@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, @c 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 @c Free Software Foundation, Inc. @c This is part of the GCC manual. @c For copying conditions, see the file gcc.texi. @ignore @c man begin INCLUDE @include gcc-vers.texi @c man end @c man begin COPYRIGHT Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being ``GNU General Public License'' and ``Funding Free Software'', the Front-Cover texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the gfdl(7) man page. (a) The FSF's Front-Cover Text is: A GNU Manual (b) The FSF's Back-Cover Text is: You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development. @c man end @c Set file name and title for the man page. @setfilename gcc @settitle GNU project C and C++ compiler @c man begin SYNOPSIS gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}] [@option{-g}] [@option{-pg}] [@option{-O}@var{level}] [@option{-W}@var{warn}@dots{}] [@option{-pedantic}] [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}] [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}] [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}] [@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{} Only the most useful options are listed here; see below for the remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. @c man end @c man begin SEEALSO 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 @file{gcc}, @file{cpp}, @file{as}, @file{ld}, @file{binutils} and @file{gdb}. @c man end @c man begin BUGS For instructions on reporting bugs, see @w{@value{BUGURL}}. @c man end @c man begin AUTHOR See the Info entry for @command{gcc}, or @w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}}, for contributors to GCC@. @c man end @end ignore @node Invoking GCC @chapter GCC Command Options @cindex GCC command options @cindex command options @cindex options, GCC command @c man begin 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 @option{-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. @cindex C compilation options 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. @cindex C++ compilation options @xref{Invoking G++,,Compiling C++ Programs}, for a summary of special options for compiling C++ programs. @cindex grouping options @cindex options, grouping The @command{gcc} program accepts options and file names as operands. Many options have multi-letter names; therefore multiple single-letter options may @emph{not} be grouped: @option{-dv} is very different from @w{@samp{-d -v}}. @cindex order of options @cindex options, order 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 @option{-L} more than once, the directories are searched in the order specified. Also, the placement of the @option{-l} option is significant. Many options have long names starting with @samp{-f} or with @samp{-W}---for example, @option{-fmove-loop-invariants}, @option{-Wformat} and so on. Most of these have both positive and negative forms; the negative form of @option{-ffoo} would be @option{-fno-foo}. This manual documents only one of these two forms, whichever one is not the default. @c man end @xref{Option Index}, for an index to GCC's options. @menu * Option Summary:: Brief list of all options, without explanations. * Overall Options:: Controlling the kind of output: an executable, object files, assembler files, or preprocessed source. * Invoking G++:: Compiling C++ programs. * C Dialect Options:: Controlling the variant of C language compiled. * C++ Dialect Options:: Variations on C++. * Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C and Objective-C++. * Language Independent Options:: Controlling how diagnostics should be formatted. * Warning Options:: How picky should the compiler be? * Debugging Options:: Symbol tables, measurements, and debugging dumps. * Optimize Options:: How much optimization? * Preprocessor Options:: Controlling header files and macro definitions. Also, getting dependency information for Make. * Assembler Options:: Passing options to the assembler. * Link Options:: Specifying libraries and so on. * Directory Options:: Where to find header files and libraries. Where to find the compiler executable files. * Spec Files:: How to pass switches to sub-processes. * Target Options:: Running a cross-compiler, or an old version of GCC. * Submodel Options:: Specifying minor hardware or convention variations, such as 68010 vs 68020. * Code Gen Options:: Specifying conventions for function calls, data layout and register usage. * Environment Variables:: Env vars that affect GCC. * Precompiled Headers:: Compiling a header once, and using it many times. @end menu @c man begin OPTIONS @node Option Summary @section Option Summary Here is a summary of all the options, grouped by type. Explanations are in the following sections. @table @emph @item Overall Options @xref{Overall Options,,Options Controlling the Kind of Output}. @gccoptlist{-c -S -E -o @var{file} -no-canonical-prefixes @gol -pipe -pass-exit-codes @gol -x @var{language} -v -### --help@r{[}=@var{class}@r{[},@dots{}@r{]]} --target-help @gol --version -wrapper @@@var{file} -fplugin=@var{file} -fplugin-arg-@var{name}=@var{arg} @gol -fdump-ada-spec@r{[}-slim@r{]} -fdump-go-spec=@var{file}} @item C Language Options @xref{C Dialect Options,,Options Controlling C Dialect}. @gccoptlist{-ansi -std=@var{standard} -fgnu89-inline @gol -aux-info @var{filename} -fallow-parameterless-variadic-functions @gol -fno-asm -fno-builtin -fno-builtin-@var{function} @gol -fhosted -ffreestanding -fopenmp -fms-extensions -fplan9-extensions @gol -trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol -fallow-single-precision -fcond-mismatch -flax-vector-conversions @gol -fsigned-bitfields -fsigned-char @gol -funsigned-bitfields -funsigned-char} @item C++ Language Options @xref{C++ Dialect Options,,Options Controlling C++ Dialect}. @gccoptlist{-fabi-version=@var{n} -fno-access-control -fcheck-new @gol -fconserve-space -fconstexpr-depth=@var{n} -ffriend-injection @gol -fno-elide-constructors @gol -fno-enforce-eh-specs @gol -ffor-scope -fno-for-scope -fno-gnu-keywords @gol -fno-implicit-templates @gol -fno-implicit-inline-templates @gol -fno-implement-inlines -fms-extensions @gol -fno-nonansi-builtins -fnothrow-opt -fno-operator-names @gol -fno-optional-diags -fpermissive @gol -fno-pretty-templates @gol -frepo -fno-rtti -fstats -ftemplate-depth=@var{n} @gol -fno-threadsafe-statics -fuse-cxa-atexit -fno-weak -nostdinc++ @gol -fno-default-inline -fvisibility-inlines-hidden @gol -fvisibility-ms-compat @gol -Wabi -Wconversion-null -Wctor-dtor-privacy @gol -Wnoexcept -Wnon-virtual-dtor -Wreorder @gol -Weffc++ -Wstrict-null-sentinel @gol -Wno-non-template-friend -Wold-style-cast @gol -Woverloaded-virtual -Wno-pmf-conversions @gol -Wsign-promo} @item Objective-C and Objective-C++ Language Options @xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling Objective-C and Objective-C++ Dialects}. @gccoptlist{-fconstant-string-class=@var{class-name} @gol -fgnu-runtime -fnext-runtime @gol -fno-nil-receivers @gol -fobjc-abi-version=@var{n} @gol -fobjc-call-cxx-cdtors @gol -fobjc-direct-dispatch @gol -fobjc-exceptions @gol -fobjc-gc @gol -fobjc-nilcheck @gol -fobjc-std=objc1 @gol -freplace-objc-classes @gol -fzero-link @gol -gen-decls @gol -Wassign-intercept @gol -Wno-protocol -Wselector @gol -Wstrict-selector-match @gol -Wundeclared-selector} @item Language Independent Options @xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. @gccoptlist{-fmessage-length=@var{n} @gol -fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol -fno-diagnostics-show-option} @item Warning Options @xref{Warning Options,,Options to Request or Suppress Warnings}. @gccoptlist{-fsyntax-only -fmax-errors=@var{n} -pedantic @gol -pedantic-errors @gol -w -Wextra -Wall -Waddress -Waggregate-return -Warray-bounds @gol -Wno-attributes -Wno-builtin-macro-redefined @gol -Wc++-compat -Wc++11-compat -Wcast-align -Wcast-qual @gol -Wchar-subscripts -Wclobbered -Wcomment @gol -Wconversion -Wcoverage-mismatch -Wno-cpp -Wno-deprecated @gol -Wno-deprecated-declarations -Wdisabled-optimization @gol -Wno-div-by-zero -Wdouble-promotion -Wempty-body -Wenum-compare @gol -Wno-endif-labels -Werror -Werror=* @gol -Wfatal-errors -Wfloat-equal -Wformat -Wformat=2 @gol -Wno-format-contains-nul -Wno-format-extra-args -Wformat-nonliteral @gol -Wformat-security -Wformat-y2k @gol -Wframe-larger-than=@var{len} -Wno-free-nonheap-object -Wjump-misses-init @gol -Wignored-qualifiers @gol -Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol -Winit-self -Winline -Wmaybe-uninitialized @gol -Wno-int-to-pointer-cast -Wno-invalid-offsetof @gol -Winvalid-pch -Wlarger-than=@var{len} -Wunsafe-loop-optimizations @gol -Wlogical-op -Wlong-long @gol -Wmain -Wmaybe-uninitialized -Wmissing-braces -Wmissing-field-initializers @gol -Wmissing-format-attribute -Wmissing-include-dirs @gol -Wno-mudflap @gol -Wno-multichar -Wnonnull -Wno-overflow @gol -Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpadded @gol -Wparentheses -Wpedantic-ms-format -Wno-pedantic-ms-format @gol -Wpointer-arith -Wno-pointer-to-int-cast @gol -Wredundant-decls @gol -Wreturn-type -Wsequence-point -Wshadow @gol -Wsign-compare -Wsign-conversion -Wstack-protector @gol -Wstack-usage=@var{len} -Wstrict-aliasing -Wstrict-aliasing=n @gol -Wstrict-overflow -Wstrict-overflow=@var{n} @gol -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{]} @gol -Wswitch -Wswitch-default -Wswitch-enum -Wsync-nand @gol -Wsystem-headers -Wtrampolines -Wtrigraphs -Wtype-limits -Wundef @gol -Wuninitialized -Wunknown-pragmas -Wno-pragmas @gol -Wunsuffixed-float-constants -Wunused -Wunused-function @gol -Wunused-label -Wunused-local-typedefs -Wunused-parameter @gol -Wno-unused-result -Wunused-value @gol -Wunused-variable @gol -Wunused-but-set-parameter -Wunused-but-set-variable @gol -Wvariadic-macros -Wvector-operation-performance -Wvla -Wvolatile-register-var -Wwrite-strings} @item C and Objective-C-only Warning Options @gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol -Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs @gol -Wold-style-declaration -Wold-style-definition @gol -Wstrict-prototypes -Wtraditional -Wtraditional-conversion @gol -Wdeclaration-after-statement -Wpointer-sign} @item Debugging Options @xref{Debugging Options,,Options for Debugging Your Program or GCC}. @gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol -fdbg-cnt-list -fdbg-cnt=@var{counter-value-list} @gol -fdisable-ipa-@var{pass_name} @gol -fdisable-rtl-@var{pass_name} @gol -fdisable-rtl-@var{pass-name}=@var{range-list} @gol -fdisable-tree-@var{pass_name} @gol -fdisable-tree-@var{pass-name}=@var{range-list} @gol -fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links @gol -fdump-translation-unit@r{[}-@var{n}@r{]} @gol -fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline @gol -fdump-passes @gol -fdump-statistics @gol -fdump-tree-all @gol -fdump-tree-original@r{[}-@var{n}@r{]} @gol -fdump-tree-optimized@r{[}-@var{n}@r{]} @gol -fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias @gol -fdump-tree-ch @gol -fdump-tree-ssa@r{[}-@var{n}@r{]} -fdump-tree-pre@r{[}-@var{n}@r{]} @gol -fdump-tree-ccp@r{[}-@var{n}@r{]} -fdump-tree-dce@r{[}-@var{n}@r{]} @gol -fdump-tree-gimple@r{[}-raw@r{]} -fdump-tree-mudflap@r{[}-@var{n}@r{]} @gol -fdump-tree-dom@r{[}-@var{n}@r{]} @gol -fdump-tree-dse@r{[}-@var{n}@r{]} @gol -fdump-tree-phiprop@r{[}-@var{n}@r{]} @gol -fdump-tree-phiopt@r{[}-@var{n}@r{]} @gol -fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol -fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol -fdump-tree-nrv -fdump-tree-vect @gol -fdump-tree-sink @gol -fdump-tree-sra@r{[}-@var{n}@r{]} @gol -fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol -fdump-tree-fre@r{[}-@var{n}@r{]} @gol -fdump-tree-vrp@r{[}-@var{n}@r{]} @gol -ftree-vectorizer-verbose=@var{n} @gol -fdump-tree-storeccp@r{[}-@var{n}@r{]} @gol -fdump-final-insns=@var{file} @gol -fcompare-debug@r{[}=@var{opts}@r{]} -fcompare-debug-second @gol -feliminate-dwarf2-dups -feliminate-unused-debug-types @gol -feliminate-unused-debug-symbols -femit-class-debug-always @gol -fenable-@var{kind}-@var{pass} @gol -fenable-@var{kind}-@var{pass}=@var{range-list} @gol -fdebug-types-section @gol -fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report -fprofile-arcs @gol -frandom-seed=@var{string} -fsched-verbose=@var{n} @gol -fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose @gol -fstack-usage -ftest-coverage -ftime-report -fvar-tracking @gol -fvar-tracking-assignments -fvar-tracking-assignments-toggle @gol -g -g@var{level} -gtoggle -gcoff -gdwarf-@var{version} @gol -ggdb -grecord-gcc-switches -gno-record-gcc-switches @gol -gstabs -gstabs+ -gstrict-dwarf -gno-strict-dwarf @gol -gvms -gxcoff -gxcoff+ @gol -fno-merge-debug-strings -fno-dwarf2-cfi-asm @gol -fdebug-prefix-map=@var{old}=@var{new} @gol -femit-struct-debug-baseonly -femit-struct-debug-reduced @gol -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol -p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol -print-multi-directory -print-multi-lib -print-multi-os-directory @gol -print-prog-name=@var{program} -print-search-dirs -Q @gol -print-sysroot -print-sysroot-headers-suffix @gol -save-temps -save-temps=cwd -save-temps=obj -time@r{[}=@var{file}@r{]}} @item Optimization Options @xref{Optimize Options,,Options that Control Optimization}. @gccoptlist{-falign-functions[=@var{n}] -falign-jumps[=@var{n}] @gol -falign-labels[=@var{n}] -falign-loops[=@var{n}] -fassociative-math @gol -fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize @gol -fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves @gol -fcheck-data-deps -fcombine-stack-adjustments -fconserve-stack @gol -fcompare-elim -fcprop-registers -fcrossjumping @gol -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules @gol -fcx-limited-range @gol -fdata-sections -fdce -fdce -fdelayed-branch @gol -fdelete-null-pointer-checks -fdse -fdevirtualize -fdse @gol -fearly-inlining -fipa-sra -fexpensive-optimizations -ffat-lto-objects @gol -ffast-math -ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol -fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol -fgcse-sm -fif-conversion -fif-conversion2 -findirect-inlining @gol -finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-matrix-reorg @gol -fipa-pta -fipa-profile -fipa-pure-const -fipa-reference @gol -fira-algorithm=@var{algorithm} @gol -fira-region=@var{region} @gol -fira-loop-pressure -fno-ira-share-save-slots @gol -fno-ira-share-spill-slots -fira-verbose=@var{n} @gol -fivopts -fkeep-inline-functions -fkeep-static-consts @gol -floop-block -floop-flatten -floop-interchange -floop-strip-mine @gol -floop-parallelize-all -flto -flto-compression-level @gol -flto-partition=@var{alg} -flto-report -fmerge-all-constants @gol -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol -fmove-loop-invariants fmudflap -fmudflapir -fmudflapth -fno-branch-count-reg @gol -fno-default-inline @gol -fno-defer-pop -fno-function-cse -fno-guess-branch-probability @gol -fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol -fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol -fomit-frame-pointer -foptimize-register-move -foptimize-sibling-calls @gol -fpartial-inlining -fpeel-loops -fpredictive-commoning @gol -fprefetch-loop-arrays @gol -fprofile-correction -fprofile-dir=@var{path} -fprofile-generate @gol -fprofile-generate=@var{path} @gol -fprofile-use -fprofile-use=@var{path} -fprofile-values @gol -freciprocal-math -fregmove -frename-registers -freorder-blocks @gol -freorder-blocks-and-partition -freorder-functions @gol -frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol -frounding-math -fsched2-use-superblocks -fsched-pressure @gol -fsched-spec-load -fsched-spec-load-dangerous @gol -fsched-stalled-insns-dep[=@var{n}] -fsched-stalled-insns[=@var{n}] @gol -fsched-group-heuristic -fsched-critical-path-heuristic @gol -fsched-spec-insn-heuristic -fsched-rank-heuristic @gol -fsched-last-insn-heuristic -fsched-dep-count-heuristic @gol -fschedule-insns -fschedule-insns2 -fsection-anchors @gol -fselective-scheduling -fselective-scheduling2 @gol -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops @gol -fshrink-wrap -fsignaling-nans -fsingle-precision-constant @gol -fsplit-ivs-in-unroller -fsplit-wide-types -fstack-protector @gol -fstack-protector-all -fstrict-aliasing -fstrict-overflow @gol -fthread-jumps -ftracer -ftree-bit-ccp @gol -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copy-prop @gol -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse @gol -ftree-forwprop -ftree-fre -ftree-loop-if-convert @gol -ftree-loop-if-convert-stores -ftree-loop-im @gol -ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns @gol -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize @gol -ftree-parallelize-loops=@var{n} -ftree-pre -ftree-pta -ftree-reassoc @gol -ftree-sink -ftree-sra -ftree-switch-conversion -ftree-tail-merge @gol -ftree-ter -ftree-vect-loop-version -ftree-vectorize -ftree-vrp @gol -funit-at-a-time -funroll-all-loops -funroll-loops @gol -funsafe-loop-optimizations -funsafe-math-optimizations -funswitch-loops @gol -fvariable-expansion-in-unroller -fvect-cost-model -fvpt -fweb @gol -fwhole-program -fwpa -fuse-linker-plugin @gol --param @var{name}=@var{value} -O -O0 -O1 -O2 -O3 -Os -Ofast} @item Preprocessor Options @xref{Preprocessor Options,,Options Controlling the Preprocessor}. @gccoptlist{-A@var{question}=@var{answer} @gol -A-@var{question}@r{[}=@var{answer}@r{]} @gol -C -dD -dI -dM -dN @gol -D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol -idirafter @var{dir} @gol -include @var{file} -imacros @var{file} @gol -iprefix @var{file} -iwithprefix @var{dir} @gol -iwithprefixbefore @var{dir} -isystem @var{dir} @gol -imultilib @var{dir} -isysroot @var{dir} @gol -M -MM -MF -MG -MP -MQ -MT -nostdinc @gol -P -fdebug-cpp -ftrack-macro-expansion -fworking-directory @gol -remap -trigraphs -undef -U@var{macro} @gol -Wp,@var{option} -Xpreprocessor @var{option}} @item Assembler Option @xref{Assembler Options,,Passing Options to the Assembler}. @gccoptlist{-Wa,@var{option} -Xassembler @var{option}} @item Linker Options @xref{Link Options,,Options for Linking}. @gccoptlist{@var{object-file-name} -l@var{library} @gol -nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic @gol -s -static -static-libgcc -static-libstdc++ -shared @gol -shared-libgcc -symbolic @gol -T @var{script} -Wl,@var{option} -Xlinker @var{option} @gol -u @var{symbol}} @item Directory Options @xref{Directory Options,,Options for Directory Search}. @gccoptlist{-B@var{prefix} -I@var{dir} -iplugindir=@var{dir} @gol -iquote@var{dir} -L@var{dir} -specs=@var{file} -I- @gol --sysroot=@var{dir}} @item Machine Dependent Options @xref{Submodel Options,,Hardware Models and Configurations}. @c This list is ordered alphanumerically by subsection name. @c Try and put the significant identifier (CPU or system) first, @c so users have a clue at guessing where the ones they want will be. @emph{ARM Options} @gccoptlist{-mapcs-frame -mno-apcs-frame @gol -mabi=@var{name} @gol -mapcs-stack-check -mno-apcs-stack-check @gol -mapcs-float -mno-apcs-float @gol -mapcs-reentrant -mno-apcs-reentrant @gol -msched-prolog -mno-sched-prolog @gol -mlittle-endian -mbig-endian -mwords-little-endian @gol -mfloat-abi=@var{name} -mfpe @gol -mfp16-format=@var{name} -mthumb-interwork -mno-thumb-interwork @gol -mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol -mstructure-size-boundary=@var{n} @gol -mabort-on-noreturn @gol -mlong-calls -mno-long-calls @gol -msingle-pic-base -mno-single-pic-base @gol -mpic-register=@var{reg} @gol -mnop-fun-dllimport @gol -mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns @gol -mpoke-function-name @gol -mthumb -marm @gol -mtpcs-frame -mtpcs-leaf-frame @gol -mcaller-super-interworking -mcallee-super-interworking @gol -mtp=@var{name} -mtls-dialect=@var{dialect} @gol -mword-relocations @gol -mfix-cortex-m3-ldrd} @emph{AVR Options} @gccoptlist{-mmcu=@var{mcu} -mno-interrupts @gol -mcall-prologues -mtiny-stack -mint8 -mstrict-X} @emph{Blackfin Options} @gccoptlist{-mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} @gol -msim -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer @gol -mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly @gol -mlow-64k -mno-low64k -mstack-check-l1 -mid-shared-library @gol -mno-id-shared-library -mshared-library-id=@var{n} @gol -mleaf-id-shared-library -mno-leaf-id-shared-library @gol -msep-data -mno-sep-data -mlong-calls -mno-long-calls @gol -mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram @gol -micplb} @emph{C6X Options} @gccoptlist{-mbig-endian -mlittle-endian -march=@var{cpu} @gol -msim -msdata=@var{sdata-type}} @emph{CRIS Options} @gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol -mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol -metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol -mstack-align -mdata-align -mconst-align @gol -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol -melf -maout -melinux -mlinux -sim -sim2 @gol -mmul-bug-workaround -mno-mul-bug-workaround} @emph{Darwin Options} @gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol -arch_only -bind_at_load -bundle -bundle_loader @gol -client_name -compatibility_version -current_version @gol -dead_strip @gol -dependency-file -dylib_file -dylinker_install_name @gol -dynamic -dynamiclib -exported_symbols_list @gol -filelist -flat_namespace -force_cpusubtype_ALL @gol -force_flat_namespace -headerpad_max_install_names @gol -iframework @gol -image_base -init -install_name -keep_private_externs @gol -multi_module -multiply_defined -multiply_defined_unused @gol -noall_load -no_dead_strip_inits_and_terms @gol -nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol -pagezero_size -prebind -prebind_all_twolevel_modules @gol -private_bundle -read_only_relocs -sectalign @gol -sectobjectsymbols -whyload -seg1addr @gol -sectcreate -sectobjectsymbols -sectorder @gol -segaddr -segs_read_only_addr -segs_read_write_addr @gol -seg_addr_table -seg_addr_table_filename -seglinkedit @gol -segprot -segs_read_only_addr -segs_read_write_addr @gol -single_module -static -sub_library -sub_umbrella @gol -twolevel_namespace -umbrella -undefined @gol -unexported_symbols_list -weak_reference_mismatches @gol -whatsloaded -F -gused -gfull -mmacosx-version-min=@var{version} @gol -mkernel -mone-byte-bool} @emph{DEC Alpha Options} @gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol -mieee -mieee-with-inexact -mieee-conformant @gol -mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol -mtrap-precision=@var{mode} -mbuild-constants @gol -mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol -mbwx -mmax -mfix -mcix @gol -mfloat-vax -mfloat-ieee @gol -mexplicit-relocs -msmall-data -mlarge-data @gol -msmall-text -mlarge-text @gol -mmemory-latency=@var{time}} @emph{DEC Alpha/VMS Options} @gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64} @emph{FR30 Options} @gccoptlist{-msmall-model -mno-lsim} @emph{FRV Options} @gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol -mhard-float -msoft-float @gol -malloc-cc -mfixed-cc -mdword -mno-dword @gol -mdouble -mno-double @gol -mmedia -mno-media -mmuladd -mno-muladd @gol -mfdpic -minline-plt -mgprel-ro -multilib-library-pic @gol -mlinked-fp -mlong-calls -malign-labels @gol -mlibrary-pic -macc-4 -macc-8 @gol -mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol -moptimize-membar -mno-optimize-membar @gol -mscc -mno-scc -mcond-exec -mno-cond-exec @gol -mvliw-branch -mno-vliw-branch @gol -mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol -mno-nested-cond-exec -mtomcat-stats @gol -mTLS -mtls @gol -mcpu=@var{cpu}} @emph{GNU/Linux Options} @gccoptlist{-mglibc -muclibc -mbionic -mandroid @gol -tno-android-cc -tno-android-ld} @emph{H8/300 Options} @gccoptlist{-mrelax -mh -ms -mn -mint32 -malign-300} @emph{HPPA Options} @gccoptlist{-march=@var{architecture-type} @gol -mbig-switch -mdisable-fpregs -mdisable-indexing @gol -mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol -mfixed-range=@var{register-range} @gol -mjump-in-delay -mlinker-opt -mlong-calls @gol -mlong-load-store -mno-big-switch -mno-disable-fpregs @gol -mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol -mno-jump-in-delay -mno-long-load-store @gol -mno-portable-runtime -mno-soft-float @gol -mno-space-regs -msoft-float -mpa-risc-1-0 @gol -mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol -mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol -munix=@var{unix-std} -nolibdld -static -threads} @emph{i386 and x86-64 Options} @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol -mfpmath=@var{unit} @gol -masm=@var{dialect} -mno-fancy-math-387 @gol -mno-fp-ret-in-387 -msoft-float @gol -mno-wide-multiply -mrtd -malign-double @gol -mpreferred-stack-boundary=@var{num} @gol -mincoming-stack-boundary=@var{num} @gol -mcld -mcx16 -msahf -mmovbe -mcrc32 @gol -mrecip -mrecip=@var{opt} @gol -mvzeroupper @gol -mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx @gol -mavx2 -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfma @gol -msse4a -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -mlzcnt @gol -mbmi2 -mlwp -mthreads -mno-align-stringops -minline-all-stringops @gol -minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol -mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol -m96bit-long-double -mregparm=@var{num} -msseregparm @gol -mveclibabi=@var{type} -mvect8-ret-in-mem @gol -mpc32 -mpc64 -mpc80 -mstackrealign @gol -momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol -mcmodel=@var{code-model} -mabi=@var{name} @gol -m32 -m64 -mx32 -mlarge-data-threshold=@var{num} @gol -msse2avx -mfentry -m8bit-idiv @gol -mavx256-split-unaligned-load -mavx256-split-unaligned-store} @emph{i386 and x86-64 Windows Options} @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol -mnop-fun-dllimport -mthread @gol -municode -mwin32 -mwindows -fno-set-stack-executable} @emph{IA-64 Options} @gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol -mvolatile-asm-stop -mregister-names -msdata -mno-sdata @gol -mconstant-gp -mauto-pic -mfused-madd @gol -minline-float-divide-min-latency @gol -minline-float-divide-max-throughput @gol -mno-inline-float-divide @gol -minline-int-divide-min-latency @gol -minline-int-divide-max-throughput @gol -mno-inline-int-divide @gol -minline-sqrt-min-latency -minline-sqrt-max-throughput @gol -mno-inline-sqrt @gol -mdwarf2-asm -mearly-stop-bits @gol -mfixed-range=@var{register-range} -mtls-size=@var{tls-size} @gol -mtune=@var{cpu-type} -milp32 -mlp64 @gol -msched-br-data-spec -msched-ar-data-spec -msched-control-spec @gol -msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec @gol -msched-spec-ldc -msched-spec-control-ldc @gol -msched-prefer-non-data-spec-insns -msched-prefer-non-control-spec-insns @gol -msched-stop-bits-after-every-cycle -msched-count-spec-in-critical-path @gol -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost @gol -msched-max-memory-insns-hard-limit -msched-max-memory-insns=@var{max-insns}} @emph{IA-64/VMS Options} @gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64} @emph{LM32 Options} @gccoptlist{-mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled @gol -msign-extend-enabled -muser-enabled} @emph{M32R/D Options} @gccoptlist{-m32r2 -m32rx -m32r @gol -mdebug @gol -malign-loops -mno-align-loops @gol -missue-rate=@var{number} @gol -mbranch-cost=@var{number} @gol -mmodel=@var{code-size-model-type} @gol -msdata=@var{sdata-type} @gol -mno-flush-func -mflush-func=@var{name} @gol -mno-flush-trap -mflush-trap=@var{number} @gol -G @var{num}} @emph{M32C Options} @gccoptlist{-mcpu=@var{cpu} -msim -memregs=@var{number}} @emph{M680x0 Options} @gccoptlist{-march=@var{arch} -mcpu=@var{cpu} -mtune=@var{tune} -m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol -m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 @gol -mcfv4e -mbitfield -mno-bitfield -mc68000 -mc68020 @gol -mnobitfield -mrtd -mno-rtd -mdiv -mno-div -mshort @gol -mno-short -mhard-float -m68881 -msoft-float -mpcrel @gol -malign-int -mstrict-align -msep-data -mno-sep-data @gol -mshared-library-id=n -mid-shared-library -mno-id-shared-library @gol -mxgot -mno-xgot} @emph{MCore Options} @gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol -mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol -m4byte-functions -mno-4byte-functions -mcallgraph-data @gol -mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol -mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} @emph{MeP Options} @gccoptlist{-mabsdiff -mall-opts -maverage -mbased=@var{n} -mbitops @gol -mc=@var{n} -mclip -mconfig=@var{name} -mcop -mcop32 -mcop64 -mivc2 @gol -mdc -mdiv -meb -mel -mio-volatile -ml -mleadz -mm -mminmax @gol -mmult -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf @gol -mtiny=@var{n}} @emph{MicroBlaze Options} @gccoptlist{-msoft-float -mhard-float -msmall-divides -mcpu=@var{cpu} @gol -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift @gol -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss @gol -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt @gol -mxl-mode-@var{app-model}} @emph{MIPS Options} @gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol -mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 @gol -mips64 -mips64r2 @gol -mips16 -mno-mips16 -mflip-mips16 @gol -minterlink-mips16 -mno-interlink-mips16 @gol -mabi=@var{abi} -mabicalls -mno-abicalls @gol -mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot @gol -mgp32 -mgp64 -mfp32 -mfp64 -mhard-float -msoft-float @gol -msingle-float -mdouble-float -mdsp -mno-dsp -mdspr2 -mno-dspr2 @gol -mfpu=@var{fpu-type} @gol -msmartmips -mno-smartmips @gol -mpaired-single -mno-paired-single -mdmx -mno-mdmx @gol -mips3d -mno-mips3d -mmt -mno-mt -mllsc -mno-llsc @gol -mlong64 -mlong32 -msym32 -mno-sym32 @gol -G@var{num} -mlocal-sdata -mno-local-sdata @gol -mextern-sdata -mno-extern-sdata -mgpopt -mno-gopt @gol -membedded-data -mno-embedded-data @gol -muninit-const-in-rodata -mno-uninit-const-in-rodata @gol -mcode-readable=@var{setting} @gol -msplit-addresses -mno-split-addresses @gol -mexplicit-relocs -mno-explicit-relocs @gol -mcheck-zero-division -mno-check-zero-division @gol -mdivide-traps -mdivide-breaks @gol -mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol -mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol -mfix-24k -mno-fix-24k @gol -mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol -mfix-r10000 -mno-fix-r10000 -mfix-vr4120 -mno-fix-vr4120 @gol -mfix-vr4130 -mno-fix-vr4130 -mfix-sb1 -mno-fix-sb1 @gol -mflush-func=@var{func} -mno-flush-func @gol -mbranch-cost=@var{num} -mbranch-likely -mno-branch-likely @gol -mfp-exceptions -mno-fp-exceptions @gol -mvr4130-align -mno-vr4130-align -msynci -mno-synci @gol -mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address} @emph{MMIX Options} @gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol -mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol -melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol -mno-base-addresses -msingle-exit -mno-single-exit} @emph{MN10300 Options} @gccoptlist{-mmult-bug -mno-mult-bug @gol -mno-am33 -mam33 -mam33-2 -mam34 @gol -mtune=@var{cpu-type} @gol -mreturn-pointer-on-d0 @gol -mno-crt0 -mrelax -mliw -msetlb} @emph{PDP-11 Options} @gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol -mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol -mint16 -mno-int32 -mfloat32 -mno-float64 @gol -mfloat64 -mno-float32 -mabshi -mno-abshi @gol -mbranch-expensive -mbranch-cheap @gol -munix-asm -mdec-asm} @emph{picoChip Options} @gccoptlist{-mae=@var{ae_type} -mvliw-lookahead=@var{N} @gol -msymbol-as-address -mno-inefficient-warnings} @emph{PowerPC Options} See RS/6000 and PowerPC Options. @emph{RS/6000 and PowerPC Options} @gccoptlist{-mcpu=@var{cpu-type} @gol -mtune=@var{cpu-type} @gol -mcmodel=@var{code-model} @gol -mpower -mno-power -mpower2 -mno-power2 @gol -mpowerpc -mpowerpc64 -mno-powerpc @gol -maltivec -mno-altivec @gol -mpowerpc-gpopt -mno-powerpc-gpopt @gol -mpowerpc-gfxopt -mno-powerpc-gfxopt @gol -mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd @gol -mfprnd -mno-fprnd @gol -mcmpb -mno-cmpb -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp @gol -mnew-mnemonics -mold-mnemonics @gol -mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol -m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol -malign-power -malign-natural @gol -msoft-float -mhard-float -mmultiple -mno-multiple @gol -msingle-float -mdouble-float -msimple-fpu @gol -mstring -mno-string -mupdate -mno-update @gol -mavoid-indexed-addresses -mno-avoid-indexed-addresses @gol -mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol -mstrict-align -mno-strict-align -mrelocatable @gol -mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol -mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol -mdynamic-no-pic -maltivec -mswdiv -msingle-pic-base @gol -mprioritize-restricted-insns=@var{priority} @gol -msched-costly-dep=@var{dependence_type} @gol -minsert-sched-nops=@var{scheme} @gol -mcall-sysv -mcall-netbsd @gol -maix-struct-return -msvr4-struct-return @gol -mabi=@var{abi-type} -msecure-plt -mbss-plt @gol -mblock-move-inline-limit=@var{num} @gol -misel -mno-isel @gol -misel=yes -misel=no @gol -mspe -mno-spe @gol -mspe=yes -mspe=no @gol -mpaired @gol -mgen-cell-microcode -mwarn-cell-microcode @gol -mvrsave -mno-vrsave @gol -mmulhw -mno-mulhw @gol -mdlmzb -mno-dlmzb @gol -mfloat-gprs=yes -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double @gol -mprototype -mno-prototype @gol -msim -mmvme -mads -myellowknife -memb -msdata @gol -msdata=@var{opt} -mvxworks -G @var{num} -pthread @gol -mrecip -mrecip=@var{opt} -mno-recip -mrecip-precision @gol -mno-recip-precision @gol -mveclibabi=@var{type} -mfriz -mno-friz @gol -mpointers-to-nested-functions -mno-pointers-to-nested-functions @gol -msave-toc-indirect -mno-save-toc-indirect} @emph{RX Options} @gccoptlist{-m64bit-doubles -m32bit-doubles -fpu -nofpu@gol -mcpu=@gol -mbig-endian-data -mlittle-endian-data @gol -msmall-data @gol -msim -mno-sim@gol -mas100-syntax -mno-as100-syntax@gol -mrelax@gol -mmax-constant-size=@gol -mint-register=@gol -mpid@gol -msave-acc-in-interrupts} @emph{S/390 and zSeries Options} @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol -mhard-float -msoft-float -mhard-dfp -mno-hard-dfp @gol -mlong-double-64 -mlong-double-128 @gol -mbackchain -mno-backchain -mpacked-stack -mno-packed-stack @gol -msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol -m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol -mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd @gol -mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard} @emph{Score Options} @gccoptlist{-meb -mel @gol -mnhwloop @gol -muls @gol -mmac @gol -mscore5 -mscore5u -mscore7 -mscore7d} @emph{SH Options} @gccoptlist{-m1 -m2 -m2e @gol -m2a-nofpu -m2a-single-only -m2a-single -m2a @gol -m3 -m3e @gol -m4-nofpu -m4-single-only -m4-single -m4 @gol -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al @gol -m5-64media -m5-64media-nofpu @gol -m5-32media -m5-32media-nofpu @gol -m5-compact -m5-compact-nofpu @gol -mb -ml -mdalign -mrelax @gol -mbigtable -mfmovd -mhitachi -mrenesas -mno-renesas -mnomacsave @gol -mieee -mbitops -misize -minline-ic_invalidate -mpadstruct -mspace @gol -mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol -mdivsi3_libfunc=@var{name} -mfixed-range=@var{register-range} @gol -madjust-unroll -mindexed-addressing -mgettrcost=@var{number} -mpt-fixed @gol -maccumulate-outgoing-args -minvalid-symbols} @emph{Solaris 2 Options} @gccoptlist{-mimpure-text -mno-impure-text @gol -pthreads -pthread} @emph{SPARC Options} @gccoptlist{-mcpu=@var{cpu-type} @gol -mtune=@var{cpu-type} @gol -mcmodel=@var{code-model} @gol -m32 -m64 -mapp-regs -mno-app-regs @gol -mfaster-structs -mno-faster-structs -mflat -mno-flat @gol -mfpu -mno-fpu -mhard-float -msoft-float @gol -mhard-quad-float -msoft-quad-float @gol -mlittle-endian @gol -mstack-bias -mno-stack-bias @gol -munaligned-doubles -mno-unaligned-doubles @gol -mv8plus -mno-v8plus -mvis -mno-vis @gol -mvis2 -mno-vis2 -mvis3 -mno-vis3 @gol -mfmaf -mno-fmaf -mpopc -mno-popc @gol -mfix-at697f} @emph{SPU Options} @gccoptlist{-mwarn-reloc -merror-reloc @gol -msafe-dma -munsafe-dma @gol -mbranch-hints @gol -msmall-mem -mlarge-mem -mstdmain @gol -mfixed-range=@var{register-range} @gol -mea32 -mea64 @gol -maddress-space-conversion -mno-address-space-conversion @gol -mcache-size=@var{cache-size} @gol -matomic-updates -mno-atomic-updates} @emph{System V Options} @gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}} @emph{V850 Options} @gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol -mprolog-function -mno-prolog-function -mspace @gol -mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol -mapp-regs -mno-app-regs @gol -mdisable-callt -mno-disable-callt @gol -mv850e2v3 @gol -mv850e2 @gol -mv850e1 -mv850es @gol -mv850e @gol -mv850 -mbig-switch} @emph{VAX Options} @gccoptlist{-mg -mgnu -munix} @emph{VxWorks Options} @gccoptlist{-mrtp -non-static -Bstatic -Bdynamic @gol -Xbind-lazy -Xbind-now} @emph{x86-64 Options} See i386 and x86-64 Options. @emph{Xstormy16 Options} @gccoptlist{-msim} @emph{Xtensa Options} @gccoptlist{-mconst16 -mno-const16 @gol -mfused-madd -mno-fused-madd @gol -mforce-no-pic @gol -mserialize-volatile -mno-serialize-volatile @gol -mtext-section-literals -mno-text-section-literals @gol -mtarget-align -mno-target-align @gol -mlongcalls -mno-longcalls} @emph{zSeries Options} See S/390 and zSeries Options. @item Code Generation Options @xref{Code Gen Options,,Options for Code Generation Conventions}. @gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol -ffixed-@var{reg} -fexceptions @gol -fnon-call-exceptions -funwind-tables @gol -fasynchronous-unwind-tables @gol -finhibit-size-directive -finstrument-functions @gol -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{} @gol -fno-common -fno-ident @gol -fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol -fno-jump-tables @gol -frecord-gcc-switches @gol -freg-struct-return -fshort-enums @gol -fshort-double -fshort-wchar @gol -fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol -fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol -fno-stack-limit -fsplit-stack @gol -fleading-underscore -ftls-model=@var{model} @gol -ftrapv -fwrapv -fbounds-check @gol -fvisibility -fstrict-volatile-bitfields} @end table @menu * Overall Options:: Controlling the kind of output: an executable, object files, assembler files, or preprocessed source. * C Dialect Options:: Controlling the variant of C language compiled. * C++ Dialect Options:: Variations on C++. * Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C and Objective-C++. * Language Independent Options:: Controlling how diagnostics should be formatted. * Warning Options:: How picky should the compiler be? * Debugging Options:: Symbol tables, measurements, and debugging dumps. * Optimize Options:: How much optimization? * Preprocessor Options:: Controlling header files and macro definitions. Also, getting dependency information for Make. * Assembler Options:: Passing options to the assembler. * Link Options:: Specifying libraries and so on. * Directory Options:: Where to find header files and libraries. Where to find the compiler executable files. * Spec Files:: How to pass switches to sub-processes. * Target Options:: Running a cross-compiler, or an old version of GCC. @end menu @node Overall Options @section Options Controlling the Kind of Output Compilation can involve up to four stages: preprocessing, compilation proper, assembly and linking, always in that order. GCC is capable of preprocessing and compiling several files either into several assembler input files, or into one assembler input file; then each assembler input file produces an object file, and linking combines all the object files (those newly compiled, and those specified as input) into an executable file. @cindex file name suffix For any given input file, the file name suffix determines what kind of compilation is done: @table @gcctabopt @item @var{file}.c