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| .\" ======================================================================== |
| .\" |
| .IX Title "GCC 1" |
| .TH GCC 1 "2007-03-17" "gcc-4.2.0" "GNU" |
| .SH "NAME" |
| gcc \- GNU project C and C++ compiler |
| .SH "SYNOPSIS" |
| .IX Header "SYNOPSIS" |
| gcc [\fB\-c\fR|\fB\-S\fR|\fB\-E\fR] [\fB\-std=\fR\fIstandard\fR] |
| [\fB\-g\fR] [\fB\-pg\fR] [\fB\-O\fR\fIlevel\fR] |
| [\fB\-W\fR\fIwarn\fR...] [\fB\-pedantic\fR] |
| [\fB\-I\fR\fIdir\fR...] [\fB\-L\fR\fIdir\fR...] |
| [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR] |
| [\fB\-f\fR\fIoption\fR...] [\fB\-m\fR\fImachine-option\fR...] |
| [\fB\-o\fR \fIoutfile\fR] [@\fIfile\fR] \fIinfile\fR... |
| .PP |
| Only the most useful options are listed here; see below for the |
| remainder. \fBg++\fR accepts mostly the same options as \fBgcc\fR. |
| .SH "DESCRIPTION" |
| .IX Header "DESCRIPTION" |
| When you invoke \s-1GCC\s0, it normally does preprocessing, compilation, |
| assembly and linking. The \*(L"overall options\*(R" 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. |
| .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. |
| .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. |
| .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\-fmove\-loop\-invariants\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 |
| 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\-combine \-pipe \-pass\-exit\-codes |
| \&\-x\fR \fIlanguage\fR \fB\-v \-### \-\-help \-\-target\-help \-\-version @\fR\fIfile\fR |
| .IP "\fIC Language Options\fR" 4 |
| .IX Item "C Language Options" |
| \&\fB\-ansi \-std=\fR\fIstandard\fR \fB\-fgnu89\-inline |
| \&\-aux\-info\fR \fIfilename\fR |
| \&\fB\-fno\-asm \-fno\-builtin \-fno\-builtin\-\fR\fIfunction\fR |
| \&\fB\-fhosted \-ffreestanding \-fopenmp \-fms\-extensions |
| \&\-trigraphs \-no\-integrated\-cpp \-traditional \-traditional\-cpp |
| \&\-fallow\-single\-precision \-fcond\-mismatch |
| \&\-fsigned\-bitfields \-fsigned\-char |
| \&\-funsigned\-bitfields \-funsigned\-char\fR |
| .IP "\fI\*(C+ Language Options\fR" 4 |
| .IX Item " Language Options" |
| \&\fB\-fabi\-version=\fR\fIn\fR \fB\-fno\-access\-control \-fcheck\-new |
| \&\-fconserve\-space \-ffriend\-injection |
| \&\-fno\-elide\-constructors |
| \&\-fno\-enforce\-eh\-specs |
| \&\-ffor\-scope \-fno\-for\-scope \-fno\-gnu\-keywords |
| \&\-fno\-implicit\-templates |
| \&\-fno\-implicit\-inline\-templates |
| \&\-fno\-implement\-inlines \-fms\-extensions |
| \&\-fno\-nonansi\-builtins \-fno\-operator\-names |
| \&\-fno\-optional\-diags \-fpermissive |
| \&\-frepo \-fno\-rtti \-fstats \-ftemplate\-depth\-\fR\fIn\fR |
| \&\fB\-fno\-threadsafe\-statics \-fuse\-cxa\-atexit \-fno\-weak \-nostdinc++ |
| \&\-fno\-default\-inline \-fvisibility\-inlines\-hidden |
| \&\-Wabi \-Wctor\-dtor\-privacy |
| \&\-Wnon\-virtual\-dtor \-Wreorder |
| \&\-Weffc++ \-Wno\-deprecated \-Wstrict\-null\-sentinel |
| \&\-Wno\-non\-template\-friend \-Wold\-style\-cast |
| \&\-Woverloaded\-virtual \-Wno\-pmf\-conversions |
| \&\-Wsign\-promo\fR |
| .IP "\fIObjective-C and Objective\-\*(C+ Language Options\fR" 4 |
| .IX Item "Objective-C and Objective- Language Options" |
| \&\fB\-fconstant\-string\-class=\fR\fIclass-name\fR |
| \&\fB\-fgnu\-runtime \-fnext\-runtime |
| \&\-fno\-nil\-receivers |
| \&\-fobjc\-call\-cxx\-cdtors |
| \&\-fobjc\-direct\-dispatch |
| \&\-fobjc\-exceptions |
| \&\-fobjc\-gc |
| \&\-freplace\-objc\-classes |
| \&\-fzero\-link |
| \&\-gen\-decls |
| \&\-Wassign\-intercept |
| \&\-Wno\-protocol \-Wselector |
| \&\-Wstrict\-selector\-match |
| \&\-Wundeclared\-selector\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] |
| \&\fB\-fdiagnostics\-show\-option\fR |
| .IP "\fIWarning Options\fR" 4 |
| .IX Item "Warning Options" |
| \&\fB\-fsyntax\-only \-pedantic \-pedantic\-errors |
| \&\-w \-Wextra \-Wall \-Waddress \-Waggregate\-return \-Wno\-attributes |
| \&\-Wc++\-compat \-Wcast\-align \-Wcast\-qual \-Wchar\-subscripts \-Wcomment |
| \&\-Wconversion \-Wno\-deprecated\-declarations |
| \&\-Wdisabled\-optimization \-Wno\-div\-by\-zero \-Wno\-endif\-labels |
| \&\-Werror \-Werror=* \-Werror\-implicit\-function\-declaration |
| \&\-Wfatal\-errors \-Wfloat\-equal \-Wformat \-Wformat=2 |
| \&\-Wno\-format\-extra\-args \-Wformat\-nonliteral |
| \&\-Wformat\-security \-Wformat\-y2k |
| \&\-Wimplicit \-Wimplicit\-function\-declaration \-Wimplicit\-int |
| \&\-Wimport \-Wno\-import \-Winit\-self \-Winline |
| \&\-Wno\-int\-to\-pointer\-cast |
| \&\-Wno\-invalid\-offsetof \-Winvalid\-pch |
| \&\-Wlarger\-than\-\fR\fIlen\fR \fB\-Wunsafe\-loop\-optimizations \-Wlong\-long |
| \&\-Wmain \-Wmissing\-braces \-Wmissing\-field\-initializers |
| \&\-Wmissing\-format\-attribute \-Wmissing\-include\-dirs |
| \&\-Wmissing\-noreturn |
| \&\-Wno\-multichar \-Wnonnull \-Wno\-overflow |
| \&\-Woverlength\-strings \-Wpacked \-Wpadded |
| \&\-Wparentheses \-Wpointer\-arith \-Wno\-pointer\-to\-int\-cast |
| \&\-Wredundant\-decls |
| \&\-Wreturn\-type \-Wsequence\-point \-Wshadow |
| \&\-Wsign\-compare \-Wstack\-protector |
| \&\-Wstrict\-aliasing \-Wstrict\-aliasing=2 |
| \&\-Wstrict\-overflow \-Wstrict\-overflow=\fR\fIn\fR |
| \&\fB\-Wswitch \-Wswitch\-default \-Wswitch\-enum |
| \&\-Wsystem\-headers \-Wtrigraphs \-Wundef \-Wuninitialized |
| \&\-Wunknown\-pragmas \-Wno\-pragmas \-Wunreachable\-code |
| \&\-Wunused \-Wunused\-function \-Wunused\-label \-Wunused\-parameter |
| \&\-Wunused\-value \-Wunused\-variable \-Wvariadic\-macros |
| \&\-Wvolatile\-register\-var \-Wwrite\-strings\fR |
| .IP "\fIC\-only Warning Options\fR" 4 |
| .IX Item "C-only Warning Options" |
| \&\fB\-Wbad\-function\-cast \-Wmissing\-declarations |
| \&\-Wmissing\-prototypes \-Wnested\-externs \-Wold\-style\-definition |
| \&\-Wstrict\-prototypes \-Wtraditional |
| \&\-Wdeclaration\-after\-statement \-Wpointer\-sign\fR |
| .IP "\fIDebugging Options\fR" 4 |
| .IX Item "Debugging Options" |
| \&\fB\-d\fR\fIletters\fR \fB\-dumpspecs \-dumpmachine \-dumpversion |
| \&\-fdump\-noaddr \-fdump\-unnumbered \-fdump\-translation\-unit\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-class\-hierarchy\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-ipa\-all \-fdump\-ipa\-cgraph |
| \&\-fdump\-tree\-all |
| \&\-fdump\-tree\-original\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-optimized\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-inlined\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-cfg \-fdump\-tree\-vcg \-fdump\-tree\-alias |
| \&\-fdump\-tree\-ch |
| \&\-fdump\-tree\-ssa\fR[\fB\-\fR\fIn\fR] \fB\-fdump\-tree\-pre\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-ccp\fR[\fB\-\fR\fIn\fR] \fB\-fdump\-tree\-dce\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-gimple\fR[\fB\-raw\fR] \fB\-fdump\-tree\-mudflap\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-dom\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-dse\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-phiopt\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-forwprop\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-copyrename\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-nrv \-fdump\-tree\-vect |
| \&\-fdump\-tree\-sink |
| \&\-fdump\-tree\-sra\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-salias |
| \&\-fdump\-tree\-fre\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-fdump\-tree\-vrp\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-ftree\-vectorizer\-verbose=\fR\fIn\fR |
| \&\fB\-fdump\-tree\-storeccp\fR[\fB\-\fR\fIn\fR] |
| \&\fB\-feliminate\-dwarf2\-dups \-feliminate\-unused\-debug\-types |
| \&\-feliminate\-unused\-debug\-symbols \-femit\-class\-debug\-always |
| \&\-fmem\-report \-fprofile\-arcs |
| \&\-frandom\-seed=\fR\fIstring\fR \fB\-fsched\-verbose=\fR\fIn\fR |
| \&\fB\-ftest\-coverage \-ftime\-report \-fvar\-tracking |
| \&\-g \-g\fR\fIlevel\fR \fB\-gcoff \-gdwarf\-2 |
| \&\-ggdb \-gstabs \-gstabs+ \-gvms \-gxcoff \-gxcoff+ |
| \&\-p \-pg \-print\-file\-name=\fR\fIlibrary\fR \fB\-print\-libgcc\-file\-name |
| \&\-print\-multi\-directory \-print\-multi\-lib |
| \&\-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\-fbounds\-check \-fmudflap \-fmudflapth \-fmudflapir |
| \&\-fbranch\-probabilities \-fprofile\-values \-fvpt \-fbranch\-target\-load\-optimize |
| \&\-fbranch\-target\-load\-optimize2 \-fbtr\-bb\-exclusive |
| \&\-fcaller\-saves \-fcprop\-registers \-fcse\-follow\-jumps |
| \&\-fcse\-skip\-blocks \-fcx\-limited\-range \-fdata\-sections |
| \&\-fdelayed\-branch \-fdelete\-null\-pointer\-checks \-fearly\-inlining |
| \&\-fexpensive\-optimizations \-ffast\-math \-ffloat\-store |
| \&\-fforce\-addr \-ffunction\-sections |
| \&\-fgcse \-fgcse\-lm \-fgcse\-sm \-fgcse\-las \-fgcse\-after\-reload |
| \&\-fcrossjumping \-fif\-conversion \-fif\-conversion2 |
| \&\-finline\-functions \-finline\-functions\-called\-once |
| \&\-finline\-limit=\fR\fIn\fR \fB\-fkeep\-inline\-functions |
| \&\-fkeep\-static\-consts \-fmerge\-constants \-fmerge\-all\-constants |
| \&\-fmodulo\-sched \-fno\-branch\-count\-reg |
| \&\-fno\-default\-inline \-fno\-defer\-pop \-fmove\-loop\-invariants |
| \&\-fno\-function\-cse \-fno\-guess\-branch\-probability |
| \&\-fno\-inline \-fno\-math\-errno \-fno\-peephole \-fno\-peephole2 |
| \&\-funsafe\-math\-optimizations \-funsafe\-loop\-optimizations \-ffinite\-math\-only |
| \&\-fno\-toplevel\-reorder \-fno\-trapping\-math \-fno\-zero\-initialized\-in\-bss |
| \&\-fomit\-frame\-pointer \-foptimize\-register\-move |
| \&\-foptimize\-sibling\-calls \-fprefetch\-loop\-arrays |
| \&\-fprofile\-generate \-fprofile\-use |
| \&\-fregmove \-frename\-registers |
| \&\-freorder\-blocks \-freorder\-blocks\-and\-partition \-freorder\-functions |
| \&\-frerun\-cse\-after\-loop |
| \&\-frounding\-math \-frtl\-abstract\-sequences |
| \&\-fschedule\-insns \-fschedule\-insns2 |
| \&\-fno\-sched\-interblock \-fno\-sched\-spec \-fsched\-spec\-load |
| \&\-fsched\-spec\-load\-dangerous |
| \&\-fsched\-stalled\-insns=\fR\fIn\fR \fB\-fsched\-stalled\-insns\-dep=\fR\fIn\fR |
| \&\fB\-fsched2\-use\-superblocks |
| \&\-fsched2\-use\-traces \-fsee \-freschedule\-modulo\-scheduled\-loops |
| \&\-fsection\-anchors \-fsignaling\-nans \-fsingle\-precision\-constant |
| \&\-fstack\-protector \-fstack\-protector\-all |
