diff options
Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/doc/invoke.texi')
| -rw-r--r-- | gcc-4.2.1-5666.3/gcc/doc/invoke.texi | 15136 |
1 files changed, 0 insertions, 15136 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/doc/invoke.texi b/gcc-4.2.1-5666.3/gcc/doc/invoke.texi deleted file mode 100644 index f8f81b46d..000000000 --- a/gcc-4.2.1-5666.3/gcc/doc/invoke.texi +++ /dev/null @@ -1,15136 +0,0 @@ -@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, -@c 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@ignore -@c man begin INCLUDE -@include gcc-vers.texi -@c man end - -@c man begin COPYRIGHT -Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 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 -any later version published by the Free Software Foundation; with the -Invariant Sections being ``GNU General Public License'' and ``Funding -Free Software'', the Front-Cover texts being (a) (see below), and with -the Back-Cover Texts being (b) (see below). A copy of the license is -included in the gfdl(7) man page. - -(a) The FSF's Front-Cover Text is: - - A GNU Manual - -(b) The FSF's Back-Cover Text is: - - You have freedom to copy and modify this GNU Manual, like GNU - software. Copies published by the Free Software Foundation raise - funds for GNU development. -@c man end -@c Set file name and title for the man page. -@setfilename gcc -@settitle GNU project C and C++ compiler -@c man begin SYNOPSIS -gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}] - [@option{-g}] [@option{-pg}] [@option{-O}@var{level}] - [@option{-W}@var{warn}@dots{}] [@option{-pedantic}] - [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}] - [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}] - [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}] - [@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{} - -Only the most useful options are listed here; see below for the -remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. - -@c APPLE LOCAL begin manual -In Apple's version of GCC, both @samp{cc} and @samp{gcc} are actually -symbolic links to a compiler named like gcc-@var{version}. -Similarly, @samp{c++} and @samp{g++} are links to a compiler named like -g++-@var{version}. - -Note that Apple's GCC includes a number of extensions to standard GCC -(flagged below with ``APPLE ONLY''), and that not all generic GCC -options are available or supported on Darwin / Mac OS X. In particular, -Apple does not currently support the compilation of Fortran, Ada, or -Java, although there are third parties who have made these work. -@c APPLE LOCAL end manual - -@c man end -@c man begin SEEALSO -gpl(7), gfdl(7), fsf-funding(7), -cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1) -and the Info entries for @file{gcc}, @file{cpp}, @file{as}, -@file{ld}, @file{binutils} and @file{gdb}. -@c man end -@c man begin BUGS -@c APPLE LOCAL begin Apple bug-report -To report bugs to Apple, see -@w{@uref{http://developer.apple.com/bugreporter}}. -@c APPLE LOCAL end Apple bug-report -@c man end -@c man begin AUTHOR -See the Info entry for @command{gcc}, or -@w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}}, -for contributors to GCC@. -@c man end -@end ignore - -@node Invoking GCC -@chapter GCC Command Options -@cindex GCC command options -@cindex command options -@cindex options, GCC command - -@c man begin DESCRIPTION -When you invoke GCC, it normally does preprocessing, compilation, -assembly and linking. The ``overall options'' allow you to stop this -process at an intermediate stage. For example, the @option{-c} option -says not to run the linker. Then the output consists of object files -output by the assembler. - -Other options are passed on to one stage of processing. Some options -control the preprocessor and others the compiler itself. Yet other -options control the assembler and linker; most of these are not -documented here, since you rarely need to use any of them. - -@cindex C compilation options -Most of the command line options that you can use with GCC are useful -for C programs; when an option is only useful with another language -(usually C++), the explanation says so explicitly. If the description -for a particular option does not mention a source language, you can use -that option with all supported languages. - -@cindex C++ compilation options -@xref{Invoking G++,,Compiling C++ Programs}, for a summary of special -options for compiling C++ programs. - -@cindex grouping options -@cindex options, grouping -The @command{gcc} program accepts options and file names as operands. Many -options have multi-letter names; therefore multiple single-letter options -may @emph{not} be grouped: @option{-dr} is very different from @w{@samp{-d --r}}. - -@cindex order of options -@cindex options, order -You can mix options and other arguments. For the most part, the order -you use doesn't matter. Order does matter when you use several options -of the same kind; for example, if you specify @option{-L} more than once, -the directories are searched in the order specified. - -Many options have long names starting with @samp{-f} or with -@samp{-W}---for example, -@option{-fmove-loop-invariants}, @option{-Wformat} and so on. Most of -these have both positive and negative forms; the negative form of -@option{-ffoo} would be @option{-fno-foo}. This manual documents -only one of these two forms, whichever one is not the default. - -@c man end - -@xref{Option Index}, for an index to GCC's options. - -@menu -* Option Summary:: Brief list of all options, without explanations. -* Overall Options:: Controlling the kind of output: - an executable, object files, assembler files, - or preprocessed source. -* Invoking G++:: Compiling C++ programs. -* C Dialect Options:: Controlling the variant of C language compiled. -* C++ Dialect Options:: Variations on C++. -* Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C - and Objective-C++. -* Language Independent Options:: Controlling how diagnostics should be - formatted. -* Warning Options:: How picky should the compiler be? -* Debugging Options:: Symbol tables, measurements, and debugging dumps. -* Optimize Options:: How much optimization? -* Preprocessor Options:: Controlling header files and macro definitions. - Also, getting dependency information for Make. -* Assembler Options:: Passing options to the assembler. -* Link Options:: Specifying libraries and so on. -* Directory Options:: Where to find header files and libraries. - Where to find the compiler executable files. -* Spec Files:: How to pass switches to sub-processes. -* Target Options:: Running a cross-compiler, or an old version of GCC. -* Submodel Options:: Specifying minor hardware or convention variations, - such as 68010 vs 68020. -* Code Gen Options:: Specifying conventions for function calls, data layout - and register usage. -* Environment Variables:: Env vars that affect GCC. -* Precompiled Headers:: Compiling a header once, and using it many times. -* Running Protoize:: Automatically adding or removing function prototypes. -@end menu - -@c man begin OPTIONS - -@node Option Summary -@section Option Summary - -Here is a summary of all the options, grouped by type. Explanations are -in the following sections. - -@table @emph -@item Overall Options -@xref{Overall Options,,Options Controlling the Kind of Output}. -@gccoptlist{-c -S -E -o @var{file} -combine -pipe -pass-exit-codes @gol -@c APPLE LOCAL -ObjC 2001-08-03 --sts ** --ObjC (APPLE ONLY) -ObjC++ (APPLE ONLY) @gol -@c APPLE LOCAL begin fat builds --arch @var{arch} (APPLE ONLY) @gol --Xarch_@var{arch} @var{option} (APPLE ONLY) @gol -@c APPLE LOCAL end fat builds -@c APPLE LOCAL ss2 --fsave-repository=@var{file} @gol --x @var{language} -v -### --help --target-help --version @@@var{file}} - -@item C Language Options -@xref{C Dialect Options,,Options Controlling C Dialect}. -@gccoptlist{-ansi -std=@var{standard} -fgnu89-inline @gol --aux-info @var{filename} @gol -@c APPLE LOCAL AltiVec --faltivec (APPLE ONLY) @gol -@c APPLE LOCAL CW asm blocks --fasm-blocks (APPLE ONLY) @gol -@c APPLE LOCAL blocks 7205047 5811887 --fno-asm -fno-blocks -fno-builtin -fno-builtin-@var{function} @gol --fhosted -ffreestanding -fopenmp -fms-extensions @gol --trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol -@c APPLE LOCAL 5612787 sse4 --fallow-single-precision -fcond-mismatch -flax-vector-conversions @gol -@c APPLE LOCAL constant cfstrings --mrs --fconstant-cfstrings (APPLE ONLY) @gol -@c APPLE LOCAL non lvalue assign --fnon-lvalue-assign (APPLE ONLY) @gol -@c APPLE LOCAL nested functions 4357979 */ --fno-nested-functions @gol -@c APPLE LOCAL pch distcc --mrs --fpch-preprocess (APPLE ONLY) @gol --fsigned-bitfields -fsigned-char @gol -@c APPLE LOCAL -Wno-#warnings --Wno-#warnings (APPLE ONLY) @gol -@c APPLE LOCAL -Wextra-tokens 2001-08-02 --sts ** --Wextra-tokens (APPLE ONLY) @gol -@c APPLE LOCAL -Wnewline-eof 2001-08-23 --sts ** --Wnewline-eof (APPLE ONLY) @gol -@c APPLE LOCAL -Wno-altivec-long-deprecated --ilr ** --Wno-altivec-long-deprecated (APPLE ONLY) -@c APPLE LOCAL begin 5695218 --fglobal-alloc-prefer-bytes (APPLE ONLY) --fno-global-alloc-prefer-bytes (APPLE ONLY) -@c APPLE LOCAL end 5695218 -@c APPLE LOCAL fwritable strings --funsigned-bitfields -funsigned-char -fwritable-strings} - -@item C++ Language Options -@xref{C++ Dialect Options,,Options Controlling C++ Dialect}. -@gccoptlist{-fabi-version=@var{n} -fno-access-control -fcheck-new @gol --fconserve-space -ffriend-injection @gol --fno-elide-constructors @gol --fno-enforce-eh-specs @gol --ffor-scope -fno-for-scope -fno-gnu-keywords @gol --fno-implicit-templates @gol --fno-implicit-inline-templates @gol --fno-implement-inlines -fms-extensions @gol --fno-nonansi-builtins -fno-operator-names @gol --fno-optional-diags -fpermissive @gol --frepo -fno-rtti -fstats -ftemplate-depth-@var{n} @gol --fno-threadsafe-statics -fuse-cxa-atexit -fno-weak -nostdinc++ @gol --fno-default-inline -fvisibility-inlines-hidden @gol -@c APPLE LOCAL mainline 2007-06-28 ms tinfo compat 4230099 --fvisibility-ms-compat --Wabi -Wctor-dtor-privacy @gol --Wnon-virtual-dtor -Wreorder @gol --Weffc++ -Wno-deprecated -Wstrict-null-sentinel @gol --Wno-non-template-friend -Wold-style-cast @gol --Woverloaded-virtual -Wno-pmf-conversions @gol --Wsign-promo} - -@item Objective-C and Objective-C++ Language Options -@xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling -Objective-C and Objective-C++ Dialects}. -@gccoptlist{-fconstant-string-class=@var{class-name} @gol --fgnu-runtime -fnext-runtime @gol --fno-nil-receivers @gol --fobjc-call-cxx-cdtors @gol --fobjc-direct-dispatch @gol -@c APPLE LOCAL radar 4512786 --fobjc-sjlj-exceptions @gol --fobjc-gc @gol --freplace-objc-classes @gol --fzero-link @gol --gen-decls @gol --Wassign-intercept @gol --Wno-protocol -Wselector @gol -@c APPLE LOCAL radar 5172645 --Wno-property-assign-default @gol --Wstrict-selector-match @gol --Wundeclared-selector} - -@item Language Independent Options -@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. -@gccoptlist{-fmessage-length=@var{n} @gol --fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol --fdiagnostics-show-option} - -@item Warning Options -@xref{Warning Options,,Options to Request or Suppress Warnings}. -@gccoptlist{-fsyntax-only -pedantic -pedantic-errors @gol --w -Wextra -Wall -Waddress -Waggregate-return -Wno-attributes @gol --Wc++-compat -Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol --Wconversion -Wno-deprecated-declarations @gol --Wdisabled-optimization -Wno-div-by-zero -Wno-endif-labels @gol --Werror -Werror=* -Werror-implicit-function-declaration @gol -@c APPLE LOCAL default to Wformat-security 5764921 --Wfatal-errors -Wfloat-equal -Wno-format -Wformat=2 @gol --Wno-format-extra-args -Wformat-nonliteral @gol -@c APPLE LOCAL default to Wformat-security 5764921 --Wno-format-security -Wformat-y2k @gol -@c APPLE LOCAL Wglobal-constructors 6324584 --Wglobal-constructors @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} -Wunsafe-loop-optimizations -Wlong-long @gol --Wmain -Wmissing-braces -Wmissing-field-initializers @gol --Wmissing-format-attribute -Wmissing-include-dirs @gol --Wmissing-noreturn @gol -@c APPLE LOCAL warn missing prototype 6261539 --Wmissing-prototypes @gol -@c APPLE LOCAL -Wmost --Wmost (APPLE ONLY) @gol --Wno-multichar -Wnonnull -Wno-overflow @gol --Woverlength-strings -Wpacked -Wpadded @gol --Wparentheses -Wpointer-arith -Wno-pointer-to-int-cast @gol --Wredundant-decls @gol --Wreturn-type -Wsequence-point -Wshadow @gol --Wsign-compare -Wstack-protector @gol --Wstrict-aliasing -Wstrict-aliasing=2 @gol --Wstrict-overflow -Wstrict-overflow=@var{n} @gol --Wswitch -Wswitch-default -Wswitch-enum @gol --Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized @gol --Wunknown-pragmas -Wno-pragmas -Wunreachable-code @gol --Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol --Wunused-value -Wunused-variable -Wvariadic-macros @gol --Wvolatile-register-var -Wwrite-strings} - -@c APPLE LOCAL begin -Wdiscard-qual 4086969 -@item C-only Warning Options -@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol -@c APPLE LOCAL warn missing prototype 6261539 --Wnested-externs -Wold-style-definition @gol --Wstrict-prototypes -Wtraditional @gol --Wdeclaration-after-statement -Wno-discard-qual -Wno-pointer-sign} -@c APPLE LOCAL end -Wdiscard-qual 4086969 - -@item Debugging Options -@xref{Debugging Options,,Options for Debugging Your Program or GCC}. -@gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol --fdump-noaddr -fdump-unnumbered -fdump-translation-unit@r{[}-@var{n}@r{]} @gol --fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol --fdump-ipa-all -fdump-ipa-cgraph @gol --fdump-tree-all @gol --fdump-tree-original@r{[}-@var{n}@r{]} @gol --fdump-tree-optimized@r{[}-@var{n}@r{]} @gol --fdump-tree-inlined@r{[}-@var{n}@r{]} @gol --fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias @gol --fdump-tree-ch @gol --fdump-tree-ssa@r{[}-@var{n}@r{]} -fdump-tree-pre@r{[}-@var{n}@r{]} @gol --fdump-tree-ccp@r{[}-@var{n}@r{]} -fdump-tree-dce@r{[}-@var{n}@r{]} @gol --fdump-tree-gimple@r{[}-raw@r{]} -fdump-tree-mudflap@r{[}-@var{n}@r{]} @gol --fdump-tree-dom@r{[}-@var{n}@r{]} @gol --fdump-tree-dse@r{[}-@var{n}@r{]} @gol --fdump-tree-phiopt@r{[}-@var{n}@r{]} @gol --fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol --fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol --fdump-tree-nrv -fdump-tree-vect @gol --fdump-tree-sink @gol --fdump-tree-sra@r{[}-@var{n}@r{]} @gol --fdump-tree-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 -@c APPLE LOCAL 4167759 --flimit-debug-info @gol --feliminate-dwarf2-dups -feliminate-unused-debug-types @gol --feliminate-unused-debug-symbols -femit-class-debug-always @gol -@c APPLE LOCAL opt diary --fmem-report -fopt-diary -fprofile-arcs @gol --frandom-seed=@var{string} -fsched-verbose=@var{n} @gol --ftest-coverage -ftime-report -fvar-tracking @gol --g -g@var{level} -gcoff -gdwarf-2 @gol --ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+ @gol --p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol --print-multi-directory -print-multi-lib @gol --print-prog-name=@var{program} -print-search-dirs -Q @gol --save-temps -time} - -@item Optimization Options -@xref{Optimize Options,,Options that Control Optimization}. -@gccoptlist{-falign-functions=@var{n} -falign-jumps=@var{n} @gol --falign-labels=@var{n} -falign-loops=@var{n} @gol -@c APPLE LOCAL -falign-loops-max-skip --falign-loops-max-skip=@var{n} -falign-jumps-max-skip=@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 -@c APPLE LOCAL add fcreate-profile --fcaller-saves -fcprop-registers -fcreate-profile -fcse-follow-jumps @gol --fcse-skip-blocks -fcx-limited-range -fdata-sections @gol --fdelayed-branch -fdelete-null-pointer-checks -fearly-inlining @gol --fexpensive-optimizations -ffast-math -ffloat-store @gol --fforce-addr -ffunction-sections @gol --fgcse -fgcse-lm -fgcse-sm -fgcse-las -fgcse-after-reload @gol --fcrossjumping -fif-conversion -fif-conversion2 @gol --finline-functions -finline-functions-called-once @gol --finline-limit=@var{n} -fkeep-inline-functions @gol -@c APPLE LOCAL begin ARM conditionally disable local RA --fkeep-static-consts @gol --flocal-alloc (APPLE ONLY) @gol --fmerge-constants -fmerge-all-constants @gol -@c APPLE LOCAL end ARM conditionally disable local RA --fmodulo-sched -fno-branch-count-reg @gol --fno-default-inline -fno-defer-pop -fmove-loop-invariants @gol --fno-function-cse -fno-guess-branch-probability @gol --fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol --funsafe-math-optimizations -funsafe-loop-optimizations -ffinite-math-only @gol --fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol -@c APPLE LOCAL 4356747 stack realign --mstackrealign @gol --fomit-frame-pointer -foptimize-register-move @gol --foptimize-sibling-calls -fprefetch-loop-arrays @gol --fprofile-generate -fprofile-use @gol --fregmove -frename-registers @gol --freorder-blocks -freorder-blocks-and-partition -freorder-functions @gol --frerun-cse-after-loop @gol --frounding-math -frtl-abstract-sequences @gol --fschedule-insns -fschedule-insns2 @gol --fno-sched-interblock -fno-sched-spec -fsched-spec-load @gol --fsched-spec-load-dangerous @gol --fsched-stalled-insns=@var{n} -fsched-stalled-insns-dep=@var{n} @gol --fsched2-use-superblocks @gol --fsched2-use-traces -fsee -freschedule-modulo-scheduled-loops @gol --fsection-anchors -fsignaling-nans -fsingle-precision-constant @gol --fstack-protector -fstack-protector-all @gol --fstrict-aliasing -fstrict-overflow -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 -ftree-sink @gol --ftree-ch -ftree-sra -ftree-ter -ftree-lrs -ftree-fre -ftree-vectorize @gol -@c APPLE LOCAL add fuse-profile --ftree-vect-loop-version -ftree-salias -fuse-profile -fipa-pta -fweb @gol --ftree-copy-prop -ftree-store-ccp -ftree-store-copy-prop -fwhole-program @gol ---param @var{name}=@var{value} -@c APPLE LOCAL -fast, -Oz --O -O0 -O1 -O2 -O3 -Os -Oz (APPLE ONLY) -fast (APPLE ONLY)} - -@item Preprocessor Options -@xref{Preprocessor Options,,Options Controlling the Preprocessor}. -@gccoptlist{-A@var{question}=@var{answer} @gol --A-@var{question}@r{[}=@var{answer}@r{]} @gol --C -dD -dI -dM -dN @gol --D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol --idirafter @var{dir} @gol --include @var{file} -imacros @var{file} @gol --iprefix @var{file} -iwithprefix @var{dir} @gol --iwithprefixbefore @var{dir} -isystem @var{dir} @gol --imultilib @var{dir} -isysroot @var{dir} @gol -@c APPLE LOCAL ARM iwithsysroot 4917039 --iwithsysroot (APPLE ONLY) @var{dir} @gol --M -MM -MF -MG -MP -MQ -MT -nostdinc @gol --P -fworking-directory -remap @gol --trigraphs -undef -U@var{macro} -Wp,@var{option} @gol --Xpreprocessor @var{option}} - -@item Assembler Option -@xref{Assembler Options,,Passing Options to the Assembler}. -@gccoptlist{-Wa,@var{option} -Xassembler @var{option}} - -@item Linker Options -@xref{Link Options,,Options for Linking}. -@gccoptlist{@var{object-file-name} -l@var{library} @gol --nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic @gol --s -static -static-libgcc -shared -shared-libgcc -symbolic @gol --Wl,@var{option} -Xlinker @var{option} @gol --u @var{symbol}} - -@item Directory Options -@xref{Directory Options,,Options for Directory Search}. -@gccoptlist{-B@var{prefix} -I@var{dir} -iquote@var{dir} -L@var{dir} --specs=@var{file} -I- --sysroot=@var{dir}} - -@item Target Options -@c I wrote this xref this way to avoid overfull hbox. -- rms -@xref{Target Options}. -@gccoptlist{-V @var{version} -b @var{machine}} - -@item Machine Dependent Options -@xref{Submodel Options,,Hardware Models and Configurations}. -@c This list is ordered alphanumerically by subsection name. -@c Try and put the significant identifier (CPU or system) first, -@c so users have a clue at guessing where the ones they want will be. - -@c APPLE LOCAL prune man page -@ignore -@emph{ARC Options} -@gccoptlist{-EB -EL @gol --mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text-section} @gol --mdata=@var{data-section} -mrodata=@var{readonly-data-section}} -@c APPLE LOCAL ARM prune man page -@end ignore - -@emph{ARM Options} -@gccoptlist{-mapcs-frame -mno-apcs-frame @gol --mabi=@var{name} @gol --mapcs-stack-check -mno-apcs-stack-check @gol --mapcs-float -mno-apcs-float @gol --mapcs-reentrant -mno-apcs-reentrant @gol --msched-prolog -mno-sched-prolog @gol --mlittle-endian -mbig-endian -mwords-little-endian @gol --mfloat-abi=@var{name} -msoft-float -mhard-float -mfpe @gol --mthumb-interwork -mno-thumb-interwork @gol --mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol --mstructure-size-boundary=@var{n} @gol --mabort-on-noreturn @gol --mlong-calls -mno-long-calls @gol --msingle-pic-base -mno-single-pic-base @gol --mpic-register=@var{reg} @gol --mnop-fun-dllimport @gol --mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns @gol --mpoke-function-name @gol --mthumb -marm @gol --mtpcs-frame -mtpcs-leaf-frame @gol --mcaller-super-interworking -mcallee-super-interworking @gol -@c APPLE LOCAL begin 5946347 ms_struct support --mtp=@var{name} @gol --mms-bitfields -mno-ms-bitfields} -@c APPLE LOCAL end 5946347 ms_struct support - -@c APPLE LOCAL ARM prune man page -@ignore -@emph{AVR Options} -@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 @gol --mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly @gol --mlow-64k -mno-low64k -mid-shared-library @gol --mno-id-shared-library -mshared-library-id=@var{n} @gol --mlong-calls -mno-long-calls} - -@emph{CRIS Options} -@gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol --mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol --metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol --mstack-align -mdata-align -mconst-align @gol --m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol --melf -maout -melinux -mlinux -sim -sim2 @gol --mmul-bug-workaround -mno-mul-bug-workaround} -@c APPLE LOCAL prune man page -@end ignore - -@emph{CRX Options} -@gccoptlist{-mmac -mpush-args} - -@emph{Darwin Options} -@gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol --arch_only -bind_at_load -bundle -bundle_loader @gol --client_name -compatibility_version -current_version @gol --dead_strip @gol --dependency-file -dylib_file -dylinker_install_name @gol --dynamic -dynamiclib -exported_symbols_list @gol --filelist -flat_namespace -force_cpusubtype_ALL @gol -@c APPLE LOCAL 7519550 force local --force_flat_namespace -force_load -headerpad_max_install_names @gol -@c APPLE LOCAL iframework for 4.3 4094959 --iframework @gol --image_base -init -install_name -keep_private_externs @gol --multi_module -multiply_defined -multiply_defined_unused @gol --noall_load -no_dead_strip_inits_and_terms @gol --nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol --pagezero_size -prebind -prebind_all_twolevel_modules @gol --private_bundle -read_only_relocs -sectalign @gol --sectobjectsymbols -whyload -seg1addr @gol --sectcreate -sectobjectsymbols -sectorder @gol --segaddr -segs_read_only_addr -segs_read_write_addr @gol --seg_addr_table -seg_addr_table_filename -seglinkedit @gol --segprot -segs_read_only_addr -segs_read_write_addr @gol --single_module -static -sub_library -sub_umbrella @gol --twolevel_namespace -umbrella -undefined @gol --unexported_symbols_list -weak_reference_mismatches @gol --whatsloaded -F -gused -gfull -mmacosx-version-min=@var{version} @gol -@c APPLE LOCAL ARM 5905142 --miphoneos-version-min=@var{version} @gol -@c APPLE LOCAL pascal strings --mpascal-strings (APPLE ONLY) @gol -@c APPLE LOCAL begin fat builds --mkernel -mone-byte-bool @gol --Xarch_@var{arch}} -@c APPLE LOCAL end fat builds - -@c APPLE LOCAL prune man page -@ignore -@emph{DEC Alpha Options} -@gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol --mieee -mieee-with-inexact -mieee-conformant @gol --mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol --mtrap-precision=@var{mode} -mbuild-constants @gol --mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol --mbwx -mmax -mfix -mcix @gol --mfloat-vax -mfloat-ieee @gol --mexplicit-relocs -msmall-data -mlarge-data @gol --msmall-text -mlarge-text @gol --mmemory-latency=@var{time}} - -@emph{DEC Alpha/VMS Options} -@gccoptlist{-mvms-return-codes} - -@emph{FRV Options} -@gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol --mhard-float -msoft-float @gol --malloc-cc -mfixed-cc -mdword -mno-dword @gol --mdouble -mno-double @gol --mmedia -mno-media -mmuladd -mno-muladd @gol --mfdpic -minline-plt -mgprel-ro -multilib-library-pic @gol --mlinked-fp -mlong-calls -malign-labels @gol --mlibrary-pic -macc-4 -macc-8 @gol --mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol --moptimize-membar -mno-optimize-membar @gol --mscc -mno-scc -mcond-exec -mno-cond-exec @gol --mvliw-branch -mno-vliw-branch @gol --mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol --mno-nested-cond-exec -mtomcat-stats @gol --mTLS -mtls @gol --mcpu=@var{cpu}} - -@emph{GNU/Linux Options} -@gccoptlist{-muclibc} - -@emph{H8/300 Options} -@gccoptlist{-mrelax -mh -ms -mn -mint32 -malign-300} - -@emph{HPPA Options} -@gccoptlist{-march=@var{architecture-type} @gol --mbig-switch -mdisable-fpregs -mdisable-indexing @gol --mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol --mfixed-range=@var{register-range} @gol --mjump-in-delay -mlinker-opt -mlong-calls @gol --mlong-load-store -mno-big-switch -mno-disable-fpregs @gol --mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol --mno-jump-in-delay -mno-long-load-store @gol --mno-portable-runtime -mno-soft-float @gol --mno-space-regs -msoft-float -mpa-risc-1-0 @gol --mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol --mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol --munix=@var{unix-std} -nolibdld -static -threads} -@c APPLE LOCAL prune man page -@end ignore - -@emph{i386 and x86-64 Options} -@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol --mfpmath=@var{unit} @gol --masm=@var{dialect} -mno-fancy-math-387 @gol --mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol --mno-wide-multiply -mrtd -malign-double @gol --mpreferred-stack-boundary=@var{num} @gol -@c APPLE LOCAL begin 5612787 sse4 --mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -msse4a @gol -@c APPLE LOCAL end 5612787 sse4 --mthreads -mno-align-stringops -minline-all-stringops @gol --mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol --m96bit-long-double -mregparm=@var{num} -msseregparm @gol --mstackrealign @gol --momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol --mcmodel=@var{code-model} @gol -@c APPLE LOCAL begin 5946347 ms_struct support --m32 -m64 -mlarge-data-threshold=@var{num} @gol --mms-bitfields -mno-ms-bitfields} -@c APPLE LOCAL end 5946347 ms_struct support - -@c APPLE LOCAL prune man page -@ignore -@emph{IA-64 Options} -@gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @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 @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 @gol --mno-sched-br-data-spec -msched-ar-data-spec -mno-sched-control-spec @gol --msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec @gol --msched-ldc -mno-sched-control-ldc -mno-sched-spec-verbose @gol --mno-sched-prefer-non-data-spec-insns @gol --mno-sched-prefer-non-control-spec-insns @gol --mno-sched-count-spec-in-critical-path} - -@emph{M32R/D Options} -@gccoptlist{-m32r2 -m32rx -m32r @gol --mdebug @gol --malign-loops -mno-align-loops @gol --missue-rate=@var{number} @gol --mbranch-cost=@var{number} @gol --mmodel=@var{code-size-model-type} @gol --msdata=@var{sdata-type} @gol --mno-flush-func -mflush-func=@var{name} @gol --mno-flush-trap -mflush-trap=@var{number} @gol --G @var{num}} - -@emph{M32C Options} -@gccoptlist{-mcpu=@var{cpu} -msim -memregs=@var{number}} - -@emph{M680x0 Options} -@gccoptlist{-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol --m68060 -mcpu32 -m5200 -mcfv4e -m68881 -mbitfield @gol --mc68000 -mc68020 @gol --mnobitfield -mrtd -mshort -msoft-float -mpcrel @gol --malign-int -mstrict-align -msep-data -mno-sep-data @gol --mshared-library-id=n -mid-shared-library -mno-id-shared-library} - -@emph{M68hc1x Options} -@gccoptlist{-m6811 -m6812 -m68hc11 -m68hc12 -m68hcs12 @gol --mauto-incdec -minmax -mlong-calls -mshort @gol --msoft-reg-count=@var{count}} - -@emph{MCore Options} -@gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol --mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol --m4byte-functions -mno-4byte-functions -mcallgraph-data @gol --mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol --mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} - -@emph{MIPS Options} -@gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol --mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips64 @gol --mips16 -mno-mips16 -mabi=@var{abi} -mabicalls -mno-abicalls @gol --mshared -mno-shared -mxgot -mno-xgot -mgp32 -mgp64 @gol --mfp32 -mfp64 -mhard-float -msoft-float @gol --msingle-float -mdouble-float -mdsp -mpaired-single -mips3d @gol --mlong64 -mlong32 -msym32 -mno-sym32 @gol --G@var{num} -membedded-data -mno-embedded-data @gol --muninit-const-in-rodata -mno-uninit-const-in-rodata @gol --msplit-addresses -mno-split-addresses @gol --mexplicit-relocs -mno-explicit-relocs @gol --mcheck-zero-division -mno-check-zero-division @gol --mdivide-traps -mdivide-breaks @gol --mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol --mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol --mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @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 --mvr4130-align -mno-vr4130-align} - -@emph{MMIX Options} -@gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol --mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol --melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol --mno-base-addresses -msingle-exit -mno-single-exit} - -@emph{MN10300 Options} -@gccoptlist{-mmult-bug -mno-mult-bug @gol --mam33 -mno-am33 @gol --mam33-2 -mno-am33-2 @gol --mreturn-pointer-on-d0 @gol --mno-crt0 -mrelax} - -@emph{MT Options} -@gccoptlist{-mno-crt0 -mbacc -msim @gol --march=@var{cpu-type} } - -@emph{PDP-11 Options} -@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol --mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol --mint16 -mno-int32 -mfloat32 -mno-float64 @gol --mfloat64 -mno-float32 -mabshi -mno-abshi @gol --mbranch-expensive -mbranch-cheap @gol --msplit -mno-split -munix-asm -mdec-asm} -@c APPLE LOCAL prune man page -@end ignore - -@emph{PowerPC Options} -See RS/6000 and PowerPC Options. - -@emph{RS/6000 and PowerPC Options} -@gccoptlist{-mcpu=@var{cpu-type} @gol --mtune=@var{cpu-type} @gol --mpower -mno-power -mpower2 -mno-power2 @gol --mpowerpc -mpowerpc64 -mno-powerpc @gol --maltivec -mno-altivec @gol -@c APPLE LOCAL AltiVec --mpim-altivec -mno-pim-altivec @gol --mpowerpc-gpopt -mno-powerpc-gpopt @gol --mpowerpc-gfxopt -mno-powerpc-gfxopt @gol --mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mfprnd -mno-fprnd @gol --mnew-mnemonics -mold-mnemonics @gol --mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol --m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol --malign-power -malign-natural @gol --msoft-float -mhard-float -mmultiple -mno-multiple @gol --mstring -mno-string -mupdate -mno-update @gol --mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol --mstrict-align -mno-strict-align -mrelocatable @gol --mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol --mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol --mdynamic-no-pic -maltivec -mswdiv @gol --mprioritize-restricted-insns=@var{priority} @gol --msched-costly-dep=@var{dependence_type} @gol --minsert-sched-nops=@var{scheme} @gol --mcall-sysv -mcall-netbsd @gol --maix-struct-return -msvr4-struct-return @gol --mabi=@var{abi-type} -msecure-plt -mbss-plt @gol --misel -mno-isel @gol --misel=yes -misel=no @gol --mspe -mno-spe @gol --mspe=yes -mspe=no @gol --mvrsave -mno-vrsave @gol --mmulhw -mno-mulhw @gol --mdlmzb -mno-dlmzb @gol --mfloat-gprs=yes -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double @gol --mprototype -mno-prototype @gol --msim -mmvme -mads -myellowknife -memb -msdata @gol -@c APPLE LOCAL begin 5946347 ms_struct support --msdata=@var{opt} -mvxworks -mwindiss -G @var{num} -pthread @gol --mms-bitfields -mno-ms-bitfields} -@c APPLE LOCAL end 5946347 ms_struct support - -@c APPLE LOCAL prune man page -@ignore -@emph{S/390 and zSeries Options} -@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol --mhard-float -msoft-float -mlong-double-64 -mlong-double-128 @gol --mbackchain -mno-backchain -mpacked-stack -mno-packed-stack @gol --msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol --m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol --mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd @gol --mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard} - -@emph{Score Options} -@gccoptlist{-meb -mel @gol --mnhwloop @gol --muls @gol --mmac @gol --mscore5 -mscore5u -mscore7 -mscore7d} - -@emph{SH Options} -@gccoptlist{-m1 -m2 -m2e -m3 -m3e @gol --m4-nofpu -m4-single-only -m4-single -m4 @gol --m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al @gol --m5-64media -m5-64media-nofpu @gol --m5-32media -m5-32media-nofpu @gol --m5-compact -m5-compact-nofpu @gol --mb -ml -mdalign -mrelax @gol --mbigtable -mfmovd -mhitachi -mrenesas -mno-renesas -mnomacsave @gol --mieee -misize -mpadstruct -mspace @gol --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 --mtune=@var{cpu-type} @gol --mcmodel=@var{code-model} @gol --m32 -m64 -mapp-regs -mno-app-regs @gol --mfaster-structs -mno-faster-structs @gol --mfpu -mno-fpu -mhard-float -msoft-float @gol --mhard-quad-float -msoft-quad-float @gol --mimpure-text -mno-impure-text -mlittle-endian @gol --mstack-bias -mno-stack-bias @gol --munaligned-doubles -mno-unaligned-doubles @gol --mv8plus -mno-v8plus -mvis -mno-vis --threads -pthreads -pthread} - -@emph{System V Options} -@gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}} - -@emph{TMS320C3x/C4x Options} -@gccoptlist{-mcpu=@var{cpu} -mbig -msmall -mregparm -mmemparm @gol --mfast-fix -mmpyi -mbk -mti -mdp-isr-reload @gol --mrpts=@var{count} -mrptb -mdb -mloop-unsigned @gol --mparallel-insns -mparallel-mpy -mpreserve-float} - -@emph{V850 Options} -@gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol --mprolog-function -mno-prolog-function -mspace @gol --mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol --mapp-regs -mno-app-regs @gol --mdisable-callt -mno-disable-callt @gol --mv850e1 @gol --mv850e @gol --mv850 -mbig-switch} - -@emph{VAX Options} -@gccoptlist{-mg -mgnu -munix} - -@emph{x86-64 Options} -See i386 and x86-64 Options. - -@emph{Xstormy16 Options} -@gccoptlist{-msim} - -@emph{Xtensa Options} -@gccoptlist{-mconst16 -mno-const16 @gol --mfused-madd -mno-fused-madd @gol --mtext-section-literals -mno-text-section-literals @gol --mtarget-align -mno-target-align @gol --mlongcalls -mno-longcalls} - -@emph{zSeries Options} -See S/390 and zSeries Options. -@c APPLE LOCAL prune man page -@end ignore - -@item Code Generation Options -@xref{Code Gen Options,,Options for Code Generation Conventions}. -@gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol --ffixed-@var{reg} -fexceptions @gol --fnon-call-exceptions -funwind-tables @gol --fasynchronous-unwind-tables @gol --finhibit-size-directive -finstrument-functions @gol --fno-common -fno-ident @gol --fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol --fno-jump-tables @gol --freg-struct-return -fshort-enums @gol --fshort-double -fshort-wchar @gol --fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol --fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol --fargument-alias -fargument-noalias @gol --fargument-noalias-global -fargument-noalias-anything --fleading-underscore -ftls-model=@var{model} @gol -@c APPLE LOCAL begin prune man page 5547358 -@c -ftrapv --fwrapv -fbounds-check @gol -@c APPLE LOCAL end prune man page --fvisibility} -@end table - -@menu -* Overall Options:: Controlling the kind of output: - an executable, object files, assembler files, - or preprocessed source. -* C Dialect Options:: Controlling the variant of C language compiled. -* C++ Dialect Options:: Variations on C++. -* Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C - and Objective-C++. -* Language Independent Options:: Controlling how diagnostics should be - formatted. -* Warning Options:: How picky should the compiler be? -* Debugging Options:: Symbol tables, measurements, and debugging dumps. -* Optimize Options:: How much optimization? -* Preprocessor Options:: Controlling header files and macro definitions. - Also, getting dependency information for Make. -* Assembler Options:: Passing options to the assembler. -* Link Options:: Specifying libraries and so on. -* Directory Options:: Where to find header files and libraries. - Where to find the compiler executable files. -* Spec Files:: How to pass switches to sub-processes. -* Target Options:: Running a cross-compiler, or an old version of GCC. -@end menu - -@node Overall Options -@section Options Controlling the Kind of Output - -Compilation can involve up to four stages: preprocessing, compilation -proper, assembly and linking, always in that order. GCC is capable of -preprocessing and compiling several files either into several -assembler input files, or into one assembler input file; then each -assembler input file produces an object file, and linking combines all -the object files (those newly compiled, and those specified as input) -into an executable file. - -@cindex file name suffix -For any given input file, the file name suffix determines what kind of -compilation is done: - -@table @gcctabopt -@item @var{file}.c -C source code which must be preprocessed. - -@item @var{file}.i -C source code which should not be preprocessed. - -@item @var{file}.ii -C++ source code which should not be preprocessed. - -@item @var{file}.m -Objective-C source code. Note that you must link with the @file{libobjc} -library to make an Objective-C program work. - -@item @var{file}.mi -Objective-C source code which should not be preprocessed. - -@item @var{file}.mm -@itemx @var{file}.M -Objective-C++ source code. Note that you must link with the @file{libobjc} -library to make an Objective-C++ program work. Note that @samp{.M} refers -to a literal capital M@. - -@item @var{file}.mii -Objective-C++ source code which should not be preprocessed. - -@item @var{file}.h -C, C++, Objective-C or Objective-C++ header file to be turned into a -precompiled header. - -@item @var{file}.cc -@itemx @var{file}.cp -@itemx @var{file}.cxx -@itemx @var{file}.cpp -@itemx @var{file}.CPP -@itemx @var{file}.c++ -@itemx @var{file}.C -C++ source code which must be preprocessed. Note that in @samp{.cxx}, -the last two letters must both be literally @samp{x}. Likewise, -@samp{.C} refers to a literal capital C@. - -@c APPLE LOCAL begin Objective-C++ -@c Delete duplicate @var{file}.mm, @var{file}.M, @var{file}.mii. -@c APPLE LOCAL end Objective-C++ - -@item @var{file}.hh -@itemx @var{file}.H -C++ header file to be turned into a precompiled header. - -@item @var{file}.f -@itemx @var{file}.for -@itemx @var{file}.FOR -Fixed form Fortran source code which should not be preprocessed. - -@item @var{file}.F -@itemx @var{file}.fpp -@itemx @var{file}.FPP -Fixed form Fortran source code which must be preprocessed (with the traditional -preprocessor). - -@item @var{file}.f90 -@itemx @var{file}.f95 -Free form Fortran source code which should not be preprocessed. - -@item @var{file}.F90 -@itemx @var{file}.F95 -Free form Fortran source code which must be preprocessed (with the -traditional preprocessor). - -@c FIXME: Descriptions of Java file types. -@c @var{file}.java -@c @var{file}.class -@c @var{file}.zip -@c @var{file}.jar - -@item @var{file}.ads -Ada source code file which contains a library unit declaration (a -declaration of a package, subprogram, or generic, or a generic -instantiation), or a library unit renaming declaration (a package, -generic, or subprogram renaming declaration). Such files are also -called @dfn{specs}. - -@itemx @var{file}.adb -Ada source code file containing a library unit body (a subprogram or -package body). Such files are also called @dfn{bodies}. - -@c GCC also knows about some suffixes for languages not yet included: -@c Pascal: -@c @var{file}.p -@c @var{file}.pas -@c Ratfor: -@c @var{file}.r - -@item @var{file}.s -@c APPLE LOCAL begin preprocess .s files -Assembler code. Apple's version of GCC runs the preprocessor -on these files as well as those ending in @samp{.S}. -@c APPLE LOCAL end preprocess .s files - -@item @var{file}.S -Assembler code which must be preprocessed. - -@item @var{other} -An object file to be fed straight into linking. -Any file name with no recognized suffix is treated this way. -@end table - -@opindex x -You can specify the input language explicitly with the @option{-x} option: - -@table @gcctabopt -@item -x @var{language} -Specify explicitly the @var{language} for the following input files -(rather than letting the compiler choose a default based on the file -name suffix). This option applies to all following input files until -the next @option{-x} option. Possible values for @var{language} are: -@smallexample -c c-header c-cpp-output -c++ c++-header c++-cpp-output -objective-c objective-c-header objective-c-cpp-output -objective-c++ objective-c++-header objective-c++-cpp-output -assembler assembler-with-cpp -ada -f95 f95-cpp-input -java -treelang -@end smallexample - -@item -x none -Turn off any specification of a language, so that subsequent files are -handled according to their file name suffixes (as they are if @option{-x} -has not been used at all). - -@c APPLE LOCAL begin -ObjC 2001-08-03 --sts ** -@item -ObjC -@itemx -ObjC++ -@opindex ObjC -@opindex ObjC++ -These are similar in effect to @option{-x objective-c} and @option{-x -objective-c++}, but affect only the choice of compiler for files already -identified as source files. (APPLE ONLY) -@c APPLE LOCAL end -ObjC 2001-08-03 --sts ** - -@c APPLE LOCAL begin fat builds -@item -arch @var{arch} -@opindex arch -Compile for the specified target architecture @var{arch}. The -allowable values are @samp{i386}, @samp{x86_64}, @samp{ppc} and -@samp{ppc64}. Multiple options work, and direct the compiler to -produce ``universal'' binaries including object code for each -architecture specified with @option{-arch}. This option only works if -assembler and libraries are available for each architecture specified. -(APPLE ONLY) - -@item -Xarch_@var{arch} @var{option} -@opindex Xarch -Apply @var{option} to the command line for architecture @var{arch}. -This is useful for specifying an option that should only apply to -one architecture when building a ``universal'' binary. (APPLE ONLY) -@c APPLE LOCAL end fat builds - -@c APPLE LOCAL begin ss2 -@item -fsave-repository=@var{file} -@opindex fsave-repository -Save debug info in separate object file. -This is available only while building PCH in -gfull mode. -@c APPLE LOCAL end ss2 - -@item -pass-exit-codes -@opindex pass-exit-codes -Normally the @command{gcc} program will exit with the code of 1 if any -phase of the compiler returns a non-success return code. If you specify -@option{-pass-exit-codes}, the @command{gcc} program will instead return with -numerically highest error produced by any phase that returned an error -indication. The C, C++, and Fortran frontends return 4, if an internal -compiler error is encountered. -@end table - -If you only want some of the stages of compilation, you can use -@option{-x} (or filename suffixes) to tell @command{gcc} where to start, and -one of the options @option{-c}, @option{-S}, or @option{-E} to say where -@command{gcc} is to stop. Note that some combinations (for example, -@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. - -@table @gcctabopt -@item -c -@opindex c -Compile or assemble the source files, but do not link. The linking -stage simply is not done. The ultimate output is in the form of an -object file for each source file. - -By default, the object file name for a source file is made by replacing -the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. - -Unrecognized input files, not requiring compilation or assembly, are -ignored. - -@item -S -@opindex S -Stop after the stage of compilation proper; do not assemble. The output -is in the form of an assembler code file for each non-assembler input -file specified. - -By default, the assembler file name for a source file is made by -replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}. - -Input files that don't require compilation are ignored. - -@item -E -@opindex E -Stop after the preprocessing stage; do not run the compiler proper. The -output is in the form of preprocessed source code, which is sent to the -standard output. - -Input files which don't require preprocessing are ignored. - -@cindex output file option -@item -o @var{file} -@opindex o -Place output in file @var{file}. This applies regardless to whatever -sort of output is being produced, whether it be an executable file, -an object file, an assembler file or preprocessed C code. - -If @option{-o} is not specified, the default is to put an executable -file in @file{a.out}, the object file for -@file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its -assembler file in @file{@var{source}.s}, a precompiled header file in -@file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on -standard output. - -@item -v -@opindex v -Print (on standard error output) the commands executed to run the stages -of compilation. Also print the version number of the compiler driver -program and of the preprocessor and the compiler proper. - -@item -### -@opindex ### -Like @option{-v} except the commands are not executed and all command -arguments are quoted. This is useful for shell scripts to capture the -driver-generated command lines. - -@item -pipe -@opindex pipe -Use pipes rather than temporary files for communication between the -various stages of compilation. This fails to work on some systems where -the assembler is unable to read from a pipe; but the GNU assembler has -no trouble. - -@item -combine -@opindex combine -If you are compiling multiple source files, this option tells the driver -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 -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 @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 -Print (on the standard output) a description of the command line options -understood by @command{gcc}. If the @option{-v} option is also specified -then @option{--help} will also be passed on to the various processes -invoked by @command{gcc}, so that they can display the command line options -they accept. If the @option{-Wextra} option is also specified then command -line options which have no documentation associated with them will also -be displayed. - -@item --target-help -@opindex target-help -Print (on the standard output) a description of target specific command -line options for each tool. - -@item --version -@opindex version -Display the version number and copyrights of the invoked GCC@. - -@include @value{srcdir}/../libiberty/at-file.texi -@end table - -@node Invoking G++ -@section Compiling C++ Programs - -@cindex suffixes for C++ source -@cindex C++ source file suffixes -C++ source files conventionally use one of the suffixes @samp{.C}, -@samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or -@samp{.cxx}; C++ header files often use @samp{.hh} or @samp{.H}; and -preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes -files with these names and compiles them as C++ programs even if you -call the compiler the same way as for compiling C programs (usually -with the name @command{gcc}). - -@findex g++ -@findex c++ -However, the use of @command{gcc} does not add the C++ library. -@command{g++} is a program that calls GCC and treats @samp{.c}, -@samp{.h} and @samp{.i} files as C++ source files instead of C source -files unless @option{-x} is used, and automatically specifies linking -against the C++ library. This program is also useful when -precompiling a C header file with a @samp{.h} extension for use in C++ -compilations. On many systems, @command{g++} is also installed with -the name @command{c++}. - -@cindex invoking @command{g++} -When you compile C++ programs, you may specify many of the same -command-line options that you use for compiling programs in any -language; or command-line options meaningful for C and related -languages; or options that are meaningful only for C++ programs. -@xref{C Dialect Options,,Options Controlling C Dialect}, for -explanations of options for languages related to C@. -@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for -explanations of options that are meaningful only for C++ programs. - -@node C Dialect Options -@section Options Controlling C Dialect -@cindex dialect options -@cindex language dialect options -@cindex options, dialect - -The following options control the dialect of C (or languages derived -from C, such as C++, Objective-C and Objective-C++) that the compiler -accepts: - -@table @gcctabopt -@cindex ANSI support -@cindex ISO support -@item -ansi -@opindex ansi -In C mode, support all ISO C90 programs. In C++ mode, -remove GNU extensions that conflict with ISO C++. - -This turns off certain features of GCC that are incompatible with ISO -C90 (when compiling C code), or of standard C++ (when compiling C++ code), -such as the @code{asm} and @code{typeof} keywords, and -predefined macros such as @code{unix} and @code{vax} that identify the -type of system you are using. It also enables the undesirable and -rarely used ISO trigraph feature. For the C compiler, -it disables recognition of C++ style @samp{//} comments as well as -the @code{inline} keyword. - -The alternate keywords @code{__asm__}, @code{__extension__}, -@code{__inline__} and @code{__typeof__} continue to work despite -@option{-ansi}. You would not want to use them in an ISO C program, of -course, but it is useful to put them in header files that might be included -in compilations done with @option{-ansi}. Alternate predefined macros -such as @code{__unix__} and @code{__vax__} are also available, with or -without @option{-ansi}. - -The @option{-ansi} option does not cause non-ISO programs to be -rejected gratuitously. For that, @option{-pedantic} is required in -addition to @option{-ansi}. @xref{Warning Options}. - -The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi} -option is used. Some header files may notice this macro and refrain -from declaring certain functions or defining certain macros that the -ISO standard doesn't call for; this is to avoid interfering with any -programs that might use these names for other things. - -Functions which would normally be built in but do not have semantics -defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in -functions with @option{-ansi} is used. @xref{Other Builtins,,Other -built-in functions provided by GCC}, for details of the functions -affected. - -@item -std= -@opindex std -Determine the language standard. This option is currently only -supported when compiling C or C++. A value for this option must be -provided; possible values are - -@table @samp -@item c89 -@itemx iso9899:1990 -ISO C90 (same as @option{-ansi}). - -@item iso9899:199409 -ISO C90 as modified in amendment 1. - -@item c99 -@itemx c9x -@itemx iso9899:1999 -@itemx iso9899:199x -ISO C99. Note that this standard is not yet fully supported; see -@w{@uref{http://gcc.gnu.org/gcc-4.2/c99status.html}} for more information. The -names @samp{c9x} and @samp{iso9899:199x} are deprecated. - -@item gnu89 -Default, ISO C90 plus GNU extensions (including some C99 features). - -@item gnu99 -@itemx gnu9x -ISO C99 plus GNU extensions. When ISO C99 is fully implemented in GCC, -this will become the default. The name @samp{gnu9x} is deprecated. - -@item c++98 -The 1998 ISO C++ standard plus amendments. - -@item gnu++98 -The same as @option{-std=c++98} plus GNU extensions. This is the -default for C++ code. -@end table - -Even when this option is not specified, you can still use some of the -features of newer standards in so far as they do not conflict with -previous C standards. For example, you may use @code{__restrict__} even -when @option{-std=c99} is not specified. - -The @option{-std} options specifying some version of ISO C have the same -effects as @option{-ansi}, except that features that were not in ISO C90 -but are in the specified version (for example, @samp{//} comments and -the @code{inline} keyword in ISO C99) are not disabled. - -@xref{Standards,,Language Standards Supported by GCC}, for details of -these standard versions. - -@item -fgnu89-inline -@opindex fgnu89-inline -The option @option{-fgnu89-inline} tells GCC to use the traditional -GNU semantics for @code{inline} functions when in C99 mode. -@xref{Inline,,An Inline Function is As Fast As a Macro}. Using this -option is roughly equivalent to adding the @code{gnu_inline} function -attribute to all inline functions (@pxref{Function Attributes}). - -This option is accepted by GCC versions 4.1.3 and up. In GCC versions -/* APPLE LOCAL extern inline */ -prior to 4.3 (4.2 for Apple's gcc), C99 inline semantics are not supported, and thus this -option is effectively assumed to be present regardless of whether or not -it is specified; the only effect of specifying it explicitly is to -disable warnings about using inline functions in C99 mode. Likewise, -the option @option{-fno-gnu89-inline} is not supported in versions of -/* APPLE LOCAL extern inline */ -GCC before 4.3 (4.2 for Apple's gcc). It is supported only in C99 or gnu99 mode, not in -C89 or gnu89 mode. - -The preprocesor macros @code{__GNUC_GNU_INLINE__} and -@code{__GNUC_STDC_INLINE__} may be used to check which semantics are -in effect for @code{inline} functions. @xref{Common Predefined -Macros,,,cpp,The C Preprocessor}. - -@item -aux-info @var{filename} -@opindex aux-info -Output to the given filename prototyped declarations for all functions -declared and/or defined in a translation unit, including those in header -files. This option is silently ignored in any language other than C@. - -Besides declarations, the file indicates, in comments, the origin of -each declaration (source file and line), whether the declaration was -implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or -@samp{O} for old, respectively, in the first character after the line -number and the colon), and whether it came from a declaration or a -definition (@samp{C} or @samp{F}, respectively, in the following -character). In the case of function definitions, a K&R-style list of -arguments followed by their declarations is also provided, inside -comments, after the declaration. - -@c APPLE LOCAL begin AltiVec -@item -faltivec -This flag is provided for compatibility with Metrowerks CodeWarrior and MrC -compilers as well as previous Apple versions of GCC. It causes the -@option{-mpim-altivec} option to be turned on. -@c APPLE LOCAL end AltiVec - -@c APPLE LOCAL begin CW asm blocks -@item -fasm-blocks -Enable the use of blocks and entire functions of assembly code within -a C or C++ file. The syntax follows that used in CodeWarrior. This -option is not supported for ARM targets. (APPLE ONLY) -@c APPLE LOCAL end CW asm blocks - -@item -fno-asm -@opindex fno-asm -Do not recognize @code{asm}, @code{inline} or @code{typeof} as a -keyword, so that code can use these words as identifiers. You can use -the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} -instead. @option{-ansi} implies @option{-fno-asm}. - -In C++, this switch only affects the @code{typeof} keyword, since -@code{asm} and @code{inline} are standard keywords. You may want to -use the @option{-fno-gnu-keywords} flag instead, which has the same -effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this -switch only affects the @code{asm} and @code{typeof} keywords, since -@code{inline} is a standard keyword in ISO C99. - -@c APPLE LOCAL begin blocks 7205047 5811887 -@item -fno-blocks -@opindex fno-blocks -Disable the use of blocks. In @option{-std=c99} mode, blocks are -turned off by default. @option{-fblocks} can be used to re-enable the -feature, if off. Runtime support for blocks first appeared in Mac OS -X 10.6. When targeting 10.6 (see @option{-mmacosx-version-min}) and -later, the extension is on by default. -@c APPLE LOCAL end blocks 7205047 5811887 - -@item -fno-builtin -@itemx -fno-builtin-@var{function} -@opindex fno-builtin -@cindex built-in functions -Don't recognize built-in functions that do not begin with -@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in -functions provided by GCC}, for details of the functions affected, -including those which are not built-in functions when @option{-ansi} or -@option{-std} options for strict ISO C conformance are used because they -do not have an ISO standard meaning. - -GCC normally generates special code to handle certain built-in functions -more efficiently; for instance, calls to @code{alloca} may become single -instructions that adjust the stack directly, and calls to @code{memcpy} -may become inline copy loops. The resulting code is often both smaller -and faster, but since the function calls no longer appear as such, you -cannot set a breakpoint on those calls, nor can you change the behavior -of the functions by linking with a different library. In addition, -when a function is recognized as a built-in function, GCC may use -information about that function to warn about problems with calls to -that function, or to generate more efficient code, even if the -resulting code still contains calls to that function. For example, -warnings are given with @option{-Wformat} for bad calls to -@code{printf}, when @code{printf} is built in, and @code{strlen} is -known not to modify global memory. - -With the @option{-fno-builtin-@var{function}} option -only the built-in function @var{function} is -disabled. @var{function} must not begin with @samp{__builtin_}. If a -function is named this is not built-in in this version of GCC, this -option is ignored. There is no corresponding -@option{-fbuiltin-@var{function}} option; if you wish to enable -built-in functions selectively when using @option{-fno-builtin} or -@option{-ffreestanding}, you may define macros such as: - -@smallexample -#define abs(n) __builtin_abs ((n)) -#define strcpy(d, s) __builtin_strcpy ((d), (s)) -@end smallexample - -@item -fhosted -@opindex fhosted -@cindex hosted environment - -Assert that compilation takes place in a hosted environment. This implies -@option{-fbuiltin}. A hosted environment is one in which the -entire standard library is available, and in which @code{main} has a return -type of @code{int}. Examples are nearly everything except a kernel. -This is equivalent to @option{-fno-freestanding}. - -@item -ffreestanding -@opindex ffreestanding -@cindex hosted environment - -Assert that compilation takes place in a freestanding environment. This -implies @option{-fno-builtin}. A freestanding environment -is one in which the standard library may not exist, and program startup may -not necessarily be at @code{main}. The most obvious example is an OS kernel. -This is equivalent to @option{-fno-hosted}. - -@xref{Standards,,Language Standards Supported by GCC}, for details of -freestanding and hosted environments. - -@item -fopenmp -@opindex fopenmp -@cindex openmp parallel -Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and -@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the -compiler generates parallel code according to the OpenMP Application -Program Interface v2.5 @w{@uref{http://www.openmp.org/}}. - -@item -fms-extensions -@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} -options for strict ISO C conformance) implies @option{-trigraphs}. - -@item -no-integrated-cpp -@opindex no-integrated-cpp -Performs a compilation in two passes: preprocessing and compiling. This -option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the -@option{-B} option. The user supplied compilation step can then add in -an additional preprocessing step after normal preprocessing but before -compiling. The default is to use the integrated cpp (internal cpp) - -The semantics of this option will change if "cc1", "cc1plus", and -"cc1obj" are merged. - -@cindex traditional C language -@cindex C language, traditional -@item -traditional -@itemx -traditional-cpp -@opindex traditional-cpp -@opindex traditional -Formerly, these options caused GCC to attempt to emulate a pre-standard -C compiler. They are now only supported with the @option{-E} switch. -The preprocessor continues to support a pre-standard mode. See the GNU -CPP manual for details. - -@item -fcond-mismatch -@opindex fcond-mismatch -Allow conditional expressions with mismatched types in the second and -third arguments. The value of such an expression is void. This option -is not supported for C++. - -@c APPLE LOCAL begin nested functions 4357979 -@item -fno-nested-functions -@opindex fno-nested-functions -Disable nested functions. This option is not supported for C++ or -Objective-C++. On Darwin, nested functions are disabled by default. -@c APPLE LOCAL end nested functions 4357979 - -@c APPLE LOCAL begin pch distcc --mrs -@item -fpch-preprocess -@opindex fpch-preprocess -Enable PCH processing even when @option{-E} or @option{-save-temps} is used. -@c APPLE LOCAL end pch distcc --mrs - -@c APPLE LOCAL begin non lvalue assign -@item -fnon-lvalue-assign -@opindex fnon-lvalue-assign -C and C++ forbid the use of casts and conditional expressions as lvalues, e.g.: - -@smallexample -float *p, q, r; -((int *)p)++; -(cond ? q : r) = 3.0; -@end smallexample - -@noindent -As a transitional measure, the Apple version of GCC 4.0 allows casts and -conditional expressions to be used as lvalues in certain situations. This -is accomplished via the @option{-fnon-lvalue-assign} switch, which is on -by default. Whenever an lvalue cast or an lvalue conditional expression is -encountered, the compiler will issue a deprecation warning and then rewrite -the expression as follows: - -@smallexample -(type)expr ---becomes---> *(type *)&expr -cond ? expr1 : expr2 ---becomes---> *(cond ? &expr1 : &expr2) -@end smallexample - -To disallow lvalue casts and lvalue conditional expressions altogether, -specify @option{-fno-non-lvalue-assign}; lvalue casts and lvalue conditional -expressions will be disallowed in future versions of Apple's GCC. -@c APPLE LOCAL end non lvalue assign - -@c APPLE LOCAL begin 5612787 sse4 -@item -flax-vector-conversions -@opindex flax-vector-conversions -Allow implicit conversions between vectors with differing numbers of -elements and/or incompatible element types. This option should not be -used for new code. -@c APPLE LOCAL end 5612787 sse4 - -@item -funsigned-char -@opindex funsigned-char -Let the type @code{char} be unsigned, like @code{unsigned char}. - -Each kind of machine has a default for what @code{char} should -be. It is either like @code{unsigned char} by default or like -@code{signed char} by default. - -Ideally, a portable program should always use @code{signed char} or -@code{unsigned char} when it depends on the signedness of an object. -But many programs have been written to use plain @code{char} and -expect it to be signed, or expect it to be unsigned, depending on the -machines they were written for. This option, and its inverse, let you -make such a program work with the opposite default. - -The type @code{char} is always a distinct type from each of -@code{signed char} or @code{unsigned char}, even though its behavior -is always just like one of those two. - -@item -fsigned-char -@opindex fsigned-char -Let the type @code{char} be signed, like @code{signed char}. - -Note that this is equivalent to @option{-fno-unsigned-char}, which is -the negative form of @option{-funsigned-char}. Likewise, the option -@option{-fno-signed-char} is equivalent to @option{-funsigned-char}. - -@item -fsigned-bitfields -@itemx -funsigned-bitfields -@itemx -fno-signed-bitfields -@itemx -fno-unsigned-bitfields -@opindex fsigned-bitfields -@opindex funsigned-bitfields -@opindex fno-signed-bitfields -@opindex fno-unsigned-bitfields -These options control whether a bit-field is signed or unsigned, when the -declaration does not use either @code{signed} or @code{unsigned}. By -default, such a bit-field is signed, because this is consistent: the -basic integer types such as @code{int} are signed types. - -@c APPLE LOCAL begin constant cfstrings -@item -fconstant-cfstrings -@opindex fconstant-cfstrings -Enable the automatic creation of a CoreFoundation-type constant string -whenever a special builtin @code{__builtin__CFStringMakeConstantString} -is called on a literal string. (APPLE ONLY) -@c APPLE LOCAL end constant cfstrings - -@c APPLE LOCAL begin radar 3506309 -@item -Wnonportable-cfstrings -@opindex Wnonportable-cfstrings -Warn if constant CFString objects contain non-portable characters -(default behavior) -@c APPLE LOCAL end radar 3506309 - -@c APPLE LOCAL begin 5695218 -@item -fglobal-alloc-prefer-bytes -@item -fno-global-alloc-prefer-bytes -@opindex fglobal-alloc-prefer-bytes -For the x86_32 architecture, prefer byte or short values to word -values during global register allocation. Some of the registers on -this target can't be used with values smaller than a 32-bit word; -allocating these values earlier increases the chance they will get a -byte-capable (or short-capable) register. Ignored for other targets. -Defaults on with global register allocation (@code{-Os}, @code{-O2}, -or @code{-O3}). (APPLE ONLY) -@c APPLE LOCAL end 5695218 -@c APPLE LOCAL begin fwritable strings. -@item -fwritable-strings -@opindex fwritable-strings -Store string constants in the writable data segment and don't uniquize -them. This is for compatibility with old programs which assume they can -write into string constants. - -Writing into string constants is a very bad idea; ``constants'' should -be constant. - -This option is deprecated. -@c APPLE LOCAL end fwritable strings. -@end table - -@node C++ Dialect Options -@section Options Controlling C++ Dialect - -@cindex compiler options, C++ -@cindex C++ options, command line -@cindex options, C++ -This section describes the command-line options that are only meaningful -for C++ programs; but you can also use most of the GNU compiler options -regardless of what language your program is in. For example, you -might compile a file @code{firstClass.C} like this: - -@smallexample -g++ -g -frepo -O -c firstClass.C -@end smallexample - -@noindent -In this example, only @option{-frepo} is an option meant -only for C++ programs; you can use the other options with any -language supported by GCC@. - -Here is a list of options that are @emph{only} for compiling C++ programs: - -@table @gcctabopt - -@item -fabi-version=@var{n} -@opindex fabi-version -Use version @var{n} of the C++ ABI@. Version 2 is the version of the -C++ ABI that first appeared in G++ 3.4. Version 1 is the version of -the C++ ABI that first appeared in G++ 3.2. Version 0 will always be -the version that conforms most closely to the C++ ABI specification. -Therefore, the ABI obtained using version 0 will change as ABI bugs -are fixed. - -The default is version 2. - -@item -fno-access-control -@opindex fno-access-control -Turn off all access checking. This switch is mainly useful for working -around bugs in the access control code. - -@item -fcheck-new -@opindex fcheck-new -Check that the pointer returned by @code{operator new} is non-null -before attempting to modify the storage allocated. This check is -normally unnecessary because the C++ standard specifies that -@code{operator new} will only return @code{0} if it is declared -@samp{throw()}, in which case the compiler will always check the -return value even without this option. In all other cases, when -@code{operator new} has a non-empty exception specification, memory -exhaustion is signalled by throwing @code{std::bad_alloc}. See also -@samp{new (nothrow)}. - -@item -fconserve-space -@opindex fconserve-space -Put uninitialized or runtime-initialized global variables into the -common segment, as C does. This saves space in the executable at the -cost of not diagnosing duplicate definitions. If you compile with this -flag and your program mysteriously crashes after @code{main()} has -completed, you may have an object that is being destroyed twice because -two definitions were merged. - -This option is no longer useful on most targets, now that support has -been added for putting variables into BSS without making them common. - -@item -ffriend-injection -@opindex ffriend-injection -Inject friend functions into the enclosing namespace, so that they are -visible outside the scope of the class in which they are declared. -Friend functions were documented to work this way in the old Annotated -C++ Reference Manual, and versions of G++ before 4.1 always worked -that way. However, in ISO C++ a friend function which is not declared -in an enclosing scope can only be found using argument dependent -lookup. This option causes friends to be injected as they were in -earlier releases. - -This option is for compatibility, and may be removed in a future -release of G++. - -@item -fno-elide-constructors -@opindex fno-elide-constructors -The C++ standard allows an implementation to omit creating a temporary -which is only used to initialize another object of the same type. -Specifying this option disables that optimization, and forces G++ to -call the copy constructor in all cases. - -@item -fno-enforce-eh-specs -@opindex fno-enforce-eh-specs -Don't generate code to check for violation of exception specifications -at runtime. This option violates the C++ standard, but may be useful -for reducing code size in production builds, much like defining -@samp{NDEBUG}. This does not give user code permission to throw -exceptions in violation of the exception specifications; the compiler -will still optimize based on the specifications, so throwing an -unexpected exception will result in undefined behavior. - -@item -ffor-scope -@itemx -fno-for-scope -@opindex ffor-scope -@opindex fno-for-scope -If @option{-ffor-scope} is specified, the scope of variables declared in -a @i{for-init-statement} is limited to the @samp{for} loop itself, -as specified by the C++ standard. -If @option{-fno-for-scope} is specified, the scope of variables declared in -a @i{for-init-statement} extends to the end of the enclosing scope, -as was the case in old versions of G++, and other (traditional) -implementations of C++. - -The default if neither flag is given to follow the standard, -but to allow and give a warning for old-style code that would -otherwise be invalid, or have different behavior. - -@item -fno-gnu-keywords -@opindex fno-gnu-keywords -Do not recognize @code{typeof} as a keyword, so that code can use this -word as an identifier. You can use the keyword @code{__typeof__} instead. -@option{-ansi} implies @option{-fno-gnu-keywords}. - -@item -fno-implicit-templates -@opindex fno-implicit-templates -Never emit code for non-inline templates which are instantiated -implicitly (i.e.