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@c Copyright (C) 1988-2021 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@c man begin INCLUDE
@include gcc-vers.texi
@c man end
@c man begin COPYRIGHT
Copyright @copyright{} 1988-2021 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{-Wpedantic}]
[@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. @command{g++} accepts mostly the same options as @command{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), dbx(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
@c man end
@c man begin AUTHOR
See the Info entry for @command{gcc}, or
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.
@xref{Overall Options,,Options Controlling the Kind of Output}.
Other options are passed on to one or more stages 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 cross compiling
@cindex specifying machine version
@cindex specifying compiler version and target machine
@cindex compiler version, specifying
@cindex target machine, specifying
The usual way to run GCC is to run the executable called @command{gcc}, or
@command{@var{machine}-gcc} when cross-compiling, or
@command{@var{machine}-gcc-@var{version}} to run a specific version of GCC.
When you compile C++ programs, you should invoke GCC as @command{g++}
instead. @xref{Invoking G++,,Compiling C++ Programs},
for information about the differences in behavior between @command{gcc}
and @command{g++} when 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
@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} is @option{-fno-foo}. This manual documents
only one of these two forms, whichever one is not the default.
Some options take one or more arguments typically separated either
by a space or by the equals sign (@samp{=}) from the option name.
Unless documented otherwise, an argument can be either numeric or
a string. Numeric arguments must typically be small unsigned decimal
or hexadecimal integers. Hexadecimal arguments must begin with
the @samp{0x} prefix. Arguments to options that specify a size
threshold of some sort may be arbitrarily large decimal or hexadecimal
integers followed by a byte size suffix designating a multiple of bytes
such as @code{kB} and @code{KiB} for kilobyte and kibibyte, respectively,
@code{MB} and @code{MiB} for megabyte and mebibyte, @code{GB} and
@code{GiB} for gigabyte and gigibyte, and so on. Such arguments are
designated by @var{byte-size} in the following text. Refer to the NIST,
IEC, and other relevant national and international standards for the full
listing and explanation of the binary and decimal byte size prefixes.
@c man end
@xref{Option Index}, for an index to GCC's options.
* 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++.
* Diagnostic Message Formatting Options:: Controlling how diagnostics should
be formatted.
* Warning Options:: How picky should the compiler be?
* Static Analyzer Options:: More expensive warnings.
* Debugging Options:: Producing debuggable code.
* Optimize Options:: How much optimization?
* Instrumentation Options:: Enabling profiling and extra run-time error checking.
* 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.
* Code Gen Options:: Specifying conventions for function calls, data layout
and register usage.
* Developer Options:: Printing GCC configuration info, statistics, and
debugging dumps.
* Submodel Options:: Target-specific options, such as compiling for a
specific processor variant.
* Spec Files:: How to pass switches to sub-processes.
* Environment Variables:: Env vars that affect GCC.
* Precompiled Headers:: Compiling a header once, and using it many times.
* C++ Modules:: Experimental C++20 module system.
@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} @gol
-dumpbase @var{dumpbase} -dumpbase-ext @var{auxdropsuf} @gol
-dumpdir @var{dumppfx} -x @var{language} @gol
-v -### --help@r{[}=@var{class}@r{[},@dots{}@r{]]} --target-help --version @gol
-pass-exit-codes -pipe -specs=@var{file} -wrapper @gol
@@@var{file} -ffile-prefix-map=@var{old}=@var{new} @gol
-fplugin=@var{file} -fplugin-arg-@var{name}=@var{arg} @gol
-fdump-ada-spec@r{[}-slim@r{]} -fada-spec-parent=@var{unit} -fdump-go-spec=@var{file}}
@item C Language Options
@xref{C Dialect Options,,Options Controlling C Dialect}.
@gccoptlist{-ansi -std=@var{standard} -aux-info @var{filename} @gol
-fallow-parameterless-variadic-functions -fno-asm @gol
-fno-builtin -fno-builtin-@var{function} -fcond-mismatch @gol
-ffreestanding -fgimple -fgnu-tm -fgnu89-inline -fhosted @gol
-flax-vector-conversions -fms-extensions @gol
-foffload=@var{arg} -foffload-options=@var{arg} @gol
-fopenacc -fopenacc-dim=@var{geom} @gol
-fopenmp -fopenmp-simd @gol
-fpermitted-flt-eval-methods=@var{standard} @gol
-fplan9-extensions -fsigned-bitfields -funsigned-bitfields @gol
-fsigned-char -funsigned-char -fsso-struct=@var{endianness}}
@item C++ Language Options
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
@gccoptlist{-fabi-version=@var{n} -fno-access-control @gol
-faligned-new=@var{n} -fargs-in-order=@var{n} -fchar8_t -fcheck-new @gol
-fconstexpr-depth=@var{n} -fconstexpr-cache-depth=@var{n} @gol
-fconstexpr-loop-limit=@var{n} -fconstexpr-ops-limit=@var{n} @gol
-fno-elide-constructors @gol
-fno-enforce-eh-specs @gol
-fno-gnu-keywords @gol
-fno-implicit-templates @gol
-fno-implicit-inline-templates @gol
-fno-implement-inlines @gol
-fmodule-header@r{[}=@var{kind}@r{]} -fmodule-only -fmodules-ts @gol
-fmodule-implicit-inline @gol
-fno-module-lazy @gol
-fmodule-mapper=@var{specification} @gol
-fmodule-version-ignore @gol
-fms-extensions @gol
-fnew-inheriting-ctors @gol
-fnew-ttp-matching @gol
-fno-nonansi-builtins -fnothrow-opt -fno-operator-names @gol
-fno-optional-diags -fpermissive @gol
-fno-pretty-templates @gol
-fno-rtti -fsized-deallocation @gol
-ftemplate-backtrace-limit=@var{n} @gol
-ftemplate-depth=@var{n} @gol
-fno-threadsafe-statics -fuse-cxa-atexit @gol
-fno-weak -nostdinc++ @gol
-fvisibility-inlines-hidden @gol
-fvisibility-ms-compat @gol
-fext-numeric-literals @gol
-flang-info-include-translate@r{[}=@var{header}@r{]} @gol
-flang-info-include-translate-not @gol
-flang-info-module-cmi@r{[}=@var{module}@r{]} @gol
-stdlib=@var{libstdc++,libc++} @gol
-Wabi-tag -Wcatch-value -Wcatch-value=@var{n} @gol
-Wno-class-conversion -Wclass-memaccess @gol
-Wcomma-subscript -Wconditionally-supported @gol
-Wno-conversion-null -Wctad-maybe-unsupported @gol
-Wctor-dtor-privacy -Wno-delete-incomplete @gol
-Wdelete-non-virtual-dtor -Wno-deprecated-array-compare @gol
-Wdeprecated-copy -Wdeprecated-copy-dtor @gol
-Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
-Weffc++ -Wno-exceptions -Wextra-semi -Wno-inaccessible-base @gol
-Wno-inherited-variadic-ctor -Wno-init-list-lifetime @gol
-Winvalid-imported-macros @gol
-Wno-invalid-offsetof -Wno-literal-suffix @gol
-Wmismatched-new-delete -Wmismatched-tags @gol
-Wmultiple-inheritance -Wnamespaces -Wnarrowing @gol
-Wnoexcept -Wnoexcept-type -Wnon-virtual-dtor @gol
-Wpessimizing-move -Wno-placement-new -Wplacement-new=@var{n} @gol
-Wrange-loop-construct -Wredundant-move -Wredundant-tags @gol
-Wreorder -Wregister @gol
-Wstrict-null-sentinel -Wno-subobject-linkage -Wtemplates @gol
-Wno-non-template-friend -Wold-style-cast @gol
-Woverloaded-virtual -Wno-pmf-conversions -Wsign-promo @gol
-Wsized-deallocation -Wsuggest-final-methods @gol
-Wsuggest-final-types -Wsuggest-override @gol
-Wno-terminate -Wuseless-cast -Wno-vexing-parse @gol
-Wvirtual-inheritance @gol
-Wno-virtual-move-assign -Wvolatile -Wzero-as-null-pointer-constant}
@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
-fno-local-ivars @gol
-fivar-visibility=@r{[}public@r{|}protected@r{|}private@r{|}package@r{]} @gol
-freplace-objc-classes @gol
-fzero-link @gol
-gen-decls @gol
-Wassign-intercept -Wno-property-assign-default @gol
-Wno-protocol -Wobjc-root-class -Wselector @gol
-Wstrict-selector-match @gol
@item Diagnostic Message Formatting Options
@xref{Diagnostic Message Formatting Options,,Options to Control Diagnostic Messages Formatting}.
@gccoptlist{-fmessage-length=@var{n} @gol
-fdiagnostics-plain-output @gol
-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol
-fdiagnostics-color=@r{[}auto@r{|}never@r{|}always@r{]} @gol
-fdiagnostics-urls=@r{[}auto@r{|}never@r{|}always@r{]} @gol
-fdiagnostics-format=@r{[}text@r{|}json@r{]} @gol
-fno-diagnostics-show-option -fno-diagnostics-show-caret @gol
-fno-diagnostics-show-labels -fno-diagnostics-show-line-numbers @gol
-fno-diagnostics-show-cwe @gol
-fdiagnostics-minimum-margin-width=@var{width} @gol
-fdiagnostics-parseable-fixits -fdiagnostics-generate-patch @gol
-fdiagnostics-show-template-tree -fno-elide-type @gol
-fdiagnostics-path-format=@r{[}none@r{|}separate-events@r{|}inline-events@r{]} @gol
-fdiagnostics-show-path-depths @gol
-fno-show-column @gol
-fdiagnostics-column-unit=@r{[}display@r{|}byte@r{]} @gol
@item Warning Options
@xref{Warning Options,,Options to Request or Suppress Warnings}.
