the directories are searched in the order specified.
Many options have long names starting with @samp{-f} or with
-@samp{-W}---for example, @option{-fforce-mem},
+@samp{-W}---for example,
@option{-fstrength-reduce}, @option{-Wformat} and so on. Most of
these have both positive and negative forms; the negative form of
@option{-ffoo} would be @option{-fno-foo}. This manual documents
-fno-default-inline -fvisibility-inlines-hidden @gol
-Wabi -Wctor-dtor-privacy @gol
-Wnon-virtual-dtor -Wreorder @gol
--Weffc++ -Wno-deprecated @gol
+-Weffc++ -Wno-deprecated -Wstrict-null-sentinel @gol
-Wno-non-template-friend -Wold-style-cast @gol
-Woverloaded-virtual -Wno-pmf-conversions @gol
-Wsign-promo}
-fconstant-string-class=@var{class-name} @gol
-fgnu-runtime -fnext-runtime @gol
-fno-nil-receivers @gol
+-fobjc-call-cxx-cdtors @gol
+-fobjc-direct-dispatch @gol
-fobjc-exceptions @gol
+-fobjc-gc @gol
-freplace-objc-classes @gol
-fzero-link @gol
-gen-decls @gol
--Wno-protocol -Wselector -Wundeclared-selector}
+-Wassign-intercept @gol
+-Wno-protocol -Wselector @gol
+-Wstrict-selector-match @gol
+-Wundeclared-selector}
@item Language Independent Options
@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}.
@gccoptlist{-fmessage-length=@var{n} @gol
--fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}}
+-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}} @gol
+-fdiagnostics-show-options
@item Warning Options
@xref{Warning Options,,Options to Request or Suppress Warnings}.
@gccoptlist{-fsyntax-only -pedantic -pedantic-errors @gol
--w -Wextra -Wall -Waggregate-return @gol
--Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol
+-w -Wextra -Wall -Waggregate-return -Wno-attributes @gol
+-Wc++-compat -Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol
-Wconversion -Wno-deprecated-declarations @gol
-Wdisabled-optimization -Wno-div-by-zero -Wno-endif-labels @gol
-Werror -Werror-implicit-function-declaration @gol
-Wformat-security -Wformat-y2k @gol
-Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol
-Wimport -Wno-import -Winit-self -Winline @gol
+-Wno-int-to-pointer-cast @gol
-Wno-invalid-offsetof -Winvalid-pch @gol
--Wlarger-than-@var{len} -Wlong-long @gol
+-Wlarger-than-@var{len} -Wunsafe-loop-optimizations -Wlong-long @gol
-Wmain -Wmissing-braces -Wmissing-field-initializers @gol
-Wmissing-format-attribute -Wmissing-include-dirs @gol
-Wmissing-noreturn @gol
-Wno-multichar -Wnonnull -Wpacked -Wpadded @gol
--Wparentheses -Wpointer-arith -Wredundant-decls @gol
+-Wparentheses -Wpointer-arith -Wno-pointer-to-int-cast @gol
+-Wredundant-decls @gol
-Wreturn-type -Wsequence-point -Wshadow @gol
--Wsign-compare -Wstrict-aliasing -Wstrict-aliasing=2 @gol
+-Wsign-compare -Wstack-protector @gol
+-Wstrict-aliasing -Wstrict-aliasing=2 @gol
-Wswitch -Wswitch-default -Wswitch-enum @gol
-Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized @gol
--Wunknown-pragmas -Wunreachable-code @gol
+-Wunknown-pragmas -Wno-pragmas -Wunreachable-code @gol
-Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol
--Wunused-value -Wunused-variable -Wwrite-strings @gol
--Wvariadic-macros}
+-Wunused-value -Wunused-variable -Wvariadic-macros @gol
+-Wwrite-strings}
@item C-only Warning Options
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
-fdump-tree-sra@r{[}-@var{n}@r{]} @gol
-fdump-tree-salias @gol
-fdump-tree-fre@r{[}-@var{n}@r{]} @gol
+-fdump-tree-vrp@r{[}-@var{n}@r{]} @gol
-ftree-vectorizer-verbose=@var{n} @gol
+-fdump-tree-storeccp@r{[}-@var{n}@r{]} @gol
-feliminate-dwarf2-dups -feliminate-unused-debug-types @gol
--feliminate-unused-debug-symbols -fmem-report -fprofile-arcs -ftree-based-profiling @gol
+-feliminate-unused-debug-symbols -fmem-report -fprofile-arcs @gol
-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
-ftest-coverage -ftime-report -fvar-tracking @gol
-g -g@var{level} -gcoff -gdwarf-2 @gol
-fbranch-probabilities -fprofile-values -fvpt -fbranch-target-load-optimize @gol
-fbranch-target-load-optimize2 -fbtr-bb-exclusive @gol
-fcaller-saves -fcprop-registers -fcse-follow-jumps @gol
--fcse-follow-jumps -fcse-skip-blocks -fcx-limited-range -fdata-sections @gol
--fdelayed-branch -fdelete-null-pointer-checks @gol
+-fcse-skip-blocks -fcx-limited-range -fdata-sections @gol
+-fdelayed-branch -fdelete-null-pointer-checks -fearly-inlining @gol
-fexpensive-optimizations -ffast-math -ffloat-store @gol
--fforce-addr -fforce-mem -ffunction-sections @gol
+-fforce-addr -ffunction-sections @gol
-fgcse -fgcse-lm -fgcse-sm -fgcse-las -fgcse-after-reload @gol
-floop-optimize -fcrossjumping -fif-conversion -fif-conversion2 @gol
-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol
-fno-default-inline -fno-defer-pop -floop-optimize2 -fmove-loop-invariants @gol
-fno-function-cse -fno-guess-branch-probability @gol
-fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol
--funsafe-math-optimizations -ffinite-math-only @gol
+-funsafe-math-optimizations -funsafe-loop-optimizations -ffinite-math-only @gol
-fno-trapping-math -fno-zero-initialized-in-bss @gol
-fomit-frame-pointer -foptimize-register-move @gol
-foptimize-sibling-calls -fprefetch-loop-arrays @gol
-frounding-math -fschedule-insns -fschedule-insns2 @gol
-fno-sched-interblock -fno-sched-spec -fsched-spec-load @gol
-fsched-spec-load-dangerous @gol
--fsched-stalled-insns=@var{n} -sched-stalled-insns-dep=@var{n} @gol
+-fsched-stalled-insns=@var{n} -fsched-stalled-insns-dep=@var{n} @gol
-fsched2-use-superblocks @gol
-fsched2-use-traces -freschedule-modulo-scheduled-loops @gol
--fsignaling-nans -fsingle-precision-constant -fspeculative-prefetching @gol
+-fsignaling-nans -fsingle-precision-constant @gol
+-fstack-protector -fstack-protector-all @gol
-fstrength-reduce -fstrict-aliasing -ftracer -fthread-jumps @gol
-funroll-all-loops -funroll-loops -fpeel-loops @gol
-fsplit-ivs-in-unroller -funswitch-loops @gol
-ftree-loop-linear -ftree-loop-im -ftree-loop-ivcanon -fivopts @gol
-ftree-dominator-opts -ftree-dse -ftree-copyrename -ftree-sink @gol
-ftree-ch -ftree-sra -ftree-ter -ftree-lrs -ftree-fre -ftree-vectorize @gol
--ftree-salias @gol
+-ftree-salias -fweb @gol
+-ftree-copy-prop -ftree-store-ccp -ftree-store-copy-prop -fwhole-program @gol
--param @var{name}=@var{value}
-O -O0 -O1 -O2 -O3 -Os}
-include @var{file} -imacros @var{file} @gol
-iprefix @var{file} -iwithprefix @var{dir} @gol
-iwithprefixbefore @var{dir} -isystem @var{dir} @gol
+-isysroot @var{dir} @gol
-M -MM -MF -MG -MP -MQ -MT -nostdinc @gol
-P -fworking-directory -remap @gol
-trigraphs -undef -U@var{macro} -Wp,@var{option} @gol
@item Linker Options
@xref{Link Options,,Options for Linking}.
@gccoptlist{@var{object-file-name} -l@var{library} @gol
--nostartfiles -nodefaultlibs -nostdlib -pie @gol
+-nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic @gol
-s -static -static-libgcc -shared -shared-libgcc -symbolic @gol
-Wl,@var{option} -Xlinker @var{option} @gol
-u @var{symbol}}
@item Directory Options
@xref{Directory Options,,Options for Directory Search}.