@: by use); only emit code for explicit instantiations. -@xref{Template Instantiation}, for more information. - -@item -fno-implicit-inline-templates -@opindex fno-implicit-inline-templates -Don't emit code for implicit instantiations of inline templates, either. -The default is to handle inlines differently so that compiles with and -without optimization will need the same set of explicit instantiations. - -@item -fno-implement-inlines -@opindex fno-implement-inlines -To save space, do not emit out-of-line copies of inline functions -controlled by @samp{#pragma implementation}. This will cause linker -errors if these functions are not inlined everywhere they are called. - -@item -fms-extensions -@opindex fms-extensions -Disable pedantic warnings about constructs used in MFC, such as implicit -int and getting a pointer to member function via non-standard syntax. - -@item -fno-nonansi-builtins -@opindex fno-nonansi-builtins -Disable built-in declarations of functions that are not mandated by -ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit}, -@code{index}, @code{bzero}, @code{conjf}, and other related functions. - -@item -fno-operator-names -@opindex fno-operator-names -Do not treat the operator name keywords @code{and}, @code{bitand}, -@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as -synonyms as keywords. - -@item -fno-optional-diags -@opindex fno-optional-diags -Disable diagnostics that the standard says a compiler does not need to -issue. Currently, the only such diagnostic issued by G++ is the one for -a name having multiple meanings within a class. - -@item -fpermissive -@opindex fpermissive -Downgrade some diagnostics about nonconformant code from errors to -warnings. Thus, using @option{-fpermissive} will allow some -nonconforming code to compile. - -@item -frepo -@opindex frepo -Enable automatic template instantiation at link time. This option also -implies @option{-fno-implicit-templates}. @xref{Template -Instantiation}, for more information. - -@item -fno-rtti -@opindex fno-rtti -Disable generation of information about every class with virtual -functions for use by the C++ runtime type identification features -(@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts -of the language, you can save some space by using this flag. Note that -exception handling uses the same information, but it will generate it as -needed. The @samp{dynamic_cast} operator can still be used for casts that -do not require runtime type information, i.e. casts to @code{void *} or to -unambiguous base classes. - -@item -fstats -@opindex fstats -Emit statistics about front-end processing at the end of the compilation. -This information is generally only useful to the G++ development team. - -@item -ftemplate-depth-@var{n} -@opindex ftemplate-depth -Set the maximum instantiation depth for template classes to @var{n}. -A limit on the template instantiation depth is needed to detect -endless recursions during template class instantiation. ANSI/ISO C++ -conforming programs must not rely on a maximum depth greater than 17. - -@item -fno-threadsafe-statics -@opindex fno-threadsafe-statics -Do not emit the extra code to use the routines specified in the C++ -ABI for thread-safe initialization of local statics. You can use this -option to reduce code size slightly in code that doesn't need to be -thread-safe. - -@item -fuse-cxa-atexit -@opindex fuse-cxa-atexit -Register destructors for objects with static storage duration with the -@code{__cxa_atexit} function rather than the @code{atexit} function. -This option is required for fully standards-compliant handling of static -destructors, but will only work if your C library supports -@code{__cxa_atexit}. - -@item -fno-use-cxa-get-exception-ptr -@opindex fno-use-cxa-get-exception-ptr -Don't use the @code{__cxa_get_exception_ptr} runtime routine. This -will cause @code{std::uncaught_exception} to be incorrect, but is necessary -if the runtime routine is not available. - -@item -fvisibility-inlines-hidden -@opindex fvisibility-inlines-hidden -This switch declares that the user does not attempt to compare -pointers to inline methods where the addresses of the two functions -were taken in different shared objects. - -The effect of this is that GCC may, effectively, mark inline methods with -@code{__attribute__ ((visibility ("hidden")))} so that they do not -appear in the export table of a DSO and do not require a PLT indirection -when used within the DSO@. Enabling this option can have a dramatic effect -on load and link times of a DSO as it massively reduces the size of the -dynamic export table when the library makes heavy use of templates. - -The behaviour of this switch is not quite the same as marking the -methods as hidden directly, because it does not affect static variables -local to the function or cause the compiler to deduce that -the function is defined in only one shared object. - -You may mark a method as having a visibility explicitly to negate the -effect of the switch for that method. For example, if you do want to -compare pointers to a particular inline method, you might mark it as -having default visibility. Marking the enclosing class with explicit -visibility will have no effect. - -Explicitly instantiated inline methods are unaffected by this option -as their linkage might otherwise cross a shared library boundary. -@xref{Template Instantiation}. - -@c APPLE LOCAL begin mainline 2007-06-28 ms tinfo compat 4230099 -@item -fvisibility-ms-compat -@opindex fvisibility-ms-compat -This flag attempts to use visibility settings to make GCC's C++ -linkage model compatible with that of Microsoft Visual Studio. - -The flag makes these changes to GCC's linkage model: - -1. It sets the default visibility to 'hidden', like -@option{-fvisibility=hidden}. -2. Types, but not their members, are not hidden by default. -3. The One Definition Rule is relaxed for types without explicit -visibility specifications which are defined in more than one different -shared object: those declarations are permitted if they would have -been permitted when this option was not used. - -This option is discouraged, rather, it is preferable for types to be -explicitly exported as desired on a per-class basis. Unfortunately -because Visual Studio can't compare two different hidden types as -unequal for the purposes of type_info and exception handling, users -are able to write code that relies upon this behavior. - -Among the consequences of these changes are that static data members -of the same type with the same name but defined in different shared -objects will be different, so changing one will not change the other; -and that pointers to function members defined in different shared -objects will not compare equal. When this flag is given, it is a -violation of the ODR to define types with the same name differently. -@c APPLE LOCAL end mainline 2007-06-28 ms tinfo compat 4230099 - -@item -fno-weak -@opindex fno-weak -Do not use weak symbol support, even if it is provided by the linker. -By default, G++ will use weak symbols if they are available. This -option exists only for testing, and should not be used by end-users; -it will result in inferior code and has no benefits. This option may -be removed in a future release of G++. - -@item -nostdinc++ -@opindex nostdinc++ -Do not search for header files in the standard directories specific to -C++, but do still search the other standard directories. (This option -is used when building the C++ library.) -@end table - -In addition, these optimization, warning, and code generation options -have meanings only for C++ programs: - -@table @gcctabopt -@item -fno-default-inline -@opindex fno-default-inline -Do not assume @samp{inline} for functions defined inside a class scope. -@xref{Optimize Options,,Options That Control Optimization}. Note that these -functions will have linkage like inline functions; they just won't be -inlined by default. - -@item -Wabi @r{(C++ 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 -all such cases, there are probably some cases that are not warned about, -even though G++ is generating incompatible code. There may also be -cases where warnings are emitted even though the code that is generated -will be compatible. - -You should rewrite your code to avoid these warnings if you are -concerned about the fact that code generated by G++ may not be binary -compatible with code generated by other compilers. - -The known incompatibilities at this point include: - -@itemize @bullet - -@item -Incorrect handling of tail-padding for bit-fields. G++ may attempt to -pack data into the same byte as a base class. For example: - -@smallexample -struct A @{ virtual void f(); int f1 : 1; @}; -struct B : public A @{ int f2 : 1; @}; -@end smallexample - -@noindent -In this case, G++ will place @code{B::f2} into the same byte -as@code{A::f1}; other compilers will not. You can avoid this problem -by explicitly padding @code{A} so that its size is a multiple of the -byte size on your platform; that will cause G++ and other compilers to -layout @code{B} identically. - -@item -Incorrect handling of tail-padding for virtual bases. G++ does not use -tail padding when laying out virtual bases. For example: - -@smallexample -struct A @{ virtual void f(); char c1; @}; -struct B @{ B(); char c2; @}; -struct C : public A, public virtual B @{@}; -@end smallexample - -@noindent -In this case, G++ will not place @code{B} into the tail-padding for -@code{A}; other compilers will. You can avoid this problem by -explicitly padding @code{A} so that its size is a multiple of its -alignment (ignoring virtual base classes); that will cause G++ and other -compilers to layout @code{C} identically. - -@item -Incorrect handling of bit-fields with declared widths greater than that -of their underlying types, when the bit-fields appear in a union. For -example: - -@smallexample -union U @{ int i : 4096; @}; -@end smallexample - -@noindent -Assuming that an @code{int} does not have 4096 bits, G++ will make the -union too small by the number of bits in an @code{int}. - -@item -Empty classes can be placed at incorrect offsets. For example: - -@smallexample -struct A @{@}; - -struct B @{ - A a; - virtual void f (); -@}; - -struct C : public B, public A @{@}; -@end smallexample - -@noindent -G++ will place the @code{A} base class of @code{C} at a nonzero offset; -it should be placed at offset zero. G++ mistakenly believes that the -@code{A} data member of @code{B} is already at offset zero. - -@item -Names of template functions whose types involve @code{typename} or -template template parameters can be mangled incorrectly. - -@smallexample -template <typename Q> -void f(typename Q::X) @{@} - -template <template <typename> class Q> -void f(typename Q<int>::X) @{@} -@end smallexample - -@noindent -Instantiations of these templates may be mangled incorrectly. - -@end itemize - -@item -Wctor-dtor-privacy @r{(C++ only)} -@opindex Wctor-dtor-privacy -Warn when a class seems unusable because all the constructors or -destructors in that class are private, and it has neither friends nor -public static member functions. - -@item -Wnon-virtual-dtor @r{(C++ only)} -@opindex Wnon-virtual-dtor -Warn when a class appears to be polymorphic, thereby requiring a virtual -destructor, yet it declares a non-virtual one. This warning is also -enabled if -Weffc++ is specified. - -@item -Wreorder @r{(C++ only)} -@opindex Wreorder -@cindex reordering, warning -@cindex warning for reordering of member initializers -Warn when the order of member initializers given in the code does not -match the order in which they must be executed. For instance: - -@smallexample -struct A @{ - int i; - int j; - A(): j (0), i (1) @{ @} -@}; -@end smallexample - -The compiler will rearrange the member initializers for @samp{i} -and @samp{j} to match the declaration order of the members, emitting -a warning to that effect. This warning is enabled by @option{-Wall}. -@end table - -The following @option{-W@dots{}} options are not affected by @option{-Wall}. - -@table @gcctabopt -@item -Weffc++ @r{(C++ only)} -@opindex Weffc++ -Warn about violations of the following style guidelines from Scott Meyers' -@cite{Effective C++} book: - -@itemize @bullet -@item -Item 11: Define a copy constructor and an assignment operator for classes -with dynamically allocated memory. - -@item -Item 12: Prefer initialization to assignment in constructors. - -@item -Item 14: Make destructors virtual in base classes. - -@item -Item 15: Have @code{operator=} return a reference to @code{*this}. - -@item -Item 23: Don't try to return a reference when you must return an object. - -@end itemize - -Also warn about violations of the following style guidelines from -Scott Meyers' @cite{More Effective C++} book: - -@itemize @bullet -@item -Item 6: Distinguish between prefix and postfix forms of increment and -decrement operators. - -@item -Item 7: Never overload @code{&&}, @code{||}, or @code{,}. - -@end itemize - -When selecting this option, be aware that the standard library -headers do not obey all of these guidelines; use @samp{grep -v} -to filter out those warnings. - -@item -Wno-deprecated @r{(C++ only)} -@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 -within a template. Since the advent of explicit template specification -support in G++, if the name of the friend is an unqualified-id (i.e., -@samp{friend foo(int)}), the C++ language specification demands that the -friend declare or define an ordinary, nontemplate function. (Section -14.5.3). Before G++ implemented explicit specification, unqualified-ids -could be interpreted as a particular specialization of a templatized -function. Because this non-conforming behavior is no longer the default -behavior for G++, @option{-Wnon-template-friend} allows the compiler to -check existing code for potential trouble spots and is on by default. -This new compiler behavior can be turned off with -@option{-Wno-non-template-friend} which keeps the conformant compiler code -but disables the helpful warning. - -@item -Wold-style-cast @r{(C++ only)} -@opindex Wold-style-cast -Warn if an old-style (C-style) cast to a non-void type is used within -a C++ program. The new-style casts (@samp{dynamic_cast}, -@samp{static_cast}, @samp{reinterpret_cast}, and @samp{const_cast}) are -less vulnerable to unintended effects and much easier to search for. - -@item -Woverloaded-virtual @r{(C++ only)} -@opindex Woverloaded-virtual -@cindex overloaded virtual fn, warning -@cindex warning for overloaded virtual fn -Warn when a function declaration hides virtual functions from a -base class. For example, in: - -@smallexample -struct A @{ - virtual void f(); -@}; - -struct B: public A @{ - void f(int); -@}; -@end smallexample - -the @code{A} class version of @code{f} is hidden in @code{B}, and code -like: - -@smallexample -B* b; -b->f(); -@end smallexample - -will fail to compile. - -@item -Wno-pmf-conversions @r{(C++ only)} -@opindex Wno-pmf-conversions -Disable the diagnostic for converting a bound pointer to member function -to a plain pointer. - -@item -Wsign-promo @r{(C++ only)} -@opindex Wsign-promo -Warn when overload resolution chooses a promotion from unsigned or -enumerated type to a signed type, over a conversion to an unsigned type of -the same size. Previous versions of G++ would try to preserve -unsignedness, but the standard mandates the current behavior. - -@smallexample -struct A @{ - operator int (); - A& operator = (int); -@}; - -main () -@{ - A a,b; - a = b; -@} -@end smallexample - -In this example, G++ will synthesize a default @samp{A& operator = -(const A&);}, while cfront will use the user-defined @samp{operator =}. -@end table - -@node Objective-C and Objective-C++ Dialect Options -@section Options Controlling Objective-C and Objective-C++ Dialects - -@cindex compiler options, Objective-C and Objective-C++ -@cindex Objective-C and Objective-C++ options, command line -@cindex options, Objective-C and Objective-C++ -(NOTE: This manual does not describe the Objective-C and Objective-C++ -languages themselves. See @xref{Standards,,Language Standards -Supported by GCC}, for references.) - -This section describes the command-line options that are only meaningful -for Objective-C and Objective-C++ programs, but you can also use most of -the language-independent GNU compiler options. -For example, you might compile a file @code{some_class.m} like this: - -@smallexample -gcc -g -fgnu-runtime -O -c some_class.m -@end smallexample - -@noindent -In this example, @option{-fgnu-runtime} is an option meant only for -Objective-C and Objective-C++ programs; you can use the other options with -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., -@option{-Wtraditional}). Similarly, Objective-C++ compilations may use -C++-specific options (e.g., @option{-Wabi}). - -Here is a list of options that are @emph{only} for compiling Objective-C -and Objective-C++ programs: - -@table @gcctabopt -@item -fconstant-string-class=@var{class-name} -@opindex fconstant-string-class -Use @var{class-name} as the name of the class to instantiate for each -literal string specified with the syntax @code{@@"@dots{}"}. The default -class name is @code{NXConstantString} if the GNU runtime is being used, and -@code{NSConstantString} if the NeXT runtime is being used (see below). The -@option{-fconstant-cfstrings} option, if also present, will override the -@option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals -to be laid out as constant CoreFoundation strings. - -@item -fgnu-runtime -@opindex fgnu-runtime -Generate object code compatible with the standard GNU Objective-C -runtime. This is the default for most types of systems. - -@item -fnext-runtime -@opindex fnext-runtime -Generate output compatible with the NeXT runtime. This is the default -for NeXT-based systems, including Darwin and Mac OS X@. The macro -@code{__NEXT_RUNTIME__} is predefined if (and only if) this option is -used. - -@item -fno-nil-receivers -@opindex fno-nil-receivers -Assume that all Objective-C message dispatches (e.g., -@code{[receiver message:arg]}) in this translation unit ensure that the receiver -is not @code{nil}. This allows for more efficient entry points in the runtime -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. - -@c APPLE LOCAL begin radar 4512786 -@item -fobjc-sjlj-exceptions -@opindex fobjc-sjlj-exceptions -Enable syntactic support for structured exception handling in Objective-C, -similar to what is offered by C++ and Java. This option is -unavailable in conjunction with the NeXT runtime on Mac OS X 10.2 and -earlier. -This option is on by default with the NeXT runtime. -@c APPLE LOCAL end radar 4512786 - -@smallexample - @@try @{ - @dots{} - @@throw expr; - @dots{} - @} - @@catch (AnObjCClass *exc) @{ - @dots{} - @@throw expr; - @dots{} - @@throw; - @dots{} - @} - @@catch (AnotherClass *exc) @{ - @dots{} - @} - @@catch (id allOthers) @{ - @dots{} - @} - @@finally @{ - @dots{} - @@throw expr; - @dots{} - @} -@end smallexample - -The @code{@@throw} statement may appear anywhere in an Objective-C or -Objective-C++ program; when used inside of a @code{@@catch} block, the -@code{@@throw} may appear without an argument (as shown above), in which case -the object caught by the @code{@@catch} will be rethrown. - -Note that only (pointers to) Objective-C objects may be thrown and -caught using this scheme. When an object is thrown, it will be caught -by the nearest @code{@@catch} clause capable of handling objects of that type, -analogously to how @code{catch} blocks work in C++ and Java. A -@code{@@catch(id @dots{})} clause (as shown above) may also be provided to catch -any and all Objective-C exceptions not caught by previous @code{@@catch} -clauses (if any). - -The @code{@@finally} clause, if present, will be executed upon exit from the -immediately preceding @code{@@try @dots{} @@catch} section. This will happen -regardless of whether any exceptions are thrown, caught or rethrown -inside the @code{@@try @dots{} @@catch} section, analogously to the behavior -of the @code{finally} clause in Java. - -There are several caveats to using the new exception mechanism: - -@itemize @bullet -@item -Although currently designed to be binary compatible with @code{NS_HANDLER}-style -idioms provided by the @code{NSException} class, the new -exceptions can only be used on Mac OS X 10.3 (Panther) and later -systems, due to additional functionality needed in the (NeXT) Objective-C -runtime. - -@item -As mentioned above, the new exceptions do not support handling -types other than Objective-C objects. Furthermore, when used from -Objective-C++, the Objective-C exception model does not interoperate with C++ -exceptions at this time. This means you cannot @code{@@throw} an exception -from Objective-C and @code{catch} it in C++, or vice versa -(i.e., @code{throw @dots{} @@catch}). -@end itemize - -@c APPLE LOCAL radar 4512786 -The @option{-fobjc-sjlj-exceptions} switch also enables the use of synchronization -blocks for thread-safe execution: - -@smallexample - @@synchronized (ObjCClass *guard) @{ - @dots{} - @} -@end smallexample - -Upon entering the @code{@@synchronized} block, a thread of execution shall -first check whether a lock has been placed on the corresponding @code{guard} -object by another thread. If it has, the current thread shall wait until -the other thread relinquishes its lock. Once @code{guard} becomes available, -the current thread will place its own lock on it, execute the code contained in -the @code{@@synchronized} block, and finally relinquish the lock (thereby -making @code{guard} available to other threads). - -Unlike Java, Objective-C does not allow for entire methods to be marked -@code{@@synchronized}. Note that throwing exceptions out of -@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. -@c APPLE LOCAL begin radar 5780114 - ObjC GC -The resulting binary requires additional runtime support which is present on -Mac OS X Version 10.5 (Leopard) and later. All Objective-C objects are presumed -to be garbage collected. To aid in this effort, compiler implements assignments -of Objective-C object pointers via runtime support functions. These functions work -correctly in non-GC environments as well, in case this code is used as part of a -library. Assignments of objects into instance variables of other objects are -intercepted, so are assignments to global object variables. In general, assignments -through pointers to objects are intercepted. Additionally, assignments of objects -as fields within structures are intercepted. - -In addition, other pointer variables may be marked with the __strong storage class -modifier to indicate to the compiler that these assignments need to use the assignment -runtime functions as well, allowing the memory referenced by these pointers to be -allocated from the collector. A __weak storage class modifier for pointers is also -introduced to indicate a zero-ing weak reference. This is permitted only for instance -variables of an object or globals. The compiler arranges for all reads as well as -writes to these variables to occur via runtime support functions. Under garbage -collection these variables are not consulted when determining what is not garbage -and they are set to nil (zero) if the memory they reference is deemed garbage and is -collected. - -@smallexample - __strong void *p; // assignments to 'p' will have runtime support calls - int *q; // assignments to 'q' ordinarly will not - @dots{} - (__strong int *)q = 0; // this assignment will call a runtime support function -@end smallexample - -Conversely, the @code{__weak} type qualifier may be used to call weak runtime -functions. - -@smallexample - __weak id q; // assignments to 'q' will have the '__weak' semantics - id p; // assignments to 'p' will have the "__strong' semantics - @dots{} - (__weak id)p = 0; // Fall back to '__weak' semantics in this assignment. -@end smallexample - -@item -fobjc-gc-only -@opindex fobjc-gc-only -Use this option to indicate that the Objective-C program supports garbage -collection (GC) only - that is, it does not contain retain/release logic. -This flag implies @option{-fobjc-gc} as well. With this flag, framework -is marked as not honoring retain/release. - -@c APPLE LOCAL end radar 5780114 - ObjC GC -@item -freplace-objc-classes -@opindex freplace-objc-classes -Emit a special marker instructing @command{ld(1)} not to statically link in -the resulting object file, and allow @command{dyld(1)} to load it in at -run time instead. This is used in conjunction with the Fix-and-Continue -debugging mode, where the object file in question may be recompiled and -dynamically reloaded in the course of program execution, without the need -to restart the program itself. Currently, Fix-and-Continue functionality -is only available in conjunction with the NeXT runtime on Mac OS X 10.3 -and later. - -@item -fzero-link -@opindex fzero-link -When compiling for the NeXT runtime, the compiler ordinarily replaces calls -to @code{objc_getClass("@dots{}")} (when the name of the class is known at -compile time) with static class references that get initialized at load time, -which improves run-time performance. Specifying the @option{-fzero-link} flag -suppresses this behavior and causes calls to @code{objc_getClass("@dots{}")} -to be retained. This is useful in Zero-Link debugging mode, since it allows -for individual class implementations to be modified during program execution. - -@item -gen-decls -@opindex gen-decls -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 @option{-Wno-protocol} option, then -methods inherited from the superclass are considered to be implemented, -and no warning is issued for them. - -@item -Wselector -@opindex Wselector -Warn if multiple methods of different types for the same selector are -found during compilation. The check is performed on the list of methods -in the final stage of compilation. Additionally, a check is performed -for each selector appearing in a @code{@@selector(@dots{})} -expression, and a corresponding method for that selector has been found -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 @option{-fsyntax-only} option is -being used. - -@c APPLE LOCAL begin radar 5172645 -@item -Wproperty-assign-default -@opindex Wproperty-assign-default -Warn if no ``assign'', ``retain'', or ``copy'' attribute is specified on -a property of pointer to object type. Property is then assumed to be -``assign'' by default. -@c APPLE LOCAL end radar 5172645 - -@c APPLE LOCAL begin radar 5376125 -@item -Wdirect-ivar-access -@opindex Wdirect-ivar-access -Warn if ivar of pointer to object type is directly accessed in non-gc -mode, instead of using property syntax access. -@c APPLE LOCAL end radar 5376125 - -@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 -undeclared selector is found. A selector is considered undeclared if no -method with that name has been declared before the -@code{@@selector(@dots{})} expression, either explicitly in 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 @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. - -@item -print-objc-runtime-info -@opindex print-objc-runtime-info -Generate C header describing the largest structure that is passed by -value, if any. - -@end table - -@node Language Independent Options -@section Options to Control Diagnostic Messages Formatting -@cindex options to control diagnostics formatting -@cindex diagnostic messages -@cindex message formatting - -Traditionally, diagnostic messages have been formatted irrespective of -the output device's aspect (e.g.@: its width, @dots{}). The options described -below can be used to control the diagnostic messages formatting -algorithm, e.g.@: how many characters per line, how often source location -information should be reported. Right now, only the C++ front end can -honor these options. However it is expected, in the near future, that -the remaining front ends would be able to digest them correctly. - -@table @gcctabopt -@item -fmessage-length=@var{n} -@opindex fmessage-length -Try to format error messages so that they fit on lines of about @var{n} -characters. The default is 72 characters for @command{g++} and 0 for the rest of -the front ends supported by GCC@. If @var{n} is zero, then no -line-wrapping will be done; each error message will appear on a single -line. - -@opindex fdiagnostics-show-location -@item -fdiagnostics-show-location=once -Only meaningful in line-wrapping mode. Instructs the diagnostic messages -reporter to emit @emph{once} source location information; that is, in -case the message is too long to fit on a single physical line and has to -be wrapped, the source location won't be emitted (as prefix) again, -over and over, in subsequent continuation lines. This is the default -behavior. - -@item -fdiagnostics-show-location=every-line -Only meaningful in line-wrapping mode. Instructs the diagnostic -messages reporter to emit the same source location information (as -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-option -@opindex fdiagnostics-show-option -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 -@section Options to Request or Suppress Warnings -@cindex options to control warnings -@cindex warning messages -@cindex messages, warning -@cindex suppressing warnings - -Warnings are diagnostic messages that report constructions which -are not inherently erroneous but which are risky or suggest there -may have been an error. - -You can request many specific warnings with options beginning @samp{-W}, -for example @option{-Wimplicit} to request warnings on implicit -declarations. Each of these specific warning options also has a -negative form beginning @samp{-Wno-} to turn off warnings; -for example, @option{-Wno-implicit}. This manual lists only one of the -two forms, whichever is not the default. - -The following options control the amount and kinds of warnings produced -by GCC; for further, language-specific options also refer to -@ref{C++ Dialect Options} and @ref{Objective-C and Objective-C++ Dialect -Options}. - -@table @gcctabopt -@cindex syntax checking -@item -fsyntax-only -@opindex fsyntax-only -Check the code for syntax errors, but don't do anything beyond that. - -@item -pedantic -@opindex pedantic -Issue all the warnings demanded by strict ISO C and ISO C++; -reject all programs that use forbidden extensions, and some other -programs that do not follow ISO C and ISO C++. For ISO C, follows the -version of the ISO C standard specified by any @option{-std} option used. - -Valid ISO C and ISO C++ programs should compile properly with or without -this option (though a rare few will require @option{-ansi} or a -@option{-std} option specifying the required version of ISO C)@. However, -without this option, certain GNU extensions and traditional C and C++ -features are supported as well. With this option, they are rejected. - -@option{-pedantic} does not cause warning messages for use of the -alternate keywords whose names begin and end with @samp{__}. Pedantic -warnings are also disabled in the expression that follows -@code{__extension__}. However, only system header files should use -these escape routes; application programs should avoid them. -@xref{Alternate Keywords}. - -Some users try to use @option{-pedantic} to check programs for strict ISO -C conformance. They soon find that it does not do quite what they want: -it finds some non-ISO practices, but not all---only those for which -ISO C @emph{requires} a diagnostic, and some others for which -diagnostics have been added. - -A feature to report any failure to conform to ISO C might be useful in -some instances, but would require considerable additional work and would -be quite different from @option{-pedantic}. We don't have plans to -support such a feature in the near future. - -Where the standard specified with @option{-std} represents a GNU -extended dialect of C, such as @samp{gnu89} or @samp{gnu99}, there is a -corresponding @dfn{base standard}, the version of ISO C on which the GNU -extended dialect is based. Warnings from @option{-pedantic} are given -where they are required by the base standard. (It would not make sense -for such warnings to be given only for features not in the specified GNU -C dialect, since by definition the GNU dialects of C include all -features the compiler supports with the given option, and there would be -nothing to warn about.) - -@item -pedantic-errors -@opindex pedantic-errors -Like @option{-pedantic}, except that errors are produced rather than -warnings. - -@item -w -@opindex w -Inhibit all warning messages. - -@item -Wno-import -@opindex Wno-import -Inhibit warning messages about the use of @samp{#import}. - -@c APPLE LOCAL begin -Wno-#warnings -@item -Wno-#warnings -@opindex Wno-#warnings -Inhibit warning messages issued by @samp{#warning}. -@c APPLE LOCAL end -Wno-#warnings - -@c APPLE LOCAL begin -Wextra-tokens 2001-08-02 --sts ** -@item -Wextra-tokens -@opindex Wextra-tokens -Warn about extra tokens at the end of prepreprocessor directives. (APPLE ONLY) -@c APPLE LOCAL end -Wextra-tokens 2001-08-02 --sts ** - -@c APPLE LOCAL begin -Wnewline-eof 2001-08-23 --sts ** -@item -Wnewline-eof -@opindex Wnewline-eof -Warn about files missing a newline at the end of the file. (APPLE ONLY) -@c APPLE LOCAL end -Wnewline-eof 2001-08-23 --sts ** - -@c APPLE LOCAL begin -Wno-altivec-long-deprecated --ilr ** -@item -Wno-altivec-long-deprecated -@opindex Wno-altivec-long-deprecated -Do not warn about the use of the deprecated 'long' keyword in -AltiVec data types. (APPLE ONLY) -@c APPLE LOCAL end -Wno-altivec-long-deprecated --ilr ** - -@item -Wchar-subscripts -@opindex Wchar-subscripts -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 -This option causes the compiler to abort compilation on the first error -occurred rather than trying to keep going and printing further error -messages. - -@c APPLE LOCAL begin default to Wformat-security 5764921 -@item -Wno-format -@opindex Wno-format -@c APPLE LOCAL end default to Wformat-security 5764921 -@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 -sense. This includes standard functions, and others specified by format -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 -as features from the Single Unix Specification and some BSD and GNU -extensions. Other library implementations may not support all these -features; GCC does not support warning about features that go beyond a -particular library's limitations. However, if @option{-pedantic} is used -with @option{-Wformat}, warnings will be given about format features not -in the selected standard version (but not for @code{strfmon} formats, -since those are not in any version of the C standard). @xref{C Dialect -Options,,Options Controlling C Dialect}. - -Since @option{-Wformat} also checks for null format arguments for -several functions, @option{-Wformat} also implies @option{-Wnonnull}. - -@option{-Wformat} is included in @option{-Wall}. For more control over some -aspects of format checking, the options @option{-Wformat-y2k}, -@option{-Wno-format-extra-args}, @option{-Wno-format-zero-length}, -@option{-Wformat-nonliteral}, @option{-Wformat-security}, and -@option{-Wformat=2} are available, but are not included in @option{-Wall}. - -@item -Wformat-y2k -@opindex Wformat-y2k -If @option{-Wformat} is specified, also warn about @code{strftime} -formats which may yield only a two-digit year. - -@item -Wno-format-extra-args -@opindex Wno-format-extra-args -If @option{-Wformat} is specified, do not warn about excess arguments to a -@code{printf} or @code{scanf} format function. The C standard specifies -that such arguments are ignored. - -Where the unused arguments lie between used arguments that are -specified with @samp{$} operand number specifications, normally -warnings are still given, since the implementation could not know what -type to pass to @code{va_arg} to skip the unused arguments. However, -in the case of @code{scanf} formats, this option will suppress the -warning if the unused arguments are all pointers, since the Single -Unix Specification says that such unused arguments are allowed. - -@item -Wno-format-zero-length -@opindex Wno-format-zero-length -If @option{-Wformat} is specified, do not warn about zero-length formats. -The C standard specifies that zero-length formats are allowed. - -@item -Wformat-nonliteral -@opindex Wformat-nonliteral -If @option{-Wformat} is specified, also warn if the format string is not a -string literal and so cannot be checked, unless the format function -takes its format arguments as a @code{va_list}. - -@c APPLE LOCAL begin default to Wformat-security 5764921 -@item -Wno-format-security -@opindex Wno-format-security -@c APPLE LOCAL end default to Wformat-security 5764921 -If @option{-Wformat} is specified, also warn about uses of format -functions that represent possible security problems. At present, this -warns about calls to @code{printf} and @code{scanf} functions where the -format string is not a string literal and there are no format arguments, -as in @code{printf (foo);}. This may be a security hole if the format -string came from untrusted input and contains @samp{%n}. (This is -currently a subset of what @option{-Wformat-nonliteral} warns about, but -in future warnings may be added to @option{-Wformat-security} that are not -included in @option{-Wformat-nonliteral}.) - -@item -Wformat=2 -@opindex Wformat=2 -Enable @option{-Wformat} plus format checks not included in -@option{-Wformat}. Currently equivalent to @samp{-Wformat --Wformat-nonliteral -Wformat-security -Wformat-y2k}. - -@item -Wnonnull -@opindex Wnonnull -Warn about passing a null pointer for arguments marked as -requiring a non-null value by the @code{nonnull} function attribute. - -@option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It -can be disabled with the @option{-Wno-nonnull} option. - -@c APPLE LOCAL begin Wglobal-constructors 6324584 -@item -Wglobal-constructors -@opindex Wglobal-constructors -Warn about namespace scope data that requires construction or -destruction, or functions that use the constructor attribute or the -destructor attribute. Additionally warn if the Objective-C GNU -runtime is used to initialize various metadata. -@c APPLE LOCAL end Wglobal-constructors 6324584 - -@item -Winit-self @r{(C, C++, Objective-C and Objective-C++ only)} -@opindex Winit-self -Warn about uninitialized variables which are initialized with themselves. -Note this option can only be used with the @option{-Wuninitialized} option, -which in turn only works with @option{-O1} and above. - -For example, GCC will warn about @code{i} being uninitialized in the -following snippet only when @option{-Winit-self} has been specified: -@smallexample -@group -int f() -@{ - int i = i; - return i; -@} -@end group -@end smallexample - -@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. 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 -Warn if an aggregate or union initializer is not fully bracketed. In -the following example, the initializer for @samp{a} is not fully -bracketed, but that for @samp{b} is fully bracketed. - -@smallexample -int a[2][2] = @{ 0, 1, 2, 3 @}; -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. - -@item -Wparentheses -@opindex Wparentheses -Warn if parentheses are omitted in certain contexts, such -as when there is an assignment in a context where a truth value -is expected, or when operators are nested whose precedence people -often get confused about. Only the warning for an assignment used as -a truth value is supported when compiling C++; the other warnings are -only supported when compiling C@. - -Also warn if a comparison like @samp{x<=y<=z} appears; this is -equivalent to @samp{(x<=y ? 1 : 0) <= z}, which is a different -interpretation from that of ordinary mathematical notation. - -Also warn about constructions where there may be confusion to which -@code{if} statement an @code{else} branch belongs. Here is an example of -such a case: - -@smallexample -@group -@{ - if (a) - if (b) - foo (); - else - bar (); -@} -@end group -@end smallexample - -In C, every @code{else} branch belongs to the innermost possible @code{if} -statement, which in this example is @code{if (b)}. This is often not -what the programmer expected, as illustrated in the above example by -indentation the programmer chose. When there is the potential for this -confusion, GCC will issue a warning when this flag is specified. -To eliminate the warning, add explicit braces around the innermost -@code{if} statement so there is no way the @code{else} could belong to -the enclosing @code{if}. The resulting code would look like this: - -@smallexample -@group -@{ - if (a) - @{ - if (b) - foo (); - else - bar (); - @} -@} -@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 -of sequence point rules in the C and C++ standards. - -The C and C++ standards defines the order in which expressions in a C/C++ -program are evaluated in terms of @dfn{sequence points}, which represent -a partial ordering between the execution of parts of the program: those -executed before the sequence point, and those executed after it. These -occur after the evaluation of a full expression (one which is not part -of a larger expression), after the evaluation of the first operand of a -@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a -function is called (but after the evaluation of its arguments and the -expression denoting the called function), and in certain other places. -Other than as expressed by the sequence point rules, the order of -evaluation of subexpressions of an expression is not specified. All -these rules describe only a partial order rather than a total order, -since, for example, if two functions are called within one expression -with no sequence point between them, the order in which the functions -are called is not specified. However, the standards committee have -ruled that function calls do not overlap. - -It is not specified when between sequence points modifications to the -values of objects take effect. Programs whose behavior depends on this -have undefined behavior; the C and C++ standards specify that ``Between -the previous and next sequence point an object shall have its stored -value modified at most once by the evaluation of an expression. -Furthermore, the prior value shall be read only to determine the value -to be stored.''. If a program breaks these rules, the results on any -particular implementation are entirely unpredictable. - -Examples of code with undefined behavior are @code{a = a++;}, @code{a[n] -= b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not -diagnosed by this option, and it may give an occasional false positive -result, but in general it has been found fairly effective at detecting -this sort of problem in programs. - -The standard is worded confusingly, therefore there is some debate -over the precise meaning of the sequence point rules in subtle cases. -Links to discussions of the problem, including proposed formal -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} for C and C++. - -@item -Wreturn-type -@opindex Wreturn-type -Warn whenever a function is defined with a return-type that defaults to -@code{int}. Also warn about any @code{return} statement with no -return-value in a function whose return-type is not @code{void}. - -For C, also warn if the return type of a function has a type qualifier -such as @code{const}. Such a type qualifier has no effect, since the -value returned by a function is not an lvalue. ISO C prohibits -qualified @code{void} return types on function definitions, so such -return types always receive a warning even without this option. - -For C++, a function without return type always produces a diagnostic -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 -and lacks a @code{case} for one or more of the named codes of that -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 -Warn whenever a @code{switch} statement does not have a @code{default} -case. - -@item -Wswitch-enum -@opindex Wswitch-enum -Warn whenever a @code{switch} statement has an index of enumerated type -and lacks a @code{case} for one or more of the named codes of that -enumeration. @code{case} labels outside the enumeration range also -provoke warnings when this option is used. - -@item -Wtrigraphs -@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}). - -@item -Wunused-parameter -@opindex Wunused-parameter -Warn whenever a function parameter is unused aside from its declaration. - -To suppress this warning use the @samp{unused} attribute -(@pxref{Variable Attributes}). - -@item -Wunused-variable -@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}. - -@item -Wunused -@opindex Wunused -All the above @option{-Wunused} options combined. - -In order to get a warning about an unused function parameter, you must -either specify @samp{-Wextra -Wunused} (note that @samp{-Wall} implies -@samp{-Wunused}), or separately specify @option{-Wunused-parameter}. - -@item -Wuninitialized -@opindex Wuninitialized -Warn if an automatic variable is used without first being initialized or -if a variable may be clobbered by a @code{setjmp} call. - -These warnings are possible only in optimizing compilation, -because they require data flow information that is computed only -when optimizing. If you do not specify @option{-O}, you will not get -these warnings. Instead, GCC will issue a warning about @option{-Wuninitialized} -requiring @option{-O}. - -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 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 -computations may be deleted by data flow analysis before the warnings -are printed. - -These warnings are made optional because GCC is not smart -enough to see all the reasons why the code might be correct -despite appearing to have an error. Here is one example of how -this can happen: - -@smallexample -@group -@{ - int x; - switch (y) - @{ - case 1: x = 1; - break; - case 2: x = 4; - break; - case 3: x = 5; - @} - foo (x); -@} -@end group -@end smallexample - -@noindent -If the value of @code{y} is always 1, 2 or 3, then @code{x} is -always initialized, but GCC doesn't know this. Here is -another common case: - -@smallexample -@{ - int save_y; - if (change_y) save_y = y, y = new_y; - @dots{} - if (change_y) y = save_y; -@} -@end smallexample - -@noindent -This has no bug because @code{save_y} is used only if it is set. - -@cindex @code{longjmp} warnings -This option also warns when a non-volatile automatic variable might be -changed by a call to @code{longjmp}. These warnings as well are possible -only in optimizing compilation. - -The compiler sees only the calls to @code{setjmp}. It cannot know -where @code{longjmp} will be called; in fact, a signal handler could -call it at any point in the code. As a result, you may get a warning -even when there is in fact no problem because @code{longjmp} cannot -in fact be called at the place which would cause a problem. - -Some spurious warnings can be avoided if you declare all the functions -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 -@cindex unknown pragmas, warning -@cindex pragmas, warning of unknown -Warn when a #pragma directive is encountered which is not understood by -GCC@. If this command line option is used, warnings will even be issued -for unknown pragmas in system header files. This is not the case if -the warnings were only enabled by the @option{-Wall} command line option. - -@item -Wno-pragmas -@opindex Wno-pragmas -@opindex Wpragmas -Do not warn about misuses of pragmas, such as incorrect parameters, -invalid syntax, or conflicts between pragmas. See also -@samp{-Wunknown-pragmas}. - -@item -Wstrict-aliasing -@opindex Wstrict-aliasing -This option is only active when @option{-fstrict-aliasing} is active. -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 -included in @option{-Wall}. - -@item -Wstrict-aliasing=2 -@opindex Wstrict-aliasing=2 -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. This warning catches more cases than -@option{-Wstrict-aliasing}, but it will also give a warning for some ambiguous -cases that are safe. - -@item -Wstrict-overflow -@item -Wstrict-overflow=@var{n} -@opindex Wstrict-overflow -This option is only active when @option{-fstrict-overflow} is active. -It warns about cases where the compiler optimizes based on the -assumption that signed overflow does not occur. Note that it does not -warn about all cases where the code might overflow: it only warns -about cases where the compiler implements some optimization. Thus -this warning depends on the optimization level. - -An optimization which assumes that signed overflow does not occur is -perfectly safe if the values of the variables involved are such that -overflow never does, in fact, occur. Therefore this warning can -easily give a false positive: a warning about code which is not -actually a problem. To help focus on important issues, several -warning levels are defined. No warnings are issued for the use of -undefined signed overflow when estimating how many iterations a loop -will require, in particular when determining whether a loop will be -executed at all. - -@c APPLE LOCAL mainline man page 6365204 -@table @gcctabopt -@item -Wstrict-overflow=1 -Warn about cases which are both questionable and easy to avoid. For -example: @code{x + 1 > x}; with @option{-fstrict-overflow}, the -compiler will simplify this to @code{1}. This level of -@option{-Wstrict-overflow} is enabled by @option{-Wall}; higher levels -are not, and must be explicitly requested. - -@item -Wstrict-overflow=2 -Also warn about other cases where a comparison is simplified to a -constant. For example: @code{abs (x) >= 0}. This can only be -simplified when @option{-fstrict-overflow} is in effect, because -@code{abs (INT_MIN)} overflows to @code{INT_MIN}, which is less than -zero. @option{-Wstrict-overflow} (with no level) is the same as -@option{-Wstrict-overflow=2}. - -@item -Wstrict-overflow=3 -Also warn about other cases where a comparison is simplified. For -example: @code{x + 1 > 1} will be simplified to @code{x > 0}. - -@item -Wstrict-overflow=4 -Also warn about other simplifications not covered by the above cases. -For example: @code{(x * 10) / 5} will be simplified to @code{x * 2}. - -@item -Wstrict-overflow=5 -Also warn about cases where the compiler reduces the magnitude of a -constant involved in a comparison. For example: @code{x + 2 > y} will -be simplified to @code{x + 1 >= y}. This is reported only at the -highest warning level because this simplification applies to many -comparisons, so this warning level will give a very large number of -false positives. -@end table - -@item -Wall -@opindex Wall -All of the above @samp{-W} options combined. This enables all the -warnings about constructions that some users consider questionable, and -that are easy to avoid (or modify to prevent the warning), even in -conjunction with macros. This also enables some language-specific -warnings described in @ref{C++ Dialect Options} and -@ref{Objective-C and Objective-C++ Dialect Options}. -@c APPLE LOCAL begin -Wmost -@item -Wmost -@opindex Wmost -This is equivalent to -Wall -Wno-parentheses. (APPLE ONLY) -@end table -@c APPLE LOCAL end -Wmost - -The following @option{-W@dots{}} options are not implied by @option{-Wall}. -Some of them warn about constructions that users generally do not -consider questionable, but which occasionally you might wish to check -for; others warn about constructions that are necessary or hard to avoid -in some cases, and there is no simple way to modify the code to suppress -the warning. - -@table @gcctabopt -@item -Wextra -@opindex W -@opindex Wextra -(This option used to be called @option{-W}. The older name is still -supported, but the newer name is more descriptive.) Print extra warning -messages for these events: - -@itemize @bullet -@item -A function can return either with or without a value. (Falling -off the end of the function body is considered returning without -a value.) For example, this function would evoke such a -warning: - -@smallexample -@group -foo (a) -@{ - if (a > 0) - return a; -@} -@end group -@end smallexample - -@item -An expression-statement or the left-hand side of a comma expression -contains no side effects. -To suppress the warning, cast the unused expression to void. -For example, an expression such as @samp{x[i,j]} will cause a warning, -but @samp{x[(void)i,j]} will not. - -@item -An unsigned value is compared against zero with @samp{<} or @samp{>=}. - -@item -Storage-class specifiers like @code{static} are not the first things in -a declaration. According to the C Standard, this usage is obsolescent. - -@item -If @option{-Wall} or @option{-Wunused} is also specified, warn about unused -arguments. - -@item -A comparison between signed and unsigned values could produce an -incorrect result when the signed value is converted to unsigned. -(But don't warn if @option{-Wno-sign-compare} is also specified.) - -@item -An aggregate has an initializer which does not initialize all members. -This warning can be independently controlled by -@option{-Wmissing-field-initializers}. - -@item -An initialized field without side effects is overridden when using -designated initializers (@pxref{Designated Inits, , Designated -Initializers}). This warning can be independently controlled by -@option{-Woverride-init}. - -@item -A function parameter is declared without a type specifier in K&R-style -functions: - -@smallexample -void foo(bar) @{ @} -@end smallexample - -@item -An empty body occurs in an @samp{if} or @samp{else} statement. - -@c APPLE LOCAL begin mainline -@c APPLE LOCAL begin pod error 6089368 -@item -(C++ only) An empty body occurs in a @samp{while} or @samp{for} statement with no -@c APPLE LOCAL end pod error 6089368 -whitespacing before the semicolon. This warning can be independently -controlled by @option{-Wempty-body}. -@c APPLE LOCAL end mainline - -@item -A pointer is compared against integer zero with @samp{<}, @samp{<=}, -@samp{>}, or @samp{>=}. - -@item -A variable might be changed by @samp{longjmp} or @samp{vfork}. - -@c APPLE LOCAL begin pod error 6089368 -@item -(C++ only) An enumerator and a non-enumerator both appear in a conditional expression. - -@item -(C++ only) A non-static reference or non-static @samp{const} member appears in a -class without constructors. - -@item -(C++ only) Ambiguous virtual bases. - -@item -(C++ only) Subscripting an array which has been declared @samp{register}. - -@item -(C++ only) Taking the address of a variable which has been declared @samp{register}. - -@item -(C++ only) A base class is not initialized in a derived class' copy constructor. -@c APPLE LOCAL end pod error 6089368 -@end itemize - -@item -Wno-div-by-zero -@opindex Wno-div-by-zero -@opindex Wdiv-by-zero -Do not warn about compile-time integer division by zero. Floating point -division by zero is not warned about, as it can be a legitimate way of -obtaining infinities and NaNs. - -@item -Wsystem-headers -@opindex Wsystem-headers -@cindex warnings from system headers -@cindex system headers, warnings from -Print warning messages for constructs found in system header files. -Warnings from system headers are normally suppressed, on the assumption -that they usually do not indicate real problems and would only make the -compiler output harder to read. Using this command line option tells -GCC to emit warnings from system headers as if they occurred in user -code. However, note that using @option{-Wall} in conjunction with this -option will @emph{not} warn about unknown pragmas in system -headers---for that, @option{-Wunknown-pragmas} must also be used. - -@item -Wfloat-equal -@opindex Wfloat-equal -Warn if floating point values are used in equality comparisons. - -The idea behind this is that sometimes it is convenient (for the -programmer) to consider floating-point values as approximations to -infinitely precise real numbers. If you are doing this, then you need -to compute (by analyzing the code, or in some other way) the maximum or -likely maximum error that the computation introduces, and allow for it -when performing comparisons (and when producing output, but that's a -different problem). In particular, instead of testing for equality, you -would check to see whether the two values have ranges that overlap; and -this is done with the relational operators, so equality comparisons are -probably mistaken. - -@c APPLE LOCAL begin -Wfour-char-constants -@item -Wfour-char-constants -@opindex Wfour-char-constants -Warn about four char constants, e.g. OSType 'APPL'. This warning is -disabled by default. -@c APPLE LOCAL end - -@item -Wtraditional @r{(C only)} -@opindex Wtraditional -Warn about certain constructs that behave differently in traditional and -ISO C@. Also warn about ISO C constructs that have no traditional C -equivalent, and/or problematic constructs which should be avoided. - -@itemize @bullet -@item -Macro parameters that appear within string literals in the macro body. -In traditional C macro replacement takes place within string literals, -but does not in ISO C@. - -@item -In traditional C, some preprocessor directives did not exist. -Traditional preprocessors would only consider a line to be a directive -if the @samp{#} appeared in column 1 on the line. Therefore -@option{-Wtraditional} warns about directives that traditional C -understands but would ignore because the @samp{#} does not appear as the -first character on the line. It also suggests you hide directives like -@samp{#pragma} not understood by traditional C by indenting them. Some -traditional implementations would not recognize @samp{#elif}, so it -suggests avoiding it altogether. - -@item -A function-like macro that appears without arguments. - -@item -The unary plus operator. - -@item -The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating point -constant suffixes. (Traditional C does support the @samp{L} suffix on integer -constants.) Note, these suffixes appear in macros defined in the system -headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}. -Use of these macros in user code might normally lead to spurious -warnings, however GCC's integrated preprocessor has enough context to -avoid warning in these cases. - -@item -A function declared external in one block and then used after the end of -the block. - -@item -A @code{switch} statement has an operand of type @code{long}. - -@item -A non-@code{static} function declaration follows a @code{static} one. -This construct is not accepted by some traditional C compilers. - -@item -The ISO type of an integer constant has a different width or -signedness from its traditional type. This warning is only issued if -the base of the constant is ten. I.e.