@gccoptlist{-fsyntax-only -fmax-errors=@var{n} -Wpedantic @gol
-pedantic-errors @gol
-w -Wextra -Wall -Wabi=@var{n} @gol
-Waddress -Wno-address-of-packed-member -Waggregate-return @gol
-Walloc-size-larger-than=@var{byte-size} -Walloc-zero @gol
-Walloca -Walloca-larger-than=@var{byte-size} @gol
-Wno-aggressive-loop-optimizations @gol
-Warith-conversion @gol
-Warray-bounds -Warray-bounds=@var{n} -Warray-compare @gol
-Wno-attributes -Wattribute-alias=@var{n} -Wno-attribute-alias @gol
-Wno-attribute-warning -Wbool-compare -Wbool-operation @gol
-Wno-builtin-declaration-mismatch @gol
-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
-Wc11-c2x-compat @gol
-Wc++-compat -Wc++11-compat -Wc++14-compat -Wc++17-compat @gol
-Wc++20-compat @gol
-Wno-c++11-extensions -Wno-c++14-extensions -Wno-c++17-extensions @gol
-Wno-c++20-extensions -Wno-c++23-extensions @gol
-Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual @gol
-Wchar-subscripts @gol
-Wclobbered -Wcomment @gol
-Wconversion -Wno-coverage-mismatch -Wno-cpp @gol
-Wdangling-else -Wdate-time @gol
-Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init @gol
-Wdisabled-optimization @gol
-Wno-discarded-array-qualifiers -Wno-discarded-qualifiers @gol
-Wno-div-by-zero -Wdouble-promotion @gol
-Wduplicated-branches -Wduplicated-cond @gol
-Wempty-body -Wno-endif-labels -Wenum-compare -Wenum-conversion @gol
-Werror -Werror=* -Wexpansion-to-defined -Wfatal-errors @gol
-Wfloat-conversion -Wfloat-equal -Wformat -Wformat=2 @gol
-Wno-format-contains-nul -Wno-format-extra-args @gol
-Wformat-nonliteral -Wformat-overflow=@var{n} @gol
-Wformat-security -Wformat-signedness -Wformat-truncation=@var{n} @gol
-Wformat-y2k -Wframe-address @gol
-Wframe-larger-than=@var{byte-size} -Wno-free-nonheap-object @gol
-Wno-if-not-aligned -Wno-ignored-attributes @gol
-Wignored-qualifiers -Wno-incompatible-pointer-types @gol
-Wimplicit -Wimplicit-fallthrough -Wimplicit-fallthrough=@var{n} @gol
-Wno-implicit-function-declaration -Wno-implicit-int @gol
-Winit-self -Winline -Wno-int-conversion -Wint-in-bool-context @gol
-Wno-int-to-pointer-cast -Wno-invalid-memory-model @gol
-Winvalid-pch -Wjump-misses-init -Wlarger-than=@var{byte-size} @gol
-Wlogical-not-parentheses -Wlogical-op -Wlong-long @gol
-Wno-lto-type-mismatch -Wmain -Wmaybe-uninitialized @gol
-Wmemset-elt-size -Wmemset-transposed-args @gol
-Wmisleading-indentation -Wmissing-attributes -Wmissing-braces @gol
-Wmissing-field-initializers -Wmissing-format-attribute @gol
-Wmissing-include-dirs -Wmissing-noreturn -Wno-missing-profile @gol
-Wno-multichar -Wmultistatement-macros -Wnonnull -Wnonnull-compare @gol
-Wnormalized=@r{[}none@r{|}id@r{|}nfc@r{|}nfkc@r{]} @gol
-Wnull-dereference -Wno-odr @gol
-Wopenacc-parallelism @gol
-Wopenmp-simd @gol
-Wno-overflow -Woverlength-strings -Wno-override-init-side-effects @gol
-Wpacked -Wno-packed-bitfield-compat -Wpacked-not-aligned -Wpadded @gol
-Wparentheses -Wno-pedantic-ms-format @gol
-Wpointer-arith -Wno-pointer-compare -Wno-pointer-to-int-cast @gol
-Wno-pragmas -Wno-prio-ctor-dtor -Wredundant-decls @gol
-Wrestrict -Wno-return-local-addr -Wreturn-type @gol
-Wno-scalar-storage-order -Wsequence-point @gol
-Wshadow -Wshadow=global -Wshadow=local -Wshadow=compatible-local @gol
-Wno-shadow-ivar @gol
-Wno-shift-count-negative -Wno-shift-count-overflow -Wshift-negative-value @gol
-Wno-shift-overflow -Wshift-overflow=@var{n} @gol
-Wsign-compare -Wsign-conversion @gol
-Wno-sizeof-array-argument @gol
-Wsizeof-array-div @gol
-Wsizeof-pointer-div -Wsizeof-pointer-memaccess @gol
-Wstack-protector -Wstack-usage=@var{byte-size} -Wstrict-aliasing @gol
-Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
-Wstring-compare @gol
-Wno-stringop-overflow -Wno-stringop-overread @gol
-Wno-stringop-truncation @gol
-Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}malloc@r{]} @gol
-Wswitch -Wno-switch-bool -Wswitch-default -Wswitch-enum @gol
-Wno-switch-outside-range -Wno-switch-unreachable -Wsync-nand @gol
-Wsystem-headers -Wtautological-compare -Wtrampolines -Wtrigraphs @gol
-Wtsan -Wtype-limits -Wundef @gol
-Wuninitialized -Wunknown-pragmas @gol
-Wunsuffixed-float-constants -Wunused @gol
-Wunused-but-set-parameter -Wunused-but-set-variable @gol
-Wunused-const-variable -Wunused-const-variable=@var{n} @gol
-Wunused-function -Wunused-label -Wunused-local-typedefs @gol
-Wunused-macros @gol
-Wunused-parameter -Wno-unused-result @gol
-Wunused-value -Wunused-variable @gol
-Wno-varargs -Wvariadic-macros @gol
-Wvector-operation-performance @gol
-Wvla -Wvla-larger-than=@var{byte-size} -Wno-vla-larger-than @gol
-Wvolatile-register-var -Wwrite-strings @gol
@item Static Analyzer Options
-fanalyzer @gol
-fanalyzer-call-summaries @gol
-fanalyzer-checker=@var{name} @gol
-fno-analyzer-feasibility @gol
-fanalyzer-fine-grained @gol
-fanalyzer-state-merge @gol
-fanalyzer-state-purge @gol
-fanalyzer-transitivity @gol
-fanalyzer-verbose-edges @gol
-fanalyzer-verbose-state-changes @gol
-fanalyzer-verbosity=@var{level} @gol
-fdump-analyzer @gol
-fdump-analyzer-stderr @gol
-fdump-analyzer-callgraph @gol
-fdump-analyzer-exploded-graph @gol
-fdump-analyzer-exploded-nodes @gol
-fdump-analyzer-exploded-nodes-2 @gol
-fdump-analyzer-exploded-nodes-3 @gol
-fdump-analyzer-exploded-paths @gol
-fdump-analyzer-feasibility @gol
-fdump-analyzer-json @gol
-fdump-analyzer-state-purge @gol
-fdump-analyzer-supergraph @gol
-Wno-analyzer-double-fclose @gol
-Wno-analyzer-double-free @gol
-Wno-analyzer-exposure-through-output-file @gol
-Wno-analyzer-file-leak @gol
-Wno-analyzer-free-of-non-heap @gol
-Wno-analyzer-malloc-leak @gol
-Wno-analyzer-mismatching-deallocation @gol
-Wno-analyzer-null-argument @gol
-Wno-analyzer-null-dereference @gol
-Wno-analyzer-possible-null-argument @gol
-Wno-analyzer-possible-null-dereference @gol
-Wno-analyzer-shift-count-negative @gol
-Wno-analyzer-shift-count-overflow @gol
-Wno-analyzer-stale-setjmp-buffer @gol
-Wno-analyzer-tainted-array-index @gol
-Wanalyzer-too-complex @gol
-Wno-analyzer-unsafe-call-within-signal-handler @gol
-Wno-analyzer-use-after-free @gol
-Wno-analyzer-use-of-pointer-in-stale-stack-frame @gol
-Wno-analyzer-use-of-uninitialized-value @gol
-Wno-analyzer-write-to-const @gol
-Wno-analyzer-write-to-string-literal @gol
@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}.
@gccoptlist{-g -g@var{level} -gdwarf -gdwarf-@var{version} @gol
-gbtf -gctf -gctf@var{level} @gol
-ggdb -grecord-gcc-switches -gno-record-gcc-switches @gol
-gstabs -gstabs+ -gstrict-dwarf -gno-strict-dwarf @gol
-gas-loc-support -gno-as-loc-support @gol
-gas-locview-support -gno-as-locview-support @gol
-gcolumn-info -gno-column-info -gdwarf32 -gdwarf64 @gol
-gstatement-frontiers -gno-statement-frontiers @gol
-gvariable-location-views -gno-variable-location-views @gol
-ginternal-reset-location-views -gno-internal-reset-location-views @gol
-ginline-points -gno-inline-points @gol
-gvms -gxcoff -gxcoff+ -gz@r{[}=@var{type}@r{]} @gol
-gsplit-dwarf -gdescribe-dies -gno-describe-dies @gol
-fdebug-prefix-map=@var{old}=@var{new} -fdebug-types-section @gol
-fno-eliminate-unused-debug-types @gol
-femit-struct-debug-baseonly -femit-struct-debug-reduced @gol
-femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol
-fno-eliminate-unused-debug-symbols -femit-class-debug-always @gol
-fno-merge-debug-strings -fno-dwarf2-cfi-asm @gol
-fvar-tracking -fvar-tracking-assignments}
@item Optimization Options
@xref{Optimize Options,,Options that Control Optimization}.
@gccoptlist{-faggressive-loop-optimizations @gol
-falign-functions[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-falign-jumps[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-falign-labels[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-falign-loops[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
-fno-allocation-dce -fallow-store-data-races @gol
-fassociative-math -fauto-profile -fauto-profile[=@var{path}] @gol
-fauto-inc-dec -fbranch-probabilities @gol
-fcaller-saves @gol
-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 -fdelayed-branch @gol
-fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively @gol
-fdevirtualize-at-ltrans -fdse @gol
-fearly-inlining -fipa-sra -fexpensive-optimizations -ffat-lto-objects @gol
-ffast-math -ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol
-ffinite-loops @gol
-fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol
-fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol
-fgcse-sm -fhoist-adjacent-loads -fif-conversion @gol
-fif-conversion2 -findirect-inlining @gol
-finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol
-finline-small-functions -fipa-modref -fipa-cp -fipa-cp-clone @gol
-fipa-bit-cp -fipa-vrp -fipa-pta -fipa-profile -fipa-pure-const @gol
-fipa-reference -fipa-reference-addressable @gol
-fipa-stack-alignment -fipa-icf -fira-algorithm=@var{algorithm} @gol
-flive-patching=@var{level} @gol
-fira-region=@var{region} -fira-hoist-pressure @gol
-fira-loop-pressure -fno-ira-share-save-slots @gol
-fno-ira-share-spill-slots @gol
-fisolate-erroneous-paths-dereference -fisolate-erroneous-paths-attribute @gol
-fivopts -fkeep-inline-functions -fkeep-static-functions @gol
-fkeep-static-consts -flimit-function-alignment -flive-range-shrinkage @gol
-floop-block -floop-interchange -floop-strip-mine @gol
-floop-unroll-and-jam -floop-nest-optimize @gol
-floop-parallelize-all -flra-remat -flto -flto-compression-level @gol
-flto-partition=@var{alg} -fmerge-all-constants @gol
-fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol
-fmove-loop-invariants -fmove-loop-stores -fno-branch-count-reg @gol
-fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol
-fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole @gol
-fno-peephole2 -fno-printf-return-value -fno-sched-interblock @gol
-fno-sched-spec -fno-signed-zeros @gol
-fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
-fomit-frame-pointer -foptimize-sibling-calls @gol
-fpartial-inlining -fpeel-loops -fpredictive-commoning @gol
-fprefetch-loop-arrays @gol
-fprofile-correction @gol
-fprofile-use -fprofile-use=@var{path} -fprofile-partial-training @gol
-fprofile-values -fprofile-reorder-functions @gol
-freciprocal-math -free -frename-registers -freorder-blocks @gol
-freorder-blocks-algorithm=@var{algorithm} @gol
-freorder-blocks-and-partition -freorder-functions @gol
-frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol
-frounding-math -fsave-optimization-record @gol
-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-fusion @gol
-fschedule-insns -fschedule-insns2 -fsection-anchors @gol
-fselective-scheduling -fselective-scheduling2 @gol
-fsel-sched-pipelining -fsel-sched-pipelining-outer-loops @gol
-fsemantic-interposition -fshrink-wrap -fshrink-wrap-separate @gol
-fsignaling-nans @gol
-fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-loops@gol
-fsplit-paths @gol
-fsplit-wide-types -fsplit-wide-types-early -fssa-backprop -fssa-phiopt @gol
-fstdarg-opt -fstore-merging -fstrict-aliasing @gol
-fthread-jumps -ftracer -ftree-bit-ccp @gol
-ftree-builtin-call-dce -ftree-ccp -ftree-ch @gol
-ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts @gol
-ftree-dse -ftree-forwprop -ftree-fre -fcode-hoisting @gol
-ftree-loop-if-convert -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-loop-vectorize @gol
-ftree-parallelize-loops=@var{n} -ftree-pre -ftree-partial-pre -ftree-pta @gol
-ftree-reassoc -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra @gol
-ftree-switch-conversion -ftree-tail-merge @gol
-ftree-ter -ftree-vectorize -ftree-vrp -ftrivial-auto-var-init @gol
-funconstrained-commons -funit-at-a-time -funroll-all-loops @gol
-funroll-loops -funsafe-math-optimizations -funswitch-loops @gol
-fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt @gol
-fweb -fwhole-program -fwpa -fuse-linker-plugin -fzero-call-used-regs @gol
--param @var{name}=@var{value}
-O -O0 -O1 -O2 -O3 -Os -Ofast -Og}
@item Program Instrumentation Options
@xref{Instrumentation Options,,Program Instrumentation Options}.
@gccoptlist{-p -pg -fprofile-arcs --coverage -ftest-coverage @gol
-fprofile-abs-path @gol
-fprofile-dir=@var{path} -fprofile-generate -fprofile-generate=@var{path} @gol
-fprofile-info-section -fprofile-info-section=@var{name} @gol
-fprofile-note=@var{path} -fprofile-prefix-path=@var{path} @gol
-fprofile-update=@var{method} -fprofile-filter-files=@var{regex} @gol
-fprofile-exclude-files=@var{regex} @gol
-fprofile-reproducible=@r{[}multithreaded@r{|}parallel-runs@r{|}serial@r{]} @gol
-fsanitize=@var{style} -fsanitize-recover -fsanitize-recover=@var{style} @gol
-fasan-shadow-offset=@var{number} -fsanitize-sections=@var{s1},@var{s2},... @gol
-fsanitize-undefined-trap-on-error -fbounds-check @gol
-fcf-protection=@r{[}full@r{|}branch@r{|}return@r{|}none@r{|}check@r{]} @gol
-fstack-protector -fstack-protector-all -fstack-protector-strong @gol
-fstack-protector-explicit -fstack-check @gol
-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol
-fno-stack-limit -fsplit-stack @gol
-fvtable-verify=@r{[}std@r{|}preinit@r{|}none@r{]} @gol
-fvtv-counts -fvtv-debug @gol
-finstrument-functions @gol
-finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol
@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 -CC -D@var{macro}@r{[}=@var{defn}@r{]} @gol
-dD -dI -dM -dN -dU @gol
-fdebug-cpp -fdirectives-only -fdollars-in-identifiers @gol
-fexec-charset=@var{charset} -fextended-identifiers @gol
-finput-charset=@var{charset} -flarge-source-files @gol
-fmacro-prefix-map=@var{old}=@var{new} -fmax-include-depth=@var{depth} @gol
-fno-canonical-system-headers -fpch-deps -fpch-preprocess @gol
-fpreprocessed -ftabstop=@var{width} -ftrack-macro-expansion @gol
-fwide-exec-charset=@var{charset} -fworking-directory @gol
-H -imacros @var{file} -include @var{file} @gol
-M -MD -MF -MG -MM -MMD -MP -MQ -MT -Mno-modules @gol
-no-integrated-cpp -P -pthread -remap @gol
-traditional -traditional-cpp -trigraphs @gol
-U@var{macro} -undef @gol
-Wp,@var{option} -Xpreprocessor @var{option}}
@item Assembler Options
@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} -fuse-ld=@var{linker} -l@var{library} @gol
-nostartfiles -nodefaultlibs -nolibc -nostdlib @gol
-e @var{entry} --entry=@var{entry} @gol
-pie -pthread -r -rdynamic @gol
-s -static -static-pie -static-libgcc -static-libstdc++ @gol
-static-libasan -static-libtsan -static-liblsan -static-libubsan @gol
-shared -shared-libgcc -symbolic @gol
-T @var{script} -Wl,@var{option} -Xlinker @var{option} @gol
-u @var{symbol} -z @var{keyword}}
@item Directory Options
@xref{Directory Options,,Options for Directory Search}.
