@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
-@c 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+@c 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
@ignore
@c man begin COPYRIGHT
Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
-1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
@c man end
@c man begin BUGS
For instructions on reporting bugs, see
-@w{@uref{http://gcc.gnu.org/bugs.html}}. Use of the @command{gccbug}
-script to report bugs is recommended.
+@w{@uref{http://gcc.gnu.org/bugs.html}}.
@c man end
@c man begin AUTHOR
See the Info entry for @command{gcc}, or
-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 -Wsynth}
+-Wsign-promo}
@item Objective-C and Objective-C++ Language Options
@xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling
-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
+-w -Wextra -Wall -Waggregate-return -Wno-attributes @gol
-Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol
-Wconversion -Wno-deprecated-declarations @gol
--Wdisabled-optimization -Wno-div-by-zero -Wendif-labels @gol
+-Wdisabled-optimization -Wno-div-by-zero -Wno-endif-labels @gol
-Werror -Werror-implicit-function-declaration @gol
-Wfatal-errors -Wfloat-equal -Wformat -Wformat=2 @gol
-Wno-format-extra-args -Wformat-nonliteral @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
-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
-Wswitch -Wswitch-default -Wswitch-enum @gol
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
-Wmissing-prototypes -Wnested-externs -Wold-style-definition @gol
-Wstrict-prototypes -Wtraditional @gol
--Wdeclaration-after-statement}
+-Wdeclaration-after-statement -Wno-pointer-sign}
@item Debugging Options
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
-fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol
-fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol
-fdump-tree-nrv -fdump-tree-vect @gol
+-fdump-tree-sink @gol
-fdump-tree-sra@r{[}-@var{n}@r{]} @gol
+-fdump-tree-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
-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
-fbounds-check -fmudflap -fmudflapth -fmudflapir @gol
-fbranch-probabilities -fprofile-values -fvpt -fbranch-target-load-optimize @gol
-fbranch-target-load-optimize2 -fbtr-bb-exclusive @gol
--fcaller-saves -fcprop-registers @gol
--fcse-follow-jumps -fcse-skip-blocks -fdata-sections @gol
+-fcaller-saves -fcprop-registers -fcse-follow-jumps @gol
+-fcse-skip-blocks -fcx-limited-range -fdata-sections @gol
-fdelayed-branch -fdelete-null-pointer-checks @gol
-fexpensive-optimizations -ffast-math -ffloat-store @gol
-fforce-addr -fforce-mem -ffunction-sections @gol
-floop-optimize -fcrossjumping -fif-conversion -fif-conversion2 @gol
-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol
-fkeep-static-consts -fmerge-constants -fmerge-all-constants @gol
--fmodulo-sched -fnew-ra -fno-branch-count-reg @gol
+-fmodulo-sched -fno-branch-count-reg @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
-fstrength-reduce -fstrict-aliasing -ftracer -fthread-jumps @gol
-funroll-all-loops -funroll-loops -fpeel-loops @gol
-fsplit-ivs-in-unroller -funswitch-loops @gol
+-fvariable-expansion-in-unroller @gol
-ftree-pre -ftree-ccp -ftree-dce -ftree-loop-optimize @gol
-ftree-loop-linear -ftree-loop-im -ftree-loop-ivcanon -fivopts @gol
--ftree-dominator-opts -ftree-dse -ftree-copyrename @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 -fweb @gol
+-ftree-copy-prop -ftree-store-ccp -ftree-store-copy-prop @gol
--param @var{name}=@var{value}
-O -O0 -O1 -O2 -O3 -Os}
@gccoptlist{-mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts @gol
-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}
+
@emph{CRIS Options}
@gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol
-mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol
-mvliw-branch -mno-vliw-branch @gol
-mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol
-mno-nested-cond-exec -mtomcat-stats @gol
+-mTLS -mtls @gol
-mcpu=@var{cpu}}
@emph{H8/300 Options}
@emph{IA-64 Options}
@gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol
--mvolatile-asm-stop -mb-step -mregister-names -mno-sdata @gol
+-mvolatile-asm-stop -mregister-names -mno-sdata @gol
-mconstant-gp -mauto-pic -minline-float-divide-min-latency @gol
-minline-float-divide-max-throughput @gol
-minline-int-divide-min-latency @gol
--minline-int-divide-max-throughput -mno-dwarf2-asm @gol
--mfixed-range=@var{register-range}}
+-minline-int-divide-max-throughput @gol
+-minline-sqrt-min-latency -minline-sqrt-max-throughput @gol
+-mno-dwarf2-asm -mearly-stop-bits @gol
+-mfixed-range=@var{register-range} -mtls-size=@var{tls-size} @gol
+-mtune=@var{cpu-type} -mt -pthread -milp32 -mlp64}
@emph{M32R/D Options}
@gccoptlist{-m32r2 -m32rx -m32r @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 @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
-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol
-mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol
-mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol
--mfix-vr4120 -mno-fix-vr4120 -mfix-sb1 -mno-fix-sb1 @gol
+-mfix-vr4120 -mno-fix-vr4120 -mfix-vr4130 @gol
+-mfix-sb1 -mno-fix-sb1 @gol
-mflush-func=@var{func} -mno-flush-func @gol
-mbranch-likely -mno-branch-likely @gol
-mfp-exceptions -mno-fp-exceptions @gol
-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol
-mnew-mnemonics -mold-mnemonics @gol
-mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol
--m64 -m32 -mxl-call -mno-xl-call -mpe @gol
+-m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol
-malign-power -malign-natural @gol
-msoft-float -mhard-float -mmultiple -mno-multiple @gol
-mstring -mno-string -mupdate -mno-update @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
--mfloat-gprs=yes -mfloat-gprs=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
-msdata=@var{opt} -mvxworks -mwindiss -G @var{num} -pthread}
@emph{S/390 and zSeries Options}
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
--mhard-float -msoft-float -mbackchain -mno-backchain -mkernel-backchain @gol
+-mhard-float -msoft-float -mbackchain -mno-backchain @gol
+-mpacked-stack -mno-packed-stack @gol
-msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol
-m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol
-mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd @gol
-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.
to pass all the source files to the compiler at once (for those
languages for which the compiler can handle this). This will allow
intermodule analysis (IMA) to be performed by the compiler. Currently the only
-language for which this is supported is C. If you pass source files for
+language for which this is supported is C@. If you pass source files for
multiple languages to the driver, using this option, the driver will invoke
the compiler(s) that support IMA once each, passing each compiler all the
source files appropriate for it. For those languages that do not support
IMA this option will be ignored, and the compiler will be invoked once for
each source file in that language. If you use this option in conjunction
-with -save-temps, the compiler will generate multiple pre-processed files
-(one for each source file), but only one (combined) .o or .s file.
+with @option{-save-temps}, the compiler will generate multiple
+pre-processed files
+(one for each source file), but only one (combined) @file{.o} or
+@file{.s} file.
@item --help
@opindex help
@item --version
@opindex version
-Display the version number and copyrights of the invoked GCC.
+Display the version number and copyrights of the invoked GCC@.
@end table
@node Invoking G++
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.
+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
@opindex fms-extensions
Accept some non-standard constructs used in Microsoft header files.
+Some cases of unnamed fields in structures and unions are only
+accepted with this option. @xref{Unnamed Fields,,Unnamed struct/union
+fields within structs/unions}, for details.
+
@item -trigraphs
@opindex trigraphs
Support ISO C trigraphs. The @option{-ansi} option (and @option{-std}
@opindex no-integrated-cpp
Performs a compilation in two passes: preprocessing and compiling. This
option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the
-@option{-B} option. The user supplied compilation step can then add in
+@option{-B} option. The user supplied compilation step can then add in
an additional preprocessing step after normal preprocessing but before
-compiling. The default is to use the integrated cpp (internal cpp)
+compiling. The default is to use the integrated cpp (internal cpp)
The semantics of this option will change if "cc1", "cc1plus", and
"cc1obj" are merged.
@item -fabi-version=@var{n}
@opindex fabi-version
-Use version @var{n} of the C++ ABI. Version 2 is the version of the
+Use version @var{n} of the C++ ABI@. Version 2 is the version of the
C++ ABI that first appeared in G++ 3.4. Version 1 is the version of
the C++ ABI that first appeared in G++ 3.2. Version 0 will always be
the version that conforms most closely to the C++ ABI specification.
Causes all inlined methods to be marked 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
+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. While
+dynamic export table when the library makes heavy use of templates. While
it can cause bloating through duplication of code within each DSO where
it is used, often the wastage is less than the considerable space occupied
by a long symbol name in the export table which is typical when using
-templates and namespaces. For even more savings, combine with the
-@code{-fvisibility=hidden} switch.
+templates and namespaces. For even more savings, combine with the
+@option{-fvisibility=hidden} switch.
@item -fno-weak
@opindex fno-weak
@item -Wabi @r{(C++ only)}
@opindex Wabi
Warn when G++ generates code that is probably not compatible with the
-vendor-neutral C++ ABI. Although an effort has been made to warn about
+vendor-neutral C++ ABI@. Although an effort has been made to warn about
all such cases, there are probably some cases that are not warned about,
even though G++ is generating incompatible code. There may also be
cases where warnings are emitted even though the code that is generated
@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
the same size. Previous versions of G++ would try to preserve
unsignedness, but the standard mandates the current behavior.
-@item -Wsynth @r{(C++ only)}
-@opindex Wsynth
-@cindex warning for synthesized methods
-@cindex synthesized methods, warning
-Warn when G++'s synthesis behavior does not match that of cfront. For
-instance:
-
@smallexample
struct A @{
operator int ();
any language supported by GCC@.
Note that since Objective-C is an extension of the C language, Objective-C
-compilations may also use options specific to the C front-end (e.g.,
+compilations may also use options specific to the C front-end (e.g.,
@option{-Wtraditional}). Similarly, Objective-C++ compilations may use
C++-specific options (e.g., @option{-Wabi}).
