fully
         standards-compliant handling of static destructors, but

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GCC(1)                         GNU                         GCC(1)

         will only work if your C library supports
         "__cxa_atexit".

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

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

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

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

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

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

         The known incompatibilities at this point include:

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

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

             In this case, G++ will place "B::f2" into the same
             byte as"A::f1"; other compilers will not.  You can
             avoid this problem by explicitly padding "A" so that

gcc-3.4.6                  2014-04-02                          23

GCC(1)                         GNU                         GCC(1)

             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 example:

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

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

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

                     union U { int i : 4096; };

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

         *   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) {}

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GCC(1)                         GNU                         GCC(1)

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

             Instantiations of these templates may be mangled
             incorrectly.

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

     -Wnon-virtual-dtor (C++ only)
         Warn when a class appears to be polymorphic, thereby
         requiring a virtual destructor, yet it declares a non-
         virtual one. This warning is 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 exe-
         cuted.  For instance:

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

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

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

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

         *   Item 11:  Define a copy constructor and an assign-
             ment 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

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GCC(1)                         GNU                         GCC(1)

             must return an object.

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

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

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

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

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

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

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

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

                 struct A {
                   virtual void f();
                 };

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GCC(1)                         GNU                         GCC(1)

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

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

                 B* b;
                 b->f();

         will fail to compile.

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

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

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

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

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

     Options Controlling Objective-C Dialect

     (NOTE: This manual does not describe the Objective-C
     language itself.  See <http://gcc.gnu.org/readings.html> for
     references.)

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

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

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

     -fobjc-exceptions
         Enable syntactic support for structured exception han-
         dling in Objective-C, similar to what is offered by C++
         and Java.  Currently, this option is only available in
         conjunction with the NeXT runtime on Mac OS X 10.3 and
         later.

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

         There are several caveats to using the new exception
         mechanism:

         *   Although currently designed to be binary compatible
             with "NS_HANDLER"-style idioms provided by the
             "NSException" class, the new exceptions can only be

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GCC(1)                         GNU                         GCC(1)

             used on Mac OS X 10.3 (Panther) and later systems,
             due to additional functionality needed in the (NeXT)
             Objective-C runtime.

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

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

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

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

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

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

     -fzero-link
         When compiling for the NeXT runtime, the compiler ordi-
         narily replaces calls to "objc_getClass("...")" (when
         the name of the class is known at compile time) with
         static class references that get initialized at load

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GCC(1)                         GNU                         GCC(1)

         time, which improves run-time performance.  Specifying
         the -fzero-link flag suppresses this behavior and causes
         calls to "objc_getClass("...")" to be retained.  This is
         useful in Zero-Link debugging mode, since it allows for
         individual class implementations to be modified during
         program execution.

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

     -Wno-protocol
         If a class is declared to implement a protocol, a warn-
         ing 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 implementa-
         tion is inherited from the superclass.  If you use the
         "-Wno-protocol" option, then methods inherited from the
         superclass are considered to be implemented, and no
         warning is issued for them.

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

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

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

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GCC(1)                         GNU                         GCC(1)

     Options to Control Diagnostic Messages Formatting

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

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

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

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

     Options to Request or Suppress Warnings

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

     -pedantic
         Issue all the warnings demanded by strict ISO C and ISO
         C++; reject all programs that use forbidden extensions,
         and some other programs that do not follow ISO C and ISO
         C++.  For ISO C, follows the version of the ISO C stan-
         dard 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, cer-
         tain GNU extensions and traditional C and C++ features
         are supported as well.  With this option, they are
         rejected.

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

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

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

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

gcc-3.4.6                  2014-04-02                          33

GCC(1)                         GNU                         GCC(1)

         than warnings.

     -w  Inhibit all warning messages.

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

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

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

     -Wformat
         Check calls to "printf" and "scanf", etc., to make sure
         that the arguments supplied have types 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 stan-
         dard) families.

         The formats are checked against the format features sup-
         ported by GNU libc version 2.2.  These include all ISO
         C90 and C99 features, as well as features from the Sin-
         gle 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.  How-
         ever, if -pedantic is used with -Wformat, warnings will
         be given about format features not in the selected stan-
         dard version (but not for "strfmon" formats, since those
         are not in any version of the C standard).

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

         Where the unused arguments lie between used arguments
         that are specified with $ operand number specifications,
         normally warnings are still given, since the implementa-
         tion 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 Sin-
         gle Unix Specification says that such unused arguments
         are allowed.

     -Wno-format-zero-length
         If -Wformat is specified, do not warn about zero-length
         formats. The C standard specifies that zero-length for-
         mats 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 currently a subset of what -Wformat-nonliteral warns
         about, but in future warnings may be added to
         -Wformat-security that are not included in
         -Wformat-nonliteral.)

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

     -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, two, or three arguments of
         appropriate types.

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

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

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

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

gcc-3.4.6                  2014-04-02                          36

GCC(1)                         GNU                         GCC(1)

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

         In C, every "else" branch belongs to the innermost pos-
         sible "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 pro-
         grammer chose.  When there is the potential for this
         confusion, GCC will issue a warning when this flag is
         specified. To eliminate the warning, add explicit braces
         around the innermost "if" statement so there is no way
         the "else" could belong to the enclosing "if".  The
         resulting code would look like this:

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

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

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

gcc-3.4.6                  2014-04-02                          37

GCC(1)                         GNU                         GCC(1)

         specified.  However, the standards committee have ruled
         that function calls do not overlap.

         It is not specified when between sequence points modifi-
         cations to the values of objects take effect.  Programs
         whose behavior depends on this have undefined behavior;
         the C standard specifies that ``Between the previous and
         next sequence point an object shall have its stored
         value modified at most once by the evaluation of an
         expression.  Furthermore, the prior value shall be read
         only to determine the value to be stored.''.  If a pro-
         gram 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 compli-
         cated cases are not diagnosed by this option, and it may
         give an occasional false positive result, but in general
         it has been found fairly effective at detecting this
         sort of problem in programs.

         The present implementation of this option only works for
         C programs.  A future implementation may also work for
         C++ programs.

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

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

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

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

     -Wswitch-default

gcc-3.4.6                  2014-04-02                          38

GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

         To suppress this warning use the unused attribute.

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

         To suppress this warning use the unused attribute.

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

         To suppress this warning use the unused attribute.

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

         To suppress this warning cast the expression to void.

     -Wunused
         All the above -Wunused options combined.

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

     -Wuninitialized
         Warn if an automatic variable is used without first

gcc-3.4.6                  2014-04-02                          39

GCC(1)                         GNU                         GCC(1)

         being initialized or if a variable may be clobbered by a
         "setjmp" call.

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

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

         These warnings occur only for variables that are candi-
         dates 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 struc-
         tures, unions or arrays, even when they are in regis-
         ters.

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

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

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

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

gcc-3.4.6                  2014-04-02                          40

GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

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

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

     The following -W... options are not implied by -Wall. Some
     of them warn about constructions that users generally do not

gcc-3.4.6                  2014-04-02                          41

GCC(1)                         GNU                         GCC(1)

     consider questionable, but which occasionally you might wish
     to check for; others warn about constructions that are
     necessary or hard to avoid in some cases, and there is no
     simple way to modify the code to suppress the warning.

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

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

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

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

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

         *   A comparison like x<=y<=z appears; this is
             equivalent to (x<=y ? 1 : 0) <= z, which is a dif-
             ferent interpretation from that of ordinary
             mathematical notation.

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

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

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

         *   A comparison between signed and unsigned values
             could produce an incorrect result when the signed

gcc-3.4.6                  2014-04-02                          42

GCC(1)                         GNU                         GCC(1)

             value is converted to unsigned. (But don't warn if
             -Wno-sign-compare is also specified.)

         *   An aggregate has an initializer which does not ini-
             tialize all members. This warning can be indepen-
             dently controlled by -Wmissing-field-initializers.

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

                     void foo(bar) { }

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

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

         *   A variable might be changed by longjmp or vfork.

         *   Any of several floating-point events that often
             indicate errors, such as overflow, underflow, loss
             of precision, etc.

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

         *   (C++ only) A non-static reference or non-static
             const member appears in a class without construc-
             tors.

         *   (C++ only) Ambiguous virtual bases.

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

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

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

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

     -Wsystem-headers
         Print warning messages for constructs found in system
         header files. Warnings from system headers are normally
         suppressed, on the assumption that they usually do not
         indicate real problems and would only make the compiler

gcc-3.4.6                  2014-04-02                          43

GCC(1)                         GNU                         GCC(1)

         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 com-
         parisons.

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

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

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

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

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

         *   The unary plus operator.

gcc-3.4.6                  2014-04-02                          44

GCC(1)                         GNU                         GCC(1)

         *   The U integer constant suffix, or the F or L float-
             ing point constant suffixes.  (Traditional C does
             support the L suffix on integer constants.)  Note,
             these suffixes appear in macros defined in the sys-
             tem headers of most modern systems, e.g. the
             _MIN/_MAX macros in "<limits.h>". Use of these mac-
             ros 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 separate namespace for labels.

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

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

         *   Use of ISO C style function definitions.  This warn-
             ing intentionally is not issued for prototype
             declarations or variadic functions because these ISO
             C features will appear in your code when using
             libiberty's traditional C compatibility macros,

gcc-3.4.6                  2014-04-02                          45

GCC(1)                         GNU                         GCC(1)

             "PARAMS" and "VPARAMS".  This warning is also
             bypassed for nested functions because that feature
             is already a GCC extension and thus not relevant to
             traditional C compatibility.

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

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

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

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

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

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

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

     -Wbounded
         Activate Anil Madhavapeddys bounds checker. This per-
         forms basic checks on functions which accept buffers and
         sizes.  An extra attribute, __bounded__, has been added
         to mark functions that can be checked.

         It only works with statically allocated fixed-size
         buffers. Since it is applied at compile-time, dynami-
         cally allocated memory buffers and non-constant argu-
         ments are ignored.

         If -Wbounded is specified together with -Wformat,

gcc-3.4.6                  2014-04-02                          46

GCC(1)                         GNU                         GCC(1)

         additional checks are performed on sscanf(3) format
         strings. The %s fields are checked for incorrect bound
         lengths by checking the size of the buffer associated
         with the format argument.

     -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 boun-
         daries.

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

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

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

     -Waggregate-return
         Warn if any functions that return structures or unions

gcc-3.4.6                  2014-04-02                          47

GCC(1)                         GNU                         GCC(1)

         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 speci-
         fying the argument types.  (An old-style function defin-
         ition is permitted without a warning if preceded by a
         declaration which specifies the argument types.)

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

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

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

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

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

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

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

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

gcc-3.4.6                  2014-04-02                          48

GCC(1)                         GNU                         GCC(1)

         get a warning for "main" in hosted C environments.

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

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

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

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

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

     -Wredundant-decls
         Warn if anything is declared more than once in the same

gcc-3.4.6                  2014-04-02                          49

GCC(1)                         GNU                         GCC(1)

         scope, even in cases where multiple declaration is valid
         and changes nothing.

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

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

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

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

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

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

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

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

     -Wno-invalid-offsetof (C++ only)
         Suppress warnings from applying the offsetof macro to a
         non-POD type.  According to the 1998 ISO C++ standard,
         applying offsetof to a non-POD type is undefined.  In

gcc-3.4.6                  2014-04-02                          50

GCC(1)                         GNU                         GCC(1)

         existing C++ implementations, however, offsetof typi-
         cally gives meaningful results even when applied to cer-
         tain kinds of non-POD types. (Such as a simple struct
         that fails to be a POD type only by virtue of having a
         constructor.)  This flag is for users who are aware that
         they are writing nonportable code and who have deli-
         berately chosen to ignore the warning about it.

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

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

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

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

     -Wstack-larger-than-len
         Warn whenever a function uses more than len bytes of
         stack or local storage size.  Set len to 0 to disable.

     -Wstack-protector
         Warn when not issuing stack smashing protection for some
         reason.

     -Wtrampolines
         Warn when emitting trampolines.

     -Werror
         Make all warnings into errors.

     -Werror-maybe-reset
         Act like -Wno-error if the GCC_NO_WERROR environment
         variable is set to anything other than 0 or empty.

     -fhonour-copts
         If GCC_HONOUR_COPTS is set to 1, abort if this option is
         not given at least once, and warn if it is given more

gcc-3.4.6                  2014-04-02                          51

GCC(1)                         GNU                         GCC(1)

         than once. If GCC_HONOUR_COPTS is set to 2, abort if
         this option is not given exactly once. If
         GCC_HONOUR_COPTS is set to 0 or unset, warn if this
         option is not given exactly once. The warning is quelled
         if GCC_HONOUR_COPTS is set to s. This flag and environ-
         ment variable only affect the C language.

     Options for Debugging Your Program or GCC

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

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

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

         Unlike most other C compilers, GCC allows you to use -g
         with -O.  The shortcuts taken by optimized code may
         occasionally produce surprising results: some variables
         you declared may not exist at all; flow of control may
         briefly move where you did not expect it; some state-
         ments 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 out-
         put.  This makes it reasonable to use the optimizer for
         programs that might have bugs.

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

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

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

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GCC(1)                         GNU                         GCC(1)

         debugging output which is not understood by DBX or SDB.
         On System V Release 4 systems this option requires the
         GNU assembler.

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

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

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

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

     -gxcoff+
         Produce debugging information in XCOFF format (if that
         is supported), using GNU extensions understood only by
         the GNU debugger (GDB).  The use of these extensions is
         likely to make other debuggers crash or refuse to read
         the program, and may cause assemblers other than the GNU
         assembler (GAS) to fail with an error.

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

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

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

gcc-3.4.6                  2014-04-02                          53

GCC(1)                         GNU                         GCC(1)

         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 vari-
         ables and no line numbers.

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

         Note that in order to avoid confusion between DWARF1
         debug level 2, and DWARF2 -gdwarf-2 does not accept a
         concatenated debug level.  Instead use an additional
         -glevel option to change the debug level for DWARF2.

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

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

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

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

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

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

     -fprofile-arcs
         Add code so that program flow arcs are instrumented.
         During execution the program records how many times each
         branch and call is executed and how many times it is
         taken or returns.  When the compiled program exits it
         saves this data to a file called auxname.gcda for each
         source file. The data may be used for profile-directed
         optimizations (-fbranch-probabilities), or for test cov-
         erage analysis (-ftest-coverage). Each object file's

gcc-3.4.6                  2014-04-02                          54

GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

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

     -ftest-coverage
         Produce a notes file that the gcov code-coverage utility
         can use to show program coverage. Each source file's

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GCC(1)                         GNU                         GCC(1)

         note file is called auxname.gcno. Refer to the
         -fprofile-arcs option above for a description of auxname
         and instructions on how to generate test coverage data.
         Coverage data will match the source files more closely,
         if you do not optimize.

     -dletters
         Says to make debugging dumps during compilation at times
         specified by letters.  This is used for debugging the
         compiler.  The file names for most of the dumps are made
         by appending a pass number and a word to the 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.01.rtl or
         foo.02.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.12.bp.

         B   Dump after block reordering, to file.31.bbro.

         c   Dump after instruction combination, to the file
             file.20.combine.

         C   Dump after the first if conversion, to the file
             file.14.ce1. Also dump after the second if conver-
             sion, to the file file.21.ce2.

         d   Dump after branch target load optimization, to to
             file.32.btl. Also dump after delayed branch schedul-
             ing, to file.36.dbr.

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

         E   Dump after the third if conversion, to file.30.ce3.

         f   Dump after control and data flow analysis, to
             file.11.cfg. Also dump after life analysis, to
             file.19.life.

         F   Dump after purging "ADDRESSOF" codes, to
             file.07.addressof.

         g   Dump after global register allocation, to
             file.25.greg.

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GCC(1)                         GNU                         GCC(1)

         G   Dump after GCSE, to file.08.gcse. Also dump after
             jump bypassing and control flow optimizations, to
             file.10.bypass.

         h   Dump after finalization of EH handling code, to
             file.03.eh.

         i   Dump after sibling call optimizations, to
             file.02.sibling.

         j   Dump after the first jump optimization, to
             file.04.jump.

         k   Dump after conversion from registers to stack, to
             file.34.stack.

         l   Dump after local register allocation, to
             file.24.lreg.

         L   Dump after loop optimization passes, to file.09.loop
             and file.16.loop2.