@gccoptlist{-B@var{prefix} -I@var{dir} -I- @gol
-idirafter @var{dir} @gol
-imacros @var{file} -imultilib @var{dir} @gol
-iplugindir=@var{dir} -iprefix @var{file} @gol
-iquote @var{dir} -isysroot @var{dir} -isystem @var{dir} @gol
-iwithprefix @var{dir} -iwithprefixbefore @var{dir} @gol
-L@var{dir} -no-canonical-prefixes --no-sysroot-suffix @gol
-nostdinc -nostdinc++ --sysroot=@var{dir}}
@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 -fdelete-dead-exceptions -funwind-tables @gol
-fasynchronous-unwind-tables @gol
-fno-gnu-unique @gol
-finhibit-size-directive -fcommon -fno-ident @gol
-fpcc-struct-return -fpic -fPIC -fpie -fPIE -fno-plt @gol
-fno-jump-tables -fno-bit-tests @gol
-frecord-gcc-switches @gol
-freg-struct-return -fshort-enums -fshort-wchar @gol
-fverbose-asm -fpack-struct[=@var{n}] @gol
-fleading-underscore -ftls-model=@var{model} @gol
-fstack-reuse=@var{reuse_level} @gol
-ftrampolines -ftrapv -fwrapv @gol
-fvisibility=@r{[}default@r{|}internal@r{|}hidden@r{|}protected@r{]} @gol
-fstrict-volatile-bitfields -fsync-libcalls}
@item Developer Options
@xref{Developer Options,,GCC Developer Options}.
@gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
-dumpfullversion -fcallgraph-info@r{[}=su,da@r{]}
-fchecking -fchecking=@var{n}
-fdbg-cnt-list @gol -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-debug -fdump-earlydebug @gol
-fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links @gol
-fdump-final-insns@r{[}=@var{file}@r{]} @gol
-fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline @gol
-fdump-lang-all @gol
-fdump-lang-@var{switch} @gol
-fdump-lang-@var{switch}-@var{options} @gol
-fdump-lang-@var{switch}-@var{options}=@var{filename} @gol
-fdump-passes @gol
-fdump-rtl-@var{pass} -fdump-rtl-@var{pass}=@var{filename} @gol
-fdump-statistics @gol
-fdump-tree-all @gol
-fdump-tree-@var{switch} @gol
-fdump-tree-@var{switch}-@var{options} @gol
-fdump-tree-@var{switch}-@var{options}=@var{filename} @gol
-fcompare-debug@r{[}=@var{opts}@r{]} -fcompare-debug-second @gol
-fenable-@var{kind}-@var{pass} @gol
-fenable-@var{kind}-@var{pass}=@var{range-list} @gol
-fira-verbose=@var{n} @gol
-flto-report -flto-report-wpa -fmem-report-wpa @gol
-fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report @gol
-fopt-info -fopt-info-@var{options}@r{[}=@var{file}@r{]} @gol
-fprofile-report @gol
-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
-fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose @gol
-fstats -fstack-usage -ftime-report -ftime-report-details @gol
-fvar-tracking-assignments-toggle -gtoggle @gol
-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 Machine-Dependent Options
@xref{Submodel Options,,Machine-Dependent Options}.
@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{AArch64 Options}
@gccoptlist{-mabi=@var{name} -mbig-endian -mlittle-endian @gol
-mgeneral-regs-only @gol
-mcmodel=tiny -mcmodel=small -mcmodel=large @gol
-mstrict-align -mno-strict-align @gol
-momit-leaf-frame-pointer @gol
-mtls-dialect=desc -mtls-dialect=traditional @gol
-mtls-size=@var{size} @gol
-mfix-cortex-a53-835769 -mfix-cortex-a53-843419 @gol
-mlow-precision-recip-sqrt -mlow-precision-sqrt -mlow-precision-div @gol
-mpc-relative-literal-loads @gol
-msign-return-address=@var{scope} @gol
+@var{b-key}]|@var{bti} @gol
-mharden-sls=@var{opts} @gol
-march=@var{name} -mcpu=@var{name} -mtune=@var{name} @gol
-moverride=@var{string} -mverbose-cost-dump @gol
-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{sysreg} @gol
-mstack-protector-guard-offset=@var{offset} -mtrack-speculation @gol
-moutline-atomics }
@emph{Adapteva Epiphany Options}
@gccoptlist{-mhalf-reg-file -mprefer-short-insn-regs @gol
-mbranch-cost=@var{num} -mcmove -mnops=@var{num} -msoft-cmpsf @gol
-msplit-lohi -mpost-inc -mpost-modify -mstack-offset=@var{num} @gol
-mround-nearest -mlong-calls -mshort-calls -msmall16 @gol
-mfp-mode=@var{mode} -mvect-double -max-vect-align=@var{num} @gol
-msplit-vecmove-early -m1reg-@var{reg}}
@emph{AMD GCN Options}
@gccoptlist{-march=@var{gpu} -mtune=@var{gpu} -mstack-size=@var{bytes}}
@emph{ARC Options}
@gccoptlist{-mbarrel-shifter -mjli-always @gol
-mcpu=@var{cpu} -mA6 -mARC600 -mA7 -mARC700 @gol
-mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr @gol
-mea -mno-mpy -mmul32x16 -mmul64 -matomic @gol
-mnorm -mspfp -mspfp-compact -mspfp-fast -msimd -msoft-float -mswap @gol
-mcrc -mdsp-packa -mdvbf -mlock -mmac-d16 -mmac-24 -mrtsc -mswape @gol
-mtelephony -mxy -misize -mannotate-align -marclinux -marclinux_prof @gol
-mlong-calls -mmedium-calls -msdata -mirq-ctrl-saved @gol
-mrgf-banked-regs -mlpc-width=@var{width} -G @var{num} @gol
-mvolatile-cache -mtp-regno=@var{regno} @gol
-malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc @gol
-mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi @gol
-mexpand-adddi -mindexed-loads -mlra -mlra-priority-none @gol
-mlra-priority-compact mlra-priority-noncompact -mmillicode @gol
-mmixed-code -mq-class -mRcq -mRcw -msize-level=@var{level} @gol
-mtune=@var{cpu} -mmultcost=@var{num} -mcode-density-frame @gol
-munalign-prob-threshold=@var{probability} -mmpy-option=@var{multo} @gol
-mdiv-rem -mcode-density -mll64 -mfpu=@var{fpu} -mrf16 -mbranch-index}
@emph{ARM Options}
@gccoptlist{-mapcs-frame -mno-apcs-frame @gol
-mabi=@var{name} @gol
-mapcs-stack-check -mno-apcs-stack-check @gol
-mapcs-reentrant -mno-apcs-reentrant @gol
-mgeneral-regs-only @gol
-msched-prolog -mno-sched-prolog @gol
-mlittle-endian -mbig-endian @gol
-mbe8 -mbe32 @gol
-mfloat-abi=@var{name} @gol
-mthumb-interwork -mno-thumb-interwork @gol
-mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol
-mtune=@var{name} -mprint-tune-info @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
-mpoke-function-name @gol
-mthumb -marm -mflip-thumb @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 @gol
-munaligned-access @gol
-mneon-for-64bits @gol
-mslow-flash-data @gol
-masm-syntax-unified @gol
-mrestrict-it @gol
-mverbose-cost-dump @gol
-mpure-code @gol
-mcmse @gol
-mfix-cmse-cve-2021-35465 @gol
@emph{AVR Options}
@gccoptlist{-mmcu=@var{mcu} -mabsdata -maccumulate-args @gol
-mbranch-cost=@var{cost} @gol
-mcall-prologues -mgas-isr-prologues -mint8 @gol
-mdouble=@var{bits} -mlong-double=@var{bits} @gol
-mn_flash=@var{size} -mno-interrupts @gol
-mmain-is-OS_task -mrelax -mrmw -mstrict-X -mtiny-stack @gol
-mfract-convert-truncate @gol
-mshort-calls -nodevicelib -nodevicespecs @gol
-Waddr-space-convert -Wmisspelled-isr}
@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
@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{CR16 Options}
@gccoptlist{-mmac @gol
-mcr16cplus -mcr16c @gol
-msim -mint32 -mbit-ops
@emph{C-SKY Options}
@gccoptlist{-march=@var{arch} -mcpu=@var{cpu} @gol
-mbig-endian -EB -mlittle-endian -EL @gol
-mhard-float -msoft-float -mfpu=@var{fpu} -mdouble-float -mfdivdu @gol
-mfloat-abi=@var{name} @gol
-melrw -mistack -mmp -mcp -mcache -msecurity -mtrust @gol
-mdsp -medsp -mvdsp @gol
-mdiv -msmart -mhigh-registers -manchor @gol
-mpushpop -mmultiple-stld -mconstpool -mstack-size -mccrt @gol
-mbranch-cost=@var{n} -mcse-cc -msched-prolog -msim}
@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 @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
@emph{eBPF Options}
@gccoptlist{-mbig-endian -mlittle-endian -mkernel=@var{version}
-mframe-limit=@var{bytes} -mxbpf -mco-re -mno-co-re
-mjmpext -mjmp32 -malu32 -mcpu=@var{version}}
@emph{FR30 Options}
@gccoptlist{-msmall-model -mno-lsim}
@emph{FT32 Options}
@gccoptlist{-msim -mlra -mnodiv -mft32b -mcompress -mnopm}
@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
@emph{GNU/Linux Options}
@gccoptlist{-mglibc -muclibc -mmusl -mbionic -mandroid @gol
-tno-android-cc -tno-android-ld}
@emph{H8/300 Options}
@gccoptlist{-mrelax -mh -ms -mn -mexr -mno-exr -mint32 -malign-300}
@emph{HPPA Options}
@gccoptlist{-march=@var{architecture-type} @gol
-mcaller-copies -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-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{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{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} @gol
-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 -mlong-jump-table-offsets}
@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
@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
-mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-@var{app-model} @gol
@emph{MIPS Options}
@gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol
-mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips32r3 -mips32r5 @gol
-mips32r6 -mips64 -mips64r2 -mips64r3 -mips64r5 -mips64r6 @gol
-mips16 -mno-mips16 -mflip-mips16 @gol
-minterlink-compressed -mno-interlink-compressed @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 -mfpxx -mfp64 -mhard-float -msoft-float @gol
-mno-float -msingle-float -mdouble-float @gol
-modd-spreg -mno-odd-spreg @gol
-mabs=@var{mode} -mnan=@var{encoding} @gol
-mdsp -mno-dsp -mdspr2 -mno-dspr2 @gol
-mmcu -mmno-mcu @gol
-meva -mno-eva @gol
-mvirt -mno-virt @gol
-mxpa -mno-xpa @gol
-mcrc -mno-crc @gol
-mginv -mno-ginv @gol
-mmicromips -mno-micromips @gol
-mmsa -mno-msa @gol
-mloongson-mmi -mno-loongson-mmi @gol
-mloongson-ext -mno-loongson-ext @gol
-mloongson-ext2 -mno-loongson-ext2 @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
-mload-store-pairs -mno-load-store-pairs @gol
-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol
-mmad -mno-mad -mimadd -mno-imadd -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-r5900 -mno-fix-r5900 @gol
-mfix-r10000 -mno-fix-r10000 -mfix-rm7000 -mno-fix-rm7000 @gol
-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
-mcompact-branches=@var{policy} @gol
-mfp-exceptions -mno-fp-exceptions @gol
-mvr4130-align -mno-vr4130-align -msynci -mno-synci @gol
-mlxc1-sxc1 -mno-lxc1-sxc1 -mmadd4 -mno-madd4 @gol
-mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address @gol
-mframe-header-opt -mno-frame-header-opt}
@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{Moxie Options}
@gccoptlist{-meb -mel -mmul.x -mno-crt0}
@emph{MSP430 Options}