-@gccoptlist{-B@var{prefix} -I@var{dir} -iquote@var{dir} -L@var{dir} -specs=@var{file} -I-}
+@gccoptlist{-B@var{prefix} -I@var{dir} -iquote@var{dir} -L@var{dir}
+-specs=@var{file} -I- --sysroot=@var{dir}}
@item Target Options
@c I wrote this xref this way to avoid overfull hbox. -- rms
-mcall-prologues -mno-tablejump -mtiny-stack -mint8}
@emph{Blackfin Options}
-@gccoptlist{-momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer -mcsync @gol
--mno-csync -mlow-64k -mno-low64k -mid-shared-library @gol
--mno-id-shared-library -mshared-library-id=@var{n} @gol}
+@gccoptlist{-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 -mid-shared-library @gol
+-mno-id-shared-library -mshared-library-id=@var{n} @gol
+-mlong-calls -mno-long-calls}
@emph{CRIS Options}
@gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol
-melf -maout -melinux -mlinux -sim -sim2 @gol
-mmul-bug-workaround -mno-mul-bug-workaround}
+@emph{CRX Options}
+@gccoptlist{-mmac -mpush-args}
+
@emph{Darwin Options}
@gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol
-arch_only -bind_at_load -bundle -bundle_loader @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 -mone-byte-bool}
+-whatsloaded -F -gused -gfull -mmacosx-min-version=@var{version} @gol
+-mone-byte-bool}
@emph{DEC Alpha Options}
@gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @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
-mmmx -msse -msse2 -msse3 -m3dnow @gol
-mthreads -mno-align-stringops -minline-all-stringops @gol
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
--m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer @gol
--mno-red-zone -mno-tls-direct-seg-refs @gol
+-m96bit-long-double -mregparm=@var{num} -msseregparm @gol
+-momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
-mcmodel=@var{code-model} @gol
--m32 -m64}
+-m32 -m64 -mlarge-data-threshold=@var{num}}
@emph{IA-64 Options}
@gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @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{-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol
-m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020 @gol
-mips16 -mno-mips16 -mabi=@var{abi} -mabicalls -mno-abicalls @gol
-mxgot -mno-xgot -mgp32 -mgp64 -mfp32 -mfp64 @gol
-mhard-float -msoft-float -msingle-float -mdouble-float @gol
--mpaired-single -mips3d @gol
--mint64 -mlong64 -mlong32 -msym32 -mno-sym32 @gol
+-mdsp -mpaired-single -mips3d @gol
+-mlong64 -mlong32 -msym32 -mno-sym32 @gol
-G@var{num} -membedded-data -mno-embedded-data @gol
-muninit-const-in-rodata -mno-uninit-const-in-rodata @gol
-msplit-addresses -mno-split-addresses @gol
-mam33-2 -mno-am33-2 @gol
-mno-crt0 -mrelax}
-@emph{NS32K Options}
-@gccoptlist{-m32032 -m32332 -m32532 -m32081 -m32381 @gol
--mmult-add -mnomult-add -msoft-float -mrtd -mnortd @gol
--mregparam -mnoregparam -msb -mnosb @gol
--mbitfield -mnobitfield -mhimem -mnohimem}
-
@emph{PDP-11 Options}
@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
-mbcopy -mbcopy-builtin -mint32 -mno-int16 @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 @gol
+-mdynamic-no-pic -maltivec -mswdiv @gol
-mprioritize-restricted-insns=@var{priority} @gol
-msched-costly-dep=@var{dependence_type} @gol
-minsert-sched-nops=@var{scheme} @gol
-mcall-sysv -mcall-netbsd @gol
-maix-struct-return -msvr4-struct-return @gol
--mabi=altivec -mabi=no-altivec @gol
--mabi=spe -mabi=no-spe @gol
+-mabi=@var{abi-type} -msecure-plt -mbss-plt @gol
+-misel -mno-isel @gol
-misel=yes -misel=no @gol
+-mspe -mno-spe @gol
-mspe=yes -mspe=no @gol
+-mvrsave -mno-vrsave @gol
-mfloat-gprs=yes -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double @gol
-mprototype -mno-prototype @gol
-msim -mmvme -mads -myellowknife -memb -msdata @gol
-mb -ml -mdalign -mrelax @gol
-mbigtable -mfmovd -mhitachi -mrenesas -mno-renesas -mnomacsave @gol
-mieee -misize -mpadstruct -mspace @gol
--mprefergot -musermode}
+-mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol
+-mdivsi3_libfunc=@var{name} @gol
+-madjust-unroll -mindexed-addressing -mgettrcost=@var{number} -mpt-fixed @gol
+ -minvalid-symbols}
@emph{SPARC Options}
@gccoptlist{-mcpu=@var{cpu-type} @gol
-finhibit-size-directive -finstrument-functions @gol
-fno-common -fno-ident @gol
-fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol
+-fno-jump-tables @gol
-freg-struct-return -fshared-data -fshort-enums @gol
-fshort-double -fshort-wchar @gol
-fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol
the last two letters must both be literally @samp{x}. Likewise,
@samp{.C} refers to a literal capital C@.
+@item @var{file}.mm
+@itemx @var{file}.M
+Objective-C++ source code which must be preprocessed.
+
+@item @var{file}.mii
+Objective-C++ source code which should not be preprocessed.
+
@item @var{file}.hh
@itemx @var{file}.H
C++ header file to be turned into a precompiled header.
@itemx @var{file}.f95
Fortran 90/95 source code which should not be preprocessed.
+@item @var{file}.F90
+@itemx @var{file}.F95
+Fortran 90/95 source code which must be preprocessed (with the
+traditional preprocessor).
+
@c FIXME: Descriptions of Java file types.
@c @var{file}.java
@c @var{file}.class
@opindex Wno-deprecated
Do not warn about usage of deprecated features. @xref{Deprecated Features}.
+@item -Wstrict-null-sentinel @r{(C++ only)}
+@opindex Wstrict-null-sentinel
+Warn also about the use of an uncasted @code{NULL} as sentinel. When
+compiling only with GCC this is a valid sentinel, as @code{NULL} is defined
+to @code{__null}. Although it is a null pointer constant not a null pointer,
+it is guaranteed to of the same size as a pointer. But this use is
+not portable across different compilers.
+
@item -Wno-non-template-friend @r{(C++ only)}
@opindex Wno-non-template-friend
Disable warnings when non-templatized friend functions are declared
@item -Wold-style-cast @r{(C++ only)}
@opindex Wold-style-cast
Warn if an old-style (C-style) cast to a non-void type is used within
-a C++ program. The new-style casts (@samp{static_cast},
-@samp{reinterpret_cast}, and @samp{const_cast}) are less vulnerable to
-unintended effects and much easier to search for.
+a C++ program. The new-style casts (@samp{dynamic_cast},
+@samp{static_cast}, @samp{reinterpret_cast}, and @samp{const_cast}) are
+less vulnerable to unintended effects and much easier to search for.
@item -Woverloaded-virtual @r{(C++ only)}
@opindex Woverloaded-virtual
to be used. Currently, this option is only available in conjunction with
the NeXT runtime on Mac OS X 10.3 and later.
+@item -fobjc-call-cxx-cdtors
+@opindex fobjc-call-cxx-cdtors
+For each Objective-C class, check if any of its instance variables is a
+C++ object with a non-trivial default constructor. If so, synthesize a
+special @code{- (id) .cxx_construct} instance method that will run
+non-trivial default constructors on any such instance variables, in order,
+and then return @code{self}. Similarly, check if any instance variable
+is a C++ object with a non-trivial destructor, and if so, synthesize a
+special @code{- (void) .cxx_destruct} method that will run
+all such default destructors, in reverse order.
+
+The @code{- (id) .cxx_construct} and/or @code{- (void) .cxx_destruct} methods
+thusly generated will only operate on instance variables declared in the
+current Objective-C class, and not those inherited from superclasses. It
+is the responsibility of the Objective-C runtime to invoke all such methods
+in an object's inheritance hierarchy. The @code{- (id) .cxx_construct} methods
+will be invoked by the runtime immediately after a new object
+instance is allocated; the @code{- (void) .cxx_destruct} methods will
+be invoked immediately before the runtime deallocates an object instance.
+
+As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
+support for invoking the @code{- (id) .cxx_construct} and
+@code{- (void) .cxx_destruct} methods.