| \&\-fstrict\-aliasing \-fstrict\-overflow \-ftracer \-fthread\-jumps |
| \&\-funroll\-all\-loops \-funroll\-loops \-fpeel\-loops |
| \&\-fsplit\-ivs\-in\-unroller \-funswitch\-loops |
| \&\-fvariable\-expansion\-in\-unroller |
| \&\-ftree\-pre \-ftree\-ccp \-ftree\-dce \-ftree\-loop\-optimize |
| \&\-ftree\-loop\-linear \-ftree\-loop\-im \-ftree\-loop\-ivcanon \-fivopts |
| \&\-ftree\-dominator\-opts \-ftree\-dse \-ftree\-copyrename \-ftree\-sink |
| \&\-ftree\-ch \-ftree\-sra \-ftree\-ter \-ftree\-lrs \-ftree\-fre \-ftree\-vectorize |
| \&\-ftree\-vect\-loop\-version \-ftree\-salias \-fipa\-pta \-fweb |
| \&\-ftree\-copy\-prop \-ftree\-store\-ccp \-ftree\-store\-copy\-prop \-fwhole\-program |
| \&\-\-param\fR \fIname\fR\fB=\fR\fIvalue\fR |
| \&\fB\-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\-imultilib\fR \fIdir\fR \fB\-isysroot\fR \fIdir\fR |
| \&\fB\-M \-MM \-MF \-MG \-MP \-MQ \-MT \-nostdinc |
| \&\-P \-fworking\-directory \-remap |
| \&\-trigraphs \-undef \-U\fR\fImacro\fR \fB\-Wp,\fR\fIoption\fR |
| \&\fB\-Xpreprocessor\fR \fIoption\fR |
| .IP "\fIAssembler Option\fR" 4 |
| .IX Item "Assembler Option" |
| \&\fB\-Wa,\fR\fIoption\fR \fB\-Xassembler\fR \fIoption\fR |
| .IP "\fILinker Options\fR" 4 |
| .IX Item "Linker Options" |
| \&\fIobject-file-name\fR \fB\-l\fR\fIlibrary\fR |
| \&\fB\-nostartfiles \-nodefaultlibs \-nostdlib \-pie \-rdynamic |
| \&\-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\-iquote\fR\fIdir\fR \fB\-L\fR\fIdir\fR |
| \&\fB\-specs=\fR\fIfile\fR \fB\-I\- \-\-sysroot=\fR\fIdir\fR |
| .IP "\fITarget Options\fR" 4 |
| .IX Item "Target Options" |
| \&\fB\-V\fR \fIversion\fR \fB\-b\fR \fImachine\fR |
| .IP "\fIMachine Dependent Options\fR" 4 |
| .IX Item "Machine Dependent Options" |
| \&\fI\s-1ARC\s0 Options\fR |
| \&\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 |
| \&\fI\s-1ARM\s0 Options\fR |
| \&\fB\-mapcs\-frame \-mno\-apcs\-frame |
| \&\-mabi=\fR\fIname\fR |
| \&\fB\-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 |
| \&\-mfloat\-abi=\fR\fIname\fR \fB\-msoft\-float \-mhard\-float \-mfpe |
| \&\-mthumb\-interwork \-mno\-thumb\-interwork |
| \&\-mcpu=\fR\fIname\fR \fB\-march=\fR\fIname\fR \fB\-mfpu=\fR\fIname\fR |
| \&\fB\-mstructure\-size\-boundary=\fR\fIn\fR |
| \&\fB\-mabort\-on\-noreturn |
| \&\-mlong\-calls \-mno\-long\-calls |
| \&\-msingle\-pic\-base \-mno\-single\-pic\-base |
| \&\-mpic\-register=\fR\fIreg\fR |
| \&\fB\-mnop\-fun\-dllimport |
| \&\-mcirrus\-fix\-invalid\-insns \-mno\-cirrus\-fix\-invalid\-insns |
| \&\-mpoke\-function\-name |
| \&\-mthumb \-marm |
| \&\-mtpcs\-frame \-mtpcs\-leaf\-frame |
| \&\-mcaller\-super\-interworking \-mcallee\-super\-interworking |
| \&\-mtp=\fR\fIname\fR |
| .Sp |
| \&\fI\s-1AVR\s0 Options\fR |
| \&\fB\-mmcu=\fR\fImcu\fR \fB\-msize \-minit\-stack=\fR\fIn\fR \fB\-mno\-interrupts |
| \&\-mcall\-prologues \-mno\-tablejump \-mtiny\-stack \-mint8\fR |
| .Sp |
| \&\fIBlackfin Options\fR |
| \&\fB\-momit\-leaf\-frame\-pointer \-mno\-omit\-leaf\-frame\-pointer |
| \&\-mspecld\-anomaly \-mno\-specld\-anomaly \-mcsync\-anomaly \-mno\-csync\-anomaly |
| \&\-mlow\-64k \-mno\-low64k \-mid\-shared\-library |
| \&\-mno\-id\-shared\-library \-mshared\-library\-id=\fR\fIn\fR |
| \&\fB\-mlong\-calls \-mno\-long\-calls\fR |
| .Sp |
| \&\fI\s-1CRIS\s0 Options\fR |
| \&\fB\-mcpu=\fR\fIcpu\fR \fB\-march=\fR\fIcpu\fR \fB\-mtune=\fR\fIcpu\fR |
| \&\fB\-mmax\-stack\-frame=\fR\fIn\fR \fB\-melinux\-stacksize=\fR\fIn\fR |
| \&\fB\-metrax4 \-metrax100 \-mpdebug \-mcc\-init \-mno\-side\-effects |
| \&\-mstack\-align \-mdata\-align \-mconst\-align |
| \&\-m32\-bit \-m16\-bit \-m8\-bit \-mno\-prologue\-epilogue \-mno\-gotplt |
| \&\-melf \-maout \-melinux \-mlinux \-sim \-sim2 |
| \&\-mmul\-bug\-workaround \-mno\-mul\-bug\-workaround\fR |
| .Sp |
| \&\fI\s-1CRX\s0 Options\fR |
| \&\fB\-mmac \-mpush\-args\fR |
| .Sp |
| \&\fIDarwin Options\fR |
| \&\fB\-all_load \-allowable_client \-arch \-arch_errors_fatal |
| \&\-arch_only \-bind_at_load \-bundle \-bundle_loader |
| \&\-client_name \-compatibility_version \-current_version |
| \&\-dead_strip |
| \&\-dependency\-file \-dylib_file \-dylinker_install_name |
| \&\-dynamic \-dynamiclib \-exported_symbols_list |
| \&\-filelist \-flat_namespace \-force_cpusubtype_ALL |
| \&\-force_flat_namespace \-headerpad_max_install_names |
| \&\-image_base \-init \-install_name \-keep_private_externs |
| \&\-multi_module \-multiply_defined \-multiply_defined_unused |
| \&\-noall_load \-no_dead_strip_inits_and_terms |
| \&\-nofixprebinding \-nomultidefs \-noprebind \-noseglinkedit |
| \&\-pagezero_size \-prebind \-prebind_all_twolevel_modules |
| \&\-private_bundle \-read_only_relocs \-sectalign |
| \&\-sectobjectsymbols \-whyload \-seg1addr |
| \&\-sectcreate \-sectobjectsymbols \-sectorder |
| \&\-segaddr \-segs_read_only_addr \-segs_read_write_addr |
| \&\-seg_addr_table \-seg_addr_table_filename \-seglinkedit |
| \&\-segprot \-segs_read_only_addr \-segs_read_write_addr |
| \&\-single_module \-static \-sub_library \-sub_umbrella |
| \&\-twolevel_namespace \-umbrella \-undefined |
| \&\-unexported_symbols_list \-weak_reference_mismatches |
| \&\-whatsloaded \-F \-gused \-gfull \-mmacosx\-version\-min=\fR\fIversion\fR |
| \&\fB\-mkernel \-mone\-byte\-bool\fR |
| .Sp |
| \&\fI\s-1DEC\s0 Alpha Options\fR |
| \&\fB\-mno\-fp\-regs \-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\-mtune=\fR\fIcpu-type\fR |
| \&\fB\-mbwx \-mmax \-mfix \-mcix |
| \&\-mfloat\-vax \-mfloat\-ieee |
| \&\-mexplicit\-relocs \-msmall\-data \-mlarge\-data |
| \&\-msmall\-text \-mlarge\-text |
| \&\-mmemory\-latency=\fR\fItime\fR |
| .Sp |
| \&\fI\s-1DEC\s0 Alpha/VMS Options\fR |
| \&\fB\-mvms\-return\-codes\fR |
| .Sp |
| \&\fI\s-1FRV\s0 Options\fR |
| \&\fB\-mgpr\-32 \-mgpr\-64 \-mfpr\-32 \-mfpr\-64 |
| \&\-mhard\-float \-msoft\-float |
| \&\-malloc\-cc \-mfixed\-cc \-mdword \-mno\-dword |
| \&\-mdouble \-mno\-double |
| \&\-mmedia \-mno\-media \-mmuladd \-mno\-muladd |
| \&\-mfdpic \-minline\-plt \-mgprel\-ro \-multilib\-library\-pic |
| \&\-mlinked\-fp \-mlong\-calls \-malign\-labels |
| \&\-mlibrary\-pic \-macc\-4 \-macc\-8 |
| \&\-mpack \-mno\-pack \-mno\-eflags \-mcond\-move \-mno\-cond\-move |
| \&\-moptimize\-membar \-mno\-optimize\-membar |
| \&\-mscc \-mno\-scc \-mcond\-exec \-mno\-cond\-exec |
| \&\-mvliw\-branch \-mno\-vliw\-branch |
| \&\-mmulti\-cond\-exec \-mno\-multi\-cond\-exec \-mnested\-cond\-exec |
| \&\-mno\-nested\-cond\-exec \-mtomcat\-stats |
| \&\-mTLS \-mtls |
| \&\-mcpu=\fR\fIcpu\fR |
| .Sp |
| \&\fIGNU/Linux Options\fR |
| \&\fB\-muclibc\fR |
| .Sp |
| \&\fIH8/300 Options\fR |
| \&\fB\-mrelax \-mh \-ms \-mn \-mint32 \-malign\-300\fR |
| .Sp |
| \&\fI\s-1HPPA\s0 Options\fR |
| \&\fB\-march=\fR\fIarchitecture-type\fR |
| \&\fB\-mbig\-switch \-mdisable\-fpregs \-mdisable\-indexing |
| \&\-mfast\-indirect\-calls \-mgas \-mgnu\-ld \-mhp\-ld |
| \&\-mfixed\-range=\fR\fIregister-range\fR |
| \&\fB\-mjump\-in\-delay \-mlinker\-opt \-mlong\-calls |
| \&\-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 \-msio \-mwsio |
| \&\-munix=\fR\fIunix-std\fR \fB\-nolibdld \-static \-threads\fR |
| .Sp |
| \&\fIi386 and x86\-64 Options\fR |
| \&\fB\-mtune=\fR\fIcpu-type\fR \fB\-march=\fR\fIcpu-type\fR |
| \&\fB\-mfpmath=\fR\fIunit\fR |
| \&\fB\-masm=\fR\fIdialect\fR \fB\-mno\-fancy\-math\-387 |
| \&\-mno\-fp\-ret\-in\-387 \-msoft\-float \-msvr3\-shlib |
| \&\-mno\-wide\-multiply \-mrtd \-malign\-double |
| \&\-mpreferred\-stack\-boundary=\fR\fInum\fR |
| \&\fB\-mmmx \-msse \-msse2 \-msse3 \-m3dnow |
| \&\-mthreads \-mno\-align\-stringops \-minline\-all\-stringops |
| \&\-mpush\-args \-maccumulate\-outgoing\-args \-m128bit\-long\-double |
| \&\-m96bit\-long\-double \-mregparm=\fR\fInum\fR \fB\-msseregparm |
| \&\-mstackrealign |
| \&\-momit\-leaf\-frame\-pointer \-mno\-red\-zone \-mno\-tls\-direct\-seg\-refs |
| \&\-mcmodel=\fR\fIcode-model\fR |
| \&\fB\-m32 \-m64 \-mlarge\-data\-threshold=\fR\fInum\fR |
| .Sp |
| \&\fI\s-1IA\-64\s0 Options\fR |
| \&\fB\-mbig\-endian \-mlittle\-endian \-mgnu\-as \-mgnu\-ld \-mno\-pic |
| \&\-mvolatile\-asm\-stop \-mregister\-names \-mno\-sdata |
| \&\-mconstant\-gp \-mauto\-pic \-minline\-float\-divide\-min\-latency |
| \&\-minline\-float\-divide\-max\-throughput |
| \&\-minline\-int\-divide\-min\-latency |
| \&\-minline\-int\-divide\-max\-throughput |
| \&\-minline\-sqrt\-min\-latency \-minline\-sqrt\-max\-throughput |
| \&\-mno\-dwarf2\-asm \-mearly\-stop\-bits |
| \&\-mfixed\-range=\fR\fIregister-range\fR \fB\-mtls\-size=\fR\fItls-size\fR |
| \&\fB\-mtune=\fR\fIcpu-type\fR \fB\-mt \-pthread \-milp32 \-mlp64 |
| \&\-mno\-sched\-br\-data\-spec \-msched\-ar\-data\-spec \-mno\-sched\-control\-spec |
| \&\-msched\-br\-in\-data\-spec \-msched\-ar\-in\-data\-spec \-msched\-in\-control\-spec |
| \&\-msched\-ldc \-mno\-sched\-control\-ldc \-mno\-sched\-spec\-verbose |
| \&\-mno\-sched\-prefer\-non\-data\-spec\-insns |
| \&\-mno\-sched\-prefer\-non\-control\-spec\-insns |
| \&\-mno\-sched\-count\-spec\-in\-critical\-path\fR |
| .Sp |
| \&\fIM32R/D Options\fR |
| \&\fB\-m32r2 \-m32rx \-m32r |
| \&\-mdebug |
| \&\-malign\-loops \-mno\-align\-loops |
| \&\-missue\-rate=\fR\fInumber\fR |
| \&\fB\-mbranch\-cost=\fR\fInumber\fR |
| \&\fB\-mmodel=\fR\fIcode-size-model-type\fR |
| \&\fB\-msdata=\fR\fIsdata-type\fR |
| \&\fB\-mno\-flush\-func \-mflush\-func=\fR\fIname\fR |
| \&\fB\-mno\-flush\-trap \-mflush\-trap=\fR\fInumber\fR |
| \&\fB\-G\fR \fInum\fR |
| .Sp |
| \&\fIM32C Options\fR |
| \&\fB\-mcpu=\fR\fIcpu\fR \fB\-msim \-memregs=\fR\fInumber\fR |
| .Sp |
| \&\fIM680x0 Options\fR |
| \&\fB\-m68000 \-m68020 \-m68020\-40 \-m68020\-60 \-m68030 \-m68040 |
| \&\-m68060 \-mcpu32 \-m5200 \-mcfv4e \-m68881 \-mbitfield |
| \&\-mc68000 \-mc68020 |
| \&\-mnobitfield \-mrtd \-mshort \-msoft\-float \-mpcrel |
| \&\-malign\-int \-mstrict\-align \-msep\-data \-mno\-sep\-data |
| \&\-mshared\-library\-id=n \-mid\-shared\-library \-mno\-id\-shared\-library\fR |
| .Sp |
| \&\fIM68hc1x Options\fR |
| \&\fB\-m6811 \-m6812 \-m68hc11 \-m68hc12 \-m68hcs12 |
| \&\-mauto\-incdec \-minmax \-mlong\-calls \-mshort |
| \&\-msoft\-reg\-count=\fR\fIcount\fR |
| .Sp |
| \&\fIMCore Options\fR |
| \&\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-1MIPS\s0 Options\fR |
| \&\fB\-EL \-EB \-march=\fR\fIarch\fR \fB\-mtune=\fR\fIarch\fR |