@: hexadecimal or octal values, which -typically represent bit patterns, are not warned about. - -@item -Usage of ISO string concatenation is detected. - -@item -Initialization of automatic aggregates. - -@item -Identifier conflicts with labels. Traditional C lacks a separate -namespace for labels. - -@item -Initialization of unions. If the initializer is zero, the warning is -omitted. This is done under the assumption that the zero initializer in -user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing -initializer warnings and relies on default initialization to zero in the -traditional C case. - -@item -Conversions by prototypes between fixed/floating point values and vice -versa. The absence of these prototypes when compiling with traditional -C would cause serious problems. This is a subset of the possible -conversion warnings, for the full set use @option{-Wconversion}. - -@item -Use of ISO C style function definitions. This warning intentionally is -@emph{not} issued for prototype declarations or variadic functions -because these ISO C features will appear in your code when using -libiberty's traditional C compatibility macros, @code{PARAMS} and -@code{VPARAMS}. This warning is also bypassed for nested functions -because that feature is already a GCC extension and thus not relevant to -traditional C compatibility. -@end itemize - -@item -Wdeclaration-after-statement @r{(C only)} -@opindex Wdeclaration-after-statement -Warn when a declaration is found after a statement in a block. This -construct, known from C++, was introduced with ISO C99 and is by default -allowed in GCC@. It is not supported by ISO C90 and was not supported by -GCC versions before GCC 3.0. @xref{Mixed Declarations}. - -@c APPLE LOCAL begin -Wdiscard-qual 4086969 -@item -Wno-discard-qual -@opindex Wno-discard-qual -This flag allows user to suppress warning that is issued when qualification -is discarded in situations like, initialization, assignment and argument -passing. -@c APPLE LOCAL end -Wdiscard-qual 4086969 - -@item -Wundef -@opindex Wundef -Warn if an undefined identifier is evaluated in an @samp{#if} directive. - -@item -Wno-endif-labels -@opindex Wno-endif-labels -@opindex Wendif-labels -Do not warn whenever an @samp{#else} or an @samp{#endif} are followed by text. - -@item -Wshadow -@opindex Wshadow -Warn whenever a local variable shadows another local variable, parameter or -global variable or whenever a built-in function is shadowed. - -@item -Wlarger-than-@var{len} -@opindex Wlarger-than -Warn whenever an object of larger than @var{len} bytes is defined. - -@item -Wunsafe-loop-optimizations -@opindex Wunsafe-loop-optimizations -Warn if the loop cannot be optimized because the compiler could not -assume anything on the bounds of the loop indices. With -@option{-funsafe-loop-optimizations} warn if the compiler made -such assumptions. - -@item -Wpointer-arith -@opindex Wpointer-arith -Warn about anything that depends on the ``size of'' a function type or -of @code{void}. GNU C assigns these types a size of 1, for -convenience in calculations with @code{void *} pointers and pointers -to functions. - -@item -Wbad-function-cast @r{(C only)} -@opindex Wbad-function-cast -Warn whenever a function call is cast to a non-matching type. -For example, warn if @code{int malloc()} is cast to @code{anything *}. - -@item -Wc++-compat -Warn about ISO C constructs that are outside of the common subset of -ISO C and ISO C++, e.g.@: request for implicit conversion from -@code{void *} to a pointer to non-@code{void} type. - -@item -Wcast-qual -@opindex Wcast-qual -Warn whenever a pointer is cast so as to remove a type qualifier from -the target type. For example, warn if a @code{const char *} is cast -to an ordinary @code{char *}. - -@item -Wcast-align -@opindex Wcast-align -Warn whenever a pointer is cast such that the required alignment of the -target is increased. For example, warn if a @code{char *} is cast to -an @code{int *} on machines where integers can only be accessed at -two- or four-byte boundaries. - -@item -Wwrite-strings -@opindex Wwrite-strings -When compiling C, give string constants the type @code{const -char[@var{length}]} so that -copying the address of one into a non-@code{const} @code{char *} -pointer will get a warning; when compiling C++, warn about the -deprecated conversion from string literals to @code{char *}. This -warning, by default, is enabled for C++ programs. -These warnings will help you find at -compile time code that can try to write into a string constant, but -only if you have been very careful about using @code{const} in -declarations and prototypes. Otherwise, it will just be a nuisance; -this is why we did not make @option{-Wall} request these warnings. - -@item -Wconversion -@opindex Wconversion -Warn if a prototype causes a type conversion that is different from what -would happen to the same argument in the absence of a prototype. This -includes conversions of fixed point to floating and vice versa, and -conversions changing the width or signedness of a fixed point argument -except when the same as the default promotion. - -Also, warn if a negative integer constant expression is implicitly -converted to an unsigned type. For example, warn about the assignment -@code{x = -1} if @code{x} is unsigned. But do not warn about explicit -casts like @code{(unsigned) -1}. - -@c APPLE LOCAL begin mainline -@item -Wshorten-64-to-32 -@opindex Wshorten-64-to-32 -Warn if a value is implicitly converted from a 64 bit type to a 32 bit type. -@c APPLE LOCAL end mainline - -@c APPLE LOCAL begin mainline -@item -Wempty-body -@opindex Wempty-body -Warn if an empty body occurs in an @samp{if} or @samp{else} -statement. Additionally, in C++, warn when an empty body occurs -in a @samp{while} or @samp{for} statement with no whitespacing before -the semicolon. This warning is also enabled by @option{-Wextra}. -@c APPLE LOCAL end mainline - -@item -Wsign-compare -@opindex Wsign-compare -@cindex warning for comparison of signed and unsigned values -@cindex comparison of signed and unsigned values, warning -@cindex signed and unsigned values, comparison warning -Warn when a comparison between signed and unsigned values could produce -an incorrect result when the signed value is converted to unsigned. -This warning is also enabled by @option{-Wextra}; to get the other warnings -of @option{-Wextra} without this warning, use @samp{-Wextra -Wno-sign-compare}. - -@item -Waddress -@opindex Waddress -@opindex Wno-address -Warn about suspicious uses of memory addresses. These include using -the address of a function in a conditional expression, such as -@code{void func(void); if (func)}, and comparisons against the memory -address of a string literal, such as @code{if (x == "abc")}. Such -uses typically indicate a programmer error: the address of a function -always evaluates to true, so their use in a conditional usually -indicate that the programmer forgot the parentheses in a function -call; and comparisons against string literals result in unspecified -behavior and are not portable in C, so they usually indicate that the -programmer intended to use @code{strcmp}. This warning is enabled by -@option{-Wall}. - -@item -Waggregate-return -@opindex Waggregate-return -Warn if any functions that return structures or unions are defined or -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 -argument types. (An old-style function definition is permitted without -a warning if preceded by a declaration which specifies the argument -types.) - -@item -Wold-style-definition @r{(C only)} -@opindex Wold-style-definition -Warn if an old-style function definition is used. A warning is given -even if there is a previous prototype. - -@c APPLE LOCAL warn missing prototype 6261539 -@item -Wmissing-prototypes -@opindex Wmissing-prototypes -Warn if a global function is defined without a previous prototype -declaration. This warning is issued even if the definition itself -provides a prototype. The aim is to detect global functions that fail -to be declared in header files. - -@item -Wmissing-declarations @r{(C only)} -@opindex Wmissing-declarations -Warn if a global function is defined without a previous declaration. -Do so even if the definition itself provides a prototype. -Use this option to detect global functions that are not declared in -header files. - -@item -Wmissing-field-initializers -@opindex Wmissing-field-initializers -@opindex W -@opindex Wextra -Warn if a structure's initializer has some fields missing. For -example, the following code would cause such a warning, because -@code{x.h} is implicitly zero: - -@smallexample -struct s @{ int f, g, h; @}; -struct s x = @{ 3, 4 @}; -@end smallexample - -This option does not warn about designated initializers, so the following -modification would not trigger a warning: - -@smallexample -struct s @{ int f, g, h; @}; -struct s x = @{ .f = 3, .g = 4 @}; -@end smallexample - -This warning is included in @option{-Wextra}. To get other @option{-Wextra} -warnings without this one, use @samp{-Wextra -Wno-missing-field-initializers}. - -@item -Wmissing-noreturn -@opindex Wmissing-noreturn -Warn about functions which might be candidates for attribute @code{noreturn}. -Note these are only possible candidates, not absolute ones. Care should -be taken to manually verify functions actually do not ever return before -adding the @code{noreturn} attribute, otherwise subtle code generation -bugs could be introduced. You will not get a warning for @code{main} in -hosted C environments. - -@item -Wmissing-format-attribute -@opindex Wmissing-format-attribute -@opindex Wformat -Warn about function pointers which might be candidates for @code{format} -attributes. Note these are only possible candidates, not absolute ones. -GCC will guess that function pointers with @code{format} attributes that -are used in assignment, initialization, parameter passing or return -statements should have a corresponding @code{format} attribute in the -resulting type. I.e.@: the left-hand side of the assignment or -initialization, the type of the parameter variable, or the return type -of the containing function respectively should also have a @code{format} -attribute to avoid the warning. - -GCC will also warn about function definitions which might be -candidates for @code{format} attributes. Again, these are only -possible candidates. GCC will guess that @code{format} attributes -might be appropriate for any function that calls a function like -@code{vprintf} or @code{vscanf}, but this might not always be the -case, and some functions for which @code{format} attributes are -appropriate may not be detected. - -@item -Wno-multichar -@opindex Wno-multichar -@opindex Wmultichar -@c APPLE LOCAL begin -Wfour-char-constants -Do not warn if a multicharacter constant (@samp{'FOO'}) is used. -Usually they indicate a typo in the user's code, as they have -implementation-defined values, and should not be used in portable code. -This flag does not control warning for a constant with four characters, -use -Wfour-char-constants instead. -@c APPLE LOCAL end -Wfour-char-constants - -@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} -normalization 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 (@pxref{Function Attributes}), -variables (@pxref{Variable Attributes}), and types (@pxref{Type -Attributes}) marked as deprecated by using the @code{deprecated} -attribute. - -@item -Wno-overflow -@opindex Wno-overflow -Do not warn about compile-time overflow in constant expressions. - -@item -Woverride-init -@opindex Woverride-init -@opindex W -@opindex Wextra -Warn if an initialized field without side effects is overridden when -using designated initializers (@pxref{Designated Inits, , Designated -Initializers}). - -This warning is included in @option{-Wextra}. To get other -@option{-Wextra} warnings without this one, use @samp{-Wextra --Wno-override-init}. - -@item -Wpacked -@opindex Wpacked -Warn if a structure is given the packed attribute, but the packed -attribute has no effect on the layout or size of the structure. -Such structures may be mis-aligned for little benefit. For -instance, in this code, the variable @code{f.x} in @code{struct bar} -will be misaligned even though @code{struct bar} does not itself -have the packed attribute: - -@smallexample -@group -struct foo @{ - int x; - char a, b, c, d; -@} __attribute__((packed)); -struct bar @{ - char z; - struct foo f; -@}; -@end group -@end smallexample - -@item -Wpadded -@opindex Wpadded -Warn if padding is included in a structure, either to align an element -of the structure or to align the whole structure. Sometimes when this -happens it is possible to rearrange the fields of the structure to -reduce the padding and so make the structure smaller. - -@item -Wredundant-decls -@opindex Wredundant-decls -Warn if anything is declared more than once in the same scope, even in -cases where multiple declaration is valid and changes nothing. - -@item -Wnested-externs @r{(C only)} -@opindex Wnested-externs -Warn if an @code{extern} declaration is encountered within a function. - -@item -Wunreachable-code -@opindex Wunreachable-code -Warn if the compiler detects that code will never be executed. - -This option is intended to warn when the compiler detects that at -least a whole line of source code will never be executed, because -some condition is never satisfied or because it is after a -procedure that never returns. - -It is possible for this option to produce a warning even though there -are circumstances under which part of the affected line can be executed, -so care should be taken when removing apparently-unreachable code. - -For instance, when a function is inlined, a warning may mean that the -line is unreachable in only one inlined copy of the function. - -This option is not made part of @option{-Wall} because in a debugging -version of a program there is often substantial code which checks -correct functioning of the program and is, hopefully, unreachable -because the program does work. Another common use of unreachable -code is to provide behavior which is selectable at compile-time. - -@item -Winline -@opindex Winline -Warn if a function can not be inlined and it was declared as inline. -Even with this option, the compiler will not warn about failures to -inline functions declared in system headers. - -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 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. - -@item -Wno-invalid-offsetof @r{(C++ only)} -@opindex Wno-invalid-offsetof -Suppress warnings from applying the @samp{offsetof} macro to a non-POD -type. According to the 1998 ISO C++ standard, applying @samp{offsetof} -to a non-POD type is undefined. In existing C++ implementations, -however, @samp{offsetof} typically gives meaningful results even when -applied to certain kinds of non-POD types. (Such as a simple -@samp{struct} that fails to be a POD type only by virtue of having a -constructor.) This flag is for users who are aware that they are -writing nonportable code and who have deliberately chosen to ignore the -warning about it. - -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 -the search path but can't be used. - -@item -Wlong-long -@opindex Wlong-long -@opindex Wno-long-long -Warn if @samp{long long} type is used. This is default. To inhibit -the warning messages, use @option{-Wno-long-long}. Flags -@option{-Wlong-long} and @option{-Wno-long-long} are taken into account -only when @option{-pedantic} flag is used. - -@item -Wvariadic-macros -@opindex Wvariadic-macros -@opindex Wno-variadic-macros -Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU -alternate syntax when in pedantic ISO C99 mode. This is default. -To inhibit the warning messages, use @option{-Wno-variadic-macros}. - -@item -Wvolatile-register-var -@opindex Wvolatile-register-var -@opindex Wno-volatile-register-var -Warn if a register variable is declared volatile. The volatile -modifier does not inhibit all optimizations that may eliminate reads -and/or writes to register variables. - -@item -Wdisabled-optimization -@opindex Wdisabled-optimization -Warn if a requested optimization pass is disabled. This warning does -not generally indicate that there is anything wrong with your code; it -merely indicates that GCC's optimizers were unable to handle the code -effectively. Often, the problem is that your code is too big or too -complex; GCC will refuse to optimize programs when the optimization -itself is likely to take inordinate amounts of time. - -@item -Wpointer-sign -@opindex Wpointer-sign -@opindex Wno-pointer-sign -Warn for pointer argument passing or assignment with different signedness. -This option is only supported for C and Objective-C@. It is implied by -@option{-Wall} and by @option{-pedantic}, which can be disabled with -@option{-Wno-pointer-sign}. - -@item -Werror -@opindex Werror -Make all warnings into errors. - -@item -Werror= -@opindex Werror= -Make the specified warning into an errors. The specifier for a -warning is appended, for example @option{-Werror=switch} turns the -warnings controlled by @option{-Wswitch} into errors. This switch -takes a negative form, to be used to negate @option{-Werror} for -specific warnings, for example @option{-Wno-error=switch} makes -@option{-Wswitch} warnings not be errors, even when @option{-Werror} -is in effect. You can use the @option{-fdiagnostics-show-option} -option to have each controllable warning amended with the option which -controls it, to determine what to use with this option. - -Note that specifying @option{-Werror=}@var{foo} automatically implies -@option{-W}@var{foo}. However, @option{-Wno-error=}@var{foo} does not -imply anything. - -@item -Wstack-protector -@opindex Wstack-protector -This option is only active when @option{-fstack-protector} is active. It -warns about functions that will not be protected against stack smashing. - -@item -Woverlength-strings -@opindex Woverlength-strings -Warn about string constants which are longer than the ``minimum -maximum'' length specified in the C standard. Modern compilers -generally allow string constants which are much longer than the -standard's minimum limit, but very portable programs should avoid -using longer strings. - -The limit applies @emph{after} string constant concatenation, and does -not count the trailing NUL@. In C89, the limit was 509 characters; in -C99, it was raised to 4095. C++98 does not specify a normative -minimum maximum, so we do not diagnose overlength strings in C++@. - -This option is implied by @option{-pedantic}, and can be disabled with -@option{-Wno-overlength-strings}. -@end table - -@node Debugging Options -@section Options for Debugging Your Program or GCC -@cindex options, debugging -@cindex debugging information options - -GCC has various special options that are used for debugging -either your program or GCC: - -@table @gcctabopt -@item -g -@opindex g -Produce debugging information in the operating system's native format -(stabs, COFF, XCOFF, or DWARF 2)@. GDB can work with this debugging -information. - -On most systems that use stabs format, @option{-g} enables use of extra -debugging information that only GDB can use; this extra information -makes debugging work better in GDB but will probably make other debuggers -crash or -refuse to read the program. If you want to control for certain whether -@c APPLE LOCAL begin prune man page -to generate the extra information, use @option{-gstabs+} or @option{-gstabs} -(see below). -@c APPLE LOCAL end prune man page - -GCC allows you to use @option{-g} with -@option{-O}. The shortcuts taken by optimized code may occasionally -produce surprising results: some variables you declared may not exist -at all; flow of control may briefly move where you did not expect it; -some statements may not be executed because they compute constant -results or their values were already at hand; some statements may -execute in different places because they were moved out of loops. - -Nevertheless it proves possible to debug optimized output. This makes -it reasonable to use the optimizer for programs that might have bugs. - -The following options are useful when GCC is generated with the -capability for more than one debugging format. - -@item -ggdb -@opindex ggdb -Produce debugging information for use by GDB@. This means to use the -most expressive format available (DWARF 2, stabs, or the native format -if neither of those are supported), including GDB extensions if at all -possible. - -@item -gstabs -@opindex gstabs -Produce debugging information in stabs format (if that is supported), -without GDB extensions. This is the format used by DBX on most BSD -systems. On MIPS, Alpha and System V Release 4 systems this option -produces stabs debugging output which is not understood by DBX or SDB@. -On System V Release 4 systems this option requires the GNU assembler. - -@c APPLE LOCAL begin 4167759 -@item -flimit-debug-info -@opindex -flimit-debug-info -Limit debug information produced to reduce size of debug binary. -@c APPLE LOCAL end 4167759 - -@item -feliminate-unused-debug-symbols -@opindex feliminate-unused-debug-symbols -Produce debugging information in stabs format (if that is supported), -for only symbols that are actually used. - -@item -femit-class-debug-always -Instead of emitting debugging information for a C++ class in only one -object file, emit it in all object files using the class. This option -should be used only with debuggers that are unable to handle the way GCC -normally emits debugging information for classes because using this -option will increase the size of debugging information by as much as a -factor of two. - -@item -gstabs+ -@opindex gstabs+ -Produce debugging information in stabs format (if that is supported), -using GNU extensions understood only by the GNU debugger (GDB)@. The -use of these extensions is likely to make other debuggers crash or -refuse to read the program. - -@c APPLE LOCAL prune man page -@ignore -@item -gcoff -@opindex gcoff -Produce debugging information in COFF format (if that is supported). -This is the format used by SDB on most System V systems prior to -System V Release 4. - -@item -gxcoff -@opindex gxcoff -Produce debugging information in XCOFF format (if that is supported). -This is the format used by the DBX debugger on IBM RS/6000 systems. - -@item -gxcoff+ -@opindex gxcoff+ -Produce debugging information in XCOFF format (if that is supported), -using GNU extensions understood only by the GNU debugger (GDB)@. The -use of these extensions is likely to make other debuggers crash or -refuse to read the program, and may cause assemblers other than the GNU -assembler (GAS) to fail with an error. -@c APPLE LOCAL prune man page -@end ignore - -@item -gdwarf-2 -@opindex gdwarf-2 -Produce debugging information in DWARF version 2 format (if that is -supported). This is the format used by DBX on IRIX 6. With this -option, GCC uses features of DWARF version 3 when they are useful; -version 3 is upward compatible with version 2, but may still cause -problems for older debuggers. - -@c APPLE LOCAL begin prune man page -(Other debug formats, such as @option{-gcoff}, are not supported in -Darwin or Mac OS X.) -@ignore -@item -gvms -@opindex gvms -Produce debugging information in VMS debug format (if that is -supported). This is the format used by DEBUG on VMS systems. -@end ignore -@c APPLE LOCAL end prune man page - -@item -g@var{level} -@itemx -ggdb@var{level} -@itemx -gstabs@var{level} -@c APPLE LOCAL prune man page -@ignore -@itemx -gcoff@var{level} -@itemx -gxcoff@var{level} -@itemx -gvms@var{level} -@c APPLE LOCAL prune man page -@end ignore -Request debugging information and also use @var{level} to specify how -much information. The default level is 2. - -@c APPLE LOCAL begin mainline 4.3 2006-12-20 4869554 -Level 0 produces no debug information at all. Thus, @option{-g0} negates -@option{-g}. -@c APPLE LOCAL end mainline 4.3 2006-12-20 4869554 - -Level 1 produces minimal information, enough for making backtraces in -parts of the program that you don't plan to debug. This includes -descriptions of functions and external variables, but no information -about local variables and no line numbers. - -Level 3 includes extra information, such as all the macro definitions -present in the program. Some debuggers support macro expansion when -you use @option{-g3}. - -@option{-gdwarf-2} does not accept a concatenated debug level, because -GCC used to support an option @option{-gdwarf} that meant to generate -debug information in version 1 of the DWARF format (which is very -different from version 2), and it would have been too confusing. That -debug format is long obsolete, but the option cannot be changed now. -Instead use an additional @option{-g@var{level}} option to change the -debug level for DWARF2. - -@item -feliminate-dwarf2-dups -@opindex feliminate-dwarf2-dups -Compress DWARF2 debugging information by eliminating duplicated -information about each symbol. This option only makes sense when -generating DWARF2 debugging information with @option{-gdwarf-2}. - -@cindex @command{prof} -@item -p -@opindex p -Generate extra code to write profile information suitable for the -analysis program @command{prof}. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. - -@cindex @command{gprof} -@item -pg -@opindex pg -Generate extra code to write profile information suitable for the -analysis program @command{gprof}. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. - -@item -Q -@opindex Q -Makes the compiler print out each function name as it is compiled, and -print some statistics about each pass when it finishes. - -@item -ftime-report -@opindex ftime-report -Makes the compiler print some statistics about the time consumed by each -pass when it finishes. - -@item -fmem-report -@opindex fmem-report -Makes the compiler print some statistics about permanent memory -allocation when it finishes. - -@c APPLE LOCAL begin opt diary -@item -fopt-diary -@opindex fopt-diary -Enable optimization diary entries using DWARF encoding. This option -does nothing unless @option{gdwarf-2} is specified. -@c APPLE LOCAL end opt diary -@item -fprofile-arcs -@opindex fprofile-arcs -Add code so that program flow @dfn{arcs} are instrumented. During -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 -profile-directed optimizations (@option{-fbranch-probabilities}), or for -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 -(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 -every source file in a program. - -@item -Link your object files with @option{-lgcov} or @option{-fprofile-arcs} -(the latter implies the former). - -@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 -concurrent instances of your program, and provided that the file system -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 profile-directed optimizations, compile the source files again with -the same optimization and code generation options plus -@option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that -Control Optimization}). - -@item -For test coverage analysis, use @command{gcov} to produce human readable -information from the @file{.gcno} and @file{.gcda} files. Refer to the -@command{gcov} documentation for further information. - -@end itemize - -With @option{-fprofile-arcs}, for each function of your program GCC -creates a program flow graph, then finds a spanning tree for the graph. -Only arcs that are not on the spanning tree have to be instrumented: the -compiler adds code to count the number of times that these arcs are -executed. When an arc is the only exit or only entrance to a block, the -instrumentation code can be added to the block; otherwise, a new basic -block must be created to hold the instrumentation code. - -@need 2000 -@item -ftest-coverage -@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 -above for a description of @var{auxname} and instructions on how to -generate test coverage data. Coverage data will match the source files -more closely, if you do not optimize. - -@c APPLE LOCAL begin mainline -@item -d@var{letters} -@item -fdump-rtl-@var{pass} -@opindex d -Says to make debugging dumps during compilation at times specified by -@var{letters}. This is used for debugging the RTL-based passes of the -compiler. The file names for most of the dumps are made by appending a -pass number and a word to the @var{dumpname}. @var{dumpname} is generated -from the name of the output file, if explicitly specified and it is not -an executable, otherwise it is the basename of the source file. These -switches may have different effects when @option{-E} is used for -preprocessing. -@c APPLE LOCAL end mainline - -Most debug dumps can be enabled either passing a letter to the @option{-d} -option, or with a long @option{-fdump-rtl} switch; here are the possible -letters for use in @var{letters} and @var{pass}, and their meanings: - -@table @gcctabopt -@item -dA -@opindex dA -Annotate the assembler output with miscellaneous debugging information. - -@item -dB -@itemx -fdump-rtl-bbro -@opindex dB -@opindex fdump-rtl-bbro -Dump after block reordering, to @file{@var{file}.148r.bbro}. - -@item -dc -@itemx -fdump-rtl-combine -@opindex dc -@opindex fdump-rtl-combine -Dump after instruction combination, to the file @file{@var{file}.129r.combine}. - -@item -dC -@itemx -fdump-rtl-ce1 -@itemx -fdump-rtl-ce2 -@opindex dC -@opindex fdump-rtl-ce1 -@opindex fdump-rtl-ce2 -@option{-dC} and @option{-fdump-rtl-ce1} enable dumping after the -first if conversion, to the file @file{@var{file}.117r.ce1}. @option{-dC} -and @option{-fdump-rtl-ce2} enable dumping after the second if -conversion, to the file @file{@var{file}.130r.ce2}. - -@item -dd -@itemx -fdump-rtl-btl -@itemx -fdump-rtl-dbr -@opindex dd -@opindex fdump-rtl-btl -@opindex fdump-rtl-dbr -@option{-dd} and @option{-fdump-rtl-btl} enable dumping after branch -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}. - -@item -dD -@opindex dD -Dump all macro definitions, at the end of preprocessing, in addition to -normal output. - -@item -dE -@itemx -fdump-rtl-ce3 -@opindex dE -@opindex fdump-rtl-ce3 -Dump after the third if conversion, to @file{@var{file}.146r.ce3}. - -@item -df -@itemx -fdump-rtl-cfg -@itemx -fdump-rtl-life -@opindex df -@opindex fdump-rtl-cfg -@opindex fdump-rtl-life -@option{-df} and @option{-fdump-rtl-cfg} enable dumping after control -and data flow analysis, to @file{@var{file}.116r.cfg}. @option{-df} -and @option{-fdump-rtl-cfg} enable dumping dump after life analysis, -to @file{@var{file}.128r.life1} and @file{@var{file}.135r.life2}. - -@item -dg -@itemx -fdump-rtl-greg -@opindex dg -@opindex fdump-rtl-greg -Dump after global register allocation, to @file{@var{file}.139r.greg}. - -@item -dG -@itemx -fdump-rtl-gcse -@itemx -fdump-rtl-bypass -@opindex dG -@opindex fdump-rtl-gcse -@opindex fdump-rtl-bypass -@option{-dG} and @option{-fdump-rtl-gcse} enable dumping after GCSE, to -@file{@var{file}.114r.gcse}. @option{-dG} and @option{-fdump-rtl-bypass} -enable dumping after jump bypassing and control flow optimizations, to -@file{@var{file}.115r.bypass}. - -@item -dh -@itemx -fdump-rtl-eh -@opindex dh -@opindex fdump-rtl-eh -Dump after finalization of EH handling code, to @file{@var{file}.02.eh}. - -@item -di -@itemx -fdump-rtl-sibling -@opindex di -@opindex fdump-rtl-sibling -Dump after sibling call optimizations, to @file{@var{file}.106r.sibling}. - -@item -dj -@itemx -fdump-rtl-jump -@opindex dj -@opindex fdump-rtl-jump -Dump after the first jump optimization, to @file{@var{file}.112r.jump}. - -@item -dk -@itemx -fdump-rtl-stack -@opindex dk -@opindex fdump-rtl-stack -Dump after conversion from registers to stack, to @file{@var{file}.152r.stack}. - -@item -dl -@itemx -fdump-rtl-lreg -@opindex dl -@opindex fdump-rtl-lreg -Dump after local register allocation, to @file{@var{file}.138r.lreg}. - -@item -dL -@itemx -fdump-rtl-loop2 -@opindex dL -@opindex fdump-rtl-loop2 -@option{-dL} and @option{-fdump-rtl-loop2} enable dumping after the -loop optimization pass, to @file{@var{file}.119r.loop2}, -@file{@var{file}.120r.loop2_init}, -@file{@var{file}.121r.loop2_invariant}, and -@file{@var{file}.125r.loop2_done}. - -@item -dm -@itemx -fdump-rtl-sms -@opindex dm -@opindex fdump-rtl-sms -Dump after modulo scheduling, to @file{@var{file}.136r.sms}. - -@item -dM -@itemx -fdump-rtl-mach -@opindex dM -@opindex fdump-rtl-mach -@c APPLE LOCAL begin mainline -Dump after performing the machine dependent reorganization pass, to -@file{@var{file}.155r.mach} if that pass exists. -@c APPLE LOCAL end mainline - -@item -dn -@itemx -fdump-rtl-rnreg -@opindex dn -@opindex fdump-rtl-rnreg -Dump after register renumbering, to @file{@var{file}.147r.rnreg}. - -@item -dN -@itemx -fdump-rtl-regmove -@opindex dN -@opindex fdump-rtl-regmove -Dump after the register move pass, to @file{@var{file}.132r.regmove}. - -@item -do -@itemx -fdump-rtl-postreload -@opindex do -@opindex fdump-rtl-postreload -Dump after post-reload optimizations, to @file{@var{file}.24.postreload}. - -@item -dr -@itemx -fdump-rtl-expand -@opindex dr -@opindex fdump-rtl-expand -Dump after RTL generation, to @file{@var{file}.104r.expand}. - -@item -dR -@itemx -fdump-rtl-sched2 -@opindex dR -@opindex fdump-rtl-sched2 -Dump after the second scheduling pass, to @file{@var{file}.150r.sched2}. - -@item -ds -@itemx -fdump-rtl-cse -@opindex ds -@opindex fdump-rtl-cse -Dump after CSE (including the jump optimization that sometimes follows -CSE), to @file{@var{file}.113r.cse}. - -@item -dS -@itemx -fdump-rtl-sched -@opindex dS -@opindex fdump-rtl-sched -Dump after the first scheduling pass, to @file{@var{file}.21.sched}. - -@item -dt -@itemx -fdump-rtl-cse2 -@opindex dt -@opindex fdump-rtl-cse2 -Dump after the second CSE pass (including the jump optimization that -sometimes follows CSE), to @file{@var{file}.127r.cse2}. - -@item -dT -@itemx -fdump-rtl-tracer -@opindex dT -@opindex fdump-rtl-tracer -Dump after running tracer, to @file{@var{file}.118r.tracer}. - -@item -dV -@itemx -fdump-rtl-vpt -@itemx -fdump-rtl-vartrack -@opindex dV -@opindex fdump-rtl-vpt -@opindex fdump-rtl-vartrack -@option{-dV} and @option{-fdump-rtl-vpt} enable dumping after the value -profile transformations, to @file{@var{file}.10.vpt}. @option{-dV} -and @option{-fdump-rtl-vartrack} enable dumping after variable tracking, -to @file{@var{file}.154r.vartrack}. - -@item -dw -@itemx -fdump-rtl-flow2 -@opindex dw -@opindex fdump-rtl-flow2 -Dump after the second flow pass, to @file{@var{file}.142r.flow2}. - -@item -dz -@itemx -fdump-rtl-peephole2 -@opindex dz -@opindex fdump-rtl-peephole2 -Dump after the peephole pass, to @file{@var{file}.145r.peephole2}. - -@item -dZ -@itemx -fdump-rtl-web -@opindex dZ -@opindex fdump-rtl-web -Dump after live range splitting, to @file{@var{file}.126r.web}. - -@item -da -@itemx -fdump-rtl-all -@opindex da -@opindex fdump-rtl-all -Produce all the dumps listed above. - -@item -dH -@opindex dH -Produce a core dump whenever an error occurs. - -@item -dm -@opindex dm -Print statistics on memory usage, at the end of the run, to -standard error. - -@item -dp -@opindex dp -Annotate the assembler output with a comment indicating which -pattern and alternative was used. The length of each instruction is -also printed. - -@item -dP -@opindex dP -Dump the RTL in the assembler output as a comment before each instruction. -Also turns on @option{-dp} annotation. - -@item -dv -@opindex dv -For each of the other indicated dump files (either with @option{-d} or -@option{-fdump-rtl-@var{pass}}), dump a representation of the control flow -graph suitable for viewing with VCG to @file{@var{file}.@var{pass}.vcg}. - -@item -dx -@opindex dx -Just generate RTL for a function instead of compiling it. Usually used -with @samp{r} (@option{-fdump-rtl-expand}). - -@item -dy -@opindex dy -Dump debugging information during parsing, to standard error. -@end table - -@item -fdump-noaddr -@opindex fdump-noaddr -When doing debugging dumps (see @option{-d} option above), suppress -address output. This makes it more feasible to use diff on debugging -dumps for compiler invocations with different compiler binaries and/or -different text / bss / data / heap / stack / dso start locations. - -@item -fdump-unnumbered -@opindex fdump-unnumbered -When doing debugging dumps (see @option{-d} option above), suppress instruction -numbers, line number note and address output. This makes it more feasible to -use diff on debugging dumps for compiler invocations with different -options, in particular with and without @option{-g}. - -@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 -source file name. If the @samp{-@var{options}} form is used, @var{options} -controls the details of the dump as described for the -@option{-fdump-tree} options. - -@item -fdump-class-hierarchy @r{(C++ only)} -@itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)} -@opindex fdump-class-hierarchy -Dump a representation of each class's hierarchy and virtual function -table layout to a file. The file name is made by appending @file{.class} -to the source file name. If the @samp{-@var{options}} form is used, -@var{options} controls the details of the dump as described for the -@option{-fdump-tree} options. - -@item -fdump-ipa-@var{switch} -@opindex fdump-ipa -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: - -@table @samp -@item all -Enables all inter-procedural analysis dumps; currently the only produced -dump is the @samp{cgraph} dump. - -@item cgraph -Dumps information about call-graph optimization, unused function removal, -and inlining decisions. -@end table - -@item -fdump-tree-@var{switch} -@itemx -fdump-tree-@var{switch}-@var{options} -@opindex fdump-tree -Control the dumping at various stages of processing the intermediate -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 -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 -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 -because that scope has been reached. Only dump such items when they -are directly reachable by some other path. When dumping pretty-printed -trees, this option inhibits dumping the bodies of control structures. -@item raw -Print a raw representation of the tree. By default, trees are -pretty-printed into a C-like representation. -@item details -Enable more detailed dumps (not honored by every dump option). -@item stats -Enable dumping various statistics about the pass (not honored by every dump -option). -@item blocks -Enable showing basic block boundaries (disabled in raw dumps). -@item vops -Enable showing virtual operands for every statement. -@item lineno -Enable showing line numbers for statements. -@item uid -Enable showing the unique ID (@code{DECL_UID}) for each variable. -@item all -Turn on all options, except @option{raw}, @option{slim} and @option{lineno}. -@end table - -The following tree dumps are possible: -@table @samp - -@item original -Dump before any tree based optimization, to @file{@var{file}.original}. - -@item optimized -Dump after all tree based optimization, to @file{@var{file}.optimized}. - -@item inlined -Dump after function inlining, to @file{@var{file}.inlined}. - -@item gimple -@opindex fdump-tree-gimple -Dump each function before and after the gimplification pass to a file. The -file name is made by appending @file{.gimple} to the source file name. - -@item cfg -@opindex fdump-tree-cfg -Dump the control flow graph of each function to a file. The file name is -made by appending @file{.cfg} to the source file name. - -@item vcg -@opindex fdump-tree-vcg -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 -graph into its own separate file first. - -@item ch -@opindex fdump-tree-ch -Dump each function after copying loop headers. The file name is made by -appending @file{.ch} to the source file name. - -@item ssa -@opindex fdump-tree-ssa -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 -appending @file{.alias} to the source file name. - -@item ccp -@opindex fdump-tree-ccp -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 -by appending @file{.pre} to the source file name. - -@item fre -@opindex fdump-tree-fre -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 -appending @file{.dce} to the source file name. - -@item mudflap -@opindex fdump-tree-mudflap -Dump each function after adding mudflap instrumentation. The file name is -made by appending @file{.mudflap} to the source file name. - -@item sra -@opindex fdump-tree-sra -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 -name is made by appending @file{.dom} to the source file name. - -@item dse -@opindex fdump-tree-dse -Dump each function after applying dead store elimination. The file -name is made by appending @file{.dse} to the source file name. - -@item phiopt -@opindex fdump-tree-phiopt -Dump each function after optimizing PHI nodes into straightline code. The file -name is made by appending @file{.phiopt} to the source file name. - -@item forwprop -@opindex fdump-tree-forwprop -Dump each function after forward propagating single use variables. The file -name is made by appending @file{.forwprop} to the source file name. - -@item copyrename -@opindex fdump-tree-copyrename -Dump each function after applying the copy rename optimization. The file -name is made by appending @file{.copyrename} to the source file name. - -@item nrv -@opindex fdump-tree-nrv -Dump each function after applying the named return value optimization on -generic trees. The file name is made by appending @file{.nrv} to the source -file name. - -@item vect -@opindex fdump-tree-vect -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}. -For @var{n}=0 no diagnostic information is reported. -If @var{n}=1 the vectorizer reports each loop that got vectorized, -and the total number of loops that got vectorized. -If @var{n}=2 the vectorizer also reports non-vectorized loops that passed -the first analysis phase (vect_analyze_loop_form) - i.e. countable, -inner-most, single-bb, single-entry/exit loops. This is the same verbosity -level that @option{-fdump-tree-vect-stats} uses. -Higher verbosity levels mean either more information dumped for each -reported loop, or same amount of information reported for more loops: -If @var{n}=3, alignment related information is added to the reports. -If @var{n}=4, data-references related information (e.g. memory dependences, -memory access-patterns) is added to the reports. -If @var{n}=5, the vectorizer reports also non-vectorized inner-most loops -that did not pass the first analysis phase (i.e. may not be countable, or -may have complicated control-flow). -If @var{n}=6, the vectorizer reports also non-vectorized nested loops. -For @var{n}=7, all the information the vectorizer generates during its -analysis and transformation is reported. This is the same verbosity level -that @option{-fdump-tree-vect-details} uses. - -@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 -place unique stamps in coverage data files and the object files that -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. - -@item -fsched-verbose=@var{n} -@opindex fsched-verbose -On targets that use instruction scheduling, this option controls the -amount of debugging output the scheduler prints. This information is -written to standard error, unless @option{-dS} or @option{-dR} is -specified, in which case it is output to the usual dump -listing file, @file{.sched} or @file{.sched2} respectively. However -for @var{n} greater than nine, the output is always printed to standard -error. - -For @var{n} greater than zero, @option{-fsched-verbose} outputs the -same information as @option{-dRS}. For @var{n} greater than one, it -also output basic block probabilities, detailed ready list information -and unit/insn info. For @var{n} greater than two, it includes RTL -at abort point, control-flow and regions info. And for @var{n} over -four, @option{-fsched-verbose} also includes dependence info. - -@item -save-temps -@opindex save-temps -Store the usual ``temporary'' intermediate files permanently; place them -in the current directory and name them based on the source file. Thus, -compiling @file{foo.c} with @samp{-c -save-temps} would produce files -@file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a -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 -sequence. For C source files, this is the compiler proper and assembler -(plus the linker if linking is done). The output looks like this: - -@smallexample -# cc1 0.12 0.01 -# 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'', -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 -(if the debugging information format supports this information). - -It is enabled by default when compiling with optimization (@option{-Os}, -@c APPLE LOCAL -Oz -@option{-O}, @option{-O2}, @option{-Oz} (APPLE ONLY), ...), debugging information (@option{-g}) and -the debug info format supports it. - -@item -print-file-name=@var{library} -@opindex print-file-name -Print the full absolute name of the library file @var{library} that -would be used when linking---and don't do anything else. With this -option, GCC does not compile or link anything; it just prints the -file name. - -@item -print-multi-directory -@opindex print-multi-directory -Print the directory name corresponding to the multilib selected by any -other switches present in the command line. This directory is supposed -to exist in @env{GCC_EXEC_PREFIX}. - -@item -print-multi-lib -@opindex print-multi-lib -Print the mapping from multilib directory names to compiler switches -that enable them. The directory name is separated from the switches by -@samp{;}, and each switch starts with an @samp{@@} instead of the -@samp{-}, without spaces between multiple switches. This is supposed to -ease shell-processing. - -@item -print-prog-name=@var{program} -@opindex print-prog-name -Like @option{-print-file-name}, but searches for a program such as @samp{cpp}. - -@item -print-libgcc-file-name -@opindex print-libgcc-file-name -Same as @option{-print-file-name=libgcc.a}. - -This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs} -but you do want to link with @file{libgcc.a}. You can do - -@smallexample -gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name` -@end smallexample - -@item -print-search-dirs -@opindex print-search-dirs -Print the name of the configured installation directory and a list of -program and library directories @command{gcc} will search---and don't do anything else. - -This is useful when @command{gcc} prints the error message -@samp{installation problem, cannot exec cpp0: No such file or directory}. -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 @samp{/}. -@xref{Environment Variables}. - -@item -dumpmachine -@opindex dumpmachine -Print the compiler's target machine (for example, -@samp{i686-pc-linux-gnu})---and don't do anything else. - -@item -dumpversion -@opindex dumpversion -Print the compiler version (for example, @samp{3.0})---and don't do -anything else. - -@item -dumpspecs -@opindex dumpspecs -Print the compiler's built-in specs---and don't do anything else. (This -is used when GCC itself is being built.) @xref{Spec Files}. - -@item -feliminate-unused-debug-types -@opindex feliminate-unused-debug-types -Normally, when producing DWARF2 output, GCC will emit debugging -information for all types declared in a compilation -unit, regardless of whether or not they are actually used -in that compilation unit. Sometimes this is useful, such as -if, in the debugger, you want to cast a value to a type that is -not actually used in your program (but is declared). More often, -however, this results in a significant amount of wasted space. -With this option, GCC will avoid producing debug symbol output -for types that are nowhere used in the source file being compiled. -@end table - -@node Optimize Options -@section Options That Control Optimization -@cindex optimize options -@cindex options, optimization - -These options control various sorts of optimizations. - -Without any optimization option, the compiler's goal is to reduce the -cost of compilation and to make debugging produce the expected -results. Statements are independent: if you stop the program with a -breakpoint between statements, you can then assign a new value to any -variable or change the program counter to any other statement in the -function and get exactly the results you would expect from the source -code. - -Turning on optimization flags makes the compiler attempt to improve -the performance and/or code size at the expense of compilation time -and possibly the ability to debug the program. - -The compiler performs optimization based on the knowledge it has of -the program. Optimization levels @option{-O} and above, in -particular, enable @emph{unit-at-a-time} mode, which allows the -compiler to consider information gained from later functions in -the file when compiling a function. Compiling multiple files at -once to a single output file in @emph{unit-at-a-time} mode allows -the compiler to use information gained from all of the files when -compiling each of them. - -Not all optimizations are controlled directly by a flag. Only -optimizations that have a flag are listed. - -@table @gcctabopt -@item -O -@itemx -O1 -@opindex O -@opindex O1 -Optimize. Optimizing compilation takes somewhat more time, and a lot -more memory for a large function. - -With @option{-O}, the compiler tries to reduce code size and execution -time, without performing any optimizations that take a great deal of -compilation time. - -@option{-O} turns on the following optimization flags: -@gccoptlist{-fdefer-pop @gol --fdelayed-branch @gol --fguess-branch-probability @gol --fcprop-registers @gol --fif-conversion @gol --fif-conversion2 @gol --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 --funit-at-a-time @gol --fmerge-constants} - -@option{-O} also turns on @option{-fomit-frame-pointer} on machines -where doing so does not interfere with debugging. - -@item -O2 -@opindex O2 -Optimize even more. GCC performs nearly all supported optimizations -that do not involve a space-speed tradeoff. The compiler does not -perform loop unrolling or function inlining when you specify @option{-O2}. -As compared to @option{-O}, this option increases both compilation time -and the performance of the generated code. - -@option{-O2} turns on all optimization flags specified by @option{-O}. It -also turns on the following optimization flags: -@gccoptlist{-fthread-jumps @gol --fcrossjumping @gol --foptimize-sibling-calls @gol --fcse-follow-jumps -fcse-skip-blocks @gol --fgcse -fgcse-lm @gol --fexpensive-optimizations @gol --frerun-cse-after-loop @gol --fcaller-saves @gol --fpeephole2 @gol --fschedule-insns -fschedule-insns2 @gol --fsched-interblock -fsched-spec @gol --fregmove @gol --fstrict-aliasing -fstrict-overflow @gol --fdelete-null-pointer-checks @gol --freorder-blocks -freorder-functions @gol --falign-functions -falign-jumps @gol --falign-loops -falign-labels @gol --ftree-vrp @gol --ftree-pre} - -Please note the warning under @option{-fgcse} about -invoking @option{-O2} on programs that use computed gotos. - -@option{-O2} doesn't turn on @option{-ftree-vrp} for the Ada compiler. -This option must be explicitly specified on the command line to be -enabled for the Ada compiler. - -@c APPLE LOCAL begin optimization -In Apple's version of GCC, @option{-fstrict-aliasing}, -@option{-freorder-blocks}, and @option{-fsched-interblock} -are disabled by default when optimizing. -@c APPLE LOCAL end optimization - -@item -O3 -@opindex O3 -Optimize yet more. @option{-O3} turns on all optimizations specified by -@option{-O2} and also turns on the @option{-finline-functions}, -@option{-funswitch-loops} and @option{-fgcse-after-reload} options. - -@item -O0 -@opindex O0 -Do not optimize. This is the default. - -@c APPLE LOCAL begin -fast or -fastf or -fastcp -@item -fast -@opindex fast -Optimize for maximum performance. @option{-fast} changes the overall optimization -strategy of GCC in order to produce the fastest possible running code for PPC7450 -and G5 architectures. By default, @option{-fast} optimizes for G5. Programs -optimized for G5 will not run on PPC7450. To optimize for PPC7450, add -@option{-mcpu=7450} on command line. - -@option{-fast} currently enables the following optimization flags (for G5 and PPC7450). -These flags may change in the future. You cannot override any of these options if you use -@option{-fast} except by setting @option{-mcpu=7450} (or @option{-fPIC}, see below). - -@gccoptlist{-O3 --falign-loops-max-skip=15 --falign-jumps-max-skip=15 --falign-loops=16 --falign-jumps=16 --falign-functions=16 --malign-natural (except when -fastf is specified) --ffast-math --fstrict-aliasing --funroll-loops --ftree-loop-linear --ftree-loop-memset --mcpu=G5 --mpowerpc-gpopt --mtune=G5 (unless -mtune=G4 is specified). --fsched-interblock --fgcse-sm --mpowerpc64} - -To build shared libraries with @option{-fast}, specify @option{-fPIC} -on the command line as @option{-fast} turns on @option{-mdynamic-no-pic} -otherwise. - -Important notes: @option{-ffast-math} results in code that is not necessarily -IEEE-compliant. @option{-fstrict-aliasing} is highly likely to break -non-standard-compliant programs. @option{-malign-natural} only works properly if -the entire program is compiled with it, and none of the standard headers/libraries -contain any code that changes alignment when this option is used. - -On Intel target, @option{-fast} currently enables the following optimization flags: - -@gccoptlist{-O3 --fomit-frame-pointer --fstrict-aliasing --momit-leaf-frame-pointer --fno-tree-pre --falign-loops} - -All choices of flags enabled by @option{-fast} are subject to change without notice. - -@c APPLE LOCAL end -fast or -fastf or -fastcp - -@c APPLE LOCAL begin 4231761 -Oz -@item -Os -@opindex Os -Optimize for size, but not at the expense of speed. -@option{-Os} enables all @option{-O2} optimizations that -do not typically increase code size. However, instructions -are chosen for best performance, regardless of size. -To optimize solely for size on Darwin, use @option{-Oz} (APPLE ONLY). - -The following options are set for @option{-O2}, but are disabled under @option{-Os}: -@gccoptlist{-falign-functions -falign-jumps -falign-loops @gol --falign-labels -freorder-blocks -freorder-blocks-and-partition @gol --fprefetch-loop-arrays -ftree-vect-loop-version} - -@c APPLE LOCAL begin 4200438 -When optimizing with @option{-Os} or @option{-Oz} (APPLE ONLY) on -Darwin, any function up to 30 ``estimated insns'' in size will be -considered for inlining. When compiling C and Objective-C sourcefiles with -@option{-Os} or @option{-Oz} on Darwin, functions explictly marked -with the @code{inline} keyword up to 450 ``estimated insns'' in size -will be considered for inlining. -@c APPLE LOCAL end 4200438 -@c APPLE LOCAL begin Disable string insns with -Os on Darwin (radar 3509006) -When compiling for Apple POWERPC targets, @option{-Os} and -@option{-Oz} (APPLE ONLY) disable use of the string instructions even though they -would usually be smaller, because the kernel can't emulate them -correctly in some rare cases. This behavior is not portable to any -other gcc environment, and will not affect most programs at all. If -you really want the string instructions, use -mstring. -@c APPLE LOCAL end Disable string insns with -Os on Darwin (radar 3509006) - -@item -Oz -@opindex Oz -(APPLE ONLY) Optimize for size, regardless of performance. -@option{-Oz} enables the same optimization flags that @option{-Os} -uses, but @option{-Oz} also enables other optimizations intended solely -to reduce code size. In particular, instructions that encode into -fewer bytes are preferred over longer instructions that execute in -fewer cycles. @option{-Oz} on Darwin is very similar to @option{-Os} -in FSF distributions of GCC. @option{-Oz} employs the same inlining -limits and avoids string instructions just like @option{-Os}. -@c APPLE LOCAL end 4231761 -Oz - -If you use multiple @option{-O} options, with or without level numbers, -the last such option is the one that is effective. -@end table - -Options of the form @option{-f@var{flag}} specify machine-independent -flags. Most flags have both positive and negative forms; the negative -form of @option{-ffoo} would be @option{-fno-foo}. In the table -below, only one of the forms is listed---the one you typically will -use. You can figure out the other form by either removing @samp{no-} -or adding it. - -The following options control specific optimizations. They are either -activated by @option{-O} options or are related to ones that are. You -can use the following flags in the rare cases when ``fine-tuning'' of -optimizations to be performed is desired. - -@table @gcctabopt -@item -fno-default-inline -@opindex fno-default-inline -Do not make member functions inline by default merely because they are -defined inside the class scope (C++ only). Otherwise, when you specify -@w{@option{-O}}, member functions defined inside class scope are compiled -inline by default; i.e., you don't need to add @samp{inline} in front of -the member function name. - -@item -fno-defer-pop -@opindex fno-defer-pop -Always pop the arguments to each function call as soon as that function -returns. For machines which must pop arguments after a function call, -the compiler normally lets arguments accumulate on the stack for several -function calls and pops them all at once. - -@c APPLE LOCAL begin 4231761 -Oz -Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, -@option{-Oz} (APPLE ONLY). -@c APPLE LOCAL end 4231761 -Oz - -@item -fforce-mem -@opindex fforce-mem -Force memory operands to be copied into registers before doing -arithmetic on them. This produces better code by making all memory -references potential common subexpressions. When they are not common -subexpressions, instruction combination should eliminate the separate -register-load. This option is now a nop and will be removed in 4.3. - -@item -fforce-addr -@opindex fforce-addr -Force memory address constants to be copied into registers before -doing arithmetic on them. - -@item -fomit-frame-pointer -@opindex fomit-frame-pointer -Don't keep the frame pointer in a register for functions that -don't need one. This avoids the instructions to save, set up and -restore frame pointers; it also makes an extra register available -in many functions. @strong{It also makes debugging impossible on -some machines.} - -On some machines, such as the VAX, this flag has no effect, because -the standard calling sequence automatically handles the frame pointer -and nothing is saved by pretending it doesn't exist. The -machine-description macro @code{FRAME_POINTER_REQUIRED} controls -whether a target machine supports this flag. @xref{Registers,,Register -Usage, gccint, GNU Compiler Collection (GCC) Internals}. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -foptimize-sibling-calls -@opindex foptimize-sibling-calls -Optimize sibling and tail recursive calls. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fno-inline -@opindex fno-inline -Don't pay attention to the @code{inline} keyword. Normally this option -is used to keep the compiler from expanding any functions inline. -Note that if you are not optimizing, no functions can be expanded inline. - -@item -finline-functions -@opindex finline-functions -Integrate all simple functions into their callers. The compiler -heuristically decides which functions are simple enough to be worth -integrating in this way. - -If all calls to a given function are integrated, and the function is -declared @code{static}, then the function is normally not output as -assembler code in its own right. - -Enabled at level @option{-O3}. - -@item -finline-functions-called-once -@opindex finline-functions-called-once -Consider all @code{static} functions called once for inlining into their -caller even if they are not marked @code{inline}. If a call to a given -function is integrated, then the function is not output as assembler code -in its own right. - -Enabled if @option{-funit-at-a-time} is enabled. - -@item -fearly-inlining -@opindex fearly-inlining -Inline functions marked by @code{always_inline} and functions whose body seems -smaller than the function call overhead early before doing -@option{-fprofile-generate} instrumentation and real inlining pass. Doing so -makes profiling significantly cheaper and usually inlining faster on programs -having large chains of nested wrapper functions. - -Enabled by default. - -@item -finline-limit=@var{n} -@opindex finline-limit -By default, GCC limits the size of functions that can be inlined. This flag -allows the control of this limit for functions that are explicitly marked as -inline (i.e., marked with the inline keyword or defined within the class -definition in c++). @var{n} is the size of functions that can be inlined in -number of pseudo instructions (not counting parameter handling). The default -value of @var{n} is 600. -Increasing this value can result in more inlined code at -the cost of compilation time and memory consumption. Decreasing usually makes -the compilation faster and less code will be inlined (which presumably -means slower programs). This option is particularly useful for programs that -use inlining heavily such as those based on recursive templates with C++. - -Inlining is actually controlled by a number of parameters, which may be -specified individually by using @option{--param @var{name}=@var{value}}. -The @option{-finline-limit=@var{n}} option sets some of these parameters -as follows: - -@table @gcctabopt -@item max-inline-insns-single - is set to @var{n}/2. -@item max-inline-insns-auto - is set to @var{n}/2. -@item min-inline-insns - is set to 130 or @var{n}/4, whichever is smaller. -@item max-inline-insns-rtl - is set to @var{n}. -@end table - -See below for a documentation of the individual -parameters controlling inlining. - -@emph{Note:} pseudo instruction represents, in this particular context, an -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. - -@item -fkeep-inline-functions -@opindex fkeep-inline-functions -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 -inline functions into the object file. - -@item -fkeep-static-consts -@opindex fkeep-static-consts -Emit variables declared @code{static const} when optimization isn't turned -on, even if the variables aren't referenced. - -GCC enables this option by default. If you want to force the compiler to -check if the variable was referenced, regardless of whether or not -optimization is turned on, use the @option{-fno-keep-static-consts} option. - -@c APPLE LOCAL begin ARM conditionally disable local RA -@item -flocal-alloc -(APPLE ONLY) Enable the local (intra-basic-block) register allocator. - -GCC enables this option by default. If you want to force the compiler to -supress register allocation within a basic block, use the -@option{-fno-local-alloc} option. This option cannot be disabled with -@option{-O0}, for correctness reasons. -@c APPLE LOCAL end ARM conditionally disable local RA - -@item -fmerge-constants -Attempt to merge identical constants (string constants and floating point -constants) across compilation units. - -This option is the default for optimized compilation if the assembler and -linker support it. Use @option{-fno-merge-constants} to inhibit this -behavior. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fmerge-all-constants -Attempt to merge identical constants and identical variables. - -This option implies @option{-fmerge-constants}. In addition to -@option{-fmerge-constants} this considers e.g.@: even constant initialized -arrays or initialized constant variables with integral or floating point -types. Languages like C or C++ require each non-automatic variable to -have distinct location, so using this option will result in non-conforming -behavior. - -@item -fmodulo-sched -@opindex fmodulo-sched -Perform swing modulo scheduling immediately before the first scheduling -pass. This pass looks at innermost loops and reorders their -instructions by overlapping different iterations. - -@item -fno-branch-count-reg -@opindex fno-branch-count-reg -Do not use ``decrement and branch'' instructions on a count register, -but instead generate a sequence of instructions that decrement a -register, compare it against zero, then branch based upon the result. -This option is only meaningful on architectures that support such -instructions, which include x86, PowerPC, IA-64 and S/390. - -The default is @option{-fbranch-count-reg}. - -@item -fno-function-cse -@opindex fno-function-cse -Do not put function addresses in registers; make each instruction that -calls a constant function contain the function's address explicitly. - -This option results in less efficient code, but some strange hacks -that alter the assembler output may be confused by the optimizations -performed when this option is not used. - -The default is @option{-ffunction-cse} - -@item -fno-zero-initialized-in-bss -@opindex fno-zero-initialized-in-bss -If the target supports a BSS section, GCC by default puts variables that -are initialized to zero into BSS@. This can save space in the resulting -code. - -This option turns off this behavior because some programs explicitly -rely on variables going to the data section. E.g., so that the -resulting executable can find the beginning of that section and/or make -assumptions based on that. - -The default is @option{-fzero-initialized-in-bss}. - -@item -fbounds-check -@opindex fbounds-check -For front-ends that support it, generate additional code to check that -indices used to access arrays are within the declared range. This is -currently only supported by the Java and Fortran front-ends, where -this option defaults to true and false respectively. - -@item -fmudflap -fmudflapth -fmudflapir -@opindex fmudflap -@opindex fmudflapth -@opindex fmudflapir -@cindex bounds checking -@cindex mudflap -For front-ends that support it (C and C++), instrument all risky -pointer/array dereferencing operations, some standard library -string/heap functions, and some other associated constructs with -range/validity tests. Modules so instrumented should be immune to -buffer overflows, invalid heap use, and some other classes of C/C++ -programming errors. The instrumentation relies on a separate runtime -library (@file{libmudflap}), which will be linked into a program if -@option{-fmudflap} is given at link time. Run-time behavior of the -instrumented program is controlled by the @env{MUDFLAP_OPTIONS} -environment variable. See @code{env MUDFLAP_OPTIONS=-help a.out} -for its options. - -Use @option{-fmudflapth} instead of @option{-fmudflap} to compile and to -link if your program is multi-threaded. Use @option{-fmudflapir}, in -addition to @option{-fmudflap} or @option{-fmudflapth}, if -instrumentation should ignore pointer reads. This produces less -instrumentation (and therefore faster execution) and still provides -some protection against outright memory corrupting writes, but allows -erroneously read data to propagate within a program. - -@item -fthread-jumps -@opindex fthread-jumps -Perform optimizations where we check to see if a jump branches to a -location where another comparison subsumed by the first is found. If -so, the first branch is redirected to either the destination of the -second branch or a point immediately following it, depending on whether -the condition is known to be true or false. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fcse-follow-jumps -@opindex fcse-follow-jumps -In common subexpression elimination, scan through jump instructions -when the target of the jump is not reached by any other path. For -example, when CSE encounters an @code{if} statement with an -@code{else} clause, CSE will follow the jump when the condition -tested is false. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fcse-skip-blocks -@opindex fcse-skip-blocks -This is similar to @option{-fcse-follow-jumps}, but causes CSE to -follow jumps which conditionally skip over blocks. When CSE -encounters a simple @code{if} statement with no else clause, -@option{-fcse-skip-blocks} causes CSE to follow the jump around the -body of the @code{if}. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -frerun-cse-after-loop -@opindex frerun-cse-after-loop -Re-run common subexpression elimination after loop optimizations has been -performed. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fgcse -@opindex fgcse -Perform a global common subexpression elimination pass. -This pass also performs global constant and copy propagation. - -@emph{Note:} When compiling a program using computed gotos, a GCC -extension, you may get better runtime performance if you disable -the global common subexpression elimination pass by adding -@option{-fno-gcse} to the command line. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fgcse-lm -@opindex fgcse-lm -When @option{-fgcse-lm} is enabled, global common subexpression elimination will -attempt to move loads which are only killed by stores into themselves. This -allows a loop containing a load/store sequence to be changed to a load outside -the loop, and a copy/store within the loop. - -Enabled by default when gcse is enabled. - -@item -fgcse-sm -@opindex fgcse-sm -When @option{-fgcse-sm} is enabled, a store motion pass is run after -global common subexpression elimination. This pass will attempt to move -stores out of loops. When used in conjunction with @option{-fgcse-lm}, -loops containing a load/store sequence can be changed to a load before -the loop and a store after the loop. - -Not enabled at any optimization level. - -@item -fgcse-las -@opindex fgcse-las -When @option{-fgcse-las} is enabled, the global common subexpression -elimination pass eliminates redundant loads that come after stores to the -same memory location (both partial and full redundancies). - -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 -redundant spilling. - -@item -funsafe-loop-optimizations -@opindex funsafe-loop-optimizations -If given, the loop optimizer will assume that loop indices do not -overflow, and that the loops with nontrivial exit condition are not -infinite. This enables a wider range of loop optimizations even if -the loop optimizer itself cannot prove that these assumptions are valid. -Using @option{-Wunsafe-loop-optimizations}, the compiler will warn you -if it finds this kind of loop. - -@item -fcrossjumping -@opindex crossjumping -Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The -resulting code may or may not perform better than without cross-jumping. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fif-conversion -@opindex if-conversion -Attempt to transform conditional jumps into branch-less equivalents. This -include use of conditional moves, min, max, set flags and abs instructions, and -some tricks doable by standard arithmetics. The use of conditional execution -on chips where it is available is controlled by @code{if-conversion2}. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fif-conversion2 -@opindex if-conversion2 -Use conditional execution (where available) to transform conditional jumps into -branch-less equivalents. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fdelete-null-pointer-checks -@opindex fdelete-null-pointer-checks -Use global dataflow analysis to identify and eliminate useless checks -for null pointers. The compiler assumes that dereferencing a null -pointer would have halted the program. If a pointer is checked after -it has already been dereferenced, it cannot be null. - -In some environments, this assumption is not true, and programs can -safely dereference null pointers. Use -@option{-fno-delete-null-pointer-checks} to disable this optimization -for programs which depend on that behavior. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fexpensive-optimizations -@opindex fexpensive-optimizations -Perform a number of minor optimizations that are relatively expensive. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -foptimize-register-move -@itemx -fregmove -@opindex foptimize-register-move -@opindex fregmove -Attempt to reassign register numbers in move instructions and as -operands of other simple instructions in order to maximize the amount of -register tying. This is especially helpful on machines with two-operand -instructions. - -Note @option{-fregmove} and @option{-foptimize-register-move} are the same -optimization. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fdelayed-branch -@opindex fdelayed-branch -If supported for the target machine, attempt to reorder instructions -to exploit instruction slots available after delayed branch -instructions. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fschedule-insns -@opindex fschedule-insns -If supported for the target machine, attempt to reorder instructions to -eliminate execution stalls due to required data being unavailable. This -helps machines that have slow floating point or memory load instructions -by allowing other instructions to be issued until the result of the load -or floating point instruction is required. - -@c APPLE LOCAL begin 4231761 5591571 -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} for PPC targets; -ignored for x86 targets (APPLE ONLY). -@c APPLE LOCAL end 4231761 5591571 - -@item -fschedule-insns2 -@opindex fschedule-insns2 -Similar to @option{-fschedule-insns}, but requests an additional pass of -instruction scheduling after register allocation has been done. This is -especially useful on machines with a relatively small number of -registers and where memory load instructions take more than one cycle. - -@c APPLE LOCAL begin 4231761 5591571 -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} for PPC targets; -ignored for x86 targets (APPLE ONLY). -@c APPLE LOCAL end 4231761 5591571 - -@item -fno-sched-interblock -@opindex fno-sched-interblock -Don't schedule instructions across basic blocks. This is normally -enabled by default when scheduling before register allocation, i.e.@: -with @option{-fschedule-insns} or at @option{-O2} or higher. - -@item -fno-sched-spec -@opindex fno-sched-spec -Don't allow speculative motion of non-load instructions. This is normally -enabled by default when scheduling before register allocation, i.e.@: -with @option{-fschedule-insns} or at @option{-O2} or higher. - -@item -fsched-spec-load -@opindex fsched-spec-load -Allow speculative motion of some load instructions. This only makes -sense when scheduling before register allocation, i.e.@: with -@option{-fschedule-insns} or at @option{-O2} or higher. - -@item -fsched-spec-load-dangerous -@opindex fsched-spec-load-dangerous -Allow speculative motion of more load instructions. This only makes -sense when scheduling before register allocation, i.e.@: with -@option{-fschedule-insns} or at @option{-O2} or higher. - -@item -fsched-stalled-insns=@var{n} -@opindex fsched-stalled-insns -Define how many insns (if any) can be moved prematurely from the queue -of stalled insns into the ready list, during the second scheduling pass. - -@item -fsched-stalled-insns-dep=@var{n} -@opindex fsched-stalled-insns-dep -Define how many insn groups (cycles) will be examined for a dependency -on a stalled insn that is candidate for premature removal from the queue -of stalled insns. Has an effect only during the second scheduling pass, -and only if @option{-fsched-stalled-insns} is used and its value is not zero. - -@item -fsched2-use-superblocks -@opindex fsched2-use-superblocks -When scheduling after register allocation, do use superblock scheduling -algorithm. Superblock scheduling allows motion across basic block boundaries -resulting on faster schedules. This option is experimental, as not all machine -descriptions used by GCC model the CPU closely enough to avoid unreliable -results from the algorithm. - -This only makes sense when scheduling after register allocation, i.e.@: with -@option{-fschedule-insns2} or at @option{-O2} or higher. - -@item -fsched2-use-traces -@opindex fsched2-use-traces -Use @option{-fsched2-use-superblocks} algorithm when scheduling after register -allocation and additionally perform code duplication in order to increase the -size of superblocks using tracer pass. See @option{-ftracer} for details on -trace formation. - -This mode should produce faster but significantly longer programs. Also -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 -fsee -@opindex fsee -Eliminates redundant extension instructions and move the non redundant -ones to optimal placement using LCM. - -@item -freschedule-modulo-scheduled-loops -@opindex fscheduling-in-modulo-scheduled-loops -The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled -we may want to prevent the later scheduling passes from changing its schedule, we use this -option to control that. - -@item -fcaller-saves -@opindex fcaller-saves -Enable values to be allocated in registers that will be clobbered by -function calls, by emitting extra instructions to save and restore the -registers around such calls. Such allocation is done only when it -seems to result in better code than would otherwise be produced. - -This option is always enabled by default on certain machines, usually -those which have no call-preserved registers to use instead. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -ftree-pre -Perform Partial Redundancy Elimination (PRE) on trees. This flag is -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 @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 -fipa-pta -Perform interprocedural pointer analysis. - -@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 -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 @option{-O} and higher. - -@item -ftree-dominator-opts -Perform a variety of simple scalar cleanups (constant/copy -propagation, redundancy elimination, range propagation and expression -simplification) based on a dominator tree traversal. This also -performs jump threading (to reduce jumps to jumps). This flag is -enabled by default at @option{-O} and higher. - -@item -ftree-ch -Perform loop header copying on trees. This is beneficial since it increases -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 -@c APPLE LOCAL 4231761 -Oz -for @option{-Os} or @option{-Oz} (APPLE ONLY), since it usually increases code size. - -@item -ftree-loop-optimize -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 -performance and allow further loop optimizations to take place. -@c APPLE LOCAL begin buggy opt 4420531 3950497 3984937 4013797 -This flag is known to have bugs that cause incorrect code to be generated in -some rare cases. Note this flag is included in -fast. -@c APPLE LOCAL end buggy opt 4420531 3950497 3984937 4013797 - -@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 -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 -in connection with unrolling. - -@item -fivopts -Perform induction variable optimizations (strength reduction, induction -variable merging and induction variable elimination) on trees. - -@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 @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 @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 @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 @option{-O} and higher. - -@item -ftree-vectorize -Perform loop vectorization on trees. - -@c APPLE LOCAL begin optimization -In Apple's version of GCC, @option{-fstrict-aliasing} is enabled by default -when loop vectorization is enabled. See @option{-fstrict-aliasing} document -for more information. -@c APPLE LOCAL end optimization - -@item -ftree-vect-loop-version -@opindex ftree-vect-loop-version -Perform loop versioning when doing loop vectorization on trees. When a loop -appears to be vectorizable except that data alignment or data dependence cannot -be determined at compile time then vectorized and non-vectorized versions of -the loop are generated along with runtime checks for alignment or dependence -to control which version is executed. This option is enabled by default -except at level @option{-Os} where it is disabled. - -@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 -simplifies the control flow of the function allowing other optimizations to do -better job. - -@item -funroll-loops -@opindex funroll-loops -Unroll loops whose number of iterations can be determined at compile -time or upon entry to the loop. @option{-funroll-loops} implies -@option{-frerun-cse-after-loop}. This option makes code larger, -and may or may not make it run faster. - -@item -funroll-all-loops -@opindex funroll-all-loops -Unroll all loops, even if their number of iterations is uncertain when -the loop is entered. This usually makes programs run more slowly. -@option{-funroll-all-loops} implies the same options as -@option{-funroll-loops}, - -@item -fsplit-ivs-in-unroller -@opindex fsplit-ivs-in-unroller -Enables expressing of values of induction variables in later iterations -of the unrolled loop using the value in the first iteration. This breaks -long dependency chains, thus improving efficiency of the scheduling passes. - -Combination of @option{-fweb} and CSE is often sufficient to obtain the -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 -memory to improve the performance of loops that access large arrays. - -This option may generate better or worse code; results are highly -dependent on the structure of loops within the source code. - -@c APPLE LOCAL 4231761 -Oz -Disabled at levels @option{-Os} and @option{-Oz} (APPLE ONLY). - -@item -fno-peephole -@itemx -fno-peephole2 -@opindex fno-peephole -@opindex fno-peephole2 -Disable any machine-specific peephole optimizations. The difference -between @option{-fno-peephole} and @option{-fno-peephole2} is in how they -are implemented in the compiler; some targets use one, some use the -other, a few use both. - -@option{-fpeephole} is enabled by default. -@c APPLE LOCAL 4231761 -Oz -@option{-fpeephole2} enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fno-guess-branch-probability -@opindex fno-guess-branch-probability -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 -@c APPLE LOCAL 4231761 -Oz -@option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -freorder-blocks -@opindex freorder-blocks -Reorder basic blocks in the compiled function in order to reduce number of -taken branches and improve code locality. - -Enabled at levels @option{-O2}, @option{-O3}. - -@item -freorder-blocks-and-partition -@opindex freorder-blocks-and-partition -In addition to reordering basic blocks in the compiled function, in order -to reduce number of taken branches, partitions hot and cold basic blocks -into separate sections of the assembly and .o files, to improve -paging and cache locality performance. - -This optimization is automatically turned off in the presence of -exception handling, for linkonce sections, for functions with a user-defined -section attribute and on any architecture that does not support named -sections. - -@item -freorder-functions -@opindex freorder-functions -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 -place them in a reasonable way. - -Also profile feedback must be available in to make this option effective. See -@option{-fprofile-arcs} for details. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fstrict-aliasing -@opindex fstrict-aliasing -Allows the compiler to assume the strictest aliasing rules applicable to -the language being compiled. For C (and C++), this activates -optimizations based on the type of expressions. In particular, an -object of one type is assumed never to reside at the same address as an -object of a different type, unless the types are almost the same. For -example, an @code{unsigned int} can alias an @code{int}, but not a -@code{void*} or a @code{double}. A character type may alias any other -type. - -Pay special attention to code like this: -@smallexample -union a_union @{ - int i; - double d; -@}; - -int f() @{ - a_union t; - t.d = 3.0; - return t.i; -@} -@end smallexample -The practice of reading from a different union member than the one most -recently written to (called ``type-punning'') is common. Even with -@option{-fstrict-aliasing}, type-punning is allowed, provided the memory -is accessed through the union type. So, the code above will work as -expected. However, this code might not: -@smallexample -int f() @{ - a_union t; - int* ip; - t.d = 3.0; - ip = &t.i; - return *ip; -@} -@end smallexample - -Every language that wishes to perform language-specific alias analysis -should define a function that computes, given an @code{tree} -node, an alias set for the node. Nodes in different alias sets are not -allowed to alias. For an example, see the C front-end function -@code{c_get_alias_set}. - -@c APPLE LOCAL 4231761 -Oz -Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, @option{-Oz} (APPLE ONLY). - -@item -fstrict-overflow -@opindex fstrict-overflow -Allow the compiler to assume strict signed overflow rules, depending -on the language being compiled. For C (and C++) this means that -overflow when doing arithmetic with signed numbers is undefined, which -means that the compiler may assume that it will not happen. This -permits various optimizations. For example, the compiler will assume -that an expression like @code{i + 10 > i} will always be true for -signed @code{i}. This assumption is only valid if signed overflow is -undefined, as the expression is false if @code{i + 10} overflows when -using twos complement arithmetic. When this option is in effect any -attempt to determine whether an operation on signed numbers will -overflow must be written carefully to not actually involve overflow. - -See also the @option{-fwrapv} option. Using @option{-fwrapv} means -that signed overflow is fully defined: it wraps. When -@option{-fwrapv} is used, there is no difference between -@option{-fstrict-overflow} and @option{-fno-strict-overflow}. With -@option{-fwrapv} certain types of overflow are permitted. For -example, if the compiler gets an overflow when doing arithmetic on -constants, the overflowed value can still be used with -@option{-fwrapv}, but not otherwise. - -The @option{-fstrict-overflow} option is enabled at levels -@option{-O2}, @option{-O3}, @option{-Os}. - -@item -falign-functions -@itemx -falign-functions=@var{n} -@opindex falign-functions -Align the start of functions to the next power-of-two greater than -@var{n}, skipping up to @var{n} bytes. For instance, -@option{-falign-functions=32} aligns functions to the next 32-byte -boundary, but @option{-falign-functions=24} would align to the next -32-byte boundary only if this can be done by skipping 23 bytes or less. - -@option{-fno-align-functions} and @option{-falign-functions=1} are -equivalent and mean that functions will not be aligned. - -Some assemblers only support this flag when @var{n} is a power of two; -in that case, it is rounded up. - -If @var{n} is not specified or is zero, use a machine-dependent default. - -Enabled at levels @option{-O2}, @option{-O3}. - -@item -falign-labels -@itemx -falign-labels=@var{n} -@opindex falign-labels -Align all branch targets to a power-of-two boundary, skipping up to -@var{n} bytes like @option{-falign-functions}. This option can easily -make code slower, because it must insert dummy operations for when the -branch target is reached in the usual flow of the code. - -@option{-fno-align-labels} and @option{-falign-labels=1} are -equivalent and mean that labels will not be aligned. - -If @option{-falign-loops} or @option{-falign-jumps} are applicable and -are greater than this value, then their values are used instead. - -If @var{n} is not specified or is zero, use a machine-dependent default -which is very likely to be @samp{1}, meaning no alignment. - -Enabled at levels @option{-O2}, @option{-O3}. - -@c APPLE LOCAL begin -falign-loops-max-skip -@item -falign-loops-max-skip -@item -falign-loops-max-skip=@var{n} -@opindex falign-loops-max-skip -Align loops to a power-of-two boundary, but do not skip more than -@var{n} bytes to do so. -@c APPLE LOCAL end -falign-loops-max-skip - -@item -falign-loops -@itemx -falign-loops=@var{n} -@opindex falign-loops -Align loops to a power-of-two boundary, skipping up to @var{n} bytes -like @option{-falign-functions}. The hope is that the loop will be -executed many times, which will make up for any execution of the dummy -operations. - -@option{-fno-align-loops} and @option{-falign-loops=1} are -equivalent and mean that loops will not be aligned. - -If @var{n} is not specified or is zero, use a machine-dependent default. - -Enabled at levels @option{-O2}, @option{-O3}. - -@item -falign-jumps -@itemx -falign-jumps=@var{n} -@opindex falign-jumps -Align branch targets to a power-of-two boundary, for branch targets -where the targets can only be reached by jumping, skipping up to @var{n} -bytes like @option{-falign-functions}. In this case, no dummy operations -need be executed. - -@c APPLE LOCAL begin -falign-jumps-max-skip -@item -falign-jumps-max-skip -@itemx -falign-jumps-max-skip=@var{n} -@opindex falign-jump-max-skips -Align branch targets to a power-of-two boundary, but do not skip more than -@var{n} bytes to do so. -@c APPLE LOCAL end -falign-jumps-max-skip - -@option{-fno-align-jumps} and @option{-falign-jumps=1} are -equivalent and mean that loops will not be aligned. - -If @var{n} is not specified or is zero, use a machine-dependent default. - -Enabled at levels @option{-O2}, @option{-O3}. - -@item -funit-at-a-time -@opindex funit-at-a-time -Parse the whole compilation unit before starting to produce code. -This allows some extra optimizations to take place but consumes -more memory (in general). There are some compatibility issues -with @emph{unit-at-a-time} mode: -@itemize @bullet -@item -enabling @emph{unit-at-a-time} mode may change the order -in which functions, variables, and top-level @code{asm} statements -are emitted, and will likely break code relying on some particular -ordering. The majority of such top-level @code{asm} statements, -though, can be replaced by @code{section} attributes. The -@option{fno-toplevel-reorder} option may be used to keep the ordering -used in the input file, at the cost of some optimizations. - -@item -@emph{unit-at-a-time} mode removes unreferenced static variables -and functions. This may result in undefined references -when an @code{asm} statement refers directly to variables or functions -that are otherwise unused. In that case either the variable/function -shall be listed as an operand of the @code{asm} statement operand or, -in the case of top-level @code{asm} statements the attribute @code{used} -shall be used on the declaration. - -@item -Static functions now can use non-standard passing conventions that -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@. - -Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. - -@item -fno-toplevel-reorder -Do not reorder top-level functions, variables, and @code{asm} -statements. Output them in the same order that they appear in the -input file. When this option is used, unreferenced static variables -will not be removed. This option is intended to support existing code -which relies on a particular ordering. For new code, it is better to -use attributes. - -@item -fweb -@opindex fweb -Constructs webs as commonly used for register allocation purposes and assign -each web individual pseudo register. This allows the register allocation pass -to operate on pseudos directly, but also strengthens several other optimization -passes, such as CSE, loop optimizer and trivial dead code remover. It can, -however, make debugging impossible, since variables will no longer stay in a -``home register''. - -Enabled by default with @option{-funroll-loops}. - -@item -fwhole-program -@opindex fwhole-program -Assume that the current compilation unit represents whole program being -compiled. All public functions and variables with the exception of @code{main} -and those merged by attribute @code{externally_visible} become static functions -and in a affect gets more aggressively optimized by interprocedural optimizers. -While this option is equivalent to proper use of @code{static} keyword for -programs consisting of single file, in combination with option -@option{--combine} this flag can be used to compile most of smaller scale C -programs since the functions and variables become local for the whole combined -compilation unit, not for the single source file itself. - - -@item -fno-cprop-registers -@opindex fno-cprop-registers -After register allocation and post-register allocation instruction splitting, -we perform a copy-propagation pass to try to reduce scheduling dependencies -and occasionally eliminate the copy. - -@c APPLE LOCAL begin 4231761 -Oz -Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}, -@option{-Oz} (APPLE ONLY). -@c APPLE LOCAL end 4231761 -Oz - -@item -fprofile-generate -@opindex fprofile-generate - -Enable options usually used for instrumenting application to produce -profile useful for later recompilation with profile feedback based -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}. - -@item -fprofile-use -@opindex fprofile-use -Enable profile feedback directed optimizations, and optimizations -generally profitable only with profile feedback available. - -The following options are enabled: @code{-fbranch-probabilities}, @code{-fvpt}, -@code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer} - -@end table - -The following options control compiler behavior regarding floating -point arithmetic. These options trade off between speed and -correctness. All must be specifically enabled. - -@table @gcctabopt -@item -ffloat-store -@opindex ffloat-store -Do not store floating point variables in registers, and inhibit other -options that might change whether a floating point value is taken from a -register or memory. - -@cindex floating point precision -This option prevents undesirable excess precision on machines such as -the 68000 where the floating registers (of the 68881) keep more -precision than a @code{double} is supposed to have. Similarly for the -x86 architecture. For most programs, the excess precision does only -good, but a few programs rely on the precise definition of IEEE floating -point. Use @option{-ffloat-store} for such programs, after modifying -them to store all pertinent intermediate computations into variables. - -@item -ffast-math -@opindex ffast-math -Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, @* -@option{-fno-trapping-math}, @option{-ffinite-math-only}, -@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. - -This option should never be turned on by any @option{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -@item -fno-math-errno -@opindex fno-math-errno -Do not set ERRNO after calling math functions that are executed -with a single instruction, e.g., sqrt. A program that relies on -IEEE exceptions for math error handling may want to use this flag -for speed while maintaining IEEE arithmetic compatibility. - -@c APPLE LOCAL begin disable math-errno -@ignore -This option should never be turned on by any @option{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @option{-fmath-errno}. -@end ignore -(APPLE ONLY) The Darwin math libraries never set errno, so there is -no point in having the compiler generate code that assumes they -might. Therefore, the default is @option{-fno-math-errno} on Darwin. -@c APPLE LOCAL end disable math-errno - -On Darwin systems, the math library never sets @code{errno}. There is therefore -no reason for the compiler to consider the possibility that it might, -and @option{-fno-math-errno} is the default. - -@item -funsafe-math-optimizations -@opindex funsafe-math-optimizations -Allow optimizations for floating-point arithmetic that (a) assume -that arguments and results are valid and (b) may violate IEEE or -ANSI standards. When used at link-time, it may include libraries -or startup files that change the default FPU control word or other -similar optimizations. - -This option should never be turned on by any @option{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @option{-fno-unsafe-math-optimizations}. - -@item -ffinite-math-only -@opindex ffinite-math-only -Allow optimizations for floating-point arithmetic that assume -that arguments and results are not NaNs or +-Infs. - -This option should never be turned on by any @option{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications. - -The default is @option{-fno-finite-math-only}. - -@item -fno-trapping-math -@opindex fno-trapping-math -Compile code assuming that floating-point operations cannot generate -user-visible traps. These traps include division by zero, overflow, -underflow, inexact result and invalid operation. This option implies -@option{-fno-signaling-nans}. Setting this option may allow faster -code if one relies on ``non-stop'' IEEE arithmetic, for example. - -This option should never be turned on by any @option{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @option{-ftrapping-math}. - -@item -frounding-math -@opindex frounding-math -Disable transformations and optimizations that assume default floating -point rounding behavior. This is round-to-zero for all floating point -to integer conversions, and round-to-nearest for all other arithmetic -truncations. This option should be specified for programs that change -the FP rounding mode dynamically, or that may be executed with a -non-default rounding mode. This option disables constant folding of -floating point expressions at compile-time (which may be affected by -rounding mode) and arithmetic transformations that are unsafe in the -presence of sign-dependent rounding modes. - -The default is @option{-fno-rounding-math}. - -This option is experimental and does not currently guarantee to -disable all GCC optimizations that are affected by rounding mode. -Future versions of GCC may provide finer control of this setting -using C99's @code{FENV_ACCESS} pragma. This command line option -will be used to specify the default state for @code{FENV_ACCESS}. - -@item -frtl-abstract-sequences -@opindex frtl-abstract-sequences -It is a size optimization method. This option is to find identical -sequences of code, which can be turned into pseudo-procedures and -then replace all occurrences with calls to the newly created -subroutine. It is kind of an opposite of @option{-finline-functions}. -This optimization runs at RTL level. - -@item -fsignaling-nans -@opindex fsignaling-nans -Compile code assuming that IEEE signaling NaNs may generate user-visible -traps during floating-point operations. Setting this option disables -optimizations that may change the number of exceptions visible with -signaling NaNs. This option implies @option{-ftrapping-math}. - -This option causes the preprocessor macro @code{__SUPPORT_SNAN__} to -be defined. - -The default is @option{-fno-signaling-nans}. - -This option is experimental and does not currently guarantee to -disable all GCC optimizations that affect signaling NaN behavior. - -@item -fsingle-precision-constant -@opindex fsingle-precision-constant -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 - -The following options control optimizations that may improve -performance, but are not enabled by any @option{-O} options. This -section includes experimental options that may produce broken code. - -@table @gcctabopt -@item -fbranch-probabilities -@opindex fbranch-probabilities -After running a program compiled with @option{-fprofile-arcs} -(@pxref{Debugging Options,, Options for Debugging Your Program or -@command{gcc}}), you can compile it a second time using -@option{-fbranch-probabilities}, to improve optimizations based on -the number of times each branch was taken. When the program -compiled with @option{-fprofile-arcs} exits it saves arc execution -counts to a file called @file{@var{sourcename}.gcda} for each source -file The information in this data file is very dependent on the -structure of the generated code, so you must use the same source code -and the same optimization options for both compilations. - -With @option{-fbranch-probabilities}, GCC puts a -@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}. -These can be used to improve optimization. Currently, they are only -used in one place: in @file{reorg.c}, instead of guessing which path a -branch is mostly to take, the @samp{REG_BR_PROB} values are used to -exactly determine which path is taken more often. - -@item -fprofile-values -@opindex fprofile-values -If combined with @option{-fprofile-arcs}, it adds code so that some -data about values of expressions in the program is gathered. - -With @option{-fbranch-probabilities}, it reads back the data gathered -from profiling values of expressions and adds @samp{REG_VALUE_PROFILE} -notes to instructions for their later usage in optimizations. - -Enabled with @option{-fprofile-generate} and @option{-fprofile-use}. - -@item -fvpt -@opindex fvpt -If combined with @option{-fprofile-arcs}, it instructs the compiler to add -a code to gather information about values of expressions. - -With @option{-fbranch-probabilities}, it reads back the data gathered -and actually performs the optimizations based on them. -Currently the optimizations include specialization of division operation -using the knowledge about the value of the denominator. - -@item -frename-registers -@opindex frename-registers -Attempt to avoid false dependencies in scheduled code by making use -of registers left over after register allocation. This optimization -will most benefit processors with lots of registers. Depending on the -debug information format adopted by the target, however, it can -make debugging impossible, since variables will no longer stay in -a ``home register''. - -Enabled by default with @option{-funroll-loops}. - -@item -ftracer -@opindex ftracer -Perform tail duplication to enlarge superblock size. This transformation -simplifies the control flow of the function allowing other optimizations to do -better job. - -Enabled with @option{-fprofile-use}. - -@item -funroll-loops -@opindex funroll-loops -Unroll loops whose number of iterations can be determined at compile time or -upon entry to the loop. @option{-funroll-loops} implies -@option{-frerun-cse-after-loop}, @option{-fweb} and @option{-frename-registers}. -It also turns on complete loop peeling (i.e.@: complete removal of loops with -small constant number of iterations). This option makes code larger, and may -or may not make it run faster. - -Enabled with @option{-fprofile-use}. - -@item -funroll-all-loops -@opindex funroll-all-loops -Unroll all loops, even if their number of iterations is uncertain when -the loop is entered. This usually makes programs run more slowly. -@option{-funroll-all-loops} implies the same options as -@option{-funroll-loops}. - -@item -fpeel-loops -@opindex fpeel-loops -Peels the loops for that there is enough information that they do not -roll much (from profile feedback). It also turns on complete loop peeling -(i.e.@: complete removal of loops with small constant number of iterations). - -Enabled with @option{-fprofile-use}. - -@item -fmove-loop-invariants -@opindex fmove-loop-invariants -Enables the loop invariant motion pass in the RTL loop optimizer. Enabled -at level @option{-O1} - -@item -funswitch-loops -@opindex funswitch-loops -Move branches with loop invariant conditions out of the loop, with duplicates -of the loop on both branches (modified according to result of the condition). - -@item -ffunction-sections -@itemx -fdata-sections -@opindex ffunction-sections -@opindex fdata-sections -Place each function or data item into its own section in the output -file if the target supports arbitrary sections. The name of the -function or the name of the data item determines the section's name -in the output file. - -Use these options on systems where the linker can perform optimizations -to improve locality of reference in the instruction space. Most systems -using the ELF object format and SPARC processors running Solaris 2 have -linkers with such optimizations. AIX may have these optimizations in -the future. - -Only use these options when there are significant benefits from doing -so. When you specify these options, the assembler and linker will -create larger object and executable files and will also be slower. -You will not be able to use @code{gprof} on all systems if you -specify this option and you may have problems with debugging if -you specify both this option and @option{-g}. - -@item -fbranch-target-load-optimize -@opindex fbranch-target-load-optimize -Perform branch target register load optimization before prologue / epilogue -threading. -The use of target registers can typically be exposed only during reload, -thus hoisting loads out of loops and doing inter-block scheduling needs -a separate optimization pass. - -@item -fbranch-target-load-optimize2 -@opindex fbranch-target-load-optimize2 -Perform branch target register load optimization after prologue / epilogue -threading. - -@item -fbtr-bb-exclusive -@opindex fbtr-bb-exclusive -When performing branch target register load optimization, don't reuse -branch target registers in within any basic block. - -@item -fstack-protector -Emit extra code to check for buffer overflows, such as stack smashing -attacks. This is done by adding a guard variable to functions with -vulnerable objects. This includes functions that call alloca, and -functions with buffers larger than 8 bytes. The guards are initialized -when a function is entered and then checked when the function exits. -If a guard check fails, an error message is printed and the program exits. - -@item -fstack-protector-all -Like @option{-fstack-protector} except that all functions are protected. - -@item -fsection-anchors -@opindex fsection-anchors -Try to reduce the number of symbolic address calculations by using -shared ``anchor'' symbols to address nearby objects. This transformation -can help to reduce the number of GOT entries and GOT accesses on some -targets. - -For example, the implementation of the following function @code{foo}: - -@smallexample -static int a, b, c; -int foo (void) @{ return a + b + c; @} -@end smallexample - -would usually calculate the addresses of all three variables, but if you -compile it with @option{-fsection-anchors}, it will access the variables -from a common anchor point instead. The effect is similar to the -following pseudocode (which isn't valid C): - -@smallexample -int foo (void) -@{ - register int *xr = &x; - return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; -@} -@end smallexample - -Not all targets support this option. - -@item --param @var{name}=@var{value} -@opindex param -In some places, GCC uses various constants to control the amount of -optimization that is done. For example, GCC will not inline functions -that contain more that a certain number of instructions. You can -control some of these constants on the command-line using the -@option{--param} option. - -The names of specific parameters, and the meaning of the values, are -tied to the internals of the compiler, and are subject to change -without notice in future releases. - -In each case, the @var{value} is an integer. The allowable choices for -@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 salias-max-array-elements -The maximum number of elements an array can have and its elements -still be tracked individually by structure aliasing. The default is 4 - -@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 -the number of edges incoming to each block. Increasing values mean -more aggressive optimization, making the compile time increase with -probably small improvement in executable size. - -@item min-crossjump-insns -The minimum number of instructions which must be matched at the end -of two blocks before crossjumping will be performed on them. This -value is ignored in the case where all instructions in the block being -crossjumped from are matched. The default value is 5. - -@item max-grow-copy-bb-insns -The maximum code size expansion factor when copying basic blocks -instead of jumping. The expansion is relative to a jump instruction. -The default value is 8. - -@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 -instructions is searched, the time savings from filling the delay slot -will be minimal so stop searching. Increasing values mean more -aggressive optimization, making the compile time increase with probably -small improvement in executable run time. - -@item max-delay-slot-live-search -When trying to fill delay slots, the maximum number of instructions to -consider when searching for a block with valid live register -information. Increasing this arbitrarily chosen value means more -aggressive optimization, increasing the compile time. This parameter -should be removed when the delay slot code is rewritten to maintain the -control-flow graph. - -@item max-gcse-memory -The approximate maximum amount of memory that will be allocated in -order to perform the global common subexpression elimination -optimization. If more memory than specified is required, the -optimization will not be done. - -@item max-gcse-passes -The maximum number of passes of GCSE to run. The default is 1. - -@item max-pending-list-length -The maximum number of pending dependencies scheduling will allow -before flushing the current state and starting over. Large functions -with few branches or calls can create excessively large lists which -needlessly consume memory and resources. - -@item max-inline-insns-single -Several parameters control the tree inliner used in gcc. -This number sets the maximum number of instructions (counted in GCC's -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 450. - -@item max-inline-insns-auto -When you use @option{-finline-functions} (included in @option{-O3}), -a lot of functions that would otherwise not be considered for inlining -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 90. - -@item large-function-insns -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 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 100 which limits large function growth to 2.0 times -the original size. - -@item large-unit-insns -The limit specifying large translation unit. Growth caused by inlining of -units larger than this limit is limited by @option{--param inline-unit-growth}. -For small units this might be too tight (consider unit consisting of function A -that is inline and B that just calls A three time. If B is small relative to -A, the growth of unit is 300\% and yet such inlining is very sane. For very -large units consisting of small inlininable functions however the overall unit -growth limit is needed to avoid exponential explosion of code size. Thus for -smaller units, the size is increased to @option{--param large-unit-insns} -before applying @option{--param inline-unit-growth}. The default is 10000 - -@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 50 which limits unit growth to 1.5 times the original -size. - -@item max-inline-insns-recursive -@itemx max-inline-insns-recursive-auto -Specifies maximum number of instructions out-of-line copy of self recursive inline -function can grow into by performing recursive inlining. - -For functions declared inline @option{--param max-inline-insns-recursive} is -taken into account. 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 450. - -@item max-inline-recursive-depth -@itemx max-inline-recursive-depth-auto -Specifies maximum recursion depth used by the recursive inlining. - -For functions declared inline @option{--param max-inline-recursive-depth} is -taken into account. 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 450. - -@item min-inline-recursive-probability -Recursive inlining is profitable only for function having deep recursion -in average and can hurt for function having little recursion depth by -increasing the prologue size or complexity of function body to other -optimizers. - -When profile feedback is available (see @option{-fprofile-generate}) the actual -recursion depth can be guessed from probability that function will recurse via -given call expression. This parameter limits inlining only to call expression -whose probability exceeds given threshold (in percents). The default value is -10. - -@item inline-call-cost -Specify cost of call instruction relative to simple arithmetics operations -(having cost of 1). Increasing this cost disqualifies inlining of non-leaf -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 -is unrolled, and if the loop is unrolled, it determines how many times -the loop code is unrolled. - -@item max-average-unrolled-insns -The maximum number of instructions biased by probabilities of their execution -that a loop should have if that loop is unrolled, and if the loop is unrolled, -it determines how many times the loop code is unrolled. - -@item max-unroll-times -The maximum number of unrollings of a single loop. - -@item max-peeled-insns -The maximum number of instructions that a loop should have if that loop -is peeled, and if the loop is peeled, it determines how many times -the loop code is peeled. - -@item max-peel-times -The maximum number of peelings of a single loop. - -@item max-completely-peeled-insns -The maximum number of insns of a completely peeled loop. - -@item max-completely-peel-times -The maximum number of iterations of a loop to be suitable for complete peeling. - -@item max-unswitch-insns -The maximum number of insns of an unswitched loop. - -@item max-unswitch-level -The maximum number of branches unswitched in a single loop. - -@item lim-expensive -The minimum cost of an expensive expression in the loop invariant motion. - -@item iv-consider-all-candidates-bound -Bound on number of candidates for induction variables below that -all candidates are considered for each use in induction variable -optimizations. Only the most relevant candidates are considered -if there are more candidates, to avoid quadratic time complexity. - -@item iv-max-considered-uses -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 vect-max-version-checks -The maximum number of runtime checks that can be performed when doing -loop versioning in the vectorizer. See option ftree-vect-loop-version -for more information. - -@item max-iterations-to-track - -The maximum number of iterations of a loop the brute force algorithm -for analysis of # of iterations of the loop tries to evaluate. - -@item hot-bb-count-fraction -Select fraction of the maximal count of repetitions of basic block in program -given basic block needs to have to be considered hot. - -@item hot-bb-frequency-fraction -Select fraction of the maximal frequency of executions of basic block in -function given basic block needs to have to be considered hot - -@item max-predicted-iterations -The maximum number of loop iterations we predict statically. This is useful -in cases where function contain single loop with known bound and other loop -with unknown. We predict the known number of iterations correctly, while -the unknown number of iterations average to roughly 10. This means that the -loop without bounds would appear artificially cold relative to the other one. - -@item tracer-dynamic-coverage -@itemx tracer-dynamic-coverage-feedback - -This value is used to limit superblock formation once the given percentage of -executed instructions is covered. This limits unnecessary code size -expansion. - -The @option{tracer-dynamic-coverage-feedback} is used only when profile -feedback is available. The real profiles (as opposed to statically estimated -ones) are much less balanced allowing the threshold to be larger value. - -@item tracer-max-code-growth -Stop tail duplication once code growth has reached given percentage. This is -rather hokey argument, as most of the duplicates will be eliminated later in -cross jumping, so it may be set to much higher values than is the desired code -growth. - -@item tracer-min-branch-ratio - -Stop reverse growth when the reverse probability of best edge is less than this -threshold (in percent). - -@item tracer-min-branch-ratio -@itemx tracer-min-branch-ratio-feedback - -Stop forward growth if the best edge do have probability lower than this -threshold. - -Similarly to @option{tracer-dynamic-coverage} two values are present, one for -compilation for profile feedback and one for compilation without. The value -for compilation with profile feedback needs to be more conservative (higher) in -order to make tracer effective. - -@item max-cse-path-length - -Maximum number of basic blocks on path that cse considers. The default is 10. - -@item max-cse-insns -The maximum instructions CSE process before flushing. The default is 1000. - -@item global-var-threshold - -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 @code{int * size_t} on the host machine; beware overflow). - -@item max-aliased-vops - -Maximum number of virtual operands allowed to represent aliases -before triggering the alias grouping heuristic. Alias grouping -reduces compile times and memory consumption needed for aliasing at -the expense of precision loss in alias information. - -@item ggc-min-expand - -GCC uses a garbage collector to manage its own memory allocation. This -parameter specifies the minimum percentage by which the garbage -collector's heap should be allowed to expand between collections. -Tuning this may improve compilation speed; it has no effect on code -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 @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 -every opportunity. This is extremely slow, but can be useful for -debugging. - -@item ggc-min-heapsize - -Minimum size of the garbage collector's heap before it begins bothering -to collect garbage. The first collection occurs after the heap expands -by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}. Again, -tuning this may improve compilation speed, and has no effect on code -generation. - -The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which -tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but -with a lower bound of 4096 (four megabytes) and an upper bound of -131072 (128 megabytes). If GCC is not able to calculate RAM on a -particular platform, the lower bound is used. Setting this parameter -very large effectively disables garbage collection. Setting this -parameter and @option{ggc-min-expand} to zero causes a full collection -to occur at every opportunity. - -@item max-reload-search-insns -The maximum number of instruction reload should look backward for equivalent -register. Increasing values mean more aggressive optimization, making the -compile time increase with probably slightly better performance. The default -value is 100. - -@item max-cselib-memory-locations -The maximum number of memory locations cselib should take into account. -Increasing values mean more aggressive optimization, making the compile time -increase with probably slightly better performance. The default value is 500. - -@item max-flow-memory-locations -Similar as @option{max-cselib-memory-locations} but for dataflow liveness. -The default value is 100. - -@item reorder-blocks-duplicate -@itemx reorder-blocks-duplicate-feedback - -Used by basic block reordering pass to decide whether to use unconditional -branch or duplicate the code on its destination. Code is duplicated when its -estimated size is smaller than this value multiplied by the estimated size of -unconditional jump in the hot spots of the program. - -The @option{reorder-block-duplicate-feedback} is used only when profile -feedback is available and may be set to higher values than -@option{reorder-block-duplicate} since information about the hot spots is more -accurate. - -@item max-sched-ready-insns -The maximum number of instructions ready to be issued the scheduler should -consider at any given time during the first scheduling pass. Increasing -values mean more thorough searches, making the compilation time increase -with probably little benefit. The default value is 100. - -@item max-sched-region-blocks -The maximum number of blocks in a region to be considered for -interblock scheduling. The default value is 10. - -@item max-sched-region-insns -The maximum number of insns in a region to be considered for -interblock scheduling. The default value is 100. - -@item min-spec-prob -The minimum probability (in percents) of reaching a source block -for interblock speculative scheduling. The default value is 40. - -@item max-sched-extend-regions-iters -The maximum number of iterations through CFG to extend regions. -0 - disable region extension, -N - do at most N iterations. -The default value is 0. - -@item max-sched-insn-conflict-delay -The maximum conflict delay for an insn to be considered for speculative motion. -The default value is 3. - -@item sched-spec-prob-cutoff -The minimal probability of speculation success (in percents), so that -speculative insn will be scheduled. -The default value is 40. - -@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. - -@item ssp-buffer-size -The minimum size of buffers (i.e. arrays) that will receive stack smashing -protection when @option{-fstack-protection} is used. - -@item max-jump-thread-duplication-stmts -Maximum number of statements allowed in a block that needs to be -duplicated when threading jumps. - -@item max-fields-for-field-sensitive -Maximum number of fields in a structure we will treat in -a field sensitive manner during pointer analysis. - -@end table -@end table - -@node Preprocessor Options -@section Options Controlling the Preprocessor -@cindex preprocessor options -@cindex options, preprocessor - -These options control the C preprocessor, which is run on each C source -file before actual compilation. - -If you use the @option{-E} option, nothing is done except preprocessing. -Some of these options make sense only together with @option{-E} because -they cause the preprocessor output to be unsuitable for actual -compilation. - -@table @gcctabopt -@c APPLE LOCAL pod error 6089368 -@item -Wp,@var{option} -@opindex Wp -You can use @option{-Wp,@var{option}} to bypass the compiler driver -and pass @var{option} directly through to the preprocessor. If -@var{option} contains commas, it is split into multiple options at the -commas. However, many options are modified, translated or interpreted -by the compiler driver before being passed to the preprocessor, and -@option{-Wp} forcibly bypasses this phase. The preprocessor's direct -interface is undocumented and subject to change, so whenever possible -you should avoid using @option{-Wp} and let the driver handle the -options instead. - -@item -Xpreprocessor @var{option} -@opindex preprocessor -Pass @var{option} as an option to the preprocessor. You can use this to -supply system-specific preprocessor options which GCC does not know how to -recognize. - -If you want to pass an option that takes an argument, you must use -@option{-Xpreprocessor} twice, once for the option and once for the argument. -@end table - -@include cppopts.texi - -@node Assembler Options -@section Passing Options to the Assembler - -@c prevent bad page break with this line -You can pass options to the assembler. - -@table @gcctabopt -@item -Wa,@var{option} -@opindex Wa -Pass @var{option} as an option to the assembler. If @var{option} -contains commas, it is split into multiple options at the commas. - -@item -Xassembler @var{option} -@opindex Xassembler -Pass @var{option} as an option to the assembler. You can use this to -supply system-specific assembler options which GCC does not know how to -recognize. - -If you want to pass an option that takes an argument, you must use -@option{-Xassembler} twice, once for the option and once for the argument. - -@end table - -@node Link Options -@section Options for Linking -@cindex link options -@cindex options, linking - -These options come into play when the compiler links object files into -an executable output file. They are meaningless if the compiler is -not doing a link step. - -@c APPLE LOCAL begin linker flags -In addition to the options listed below, Apple's GCC also accepts and -passes nearly all of the options defined by the linker @samp{ld} and by -the library tool @samp{libtool}. Common options include -@samp{-framework}, @samp{-dynamic}, @samp{-bundle}, -@samp{-flat_namespace}, and so forth. See the ld and libtool man pages -for further details. -@c APPLE LOCAL end linker flags - -@table @gcctabopt -@cindex file names -@item @var{object-file-name} -A file name that does not end in a special recognized suffix is -considered to name an object file or library. (Object files are -distinguished from libraries by the linker according to the file -contents.) If linking is done, these object files are used as input -to the linker. - -@item -c -@itemx -S -@itemx -E -@opindex c -@opindex S -@opindex E -If any of these options is used, then the linker is not run, and -object file names should not be used as arguments. @xref{Overall -Options}. - -@cindex Libraries -@item -l@var{library} -@itemx -l @var{library} -@opindex l -Search the library named @var{library} when linking. (The second -alternative with the library as a separate argument is only for -POSIX compliance and is not recommended.) - -It makes a difference where in the command you write this option; the -linker searches and processes libraries and object files in the order they -are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z} -after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers -to functions in @samp{z}, those functions may not be loaded. - -The linker searches a standard list of directories for the library, -which is actually a file named @file{lib@var{library}.a}. The linker -then uses this file as if it had been specified precisely by name. - -The directories searched include several standard system directories -plus any that you specify with @option{-L}. - -Normally the files found this way are library files---archive files -whose members are object files. The linker handles an archive file by -scanning through it for members which define symbols that have so far -been referenced but not defined. But if the file that is found is an -ordinary object file, it is linked in the usual fashion. The only -difference between using an @option{-l} option and specifying a file name -is that @option{-l} surrounds @var{library} with @samp{lib} and @samp{.a} -and searches several directories. - -@item -lobjc -@opindex lobjc -You need this special case of the @option{-l} option in order to -link an Objective-C or Objective-C++ program. - -@item -nostartfiles -@opindex nostartfiles -Do not use the standard system startup files when linking. -The standard system libraries are used normally, unless @option{-nostdlib} -or @option{-nodefaultlibs} is used. - -@item -nodefaultlibs -@opindex nodefaultlibs -Do not use the standard system libraries when linking. -Only the libraries you specify will be passed to the linker. -The standard startup files are used normally, unless @option{-nostartfiles} -is used. The compiler may generate calls to @code{memcmp}, -@code{memset}, @code{memcpy} and @code{memmove}. -These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. - -@item -nostdlib -@opindex nostdlib -Do not use the standard system startup files or libraries when linking. -No startup files and only the libraries you specify will be passed to -the linker. The compiler may generate calls to @code{memcmp}, @code{memset}, -@code{memcpy} and @code{memmove}. -These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. - -@cindex @option{-lgcc}, use with @option{-nostdlib} -@cindex @option{-nostdlib} and unresolved references -@cindex unresolved references and @option{-nostdlib} -@cindex @option{-lgcc}, use with @option{-nodefaultlibs} -@cindex @option{-nodefaultlibs} and unresolved references -@cindex unresolved references and @option{-nodefaultlibs} -One of the standard libraries bypassed by @option{-nostdlib} and -@option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines -that GCC uses to overcome shortcomings of particular machines, or special -needs for some languages. -(@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler -Collection (GCC) Internals}, -for more discussion of @file{libgcc.a}.) -In most cases, you need @file{libgcc.a} even when you want to avoid -other standard libraries. In other words, when you specify @option{-nostdlib} -or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well. -This ensures that you have no unresolved references to internal GCC -library subroutines. (For example, @samp{__main}, used to ensure C++ -constructors will be called; @pxref{Collect2,,@code{collect2}, gccint, -GNU Compiler Collection (GCC) Internals}.) - -@item -pie -@opindex pie -Produce a position independent executable on targets which support it. -For predictable results, you must also specify the same set of options -that were used to generate code (@option{-fpie}, @option{-fPIE}, -or model suboptions) when you specify this option. - -@item -rdynamic -@opindex rdynamic -Pass the flag @option{-export-dynamic} to the ELF linker, on targets -that support it. This instructs the linker to add all symbols, not -only used ones, to the dynamic symbol table. This option is needed -for some uses of @code{dlopen} or to allow obtaining backtraces -from within a program. - -@item -s -@opindex s -Remove all symbol table and relocation information from the executable. - -@item -static -@opindex static -On systems that support dynamic linking, this prevents linking with the shared -libraries. On other systems, this option has no effect. - -@c APPLE LOCAL begin manual -This option will not work on Mac OS X unless all libraries (including -@file{libgcc.a}) have also been compiled with @option{-static}. Since -neither a static version of libSystem.dylib nor crt0.o are provided, this -option is not useful to most people. -@c APPLE LOCAL end manual - -@item -shared -@opindex shared -Produce a shared object which can then be linked with other objects to -form an executable. Not all systems support this option. For predictable -results, you must also specify the same set of options that were used to -generate code (@option{-fpic}, @option{-fPIC}, or model suboptions) -when you specify this option.@footnote{On some systems, @samp{gcc -shared} -needs to build supplementary stub code for constructors to work. On -multi-libbed systems, @samp{gcc -shared} must select the correct support -libraries to link against. Failing to supply the correct flags may lead -to subtle defects. Supplying them in cases where they are not necessary -is innocuous.