         M   Dump after performing the machine dependent reorgan-
             ization pass, to file.35.mach.

         n   Dump after register renumbering, to file.29.rnreg.

         N   Dump after the register move pass, to
             file.22.regmove.

         o   Dump after post-reload optimizations, to
             file.26.postreload.

         r   Dump after RTL generation, to file.01.rtl.

         R   Dump after the second scheduling pass, to
             file.33.sched2.

         s   Dump after CSE (including the jump optimization that
             sometimes follows CSE), to file.06.cse.

         S   Dump after the first scheduling pass, to
             file.23.sched.

         t   Dump after the second CSE pass (including the jump
             optimization that sometimes follows CSE), to
             file.18.cse2.

         T   Dump after running tracer, to file.15.tracer.

         u   Dump after null pointer elimination pass to
             file.05.null.

gcc-3.4.6                  2014-04-02                          57

GCC(1)                         GNU                         GCC(1)

         U   Dump callgraph and unit-at-a-time optimization
             file.00.unit.

         V   Dump after the value profile transformations, to
             file.13.vpt.

         w   Dump after the second flow pass, to file.27.flow2.

         z   Dump after the peephole pass, to file.28.peephole2.

         Z   Dump after constructing the web, to file.17.web.

         a   Produce all the dumps listed above.

         H   Produce a core dump whenever an error occurs.

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

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

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

         v   For each of the other indicated dump files (except
             for file.01.rtl), dump a representation of the con-
             trol flow graph suitable for viewing with VCG to
             file.pass.vcg.

         x   Just generate RTL for a function instead of compil-
             ing it.  Usually used with r.

         y   Dump debugging information during parsing, to stan-
             dard error.

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

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

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

         all Turn on all options.

         The following tree dumps are possible:

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

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

         inlined
             Dump after function inlining, to file.inlined.

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

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GCC(1)                         GNU                         GCC(1)

         them. You can use the -frandom-seed option to produce
         reproducibly identical object files.

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

     -fsched-verbose=n
         On targets that use instruction scheduling, this option
         controls the amount of debugging output the scheduler
         prints.  This information is written to standard error,
         unless -dS or -dR is specified, in which case it is out-
         put 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 information as -dRS.  For n greater than one, it
         also output basic block probabilities, detailed ready
         list information and unit/insn info.  For n greater than
         two, it includes RTL at abort point, control-flow and
         regions info.  And for n over four, -fsched-verbose also
         includes dependence info.

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

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

                 # cc1 0.12 0.01
                 # as 0.00 0.01

         The first number on each line is the ``user time,'' that
         is time spent executing the program itself.  The second
         number is ``system time,'' time spent executing operat-
         ing system routines on behalf of the program. Both
         numbers are in seconds.

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

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GCC(1)                         GNU                         GCC(1)

     -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 com-
         piler switches that enable them.  The directory name is
         separated from the switches by ;, and each switch starts
         with an @} instead of the @samp{-, without spaces
         between multiple switches.  This is supposed to ease
         shell-processing.

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

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

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

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

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

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

     Options That Control Optimization

     These options control various sorts of optimizations.

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

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

     The compiler performs optimization based on the knowledge it
     has of the program.  Using the -funit-at-a-time flag will
     allow the compiler to consider information gained from later
     functions in the file when compiling a function.  Compiling
     multiple files at once to a single output file (and using
     -funit-at-a-time) will allow the compiler to use information
     gained from all of the files when compiling each of them.

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

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

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

         -O turns on the following optimization flags:
         -fdefer-pop -fmerge-constants -fthread-jumps

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GCC(1)                         GNU                         GCC(1)

         -floop-optimize -fif-conversion -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
         optimizations that do not involve a space-speed trade-
         off.  The compiler does not perform loop unrolling or
         function inlining when you specify -O2. As compared to
         -O, this option increases both compilation time and the
         performance of the generated code.

         In MirOS, some security-tradeoff optimisations are not
         enabled at this level.

         -O2 turns on all optimization flags specified by -O.  It
         also turns on the following optimization flags:
         -fforce-mem -foptimize-sibling-calls -fstrength-reduce
         -fcse-follow-jumps  -fcse-skip-blocks
         -frerun-cse-after-loop  -frerun-loop-opt -fgcse
         -fgcse-lm  -fgcse-sm  -fgcse-las
         -fexpensive-optimizations -fregmove -fschedule-insns
         -fschedule-insns2 -fsched-interblock  -fsched-spec
         -fcaller-saves -fpeephole2 -freorder-blocks
         -freorder-functions -funit-at-a-time -falign-functions
         -falign-jumps -falign-loops  -falign-labels -fcrossjump-
         ing

         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, -fdelete-null-pointer-checks,
         -fstrict-aliasing, -fweb, -frename-registers and
         -funswitch-loops 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 per-
         forms further optimizations designed to reduce code
         size.

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

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

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GCC(1)                         GNU                         GCC(1)

         effective.

     FSF releases default to -fident instead of -fno-ident like
     MirOS releases; furthermore, they enable trampolines by
     default instead of requiring -ftrampolines, do not have
     stack protection, bounds checking, stack frame size limit
     warnings; the optimisation options
     -fdelete-null-pointer-checks and -fstrict-aliasing are
     enabled at -O2 and -Os already in FSF versions instead of at
     -O3 only like in MirOS versions.

     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 typi-
     cally will use.  You can figure out the other form by either
     removing no- or adding it.

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

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

     -fno-defer-pop
         Always pop the arguments to each function call as soon
         as that function returns.  For machines which must pop
         arguments after a function call, the compiler normally
         lets arguments accumulate on the stack for several func-
         tion 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 subexpres-
         sions.  When they are not common subexpressions,
         instruction combination should eliminate the separate
         register-load.

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

     -fforce-addr

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         Force memory address constants to be copied into regis-
         ters 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 automati-
         cally 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 optimiz-
         ing, no functions can be expanded inline.

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

         If all calls to a given function are integrated, and the
         function is declared "static", then the function is nor-
         mally not output as assembler code in its own right.

         Enabled at level -O3.

     -finline-limit=n
         By default, GCC limits the size of functions that can be
         inlined.  This flag allows the control of this limit for
         functions that are explicitly marked as inline (i.e.,
         marked with the inline keyword or defined within the
         class definition in c++).  n is the size of functions
         that can be inlined in number of pseudo instructions
         (not counting parameter handling).  The default value of
         n is 600. Increasing this value can result in more
         inlined code at the cost of compilation time and memory

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

          @item max-inline-insns-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>.

         See below for a documentation of the individual parame-
         ters 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 function is declared "static", nevertheless out-
         put a separate run-time callable version of the func-
         tion.  This switch does not affect "extern inline" func-
         tions.

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

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

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

         This option is the default for optimized compilation if
         the assembler and linker support it.  Use

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GCC(1)                         GNU                         GCC(1)

         -fno-merge-constants to inhibit this behavior.

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

     -fmerge-all-constants
         Attempt to merge identical constants and identical vari-
         ables.

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

     -fnew-ra
         Use a graph coloring register allocator.  Currently this
         option is meant only for testing.  Users should not
         specify this option, since it is not yet ready for pro-
         duction use.

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

         The default is -fbranch-count-reg, 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

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         programs explicitly rely on variables going to the data
         section.  E.g., so that the resulting executable can
         find the beginning of that section and/or make assump-
         tions based on that.

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

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

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

     -fthread-jumps
         Perform optimizations where we check to see if a jump
         branches to a location where another comparison 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 when the target of the jump is not reached
         by any other path.  For example, when CSE encounters an
         "if" statement with an "else" clause, CSE will follow
         the jump when the condition tested is false.

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

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

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

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

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

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

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

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

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

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

     -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.

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

         Enabled by default when gcse is enabled.

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

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

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

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

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

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

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

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

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

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

         Enabled at level -O3.

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

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

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

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

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

     -fdelayed-branch

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

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

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

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

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

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

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

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

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

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

     -fsched-stalled-insns=n
         Define how many insns (if any) can be moved prematurely

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         from the queue of stalled insns into the ready list,
         during the second scheduling pass.

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

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

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

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

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

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

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

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

     -fmove-all-movables

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

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

         Note: When compiling programs written in Fortran,
         -fmove-all-movables and -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 improving loop optimizations.

         Please contact <gcc@gcc.gnu.org>, and describe how use
         of these options affects the performance of your produc-
         tion code. Examples of code that runs slower when these
         options are enabled are very valuable.

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

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

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

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

         In a hard real-time system, people don't want different
         runs of the compiler to 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.

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         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.

     -freorder-functions
         Reorder basic blocks in the compiled function in order
         to reduce number of taken branches and improve code
         locality. This is implemented by using special subsec-
         tions ".text.hot" for most frequently executed functions
         and ".text.unlikely" for unlikely executed functions.
         Reordering is done by the linker so object file format
         must support named sections and linker must place them
         in a reasonable way.

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

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

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

         Pay special attention to code like this:

                 union a_union {
                   int i;
                   double d;
                 };

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

         The practice of reading from a different union member
         than the one most recently written to (called
         ``type-punning'') is common.  Even with

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GCC(1)                         GNU                         GCC(1)

         -fstrict-aliasing, type-punning is allowed, provided the
         memory is accessed through the union type.  So, the code
         above will work as expected.  However, this code might
         not:

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

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

         Enabled at level -O3.

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

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

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

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

         Enabled at levels -O2, -O3.

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

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

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

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

         Enabled at levels -O2, -O3.

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

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

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

         Enabled at levels -O2, -O3.

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

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

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

         Enabled at levels -O2, -O3.

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

     -fweb
         Constructs webs as commonly used for register allocation
         purposes and assign each web individual pseudo register.
         This allows the register allocation pass to operate on

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GCC(1)                         GNU                         GCC(1)

         pseudos directly, but also strengthens several other
         optimization passes, such as CSE, loop optimizer and
         trivial dead code remover.  It can, however, make debug-
         ging impossible, since variables will no longer stay in
         a ``home register''.

         Enabled at level -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 occa-
         sionally eliminate the copy.

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

     -fprofile-generate
         Enable options usually used for instrumenting applica-
         tion to produce profile useful for later recompilation
         with profile feedback based optimization.  You must use
         "-fprofile-generate" both when compiling and when link-
         ing your program.

         The following options are enabled: "-fprofile-arcs",
         "-fprofile-values", "-fvpt".

     -fprofile-use
         Enable profile feedback directed optimizations, and
         optimizations generally profitable only with profile
         feedback available.

         The following options are enabled:
         "-fbranch-probabilities", "-fvpt", "-funroll-loops",
         "-fpeel-loops", "-ftracer".

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

     -ffloat-store
         Do not store floating point variables in registers, and
         inhibit other options that might change whether a float-
         ing 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 pro-
         grams, after modifying them to store all pertinent

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GCC(1)                         GNU                         GCC(1)

         intermediate computations into variables.

     -ffast-math
         Sets -fno-math-errno, -funsafe-math-optimizations,
         -fno-trapping-math, -ffinite-math-only,
         -fno-rounding-math 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 functions.

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

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

         The default is -fmath-errno.

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

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

         rules/specifications.

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

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

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

         The default is -ftrapping-math.

     -frounding-math
         Disable transformations and optimizations that assume
         default floating point rounding behavior.  This is
         round-to-zero for all floating point to integer conver-
         sions, and round-to-nearest for all other arithmetic
         truncations.  This option should be specified for pro-
         grams that change the FP rounding mode dynamically, or
         that may be executed with a non-default rounding mode.
         This option disables constant folding of floating point
         expressions at compile-time (which may be affected by
         rounding mode) and arithmetic transformations that are
         unsafe in the presence of sign-dependent rounding modes.

         The default is -fno-rounding-math.

         This option is experimental and does not currently
         guarantee to disable all GCC optimizations that are
         affected by rounding mode. Future versions of GCC may
         provide finer control of this setting using C99's
         "FENV_ACCESS" pragma.  This command line option will be
         used to specify the default state for "FENV_ACCESS".

     -fsignaling-nans
         Compile code assuming that IEEE signaling NaNs may gen-
         erate user-visible traps during floating-point opera-
         tions.  Setting this option disables optimizations that
         may change the number of exceptions visible with signal-
         ing NaNs.  This option implies -ftrapping-math.

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

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GCC(1)                         GNU                         GCC(1)

         The default is -fno-signaling-nans.

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

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

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

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

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

     -fprofile-values
         If combined with -fprofile-arcs, it adds code so that
         some data about values of expressions in the program is
         gathered.

         With -fbranch-probabilities, it reads back the data
         gathered from profiling values of expressions and adds
         REG_VALUE_PROFILE notes to instructions for their later
         usage in optimizations.

     -fvpt
         If combined with -fprofile-arcs, it instructs the com-
         piler to add a code to gather information about values
         of expressions.

         With -fbranch-probabilities, it reads back the data

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GCC(1)                         GNU                         GCC(1)

         gathered and actually performs the optimizations based
         on them. Currently the optimizations include specializa-
         tion of division operation using the knowledge about the
         value of the denominator.

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

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

     -funit-at-a-time
         Parse the whole compilation unit before starting to pro-
         duce code. This allows some extra optimizations to take
         place but consumes more memory.

     -funroll-loops
         Unroll loops whose number of iterations can be deter-
         mined at compile time or upon entry to the loop.
         -funroll-loops implies -frerun-cse-after-loop.  It also
         turns on complete loop peeling (i.e. complete removal of
         loops with small constant number of iterations). This
         option makes code larger, and may or may not make it run
         faster.

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

     -fpeel-loops
         Peels the loops for that there is enough information
         that they do not roll much (from profile feedback).  It
         also turns on complete loop peeling (i.e. complete remo-
         val of loops with small constant number of iterations).

     -funswitch-loops
         Move branches with loop invariant conditions out of the
         loop, with duplicates of the loop on both branches
         (modified according to result of the condition).

     -fold-unroll-loops
         Unroll loops whose number of iterations can be deter-
         mined at compile time or upon entry to the loop, using
         the old loop unroller whose loop recognition is based on
         notes from frontend.  -fold-unroll-loops implies both
         -fstrength-reduce and -frerun-cse-after-loop.  This

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GCC(1)                         GNU                         GCC(1)

         option makes code larger, and may or may not make it run
         faster.

     -fold-unroll-all-loops
         Unroll all loops, even if their number of iterations is
         uncertain when the loop is entered. This is done using
         the old loop unroller whose loop recognition is based on
         notes from frontend.  This usually makes programs run
         more slowly. -fold-unroll-all-loops implies the same
         options as -fold-unroll-loops.

     -funswitch-loops
         Move branches with loop invariant conditions out of the
         loop, with duplicates of the loop on both branches
         (modified according to result of the condition).

     -funswitch-loops
         Move branches with loop invariant conditions out of the
         loop, with duplicates of the loop on both branches
         (modified according to result of the condition).

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

         Disabled at level -Os.

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

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

         Only use these options when there are significant bene-
         fits from doing so.  When you specify these options, the
         assembler and linker will create larger object and exe-
         cutable files and will also be slower. You will not be
         able to use "gprof" on all systems if you specify this
         option and you may have problems with debugging if you
         specify both this option and -g.

     -fbranch-target-load-optimize
         Perform branch target register load optimization before

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GCC(1)                         GNU                         GCC(1)

         prologue / epilogue threading. The use of target regis-
         ters can typically be exposed only during reload, thus
         hoisting loads out of loops and doing inter-block
         scheduling needs a separate optimization pass.

     -fbranch-target-load-optimize2
         Perform branch target register load optimization after
         prologue / epilogue threading.

     --param name=value
         In some places, GCC uses various constants to control
         the amount of optimization that is done.  For example,
         GCC will not inline functions that contain more that a
         certain number of instructions.  You can control some of
         these constants on the command-line using the --param
         option.

         The names of specific parameters, and the meaning of the
         values, are tied to the internals of the compiler, and
         are subject to change without notice in future releases.

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

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

         max-delay-slot-insn-search
             The maximum number of instructions to consider when
             looking for an instruction to fill a delay slot.  If
             more than this arbitrary number of instructions is
             searched, the time savings from filling the delay
             slot will be minimal so stop searching.  Increasing
             values mean more aggressive optimization, making the
             compile time increase with probably small improve-
             ment in executable run time.

