Chapter 4. GCC Command Options
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.
Section 4.3 Compiling C++ Programs, for a summary of special
options for compiling C++ programs.
The gcc program accepts options and file names as operands. Many
options have multi-letter names; therefore multiple single-letter options
may not be grouped: -dr is very different from -d
-r.
You can mix options and other arguments. For the most part, the order
you use doesn't matter. Order does matter when you use several options
of the same kind; for example, if you specify -L more than once,
the directories are searched in the order specified.
Many options have long names starting with -f or with
-W--for example, -fforce-mem,
-fstrength-reduce, -Wformat and so on. Most of
these have both positive and negative forms; the negative form of
-ffoo would be -fno-foo. This manual documents
only one of these two forms, whichever one is not the default.
4.1. Option Summary
Here is a summary of all the options, grouped by type. Explanations are
in the following sections.
- Overall Options
Section 4.2 Options Controlling the Kind of Output.
-c -S -E -o file -pipe -pass-exit-codes
-x language -v -### --help --target-help --version |
- C Language Options
Section 4.4 Options Controlling C Dialect.
-ansi -std=standard -aux-info filename
-fno-asm -fno-builtin -fno-builtin-function
-fhosted -ffreestanding -fms-extensions
-trigraphs -no-integrated-cpp -traditional -traditional-cpp
-fallow-single-precision -fcond-mismatch
-fsigned-bitfields -fsigned-char
-funsigned-bitfields -funsigned-char
-fwritable-strings |
- C++ Language Options
Section 4.5 Options Controlling C++ Dialect.
-fabi-version=n -fno-access-control -fcheck-new
-fconserve-space -fno-const-strings
-fno-elide-constructors
-fno-enforce-eh-specs
-ffor-scope -fno-for-scope -fno-gnu-keywords
-fno-implicit-templates
-fno-implicit-inline-templates
-fno-implement-inlines -fms-extensions
-fno-nonansi-builtins -fno-operator-names
-fno-optional-diags -fpermissive
-frepo -fno-rtti -fstats -ftemplate-depth-n
-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
-Wno-non-template-friend -Wold-style-cast
-Woverloaded-virtual -Wno-pmf-conversions
-Wsign-promo -Wsynth |
- Objective-C Language Options
Section 4.6 Options Controlling Objective-C Dialect.
-fconstant-string-class=class-name
-fgnu-runtime -fnext-runtime
-fno-nil-receivers
-fobjc-exceptions
-freplace-objc-classes
-fzero-link
-gen-decls
-Wno-protocol -Wselector -Wundeclared-selector |
- Language Independent Options
Section 4.7 Options to Control Diagnostic Messages Formatting.
-fmessage-length=n
-fdiagnostics-show-location=[once|every-line] |
- Warning Options
Section 4.8 Options to Request or Suppress Warnings.
-fsyntax-only -pedantic -pedantic-errors
-w -Wextra -Wall -Waggregate-return
-Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment
-Wconversion -Wno-deprecated-declarations
-Wdisabled-optimization -Wno-div-by-zero -Wendif-labels
-Werror -Werror-implicit-function-declaration
-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-invalid-offsetof -Winvalid-pch
-Wlarger-than-len -Wlong-long
-Wmain -Wmissing-braces
-Wmissing-format-attribute -Wmissing-noreturn
-Wno-multichar -Wnonnull -Wpacked -Wpadded
-Wparentheses -Wpointer-arith -Wredundant-decls
-Wreturn-type -Wsequence-point -Wshadow
-Wsign-compare -Wstrict-aliasing
-Wswitch -Wswitch-default -Wswitch-enum
-Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized
-Wunknown-pragmas -Wunreachable-code
-Wunused -Wunused-function -Wunused-label -Wunused-parameter
-Wunused-value -Wunused-variable -Wwrite-strings |
- C-only Warning Options
-Wbad-function-cast -Wmissing-declarations
-Wmissing-prototypes -Wnested-externs -Wold-style-definition
-Wstrict-prototypes -Wtraditional
-Wdeclaration-after-statement |
- Debugging Options
Section 4.9 Options for Debugging Your Program or GCC.