} - -@c APPLE LOCAL begin manual -This option is not supported on Mac OS X. -@c APPLE LOCAL end manual - -@item -shared-libgcc -@itemx -static-libgcc -@opindex shared-libgcc -@opindex static-libgcc -On systems that provide @file{libgcc} as a shared library, these options -force the use of either the shared or static version respectively. -If no shared version of @file{libgcc} was built when the compiler was -configured, these options have no effect. - -There are several situations in which an application should use the -shared @file{libgcc} instead of the static version. The most common -of these is when the application wishes to throw and catch exceptions -across different shared libraries. In that case, each of the libraries -as well as the application itself should use the shared @file{libgcc}. - -Therefore, the G++ and GCJ drivers automatically add -@option{-shared-libgcc} whenever you build a shared library or a main -executable, because C++ and Java programs typically use exceptions, so -this is the right thing to do. - -If, instead, you use the GCC driver to create shared libraries, you may -find that they will not always be linked with the shared @file{libgcc}. -If GCC finds, at its configuration time, that you have a non-GNU linker -or a GNU linker that does not support option @option{--eh-frame-hdr}, -it will link the shared version of @file{libgcc} into shared libraries -by default. Otherwise, it will take advantage of the linker and optimize -away the linking with the shared version of @file{libgcc}, linking with -the static version of libgcc by default. This allows exceptions to -propagate through such shared libraries, without incurring relocation -costs at library load time. - -However, if a library or main executable is supposed to throw or catch -exceptions, you must link it using the G++ or GCJ driver, as appropriate -for the languages used in the program, or using the option -@option{-shared-libgcc}, such that it is linked with the shared -@file{libgcc}. - -@item -symbolic -@opindex symbolic -Bind references to global symbols when building a shared object. Warn -about any unresolved references (unless overridden by the link editor -option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support -this option. - -@item -Xlinker @var{option} -@opindex Xlinker -Pass @var{option} as an option to the linker. You can use this to -supply system-specific linker options which GCC does not know how to -recognize. - -If you want to pass an option that takes an argument, you must use -@option{-Xlinker} twice, once for the option and once for the argument. -For example, to pass @option{-assert definitions}, you must write -@samp{-Xlinker -assert -Xlinker definitions}. It does not work to write -@option{-Xlinker "-assert definitions"}, because this passes the entire -string as a single argument, which is not what the linker expects. - -@item -Wl,@var{option} -@opindex Wl -Pass @var{option} as an option to the linker. If @var{option} contains -commas, it is split into multiple options at the commas. - -@item -u @var{symbol} -@opindex u -Pretend the symbol @var{symbol} is undefined, to force linking of -library modules to define it. You can use @option{-u} multiple times with -different symbols to force loading of additional library modules. -@end table - -@node Directory Options -@section Options for Directory Search -@cindex directory options -@cindex options, directory search -@cindex search path - -These options specify directories to search for header files, for -libraries and for parts of the compiler: - -@table @gcctabopt -@item -I@var{dir} -@opindex I -Add the directory @var{dir} to the head of the list of directories to be -searched for header files. This can be used to override a system header -file, substituting your own version, since these directories are -searched before the system header file directories. However, you should -not use this option to add directories that contain vendor-supplied -system header files (use @option{-isystem} for that). If you use more than -one @option{-I} option, the directories are scanned in left-to-right -order; the standard system directories come after. - -If a standard system include directory, or a directory specified with -@option{-isystem}, is also specified with @option{-I}, the @option{-I} -option will be ignored. The directory will still be searched but as a -system directory at its normal position in the system include chain. -This is to ensure that GCC's procedure to fix buggy system headers and -the ordering for the include_next directive are not inadvertently changed. -If you really need to change the search order for system directories, -use the @option{-nostdinc} and/or @option{-isystem} options. - -@c APPLE LOCAL begin ARM iwithsysroot 4917039 -The option @option{-iwithsysroot} (APPLE ONLY), if specified with an -absolute path, will prepend the system root directory (if applicable) to -the path and add it to the beginning of the system search paths. If -specified with a relative path, @option{-iwithsysroot} will behave -identically to @option{-isystem}. -@c APPLE LOCAL end ARM iwithsysroot 4917039 - -@item -iquote@var{dir} -@opindex iquote -Add the directory @var{dir} to the head of the list of directories to -be searched for header files only for the case of @samp{#include -"@var{file}"}; they are not searched for @samp{#include <@var{file}>}, -otherwise just like @option{-I}. - -@item -L@var{dir} -@opindex L -Add directory @var{dir} to the list of directories to be searched -for @option{-l}. - -@item -B@var{prefix} -@opindex B -This option specifies where to find the executables, libraries, -include files, and data files of the compiler itself. - -The compiler driver program runs one or more of the subprograms -@file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries -@var{prefix} as a prefix for each program it tries to run, both with and -without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}). - -For each subprogram to be run, the compiler driver first tries the -@option{-B} prefix, if any. If that name is not found, or if @option{-B} -was not specified, the driver tries two standard prefixes, which are -@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc/}. If neither of -those results in a file name that is found, the unmodified program -name is searched for using the directories specified in your -@env{PATH} environment variable. - -The compiler will check to see if the path provided by the @option{-B} -refers to a directory, and if necessary it will add a directory -separator character at the end of the path. - -@option{-B} prefixes that effectively specify directory names also apply -to libraries in the linker, because the compiler translates these -options into @option{-L} options for the linker. They also apply to -includes files in the preprocessor, because the compiler translates these -options into @option{-isystem} options for the preprocessor. In this case, -the compiler appends @samp{include} to the prefix. - -The run-time support file @file{libgcc.a} can also be searched for using -the @option{-B} prefix, if needed. If it is not found there, the two -standard prefixes above are tried, and that is all. The file is left -out of the link if it is not found by those means. - -Another way to specify a prefix much like the @option{-B} prefix is to use -the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment -Variables}. - -As a special kludge, if the path provided by @option{-B} is -@file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to -9, then it will be replaced by @file{[dir/]include}. This is to help -with boot-strapping the compiler. - -@item -specs=@var{file} -@opindex specs -Process @var{file} after the compiler reads in the standard @file{specs} -file, in order to override the defaults that the @file{gcc} driver -program uses when determining what switches to pass to @file{cc1}, -@file{cc1plus}, @file{as}, @file{ld}, etc. More than one -@option{-specs=@var{file}} can be specified on the command line, and they -are processed in order, from left to right. - -@item --sysroot=@var{dir} -@opindex sysroot -Use @var{dir} as the logical root directory for headers and libraries. -For example, if the compiler would normally search for headers in -@file{/usr/include} and libraries in @file{/usr/lib}, it will instead -search @file{@var{dir}/usr/include} and @file{@var{dir}/usr/lib}. - -With Apple's version of GCC, this option is effectively replaced by -@option{-isysroot}, which you should use instead of @option{--sysroot}. -For other (non-Apple) versions of GCC, -if you use both this option and the @option{-isysroot} option, then -the @option{--sysroot} option will apply to libraries, but the -@option{-isysroot} option will apply to header files. - -The GNU linker (beginning with version 2.16) has the necessary support -for this option. If your linker does not support this option, the -header file aspect of @option{--sysroot} will still work, but the -library aspect will not. - -@item -I- -@opindex I- -This option has been deprecated. Please use @option{-iquote} instead for -@option{-I} directories before the @option{-I-} and remove the @option{-I-}. -Any directories you specify with @option{-I} options before the @option{-I-} -option are searched only for the case of @samp{#include "@var{file}"}; -they are not searched for @samp{#include <@var{file}>}. - -If additional directories are specified with @option{-I} options after -the @option{-I-}, these directories are searched for all @samp{#include} -directives. (Ordinarily @emph{all} @option{-I} directories are used -this way.) - -In addition, the @option{-I-} option inhibits the use of the current -directory (where the current input file came from) as the first search -directory for @samp{#include "@var{file}"}. There is no way to -override this effect of @option{-I-}. With @option{-I.} you can specify -searching the directory which was current when the compiler was -invoked. That is not exactly the same as what the preprocessor does -by default, but it is often satisfactory. - -@option{-I-} does not inhibit the use of the standard system directories -for header files. Thus, @option{-I-} and @option{-nostdinc} are -independent. -@end table - -@c man end - -@node Spec Files -@section Specifying subprocesses and the switches to pass to them -@cindex Spec Files - -@command{gcc} is a driver program. It performs its job by invoking a -sequence of other programs to do the work of compiling, assembling and -linking. GCC interprets its command-line parameters and uses these to -deduce which programs it should invoke, and which command-line options -it ought to place on their command lines. This behavior is controlled -by @dfn{spec strings}. In most cases there is one spec string for each -program that GCC can invoke, but a few programs have multiple spec -strings to control their behavior. The spec strings built into GCC can -be overridden by using the @option{-specs=} command-line switch to specify -a spec file. - -@dfn{Spec files} are plaintext files that are used to construct spec -strings. They consist of a sequence of directives separated by blank -lines. The type of directive is determined by the first non-whitespace -character on the line and it can be one of the following: - -@table @code -@item %@var{command} -Issues a @var{command} to the spec file processor. The commands that can -appear here are: - -@table @code -@item %include <@var{file}> -@cindex %include -Search for @var{file} and insert its text at the current point in the -specs file. - -@item %include_noerr <@var{file}> -@cindex %include_noerr -Just like @samp{%include}, but do not generate an error message if the include -file cannot be found. - -@item %rename @var{old_name} @var{new_name} -@cindex %rename -Rename the spec string @var{old_name} to @var{new_name}. - -@end table - -@item *[@var{spec_name}]: -This tells the compiler to create, override or delete the named spec -string. All lines after this directive up to the next directive or -blank line are considered to be the text for the spec string. If this -results in an empty string then the spec will be deleted. (Or, if the -spec did not exist, then nothing will happened.) Otherwise, if the spec -does not currently exist a new spec will be created. If the spec does -exist then its contents will be overridden by the text of this -directive, unless the first character of that text is the @samp{+} -character, in which case the text will be appended to the spec. - -@item [@var{suffix}]: -Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive -and up to the next directive or blank line are considered to make up the -spec string for the indicated suffix. When the compiler encounters an -input file with the named suffix, it will processes the spec string in -order to work out how to compile that file. For example: - -@smallexample -.ZZ: -z-compile -input %i -@end smallexample - -This says that any input file whose name ends in @samp{.ZZ} should be -passed to the program @samp{z-compile}, which should be invoked with the -command-line switch @option{-input} and with the result of performing the -@samp{%i} substitution. (See below.) - -As an alternative to providing a spec string, the text that follows a -suffix directive can be one of the following: - -@table @code -@item @@@var{language} -This says that the suffix is an alias for a known @var{language}. This is -similar to using the @option{-x} command-line switch to GCC to specify a -language explicitly. For example: - -@smallexample -.ZZ: -@@c++ -@end smallexample - -Says that .ZZ files are, in fact, C++ source files. - -@item #@var{name} -This causes an error messages saying: - -@smallexample -@var{name} compiler not installed on this system. -@end smallexample -@end table - -GCC already has an extensive list of suffixes built into it. -This directive will add an entry to the end of the list of suffixes, but -since the list is searched from the end backwards, it is effectively -possible to override earlier entries using this technique. - -@end table - -GCC has the following spec strings built into it. Spec files can -override these strings or create their own. Note that individual -targets can also add their own spec strings to this list. - -@smallexample -asm Options to pass to the assembler -asm_final Options to pass to the assembler post-processor -cpp Options to pass to the C preprocessor -cc1 Options to pass to the C compiler -cc1plus Options to pass to the C++ compiler -endfile Object files to include at the end of the link -link Options to pass to the linker -lib Libraries to include on the command line to the linker -libgcc Decides which GCC support library to pass to the linker -linker Sets the name of the linker -predefines Defines to be passed to the C preprocessor -signed_char Defines to pass to CPP to say whether @code{char} is signed - by default -startfile Object files to include at the start of the link -@end smallexample - -Here is a small example of a spec file: - -@smallexample -%rename lib old_lib - -*lib: ---start-group -lgcc -lc -leval1 --end-group %(old_lib) -@end smallexample - -This example renames the spec called @samp{lib} to @samp{old_lib} and -then overrides the previous definition of @samp{lib} with a new one. -The new definition adds in some extra command-line options before -including the text of the old definition. - -@dfn{Spec strings} are a list of command-line options to be passed to their -corresponding program. In addition, the spec strings can contain -@samp{%}-prefixed sequences to substitute variable text or to -conditionally insert text into the command line. Using these constructs -it is possible to generate quite complex command lines. - -Here is a table of all defined @samp{%}-sequences for spec -strings. Note that spaces are not generated automatically around the -results of expanding these sequences. Therefore you can concatenate them -together or combine them with constant text in a single argument. - -@table @code -@item %% -Substitute one @samp{%} into the program name or argument. - -@item %i -Substitute the name of the input file being processed. - -@item %b -Substitute the basename of the input file being processed. -This is the substring up to (and not including) the last period -and not including the directory. - -@item %B -This is the same as @samp{%b}, but include the file suffix (text after -the last period). - -@item %d -Marks the argument containing or following the @samp{%d} as a -temporary file name, so that that file will be deleted if GCC exits -successfully. Unlike @samp{%g}, this contributes no text to the -argument. - -@item %g@var{suffix} -Substitute a file name that has suffix @var{suffix} and is chosen -once per compilation, and mark the argument in the same way as -@samp{%d}. To reduce exposure to denial-of-service attacks, the file -name is now chosen in a way that is hard to predict even when previously -chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s} -might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches -the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is -treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g} -was simply substituted with a file name chosen once per compilation, -without regard to any appended suffix (which was therefore treated -just like ordinary text), making such attacks more likely to succeed. - -@item %u@var{suffix} -Like @samp{%g}, but generates a new temporary file name even if -@samp{%u@var{suffix}} was already seen. - -@item %U@var{suffix} -Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a -new one if there is no such last file name. In the absence of any -@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share -the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s} -would involve the generation of two distinct file names, one -for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was -simply substituted with a file name chosen for the previous @samp{%u}, -without regard to any appended suffix. - -@item %j@var{suffix} -Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is -writable, and if save-temps is off; otherwise, substitute the name -of a temporary file, just like @samp{%u}. This temporary file is not -meant for communication between processes, but rather as a junk -disposal mechanism. - -@item %|@var{suffix} -@itemx %m@var{suffix} -Like @samp{%g}, except if @option{-pipe} is in effect. In that case -@samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at -all. These are the two most common ways to instruct a program that it -should read from standard input or write to standard output. If you -need something more elaborate you can use an @samp{%@{pipe:@code{X}@}} -construct: see for example @file{f/lang-specs.h}. - -@item %.@var{SUFFIX} -Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args -when it is subsequently output with @samp{%*}. @var{SUFFIX} is -terminated by the next space or %. - -@item %w -Marks the argument containing or following the @samp{%w} as the -designated output file of this compilation. This puts the argument -into the sequence of arguments that @samp{%o} will substitute later. - -@item %o -Substitutes the names of all the output files, with spaces -automatically placed around them. You should write spaces -around the @samp{%o} as well or the results are undefined. -@samp{%o} is for use in the specs for running the linker. -Input files whose names have no recognized suffix are not compiled -at all, but they are included among the output files, so they will -be linked. - -@item %O -Substitutes the suffix for object files. Note that this is -handled specially when it immediately follows @samp{%g, %u, or %U}, -because of the need for those to form complete file names. The -handling is such that @samp{%O} is treated exactly as if it had already -been substituted, except that @samp{%g, %u, and %U} do not currently -support additional @var{suffix} characters following @samp{%O} as they would -following, for example, @samp{.o}. - -@item %p -Substitutes the standard macro predefinitions for the -current target machine. Use this when running @code{cpp}. - -@item %P -Like @samp{%p}, but puts @samp{__} before and after the name of each -predefined macro, except for macros that start with @samp{__} or with -@samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO -C@. - -@item %I -Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}), -@option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}), -@option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options) -and @option{-imultilib} as necessary. - -@item %s -Current argument is the name of a library or startup file of some sort. -Search for that file in a standard list of directories and substitute -the full name found. - -@item %e@var{str} -Print @var{str} as an error message. @var{str} is terminated by a newline. -Use this when inconsistent options are detected. - -@item %(@var{name}) -Substitute the contents of spec string @var{name} at this point. - -@item %[@var{name}] -Like @samp{%(@dots{})} but put @samp{__} around @option{-D} arguments. - -@item %x@{@var{option}@} -Accumulate an option for @samp{%X}. - -@item %X -Output the accumulated linker options specified by @option{-Wl} or a @samp{%x} -spec string. - -@item %Y -Output the accumulated assembler options specified by @option{-Wa}. - -@item %Z -Output the accumulated preprocessor options specified by @option{-Wp}. - -@item %a -Process the @code{asm} spec. This is used to compute the -switches to be passed to the assembler. - -@item %A -Process the @code{asm_final} spec. This is a spec string for -passing switches to an assembler post-processor, if such a program is -needed. - -@item %l -Process the @code{link} spec. This is the spec for computing the -command line passed to the linker. Typically it will make use of the -@samp{%L %G %S %D and %E} sequences. - -@item %D -Dump out a @option{-L} option for each directory that GCC believes might -contain startup files. If the target supports multilibs then the -current multilib directory will be prepended to each of these paths. - -@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. - -@item %G -Process the @code{libgcc} spec. This is a spec string for deciding -which GCC support library should be included on the command line to the linker. - -@item %S -Process the @code{startfile} spec. This is a spec for deciding which -object files should be the first ones passed to the linker. Typically -this might be a file named @file{crt0.o}. - -@item %E -Process the @code{endfile} spec. This is a spec string that specifies -the last object files that will be passed to the linker. - -@item %C -Process the @code{cpp} spec. This is used to construct the arguments -to be passed to the C preprocessor. - -@item %1 -Process the @code{cc1} spec. This is used to construct the options to be -passed to the actual C compiler (@samp{cc1}). - -@item %2 -Process the @code{cc1plus} spec. This is used to construct the options to be -passed to the actual C++ compiler (@samp{cc1plus}). - -@item %* -Substitute the variable part of a matched option. See below. -Note that each comma in the substituted string is replaced by -a single space. - -@item %<@code{S} -Remove all occurrences of @code{-S} from the command line. Note---this -command is position dependent. @samp{%} commands in the spec string -before this one will see @code{-S}, @samp{%} commands in the spec string -after this one will not. - -@item %:@var{function}(@var{args}) -Call the named function @var{function}, passing it @var{args}. -@var{args} is first processed as a nested spec string, then split -into an argument vector in the usual fashion. The function returns -a string which is processed as if it had appeared literally as part -of the current spec. - -The following built-in spec functions are provided: - -@table @code -@item @code{if-exists} -The @code{if-exists} spec function takes one argument, an absolute -pathname to a file. If the file exists, @code{if-exists} returns the -pathname. Here is a small example of its usage: - -@smallexample -*startfile: -crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s -@end smallexample - -@item @code{if-exists-else} -The @code{if-exists-else} spec function is similar to the @code{if-exists} -spec function, except that it takes two arguments. The first argument is -an absolute pathname to a file. If the file exists, @code{if-exists-else} -returns the pathname. If it does not exist, it returns the second argument. -This way, @code{if-exists-else} can be used to select one file or another, -based on the existence of the first. Here is a small example of its usage: - -@smallexample -*startfile: -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}@} -Substitutes the @code{-S} switch, if that switch was given to GCC@. -If that switch was not specified, this substitutes nothing. Note that -the leading dash is omitted when specifying this option, and it is -automatically inserted if the substitution is performed. Thus the spec -string @samp{%@{foo@}} would match the command-line option @option{-foo} -and would output the command line option @option{-foo}. - -@item %W@{@code{S}@} -Like %@{@code{S}@} but mark last argument supplied within as a file to be -deleted on failure. - -@item %@{@code{S}*@} -Substitutes all the switches specified to GCC whose names start -with @code{-S}, but which also take an argument. This is used for -switches like @option{-o}, @option{-D}, @option{-I}, etc. -GCC considers @option{-o foo} as being -one switch whose names starts with @samp{o}. %@{o*@} would substitute this -text, including the space. Thus two arguments would be generated. - -@item %@{@code{S}*&@code{T}*@} -Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options -(the order of @code{S} and @code{T} in the spec is not significant). -There can be any number of ampersand-separated variables; for each the -wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}. - -@item %@{@code{S}:@code{X}@} -Substitutes @code{X}, if the @samp{-S} switch was given to GCC@. - -@item %@{!@code{S}:@code{X}@} -Substitutes @code{X}, if the @samp{-S} switch was @emph{not} given to GCC@. - -@item %@{@code{S}*:@code{X}@} -Substitutes @code{X} if one or more switches whose names start with -@code{-S} are specified to GCC@. Normally @code{X} is substituted only -once, no matter how many such switches appeared. However, if @code{%*} -appears somewhere in @code{X}, then @code{X} will be substituted once -for each matching switch, with the @code{%*} replaced by the part of -that switch that matched the @code{*}. - -@item %@{.@code{S}:@code{X}@} -Substitutes @code{X}, if processing a file with suffix @code{S}. - -@item %@{!.@code{S}:@code{X}@} -Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}. - -@c APPLE LOCAL begin mainline 2007-03-13 5040758 -@item %@{,@code{S}:@code{X}@} -Substitutes @code{X}, if processing a file for language @code{S}. - -@item %@{!,@code{S}:@code{X}@} -Substitutes @code{X}, if not processing a file for language @code{S}. - -@item %@{@code{S}|@code{P}:@code{X}@} -Substitutes @code{X} if either @code{-S} or @code{-P} was given to -GCC@. This may be combined with @samp{!}, @samp{.}, @samp{,}, and -@code{*} sequences as well, although they have a stronger binding than -the @samp{|}. If @code{%*} appears in @code{X}, all of the -alternatives must be starred, and only the first matching alternative -is substituted. - -@c APPLE LOCAL end mainline 2007-03-13 5040758 -For example, a spec string like this: - -@smallexample -%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@} -@end smallexample - -will output the following command-line options from the following input -command-line options: - -@smallexample -fred.c -foo -baz -jim.d -bar -boggle --d fred.c -foo -baz -boggle --d jim.d -bar -baz -boggle -@end smallexample - -@item %@{S:X; T:Y; :D@} - -@c APPLE LOCAL begin mainline 2007-03-13 5040758 -If @code{S} was given to GCC, substitutes @code{X}; else if @code{T} was -given to GCC, substitutes @code{Y}; else substitutes @code{D}. There can -be as many clauses as you need. This may be combined with @code{.}, -@code{,}, @code{!}, @code{|}, and @code{*} as needed. -@c APPLE LOCAL end mainline 2007-03-13 5040758 - - -@end table - -The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar -construct may contain other nested @samp{%} constructs or spaces, or -even newlines. They are processed as usual, as described above. -Trailing white space in @code{X} is ignored. White space may also -appear anywhere on the left side of the colon in these constructs, -except between @code{.} or @code{*} and the corresponding word. - -The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are -handled specifically in these constructs. If another value of -@option{-O} or the negated form of a @option{-f}, @option{-m}, or -@option{-W} switch is found later in the command line, the earlier -switch value is ignored, except with @{@code{S}*@} where @code{S} is -just one letter, which passes all matching options. - -The character @samp{|} at the beginning of the predicate text is used to -indicate that a command should be piped to the following command, but -only if @option{-pipe} is specified. - -It is built into GCC which switches take arguments and which do not. -(You might think it would be useful to generalize this to allow each -compiler's spec to say which switches take arguments. But this cannot -be done in a consistent fashion. GCC cannot even decide which input -files have been specified without knowing which switches take arguments, -and it must know which input files to compile in order to tell which -compilers to run). - -GCC also knows implicitly that arguments starting in @option{-l} are to be -treated as compiler output files, and passed to the linker in their -proper position among the other output files. - -@c man begin OPTIONS - -@node Target Options -@section Specifying Target Machine and Compiler Version -@cindex target options -@cindex cross compiling -@cindex specifying machine version -@cindex specifying compiler version and target machine -@cindex compiler version, specifying -@cindex target machine, specifying - -The usual way to run GCC is to run the executable called @file{gcc}, or -@file{<machine>-gcc} when cross-compiling, or -@file{<machine>-gcc-<version>} to run a version other than the one that -was installed last. Sometimes this is inconvenient, so GCC provides -options that will switch to another cross-compiler or version. - -@table @gcctabopt -@item -b @var{machine} -@opindex b -The argument @var{machine} specifies the target machine for compilation. - -The value to use for @var{machine} is the same as was specified as the -machine type when configuring GCC as a cross-compiler. For -example, if a cross-compiler was configured with @samp{configure -arm-elf}, meaning to compile for an arm processor with elf binaries, -then you would specify @option{-b arm-elf} to run that cross compiler. -Because there are other options beginning with @option{-b}, the -configuration must contain a hyphen. - -@item -V @var{version} -@opindex V -The argument @var{version} specifies which version of GCC to run. -This is useful when multiple versions are installed. For example, -@var{version} might be @samp{4.0}, meaning to run GCC version 4.0. -@end table - -The @option{-V} and @option{-b} options work by running the -@file{<machine>-gcc-<version>} executable, so there's no real reason to -use them if you can just run that directly. - -@node Submodel Options -@section Hardware Models and Configurations -@cindex submodel options -@cindex specifying hardware config -@cindex hardware models and configurations, specifying -@cindex machine dependent options - -Earlier we discussed the standard option @option{-b} which chooses among -different installed compilers for completely different target -machines, such as VAX vs.@: 68000 vs.@: 80386. - -In addition, each of these target machine types can have its own -special options, starting with @samp{-m}, to choose among various -hardware models or configurations---for example, 68010 vs 68020, -floating coprocessor or none. A single installed version of the -compiler can compile for any model or configuration, according to the -options specified. - -Some configurations of the compiler also support additional special -options, usually for compatibility with other compilers on the same -platform. - -@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 - -@menu -@c APPLE LOCAL prune man page -@ignore -* ARC Options:: -@c APPLE LOCAL ARM prune man page -@end ignore -* ARM Options:: -@c APPLE LOCAL ARM prune man page -@ignore -* AVR Options:: -* Blackfin Options:: -* CRIS Options:: -* CRX Options:: -@c APPLE LOCAL prune man page -@end ignore -* Darwin Options:: -@c APPLE LOCAL prune man page -@ignore -* DEC Alpha Options:: -* DEC Alpha/VMS Options:: -* FRV Options:: -* GNU/Linux Options:: -* H8/300 Options:: -* HPPA Options:: -@c APPLE LOCAL prune man page -@end ignore -* i386 and x86-64 Options:: -@c APPLE LOCAL prune man page -@ignore -* IA-64 Options:: -* M32C Options:: -* M32R/D Options:: -* M680x0 Options:: -* M68hc1x Options:: -* MCore Options:: -* MIPS Options:: -* MMIX Options:: -* MN10300 Options:: -* MT Options:: -* PDP-11 Options:: -@c APPLE LOCAL prune man page -@end ignore -* PowerPC Options:: -* RS/6000 and PowerPC Options:: -@c APPLE LOCAL prune man page -@ignore -* S/390 and zSeries Options:: -* Score Options:: -* SH Options:: -* SPARC Options:: -* System V Options:: -* TMS320C3x/C4x Options:: -* V850 Options:: -* VAX Options:: -* x86-64 Options:: -* Xstormy16 Options:: -* Xtensa Options:: -* zSeries Options:: -@c APPLE LOCAL prune man page -@end ignore -@end menu - -@c APPLE LOCAL prune man page -@ignore -@node ARC Options -@subsection ARC Options -@cindex ARC Options - -These options are defined for ARC implementations: - -@table @gcctabopt -@item -EL -@opindex EL -Compile code for little endian mode. This is the default. - -@item -EB -@opindex EB -Compile code for big endian mode. - -@item -mmangle-cpu -@opindex mmangle-cpu -Prepend the name of the cpu to all public symbol names. -In multiple-processor systems, there are many ARC variants with different -instruction and register set characteristics. This flag prevents code -compiled for one cpu to be linked with code compiled for another. -No facility exists for handling variants that are ``almost identical''. -This is an all or nothing option. - -@item -mcpu=@var{cpu} -@opindex mcpu -Compile code for ARC variant @var{cpu}. -Which variants are supported depend on the configuration. -All variants support @option{-mcpu=base}, this is the default. - -@item -mtext=@var{text-section} -@itemx -mdata=@var{data-section} -@itemx -mrodata=@var{readonly-data-section} -@opindex mtext -@opindex mdata -@opindex mrodata -Put functions, data, and readonly data in @var{text-section}, -@var{data-section}, and @var{readonly-data-section} respectively -by default. This can be overridden with the @code{section} attribute. -@xref{Variable Attributes}. - -@end table -@c APPLE LOCAL ARM prune man page -@end ignore - -@node ARM Options -@subsection ARM Options -@cindex ARM options - -These @samp{-m} options are defined for Advanced RISC Machines (ARM) -architectures: - -@table @gcctabopt -@item -mabi=@var{name} -@opindex mabi -Generate code for the specified ABI@. Permissible values are: @samp{apcs-gnu}, -@samp{atpcs}, @samp{aapcs}, @samp{aapcs-linux} and @samp{iwmmxt}. - -@item -mapcs-frame -@opindex mapcs-frame -Generate a stack frame that is compliant with the ARM Procedure Call -Standard for all functions, even if this is not strictly necessary for -correct execution of the code. Specifying @option{-fomit-frame-pointer} -with this option will cause the stack frames not to be generated for -leaf functions. The default is @option{-mno-apcs-frame}. - -@item -mapcs -@opindex mapcs -This is a synonym for @option{-mapcs-frame}. - -@c APPLE LOCAL We already have ignore running -- do not do this one --bowdidge -@c @ignore -@c not currently implemented -@item -mapcs-stack-check -@opindex mapcs-stack-check -Generate code to check the amount of stack space available upon entry to -every function (that actually uses some stack space). If there is -insufficient space available then either the function -@samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be -called, depending upon the amount of stack space required. The run time -system is required to provide these functions. The default is -@option{-mno-apcs-stack-check}, since this produces smaller code. - -@c not currently implemented -@item -mapcs-float -@opindex mapcs-float -Pass floating point arguments using the float point registers. This is -one of the variants of the APCS@. This option is recommended if the -target hardware has a floating point unit or if a lot of floating point -arithmetic is going to be performed by the code. The default is -@option{-mno-apcs-float}, since integer only code is slightly increased in -size if @option{-mapcs-float} is used. - -@c not currently implemented -@item -mapcs-reentrant -@opindex mapcs-reentrant -Generate reentrant, position independent code. The default is -@option{-mno-apcs-reentrant}. -@c APPLE LOCAL We already have ignore running -- do not do this one --bowdidge -@c @end ignore - -@item -mthumb-interwork -@opindex mthumb-interwork -Generate code which supports calling between the ARM and Thumb -instruction sets. Without this option the two instruction sets cannot -be reliably used inside one program. The default is -@option{-mno-thumb-interwork}, since slightly larger code is generated -when @option{-mthumb-interwork} is specified. - -@item -mno-sched-prolog -@opindex mno-sched-prolog -Prevent the reordering of instructions in the function prolog, or the -merging of those instruction with the instructions in the function's -body. This means that all functions will start with a recognizable set -of instructions (or in fact one of a choice from a small set of -different function prologues), and this information can be used to -locate the start if functions inside an executable piece of code. The -default is @option{-msched-prolog}. - -@item -mhard-float -@opindex mhard-float -Generate output containing floating point instructions. This is the -default. - -@item -msoft-float -@opindex msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all ARM -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. - -@option{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @option{-msoft-float} in order for -this to work. - -@item -mfloat-abi=@var{name} -@opindex mfloat-abi -Specifies which ABI to use for floating point values. Permissible values -are: @samp{soft}, @samp{softfp} and @samp{hard}. - -@samp{soft} and @samp{hard} are equivalent to @option{-msoft-float} -and @option{-mhard-float} respectively. @samp{softfp} allows the generation -of floating point instructions, but still uses the soft-float calling -conventions. - -@item -mlittle-endian -@opindex mlittle-endian -Generate code for a processor running in little-endian mode. This is -the default for all standard configurations. - -@item -mbig-endian -@opindex mbig-endian -Generate code for a processor running in big-endian mode; the default is -to compile code for a little-endian processor. - -@item -mwords-little-endian -@opindex mwords-little-endian -This option only applies when generating code for big-endian processors. -Generate code for a little-endian word order but a big-endian byte -order. That is, a byte order of the form @samp{32107654}. Note: this -option should only be used if you require compatibility with code for -big-endian ARM processors generated by versions of the compiler prior to -2.8. - -@item -mcpu=@var{name} -@opindex mcpu -This specifies the name of the target ARM processor. GCC uses this name -to determine what kind of instructions it can emit when generating -assembly code. Permissible names are: @samp{arm2}, @samp{arm250}, -@samp{arm3}, @samp{arm6}, @samp{arm60}, @samp{arm600}, @samp{arm610}, -@samp{arm620}, @samp{arm7}, @samp{arm7m}, @samp{arm7d}, @samp{arm7dm}, -@samp{arm7di}, @samp{arm7dmi}, @samp{arm70}, @samp{arm700}, -@samp{arm700i}, @samp{arm710}, @samp{arm710c}, @samp{arm7100}, -@samp{arm7500}, @samp{arm7500fe}, @samp{arm7tdmi}, @samp{arm7tdmi-s}, -@samp{arm8}, @samp{strongarm}, @samp{strongarm110}, @samp{strongarm1100}, -@samp{arm8}, @samp{arm810}, @samp{arm9}, @samp{arm9e}, @samp{arm920}, -@samp{arm920t}, @samp{arm922t}, @samp{arm946e-s}, @samp{arm966e-s}, -@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{mpcore}, @samp{mpcorenovfp}, -@samp{arm1176jz-s}, @samp{arm1176jzf-s}, @samp{xscale}, @samp{iwmmxt}, -@samp{ep9312}. - -@itemx -mtune=@var{name} -@opindex mtune -This option is very similar to the @option{-mcpu=} option, except that -instead of specifying the actual target processor type, and hence -restricting which instructions can be used, it specifies that GCC should -tune the performance of the code as if the target were of the type -specified in this option, but still choosing the instructions that it -will generate based on the cpu specified by a @option{-mcpu=} option. -For some ARM implementations better performance can be obtained by using -this option. - -@item -march=@var{name} -@opindex march -This specifies the name of the target ARM architecture. GCC uses this -name to determine what kind of instructions it can emit when generating -assembly code. This option can be used in conjunction with or instead -of the @option{-mcpu=} option. Permissible names are: @samp{armv2}, -@samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t}, -@samp{armv5}, @samp{armv5t}, @samp{armv5te}, @samp{armv6}, @samp{armv6j}, -@samp{iwmmxt}, @samp{ep9312}. - -@item -mfpu=@var{name} -@itemx -mfpe=@var{number} -@itemx -mfp=@var{number} -@opindex mfpu -@opindex mfpe -@opindex mfp -This specifies what floating point hardware (or hardware emulation) is -available on the target. Permissible names are: @samp{fpa}, @samp{fpe2}, -@samp{fpe3}, @samp{maverick}, @samp{vfp}. @option{-mfp} and @option{-mfpe} -are synonyms for @option{-mfpu}=@samp{fpe}@var{number}, for compatibility -with older versions of GCC@. - -If @option{-msoft-float} is specified this specifies the format of -floating point values. - -@item -mstructure-size-boundary=@var{n} -@opindex mstructure-size-boundary -The size of all structures and unions will be rounded up to a multiple -of the number of bits set by this option. Permissible values are 8, 32 -and 64. The default value varies for different toolchains. For the COFF -targeted toolchain the default value is 8. A value of 64 is only allowed -if the underlying ABI supports it. - -Specifying the larger number can produce faster, more efficient code, but -can also increase the size of the program. Different values are potentially -incompatible. Code compiled with one value cannot necessarily expect to -work with code or libraries compiled with another value, if they exchange -information using structures or unions. - -@item -mabort-on-noreturn -@opindex mabort-on-noreturn -Generate a call to the function @code{abort} at the end of a -@code{noreturn} function. It will be executed if the function tries to -return. - -@item -mlong-calls -@itemx -mno-long-calls -@opindex mlong-calls -@opindex mno-long-calls -Tells the compiler to perform function calls by first loading the -address of the function into a register and then performing a subroutine -call on this register. This switch is needed if the target function -will lie outside of the 64 megabyte addressing range of the offset based -version of subroutine call instruction. - -Even if this switch is enabled, not all function calls will be turned -into long calls. The heuristic is that static functions, functions -which have the @samp{short-call} attribute, functions that are inside -the scope of a @samp{#pragma no_long_calls} directive and functions whose -definitions have already been compiled within the current compilation -unit, will not be turned into long calls. The exception to this rule is -that weak function definitions, functions with the @samp{long-call} -attribute or the @samp{section} attribute, and functions that are within -the scope of a @samp{#pragma long_calls} directive, will always be -turned into long calls. - -This feature is not enabled by default. Specifying -@option{-mno-long-calls} will restore the default behavior, as will -placing the function calls within the scope of a @samp{#pragma -long_calls_off} directive. Note these switches have no effect on how -the compiler generates code to handle function calls via function -pointers. - -@item -mnop-fun-dllimport -@opindex mnop-fun-dllimport -Disable support for the @code{dllimport} attribute. - -@item -msingle-pic-base -@opindex msingle-pic-base -Treat the register used for PIC addressing as read-only, rather than -loading it in the prologue for each function. The run-time system is -responsible for initializing this register with an appropriate value -before execution begins. - -@item -mpic-register=@var{reg} -@opindex mpic-register -Specify the register to be used for PIC addressing. The default is R10 -unless stack-checking is enabled, when R9 is used. - -@item -mcirrus-fix-invalid-insns -@opindex mcirrus-fix-invalid-insns -@opindex mno-cirrus-fix-invalid-insns -Insert NOPs into the instruction stream to in order to work around -problems with invalid Maverick instruction combinations. This option -is only valid if the @option{-mcpu=ep9312} option has been used to -enable generation of instructions for the Cirrus Maverick floating -point co-processor. This option is not enabled by default, since the -problem is only present in older Maverick implementations. The default -can be re-enabled by use of the @option{-mno-cirrus-fix-invalid-insns} -switch. - -@item -mpoke-function-name -@opindex mpoke-function-name -Write the name of each function into the text section, directly -preceding the function prologue. The generated code is similar to this: - -@smallexample - t0 - .ascii "arm_poke_function_name", 0 - .align - t1 - .word 0xff000000 + (t1 - t0) - arm_poke_function_name - mov ip, sp - stmfd sp!, @{fp, ip, lr, pc@} - sub fp, ip, #4 -@end smallexample - -When performing a stack backtrace, code can inspect the value of -@code{pc} stored at @code{fp + 0}. If the trace function then looks at -location @code{pc - 12} and the top 8 bits are set, then we know that -there is a function name embedded immediately preceding this location -and has length @code{((pc[-3]) & 0xff000000)}. - -@c APPLE LOCAL begin v7 thumb is default -@item -mthumb -@opindex mthumb -Generate code for the 16-bit Thumb instruction set. For ARMv7, the default -is to use the THUMB2 instruction set. For all other architectures, the default -is to use the 32-bit ARM instruction set. The ARM instruction set may be -explicitly selected via @option{-mno-thumb} or @option{-marm}. -@c APPLE LOCAL end v7 thumb is default - -@item -mtpcs-frame -@opindex mtpcs-frame -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all non-leaf functions. (A leaf function is one that does -not call any other functions.) The default is @option{-mno-tpcs-frame}. - -@item -mtpcs-leaf-frame -@opindex mtpcs-leaf-frame -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all leaf functions. (A leaf function is one that does -not call any other functions.) The default is @option{-mno-apcs-leaf-frame}. - -@item -mcallee-super-interworking -@opindex mcallee-super-interworking -Gives all externally visible functions in the file being compiled an ARM -instruction set header which switches to Thumb mode before executing the -rest of the function. This allows these functions to be called from -non-interworking code. - -@item -mcaller-super-interworking -@opindex mcaller-super-interworking -Allows calls via function pointers (including virtual functions) to -execute correctly regardless of whether the target code has been -compiled for interworking or not. There is a small overhead in the cost -of executing a function pointer if this option is enabled. - -@item -mtp=@var{name} -@opindex mtp -Specify the access model for the thread local storage pointer. The valid -models are @option{soft}, which generates calls to @code{__aeabi_read_tp}, -@option{cp15}, which fetches the thread pointer from @code{cp15} directly -(supported in the arm6k architecture), and @option{auto}, which uses the -best available method for the selected processor. The default setting is -@option{auto}. - -@c APPLE LOCAL begin 5946347 ms_struct support -@item -mms-bitfields -@opindex mms-bitfields -Set the default structure layout to be compatible with the Microsoft -compiler standard. This is equivalent to adding an @code{ms_struct} -attribute to each structure and union tag definition. The default is -@option{mno-ms-bitfields}. -@c APPLE LOCAL end 5946347 ms_struct support - -@end table - -@c APPLE LOCAL ARM prune man page -@ignore -@node AVR Options -@subsection AVR Options -@cindex AVR Options - -These options are defined for AVR implementations: - -@table @gcctabopt -@item -mmcu=@var{mcu} -@opindex mmcu -Specify ATMEL AVR instruction set or MCU type. - -Instruction set avr1 is for the minimal AVR core, not supported by the C -compiler, only for assembler programs (MCU types: at90s1200, attiny10, -attiny11, attiny12, attiny15, attiny28). - -Instruction set avr2 (default) is for the classic AVR core with up to -8K program memory space (MCU types: at90s2313, at90s2323, attiny22, -at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, -at90c8534, at90s8535). - -Instruction set avr3 is for the classic AVR core with up to 128K program -memory space (MCU types: atmega103, atmega603, at43usb320, at76c711). - -Instruction set avr4 is for the enhanced AVR core with up to 8K program -memory space (MCU types: atmega8, atmega83, atmega85). - -Instruction set avr5 is for the enhanced AVR core with up to 128K program -memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323, -atmega64, atmega128, at43usb355, at94k). - -@item -msize -@opindex msize -Output instruction sizes to the asm file. - -@item -minit-stack=@var{N} -@opindex minit-stack -Specify the initial stack address, which may be a symbol or numeric value, -@samp{__stack} is the default. - -@item -mno-interrupts -@opindex mno-interrupts -Generated code is not compatible with hardware interrupts. -Code size will be smaller. - -@item -mcall-prologues -@opindex mcall-prologues -Functions prologues/epilogues expanded as call to appropriate -subroutines. Code size will be smaller. - -@item -mno-tablejump -@opindex mno-tablejump -Do not generate tablejump insns which sometimes increase code size. - -@item -mtiny-stack -@opindex mtiny-stack -Change only the low 8 bits of the stack pointer. - -@item -mint8 -@opindex mint8 -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 -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 -mspecld-anomaly -@opindex mspecld-anomaly -When enabled, the compiler will ensure that the generated code does not -contain speculative loads after jump instructions. This option is enabled -by default. - -@item -mno-specld-anomaly -@opindex mno-specld-anomaly -Don't generate extra code to prevent speculative loads from occurring. - -@item -mcsync-anomaly -@opindex mcsync-anomaly -When enabled, the compiler will ensure that the generated code does not -contain CSYNC or SSYNC instructions too soon after conditional branches. -This option is enabled by default. - -@item -mno-csync-anomaly -@opindex mno-csync-anomaly -Don't generate extra code to prevent CSYNC or SSYNC instructions from -occurring too soon after a conditional branch. - -@item -mlow-64k -@opindex 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. - -@item -mlong-calls -@itemx -mno-long-calls -@opindex mlong-calls -@opindex mno-long-calls -Tells the compiler to perform function calls by first loading the -address of the function into a register and then performing a subroutine -call on this register. This switch is needed if the target function -will lie outside of the 24 bit addressing range of the offset based -version of subroutine call instruction. - -This feature is not enabled by default. Specifying -@option{-mno-long-calls} will restore the default behavior. Note these -switches have no effect on how the compiler generates code to handle -function calls via function pointers. -@end table - -@node CRIS Options -@subsection CRIS Options -@cindex CRIS Options - -These options are defined specifically for the CRIS ports. - -@table @gcctabopt -@item -march=@var{architecture-type} -@itemx -mcpu=@var{architecture-type} -@opindex march -@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@. -Default is @samp{v0} except for cris-axis-linux-gnu, where the default is -@samp{v10}. - -@item -mtune=@var{architecture-type} -@opindex mtune -Tune to @var{architecture-type} everything applicable about the generated -code, except for the ABI and the set of available instructions. The -choices for @var{architecture-type} are the same as for -@option{-march=@var{architecture-type}}. - -@item -mmax-stack-frame=@var{n} -@opindex mmax-stack-frame -Warn when the stack frame of a function exceeds @var{n} bytes. - -@item -melinux-stacksize=@var{n} -@opindex melinux-stacksize -Only available with the @samp{cris-axis-aout} target. Arranges for -indications in the program to the kernel loader that the stack of the -program should be set to @var{n} bytes. - -@item -metrax4 -@itemx -metrax100 -@opindex metrax4 -@opindex metrax100 -The options @option{-metrax4} and @option{-metrax100} are synonyms for -@option{-march=v3} and @option{-march=v8} respectively. - -@item -mmul-bug-workaround -@itemx -mno-mul-bug-workaround -@opindex mmul-bug-workaround -@opindex mno-mul-bug-workaround -Work around a bug in the @code{muls} and @code{mulu} instructions for CPU -models where it applies. This option is active by default. - -@item -mpdebug -@opindex mpdebug -Enable CRIS-specific verbose debug-related information in the assembly -code. This option also has the effect to turn off the @samp{#NO_APP} -formatted-code indicator to the assembler at the beginning of the -assembly file. - -@item -mcc-init -@opindex mcc-init -Do not use condition-code results from previous instruction; always emit -compare and test instructions before use of condition codes. - -@item -mno-side-effects -@opindex mno-side-effects -Do not emit instructions with side-effects in addressing modes other than -post-increment. - -@item -mstack-align -@itemx -mno-stack-align -@itemx -mdata-align -@itemx -mno-data-align -@itemx -mconst-align -@itemx -mno-const-align -@opindex mstack-align -@opindex mno-stack-align -@opindex mdata-align -@opindex mno-data-align -@opindex mconst-align -@opindex mno-const-align -These options (no-options) arranges (eliminate arrangements) for the -stack-frame, individual data and constants to be aligned for the maximum -single data access size for the chosen CPU model. The default is to -arrange for 32-bit alignment. ABI details such as structure layout are -not affected by these options. - -@item -m32-bit -@itemx -m16-bit -@itemx -m8-bit -@opindex m32-bit -@opindex m16-bit -@opindex m8-bit -Similar to the stack- data- and const-align options above, these options -arrange for stack-frame, writable data and constants to all be 32-bit, -16-bit or 8-bit aligned. The default is 32-bit alignment. - -@item -mno-prologue-epilogue -@itemx -mprologue-epilogue -@opindex mno-prologue-epilogue -@opindex mprologue-epilogue -With @option{-mno-prologue-epilogue}, the normal function prologue and -epilogue that sets up the stack-frame are omitted and no return -instructions or return sequences are generated in the code. Use this -option only together with visual inspection of the compiled code: no -warnings or errors are generated when call-saved registers must be saved, -or storage for local variable needs to be allocated. - -@item -mno-gotplt -@itemx -mgotplt -@opindex mno-gotplt -@opindex mgotplt -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}. - -@item -maout -@opindex maout -Legacy no-op option only recognized with the cris-axis-aout target. - -@item -melf -@opindex melf -Legacy no-op option only recognized with the cris-axis-elf and -cris-axis-linux-gnu targets. - -@item -melinux -@opindex melinux -Only recognized with the cris-axis-aout target, where it selects a -GNU/linux-like multilib, include files and instruction set for -@option{-march=v8}. - -@item -mlinux -@opindex mlinux -Legacy no-op option only recognized with the cris-axis-linux-gnu target. - -@item -sim -@opindex sim -This option, recognized for the cris-axis-aout and cris-axis-elf arranges -to link with input-output functions from a simulator library. Code, -initialized data and zero-initialized data are allocated consecutively. - -@item -sim2 -@opindex sim2 -Like @option{-sim}, but pass linker options to locate initialized data at -0x40000000 and zero-initialized data at 0x80000000. -@end table - -@node CRX Options -@subsection CRX Options -@cindex CRX Options - -These options are defined specifically for the CRX ports. - -@table @gcctabopt - -@item -mmac -@opindex mmac -Enable the use of multiply-accumulate instructions. Disabled by default. - -@item -mpush-args -@opindex mpush-args -Push instructions will be used to pass outgoing arguments when functions -are called. Enabled by default. -@end table -@c APPLE LOCAL prune man page -@end ignore - -@node Darwin Options -@subsection Darwin Options -@cindex Darwin options - -These options are defined for all architectures running the Darwin operating -system. - -@c APPLE LOCAL universal -FSF GCC on Darwin does not create ``universal'' object files; it will create -an object file for the single architecture that it was built to -@c APPLE LOCAL universal -target. Apple's GCC on Darwin does create ``universal'' 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} -@opindex F -Add the framework directory @var{dir} to the head of the list of -directories to be searched for header files. These directories are -interleaved with those specified by @option{-I} options and are -scanned in a left-to-right order. - -A framework directory is a directory with frameworks in it. A -framework is a directory with a @samp{"Headers"} and/or -@samp{"PrivateHeaders"} directory contained directly in it that ends -in @samp{".framework"}. The name of a framework is the name of this -directory excluding the @samp{".framework"}. Headers associated with -the framework are found in one of those two directories, with -@samp{"Headers"} being searched first. A subframework is a framework -directory that is in a framework's @samp{"Frameworks"} directory. -Includes of subframework headers can only appear in a header of a -framework that contains the subframework, or in a sibling subframework -header. Two subframeworks are siblings if they occur in the same -framework. A subframework should not have the same name as a -framework, a warning will be issued if this is violated. Currently a -subframework cannot have subframeworks, in the future, the mechanism -may be extended to support this. The standard frameworks can be found -in @samp{"/System/Library/Frameworks"} and -@samp{"/Library/Frameworks"}. An example include looks like -@code{#include <Framework/header.h>}, where @samp{Framework} denotes -the name of the framework and header.h is found in the -@samp{"PrivateHeaders"} or @samp{"Headers"} directory. - -@c APPLE LOCAL begin iframework for 4.3 4094959 -@item -iframework@var{dir} -@opindex iframework -Like @option{-F} except the directory is a treated as a system -directory. The main effect is to not warn about constructs contained -within header files found via @var{dir}. -@c APPLE LOCAL end iframework for 4.3 4094959 - -@item -gused -@opindex gused -Emit debugging information for symbols that are used. For STABS -debugging format, this enables @option{-feliminate-unused-debug-symbols}. -This is by default ON@. - -@item -gfull -@opindex gfull -Emit debugging information for all symbols and types. - -@item -mmacosx-version-min=@var{version} -The earliest version of MacOS X that this executable will run on -is @var{version}. Typical values of @var{version} include @code{10.1}, -@code{10.2}, and @code{10.3.9}. - -@c APPLE LOCAL begin ARM 5905142 -This value can also be set with the @env{MACOSX_DEPLOYMENT_TARGET} -environment variable. If both the command-line option is specified -and the environment variable is set, the command-line option will -take precedence. -@c APPLE LOCAL end ARM 5905142 - -@c APPLE LOCAL begin mainline 2007-06-14 5235474 -If the compiler was built to use the system's headers by default, -then the default for this option is the system version on which the -compiler is running, otherwise the default is to make choices which -are compatible with as many systems and code bases as possible. -@c APPLE LOCAL end mainline 2007-06-14 5235474 - -@c APPLE LOCAL begin ARM 5905142 -This value is not set by default for ARM targets. - -@item -miphoneos-version-min=@var{version} -The earliest version of iPhone OS that this executable will run on -is @var{version}. - -This value can also be set with the @env{IPHONEOS_DEPLOYMENT_TARGET} -environment variable. If both the command-line option is specified -and the environment variable is set, the command-line option will -take precedence. - -On ARM targets, if not specified by the command-line option or -environment variable, this value defaults to 2.0. -@c APPLE LOCAL end ARM 5905142 - -@item -mkernel -@opindex mkernel -Enable kernel development mode. The @option{-mkernel} option sets -@c APPLE LOCAL 5731065 -@option{-static}, @option{-fno-common}, @option{-fno-builtin}, @option{-fno-cxa-atexit}, -@c APPLE LOCAL 5628030 -@option{-fno-exceptions}, @option{-fno-non-call-exceptions}, @option{-fno-asynchronous-unwind-tables}, -@option{-fapple-kext}, @option{-fno-weak} and @option{-fno-rtti} where -applicable. This mode also sets @option{-mno-altivec}, -@c APPLE LOCAL begin 5731065 6268204 -@option{-msoft-float} and @option{-mlong-branch} for PowerPC targets, -@option{-mno-red-zone} on x86_64, and @option{-mlong-branch} for ARM -targets. Of these, only -msoft-float can be changed which is useful in -a kext that wishes to use the hardware floating point unit. -@c APPLE LOCAL end 5731065 6268204 -@c APPLE LOCAL begin kext weak_import 5935650 -@option{-dynamic} can be used to override the effects of -static on -the assembler to enable the use of weak_import. -@c APPLE LOCAL end kext weak_import 5935650 - -@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 -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 -switch to conform to a non-default data model. - -@item -mfix-and-continue -@itemx -ffix-and-continue -@itemx -findirect-data -@opindex mfix-and-continue -@opindex ffix-and-continue -@opindex findirect-data -Generate code suitable for fast turn around development. Needed to -enable gdb to dynamically load @code{.o} files into already running -programs. @option{-findirect-data} and @option{-ffix-and-continue} -are provided for backwards compatibility. - -@c APPLE LOCAL KEXT -@item -fapple-kext -@c APPLE LOCAL KEXT indirect-virtual-calls --sts -@itemx -findirect-virtual-calls -@c APPLE LOCAL KEXT terminated-vtables -@itemx -fterminated-vtables -@c APPLE LOCAL KEXT -@opindex fapple-kext -@c APPLE LOCAL KEXT indirect-virtual-calls --sts -@opindex findirect-virtual-calls -@c APPLE LOCAL KEXT terminated-vtables -@opindex fterminated-vtables -@c APPLE LOCAL begin KEXT -Alter vtables, destructors, and other implementation details to more -closely resemble the GCC 2.95 ABI for PowerPC and 32-bit i386. This -is to make kernel extensions loadable by Darwin kernels, and is -required to build any Darwin kernel extension. In addition, virtual -calls are not made directly, instead, code is generated to always go -through the virtual table, as virtual tables can be patched by the -kernel module loader. Vtables are altered by adding a zero word at -the end of every vtable. @option{-findirect-virtual-calls} and -@option{-fterminated-vtables} are accepted for backwards compatibility -but will be removed in the future. Additionally implies -most of @option{-mkernel} except for @option{-msoft-float} and -@option{-mlong-branch} for PowerPC targets. (APPLE ONLY) -@c APPLE LOCAL end KEXT - -@c APPLE LOCAL begin pascal strings -@item -mpascal-strings -Allow Pascal-style string literals to be constructed. This option -implies @option{-Wpointer-sign} so that conversions between -Pascal-style strings and C-style strings are warned about. (APPLE -ONLY) - -@xref{Pascal Strings,,Constructing String Literals with a Pascal-style -Length Byte}, for more information on the syntax and semantics of Pascal -string literals. -@c APPLE LOCAL end pascal strings - -@item -all_load -@opindex all_load -Loads all members of static archive libraries. -See man ld(1) for more information. - -@item -arch_errors_fatal -@opindex arch_errors_fatal -Cause the errors having to do with files that have the wrong architecture -to be fatal. - -@item -bind_at_load -@opindex bind_at_load -Causes the output file to be marked such that the dynamic linker will -bind all undefined references when the file is loaded or launched. - -@item -bundle -@opindex bundle -Produce a Mach-o bundle format file. -See man ld(1) for more information. - -@item -bundle_loader @var{executable} -@opindex bundle_loader -This option specifies the @var{executable} that will be loading the build -output file being linked. See man ld(1) for more information. - -@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. - -@c APPLE LOCAL begin 7519550 force local -@item -force_load @var{library_name} -@opindex force_load -Loads all members of named static archive library. -See man ld(1) for more information. -@c APPLE LOCAL end 7519550 force local - -@item -allowable_client @var{client_name} -@itemx -client_name -@itemx -compatibility_version -@itemx -current_version -@itemx -dead_strip -@itemx -dependency-file -@itemx -dylib_file -@itemx -dylinker_install_name -@itemx -dynamic -@itemx -exported_symbols_list -@itemx -filelist -@itemx -flat_namespace -@itemx -force_flat_namespace -@itemx -headerpad_max_install_names -@itemx -image_base -@itemx -init -@itemx -install_name -@itemx -keep_private_externs -@itemx -multi_module -@itemx -multiply_defined -@itemx -multiply_defined_unused -@itemx -noall_load -@itemx -no_dead_strip_inits_and_terms -@itemx -nofixprebinding -@itemx -nomultidefs -@itemx -noprebind -@itemx -noseglinkedit -@itemx -pagezero_size -@itemx -prebind -@itemx -prebind_all_twolevel_modules -@itemx -private_bundle -@itemx -read_only_relocs -@itemx -sectalign -@itemx -sectobjectsymbols -@itemx -whyload -@itemx -seg1addr -@itemx -sectcreate -@itemx -sectobjectsymbols -@itemx -sectorder -@itemx -segaddr -@itemx -segs_read_only_addr -@itemx -segs_read_write_addr -@itemx -seg_addr_table -@itemx -seg_addr_table_filename -@itemx -seglinkedit -@itemx -segprot -@itemx -segs_read_only_addr -@itemx -segs_read_write_addr -@itemx -single_module -@itemx -static -@itemx -sub_library -@itemx -sub_umbrella -@itemx -twolevel_namespace -@itemx -umbrella -@itemx -undefined -@itemx -unexported_symbols_list -@itemx -weak_reference_mismatches -@itemx -whatsloaded - -@opindex allowable_client -@opindex client_name -@opindex compatibility_version -@opindex current_version -@opindex dead_strip -@opindex dependency-file -@opindex dylib_file -@opindex dylinker_install_name -@opindex dynamic -@opindex exported_symbols_list -@opindex filelist -@opindex flat_namespace -@opindex force_flat_namespace -@opindex headerpad_max_install_names -@opindex image_base -@opindex init -@opindex install_name -@opindex keep_private_externs -@opindex multi_module -@opindex multiply_defined -@opindex multiply_defined_unused -@opindex noall_load -@opindex no_dead_strip_inits_and_terms -@opindex nofixprebinding -@opindex nomultidefs -@opindex noprebind -@opindex noseglinkedit -@opindex pagezero_size -@opindex prebind -@opindex prebind_all_twolevel_modules -@opindex private_bundle -@opindex read_only_relocs -@opindex sectalign -@opindex sectobjectsymbols -@opindex whyload -@opindex seg1addr -@opindex sectcreate -@opindex sectobjectsymbols -@opindex