7844 lines
336 KiB
Groff
7844 lines
336 KiB
Groff
.\" Automatically generated by Pod::Man version 1.1
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.\" Wed Jan 24 19:43:11 2001
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.\" ======================================================================
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.\"
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.IX Title "GCC 1"
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.TH GCC 1 "gcc-2.97" "2001-01-24" "GNU"
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.UC
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.SH "NAME"
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gcc \- \s-1GNU\s0 project C and \*(C+ compiler
|
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.SH "SYNOPSIS"
|
|
.IX Header "SYNOPSIS"
|
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gcc [\fB\-c\fR|\fB\-S\fR|\fB\-E\fR] [\fB\-std=\fR\fIstandard\fR]
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[\fB\-g\fR] [\fB\-pg\fR] [\fB\-O\fR\fIlevel\fR]
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[\fB\-W\fR\fIwarn\fR...] [\fB\-pedantic\fR]
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[\fB\-I\fR\fIdir\fR...] [\fB\-L\fR\fIdir\fR...]
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[\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
|
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[\fB\-f\fR\fIoption\fR...] [\fB\-m\fR\fImachine-option\fR...]
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[\fB\-o\fR \fIoutfile\fR] \fIinfile\fR...
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.PP
|
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Only the most useful options are listed here; see below for the
|
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remainder. \fBg++\fR accepts mostly the same options as \fBgcc\fR.
|
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.SH "DESCRIPTION"
|
|
.IX Header "DESCRIPTION"
|
|
When you invoke \s-1GCC\s0, it normally does preprocessing, compilation,
|
|
assembly and linking. The ``overall options'' allow you to stop this
|
|
process at an intermediate stage. For example, the \fB\-c\fR option
|
|
says not to run the linker. Then the output consists of object files
|
|
output by the assembler.
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.PP
|
|
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.
|
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.PP
|
|
Most of the command line options that you can use with \s-1GCC\s0 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.
|
|
.PP
|
|
The \fBgcc\fR program accepts options and file names as operands. Many
|
|
options have multi-letter names; therefore multiple single-letter options
|
|
may \fInot\fR be grouped: \fB\-dr\fR is very different from \fB\-d\ \-r\fR.
|
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.PP
|
|
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 \fB\-L\fR more than once,
|
|
the directories are searched in the order specified.
|
|
.PP
|
|
Many options have long names starting with \fB\-f\fR or with
|
|
\&\fB\-W\fR\-\-\-for example, \fB\-fforce-mem\fR,
|
|
\&\fB\-fstrength-reduce\fR, \fB\-Wformat\fR and so on. Most of
|
|
these have both positive and negative forms; the negative form of
|
|
\&\fB\-ffoo\fR would be \fB\-fno-foo\fR. This manual documents
|
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only one of these two forms, whichever one is not the default.
|
|
.SH "OPTIONS"
|
|
.IX Header "OPTIONS"
|
|
.Sh "Option Summary"
|
|
.IX Subsection "Option Summary"
|
|
Here is a summary of all the options, grouped by type. Explanations are
|
|
in the following sections.
|
|
.Ip "\fIOverall Options\fR" 4
|
|
.IX Item "Overall Options"
|
|
\&\fB\-c \-S \-E \-o\fR \fIfile\fR \fB\-pipe \-pass-exit-codes \-x\fR \fIlanguage\fR
|
|
\&\fB\-v \-\-target-help \-\-help\fR
|
|
.Ip "\fIC Language Options\fR" 4
|
|
.IX Item "C Language Options"
|
|
\&\fB\-ansi \-std=\fR\fIstandard\fR \fB\-fno-asm \-fno-builtin
|
|
\&\-fhosted \-ffreestanding
|
|
\&\-trigraphs \-traditional \-traditional-cpp
|
|
\&\-fallow-single-precision \-fcond-mismatch
|
|
\&\-fsigned-bitfields \-fsigned-char
|
|
\&\-funsigned-bitfields \-funsigned-char
|
|
\&\-fwritable-strings \-fshort-wchar\fR
|
|
.Ip "\fI\*(C+ Language Options\fR" 4
|
|
.IX Item " Language Options"
|
|
\&\fB\-fno-access-control \-fcheck-new \-fconserve-space
|
|
\&\-fdollars-in-identifiers \-fno-elide-constructors
|
|
\&\-fno-enforce-eh-specs \-fexternal-templates
|
|
\&\-falt-external-templates
|
|
\&\-ffor-scope \-fno-for-scope \-fno-gnu-keywords \-fhonor-std
|
|
\&\-fhuge-objects \-fno-implicit-templates
|
|
\&\-fno-implicit-inline-templates
|
|
\&\-fno-implement-inlines \-fms-extensions
|
|
\&\-fname-mangling-version-\fR\fIn\fR \fB\-fno-operator-names
|
|
\&\-fno-optional-diags \-fpermissive
|
|
\&\-frepo \-fno-rtti \-fsquangle \-ftemplate-depth-\fR\fIn\fR
|
|
\&\fB\-fuse-cxa-atexit \-fvtable-thunks \-nostdinc++
|
|
\&\-fno-default-inline \-Wctor-dtor-privacy
|
|
\&\-Wnon-virtual-dtor \-Wreorder
|
|
\&\-Weffc++ \-Wno-deprecated
|
|
\&\-Wno-non-template-friend \-Wold-style-cast
|
|
\&\-Woverloaded-virtual \-Wno-pmf-conversions
|
|
\&\-Wsign-promo \-Wsynth\fR
|
|
.Ip "\fILanguage Independent Options\fR" 4
|
|
.IX Item "Language Independent Options"
|
|
\&\fB\-fmessage-length=\fR\fIn\fR
|
|
\&\fB\-fdiagnostics-show-location=\fR[\fBonce\fR|\fBevery-line\fR]
|
|
.Ip "\fIWarning Options\fR" 4
|
|
.IX Item "Warning Options"
|
|
\&\fB\-fsyntax-only \-pedantic \-pedantic-errors
|
|
\&\-w \-W \-Wall \-Waggregate-return
|
|
\&\-Wcast-align \-Wcast-qual \-Wchar-subscripts \-Wcomment
|
|
\&\-Wconversion \-Wdisabled-optimization \-Werror
|
|
\&\-Wfloat-equal \-Wformat \-Wformat=2
|
|
\&\-Wformat-nonliteral \-Wformat-security
|
|
\&\-Wid-clash-\fR\fIlen\fR \fB\-Wimplicit \-Wimplicit-int
|
|
\&\-Wimplicit-function-declaration
|
|
\&\-Werror-implicit-function-declaration
|
|
\&\-Wimport \-Winline
|
|
\&\-Wlarger-than-\fR\fIlen\fR \fB\-Wlong-long
|
|
\&\-Wmain \-Wmissing-declarations
|
|
\&\-Wmissing-format-attribute \-Wmissing-noreturn
|
|
\&\-Wmultichar \-Wno-format-extra-args \-Wno-format-y2k
|
|
\&\-Wno-import \-Wpacked \-Wpadded
|
|
\&\-Wparentheses \-Wpointer-arith \-Wredundant-decls
|
|
\&\-Wreturn-type \-Wsequence-point \-Wshadow
|
|
\&\-Wsign-compare \-Wswitch \-Wsystem-headers
|
|
\&\-Wtrigraphs \-Wundef \-Wuninitialized
|
|
\&\-Wunknown-pragmas \-Wunreachable-code
|
|
\&\-Wunused \-Wunused-function \-Wunused-label \-Wunused-parameter
|
|
\&\-Wunused-value \-Wunused-variable \-Wwrite-strings\fR
|
|
.Ip "\fIC-only Warning Options\fR" 4
|
|
.IX Item "C-only Warning Options"
|
|
\&\fB\-Wbad-function-cast \-Wmissing-prototypes \-Wnested-externs
|
|
\&\-Wstrict-prototypes \-Wtraditional\fR
|
|
.Ip "\fIDebugging Options\fR" 4
|
|
.IX Item "Debugging Options"
|
|
\&\fB\-a \-ax \-d\fR\fIletters\fR \fB\-fdump-unnumbered \-fdump-translation-unit-\fR\fIfile\fR
|
|
\&\fB\-fpretend-float \-fprofile-arcs \-ftest-coverage
|
|
\&\-g \-g\fR\fIlevel\fR \fB\-gcoff \-gdwarf \-gdwarf-1 \-gdwarf-1+ \-gdwarf-2
|
|
\&\-ggdb \-gstabs \-gstabs+ \-gxcoff \-gxcoff+
|
|
\&\-p \-pg \-print-file-name=\fR\fIlibrary\fR \fB\-print-libgcc-file-name
|
|
\&\-print-prog-name=\fR\fIprogram\fR \fB\-print-search-dirs \-Q
|
|
\&\-save-temps \-time\fR
|
|
.Ip "\fIOptimization Options\fR" 4
|
|
.IX Item "Optimization Options"
|
|
\&\fB\-falign-functions=\fR\fIn\fR \fB\-falign-jumps=\fR\fIn\fR
|
|
\&\fB\-falign-labels=\fR\fIn\fR \fB\-falign-loops=\fR\fIn\fR
|
|
\&\fB\-fbranch-probabilities \-fcaller-saves
|
|
\&\-fcse-follow-jumps \-fcse-skip-blocks \-fdata-sections \-fdce
|
|
\&\-fdelayed-branch \-fdelete-null-pointer-checks
|
|
\&\-fexpensive-optimizations \-ffast-math \-ffloat-store
|
|
\&\-fforce-addr \-fforce-mem \-ffunction-sections \-fgcse
|
|
\&\-finline-functions \-finline-limit=\fR\fIn\fR \fB\-fkeep-inline-functions
|
|
\&\-fkeep-static-consts \-fmove-all-movables
|
|
\&\-fno-default-inline \-fno-defer-pop
|
|
\&\-fno-function-cse \-fno-guess-branch-probability
|
|
\&\-fno-inline \-fno-math-errno \-fno-peephole
|
|
\&\-fomit-frame-pointer \-foptimize-register-move
|
|
\&\-foptimize-sibling-calls \-freduce-all-givs
|
|
\&\-fregmove \-frename-registers
|
|
\&\-frerun-cse-after-loop \-frerun-loop-opt
|
|
\&\-fschedule-insns \-fschedule-insns2
|
|
\&\-fsingle-precision-constant \-fssa
|
|
\&\-fstrength-reduce \-fstrict-aliasing \-fthread-jumps \-ftrapv
|
|
\&\-funroll-all-loops \-funroll-loops
|
|
\&\-O \-O0 \-O1 \-O2 \-O3 \-Os\fR
|
|
.Ip "\fIPreprocessor Options\fR" 4
|
|
.IX Item "Preprocessor Options"
|
|
\&\fB\-$ \-A\fR\fIquestion\fR\fB=\fR\fIanswer\fR \fB\-A-\fR\fIquestion\fR[\fB=\fR\fIanswer\fR]
|
|
\&\fB\-C \-dD \-dI \-dM \-dN
|
|
\&\-D\fR\fImacro\fR[\fB=\fR\fIdefn\fR] \fB\-E \-H
|
|
\&\-idirafter\fR \fIdir\fR
|
|
\&\fB\-include\fR \fIfile\fR \fB\-imacros\fR \fIfile\fR
|
|
\&\fB\-iprefix\fR \fIfile\fR \fB\-iwithprefix\fR \fIdir\fR
|
|
\&\fB\-iwithprefixbefore\fR \fIdir\fR \fB\-isystem\fR \fIdir\fR \fB\-isystem-c++\fR \fIdir\fR
|
|
\&\fB\-M \-MM \-MF \-MG \-MP \-MQ \-MT \-nostdinc \-P \-remap
|
|
\&\-trigraphs \-undef \-U\fR\fImacro\fR \fB\-Wp,\fR\fIoption\fR
|
|
.Ip "\fIAssembler Option\fR" 4
|
|
.IX Item "Assembler Option"
|
|
\&\fB\-Wa,\fR\fIoption\fR
|
|
.Ip "\fILinker Options\fR" 4
|
|
.IX Item "Linker Options"
|
|
\&\fB
|
|
\&\fR\fIobject-file-name\fR \fB\-l\fR\fIlibrary\fR
|
|
\&\fB\-nostartfiles \-nodefaultlibs \-nostdlib
|
|
\&\-s \-static \-static-libgcc \-shared \-shared-libgcc \-symbolic
|
|
\&\-Wl,\fR\fIoption\fR \fB\-Xlinker\fR \fIoption\fR
|
|
\&\fB\-u\fR \fIsymbol\fR
|
|
.Ip "\fIDirectory Options\fR" 4
|
|
.IX Item "Directory Options"
|
|
\&\fB\-B\fR\fIprefix\fR \fB\-I\fR\fIdir\fR \fB\-I- \-L\fR\fIdir\fR \fB\-specs=\fR\fIfile\fR
|
|
.Ip "\fITarget Options\fR" 4
|
|
.IX Item "Target Options"
|
|
\&\fB\-b\fR \fImachine\fR \fB\-V\fR \fIversion\fR
|
|
.Ip "\fIMachine Dependent Options\fR" 4
|
|
.IX Item "Machine Dependent Options"
|
|
\&\fIM680x0 Options\fR
|
|
.Sp
|
|
\&\fB\-m68000 \-m68020 \-m68020\-40 \-m68020\-60 \-m68030 \-m68040
|
|
\&\-m68060 \-mcpu32 \-m5200 \-m68881 \-mbitfield \-mc68000 \-mc68020
|
|
\&\-mfpa \-mnobitfield \-mrtd \-mshort \-msoft-float \-mpcrel
|
|
\&\-malign-int \-mstrict-align\fR
|
|
.Sp
|
|
\&\fIM68hc1x Options\fR
|
|
.Sp
|
|
\&\fB\-m6811 \-m6812 \-m68hc11 \-m68hc12
|
|
\&\-mauto-incdec \-mshort \-msoft-reg-count=\fR\fIcount\fR
|
|
.Sp
|
|
\&\fI\s-1VAX\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mg \-mgnu \-munix\fR
|
|
.Sp
|
|
\&\fI\s-1SPARC\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mcpu=\fR\fIcpu type\fR
|
|
\&\fB\-mtune=\fR\fIcpu type\fR
|
|
\&\fB\-mcmodel=\fR\fIcode model\fR
|
|
\&\fB\-m32 \-m64
|
|
\&\-mapp-regs \-mbroken-saverestore \-mcypress
|
|
\&\-mepilogue \-mfaster-structs \-mflat
|
|
\&\-mfpu \-mhard-float \-mhard-quad-float
|
|
\&\-mimpure-text \-mlive-g0 \-mno-app-regs
|
|
\&\-mno-epilogue \-mno-faster-structs \-mno-flat \-mno-fpu
|
|
\&\-mno-impure-text \-mno-stack-bias \-mno-unaligned-doubles
|
|
\&\-msoft-float \-msoft-quad-float \-msparclite \-mstack-bias
|
|
\&\-msupersparc \-munaligned-doubles \-mv8\fR
|
|
.Sp
|
|
\&\fIConvex Options\fR
|
|
.Sp
|
|
\&\fB\-mc1 \-mc2 \-mc32 \-mc34 \-mc38
|
|
\&\-margcount \-mnoargcount
|
|
\&\-mlong32 \-mlong64
|
|
\&\-mvolatile-cache \-mvolatile-nocache\fR
|
|
.Sp
|
|
\&\fI\s-1AMD29K\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-m29000 \-m29050 \-mbw \-mnbw \-mdw \-mndw
|
|
\&\-mlarge \-mnormal \-msmall
|
|
\&\-mkernel-registers \-mno-reuse-arg-regs
|
|
\&\-mno-stack-check \-mno-storem-bug
|
|
\&\-mreuse-arg-regs \-msoft-float \-mstack-check
|
|
\&\-mstorem-bug \-muser-registers\fR
|
|
.Sp
|
|
\&\fI\s-1ARM\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mapcs-frame \-mno-apcs-frame
|
|
\&\-mapcs-26 \-mapcs-32
|
|
\&\-mapcs-stack-check \-mno-apcs-stack-check
|
|
\&\-mapcs-float \-mno-apcs-float
|
|
\&\-mapcs-reentrant \-mno-apcs-reentrant
|
|
\&\-msched-prolog \-mno-sched-prolog
|
|
\&\-mlittle-endian \-mbig-endian \-mwords-little-endian
|
|
\&\-malignment-traps \-mno-alignment-traps
|
|
\&\-msoft-float \-mhard-float \-mfpe
|
|
\&\-mthumb-interwork \-mno-thumb-interwork
|
|
\&\-mcpu= \-march= \-mfpe=
|
|
\&\-mstructure-size-boundary=
|
|
\&\-mbsd \-mxopen \-mno-symrename
|
|
\&\-mabort-on-noreturn
|
|
\&\-mlong-calls \-mno-long-calls
|
|
\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport
|
|
\&\-msingle-pic-base \-mno-single-pic-base
|
|
\&\-mpic-register=\fR
|
|
.Sp
|
|
\&\fIThumb Options\fR
|
|
.Sp
|
|
\&\fB\-mtpcs-frame \-mno-tpcs-frame
|
|
\&\-mtpcs-leaf-frame \-mno-tpcs-leaf-frame
|
|
\&\-mlittle-endian \-mbig-endian
|
|
\&\-mthumb-interwork \-mno-thumb-interwork
|
|
\&\-mstructure-size-boundary=
|
|
\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport
|
|
\&\-mcallee-super-interworking \-mno-callee-super-interworking
|
|
\&\-mcaller-super-interworking \-mno-caller-super-interworking
|
|
\&\-msingle-pic-base \-mno-single-pic-base
|
|
\&\-mpic-register=\fR
|
|
.Sp
|
|
\&\fI\s-1MN10200\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mrelax\fR
|
|
.Sp
|
|
\&\fI\s-1MN10300\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mmult-bug
|
|
\&\-mno-mult-bug
|
|
\&\-mam33
|
|
\&\-mno-am33
|
|
\&\-mrelax\fR
|
|
.Sp
|
|
\&\fIM32R/D Options\fR
|
|
.Sp
|
|
\&\fB\-mcode-model=\fR\fImodel type\fR \fB\-msdata=\fR\fIsdata type\fR
|
|
\&\fB\-G\fR \fInum\fR
|
|
.Sp
|
|
\&\fIM88K Options\fR
|
|
.Sp
|
|
\&\fB\-m88000 \-m88100 \-m88110 \-mbig-pic
|
|
\&\-mcheck-zero-division \-mhandle-large-shift
|
|
\&\-midentify-revision \-mno-check-zero-division
|
|
\&\-mno-ocs-debug-info \-mno-ocs-frame-position
|
|
\&\-mno-optimize-arg-area \-mno-serialize-volatile
|
|
\&\-mno-underscores \-mocs-debug-info
|
|
\&\-mocs-frame-position \-moptimize-arg-area
|
|
\&\-mserialize-volatile \-mshort-data-\fR\fInum\fR \fB\-msvr3
|
|
\&\-msvr4 \-mtrap-large-shift \-muse-div-instruction
|
|
\&\-mversion-03.00 \-mwarn-passed-structs\fR
|
|
.Sp
|
|
\&\fI\s-1RS/6000\s0 and PowerPC Options\fR
|
|
.Sp
|
|
\&\fB\-mcpu=\fR\fIcpu type\fR
|
|
\&\fB\-mtune=\fR\fIcpu type\fR
|
|
\&\fB\-mpower \-mno-power \-mpower2 \-mno-power2
|
|
\&\-mpowerpc \-mpowerpc64 \-mno-powerpc
|
|
\&\-mpowerpc-gpopt \-mno-powerpc-gpopt
|
|
\&\-mpowerpc-gfxopt \-mno-powerpc-gfxopt
|
|
\&\-mnew-mnemonics \-mold-mnemonics
|
|
\&\-mfull-toc \-mminimal-toc \-mno-fop-in-toc \-mno-sum-in-toc
|
|
\&\-m64 \-m32 \-mxl-call \-mno-xl-call \-mthreads \-mpe
|
|
\&\-msoft-float \-mhard-float \-mmultiple \-mno-multiple
|
|
\&\-mstring \-mno-string \-mupdate \-mno-update
|
|
\&\-mfused-madd \-mno-fused-madd \-mbit-align \-mno-bit-align
|
|
\&\-mstrict-align \-mno-strict-align \-mrelocatable
|
|
\&\-mno-relocatable \-mrelocatable-lib \-mno-relocatable-lib
|
|
\&\-mtoc \-mno-toc \-mlittle \-mlittle-endian \-mbig \-mbig-endian
|
|
\&\-mcall-aix \-mcall-sysv \-mprototype \-mno-prototype
|
|
\&\-msim \-mmvme \-mads \-myellowknife \-memb \-msdata
|
|
\&\-msdata=\fR\fIopt\fR \fB\-mvxworks \-G\fR \fInum\fR
|
|
.Sp
|
|
\&\fI\s-1RT\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mcall-lib-mul \-mfp-arg-in-fpregs \-mfp-arg-in-gregs
|
|
\&\-mfull-fp-blocks \-mhc-struct-return \-min-line-mul
|
|
\&\-mminimum-fp-blocks \-mnohc-struct-return\fR
|
|
.Sp
|
|
\&\fI\s-1MIPS\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mabicalls \-mcpu=\fR\fIcpu type\fR
|
|
\&\fB\-membedded-data \-muninit-const-in-rodata
|
|
\&\-membedded-pic \-mfp32 \-mfp64 \-mgas \-mgp32 \-mgp64
|
|
\&\-mgpopt \-mhalf-pic \-mhard-float \-mint64 \-mips1
|
|
\&\-mips2 \-mips3 \-mips4 \-mlong64 \-mlong32 \-mlong-calls \-mmemcpy
|
|
\&\-mmips-as \-mmips-tfile \-mno-abicalls
|
|
\&\-mno-embedded-data \-mno-uninit-const-in-rodata \-mno-embedded-pic
|
|
\&\-mno-gpopt \-mno-long-calls
|
|
\&\-mno-memcpy \-mno-mips-tfile \-mno-rnames \-mno-stats
|
|
\&\-mrnames \-msoft-float
|
|
\&\-m4650 \-msingle-float \-mmad
|
|
\&\-mstats \-EL \-EB \-G\fR \fInum\fR \fB\-nocpp
|
|
\&\-mabi=32 \-mabi=n32 \-mabi=64 \-mabi=eabi
|
|
\&\-mfix7000 \-mno-crt0\fR
|
|
.Sp
|
|
\&\fIi386 Options\fR
|
|
.Sp
|
|
\&\fB\-mcpu=\fR\fIcpu type\fR \fB\-march=\fR\fIcpu type\fR
|
|
\&\fB\-mintel-syntax \-mieee-fp \-mno-fancy-math-387
|
|
\&\-mno-fp-ret-in-387 \-msoft-float \-msvr3\-shlib
|
|
\&\-mno-wide-multiply \-mrtd \-malign-double
|
|
\&\-mreg-alloc=\fR\fIlist\fR \fB\-mregparm=\fR\fInum\fR
|
|
\&\fB\-malign-jumps=\fR\fInum\fR \fB\-malign-loops=\fR\fInum\fR
|
|
\&\fB\-malign-functions=\fR\fInum\fR \fB\-mpreferred-stack-boundary=\fR\fInum\fR
|
|
\&\fB\-mthreads \-mno-align-stringops \-minline-all-stringops
|
|
\&\-mpush-args \-maccumulate-outgoing-args \-m128bit-long-double
|
|
\&\-m96bit-long-double\fR
|
|
.Sp
|
|
\&\fI\s-1HPPA\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-march=\fR\fIarchitecture type\fR
|
|
\&\fB\-mbig-switch \-mdisable-fpregs \-mdisable-indexing
|
|
\&\-mfast-indirect-calls \-mgas \-mjump-in-delay
|
|
\&\-mlong-load-store \-mno-big-switch \-mno-disable-fpregs
|
|
\&\-mno-disable-indexing \-mno-fast-indirect-calls \-mno-gas
|
|
\&\-mno-jump-in-delay \-mno-long-load-store
|
|
\&\-mno-portable-runtime \-mno-soft-float
|
|
\&\-mno-space-regs \-msoft-float \-mpa-risc-1\-0
|
|
\&\-mpa-risc-1\-1 \-mpa-risc-2\-0 \-mportable-runtime
|
|
\&\-mschedule=\fR\fIcpu type\fR \fB\-mspace-regs\fR
|
|
.Sp
|
|
\&\fIIntel 960 Options\fR
|
|
.Sp
|
|
\&\fB\-m\fR\fIcpu type\fR \fB\-masm-compat \-mclean-linkage
|
|
\&\-mcode-align \-mcomplex-addr \-mleaf-procedures
|
|
\&\-mic-compat \-mic2.0\-compat \-mic3.0\-compat
|
|
\&\-mintel-asm \-mno-clean-linkage \-mno-code-align
|
|
\&\-mno-complex-addr \-mno-leaf-procedures
|
|
\&\-mno-old-align \-mno-strict-align \-mno-tail-call
|
|
\&\-mnumerics \-mold-align \-msoft-float \-mstrict-align
|
|
\&\-mtail-call\fR
|
|
.Sp
|
|
\&\fI\s-1DEC\s0 Alpha Options\fR
|
|
.Sp
|
|
\&\fB\-mfp-regs \-mno-fp-regs \-mno-soft-float \-msoft-float
|
|
\&\-malpha-as \-mgas
|
|
\&\-mieee \-mieee-with-inexact \-mieee-conformant
|
|
\&\-mfp-trap-mode=\fR\fImode\fR \fB\-mfp-rounding-mode=\fR\fImode\fR
|
|
\&\fB\-mtrap-precision=\fR\fImode\fR \fB\-mbuild-constants
|
|
\&\-mcpu=\fR\fIcpu type\fR
|
|
\&\fB\-mbwx \-mno-bwx \-mcix \-mno-cix \-mmax \-mno-max
|
|
\&\-mmemory-latency=\fR\fItime\fR
|
|
.Sp
|
|
\&\fIClipper Options\fR
|
|
.Sp
|
|
\&\fB\-mc300 \-mc400\fR
|
|
.Sp
|
|
\&\fIH8/300 Options\fR
|
|
.Sp
|
|
\&\fB\-mrelax \-mh \-ms \-mint32 \-malign-300\fR
|
|
.Sp
|
|
\&\fI\s-1SH\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-m1 \-m2 \-m3 \-m3e
|
|
\&\-m4\-nofpu \-m4\-single-only \-m4\-single \-m4
|
|
\&\-mb \-ml \-mdalign \-mrelax
|
|
\&\-mbigtable \-mfmovd \-mhitachi \-mnomacsave
|
|
\&\-misize \-mpadstruct \-mspace
|
|
\&\-mprefergot
|
|
\&\-musermode\fR
|
|
.Sp
|
|
\&\fISystem V Options\fR
|
|
.Sp
|
|
\&\fB\-Qy \-Qn \-YP,\fR\fIpaths\fR \fB\-Ym,\fR\fIdir\fR
|
|
.Sp
|
|
\&\fI\s-1ARC\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-EB \-EL
|
|
\&\-mmangle-cpu \-mcpu=\fR\fIcpu\fR \fB\-mtext=\fR\fItext section\fR
|
|
\&\fB\-mdata=\fR\fIdata section\fR \fB\-mrodata=\fR\fIreadonly data section\fR
|
|
.Sp
|
|
\&\fITMS320C3x/C4x Options\fR
|
|
.Sp
|
|
\&\fB\-mcpu=\fR\fIcpu\fR \fB\-mbig \-msmall \-mregparm \-mmemparm
|
|
\&\-mfast-fix \-mmpyi \-mbk \-mti \-mdp-isr-reload
|
|
\&\-mrpts=\fR\fIcount\fR \fB\-mrptb \-mdb \-mloop-unsigned
|
|
\&\-mparallel-insns \-mparallel-mpy \-mpreserve-float\fR
|
|
.Sp
|
|
\&\fIV850 Options\fR
|
|
.Sp
|
|
\&\fB\-mlong-calls \-mno-long-calls \-mep \-mno-ep
|
|
\&\-mprolog-function \-mno-prolog-function \-mspace
|
|
\&\-mtda=\fR\fIn\fR \fB\-msda=\fR\fIn\fR \fB\-mzda=\fR\fIn\fR
|
|
\&\fB\-mv850 \-mbig-switch\fR
|
|
.Sp
|
|
\&\fI\s-1NS32K\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-m32032 \-m32332 \-m32532 \-m32081 \-m32381 \-mmult-add \-mnomult-add
|
|
\&\-msoft-float \-mrtd \-mnortd \-mregparam \-mnoregparam \-msb \-mnosb
|
|
\&\-mbitfield \-mnobitfield \-mhimem \-mnohimem\fR
|
|
.Sp
|
|
\&\fI\s-1AVR\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mmcu=\fR\fImcu\fR \fB\-msize \-minit-stack=\fR\fIn\fR \fB\-mno-interrupts
|
|
\&\-mcall-prologues \-mno-tablejump \-mtiny-stack\fR
|
|
.Sp
|
|
\&\fIMCore Options\fR
|
|
.Sp
|
|
\&\fB\-mhardlit \-mno-hardlit \-mdiv \-mno-div \-mrelax-immediates
|
|
\&\-mno-relax-immediates \-mwide-bitfields \-mno-wide-bitfields
|
|
\&\-m4byte-functions \-mno-4byte-functions \-mcallgraph-data
|
|
\&\-mno-callgraph-data \-mslow-bytes \-mno-slow-bytes \-mno-lsim
|
|
\&\-mlittle-endian \-mbig-endian \-m210 \-m340 \-mstack-increment\fR
|
|
.Sp
|
|
\&\fI\s-1IA-64\s0 Options\fR
|
|
.Sp
|
|
\&\fB\-mbig-endian \-mlittle-endian \-mgnu-as \-mgnu-ld \-mno-pic
|
|
\&\-mvolatile-asm-stop \-mb-step \-mregister-names \-mno-sdata
|
|
\&\-mconstant-gp \-mauto-pic \-minline-divide-min-latency
|
|
\&\-minline-divide-max-throughput \-mno-dwarf2\-asm
|
|
\&\-mfixed-range=\fR\fIregister range\fR
|
|
.Ip "\fICode Generation Options\fR" 4
|
|
.IX Item "Code Generation Options"
|
|
\&\fB\-fcall-saved-\fR\fIreg\fR \fB\-fcall-used-\fR\fIreg\fR
|
|
\&\fB\-fexceptions \-funwind-tables \-ffixed-\fR\fIreg\fR
|
|
\&\fB\-finhibit-size-directive \-finstrument-functions
|
|
\&\-fcheck-memory-usage \-fprefix-function-name
|
|
\&\-fno-common \-fno-ident \-fno-gnu-linker
|
|
\&\-fpcc-struct-return \-fpic \-fPIC
|
|
\&\-freg-struct-return \-fshared-data \-fshort-enums
|
|
\&\-fshort-double \-fvolatile \-fvolatile-global \-fvolatile-static
|
|
\&\-fverbose-asm \-fpack-struct \-fstack-check
|
|
\&\-fstack-limit-register=\fR\fIreg\fR \fB\-fstack-limit-symbol=\fR\fIsym\fR
|
|
\&\fB\-fargument-alias \-fargument-noalias
|
|
\&\-fargument-noalias-global
|
|
\&\-fleading-underscore\fR
|
|
.Sh "Options Controlling the Kind of Output"
|
|
.IX Subsection "Options Controlling the Kind of Output"
|
|
Compilation can involve up to four stages: preprocessing, compilation
|
|
proper, assembly and linking, always in that order. The first three
|
|
stages apply to an individual source file, and end by producing an
|
|
object file; linking combines all the object files (those newly
|
|
compiled, and those specified as input) into an executable file.
|
|
.PP
|
|
For any given input file, the file name suffix determines what kind of
|
|
compilation is done:
|
|
.Ip "\fIfile\fR\fB.c\fR" 4
|
|
.IX Item "file.c"
|
|
C source code which must be preprocessed.
|
|
.Ip "\fIfile\fR\fB.i\fR" 4
|
|
.IX Item "file.i"
|
|
C source code which should not be preprocessed.
|
|
.Ip "\fIfile\fR\fB.ii\fR" 4
|
|
.IX Item "file.ii"
|
|
\&\*(C+ source code which should not be preprocessed.
|
|
.Ip "\fIfile\fR\fB.m\fR" 4
|
|
.IX Item "file.m"
|
|
Objective-C source code. Note that you must link with the library
|
|
\&\fIlibobjc.a\fR to make an Objective-C program work.
|
|
.Ip "\fIfile\fR\fB.mi\fR" 4
|
|
.IX Item "file.mi"
|
|
Objective-C source code which should not be preprocessed.
|
|
.Ip "\fIfile\fR\fB.h\fR" 4
|
|
.IX Item "file.h"
|
|
C header file (not to be compiled or linked).
|
|
.Ip "\fIfile\fR\fB.cc\fR" 4
|
|
.IX Item "file.cc"
|
|
.PD 0
|
|
.Ip "\fIfile\fR\fB.cp\fR" 4
|
|
.IX Item "file.cp"
|
|
.Ip "\fIfile\fR\fB.cxx\fR" 4
|
|
.IX Item "file.cxx"
|
|
.Ip "\fIfile\fR\fB.cpp\fR" 4
|
|
.IX Item "file.cpp"
|
|
.Ip "\fIfile\fR\fB.c++\fR" 4
|
|
.IX Item "file.c++"
|
|
.Ip "\fIfile\fR\fB.C\fR" 4
|
|
.IX Item "file.C"
|
|
.PD
|
|
\&\*(C+ source code which must be preprocessed. Note that in \fB.cxx\fR,
|
|
the last two letters must both be literally \fBx\fR. Likewise,
|
|
\&\fB.C\fR refers to a literal capital C.
|
|
.Ip "\fIfile\fR\fB.f\fR" 4
|
|
.IX Item "file.f"
|
|
.PD 0
|
|
.Ip "\fIfile\fR\fB.for\fR" 4
|
|
.IX Item "file.for"
|
|
.Ip "\fIfile\fR\fB.FOR\fR" 4
|
|
.IX Item "file.FOR"
|
|
.PD
|
|
Fortran source code which should not be preprocessed.
|
|
.Ip "\fIfile\fR\fB.F\fR" 4
|
|
.IX Item "file.F"
|
|
.PD 0
|
|
.Ip "\fIfile\fR\fB.fpp\fR" 4
|
|
.IX Item "file.fpp"
|
|
.Ip "\fIfile\fR\fB.FPP\fR" 4
|
|
.IX Item "file.FPP"
|
|
.PD
|
|
Fortran source code which must be preprocessed (with the traditional
|
|
preprocessor).
|
|
.Ip "\fIfile\fR\fB.r\fR" 4
|
|
.IX Item "file.r"
|
|
Fortran source code which must be preprocessed with a \s-1RATFOR\s0
|
|
preprocessor (not included with \s-1GCC\s0).
|
|
.Ip "\fIfile\fR\fB.ch\fR" 4
|
|
.IX Item "file.ch"
|
|
.PD 0
|
|
.Ip "\fIfile\fR\fB.chi\fR" 4
|
|
.IX Item "file.chi"
|
|
.PD
|
|
\&\s-1CHILL\s0 source code (preprocessed with the traditional preprocessor).
|
|
.Ip "\fIfile\fR\fB.s\fR" 4
|
|
.IX Item "file.s"
|
|
Assembler code.
|
|
.Ip "\fIfile\fR\fB.S\fR" 4
|
|
.IX Item "file.S"
|
|
Assembler code which must be preprocessed.
|
|
.Ip "\fIother\fR" 4
|
|
.IX Item "other"
|
|
An object file to be fed straight into linking.
|
|
Any file name with no recognized suffix is treated this way.
|
|
.PP
|
|
You can specify the input language explicitly with the \fB\-x\fR option:
|
|
.Ip "\fB\-x\fR \fIlanguage\fR" 4
|
|
.IX Item "-x language"
|
|
Specify explicitly the \fIlanguage\fR 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 \fB\-x\fR option. Possible values for \fIlanguage\fR are:
|
|
.Sp
|
|
.Vb 6
|
|
\& c c-header cpp-output
|
|
\& c++ c++-cpp-output
|
|
\& objective-c objc-cpp-output
|
|
\& assembler assembler-with-cpp
|
|
\& f77 f77-cpp-input ratfor
|
|
\& java chill
|
|
.Ve
|
|
.Ip "\fB\-x none\fR" 4
|
|
.IX 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 \fB\-x\fR
|
|
has not been used at all).
|
|
.Ip "\fB\-pass-exit-codes\fR" 4
|
|
.IX Item "-pass-exit-codes"
|
|
Normally the \fBgcc\fR program will exit with the code of 1 if any
|
|
phase of the compiler returns a non-success return code. If you specify
|
|
\&\fB\-pass-exit-codes\fR, the \fBgcc\fR program will instead return with
|
|
numerically highest error produced by any phase that returned an error
|
|
indication.
|
|
.PP
|
|
If you only want some of the stages of compilation, you can use
|
|
\&\fB\-x\fR (or filename suffixes) to tell \fBgcc\fR where to start, and
|
|
one of the options \fB\-c\fR, \fB\-S\fR, or \fB\-E\fR to say where
|
|
\&\fBgcc\fR is to stop. Note that some combinations (for example,
|
|
\&\fB\-x cpp-output \-E\fR) instruct \fBgcc\fR to do nothing at all.
|
|
.Ip "\fB\-c\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
By default, the object file name for a source file is made by replacing
|
|
the suffix \fB.c\fR, \fB.i\fR, \fB.s\fR, etc., with \fB.o\fR.
|
|
.Sp
|
|
Unrecognized input files, not requiring compilation or assembly, are
|
|
ignored.
|
|
.Ip "\fB\-S\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
By default, the assembler file name for a source file is made by
|
|
replacing the suffix \fB.c\fR, \fB.i\fR, etc., with \fB.s\fR.
|
|
.Sp
|
|
Input files that don't require compilation are ignored.
|
|
.Ip "\fB\-E\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
Input files which don't require preprocessing are ignored.
|
|
.Ip "\fB\-o\fR \fIfile\fR" 4
|
|
.IX Item "-o file"
|
|
Place output in file \fIfile\fR. 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.
|
|
.Sp
|
|
Since only one output file can be specified, it does not make sense to
|
|
use \fB\-o\fR when compiling more than one input file, unless you are
|
|
producing an executable file as output.
|
|
.Sp
|
|
If \fB\-o\fR is not specified, the default is to put an executable file
|
|
in \fIa.out\fR, the object file for \fI\fIsource\fI.\fIsuffix\fI\fR in
|
|
\&\fI\fIsource\fI.o\fR, its assembler file in \fI\fIsource\fI.s\fR, and
|
|
all preprocessed C source on standard output.
|
|
.Ip "\fB\-v\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-pipe\fR" 4
|
|
.IX Item "-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 \s-1GNU\s0 assembler has
|
|
no trouble.
|
|
.Ip "\fB\*(--help\fR" 4
|
|
.IX Item "help"
|
|
Print (on the standard output) a description of the command line options
|
|
understood by \fBgcc\fR. If the \fB\-v\fR option is also specified
|
|
then \fB\*(--help\fR will also be passed on to the various processes
|
|
invoked by \fBgcc\fR, so that they can display the command line options
|
|
they accept. If the \fB\-W\fR option is also specified then command
|
|
line options which have no documentation associated with them will also
|
|
be displayed.
|
|
.Ip "\fB\*(--target-help\fR" 4
|
|
.IX Item "target-help"
|
|
Print (on the standard output) a description of target specific command
|
|
line options for each tool.
|
|
.Sh "Compiling \*(C+ Programs"
|
|
.IX Subsection "Compiling Programs"
|
|
\&\*(C+ source files conventionally use one of the suffixes \fB.C\fR,
|
|
\&\fB.cc\fR, \fB.cpp\fR, \fB.c++\fR, \fB.cp\fR, or \fB.cxx\fR;
|
|
preprocessed \*(C+ files use the suffix \fB.ii\fR. \s-1GCC\s0 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 \fBgcc\fR).
|
|
.PP
|
|
However, \*(C+ programs often require class libraries as well as a
|
|
compiler that understands the \*(C+ language\-\-\-and under some
|
|
circumstances, you might want to compile programs from standard input,
|
|
or otherwise without a suffix that flags them as \*(C+ programs.
|
|
\&\fBg++\fR is a program that calls \s-1GCC\s0 with the default language
|
|
set to \*(C+, and automatically specifies linking against the \*(C+
|
|
library. On many systems, \fBg++\fR is also
|
|
installed with the name \fBc++\fR.
|
|
.PP
|
|
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.
|
|
.Sh "Options Controlling C Dialect"
|
|
.IX Subsection "Options Controlling C Dialect"
|
|
The following options control the dialect of C (or languages derived
|
|
from C, such as \*(C+ and Objective C) that the compiler accepts:
|
|
.Ip "\fB\-ansi\fR" 4
|
|
.IX Item "-ansi"
|
|
In C mode, support all \s-1ISO\s0 C89 programs. In \*(C+ mode,
|
|
remove \s-1GNU\s0 extensions that conflict with \s-1ISO\s0 \*(C+.
|
|
.Sp
|
|
This turns off certain features of \s-1GCC\s0 that are incompatible with \s-1ISO\s0
|
|
C (when compiling C code), or of standard \*(C+ (when compiling \*(C+ code),
|
|
such as the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, and
|
|
predefined macros such as \f(CW\*(C`unix\*(C'\fR and \f(CW\*(C`vax\*(C'\fR that identify the
|
|
type of system you are using. It also enables the undesirable and
|
|
rarely used \s-1ISO\s0 trigraph feature. For the C compiler,
|
|
it disables recognition of \*(C+ style \fB//\fR comments as well as
|
|
the \f(CW\*(C`inline\*(C'\fR keyword.
|
|
.Sp
|
|
The alternate keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_extension_\|_\*(C'\fR,
|
|
\&\f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR continue to work despite
|
|
\&\fB\-ansi\fR. You would not want to use them in an \s-1ISO\s0 C program, of
|
|
course, but it is useful to put them in header files that might be included
|
|
in compilations done with \fB\-ansi\fR. Alternate predefined macros
|
|
such as \f(CW\*(C`_\|_unix_\|_\*(C'\fR and \f(CW\*(C`_\|_vax_\|_\*(C'\fR are also available, with or
|
|
without \fB\-ansi\fR.
|
|
.Sp
|
|
The \fB\-ansi\fR option does not cause non-ISO programs to be
|
|
rejected gratuitously. For that, \fB\-pedantic\fR is required in
|
|
addition to \fB\-ansi\fR.
|
|
.Sp
|
|
The macro \f(CW\*(C`_\|_STRICT_ANSI_\|_\*(C'\fR is predefined when the \fB\-ansi\fR
|
|
option is used. Some header files may notice this macro and refrain
|
|
from declaring certain functions or defining certain macros that the
|
|
\&\s-1ISO\s0 standard doesn't call for; this is to avoid interfering with any
|
|
programs that might use these names for other things.
|
|
.Sp
|
|
Functions which would normally be builtin but do not have semantics
|
|
defined by \s-1ISO\s0 C (such as \f(CW\*(C`alloca\*(C'\fR and \f(CW\*(C`ffs\*(C'\fR) are not builtin
|
|
functions with \fB\-ansi\fR is used.
|
|
.Ip "\fB\-std=\fR" 4
|
|
.IX Item "-std="
|
|
Determine the language standard. A value for this option must be provided;
|
|
possible values are
|
|
.RS 4
|
|
.Ip "\fBiso9899:1990\fR" 4
|
|
.IX Item "iso9899:1990"
|
|
Same as \fB\-ansi\fR
|
|
.Ip "\fBiso9899:199409\fR" 4
|
|
.IX Item "iso9899:199409"
|
|
\&\s-1ISO\s0 C as modified in amend. 1
|
|
.Ip "\fBiso9899:1999\fR" 4
|
|
.IX Item "iso9899:1999"
|
|
\&\s-1ISO\s0 C99. Note that this standard is not yet fully supported; see
|
|
<\fBhttp://gcc.gnu.org/c99status.html\fR> for more information.
|
|
.Ip "\fBc89\fR" 4
|
|
.IX Item "c89"
|
|
same as \fB\-std=iso9899:1990\fR
|
|
.Ip "\fBc99\fR" 4
|
|
.IX Item "c99"
|
|
same as \fB\-std=iso9899:1999\fR
|
|
.Ip "\fBgnu89\fR" 4
|
|
.IX Item "gnu89"
|
|
default, iso9899:1990 + gnu extensions
|
|
.Ip "\fBgnu99\fR" 4
|
|
.IX Item "gnu99"
|
|
iso9899:1999 + gnu extensions
|
|
.Ip "\fBiso9899:199x\fR" 4
|
|
.IX Item "iso9899:199x"
|
|
same as \fB\-std=iso9899:1999\fR, deprecated
|
|
.Ip "\fBc9x\fR" 4
|
|
.IX Item "c9x"
|
|
same as \fB\-std=iso9899:1999\fR, deprecated
|
|
.Ip "\fBgnu9x\fR" 4
|
|
.IX Item "gnu9x"
|
|
same as \fB\-std=gnu99\fR, deprecated
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
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 \f(CW\*(C`_\|_restrict_\|_\*(C'\fR even
|
|
when \fB\-std=c99\fR is not specified.
|
|
.Sp
|
|
The \fB\-std\fR options specifying some version of \s-1ISO\s0 C have the same
|
|
effects as \fB\-ansi\fR, except that features that were not in \s-1ISO\s0 C89
|
|
but are in the specified version (for example, \fB//\fR comments and
|
|
the \f(CW\*(C`inline\*(C'\fR keyword in \s-1ISO\s0 C99) are not disabled.
|
|
.RE
|
|
.Ip "\fB\-fno-asm\fR" 4
|
|
.IX Item "-fno-asm"
|
|
Do not recognize \f(CW\*(C`asm\*(C'\fR, \f(CW\*(C`inline\*(C'\fR or \f(CW\*(C`typeof\*(C'\fR as a
|
|
keyword, so that code can use these words as identifiers. You can use
|
|
the keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR
|
|
instead. \fB\-ansi\fR implies \fB\-fno-asm\fR.
|
|
.Sp
|
|
In \*(C+, this switch only affects the \f(CW\*(C`typeof\*(C'\fR keyword, since
|
|
\&\f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`inline\*(C'\fR are standard keywords. You may want to
|
|
use the \fB\-fno-gnu-keywords\fR flag instead, which has the same
|
|
effect. In C99 mode (\fB\-std=c99\fR or \fB\-std=gnu99\fR), this
|
|
switch only affects the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, since
|
|
\&\f(CW\*(C`inline\*(C'\fR is a standard keyword in \s-1ISO\s0 C99.
|
|
.Ip "\fB\-fno-builtin\fR" 4
|
|
.IX Item "-fno-builtin"
|
|
Don't recognize builtin functions that do not begin with
|
|
\&\fB_\|_builtin_\fR as prefix.
|
|
.Sp
|
|
\&\s-1GCC\s0 normally generates special code to handle certain builtin functions
|
|
more efficiently; for instance, calls to \f(CW\*(C`alloca\*(C'\fR may become single
|
|
instructions that adjust the stack directly, and calls to \f(CW\*(C`memcpy\*(C'\fR
|
|
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.
|
|
.Ip "\fB\-fhosted\fR" 4
|
|
.IX Item "-fhosted"
|
|
Assert that compilation takes place in a hosted environment. This implies
|
|
\&\fB\-fbuiltin\fR. A hosted environment is one in which the
|
|
entire standard library is available, and in which \f(CW\*(C`main\*(C'\fR has a return
|
|
type of \f(CW\*(C`int\*(C'\fR. Examples are nearly everything except a kernel.
|
|
This is equivalent to \fB\-fno-freestanding\fR.
|
|
.Ip "\fB\-ffreestanding\fR" 4
|
|
.IX Item "-ffreestanding"
|
|
Assert that compilation takes place in a freestanding environment. This
|
|
implies \fB\-fno-builtin\fR. A freestanding environment
|
|
is one in which the standard library may not exist, and program startup may
|
|
not necessarily be at \f(CW\*(C`main\*(C'\fR. The most obvious example is an \s-1OS\s0 kernel.
|
|
This is equivalent to \fB\-fno-hosted\fR.
|
|
.Ip "\fB\-trigraphs\fR" 4
|
|
.IX Item "-trigraphs"
|
|
Support \s-1ISO\s0 C trigraphs. You don't want to know about this
|
|
brain-damage. The \fB\-ansi\fR option (and \fB\-std\fR options for
|
|
strict \s-1ISO\s0 C conformance) implies \fB\-trigraphs\fR.
|
|
.Ip "\fB\-traditional\fR" 4
|
|
.IX Item "-traditional"
|
|
Attempt to support some aspects of traditional C compilers.
|
|
Specifically:
|
|
.RS 4
|
|
.Ip "\(bu" 4
|
|
All \f(CW\*(C`extern\*(C'\fR declarations take effect globally even if they
|
|
are written inside of a function definition. This includes implicit
|
|
declarations of functions.
|
|
.Ip "\(bu" 4
|
|
The newer keywords \f(CW\*(C`typeof\*(C'\fR, \f(CW\*(C`inline\*(C'\fR, \f(CW\*(C`signed\*(C'\fR, \f(CW\*(C`const\*(C'\fR
|
|
and \f(CW\*(C`volatile\*(C'\fR are not recognized. (You can still use the
|
|
alternative keywords such as \f(CW\*(C`_\|_typeof_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR, and
|
|
so on.)
|
|
.Ip "\(bu" 4
|
|
Comparisons between pointers and integers are always allowed.
|
|
.Ip "\(bu" 4
|
|
Integer types \f(CW\*(C`unsigned short\*(C'\fR and \f(CW\*(C`unsigned char\*(C'\fR promote
|
|
to \f(CW\*(C`unsigned int\*(C'\fR.
|
|
.Ip "\(bu" 4
|
|
Out-of-range floating point literals are not an error.
|
|
.Ip "\(bu" 4
|
|
Certain constructs which \s-1ISO\s0 regards as a single invalid preprocessing
|
|
number, such as \fB0xe-0xd\fR, are treated as expressions instead.
|
|
.Ip "\(bu" 4
|
|
String ``constants'' are not necessarily constant; they are stored in
|
|
writable space, and identical looking constants are allocated
|
|
separately. (This is the same as the effect of
|
|
\&\fB\-fwritable-strings\fR.)
|
|
.Ip "\(bu" 4
|
|
All automatic variables not declared \f(CW\*(C`register\*(C'\fR are preserved by
|
|
\&\f(CW\*(C`longjmp\*(C'\fR. Ordinarily, \s-1GNU\s0 C follows \s-1ISO\s0 C: automatic variables
|
|
not declared \f(CW\*(C`volatile\*(C'\fR may be clobbered.
|
|
.Ip "\(bu" 4
|
|
The character escape sequences \fB\ex\fR and \fB\ea\fR evaluate as the
|
|
literal characters \fBx\fR and \fBa\fR respectively. Without
|
|
\&\fB\-traditional\fR, \fB\ex\fR is a prefix for the hexadecimal
|
|
representation of a character, and \fB\ea\fR produces a bell.