-dletters -dumpspecs -dumpmachine -dumpversion
-fdump-unnumbered -fdump-translation-unit[-n]
-fdump-class-hierarchy[-n]
-fdump-tree-original[-n]
-fdump-tree-optimized[-n]
-fdump-tree-inlined[-n]
-feliminate-dwarf2-dups -feliminate-unused-debug-types
-feliminate-unused-debug-symbols -fmem-report -fprofile-arcs
-frandom-seed=string -fsched-verbose=n
-ftest-coverage -ftime-report
-g -glevel -gcoff -gdwarf-2
-ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+
-p -pg -print-file-name=library -print-libgcc-file-name
-print-multi-directory -print-multi-lib
-print-prog-name=program -print-search-dirs -Q
-save-temps -time |
- Optimization Options
Section 4.10 Options That Control Optimization.
-falign-functions=n -falign-jumps=n
-falign-labels=n -falign-loops=n
-fbranch-probabilities -fprofile-values -fvpt -fbranch-target-load-optimize
-fbranch-target-load-optimize2 -fcaller-saves -fcprop-registers
-fcse-follow-jumps -fcse-skip-blocks -fdata-sections
-fdelayed-branch -fdelete-null-pointer-checks
-fexpensive-optimizations -ffast-math -ffloat-store
-fforce-addr -fforce-mem -ffunction-sections
-fgcse -fgcse-lm -fgcse-sm -fgcse-las -floop-optimize
-fcrossjumping -fif-conversion -fif-conversion2
-finline-functions -finline-limit=n -fkeep-inline-functions
-fkeep-static-consts -fmerge-constants -fmerge-all-constants
-fmove-all-movables -fnew-ra -fno-branch-count-reg
-fno-default-inline -fno-defer-pop
-fno-function-cse -fno-guess-branch-probability
-fno-inline -fno-math-errno -fno-peephole -fno-peephole2
-funsafe-math-optimizations -ffinite-math-only
-fno-trapping-math -fno-zero-initialized-in-bss
-fomit-frame-pointer -foptimize-register-move
-foptimize-sibling-calls -fprefetch-loop-arrays
-fprofile-generate -fprofile-use
-freduce-all-givs -fregmove -frename-registers
-freorder-blocks -freorder-functions
-frerun-cse-after-loop -frerun-loop-opt
-frounding-math -fschedule-insns -fschedule-insns2
-fno-sched-interblock -fno-sched-spec -fsched-spec-load
-fsched-spec-load-dangerous
-fsched-stalled-insns=n -sched-stalled-insns-dep=n
-fsched2-use-superblocks
-fsched2-use-traces -fsignaling-nans
-fsingle-precision-constant
-fstrength-reduce -fstrict-aliasing -ftracer -fthread-jumps
-funroll-all-loops -funroll-loops -fpeel-loops
-funswitch-loops -fold-unroll-loops -fold-unroll-all-loops
--param name=value
-O -O0 -O1 -O2 -O3 -Os |
- Preprocessor Options
Section 4.11 Options Controlling the Preprocessor.
-Aquestion=answer
-A-question[=answer]
-C -dD -dI -dM -dN
-Dmacro[=defn] -E -H
-idirafter dir
-include file -imacros file
-iprefix file -iwithprefix dir
-iwithprefixbefore dir -isystem dir
-M -MM -MF -MG -MP -MQ -MT -nostdinc
-P -fworking-directory -remap
-trigraphs -undef -Umacro -Wp,option
-Xpreprocessor option |
- Assembler Option
Section 4.12 Passing Options to the Assembler.
-Wa,option -Xassembler option |
- Linker Options
Section 4.13 Options for Linking.
object-file-name -llibrary
-nostartfiles -nodefaultlibs -nostdlib -pie
-s -static -static-libgcc -shared -shared-libgcc -symbolic
-Wl,option -Xlinker option
-u symbol |
- Directory Options
Section 4.14 Options for Directory Search.
-Bprefix -Idir -I- -Ldir -specs=file |
- Target Options
Section 4.16 Specifying Target Machine and Compiler Version.
- Machine Dependent Options
Section 4.17 Hardware Models and Configurations.