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

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         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 schedul-
             ing will allow before flushing the current state and
             starting over.  Large functions with few branches or
             calls can create excessively large lists which need-
             lessly consume memory and resources.

         max-inline-insns-single
             Several parameters control the tree inliner used in
             gcc. This number sets the maximum number of instruc-
             tions (counted in GCC's internal representation) in
             a single function that the tree inliner will con-
             sider for inlining.  This only affects functions
             declared inline and methods implemented in a class
             declaration (C++). The default value is 500.

         max-inline-insns-auto
             When you use -finline-functions (included in -O3), a
             lot of functions that would otherwise not be con-
             sidered for inlining by the compiler will be inves-
             tigated.  To those functions, a different (more res-
             trictive) limit compared to functions declared
             inline can be applied. The default value is 100.

         large-function-insns
             The limit specifying really large functions.  For
             functions greater than this limit inlining is con-
             strained by --param large-function-growth. This
             parameter is useful primarily to avoid extreme com-
             pilation time caused by non-linear algorithms used
             by the backend. This parameter is ignored when
             -funit-at-a-time is not used. The default value is
             3000.

         large-function-growth
             Specifies maximal growth of large function caused by
             inlining in percents. This parameter is ignored when
             -funit-at-a-time is not used. The default value is
             200.

         inline-unit-growth
             Specifies maximal overall growth of the compilation

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GCC(1)                         GNU                         GCC(1)

             unit caused by inlining. This parameter is ignored
             when -funit-at-a-time is not used. The default value
             is 150.

         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 instruc-
             tions) 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 determines how many times the
             loop code is unrolled.

         max-average-unrolled-insns
             The maximum number of instructions biased by proba-
             bilities of their execution that a loop should have
             if that loop is unrolled, and if the loop is
             unrolled, it determines how many times the loop code
             is unrolled.

         max-unroll-times
             The maximum number of unrollings of a single loop.

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

         max-peel-times
             The maximum number of peelings of a single loop.

         max-completely-peeled-insns
             The maximum number of insns of a completely peeled
             loop.

         max-completely-peel-times
             The maximum number of iterations of a loop to be
             suitable for complete peeling.

         max-unswitch-insns
             The maximum number of insns of an unswitched loop.

         max-unswitch-level
             The maximum number of branches unswitched in a sin-
             gle loop.

         hot-bb-count-fraction

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GCC(1)                         GNU                         GCC(1)

             Select fraction of the maximal count of repetitions
             of basic block in program given basic block needs to
             have to be considered hot.

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

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

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

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

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

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

             Similarly to tracer-dynamic-coverage two values are
             present, one for compilation for profile feedback
             and one for compilation without.  The value for com-
             pilation with profile feedback needs to be more con-
             servative (higher) in order to make tracer effec-
             tive.

         max-cse-path-length
             Maximum number of basic blocks on path that cse con-
             siders.

         max-last-value-rtl
             The maximum size measured as number of RTLs that can
             be recorded in an expression in combiner for a

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GCC(1)                         GNU                         GCC(1)

             pseudo register as last known value of that regis-
             ter.  The default is 10000.

         ggc-min-expand
             GCC uses a garbage collector to manage its own
             memory allocation.  This parameter specifies the
             minimum percentage by which the garbage collector's
             heap should be allowed to expand between collec-
             tions. 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 particular
             platform, the lower bound of 30% is used.  Setting
             this parameter and ggc-min-heapsize to zero causes a
             full collection to occur at every opportunity.  This
             is extremely slow, but can be useful for debugging.

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

             The default is 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
             effectively disables garbage collection.  Setting
             this parameter and ggc-min-expand to zero causes a
             full collection to occur at every opportunity.

         max-reload-search-insns
             The maximum number of instruction reload should look
             backward for equivalent register.  Increasing values
             mean more aggressive optimization, making the com-
             pile time increase with probably slightly better
             performance.  The default value is 100.

         max-cselib-memory-location
             The maximum number of memory locations cselib should
             take into acount. Increasing values mean more
             aggressive optimization, making the compile time
             increase with probably slightly better performance.

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GCC(1)                         GNU                         GCC(1)

             The default value is 500.

         reorder-blocks-duplicate
         reorder-blocks-duplicate-feedback
             Used by basic block reordering pass to decide
             whether to use unconditional branch or duplicate the
             code on its destination.  Code is duplicated when
             its estimated size is smaller than this value multi-
             plied by the estimated size of unconditional jump in
             the hot spots of the program.

             The reorder-block-duplicate-feedback is used only
             when profile feedback is available and may be set to
             higher values than reorder-block-duplicate since
             information about the hot spots is more accurate.

     Options Controlling the Preprocessor

     These options control the C preprocessor, which is run on
     each C source file before actual compilation.

     If you use the -E option, nothing is done except preprocess-
     ing. Some of these options make sense only together with -E
     because they cause the preprocessor output to be unsuitable
     for actual compilation.

     -Wp,option
         You can use -Wp,option to bypass the compiler driver and
         pass option directly through to the preprocessor.  If
         option contains commas, it is split into multiple
         options at the commas.  However, many options are modi-
         fied, translated or interpreted by the compiler driver
         before being passed to the preprocessor, and -Wp forci-
         bly bypasses this phase.  The preprocessor's direct
         interface is undocumented and subject to change, so
         whenever possible you should avoid using -Wp and let the
         driver handle the options instead.

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

         If you want to pass an option that takes an argument,
         you must use -Xpreprocessor twice, once for the option
         and once for the argument.

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

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

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GCC(1)                         GNU                         GCC(1)

         The contents of definition are tokenized and processed
         as if they appeared during translation phase three in a
         #define directive.  In particular, the definition will
         be truncated by embedded newline characters.

         If you are invoking the preprocessor from a shell or
         shell-like program you may need to use the shell's quot-
         ing 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 com-
         mand line, write its argument list with surrounding
         parentheses before the equals sign (if any).
         Parentheses are meaningful to most shells, so you will
         need to quote the option.  With sh and csh,
         -D'name(args...)=definition' works.

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

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

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

     -I dir
         Add the directory dir to the list of directories to be
         searched for header files. Directories named by -I are
         searched before the standard system include directories.
         If the directory dir is a standard system include direc-
         tory, the option is ignored to ensure that the default
         search order for system directories and the special
         treatment of system headers are not defeated .

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

     -Wall
         Turns on all optional warnings which are desirable for
         normal code. At present this is -Wcomment, -Wtrigraphs,
         -Wmultichar and a warning about integer promotion caus-
         ing a change of sign in "#if" expressions.  Note that
         many of the preprocessor's warnings are on by default
         and have no options to control them.

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

     -Wtrigraphs
         @anchor{Wtrigraphs} Most trigraphs in comments cannot
         affect the meaning of the program. However, a trigraph
         that would form an escaped newline (??/ at the end of a
         line) can, by changing where the comment begins or ends.
         Therefore, only trigraphs that would form escaped new-
         lines produce warnings inside a comment.

         This option is implied by -Wall.  If -Wall is not given,
         this option is still enabled unless trigraphs are
         enabled.  To get trigraph conversion without warnings,
         but get the other -Wall warnings, use -trigraphs -Wall
         -Wno-trigraphs.

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

     -Wimport
         Warn the first time #import is used.

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

                 #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.

     -Werror-maybe-reset
         Act like -Wno-error if the GCC_NO_WERROR environment
         variable is set to anything other than 0 or empty.

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

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

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

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

     -M  Instead of outputting the result of preprocessing, out-
         put 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.

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GCC(1)                         GNU                         GCC(1)

         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 com-
         mands.

         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 environ-
         ment variable like DEPENDENCIES_OUTPUT.  Debug output
         will still be sent to the regular output stream as nor-
         mal.

         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 depen-
         dency output.  This is a slight change in semantics from
         GCC versions 3.0 and earlier.

         @anchor{dashMF}

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

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

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

         This feature is used in automatic updating of makefiles.

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

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         make gives if you remove header files without updating
         the Makefile to match.

         This is typical output:

                 test.o: test.c test.h

                 test.h:

     -MT target
         Change the target of the rule emitted by dependency gen-
         eration.  By default CPP takes the name of the main
         input file, including any path, deletes any file suffix
         such as .c, and appends the platform's usual object suf-
         fix.  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 spe-
         cial 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 argu-
         ment 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{dashMF,,-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 compila-
         tion process.

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

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     -fpch-deps
         When using precompiled headers, this flag will cause the
         dependency-output flags to also list the files from the
         precompiled header's dependencies.  If not specified
         only the precompiled header would be listed and not the
         files that were used to create it because those files
         are not consulted when a precompiled header is used.

     -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 confor-
         mance or extensions; it merely selects which base syntax
         to expect.  If you give none of these options, cpp will
         deduce the language from the extension of the source
         file: .c, .cc, .m, or .S.  Some other common extensions
         for C++ and assembly are also recognized.  If cpp does
         not recognize the extension, it will treat the file as
         C; this is the most generic mode.

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

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

         standard may be one of:

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

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

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

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

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

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

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

     -imacros file
         Exactly like -include, except that any output produced

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GCC(1)                         GNU                         GCC(1)

         by scanning file is thrown away.  Macros it defines
         remain defined. This allows you to acquire all the mac-
         ros from a header without also processing its declara-
         tions.

         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 direc-
         tories specified with -I and the standard system direc-
         tories have been exhausted.  dir is treated as a system
         include directory.

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

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

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

     -fdollars-in-identifiers
         @anchor{fdollars-in-identifiers} Accept $ in identif-
         iers.

     -fpreprocessed
         Indicate to the preprocessor that the input file has
         already been preprocessed.  This suppresses things like
         macro expansion, trigraph conversion, escaped newline
         splicing, and processing of most directives. The prepro-
         cessor still recognizes and removes comments, so that
         you can pass a file preprocessed with -C to the compiler
         without problems.  In this mode the integrated prepro-
         cessor is little more than a tokenizer for the front
         ends.

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

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GCC(1)                         GNU                         GCC(1)

         -save-temps.

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

     -fexec-charset=charset
         Set the execution character set, used for string and
         character constants.  The default is UTF-8.  charset can
         be any encoding supported by the system's "iconv"
         library routine.

     -fwide-exec-charset=charset
         Set the wide execution character set, used for wide
         string and character constants.  The default is UTF-32
         or UTF-16, whichever corresponds to the width of
         "wchar_t".  As with -ftarget-charset, charset can be any
         encoding supported by the system's "iconv" library rou-
         tine; however, you will have problems with encodings
         that do not fit exactly in "wchar_t".

     -finput-charset=charset
         Set the input character set, used for translation from
         the character set of the input file to the source char-
         acter set used by GCC. If the locale does not specify,
         or GCC cannot get this information from the locale, the
         default is UTF-8. This can be overridden by either the
         locale or this command line option. Currently the com-
         mand line option takes precedence if there's a conflict.
         charset can be any encoding supported by the system's
         "iconv" library routine.

     -fworking-directory
         Enable generation of linemarkers in the preprocessor
         output that will let the compiler know the current work-
         ing directory at the time of preprocessing.  When this
         option is enabled, the preprocessor will emit, after the
         initial linemarker, a second linemarker with the current
         working directory followed by two slashes.  GCC will use
         this directory, when it's present in the preprocessed
         input, as the directory emitted as the current working
         directory in some debugging information formats.  This
         option is implicitly enabled if debugging information is
         enabled, but this can be inhibited with the negated form
         -fno-working-directory.  If the -P flag is present in
         the command line, this option has no effect, since no
         "#line" directives are emitted whatsoever.

     -fno-show-column

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

         M   Instead of the normal output, generate a list of
             #define directives for all the macros defined during
             the execution of the preprocessor, including prede-
             fined macros.  This gives you a way of finding out
             what is predefined in your version of the preproces-
             sor. Assuming you have no file foo.h, the command

                     touch foo.h; cpp -dM foo.h

             will show all the predefined macros.

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

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

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

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

     -C  Do not discard comments.  All comments are passed

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GCC(1)                         GNU                         GCC(1)

         through to the output file, except for comments in pro-
         cessed directives, which are deleted along with the
         directive.

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

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

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

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

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

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

         The nine trigraphs and their replacements are

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

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

     --help
     --target-help
         Print text describing all the command line options
         instead of preprocessing anything.

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GCC(1)                         GNU                         GCC(1)

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

     -H  Print the name of each header file used, in addition to
         other normal activities.  Each name is indented to show
         how deep in the #include stack it is.  Precompiled
         header files are also printed, even if they are found to
         be invalid; an invalid precompiled header file is
         printed with ...x and a valid one with ...! .

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

     Passing Options to the Assembler

     You can pass options to the assembler.

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

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

         If you want to pass an option that takes an argument,
         you must use -Xassembler twice, once for the option and
         once for the argument.

     Options for Linking

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

     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

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GCC(1)                         GNU                         GCC(1)

         run, and object file names should not be used as argu-
         ments.

     -llibrary
     -l library
         Search the library named library when linking.  (The
         second alternative with the library as a separate argu-
         ment is only for POSIX compliance and is not recom-
         mended.)

         It makes a difference where in the command you write
         this option; the linker searches and processes libraries
         and object files in the order they are specified.  Thus,
         foo.o -lz bar.o searches library z after file foo.o but
         before bar.o.  If bar.o refers to functions in z, those
         functions may not be loaded.

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

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

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

     -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 link-
         ing. The standard system libraries are used normally,
         unless -nostdlib or -nodefaultlibs is used.

     -nodefaultlibs
         Do not use the standard system libraries when linking.
         Only the libraries you specify will be passed to the
         linker. The standard startup files are used normally,
         unless -nostartfiles is used.  The compiler may generate
         calls to memcmp, memset, and memcpy for System V (and
         ISO C) environments or to bcopy and bzero for BSD

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GCC(1)                         GNU                         GCC(1)

         environments.  These entries are usually resolved by
         entries in libc.  These entry points should be supplied
         through some other mechanism when this option is speci-
         fied.

     -nostdlib
         Do not use the standard system startup files or
         libraries when linking. No startup files and only the
         libraries you specify will be passed to the linker.  The
         compiler may generate calls to memcmp, memset, and
         memcpy for System V (and ISO C) environments or to bcopy
         and bzero for BSD environments.  These entries are usu-
         ally resolved by entries in libc.  These entry points
         should be supplied through some other mechanism when
         this option is specified.

         One of the standard libraries bypassed by -nostdlib and
         -nodefaultlibs is libgcc.a, a library of internal sub-
         routines that GCC uses to overcome shortcomings of par-
         ticular 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 usu-
         ally specify -lgcc as well. This ensures that you have
         no unresolved references to internal GCC library subrou-
         tines.  (For example, __main, used to ensure C++ con-
         structors will be called.)

     -pie
         Produce a position independent executable on targets
         which support it. For predictable results, you must also
         specify the same set of options that were used to gen-
         erate code (-fpie, -fPIE, or model suboptions) when you
         specify this option.

     -s  Remove all symbol table and relocation information from
         the executable.

     -static
         On systems that support dynamic linking, this prevents
         linking with the shared libraries.  On other systems,
         this option has no effect.

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

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GCC(1)                         GNU                         GCC(1)

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

         There are several situations in which an application
         should use the shared libgcc instead of the static ver-
         sion.  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 con-
         figuration time, that you have a non-GNU linker or a GNU
         linker that does not support option --eh-frame-hdr, it
         will link the shared version of libgcc into shared
         libraries by default.  Otherwise, it will take advantage
         of the linker and optimize away the linking with the
         shared version of libgcc, linking with the static ver-
         sion of libgcc by default.  This allows exceptions to
         propagate through such shared libraries, without incur-
         ring relocation costs at library load time.

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

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

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

         If you want to pass an option that takes an argument,

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GCC(1)                         GNU                         GCC(1)

         you must use -Xlinker twice, once for the option and
         once for the argument. For example, to pass -assert
         definitions, you must write -Xlinker -assert -Xlinker
         definitions.  It does not work to write -Xlinker
         "-assert definitions", because this passes the entire
         string as a single argument, which is not what the
         linker expects.

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

     -u symbol
         Pretend the symbol symbol is undefined, to force linking
         of library modules to define it.  You can use -u multi-
         ple 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 direc-
         tories to be searched for header files.  This can be
         used to override a system header file, substituting your
         own version, since these directories are searched before
         the system header file directories.  However, you should
         not use this option to add directories that contain
         vendor-supplied system header files (use -isystem for
         that).  If you use more than one -I option, the direc-
         tories 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 posi-
         tion in the system include chain. This is to ensure that
         GCC's procedure to fix buggy system headers and the ord-
         ering for the include_next directive are not inadver-
         tently 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

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GCC(1)                         GNU                         GCC(1)

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

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

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

     -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 sub-
         programs cpp, cc1, as and ld.  It tries prefix as a pre-
         fix for each program it tries to run, both with and
         without machine/version/.