@gccoptlist{-msim -masm-hex -mmcu= -mcpu= -mlarge -msmall -mrelax @gol
-mwarn-mcu @gol
-mcode-region= -mdata-region= @gol
-msilicon-errata= -msilicon-errata-warn= @gol
-mhwmult= -minrt -mtiny-printf -mmax-inline-shift=}
@emph{NDS32 Options}
@gccoptlist{-mbig-endian -mlittle-endian @gol
-mreduced-regs -mfull-regs @gol
-mcmov -mno-cmov @gol
-mext-perf -mno-ext-perf @gol
-mext-perf2 -mno-ext-perf2 @gol
-mext-string -mno-ext-string @gol
-mv3push -mno-v3push @gol
-m16bit -mno-16bit @gol
-misr-vector-size=@var{num} @gol
-mcache-block-size=@var{num} @gol
-march=@var{arch} @gol
-mcmodel=@var{code-model} @gol
-mctor-dtor -mrelax}
@emph{Nios II Options}
@gccoptlist{-G @var{num} -mgpopt=@var{option} -mgpopt -mno-gpopt @gol
-mgprel-sec=@var{regexp} -mr0rel-sec=@var{regexp} @gol
-mel -meb @gol
-mno-bypass-cache -mbypass-cache @gol
-mno-cache-volatile -mcache-volatile @gol
-mno-fast-sw-div -mfast-sw-div @gol
-mhw-mul -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div @gol
-mcustom-@var{insn}=@var{N} -mno-custom-@var{insn} @gol
-mcustom-fpu-cfg=@var{name} @gol
-mhal -msmallc -msys-crt0=@var{name} -msys-lib=@var{name} @gol
-march=@var{arch} -mbmx -mno-bmx -mcdx -mno-cdx}
@emph{Nvidia PTX Options}
@gccoptlist{-m64 -mmainkernel -moptimize}
@emph{OpenRISC Options}
@gccoptlist{-mboard=@var{name} -mnewlib -mhard-mul -mhard-div @gol
-msoft-mul -msoft-div @gol
-msoft-float -mhard-float -mdouble-float -munordered-float @gol
-mcmov -mror -mrori -msext -msfimm -mshftimm @gol
@emph{PDP-11 Options}
@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
-mint32 -mno-int16 -mint16 -mno-int32 @gol
-msplit -munix-asm -mdec-asm -mgnu-asm -mlra}
@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{PRU Options}
@gccoptlist{-mmcu=@var{mcu} -minrt -mno-relax -mloop @gol
-mabi=@var{variant} @gol}
@emph{RISC-V Options}
@gccoptlist{-mbranch-cost=@var{N-instruction} @gol
-mplt -mno-plt @gol
-mabi=@var{ABI-string} @gol
-mfdiv -mno-fdiv @gol
-mdiv -mno-div @gol
-march=@var{ISA-string} @gol
-mtune=@var{processor-string} @gol
-mpreferred-stack-boundary=@var{num} @gol
-msmall-data-limit=@var{N-bytes} @gol
-msave-restore -mno-save-restore @gol
-mshorten-memrefs -mno-shorten-memrefs @gol
-mstrict-align -mno-strict-align @gol
-mcmodel=medlow -mcmodel=medany @gol
-mexplicit-relocs -mno-explicit-relocs @gol
-mrelax -mno-relax @gol
-mriscv-attribute -mmo-riscv-attribute @gol
-malign-data=@var{type} @gol
-mbig-endian -mlittle-endian @gol
-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} @gol
@emph{RL78 Options}
@gccoptlist{-msim -mmul=none -mmul=g13 -mmul=g14 -mallregs @gol
-mcpu=g10 -mcpu=g13 -mcpu=g14 -mg10 -mg13 -mg14 @gol
-m64bit-doubles -m32bit-doubles -msave-mduc-in-interrupts}
@emph{RS/6000 and PowerPC Options}
@gccoptlist{-mcpu=@var{cpu-type} @gol
-mtune=@var{cpu-type} @gol
-mcmodel=@var{code-model} @gol
-mpowerpc64 @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 -mhard-dfp -mno-hard-dfp @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
-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 -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-aixdesc -mcall-eabi -mcall-freebsd @gol
-mcall-linux -mcall-netbsd -mcall-openbsd @gol
-mcall-sysv -mcall-sysv-eabi -mcall-sysv-noeabi @gol
-mtraceback=@var{traceback_type} @gol
-maix-struct-return -msvr4-struct-return @gol
-mabi=@var{abi-type} -msecure-plt -mbss-plt @gol
-mlongcall -mno-longcall -mpltseq -mno-pltseq @gol
-mblock-move-inline-limit=@var{num} @gol
-mblock-compare-inline-limit=@var{num} @gol
-mblock-compare-inline-loop-limit=@var{num} @gol
-mno-block-ops-unaligned-vsx @gol
-mstring-compare-inline-limit=@var{num} @gol
-misel -mno-isel @gol
-mvrsave -mno-vrsave @gol
-mmulhw -mno-mulhw @gol
-mdlmzb -mno-dlmzb @gol
-mprototype -mno-prototype @gol
-msim -mmvme -mads -myellowknife -memb -msdata @gol
-msdata=@var{opt} -mreadonly-in-sdata -mvxworks -G @var{num} @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 @gol
-mpower8-fusion -mno-mpower8-fusion -mpower8-vector -mno-power8-vector @gol
-mcrypto -mno-crypto -mhtm -mno-htm @gol
-mquad-memory -mno-quad-memory @gol
-mquad-memory-atomic -mno-quad-memory-atomic @gol
-mcompat-align-parm -mno-compat-align-parm @gol
-mfloat128 -mno-float128 -mfloat128-hardware -mno-float128-hardware @gol
-mgnu-attribute -mno-gnu-attribute @gol
-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} @gol
-mstack-protector-guard-offset=@var{offset} -mprefixed -mno-prefixed @gol
-mpcrel -mno-pcrel -mmma -mno-mmma -mrop-protect -mno-rop-protect @gol
-mprivileged -mno-privileged}
@emph{RX Options}
@gccoptlist{-m64bit-doubles -m32bit-doubles -fpu -nofpu@gol
-mbig-endian-data -mlittle-endian-data @gol
-msmall-data @gol
-msim -mno-sim@gol
-mas100-syntax -mno-as100-syntax@gol
-mallow-string-insns -mno-allow-string-insns@gol
@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
-mhtm -mvx -mzvector @gol
-mtpf-trace -mno-tpf-trace -mtpf-trace-skip -mno-tpf-trace-skip @gol
-mfused-madd -mno-fused-madd @gol
-mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard @gol
@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
-mb -ml -mdalign -mrelax @gol
-mbigtable -mfmovd -mrenesas -mno-renesas -mnomacsave @gol
-mieee -mno-ieee -mbitops -misize -minline-ic_invalidate -mpadstruct @gol
-mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol
-mdivsi3_libfunc=@var{name} -mfixed-range=@var{register-range} @gol
-maccumulate-outgoing-args @gol
-matomic-model=@var{atomic-model} @gol
-mbranch-cost=@var{num} -mzdcbranch -mno-zdcbranch @gol
-mcbranch-force-delay-slot @gol
-mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra @gol
-mpretend-cmove -mtas}
@emph{Solaris 2 Options}
@gccoptlist{-mclear-hwcap -mno-clear-hwcap -mimpure-text -mno-impure-text @gol
@emph{SPARC Options}
@gccoptlist{-mcpu=@var{cpu-type} @gol
-mtune=@var{cpu-type} @gol
-mcmodel=@var{code-model} @gol
-mmemory-model=@var{mem-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
-mstack-bias -mno-stack-bias @gol
-mstd-struct-return -mno-std-struct-return @gol
-munaligned-doubles -mno-unaligned-doubles @gol
-muser-mode -mno-user-mode @gol
-mv8plus -mno-v8plus -mvis -mno-vis @gol
-mvis2 -mno-vis2 -mvis3 -mno-vis3 @gol
-mvis4 -mno-vis4 -mvis4b -mno-vis4b @gol
-mcbcond -mno-cbcond -mfmaf -mno-fmaf -mfsmuld -mno-fsmuld @gol
-mpopc -mno-popc -msubxc -mno-subxc @gol
-mfix-at697f -mfix-ut699 -mfix-ut700 -mfix-gr712rc @gol
-mlra -mno-lra}
@emph{System V Options}
@gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}}
@emph{TILE-Gx Options}
@gccoptlist{-mcpu=CPU -m32 -m64 -mbig-endian -mlittle-endian @gol
@emph{TILEPro Options}
@gccoptlist{-mcpu=@var{cpu} -m32}
@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 -mv850e2 -mv850e1 -mv850es @gol
-mv850e -mv850 -mv850e3v5 @gol
-mloop @gol
-mrelax @gol
-mlong-jumps @gol
-msoft-float @gol
-mhard-float @gol
-mgcc-abi @gol
-mrh850-abi @gol
@emph{VAX Options}
@gccoptlist{-mg -mgnu -munix}
@emph{Visium Options}
@gccoptlist{-mdebug -msim -mfpu -mno-fpu -mhard-float -msoft-float @gol
-mcpu=@var{cpu-type} -mtune=@var{cpu-type} -msv-mode -muser-mode}
@emph{VMS Options}
@gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64 @gol
@emph{VxWorks Options}
@gccoptlist{-mrtp -non-static -Bstatic -Bdynamic @gol
-Xbind-lazy -Xbind-now}
@emph{x86 Options}
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
-mtune-ctrl=@var{feature-list} -mdump-tune-features -mno-default @gol
-mfpmath=@var{unit} @gol
-masm=@var{dialect} -mno-fancy-math-387 @gol
-mno-fp-ret-in-387 -m80387 -mhard-float -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 -mmwait @gol
-mrecip -mrecip=@var{opt} @gol
-mvzeroupper -mprefer-avx128 -mprefer-vector-width=@var{opt} @gol
-mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx @gol
-mavx2 -mavx512f -mavx512pf -mavx512er -mavx512cd -mavx512vl @gol
-mavx512bw -mavx512dq -mavx512ifma -mavx512vbmi -msha -maes @gol
-mpclmul -mfsgsbase -mrdrnd -mf16c -mfma -mpconfig -mwbnoinvd @gol
-mptwrite -mprefetchwt1 -mclflushopt -mclwb -mxsavec -mxsaves @gol
-msse4a -m3dnow -m3dnowa -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop @gol
-madx -mlzcnt -mbmi2 -mfxsr -mxsave -mxsaveopt -mrtm -mhle -mlwp @gol
-mmwaitx -mclzero -mpku -mthreads -mgfni -mvaes -mwaitpkg @gol
-mshstk -mmanual-endbr -mforce-indirect-call -mavx512vbmi2 -mavx512bf16 -menqcmd @gol
-mvpclmulqdq -mavx512bitalg -mmovdiri -mmovdir64b -mavx512vpopcntdq @gol
-mavx5124fmaps -mavx512vnni -mavx5124vnniw -mprfchw -mrdpid @gol
-mrdseed -msgx -mavx512vp2intersect -mserialize -mtsxldtrk@gol
-mamx-tile -mamx-int8 -mamx-bf16 -muintr -mhreset -mavxvnni@gol
-mavx512fp16 @gol
-mcldemote -mms-bitfields -mno-align-stringops -minline-all-stringops @gol
-minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol
-mkl -mwidekl @gol
-mmemcpy-strategy=@var{strategy} -mmemset-strategy=@var{strategy} @gol
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
-m96bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128 @gol
-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} -maddress-mode=@var{mode} @gol
-m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=@var{num} @gol
-msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv @gol
-minstrument-return=@var{type} -mfentry-name=@var{name} -mfentry-section=@var{name} @gol
-mavx256-split-unaligned-load -mavx256-split-unaligned-store @gol
-malign-data=@var{type} -mstack-protector-guard=@var{guard} @gol
-mstack-protector-guard-reg=@var{reg} @gol
-mstack-protector-guard-offset=@var{offset} @gol
-mstack-protector-guard-symbol=@var{symbol} @gol
-mgeneral-regs-only -mcall-ms2sysv-xlogues @gol
-mindirect-branch=@var{choice} -mfunction-return=@var{choice} @gol
-mindirect-branch-register -mneeded}
@emph{x86 Windows Options}
@gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
-mnop-fun-dllimport -mthread @gol
-municode -mwin32 -mwindows -fno-set-stack-executable}
@emph{Xstormy16 Options}
@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
-mauto-litpools -mno-auto-litpools @gol
-mtarget-align -mno-target-align @gol
-mlongcalls -mno-longcalls @gol
@emph{zSeries Options}
See S/390 and zSeries Options.
