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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



 NAME
      gcc - GNU project C and C++ compiler

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

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

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

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

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

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

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

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

 OPTIONS



                                    - 1 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      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  -combine -pipe  -pass-exit-codes -x language
          -v  -###  --help  --target-help  --version @file

      C Language Options
          -ansi  -std=standard  -fgnu89-inline -aux-info filename -fno-asm
          -fno-builtin  -fno-builtin-function -fhosted  -ffreestanding
          -fopenmp -fms-extensions -trigraphs  -no-integrated-cpp
          -traditional  -traditional-cpp -fallow-single-precision
          -fcond-mismatch -fsigned-bitfields  -fsigned-char
          -funsigned-bitfields  -funsigned-char

      C++ Language Options
          -fabi-version=n  -fno-access-control  -fcheck-new -fconserve-space
          -ffriend-injection -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 -fno-threadsafe-statics
          -fuse-cxa-atexit  -fno-weak  -nostdinc++ -fno-default-inline
          -fvisibility-inlines-hidden -Wabi  -Wctor-dtor-privacy
          -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wno-deprecated
          -Wstrict-null-sentinel -Wno-non-template-friend  -Wold-style-cast
          -Woverloaded-virtual  -Wno-pmf-conversions -Wsign-promo

      Objective-C and Objective-C++ Language Options
          -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
          -fno-nil-receivers -fobjc-call-cxx-cdtors -fobjc-direct-dispatch
          -fobjc-exceptions -fobjc-gc -freplace-objc-classes -fzero-link
          -gen-decls -Wassign-intercept -Wno-protocol  -Wselector
          -Wstrict-selector-match -Wundeclared-selector

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

      Warning Options
          -fsyntax-only  -pedantic  -pedantic-errors -w  -Wextra  -Wall
          -Waddress  -Waggregate-return -Wno-attributes -Wc++-compat
          -Wcast-align  -Wcast-qual  -Wchar-subscripts  -Wcomment
          -Wconversion  -Wno-deprecated-declarations -Wdisabled-optimization
          -Wno-div-by-zero  -Wno-endif-labels -Werror  -Werror=*
          -Werror-implicit-function-declaration -Wfatal-errors



                                    - 2 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -Wfloat-equal  -Wformat  -Wformat=2 -Wno-format-extra-args
          -Wformat-nonliteral -Wformat-security  -Wformat-y2k -Wimplicit
          -Wimplicit-function-declaration  -Wimplicit-int -Wimport
          -Wno-import  -Winit-self  -Winline -Wno-int-to-pointer-cast
          -Wno-invalid-offsetof  -Winvalid-pch -Wlarger-than-len
          -Wunsafe-loop-optimizations  -Wlong-long -Wmain  -Wmissing-braces
          -Wmissing-field-initializers -Wmissing-format-attribute
          -Wmissing-include-dirs -Wmissing-noreturn -Wno-multichar
          -Wnonnull  -Wno-overflow -Woverlength-strings  -Wpacked  -Wpadded
          -Wparentheses  -Wpointer-arith  -Wno-pointer-to-int-cast
          -Wredundant-decls -Wreturn-type  -Wsequence-point  -Wshadow
          -Wsign-compare  -Wstack-protector -Wstrict-aliasing
          -Wstrict-aliasing=2 -Wstrict-overflow -Wstrict-overflow=n -Wswitch
          -Wswitch-default  -Wswitch-enum -Wsystem-headers  -Wtrigraphs
          -Wundef  -Wuninitialized -Wunknown-pragmas  -Wno-pragmas
          -Wunreachable-code -Wunused  -Wunused-function  -Wunused-label
          -Wunused-parameter -Wunused-value  -Wunused-variable
          -Wvariadic-macros -Wvolatile-register-var  -Wwrite-strings

      C-only Warning Options
          -Wbad-function-cast  -Wmissing-declarations -Wmissing-prototypes
          -Wnested-externs  -Wold-style-definition -Wstrict-prototypes
          -Wtraditional -Wdeclaration-after-statement -Wpointer-sign

      Debugging Options
          -dletters  -dumpspecs  -dumpmachine  -dumpversion -fdump-noaddr
          -fdump-unnumbered  -fdump-translation-unit[-n]
          -fdump-class-hierarchy[-n] -fdump-ipa-all -fdump-ipa-cgraph
          -fdump-tree-all -fdump-tree-original[-n] -fdump-tree-optimized[-n]
          -fdump-tree-inlined[-n] -fdump-tree-cfg -fdump-tree-vcg
          -fdump-tree-alias -fdump-tree-ch -fdump-tree-ssa[-n]
          -fdump-tree-pre[-n] -fdump-tree-ccp[-n] -fdump-tree-dce[-n]
          -fdump-tree-gimple[-raw] -fdump-tree-mudflap[-n]
          -fdump-tree-dom[-n] -fdump-tree-dse[-n] -fdump-tree-phiopt[-n]
          -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n]
          -fdump-tree-nrv -fdump-tree-vect -fdump-tree-sink
          -fdump-tree-sra[-n] -fdump-tree-salias -fdump-tree-fre[-n]
          -fdump-tree-vrp[-n] -ftree-vectorizer-verbose=n
          -fdump-tree-storeccp[-n] -feliminate-dwarf2-dups
          -feliminate-unused-debug-types -feliminate-unused-debug-symbols
          -femit-class-debug-always -fmem-report -fprofile-arcs
          -frandom-seed=string -fsched-verbose=n -ftest-coverage
          -ftime-report -fvar-tracking -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



                                    - 3 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -falign-functions[=n]  -falign-jumps[=n] -falign-labels[=n]
          -falign-loops[=n] -fmudflap -fmudflapth -fmudflapir
          -fbranch-probabilities -fprofile-values -fvpt
          -fbranch-target-load-optimize -fbranch-target-load-optimize2
          -fbtr-bb-exclusive -fcaller-saves  -fcprop-registers
          -fcse-follow-jumps -fcse-skip-blocks  -fcx-limited-range
          -fdata-sections -fdelayed-branch  -fdelete-null-pointer-checks
          -fearly-inlining -fexpensive-optimizations  -ffast-math
          -ffloat-store -fforce-addr  -ffunction-sections -fgcse  -fgcse-lm
          -fgcse-sm  -fgcse-las  -fgcse-after-reload -fcrossjumping
          -fif-conversion  -fif-conversion2 -finline-functions
          -finline-functions-called-once -finline-limit=n
          -fkeep-inline-functions -fkeep-static-consts  -fmerge-constants
          -fmerge-all-constants -fmodulo-sched -fno-branch-count-reg
          -fno-default-inline  -fno-defer-pop -fmove-loop-invariants
          -fno-function-cse  -fno-guess-branch-probability -fno-inline
          -fno-math-errno  -fno-peephole  -fno-peephole2
          -funsafe-math-optimizations  -funsafe-loop-optimizations
          -ffinite-math-only -fno-toplevel-reorder -fno-trapping-math
          -fno-zero-initialized-in-bss -fomit-frame-pointer
          -foptimize-register-move -foptimize-sibling-calls
          -fprefetch-loop-arrays -fprofile-generate -fprofile-use -fregmove
          -frename-registers -freorder-blocks
          -freorder-blocks-and-partition -freorder-functions
          -frerun-cse-after-loop -frounding-math -frtl-abstract-sequences
          -fschedule-insns  -fschedule-insns2 -fno-sched-interblock
          -fno-sched-spec  -fsched-spec-load -fsched-spec-load-dangerous
          -fsched-stalled-insns[=n] -fsched-stalled-insns-dep[=n]
          -fsched2-use-superblocks -fsched2-use-traces -fsee
          -freschedule-modulo-scheduled-loops -fsection-anchors
          -fsignaling-nans  -fsingle-precision-constant -fstack-protector
          -fstack-protector-all -fstrict-aliasing  -fstrict-overflow
          -ftracer  -fthread-jumps -funroll-all-loops  -funroll-loops
          -fpeel-loops -fsplit-ivs-in-unroller -funswitch-loops
          -fvariable-expansion-in-unroller -ftree-pre  -ftree-ccp
          -ftree-dce -ftree-loop-optimize -ftree-loop-linear -ftree-loop-im
          -ftree-loop-ivcanon -fivopts -ftree-dominator-opts -ftree-dse
          -ftree-copyrename -ftree-sink -ftree-ch -ftree-sra -ftree-ter
          -ftree-lrs -ftree-fre -ftree-vectorize -ftree-vect-loop-version
          -ftree-salias -fipa-pta -fweb -ftree-copy-prop -ftree-store-ccp
          -ftree-store-copy-prop -ftree-vrp -funit-at-a-time -fwhole-program
          --param name=value -O  -O0  -O1  -O2  -O3  -Os

      Preprocessor Options
          -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM  -dN
          -Dmacro[=defn]  -E  -H -idirafter dir -include file  -imacros file
          -iprefix file  -iwithprefix dir -iwithprefixbefore dir  -isystem
          dir -imultilib dir -isysroot dir -M  -MM  -MF  -MG  -MP  -MQ  -MT
          -nostdinc -P  -fworking-directory  -remap -trigraphs  -undef



                                    - 4 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -Umacro  -Wp,option -Xpreprocessor option

      Assembler Option
          -Wa,option  -Xassembler option

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

      Directory Options
          -Bprefix  -Idir  -iquotedir  -Ldir -specs=file  -I- --sysroot=dir

      Target Options
          -V version  -b machine

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

          ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
          -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 -mfloat-abi=name  -msoft-float  -mhard-float
          -mfpe -mthumb-interwork  -mno-thumb-interwork -mcpu=name
          -march=name  -mfpu=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 -mtp=name

          AVR Options -mmcu=mcu  -msize  -minit-stack=n  -mno-interrupts
          -mcall-prologues  -mno-tablejump  -mtiny-stack  -mint8

          Blackfin Options -momit-leaf-frame-pointer
          -mno-omit-leaf-frame-pointer -mspecld-anomaly -mno-specld-anomaly
          -mcsync-anomaly -mno-csync-anomaly -mlow-64k -mno-low64k
          -mid-shared-library -mno-id-shared-library -mshared-library-id=n
          -mlong-calls  -mno-long-calls

          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



                                    - 5 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          CRX Options -mmac -mpush-args

          Darwin Options -all_load  -allowable_client  -arch
          -arch_errors_fatal -arch_only  -bind_at_load  -bundle
          -bundle_loader -client_name  -compatibility_version
          -current_version -dead_strip -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
          -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs
          -noprebind  -noseglinkedit -pagezero_size  -prebind
          -prebind_all_twolevel_modules -private_bundle  -read_only_relocs
          -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
          -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr
          -segs_read_write_addr -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
          -F -gused -gfull -mmacosx-version-min=version -mkernel
          -mone-byte-bool

          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

          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 -mfdpic
          -minline-plt -mgprel-ro  -multilib-library-pic -mlinked-fp
          -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8
          -mpack  -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move
          -moptimize-membar -mno-optimize-membar -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 -mTLS -mtls -mcpu=cpu

          GNU/Linux Options -muclibc

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




                                    - 6 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          HPPA Options -march=architecture-type -mbig-switch
          -mdisable-fpregs  -mdisable-indexing -mfast-indirect-calls  -mgas
          -mgnu-ld   -mhp-ld -mfixed-range=register-range -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 -munix=unix-std  -nolibdld  -static
          -threads

          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
          -msseregparm -mstackrealign -momit-leaf-frame-pointer
          -mno-red-zone -mno-tls-direct-seg-refs -mcmodel=code-model -m32
          -m64 -mlarge-data-threshold=num

          IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld
          -mno-pic -mvolatile-asm-stop  -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
          -mno-sched-br-data-spec -msched-ar-data-spec
          -mno-sched-control-spec -msched-br-in-data-spec
          -msched-ar-in-data-spec -msched-in-control-spec -msched-ldc
          -mno-sched-control-ldc -mno-sched-spec-verbose
          -mno-sched-prefer-non-data-spec-insns
          -mno-sched-prefer-non-control-spec-insns
          -mno-sched-count-spec-in-critical-path

          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

          M32C Options -mcpu=cpu -msim -memregs=number

          M680x0 Options -m68000  -m68020  -m68020-40  -m68020-60  -m68030
          -m68040 -m68060  -mcpu32  -m5200  -mcfv4e -m68881  -mbitfield
          -mc68000  -mc68020 -mnobitfield  -mrtd  -mshort  -msoft-float



                                    - 7 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -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

          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

          MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
          -mips3  -mips4  -mips32  -mips32r2  -mips64 -mips16  -mno-mips16
          -mabi=abi  -mabicalls  -mno-abicalls -mshared  -mno-shared  -mxgot
          -mno-xgot  -mgp32  -mgp64 -mfp32  -mfp64  -mhard-float
          -msoft-float -msingle-float  -mdouble-float  -mdsp
          -mpaired-single  -mips3d -mlong64  -mlong32  -msym32  -mno-sym32
          -Gnum  -membedded-data  -mno-embedded-data
          -muninit-const-in-rodata  -mno-uninit-const-in-rodata
          -msplit-addresses  -mno-split-addresses -mexplicit-relocs
          -mno-explicit-relocs -mcheck-zero-division
          -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy
          -mno-memcpy  -mlong-calls  -mno-long-calls -mmad  -mno-mad
          -mfused-madd  -mno-fused-madd  -nocpp -mfix-r4000  -mno-fix-r4000
          -mfix-r4400  -mno-fix-r4400 -mfix-vr4120  -mno-fix-vr4120
          -mfix-vr4130 -mfix-sb1  -mno-fix-sb1 -mflush-func=func
          -mno-flush-func -mbranch-likely  -mno-branch-likely
          -mfp-exceptions -mno-fp-exceptions -mvr4130-align
          -mno-vr4130-align

          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

          MN10300 Options -mmult-bug  -mno-mult-bug -mam33  -mno-am33
          -mam33-2  -mno-am33-2 -mreturn-pointer-on-d0 -mno-crt0  -mrelax

          MT Options -mno-crt0 -mbacc -msim -march=cpu-type

          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



                                    - 8 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          PowerPC Options See RS/6000 and PowerPC Options.

          RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mpower
          -mno-power  -mpower2  -mno-power2 -mpowerpc  -mpowerpc64
          -mno-powerpc -maltivec  -mno-altivec -mpowerpc-gpopt
          -mno-powerpc-gpopt -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mmfcrf
          -mno-mfcrf  -mpopcntb  -mno-popcntb  -mfprnd  -mno-fprnd
          -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  -maltivec  -mswdiv
          -mprioritize-restricted-insns=priority
          -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
          -mcall-sysv  -mcall-netbsd -maix-struct-return
          -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt -misel
          -mno-isel -misel=yes  -misel=no -mspe -mno-spe -mspe=yes  -mspe=no
          -mvrsave -mno-vrsave -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb
          -mfloat-gprs=yes  -mfloat-gprs=no -mfloat-gprs=single
          -mfloat-gprs=double -mprototype  -mno-prototype -msim  -mmvme
          -mads  -myellowknife  -memb  -msdata -msdata=opt  -mvxworks
          -mwindiss  -G num  -pthread

          S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
          -mhard-float  -msoft-float -mlong-double-64 -mlong-double-128
          -mbackchain  -mno-backchain -mpacked-stack  -mno-packed-stack
          -msmall-exec  -mno-small-exec  -mmvcle -mno-mvcle -m64  -m31
          -mdebug  -mno-debug  -mesa  -mzarch -mtpf-trace -mno-tpf-trace
          -mfused-madd  -mno-fused-madd -mwarn-framesize
          -mwarn-dynamicstack  -mstack-size -mstack-guard

          Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u
          -mscore7 -mscore7d

          SH Options -m1  -m2  -m2e  -m3  -m3e -m4-nofpu  -m4-single-only
          -m4-single  -m4 -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al
          -m5-64media  -m5-64media-nofpu -m5-32media  -m5-32media-nofpu
          -m5-compact  -m5-compact-nofpu -mb  -ml  -mdalign  -mrelax
          -mbigtable  -mfmovd  -mhitachi -mrenesas -mno-renesas -mnomacsave
          -mieee  -misize  -mpadstruct  -mspace -mprefergot  -musermode
          -multcost=number -mdiv=strategy -mdivsi3_libfunc=name
          -madjust-unroll -mindexed-addressing -mgettrcost=number -mpt-fixed
           -minvalid-symbols

          SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model



                                    - 9 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -m32  -m64  -mapp-regs  -mno-app-regs -mfaster-structs
          -mno-faster-structs -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 -threads -pthreads -pthread

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

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

          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

          VAX Options -mg  -mgnu  -munix

          x86-64 Options See i386 and x86-64 Options.

          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

          zSeries Options See S/390 and zSeries Options.

      Code Generation Options
          -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
          -fnon-call-exceptions  -funwind-tables
          -fasynchronous-unwind-tables -finhibit-size-directive
          -finstrument-functions -fno-common  -fno-ident -fpcc-struct-return
          -fpic  -fPIC -fpie -fPIE -fno-jump-tables -freg-struct-return
          -fshort-enums -fshort-double  -fshort-wchar -fverbose-asm
          -fpack-struct[=n]  -fstack-check -fstack-limit-register=reg
          -fstack-limit-symbol=sym -fno-stack-limit -fargument-alias
          -fargument-noalias -fargument-noalias-global
          -fargument-noalias-anything -fleading-underscore
          -ftls-model=model -ftrapv  -fwrapv  -fbounds-check -fvisibility

      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



                                   - 10 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      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 libobjc
          library to make an Objective-C program work.

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

      file.mm
      file.M
          Objective-C++ source code.  Note that you must link with the
          libobjc library to make an Objective-C++ program work.  Note that
          .M refers to a literal capital M.

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

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

      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.




                                   - 11 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      file.mm
      file.M
          Objective-C++ source code which must be preprocessed.

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

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

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

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

      file.f90
      file.f95
          Free form Fortran source code which should not be preprocessed.

      file.F90
      file.F95
          Free form Fortran source code which must be preprocessed (with the
          traditional preprocessor).

      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



                                   - 12 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

                  c  c-header  c-cpp-output
                  c++  c++-header  c++-cpp-output
                  objective-c  objective-c-header  objective-c-cpp-output
                  objective-c++ objective-c++-header objective-c++-cpp-output
                  assembler  assembler-with-cpp
                  ada
                  f95  f95-cpp-input
                  java
                  treelang

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

      -pass-exit-codes
          Normally the gcc program will exit with the code of 1 if any phase
          of the compiler returns a non-success return code.  If you specify
          -pass-exit-codes, the gcc program will instead return with
          numerically highest error produced by any phase that returned an
          error indication.  The C, C++, and Fortran frontends return 4, if
          an internal compiler error is encountered.

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

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

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

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



                                   - 13 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

          Input files that don't require compilation are ignored.

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

          Input files which don't require preprocessing are ignored.

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

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

      -v  Print (on standard error output) the commands executed to run the
          stages of compilation.  Also print the version number of the
          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.

      -combine
          If you are compiling multiple source files, this option tells the
          driver to pass all the source files to the compiler at once (for
          those languages for which the compiler can handle this).  This
          will allow intermodule analysis (IMA) to be performed by the
          compiler.  Currently the only language for which this is supported
          is C.  If you pass source files for multiple languages to the



                                   - 14 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          driver, using this option, the driver will invoke the compiler(s)
          that support IMA once each, passing each compiler all the source
          files appropriate for it.  For those languages that do not support
          IMA this option will be ignored, and the compiler will be invoked
          once for each source file in that language.  If you use this
          option in conjunction with -save-temps, the compiler will generate
          multiple pre-processed files (one for each source file), but only
          one (combined) .o or .s file.

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

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

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

      @file
          Read command-line options from file.  The options read are
          inserted in place of the original @file option.  If file does not
          exist, or cannot be read, then the option will be treated
          literally, and not removed.

          Options in file are separated by whitespace.  A whitespace
          character may be included in an option by surrounding the entire
          option in either single or double quotes.  Any character
          (including a backslash) may be included by prefixing the character
          to be included with a backslash.  The file may itself contain
          additional @file options; any such options will be processed
          recursively.

      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, the use of gcc does not add the C++ library.  g++ is a



                                   - 15 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      program that calls GCC and treats .c, .h and .i files as C++ source
      files instead of C source files unless -x is used, and automatically
      specifies linking against the C++ library.  This program is also
      useful when precompiling a C header file with a .h extension for use
      in C++ compilations.  On many systems, g++ is also installed with the
      name c++.

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

      Options Controlling C Dialect

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

      -ansi
          In C mode, this is equivalent to -std=c89. In C++ mode, it is
          equivalent to -std=c++98.

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

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

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

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

          Functions that would normally be built in but do not have



                                   - 16 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          semantics defined by ISO C (such as "alloca" and "ffs") are not
          built-in functions when -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-4.2/c99status.html> for more
              information.  The names c9x and iso9899:199x are deprecated.

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

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

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

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

          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



                                   - 17 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          "inline" keyword in ISO C99) are not disabled.

      -fgnu89-inline
          The option -fgnu89-inline tells GCC to use the traditional GNU
          semantics for "inline" functions when in C99 mode.
            Using this option is roughly equivalent to adding the
          "gnu_inline" function attribute to all inline functions.

          This option is accepted by GCC versions 4.1.3 and up.  In GCC
          versions prior to 4.3, C99 inline semantics are not supported, and
          thus this option is effectively assumed to be present regardless
          of whether or not it is specified; the only effect of specifying
          it explicitly is to disable warnings about using inline functions
          in C99 mode.  Likewise, the option -fno-gnu89-inline is not
          supported in versions of GCC before 4.3.  It will be supported
          only in C99 or gnu99 mode, not in C89 or gnu89 mode.

          The preprocesor macros "__GNUC_GNU_INLINE__" and
          "__GNUC_STDC_INLINE__" may be used to check which semantics are in
          effect for "inline" functions.

      -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 character).  In
          the case of function definitions, a K&R-style list of arguments
          followed by their declarations is also provided, inside comments,
          after the declaration.

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

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



                                   - 18 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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.  In addition, when a function is
          recognized as a built-in function, GCC may use information about
          that function to warn about problems with calls to that function,
          or to generate more efficient code, even if the resulting code
          still contains calls to that function.  For example, warnings are
          given with -Wformat for bad calls to "printf", when "printf" is
          built in, and "strlen" is known not to modify global memory.

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

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

      -fopenmp
          Enable handling of OpenMP directives "#pragma omp" in C/C++ and
          "!$omp" in Fortran.  When -fopenmp is specified, the compiler
          generates parallel code according to the OpenMP Application



                                   - 19 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Program Interface v2.5 <http://www.openmp.org/>.

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

          Some cases of unnamed fields in structures and unions are only
          accepted with this option.