| \&\fB\-mips1 \-mips2 \-mips3 \-mips4 \-mips32 \-mips32r2 \-mips64 |
| \&\-mips16 \-mno\-mips16 \-mabi=\fR\fIabi\fR \fB\-mabicalls \-mno\-abicalls |
| \&\-mshared \-mno\-shared \-mxgot \-mno\-xgot \-mgp32 \-mgp64 |
| \&\-mfp32 \-mfp64 \-mhard\-float \-msoft\-float |
| \&\-msingle\-float \-mdouble\-float \-mdsp \-mpaired\-single \-mips3d |
| \&\-mlong64 \-mlong32 \-msym32 \-mno\-sym32 |
| \&\-G\fR\fInum\fR \fB\-membedded\-data \-mno\-embedded\-data |
| \&\-muninit\-const\-in\-rodata \-mno\-uninit\-const\-in\-rodata |
| \&\-msplit\-addresses \-mno\-split\-addresses |
| \&\-mexplicit\-relocs \-mno\-explicit\-relocs |
| \&\-mcheck\-zero\-division \-mno\-check\-zero\-division |
| \&\-mdivide\-traps \-mdivide\-breaks |
| \&\-mmemcpy \-mno\-memcpy \-mlong\-calls \-mno\-long\-calls |
| \&\-mmad \-mno\-mad \-mfused\-madd \-mno\-fused\-madd \-nocpp |
| \&\-mfix\-r4000 \-mno\-fix\-r4000 \-mfix\-r4400 \-mno\-fix\-r4400 |
| \&\-mfix\-vr4120 \-mno\-fix\-vr4120 \-mfix\-vr4130 |
| \&\-mfix\-sb1 \-mno\-fix\-sb1 |
| \&\-mflush\-func=\fR\fIfunc\fR \fB\-mno\-flush\-func |
| \&\-mbranch\-likely \-mno\-branch\-likely |
| \&\-mfp\-exceptions \-mno\-fp\-exceptions |
| \&\-mvr4130\-align \-mno\-vr4130\-align\fR |
| .Sp |
| \&\fI\s-1MMIX\s0 Options\fR |
| \&\fB\-mlibfuncs \-mno\-libfuncs \-mepsilon \-mno\-epsilon \-mabi=gnu |
| \&\-mabi=mmixware \-mzero\-extend \-mknuthdiv \-mtoplevel\-symbols |
| \&\-melf \-mbranch\-predict \-mno\-branch\-predict \-mbase\-addresses |
| \&\-mno\-base\-addresses \-msingle\-exit \-mno\-single\-exit\fR |
| .Sp |
| \&\fI\s-1MN10300\s0 Options\fR |
| \&\fB\-mmult\-bug \-mno\-mult\-bug |
| \&\-mam33 \-mno\-am33 |
| \&\-mam33\-2 \-mno\-am33\-2 |
| \&\-mreturn\-pointer\-on\-d0 |
| \&\-mno\-crt0 \-mrelax\fR |
| .Sp |
| \&\fI\s-1MT\s0 Options\fR |
| \&\fB\-mno\-crt0 \-mbacc \-msim |
| \&\-march=\fR\fIcpu-type\fR\fB \fR |
| .Sp |
| \&\fI\s-1PDP\-11\s0 Options\fR |
| \&\fB\-mfpu \-msoft\-float \-mac0 \-mno\-ac0 \-m40 \-m45 \-m10 |
| \&\-mbcopy \-mbcopy\-builtin \-mint32 \-mno\-int16 |
| \&\-mint16 \-mno\-int32 \-mfloat32 \-mno\-float64 |
| \&\-mfloat64 \-mno\-float32 \-mabshi \-mno\-abshi |
| \&\-mbranch\-expensive \-mbranch\-cheap |
| \&\-msplit \-mno\-split \-munix\-asm \-mdec\-asm\fR |
| .Sp |
| \&\fIPowerPC Options\fR |
| See \s-1RS/6000\s0 and PowerPC Options. |
| .Sp |
| \&\fI\s-1RS/6000\s0 and PowerPC Options\fR |
| \&\fB\-mcpu=\fR\fIcpu-type\fR |
| \&\fB\-mtune=\fR\fIcpu-type\fR |
| \&\fB\-mpower \-mno\-power \-mpower2 \-mno\-power2 |
| \&\-mpowerpc \-mpowerpc64 \-mno\-powerpc |
| \&\-maltivec \-mno\-altivec |
| \&\-mpowerpc\-gpopt \-mno\-powerpc\-gpopt |
| \&\-mpowerpc\-gfxopt \-mno\-powerpc\-gfxopt |
| \&\-mmfcrf \-mno\-mfcrf \-mpopcntb \-mno\-popcntb \-mfprnd \-mno\-fprnd |
| \&\-mnew\-mnemonics \-mold\-mnemonics |
| \&\-mfull\-toc \-mminimal\-toc \-mno\-fp\-in\-toc \-mno\-sum\-in\-toc |
| \&\-m64 \-m32 \-mxl\-compat \-mno\-xl\-compat \-mpe |
| \&\-malign\-power \-malign\-natural |
| \&\-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 |
| \&\-mdynamic\-no\-pic \-maltivec \-mswdiv |
| \&\-mprioritize\-restricted\-insns=\fR\fIpriority\fR |
| \&\fB\-msched\-costly\-dep=\fR\fIdependence_type\fR |
| \&\fB\-minsert\-sched\-nops=\fR\fIscheme\fR |
| \&\fB\-mcall\-sysv \-mcall\-netbsd |
| \&\-maix\-struct\-return \-msvr4\-struct\-return |
| \&\-mabi=\fR\fIabi-type\fR \fB\-msecure\-plt \-mbss\-plt |
| \&\-misel \-mno\-isel |
| \&\-misel=yes \-misel=no |
| \&\-mspe \-mno\-spe |
| \&\-mspe=yes \-mspe=no |
| \&\-mvrsave \-mno\-vrsave |
| \&\-mmulhw \-mno\-mulhw |
| \&\-mdlmzb \-mno\-dlmzb |
| \&\-mfloat\-gprs=yes \-mfloat\-gprs=no \-mfloat\-gprs=single \-mfloat\-gprs=double |
| \&\-mprototype \-mno\-prototype |
| \&\-msim \-mmvme \-mads \-myellowknife \-memb \-msdata |
| \&\-msdata=\fR\fIopt\fR \fB\-mvxworks \-mwindiss \-G\fR \fInum\fR \fB\-pthread\fR |
| .Sp |
| \&\fIS/390 and zSeries Options\fR |
| \&\fB\-mtune=\fR\fIcpu-type\fR \fB\-march=\fR\fIcpu-type\fR |
| \&\fB\-mhard\-float \-msoft\-float \-mlong\-double\-64 \-mlong\-double\-128 |
| \&\-mbackchain \-mno\-backchain \-mpacked\-stack \-mno\-packed\-stack |
| \&\-msmall\-exec \-mno\-small\-exec \-mmvcle \-mno\-mvcle |
| \&\-m64 \-m31 \-mdebug \-mno\-debug \-mesa \-mzarch |
| \&\-mtpf\-trace \-mno\-tpf\-trace \-mfused\-madd \-mno\-fused\-madd |
| \&\-mwarn\-framesize \-mwarn\-dynamicstack \-mstack\-size \-mstack\-guard\fR |
| .Sp |
| \&\fIScore Options\fR |
| \&\fB\-mel \-mel |
| \&\-mmac |
| \&\-mscore5u \-mscore7\fR |
| .Sp |
| \&\fI\s-1SH\s0 Options\fR |
| \&\fB\-m1 \-m2 \-m2e \-m3 \-m3e |
| \&\-m4\-nofpu \-m4\-single\-only \-m4\-single \-m4 |
| \&\-m4a\-nofpu \-m4a\-single\-only \-m4a\-single \-m4a \-m4al |
| \&\-m5\-64media \-m5\-64media\-nofpu |
| \&\-m5\-32media \-m5\-32media\-nofpu |
| \&\-m5\-compact \-m5\-compact\-nofpu |
| \&\-mb \-ml \-mdalign \-mrelax |
| \&\-mbigtable \-mfmovd \-mhitachi \-mrenesas \-mno\-renesas \-mnomacsave |
| \&\-mieee \-misize \-mpadstruct \-mspace |
| \&\-mprefergot \-musermode \-multcost=\fR\fInumber\fR \fB\-mdiv=\fR\fIstrategy\fR |
| \&\fB\-mdivsi3_libfunc=\fR\fIname\fR |
| \&\fB\-madjust\-unroll \-mindexed\-addressing \-mgettrcost=\fR\fInumber\fR \fB\-mpt\-fixed |
| \-minvalid\-symbols\fR |
| .Sp |
| \&\fI\s-1SPARC\s0 Options\fR |
| \&\fB\-mcpu=\fR\fIcpu-type\fR |
| \&\fB\-mtune=\fR\fIcpu-type\fR |
| \&\fB\-mcmodel=\fR\fIcode-model\fR |
| \&\fB\-m32 \-m64 \-mapp\-regs \-mno\-app\-regs |
| \&\-mfaster\-structs \-mno\-faster\-structs |
| \&\-mfpu \-mno\-fpu \-mhard\-float \-msoft\-float |
| \&\-mhard\-quad\-float \-msoft\-quad\-float |
| \&\-mimpure\-text \-mno\-impure\-text \-mlittle\-endian |
| \&\-mstack\-bias \-mno\-stack\-bias |
| \&\-munaligned\-doubles \-mno\-unaligned\-doubles |
| \&\-mv8plus \-mno\-v8plus \-mvis \-mno\-vis |
| \&\-threads \-pthreads \-pthread\fR |
| .Sp |
| \&\fISystem V Options\fR |
| \&\fB\-Qy \-Qn \-YP,\fR\fIpaths\fR \fB\-Ym,\fR\fIdir\fR |
| .Sp |
| \&\fITMS320C3x/C4x Options\fR |
| \&\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 |
| \&\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\-mapp\-regs \-mno\-app\-regs |
| \&\-mdisable\-callt \-mno\-disable\-callt |
| \&\-mv850e1 |
| \&\-mv850e |
| \&\-mv850 \-mbig\-switch\fR |
| .Sp |
| \&\fI\s-1VAX\s0 Options\fR |
| \&\fB\-mg \-mgnu \-munix\fR |
| .Sp |
| \&\fIx86\-64 Options\fR |
| See i386 and x86\-64 Options. |
| .Sp |
| \&\fIXstormy16 Options\fR |
| \&\fB\-msim\fR |
| .Sp |
| \&\fIXtensa Options\fR |
| \&\fB\-mconst16 \-mno\-const16 |
| \&\-mfused\-madd \-mno\-fused\-madd |
| \&\-mtext\-section\-literals \-mno\-text\-section\-literals |
| \&\-mtarget\-align \-mno\-target\-align |
| \&\-mlongcalls \-mno\-longcalls\fR |
| .Sp |
| \&\fIzSeries Options\fR |
| See S/390 and zSeries Options. |
| .IP "\fICode Generation Options\fR" 4 |
| .IX Item "Code Generation Options" |
| \&\fB\-fcall\-saved\-\fR\fIreg\fR \fB\-fcall\-used\-\fR\fIreg\fR |
| \&\fB\-ffixed\-\fR\fIreg\fR \fB\-fexceptions |
| \&\-fnon\-call\-exceptions \-funwind\-tables |
| \&\-fasynchronous\-unwind\-tables |
| \&\-finhibit\-size\-directive \-finstrument\-functions |
| \&\-fno\-common \-fno\-ident |
| \&\-fpcc\-struct\-return \-fpic \-fPIC \-fpie \-fPIE |
| \&\-fno\-jump\-tables |
| \&\-freg\-struct\-return \-fshort\-enums |
| \&\-fshort\-double \-fshort\-wchar |
| \&\-fverbose\-asm \-fpack\-struct[=\fR\fIn\fR\fB] \-fstack\-check |
| \&\-fstack\-limit\-register=\fR\fIreg\fR \fB\-fstack\-limit\-symbol=\fR\fIsym\fR |
| \&\fB\-fargument\-alias \-fargument\-noalias |
| \&\-fargument\-noalias\-global \-fargument\-noalias\-anything |
| \&\-fleading\-underscore \-ftls\-model=\fR\fImodel\fR |
| \&\fB\-ftrapv \-fwrapv \-fbounds\-check |
| \&\-fvisibility\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. \s-1GCC\s0 is capable of |
| preprocessing and compiling several files either into several |
| assembler input files, or into one assembler input file; then each |
| assembler input file produces an object file, and linking combines all |
| the object files (those newly compiled, and those specified as input) |
| into an executable file. |
| .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 \fIlibobjc\fR |
| library 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.mm\fR" 4 |
| .IX Item "file.mm" |
| .PD 0 |
| .IP "\fIfile\fR\fB.M\fR" 4 |
| .IX Item "file.M" |
| .PD |
| Objective\-\*(C+ source code. Note that you must link with the \fIlibobjc\fR |
| library to make an Objective\-\*(C+ program work. Note that \fB.M\fR refers |
| to a literal capital M. |
| .IP "\fIfile\fR\fB.mii\fR" 4 |
| .IX Item "file.mii" |
| Objective\-\*(C+ source code which should not be preprocessed. |
| .IP "\fIfile\fR\fB.h\fR" 4 |
| .IX Item "file.h" |
| C, \*(C+, Objective-C or Objective\-\*(C+ header file to be turned into a |
| precompiled header. |
| .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.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.mm\fR" 4 |
| .IX Item "file.mm" |
| .PD 0 |
| .IP "\fIfile\fR\fB.M\fR" 4 |
| .IX Item "file.M" |
| .PD |
| Objective\-\*(C+ source code which must be preprocessed. |
| .IP "\fIfile\fR\fB.mii\fR" 4 |
| .IX Item "file.mii" |
| Objective\-\*(C+ source code which should not be preprocessed. |
| .IP "\fIfile\fR\fB.hh\fR" 4 |
| .IX Item "file.hh" |
| .PD 0 |
| .IP "\fIfile\fR\fB.H\fR" 4 |
| .IX Item "file.H" |
| .PD |
| \&\*(C+ header file to be turned into a precompiled header. |
| .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 |
| Fixed form 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 |
| Fixed form Fortran source code which must be preprocessed (with the traditional |
| preprocessor). |
| .IP "\fIfile\fR\fB.f90\fR" 4 |
| .IX Item "file.f90" |
| .PD 0 |
| .IP "\fIfile\fR\fB.f95\fR" 4 |
| .IX Item "file.f95" |
| .PD |
| Free form Fortran source code which should not be preprocessed. |
| .IP "\fIfile\fR\fB.F90\fR" 4 |
| .IX Item "file.F90" |
| .PD 0 |
| .IP "\fIfile\fR\fB.F95\fR" 4 |
| .IX Item "file.F95" |
| .PD |
| Free form Fortran source code which must be preprocessed (with the |
| traditional preprocessor). |
| .IP "\fIfile\fR\fB.ads\fR" 4 |
| .IX Item "file.ads" |
| Ada source code file which contains a library unit declaration (a |
| declaration of a package, subprogram, or generic, or a generic |
| instantiation), or a library unit renaming declaration (a package, |
| generic, or subprogram renaming declaration). Such files are also |