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR
|
|
if your program uses names that are normally \s-1GNU\s0 C builtin functions for
|
|
other purposes of its own.
|
|
.Sp
|
|
You cannot use \fB\-traditional\fR if you include any header files that
|
|
rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with
|
|
\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such
|
|
systems to compile files that include any system headers.
|
|
.Sp
|
|
The \fB\-traditional\fR option also enables \fB\-traditional-cpp\fR,
|
|
which is described next.
|
|
.RE
|
|
.Ip "\fB\-traditional-cpp\fR" 4
|
|
.IX Item "-traditional-cpp"
|
|
Attempt to support some aspects of traditional C preprocessors.
|
|
Specifically:
|
|
.RS 4
|
|
.Ip "\(bu" 4
|
|
Comments convert to nothing at all, rather than to a space. This allows
|
|
traditional token concatenation.
|
|
.Ip "\(bu" 4
|
|
In a preprocessing directive, the \fB#\fR symbol must appear as the first
|
|
character of a line.
|
|
.Ip "\(bu" 4
|
|
Macro arguments are recognized within string constants in a macro
|
|
definition (and their values are stringified, though without additional
|
|
quote marks, when they appear in such a context). The preprocessor
|
|
always considers a string constant to end at a newline.
|
|
.Ip "\(bu" 4
|
|
The predefined macro \f(CW\*(C`_\|_STDC_\|_\*(C'\fR is not defined when you use
|
|
\&\fB\-traditional\fR, but \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR is (since the \s-1GNU\s0 extensions
|
|
which \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR indicates are not affected by
|
|
\&\fB\-traditional\fR). If you need to write header files that work
|
|
differently depending on whether \fB\-traditional\fR is in use, by
|
|
testing both of these predefined macros you can distinguish four
|
|
situations: \s-1GNU\s0 C, traditional \s-1GNU\s0 C, other \s-1ISO\s0 C compilers, and other
|
|
old C compilers. The predefined macro \f(CW\*(C`_\|_STDC_VERSION_\|_\*(C'\fR is also
|
|
not defined when you use \fB\-traditional\fR.
|
|
.Ip "\(bu" 4
|
|
The preprocessor considers a string constant to end at a newline (unless
|
|
the newline is escaped with \fB\e\fR). (Without \fB\-traditional\fR,
|
|
string constants can contain the newline character as typed.)
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-fcond-mismatch\fR" 4
|
|
.IX Item "-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+.
|
|
.Ip "\fB\-funsigned-char\fR" 4
|
|
.IX Item "-funsigned-char"
|
|
Let the type \f(CW\*(C`char\*(C'\fR be unsigned, like \f(CW\*(C`unsigned char\*(C'\fR.
|
|
.Sp
|
|
Each kind of machine has a default for what \f(CW\*(C`char\*(C'\fR should
|
|
be. It is either like \f(CW\*(C`unsigned char\*(C'\fR by default or like
|
|
\&\f(CW\*(C`signed char\*(C'\fR by default.
|
|
.Sp
|
|
Ideally, a portable program should always use \f(CW\*(C`signed char\*(C'\fR or
|
|
\&\f(CW\*(C`unsigned char\*(C'\fR when it depends on the signedness of an object.
|
|
But many programs have been written to use plain \f(CW\*(C`char\*(C'\fR 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.
|
|
.Sp
|
|
The type \f(CW\*(C`char\*(C'\fR is always a distinct type from each of
|
|
\&\f(CW\*(C`signed char\*(C'\fR or \f(CW\*(C`unsigned char\*(C'\fR, even though its behavior
|
|
is always just like one of those two.
|
|
.Ip "\fB\-fsigned-char\fR" 4
|
|
.IX Item "-fsigned-char"
|
|
Let the type \f(CW\*(C`char\*(C'\fR be signed, like \f(CW\*(C`signed char\*(C'\fR.
|
|
.Sp
|
|
Note that this is equivalent to \fB\-fno-unsigned-char\fR, which is
|
|
the negative form of \fB\-funsigned-char\fR. Likewise, the option
|
|
\&\fB\-fno-signed-char\fR is equivalent to \fB\-funsigned-char\fR.
|
|
.Sp
|
|
You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR
|
|
if your program uses names that are normally \s-1GNU\s0 C builtin functions for
|
|
other purposes of its own.
|
|
.Sp
|
|
You cannot use \fB\-traditional\fR if you include any header files that
|
|
rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with
|
|
\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such
|
|
systems to compile files that include any system headers.
|
|
.Ip "\fB\-fsigned-bitfields\fR" 4
|
|
.IX Item "-fsigned-bitfields"
|
|
.PD 0
|
|
.Ip "\fB\-funsigned-bitfields\fR" 4
|
|
.IX Item "-funsigned-bitfields"
|
|
.Ip "\fB\-fno-signed-bitfields\fR" 4
|
|
.IX Item "-fno-signed-bitfields"
|
|
.Ip "\fB\-fno-unsigned-bitfields\fR" 4
|
|
.IX Item "-fno-unsigned-bitfields"
|
|
.PD
|
|
These options control whether a bitfield is signed or unsigned, when the
|
|
declaration does not use either \f(CW\*(C`signed\*(C'\fR or \f(CW\*(C`unsigned\*(C'\fR. By
|
|
default, such a bitfield is signed, because this is consistent: the
|
|
basic integer types such as \f(CW\*(C`int\*(C'\fR are signed types.
|
|
.Sp
|
|
However, when \fB\-traditional\fR is used, bitfields are all unsigned
|
|
no matter what.
|
|
.Ip "\fB\-fwritable-strings\fR" 4
|
|
.IX Item "-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. The option \fB\-traditional\fR also has
|
|
this effect.
|
|
.Sp
|
|
Writing into string constants is a very bad idea; ``constants'' should
|
|
be constant.
|
|
.Ip "\fB\-fallow-single-precision\fR" 4
|
|
.IX Item "-fallow-single-precision"
|
|
Do not promote single precision math operations to double precision,
|
|
even when compiling with \fB\-traditional\fR.
|
|
.Sp
|
|
Traditional K&R C promotes all floating point operations to double
|
|
precision, regardless of the sizes of the operands. On the
|
|
architecture for which you are compiling, single precision may be faster
|
|
than double precision. If you must use \fB\-traditional\fR, but want
|
|
to use single precision operations when the operands are single
|
|
precision, use this option. This option has no effect when compiling
|
|
with \s-1ISO\s0 or \s-1GNU\s0 C conventions (the default).
|
|
.Ip "\fB\-fshort-wchar\fR" 4
|
|
.IX Item "-fshort-wchar"
|
|
Override the underlying type for \fBwchar_t\fR to be \fBshort
|
|
unsigned int\fR instead of the default for the target. This option is
|
|
useful for building programs to run under \s-1WINE\s0.
|
|
.Sh "Options Controlling \*(C+ Dialect"
|
|
.IX Subsection "Options Controlling Dialect"
|
|
This section describes the command-line options that are only meaningful
|
|
for \*(C+ programs; but you can also use most of the \s-1GNU\s0 compiler options
|
|
regardless of what language your program is in. For example, you
|
|
might compile a file \f(CW\*(C`firstClass.C\*(C'\fR like this:
|
|
.PP
|
|
.Vb 1
|
|
\& g++ -g -frepo -O -c firstClass.C
|
|
.Ve
|
|
In this example, only \fB\-frepo\fR is an option meant
|
|
only for \*(C+ programs; you can use the other options with any
|
|
language supported by \s-1GCC\s0.
|
|
.PP
|
|
Here is a list of options that are \fIonly\fR for compiling \*(C+ programs:
|
|
.Ip "\fB\-fno-access-control\fR" 4
|
|
.IX Item "-fno-access-control"
|
|
Turn off all access checking. This switch is mainly useful for working
|
|
around bugs in the access control code.
|
|
.Ip "\fB\-fcheck-new\fR" 4
|
|
.IX Item "-fcheck-new"
|
|
Check that the pointer returned by \f(CW\*(C`operator new\*(C'\fR is non-null
|
|
before attempting to modify the storage allocated. The current Working
|
|
Paper requires that \f(CW\*(C`operator new\*(C'\fR never return a null pointer, so
|
|
this check is normally unnecessary.
|
|
.Sp
|
|
An alternative to using this option is to specify that your
|
|
\&\f(CW\*(C`operator new\*(C'\fR does not throw any exceptions; if you declare it
|
|
\&\fB\f(BIthrow()\fB\fR, g++ will check the return value. See also \fBnew
|
|
(nothrow)\fR.
|
|
.Ip "\fB\-fconserve-space\fR" 4
|
|
.IX Item "-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 \f(CW\*(C`main()\*(C'\fR has
|
|
completed, you may have an object that is being destroyed twice because
|
|
two definitions were merged.
|
|
.Sp
|
|
This option is no longer useful on most targets, now that support has
|
|
been added for putting variables into \s-1BSS\s0 without making them common.
|
|
.Ip "\fB\-fdollars-in-identifiers\fR" 4
|
|
.IX Item "-fdollars-in-identifiers"
|
|
Accept \fB$\fR in identifiers. You can also explicitly prohibit use of
|
|
\&\fB$\fR with the option \fB\-fno-dollars-in-identifiers\fR. (\s-1GNU\s0 C allows
|
|
\&\fB$\fR by default on most target systems, but there are a few exceptions.)
|
|
Traditional C allowed the character \fB$\fR to form part of
|
|
identifiers. However, \s-1ISO\s0 C and \*(C+ forbid \fB$\fR in identifiers.
|
|
.Ip "\fB\-fno-elide-constructors\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fno-enforce-eh-specs\fR" 4
|
|
.IX Item "-fno-enforce-eh-specs"
|
|
Don't 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 \fB\s-1NDEBUG\s0\fR. The compiler
|
|
will still optimize based on the exception specifications.
|
|
.Ip "\fB\-fexternal-templates\fR" 4
|
|
.IX Item "-fexternal-templates"
|
|
Cause template instantiations to obey \fB#pragma interface\fR and
|
|
\&\fBimplementation\fR; template instances are emitted or not according
|
|
to the location of the template definition.
|
|
.Sp
|
|
This option is deprecated.
|
|
.Ip "\fB\-falt-external-templates\fR" 4
|
|
.IX Item "-falt-external-templates"
|
|
Similar to \-fexternal-templates, but template instances are emitted or
|
|
not according to the place where they are first instantiated.
|
|
.Sp
|
|
This option is deprecated.
|
|
.Ip "\fB\-ffor-scope\fR" 4
|
|
.IX Item "-ffor-scope"
|
|
.PD 0
|
|
.Ip "\fB\-fno-for-scope\fR" 4
|
|
.IX Item "-fno-for-scope"
|
|
.PD
|
|
If \-ffor-scope is specified, the scope of variables declared in
|
|
a \fIfor-init-statement\fR is limited to the \fBfor\fR loop itself,
|
|
as specified by the \*(C+ standard.
|
|
If \-fno-for-scope is specified, the scope of variables declared in
|
|
a \fIfor-init-statement\fR extends to the end of the enclosing scope,
|
|
as was the case in old versions of gcc, and other (traditional)
|
|
implementations of \*(C+.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-fno-gnu-keywords\fR" 4
|
|
.IX Item "-fno-gnu-keywords"
|
|
Do not recognize \f(CW\*(C`typeof\*(C'\fR as a keyword, so that code can use this
|
|
word as an identifier. You can use the keyword \f(CW\*(C`_\|_typeof_\|_\*(C'\fR instead.
|
|
\&\fB\-ansi\fR implies \fB\-fno-gnu-keywords\fR.
|
|
.Ip "\fB\-fhonor-std\fR" 4
|
|
.IX Item "-fhonor-std"
|
|
Treat the \f(CW\*(C`namespace std\*(C'\fR as a namespace, instead of ignoring
|
|
it. For compatibility with earlier versions of g++, the compiler will,
|
|
by default, ignore \f(CW\*(C`namespace\-declarations\*(C'\fR,
|
|
\&\f(CW\*(C`using\-declarations\*(C'\fR, \f(CW\*(C`using\-directives\*(C'\fR, and
|
|
\&\f(CW\*(C`namespace\-names\*(C'\fR, if they involve \f(CW\*(C`std\*(C'\fR.
|
|
.Ip "\fB\-fhuge-objects\fR" 4
|
|
.IX Item "-fhuge-objects"
|
|
Support virtual function calls for objects that exceed the size
|
|
representable by a \fBshort int\fR. Users should not use this flag by
|
|
default; if you need to use it, the compiler will tell you so.
|
|
.Sp
|
|
This flag is not useful when compiling with \-fvtable-thunks.
|
|
.Sp
|
|
Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding
|
|
libgcc\fR must be built with the same setting of this option.
|
|
.Ip "\fB\-fno-implicit-templates\fR" 4
|
|
.IX Item "-fno-implicit-templates"
|
|
Never emit code for non-inline templates which are instantiated
|
|
implicitly (i.e. by use); only emit code for explicit instantiations.
|
|
.Ip "\fB\-fno-implicit-inline-templates\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fno-implement-inlines\fR" 4
|
|
.IX Item "-fno-implement-inlines"
|
|
To save space, do not emit out-of-line copies of inline functions
|
|
controlled by \fB#pragma implementation\fR. This will cause linker
|
|
errors if these functions are not inlined everywhere they are called.
|
|
.Ip "\fB\-fms-extensions\fR" 4
|
|
.IX Item "-fms-extensions"
|
|
Disable pedantic warnings about constructs used in \s-1MFC\s0, such as implicit
|
|
int and getting a pointer to member function via non-standard syntax.
|
|
.Ip "\fB\-fname-mangling-version-\fR\fIn\fR" 4
|
|
.IX Item "-fname-mangling-version-n"
|
|
Control the way in which names are mangled. Version 0 is compatible
|
|
with versions of g++ before 2.8. Version 1 is the default. Version 1
|
|
will allow correct mangling of function templates. For example,
|
|
version 0 mangling does not mangle foo<int, double> and foo<int, char>
|
|
given this declaration:
|
|
.Sp
|
|
.Vb 1
|
|
\& template <class T, class U> void foo(T t);
|
|
.Ve
|
|
Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding
|
|
libgcc\fR must be built with the same setting of this option.
|
|
.Ip "\fB\-fno-operator-names\fR" 4
|
|
.IX Item "-fno-operator-names"
|
|
Do not treat the operator name keywords \f(CW\*(C`and\*(C'\fR, \f(CW\*(C`bitand\*(C'\fR,
|
|
\&\f(CW\*(C`bitor\*(C'\fR, \f(CW\*(C`compl\*(C'\fR, \f(CW\*(C`not\*(C'\fR, \f(CW\*(C`or\*(C'\fR and \f(CW\*(C`xor\*(C'\fR as
|
|
synonyms as keywords.
|
|
.Ip "\fB\-fno-optional-diags\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fpermissive\fR" 4
|
|
.IX Item "-fpermissive"
|
|
Downgrade messages about nonconformant code from errors to warnings. By
|
|
default, g++ effectively sets \fB\-pedantic-errors\fR without
|
|
\&\fB\-pedantic\fR; this option reverses that. This behavior and this
|
|
option are superseded by \fB\-pedantic\fR, which works as it does for \s-1GNU\s0 C.
|
|
.Ip "\fB\-frepo\fR" 4
|
|
.IX Item "-frepo"
|
|
Enable automatic template instantiation. This option also implies
|
|
\&\fB\-fno-implicit-templates\fR.
|
|
.Ip "\fB\-fno-rtti\fR" 4
|
|
.IX Item "-fno-rtti"
|
|
Disable generation of information about every class with virtual
|
|
functions for use by the \*(C+ runtime type identification features
|
|
(\fBdynamic_cast\fR and \fBtypeid\fR). 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.
|
|
.Ip "\fB\-fsquangle\fR" 4
|
|
.IX Item "-fsquangle"
|
|
.PD 0
|
|
.Ip "\fB\-fno-squangle\fR" 4
|
|
.IX Item "-fno-squangle"
|
|
.PD
|
|
\&\fB\-fsquangle\fR will enable a compressed form of name mangling for
|
|
identifiers. In particular, it helps to shorten very long names by recognizing
|
|
types and class names which occur more than once, replacing them with special
|
|
short \s-1ID\s0 codes. This option also requires any \*(C+ libraries being used to
|
|
be compiled with this option as well. The compiler has this disabled (the
|
|
equivalent of \fB\-fno-squangle\fR) by default.
|
|
.Sp
|
|
Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding
|
|
libgcc.a\fR must be built with the same setting of this option.
|
|
.Ip "\fB\-ftemplate-depth-\fR\fIn\fR" 4
|
|
.IX Item "-ftemplate-depth-n"
|
|
Set the maximum instantiation depth for template classes to \fIn\fR.
|
|
A limit on the template instantiation depth is needed to detect
|
|
endless recursions during template class instantiation. \s-1ANSI/ISO\s0 \*(C+
|
|
conforming programs must not rely on a maximum depth greater than 17.
|
|
.Ip "\fB\-fuse-cxa-atexit\fR" 4
|
|
.IX Item "-fuse-cxa-atexit"
|
|
Register destructors for objects with static storage duration with the
|
|
\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR function rather than the \f(CW\*(C`atexit\*(C'\fR function.
|
|
This option is required for fully standards-compliant handling of static
|
|
destructors, but will only work if your C library supports
|
|
\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR.
|
|
.Ip "\fB\-fvtable-thunks\fR" 4
|
|
.IX Item "-fvtable-thunks"
|
|
Use \fBthunks\fR to implement the virtual function dispatch table
|
|
(\fBvtable\fR). The traditional (cfront-style) approach to
|
|
implementing vtables was to store a pointer to the function and two
|
|
offsets for adjusting the \fBthis\fR pointer at the call site. Newer
|
|
implementations store a single pointer to a \fBthunk\fR function which
|
|
does any necessary adjustment and then calls the target function.
|
|
.Sp
|
|
This option also enables a heuristic for controlling emission of
|
|
vtables; if a class has any non-inline virtual functions, the vtable
|
|
will be emitted in the translation unit containing the first one of
|
|
those.
|
|
.Sp
|
|
Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding
|
|
libgcc.a\fR must be built with the same setting of this option.
|
|
.Ip "\fB\-nostdinc++\fR" 4
|
|
.IX Item "-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.)
|
|
.PP
|
|
In addition, these optimization, warning, and code generation options
|
|
have meanings only for \*(C+ programs:
|
|
.Ip "\fB\-fno-default-inline\fR" 4
|
|
.IX Item "-fno-default-inline"
|
|
Do not assume \fBinline\fR for functions defined inside a class scope.
|
|
Note that these
|
|
functions will have linkage like inline functions; they just won't be
|
|
inlined by default.
|
|
.Ip "\fB\-Wctor-dtor-privacy (\*(C+ only)\fR" 4
|
|
.IX Item "-Wctor-dtor-privacy ( only)"
|
|
Warn when a class seems unusable, because all the constructors or
|
|
destructors in a class are private and the class has no friends or
|
|
public static member functions.
|
|
.Ip "\fB\-Wnon-virtual-dtor (\*(C+ only)\fR" 4
|
|
.IX Item "-Wnon-virtual-dtor ( only)"
|
|
Warn when a class declares a non-virtual destructor that should probably
|
|
be virtual, because it looks like the class will be used polymorphically.
|
|
.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4
|
|
.IX Item "-Wreorder ( only)"
|
|
Warn when the order of member initializers given in the code does not
|
|
match the order in which they must be executed. For instance:
|
|
.Sp
|
|
.Vb 5
|
|
\& struct A {
|
|
\& int i;
|
|
\& int j;
|
|
\& A(): j (0), i (1) { }
|
|
\& };
|
|
.Ve
|
|
Here the compiler will warn that the member initializers for \fBi\fR
|
|
and \fBj\fR will be rearranged to match the declaration order of the
|
|
members.
|
|
.PP
|
|
The following \fB\-W...\fR options are not affected by \fB\-Wall\fR.
|
|
.Ip "\fB\-Weffc++ (\*(C+ only)\fR" 4
|
|
.IX Item "-Weffc++ ( only)"
|
|
Warn about violations of various style guidelines from Scott Meyers'
|
|
\&\fIEffective \*(C+\fR books. If you use this option, you should be aware
|
|
that the standard library headers do not obey all of these guidelines;
|
|
you can use \fBgrep \-v\fR to filter out those warnings.
|
|
.Ip "\fB\-Wno-deprecated (\*(C+ only)\fR" 4
|
|
.IX Item "-Wno-deprecated ( only)"
|
|
Do not warn about usage of deprecated features.
|
|
.Ip "\fB\-Wno-non-template-friend (\*(C+ only)\fR" 4
|
|
.IX Item "-Wno-non-template-friend ( only)"
|
|
Disable warnings when non-templatized friend functions are declared
|
|
within a template. With the advent of explicit template specification
|
|
support in g++, if the name of the friend is an unqualified-id (ie,
|
|
\&\fBfriend foo(int)\fR), 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++, \fB\-Wnon-template-friend\fR 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
|
|
\&\fB\-Wno-non-template-friend\fR which keeps the conformant compiler code
|
|
but disables the helpful warning.
|
|
.Ip "\fB\-Wold-style-cast (\*(C+ only)\fR" 4
|
|
.IX Item "-Wold-style-cast ( only)"
|
|
Warn if an old-style (C-style) cast is used within a \*(C+ program. The
|
|
new-style casts (\fBstatic_cast\fR, \fBreinterpret_cast\fR, and
|
|
\&\fBconst_cast\fR) are less vulnerable to unintended effects.
|
|
.Ip "\fB\-Woverloaded-virtual (\*(C+ only)\fR" 4
|
|
.IX Item "-Woverloaded-virtual ( only)"
|
|
Warn when a derived class function declaration may be an error in
|
|
defining a virtual function. In a derived class, the
|
|
definitions of virtual functions must match the type signature of a
|
|
virtual function declared in the base class. With this option, the
|
|
compiler warns when you define a function with the same name as a
|
|
virtual function, but with a type signature that does not match any
|
|
declarations from the base class.
|
|
.Ip "\fB\-Wno-pmf-conversions (\*(C+ only)\fR" 4
|
|
.IX Item "-Wno-pmf-conversions ( only)"
|
|
Disable the diagnostic for converting a bound pointer to member function
|
|
to a plain pointer.
|
|
.Ip "\fB\-Wsign-promo (\*(C+ only)\fR" 4
|
|
.IX Item "-Wsign-promo ( only)"
|
|
Warn when overload resolution chooses a promotion from unsigned or
|
|
enumeral 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.
|
|
.Ip "\fB\-Wsynth (\*(C+ only)\fR" 4
|
|
.IX Item "-Wsynth ( only)"
|
|
Warn when g++'s synthesis behavior does not match that of cfront. For
|
|
instance:
|
|
.Sp
|
|
.Vb 4
|
|
\& struct A {
|
|
\& operator int ();
|
|
\& A& operator = (int);
|
|
\& };
|
|
.Ve
|
|
.Vb 5
|
|
\& main ()
|
|
\& {
|
|
\& A a,b;
|
|
\& a = b;
|
|
\& }
|
|
.Ve
|
|
In this example, g++ will synthesize a default \fBA& operator =
|
|
(const A&);\fR, while cfront will use the user-defined \fBoperator =\fR.
|
|
.Sh "Options to Control Diagnostic Messages Formatting"
|
|
.IX Subsection "Options to Control Diagnostic Messages Formatting"
|
|
Traditionally, diagnostic messages have been formatted irrespective of
|
|
the output device's aspect (e.g. its width, ...). 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.
|
|
.Ip "\fB\-fmessage-length=\fR\fIn\fR" 4
|
|
.IX Item "-fmessage-length=n"
|
|
Try to format error messages so that they fit on lines of about \fIn\fR
|
|
characters. The default is 72 characters for g++ and 0 for the rest of
|
|
the front-ends supported by \s-1GCC\s0. If \fIn\fR is zero, then no
|
|
line-wrapping will be done; each error message will appear on a single
|
|
line.
|
|
.Ip "\fB\-fdiagnostics-show-location=once\fR" 4
|
|
.IX Item "-fdiagnostics-show-location=once"
|
|
Only meaningful in line-wrapping mode. Instructs the diagnostic messages
|
|
reporter to emit \fIonce\fR 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
|
|
behaviour.
|
|
.Ip "\fB\-fdiagnostics-show-location=every-line\fR" 4
|
|
.IX 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
|
|
a message which is too long to fit on a single line.
|
|
.Sh "Options to Request or Suppress Warnings"
|
|
.IX Subsection "Options to Request or Suppress 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.
|
|
.PP
|
|
You can request many specific warnings with options beginning \fB\-W\fR,
|
|
for example \fB\-Wimplicit\fR to request warnings on implicit
|
|
declarations. Each of these specific warning options also has a
|
|
negative form beginning \fB\-Wno-\fR to turn off warnings;
|
|
for example, \fB\-Wno-implicit\fR. This manual lists only one of the
|
|
two forms, whichever is not the default.
|
|
.PP
|
|
These options control the amount and kinds of warnings produced by \s-1GCC:\s0
|
|
.Ip "\fB\-fsyntax-only\fR" 4
|
|
.IX Item "-fsyntax-only"
|
|
Check the code for syntax errors, but don't do anything beyond that.
|
|
.Ip "\fB\-pedantic\fR" 4
|
|
.IX Item "-pedantic"
|
|
Issue all the warnings demanded by strict \s-1ISO\s0 C and \s-1ISO\s0 \*(C+;
|
|
reject all programs that use forbidden extensions, and some other
|
|
programs that do not follow \s-1ISO\s0 C and \s-1ISO\s0 \*(C+. For \s-1ISO\s0 C, follows the
|
|
version of the \s-1ISO\s0 C standard specified by any \fB\-std\fR option used.
|
|
.Sp
|
|
Valid \s-1ISO\s0 C and \s-1ISO\s0 \*(C+ programs should compile properly with or without
|
|
this option (though a rare few will require \fB\-ansi\fR or a
|
|
\&\fB\-std\fR option specifying the required version of \s-1ISO\s0 C). However,
|
|
without this option, certain \s-1GNU\s0 extensions and traditional C and \*(C+
|
|
features are supported as well. With this option, they are rejected.
|
|
.Sp
|
|
\&\fB\-pedantic\fR does not cause warning messages for use of the
|
|
alternate keywords whose names begin and end with \fB_\|_\fR. Pedantic
|
|
warnings are also disabled in the expression that follows
|
|
\&\f(CW\*(C`_\|_extension_\|_\*(C'\fR. However, only system header files should use
|
|
these escape routes; application programs should avoid them.
|
|
.Sp
|
|
Some users try to use \fB\-pedantic\fR to check programs for strict \s-1ISO\s0
|
|
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
|
|
\&\s-1ISO\s0 C \fIrequires\fR a diagnostic, and some others for which
|
|
diagnostics have been added.
|
|
.Sp
|
|
A feature to report any failure to conform to \s-1ISO\s0 C might be useful in
|
|
some instances, but would require considerable additional work and would
|
|
be quite different from \fB\-pedantic\fR. We don't have plans to
|
|
support such a feature in the near future.
|
|
.Ip "\fB\-pedantic-errors\fR" 4
|
|
.IX Item "-pedantic-errors"
|
|
Like \fB\-pedantic\fR, except that errors are produced rather than
|
|
warnings.
|
|
.Ip "\fB\-w\fR" 4
|
|
.IX Item "-w"
|
|
Inhibit all warning messages.
|
|
.Ip "\fB\-Wno-import\fR" 4
|
|
.IX Item "-Wno-import"
|
|
Inhibit warning messages about the use of \fB#import\fR.
|
|
.Ip "\fB\-Wchar-subscripts\fR" 4
|
|
.IX Item "-Wchar-subscripts"
|
|
Warn if an array subscript has type \f(CW\*(C`char\*(C'\fR. This is a common cause
|
|
of error, as programmers often forget that this type is signed on some
|
|
machines.
|
|
.Ip "\fB\-Wcomment\fR" 4
|
|
.IX Item "-Wcomment"
|
|
Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
|
|
comment, or whenever a Backslash-Newline appears in a \fB//\fR comment.
|
|
.Ip "\fB\-Wformat\fR" 4
|
|
.IX Item "-Wformat"
|
|
Check calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR, 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, in the \f(CW\*(C`printf\*(C'\fR,
|
|
\&\f(CW\*(C`scanf\*(C'\fR, \f(CW\*(C`strftime\*(C'\fR and \f(CW\*(C`strfmon\*(C'\fR (an X/Open extension,
|
|
not in the C standard) families.
|
|
.Sp
|
|
The formats are checked against the format features supported by \s-1GNU\s0
|
|
libc version 2.2. These include all \s-1ISO\s0 C89 and C99 features, as well
|
|
as features from the Single Unix Specification and some \s-1BSD\s0 and \s-1GNU\s0
|
|
extensions. Other library implementations may not support all these
|
|
features; \s-1GCC\s0 does not support warning about features that go beyond a
|
|
particular library's limitations. However, if \fB\-pedantic\fR is used
|
|
with \fB\-Wformat\fR, warnings will be given about format features not
|
|
in the selected standard version (but not for \f(CW\*(C`strfmon\*(C'\fR formats,
|
|
since those are not in any version of the C standard).
|
|
.Sp
|
|
\&\fB\-Wformat\fR is included in \fB\-Wall\fR. For more control over some
|
|
aspects of format checking, the options \fB\-Wno-format-y2k\fR,
|
|
\&\fB\-Wno-format-extra-args\fR, \fB\-Wformat-nonliteral\fR,
|
|
\&\fB\-Wformat-security\fR and \fB\-Wformat=2\fR are available, but are
|
|
not included in \fB\-Wall\fR.
|
|
.Ip "\fB\-Wno-format-y2k\fR" 4
|
|
.IX Item "-Wno-format-y2k"
|
|
If \fB\-Wformat\fR is specified, do not warn about \f(CW\*(C`strftime\*(C'\fR
|
|
formats which may yield only a two-digit year.
|
|
.Ip "\fB\-Wno-format-extra-args\fR" 4
|
|
.IX Item "-Wno-format-extra-args"
|
|
If \fB\-Wformat\fR is specified, do not warn about excess arguments to a
|
|
\&\f(CW\*(C`printf\*(C'\fR or \f(CW\*(C`scanf\*(C'\fR format function. The C standard specifies
|
|
that such arguments are ignored.
|
|
.Ip "\fB\-Wformat-nonliteral\fR" 4
|
|
.IX Item "-Wformat-nonliteral"
|
|
If \fB\-Wformat\fR 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 \f(CW\*(C`va_list\*(C'\fR.
|
|
.Ip "\fB\-Wformat-security\fR" 4
|
|
.IX Item "-Wformat-security"
|
|
If \fB\-Wformat\fR is specified, also warn about uses of format
|
|
functions that represent possible security problems. At present, this
|
|
warns about calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR functions where the
|
|
format string is not a string literal and there are no format arguments,
|
|
as in \f(CW\*(C`printf (foo);\*(C'\fR. This may be a security hole if the format
|
|
string came from untrusted input and contains \fB%n\fR. (This is
|
|
currently a subset of what \fB\-Wformat-nonliteral\fR warns about, but
|
|
in future warnings may be added to \fB\-Wformat-security\fR that are not
|
|
included in \fB\-Wformat-nonliteral\fR.)
|
|
.Ip "\fB\-Wformat=2\fR" 4
|
|
.IX Item "-Wformat=2"
|
|
Enable \fB\-Wformat\fR plus format checks not included in
|
|
\&\fB\-Wformat\fR. Currently equivalent to \fB\-Wformat
|
|
\&\-Wformat-nonliteral \-Wformat-security\fR.
|
|
.Ip "\fB\-Wimplicit-int\fR" 4
|
|
.IX Item "-Wimplicit-int"
|
|
Warn when a declaration does not specify a type.
|
|
.Ip "\fB\-Wimplicit-function-declaration\fR" 4
|
|
.IX Item "-Wimplicit-function-declaration"
|
|
.PD 0
|
|
.Ip "\fB\-Werror-implicit-function-declaration\fR" 4
|
|
.IX Item "-Werror-implicit-function-declaration"
|
|
.PD
|
|
Give a warning (or error) whenever a function is used before being
|
|
declared.
|
|
.Ip "\fB\-Wimplicit\fR" 4
|
|
.IX Item "-Wimplicit"
|
|
Same as \fB\-Wimplicit-int\fR and \fB\-Wimplicit-function-\fR\fBdeclaration\fR.
|
|
.Ip "\fB\-Wmain\fR" 4
|
|
.IX Item "-Wmain"
|
|
Warn if the type of \fBmain\fR is suspicious. \fBmain\fR should be a
|
|
function with external linkage, returning int, taking either zero
|
|
arguments, two, or three arguments of appropriate types.
|
|
.Ip "\fB\-Wmultichar\fR" 4
|
|
.IX Item "-Wmultichar"
|
|
Warn if a multicharacter constant (\fB'\s-1FOOF\s0'\fR) 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.
|
|
.Ip "\fB\-Wparentheses\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
Also warn about constructions where there may be confusion to which
|
|
\&\f(CW\*(C`if\*(C'\fR statement an \f(CW\*(C`else\*(C'\fR branch belongs. Here is an example of
|
|
such a case:
|
|
.Sp
|
|
.Vb 7
|
|
\& {
|
|
\& if (a)
|
|
\& if (b)
|
|
\& foo ();
|
|
\& else
|
|
\& bar ();
|
|
\& }
|
|
.Ve
|
|
In C, every \f(CW\*(C`else\*(C'\fR branch belongs to the innermost possible \f(CW\*(C`if\*(C'\fR
|
|
statement, which in this example is \f(CW\*(C`if (b)\*(C'\fR. 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, \s-1GNU\s0 C will issue a warning when this flag is specified.
|
|
To eliminate the warning, add explicit braces around the innermost
|
|
\&\f(CW\*(C`if\*(C'\fR statement so there is no way the \f(CW\*(C`else\*(C'\fR could belong to
|
|
the enclosing \f(CW\*(C`if\*(C'\fR. The resulting code would look like this:
|
|
.Sp
|
|
.Vb 9
|
|
\& {
|
|
\& if (a)
|
|
\& {
|
|
\& if (b)
|
|
\& foo ();
|
|
\& else
|
|
\& bar ();
|
|
\& }
|
|
\& }
|
|
.Ve
|
|
.Ip "\fB\-Wsequence-point\fR" 4
|
|
.IX Item "-Wsequence-point"
|
|
Warn about code that may have undefined semantics because of violations
|
|
of sequence point rules in the C standard.
|
|
.Sp
|
|
The C standard defines the order in which expressions in a C program are
|
|
evaluated in terms of \fIsequence points\fR, 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
|
|
\&\f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, \f(CW\*(C`? :\*(C'\fR or \f(CW\*(C`,\*(C'\fR (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.
|
|
.Sp
|
|
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 standard specifies 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.
|
|
.Sp
|
|
Examples of code with undefined behavior are \f(CW\*(C`a = a++;\*(C'\fR, \f(CW\*(C`a[n]
|
|
= b[n++]\*(C'\fR and \f(CW\*(C`a[i++] = i;\*(C'\fR. 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.
|
|
.Sp
|
|
The present implementation of this option only works for C programs. A
|
|
future implementation may also work for \*(C+ programs.
|
|
.Sp
|
|
There is some controversy over the precise meaning of the sequence point
|
|
rules in subtle cases. Alternative formal definitions may be found in
|
|
Clive Feather's ``Annex S''
|
|
<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n925.htm\fR> and in
|
|
Michael Norrish's thesis
|
|
<\fBhttp://www.cl.cam.ac.uk/users/mn200/PhD/thesis-report.ps.gz\fR>.
|
|
Other discussions are by Raymond Mak
|
|
<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n926.htm\fR> and
|
|
D. Hugh Redelmeier
|
|
<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n927.htm\fR>.
|
|
.Ip "\fB\-Wreturn-type\fR" 4
|
|
.IX Item "-Wreturn-type"
|
|
Warn whenever a function is defined with a return-type that defaults to
|
|
\&\f(CW\*(C`int\*(C'\fR. Also warn about any \f(CW\*(C`return\*(C'\fR statement with no
|
|
return-value in a function whose return-type is not \f(CW\*(C`void\*(C'\fR.
|
|
.Sp
|
|
For \*(C+, a function without return type always produces a diagnostic
|
|
message, even when \fB\-Wno-return-type\fR is specified. The only
|
|
exceptions are \fBmain\fR and functions defined in system headers.
|
|
.Ip "\fB\-Wswitch\fR" 4
|
|
.IX Item "-Wswitch"
|
|
Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of enumeral type
|
|
and lacks a \f(CW\*(C`case\*(C'\fR for one or more of the named codes of that
|
|
enumeration. (The presence of a \f(CW\*(C`default\*(C'\fR label prevents this
|
|
warning.) \f(CW\*(C`case\*(C'\fR labels outside the enumeration range also
|
|
provoke warnings when this option is used.
|
|
.Ip "\fB\-Wtrigraphs\fR" 4
|
|
.IX Item "-Wtrigraphs"
|
|
Warn if any trigraphs are encountered that might change the meaning of
|
|
the program (trigraphs within comments are not warned about).
|
|
.Ip "\fB\-Wunused-function\fR" 4
|
|
.IX Item "-Wunused-function"
|
|
Warn whenever a static function is declared but not defined or a
|
|
non\e-inline static function is unused.
|
|
.Ip "\fB\-Wunused-label\fR" 4
|
|
.IX Item "-Wunused-label"
|
|
Warn whenever a label is declared but not used.
|
|
.Sp
|
|
To suppress this warning use the \fBunused\fR attribute.
|
|
.Ip "\fB\-Wunused-parameter\fR" 4
|
|
.IX Item "-Wunused-parameter"
|
|
Warn whenever a function parameter is unused aside from its declaration.
|
|
.Sp
|
|
To suppress this warning use the \fBunused\fR attribute.
|
|
.Ip "\fB\-Wunused-variable\fR" 4
|
|
.IX Item "-Wunused-variable"
|
|
Warn whenever a local variable or non-constant static variable is unused
|
|
aside from its declaration
|
|
.Sp
|
|
To suppress this warning use the \fBunused\fR attribute.
|
|
.Ip "\fB\-Wunused-value\fR" 4
|
|
.IX Item "-Wunused-value"
|
|
Warn whenever a statement computes a result that is explicitly not used.
|
|
.Sp
|
|
To suppress this warning cast the expression to \fBvoid\fR.
|
|
.Ip "\fB\-Wunused\fR" 4
|
|
.IX Item "-Wunused"
|
|
All all the above \fB\-Wunused\fR options combined.
|
|
.Sp
|
|
In order to get a warning about an unused function parameter, you must
|
|
either specify \fB\-W \-Wunused\fR or separately specify
|
|
\&\fB\-Wunused-parameter\fR.
|
|
.Ip "\fB\-Wuninitialized\fR" 4
|
|
.IX Item "-Wuninitialized"
|
|
Warn if an automatic variable is used without first being initialized or
|
|
if a variable may be clobbered by a \f(CW\*(C`setjmp\*(C'\fR call.
|
|
.Sp
|
|
These warnings are possible only in optimizing compilation,
|
|
because they require data flow information that is computed only
|
|
when optimizing. If you don't specify \fB\-O\fR, you simply won't
|
|
get these warnings.
|
|
.Sp
|
|
These warnings occur only for variables that are candidates for
|
|
register allocation. Therefore, they do not occur for a variable that
|
|
is declared \f(CW\*(C`volatile\*(C'\fR, or whose address is taken, or whose size
|
|
is other than 1, 2, 4 or 8 bytes. Also, they do not occur for
|
|
structures, unions or arrays, even when they are in registers.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
These warnings are made optional because \s-1GCC\s0 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:
|
|
.Sp
|
|
.Vb 12
|
|
\& {
|
|
\& int x;
|
|
\& switch (y)
|
|
\& {
|
|
\& case 1: x = 1;
|
|
\& break;
|
|
\& case 2: x = 4;
|
|
\& break;
|
|
\& case 3: x = 5;
|
|
\& }
|
|
\& foo (x);
|
|
\& }
|
|
.Ve
|
|
If the value of \f(CW\*(C`y\*(C'\fR is always 1, 2 or 3, then \f(CW\*(C`x\*(C'\fR is
|
|
always initialized, but \s-1GCC\s0 doesn't know this. Here is
|
|
another common case:
|
|
.Sp
|
|
.Vb 6
|
|
\& {
|
|
\& int save_y;
|
|
\& if (change_y) save_y = y, y = new_y;
|
|
\& ...
|
|
\& if (change_y) y = save_y;
|
|
\& }
|
|
.Ve
|
|
This has no bug because \f(CW\*(C`save_y\*(C'\fR is used only if it is set.
|
|
.Sp
|
|
This option also warns when a non-volatile automatic variable might be
|
|
changed by a call to \f(CW\*(C`longjmp\*(C'\fR. These warnings as well are possible
|
|
only in optimizing compilation.
|
|
.Sp
|
|
The compiler sees only the calls to \f(CW\*(C`setjmp\*(C'\fR. It cannot know
|
|
where \f(CW\*(C`longjmp\*(C'\fR 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 \f(CW\*(C`longjmp\*(C'\fR cannot
|
|
in fact be called at the place which would cause a problem.
|
|
.Sp
|
|
Some spurious warnings can be avoided if you declare all the functions
|
|
you use that never return as \f(CW\*(C`noreturn\*(C'\fR.
|
|
.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4
|
|
.IX Item "-Wreorder ( only)"
|
|
Warn when the order of member initializers given in the code does not
|
|
match the order in which they must be executed. For instance:
|
|
.Ip "\fB\-Wunknown-pragmas\fR" 4
|
|
.IX Item "-Wunknown-pragmas"
|
|
Warn when a #pragma directive is encountered which is not understood by
|
|
\&\s-1GCC\s0. 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 \fB\-Wall\fR command line option.
|
|
.Ip "\fB\-Wall\fR" 4
|
|
.IX Item "-Wall"
|
|
All of the above \fB\-W\fR 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.
|
|
.Ip "\fB\-Wsystem-headers\fR" 4
|
|
.IX Item "-Wsystem-headers"
|
|
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
|
|
\&\s-1GCC\s0 to emit warnings from system headers as if they occurred in user
|
|
code. However, note that using \fB\-Wall\fR in conjunction with this
|
|
option will \fInot\fR warn about unknown pragmas in system
|
|
headers\-\-\-for that, \fB\-Wunknown-pragmas\fR must also be used.
|
|
.PP
|
|
The following \fB\-W...\fR options are not implied by \fB\-Wall\fR.
|
|
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.
|
|
.Ip "\fB\-W\fR" 4
|
|
.IX Item "-W"
|
|
Print extra warning messages for these events:
|
|
.RS 4
|
|
.Ip "\(bu" 4
|
|
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:
|
|
.Sp
|
|
.Vb 5
|
|
\& foo (a)
|
|
\& {
|
|
\& if (a > 0)
|
|
\& return a;
|
|
\& }
|
|
.Ve
|
|
.Ip "\(bu" 4
|
|
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 \fBx[i,j]\fR will cause a warning,
|
|
but \fBx[(void)i,j]\fR will not.
|
|
.Ip "\(bu" 4
|
|
An unsigned value is compared against zero with \fB<\fR or \fB<=\fR.
|
|
.Ip "\(bu" 4
|
|
A comparison like \fBx<=y<=z\fR appears; this is equivalent to
|
|
\&\fB(x<=y ? 1 : 0) <= z\fR, which is a different interpretation from
|
|
that of ordinary mathematical notation.
|
|
.Ip "\(bu" 4
|
|
Storage-class specifiers like \f(CW\*(C`static\*(C'\fR are not the first things in
|
|
a declaration. According to the C Standard, this usage is obsolescent.
|
|
.Ip "\(bu" 4
|
|
The return type of a function has a type qualifier such as \f(CW\*(C`const\*(C'\fR.
|
|
Such a type qualifier has no effect, since the value returned by a
|
|
function is not an lvalue. (But don't warn about the \s-1GNU\s0 extension of
|
|
\&\f(CW\*(C`volatile void\*(C'\fR return types. That extension will be warned about
|
|
if \fB\-pedantic\fR is specified.)
|
|
.Ip "\(bu" 4
|
|
If \fB\-Wall\fR or \fB\-Wunused\fR is also specified, warn about unused
|
|
arguments.
|
|
.Ip "\(bu" 4
|
|
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 \fB\-Wno-sign-compare\fR is also specified.)
|
|
.Ip "\(bu" 4
|
|
An aggregate has a partly bracketed initializer.
|
|
For example, the following code would evoke such a warning,
|
|
because braces are missing around the initializer for \f(CW\*(C`x.h\*(C'\fR:
|
|
.Sp
|
|
.Vb 3
|
|
\& struct s { int f, g; };
|
|
\& struct t { struct s h; int i; };
|
|
\& struct t x = { 1, 2, 3 };
|
|
.Ve
|
|
.Ip "\(bu" 4
|
|
An aggregate has an initializer which does not initialize all members.
|
|
For example, the following code would cause such a warning, because
|
|
\&\f(CW\*(C`x.h\*(C'\fR would be implicitly initialized to zero:
|
|
.Sp
|
|
.Vb 2
|
|
\& struct s { int f, g, h; };
|
|
\& struct s x = { 3, 4 };
|
|
.Ve
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-Wfloat-equal\fR" 4
|
|
.IX Item "-Wfloat-equal"
|
|
Warn if floating point values are used in equality comparisons.
|
|
.Sp
|
|
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 analysing 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.
|
|
.Ip "\fB\-Wtraditional (C only)\fR" 4
|
|
.IX Item "-Wtraditional (C only)"
|
|
Warn about certain constructs that behave differently in traditional and
|
|
\&\s-1ISO\s0 C.
|
|
.RS 4
|
|
.Ip "\(bu" 4
|
|
Macro arguments occurring within string constants in the macro body.
|
|
These would substitute the argument in traditional C, but are part of
|
|
the constant in \s-1ISO\s0 C.
|
|
.Ip "\(bu" 4
|
|
A function declared external in one block and then used after the end of
|
|
the block.
|
|
.Ip "\(bu" 4
|
|
A \f(CW\*(C`switch\*(C'\fR statement has an operand of type \f(CW\*(C`long\*(C'\fR.
|
|
.Ip "\(bu" 4
|
|
A non-\f(CW\*(C`static\*(C'\fR function declaration follows a \f(CW\*(C`static\*(C'\fR one.
|
|
This construct is not accepted by some traditional C compilers.
|
|
.Ip "\(bu" 4
|
|
The \s-1ISO\s0 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.
|
|
.Ip "\(bu" 4
|
|
Usage of \s-1ISO\s0 string concatenation is detected.
|
|
.Ip "\(bu" 4
|
|
A function macro appears without arguments.
|
|
.Ip "\(bu" 4
|
|
The unary plus operator.
|
|
.Ip "\(bu" 4
|
|
Initialization of automatic aggregates.