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

      -no-integrated-cpp
          Performs a compilation in two passes: preprocessing and compiling.
          This option allows a user supplied "cc1", "cc1plus", or "cc1obj"
          via the -B option.  The user supplied compilation step can then
          add in an additional preprocessing step after normal preprocessing
          but before compiling.  The default is to use the integrated cpp
          (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 support a pre-standard
          mode.  See the GNU CPP manual for details.

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

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

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

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



                                   - 20 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

      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 conforms most closely to the C++ ABI
          specification.  Therefore, the ABI obtained using version 0 will
          change as ABI bugs are fixed.

          The default is version 2.

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




                                   - 21 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -fcheck-new
          Check that the pointer returned by "operator new" is non-null
          before attempting to modify the storage allocated.  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 exhaustion is
          signalled by throwing "std::bad_alloc".  See also new (nothrow).

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

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

      -ffriend-injection
          Inject friend functions into the enclosing namespace, so that they
          are visible outside the scope of the class in which they are
          declared.  Friend functions were documented to work this way in
          the old Annotated C++ Reference Manual, and versions of G++ before
          4.1 always worked that way.  However, in ISO C++ a friend function
          which is not declared in an enclosing scope can only be found
          using argument dependent lookup.  This option causes friends to be
          injected as they were in earlier releases.

          This option is for compatibility, and may be removed in a future
          release of G++.

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

      -fno-enforce-eh-specs
          Don't generate code to 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.  This does not give user code
          permission to throw exceptions in violation of the exception
          specifications; the compiler will still optimize based on the
          specifications, so throwing an unexpected exception will result in



                                   - 22 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          undefined behavior.

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

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

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

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

      -fno-implicit-inline-templates
          Don't emit code for implicit instantiations of inline templates,
          either.  The default is to handle inlines differently so that
          compiles with and without 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.

      -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",



                                   - 23 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          "compl", "not", "or" and "xor" as synonyms as keywords.

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

      -fpermissive
          Downgrade 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 identification features
          (dynamic_cast and typeid).  If you don't use those parts of the
          language, you can save some space by using this flag.  Note that
          exception handling uses the same information, but it will generate
          it as needed. The dynamic_cast operator can still be used for
          casts that do not require runtime type information, i.e. casts to
          "void *" or to unambiguous base classes.

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

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

      -fno-threadsafe-statics
          Do not emit the extra code to use the routines specified in the
          C++ ABI for thread-safe initialization of local statics.  You can
          use this option to reduce code size slightly in code that doesn't
          need to be thread-safe.

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



                                   - 24 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          "__cxa_atexit".

      -fno-use-cxa-get-exception-ptr
          Don't use the "__cxa_get_exception_ptr" runtime routine.  This
          will cause "std::uncaught_exception" to be incorrect, but is
          necessary if the runtime routine is not available.

      -fvisibility-inlines-hidden
          This switch declares that the user does not attempt to compare
          pointers to inline methods where the addresses of the two
          functions were taken in different shared objects.

          The effect of this is that GCC may, effectively, mark inline
          methods with "__attribute__ ((visibility ("hidden")))" so that
          they do not appear in the export table of a DSO and do not require
          a PLT indirection when used within the DSO.  Enabling this option
          can have a dramatic effect on load and link times of a DSO as it
          massively reduces the size of the dynamic export table when the
          library makes heavy use of templates.

          The behaviour of this switch is not quite the same as marking the
          methods as hidden directly, because it does not affect static
          variables local to the function or cause the compiler to deduce
          that the function is defined in only one shared object.

          You may mark a method as having a visibility explicitly to negate
          the effect of the switch for that method.  For example, if you do
          want to compare pointers to a particular inline method, you might
          mark it as having default visibility.  Marking the enclosing class
          with explicit visibility will have no effect.

          Explicitly instantiated inline methods are unaffected by this
          option as their linkage might otherwise cross a shared library
          boundary.

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

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

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



                                   - 25 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

      -Wabi (C++ only)
          Warn when G++ generates code that is probably not compatible with
          the vendor-neutral C++ ABI.  Although an effort has been made to
          warn about all such cases, there are probably some cases that are
          not warned about, even though G++ is generating 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 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:



                                   - 26 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



                      union U { int i : 4096; };

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

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

                      struct A {};

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

                      struct C : public B, public A {};

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

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

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

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

              Instantiations of these templates may be mangled incorrectly.

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

      -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 also enabled if -Weffc++ is specified.

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







                                   - 27 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



                  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 assignment operator
              for classes with dynamically allocated memory.

          *   Item 12:  Prefer initialization to assignment in constructors.

          *   Item 14:  Make destructors virtual in base classes.

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

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

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

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

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

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

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

      -Wstrict-null-sentinel (C++ only)
          Warn also about the use of an uncasted "NULL" as sentinel.  When
          compiling only with GCC this is a valid sentinel, as "NULL" is
          defined to "__null".  Although it is a null pointer constant not a
          null pointer, it is guaranteed to of the same size as a pointer.
          But this use is not portable across different compilers.



                                   - 28 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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
          interpreted 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 (dynamic_cast,
          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();
                  };

                  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.  Previous versions of G++ would try to



                                   - 29 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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& operator =
          (const A&);, while cfront will use the user-defined operator =.

      Options Controlling Objective-C and Objective-C++ Dialects

      (NOTE: This manual does not describe the Objective-C and Objective-C++
      languages themselves.  See

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

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

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

      Note that since Objective-C is an extension of the C language,
      Objective-C compilations may also use options specific to the C
      front-end (e.g., -Wtraditional).  Similarly, Objective-C++
      compilations may use C++-specific options (e.g., -Wabi).

      Here is a list of options that are only for compiling Objective-C and
      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
          override the -fconstant-string-class setting and cause "@"...""
          literals to be laid out as constant CoreFoundation strings.



                                   - 30 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -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-call-cxx-cdtors
          For each Objective-C class, check if any of its instance variables
          is a C++ object with a non-trivial default constructor.  If so,
          synthesize a special "- (id) .cxx_construct" instance method that
          will run non-trivial default constructors on any such instance
          variables, in order, and then return "self".  Similarly, check if
          any instance variable is a C++ object with a non-trivial
          destructor, and if so, synthesize a special "- (void)
          .cxx_destruct" method that will run all such default destructors,
          in reverse order.

          The "- (id) .cxx_construct" and/or "- (void) .cxx_destruct"
          methods thusly generated will only operate on instance variables
          declared in the current Objective-C class, and not those inherited
          from superclasses.  It is the responsibility of the Objective-C
          runtime to invoke all such methods in an object's inheritance
          hierarchy.  The "- (id) .cxx_construct" methods will be invoked by
          the runtime immediately after a new object instance is allocated;
          the "- (void) .cxx_destruct" methods will be invoked immediately
          before the runtime deallocates an object instance.

          As of this writing, only the NeXT runtime on Mac OS X 10.4 and
          later has support for invoking the "- (id) .cxx_construct" and "-
          (void) .cxx_destruct" methods.

      -fobjc-direct-dispatch
          Allow fast jumps to the message dispatcher.  On Darwin this is
          accomplished via the comm page.

      -fobjc-exceptions
          Enable syntactic support for structured exception handling in
          Objective-C, similar to what is offered by C++ and Java.  This



                                   - 31 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          option is unavailable in conjunction with the NeXT runtime on Mac
          OS X 10.2 and earlier.

                    @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



                                   - 32 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              "NS_HANDLER"-style idioms provided by the "NSException" class,
              the new exceptions can only be 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 support 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 execution 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.

      -fobjc-gc
          Enable garbage collection (GC) in Objective-C and Objective-C++
          programs.

      -freplace-objc-classes
          Emit a special marker instructing ld(1) not to statically 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 available in
          conjunction with the NeXT runtime on Mac OS X 10.3 and later.

      -fzero-link
          When compiling for the NeXT runtime, the compiler ordinarily



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 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.

      -Wassign-intercept
          Warn whenever an Objective-C assignment is being intercepted by
          the garbage collector.

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

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

      -Wstrict-selector-match
          Warn if multiple methods with differing argument and/or return
          types are found for a given selector when attempting to send a
          message using this selector to a receiver of type "id" or "Class".
          When this flag is off (which is the default behavior), the
          compiler will omit such warnings if any differences found are
          confined to types which share the same size and alignment.

      -Wundeclared-selector
          Warn if a "@selector(...)" expression referring to an undeclared
          selector is found.  A selector is considered undeclared if no



                                   - 34 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          method with that name has been declared before the
          "@selector(...)" expression, either explicitly 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.

      Options to Control Diagnostic Messages Formatting

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

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

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

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

      -fdiagnostics-show-option
          This option instructs the diagnostic machinery to add text to each
          diagnostic emitted, which indicates which command line option
          directly controls that diagnostic, when such an option is known to



                                   - 35 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          the diagnostic machinery.

      Options to Request or Suppress Warnings

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

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

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

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

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

          Valid ISO C and ISO C++ programs should compile properly with or
          without this option (though a rare few will require -ansi or a
          -std option specifying the required version of ISO C).  However,
          without this option, certain GNU extensions and traditional C and
          C++ features are supported as well.  With this option, they are
          rejected.

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

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

          A feature to report any failure to conform to ISO C might be



                                   - 36 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          useful in some instances, but would require considerable
          additional work and would be quite different from -pedantic.  We
          don't have plans to support such a feature in the near future.

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

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

      -w  Inhibit all warning messages.

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

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

      -Wcomment
          Warn whenever a comment-start sequence /* appears in a /* comment,
          or whenever a Backslash-Newline appears in a // comment.  This
          warning is enabled by -Wall.

      -Wfatal-errors
          This option causes the compiler to abort compilation on the first
          error occurred rather than trying to keep going and printing
          further error messages.

      -Wformat
          Check calls to "printf" and "scanf", etc., to make sure that the
          arguments supplied have types appropriate to the format string
          specified, and that the conversions specified in the format string
          make sense.  This includes standard functions, and others
          specified by format attributes, in the "printf", "scanf",
          "strftime" and "strfmon" (an X/Open extension, not in the C
          standard) families (or other target-specific families).  Which
          functions are checked without format attributes having been
          specified depends on the standard version selected, and such
          checks of functions without the attribute specified are disabled



                                   - 37 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          by -ffreestanding or -fno-builtin.

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

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

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

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

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

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

      -Wformat-security



                                   - 38 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -Winit-self (C, C++, Objective-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.  This warning is
          enabled by -Wall.

      -Wimplicit-function-declaration
      -Werror-implicit-function-declaration
          Give a warning (or error) whenever a function is used before being
          declared.  The form -Wno-error-implicit-function-declaration is
          not supported.  This warning is enabled by -Wall (as a warning,
          not an error).

      -Wimplicit



                                   - 39 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Same as -Wimplicit-int and -Wimplicit-function-declaration.  This
          warning is enabled by -Wall.

      -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.  This
          warning is enabled by -Wall.

      -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 } };

          This warning is enabled by -Wall.

      -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
          Warn if a user-supplied include directory does not exist.

      -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.  Only the warning for an assignment used
          as a truth value is supported when compiling C++; the other
          warnings are only supported when compiling C.

          Also warn if a comparison like x<=y<=z appears; this is equivalent
          to (x<=y ? 1 : 0) <= z, which is a different interpretation from
          that of ordinary mathematical notation.

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

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

          In C, every "else" branch belongs to the innermost possible "if"
          statement, which in this example is "if (b)".  This is often not
          what the programmer expected, as illustrated in the above example



                                   - 40 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          by indentation the programmer chose.  When there is the potential
          for this confusion, GCC will issue a warning when this flag is
          specified.  To eliminate the warning, add explicit braces around
          the innermost "if" statement so there is no way the "else" could
          belong to the enclosing "if".  The resulting code would look like
          this:

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

          This warning is enabled by -Wall.

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

          The C and C++ standards defines the order in which expressions in
          a C/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 specified.  However, the standards
          committee have ruled that function calls do not overlap.

          It is not specified when between sequence points modifications to
          the values of objects take effect.  Programs whose behavior
          depends on this have undefined behavior; the C and C++ standards
          specify that "Between the previous and next sequence point an
          object shall have its stored value modified at most once by the
          evaluation of an expression. Furthermore, the prior value shall be
          read only to determine the value to be stored.".  If a program
          breaks these rules, the results on any particular implementation



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 GCC(1)                           gcc-4.2.3                           GCC(1)
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                                 2008-02-01



          are entirely unpredictable.

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

          The 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>.

          This warning is enabled by -Wall for C and C++.

      -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, also warn if 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.  ISO C
          prohibits qualified "void" return types on function definitions,
          so such return types always receive a warning even without this
          option.

          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.

          This warning is enabled by -Wall.

      -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.  This warning is
          enabled by -Wall.

      -Wswitch-default
          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 outside the enumeration range also



                                   - 42 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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).  This warning is enabled by -Wall.

      -Wunused-function
          Warn whenever a static function is declared but not defined or a
          non-inline static function is unused.  This warning is enabled by
          -Wall.

      -Wunused-label
          Warn whenever a label is declared but not used.  This warning is
          enabled by -Wall.

          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.  This warning is enabled by
          -Wall.

          To suppress this warning use the unused attribute.

      -Wunused-value
          Warn whenever a statement computes a result that is explicitly not
          used.  This warning is enabled by -Wall.

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

          These warnings are possible only in optimizing compilation,



                                   - 43 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          because they require data flow information that is computed only
          when optimizing.  If you do not specify -O, you will not get these
          warnings. Instead, GCC will issue a warning about -Wuninitialized
          requiring -O.

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

          These warnings occur for individual uninitialized or clobbered
          elements of structure, union or array variables as well as for
          variables which are uninitialized or clobbered as a whole.  They
          do not occur for variables or elements declared "volatile".
          Because these warnings depend on optimization, the exact variables
          or elements for which there are warnings will depend on the
          precise optimization options and version of GCC used.

          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:









                                   - 44 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

          The compiler sees only the calls to "setjmp".  It 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".

          This warning is enabled by -Wall.

      -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.

      -Wno-pragmas
          Do not warn about misuses of pragmas, such as incorrect
          parameters, invalid syntax, or conflicts between pragmas.  See
          also -Wunknown-pragmas.

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

      -Wstrict-aliasing=2
          This option is only active when -fstrict-aliasing is active.  It
          warns about code which might break the strict aliasing rules that
          the compiler is using for optimization.  This warning catches more
          cases than -Wstrict-aliasing, but it will also give a warning for
          some ambiguous cases that are safe.



                                   - 45 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -Wstrict-overflow
      -Wstrict-overflow=n
          This option is only active when -fstrict-overflow is active.  It
          warns about cases where the compiler optimizes based on the
          assumption that signed overflow does not occur.  Note that it does
          not warn about all cases where the code might overflow: it only
          warns about cases where the compiler implements some optimization.
          Thus this warning depends on the optimization level.

          An optimization which assumes that signed overflow does not occur
          is perfectly safe if the values of the variables involved are such
          that overflow never does, in fact, occur.  Therefore this warning
          can easily give a false positive: a warning about code which is
          not actually a problem.  To help focus on important issues,
          several warning levels are defined.  No warnings are issued for
          the use of undefined signed overflow when estimating how many
          iterations a loop will require, in particular when determining
          whether a loop will be executed at all.

          -Wstrict-overflow=1
              Warn about cases which are both questionable and easy to
              avoid.  For example: "x + 1 > x"; with -fstrict-overflow, the
              compiler will simplify this to 1.  This level of
              -Wstrict-overflow is enabled by -Wall; higher levels are not,
              and must be explicitly requested.

          -Wstrict-overflow=2
              Also warn about other cases where a comparison is simplified
              to a constant.  For example: "abs (x) >= 0".  This can only be
              simplified when -fstrict-overflow is in effect, because "abs
              (INT_MIN)" overflows to "INT_MIN", which is less than zero.
              -Wstrict-overflow (with no level) is the same as
              -Wstrict-overflow=2.

          -Wstrict-overflow=3
              Also warn about other cases where a comparison is simplified.
              For example: "x + 1 > 1" will be simplified to "x > 0".

          -Wstrict-overflow=4
              Also warn about other simplifications not covered by the above
              cases.  For example: "(x * 10) / 5" will be simplified to "x *
              2".

          -Wstrict-overflow=5
              Also warn about cases where the compiler reduces the magnitude
              of a constant involved in a comparison.  For example: "x + 2 >
              y" will be simplified to "x + 1 >= y".  This is reported only
              at the highest warning level because this simplification
              applies to many comparisons, so this warning level will give a



                                   - 46 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              very large number of false positives.

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

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

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

          *   A comparison between signed and unsigned values could produce



                                   - 47 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              an incorrect result when the signed value is converted to
              unsigned.  (But don't warn if -Wno-sign-compare is also
              specified.)

          *   An aggregate has an initializer which does not initialize all
              members.  This warning can be independently controlled by
              -Wmissing-field-initializers.

          *   An initialized field without side effects is overridden when
              using designated initializers.  This warning can be
              independently controlled by -Woverride-init.

          *   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.

          *<(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 constructors.

          *<(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



                                   - 48 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 output harder to read.  Using this
          command line option tells GCC to emit warnings from system headers
          as if they occurred in user code.  However, note that using -Wall
          in conjunction with this option will not warn about unknown
          pragmas in system headers---for that, -Wunknown-pragmas must also
          be used.

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

          The idea behind this is that sometimes it is convenient (for the
          programmer) to consider floating-point values as approximations to
          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 problematic constructs which
          should be avoided.

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

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




                                   - 49 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          *   A function-like macro that appears without arguments.

          *   The unary plus operator.

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

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

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

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

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

          *   Usage of ISO string concatenation is detected.

          *   Initialization of automatic aggregates.

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

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

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

          *   Use of ISO C style function definitions.  This warning
              intentionally is not issued for prototype declarations or



                                   - 50 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              variadic functions because these ISO C features will appear in
              your code when using libiberty's traditional C compatibility
              macros, "PARAMS" and "VPARAMS".  This warning is also bypassed
              for nested functions because that feature is already a GCC
              extension and thus not relevant to traditional C
              compatibility.

      -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.

      -Wno-endif-labels
          Do not 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.

      -Wunsafe-loop-optimizations
          Warn if the loop cannot be optimized because the compiler could
          not assume anything on the bounds of the loop indices.  With
          -funsafe-loop-optimizations warn if the compiler made such
          assumptions.

      -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 *".

      -Wc++-compat
          Warn about ISO C constructs that are outside of the common subset
          of ISO C and ISO C++, e.g. request for implicit conversion from
          "void *" to a pointer to non-"void" type.

      -Wcast-qual



                                   - 51 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -Wwrite-strings
          When compiling C, give string constants the type "const
          char[length]" so that copying the address of one into a
          non-"const" "char *" pointer will get a warning; when compiling
          C++, warn about the deprecated conversion from string literals to
          "char *".  This warning, by default, is enabled for C++ programs.
          These warnings will help you find at compile time code that can
          try to write into a string constant, but only if you have been
          very careful about using "const" in 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 conversions changing the width or signedness
          of a fixed point argument except when the same as the default
          promotion.

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

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

      -Waddress
          Warn about suspicious uses of memory addresses. These include
          using the address of a function in a conditional expression, such
          as "void func(void); if (func)", and comparisons against the
          memory address of a string literal, such as "if (x == "abc")".
          Such uses typically indicate a programmer error: the address of a
          function always evaluates to true, so their use in a conditional



                                   - 52 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          usually indicate that the programmer forgot the parentheses in a
          function call; and comparisons against string literals result in
          unspecified behavior and are not portable in C, so they usually
          indicate that the programmer intended to use "strcmp".  This
          warning is enabled by -Wall.

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

      -Wno-attributes
          Do not warn if an unexpected "__attribute__" is used, such as
          unrecognized attributes, function attributes applied to variables,
          etc.  This will not stop errors for incorrect use of supported
          attributes.

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

      -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 provides 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 missing.  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 warning:



                                   - 53 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          This warning is included in -Wextra.  To get other -Wextra
          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 candidates, not absolute
          ones.  Care should be taken to manually verify functions actually
          do not ever return before adding the "noreturn" attribute,
          otherwise subtle code generation bugs could be introduced.  You
          will not get a warning for "main" in hosted C environments.

      -Wmissing-format-attribute
          Warn about function pointers which might be candidates for
          "format" attributes.  Note these are only possible candidates, not
          absolute ones.  GCC will guess that function pointers with
          "format" attributes that are used in assignment, initialization,
          parameter passing or return statements should have a corresponding
          "format" attribute in the resulting type.  I.e. the left-hand side
          of the assignment or initialization, the type of the parameter
          variable, or the return type of the containing function
          respectively should also have a "format" attribute to avoid the
          warning.

          GCC will also warn about function definitions which might be
          candidates for "format" attributes.  Again, these are only
          possible candidates.  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.

      -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.

      -Wnormalized=<none|id|nfc|nfkc>
          In ISO C and ISO C++, two identifiers are different if they are
          different sequences of characters.  However, sometimes when
          characters outside the basic ASCII character set are used, you can
          have two different character sequences that look the same.  To
          avoid confusion, the ISO 10646 standard sets out some
          normalization rules which when applied ensure that two sequences
          that look the same are turned into the same sequence.  GCC can



                                   - 54 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          warn you if you are using identifiers which have not been
          normalized; this option controls that warning.

          There are four levels of warning that GCC supports.  The default
          is -Wnormalized=nfc, which warns about any identifier which is not
          in the ISO 10646 "C" normalized form, NFC.  NFC is the recommended
          form for most uses.

          Unfortunately, there are some characters which ISO C and ISO C++
          allow in identifiers that when turned into NFC aren't allowable as
          identifiers.  That is, there's no way to use these symbols in
          portable ISO C or C++ and have all your identifiers in NFC.
          -Wnormalized=id suppresses the warning for these characters.  It
          is hoped that future versions of the standards involved will
          correct this, which is why this option is not the default.

          You can switch the warning off for all characters by writing
          -Wnormalized=none.  You would only want to do this if you were
          using some other normalization scheme (like "D"), because
          otherwise you can easily create bugs that are literally impossible
          to see.

          Some characters in ISO 10646 have distinct meanings but look
          identical in some fonts or display methodologies, especially once
          formatting has been applied.  For instance "\u207F", "SUPERSCRIPT
          LATIN SMALL LETTER N", will display just like a regular "n" which
          has been placed in a superscript.  ISO 10646 defines the NFKC
          normalization scheme to convert all these into a standard form as
          well, and GCC will warn if your code is not in NFKC if you use
          -Wnormalized=nfkc.  This warning is comparable to warning about
          every identifier that contains the letter O because it might be
          confused with the digit 0, and so is not the default, but may be
          useful as a local coding convention if the programming environment
          is unable to be fixed to display these characters distinctly.