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
every method in the protocol that is not implemented by the class. The
default behavior is to issue a warning for every method not explicitly
implemented in the class, even if a method implementation is inherited
-from the superclass. If you use the @code{-Wno-protocol} option, then
+from the superclass. If you use the @option{-Wno-protocol} option, then
methods inherited from the superclass are considered to be implemented,
and no warning is issued for them.
during compilation. Because these checks scan the method table only at
the end of compilation, these warnings are not produced if the final
stage of compilation is not reached, for example because an error is
-found during compilation, or because the @code{-fsyntax-only} option is
+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
@code{@@interface} or @code{@@protocol} declaration, or implicitly in
an @code{@@implementation} section. This option always performs its
checks as soon as a @code{@@selector(@dots{})} expression is found,
-while @code{-Wselector} only performs its checks in the final stage of
+while @option{-Wselector} only performs its checks in the final stage of
compilation. This also enforces the coding style convention
that methods and selectors must be declared before being used.
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
Warn if an array subscript has type @code{char}. This is a common cause
of error, as programmers often forget that this type is signed on some
machines.
+This warning is enabled by @option{-Wall}.
@item -Wcomment
@opindex Wcomment
Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}
comment, or whenever a Backslash-Newline appears in a @samp{//} comment.
+This warning is enabled by @option{-Wall}.
@item -Wfatal-errors
@opindex Wfatal-errors
@item -Wformat
@opindex Wformat
+@opindex ffreestanding
+@opindex fno-builtin
Check calls to @code{printf} and @code{scanf}, etc., to make sure that
the arguments supplied have types appropriate to the format string
specified, and that the conversions specified in the format string make
attributes (@pxref{Function Attributes}), in the @code{printf},
@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
not in the C standard) families (or other target-specific families).
+Which functions are checked without format attributes having been
+specified depends on the standard version selected, and such checks of
+functions without the attribute specified are disabled by
+@option{-ffreestanding} or @option{-fno-builtin}.
The formats are checked against the format features supported by GNU
libc version 2.2. These include all ISO C90 and C99 features, as well
@item -Wimplicit-int
@opindex Wimplicit-int
Warn when a declaration does not specify a type.
+This warning is enabled by @option{-Wall}.
@item -Wimplicit-function-declaration
@itemx -Werror-implicit-function-declaration
@opindex Wimplicit-function-declaration
@opindex Werror-implicit-function-declaration
Give a warning (or error) whenever a function is used before being
-declared.
+declared. The form @option{-Wno-error-implicit-function-declaration}
+is not supported.
+This warning is enabled by @option{-Wall} (as a warning, not an error).
@item -Wimplicit
@opindex Wimplicit
Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}.
+This warning is enabled by @option{-Wall}.
@item -Wmain
@opindex Wmain
Warn if the type of @samp{main} is suspicious. @samp{main} should be a
function with external linkage, returning int, taking either zero
arguments, two, or three arguments of appropriate types.
+This warning is enabled by @option{-Wall}.
@item -Wmissing-braces
@opindex Wmissing-braces
int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
@end smallexample
+This warning is enabled by @option{-Wall}.
+
@item -Wmissing-include-dirs @r{(C, C++, Objective-C and Objective-C++ only)}
@opindex Wmissing-include-dirs
Warn if a user-supplied include directory does not exist.
@end group
@end smallexample
+This warning is enabled by @option{-Wall}.
+
@item -Wsequence-point
@opindex Wsequence-point
Warn about code that may have undefined semantics because of violations
definitions, may be found on the GCC readings page, at
@w{@uref{http://gcc.gnu.org/readings.html}}.
+This warning is enabled by @option{-Wall}.
+
@item -Wreturn-type
@opindex Wreturn-type
Warn whenever a function is defined with a return-type that defaults to
message, even when @option{-Wno-return-type} is specified. The only
exceptions are @samp{main} and functions defined in system headers.
+This warning is enabled by @option{-Wall}.
+
@item -Wswitch
@opindex Wswitch
Warn whenever a @code{switch} statement has an index of enumerated type
enumeration. (The presence of a @code{default} label prevents this
warning.) @code{case} labels outside the enumeration range also
provoke warnings when this option is used.
+This warning is enabled by @option{-Wall}.
@item -Wswitch-default
@opindex Wswitch-switch
@opindex Wtrigraphs
Warn if any trigraphs are encountered that might change the meaning of
the program (trigraphs within comments are not warned about).
+This warning is enabled by @option{-Wall}.
@item -Wunused-function
@opindex Wunused-function
Warn whenever a static function is declared but not defined or a
non\-inline static function is unused.
+This warning is enabled by @option{-Wall}.
@item -Wunused-label
@opindex Wunused-label
Warn whenever a label is declared but not used.
+This warning is enabled by @option{-Wall}.
To suppress this warning use the @samp{unused} attribute
(@pxref{Variable Attributes}).
@opindex Wunused-variable
Warn whenever a local variable or non-constant static variable is unused
aside from its declaration
+This warning is enabled by @option{-Wall}.
To suppress this warning use the @samp{unused} attribute
(@pxref{Variable Attributes}).
@item -Wunused-value
@opindex Wunused-value
Warn whenever a statement computes a result that is explicitly not used.
+This warning is enabled by @option{-Wall}.
To suppress this warning cast the expression to @samp{void}.
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
you use that never return as @code{noreturn}. @xref{Function
Attributes}.
+This warning is enabled by @option{-Wall}.
+
@item -Wunknown-pragmas
@opindex Wunknown-pragmas
@cindex warning for unknown pragmas
@opindex Wstrict-aliasing
This option is only active when @option{-fstrict-aliasing} is active.
It warns about code which might break the strict aliasing rules that the
-compiler is using for optimization. The warning does not catch all
-cases, but does attempt to catch the more common pitfalls. It is
+compiler is using for optimization. The warning does not catch all
+cases, but does attempt to catch the more common pitfalls. It is
included in @option{-Wall}.
@item -Wstrict-aliasing=2
@opindex Wundef
Warn if an undefined identifier is evaluated in an @samp{#if} directive.
-@item -Wendif-labels
+@item -Wno-endif-labels
+@opindex Wno-endif-labels
@opindex Wendif-labels
-Warn whenever an @samp{#else} or an @samp{#endif} are followed by text.
+Do not warn whenever an @samp{#else} or an @samp{#endif} are followed by text.
@item -Wshadow
@opindex Wshadow
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
Usually they indicate a typo in the user's code, as they have
implementation-defined values, and should not be used in portable code.
+@item -Wnormalized=<none|id|nfc|nfkc>
+@opindex Wnormalized
+@cindex NFC
+@cindex NFKC
+@cindex character set, input normalization
+In ISO C and ISO C++, two identifiers are different if they are
+different sequences of characters. However, sometimes when characters
+outside the basic ASCII character set are used, you can have two
+different character sequences that look the same. To avoid confusion,
+the ISO 10646 standard sets out some @dfn{normalization rules} which
+when applied ensure that two sequences that look the same are turned into
+the same sequence. GCC can warn you if you are using identifiers which
+have not been normalized; this option controls that warning.
+
+There are four levels of warning that GCC supports. The default is
+@option{-Wnormalized=nfc}, which warns about any identifier which is
+not in the ISO 10646 ``C'' normalized form, @dfn{NFC}. NFC is the
+recommended form for most uses.
+
+Unfortunately, there are some characters which ISO C and ISO C++ allow
+in identifiers that when turned into NFC aren't allowable as
+identifiers. That is, there's no way to use these symbols in portable
+ISO C or C++ and have all your identifiers in NFC.
+@option{-Wnormalized=id} suppresses the warning for these characters.
+It is hoped that future versions of the standards involved will correct
+this, which is why this option is not the default.
+
+You can switch the warning off for all characters by writing
+@option{-Wnormalized=none}. You would only want to do this if you
+were using some other normalization scheme (like ``D''), because
+otherwise you can easily create bugs that are literally impossible to see.
+
+Some characters in ISO 10646 have distinct meanings but look identical
+in some fonts or display methodologies, especially once formatting has
+been applied. For instance @code{\u207F}, ``SUPERSCRIPT LATIN SMALL
+LETTER N'', will display just like a regular @code{n} which has been
+placed in a superscript. ISO 10646 defines the @dfn{NFKC}
+normalisation scheme to convert all these into a standard form as
+well, and GCC will warn if your code is not in NFKC if you use
+@option{-Wnormalized=nfkc}. This warning is comparable to warning
+about every identifier that contains the letter O because it might be
+confused with the digit 0, and so is not the default, but may be
+useful as a local coding convention if the programming environment is
+unable to be fixed to display these characters distinctly.
+
@item -Wno-deprecated-declarations
@opindex Wno-deprecated-declarations
Do not warn about uses of functions, variables, and types marked as
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
complex; GCC will refuse to optimize programs when the optimization
itself is likely to take inordinate amounts of time.
+@item -Wno-pointer-sign
+@opindex Wno-pointer-sign
+Don't warn for pointer argument passing or assignment with different signedness.
+Only useful in the negative form since this warning is enabled by default.
+This option is only supported for C and Objective-C@.
+
@item -Werror
@opindex Werror
Make all warnings into errors.
execution the program records how many times each branch and call is
executed and how many times it is taken or returns. When the compiled
program exits it saves this data to a file called
-@file{@var{auxname}.gcda} for each source file. The data may be used for
+@file{@var{auxname}.gcda} for each source file. The data may be used for
profile-directed optimizations (@option{-fbranch-probabilities}), or for
-test coverage analysis (@option{-ftest-coverage}). Each object file's
+test coverage analysis (@option{-ftest-coverage}). Each object file's
@var{auxname} is generated from the name of the output file, if
explicitly specified and it is not the final executable, otherwise it is
-the basename of the source file. In both cases any suffix is removed
+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
+@opindex coverage
+
+This option is used to compile and link code instrumented for coverage
+analysis. The option is a synonym for @option{-fprofile-arcs}
+@option{-ftest-coverage} (when compiling) and @option{-lgcov} (when
+linking). See the documentation for those options for more details.