|
|
.Ip "\(bu" 4
|
|
Identifier conflicts with labels. Traditional C lacks a separate
|
|
namespace for labels.
|
|
.Ip "\(bu" 4
|
|
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. \f(CW\*(C`_\|_STDC_\|_\*(C'\fR to avoid missing
|
|
initializer warnings and relies on default initialization to zero in the
|
|
traditional C case.
|
|
.Ip "\(bu" 4
|
|
The `U' integer constant suffix, or the `F' or `L' floating point
|
|
constant suffixes. (Traditonal C does support the `L' suffix on integer
|
|
constants.) Note, these suffixes appear in macros defined in the system
|
|
headers of most modern systems, e.g. the _MIN/_MAX macros in limits.h.
|
|
Use of these macros can lead to spurious warnings as they do not
|
|
necessarily reflect whether the code in question is any less portable to
|
|
traditional C given that suitable backup definitions are provided.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-Wundef\fR" 4
|
|
.IX Item "-Wundef"
|
|
Warn if an undefined identifier is evaluated in an \fB#if\fR directive.
|
|
.Ip "\fB\-Wshadow\fR" 4
|
|
.IX Item "-Wshadow"
|
|
Warn whenever a local variable shadows another local variable.
|
|
.Ip "\fB\-Wid-clash-\fR\fIlen\fR" 4
|
|
.IX Item "-Wid-clash-len"
|
|
Warn whenever two distinct identifiers match in the first \fIlen\fR
|
|
characters. This may help you prepare a program that will compile
|
|
with certain obsolete, brain-damaged compilers.
|
|
.Ip "\fB\-Wlarger-than-\fR\fIlen\fR" 4
|
|
.IX Item "-Wlarger-than-len"
|
|
Warn whenever an object of larger than \fIlen\fR bytes is defined.
|
|
.Ip "\fB\-Wpointer-arith\fR" 4
|
|
.IX Item "-Wpointer-arith"
|
|
Warn about anything that depends on the ``size of'' a function type or
|
|
of \f(CW\*(C`void\*(C'\fR. \s-1GNU\s0 C assigns these types a size of 1, for
|
|
convenience in calculations with \f(CW\*(C`void *\*(C'\fR pointers and pointers
|
|
to functions.
|
|
.Ip "\fB\-Wbad-function-cast (C only)\fR" 4
|
|
.IX Item "-Wbad-function-cast (C only)"
|
|
Warn whenever a function call is cast to a non-matching type.
|
|
For example, warn if \f(CW\*(C`int malloc()\*(C'\fR is cast to \f(CW\*(C`anything *\*(C'\fR.
|
|
.Ip "\fB\-Wcast-qual\fR" 4
|
|
.IX Item "-Wcast-qual"
|
|
Warn whenever a pointer is cast so as to remove a type qualifier from
|
|
the target type. For example, warn if a \f(CW\*(C`const char *\*(C'\fR is cast
|
|
to an ordinary \f(CW\*(C`char *\*(C'\fR.
|
|
.Ip "\fB\-Wcast-align\fR" 4
|
|
.IX Item "-Wcast-align"
|
|
Warn whenever a pointer is cast such that the required alignment of the
|
|
target is increased. For example, warn if a \f(CW\*(C`char *\*(C'\fR is cast to
|
|
an \f(CW\*(C`int *\*(C'\fR on machines where integers can only be accessed at
|
|
two- or four-byte boundaries.
|
|
.Ip "\fB\-Wwrite-strings\fR" 4
|
|
.IX Item "-Wwrite-strings"
|
|
Give string constants the type \f(CW\*(C`const char[\f(CIlength\f(CW]\*(C'\fR so that
|
|
copying the address of one into a non-\f(CW\*(C`const\*(C'\fR \f(CW\*(C`char *\*(C'\fR
|
|
pointer will get a warning. 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 \f(CW\*(C`const\*(C'\fR in
|
|
declarations and prototypes. Otherwise, it will just be a nuisance;
|
|
this is why we did not make \fB\-Wall\fR request these warnings.
|
|
.Ip "\fB\-Wconversion\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
Also, warn if a negative integer constant expression is implicitly
|
|
converted to an unsigned type. For example, warn about the assignment
|
|
\&\f(CW\*(C`x = \-1\*(C'\fR if \f(CW\*(C`x\*(C'\fR is unsigned. But do not warn about explicit
|
|
casts like \f(CW\*(C`(unsigned) \-1\*(C'\fR.
|
|
.Ip "\fB\-Wsign-compare\fR" 4
|
|
.IX Item "-Wsign-compare"
|
|
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 \fB\-W\fR; to get the other warnings
|
|
of \fB\-W\fR without this warning, use \fB\-W \-Wno-sign-compare\fR.
|
|
.Ip "\fB\-Waggregate-return\fR" 4
|
|
.IX Item "-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.)
|
|
.Ip "\fB\-Wstrict-prototypes (C only)\fR" 4
|
|
.IX Item "-Wstrict-prototypes (C only)"
|
|
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.)
|
|
.Ip "\fB\-Wmissing-prototypes (C only)\fR" 4
|
|
.IX Item "-Wmissing-prototypes (C only)"
|
|
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.
|
|
.Ip "\fB\-Wmissing-declarations\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-Wmissing-noreturn\fR" 4
|
|
.IX Item "-Wmissing-noreturn"
|
|
Warn about functions which might be candidates for attribute \f(CW\*(C`noreturn\*(C'\fR.
|
|
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 \f(CW\*(C`noreturn\*(C'\fR attribute, otherwise subtle code generation
|
|
bugs could be introduced. You will not get a warning for \f(CW\*(C`main\*(C'\fR in
|
|
hosted C environments.
|
|
.Ip "\fB\-Wmissing-format-attribute\fR" 4
|
|
.IX Item "-Wmissing-format-attribute"
|
|
If \fB\-Wformat\fR is enabled, also warn about functions which might be
|
|
candidates for \f(CW\*(C`format\*(C'\fR attributes. Note these are only possible
|
|
candidates, not absolute ones. \s-1GCC\s0 will guess that \f(CW\*(C`format\*(C'\fR
|
|
attributes might be appropriate for any function that calls a function
|
|
like \f(CW\*(C`vprintf\*(C'\fR or \f(CW\*(C`vscanf\*(C'\fR, but this might not always be the
|
|
case, and some functions for which \f(CW\*(C`format\*(C'\fR attributes are
|
|
appropriate may not be detected. This option has no effect unless
|
|
\&\fB\-Wformat\fR is enabled (possibly by \fB\-Wall\fR).
|
|
.Ip "\fB\-Wpacked\fR" 4
|
|
.IX Item "-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 \f(CW\*(C`f.x\*(C'\fR in \f(CW\*(C`struct bar\*(C'\fR
|
|
will be misaligned even though \f(CW\*(C`struct bar\*(C'\fR does not itself
|
|
have the packed attribute:
|
|
.Sp
|
|
.Vb 8
|
|
\& struct foo {
|
|
\& int x;
|
|
\& char a, b, c, d;
|
|
\& } __attribute__((packed));
|
|
\& struct bar {
|
|
\& char z;
|
|
\& struct foo f;
|
|
\& };
|
|
.Ve
|
|
.Ip "\fB\-Wpadded\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-Wredundant-decls\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-Wnested-externs (C only)\fR" 4
|
|
.IX Item "-Wnested-externs (C only)"
|
|
Warn if an \f(CW\*(C`extern\*(C'\fR declaration is encountered within a function.
|
|
.Ip "\fB\-Wunreachable-code\fR" 4
|
|
.IX Item "-Wunreachable-code"
|
|
Warn if the compiler detects that code will never be executed.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
For instance, when a function is inlined, a warning may mean that the
|
|
line is unreachable in only one inlined copy of the function.
|
|
.Sp
|
|
This option is not made part of \fB\-Wall\fR 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 behaviour which is selectable at compile-time.
|
|
.Ip "\fB\-Winline\fR" 4
|
|
.IX Item "-Winline"
|
|
Warn if a function can not be inlined and it was declared as inline.
|
|
.Ip "\fB\-Wlong-long\fR" 4
|
|
.IX Item "-Wlong-long"
|
|
Warn if \fBlong long\fR type is used. This is default. To inhibit
|
|
the warning messages, use \fB\-Wno-long-long\fR. Flags
|
|
\&\fB\-Wlong-long\fR and \fB\-Wno-long-long\fR are taken into account
|
|
only when \fB\-pedantic\fR flag is used.
|
|
.Ip "\fB\-Wdisabled-optimization\fR" 4
|
|
.IX Item "-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 \s-1GCC\s0's optimizers were unable to handle the code
|
|
effectively. Often, the problem is that your code is too big or too
|
|
complex; \s-1GCC\s0 will refuse to optimize programs when the optimization
|
|
itself is likely to take inordinate amounts of time.
|
|
.Ip "\fB\-Werror\fR" 4
|
|
.IX Item "-Werror"
|
|
Make all warnings into errors.
|
|
.Sh "Options for Debugging Your Program or \s-1GCC\s0"
|
|
.IX Subsection "Options for Debugging Your Program or GCC"
|
|
\&\s-1GCC\s0 has various special options that are used for debugging
|
|
either your program or \s-1GCC:\s0
|
|
.Ip "\fB\-g\fR" 4
|
|
.IX Item "-g"
|
|
Produce debugging information in the operating system's native format
|
|
(stabs, \s-1COFF\s0, \s-1XCOFF\s0, or \s-1DWARF\s0). \s-1GDB\s0 can work with this debugging
|
|
information.
|
|
.Sp
|
|
On most systems that use stabs format, \fB\-g\fR enables use of extra
|
|
debugging information that only \s-1GDB\s0 can use; this extra information
|
|
makes debugging work better in \s-1GDB\s0 but will probably make other debuggers
|
|
crash or
|
|
refuse to read the program. If you want to control for certain whether
|
|
to generate the extra information, use \fB\-gstabs+\fR, \fB\-gstabs\fR,
|
|
\&\fB\-gxcoff+\fR, \fB\-gxcoff\fR, \fB\-gdwarf-1+\fR, or \fB\-gdwarf-1\fR
|
|
(see below).
|
|
.Sp
|
|
Unlike most other C compilers, \s-1GCC\s0 allows you to use \fB\-g\fR with
|
|
\&\fB\-O\fR. 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.
|
|
.Sp
|
|
Nevertheless it proves possible to debug optimized output. This makes
|
|
it reasonable to use the optimizer for programs that might have bugs.
|
|
.Sp
|
|
The following options are useful when \s-1GCC\s0 is generated with the
|
|
capability for more than one debugging format.
|
|
.Ip "\fB\-ggdb\fR" 4
|
|
.IX Item "-ggdb"
|
|
Produce debugging information for use by \s-1GDB\s0. This means to use the
|
|
most expressive format available (\s-1DWARF\s0 2, stabs, or the native format
|
|
if neither of those are supported), including \s-1GDB\s0 extensions if at all
|
|
possible.
|
|
.Ip "\fB\-gstabs\fR" 4
|
|
.IX Item "-gstabs"
|
|
Produce debugging information in stabs format (if that is supported),
|
|
without \s-1GDB\s0 extensions. This is the format used by \s-1DBX\s0 on most \s-1BSD\s0
|
|
systems. On \s-1MIPS\s0, Alpha and System V Release 4 systems this option
|
|
produces stabs debugging output which is not understood by \s-1DBX\s0 or \s-1SDB\s0.
|
|
On System V Release 4 systems this option requires the \s-1GNU\s0 assembler.
|
|
.Ip "\fB\-gstabs+\fR" 4
|
|
.IX Item "-gstabs+"
|
|
Produce debugging information in stabs format (if that is supported),
|
|
using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). The
|
|
use of these extensions is likely to make other debuggers crash or
|
|
refuse to read the program.
|
|
.Ip "\fB\-gcoff\fR" 4
|
|
.IX Item "-gcoff"
|
|
Produce debugging information in \s-1COFF\s0 format (if that is supported).
|
|
This is the format used by \s-1SDB\s0 on most System V systems prior to
|
|
System V Release 4.
|
|
.Ip "\fB\-gxcoff\fR" 4
|
|
.IX Item "-gxcoff"
|
|
Produce debugging information in \s-1XCOFF\s0 format (if that is supported).
|
|
This is the format used by the \s-1DBX\s0 debugger on \s-1IBM\s0 \s-1RS/6000\s0 systems.
|
|
.Ip "\fB\-gxcoff+\fR" 4
|
|
.IX Item "-gxcoff+"
|
|
Produce debugging information in \s-1XCOFF\s0 format (if that is supported),
|
|
using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). 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 \s-1GNU\s0
|
|
assembler (\s-1GAS\s0) to fail with an error.
|
|
.Ip "\fB\-gdwarf\fR" 4
|
|
.IX Item "-gdwarf"
|
|
Produce debugging information in \s-1DWARF\s0 version 1 format (if that is
|
|
supported). This is the format used by \s-1SDB\s0 on most System V Release 4
|
|
systems.
|
|
.Ip "\fB\-gdwarf+\fR" 4
|
|
.IX Item "-gdwarf+"
|
|
Produce debugging information in \s-1DWARF\s0 version 1 format (if that is
|
|
supported), using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger
|
|
(\s-1GDB\s0). The use of these extensions is likely to make other debuggers
|
|
crash or refuse to read the program.
|
|
.Ip "\fB\-gdwarf-2\fR" 4
|
|
.IX Item "-gdwarf-2"
|
|
Produce debugging information in \s-1DWARF\s0 version 2 format (if that is
|
|
supported). This is the format used by \s-1DBX\s0 on \s-1IRIX\s0 6.
|
|
.Ip "\fB\-g\fR\fIlevel\fR" 4
|
|
.IX Item "-glevel"
|
|
.PD 0
|
|
.Ip "\fB\-ggdb\fR\fIlevel\fR" 4
|
|
.IX Item "-ggdblevel"
|
|
.Ip "\fB\-gstabs\fR\fIlevel\fR" 4
|
|
.IX Item "-gstabslevel"
|
|
.Ip "\fB\-gcoff\fR\fIlevel\fR" 4
|
|
.IX Item "-gcofflevel"
|
|
.Ip "\fB\-gxcoff\fR\fIlevel\fR" 4
|
|
.IX Item "-gxcofflevel"
|
|
.Ip "\fB\-gdwarf\fR\fIlevel\fR" 4
|
|
.IX Item "-gdwarflevel"
|
|
.Ip "\fB\-gdwarf-2\fR\fIlevel\fR" 4
|
|
.IX Item "-gdwarf-2level"
|
|
.PD
|
|
Request debugging information and also use \fIlevel\fR to specify how
|
|
much information. The default level is 2.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
Level 3 includes extra information, such as all the macro definitions
|
|
present in the program. Some debuggers support macro expansion when
|
|
you use \fB\-g3\fR.
|
|
.Ip "\fB\-p\fR" 4
|
|
.IX Item "-p"
|
|
Generate extra code to write profile information suitable for the
|
|
analysis program \f(CW\*(C`prof\*(C'\fR. You must use this option when compiling
|
|
the source files you want data about, and you must also use it when
|
|
linking.
|
|
.Ip "\fB\-pg\fR" 4
|
|
.IX Item "-pg"
|
|
Generate extra code to write profile information suitable for the
|
|
analysis program \f(CW\*(C`gprof\*(C'\fR. You must use this option when compiling
|
|
the source files you want data about, and you must also use it when
|
|
linking.
|
|
.Ip "\fB\-a\fR" 4
|
|
.IX Item "-a"
|
|
Generate extra code to write profile information for basic blocks, which will
|
|
record the number of times each basic block is executed, the basic block start
|
|
address, and the function name containing the basic block. If \fB\-g\fR is
|
|
used, the line number and filename of the start of the basic block will also be
|
|
recorded. If not overridden by the machine description, the default action is
|
|
to append to the text file \fIbb.out\fR.
|
|
.Sp
|
|
This data could be analyzed by a program like \f(CW\*(C`tcov\*(C'\fR. Note,
|
|
however, that the format of the data is not what \f(CW\*(C`tcov\*(C'\fR expects.
|
|
Eventually \s-1GNU\s0 \f(CW\*(C`gprof\*(C'\fR should be extended to process this data.
|
|
.Ip "\fB\-Q\fR" 4
|
|
.IX Item "-Q"
|
|
Makes the compiler print out each function name as it is compiled, and
|
|
print some statistics about each pass when it finishes.
|
|
.Ip "\fB\-ax\fR" 4
|
|
.IX Item "-ax"
|
|
Generate extra code to profile basic blocks. Your executable will
|
|
produce output that is a superset of that produced when \fB\-a\fR is
|
|
used. Additional output is the source and target address of the basic
|
|
blocks where a jump takes place, the number of times a jump is executed,
|
|
and (optionally) the complete sequence of basic blocks being executed.
|
|
The output is appended to file \fIbb.out\fR.
|
|
.Sp
|
|
You can examine different profiling aspects without recompilation. Your
|
|
executable will read a list of function names from file \fIbb.in\fR.
|
|
Profiling starts when a function on the list is entered and stops when
|
|
that invocation is exited. To exclude a function from profiling, prefix
|
|
its name with `\-'. If a function name is not unique, you can
|
|
disambiguate it by writing it in the form
|
|
\&\fB/path/filename.d:functionname\fR. Your executable will write the
|
|
available paths and filenames in file \fIbb.out\fR.
|
|
.Sp
|
|
Several function names have a special meaning:
|
|
.RS 4
|
|
.if n .Ip "\f(CW""_\|_bb_jumps_\|_""\fR" 4
|
|
.el .Ip "\f(CW_\|_bb_jumps_\|_\fR" 4
|
|
.IX Item "__bb_jumps__"
|
|
Write source, target and frequency of jumps to file \fIbb.out\fR.
|
|
.if n .Ip "\f(CW""_\|_bb_hidecall_\|_""\fR" 4
|
|
.el .Ip "\f(CW_\|_bb_hidecall_\|_\fR" 4
|
|
.IX Item "__bb_hidecall__"
|
|
Exclude function calls from frequency count.
|
|
.if n .Ip "\f(CW""_\|_bb_showret_\|_""\fR" 4
|
|
.el .Ip "\f(CW_\|_bb_showret_\|_\fR" 4
|
|
.IX Item "__bb_showret__"
|
|
Include function returns in frequency count.
|
|
.if n .Ip "\f(CW""_\|_bb_trace_\|_""\fR" 4
|
|
.el .Ip "\f(CW_\|_bb_trace_\|_\fR" 4
|
|
.IX Item "__bb_trace__"
|
|
Write the sequence of basic blocks executed to file \fIbbtrace.gz\fR.
|
|
The file will be compressed using the program \fBgzip\fR, which must
|
|
exist in your \fB\s-1PATH\s0\fR. On systems without the \fBpopen\fR
|
|
function, the file will be named \fIbbtrace\fR and will not be
|
|
compressed. \fBProfiling for even a few seconds on these systems
|
|
will produce a very large file.\fR Note: \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR and
|
|
\&\f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR will not affect the sequence written to
|
|
\&\fIbbtrace.gz\fR.
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
Here's a short example using different profiling parameters
|
|
in file \fIbb.in\fR. Assume function \f(CW\*(C`foo\*(C'\fR consists of basic blocks
|
|
1 and 2 and is called twice from block 3 of function \f(CW\*(C`main\*(C'\fR. After
|
|
the calls, block 3 transfers control to block 4 of \f(CW\*(C`main\*(C'\fR.
|
|
.Sp
|
|
With \f(CW\*(C`_\|_bb_trace_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR,
|
|
the following sequence of blocks is written to file \fIbbtrace.gz\fR:
|
|
0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because
|
|
the return is to a point inside the block and not to the top. The
|
|
block address 0 always indicates, that control is transferred
|
|
to the trace from somewhere outside the observed functions. With
|
|
\&\fB\-foo\fR added to \fIbb.in\fR, the blocks of function
|
|
\&\f(CW\*(C`foo\*(C'\fR are removed from the trace, so only 0 3 4 remains.
|
|
.Sp
|
|
With \f(CW\*(C`_\|_bb_jumps_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR,
|
|
jump frequencies will be written to file \fIbb.out\fR. The
|
|
frequencies are obtained by constructing a trace of blocks
|
|
and incrementing a counter for every neighbouring pair of blocks
|
|
in the trace. The trace 0 3 1 2 1 2 4 displays the following
|
|
frequencies:
|
|
.Sp
|
|
.Vb 5
|
|
\& Jump from block 0x0 to block 0x3 executed 1 time(s)
|
|
\& Jump from block 0x3 to block 0x1 executed 1 time(s)
|
|
\& Jump from block 0x1 to block 0x2 executed 2 time(s)
|
|
\& Jump from block 0x2 to block 0x1 executed 1 time(s)
|
|
\& Jump from block 0x2 to block 0x4 executed 1 time(s)
|
|
.Ve
|
|
With \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR, control transfer due to call instructions
|
|
is removed from the trace, that is the trace is cut into three parts: 0
|
|
3 4, 0 1 2 and 0 1 2. With \f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR, control transfer due
|
|
to return instructions is added to the trace. The trace becomes: 0 3 1
|
|
2 3 1 2 3 4. Note, that this trace is not the same, as the sequence
|
|
written to \fIbbtrace.gz\fR. It is solely used for counting jump
|
|
frequencies.
|
|
.RE
|
|
.Ip "\fB\-fprofile-arcs\fR" 4
|
|
.IX Item "-fprofile-arcs"
|
|
Instrument \fIarcs\fR during compilation. For each function of your
|
|
program, \s-1GCC\s0 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.
|
|
.Sp
|
|
Since not every arc in the program must be instrumented, programs
|
|
compiled with this option run faster than programs compiled with
|
|
\&\fB\-a\fR, which adds instrumentation code to every basic block in the
|
|
program. The tradeoff: since \f(CW\*(C`gcov\*(C'\fR does not have
|
|
execution counts for all branches, it must start with the execution
|
|
counts for the instrumented branches, and then iterate over the program
|
|
flow graph until the entire graph has been solved. Hence, \f(CW\*(C`gcov\*(C'\fR
|
|
runs a little more slowly than a program which uses information from
|
|
\&\fB\-a\fR.
|
|
.Sp
|
|
\&\fB\-fprofile-arcs\fR also makes it possible to estimate branch
|
|
probabilities, and to calculate basic block execution counts. In
|
|
general, basic block execution counts do not give enough information to
|
|
estimate all branch probabilities. When the compiled program exits, it
|
|
saves the arc execution counts to a file called
|
|
\&\fI\fIsourcename\fI.da\fR. Use the compiler option
|
|
\&\fB\-fbranch-probabilities\fR when recompiling, to optimize using estimated
|
|
branch probabilities.
|
|
.Ip "\fB\-ftest-coverage\fR" 4
|
|
.IX Item "-ftest-coverage"
|
|
Create data files for the \f(CW\*(C`gcov\*(C'\fR code-coverage utility.
|
|
The data file names begin with the name of your source file:
|
|
.RS 4
|
|
.Ip "\fIsourcename\fR\fB.bb\fR" 4
|
|
.IX Item "sourcename.bb"
|
|
A mapping from basic blocks to line numbers, which \f(CW\*(C`gcov\*(C'\fR uses to
|
|
associate basic block execution counts with line numbers.
|
|
.Ip "\fIsourcename\fR\fB.bbg\fR" 4
|
|
.IX Item "sourcename.bbg"
|
|
A list of all arcs in the program flow graph. This allows \f(CW\*(C`gcov\*(C'\fR
|
|
to reconstruct the program flow graph, so that it can compute all basic
|
|
block and arc execution counts from the information in the
|
|
\&\f(CW\*(C`\f(CIsourcename\f(CW.da\*(C'\fR file (this last file is the output from
|
|
\&\fB\-fprofile-arcs\fR).
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-d\fR\fIletters\fR" 4
|
|
.IX Item "-dletters"
|
|
Says to make debugging dumps during compilation at times specified by
|
|
\&\fIletters\fR. This is used for debugging the compiler. The file names
|
|
for most of the dumps are made by appending a pass number and a word to
|
|
the source file name (e.g. \fIfoo.c.00.rtl\fR or \fIfoo.c.01.sibling\fR).
|
|
Here are the possible letters for use in \fIletters\fR, and their meanings:
|
|
.RS 4
|
|
.Ip "\fBA\fR" 4
|
|
.IX Item "A"
|
|
Annotate the assembler output with miscellaneous debugging information.
|
|
.Ip "\fBb\fR" 4
|
|
.IX Item "b"
|
|
Dump after computing branch probabilities, to \fI\fIfile\fI.11.bp\fR.
|
|
.Ip "\fBB\fR" 4
|
|
.IX Item "B"
|
|
Dump after block reordering, to \fI\fIfile\fI.26.bbro\fR.
|
|
.Ip "\fBc\fR" 4
|
|
.IX Item "c"
|
|
Dump after instruction combination, to the file \fI\fIfile\fI.14.combine\fR.
|
|
.Ip "\fBC\fR" 4
|
|
.IX Item "C"
|
|
Dump after the first if conversion, to the file \fI\fIfile\fI.15.ce\fR.
|
|
.Ip "\fBd\fR" 4
|
|
.IX Item "d"
|
|
Dump after delayed branch scheduling, to \fI\fIfile\fI.29.dbr\fR.
|
|
.Ip "\fBD\fR" 4
|
|
.IX Item "D"
|
|
Dump all macro definitions, at the end of preprocessing, in addition to
|
|
normal output.
|
|
.Ip "\fBe\fR" 4
|
|
.IX Item "e"
|
|
Dump after \s-1SSA\s0 optimizations, to \fI\fIfile\fI.05.ssa\fR and
|
|
\&\fI\fIfile\fI.06.ussa\fR.
|
|
.Ip "\fBE\fR" 4
|
|
.IX Item "E"
|
|
Dump after the second if conversion, to \fI\fIfile\fI.24.ce2\fR.
|
|
.Ip "\fBf\fR" 4
|
|
.IX Item "f"
|
|
Dump after life analysis, to \fI\fIfile\fI.13.life\fR.
|
|
.Ip "\fBF\fR" 4
|
|
.IX Item "F"
|
|
Dump after purging \f(CW\*(C`ADDRESSOF\*(C'\fR codes, to \fI\fIfile\fI.04.addressof\fR.
|
|
.Ip "\fBg\fR" 4
|
|
.IX Item "g"
|
|
Dump after global register allocation, to \fI\fIfile\fI.19.greg\fR.
|
|
.Ip "\fBo\fR" 4
|
|
.IX Item "o"
|
|
Dump after post-reload \s-1CSE\s0 and other optimizations, to \fI\fIfile\fI.20.postreload\fR.
|
|
.Ip "\fBG\fR" 4
|
|
.IX Item "G"
|
|
Dump after \s-1GCSE\s0, to \fI\fIfile\fI.08.gcse\fR.
|
|
.Ip "\fBi\fR" 4
|
|
.IX Item "i"
|
|
Dump after sibling call optimizations, to \fI\fIfile\fI.01.sibling\fR.
|
|
.Ip "\fBj\fR" 4
|
|
.IX Item "j"
|
|
Dump after the first jump optimization, to \fI\fIfile\fI.02.jump\fR.
|
|
.Ip "\fBJ\fR" 4
|
|
.IX Item "J"
|
|
Dump after the last jump optimization, to \fI\fIfile\fI.27.jump2\fR.
|
|
.Ip "\fBk\fR" 4
|
|
.IX Item "k"
|
|
Dump after conversion from registers to stack, to \fI\fIfile\fI.29.stack\fR.
|
|
.Ip "\fBl\fR" 4
|
|
.IX Item "l"
|
|
Dump after local register allocation, to \fI\fIfile\fI.18.lreg\fR.
|
|
.Ip "\fBL\fR" 4
|
|
.IX Item "L"
|
|
Dump after loop optimization, to \fI\fIfile\fI.09.loop\fR.
|
|
.Ip "\fBM\fR" 4
|
|
.IX Item "M"
|
|
Dump after performing the machine dependent reorganisation pass, to
|
|
\&\fI\fIfile\fI.28.mach\fR.
|
|
.Ip "\fBn\fR" 4
|
|
.IX Item "n"
|
|
Dump after register renumbering, to \fI\fIfile\fI.23.rnreg\fR.
|
|
.Ip "\fBN\fR" 4
|
|
.IX Item "N"
|
|
Dump after the register move pass, to \fI\fIfile\fI.16.regmove\fR.
|
|
.Ip "\fBr\fR" 4
|
|
.IX Item "r"
|
|
Dump after \s-1RTL\s0 generation, to \fI\fIfile\fI.00.rtl\fR.
|
|
.Ip "\fBR\fR" 4
|
|
.IX Item "R"
|
|
Dump after the second instruction scheduling pass, to
|
|
\&\fI\fIfile\fI.25.sched2\fR.
|
|
.Ip "\fBs\fR" 4
|
|
.IX Item "s"
|
|
Dump after \s-1CSE\s0 (including the jump optimization that sometimes follows
|
|
\&\s-1CSE\s0), to \fI\fIfile\fI.03.cse\fR.
|
|
.Ip "\fBS\fR" 4
|
|
.IX Item "S"
|
|
Dump after the first instruction scheduling pass, to
|
|
\&\fI\fIfile\fI.17.sched\fR.
|
|
.Ip "\fBt\fR" 4
|
|
.IX Item "t"
|
|
Dump after the second \s-1CSE\s0 pass (including the jump optimization that
|
|
sometimes follows \s-1CSE\s0), to \fI\fIfile\fI.10.cse2\fR.
|
|
.Ip "\fBw\fR" 4
|
|
.IX Item "w"
|
|
Dump after the second flow pass, to \fI\fIfile\fI.21.flow2\fR.
|
|
.Ip "\fBX\fR" 4
|
|
.IX Item "X"
|
|
Dump after dead code elimination, to \fI\fIfile\fI.06.dce\fR.
|
|
.Ip "\fBz\fR" 4
|
|
.IX Item "z"
|
|
Dump after the peephole pass, to \fI\fIfile\fI.22.peephole2\fR.
|
|
.Ip "\fBa\fR" 4
|
|
.IX Item "a"
|
|
Produce all the dumps listed above.
|
|
.Ip "\fBm\fR" 4
|
|
.IX Item "m"
|
|
Print statistics on memory usage, at the end of the run, to
|
|
standard error.
|
|
.Ip "\fBp\fR" 4
|
|
.IX Item "p"
|
|
Annotate the assembler output with a comment indicating which
|
|
pattern and alternative was used. The length of each instruction is
|
|
also printed.
|
|
.Ip "\fBP\fR" 4
|
|
.IX Item "P"
|
|
Dump the \s-1RTL\s0 in the assembler output as a comment before each instruction.
|
|
Also turns on \fB\-dp\fR annotation.
|
|
.Ip "\fBv\fR" 4
|
|
.IX Item "v"
|
|
For each of the other indicated dump files (except for
|
|
\&\fI\fIfile\fI.00.rtl\fR), dump a representation of the control flow graph
|
|
suitable for viewing with \s-1VCG\s0 to \fI\fIfile\fI.\fIpass\fI.vcg\fR.
|
|
.Ip "\fBx\fR" 4
|
|
.IX Item "x"
|
|
Just generate \s-1RTL\s0 for a function instead of compiling it. Usually used
|
|
with \fBr\fR.
|
|
.Ip "\fBy\fR" 4
|
|
.IX Item "y"
|
|
Dump debugging information during parsing, to standard error.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-fdump-unnumbered\fR" 4
|
|
.IX Item "-fdump-unnumbered"
|
|
When doing debugging dumps (see \-d option above), suppress instruction
|
|
numbers and line number note output. This makes it more feasible to
|
|
use diff on debugging dumps for compiler invocations with different
|
|
options, in particular with and without \-g.
|
|
.Ip "\fB\-fdump-translation-unit-\fR\fIfile\fR \fB(C and \*(C+ only)\fR" 4
|
|
.IX Item "-fdump-translation-unit-file (C and only)"
|
|
Dump a representation of the tree structure for the entire translation
|
|
unit to \fIfile\fR.
|
|
.Ip "\fB\-fpretend-float\fR" 4
|
|
.IX Item "-fpretend-float"
|
|
When running a cross-compiler, pretend that the target machine uses the
|
|
same floating point format as the host machine. This causes incorrect
|
|
output of the actual floating constants, but the actual instruction
|
|
sequence will probably be the same as \s-1GCC\s0 would make when running on
|
|
the target machine.
|
|
.Ip "\fB\-save-temps\fR" 4
|
|
.IX Item "-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 \fIfoo.c\fR with \fB\-c \-save-temps\fR would produce files
|
|
\&\fIfoo.i\fR and \fIfoo.s\fR, as well as \fIfoo.o\fR. This creates a
|
|
preprocessed \fIfoo.i\fR output file even though the compiler now
|
|
normally uses an integrated preprocessor.
|
|
.Ip "\fB\-time\fR" 4
|
|
.IX Item "-time"
|
|
Report the \s-1CPU\s0 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:
|
|
.Sp
|
|
.Vb 2
|
|
\& # cc1 0.12 0.01
|
|
\& # as 0.00 0.01
|
|
.Ve
|
|
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.
|
|
.Ip "\fB\-print-file-name=\fR\fIlibrary\fR" 4
|
|
.IX Item "-print-file-name=library"
|
|
Print the full absolute name of the library file \fIlibrary\fR that
|
|
would be used when linking\-\-\-and don't do anything else. With this
|
|
option, \s-1GCC\s0 does not compile or link anything; it just prints the
|
|
file name.
|
|
.Ip "\fB\-print-prog-name=\fR\fIprogram\fR" 4
|
|
.IX Item "-print-prog-name=program"
|
|
Like \fB\-print-file-name\fR, but searches for a program such as \fBcpp\fR.
|
|
.Ip "\fB\-print-libgcc-file-name\fR" 4
|
|
.IX Item "-print-libgcc-file-name"
|
|
Same as \fB\-print-file-name=libgcc.a\fR.
|
|
.Sp
|
|
This is useful when you use \fB\-nostdlib\fR or \fB\-nodefaultlibs\fR
|
|
but you do want to link with \fIlibgcc.a\fR. You can do
|
|
.Sp
|
|
.Vb 1
|
|
\& gcc -nostdlib I<files>... `gcc -print-libgcc-file-name`
|
|
.Ve
|
|
.Ip "\fB\-print-search-dirs\fR" 4
|
|
.IX Item "-print-search-dirs"
|
|
Print the name of the configured installation directory and a list of
|
|
program and library directories gcc will search\-\-\-and don't do anything else.
|
|
.Sp
|
|
This is useful when gcc prints the error message
|
|
\&\fBinstallation problem, cannot exec cpp0: No such file or directory\fR.
|
|
To resolve this you either need to put \fIcpp0\fR and the other compiler
|
|
components where gcc expects to find them, or you can set the environment
|
|
variable \fB\s-1GCC_EXEC_PREFIX\s0\fR to the directory where you installed them.
|
|
Don't forget the trailing '/'.
|
|
.Sh "Options That Control Optimization"
|
|
.IX Subsection "Options That Control Optimization"
|
|
These options control various sorts of optimizations:
|
|
.Ip "\fB\-O\fR" 4
|
|
.IX Item "-O"
|
|
.PD 0
|
|
.Ip "\fB\-O1\fR" 4
|
|
.IX Item "-O1"
|
|
.PD
|
|
Optimize. Optimizing compilation takes somewhat more time, and a lot
|
|
more memory for a large function.
|
|
.Sp
|
|
Without \fB\-O\fR, 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.
|
|
.Sp
|
|
Without \fB\-O\fR, the compiler only allocates variables declared
|
|
\&\f(CW\*(C`register\*(C'\fR in registers. The resulting compiled code is a little
|
|
worse than produced by \s-1PCC\s0 without \fB\-O\fR.
|
|
.Sp
|
|
With \fB\-O\fR, the compiler tries to reduce code size and execution
|
|
time.
|
|
.Sp
|
|
When you specify \fB\-O\fR, the compiler turns on \fB\-fthread-jumps\fR
|
|
and \fB\-fdefer-pop\fR on all machines. The compiler turns on
|
|
\&\fB\-fdelayed-branch\fR on machines that have delay slots, and
|
|
\&\fB\-fomit-frame-pointer\fR on machines that can support debugging even
|
|
without a frame pointer. On some machines the compiler also turns
|
|
on other flags.
|
|
.Ip "\fB\-O2\fR" 4
|
|
.IX Item "-O2"
|
|
Optimize even more. \s-1GCC\s0 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 \fB\-O2\fR.
|
|
As compared to \fB\-O\fR, this option increases both compilation time
|
|
and the performance of the generated code.
|
|
.Sp
|
|
\&\fB\-O2\fR turns on all optional optimizations except for loop unrolling,
|
|
function inlining, and register renaming. It also turns on the
|
|
\&\fB\-fforce-mem\fR option on all machines and frame pointer elimination
|
|
on machines where doing so does not interfere with debugging.
|
|
.Ip "\fB\-O3\fR" 4
|
|
.IX Item "-O3"
|
|
Optimize yet more. \fB\-O3\fR turns on all optimizations specified by
|
|
\&\fB\-O2\fR and also turns on the \fB\-finline-functions\fR and
|
|
\&\fB\-frename-registers\fR options.
|
|
.Ip "\fB\-O0\fR" 4
|
|
.IX Item "-O0"
|
|
Do not optimize.
|
|
.Ip "\fB\-Os\fR" 4
|
|
.IX Item "-Os"
|
|
Optimize for size. \fB\-Os\fR enables all \fB\-O2\fR optimizations that
|
|
do not typically increase code size. It also performs further
|
|
optimizations designed to reduce code size.
|
|
.Sp
|
|
If you use multiple \fB\-O\fR options, with or without level numbers,
|
|
the last such option is the one that is effective.
|
|
.PP
|
|
Options of the form \fB\-f\fR\fIflag\fR specify machine-independent
|
|
flags. Most flags have both positive and negative forms; the negative
|
|
form of \fB\-ffoo\fR would be \fB\-fno-foo\fR. 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 \fBno-\fR or
|
|
adding it.
|
|
.Ip "\fB\-ffloat-store\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
This option prevents undesirable excess precision on machines such as
|
|
the 68000 where the floating registers (of the 68881) keep more
|
|
precision than a \f(CW\*(C`double\*(C'\fR 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 \s-1IEEE\s0 floating
|
|
point. Use \fB\-ffloat-store\fR for such programs, after modifying
|
|
them to store all pertinent intermediate computations into variables.
|
|
.Ip "\fB\-fno-default-inline\fR" 4
|
|
.IX Item "-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
|
|
\&\fB\-O\fR, member functions defined inside class scope are compiled
|
|
inline by default; i.e., you don't need to add \fBinline\fR in front of
|
|
the member function name.
|
|
.Ip "\fB\-fno-defer-pop\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fforce-mem\fR" 4
|
|
.IX Item "-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. The \fB\-O2\fR option turns on this option.
|
|
.Ip "\fB\-fforce-addr\fR" 4
|
|
.IX Item "-fforce-addr"
|
|
Force memory address constants to be copied into registers before
|
|
doing arithmetic on them. This may produce better code just as
|
|
\&\fB\-fforce-mem\fR may.
|
|
.Ip "\fB\-fomit-frame-pointer\fR" 4
|
|
.IX Item "-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. \fBIt also makes debugging impossible on
|
|
some machines.\fR
|
|
.Sp
|
|
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 \f(CW\*(C`FRAME_POINTER_REQUIRED\*(C'\fR controls
|
|
whether a target machine supports this flag.
|
|
.Ip "\fB\-foptimize-sibling-calls\fR" 4
|
|
.IX Item "-foptimize-sibling-calls"
|
|
Optimize sibling and tail recursive calls.
|
|
.Ip "\fB\-ftrapv\fR" 4
|
|
.IX Item "-ftrapv"
|
|
This option generates traps for signed overflow on addition, subtraction,
|
|
multiplication operations.
|
|
.Ip "\fB\-fno-inline\fR" 4
|
|
.IX Item "-fno-inline"
|
|
Don't pay attention to the \f(CW\*(C`inline\*(C'\fR 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.
|
|
.Ip "\fB\-finline-functions\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
If all calls to a given function are integrated, and the function is
|
|
declared \f(CW\*(C`static\*(C'\fR, then the function is normally not output as
|
|
assembler code in its own right.
|
|
.Ip "\fB\-finline-limit=\fR\fIn\fR" 4
|
|
.IX Item "-finline-limit=n"
|
|
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 (ie marked with the inline keyword or defined within the class
|
|
definition in c++). \fIn\fR is the size of functions that can be inlined in
|
|
number of pseudo instructions (not counting parameter handling). The default
|
|
value of n is 10000. 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++.
|
|
.Sp
|
|
\&\fINote:\fR pseudo instruction represents, in this particular context, an
|
|
abstract measurement of function's size. In no way, it represents a count
|
|
of assembly instructions and as such its exact meaning might change from one
|
|
release to an another.
|
|
.Ip "\fB\-fkeep-inline-functions\fR" 4
|
|
.IX Item "-fkeep-inline-functions"
|
|
Even if all calls to a given function are integrated, and the function
|
|
is declared \f(CW\*(C`static\*(C'\fR, nevertheless output a separate run-time
|
|
callable version of the function. This switch does not affect
|
|
\&\f(CW\*(C`extern inline\*(C'\fR functions.
|
|
.Ip "\fB\-fkeep-static-consts\fR" 4
|
|
.IX Item "-fkeep-static-consts"
|
|
Emit variables declared \f(CW\*(C`static const\*(C'\fR when optimization isn't turned
|
|
on, even if the variables aren't referenced.
|
|
.Sp
|
|
\&\s-1GCC\s0 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 \fB\-fno-keep-static-consts\fR option.
|
|
.Ip "\fB\-fno-function-cse\fR" 4
|
|
.IX Item "-fno-function-cse"
|
|
Do not put function addresses in registers; make each instruction that
|
|
calls a constant function contain the function's address explicitly.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-ffast-math\fR" 4
|
|
.IX Item "-ffast-math"
|
|
This option allows \s-1GCC\s0 to violate some \s-1ISO\s0 or \s-1IEEE\s0 rules and/or
|
|
specifications in the interest of optimizing code for speed. For
|
|
example, it allows the compiler to assume arguments to the \f(CW\*(C`sqrt\*(C'\fR
|
|
function are non-negative numbers and that no floating-point values
|
|
are NaNs.
|
|
.Sp
|
|
This option should never be turned on by any \fB\-O\fR option since
|
|
it can result in incorrect output for programs which depend on
|
|
an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for
|
|
math functions.
|
|
.Ip "\fB\-fno-math-errno\fR" 4
|
|
.IX Item "-fno-math-errno"
|
|
Do not set \s-1ERRNO\s0 after calling math functions that are executed
|
|
with a single instruction, e.g., sqrt. A program that relies on
|
|
\&\s-1IEEE\s0 exceptions for math error handling may want to use this flag
|
|
for speed while maintaining \s-1IEEE\s0 arithmetic compatibility.
|
|
.Sp
|
|
The default is \fB\-fmath-errno\fR. The \fB\-ffast-math\fR option
|
|
sets \fB\-fno-math-errno\fR.
|
|
.PP
|
|
The following options control specific optimizations. The \fB\-O2\fR
|
|
option turns on all of these optimizations except \fB\-funroll-loops\fR
|
|
and \fB\-funroll-all-loops\fR. On most machines, the \fB\-O\fR option
|
|
turns on the \fB\-fthread-jumps\fR and \fB\-fdelayed-branch\fR options,
|
|
but specific machines may handle it differently.
|
|
.PP
|
|
You can use the following flags in the rare cases when ``fine-tuning''
|
|
of optimizations to be performed is desired.
|
|
.Ip "\fB\-fstrength-reduce\fR" 4
|
|
.IX Item "-fstrength-reduce"
|
|
Perform the optimizations of loop strength reduction and
|
|
elimination of iteration variables.
|
|
.Ip "\fB\-fthread-jumps\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fcse-follow-jumps\fR" 4
|
|
.IX Item "-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 \s-1CSE\s0 encounters an \f(CW\*(C`if\*(C'\fR statement with an
|
|
\&\f(CW\*(C`else\*(C'\fR clause, \s-1CSE\s0 will follow the jump when the condition
|
|
tested is false.
|
|
.Ip "\fB\-fcse-skip-blocks\fR" 4
|
|
.IX Item "-fcse-skip-blocks"
|
|
This is similar to \fB\-fcse-follow-jumps\fR, but causes \s-1CSE\s0 to
|
|
follow jumps which conditionally skip over blocks. When \s-1CSE\s0
|
|
encounters a simple \f(CW\*(C`if\*(C'\fR statement with no else clause,
|
|
\&\fB\-fcse-skip-blocks\fR causes \s-1CSE\s0 to follow the jump around the
|
|
body of the \f(CW\*(C`if\*(C'\fR.
|
|
.Ip "\fB\-frerun-cse-after-loop\fR" 4
|
|
.IX Item "-frerun-cse-after-loop"
|
|
Re-run common subexpression elimination after loop optimizations has been
|
|
performed.
|
|
.Ip "\fB\-frerun-loop-opt\fR" 4
|
|
.IX Item "-frerun-loop-opt"
|
|
Run the loop optimizer twice.
|
|
.Ip "\fB\-fgcse\fR" 4
|
|
.IX Item "-fgcse"
|
|
Perform a global common subexpression elimination pass.
|
|
This pass also performs global constant and copy propagation.
|
|
.Ip "\fB\-fdelete-null-pointer-checks\fR" 4
|
|
.IX Item "-fdelete-null-pointer-checks"
|
|
Use global dataflow analysis to identify and eliminate useless null
|
|
pointer checks. Programs which rely on \s-1NULL\s0 pointer dereferences \fInot\fR
|
|
halting the program may not work properly with this option. Use
|
|
\&\-fno-delete-null-pointer-checks to disable this optimizing for programs
|
|
which depend on that behavior.
|
|
.Ip "\fB\-fexpensive-optimizations\fR" 4
|
|
.IX Item "-fexpensive-optimizations"
|
|
Perform a number of minor optimizations that are relatively expensive.
|
|
.Ip "\fB\-foptimize-register-move\fR" 4
|
|
.IX Item "-foptimize-register-move"
|
|
.PD 0
|
|
.Ip "\fB\-fregmove\fR" 4
|
|
.IX Item "-fregmove"
|
|
.PD
|
|
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. \s-1GCC\s0 enables this optimization by default with \fB\-O2\fR
|
|
or higher.
|
|
.Sp
|
|
Note \fB\-fregmove\fR and \fB\-foptimize-register-move\fR are the same
|
|
optimization.
|
|
.Ip "\fB\-fdelayed-branch\fR" 4
|
|
.IX Item "-fdelayed-branch"
|
|
If supported for the target machine, attempt to reorder instructions
|
|
to exploit instruction slots available after delayed branch
|
|
instructions.
|
|
.Ip "\fB\-fschedule-insns\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-fschedule-insns2\fR" 4
|
|
.IX Item "-fschedule-insns2"
|
|
Similar to \fB\-fschedule-insns\fR, 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.
|
|
.Ip "\fB\-ffunction-sections\fR" 4
|
|
.IX Item "-ffunction-sections"
|
|
.PD 0
|
|
.Ip "\fB\-fdata-sections\fR" 4
|
|
.IX Item "-fdata-sections"
|
|
.PD
|
|
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.
|
|
.Sp
|
|
Use these options on systems where the linker can perform optimizations
|
|
to improve locality of reference in the instruction space. \s-1HPPA\s0
|
|
processors running \s-1HP-UX\s0 and Sparc processors running Solaris 2 have
|
|
linkers with such optimizations. Other systems using the \s-1ELF\s0 object format
|
|
as well as \s-1AIX\s0 may have these optimizations in the future.
|
|
.Sp
|
|
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 \f(CW\*(C`gprof\*(C'\fR on all systems if you
|
|
specify this option and you may have problems with debugging if
|
|
you specify both this option and \fB\-g\fR.
|
|
.Ip "\fB\-fcaller-saves\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
This option is always enabled by default on certain machines, usually
|
|
those which have no call-preserved registers to use instead.
|
|
.Sp
|
|
For all machines, optimization level 2 and higher enables this flag by
|
|
default.
|
|
.Ip "\fB\-funroll-loops\fR" 4
|
|
.IX Item "-funroll-loops"
|
|
Perform the optimization of loop unrolling. This is only done for loops
|
|
whose number of iterations can be determined at compile time or run time.
|
|
\&\fB\-funroll-loops\fR implies both \fB\-fstrength-reduce\fR and
|
|
\&\fB\-frerun-cse-after-loop\fR.
|
|
.Ip "\fB\-funroll-all-loops\fR" 4
|
|
.IX Item "-funroll-all-loops"
|
|
Perform the optimization of loop unrolling. This is done for all loops
|
|
and usually makes programs run more slowly. \fB\-funroll-all-loops\fR
|
|
implies \fB\-fstrength-reduce\fR as well as \fB\-frerun-cse-after-loop\fR.
|
|
.Ip "\fB\-fmove-all-movables\fR" 4
|
|
.IX Item "-fmove-all-movables"
|
|
Forces all invariant computations in loops to be moved
|
|
outside the loop.