      -Wno-deprecated-declarations
          Do not warn about uses of functions, variables, and types marked
          as deprecated by using the "deprecated" attribute.

      -Wno-overflow
          Do not warn about compile-time overflow in constant expressions.

      -Woverride-init
          Warn if an initialized field without side effects is overridden
          when using designated initializers.

          This warning is included in -Wextra.  To get other -Wextra
          warnings without this one, use -Wextra -Wno-override-init.




                                   - 55 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

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

          This option is not made part of -Wall because in a debugging



                                   - 56 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          version of a program there is often substantial code which checks
          correct functioning of the program and is, hopefully, unreachable
          because the program does work.  Another common use of unreachable
          code is to provide behavior which is selectable at compile-time.

      -Winline
          Warn if a function can not be inlined and it was declared as
          inline.  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 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 existing C++ implementations,
          however, offsetof typically gives meaningful results even when
          applied to certain 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 deliberately chosen to
          ignore the warning about it.

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

      -Wno-int-to-pointer-cast (C only)
          Suppress warnings from casts to pointer type of an integer of a
          different size.

      -Wno-pointer-to-int-cast (C only)
          Suppress warnings from casts from a pointer to an integer type of
          a different size.

      -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.



                                   - 57 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -Wvariadic-macros
          Warn if variadic macros are used in pedantic ISO C90 mode, or the
          GNU alternate syntax when in pedantic ISO C99 mode.  This is
          default.  To inhibit the warning messages, use
          -Wno-variadic-macros.

      -Wvolatile-register-var
          Warn if a register variable is declared volatile.  The volatile
          modifier does not inhibit all optimizations that may eliminate
          reads and/or writes to register variables.

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

      -Wpointer-sign
          Warn for pointer argument passing or assignment with different
          signedness.  This option is only supported for C and Objective-C.
          It is implied by -Wall and by -pedantic, which can be disabled
          with -Wno-pointer-sign.

      -Werror
          Make all warnings into errors.

      -Werror=
          Make the specified warning into an errors.  The specifier for a
          warning is appended, for example -Werror=switch turns the warnings
          controlled by -Wswitch into errors.  This switch takes a negative
          form, to be used to negate -Werror for specific warnings, for
          example -Wno-error=switch makes -Wswitch warnings not be errors,
          even when -Werror is in effect.  You can use the
          -fdiagnostics-show-option option to have each controllable warning
          amended with the option which controls it, to determine what to
          use with this option.

          Note that specifying -Werror=foo automatically implies -Wfoo.
          However, -Wno-error=foo does not imply anything.

      -Wstack-protector
          This option is only active when -fstack-protector is active.  It
          warns about functions that will not be protected against stack
          smashing.

      -Woverlength-strings



                                   - 58 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Warn about string constants which are longer than the "minimum
          maximum" length specified in the C standard.  Modern compilers
          generally allow string constants which are much longer than the
          standard's minimum limit, but very portable programs should avoid
          using longer strings.

          The limit applies after string constant concatenation, and does
          not count the trailing NUL.  In C89, the limit was 509 characters;
          in C99, it was raised to 4095.  C++98 does not specify a normative
          minimum maximum, so we do not diagnose overlength strings in C++.

          This option is implied by -pedantic, and can be disabled with
          -Wno-overlength-strings.

      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 2).  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).

          GCC allows you to use -g with -O.  The shortcuts taken by
          optimized code may occasionally produce surprising results: some
          variables you declared may not exist at all; flow of control may
          briefly move where you did not expect it; some statements may not
          be executed because they compute constant results or their values
          were already at hand; some statements may execute in different
          places because they were moved out of loops.

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

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

      -ggdb
          Produce debugging information for use by GDB.  This means to use
          the most expressive format available (DWARF 2, stabs, or the



                                   - 59 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          native format if neither of those are supported), including GDB
          extensions if at all possible.

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

      -femit-class-debug-always
          Instead of emitting debugging information for a C++ class in only
          one object file, emit it in all object files using the class.
          This option should be used only with debuggers that are unable to
          handle the way GCC normally emits debugging information for
          classes because using this option will increase the size of
          debugging information by as much as a factor of two.

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

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

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

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

      -gdwarf-2
          Produce debugging information in DWARF version 2 format (if that



                                   - 60 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          is supported).  This is the format used by DBX on IRIX 6.  With
          this option, GCC uses features of DWARF version 3 when they are
          useful; version 3 is upward compatible with version 2, but may
          still cause problems for older debuggers.

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

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

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

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

          -gdwarf-2 does not accept a concatenated debug level, because GCC
          used to support an option -gdwarf that meant to generate debug
          information in version 1 of the DWARF format (which is very
          different from version 2), and it would have been too confusing.
          That debug format is long obsolete, but the option cannot be
          changed now.  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 information with -gdwarf-2.

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

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



                                   - 61 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

      --coverage
          This option is used to compile and link code instrumented for
          coverage analysis.  The option is a synonym for -fprofile-arcs
          -ftest-coverage (when compiling) and -lgcov (when linking).  See
          the documentation for those options for more details.

          *   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.

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

          *   Run the program on a representative workload to generate 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 happen).

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



                                   - 62 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          *   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 spanning 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 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
      -fdump-rtl-pass
          Says to make debugging dumps during compilation at times specified
          by letters.    This is used for debugging the RTL-based passes of
          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.

          Most debug dumps can be enabled either passing a letter to the -d
          option, or with a long -fdump-rtl switch; here are the possible
          letters for use in letters and pass, and their meanings:

          -dA Annotate the assembler output with miscellaneous debugging
              information.

          -dB
          -fdump-rtl-bbro
              Dump after block reordering, to file.148r.bbro.

          -dc
          -fdump-rtl-combine
              Dump after instruction combination, to the file
              file.129r.combine.

          -dC
          -fdump-rtl-ce1



                                   - 63 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -fdump-rtl-ce2
              -dC and -fdump-rtl-ce1 enable dumping after the first if
              conversion, to the file file.117r.ce1.  -dC and -fdump-rtl-ce2
              enable dumping after the second if conversion, to the file
              file.130r.ce2.

          -dd
          -fdump-rtl-btl
          -fdump-rtl-dbr
              -dd and -fdump-rtl-btl enable dumping after branch target load
              optimization, to file.31.btl.  -dd and -fdump-rtl-dbr enable
              dumping after delayed branch scheduling, to file.36.dbr.

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

          -dE
          -fdump-rtl-ce3
              Dump after the third if conversion, to file.146r.ce3.

          -df
          -fdump-rtl-cfg
          -fdump-rtl-life
              -df and -fdump-rtl-cfg enable dumping after control and data
              flow analysis, to file.116r.cfg.  -df and -fdump-rtl-cfg
              enable dumping dump after life analysis, to file.128r.life1
              and file.135r.life2.

          -dg
          -fdump-rtl-greg
              Dump after global register allocation, to file.139r.greg.

          -dG
          -fdump-rtl-gcse
          -fdump-rtl-bypass
              -dG and -fdump-rtl-gcse enable dumping after GCSE, to
              file.114r.gcse.  -dG and -fdump-rtl-bypass enable dumping
              after jump bypassing and control flow optimizations, to
              file.115r.bypass.

          -dh
          -fdump-rtl-eh
              Dump after finalization of EH handling code, to file.02.eh.

          -di
          -fdump-rtl-sibling
              Dump after sibling call optimizations, to file.106r.sibling.

          -dj



                                   - 64 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -fdump-rtl-jump
              Dump after the first jump optimization, to file.112r.jump.

          -dk
          -fdump-rtl-stack
              Dump after conversion from registers to stack, to
              file.152r.stack.

          -dl
          -fdump-rtl-lreg
              Dump after local register allocation, to file.138r.lreg.

          -dL
          -fdump-rtl-loop2
              -dL and -fdump-rtl-loop2 enable dumping after the loop
              optimization pass, to file.119r.loop2, file.120r.loop2_init,
              file.121r.loop2_invariant, and file.125r.loop2_done.

          -dm
          -fdump-rtl-sms
              Dump after modulo scheduling, to file.136r.sms.

          -dM
          -fdump-rtl-mach
              Dump after performing the machine dependent reorganization
              pass, to file.155r.mach.

          -dn
          -fdump-rtl-rnreg
              Dump after register renumbering, to file.147r.rnreg.

          -dN
          -fdump-rtl-regmove
              Dump after the register move pass, to file.132r.regmove.

          -do
          -fdump-rtl-postreload
              Dump after post-reload optimizations, to file.24.postreload.

          -dr
          -fdump-rtl-expand
              Dump after RTL generation, to file.104r.expand.

          -dR
          -fdump-rtl-sched2
              Dump after the second scheduling pass, to file.150r.sched2.

          -ds
          -fdump-rtl-cse



                                   - 65 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              Dump after CSE (including the jump optimization that sometimes
              follows CSE), to file.113r.cse.

          -dS
          -fdump-rtl-sched
              Dump after the first scheduling pass, to file.21.sched.

          -dt
          -fdump-rtl-cse2
              Dump after the second CSE pass (including the jump
              optimization that sometimes follows CSE), to file.127r.cse2.

          -dT
          -fdump-rtl-tracer
              Dump after running tracer, to file.118r.tracer.

          -dV
          -fdump-rtl-vpt
          -fdump-rtl-vartrack
              -dV and -fdump-rtl-vpt enable dumping after the value profile
              transformations, to file.10.vpt.  -dV and -fdump-rtl-vartrack
              enable dumping after variable tracking, to file.154r.vartrack.

          -dw
          -fdump-rtl-flow2
              Dump after the second flow pass, to file.142r.flow2.

          -dz
          -fdump-rtl-peephole2
              Dump after the peephole pass, to file.145r.peephole2.

          -dZ
          -fdump-rtl-web
              Dump after live range splitting, to file.126r.web.

          -da
          -fdump-rtl-all
              Produce all the dumps listed above.

          -dH Produce a core dump whenever an error occurs.

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

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

          -dP Dump the RTL in the assembler output as a comment before each



                                   - 66 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              instruction.  Also turns on -dp annotation.

          -dv For each of the other indicated dump files (either with -d or
              -fdump-rtl-pass), dump a representation of the control flow
              graph suitable for viewing with VCG to file.pass.vcg.

          -dx Just generate RTL for a function instead of compiling it.
              Usually used with r (-fdump-rtl-expand).

          -dy Dump debugging information during parsing, to standard error.

      -fdump-noaddr
          When doing debugging dumps (see -d option above), suppress address
          output.  This makes it more feasible to use diff on debugging
          dumps for compiler invocations with different compiler binaries
          and/or different text / bss / data / heap / stack / dso start
          locations.

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

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

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

      -fdump-ipa-switch
          Control the dumping at various stages of inter-procedural analysis
          language tree to a file.  The file name is generated by appending
          a switch specific suffix to the source file name.  The following
          dumps are possible:

          all Enables all inter-procedural analysis dumps; currently the
              only produced dump is the cgraph dump.



                                   - 67 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          cgraph
              Dumps information about call-graph optimization, unused
              function removal, and inlining decisions.

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

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

          slim
              Inhibit dumping of members of a scope or body of a function
              merely because that scope has been reached.  Only dump such
              items when they are directly reachable by some other path.
              When dumping pretty-printed trees, this option inhibits
              dumping the bodies of control structures.

          raw Print a raw representation of the tree.  By default, trees are
              pretty-printed into a C-like representation.

          details
              Enable more detailed dumps (not honored by every dump option).

          stats
              Enable dumping various statistics about the pass (not honored
              by every dump option).

          blocks
              Enable showing basic block boundaries (disabled in raw dumps).

          vops
              Enable showing virtual operands for every statement.

          lineno
              Enable showing line numbers for statements.

          uid Enable showing the unique ID ("DECL_UID") for each variable.

          all Turn on all options, except raw, slim and lineno.



                                   - 68 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

          gimple
              Dump each function before and after the gimplification pass to
              a file.  The file name is made by appending .gimple to the
              source file name.

          cfg Dump the control flow graph of each function to a file.  The
              file name is made by appending .cfg to the source file name.

          vcg Dump the control flow graph of each function to a file in VCG
              format.  The file name is made by appending .vcg to the source
              file name.  Note that if the file contains more than one
              function, the generated file cannot be used directly by VCG.
              You will need to cut and paste each function's graph into its
              own separate file first.

          ch  Dump each function after copying loop headers.  The file name
              is made by appending .ch to the source file name.

          ssa Dump SSA related information to a file.  The file name is made
              by appending .ssa to the source file name.

          salias
              Dump structure aliasing variable information to a file.  This
              file name is made by appending .salias to the source file
              name.

          alias
              Dump aliasing information for each function.  The file name is
              made by appending .alias to the source file name.

          ccp Dump each function after CCP.  The file name is made by
              appending .ccp to the source file name.

          storeccp
              Dump each function after STORE-CCP.  The file name is made by
              appending .storeccp to the source file name.

          pre Dump trees after partial redundancy elimination.  The file



                                   - 69 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              name is made by appending .pre to the source file name.

          fre Dump trees after full redundancy elimination.  The file name
              is made by appending .fre to the source file name.

          copyprop
              Dump trees after copy propagation.  The file name is made by
              appending .copyprop to the source file name.

          store_copyprop
              Dump trees after store copy-propagation.  The file name is
              made by appending .store_copyprop to the source file name.

          dce Dump each function after dead code elimination.  The file name
              is made by appending .dce to the source file name.

          mudflap
              Dump each function after adding mudflap instrumentation.  The
              file name is made by appending .mudflap to the source file
              name.

          sra Dump each function after performing scalar replacement of
              aggregates.  The file name is made by appending .sra to the
              source file name.

          sink
              Dump each function after performing code sinking.  The file
              name is made by appending .sink to the source file name.

          dom Dump each function after applying dominator tree
              optimizations.  The file name is made by appending .dom to the
              source file name.

          dse Dump each function after applying dead store elimination.  The
              file name is made by appending .dse to the source file name.

          phiopt
              Dump each function after optimizing PHI nodes into
              straightline code.  The file name is made by appending .phiopt
              to the source file name.

          forwprop
              Dump each function after forward propagating single use
              variables.  The file name is made by appending .forwprop to
              the source file name.

          copyrename
              Dump each function after applying the copy rename
              optimization.  The file name is made by appending .copyrename



                                   - 70 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              to the source file name.

          nrv Dump each function after applying the named return value
              optimization on generic trees.  The file name is made by
              appending .nrv to the source file name.

          vect
              Dump each function after applying vectorization of loops.  The
              file name is made by appending .vect to the source file name.

          vrp Dump each function after Value Range Propagation (VRP).  The
              file name is made by appending .vrp to the source file name.

          all Enable all the available tree dumps with the flags provided in
              this option.

      -ftree-vectorizer-verbose=n
          This option controls the amount of debugging output the vectorizer
          prints.  This information is written to standard error, unless
          -fdump-tree-all or -fdump-tree-vect is specified, in which case it
          is output to the usual dump listing file, .vect.  For n=0 no
          diagnostic information is reported.  If n=1 the vectorizer reports
          each loop that got vectorized, and the total number of loops that
          got vectorized.  If n=2 the vectorizer also reports non-vectorized
          loops that passed the first analysis phase
          (vect_analyze_loop_form) - i.e. countable, inner-most, single-bb,
          single-entry/exit loops.  This is the same verbosity level that
          -fdump-tree-vect-stats uses.  Higher verbosity levels mean either
          more information dumped for each reported loop, or same amount of
          information reported for more loops: If n=3, alignment related
          information is added to the reports.  If n=4, data-references
          related information (e.g. memory dependences, memory
          access-patterns) is added to the reports.  If n=5, the vectorizer
          reports also non-vectorized inner-most loops that did not pass the
          first analysis phase (i.e. may not be countable, or may have
          complicated control-flow).  If n=6, the vectorizer reports also
          non-vectorized nested loops.  For n=7, all the information the
          vectorizer generates during its analysis and transformation is
          reported.  This is the same verbosity level that
          -fdump-tree-vect-details uses.

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




                                   - 71 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          The string should be different for every file you compile.

      -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 output to the usual dump listing
          file, .sched or .sched2 respectively.  However for n greater than
          nine, the output is always printed to standard error.

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

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

          When used in combination with the -x command line option,
          -save-temps is sensible enough to avoid over writing an input
          source file with the same extension as an intermediate file.  The
          corresponding intermediate file may be obtained by renaming the
          source file before using -save-temps.

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

                  # cc1 0.12 0.01
                  # as 0.00 0.01

          The first number on each line is the "user time", that is time
          spent executing the program itself.  The second number is "system
          time", time spent executing operating system routines on behalf of
          the program.  Both numbers are in seconds.

      -fvar-tracking
          Run variable tracking pass.  It computes where variables are
          stored at each position in code.  Better debugging information is
          then generated (if the debugging information format supports this



                                   - 72 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          information).

          It is enabled by default when compiling with optimization (-Os,
          -O, -O2, ...), debugging information (-g) and the debug info
          format supports it.

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

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

      -print-multi-lib
          Print the mapping from multilib directory names to compiler
          switches that enable them.  The directory name is separated from
          the switches by ;, and each switch starts with an @} instead of
          the @samp{-, without spaces between multiple switches.  This is
          supposed to ease shell-processing.

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

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

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

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          i686-pc-linux-gnu)---and don't do anything else.

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

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

      -feliminate-unused-debug-types
          Normally, when producing DWARF2 output, GCC will emit debugging
          information for all types declared in a compilation unit,
          regardless of whether or not they are actually 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 program (but is declared).  More often, however, this
          results in a significant amount of wasted space.  With this
          option, GCC will avoid producing debug symbol output 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 program.

      The compiler performs optimization based on the knowledge it has of
      the program.  Optimization levels -O and above, in particular, enable
      unit-at-a-time mode, which allows 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 in unit-at-
      a-time mode allows 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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

          -O turns on the following optimization flags: -fdefer-pop
          -fdelayed-branch -fguess-branch-probability -fcprop-registers
          -fif-conversion -fif-conversion2 -ftree-ccp -ftree-dce
          -ftree-dominator-opts -ftree-dse -ftree-ter -ftree-lrs -ftree-sra
          -ftree-copyrename -ftree-fre -ftree-ch -funit-at-a-time
          -fmerge-constants

          -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 tradeoff.  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.

          -O2 turns on all optimization flags specified by -O.  It also
          turns on the following optimization flags: -fthread-jumps
          -fcrossjumping -foptimize-sibling-calls -fcse-follow-jumps
          -fcse-skip-blocks -fgcse  -fgcse-lm -fexpensive-optimizations
          -frerun-cse-after-loop -fcaller-saves -fpeephole2 -fschedule-insns
          -fschedule-insns2 -fsched-interblock  -fsched-spec -fregmove
          -fstrict-aliasing -fstrict-overflow -fdelete-null-pointer-checks
          -freorder-blocks  -freorder-functions -falign-functions
          -falign-jumps -falign-loops  -falign-labels -ftree-vrp -ftree-pre

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

          -O2 doesn't turn on -ftree-vrp for the Ada compiler.  This option
          must be explicitly specified on the command line to be enabled for
          the Ada compiler.

      -O3 Optimize yet more.  -O3 turns on all optimizations specified by
          -O2 and also turns on the -finline-functions, -funswitch-loops and
          -fgcse-after-reload options.

      -O0 Do not optimize.  This is the default.

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -Os disables the following optimization flags: -falign-functions
          -falign-jumps  -falign-loops -falign-labels  -freorder-blocks
          -freorder-blocks-and-partition -fprefetch-loop-arrays
          -ftree-vect-loop-version

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

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

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

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

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

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

      -fforce-mem
          Force memory operands to be copied into registers before doing
          arithmetic on them.  This produces better code by making all
          memory references potential common subexpressions.  When they are
          not common subexpressions, instruction combination should
          eliminate the separate register-load. This option is now a nop and
          will be removed in 4.3.

      -fforce-addr
          Force memory address constants to be copied into registers before
          doing arithmetic on them.

      -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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          restore frame pointers; it also makes an extra register available
          in many functions.  It also makes debugging impossible on some
          machines.

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

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

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

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

      -fno-inline
          Don't pay attention to the "inline" keyword.  Normally this option
          is used to keep the compiler from expanding any functions inline.
          Note that if you are not optimizing, no functions can be expanded
          inline.

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

          If all calls to a given function are integrated, and the function
          is declared "static", then the function is normally not output as
          assembler code in its own right.

          Enabled at level -O3.

      -finline-functions-called-once
          Consider all "static" functions called once for inlining into
          their caller even if they are not marked "inline".  If a call to a
          given function is integrated, then the function is not output as
          assembler code in its own right.

          Enabled if -funit-at-a-time is enabled.

      -fearly-inlining
          Inline functions marked by "always_inline" and functions whose
          body seems smaller than the function call overhead early before
          doing -fprofile-generate instrumentation and real inlining pass.
          Doing so makes profiling significantly cheaper and usually
          inlining faster on programs having large chains of nested wrapper
          functions.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Enabled by default.

      -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 consumption.  Decreasing usually
          makes the compilation faster and less code will be inlined (which
          presumably means slower programs).  This option is particularly
          useful for programs that use inlining heavily such as those based
          on recursive templates with C++.

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

          max-inline-insns-single
               is set to I<n>/2.

          max-inline-insns-auto
               is set to I<n>/2.

          min-inline-insns
               is set to 130 or I<n>/4, whichever is smaller.

          max-inline-insns-rtl
               is set to I<n>.

          See below for a documentation of the individual parameters
          controlling inlining.

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

      -fkeep-inline-functions
          In C, emit "static" functions that are declared "inline" into the
          object file, even if the function has been inlined into all of its
          callers.  This switch does not affect functions using the "extern
          inline" extension in GNU C.  In C++, emit any and all inline
          functions into the object file.

      -fkeep-static-consts
          Emit variables declared "static const" when optimization isn't



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          turned on, even if the variables aren't referenced.

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

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

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

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

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

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

      -fmodulo-sched
          Perform swing modulo scheduling immediately before the first
          scheduling pass.  This pass looks at innermost loops and reorders
          their instructions by overlapping different iterations.

      -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.

      -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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          optimizations performed when this option is not used.

          The default is -ffunction-cse

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

          This option turns off this behavior because some programs
          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 assumptions based on that.

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

      -fmudflap -fmudflapth -fmudflapir
          For front-ends that support it (C and C++), instrument all risky
          pointer/array dereferencing operations, some standard library
          string/heap functions, and some other associated constructs with
          range/validity tests.  Modules so instrumented should be immune to
          buffer overflows, invalid heap use, and some other classes of
          C/C++ programming errors.  The instrumentation relies on a
          separate runtime library (libmudflap), which will be linked into a
          program if -fmudflap is given at link time.  Run-time behavior of
          the instrumented program is controlled by the MUDFLAP_OPTIONS
          environment variable.  See "env MUDFLAP_OPTIONS=-help a.out" for
          its options.