M680x0 Options
-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040
-m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020
-mnobitfield -mrtd -mshort -msoft-float -mpcrel
-malign-int -mstrict-align -msep-data -mno-sep-data
-mshared-library-id=n -mid-shared-library -mno-id-shared-library |
M68hc1x Options
-m6811 -m6812 -m68hc11 -m68hc12 -m68hcs12
-mauto-incdec -minmax -mlong-calls -mshort
-msoft-reg-count=count |
VAX Options
SPARC Options
-mcpu=cpu-type
-mtune=cpu-type
-mcmodel=code-model
-m32 -m64 -mapp-regs -mno-app-regs
-mfaster-structs -mno-faster-structs
-mflat -mno-flat -mfpu -mno-fpu
-mhard-float -msoft-float
-mhard-quad-float -msoft-quad-float
-mimpure-text -mno-impure-text -mlittle-endian
-mstack-bias -mno-stack-bias
-munaligned-doubles -mno-unaligned-doubles
-mv8plus -mno-v8plus -mvis -mno-vis
-mcypress -mf930 -mf934
-msparclite -msupersparc -mv8
-threads -pthreads |
ARM Options
-mapcs-frame -mno-apcs-frame
-mapcs-26 -mapcs-32
-mapcs-stack-check -mno-apcs-stack-check
-mapcs-float -mno-apcs-float
-mapcs-reentrant -mno-apcs-reentrant
-msched-prolog -mno-sched-prolog
-mlittle-endian -mbig-endian -mwords-little-endian
-malignment-traps -mno-alignment-traps
-msoft-float -mhard-float -mfpe
-mthumb-interwork -mno-thumb-interwork
-mcpu=name -march=name -mfpe=name
-mstructure-size-boundary=n
-mabort-on-noreturn
-mlong-calls -mno-long-calls
-msingle-pic-base -mno-single-pic-base
-mpic-register=reg
-mnop-fun-dllimport
-mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns
-mpoke-function-name
-mthumb -marm
-mtpcs-frame -mtpcs-leaf-frame
-mcaller-super-interworking -mcallee-super-interworking |
MN10300 Options
-mmult-bug -mno-mult-bug
-mam33 -mno-am33
-mam33-2 -mno-am33-2
-mno-crt0 -mrelax |
M32R/D Options
-m32r2 -m32rx -m32r
-mdebug
-malign-loops -mno-align-loops
-missue-rate=number
-mbranch-cost=number
-mmodel=code-size-model-type
-msdata=sdata-type
-mno-flush-func -mflush-func=name
-mno-flush-trap -mflush-trap=number
-G num |
RS/6000 and PowerPC Options
-mcpu=cpu-type
-mtune=cpu-type
-mpower -mno-power -mpower2 -mno-power2
-mpowerpc -mpowerpc64 -mno-powerpc
-maltivec -mno-altivec
-mpowerpc-gpopt -mno-powerpc-gpopt
-mpowerpc-gfxopt -mno-powerpc-gfxopt
-mnew-mnemonics -mold-mnemonics
-mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc
-m64 -m32 -mxl-call -mno-xl-call -mpe
-malign-power -malign-natural
-msoft-float -mhard-float -mmultiple -mno-multiple
-mstring -mno-string -mupdate -mno-update
-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align
-mstrict-align -mno-strict-align -mrelocatable
-mno-relocatable -mrelocatable-lib -mno-relocatable-lib
-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian
-mdynamic-no-pic
-mprioritize-restricted-insns=priority
-msched-costly-dep=dependence_type
-minsert-sched-nops=scheme
-mcall-sysv -mcall-netbsd
-maix-struct-return -msvr4-struct-return
-mabi=altivec -mabi=no-altivec
-mabi=spe -mabi=no-spe
-misel=yes -misel=no
-mspe=yes -mspe=no
-mfloat-gprs=yes -mfloat-gprs=no
-mprototype -mno-prototype
-msim -mmvme -mads -myellowknife -memb -msdata
-msdata=opt -mvxworks -mwindiss -G num -pthread |
Darwin Options
-all_load -allowable_client -arch -arch_errors_fatal
-arch_only -bind_at_load -bundle -bundle_loader
-client_name -compatibility_version -current_version
-dependency-file -dylib_file -dylinker_install_name
-dynamic -dynamiclib -exported_symbols_list
-filelist -flat_namespace -force_cpusubtype_ALL
-force_flat_namespace -headerpad_max_install_names
-image_base -init -install_name -keep_private_externs
-multi_module -multiply_defined -multiply_defined_unused
-noall_load -nofixprebinding -nomultidefs -noprebind -noseglinkedit