|
|
.Ip "\fB\-freduce-all-givs\fR" 4
|
|
.IX Item "-freduce-all-givs"
|
|
Forces all general-induction variables in loops to be
|
|
strength-reduced.
|
|
.Sp
|
|
\&\fINote:\fR When compiling programs written in Fortran,
|
|
\&\fB\-fmove-all-movables\fR and \fB\-freduce-all-givs\fR are enabled
|
|
by default when you use the optimizer.
|
|
.Sp
|
|
These options may generate better or worse code; results are highly
|
|
dependent on the structure of loops within the source code.
|
|
.Sp
|
|
These two options are intended to be removed someday, once
|
|
they have helped determine the efficacy of various
|
|
approaches to improving loop optimizations.
|
|
.Sp
|
|
Please let us (<\fBgcc@gcc.gnu.org\fR> and <\fBfortran@gnu.org\fR>)
|
|
know how use of these options affects
|
|
the performance of your production code.
|
|
We're very interested in code that runs \fIslower\fR
|
|
when these options are \fIenabled\fR.
|
|
.Ip "\fB\-fno-peephole\fR" 4
|
|
.IX Item "-fno-peephole"
|
|
Disable any machine-specific peephole optimizations.
|
|
.Ip "\fB\-fbranch-probabilities\fR" 4
|
|
.IX Item "-fbranch-probabilities"
|
|
After running a program compiled with \fB\-fprofile-arcs\fR, you can compile it a second time using
|
|
\&\fB\-fbranch-probabilities\fR, to improve optimizations based on
|
|
guessing the path a branch might take.
|
|
.Ip "\fB\-fno-guess-branch-probability\fR" 4
|
|
.IX Item "-fno-guess-branch-probability"
|
|
Sometimes gcc will opt to guess branch probabilities when none are
|
|
available from either profile directed feedback (\fB\-fprofile-arcs\fR)
|
|
or \fB_\|_builtin_expect\fR. In a hard real-time system, people don't
|
|
want different runs of the compiler to produce code that has different
|
|
behavior; minimizing non-determinism is of paramount import. This
|
|
switch allows users to reduce non-determinism, possibly at the expense
|
|
of inferior optimization.
|
|
.Ip "\fB\-fstrict-aliasing\fR" 4
|
|
.IX Item "-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 \f(CW\*(C`unsigned int\*(C'\fR can alias an \f(CW\*(C`int\*(C'\fR, but not a
|
|
\&\f(CW\*(C`void*\*(C'\fR or a \f(CW\*(C`double\*(C'\fR. A character type may alias any other
|
|
type.
|
|
.Sp
|
|
Pay special attention to code like this:
|
|
.Sp
|
|
.Vb 4
|
|
\& union a_union {
|
|
\& int i;
|
|
\& double d;
|
|
\& };
|
|
.Ve
|
|
.Vb 5
|
|
\& int f() {
|
|
\& a_union t;
|
|
\& t.d = 3.0;
|
|
\& return t.i;
|
|
\& }
|
|
.Ve
|
|
The practice of reading from a different union member than the one most
|
|
recently written to (called ``type-punning'') is common. Even with
|
|
\&\fB\-fstrict-aliasing\fR, 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:
|
|
.Sp
|
|
.Vb 7
|
|
\& int f() {
|
|
\& a_union t;
|
|
\& int* ip;
|
|
\& t.d = 3.0;
|
|
\& ip = &t.i;
|
|
\& return *ip;
|
|
\& }
|
|
.Ve
|
|
.Ip "\fB\-falign-functions\fR" 4
|
|
.IX Item "-falign-functions"
|
|
.PD 0
|
|
.Ip "\fB\-falign-functions=\fR\fIn\fR" 4
|
|
.IX Item "-falign-functions=n"
|
|
.PD
|
|
Align the start of functions to the next power-of-two greater than
|
|
\&\fIn\fR, skipping up to \fIn\fR bytes. For instance,
|
|
\&\fB\-falign-functions=32\fR aligns functions to the next 32\-byte
|
|
boundary, but \fB\-falign-functions=24\fR would align to the next
|
|
32\-byte boundary only if this can be done by skipping 23 bytes or less.
|
|
.Sp
|
|
\&\fB\-fno-align-functions\fR and \fB\-falign-functions=1\fR are
|
|
equivalent and mean that functions will not be aligned.
|
|
.Sp
|
|
Some assemblers only support this flag when \fIn\fR is a power of two;
|
|
in that case, it is rounded up.
|
|
.Sp
|
|
If \fIn\fR is not specified, use a machine-dependent default.
|
|
.Ip "\fB\-falign-labels\fR" 4
|
|
.IX Item "-falign-labels"
|
|
.PD 0
|
|
.Ip "\fB\-falign-labels=\fR\fIn\fR" 4
|
|
.IX Item "-falign-labels=n"
|
|
.PD
|
|
Align all branch targets to a power-of-two boundary, skipping up to
|
|
\&\fIn\fR bytes like \fB\-falign-functions\fR. 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.
|
|
.Sp
|
|
If \fB\-falign-loops\fR or \fB\-falign-jumps\fR are applicable and
|
|
are greater than this value, then their values are used instead.
|
|
.Sp
|
|
If \fIn\fR is not specified, use a machine-dependent default which is
|
|
very likely to be \fB1\fR, meaning no alignment.
|
|
.Ip "\fB\-falign-loops\fR" 4
|
|
.IX Item "-falign-loops"
|
|
.PD 0
|
|
.Ip "\fB\-falign-loops=\fR\fIn\fR" 4
|
|
.IX Item "-falign-loops=n"
|
|
.PD
|
|
Align loops to a power-of-two boundary, skipping up to \fIn\fR bytes
|
|
like \fB\-falign-functions\fR. The hope is that the loop will be
|
|
executed many times, which will make up for any execution of the dummy
|
|
operations.
|
|
.Sp
|
|
If \fIn\fR is not specified, use a machine-dependent default.
|
|
.Ip "\fB\-falign-jumps\fR" 4
|
|
.IX Item "-falign-jumps"
|
|
.PD 0
|
|
.Ip "\fB\-falign-jumps=\fR\fIn\fR" 4
|
|
.IX Item "-falign-jumps=n"
|
|
.PD
|
|
Align branch targets to a power-of-two boundary, for branch targets
|
|
where the targets can only be reached by jumping, skipping up to \fIn\fR
|
|
bytes like \fB\-falign-functions\fR. In this case, no dummy operations
|
|
need be executed.
|
|
.Sp
|
|
If \fIn\fR is not specified, use a machine-dependent default.
|
|
.Ip "\fB\-fssa\fR" 4
|
|
.IX Item "-fssa"
|
|
Perform optimizations in static single assignment form. Each function's
|
|
flow graph is translated into \s-1SSA\s0 form, optimizations are performed, and
|
|
the flow graph is translated back from \s-1SSA\s0 form. User's should not
|
|
specify this option, since it is not yet ready for production use.
|
|
.Ip "\fB\-fdce\fR" 4
|
|
.IX Item "-fdce"
|
|
Perform dead-code elimination in \s-1SSA\s0 form. Requires \fB\-fssa\fR. Like
|
|
\&\fB\-fssa\fR, this is an experimental feature.
|
|
.Ip "\fB\-fsingle-precision-constant\fR" 4
|
|
.IX Item "-fsingle-precision-constant"
|
|
Treat floating point constant as single precision constant instead of
|
|
implicitly converting it to double precision constant.
|
|
.Ip "\fB\-frename-registers\fR" 4
|
|
.IX Item "-frename-registers"
|
|
Attempt to avoid false dependancies in scheduled code by making use
|
|
of registers left over after register allocation. This optimization
|
|
will most benefit processors with lots of registers. It can, however,
|
|
make debugging impossible, since variables will no longer stay in
|
|
a ``home register''.
|
|
.Sh "Options Controlling the Preprocessor"
|
|
.IX Subsection "Options Controlling the Preprocessor"
|
|
These options control the C preprocessor, which is run on each C source
|
|
file before actual compilation.
|
|
.PP
|
|
If you use the \fB\-E\fR option, nothing is done except preprocessing.
|
|
Some of these options make sense only together with \fB\-E\fR because
|
|
they cause the preprocessor output to be unsuitable for actual
|
|
compilation.
|
|
.Ip "\fB\-include\fR \fIfile\fR" 4
|
|
.IX Item "-include file"
|
|
Process \fIfile\fR as input before processing the regular input file.
|
|
In effect, the contents of \fIfile\fR are compiled first. Any \fB\-D\fR
|
|
and \fB\-U\fR options on the command line are always processed before
|
|
\&\fB\-include\fR \fIfile\fR, regardless of the order in which they are
|
|
written. All the \fB\-include\fR and \fB\-imacros\fR options are
|
|
processed in the order in which they are written.
|
|
.Ip "\fB\-imacros\fR \fIfile\fR" 4
|
|
.IX Item "-imacros file"
|
|
Process \fIfile\fR as input, discarding the resulting output, before
|
|
processing the regular input file. Because the output generated from
|
|
\&\fIfile\fR is discarded, the only effect of \fB\-imacros\fR \fIfile\fR
|
|
is to make the macros defined in \fIfile\fR available for use in the
|
|
main input. All the \fB\-include\fR and \fB\-imacros\fR options are
|
|
processed in the order in which they are written.
|
|
.Ip "\fB\-idirafter\fR \fIdir\fR" 4
|
|
.IX Item "-idirafter dir"
|
|
Add the directory \fIdir\fR to the second include path. The directories
|
|
on the second include path are searched when a header file is not found
|
|
in any of the directories in the main include path (the one that
|
|
\&\fB\-I\fR adds to).
|
|
.Ip "\fB\-iprefix\fR \fIprefix\fR" 4
|
|
.IX Item "-iprefix prefix"
|
|
Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
|
|
options.
|
|
.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4
|
|
.IX Item "-iwithprefix dir"
|
|
Add a directory to the second include path. The directory's name is
|
|
made by concatenating \fIprefix\fR and \fIdir\fR, where \fIprefix\fR was
|
|
specified previously with \fB\-iprefix\fR. If you have not specified a
|
|
prefix yet, the directory containing the installed passes of the
|
|
compiler is used as the default.
|
|
.Ip "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
|
|
.IX Item "-iwithprefixbefore dir"
|
|
Add a directory to the main include path. The directory's name is made
|
|
by concatenating \fIprefix\fR and \fIdir\fR, as in the case of
|
|
\&\fB\-iwithprefix\fR.
|
|
.Ip "\fB\-isystem\fR \fIdir\fR" 4
|
|
.IX Item "-isystem dir"
|
|
Add a directory to the beginning of the second include path, marking it
|
|
as a system directory, so that it gets the same special treatment as
|
|
is applied to the standard system directories.
|
|
.Ip "\fB\-nostdinc\fR" 4
|
|
.IX Item "-nostdinc"
|
|
Do not search the standard system directories for header files. Only
|
|
the directories you have specified with \fB\-I\fR options (and the
|
|
current directory, if appropriate) are searched.
|
|
.Sp
|
|
By using both \fB\-nostdinc\fR and \fB\-I-\fR, you can limit the include-file
|
|
search path to only those directories you specify explicitly.
|
|
.Ip "\fB\-remap\fR" 4
|
|
.IX Item "-remap"
|
|
When searching for a header file in a directory, remap file names if a
|
|
file named \fIheader.gcc\fR exists in that directory. This can be used
|
|
to work around limitations of file systems with file name restrictions.
|
|
The \fIheader.gcc\fR file should contain a series of lines with two
|
|
tokens on each line: the first token is the name to map, and the second
|
|
token is the actual name to use.
|
|
.Ip "\fB\-undef\fR" 4
|
|
.IX Item "-undef"
|
|
Do not predefine any nonstandard macros. (Including architecture flags).
|
|
.Ip "\fB\-E\fR" 4
|
|
.IX Item "-E"
|
|
Run only the C preprocessor. Preprocess all the C source files
|
|
specified and output the results to standard output or to the
|
|
specified output file.
|
|
.Ip "\fB\-C\fR" 4
|
|
.IX Item "-C"
|
|
Tell the preprocessor not to discard comments. Used with the
|
|
\&\fB\-E\fR option.
|
|
.Ip "\fB\-P\fR" 4
|
|
.IX Item "-P"
|
|
Tell the preprocessor not to generate \fB#line\fR directives.
|
|
Used with the \fB\-E\fR option.
|
|
.Ip "\fB\-M\fR" 4
|
|
.IX Item "-M"
|
|
Instead of outputting the result of preprocessing, output a rule
|
|
suitable for \f(CW\*(C`make\*(C'\fR describing the dependencies of the main source
|
|
file. The preprocessor outputs one \f(CW\*(C`make\*(C'\fR rule containing the
|
|
object file name for that source file, a colon, and the names of all the
|
|
included files. If there are many included files then the rule is split
|
|
into several lines using \fB\e\fR\-newline.
|
|
.Sp
|
|
\&\fB\-M\fR implies \fB\-E\fR.
|
|
.Ip "\fB\-MM\fR" 4
|
|
.IX Item "-MM"
|
|
Like \fB\-M\fR, but mention only the files included with \fB#include
|
|
"\fR\fIfile\fR\fB"\fR. System header files included with \fB#include
|
|
<\fR\fIfile\fR\fB>\fR are omitted.
|
|
.Ip "\fB\-MD\fR" 4
|
|
.IX Item "-MD"
|
|
Like \fB\-M\fR but the dependency information is written to a file
|
|
rather than stdout. \f(CW\*(C`gcc\*(C'\fR will use the same file name and
|
|
directory as the object file, but with the suffix \*(L".d\*(R" instead.
|
|
.Sp
|
|
This is in addition to compiling the main file as specified \-\-\-
|
|
\&\fB\-MD\fR does not inhibit ordinary compilation the way \fB\-M\fR does,
|
|
unless you also specify \fB\-MG\fR.
|
|
.Sp
|
|
With Mach, you can use the utility \f(CW\*(C`md\*(C'\fR to merge multiple
|
|
dependency files into a single dependency file suitable for using with
|
|
the \fBmake\fR command.
|
|
.Ip "\fB\-MMD\fR" 4
|
|
.IX Item "-MMD"
|
|
Like \fB\-MD\fR except mention only user header files, not system
|
|
\&\-header files.
|
|
.Ip "\fB\-MF\fR \fIfile\fR" 4
|
|
.IX Item "-MF file"
|
|
When used with \fB\-M\fR or \fB\-MM\fR, specifies a file to write the
|
|
dependencies to. This allows the preprocessor to write the preprocessed
|
|
file to stdout normally. If no \fB\-MF\fR switch is given, \s-1CPP\s0 sends
|
|
the rules to stdout and suppresses normal preprocessed output.
|
|
.Sp
|
|
Another way to specify output of a \f(CW\*(C`make\*(C'\fR rule is by setting
|
|
the environment variable \fB\s-1DEPENDENCIES_OUTPUT\s0\fR.
|
|
.Ip "\fB\-MG\fR" 4
|
|
.IX Item "-MG"
|
|
When used with \fB\-M\fR or \fB\-MM\fR, \fB\-MG\fR says to treat missing
|
|
header files as generated files and assume they live in the same
|
|
directory as the source file. It suppresses preprocessed output, as a
|
|
missing header file is ordinarily an error.
|
|
.Sp
|
|
This feature is used in automatic updating of makefiles.
|
|
.Ip "\fB\-MP\fR" 4
|
|
.IX Item "-MP"
|
|
This option instructs \s-1CPP\s0 to add a phony target for each dependency
|
|
other than the main file, causing each to depend on nothing. These
|
|
dummy rules work around errors \f(CW\*(C`make\*(C'\fR gives if you remove header
|
|
files without updating the \f(CW\*(C`Makefile\*(C'\fR to match.
|
|
.Sp
|
|
This is typical output:\-
|
|
.Sp
|
|
.Vb 1
|
|
\& /tmp/test.o: /tmp/test.c /tmp/test.h
|
|
.Ve
|
|
.Vb 1
|
|
\& /tmp/test.h:
|
|
.Ve
|
|
.Ip "\fB\-MQ\fR \fItarget\fR" 4
|
|
.IX Item "-MQ target"
|
|
.PD 0
|
|
.Ip "\fB\-MT\fR \fItarget\fR" 4
|
|
.IX Item "-MT target"
|
|
.PD
|
|
By default \s-1CPP\s0 uses the main file name, including any path, and appends
|
|
the object suffix, normally ``.o'', to it to obtain the name of the
|
|
target for dependency generation. With \fB\-MT\fR you can specify a
|
|
target yourself, overriding the default one.
|
|
.Sp
|
|
If you want multiple targets, you can specify them as a single argument
|
|
to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
|
|
.Sp
|
|
The targets you specify are output in the order they appear on the
|
|
command line. \fB\-MQ\fR is identical to \fB\-MT\fR, except that the
|
|
target name is quoted for Make, but with \fB\-MT\fR it isn't. For
|
|
example, \-MT '$(objpfx)foo.o' gives
|
|
.Sp
|
|
.Vb 1
|
|
\& $(objpfx)foo.o: /tmp/foo.c
|
|
.Ve
|
|
but \-MQ '$(objpfx)foo.o' gives
|
|
.Sp
|
|
.Vb 1
|
|
\& $$(objpfx)foo.o: /tmp/foo.c
|
|
.Ve
|
|
The default target is automatically quoted, as if it were given with
|
|
\&\fB\-MQ\fR.
|
|
.Ip "\fB\-H\fR" 4
|
|
.IX Item "-H"
|
|
Print the name of each header file used, in addition to other normal
|
|
activities.
|
|
.Ip "\fB\-A\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR" 4
|
|
.IX Item "-Aquestion(answer)"
|
|
Assert the answer \fIanswer\fR for \fIquestion\fR, in case it is tested
|
|
with a preprocessing conditional such as \fB#if
|
|
#\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR. \fB\-A-\fR disables the standard
|
|
assertions that normally describe the target machine.
|
|
.Ip "\fB\-D\fR\fImacro\fR" 4
|
|
.IX Item "-Dmacro"
|
|
Define macro \fImacro\fR with the string \fB1\fR as its definition.
|
|
.Ip "\fB\-D\fR\fImacro\fR\fB=\fR\fIdefn\fR" 4
|
|
.IX Item "-Dmacro=defn"
|
|
Define macro \fImacro\fR as \fIdefn\fR. All instances of \fB\-D\fR on
|
|
the command line are processed before any \fB\-U\fR options.
|
|
.Sp
|
|
Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in
|
|
order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the
|
|
order in which they are written.
|
|
.Ip "\fB\-U\fR\fImacro\fR" 4
|
|
.IX Item "-Umacro"
|
|
Undefine macro \fImacro\fR. \fB\-U\fR options are evaluated after all
|
|
\&\fB\-D\fR options, but before any \fB\-include\fR and \fB\-imacros\fR
|
|
options.
|
|
.Sp
|
|
Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in
|
|
order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the
|
|
order in which they are written.
|
|
.Ip "\fB\-dM\fR" 4
|
|
.IX Item "-dM"
|
|
Tell the preprocessor to output only a list of the macro definitions
|
|
that are in effect at the end of preprocessing. Used with the \fB\-E\fR
|
|
option.
|
|
.Ip "\fB\-dD\fR" 4
|
|
.IX Item "-dD"
|
|
Tell the preprocessing to pass all macro definitions into the output, in
|
|
their proper sequence in the rest of the output.
|
|
.Ip "\fB\-dN\fR" 4
|
|
.IX Item "-dN"
|
|
Like \fB\-dD\fR except that the macro arguments and contents are omitted.
|
|
Only \fB#define\fR \fIname\fR is included in the output.
|
|
.Ip "\fB\-dI\fR" 4
|
|
.IX Item "-dI"
|
|
Output \fB#include\fR directives in addition to the result of
|
|
preprocessing.
|
|
.Ip "\fB\-trigraphs\fR" 4
|
|
.IX Item "-trigraphs"
|
|
Process \s-1ISO\s0 standard trigraph sequences. These are three-character
|
|
sequences, all starting with \fB??\fR, that are defined by \s-1ISO\s0 C to
|
|
stand for single characters. For example, \fB??/\fR stands for
|
|
\&\fB\e\fR, so \fB'??/n'\fR is a character constant for a newline. By
|
|
default, \s-1GCC\s0 ignores trigraphs, but in standard-conforming modes it
|
|
converts them. See the \fB\-std\fR and \fB\-ansi\fR options.
|
|
.Sp
|
|
The nine trigraph sequences are
|
|
.RS 4
|
|
.Ip "\fB??(\fR" 4
|
|
.IX Item "??("
|
|
-> \fB[\fR
|
|
.Ip "\fB??)\fR" 4
|
|
.IX Item "??)"
|
|
-> \fB]\fR
|
|
.Ip "\fB??<\fR" 4
|
|
.IX Item "??<"
|
|
-> \fB{\fR
|
|
.Ip "\fB??>\fR" 4
|
|
.IX Item "??>"
|
|
-> \fB}\fR
|
|
.Ip "\fB??=\fR" 4
|
|
.IX Item "??="
|
|
-> \fB#\fR
|
|
.Ip "\fB??/\fR" 4
|
|
.IX Item "??/"
|
|
-> \fB\e\fR
|
|
.Ip "\fB??'\fR" 4
|
|
.IX Item "??'"
|
|
-> \fB^\fR
|
|
.Ip "\fB??!\fR" 4
|
|
.IX Item "??!"
|
|
-> \fB|\fR
|
|
.Ip "\fB??-\fR" 4
|
|
.IX Item "??-"
|
|
-> \fB~\fR
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
Trigraph support is not popular, so many compilers do not implement it
|
|
properly. Portable code should not rely on trigraphs being either
|
|
converted or ignored.
|
|
.RE
|
|
.Ip "\fB\-Wp,\fR\fIoption\fR" 4
|
|
.IX Item "-Wp,option"
|
|
Pass \fIoption\fR as an option to the preprocessor. If \fIoption\fR
|
|
contains commas, it is split into multiple options at the commas.
|
|
.Sh "Passing Options to the Assembler"
|
|
.IX Subsection "Passing Options to the Assembler"
|
|
You can pass options to the assembler.
|
|
.Ip "\fB\-Wa,\fR\fIoption\fR" 4
|
|
.IX Item "-Wa,option"
|
|
Pass \fIoption\fR as an option to the assembler. If \fIoption\fR
|
|
contains commas, it is split into multiple options at the commas.
|
|
.Sh "Options for Linking"
|
|
.IX Subsection "Options for 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.
|
|
.Ip "\fIobject-file-name\fR" 4
|
|
.IX Item "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.
|
|
.Ip "\fB\-c\fR" 4
|
|
.IX Item "-c"
|
|
.PD 0
|
|
.Ip "\fB\-S\fR" 4
|
|
.IX Item "-S"
|
|
.Ip "\fB\-E\fR" 4
|
|
.IX Item "-E"
|
|
.PD
|
|
If any of these options is used, then the linker is not run, and
|
|
object file names should not be used as arguments.
|
|
.Ip "\fB\-l\fR\fIlibrary\fR" 4
|
|
.IX Item "-llibrary"
|
|
Search the library named \fIlibrary\fR when linking.
|
|
.Sp
|
|
It makes a difference where in the command you write this option; the
|
|
linker searches processes libraries and object files in the order they
|
|
are specified. Thus, \fBfoo.o \-lz bar.o\fR searches library \fBz\fR
|
|
after file \fIfoo.o\fR but before \fIbar.o\fR. If \fIbar.o\fR refers
|
|
to functions in \fBz\fR, those functions may not be loaded.
|
|
.Sp
|
|
The linker searches a standard list of directories for the library,
|
|
which is actually a file named \fIlib\fIlibrary\fI.a\fR. The linker
|
|
then uses this file as if it had been specified precisely by name.
|
|
.Sp
|
|
The directories searched include several standard system directories
|
|
plus any that you specify with \fB\-L\fR.
|
|
.Sp
|
|
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 \fB\-l\fR option and specifying a file name
|
|
is that \fB\-l\fR surrounds \fIlibrary\fR with \fBlib\fR and \fB.a\fR
|
|
and searches several directories.
|
|
.Ip "\fB\-lobjc\fR" 4
|
|
.IX Item "-lobjc"
|
|
You need this special case of the \fB\-l\fR option in order to
|
|
link an Objective C program.
|
|
.Ip "\fB\-nostartfiles\fR" 4
|
|
.IX Item "-nostartfiles"
|
|
Do not use the standard system startup files when linking.
|
|
The standard system libraries are used normally, unless \fB\-nostdlib\fR
|
|
or \fB\-nodefaultlibs\fR is used.
|
|
.Ip "\fB\-nodefaultlibs\fR" 4
|
|
.IX Item "-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 \fB\-nostartfiles\fR
|
|
is used. The compiler may generate calls to memcmp, memset, and memcpy
|
|
for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for
|
|
\&\s-1BSD\s0 environments. These entries are usually resolved by entries in
|
|
libc. These entry points should be supplied through some other
|
|
mechanism when this option is specified.
|
|
.Ip "\fB\-nostdlib\fR" 4
|
|
.IX Item "-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 memcmp, memset, and memcpy
|
|
for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for
|
|
\&\s-1BSD\s0 environments. These entries are usually resolved by entries in
|
|
libc. These entry points should be supplied through some other
|
|
mechanism when this option is specified.
|
|
.Sp
|
|
One of the standard libraries bypassed by \fB\-nostdlib\fR and
|
|
\&\fB\-nodefaultlibs\fR is \fIlibgcc.a\fR, a library of internal subroutines
|
|
that \s-1GCC\s0 uses to overcome shortcomings of particular machines, or special
|
|
needs for some languages.
|
|
.Sp
|
|
In most cases, you need \fIlibgcc.a\fR even when you want to avoid
|
|
other standard libraries. In other words, when you specify \fB\-nostdlib\fR
|
|
or \fB\-nodefaultlibs\fR you should usually specify \fB\-lgcc\fR as well.
|
|
This ensures that you have no unresolved references to internal \s-1GCC\s0
|
|
library subroutines. (For example, \fB_\|_main\fR, used to ensure \*(C+
|
|
constructors will be called.)
|
|
.Ip "\fB\-s\fR" 4
|
|
.IX Item "-s"
|
|
Remove all symbol table and relocation information from the executable.
|
|
.Ip "\fB\-static\fR" 4
|
|
.IX Item "-static"
|
|
On systems that support dynamic linking, this prevents linking with the shared
|
|
libraries. On other systems, this option has no effect.
|
|
.Ip "\fB\-shared\fR" 4
|
|
.IX Item "-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 (\fB\-fpic\fR, \fB\-fPIC\fR, or model suboptions)
|
|
when you specify this option.[1]
|
|
.Ip "\fB\-shared-libgcc\fR" 4
|
|
.IX Item "-shared-libgcc"
|
|
.PD 0
|
|
.Ip "\fB\-static-libgcc\fR" 4
|
|
.IX Item "-static-libgcc"
|
|
.PD
|
|
On systems that provide \fIlibgcc\fR as a shared library, these options
|
|
force the use of either the shared or static version respectively.
|
|
If no shared version of \fIlibgcc\fR was built when the compiler was
|
|
configured, these options have no effect.
|
|
.Sp
|
|
There are several situations in which an application should use the
|
|
shared \fIlibgcc\fR 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 \fIlibgcc\fR.
|
|
.Sp
|
|
At present the \s-1GCC\s0 driver makes no attempt to recognize the situations
|
|
in which the shared \fIlibgcc\fR should be used, and defaults to using
|
|
the static \fIlibgcc\fR always. This will likely change in the future,
|
|
at which time \fB\-static-libgcc\fR becomes useful as a means for
|
|
overriding \s-1GCC\s0's choice.
|
|
.Ip "\fB\-symbolic\fR" 4
|
|
.IX Item "-symbolic"
|
|
Bind references to global symbols when building a shared object. Warn
|
|
about any unresolved references (unless overridden by the link editor
|
|
option \fB\-Xlinker \-z \-Xlinker defs\fR). Only a few systems support
|
|
this option.
|
|
.Ip "\fB\-Xlinker\fR \fIoption\fR" 4
|
|
.IX Item "-Xlinker option"
|
|
Pass \fIoption\fR as an option to the linker. You can use this to
|
|
supply system-specific linker options which \s-1GCC\s0 does not know how to
|
|
recognize.
|
|
.Sp
|
|
If you want to pass an option that takes an argument, you must use
|
|
\&\fB\-Xlinker\fR twice, once for the option and once for the argument.
|
|
For example, to pass \fB\-assert definitions\fR, you must write
|
|
\&\fB\-Xlinker \-assert \-Xlinker definitions\fR. It does not work to write
|
|
\&\fB\-Xlinker \*(L"\-assert definitions\*(R"\fR, because this passes the entire
|
|
string as a single argument, which is not what the linker expects.
|
|
.Ip "\fB\-Wl,\fR\fIoption\fR" 4
|
|
.IX Item "-Wl,option"
|
|
Pass \fIoption\fR as an option to the linker. If \fIoption\fR contains
|
|
commas, it is split into multiple options at the commas.
|
|
.Ip "\fB\-u\fR \fIsymbol\fR" 4
|
|
.IX Item "-u symbol"
|
|
Pretend the symbol \fIsymbol\fR is undefined, to force linking of
|
|
library modules to define it. You can use \fB\-u\fR multiple times with
|
|
different symbols to force loading of additional library modules.
|
|
.Sh "Options for Directory Search"
|
|
.IX Subsection "Options for Directory Search"
|
|
These options specify directories to search for header files, for
|
|
libraries and for parts of the compiler:
|
|
.Ip "\fB\-I\fR\fIdir\fR" 4
|
|
.IX Item "-Idir"
|
|
Add the directory \fIdir\fR 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. If you use more
|
|
than one \fB\-I\fR option, the directories are scanned in left-to-right
|
|
order; the standard system directories come after.
|
|
.Ip "\fB\-I-\fR" 4
|
|
.IX Item "-I-"
|
|
Any directories you specify with \fB\-I\fR options before the \fB\-I-\fR
|
|
option are searched only for the case of \fB#include "\fR\fIfile\fR\fB"\fR;
|
|
they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR.
|
|
.Sp
|
|
If additional directories are specified with \fB\-I\fR options after
|
|
the \fB\-I-\fR, these directories are searched for all \fB#include\fR
|
|
directives. (Ordinarily \fIall\fR \fB\-I\fR directories are used
|
|
this way.)
|
|
.Sp
|
|
In addition, the \fB\-I-\fR option inhibits the use of the current
|
|
directory (where the current input file came from) as the first search
|
|
directory for \fB#include "\fR\fIfile\fR\fB"\fR. There is no way to
|
|
override this effect of \fB\-I-\fR. With \fB\-I.\fR 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.
|
|
.Sp
|
|
\&\fB\-I-\fR does not inhibit the use of the standard system directories
|
|
for header files. Thus, \fB\-I-\fR and \fB\-nostdinc\fR are
|
|
independent.
|
|
.Ip "\fB\-L\fR\fIdir\fR" 4
|
|
.IX Item "-Ldir"
|
|
Add directory \fIdir\fR to the list of directories to be searched
|
|
for \fB\-l\fR.
|
|
.Ip "\fB\-B\fR\fIprefix\fR" 4
|
|
.IX Item "-Bprefix"
|
|
This option specifies where to find the executables, libraries,
|
|
include files, and data files of the compiler itself.
|
|
.Sp
|
|
The compiler driver program runs one or more of the subprograms
|
|
\&\fIcpp\fR, \fIcc1\fR, \fIas\fR and \fIld\fR. It tries
|
|
\&\fIprefix\fR as a prefix for each program it tries to run, both with and
|
|
without \fImachine\fR\fB/\fR\fIversion\fR\fB/\fR.
|
|
.Sp
|
|
For each subprogram to be run, the compiler driver first tries the
|
|
\&\fB\-B\fR prefix, if any. If that name is not found, or if \fB\-B\fR
|
|
was not specified, the driver tries two standard prefixes, which are
|
|
\&\fI/usr/lib/gcc/\fR and \fI/usr/local/lib/gcc-lib/\fR. 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
|
|
\&\fB\s-1PATH\s0\fR environment variable.
|
|
.Sp
|
|
\&\fB\-B\fR prefixes that effectively specify directory names also apply
|
|
to libraries in the linker, because the compiler translates these
|
|
options into \fB\-L\fR options for the linker. They also apply to
|
|
includes files in the preprocessor, because the compiler translates these
|
|
options into \fB\-isystem\fR options for the preprocessor. In this case,
|
|
the compiler appends \fBinclude\fR to the prefix.
|
|
.Sp
|
|
The run-time support file \fIlibgcc.a\fR can also be searched for using
|
|
the \fB\-B\fR 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.
|
|
.Sp
|
|
Another way to specify a prefix much like the \fB\-B\fR prefix is to use
|
|
the environment variable \fB\s-1GCC_EXEC_PREFIX\s0\fR.
|
|
.Ip "\fB\-specs=\fR\fIfile\fR" 4
|
|
.IX Item "-specs=file"
|
|
Process \fIfile\fR after the compiler reads in the standard \fIspecs\fR
|
|
file, in order to override the defaults that the \fIgcc\fR driver
|
|
program uses when determining what switches to pass to \fIcc1\fR,
|
|
\&\fIcc1plus\fR, \fIas\fR, \fIld\fR, etc. More than one
|
|
\&\fB\-specs=\fR\fIfile\fR can be specified on the command line, and they
|
|
are processed in order, from left to right.
|
|
.Sh "Specifying Target Machine and Compiler Version"
|
|
.IX Subsection "Specifying Target Machine and Compiler Version"
|
|
By default, \s-1GCC\s0 compiles code for the same type of machine that you
|
|
are using. However, it can also be installed as a cross-compiler, to
|
|
compile for some other type of machine. In fact, several different
|
|
configurations of \s-1GCC\s0, for different target machines, can be
|
|
installed side by side. Then you specify which one to use with the
|
|
\&\fB\-b\fR option.
|
|
.PP
|
|
In addition, older and newer versions of \s-1GCC\s0 can be installed side
|
|
by side. One of them (probably the newest) will be the default, but
|
|
you may sometimes wish to use another.
|
|
.Ip "\fB\-b\fR \fImachine\fR" 4
|
|
.IX Item "-b machine"
|
|
The argument \fImachine\fR specifies the target machine for compilation.
|
|
This is useful when you have installed \s-1GCC\s0 as a cross-compiler.
|
|
.Sp
|
|
The value to use for \fImachine\fR is the same as was specified as the
|
|
machine type when configuring \s-1GCC\s0 as a cross-compiler. For
|
|
example, if a cross-compiler was configured with \fBconfigure
|
|
i386v\fR, meaning to compile for an 80386 running System V, then you
|
|
would specify \fB\-b i386v\fR to run that cross compiler.
|
|
.Sp
|
|
When you do not specify \fB\-b\fR, it normally means to compile for
|
|
the same type of machine that you are using.
|
|
.Ip "\fB\-V\fR \fIversion\fR" 4
|
|
.IX Item "-V version"
|
|
The argument \fIversion\fR specifies which version of \s-1GCC\s0 to run.
|
|
This is useful when multiple versions are installed. For example,
|
|
\&\fIversion\fR might be \fB2.0\fR, meaning to run \s-1GCC\s0 version 2.0.
|
|
.Sp
|
|
The default version, when you do not specify \fB\-V\fR, is the last
|
|
version of \s-1GCC\s0 that you installed.
|
|
.PP
|
|
The \fB\-b\fR and \fB\-V\fR options actually work by controlling part of
|
|
the file name used for the executable files and libraries used for
|
|
compilation. A given version of \s-1GCC\s0, for a given target machine, is
|
|
normally kept in the directory \fI/usr/local/lib/gcc-lib/\fImachine\fI/\fIversion\fI\fR.
|
|
.PP
|
|
Thus, sites can customize the effect of \fB\-b\fR or \fB\-V\fR either by
|
|
changing the names of these directories or adding alternate names (or
|
|
symbolic links). If in directory \fI/usr/local/lib/gcc-lib/\fR the
|
|
file \fI80386\fR is a link to the file \fIi386v\fR, then \fB\-b
|
|
80386\fR becomes an alias for \fB\-b i386v\fR.
|
|
.PP
|
|
In one respect, the \fB\-b\fR or \fB\-V\fR do not completely change
|
|
to a different compiler: the top-level driver program \fBgcc\fR
|
|
that you originally invoked continues to run and invoke the other
|
|
executables (preprocessor, compiler per se, assembler and linker)
|
|
that do the real work. However, since no real work is done in the
|
|
driver program, it usually does not matter that the driver program
|
|
in use is not the one for the specified target. It is common for the
|
|
interface to the other executables to change incompatibly between
|
|
compiler versions, so unless the version specified is very close to that
|
|
of the driver (for example, \fB\-V 3.0\fR with a driver program from \s-1GCC\s0
|
|
version 3.0.1), use of \fB\-V\fR may not work; for example, using
|
|
\&\fB\-V 2.95.2\fR will not work with a driver program from \s-1GCC\s0 3.0.
|
|
.PP
|
|
The only way that the driver program depends on the target machine is
|
|
in the parsing and handling of special machine-specific options.
|
|
However, this is controlled by a file which is found, along with the
|
|
other executables, in the directory for the specified version and
|
|
target machine. As a result, a single installed driver program adapts
|
|
to any specified target machine, and sufficiently similar compiler
|
|
versions.
|
|
.PP
|
|
The driver program executable does control one significant thing,
|
|
however: the default version and target machine. Therefore, you can
|
|
install different instances of the driver program, compiled for
|
|
different targets or versions, under different names.
|
|
.PP
|
|
For example, if the driver for version 2.0 is installed as \fBogcc\fR
|
|
and that for version 2.1 is installed as \fBgcc\fR, then the command
|
|
\&\fBgcc\fR will use version 2.1 by default, while \fBogcc\fR will use
|
|
2.0 by default. However, you can choose either version with either
|
|
command with the \fB\-V\fR option.
|
|
.Sh "Hardware Models and Configurations"
|
|
.IX Subsection "Hardware Models and Configurations"
|
|
Earlier we discussed the standard option \fB\-b\fR which chooses among
|
|
different installed compilers for completely different target
|
|
machines, such as Vax vs. 68000 vs. 80386.
|
|
.PP
|
|
In addition, each of these target machine types can have its own
|
|
special options, starting with \fB\-m\fR, 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.
|
|
.PP
|
|
Some configurations of the compiler also support additional special
|
|
options, usually for compatibility with other compilers on the same
|
|
platform.
|
|
.PP
|
|
.I "M680x0 Options"
|
|
.IX Subsection "M680x0 Options"
|
|
.PP
|
|
These are the \fB\-m\fR 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.
|
|
.Ip "\fB\-m68000\fR" 4
|
|
.IX Item "-m68000"
|
|
.PD 0
|
|
.Ip "\fB\-mc68000\fR" 4
|
|
.IX Item "-mc68000"
|
|
.PD
|
|
Generate output for a 68000. This is the default
|
|
when the compiler is configured for 68000\-based systems.
|
|
.Sp
|
|
Use this option for microcontrollers with a 68000 or \s-1EC000\s0 core,
|
|
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
|
|
.Ip "\fB\-m68020\fR" 4
|
|
.IX Item "-m68020"
|
|
.PD 0
|
|
.Ip "\fB\-mc68020\fR" 4
|
|
.IX Item "-mc68020"
|
|
.PD
|
|
Generate output for a 68020. This is the default
|
|
when the compiler is configured for 68020\-based systems.
|
|
.Ip "\fB\-m68881\fR" 4
|
|
.IX Item "-m68881"
|
|
Generate output containing 68881 instructions for floating point.
|
|
This is the default for most 68020 systems unless \fB\-nfp\fR was
|
|
specified when the compiler was configured.
|
|
.Ip "\fB\-m68030\fR" 4
|
|
.IX Item "-m68030"
|
|
Generate output for a 68030. This is the default when the compiler is
|
|
configured for 68030\-based systems.
|
|
.Ip "\fB\-m68040\fR" 4
|
|
.IX Item "-m68040"
|
|
Generate output for a 68040. This is the default when the compiler is
|
|
configured for 68040\-based systems.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-m68060\fR" 4
|
|
.IX Item "-m68060"
|
|
Generate output for a 68060. This is the default when the compiler is
|
|
configured for 68060\-based systems.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-mcpu32\fR" 4
|
|
.IX Item "-mcpu32"
|
|
Generate output for a \s-1CPU32\s0. This is the default
|
|
when the compiler is configured for CPU32\-based systems.
|
|
.Sp
|
|
Use this option for microcontrollers with a
|
|
\&\s-1CPU32\s0 or \s-1CPU32+\s0 core, including the 68330, 68331, 68332, 68333, 68334,
|
|
68336, 68340, 68341, 68349 and 68360.
|
|
.Ip "\fB\-m5200\fR" 4
|
|
.IX Item "-m5200"
|
|
Generate output for a 520X \*(L"coldfire\*(R" family cpu. This is the default
|
|
when the compiler is configured for 520X-based systems.
|
|
.Sp
|
|
Use this option for microcontroller with a 5200 core, including
|
|
the \s-1MCF5202\s0, \s-1MCF5203\s0, \s-1MCF5204\s0 and \s-1MCF5202\s0.
|
|
.Ip "\fB\-m68020\-40\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-m68020\-60\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-mfpa\fR" 4
|
|
.IX Item "-mfpa"
|
|
Generate output containing Sun \s-1FPA\s0 instructions for floating point.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR 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 \fBm68k-*\-aout\fR and
|
|
\&\fBm68k-*\-coff\fR do provide software floating point support.
|
|
.Ip "\fB\-mshort\fR" 4
|
|
.IX Item "-mshort"
|
|
Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR.
|
|
.Ip "\fB\-mnobitfield\fR" 4
|
|
.IX Item "-mnobitfield"
|
|
Do not use the bit-field instructions. The \fB\-m68000\fR, \fB\-mcpu32\fR
|
|
and \fB\-m5200\fR options imply \fB\-mnobitfield\fR.
|
|
.Ip "\fB\-mbitfield\fR" 4
|
|
.IX Item "-mbitfield"
|
|
Do use the bit-field instructions. The \fB\-m68020\fR option implies
|
|
\&\fB\-mbitfield\fR. This is the default if you use a configuration
|
|
designed for a 68020.
|
|
.Ip "\fB\-mrtd\fR" 4
|
|
.IX Item "-mrtd"
|
|
Use a different function-calling convention, in which functions
|
|
that take a fixed number of arguments return with the \f(CW\*(C`rtd\*(C'\fR
|
|
instruction, which pops their arguments while returning. This
|
|
saves one instruction in the caller since there is no need to pop
|
|
the arguments there.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR);
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
.Sp
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
.Sp
|
|
The \f(CW\*(C`rtd\*(C'\fR instruction is supported by the 68010, 68020, 68030,
|
|
68040, 68060 and \s-1CPU32\s0 processors, but not by the 68000 or 5200.
|
|
.Ip "\fB\-malign-int\fR" 4
|
|
.IX Item "-malign-int"
|
|
.PD 0
|
|
.Ip "\fB\-mno-align-int\fR" 4
|
|
.IX Item "-mno-align-int"
|
|
.PD
|
|
Control whether \s-1GCC\s0 aligns \f(CW\*(C`int\*(C'\fR, \f(CW\*(C`long\*(C'\fR, \f(CW\*(C`long long\*(C'\fR,
|
|
\&\f(CW\*(C`float\*(C'\fR, \f(CW\*(C`double\*(C'\fR, and \f(CW\*(C`long double\*(C'\fR variables on a 32\-bit
|
|
boundary (\fB\-malign-int\fR) or a 16\-bit boundary (\fB\-mno-align-int\fR).
|
|
Aligning variables on 32\-bit boundaries produces code that runs somewhat
|
|
faster on processors with 32\-bit busses at the expense of more memory.
|
|
.Sp
|
|
\&\fBWarning:\fR if you use the \fB\-malign-int\fR switch, \s-1GCC\s0 will
|
|
align structures containing the above types differently than
|
|
most published application binary interface specifications for the m68k.
|
|
.Ip "\fB\-mpcrel\fR" 4
|
|
.IX Item "-mpcrel"
|
|
Use the pc-relative addressing mode of the 68000 directly, instead of
|
|
using a global offset table. At present, this option implies \-fpic,
|
|
allowing at most a 16\-bit offset for pc-relative addressing. \-fPIC is
|
|
not presently supported with \-mpcrel, though this could be supported for
|
|
68020 and higher processors.
|
|
.Ip "\fB\-mno-strict-align\fR" 4
|
|
.IX Item "-mno-strict-align"
|
|
.PD 0
|
|
.Ip "\fB\-mstrict-align\fR" 4
|
|
.IX Item "-mstrict-align"
|
|
.PD
|
|
Do not (do) assume that unaligned memory references will be handled by
|
|
the system.
|
|
.PP
|
|
.I "M68hc1x Options"
|
|
.IX Subsection "M68hc1x Options"
|
|
.PP
|
|
These are the \fB\-m\fR 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.
|
|
.Ip "\fB\-m6811\fR" 4
|
|
.IX Item "-m6811"
|
|
.PD 0
|
|
.Ip "\fB\-m68hc11\fR" 4
|
|
.IX Item "-m68hc11"
|
|
.PD
|
|
Generate output for a 68HC11. This is the default
|
|
when the compiler is configured for 68HC11\-based systems.
|
|
.Ip "\fB\-m6812\fR" 4
|
|
.IX Item "-m6812"
|
|
.PD 0
|
|
.Ip "\fB\-m68hc12\fR" 4
|
|
.IX Item "-m68hc12"
|
|
.PD
|
|
Generate output for a 68HC12. This is the default
|
|
when the compiler is configured for 68HC12\-based systems.
|
|
.Ip "\fB\-mauto-incdec\fR" 4
|
|
.IX Item "-mauto-incdec"
|
|
Enable the use of 68HC12 pre and post auto-increment and auto-decrement
|
|
addressing modes.
|
|
.Ip "\fB\-mshort\fR" 4
|
|
.IX Item "-mshort"
|
|
Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR.
|
|
.Ip "\fB\-msoft-reg-count=\fR\fIcount\fR" 4
|
|
.IX Item "-msoft-reg-count=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.
|
|
.PP
|
|
.I "\s-1VAX\s0 Options"
|
|
.IX Subsection "VAX Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the Vax:
|
|
.Ip "\fB\-munix\fR" 4
|
|
.IX Item "-munix"
|
|
Do not output certain jump instructions (\f(CW\*(C`aobleq\*(C'\fR and so on)
|
|
that the Unix assembler for the Vax cannot handle across long
|
|
ranges.
|
|
.Ip "\fB\-mgnu\fR" 4
|
|
.IX Item "-mgnu"
|
|
Do output those jump instructions, on the assumption that you
|
|
will assemble with the \s-1GNU\s0 assembler.
|
|
.Ip "\fB\-mg\fR" 4
|
|
.IX Item "-mg"
|
|
Output code for g-format floating point numbers instead of d-format.
|
|
.PP
|
|
.I "\s-1SPARC\s0 Options"
|
|
.IX Subsection "SPARC Options"
|
|
.PP
|
|
These \fB\-m\fR switches are supported on the \s-1SPARC:\s0
|
|
.Ip "\fB\-mno-app-regs\fR" 4
|
|
.IX Item "-mno-app-regs"
|
|
.PD 0
|
|
.Ip "\fB\-mapp-regs\fR" 4
|
|
.IX Item "-mapp-regs"
|
|
.PD
|
|
Specify \fB\-mapp-regs\fR to generate output using the global registers
|
|
2 through 4, which the \s-1SPARC\s0 \s-1SVR4\s0 \s-1ABI\s0 reserves for applications. This
|
|
is the default.
|
|
.Sp
|
|
To be fully \s-1SVR4\s0 \s-1ABI\s0 compliant at the cost of some performance loss,
|
|
specify \fB\-mno-app-regs\fR. You should compile libraries and system
|
|
software with this option.
|
|
.Ip "\fB\-mfpu\fR" 4
|
|
.IX Item "-mfpu"
|
|
.PD 0
|
|
.Ip "\fB\-mhard-float\fR" 4
|
|
.IX Item "-mhard-float"
|
|
.PD
|
|
Generate output containing floating point instructions. This is the
|
|
default.
|
|
.Ip "\fB\-mno-fpu\fR" 4
|
|
.IX Item "-mno-fpu"
|
|
.PD 0
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
.PD
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not available for all \s-1SPARC\s0
|
|
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 \fBsparc-*\-aout\fR and
|
|
\&\fBsparclite-*\-*\fR do provide software floating point support.
|
|
.Sp
|
|
\&\fB\-msoft-float\fR changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile \fIall\fR of a program with
|
|
this option. In particular, you need to compile \fIlibgcc.a\fR, the
|
|
library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for
|
|
this to work.
|
|
.Ip "\fB\-mhard-quad-float\fR" 4
|
|
.IX Item "-mhard-quad-float"
|
|
Generate output containing quad-word (long double) floating point
|
|
instructions.