+
+@item -fobjc-direct-dispatch
+@opindex fobjc-direct-dispatch
+Allow fast jumps to the message dispatcher. On Darwin this is
+accomplished via the comm page.
+
@item -fobjc-exceptions
@opindex fobjc-exceptions
Enable syntactic support for structured exception handling in Objective-C,
@code{@@synchronized} blocks is allowed, and will cause the guarding object
to be unlocked properly.
+@item -fobjc-gc
+@opindex fobjc-gc
+Enable garbage collection (GC) in Objective-C and Objective-C++ programs.
+
@item -freplace-objc-classes
@opindex freplace-objc-classes
Emit a special marker instructing @command{ld(1)} not to statically link in
Dump interface declarations for all classes seen in the source file to a
file named @file{@var{sourcename}.decl}.
+@item -Wassign-intercept
+@opindex Wassign-intercept
+Warn whenever an Objective-C assignment is being intercepted by the
+garbage collector.
+
@item -Wno-protocol
@opindex Wno-protocol
If a class is declared to implement a protocol, a warning is issued for
found during compilation, or because the @option{-fsyntax-only} option is
being used.
+@item -Wstrict-selector-match
+@opindex Wstrict-selector-match
+Warn if multiple methods with differing argument and/or return types are
+found for a given selector when attempting to send a message using this
+selector to a receiver of type @code{id} or @code{Class}. When this flag
+is off (which is the default behavior), the compiler will omit such warnings
+if any differences found are confined to types which share the same size
+and alignment.
+
@item -Wundeclared-selector
@opindex Wundeclared-selector
Warn if a @code{@@selector(@dots{})} expression referring to an
prefix) for physical lines that result from the process of breaking
a message which is too long to fit on a single line.
+@item -fdiagnostics-show-options
+@opindex fdiagnostics-show-options
+This option instructs the diagnostic machinery to add text to each
+diagnostic emitted, which indicates which command line option directly
+controls that diagnostic, when such an option is known to the
+diagnostic machinery.
+
@end table
@node Warning Options
If you want to warn about code which uses the uninitialized value of the
variable in its own initializer, use the @option{-Winit-self} option.
-These warnings occur only for variables that are candidates for
-register allocation. Therefore, they do not occur for a variable that
-is declared @code{volatile}, or whose address is taken, or whose size
-is other than 1, 2, 4 or 8 bytes. Also, they do not occur for
-structures, unions or arrays, even when they are in registers.
+These warnings occur for individual uninitialized or clobbered
+elements of structure, union or array variables as well as for
+variables which are uninitialized or clobbered as a whole. They do
+not occur for variables or elements declared @code{volatile}. Because
+these warnings depend on optimization, the exact variables or elements
+for which there are warnings will depend on the precise optimization
+options and version of GCC used.
Note that there may be no warning about a variable that is used only
to compute a value that itself is never used, because such
for unknown pragmas in system header files. This is not the case if
the warnings were only enabled by the @option{-Wall} command line option.
+@item -Wno-pragmas
+@opindex Wno-pragmas
+@opindex Wpragmas
+Do not warn about misuses of pragmas, such as incorrect parameters,
+invalid syntax, or conflicts between pragmas. See also
+@samp{-Wunknown-pragmas}.
+
@item -Wstrict-aliasing
@opindex Wstrict-aliasing
This option is only active when @option{-fstrict-aliasing} is active.
@item -Wstrict-aliasing=2
@opindex Wstrict-aliasing=2
This option is only active when @option{-fstrict-aliasing} is active.
-It warns about all code which might break the strict aliasing rules that the
-compiler is using for optimization. This warning catches all cases, but
-it will also give a warning for some ambiguous cases that are safe.
+It warns about code which might break the strict aliasing rules that the
+compiler is using for optimization. This warning catches more cases than
+@option{-Wstrict-aliasing}, but it will also give a warning for some ambiguous
+cases that are safe.
@item -Wall
@opindex Wall
@opindex Wlarger-than
Warn whenever an object of larger than @var{len} bytes is defined.
+@item -Wunsafe-loop-optimizations
+@opindex Wunsafe-loop-optimizations
+Warn if the loop cannot be optimized because the compiler could not
+assume anything on the bounds of the loop indices. With
+@option{-funsafe-loop-optimizations} warn if the compiler made
+such assumptions.
+
@item -Wpointer-arith
@opindex Wpointer-arith
Warn about anything that depends on the ``size of'' a function type or
Warn whenever a function call is cast to a non-matching type.
For example, warn if @code{int malloc()} is cast to @code{anything *}.
+@item -Wc++-compat
+Warn about ISO C constructs that are outside of the common subset of
+ISO C and ISO C++, e.g.@: request for implicit conversion from
+@code{void *} to a pointer to non-@code{void} type.
+
@item -Wcast-qual
@opindex Wcast-qual
Warn whenever a pointer is cast so as to remove a type qualifier from
called. (In languages where you can return an array, this also elicits
a warning.)
+@item -Wno-attributes
+@opindex Wno-attributes
+@opindex Wattributes
+Do not warn if an unexpected @code{__attribute__} is used, such as
+unrecognized attributes, function attributes applied to variables,
+etc. This will not stop errors for incorrect use of supported
+attributes.
+
@item -Wstrict-prototypes @r{(C only)}
@opindex Wstrict-prototypes
Warn if a function is declared or defined without specifying the
@item -Wmissing-format-attribute
@opindex Wmissing-format-attribute
@opindex Wformat
-If @option{-Wformat} is enabled, also warn about functions which might be
-candidates for @code{format} attributes. Note these are only possible
-candidates, not absolute ones. GCC will guess that @code{format}
-attributes might be appropriate for any function that calls a function
-like @code{vprintf} or @code{vscanf}, but this might not always be the
+Warn about function pointers which might be candidates for @code{format}
+attributes. Note these are only possible candidates, not absolute ones.
+GCC will guess that function pointers with @code{format} attributes that
+are used in assignment, initialization, parameter passing or return
+statements should have a corresponding @code{format} attribute in the
+resulting type. I.e.@: the left-hand side of the assignment or
+initialization, the type of the parameter variable, or the return type
+of the containing function respectively should also have a @code{format}
+attribute to avoid the warning.
+
+GCC will also warn about function definitions which might be
+candidates for @code{format} attributes. Again, these are only
+possible candidates. GCC will guess that @code{format} attributes
+might be appropriate for any function that calls a function like
+@code{vprintf} or @code{vscanf}, but this might not always be the
case, and some functions for which @code{format} attributes are
-appropriate may not be detected. This option has no effect unless
-@option{-Wformat} is enabled (possibly by @option{-Wall}).
+appropriate may not be detected.
@item -Wno-multichar
@opindex Wno-multichar
The compiler uses a variety of heuristics to determine whether or not
to inline a function. For example, the compiler takes into account
-the size of the function being inlined and the the amount of inlining
+the size of the function being inlined and the amount of inlining
that has already been done in the current function. Therefore,
seemingly insignificant changes in the source program can cause the
warnings produced by @option{-Winline} to appear or disappear.
The restrictions on @samp{offsetof} may be relaxed in a future version
of the C++ standard.
+@item -Wno-int-to-pointer-cast @r{(C only)}
+@opindex Wno-int-to-pointer-cast
+Suppress warnings from casts to pointer type of an integer of a
+different size.
+
+@item -Wno-pointer-to-int-cast @r{(C only)}
+@opindex Wno-pointer-to-int-cast
+Suppress warnings from casts from a pointer to an integer type of a
+different size.
+
@item -Winvalid-pch
@opindex Winvalid-pch
Warn if a precompiled header (@pxref{Precompiled Headers}) is found in
@item -Werror
@opindex Werror
Make all warnings into errors.
+
+@item -Wstack-protector
+This option is only active when @option{-fstack-protector} is active. It
+warns about functions that will not be protected against stack smashing.
+
@end table
@node Debugging Options
the basename of the source file. In both cases any suffix is removed
(e.g.@: @file{foo.gcda} for input file @file{dir/foo.c}, or
@file{dir/foo.gcda} for output file specified as @option{-o dir/foo.o}).
+@xref{Cross-profiling}.
@cindex @command{gcov}
@item --coverage
instrumentation code can be added to the block; otherwise, a new basic
block must be created to hold the instrumentation code.
-@item -ftree-based-profiling
-@opindex ftree-based-profiling
-This option is used in addition to @option{-fprofile-arcs} or
-@option{-fbranch-probabilities} to control whether those optimizations
-are performed on a tree-based or rtl-based internal representation.