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

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

         -B prefixes that effectively specify directory names
         also apply to libraries in the linker, because the com-
         piler 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.

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

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

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     Hardware Models and Configurations

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

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

     Some configurations of the compiler also support additional
     special options, usually for compatibility with other com-
     pilers 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 float-
         ing point. This is the default for most 68020 systems
         unless --nfp was specified when the compiler was config-
         ured.

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

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

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

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

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

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

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

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

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

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

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

     -msoft-float
         Generate output containing library calls for floating
         point. Warning: the requisite libraries are not avail-
         able for all m68k targets.  Normally the facilities of

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         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 func-
         tions 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 compiled with the Unix compiler.

         Also, you must provide function prototypes for all func-
         tions 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.)

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

     -malign-int
     -mno-align-int
         Control whether GCC aligns "int", "long", "long long",
         "float", "double", and "long double" variables on a
         32-bit boundary (-malign-int) or a 16-bit boundary
         (-mno-align-int). Aligning variables on 32-bit boun-
         daries produces code that runs somewhat faster on

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GCC(1)                         GNU                         GCC(1)

         processors with 32-bit busses at the expense of more
         memory.

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

     -msep-data
         Generate code that allows the data segment to be located
         in a different area of memory from the text segment.
         This allows for execute in place in an environment
         without virtual memory management.  This option implies
         -fPIC.

     -mno-sep-data
         Generate code that assumes that the data segment follows
         the text segment. This is the default.

     -mid-shared-library
         Generate code that supports shared libraries via the
         library ID method. This allows for execute in place and
         shared libraries in an environment without virtual
         memory management.  This option implies -fPIC.

     -mno-id-shared-library
         Generate code that doesn't assume ID based shared
         libraries are being used. This is the default.

     -mshared-library-id=n
         Specified the identification number of the ID based
         shared library being compiled.  Specifying a value of 0
         will generate more compact code, specifying other values
         will force the allocation of that number to the current
         library but is no more space or time efficient than
         omitting this option.

     M68hc1x Options

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

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

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

     -m68S12
     -m68hcs12
         Generate output for a 68HCS12.

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

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

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

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

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

     VAX Options

     These -m options are defined for the VAX:

     -munix
         Do not output certain jump instructions ("aobleq" and so

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GCC(1)                         GNU                         GCC(1)

         on) that the Unix assembler for the VAX cannot handle
         across long ranges.

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

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

     SPARC Options

     These -m options 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, except on
         Solaris.

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

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

     -mno-fpu
     -msoft-float
         Generate output containing library calls for floating
         point. Warning: the requisite libraries are not avail-
         able for all SPARC 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 func-
         tions for cross-compilation.  The embedded targets
         sparc-*-aout and sparclite-*-* do provide software
         floating point support.

         -msoft-float changes the calling convention in the out-
         put 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.

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

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

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

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

         These options are deprecated and will be deleted in a
         future GCC release.

     -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 struc-
         tures should have 8 byte alignment.  This enables the
         use of pairs of "ldd" and "std" instructions for copies

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GCC(1)                         GNU                         GCC(1)

         in structure assignment, in place of twice as many "ld"
         and "st" pairs. However, the use of this changed align-
         ment directly violates the SPARC ABI.  Thus, it's
         intended only for use on targets where the developer
         acknowledges that their resulting code will not be
         directly in line with the rules of the ABI.

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

         -mimpure-text suppresses the ``relocations remain
         against allocatable but non-writable sections'' linker
         error message. However, the necessary relocations will
         trigger copy-on-write, and the shared object is not
         actually shared across processes.  Instead of using
         -mimpure-text, you should compile all source code with
         -fpic or -fPIC.

         This option is only available on SunOS and Solaris.

     -mv8
     -msparclite
         These two options select variations on the SPARC archi-
         tecture. These options are deprecated and will be
         deleted in a future GCC release. They have been replaced
         with -mcpu=xxx.

     -mcypress
     -msupersparc
     -mf930
     -mf934
         These four options select the processor for which the
         code is optimized. These options are deprecated and will
         be deleted in a future GCC release. They have been
         replaced with -mcpu=xxx.

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

         By default (unless configured otherwise), GCC generates
         code for the V7 variant of the SPARC architecture.  With
         -mcpu=cypress, the compiler additionally optimizes it
         for the Cypress CY7C602 chip, as used in the
         SPARCStation/SPARCServer 3xx series.  This is also
         appropriate for the older SPARCStation 1, 2, IPX etc.

         With -mcpu=v8, GCC generates code for the V8 variant of
         the SPARC architecture.  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.  With -mcpu=supersparc, the compiler
         additionally optimizes it for the SuperSPARC chip, as
         used in the SPARCStation 10, 1000 and 2000 series.

         With -mcpu=sparclite, GCC generates code for the SPAR-
         Clite variant of the SPARC architecture.  This adds the
         integer multiply, integer divide step and scan ("ffs")
         instructions which exist in SPARClite but not in
         SPARC-V7. With -mcpu=f930, the compiler additionally
         optimizes it for the Fujitsu MB86930 chip, which is the
         original SPARClite, with no FPU.  With -mcpu=f934, the
         compiler additionally optimizes it for the Fujitsu
         MB86934 chip, which is the more recent SPARClite with
         FPU.

         With -mcpu=sparclet, GCC generates code for the SPARClet
         variant of the SPARC architecture.  This adds the
         integer multiply, multiply/accumulate, integer divide
         step and scan ("ffs") instructions which exist in SPAR-
         Clet but not in SPARC-V7.  With -mcpu=tsc701, the com-
         piler additionally optimizes it for the TEMIC SPARClet
         chip.

         With -mcpu=v9, GCC generates code for the V9 variant of
         the SPARC architecture.  This adds 64-bit integer and
         floating-point move instructions, 3 additional
         floating-point condition code registers and conditional
         move instructions.  With -mcpu=ultrasparc, the compiler
         additionally optimizes it for the Sun UltraSPARC I/II
         chips.  With -mcpu=ultrasparc3, the compiler addition-
         ally optimizes it for the Sun UltraSPARC III chip.

     -mtune=cpu_type
         Set the instruction scheduling parameters for machine
         type cpu_type, but do not set the instruction set or

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GCC(1)                         GNU                         GCC(1)

         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.

     -mv8plus
     -mno-v8plus
         With -mv8plus, GCC generates code for the SPARC-V8+ ABI.
         The difference from the V8 ABI is that the global and
         out registers are considered 64-bit wide.  This is
         enabled by default on Solaris in 32-bit mode for all
         SPARC-V9 processors.

     -mvis
     -mno-vis
         With -mvis, GCC generates code that takes advantage of
         the UltraSPARC Visual Instruction Set extensions.  The
         default is -mno-vis.

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

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

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

     -mcmodel=medlow
         Generate code for the Medium/Low code model: 64-bit
         addresses, programs must be linked in the low 32 bits of
         memory.  Programs can be statically or dynamically
         linked.

     -mcmodel=medmid
         Generate code for the Medium/Middle code model: 64-bit
         addresses, programs must be linked in the low 44 bits of
         memory, the text and data segments must be less than 2GB
         in size and the data segment must be located within 2GB
         of the text segment.

     -mcmodel=medany
         Generate code for the Medium/Anywhere code model: 64-bit

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GCC(1)                         GNU                         GCC(1)

         addresses, programs may be linked anywhere in memory,
         the text and data segments must be less than 2GB in size
         and the data segment must be located within 2GB of the
         text segment.

     -mcmodel=embmedany
         Generate code for the Medium/Anywhere code model for
         embedded systems: 64-bit addresses, the text and data
         segments must be less than 2GB in size, both starting
         anywhere in memory (determined at link time).  The glo-
         bal register %g4 points to the base of the data segment.
         Programs are statically linked and 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.
         This is the default in 64-bit mode. Otherwise, assume no
         such offset is present.

     These switches are supported in addition to the above on
     Solaris:

     -threads
         Add support for multithreading using the Solaris threads
         library.  This option sets flags for both the preproces-
         sor and linker.  This option does not affect the thread
         safety of object code produced by the compiler or that
         of libraries supplied with it.

     -pthreads
         Add support for multithreading using the POSIX threads
         library.  This option sets flags for both the preproces-
         sor and linker.  This option does not affect the thread
         safety of object code produced  by the compiler or that
         of libraries supplied with it.

     ARM Options

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

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

     -mapcs

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GCC(1)                         GNU                         GCC(1)

         This is a synonym for -mapcs-frame.

     -mapcs-26
         Generate code for a processor running with a 26-bit pro-
         gram counter, and conforming to the function calling
         standards for the APCS 26-bit option.

         This option is deprecated.  Future releases of the GCC
         will only support generating code that runs in apcs-32
         mode.

     -mapcs-32
         Generate code for a processor running with a 32-bit pro-
         gram counter, and conforming to the function calling
         standards for the APCS 32-bit option.

         This flag is deprecated.  Future releases of GCC will
         make this flag unconditional.

     -mthumb-interwork
         Generate code which supports calling between the ARM and
         Thumb instruction sets.  Without this option the two
         instruction sets cannot be reliably used inside one pro-
         gram.  The default is -mno-thumb-interwork, since
         slightly larger code is generated when -mthumb-interwork
         is specified.

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

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

     -msoft-float
         Generate output containing library calls for floating
         point. Warning: the requisite libraries are not avail-
         able 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 func-
         tions for cross-compilation.

         -msoft-float changes the calling convention in the

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GCC(1)                         GNU                         GCC(1)

         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 configura-
         tions.

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

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

     -malignment-traps
         Generate code that will not trap if the MMU has align-
         ment traps enabled. On ARM architectures prior to ARMv4,
         there were no instructions to access half-word objects
         stored in memory.  However, when reading from memory a
         feature of the ARM architecture allows a word load to be
         used, even if the address is unaligned, and the proces-
         sor 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 to
         load half-word data if it knows that the address is
         aligned to a word boundary.

         This option has no effect when compiling for ARM archi-
         tecture 4 or later, since these processors have instruc-
         tions to directly access half-word objects in memory.

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

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

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GCC(1)                         GNU                         GCC(1)

         The default setting is -malignment-traps, since this
         produces code that will also run on processors imple-
         menting ARM architecture version 6 or later.

         This option is deprecated and will be removed in the
         next release of GCC.

     -mcpu=name
         This specifies the name of the target ARM processor.
         GCC uses this name to determine what kind of instruc-
         tions it can emit when generating assembly code.  Per-
         missible names are: arm2, arm250, arm3, arm6, arm60,
         arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm,
         arm7di, arm7dmi, arm70, arm700, arm700i, arm710,
         arm710c, arm7100, arm7500, arm7500fe, arm7tdmi, arm8,
         strongarm, strongarm110, strongarm1100, arm8, arm810,
         arm9, arm9e, arm920, arm920t, arm926ejs, arm940t,
         arm9tdmi, arm10tdmi, arm1020t, arm1026ejs, arm1136js,
         arm1136jfs ,xscale, iwmmxt, ep9312.

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

     -march=name
         This specifies the name of the target ARM architecture.
         GCC uses this name to determine what kind of instruc-
         tions 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,
         armv6j, iwmmxt, ep9312.

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

     -mstructure-size-boundary=n
         The size of all structures and unions will be rounded up
         to a multiple of the number of bits set by this option.
         Permissible values are 8 and 32.  The default value
         varies for different toolchains.  For the COFF targeted

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GCC(1)                         GNU                         GCC(1)

         toolchain the default value is 8.  Specifying the larger
         number can produce faster, more efficient code, but can
         also increase the size of the program.  The two values
         are potentially incompatible.  Code compiled with one
         value cannot necessarily expect to work with code or
         libraries compiled with the other value, if they
         exchange information using structures or unions.

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

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

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

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

     -mcirrus-fix-invalid-insns
         Insert NOPs into the instruction stream to in order to
         work around problems with invalid Maverick instruction
         combinations.  This option is only valid if the
         -mcpu=ep9312 option has been used to enable generation
         of instructions for the Cirrus Maverick floating point
         co-processor.  This option is not enabled by default,
         since the problem is only present in older Maverick
         implementations.  The default can be re-enabled by use
         of the -mno-cirrus-fix-invalid-insns switch.

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

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

         When performing a stack backtrace, code can inspect the
         value of "pc" stored at "fp + 0".  If the trace function
         then looks at location "pc - 12" and the top 8 bits are
         set, then we know that there is a function name embedded
         immediately preceding this location and has length
         "((pc[-3]) & 0xff000000)".

     -mthumb
         Generate code for the 16-bit Thumb instruction set.  The
         default is to use the 32-bit ARM instruction set.

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

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

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GCC(1)                         GNU                         GCC(1)

         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.

     MN10300 Options

     These -m options are defined for Matsushita MN10300 archi-
     tectures:

     -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 processor.  This is the default.

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

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

         This option makes symbolic debugging impossible.

     M32R/D Options

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GCC(1)                         GNU                         GCC(1)

     These -m options are defined for Renesas M32R/D architec-
     tures:

     -m32r2
         Generate code for the M32R/2.

     -m32rx
         Generate code for the M32R/X.

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

     -mmodel=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.

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

     -mmodel=large
         Assume objects may be anywhere in the 32-bit address
         space (the compiler will generate "seth/add3" instruc-
         tions to load their addresses), and assume subroutines
         may not be reachable with the "bl" instruction (the com-
         piler 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 "sec-
         tion" 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,

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GCC(1)                         GNU                         GCC(1)

         and generate special instructions to reference them.

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

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

     -mdebug
         Makes the M32R specific code in the compiler display
         some statistics that might help in debugging programs.

     -malign-loops
         Align all loops to a 32-byte boundary.

     -mno-align-loops
         Do not enforce a 32-byte alignment for loops.  This is
         the default.

     -missue-rate=number
         Issue number instructions per cycle.  number can only be
         1 or 2.

     -mbranch-cost=number
         number can only be 1 or 2.  If it is 1 then branches
         will be preferred over conditional code, if it is 2,
         then the opposite will apply.

     -mflush-trap=number
         Specifies the trap number to use to flush the cache.
         The default is 12.  Valid numbers are between 0 and 15
         inclusive.

     -mno-flush-trap
         Specifies that the cache cannot be flushed by using a
         trap.

     -mflush-func=name
         Specifies the name of the operating system function to
         call to flush the cache.  The default is _flush_cache,
         but a function call will only be used if a trap is not
         available.

     -mno-flush-func
         Indicates that there is no OS function for flushing the
         cache.

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GCC(1)                         GNU                         GCC(1)

     IBM RS/6000 and PowerPC Options

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

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

         Neither architecture is a subset of the other.  However
         there is a large common subset of instructions supported
         by both.  An MQ register is included in processors sup-
         porting the POWER architecture.

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

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

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

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GCC(1)                         GNU                         GCC(1)

         to use the optional PowerPC architecture instructions in
         the Graphics group, including floating-point select.

         The -mpowerpc64 option allows GCC to generate the addi-
         tional 64-bit instructions that are found in the full
         PowerPC64 architecture and to treat GPRs as 64-bit, dou-
         bleword quantities.  GCC defaults to -mno-powerpc64.

         If you specify both -mno-power and -mno-powerpc, GCC
         will use only the instructions in the common subset of
         both architectures plus some special AIX common-mode
         calls, and will not use the MQ register.  Specifying
         both -mpower and -mpowerpc permits GCC to use any
         instruction from either architecture and to allow use of
         the MQ register; specify this for the Motorola MPC601.

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

         GCC defaults to the mnemonics appropriate for the archi-
         tecture 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 mnemon-
         ics, and instruction scheduling parameters for machine
         type cpu_type. Supported values for cpu_type are 401,
         403, 405, 405fp, 440, 440fp, 505, 601, 602, 603, 603e,
         604, 604e, 620, 630, 740, 7400, 7450, 750, 801, 821,
         823, 860, 970, 8540, common, ec603e, G3, G4, G5, power,
         power2, power3, power4, power5, powerpc, powerpc64,
         rios, rios1, rios2, rsc, and rs64a.