sectorder -@opindex segaddr -@opindex segs_read_only_addr -@opindex segs_read_write_addr -@opindex seg_addr_table -@opindex seg_addr_table_filename -@opindex seglinkedit -@opindex segprot -@opindex segs_read_only_addr -@opindex segs_read_write_addr -@opindex single_module -@opindex static -@opindex sub_library -@opindex sub_umbrella -@opindex twolevel_namespace -@opindex umbrella -@opindex undefined -@opindex unexported_symbols_list -@opindex weak_reference_mismatches -@opindex whatsloaded - -These options are passed to the Darwin linker. The Darwin linker man page -describes them in detail. -@end table - -@c APPLE LOCAL prune man page -@ignore -@node DEC Alpha Options -@subsection DEC Alpha Options - -These @samp{-m} options are defined for the DEC Alpha implementations: - -@table @gcctabopt -@item -mno-soft-float -@itemx -msoft-float -@opindex mno-soft-float -@opindex msoft-float -Use (do not use) the hardware floating-point instructions for -floating-point operations. When @option{-msoft-float} is specified, -functions in @file{libgcc.a} will be used to perform floating-point -operations. Unless they are replaced by routines that emulate the -floating-point operations, or compiled in such a way as to call such -emulations routines, these routines will issue floating-point -operations. If you are compiling for an Alpha without floating-point -operations, you must ensure that the library is built so as not to call -them. - -Note that Alpha implementations without floating-point operations are -required to have floating-point registers. - -@item -mfp-reg -@itemx -mno-fp-regs -@opindex mfp-reg -@opindex mno-fp-regs -Generate code that uses (does not use) the floating-point register set. -@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point -register set is not used, floating point operands are passed in integer -registers as if they were integers and floating-point results are passed -in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence, -so any function with a floating-point argument or return value called by code -compiled with @option{-mno-fp-regs} must also be compiled with that -option. - -A typical use of this option is building a kernel that does not use, -and hence need not save and restore, any floating-point registers. - -@item -mieee -@opindex mieee -The Alpha architecture implements floating-point hardware optimized for -maximum performance. It is mostly compliant with the IEEE floating -point standard. However, for full compliance, software assistance is -required. This option generates code fully IEEE compliant code -@emph{except} that the @var{inexact-flag} is not maintained (see below). -If this option is turned on, the preprocessor macro @code{_IEEE_FP} is -defined during compilation. The resulting code is less efficient but is -able to correctly support denormalized numbers and exceptional IEEE -values such as not-a-number and plus/minus infinity. Other Alpha -compilers call this option @option{-ieee_with_no_inexact}. - -@item -mieee-with-inexact -@opindex mieee-with-inexact -This is like @option{-mieee} except the generated code also maintains -the IEEE @var{inexact-flag}. Turning on this option causes the -generated code to implement fully-compliant IEEE math. In addition to -@code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor -macro. On some Alpha implementations the resulting code may execute -significantly slower than the code generated by default. Since there is -very little code that depends on the @var{inexact-flag}, you should -normally not specify this option. Other Alpha compilers call this -option @option{-ieee_with_inexact}. - -@item -mfp-trap-mode=@var{trap-mode} -@opindex mfp-trap-mode -This option controls what floating-point related traps are enabled. -Other Alpha compilers call this option @option{-fptm @var{trap-mode}}. -The trap mode can be set to one of four values: - -@table @samp -@item n -This is the default (normal) setting. The only traps that are enabled -are the ones that cannot be disabled in software (e.g., division by zero -trap). - -@item u -In addition to the traps enabled by @samp{n}, underflow traps are enabled -as well. - -@item su -Like @samp{u}, but the instructions are marked to be safe for software -completion (see Alpha architecture manual for details). - -@item sui -Like @samp{su}, but inexact traps are enabled as well. -@end table - -@item -mfp-rounding-mode=@var{rounding-mode} -@opindex mfp-rounding-mode -Selects the IEEE rounding mode. Other Alpha compilers call this option -@option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one -of: - -@table @samp -@item n -Normal IEEE rounding mode. Floating point numbers are rounded towards -the nearest machine number or towards the even machine number in case -of a tie. - -@item m -Round towards minus infinity. - -@item c -Chopped rounding mode. Floating point numbers are rounded towards zero. - -@item d -Dynamic rounding mode. A field in the floating point control register -(@var{fpcr}, see Alpha architecture reference manual) controls the -rounding mode in effect. The C library initializes this register for -rounding towards plus infinity. Thus, unless your program modifies the -@var{fpcr}, @samp{d} corresponds to round towards plus infinity. -@end table - -@item -mtrap-precision=@var{trap-precision} -@opindex mtrap-precision -In the Alpha architecture, floating point traps are imprecise. This -means without software assistance it is impossible to recover from a -floating trap and program execution normally needs to be terminated. -GCC can generate code that can assist operating system trap handlers -in determining the exact location that caused a floating point trap. -Depending on the requirements of an application, different levels of -precisions can be selected: - -@table @samp -@item p -Program precision. This option is the default and means a trap handler -can only identify which program caused a floating point exception. - -@item f -Function precision. The trap handler can determine the function that -caused a floating point exception. - -@item i -Instruction precision. The trap handler can determine the exact -instruction that caused a floating point exception. -@end table - -Other Alpha compilers provide the equivalent options called -@option{-scope_safe} and @option{-resumption_safe}. - -@item -mieee-conformant -@opindex mieee-conformant -This option marks the generated code as IEEE conformant. You must not -use this option unless you also specify @option{-mtrap-precision=i} and either -@option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect -is to emit the line @samp{.eflag 48} in the function prologue of the -generated assembly file. Under DEC Unix, this has the effect that -IEEE-conformant math library routines will be linked in. - -@item -mbuild-constants -@opindex mbuild-constants -Normally GCC examines a 32- or 64-bit integer constant to -see if it can construct it from smaller constants in two or three -instructions. If it cannot, it will output the constant as a literal and -generate code to load it from the data segment at runtime. - -Use this option to require GCC to construct @emph{all} integer constants -using code, even if it takes more instructions (the maximum is six). - -You would typically use this option to build a shared library dynamic -loader. Itself a shared library, it must relocate itself in memory -before it can find the variables and constants in its own data segment. - -@item -malpha-as -@itemx -mgas -@opindex malpha-as -@opindex mgas -Select whether to generate code to be assembled by the vendor-supplied -assembler (@option{-malpha-as}) or by the GNU assembler @option{-mgas}. - -@item -mbwx -@itemx -mno-bwx -@itemx -mcix -@itemx -mno-cix -@itemx -mfix -@itemx -mno-fix -@itemx -mmax -@itemx -mno-max -@opindex mbwx -@opindex mno-bwx -@opindex mcix -@opindex mno-cix -@opindex mfix -@opindex mno-fix -@opindex mmax -@opindex mno-max -Indicate whether GCC should generate code to use the optional BWX, -CIX, FIX and MAX instruction sets. The default is to use the instruction -sets supported by the CPU type specified via @option{-mcpu=} option or that -of the CPU on which GCC was built if none was specified. - -@item -mfloat-vax -@itemx -mfloat-ieee -@opindex mfloat-vax -@opindex mfloat-ieee -Generate code that uses (does not use) VAX F and G floating point -arithmetic instead of IEEE single and double precision. - -@item -mexplicit-relocs -@itemx -mno-explicit-relocs -@opindex mexplicit-relocs -@opindex mno-explicit-relocs -Older Alpha assemblers provided no way to generate symbol relocations -except via assembler macros. Use of these macros does not allow -optimal instruction scheduling. GNU binutils as of version 2.12 -supports a new syntax that allows the compiler to explicitly mark -which relocations should apply to which instructions. This option -is mostly useful for debugging, as GCC detects the capabilities of -the assembler when it is built and sets the default accordingly. - -@item -msmall-data -@itemx -mlarge-data -@opindex msmall-data -@opindex mlarge-data -When @option{-mexplicit-relocs} is in effect, static data is -accessed via @dfn{gp-relative} relocations. When @option{-msmall-data} -is used, objects 8 bytes long or smaller are placed in a @dfn{small data area} -(the @code{.sdata} and @code{.sbss} sections) and are accessed via -16-bit relocations off of the @code{$gp} register. This limits the -size of the small data area to 64KB, but allows the variables to be -directly accessed via a single instruction. - -The default is @option{-mlarge-data}. With this option the data area -is limited to just below 2GB@. Programs that require more than 2GB of -data must use @code{malloc} or @code{mmap} to allocate the data in the -heap instead of in the program's data segment. - -When generating code for shared libraries, @option{-fpic} implies -@option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}. - -@item -msmall-text -@itemx -mlarge-text -@opindex msmall-text -@opindex mlarge-text -When @option{-msmall-text} is used, the compiler assumes that the -code of the entire program (or shared library) fits in 4MB, and is -thus reachable with a branch instruction. When @option{-msmall-data} -is used, the compiler can assume that all local symbols share the -same @code{$gp} value, and thus reduce the number of instructions -required for a function call from 4 to 1. - -The default is @option{-mlarge-text}. - -@item -mcpu=@var{cpu_type} -@opindex mcpu -Set the instruction set and instruction scheduling parameters for -machine type @var{cpu_type}. You can specify either the @samp{EV} -style name or the corresponding chip number. GCC supports scheduling -parameters for the EV4, EV5 and EV6 family of processors and will -choose the default values for the instruction set from the processor -you specify. If you do not specify a processor type, GCC will default -to the processor on which the compiler was built. - -Supported values for @var{cpu_type} are - -@table @samp -@item ev4 -@itemx ev45 -@itemx 21064 -Schedules as an EV4 and has no instruction set extensions. - -@item ev5 -@itemx 21164 -Schedules as an EV5 and has no instruction set extensions. - -@item ev56 -@itemx 21164a -Schedules as an EV5 and supports the BWX extension. - -@item pca56 -@itemx 21164pc -@itemx 21164PC -Schedules as an EV5 and supports the BWX and MAX extensions. - -@item ev6 -@itemx 21264 -Schedules as an EV6 and supports the BWX, FIX, and MAX extensions. - -@item ev67 -@itemx 21264a -Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions. -@end table - -@item -mtune=@var{cpu_type} -@opindex mtune -Set only the instruction scheduling parameters for machine type -@var{cpu_type}. The instruction set is not changed. - -@item -mmemory-latency=@var{time} -@opindex mmemory-latency -Sets the latency the scheduler should assume for typical memory -references as seen by the application. This number is highly -dependent on the memory access patterns used by the application -and the size of the external cache on the machine. - -Valid options for @var{time} are - -@table @samp -@item @var{number} -A decimal number representing clock cycles. - -@item L1 -@itemx L2 -@itemx L3 -@itemx main -The compiler contains estimates of the number of clock cycles for -``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches -(also called Dcache, Scache, and Bcache), as well as to main memory. -Note that L3 is only valid for EV5. - -@end table -@end table - -@node DEC Alpha/VMS Options -@subsection DEC Alpha/VMS Options - -These @samp{-m} options are defined for the DEC Alpha/VMS implementations: - -@table @gcctabopt -@item -mvms-return-codes -@opindex mvms-return-codes -Return VMS condition codes from main. The default is to return POSIX -style condition (e.g.@ error) codes. -@end table - -@node FRV Options -@subsection FRV Options -@cindex FRV Options - -@table @gcctabopt -@item -mgpr-32 -@opindex mgpr-32 - -Only use the first 32 general purpose registers. - -@item -mgpr-64 -@opindex mgpr-64 - -Use all 64 general purpose registers. - -@item -mfpr-32 -@opindex mfpr-32 - -Use only the first 32 floating point registers. - -@item -mfpr-64 -@opindex mfpr-64 - -Use all 64 floating point registers - -@item -mhard-float -@opindex mhard-float - -Use hardware instructions for floating point operations. - -@item -msoft-float -@opindex msoft-float - -Use library routines for floating point operations. - -@item -malloc-cc -@opindex malloc-cc - -Dynamically allocate condition code registers. - -@item -mfixed-cc -@opindex mfixed-cc - -Do not try to dynamically allocate condition code registers, only -use @code{icc0} and @code{fcc0}. - -@item -mdword -@opindex mdword - -Change ABI to use double word insns. - -@item -mno-dword -@opindex mno-dword - -Do not use double word instructions. - -@item -mdouble -@opindex mdouble - -Use floating point double instructions. - -@item -mno-double -@opindex mno-double - -Do not use floating point double instructions. - -@item -mmedia -@opindex mmedia - -Use media instructions. - -@item -mno-media -@opindex mno-media - -Do not use media instructions. - -@item -mmuladd -@opindex mmuladd - -Use multiply and add/subtract instructions. - -@item -mno-muladd -@opindex mno-muladd - -Do not use multiply and add/subtract instructions. - -@item -mfdpic -@opindex mfdpic - -Select the FDPIC ABI, that uses function descriptors to represent -pointers to functions. Without any PIC/PIE-related options, it -implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it -assumes GOT entries and small data are within a 12-bit range from the -GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets -are computed with 32 bits. - -@item -minline-plt -@opindex minline-plt - -Enable inlining of PLT entries in function calls to functions that are -not known to bind locally. It has no effect without @option{-mfdpic}. -It's enabled by default if optimizing for speed and compiling for -shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an -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 - -Enable the use of @code{GPREL} relocations in the FDPIC ABI for data -that is known to be in read-only sections. It's enabled by default, -except for @option{-fpic} or @option{-fpie}: even though it may help -make the global offset table smaller, it trades 1 instruction for 4. -With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4, -one of which may be shared by multiple symbols, and it avoids the need -for a GOT entry for the referenced symbol, so it's more likely to be a -win. If it is not, @option{-mno-gprel-ro} can be used to disable it. - -@item -multilib-library-pic -@opindex multilib-library-pic - -Link with the (library, not FD) pic libraries. It's implied by -@option{-mlibrary-pic}, as well as by @option{-fPIC} and -@option{-fpic} without @option{-mfdpic}. You should never have to use -it explicitly. - -@item -mlinked-fp -@opindex mlinked-fp - -Follow the EABI requirement of always creating a frame pointer whenever -a stack frame is allocated. This option is enabled by default and can -be disabled with @option{-mno-linked-fp}. - -@item -mlong-calls -@opindex mlong-calls - -Use indirect addressing to call functions outside the current -compilation unit. This allows the functions to be placed anywhere -within the 32-bit address space. - -@item -malign-labels -@opindex malign-labels - -Try to align labels to an 8-byte boundary by inserting nops into the -previous packet. This option only has an effect when VLIW packing -is enabled. It doesn't create new packets; it merely adds nops to -existing ones. - -@item -mlibrary-pic -@opindex mlibrary-pic - -Generate position-independent EABI code. - -@item -macc-4 -@opindex macc-4 - -Use only the first four media accumulator registers. - -@item -macc-8 -@opindex macc-8 - -Use all eight media accumulator registers. - -@item -mpack -@opindex mpack - -Pack VLIW instructions. - -@item -mno-pack -@opindex mno-pack - -Do not pack VLIW instructions. - -@item -mno-eflags -@opindex mno-eflags - -Do not mark ABI switches in e_flags. - -@item -mcond-move -@opindex mcond-move - -Enable the use of conditional-move instructions (default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-cond-move -@opindex mno-cond-move - -Disable the use of conditional-move instructions. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mscc -@opindex mscc - -Enable the use of conditional set instructions (default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-scc -@opindex mno-scc - -Disable the use of conditional set instructions. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mcond-exec -@opindex mcond-exec - -Enable the use of conditional execution (default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-cond-exec -@opindex mno-cond-exec - -Disable the use of conditional execution. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mvliw-branch -@opindex mvliw-branch - -Run a pass to pack branches into VLIW instructions (default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-vliw-branch -@opindex mno-vliw-branch - -Do not run a pass to pack branches into VLIW instructions. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mmulti-cond-exec -@opindex mmulti-cond-exec - -Enable optimization of @code{&&} and @code{||} in conditional execution -(default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-multi-cond-exec -@opindex mno-multi-cond-exec - -Disable optimization of @code{&&} and @code{||} in conditional execution. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mnested-cond-exec -@opindex mnested-cond-exec - -Enable nested conditional execution optimizations (default). - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -mno-nested-cond-exec -@opindex mno-nested-cond-exec - -Disable nested conditional execution optimizations. - -This switch is mainly for debugging the compiler and will likely be removed -in a future version. - -@item -moptimize-membar -@opindex moptimize-membar - -This switch removes redundant @code{membar} instructions from the -compiler generated code. It is enabled by default. - -@item -mno-optimize-membar -@opindex mno-optimize-membar - -This switch disables the automatic removal of redundant @code{membar} -instructions from the generated code. - -@item -mtomcat-stats -@opindex mtomcat-stats - -Cause gas to print out tomcat statistics. - -@item -mcpu=@var{cpu} -@opindex mcpu - -Select the processor type for which to generate code. Possible values are -@samp{frv}, @samp{fr550}, @samp{tomcat}, @samp{fr500}, @samp{fr450}, -@samp{fr405}, @samp{fr400}, @samp{fr300} and @samp{simple}. - -@end table - -@node GNU/Linux Options -@subsection GNU/Linux Options - -These @samp{-m} options are defined for GNU/Linux targets: - -@table @gcctabopt -@item -mglibc -@opindex mglibc -Use the GNU C library instead of uClibc. This is the default except -on @samp{*-*-linux-*uclibc*} targets. - -@item -muclibc -@opindex muclibc -Use uClibc instead of the GNU C library. This is the default on -@samp{*-*-linux-*uclibc*} targets. -@end table - -@node H8/300 Options -@subsection H8/300 Options - -These @samp{-m} options are defined for the H8/300 implementations: - -@table @gcctabopt -@item -mrelax -@opindex mrelax -Shorten some address references at link time, when possible; uses the -linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300, -ld, Using ld}, for a fuller description. - -@item -mh -@opindex mh -Generate code for the H8/300H@. - -@item -ms -@opindex ms -Generate code for the H8S@. - -@item -mn -@opindex mn -Generate code for the H8S and H8/300H in the normal mode. This switch -must be used either with @option{-mh} or @option{-ms}. - -@item -ms2600 -@opindex ms2600 -Generate code for the H8S/2600. This switch must be used with @option{-ms}. - -@item -mint32 -@opindex mint32 -Make @code{int} data 32 bits by default. - -@item -malign-300 -@opindex malign-300 -On the H8/300H and H8S, use the same alignment rules as for the H8/300. -The default for the H8/300H and H8S is to align longs and floats on 4 -byte boundaries. -@option{-malign-300} causes them to be aligned on 2 byte boundaries. -This option has no effect on the H8/300. -@end table - -@node HPPA Options -@subsection HPPA Options -@cindex HPPA Options - -These @samp{-m} options are defined for the HPPA family of computers: - -@table @gcctabopt -@item -march=@var{architecture-type} -@opindex march -Generate code for the specified architecture. The choices for -@var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA -1.1, and @samp{2.0} for PA 2.0 processors. Refer to -@file{/usr/lib/sched.models} on an HP-UX system to determine the proper -architecture option for your machine. Code compiled for lower numbered -architectures will run on higher numbered architectures, but not the -other way around. - -@item -mpa-risc-1-0 -@itemx -mpa-risc-1-1 -@itemx -mpa-risc-2-0 -@opindex mpa-risc-1-0 -@opindex mpa-risc-1-1 -@opindex mpa-risc-2-0 -Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively. - -@item -mbig-switch -@opindex mbig-switch -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. - -@item -mjump-in-delay -@opindex mjump-in-delay -Fill delay slots of function calls with unconditional jump instructions -by modifying the return pointer for the function call to be the target -of the conditional jump. - -@item -mdisable-fpregs -@opindex mdisable-fpregs -Prevent floating point registers from being used in any manner. This is -necessary for compiling kernels which perform lazy context switching of -floating point registers. If you use this option and attempt to perform -floating point operations, the compiler will abort. - -@item -mdisable-indexing -@opindex mdisable-indexing -Prevent the compiler from using indexing address modes. This avoids some -rather obscure problems when compiling MIG generated code under MACH@. - -@item -mno-space-regs -@opindex mno-space-regs -Generate code that assumes the target has no space registers. This allows -GCC to generate faster indirect calls and use unscaled index address modes. - -Such code is suitable for level 0 PA systems and kernels. - -@item -mfast-indirect-calls -@opindex mfast-indirect-calls -Generate code that assumes calls never cross space boundaries. This -allows GCC to emit code which performs faster indirect calls. - -This option will not work in the presence of shared libraries or nested -functions. - -@item -mfixed-range=@var{register-range} -@opindex mfixed-range -Generate code treating the given register range as fixed registers. -A fixed register is one that the register allocator can not use. This is -useful when compiling kernel code. A register range is specified as -two registers separated by a dash. Multiple register ranges can be -specified separated by a comma. - -@item -mlong-load-store -@opindex mlong-load-store -Generate 3-instruction load and store sequences as sometimes required by -the HP-UX 10 linker. This is equivalent to the @samp{+k} option to -the HP compilers. - -@item -mportable-runtime -@opindex mportable-runtime -Use the portable calling conventions proposed by HP for ELF systems. - -@item -mgas -@opindex mgas -Enable the use of assembler directives only GAS understands. - -@item -mschedule=@var{cpu-type} -@opindex mschedule -Schedule code according to the constraints for the machine type -@var{cpu-type}. The choices for @var{cpu-type} are @samp{700} -@samp{7100}, @samp{7100LC}, @samp{7200}, @samp{7300} and @samp{8000}. Refer -to @file{/usr/lib/sched.models} on an HP-UX system to determine the -proper scheduling option for your machine. The default scheduling is -@samp{8000}. - -@item -mlinker-opt -@opindex mlinker-opt -Enable the optimization pass in the HP-UX linker. Note this makes symbolic -debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9 -linkers in which they give bogus error messages when linking some programs. - -@item -msoft-float -@opindex msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all HPPA -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded target @samp{hppa1.1-*-pro} -does provide software floating point support. - -@option{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @option{-msoft-float} in order for -this to work. - -@item -msio -@opindex msio -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@. - -@item -mgnu-ld -@opindex gnu-ld -Use GNU ld specific options. This passes @option{-shared} to ld when -building a shared library. It is the default when GCC is configured, -explicitly or implicitly, with the GNU linker. This option does not -have any affect on which ld is called, it only changes what parameters -are passed to that ld. The ld that is called is determined by the -@option{--with-ld} configure option, GCC's program search path, and -finally by the user's @env{PATH}. The linker used by GCC can be printed -using @samp{which `gcc -print-prog-name=ld`}. This option is only available -on the 64 bit HP-UX GCC, i.e. configured with @samp{hppa*64*-*-hpux*}. - -@item -mhp-ld -@opindex hp-ld -Use HP ld specific options. This passes @option{-b} to ld when building -a shared library and passes @option{+Accept TypeMismatch} to ld on all -links. It is the default when GCC is configured, explicitly or -implicitly, with the HP linker. This option does not have any affect on -which ld is called, it only changes what parameters are passed to that -ld. The ld that is called is determined by the @option{--with-ld} -configure option, GCC's program search path, and finally by the user's -@env{PATH}. The linker used by GCC can be printed using @samp{which -`gcc -print-prog-name=ld`}. This option is only available on the 64 bit -HP-UX GCC, i.e. configured with @samp{hppa*64*-*-hpux*}. - -@item -mlong-calls -@opindex mno-long-calls -Generate code that uses long call sequences. This ensures that a call -is always able to reach linker generated stubs. The default is to generate -long calls only when the distance from the call site to the beginning -of the function or translation unit, as the case may be, exceeds a -predefined limit set by the branch type being used. The limits for -normal calls are 7,600,000 and 240,000 bytes, respectively for the -PA 2.0 and PA 1.X architectures. Sibcalls are always limited at -240,000 bytes. - -Distances are measured from the beginning of functions when using the -@option{-ffunction-sections} option, or when using the @option{-mgas} -and @option{-mno-portable-runtime} options together under HP-UX with -the SOM linker. - -It is normally not desirable to use this option as it will degrade -performance. However, it may be useful in large applications, -particularly when partial linking is used to build the application. - -The types of long calls used depends on the capabilities of the -assembler and linker, and the type of code being generated. The -impact on systems that support long absolute calls, and long pic -symbol-difference or pc-relative calls should be relatively small. -However, an indirect call is used on 32-bit ELF systems in pic code -and it is quite long. - -@item -munix=@var{unix-std} -@opindex march -Generate compiler predefines and select a startfile for the specified -UNIX standard. The choices for @var{unix-std} are @samp{93}, @samp{95} -and @samp{98}. @samp{93} is supported on all HP-UX versions. @samp{95} -is available on HP-UX 10.10 and later. @samp{98} is available on HP-UX -11.11 and later. The default values are @samp{93} for HP-UX 10.00, -@samp{95} for HP-UX 10.10 though to 11.00, and @samp{98} for HP-UX 11.11 -and later. - -@option{-munix=93} provides the same predefines as GCC 3.3 and 3.4. -@option{-munix=95} provides additional predefines for @code{XOPEN_UNIX} -and @code{_XOPEN_SOURCE_EXTENDED}, and the startfile @file{unix95.o}. -@option{-munix=98} provides additional predefines for @code{_XOPEN_UNIX}, -@code{_XOPEN_SOURCE_EXTENDED}, @code{_INCLUDE__STDC_A1_SOURCE} and -@code{_INCLUDE_XOPEN_SOURCE_500}, and the startfile @file{unix98.o}. - -It is @emph{important} to note that this option changes the interfaces -for various library routines. It also affects the operational behavior -of the C library. Thus, @emph{extreme} care is needed in using this -option. - -Library code that is intended to operate with more than one UNIX -standard must test, set and restore the variable @var{__xpg4_extended_mask} -as appropriate. Most GNU software doesn't provide this capability. - -@item -nolibdld -@opindex nolibdld -Suppress the generation of link options to search libdld.sl when the -@option{-static} option is specified on HP-UX 10 and later. - -@item -static -@opindex static -The HP-UX implementation of setlocale in libc has a dependency on -libdld.sl. There isn't an archive version of libdld.sl. Thus, -when the @option{-static} option is specified, special link options -are needed to resolve this dependency. - -On HP-UX 10 and later, the GCC driver adds the necessary options to -link with libdld.sl when the @option{-static} option is specified. -This causes the resulting binary to be dynamic. On the 64-bit port, -the linkers generate dynamic binaries by default in any case. The -@option{-nolibdld} option can be used to prevent the GCC driver from -adding these link options. - -@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 -linker. -@end table -@c APPLE LOCAL prune man page -@end ignore - -@node i386 and x86-64 Options -@subsection Intel 386 and AMD x86-64 Options -@cindex i386 Options -@cindex x86-64 Options -@cindex Intel 386 Options -@cindex AMD x86-64 Options - -These @samp{-m} options are defined for the i386 and x86-64 family of -computers: - -@table @gcctabopt -@item -mtune=@var{cpu-type} -@opindex mtune -Tune to @var{cpu-type} everything applicable about the generated code, except -for the ABI and the set of available instructions. The choices for -@var{cpu-type} are: -@table @emph -@item generic -Produce code optimized for the most common IA32/AMD64/EM64T processors. -If you know the CPU on which your code will run, then you should use -the corresponding @option{-mtune} option instead of -@option{-mtune=generic}. But, if you do not know exactly what CPU users -of your application will have, then you should use this option. - -As new processors are deployed in the marketplace, the behavior of this -option will change. Therefore, if you upgrade to a newer version of -GCC, the code generated option will change to reflect the processors -that were most common when that version of GCC was released. - -There is no @option{-march=generic} option because @option{-march} -indicates the instruction set the compiler can use, and there is no -generic instruction set applicable to all processors. In contrast, -@option{-mtune} indicates the processor (or, in this case, collection of -processors) for which the code is optimized. -@item native -This selects the CPU to tune for at compilation time by determining -the processor type of the compiling machine. Using @option{-mtune=native} -will produce code optimized for the local machine under the constraints -of the selected instruction set. Using @option{-march=native} will -enable all instruction subsets supported by the local machine (hence -the result might not run on different machines). -@item i386 -Original Intel's i386 CPU@. -@item i486 -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 pentiumpro -Intel PentiumPro CPU@. -@item i686 -Same as @code{generic}, but when used as @code{march} option, PentiumPro -instruction set will be used, so the code will run on all i686 family chips. -@item pentium2 -Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support. -@item pentium3, pentium3m -Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set -support. -@item pentium-m -Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set -support. Used by Centrino notebooks. -@item pentium4, pentium4m -Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support. -@item prescott -Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction -set support. -@item nocona -Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, -SSE2 and SSE3 instruction set support. -@c APPLE LOCAL begin mainline -@item core2 -Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 -instruction set support. -@c APPLE LOCAL end mainline -@item k6 -AMD K6 CPU with MMX instruction set support. -@item k6-2, k6-3 -Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support. -@item athlon, athlon-tbird -AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions -support. -@item athlon-4, athlon-xp, athlon-mp -Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE -instruction set support. -@item k8, opteron, athlon64, athlon-fx -AMD K8 core based CPUs with x86-64 instruction set support. (This supersets -MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.) -@item winchip-c6 -IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction -set support. -@item winchip2 -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 -implemented for this chip.) -@item c3-2 -Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is -implemented for this chip.) -@end table - -While picking a specific @var{cpu-type} will schedule things appropriately -for that particular chip, the compiler will not generate any code that -does not run on the i386 without the @option{-march=@var{cpu-type}} option -being used. - -@item -march=@var{cpu-type} -@opindex march -Generate instructions for the machine type @var{cpu-type}. The choices -for @var{cpu-type} are the same as for @option{-mtune}. Moreover, -specifying @option{-march=@var{cpu-type}} implies @option{-mtune=@var{cpu-type}}. - -@item -mcpu=@var{cpu-type} -@opindex mcpu -A deprecated synonym for @option{-mtune}. - -@item -m386 -@itemx -m486 -@itemx -mpentium -@itemx -mpentiumpro -@opindex m386 -@opindex m486 -@opindex mpentium -@opindex mpentiumpro -These options are synonyms for @option{-mtune=i386}, @option{-mtune=i486}, -@option{-mtune=pentium}, and @option{-mtune=pentiumpro} respectively. -These synonyms are deprecated. - -@item -mfpmath=@var{unit} -@opindex march -Generate floating point arithmetics for selected unit @var{unit}. The choices -for @var{unit} are: - -@table @samp -@item 387 -Use the standard 387 floating point coprocessor present majority of chips and -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. - -This is the default choice for i386 compiler. - -@item sse -Use scalar floating point instructions present in the SSE instruction set. -This instruction set is supported by Pentium3 and newer chips, in the AMD line -by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE -instruction set supports only single precision arithmetics, thus the double and -extended precision arithmetics is still done using 387. Later version, present -only in Pentium4 and the future AMD x86-64 chips supports double precision -arithmetics too. - -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 -code that expects temporaries to be 80bit. - -This is the default choice for the x86-64 compiler. - -@item sse,387 -Attempt to utilize both instruction sets at once. This effectively double the -amount of available registers and on chips with separate execution units for -387 and SSE the execution resources too. Use this option with care, as it is -still experimental, because the GCC register allocator does not model separate -functional units well resulting in instable performance. -@end table - -@item -masm=@var{dialect} -@opindex masm=@var{dialect} -Output asm instructions using selected @var{dialect}. Supported -choices are @samp{intel} or @samp{att} (the default one). Darwin does -not support @samp{intel}. - -@item -mieee-fp -@itemx -mno-ieee-fp -@opindex mieee-fp -@opindex mno-ieee-fp -Control whether or not the compiler uses IEEE floating point -comparisons. These handle correctly the case where the result of a -comparison is unordered. - -@item -msoft-float -@opindex msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not part of GCC@. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. - -On machines where a function returns floating point results in the 80387 -register stack, some floating point opcodes may be emitted even if -@option{-msoft-float} is used. - -@item -mno-fp-ret-in-387 -@opindex mno-fp-ret-in-387 -Do not use the FPU registers for return values of functions. - -The usual calling convention has functions return values of types -@code{float} and @code{double} in an FPU register, even if there -is no FPU@. The idea is that the operating system should emulate -an FPU@. - -The option @option{-mno-fp-ret-in-387} causes such values to be returned -in ordinary CPU registers instead. - -@item -mno-fancy-math-387 -@opindex mno-fancy-math-387 -Some 387 emulators do not support the @code{sin}, @code{cos} and -@code{sqrt} instructions for the 387. Specify this option to avoid -generating those instructions. This option is the default on FreeBSD, -OpenBSD and NetBSD@. This option is overridden when @option{-march} -indicates that the target cpu will always have an FPU and so the -instruction will not need emulation. As of revision 2.6.1, these -instructions are not generated unless you also use the -@option{-funsafe-math-optimizations} switch. - -@item -malign-double -@itemx -mno-align-double -@opindex malign-double -@opindex mno-align-double -Control whether GCC aligns @code{double}, @code{long double}, and -@code{long long} variables on a two word boundary or a one word -boundary. Aligning @code{double} variables on a two word boundary will -produce code that runs somewhat faster on a @samp{Pentium} at the -expense of more memory. - -On x86-64, @option{-malign-double} is enabled by default. - -@strong{Warning:} if you use the @option{-malign-double} switch, -structures containing the above types will be aligned differently than -the published application binary interface specifications for the 386 -and will not be binary compatible with structures in code compiled -without that switch. - -@item -m96bit-long-double -@itemx -m128bit-long-double -@opindex m96bit-long-double -@opindex m128bit-long-double -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. - -Modern architectures (Pentium and newer) would prefer @code{long double} -to be aligned to an 8 or 16 byte boundary. In arrays or structures -conforming to the ABI, this would not be possible. So specifying a -@option{-m128bit-long-double} will align @code{long double} -to a 16 byte boundary by padding the @code{long double} with an additional -32 bit zero. - -In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as -its ABI specifies that @code{long double} is to be aligned on 16 byte boundary. - -Notice that neither of these options enable any extra precision over the x87 -standard of 80 bits for a @code{long double}. - -@strong{Warning:} if you override the default value for your target ABI, the -structures and arrays containing @code{long double} variables will change -their size as well as function calling convention for function taking -@code{long double} will be modified. Hence they will not be binary -compatible with arrays or structures in code compiled without that switch. - -@item -mmlarge-data-threshold=@var{number} -@opindex mlarge-data-threshold=@var{number} -When @option{-mcmodel=medium} is specified, the data greater than -@var{threshold} are placed in large data section. This value must be the -same across all object linked into the binary and defaults to 65535. - -@item -msvr3-shlib -@itemx -mno-svr3-shlib -@opindex msvr3-shlib -@opindex mno-svr3-shlib -Control whether GCC places uninitialized local variables into the -@code{bss} or @code{data} segments. @option{-msvr3-shlib} places them -into @code{bss}. These options are meaningful only on System V Release 3. - -@item -mrtd -@opindex mrtd -Use a different function-calling convention, in which functions that -take a fixed number of arguments return with the @code{ret} @var{num} -instruction, which pops their arguments while returning. This saves one -instruction in the caller since there is no need to pop the arguments -there. - -You can specify that an individual function is called with this calling -sequence with the function attribute @samp{stdcall}. You can also -override the @option{-mrtd} option by using the function attribute -@samp{cdecl}. @xref{Function Attributes}. - -@strong{Warning:} this calling convention is incompatible with the one -normally used on Unix, so you cannot use it if you need to call -libraries compiled with the Unix compiler. - -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including @code{printf}); -otherwise incorrect code will be generated for calls to those -functions. - -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) - -@item -mregparm=@var{num} -@opindex mregparm -Control how many registers are used to pass integer arguments. By -default, no registers are used to pass arguments, and at most 3 -registers can be used. You can control this behavior for a specific -function by using the function attribute @samp{regparm}. -@xref{Function Attributes}. - -@strong{Warning:} if you use this switch, and -@var{num} is nonzero, then you must build all modules with the same -value, including any libraries. This includes the system libraries and -startup modules. - -@item -msseregparm -@opindex msseregparm -Use SSE register passing conventions for float and double arguments -and return values. You can control this behavior for a specific -function by using the function attribute @samp{sseregparm}. -@xref{Function Attributes}. - -@strong{Warning:} if you use this switch then you must build all -modules with the same value, including any libraries. This includes -the system libraries and startup modules. - -@item -mstackrealign -@opindex mstackrealign -Realign the stack at entry. On the Intel x86, the -@option{-mstackrealign} option will generate an alternate prologue and -epilogue that realigns the runtime stack. This supports mixing legacy -codes that keep a 4-byte aligned stack with modern codes that keep a -16-byte stack for SSE compatibility. The alternate prologue and -epilogue are slower and bigger than the regular ones, and the -alternate prologue requires an extra scratch register; this lowers the -number of registers available if used in conjunction with the -@code{regparm} attribute. The @option{-mstackrealign} option is -incompatible with the nested function prologue; this is considered a -hard error. See also the attribute @code{force_align_arg_pointer}, -applicable to individual functions. - -@item -mpreferred-stack-boundary=@var{num} -@opindex mpreferred-stack-boundary -Attempt to keep the stack boundary aligned to a 2 raised to @var{num} -byte boundary. If @option{-mpreferred-stack-boundary} is not specified, -the default is 4 (16 bytes or 128 bits). - -On Pentium and PentiumPro, @code{double} and @code{long double} values -should be aligned to an 8 byte boundary (see @option{-malign-double}) or -suffer significant run time performance penalties. On Pentium III, the -Streaming SIMD Extension (SSE) data type @code{__m128} may not work -properly if it is not 16 byte aligned. - -To ensure proper alignment of this values on the stack, the stack boundary -must be as aligned as that required by any value stored on the stack. -Further, every function must be generated such that it keeps the stack -aligned. Thus calling a function compiled with a higher preferred -stack boundary from a function compiled with a lower preferred stack -boundary will most likely misalign the stack. It is recommended that -libraries that use callbacks always use the default setting. - -This extra alignment does consume extra stack space, and generally -increases code size. Code that is sensitive to stack space usage, such -as embedded systems and operating system kernels, may want to reduce the -preferred alignment to @option{-mpreferred-stack-boundary=2}. - -@item -mmmx -@itemx -mno-mmx -@item -msse -@itemx -mno-sse -@item -msse2 -@itemx -mno-sse2 -@item -msse3 -@itemx -mno-sse3 -@c APPLE LOCAL begin mainline -@item -mssse3 -@itemx -mno-ssse3 -@c APPLE LOCAL end mainline -@c APPLE LOCAL begin 5612787 sse4 -@item -msse4.1 -@itemx -mno-sse4.1 -@item -msse4.2 -@itemx -mno-sse4.2 -@item -msse4 -@itemx -mno-sse4 -@item -msse4a -@item -mno-sse4a -@c APPLE LOCAL end 5612787 sse4 -@item -m3dnow -@itemx -mno-3dnow -@opindex mmmx -@opindex mno-mmx -@opindex msse -@opindex mno-sse -@opindex m3dnow -@opindex mno-3dnow -These switches enable or disable the use of instructions in the MMX, -@c APPLE LOCAL begin 5612787 sse4 -SSE, SSE2, SSE3, SSSE3, 3Dnow, SSE4.1, SSE4.2, and SSE4A extended -instruction sets. These extensions are -@c APPLE LOCAL end 5612787 sse4 -also available as built-in functions: see @ref{X86 Built-in Functions}, -for details of the functions enabled and disabled by these switches. - -To have SSE/SSE2 instructions generated automatically from floating-point -code (as opposed to 387 instructions), see @option{-mfpmath=sse}. - -These options will enable GCC to use these extended instructions in -generated code, even without @option{-mfpmath=sse}. Applications which -perform runtime CPU detection must compile separate files for each -supported architecture, using the appropriate flags. In particular, -the file containing the CPU detection code should be compiled without -these options. - -@item -mpush-args -@itemx -mno-push-args -@opindex mpush-args -@opindex mno-push-args -Use PUSH operations to store outgoing parameters. This method is shorter -and usually equally fast as method using SUB/MOV operations and is enabled -by default. In some cases disabling it may improve performance because of -improved scheduling and reduced dependencies. - -@item -maccumulate-outgoing-args -@opindex maccumulate-outgoing-args -If enabled, the maximum amount of space required for outgoing arguments will be -computed in the function prologue. This is faster on most modern CPUs -because of reduced dependencies, improved scheduling and reduced stack usage -when preferred stack boundary is not equal to 2. The drawback is a notable -increase in code size. This switch implies @option{-mno-push-args}. - -@item -mthreads -@opindex mthreads -Support thread-safe exception handling on @samp{Mingw32}. Code that relies -on thread-safe exception handling must compile and link all code with the -@option{-mthreads} option. When compiling, @option{-mthreads} defines -@option{-D_MT}; when linking, it links in a special thread helper library -@option{-lmingwthrd} which cleans up per thread exception handling data. - -@item -mno-align-stringops -@opindex mno-align-stringops -Do not align destination of inlined string operations. This switch reduces -code size and improves performance in case the destination is already aligned, -but GCC doesn't know about it. - -@item -minline-all-stringops -@opindex minline-all-stringops -By default GCC inlines string operations only when destination is known to be -aligned at least to 4 byte boundary. This enables more inlining, increase code -size, but may improve performance of code that depends on fast memcpy, strlen -and memset for short lengths. - -@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 -mtls-direct-seg-refs -@itemx -mno-tls-direct-seg-refs -@opindex mtls-direct-seg-refs -Controls whether TLS variables may be accessed with offsets from the -TLS segment register (@code{%gs} for 32-bit, @code{%fs} for 64-bit), -or whether the thread base pointer must be added. Whether or not this -is legal depends on the operating system, and whether it maps the -segment to cover the entire TLS area. - -For systems that use GNU libc, the default is on. -@end table - -These @samp{-m} switches are supported in addition to the above -on AMD x86-64 processors in 64-bit environments. - -@table @gcctabopt -@item -m32 -@itemx -m64 -@opindex m32 -@opindex m64 -Generate code for a 32-bit or 64-bit environment. -The 32-bit environment sets int, long and pointer to 32 bits and -generates code that runs on any i386 system. -The 64-bit environment sets int to 32 bits and long and pointer -to 64 bits and generates code for AMD's x86-64 architecture. For -darwin only the -m64 option turns off the @option{-fno-pic} and -@option{-mdynamic-no-pic} options. - -@item -mno-red-zone -@opindex no-red-zone -Do not use a so called red zone for x86-64 code. The red zone is mandated -by the x86-64 ABI, it is a 128-byte area beyond the location of the -stack pointer that will not be modified by signal or interrupt handlers -and therefore can be used for temporary data without adjusting the stack -pointer. The flag @option{-mno-red-zone} disables this red zone. - -@item -mcmodel=small -@opindex mcmodel=small -Generate code for the small code model: the program and its symbols must -be linked in the lower 2 GB of the address space. Pointers are 64 bits. -Programs can be statically or dynamically linked. This is the default -code model. - -@item -mcmodel=kernel -@opindex mcmodel=kernel -Generate code for the kernel code model. The kernel runs in the -negative 2 GB of the address space. -This model has to be used for Linux kernel code. - -@item -mcmodel=medium -@opindex mcmodel=medium -Generate code for the medium model: The program is linked in the lower 2 -GB of the address space but symbols can be located anywhere in the -address space. Programs can be statically or dynamically linked, but -building of shared libraries are not supported with the medium model. - -@item -mcmodel=large -@opindex mcmodel=large -Generate code for the large model: This model makes no assumptions -about addresses and sizes of sections. Currently GCC does not implement -this model. - -@c APPLE LOCAL begin 5946347 ms_struct support -@item -mms-bitfields -@opindex mms-bitfields -Set the default structure layout to be compatible with the Microsoft -compiler standard. This is equivalent to adding an @code{ms_struct} -attribute to each structure and union tag definition. The default is -@option{mno-ms-bitfields}. -@c APPLE LOCAL end 5946347 ms_struct support - -@end table - -@c APPLE LOCAL prune man page -@ignore -@node IA-64 Options -@subsection IA-64 Options -@cindex IA-64 Options - -These are the @samp{-m} options defined for the Intel IA-64 architecture. - -@table @gcctabopt -@item -mbig-endian -@opindex mbig-endian -Generate code for a big endian target. This is the default for HP-UX@. - -@item -mlittle-endian -@opindex mlittle-endian -Generate code for a little endian target. This is the default for AIX5 -and GNU/Linux. - -@item -mgnu-as -@itemx -mno-gnu-as -@opindex mgnu-as -@opindex mno-gnu-as -Generate (or don't) code for the GNU assembler. This is the default. -@c Also, this is the default if the configure option @option{--with-gnu-as} -@c is used. - -@item -mgnu-ld -@itemx -mno-gnu-ld -@opindex mgnu-ld -@opindex mno-gnu-ld -Generate (or don't) code for the GNU linker. This is the default. -@c Also, this is the default if the configure option @option{--with-gnu-ld} -@c is used. - -@item -mno-pic -@opindex mno-pic -Generate code that does not use a global pointer register. The result -is not position independent code, and violates the IA-64 ABI@. - -@item -mvolatile-asm-stop -@itemx -mno-volatile-asm-stop -@opindex mvolatile-asm-stop -@opindex mno-volatile-asm-stop -Generate (or don't) a stop bit immediately before and after volatile asm -statements. - -@item -mregister-names -@itemx -mno-register-names -@opindex mregister-names -@opindex mno-register-names -Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for -the stacked registers. This may make assembler output more readable. - -@item -mno-sdata -@itemx -msdata -@opindex mno-sdata -@opindex msdata -Disable (or enable) optimizations that use the small data section. This may -be useful for working around optimizer bugs. - -@item -mconstant-gp -@opindex mconstant-gp -Generate code that uses a single constant global pointer value. This is -useful when compiling kernel code. - -@item -mauto-pic -@opindex mauto-pic -Generate code that is self-relocatable. This implies @option{-mconstant-gp}. -This is useful when compiling firmware code. - -@item -minline-float-divide-min-latency -@opindex minline-float-divide-min-latency -Generate code for inline divides of floating point values -using the minimum latency algorithm. - -@item -minline-float-divide-max-throughput -@opindex minline-float-divide-max-throughput -Generate code for inline divides of floating point values -using the maximum throughput algorithm. - -@item -minline-int-divide-min-latency -@opindex minline-int-divide-min-latency -Generate code for inline divides of integer values -using the minimum latency algorithm. - -@item -minline-int-divide-max-throughput -@opindex minline-int-divide-max-throughput -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 -@opindex mdwarf2-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. -A fixed register is one that the register allocator can not use. This is -useful when compiling kernel code. A register range is specified as -two registers separated by a dash. Multiple register ranges can be -specified separated by a comma. - -@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=@var{cpu-type} -@opindex mtune -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. - -@item -mno-sched-br-data-spec -@itemx -msched-br-data-spec -@opindex mno-sched-br-data-spec -@opindex msched-br-data-spec -(Dis/En)able data speculative scheduling before reload. -This will result in generation of the ld.a instructions and -the corresponding check instructions (ld.c / chk.a). -The default is 'disable'. - -@item -msched-ar-data-spec -@itemx -mno-sched-ar-data-spec -@opindex msched-ar-data-spec -@opindex mno-sched-ar-data-spec -(En/Dis)able data speculative scheduling after reload. -This will result in generation of the ld.a instructions and -the corresponding check instructions (ld.c / chk.a). -The default is 'enable'. - -@item -mno-sched-control-spec -@itemx -msched-control-spec -@opindex mno-sched-control-spec -@opindex msched-control-spec -(Dis/En)able control speculative scheduling. This feature is -available only during region scheduling (i.e. before reload). -This will result in generation of the ld.s instructions and -the corresponding check instructions chk.s . -The default is 'disable'. - -@item -msched-br-in-data-spec -@itemx -mno-sched-br-in-data-spec -@opindex msched-br-in-data-spec -@opindex mno-sched-br-in-data-spec -(En/Dis)able speculative scheduling of the instructions that -are dependent on the data speculative loads before reload. -This is effective only with @option{-msched-br-data-spec} enabled. -The default is 'enable'. - -@item -msched-ar-in-data-spec -@itemx -mno-sched-ar-in-data-spec -@opindex msched-ar-in-data-spec -@opindex mno-sched-ar-in-data-spec -(En/Dis)able speculative scheduling of the instructions that -are dependent on the data speculative loads after reload. -This is effective only with @option{-msched-ar-data-spec} enabled. -The default is 'enable'. - -@item -msched-in-control-spec -@itemx -mno-sched-in-control-spec -@opindex msched-in-control-spec -@opindex mno-sched-in-control-spec -(En/Dis)able speculative scheduling of the instructions that -are dependent on the control speculative loads. -This is effective only with @option{-msched-control-spec} enabled. -The default is 'enable'. - -@item -msched-ldc -@itemx -mno-sched-ldc -@opindex msched-ldc -@opindex mno-sched-ldc -(En/Dis)able use of simple data speculation checks ld.c . -If disabled, only chk.a instructions will be emitted to check -data speculative loads. -The default is 'enable'. - -@item -mno-sched-control-ldc -@itemx -msched-control-ldc -@opindex mno-sched-control-ldc -@opindex msched-control-ldc -(Dis/En)able use of ld.c instructions to check control speculative loads. -If enabled, in case of control speculative load with no speculatively -scheduled dependent instructions this load will be emitted as ld.sa and -ld.c will be used to check it. -The default is 'disable'. - -@item -mno-sched-spec-verbose -@itemx -msched-spec-verbose -@opindex mno-sched-spec-verbose -@opindex msched-spec-verbose -(Dis/En)able printing of the information about speculative motions. - -@item -mno-sched-prefer-non-data-spec-insns -@itemx -msched-prefer-non-data-spec-insns -@opindex mno-sched-prefer-non-data-spec-insns -@opindex msched-prefer-non-data-spec-insns -If enabled, data speculative instructions will be chosen for schedule -only if there are no other choices at the moment. This will make -the use of the data speculation much more conservative. -The default is 'disable'. - -@item -mno-sched-prefer-non-control-spec-insns -@itemx -msched-prefer-non-control-spec-insns -@opindex mno-sched-prefer-non-control-spec-insns -@opindex msched-prefer-non-control-spec-insns -If enabled, control speculative instructions will be chosen for schedule -only if there are no other choices at the moment. This will make -the use of the control speculation much more conservative. -The default is 'disable'. - -@item -mno-sched-count-spec-in-critical-path -@itemx -msched-count-spec-in-critical-path -@opindex mno-sched-count-spec-in-critical-path -@opindex msched-count-spec-in-critical-path -If enabled, speculative dependencies will be considered during -computation of the instructions priorities. This will make the use of the -speculation a bit more conservative. -The default is 'disable'. - -@end table - -@node M32C Options -@subsection M32C Options -@cindex M32C options - -@table @gcctabopt -@item -mcpu=@var{name} -@opindex mcpu= -Select the CPU for which code is generated. @var{name} may be one of -@samp{r8c} for the R8C/Tiny series, @samp{m16c} for the M16C (up to -/60) series, @samp{m32cm} for the M16C/80 series, or @samp{m32c} for -the M32C/80 series. - -@item -msim -@opindex msim -Specifies that the program will be run on the simulator. This causes -an alternate runtime library to be linked in which supports, for -example, file I/O. You must not use this option when generating -programs that will run on real hardware; you must provide your own -runtime library for whatever I/O functions are needed. - -@item -memregs=@var{number} -@opindex memregs= -Specifies the number of memory-based pseudo-registers GCC will use -during code generation. These pseudo-registers will be used like real -registers, so there is a tradeoff between GCC's ability to fit the -code into available registers, and the performance penalty of using -memory instead of registers. Note that all modules in a program must -be compiled with the same value for this option. Because of that, you -must not use this option with the default runtime libraries gcc -builds. - -@end table - -@node M32R/D Options -@subsection M32R/D Options -@cindex M32R/D options - -These @option{-m} options are defined for Renesas M32R/D architectures: - -@table @gcctabopt -@item -m32r2 -@opindex m32r2 -Generate code for the M32R/2@. - -@item -m32rx -@opindex m32rx -Generate code for the M32R/X@. - -@item -m32r -@opindex m32r -Generate code for the M32R@. This is the default. - -@item -mmodel=small -@opindex mmodel=small -Assume all objects live in the lower 16MB of memory (so that their addresses -can be loaded with the @code{ld24} instruction), and assume all subroutines -are reachable with the @code{bl} instruction. -This is the default. - -The addressability of a particular object can be set with the -@code{model} attribute. - -@item -mmodel=medium -@opindex mmodel=medium -Assume objects may be anywhere in the 32-bit address space (the compiler -will generate @code{seth/add3} instructions to load their addresses), and -assume all subroutines are reachable with the @code{bl} instruction. - -@item -mmodel=large -@opindex mmodel=large -Assume objects may be anywhere in the 32-bit address space (the compiler -will generate @code{seth/add3} instructions to load their addresses), and -assume subroutines may not be reachable with the @code{bl} instruction -(the compiler will generate the much slower @code{seth/add3/jl} -instruction sequence). - -@item -msdata=none -@opindex msdata=none -Disable use of the small data area. Variables will be put into -one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the -@code{section} attribute has been specified). -This is the default. - -The small data area consists of sections @samp{.sdata} and @samp{.sbss}. -Objects may be explicitly put in the small data area with the -@code{section} attribute using one of these sections. - -@item -msdata=sdata -@opindex msdata=sdata -Put small global and static data in the small data area, but do not -generate special code to reference them. - -@item -msdata=use -@opindex msdata=use -Put small global and static data in the small data area, and generate -special instructions to reference them. - -@item -G @var{num} -@opindex G -@cindex smaller data references -Put global and static objects less than or equal to @var{num} bytes -into the small data or bss sections instead of the normal data or bss -sections. The default value of @var{num} is 8. -The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use} -for this option to have any effect. - -All modules should be compiled with the same @option{-G @var{num}} value. -Compiling with different values of @var{num} may or may not work; if it -doesn't the linker will give an error message---incorrect code will not be -generated. - -@item -mdebug -@opindex mdebug -Makes the M32R specific code in the compiler display some statistics -that might help in debugging programs. - -@item -malign-loops -@opindex malign-loops -Align all loops to a 32-byte boundary. - -@item -mno-align-loops -@opindex mno-align-loops -Do not enforce a 32-byte alignment for loops. This is the default. - -@item -missue-rate=@var{number} -@opindex missue-rate=@var{number} -Issue @var{number} instructions per cycle. @var{number} can only be 1 -or 2. - -@item -mbranch-cost=@var{number} -@opindex mbranch-cost=@var{number} -@var{number} can only be 1 or 2. If it is 1 then branches will be -preferred over conditional code, if it is 2, then the opposite will -apply. - -@item -mflush-trap=@var{number} -@opindex mflush-trap=@var{number} -Specifies the trap number to use to flush the cache. The default is -12. Valid numbers are between 0 and 15 inclusive. - -@item -mno-flush-trap -@opindex mno-flush-trap -Specifies that the cache cannot be flushed by using a trap. - -@item -mflush-func=@var{name} -@opindex mflush-func=@var{name} -Specifies the name of the operating system function to call to flush -the cache. The default is @emph{_flush_cache}, but a function call -will only be used if a trap is not available. - -@item -mno-flush-func -@opindex mno-flush-func -Indicates that there is no OS function for flushing the cache. - -@end table - -@node M680x0 Options -@subsection M680x0 Options -@cindex M680x0 options - -These are the @samp{-m} options defined for the 68000 series. The default -values for these options depends on which style of 68000 was selected when -the compiler was configured; the defaults for the most common choices are -given below. - -@table @gcctabopt -@item -m68000 -@itemx -mc68000 -@opindex m68000 -@opindex mc68000 -Generate output for a 68000. This is the default -when the compiler is configured for 68000-based systems. - -Use this option for microcontrollers with a 68000 or EC000 core, -including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. - -@item -m68020 -@itemx -mc68020 -@opindex m68020 -@opindex mc68020 -Generate output for a 68020. This is the default -when the compiler is configured for 68020-based systems. - -@item -m68881 -@opindex m68881 -Generate output containing 68881 instructions for floating point. -This is the default for most 68020 systems unless @option{--nfp} was -specified when the compiler was configured. - -@item -m68030 -@opindex m68030 -Generate output for a 68030. This is the default when the compiler is -configured for 68030-based systems. - -@item -m68040 -@opindex m68040 -Generate output for a 68040. This is the default when the compiler is -configured for 68040-based systems. - -This option inhibits the use of 68881/68882 instructions that have to be -emulated by software on the 68040. Use this option if your 68040 does not -have code to emulate those instructions. - -@item -m68060 -@opindex m68060 -Generate output for a 68060. This is the default when the compiler is -configured for 68060-based systems. - -This option inhibits the use of 68020 and 68881/68882 instructions that -have to be emulated by software on the 68060. Use this option if your 68060 -does not have code to emulate those instructions. - -@item -mcpu32 -@opindex mcpu32 -Generate output for a CPU32. This is the default -when the compiler is configured for CPU32-based systems. - -Use this option for microcontrollers with a -CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, -68336, 68340, 68341, 68349 and 68360. - -@item -m5200 -@opindex m5200 -Generate output for a 520X ``coldfire'' family cpu. This is the default -when the compiler is configured for 520X-based systems. - -Use this option for microcontroller with a 5200 core, including -the MCF5202, MCF5203, MCF5204 and MCF5202. - -@item -mcfv4e -@opindex mcfv4e -Generate output for a ColdFire V4e family cpu (e.g.