-If you use this option when compiling with @option{-fprofile-arcs},
-you must also use it when compiling later with @option{-fbranch-probabilities}.
-Currently the tree-based optimization is in an early stage of
-development, and this option is recommended only for those people
-working on improving it.
-
@need 2000
@item -ftest-coverage
@opindex ftest-coverage
@opindex fdump-rtl-btl
@opindex fdump-rtl-dbr
@option{-dd} and @option{-fdump-rtl-btl} enable dumping after branch
-target load optimization, to to @file{@var{file}.31.btl}. @option{-dd}
+target load optimization, to @file{@var{file}.31.btl}. @option{-dd}
and @option{-fdump-rtl-dbr} enable dumping after delayed branch
scheduling, to @file{@var{file}.36.dbr}.
use diff on debugging dumps for compiler invocations with different
options, in particular with and without @option{-g}.
-@item -fdump-translation-unit @r{(C and C++ only)}
-@itemx -fdump-translation-unit-@var{options} @r{(C and C++ only)}
+@item -fdump-translation-unit @r{(C++ only)}
+@itemx -fdump-translation-unit-@var{options} @r{(C++ only)}
@opindex fdump-translation-unit
Dump a representation of the tree structure for the entire translation
unit to a file. The file name is made by appending @file{.tu} to the
Dump each function after CCP@. The file name is made by appending
@file{.ccp} to the source file name.
+@item storeccp
+@opindex fdump-tree-storeccp
+Dump each function after STORE-CCP. The file name is made by appending
+@file{.storeccp} to the source file name.
+
@item pre
@opindex fdump-tree-pre
Dump trees after partial redundancy elimination. The file name is made
Dump trees after full redundancy elimination. The file name is made
by appending @file{.fre} to the source file name.
+@item copyprop
+@opindex fdump-tree-copyprop
+Dump trees after copy propagation. The file name is made
+by appending @file{.copyprop} to the source file name.
+
+@item store_copyprop
+@opindex fdump-tree-store_copyprop
+Dump trees after store copy-propagation. The file name is made
+by appending @file{.store_copyprop} to the source file name.
+
@item dce
@opindex fdump-tree-dce
Dump each function after dead code elimination. The file name is made by
Dump each function after applying vectorization of loops. The file name is
made by appending @file{.vect} to the source file name.
+@item vrp
+@opindex fdump-tree-vrp
+Dump each function after Value Range Propagation (VRP). The file name
+is made by appending @file{.vrp} to the source file name.
+
@item all
@opindex fdump-tree-all
Enable all the available tree dumps with the flags provided in this option.
-fif-conversion2 @gol
-ftree-ccp @gol
-ftree-dce @gol
--ftree-dom @gol
+-ftree-dominator-opts @gol
-ftree-dse @gol
-ftree-ter @gol
--ftree-live_range_split @gol
+-ftree-lrs @gol
-ftree-sra @gol
-ftree-copyrename @gol
-ftree-fre @gol
-fstrength-reduce @gol
-frerun-cse-after-loop -frerun-loop-opt @gol
-fcaller-saves @gol
--fforce-mem @gol
-fpeephole2 @gol
-fschedule-insns -fschedule-insns2 @gol
-fsched-interblock -fsched-spec @gol
-funit-at-a-time @gol
-falign-functions -falign-jumps @gol
-falign-loops -falign-labels @gol
+-ftree-vrp @gol
-ftree-pre}
Please note the warning under @option{-fgcse} about
arithmetic on them. This produces better code by making all memory
references potential common subexpressions. When they are not common
subexpressions, instruction combination should eliminate the separate
-register-load.
-
-Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+register-load. This option is now a nop and will be removed in 4.2.
@item -fforce-addr
@opindex fforce-addr
Force memory address constants to be copied into registers before
-doing arithmetic on them. This may produce better code just as
-@option{-fforce-mem} may.
+doing arithmetic on them.
@item -fomit-frame-pointer
@opindex fomit-frame-pointer
Enabled at level @option{-O3}.
+@item -fearly-inlining
+@opindex fearly-inlining
+Inline functions marked by @code{always_inline} and functions whose body seems
+smaller than the function call overhead early before doing
+@option{-fprofile-generate} instrumentation and real inlining pass. Doing so
+makes profiling significantly cheaper and usually inlining faster on programs
+having large chains of nested wrapper functions.
+
+Enabled by default.
+
@item -finline-limit=@var{n}
@opindex finline-limit
By default, GCC limits the size of functions that can be inlined. This flag
parameters controlling inlining.
@emph{Note:} pseudo instruction represents, in this particular context, an
-abstract measurement of function's size. In no way, it represents a count
+abstract measurement of function's size. In no way does it represent a count
of assembly instructions and as such its exact meaning might change from one
release to an another.
(loop unrolling, peeling and unswitching, loop invariant motion) are enabled
by separate flags.
+@item -funsafe-loop-optimizations
+@opindex funsafe-loop-optimizations
+If given, the loop optimizer will assume that loop indices do not
+overflow, and that the loops with nontrivial exit condition are not
+infinite. This enables a wider range of loop optimizations even if
+the loop optimizer itself cannot prove that these assumptions are valid.
+Using @option{-Wunsafe-loop-optimizations}, the compiler will warn you
+if it finds this kind of loop.
+
@item -fcrossjumping
@opindex crossjumping
Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The
This analysis faster than PRE, though it exposes fewer redundancies.
This flag is enabled by default at @option{-O} and higher.
+@item -ftree-copy-prop
+Perform copy propagation on trees. This pass eliminates unnecessary
+copy operations. This flag is enabled by default at @option{-O} and
+higher.
+
+@item -ftree-store-copy-prop
+Perform copy propagation of memory loads and stores. This pass
+eliminates unnecessary copy operations in memory references
+(structures, global variables, arrays, etc). This flag is enabled by
+default at @option{-O2} and higher.
+
@item -ftree-salias
Perform structural alias analysis on trees. This flag
is enabled by default at @option{-O} and higher.
enabled by default at @option{-O} and higher.
@item -ftree-ccp
-Perform sparse conditional constant propagation (CCP) on trees. This flag
-is enabled by default at @option{-O} and higher.
+Perform sparse conditional constant propagation (CCP) on trees. This
+pass only operates on local scalar variables and is enabled by default
+at @option{-O} and higher.
+
+@item -ftree-store-ccp
+Perform sparse conditional constant propagation (CCP) on trees. This
+pass operates on both local scalar variables and memory stores and
+loads (global variables, structures, arrays, etc). This flag is
+enabled by default at @option{-O2} and higher.
@item -ftree-dce
Perform dead code elimination (DCE) on trees. This flag is enabled by
Perform linear loop transformations on tree. This flag can improve cache
performance and allow further loop optimizations to take place.
-@item -ftree-lim
-Perform loop invariant motion on trees. This pass moves only invartiants that
-would be hard to handle on rtl level (function calls, operations that expand to
+@item -ftree-loop-im
+Perform loop invariant motion on trees. This pass moves only invariants that
+would be hard to handle at RTL level (function calls, operations that expand to
nontrivial sequences of insns). With @option{-funswitch-loops} it also moves
operands of conditions that are invariant out of the loop, so that we can use
just trivial invariantness analysis in loop unswitching. The pass also includes
store motion.
-@item -fivcanon
+@item -ftree-loop-ivcanon
Create a canonical counter for number of iterations in the loop for that
determining number of iterations requires complicated analysis. Later
optimizations then may determine the number easily. Useful especially
@item -ftree-vectorize
Perform loop vectorization on trees.
+@item -ftree-vrp
+Perform Value Range Propagation on trees. This is similar to the
+constant propagation pass, but instead of values, ranges of values are
+propagated. This allows the optimizers to remove unnecessary range
+checks like array bound checks and null pointer checks. This is
+enabled by default at @option{-O2} and higher. Null pointer check
+elimination is only done if @option{-fdelete-null-pointer-checks} is
+enabled.
+
@item -ftracer
@opindex ftracer
Perform tail duplication to enlarge superblock size. This transformation
@opindex -fsplit-ivs-in-unroller
Enables expressing of values of induction variables in later iterations
of the unrolled loop using the value in the first iteration. This breaks
-long dependency chains, thus improving efficiency of the scheduling passes
-(for best results, @option{-fweb} should be used as well).
+long dependency chains, thus improving efficiency of the scheduling passes.