          Use -fmudflapth instead of -fmudflap to compile and to link if
          your program is multi-threaded.  Use -fmudflapir, in addition to
          -fmudflap or -fmudflapth, if instrumentation should ignore pointer
          reads.  This produces less instrumentation (and therefore faster
          execution) and still provides some protection against outright
          memory corrupting writes, but allows erroneously read data to
          propagate within a program.

      -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 -O2, -O3, -Os.

      -fcse-follow-jumps
          In common subexpression elimination, scan through jump



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

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

          Note: When compiling a program using computed gotos, a GCC
          extension, you may get better runtime performance if you disable
          the global common subexpression 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.

          Not enabled at any optimization level.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          Not enabled at any optimization level.

      -fgcse-after-reload
          When -fgcse-after-reload is enabled, a redundant load elimination
          pass is performed after reload.  The purpose of this pass is to
          cleanup redundant spilling.

      -funsafe-loop-optimizations
          If given, the loop optimizer will assume that loop indices do not
          overflow, and that the loops with nontrivial exit condition are
          not infinite.  This enables a wider range of loop optimizations
          even if the loop optimizer itself cannot prove that these
          assumptions are valid.  Using -Wunsafe-loop-optimizations, the
          compiler will warn you if it finds this kind of loop.

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          can safely dereference null pointers.  Use
          -fno-delete-null-pointer-checks to disable this optimization for
          programs which depend on that behavior.

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

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

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

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

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

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

      -fdelayed-branch
          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 instructions by allowing other instructions
          to be issued until the result of the load or floating point
          instruction is required.

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

      -fschedule-insns2
          Similar to -fschedule-insns, but requests an 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.



                                   - 83 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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
      -fsched-stalled-insns=n
          Define how many insns (if any) can be moved prematurely from the
          queue of stalled insns into the ready list, during the second
          scheduling pass.  -fno-fsched-stalled-insns and
          -fsched-stalled-insns=0 are equivalent and mean that no insns will
          be moved prematurely.  If n is unspecified then there is no limit
          on how many queued insns can be moved prematurely.

      -fsched-stalled-insns-dep
      -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.  This has an effect only
          during the second scheduling pass, and only if
          -fsched-stalled-insns is used and its value is not zero.
          -fno-sched-stalled-insns-dep is equivalent to
          -fsched-stalled-insns-dep=0.  -fsched-stalled-insns-dep without a
          value is equivalent to -fsched-stalled-insns-dep=1.

      -fsched2-use-superblocks
          When scheduling after register allocation, do use superblock
          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,



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -fsee
          Eliminates redundant extension instructions and move the non
          redundant ones to optimal placement using LCM.

      -freschedule-modulo-scheduled-loops
          The modulo scheduling comes before the traditional scheduling, if
          a loop was modulo scheduled we may want to prevent the later
          scheduling passes from changing its schedule, we use this option
          to control that.

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

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

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

      -ftree-pre
          Perform Partial Redundancy Elimination (PRE) on trees.  This flag
          is enabled by default at -O2 and -O3.

      -ftree-fre
          Perform Full Redundancy Elimination (FRE) on trees.  The
          difference between FRE and PRE is that FRE only considers
          expressions that are computed on all paths leading to the
          redundant computation.  This analysis faster than PRE, though it
          exposes fewer redundancies.  This flag is enabled by default at -O
          and higher.




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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -ftree-copy-prop
          Perform copy propagation on trees.  This pass eliminates
          unnecessary copy operations.  This flag is enabled by default at
          -O and higher.

      -ftree-store-copy-prop
          Perform copy propagation of memory loads and stores.  This pass
          eliminates unnecessary copy operations in memory references
          (structures, global variables, arrays, etc).  This flag is enabled
          by default at -O2 and higher.

      -ftree-salias
          Perform structural alias analysis on trees.  This flag is enabled
          by default at -O and higher.

      -fipa-pta
          Perform interprocedural pointer analysis.

      -ftree-sink
          Perform forward store motion  on trees.  This flag is enabled by
          default at -O and higher.

      -ftree-ccp
          Perform sparse conditional constant propagation (CCP) on trees.
          This pass only operates on local scalar variables and is enabled
          by default at -O and higher.

      -ftree-store-ccp
          Perform sparse conditional constant propagation (CCP) on trees.
          This pass operates on both local scalar variables and memory
          stores and loads (global variables, structures, arrays, etc).
          This flag is enabled by default at -O2 and higher.

      -ftree-dce
          Perform dead code elimination (DCE) on trees.  This flag is
          enabled by default at -O and higher.

      -ftree-dominator-opts
          Perform a variety of simple scalar cleanups (constant/copy
          propagation, redundancy elimination, range propagation and
          expression simplification) based on a dominator tree traversal.
          This also performs jump threading (to reduce jumps to jumps). This
          flag is enabled by default at -O and higher.

      -ftree-ch
          Perform loop header copying on trees.  This is beneficial since it
          increases effectiveness of code motion optimizations.  It also
          saves one jump.  This flag is enabled by default at -O and higher.
          It is not enabled for -Os, since it usually increases code size.



                                   - 86 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -ftree-loop-optimize
          Perform loop optimizations on trees.  This flag is enabled by
          default at -O and higher.

      -ftree-loop-linear
          Perform linear loop transformations on tree.  This flag can
          improve cache performance and allow further loop optimizations to
          take place.

      -ftree-loop-im
          Perform loop invariant motion on trees.  This pass moves only
          invariants that would be hard to handle at RTL level (function
          calls, operations that expand to nontrivial sequences of insns).
          With -funswitch-loops it also moves operands of conditions that
          are invariant out of the loop, so that we can use just trivial
          invariantness analysis in loop unswitching.  The pass also
          includes store motion.

      -ftree-loop-ivcanon
          Create a canonical counter for number of iterations in the loop
          for that determining number of iterations requires complicated
          analysis.  Later optimizations then may determine the number
          easily.  Useful especially in connection with unrolling.

      -fivopts
          Perform induction variable optimizations (strength reduction,
          induction variable merging and induction variable elimination) on
          trees.

      -ftree-sra
          Perform scalar replacement of aggregates.  This pass replaces
          structure references with scalars to prevent committing structures
          to memory too early.  This flag is enabled by default at -O and
          higher.

      -ftree-copyrename
          Perform copy renaming on trees.  This pass attempts to rename
          compiler temporaries to other variables at copy locations, usually
          resulting in variable names which more closely resemble the
          original variables.  This flag is enabled by default at -O and
          higher.

      -ftree-ter
          Perform temporary expression replacement during the SSA->normal
          phase.  Single use/single def temporaries are replaced at their
          use location with their defining expression.  This results in
          non-GIMPLE code, but gives the expanders much more complex trees
          to work on resulting in better RTL generation.  This is enabled by
          default at -O and higher.



                                   - 87 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -ftree-lrs
          Perform live range splitting during the SSA->normal phase.
          Distinct live ranges of a variable are split into unique
          variables, allowing for better optimization later.  This is
          enabled by default at -O and higher.

      -ftree-vectorize
          Perform loop vectorization on trees.

      -ftree-vect-loop-version
          Perform loop versioning when doing loop vectorization on trees.
          When a loop appears to be vectorizable except that data alignment
          or data dependence cannot be determined at compile time then
          vectorized and non-vectorized versions of the loop are generated
          along with runtime checks for alignment or dependence to control
          which version is executed.  This option is enabled by default
          except at level -Os where it is disabled.

      -ftree-vrp
          Perform Value Range Propagation on trees.  This is similar to the
          constant propagation pass, but instead of values, ranges of values
          are propagated.  This allows the optimizers to remove unnecessary
          range checks like array bound checks and null pointer checks.
          This is enabled by default at -O2 and higher.  Null pointer check
          elimination is only done if -fdelete-null-pointer-checks is
          enabled.

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

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

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

      -fsplit-ivs-in-unroller
          Enables expressing of values of induction variables in later
          iterations of the unrolled loop using the value in the first
          iteration.  This breaks long dependency chains, thus improving
          efficiency of the scheduling passes.



                                   - 88 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Combination of -fweb and CSE is often sufficient to obtain the
          same effect.  However in cases the loop body is more complicated
          than a single basic block, this is not reliable.  It also does not
          work at all on some of the architectures due to restrictions in
          the CSE pass.

          This optimization is enabled by default.

      -fvariable-expansion-in-unroller
          With this option, the compiler will create multiple copies of some
          local variables when unrolling a loop which can result in superior
          code.

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

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

          Disabled at level -Os.

      -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 heuristics.

          GCC will use heuristics to guess branch probabilities if they are
          not provided by profiling feedback (-fprofile-arcs).  These
          heuristics are based on the control flow graph.  If some branch
          probabilities are specified by __builtin_expect, then the
          heuristics will be used to guess branch probabilities for the rest
          of the control flow graph, taking the __builtin_expect info into
          account.  The interactions between the heuristics and
          __builtin_expect can be complex, and in some cases, it may be
          useful to disable the heuristics so that the effects of
          __builtin_expect are easier to understand.

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



                                   - 89 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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-blocks-and-partition
          In addition to reordering basic blocks in the compiled function,
          in order to reduce number of taken branches, partitions hot and
          cold basic blocks into separate sections of the assembly and .o
          files, to improve paging and cache locality performance.

          This optimization is automatically turned off in the presence of
          exception handling, for linkonce sections, for functions with a
          user-defined section attribute and on any architecture that does
          not support named sections.

      -freorder-functions
          Reorder functions in the object file in order to improve code
          locality.  This is implemented by using special subsections
          ".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;
                  };






                                   - 90 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

          Every language that wishes to perform language-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 levels -O2, -O3, -Os.

      -fstrict-overflow
          Allow the compiler to assume strict signed overflow rules,
          depending on the language being compiled.  For C (and C++) this
          means that overflow when doing arithmetic with signed numbers is
          undefined, which means that the compiler may assume that it will
          not happen.  This permits various optimizations.  For example, the
          compiler will assume that an expression like "i + 10 > i" will
          always be true for signed "i".  This assumption is only valid if
          signed overflow is undefined, as the expression is false if "i +
          10" overflows when using twos complement arithmetic.  When this
          option is in effect any attempt to determine whether an operation
          on signed numbers will overflow must be written carefully to not
          actually involve overflow.

          See also the -fwrapv option.  Using -fwrapv means that signed
          overflow is fully defined: it wraps.  When -fwrapv is used, there
          is no difference between -fstrict-overflow and
          -fno-strict-overflow.  With -fwrapv certain types of overflow are
          permitted.  For example, if the compiler gets an overflow when
          doing arithmetic on constants, the overflowed value can still be
          used with -fwrapv, but not otherwise.



                                   - 91 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

      -falign-functions
      -falign-functions=n
          Align the start of functions to the next power-of-two greater than
          n, skipping up to n bytes.  For instance, -falign-functions=32
          aligns functions to the next 32-byte boundary, but
          -falign-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.

          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.



                                   - 92 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -funit-at-a-time
          Parse the whole compilation unit before starting to produce code.
          This allows some extra optimizations to take place but consumes
          more memory (in general).  There are some compatibility issues
          with unit-at-a-time mode:

          *   enabling unit-at-a-time mode may change the order in which
              functions, variables, and top-level "asm" statements are
              emitted, and will likely break code relying on some particular
              ordering.  The majority of such top-level "asm" statements,
              though, can be replaced by "section" attributes.  The fno-
              toplevel-reorder option may be used to keep the ordering used
              in the input file, at the cost of some optimizations.

          *   unit-at-a-time mode removes unreferenced static variables and
              functions.  This may result in undefined references when an
              "asm" statement refers directly to variables or functions that
              are otherwise unused.  In that case either the
              variable/function shall be listed as an operand of the "asm"
              statement operand or, in the case of top-level "asm"
              statements the attribute "used" shall be used on the
              declaration.

          *   Static functions now can use non-standard passing conventions
              that may break "asm" statements calling functions directly.
              Again, attribute "used" will prevent this behavior.

          As a temporary workaround, -fno-unit-at-a-time can be used, but
          this scheme may not be supported by future releases of GCC.

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

      -fno-toplevel-reorder



                                   - 93 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Do not reorder top-level functions, variables, and "asm"
          statements.  Output them in the same order that they appear in the
          input file.  When this option is used, unreferenced static
          variables will not be removed.  This option is intended to support
          existing code which relies on a particular ordering.  For new
          code, it is better to use attributes.

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

          Enabled by default with -funroll-loops.

      -fwhole-program
          Assume that the current compilation unit represents whole program
          being compiled.  All public functions and variables with the
          exception of "main" and those merged by attribute
          "externally_visible" become static functions and in a affect gets
          more aggressively optimized by interprocedural optimizers.  While
          this option is equivalent to proper use of "static" keyword for
          programs consisting of single file, in combination with option
          --combine this flag can be used to compile most of smaller scale C
          programs since the functions and variables become local for the
          whole combined compilation unit, not for the single source file
          itself.

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

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

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

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

      -fprofile-use
          Enable profile feedback directed optimizations, and optimizations



                                   - 94 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 floating point value is
          taken from a register or memory.

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

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

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

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

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

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

          The default is -fmath-errno.




                                   - 95 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          On Darwin systems, the math library never sets "errno".  There is
          therefore no reason for the compiler to consider the possibility
          that it might, and -fno-math-errno is the default.

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

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

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

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

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

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

      -fno-trapping-math
          Compile code assuming that floating-point operations cannot
          generate user-visible traps.  These traps include division by
          zero, overflow, underflow, inexact result and invalid operation.
          This option implies -fno-signaling-nans.  Setting this option may
          allow faster code if one relies on "non-stop" IEEE 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 conversions, and round-to-nearest for
          all other arithmetic truncations.  This option should be specified
          for programs that change the FP rounding mode dynamically, or that



                                   - 96 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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".

      -frtl-abstract-sequences
          It is a size optimization method. This option is to find identical
          sequences of code, which can be turned into pseudo-procedures  and
          then  replace  all  occurrences with  calls to  the  newly created
          subroutine. It is kind of an opposite of -finline-functions.  This
          optimization runs at RTL level.

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

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

          The default is -fno-signaling-nans.

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

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

      -fcx-limited-range
          When enabled, this option states that a range reduction step is
          not needed when performing complex division.  The default is
          -fno-cx-limited-range, but is enabled by -ffast-math.

          This option controls the default setting of the ISO C99
          "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies to
          all languages.




                                   - 97 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

          With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each
          JUMP_INSN and CALL_INSN.  These can be used to improve
          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.

          Enabled with -fprofile-generate and -fprofile-use.

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

          With -fbranch-probabilities, it reads back the data gathered and
          actually performs the optimizations based on them.  Currently the
          optimizations include specialization of division operation using
          the knowledge about the value of the denominator.

      -frename-registers
          Attempt to avoid false dependencies in scheduled code by making
          use of registers left over after register allocation.  This
          optimization will most benefit processors with lots of registers.
          Depending on the debug information format adopted by the target,
          however, it can make debugging impossible, since variables will no
          longer stay in a "home register".

          Enabled by default with -funroll-loops.



                                   - 98 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          Enabled with -fprofile-use.

      -funroll-loops
          Unroll loops whose number of iterations can be determined at
          compile time or upon entry to the loop.  -funroll-loops implies
          -frerun-cse-after-loop, -fweb and -frename-registers. 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.

          Enabled with -fprofile-use.

      -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 removal of loops with small constant
          number of iterations).

          Enabled with -fprofile-use.

      -fmove-loop-invariants
          Enables the loop invariant motion pass in the RTL loop optimizer.
          Enabled at level -O1

      -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).

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

          Use these options on systems where the linker can perform
          optimizations to improve locality of reference in the instruction



                                   - 99 -        Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 benefits from
          doing so.  When you specify these options, the assembler and
          linker will create larger object and executable files and will
          also be slower.  You will not be able to use "gprof" on all
          systems if you 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 prologue /
          epilogue threading.  The use of target registers 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.

      -fbtr-bb-exclusive
          When performing branch target register load optimization, don't
          reuse branch target registers in within any basic block.

      -fstack-protector
          Emit extra code to check for buffer overflows, such as stack
          smashing attacks.  This is done by adding a guard variable to
          functions with vulnerable objects.  This includes functions that
          call alloca, and functions with buffers larger than 8 bytes.  The
          guards are initialized when a function is entered and then checked
          when the function exits.  If a guard check fails, an error message
          is printed and the program exits.

      -fstack-protector-all
          Like -fstack-protector except that all functions are protected.

      -fsection-anchors
          Try to reduce the number of symbolic address calculations by using
          shared "anchor" symbols to address nearby objects.  This
          transformation can help to reduce the number of GOT entries and
          GOT accesses on some targets.

          For example, the implementation of the following function "foo":

                  static int a, b, c;
                  int foo (void) { return a + b + c; }

          would usually calculate the addresses of all three variables, but



                                   - 100 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          if you compile it with -fsection-anchors, it will access the
          variables from a common anchor point instead.  The effect is
          similar to the following pseudocode (which isn't valid C):

                  int foo (void)
                  {
                    register int *xr = &x;
                    return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                  }

          Not all targets support this option.

      --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:

          salias-max-implicit-fields
              The maximum number of fields in a variable without direct
              structure accesses for which structure aliasing will consider
              trying to track each field.  The default is 5

          salias-max-array-elements
              The maximum number of elements an array can have and its
              elements still be tracked individually by structure aliasing.
              The default is 4

          sra-max-structure-size
              The maximum structure size, in bytes, at which the scalar
              replacement of aggregates (SRA) optimization will perform
              block copies.  The default value, 0, implies that GCC will
              select the most appropriate size itself.

          sra-field-structure-ratio
              The threshold ratio (as a percentage) between instantiated
              fields and the complete structure size.  We say that if the
              ratio of the number of bytes in instantiated fields to the
              number of bytes in the complete structure exceeds this
              parameter, then block copies are not used.  The default is 75.




                                   - 101 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

          min-crossjump-insns
              The minimum number of instructions which must be matched at
              the end of two blocks before crossjumping will be performed on
              them.  This value is ignored in the case where all
              instructions in the block being crossjumped from are matched.
              The default value is 5.

          max-grow-copy-bb-insns
              The maximum code size expansion factor when copying basic
              blocks instead of jumping.  The expansion is relative to a
              jump instruction.  The default value is 8.

          max-goto-duplication-insns
              The maximum number of instructions to duplicate to a block
              that jumps to a computed goto.  To avoid O(N^2) behavior in a
              number of passes, GCC factors computed gotos early in the
              compilation process, and unfactors them as late as possible.
              Only computed jumps at the end of a basic blocks with no more
              than max-goto-duplication-insns are unfactored.  The default
              value is 8.

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

          max-delay-slot-live-search
              When trying to fill delay slots, the maximum 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.

          max-gcse-memory
              The approximate maximum amount of memory that will be
              allocated in order to perform the global common subexpression



                                   - 102 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              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.  The default is
              1.

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

          max-inline-insns-single
              Several parameters control the tree inliner used in gcc.  This
              number sets the maximum number of instructions (counted in
              GCC's internal representation) in a single function that the
              tree inliner will consider for inlining.  This only affects
              functions declared inline and methods implemented in a class
              declaration (C++).  The default value is 450.

          max-inline-insns-auto
              When you use -finline-functions (included in -O3), a lot of
              functions that would otherwise not be considered for inlining
              by the compiler will be investigated.  To those functions, a
              different (more restrictive) limit compared to functions
              declared inline can be applied.  The default value is 90.

          large-function-insns
              The limit specifying really large functions.  For functions
              larger than this limit after inlining inlining is constrained
              by --param large-function-growth.  This parameter is useful
              primarily to avoid extreme compilation 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 2700.

          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 100 which limits large
              function growth to 2.0 times the original size.

          large-unit-insns
              The limit specifying large translation unit.  Growth caused by
              inlining of units larger than this limit is limited by --param
              inline-unit-growth.  For small units this might be too tight
              (consider unit consisting of function A that is inline and B



                                   - 103 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              that just calls A three time.  If B is small relative to A,
              the growth of unit is 300\% and yet such inlining is very
              sane.  For very large units consisting of small inlininable
              functions however the overall unit growth limit is needed to
              avoid exponential explosion of code size.  Thus for smaller
              units, the size is increased to --param large-unit-insns
              before applying --param inline-unit-growth.  The default is
              10000

          inline-unit-growth
              Specifies maximal overall growth of the compilation unit
              caused by inlining.  This parameter is ignored when
              -funit-at-a-time is not used.  The default value is 50 which
              limits unit growth to 1.5 times the original size.

          max-inline-insns-recursive
          max-inline-insns-recursive-auto
              Specifies maximum number of instructions out-of-line copy of
              self recursive inline function can grow into by performing
              recursive inlining.

              For functions declared inline --param max-inline-insns-
              recursive is taken into account.  For function not declared
              inline, recursive inlining happens only when
              -finline-functions (included in -O3) is enabled and --param
              max-inline-insns-recursive-auto is used.  The default value is
              450.

          max-inline-recursive-depth
          max-inline-recursive-depth-auto
              Specifies maximum recursion depth used by the recursive
              inlining.

              For functions declared inline --param max-inline-recursive-
              depth is taken into account.  For function not declared
              inline, recursive inlining happens only when
              -finline-functions (included in -O3) is enabled and --param
              max-inline-recursive-depth-auto is used.  The default value is
              450.

          min-inline-recursive-probability
              Recursive inlining is profitable only for function having deep
              recursion in average and can hurt for function having little
              recursion depth by increasing the prologue size or complexity
              of function body to other optimizers.

              When profile feedback is available (see -fprofile-generate)
              the actual recursion depth can be guessed from probability
              that function will recurse via given call expression.  This



                                   - 104 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              parameter limits inlining only to call expression whose
              probability exceeds given threshold (in percents).  The
              default value is 10.

          inline-call-cost
              Specify cost of call instruction relative to simple
              arithmetics operations (having cost of 1).  Increasing this
              cost disqualifies inlining of non-leaf functions and at the
              same time increases size of leaf function that is believed to
              reduce function size by being inlined.  In effect it increases
              amount of inlining for code having large abstraction penalty
              (many functions that just pass the arguments to other
              functions) and decrease inlining for code with low abstraction
              penalty.  The default value is 16.

          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 probabilities 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 single loop.