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

         -mcpu=power, -mcpu=power2, -mcpu=powerpc, and

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GCC(1)                         GNU                         GCC(1)

         -mcpu=powerpc64 specify generic POWER, POWER2, pure
         32-bit PowerPC (i.e., not MPC601), and 64-bit PowerPC
         architecture machine types, with an appropriate, generic
         processor model assumed for scheduling purposes.

         The other options specify a specific processor.  Code
         generated under those options will run best on that pro-
         cessor, and may not run at all on others.

         The -mcpu options automatically enable or disable the
         following options: -maltivec, -mhard-float, -mmfcrf,
         -mmultiple, -mnew-mnemonics, -mpower, -mpower2,
         -mpowerpc64, -mpowerpc-gpopt, -mpowerpc-gfxopt,
         -mstring.  The particular options set for any particular
         CPU will vary between compiler versions, depending on
         what setting seems to produce optimal code for that CPU;
         it doesn't necessarily reflect the actual hardware's
         capabilities.  If you wish to set an individual option
         to a particular value, you may specify it after the
         -mcpu option, like -mcpu=970 -mno-altivec.

         On AIX, the -maltivec and -mpowerpc64 options are not
         enabled or disabled by the -mcpu option at present,
         since AIX does not have full support for these options.
         You may still enable or disable them individually if
         you're sure it'll work in your environment.

     -mtune=cpu_type
         Set the instruction scheduling parameters for machine
         type cpu_type, but do not set the architecture type,
         register usage, or choice of mnemonics, as
         -mcpu=cpu_type would.  The same values for cpu_type are
         used for -mtune as for -mcpu.  If both are specified,
         the code generated will use the architecture, registers,
         and mnemonics set by -mcpu, but the scheduling parame-
         ters 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.

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GCC(1)                         GNU                         GCC(1)

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

     -mspe=yes/no
     -mspe
         This switch enables or disables the generation of SPE
         simd instructions.

     -mfloat-gprs=yes/no
     -mfloat-gprs
         This switch enables or disables the generation of float-
         ing point operations on the general purpose registers
         for architectures that support it.  This option is
         currently only available on the MPC8540.

     -mfull-toc
     -mno-fp-in-toc
     -mno-sum-in-toc
     -mminimal-toc
         Modify generation of the TOC (Table Of Contents), which
         is created for every executable file.  The -mfull-toc
         option is selected by default.  In that case, GCC will
         allocate at least one TOC entry for each unique non-
         automatic variable reference in your program.  GCC will
         also place floating-point constants in the TOC.  How-
         ever, only 16,384 entries are available in the TOC.

         If you receive a linker error message that saying you
         have overflowed the available TOC space, you can reduce
         the amount of TOC space used with the -mno-fp-in-toc and
         -mno-sum-in-toc options. -mno-fp-in-toc prevents GCC
         from putting floating-point constants in the TOC and
         -mno-sum-in-toc forces GCC to generate code to calculate
         the sum of an address and a constant at run-time instead
         of putting that sum into the TOC.  You may specify one
         or both of these options.  Each causes GCC to produce
         very slightly slower and larger code at the expense of
         conserving TOC space.

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

     -maix64
     -maix32

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GCC(1)                         GNU                         GCC(1)

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

     -mxl-compat
     -mno-xl-compat
         Produce code that conforms more closely to IBM XLC
         semantics when using AIX-compatible ABI.  Pass
         floating-point arguments to prototyped functions beyond
         the register save area (RSA) on the stack in addition to
         argument FPRs.  Do not assume that most significant dou-
         ble in 128 bit long double value is properly rounded
         when comparing values.

         The AIX calling convention was extended but not ini-
         tially documented to handle an obscure K&R C case of
         calling a function that takes the address of its argu-
         ments with fewer arguments than declared.  AIX XL com-
         pilers access floating point arguments which do not fit
         in the RSA from the stack when a subroutine is compiled
         without optimization.  Because always storing floating-
         point arguments on the stack is inefficient and rarely
         needed, this option is not enabled by default and only
         is necessary when calling subroutines compiled by AIX XL
         compilers without optimization.

     -mpe
         Support IBM RS/6000 SP Parallel Environment (PE).  Link
         an application written to use message passing with spe-
         cial 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 overrid-
         den with the -specs= option to specify the appropriate
         directory location.  The Parallel Environment does not
         support threads, so the -mpe option and the -pthread
         option are incompatible.

     -malign-natural
     -malign-power
         On AIX, Darwin, and 64-bit PowerPC GNU/Linux, the option
         -malign-natural overrides the ABI-defined alignment of
         larger types, such as floating-point doubles, on their
         natural size-based boundary. The option -malign-power
         instructs GCC to follow the ABI-specified alignment
         rules.  GCC defaults to the standard alignment defined
         in the ABI.

     -msoft-float
     -mhard-float

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GCC(1)                         GNU                         GCC(1)

         Generate code that does not use (uses) the floating-
         point register set. Software floating point emulation is
         provided if you use the -msoft-float option, and pass
         the option to GCC when linking.

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

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

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

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

     -mno-bit-align
     -mbit-align
         On System V.4 and embedded PowerPC systems do not (do)
         force structures and unions that contain bit-fields to

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GCC(1)                         GNU                         GCC(1)

         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 dif-
         ferent address at runtime.  If you use -mrelocatable on
         any module, all objects linked together must be compiled
         with -mrelocatable or -mrelocatable-lib.

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

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

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

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

     -mdynamic-no-pic
         On Darwin and Mac OS X systems, compile code so that it
         is not relocatable, but that its external references are

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GCC(1)                         GNU                         GCC(1)

         relocatable.  The resulting code is suitable for appli-
         cations, but not shared libraries.

     -mprioritize-restricted-insns=priority
         This option controls the priority that is assigned to
         dispatch-slot restricted instructions during the second
         scheduling pass.  The argument priority takes the value
         0/1/2 to assign no/highest/second-highest priority to
         dispatch slot restricted instructions.

     -msched-costly-dep=dependence_type
         This option controls which dependences are considered
         costly by the target during instruction scheduling.  The
         argument dependence_type takes one of the following
         values: no: no dependence is costly, all: all depen-
         dences are costly, true_store_to_load: a true dependence
         from store to load is costly, store_to_load: any depen-
         dence from store to load is costly, number: any depen-
         dence which latency >= number is costly.

     -minsert-sched-nops=scheme
         This option controls which nop insertion scheme will be
         used during the second scheduling pass. The argument
         scheme takes one of the following values: no: Don't
         insert nops. pad: Pad with nops any dispatch group which
         has vacant issue slots, according to the scheduler's
         grouping. regroup_exact: Insert nops to force costly
         dependent insns into separate groups.  Insert exactly as
         many nops as needed to force an insn to a new group,
         according to the estimated processor grouping. number:
         Insert nops to force costly dependent insns into
         separate groups.  Insert number nops to force an insn to
         a new group.

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

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

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

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

     -mcall-linux

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

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

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

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

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

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

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

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

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

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

     -mads

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

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

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

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

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

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

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

     -msdata=sysv

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

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

     -msdata-data
         On System V.4 and embedded PowerPC systems, put small
         global and static data in the .sdata section.  Put small
         uninitialized global and static data in the .sbss sec-
         tion.  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 uninitial-
         ized data in the .bss section.

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

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

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

         Some linkers are capable of detecting out-of-range calls
         and generating glue code on the fly.  On these systems,
         long calls are unnecessary and generate slower code.  As

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GCC(1)                         GNU                         GCC(1)

         of this writing, the AIX linker can do this, as can the
         GNU linker for PowerPC/64.  It is planned to add this
         feature to the GNU linker for 32-bit PowerPC systems as
         well.

         On Mach-O (Darwin) systems, this option directs the com-
         piler emit to the glue for every direct call, and the
         Darwin linker decides whether to use or discard it.

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

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

         Use this on MirOS to compile and link threaded code,
         isolating the program from operating system details.

     Darwin Options

     These options are defined for all architectures running the
     Darwin operating system.  They are useful for compatibility
     with other Mac OS compilers.

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

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

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

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

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

     -allowable_client  client_name
     -arch_only
     -client_name

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     -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
     -nofixprebinding
     -nomultidefs
     -noprebind
     -noseglinkedit
     -pagezero_size
     -prebind
     -prebind_all_twolevel_modules
     -private_bundle
     -read_only_relocs
     -sectalign
     -sectobjectsymbols
     -whyload
     -seg1addr
     -sectcreate
     -sectobjectsymbols
     -sectorder
     -seg_addr_table
     -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

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     -whatsloaded
         These options are available for Darwin linker. Darwin
         linker man page describes them in detail.

     MIPS Options

     -EB Generate big-endian code.

     -EL Generate little-endian code.  This is the default for
         mips*el-*-* configurations.

     -march=arch
         Generate code that will run on arch, which can be the
         name of a generic MIPS ISA, or the name of a particular
         processor. The ISA names are: mips1, mips2, mips3,
         mips4, mips32, mips32r2, and mips64. The processor names
         are: 4kc, 4kp, 5kc, 20kc, m4k, r2000, r3000, r3900,
         r4000, r4400, r4600, r4650, r6000, r8000, rm7000,
         rm9000, orion, sb1, vr4100, vr4111, vr4120, vr4300,
         vr5000, vr5400 and vr5500. The special value from-abi
         selects the most compatible architecture for the
         selected ABI (that is, mips1 for 32-bit ABIs and mips3
         for 64-bit ABIs).

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

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

         Note that the _MIPS_ARCH macro uses the processor names
         given above.  In other words, it will have the full pre-
         fix 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 con-
         trols the way instructions are scheduled, and the per-
         ceived cost of arithmetic operations.  The list of arch
         values is the same as for -march.

         When this option is not used, GCC will optimize for the
         processor specified by -march.  By using -march and
         -mtune together, it is possible to generate code that

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GCC(1)                         GNU                         GCC(1)

         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.

     -mips32r2
         Equivalent to -march=mips32r2.

     -mips64
         Equivalent to -march=mips64.

     -mips16
     -mno-mips16
         Use (do not use) the MIPS16 ISA.

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

         Note that the EABI has a 32-bit and a 64-bit variant.
         GCC normally generates 64-bit code when you select a
         64-bit architecture, but you can use -mgp32 to get
         32-bit code instead.

     -mabicalls
     -mno-abicalls
         Generate (do not generate) SVR4-style position-
         independent code. -mabicalls is the default for
         SVR4-based systems.

     -mxgot
     -mno-xgot

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GCC(1)                         GNU                         GCC(1)

         Lift (do not lift) the usual restrictions on the size of
         the global offset table.

         GCC normally uses a single instruction to load values
         from the GOT. While this is relatively efficient, it
         will only work if the GOT is smaller than about 64k.
         Anything larger will cause the linker to report an error
         such as:

                 relocation truncated to fit: R_MIPS_GOT16 foobar

         If this happens, you should recompile your code with
         -mxgot. It should then work with very large GOTs,
         although it will also be less efficient, since it will
         take three instructions to fetch the value of a global
         symbol.

         Note that some linkers can create multiple GOTs.  If you
         have such a linker, you should only need to use -mxgot
         when a single object file accesses more than 64k's worth
         of GOT entries.  Very few do.

         These options have no effect unless GCC is generating
         position independent code.

     -membedded-pic
     -mno-embedded-pic
         Generate (do not generate) position-independent code
         suitable for some embedded systems.  All calls are made
         using PC relative addresses, 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.

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

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

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

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

     -mhard-float
         Use floating-point coprocessor instructions.

     -msoft-float
         Do not use floating-point coprocessor instructions.
         Implement floating-point calculations using library

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GCC(1)                         GNU                         GCC(1)

         calls instead.

     -msingle-float
         Assume that the floating-point coprocessor only supports
         single-precision operations.

     -mdouble-float
         Assume that the floating-point coprocessor supports
         double-precision operations.  This is the default.

     -mint64
         Force "int" and "long" types to be 64 bits wide.  See
         -mlong32 for an explanation of the default and the way
         that the pointer size is determined.

     -mlong64
         Force "long" types to be 64 bits wide.  See -mlong32 for
         an explanation of the default and the way that the
         pointer size is determined.

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

         The default size of "int"s, "long"s and pointers depends
         on the ABI.  All the supported ABIs use 32-bit "int"s.
         The n64 ABI uses 64-bit "long"s, as does the 64-bit
         EABI; the others use 32-bit "long"s.  Pointers are the
         same size as "long"s, or the same size as integer regis-
         ters, whichever is smaller.

     -G num
         Put global and static items less than or equal to num
         bytes into the small data or bss section instead of the
         normal data or bss section. This allows the data to be
         accessed using a single instruction.

         All modules should be compiled with the same -G num
         value.

     -membedded-data
     -mno-embedded-data
         Allocate variables to the read-only data section first
         if possible, then next in the small data section if pos-
         sible, 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
         Put uninitialized "const" variables in the read-only

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GCC(1)                         GNU                         GCC(1)

         data section. This option is only meaningful in conjunc-
         tion with -membedded-data.

     -msplit-addresses
     -mno-split-addresses
         Enable (disable) use of the "%hi()" and "%lo()" assem-
         bler relocation operators.  This option has been super-
         ceded by -mexplicit-relocs but is retained for backwards
         compatibility.

     -mexplicit-relocs
     -mno-explicit-relocs
         Use (do not use) assembler relocation operators when
         dealing with symbolic addresses.  The alternative,
         selected by -mno-explicit-relocs, is to use assembler
         macros instead.

         -mexplicit-relocs is usually the default if GCC was con-
         figured to use an assembler that supports relocation
         operators. However, there are two exceptions:

         *   GCC is not yet able to generate explicit relocations
             for the combination of -mabi=64 and -mno-abicalls.
             This will be addressed in a future release.

         *   The combination of -mabicalls and
             -fno-unit-at-a-time implies -mno-explicit-relocs
             unless explicitly overridden. This is because, when
             generating abicalls, the choice of relocation
             depends on whether a symbol is local or global.  In
             some rare cases, GCC will not be able to decide this
             until the whole compilation unit has been read.

     -mrnames
     -mno-rnames
         Generate (do not generate) code that refers to registers
         using their software names.  The default is -mno-rnames,
         which tells GCC to use hardware names like $4 instead of
         software names like a0.  The only assembler known to
         support -rnames is the Algorithmics assembler.

     -mcheck-zero-division
     -mno-check-zero-division
         Trap (do not trap) on integer division by zero.  The
         default is -mcheck-zero-division.

     -mmemcpy
     -mno-memcpy
         Force (do not force) the use of "memcpy()" for non-
         trivial block moves.  The default is -mno-memcpy, which
         allows GCC to inline most constant-sized copies.

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     -mlong-calls
     -mno-long-calls
         Disable (do not disable) use of the "jal" instruction.
         Calling functions using "jal" is more efficient but
         requires the caller and callee to be in the same 256
         megabyte segment.

         This option has no effect on abicalls code.  The default
         is -mno-long-calls.

     -mmad
     -mno-mad
         Enable (disable) use of the "mad", "madu" and "mul"
         instructions, as provided by the R4650 ISA.

     -mfused-madd
     -mno-fused-madd
         Enable (disable) use of the floating point multiply-
         accumulate instructions, when they are available.  The
         default is -mfused-madd.

         When multiply-accumulate instructions are used, the
         intermediate product is calculated to infinite precision
         and is not subject to the FCSR Flush to Zero bit.  This
         may be undesirable in some circumstances.

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

     -mfix-sb1
     -mno-fix-sb1
         Work around certain SB-1 CPU core errata. (This flag
         currently works around the SB-1 revision 2 ``F1'' and
         ``F2'' floating point errata.)

     -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 con-
         figured for, but commonly is either _flush_func or
         __cpu_flush.

     -mbranch-likely
     -mno-branch-likely
         Enable or disable use of Branch Likely instructions,

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GCC(1)                         GNU                         GCC(1)

         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 computers:

     -mtune=cpu-type
         Tune to cpu-type everything applicable about the gen-
         erated code, except for the ABI and the set of available
         instructions.  The choices for cpu-type are:

         i386
             Original Intel's i386 CPU.

         i486
             Intel's i486 CPU.  (No scheduling is implemented for
             this chip.)

         i586, pentium
             Intel Pentium CPU with no MMX support.

         pentium-mmx
             Intel PentiumMMX CPU based on Pentium core with MMX
             instruction set support.

         i686, pentiumpro
             Intel PentiumPro CPU.

         pentium2
             Intel Pentium2 CPU based on PentiumPro core with MMX
             instruction set support.

         pentium3, pentium3m
             Intel Pentium3 CPU based on PentiumPro core with MMX
             and SSE instruction set support.

         pentium-m
             Low power version of Intel Pentium3 CPU with MMX,
             SSE and SSE2 instruction set support.  Used by Cen-
             trino notebooks.

         pentium4, pentium4m
             Intel Pentium4 CPU with MMX, SSE and SSE2 instruc-
             tion set support.