-pagezero_size -prebind -prebind_all_twolevel_modules
-private_bundle -read_only_relocs -sectalign
-sectobjectsymbols -whyload -seg1addr
-sectcreate -sectobjectsymbols -sectorder
-seg_addr_table -seg_addr_table_filename -seglinkedit
-segprot -segs_read_only_addr -segs_read_write_addr
-single_module -static -sub_library -sub_umbrella
-twolevel_namespace -umbrella -undefined
-unexported_symbols_list -weak_reference_mismatches
-whatsloaded |
MIPS Options
-EL -EB -march=arch -mtune=arch
-mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips64
-mips16 -mno-mips16 -mabi=abi -mabicalls -mno-abicalls
-mxgot -mno-xgot -membedded-pic -mno-embedded-pic
-mgp32 -mgp64 -mfp32 -mfp64 -mhard-float -msoft-float
-msingle-float -mdouble-float -mint64 -mlong64 -mlong32
-Gnum -membedded-data -mno-embedded-data
-muninit-const-in-rodata -mno-uninit-const-in-rodata
-msplit-addresses -mno-split-addresses
-mexplicit-relocs -mno-explicit-relocs
-mrnames -mno-rnames
-mcheck-zero-division -mno-check-zero-division
-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls
-mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp
-mfix-sb1 -mno-fix-sb1 -mflush-func=func
-mno-flush-func -mbranch-likely -mno-branch-likely |
i386 and x86-64 Options
-mtune=cpu-type -march=cpu-type
-mfpmath=unit
-masm=dialect -mno-fancy-math-387
-mno-fp-ret-in-387 -msoft-float -msvr3-shlib
-mno-wide-multiply -mrtd -malign-double
-mpreferred-stack-boundary=num
-mmmx -msse -msse2 -msse3 -m3dnow
-mthreads -mno-align-stringops -minline-all-stringops
-mpush-args -maccumulate-outgoing-args -m128bit-long-double
-m96bit-long-double -mregparm=num -momit-leaf-frame-pointer
-mno-red-zone -mno-tls-direct-seg-refs
-mcmodel=code-model
-m32 -m64 |
HPPA Options
-march=architecture-type
-mbig-switch -mdisable-fpregs -mdisable-indexing
-mfast-indirect-calls -mgas -mgnu-ld -mhp-ld
-mjump-in-delay -mlinker-opt -mlong-calls
-mlong-load-store -mno-big-switch -mno-disable-fpregs
-mno-disable-indexing -mno-fast-indirect-calls -mno-gas
-mno-jump-in-delay -mno-long-load-store
-mno-portable-runtime -mno-soft-float
-mno-space-regs -msoft-float -mpa-risc-1-0
-mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime
-mschedule=cpu-type -mspace-regs -msio -mwsio
-nolibdld -static -threads |
Intel 960 Options
-mcpu-type -masm-compat -mclean-linkage
-mcode-align -mcomplex-addr -mleaf-procedures
-mic-compat -mic2.0-compat -mic3.0-compat
-mintel-asm -mno-clean-linkage -mno-code-align
-mno-complex-addr -mno-leaf-procedures
-mno-old-align -mno-strict-align -mno-tail-call
-mnumerics -mold-align -msoft-float -mstrict-align
-mtail-call |
DEC Alpha Options
-mno-fp-regs -msoft-float -malpha-as -mgas
-mieee -mieee-with-inexact -mieee-conformant
-mfp-trap-mode=mode -mfp-rounding-mode=mode
-mtrap-precision=mode -mbuild-constants
-mcpu=cpu-type -mtune=cpu-type
-mbwx -mmax -mfix -mcix
-mfloat-vax -mfloat-ieee
-mexplicit-relocs -msmall-data -mlarge-data
-msmall-text -mlarge-text
-mmemory-latency=time |
DEC Alpha/VMS Options
H8/300 Options
-mrelax -mh -ms -mn -mint32 -malign-300 |
SH Options
-m1 -m2 -m2e -m3 -m3e
-m4-nofpu -m4-single-only -m4-single -m4
-m5-64media -m5-64media-nofpu
-m5-32media -m5-32media-nofpu
-m5-compact -m5-compact-nofpu
-mb -ml -mdalign -mrelax
-mbigtable -mfmovd -mhitachi -mnomacsave
-mieee -misize -mpadstruct -mspace
-mprefergot -musermode |
System V Options
-Qy -Qn -YP,paths -Ym,dir |
ARC Options
-EB -EL
-mmangle-cpu -mcpu=cpu -mtext=text-section
-mdata=data-section -mrodata=readonly-data-section |
TMS320C3x/C4x Options
-mcpu=cpu -mbig -msmall -mregparm -mmemparm
-mfast-fix -mmpyi -mbk -mti -mdp-isr-reload