                                   - 105 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          lim-expensive
              The minimum cost of an expensive expression in the loop
              invariant motion.

          iv-consider-all-candidates-bound
              Bound on number of candidates for induction variables below
              that all candidates are considered for each use in induction
              variable optimizations.  Only the most relevant candidates are
              considered if there are more candidates, to avoid quadratic
              time complexity.

          iv-max-considered-uses
              The induction variable optimizations give up on loops that
              contain more induction variable uses.

          iv-always-prune-cand-set-bound
              If number of candidates in the set is smaller than this value,
              we always try to remove unnecessary ivs from the set during
              its optimization when a new iv is added to the set.

          scev-max-expr-size
              Bound on size of expressions used in the scalar evolutions
              analyzer.  Large expressions slow the analyzer.

          vect-max-version-checks
              The maximum number of runtime checks that can be performed
              when doing loop versioning in the vectorizer.  See option
              ftree-vect-loop-version for more information.

          max-iterations-to-track
              The maximum number of iterations of a loop the brute force
              algorithm for analysis of # of iterations of the loop tries to
              evaluate.

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

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

          max-predicted-iterations
              The maximum number of loop iterations we predict statically.
              This is useful in cases where function contain single loop
              with known bound and other loop with unknown.  We predict the
              known number of iterations correctly, while the unknown number



                                   - 106 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              of iterations average to roughly 10.  This means that the loop
              without bounds would appear artificially cold relative to the
              other one.

          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 profiles (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 probability 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 compilation with profile
              feedback needs to be more conservative (higher) in order to
              make tracer effective.

          max-cse-path-length
              Maximum number of basic blocks on path that cse considers.
              The default is 10.

          max-cse-insns
              The maximum instructions CSE process before flushing. The
              default is 1000.

          global-var-threshold
              Counts the number of function calls (n) and the number of
              call-clobbered variables (v).  If nxv is larger than this
              limit, a single artificial variable will be created to



                                   - 107 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              represent all the call-clobbered variables at function call
              sites.  This artificial variable will then be made to alias
              every call-clobbered variable.  (done as "int * size_t" on the
              host machine; beware overflow).

          max-aliased-vops
              Maximum number of virtual operands allowed to represent
              aliases before triggering the alias grouping heuristic.  Alias
              grouping reduces compile times and memory consumption needed
              for aliasing at the expense of precision loss in alias
              information.

          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 collections.  Tuning this may improve
              compilation speed; it has no effect on code generation.

              The default is 30% + 70% * (RAM/1GB) with an upper bound of
              100% when RAM >= 1GB.  If "getrlimit" is available, the notion
              of "RAM" is the smallest of actual RAM and "RLIMIT_DATA" or
              "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 the smaller of RAM/8, RLIMIT_RSS, or a limit
              which tries to ensure that RLIMIT_DATA or RLIMIT_AS are not
              exceeded, but with a lower bound of 4096 (four megabytes) and
              an upper bound of 131072 (128 megabytes).  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 compile time increase with



                                   - 108 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              probably slightly better performance.  The default value is
              100.

          max-cselib-memory-locations
              The maximum number of memory locations cselib should take into
              account.  Increasing values mean more aggressive optimization,
              making the compile time increase with probably slightly better
              performance.  The default value is 500.

          max-flow-memory-locations
              Similar as max-cselib-memory-locations but for dataflow
              liveness.  The default value is 100.

          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 multiplied 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.

          max-sched-ready-insns
              The maximum number of instructions ready to be issued the
              scheduler should consider at any given time during the first
              scheduling pass.  Increasing values mean more thorough
              searches, making the compilation time increase with probably
              little benefit.  The default value is 100.

          max-sched-region-blocks
              The maximum number of blocks in a region to be considered for
              interblock scheduling.  The default value is 10.

          max-sched-region-insns
              The maximum number of insns in a region to be considered for
              interblock scheduling.  The default value is 100.

          min-spec-prob
              The minimum probability (in percents) of reaching a source
              block for interblock speculative scheduling.  The default
              value is 40.

          max-sched-extend-regions-iters
              The maximum number of iterations through CFG to extend
              regions.  0 - disable region extension, N - do at most N



                                   - 109 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              iterations.  The default value is 0.

          max-sched-insn-conflict-delay
              The maximum conflict delay for an insn to be considered for
              speculative motion.  The default value is 3.

          sched-spec-prob-cutoff
              The minimal probability of speculation success (in percents),
              so that speculative insn will be scheduled.  The default value
              is 40.

          max-last-value-rtl
              The maximum size measured as number of RTLs that can be
              recorded in an expression in combiner for a pseudo register as
              last known value of that register.  The default is 10000.

          integer-share-limit
              Small integer constants can use a shared data structure,
              reducing the compiler's memory usage and increasing its speed.
              This sets the maximum value of a shared integer constant's.
              The default value is 256.

          min-virtual-mappings
              Specifies the minimum number of virtual mappings in the
              incremental SSA updater that should be registered to trigger
              the virtual mappings heuristic defined by
              virtual-mappings-ratio.  The default value is 100.

          virtual-mappings-ratio
              If the number of virtual mappings is virtual-mappings-ratio
              bigger than the number of virtual symbols to be updated, then
              the incremental SSA updater switches to a full update for
              those symbols.  The default ratio is 3.

          ssp-buffer-size
              The minimum size of buffers (i.e. arrays) that will receive
              stack smashing protection when -fstack-protection is used.

          max-jump-thread-duplication-stmts
              Maximum number of statements allowed in a block that needs to
              be duplicated when threading jumps.

          max-fields-for-field-sensitive
              Maximum number of fields in a structure we will treat in a
              field sensitive manner during pointer analysis.







                                   - 110 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      Options Controlling the Preprocessor

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

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

          You can use -Wp,option to bypass the compiler driver and pass
          option directly through to the preprocessor.  If option contains
          commas, it is split into multiple options at the commas.  However,
          many options are modified, translated or interpreted by the
          compiler driver before being passed to the preprocessor, and -Wp
          forcibly bypasses this phase.  The preprocessor's direct interface
          is undocumented and subject to change, so whenever possible you
          should avoid using -Wp and let the driver 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
          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 quoting syntax to protect
          characters such as spaces that have a meaning in the shell syntax.

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

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



                                   - 111 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 directory, the option is ignored to ensure
          that the default search order for system directories and the
          special treatment of system headers are not defeated .

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

      -Wall
          Turns on all optional warnings which are desirable for normal
          code.  At present this is -Wcomment, -Wtrigraphs, -Wmultichar and
          a warning about integer promotion causing 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.

      -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
          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
          newlines 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.




                                   - 112 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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 redefined or undefined.

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

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

                  #if defined the_macro_causing_the_warning
                  #endif

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

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

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

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



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                                 2008-02-01



          change in semantics from GCC versions 3.0 and earlier.

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

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

      -MG In conjunction with an option such as -M requesting dependency
          generation, -MG assumes missing header files are generated files
          and adds them to the 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 make gives if you
          remove header files without updating the Makefile to match.

          This is typical output:

                  test.o: test.c test.h

                  test.h:

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

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

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

                  $(objpfx)foo.o: foo.c

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



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                                 2008-02-01



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

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

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

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

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

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

      -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.

      -fpch-preprocess
          This option allows use of a precompiled header together with -E.
          It inserts a special "#pragma", "#pragma GCC pch_preprocess
          "<filename>"" in the output to mark the place where the
          precompiled header was found, and its filename.  When
          -fpreprocessed is in use, GCC recognizes this "#pragma" and loads
          the PCH.

          This option is off by default, because the resulting preprocessed
          output is only really suitable as input to GCC.  It is switched on
          by -save-temps.

          You should not write this "#pragma" in your own code, but it is
          safe to edit the filename if the PCH file is available in a
          different location.  The filename may be absolute or it may be
          relative to GCC's current directory.

      -x c
      -x c++



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                                 2008-02-01



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

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

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

          standard may be one of:

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

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

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

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

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

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

          "c++98"



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              The 1998 ISO C++ standard plus amendments.

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

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

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

      -nostdinc
          Do not search the standard system directories for header files.
          Only the directories you have specified with -I options (and the
          directory of the current file, if appropriate) are searched.

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

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

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

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

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

      -idirafter dir
          Search dir for header files, but do it after all directories
          specified with -I and the standard system directories have been



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 GNU                                                                     GNU

                                 2008-02-01



          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.

      -isysroot dir
          This option is like the --sysroot option, but applies only to
          header files.  See the --sysroot option for more information.

      -imultilib dir
          Use dir as a subdirectory of the directory containing target-
          specific C++ headers.

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

      -iquote dir
          Search dir only for header files requested with "#include "file"";
          they are not searched for "#include <file>", before all
          directories specified by -I and before the standard system
          directories.

      -fdollars-in-identifiers
          Accept $ in identifiers.

      -fextended-identifiers
          Accept universal character names in identifiers.  This option is
          experimental; in a future version of GCC, it will be enabled by
          default for C99 and C++.

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



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                                 2008-02-01



          preprocessor is little more than a tokenizer for the front ends.

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

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

      -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 -fexec-charset,
          charset can be any encoding supported by the system's "iconv"
          library routine; 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 character 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 command 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 working 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.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

                      touch foo.h; cpp -dM foo.h

              will show all the predefined macros.

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

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

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

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

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



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                                 2008-02-01



          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 expansion.  This
          is like -C, except that comments contained within macros are also
          passed through to the output file where the macro is expanded.

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

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

      -traditional-cpp
          Try to imitate the behavior of old-fashioned C preprocessors, 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.

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




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                                 2008-02-01



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

      -llibrary
      -l library
          Search the library named library when linking.  (The second
          alternative with the library as a separate argument is only for



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                                 2008-02-01



          POSIX compliance and is not recommended.)

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

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

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

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

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

      -nostartfiles
          Do not use the standard system startup files when linking.  The
          standard system libraries are used normally, unless -nostdlib or
          -nodefaultlibs is used.

      -nodefaultlibs
          Do not use the standard system libraries when linking.  Only the
          libraries you specify will be passed to the linker.  The standard
          startup files are used normally, unless -nostartfiles is used.
          The compiler may generate calls to "memcmp", "memset", "memcpy"
          and "memmove".  These entries are usually resolved by entries in
          libc.  These entry points should be supplied through some other
          mechanism when this option is specified.

      -nostdlib
          Do not use the standard system startup files or libraries when
          linking.  No startup files and only the libraries you specify will
          be passed to the linker.  The compiler may generate calls to
          "memcmp", "memset", "memcpy" and "memmove".  These entries are
          usually resolved by entries in libc.  These entry points should be
          supplied through some other mechanism when this option is



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                                 2008-02-01



          specified.

          One of the standard libraries bypassed by -nostdlib and
          -nodefaultlibs is libgcc.a, a library of internal subroutines that
          GCC uses to overcome shortcomings of particular machines, or
          special needs for some languages.

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

      -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 generate code (-fpie, -fPIE, or model
          suboptions) when you specify this option.

      -rdynamic
          Pass the flag -export-dynamic to the ELF linker, on targets that
          support it. This instructs the linker to add all symbols, not only
          used ones, to the dynamic symbol table. This option is needed for
          some uses of "dlopen" or to allow obtaining backtraces from within
          a program.

      -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]

      -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.




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                                 2008-02-01



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

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

          If, instead, you use the GCC driver to create shared libraries,
          you may find that they will not always be linked with the shared
          libgcc.  If GCC finds, at its configuration time, that you have a
          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 version of libgcc by default.
          This allows exceptions to propagate through such shared libraries,
          without incurring relocation costs at library load time.

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

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

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

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

      -Wl,option
          Pass option as an option to the linker.  If option contains



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          commas, it is split into multiple options at the commas.

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

      Options for Directory Search

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

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

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

      -iquotedir
          Add the directory dir to the head of the list of directories to be
          searched for header files only for the case of #include "file";
          they are not searched for #include <file>, otherwise just like -I.

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

      --sysroot=dir
          Use dir as the logical root directory for headers and libraries.
          For example, if the compiler would normally search for headers in
          /usr/include and libraries in /usr/lib, it will instead search
          dir/usr/include and dir/usr/lib.

          If you use both this option and the -isysroot option, then the
          --sysroot option will apply to libraries, but the -isysroot option
          will apply to header files.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          The GNU linker (beginning with version 2.16) has the necessary
          support for this option.  If your linker does not support this
          option, the header file aspect of --sysroot will still work, but
          the library aspect will not.

      -I- This option has been deprecated.  Please use -iquote instead for
          -I directories before the -I- and remove the -I-.  Any directories
          you specify with -I options before the -I- option are searched
          only for the case of #include "file"; they are not searched for
          #include <file>.

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

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

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

      Specifying Target Machine and Compiler Version

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

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

          The value to use for machine is the same as was specified as the
          machine type when configuring GCC as a cross-compiler.  For
          example, if a cross-compiler was configured with configure arm-
          elf, meaning to compile for an arm processor with elf binaries,
          then you would specify -b arm-elf to run that cross compiler.
          Because there are other options beginning with -b, the
          configuration must contain a hyphen.

      -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 4.0, meaning to run GCC version 4.0.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

      Hardware Models and Configurations

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

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

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

      ARC Options

      These options are defined for ARC implementations:

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

      -EB Compile code for big endian mode.

      -mmangle-cpu
          Prepend the name of the cpu to all public symbol names.  In
          multiple-processor systems, there are many ARC variants with
          different instruction and register set characteristics.  This flag
          prevents code compiled for one cpu to be linked with code compiled
          for another.  No facility exists for handling variants that are
          "almost identical".  This is an all or nothing option.

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

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




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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      ARM Options

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

      -mabi=name
          Generate code for the specified ABI.  Permissible values are:
          apcs-gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

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

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

      -mthumb-interwork
          Generate code which supports calling between the ARM and Thumb
          instruction sets.  Without this option the two instruction sets
          cannot be reliably used inside one program.  The default is
          -mno-thumb-interwork, since slightly larger code is generated when
          -mthumb-interwork is specified.

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

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

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

          -msoft-float changes the calling convention in the output file;



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -mfloat-abi=name
          Specifies which ABI to use for floating point values.  Permissible
          values are: soft, softfp and hard.

          soft and hard are equivalent to -msoft-float and -mhard-float
          respectively.  softfp allows the generation of floating point
          instructions, but still uses the soft-float calling conventions.

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

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

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

      -mcpu=name
          This specifies the name of the target ARM processor.  GCC uses
          this name to determine what kind of instructions it can emit when
          generating assembly code.  Permissible names are: arm2, arm250,
          arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7m, arm7d,
          arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710c,
          arm7100, arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm8,
          strongarm, strongarm110, strongarm1100, arm8, arm810, arm9, arm9e,
          arm920, arm920t, arm922t, arm946e-s, arm966e-s, arm968e-s,
          arm926ej-s, arm940t, arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s,
          arm10e, arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore,
          mpcorenovfp, arm1176jz-s, arm1176jzf-s, 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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -mcpu= option.  For some ARM implementations better performance
          can be obtained by using this option.

      -march=name
          This specifies the name of the target ARM architecture.  GCC uses
          this name to determine what kind of instructions it can emit when
          generating assembly code.  This option can be used in conjunction
          with or instead of the -mcpu= option.  Permissible names are:
          armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t,
          armv5te, armv6, armv6j, iwmmxt, ep9312.

      -mfpu=name
      -mfpe=number
      -mfp=number
          This specifies what floating point hardware (or hardware
          emulation) is available on the target.  Permissible names are:
          fpa, fpe2, fpe3, maverick, vfp.  -mfp and -mfpe are synonyms for
          -mfpu=fpenumber, for compatibility with older versions of GCC.

          If -msoft-float is specified this specifies the format of floating
          point values.

      -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, 32 and 64.  The default value varies for different
          toolchains.  For the COFF targeted toolchain the default value is
          8.  A value of 64 is only allowed if the underlying ABI supports
          it.

          Specifying the larger number can produce faster, more efficient
          code, but can also increase the size of the program.  Different
          values are potentially incompatible.  Code compiled with one value
          cannot necessarily expect to work with code or libraries compiled
          with another value, if they exchange information using structures
          or unions.

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

      -mlong-calls
      -mno-long-calls
          Tells the compiler to perform function calls by first loading the
          address of the function into a register and then performing a
          subroutine call on this 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.




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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 function.  The run-time
          system is responsible for initializing this register with an
          appropriate value before execution begins.

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

      -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:








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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



                       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 functions.)  The default is
          -mno-tpcs-frame.

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

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

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

      -mtp=name
          Specify the access model for the thread local storage pointer.
          The valid models are soft, which generates calls to
          "__aeabi_read_tp", cp15, which fetches the thread pointer from



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          "cp15" directly (supported in the arm6k architecture), and auto,
          which uses the best available method for the selected processor.
          The default setting is auto.

      AVR Options

      These options are defined for AVR implementations:

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

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

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

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

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

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

      -msize
          Output instruction sizes to the asm file.

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

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

      -mint8
          Assume int to be 8 bit integer.  This affects the sizes of all
          types: A char will be 1 byte, an int will be 1 byte, an long will
          be 2 bytes and long long will be 4 bytes.  Please note that this
          option does not comply to the C standards, but it will provide you
          with smaller code size.

      Blackfin Options

      -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.

      -mspecld-anomaly
          When enabled, the compiler will ensure that the generated code
          does not contain speculative loads after jump instructions.  This
          option is enabled by default.

      -mno-specld-anomaly
          Don't generate extra code to prevent speculative loads from
          occurring.

      -mcsync-anomaly
          When enabled, the compiler will ensure that the generated code
          does not contain CSYNC or SSYNC instructions too soon after
          conditional branches.  This option is enabled by default.

      -mno-csync-anomaly
          Don't generate extra code to prevent CSYNC or SSYNC instructions
          from occurring too soon after a conditional branch.

      -mlow-64k
          When enabled, the compiler is free to take advantage of the
          knowledge that the entire program fits into the low 64k of memory.

      -mno-low-64k
          Assume that the program is arbitrarily large.  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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -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 24 bit addressing range of
          the offset based version of subroutine call instruction.

          This feature is not enabled by default.  Specifying
          -mno-long-calls will restore the default behavior.  Note these
          switches have no effect on how the compiler generates code to
          handle function calls via function pointers.

      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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          the program should be set to n bytes.

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

      -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 instruction;
          always emit compare and test instructions before use of condition
          codes.

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

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

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

      -mno-prologue-epilogue
      -mprologue-epilogue



                                   - 139 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -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 functions from a simulator
          library.  Code, initialized data and zero-initialized data are
          allocated consecutively.

      -sim2
          Like -sim, but pass linker options to locate initialized data at
          0x40000000 and zero-initialized data at 0x80000000.

      CRX Options

      These options are defined specifically for the CRX ports.

      -mmac
          Enable the use of multiply-accumulate instructions. Disabled by
          default.



                                   - 140 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mpush-args
          Push instructions will be used to pass outgoing arguments when
          functions are called. Enabled by default.

      Darwin Options

      These options are defined for all architectures running the Darwin
      operating system.

      FSF GCC on Darwin does not create "fat" object files; it will create
      an object file for the single architecture that it was built to
      target.  Apple's GCC on Darwin does create "fat" files if multiple
      -arch options are used; it does so by running the compiler or linker
      multiple times and joining the results together with lipo.

      The subtype of the file created (like ppc7400 or ppc970 or i686) is
      determined by the flags that specify the ISA that GCC is targetting,
      like -mcpu or -march.  The -force_cpusubtype_ALL option can be used to
      override this.

      The Darwin tools vary in their behavior when presented with an ISA
      mismatch.  The assembler, as, will only permit instructions to be used
      that are valid for the subtype of the file it is generating, so you
      cannot put 64-bit instructions in an ppc750 object file.  The linker
      for shared libraries, /usr/bin/libtool, will fail and print an error
      if asked to create a shared library with a less restrictive subtype
      than its input files (for instance, trying to put a ppc970 object file
      in a ppc7400 library).  The linker for executables, ld, will quietly
      give the executable the most restrictive subtype of any of its input
      files.

      -Fdir
          Add the framework directory dir to the head of the list of
          directories to be searched for header files.  These directories
          are interleaved with those specified by -I options and are scanned
          in a left-to-right order.

          A framework directory is a directory with frameworks in it.  A
          framework is a directory with a "Headers" and/or "PrivateHeaders"
          directory contained directly in it that ends in ".framework".  The
          name of a framework is the name of this directory excluding the
          ".framework".  Headers associated with the framework are found in
          one of those two directories, with "Headers" being searched first.
          A subframework is a framework directory that is in a framework's
          "Frameworks" directory.  Includes of subframework headers can only
          appear in a header of a framework that contains the subframework,
          or in a sibling subframework header.  Two subframeworks are
          siblings if they occur in the same framework.  A subframework
          should not have the same name as a framework, a warning will be



                                   - 141 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          issued if this is violated.  Currently a subframework cannot have
          subframeworks, in the future, the mechanism may be extended to
          support this.  The standard frameworks can be found in
          "/System/Library/Frameworks" and "/Library/Frameworks".  An
          example include looks like "#include <Framework/header.h>", where
          Framework denotes the name of the framework and header.h is found
          in the "PrivateHeaders" or "Headers" directory.

      -gused
          Emit debugging information for symbols that are used.  For STABS
          debugging format, this enables -feliminate-unused-debug-symbols.
          This is by default ON.

      -gfull
          Emit debugging information for all symbols and types.

      -mmacosx-version-min=version
          The earliest version of MacOS X that this executable will run on
          is version.  Typical values of version include 10.1, 10.2, and
          10.3.9.

          The default for this option is to make choices that seem to be
          most useful.

      -mkernel
          Enable kernel development mode.  The -mkernel option sets -static,
          -fno-common, -fno-cxa-atexit, -fno-exceptions,
          -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti
          where applicable.  This mode also sets -mno-altivec, -msoft-float,
          -fno-builtin and -mlong-branch for PowerPC targets.

      -mone-byte-bool
          Override the defaults for bool so that sizeof(bool)==1.  By
          default sizeof(bool) is 4 when compiling for Darwin/PowerPC and 1
          when compiling for Darwin/x86, so this option has no effect on
          x86.

          Warning: The -mone-byte-bool switch causes GCC to generate code
          that is not binary compatible with code generated without that
          switch.  Using this switch may require recompiling all other
          modules in a program, including system libraries.  Use this switch
          to conform to a non-default data model.

      -mfix-and-continue
      -ffix-and-continue
      -findirect-data
          Generate code suitable for fast turn around development.  Needed
          to enable gdb to dynamically load ".o" files into already running
          programs.  -findirect-data and -ffix-and-continue are provided for



                                   - 142 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          backwards compatibility.

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

      -dynamiclib
          When passed this option, GCC will produce a dynamic library
          instead of an executable when linking, using the Darwin libtool
          command.

      -force_cpusubtype_ALL
          This causes GCC's output file to have the ALL subtype, instead of
          one controlled by the -mcpu or -march option.