| called \fIspecs\fR. |
| .IP "\fIfile\fR\fB.adb\fR" 4 |
| .IX Item "file.adb" |
| Ada source code file containing a library unit body (a subprogram or |
| package body). Such files are also called \fIbodies\fR. |
| .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 9 |
| \& c c-header c-cpp-output |
| \& c++ c++-header c++-cpp-output |
| \& objective-c objective-c-header objective-c-cpp-output |
| \& objective-c++ objective-c++-header objective-c++-cpp-output |
| \& assembler assembler-with-cpp |
| \& ada |
| \& f95 f95-cpp-input |
| \& java |
| \& treelang |
| .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. The C, \*(C+, and Fortran frontends return 4, if an internal |
| compiler error is encountered. |
| .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 |
| 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, a precompiled header file in |
| \&\fI\fIsource\fI.\fIsuffix\fI.gch\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\-###\fR" 4 |
| .IX Item "-###" |
| Like \fB\-v\fR except the commands are not executed and all command |
| arguments are quoted. This is useful for shell scripts to capture the |
| driver-generated command lines. |
| .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\-combine\fR" 4 |
| .IX Item "-combine" |
| If you are compiling multiple source files, this option tells the driver |
| to pass all the source files to the compiler at once (for those |
| languages for which the compiler can handle this). This will allow |
| intermodule analysis (\s-1IMA\s0) to be performed by the compiler. Currently the only |
| language for which this is supported is C. If you pass source files for |
| multiple languages to the driver, using this option, the driver will invoke |
| the compiler(s) that support \s-1IMA\s0 once each, passing each compiler all the |
| source files appropriate for it. For those languages that do not support |
| \&\s-1IMA\s0 this option will be ignored, and the compiler will be invoked once for |
| each source file in that language. If you use this option in conjunction |
| with \fB\-save\-temps\fR, the compiler will generate multiple |
| pre-processed files |
| (one for each source file), but only one (combined) \fI.o\fR or |
| \&\fI.s\fR file. |
| .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\-Wextra\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. |
| .IP "\fB\-\-version\fR" 4 |
| .IX Item "--version" |
| Display the version number and copyrights of the invoked \s-1GCC\s0. |
| .IP "\fB@\fR\fIfile\fR" 4 |
| .IX Item "@file" |
| Read command-line options from \fIfile\fR. The options read are |
| inserted in place of the original @\fIfile\fR option. If \fIfile\fR |
| does not exist, or cannot be read, then the option will be treated |
| literally, and not removed. |
| .Sp |
| Options in \fIfile\fR are separated by whitespace. A whitespace |
| character may be included in an option by surrounding the entire |
| option in either single or double quotes. Any character (including a |
| backslash) may be included by prefixing the character to be included |
| with a backslash. The \fIfile\fR may itself contain additional |
| @\fIfile\fR options; any such options will be processed recursively. |
| .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.CPP\fR, \fB.c++\fR, \fB.cp\fR, or |
| \&\fB.cxx\fR; \*(C+ header files often use \fB.hh\fR or \fB.H\fR; and |
| 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, the use of \fBgcc\fR does not add the \*(C+ library. |
| \&\fBg++\fR is a program that calls \s-1GCC\s0 and treats \fB.c\fR, |
| \&\fB.h\fR and \fB.i\fR files as \*(C+ source files instead of C source |
| files unless \fB\-x\fR is used, and automatically specifies linking |
| against the \*(C+ library. This program is also useful when |
| precompiling a C header file with a \fB.h\fR extension for use in \*(C+ |
| compilations. 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+, Objective-C and Objective\-\*(C+) that the compiler |
| accepts: |
| .IP "\fB\-ansi\fR" 4 |
| .IX Item "-ansi" |
| In C mode, support all \s-1ISO\s0 C90 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 |
| C90 (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 built in 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 built-in |
| functions with \fB\-ansi\fR is used. |
| .IP "\fB\-std=\fR" 4 |
| .IX Item "-std=" |
| Determine the language standard. This option is currently only |
| supported when compiling C or \*(C+. A value for this option must be |
| provided; possible values are |
| .RS 4 |
| .IP "\fBc89\fR" 4 |
| .IX Item "c89" |
| .PD 0 |
| .IP "\fBiso9899:1990\fR" 4 |
| .IX Item "iso9899:1990" |
| .PD |
| \&\s-1ISO\s0 C90 (same as \fB\-ansi\fR). |
| .IP "\fBiso9899:199409\fR" 4 |
| .IX Item "iso9899:199409" |
| \&\s-1ISO\s0 C90 as modified in amendment 1. |
| .IP "\fBc99\fR" 4 |
| .IX Item "c99" |
| .PD 0 |
| .IP "\fBc9x\fR" 4 |
| .IX Item "c9x" |
| .IP "\fBiso9899:1999\fR" 4 |
| .IX Item "iso9899:1999" |
| .IP "\fBiso9899:199x\fR" 4 |
| .IX Item "iso9899:199x" |
| .PD |
| \&\s-1ISO\s0 C99. Note that this standard is not yet fully supported; see |
| <\fBhttp://gcc.gnu.org/gcc\-4.2/c99status.html\fR> for more information. The |
| names \fBc9x\fR and \fBiso9899:199x\fR are deprecated. |
| .IP "\fBgnu89\fR" 4 |
| .IX Item "gnu89" |
| Default, \s-1ISO\s0 C90 plus \s-1GNU\s0 extensions (including some C99 features). |
| .IP "\fBgnu99\fR" 4 |
| .IX Item "gnu99" |
| .PD 0 |
| .IP "\fBgnu9x\fR" 4 |
| .IX Item "gnu9x" |
| .PD |
| \&\s-1ISO\s0 C99 plus \s-1GNU\s0 extensions. When \s-1ISO\s0 C99 is fully implemented in \s-1GCC\s0, |
| this will become the default. The name \fBgnu9x\fR is deprecated. |
| .IP "\fBc++98\fR" 4 |
| .IX Item "c++98" |
| The 1998 \s-1ISO\s0 \*(C+ standard plus amendments. |
| .IP "\fBgnu++98\fR" 4 |
| .IX Item "gnu++98" |
| The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the |
| default for \*(C+ code. |
| .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 C90 |
| 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\-fgnu89\-inline\fR" 4 |
| .IX Item "-fgnu89-inline" |
| The option \fB\-fgnu89\-inline\fR tells \s-1GCC\s0 to use the traditional |
| \&\s-1GNU\s0 semantics for \f(CW\*(C`inline\*(C'\fR functions when in C99 mode. |
| Using this |
| option is roughly equivalent to adding the \f(CW\*(C`gnu_inline\*(C'\fR function |
| attribute to all inline functions. |
| .Sp |
| This option is accepted by \s-1GCC\s0 versions 4.1.3 and up. In \s-1GCC\s0 versions |
| prior to 4.3, C99 inline semantics are not supported, and thus this |
| option is effectively assumed to be present regardless of whether or not |
| it is specified; the only effect of specifying it explicitly is to |
| disable warnings about using inline functions in C99 mode. Likewise, |
| the option \fB\-fno\-gnu89\-inline\fR is not supported in versions of |
| \&\s-1GCC\s0 before 4.3. It will be supported only in C99 or gnu99 mode, not in |
| C89 or gnu89 mode. |
| .Sp |
| The preprocesor macros \f(CW\*(C`_\|_GNUC_GNU_INLINE_\|_\*(C'\fR and |
| \&\f(CW\*(C`_\|_GNUC_STDC_INLINE_\|_\*(C'\fR may be used to check which semantics are |
| in effect for \f(CW\*(C`inline\*(C'\fR functions. |
| .IP "\fB\-aux\-info\fR \fIfilename\fR" 4 |
| .IX Item "-aux-info filename" |
| Output to the given filename prototyped declarations for all functions |
| declared and/or defined in a translation unit, including those in header |
| files. This option is silently ignored in any language other than C. |
| .Sp |
| Besides declarations, the file indicates, in comments, the origin of |
| each declaration (source file and line), whether the declaration was |
| implicit, prototyped or unprototyped (\fBI\fR, \fBN\fR for new or |
| \&\fBO\fR for old, respectively, in the first character after the line |
| number and the colon), and whether it came from a declaration or a |
| definition (\fBC\fR or \fBF\fR, respectively, in the following |
| character). In the case of function definitions, a K&R\-style list of |
| arguments followed by their declarations is also provided, inside |
| comments, after the declaration. |
| .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" |
| .PD 0 |
| .IP "\fB\-fno\-builtin\-\fR\fIfunction\fR" 4 |
| .IX Item "-fno-builtin-function" |
| .PD |
| Don't recognize built-in functions that do not begin with |
| \&\fB_\|_builtin_\fR as prefix. |
| .Sp |
| \&\s-1GCC\s0 normally generates special code to handle certain built-in 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. In addition, |
| when a function is recognized as a built-in function, \s-1GCC\s0 may use |
| information about that function to warn about problems with calls to |
| that function, or to generate more efficient code, even if the |
| resulting code still contains calls to that function. For example, |
| warnings are given with \fB\-Wformat\fR for bad calls to |
| \&\f(CW\*(C`printf\*(C'\fR, when \f(CW\*(C`printf\*(C'\fR is built in, and \f(CW\*(C`strlen\*(C'\fR is |
| known not to modify global memory. |
| .Sp |
| With the \fB\-fno\-builtin\-\fR\fIfunction\fR option |
| only the built-in function \fIfunction\fR is |
| disabled. \fIfunction\fR must not begin with \fB_\|_builtin_\fR. If a |
| function is named this is not built-in in this version of \s-1GCC\s0, this |
| option is ignored. There is no corresponding |
| \&\fB\-fbuiltin\-\fR\fIfunction\fR option; if you wish to enable |
| built-in functions selectively when using \fB\-fno\-builtin\fR or |
| \&\fB\-ffreestanding\fR, you may define macros such as: |
| .Sp |
| .Vb 2 |
| \& #define abs(n) __builtin_abs ((n)) |
| \& #define strcpy(d, s) __builtin_strcpy ((d), (s)) |
| .Ve |
| .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\-fopenmp\fR" 4 |
| .IX Item "-fopenmp" |
| Enable handling of OpenMP directives \f(CW\*(C`#pragma omp\*(C'\fR in C/\*(C+ and |
| \&\f(CW\*(C`!$omp\*(C'\fR in Fortran. When \fB\-fopenmp\fR is specified, the |
| compiler generates parallel code according to the OpenMP Application |
| Program Interface v2.5 <\fBhttp://www.openmp.org/\fR>. |
| .IP "\fB\-fms\-extensions\fR" 4 |
| .IX Item "-fms-extensions" |
| Accept some non-standard constructs used in Microsoft header files. |
| .Sp |
| Some cases of unnamed fields in structures and unions are only |
| accepted with this option. |