C source code which must be preprocessed. @item @var{file}.i C source code which should not be preprocessed. @item @var{file}.ii C++ source code which should not be preprocessed. @item @var{file}.m Objective-C source code. Note that you must link with the @file{libobjc} library to make an Objective-C program work. @item @var{file}.mi Objective-C source code which should not be preprocessed. @item @var{file}.mm @itemx @var{file}.M Objective-C++ source code. Note that you must link with the @file{libobjc} library to make an Objective-C++ program work. Note that @samp{.M} refers to a literal capital M@. @item @var{file}.mii Objective-C++ source code which should not be preprocessed. @item @var{file}.h C, C++, Objective-C or Objective-C++ header file to be turned into a precompiled header (default), or C, C++ header file to be turned into an Ada spec (via the @option{-fdump-ada-spec} switch). @item @var{file}.cc @itemx @var{file}.cp @itemx @var{file}.cxx @itemx @var{file}.cpp @itemx @var{file}.CPP @itemx @var{file}.c++ @itemx @var{file}.C C++ source code which must be preprocessed. Note that in @samp{.cxx}, the last two letters must both be literally @samp{x}. Likewise, @samp{.C} refers to a literal capital C@. @item @var{file}.mm @itemx @var{file}.M Objective-C++ source code which must be preprocessed. @item @var{file}.mii Objective-C++ source code which should not be preprocessed. @item @var{file}.hh @itemx @var{file}.H @itemx @var{file}.hp @itemx @var{file}.hxx @itemx @var{file}.hpp @itemx @var{file}.HPP @itemx @var{file}.h++ @itemx @var{file}.tcc C++ header file to be turned into a precompiled header or Ada spec. @item @var{file}.f @itemx @var{file}.for @itemx @var{file}.ftn Fixed form Fortran source code which should not be preprocessed. @item @var{file}.F @itemx @var{file}.FOR @itemx @var{file}.fpp @itemx @var{file}.FPP @itemx @var{file}.FTN Fixed form Fortran source code which must be preprocessed (with the traditional preprocessor). @item @var{file}.f90 @itemx @var{file}.f95 @itemx @var{file}.f03 @itemx @var{file}.f08 Free form Fortran source code which should not be preprocessed. @item @var{file}.F90 @itemx @var{file}.F95 @itemx @var{file}.F03 @itemx @var{file}.F08 Free form Fortran source code which must be preprocessed (with the traditional preprocessor). @item @var{file}.go Go source code. @c FIXME: Descriptions of Java file types. @c @var{file}.java @c @var{file}.class @c @var{file}.zip @c @var{file}.jar @item @var{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 @dfn{specs}. @item @var{file}.adb Ada source code file containing a library unit body (a subprogram or package body). Such files are also called @dfn{bodies}. @c GCC also knows about some suffixes for languages not yet included: @c Pascal: @c @var{file}.p @c @var{file}.pas @c Ratfor: @c @var{file}.r @item @var{file}.s Assembler code. @item @var{file}.S @itemx @var{file}.sx Assembler code which must be preprocessed. @item @var{other} An object file to be fed straight into linking. Any file name with no recognized suffix is treated this way. @end table @opindex x You can specify the input language explicitly with the @option{-x} option: @table @gcctabopt @item -x @var{language} Specify explicitly the @var{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 @option{-x} option. Possible values for @var{language} are: @smallexample c c-header 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 f77 f77-cpp-input f95 f95-cpp-input go java @end smallexample @item -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 @option{-x} has not been used at all). @item -pass-exit-codes @opindex pass-exit-codes Normally the @command{gcc} program will exit with the code of 1 if any phase of the compiler returns a non-success return code. If you specify @option{-pass-exit-codes}, the @command{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. @end table If you only want some of the stages of compilation, you can use @option{-x} (or filename suffixes) to tell @command{gcc} where to start, and one of the options @option{-c}, @option{-S}, or @option{-E} to say where @command{gcc} is to stop. Note that some combinations (for example, @samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. @table @gcctabopt @item -c @opindex 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 @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. Unrecognized input files, not requiring compilation or assembly, are ignored. @item -S @opindex 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 @samp{.c}, @samp{.i}, etc., with @samp{.s}. Input files that don't require compilation are ignored. @item -E @opindex 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. @cindex output file option @item -o @var{file} @opindex o Place output in file @var{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 @option{-o} is not specified, the default is to put an executable file in @file{a.out}, the object file for @file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its assembler file in @file{@var{source}.s}, a precompiled header file in @file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on standard output. @item -v @opindex 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. @item -### @opindex ### Like @option{-v} except the commands are not executed and arguments are quoted unless they contain only alphanumeric characters or @code{./-_}. This is useful for shell scripts to capture the driver-generated command lines. @item -pipe @opindex 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. @item --help @opindex help Print (on the standard output) a description of the command line options understood by @command{gcc}. If the @option{-v} option is also specified then @option{--help} will also be passed on to the various processes invoked by @command{gcc}, so that they can display the command line options they accept. If the @option{-Wextra} option has also been specified (prior to the @option{--help} option), then command line options which have no documentation associated with them will also be displayed. @item --target-help @opindex target-help Print (on the standard output) a description of target-specific command line options for each tool. For some targets extra target-specific information may also be printed. @item --help=@{@var{class}@r{|[}^@r{]}@var{qualifier}@}@r{[},@dots{}@r{]} Print (on the standard output) a description of the command line options understood by the compiler that fit into all specified classes and qualifiers. These are the supported classes: @table @asis @item @samp{optimizers} This will display all of the optimization options supported by the compiler. @item @samp{warnings} This will display all of the options controlling warning messages produced by the compiler. @item @samp{target} This will display target-specific options. Unlike the @option{--target-help} option however, target-specific options of the linker and assembler will not be displayed. This is because those tools do not currently support the extended @option{--help=} syntax. @item @samp{params} This will display the values recognized by the @option{--param} option. @item @var{language} This will display the options supported for @var{language}, where @var{language} is the name of one of the languages supported in this version of GCC. @item @samp{common} This will display the options that are common to all languages. @end table These are the supported qualifiers: @table @asis @item @samp{undocumented} Display only those options which are undocumented. @item @samp{joined} Display options which take an argument that appears after an equal sign in the same continuous piece of text, such as: @samp{--help=target}. @item @samp{separate} Display options which take an argument that appears as a separate word following the original option, such as: @samp{-o output-file}. @end table Thus for example to display all the undocumented target-specific switches supported by the compiler the following can be used: @smallexample --help=target,undocumented @end smallexample The sense of a qualifier can be inverted by prefixing it with the @samp{^} character, so for example to display all binary warning options (i.e., ones that are either on or off and that do not take an argument), which have a description the following can be used: @smallexample --help=warnings,^joined,^undocumented @end smallexample The argument to @option{--help=} should not consist solely of inverted qualifiers. Combining several classes is possible, although this usually restricts the output by so much that there is nothing to display. One case where it does work however is when one of the classes is @var{target}. So for example to display all the target-specific optimization options the following can be used: @smallexample --help=target,optimizers @end smallexample The @option{--help=} option can be repeated on the command line. Each successive use will display its requested class of options, skipping those that have already been displayed. If the @option{-Q} option appears on the command line before the @option{--help=} option, then the descriptive text displayed by @option{--help=} is changed. Instead of describing the displayed options, an indication is given as to whether the option is enabled, disabled or set to a specific value (assuming that the compiler knows this at the point where the @option{--help=} option is used). Here is a truncated example from the ARM port of @command{gcc}: @smallexample % gcc -Q -mabi=2 --help=target -c The following options are target specific: -mabi= 2 -mabort-on-noreturn [disabled] -mapcs [disabled] @end smallexample The output is sensitive to the effects of previous command line options, so for example it is possible to find out which optimizations are enabled at @option{-O2} by using: @smallexample -Q -O2 --help=optimizers @end smallexample Alternatively you can discover which binary optimizations are enabled by @option{-O3} by using: @smallexample gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts diff /tmp/O2-opts /tmp/O3-opts | grep enabled @end smallexample @item -no-canonical-prefixes @opindex no-canonical-prefixes Do not expand any symbolic links, resolve references to @samp{/../} or @samp{/./}, or make the path absolute when generating a relative prefix. @item --version @opindex version Display the version number and copyrights of the invoked GCC@. @item -wrapper @opindex wrapper Invoke all subcommands under a wrapper program. The name of the wrapper program and its parameters are passed as a comma separated list. @smallexample gcc -c t.c -wrapper gdb,--args @end smallexample This will invoke all subprograms of @command{gcc} under @samp{gdb --args}, thus the invocation of @command{cc1} will be @samp{gdb --args cc1 @dots{}}. @item -fplugin=@var{name}.so Load the plugin code in file @var{name}.so, assumed to be a shared object to be dlopen'd by the compiler. The base name of the shared object file is used to identify the plugin for the purposes of argument parsing (See @option{-fplugin-arg-@var{name}-@var{key}=@var{value}} below). Each plugin should define the callback functions specified in the Plugins API. @item -fplugin-arg-@var{name}-@var{key}=@var{value} Define an argument called @var{key} with a value of @var{value} for the plugin called @var{name}. @item -fdump-ada-spec@r{[}-slim@r{]} For C and C++ source and include files, generate corresponding Ada specs. @xref{Generating Ada Bindings for C and C++ headers,,, gnat_ugn, GNAT User's Guide}, which provides detailed documentation on this feature. @item -fdump-go-spec=@var{file} For input files in any language, generate corresponding Go declarations in @var{file}. This generates Go @code{const}, @code{type}, @code{var}, and @code{func} declarations which may be a useful way to start writing a Go interface to code written in some other language. @include @value{srcdir}/../libiberty/at-file.texi @end table @node Invoking G++ @section Compiling C++ Programs @cindex suffixes for C++ source @cindex C++ source file suffixes C++ source files conventionally use one of the suffixes @samp{.C}, @samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or @samp{.cxx}; C++ header files often use @samp{.hh}, @samp{.hpp}, @samp{.H}, or (for shared template code) @samp{.tcc}; and preprocessed C++ files use the suffix @samp{.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 @command{gcc}). @findex g++ @findex c++ However, the use of @command{gcc} does not add the C++ library. @command{g++} is a program that calls GCC and treats @samp{.c}, @samp{.h} and @samp{.i} files as C++ source files instead of C source files unless @option{-x} is used, and automatically specifies linking against the C++ library. This program is also useful when precompiling a C header file with a @samp{.h} extension for use in C++ compilations. On many systems, @command{g++} is also installed with the name @command{c++}. @cindex invoking @command{g++} 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. @xref{C Dialect Options,,Options Controlling C Dialect}, for explanations of options for languages related to C@. @xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for explanations of options that are meaningful only for C++ programs. @node C Dialect Options @section Options Controlling C Dialect @cindex dialect options @cindex language dialect options @cindex options, 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: @table @gcctabopt @cindex ANSI support @cindex ISO support @item -ansi @opindex ansi In C mode, this is equivalent to @samp{-std=c90}. In C++ mode, it is equivalent to @samp{-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 @code{asm} and @code{typeof} keywords, and predefined macros such as @code{unix} and @code{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 @samp{//} comments as well as the @code{inline} keyword. The alternate keywords @code{__asm__}, @code{__extension__}, @code{__inline__} and @code{__typeof__} continue to work despite @option{-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 @option{-ansi}. Alternate predefined macros such as @code{__unix__} and @code{__vax__} are also available, with or without @option{-ansi}. The @option{-ansi} option does not cause non-ISO programs to be rejected gratuitously. For that, @option{-pedantic} is required in addition to @option{-ansi}. @xref{Warning Options}. The macro @code{__STRICT_ANSI__} is predefined when the @option{-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 semantics defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in functions when @option{-ansi} is used. @xref{Other Builtins,,Other built-in functions provided by GCC}, for details of the functions affected. @item -std= @opindex std Determine the language standard. @xref{Standards,,Language Standards Supported by GCC}, for details of these standard versions. This option is currently only supported when compiling C or C++. The compiler can accept several base standards, such as @samp{c90} or @samp{c++98}, and GNU dialects of those standards, such as @samp{gnu90} or @samp{gnu++98}. By specifying a base standard, the compiler will accept all programs following that standard and those using GNU extensions that do not contradict it. For example, @samp{-std=c90} turns off certain features of GCC that are incompatible with ISO C90, such as the @code{asm} and @code{typeof} keywords, but not other GNU extensions that do not have a meaning in ISO C90, such as omitting the middle term of a @code{?:} expression. On the other hand, by specifying a GNU dialect of a standard, all features the compiler support are enabled, even when those features change the meaning of the base standard and some strict-conforming programs may be rejected. The particular standard is used by @option{-pedantic} to identify which features are GNU extensions given that version of the standard. For example @samp{-std=gnu90 -pedantic} would warn about C++ style @samp{//} comments, while @samp{-std=gnu99 -pedantic} would not. A value for this option must be provided; possible values are @table @samp @item c90 @itemx c89 @itemx iso9899:1990 Support all ISO C90 programs (certain GNU extensions that conflict with ISO C90 are disabled). Same as @option{-ansi} for C code. @item iso9899:199409 ISO C90 as modified in amendment 1. @item c99 @itemx c9x @itemx iso9899:1999 @itemx iso9899:199x ISO C99. Note that this standard is not yet fully supported; see @w{@uref{http://gcc.gnu.org/c99status.html}} for more information. The names @samp{c9x} and @samp{iso9899:199x} are deprecated. @item c1x ISO C1X, the draft of the next revision of the ISO C standard. Support is limited and experimental and features enabled by this option may be changed or removed if changed in or removed from the standard draft. @item gnu90 @itemx gnu89 GNU dialect of ISO C90 (including some C99 features). This is the default for C code. @item gnu99 @itemx gnu9x GNU dialect of ISO C99. When ISO C99 is fully implemented in GCC, this will become the default. The name @samp{gnu9x} is deprecated. @item gnu1x GNU dialect of ISO C1X. Support is limited and experimental and features enabled by this option may be changed or removed if changed in or removed from the standard draft. @item c++98 The 1998 ISO C++ standard plus amendments. Same as @option{-ansi} for C++ code. @item gnu++98 GNU dialect of @option{-std=c++98}. This is the default for C++ code. @item c++11 The 2011 ISO C++ standard plus amendments. Support for C++11 is still experimental, and may change in incompatible ways in future releases. @item gnu++11 GNU dialect of @option{-std=c++11}. Support for C++11 is still experimental, and may change in incompatible ways in future releases. @end table @item -fgnu89-inline @opindex fgnu89-inline The option @option{-fgnu89-inline} tells GCC to use the traditional GNU semantics for @code{inline} functions when in C99 mode. @xref{Inline,,An Inline Function is As Fast As a Macro}. This option is accepted and ignored by GCC versions 4.1.3 up to but not including 4.3. In GCC versions 4.3 and later it changes the behavior of GCC in C99 mode. Using this option is roughly equivalent to adding the @code{gnu_inline} function attribute to all inline functions (@pxref{Function Attributes}). The option @option{-fno-gnu89-inline} explicitly tells GCC to use the C99 semantics for @code{inline} when in C99 or gnu99 mode (i.e., it specifies the default behavior). This option was first supported in GCC 4.3. This option is not supported in @option{-std=c90} or @option{-std=gnu90} mode. The preprocessor macros @code{__GNUC_GNU_INLINE__} and @code{__GNUC_STDC_INLINE__} may be used to check which semantics are in effect for @code{inline} functions. @xref{Common Predefined Macros,,,cpp,The C Preprocessor}. @item -aux-info @var{filename} @opindex aux-info 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 (@samp{I}, @samp{N} for new or @samp{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 (@samp{C} or @samp{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. @item -fallow-parameterless-variadic-functions Accept variadic functions without named parameters. Although it is possible to define such a function, this is not very useful as it is not possible to read the arguments. This is only supported for C as this construct is allowed by C++. @item -fno-asm @opindex fno-asm Do not recognize @code{asm}, @code{inline} or @code{typeof} as a keyword, so that code can use these words as identifiers. You can use the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} instead. @option{-ansi} implies @option{-fno-asm}. In C++, this switch only affects the @code{typeof} keyword, since @code{asm} and @code{inline} are standard keywords. You may want to use the @option{-fno-gnu-keywords} flag instead, which has the same effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this switch only affects the @code{asm} and @code{typeof} keywords, since @code{inline} is a standard keyword in ISO C99. @item -fno-builtin @itemx -fno-builtin-@var{function} @opindex fno-builtin @cindex built-in functions Don't recognize built-in