@itemize
@item
Compile the source files with @option{-fprofile-arcs} plus optimization
-and code generation options. For test coverage analysis, use the
-additional @option{-ftest-coverage} option. You do not need to profile
+and code generation options. For test coverage analysis, use the
+additional @option{-ftest-coverage} option. You do not need to profile
every source file in a program.
@item
@item
Run the program on a representative workload to generate the arc profile
-information. This may be repeated any number of times. You can run
+information. This may be repeated any number of times. You can run
concurrent instances of your program, and provided that the file system
-supports locking, the data files will be correctly updated. Also
+supports locking, the data files will be correctly updated. Also
@code{fork} calls are detected and correctly handled (double counting
will not happen).
@item
For test coverage analysis, use @command{gcov} to produce human readable
-information from the @file{.gcno} and @file{.gcda} files. Refer to the
+information from the @file{.gcno} and @file{.gcda} files. Refer to the
@command{gcov} documentation for further information.
@end itemize
@opindex ftest-coverage
Produce a notes file that the @command{gcov} code-coverage utility
(@pxref{Gcov,, @command{gcov}---a Test Coverage Program}) can use to
-show program coverage. Each source file's note file is called
-@file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option
+show program coverage. Each source file's note file is called
+@file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option
above for a description of @var{auxname} and instructions on how to
-generate test coverage data. Coverage data will match the source files
+generate test coverage data. Coverage data will match the source files
more closely, if you do not optimize.
@item -d@var{letters}
@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}.
@itemx -fdump-rtl-sms
@opindex dm
@opindex fdump-rtl-sms
-Dump after modulo scheduling, to @file{@var{file}.20.sms}.
+Dump after modulo scheduling, to @file{@var{file}.20.sms}.
@item -dM
@itemx -fdump-rtl-mach
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
@item -fdump-ipa-@var{switch}
@opindex fdump-ipa
-Control the dumping at various stages of inter-procedural analyisis
+Control the dumping at various stages of inter-procedural analysis
language tree to a file. The file name is generated by appending a switch
-specific suffix to the source file name. The following dumps are possible:
+specific suffix to the source file name. The following dumps are possible:
@table @samp
@item all
language tree to a file. The file name is generated by appending a switch
specific suffix to the source file name. If the @samp{-@var{options}}
form is used, @var{options} is a list of @samp{-} separated options that
-control the details of the dump. Not all options are applicable to all
-dumps, those which are not meaningful will be ignored. The following
+control the details of the dump. Not all options are applicable to all
+dumps, those which are not meaningful will be ignored. The following
options are available
@table @samp
@item address
Print the address of each node. Usually this is not meaningful as it
-changes according to the environment and source file. Its primary use
+changes according to the environment and source file. Its primary use
is for tying up a dump file with a debug environment.
@item slim
Inhibit dumping of members of a scope or body of a function merely
Dump the control flow graph of each function to a file in VCG format. The
file name is made by appending @file{.vcg} to the source file name. Note
that if the file contains more than one function, the generated file cannot
-be used directly by VCG. You will need to cut and paste each function's
+be used directly by VCG@. You will need to cut and paste each function's
graph into its own separate file first.
@item ch
Dump SSA related information to a file. The file name is made by appending
@file{.ssa} to the source file name.
+@item salias
+@opindex fdump-tree-salias
+Dump structure aliasing variable information to a file. This file name
+is made by appending @file{.salias} to the source file name.
+
@item alias
@opindex fdump-tree-alias
Dump aliasing information for each function. The file name is made by
@item ccp
@opindex fdump-tree-ccp
-Dump each function after CCP. The file name is made by appending
+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 performing scalar replacement of aggregates. The
file name is made by appending @file{.sra} to the source file name.
+@item sink
+@opindex fdump-tree-sink
+Dump each function after performing code sinking. The file name is made
+by appending @file{.sink} to the source file name.
+
@item dom
@opindex fdump-tree-dom
Dump each function after applying dominator tree optimizations. The file
@item vect
@opindex fdump-tree-vect
-Dump each function after applying vectorization of loops. The file name is
+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.
@end table
+@item -ftree-vectorizer-verbose=@var{n}
+@opindex ftree-vectorizer-verbose
+This option controls the amount of debugging output the vectorizer prints.
+This information is written to standard error, unless @option{-fdump-tree-all}
+or @option{-fdump-tree-vect} is specified, in which case it is output to the
+usual dump listing file, @file{.vect}.
+
@item -frandom-seed=@var{string}
@opindex frandom-string
This option provides a seed that GCC uses when it would otherwise use
random numbers. It is used to generate certain symbol names
-that have to be different in every compiled file. It is also used to
+that have to be different in every compiled file. It is also used to
place unique stamps in coverage data files and the object files that
-produce them. You can use the @option{-frandom-seed} option to produce
+produce them. You can use the @option{-frandom-seed} option to produce
reproducibly identical object files.
The @var{string} should be different for every file you compile.
preprocessed @file{foo.i} output file even though the compiler now
normally uses an integrated preprocessor.
+When used in combination with the @option{-x} command line option,
+@option{-save-temps} is sensible enough to avoid over writing an
+input source file with the same extension as an intermediate file.
+The corresponding intermediate file may be obtained by renaming the
+source file before using @option{-save-temps}.
+
@item -time
@opindex time
Report the CPU time taken by each subprocess in the compilation
# as 0.00 0.01
@end smallexample
-The first number on each line is the ``user time,'' that is time spent
-executing the program itself. The second number is ``system time,''
+The first number on each line is the ``user time'', that is time spent
+executing the program itself. The second number is ``system time'',
time spent executing operating system routines on behalf of the program.
Both numbers are in seconds.
@item -fvar-tracking
@opindex fvar-tracking
-Run variable tracking pass. It computes where variables are stored at each
-position in code. Better debugging information is then generated
+Run variable tracking pass. It computes where variables are stored at each
+position in code. Better debugging information is then generated
(if the debugging information format supports this information).
It is enabled by default when compiling with optimization (@option{-Os},
To resolve this you either need to put @file{cpp0} and the other compiler
components where @command{gcc} expects to find them, or you can set the environment
variable @env{GCC_EXEC_PREFIX} to the directory where you installed them.
-Don't forget the trailing '/'.
+Don't forget the trailing @samp{/}.
@xref{Environment Variables}.
@item -dumpmachine
@option{-O} turns on the following optimization flags:
@gccoptlist{-fdefer-pop @gol
--fmerge-constants @gol
--fthread-jumps @gol
+-fdelayed-branch @gol
+-fguess-branch-probability @gol
+-fcprop-registers @gol
-floop-optimize @gol
-fif-conversion @gol
-fif-conversion2 @gol
--fdelayed-branch @gol
--fguess-branch-probability @gol
--fcprop-registers}
+-ftree-ccp @gol
+-ftree-dce @gol
+-ftree-dominator-opts @gol
+-ftree-dse @gol
+-ftree-ter @gol
+-ftree-lrs @gol
+-ftree-sra @gol
+-ftree-copyrename @gol
+-ftree-fre @gol
+-ftree-ch @gol
+-fmerge-constants}
@option{-O} also turns on @option{-fomit-frame-pointer} on machines
where doing so does not interfere with debugging.
@option{-O2} turns on all optimization flags specified by @option{-O}. It
also turns on the following optimization flags:
-@gccoptlist{-fforce-mem @gol
+@gccoptlist{-fthread-jumps @gol
+-fcrossjumping @gol
-foptimize-sibling-calls @gol
--fstrength-reduce @gol
-fcse-follow-jumps -fcse-skip-blocks @gol
--frerun-cse-after-loop -frerun-loop-opt @gol
--fgcse -fgcse-lm -fgcse-sm -fgcse-las @gol
--fdelete-null-pointer-checks @gol
+-fgcse -fgcse-lm @gol
-fexpensive-optimizations @gol
--fregmove @gol
--fschedule-insns -fschedule-insns2 @gol
--fsched-interblock -fsched-spec @gol
+-fstrength-reduce @gol
+-frerun-cse-after-loop -frerun-loop-opt @gol
-fcaller-saves @gol
+-fforce-mem @gol
-fpeephole2 @gol
--freorder-blocks -freorder-functions @gol
+-fschedule-insns -fschedule-insns2 @gol
+-fsched-interblock -fsched-spec @gol
+-fregmove @gol
-fstrict-aliasing @gol
+-fdelete-null-pointer-checks @gol
+-freorder-blocks -freorder-functions @gol
-funit-at-a-time @gol
-falign-functions -falign-jumps @gol
-falign-loops -falign-labels @gol
--fcrossjumping}
+-ftree-vrp @gol
+-ftree-pre}
Please note the warning under @option{-fgcse} about
invoking @option{-O2} on programs that use computed gotos.
@opindex O3
Optimize yet more. @option{-O3} turns on all optimizations specified by
@option{-O2} and also turns on the @option{-finline-functions},
-@option{-fweb} and @option{-fgcse-after-reload} options.
+@option{-funswitch-loops} and @option{-fgcse-after-reload} options.
@item -O0
@opindex O0
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.
In C, emit @code{static} functions that are declared @code{inline}
into the object file, even if the function has been inlined into all
of its callers. This switch does not affect functions using the
-@code{extern inline} extension in GNU C. In C++, emit any and all
+@code{extern inline} extension in GNU C@. In C++, emit any and all
inline functions into the object file.
@item -fkeep-static-consts
pass. This pass looks at innermost loops and reorders their
instructions by overlapping different iterations.
-@item -fnew-ra
-@opindex fnew-ra
-Use a graph coloring register allocator. Currently this option is meant
-only for testing. Users should not specify this option, since it is not
-yet ready for production use.