| .IP "\fB\-trigraphs\fR" 4 |
| .IX Item "-trigraphs" |
| Support \s-1ISO\s0 C trigraphs. The \fB\-ansi\fR option (and \fB\-std\fR |
| options for strict \s-1ISO\s0 C conformance) implies \fB\-trigraphs\fR. |
| .IP "\fB\-no\-integrated\-cpp\fR" 4 |
| .IX Item "-no-integrated-cpp" |
| Performs a compilation in two passes: preprocessing and compiling. This |
| option allows a user supplied \*(L"cc1\*(R", \*(L"cc1plus\*(R", or \*(L"cc1obj\*(R" via the |
| \&\fB\-B\fR option. The user supplied compilation step can then add in |
| an additional preprocessing step after normal preprocessing but before |
| compiling. The default is to use the integrated cpp (internal cpp) |
| .Sp |
| The semantics of this option will change if \*(L"cc1\*(R", \*(L"cc1plus\*(R", and |
| \&\*(L"cc1obj\*(R" are merged. |
| .IP "\fB\-traditional\fR" 4 |
| .IX Item "-traditional" |
| .PD 0 |
| .IP "\fB\-traditional\-cpp\fR" 4 |
| .IX Item "-traditional-cpp" |
| .PD |
| Formerly, these options caused \s-1GCC\s0 to attempt to emulate a pre-standard |
| C compiler. They are now only supported with the \fB\-E\fR switch. |
| The preprocessor continues to support a pre-standard mode. See the \s-1GNU\s0 |
| \&\s-1CPP\s0 manual for details. |
| .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. |
| .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 bit-field 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 bit-field is signed, because this is consistent: the |
| basic integer types such as \f(CW\*(C`int\*(C'\fR are signed types. |
| .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 |
| .PP |
| 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\-fabi\-version=\fR\fIn\fR" 4 |
| .IX Item "-fabi-version=n" |
| Use version \fIn\fR of the \*(C+ \s-1ABI\s0. Version 2 is the version of the |
| \&\*(C+ \s-1ABI\s0 that first appeared in G++ 3.4. Version 1 is the version of |
| the \*(C+ \s-1ABI\s0 that first appeared in G++ 3.2. Version 0 will always be |
| the version that conforms most closely to the \*(C+ \s-1ABI\s0 specification. |
| Therefore, the \s-1ABI\s0 obtained using version 0 will change as \s-1ABI\s0 bugs |
| are fixed. |
| .Sp |
| The default is version 2. |
| .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. This check is |
| normally unnecessary because the \*(C+ standard specifies that |
| \&\f(CW\*(C`operator new\*(C'\fR will only return \f(CW0\fR if it is declared |
| \&\fB\f(BIthrow()\fB\fR, in which case the compiler will always check the |
| return value even without this option. In all other cases, when |
| \&\f(CW\*(C`operator new\*(C'\fR has a non-empty exception specification, memory |
| exhaustion is signalled by throwing \f(CW\*(C`std::bad_alloc\*(C'\fR. 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\-ffriend\-injection\fR" 4 |
| .IX Item "-ffriend-injection" |
| Inject friend functions into the enclosing namespace, so that they are |
| visible outside the scope of the class in which they are declared. |
| Friend functions were documented to work this way in the old Annotated |
| \&\*(C+ Reference Manual, and versions of G++ before 4.1 always worked |
| that way. However, in \s-1ISO\s0 \*(C+ a friend function which is not declared |
| in an enclosing scope can only be found using argument dependent |
| lookup. This option causes friends to be injected as they were in |
| earlier releases. |
| .Sp |
| This option is for compatibility, and may be removed in a future |
| release of G++. |
| .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 generate code to check for violation of exception specifications |
| at runtime. This option violates the \*(C+ standard, but may be useful |
| for reducing code size in production builds, much like defining |
| \&\fB\s-1NDEBUG\s0\fR. This does not give user code permission to throw |
| exceptions in violation of the exception specifications; the compiler |
| will still optimize based on the specifications, so throwing an |
| unexpected exception will result in undefined behavior. |
| .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 \fB\-ffor\-scope\fR 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 \fB\-fno\-for\-scope\fR 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 G++, 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\-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\-fno\-nonansi\-builtins\fR" 4 |
| .IX Item "-fno-nonansi-builtins" |
| Disable built-in declarations of functions that are not mandated by |
| \&\s-1ANSI/ISO\s0 C. These include \f(CW\*(C`ffs\*(C'\fR, \f(CW\*(C`alloca\*(C'\fR, \f(CW\*(C`_exit\*(C'\fR, |
| \&\f(CW\*(C`index\*(C'\fR, \f(CW\*(C`bzero\*(C'\fR, \f(CW\*(C`conjf\*(C'\fR, and other related functions. |
| .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 some diagnostics about nonconformant code from errors to |
| warnings. Thus, using \fB\-fpermissive\fR will allow some |
| nonconforming code to compile. |
| .IP "\fB\-frepo\fR" 4 |
| .IX Item "-frepo" |
| Enable automatic template instantiation at link time. 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. The \fBdynamic_cast\fR operator can still be used for casts that |
| do not require runtime type information, i.e. casts to \f(CW\*(C`void *\*(C'\fR or to |
| unambiguous base classes. |
| .IP "\fB\-fstats\fR" 4 |
| .IX Item "-fstats" |
| Emit statistics about front-end processing at the end of the compilation. |
| This information is generally only useful to the G++ development team. |
| .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\-fno\-threadsafe\-statics\fR" 4 |
| .IX Item "-fno-threadsafe-statics" |
| Do not emit the extra code to use the routines specified in the \*(C+ |
| \&\s-1ABI\s0 for thread-safe initialization of local statics. You can use this |
| option to reduce code size slightly in code that doesn't need to be |
| thread\-safe. |
| .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\-fno\-use\-cxa\-get\-exception\-ptr\fR" 4 |
| .IX Item "-fno-use-cxa-get-exception-ptr" |
| Don't use the \f(CW\*(C`_\|_cxa_get_exception_ptr\*(C'\fR runtime routine. This |
| will cause \f(CW\*(C`std::uncaught_exception\*(C'\fR to be incorrect, but is necessary |
| if the runtime routine is not available. |
| .IP "\fB\-fvisibility\-inlines\-hidden\fR" 4 |
| .IX Item "-fvisibility-inlines-hidden" |
| This switch declares that the user does not attempt to compare |
| pointers to inline methods where the addresses of the two functions |
| were taken in different shared objects. |
| .Sp |
| The effect of this is that \s-1GCC\s0 may, effectively, mark inline methods with |
| \&\f(CW\*(C`_\|_attribute_\|_ ((visibility ("hidden")))\*(C'\fR so that they do not |
| appear in the export table of a \s-1DSO\s0 and do not require a \s-1PLT\s0 indirection |
| when used within the \s-1DSO\s0. Enabling this option can have a dramatic effect |
| on load and link times of a \s-1DSO\s0 as it massively reduces the size of the |
| dynamic export table when the library makes heavy use of templates. |
| .Sp |
| The behaviour of this switch is not quite the same as marking the |
| methods as hidden directly, because it does not affect static variables |
| local to the function or cause the compiler to deduce that |
| the function is defined in only one shared object. |
| .Sp |
| You may mark a method as having a visibility explicitly to negate the |
| effect of the switch for that method. For example, if you do want to |
| compare pointers to a particular inline method, you might mark it as |
| having default visibility. Marking the enclosing class with explicit |
| visibility will have no effect. |
| .Sp |
| Explicitly instantiated inline methods are unaffected by this option |
| as their linkage might otherwise cross a shared library boundary. |
| .IP "\fB\-fno\-weak\fR" 4 |
| .IX Item "-fno-weak" |
| Do not use weak symbol support, even if it is provided by the linker. |
| By default, G++ will use weak symbols if they are available. This |
| option exists only for testing, and should not be used by end\-users; |
| it will result in inferior code and has no benefits. This option may |
| be removed in a future release of G++. |
| .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\-Wabi\fR (\*(C+ only)" 4 |
| .IX Item "-Wabi ( only)" |
| Warn when G++ generates code that is probably not compatible with the |
| vendor-neutral \*(C+ \s-1ABI\s0. Although an effort has been made to warn about |
| all such cases, there are probably some cases that are not warned about, |
| even though G++ is generating incompatible code. There may also be |
| cases where warnings are emitted even though the code that is generated |
| will be compatible. |
| .Sp |
| You should rewrite your code to avoid these warnings if you are |
| concerned about the fact that code generated by G++ may not be binary |
| compatible with code generated by other compilers. |
| .Sp |
| The known incompatibilities at this point include: |
| .RS 4 |
| .IP "*" 4 |
| Incorrect handling of tail-padding for bit\-fields. G++ may attempt to |
| pack data into the same byte as a base class. For example: |
| .Sp |
| .Vb 2 |
| \& struct A { virtual void f(); int f1 : 1; }; |
| \& struct B : public A { int f2 : 1; }; |
| .Ve |
| .Sp |
| In this case, G++ will place \f(CW\*(C`B::f2\*(C'\fR into the same byte |
| as\f(CW\*(C`A::f1\*(C'\fR; other compilers will not. You can avoid this problem |
| by explicitly padding \f(CW\*(C`A\*(C'\fR so that its size is a multiple of the |
| byte size on your platform; that will cause G++ and other compilers to |
| layout \f(CW\*(C`B\*(C'\fR identically. |
| .IP "*" 4 |
| Incorrect handling of tail-padding for virtual bases. G++ does not use |
| tail padding when laying out virtual bases. For example: |
| .Sp |
| .Vb 3 |
| \& struct A { virtual void f(); char c1; }; |
| \& struct B { B(); char c2; }; |
| \& struct C : public A, public virtual B {}; |
| .Ve |
| .Sp |
| In this case, G++ will not place \f(CW\*(C`B\*(C'\fR into the tail-padding for |
| \&\f(CW\*(C`A\*(C'\fR; other compilers will. You can avoid this problem by |
| explicitly padding \f(CW\*(C`A\*(C'\fR so that its size is a multiple of its |
| alignment (ignoring virtual base classes); that will cause G++ and other |
| compilers to layout \f(CW\*(C`C\*(C'\fR identically. |
| .IP "*" 4 |