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GCC(1)                         GNU                         GCC(1)

         prescott
             Improved version of Intel Pentium4 CPU with MMX,
             SSE, SSE2 and SSE3 instruction set support.

         nocona
             Improved version of Intel Pentium4 CPU with 64-bit
             extensions, MMX, SSE, SSE2 and SSE3 instruction set
             support.

         k6  AMD K6 CPU with MMX instruction set support.

         k6-2, k6-3
             Improved versions of AMD K6 CPU with MMX and 3dNOW!
             instruction set support.

         athlon, athlon-tbird
             AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and
             SSE prefetch instructions support.

         athlon-4, athlon-xp, athlon-mp
             Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced
             3dNOW! and full SSE instruction set support.

         k8, opteron, athlon64, athlon-fx
             AMD K8 core based CPUs with x86-64 instruction set
             support.  (This supersets MMX, SSE, SSE2, 3dNOW!,
             enhanced 3dNOW! and 64-bit instruction set exten-
             sions.)

         winchip-c6
             IDT Winchip C6 CPU, dealt in same way as i486 with
             additional MMX instruction set support.

         winchip2
             IDT Winchip2 CPU, dealt in same way as i486 with
             additional MMX and 3dNOW! instruction set support.

         c3  Via C3 CPU with MMX and 3dNOW!  instruction set sup-
             port.  (No scheduling is implemented for this chip.)

         c3-2
             Via C3-2 CPU with MMX and SSE instruction set sup-
             port.  (No scheduling is implemented for this chip.)

         While picking a specific cpu-type will schedule things
         appropriately for that particular chip, the compiler
         will not generate any code that does not run on the i386
         without the -march=cpu-type option being used.

     -march=cpu-type
         Generate instructions for the machine type cpu-type.
         The choices for cpu-type are the same as for -mtune.

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         Moreover, specifying -march=cpu-type implies
         -mtune=cpu-type.

     -mcpu=cpu-type
         A deprecated synonym for -mtune.

     -m386
     -m486
     -mpentium
     -mpentiumpro
         These options are synonyms for -mtune=i386, -mtune=i486,
         -mtune=pentium, and -mtune=pentiumpro respectively.
         These synonyms are deprecated.

     -mfpmath=unit
         Generate floating point arithmetics for selected unit
         unit.  The choices for unit are:

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

             This is the default choice for i386 compiler.

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

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

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

             This is the default choice for the x86-64 compiler.

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

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

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

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

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

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

         The usual calling convention has functions return values
         of types "float" and "double" in an FPU register, even
         if there is no FPU.  The idea is that the operating sys-
         tem should emulate an FPU.

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

     -mno-fancy-math-387
         Some 387 emulators do not support the "sin", "cos" and
         "sqrt" instructions for the 387.  Specify this option to
         avoid generating those instructions.  This option is the
         default on FreeBSD, OpenBSD and NetBSD.  This option is
         overridden when -march indicates that the target cpu
         will always have an FPU and so the instruction will not

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         need emulation.  As of revision 2.6.1, these instruc-
         tions 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 fas-
         ter on a Pentium at the expense of more memory.

         Warning: if you use the -malign-double switch, struc-
         tures containing the above types will be aligned dif-
         ferently than the published application binary interface
         specifications for the 386 and will not be binary compa-
         tible with structures in code compiled without that
         switch.

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

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

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

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

         Warning: if you override the default value for your tar-
         get ABI, the structures and arrays containing "long dou-
         ble" variables will change their size as well as func-
         tion calling convention for function taking "long dou-
         ble" will be modified.  Hence they will not be binary
         compatible with arrays or structures in code compiled
         without that switch.

     -msvr3-shlib
     -mno-svr3-shlib

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         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 argu-
         ments while returning.  This saves one instruction in
         the caller since there is no need to pop the arguments
         there.

         You can specify that an individual function is called
         with this calling sequence with the function attribute
         stdcall.  You can also override the -mrtd option by
         using the function attribute cdecl.

         Warning: this calling convention is incompatible with
         the one normally used on Unix, so you cannot use it if
         you need to call libraries compiled with the Unix com-
         piler.

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

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

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

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

     -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).

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         On Pentium and PentiumPro, "double" and "long double"
         values should be aligned to an 8 byte boundary (see
         -malign-double) or suffer significant run time perfor-
         mance penalties.  On Pentium III, the Streaming SIMD
         Extension (SSE) data type "__m128" suffers similar
         penalties if it is not 16 byte aligned.

         To ensure proper alignment of this values on the stack,
         the stack boundary must be as aligned as that required
         by any value stored on the stack. Further, every func-
         tion 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 pre-
         ferred alignment to -mpreferred-stack-boundary=2.

     -mmmx
     -mno-mmx
     -msse
     -mno-sse
     -msse2
     -mno-sse2
     -msse3
     -mno-sse3
     -m3dnow
     -mno-3dnow
         These switches enable or disable the use of built-in
         functions that allow direct access to the MMX, SSE,
         SSE2, SSE3 and 3Dnow extensions of the instruction set.

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

     -mpush-args
     -mno-push-args
         Use PUSH operations to store outgoing parameters.  This
         method is shorter and usually equally fast as method
         using SUB/MOV operations and is enabled by default.  In
         some cases disabling it may improve performance because
         of improved scheduling and reduced dependencies.

     -maccumulate-outgoing-args
         If enabled, the maximum amount of space required for
         outgoing arguments will be computed in the function pro-
         logue.  This is faster on most modern CPUs because of

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         reduced dependencies, improved scheduling and reduced
         stack usage when preferred stack boundary is not equal
         to 2.  The drawback is a notable increase in code size.
         This switch implies -mno-push-args.

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

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

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

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

     -mtls-direct-seg-refs
     -mno-tls-direct-seg-refs
         Controls whether TLS variables may be accessed with
         offsets from the TLS segment register (%gs for 32-bit,
         %fs for 64-bit), or whether the thread base pointer must
         be added.  Whether or not this is legal depends on the
         operating system, and whether it maps the segment to
         cover the entire TLS area.

         For systems that use GNU libc, the default is on.

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

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

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         and generates code that runs on any i386 system. The
         64-bit environment sets int to 32 bits and long and
         pointer to 64 bits and generates code for AMD's x86-64
         architecture.

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

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

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

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

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

     HPPA Options

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

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

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         around.

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

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

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

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

     -mdisable-fpregs
         Prevent floating point registers from being used in any
         manner.  This is necessary for compiling kernels which
         perform lazy context switching of floating point regis-
         ters.  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 ker-
         nels.

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

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

     -mlong-load-store

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

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

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

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

     -mlinker-opt
         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. Warning: the requisite libraries are not avail-
         able for all HPPA 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 func-
         tions for cross-compilation.  The embedded target
         hppa1.1-*-pro does provide software floating point sup-
         port.

         -msoft-float changes the calling convention in the out-
         put 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 works-
         tation IO.  These options are available under HP-UX and
         HI-UX.

     -mgnu-ld

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         Use GNU ld specific options.  This passes -shared to ld
         when building a shared library.  It is the default when
         GCC is configured, explicitly or implicitly, with the
         GNU linker.  This option does not have any affect on
         which ld is called, it only changes what parameters are
         passed to that ld.  The ld that is called is determined
         by the --with-ld configure option, GCC's program search
         path, and finally by the user's PATH.  The linker used
         by GCC can be printed using which `gcc
         -print-prog-name=ld`.  This option is only available on
         the 64 bit HP-UX GCC, i.e. configured with
         hppa*64*-*-hpux*.

     -mhp-ld
         Use HP ld specific options.  This passes -b to ld when
         building a shared library and passes +Accept TypeM-
         ismatch to ld on all links.  It is the default when GCC
         is configured, explicitly or implicitly, with the HP
         linker.  This option does not have any affect on which
         ld is called, it only changes what parameters are passed
         to that ld.  The ld that is called is determined by the
         --with-ld configure option, GCC's program search path,
         and finally by the user's PATH.  The linker used by GCC
         can be printed using which `gcc -print-prog-name=ld`.
         This option is only available on the 64 bit HP-UX GCC,
         i.e. configured with hppa*64*-*-hpux*.

     -mlong-calls
         Generate code that uses long call sequences.  This
         ensures that a call is always able to reach linker gen-
         erated stubs.  The default is to generate long calls
         only when the distance from the call site to the begin-
         ning 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, particularly 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

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GCC(1)                         GNU                         GCC(1)

         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 speci-
         fied, 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 implementa-
     tions:

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

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

     -mleaf-procedures
     -mno-leaf-procedures
         Do (or do not) attempt to alter leaf procedures to be

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GCC(1)                         GNU                         GCC(1)

         callable with the "bal" instruction as well as "call".
         This will result in more efficient code for explicit
         calls when the "bal" instruction can be substituted by
         the assembler or linker, but less efficient code in
         other cases, such as calls via function pointers, or
         using a linker that doesn't support this optimization.

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

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

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

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

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

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

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

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

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GCC(1)                         GNU                         GCC(1)

         by 80-bit floating point numbers.  The only reason we
         have it because there is no 128-bit long double support
         in fp-bit.c yet.  So it is only useful for people using
         soft-float targets.  Otherwise, we should recommend
         against use of it.

     DEC Alpha Options

     These -m options are defined for the DEC Alpha implementa-
     tions:

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

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

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

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

     -mieee
         The Alpha architecture implements floating-point
         hardware optimized for maximum 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 compli-
         ant code except that the inexact-flag is not maintained
         (see below). If this option is turned on, the

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GCC(1)                         GNU                         GCC(1)

         preprocessor macro "_IEEE_FP" is defined during compila-
         tion.  The resulting code is less efficient but is able
         to correctly support denormalized numbers and excep-
         tional 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 main-
         tains 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 signifi-
         cantly slower than the code generated by default.  Since
         there is very little code that depends on the inexact-
         flag, you should normally not specify this option.
         Other Alpha compilers call this option
         -ieee_with_inexact.

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

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

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

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

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

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

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

         m   Round towards minus infinity.

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

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         d   Dynamic rounding mode.  A field in the floating
             point control register (fpcr, see Alpha architecture
             reference manual) controls the rounding mode in
             effect.  The C library initializes this register for
             rounding towards plus infinity.  Thus, unless your
             program modifies the fpcr, d corresponds to round
             towards plus 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 gen-
         erate code that can assist operating system trap
         handlers in determining the exact location that caused a
         floating point trap. Depending on the requirements of an
         application, different levels of precisions can be
         selected:

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

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

         i   Instruction precision.  The trap handler can deter-
             mine 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 generated
         assembly file.  Under DEC Unix, this has the effect that
         IEEE-conformant math library routines will be linked in.

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

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

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

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

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

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

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

     -msmall-data
     -mlarge-data
         When -mexplicit-relocs is in effect, static data is
         accessed via gp-relative 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

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GCC(1)                         GNU                         GCC(1)

         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.

     -msmall-text
     -mlarge-text
         When -msmall-text is used, the compiler assumes that the
         code of the entire program (or shared library) fits in
         4MB, and is thus reachable with a branch instruction.
         When -msmall-data is used, the compiler can assume that
         all local symbols share the same $gp value, and thus
         reduce the number of instructions required for a func-
         tion call from 4 to 1.

         The default is -mlarge-text.

     -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 proces-
         sor you specify.  If you do not specify a processor
         type, GCC will default to the processor on which the
         compiler was built.

         Supported values for cpu_type are

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

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

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

         pca56

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

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

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

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

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

         Valid options for time are

         number
             A decimal number representing clock cycles.

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

     DEC Alpha/VMS Options

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

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

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GCC(1)                         GNU                         GCC(1)

     H8/300 Options

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

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

     -mh Generate code for the H8/300H.

     -ms Generate code for the H8S.

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

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

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

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

     -m2e
         Generate code for the SH2e.

     -m3 Generate code for the SH3.

     -m3e
         Generate code for the SH3e.

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

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

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     -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 pos-
         sible; uses the linker option -relax.

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

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

     -mhitachi
         Comply with the calling conventions defined by Renesas.

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

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

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

     -mpadstruct
         This option is deprecated.  It pads structures to multi-
         ple 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 Pro-
         cedure Linkage Table.

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

     Options for System V

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

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

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

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

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

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

     TMS320C3x/C4x Options

     These -m options are defined for TMS320C3x/C4x implementa-
     tions:

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

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

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

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

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

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

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

     -mrptb

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     -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 boun-
         daries.  There is no advantage having nested RPTB loops
         due to the overhead required to save and restore the RC,
         RS, and RE registers. This is enabled by default with
         -O2.

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

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

     -mti
         Try to emit an assembler syntax that the TI assembler
         (asm30) is happy with.  This also enforces compatibility
         with the API employed by the TI C3x C compiler.  For
         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 argu-
         ments on to the stack.

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

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     -mparallel-mpy
     -mno-parallel-mpy
         Allow the generation of MPY||ADD and MPY||SUB parallel
         instructions, provided -mparallel-insns is also speci-
         fied.  These instructions have tight register con-
         straints which can pessimize the code generation of
         large functions.

     V850 Options

     These -m options are defined for V850 implementations:

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

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

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

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

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

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

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     -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.

     -mv850e1
         Specify that the target processor is the V850E1.  The
         preprocessor constants __v850e1__ and __v850e__ will be
         defined if this option is used.

     -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 nor -mv850e1 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 and v850e1 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.

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     -EB Compile code for big endian mode.

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

     -mcpu=cpu
         Compile code for ARC variant cpu. Which variants are
         supported depend on the configuration. All variants sup-
         port -mcpu=base, this is the default.

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

     NS32K Options

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

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

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

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

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

     -m32381

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         Generate output containing 32381 instructions for float-
         ing 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 instruc-
         tions "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. Warning: the requisite libraries may not be
         available.

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

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

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

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

         This calling convention is incompatible with the one
         normally used on Unix, so you cannot use it if you need
         to call libraries compiled with the Unix compiler.

         Also, you must provide function prototypes for all

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GCC(1)                         GNU                         GCC(1)

         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" instruc-
         tion.

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

         This calling convention is incompatible with the one
         normally used on Unix, so you cannot use it if you need
         to call libraries compiled with the Unix compiler.

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

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

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

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

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

     AVR Options

     These options are defined for AVR implementations:

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

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GCC(1)                         GNU                         GCC(1)

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

         Instruction set avr2 (default) is for the classic AVR
         core with up to 8K program 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 inter-
         rupts. Code size will be smaller.

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

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

     -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

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GCC(1)                         GNU                         GCC(1)

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

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

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

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

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

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

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

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

     -m210
     -m340
         Generate code for the 210 processor.

     IA-64 Options

     These are the -m options defined for the Intel IA-64 archi-
     tecture.

     -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 GNU/Linux.

     -mgnu-as
     -mno-gnu-as

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GCC(1)                         GNU                         GCC(1)

         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 regis-
         ter.  The result is not position independent code, and
         violates the IA-64 ABI.

     -mvolatile-asm-stop
     -mno-volatile-asm-stop
         Generate (or don't) a stop bit immediately before and
         after volatile asm statements.

     -mb-step
         Generate code that works around Itanium B step errata.

     -mregister-names
     -mno-register-names
         Generate (or don't) in, loc, and out register names for
         the stacked registers.  This may make assembler output
         more readable.

     -mno-sdata
     -msdata
         Disable (or enable) optimizations that use the small
         data section.  This may be useful for working around
         optimizer bugs.

     -mconstant-gp
         Generate code that uses a single constant global pointer
         value.  This is useful when compiling kernel code.

     -mauto-pic
         Generate code that is self-relocatable.  This implies
         -mconstant-gp. This is useful when compiling firmware
         code.

     -minline-float-divide-min-latency
         Generate code for inline divides of floating point
         values using the minimum latency algorithm.

     -minline-float-divide-max-throughput
         Generate code for inline divides of floating point
         values using the maximum throughput algorithm.