@end table
@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 that must be preprocessed.
@item @var{file}.i
C source code that should not be preprocessed.
@item @var{file}.ii
C++ source code that 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 that 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 that 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 that 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 that must be preprocessed.
@item @var{file}.mii
Objective-C++ source code that 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 that 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 that must be preprocessed (with the traditional
@item @var{file}.f90
@itemx @var{file}.f95
@itemx @var{file}.f03
@itemx @var{file}.f08
Free form Fortran source code that 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 that must be preprocessed (with the
traditional preprocessor).
@item @var{file}.go
Go source code.
@item @var{file}.d
D source code.
@item @var{file}.di
D interface file.
@item @var{file}.dd
D documentation code (Ddoc).
@item @var{file}.ads
Ada source code file that 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 Ratfor:
@c @var{file}.r
@item @var{file}.s
Assembler code.
@item @var{file}.S
@itemx @var{file}.sx
Assembler code that 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:
c c-header cpp-output
c++ c++-header c++-system-header c++-user-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
f77 f77-cpp-input f95 f95-cpp-input
@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).
@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
@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 that don't require preprocessing are ignored.
@cindex output file option
@item -o @var{file}
@opindex o
Place the primary output in file @var{file}. This applies 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.
Though @option{-o} names only the primary output, it also affects the
naming of auxiliary and dump outputs. See the examples below. Unless
overridden, both auxiliary outputs and dump outputs are placed in the
same directory as the primary output. In auxiliary outputs, the suffix
of the input file is replaced with that of the auxiliary output file
type; in dump outputs, the suffix of the dump file is appended to the
input file suffix. In compilation commands, the base name of both
auxiliary and dump outputs is that of the primary output; in compile and
link commands, the primary output name, minus the executable suffix, is
combined with the input file name. If both share the same base name,
disregarding the suffix, the result of the combination is that base
name, otherwise, they are concatenated, separated by a dash.
gcc -c foo.c ...
@end smallexample
will use @file{foo.o} as the primary output, and place aux outputs and
dumps next to it, e.g., aux file @file{foo.dwo} for
@option{-gsplit-dwarf}, and dump file @file{foo.c.???} for
If a non-linker output file is explicitly specified, aux and dump files
by default take the same base name:
gcc -c foo.c -o dir/foobar.o ...
@end smallexample
will name aux outputs @file{dir/foobar.*} and dump outputs
A linker output will instead prefix aux and dump outputs:
gcc foo.c bar.c -o dir/foobar ...
@end smallexample
will generally name aux outputs @file{dir/foobar-foo.*} and
@file{dir/foobar-bar.*}, and dump outputs @file{dir/foobar-foo.c.*} and
The one exception to the above is when the executable shares the base
name with the single input:
gcc foo.c -o dir/foo ...
@end smallexample
in which case aux outputs are named @file{dir/foo.*} and dump outputs
named @file{dir/foo.c.*}.
The location and the names of auxiliary and dump outputs can be adjusted
by the options @option{-dumpbase}, @option{-dumpbase-ext},
@option{-dumpdir}, @option{-save-temps=cwd}, and
@item -dumpbase @var{dumpbase}
@opindex dumpbase
This option sets the base name for auxiliary and dump output files. It
does not affect the name of the primary output file. Intermediate
outputs, when preserved, are not regarded as primary outputs, but as
auxiliary outputs:
gcc -save-temps -S foo.c
@end smallexample
saves the (no longer) temporary preprocessed file in @file{foo.i}, and
then compiles to the (implied) output file @file{foo.s}, whereas:
gcc -save-temps -dumpbase save-foo -c foo.c
@end smallexample
preprocesses to in @file{save-foo.i}, compiles to @file{save-foo.s} (now
an intermediate, thus auxiliary output), and then assembles to the
(implied) output file @file{foo.o}.
Absent this option, dump and aux files take their names from the input
file, or from the (non-linker) output file, if one is explicitly
specified: dump output files (e.g. those requested by @option{-fdump-*}
options) with the input name suffix, and aux output files (those
requested by other non-dump options, e.g. @code{-save-temps},
@code{-gsplit-dwarf}, @code{-fcallgraph-info}) without it.
Similar suffix differentiation of dump and aux outputs can be attained
for explicitly-given @option{-dumpbase basename.suf} by also specifying
@option{-dumpbase-ext .suf}.
If @var{dumpbase} is explicitly specified with any directory component,
any @var{dumppfx} specification (e.g. @option{-dumpdir} or
@option{-save-temps=*}) is ignored, and instead of appending to it,
@var{dumpbase} fully overrides it:
gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \
-dumpdir pfx- -save-temps=cwd ...
@end smallexample
creates auxiliary and dump outputs named @file{alt/foo.*}, disregarding
@file{dir/} in @option{-o}, the @file{./} prefix implied by
@option{-save-temps=cwd}, and @file{pfx-} in @option{-dumpdir}.
When @option{-dumpbase} is specified in a command that compiles multiple
inputs, or that compiles and then links, it may be combined with
@var{dumppfx}, as specified under @option{-dumpdir}. Then, each input
file is compiled using the combined @var{dumppfx}, and default values
for @var{dumpbase} and @var{auxdropsuf} are computed for each input
gcc foo.c bar.c -c -dumpbase main ...
@end smallexample
creates @file{foo.o} and @file{bar.o} as primary outputs, and avoids
overwriting the auxiliary and dump outputs by using the @var{dumpbase}
as a prefix, creating auxiliary and dump outputs named @file{main-foo.*}
and @file{main-bar.*}.
An empty string specified as @var{dumpbase} avoids the influence of the
output basename in the naming of auxiliary and dump outputs during
compilation, computing default values :
gcc -c foo.c -o dir/foobar.o -dumpbase '' ...
@end smallexample
will name aux outputs @file{dir/foo.*} and dump outputs
@file{dir/foo.c.*}. Note how their basenames are taken from the input
name, but the directory still defaults to that of the output.
The empty-string dumpbase does not prevent the use of the output
basename for outputs during linking:
gcc foo.c bar.c -o dir/foobar -dumpbase '' -flto ...
@end smallexample
The compilation of the source files will name auxiliary outputs
@file{dir/foo.*} and @file{dir/bar.*}, and dump outputs
@file{dir/foo.c.*} and @file{dir/bar.c.*}. LTO recompilation during
linking will use @file{dir/foobar.} as the prefix for dumps and
auxiliary files.
@item -dumpbase-ext @var{auxdropsuf}
@opindex dumpbase-ext
When forming the name of an auxiliary (but not a dump) output file, drop
trailing @var{auxdropsuf} from @var{dumpbase} before appending any
suffixes. If not specified, this option defaults to the suffix of a
default @var{dumpbase}, i.e., the suffix of the input file when
@option{-dumpbase} is not present in the command line, or @var{dumpbase}
is combined with @var{dumppfx}.
gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ...
@end smallexample
creates @file{dir/foo.o} as the main output, and generates auxiliary
outputs in @file{dir/x-foo.*}, taking the location of the primary
output, and dropping the @file{.c} suffix from the @var{dumpbase}. Dump
outputs retain the suffix: @file{dir/x-foo.c.*}.
This option is disregarded if it does not match the suffix of a
specified @var{dumpbase}, except as an alternative to the executable
suffix when appending the linker output base name to @var{dumppfx}, as
specified below:
gcc foo.c bar.c -o main.out -dumpbase-ext .out ...
@end smallexample
creates @file{main.out} as the primary output, and avoids overwriting
the auxiliary and dump outputs by using the executable name minus
@var{auxdropsuf} as a prefix, creating auxiliary outputs named
@file{main-foo.*} and @file{main-bar.*} and dump outputs named
@file{main-foo.c.*} and @file{main-bar.c.*}.
@item -dumpdir @var{dumppfx}
@opindex dumpdir
When forming the name of an auxiliary or dump output file, use
@var{dumppfx} as a prefix:
gcc -dumpdir pfx- -c foo.c ...
@end smallexample
creates @file{foo.o} as the primary output, and auxiliary outputs named
@file{pfx-foo.*}, combining the given @var{dumppfx} with the default
@var{dumpbase} derived from the default primary output, derived in turn
from the input name. Dump outputs also take the input name suffix:
If @var{dumppfx} is to be used as a directory name, it must end with a
directory separator:
gcc -dumpdir dir/ -c foo.c -o obj/bar.o ...
@end smallexample
creates @file{obj/bar.o} as the primary output, and auxiliary outputs
named @file{dir/bar.*}, combining the given @var{dumppfx} with the
default @var{dumpbase} derived from the primary output name. Dump
outputs also take the input name suffix: @file{dir/bar.c.*}.
It defaults to the location of the output file; options
@option{-save-temps=cwd} and @option{-save-temps=obj} override this
default, just like an explicit @option{-dumpdir} option. In case
multiple such options are given, the last one prevails:
gcc -dumpdir pfx- -c foo.c -save-temps=obj ...
@end smallexample
outputs @file{foo.o}, with auxiliary outputs named @file{foo.*} because
@option{-save-temps=*} overrides the @var{dumppfx} given by the earlier
@option{-dumpdir} option. It does not matter that @option{=obj} is the
default for @option{-save-temps}, nor that the output directory is
implicitly the current directory. Dump outputs are named
When compiling from multiple input files, if @option{-dumpbase} is
specified, @var{dumpbase}, minus a @var{auxdropsuf} suffix, and a dash
are appended to (or override, if containing any directory components) an
explicit or defaulted @var{dumppfx}, so that each of the multiple
compilations gets differently-named aux and dump outputs.
gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ...
@end smallexample
outputs auxiliary dumps to @file{dir/pfx-main-foo.*} and
@file{dir/pfx-main-bar.*}, appending @var{dumpbase}- to @var{dumppfx}.
Dump outputs retain the input file suffix: @file{dir/pfx-main-foo.c.*}
and @file{dir/pfx-main-bar.c.*}, respectively. Contrast with the
single-input compilation:
gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ...
@end smallexample
that, applying @option{-dumpbase} to a single source, does not compute
and append a separate @var{dumpbase} per input file. Its auxiliary and
dump outputs go in @file{dir/pfx-main.*}.
When compiling and then linking from multiple input files, a defaulted
or explicitly specified @var{dumppfx} also undergoes the @var{dumpbase}-
transformation above (e.g. the compilation of @file{foo.c} and
@file{bar.c} above, but without @option{-c}). If neither
@option{-dumpdir} nor @option{-dumpbase} are given, the linker output
base name, minus @var{auxdropsuf}, if specified, or the executable
suffix otherwise, plus a dash is appended to the default @var{dumppfx}
instead. Note, however, that unlike earlier cases of linking:
gcc foo.c bar.c -dumpdir dir/pfx- -o main ...
@end smallexample
does not append the output name @file{main} to @var{dumppfx}, because
@option{-dumpdir} is explicitly specified. The goal is that the
explicitly-specified @var{dumppfx} may contain the specified output name
as part of the prefix, if desired; only an explicitly-specified
@option{-dumpbase} would be combined with it, in order to avoid simply
discarding a meaningful option.
When compiling and then linking from a single input file, the linker
output base name will only be appended to the default @var{dumppfx} as
above if it does not share the base name with the single input file
name. This has been covered in single-input linking cases above, but
not with an explicit @option{-dumpdir} that inhibits the combination,
even if overridden by @option{-save-temps=*}:
gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...
@end smallexample
Auxiliary outputs are named @file{foo.*}, and dump outputs
@file{foo.c.*}, in the current working directory as ultimately requested
by @option{-save-temps=cwd}.
Summing it all up for an intuitive though slightly imprecise data flow:
the primary output name is broken into a directory part and a basename
part; @var{dumppfx} is set to the former, unless overridden by
@option{-dumpdir} or @option{-save-temps=*}, and @var{dumpbase} is set
to the latter, unless overriden by @option{-dumpbase}. If there are
multiple inputs or linking, this @var{dumpbase} may be combined with
@var{dumppfx} and taken from each input file. Auxiliary output names
for each input are formed by combining @var{dumppfx}, @var{dumpbase}
minus suffix, and the auxiliary output suffix; dump output names are
only different in that the suffix from @var{dumpbase} is retained.
When it comes to auxiliary and dump outputs created during LTO
recompilation, a combination of @var{dumppfx} and @var{dumpbase}, as
given or as derived from the linker output name but not from inputs,
even in cases in which this combination would not otherwise be used as
such, is passed down with a trailing period replacing the compiler-added
dash, if any, as a @option{-dumpdir} option to @command{lto-wrapper};
being involved in linking, this program does not normally get any
@option{-dumpbase} and @option{-dumpbase-ext}, and it ignores them.