| Incorrect handling of bit-fields with declared widths greater than that |
| of their underlying types, when the bit-fields appear in a union. For |
| example: |
| .Sp |
| .Vb 1 |
| \& union U { int i : 4096; }; |
| .Ve |
| .Sp |
| Assuming that an \f(CW\*(C`int\*(C'\fR does not have 4096 bits, G++ will make the |
| union too small by the number of bits in an \f(CW\*(C`int\*(C'\fR. |
| .IP "*" 4 |
| Empty classes can be placed at incorrect offsets. For example: |
| .Sp |
| .Vb 1 |
| \& struct A {}; |
| .Ve |
| .Sp |
| .Vb 4 |
| \& struct B { |
| \& A a; |
| \& virtual void f (); |
| \& }; |
| .Ve |
| .Sp |
| .Vb 1 |
| \& struct C : public B, public A {}; |
| .Ve |
| .Sp |
| G++ will place the \f(CW\*(C`A\*(C'\fR base class of \f(CW\*(C`C\*(C'\fR at a nonzero offset; |
| it should be placed at offset zero. G++ mistakenly believes that the |
| \&\f(CW\*(C`A\*(C'\fR data member of \f(CW\*(C`B\*(C'\fR is already at offset zero. |
| .IP "*" 4 |
| Names of template functions whose types involve \f(CW\*(C`typename\*(C'\fR or |
| template template parameters can be mangled incorrectly. |
| .Sp |
| .Vb 2 |
| \& template <typename Q> |
| \& void f(typename Q::X) {} |
| .Ve |
| .Sp |
| .Vb 2 |
| \& template <template <typename> class Q> |
| \& void f(typename Q<int>::X) {} |
| .Ve |
| .Sp |
| Instantiations of these templates may be mangled incorrectly. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-Wctor\-dtor\-privacy\fR (\*(C+ only)" 4 |
| .IX Item "-Wctor-dtor-privacy ( only)" |
| Warn when a class seems unusable because all the constructors or |
| destructors in that class are private, and it has neither friends nor |
| public static member functions. |
| .IP "\fB\-Wnon\-virtual\-dtor\fR (\*(C+ only)" 4 |
| .IX Item "-Wnon-virtual-dtor ( only)" |
| Warn when a class appears to be polymorphic, thereby requiring a virtual |
| destructor, yet it declares a non-virtual one. This warning is also |
| enabled if \-Weffc++ is specified. |
| .IP "\fB\-Wreorder\fR (\*(C+ only)" 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 |
| .Sp |
| The compiler will rearrange the member initializers for \fBi\fR |
| and \fBj\fR to match the declaration order of the members, emitting |
| a warning to that effect. This warning is enabled by \fB\-Wall\fR. |
| .PP |
| The following \fB\-W...\fR options are not affected by \fB\-Wall\fR. |
| .IP "\fB\-Weffc++\fR (\*(C+ only)" 4 |
| .IX Item "-Weffc++ ( only)" |
| Warn about violations of the following style guidelines from Scott Meyers' |
| \&\fIEffective \*(C+\fR book: |
| .RS 4 |
| .IP "*" 4 |
| Item 11: Define a copy constructor and an assignment operator for classes |
| with dynamically allocated memory. |
| .IP "*" 4 |
| Item 12: Prefer initialization to assignment in constructors. |
| .IP "*" 4 |
| Item 14: Make destructors virtual in base classes. |
| .IP "*" 4 |
| Item 15: Have \f(CW\*(C`operator=\*(C'\fR return a reference to \f(CW*this\fR. |
| .IP "*" 4 |
| Item 23: Don't try to return a reference when you must return an object. |
| .RE |
| .RS 4 |
| .Sp |
| Also warn about violations of the following style guidelines from |
| Scott Meyers' \fIMore Effective \*(C+\fR book: |
| .IP "*" 4 |
| Item 6: Distinguish between prefix and postfix forms of increment and |
| decrement operators. |
| .IP "*" 4 |
| Item 7: Never overload \f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, or \f(CW\*(C`,\*(C'\fR. |
| .RE |
| .RS 4 |
| .Sp |
| When selecting this option, be aware that the standard library |
| headers do not obey all of these guidelines; use \fBgrep \-v\fR |
| to filter out those warnings. |
| .RE |
| .IP "\fB\-Wno\-deprecated\fR (\*(C+ only)" 4 |
| .IX Item "-Wno-deprecated ( only)" |
| Do not warn about usage of deprecated features. |
| .IP "\fB\-Wstrict\-null\-sentinel\fR (\*(C+ only)" 4 |
| .IX Item "-Wstrict-null-sentinel ( only)" |
| Warn also about the use of an uncasted \f(CW\*(C`NULL\*(C'\fR as sentinel. When |
| compiling only with \s-1GCC\s0 this is a valid sentinel, as \f(CW\*(C`NULL\*(C'\fR is defined |
| to \f(CW\*(C`_\|_null\*(C'\fR. Although it is a null pointer constant not a null pointer, |
| it is guaranteed to of the same size as a pointer. But this use is |
| not portable across different compilers. |
| .IP "\fB\-Wno\-non\-template\-friend\fR (\*(C+ only)" 4 |
| .IX Item "-Wno-non-template-friend ( only)" |
| Disable warnings when non-templatized friend functions are declared |
| within a template. Since the advent of explicit template specification |
| support in G++, if the name of the friend is an unqualified-id (i.e., |
| \&\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\fR (\*(C+ only)" 4 |
| .IX Item "-Wold-style-cast ( only)" |
| Warn if an old-style (C\-style) cast to a non-void type is used within |
| a \*(C+ program. The new-style casts (\fBdynamic_cast\fR, |
| \&\fBstatic_cast\fR, \fBreinterpret_cast\fR, and \fBconst_cast\fR) are |
| less vulnerable to unintended effects and much easier to search for. |
| .IP "\fB\-Woverloaded\-virtual\fR (\*(C+ only)" 4 |
| .IX Item "-Woverloaded-virtual ( only)" |
| Warn when a function declaration hides virtual functions from a |
| base class. For example, in: |
| .Sp |
| .Vb 3 |
| \& struct A { |
| \& virtual void f(); |
| \& }; |
| .Ve |
| .Sp |
| .Vb 3 |
| \& struct B: public A { |
| \& void f(int); |
| \& }; |
| .Ve |
| .Sp |
| the \f(CW\*(C`A\*(C'\fR class version of \f(CW\*(C`f\*(C'\fR is hidden in \f(CW\*(C`B\*(C'\fR, and code |
| like: |
| .Sp |
| .Vb 2 |
| \& B* b; |
| \& b->f(); |
| .Ve |
| .Sp |
| will fail to compile. |
| .IP "\fB\-Wno\-pmf\-conversions\fR (\*(C+ only)" 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\fR (\*(C+ only)" 4 |
| .IX Item "-Wsign-promo ( only)" |
| Warn when overload resolution chooses a promotion from unsigned or |
| enumerated type to a signed type, over a conversion to an unsigned type of |
| the same size. Previous versions of G++ would try to preserve |
| unsignedness, but the standard mandates the current behavior. |
| .Sp |
| .Vb 4 |
| \& struct A { |
| \& operator int (); |
| \& A& operator = (int); |
| \& }; |
| .Ve |
| .Sp |
| .Vb 5 |
| \& main () |
| \& { |
| \& A a,b; |
| \& a = b; |
| \& } |
| .Ve |
| .Sp |
| In this example, G++ will synthesize a default \fBA& operator = |
| (const A&);\fR, while cfront will use the user-defined \fBoperator =\fR. |
| .Sh "Options Controlling Objective-C and Objective\-\*(C+ Dialects" |
| .IX Subsection "Options Controlling Objective-C and Objective- Dialects" |
| (\s-1NOTE:\s0 This manual does not describe the Objective-C and Objective\-\*(C+ |
| languages themselves. See |
| .PP |
| This section describes the command-line options that are only meaningful |
| for Objective-C and Objective\-\*(C+ programs, but you can also use most of |
| the language-independent \s-1GNU\s0 compiler options. |
| For example, you might compile a file \f(CW\*(C`some_class.m\*(C'\fR like this: |
| .PP |
| .Vb 1 |
| \& gcc -g -fgnu-runtime -O -c some_class.m |
| .Ve |
| .PP |
| In this example, \fB\-fgnu\-runtime\fR is an option meant only for |
| Objective-C and Objective\-\*(C+ programs; you can use the other options with |
| any language supported by \s-1GCC\s0. |
| .PP |
| Note that since Objective-C is an extension of the C language, Objective-C |
| compilations may also use options specific to the C front-end (e.g., |
| \&\fB\-Wtraditional\fR). Similarly, Objective\-\*(C+ compilations may use |
| \&\*(C+\-specific options (e.g., \fB\-Wabi\fR). |
| .PP |
| Here is a list of options that are \fIonly\fR for compiling Objective-C |
| and Objective\-\*(C+ programs: |
| .IP "\fB\-fconstant\-string\-class=\fR\fIclass-name\fR" 4 |
| .IX Item "-fconstant-string-class=class-name" |
| Use \fIclass-name\fR as the name of the class to instantiate for each |
| literal string specified with the syntax \f(CW\*(C`@"..."\*(C'\fR. The default |
| class name is \f(CW\*(C`NXConstantString\*(C'\fR if the \s-1GNU\s0 runtime is being used, and |
| \&\f(CW\*(C`NSConstantString\*(C'\fR if the NeXT runtime is being used (see below). The |
| \&\fB\-fconstant\-cfstrings\fR option, if also present, will override the |
| \&\fB\-fconstant\-string\-class\fR setting and cause \f(CW\*(C`@"..."\*(C'\fR literals |
| to be laid out as constant CoreFoundation strings. |
| .IP "\fB\-fgnu\-runtime\fR" 4 |
| .IX Item "-fgnu-runtime" |
| Generate object code compatible with the standard \s-1GNU\s0 Objective-C |
| runtime. This is the default for most types of systems. |
| .IP "\fB\-fnext\-runtime\fR" 4 |
| .IX Item "-fnext-runtime" |
| Generate output compatible with the NeXT runtime. This is the default |
| for NeXT-based systems, including Darwin and Mac \s-1OS\s0 X. The macro |
| \&\f(CW\*(C`_\|_NEXT_RUNTIME_\|_\*(C'\fR is predefined if (and only if) this option is |
| used. |
| .IP "\fB\-fno\-nil\-receivers\fR" 4 |
| .IX Item "-fno-nil-receivers" |
| Assume that all Objective-C message dispatches (e.g., |
| \&\f(CW\*(C`[receiver message:arg]\*(C'\fR) in this translation unit ensure that the receiver |
| is not \f(CW\*(C`nil\*(C'\fR. This allows for more efficient entry points in the runtime |
| to be used. Currently, this option is only available in conjunction with |
| the NeXT runtime on Mac \s-1OS\s0 X 10.3 and later. |
| .IP "\fB\-fobjc\-call\-cxx\-cdtors\fR" 4 |
| .IX Item "-fobjc-call-cxx-cdtors" |
| For each Objective-C class, check if any of its instance variables is a |
| \&\*(C+ object with a non-trivial default constructor. If so, synthesize a |
| special \f(CW\*(C`\- (id) .cxx_construct\*(C'\fR instance method that will run |
| non-trivial default constructors on any such instance variables, in order, |
| and then return \f(CW\*(C`self\*(C'\fR. Similarly, check if any instance variable |
| is a \*(C+ object with a non-trivial destructor, and if so, synthesize a |
| special \f(CW\*(C`\- (void) .cxx_destruct\*(C'\fR method that will run |
| all such default destructors, in reverse order. |
| .Sp |
| The \f(CW\*(C`\- (id) .cxx_construct\*(C'\fR and/or \f(CW\*(C`\- (void) .cxx_destruct\*(C'\fR methods |
| thusly generated will only operate on instance variables declared in the |
| current Objective-C class, and not those inherited from superclasses. It |
| is the responsibility of the Objective-C runtime to invoke all such methods |