@: 547x/548x). -This includes use of hardware floating point instructions. - -@item -m68020-40 -@opindex m68020-40 -Generate output for a 68040, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68040. - -@item -m68020-60 -@opindex m68020-60 -Generate output for a 68060, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68060. - -@item -msoft-float -@opindex msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all m68k -targets. Normally the facilities of the machine's usual C compiler are -used, but this can't be done directly in cross-compilation. You must -make your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets @samp{m68k-*-aout} and -@samp{m68k-*-coff} do provide software floating point support. - -@item -mshort -@opindex mshort -Consider type @code{int} to be 16 bits wide, like @code{short int}. -Additionally, parameters passed on the stack are also aligned to a -16-bit boundary even on targets whose API mandates promotion to 32-bit. - -@item -mnobitfield -@opindex mnobitfield -Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32} -and @option{-m5200} options imply @w{@option{-mnobitfield}}. - -@item -mbitfield -@opindex mbitfield -Do use the bit-field instructions. The @option{-m68020} option implies -@option{-mbitfield}. This is the default if you use a configuration -designed for a 68020. - -@item -mrtd -@opindex mrtd -Use a different function-calling convention, in which functions -that take a fixed number of arguments return with the @code{rtd} -instruction, which pops their arguments while returning. This -saves one instruction in the caller since there is no need to pop -the arguments there. - -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. - -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including @code{printf}); -otherwise incorrect code will be generated for calls to those -functions. - -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) - -The @code{rtd} instruction is supported by the 68010, 68020, 68030, -68040, 68060 and CPU32 processors, but not by the 68000 or 5200. - -@item -malign-int -@itemx -mno-align-int -@opindex malign-int -@opindex mno-align-int -Control whether GCC aligns @code{int}, @code{long}, @code{long long}, -@code{float}, @code{double}, and @code{long double} variables on a 32-bit -boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}). -Aligning variables on 32-bit boundaries produces code that runs somewhat -faster on processors with 32-bit busses at the expense of more memory. - -@strong{Warning:} if you use the @option{-malign-int} switch, GCC will -align structures containing the above types differently than -most published application binary interface specifications for the m68k. - -@item -mpcrel -@opindex mpcrel -Use the pc-relative addressing mode of the 68000 directly, instead of -using a global offset table. At present, this option implies @option{-fpic}, -allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is -not presently supported with @option{-mpcrel}, though this could be supported for -68020 and higher processors. - -@item -mno-strict-align -@itemx -mstrict-align -@opindex mno-strict-align -@opindex mstrict-align -Do not (do) assume that unaligned memory references will be handled by -the system. - -@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 -@option{-fPIC}. - -@item -mno-sep-data -Generate code that assumes that the data segment follows the text segment. -This is the default. - -@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 @option{-fPIC}. - -@item -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 -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 M68hc1x Options -@subsection M68hc1x Options -@cindex M68hc1x options - -These are the @samp{-m} options defined for the 68hc11 and 68hc12 -microcontrollers. The default values for these options depends on -which style of microcontroller was selected when the compiler was configured; -the defaults for the most common choices are given below. - -@table @gcctabopt -@item -m6811 -@itemx -m68hc11 -@opindex m6811 -@opindex m68hc11 -Generate output for a 68HC11. This is the default -when the compiler is configured for 68HC11-based systems. - -@item -m6812 -@itemx -m68hc12 -@opindex m6812 -@opindex m68hc12 -Generate output for a 68HC12. This is the default -when the compiler is configured for 68HC12-based systems. - -@item -m68S12 -@itemx -m68hcs12 -@opindex m68S12 -@opindex m68hcs12 -Generate output for a 68HCS12. - -@item -mauto-incdec -@opindex mauto-incdec -Enable the use of 68HC12 pre and post auto-increment and auto-decrement -addressing modes. - -@item -minmax -@itemx -nominmax -@opindex minmax -@opindex mnominmax -Enable the use of 68HC12 min and max instructions. - -@item -mlong-calls -@itemx -mno-long-calls -@opindex mlong-calls -@opindex mno-long-calls -Treat all calls as being far away (near). If calls are assumed to be -far away, the compiler will use the @code{call} instruction to -call a function and the @code{rtc} instruction for returning. - -@item -mshort -@opindex mshort -Consider type @code{int} to be 16 bits wide, like @code{short int}. - -@item -msoft-reg-count=@var{count} -@opindex msoft-reg-count -Specify the number of pseudo-soft registers which are used for the -code generation. The maximum number is 32. Using more pseudo-soft -register may or may not result in better code depending on the program. -The default is 4 for 68HC11 and 2 for 68HC12. - -@end table - -@node MCore Options -@subsection MCore Options -@cindex MCore options - -These are the @samp{-m} options defined for the Motorola M*Core -processors. - -@table @gcctabopt - -@item -mhardlit -@itemx -mno-hardlit -@opindex mhardlit -@opindex mno-hardlit -Inline constants into the code stream if it can be done in two -instructions or less. - -@item -mdiv -@itemx -mno-div -@opindex mdiv -@opindex mno-div -Use the divide instruction. (Enabled by default). - -@item -mrelax-immediate -@itemx -mno-relax-immediate -@opindex mrelax-immediate -@opindex mno-relax-immediate -Allow arbitrary sized immediates in bit operations. - -@item -mwide-bitfields -@itemx -mno-wide-bitfields -@opindex mwide-bitfields -@opindex mno-wide-bitfields -Always treat bit-fields as int-sized. - -@item -m4byte-functions -@itemx -mno-4byte-functions -@opindex m4byte-functions -@opindex mno-4byte-functions -Force all functions to be aligned to a four byte boundary. - -@item -mcallgraph-data -@itemx -mno-callgraph-data -@opindex mcallgraph-data -@opindex mno-callgraph-data -Emit callgraph information. - -@item -mslow-bytes -@itemx -mno-slow-bytes -@opindex mslow-bytes -@opindex mno-slow-bytes -Prefer word access when reading byte quantities. - -@item -mlittle-endian -@itemx -mbig-endian -@opindex mlittle-endian -@opindex mbig-endian -Generate code for a little endian target. - -@item -m210 -@itemx -m340 -@opindex m210 -@opindex m340 -Generate code for the 210 processor. -@end table - -@node MIPS Options -@subsection MIPS Options -@cindex MIPS options - -@table @gcctabopt - -@item -EB -@opindex EB -Generate big-endian code. - -@item -EL -@opindex EL -Generate little-endian code. This is the default for @samp{mips*el-*-*} -configurations. - -@item -march=@var{arch} -@opindex march -Generate code that will run on @var{arch}, which can be the name of a -generic MIPS ISA, or the name of a particular processor. -The ISA names are: -@samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4}, -@samp{mips32}, @samp{mips32r2}, and @samp{mips64}. -The processor names are: -@samp{4kc}, @samp{4km}, @samp{4kp}, -@samp{5kc}, @samp{5kf}, -@samp{20kc}, -@samp{24k}, @samp{24kc}, @samp{24kf}, @samp{24kx}, -@samp{m4k}, -@samp{orion}, -@samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400}, -@samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000}, -@samp{rm7000}, @samp{rm9000}, -@samp{sb1}, -@samp{sr71000}, -@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300}, -@samp{vr5000}, @samp{vr5400} and @samp{vr5500}. -The special value @samp{from-abi} selects the -most compatible architecture for the selected ABI (that is, -@samp{mips1} for 32-bit ABIs and @samp{mips3} for 64-bit ABIs)@. - -In processor names, a final @samp{000} can be abbreviated as @samp{k} -(for example, @samp{-march=r2k}). Prefixes are optional, and -@samp{vr} may be written @samp{r}. - -GCC defines two macros based on the value of this option. The first -is @samp{_MIPS_ARCH}, which gives the name of target architecture, as -a string. The second has the form @samp{_MIPS_ARCH_@var{foo}}, -where @var{foo} is the capitalized value of @samp{_MIPS_ARCH}@. -For example, @samp{-march=r2000} will set @samp{_MIPS_ARCH} -to @samp{"r2000"} and define the macro @samp{_MIPS_ARCH_R2000}. - -Note that the @samp{_MIPS_ARCH} macro uses the processor names given -above. In other words, it will have the full prefix and will not -abbreviate @samp{000} as @samp{k}. In the case of @samp{from-abi}, -the macro names the resolved architecture (either @samp{"mips1"} or -@samp{"mips3"}). It names the default architecture when no -@option{-march} option is given. - -@item -mtune=@var{arch} -@opindex mtune -Optimize for @var{arch}. Among other things, this option controls -the way instructions are scheduled, and the perceived cost of arithmetic -operations. The list of @var{arch} values is the same as for -@option{-march}. - -When this option is not used, GCC will optimize for the processor -specified by @option{-march}. By using @option{-march} and -@option{-mtune} together, it is possible to generate code that will -run on a family of processors, but optimize the code for one -particular member of that family. - -@samp{-mtune} defines the macros @samp{_MIPS_TUNE} and -@samp{_MIPS_TUNE_@var{foo}}, which work in the same way as the -@samp{-march} ones described above. - -@item -mips1 -@opindex mips1 -Equivalent to @samp{-march=mips1}. - -@item -mips2 -@opindex mips2 -Equivalent to @samp{-march=mips2}. - -@item -mips3 -@opindex mips3 -Equivalent to @samp{-march=mips3}. - -@item -mips4 -@opindex mips4 -Equivalent to @samp{-march=mips4}. - -@item -mips32 -@opindex mips32 -Equivalent to @samp{-march=mips32}. - -@item -mips32r2 -@opindex mips32r2 -Equivalent to @samp{-march=mips32r2}. - -@item -mips64 -@opindex mips64 -Equivalent to @samp{-march=mips64}. - -@item -mips16 -@itemx -mno-mips16 -@opindex mips16 -@opindex mno-mips16 -Generate (do not generate) MIPS16 code. If GCC is targetting a -MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE@. - -@item -mabi=32 -@itemx -mabi=o64 -@itemx -mabi=n32 -@itemx -mabi=64 -@itemx -mabi=eabi -@opindex mabi=32 -@opindex mabi=o64 -@opindex mabi=n32 -@opindex mabi=64 -@opindex mabi=eabi -Generate code for the given ABI@. - -Note that the EABI has a 32-bit and a 64-bit variant. GCC normally -generates 64-bit code when you select a 64-bit architecture, but you -can use @option{-mgp32} to get 32-bit code instead. - -For information about the O64 ABI, see -@w{@uref{http://gcc.gnu.org/projects/mipso64-abi.html}}. - -@item -mabicalls -@itemx -mno-abicalls -@opindex mabicalls -@opindex mno-abicalls -Generate (do not generate) code that is suitable for SVR4-style -dynamic objects. @option{-mabicalls} is the default for SVR4-based -systems. - -@item -mshared -@itemx -mno-shared -Generate (do not generate) code that is fully position-independent, -and that can therefore be linked into shared libraries. This option -only affects @option{-mabicalls}. - -All @option{-mabicalls} code has traditionally been position-independent, -regardless of options like @option{-fPIC} and @option{-fpic}. However, -as an extension, the GNU toolchain allows executables to use absolute -accesses for locally-binding symbols. It can also use shorter GP -initialization sequences and generate direct calls to locally-defined -functions. This mode is selected by @option{-mno-shared}. - -@option{-mno-shared} depends on binutils 2.16 or higher and generates -objects that can only be linked by the GNU linker. However, the option -does not affect the ABI of the final executable; it only affects the ABI -of relocatable objects. Using @option{-mno-shared} will generally make -executables both smaller and quicker. - -@option{-mshared} is the default. - -@item -mxgot -@itemx -mno-xgot -@opindex mxgot -@opindex mno-xgot -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@. -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: - -@cindex relocation truncated to fit (MIPS) -@smallexample -relocation truncated to fit: R_MIPS_GOT16 foobar -@end smallexample - -If this happens, you should recompile your code with @option{-mxgot}. -It should then work with very large GOTs, although it will also be -less efficient, since it will take three instructions to fetch the -value of a global symbol. - -Note that some linkers can create multiple GOTs. If you have such a -linker, you should only need to use @option{-mxgot} when a single object -file accesses more than 64k's worth of GOT entries. Very few do. - -These options have no effect unless GCC is generating position -independent code. - -@item -mgp32 -@opindex mgp32 -Assume that general-purpose registers are 32 bits wide. - -@item -mgp64 -@opindex mgp64 -Assume that general-purpose registers are 64 bits wide. - -@item -mfp32 -@opindex mfp32 -Assume that floating-point registers are 32 bits wide. - -@item -mfp64 -@opindex mfp64 -Assume that floating-point registers are 64 bits wide. - -@item -mhard-float -@opindex mhard-float -Use floating-point coprocessor instructions. - -@item -msoft-float -@opindex msoft-float -Do not use floating-point coprocessor instructions. Implement -floating-point calculations using library calls instead. - -@item -msingle-float -@opindex msingle-float -Assume that the floating-point coprocessor only supports single-precision -operations. - -@itemx -mdouble-float -@opindex mdouble-float -Assume that the floating-point coprocessor supports double-precision -operations. This is the default. - -@itemx -mdsp -@itemx -mno-dsp -@opindex mdsp -@opindex mno-dsp -Use (do not use) the MIPS DSP ASE. @xref{MIPS DSP Built-in Functions}. - -@itemx -mpaired-single -@itemx -mno-paired-single -@opindex mpaired-single -@opindex mno-paired-single -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@. @xref{MIPS-3D Built-in Functions}. -The option @option{-mips3d} implies @option{-mpaired-single}. - -@item -mlong64 -@opindex mlong64 -Force @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. - -@item -mlong32 -@opindex mlong32 -Force @code{long}, @code{int}, and pointer types to be 32 bits wide. - -The default size of @code{int}s, @code{long}s and pointers depends on -the ABI@. All the supported ABIs use 32-bit @code{int}s. The n64 ABI -uses 64-bit @code{long}s, as does the 64-bit EABI; the others use -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) -@cindex gp-relative references (MIPS) -Put global and static items less than or equal to @var{num} bytes into -the small data or bss section instead of the normal data or bss section. -This allows the data to be accessed using a single instruction. - -All modules should be compiled with the same @option{-G @var{num}} -value. - -@item -membedded-data -@itemx -mno-embedded-data -@opindex membedded-data -@opindex mno-embedded-data -Allocate variables to the read-only data section first if possible, then -next in the small data section if possible, otherwise in data. This gives -slightly slower code than the default, but reduces the amount of RAM required -when executing, and thus may be preferred for some embedded systems. - -@item -muninit-const-in-rodata -@itemx -mno-uninit-const-in-rodata -@opindex muninit-const-in-rodata -@opindex mno-uninit-const-in-rodata -Put uninitialized @code{const} variables in the read-only data section. -This option is only meaningful in conjunction with @option{-membedded-data}. - -@item -msplit-addresses -@itemx -mno-split-addresses -@opindex msplit-addresses -@opindex mno-split-addresses -Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler -relocation operators. This option has been superseded by -@option{-mexplicit-relocs} but is retained for backwards compatibility. - -@item -mexplicit-relocs -@itemx -mno-explicit-relocs -@opindex mexplicit-relocs -@opindex mno-explicit-relocs -Use (do not use) assembler relocation operators when dealing with symbolic -addresses. The alternative, selected by @option{-mno-explicit-relocs}, -is to use assembler macros instead. - -@option{-mexplicit-relocs} is the default if GCC was configured -to use an assembler that supports relocation operators. - -@item -mcheck-zero-division -@itemx -mno-check-zero-division -@opindex mcheck-zero-division -@opindex mno-check-zero-division -Trap (do not trap) on integer division by zero. The default is -@option{-mcheck-zero-division}. - -@item -mdivide-traps -@itemx -mdivide-breaks -@opindex mdivide-traps -@opindex mdivide-breaks -MIPS systems check for division by zero by generating either a -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 (@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. - -The default is usually @option{-mdivide-traps}, but this can be -overridden at configure time using @option{--with-divide=breaks}. -Divide-by-zero checks can be completely disabled using -@option{-mno-check-zero-division}. - -@item -mmemcpy -@itemx -mno-memcpy -@opindex mmemcpy -@opindex mno-memcpy -Force (do not force) the use of @code{memcpy()} for non-trivial block -moves. The default is @option{-mno-memcpy}, which allows GCC to inline -most constant-sized copies. - -@item -mlong-calls -@itemx -mno-long-calls -@opindex mlong-calls -@opindex mno-long-calls -Disable (do not disable) use of the @code{jal} instruction. Calling -functions using @code{jal} is more efficient but requires the caller -and callee to be in the same 256 megabyte segment. - -This option has no effect on abicalls code. The default is -@option{-mno-long-calls}. - -@item -mmad -@itemx -mno-mad -@opindex mmad -@opindex mno-mad -Enable (disable) use of the @code{mad}, @code{madu} and @code{mul} -instructions, as provided by the R4650 ISA@. - -@item -mfused-madd -@itemx -mno-fused-madd -@opindex mfused-madd -@opindex mno-fused-madd -Enable (disable) use of the floating point multiply-accumulate -instructions, when they are available. The default is -@option{-mfused-madd}. - -When multiply-accumulate instructions are used, the intermediate -product is calculated to infinite precision and is not subject to -the FCSR Flush to Zero bit. This may be undesirable in some -circumstances. - -@item -nocpp -@opindex nocpp -Tell the MIPS assembler to not run its preprocessor over user -assembler files (with a @samp{.s} suffix) when assembling them. - -@item -mfix-r4000 -@itemx -mno-fix-r4000 -@opindex mfix-r4000 -@opindex mno-fix-r4000 -Work around certain R4000 CPU errata: -@itemize @minus -@item -A double-word or a variable shift may give an incorrect result if executed -immediately after starting an integer division. -@item -A double-word or a variable shift may give an incorrect result if executed -while an integer multiplication is in progress. -@item -An integer division may give an incorrect result if started in a delay slot -of a taken branch or a jump. -@end itemize - -@item -mfix-r4400 -@itemx -mno-fix-r4400 -@opindex mfix-r4400 -@opindex mno-fix-r4400 -Work around certain R4400 CPU errata: -@itemize @minus -@item -A double-word or a variable shift may give an incorrect result if executed -immediately after starting an integer division. -@end itemize - -@item -mfix-vr4120 -@itemx -mno-fix-vr4120 -@opindex mfix-vr4120 -Work around certain VR4120 errata: -@itemize @minus -@item -@code{dmultu} does not always produce the correct result. -@item -@code{div} and @code{ddiv} do not always produce the correct result if one -of the operands is negative. -@end itemize -The workarounds for the division errata rely on special functions in -@file{libgcc.a}. At present, these functions are only provided by -the @code{mips64vr*-elf} configurations. - -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 -Work around certain SB-1 CPU core errata. -(This flag currently works around the SB-1 revision 2 -``F1'' and ``F2'' floating point errata.) - -@item -mflush-func=@var{func} -@itemx -mno-flush-func -@opindex mflush-func -Specifies the function to call to flush the I and D caches, or to not -call any such function. If called, the function must take the same -arguments as the common @code{_flush_func()}, that is, the address of the -memory range for which the cache is being flushed, the size of the -memory range, and the number 3 (to flush both caches). The default -depends on the target GCC was configured for, but commonly is either -@samp{_flush_func} or @samp{__cpu_flush}. - -@item -mbranch-likely -@itemx -mno-branch-likely -@opindex mbranch-likely -@opindex mno-branch-likely -Enable or disable use of Branch Likely instructions, regardless of the -default for the selected architecture. By default, Branch Likely -instructions may be generated if they are supported by the selected -architecture. An exception is for the MIPS32 and MIPS64 architectures -and processors which implement those architectures; for those, Branch -Likely instructions will not be generated by default because the MIPS32 -and MIPS64 architectures specifically deprecate their use. - -@item -mfp-exceptions -@itemx -mno-fp-exceptions -@opindex mfp-exceptions -Specifies whether FP exceptions are enabled. This affects how we schedule -FP instructions for some processors. The default is that FP exceptions are -enabled. - -For instance, on the SB-1, if FP exceptions are disabled, and we are emitting -64-bit code, then we can use both FP pipes. Otherwise, we can only use one -FP pipe. - -@item -mvr4130-align -@itemx -mno-vr4130-align -@opindex mvr4130-align -The VR4130 pipeline is two-way superscalar, but can only issue two -instructions together if the first one is 8-byte aligned. When this -option is enabled, GCC will align pairs of instructions that it -thinks should execute in parallel. - -This option only has an effect when optimizing for the VR4130. -It normally makes code faster, but at the expense of making it bigger. -It is enabled by default at optimization level @option{-O3}. -@end table - -@node MMIX Options -@subsection MMIX Options -@cindex MMIX Options - -These options are defined for the MMIX: - -@table @gcctabopt -@item -mlibfuncs -@itemx -mno-libfuncs -@opindex mlibfuncs -@opindex mno-libfuncs -Specify that intrinsic library functions are being compiled, passing all -values in registers, no matter the size. - -@item -mepsilon -@itemx -mno-epsilon -@opindex mepsilon -@opindex mno-epsilon -Generate floating-point comparison instructions that compare with respect -to the @code{rE} epsilon register. - -@item -mabi=mmixware -@itemx -mabi=gnu -@opindex mabi-mmixware -@opindex mabi=gnu -Generate code that passes function parameters and return values that (in -the called function) are seen as registers @code{$0} and up, as opposed to -the GNU ABI which uses global registers @code{$231} and up. - -@item -mzero-extend -@itemx -mno-zero-extend -@opindex mzero-extend -@opindex mno-zero-extend -When reading data from memory in sizes shorter than 64 bits, use (do not -use) zero-extending load instructions by default, rather than -sign-extending ones. - -@item -mknuthdiv -@itemx -mno-knuthdiv -@opindex mknuthdiv -@opindex mno-knuthdiv -Make the result of a division yielding a remainder have the same sign as -the divisor. With the default, @option{-mno-knuthdiv}, the sign of the -remainder follows the sign of the dividend. Both methods are -arithmetically valid, the latter being almost exclusively used. - -@item -mtoplevel-symbols -@itemx -mno-toplevel-symbols -@opindex mtoplevel-symbols -@opindex mno-toplevel-symbols -Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly -code can be used with the @code{PREFIX} assembly directive. - -@item -melf -@opindex melf -Generate an executable in the ELF format, rather than the default -@samp{mmo} format used by the @command{mmix} simulator. - -@item -mbranch-predict -@itemx -mno-branch-predict -@opindex mbranch-predict -@opindex mno-branch-predict -Use (do not use) the probable-branch instructions, when static branch -prediction indicates a probable branch. - -@item -mbase-addresses -@itemx -mno-base-addresses -@opindex mbase-addresses -@opindex mno-base-addresses -Generate (do not generate) code that uses @emph{base addresses}. Using a -base address automatically generates a request (handled by the assembler -and the linker) for a constant to be set up in a global register. The -register is used for one or more base address requests within the range 0 -to 255 from the value held in the register. The generally leads to short -and fast code, but the number of different data items that can be -addressed is limited. This means that a program that uses lots of static -data may require @option{-mno-base-addresses}. - -@item -msingle-exit -@itemx -mno-single-exit -@opindex msingle-exit -@opindex mno-single-exit -Force (do not force) generated code to have a single exit point in each -function. -@end table - -@node MN10300 Options -@subsection MN10300 Options -@cindex MN10300 options - -These @option{-m} options are defined for Matsushita MN10300 architectures: - -@table @gcctabopt -@item -mmult-bug -@opindex mmult-bug -Generate code to avoid bugs in the multiply instructions for the MN10300 -processors. This is the default. - -@item -mno-mult-bug -@opindex mno-mult-bug -Do not generate code to avoid bugs in the multiply instructions for the -MN10300 processors. - -@item -mam33 -@opindex mam33 -Generate code which uses features specific to the AM33 processor. - -@item -mno-am33 -@opindex mno-am33 -Do not generate code which uses features specific to the AM33 processor. This -is the default. - -@item -mreturn-pointer-on-d0 -@opindex mreturn-pointer-on-d0 -When generating a function which returns a pointer, return the pointer -in both @code{a0} and @code{d0}. Otherwise, the pointer is returned -only in a0, and attempts to call such functions without a prototype -would result in errors. Note that this option is on by default; use -@option{-mno-return-pointer-on-d0} to disable it. - -@item -mno-crt0 -@opindex mno-crt0 -Do not link in the C run-time initialization object file. - -@item -mrelax -@opindex mrelax -Indicate to the linker that it should perform a relaxation optimization pass -to shorten branches, calls and absolute memory addresses. This option only -has an effect when used on the command line for the final link step. - -This option makes symbolic debugging impossible. -@end table - -@node MT Options -@subsection MT Options -@cindex MT options - -These @option{-m} options are defined for Morpho MT architectures: - -@table @gcctabopt - -@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 -@var{cpu-type} are @samp{ms1-64-001}, @samp{ms1-16-002}, -@samp{ms1-16-003} and @samp{ms2}. - -When this option is not used, the default is @option{-march=ms1-16-002}. - -@item -mbacc -@opindex mbacc -Use byte loads and stores when generating code. - -@item -mno-bacc -@opindex mno-bacc -Do not use byte loads and stores when generating code. - -@item -msim -@opindex msim -Use simulator runtime - -@item -mno-crt0 -@opindex mno-crt0 -Do not link in the C run-time initialization object file -@file{crti.o}. Other run-time initialization and termination files -such as @file{startup.o} and @file{exit.o} are still included on the -linker command line. - -@end table - -@node PDP-11 Options -@subsection PDP-11 Options -@cindex PDP-11 Options - -These options are defined for the PDP-11: - -@table @gcctabopt -@item -mfpu -@opindex mfpu -Use hardware FPP floating point. This is the default. (FIS floating -point on the PDP-11/40 is not supported.) - -@item -msoft-float -@opindex msoft-float -Do not use hardware floating point. - -@item -mac0 -@opindex mac0 -Return floating-point results in ac0 (fr0 in Unix assembler syntax). - -@item -mno-ac0 -@opindex mno-ac0 -Return floating-point results in memory. This is the default. - -@item -m40 -@opindex m40 -Generate code for a PDP-11/40. - -@item -m45 -@opindex m45 -Generate code for a PDP-11/45. This is the default. - -@item -m10 -@opindex m10 -Generate code for a PDP-11/10. - -@item -mbcopy-builtin -@opindex bcopy-builtin -Use inline @code{movmemhi} patterns for copying memory. This is the -default. - -@item -mbcopy -@opindex mbcopy -Do not use inline @code{movmemhi} patterns for copying memory. - -@item -mint16 -@itemx -mno-int32 -@opindex mint16 -@opindex mno-int32 -Use 16-bit @code{int}. This is the default. - -@item -mint32 -@itemx -mno-int16 -@opindex mint32 -@opindex mno-int16 -Use 32-bit @code{int}. - -@item -mfloat64 -@itemx -mno-float32 -@opindex mfloat64 -@opindex mno-float32 -Use 64-bit @code{float}. This is the default. - -@item -mfloat32 -@itemx -mno-float64 -@opindex mfloat32 -@opindex mno-float64 -Use 32-bit @code{float}. - -@item -mabshi -@opindex mabshi -Use @code{abshi2} pattern. This is the default. - -@item -mno-abshi -@opindex mno-abshi -Do not use @code{abshi2} pattern. - -@item -mbranch-expensive -@opindex mbranch-expensive -Pretend that branches are expensive. This is for experimenting with -code generation only. - -@item -mbranch-cheap -@opindex mbranch-cheap -Do not pretend that branches are expensive. This is the default. - -@item -msplit -@opindex msplit -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. - -@item -munix-asm -@opindex munix-asm -Use Unix assembler syntax. This is the default when configured for -@samp{pdp11-*-bsd}. - -@item -mdec-asm -@opindex mdec-asm -Use DEC assembler syntax. This is the default when configured for any -PDP-11 target other than @samp{pdp11-*-bsd}. -@end table -@c APPLE LOCAL prune man page -@end ignore - -@node PowerPC Options -@subsection PowerPC Options -@cindex PowerPC options - -These are listed under @xref{RS/6000 and PowerPC Options}. - -@node RS/6000 and PowerPC Options -@subsection IBM RS/6000 and PowerPC Options -@cindex RS/6000 and PowerPC Options -@cindex IBM RS/6000 and PowerPC Options - -These @samp{-m} options are defined for the IBM RS/6000 and PowerPC: -@table @gcctabopt -@item -mpower -@itemx -mno-power -@itemx -mpower2 -@itemx -mno-power2 -@itemx -mpowerpc -@itemx -mno-powerpc -@itemx -mpowerpc-gpopt -@itemx -mno-powerpc-gpopt -@itemx -mpowerpc-gfxopt -@itemx -mno-powerpc-gfxopt -@itemx -mpowerpc64 -@itemx -mno-powerpc64 -@itemx -mmfcrf -@itemx -mno-mfcrf -@itemx -mpopcntb -@itemx -mno-popcntb -@itemx -mfprnd -@itemx -mno-fprnd -@opindex mpower -@opindex mno-power -@opindex mpower2 -@opindex mno-power2 -@opindex mpowerpc -@opindex mno-powerpc -@opindex mpowerpc-gpopt -@opindex mno-powerpc-gpopt -@opindex mpowerpc-gfxopt -@opindex mno-powerpc-gfxopt -@opindex mpowerpc64 -@opindex mno-powerpc64 -@opindex mmfcrf -@opindex mno-mfcrf -@opindex mpopcntb -@opindex mno-popcntb -@opindex mfprnd -@opindex mno-fprnd -GCC supports two related instruction set architectures for the -RS/6000 and PowerPC@. The @dfn{POWER} instruction set are those -instructions supported by the @samp{rios} chip set used in the original -RS/6000 systems and the @dfn{PowerPC} instruction set is the -architecture of the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and -the IBM 4xx, 6xx, and follow-on microprocessors. - -Neither architecture is a subset of the other. However there is a -large common subset of instructions supported by both. An MQ -register is included in processors supporting the POWER architecture. - -You use these options to specify which instructions are available on the -processor you are using. The default value of these options is -determined when configuring GCC@. Specifying the -@option{-mcpu=@var{cpu_type}} overrides the specification of these -options. We recommend you use the @option{-mcpu=@var{cpu_type}} option -rather than the options listed above. - -The @option{-mpower} option allows GCC to generate instructions that -are found only in the POWER architecture and to use the MQ register. -Specifying @option{-mpower2} implies @option{-power} and also allows GCC -to generate instructions that are present in the POWER2 architecture but -not the original POWER architecture. - -The @option{-mpowerpc} option allows GCC to generate instructions that -are found only in the 32-bit subset of the PowerPC architecture. -Specifying @option{-mpowerpc-gpopt} implies @option{-mpowerpc} and also allows -GCC to use the optional PowerPC architecture instructions in the -General Purpose group, including floating-point square root. Specifying -@option{-mpowerpc-gfxopt} implies @option{-mpowerpc} and also allows GCC to -use the optional PowerPC architecture instructions in the Graphics -group, including floating-point select. - -The @option{-mmfcrf} option allows GCC to generate the move from -condition register field instruction implemented on the POWER4 -processor and other processors that support the PowerPC V2.01 -architecture. -The @option{-mpopcntb} option allows GCC to generate the popcount and -double precision FP reciprocal estimate instruction implemented on the -POWER5 processor and other processors that support the PowerPC V2.02 -architecture. -The @option{-mfprnd} option allows GCC to generate the FP round to -integer instructions implemented on the POWER5+ processor and other -processors that support the PowerPC V2.03 architecture. - -The @option{-mpowerpc64} option allows GCC to generate the additional -64-bit instructions that are found in the full PowerPC64 architecture -and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to -@option{-mno-powerpc64}. - -If you specify both @option{-mno-power} and @option{-mno-powerpc}, GCC -will use only the instructions in the common subset of both -architectures plus some special AIX common-mode calls, and will not use -the MQ register. Specifying both @option{-mpower} and @option{-mpowerpc} -permits GCC to use any instruction from either architecture and to -allow use of the MQ register; specify this for the Motorola MPC601. - -@item -mnew-mnemonics -@itemx -mold-mnemonics -@opindex mnew-mnemonics -@opindex mold-mnemonics -Select which mnemonics to use in the generated assembler code. With -@option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for -the PowerPC architecture. With @option{-mold-mnemonics} it uses the -assembler mnemonics defined for the POWER architecture. Instructions -defined in only one architecture have only one mnemonic; GCC uses that -mnemonic irrespective of which of these options is specified. - -GCC defaults to the mnemonics appropriate for the architecture in -use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the -value of these option. Unless you are building a cross-compiler, you -should normally not specify either @option{-mnew-mnemonics} or -@option{-mold-mnemonics}, but should instead accept the default. - -@item -mcpu=@var{cpu_type} -@opindex mcpu -Set architecture type, register usage, choice of mnemonics, and -instruction scheduling parameters for machine type @var{cpu_type}. -Supported values for @var{cpu_type} are @samp{401}, @samp{403}, -@samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{505}, -@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{8540}, @samp{ec603e}, @samp{G3}, -@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3}, -@samp{power4}, @samp{power5}, @samp{power5+}, @samp{power6}, -@samp{common}, @samp{powerpc}, @samp{powerpc64}, -@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. -GCC will use only the instructions in the common subset of both -architectures, and will not use the MQ register. GCC assumes a generic -processor model for scheduling purposes. - -@option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and -@option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit -PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine -types, with an appropriate, generic processor model assumed for -scheduling purposes. - -The other options specify a specific processor. Code generated under -those options will run best on that processor, and may not run at all on -others. - -The @option{-mcpu} options automatically enable or disable the -following options: @option{-maltivec}, @option{-mfprnd}, -@option{-mhard-float}, @option{-mmfcrf}, @option{-mmultiple}, -@option{-mnew-mnemonics}, @option{-mpopcntb}, @option{-mpower}, -@option{-mpower2}, @option{-mpowerpc64}, @option{-mpowerpc-gpopt}, -@option{-mpowerpc-gfxopt}, @option{-mstring}, @option{-mmulhw}, @option{-mdlmzb}. -The particular options -set for any particular CPU will vary between compiler versions, -depending on what setting seems to produce optimal code for that CPU; -it doesn't necessarily reflect the actual hardware's capabilities. If -you wish to set an individual option to a particular value, you may -specify it after the @option{-mcpu} option, like @samp{-mcpu=970 --mno-altivec}. - -On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are -not enabled or disabled by the @option{-mcpu} option at present because -AIX does not have full support for these options. You may still -enable or disable them individually if you're sure it'll work in your -environment. - -@item -mtune=@var{cpu_type} -@opindex mtune -Set the instruction scheduling parameters for machine type -@var{cpu_type}, but do not set the architecture type, register usage, or -choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same -values for @var{cpu_type} are used for @option{-mtune} as for -@option{-mcpu}. If both are specified, the code generated will use the -architecture, registers, and mnemonics set by @option{-mcpu}, but the -scheduling parameters set by @option{-mtune}. - -@item -mswdiv -@itemx -mno-swdiv -@opindex mswdiv -@opindex mno-swdiv -Generate code to compute division as reciprocal estimate and iterative -refinement, creating opportunities for increased throughput. This -feature requires: optional PowerPC Graphics instruction set for single -precision and FRE instruction for double precision, assuming divides -cannot generate user-visible traps, and the domain values not include -Infinities, denormals or zero denominator. - -@item -maltivec -@itemx -mno-altivec -@opindex maltivec -@opindex mno-altivec -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. - -@c APPLE LOCAL begin AltiVec -@item -mpim-altivec -@itemx -mno-pim-altivec -@opindex mpim-altivec -@opindex mno-pim-altivec -Enable (or disable) built-in compiler support for the syntactic extensions as -well as operations and predicates defined in the Motorola AltiVec -Technology Programming Interface Manual (PIM). This includes the -recognition of @code{vector} and @code{pixel} as (context-dependent) -keywords, the definition of built-in functions such as @code{vec_add}, -and the use of parenthesized comma expression as AltiVec literals. -Note that unlike the option @option{-maltivec}, the extension does not require -the inclusion of any special header files; if @code{<altivec.h>} is included, -a warning will be issued and the contents of the header will be -ignored. The preprocessor shall provide an @code{__APPLE_ALTIVEC__} -manifest constant when @option{-mpim-altivec} is specified. (APPLE ONLY) - -In addition, the @option{-mpim-altivec} option disables the inlining of -functions containing AltiVec instructions into functions that do not make -use of the vector unit. Certain other optimizations, such as inline -vectorization of @code{memset} and @code{memcpy} calls, are also disabled. -These adjustments make it possible to compile programs whose use of AltiVec -instructions is preceded by a run-time check for the presence of AltiVec -functionality, and that can therefore be made to run on G3 processors. -Note that all of these optimizations may be re-enabled by supplying -the @option{-maltivec} option, or an @option{-mcpu} option specifying -a processor that supports AltiVec instructions. -@c APPLE LOCAL end AltiVec - -@item -mvrsave -@item -mno-vrsave -@opindex mvrsave -@opindex mno-vrsave -Generate VRSAVE instructions when generating AltiVec code. - -@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 -misel=@var{yes/no} -This switch has been deprecated. Use @option{-misel} and -@option{-mno-isel} instead. - -@item -mspe -@itemx -mno-spe -@opindex mspe -@opindex mno-spe -This switch enables or disables the generation of SPE simd -instructions. - -@item -mspe=@var{yes/no} -This option has been deprecated. Use @option{-mspe} and -@option{-mno-spe} instead. - -@item -mfloat-gprs=@var{yes/single/double/no} -@itemx -mfloat-gprs -@opindex mfloat-gprs -This switch enables or disables the generation of floating point -operations on the general purpose registers for architectures that -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 -@opindex m32 -@opindex m64 -Generate code for 32-bit or 64-bit environments of Darwin and SVR4 -targets (including GNU/Linux). The 32-bit environment sets int, long -and pointer to 32 bits and generates code that runs on any PowerPC -variant. The 64-bit environment sets int to 32 bits and long and -pointer to 64 bits, and generates code for PowerPC64, as for -@option{-mpowerpc64}. - -@item -mfull-toc -@itemx -mno-fp-in-toc -@itemx -mno-sum-in-toc -@itemx -mminimal-toc -@opindex mfull-toc -@opindex mno-fp-in-toc -@opindex mno-sum-in-toc -@opindex mminimal-toc -Modify generation of the TOC (Table Of Contents), which is created for -every executable file. The @option{-mfull-toc} option is selected by -default. In that case, GCC will allocate at least one TOC entry for -each unique non-automatic variable reference in your program. GCC -will also place floating-point constants in the TOC@. However, only -16,384 entries are available in the TOC@. - -If you receive a linker error message that saying you have overflowed -the available TOC space, you can reduce the amount of TOC space used -with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options. -@option{-mno-fp-in-toc} prevents GCC from putting floating-point -constants in the TOC and @option{-mno-sum-in-toc} forces GCC to -generate code to calculate the sum of an address and a constant at -run-time instead of putting that sum into the TOC@. You may specify one -or both of these options. Each causes GCC to produce very slightly -slower and larger code at the expense of conserving TOC space. - -If you still run out of space in the TOC even when you specify both of -these options, specify @option{-mminimal-toc} instead. This option causes -GCC to make only one TOC entry for every file. When you specify this -option, GCC will produce code that is slower and larger but which -uses extremely little TOC space. You may wish to use this option -only on files that contain less frequently executed code. - -@item -maix64 -@itemx -maix32 -@opindex maix64 -@opindex maix32 -Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit -@code{long} type, and the infrastructure needed to support them. -Specifying @option{-maix64} implies @option{-mpowerpc64} and -@option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and -implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}. - -@item -mxl-compat -@itemx -mno-xl-compat -@opindex mxl-compat -@opindex mno-xl-compat -Produce code that conforms more closely to IBM XL compiler 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 and converting to double. Use XL symbol names for long double -support routines. - -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. IBM XL -compilers access floating point arguments which do not fit in the -RSA from the stack when a subroutine is compiled without -optimization. Because always storing floating-point arguments on the -stack is inefficient and rarely needed, this option is not enabled by -default and only is necessary when calling subroutines compiled by IBM -XL compilers without optimization. - -@item -mpe -@opindex mpe -Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an -application written to use message passing with special startup code to -enable the application to run. The system must have PE installed in the -standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file -must be overridden with the @option{-specs=} option to specify the -appropriate directory location. The Parallel Environment does not -support threads, so the @option{-mpe} option and the @option{-pthread} -option are incompatible. - -@item -malign-natural -@itemx -malign-power -@opindex malign-natural -@opindex malign-power -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@. - -On 64-bit Darwin, natural alignment is the default, and @option{-malign-power} -is not supported. - -@item -msoft-float -@itemx -mhard-float -@opindex msoft-float -@opindex mhard-float -Generate code that does not use (uses) the floating-point register set. -Software floating point emulation is provided if you use the -@option{-msoft-float} option, and pass the option to GCC when linking. - -@c APPLE LOCAL begin describe actual behavior 3888787 -(APPLE ONLY) While the -msoft-float option is supported, the libraries that -do the floating point emulation are not shipped on Apple PowerPCs, with the -effect that the emulation does not work. However, the option -may be useful for a different reason. Normally the compiler can use floating -point registers in contexts where you might not expect it, for example, to -copy data from one memory location to another. The -msoft-float option will -prevent it from doing this. -@c APPLE LOCAL end describe actual behavior 3888787 - -@item -mmultiple -@itemx -mno-multiple -@opindex mmultiple -@opindex mno-multiple -Generate code that uses (does not use) the load multiple word -instructions and the store multiple word instructions. These -instructions are generated by default on POWER systems, and not -generated on PowerPC systems. Do not use @option{-mmultiple} on little -endian PowerPC systems, since those instructions do not work when the -processor is in little endian mode. The exceptions are PPC740 and -PPC750 which permit the instructions usage in little endian mode. - -@item -mstring -@itemx -mno-string -@opindex mstring -@opindex mno-string -Generate code that uses (does not use) the load string instructions -and the store string word instructions to save multiple registers and -do small block moves. These instructions are generated by default on -POWER systems, and not generated on PowerPC systems. Do not use -@option{-mstring} on little endian PowerPC systems, since those -instructions do not work when the processor is in little endian mode. -The exceptions are PPC740 and PPC750 which permit the instructions -usage in little endian mode. - -@item -mupdate -@itemx -mno-update -@opindex mupdate -@opindex mno-update -Generate code that uses (does not use) the load or store instructions -that update the base register to the address of the calculated memory -location. These instructions are generated by default. If you use -@option{-mno-update}, there is a small window between the time that the -stack pointer is updated and the address of the previous frame is -stored, which means code that walks the stack frame across interrupts or -signals may get corrupted data. - -@item -mfused-madd -@itemx -mno-fused-madd -@opindex mfused-madd -@opindex mno-fused-madd -Generate code that uses (does not use) the floating point multiply and -accumulate instructions. These instructions are generated by default if -hardware floating is used. - -@item -mmulhw -@itemx -mno-mulhw -@opindex mmulhw -@opindex mno-mulhw -Generate code that uses (does not use) the half-word multiply and -multiply-accumulate instructions on the IBM 405 and 440 processors. -These instructions are generated by default when targetting those -processors. - -@item -mdlmzb -@itemx -mno-dlmzb -@opindex mdlmzb -@opindex mno-dlmzb -Generate code that uses (does not use) the string-search @samp{dlmzb} -instruction on the IBM 405 and 440 processors. This instruction is -generated by default when targetting those processors. - -@item -mno-bit-align -@itemx -mbit-align -@opindex mno-bit-align -@opindex mbit-align -On System V.4 and embedded PowerPC systems do not (do) force structures -and unions that contain bit-fields to be aligned to the base type of the -bit-field. - -For example, by default a structure containing nothing but 8 -@code{unsigned} bit-fields of length 1 would be aligned to a 4 byte -boundary and have a size of 4 bytes. By using @option{-mno-bit-align}, -the structure would be aligned to a 1 byte boundary and be one byte in -size. - -@item -mno-strict-align -@itemx -mstrict-align -@opindex mno-strict-align -@opindex mstrict-align -On System V.4 and embedded PowerPC systems do not (do) assume that -unaligned memory references will be handled by the system. - -@item -mrelocatable -@itemx -mno-relocatable -@opindex mrelocatable -@opindex mno-relocatable -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. If you -use @option{-mrelocatable} on any module, all objects linked together must -be compiled with @option{-mrelocatable} or @option{-mrelocatable-lib}. - -@item -mrelocatable-lib -@itemx -mno-relocatable-lib -@opindex mrelocatable-lib -@opindex mno-relocatable-lib -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. Modules -compiled with @option{-mrelocatable-lib} can be linked with either modules -compiled without @option{-mrelocatable} and @option{-mrelocatable-lib} or -with modules compiled with the @option{-mrelocatable} options. - -@item -mno-toc -@itemx -mtoc -@opindex mno-toc -@opindex mtoc -On System V.4 and embedded PowerPC systems do not (do) assume that -register 2 contains a pointer to a global area pointing to the addresses -used in the program. - -@item -mlittle -@itemx -mlittle-endian -@opindex mlittle -@opindex mlittle-endian -On System V.4 and embedded PowerPC systems compile code for the -processor in little endian mode. The @option{-mlittle-endian} option is -the same as @option{-mlittle}. - -@item -mbig -@itemx -mbig-endian -@opindex mbig -@opindex mbig-endian -On System V.4 and embedded PowerPC systems compile code for the -processor in big endian mode. The @option{-mbig-endian} option is -the same as @option{-mbig}. - -@item -mdynamic-no-pic -@opindex mdynamic-no-pic -On Darwin and Mac OS X systems, compile code so that it is not -relocatable, but that its external references are relocatable. The -resulting code is suitable for applications, but not shared -libraries. - -@item -mprioritize-restricted-insns=@var{priority} -@opindex mprioritize-restricted-insns -This option controls the priority that is assigned to -dispatch-slot restricted instructions during the second scheduling -pass. The argument @var{priority} takes the value @var{0/1/2} to assign -@var{no/highest/second-highest} priority to dispatch slot restricted -instructions. - -@item -msched-costly-dep=@var{dependence_type} -@opindex msched-costly-dep -This option controls which dependences are considered costly -by the target during instruction scheduling. The argument -@var{dependence_type} takes one of the following values: -@var{no}: no dependence is costly, -@var{all}: all dependences are costly, -@var{true_store_to_load}: a true dependence from store to load is costly, -@var{store_to_load}: any dependence from store to load is costly, -@var{number}: any dependence which latency >= @var{number} is costly. - -@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 -following values: -@var{no}: Don't insert nops. -@var{pad}: Pad with nops any dispatch group which has vacant issue slots, -according to the scheduler's grouping. -@var{regroup_exact}: Insert nops to force costly dependent insns into -separate groups. Insert exactly as many nops as needed to force an insn -to a new group, according to the estimated processor grouping. -@var{number}: Insert nops to force costly dependent insns into -separate groups. Insert @var{number} nops to force an insn to a new group. - -@item -mcall-sysv -@opindex mcall-sysv -On System V.4 and embedded PowerPC systems compile code using calling -conventions that adheres to the March 1995 draft of the System V -Application Binary Interface, PowerPC processor supplement. This is the -default unless you configured GCC using @samp{powerpc-*-eabiaix}. - -@item -mcall-sysv-eabi -@opindex mcall-sysv-eabi -Specify both @option{-mcall-sysv} and @option{-meabi} options. - -@item -mcall-sysv-noeabi -@opindex mcall-sysv-noeabi -Specify both @option{-mcall-sysv} and @option{-mno-eabi} options. - -@item -mcall-solaris -@opindex mcall-solaris -On System V.4 and embedded PowerPC systems compile code for the Solaris -operating system. - -@item -mcall-linux -@opindex mcall-linux -On System V.4 and embedded PowerPC systems compile code for the -Linux-based GNU system. - -@item -mcall-gnu -@opindex mcall-gnu -On System V.4 and embedded PowerPC systems compile code for the -Hurd-based GNU system. - -@item -mcall-netbsd -@opindex mcall-netbsd -On System V.4 and embedded PowerPC systems compile code for the -NetBSD operating system. - -@item -maix-struct-return -@opindex maix-struct-return -Return all structures in memory (as specified by the AIX ABI)@. - -@item -msvr4-struct-return -@opindex msvr4-struct-return -Return structures smaller than 8 bytes in registers (as specified by the -SVR4 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}, @var{ibmlongdouble}, @var{ieeelongdouble}@. - -@item -mabi=spe -@opindex mabi=spe -Extend the current ABI with SPE ABI extensions. This does not change -the default ABI, instead it adds the SPE ABI extensions to the current -ABI@. - -@item -mabi=no-spe -@opindex mabi=no-spe -Disable Booke SPE ABI extensions for the current ABI@. - -@item -mabi=ibmlongdouble -@opindex mabi=ibmlongdouble -Change the current ABI to use IBM extended precision long double. -This is a PowerPC 32-bit SYSV ABI option. - -@item -mabi=ieeelongdouble -@opindex mabi=ieeelongdouble -Change the current ABI to use IEEE extended precision long double. -This is a PowerPC 32-bit Linux ABI option. - -@item -mprototype -@itemx -mno-prototype -@opindex mprototype -@opindex mno-prototype -On System V.4 and embedded PowerPC systems assume that all calls to -variable argument functions are properly prototyped. Otherwise, the -compiler must insert an instruction before every non prototyped call to -set or clear bit 6 of the condition code register (@var{CR}) to -indicate whether floating point values were passed in the floating point -registers in case the function takes a variable arguments. With -@option{-mprototype}, only calls to prototyped variable argument functions -will set or clear the bit. - -@item -msim -@opindex msim -On embedded PowerPC systems, assume that the startup module is called -@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and -@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}. -configurations. - -@item -mmvme -@opindex mmvme -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libmvme.a} and -@file{libc.a}. - -@item -mads -@opindex mads -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libads.a} and -@file{libc.a}. - -@item -myellowknife -@opindex myellowknife -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libyk.a} and -@file{libc.a}. - -@item -mvxworks -@opindex mvxworks -On System V.4 and embedded PowerPC systems, specify that you are -compiling for a VxWorks system. - -@item -mwindiss -@opindex mwindiss -Specify that you are compiling for the WindISS simulation environment. - -@item -memb -@opindex memb -On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags -header to indicate that @samp{eabi} extended relocations are used. - -@item -meabi -@itemx -mno-eabi -@opindex meabi -@opindex mno-eabi -On System V.4 and embedded PowerPC systems do (do not) adhere to the -Embedded Applications Binary Interface (eabi) which is a set of -modifications to the System V.4 specifications. Selecting @option{-meabi} -means that the stack is aligned to an 8 byte boundary, a function -@code{__eabi} is called to from @code{main} to set up the eabi -environment, and the @option{-msdata} option can use both @code{r2} and -@code{r13} to point to two separate small data areas. Selecting -@option{-mno-eabi} means that the stack is aligned to a 16 byte boundary, -do not call an initialization function from @code{main}, and the -@option{-msdata} option will only use @code{r13} to point to a single -small data area. The @option{-meabi} option is on by default if you -configured GCC using one of the @samp{powerpc*-*-eabi*} options. - -@item -msdata=eabi -@opindex msdata=eabi -On System V.4 and embedded PowerPC systems, put small initialized -@code{const} global and static data in the @samp{.sdata2} section, which -is pointed to by register @code{r2}. Put small initialized -non-@code{const} global and static data in the @samp{.sdata} section, -which is pointed to by register @code{r13}. Put small uninitialized -global and static data in the @samp{.sbss} section, which is adjacent to -the @samp{.sdata} section. The @option{-msdata=eabi} option is -incompatible with the @option{-mrelocatable} option. The -@option{-msdata=eabi} option also sets the @option{-memb} option. - -@item -msdata=sysv -@opindex msdata=sysv -On System V.4 and embedded PowerPC systems, put small global and static -data in the @samp{.sdata} section, which is pointed to by register -@code{r13}. Put small uninitialized global and static data in the -@samp{.sbss} section, which is adjacent to the @samp{.sdata} section. -The @option{-msdata=sysv} option is incompatible with the -@option{-mrelocatable} option. - -@item -msdata=default -@itemx -msdata -@opindex msdata=default -@opindex msdata -On System V.4 and embedded PowerPC systems, if @option{-meabi} is used, -compile code the same as @option{-msdata=eabi}, otherwise compile code the -same as @option{-msdata=sysv}. - -@item -msdata-data -@opindex msdata-data -On System V.4 and embedded PowerPC systems, put small global -data in the @samp{.sdata} section. Put small uninitialized global -data in the @samp{.sbss} section. Do not use register @code{r13} -to address small data however. This is the default behavior unless -other @option{-msdata} options are used. - -@item -msdata=none -@itemx -mno-sdata -@opindex msdata=none -@opindex mno-sdata -On embedded PowerPC systems, put all initialized global and static data -in the @samp{.data} section, and all uninitialized data in the -@samp{.bss} section. - -@item -G @var{num} -@opindex G -@cindex smaller data references (PowerPC) -@cindex .sdata/.sdata2 references (PowerPC) -On embedded PowerPC systems, put global and static items less than or -equal to @var{num} bytes into the small data or bss sections instead of -the normal data or bss section. By default, @var{num} is 8. The -@option{-G @var{num}} switch is also passed to the linker. -All modules should be compiled with the same @option{-G @var{num}} value. - -@item -mregnames -@itemx -mno-regnames -@opindex mregnames -@opindex mno-regnames -On System V.4 and embedded PowerPC systems do (do not) emit register -names in the assembly language output using symbolic forms. - -@item -mlongcall -@itemx -mno-longcall -@opindex mlongcall -@opindex mno-longcall -@c APPLE LOCAL begin 4222119 -@itemx -mlong-branch -@itemx -mno-long-branch -@opindex mlong-branch -@opindex mno-long-branch -@c APPLE LOCAL end 4222119 -By default assume that all calls are far away so that a longer more -expensive calling sequence is required. This is required for calls -further than 32 megabytes (33,554,432 bytes) from the current location. -A short call will be generated if the compiler knows -the call cannot be that far away. This setting can be overridden by -the @code{shortcall} function attribute, or by @code{#pragma -longcall(0)}. - -Some linkers are capable of detecting out-of-range calls and generating -glue code on the fly. On these systems, long calls are unnecessary and -generate slower code. As of this writing, the AIX linker can do this, -as can the GNU linker for PowerPC/64. It is planned to add this feature -to the GNU linker for 32-bit PowerPC systems as well. - -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 -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 -calling function; it computes the full 32-bit address of the callee -and jumps to it. - -@c APPLE LOCAL begin 4222119 -On Mach-O (Darwin) systems, @option{-mlongcall} directs the compiler -emit to the glue for every direct call, and the Darwin linker decides -whether to use or discard it. @option{-mlong-branch} is a synonym for -@option{-mlongcall}. -@c APPLE LOCAL end 4222119 - -In the future, we may cause GCC to ignore all longcall specifications -when the linker is known to generate glue. - -@item -pthread -@opindex pthread -Adds support for multithreading with the @dfn{pthreads} library. -This option sets flags for both the preprocessor and linker. - -@c APPLE LOCAL begin 5946347 ms_struct support -@item -mms-bitfields -@opindex mms-bitfields -Set the default structure layout to be compatible with the Microsoft -compiler standard. This is equivalent to adding an @code{ms_struct} -attribute to each structure and union tag definition. The default is -@option{mno-ms-bitfields}. -@c APPLE LOCAL end 5946347 ms_struct support - -@end table - -@c APPLE LOCAL prune man page -@ignore -@node S/390 and zSeries Options -@subsection S/390 and zSeries Options -@cindex S/390 and zSeries Options - -These are the @samp{-m} options defined for the S/390 and zSeries architecture. - -@table @gcctabopt -@item -mhard-float -@itemx -msoft-float -@opindex mhard-float -@opindex msoft-float -Use (do not use) the hardware floating-point instructions and registers -for floating-point operations. When @option{-msoft-float} is specified, -functions in @file{libgcc.a} will be used to perform floating-point -operations. When @option{-mhard-float} is specified, the compiler -generates IEEE floating-point instructions. This is the default. - -@item -mlong-double-64 -@itemx -mlong-double-128 -@opindex mlong-double-64 -@opindex mlong-double-128 -These switches control the size of @code{long double} type. A size -of 64bit makes the @code{long double} type equivalent to the @code{double} -type. This is the default. - -@item -mbackchain -@itemx -mno-backchain -@opindex mbackchain -@opindex mno-backchain -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. -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 -@opindex msmall-exec -@opindex mno-small-exec -Generate (or do not generate) code using the @code{bras} instruction -to do subroutine calls. -This only works reliably if the total executable size does not -exceed 64k. The default is to use the @code{basr} instruction instead, -which does not have this limitation. - -@item -m64 -@itemx -m31 -@opindex m64 -@opindex m31 -When @option{-m31} is specified, generate code compliant to the -GNU/Linux for S/390 ABI@. When @option{-m64} is specified, generate -code compliant to the GNU/Linux for zSeries ABI@. This allows GCC in -particular to generate 64-bit instructions. For the @samp{s390} -targets, the default is @option{-m31}, while the @samp{s390x} -targets default to @option{-m64}. - -@item -mzarch -@itemx -mesa -@opindex mzarch -@opindex mesa -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 -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 -to the GNU/Linux for zSeries ABI, the default is @option{-mzarch}. - -@item -mmvcle -@itemx -mno-mvcle -@opindex mmvcle -@opindex mno-mvcle -Generate (or do not generate) code using the @code{mvcle} instruction -to perform block moves. When @option{-mno-mvcle} is specified, -use a @code{mvc} loop instead. This is the default unless optimizing for -size. - -@item -mdebug -@itemx -mno-debug -@opindex mdebug -@opindex mno-debug -Print (or do not print) additional debug information when compiling. -The default is to not print debug information. - -@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 -@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 -@option{-march=g5}. - -@item -mtune=@var{cpu-type} -@opindex mtune -Tune to @var{cpu-type} everything applicable about the generated code, -except for the ABI and the set of available instructions. -The list of @var{cpu-type} values is the same as for @option{-march}. -The default is the value used for @option{-march}. - -@item -mtpf-trace -@itemx -mno-tpf-trace -@opindex mtpf-trace -@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@. - -@item -mfused-madd -@itemx -mno-fused-madd -@opindex mfused-madd -@opindex mno-fused-madd -Generate code that uses (does not use) the floating point multiply and -accumulate instructions. These instructions are generated by default if -hardware floating point is used. - -@item -mwarn-framesize=@var{framesize} -@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 -size e.g.