When running sub-compilers, @command{lto-wrapper} appends LTO stage
names to the received @var{dumppfx}, ensures it contains a directory
component so that it overrides any @option{-dumpdir}, and passes that as
@option{-dumpbase} to sub-compilers.
@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 --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} is also 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 that
have no documentation associated with them are also 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}
Display all of the optimization options supported by the
@item @samp{warnings}
Display all of the options controlling warning messages
produced by the compiler.
@item @samp{target}
Display target-specific options. Unlike the
@option{--target-help} option however, target-specific options of the
linker and assembler are not displayed. This is because those
tools do not currently support the extended @option{--help=} syntax.
@item @samp{params}
Display the values recognized by the @option{--param}
@item @var{language}
Display the options supported for @var{language}, where
@var{language} is the name of one of the languages supported in this
version of GCC@. If an option is supported by all languages, one needs
to select @samp{common} class.
@item @samp{common}
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 that are undocumented.
@item @samp{joined}
Display options taking an argument that appears after an equal
sign in the same continuous piece of text, such as:
@item @samp{separate}
Display options taking 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, use:
@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) that have a description, use:
@end smallexample
The argument to @option{--help=} should not consist solely of inverted
Combining several classes is possible, although this usually
restricts the output so much that there is nothing to display. One
case where it does work, however, is when one of the classes is
@var{target}. For example, to display all the target-specific
optimization options, use:
@end smallexample
The @option{--help=} option can be repeated on the command line. Each
successive use displays its requested class of options, skipping
those that have already been displayed. If @option{--help} is also
specified anywhere on the command line then this takes precedence
over any @option{--help=} option.
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}:
% 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:
-Q -O2 --help=optimizers
@end smallexample
Alternatively you can discover which binary optimizations are enabled
by @option{-O3} by using:
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 --version
@opindex version
Display the version number and copyrights of the invoked GCC@.
@item -pass-exit-codes
@opindex pass-exit-codes
Normally the @command{gcc} program exits 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 instead returns with
the numerically highest error produced by any phase returning an error
indication. The C, C++, and Fortran front ends return 4 if an internal
compiler error is encountered.
@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 -specs=@var{file}
@opindex specs
Process @var{file} after the compiler reads in the standard @file{specs}
file, in order to override the defaults which the @command{gcc} driver
program uses when determining what switches to pass to @command{cc1},
@command{cc1plus}, @command{as}, @command{ld}, etc. More than one
@option{-specs=@var{file}} can be specified on the command line, and they
are processed in order, from left to right. @xref{Spec Files}, for
information about the format of the @var{file}.
@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
gcc -c t.c -wrapper gdb,--args
@end smallexample
This invokes all subprograms of @command{gcc} under
@samp{gdb --args}, thus the invocation of @command{cc1} is
@samp{gdb --args cc1 @dots{}}.
@item -ffile-prefix-map=@var{old}=@var{new}
@opindex ffile-prefix-map
When compiling files residing in directory @file{@var{old}}, record
any references to them in the result of the compilation as if the
files resided in directory @file{@var{new}} instead. Specifying this
option is equivalent to specifying all the individual
@option{-f*-prefix-map} options. This can be used to make reproducible
builds that are location independent. See also
@option{-fmacro-prefix-map} and @option{-fdebug-prefix-map}.
@item -fplugin=@var{name}.so
@opindex fplugin
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}
@opindex fplugin-arg
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{]}
@opindex fdump-ada-spec
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 -fada-spec-parent=@var{unit}
@opindex fada-spec-parent
In conjunction with @option{-fdump-ada-spec@r{[}-slim@r{]}} above, generate
Ada specs as child units of parent @var{unit}.
@item -fdump-go-spec=@var{file}
@opindex fdump-go-spec
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 automatically specifies linking
against the C++ library. It treats @samp{.c},
@samp{.h} and @samp{.i} files as C++ source files instead of C source
files unless @option{-x} is used. 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
@table @gcctabopt
@cindex ANSI support
@cindex ISO support
@item -ansi
@opindex ansi
In C mode, this is equivalent to @option{-std=c90}. In C++ mode, it is
equivalent to @option{-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{-Wpedantic} 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 are normally 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
@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}. When a base standard is specified, the
compiler accepts all programs following that standard plus those
using GNU extensions that do not contradict it. For example,
@option{-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, when a GNU dialect of a standard is
specified, all features supported by the compiler are enabled, even when
those features change the meaning of the base standard. As a result, some
strict-conforming programs may be rejected. The particular standard
is used by @option{-Wpedantic} to identify which features are GNU
extensions given that version of the standard. For example
@option{-std=gnu90 -Wpedantic} warns about C++ style @samp{//}
comments, while @option{-std=gnu99 -Wpedantic} does 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. This standard is substantially completely supported, modulo
bugs and floating-point issues
(mainly but not entirely relating to optional C99 features from
Annexes F and G). See
@w{@uref{}} for more information. The
names @samp{c9x} and @samp{iso9899:199x} are deprecated.
@item c11
@itemx c1x
@itemx iso9899:2011
ISO C11, the 2011 revision of the ISO C standard. This standard is
substantially completely supported, modulo bugs, floating-point issues
(mainly but not entirely relating to optional C11 features from
Annexes F and G) and the optional Annexes K (Bounds-checking
interfaces) and L (Analyzability). The name @samp{c1x} is deprecated.
@item c17
@itemx c18
@itemx iso9899:2017
@itemx iso9899:2018
ISO C17, the 2017 revision of the ISO C standard
(published in 2018). This standard is
same as C11 except for corrections of defects (all of which are also
applied with @option{-std=c11}) and a new value of
@code{__STDC_VERSION__}, and so is supported to the same extent as C11.
@item c2x
The next version of the ISO C standard, still under development. The
support for this version is experimental and incomplete.
@item gnu90
@itemx gnu89
GNU dialect of ISO C90 (including some C99 features).
@item gnu99
@itemx gnu9x
GNU dialect of ISO C99. The name @samp{gnu9x} is deprecated.
@item gnu11
@itemx gnu1x
GNU dialect of ISO C11.
The name @samp{gnu1x} is deprecated.
@item gnu17
@itemx gnu18
GNU dialect of ISO C17. This is the default for C code.
@item gnu2x
The next version of the ISO C standard, still under development, plus
GNU extensions. The support for this version is experimental and
@item c++98
@itemx c++03
The 1998 ISO C++ standard plus the 2003 technical corrigendum and some
additional defect reports. Same as @option{-ansi} for C++ code.
@item gnu++98
@itemx gnu++03
GNU dialect of @option{-std=c++98}.
@item c++11
@itemx c++0x
The 2011 ISO C++ standard plus amendments.
The name @samp{c++0x} is deprecated.
@item gnu++11
@itemx gnu++0x
GNU dialect of @option{-std=c++11}.
The name @samp{gnu++0x} is deprecated.
@item c++14
@itemx c++1y
The 2014 ISO C++ standard plus amendments.
The name @samp{c++1y} is deprecated.
@item gnu++14
@itemx gnu++1y
GNU dialect of @option{-std=c++14}.
The name @samp{gnu++1y} is deprecated.
@item c++17
@itemx c++1z
The 2017 ISO C++ standard plus amendments.
The name @samp{c++1z} is deprecated.
@item gnu++17
@itemx gnu++1z
GNU dialect of @option{-std=c++17}.
This is the default for C++ code.
The name @samp{gnu++1z} is deprecated.
@item c++20
@itemx c++2a
The 2020 ISO C++ standard plus amendments.
Support is experimental, and could change in incompatible ways in
future releases.
The name @samp{c++2a} is deprecated.
@item gnu++20
@itemx gnu++2a
GNU dialect of @option{-std=c++20}.
Support is experimental, and could change in incompatible ways in
future releases.
The name @samp{gnu++2a} is deprecated.
@item c++2b
@itemx c++23
The next revision of the ISO C++ standard, planned for
2023. Support is highly experimental, and will almost certainly
change in incompatible ways in future releases.
@item gnu++2b
@itemx gnu++23
GNU dialect of @option{-std=c++2b}. Support is highly experimental,
and will almost certainly change in incompatible ways in future
@end table
@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
@opindex 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
@opindex fasm
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. In C, @option{-ansi} implies @option{-fno-asm}.
In C++, @code{inline} is a standard keyword and is not affected by
this switch. You may want to use the @option{-fno-gnu-keywords} flag
instead, which disables @code{typeof} but not @code{asm} and
@code{inline}. 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
@opindex fbuiltin
@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 which 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:
#define abs(n) __builtin_abs ((n))
#define strcpy(d, s) __builtin_strcpy ((d), (s))
@end smallexample
@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 -ffreestanding
@opindex ffreestanding
@cindex hosted environment
Assert that compilation targets 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 -fgimple
@opindex fgimple
Enable parsing of function definitions marked with @code{__GIMPLE}.
This is an experimental feature that allows unit testing of GIMPLE
@item -fgnu-tm
@opindex fgnu-tm
When the option @option{-fgnu-tm} is specified, the compiler
generates code for the Linux variant of Intel's current Transactional
Memory ABI specification document (Revision 1.1, May 6 2009). This is
an experimental feature whose interface may change in future versions
of GCC, as the official specification changes. Please note that not
all architectures are supported for this feature.
For more information on GCC's support for transactional memory,
@xref{Enabling libitm,,The GNU Transactional Memory Library,libitm,GNU
Transactional Memory Library}.
Note that the transactional memory feature is not supported with
non-call exceptions (@option{-fnon-call-exceptions}).
@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}.
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 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 -fhosted
@opindex fhosted
@cindex hosted environment
Assert that compilation targets 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 -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 -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.
typedef int UOW;
struct ABC @{
@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.
Note that this option is off for all targets except for x86
targets using ms-abi.
@item -foffload=disable
@itemx -foffload=default
@itemx -foffload=@var{target-list}
@opindex foffload
@cindex Offloading targets
@cindex OpenACC offloading targets
@cindex OpenMP offloading targets
Specify for which OpenMP and OpenACC offload targets code should be generated.
The default behavior, equivalent to @option{-foffload=default}, is to generate
code for all supported offload targets. The @option{-foffload=disable} form
generates code only for the host fallback, while
@option{-foffload=@var{target-list}} generates code only for the specified
comma-separated list of offload targets.
Offload targets are specified in GCC's internal target-triplet format. You can
run the compiler with @option{-v} to show the list of configured offload targets
@item -foffload-options=@var{options}
@itemx -foffload-options=@var{target-triplet-list}=@var{options}
@opindex foffload-options
@cindex Offloading options
@cindex OpenACC offloading options
@cindex OpenMP offloading options
With @option{-foffload-options=@var{options}}, GCC passes the specified
@var{options} to the compilers for all enabled offloading targets. You can
specify options that apply only to a specific target or targets by using
the @option{-foffload-options=@var{target-list}=@var{options}} form. The
@var{target-list} is a comma-separated list in the same format as for the
@option{-foffload=} option.
Typical command lines are
-foffload-options=-lgfortran -foffload-options=-lm
-foffload-options="-lgfortran -lm" -foffload-options=nvptx-none=-latomic
-foffload-options=amdgcn-amdhsa=-march=gfx906 -foffload-options=-lm
@end smallexample
@item -fopenacc
@opindex fopenacc
@cindex OpenACC accelerator programming
Enable handling of OpenACC directives @code{#pragma acc} in C/C++ and
@code{!$acc} in Fortran. When @option{-fopenacc} is specified, the
compiler generates accelerated code according to the OpenACC Application
Programming Interface v2.6 @w{@uref{}}. This option
implies @option{-pthread}, and thus is only supported on targets that
have support for @option{-pthread}.
@item -fopenacc-dim=@var{geom}
@opindex fopenacc-dim
@cindex OpenACC accelerator programming
Specify default compute dimensions for parallel offload regions that do
not explicitly specify. The @var{geom} value is a triple of
':'-separated sizes, in order 'gang', 'worker' and, 'vector'. A size
can be omitted, to use a target-specific default value.
@item -fopenmp
@opindex fopenmp
@cindex OpenMP parallel
Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and
@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the
compiler generates parallel code according to the OpenMP Application
Program Interface v4.5 @w{@uref{}}. This option
implies @option{-pthread}, and thus is only supported on targets that
have support for @option{-pthread}. @option{-fopenmp} implies
@item -fopenmp-simd
@opindex fopenmp-simd
@cindex OpenMP SIMD
@cindex SIMD
Enable handling of OpenMP's SIMD directives with @code{#pragma omp}
in C/C++ and @code{!$omp} in Fortran. Other OpenMP directives
are ignored.
@item -fpermitted-flt-eval-methods=@var{style}
@opindex fpermitted-flt-eval-methods
@opindex fpermitted-flt-eval-methods=c11
@opindex fpermitted-flt-eval-methods=ts-18661-3
ISO/IEC TS 18661-3 defines new permissible values for
@code{FLT_EVAL_METHOD} that indicate that operations and constants with
a semantic type that is an interchange or extended format should be
evaluated to the precision and range of that type. These new values are
a superset of those permitted under C99/C11, which does not specify the
meaning of other positive values of @code{FLT_EVAL_METHOD}. As such, code
conforming to C11 may not have been written expecting the possibility of
the new values.