| in an object's inheritance hierarchy. The \f(CW\*(C`\- (id) .cxx_construct\*(C'\fR methods |
| will be invoked by the runtime immediately after a new object |
| instance is allocated; the \f(CW\*(C`\- (void) .cxx_destruct\*(C'\fR methods will |
| be invoked immediately before the runtime deallocates an object instance. |
| .Sp |
| As of this writing, only the NeXT runtime on Mac \s-1OS\s0 X 10.4 and later has |
| support for invoking the \f(CW\*(C`\- (id) .cxx_construct\*(C'\fR and |
| \&\f(CW\*(C`\- (void) .cxx_destruct\*(C'\fR methods. |
| .IP "\fB\-fobjc\-direct\-dispatch\fR" 4 |
| .IX Item "-fobjc-direct-dispatch" |
| Allow fast jumps to the message dispatcher. On Darwin this is |
| accomplished via the comm page. |
| .IP "\fB\-fobjc\-exceptions\fR" 4 |
| .IX Item "-fobjc-exceptions" |
| Enable syntactic support for structured exception handling in Objective\-C, |
| similar to what is offered by \*(C+ and Java. This option is |
| unavailable in conjunction with the NeXT runtime on Mac \s-1OS\s0 X 10.2 and |
| earlier. |
| .Sp |
| .Vb 23 |
| \& @try { |
| \& ... |
| \& @throw expr; |
| \& ... |
| \& } |
| \& @catch (AnObjCClass *exc) { |
| \& ... |
| \& @throw expr; |
| \& ... |
| \& @throw; |
| \& ... |
| \& } |
| \& @catch (AnotherClass *exc) { |
| \& ... |
| \& } |
| \& @catch (id allOthers) { |
| \& ... |
| \& } |
| \& @finally { |
| \& ... |
| \& @throw expr; |
| \& ... |
| \& } |
| .Ve |
| .Sp |
| The \f(CW@throw\fR statement may appear anywhere in an Objective-C or |
| Objective\-\*(C+ program; when used inside of a \f(CW@catch\fR block, the |
| \&\f(CW@throw\fR may appear without an argument (as shown above), in which case |
| the object caught by the \f(CW@catch\fR will be rethrown. |
| .Sp |
| Note that only (pointers to) Objective-C objects may be thrown and |
| caught using this scheme. When an object is thrown, it will be caught |
| by the nearest \f(CW@catch\fR clause capable of handling objects of that type, |
| analogously to how \f(CW\*(C`catch\*(C'\fR blocks work in \*(C+ and Java. A |
| \&\f(CW\*(C`@catch(id ...)\*(C'\fR clause (as shown above) may also be provided to catch |
| any and all Objective-C exceptions not caught by previous \f(CW@catch\fR |
| clauses (if any). |
| .Sp |
| The \f(CW@finally\fR clause, if present, will be executed upon exit from the |
| immediately preceding \f(CW\*(C`@try ... @catch\*(C'\fR section. This will happen |
| regardless of whether any exceptions are thrown, caught or rethrown |
| inside the \f(CW\*(C`@try ... @catch\*(C'\fR section, analogously to the behavior |
| of the \f(CW\*(C`finally\*(C'\fR clause in Java. |
| .Sp |
| There are several caveats to using the new exception mechanism: |
| .RS 4 |
| .IP "*" 4 |
| Although currently designed to be binary compatible with \f(CW\*(C`NS_HANDLER\*(C'\fR\-style |
| idioms provided by the \f(CW\*(C`NSException\*(C'\fR class, the new |
| exceptions can only be used on Mac \s-1OS\s0 X 10.3 (Panther) and later |
| systems, due to additional functionality needed in the (NeXT) Objective-C |
| runtime. |
| .IP "*" 4 |
| As mentioned above, the new exceptions do not support handling |
| types other than Objective-C objects. Furthermore, when used from |
| Objective\-\*(C+, the Objective-C exception model does not interoperate with \*(C+ |
| exceptions at this time. This means you cannot \f(CW@throw\fR an exception |
| from Objective-C and \f(CW\*(C`catch\*(C'\fR it in \*(C+, or vice versa |
| (i.e., \f(CW\*(C`throw ... @catch\*(C'\fR). |
| .RE |
| .RS 4 |
| .Sp |
| The \fB\-fobjc\-exceptions\fR switch also enables the use of synchronization |
| blocks for thread-safe execution: |
| .Sp |
| .Vb 3 |
| \& @synchronized (ObjCClass *guard) { |
| \& ... |
| \& } |
| .Ve |
| .Sp |
| Upon entering the \f(CW@synchronized\fR block, a thread of execution shall |
| first check whether a lock has been placed on the corresponding \f(CW\*(C`guard\*(C'\fR |
| object by another thread. If it has, the current thread shall wait until |
| the other thread relinquishes its lock. Once \f(CW\*(C`guard\*(C'\fR becomes available, |
| the current thread will place its own lock on it, execute the code contained in |
| the \f(CW@synchronized\fR block, and finally relinquish the lock (thereby |
| making \f(CW\*(C`guard\*(C'\fR available to other threads). |
| .Sp |
| Unlike Java, Objective-C does not allow for entire methods to be marked |
| \&\f(CW@synchronized\fR. Note that throwing exceptions out of |
| \&\f(CW@synchronized\fR blocks is allowed, and will cause the guarding object |
| to be unlocked properly. |
| .RE |
| .IP "\fB\-fobjc\-gc\fR" 4 |
| .IX Item "-fobjc-gc" |
| Enable garbage collection (\s-1GC\s0) in Objective-C and Objective\-\*(C+ programs. |
| .IP "\fB\-freplace\-objc\-classes\fR" 4 |
| .IX Item "-freplace-objc-classes" |
| Emit a special marker instructing \fB\f(BIld\fB\|(1)\fR not to statically link in |
| the resulting object file, and allow \fB\f(BIdyld\fB\|(1)\fR to load it in at |
| run time instead. This is used in conjunction with the Fix-and-Continue |
| debugging mode, where the object file in question may be recompiled and |
| dynamically reloaded in the course of program execution, without the need |
| to restart the program itself. Currently, Fix-and-Continue functionality |
| is only available in conjunction with the NeXT runtime on Mac \s-1OS\s0 X 10.3 |
| and later. |
| .IP "\fB\-fzero\-link\fR" 4 |
| .IX Item "-fzero-link" |
| When compiling for the NeXT runtime, the compiler ordinarily replaces calls |
| to \f(CW\*(C`objc_getClass("...")\*(C'\fR (when the name of the class is known at |
| compile time) with static class references that get initialized at load time, |
| which improves run-time performance. Specifying the \fB\-fzero\-link\fR flag |
| suppresses this behavior and causes calls to \f(CW\*(C`objc_getClass("...")\*(C'\fR |
| to be retained. This is useful in Zero-Link debugging mode, since it allows |
| for individual class implementations to be modified during program execution. |
| .IP "\fB\-gen\-decls\fR" 4 |
| .IX Item "-gen-decls" |
| Dump interface declarations for all classes seen in the source file to a |
| file named \fI\fIsourcename\fI.decl\fR. |
| .IP "\fB\-Wassign\-intercept\fR" 4 |
| .IX Item "-Wassign-intercept" |
| Warn whenever an Objective-C assignment is being intercepted by the |
| garbage collector. |
| .IP "\fB\-Wno\-protocol\fR" 4 |
| .IX Item "-Wno-protocol" |
| If a class is declared to implement a protocol, a warning is issued for |
| every method in the protocol that is not implemented by the class. The |
| default behavior is to issue a warning for every method not explicitly |
| implemented in the class, even if a method implementation is inherited |
| from the superclass. If you use the \fB\-Wno\-protocol\fR option, then |
| methods inherited from the superclass are considered to be implemented, |
| and no warning is issued for them. |
| .IP "\fB\-Wselector\fR" 4 |
| .IX Item "-Wselector" |
| Warn if multiple methods of different types for the same selector are |
| found during compilation. The check is performed on the list of methods |
| in the final stage of compilation. Additionally, a check is performed |
| for each selector appearing in a \f(CW\*(C`@selector(...)\*(C'\fR |
| expression, and a corresponding method for that selector has been found |
| during compilation. Because these checks scan the method table only at |
| the end of compilation, these warnings are not produced if the final |
| stage of compilation is not reached, for example because an error is |
| found during compilation, or because the \fB\-fsyntax\-only\fR option is |
| being used. |
| .IP "\fB\-Wstrict\-selector\-match\fR" 4 |
| .IX Item "-Wstrict-selector-match" |
| Warn if multiple methods with differing argument and/or return types are |
| found for a given selector when attempting to send a message using this |
| selector to a receiver of type \f(CW\*(C`id\*(C'\fR or \f(CW\*(C`Class\*(C'\fR. When this flag |
| is off (which is the default behavior), the compiler will omit such warnings |
| if any differences found are confined to types which share the same size |
| and alignment. |
| .IP "\fB\-Wundeclared\-selector\fR" 4 |
| .IX Item "-Wundeclared-selector" |
| Warn if a \f(CW\*(C`@selector(...)\*(C'\fR expression referring to an |
| undeclared selector is found. A selector is considered undeclared if no |
| method with that name has been declared before the |
| \&\f(CW\*(C`@selector(...)\*(C'\fR expression, either explicitly in an |
| \&\f(CW@interface\fR or \f(CW@protocol\fR declaration, or implicitly in |
| an \f(CW@implementation\fR section. This option always performs its |
| checks as soon as a \f(CW\*(C`@selector(...)\*(C'\fR expression is found, |
| while \fB\-Wselector\fR only performs its checks in the final stage of |
| compilation. This also enforces the coding style convention |
| that methods and selectors must be declared before being used. |
| .IP "\fB\-print\-objc\-runtime\-info\fR" 4 |
| .IX Item "-print-objc-runtime-info" |
| Generate C header describing the largest structure that is passed by |
| value, if any. |
| .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 \fBg++\fR 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 |
| behavior. |
| .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 message which is too long to fit on a single line. |
| .IP "\fB\-fdiagnostics\-show\-option\fR" 4 |
| .IX Item "-fdiagnostics-show-option" |
| This option instructs the diagnostic machinery to add text to each |
| diagnostic emitted, which indicates which command line option directly |
| controls that diagnostic, when such an option is known to the |
| diagnostic machinery. |
| .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 |
| The following options control the amount and kinds of warnings produced |
| by \s-1GCC\s0; for further, language-specific options also refer to |
| \&\fB\*(C+ Dialect Options\fR and \fBObjective-C and Objective\-\*(C+ Dialect |
| Options\fR. |
| .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. |
| .Sp |
| Where the standard specified with \fB\-std\fR represents a \s-1GNU\s0 |
| extended dialect of C, such as \fBgnu89\fR or \fBgnu99\fR, there is a |
| corresponding \fIbase standard\fR, the version of \s-1ISO\s0 C on which the \s-1GNU\s0 |