      -allowable_client  client_name
      -client_name
      -compatibility_version
      -current_version
      -dead_strip
      -dependency-file
      -dylib_file
      -dylinker_install_name
      -dynamic
      -exported_symbols_list
      -filelist
      -flat_namespace
      -force_flat_namespace
      -headerpad_max_install_names
      -image_base
      -init



                                   - 143 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -install_name
      -keep_private_externs
      -multi_module
      -multiply_defined
      -multiply_defined_unused
      -noall_load
      -no_dead_strip_inits_and_terms
      -nofixprebinding
      -nomultidefs
      -noprebind
      -noseglinkedit
      -pagezero_size
      -prebind
      -prebind_all_twolevel_modules
      -private_bundle
      -read_only_relocs
      -sectalign
      -sectobjectsymbols
      -whyload
      -seg1addr
      -sectcreate
      -sectobjectsymbols
      -sectorder
      -segaddr
      -segs_read_only_addr
      -segs_read_write_addr
      -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
          These options are passed to the Darwin linker.  The Darwin linker
          man page describes them in detail.

      DEC Alpha Options

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




                                   - 144 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mno-soft-float
      -msoft-float
          Use (do not use) the hardware floating-point instructions for
          floating-point operations.  When -msoft-float is specified,
          functions in libgcc.a will be used to perform floating-point
          operations.  Unless they are replaced by routines that emulate the
          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 registers.

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

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

      -mieee
          The Alpha architecture implements floating-point hardware
          optimized for maximum 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 compliant code except that the inexact-flag is not maintained
          (see below).  If this option is turned on, the preprocessor macro
          "_IEEE_FP" is defined during compilation.  The resulting code is
          less efficient but is able to correctly support denormalized
          numbers and exceptional IEEE values such as not-a-number and
          plus/minus infinity.  Other Alpha compilers call this option
          -ieee_with_no_inexact.

      -mieee-with-inexact
          This is like -mieee except the generated code also maintains the
          IEEE inexact-flag.  Turning on this option causes the generated
          code to implement fully-compliant IEEE math.  In addition to
          "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
          On some Alpha implementations the resulting code may execute



                                   - 145 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          significantly slower than the code generated by default.  Since
          there is very little code that depends on the inexact-flag, you
          should normally not specify this option.  Other Alpha compilers
          call this option -ieee_with_inexact.

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

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

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

          su  Like u, 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.

          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 generate code that can assist operating
          system trap handlers in determining the exact location that caused



                                   - 146 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 determine the
              exact instruction that caused a floating point exception.

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

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

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

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

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

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

      -mbwx
      -mno-bwx
      -mcix
      -mno-cix



                                   - 147 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -mexplicit-relocs
      -mno-explicit-relocs
          Older Alpha assemblers provided no way to generate symbol
          relocations except via assembler macros.  Use of these macros does
          not allow optimal instruction scheduling.  GNU binutils as of
          version 2.12 supports a new syntax that allows the compiler to
          explicitly mark which relocations should apply to which
          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
          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,



                                   - 148 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          the compiler can assume that all local symbols share the same $gp
          value, and thus reduce the number of instructions required for a
          function 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
          processor you specify.  If you do not specify a processor type,
          GCC will default to the processor on which the compiler was built.

          Supported values for cpu_type are

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

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

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

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

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

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

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




                                   - 149 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          Valid options for time are

          number
              A decimal number representing clock cycles.

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

      DEC Alpha/VMS Options

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

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

      FRV Options

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

      -mgpr-64
          Use all 64 general purpose registers.

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

      -mfpr-64
          Use all 64 floating point registers

      -mhard-float
          Use hardware instructions for floating point operations.

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

      -malloc-cc



                                   - 150 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Dynamically allocate condition code registers.

      -mfixed-cc
          Do not try to dynamically allocate condition code registers, 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.

      -mfdpic
          Select the FDPIC ABI, that uses function descriptors to represent
          pointers to functions.  Without any PIC/PIE-related options, it
          implies -fPIE.  With -fpic or -fpie, it assumes GOT entries and
          small data are within a 12-bit range from the GOT base address;
          with -fPIC or -fPIE, GOT offsets are computed with 32 bits.

      -minline-plt
          Enable inlining of PLT entries in function calls to functions that
          are not known to bind locally.  It has no effect without -mfdpic.
          It's enabled by default if optimizing for speed and compiling for
          shared libraries (i.e., -fPIC or -fpic), or when an optimization
          option such as -O3 or above is present in the command line.

      -mTLS
          Assume a large TLS segment when generating thread-local code.

      -mtls
          Do not assume a large TLS segment when generating thread-local



                                   - 151 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          code.

      -mgprel-ro
          Enable the use of "GPREL" relocations in the FDPIC ABI for data
          that is known to be in read-only sections.  It's enabled by
          default, except for -fpic or -fpie: even though it may help make
          the global offset table smaller, it trades 1 instruction for 4.
          With -fPIC or -fPIE, it trades 3 instructions for 4, one of which
          may be shared by multiple symbols, and it avoids the need for a
          GOT entry for the referenced symbol, so it's more likely to be a
          win.  If it is not, -mno-gprel-ro can be used to disable it.

      -multilib-library-pic
          Link with the (library, not FD) pic libraries.  It's implied by
          -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic.  You
          should never have to use it explicitly.

      -mlinked-fp
          Follow the EABI requirement of always creating a frame pointer
          whenever a stack frame is allocated.  This option is enabled by
          default and can be disabled with -mno-linked-fp.

      -mlong-calls
          Use indirect addressing to call functions outside the current
          compilation unit.  This allows the functions to be placed anywhere
          within the 32-bit address space.

      -malign-labels
          Try to align labels to an 8-byte boundary by inserting nops into
          the previous packet.  This option only has an effect when VLIW
          packing is enabled.  It doesn't create new packets; it merely adds
          nops to existing ones.

      -mlibrary-pic
          Generate position-independent EABI code.

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

      -macc-8
          Use all eight media accumulator registers.

      -mpack
          Pack VLIW instructions.

      -mno-pack
          Do not pack VLIW instructions.

      -mno-eflags



                                   - 152 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 instructions.

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



                                   - 153 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

      -moptimize-membar
          This switch removes redundant "membar" instructions from the
          compiler generated code.  It is enabled by default.

      -mno-optimize-membar
          This switch disables the automatic removal of redundant "membar"
          instructions from the generated code.

      -mtomcat-stats
          Cause gas to print out tomcat statistics.

      -mcpu=cpu
          Select the processor type for which to generate code.  Possible
          values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300
          and simple.

      GNU/Linux Options

      These -m options are defined for GNU/Linux targets:

      -mglibc
          Use the GNU C library instead of uClibc.  This is the default
          except on *-*-linux-*uclibc* targets.




                                   - 154 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -muclibc
          Use uClibc instead of the GNU C library.  This is the default on
          *-*-linux-*uclibc* targets.

      H8/300 Options

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

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

      -mh Generate code for the H8/300H.

      -ms Generate code for the 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 boundaries.  This option has no effect on the
          H8/300.

      HPPA Options

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

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

      -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.



                                   - 155 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

      -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.

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

      -mportable-runtime



                                   - 156 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -mschedule=cpu-type
          Schedule code according to the constraints for the machine type
          cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
          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 available for all HPPA
          targets.  Normally the facilities of the machine's usual C
          compiler are used, but this cannot be done directly in
          cross-compilation.  You must make your own arrangements to provide
          suitable library functions for cross-compilation.  The embedded
          target hppa1.1-*-pro does provide software floating point support.

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

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

      -mgnu-ld
          Use GNU ld specific options.  This passes -shared to ld when
          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`.



                                   - 157 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 TypeMismatch 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 generated stubs.  The default
          is to generate long calls only when the distance from the call
          site to the beginning of the function or translation unit, as the
          case may be, exceeds a predefined limit set by the branch type
          being used.  The limits for normal calls are 7,600,000 and 240,000
          bytes, respectively for the PA 2.0 and PA 1.X architectures.
          Sibcalls are always limited at 240,000 bytes.

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

          It is normally not desirable to use this option as it will degrade
          performance.  However, it may be useful in large applications,
          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 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.

      -munix=unix-std
          Generate compiler predefines and select a startfile for the
          specified UNIX standard.  The choices for unix-std are 93, 95 and
          98.  93 is supported on all HP-UX versions.  95 is available on
          HP-UX 10.10 and later.  98 is available on HP-UX 11.11 and later.
          The default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10
          though to 11.00, and 98 for HP-UX 11.11 and later.



                                   - 158 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          -munix=93 provides the same predefines as GCC 3.3 and 3.4.
          -munix=95 provides additional predefines for "XOPEN_UNIX" and
          "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
          provides additional predefines for "_XOPEN_UNIX",
          "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
          "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

          It is important to note that this option changes the interfaces
          for various library routines.  It also affects the operational
          behavior of the C library.  Thus, extreme care is needed in using
          this option.

          Library code that is intended to operate with more than one UNIX
          standard must test, set and restore the variable
          __xpg4_extended_mask as appropriate.  Most GNU software doesn't
          provide this capability.

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

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

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

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

      Intel 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 generated code,
          except for the ABI and the set of available instructions.  The
          choices for cpu-type are:




                                   - 159 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          generic
              Produce code optimized for the most common IA32/AMD64/EM64T
              processors.  If you know the CPU on which your code will run,
              then you should use the corresponding -mtune option instead of
              -mtune=generic.  But, if you do not know exactly what CPU
              users of your application will have, then you should use this
              option.

              As new processors are deployed in the marketplace, the
              behavior of this option will change.  Therefore, if you
              upgrade to a newer version of GCC, the code generated option
              will change to reflect the processors that were most common
              when that version of GCC was released.

              There is no -march=generic option because -march indicates the
              instruction set the compiler can use, and there is no generic
              instruction set applicable to all processors.  In contrast,
              -mtune indicates the processor (or, in this case, collection
              of processors) for which the code is optimized.

          native
              This selects the CPU to tune for at compilation time by
              determining the processor type of the compiling machine.
              Using -mtune=native will produce code optimized for the local
              machine under the constraints of the selected instruction set.
              Using -march=native will enable all instruction subsets
              supported by the local machine (hence the result might not run
              on different machines).

          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.

          pentiumpro
              Intel PentiumPro CPU.

          i686
              Same as "generic", but when used as "march" option, PentiumPro
              instruction set will be used, so the code will run on all i686



                                   - 160 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              family chips.

          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 Centrino notebooks.

          pentium4, pentium4m
              Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set
              support.

          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 extensions.)

          winchip-c6
              IDT Winchip C6 CPU, dealt in same way as i486 with additional
              MMX instruction set support.




                                   - 161 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 support.  (No
              scheduling is implemented for this chip.)

          c3-2
              Via C3-2 CPU with MMX and SSE instruction set support.  (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.  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,



                                   - 162 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



              Athlon-xp and Athlon-mp chips.  The earlier version of SSE
              instruction set supports only single precision arithmetics,
              thus the double and extended precision arithmetics is still
              done using 387.  Later version, present only in Pentium4 and
              the future AMD x86-64 chips supports double precision
              arithmetics too.

              For the i386 compiler, you need to use -march=cpu-type, -msse
              or -msse2 switches to enable SSE extensions and make this
              option effective.  For the 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 instability 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.

          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.  Supported choices
          are intel or att (the default one).  Darwin does not support
          intel.

      -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



                                   - 163 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          even if -msoft-float is used.

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

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

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

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

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

          On x86-64, -malign-double is enabled by default.

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

      -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 additional 32



                                   - 164 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          bit zero.

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

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

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

      -mmlarge-data-threshold=number
          When -mcmodel=medium is specified, the data greater than threshold
          are placed in large data section.  This value must be the same
          across all object linked into the binary and defaults to 65535.

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

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

          You can specify that an individual function is called with this
          calling sequence with the function attribute stdcall.  You can
          also override the -mrtd option by using the function attribute
          cdecl.

          Warning: this calling convention is incompatible with the one
          normally used on Unix, so you cannot use it if you need to call
          libraries compiled with the Unix compiler.

          Also, you must provide function prototypes for all functions that
          take variable 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



                                   - 165 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -msseregparm
          Use SSE register passing conventions for float and double
          arguments and return values.  You can control this behavior for a
          specific function by using the function attribute sseregparm.

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

      -mstackrealign
          Realign the stack at entry.  On the Intel x86, the -mstackrealign
          option will generate an alternate prologue and epilogue that
          realigns the runtime stack.  This supports mixing legacy codes
          that keep a 4-byte aligned stack with modern codes that keep a
          16-byte stack for SSE compatibility.  The alternate prologue and
          epilogue are slower and bigger than the regular ones, and the
          alternate prologue requires an extra scratch register; this lowers
          the number of registers available if used in conjunction with the
          "regparm" attribute.  The -mstackrealign option is incompatible
          with the nested function prologue; this is considered a hard
          error.  See also the attribute "force_align_arg_pointer",
          applicable to individual functions.

      -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).

          On Pentium and PentiumPro, "double" and "long double" values
          should be aligned to an 8 byte boundary (see -malign-double) or
          suffer significant run time performance penalties.  On Pentium
          III, the Streaming SIMD Extension (SSE) data type "__m128" may not
          work properly if it is not 16 byte aligned.

          To ensure proper alignment of this values on the stack, the stack
          boundary must be as aligned as that required by any value stored
          on the stack.  Further, every function must be generated such that



                                   - 166 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          it keeps the stack aligned.  Thus calling a function compiled with
          a higher preferred stack boundary from a function compiled with a
          lower preferred stack boundary will most likely misalign the
          stack.  It is recommended that libraries that use callbacks always
          use the default setting.

          This extra alignment does consume extra stack space, and generally
          increases code size.  Code that is sensitive to stack space usage,
          such as embedded systems and operating system kernels, may want to
          reduce the preferred alignment to -mpreferred-stack-boundary=2.

      -mmmx
      -mno-mmx
      -msse
      -mno-sse
      -msse2
      -mno-sse2
      -msse3
      -mno-sse3
      -m3dnow
      -mno-3dnow
          These switches enable or disable the use of instructions in the
          MMX, SSE, SSE2 or 3DNow! extended instruction sets.  These
          extensions are also available as built-in functions: see X86
          Built-in Functions, for details of the functions enabled and
          disabled by these switches.

          To have SSE/SSE2 instructions generated automatically from
          floating-point code (as opposed to 387 instructions), see
          -mfpmath=sse.

          These options will enable GCC to use these extended instructions
          in generated code, even without -mfpmath=sse.  Applications which
          perform runtime CPU detection must compile separate files for each
          supported architecture, using the appropriate flags.  In
          particular, the file containing the CPU detection code should be
          compiled without these options.

      -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 prologue.  This is



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                                 2008-02-01



          faster on most modern CPUs because of reduced dependencies,
          improved scheduling and reduced stack usage when preferred stack
          boundary is not equal to 2.  The drawback is a notable increase in
          code size.  This switch implies -mno-push-args.

      -mthreads
          Support thread-safe exception handling on Mingw32.  Code that
          relies on thread-safe exception handling must compile and link all
          code with the -mthreads option.  When compiling, -mthreads defines
          -D_MT; when linking, it links in a special thread helper library
          -lmingwthrd which cleans up per thread exception 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 destination is
          known to be aligned at least to 4 byte boundary.  This enables
          more inlining, increase code size, but may improve performance of
          code that depends on fast memcpy, strlen and memset for short
          lengths.

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

      -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 and generates
          code that runs on any i386 system.  The 64-bit environment sets



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                                 2008-02-01



          int to 32 bits and long and pointer to 64 bits and generates code
          for AMD's x86-64 architecture. For darwin only the -m64 option
          turns off the -fno-pic and -mdynamic-no-pic options.

      -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 adjusting the stack pointer.  The flag -mno-red-zone
          disables this red zone.

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

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

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

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

      IA-64 Options

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

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

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

      -mgnu-as
      -mno-gnu-as



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 GCC(1)                           gcc-4.2.3                           GCC(1)
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                                 2008-02-01



          Generate (or don't) code for the GNU assembler.  This is the
          default.

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

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

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

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

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

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

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

      -minline-float-divide-min-latency
          Generate code for inline divides of floating point values using
          the minimum latency algorithm.

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

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

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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
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                                 2008-02-01



          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 preprocessor 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.

      -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



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                                 2008-02-01



          environment sets int to 32 bits and long and pointer to 64 bits.
          These are HP-UX specific flags.

      -mno-sched-br-data-spec
      -msched-br-data-spec
          (Dis/En)able data speculative scheduling before reload.  This will
          result in generation of the ld.a instructions and the
          corresponding check instructions (ld.c / chk.a).  The default is
          'disable'.

      -msched-ar-data-spec
      -mno-sched-ar-data-spec
          (En/Dis)able data speculative scheduling after reload.  This will
          result in generation of the ld.a instructions and the
          corresponding check instructions (ld.c / chk.a).  The default is
          'enable'.

      -mno-sched-control-spec
      -msched-control-spec
          (Dis/En)able control speculative scheduling.  This feature is
          available only during region scheduling (i.e. before reload).
          This will result in generation of the ld.s instructions and the
          corresponding check instructions chk.s .  The default is
          'disable'.

      -msched-br-in-data-spec
      -mno-sched-br-in-data-spec
          (En/Dis)able speculative scheduling of the instructions that are
          dependent on the data speculative loads before reload.  This is
          effective only with -msched-br-data-spec enabled.  The default is
          'enable'.

      -msched-ar-in-data-spec
      -mno-sched-ar-in-data-spec
          (En/Dis)able speculative scheduling of the instructions that are
          dependent on the data speculative loads after reload.  This is
          effective only with -msched-ar-data-spec enabled.  The default is
          'enable'.

      -msched-in-control-spec
      -mno-sched-in-control-spec
          (En/Dis)able speculative scheduling of the instructions that are
          dependent on the control speculative loads.  This is effective
          only with -msched-control-spec enabled.  The default is 'enable'.

      -msched-ldc
      -mno-sched-ldc
          (En/Dis)able use of simple data speculation checks ld.c .  If
          disabled, only chk.a instructions will be emitted to check data



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          speculative loads.  The default is 'enable'.

      -mno-sched-control-ldc
      -msched-control-ldc
          (Dis/En)able use of ld.c instructions to check control speculative
          loads.  If enabled, in case of control speculative load with no
          speculatively scheduled dependent instructions this load will be
          emitted as ld.sa and ld.c will be used to check it.  The default
          is 'disable'.

      -mno-sched-spec-verbose
      -msched-spec-verbose
          (Dis/En)able printing of the information about speculative
          motions.

      -mno-sched-prefer-non-data-spec-insns
      -msched-prefer-non-data-spec-insns
          If enabled, data speculative instructions will be chosen for
          schedule only if there are no other choices at the moment.  This
          will make the use of the data speculation much more conservative.
          The default is 'disable'.

      -mno-sched-prefer-non-control-spec-insns
      -msched-prefer-non-control-spec-insns
          If enabled, control speculative instructions will be chosen for
          schedule only if there are no other choices at the moment.  This
          will make the use of the control speculation much more
          conservative.  The default is 'disable'.

      -mno-sched-count-spec-in-critical-path
      -msched-count-spec-in-critical-path
          If enabled, speculative dependencies will be considered during
          computation of the instructions priorities.  This will make the
          use of the speculation a bit more conservative.  The default is
          'disable'.

      M32C Options

      -mcpu=name
          Select the CPU for which code is generated.  name may be one of
          r8c for the R8C/Tiny series, m16c for the M16C (up to /60) series,
          m32cm for the M16C/80 series, or m32c for the M32C/80 series.

      -msim
          Specifies that the program will be run on the simulator.  This
          causes an alternate runtime library to be linked in which
          supports, for example, file I/O.  You must not use this option
          when generating programs that will run on real hardware; you must
          provide your own runtime library for whatever I/O functions are



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                                 2008-02-01



          needed.

      -memregs=number
          Specifies the number of memory-based pseudo-registers GCC will use
          during code generation.  These pseudo-registers will be used like
          real registers, so there is a tradeoff between GCC's ability to
          fit the code into available registers, and the performance penalty
          of using memory instead of registers.  Note that all modules in a
          program must be compiled with the same value for this option.
          Because of that, you must not use this option with the default
          runtime libraries gcc builds.

      M32R/D Options

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

      -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" instructions to load their
          addresses), and assume all subroutines 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" instructions to load their
          addresses), and assume subroutines may not be reachable with the
          "bl" instruction (the compiler will generate the much slower
          "seth/add3/jl" instruction sequence).

      -msdata=none
          Disable use of the small data area.  Variables will be put into



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                                 2008-02-01



          one of .data, bss, or .rodata (unless the "section" attribute has
          been specified).  This is the default.

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

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

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

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

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

      -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.




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                                 2008-02-01



      -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.

      M680x0 Options

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

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

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

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

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

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

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

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

      -m68060



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                                 2008-02-01



          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.

      -mcfv4e
          Generate output for a ColdFire V4e family cpu (e.g. 547x/548x).
          This includes use of hardware floating point instructions.

      -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 available for all m68k
          targets.  Normally the facilities of the machine's usual C
          compiler are used, but this can't be done directly in
          cross-compilation.  You must make your own arrangements to provide
          suitable library functions for cross-compilation.  The embedded
          targets m68k-*-aout and m68k-*-coff do provide software floating



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                                 2008-02-01



          point support.

      -mshort
          Consider type "int" to be 16 bits wide, like "short int".
          Additionally, parameters passed on the stack are also aligned to a
          16-bit boundary even on targets whose API mandates promotion to
          32-bit.

      -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 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.)

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

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

          Warning: if you use the -malign-int switch, GCC will align



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                                 2008-02-01



          structures containing the above types  differently than most
          published application binary interface specifications for the
          m68k.

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

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

      -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

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



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                                 2008-02-01



      -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.

      MCore Options

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

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

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



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                                 2008-02-01



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

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

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

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

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

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

      -m210
      -m340
          Generate code for the 210 processor.

      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, 4km, 4kp, 5kc, 5kf, 20kc,
          24k, 24kc, 24kf, 24kx, m4k, orion, r2000, r3000, r3900, r4000,
          r4400, r4600, r4650, r6000, r8000, rm7000, rm9000, sb1, sr71000,
          vr4100, vr4111, vr4120, vr4130, 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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          written r.

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

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

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

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

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

      -mips1
          Equivalent to -march=mips1.

      -mips2
          Equivalent to -march=mips2.

      -mips3
          Equivalent to -march=mips3.

      -mips4
          Equivalent to -march=mips4.

      -mips32
          Equivalent to -march=mips32.

      -mips32r2
          Equivalent to -march=mips32r2.

      -mips64
          Equivalent to -march=mips64.