Combination of @option{-fweb} and CSE is often sufficient to obtain the
same effect. However in cases the loop body is more complicated than
@item
@emph{unit-at-a-time} mode removes unreferenced static variables
-and functions are removed. This may result in undefined references
+and functions. This may result in undefined references
when an @code{asm} statement refers directly to variables or functions
that are otherwise unused. In that case either the variable/function
shall be listed as an operand of the @code{asm} statement operand or,
however, make debugging impossible, since variables will no longer stay in a
``home register''.
-Enabled at levels @option{-O2}, @option{-O3}, @option{-Os},
-on targets where the default format for debugging information supports
-variable tracking.
+Enabled by default with @option{-funroll-loops}.
+
+@item -fwhole-program
+@opindex fwhole-program
+Assume that the current compilation unit represents whole program being
+compiled. All public functions and variables with the exception of @code{main}
+and those merged by attribute @code{externally_visible} become static functions
+and in a affect gets more aggressively optimized by interprocedural optimizers.
+While this option is equivalent to proper use of @code{static} keyword for
+programs consisting of single file, in combination with option
+@option{--combine} this flag can be used to compile most of smaller scale C
+programs since the functions and variables become local for the whole combined
+compilation unit, not for the single source file itself.
+
@item -fno-cprop-registers
@opindex fno-cprop-registers
Enable profile feedback directed optimizations, and optimizations
generally profitable only with profile feedback available.
-The following options are enabled: @code{-fbranch-probabilities},
-@code{-fvpt}, @code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer}.
+The following options are enabled: @code{-fbranch-probabilities}, @code{-fvpt},
+@code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer},
+@code{-fno-loop-optimize}.
@end table
The default is @option{-fmath-errno}.
+On Darwin systems, the math library never sets @code{errno}. There is therefore
+no reason for the compiler to consider the possibility that it might,
+and @option{-fno-math-errno} is the default.
+
@item -funsafe-math-optimizations
@opindex funsafe-math-optimizations
Allow optimizations for floating-point arithmetic that (a) assume
Currently the optimizations include specialization of division operation
using the knowledge about the value of the denominator.
-@item -fspeculative-prefetching
-@opindex fspeculative-prefetching
-If combined with @option{-fprofile-arcs}, it instructs the compiler to add
-a code to gather information about addresses of memory references in the
-program.
-
-With @option{-fbranch-probabilities}, it reads back the data gathered
-and issues prefetch instructions according to them. In addition to the opportunities
-noticed by @option{-fprefetch-loop-arrays}, it also notices more complicated
-memory access patterns---for example accesses to the data stored in linked
-list whose elements are usually allocated sequentially.
-
-In order to prevent issuing double prefetches, usage of
-@option{-fspeculative-prefetching} implies @option{-fno-prefetch-loop-arrays}.
-
-Enabled with @option{-fprofile-generate} and @option{-fprofile-use}.
-
@item -frename-registers
@opindex frename-registers
Attempt to avoid false dependencies in scheduled code by making use
make debugging impossible, since variables will no longer stay in
a ``home register''.
-Not enabled by default at any level because it has known bugs.
+Enabled by default with @option{-funroll-loops}.
@item -ftracer
@opindex ftracer
@opindex funroll-loops
Unroll loops whose number of iterations can be determined at compile time or
upon entry to the loop. @option{-funroll-loops} implies
-@option{-frerun-cse-after-loop}. It also turns on complete loop peeling
-(i.e.@: complete removal of loops with small constant number of iterations).
-This option makes code larger, and may or may not make it run faster.
+@option{-frerun-cse-after-loop}, @option{-fweb} and @option{-frename-registers}.
+It also turns on complete loop peeling (i.e.@: complete removal of loops with
+small constant number of iterations). This option makes code larger, and may
+or may not make it run faster.
Enabled with @option{-fprofile-use}.
When performing branch target register load optimization, don't reuse
branch target registers in within any basic block.
+@item -fstack-protector
+Emit extra code to check for buffer overflows, such as stack smashing
+attacks. This is done by adding a guard variable to functions with
+vulnerable objects. This includes functions that call alloca, and
+functions with buffers larger than 8 bytes. The guards are initialized
+when a function is entered and then checked when the function exits.
+If a guard check fails, an error message is printed and the program exits.
+
+@item -fstack-protector-all
+Like @option{-fstack-protector} except that all functions are protected.
+
@item --param @var{name}=@var{value}
@opindex param
In some places, GCC uses various constants to control the amount of
@var{name} are given in the following table:
@table @gcctabopt
+@item salias-max-implicit-fields
+The maximum number of fields in a variable without direct
+structure accesses for which structure aliasing will consider trying
+to track each field. The default is 5
+
@item sra-max-structure-size
The maximum structure size, in bytes, at which the scalar replacement
of aggregates (SRA) optimization will perform block copies. The
enabled and @option{--param max-inline-recursive-depth-auto} is used. The
default value is 450.
+@item min-inline-recursive-probability
+Recursive inlining is profitable only for function having deep recursion
+in average and can hurt for function having little recursion depth by
+increasing the prologue size or complexity of function body to other
+optimizers.
+
+When profile feedback is available (see @option{-fprofile-generate}) the actual
+recursion depth can be guessed from probability that function will recurse via
+given call expression. This parameter limits inlining only to call expression
+whose probability exceeds given threshold (in percents). The default value is
+10.
+
@item inline-call-cost
Specify cost of call instruction relative to simple arithmetics operations
(having cost of 1). Increasing this cost disqualifies inlining of non-leaf
we always try to remove unnecessary ivs from the set during its
optimization when a new iv is added to the set.
+@item scev-max-expr-size
+Bound on size of expressions used in the scalar evolutions analyzer.
+Large expressions slow the analyzer.
+
@item max-iterations-to-track
The maximum number of iterations of a loop the brute force algorithm
compiler's memory usage and increasing its speed. This sets the maximum
value of a shared integer constant's. The default value is 256.
+@item min-virtual-mappings
+Specifies the minimum number of virtual mappings in the incremental
+SSA updater that should be registered to trigger the virtual mappings
+heuristic defined by virtual-mappings-ratio. The default value is
+100.
+
+@item virtual-mappings-ratio
+If the number of virtual mappings is virtual-mappings-ratio bigger
+than the number of virtual symbols to be updated, then the incremental
+SSA updater switches to a full update for those symbols. The default
+ratio is 3.
+
+@item ssp-buffer-size
+The minimum size of buffers (i.e. arrays) that will receive stack smashing
+protection when @option{-fstack-protection} is used.
+
@end table
@end table
that were used to generate code (@option{-fpie}, @option{-fPIE},
or model suboptions) when you specify this option.
+@item -rdynamic
+@opindex rdynamic
+Pass the flag @option{-export-dynamic} to the ELF linker, on targets
+that support it. This instructs the linker to add all symbols, not
+only used ones, to the dynamic symbol table. This option is needed
+for some uses of @code{dlopen} or to allow obtaining backtraces
+from within a program.
+
@item -s
@opindex s
Remove all symbol table and relocation information from the executable.
@option{-specs=@var{file}} can be specified on the command line, and they
are processed in order, from left to right.
+@item --sysroot=@var{dir}
+@opindex sysroot
+Use @var{dir} as the logical root directory for headers and libraries.
+For example, if the compiler would normally search for headers in
+@file{/usr/include} and libraries in @file{/usr/lib}, it will instead
+search @file{@var{dir}/usr/include} and @file{@var{dir}/usr/lib}.
+
+If you use both this option and the @option{-isysroot} option, then
+the @option{--sysroot} option will apply to libraries, but the
+@option{-isysroot} option will apply to header files.
+
+The GNU linker (beginning with version 2.16) has the necessary support
+for this option. If your linker does not support this option, the
+header file aspect of @option{--sysroot} will still work, but the
+library aspect will not.
+
@item -I-
@opindex I-
This option has been deprecated. Please use @option{-iquote} instead for
The value to use for @var{machine} is the same as was specified as the
machine type when configuring GCC as a cross-compiler. For
example, if a cross-compiler was configured with @samp{configure
-i386v}, meaning to compile for an 80386 running System V, then you
-would specify @option{-b i386v} to run that cross compiler.
+arm-elf}, meaning to compile for an arm processor with elf binaries,
+then you would specify @option{-b arm-elf} to run that cross compiler.
+Because there are other options beginning with @option{-b}, the
+configuration must contain a hyphen.
@item -V @var{version}
@opindex V
The argument @var{version} specifies which version of GCC to run.
This is useful when multiple versions are installed. For example,
-@var{version} might be @samp{2.0}, meaning to run GCC version 2.0.