functions that do not begin with @samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in functions provided by GCC}, for details of the functions affected, including those which are not built-in functions when @option{-ansi} or @option{-std} options for strict ISO C conformance are used because they do not have an ISO standard meaning. GCC normally generates special code to handle certain built-in functions more efficiently; for instance, calls to @code{alloca} may become single instructions that adjust the stack directly, and calls to @code{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 @option{-Wformat} for bad calls to @code{printf}, when @code{printf} is built in, and @code{strlen} is known not to modify global memory. With the @option{-fno-builtin-@var{function}} option only the built-in function @var{function} is disabled. @var{function} must not begin with @samp{__builtin_}. If a function is named that is not built-in in this version of GCC, this option is ignored. There is no corresponding @option{-fbuiltin-@var{function}} option; if you wish to enable built-in functions selectively when using @option{-fno-builtin} or @option{-ffreestanding}, you may define macros such as: @smallexample #define abs(n) __builtin_abs ((n)) #define strcpy(d, s) __builtin_strcpy ((d), (s)) @end smallexample @item -fhosted @opindex fhosted @cindex hosted environment Assert that compilation takes place in a hosted environment. This implies @option{-fbuiltin}. A hosted environment is one in which the entire standard library is available, and in which @code{main} has a return type of @code{int}. Examples are nearly everything except a kernel. This is equivalent to @option{-fno-freestanding}. @item -ffreestanding @opindex ffreestanding @cindex hosted environment Assert that compilation takes place in a freestanding environment. This implies @option{-fno-builtin}. A freestanding environment is one in which the standard library may not exist, and program startup may not necessarily be at @code{main}. The most obvious example is an OS kernel. This is equivalent to @option{-fno-hosted}. @xref{Standards,,Language Standards Supported by GCC}, for details of freestanding and hosted environments. @item -fopenmp @opindex fopenmp @cindex OpenMP parallel Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and @code{!$omp} in Fortran. When @option{-fopenmp} is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v3.0 @w{@uref{http://www.openmp.org/}}. This option implies @option{-pthread}, and thus is only supported on targets that have support for @option{-pthread}. @item -fms-extensions @opindex fms-extensions Accept some non-standard constructs used in Microsoft header files. In C++ code, this allows member names in structures to be similar to previous types declarations. @smallexample typedef int UOW; struct ABC @{ UOW UOW; @}; @end smallexample Some cases of unnamed fields in structures and unions are only accepted with this option. @xref{Unnamed Fields,,Unnamed struct/union fields within structs/unions}, for details. @item -fplan9-extensions Accept some non-standard constructs used in Plan 9 code. This enables @option{-fms-extensions}, permits passing pointers to structures with anonymous fields to functions which expect pointers to elements of the type of the field, and permits referring to anonymous fields declared using a typedef. @xref{Unnamed Fields,,Unnamed struct/union fields within structs/unions}, for details. This is only supported for C, not C++. @item -trigraphs @opindex trigraphs Support ISO C trigraphs. The @option{-ansi} option (and @option{-std} options for strict ISO C conformance) implies @option{-trigraphs}. @item -no-integrated-cpp @opindex no-integrated-cpp Performs a compilation in two passes: preprocessing and compiling. This option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the @option{-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. @cindex traditional C language @cindex C language, traditional @item -traditional @itemx -traditional-cpp @opindex traditional-cpp @opindex traditional Formerly, these options caused GCC to attempt to emulate a pre-standard C compiler. They are now only supported with the @option{-E} switch. The preprocessor continues to support a pre-standard mode. See the GNU CPP manual for details. @item -fcond-mismatch @opindex 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++. @item -flax-vector-conversions @opindex flax-vector-conversions Allow implicit conversions between vectors with differing numbers of elements and/or incompatible element types. This option should not be used for new code. @item -funsigned-char @opindex funsigned-char Let the type @code{char} be unsigned, like @code{unsigned char}. Each kind of machine has a default for what @code{char} should be. It is either like @code{unsigned char} by default or like @code{signed char} by default. Ideally, a portable program should always use @code{signed char} or @code{unsigned char} when it depends on the signedness of an object. But many programs have been written to use plain @code{char} and expect it to be signed, or expect it to be unsigned, depending on the machines they were written for. This option, and its inverse, let you make such a program work with the opposite default. The type @code{char} is always a distinct type from each of @code{signed char} or @code{unsigned char}, even though its behavior is always just like one of those two. @item -fsigned-char @opindex fsigned-char Let the type @code{char} be signed, like @code{signed char}. Note that this is equivalent to @option{-fno-unsigned-char}, which is the negative form of @option{-funsigned-char}. Likewise, the option @option{-fno-signed-char} is equivalent to @option{-funsigned-char}. @item -fsigned-bitfields @itemx -funsigned-bitfields @itemx -fno-signed-bitfields @itemx -fno-unsigned-bitfields @opindex fsigned-bitfields @opindex funsigned-bitfields @opindex fno-signed-bitfields @opindex fno-unsigned-bitfields These options control whether a bit-field is signed or unsigned, when the declaration does not use either @code{signed} or @code{unsigned}. By default, such a bit-field is signed, because this is consistent: the basic integer types such as @code{int} are signed types. @end table @node C++ Dialect Options @section Options Controlling C++ Dialect @cindex compiler options, C++ @cindex C++ options, command line @cindex options, C++ 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 @code{firstClass.C} like this: @smallexample g++ -g -frepo -O -c firstClass.C @end smallexample @noindent In this example, only @option{-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 @emph{only} for compiling C++ programs: @table @gcctabopt @item -fabi-version=@var{n} @opindex fabi-version Use version @var{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. Version 3 corrects an error in mangling a constant address as a template argument. Version 4 implements a standard mangling for vector types. Version 5 corrects the mangling of attribute const/volatile on function pointer types, decltype of a plain decl, and use of a function parameter in the declaration of another parameter. Version 6 corrects the promotion behavior of C++11 scoped enums. See also @option{-Wabi}. @item -fno-access-control @opindex fno-access-control Turn off all access checking. This switch is mainly useful for working around bugs in the access control code. @item -fcheck-new @opindex fcheck-new Check that the pointer returned by @code{operator new} is non-null before attempting to modify the storage allocated. This check is normally unnecessary because the C++ standard specifies that @code{operator new} will only return @code{0} if it is declared @samp{throw()}, in which case the compiler will always check the return value even without this option. In all other cases, when @code{operator new} has a non-empty exception specification, memory exhaustion is signalled by throwing @code{std::bad_alloc}. See also @samp{new (nothrow)}. @item -fconserve-space @opindex 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 @code{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. @item -fconstexpr-depth=@var{n} @opindex fconstexpr-depth Set the maximum nested evaluation depth for C++11 constexpr functions to @var{n}. A limit is needed to detect endless recursion during constant expression evaluation. The minimum specified by the standard is 512. @item -fdeduce-init-list @opindex fdeduce-init-list Enable deduction of a template type parameter as std::initializer_list from a brace-enclosed initializer list, i.e. @smallexample template auto forward(T t) -> decltype (realfn (t)) @{ return realfn (t); @} void f() @{ forward(@{1,2@}); // call forward> @} @end smallexample This deduction was implemented as a possible extension to the originally proposed semantics for the C++11 standard, but was not part of the final standard, so it is disabled by default. This option is deprecated, and may be removed in a future version of G++. @item -ffriend-injection @opindex 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++. @item -fno-elide-constructors @opindex 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. @item -fno-enforce-eh-specs @opindex 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 @samp{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 undefined behavior. @item -ffor-scope @itemx -fno-for-scope @opindex ffor-scope @opindex fno-for-scope If @option{-ffor-scope} is specified, the scope of variables declared in a @i{for-init-statement} is limited to the @samp{for} loop itself, as specified by the C++ standard. If @option{-fno-for-scope} is specified, the scope of variables declared in a @i{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. @item -fno-gnu-keywords @opindex fno-gnu-keywords Do not recognize @code{typeof} as a keyword, so that code can use this word as an identifier. You can use the keyword @code{__typeof__} instead. @option{-ansi} implies @option{-fno-gnu-keywords}. @item -fno-implicit-templates @opindex fno-implicit-templates Never emit code for non-inline templates which are instantiated implicitly (i.e.