|
|
.Ip "\fB\-msoft-quad-float\fR" 4
|
|
.IX Item "-msoft-quad-float"
|
|
Generate output containing library calls for quad-word (long double)
|
|
floating point instructions. The functions called are those specified
|
|
in the \s-1SPARC\s0 \s-1ABI\s0. This is the default.
|
|
.Sp
|
|
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 \s-1ABI\s0 library routines. Thus the
|
|
\&\fB\-msoft-quad-float\fR option is the default.
|
|
.Ip "\fB\-mno-epilogue\fR" 4
|
|
.IX Item "-mno-epilogue"
|
|
.PD 0
|
|
.Ip "\fB\-mepilogue\fR" 4
|
|
.IX Item "-mepilogue"
|
|
.PD
|
|
With \fB\-mepilogue\fR (the default), the compiler always emits code for
|
|
function exit at the end of each function. Any function exit in
|
|
the middle of the function (such as a return statement in C) will
|
|
generate a jump to the exit code at the end of the function.
|
|
.Sp
|
|
With \fB\-mno-epilogue\fR, the compiler tries to emit exit code inline
|
|
at every function exit.
|
|
.Ip "\fB\-mno-flat\fR" 4
|
|
.IX Item "-mno-flat"
|
|
.PD 0
|
|
.Ip "\fB\-mflat\fR" 4
|
|
.IX Item "-mflat"
|
|
.PD
|
|
With \fB\-mflat\fR, the compiler does not generate save/restore instructions
|
|
and will use a \*(L"flat\*(R" or single register window calling convention.
|
|
This model uses \f(CW%i7\fR as the frame pointer and is compatible with the normal
|
|
register window model. Code from either may be intermixed.
|
|
The local registers and the input registers (0\-5) are still treated as
|
|
\&\*(L"call saved\*(R" registers and will be saved on the stack as necessary.
|
|
.Sp
|
|
With \fB\-mno-flat\fR (the default), the compiler emits save/restore
|
|
instructions (except for leaf functions) and is the normal mode of operation.
|
|
.Ip "\fB\-mno-unaligned-doubles\fR" 4
|
|
.IX Item "-mno-unaligned-doubles"
|
|
.PD 0
|
|
.Ip "\fB\-munaligned-doubles\fR" 4
|
|
.IX Item "-munaligned-doubles"
|
|
.PD
|
|
Assume that doubles have 8 byte alignment. This is the default.
|
|
.Sp
|
|
With \fB\-munaligned-doubles\fR, \s-1GCC\s0 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.
|
|
.Ip "\fB\-mno-faster-structs\fR" 4
|
|
.IX Item "-mno-faster-structs"
|
|
.PD 0
|
|
.Ip "\fB\-mfaster-structs\fR" 4
|
|
.IX Item "-mfaster-structs"
|
|
.PD
|
|
With \fB\-mfaster-structs\fR, the compiler assumes that structures
|
|
should have 8 byte alignment. This enables the use of pairs of
|
|
\&\f(CW\*(C`ldd\*(C'\fR and \f(CW\*(C`std\*(C'\fR instructions for copies in structure
|
|
assignment, in place of twice as many \f(CW\*(C`ld\*(C'\fR and \f(CW\*(C`st\*(C'\fR pairs.
|
|
However, the use of this changed alignment directly violates the Sparc
|
|
\&\s-1ABI\s0. 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 \s-1ABI\s0.
|
|
.Ip "\fB\-mv8\fR" 4
|
|
.IX Item "-mv8"
|
|
.PD 0
|
|
.Ip "\fB\-msparclite\fR" 4
|
|
.IX Item "-msparclite"
|
|
.PD
|
|
These two options select variations on the \s-1SPARC\s0 architecture.
|
|
.Sp
|
|
By default (unless specifically configured for the Fujitsu SPARClite),
|
|
\&\s-1GCC\s0 generates code for the v7 variant of the \s-1SPARC\s0 architecture.
|
|
.Sp
|
|
\&\fB\-mv8\fR will give you \s-1SPARC\s0 v8 code. The only difference from v7
|
|
code is that the compiler emits the integer multiply and integer
|
|
divide instructions which exist in \s-1SPARC\s0 v8 but not in \s-1SPARC\s0 v7.
|
|
.Sp
|
|
\&\fB\-msparclite\fR will give you SPARClite code. This adds the integer
|
|
multiply, integer divide step and scan (\f(CW\*(C`ffs\*(C'\fR) instructions which
|
|
exist in SPARClite but not in \s-1SPARC\s0 v7.
|
|
.Sp
|
|
These options are deprecated and will be deleted in a future \s-1GCC\s0 release.
|
|
They have been replaced with \fB\-mcpu=xxx\fR.
|
|
.Ip "\fB\-mcypress\fR" 4
|
|
.IX Item "-mcypress"
|
|
.PD 0
|
|
.Ip "\fB\-msupersparc\fR" 4
|
|
.IX Item "-msupersparc"
|
|
.PD
|
|
These two options select the processor for which the code is optimised.
|
|
.Sp
|
|
With \fB\-mcypress\fR (the default), the compiler optimizes code for the
|
|
Cypress \s-1CY7C602\s0 chip, as used in the SparcStation/SparcServer 3xx series.
|
|
This is also appropriate for the older SparcStation 1, 2, \s-1IPX\s0 etc.
|
|
.Sp
|
|
With \fB\-msupersparc\fR the compiler optimizes code for the SuperSparc cpu, as
|
|
used in the SparcStation 10, 1000 and 2000 series. This flag also enables use
|
|
of the full \s-1SPARC\s0 v8 instruction set.
|
|
.Sp
|
|
These options are deprecated and will be deleted in a future \s-1GCC\s0 release.
|
|
They have been replaced with \fB\-mcpu=xxx\fR.
|
|
.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mcpu=cpu_type"
|
|
Set the instruction set, register set, and instruction scheduling parameters
|
|
for machine type \fIcpu_type\fR. Supported values for \fIcpu_type\fR are
|
|
\&\fBv7\fR, \fBcypress\fR, \fBv8\fR, \fBsupersparc\fR, \fBsparclite\fR,
|
|
\&\fBhypersparc\fR, \fBsparclite86x\fR, \fBf930\fR, \fBf934\fR,
|
|
\&\fBsparclet\fR, \fBtsc701\fR, \fBv9\fR, and \fBultrasparc\fR.
|
|
.Sp
|
|
Default instruction scheduling parameters are used for values that select
|
|
an architecture and not an implementation. These are \fBv7\fR, \fBv8\fR,
|
|
\&\fBsparclite\fR, \fBsparclet\fR, \fBv9\fR.
|
|
.Sp
|
|
Here is a list of each supported architecture and their supported
|
|
implementations.
|
|
.Sp
|
|
.Vb 5
|
|
\& v7: cypress
|
|
\& v8: supersparc, hypersparc
|
|
\& sparclite: f930, f934, sparclite86x
|
|
\& sparclet: tsc701
|
|
\& v9: ultrasparc
|
|
.Ve
|
|
.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mtune=cpu_type"
|
|
Set the instruction scheduling parameters for machine type
|
|
\&\fIcpu_type\fR, but do not set the instruction set or register set that the
|
|
option \fB\-mcpu=\fR\fIcpu_type\fR would.
|
|
.Sp
|
|
The same values for \fB\-mcpu=\fR\fIcpu_type\fR are used for
|
|
\&\fB\-mtune=\fR\fIcpu_type\fR, though the only useful values are those that
|
|
select a particular cpu implementation: \fBcypress\fR, \fBsupersparc\fR,
|
|
\&\fBhypersparc\fR, \fBf930\fR, \fBf934\fR, \fBsparclite86x\fR,
|
|
\&\fBtsc701\fR, \fBultrasparc\fR.
|
|
.PP
|
|
These \fB\-m\fR switches are supported in addition to the above
|
|
on the \s-1SPARCLET\s0 processor.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
Generate code for a processor running in little-endian mode.
|
|
.Ip "\fB\-mlive-g0\fR" 4
|
|
.IX Item "-mlive-g0"
|
|
Treat register \f(CW\*(C`%g0\*(C'\fR as a normal register.
|
|
\&\s-1GCC\s0 will continue to clobber it as necessary but will not assume
|
|
it always reads as 0.
|
|
.Ip "\fB\-mbroken-saverestore\fR" 4
|
|
.IX Item "-mbroken-saverestore"
|
|
Generate code that does not use non-trivial forms of the \f(CW\*(C`save\*(C'\fR and
|
|
\&\f(CW\*(C`restore\*(C'\fR instructions. Early versions of the \s-1SPARCLET\s0 processor do
|
|
not correctly handle \f(CW\*(C`save\*(C'\fR and \f(CW\*(C`restore\*(C'\fR instructions used with
|
|
arguments. They correctly handle them used without arguments. A \f(CW\*(C`save\*(C'\fR
|
|
instruction used without arguments increments the current window pointer
|
|
but does not allocate a new stack frame. It is assumed that the window
|
|
overflow trap handler will properly handle this case as will interrupt
|
|
handlers.
|
|
.PP
|
|
These \fB\-m\fR switches are supported in addition to the above
|
|
on \s-1SPARC\s0 V9 processors in 64 bit environments.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
Generate code for a processor running in little-endian mode.
|
|
.Ip "\fB\-m32\fR" 4
|
|
.IX Item "-m32"
|
|
.PD 0
|
|
.Ip "\fB\-m64\fR" 4
|
|
.IX Item "-m64"
|
|
.PD
|
|
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.
|
|
.Ip "\fB\-mcmodel=medlow\fR" 4
|
|
.IX Item "-mcmodel=medlow"
|
|
Generate code for the Medium/Low code model: the program must be linked
|
|
in the low 32 bits of the address space. Pointers are 64 bits.
|
|
Programs can be statically or dynamically linked.
|
|
.Ip "\fB\-mcmodel=medmid\fR" 4
|
|
.IX Item "-mcmodel=medmid"
|
|
Generate code for the Medium/Middle code model: the program must be linked
|
|
in the low 44 bits of the address space, the text segment must be less than
|
|
2G bytes, and data segment must be within 2G of the text segment.
|
|
Pointers are 64 bits.
|
|
.Ip "\fB\-mcmodel=medany\fR" 4
|
|
.IX Item "-mcmodel=medany"
|
|
Generate code for the Medium/Anywhere code model: the program may be linked
|
|
anywhere in the address space, the text segment must be less than
|
|
2G bytes, and data segment must be within 2G of the text segment.
|
|
Pointers are 64 bits.
|
|
.Ip "\fB\-mcmodel=embmedany\fR" 4
|
|
.IX Item "-mcmodel=embmedany"
|
|
Generate code for the Medium/Anywhere code model for embedded systems:
|
|
assume a 32 bit text and a 32 bit data segment, both starting anywhere
|
|
(determined at link time). Register \f(CW%g4\fR points to the base of the
|
|
data segment. Pointers still 64 bits.
|
|
Programs are statically linked, \s-1PIC\s0 is not supported.
|
|
.Ip "\fB\-mstack-bias\fR" 4
|
|
.IX Item "-mstack-bias"
|
|
.PD 0
|
|
.Ip "\fB\-mno-stack-bias\fR" 4
|
|
.IX Item "-mno-stack-bias"
|
|
.PD
|
|
With \fB\-mstack-bias\fR, \s-1GCC\s0 assumes that the stack pointer, and
|
|
frame pointer if present, are offset by \-2047 which must be added back
|
|
when making stack frame references.
|
|
Otherwise, assume no such offset is present.
|
|
.PP
|
|
.I "Convex Options"
|
|
.IX Subsection "Convex Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Convex:
|
|
.Ip "\fB\-mc1\fR" 4
|
|
.IX Item "-mc1"
|
|
Generate output for C1. The code will run on any Convex machine.
|
|
The preprocessor symbol \f(CW\*(C`_\|_convex_\|_c1_\|_\*(C'\fR is defined.
|
|
.Ip "\fB\-mc2\fR" 4
|
|
.IX Item "-mc2"
|
|
Generate output for C2. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C2.
|
|
The preprocessor symbol \f(CW\*(C`_\|_convex_c2_\|_\*(C'\fR is defined.
|
|
.Ip "\fB\-mc32\fR" 4
|
|
.IX Item "-mc32"
|
|
Generate output for C32xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C32.
|
|
The preprocessor symbol \f(CW\*(C`_\|_convex_c32_\|_\*(C'\fR is defined.
|
|
.Ip "\fB\-mc34\fR" 4
|
|
.IX Item "-mc34"
|
|
Generate output for C34xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C34.
|
|
The preprocessor symbol \f(CW\*(C`_\|_convex_c34_\|_\*(C'\fR is defined.
|
|
.Ip "\fB\-mc38\fR" 4
|
|
.IX Item "-mc38"
|
|
Generate output for C38xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C38.
|
|
The preprocessor symbol \f(CW\*(C`_\|_convex_c38_\|_\*(C'\fR is defined.
|
|
.Ip "\fB\-margcount\fR" 4
|
|
.IX Item "-margcount"
|
|
Generate code which puts an argument count in the word preceding each
|
|
argument list. This is compatible with regular \s-1CC\s0, and a few programs
|
|
may need the argument count word. \s-1GDB\s0 and other source-level debuggers
|
|
do not need it; this info is in the symbol table.
|
|
.Ip "\fB\-mnoargcount\fR" 4
|
|
.IX Item "-mnoargcount"
|
|
Omit the argument count word. This is the default.
|
|
.Ip "\fB\-mvolatile-cache\fR" 4
|
|
.IX Item "-mvolatile-cache"
|
|
Allow volatile references to be cached. This is the default.
|
|
.Ip "\fB\-mvolatile-nocache\fR" 4
|
|
.IX Item "-mvolatile-nocache"
|
|
Volatile references bypass the data cache, going all the way to memory.
|
|
This is only needed for multi-processor code that does not use standard
|
|
synchronization instructions. Making non-volatile references to volatile
|
|
locations will not necessarily work.
|
|
.Ip "\fB\-mlong32\fR" 4
|
|
.IX Item "-mlong32"
|
|
Type long is 32 bits, the same as type int. This is the default.
|
|
.Ip "\fB\-mlong64\fR" 4
|
|
.IX Item "-mlong64"
|
|
Type long is 64 bits, the same as type long long. This option is useless,
|
|
because no library support exists for it.
|
|
.PP
|
|
.I "\s-1AMD29K\s0 Options"
|
|
.IX Subsection "AMD29K Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1AMD\s0 Am29000:
|
|
.Ip "\fB\-mdw\fR" 4
|
|
.IX Item "-mdw"
|
|
Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is set, i.e., that byte and
|
|
halfword operations are directly supported by the hardware. This is the
|
|
default.
|
|
.Ip "\fB\-mndw\fR" 4
|
|
.IX Item "-mndw"
|
|
Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is not set.
|
|
.Ip "\fB\-mbw\fR" 4
|
|
.IX Item "-mbw"
|
|
Generate code that assumes the system supports byte and halfword write
|
|
operations. This is the default.
|
|
.Ip "\fB\-mnbw\fR" 4
|
|
.IX Item "-mnbw"
|
|
Generate code that assumes the systems does not support byte and
|
|
halfword write operations. \fB\-mnbw\fR implies \fB\-mndw\fR.
|
|
.Ip "\fB\-msmall\fR" 4
|
|
.IX Item "-msmall"
|
|
Use a small memory model that assumes that all function addresses are
|
|
either within a single 256 \s-1KB\s0 segment or at an absolute address of less
|
|
than 256k. This allows the \f(CW\*(C`call\*(C'\fR instruction to be used instead
|
|
of a \f(CW\*(C`const\*(C'\fR, \f(CW\*(C`consth\*(C'\fR, \f(CW\*(C`calli\*(C'\fR sequence.
|
|
.Ip "\fB\-mnormal\fR" 4
|
|
.IX Item "-mnormal"
|
|
Use the normal memory model: Generate \f(CW\*(C`call\*(C'\fR instructions only when
|
|
calling functions in the same file and \f(CW\*(C`calli\*(C'\fR instructions
|
|
otherwise. This works if each file occupies less than 256 \s-1KB\s0 but allows
|
|
the entire executable to be larger than 256 \s-1KB\s0. This is the default.
|
|
.Ip "\fB\-mlarge\fR" 4
|
|
.IX Item "-mlarge"
|
|
Always use \f(CW\*(C`calli\*(C'\fR instructions. Specify this option if you expect
|
|
a single file to compile into more than 256 \s-1KB\s0 of code.
|
|
.Ip "\fB\-m29050\fR" 4
|
|
.IX Item "-m29050"
|
|
Generate code for the Am29050.
|
|
.Ip "\fB\-m29000\fR" 4
|
|
.IX Item "-m29000"
|
|
Generate code for the Am29000. This is the default.
|
|
.Ip "\fB\-mkernel-registers\fR" 4
|
|
.IX Item "-mkernel-registers"
|
|
Generate references to registers \f(CW\*(C`gr64\-gr95\*(C'\fR instead of to
|
|
registers \f(CW\*(C`gr96\-gr127\*(C'\fR. This option can be used when compiling
|
|
kernel code that wants a set of global registers disjoint from that used
|
|
by user-mode code.
|
|
.Sp
|
|
Note that when this option is used, register names in \fB\-f\fR flags
|
|
must use the normal, user-mode, names.
|
|
.Ip "\fB\-muser-registers\fR" 4
|
|
.IX Item "-muser-registers"
|
|
Use the normal set of global registers, \f(CW\*(C`gr96\-gr127\*(C'\fR. This is the
|
|
default.
|
|
.Ip "\fB\-mstack-check\fR" 4
|
|
.IX Item "-mstack-check"
|
|
.PD 0
|
|
.Ip "\fB\-mno-stack-check\fR" 4
|
|
.IX Item "-mno-stack-check"
|
|
.PD
|
|
Insert (or do not insert) a call to \f(CW\*(C`_\|_msp_check\*(C'\fR after each stack
|
|
adjustment. This is often used for kernel code.
|
|
.Ip "\fB\-mstorem-bug\fR" 4
|
|
.IX Item "-mstorem-bug"
|
|
.PD 0
|
|
.Ip "\fB\-mno-storem-bug\fR" 4
|
|
.IX Item "-mno-storem-bug"
|
|
.PD
|
|
\&\fB\-mstorem-bug\fR handles 29k processors which cannot handle the
|
|
separation of a mtsrim insn and a storem instruction (most 29000 chips
|
|
to date, but not the 29050).
|
|
.Ip "\fB\-mno-reuse-arg-regs\fR" 4
|
|
.IX Item "-mno-reuse-arg-regs"
|
|
.PD 0
|
|
.Ip "\fB\-mreuse-arg-regs\fR" 4
|
|
.IX Item "-mreuse-arg-regs"
|
|
.PD
|
|
\&\fB\-mno-reuse-arg-regs\fR tells the compiler to only use incoming argument
|
|
registers for copying out arguments. This helps detect calling a function
|
|
with fewer arguments than it was declared with.
|
|
.Ip "\fB\-mno-impure-text\fR" 4
|
|
.IX Item "-mno-impure-text"
|
|
.PD 0
|
|
.Ip "\fB\-mimpure-text\fR" 4
|
|
.IX Item "-mimpure-text"
|
|
.PD
|
|
\&\fB\-mimpure-text\fR, used in addition to \fB\-shared\fR, tells the compiler to
|
|
not pass \fB\-assert pure-text\fR to the linker when linking a shared object.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0.
|
|
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.
|
|
.Ip "\fB\-mno-multm\fR" 4
|
|
.IX Item "-mno-multm"
|
|
Do not generate multm or multmu instructions. This is useful for some embedded
|
|
systems which do not have trap handlers for these instructions.
|
|
.PP
|
|
.I "\s-1ARM\s0 Options"
|
|
.IX Subsection "ARM Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Advanced \s-1RISC\s0 Machines (\s-1ARM\s0)
|
|
architectures:
|
|
.Ip "\fB\-mapcs-frame\fR" 4
|
|
.IX Item "-mapcs-frame"
|
|
Generate a stack frame that is compliant with the \s-1ARM\s0 Procedure Call
|
|
Standard for all functions, even if this is not strictly necessary for
|
|
correct execution of the code. Specifying \fB\-fomit-frame-pointer\fR
|
|
with this option will cause the stack frames not to be generated for
|
|
leaf functions. The default is \fB\-mno-apcs-frame\fR.
|
|
.Ip "\fB\-mapcs\fR" 4
|
|
.IX Item "-mapcs"
|
|
This is a synonym for \fB\-mapcs-frame\fR.
|
|
.Ip "\fB\-mapcs-26\fR" 4
|
|
.IX Item "-mapcs-26"
|
|
Generate code for a processor running with a 26\-bit program counter,
|
|
and conforming to the function calling standards for the \s-1APCS\s0 26\-bit
|
|
option. This option replaces the \fB\-m2\fR and \fB\-m3\fR options
|
|
of previous releases of the compiler.
|
|
.Ip "\fB\-mapcs-32\fR" 4
|
|
.IX Item "-mapcs-32"
|
|
Generate code for a processor running with a 32\-bit program counter,
|
|
and conforming to the function calling standards for the \s-1APCS\s0 32\-bit
|
|
option. This option replaces the \fB\-m6\fR option of previous releases
|
|
of the compiler.
|
|
.Ip "\fB\-mapcs-stack-check\fR" 4
|
|
.IX Item "-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
|
|
\&\fB_\|_rt_stkovf_split_small\fR or \fB_\|_rt_stkovf_split_big\fR will be
|
|
called, depending upon the amount of stack space required. The run time
|
|
system is required to provide these functions. The default is
|
|
\&\fB\-mno-apcs-stack-check\fR, since this produces smaller code.
|
|
.Ip "\fB\-mapcs-float\fR" 4
|
|
.IX Item "-mapcs-float"
|
|
Pass floating point arguments using the float point registers. This is
|
|
one of the variants of the \s-1APCS\s0. 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
|
|
\&\fB\-mno-apcs-float\fR, since integer only code is slightly increased in
|
|
size if \fB\-mapcs-float\fR is used.
|
|
.Ip "\fB\-mapcs-reentrant\fR" 4
|
|
.IX Item "-mapcs-reentrant"
|
|
Generate reentrant, position independent code. This is the equivalent
|
|
to specifying the \fB\-fpic\fR option. The default is
|
|
\&\fB\-mno-apcs-reentrant\fR.
|
|
.Ip "\fB\-mthumb-interwork\fR" 4
|
|
.IX Item "-mthumb-interwork"
|
|
Generate code which supports calling between the \s-1ARM\s0 and \s-1THUMB\s0
|
|
instruction sets. Without this option the two instruction sets cannot
|
|
be reliably used inside one program. The default is
|
|
\&\fB\-mno-thumb-interwork\fR, since slightly larger code is generated
|
|
when \fB\-mthumb-interwork\fR is specified.
|
|
.Ip "\fB\-mno-sched-prolog\fR" 4
|
|
.IX Item "-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 \fB\-msched-prolog\fR.
|
|
.Ip "\fB\-mhard-float\fR" 4
|
|
.IX Item "-mhard-float"
|
|
Generate output containing floating point instructions. This is the
|
|
default.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not available for all \s-1ARM\s0
|
|
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.
|
|
.Sp
|
|
\&\fB\-msoft-float\fR changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile \fIall\fR of a program with
|
|
this option. In particular, you need to compile \fIlibgcc.a\fR, the
|
|
library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for
|
|
this to work.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
Generate code for a processor running in little-endian mode. This is
|
|
the default for all standard configurations.
|
|
.Ip "\fB\-mbig-endian\fR" 4
|
|
.IX Item "-mbig-endian"
|
|
Generate code for a processor running in big-endian mode; the default is
|
|
to compile code for a little-endian processor.
|
|
.Ip "\fB\-mwords-little-endian\fR" 4
|
|
.IX Item "-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 \fB32107654\fR. Note: this
|
|
option should only be used if you require compatibility with code for
|
|
big-endian \s-1ARM\s0 processors generated by versions of the compiler prior to
|
|
2.8.
|
|
.Ip "\fB\-malignment-traps\fR" 4
|
|
.IX Item "-malignment-traps"
|
|
Generate code that will not trap if the \s-1MMU\s0 has alignment traps enabled.
|
|
On \s-1ARM\s0 architectures prior to ARMv4, there were no instructions to
|
|
access half-word objects stored in memory. However, when reading from
|
|
memory a feature of the \s-1ARM\s0 architecture allows a word load to be used,
|
|
even if the address is unaligned, and the processor core will rotate the
|
|
data as it is being loaded. This option tells the compiler that such
|
|
misaligned accesses will cause a \s-1MMU\s0 trap and that it should instead
|
|
synthesise the access as a series of byte accesses. The compiler can
|
|
still use word accesses to load half-word data if it knows that the
|
|
address is aligned to a word boundary.
|
|
.Sp
|
|
This option is ignored when compiling for \s-1ARM\s0 architecture 4 or later,
|
|
since these processors have instructions to directly access half-word
|
|
objects in memory.
|
|
.Ip "\fB\-mno-alignment-traps\fR" 4
|
|
.IX Item "-mno-alignment-traps"
|
|
Generate code that assumes that the \s-1MMU\s0 will not trap unaligned
|
|
accesses. This produces better code when the target instruction set
|
|
does not have half-word memory operations (implementations prior to
|
|
ARMv4).
|
|
.Sp
|
|
Note that you cannot use this option to access unaligned word objects,
|
|
since the processor will only fetch one 32\-bit aligned object from
|
|
memory.
|
|
.Sp
|
|
The default setting for most targets is \-mno-alignment-traps, since
|
|
this produces better code when there are no half-word memory
|
|
instructions available.
|
|
.Ip "\fB\-mshort-load-bytes\fR" 4
|
|
.IX Item "-mshort-load-bytes"
|
|
This is a deprecated alias for \fB\-malignment-traps\fR.
|
|
.Ip "\fB\-mno-short-load-bytes\fR" 4
|
|
.IX Item "-mno-short-load-bytes"
|
|
This is a deprecated alias for \fB\-mno-alignment-traps\fR.
|
|
.Ip "\fB\-mshort-load-words\fR" 4
|
|
.IX Item "-mshort-load-words"
|
|
This is a deprecated alias for \fB\-mno-alignment-traps\fR.
|
|
.Ip "\fB\-mno-short-load-words\fR" 4
|
|
.IX Item "-mno-short-load-words"
|
|
This is a deprecated alias for \fB\-malignment-traps\fR.
|
|
.Ip "\fB\-mbsd\fR" 4
|
|
.IX Item "-mbsd"
|
|
This option only applies to \s-1RISC\s0 iX. Emulate the native BSD-mode
|
|
compiler. This is the default if \fB\-ansi\fR is not specified.
|
|
.Ip "\fB\-mxopen\fR" 4
|
|
.IX Item "-mxopen"
|
|
This option only applies to \s-1RISC\s0 iX. Emulate the native X/Open-mode
|
|
compiler.
|
|
.Ip "\fB\-mno-symrename\fR" 4
|
|
.IX Item "-mno-symrename"
|
|
This option only applies to \s-1RISC\s0 iX. Do not run the assembler
|
|
post-processor, \fBsymrename\fR, after code has been assembled.
|
|
Normally it is necessary to modify some of the standard symbols in
|
|
preparation for linking with the \s-1RISC\s0 iX C library; this option
|
|
suppresses this pass. The post-processor is never run when the
|
|
compiler is built for cross-compilation.
|
|
.Ip "\fB\-mcpu=<name>\fR" 4
|
|
.IX Item "-mcpu=<name>"
|
|
This specifies the name of the target \s-1ARM\s0 processor. \s-1GCC\s0 uses this name
|
|
to determine what kind of instructions it can use when generating
|
|
assembly code. Permissible names are: arm2, arm250, arm3, arm6, arm60,
|
|
arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi,
|
|
arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe,
|
|
arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810,
|
|
arm9, arm920, arm920t, arm9tdmi.
|
|
.Ip "\fB\-mtune=<name>\fR" 4
|
|
.IX Item "-mtune=<name>"
|
|
This option is very similar to the \fB\-mcpu=\fR option, except that
|
|
instead of specifying the actual target processor type, and hence
|
|
restricting which instructions can be used, it specifies that \s-1GCC\s0 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 \fB\-mcpu=\fR option.
|
|
For some arm implementations better performance can be obtained by using
|
|
this option.
|
|
.Ip "\fB\-march=<name>\fR" 4
|
|
.IX Item "-march=<name>"
|
|
This specifies the name of the target \s-1ARM\s0 architecture. \s-1GCC\s0 uses this
|
|
name to determine what kind of instructions it can use when generating
|
|
assembly code. This option can be used in conjunction with or instead
|
|
of the \fB\-mcpu=\fR option. Permissible names are: armv2, armv2a,
|
|
armv3, armv3m, armv4, armv4t, armv5.
|
|
.Ip "\fB\-mfpe=<number>\fR" 4
|
|
.IX Item "-mfpe=<number>"
|
|
.PD 0
|
|
.Ip "\fB\-mfp=<number>\fR" 4
|
|
.IX Item "-mfp=<number>"
|
|
.PD
|
|
This specifies the version of the floating point emulation available on
|
|
the target. Permissible values are 2 and 3. \fB\-mfp=\fR is a synonym
|
|
for \fB\-mfpe=\fR to support older versions of \s-1GCC\s0.
|
|
.Ip "\fB\-mstructure-size-boundary=<n>\fR" 4
|
|
.IX Item "-mstructure-size-boundary=<n>"
|
|
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 and
|
|
32. The default value varies for different toolchains. For the \s-1COFF\s0
|
|
targeted toolchain the default value is 8. Specifying the larger number
|
|
can produce faster, more efficient code, but can also increase the size
|
|
of the program. The two values are potentially incompatible. Code
|
|
compiled with one value cannot necessarily expect to work with code or
|
|
libraries compiled with the other value, if they exchange information
|
|
using structures or unions. Programmers are encouraged to use the 32
|
|
value as future versions of the toolchain may default to this value.
|
|
.Ip "\fB\-mabort-on-noreturn\fR" 4
|
|
.IX Item "-mabort-on-noreturn"
|
|
Generate a call to the function abort at the end of a noreturn function.
|
|
It will be executed if the function tries to return.
|
|
.Ip "\fB\-mlong-calls\fR" 4
|
|
.IX Item "-mlong-calls"
|
|
.PD 0
|
|
.Ip "\fB\-mno-long-calls\fR" 4
|
|
.IX Item "-mno-long-calls"
|
|
.PD
|
|
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.
|
|
.Sp
|
|
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 \fBshort-call\fR attribute, functions that are inside
|
|
the scope of a \fB#pragma no_long_calls\fR 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 \fBlong-call\fR
|
|
attribute or the \fBsection\fR attribute, and functions that are within
|
|
the scope of a \fB#pragma long_calls\fR directive, will always be
|
|
turned into long calls.
|
|
.Sp
|
|
This feature is not enabled by default. Specifying
|
|
\&\fB\*(--no-long-calls\fR will restore the default behaviour, as will
|
|
placing the function calls within the scope of a \fB#pragma
|
|
long_calls_off\fR directive. Note these switches have no effect on how
|
|
the compiler generates code to handle function calls via function
|
|
pointers.
|
|
.Ip "\fB\-mnop-fun-dllimport\fR" 4
|
|
.IX Item "-mnop-fun-dllimport"
|
|
Disable the support for the \fIdllimport\fR attribute.
|
|
.Ip "\fB\-msingle-pic-base\fR" 4
|
|
.IX Item "-msingle-pic-base"
|
|
Treat the register used for \s-1PIC\s0 addressing as read-only, rather than
|
|
loading it in the prologue for each function. The run-time system is
|
|
responsible for initialising this register with an appropriate value
|
|
before execution begins.
|
|
.Ip "\fB\-mpic-register=<reg>\fR" 4
|
|
.IX Item "-mpic-register=<reg>"
|
|
Specify the register to be used for \s-1PIC\s0 addressing. The default is R10
|
|
unless stack-checking is enabled, when R9 is used.
|
|
.PP
|
|
.I "Thumb Options"
|
|
.IX Subsection "Thumb Options"
|
|
.Ip "\fB\-mthumb-interwork\fR" 4
|
|
.IX Item "-mthumb-interwork"
|
|
Generate code which supports calling between the \s-1THUMB\s0 and \s-1ARM\s0
|
|
instruction sets. Without this option the two instruction sets cannot
|
|
be reliably used inside one program. The default is
|
|
\&\fB\-mno-thumb-interwork\fR, since slightly smaller code is generated
|
|
with this option.
|
|
.Ip "\fB\-mtpcs-frame\fR" 4
|
|
.IX Item "-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 \fB\-mno-apcs-frame\fR.
|
|
.Ip "\fB\-mtpcs-leaf-frame\fR" 4
|
|
.IX Item "-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 \fB\-mno-apcs-leaf-frame\fR.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
Generate code for a processor running in little-endian mode. This is
|
|
the default for all standard configurations.
|
|
.Ip "\fB\-mbig-endian\fR" 4
|
|
.IX Item "-mbig-endian"
|
|
Generate code for a processor running in big-endian mode.
|
|
.Ip "\fB\-mstructure-size-boundary=<n>\fR" 4
|
|
.IX Item "-mstructure-size-boundary=<n>"
|
|
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 and
|
|
32. The default value varies for different toolchains. For the \s-1COFF\s0
|
|
targeted toolchain the default value is 8. Specifying the larger number
|
|
can produced faster, more efficient code, but can also increase the size
|
|
of the program. The two values are potentially incompatible. Code
|
|
compiled with one value cannot necessarily expect to work with code or
|
|
libraries compiled with the other value, if they exchange information
|
|
using structures or unions. Programmers are encouraged to use the 32
|
|
value as future versions of the toolchain may default to this value.
|
|
.Ip "\fB\-mnop-fun-dllimport\fR" 4
|
|
.IX Item "-mnop-fun-dllimport"
|
|
Disable the support for the \fIdllimport\fR attribute.
|
|
.Ip "\fB\-mcallee-super-interworking\fR" 4
|
|
.IX Item "-mcallee-super-interworking"
|
|
Gives all externally visible functions in the file being compiled an \s-1ARM\s0
|
|
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.
|
|
.Ip "\fB\-mcaller-super-interworking\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-msingle-pic-base\fR" 4
|
|
.IX Item "-msingle-pic-base"
|
|
Treat the register used for \s-1PIC\s0 addressing as read-only, rather than
|
|
loading it in the prologue for each function. The run-time system is
|
|
responsible for initialising this register with an appropriate value
|
|
before execution begins.
|
|
.Ip "\fB\-mpic-register=<reg>\fR" 4
|
|
.IX Item "-mpic-register=<reg>"
|
|
Specify the register to be used for \s-1PIC\s0 addressing. The default is R10.
|
|
.PP
|
|
.I "\s-1MN10200\s0 Options"
|
|
.IX Subsection "MN10200 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Matsushita \s-1MN10200\s0 architectures:
|
|
.Ip "\fB\-mrelax\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
This option makes symbolic debugging impossible.
|
|
.PP
|
|
.I "\s-1MN10300\s0 Options"
|
|
.IX Subsection "MN10300 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Matsushita \s-1MN10300\s0 architectures:
|
|
.Ip "\fB\-mmult-bug\fR" 4
|
|
.IX Item "-mmult-bug"
|
|
Generate code to avoid bugs in the multiply instructions for the \s-1MN10300\s0
|
|
processors. This is the default.
|
|
.Ip "\fB\-mno-mult-bug\fR" 4
|
|
.IX Item "-mno-mult-bug"
|
|
Do not generate code to avoid bugs in the multiply instructions for the
|
|
\&\s-1MN10300\s0 processors.
|
|
.Ip "\fB\-mam33\fR" 4
|
|
.IX Item "-mam33"
|
|
Generate code which uses features specific to the \s-1AM33\s0 processor.
|
|
.Ip "\fB\-mno-am33\fR" 4
|
|
.IX Item "-mno-am33"
|
|
Do not generate code which uses features specific to the \s-1AM33\s0 processor. This
|
|
is the default.
|
|
.Ip "\fB\-mrelax\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
This option makes symbolic debugging impossible.
|
|
.PP
|
|
.I "M32R/D Options"
|
|
.IX Subsection "M32R/D Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Mitsubishi M32R/D architectures:
|
|
.Ip "\fB\-mcode-model=small\fR" 4
|
|
.IX Item "-mcode-model=small"
|
|
Assume all objects live in the lower 16MB of memory (so that their addresses
|
|
can be loaded with the \f(CW\*(C`ld24\*(C'\fR instruction), and assume all subroutines
|
|
are reachable with the \f(CW\*(C`bl\*(C'\fR instruction.
|
|
This is the default.
|
|
.Sp
|
|
The addressability of a particular object can be set with the
|
|
\&\f(CW\*(C`model\*(C'\fR attribute.
|
|
.Ip "\fB\-mcode-model=medium\fR" 4
|
|
.IX Item "-mcode-model=medium"
|
|
Assume objects may be anywhere in the 32 bit address space (the compiler
|
|
will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and
|
|
assume all subroutines are reachable with the \f(CW\*(C`bl\*(C'\fR instruction.
|
|
.Ip "\fB\-mcode-model=large\fR" 4
|
|
.IX Item "-mcode-model=large"
|
|
Assume objects may be anywhere in the 32 bit address space (the compiler
|
|
will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and
|
|
assume subroutines may not be reachable with the \f(CW\*(C`bl\*(C'\fR instruction
|
|
(the compiler will generate the much slower \f(CW\*(C`seth/add3/jl\*(C'\fR
|
|
instruction sequence).
|
|
.Ip "\fB\-msdata=none\fR" 4
|
|
.IX Item "-msdata=none"
|
|
Disable use of the small data area. Variables will be put into
|
|
one of \fB.data\fR, \fBbss\fR, or \fB.rodata\fR (unless the
|
|
\&\f(CW\*(C`section\*(C'\fR attribute has been specified).
|
|
This is the default.
|
|
.Sp
|
|
The small data area consists of sections \fB.sdata\fR and \fB.sbss\fR.
|
|
Objects may be explicitly put in the small data area with the
|
|
\&\f(CW\*(C`section\*(C'\fR attribute using one of these sections.
|
|
.Ip "\fB\-msdata=sdata\fR" 4
|
|
.IX Item "-msdata=sdata"
|
|
Put small global and static data in the small data area, but do not
|
|
generate special code to reference them.
|
|
.Ip "\fB\-msdata=use\fR" 4
|
|
.IX Item "-msdata=use"
|
|
Put small global and static data in the small data area, and generate
|
|
special instructions to reference them.
|
|
.Ip "\fB\-G\fR \fInum\fR" 4
|
|
.IX Item "-G num"
|
|
Put global and static objects less than or equal to \fInum\fR bytes
|
|
into the small data or bss sections instead of the normal data or bss
|
|
sections. The default value of \fInum\fR is 8.
|
|
The \fB\-msdata\fR option must be set to one of \fBsdata\fR or \fBuse\fR
|
|
for this option to have any effect.
|
|
.Sp
|
|
All modules should be compiled with the same \fB\-G\fR \fInum\fR value.
|
|
Compiling with different values of \fInum\fR may or may not work; if it
|
|
doesn't the linker will give an error message \- incorrect code will not be
|
|
generated.
|
|
.PP
|
|
.I "M88K Options"
|
|
.IX Subsection "M88K Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for Motorola 88k architectures:
|
|
.Ip "\fB\-m88000\fR" 4
|
|
.IX Item "-m88000"
|
|
Generate code that works well on both the m88100 and the
|
|
m88110.
|
|
.Ip "\fB\-m88100\fR" 4
|
|
.IX Item "-m88100"
|
|
Generate code that works best for the m88100, but that also
|
|
runs on the m88110.
|
|
.Ip "\fB\-m88110\fR" 4
|
|
.IX Item "-m88110"
|
|
Generate code that works best for the m88110, and may not run
|
|
on the m88100.
|
|
.Ip "\fB\-mbig-pic\fR" 4
|
|
.IX Item "-mbig-pic"
|
|
Obsolete option to be removed from the next revision.
|
|
Use \fB\-fPIC\fR.
|
|
.Ip "\fB\-midentify-revision\fR" 4
|
|
.IX Item "-midentify-revision"
|
|
Include an \f(CW\*(C`ident\*(C'\fR directive in the assembler output recording the
|
|
source file name, compiler name and version, timestamp, and compilation
|
|
flags used.
|
|
.Ip "\fB\-mno-underscores\fR" 4
|
|
.IX Item "-mno-underscores"
|
|
In assembler output, emit symbol names without adding an underscore
|
|
character at the beginning of each name. The default is to use an
|
|
underscore as prefix on each name.
|
|
.Ip "\fB\-mocs-debug-info\fR" 4
|
|
.IX Item "-mocs-debug-info"
|
|
.PD 0
|
|
.Ip "\fB\-mno-ocs-debug-info\fR" 4
|
|
.IX Item "-mno-ocs-debug-info"
|
|
.PD
|
|
Include (or omit) additional debugging information (about registers used
|
|
in each stack frame) as specified in the 88open Object Compatibility
|
|
Standard, ``\s-1OCS\s0''. This extra information allows debugging of code that
|
|
has had the frame pointer eliminated. The default for \s-1DG/UX\s0, SVr4, and
|
|
Delta 88 SVr3.2 is to include this information; other 88k configurations
|
|
omit this information by default.
|
|
.Ip "\fB\-mocs-frame-position\fR" 4
|
|
.IX Item "-mocs-frame-position"
|
|
When emitting \s-1COFF\s0 debugging information for automatic variables and
|
|
parameters stored on the stack, use the offset from the canonical frame
|
|
address, which is the stack pointer (register 31) on entry to the
|
|
function. The \s-1DG/UX\s0, SVr4, Delta88 SVr3.2, and \s-1BCS\s0 configurations use
|
|
\&\fB\-mocs-frame-position\fR; other 88k configurations have the default
|
|
\&\fB\-mno-ocs-frame-position\fR.
|
|
.Ip "\fB\-mno-ocs-frame-position\fR" 4
|
|
.IX Item "-mno-ocs-frame-position"
|
|
When emitting \s-1COFF\s0 debugging information for automatic variables and
|
|
parameters stored on the stack, use the offset from the frame pointer
|
|
register (register 30). When this option is in effect, the frame
|
|
pointer is not eliminated when debugging information is selected by the
|
|
\&\-g switch.
|
|
.Ip "\fB\-moptimize-arg-area\fR" 4
|
|
.IX Item "-moptimize-arg-area"
|
|
.PD 0
|
|
.Ip "\fB\-mno-optimize-arg-area\fR" 4
|
|
.IX Item "-mno-optimize-arg-area"
|
|
.PD
|
|
Control how function arguments are stored in stack frames.
|
|
\&\fB\-moptimize-arg-area\fR saves space by optimizing them, but this
|
|
conflicts with the 88open specifications. The opposite alternative,
|
|
\&\fB\-mno-optimize-arg-area\fR, agrees with 88open standards. By default
|
|
\&\s-1GCC\s0 does not optimize the argument area.
|
|
.Ip "\fB\-mshort-data-\fR\fInum\fR" 4
|
|
.IX Item "-mshort-data-num"
|
|
Generate smaller data references by making them relative to \f(CW\*(C`r0\*(C'\fR,
|
|
which allows loading a value using a single instruction (rather than the
|
|
usual two). You control which data references are affected by
|
|
specifying \fInum\fR with this option. For example, if you specify
|
|
\&\fB\-mshort-data-512\fR, then the data references affected are those
|
|
involving displacements of less than 512 bytes.
|
|
\&\fB\-mshort-data-\fR\fInum\fR is not effective for \fInum\fR greater
|
|
than 64k.
|
|
.Ip "\fB\-mserialize-volatile\fR" 4
|
|
.IX Item "-mserialize-volatile"
|
|
.PD 0
|
|
.Ip "\fB\-mno-serialize-volatile\fR" 4
|
|
.IX Item "-mno-serialize-volatile"
|
|
.PD
|
|
Do, or don't, generate code to guarantee sequential consistency
|
|
of volatile memory references. By default, consistency is
|
|
guaranteed.
|
|
.Sp
|
|
The order of memory references made by the \s-1MC88110\s0 processor does
|
|
not always match the order of the instructions requesting those
|
|
references. In particular, a load instruction may execute before
|
|
a preceding store instruction. Such reordering violates
|
|
sequential consistency of volatile memory references, when there
|
|
are multiple processors. When consistency must be guaranteed,
|
|
\&\s-1GNU\s0 C generates special instructions, as needed, to force
|
|
execution in the proper order.
|
|
.Sp
|
|
The \s-1MC88100\s0 processor does not reorder memory references and so
|
|
always provides sequential consistency. However, by default, \s-1GNU\s0
|
|
C generates the special instructions to guarantee consistency
|
|
even when you use \fB\-m88100\fR, so that the code may be run on an
|
|
\&\s-1MC88110\s0 processor. If you intend to run your code only on the
|
|
\&\s-1MC88100\s0 processor, you may use \fB\-mno-serialize-volatile\fR.
|
|
.Sp
|
|
The extra code generated to guarantee consistency may affect the
|
|
performance of your application. If you know that you can safely
|
|
forgo this guarantee, you may use \fB\-mno-serialize-volatile\fR.
|
|
.Ip "\fB\-msvr4\fR" 4
|
|
.IX Item "-msvr4"
|
|
.PD 0
|
|
.Ip "\fB\-msvr3\fR" 4
|
|
.IX Item "-msvr3"
|
|
.PD
|
|
Turn on (\fB\-msvr4\fR) or off (\fB\-msvr3\fR) compiler extensions
|
|
related to System V release 4 (SVr4). This controls the following:
|
|
.RS 4
|
|
.Ip "1." 4
|
|
Which variant of the assembler syntax to emit.
|
|
.Ip "2." 4
|
|
\&\fB\-msvr4\fR makes the C preprocessor recognize \fB#pragma weak\fR
|
|
that is used on System V release 4.
|
|
.Ip "3." 4
|
|
\&\fB\-msvr4\fR makes \s-1GCC\s0 issue additional declaration directives used in
|
|
SVr4.