+@var{version} might be @samp{4.0}, meaning to run GCC version 4.0.
@end table
The @option{-V} and @option{-b} options work by running the
options, usually for compatibility with other compilers on the same
platform.
-These options are defined by the macro @code{TARGET_SWITCHES} in the
-machine description. The default for the options is also defined by
-that macro, which enables you to change the defaults.
-
@c This list is ordered alphanumerically by subsection name.
@c It should be the same order and spelling as these options are listed
@c in Machine Dependent Options
* AVR Options::
* Blackfin Options::
* CRIS Options::
+* CRX Options::
* Darwin Options::
* DEC Alpha Options::
* DEC Alpha/VMS Options::
* HPPA Options::
* i386 and x86-64 Options::
* IA-64 Options::
+* M32C Options::
* M32R/D Options::
* M680x0 Options::
* M68hc1x Options::
* MIPS Options::
* MMIX Options::
* MN10300 Options::
-* NS32K Options::
* PDP-11 Options::
* PowerPC Options::
* RS/6000 and PowerPC Options::
@option{-fomit-frame-pointer} removes the frame pointer for all functions
which might make debugging harder.
-@item -mcsync
-@opindex mcsync
+@item -mspecld-anomaly
+@opindex mspecld-anomaly
When enabled, the compiler will ensure that the generated code does not
contain speculative loads after jump instructions. This option is enabled
by default.
-@item -mno-csync
-@opindex mno-csync
+@item -mno-specld-anomaly
+@opindex mno-specld-anomaly
Don't generate extra code to prevent speculative loads from occurring.
+@item -mcsync-anomaly
+@opindex mcsync-anomaly
+When enabled, the compiler will ensure that the generated code does not
+contain CSYNC or SSYNC instructions too soon after conditional branches.
+This option is enabled by default.
+
+@item -mno-csync-anomaly
+@opindex mno-csync-anomaly
+Don't generate extra code to prevent CSYNC or SSYNC instructions from
+occurring too soon after a conditional branch.
+
@item -mlow-64k
-@opindex
+@opindex mlow-64k
When enabled, the compiler is free to take advantage of the knowledge that
the entire program fits into the low 64k of memory.
compiled. Specifying a value of 0 will generate more compact code, specifying
other values will force the allocation of that number to the current
library but is no more space or time efficient than omitting this option.
+
+@item -mlong-calls
+@itemx -mno-long-calls
+@opindex mlong-calls
+@opindex mno-long-calls
+Tells the compiler to perform function calls by first loading the
+address of the function into a register and then performing a subroutine
+call on this register. This switch is needed if the target function
+will lie outside of the 24 bit addressing range of the offset based
+version of subroutine call instruction.
+
+This feature is not enabled by default. Specifying
+@option{-mno-long-calls} will restore the default behavior. Note these
+switches have no effect on how the compiler generates code to handle
+function calls via function pointers.
@end table
@node CRIS Options
0x40000000 and zero-initialized data at 0x80000000.
@end table
+@node CRX Options
+@subsection CRX Options
+@cindex CRX Options
+
+These options are defined specifically for the CRX ports.
+
+@table @gcctabopt
+
+@item -mmac
+@opindex mmac
+Enable the use of multiply-accumulate instructions. Disabled by default.
+
+@item -mpush-args
+@opindex mpush-args
+Push instructions will be used to pass outgoing arguments when functions
+are called. Enabled by default.
+@end table
+
@node Darwin Options
@subsection Darwin Options
@cindex Darwin options
@opindex -gfull
Emit debugging information for all symbols and types.
+@item -mmacosx-version-min=@var{version}
+The earliest version of MacOS X that this executable will run on
+is @var{version}. Typical values of @var{version} include @code{10.1},
+@code{10.2}, and @code{10.3.9}.
+
+The default for this option is to make choices that seem to be most
+useful.
+
@item -mone-byte-bool
@opindex -mone-byte-bool
Override the defaults for @samp{bool} so that @samp{sizeof(bool)==1}.
This switch is mainly for debugging the compiler and will likely be removed
in a future version.
+@item -moptimize-membar
+@opindex moptimize-membar
+
+This switch removes redundant @code{membar} instructions from the
+compiler generated code. It is enabled by default.
+
+@item -mno-optimize-membar
+@opindex mno-optimize-membar
+
+This switch disables the automatic removal of redundant @code{membar}
+instructions from the generated code.
+
@item -mtomcat-stats
@opindex mtomcat-stats
@code{long double} will be modified. Hence they will not be binary
compatible with arrays or structures in code compiled without that switch.
+@item -mmlarge-data-threshold=@var{number}
+@opindex mlarge-data-threshold=@var{number}
+When @option{-mcmodel=medium} is specified, the data greater than
+@var{threshold} are placed in large data section. This value must be the
+same across all object linked into the binary and defaults to 65535.
@item -msvr3-shlib
@itemx -mno-svr3-shlib
value, including any libraries. This includes the system libraries and
startup modules.
+@item -msseregparm
+@opindex msseregparm
+Use SSE register passing conventions for float and double arguments
+and return values. You can control this behavior for a specific
+function by using the function attribute @samp{sseregparm}.
+@xref{Function Attributes}.
+
+@strong{Warning:} if you use this switch then you must build all
+modules with the same value, including any libraries. This includes
+the system libraries and startup modules.
+
@item -mpreferred-stack-boundary=@var{num}
@opindex mpreferred-stack-boundary
Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
@end table
+@node M32C Options
+@subsection M32C Options
+@cindex M32C options
+
+@table @gcctabopt
+@item -mcpu=@var{name}
+@opindex mcpu=
+Select the CPU for which code is generated. @var{name} may be one of
+@samp{r8c} for the R8C/Tiny series, @samp{m16c} for the M16C (up to
+/60) series, @samp{m32cm} for the M16C/80 series, or @samp{m32c} for
+the M32C/80 series.
+
+@item -msim
+@opindex msim
+Specifies that the program will be run on the simulator. This causes
+an alternate runtime library to be linked in which supports, for
+example, file I/O. You must not use this option when generating
+programs that will run on real hardware; you must provide your own
+runtime library for whatever I/O functions are needed.
+
+@item -memregs=@var{number}
+@opindex memregs=
+Specifies the number of memory-based pseudo-registers GCC will use
+during code generation. These pseudo-registers will be used like real
+registers, so there is a tradeoff between GCC's ability to fit the
+code into available registers, and the performance penalty of using
+memory instead of registers. Note that all modules in a program must
+be compiled with the same value for this option. Because of that, you
+must not use this option with the default runtime libraries gcc
+builds.
+
+@end table
+
@node M32R/D Options
@subsection M32R/D Options
@cindex M32R/D options
@samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4},
@samp{mips32}, @samp{mips32r2}, and @samp{mips64}.
The processor names are:
-@samp{4kc}, @samp{4kp}, @samp{5kc}, @samp{20kc},
+@samp{4kc}, @samp{4km}, @samp{4kp},
+@samp{5kc}, @samp{5kf},
+@samp{20kc},
+@samp{24k}, @samp{24kc}, @samp{24kf}, @samp{24kx},
@samp{m4k},
-@samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400},
-@samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000}, @samp{rm7000},
-@samp{rm9000},
@samp{orion},
+@samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400},
+@samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000},
+@samp{rm7000}, @samp{rm9000},
@samp{sb1},
+@samp{sr71000},
@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300},
@samp{vr5000}, @samp{vr5400} and @samp{vr5500}.
The special value @samp{from-abi} selects the
@itemx -mno-mips16
@opindex mips16
@opindex mno-mips16
-Use (do not use) the MIPS16 ISA@.
+Generate (do not generate) MIPS16 code. If GCC is targetting a
+MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE@.
@item -mabi=32
@itemx -mabi=o64
Assume that the floating-point coprocessor supports double-precision
operations. This is the default.
+@itemx -mdsp
+@itemx -mno-dsp
+@opindex mdsp
+@opindex mno-dsp
+Use (do not use) the MIPS DSP ASE. @xref{MIPS DSP Built-in Functions}.
+
@itemx -mpaired-single
@itemx -mno-paired-single
@opindex mpaired-single
Use (do not use) the MIPS-3D ASE@. @xref{MIPS-3D Built-in Functions}.
The option @option{-mips3d} implies @option{-mpaired-single}.
-@item -mint64
-@opindex mint64
-Force @code{int} and @code{long} types to be 64 bits wide. See
-@option{-mlong32} for an explanation of the default and the way
-that the pointer size is determined.