@: by use); only emit code for explicit instantiations. @xref{Template Instantiation}, for more information. @item -fno-implicit-inline-templates @opindex 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. @item -fno-implement-inlines @opindex fno-implement-inlines To save space, do not emit out-of-line copies of inline functions controlled by @samp{#pragma implementation}. This will cause linker errors if these functions are not inlined everywhere they are called. @item -fms-extensions @opindex 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. @item -fno-nonansi-builtins @opindex fno-nonansi-builtins Disable built-in declarations of functions that are not mandated by ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit}, @code{index}, @code{bzero}, @code{conjf}, and other related functions. @item -fnothrow-opt @opindex fnothrow-opt Treat a @code{throw()} exception specification as though it were a @code{noexcept} specification to reduce or eliminate the text size overhead relative to a function with no exception specification. If the function has local variables of types with non-trivial destructors, the exception specification will actually make the function smaller because the EH cleanups for those variables can be optimized away. The semantic effect is that an exception thrown out of a function with such an exception specification will result in a call to @code{terminate} rather than @code{unexpected}. @item -fno-operator-names @opindex fno-operator-names Do not treat the operator name keywords @code{and}, @code{bitand}, @code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as synonyms as keywords. @item -fno-optional-diags @opindex 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. @item -fpermissive @opindex fpermissive Downgrade some diagnostics about nonconformant code from errors to warnings. Thus, using @option{-fpermissive} will allow some nonconforming code to compile. @item -fno-pretty-templates @opindex fno-pretty-templates When an error message refers to a specialization of a function template, the compiler will normally print the signature of the template followed by the template arguments and any typedefs or typenames in the signature (e.g. @code{void f(T) [with T = int]} rather than @code{void f(int)}) so that it's clear which template is involved. When an error message refers to a specialization of a class template, the compiler will omit any template arguments which match the default template arguments for that template. If either of these behaviors make it harder to understand the error message rather than easier, using @option{-fno-pretty-templates} will disable them. @item -frepo @opindex frepo Enable automatic template instantiation at link time. This option also implies @option{-fno-implicit-templates}. @xref{Template Instantiation}, for more information. @item -fno-rtti @opindex fno-rtti Disable generation of information about every class with virtual functions for use by the C++ runtime type identification features (@samp{dynamic_cast} and @samp{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 @samp{dynamic_cast} operator can still be used for casts that do not require runtime type information, i.e.@: casts to @code{void *} or to unambiguous base classes. @item -fstats @opindex fstats Emit statistics about front-end processing at the end of the compilation. This information is generally only useful to the G++ development team. @item -fstrict-enums @opindex fstrict-enums Allow the compiler to optimize using the assumption that a value of enumeration type can only be one of the values of the enumeration (as defined in the C++ standard; basically, a value which can be represented in the minimum number of bits needed to represent all the enumerators). This assumption may not be valid if the program uses a cast to convert an arbitrary integer value to the enumeration type. @item -ftemplate-depth=@var{n} @opindex ftemplate-depth Set the maximum instantiation depth for template classes to @var{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 (changed to 1024 in C++11). The default value is 900, as the compiler can run out of stack space before hitting 1024 in some situations. @item -fno-threadsafe-statics @opindex 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. @item -fuse-cxa-atexit @opindex fuse-cxa-atexit Register destructors for objects with static storage duration with the @code{__cxa_atexit} function rather than the @code{atexit} function. This option is required for fully standards-compliant handling of static destructors, but will only work if your C library supports @code{__cxa_atexit}. @item -fno-use-cxa-get-exception-ptr @opindex fno-use-cxa-get-exception-ptr Don't use the @code{__cxa_get_exception_ptr} runtime routine. This will cause @code{std::uncaught_exception} to be incorrect, but is necessary if the runtime routine is not available. @item -fvisibility-inlines-hidden @opindex fvisibility-inlines-hidden This switch declares that the user does not attempt to compare pointers to inline functions or 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 @code{__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 behavior 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. @xref{Template Instantiation}. @item -fvisibility-ms-compat @opindex fvisibility-ms-compat This flag attempts to use visibility settings to make GCC's C++ linkage model compatible with that of Microsoft Visual Studio. The flag makes these changes to GCC's linkage model: @enumerate @item It sets the default visibility to @code{hidden}, like @option{-fvisibility=hidden}. @item Types, but not their members, are not hidden by default. @item The One Definition Rule is relaxed for types without explicit visibility specifications which are defined in more than one different shared object: those declarations are permitted if they would have been permitted when this option was not used. @end enumerate In new code it is better to use @option{-fvisibility=hidden} and export those classes which are intended to be externally visible. Unfortunately it is possible for code to rely, perhaps accidentally, on the Visual Studio behavior. Among the consequences of these changes are that static data members of the same type with the same name but defined in different shared objects will be different, so changing one will not change the other; and that pointers to function members defined in different shared objects may not compare equal. When this flag is given, it is a violation of the ODR to define types with the same name differently. @item -fno-weak @opindex 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++. @item -nostdinc++ @opindex 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.) @end table In addition, these optimization, warning, and code generation options have meanings only for C++ programs: @table @gcctabopt @item -fno-default-inline @opindex fno-default-inline Do not assume @samp{inline} for functions defined inside a class scope. @xref{Optimize Options,,Options That Control Optimization}. Note that these functions will have linkage like inline functions; they just won't be inlined by default. @item -Wabi @r{(C, Objective-C, C++ and Objective-C++ only)} @opindex Wabi @opindex Wno-abi 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 in @option{-fabi-version=2} (the default) include: @itemize @bullet @item A template with a non-type template parameter of reference type is mangled incorrectly: @smallexample extern int N; template struct S @{@}; void n (S) @{2@} @end smallexample This is fixed in @option{-fabi-version=3}. @item SIMD vector types declared using @code{__attribute ((vector_size))} are mangled in a non-standard way that does not allow for overloading of functions taking vectors of different sizes. The mangling is changed in @option{-fabi-version=4}. @end itemize The known incompatibilities in @option{-fabi-version=1} include: @itemize @bullet @item Incorrect handling of tail-padding for bit-fields. G++ may attempt to pack data into the same byte as a base class. For example: @smallexample struct A @{ virtual void f(); int f1 : 1; @}; struct B : public A @{ int f2 : 1; @}; @end smallexample @noindent In this case, G++ will place @code{B::f2} into the same byte as@code{A::f1}; other compilers will not. You can avoid this problem by explicitly padding @code{A} so that its size is a multiple of the byte size on your platform; that will cause G++ and other compilers to layout @code{B} identically. @item Incorrect handling of tail-padding for virtual bases. G++ does not use tail padding when laying out virtual bases. For example: @smallexample struct A @{ virtual void f(); char c1; @}; struct B @{ B(); char c2; @}; struct C : public A, public virtual B @{@}; @end smallexample @noindent In this case, G++ will not place @code{B} into the tail-padding for @code{A}; other compilers will. You can avoid this problem by explicitly padding @code{A} so that its size is a multiple of its alignment (ignoring virtual base classes); that will cause G++ and other compilers to layout @code{C} identically. @item 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: @smallexample union U @{ int i : 4096; @}; @end smallexample @noindent Assuming that an @code{int} does not have 4096 bits, G++ will make the union too small by the number of bits in an @code{int}. @item Empty classes can be placed at incorrect offsets. For example: @smallexample struct A @{@}; struct B @{ A a; virtual void f (); @}; struct C : public B, public A @{@}; @end smallexample @noindent G++ will place the @code{A} base class of @code{C} at a nonzero offset; it should be placed at offset zero. G++ mistakenly believes that the @code{A} data member of @code{B} is already at offset zero. @item Names of template functions whose types involve @code{typename} or template template parameters can be mangled incorrectly. @smallexample template void f(typename Q::X) @{@} template