-
@item -fno-branch-count-reg
@opindex fno-branch-count-reg
Do not use ``decrement and branch'' instructions on a count register,
second branch or a point immediately following it, depending on whether
the condition is known to be true or false.
-Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
@item -fcse-follow-jumps
@opindex fcse-follow-jumps
loops containing a load/store sequence can be changed to a load before
the loop and a store after the loop.
-Enabled by default when gcse is enabled.
+Not enabled at any optimization level.
@item -fgcse-las
@opindex fgcse-las
elimination pass eliminates redundant loads that come after stores to the
same memory location (both partial and full redundancies).
-Enabled by default when gcse is enabled.
+Not enabled at any optimization level.
@item -fgcse-after-reload
@opindex fgcse-after-reload
When @option{-fgcse-after-reload} is enabled, a redundant load elimination
-pass is performed after reload. The purpose of this pass is to cleanup
+pass is performed after reload. The purpose of this pass is to cleanup
redundant spilling.
@item -floop-optimize
@item -fcrossjumping
@opindex crossjumping
-Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The
+Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The
resulting code may or may not perform better than without cross-jumping.
-Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
@item -fif-conversion
@opindex if-conversion
trace formation.
This mode should produce faster but significantly longer programs. Also
-without @code{-fbranch-probabilities} the traces constructed may not match the
-reality and hurt the performance. This only makes
+without @option{-fbranch-probabilities} the traces constructed may not
+match the reality and hurt the performance. This only makes
sense when scheduling after register allocation, i.e.@: with
@option{-fschedule-insns2} or at @option{-O2} or higher.
@item -ftree-pre
Perform Partial Redundancy Elimination (PRE) on trees. This flag is
-enabled by default at -O and higher.
+enabled by default at @option{-O2} and @option{-O3}.
@item -ftree-fre
Perform Full Redundancy Elimination (FRE) on trees. The difference
between FRE and PRE is that FRE only considers expressions
that are computed on all paths leading to the redundant computation.
This analysis faster than PRE, though it exposes fewer redundancies.
-This flag is enabled by default at -O and higher.
+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.
+
+@item -ftree-sink
+Perform forward store motion on trees. This flag is
+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 -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
-default at -O and higher.
+default at @option{-O} and higher.
@item -ftree-dominator-opts
Perform dead code elimination (DCE) on trees. This flag is enabled by
-default at -O and higher.
+default at @option{-O} and higher.
@item -ftree-ch
Perform loop header copying on trees. This is beneficial since it increases
-effectivity of code motion optimizations. It also saves one jump. This flag
-is enabled by default at -O and higher. It is not enabled for -Os, since it
-usually increases code size.
+effectiveness of code motion optimizations. It also saves one jump. This flag
+is enabled by default at @option{-O} and higher. It is not enabled
+for @option{-Os}, since it usually increases code size.
@item -ftree-loop-optimize
-Perform loop optimizations on trees. This flag is enabled by default at -O
-and higher.
+Perform loop optimizations on trees. This flag is enabled by default
+at @option{-O} and higher.
@item -ftree-loop-linear
-Perform linear loop transformations on tree. This flag can improve cache
+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-sra
Perform scalar replacement of aggregates. This pass replaces structure
references with scalars to prevent committing structures to memory too
-early. This flag is enabled by default at -O and higher.
+early. This flag is enabled by default at @option{-O} and higher.
@item -ftree-copyrename
Perform copy renaming on trees. This pass attempts to rename compiler
temporaries to other variables at copy locations, usually resulting in
variable names which more closely resemble the original variables. This flag
-is enabled by default at -O and higher.
+is enabled by default at @option{-O} and higher.
@item -ftree-ter
Perform temporary expression replacement during the SSA->normal phase. Single
use/single def temporaries are replaced at their use location with their
defining expression. This results in non-GIMPLE code, but gives the expanders
much more complex trees to work on resulting in better RTL generation. This is
-enabled by default at -O and higher.
+enabled by default at @option{-O} and higher.
@item -ftree-lrs
Perform live range splitting during the SSA->normal phase. Distinct live
ranges of a variable are split into unique variables, allowing for better
-optimization later. This is enabled by default at -O and higher.
+optimization later. This is enabled by default at @option{-O} and higher.
@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
+Perform tail duplication to enlarge superblock size. This transformation
simplifies the control flow of the function allowing other optimizations to do
better job.
(for best results, @option{-fweb} should be used as well).
Combination of @option{-fweb} and CSE is often sufficient to obtain the
-same effect. However in cases the loop body is more complicated than
+same effect. However in cases the loop body is more complicated than
a single basic block, this is not reliable. It also does not work at all
on some of the architectures due to restrictions in the CSE pass.
This optimization is enabled by default.
+@item -fvariable-expansion-in-unroller
+@opindex -fvariable-expansion-in-unroller
+With this option, the compiler will create multiple copies of some
+local variables when unrolling a loop which can result in superior code.
+
@item -fprefetch-loop-arrays
@opindex fprefetch-loop-arrays
If supported by the target machine, generate instructions to prefetch
These options may generate better or worse code; results are highly
dependent on the structure of loops within the source code.
-These two options are intended to be removed someday, once
-they have helped determine the efficacy of various
-approaches to improving loop optimizations.
-
-Please contact @w{@email{gcc@@gcc.gnu.org}}, and describe how use of
-these options affects the performance of your production code.
-Examples of code that runs @emph{slower} when these options are
-@emph{enabled} are very valuable.
-
@item -fno-peephole
@itemx -fno-peephole2
@opindex fno-peephole
@item -fno-guess-branch-probability
@opindex fno-guess-branch-probability
-Do not guess branch probabilities using a randomized model.
-
-Sometimes GCC will opt to use a randomized model to guess branch
-probabilities, when none are available from either profiling feedback
-(@option{-fprofile-arcs}) or @samp{__builtin_expect}. This means that
-different runs of the compiler on the same program may produce different
-object code.
-
-In a hard real-time system, people don't want different runs of the
-compiler to produce code that has different behavior; minimizing
-non-determinism is of paramount import. This switch allows users to
-reduce non-determinism, possibly at the expense of inferior
-optimization.
+Do not guess branch probabilities using heuristics.
+
+GCC will use heuristics to guess branch probabilities if they are
+not provided by profiling feedback (@option{-fprofile-arcs}). These
+heuristics are based on the control flow graph. If some branch probabilities
+are specified by @samp{__builtin_expect}, then the heuristics will be
+used to guess branch probabilities for the rest of the control flow graph,
+taking the @samp{__builtin_expect} info into account. The interactions
+between the heuristics and @samp{__builtin_expect} can be complex, and in
+some cases, it may be useful to disable the heuristics so that the effects
+of @samp{__builtin_expect} are easier to understand.
The default is @option{-fguess-branch-probability} at levels
@option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
@item -freorder-functions
@opindex freorder-functions
-Reorder basic blocks in the compiled function in order to reduce number of
-taken branches and improve code locality. This is implemented by using special
+Reorder functions in the object file in order to
+improve code locality. This is implemented by using special
subsections @code{.text.hot} for most frequently executed functions and
@code{.text.unlikely} for unlikely executed functions. Reordering is done by
the linker so object file format must support named sections and linker must
@item
Static functions now can use non-standard passing conventions that
-may break @code{asm} statements calling functions directly. Again,
+may break @code{asm} statements calling functions directly. Again,
attribute @code{used} will prevent this behavior.
@end itemize
As a temporary workaround, @option{-fno-unit-at-a-time} can be used,
-but this scheme may not be supported by future releases of GCC.
+but this scheme may not be supported by future releases of GCC@.
Enabled at levels @option{-O2}, @option{-O3}.
Enable options usually used for instrumenting application to produce
profile useful for later recompilation with profile feedback based
-optimization. You must use @code{-fprofile-generate} both when
+optimization. You must use @option{-fprofile-generate} both when
compiling and when linking your program.
The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}.
@opindex ffast-math
Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, @*
@option{-fno-trapping-math}, @option{-ffinite-math-only},
-@option{-fno-rounding-math} and @option{-fno-signaling-nans}.
+@option{-fno-rounding-math}, @option{-fno-signaling-nans}
+and @option{fcx-limited-range}.
This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
Treat floating point constant as single precision constant instead of
implicitly converting it to double precision constant.
+@item -fcx-limited-range
+@itemx -fno-cx-limited-range
+@opindex fcx-limited-range
+@opindex fno-cx-limited-range
+When enabled, this option states that a range reduction step is not
+needed when performing complex division. The default is
+@option{-fno-cx-limited-range}, but is enabled by @option{-ffast-math}.
+
+This option controls the default setting of the ISO C99
+@code{CX_LIMITED_RANGE} pragma. Nevertheless, the option applies to
+all languages.
@end table
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
+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
Not enabled by default at any level because it has known bugs.
-@item -fnew-ra
-@opindex fnew-ra
-Use a graph coloring register allocator. Currently this option is meant
-for testing, so we are interested to hear about miscompilations with
-@option{-fnew-ra}.
-
@item -ftracer
@opindex ftracer
-Perform tail duplication to enlarge superblock size. This transformation
+Perform tail duplication to enlarge superblock size. This transformation
simplifies the control flow of the function allowing other optimizations to do
better job.
@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
+default value, 0, implies that GCC will select the most appropriate
+size itself.
+
+@item sra-field-structure-ratio
+The threshold ratio (as a percentage) between instantiated fields and
+the complete structure size. We say that if the ratio of the number
+of bytes in instantiated fields to the number of bytes in the complete
+structure exceeds this parameter, then block copies are not used. The
+default is 75.
+
@item max-crossjump-edges
The maximum number of incoming edges to consider for crossjumping.
The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in
value is ignored in the case where all instructions in the block being
crossjumped from are matched. The default value is 5.