@option{-fpermitted-flt-eval-methods} specifies whether the compiler
should allow only the values of @code{FLT_EVAL_METHOD} specified in C99/C11,
or the extended set of values specified in ISO/IEC TS 18661-3.
@var{style} is either @code{c11} or @code{ts-18661-3} as appropriate.
The default when in a standards compliant mode (@option{-std=c11} or similar)
is @option{-fpermitted-flt-eval-methods=c11}. The default when in a GNU
dialect (@option{-std=gnu11} or similar) is
@item -fplan9-extensions
@opindex 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 that 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 -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.
@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 -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 -fsso-struct=@var{endianness}
@opindex fsso-struct
Set the default scalar storage order of structures and unions to the
specified endianness. The accepted values are @samp{big-endian},
@samp{little-endian} and @samp{native} for the native endianness of
the target (the default). This option is not supported for C++.
@strong{Warning:} the @option{-fsso-struct} switch causes GCC to generate
code that is not binary compatible with code generated without it if the
specified endianness is not the native endianness of the target.
@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. 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 @file{firstClass.C} like this:
g++ -g -fstrict-enums -O -c firstClass.C
@end smallexample
In this example, only @option{-fstrict-enums} is an option meant
only for C++ programs; you can use the other options with any
language supported by GCC@.
Some options for compiling C programs, such as @option{-std}, are also
relevant for C++ programs.
@xref{C Dialect Options,,Options Controlling C Dialect}.
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@. The default is version 0.
Version 0 refers to the version conforming most closely to
the C++ ABI specification. Therefore, the ABI obtained using version 0
will change in different versions of G++ as ABI bugs are fixed.
Version 1 is the version of the C++ ABI that first appeared in G++ 3.2.
Version 2 is the version of the C++ ABI that first appeared in G++
3.4, and was the default through G++ 4.9.
Version 3 corrects an error in mangling a constant address as a
template argument.
Version 4, which first appeared in G++ 4.5, implements a standard
mangling for vector types.
Version 5, which first appeared in G++ 4.6, 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, which first appeared in G++ 4.7, corrects the promotion
behavior of C++11 scoped enums and the mangling of template argument
packs, const/static_cast, prefix ++ and --, and a class scope function
used as a template argument.
Version 7, which first appeared in G++ 4.8, that treats nullptr_t as a
builtin type and corrects the mangling of lambdas in default argument
Version 8, which first appeared in G++ 4.9, corrects the substitution
behavior of function types with function-cv-qualifiers.
Version 9, which first appeared in G++ 5.2, corrects the alignment of
Version 10, which first appeared in G++ 6.1, adds mangling of
attributes that affect type identity, such as ia32 calling convention
attributes (e.g.@: @samp{stdcall}).
Version 11, which first appeared in G++ 7, corrects the mangling of
sizeof... expressions and operator names. For multiple entities with
the same name within a function, that are declared in different scopes,
the mangling now changes starting with the twelfth occurrence. It also
implies @option{-fnew-inheriting-ctors}.
Version 12, which first appeared in G++ 8, corrects the calling
conventions for empty classes on the x86_64 target and for classes
with only deleted copy/move constructors. It accidentally changes the
calling convention for classes with a deleted copy constructor and a
trivial move constructor.
Version 13, which first appeared in G++ 8.2, fixes the accidental
change in version 12.
Version 14, which first appeared in G++ 10, corrects the mangling of
the nullptr expression.
Version 15, which first appeared in G++ 11, changes the mangling of
@code{__alignof__} to be distinct from that of @code{alignof}, and
dependent operator names.
See also @option{-Wabi}.
@item -fabi-compat-version=@var{n}
@opindex fabi-compat-version
On targets that support strong aliases, G++
works around mangling changes by creating an alias with the correct
mangled name when defining a symbol with an incorrect mangled name.
This switch specifies which ABI version to use for the alias.
With @option{-fabi-version=0} (the default), this defaults to 11 (GCC 7
compatibility). If another ABI version is explicitly selected, this
defaults to 0. For compatibility with GCC versions 3.2 through 4.9,
use @option{-fabi-compat-version=2}.
If this option is not provided but @option{-Wabi=@var{n}} is, that
version is used for compatibility aliases. If this option is provided
along with @option{-Wabi} (without the version), the version from this
option is used for the warning.
@item -fno-access-control
@opindex fno-access-control
@opindex faccess-control
Turn off all access checking. This switch is mainly useful for working
around bugs in the access control code.
@item -faligned-new
@opindex faligned-new
Enable support for C++17 @code{new} of types that require more
alignment than @code{void* ::operator new(std::size_t)} provides. A
numeric argument such as @code{-faligned-new=32} can be used to
specify how much alignment (in bytes) is provided by that function,
but few users will need to override the default of
This flag is enabled by default for @option{-std=c++17}.
@item -fchar8_t
@itemx -fno-char8_t
@opindex fchar8_t
@opindex fno-char8_t
Enable support for @code{char8_t} as adopted for C++20. This includes
the addition of a new @code{char8_t} fundamental type, changes to the
types of UTF-8 string and character literals, new signatures for
user-defined literals, associated standard library updates, and new
@code{__cpp_char8_t} and @code{__cpp_lib_char8_t} feature test macros.
This option enables functions to be overloaded for ordinary and UTF-8
int f(const char *); // #1
int f(const char8_t *); // #2
int v1 = f("text"); // Calls #1
int v2 = f(u8"text"); // Calls #2
@end smallexample
and introduces new signatures for user-defined literals:
int operator""_udl1(char8_t);
int v3 = u8'x'_udl1;
int operator""_udl2(const char8_t*, std::size_t);
int v4 = u8"text"_udl2;
template<typename T, T...> int operator""_udl3();
int v5 = u8"text"_udl3;
@end smallexample
The change to the types of UTF-8 string and character literals introduces
incompatibilities with ISO C++11 and later standards. For example, the
following code is well-formed under ISO C++11, but is ill-formed when
@option{-fchar8_t} is specified.
char ca[] = u8"xx"; // error: char-array initialized from wide
// string
const char *cp = u8"xx";// error: invalid conversion from
// `const char8_t*' to `const char*'
int f(const char*);
auto v = f(u8"xx"); // error: invalid conversion from
// `const char8_t*' to `const char*'
std::string s@{u8"xx"@}; // error: no matching function for call to
// `std::basic_string<char>::basic_string()'
using namespace std::literals;
s = u8"xx"s; // error: conversion from
// `basic_string<char8_t>' to non-scalar
// type `basic_string<char>' requested
@end smallexample
@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} only returns @code{0} if it is declared
@code{throw()}, in which case the compiler always checks 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 -fconcepts
@itemx -fconcepts-ts
@opindex fconcepts
@opindex fconcepts-ts
Below @option{-std=c++20}, @option{-fconcepts} enables support for the
C++ Extensions for Concepts Technical Specification, ISO 19217 (2015).
With @option{-std=c++20} and above, Concepts are part of the language
standard, so @option{-fconcepts} defaults to on. But the standard
specification of Concepts differs significantly from the TS, so some
constructs that were allowed in the TS but didn't make it into the
standard can still be enabled by @option{-fconcepts-ts}.
@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 -fconstexpr-cache-depth=@var{n}
@opindex fconstexpr-cache-depth
Set the maximum level of nested evaluation depth for C++11 constexpr
functions that will be cached to @var{n}. This is a heuristic that
trades off compilation speed (when the cache avoids repeated
calculations) against memory consumption (when the cache grows very
large from highly recursive evaluations). The default is 8. Very few
users are likely to want to adjust it, but if your code does heavy
constexpr calculations you might want to experiment to find which
value works best for you.
@item -fconstexpr-loop-limit=@var{n}
@opindex fconstexpr-loop-limit
Set the maximum number of iterations for a loop in C++14 constexpr functions
to @var{n}. A limit is needed to detect infinite loops during
constant expression evaluation. The default is 262144 (1<<18).
@item -fconstexpr-ops-limit=@var{n}
@opindex fconstexpr-ops-limit
Set the maximum number of operations during a single constexpr evaluation.
Even when number of iterations of a single loop is limited with the above limit,
if there are several nested loops and each of them has many iterations but still
smaller than the above limit, or if in a body of some loop or even outside
of a loop too many expressions need to be evaluated, the resulting constexpr
evaluation might take too long.
The default is 33554432 (1<<25).
@item -fcoroutines
@opindex fcoroutines
Enable support for the C++ coroutines extension (experimental).
@item -fno-elide-constructors
@opindex fno-elide-constructors
@opindex felide-constructors
The C++ standard allows an implementation to omit creating a temporary
that 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. This option also causes G++
to call trivial member functions which otherwise would be expanded inline.
In C++17, the compiler is required to omit these temporaries, but this
option still affects trivial member functions.
@item -fno-enforce-eh-specs
@opindex fno-enforce-eh-specs
@opindex fenforce-eh-specs
Don't generate code to check for violation of exception specifications
at run time. This option violates the C++ standard, but may be useful
for reducing code size in production builds, much like defining
@code{NDEBUG}. This does not give user code permission to throw
exceptions in violation of the exception specifications; the compiler
still optimizes based on the specifications, so throwing an
unexpected exception results in undefined behavior at run time.
@item -fextern-tls-init
@itemx -fno-extern-tls-init
@opindex fextern-tls-init
@opindex fno-extern-tls-init
The C++11 and OpenMP standards allow @code{thread_local} and
@code{threadprivate} variables to have dynamic (runtime)
initialization. To support this, any use of such a variable goes
through a wrapper function that performs any necessary initialization.
When the use and definition of the variable are in the same
translation unit, this overhead can be optimized away, but when the
use is in a different translation unit there is significant overhead
even if the variable doesn't actually need dynamic initialization. If
the programmer can be sure that no use of the variable in a
non-defining TU needs to trigger dynamic initialization (either
because the variable is statically initialized, or a use of the
variable in the defining TU will be executed before any uses in
another TU), they can avoid this overhead with the
@option{-fno-extern-tls-init} option.
On targets that support symbol aliases, the default is
@option{-fextern-tls-init}. On targets that do not support symbol
aliases, the default is @option{-fno-extern-tls-init}.
@item -fno-gnu-keywords
@opindex fno-gnu-keywords
@opindex fgnu-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.
This option is implied by the strict ISO C++ dialects: @option{-ansi},
@option{-std=c++98}, @option{-std=c++11}, etc.
@item -fno-implicit-templates
@opindex fno-implicit-templates
@opindex fimplicit-templates
Never emit code for non-inline templates that are instantiated
implicitly (i.e.@: by use); only emit code for explicit instantiations.
If you use this option, you must take care to structure your code to
include all the necessary explicit instantiations to avoid getting
undefined symbols at link time.
@xref{Template Instantiation}, for more information.
@item -fno-implicit-inline-templates
@opindex fno-implicit-inline-templates
@opindex fimplicit-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 need the same set of explicit instantiations.
@item -fno-implement-inlines
@opindex fno-implement-inlines
@opindex fimplement-inlines
To save space, do not emit out-of-line copies of inline functions
controlled by @code{#pragma implementation}. This causes linker
errors if these functions are not inlined everywhere they are called.
@item -fmodules-ts
@itemx -fno-modules-ts
@opindex fmodules-ts
@opindex fno-modules-ts
Enable support for C++20 modules (@pxref{C++ Modules}). The
@option{-fno-modules-ts} is usually not needed, as that is the
default. Even though this is a C++20 feature, it is not currently
implicitly enabled by selecting that standard version.
@item -fmodule-header
@itemx -fmodule-header=user
@itemx -fmodule-header=system
@opindex fmodule-header
Compile a header file to create an importable header unit.
@item -fmodule-implicit-inline
@opindex fmodule-implicit-inline
Member functions defined in their class definitions are not implicitly
inline for modular code. This is different to traditional C++
behavior, for good reasons. However, it may result in a difficulty
during code porting. This option makes such function definitions
implicitly inline. It does however generate an ABI incompatibility,
so you must use it everywhere or nowhere. (Such definitions outside
of a named module remain implicitly inline, regardless.)
@item -fno-module-lazy
@opindex fno-module-lazy
@opindex fmodule-lazy
Disable lazy module importing and module mapper creation.