-mrpts=count -mrptb -mdb -mloop-unsigned
-mparallel-insns -mparallel-mpy -mpreserve-float |
V850 Options
-mlong-calls -mno-long-calls -mep -mno-ep
-mprolog-function -mno-prolog-function -mspace
-mtda=n -msda=n -mzda=n
-mapp-regs -mno-app-regs
-mdisable-callt -mno-disable-callt
-mv850e1
-mv850e
-mv850 -mbig-switch |
NS32K Options
-m32032 -m32332 -m32532 -m32081 -m32381
-mmult-add -mnomult-add -msoft-float -mrtd -mnortd
-mregparam -mnoregparam -msb -mnosb
-mbitfield -mnobitfield -mhimem -mnohimem |
AVR Options
-mmcu=mcu -msize -minit-stack=n -mno-interrupts
-mcall-prologues -mno-tablejump -mtiny-stack |
MCore Options
-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates
-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields
-m4byte-functions -mno-4byte-functions -mcallgraph-data
-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim
-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment |
MMIX Options
-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu
-mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols
-melf -mbranch-predict -mno-branch-predict -mbase-addresses
-mno-base-addresses -msingle-exit -mno-single-exit |
IA-64 Options
-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic
-mvolatile-asm-stop -mb-step -mregister-names -mno-sdata
-mconstant-gp -mauto-pic -minline-float-divide-min-latency
-minline-float-divide-max-throughput
-minline-int-divide-min-latency
-minline-int-divide-max-throughput -mno-dwarf2-asm
-mfixed-range=register-range |
D30V Options
-mextmem -mextmemory -monchip -mno-asm-optimize
-masm-optimize -mbranch-cost=n -mcond-exec=n |
S/390 and zSeries Options
-mtune=cpu-type -march=cpu-type
-mhard-float -msoft-float -mbackchain -mno-backchain -mkernel-backchain
-msmall-exec -mno-small-exec -mmvcle -mno-mvcle
-m64 -m31 -mdebug -mno-debug -mesa -mzarch
-mfused-madd -mno-fused-madd
-mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard |
CRIS Options
-mcpu=cpu -march=cpu -mtune=cpu
-mmax-stack-frame=n -melinux-stacksize=n
-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects
-mstack-align -mdata-align -mconst-align
-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt
-melf -maout -melinux -mlinux -sim -sim2
-mmul-bug-workaround -mno-mul-bug-workaround |
PDP-11 Options
-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10
-mbcopy -mbcopy-builtin -mint32 -mno-int16
-mint16 -mno-int32 -mfloat32 -mno-float64
-mfloat64 -mno-float32 -mabshi -mno-abshi
-mbranch-expensive -mbranch-cheap
-msplit -mno-split -munix-asm -mdec-asm |
Xstormy16 Options
Xtensa Options
-mconst16 -mno-const16
-mfused-madd -mno-fused-madd
-mtext-section-literals -mno-text-section-literals
-mtarget-align -mno-target-align
-mlongcalls -mno-longcalls |
FRV Options
-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64
-mhard-float -msoft-float
-malloc-cc -mfixed-cc -mdword -mno-dword
-mdouble -mno-double
-mmedia -mno-media -mmuladd -mno-muladd
-mlibrary-pic -macc-4 -macc-8
-mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move
-mscc -mno-scc -mcond-exec -mno-cond-exec
-mvliw-branch -mno-vliw-branch
-mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec
-mno-nested-cond-exec -mtomcat-stats
-mcpu=cpu |
- Code Generation Options
Section 4.18 Options for Code Generation Conventions.
-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
-freg-struct-return -fshared-data -fshort-enums
-fshort-double -fshort-wchar
-fverbose-asm -fpack-struct -fstack-check
-fstack-limit-register=reg -fstack-limit-symbol=sym
-fargument-alias -fargument-noalias
-fargument-noalias-global -fleading-underscore
-ftls-model=model
-ftrapv -fwrapv -fbounds-check
-fvisibility |