     -minline-int-divide-min-latency
         Generate code for inline divides of integer values using

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GCC(1)                         GNU                         GCC(1)

         the minimum latency algorithm.

     -minline-int-divide-max-throughput
         Generate code for inline divides of integer values using
         the maximum throughput algorithm.

     -minline-sqrt-min-latency
         Generate code for inline square roots using the minimum
         latency algorithm.

     -minline-sqrt-max-throughput
         Generate code for inline square roots using the maximum
         throughput algorithm.

     -mno-dwarf2-asm
     -mdwarf2-asm
         Don't (or do) generate assembler code for the DWARF2
         line number debugging info.  This may be useful when not
         using the GNU assembler.

     -mearly-stop-bits
     -mno-early-stop-bits
         Allow stop bits to be placed earlier than immediately
         preceding the instruction that triggered the stop bit.
         This can improve instruction scheduling, but does not
         always do so.

     -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.

     -mtls-size=tls-size
         Specify bit size of immediate TLS offsets.  Valid values
         are 14, 22, and 64.

     -mtune=cpu-type
         Tune the instruction scheduling for a particular CPU,
         Valid values are itanium, itanium1, merced, itanium2,
         and mckinley.

     -mt
     -pthread
         Add support for multithreading using the POSIX threads
         library.  This option sets flags for both the preproces-
         sor and linker.  It does not affect the thread safety of
         object code produced by the compiler or that of
         libraries supplied with it.  These are HP-UX specific
         flags.

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     -milp32
     -mlp64
         Generate code for a 32-bit or 64-bit environment. The
         32-bit environment sets int, long and pointer to 32
         bits. The 64-bit environment sets int to 32 bits and
         long and pointer to 64 bits.  These are HP-UX specific
         flags.

     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 optim-
         izing. 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 instruc-
         tions to avoid doing a branch. The default is 2.

     -mcond-exec=n
         Specify the maximum number of conditionally executed
         instructions that replace a branch.  The default is 4.

     S/390 and zSeries Options

     These are the -m options defined for the S/390 and zSeries
     architecture.

     -mhard-float
     -msoft-float
         Use (do not use) the hardware floating-point instruc-
         tions and registers for floating-point operations.  When
         -msoft-float is specified, functions in libgcc.a will be
         used to perform floating-point operations.  When

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GCC(1)                         GNU                         GCC(1)

         -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 may be needed to allow debug-
         ging using tools that do not understand DWARF-2 call
         frame information.  The default is not to generate the
         backchain.

     -msmall-exec
     -mno-small-exec
         Generate (or do not generate) code using the "bras"
         instruction to do subroutine calls. This only works
         reliably if the total executable size does not exceed
         64k.  The default is to use the "basr" instruction
         instead, which does not have this limitation.

     -m64
     -m31
         When -m31 is specified, generate code compliant to the
         GNU/Linux for S/390 ABI.  When -m64 is specified, gen-
         erate code compliant to the GNU/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.

     -mzarch
     -mesa
         When -mzarch is specified, generate code using the
         instructions available on z/Architecture. When -mesa is
         specified, generate code using the instructions avail-
         able on ESA/390. Note that -mesa is not possible with
         -m64. When generating code compliant to the GNU/Linux
         for S/390 ABI, the default is -mesa.  When generating
         code compliant to the GNU/Linux for zSeries ABI, the
         default is -mzarch.

     -mmvcle
     -mno-mvcle
         Generate (or do not generate) code using the "mvcle"
         instruction to perform block moves.  When -mno-mvcle is
         specified, use a "mvc" loop instead.  This is the
         default.

     -mdebug
     -mno-debug
         Print (or do not print) additional debug information
         when compiling. The default is to not print debug infor-
         mation.

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GCC(1)                         GNU                         GCC(1)

     -march=cpu-type
         Generate code that will run on cpu-type, which is the
         name of a system representing a certain processor type.
         Possible values for cpu-type are g5, g6, z900, and z990.
         When generating code using the instructions available on
         z/Architecture, the default is -march=z900.  Otherwise,
         the default is -march=g5.

     -mtune=cpu-type
         Tune to cpu-type everything applicable about the gen-
         erated code, except for the ABI and the set of available
         instructions. The list of cpu-type values is the same as
         for -march. The default is the value used for -march.

     -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 float-
         ing point is used.

     CRIS Options

     These options are defined specifically for the CRIS ports.

     -march=architecture-type
     -mcpu=architecture-type
         Generate code for the specified architecture.  The
         choices for architecture-type are v3, v8 and v10 for
         respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.
         Default is v0 except for cris-axis-linux-gnu, where the
         default is v10.

     -mtune=architecture-type
         Tune to architecture-type everything applicable about
         the generated code, except for the ABI and the set of
         available instructions.  The choices for architecture-
         type are the same as for -march=architecture-type.

     -mmax-stack-frame=n
         Warn when the stack frame of a function exceeds n bytes.

     -melinux-stacksize=n
         Only available with the cris-axis-aout target.  Arranges
         for indications in the program to the kernel loader that
         the stack of the program should be set to n bytes.

     -metrax4
     -metrax100
         The options -metrax4 and -metrax100 are synonyms for
         -march=v3 and -march=v8 respectively.

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GCC(1)                         GNU                         GCC(1)

     -mmul-bug-workaround
     -mno-mul-bug-workaround
         Work around a bug in the "muls" and "mulu" instructions
         for CPU models where it applies.  This option is active
         by default.

     -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 instruc-
         tion; 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 arrange-
         ments) for the stack-frame, individual data and con-
         stants to be aligned for the maximum single data access
         size for the chosen CPU model.  The default is to
         arrange for 32-bit alignment.  ABI details such as
         structure layout are not affected by these options.

     -m32-bit
     -m16-bit
     -m8-bit
         Similar to the stack- data- and const-align options
         above, these options arrange for stack-frame, writable
         data and constants to all be 32-bit, 16-bit or 8-bit
         aligned.  The default is 32-bit alignment.

     -mno-prologue-epilogue
     -mprologue-epilogue
         With -mno-prologue-epilogue, the normal function prolo-
         gue and epilogue that sets up the stack-frame are omit-
         ted 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.

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GCC(1)                         GNU                         GCC(1)

     -mno-gotplt
     -mgotplt
         With -fpic and -fPIC, don't generate (do generate)
         instruction sequences that load addresses for functions
         from the PLT part of the GOT rather than (traditional on
         other architectures) calls to the PLT.  The default is
         -mgotplt.

     -maout
         Legacy no-op option only recognized with the cris-axis-
         aout target.

     -melf
         Legacy no-op option only recognized with the cris-axis-
         elf and cris-axis-linux-gnu targets.

     -melinux
         Only recognized with the cris-axis-aout target, where it
         selects a GNU/linux-like multilib, include files and
         instruction set for -march=v8.

     -mlinux
         Legacy no-op option only recognized with the cris-axis-
         linux-gnu target.

     -sim
         This option, recognized for the cris-axis-aout and
         cris-axis-elf arranges to link with input-output func-
         tions from a simulator library.  Code, initialized data
         and zero-initialized data are allocated 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 com-
         piled, passing all values in registers, no matter the
         size.

     -mepsilon
     -mno-epsilon
         Generate floating-point comparison instructions that
         compare with respect to the "rE" epsilon register.

     -mabi=mmixware

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GCC(1)                         GNU                         GCC(1)

     -mabi=gnu
         Generate code that passes function parameters and return
         values that (in the called function) are seen as regis-
         ters $0 and up, as opposed to the GNU ABI which uses
         global registers $231 and up.

     -mzero-extend
     -mno-zero-extend
         When reading data from memory in sizes shorter than 64
         bits, use (do not use) zero-extending load instructions
         by default, rather than sign-extending ones.

     -mknuthdiv
     -mno-knuthdiv
         Make the result of a division yielding a remainder have
         the same sign as the divisor.  With the default,
         -mno-knuthdiv, the sign of the remainder follows the
         sign of the dividend.  Both methods are arithmetically
         valid, the latter being almost exclusively used.

     -mtoplevel-symbols
     -mno-toplevel-symbols
         Prepend (do not prepend) a : to all global symbols, so
         the assembly code can be used with the "PREFIX" assembly
         directive.

     -melf
         Generate an executable in the ELF format, rather than
         the default mmo format used by the mmix simulator.

     -mbranch-predict
     -mno-branch-predict
         Use (do not use) the probable-branch instructions, when
         static branch prediction indicates a probable branch.

     -mbase-addresses
     -mno-base-addresses
         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
         register.  The generally leads to short and fast code,
         but the number of different data items that can be
         addressed is limited.  This means that a program that
         uses lots of static data may require
         -mno-base-addresses.

     -msingle-exit
     -mno-single-exit
         Force (do not force) generated code to have a single

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GCC(1)                         GNU                         GCC(1)

         exit point in each function.

     PDP-11 Options

     These options are defined for the PDP-11:

     -mfpu
         Use hardware FPP floating point.  This is the default.
         (FIS floating point on the PDP-11/40 is not supported.)

     -msoft-float
         Do not use hardware floating point.

     -mac0
         Return floating-point results in ac0 (fr0 in Unix assem-
         bler syntax).

     -mno-ac0
         Return floating-point results in memory.  This is the
         default.

     -m40
         Generate code for a PDP-11/40.

     -m45
         Generate code for a PDP-11/45.  This is the default.

     -m10
         Generate code for a PDP-11/10.

     -mbcopy-builtin
         Use inline "movstrhi" patterns for copying memory.  This
         is the default.

     -mbcopy
         Do not use inline "movstrhi" patterns for copying
         memory.

     -mint16
     -mno-int32
         Use 16-bit "int".  This is the default.

     -mint32
     -mno-int16
         Use 32-bit "int".

     -mfloat64
     -mno-float32
         Use 64-bit "float".  This is the default.

     -mfloat32
     -mno-float64

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GCC(1)                         GNU                         GCC(1)

         Use 32-bit "float".

     -mabshi
         Use "abshi2" pattern.  This is the default.

     -mno-abshi
         Do not use "abshi2" pattern.

     -mbranch-expensive
         Pretend that branches are expensive.  This is for exper-
         imenting 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 con-
         figured 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

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GCC(1)                         GNU                         GCC(1)

     -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
         Do not try to dynamically allocate condition code regis-
         ters, only use "icc0" and "fcc0".

     -mdword
         Change ABI to use double word insns.

     -mno-dword
         Do not use double word instructions.

     -mdouble
         Use floating point double instructions.

     -mno-double
         Do not use floating point double instructions.

     -mmedia
         Use media instructions.

     -mno-media
         Do not use media instructions.

     -mmuladd
         Use multiply and add/subtract instructions.

     -mno-muladd
         Do not use multiply and add/subtract instructions.

     -mlibrary-pic
         Enable PIC support for building libraries

     -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.

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GCC(1)                         GNU                         GCC(1)

     -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.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mcond-exec
         Enable the use of conditional execution (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-cond-exec
         Disable the use of conditional execution.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mvliw-branch
         Run a pass to pack branches into VLIW instructions
         (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-vliw-branch
         Do not run a pass to pack branches into VLIW instruc-
         tions.

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GCC(1)                         GNU                         GCC(1)

         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 exe-
         cution (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

     These options are supported for Xtensa targets:

     -mconst16
     -mno-const16
         Enable or disable use of "CONST16" instructions for
         loading constant values.  The "CONST16" instruction is
         currently not a standard option from Tensilica.  When
         enabled, "CONST16" instructions are always used in place
         of the standard "L32R" instructions.  The use of
         "CONST16" is enabled by default only if the "L32R"
         instruction is not available.

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GCC(1)                         GNU                         GCC(1)

     -mfused-madd
     -mno-fused-madd
         Enable or disable use of fused multiply/add and
         multiply/subtract instructions in the floating-point
         option.  This has no effect if the floating-point option
         is not also enabled.  Disabling fused multiply/add and
         multiply/subtract instructions forces the compiler to
         use separate instructions for the multiply and
         add/subtract operations.  This may be desirable in some
         cases where strict IEEE 754-compliant results are
         required: the fused multiply add/subtract instructions
         do not round the intermediate result, thereby producing
         results with more bits of precision than specified by
         the IEEE standard.  Disabling fused multiply
         add/subtract instructions also ensures that the program
         output is not sensitive to the compiler's ability to
         combine multiply and add/subtract operations.

     -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 automatically align instructions to reduce branch
         penalties at the expense of some code density.  The
         assembler attempts to widen density instructions to
         align branch targets and the instructions following call
         instructions.  If there are not enough preceding safe
         density instructions to align a target, no widening will
         be performed.  The default is -mtarget-align.  These
         options do not affect the treatment of auto-aligned
         instructions like "LOOP", which the assembler will
         always align, either by widening density instructions or
         by inserting no-op instructions.

     -mlongcalls
     -mno-longcalls
         When this option is enabled, GCC instructs the assembler
         to translate direct calls to indirect calls unless it
         can determine that the target of a direct call is in the
         range allowed by the call instruction.  This translation

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GCC(1)                         GNU                         GCC(1)

         typically occurs for calls to functions in other source
         files.  Specifically, the assembler translates a direct
         "CALL" instruction into an "L32R" followed by a "CALLX"
         instruction. The default is -mno-longcalls.  This option
         should be used in programs where the call target can
         potentially be out of range.  This option is implemented
         in the assembler, not the compiler, so the assembly code
         generated by GCC will still show direct call
         instructions---look at the disassembled object code to
         see the actual instructions.  Note that the assembler
         will use an indirect call for every cross-file call, not
         just those that really will be out of range.

     Options for Code Generation Conventions

     These machine-independent options control the interface con-
     ventions used in code generation.

     Most of them have both positive and negative forms; the
     negative form of -ffoo would be -fno-foo.  In the table
     below, only one of the forms is listed---the one which is
     not the default.  You can figure out the other form by
     either removing no- or adding it.

     -fbounds-check
         For front-ends that support it, generate additional code
         to check that indices used to access arrays are within
         the declared range.  This is currently only supported by
         the Java and Fortran 77 front-ends, where this option
         defaults to true and false respectively.

     -ftrapv
         This option generates traps for signed overflow on addi-
         tion, subtraction, multiplication operations.

     -fwrapv
         This option instructs the compiler to assume that signed
         arithmetic overflow of addition, subtraction and multi-
         plication wraps around using twos-complement representa-
         tion.  This flag enables some optimizations and disables
         other.  This option is enabled by default for the Java
         front-end, as required by the Java language specifica-
         tion.

     -fexceptions
         Enable exception handling.  Generates extra code needed
         to propagate exceptions.  For some targets, this implies
         GCC will generate frame unwind information for all func-
         tions, which can produce significant data size overhead,
         although it does not affect execution.  If you do not
         specify this option, GCC will enable it by default for
         languages like C++ which normally require exception

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GCC(1)                         GNU                         GCC(1)

         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 excep-
         tion handling.

     -fnon-call-exceptions
         Generate code that allows trapping instructions to throw
         exceptions. Note that this requires platform-specific
         runtime support that does not exist everywhere.  More-
         over, it only allows trapping instructions to throw
         exceptions, i.e. memory references or floating point
         instructions.  It does not allow exceptions to be thrown
         from arbitrary signal handlers such as "SIGALRM".

     -funwind-tables
         Similar to -fexceptions, except that it will just gen-
         erate any needed static data, but will not affect the
         generated code in any other way. You will normally not
         enable this option; instead, a language processor that
         needs this handling would enable it on your behalf.

     -fasynchronous-unwind-tables
         Generate unwind table in dwarf2 format, if supported by
         target machine.  The table is exact at each instruction
         boundary, so it can be used for stack unwinding from
         asynchronous events (such as debugger or garbage collec-
         tor).

     -fpcc-struct-return
         Return ``short'' "struct" and "union" values in memory
         like longer ones, rather than in registers.  This con-
         vention is less efficient, but it has the advantage of
         allowing intercallability between GCC-compiled files and
         files compiled with other compilers, particularly the
         Portable C Compiler (pcc).

         The precise convention for returning structures in
         memory depends on the target configuration macros.

         Short structures and unions are those whose size and
         alignment match that of some integer type.

         Warning: code compiled with the -fpcc-struct-return
         switch is not binary compatible with code compiled with
         the -freg-struct-return switch. Use it to conform to a
         non-default application binary interface.