@item -fmodule-mapper=@r{[}@var{hostname}@r{]}:@var{port}@r{[}?@var{ident}@r{]}
@itemx -fmodule-mapper=|@var{program}@r{[}?@var{ident}@r{]} @var{args...}
@itemx -fmodule-mapper==@var{socket}@r{[}?@var{ident}@r{]}
@itemx -fmodule-mapper=<>@r{[}@var{inout}@r{]}@r{[}?@var{ident}@r{]}
@itemx -fmodule-mapper=<@var{in}>@var{out}@r{[}?@var{ident}@r{]}
@itemx -fmodule-mapper=@var{file}@r{[}?@var{ident}@r{]}
@vindex CXX_MODULE_MAPPER @r{environment variable}
@opindex fmodule-mapper
An oracle to query for module name to filename mappings. If
unspecified the @env{CXX_MODULE_MAPPER} environment variable is used,
and if that is unset, an in-process default is provided.
@item -fmodule-only
@opindex fmodule-only
Only emit the Compiled Module Interface, inhibiting any object file.
@item -fms-extensions
@opindex fms-extensions
Disable Wpedantic warnings about constructs used in MFC, such as implicit
int and getting a pointer to member function via non-standard syntax.
@item -fnew-inheriting-ctors
@opindex fnew-inheriting-ctors
Enable the P0136 adjustment to the semantics of C++11 constructor
inheritance. This is part of C++17 but also considered to be a Defect
Report against C++11 and C++14. This flag is enabled by default
unless @option{-fabi-version=10} or lower is specified.
@item -fnew-ttp-matching
@opindex fnew-ttp-matching
Enable the P0522 resolution to Core issue 150, template template
parameters and default arguments: this allows a template with default
template arguments as an argument for a template template parameter
with fewer template parameters. This flag is enabled by default for
@item -fno-nonansi-builtins
@opindex fno-nonansi-builtins
@opindex fnonansi-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 if 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 actually makes 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 results in a call
to @code{terminate} rather than @code{unexpected}.
@item -fno-operator-names
@opindex fno-operator-names
@opindex foperator-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
@opindex foptional-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} allows some
nonconforming code to compile.
@item -fno-pretty-templates
@opindex fno-pretty-templates
@opindex fpretty-templates
When an error message refers to a specialization of a function
template, the compiler normally prints 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 omits any template arguments that match
the default template arguments for that template. If either of these
behaviors make it harder to understand the error message rather than
easier, you can use @option{-fno-pretty-templates} to disable them.
@item -fno-rtti
@opindex fno-rtti
@opindex frtti
Disable generation of information about every class with virtual
functions for use by the C++ run-time type identification features
(@code{dynamic_cast} and @code{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 G++ generates it as
needed. The @code{dynamic_cast} operator can still be used for casts that
do not require run-time type information, i.e.@: casts to @code{void *} or to
unambiguous base classes.
Mixing code compiled with @option{-frtti} with that compiled with
@option{-fno-rtti} may not work. For example, programs may
fail to link if a class compiled with @option{-fno-rtti} is used as a base
for a class compiled with @option{-frtti}.
@item -fsized-deallocation
@opindex fsized-deallocation
Enable the built-in global declarations
void operator delete (void *, std::size_t) noexcept;
void operator delete[] (void *, std::size_t) noexcept;
@end smallexample
as introduced in C++14. This is useful for user-defined replacement
deallocation functions that, for example, use the size of the object
to make deallocation faster. Enabled by default under
@option{-std=c++14} and above. The flag @option{-Wsized-deallocation}
warns about places that might want to add a definition.
@item -fstrict-enums
@opindex fstrict-enums
Allow the compiler to optimize using the assumption that a value of
enumerated type can only be one of the values of the enumeration (as
defined in the C++ standard; basically, a value that 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 enumerated type.
@item -fstrong-eval-order
@opindex fstrong-eval-order
Evaluate member access, array subscripting, and shift expressions in
left-to-right order, and evaluate assignment in right-to-left order,
as adopted for C++17. Enabled by default with @option{-std=c++17}.
@option{-fstrong-eval-order=some} enables just the ordering of member
access and shift expressions, and is the default without
@item -ftemplate-backtrace-limit=@var{n}
@opindex ftemplate-backtrace-limit
Set the maximum number of template instantiation notes for a single
warning or error to @var{n}. The default value is 10.
@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
@opindex fthreadsafe-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
@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 only works if your C library supports
@item -fno-use-cxa-get-exception-ptr
@opindex fno-use-cxa-get-exception-ptr
@opindex fuse-cxa-get-exception-ptr
Don't use the @code{__cxa_get_exception_ptr} runtime routine. This
causes @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
are 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 has 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:
It sets the default visibility to @code{hidden}, like
Types, but not their members, are not hidden by default.
The One Definition Rule is relaxed for types without explicit
visibility specifications that are defined in more than one
shared object: those declarations are permitted if they are
permitted when this option is not used.
@end enumerate
In new code it is better to use @option{-fvisibility=hidden} and
export those classes that 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 are different, so changing one does 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
@opindex fweak
Do not use weak symbol support, even if it is provided by the linker.
By default, G++ uses weak symbols if they are available. This
option exists only for testing, and should not be used by end-users;
it results in inferior code and has no benefits. This option may
be removed in a future release of G++.
@item -fext-numeric-literals @r{(C++ and Objective-C++ only)}
@opindex fext-numeric-literals
@opindex fno-ext-numeric-literals
Accept imaginary, fixed-point, or machine-defined
literal number suffixes as GNU extensions.
When this option is turned off these suffixes are treated
as C++11 user-defined literal numeric suffixes.
This is on by default for all pre-C++11 dialects and all GNU dialects:
@option{-std=c++98}, @option{-std=gnu++98}, @option{-std=gnu++11},
This option is off by default
for ISO C++11 onwards (@option{-std=c++11}, ...).
@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.)
@item -flang-info-include-translate
@itemx -flang-info-include-translate-not
@itemx -flang-info-include-translate=@var{header}
@opindex flang-info-include-translate
@opindex flang-info-include-translate-not
Inform of include translation events. The first will note accepted
include translations, the second will note declined include
translations. The @var{header} form will inform of include
translations relating to that specific header. If @var{header} is of
the form @code{"user"} or @code{<system>} it will be resolved to a
specific user or system header using the include path.
@item -flang-info-module-cmi
@itemx -flang-info-module-cmi=@var{module}
@opindex flang-info-module-cmi
Inform of Compiled Module Interface pathnames. The first will note
all read CMI pathnames. The @var{module} form will not reading a
specific module's CMI. @var{module} may be a named module or a
header-unit (the latter indicated by either being a pathname containing
directory separators or enclosed in @code{<>} or @code{""}).
@item -stdlib=@var{libstdc++,libc++}
@opindex stdlib
When G++ is configured to support this option, it allows specification of
alternate C++ runtime libraries. Two options are available: @var{libstdc++}
(the default, native C++ runtime for G++) and @var{libc++} which is the
C++ runtime installed on some operating systems (e.g. Darwin versions from
Darwin11 onwards). The option switches G++ to use the headers from the
specified library and to emit @code{-lstdc++} or @code{-lc++} respectively,
when a C++ runtime is required for linking.
@end table
In addition, these warning options have meanings only for C++ programs:
@table @gcctabopt
@item -Wabi-tag @r{(C++ and Objective-C++ only)}
@opindex Wabi-tag
Warn when a type with an ABI tag is used in a context that does not
have that ABI tag. See @ref{C++ Attributes} for more information
about ABI tags.
@item -Wcomma-subscript @r{(C++ and Objective-C++ only)}
@opindex Wcomma-subscript
@opindex Wno-comma-subscript
Warn about uses of a comma expression within a subscripting expression.
This usage was deprecated in C++20. However, a comma expression wrapped
in @code{( )} is not deprecated. Example:
void f(int *a, int b, int c) @{
a[b,c]; // deprecated
a[(b,c)]; // OK
@end group
@end smallexample
Enabled by default with @option{-std=c++20}.
@item -Wctad-maybe-unsupported @r{(C++ and Objective-C++ only)}
@opindex Wctad-maybe-unsupported
@opindex Wno-ctad-maybe-unsupported
Warn when performing class template argument deduction (CTAD) on a type with
no explicitly written deduction guides. This warning will point out cases
where CTAD succeeded only because the compiler synthesized the implicit
deduction guides, which might not be what the programmer intended. Certain
style guides allow CTAD only on types that specifically "opt-in"; i.e., on
types that are designed to support CTAD. This warning can be suppressed with
the following pattern:
struct allow_ctad_t; // any name works
template <typename T> struct S @{
S(T) @{ @}
S(allow_ctad_t) -> S<void>; // guide with incomplete parameter type will never be considered
@end smallexample
@item -Wctor-dtor-privacy @r{(C++ and Objective-C++ only)}
@opindex Wctor-dtor-privacy
@opindex Wno-ctor-dtor-privacy
Warn when a class seems unusable because all the constructors or
destructors in that class are private, and it has neither friends nor
public static member functions. Also warn if there are no non-private
methods, and there's at least one private member function that isn't
a constructor or destructor.
@item -Wdelete-non-virtual-dtor @r{(C++ and Objective-C++ only)}
@opindex Wdelete-non-virtual-dtor
@opindex Wno-delete-non-virtual-dtor
Warn when @code{delete} is used to destroy an instance of a class that
has virtual functions and non-virtual destructor. It is unsafe to delete
an instance of a derived class through a pointer to a base class if the
base class does not have a virtual destructor. This warning is enabled
by @option{-Wall}.
@item -Wdeprecated-copy @r{(C++ and Objective-C++ only)}
@opindex Wdeprecated-copy
@opindex Wno-deprecated-copy
Warn that the implicit declaration of a copy constructor or copy
assignment operator is deprecated if the class has a user-provided
copy constructor or copy assignment operator, in C++11 and up. This
warning is enabled by @option{-Wextra}. With
@option{-Wdeprecated-copy-dtor}, also deprecate if the class has a
user-provided destructor.
@item -Wno-deprecated-enum-enum-conversion @r{(C++ and Objective-C++ only)}
@opindex Wdeprecated-enum-enum-conversion
@opindex Wno-deprecated-enum-enum-conversion
Disable the warning about the case when the usual arithmetic conversions
are applied on operands where one is of enumeration type and the other is
of a different enumeration type. This conversion was deprecated in C++20.
For example:
enum E1 @{ e @};
enum E2 @{ f @};
int k = f - e;
@end smallexample
@option{-Wdeprecated-enum-enum-conversion} is enabled by default with
@option{-std=c++20}. In pre-C++20 dialects, this warning can be enabled
by @option{-Wenum-conversion}.
@item -Wno-deprecated-enum-float-conversion @r{(C++ and Objective-C++ only)}
@opindex Wdeprecated-enum-float-conversion
@opindex Wno-deprecated-enum-float-conversion
Disable the warning about the case when the usual arithmetic conversions
are applied on operands where one is of enumeration type and the other is
of a floating-point type. This conversion was deprecated in C++20. For
enum E1 @{ e @};
enum E2 @{ f @};
bool b = e <= 3.7;
@end smallexample
@option{-Wdeprecated-enum-float-conversion} is enabled by default with
@option{-std=c++20}. In pre-C++20 dialects, this warning can be enabled
by @option{-Wenum-conversion}.
@item -Wno-init-list-lifetime @r{(C++ and Objective-C++ only)}
@opindex Winit-list-lifetime
@opindex Wno-init-list-lifetime
Do not warn about uses of @code{std::initializer_list} that are likely
to result in dangling pointers. Since the underlying array for an
@code{initializer_list} is handled like a normal C++ temporary object,
it is easy to inadvertently keep a pointer to the array past the end
of the array's lifetime. For example:
@itemize @bullet
If a function returns a temporary @code{initializer_list}, or a local
@code{initializer_list} variable, the array's lifetime ends at the end
of the return statement, so the value returned has a dangling pointer.
If a new-expression creates an @code{initializer_list}, the array only
lives until the end of the enclosing full-expression, so the
@code{initializer_list} in the heap has a dangling pointer.
When an @code{initializer_list} variable is assigned from a
brace-enclosed initializer list, the temporary array created for the
right side of the assignment only lives until the end of the
full-expression, so at the next statement the @code{initializer_list}
variable has a dangling pointer.
// li's initial underlying array lives as long as li
std::initializer_list<int> li = @{ 1,2,3 @};
// assignment changes li to point to a temporary array
li = @{ 4, 5 @};
// now the temporary is gone and li has a dangling pointer
int i = li.begin()[0] // undefined behavior
@end smallexample
When a list constructor stores the @code{begin} pointer from the
@code{initializer_list} argument, this doesn't extend the lifetime of
the array, so if a class variable is constructed from a temporary
@code{initializer_list}, the pointer is left dangling by the end of
the variable declaration statement.
@end itemize
@item -Winvalid-imported-macros
@opindex Winvalid-imported-macros
@opindex Wno-invalid-imported-macros
Verify all imported macro definitions are valid at the end of
compilation. This is not enabled by default, as it requires
additional processing to determine. It may be useful when preparing
sets of header-units to ensure consistent macros.
@item -Wno-literal-suffix @r{(C++ and Objective-C++ only)}
@opindex Wliteral-suffix