-
-This option has been deprecated and will be removed in a future release.
-
@item -mlong64
@opindex mlong64
Force @code{long} types to be 64 bits wide. See @option{-mlong32} for
This option makes symbolic debugging impossible.
@end table
-@node NS32K Options
-@subsection NS32K Options
-@cindex NS32K options
-
-These are the @samp{-m} options defined for the 32000 series. The default
-values for these options depends on which style of 32000 was selected when
-the compiler was configured; the defaults for the most common choices are
-given below.
-
-@table @gcctabopt
-@item -m32032
-@itemx -m32032
-@opindex m32032
-@opindex m32032
-Generate output for a 32032. This is the default
-when the compiler is configured for 32032 and 32016 based systems.
-
-@item -m32332
-@itemx -m32332
-@opindex m32332
-@opindex m32332
-Generate output for a 32332. This is the default
-when the compiler is configured for 32332-based systems.
-
-@item -m32532
-@itemx -m32532
-@opindex m32532
-@opindex m32532
-Generate output for a 32532. This is the default
-when the compiler is configured for 32532-based systems.
-
-@item -m32081
-@opindex m32081
-Generate output containing 32081 instructions for floating point.
-This is the default for all systems.
-
-@item -m32381
-@opindex m32381
-Generate output containing 32381 instructions for floating point. This
-also implies @option{-m32081}. The 32381 is only compatible with the 32332
-and 32532 cpus. This is the default for the pc532-netbsd configuration.
-
-@item -mmulti-add
-@opindex mmulti-add
-Try and generate multiply-add floating point instructions @code{polyF}
-and @code{dotF}. This option is only available if the @option{-m32381}
-option is in effect. Using these instructions requires changes to
-register allocation which generally has a negative impact on
-performance. This option should only be enabled when compiling code
-particularly likely to make heavy use of multiply-add instructions.
-
-@item -mnomulti-add
-@opindex mnomulti-add
-Do not try and generate multiply-add floating point instructions
-@code{polyF} and @code{dotF}. This is the default on all platforms.
-
-@item -msoft-float
-@opindex msoft-float
-Generate output containing library calls for floating point.
-@strong{Warning:} the requisite libraries may not be available.
-
-@item -mieee-compare
-@itemx -mno-ieee-compare
-@opindex mieee-compare
-@opindex mno-ieee-compare
-Control whether or not the compiler uses IEEE floating point
-comparisons. These handle correctly the case where the result of a
-comparison is unordered.
-@strong{Warning:} the requisite kernel support may not be available.
-
-@item -mnobitfield
-@opindex mnobitfield
-Do not use the bit-field instructions. On some machines it is faster to
-use shifting and masking operations. This is the default for the pc532.
-
-@item -mbitfield
-@opindex mbitfield
-Do use the bit-field instructions. This is the default for all platforms
-except the pc532.
-
-@item -mrtd
-@opindex mrtd
-Use a different function-calling convention, in which functions
-that take a fixed number of arguments return pop their
-arguments on return with the @code{ret} instruction.
-
-This calling convention is incompatible with the one normally
-used on Unix, so you cannot use it if you need to call libraries
-compiled with the Unix compiler.
-
-Also, you must provide function prototypes for all functions that
-take variable numbers of arguments (including @code{printf});
-otherwise incorrect code will be generated for calls to those
-functions.
-
-In addition, seriously incorrect code will result if you call a
-function with too many arguments. (Normally, extra arguments are
-harmlessly ignored.)
-
-This option takes its name from the 680x0 @code{rtd} instruction.
-
-
-@item -mregparam
-@opindex mregparam
-Use a different function-calling convention where the first two arguments
-are passed in registers.
-
-This calling convention is incompatible with the one normally
-used on Unix, so you cannot use it if you need to call libraries
-compiled with the Unix compiler.
-
-@item -mnoregparam
-@opindex mnoregparam
-Do not pass any arguments in registers. This is the default for all
-targets.
-
-@item -msb
-@opindex msb
-It is OK to use the sb as an index register which is always loaded with
-zero. This is the default for the pc532-netbsd target.
-
-@item -mnosb
-@opindex mnosb
-The sb register is not available for use or has not been initialized to
-zero by the run time system. This is the default for all targets except
-the pc532-netbsd. It is also implied whenever @option{-mhimem} or
-@option{-fpic} is set.
-
-@item -mhimem
-@opindex mhimem
-Many ns32000 series addressing modes use displacements of up to 512MB@.
-If an address is above 512MB then displacements from zero can not be used.
-This option causes code to be generated which can be loaded above 512MB@.
-This may be useful for operating systems or ROM code.
-
-@item -mnohimem
-@opindex mnohimem
-Assume code will be loaded in the first 512MB of virtual address space.
-This is the default for all platforms.
-
-@end table
-
@node PDP-11 Options
@subsection PDP-11 Options
@cindex PDP-11 Options
@samp{860}, @samp{970}, @samp{8540}, @samp{common}, @samp{ec603e}, @samp{G3},
@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3},
@samp{power4}, @samp{power5}, @samp{powerpc}, @samp{powerpc64},
-@samp{rios}, @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64a}.
+@samp{rios}, @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64}.
@option{-mcpu=common} selects a completely generic processor. Code
generated under this option will run on any POWER or PowerPC processor.
architecture, registers, and mnemonics set by @option{-mcpu}, but the
scheduling parameters set by @option{-mtune}.
+@item -mswdiv
+@itemx -mno-swdiv
+@opindex mswdiv
+@opindex mno-swdiv
+Generate code to compute division as reciprocal estimate and iterative
+refinement, creating opportunities for increased throughput. This
+feature requires: optional PowerPC Graphics instruction set for single
+precision and FRE instruction for double precision, assuming divides
+cannot generate user-visible traps, and the domain values not include
+Infinities, denormals or zero denominator.
+
@item -maltivec
@itemx -mno-altivec
@opindex maltivec
@option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
enhancements.
+@item -mvrsave
+@item -mno-vrsave
+@opindex mvrsave
+@opindex mno-vrsave
+Generate VRSAVE instructions when generating AltiVec code.
+
@item -mabi=spe
@opindex mabi=spe
Extend the current ABI with SPE ABI extensions. This does not change
@opindex mabi=no-spe
Disable Booke SPE ABI extensions for the current ABI@.
-@item -misel=@var{yes/no}
-@itemx -misel
+@item -msecure-plt
+@opindex msecure-plt
+Generate code that allows ld and ld.so to build executables and shared
+libraries with non-exec .plt and .got sections. This is a PowerPC
+32-bit SYSV ABI option.
+
+@item -mbss-plt
+@opindex mbss-plt
+Generate code that uses a BSS .plt section that ld.so fills in, and
+requires .plt and .got sections that are both writable and executable.
+This is a PowerPC 32-bit SYSV ABI option.
+
+@item -misel
+@itemx -mno-isel
@opindex misel
+@opindex mno-isel
This switch enables or disables the generation of ISEL instructions.
-@item -mspe=@var{yes/no}
-@itemx -mspe
+@item -misel=@var{yes/no}
+This switch has been deprecated. Use @option{-misel} and
+@option{-mno-isel} instead.
+
+@item -mspe
+@itemx -mno-isel
@opindex mspe
+@opindex mno-spe
This switch enables or disables the generation of SPE simd
instructions.
+@item -mspe=@var{yes/no}
+This option has been deprecated. Use @option{-mspe} and
+@option{-mno-spe} instead.
+
@item -mfloat-gprs=@var{yes/single/double/no}
@itemx -mfloat-gprs
@opindex mfloat-gprs
Return structures smaller than 8 bytes in registers (as specified by the
SVR4 ABI)@.
-@item -mabi=altivec
-@opindex mabi=altivec
-Extend the current ABI with AltiVec ABI extensions. This does not
-change the default ABI, instead it adds the AltiVec ABI extensions to
-the current ABI@.
-
-@item -mabi=no-altivec
-@opindex mabi=no-altivec
-Disable AltiVec ABI extensions for the current ABI@.
+@item -mabi=@var{abi-type}
+@opindex mabi
+Extend the current ABI with a particular extension, or remove such extension.
+Valid values are @var{altivec}, @var{no-altivec}, @var{spe},
+@var{no-spe}@.
@item -mprototype
@itemx -mno-prototype
@opindex mno-mvcle
Generate (or do not generate) code using the @code{mvcle} instruction
to perform block moves. When @option{-mno-mvcle} is specified,
-use a @code{mvc} loop instead. This is the default.