@: the linux kernel. - -@item -mwarn-dynamicstack -@opindex mwarn-dynamicstack -Emit a warning if the function calls alloca or uses dynamically -sized arrays. This is generally a bad idea with a limited stack size. - -@item -mstack-guard=@var{stack-guard} -@item -mstack-size=@var{stack-size} -@opindex mstack-guard -@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 -causes 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} without -exceeding 64k. -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}. -@end table - -@node Score Options -@subsection Score Options -@cindex Score Options - -These options are defined for Score implementations: - -@table @gcctabopt -@item -meb -@opindex meb -Compile code for big endian mode. This is the default. - -@item -mel -@opindex mel -Compile code for little endian mode. - -@item -mnhwloop -@opindex mnhwloop -Disable generate bcnz instruction. - -@item -muls -@opindex muls -Enable generate unaligned load and store instruction. - -@item -mmac -@opindex mmac -Enable the use of multiply-accumulate instructions. Disabled by default. - -@item -mscore5 -@opindex mscore5 -Specify the SCORE5 as the target architecture. - -@item -mscore5u -@opindex mscore5u -Specify the SCORE5U of the target architecture. - -@item -mscore7 -@opindex mscore7 -Specify the SCORE7 as the target architecture. This is the default. - -@item -mscore7d -@opindex mscore7d -Specify the SCORE7D as the target architecture. -@end table - -@node SH Options -@subsection SH Options - -These @samp{-m} options are defined for the SH implementations: - -@table @gcctabopt -@item -m1 -@opindex m1 -Generate code for the SH1. - -@item -m2 -@opindex m2 -Generate code for the SH2. - -@item -m2e -Generate code for the SH2e. - -@item -m3 -@opindex m3 -Generate code for the SH3. - -@item -m3e -@opindex m3e -Generate code for the SH3e. - -@item -m4-nofpu -@opindex m4-nofpu -Generate code for the SH4 without a floating-point unit. - -@item -m4-single-only -@opindex m4-single-only -Generate code for the SH4 with a floating-point unit that only -supports single-precision arithmetic. - -@item -m4-single -@opindex m4-single -Generate code for the SH4 assuming the floating-point unit is in -single-precision mode by default. - -@item -m4 -@opindex m4 -Generate code for the SH4. - -@item -m4a-nofpu -@opindex m4a-nofpu -Generate code for the SH4al-dsp, or for a SH4a in such a way that the -floating-point unit is not used. - -@item -m4a-single-only -@opindex m4a-single-only -Generate code for the SH4a, in such a way that no double-precision -floating point operations are used. - -@item -m4a-single -@opindex m4a-single -Generate code for the SH4a assuming the floating-point unit is in -single-precision mode by default. - -@item -m4a -@opindex m4a -Generate code for the SH4a. - -@item -m4al -@opindex m4al -Same as @option{-m4a-nofpu}, except that it implicitly passes -@option{-dsp} to the assembler. GCC doesn't generate any DSP -instructions at the moment. - -@item -mb -@opindex mb -Compile code for the processor in big endian mode. - -@item -ml -@opindex ml -Compile code for the processor in little endian mode. - -@item -mdalign -@opindex mdalign -Align doubles at 64-bit boundaries. Note that this changes the calling -conventions, and thus some functions from the standard C library will -not work unless you recompile it first with @option{-mdalign}. - -@item -mrelax -@opindex mrelax -Shorten some address references at link time, when possible; uses the -linker option @option{-relax}. - -@item -mbigtable -@opindex mbigtable -Use 32-bit offsets in @code{switch} tables. The default is to use -16-bit offsets. - -@item -mfmovd -@opindex mfmovd -Enable the use of the instruction @code{fmovd}. - -@item -mhitachi -@opindex mhitachi -Comply with the calling conventions defined by Renesas. - -@item -mrenesas -@opindex mhitachi -Comply with the calling conventions defined by Renesas. - -@item -mno-renesas -@opindex mhitachi -Comply with the calling conventions defined for GCC before the Renesas -conventions were available. This option is the default for all -targets of the SH toolchain except for @samp{sh-symbianelf}. - -@item -mnomacsave -@opindex mnomacsave -Mark the @code{MAC} register as call-clobbered, even if -@option{-mhitachi} is given. - -@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 -Dump instruction size and location in the assembly code. - -@item -mpadstruct -@opindex mpadstruct -This option is deprecated. It pads structures to multiple of 4 bytes, -which is incompatible with the SH ABI@. - -@item -mspace -@opindex mspace -@c APPLE LOCAL 4231761 -Oz -Optimize for space instead of speed. Implied by @option{-Os} and @option{-Oz} (APPLE ONLY). - -@item -mprefergot -@opindex mprefergot -When generating position-independent code, emit function calls using -the Global Offset Table instead of the Procedure Linkage Table. - -@item -musermode -@opindex musermode -Generate a library function call to invalidate instruction cache -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 -@subsection SPARC Options -@cindex SPARC options - -These @samp{-m} options are supported on the SPARC: - -@table @gcctabopt -@item -mno-app-regs -@itemx -mapp-regs -@opindex mno-app-regs -@opindex mapp-regs -Specify @option{-mapp-regs} to generate output using the global registers -2 through 4, which the SPARC SVR4 ABI reserves for applications. This -is the default. - -To be fully SVR4 ABI compliant at the cost of some performance loss, -specify @option{-mno-app-regs}. You should compile libraries and system -software with this option. - -@item -mfpu -@itemx -mhard-float -@opindex mfpu -@opindex mhard-float -Generate output containing floating point instructions. This is the -default. - -@item -mno-fpu -@itemx -msoft-float -@opindex mno-fpu -@opindex msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all SPARC -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets @samp{sparc-*-aout} and -@samp{sparclite-*-*} do provide software floating point support. - -@option{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @option{-msoft-float} in order for -this to work. - -@item -mhard-quad-float -@opindex mhard-quad-float -Generate output containing quad-word (long double) floating point -instructions. - -@item -msoft-quad-float -@opindex msoft-quad-float -Generate output containing library calls for quad-word (long double) -floating point instructions. The functions called are those specified -in the SPARC ABI@. This is the default. - -As of this writing, there are no SPARC implementations that have hardware -support for the quad-word floating point instructions. They all invoke -a trap handler for one of these instructions, and then the trap handler -emulates the effect of the instruction. Because of the trap handler overhead, -this is much slower than calling the ABI library routines. Thus the -@option{-msoft-quad-float} option is the default. - -@item -mno-unaligned-doubles -@itemx -munaligned-doubles -@opindex mno-unaligned-doubles -@opindex munaligned-doubles -Assume that doubles have 8 byte alignment. This is the default. - -With @option{-munaligned-doubles}, GCC assumes that doubles have 8 byte -alignment only if they are contained in another type, or if they have an -absolute address. Otherwise, it assumes they have 4 byte alignment. -Specifying this option avoids some rare compatibility problems with code -generated by other compilers. It is not the default because it results -in a performance loss, especially for floating point code. - -@item -mno-faster-structs -@itemx -mfaster-structs -@opindex mno-faster-structs -@opindex mfaster-structs -With @option{-mfaster-structs}, the compiler assumes that structures -should have 8 byte alignment. This enables the use of pairs of -@code{ldd} and @code{std} instructions for copies in structure -assignment, in place of twice as many @code{ld} and @code{st} pairs. -However, the use of this changed alignment directly violates the SPARC -ABI@. Thus, it's intended only for use on targets where the developer -acknowledges that their resulting code will not be directly in line with -the rules of the ABI@. - -@item -mimpure-text -@opindex mimpure-text -@option{-mimpure-text}, used in addition to @option{-shared}, tells -the compiler to not pass @option{-z text} to the linker when linking a -shared object. Using this option, you can link position-dependent -code into a shared object. - -@option{-mimpure-text} suppresses the ``relocations remain against -allocatable but non-writable sections'' linker error message. -However, the necessary relocations will trigger copy-on-write, and the -shared object is not actually shared across processes. Instead of -using @option{-mimpure-text}, you should compile all source code with -@option{-fpic} or @option{-fPIC}. - -This option is only available on SunOS and Solaris. - -@item -mcpu=@var{cpu_type} -@opindex mcpu -Set the instruction set, register set, and instruction scheduling parameters -for machine type @var{cpu_type}. Supported values for @var{cpu_type} are -@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite}, -@samp{f930}, @samp{f934}, @samp{hypersparc}, @samp{sparclite86x}, -@samp{sparclet}, @samp{tsc701}, @samp{v9}, @samp{ultrasparc}, -@samp{ultrasparc3}, and @samp{niagara}. - -Default instruction scheduling parameters are used for values that select -an architecture and not an implementation. These are @samp{v7}, @samp{v8}, -@samp{sparclite}, @samp{sparclet}, @samp{v9}. - -Here is a list of each supported architecture and their supported -implementations. - -@smallexample - v7: cypress - v8: supersparc, hypersparc - sparclite: f930, f934, sparclite86x - sparclet: tsc701 - v9: ultrasparc, ultrasparc3, niagara -@end smallexample - -By default (unless configured otherwise), GCC generates code for the V7 -variant of the SPARC architecture. With @option{-mcpu=cypress}, the compiler -additionally optimizes it for the Cypress CY7C602 chip, as used in the -SPARCStation/SPARCServer 3xx series. This is also appropriate for the older -SPARCStation 1, 2, IPX etc. - -With @option{-mcpu=v8}, GCC generates code for the V8 variant of the SPARC -architecture. The only difference from V7 code is that the compiler emits -the integer multiply and integer divide instructions which exist in SPARC-V8 -but not in SPARC-V7. With @option{-mcpu=supersparc}, the compiler additionally -optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and -2000 series. - -With @option{-mcpu=sparclite}, GCC generates code for the SPARClite variant of -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 -@option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu -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, -integer divide step and scan (@code{ffs}) instructions which exist in SPARClet -but not in SPARC-V7. With @option{-mcpu=tsc701}, the compiler additionally -optimizes it for the TEMIC SPARClet chip. - -With @option{-mcpu=v9}, GCC generates code for the V9 variant of the SPARC -architecture. This adds 64-bit integer and floating-point move instructions, -3 additional floating-point condition code registers and conditional move -instructions. With @option{-mcpu=ultrasparc}, the compiler additionally -optimizes it for the Sun UltraSPARC I/II/IIi chips. With -@option{-mcpu=ultrasparc3}, the compiler additionally optimizes it for the -Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With -@option{-mcpu=niagara}, the compiler additionally optimizes it for -Sun UltraSPARC T1 chips. - -@item -mtune=@var{cpu_type} -@opindex mtune -Set the instruction scheduling parameters for machine type -@var{cpu_type}, but do not set the instruction set or register set that the -option @option{-mcpu=@var{cpu_type}} would. - -The same values for @option{-mcpu=@var{cpu_type}} can be used for -@option{-mtune=@var{cpu_type}}, but the only useful values are those -that select a particular cpu implementation. Those are @samp{cypress}, -@samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934}, -@samp{sparclite86x}, @samp{tsc701}, @samp{ultrasparc}, -@samp{ultrasparc3}, and @samp{niagara}. - -@item -mv8plus -@itemx -mno-v8plus -@opindex mv8plus -@opindex mno-v8plus -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. - -@item -mvis -@itemx -mno-vis -@opindex mvis -@opindex mno-vis -With @option{-mvis}, GCC generates code that takes advantage of the UltraSPARC -Visual Instruction Set extensions. The default is @option{-mno-vis}. -@end table - -These @samp{-m} options are supported in addition to the above -on SPARC-V9 processors in 64-bit environments: - -@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 and Linux. - -@item -m32 -@itemx -m64 -@opindex m32 -@opindex m64 -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. - -@item -mcmodel=medlow -@opindex mcmodel=medlow -Generate code for the Medium/Low code model: 64-bit addresses, programs -must be linked in the low 32 bits of memory. Programs can be statically -or dynamically linked. - -@item -mcmodel=medmid -@opindex mcmodel=medmid -Generate code for the Medium/Middle code model: 64-bit addresses, programs -must be linked in the low 44 bits of memory, the text and data segments must -be less than 2GB in size and the data segment must be located within 2GB of -the text segment. - -@item -mcmodel=medany -@opindex mcmodel=medany -Generate code for the Medium/Anywhere code model: 64-bit addresses, programs -may be linked anywhere in memory, the text and data segments must be less -than 2GB in size and the data segment must be located within 2GB of the -text segment. - -@item -mcmodel=embmedany -@opindex mcmodel=embmedany -Generate code for the Medium/Anywhere code model for embedded systems: -64-bit addresses, the text and data segments must be less than 2GB in -size, both starting anywhere in memory (determined at link time). The -global register %g4 points to the base of the data segment. Programs -are statically linked and PIC is not supported. - -@item -mstack-bias -@itemx -mno-stack-bias -@opindex mstack-bias -@opindex mno-stack-bias -With @option{-mstack-bias}, GCC assumes that the stack pointer, and -frame pointer if present, are offset by @minus{}2047 which must be added back -when making stack frame references. This is the default in 64-bit mode. -Otherwise, assume no such offset is present. -@end table - -These switches are supported in addition to the above on Solaris: - -@table @gcctabopt -@item -threads -@opindex threads -Add support for multithreading using the Solaris threads library. This -option sets flags for both the preprocessor and linker. This option does -not affect the thread safety of object code produced by the compiler or -that of libraries supplied with it. - -@item -pthreads -@opindex pthreads -Add support for multithreading using the POSIX threads library. This -option sets flags for both the preprocessor and linker. This option does -not affect the thread safety of object code produced by the compiler or -that of libraries supplied with it. - -@item -pthread -@opindex pthread -This is a synonym for @option{-pthreads}. -@end table - -@node System V Options -@subsection Options for System V - -These additional options are available on System V Release 4 for -compatibility with other compilers on those systems: - -@table @gcctabopt -@item -G -@opindex G -Create a shared object. -It is recommended that @option{-symbolic} or @option{-shared} be used instead. - -@item -Qy -@opindex Qy -Identify the versions of each tool used by the compiler, in a -@code{.ident} assembler directive in the output. - -@item -Qn -@opindex Qn -Refrain from adding @code{.ident} directives to the output file (this is -the default). - -@item -YP,@var{dirs} -@opindex YP -Search the directories @var{dirs}, and no others, for libraries -specified with @option{-l}. - -@item -Ym,@var{dir} -@opindex Ym -Look in the directory @var{dir} to find the M4 preprocessor. -The assembler uses this option. -@c This is supposed to go with a -Yd for predefined M4 macro files, but -@c the generic assembler that comes with Solaris takes just -Ym. -@end table - -@node TMS320C3x/C4x Options -@subsection TMS320C3x/C4x Options -@cindex TMS320C3x/C4x Options - -These @samp{-m} options are defined for TMS320C3x/C4x implementations: - -@table @gcctabopt - -@item -mcpu=@var{cpu_type} -@opindex mcpu -Set the instruction set, register set, and instruction scheduling -parameters for machine type @var{cpu_type}. Supported values for -@var{cpu_type} are @samp{c30}, @samp{c31}, @samp{c32}, @samp{c40}, and -@samp{c44}. The default is @samp{c40} to generate code for the -TMS320C40. - -@item -mbig-memory -@itemx -mbig -@itemx -msmall-memory -@itemx -msmall -@opindex mbig-memory -@opindex mbig -@opindex msmall-memory -@opindex msmall -Generates code for the big or small memory model. The small memory -model assumed that all data fits into one 64K word page. At run-time -the data page (DP) register must be set to point to the 64K page -containing the .bss and .data program sections. The big memory model is -the default and requires reloading of the DP register for every direct -memory access. - -@item -mbk -@itemx -mno-bk -@opindex mbk -@opindex mno-bk -Allow (disallow) allocation of general integer operands into the block -count register BK@. - -@item -mdb -@itemx -mno-db -@opindex mdb -@opindex mno-db -Enable (disable) generation of code using decrement and branch, -DBcond(D), instructions. This is enabled by default for the C4x. To be -on the safe side, this is disabled for the C3x, since the maximum -iteration count on the C3x is @math{2^{23} + 1} (but who iterates loops more than -@math{2^{23}} times on the C3x?). Note that GCC will try to reverse a loop so -that it can utilize the decrement and branch instruction, but will give -up if there is more than one memory reference in the loop. Thus a loop -where the loop counter is decremented can generate slightly more -efficient code, in cases where the RPTB instruction cannot be utilized. - -@item -mdp-isr-reload -@itemx -mparanoid -@opindex mdp-isr-reload -@opindex mparanoid -Force the DP register to be saved on entry to an interrupt service -routine (ISR), reloaded to point to the data section, and restored on -exit from the ISR@. This should not be required unless someone has -violated the small memory model by modifying the DP register, say within -an object library. - -@item -mmpyi -@itemx -mno-mpyi -@opindex mmpyi -@opindex mno-mpyi -For the C3x use the 24-bit MPYI instruction for integer multiplies -instead of a library call to guarantee 32-bit results. Note that if one -of the operands is a constant, then the multiplication will be performed -using shifts and adds. If the @option{-mmpyi} option is not specified for the C3x, -then squaring operations are performed inline instead of a library call. - -@item -mfast-fix -@itemx -mno-fast-fix -@opindex mfast-fix -@opindex mno-fast-fix -The C3x/C4x FIX instruction to convert a floating point value to an -integer value chooses the nearest integer less than or equal to the -floating point value rather than to the nearest integer. Thus if the -floating point number is negative, the result will be incorrectly -truncated an additional code is necessary to detect and correct this -case. This option can be used to disable generation of the additional -code required to correct the result. - -@item -mrptb -@itemx -mno-rptb -@opindex mrptb -@opindex mno-rptb -Enable (disable) generation of repeat block sequences using the RPTB -instruction for zero overhead looping. The RPTB construct is only used -for innermost loops that do not call functions or jump across the loop -boundaries. There is no advantage having nested RPTB loops due to the -overhead required to save and restore the RC, RS, and RE registers. -This is enabled by default with @option{-O2}. - -@item -mrpts=@var{count} -@itemx -mno-rpts -@opindex mrpts -@opindex mno-rpts -Enable (disable) the use of the single instruction repeat instruction -RPTS@. If a repeat block contains a single instruction, and the loop -count can be guaranteed to be less than the value @var{count}, GCC will -emit a RPTS instruction instead of a RPTB@. If no value is specified, -then a RPTS will be emitted even if the loop count cannot be determined -at compile time. Note that the repeated instruction following RPTS does -not have to be reloaded from memory each iteration, thus freeing up the -CPU buses for operands. However, since interrupts are blocked by this -instruction, it is disabled by default. - -@item -mloop-unsigned -@itemx -mno-loop-unsigned -@opindex mloop-unsigned -@opindex mno-loop-unsigned -The maximum iteration count when using RPTS and RPTB (and DB on the C40) -is @math{2^{31} + 1} since these instructions test if the iteration count is -negative to terminate the loop. If the iteration count is unsigned -there is a possibility than the @math{2^{31} + 1} maximum iteration count may be -exceeded. This switch allows an unsigned iteration count. - -@item -mti -@opindex mti -Try to emit an assembler syntax that the TI assembler (asm30) is happy -with. This also enforces compatibility with the API employed by the TI -C3x C compiler. For example, long doubles are passed as structures -rather than in floating point registers. - -@item -mregparm -@itemx -mmemparm -@opindex mregparm -@opindex mmemparm -Generate code that uses registers (stack) for passing arguments to functions. -By default, arguments are passed in registers where possible rather -than by pushing arguments on to the stack. - -@item -mparallel-insns -@itemx -mno-parallel-insns -@opindex mparallel-insns -@opindex mno-parallel-insns -Allow the generation of parallel instructions. This is enabled by -default with @option{-O2}. - -@item -mparallel-mpy -@itemx -mno-parallel-mpy -@opindex mparallel-mpy -@opindex mno-parallel-mpy -Allow the generation of MPY||ADD and MPY||SUB parallel instructions, -provided @option{-mparallel-insns} is also specified. These instructions have -tight register constraints which can pessimize the code generation -of large functions. - -@end table - -@node V850 Options -@subsection V850 Options -@cindex V850 Options - -These @samp{-m} options are defined for V850 implementations: - -@table @gcctabopt -@item -mlong-calls -@itemx -mno-long-calls -@opindex mlong-calls -@opindex mno-long-calls -Treat all calls as being far away (near). If calls are assumed to be -far away, the compiler will always load the functions address up into a -register, and call indirect through the pointer. - -@item -mno-ep -@itemx -mep -@opindex mno-ep -@opindex mep -Do not optimize (do optimize) basic blocks that use the same index -pointer 4 or more times to copy pointer into the @code{ep} register, and -use the shorter @code{sld} and @code{sst} instructions. The @option{-mep} -option is on by default if you optimize. - -@item -mno-prolog-function -@itemx -mprolog-function -@opindex mno-prolog-function -@opindex mprolog-function -Do not use (do use) external functions to save and restore registers -at the prologue and epilogue of a function. The external functions -are slower, but use less code space if more than one function saves -the same number of registers. The @option{-mprolog-function} option -is on by default if you optimize. - -@item -mspace -@opindex mspace -Try to make the code as small as possible. At present, this just turns -on the @option{-mep} and @option{-mprolog-function} options. - -@item -mtda=@var{n} -@opindex mtda -Put static or global variables whose size is @var{n} bytes or less into -the tiny data area that register @code{ep} points to. The tiny data -area can hold up to 256 bytes in total (128 bytes for byte references). - -@item -msda=@var{n} -@opindex msda -Put static or global variables whose size is @var{n} bytes or less into -the small data area that register @code{gp} points to. The small data -area can hold up to 64 kilobytes. - -@item -mzda=@var{n} -@opindex mzda -Put static or global variables whose size is @var{n} bytes or less into -the first 32 kilobytes of memory. - -@item -mv850 -@opindex mv850 -Specify that the target processor is the V850. - -@item -mbig-switch -@opindex mbig-switch -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. - -@item -mapp-regs -@opindex mapp-regs -This option will cause r2 and r5 to be used in the code generated by -the compiler. This setting is the default. - -@item -mno-app-regs -@opindex mno-app-regs -This option will cause r2 and r5 to be treated as fixed registers. - -@item -mv850e1 -@opindex mv850e1 -Specify that the target processor is the V850E1. The preprocessor -constants @samp{__v850e1__} and @samp{__v850e__} will be defined if -this option is used. - -@item -mv850e -@opindex mv850e -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} -are defined then a default target processor will be chosen and the -relevant @samp{__v850*__} preprocessor constant will be defined. - -The preprocessor constants @samp{__v850} and @samp{__v851__} are always -defined, regardless of which processor variant is the target. - -@item -mdisable-callt -@opindex mdisable-callt -This option will suppress generation of the CALLT instruction for the -v850e and v850e1 flavors of the v850 architecture. The default is -@option{-mno-disable-callt} which allows the CALLT instruction to be used. - -@end table - -@node VAX Options -@subsection VAX Options -@cindex VAX options - -These @samp{-m} options are defined for the VAX: - -@table @gcctabopt -@item -munix -@opindex munix -Do not output certain jump instructions (@code{aobleq} and so on) -that the Unix assembler for the VAX cannot handle across long -ranges. - -@item -mgnu -@opindex mgnu -Do output those jump instructions, on the assumption that you -will assemble with the GNU assembler. - -@item -mg -@opindex mg -Output code for g-format floating point numbers instead of d-format. -@end table - -@node x86-64 Options -@subsection x86-64 Options -@cindex x86-64 options - -These are listed under @xref{i386 and x86-64 Options}. - -@node Xstormy16 Options -@subsection Xstormy16 Options -@cindex Xstormy16 Options - -These options are defined for Xstormy16: - -@table @gcctabopt -@item -msim -@opindex msim -Choose startup files and linker script suitable for the simulator. -@end table - -@node Xtensa Options -@subsection Xtensa Options -@cindex Xtensa Options - -These options are supported for Xtensa targets: - -@table @gcctabopt -@item -mconst16 -@itemx -mno-const16 -@opindex mconst16 -@opindex mno-const16 -Enable or disable use of @code{CONST16} instructions for loading -constant values. The @code{CONST16} instruction is currently not a -standard option from Tensilica. When enabled, @code{CONST16} -instructions are always used in place of the standard @code{L32R} -instructions. The use of @code{CONST16} is enabled by default only if -the @code{L32R} instruction is not available. - -@item -mfused-madd -@itemx -mno-fused-madd -@opindex mfused-madd -@opindex mno-fused-madd -Enable or disable use of fused multiply/add and multiply/subtract -instructions in the floating-point option. This has no effect if the -floating-point option is not also enabled. Disabling fused multiply/add -and multiply/subtract instructions forces the compiler to use separate -instructions for the multiply and add/subtract operations. This may be -desirable in some cases where strict IEEE 754-compliant results are -required: the fused multiply add/subtract instructions do not round the -intermediate result, thereby producing results with @emph{more} bits of -precision than specified by the IEEE standard. Disabling fused multiply -add/subtract instructions also ensures that the program output is not -sensitive to the compiler's ability to combine multiply and add/subtract -operations. - -@item -mtext-section-literals -@itemx -mno-text-section-literals -@opindex mtext-section-literals -@opindex mno-text-section-literals -Control the treatment of literal pools. The default is -@option{-mno-text-section-literals}, which places literals in a separate -section in the output file. This allows the literal pool to be placed -in a data RAM/ROM, and it also allows the linker to combine literal -pools from separate object files to remove redundant literals and -improve code size. With @option{-mtext-section-literals}, the literals -are interspersed in the text section in order to keep them as close as -possible to their references. This may be necessary for large assembly -files. - -@item -mtarget-align -@itemx -mno-target-align -@opindex mtarget-align -@opindex mno-target-align -When this option is enabled, GCC instructs the assembler to -automatically align instructions to reduce branch penalties at the -expense of some code density. The assembler attempts to widen density -instructions to align branch targets and the instructions following call -instructions. If there are not enough preceding safe density -instructions to align a target, no widening will be performed. The -default is @option{-mtarget-align}. These options do not affect the -treatment of auto-aligned instructions like @code{LOOP}, which the -assembler will always align, either by widening density instructions or -by inserting no-op instructions. - -@item -mlongcalls -@itemx -mno-longcalls -@opindex mlongcalls -@opindex mno-longcalls -When this option is enabled, GCC instructs the assembler to translate -direct calls to indirect calls unless it can determine that the target -of a direct call is in the range allowed by the call instruction. This -translation typically occurs for calls to functions in other source -files. Specifically, the assembler translates a direct @code{CALL} -instruction into an @code{L32R} followed by a @code{CALLX} instruction. -The default is @option{-mno-longcalls}. This option should be used in -programs where the call target can potentially be out of range. This -option is implemented in the assembler, not the compiler, so the -assembly code generated by GCC will still show direct call -instructions---look at the disassembled object code to see the actual -instructions. Note that the assembler will use an indirect call for -every cross-file call, not just those that really will be out of range. -@end table - -@node zSeries Options -@subsection zSeries Options -@cindex zSeries options - -These are listed under @xref{S/390 and zSeries Options}. -@c APPLE LOCAL prune man page -@end ignore - -@node Code Gen Options -@section Options for Code Generation Conventions -@cindex code generation conventions -@cindex options, code generation -@cindex run-time options - -These machine-independent options control the interface conventions -used in code generation. - -Most of them have both positive and negative forms; the negative form -of @option{-ffoo} would be @option{-fno-foo}. In the table below, only -one of the forms is listed---the one which is not the default. You -can figure out the other form by either removing @samp{no-} or adding -it. - -@table @gcctabopt -@item -fbounds-check -@opindex fbounds-check -For front-ends that support it, generate additional code to check that -indices used to access arrays are within the declared range. This is -currently only supported by the Java and Fortran front-ends, where -this option defaults to true and false respectively. - -@c APPLE LOCAL prune man page 5547358 -@ignore -@item -ftrapv -@opindex ftrapv -This option generates traps for signed overflow on addition, subtraction, -multiplication operations. -@c APPLE LOCAL prune man page 5547358 -@end ignore - -@item -fwrapv -@opindex fwrapv -This option instructs the compiler to assume that signed arithmetic -overflow of addition, subtraction and multiplication wraps around -using twos-complement representation. This flag enables some optimizations -and disables others. This option is enabled by default for the Java -front-end, as required by the Java language specification. - -@item -fexceptions -@opindex fexceptions -Enable exception handling. Generates extra code needed to propagate -exceptions. For some targets, this implies GCC will generate frame -unwind information for all functions, which can produce significant data -size overhead, although it does not affect execution. If you do not -specify this option, GCC will enable it by default for languages like -C++ which normally require exception handling, and disable it for -languages like C that do not normally require it. However, you may need -to enable this option when compiling C code that needs to interoperate -properly with exception handlers written in C++. You may also wish to -disable this option if you are compiling older C++ programs that don't -use exception handling. - -@item -fnon-call-exceptions -@opindex fnon-call-exceptions -Generate code that allows trapping instructions to throw exceptions. -Note that this requires platform-specific runtime support that does -not exist everywhere. Moreover, it only allows @emph{trapping} -instructions to throw exceptions, i.e.@: memory references or floating -point instructions. It does not allow exceptions to be thrown from -arbitrary signal handlers such as @code{SIGALRM}. - -@item -funwind-tables -@opindex funwind-tables -Similar to @option{-fexceptions}, except that it will just generate any needed -static data, but will not affect the generated code in any other way. -You will normally not enable this option; instead, a language processor -that needs this handling would enable it on your behalf. - -@item -fasynchronous-unwind-tables -@opindex fasynchronous-unwind-tables -Generate unwind table in dwarf2 format, if supported by target machine. The -table is exact at each instruction boundary, so it can be used for stack -unwinding from asynchronous events (such as debugger or garbage collector). - -@item -fpcc-struct-return -@opindex fpcc-struct-return -Return ``short'' @code{struct} and @code{union} values in memory like -longer ones, rather than in registers. This convention is less -efficient, but it has the advantage of allowing intercallability between -GCC-compiled files and files compiled with other compilers, particularly -the Portable C Compiler (pcc). - -The precise convention for returning structures in memory depends -on the target configuration macros. - -Short structures and unions are those whose size and alignment match -that of some integer type. - -@strong{Warning:} code compiled with the @option{-fpcc-struct-return} -switch is not binary compatible with code compiled with the -@option{-freg-struct-return} switch. -Use it to conform to a non-default application binary interface. - -@item -freg-struct-return -@opindex freg-struct-return -Return @code{struct} and @code{union} values in registers when possible. -This is more efficient for small structures than -@option{-fpcc-struct-return}. - -If you specify neither @option{-fpcc-struct-return} nor -@option{-freg-struct-return}, GCC defaults to whichever convention is -standard for the target. If there is no standard convention, GCC -defaults to @option{-fpcc-struct-return}, except on targets where GCC is -the principal compiler. In those cases, we can choose the standard, and -we chose the more efficient register return alternative. - -@strong{Warning:} code compiled with the @option{-freg-struct-return} -switch is not binary compatible with code compiled with the -@option{-fpcc-struct-return} switch. -Use it to conform to a non-default application binary interface. - -@item -fshort-enums -@opindex fshort-enums -Allocate to an @code{enum} type only as many bytes as it needs for the -declared range of possible values. Specifically, the @code{enum} type -will be equivalent to the smallest integer type which has enough room. - -@strong{Warning:} the @option{-fshort-enums} switch causes GCC to generate -code that is not binary compatible with code generated without that switch. -Use it to conform to a non-default application binary interface. - -@item -fshort-double -@opindex fshort-double -Use the same size for @code{double} as for @code{float}. - -@strong{Warning:} the @option{-fshort-double} switch causes GCC to generate -code that is not binary compatible with code generated without that switch. -Use it to conform to a non-default application binary interface. - -@item -fshort-wchar -@opindex fshort-wchar -Override the underlying type for @samp{wchar_t} to be @samp{short -unsigned int} instead of the default for the target. This option is -useful for building programs to run under WINE@. - -@strong{Warning:} the @option{-fshort-wchar} switch causes GCC to generate -code that is not binary compatible with code generated without that switch. -Use it to conform to a non-default application binary interface. - -@item -fno-common -@opindex fno-common -In C, allocate even uninitialized global variables in the data section of the -object file, rather than generating them as common blocks. This has the -effect that if the same variable is declared (without @code{extern}) in -two different compilations, you will get an error when you link them. -The only reason this might be useful is if you wish to verify that the -program will work on other systems which always work this way. - -@item -fno-ident -@opindex fno-ident -Ignore the @samp{#ident} directive. - -@item -finhibit-size-directive -@opindex finhibit-size-directive -Don't output a @code{.size} assembler directive, or anything else that -would cause trouble if the function is split in the middle, and the -two halves are placed at locations far apart in memory. This option is -used when compiling @file{crtstuff.c}; you should not need to use it -for anything else. - -@item -fverbose-asm -@opindex fverbose-asm -Put extra commentary information in the generated assembly code to -make it more readable. This option is generally only of use to those -who actually need to read the generated assembly code (perhaps while -debugging the compiler itself). - -@option{-fno-verbose-asm}, the default, causes the -extra information to be omitted and is useful when comparing two assembler -files. - -@item -fpic -@opindex fpic -@cindex global offset table -@cindex PIC -Generate position-independent code (PIC) suitable for use in a shared -library, if supported for the target machine. Such code accesses all -constant addresses through a global offset table (GOT)@. The dynamic -loader resolves the GOT entries when the program starts (the dynamic -loader is not part of GCC; it is part of the operating system). If -the GOT size for the linked executable exceeds a machine-specific -maximum size, you get an error message from the linker indicating that -@option{-fpic} does not work; in that case, recompile with @option{-fPIC} -instead. (These maximums are 8k on the SPARC and 32k -on the m68k and RS/6000. The 386 has no such limit.) - -Position-independent code requires special support, and therefore works -only on certain machines. For the 386, GCC supports PIC for System V -but not for the Sun 386i. Code generated for the IBM RS/6000 is always -position-independent. - -When this flag is set, the macros @code{__pic__} and @code{__PIC__} -are defined to 1. - -@item -fPIC -@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, -PowerPC and SPARC@. - -Position-independent code requires special support, and therefore works -only on certain machines. - -When this flag is set, the macros @code{__pic__} and @code{__PIC__} -are defined to 2. - -@c APPLE LOCAL begin manual -@option{-fPIC} is the default on Darwin and Mac OS X. -@c APPLE LOCAL end manual - -@item -fpie -@itemx -fPIE -@opindex fpie -@opindex fPIE -These options are similar to @option{-fpic} and @option{-fPIC}, but -generated position independent code can be only linked into executables. -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 -should never refer to it (except perhaps as a stack pointer, frame -pointer or in some other fixed role). - -@var{reg} must be the name of a register. The register names accepted -are machine-specific and are defined in the @code{REGISTER_NAMES} -macro in the machine description macro file. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@item -fcall-used-@var{reg} -@opindex fcall-used -Treat the register named @var{reg} as an allocable register that is -clobbered by function calls. It may be allocated for temporaries or -variables that do not live across a call. Functions compiled this way -will not save and restore the register @var{reg}. - -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@item -fcall-saved-@var{reg} -@opindex fcall-saved -Treat the register named @var{reg} as an allocable register saved by -functions. It may be allocated even for temporaries or variables that -live across a call. Functions compiled this way will save and restore -the register @var{reg} if they use it. - -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. - -A different sort of disaster will result from the use of this flag for -a register in which function values may be returned. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@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 -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. - -@strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate -code that is not binary compatible with code generated without that switch. -Additionally, it makes the code suboptimal. -Use it to conform to a non-default application binary interface. - -@item -finstrument-functions -@opindex finstrument-functions -Generate instrumentation calls for entry and exit to functions. Just -after function entry and just before function exit, the following -profiling functions will be called with the address of the current -function and its call site. (On some platforms, -@code{__builtin_return_address} does not work beyond the current -function, so the call site information may not be available to the -profiling functions otherwise.) - -@smallexample -void __cyg_profile_func_enter (void *this_fn, - void *call_site); -void __cyg_profile_func_exit (void *this_fn, - void *call_site); -@end smallexample - -The first argument is the address of the start of the current function, -which may be looked up exactly in the symbol table. - -This instrumentation is also done for functions expanded inline in other -functions. The profiling calls will indicate where, conceptually, the -inline function is entered and exited. This means that addressable -versions of such functions must be available. If all your uses of a -function are expanded inline, this may mean an additional expansion of -code size. If you use @samp{extern inline} in your C code, an -addressable version of such functions must be provided. (This is -normally the case anyways, but if you get lucky and the optimizer always -expands the functions inline, you might have gotten away without -providing static copies.) - -A function may be given the attribute @code{no_instrument_function}, in -which case this instrumentation will not be done. This can be used, for -example, for the profiling functions listed above, high-priority -interrupt routines, and any functions from which the profiling functions -cannot safely be called (perhaps signal handlers, if the profiling -routines generate output or allocate memory). - -@item -fstack-check -@opindex fstack-check -Generate code to verify that you do not go beyond the boundary of the -stack. You should specify this flag if you are running in an -environment with multiple threads, but only rarely need to specify it in -a single-threaded environment since stack overflow is automatically -detected on nearly all systems if there is only one stack. - -Note that this switch does not actually cause checking to be done; the -operating system must do that. The switch causes generation of code -to ensure that the operating system sees the stack being extended. - -@item -fstack-limit-register=@var{reg} -@itemx -fstack-limit-symbol=@var{sym} -@itemx -fno-stack-limit -@opindex fstack-limit-register -@opindex fstack-limit-symbol -@opindex fno-stack-limit -Generate code to ensure that the stack does not grow beyond a certain value, -either the value of a register or the address of a symbol. If the stack -would grow beyond the value, a signal is raised. For most targets, -the signal is raised before the stack overruns the boundary, so -it is possible to catch the signal without taking special precautions. - -For instance, if the stack starts at absolute address @samp{0x80000000} -and grows downwards, you can use the flags -@option{-fstack-limit-symbol=__stack_limit} and -@option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit -of 128KB@. Note that this may only work with the GNU linker. - -@cindex aliasing of parameters -@cindex parameters, aliased -@item -fargument-alias -@itemx -fargument-noalias -@itemx -fargument-noalias-global -@itemx -fargument-noalias-anything -@opindex fargument-alias -@opindex fargument-noalias -@opindex fargument-noalias-global -@opindex fargument-noalias-anything -Specify the possible relationships among parameters and between -parameters and global data. - -@option{-fargument-alias} specifies that arguments (parameters) may -alias each other and may alias global storage.@* -@option{-fargument-noalias} specifies that arguments do not alias -each other, but may alias global storage.@* -@option{-fargument-noalias-global} specifies that arguments do not -alias each other and do not alias global storage. -@option{-fargument-noalias-anything} specifies that arguments do not -alias any other storage. - -Each language will automatically use whatever option is required by -the language standard. You should not need to use these options yourself. - -@item -fleading-underscore -@opindex fleading-underscore -This option and its counterpart, @option{-fno-leading-underscore}, forcibly -change the way C symbols are represented in the object file. One use -is to help link with legacy assembly code. - -@strong{Warning:} the @option{-fleading-underscore} switch causes GCC to -generate code that is not binary compatible with code generated without that -switch. Use it to conform to a non-default application binary interface. -Not all targets provide complete support for this switch. - -@item -ftls-model=@var{model} -Alter the thread-local storage model to be used (@pxref{Thread-Local}). -The @var{model} argument should be one of @code{global-dynamic}, -@code{local-dynamic}, @code{initial-exec} or @code{local-exec}. - -The default without @option{-fpic} is @code{initial-exec}; with -@option{-fpic} the default is @code{global-dynamic}. - -@item -fvisibility=@var{default|internal|hidden|protected} -@opindex fvisibility -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 @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 -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} -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 -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 -the declarations you wish to set visibility for with (for example) -@samp{#pragma GCC visibility push(hidden)} and -@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 -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. - -Be aware that headers from outside your project, in particular system -headers and headers from any other library you use, may not be -expecting to be compiled with visibility other than the default. You -may need to explicitly say @samp{#pragma GCC visibility push(default)} -before including any such headers. - -@samp{extern} declarations are not affected by @samp{-fvisibility}, so -a lot of code can be recompiled with @samp{-fvisibility=hidden} with -no modifications. However, this means that calls to @samp{extern} -functions with no explicit visibility will use the PLT, so it is more -effective to use @samp{__attribute ((visibility))} and/or -@samp{#pragma GCC visibility} to tell the compiler which @samp{extern} -declarations should be treated as hidden. - -Note that @samp{-fvisibility} does affect C++ vague linkage -entities. This means that, for instance, an exception class that will -be thrown between DSOs must be explicitly marked with default -visibility so that the @samp{type_info} nodes will be unified between -the DSOs. - -An overview of these techniques, their benefits and how to use them -is at @w{@uref{http://gcc.gnu.org/wiki/Visibility}}. - -@end table - -@c man end - -@node Environment Variables -@section Environment Variables Affecting GCC -@cindex environment variables - -@c man begin ENVIRONMENT -This section describes several environment variables that affect how GCC -operates. Some of them work by specifying directories or prefixes to use -when searching for various kinds of files. Some are used to specify other -aspects of the compilation environment. - -Note that you can also specify places to search using options such as -@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These -take precedence over places specified using environment variables, which -in turn take precedence over those specified by the configuration of GCC@. -@xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint, -GNU Compiler Collection (GCC) Internals}. - -@table @env -@item LANG -@itemx LC_CTYPE -@c @itemx LC_COLLATE -@itemx LC_MESSAGES -@c @itemx LC_MONETARY -@c @itemx LC_NUMERIC -@c @itemx LC_TIME -@itemx LC_ALL -@findex LANG -@findex LC_CTYPE -@c @findex LC_COLLATE -@findex LC_MESSAGES -@c @findex LC_MONETARY -@c @findex LC_NUMERIC -@c @findex LC_TIME -@findex LC_ALL -@cindex locale -These environment variables control the way that GCC uses -localization information that allow GCC to work with different -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_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 -a string; this is needed for some multibyte encodings that contain quote -and escape characters that would otherwise be interpreted as a string -end or escape. - -The @env{LC_MESSAGES} environment variable specifies the language to -use in diagnostic messages. - -If the @env{LC_ALL} environment variable is set, it overrides the value -of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE} -and @env{LC_MESSAGES} default to the value of the @env{LANG} -environment variable. If none of these variables are set, GCC -defaults to traditional C English behavior. - -@item TMPDIR -@findex TMPDIR -If @env{TMPDIR} is set, it specifies the directory to use for temporary -files. GCC uses temporary files to hold the output of one stage of -compilation which is to be used as input to the next stage: for example, -the output of the preprocessor, which is the input to the compiler -proper. - -@item GCC_EXEC_PREFIX -@findex GCC_EXEC_PREFIX -If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the -names of the subprograms executed by the compiler. No slash is added -when this prefix is combined with the name of a subprogram, but you can -specify a prefix that ends with a slash if you wish. - -If @env{GCC_EXEC_PREFIX} is not set, GCC will attempt to figure out -an appropriate prefix to use based on the pathname it was invoked with. - -If GCC cannot find the subprogram using the specified prefix, it -tries looking in the usual places for the subprogram. - -The default value of @env{GCC_EXEC_PREFIX} is -@file{@var{prefix}/lib/gcc/} where @var{prefix} is the value -of @code{prefix} when you ran the @file{configure} script. - -Other prefixes specified with @option{-B} take precedence over this prefix. - -This prefix is also used for finding files such as @file{crt0.o} that are -used for linking. - -In addition, the prefix is used in an unusual way in finding the -directories to search for header files. For each of the standard -directories whose name normally begins with @samp{/usr/local/lib/gcc} -(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries -replacing that beginning with the specified prefix to produce an -alternate directory name. Thus, with @option{-Bfoo/}, GCC will search -@file{foo/bar} where it would normally search @file{/usr/local/lib/bar}. -These alternate directories are searched first; the standard directories -come next. - -@item COMPILER_PATH -@findex COMPILER_PATH -The value of @env{COMPILER_PATH} is a colon-separated list of -directories, much like @env{PATH}. GCC tries the directories thus -specified when searching for subprograms, if it can't find the -subprograms using @env{GCC_EXEC_PREFIX}. - -@item LIBRARY_PATH -@findex LIBRARY_PATH -The value of @env{LIBRARY_PATH} is a colon-separated list of -directories, much like @env{PATH}. When configured as a native compiler, -GCC tries the directories thus specified when searching for special -linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking -using GCC also uses these directories when searching for ordinary -libraries for the @option{-l} option (but directories specified with -@option{-L} come first). - -@item LANG -@findex LANG -@cindex locale definition -This variable is used to pass locale information to the compiler. One way in -which this information is used is to determine the character set to be used -when character literals, string literals and comments are parsed in C and C++. -When the compiler is configured to allow multibyte characters, -the following values for @env{LANG} are recognized: - -@table @samp -@item C-JIS -Recognize JIS characters. -@item C-SJIS -Recognize SJIS characters. -@item C-EUCJP -Recognize EUCJP characters. -@end table - -If @env{LANG} is not defined, or if it has some other value, then the -compiler will use mblen and mbtowc as defined by the default locale to -recognize and translate multibyte characters. - -@c APPLE LOCAL begin ARM 5905142 -@item MACOSX_DEPLOYMENT_TARGET -@itemx IPHONEOS_DEPLOYMENT_TARGET -These variables are used to set the target OS version, as described -for command-line options @option{-mmacosx-version-min} and -@option{-miphoneos-version-min}. Only one OS version can be specified -per architecture, with @env{MACOSX_DEPLOYMENT_TARGET} taking precedence -on non-ARM targets and @env{IPHONEOS_DEPLOYMENT_TARGET} taking -precedence on ARM targets. - -If either command-line option @option{-mmacosx-version-min} or -@option{-miphoneos-version-min} is specified, both of these -environment variables are ignored. -@c APPLE LOCAL end ARM 5905142 -@end table - -@noindent -Some additional environments variables affect the behavior of the -preprocessor. - -@include cppenv.texi - -@c man end - -@node Precompiled Headers -@section Using Precompiled Headers -@cindex precompiled headers -@cindex speed of compilation - -Often large projects have many header files that are included in every -source file. The time the compiler takes to process these header files -over and over again can account for nearly all of the time required to -build the project. To make builds faster, GCC allows users to -`precompile' a header file; then, if builds can use the precompiled -header file they will be much faster. - -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 -tool like @command{make} to keep the precompiled header up-to-date when -the headers it contains change. - -A precompiled header file will be searched for when @code{#include} is -seen in the compilation. As it searches for the included file -(@pxref{Search Path,,Search Path,cpp,The C Preprocessor}) the -compiler looks for a precompiled header in each directory just before it -looks for the include file in that directory. The name searched for is -the name specified in the @code{#include} with @samp{.gch} appended. If -the precompiled header file can't be used, it is ignored. - -For instance, if you have @code{#include "all.h"}, and you have -@file{all.h.gch} in the same directory as @file{all.h}, then the -precompiled header file will be used if possible, and the original -header will be used otherwise. - -Alternatively, you might decide to put the precompiled header file in a -directory and use @option{-I} to ensure that directory is searched -before (or instead of) the directory containing the original header. -Then, if you want to check that the precompiled header file is always -used, you can put a file of the same name as the original header in this -directory containing an @code{#error} command. - -This also works with @option{-include}. So yet another way to use -precompiled headers, good for projects not designed with precompiled -header files in mind, is to simply take most of the header files used by -a project, include them from another header file, precompile that header -file, and @option{-include} the precompiled header. If the header files -have guards against multiple inclusion, they will be skipped because -they've already been included (in the precompiled header). - -If you need to precompile the same header file for different -languages, targets, or compiler options, you can instead make a -@emph{directory} named like @file{all.h.gch}, and put each precompiled -header in the directory, perhaps using @option{-o}. It doesn't matter -what you call the files in the directory, every precompiled header in -the directory will be considered. The first precompiled header -encountered in the directory that is valid for this compilation will -be used; they're searched in no particular order. - -There are many other possibilities, limited only by your imagination, -good sense, and the constraints of your build system. - -A precompiled header file can be used only when these conditions apply: - -@itemize -@item -Only one precompiled header can be used in a particular compilation. - -@item -A precompiled header can't be used once the first C token is seen. You -can have preprocessor directives before a precompiled header; you can -even include a precompiled header from inside another header, so long as -there are no C tokens before the @code{#include}. - -@item -The precompiled header file must be produced for the same language as -the current compilation. You can't use a C precompiled header for a C++ -compilation. - -@item -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 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. -There are also some options that define macros implicitly, like -@option{-O} and @option{-Wdeprecated}; the same rule applies to macros -defined this way. - -@item If debugging information is output when using the precompiled -header, using @option{-g} or similar, the same kind of debugging information -must have been output when building the precompiled header. However, -a precompiled header built using @option{-g} can be used in a compilation -when no debugging information is being output. - -@item The same @option{-m} options must generally be used when building -and using the precompiled header. @xref{Submodel Options}, -for any cases where this rule is relaxed. - -@item Each of the following options must be the same when building and using -the precompiled header: - -@gccoptlist{-fexceptions -funit-at-a-time} - -@item -Some other command-line options starting with @option{-f}, -@option{-p}, or @option{-O} must be defined in the same way as when -the precompiled header was generated. At present, it's not clear -which options are safe to change and which are not; the safest choice -is to use exactly the same options when generating and using the -precompiled header. The following are known to be safe: - -@gccoptlist{-fmessage-length= -fpreprocessed --fsched-interblock -fsched-spec -fsched-spec-load -fsched-spec-load-dangerous --fsched-verbose=<number> -fschedule-insns -fvisibility= --pedantic-errors} - -@end itemize - -For all of these except the last, the compiler will automatically -ignore the precompiled header if the conditions aren't met. If you -find an option combination that doesn't work and doesn't cause the -precompiled header to be ignored, please consider filing a bug report, -see @ref{Bugs}. - -If you do use differing options when generating and using the -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. - -@node Running Protoize -@section Running Protoize - -The program @code{protoize} is an optional part of GCC@. You can use -it to add prototypes to a program, thus converting the program to ISO -C in one respect. The companion program @code{unprotoize} does the -reverse: it removes argument types from any prototypes that are found. - -When you run these programs, you must specify a set of source files as -command line arguments. The conversion programs start out by compiling -these files to see what functions they define. The information gathered -about a file @var{foo} is saved in a file named @file{@var{foo}.X}. - -After scanning comes actual conversion. The specified files are all -eligible to be converted; any files they include (whether sources or -just headers) are eligible as well. - -But not all the eligible files are converted. By default, -@code{protoize} and @code{unprotoize} convert only source and header -files in the current directory. You can specify additional directories -whose files should be converted with the @option{-d @var{directory}} -option. You can also specify particular files to exclude with the -@option{-x @var{file}} option. A file is converted if it is eligible, its -directory name matches one of the specified directory names, and its -name within the directory has not been excluded. - -Basic conversion with @code{protoize} consists of rewriting most -function definitions and function declarations to specify the types of -the arguments. The only ones not rewritten are those for varargs -functions. - -@code{protoize} optionally inserts prototype declarations at the -beginning of the source file, to make them available for any calls that -precede the function's definition. Or it can insert prototype -declarations with block scope in the blocks where undeclared functions -are called. - -Basic conversion with @code{unprotoize} consists of rewriting most -function declarations to remove any argument types, and rewriting -function definitions to the old-style pre-ISO form. - -Both conversion programs print a warning for any function declaration or -definition that they can't convert. You can suppress these warnings -with @option{-q}. - -The output from @code{protoize} or @code{unprotoize} replaces the -original source file. The original file is renamed to a name ending -with @samp{.save} (for DOS, the saved filename ends in @samp{.sav} -without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav} -for DOS) file already exists, then the source file is simply discarded. - -@code{protoize} and @code{unprotoize} both depend on GCC itself to -scan the program and collect information about the functions it uses. -So neither of these programs will work until GCC is installed. - -Here is a table of the options you can use with @code{protoize} and -@code{unprotoize}. Each option works with both programs unless -otherwise stated. - -@table @code -@item -B @var{directory} -Look for the file @file{SYSCALLS.c.X} in @var{directory}, instead of the -usual directory (normally @file{/usr/local/lib}). This file contains -prototype information about standard system functions. This option -applies only to @code{protoize}. - -@item -c @var{compilation-options} -Use @var{compilation-options} as the options when running @command{gcc} to -produce the @samp{.X} files. The special option @option{-aux-info} is -always passed in addition, to tell @command{gcc} to write a @samp{.X} file. - -Note that the compilation options must be given as a single argument to -@code{protoize} or @code{unprotoize}. If you want to specify several -@command{gcc} options, you must quote the entire set of compilation options -to make them a single word in the shell. - -There are certain @command{gcc} arguments that you cannot use, because they -would produce the wrong kind of output. These include @option{-g}, -@option{-O}, @option{-c}, @option{-S}, and @option{-o} If you include these in -the @var{compilation-options}, they are ignored. - -@item -C -Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file -systems) instead of @samp{.c}. This is convenient if you are converting -a C program to C++. This option applies only to @code{protoize}. - -@item -g -Add explicit global declarations. This means inserting explicit -declarations at the beginning of each source file for each function -that is called in the file and was not declared. These declarations -precede the first function definition that contains a call to an -undeclared function. This option applies only to @code{protoize}. - -@item -i @var{string} -Indent old-style parameter declarations with the string @var{string}. -This option applies only to @code{protoize}. - -@code{unprotoize} converts prototyped function definitions to old-style -function definitions, where the arguments are declared between the -argument list and the initial @samp{@{}. By default, @code{unprotoize} -uses five spaces as the indentation. If you want to indent with just -one space instead, use @option{-i " "}. - -@item -k -Keep the @samp{.X} files. Normally, they are deleted after conversion -is finished. - -@item -l -Add explicit local declarations. @code{protoize} with @option{-l} inserts -a prototype declaration for each function in each block which calls the -function without any declaration. This option applies only to -@code{protoize}. - -@item -n -Make no real changes. This mode just prints information about the conversions -that would have been done without @option{-n}. - -@item -N -Make no @samp{.save} files. The original files are simply deleted. -Use this option with caution. - -@item -p @var{program} -Use the program @var{program} as the compiler. Normally, the name -@file{gcc} is used. - -@item -q -Work quietly. Most warnings are suppressed. - -@item -v -Print the version number, just like @option{-v} for @command{gcc}. -@end table - -If you need special compiler options to compile one of your program's -source files, then you should generate that file's @samp{.X} file -specially, by running @command{gcc} on that source file with the -appropriate options and the option @option{-aux-info}. Then run -@code{protoize} on the entire set of files. @code{protoize} will use -the existing @samp{.X} file because it is newer than the source file. -For example: - -@smallexample -gcc -Dfoo=bar file1.c -aux-info file1.X -protoize *.c -@end smallexample - -@noindent -You need to include the special files along with the rest in the -@code{protoize} command, even though their @samp{.X} files already -exist, because otherwise they won't get converted. - -@xref{Protoize Caveats}, for more information on how to use -@code{protoize} successfully. |