     -freg-struct-return
         Return "struct" and "union" values in registers when

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GCC(1)                         GNU                         GCC(1)

         possible. This is more efficient for small structures
         than -fpcc-struct-return.

         If you specify neither -fpcc-struct-return nor
         -freg-struct-return, GCC defaults to whichever conven-
         tion is standard for the target.  If there is no stan-
         dard convention, GCC defaults to -fpcc-struct-return,
         except on targets where GCC is the principal compiler.
         In those cases, we can choose the standard, and we chose
         the more efficient register return alternative.

         Warning: code compiled with the -freg-struct-return
         switch is not binary compatible with code compiled with
         the -fpcc-struct-return switch. Use it to 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 gen-
         erate code that is not binary compatible with code gen-
         erated without that switch. Use it to conform to a non-
         default application binary interface.

     -fshort-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
         compilation be shared data rather than private data.
         The distinction makes sense only on certain operating
         systems, where shared data is shared between processes
         running the same program, while private data exists in

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         one copy per process.

     -fno-common
         In C, allocate even uninitialized global variables in
         the data section of the object file, rather than gen-
         erating them as common blocks.  This has the effect that
         if the same variable is declared (without "extern") in
         two different compilations, you will get an error when
         you link them. The only reason this might be useful is
         if you wish to verify that the program will work on
         other systems which always work this way.

     -fident
         The compiler does not store its version string in
         objects by default. Use this option to turn back on the
         GNU behaviour.

     -fno-ident
         Ignore the #ident directive.

     -finhibit-size-directive
         Don't output a ".size" assembler directive, or anything
         else that would cause trouble if the function is split
         in the middle, and the two halves are placed at loca-
         tions 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 assem-
         bly code to make it more readable.  This option is gen-
         erally only of use to those who actually need to read
         the generated assembly code (perhaps while debugging the
         compiler itself).

         -fno-verbose-asm, the default, causes the extra informa-
         tion to be omitted and is useful when comparing two
         assembler files.

     -fpic
         Generate position-independent code (PIC) suitable for
         use in a shared library, if supported for the target
         machine.  Such code accesses all constant addresses
         through a global offset table (GOT).  The dynamic loader
         resolves the GOT entries when the program starts (the
         dynamic loader is not part of GCC; it is part of the
         operating system).  If the GOT size for the linked exe-
         cutable exceeds a machine-specific maximum size, you get
         an error message from the linker indicating that -fpic
         does not work; in that case, recompile with -fPIC
         instead.  (These maximums are 8k on the SPARC and 32k on
         the m68k and RS/6000.  The 386 has no such limit.)

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         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 and
         the SPARC.

         Position-independent code requires special support, and
         therefore works only on certain machines.

     -fpie
     -fPIE
         These options are similar to -fpic and -fPIC, but gen-
         erated position independent code can be only linked into
         executables. Usually these options are used when -pie
         GCC option will be used during linking.

     -ffixed-reg
         Treat the register named reg as a fixed register; gen-
         erated code should never refer to it (except perhaps as
         a stack pointer, frame pointer or in some other fixed
         role).

         reg must be the name of a register.  The register names
         accepted are machine-specific and are defined in the
         "REGISTER_NAMES" macro in the machine description macro
         file.

         This flag does not have a negative form, because it
         specifies a three-way choice.

     -fcall-used-reg
         Treat the register named reg as an allocable register
         that is clobbered by function calls.  It may be allo-
         cated for temporaries or variables that do not live
         across a call.  Functions compiled this way will not
         save and restore the register reg.

         It is an error to used this flag with the frame pointer
         or stack pointer. Use of this flag for other registers
         that have fixed pervasive roles in the machine's execu-
         tion model will produce disastrous results.

         This flag does not have a negative form, because it
         specifies a three-way choice.

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     -fcall-saved-reg
         Treat the register named reg as an allocable register
         saved by functions.  It may be allocated even for tem-
         poraries or variables that live across a call.  Func-
         tions compiled this way will save and restore the regis-
         ter reg if they use it.

         It is an error to used this flag with the frame pointer
         or stack pointer. Use of this flag for other registers
         that have fixed pervasive roles in the machine's execu-
         tion model will produce disastrous results.

         A different sort of disaster will result from the use of
         this flag for a register in which function values may be
         returned.

         This flag does not have a negative form, because it
         specifies a three-way choice.

     -fpack-struct
         Pack all structure members together without holes.

         Warning: the -fpack-struct switch causes GCC to generate
         code that is not binary compatible with code generated
         without that switch. Additionally, it makes the code
         suboptimal. Use it to conform to a non-default applica-
         tion binary interface.

     -finstrument-functions
         Generate instrumentation calls for entry and exit to
         functions.  Just after function entry and just before
         function exit, the following profiling functions will be
         called with the address of the current function and its
         call site.  (On some platforms,
         "__builtin_return_address" does not work beyond the
         current function, so the call site information may not
         be available to the profiling functions otherwise.)

                 void __cyg_profile_func_enter (void *this_fn,
                                                void *call_site);
                 void __cyg_profile_func_exit  (void *this_fn,
                                                void *call_site);

         The first argument is the address of the start of the
         current function, which may be looked up exactly in the
         symbol table.

         This currently disables function inlining.  This res-
         triction is expected to be removed in future releases.

         A function may be given the attribute
         "no_instrument_function", in which case this

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GCC(1)                         GNU                         GCC(1)

         instrumentation will not be done.  This can be used, for
         example, for the profiling functions listed above,
         high-priority interrupt routines, and any functions from
         which the profiling functions cannot safely be called
         (perhaps signal handlers, if the profiling routines gen-
         erate output or allocate memory).

     -fstack-check
         Generate code to verify that you do not go beyond the
         boundary of the stack.  You should specify this flag if
         you are running in an environment with multiple threads,
         but only rarely need to specify it in a single-threaded
         environment since stack overflow is automatically
         detected on nearly all systems if there is only one
         stack.

         Note that this switch does not actually cause checking
         to be done; the operating system must do that.  The
         switch causes generation of code to ensure that the
         operating system sees the stack being extended.

     -fstack-limit-register=reg
     -fstack-limit-symbol=sym
     -fno-stack-limit
         Generate code to ensure that the stack does not grow
         beyond a certain value, either the value of a register
         or the address of a symbol.  If the stack would grow
         beyond the value, a signal is raised.  For most targets,
         the signal is raised before the stack overruns the boun-
         dary, so it is possible to catch the signal without tak-
         ing special precautions.

         For instance, if the stack starts at absolute address
         0x80000000 and grows downwards, you can use the flags
         -fstack-limit-symbol=__stack_limit and
         -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack
         limit of 128KB.  Note that this may only work with the
         GNU linker.

     -fstack-protector
     -fstack-protector-all
         Generate code to protect an application from a stack
         smashing attack. The features are (1) the insertion of
         random value next to the frame pointer to detect the
         integrity of the stack, (2) the reordering of local
         variables to place buffers after pointers to avoid the
         corruption of pointers that could be used to further
         corrupt arbitrary memory locations, (3) the copying of
         pointers in function arguments to an area preceding
         local variable buffers to prevent the corruption of
         pointers that could be used to further corrupt arbitrary
         memory locations, and the (4) omission of

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GCC(1)                         GNU                         GCC(1)

         instrumentation code from some functions to decrease the
         performance overhead.  If the integrity would be broken,
         the program is aborted.  If stack-protector-all is
         specified, instrumentation codes are generated at every
         functions.

         Stack consistency checks at run time are added by this
         extension as well, in order to detect stack overflows,
         and it will attempt to report the problem in the system
         logs by calling syslog(3) with a LOG_CRIT priority mes-
         sage: "stack overflow in function XXX", and abort the
         faulting process.

         Note that the stack protector relies on some support
         code in libc. Stand-alone programs not linked against
         libc must either provide their own support bits, or dis-
         able SSP.

         On MirOS, stack-protector-all is the default.

         The ProPolice home page is at
         <http://researchweb.watson.ibm.com/trl/projects/security/ssp/>.

     -ftrampolines
         Allow the compiler to generate trampoline code. Since
         trampolines require the stack to be executable, this is
         commonly considered very bad code. In C, trampolines are
         only needed for nested functions, which is a GCC exten-
         sion to be deprecated soon.

         On most MirOS architectures, trampoline code marks the
         smallest possible area around the trampoline stub exe-
         cutable using mprotect(2), since the stack area is by
         default non-executable.

     -fargument-alias
     -fargument-noalias
     -fargument-noalias-global
         Specify the possible relationships among parameters and
         between parameters and global data.

         -fargument-alias specifies that arguments (parameters)
         may alias each other and may alias global
         storage.-fargument-noalias specifies that arguments do
         not alias each other, but may alias global
         storage.-fargument-noalias-global specifies that argu-
         ments do not alias each other and do not alias global
         storage.

         Each language will automatically use whatever option is
         required by the language standard.  You should not need
         to use these options yourself.

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     -fleading-underscore
         This option and its counterpart,
         -fno-leading-underscore, forcibly change the way C sym-
         bols are represented in the object file.  One use is to
         help link with legacy assembly code.

         Warning: the -fleading-underscore switch causes GCC to
         generate code that is not binary compatible with code
         generated without that switch.  Use it to conform to a
         non-default application binary interface. Not all tar-
         gets provide complete support for this switch.

     -ftls-model=model
         Alter the thread-local storage model to be used. The
         model argument should be one of "global-dynamic",
         "local-dynamic", "initial-exec" or "local-exec".

         The default without -fpic is "initial-exec"; with -fpic
         the default is "global-dynamic".

ENVIRONMENT

     This section describes several environment variables that
     affect how GCC operates.  Some of them work by specifying
     directories or prefixes to use when searching for various
     kinds of files.  Some are used to specify other aspects of
     the compilation environment.

     Note that you can also specify places to search using
     options such as -B, -I and -L.  These take precedence over
     places specified using environment variables, which in turn
     take precedence over those specified by the configuration of
     GCC.

     LANG
     LC_CTYPE
     LC_MESSAGES
     LC_ALL
         These environment variables control the way that GCC
         uses localization information that allow GCC to work
         with different national conventions.  GCC inspects the
         locale categories LC_CTYPE and LC_MESSAGES if it has
         been configured to do so.  These locale categories can
         be set to any value supported by your installation.  A
         typical value is en_GB.UTF-8 for English in the United
         Kingdom encoded in UTF-8.

         The LC_CTYPE environment variable specifies character
         classification.  GCC uses it to determine the character
         boundaries in a string; this is needed for some multi-
         byte encodings that contain quote and escape characters
         that would otherwise be interpreted as a string end or
         escape.

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GCC(1)                         GNU                         GCC(1)

         The LC_MESSAGES environment variable specifies the
         language to use in diagnostic messages.

         If the LC_ALL environment variable is set, it overrides
         the value of LC_CTYPE and LC_MESSAGES; otherwise,
         LC_CTYPE and LC_MESSAGES default to the value of the
         LANG environment variable.  If none of these variables
         are set, GCC defaults to traditional C English behavior.

     TMPDIR
         If TMPDIR is set, it specifies the directory to use for
         temporary files.  GCC uses temporary files to hold the
         output of one stage of compilation which is to be used
         as input to the next stage: for example, the output of
         the preprocessor, which is the input to the compiler
         proper.

     GCC_EXEC_PREFIX
         If GCC_EXEC_PREFIX is set, it specifies a prefix to use
         in the names of the subprograms executed by the com-
         piler.  No slash is added when this prefix is combined
         with the name of a subprogram, but you can specify a
         prefix that ends with a slash if you wish.

         If GCC_EXEC_PREFIX is not set, GCC will attempt to fig-
         ure out an appropriate prefix to use based on the path-
         name it was invoked with.

         If GCC cannot find the subprogram using the specified
         prefix, it tries looking in the usual places for the
         subprogram.

         The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/
         where prefix is the value of "prefix" when you ran the
         configure script.

         Other prefixes specified with -B take precedence over
         this prefix.

         This prefix is also used for finding files such as
         crt0.o that are used for linking.

         In addition, the prefix is used in an unusual way in
         finding the directories to search for header files.  For
         each of the standard directories whose name normally
         begins with /usr/local/lib/gcc (more precisely, with the
         value of GCC_INCLUDE_DIR), GCC tries replacing that
         beginning with the specified prefix to produce an alter-
         nate 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.

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GCC(1)                         GNU                         GCC(1)

     COMPILER_PATH
         The value of COMPILER_PATH is a colon-separated list of
         directories, much like PATH.  GCC tries the directories
         thus specified when searching for subprograms, if it
         can't find the subprograms using GCC_EXEC_PREFIX.

     LIBRARY_PATH
         The value of LIBRARY_PATH is a colon-separated list of
         directories, much like PATH.  When configured as a
         native compiler, GCC tries the directories thus speci-
         fied when searching for special linker files, if it
         can't find them using GCC_EXEC_PREFIX.  Linking using
         GCC also uses these directories when searching for ordi-
         nary libraries for the -l option (but directories speci-
         fied with -L come first).

     LANG
         This variable is used to pass locale information to the
         compiler.  One way in which this information is used is
         to determine the character set to be used when character
         literals, string literals and comments are parsed in C
         and C++. When the compiler is configured to allow multi-
         byte 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 multi-
         byte characters.

     Some additional environments variables affect the behavior
     of the preprocessor.

     CPATH
     C_INCLUDE_PATH
     CPLUS_INCLUDE_PATH
     OBJC_INCLUDE_PATH
         Each variable's value is a list of directories separated
         by a special character, much like PATH, in which to look
         for header files. The special character,
         "PATH_SEPARATOR", is target-dependent and determined at
         GCC build time.  For Microsoft Windows-based targets it
         is a semicolon, and for almost all other targets it is a

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GCC(1)                         GNU                         GCC(1)

         colon.

         CPATH specifies a list of directories to be searched as
         if specified with -I, but after any paths given with -I
         options on the command line.  This environment variable
         is used regardless of which language is being prepro-
         cessed.

         The remaining environment variables apply only when
         preprocessing the particular language indicated.  Each
         specifies a list of directories to be searched as if
         specified with -isystem, but after any paths given with
         -isystem options on the command line.

         In all these variables, an empty element instructs the
         compiler to search its current working directory.  Empty
         elements can appear at the beginning or end of a path.
         For instance, if the value of CPATH is
         ":/special/include", that has the same effect as
         -I. -I/special/include.

     DEPENDENCIES_OUTPUT
         If this variable is set, its value specifies how to out-
         put dependencies for Make based on the non-system header
         files processed by the compiler.  System header files
         are ignored in the dependency output.

         The value of DEPENDENCIES_OUTPUT can be just a file
         name, in which case the Make rules are written to that
         file, guessing the target name from the source file
         name.  Or the value can have the form file target, in
         which case the rules are written to file file using tar-
         get 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 depen-
         dence on the main input file is omitted.

BUGS

     For instructions on reporting bugs, see
     <http://gcc.gnu.org/bugs.html>.  Use of the gccbug script to
     report bugs is recommended.

FOOTNOTES

     1.  On some systems, gcc -shared needs to build supplemen-
         tary stub code for constructors to work.  On multi-

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GCC(1)                         GNU                         GCC(1)

         libbed systems, gcc -shared must select the correct sup-
         port 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), mcpp(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:
     gcc(GNU), cpp(GNU), as(GNU), ld(GNU), binutils(GNU),
     gdb(GNU), gccint(GNU), cppinternals(GNU), gnat_rm(GNU),
     gnat_ugn_unw(GNU), gnat-style(GNU), gpc(1).

AUTHOR

     See the Info entry for gcc, or
     <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
     contributors to GCC.

COPYRIGHT

     Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996,
     1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free
     Software Foundation, Inc. Copyright (c) 1998-2004 Hiroaki
     Etoh, assigned to the FSF. Copyright (c) 2004-2007, 2009
     Thorsten Glaser, assigned to the FSF.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation
     License, Version 1.2 or any later version published by the
     Free Software Foundation; with the Invariant Sections being
     ``GNU General Public License'' and ``Funding Free
     Software'', the Front-Cover texts being (a) (see below), and
     with the Back-Cover Texts being (b) (see below).  A copy of
     the license is included in the gfdl(7) man page.

     (a) The FSF's Front-Cover Text is:

          A GNU Manual

     (b) The FSF's Back-Cover Text is:

          You have freedom to copy and modify this GNU Manual, like GNU
          software.  Copies published by the Free Software Foundation raise
          funds for GNU development.

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