                                   - 182 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mips16
      -mno-mips16
          Generate (do not generate) MIPS16 code.  If GCC is targetting a
          MIPS32 or MIPS64 architecture, it will make use of the MIPS16e
          ASE.

      -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.

          For information about the O64 ABI, see
          <http://gcc.gnu.org/projects/mipso64-abi.html>.

      -mabicalls
      -mno-abicalls
          Generate (do not generate) code that is suitable for SVR4-style
          dynamic objects.  -mabicalls is the default for SVR4-based
          systems.

      -mshared
      -mno-shared
          Generate (do not generate) code that is fully
          position-independent, and that can therefore be linked into shared
          libraries.  This option only affects -mabicalls.

          All -mabicalls code has traditionally been position-independent,
          regardless of options like -fPIC and -fpic.  However, as an
          extension, the GNU toolchain allows executables to use absolute
          accesses for locally-binding symbols.  It can also use shorter GP
          initialization sequences and generate direct calls to locally-
          defined functions.  This mode is selected by -mno-shared.

          -mno-shared depends on binutils 2.16 or higher and generates
          objects that can only be linked by the GNU linker.  However, the
          option does not affect the ABI of the final executable; it only
          affects the ABI of relocatable objects.  Using -mno-shared will
          generally make executables both smaller and quicker.

          -mshared is the default.

      -mxgot
      -mno-xgot



                                   - 183 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -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 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.




                                   - 184 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mdsp
      -mno-dsp
          Use (do not use) the MIPS DSP ASE.

      -mpaired-single
      -mno-paired-single
          Use (do not use) paired-single floating-point instructions.
            This option can only be used when generating 64-bit code and
          requires hardware floating-point support to be enabled.

      -mips3d
      -mno-mips3d
          Use (do not use) the MIPS-3D ASE. The option -mips3d implies
          -mpaired-single.

      -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 registers, whichever is smaller.

      -msym32
      -mno-sym32
          Assume (do not assume) that all symbols have 32-bit values,
          regardless of the selected ABI.  This option is useful in
          combination with -mabi=64 and -mno-abicalls because it allows GCC
          to generate shorter and faster references to symbolic addresses.

      -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 possible,
          otherwise in data.  This gives slightly slower code than the



                                   - 185 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 data section.
          This option is only meaningful in conjunction with
          -membedded-data.

      -msplit-addresses
      -mno-split-addresses
          Enable (disable) use of the "%hi()" and "%lo()" assembler
          relocation operators.  This option has been superseded 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 the default if GCC was configured to use an
          assembler that supports relocation operators.

      -mcheck-zero-division
      -mno-check-zero-division
          Trap (do not trap) on integer division by zero.  The default is
          -mcheck-zero-division.

      -mdivide-traps
      -mdivide-breaks
          MIPS systems check for division by zero by generating either a
          conditional trap or a break instruction.  Using traps results in
          smaller code, but is only supported on MIPS II and later.  Also,
          some versions of the Linux kernel have a bug that prevents trap
          from generating the proper signal ("SIGFPE").  Use -mdivide-traps
          to allow conditional traps on architectures that support them and
          -mdivide-breaks to force the use of breaks.

          The default is usually -mdivide-traps, but this can be overridden
          at configure time using --with-divide=breaks.  Divide-by-zero
          checks can be completely disabled using -mno-check-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.




                                   - 186 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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-r4000
      -mno-fix-r4000
          Work around certain R4000 CPU errata:

          -   A double-word or a variable shift may give an incorrect result
              if executed immediately after starting an integer division.

          -   A double-word or a variable shift may give an incorrect result
              if executed while an integer multiplication is in progress.

          -   An integer division may give an incorrect result if started in
              a delay slot of a taken branch or a jump.

      -mfix-r4400
      -mno-fix-r4400
          Work around certain R4400 CPU errata:

          -   A double-word or a variable shift may give an incorrect result
              if executed immediately after starting an integer division.




                                   - 187 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mfix-vr4120
      -mno-fix-vr4120
          Work around certain VR4120 errata:

          -   "dmultu" does not always produce the correct result.

          -   "div" and "ddiv" do not always produce the correct result if
              one of the operands is negative.

          The workarounds for the division errata rely on special functions
          in libgcc.a.  At present, these functions are only provided by the
          "mips64vr*-elf" configurations.

          Other VR4120 errata require a nop to be inserted between certain
          pairs of instructions.  These errata are handled by the assembler,
          not by GCC itself.

      -mfix-vr4130
          Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are
          implemented by the assembler rather than by GCC, although GCC will
          avoid using "mflo" and "mfhi" if the VR4130 "macc", "macchi",
          "dmacc" and "dmacchi" instructions are available instead.

      -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 configured for, but commonly
          is either _flush_func or __cpu_flush.

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



                                   - 188 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mfp-exceptions
      -mno-fp-exceptions
          Specifies whether FP exceptions are enabled.  This affects how we
          schedule FP instructions for some processors.  The default is that
          FP exceptions are enabled.

          For instance, on the SB-1, if FP exceptions are disabled, and we
          are emitting 64-bit code, then we can use both FP pipes.
          Otherwise, we can only use one FP pipe.

      -mvr4130-align
      -mno-vr4130-align
          The VR4130 pipeline is two-way superscalar, but can only issue two
          instructions together if the first one is 8-byte aligned.  When
          this option is enabled, GCC will align pairs of instructions that
          it thinks should execute in parallel.

          This option only has an effect when optimizing for the VR4130.  It
          normally makes code faster, but at the expense of making it
          bigger.  It is enabled by default at optimization level -O3.

      MMIX Options

      These options are defined for the MMIX:

      -mlibfuncs
      -mno-libfuncs
          Specify that intrinsic library functions are being compiled,
          passing all values in registers, no matter the size.

      -mepsilon
      -mno-epsilon
          Generate floating-point comparison instructions that compare with
          respect to the "rE" epsilon register.

      -mabi=mmixware
      -mabi=gnu
          Generate code that passes function parameters and return values
          that (in the called function) are seen as registers $0 and up, as
          opposed to the GNU ABI which uses global registers $231 and up.

      -mzero-extend
      -mno-zero-extend
          When reading data from memory in sizes shorter than 64 bits, use
          (do not use) zero-extending load instructions by default, rather
          than sign-extending ones.

      -mknuthdiv
      -mno-knuthdiv



                                   - 189 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 exit point in
          each function.

      MN10300 Options

      These -m options are defined for Matsushita MN10300 architectures:

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

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

      -mam33



                                   - 190 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      -mreturn-pointer-on-d0
          When generating a function which returns a pointer, return the
          pointer in both "a0" and "d0".  Otherwise, the pointer is returned
          only in a0, and attempts to call such functions without a
          prototype would result in errors.  Note that this option is on by
          default; use -mno-return-pointer-on-d0 to disable it.

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

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

          This option makes symbolic debugging impossible.

      MT Options

      These -m options are defined for Morpho MT architectures:

      -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 ms1-64-001, ms1-16-002, ms1-16-003 and ms2.

          When this option is not used, the default is -march=ms1-16-002.

      -mbacc
          Use byte loads and stores when generating code.

      -mno-bacc
          Do not use byte loads and stores when generating code.

      -msim
          Use simulator runtime

      -mno-crt0
          Do not link in the C run-time initialization object file crti.o.
          Other run-time initialization and termination files such as
          startup.o and exit.o are still included on the linker command
          line.



                                   - 191 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      PDP-11 Options

      These options are defined for the PDP-11:

      -mfpu
          Use hardware FPP floating point.  This is the default.  (FIS
          floating point on the PDP-11/40 is not supported.)

      -msoft-float
          Do not use hardware floating point.

      -mac0
          Return floating-point results in ac0 (fr0 in Unix assembler
          syntax).

      -mno-ac0
          Return floating-point results in memory.  This is the default.

      -m40
          Generate code for a PDP-11/40.

      -m45
          Generate code for a PDP-11/45.  This is the default.

      -m10
          Generate code for a PDP-11/10.

      -mbcopy-builtin
          Use inline "movmemhi" patterns for copying memory.  This is the
          default.

      -mbcopy
          Do not use inline "movmemhi" patterns for copying memory.

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

      -mint32
      -mno-int16
          Use 32-bit "int".

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

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



                                   - 192 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

      -mdec-asm
          Use DEC assembler syntax.  This is the default when configured for
          any PDP-11 target other than pdp11-*-bsd.

      PowerPC Options

      These are listed under

      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
      -mmfcrf



                                   - 193 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mno-mfcrf
      -mpopcntb
      -mno-popcntb
      -mfprnd
      -mno-fprnd
          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 Freescale MPC5xx, MPC6xx, MPC8xx
          microprocessors, and the IBM 4xx, 6xx, and follow-on
          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 supporting the POWER
          architecture.

          You use these options to specify which instructions are available
          on the processor you are using.  The default value of these
          options is determined when 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
          to use the optional PowerPC architecture instructions in the
          Graphics group, including floating-point select.

          The -mmfcrf option allows GCC to generate the move from condition
          register field instruction implemented on the POWER4 processor and
          other processors that support the PowerPC V2.01 architecture.  The
          -mpopcntb option allows GCC to generate the popcount and double
          precision FP reciprocal estimate instruction implemented on the
          POWER5 processor and other processors that support the PowerPC
          V2.02 architecture.  The -mfprnd option allows GCC to generate the
          FP round to integer instructions implemented on the POWER5+
          processor and other processors that support the PowerPC V2.03



                                   - 194 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          architecture.

          The -mpowerpc64 option allows GCC to generate the additional
          64-bit instructions that are found in the full PowerPC64
          architecture and to treat GPRs as 64-bit, doubleword quantities.
          GCC defaults to -mno-powerpc64.

          If you specify both -mno-power and -mno-powerpc, GCC will use only
          the instructions in the common subset of both architectures plus
          some special AIX common-mode calls, and will not use the MQ
          register.  Specifying both -mpower and -mpowerpc permits GCC to
          use any instruction from either architecture and to allow use of
          the MQ register; specify this for the Motorola MPC601.

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

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

      -mcpu=cpu_type
          Set architecture type, register usage, choice of mnemonics, and
          instruction scheduling parameters for machine type cpu_type.
          Supported values for cpu_type are 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, ec603e, G3, G4, G5,
          power, power2, power3, power4, power5, power5+, power6, common,
          powerpc, powerpc64, rios, rios1, rios2, rsc, and rs64.

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

          -mcpu=power, -mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64
          specify generic POWER, POWER2, pure 32-bit PowerPC (i.e., not
          MPC601), and 64-bit PowerPC architecture machine types, with an
          appropriate, generic processor model assumed for scheduling



                                   - 195 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          purposes.

          The other options specify a specific processor.  Code generated
          under those options will run best on that processor, and may not
          run at all on others.

          The -mcpu options automatically enable or disable the following
          options: -maltivec, -mfprnd, -mhard-float, -mmfcrf, -mmultiple,
          -mnew-mnemonics, -mpopcntb, -mpower, -mpower2, -mpowerpc64,
          -mpowerpc-gpopt, -mpowerpc-gfxopt, -mstring, -mmulhw, -mdlmzb.
          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 because 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 parameters set by
          -mtune.

      -mswdiv
      -mno-swdiv
          Generate code to compute division as reciprocal estimate and
          iterative refinement, creating opportunities for increased
          throughput.  This feature requires: optional PowerPC Graphics
          instruction set for single precision and FRE instruction for
          double precision, assuming divides cannot generate user-visible
          traps, and the domain values not include Infinities, denormals or
          zero denominator.

      -maltivec
      -mno-altivec
          Generate code that uses (does not use) AltiVec instructions, and
          also enable the use of built-in functions that allow more direct
          access to the AltiVec instruction set.  You may also need to set
          -mabi=altivec to adjust the current ABI with AltiVec ABI
          enhancements.




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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mvrsave
      -mno-vrsave
          Generate VRSAVE instructions when generating AltiVec code.

      -msecure-plt
          Generate code that allows ld and ld.so to build executables and
          shared libraries with non-exec .plt and .got sections.  This is a
          PowerPC 32-bit SYSV ABI option.

      -mbss-plt
          Generate code that uses a BSS .plt section that ld.so fills in,
          and requires .plt and .got sections that are both writable and
          executable.  This is a PowerPC 32-bit SYSV ABI option.

      -misel
      -mno-isel
          This switch enables or disables the generation of ISEL
          instructions.

      -misel=yes/no
          This switch has been deprecated.  Use -misel and -mno-isel
          instead.

      -mspe
      -mno-spe
          This switch enables or disables the generation of SPE simd
          instructions.

      -mspe=yes/no
          This option has been deprecated.  Use -mspe and -mno-spe instead.

      -mfloat-gprs=yes/single/double/no
      -mfloat-gprs
          This switch enables or disables the generation of floating point
          operations on the general purpose registers for architectures that
          support it.

          The argument yes or single enables the use of single-precision
          floating point operations.

          The argument double enables the use of single and double-precision
          floating point operations.

          The argument no disables floating point operations on the general
          purpose registers.

          This option is currently only available on the MPC854x.

      -m32



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -m64
          Generate code for 32-bit or 64-bit environments of Darwin and SVR4
          targets (including GNU/Linux).  The 32-bit environment sets int,
          long and pointer to 32 bits and generates code that runs on any
          PowerPC variant.  The 64-bit environment sets int to 32 bits and
          long and pointer to 64 bits, and generates code for PowerPC64, as
          for -mpowerpc64.

      -mfull-toc
      -mno-fp-in-toc
      -mno-sum-in-toc
      -mminimal-toc
          Modify generation of the TOC (Table Of Contents), which is created
          for every executable file.  The -mfull-toc option is selected by
          default.  In that case, GCC will allocate at least one TOC entry
          for each unique non-automatic variable reference in your program.
          GCC will also place floating-point constants in the TOC.  However,
          only 16,384 entries are 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
          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 XL compiler
          semantics when using AIX-compatible ABI.  Pass floating-point



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          arguments to prototyped functions beyond the register save area
          (RSA) on the stack in addition to argument FPRs.  Do not assume
          that most significant double in 128-bit long double value is
          properly rounded when comparing values and converting to double.
          Use XL symbol names for long double support routines.

          The AIX calling convention was extended but not initially
          documented to handle an obscure K&R C case of calling a function
          that takes the address of its arguments with fewer arguments than
          declared.  IBM XL compilers access floating point arguments which
          do not fit in the RSA from the stack when a subroutine is compiled
          without optimization.  Because always storing floating-point
          arguments on the stack is inefficient and rarely needed, this
          option is not enabled by default and only is necessary when
          calling subroutines compiled by IBM XL compilers without
          optimization.

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

      -malign-natural
      -malign-power
          On AIX, 32-bit 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.

          On 64-bit Darwin, natural alignment is the default, and
          -malign-power is not supported.

      -msoft-float
      -mhard-float
          Generate code that does not use (uses) the floating-point register
          set.  Software floating point emulation is provided if you use the
          -msoft-float option, and pass the option to GCC when linking.

      -mmultiple
      -mno-multiple
          Generate code that uses (does not use) the load multiple word
          instructions and the store multiple word instructions.  These



                                   - 199 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 floating is used.

      -mmulhw
      -mno-mulhw
          Generate code that uses (does not use) the half-word multiply and
          multiply-accumulate instructions on the IBM 405 and 440
          processors.  These instructions are generated by default when
          targetting those processors.

      -mdlmzb
      -mno-dlmzb
          Generate code that uses (does not use) the string-search dlmzb
          instruction on the IBM 405 and 440 processors.  This instruction
          is generated by default when targetting those processors.

      -mno-bit-align
      -mbit-align



                                   - 200 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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



                                   - 201 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mdynamic-no-pic
          On Darwin and Mac OS X systems, compile code so that it is not
          relocatable, but that its external references are relocatable.
          The resulting code is suitable for applications, 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 dependences are costly,
          true_store_to_load: a true dependence from store to load is
          costly, store_to_load: any dependence from store to load is
          costly, number: any dependence 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



                                   - 202 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Solaris operating system.

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

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

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

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

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

      -mabi=abi-type
          Extend the current ABI with a particular extension, or remove such
          extension.  Valid values are altivec, no-altivec, spe, no-spe,
          ibmlongdouble, ieeelongdouble.

      -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.

      -mabi=ibmlongdouble
          Change the current ABI to use IBM extended precision long double.
          This is a PowerPC 32-bit SYSV ABI option.

      -mabi=ieeelongdouble
          Change the current ABI to use IEEE extended precision long double.
          This is a PowerPC 32-bit Linux ABI option.

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



                                   - 203 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

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



                                   - 204 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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
          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 data
          in the .sdata section.  Put small uninitialized global data in the
          .sbss section.  Do not use register "r13" to address small data
          however.  This is the default behavior unless other -msdata
          options are used.

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

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

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



                                   - 205 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          forms.

      -mlongcall
      -mno-longcall
          By default assume that all calls are far away so that a longer
          more expensive calling sequence is required.  This is required for
          calls further than 32 megabytes (33,554,432 bytes) from the
          current location.  A short call will be generated if the compiler
          knows the call cannot be that far away.  This setting can be
          overridden by the "shortcall" function attribute, or by "#pragma
          longcall(0)".

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

          On Darwin/PPC systems, "#pragma longcall" will generate "jbsr
          callee, L42", plus a "branch island" (glue code).  The two target
          addresses represent the callee and the "branch island".  The
          Darwin/PPC linker will prefer the first address and generate a "bl
          callee" if the PPC "bl" instruction will reach the callee
          directly; otherwise, the linker will generate "bl L42" to call the
          "branch island".  The "branch island" is appended to the body of
          the calling function; it computes the full 32-bit address of the
          callee and jumps to it.

          On Mach-O (Darwin) systems, this option directs the compiler 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 preprocessor and linker.

      S/390 and zSeries Options

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

      -mhard-float
      -msoft-float
          Use (do not use) the hardware floating-point instructions and
          registers for floating-point operations.  When -msoft-float is



                                   - 206 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          specified, functions in libgcc.a will be used to perform
          floating-point operations.  When -mhard-float is specified, the
          compiler generates IEEE floating-point instructions.  This is the
          default.

      -mlong-double-64
      -mlong-double-128
          These switches control the size of "long double" type. A size of
          64bit makes the "long double" type equivalent to the "double"
          type. This is the default.

      -mbackchain
      -mno-backchain
          Store (do not store) the address of the caller's frame as
          backchain pointer into the callee's stack frame.  A backchain may
          be needed to allow debugging using tools that do not understand
          DWARF-2 call frame information.  When -mno-packed-stack is in
          effect, the backchain pointer is stored at the bottom of the stack
          frame; when -mpacked-stack is in effect, the backchain is placed
          into the topmost word of the 96/160 byte register save area.

          In general, code compiled with -mbackchain is call-compatible with
          code compiled with -mmo-backchain; however, use of the backchain
          for debugging purposes usually requires that the whole binary is
          built with -mbackchain.  Note that the combination of -mbackchain,
          -mpacked-stack and -mhard-float is not supported.  In order to
          build a linux kernel use -msoft-float.

          The default is to not maintain the backchain.

      -mpacked-stack
      -mno-packed-stack
          Use (do not use) the packed stack layout.  When -mno-packed-stack
          is specified, the compiler uses the all fields of the 96/160 byte
          register save area only for their default purpose; unused fields
          still take up stack space.  When -mpacked-stack is specified,
          register save slots are densely packed at the top of the register
          save area; unused space is reused for other purposes, allowing for
          more efficient use of the available stack space.  However, when
          -mbackchain is also in effect, the topmost word of the save area
          is always used to store the backchain, and the return address
          register is always saved two words below the backchain.

          As long as the stack frame backchain is not used, code generated
          with -mpacked-stack is call-compatible with code generated with
          -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95
          for S/390 or zSeries generated code that uses the stack frame
          backchain at run time, not just for debugging purposes.  Such code
          is not call-compatible with code compiled with -mpacked-stack.



                                   - 207 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Also, note that the combination of -mbackchain, -mpacked-stack and
          -mhard-float is not supported.  In order to build a linux kernel
          use -msoft-float.

          The default is to not use the packed stack layout.

      -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, generate 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 available 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 unless optimizing for size.

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

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




                                   - 208 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mtune=cpu-type
          Tune to cpu-type everything applicable about the generated 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.

      -mtpf-trace
      -mno-tpf-trace
          Generate code that adds (does not add) in TPF OS specific branches
          to trace routines in the operating system.  This option is off by
          default, even when compiling for the TPF OS.

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

      -mwarn-framesize=framesize
          Emit a warning if the current function exceeds the given frame
          size.  Because this is a compile time check it doesn't need to be
          a real problem when the program runs.  It is intended to identify
          functions which most probably cause a stack overflow.  It is
          useful to be used in an environment with limited stack size e.g.
          the linux kernel.

      -mwarn-dynamicstack
          Emit a warning if the function calls alloca or uses dynamically
          sized arrays.  This is generally a bad idea with a limited stack
          size.

      -mstack-guard=stack-guard
      -mstack-size=stack-size
          These arguments always have to be used in conjunction.  If they
          are present the s390 back end emits additional instructions in the
          function prologue which trigger a trap if the stack size is
          stack-guard bytes above the stack-size (remember that the stack on
          s390 grows downward).  These options are intended to be used to
          help debugging stack overflow problems.  The additionally emitted
          code causes only little overhead and hence can also be used in
          production like systems without greater performance degradation.
          The given values have to be exact powers of 2 and stack-size has
          to be greater than stack-guard without exceeding 64k.  In order to
          be efficient the extra code makes the assumption that the stack
          starts at an address aligned to the value given by stack-size.

      Score Options

      These options are defined for Score implementations:



                                   - 209 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -meb
          Compile code for big endian mode.  This is the default.

      -mel
          Compile code for little endian mode.

      -mnhwloop
          Disable generate bcnz instruction.

      -muls
          Enable generate unaligned load and store instruction.

      -mmac
          Enable the use of multiply-accumulate instructions. Disabled by
          default.

      -mscore5
          Specify the SCORE5 as the target architecture.

      -mscore5u
          Specify the SCORE5U of the target architecture.

      -mscore7
          Specify the SCORE7 as the target architecture. This is the
          default.

      -mscore7d
          Specify the SCORE7D as the target architecture.

      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



                                   - 210 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      -m4 Generate code for the SH4.

      -m4a-nofpu
          Generate code for the SH4al-dsp, or for a SH4a in such a way that
          the floating-point unit is not used.

      -m4a-single-only
          Generate code for the SH4a, in such a way that no double-precision
          floating point operations are used.

      -m4a-single
          Generate code for the SH4a assuming the floating-point unit is in
          single-precision mode by default.

      -m4a
          Generate code for the SH4a.