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
\&\fB\-msvr4\fR is the default for the m88k-motorola-sysv4 and
|
|
m88k-dg-dgux m88k configurations. \fB\-msvr3\fR is the default for all
|
|
other m88k configurations.
|
|
.RE
|
|
.Ip "\fB\-mversion-03.00\fR" 4
|
|
.IX Item "-mversion-03.00"
|
|
This option is obsolete, and is ignored.
|
|
.Ip "\fB\-mno-check-zero-division\fR" 4
|
|
.IX Item "-mno-check-zero-division"
|
|
.PD 0
|
|
.Ip "\fB\-mcheck-zero-division\fR" 4
|
|
.IX Item "-mcheck-zero-division"
|
|
.PD
|
|
Do, or don't, generate code to guarantee that integer division by
|
|
zero will be detected. By default, detection is guaranteed.
|
|
.Sp
|
|
Some models of the \s-1MC88100\s0 processor fail to trap upon integer
|
|
division by zero under certain conditions. By default, when
|
|
compiling code that might be run on such a processor, \s-1GNU\s0 C
|
|
generates code that explicitly checks for zero-valued divisors
|
|
and traps with exception number 503 when one is detected. Use of
|
|
mno-check-zero-division suppresses such checking for code
|
|
generated to run on an \s-1MC88100\s0 processor.
|
|
.Sp
|
|
\&\s-1GNU\s0 C assumes that the \s-1MC88110\s0 processor correctly detects all
|
|
instances of integer division by zero. When \fB\-m88110\fR is
|
|
specified, both \fB\-mcheck-zero-division\fR and
|
|
\&\fB\-mno-check-zero-division\fR are ignored, and no explicit checks for
|
|
zero-valued divisors are generated.
|
|
.Ip "\fB\-muse-div-instruction\fR" 4
|
|
.IX Item "-muse-div-instruction"
|
|
Use the div instruction for signed integer division on the
|
|
\&\s-1MC88100\s0 processor. By default, the div instruction is not used.
|
|
.Sp
|
|
On the \s-1MC88100\s0 processor the signed integer division instruction
|
|
div) traps to the operating system on a negative operand. The
|
|
operating system transparently completes the operation, but at a
|
|
large cost in execution time. By default, when compiling code
|
|
that might be run on an \s-1MC88100\s0 processor, \s-1GNU\s0 C emulates signed
|
|
integer division using the unsigned integer division instruction
|
|
divu), thereby avoiding the large penalty of a trap to the
|
|
operating system. Such emulation has its own, smaller, execution
|
|
cost in both time and space. To the extent that your code's
|
|
important signed integer division operations are performed on two
|
|
nonnegative operands, it may be desirable to use the div
|
|
instruction directly.
|
|
.Sp
|
|
On the \s-1MC88110\s0 processor the div instruction (also known as the
|
|
divs instruction) processes negative operands without trapping to
|
|
the operating system. When \fB\-m88110\fR is specified,
|
|
\&\fB\-muse-div-instruction\fR is ignored, and the div instruction is used
|
|
for signed integer division.
|
|
.Sp
|
|
Note that the result of dividing \s-1INT_MIN\s0 by \-1 is undefined. In
|
|
particular, the behavior of such a division with and without
|
|
\&\fB\-muse-div-instruction\fR may differ.
|
|
.Ip "\fB\-mtrap-large-shift\fR" 4
|
|
.IX Item "-mtrap-large-shift"
|
|
.PD 0
|
|
.Ip "\fB\-mhandle-large-shift\fR" 4
|
|
.IX Item "-mhandle-large-shift"
|
|
.PD
|
|
Include code to detect bit-shifts of more than 31 bits; respectively,
|
|
trap such shifts or emit code to handle them properly. By default \s-1GCC\s0
|
|
makes no special provision for large bit shifts.
|
|
.Ip "\fB\-mwarn-passed-structs\fR" 4
|
|
.IX Item "-mwarn-passed-structs"
|
|
Warn when a function passes a struct as an argument or result.
|
|
Structure-passing conventions have changed during the evolution of the C
|
|
language, and are often the source of portability problems. By default,
|
|
\&\s-1GCC\s0 issues no such warning.
|
|
.PP
|
|
.I "\s-1IBM\s0 \s-1RS/6000\s0 and PowerPC Options"
|
|
.IX Subsection "IBM RS/6000 and PowerPC Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RS/6000\s0 and PowerPC:
|
|
.Ip "\fB\-mpower\fR" 4
|
|
.IX Item "-mpower"
|
|
.PD 0
|
|
.Ip "\fB\-mno-power\fR" 4
|
|
.IX Item "-mno-power"
|
|
.Ip "\fB\-mpower2\fR" 4
|
|
.IX Item "-mpower2"
|
|
.Ip "\fB\-mno-power2\fR" 4
|
|
.IX Item "-mno-power2"
|
|
.Ip "\fB\-mpowerpc\fR" 4
|
|
.IX Item "-mpowerpc"
|
|
.Ip "\fB\-mno-powerpc\fR" 4
|
|
.IX Item "-mno-powerpc"
|
|
.Ip "\fB\-mpowerpc-gpopt\fR" 4
|
|
.IX Item "-mpowerpc-gpopt"
|
|
.Ip "\fB\-mno-powerpc-gpopt\fR" 4
|
|
.IX Item "-mno-powerpc-gpopt"
|
|
.Ip "\fB\-mpowerpc-gfxopt\fR" 4
|
|
.IX Item "-mpowerpc-gfxopt"
|
|
.Ip "\fB\-mno-powerpc-gfxopt\fR" 4
|
|
.IX Item "-mno-powerpc-gfxopt"
|
|
.Ip "\fB\-mpowerpc64\fR" 4
|
|
.IX Item "-mpowerpc64"
|
|
.Ip "\fB\-mno-powerpc64\fR" 4
|
|
.IX Item "-mno-powerpc64"
|
|
.PD
|
|
\&\s-1GCC\s0 supports two related instruction set architectures for the
|
|
\&\s-1RS/6000\s0 and PowerPC. The \fI\s-1POWER\s0\fR instruction set are those
|
|
instructions supported by the \fBrios\fR chip set used in the original
|
|
\&\s-1RS/6000\s0 systems and the \fIPowerPC\fR instruction set is the
|
|
architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and
|
|
the \s-1IBM\s0 4xx microprocessors.
|
|
.Sp
|
|
Neither architecture is a subset of the other. However there is a
|
|
large common subset of instructions supported by both. An \s-1MQ\s0
|
|
register is included in processors supporting the \s-1POWER\s0 architecture.
|
|
.Sp
|
|
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 \s-1GCC\s0. Specifying the
|
|
\&\fB\-mcpu=\fR\fIcpu_type\fR overrides the specification of these
|
|
options. We recommend you use the \fB\-mcpu=\fR\fIcpu_type\fR option
|
|
rather than the options listed above.
|
|
.Sp
|
|
The \fB\-mpower\fR option allows \s-1GCC\s0 to generate instructions that
|
|
are found only in the \s-1POWER\s0 architecture and to use the \s-1MQ\s0 register.
|
|
Specifying \fB\-mpower2\fR implies \fB\-power\fR and also allows \s-1GCC\s0
|
|
to generate instructions that are present in the \s-1POWER2\s0 architecture but
|
|
not the original \s-1POWER\s0 architecture.
|
|
.Sp
|
|
The \fB\-mpowerpc\fR option allows \s-1GCC\s0 to generate instructions that
|
|
are found only in the 32\-bit subset of the PowerPC architecture.
|
|
Specifying \fB\-mpowerpc-gpopt\fR implies \fB\-mpowerpc\fR and also allows
|
|
\&\s-1GCC\s0 to use the optional PowerPC architecture instructions in the
|
|
General Purpose group, including floating-point square root. Specifying
|
|
\&\fB\-mpowerpc-gfxopt\fR implies \fB\-mpowerpc\fR and also allows \s-1GCC\s0 to
|
|
use the optional PowerPC architecture instructions in the Graphics
|
|
group, including floating-point select.
|
|
.Sp
|
|
The \fB\-mpowerpc64\fR option allows \s-1GCC\s0 to generate the additional
|
|
64\-bit instructions that are found in the full PowerPC64 architecture
|
|
and to treat GPRs as 64\-bit, doubleword quantities. \s-1GCC\s0 defaults to
|
|
\&\fB\-mno-powerpc64\fR.
|
|
.Sp
|
|
If you specify both \fB\-mno-power\fR and \fB\-mno-powerpc\fR, \s-1GCC\s0
|
|
will use only the instructions in the common subset of both
|
|
architectures plus some special \s-1AIX\s0 common-mode calls, and will not use
|
|
the \s-1MQ\s0 register. Specifying both \fB\-mpower\fR and \fB\-mpowerpc\fR
|
|
permits \s-1GCC\s0 to use any instruction from either architecture and to
|
|
allow use of the \s-1MQ\s0 register; specify this for the Motorola \s-1MPC601\s0.
|
|
.Ip "\fB\-mnew-mnemonics\fR" 4
|
|
.IX Item "-mnew-mnemonics"
|
|
.PD 0
|
|
.Ip "\fB\-mold-mnemonics\fR" 4
|
|
.IX Item "-mold-mnemonics"
|
|
.PD
|
|
Select which mnemonics to use in the generated assembler code.
|
|
\&\fB\-mnew-mnemonics\fR requests output that uses the assembler mnemonics
|
|
defined for the PowerPC architecture, while \fB\-mold-mnemonics\fR
|
|
requests the assembler mnemonics defined for the \s-1POWER\s0 architecture.
|
|
Instructions defined in only one architecture have only one mnemonic;
|
|
\&\s-1GCC\s0 uses that mnemonic irrespective of which of these options is
|
|
specified.
|
|
.Sp
|
|
\&\s-1GCC\s0 defaults to the mnemonics appropriate for the architecture in
|
|
use. Specifying \fB\-mcpu=\fR\fIcpu_type\fR sometimes overrides the
|
|
value of these option. Unless you are building a cross-compiler, you
|
|
should normally not specify either \fB\-mnew-mnemonics\fR or
|
|
\&\fB\-mold-mnemonics\fR, but should instead accept the default.
|
|
.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mcpu=cpu_type"
|
|
Set architecture type, register usage, choice of mnemonics, and
|
|
instruction scheduling parameters for machine type \fIcpu_type\fR.
|
|
Supported values for \fIcpu_type\fR are \fBrios\fR, \fBrios1\fR,
|
|
\&\fBrsc\fR, \fBrios2\fR, \fBrs64a\fR, \fB601\fR, \fB602\fR,
|
|
\&\fB603\fR, \fB603e\fR, \fB604\fR, \fB604e\fR, \fB620\fR,
|
|
\&\fB630\fR, \fB740\fR, \fB750\fR, \fBpower\fR, \fBpower2\fR,
|
|
\&\fBpowerpc\fR, \fB403\fR, \fB505\fR, \fB801\fR, \fB821\fR,
|
|
\&\fB823\fR, and \fB860\fR and \fBcommon\fR. \fB\-mcpu=power\fR,
|
|
\&\fB\-mcpu=power2\fR, \fB\-mcpu=powerpc\fR, and \fB\-mcpu=powerpc64\fR
|
|
specify generic \s-1POWER\s0, \s-1POWER2\s0, pure 32\-bit PowerPC (i.e., not \s-1MPC601\s0),
|
|
and 64\-bit PowerPC architecture machine types, with an appropriate,
|
|
generic processor model assumed for scheduling purposes.
|
|
.Sp
|
|
Specifying any of the following options:
|
|
\&\fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR, \fB\-mcpu=rsc\fR,
|
|
\&\fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR
|
|
enables the \fB\-mpower\fR option and disables the \fB\-mpowerpc\fR option;
|
|
\&\fB\-mcpu=601\fR enables both the \fB\-mpower\fR and \fB\-mpowerpc\fR options.
|
|
All of \fB\-mcpu=rs64a\fR, \fB\-mcpu=602\fR, \fB\-mcpu=603\fR,
|
|
\&\fB\-mcpu=603e\fR, \fB\-mcpu=604\fR, \fB\-mcpu=620\fR, \fB\-mcpu=630\fR,
|
|
\&\fB\-mcpu=740\fR, and \fB\-mcpu=750\fR
|
|
enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option.
|
|
Exactly similarly, all of \fB\-mcpu=403\fR,
|
|
\&\fB\-mcpu=505\fR, \fB\-mcpu=821\fR, \fB\-mcpu=860\fR and \fB\-mcpu=powerpc\fR
|
|
enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option.
|
|
\&\fB\-mcpu=common\fR disables both the
|
|
\&\fB\-mpower\fR and \fB\-mpowerpc\fR options.
|
|
.Sp
|
|
\&\s-1AIX\s0 versions 4 or greater selects \fB\-mcpu=common\fR by default, so
|
|
that code will operate on all members of the \s-1RS/6000\s0 \s-1POWER\s0 and PowerPC
|
|
families. In that case, \s-1GCC\s0 will use only the instructions in the
|
|
common subset of both architectures plus some special \s-1AIX\s0 common-mode
|
|
calls, and will not use the \s-1MQ\s0 register. \s-1GCC\s0 assumes a generic
|
|
processor model for scheduling purposes.
|
|
.Sp
|
|
Specifying any of the options \fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR,
|
|
\&\fB\-mcpu=rsc\fR, \fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR also
|
|
disables the \fBnew-mnemonics\fR option. Specifying \fB\-mcpu=601\fR,
|
|
\&\fB\-mcpu=602\fR, \fB\-mcpu=603\fR, \fB\-mcpu=603e\fR, \fB\-mcpu=604\fR,
|
|
\&\fB\-mcpu=620\fR, \fB\-mcpu=630\fR, \fB\-mcpu=403\fR, \fB\-mcpu=505\fR,
|
|
\&\fB\-mcpu=821\fR, \fB\-mcpu=860\fR or \fB\-mcpu=powerpc\fR also enables
|
|
the \fBnew-mnemonics\fR option.
|
|
.Sp
|
|
Specifying \fB\-mcpu=403\fR, \fB\-mcpu=821\fR, or \fB\-mcpu=860\fR also
|
|
enables the \fB\-msoft-float\fR option.
|
|
.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mtune=cpu_type"
|
|
Set the instruction scheduling parameters for machine type
|
|
\&\fIcpu_type\fR, but do not set the architecture type, register usage,
|
|
choice of mnemonics like \fB\-mcpu=\fR\fIcpu_type\fR would. The same
|
|
values for \fIcpu_type\fR are used for \fB\-mtune=\fR\fIcpu_type\fR as
|
|
for \fB\-mcpu=\fR\fIcpu_type\fR. The \fB\-mtune=\fR\fIcpu_type\fR
|
|
option overrides the \fB\-mcpu=\fR\fIcpu_type\fR option in terms of
|
|
instruction scheduling parameters.
|
|
.Ip "\fB\-mfull-toc\fR" 4
|
|
.IX Item "-mfull-toc"
|
|
.PD 0
|
|
.Ip "\fB\-mno-fp-in-toc\fR" 4
|
|
.IX Item "-mno-fp-in-toc"
|
|
.Ip "\fB\-mno-sum-in-toc\fR" 4
|
|
.IX Item "-mno-sum-in-toc"
|
|
.Ip "\fB\-mminimal-toc\fR" 4
|
|
.IX Item "-mminimal-toc"
|
|
.PD
|
|
Modify generation of the \s-1TOC\s0 (Table Of Contents), which is created for
|
|
every executable file. The \fB\-mfull-toc\fR option is selected by
|
|
default. In that case, \s-1GCC\s0 will allocate at least one \s-1TOC\s0 entry for
|
|
each unique non-automatic variable reference in your program. \s-1GCC\s0
|
|
will also place floating-point constants in the \s-1TOC\s0. However, only
|
|
16,384 entries are available in the \s-1TOC\s0.
|
|
.Sp
|
|
If you receive a linker error message that saying you have overflowed
|
|
the available \s-1TOC\s0 space, you can reduce the amount of \s-1TOC\s0 space used
|
|
with the \fB\-mno-fp-in-toc\fR and \fB\-mno-sum-in-toc\fR options.
|
|
\&\fB\-mno-fp-in-toc\fR prevents \s-1GCC\s0 from putting floating-point
|
|
constants in the \s-1TOC\s0 and \fB\-mno-sum-in-toc\fR forces \s-1GCC\s0 to
|
|
generate code to calculate the sum of an address and a constant at
|
|
run-time instead of putting that sum into the \s-1TOC\s0. You may specify one
|
|
or both of these options. Each causes \s-1GCC\s0 to produce very slightly
|
|
slower and larger code at the expense of conserving \s-1TOC\s0 space.
|
|
.Sp
|
|
If you still run out of space in the \s-1TOC\s0 even when you specify both of
|
|
these options, specify \fB\-mminimal-toc\fR instead. This option causes
|
|
\&\s-1GCC\s0 to make only one \s-1TOC\s0 entry for every file. When you specify this
|
|
option, \s-1GCC\s0 will produce code that is slower and larger but which
|
|
uses extremely little \s-1TOC\s0 space. You may wish to use this option
|
|
only on files that contain less frequently executed code.
|
|
.Ip "\fB\-maix64\fR" 4
|
|
.IX Item "-maix64"
|
|
.PD 0
|
|
.Ip "\fB\-maix32\fR" 4
|
|
.IX Item "-maix32"
|
|
.PD
|
|
Enable 64\-bit \s-1AIX\s0 \s-1ABI\s0 and calling convention: 64\-bit pointers, 64\-bit
|
|
\&\f(CW\*(C`long\*(C'\fR type, and the infrastructure needed to support them.
|
|
Specifying \fB\-maix64\fR implies \fB\-mpowerpc64\fR and
|
|
\&\fB\-mpowerpc\fR, while \fB\-maix32\fR disables the 64\-bit \s-1ABI\s0 and
|
|
implies \fB\-mno-powerpc64\fR. \s-1GCC\s0 defaults to \fB\-maix32\fR.
|
|
.Ip "\fB\-mxl-call\fR" 4
|
|
.IX Item "-mxl-call"
|
|
.PD 0
|
|
.Ip "\fB\-mno-xl-call\fR" 4
|
|
.IX Item "-mno-xl-call"
|
|
.PD
|
|
On \s-1AIX\s0, pass floating-point arguments to prototyped functions beyond the
|
|
register save area (\s-1RSA\s0) on the stack in addition to argument FPRs. The
|
|
\&\s-1AIX\s0 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. \s-1AIX\s0 \s-1XL\s0
|
|
compilers access floating point arguments which do not fit in the
|
|
\&\s-1RSA\s0 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 \s-1AIX\s0
|
|
\&\s-1XL\s0 compilers without optimization.
|
|
.Ip "\fB\-mthreads\fR" 4
|
|
.IX Item "-mthreads"
|
|
Support \fI\s-1AIX\s0 Threads\fR. Link an application written to use
|
|
\&\fIpthreads\fR with special libraries and startup code to enable the
|
|
application to run.
|
|
.Ip "\fB\-mpe\fR" 4
|
|
.IX Item "-mpe"
|
|
Support \fI\s-1IBM\s0 \s-1RS/6000\s0 \s-1SP\s0\fR \fIParallel Environment\fR (\s-1PE\s0). Link an
|
|
application written to use message passing with special startup code to
|
|
enable the application to run. The system must have \s-1PE\s0 installed in the
|
|
standard location (\fI/usr/lpp/ppe.poe/\fR), or the \fIspecs\fR file
|
|
must be overridden with the \fB\-specs=\fR option to specify the
|
|
appropriate directory location. The Parallel Environment does not
|
|
support threads, so the \fB\-mpe\fR option and the \fB\-mthreads\fR
|
|
option are incompatible.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
.PD 0
|
|
.Ip "\fB\-mhard-float\fR" 4
|
|
.IX Item "-mhard-float"
|
|
.PD
|
|
Generate code that does not use (uses) the floating-point register set.
|
|
Software floating point emulation is provided if you use the
|
|
\&\fB\-msoft-float\fR option, and pass the option to \s-1GCC\s0 when linking.
|
|
.Ip "\fB\-mmultiple\fR" 4
|
|
.IX Item "-mmultiple"
|
|
.PD 0
|
|
.Ip "\fB\-mno-multiple\fR" 4
|
|
.IX Item "-mno-multiple"
|
|
.PD
|
|
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 \s-1POWER\s0 systems, and not
|
|
generated on PowerPC systems. Do not use \fB\-mmultiple\fR on little
|
|
endian PowerPC systems, since those instructions do not work when the
|
|
processor is in little endian mode. The exceptions are \s-1PPC740\s0 and
|
|
\&\s-1PPC750\s0 which permit the instructions usage in little endian mode.
|
|
.Ip "\fB\-mstring\fR" 4
|
|
.IX Item "-mstring"
|
|
.PD 0
|
|
.Ip "\fB\-mno-string\fR" 4
|
|
.IX Item "-mno-string"
|
|
.PD
|
|
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
|
|
\&\s-1POWER\s0 systems, and not generated on PowerPC systems. Do not use
|
|
\&\fB\-mstring\fR on little endian PowerPC systems, since those
|
|
instructions do not work when the processor is in little endian mode.
|
|
The exceptions are \s-1PPC740\s0 and \s-1PPC750\s0 which permit the instructions
|
|
usage in little endian mode.
|
|
.Ip "\fB\-mupdate\fR" 4
|
|
.IX Item "-mupdate"
|
|
.PD 0
|
|
.Ip "\fB\-mno-update\fR" 4
|
|
.IX Item "-mno-update"
|
|
.PD
|
|
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
|
|
\&\fB\-mno-update\fR, 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.
|
|
.Ip "\fB\-mfused-madd\fR" 4
|
|
.IX Item "-mfused-madd"
|
|
.PD 0
|
|
.Ip "\fB\-mno-fused-madd\fR" 4
|
|
.IX Item "-mno-fused-madd"
|
|
.PD
|
|
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.
|
|
.Ip "\fB\-mno-bit-align\fR" 4
|
|
.IX Item "-mno-bit-align"
|
|
.PD 0
|
|
.Ip "\fB\-mbit-align\fR" 4
|
|
.IX Item "-mbit-align"
|
|
.PD
|
|
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.
|
|
.Sp
|
|
For example, by default a structure containing nothing but 8
|
|
\&\f(CW\*(C`unsigned\*(C'\fR bitfields of length 1 would be aligned to a 4 byte
|
|
boundary and have a size of 4 bytes. By using \fB\-mno-bit-align\fR,
|
|
the structure would be aligned to a 1 byte boundary and be one byte in
|
|
size.
|
|
.Ip "\fB\-mno-strict-align\fR" 4
|
|
.IX Item "-mno-strict-align"
|
|
.PD 0
|
|
.Ip "\fB\-mstrict-align\fR" 4
|
|
.IX Item "-mstrict-align"
|
|
.PD
|
|
On System V.4 and embedded PowerPC systems do not (do) assume that
|
|
unaligned memory references will be handled by the system.
|
|
.Ip "\fB\-mrelocatable\fR" 4
|
|
.IX Item "-mrelocatable"
|
|
.PD 0
|
|
.Ip "\fB\-mno-relocatable\fR" 4
|
|
.IX Item "-mno-relocatable"
|
|
.PD
|
|
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 \fB\-mrelocatable\fR on any module, all objects linked together must
|
|
be compiled with \fB\-mrelocatable\fR or \fB\-mrelocatable-lib\fR.
|
|
.Ip "\fB\-mrelocatable-lib\fR" 4
|
|
.IX Item "-mrelocatable-lib"
|
|
.PD 0
|
|
.Ip "\fB\-mno-relocatable-lib\fR" 4
|
|
.IX Item "-mno-relocatable-lib"
|
|
.PD
|
|
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 \fB\-mrelocatable-lib\fR can be linked with either modules
|
|
compiled without \fB\-mrelocatable\fR and \fB\-mrelocatable-lib\fR or
|
|
with modules compiled with the \fB\-mrelocatable\fR options.
|
|
.Ip "\fB\-mno-toc\fR" 4
|
|
.IX Item "-mno-toc"
|
|
.PD 0
|
|
.Ip "\fB\-mtoc\fR" 4
|
|
.IX Item "-mtoc"
|
|
.PD
|
|
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.
|
|
.Ip "\fB\-mlittle\fR" 4
|
|
.IX Item "-mlittle"
|
|
.PD 0
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
.PD
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
processor in little endian mode. The \fB\-mlittle-endian\fR option is
|
|
the same as \fB\-mlittle\fR.
|
|
.Ip "\fB\-mbig\fR" 4
|
|
.IX Item "-mbig"
|
|
.PD 0
|
|
.Ip "\fB\-mbig-endian\fR" 4
|
|
.IX Item "-mbig-endian"
|
|
.PD
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
processor in big endian mode. The \fB\-mbig-endian\fR option is
|
|
the same as \fB\-mbig\fR.
|
|
.Ip "\fB\-mcall-sysv\fR" 4
|
|
.IX Item "-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 \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR.
|
|
.Ip "\fB\-mcall-sysv-eabi\fR" 4
|
|
.IX Item "-mcall-sysv-eabi"
|
|
Specify both \fB\-mcall-sysv\fR and \fB\-meabi\fR options.
|
|
.Ip "\fB\-mcall-sysv-noeabi\fR" 4
|
|
.IX Item "-mcall-sysv-noeabi"
|
|
Specify both \fB\-mcall-sysv\fR and \fB\-mno-eabi\fR options.
|
|
.Ip "\fB\-mcall-aix\fR" 4
|
|
.IX Item "-mcall-aix"
|
|
On System V.4 and embedded PowerPC systems compile code using calling
|
|
conventions that are similar to those used on \s-1AIX\s0. This is the
|
|
default if you configured \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR.
|
|
.Ip "\fB\-mcall-solaris\fR" 4
|
|
.IX Item "-mcall-solaris"
|
|
On System V.4 and embedded PowerPC systems compile code for the Solaris
|
|
operating system.
|
|
.Ip "\fB\-mcall-linux\fR" 4
|
|
.IX Item "-mcall-linux"
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
Linux-based \s-1GNU\s0 system.
|
|
.Ip "\fB\-mprototype\fR" 4
|
|
.IX Item "-mprototype"
|
|
.PD 0
|
|
.Ip "\fB\-mno-prototype\fR" 4
|
|
.IX Item "-mno-prototype"
|
|
.PD
|
|
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 (\fI\s-1CR\s0\fR) to
|
|
indicate whether floating point values were passed in the floating point
|
|
registers in case the function takes a variable arguments. With
|
|
\&\fB\-mprototype\fR, only calls to prototyped variable argument functions
|
|
will set or clear the bit.
|
|
.Ip "\fB\-msim\fR" 4
|
|
.IX Item "-msim"
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
\&\fIsim-crt0.o\fR and that the standard C libraries are \fIlibsim.a\fR and
|
|
\&\fIlibc.a\fR. This is the default for \fBpowerpc-*\-eabisim\fR.
|
|
configurations.
|
|
.Ip "\fB\-mmvme\fR" 4
|
|
.IX Item "-mmvme"
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
\&\fIcrt0.o\fR and the standard C libraries are \fIlibmvme.a\fR and
|
|
\&\fIlibc.a\fR.
|
|
.Ip "\fB\-mads\fR" 4
|
|
.IX Item "-mads"
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
\&\fIcrt0.o\fR and the standard C libraries are \fIlibads.a\fR and
|
|
\&\fIlibc.a\fR.
|
|
.Ip "\fB\-myellowknife\fR" 4
|
|
.IX Item "-myellowknife"
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
\&\fIcrt0.o\fR and the standard C libraries are \fIlibyk.a\fR and
|
|
\&\fIlibc.a\fR.
|
|
.Ip "\fB\-mvxworks\fR" 4
|
|
.IX Item "-mvxworks"
|
|
On System V.4 and embedded PowerPC systems, specify that you are
|
|
compiling for a VxWorks system.
|
|
.Ip "\fB\-memb\fR" 4
|
|
.IX Item "-memb"
|
|
On embedded PowerPC systems, set the \fI\s-1PPC_EMB\s0\fR bit in the \s-1ELF\s0 flags
|
|
header to indicate that \fBeabi\fR extended relocations are used.
|
|
.Ip "\fB\-meabi\fR" 4
|
|
.IX Item "-meabi"
|
|
.PD 0
|
|
.Ip "\fB\-mno-eabi\fR" 4
|
|
.IX Item "-mno-eabi"
|
|
.PD
|
|
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 \fB\-meabi\fR
|
|
means that the stack is aligned to an 8 byte boundary, a function
|
|
\&\f(CW\*(C`_\|_eabi\*(C'\fR is called to from \f(CW\*(C`main\*(C'\fR to set up the eabi
|
|
environment, and the \fB\-msdata\fR option can use both \f(CW\*(C`r2\*(C'\fR and
|
|
\&\f(CW\*(C`r13\*(C'\fR to point to two separate small data areas. Selecting
|
|
\&\fB\-mno-eabi\fR means that the stack is aligned to a 16 byte boundary,
|
|
do not call an initialization function from \f(CW\*(C`main\*(C'\fR, and the
|
|
\&\fB\-msdata\fR option will only use \f(CW\*(C`r13\*(C'\fR to point to a single
|
|
small data area. The \fB\-meabi\fR option is on by default if you
|
|
configured \s-1GCC\s0 using one of the \fBpowerpc*\-*\-eabi*\fR options.
|
|
.Ip "\fB\-msdata=eabi\fR" 4
|
|
.IX Item "-msdata=eabi"
|
|
On System V.4 and embedded PowerPC systems, put small initialized
|
|
\&\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata2\fR section, which
|
|
is pointed to by register \f(CW\*(C`r2\*(C'\fR. Put small initialized
|
|
non-\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata\fR section,
|
|
which is pointed to by register \f(CW\*(C`r13\*(C'\fR. Put small uninitialized
|
|
global and static data in the \fB.sbss\fR section, which is adjacent to
|
|
the \fB.sdata\fR section. The \fB\-msdata=eabi\fR option is
|
|
incompatible with the \fB\-mrelocatable\fR option. The
|
|
\&\fB\-msdata=eabi\fR option also sets the \fB\-memb\fR option.
|
|
.Ip "\fB\-msdata=sysv\fR" 4
|
|
.IX Item "-msdata=sysv"
|
|
On System V.4 and embedded PowerPC systems, put small global and static
|
|
data in the \fB.sdata\fR section, which is pointed to by register
|
|
\&\f(CW\*(C`r13\*(C'\fR. Put small uninitialized global and static data in the
|
|
\&\fB.sbss\fR section, which is adjacent to the \fB.sdata\fR section.
|
|
The \fB\-msdata=sysv\fR option is incompatible with the
|
|
\&\fB\-mrelocatable\fR option.
|
|
.Ip "\fB\-msdata=default\fR" 4
|
|
.IX Item "-msdata=default"
|
|
.PD 0
|
|
.Ip "\fB\-msdata\fR" 4
|
|
.IX Item "-msdata"
|
|
.PD
|
|
On System V.4 and embedded PowerPC systems, if \fB\-meabi\fR is used,
|
|
compile code the same as \fB\-msdata=eabi\fR, otherwise compile code the
|
|
same as \fB\-msdata=sysv\fR.
|
|
.Ip "\fB\-msdata-data\fR" 4
|
|
.IX Item "-msdata-data"
|
|
On System V.4 and embedded PowerPC systems, put small global and static
|
|
data in the \fB.sdata\fR section. Put small uninitialized global and
|
|
static data in the \fB.sbss\fR section. Do not use register \f(CW\*(C`r13\*(C'\fR
|
|
to address small data however. This is the default behavior unless
|
|
other \fB\-msdata\fR options are used.
|
|
.Ip "\fB\-msdata=none\fR" 4
|
|
.IX Item "-msdata=none"
|
|
.PD 0
|
|
.Ip "\fB\-mno-sdata\fR" 4
|
|
.IX Item "-mno-sdata"
|
|
.PD
|
|
On embedded PowerPC systems, put all initialized global and static data
|
|
in the \fB.data\fR section, and all uninitialized data in the
|
|
\&\fB.bss\fR section.
|
|
.Ip "\fB\-G\fR \fInum\fR" 4
|
|
.IX Item "-G num"
|
|
On embedded PowerPC systems, put global and static items less than or
|
|
equal to \fInum\fR bytes into the small data or bss sections instead of
|
|
the normal data or bss section. By default, \fInum\fR is 8. The
|
|
\&\fB\-G\fR \fInum\fR switch is also passed to the linker.
|
|
All modules should be compiled with the same \fB\-G\fR \fInum\fR value.
|
|
.Ip "\fB\-mregnames\fR" 4
|
|
.IX Item "-mregnames"
|
|
.PD 0
|
|
.Ip "\fB\-mno-regnames\fR" 4
|
|
.IX Item "-mno-regnames"
|
|
.PD
|
|
On System V.4 and embedded PowerPC systems do (do not) emit register
|
|
names in the assembly language output using symbolic forms.
|
|
.PP
|
|
.I "\s-1IBM\s0 \s-1RT\s0 Options"
|
|
.IX Subsection "IBM RT Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RT\s0 \s-1PC:\s0
|
|
.Ip "\fB\-min-line-mul\fR" 4
|
|
.IX Item "-min-line-mul"
|
|
Use an in-line code sequence for integer multiplies. This is the
|
|
default.
|
|
.Ip "\fB\-mcall-lib-mul\fR" 4
|
|
.IX Item "-mcall-lib-mul"
|
|
Call \f(CW\*(C`lmul$$\*(C'\fR for integer multiples.
|
|
.Ip "\fB\-mfull-fp-blocks\fR" 4
|
|
.IX Item "-mfull-fp-blocks"
|
|
Generate full-size floating point data blocks, including the minimum
|
|
amount of scratch space recommended by \s-1IBM\s0. This is the default.
|
|
.Ip "\fB\-mminimum-fp-blocks\fR" 4
|
|
.IX Item "-mminimum-fp-blocks"
|
|
Do not include extra scratch space in floating point data blocks. This
|
|
results in smaller code, but slower execution, since scratch space must
|
|
be allocated dynamically.
|
|
.Ip "\fB\-mfp-arg-in-fpregs\fR" 4
|
|
.IX Item "-mfp-arg-in-fpregs"
|
|
Use a calling sequence incompatible with the \s-1IBM\s0 calling convention in
|
|
which floating point arguments are passed in floating point registers.
|
|
Note that \f(CW\*(C`varargs.h\*(C'\fR and \f(CW\*(C`stdargs.h\*(C'\fR will not work with
|
|
floating point operands if this option is specified.
|
|
.Ip "\fB\-mfp-arg-in-gregs\fR" 4
|
|
.IX Item "-mfp-arg-in-gregs"
|
|
Use the normal calling convention for floating point arguments. This is
|
|
the default.
|
|
.Ip "\fB\-mhc-struct-return\fR" 4
|
|
.IX Item "-mhc-struct-return"
|
|
Return structures of more than one word in memory, rather than in a
|
|
register. This provides compatibility with the MetaWare HighC (hc)
|
|
compiler. Use the option \fB\-fpcc-struct-return\fR for compatibility
|
|
with the Portable C Compiler (pcc).
|
|
.Ip "\fB\-mnohc-struct-return\fR" 4
|
|
.IX Item "-mnohc-struct-return"
|
|
Return some structures of more than one word in registers, when
|
|
convenient. This is the default. For compatibility with the
|
|
IBM-supplied compilers, use the option \fB\-fpcc-struct-return\fR or the
|
|
option \fB\-mhc-struct-return\fR.
|
|
.PP
|
|
.I "\s-1MIPS\s0 Options"
|
|
.IX Subsection "MIPS Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1MIPS\s0 family of computers:
|
|
.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4
|
|
.IX Item "-mcpu=cpu type"
|
|
Assume the defaults for the machine type \fIcpu type\fR when scheduling
|
|
instructions. The choices for \fIcpu type\fR are \fBr2000\fR, \fBr3000\fR,
|
|
\&\fBr3900\fR, \fBr4000\fR, \fBr4100\fR, \fBr4300\fR, \fBr4400\fR,
|
|
\&\fBr4600\fR, \fBr4650\fR, \fBr5000\fR, \fBr6000\fR, \fBr8000\fR,
|
|
and \fBorion\fR. Additionally, the \fBr2000\fR, \fBr3000\fR,
|
|
\&\fBr4000\fR, \fBr5000\fR, and \fBr6000\fR can be abbreviated as
|
|
\&\fBr2k\fR (or \fBr2K\fR), \fBr3k\fR, etc. While picking a specific
|
|
\&\fIcpu type\fR will schedule things appropriately for that particular
|
|
chip, the compiler will not generate any code that does not meet level 1
|
|
of the \s-1MIPS\s0 \s-1ISA\s0 (instruction set architecture) without a \fB\-mipsX\fR
|
|
or \fB\-mabi\fR switch being used.
|
|
.Ip "\fB\-mips1\fR" 4
|
|
.IX Item "-mips1"
|
|
Issue instructions from level 1 of the \s-1MIPS\s0 \s-1ISA\s0. This is the default.
|
|
\&\fBr3000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level.
|
|
.Ip "\fB\-mips2\fR" 4
|
|
.IX Item "-mips2"
|
|
Issue instructions from level 2 of the \s-1MIPS\s0 \s-1ISA\s0 (branch likely, square
|
|
root instructions). \fBr6000\fR is the default \fIcpu type\fR at this
|
|
\&\s-1ISA\s0 level.
|
|
.Ip "\fB\-mips3\fR" 4
|
|
.IX Item "-mips3"
|
|
Issue instructions from level 3 of the \s-1MIPS\s0 \s-1ISA\s0 (64 bit instructions).
|
|
\&\fBr4000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level.
|
|
.Ip "\fB\-mips4\fR" 4
|
|
.IX Item "-mips4"
|
|
Issue instructions from level 4 of the \s-1MIPS\s0 \s-1ISA\s0 (conditional move,
|
|
prefetch, enhanced \s-1FPU\s0 instructions). \fBr8000\fR is the default
|
|
\&\fIcpu type\fR at this \s-1ISA\s0 level.
|
|
.Ip "\fB\-mfp32\fR" 4
|
|
.IX Item "-mfp32"
|
|
Assume that 32 32\-bit floating point registers are available. This is
|
|
the default.
|
|
.Ip "\fB\-mfp64\fR" 4
|
|
.IX Item "-mfp64"
|
|
Assume that 32 64\-bit floating point registers are available. This is
|
|
the default when the \fB\-mips3\fR option is used.
|
|
.Ip "\fB\-mgp32\fR" 4
|
|
.IX Item "-mgp32"
|
|
Assume that 32 32\-bit general purpose registers are available. This is
|
|
the default.
|
|
.Ip "\fB\-mgp64\fR" 4
|
|
.IX Item "-mgp64"
|
|
Assume that 32 64\-bit general purpose registers are available. This is
|
|
the default when the \fB\-mips3\fR option is used.
|
|
.Ip "\fB\-mint64\fR" 4
|
|
.IX Item "-mint64"
|
|
Force int and long types to be 64 bits wide. See \fB\-mlong32\fR for an
|
|
explanation of the default, and the width of pointers.
|
|
.Ip "\fB\-mlong64\fR" 4
|
|
.IX Item "-mlong64"
|
|
Force long types to be 64 bits wide. See \fB\-mlong32\fR for an
|
|
explanation of the default, and the width of pointers.
|
|
.Ip "\fB\-mlong32\fR" 4
|
|
.IX Item "-mlong32"
|
|
Force long, int, and pointer types to be 32 bits wide.
|
|
.Sp
|
|
If none of \fB\-mlong32\fR, \fB\-mlong64\fR, or \fB\-mint64\fR are set,
|
|
the size of ints, longs, and pointers depends on the \s-1ABI\s0 and \s-1ISA\s0 chosen.
|
|
For \fB\-mabi=32\fR, and \fB\-mabi=n32\fR, ints and longs are 32 bits
|
|
wide. For \fB\-mabi=64\fR, ints are 32 bits, and longs are 64 bits wide.
|
|
For \fB\-mabi=eabi\fR and either \fB\-mips1\fR or \fB\-mips2\fR, ints
|
|
and longs are 32 bits wide. For \fB\-mabi=eabi\fR and higher ISAs, ints
|
|
are 32 bits, and longs are 64 bits wide. The width of pointer types is
|
|
the smaller of the width of longs or the width of general purpose
|
|
registers (which in turn depends on the \s-1ISA\s0).
|
|
.Ip "\fB\-mabi=32\fR" 4
|
|
.IX Item "-mabi=32"
|
|
.PD 0
|
|
.Ip "\fB\-mabi=o64\fR" 4
|
|
.IX Item "-mabi=o64"
|
|
.Ip "\fB\-mabi=n32\fR" 4
|
|
.IX Item "-mabi=n32"
|
|
.Ip "\fB\-mabi=64\fR" 4
|
|
.IX Item "-mabi=64"
|
|
.Ip "\fB\-mabi=eabi\fR" 4
|
|
.IX Item "-mabi=eabi"
|
|
.PD
|
|
Generate code for the indicated \s-1ABI\s0. The default instruction level is
|
|
\&\fB\-mips1\fR for \fB32\fR, \fB\-mips3\fR for \fBn32\fR, and
|
|
\&\fB\-mips4\fR otherwise. Conversely, with \fB\-mips1\fR or
|
|
\&\fB\-mips2\fR, the default \s-1ABI\s0 is \fB32\fR; otherwise, the default \s-1ABI\s0
|
|
is \fB64\fR.
|
|
.Ip "\fB\-mmips-as\fR" 4
|
|
.IX Item "-mmips-as"
|
|
Generate code for the \s-1MIPS\s0 assembler, and invoke \fImips-tfile\fR to
|
|
add normal debug information. This is the default for all
|
|
platforms except for the \s-1OSF/1\s0 reference platform, using the OSF/rose
|
|
object format. If the either of the \fB\-gstabs\fR or \fB\-gstabs+\fR
|
|
switches are used, the \fImips-tfile\fR program will encapsulate the
|
|
stabs within \s-1MIPS\s0 \s-1ECOFF\s0.
|
|
.Ip "\fB\-mgas\fR" 4
|
|
.IX Item "-mgas"
|
|
Generate code for the \s-1GNU\s0 assembler. This is the default on the \s-1OSF/1\s0
|
|
reference platform, using the OSF/rose object format. Also, this is
|
|
the default if the configure option \fB\*(--with-gnu-as\fR is used.
|
|
.Ip "\fB\-msplit-addresses\fR" 4
|
|
.IX Item "-msplit-addresses"
|
|
.PD 0
|
|
.Ip "\fB\-mno-split-addresses\fR" 4
|
|
.IX Item "-mno-split-addresses"
|
|
.PD
|
|
Generate code to load the high and low parts of address constants separately.
|
|
This allows \f(CW\*(C`gcc\*(C'\fR to optimize away redundant loads of the high order
|
|
bits of addresses. This optimization requires \s-1GNU\s0 as and \s-1GNU\s0 ld.
|
|
This optimization is enabled by default for some embedded targets where
|
|
\&\s-1GNU\s0 as and \s-1GNU\s0 ld are standard.
|
|
.Ip "\fB\-mrnames\fR" 4
|
|
.IX Item "-mrnames"
|
|
.PD 0
|
|
.Ip "\fB\-mno-rnames\fR" 4
|
|
.IX Item "-mno-rnames"
|
|
.PD
|
|
The \fB\-mrnames\fR switch says to output code using the \s-1MIPS\s0 software
|
|
names for the registers, instead of the hardware names (ie, \fIa0\fR
|
|
instead of \fI$4\fR). The only known assembler that supports this option
|
|
is the Algorithmics assembler.
|
|
.Ip "\fB\-mgpopt\fR" 4
|
|
.IX Item "-mgpopt"
|
|
.PD 0
|
|
.Ip "\fB\-mno-gpopt\fR" 4
|
|
.IX Item "-mno-gpopt"
|
|
.PD
|
|
The \fB\-mgpopt\fR switch says to write all of the data declarations
|
|
before the instructions in the text section, this allows the \s-1MIPS\s0
|
|
assembler to generate one word memory references instead of using two
|
|
words for short global or static data items. This is on by default if
|
|
optimization is selected.
|
|
.Ip "\fB\-mstats\fR" 4
|
|
.IX Item "-mstats"
|
|
.PD 0
|
|
.Ip "\fB\-mno-stats\fR" 4
|
|
.IX Item "-mno-stats"
|
|
.PD
|
|
For each non-inline function processed, the \fB\-mstats\fR switch
|
|
causes the compiler to emit one line to the standard error file to
|
|
print statistics about the program (number of registers saved, stack
|
|
size, etc.).
|
|
.Ip "\fB\-mmemcpy\fR" 4
|
|
.IX Item "-mmemcpy"
|
|
.PD 0
|
|
.Ip "\fB\-mno-memcpy\fR" 4
|
|
.IX Item "-mno-memcpy"
|
|
.PD
|
|
The \fB\-mmemcpy\fR switch makes all block moves call the appropriate
|
|
string function (\fBmemcpy\fR or \fBbcopy\fR) instead of possibly
|
|
generating inline code.
|
|
.Ip "\fB\-mmips-tfile\fR" 4
|
|
.IX Item "-mmips-tfile"
|
|
.PD 0
|
|
.Ip "\fB\-mno-mips-tfile\fR" 4
|
|
.IX Item "-mno-mips-tfile"
|
|
.PD
|
|
The \fB\-mno-mips-tfile\fR switch causes the compiler not
|
|
postprocess the object file with the \fImips-tfile\fR program,
|
|
after the \s-1MIPS\s0 assembler has generated it to add debug support. If
|
|
\&\fImips-tfile\fR is not run, then no local variables will be
|
|
available to the debugger. In addition, \fIstage2\fR and
|
|
\&\fIstage3\fR objects will have the temporary file names passed to the
|
|
assembler embedded in the object file, which means the objects will
|
|
not compare the same. The \fB\-mno-mips-tfile\fR switch should only
|
|
be used when there are bugs in the \fImips-tfile\fR program that
|
|
prevents compilation.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0.
|
|
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.
|
|
.Ip "\fB\-mhard-float\fR" 4
|
|
.IX Item "-mhard-float"
|
|
Generate output containing floating point instructions. This is the
|
|
default if you use the unmodified sources.
|
|
.Ip "\fB\-mabicalls\fR" 4
|
|
.IX Item "-mabicalls"
|
|
.PD 0
|
|
.Ip "\fB\-mno-abicalls\fR" 4
|
|
.IX Item "-mno-abicalls"
|
|
.PD
|
|
Emit (or do not emit) the pseudo operations \fB.abicalls\fR,
|
|
\&\fB.cpload\fR, and \fB.cprestore\fR that some System V.4 ports use for
|
|
position independent code.
|
|
.Ip "\fB\-mlong-calls\fR" 4
|
|
.IX Item "-mlong-calls"
|
|
.PD 0
|
|
.Ip "\fB\-mno-long-calls\fR" 4
|
|
.IX Item "-mno-long-calls"
|
|
.PD
|
|
Do all calls with the \fB\s-1JALR\s0\fR instruction, which requires
|
|
loading up a function's address into a register before the call.
|
|
You need to use this switch, if you call outside of the current
|
|
512 megabyte segment to functions that are not through pointers.
|
|
.Ip "\fB\-mhalf-pic\fR" 4
|
|
.IX Item "-mhalf-pic"
|
|
.PD 0
|
|
.Ip "\fB\-mno-half-pic\fR" 4
|
|
.IX Item "-mno-half-pic"
|
|
.PD
|
|
Put pointers to extern references into the data section and load them
|
|
up, rather than put the references in the text section.
|
|
.Ip "\fB\-membedded-pic\fR" 4
|
|
.IX Item "-membedded-pic"
|
|
.PD 0
|
|
.Ip "\fB\-mno-embedded-pic\fR" 4
|
|
.IX Item "-mno-embedded-pic"
|
|
.PD
|
|
Generate \s-1PIC\s0 code suitable for some embedded systems. All calls are
|
|
made using \s-1PC\s0 relative address, and all data is addressed using the \f(CW$gp\fR
|
|
register. No more than 65536 bytes of global data may be used. This
|
|
requires \s-1GNU\s0 as and \s-1GNU\s0 ld which do most of the work. This currently
|
|
only works on targets which use \s-1ECOFF\s0; it does not work with \s-1ELF\s0.
|
|
.Ip "\fB\-membedded-data\fR" 4
|
|
.IX Item "-membedded-data"
|
|
.PD 0
|
|
.Ip "\fB\-mno-embedded-data\fR" 4
|
|
.IX Item "-mno-embedded-data"
|
|
.PD
|
|
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 \s-1RAM\s0 required
|
|
when executing, and thus may be preferred for some embedded systems.
|
|
.Ip "\fB\-muninit-const-in-rodata\fR" 4
|
|
.IX Item "-muninit-const-in-rodata"
|
|
.PD 0
|
|
.Ip "\fB\-mno-uninit-const-in-rodata\fR" 4
|
|
.IX Item "-mno-uninit-const-in-rodata"
|
|
.PD
|
|
When used together with \-membedded-data, it will always store uninitialized
|
|
const variables in the read-only data section.
|
|
.Ip "\fB\-msingle-float\fR" 4
|
|
.IX Item "-msingle-float"
|
|
.PD 0
|
|
.Ip "\fB\-mdouble-float\fR" 4
|
|
.IX Item "-mdouble-float"
|
|
.PD
|
|
The \fB\-msingle-float\fR switch tells gcc to assume that the floating
|
|
point coprocessor only supports single precision operations, as on the
|
|
\&\fBr4650\fR chip. The \fB\-mdouble-float\fR switch permits gcc to use
|
|
double precision operations. This is the default.
|
|
.Ip "\fB\-mmad\fR" 4
|
|
.IX Item "-mmad"
|
|
.PD 0
|
|
.Ip "\fB\-mno-mad\fR" 4
|
|
.IX Item "-mno-mad"
|
|
.PD
|
|
Permit use of the \fBmad\fR, \fBmadu\fR and \fBmul\fR instructions,
|
|
as on the \fBr4650\fR chip.
|
|
.Ip "\fB\-m4650\fR" 4
|
|
.IX Item "-m4650"
|
|
Turns on \fB\-msingle-float\fR, \fB\-mmad\fR, and, at least for now,
|
|
\&\fB\-mcpu=r4650\fR.
|
|
.Ip "\fB\-mips16\fR" 4
|
|
.IX Item "-mips16"
|
|
.PD 0
|
|
.Ip "\fB\-mno-mips16\fR" 4
|
|
.IX Item "-mno-mips16"
|
|
.PD
|
|
Enable 16\-bit instructions.
|
|
.Ip "\fB\-mentry\fR" 4
|
|
.IX Item "-mentry"
|
|
Use the entry and exit pseudo ops. This option can only be used with
|
|
\&\fB\-mips16\fR.
|
|
.Ip "\fB\-EL\fR" 4
|
|
.IX Item "-EL"
|
|
Compile code for the processor in little endian mode.
|
|
The requisite libraries are assumed to exist.
|
|
.Ip "\fB\-EB\fR" 4
|
|
.IX Item "-EB"
|
|
Compile code for the processor in big endian mode.
|
|
The requisite libraries are assumed to exist.
|
|
.Ip "\fB\-G\fR \fInum\fR" 4
|
|
.IX Item "-G num"
|
|
Put global and static items less than or equal to \fInum\fR bytes into
|
|
the small data or bss sections instead of the normal data or bss
|
|
section. This allows the assembler to emit one word memory reference
|
|
instructions based on the global pointer (\fIgp\fR or \fI$28\fR),
|
|
instead of the normal two words used. By default, \fInum\fR is 8 when
|
|
the \s-1MIPS\s0 assembler is used, and 0 when the \s-1GNU\s0 assembler is used. The
|
|
\&\fB\-G\fR \fInum\fR switch is also passed to the assembler and linker.
|
|
All modules should be compiled with the same \fB\-G\fR \fInum\fR
|
|
value.
|
|
.Ip "\fB\-nocpp\fR" 4
|
|
.IX Item "-nocpp"
|
|
Tell the \s-1MIPS\s0 assembler to not run its preprocessor over user
|
|
assembler files (with a \fB.s\fR suffix) when assembling them.