+@item max-goto-duplication-insns
+The maximum number of instructions to duplicate to a block that jumps
+to a computed goto. To avoid @math{O(N^2)} behavior in a number of
+passes, GCC factors computed gotos early in the compilation process,
+and unfactors them as late as possible. Only computed jumps at the
+end of a basic blocks with no more than max-goto-duplication-insns are
+unfactored. The default value is 8.
+
@item max-delay-slot-insn-search
The maximum number of instructions to consider when looking for an
instruction to fill a delay slot. If more than this arbitrary number of
internal representation) in a single function that the tree inliner
will consider for inlining. This only affects functions declared
inline and methods implemented in a class declaration (C++).
-The default value is 500.
+The default value is 450.
@item max-inline-insns-auto
When you use @option{-finline-functions} (included in @option{-O3}),
by the compiler will be investigated. To those functions, a different
(more restrictive) limit compared to functions declared inline can
be applied.
-The default value is 120.
+The default value is 90.
@item large-function-insns
-The limit specifying really large functions. For functions greater than this
-limit inlining is constrained by @option{--param large-function-growth}.
-This parameter is useful primarily to avoid extreme compilation time caused by non-linear
-algorithms used by the backend.
+The limit specifying really large functions. For functions larger than this
+limit after inlining inlining is constrained by
+@option{--param large-function-growth}. This parameter is useful primarily
+to avoid extreme compilation time caused by non-linear algorithms used by the
+backend.
This parameter is ignored when @option{-funit-at-a-time} is not used.
-The default value is 3000.
+The default value is 2700.
@item large-function-growth
Specifies maximal growth of large function caused by inlining in percents.
This parameter is ignored when @option{-funit-at-a-time} is not used.
-The default value is 200.
+The default value is 100 which limits large function growth to 2.0 times
+the original size.
@item inline-unit-growth
Specifies maximal overall growth of the compilation unit caused by inlining.
This parameter is ignored when @option{-funit-at-a-time} is not used.
-The default value is 150.
+The default value is 50 which limits unit growth to 1.5 times the original
+size.
@item max-inline-insns-recursive
@itemx max-inline-insns-recursive-auto
taken into acount. For function not declared inline, recursive inlining
happens only when @option{-finline-functions} (included in @option{-O3}) is
enabled and @option{--param max-inline-insns-recursive-auto} is used. The
-default value is 500.
+default value is 450.
@item max-inline-recursive-depth
@itemx max-inline-recursive-depth-auto
taken into acount. For function not declared inline, recursive inlining
happens only when @option{-finline-functions} (included in @option{-O3}) is
enabled and @option{--param max-inline-recursive-depth-auto} is used. The
-default value is 500.
+default value is 450.
-@item max-inline-insns-rtl
-For languages that use the RTL inliner (this happens at a later stage
-than tree inlining), you can set the maximum allowable size (counted
-in RTL instructions) for the RTL inliner with this parameter.
-The default value is 600.
+@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
+functions and at the same time increases size of leaf function that is believed to
+reduce function size by being inlined. In effect it increases amount of
+inlining for code having large abstraction penalty (many functions that just
+pass the arguments to other functions) and decrease inlining for code with low
+abstraction penalty. The default value is 16.
@item max-unrolled-insns
The maximum number of instructions that a loop should have if that loop
The induction variable optimizations give up on loops that contain more
induction variable uses.
+@item iv-always-prune-cand-set-bound
+If number of candidates in the set is smaller than this value,
+we always try to remove unnecessary ivs from the set during its
+optimization when a new iv is added to the set.
+
+@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
@item global-var-threshold
-Counts the number of function calls (N) and the number of
-call-clobbered variables (V). If NxV is larger than this limit, a
+Counts the number of function calls (@var{n}) and the number of
+call-clobbered variables (@var{v}). If @var{n}x@var{v} is larger than this limit, a
single artificial variable will be created to represent all the
call-clobbered variables at function call sites. This artificial
variable will then be made to alias every call-clobbered variable.
-(done as int * size_t on the host machine; beware overflow).
+(done as @code{int * size_t} on the host machine; beware overflow).
@item max-aliased-vops
generation.
The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when
-RAM >= 1GB. If @code{getrlimit} is available, the notion of "RAM" is
-the smallest of actual RAM and RLIMIT_DATA or RLIMIT_AS. If
+RAM >= 1GB@. If @code{getrlimit} is available, the notion of "RAM" is
+the smallest of actual RAM and @code{RLIMIT_DATA} or @code{RLIMIT_AS}. If
GCC is not able to calculate RAM on a particular platform, the lower
bound of 30% is used. Setting this parameter and
@option{ggc-min-heapsize} to zero causes a full collection to occur at
The maximum number of insns in a region to be considered for
interblock scheduling. The default value is 100.
+@item max-last-value-rtl
+
+The maximum size measured as number of RTLs that can be recorded in an expression
+in combiner for a pseudo register as last known value of that register. The default
+is 10000.
+
@item integer-share-limit
Small integer constants can use a shared data structure, reducing the
compiler's memory usage and increasing its speed. This sets the maximum
value of a shared integer constant's. The default value is 256.
+@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.
+
@end table
@end table
contain startup files. If the target supports multilibs then the
current multilib directory will be prepended to each of these paths.
-@item %M
-Output the multilib directory with directory separators replaced with
-@samp{_}. If multilib directories are not set, or the multilib directory is
-@file{.} then this option emits nothing.
-
@item %L
Process the @code{lib} spec. This is a spec string for deciding which
libraries should be included on the command line to the linker.
crt0%O%s %:if-exists(crti%O%s) \
%:if-exists-else(crtbeginT%O%s crtbegin%O%s)
@end smallexample
+
+@item @code{replace-outfile}
+The @code{replace-outfile} spec function takes two arguments. It looks for the
+first argument in the outfiles array and replaces it with the second argument. Here
+is a small example of its usage:
+
+@smallexample
+%@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@}
+@end smallexample
+
@end table
@item %@{@code{S}@}
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
* ARC Options::
* ARM Options::
* AVR Options::
+* Blackfin Options::
* CRIS Options::
* Darwin Options::
* DEC Alpha Options::
@table @gcctabopt
@item -mabi=@var{name}
@opindex mabi
-Generate code for the specified ABI. Permissible values are: @samp{apcs-gnu},
+Generate code for the specified ABI@. Permissible values are: @samp{apcs-gnu},
@samp{atpcs}, @samp{aapcs} and @samp{iwmmxt}.
@item -mapcs-frame
@samp{arm968e-s}, @samp{arm926ej-s}, @samp{arm940t}, @samp{arm9tdmi},
@samp{arm10tdmi}, @samp{arm1020t}, @samp{arm1026ej-s},
@samp{arm10e}, @samp{arm1020e}, @samp{arm1022e},
-@samp{arm1136j-s}, @samp{arm1136jf-s} ,@samp{xscale}, @samp{iwmmxt},
+@samp{arm1136j-s}, @samp{arm1136jf-s}, @samp{mpcore}, @samp{mpcorenovfp},
+@samp{arm1176jz-s}, @samp{arm1176jzf-s}, @samp{xscale}, @samp{iwmmxt},
@samp{ep9312}.
@itemx -mtune=@var{name}
@item -mint8
@opindex mint8
-Assume int to be 8 bit integer. This affects the sizes of all types: A
+Assume int to be 8 bit integer. This affects the sizes of all types: A
char will be 1 byte, an int will be 1 byte, an long will be 2 bytes
-and long long will be 4 bytes. Please note that this option does not
+and long long will be 4 bytes. Please note that this option does not
comply to the C standards, but it will provide you with smaller code
size.
@end table
+@node Blackfin Options
+@subsection Blackfin Options
+@cindex Blackfin Options
+
+@table @gcctabopt
+@item -momit-leaf-frame-pointer
+@opindex momit-leaf-frame-pointer
+Don't keep the frame pointer in a register for leaf functions. This
+avoids the instructions to save, set up and restore frame pointers and
+makes an extra register available in leaf functions. The option
+@option{-fomit-frame-pointer} removes the frame pointer for all functions
+which might make debugging harder.
+
+@item -mcsync
+@opindex mcsync
+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
+Don't generate extra code to prevent speculative loads from occurring.
+
+@item -mlow-64k
+@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.
+
+@item -mno-low-64k
+@opindex mno-low-64k
+Assume that the program is arbitrarily large. This is the default.
+
+@item -mid-shared-library
+@opindex mid-shared-library
+Generate code that supports shared libraries via the library ID method.
+This allows for execute in place and shared libraries in an environment
+without virtual memory management. This option implies @option{-fPIC}.
+
+@item -mno-id-shared-library
+@opindex mno-id-shared-library
+Generate code that doesn't assume ID based shared libraries are being used.
+This is the default.
+
+@item -mshared-library-id=n
+@opindex mshared-library-id
+Specified the identification number of the ID based shared library being
+compiled. Specifying a value of 0 will generate more compact code, specifying
+other values will force the allocation of that number to the current
+library but is no more space or time efficient than omitting this option.
+@end table
+
@node CRIS Options
@subsection CRIS Options
@cindex CRIS Options
@opindex mcpu
Generate code for the specified architecture. The choices for
@var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for
-respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX.
+respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX@.
Default is @samp{v0} except for cris-axis-linux-gnu, where the default is
@samp{v10}.
With @option{-fpic} and @option{-fPIC}, don't generate (do generate)
instruction sequences that load addresses for functions from the PLT part
of the GOT rather than (traditional on other architectures) calls to the
-PLT. The default is @option{-mgotplt}.
+PLT@. The default is @option{-mgotplt}.
@item -maout
@opindex maout
@cindex Darwin options
These options are defined for all architectures running the Darwin operating
-system. They are useful for compatibility with other Mac OS compilers.
+system.
+
+FSF GCC on Darwin does not create ``fat'' object files; it will create
+an object file for the single architecture that it was built to
+target. Apple's GCC on Darwin does create ``fat'' files if multiple
+@option{-arch} options are used; it does so by running the compiler or
+linker multiple times and joining the results together with
+@file{lipo}.