      -m4al
          Same as -m4a-nofpu, except that it implicitly passes -dsp to the
          assembler.  GCC doesn't generate any DSP instructions at the
          moment.

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

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

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

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

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

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




                                   - 211 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mhitachi
          Comply with the calling conventions defined by Renesas.

      -mrenesas
          Comply with the calling conventions defined by Renesas.

      -mno-renesas
          Comply with the calling conventions defined for GCC before the
          Renesas conventions were available.  This option is the default
          for all targets of the SH toolchain except for sh-symbianelf.

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

      -mieee
          Increase IEEE-compliance of floating-point code.  At the moment,
          this is equivalent to -fno-finite-math-only.  When generating 16
          bit SH opcodes, getting IEEE-conforming results for comparisons of
          NANs / infinities incurs extra overhead in every floating point
          comparison, therefore the default is set to -ffinite-math-only.

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

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

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

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

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

      -multcost=number
          Set the cost to assume for a multiply insn.

      -mdiv=strategy
          Set the division strategy to use for SHmedia code.  strategy must
          be one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l,



                                   - 212 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          inv:call, inv:call2, inv:fp .  "fp" performs the operation in
          floating point.  This has a very high latency, but needs only a
          few instructions, so it might be a good choice if your code has
          enough easily exploitable ILP to allow the compiler to schedule
          the floating point instructions together with other instructions.
          Division by zero causes a floating point exception.  "inv" uses
          integer operations to calculate the inverse of the divisor, and
          then multiplies the dividend with the inverse.  This strategy
          allows cse and hoisting of the inverse calculation.  Division by
          zero calculates an unspecified result, but does not trap.
          "inv:minlat" is a variant of "inv" where if no cse / hoisting
          opportunities have been found, or if the entire operation has been
          hoisted to the same place, the last stages of the inverse
          calculation are intertwined with the final multiply to reduce the
          overall latency, at the expense of using a few more instructions,
          and thus offering fewer scheduling opportunities with other code.
          "call" calls a library function that usually implements the
          inv:minlat strategy.  This gives high code density for
          m5-*media-nofpu compilations.  "call2" uses a different entry
          point of the same library function, where it assumes that a
          pointer to a lookup table has already been set up, which exposes
          the pointer load to cse / code hoisting optimizations.
          "inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm
          for initial code generation, but if the code stays unoptimized,
          revert to the "call", "call2", or "fp" strategies, respectively.
          Note that the potentially-trapping side effect of division by zero
          is carried by a separate instruction, so it is possible that all
          the integer instructions are hoisted out, but the marker for the
          side effect stays where it is.  A recombination to fp operations
          or a call is not possible in that case.  "inv20u" and "inv20l" are
          variants of the "inv:minlat" strategy.  In the case that the
          inverse calculation was nor separated from the multiply, they
          speed up division where the dividend fits into 20 bits (plus sign
          where applicable), by inserting a test to skip a number of
          operations in this case; this test slows down the case of larger
          dividends.  inv20u assumes the case of a such a small dividend to
          be unlikely, and inv20l assumes it to be likely.

      -mdivsi3_libfunc=name
          Set the name of the library function used for 32 bit signed
          division to name.  This only affect the name used in the call and
          inv:call division strategies, and the compiler will still expect
          the same sets of input/output/clobbered registers as if this
          option was not present.

      -madjust-unroll
          Throttle unrolling to avoid thrashing target registers.  This
          option only has an effect if the gcc code base supports the
          TARGET_ADJUST_UNROLL_MAX target hook.



                                   - 213 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -mindexed-addressing
          Enable the use of the indexed addressing mode for
          SHmedia32/SHcompact.  This is only safe if the hardware and/or OS
          implement 32 bit wrap-around semantics for the indexed addressing
          mode.  The architecture allows the implementation of processors
          with 64 bit MMU, which the OS could use to get 32 bit addressing,
          but since no current hardware implementation supports this or any
          other way to make the indexed addressing mode safe to use in the
          32 bit ABI, the default is -mno-indexed-addressing.

      -mgettrcost=number
          Set the cost assumed for the gettr instruction to number.  The
          default is 2 if -mpt-fixed is in effect, 100 otherwise.

      -mpt-fixed
          Assume pt* instructions won't trap.  This will generally generate
          better scheduled code, but is unsafe on current hardware.  The
          current architecture definition says that ptabs and ptrel trap
          when the target anded with 3 is 3.  This has the unintentional
          effect of making it unsafe to schedule ptabs / ptrel before a
          branch, or hoist it out of a loop.  For example,
          __do_global_ctors, a part of libgcc that runs constructors at
          program startup, calls functions in a list which is delimited by
          -1.  With the -mpt-fixed option, the ptabs will be done before
          testing against -1.  That means that all the constructors will be
          run a bit quicker, but when the loop comes to the end of the list,
          the program crashes because ptabs loads -1 into a target register.
          Since this option is unsafe for any hardware implementing the
          current architecture specification, the default is -mno-pt-fixed.
          Unless the user specifies a specific cost with -mgettrcost,
          -mno-pt-fixed also implies -mgettrcost=100; this deters register
          allocation using target registers for storing ordinary integers.

      -minvalid-symbols
          Assume symbols might be invalid.  Ordinary function symbols
          generated by the compiler will always be valid to load with
          movi/shori/ptabs or movi/shori/ptrel, but with assembler and/or
          linker tricks it is possible to generate symbols that will cause
          ptabs / ptrel to trap.  This option is only meaningful when
          -mno-pt-fixed is in effect.  It will then prevent cross-basic-
          block cse, hoisting and most scheduling of symbol loads.  The
          default is -mno-invalid-symbols.

      SPARC Options

      These -m options are supported on the SPARC:

      -mno-app-regs
      -mapp-regs



                                   - 214 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

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

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

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

      -mno-unaligned-doubles
      -munaligned-doubles



                                   - 215 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          Assume that doubles have 8 byte alignment.  This is the default.

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

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

      -mimpure-text
          -mimpure-text, used in addition to -shared, tells the compiler to
          not pass -z text to the linker when 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.

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

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

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



                                   - 216 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          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 SPARClite 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 SPARClet but not in SPARC-V7.  With
          -mcpu=tsc701, the compiler 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/IIi
          chips.  With -mcpu=ultrasparc3, the compiler additionally
          optimizes it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+
          chips.  With -mcpu=niagara, the compiler additionally optimizes it
          for Sun UltraSPARC T1 chips.

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



                                   - 217 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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,
          ultrasparc3, and niagara.

      -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
          addresses, programs may be linked anywhere in memory, the text and



                                   - 218 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 global 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 preprocessor 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 preprocessor and linker.  This
          option does not affect the thread safety of object code produced
          by the compiler or that of libraries supplied with it.

      -pthread
          This is a synonym for -pthreads.

      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).




                                   - 219 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

      TMS320C3x/C4x Options

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

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

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

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

      -mdb
      -mno-db
          Enable (disable) generation of code using decrement and branch,
          DBcond(D), 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



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

      -mloop-unsigned
      -mno-loop-unsigned



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

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

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

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

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

      V850 Options

      These -m options are defined for V850 implementations:

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

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

      -mno-prolog-function



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -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.

      -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.



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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.

      VAX Options

      These -m options are defined for the VAX:

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

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

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

      x86-64 Options

      These are listed under

      Xstormy16 Options

      These options are defined for Xstormy16:

      -msim
          Choose startup files and linker script suitable for the simulator.

      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"



                                   - 224 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          instructions.  The use of "CONST16" is enabled by default only if
          the "L32R" instruction is not available.

      -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



                                   - 225 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          call instruction.  This translation typically occurs for calls to
          functions in other source files.  Specifically, the assembler
          translates a direct "CALL" instruction into an "L32R" followed by
          a "CALLX" instruction.  The default is -mno-longcalls.  This
          option should be used in programs where the call target can
          potentially be out of range.  This option is implemented in the
          assembler, not the compiler, so the assembly code generated by GCC
          will still show direct call 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.

      zSeries Options

      These are listed under

      Options for Code Generation Conventions

      These machine-independent options control the interface conventions
      used in code generation.

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

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

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

      -fwrapv
          This option instructs the compiler to assume that signed
          arithmetic overflow of addition, subtraction and multiplication
          wraps around using twos-complement representation.  This flag
          enables some optimizations and disables others.  This option is
          enabled by default for the Java front-end, as required by the Java
          language specification.

      -fexceptions
          Enable exception handling.  Generates extra code needed to
          propagate exceptions.  For some targets, this implies GCC will
          generate frame unwind information for all functions, which can



                                   - 226 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          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 handling, and disable it for languages like C that do
          not normally require it.  However, you may need to enable this
          option when compiling C code that needs to interoperate properly
          with exception handlers written in C++.  You may also wish to
          disable this option if you are compiling older C++ programs that
          don't use exception handling.

      -fnon-call-exceptions
          Generate code that allows trapping instructions to throw
          exceptions.  Note that this requires platform-specific runtime
          support that does not exist everywhere.  Moreover, it only allows
          trapping instructions to throw exceptions, i.e. memory references
          or floating point instructions.  It does not allow exceptions to
          be thrown from arbitrary signal handlers such as "SIGALRM".

      -funwind-tables
          Similar to -fexceptions, except that it will just generate any
          needed static data, but will not affect the generated code in any
          other way.  You will normally not enable this option; instead, a
          language processor that needs this handling would enable it on
          your behalf.

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

      -fpcc-struct-return
          Return "short" "struct" and "union" values in memory like longer
          ones, rather than in registers.  This convention is less
          efficient, but it has the advantage of allowing intercallability
          between GCC-compiled files and files compiled with other
          compilers, 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.




                                   - 227 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -freg-struct-return
          Return "struct" and "union" values in registers when possible.
          This is more efficient for small structures than
          -fpcc-struct-return.

          If you specify neither -fpcc-struct-return nor
          -freg-struct-return, GCC defaults to whichever convention is
          standard for the target.  If there is no standard convention, GCC
          defaults to -fpcc-struct-return, except on targets where GCC is
          the principal compiler.  In those cases, we can choose the
          standard, and we chose the more efficient register return
          alternative.

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

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

          Warning: the -fshort-enums switch causes GCC to generate code that
          is not binary compatible with code generated without that switch.
          Use it to conform to a non-default application binary interface.

      -fshort-double
          Use the same size for "double" as for "float".

          Warning: the -fshort-double switch causes GCC to generate code
          that is not binary compatible with code generated without that
          switch.  Use it to conform to a non-default application binary
          interface.

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

          Warning: the -fshort-wchar switch causes GCC to generate code that
          is not binary compatible with code generated without that switch.
          Use it to conform to a non-default application binary interface.

      -fno-common
          In C, allocate even uninitialized global variables in the data
          section of the object file, rather than generating them as common
          blocks.  This has the effect that if the same variable is declared



                                   - 228 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          (without "extern") in two different compilations, you will get an
          error when you link them.  The only reason this might be useful is
          if you wish to verify that the program will work on other systems
          which always work this way.

      -fno-ident
          Ignore the #ident directive.

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

      -fverbose-asm
          Put extra commentary information in the generated assembly code to
          make it more readable.  This option is generally only of use to
          those who actually need to read the generated assembly code
          (perhaps while debugging the compiler itself).

          -fno-verbose-asm, the default, causes the extra information to be
          omitted and is useful when comparing two assembler files.

      -fpic
          Generate position-independent code (PIC) suitable for use in a
          shared library, if supported for the target machine.  Such code
          accesses all constant addresses through a global offset table
          (GOT).  The dynamic loader resolves the GOT entries when the
          program starts (the dynamic loader is not part of GCC; it is part
          of the operating system).  If the GOT size for the linked
          executable exceeds a machine-specific 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.)

          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.

          When this flag is set, the macros "__pic__" and "__PIC__" are
          defined to 1.

      -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



                                   - 229 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          on the m68k, PowerPC and SPARC.

          Position-independent code requires special support, and therefore
          works only on certain machines.

          When this flag is set, the macros "__pic__" and "__PIC__" are
          defined to 2.

      -fpie
      -fPIE
          These options are similar to -fpic and -fPIC, but generated
          position independent code can be only linked into executables.
          Usually these options are used when -pie GCC option will be used
          during linking.

      -fno-jump-tables
          Do not use jump tables for switch statements even where it would
          be more efficient than other code generation strategies.  This
          option is of use in conjunction with -fpic or -fPIC for building
          code which forms part of a dynamic linker and cannot reference the
          address of a jump table.  On some targets, jump tables do not
          require a GOT and this option is not needed.

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

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

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

      -fcall-used-reg
          Treat the register named reg as an allocable register that is
          clobbered by function calls.  It may be allocated for temporaries
          or variables that do not live across a call.  Functions compiled
          this way will not save and restore the register reg.

          It is an error to used this flag with the frame pointer or stack
          pointer.  Use of this flag for other registers that have fixed
          pervasive roles in the machine's execution model will produce
          disastrous results.

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




                                   - 230 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



      -fcall-saved-reg
          Treat the register named reg as an allocable register saved by
          functions.  It may be allocated even for temporaries or variables
          that live across a call.  Functions compiled this way will save
          and restore the register reg if they use it.

          It is an error to used this flag with the frame pointer or stack
          pointer.  Use of this flag for other registers that have fixed
          pervasive roles in the machine's execution model will produce
          disastrous results.

          A different sort of disaster will result from the use of this flag
          for a register in which function values may be returned.

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

      -fpack-struct[=n]
          Without a value specified, pack all structure members together
          without holes.  When a value is specified (which must be a small
          power of two), pack structure members according to this value,
          representing the maximum alignment (that is, objects with default
          alignment requirements larger than this will be output potentially
          unaligned at the next fitting location.

          Warning: the -fpack-struct switch causes GCC to generate code that
          is not binary compatible with code generated without that switch.
          Additionally, it makes the code suboptimal.  Use it to conform to
          a non-default application binary interface.

      -finstrument-functions
          Generate instrumentation calls for entry and exit to functions.
          Just after function entry and just before function exit, the
          following profiling functions will be called with the address of
          the current function and its call site.  (On some platforms,
          "__builtin_return_address" does not work beyond the current
          function, so the call site information may not be available to the
          profiling functions otherwise.)

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

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

          This instrumentation is also done for functions expanded inline in
          other functions.  The profiling calls will indicate where,



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 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



          conceptually, the inline function is entered and exited.  This
          means that addressable versions of such functions must be
          available.  If all your uses of a function are expanded inline,
          this may mean an additional expansion of code size.  If you use
          extern inline in your C code, an addressable version of such
          functions must be provided.  (This is normally the case anyways,
          but if you get lucky and the optimizer always expands the
          functions inline, you might have gotten away without providing
          static copies.)

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

      -fstack-check
          Generate code to verify that you do not go beyond the boundary of
          the stack.  You should specify this flag if you are running in an
          environment with multiple threads, but only rarely need to specify
          it in a single-threaded environment since stack overflow is
          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 boundary, so it is possible to catch the signal
          without taking special precautions.

          For instance, if the stack starts at absolute address 0x80000000
          and grows downwards, you can use the flags
          -fstack-limit-symbol=__stack_limit and
          -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of
          128KB.  Note that this may only work with the GNU linker.

      -fargument-alias
      -fargument-noalias



                                   - 232 -       Formatted:  August 20, 2017






 GCC(1)                           gcc-4.2.3                           GCC(1)
 GNU                                                                     GNU

                                 2008-02-01



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

          -fargument-alias specifies that arguments (parameters) may alias
          each other and may alias global storage.-fargument-noalias
          specifies that arguments do not alias each other, but may alias
          global storage.-fargument-noalias-global specifies that arguments
          do not alias each other and do not alias global storage.
          -fargument-noalias-anything specifies that arguments do not alias
          any other storage.

          Each language will automatically use whatever option is required
          by the language standard.  You should not need to use these
          options yourself.

      -fleading-underscore
          This option and its counterpart, -fno-leading-underscore, forcibly
          change the way C symbols are represented in the object file.  One
          use is to help link with legacy assembly code.

          Warning: the -fleading-underscore switch causes GCC to generate
          code that is not binary compatible with code generated without
          that switch.  Use it to conform to a non-default application
          binary interface.  Not all targets provide complete support for
          this switch.

      -ftls-model=model
          Alter the thread-local storage model to be used.  The model
          argument should be one of "global-dynamic", "local-dynamic",
          "initial-exec" or "local-exec".

          The default without -fpic is "initial-exec"; with -fpic the
          default is "global-dynamic".

      -fvisibility=default|internal|hidden|protected
          Set the default ELF image symbol visibility to the specified
          option---all symbols will be marked with this unless overridden
          within the code.  Using this feature can very substantially
          improve linking and load times of shared object libraries, produce
          more optimized code, provide near-perfect API export and prevent
          symbol clashes.  It is strongly recommended that you use this in
          any shared objects you distribute.

          Despite the nomenclature, "default" always means public ie;
          available to be linked against from outside the shared object.
          "protected" and "internal" are pretty useless in real-world usage
          so the only other commonly used option will be "hidden".  The



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                                 2008-02-01



          default if -fvisibility isn't specified is "default", i.e., make
          every symbol public---this causes the same behavior as previous
          versions of GCC.

          A good explanation of the benefits offered by ensuring ELF symbols
          have the correct visibility is given by "How To Write Shared
          Libraries" by Ulrich Drepper (which can be found at
          <http://people.redhat.com/~drepper/>)---however a superior
          solution made possible by this option to marking things hidden
          when the default is public is to make the default hidden and mark
          things public.  This is the norm with DLL's on Windows and with
          -fvisibility=hidden and "__attribute__ ((visibility("default")))"
          instead of "__declspec(dllexport)" you get almost identical
          semantics with identical syntax.  This is a great boon to those
          working with cross-platform projects.

          For those adding visibility support to existing code, you may find
          #pragma GCC visibility of use.  This works by you enclosing the
          declarations you wish to set visibility for with (for example)
          #pragma GCC visibility push(hidden) and #pragma GCC visibility
          pop.  Bear in mind that symbol visibility should be viewed as part
          of the API interface contract and thus all new code should always
          specify visibility when it is not the default ie; declarations
          only for use within the local DSO should always be marked
          explicitly as hidden as so to avoid PLT indirection
          overheads---making this abundantly clear also aids readability and
          self-documentation of the code.  Note that due to ISO C++
          specification requirements, operator new and operator delete must
          always be of default visibility.

          Be aware that headers from outside your project, in particular
          system headers and headers from any other library you use, may not
          be expecting to be compiled with visibility other than the
          default.  You may need to explicitly say #pragma GCC visibility
          push(default) before including any such headers.

          extern declarations are not affected by -fvisibility, so a lot of
          code can be recompiled with -fvisibility=hidden with no
          modifications.  However, this means that calls to extern functions
          with no explicit visibility will use the PLT, so it is more
          effective to use __attribute ((visibility)) and/or #pragma GCC
          visibility to tell the compiler which extern declarations should
          be treated as hidden.

          Note that -fvisibility does affect C++ vague linkage entities.
          This means that, for instance, an exception class that will be
          thrown between DSOs must be explicitly marked with default
          visibility so that the type_info nodes will be unified between the
          DSOs.



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                                 2008-02-01



          An overview of these techniques, their benefits and how to use
          them is at <http://gcc.gnu.org/wiki/Visibility>.

 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 multibyte encodings that
          contain quote and escape characters that would otherwise be
          interpreted as a string end or escape.

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

          If the LC_ALL environment variable is set, it overrides the value
          of LC_CTYPE and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES
          default to the value of the LANG environment variable.  If none of
          these variables are set, GCC defaults to traditional C English
          behavior.

      TMPDIR
          If TMPDIR is set, it specifies the directory to use for temporary
          files.  GCC uses temporary files to hold the output of one stage
          of compilation which is to be used as input to the next stage: for
          example, the output of the preprocessor, which is the input to the
          compiler proper.

      GCC_EXEC_PREFIX



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 GNU                                                                     GNU

                                 2008-02-01



          If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the
          names of the subprograms executed by the compiler.  No slash is
          added when this prefix is combined with the name of a subprogram,
          but you can specify a prefix that ends with a slash if you wish.

          If GCC_EXEC_PREFIX is not set, GCC will attempt to figure out an
          appropriate prefix to use based on the pathname it was invoked
          with.

          If GCC cannot find the subprogram using the specified prefix, it
          tries looking in the usual places for the subprogram.

          The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ 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
          alternate directory name.  Thus, with -Bfoo/, GCC will search
          foo/bar where it would normally search /usr/local/lib/bar.  These
          alternate directories are searched first; the standard directories
          come next.

      COMPILER_PATH
          The value of COMPILER_PATH is a colon-separated list of
          directories, much like PATH.  GCC tries the directories thus
          specified when searching for subprograms, if it can't find the
          subprograms using GCC_EXEC_PREFIX.

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

      LANG
          This variable is used to pass locale information to the compiler.
          One way in which this information is used is to determine the
          character set to be used when character literals, string literals



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                                 2008-02-01



          and comments are parsed in C and C++.  When the compiler is
          configured to allow multibyte characters, the following values for
          LANG are recognized:

          C-JIS
              Recognize JIS characters.

          C-SJIS
              Recognize SJIS characters.

          C-EUCJP
              Recognize EUCJP characters.

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

      Some additional environments variables affect the behavior of the
      preprocessor.

      CPATH
      C_INCLUDE_PATH
      CPLUS_INCLUDE_PATH
      OBJC_INCLUDE_PATH
          Each variable's value is a list of directories 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 colon.

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

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

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

      DEPENDENCIES_OUTPUT
          If this variable is set, its value specifies how to output



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                                 2008-02-01



          dependencies for Make based on the non-system header files
          processed by the compiler.  System header files are ignored in the
          dependency output.

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

          In other words, this environment variable is equivalent to
          combining the options -MM and -MF, with an optional -MT switch
          too.

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

 BUGS
      For instructions on reporting bugs, see
      <http://gcc.gnu.org/bugs.html>.

 FOOTNOTES
      1.  On some systems, gcc -shared needs to build supplementary stub
          code for constructors to work.  On multi-libbed systems, gcc
          -shared must select the correct support libraries to link against.
          Failing to supply the correct flags may lead to subtle defects.
          Supplying them in cases where they are not necessary is innocuous.

 SEE ALSO
      gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1),
      gdb(1), adb(1), dbx(1), sdb(1) and the Info entries for gcc, cpp, as,
      ld, binutils and gdb.

 AUTHOR
      See the Info entry for gcc, or
      <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
      contributors to GCC.

 COPYRIGHT
      Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
      1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
      Foundation, Inc.

      Permission is granted to copy, distribute and/or modify this document
      under the terms of the GNU Free Documentation License, Version 1.2 or
      any later version published by the Free Software Foundation; with the



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                                 2008-02-01



      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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