+use a @code{mvc} loop instead. This is the default unless optimizing for
+size.
@item -mdebug
@itemx -mno-debug
@item -mieee
@opindex mieee
Increase IEEE-compliance of floating-point code.
+At the moment, this is equivalent to @option{-fno-finite-math-only}.
+When generating 16 bit SH opcodes, getting IEEE-conforming results for
+comparisons of NANs / infinities incurs extra overhead in every
+floating point comparison, therefore the default is set to
+@option{-ffinite-math-only}.
@item -misize
@opindex misize
entries, after fixing up a trampoline. This library function call
doesn't assume it can write to the whole memory address space. This
is the default when the target is @code{sh-*-linux*}.
+
+@item -multcost=@var{number}
+@opindex multcost=@var{number}
+Set the cost to assume for a multiply insn.
+
+@item -mdiv=@var{strategy}
+@opindex mdiv=@var{strategy}
+Set the division strategy to use for SHmedia code. @var{strategy} must be
+one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call,
+inv:call2, inv:fp .
+"fp" performs the operation in floating point. This has a very high latency,
+but needs only a few instructions, so it might be a good choice if
+your code has enough easily exploitable ILP to allow the compiler to
+schedule the floating point instructions together with other instructions.
+Division by zero causes a floating point exception.
+"inv" uses integer operations to calculate the inverse of the divisor,
+and then multiplies the dividend with the inverse. This strategy allows
+cse and hoisting of the inverse calculation. Division by zero calculates
+an unspecified result, but does not trap.
+"inv:minlat" is a variant of "inv" where if no cse / hoisting opportunities
+have been found, or if the entire operation has been hoisted to the same
+place, the last stages of the inverse calculation are intertwined with the
+final multiply to reduce the overall latency, at the expense of using a few
+more instructions, and thus offering fewer scheduling opportunities with
+other code.
+"call" calls a library function that usually implements the inv:minlat
+strategy.
+This gives high code density for m5-*media-nofpu compilations.
+"call2" uses a different entry point of the same library function, where it
+assumes that a pointer to a lookup table has already been set up, which
+exposes the pointer load to cse / code hoisting optimizations.
+"inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm for initial
+code generation, but if the code stays unoptimized, revert to the "call",
+"call2", or "fp" strategies, respectively. Note that the
+potentially-trapping side effect of division by zero is carried by a
+separate instruction, so it is possible that all the integer instructions
+are hoisted out, but the marker for the side effect stays where it is.
+A recombination to fp operations or a call is not possible in that case.
+"inv20u" and "inv20l" are variants of the "inv:minlat" strategy. In the case
+that the inverse calculation was nor separated from the multiply, they speed
+up division where the dividend fits into 20 bits (plus sign where applicable),
+by inserting a test to skip a number of operations in this case; this test
+slows down the case of larger dividends. inv20u assumes the case of a such
+a small dividend to be unlikely, and inv20l assumes it to be likely.
+
+@item -mdivsi3_libfunc=@var{name}
+@opindex mdivsi3_libfunc=@var{name}
+Set the name of the library function used for 32 bit signed division to
+@var{name}. This only affect the name used in the call and inv:call
+division strategies, and the compiler will still expect the same
+sets of input/output/clobbered registers as if this option was not present.
+
+@item -madjust-unroll
+@opindex madjust-unroll
+Throttle unrolling to avoid thrashing target registers.
+This option only has an effect if the gcc code base supports the
+TARGET_ADJUST_UNROLL_MAX target hook.
+
+@item -mindexed-addressing
+@opindex mindexed-addressing
+Enable the use of the indexed addressing mode for SHmedia32/SHcompact.
+This is only safe if the hardware and/or OS implement 32 bit wrap-around
+semantics for the indexed addressing mode. The architecture allows the
+implementation of processors with 64 bit MMU, which the OS could use to
+get 32 bit addressing, but since no current hardware implementation supports
+this or any other way to make the indexed addressing mode safe to use in
+the 32 bit ABI, the default is -mno-indexed-addressing.
+
+@item -mgettrcost=@var{number}
+@opindex mgettrcost=@var{number}
+Set the cost assumed for the gettr instruction to @var{number}.
+The default is 2 if @option{-mpt-fixed} is in effect, 100 otherwise.
+
+@item -mpt-fixed
+@opindex mpt-fixed
+Assume pt* instructions won't trap. This will generally generate better
+scheduled code, but is unsafe on current hardware. The current architecture
+definition says that ptabs and ptrel trap when the target anded with 3 is 3.
+This has the unintentional effect of making it unsafe to schedule ptabs /
+ptrel before a branch, or hoist it out of a loop. For example,
+__do_global_ctors, a part of libgcc that runs constructors at program
+startup, calls functions in a list which is delimited by -1. With the
+-mpt-fixed option, the ptabs will be done before testing against -1.
+That means that all the constructors will be run a bit quicker, but when
+the loop comes to the end of the list, the program crashes because ptabs
+loads -1 into a target register. Since this option is unsafe for any
+hardware implementing the current architecture specification, the default
+is -mno-pt-fixed. Unless the user specifies a specific cost with
+@option{-mgettrcost}, -mno-pt-fixed also implies @option{-mgettrcost=100};
+this deters register allocation using target registers for storing
+ordinary integers.
+
+@item -minvalid-symbols
+@opindex minvalid-symbols
+Assume symbols might be invalid. Ordinary function symbols generated by
+the compiler will always be valid to load with movi/shori/ptabs or
+movi/shori/ptrel, but with assembler and/or linker tricks it is possible
+to generate symbols that will cause ptabs / ptrel to trap.
+This option is only meaningful when @option{-mno-pt-fixed} is in effect.
+It will then prevent cross-basic-block cse, hoisting and most scheduling
+of symbol loads. The default is @option{-mno-invalid-symbols}.
@end table
@node SPARC Options
Usually these options are used when @option{-pie} GCC option will be
used during linking.
+@item -fno-jump-tables
+@opindex fno-jump-tables
+Do not use jump tables for switch statements even where it would be
+more efficient than other code generation strategies. This option is
+of use in conjunction with @option{-fpic} or @option{-fPIC} for
+building code which forms part of a dynamic linker and cannot
+reference the address of a jump table. On some targets, jump tables
+do not require a GOT and this option is not needed.
+
@item -ffixed-@var{reg}
@opindex ffixed
Treat the register named @var{reg} as a fixed register; generated code
@samp{#pragma GCC visibility} of use. This works by you enclosing
the declarations you wish to set visibility for with (for example)
@samp{#pragma GCC visibility push(hidden)} and
-@samp{#pragma GCC visibility pop}. These can be nested up to sixteen
-times. Bear in mind that symbol visibility should be viewed @strong{as
+@samp{#pragma GCC visibility pop}.
+Bear in mind that symbol visibility should be viewed @strong{as
part of the API interface contract} and thus all new code should
always specify visibility when it is not the default ie; declarations
only for use within the local DSO should @strong{always} be marked explicitly
`precompile' a header file; then, if builds can use the precompiled
header file they will be much faster.
-@strong{Caution:} There are a few known situations where GCC will
-crash when trying to use a precompiled header. If you have trouble
-with a precompiled header, you should remove the precompiled header
-and compile without it. In addition, please use GCC's on-line
-defect-tracking system to report any problems you encounter with
-precompiled headers. @xref{Bugs}.
-
To create a precompiled header file, simply compile it as you would any
other file, if necessary using the @option{-x} option to make the driver
treat it as a C or C++ header file. You will probably want to use a
compilation.
@item
-The precompiled header file must be produced by the same compiler
-version and configuration as the current compilation is using.
-The easiest way to guarantee this is to use the same compiler binary
-for creating and using precompiled headers.
+The precompiled header file must have been produced by the same compiler
+binary as the current compilation is using.
@item
Any macros defined before the precompiled header is included must
either be defined in the same way as when the precompiled header was
generated, or must not affect the precompiled header, which usually
-means that the they don't appear in the precompiled header at all.
+means that they don't appear in the precompiled header at all.
The @option{-D} option is one way to define a macro before a
precompiled header is included; using a @code{#define} can also do it.
is to use exactly the same options when generating and using the
precompiled header. The following are known to be safe:
-@gccoptlist{-fpreprocessed -pedantic-errors}
+@gccoptlist{-fpreprocessed
+-fsched-interblock -fsched-spec -fsched-spec-load -fsched-spec-load-dangerous
+-fsched-verbose=<number> -fschedule-insns
+-pedantic-errors}
@end itemize
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