+
+The subtype of the file created (like @samp{ppc7400} or @samp{ppc970} or
+@samp{i686}) is determined by the flags that specify the ISA
+that GCC is targetting, like @option{-mcpu} or @option{-march}. The
+@option{-force_cpusubtype_ALL} option can be used to override this.
+
+The Darwin tools vary in their behavior when presented with an ISA
+mismatch. The assembler, @file{as}, will only permit instructions to
+be used that are valid for the subtype of the file it is generating,
+so you cannot put 64-bit instructions in an @samp{ppc750} object file.
+The linker for shared libraries, @file{/usr/bin/libtool}, will fail
+and print an error if asked to create a shared library with a less
+restrictive subtype than its input files (for instance, trying to put
+a @samp{ppc970} object file in a @samp{ppc7400} library). The linker
+for executables, @file{ld}, will quietly give the executable the most
+restrictive subtype of any of its input files.
@table @gcctabopt
@item -F@var{dir}
@item -gused
@opindex -gused
-Emit debugging information for symbols that are used. For STABS
+Emit debugging information for symbols that are used. For STABS
debugging format, this enables @option{-feliminate-unused-debug-symbols}.
-This is by default ON.
+This is by default ON@.
@item -gfull
@opindex -gfull
@item -mone-byte-bool
@opindex -mone-byte-bool
Override the defaults for @samp{bool} so that @samp{sizeof(bool)==1}.
-By default @samp{sizeof(bool)} is @samp{4} when compiling for
+By default @samp{sizeof(bool)} is @samp{4} when compiling for
Darwin/PowerPC and @samp{1} when compiling for Darwin/x86, so this
option has no effect on x86.
@strong{Warning:} The @option{-mone-byte-bool} switch causes GCC
to generate code that is not binary compatible with code generated
without that switch. Using this switch may require recompiling all
-other modules in a program, including system libraries. Use this
+other modules in a program, including system libraries. Use this
switch to conform to a non-default data model.
@item -mfix-and-continue
@item -bundle_loader @var{executable}
@opindex bundle_loader
-This specifies the @var{executable} that will be loading the build
-output file being linked. See man ld(1) for more information.
+This option specifies the @var{executable} that will be loading the build
+output file being linked. See man ld(1) for more information.
-@item -allowable_client @var{client_name}
-@itemx -arch_only
+@item -dynamiclib
+@opindex -dynamiclib
+When passed this option, GCC will produce a dynamic library instead of
+an executable when linking, using the Darwin @file{libtool} command.
+
+@item -force_cpusubtype_ALL
+@opindex -force_cpusubtype_ALL
+This causes GCC's output file to have the @var{ALL} subtype, instead of
+one controlled by the @option{-mcpu} or @option{-march} option.
+@item -allowable_client @var{client_name}
@itemx -client_name
@itemx -compatibility_version
@itemx -current_version
@itemx -dylib_file
@itemx -dylinker_install_name
@itemx -dynamic
-@itemx -dynamiclib
@itemx -exported_symbols_list
@itemx -filelist
@itemx -flat_namespace
-@itemx -force_cpusubtype_ALL
@itemx -force_flat_namespace
@itemx -headerpad_max_install_names
@itemx -image_base
@itemx -whatsloaded
@opindex allowable_client
-@opindex arch_only
@opindex client_name
@opindex compatibility_version
@opindex current_version
@opindex dylib_file
@opindex dylinker_install_name
@opindex dynamic
-@opindex dynamiclib
@opindex exported_symbols_list
@opindex filelist
@opindex flat_namespace
-@opindex force_cpusubtype_ALL
@opindex force_flat_namespace
@opindex headerpad_max_install_names
@opindex image_base
@opindex weak_reference_mismatches
@opindex whatsloaded
-These options are available for Darwin linker. Darwin linker man page
+These options are passed to the Darwin linker. The Darwin linker man page
describes them in detail.
@end table
directly accessed via a single instruction.
The default is @option{-mlarge-data}. With this option the data area
-is limited to just below 2GB. Programs that require more than 2GB of
+is limited to just below 2GB@. Programs that require more than 2GB of
data must use @code{malloc} or @code{mmap} to allocate the data in the
heap instead of in the program's data segment.
optimization option such as @option{-O3} or above is present in the
command line.
+@item -mTLS
+@opindex TLS
+
+Assume a large TLS segment when generating thread-local code.
+
+@item -mtls
+@opindex tls
+
+Do not assume a large TLS segment when generating thread-local code.
+
@item -mgprel-ro
@opindex mgprel-ro
@item -mn
@opindex mn
Generate code for the H8S and H8/300H in the normal mode. This switch
-must be used either with -mh or -ms.
+must be used either with @option{-mh} or @option{-ms}.
@item -ms2600
@opindex ms2600
@item -msio
@opindex msio
-Generate the predefine, @code{_SIO}, for server IO. The default is
+Generate the predefine, @code{_SIO}, for server IO@. The default is
@option{-mwsio}. This generates the predefines, @code{__hp9000s700},
-@code{__hp9000s700__} and @code{_WSIO}, for workstation IO. These
-options are available under HP-UX and HI-UX.
+@code{__hp9000s700__} and @code{_WSIO}, for workstation IO@. These
+options are available under HP-UX and HI-UX@.
@item -mgnu-ld
@opindex gnu-ld
@item -threads
@opindex threads
Add support for multithreading with the @dfn{dce thread} library
-under HP-UX. This option sets flags for both the preprocessor and
+under HP-UX@. This option sets flags for both the preprocessor and
linker.
@end table
@var{cpu-type} are:
@table @emph
@item i386
-Original Intel's i386 CPU.
+Original Intel's i386 CPU@.
@item i486
-Intel's i486 CPU. (No scheduling is implemented for this chip.)
+Intel's i486 CPU@. (No scheduling is implemented for this chip.)
@item i586, pentium
Intel Pentium CPU with no MMX support.
@item pentium-mmx
Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
@item i686, pentiumpro
-Intel PentiumPro CPU.
+Intel PentiumPro CPU@.
@item pentium2
Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
@item pentium3, pentium3m
IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW!
instruction set support.
@item c3
-Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is
+Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is
implemented for this chip.)
@item c3-2
Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is
emulated otherwise. Code compiled with this option will run almost everywhere.
The temporary results are computed in 80bit precision instead of precision
specified by the type resulting in slightly different results compared to most
-of other chips. See @option{-ffloat-store} for more detailed description.
+of other chips. See @option{-ffloat-store} for more detailed description.
This is the default choice for i386 compiler.
only in Pentium4 and the future AMD x86-64 chips supports double precision
arithmetics too.
-For i387 you need to use @option{-march=@var{cpu-type}}, @option{-msse} or
-@option{-msse2} switches to enable SSE extensions and make this option
-effective. For x86-64 compiler, these extensions are enabled by default.
+For the i386 compiler, you need to use @option{-march=@var{cpu-type}}, @option{-msse}
+or @option{-msse2} switches to enable SSE extensions and make this option
+effective. For the x86-64 compiler, these extensions are enabled by default.
The resulting code should be considerably faster in the majority of cases and avoid
the numerical instability problems of 387 code, but may break some existing
@item -masm=@var{dialect}
@opindex masm=@var{dialect}
-Output asm instructions using selected @var{dialect}. Supported choices are
+Output asm instructions using selected @var{dialect}. Supported choices are
@samp{intel} or @samp{att} (the default one).
@item -mieee-fp
@itemx -m128bit-long-double
@opindex m96bit-long-double
@opindex m128bit-long-double
-These switches control the size of @code{long double} type. The i386
+These switches control the size of @code{long double} type. The i386
application binary interface specifies the size to be 96 bits,
so @option{-m96bit-long-double} is the default in 32 bit mode.
Generate (or don't) a stop bit immediately before and after volatile asm
statements.
-@item -mb-step
-@opindex mb-step
-Generate code that works around Itanium B step errata.
-
@item -mregister-names
@itemx -mno-register-names
@opindex mregister-names
Generate code for inline divides of integer values
using the maximum throughput algorithm.
+@item -minline-sqrt-min-latency
+@opindex minline-sqrt-min-latency
+Generate code for inline square roots
+using the minimum latency algorithm.
+
+@item -minline-sqrt-max-throughput
+@opindex minline-sqrt-max-throughput
+Generate code for inline square roots
+using the maximum throughput algorithm.
+
@item -mno-dwarf2-asm
@itemx -mdwarf2-asm
@opindex mno-dwarf2-asm
Don't (or do) generate assembler code for the DWARF2 line number debugging
info. This may be useful when not using the GNU assembler.
+@item -mearly-stop-bits
+@itemx -mno-early-stop-bits
+@opindex mearly-stop-bits
+@opindex mno-early-stop-bits
+Allow stop bits to be placed earlier than immediately preceding the
+instruction that triggered the stop bit. This can improve instruction
+scheduling, but does not always do so.
+
@item -mfixed-range=@var{register-range}
@opindex mfixed-range
Generate code treating the given register range as fixed registers.
two registers separated by a dash. Multiple register ranges can be
specified separated by a comma.
-@item -mearly-stop-bits
-@itemx -mno-early-stop-bits
-@opindex mearly-stop-bits
-@opindex mno-early-stop-bits
-Allow stop bits to be placed earlier than immediately preceding the
-instruction that triggered the stop bit. This can improve instruction
-scheduling, but does not always do so.
+@item -mtls-size=@var{tls-size}
+@opindex mtls-size
+Specify bit size of immediate TLS offsets. Valid values are 14, 22, and
+64.
+
+@item -mtune-arch=@var{cpu-type}
+@opindex mtune-arch
+Tune the instruction scheduling for a particular CPU, Valid values are
+itanium, itanium1, merced, itanium2, and mckinley.