|
|
.Ip "\fB\-mfix7000\fR" 4
|
|
.IX Item "-mfix7000"
|
|
Pass an option to gas which will cause nops to be inserted if
|
|
the read of the destination register of an mfhi or mflo instruction
|
|
occurs in the following two instructions.
|
|
.Ip "\fB\-no-crt0\fR" 4
|
|
.IX Item "-no-crt0"
|
|
Do not include the default crt0.
|
|
.PP
|
|
.I "Intel 386 Options"
|
|
.IX Subsection "Intel 386 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the i386 family of computers:
|
|
.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4
|
|
.IX Item "-mcpu=cpu type"
|
|
Assume the defaults for the machine type \fIcpu type\fR when scheduling
|
|
instructions. The choices for \fIcpu type\fR are \fBi386\fR,
|
|
\&\fBi486\fR, \fBi586\fR, \fBi686\fR, \fBpentium\fR,
|
|
\&\fBpentiumpro\fR, \fBk6\fR, and \fBathlon\fR
|
|
.Sp
|
|
While picking a specific \fIcpu type\fR will schedule things appropriately
|
|
for that particular chip, the compiler will not generate any code that
|
|
does not run on the i386 without the \fB\-march=\fR\fIcpu type\fR option
|
|
being used. \fBi586\fR is equivalent to \fBpentium\fR and \fBi686\fR
|
|
is equivalent to \fBpentiumpro\fR. \fBk6\fR is the \s-1AMD\s0 chip as
|
|
opposed to the Intel ones.
|
|
.Ip "\fB\-march=\fR\fIcpu type\fR" 4
|
|
.IX Item "-march=cpu type"
|
|
Generate instructions for the machine type \fIcpu type\fR. The choices
|
|
for \fIcpu type\fR are the same as for \fB\-mcpu\fR. Moreover,
|
|
specifying \fB\-march=\fR\fIcpu type\fR implies \fB\-mcpu=\fR\fIcpu type\fR.
|
|
.Ip "\fB\-m386\fR" 4
|
|
.IX Item "-m386"
|
|
.PD 0
|
|
.Ip "\fB\-m486\fR" 4
|
|
.IX Item "-m486"
|
|
.Ip "\fB\-mpentium\fR" 4
|
|
.IX Item "-mpentium"
|
|
.Ip "\fB\-mpentiumpro\fR" 4
|
|
.IX Item "-mpentiumpro"
|
|
.PD
|
|
Synonyms for \-mcpu=i386, \-mcpu=i486, \-mcpu=pentium, and \-mcpu=pentiumpro
|
|
respectively. These synonyms are deprecated.
|
|
.Ip "\fB\-mintel-syntax\fR" 4
|
|
.IX Item "-mintel-syntax"
|
|
Emit assembly using Intel syntax opcodes instead of \s-1AT&T\s0 syntax.
|
|
.Ip "\fB\-mieee-fp\fR" 4
|
|
.IX Item "-mieee-fp"
|
|
.PD 0
|
|
.Ip "\fB\-mno-ieee-fp\fR" 4
|
|
.IX Item "-mno-ieee-fp"
|
|
.PD
|
|
Control whether or not the compiler uses \s-1IEEE\s0 floating point
|
|
comparisons. These handle correctly the case where the result of a
|
|
comparison is unordered.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0.
|
|
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.
|
|
.Sp
|
|
On machines where a function returns floating point results in the 80387
|
|
register stack, some floating point opcodes may be emitted even if
|
|
\&\fB\-msoft-float\fR is used.
|
|
.Ip "\fB\-mno-fp-ret-in-387\fR" 4
|
|
.IX Item "-mno-fp-ret-in-387"
|
|
Do not use the \s-1FPU\s0 registers for return values of functions.
|
|
.Sp
|
|
The usual calling convention has functions return values of types
|
|
\&\f(CW\*(C`float\*(C'\fR and \f(CW\*(C`double\*(C'\fR in an \s-1FPU\s0 register, even if there
|
|
is no \s-1FPU\s0. The idea is that the operating system should emulate
|
|
an \s-1FPU\s0.
|
|
.Sp
|
|
The option \fB\-mno-fp-ret-in-387\fR causes such values to be returned
|
|
in ordinary \s-1CPU\s0 registers instead.
|
|
.Ip "\fB\-mno-fancy-math-387\fR" 4
|
|
.IX Item "-mno-fancy-math-387"
|
|
Some 387 emulators do not support the \f(CW\*(C`sin\*(C'\fR, \f(CW\*(C`cos\*(C'\fR and
|
|
\&\f(CW\*(C`sqrt\*(C'\fR instructions for the 387. Specify this option to avoid
|
|
generating those instructions. This option is the default on FreeBSD.
|
|
As of revision 2.6.1, these instructions are not generated unless you
|
|
also use the \fB\-ffast-math\fR switch.
|
|
.Ip "\fB\-malign-double\fR" 4
|
|
.IX Item "-malign-double"
|
|
.PD 0
|
|
.Ip "\fB\-mno-align-double\fR" 4
|
|
.IX Item "-mno-align-double"
|
|
.PD
|
|
Control whether \s-1GCC\s0 aligns \f(CW\*(C`double\*(C'\fR, \f(CW\*(C`long double\*(C'\fR, and
|
|
\&\f(CW\*(C`long long\*(C'\fR variables on a two word boundary or a one word
|
|
boundary. Aligning \f(CW\*(C`double\*(C'\fR variables on a two word boundary will
|
|
produce code that runs somewhat faster on a \fBPentium\fR at the
|
|
expense of more memory.
|
|
.Ip "\fB\-m128bit-long-double\fR" 4
|
|
.IX Item "-m128bit-long-double"
|
|
.PD 0
|
|
.Ip "\fB\-m128bit-long-double\fR" 4
|
|
.IX Item "-m128bit-long-double"
|
|
.PD
|
|
Control the size of \f(CW\*(C`long double\*(C'\fR type. i386 application binary interface
|
|
specify the size to be 12 bytes, while modern architectures (Pentium and newer)
|
|
preffer \f(CW\*(C`long double\*(C'\fR aligned to 8 or 16 byte boundary. This is
|
|
impossible to reach with 12 byte long doubles in the array accesses.
|
|
.Sp
|
|
\&\fBWarning:\fR if you use the \fB\-m128bit-long-double\fR switch, the
|
|
structures and arrays containing \f(CW\*(C`long double\*(C'\fR will change their size as
|
|
well as function calling convention for function taking \f(CW\*(C`long double\*(C'\fR
|
|
will be modified.
|
|
.Ip "\fB\-m96bit-long-double\fR" 4
|
|
.IX Item "-m96bit-long-double"
|
|
.PD 0
|
|
.Ip "\fB\-m96bit-long-double\fR" 4
|
|
.IX Item "-m96bit-long-double"
|
|
.PD
|
|
Set the size of \f(CW\*(C`long double\*(C'\fR to 96 bits as required by the i386
|
|
application binary interface. This is the default.
|
|
.Ip "\fB\-msvr3\-shlib\fR" 4
|
|
.IX Item "-msvr3-shlib"
|
|
.PD 0
|
|
.Ip "\fB\-mno-svr3\-shlib\fR" 4
|
|
.IX Item "-mno-svr3-shlib"
|
|
.PD
|
|
Control whether \s-1GCC\s0 places uninitialized locals into \f(CW\*(C`bss\*(C'\fR or
|
|
\&\f(CW\*(C`data\*(C'\fR. \fB\-msvr3\-shlib\fR places these locals into \f(CW\*(C`bss\*(C'\fR.
|
|
These options are meaningful only on System V Release 3.
|
|
.Ip "\fB\-mno-wide-multiply\fR" 4
|
|
.IX Item "-mno-wide-multiply"
|
|
.PD 0
|
|
.Ip "\fB\-mwide-multiply\fR" 4
|
|
.IX Item "-mwide-multiply"
|
|
.PD
|
|
Control whether \s-1GCC\s0 uses the \f(CW\*(C`mul\*(C'\fR and \f(CW\*(C`imul\*(C'\fR that produce
|
|
64 bit results in \f(CW\*(C`eax:edx\*(C'\fR from 32 bit operands to do \f(CW\*(C`long
|
|
long\*(C'\fR multiplies and 32\-bit division by constants.
|
|
.Ip "\fB\-mrtd\fR" 4
|
|
.IX Item "-mrtd"
|
|
Use a different function-calling convention, in which functions that
|
|
take a fixed number of arguments return with the \f(CW\*(C`ret\*(C'\fR \fInum\fR
|
|
instruction, which pops their arguments while returning. This saves one
|
|
instruction in the caller since there is no need to pop the arguments
|
|
there.
|
|
.Sp
|
|
You can specify that an individual function is called with this calling
|
|
sequence with the function attribute \fBstdcall\fR. You can also
|
|
override the \fB\-mrtd\fR option by using the function attribute
|
|
\&\fBcdecl\fR.
|
|
.Sp
|
|
\&\fBWarning:\fR 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.
|
|
.Sp
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR);
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
.Sp
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
.Ip "\fB\-mreg-alloc=\fR\fIregs\fR" 4
|
|
.IX Item "-mreg-alloc=regs"
|
|
Control the default allocation order of integer registers. The
|
|
string \fIregs\fR is a series of letters specifying a register. The
|
|
supported letters are: \f(CW\*(C`a\*(C'\fR allocate \s-1EAX\s0; \f(CW\*(C`b\*(C'\fR allocate \s-1EBX\s0;
|
|
\&\f(CW\*(C`c\*(C'\fR allocate \s-1ECX\s0; \f(CW\*(C`d\*(C'\fR allocate \s-1EDX\s0; \f(CW\*(C`S\*(C'\fR allocate \s-1ESI\s0;
|
|
\&\f(CW\*(C`D\*(C'\fR allocate \s-1EDI\s0; \f(CW\*(C`B\*(C'\fR allocate \s-1EBP\s0.
|
|
.Ip "\fB\-mregparm=\fR\fInum\fR" 4
|
|
.IX Item "-mregparm=num"
|
|
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 \fBregparm\fR.
|
|
.Sp
|
|
\&\fBWarning:\fR if you use this switch, and
|
|
\&\fInum\fR is nonzero, then you must build all modules with the same
|
|
value, including any libraries. This includes the system libraries and
|
|
startup modules.
|
|
.Ip "\fB\-malign-loops=\fR\fInum\fR" 4
|
|
.IX Item "-malign-loops=num"
|
|
Align loops to a 2 raised to a \fInum\fR byte boundary. If
|
|
\&\fB\-malign-loops\fR is not specified, the default is 2 unless
|
|
gas 2.8 (or later) is being used in which case the default is
|
|
to align the loop on a 16 byte boundary if it is less than 8
|
|
bytes away.
|
|
.Ip "\fB\-malign-jumps=\fR\fInum\fR" 4
|
|
.IX Item "-malign-jumps=num"
|
|
Align instructions that are only jumped to to a 2 raised to a \fInum\fR
|
|
byte boundary. If \fB\-malign-jumps\fR is not specified, the default is
|
|
2 if optimizing for a 386, and 4 if optimizing for a 486 unless
|
|
gas 2.8 (or later) is being used in which case the default is
|
|
to align the instruction on a 16 byte boundary if it is less
|
|
than 8 bytes away.
|
|
.Ip "\fB\-malign-functions=\fR\fInum\fR" 4
|
|
.IX Item "-malign-functions=num"
|
|
Align the start of functions to a 2 raised to \fInum\fR byte boundary.
|
|
If \fB\-malign-functions\fR is not specified, the default is 2 if optimizing
|
|
for a 386, and 4 if optimizing for a 486.
|
|
.Ip "\fB\-mpreferred-stack-boundary=\fR\fInum\fR" 4
|
|
.IX Item "-mpreferred-stack-boundary=num"
|
|
Attempt to keep the stack boundary aligned to a 2 raised to \fInum\fR
|
|
byte boundary. If \fB\-mpreferred-stack-boundary\fR is not specified,
|
|
the default is 4 (16 bytes or 128 bits).
|
|
.Sp
|
|
The stack is required to be aligned on a 4 byte boundary. On Pentium
|
|
and PentiumPro, \f(CW\*(C`double\*(C'\fR and \f(CW\*(C`long double\*(C'\fR values should be
|
|
aligned to an 8 byte boundary (see \fB\-malign-double\fR) or suffer
|
|
significant run time performance penalties. On Pentium \s-1III\s0, the
|
|
Streaming \s-1SIMD\s0 Extension (\s-1SSE\s0) data type \f(CW\*(C`_\|_m128\*(C'\fR suffers similar
|
|
penalties if it is not 16 byte aligned.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
This extra alignment does consume extra stack space. Code that is sensitive
|
|
to stack space usage, such as embedded systems and operating system kernels,
|
|
may want to reduce the preferred alignment to
|
|
\&\fB\-mpreferred-stack-boundary=2\fR.
|
|
.Ip "\fB\-mpush-args\fR" 4
|
|
.IX Item "-mpush-args"
|
|
Use \s-1PUSH\s0 operations to store outgoing parameters. This method is shorter
|
|
and usually equally fast as method using \s-1SUB/MOV\s0 operations and is enabled
|
|
by default. In some cases disabling it may improve performance because of
|
|
improved scheduling and reduced dependencies.
|
|
.Ip "\fB\-maccumulate-outgoing-args\fR" 4
|
|
.IX Item "-maccumulate-outgoing-args"
|
|
If enabled, the maximum amount of space required for outgoing arguments will be
|
|
computed in the function prologue. This in 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 \-mno-push-args.
|
|
.Ip "\fB\-mthreads\fR" 4
|
|
.IX Item "-mthreads"
|
|
Support thread-safe exception handling on \fBMingw32\fR. Code that relies
|
|
on thread-safe exception handling must compile and link all code with the
|
|
\&\fB\-mthreads\fR option. When compiling, \fB\-mthreads\fR defines
|
|
\&\fB\-D_MT\fR; when linking, it links in a special thread helper library
|
|
\&\fB\-lmingwthrd\fR which cleans up per thread exception handling data.
|
|
.Ip "\fB\-mno-align-stringops\fR" 4
|
|
.IX Item "-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 don't know about it.
|
|
.Ip "\fB\-minline-all-stringops\fR" 4
|
|
.IX Item "-minline-all-stringops"
|
|
By default \s-1GCC\s0 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.
|
|
.PP
|
|
.I "\s-1HPPA\s0 Options"
|
|
.IX Subsection "HPPA Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1HPPA\s0 family of computers:
|
|
.Ip "\fB\-march=\fR\fIarchitecture type\fR" 4
|
|
.IX Item "-march=architecture type"
|
|
Generate code for the specified architecture. The choices for
|
|
\&\fIarchitecture type\fR are \fB1.0\fR for \s-1PA\s0 1.0, \fB1.1\fR for \s-1PA\s0
|
|
1.1, and \fB2.0\fR for \s-1PA\s0 2.0 processors. Refer to
|
|
\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 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.
|
|
.Sp
|
|
\&\s-1PA\s0 2.0 support currently requires gas snapshot 19990413 or later. The
|
|
next release of binutils (current is 2.9.1) will probably contain \s-1PA\s0 2.0
|
|
support.
|
|
.Ip "\fB\-mpa-risc-1\-0\fR" 4
|
|
.IX Item "-mpa-risc-1-0"
|
|
.PD 0
|
|
.Ip "\fB\-mpa-risc-1\-1\fR" 4
|
|
.IX Item "-mpa-risc-1-1"
|
|
.Ip "\fB\-mpa-risc-2\-0\fR" 4
|
|
.IX Item "-mpa-risc-2-0"
|
|
.PD
|
|
Synonyms for \-march=1.0, \-march=1.1, and \-march=2.0 respectively.
|
|
.Ip "\fB\-mbig-switch\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-mjump-in-delay\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-mdisable-fpregs\fR" 4
|
|
.IX Item "-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.
|
|
.Ip "\fB\-mdisable-indexing\fR" 4
|
|
.IX Item "-mdisable-indexing"
|
|
Prevent the compiler from using indexing address modes. This avoids some
|
|
rather obscure problems when compiling \s-1MIG\s0 generated code under \s-1MACH\s0.
|
|
.Ip "\fB\-mno-space-regs\fR" 4
|
|
.IX Item "-mno-space-regs"
|
|
Generate code that assumes the target has no space registers. This allows
|
|
\&\s-1GCC\s0 to generate faster indirect calls and use unscaled index address modes.
|
|
.Sp
|
|
Such code is suitable for level 0 \s-1PA\s0 systems and kernels.
|
|
.Ip "\fB\-mfast-indirect-calls\fR" 4
|
|
.IX Item "-mfast-indirect-calls"
|
|
Generate code that assumes calls never cross space boundaries. This
|
|
allows \s-1GCC\s0 to emit code which performs faster indirect calls.
|
|
.Sp
|
|
This option will not work in the presence of shared libraries or nested
|
|
functions.
|
|
.Ip "\fB\-mlong-load-store\fR" 4
|
|
.IX Item "-mlong-load-store"
|
|
Generate 3\-instruction load and store sequences as sometimes required by
|
|
the \s-1HP-UX\s0 10 linker. This is equivalent to the \fB+k\fR option to
|
|
the \s-1HP\s0 compilers.
|
|
.Ip "\fB\-mportable-runtime\fR" 4
|
|
.IX Item "-mportable-runtime"
|
|
Use the portable calling conventions proposed by \s-1HP\s0 for \s-1ELF\s0 systems.
|
|
.Ip "\fB\-mgas\fR" 4
|
|
.IX Item "-mgas"
|
|
Enable the use of assembler directives only \s-1GAS\s0 understands.
|
|
.Ip "\fB\-mschedule=\fR\fIcpu type\fR" 4
|
|
.IX Item "-mschedule=cpu type"
|
|
Schedule code according to the constraints for the machine type
|
|
\&\fIcpu type\fR. The choices for \fIcpu type\fR are \fB700\fR
|
|
\&\fB7100\fR, \fB7100LC\fR, \fB7200\fR, and \fB8000\fR. Refer to
|
|
\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 system to determine the
|
|
proper scheduling option for your machine.
|
|
.Ip "\fB\-mlinker-opt\fR" 4
|
|
.IX Item "-mlinker-opt"
|
|
Enable the optimization pass in the \s-1HPUX\s0 linker. Note this makes symbolic
|
|
debugging impossible. It also triggers a bug in the \s-1HPUX\s0 8 and \s-1HPUX\s0 9 linkers
|
|
in which they give bogus error messages when linking some programs.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries are not available for all \s-1HPPA\s0
|
|
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 \fBhppa1.1\-*\-pro\fR
|
|
does provide software floating point support.
|
|
.Sp
|
|
\&\fB\-msoft-float\fR changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile \fIall\fR of a program with
|
|
this option. In particular, you need to compile \fIlibgcc.a\fR, the
|
|
library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for
|
|
this to work.
|
|
.PP
|
|
.I "Intel 960 Options"
|
|
.IX Subsection "Intel 960 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the Intel 960 implementations:
|
|
.Ip "\fB\-m\fR\fIcpu type\fR" 4
|
|
.IX Item "-mcpu type"
|
|
Assume the defaults for the machine type \fIcpu type\fR for some of
|
|
the other options, including instruction scheduling, floating point
|
|
support, and addressing modes. The choices for \fIcpu type\fR are
|
|
\&\fBka\fR, \fBkb\fR, \fBmc\fR, \fBca\fR, \fBcf\fR,
|
|
\&\fBsa\fR, and \fBsb\fR.
|
|
The default is
|
|
\&\fBkb\fR.
|
|
.Ip "\fB\-mnumerics\fR" 4
|
|
.IX Item "-mnumerics"
|
|
.PD 0
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
.PD
|
|
The \fB\-mnumerics\fR option indicates that the processor does support
|
|
floating-point instructions. The \fB\-msoft-float\fR option indicates
|
|
that floating-point support should not be assumed.
|
|
.Ip "\fB\-mleaf-procedures\fR" 4
|
|
.IX Item "-mleaf-procedures"
|
|
.PD 0
|
|
.Ip "\fB\-mno-leaf-procedures\fR" 4
|
|
.IX Item "-mno-leaf-procedures"
|
|
.PD
|
|
Do (or do not) attempt to alter leaf procedures to be callable with the
|
|
\&\f(CW\*(C`bal\*(C'\fR instruction as well as \f(CW\*(C`call\*(C'\fR. This will result in more
|
|
efficient code for explicit calls when the \f(CW\*(C`bal\*(C'\fR instruction can be
|
|
substituted by the assembler or linker, but less efficient code in other
|
|
cases, such as calls via function pointers, or using a linker that doesn't
|
|
support this optimization.
|
|
.Ip "\fB\-mtail-call\fR" 4
|
|
.IX Item "-mtail-call"
|
|
.PD 0
|
|
.Ip "\fB\-mno-tail-call\fR" 4
|
|
.IX Item "-mno-tail-call"
|
|
.PD
|
|
Do (or do not) make additional attempts (beyond those of the
|
|
machine-independent portions of the compiler) to optimize tail-recursive
|
|
calls into branches. You may not want to do this because the detection of
|
|
cases where this is not valid is not totally complete. The default is
|
|
\&\fB\-mno-tail-call\fR.
|
|
.Ip "\fB\-mcomplex-addr\fR" 4
|
|
.IX Item "-mcomplex-addr"
|
|
.PD 0
|
|
.Ip "\fB\-mno-complex-addr\fR" 4
|
|
.IX Item "-mno-complex-addr"
|
|
.PD
|
|
Assume (or do not assume) that the use of a complex addressing mode is a
|
|
win on this implementation of the i960. Complex addressing modes may not
|
|
be worthwhile on the K-series, but they definitely are on the C-series.
|
|
The default is currently \fB\-mcomplex-addr\fR for all processors except
|
|
the \s-1CB\s0 and \s-1CC\s0.
|
|
.Ip "\fB\-mcode-align\fR" 4
|
|
.IX Item "-mcode-align"
|
|
.PD 0
|
|
.Ip "\fB\-mno-code-align\fR" 4
|
|
.IX Item "-mno-code-align"
|
|
.PD
|
|
Align code to 8\-byte boundaries for faster fetching (or don't bother).
|
|
Currently turned on by default for C-series implementations only.
|
|
.Ip "\fB\-mic-compat\fR" 4
|
|
.IX Item "-mic-compat"
|
|
.PD 0
|
|
.Ip "\fB\-mic2.0\-compat\fR" 4
|
|
.IX Item "-mic2.0-compat"
|
|
.Ip "\fB\-mic3.0\-compat\fR" 4
|
|
.IX Item "-mic3.0-compat"
|
|
.PD
|
|
Enable compatibility with iC960 v2.0 or v3.0.
|
|
.Ip "\fB\-masm-compat\fR" 4
|
|
.IX Item "-masm-compat"
|
|
.PD 0
|
|
.Ip "\fB\-mintel-asm\fR" 4
|
|
.IX Item "-mintel-asm"
|
|
.PD
|
|
Enable compatibility with the iC960 assembler.
|
|
.Ip "\fB\-mstrict-align\fR" 4
|
|
.IX Item "-mstrict-align"
|
|
.PD 0
|
|
.Ip "\fB\-mno-strict-align\fR" 4
|
|
.IX Item "-mno-strict-align"
|
|
.PD
|
|
Do not permit (do permit) unaligned accesses.
|
|
.Ip "\fB\-mold-align\fR" 4
|
|
.IX Item "-mold-align"
|
|
Enable structure-alignment compatibility with Intel's gcc release version
|
|
1.3 (based on gcc 1.37). This option implies \fB\-mstrict-align\fR.
|
|
.Ip "\fB\-mlong-double-64\fR" 4
|
|
.IX Item "-mlong-double-64"
|
|
Implement type \fBlong double\fR as 64\-bit floating point numbers.
|
|
Without the option \fBlong double\fR is implemented by 80\-bit
|
|
floating point numbers. The only reason we have it because there is
|
|
no 128\-bit \fBlong double\fR support in \fBfp-bit.c\fR yet. So it
|
|
is only useful for people using soft-float targets. Otherwise, we
|
|
should recommend against use of it.
|
|
.PP
|
|
.I "\s-1DEC\s0 Alpha Options"
|
|
.IX Subsection "DEC Alpha Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1DEC\s0 Alpha implementations:
|
|
.Ip "\fB\-mno-soft-float\fR" 4
|
|
.IX Item "-mno-soft-float"
|
|
.PD 0
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
.PD
|
|
Use (do not use) the hardware floating-point instructions for
|
|
floating-point operations. When \fB\-msoft-float\fR is specified,
|
|
functions in \fIlibgcc1.c\fR 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.
|
|
.Sp
|
|
Note that Alpha implementations without floating-point operations are
|
|
required to have floating-point registers.
|
|
.Ip "\fB\-mfp-reg\fR" 4
|
|
.IX Item "-mfp-reg"
|
|
.PD 0
|
|
.Ip "\fB\-mno-fp-regs\fR" 4
|
|
.IX Item "-mno-fp-regs"
|
|
.PD
|
|
Generate code that uses (does not use) the floating-point register set.
|
|
\&\fB\-mno-fp-regs\fR implies \fB\-msoft-float\fR. 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 \f(CW$0\fR instead of \f(CW$f0\fR. This is a non-standard calling sequence, so any
|
|
function with a floating-point argument or return value called by code
|
|
compiled with \fB\-mno-fp-regs\fR must also be compiled with that
|
|
option.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-mieee\fR" 4
|
|
.IX Item "-mieee"
|
|
The Alpha architecture implements floating-point hardware optimized for
|
|
maximum performance. It is mostly compliant with the \s-1IEEE\s0 floating
|
|
point standard. However, for full compliance, software assistance is
|
|
required. This option generates code fully \s-1IEEE\s0 compliant code
|
|
\&\fIexcept\fR that the \fIinexact flag\fR is not maintained (see below).
|
|
If this option is turned on, the \s-1CPP\s0 macro \f(CW\*(C`_IEEE_FP\*(C'\fR is defined
|
|
during compilation. The option is a shorthand for: \fB\-D_IEEE_FP
|
|
\&\-mfp-trap-mode=su \-mtrap-precision=i \-mieee-conformant\fR. The resulting
|
|
code is less efficient but is able to correctly support denormalized
|
|
numbers and exceptional \s-1IEEE\s0 values such as not-a-number and plus/minus
|
|
infinity. Other Alpha compilers call this option
|
|
\&\fB\-ieee_with_no_inexact\fR.
|
|
.Ip "\fB\-mieee-with-inexact\fR" 4
|
|
.IX Item "-mieee-with-inexact"
|
|
This is like \fB\-mieee\fR except the generated code also maintains the
|
|
\&\s-1IEEE\s0 \fIinexact flag\fR. Turning on this option causes the generated
|
|
code to implement fully-compliant \s-1IEEE\s0 math. The option is a shorthand
|
|
for \fB\-D_IEEE_FP \-D_IEEE_FP_INEXACT\fR plus the three following:
|
|
\&\fB\-mieee-conformant\fR,
|
|
\&\fB\-mfp-trap-mode=sui\fR,
|
|
and \fB\-mtrap-precision=i\fR.
|
|
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 \fIinexact flag\fR, you should
|
|
normally not specify this option. Other Alpha compilers call this
|
|
option \fB\-ieee_with_inexact\fR.
|
|
.Ip "\fB\-mfp-trap-mode=\fR\fItrap mode\fR" 4
|
|
.IX Item "-mfp-trap-mode=trap mode"
|
|
This option controls what floating-point related traps are enabled.
|
|
Other Alpha compilers call this option \fB\-fptm\fR \fItrap mode\fR.
|
|
The trap mode can be set to one of four values:
|
|
.RS 4
|
|
.Ip "\fBn\fR" 4
|
|
.IX 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).
|
|
.Ip "\fBu\fR" 4
|
|
.IX Item "u"
|
|
In addition to the traps enabled by \fBn\fR, underflow traps are enabled
|
|
as well.
|
|
.Ip "\fBsu\fR" 4
|
|
.IX Item "su"
|
|
Like \fBsu\fR, but the instructions are marked to be safe for software
|
|
completion (see Alpha architecture manual for details).
|
|
.Ip "\fBsui\fR" 4
|
|
.IX Item "sui"
|
|
Like \fBsu\fR, but inexact traps are enabled as well.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-mfp-rounding-mode=\fR\fIrounding mode\fR" 4
|
|
.IX Item "-mfp-rounding-mode=rounding mode"
|
|
Selects the \s-1IEEE\s0 rounding mode. Other Alpha compilers call this option
|
|
\&\fB\-fprm\fR \fIrounding mode\fR. The \fIrounding mode\fR can be one
|
|
of:
|
|
.RS 4
|
|
.Ip "\fBn\fR" 4
|
|
.IX Item "n"
|
|
Normal \s-1IEEE\s0 rounding mode. Floating point numbers are rounded towards
|
|
the nearest machine number or towards the even machine number in case
|
|
of a tie.
|
|
.Ip "\fBm\fR" 4
|
|
.IX Item "m"
|
|
Round towards minus infinity.
|
|
.Ip "\fBc\fR" 4
|
|
.IX Item "c"
|
|
Chopped rounding mode. Floating point numbers are rounded towards zero.
|
|
.Ip "\fBd\fR" 4
|
|
.IX Item "d"
|
|
Dynamic rounding mode. A field in the floating point control register
|
|
(\fIfpcr\fR, 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
|
|
\&\fIfpcr\fR, \fBd\fR corresponds to round towards plus infinity.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-mtrap-precision=\fR\fItrap precision\fR" 4
|
|
.IX Item "-mtrap-precision=trap 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.
|
|
\&\s-1GCC\s0 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:
|
|
.RS 4
|
|
.Ip "\fBp\fR" 4
|
|
.IX Item "p"
|
|
Program precision. This option is the default and means a trap handler
|
|
can only identify which program caused a floating point exception.
|
|
.Ip "\fBf\fR" 4
|
|
.IX Item "f"
|
|
Function precision. The trap handler can determine the function that
|
|
caused a floating point exception.
|
|
.Ip "\fBi\fR" 4
|
|
.IX Item "i"
|
|
Instruction precision. The trap handler can determine the exact
|
|
instruction that caused a floating point exception.
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
Other Alpha compilers provide the equivalent options called
|
|
\&\fB\-scope_safe\fR and \fB\-resumption_safe\fR.
|
|
.RE
|
|
.Ip "\fB\-mieee-conformant\fR" 4
|
|
.IX Item "-mieee-conformant"
|
|
This option marks the generated code as \s-1IEEE\s0 conformant. You must not
|
|
use this option unless you also specify \fB\-mtrap-precision=i\fR and either
|
|
\&\fB\-mfp-trap-mode=su\fR or \fB\-mfp-trap-mode=sui\fR. Its only effect
|
|
is to emit the line \fB.eflag 48\fR in the function prologue of the
|
|
generated assembly file. Under \s-1DEC\s0 Unix, this has the effect that
|
|
IEEE-conformant math library routines will be linked in.
|
|
.Ip "\fB\-mbuild-constants\fR" 4
|
|
.IX Item "-mbuild-constants"
|
|
Normally \s-1GCC\s0 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.
|
|
.Sp
|
|
Use this option to require \s-1GCC\s0 to construct \fIall\fR integer constants
|
|
using code, even if it takes more instructions (the maximum is six).
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-malpha-as\fR" 4
|
|
.IX Item "-malpha-as"
|
|
.PD 0
|
|
.Ip "\fB\-mgas\fR" 4
|
|
.IX Item "-mgas"
|
|
.PD
|
|
Select whether to generate code to be assembled by the vendor-supplied
|
|
assembler (\fB\-malpha-as\fR) or by the \s-1GNU\s0 assembler \fB\-mgas\fR.
|
|
.Ip "\fB\-mbwx\fR" 4
|
|
.IX Item "-mbwx"
|
|
.PD 0
|
|
.Ip "\fB\-mno-bwx\fR" 4
|
|
.IX Item "-mno-bwx"
|
|
.Ip "\fB\-mcix\fR" 4
|
|
.IX Item "-mcix"
|
|
.Ip "\fB\-mno-cix\fR" 4
|
|
.IX Item "-mno-cix"
|
|
.Ip "\fB\-mmax\fR" 4
|
|
.IX Item "-mmax"
|
|
.Ip "\fB\-mno-max\fR" 4
|
|
.IX Item "-mno-max"
|
|
.PD
|
|
Indicate whether \s-1GCC\s0 should generate code to use the optional \s-1BWX\s0,
|
|
\&\s-1CIX\s0, and \s-1MAX\s0 instruction sets. The default is to use the instruction sets
|
|
supported by the \s-1CPU\s0 type specified via \fB\-mcpu=\fR option or that
|
|
of the \s-1CPU\s0 on which \s-1GCC\s0 was built if none was specified.
|
|
.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mcpu=cpu_type"
|
|
Set the instruction set, register set, and instruction scheduling
|
|
parameters for machine type \fIcpu_type\fR. You can specify either the
|
|
\&\fB\s-1EV\s0\fR style name or the corresponding chip number. \s-1GCC\s0
|
|
supports scheduling parameters for the \s-1EV4\s0 and \s-1EV5\s0 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,
|
|
\&\s-1GCC\s0 will default to the processor on which the compiler was built.
|
|
.Sp
|
|
Supported values for \fIcpu_type\fR are
|
|
.RS 4
|
|
.Ip "\fBev4\fR" 4
|
|
.IX Item "ev4"
|
|
.PD 0
|
|
.Ip "\fB21064\fR" 4
|
|
.IX Item "21064"
|
|
.PD
|
|
Schedules as an \s-1EV4\s0 and has no instruction set extensions.
|
|
.Ip "\fBev5\fR" 4
|
|
.IX Item "ev5"
|
|
.PD 0
|
|
.Ip "\fB21164\fR" 4
|
|
.IX Item "21164"
|
|
.PD
|
|
Schedules as an \s-1EV5\s0 and has no instruction set extensions.
|
|
.Ip "\fBev56\fR" 4
|
|
.IX Item "ev56"
|
|
.PD 0
|
|
.Ip "\fB21164a\fR" 4
|
|
.IX Item "21164a"
|
|
.PD
|
|
Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 extension.
|
|
.Ip "\fBpca56\fR" 4
|
|
.IX Item "pca56"
|
|
.PD 0
|
|
.Ip "\fB21164pc\fR" 4
|
|
.IX Item "21164pc"
|
|
.Ip "\fB21164PC\fR" 4
|
|
.IX Item "21164PC"
|
|
.PD
|
|
Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 and \s-1MAX\s0 extensions.
|
|
.Ip "\fBev6\fR" 4
|
|
.IX Item "ev6"
|
|
.PD 0
|
|
.Ip "\fB21264\fR" 4
|
|
.IX Item "21264"
|
|
.PD
|
|
Schedules as an \s-1EV5\s0 (until Digital releases the scheduling parameters
|
|
for the \s-1EV6\s0) and supports the \s-1BWX\s0, \s-1CIX\s0, and \s-1MAX\s0 extensions.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.Ip "\fB\-mmemory-latency=\fR\fItime\fR" 4
|
|
.IX Item "-mmemory-latency=time"
|
|
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.
|
|
.Sp
|
|
Valid options for \fItime\fR are
|
|
.RS 4
|
|
.Ip "\fInumber\fR" 4
|
|
.IX Item "number"
|
|
A decimal number representing clock cycles.
|
|
.Ip "\fBL1\fR" 4
|
|
.IX Item "L1"
|
|
.PD 0
|
|
.Ip "\fBL2\fR" 4
|
|
.IX Item "L2"
|
|
.Ip "\fBL3\fR" 4
|
|
.IX Item "L3"
|
|
.Ip "\fBmain\fR" 4
|
|
.IX Item "main"
|
|
.PD
|
|
The compiler contains estimates of the number of clock cycles for
|
|
``typical'' \s-1EV4\s0 & \s-1EV5\s0 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 \s-1EV5\s0.
|
|
.RE
|
|
.RS 4
|
|
.RE
|
|
.PP
|
|
.I "Clipper Options"
|
|
.IX Subsection "Clipper Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the Clipper implementations:
|
|
.Ip "\fB\-mc300\fR" 4
|
|
.IX Item "-mc300"
|
|
Produce code for a C300 Clipper processor. This is the default.
|
|
.Ip "\fB\-mc400\fR" 4
|
|
.IX Item "-mc400"
|
|
Produce code for a C400 Clipper processor i.e. use floating point
|
|
registers f8..f15.
|
|
.PP
|
|
.I "H8/300 Options"
|
|
.IX Subsection "H8/300 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the H8/300 implementations:
|
|
.Ip "\fB\-mrelax\fR" 4
|
|
.IX Item "-mrelax"
|
|
Shorten some address references at link time, when possible; uses the
|
|
linker option \fB\-relax\fR.
|
|
.Ip "\fB\-mh\fR" 4
|
|
.IX Item "-mh"
|
|
Generate code for the H8/300H.
|
|
.Ip "\fB\-ms\fR" 4
|
|
.IX Item "-ms"
|
|
Generate code for the H8/S.
|
|
.Ip "\fB\-ms2600\fR" 4
|
|
.IX Item "-ms2600"
|
|
Generate code for the H8/S2600. This switch must be used with \-ms.
|
|
.Ip "\fB\-mint32\fR" 4
|
|
.IX Item "-mint32"
|
|
Make \f(CW\*(C`int\*(C'\fR data 32 bits by default.
|
|
.Ip "\fB\-malign-300\fR" 4
|
|
.IX Item "-malign-300"
|
|
On the H8/300H and H8/S, use the same alignment rules as for the H8/300.
|
|
The default for the H8/300H and H8/S is to align longs and floats on 4
|
|
byte boundaries.
|
|
\&\fB\-malign-300\fR causes them to be aligned on 2 byte boundaries.
|
|
This option has no effect on the H8/300.
|
|
.PP
|
|
.I "\s-1SH\s0 Options"
|
|
.IX Subsection "SH Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for the \s-1SH\s0 implementations:
|
|
.Ip "\fB\-m1\fR" 4
|
|
.IX Item "-m1"
|
|
Generate code for the \s-1SH1\s0.
|
|
.Ip "\fB\-m2\fR" 4
|
|
.IX Item "-m2"
|
|
Generate code for the \s-1SH2\s0.
|
|
.Ip "\fB\-m3\fR" 4
|
|
.IX Item "-m3"
|
|
Generate code for the \s-1SH3\s0.
|
|
.Ip "\fB\-m3e\fR" 4
|
|
.IX Item "-m3e"
|
|
Generate code for the SH3e.
|
|
.Ip "\fB\-m4\-nofpu\fR" 4
|
|
.IX Item "-m4-nofpu"
|
|
Generate code for the \s-1SH4\s0 without a floating-point unit.
|
|
.Ip "\fB\-m4\-single-only\fR" 4
|
|
.IX Item "-m4-single-only"
|
|
Generate code for the \s-1SH4\s0 with a floating-point unit that only
|
|
supports single-precision arithmentic.
|
|
.Ip "\fB\-m4\-single\fR" 4
|
|
.IX Item "-m4-single"
|
|
Generate code for the \s-1SH4\s0 assuming the floating-point unit is in
|
|
single-precision mode by default.
|
|
.Ip "\fB\-m4\fR" 4
|
|
.IX Item "-m4"
|
|
Generate code for the \s-1SH4\s0.
|
|
.Ip "\fB\-mb\fR" 4
|
|
.IX Item "-mb"
|
|
Compile code for the processor in big endian mode.
|
|
.Ip "\fB\-ml\fR" 4
|
|
.IX Item "-ml"
|
|
Compile code for the processor in little endian mode.
|
|
.Ip "\fB\-mdalign\fR" 4
|
|
.IX Item "-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 \-mdalign.
|
|
.Ip "\fB\-mrelax\fR" 4
|
|
.IX Item "-mrelax"
|
|
Shorten some address references at link time, when possible; uses the
|
|
linker option \fB\-relax\fR.
|
|
.Ip "\fB\-mbigtable\fR" 4
|
|
.IX Item "-mbigtable"
|
|
Use 32\-bit offsets in \f(CW\*(C`switch\*(C'\fR tables. The default is to use
|
|
16\-bit offsets.
|
|
.Ip "\fB\-mfmovd\fR" 4
|
|
.IX Item "-mfmovd"
|
|
Enable the use of the instruction \f(CW\*(C`fmovd\*(C'\fR.
|
|
.Ip "\fB\-mhitachi\fR" 4
|
|
.IX Item "-mhitachi"
|
|
Comply with the calling conventions defined by Hitachi.
|
|
.Ip "\fB\-mnomacsave\fR" 4
|
|
.IX Item "-mnomacsave"
|
|
Mark the \f(CW\*(C`MAC\*(C'\fR register as call-clobbered, even if
|
|
\&\fB\-mhitachi\fR is given.
|
|
.Ip "\fB\-misize\fR" 4
|
|
.IX Item "-misize"
|
|
Dump instruction size and location in the assembly code.
|
|
.Ip "\fB\-mpadstruct\fR" 4
|
|
.IX Item "-mpadstruct"
|
|
This option is deprecated. It pads structures to multiple of 4 bytes,
|
|
which is incompatible with the \s-1SH\s0 \s-1ABI\s0.
|
|
.Ip "\fB\-mspace\fR" 4
|
|
.IX Item "-mspace"
|
|
Optimize for space instead of speed. Implied by \fB\-Os\fR.
|
|
.Ip "\fB\-mprefergot\fR" 4
|
|
.IX Item "-mprefergot"
|
|
When generating position-independent code, emit function calls using
|
|
the Global Offset Table instead of the Procedure Linkage Table.
|
|
.Ip "\fB\-musermode\fR" 4
|
|
.IX Item "-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 \f(CW\*(C`sh\-*\-linux*\*(C'\fR.
|
|
.PP
|
|
.I "Options for System V"
|
|
.IX Subsection "Options for System V"
|
|
.PP
|
|
These additional options are available on System V Release 4 for
|
|
compatibility with other compilers on those systems:
|
|
.Ip "\fB\-G\fR" 4
|
|
.IX Item "-G"
|
|
Create a shared object.
|
|
It is recommended that \fB\-symbolic\fR or \fB\-shared\fR be used instead.
|
|
.Ip "\fB\-Qy\fR" 4
|
|
.IX Item "-Qy"
|
|
Identify the versions of each tool used by the compiler, in a
|
|
\&\f(CW\*(C`.ident\*(C'\fR assembler directive in the output.
|
|
.Ip "\fB\-Qn\fR" 4
|
|
.IX Item "-Qn"
|
|
Refrain from adding \f(CW\*(C`.ident\*(C'\fR directives to the output file (this is
|
|
the default).
|
|
.Ip "\fB\-YP,\fR\fIdirs\fR" 4
|
|
.IX Item "-YP,dirs"
|
|
Search the directories \fIdirs\fR, and no others, for libraries
|
|
specified with \fB\-l\fR.
|
|
.Ip "\fB\-Ym,\fR\fIdir\fR" 4
|
|
.IX Item "-Ym,dir"
|
|
Look in the directory \fIdir\fR to find the M4 preprocessor.
|
|
The assembler uses this option.
|
|
.PP
|
|
.I "TMS320C3x/C4x Options"
|
|
.IX Subsection "TMS320C3x/C4x Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for TMS320C3x/C4x implementations:
|
|
.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4
|
|
.IX Item "-mcpu=cpu_type"
|
|
Set the instruction set, register set, and instruction scheduling
|
|
parameters for machine type \fIcpu_type\fR. Supported values for
|
|
\&\fIcpu_type\fR are \fBc30\fR, \fBc31\fR, \fBc32\fR, \fBc40\fR, and
|
|
\&\fBc44\fR. The default is \fBc40\fR to generate code for the
|
|
\&\s-1TMS320C40\s0.
|
|
.Ip "\fB\-mbig-memory\fR" 4
|
|
.IX Item "-mbig-memory"
|
|
.PD 0
|
|
.Ip "\fB\-mbig\fR" 4
|
|
.IX Item "-mbig"
|
|
.Ip "\fB\-msmall-memory\fR" 4
|
|
.IX Item "-msmall-memory"
|
|
.Ip "\fB\-msmall\fR" 4
|
|
.IX Item "-msmall"
|
|
.PD
|
|
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 (\s-1DP\s0) 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 \s-1DP\s0 register for every direct
|
|
memory access.
|
|
.Ip "\fB\-mbk\fR" 4
|
|
.IX Item "-mbk"
|
|
.PD 0
|
|
.Ip "\fB\-mno-bk\fR" 4
|
|
.IX Item "-mno-bk"
|
|
.PD
|
|
Allow (disallow) allocation of general integer operands into the block
|
|
count register \s-1BK\s0.
|
|
.Ip "\fB\-mdb\fR" 4
|
|
.IX Item "-mdb"
|
|
.PD 0
|
|
.Ip "\fB\-mno-db\fR" 4
|
|
.IX Item "-mno-db"
|
|
.PD
|
|
Enable (disable) generation of code using decrement and branch,
|
|
\&\fIDBcond\fR\|(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 2^23 + 1 (but who iterates loops more than
|
|
2^23 times on the C3x?). Note that \s-1GCC\s0 will try to reverse a loop so
|
|
that it can utilise 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 \s-1RPTB\s0 instruction cannot be utilised.
|
|
.Ip "\fB\-mdp-isr-reload\fR" 4
|
|
.IX Item "-mdp-isr-reload"
|
|
.PD 0
|
|
.Ip "\fB\-mparanoid\fR" 4
|
|
.IX Item "-mparanoid"
|
|
.PD
|
|
Force the \s-1DP\s0 register to be saved on entry to an interrupt service
|
|
routine (\s-1ISR\s0), reloaded to point to the data section, and restored on
|
|
exit from the \s-1ISR\s0. This should not be required unless someone has
|
|
violated the small memory model by modifying the \s-1DP\s0 register, say within
|
|
an object library.
|
|
.Ip "\fB\-mmpyi\fR" 4
|
|
.IX Item "-mmpyi"
|
|
.PD 0
|
|
.Ip "\fB\-mno-mpyi\fR" 4
|
|
.IX Item "-mno-mpyi"
|
|
.PD
|
|
For the C3x use the 24\-bit \s-1MPYI\s0 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 \-mmpyi option is not specified for the C3x,
|
|
then squaring operations are performed inline instead of a library call.
|
|
.Ip "\fB\-mfast-fix\fR" 4
|
|
.IX Item "-mfast-fix"
|
|
.PD 0
|
|
.Ip "\fB\-mno-fast-fix\fR" 4
|
|
.IX Item "-mno-fast-fix"
|
|
.PD
|
|
The C3x/C4x \s-1FIX\s0 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.
|
|
.Ip "\fB\-mrptb\fR" 4
|
|
.IX Item "-mrptb"
|
|
.PD 0
|
|
.Ip "\fB\-mno-rptb\fR" 4
|
|
.IX Item "-mno-rptb"
|
|
.PD
|
|
Enable (disable) generation of repeat block sequences using the \s-1RPTB\s0
|
|
instruction for zero overhead looping. The \s-1RPTB\s0 construct is only used
|
|
for innermost loops that do not call functions or jump across the loop
|
|
boundaries. There is no advantage having nested \s-1RPTB\s0 loops due to the
|
|
overhead required to save and restore the \s-1RC\s0, \s-1RS\s0, and \s-1RE\s0 registers.
|
|
This is enabled by default with \-O2.
|
|
.Ip "\fB\-mrpts=\fR\fIcount\fR" 4
|
|
.IX Item "-mrpts=count"
|
|
.PD 0
|
|
.Ip "\fB\-mno-rpts\fR" 4
|
|
.IX Item "-mno-rpts"
|
|
.PD
|
|
Enable (disable) the use of the single instruction repeat instruction
|
|
\&\s-1RPTS\s0. If a repeat block contains a single instruction, and the loop
|
|
count can be guaranteed to be less than the value \fIcount\fR, \s-1GCC\s0 will
|
|
emit a \s-1RPTS\s0 instruction instead of a \s-1RPTB\s0. If no value is specified,
|
|
then a \s-1RPTS\s0 will be emitted even if the loop count cannot be determined
|
|
at compile time. Note that the repeated instruction following \s-1RPTS\s0 does
|
|
not have to be reloaded from memory each iteration, thus freeing up the
|
|
\&\s-1CPU\s0 buses for operands. However, since interrupts are blocked by this
|
|
instruction, it is disabled by default.
|
|
.Ip "\fB\-mloop-unsigned\fR" 4
|
|
.IX Item "-mloop-unsigned"
|
|
.PD 0
|
|
.Ip "\fB\-mno-loop-unsigned\fR" 4
|
|
.IX Item "-mno-loop-unsigned"
|
|
.PD
|
|
The maximum iteration count when using \s-1RPTS\s0 and \s-1RPTB\s0 (and \s-1DB\s0 on the C40)
|
|
is 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 2^31 + 1 maximum iteration count may be
|
|
exceeded. This switch allows an unsigned iteration count.