+
+@item -mt
+@itemx -pthread
+@opindex mt
+@opindex pthread
+Add support for multithreading using the POSIX threads library. This
+option sets flags for both the preprocessor and linker. It does
+not affect the thread safety of object code produced by the compiler or
+that of libraries supplied with it. These are HP-UX specific flags.
+
+@item -milp32
+@itemx -mlp64
+@opindex milp32
+@opindex mlp64
+Generate code for a 32-bit or 64-bit environment.
+The 32-bit environment sets int, long and pointer to 32 bits.
+The 64-bit environment sets int to 32 bits and long and pointer
+to 64 bits. These are HP-UX specific flags.
+
@end table
@node M32R/D Options
@item -msep-data
Generate code that allows the data segment to be located in a different
area of memory from the text segment. This allows for execute in place in
-an environment without virtual memory management. This option implies -fPIC.
+an environment without virtual memory management. This option implies
+@option{-fPIC}.
@item -mno-sep-data
Generate code that assumes that the data segment follows the text segment.
@item -mid-shared-library
Generate code that supports shared libraries via the library ID method.
This allows for execute in place and shared libraries in an environment
-without virtual memory management. This option implies -fPIC.
+without virtual memory management. This option implies @option{-fPIC}.
@item -mno-id-shared-library
Generate code that doesn't assume ID based shared libraries are being used.
@itemx -mno-mips16
@opindex mips16
@opindex mno-mips16
-Use (do not use) the MIPS16 ISA.
+Use (do not use) the MIPS16 ISA@.
@item -mabi=32
@itemx -mabi=o64
Lift (do not lift) the usual restrictions on the size of the global
offset table.
-GCC normally uses a single instruction to load values from the GOT.
+GCC normally uses a single instruction to load values from the GOT@.
While this is relatively efficient, it will only work if the GOT
is smaller than about 64k. Anything larger will cause the linker
to report an error such as:
@itemx -mno-paired-single
@opindex mpaired-single
@opindex mno-paired-single
-Use (do not use) the paired single instructions.
+Use (do not use) paired-single floating-point instructions.
+@xref{MIPS Paired-Single Support}. This option can only be used
+when generating 64-bit code and requires hardware floating-point
+support to be enabled.
@itemx -mips3d
@itemx -mno-mips3d
@opindex mips3d
@opindex mno-mips3d
-Use (do not use) the MIPS-3D ASE. 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.
+Use (do not use) the MIPS-3D ASE@. @xref{MIPS-3D Built-in Functions}.
+The option @option{-mips3d} implies @option{-mpaired-single}.
@item -mlong64
@opindex mlong64
32-bit @code{long}s. Pointers are the same size as @code{long}s,
or the same size as integer registers, whichever is smaller.
+@item -msym32
+@itemx -mno-sym32
+@opindex msym32
+@opindex mno-sym32
+Assume (do not assume) that all symbols have 32-bit values, regardless
+of the selected ABI@. This option is useful in combination with
+@option{-mabi=64} and @option{-mno-abicalls} because it allows GCC
+to generate shorter and faster references to symbolic addresses.
+
@item -G @var{num}
@opindex G
@cindex smaller data references (MIPS)
@opindex msplit-addresses
@opindex mno-split-addresses
Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler
-relocation operators. This option has been superceded by
+relocation operators. This option has been superseded by
@option{-mexplicit-relocs} but is retained for backwards compatibility.
@item -mexplicit-relocs
conditional trap or a break instruction. Using traps results in
smaller code, but is only supported on MIPS II and later. Also, some
versions of the Linux kernel have a bug that prevents trap from
-generating the proper signal (SIGFPE). Use @option{-mdivide-traps} to
+generating the proper signal (@code{SIGFPE}). Use @option{-mdivide-traps} to
allow conditional traps on architectures that support them and
@option{-mdivide-breaks} to force the use of breaks.
@opindex mmad
@opindex mno-mad
Enable (disable) use of the @code{mad}, @code{madu} and @code{mul}
-instructions, as provided by the R4650 ISA.
+instructions, as provided by the R4650 ISA@.
@item -mfused-madd
@itemx -mno-fused-madd
Other VR4120 errata require a nop to be inserted between certain pairs of
instructions. These errata are handled by the assembler, not by GCC itself.
+@item -mfix-vr4130
+@opindex mfix-vr4130
+Work around the VR4130 @code{mflo}/@code{mfhi} errata. The
+workarounds are implemented by the assembler rather than by GCC,
+although GCC will avoid using @code{mflo} and @code{mfhi} if the
+VR4130 @code{macc}, @code{macchi}, @code{dmacc} and @code{dmacchi}
+instructions are available instead.
+
@item -mfix-sb1
@itemx -mno-fix-sb1
@opindex mfix-sb1
@item -msplit
@opindex msplit
-Generate code for a system with split I&D.
+Generate code for a system with split I&D@.
@item -mno-split
@opindex mno-split
-Generate code for a system without split I&D. This is the default.
+Generate code for a system without split I&D@. This is the default.
@item -munix-asm
@opindex munix-asm
@samp{601}, @samp{602}, @samp{603}, @samp{603e}, @samp{604},
@samp{604e}, @samp{620}, @samp{630}, @samp{740}, @samp{7400},
@samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
-@samp{860}, @samp{970}, @samp{common}, @samp{ec603e}, @samp{G3},
+@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.
@itemx -mno-altivec
@opindex maltivec
@opindex mno-altivec
-These switches enable or disable the use of built-in functions that
-allow access to the AltiVec instruction set. You may also need to set
+Generate code that uses (does not use) AltiVec instructions, and also
+enable the use of built-in functions that allow more direct access to
+the AltiVec instruction set. You may also need to set
@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
@item -mabi=no-spe
@opindex mabi=no-spe
-Disable Booke SPE ABI extensions for the current ABI.
-
-@item -misel=@var{yes/no}
-@itemx -misel
+Disable Booke SPE ABI extensions for the current ABI@.
+
+@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 -mfloat-gprs=@var{yes/no}
+@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
This switch enables or disables the generation of floating point
operations on the general purpose registers for architectures that
-support it. This option is currently only available on the MPC8540.
+support it.
+
+The argument @var{yes} or @var{single} enables the use of
+single-precision floating point operations.
+
+The argument @var{double} enables the use of single and
+double-precision floating point operations.
+
+The argument @var{no} disables floating point operations on the
+general purpose registers.
+
+This option is currently only available on the MPC854x.
@item -m32
@itemx -m64
@option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and
implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}.
-@item -mxl-call
-@itemx -mno-xl-call
-@opindex mxl-call
-@opindex mno-xl-call
-On AIX, pass floating-point arguments to prototyped functions beyond the
-register save area (RSA) on the stack in addition to argument FPRs. The
-AIX calling convention was extended but not initially documented to
+@item -mxl-compat
+@itemx -mno-xl-compat
+@opindex mxl-compat
+@opindex mno-xl-compat
+Produce code that conforms more closely to IBM XLC semantics when using
+AIX-compatible ABI. Pass floating-point arguments to prototyped
+functions beyond the register save area (RSA) on the stack in addition
+to argument FPRs. Do not assume that most significant double in 128
+bit long double value is properly rounded when comparing values.
+
+The AIX calling convention was extended but not initially documented to
handle an obscure K&R C case of calling a function that takes the
address of its arguments with fewer arguments than declared. AIX XL
compilers access floating point arguments which do not fit in the
@itemx -malign-power
@opindex malign-natural
@opindex malign-power
-On AIX, Darwin, and 64-bit PowerPC GNU/Linux, the option
+On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
@option{-malign-natural} overrides the ABI-defined alignment of larger
types, such as floating-point doubles, on their natural size-based boundary.
The option @option{-malign-power} instructs GCC to follow the ABI-specified
-alignment rules. GCC defaults to the standard alignment defined in the ABI.
+alignment rules. GCC defaults to the standard alignment defined in the ABI@.
+
+On 64-bit Darwin, natural alignment is the default, and @option{-malign-power}
+is not supported.
@item -msoft-float
@itemx -mhard-float
@item -minsert-sched-nops=@var{scheme}
@opindex minsert-sched-nops
This option controls which nop insertion scheme will be used during
-the second scheduling pass. The argument @var{scheme} takes one of the
+the second scheduling pass. The argument @var{scheme} takes one of the
following values:
@var{no}: Don't insert nops.
@var{pad}: Pad with nops any dispatch group which has vacant issue slots,
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
On Darwin/PPC systems, @code{#pragma longcall} will generate ``jbsr
callee, L42'', plus a ``branch island'' (glue code). The two target
-addresses represent the callee and the ``branch island.'' The
+addresses represent the callee and the ``branch island''. The
Darwin/PPC linker will prefer the first address and generate a ``bl
callee'' if the PPC ``bl'' instruction will reach the callee directly;
otherwise, the linker will generate ``bl L42'' to call the ``branch
-island.'' The ``branch island'' is appended to the body of the
+island''. The ``branch island'' is appended to the body of the
calling function; it computes the full 32-bit address of the callee
and jumps to it.
@item -mbackchain
@itemx -mno-backchain
-@itemx -mkernel-backchain
@opindex mbackchain
@opindex mno-backchain
-@opindex mkernel-backchain
-In order to provide a backchain the address of the caller's frame
-is stored within the callee's stack frame.
+Store (do not store) the address of the caller's frame as backchain pointer
+into the callee's stack frame.
A backchain may be needed to allow debugging using tools that do not understand
DWARF-2 call frame information.
-For @option{-mno-backchain} no backchain is maintained at all which is the
-default.
-If one of the other options is present the backchain pointer is placed either
-on top of the stack frame (@option{-mkernel-backchain}) or on
-the bottom (@option{-mbackchain}).
-Beside the different backchain location @option{-mkernel-backchain}
-also changes stack frame layout breaking the ABI. This option
-is intended to be used for code which internally needs a backchain but has
-to get by with a limited stack size e.g.@: the linux kernel.
-Internal unwinding code not using DWARF-2 info has to be able to locate the
-return address of a function. That will be eased be the fact that
-the return address of a function is placed two words below the backchain
-pointer.
+When @option{-mno-packed-stack} is in effect, the backchain pointer is stored
+at the bottom of the stack frame; when @option{-mpacked-stack} is in effect,
+the backchain is placed into the topmost word of the 96/160 byte register
+save area.
+
+In general, code compiled with @option{-mbackchain} is call-compatible with
+code compiled with @option{-mmo-backchain}; however, use of the backchain
+for debugging purposes usually requires that the whole binary is built with
+@option{-mbackchain}. Note that the combination of @option{-mbackchain},
+@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
+to build a linux kernel use @option{-msoft-float}.
+
+The default is to not maintain the backchain.
+
+@item -mpacked-stack
+@item -mno-packed-stack
+@opindex mpacked-stack
+@opindex mno-packed-stack
+Use (do not use) the packed stack layout. When @option{-mno-packed-stack} is
+specified, the compiler uses the all fields of the 96/160 byte register save
+area only for their default purpose; unused fields still take up stack space.
+When @option{-mpacked-stack} is specified, register save slots are densely
+packed at the top of the register save area; unused space is reused for other
+purposes, allowing for more efficient use of the available stack space.
+However, when @option{-mbackchain} is also in effect, the topmost word of
+the save area is always used to store the backchain, and the return address
+register is always saved two words below the backchain.
+
+As long as the stack frame backchain is not used, code generated with
+@option{-mpacked-stack} is call-compatible with code generated with
+@option{-mno-packed-stack}. Note that some non-FSF releases of GCC 2.95 for
+S/390 or zSeries generated code that uses the stack frame backchain at run
+time, not just for debugging purposes. Such code is not call-compatible
+with code compiled with @option{-mpacked-stack}. Also, note that the
+combination of @option{-mbackchain},
+@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
+to build a linux kernel use @option{-msoft-float}.
+
+The default is to not use the packed stack layout.
@item -msmall-exec
@itemx -mno-small-exec
When @option{-mzarch} is specified, generate code using the
instructions available on z/Architecture.
When @option{-mesa} is specified, generate code using the
-instructions available on ESA/390. Note that @option{-mesa} is
+instructions available on ESA/390. Note that @option{-mesa} is
not possible with @option{-m64}.
When generating code compliant to the GNU/Linux for S/390 ABI,
the default is @option{-mesa}. When generating code compliant
@item -march=@var{cpu-type}
@opindex march
Generate code that will run on @var{cpu-type}, which is the name of a system
-representing a certain processor type. Possible values for
+representing a certain processor type. Possible values for
@var{cpu-type} are @samp{g5}, @samp{g6}, @samp{z900}, and @samp{z990}.
When generating code using the instructions available on z/Architecture,
the default is @option{-march=z900}. Otherwise, the default is
@opindex mno-tpf-trace
Generate code that adds (does not add) in TPF OS specific branches to trace
routines in the operating system. This option is off by default, even
-when compiling for the TPF OS.
+when compiling for the TPF OS@.
@item -mfused-madd
@itemx -mno-fused-madd
@opindex mwarn-framesize
Emit a warning if the current function exceeds the given frame size. Because
this is a compile time check it doesn't need to be a real problem when the program
-runs. It is intended to identify functions which most probably cause
-a stack overflow. It is useful to be used in an environment with limited stack
+runs. It is intended to identify functions which most probably cause
+a stack overflow. It is useful to be used in an environment with limited stack
size e.g.@: the linux kernel.
@item -mwarn-dynamicstack
@opindex mstack-size
These arguments always have to be used in conjunction. If they are present the s390
back end emits additional instructions in the function prologue which trigger a trap
-if the stack size is @var{stack-guard} bytes above the @var{stack-size}
-(remember that the stack on s390 grows downward). These options are intended to
-be used to help debugging stack overflow problems. The additionally emitted code
-cause only little overhead and hence can also be used in production like systems
-without greater performance degradation. The given values have to be exact
+if the stack size is @var{stack-guard} bytes above the @var{stack-size}
+(remember that the stack on s390 grows downward). These options are intended to
+be used to help debugging stack overflow problems. The additionally emitted code
+cause only little overhead and hence can also be used in production like systems
+without greater performance degradation. The given values have to be exact
powers of 2 and @var{stack-size} has to be greater than @var{stack-guard}.
In order to be efficient the extra code makes the assumption that the stack starts
at an address aligned to the value given by @var{stack-size}.
@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
the SPARC architecture. This adds the integer multiply, integer divide step
and scan (@code{ffs}) instructions which exist in SPARClite but not in SPARC-V7.
With @option{-mcpu=f930}, the compiler additionally optimizes it for the
-Fujitsu MB86930 chip, which is the original SPARClite, with no FPU. With
+Fujitsu MB86930 chip, which is the original SPARClite, with no FPU@. With
@option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu
-MB86934 chip, which is the more recent SPARClite with FPU.
+MB86934 chip, which is the more recent SPARClite with FPU@.
With @option{-mcpu=sparclet}, GCC generates code for the SPARClet variant of
the SPARC architecture. This adds the integer multiply, multiply/accumulate,
@itemx -mno-v8plus
@opindex mv8plus
@opindex mno-v8plus
-With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI. The
+With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI@. The
difference from the V8 ABI is that the global and out registers are
considered 64-bit wide. This is enabled by default on Solaris in 32-bit
mode for all SPARC-V9 processors.
@table @gcctabopt
@item -mlittle-endian
@opindex mlittle-endian
-Generate code for a processor running in little-endian mode. It is only
-available for a few configurations and most notably not on Solaris.
+Generate code for a processor running in little-endian mode. It is only
+available for a few configurations and most notably not on Solaris and Linux.
@item -m32
@itemx -m64
@item -mv850e
@opindex mv850e
-Specify that the target processor is the V850E. The preprocessor
+Specify that the target processor is the V850E@. The preprocessor
constant @samp{__v850e__} will be defined if this option is used.
If neither @option{-mv850} nor @option{-mv850e} nor @option{-mv850e1}
@opindex fPIC
If supported for the target machine, emit position-independent code,
suitable for dynamic linking and avoiding any limit on the size of the
-global offset table. This option makes a difference on the m68k
-and the SPARC.
+global offset table. This option makes a difference on the m68k,
+PowerPC and SPARC@.
Position-independent code requires special support, and therefore works
only on certain machines.
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
@item -fpack-struct[=@var{n}]
@opindex fpack-struct
Without a value specified, pack all structure members together without
-holes. When a value is specified (which must be a small power of two), pack
+holes. When a value is specified (which must be a small power of two), pack
structure members according to this value, representing the maximum
alignment (that is, objects with default alignment requirements larger than
this will be output potentially unaligned at the next fitting location.
@item -fvisibility=@var{default|internal|hidden|protected}
@opindex fvisibility
-Set the default ELF image symbol visibility to the specified option - all
+Set the default ELF image symbol visibility to the specified option---all
symbols will be marked with this unless overridden within the code.
Using this feature can very substantially improve linking and
load times of shared object libraries, produce more optimized
code, provide near-perfect API export and prevent symbol clashes.
It is @strong{strongly} recommended that you use this in any shared objects
you distribute.
-
+
Despite the nomenclature, @code{default} always means public ie;
available to be linked against from outside the shared object.
@code{protected} and @code{internal} are pretty useless in real-world
usage so the only other commonly used option will be @code{hidden}.
-The default if -fvisibility isn't specified is @code{default} ie; make every
-symbol public - this causes the same behaviour as previous versions of
-GCC.
-
+The default if @option{-fvisibility} isn't specified is
+@code{default}, i.e., make every
+symbol public---this causes the same behavior as previous versions of
+GCC@.
+
A good explanation of the benefits offered by ensuring ELF
symbols have the correct visibility is given by ``How To Write
Shared Libraries'' by Ulrich Drepper (which can be found at
-@w{@uref{http://people.redhat.com/~drepper/}}) - however a superior
+@w{@uref{http://people.redhat.com/~drepper/}})---however a superior
solution made possible by this option to marking things hidden when
the default is public is to make the default hidden and mark things
-public. This is the norm with DLL's on Windows and with @option{-fvisibility=hidden}
+public. This is the norm with DLL's on Windows and with @option{-fvisibility=hidden}
and @code{__attribute__ ((visibility("default")))} instead of
@code{__declspec(dllexport)} you get almost identical semantics with
-identical syntax. This is a great boon to those working with
+identical syntax. This is a great boon to those working with
cross-platform projects.
For those adding visibility support to existing code, you may find
-@samp{#pragma GCC visibility} of use. This works by you enclosing
+@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
-as hidden as so to avoid PLT indirection overheads - making this
+as hidden as so to avoid PLT indirection overheads---making this
abundantly clear also aids readability and self-documentation of the code.
Note that due to ISO C++ specification requirements, operator new and
operator delete must always be of default visibility.
An overview of these techniques, their benefits and how to use them
-is at @w{@uref{http://www.nedprod.com/programs/gccvisibility.html}}.
+is at @w{@uref{http://gcc.gnu.org/wiki/Visibility}}.
@end table
national conventions. GCC inspects the locale categories
@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do
so. These locale categories can be set to any value supported by your
-installation. A typical value is @samp{en_UK} for English in the United
-Kingdom.
+installation. A typical value is @samp{en_GB.UTF-8} for English in the United
+Kingdom encoded in UTF-8.
The @env{LC_CTYPE} environment variable specifies character
classification. GCC uses it to determine the character boundaries in
`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
see @ref{Bugs}.
If you do use differing options when generating and using the
-precompiled header, the actual behaviour will be a mixture of the
-behaviour for the options. For instance, if you use @option{-g} to
+precompiled header, the actual behavior will be a mixture of the
+behavior for the options. For instance, if you use @option{-g} to
generate the precompiled header but not when using it, you may or may
not get debugging information for routines in the precompiled header.
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