|
|
.Ip "\fB\-mti\fR" 4
|
|
.IX Item "-mti"
|
|
Try to emit an assembler syntax that the \s-1TI\s0 assembler (asm30) is happy
|
|
with. This also enforces compatibility with the \s-1API\s0 employed by the \s-1TI\s0
|
|
C3x C compiler. For example, long doubles are passed as structures
|
|
rather than in floating point registers.
|
|
.Ip "\fB\-mregparm\fR" 4
|
|
.IX Item "-mregparm"
|
|
.PD 0
|
|
.Ip "\fB\-mmemparm\fR" 4
|
|
.IX Item "-mmemparm"
|
|
.PD
|
|
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.
|
|
.Ip "\fB\-mparallel-insns\fR" 4
|
|
.IX Item "-mparallel-insns"
|
|
.PD 0
|
|
.Ip "\fB\-mno-parallel-insns\fR" 4
|
|
.IX Item "-mno-parallel-insns"
|
|
.PD
|
|
Allow the generation of parallel instructions. This is enabled by
|
|
default with \-O2.
|
|
.Ip "\fB\-mparallel-mpy\fR" 4
|
|
.IX Item "-mparallel-mpy"
|
|
.PD 0
|
|
.Ip "\fB\-mno-parallel-mpy\fR" 4
|
|
.IX Item "-mno-parallel-mpy"
|
|
.PD
|
|
Allow the generation of MPY||ADD and MPY||SUB parallel instructions,
|
|
provided \-mparallel-insns is also specified. These instructions have
|
|
tight register constraints which can pessimize the code generation
|
|
of large functions.
|
|
.PP
|
|
.I "V850 Options"
|
|
.IX Subsection "V850 Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for V850 implementations:
|
|
.Ip "\fB\-mlong-calls\fR" 4
|
|
.IX Item "-mlong-calls"
|
|
.PD 0
|
|
.Ip "\fB\-mno-long-calls\fR" 4
|
|
.IX Item "-mno-long-calls"
|
|
.PD
|
|
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.
|
|
.Ip "\fB\-mno-ep\fR" 4
|
|
.IX Item "-mno-ep"
|
|
.PD 0
|
|
.Ip "\fB\-mep\fR" 4
|
|
.IX Item "-mep"
|
|
.PD
|
|
Do not optimize (do optimize) basic blocks that use the same index
|
|
pointer 4 or more times to copy pointer into the \f(CW\*(C`ep\*(C'\fR register, and
|
|
use the shorter \f(CW\*(C`sld\*(C'\fR and \f(CW\*(C`sst\*(C'\fR instructions. The \fB\-mep\fR
|
|
option is on by default if you optimize.
|
|
.Ip "\fB\-mno-prolog-function\fR" 4
|
|
.IX Item "-mno-prolog-function"
|
|
.PD 0
|
|
.Ip "\fB\-mprolog-function\fR" 4
|
|
.IX Item "-mprolog-function"
|
|
.PD
|
|
Do not use (do use) external functions to save and restore registers at
|
|
the prolog and epilog 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 \fB\-mprolog-function\fR option is on by default if
|
|
you optimize.
|
|
.Ip "\fB\-mspace\fR" 4
|
|
.IX Item "-mspace"
|
|
Try to make the code as small as possible. At present, this just turns
|
|
on the \fB\-mep\fR and \fB\-mprolog-function\fR options.
|
|
.Ip "\fB\-mtda=\fR\fIn\fR" 4
|
|
.IX Item "-mtda=n"
|
|
Put static or global variables whose size is \fIn\fR bytes or less into
|
|
the tiny data area that register \f(CW\*(C`ep\*(C'\fR points to. The tiny data
|
|
area can hold up to 256 bytes in total (128 bytes for byte references).
|
|
.Ip "\fB\-msda=\fR\fIn\fR" 4
|
|
.IX Item "-msda=n"
|
|
Put static or global variables whose size is \fIn\fR bytes or less into
|
|
the small data area that register \f(CW\*(C`gp\*(C'\fR points to. The small data
|
|
area can hold up to 64 kilobytes.
|
|
.Ip "\fB\-mzda=\fR\fIn\fR" 4
|
|
.IX Item "-mzda=n"
|
|
Put static or global variables whose size is \fIn\fR bytes or less into
|
|
the first 32 kilobytes of memory.
|
|
.Ip "\fB\-mv850\fR" 4
|
|
.IX Item "-mv850"
|
|
Specify that the target processor is the V850.
|
|
.Ip "\fB\-mbig-switch\fR" 4
|
|
.IX Item "-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.
|
|
.PP
|
|
.I "\s-1ARC\s0 Options"
|
|
.IX Subsection "ARC Options"
|
|
.PP
|
|
These options are defined for \s-1ARC\s0 implementations:
|
|
.Ip "\fB\-EL\fR" 4
|
|
.IX Item "-EL"
|
|
Compile code for little endian mode. This is the default.
|
|
.Ip "\fB\-EB\fR" 4
|
|
.IX Item "-EB"
|
|
Compile code for big endian mode.
|
|
.Ip "\fB\-mmangle-cpu\fR" 4
|
|
.IX Item "-mmangle-cpu"
|
|
Prepend the name of the cpu to all public symbol names.
|
|
In multiple-processor systems, there are many \s-1ARC\s0 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 \*(L"almost identical\*(R".
|
|
This is an all or nothing option.
|
|
.Ip "\fB\-mcpu=\fR\fIcpu\fR" 4
|
|
.IX Item "-mcpu=cpu"
|
|
Compile code for \s-1ARC\s0 variant \fIcpu\fR.
|
|
Which variants are supported depend on the configuration.
|
|
All variants support \fB\-mcpu=base\fR, this is the default.
|
|
.Ip "\fB\-mtext=\fR\fItext section\fR" 4
|
|
.IX Item "-mtext=text section"
|
|
.PD 0
|
|
.Ip "\fB\-mdata=\fR\fIdata section\fR" 4
|
|
.IX Item "-mdata=data section"
|
|
.Ip "\fB\-mrodata=\fR\fIreadonly data section\fR" 4
|
|
.IX Item "-mrodata=readonly data section"
|
|
.PD
|
|
Put functions, data, and readonly data in \fItext section\fR,
|
|
\&\fIdata section\fR, and \fIreadonly data section\fR respectively
|
|
by default. This can be overridden with the \f(CW\*(C`section\*(C'\fR attribute.
|
|
.PP
|
|
.I "\s-1NS32K\s0 Options"
|
|
.IX Subsection "NS32K Options"
|
|
.PP
|
|
These are the \fB\-m\fR options defined for the 32000 series. The default
|
|
values for these options depends on which style of 32000 was selected when
|
|
the compiler was configured; the defaults for the most common choices are
|
|
given below.
|
|
.Ip "\fB\-m32032\fR" 4
|
|
.IX Item "-m32032"
|
|
.PD 0
|
|
.Ip "\fB\-m32032\fR" 4
|
|
.IX Item "-m32032"
|
|
.PD
|
|
Generate output for a 32032. This is the default
|
|
when the compiler is configured for 32032 and 32016 based systems.
|
|
.Ip "\fB\-m32332\fR" 4
|
|
.IX Item "-m32332"
|
|
.PD 0
|
|
.Ip "\fB\-m32332\fR" 4
|
|
.IX Item "-m32332"
|
|
.PD
|
|
Generate output for a 32332. This is the default
|
|
when the compiler is configured for 32332\-based systems.
|
|
.Ip "\fB\-m32532\fR" 4
|
|
.IX Item "-m32532"
|
|
.PD 0
|
|
.Ip "\fB\-m32532\fR" 4
|
|
.IX Item "-m32532"
|
|
.PD
|
|
Generate output for a 32532. This is the default
|
|
when the compiler is configured for 32532\-based systems.
|
|
.Ip "\fB\-m32081\fR" 4
|
|
.IX Item "-m32081"
|
|
Generate output containing 32081 instructions for floating point.
|
|
This is the default for all systems.
|
|
.Ip "\fB\-m32381\fR" 4
|
|
.IX Item "-m32381"
|
|
Generate output containing 32381 instructions for floating point. This
|
|
also implies \fB\-m32081\fR. The 32381 is only compatible with the 32332
|
|
and 32532 cpus. This is the default for the pc532\-netbsd configuration.
|
|
.Ip "\fB\-mmulti-add\fR" 4
|
|
.IX Item "-mmulti-add"
|
|
Try and generate multiply-add floating point instructions \f(CW\*(C`polyF\*(C'\fR
|
|
and \f(CW\*(C`dotF\*(C'\fR. This option is only available if the \fB\-m32381\fR
|
|
option is in effect. Using these instructions requires changes to to
|
|
register allocation which generally has a negative impact on
|
|
performance. This option should only be enabled when compiling code
|
|
particularly likely to make heavy use of multiply-add instructions.
|
|
.Ip "\fB\-mnomulti-add\fR" 4
|
|
.IX Item "-mnomulti-add"
|
|
Do not try and generate multiply-add floating point instructions
|
|
\&\f(CW\*(C`polyF\*(C'\fR and \f(CW\*(C`dotF\*(C'\fR. This is the default on all platforms.
|
|
.Ip "\fB\-msoft-float\fR" 4
|
|
.IX Item "-msoft-float"
|
|
Generate output containing library calls for floating point.
|
|
\&\fBWarning:\fR the requisite libraries may not be available.
|
|
.Ip "\fB\-mnobitfield\fR" 4
|
|
.IX Item "-mnobitfield"
|
|
Do not use the bit-field instructions. On some machines it is faster to
|
|
use shifting and masking operations. This is the default for the pc532.
|
|
.Ip "\fB\-mbitfield\fR" 4
|
|
.IX Item "-mbitfield"
|
|
Do use the bit-field instructions. This is the default for all platforms
|
|
except the pc532.
|
|
.Ip "\fB\-mrtd\fR" 4
|
|
.IX Item "-mrtd"
|
|
Use a different function-calling convention, in which functions
|
|
that take a fixed number of arguments return pop their
|
|
arguments on return with the \f(CW\*(C`ret\*(C'\fR instruction.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR);
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
.Sp
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
.Sp
|
|
This option takes its name from the 680x0 \f(CW\*(C`rtd\*(C'\fR instruction.
|
|
.Ip "\fB\-mregparam\fR" 4
|
|
.IX Item "-mregparam"
|
|
Use a different function-calling convention where the first two arguments
|
|
are passed in registers.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-mnoregparam\fR" 4
|
|
.IX Item "-mnoregparam"
|
|
Do not pass any arguments in registers. This is the default for all
|
|
targets.
|
|
.Ip "\fB\-msb\fR" 4
|
|
.IX Item "-msb"
|
|
It is \s-1OK\s0 to use the sb as an index register which is always loaded with
|
|
zero. This is the default for the pc532\-netbsd target.
|
|
.Ip "\fB\-mnosb\fR" 4
|
|
.IX Item "-mnosb"
|
|
The sb register is not available for use or has not been initialized to
|
|
zero by the run time system. This is the default for all targets except
|
|
the pc532\-netbsd. It is also implied whenever \fB\-mhimem\fR or
|
|
\&\fB\-fpic\fR is set.
|
|
.Ip "\fB\-mhimem\fR" 4
|
|
.IX Item "-mhimem"
|
|
Many ns32000 series addressing modes use displacements of up to 512MB.
|
|
If an address is above 512MB then displacements from zero can not be used.
|
|
This option causes code to be generated which can be loaded above 512MB.
|
|
This may be useful for operating systems or \s-1ROM\s0 code.
|
|
.Ip "\fB\-mnohimem\fR" 4
|
|
.IX Item "-mnohimem"
|
|
Assume code will be loaded in the first 512MB of virtual address space.
|
|
This is the default for all platforms.
|
|
.PP
|
|
.I "\s-1AVR\s0 Options"
|
|
.IX Subsection "AVR Options"
|
|
.PP
|
|
These options are defined for \s-1AVR\s0 implementations:
|
|
.Ip "\fB\-mmcu=\fR\fImcu\fR" 4
|
|
.IX Item "-mmcu=mcu"
|
|
Specify \s-1ATMEL\s0 \s-1AVR\s0 instruction set or \s-1MCU\s0 type.
|
|
.Sp
|
|
Instruction set avr1 is for the minimal \s-1AVR\s0 core, not supported by the C
|
|
compiler, only for assembler programs (\s-1MCU\s0 types: at90s1200, attiny10,
|
|
attiny11, attiny12, attiny15, attiny28).
|
|
.Sp
|
|
Instruction set avr2 (default) is for the classic \s-1AVR\s0 core with up to
|
|
8K program memory space (\s-1MCU\s0 types: at90s2313, at90s2323, attiny22,
|
|
at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515,
|
|
at90c8534, at90s8535).
|
|
.Sp
|
|
Instruction set avr3 is for the classic \s-1AVR\s0 core with up to 128K program
|
|
memory space (\s-1MCU\s0 types: atmega103, atmega603).
|
|
.Sp
|
|
Instruction set avr4 is for the enhanced \s-1AVR\s0 core with up to 8K program
|
|
memory space (\s-1MCU\s0 types: atmega83, atmega85).
|
|
.Sp
|
|
Instruction set avr5 is for the enhanced \s-1AVR\s0 core with up to 128K program
|
|
memory space (\s-1MCU\s0 types: atmega161, atmega163, atmega32, at94k).
|
|
.Ip "\fB\-msize\fR" 4
|
|
.IX Item "-msize"
|
|
Output instruction sizes to the asm file.
|
|
.Ip "\fB\-minit-stack=\fR\fIN\fR" 4
|
|
.IX Item "-minit-stack=N"
|
|
Specify the initial stack address, which may be a symbol or numeric value,
|
|
_\|_stack is the default.
|
|
.Ip "\fB\-mno-interrupts\fR" 4
|
|
.IX Item "-mno-interrupts"
|
|
Generated code is not compatible with hardware interrupts.
|
|
Code size will be smaller.
|
|
.Ip "\fB\-mcall-prologues\fR" 4
|
|
.IX Item "-mcall-prologues"
|
|
Functions prologues/epilogues expanded as call to appropriate
|
|
subroutines. Code size will be smaller.
|
|
.Ip "\fB\-mno-tablejump\fR" 4
|
|
.IX Item "-mno-tablejump"
|
|
Do not generate tablejump insns which sometimes increase code size.
|
|
.Ip "\fB\-mtiny-stack\fR" 4
|
|
.IX Item "-mtiny-stack"
|
|
Change only the low 8 bits of the stack pointer.
|
|
.PP
|
|
.I "MCore Options"
|
|
.IX Subsection "MCore Options"
|
|
.PP
|
|
These are the \fB\-m\fR options defined for the Motorola M*Core
|
|
processors.
|
|
.Ip "\fB\-mhardlit\fR" 4
|
|
.IX Item "-mhardlit"
|
|
.PD 0
|
|
.Ip "\fB\-mhardlit\fR" 4
|
|
.IX Item "-mhardlit"
|
|
.Ip "\fB\-mno-hardlit\fR" 4
|
|
.IX Item "-mno-hardlit"
|
|
.PD
|
|
Inline constants into the code stream if it can be done in two
|
|
instructions or less.
|
|
.Ip "\fB\-mdiv\fR" 4
|
|
.IX Item "-mdiv"
|
|
.PD 0
|
|
.Ip "\fB\-mdiv\fR" 4
|
|
.IX Item "-mdiv"
|
|
.Ip "\fB\-mno-div\fR" 4
|
|
.IX Item "-mno-div"
|
|
.PD
|
|
Use the divide instruction. (Enabled by default).
|
|
.Ip "\fB\-mrelax-immediate\fR" 4
|
|
.IX Item "-mrelax-immediate"
|
|
.PD 0
|
|
.Ip "\fB\-mrelax-immediate\fR" 4
|
|
.IX Item "-mrelax-immediate"
|
|
.Ip "\fB\-mno-relax-immediate\fR" 4
|
|
.IX Item "-mno-relax-immediate"
|
|
.PD
|
|
Allow arbitrary sized immediates in bit operations.
|
|
.Ip "\fB\-mwide-bitfields\fR" 4
|
|
.IX Item "-mwide-bitfields"
|
|
.PD 0
|
|
.Ip "\fB\-mwide-bitfields\fR" 4
|
|
.IX Item "-mwide-bitfields"
|
|
.Ip "\fB\-mno-wide-bitfields\fR" 4
|
|
.IX Item "-mno-wide-bitfields"
|
|
.PD
|
|
Always treat bitfields as int-sized.
|
|
.Ip "\fB\-m4byte-functions\fR" 4
|
|
.IX Item "-m4byte-functions"
|
|
.PD 0
|
|
.Ip "\fB\-m4byte-functions\fR" 4
|
|
.IX Item "-m4byte-functions"
|
|
.Ip "\fB\-mno-4byte-functions\fR" 4
|
|
.IX Item "-mno-4byte-functions"
|
|
.PD
|
|
Force all functions to be aligned to a four byte boundary.
|
|
.Ip "\fB\-mcallgraph-data\fR" 4
|
|
.IX Item "-mcallgraph-data"
|
|
.PD 0
|
|
.Ip "\fB\-mcallgraph-data\fR" 4
|
|
.IX Item "-mcallgraph-data"
|
|
.Ip "\fB\-mno-callgraph-data\fR" 4
|
|
.IX Item "-mno-callgraph-data"
|
|
.PD
|
|
Emit callgraph information.
|
|
.Ip "\fB\-mslow-bytes\fR" 4
|
|
.IX Item "-mslow-bytes"
|
|
.PD 0
|
|
.Ip "\fB\-mslow-bytes\fR" 4
|
|
.IX Item "-mslow-bytes"
|
|
.Ip "\fB\-mno-slow-bytes\fR" 4
|
|
.IX Item "-mno-slow-bytes"
|
|
.PD
|
|
Prefer word access when reading byte quantities.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
.PD 0
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
.Ip "\fB\-mbig-endian\fR" 4
|
|
.IX Item "-mbig-endian"
|
|
.PD
|
|
Generate code for a little endian target.
|
|
.Ip "\fB\-m210\fR" 4
|
|
.IX Item "-m210"
|
|
.PD 0
|
|
.Ip "\fB\-m210\fR" 4
|
|
.IX Item "-m210"
|
|
.Ip "\fB\-m340\fR" 4
|
|
.IX Item "-m340"
|
|
.PD
|
|
Generate code for the 210 processor.
|
|
.PP
|
|
.I "\s-1IA-64\s0 Options"
|
|
.IX Subsection "IA-64 Options"
|
|
.PP
|
|
These are the \fB\-m\fR options defined for the Intel \s-1IA-64\s0 architecture.
|
|
.Ip "\fB\-mbig-endian\fR" 4
|
|
.IX Item "-mbig-endian"
|
|
Generate code for a big endian target. This is the default for \s-1HPUX\s0.
|
|
.Ip "\fB\-mlittle-endian\fR" 4
|
|
.IX Item "-mlittle-endian"
|
|
Generate code for a little endian target. This is the default for \s-1AIX5\s0
|
|
and Linux.
|
|
.Ip "\fB\-mgnu-as\fR" 4
|
|
.IX Item "-mgnu-as"
|
|
.PD 0
|
|
.Ip "\fB\-mno-gnu-as\fR" 4
|
|
.IX Item "-mno-gnu-as"
|
|
.PD
|
|
Generate (or don't) code for the \s-1GNU\s0 assembler. This is the default.
|
|
.Ip "\fB\-mgnu-ld\fR" 4
|
|
.IX Item "-mgnu-ld"
|
|
.PD 0
|
|
.Ip "\fB\-mno-gnu-ld\fR" 4
|
|
.IX Item "-mno-gnu-ld"
|
|
.PD
|
|
Generate (or don't) code for the \s-1GNU\s0 linker. This is the default.
|
|
.Ip "\fB\-mno-pic\fR" 4
|
|
.IX Item "-mno-pic"
|
|
Generate code that does not use a global pointer register. The result
|
|
is not position independent code, and violates the \s-1IA-64\s0 \s-1ABI\s0.
|
|
.Ip "\fB\-mvolatile-asm-stop\fR" 4
|
|
.IX Item "-mvolatile-asm-stop"
|
|
.PD 0
|
|
.Ip "\fB\-mno-volatile-asm-stop\fR" 4
|
|
.IX Item "-mno-volatile-asm-stop"
|
|
.PD
|
|
Generate (or don't) a stop bit immediately before and after volatile asm
|
|
statements.
|
|
.Ip "\fB\-mb-step\fR" 4
|
|
.IX Item "-mb-step"
|
|
Generate code that works around Itanium B step errata.
|
|
.Ip "\fB\-mregister-names\fR" 4
|
|
.IX Item "-mregister-names"
|
|
.PD 0
|
|
.Ip "\fB\-mno-register-names\fR" 4
|
|
.IX Item "-mno-register-names"
|
|
.PD
|
|
Generate (or don't) \fBin\fR, \fBloc\fR, and \fBout\fR register names for
|
|
the stacked registers. This may make assembler output more readable.
|
|
.Ip "\fB\-mno-sdata\fR" 4
|
|
.IX Item "-mno-sdata"
|
|
.PD 0
|
|
.Ip "\fB\-msdata\fR" 4
|
|
.IX Item "-msdata"
|
|
.PD
|
|
Disable (or enable) optimizations that use the small data section. This may
|
|
be useful for working around optimizer bugs.
|
|
.Ip "\fB\-mconstant-gp\fR" 4
|
|
.IX Item "-mconstant-gp"
|
|
Generate code that uses a single constant global pointer value. This is
|
|
useful when compiling kernel code.
|
|
.Ip "\fB\-mauto-pic\fR" 4
|
|
.IX Item "-mauto-pic"
|
|
Generate code that is self-relocatable. This implies \fB\-mconstant-gp\fR.
|
|
This is useful when compiling firmware code.
|
|
.Ip "\fB\-minline-divide-min-latency\fR" 4
|
|
.IX Item "-minline-divide-min-latency"
|
|
Generate code for inline divides using the minimum latency algorithm.
|
|
.Ip "\fB\-minline-divide-max-throughput\fR" 4
|
|
.IX Item "-minline-divide-max-throughput"
|
|
Generate code for inline divides using the maximum throughput algorithm.
|
|
.Ip "\fB\-mno-dwarf2\-asm\fR" 4
|
|
.IX Item "-mno-dwarf2-asm"
|
|
.PD 0
|
|
.Ip "\fB\-mdwarf2\-asm\fR" 4
|
|
.IX Item "-mdwarf2-asm"
|
|
.PD
|
|
Don't (or do) generate assembler code for the \s-1DWARF2\s0 line number debugging
|
|
info. This may be useful when not using the \s-1GNU\s0 assembler.
|
|
.Ip "\fB\-mfixed-range=\fR\fIregister range\fR" 4
|
|
.IX Item "-mfixed-range=register 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.
|
|
.PP
|
|
.I "D30V Options"
|
|
.IX Subsection "D30V Options"
|
|
.PP
|
|
These \fB\-m\fR options are defined for D30V implementations:
|
|
.Ip "\fB\-mextmem\fR" 4
|
|
.IX Item "-mextmem"
|
|
Link the \fB.text\fR, \fB.data\fR, \fB.bss\fR, \fB.strings\fR,
|
|
\&\fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections into external
|
|
memory, which starts at location \f(CW\*(C`0x80000000\*(C'\fR.
|
|
.Ip "\fB\-mextmemory\fR" 4
|
|
.IX Item "-mextmemory"
|
|
Same as the \fB\-mextmem\fR switch.
|
|
.Ip "\fB\-monchip\fR" 4
|
|
.IX Item "-monchip"
|
|
Link the \fB.text\fR section into onchip text memory, which starts at
|
|
location \f(CW\*(C`0x0\*(C'\fR. Also link \fB.data\fR, \fB.bss\fR,
|
|
\&\fB.strings\fR, \fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections
|
|
into onchip data memory, which starts at location \f(CW\*(C`0x20000000\*(C'\fR.
|
|
.Ip "\fB\-mno-asm-optimize\fR" 4
|
|
.IX Item "-mno-asm-optimize"
|
|
.PD 0
|
|
.Ip "\fB\-masm-optimize\fR" 4
|
|
.IX Item "-masm-optimize"
|
|
.PD
|
|
Disable (enable) passing \fB\-O\fR to the assembler when optimizing.
|
|
The assembler uses the \fB\-O\fR option to automatically parallelize
|
|
adjacent short instructions where possible.
|
|
.Ip "\fB\-mbranch-cost=\fR\fIn\fR" 4
|
|
.IX Item "-mbranch-cost=n"
|
|
Increase the internal costs of branches to \fIn\fR. Higher costs means
|
|
that the compiler will issue more instructions to avoid doing a branch.
|
|
The default is 2.
|
|
.Ip "\fB\-mcond-exec=\fR\fIn\fR" 4
|
|
.IX Item "-mcond-exec=n"
|
|
Specify the maximum number of conditionally executed instructions that
|
|
replace a branch. The default is 4.
|
|
.Sh "Options for Code Generation Conventions"
|
|
.IX Subsection "Options for Code Generation Conventions"
|
|
These machine-independent options control the interface conventions
|
|
used in code generation.
|
|
.PP
|
|
Most of them have both positive and negative forms; the negative form
|
|
of \fB\-ffoo\fR would be \fB\-fno-foo\fR. 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 \fBno-\fR or adding
|
|
it.
|
|
.Ip "\fB\-fexceptions\fR" 4
|
|
.IX Item "-fexceptions"
|
|
Enable exception handling. Generates extra code needed to propagate
|
|
exceptions. For some targets, this implies \s-1GNU\s0 \s-1CC\s0 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, \s-1GNU\s0 \s-1CC\s0 will enable it by default for languages like
|
|
\&\*(C+ which normally require exception handling, and disable itfor
|
|
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.
|
|
.Ip "\fB\-funwind-tables\fR" 4
|
|
.IX Item "-funwind-tables"
|
|
Similar to \fB\-fexceptions\fR, 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.
|
|
.Ip "\fB\-fpcc-struct-return\fR" 4
|
|
.IX Item "-fpcc-struct-return"
|
|
Return ``short'' \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR 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.
|
|
.Sp
|
|
The precise convention for returning structures in memory depends
|
|
on the target configuration macros.
|
|
.Sp
|
|
Short structures and unions are those whose size and alignment match
|
|
that of some integer type.
|
|
.Ip "\fB\-freg-struct-return\fR" 4
|
|
.IX Item "-freg-struct-return"
|
|
Use the convention that \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values are
|
|
returned in registers when possible. This is more efficient for small
|
|
structures than \fB\-fpcc-struct-return\fR.
|
|
.Sp
|
|
If you specify neither \fB\-fpcc-struct-return\fR nor its contrary
|
|
\&\fB\-freg-struct-return\fR, \s-1GCC\s0 defaults to whichever convention is
|
|
standard for the target. If there is no standard convention, \s-1GCC\s0
|
|
defaults to \fB\-fpcc-struct-return\fR, except on targets where \s-1GCC\s0
|
|
is the principal compiler. In those cases, we can choose the standard,
|
|
and we chose the more efficient register return alternative.
|
|
.Ip "\fB\-fshort-enums\fR" 4
|
|
.IX Item "-fshort-enums"
|
|
Allocate to an \f(CW\*(C`enum\*(C'\fR type only as many bytes as it needs for the
|
|
declared range of possible values. Specifically, the \f(CW\*(C`enum\*(C'\fR type
|
|
will be equivalent to the smallest integer type which has enough room.
|
|
.Ip "\fB\-fshort-double\fR" 4
|
|
.IX Item "-fshort-double"
|
|
Use the same size for \f(CW\*(C`double\*(C'\fR as for \f(CW\*(C`float\*(C'\fR.
|
|
.Ip "\fB\-fshared-data\fR" 4
|
|
.IX Item "-fshared-data"
|
|
Requests that the data and non-\f(CW\*(C`const\*(C'\fR variables of this
|
|
compilation be shared data rather than private data. The distinction
|
|
makes sense only on certain operating systems, where shared data is
|
|
shared between processes running the same program, while private data
|
|
exists in one copy per process.
|
|
.Ip "\fB\-fno-common\fR" 4
|
|
.IX Item "-fno-common"
|
|
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 \f(CW\*(C`extern\*(C'\fR) 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.
|
|
.Ip "\fB\-fno-ident\fR" 4
|
|
.IX Item "-fno-ident"
|
|
Ignore the \fB#ident\fR directive.
|
|
.Ip "\fB\-fno-gnu-linker\fR" 4
|
|
.IX Item "-fno-gnu-linker"
|
|
Do not output global initializations (such as \*(C+ constructors and
|
|
destructors) in the form used by the \s-1GNU\s0 linker (on systems where the \s-1GNU\s0
|
|
linker is the standard method of handling them). Use this option when
|
|
you want to use a non-GNU linker, which also requires using the
|
|
\&\fBcollect2\fR program to make sure the system linker includes
|
|
constructors and destructors. (\fBcollect2\fR is included in the \s-1GCC\s0
|
|
distribution.) For systems which \fImust\fR use \fBcollect2\fR, the
|
|
compiler driver \fBgcc\fR is configured to do this automatically.
|
|
.Ip "\fB\-finhibit-size-directive\fR" 4
|
|
.IX Item "-finhibit-size-directive"
|
|
Don't output a \f(CW\*(C`.size\*(C'\fR 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 \fIcrtstuff.c\fR; you should not need to use it
|
|
for anything else.
|
|
.Ip "\fB\-fverbose-asm\fR" 4
|
|
.IX Item "-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).
|
|
.Sp
|
|
\&\fB\-fno-verbose-asm\fR, the default, causes the
|
|
extra information to be omitted and is useful when comparing two assembler
|
|
files.
|
|
.Ip "\fB\-fvolatile\fR" 4
|
|
.IX Item "-fvolatile"
|
|
Consider all memory references through pointers to be volatile.
|
|
.Ip "\fB\-fvolatile-global\fR" 4
|
|
.IX Item "-fvolatile-global"
|
|
Consider all memory references to extern and global data items to
|
|
be volatile. \s-1GCC\s0 does not consider static data items to be volatile
|
|
because of this switch.
|
|
.Ip "\fB\-fvolatile-static\fR" 4
|
|
.IX Item "-fvolatile-static"
|
|
Consider all memory references to static data to be volatile.
|
|
.Ip "\fB\-fpic\fR" 4
|
|
.IX Item "-fpic"
|
|
Generate position-independent code (\s-1PIC\s0) suitable for use in a shared
|
|
library, if supported for the target machine. Such code accesses all
|
|
constant addresses through a global offset table (\s-1GOT\s0). The dynamic
|
|
loader resolves the \s-1GOT\s0 entries when the program starts (the dynamic
|
|
loader is not part of \s-1GCC\s0; it is part of the operating system). If
|
|
the \s-1GOT\s0 size for the linked executable exceeds a machine-specific
|
|
maximum size, you get an error message from the linker indicating that
|
|
\&\fB\-fpic\fR does not work; in that case, recompile with \fB\-fPIC\fR
|
|
instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k
|
|
on the m68k and \s-1RS/6000\s0. The 386 has no such limit.)
|
|
.Sp
|
|
Position-independent code requires special support, and therefore works
|
|
only on certain machines. For the 386, \s-1GCC\s0 supports \s-1PIC\s0 for System V
|
|
but not for the Sun 386i. Code generated for the \s-1IBM\s0 \s-1RS/6000\s0 is always
|
|
position-independent.
|
|
.Ip "\fB\-fPIC\fR" 4
|
|
.IX Item "-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, m88k,
|
|
and the Sparc.
|
|
.Sp
|
|
Position-independent code requires special support, and therefore works
|
|
only on certain machines.
|
|
.Ip "\fB\-ffixed-\fR\fIreg\fR" 4
|
|
.IX Item "-ffixed-reg"
|
|
Treat the register named \fIreg\fR 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).
|
|
.Sp
|
|
\&\fIreg\fR must be the name of a register. The register names accepted
|
|
are machine-specific and are defined in the \f(CW\*(C`REGISTER_NAMES\*(C'\fR
|
|
macro in the machine description macro file.
|
|
.Sp
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
.Ip "\fB\-fcall-used-\fR\fIreg\fR" 4
|
|
.IX Item "-fcall-used-reg"
|
|
Treat the register named \fIreg\fR 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 \fIreg\fR.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
.Ip "\fB\-fcall-saved-\fR\fIreg\fR" 4
|
|
.IX Item "-fcall-saved-reg"
|
|
Treat the register named \fIreg\fR 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 \fIreg\fR if they use it.
|
|
.Sp
|
|
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.
|
|
.Sp
|
|
A different sort of disaster will result from the use of this flag for
|
|
a register in which function values may be returned.
|
|
.Sp
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
.Ip "\fB\-fpack-struct\fR" 4
|
|
.IX Item "-fpack-struct"
|
|
Pack all structure members together without holes. Usually you would
|
|
not want to use this option, since it makes the code suboptimal, and
|
|
the offsets of structure members won't agree with system libraries.
|
|
.Ip "\fB\-fcheck-memory-usage\fR" 4
|
|
.IX Item "-fcheck-memory-usage"
|
|
Generate extra code to check each memory access. \s-1GCC\s0 will generate
|
|
code that is suitable for a detector of bad memory accesses such as
|
|
\&\fIChecker\fR.
|
|
.Sp
|
|
Normally, you should compile all, or none, of your code with this option.
|
|
.Sp
|
|
If you do mix code compiled with and without this option,
|
|
you must ensure that all code that has side effects
|
|
and that is called by code compiled with this option
|
|
is, itself, compiled with this option.
|
|
If you do not, you might get erroneous messages from the detector.
|
|
.Sp
|
|
If you use functions from a library that have side-effects (such as
|
|
\&\f(CW\*(C`read\*(C'\fR), you might not be able to recompile the library and
|
|
specify this option. In that case, you can enable the
|
|
\&\fB\-fprefix-function-name\fR option, which requests \s-1GCC\s0 to encapsulate
|
|
your code and make other functions look as if they were compiled with
|
|
\&\fB\-fcheck-memory-usage\fR. This is done by calling ``stubs'',
|
|
which are provided by the detector. If you cannot find or build
|
|
stubs for every function you call, you might have to specify
|
|
\&\fB\-fcheck-memory-usage\fR without \fB\-fprefix-function-name\fR.
|
|
.Sp
|
|
If you specify this option, you can not use the \f(CW\*(C`asm\*(C'\fR or
|
|
\&\f(CW\*(C`_\|_asm_\|_\*(C'\fR keywords in functions with memory checking enabled. \s-1GNU\s0
|
|
\&\s-1CC\s0 cannot understand what the \f(CW\*(C`asm\*(C'\fR statement may do, and therefore
|
|
cannot generate the appropriate code, so it will reject it. However, if
|
|
you specify the function attribute \f(CW\*(C`no_check_memory_usage\*(C'\fR, \s-1GNU\s0 \s-1CC\s0 will disable memory checking within a
|
|
function; you may use \f(CW\*(C`asm\*(C'\fR statements inside such functions. You
|
|
may have an inline expansion of a non-checked function within a checked
|
|
function; in that case \s-1GNU\s0 \s-1CC\s0 will not generate checks for the inlined
|
|
function's memory accesses.
|
|
.Sp
|
|
If you move your \f(CW\*(C`asm\*(C'\fR statements to non-checked inline functions
|
|
and they do access memory, you can add calls to the support code in your
|
|
inline function, to indicate any reads, writes, or copies being done.
|
|
These calls would be similar to those done in the stubs described above.
|
|
.Ip "\fB\-fprefix-function-name\fR" 4
|
|
.IX Item "-fprefix-function-name"
|
|
Request \s-1GCC\s0 to add a prefix to the symbols generated for function names.
|
|
\&\s-1GCC\s0 adds a prefix to the names of functions defined as well as
|
|
functions called. Code compiled with this option and code compiled
|
|
without the option can't be linked together, unless stubs are used.
|
|
.Sp
|
|
If you compile the following code with \fB\-fprefix-function-name\fR
|
|
.Sp
|
|
.Vb 6
|
|
\& extern void bar (int);
|
|
\& void
|
|
\& foo (int a)
|
|
\& {
|
|
\& return bar (a + 5);
|
|
\& }
|
|
.Ve
|
|
\&\s-1GCC\s0 will compile the code as if it was written:
|
|
.Sp
|
|
.Vb 6
|
|
\& extern void prefix_bar (int);
|
|
\& void
|
|
\& prefix_foo (int a)
|
|
\& {
|
|
\& return prefix_bar (a + 5);
|
|
\& }
|
|
.Ve
|
|
This option is designed to be used with \fB\-fcheck-memory-usage\fR.
|
|
.Ip "\fB\-finstrument-functions\fR" 4
|
|
.IX Item "-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,
|
|
\&\f(CW\*(C`_\|_builtin_return_address\*(C'\fR does not work beyond the current
|
|
function, so the call site information may not be available to the
|
|
profiling functions otherwise.)
|
|
.Sp
|
|
.Vb 2
|
|
\& void __cyg_profile_func_enter (void *this_fn, void *call_site);
|
|
\& void __cyg_profile_func_exit (void *this_fn, void *call_site);
|
|
.Ve
|
|
The first argument is the address of the start of the current function,
|
|
which may be looked up exactly in the symbol table.
|
|
.Sp
|
|
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 \fBextern inline\fR 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.)
|
|
.Sp
|
|
A function may be given the attribute \f(CW\*(C`no_instrument_function\*(C'\fR, 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).
|
|
.Ip "\fB\-fstack-check\fR" 4
|
|
.IX Item "-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.
|
|
.Sp
|
|
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.
|
|
.Ip "\fB\-fstack-limit-register=\fR\fIreg\fR" 4
|
|
.IX Item "-fstack-limit-register=reg"
|
|
.PD 0
|
|
.Ip "\fB\-fstack-limit-symbol=\fR\fIsym\fR" 4
|
|
.IX Item "-fstack-limit-symbol=sym"
|
|
.Ip "\fB\-fno-stack-limit\fR" 4
|
|
.IX Item "-fno-stack-limit"
|
|
.PD
|
|
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.
|
|
.Sp
|
|
For instance, if the stack starts at address \fB0x80000000\fR and grows
|
|
downwards you can use the flags
|
|
\&\fB\-fstack-limit-symbol=_\|_stack_limit\fR
|
|
\&\fB\-Wl,\-\-defsym,_\|_stack_limit=0x7ffe0000\fR which will enforce a stack
|
|
limit of 128K.
|
|
.Ip "\fB\-fargument-alias\fR" 4
|
|
.IX Item "-fargument-alias"
|
|
.PD 0
|
|
.Ip "\fB\-fargument-noalias\fR" 4
|
|
.IX Item "-fargument-noalias"
|
|
.Ip "\fB\-fargument-noalias-global\fR" 4
|
|
.IX Item "-fargument-noalias-global"
|
|
.PD
|
|
Specify the possible relationships among parameters and between
|
|
parameters and global data.
|
|
.Sp
|
|
\&\fB\-fargument-alias\fR specifies that arguments (parameters) may
|
|
alias each other and may alias global storage.
|
|
\&\fB\-fargument-noalias\fR specifies that arguments do not alias
|
|
each other, but may alias global storage.
|
|
\&\fB\-fargument-noalias-global\fR specifies that arguments do not
|
|
alias each other and do not alias global storage.
|
|
.Sp
|
|
Each language will automatically use whatever option is required by
|
|
the language standard. You should not need to use these options yourself.
|
|
.Ip "\fB\-fleading-underscore\fR" 4
|
|
.IX Item "-fleading-underscore"
|
|
This option and its counterpart, \-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.
|
|
.Sp
|
|
Be warned that you should know what you are doing when invoking this
|
|
option, and that not all targets provide complete support for it.
|
|
.SH "ENVIRONMENT"
|
|
.IX Header "ENVIRONMENT"
|
|
This section describes several environment variables that affect how \s-1GCC\s0
|
|
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.
|
|
.PP
|
|
Note that you can also specify places to search using options such as
|
|
\&\fB\-B\fR, \fB\-I\fR and \fB\-L\fR. These
|
|
take precedence over places specified using environment variables, which
|
|
in turn take precedence over those specified by the configuration of \s-1GCC\s0.
|
|
.Ip "\fB\s-1LANG\s0\fR" 4
|
|
.IX Item "LANG"
|
|
.PD 0
|
|
.Ip "\fB\s-1LC_CTYPE\s0\fR" 4
|
|
.IX Item "LC_CTYPE"
|
|
.Ip "\fB\s-1LC_MESSAGES\s0\fR" 4
|
|
.IX Item "LC_MESSAGES"
|
|
.Ip "\fB\s-1LC_ALL\s0\fR" 4
|
|
.IX Item "LC_ALL"
|
|
.PD
|
|
These environment variables control the way that \s-1GCC\s0 uses
|
|
localization information that allow \s-1GCC\s0 to work with different
|
|
national conventions. \s-1GCC\s0 inspects the locale categories
|
|
\&\fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR 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 \fBen_UK\fR for English in the United
|
|
Kingdom.
|
|
.Sp
|
|
The \fB\s-1LC_CTYPE\s0\fR environment variable specifies character
|
|
classification. \s-1GCC\s0 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.
|
|
.Sp
|
|
The \fB\s-1LC_MESSAGES\s0\fR environment variable specifies the language to
|
|
use in diagnostic messages.
|
|
.Sp
|
|
If the \fB\s-1LC_ALL\s0\fR environment variable is set, it overrides the value
|
|
of \fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR; otherwise, \fB\s-1LC_CTYPE\s0\fR
|
|
and \fB\s-1LC_MESSAGES\s0\fR default to the value of the \fB\s-1LANG\s0\fR
|
|
environment variable. If none of these variables are set, \s-1GCC\s0
|
|
defaults to traditional C English behavior.
|
|
.Ip "\fB\s-1TMPDIR\s0\fR" 4
|
|
.IX Item "TMPDIR"
|
|
If \fB\s-1TMPDIR\s0\fR is set, it specifies the directory to use for temporary
|
|
files. \s-1GCC\s0 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.
|
|
.Ip "\fB\s-1GCC_EXEC_PREFIX\s0\fR" 4
|
|
.IX Item "GCC_EXEC_PREFIX"
|
|
If \fB\s-1GCC_EXEC_PREFIX\s0\fR 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.
|
|
.Sp
|
|
If \fB\s-1GCC_EXEC_PREFIX\s0\fR is not set, \s-1GNU\s0 \s-1CC\s0 will attempt to figure out
|
|
an appropriate prefix to use based on the pathname it was invoked with.
|
|
.Sp
|
|
If \s-1GCC\s0 cannot find the subprogram using the specified prefix, it
|
|
tries looking in the usual places for the subprogram.
|
|
.Sp
|
|
The default value of \fB\s-1GCC_EXEC_PREFIX\s0\fR is
|
|
\&\fI\fIprefix\fI/lib/gcc-lib/\fR where \fIprefix\fR is the value
|
|
of \f(CW\*(C`prefix\*(C'\fR when you ran the \fIconfigure\fR script.
|
|
.Sp
|
|
Other prefixes specified with \fB\-B\fR take precedence over this prefix.
|
|
.Sp
|
|
This prefix is also used for finding files such as \fIcrt0.o\fR that are
|
|
used for linking.
|
|
.Sp
|
|
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 \fB/usr/local/lib/gcc-lib\fR
|
|
(more precisely, with the value of \fB\s-1GCC_INCLUDE_DIR\s0\fR), \s-1GCC\s0 tries
|
|
replacing that beginning with the specified prefix to produce an
|
|
alternate directory name. Thus, with \fB\-Bfoo/\fR, \s-1GCC\s0 will search
|
|
\&\fIfoo/bar\fR where it would normally search \fI/usr/local/lib/bar\fR.
|
|
These alternate directories are searched first; the standard directories
|
|
come next.
|
|
.Ip "\fB\s-1COMPILER_PATH\s0\fR" 4
|
|
.IX Item "COMPILER_PATH"
|
|
The value of \fB\s-1COMPILER_PATH\s0\fR is a colon-separated list of
|
|
directories, much like \fB\s-1PATH\s0\fR. \s-1GCC\s0 tries the directories thus
|
|
specified when searching for subprograms, if it can't find the
|
|
subprograms using \fB\s-1GCC_EXEC_PREFIX\s0\fR.
|
|
.Ip "\fB\s-1LIBRARY_PATH\s0\fR" 4
|
|
.IX Item "LIBRARY_PATH"
|
|
The value of \fB\s-1LIBRARY_PATH\s0\fR is a colon-separated list of
|
|
directories, much like \fB\s-1PATH\s0\fR. When configured as a native compiler,
|
|
\&\s-1GCC\s0 tries the directories thus specified when searching for special
|
|
linker files, if it can't find them using \fB\s-1GCC_EXEC_PREFIX\s0\fR. Linking
|
|
using \s-1GCC\s0 also uses these directories when searching for ordinary
|
|
libraries for the \fB\-l\fR option (but directories specified with
|
|
\&\fB\-L\fR come first).
|
|
.Ip "\fBC_INCLUDE_PATH\fR" 4
|
|
.IX Item "C_INCLUDE_PATH"
|
|
.PD 0
|
|
.Ip "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
|
|
.IX Item "CPLUS_INCLUDE_PATH"
|
|
.Ip "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
|
|
.IX Item "OBJC_INCLUDE_PATH"
|
|
.PD
|
|
These environment variables pertain to particular languages. Each
|
|
variable's value is a colon-separated list of directories, much like
|
|
\&\fB\s-1PATH\s0\fR. When \s-1GCC\s0 searches for header files, it tries the
|
|
directories listed in the variable for the language you are using, after
|
|
the directories specified with \fB\-I\fR but before the standard header
|
|
file directories.
|
|
.Ip "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
|
|
.IX Item "DEPENDENCIES_OUTPUT"
|
|
If this variable is set, its value specifies how to output dependencies
|
|
for Make based on the header files processed by the compiler. This
|
|
output looks much like the output from the \fB\-M\fR option, but it goes to a separate file, and is
|
|
in addition to the usual results of compilation.
|
|
.Sp
|
|
The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
|
|
which case the Make rules are written to that file, guessing the target
|
|
name from the source file name. Or the value can have the form
|
|
\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
|
|
file \fIfile\fR using \fItarget\fR as the target name.
|
|
.Ip "\fB\s-1LANG\s0\fR" 4
|
|
.IX Item "LANG"
|
|
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 \fB\s-1LANG\s0\fR are recognized:
|
|
.RS 4
|
|
.Ip "\fBC-JIS\fR" 4
|
|
.IX Item "C-JIS"
|
|
Recognize \s-1JIS\s0 characters.
|
|
.Ip "\fBC-SJIS\fR" 4
|
|
.IX Item "C-SJIS"
|
|
Recognize \s-1SJIS\s0 characters.
|
|
.Ip "\fBC-EUCJP\fR" 4
|
|
.IX Item "C-EUCJP"
|
|
Recognize \s-1EUCJP\s0 characters.
|
|
.RE
|
|
.RS 4
|
|
.Sp
|
|
If \fB\s-1LANG\s0\fR 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.
|
|
.RE
|
|
.SH "BUGS"
|
|
.IX Header "BUGS"
|
|
For instructions on reporting bugs, see
|
|
<\fBhttp://gcc.gnu.org/bugs.html\fR>. Use of the \fBgccbug\fR
|
|
script to report bugs is recommended.
|
|
.SH "FOOTNOTES"
|
|
.IX Header "FOOTNOTES"
|
|
.Ip "1." 4
|
|
On some systems, \fBgcc \-shared\fR
|
|
needs to build supplementary stub code for constructors to work. On
|
|
multi-libbed systems, \fBgcc \-shared\fR 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.
|
|
.SH "SEE ALSO"
|
|
.IX Header "SEE ALSO"
|
|
\&\fIcpp\fR\|(1), \fIgcov\fR\|(1), \fIg77\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), \fIgdb\fR\|(1), \fIadb\fR\|(1), \fIdbx\fR\|(1), \fIsdb\fR\|(1)
|
|
and the Info entries for \fIgcc\fR, \fIcpp\fR, \fIg77\fR, \fIas\fR,
|
|
\&\fIld\fR, \fIbinutils\fR and \fIgdb\fR.
|
|
.SH "AUTHOR"
|
|
.IX Header "AUTHOR"
|
|
See the Info entry for \fIgcc\fR, or
|
|
<\fBhttp://gcc.gnu.org/thanks.html\fR>, for contributors to \s-1GCC\s0.
|
|
.SH "COPYRIGHT"
|
|
.IX Header "COPYRIGHT"
|
|
Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
|
|
1998, 1999, 2000, 2001 Free Software Foundation, Inc.
|
|
.PP
|
|
Permission is granted to make and distribute verbatim copies of this
|
|
manual provided the copyright notice and this permission notice are
|
|
preserved on all copies.
|
|
.PP
|
|
Permission is granted to copy and distribute modified versions of this
|
|
manual under the conditions for verbatim copying, provided also that the
|
|
entire resulting derived work is distributed under the terms of a
|
|
permission notice identical to this one.
|
|
.PP
|
|
Permission is granted to copy and distribute translations of this manual
|
|
into another language, under the above conditions for modified versions,
|
|
except that this permission notice may be included in translations
|
|
approved by the Free Software Foundation instead of in the original
|
|
English.
|