| extended dialect is based. Warnings from \fB\-pedantic\fR are given |
| where they are required by the base standard. (It would not make sense |
| for such warnings to be given only for features not in the specified \s-1GNU\s0 |
| C dialect, since by definition the \s-1GNU\s0 dialects of C include all |
| features the compiler supports with the given option, and there would be |
| nothing to warn about.) |
| .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. |
| This warning is enabled by \fB\-Wall\fR. |
| .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. |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wfatal\-errors\fR" 4 |
| .IX Item "-Wfatal-errors" |
| This option causes the compiler to abort compilation on the first error |
| occurred rather than trying to keep going and printing further error |
| messages. |
| .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 (or other target-specific families). |
| Which functions are checked without format attributes having been |
| specified depends on the standard version selected, and such checks of |
| functions without the attribute specified are disabled by |
| \&\fB\-ffreestanding\fR or \fB\-fno\-builtin\fR. |
| .Sp |
| The formats are checked against the format features supported by \s-1GNU\s0 |
| libc version 2.2. These include all \s-1ISO\s0 C90 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 |
| Since \fB\-Wformat\fR also checks for null format arguments for |
| several functions, \fB\-Wformat\fR also implies \fB\-Wnonnull\fR. |
| .Sp |
| \&\fB\-Wformat\fR is included in \fB\-Wall\fR. For more control over some |
| aspects of format checking, the options \fB\-Wformat\-y2k\fR, |
| \&\fB\-Wno\-format\-extra\-args\fR, \fB\-Wno\-format\-zero\-length\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\-Wformat\-y2k\fR" 4 |
| .IX Item "-Wformat-y2k" |
| If \fB\-Wformat\fR is specified, also 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. |
| .Sp |
| Where the unused arguments lie between used arguments that are |
| specified with \fB$\fR operand number specifications, normally |
| warnings are still given, since the implementation could not know what |
| type to pass to \f(CW\*(C`va_arg\*(C'\fR to skip the unused arguments. However, |
| in the case of \f(CW\*(C`scanf\*(C'\fR formats, this option will suppress the |
| warning if the unused arguments are all pointers, since the Single |
| Unix Specification says that such unused arguments are allowed. |
| .IP "\fB\-Wno\-format\-zero\-length\fR" 4 |
| .IX Item "-Wno-format-zero-length" |
| If \fB\-Wformat\fR is specified, do not warn about zero-length formats. |
| The C standard specifies that zero-length formats are allowed. |
| .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 \-Wformat\-y2k\fR. |
| .IP "\fB\-Wnonnull\fR" 4 |
| .IX Item "-Wnonnull" |
| Warn about passing a null pointer for arguments marked as |
| requiring a non-null value by the \f(CW\*(C`nonnull\*(C'\fR function attribute. |
| .Sp |
| \&\fB\-Wnonnull\fR is included in \fB\-Wall\fR and \fB\-Wformat\fR. It |
| can be disabled with the \fB\-Wno\-nonnull\fR option. |
| .IP "\fB\-Winit\-self\fR (C, \*(C+, Objective-C and Objective\-\*(C+ only)" 4 |
| .IX Item "-Winit-self (C, , Objective-C and Objective- only)" |
| Warn about uninitialized variables which are initialized with themselves. |
| Note this option can only be used with the \fB\-Wuninitialized\fR option, |
| which in turn only works with \fB\-O1\fR and above. |
| .Sp |
| For example, \s-1GCC\s0 will warn about \f(CW\*(C`i\*(C'\fR being uninitialized in the |
| following snippet only when \fB\-Winit\-self\fR has been specified: |
| .Sp |
| .Vb 5 |
| \& int f() |
| \& { |
| \& int i = i; |
| \& return i; |
| \& } |
| .Ve |
| .IP "\fB\-Wimplicit\-int\fR" 4 |
| .IX Item "-Wimplicit-int" |
| Warn when a declaration does not specify a type. |
| This warning is enabled by \fB\-Wall\fR. |
| .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. The form \fB\-Wno\-error\-implicit\-function\-declaration\fR |
| is not supported. |
| This warning is enabled by \fB\-Wall\fR (as a warning, not an error). |
| .IP "\fB\-Wimplicit\fR" 4 |
| .IX Item "-Wimplicit" |
| Same as \fB\-Wimplicit\-int\fR and \fB\-Wimplicit\-function\-declaration\fR. |
| This warning is enabled by \fB\-Wall\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. |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wmissing\-braces\fR" 4 |
| .IX Item "-Wmissing-braces" |
| Warn if an aggregate or union initializer is not fully bracketed. In |
| the following example, the initializer for \fBa\fR is not fully |
| bracketed, but that for \fBb\fR is fully bracketed. |
| .Sp |
| .Vb 2 |
| \& int a[2][2] = { 0, 1, 2, 3 }; |
| \& int b[2][2] = { { 0, 1 }, { 2, 3 } }; |
| .Ve |
| .Sp |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wmissing\-include\-dirs\fR (C, \*(C+, Objective-C and Objective\-\*(C+ only)" 4 |
| .IX Item "-Wmissing-include-dirs (C, , Objective-C and Objective- only)" |
| Warn if a user-supplied include directory does not exist. |
| .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. Only the warning for an assignment used as |
| a truth value is supported when compiling \*(C+; the other warnings are |
| only supported when compiling C. |
| .Sp |
| Also warn if 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. |
| .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 |
| .Sp |
| 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-1GCC\s0 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 |
| .Sp |
| This warning is enabled by \fB\-Wall\fR. |
| .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 and \*(C+ standards. |
| .Sp |
| The C and \*(C+ standards defines the order in which expressions in a C/\*(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 and \*(C+ standards specify that \*(L"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.\*(R". 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 standard is worded confusingly, therefore there is some debate |
| over the precise meaning of the sequence point rules in subtle cases. |
| Links to discussions of the problem, including proposed formal |
| definitions, may be found on the \s-1GCC\s0 readings page, at |
| <\fBhttp://gcc.gnu.org/readings.html\fR>. |
| .Sp |
| This warning is enabled by \fB\-Wall\fR for C and \*(C+. |
| .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, also warn if 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. \s-1ISO\s0 C prohibits |
| qualified \f(CW\*(C`void\*(C'\fR return types on function definitions, so such |
| return types always receive a warning even without this option. |
| .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. |
| .Sp |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wswitch\fR" 4 |
| .IX Item "-Wswitch" |
| Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of enumerated 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. |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wswitch\-default\fR" 4 |
| .IX Item "-Wswitch-default" |
| Warn whenever a \f(CW\*(C`switch\*(C'\fR statement does not have a \f(CW\*(C`default\*(C'\fR |
| case. |
| .IP "\fB\-Wswitch\-enum\fR" 4 |
| .IX Item "-Wswitch-enum" |
| Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of enumerated type |
| and lacks a \f(CW\*(C`case\*(C'\fR for one or more of the named codes of that |
| enumeration. \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). |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wunused\-function\fR" 4 |
| .IX Item "-Wunused-function" |
| Warn whenever a static function is declared but not defined or a |
| non-inline static function is unused. |
| This warning is enabled by \fB\-Wall\fR. |
| .IP "\fB\-Wunused\-label\fR" 4 |
| .IX Item "-Wunused-label" |
| Warn whenever a label is declared but not used. |
| This warning is enabled by \fB\-Wall\fR. |
| .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. |
| This warning is enabled by \fB\-Wall\fR. |
| .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. |
| This warning is enabled by \fB\-Wall\fR. |
| .Sp |
| To suppress this warning cast the expression to \fBvoid\fR. |
| .IP "\fB\-Wunused\fR" 4 |
| .IX Item "-Wunused" |
| 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\-Wextra \-Wunused\fR (note that \fB\-Wall\fR implies |
| \&\fB\-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 do not specify \fB\-O\fR, you will not get |
| these warnings. Instead, \s-1GCC\s0 will issue a warning about \fB\-Wuninitialized\fR |
| requiring \fB\-O\fR. |
| .Sp |
| If you want to warn about code which uses the uninitialized value of the |
| variable in its own initializer, use the \fB\-Winit\-self\fR option. |
| .Sp |
| These warnings occur for individual uninitialized or clobbered |
| elements of structure, union or array variables as well as for |
| variables which are uninitialized or clobbered as a whole. They do |
| not occur for variables or elements declared \f(CW\*(C`volatile\*(C'\fR. Because |
| these warnings depend on optimization, the exact variables or elements |
| for which there are warnings will depend on the precise optimization |
| options and version of \s-1GCC\s0 used. |
| .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 |
| .Sp |
| 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 |
| .Sp |
| 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. |
| .Sp |
| This warning is enabled by \fB\-Wall\fR. |
| .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\-Wno\-pragmas\fR" 4 |
| .IX Item "-Wno-pragmas" |
| Do not warn about misuses of pragmas, such as incorrect parameters, |
| invalid syntax, or conflicts between pragmas. See also |
| \&\fB\-Wunknown\-pragmas\fR. |
| .IP "\fB\-Wstrict\-aliasing\fR" 4 |
| .IX Item "-Wstrict-aliasing" |
| This option is only active when \fB\-fstrict\-aliasing\fR is active. |
| It warns about code which might break the strict aliasing rules that the |
| compiler is using for optimization. The warning does not catch all |
| cases, but does attempt to catch the more common pitfalls. It is |
| included in \fB\-Wall\fR. |
| .IP "\fB\-Wstrict\-aliasing=2\fR" 4 |
| .IX Item "-Wstrict-aliasing=2" |
| This option is only active when \fB\-fstrict\-aliasing\fR is active. |
| It warns about code which might break the strict aliasing rules that the |
| compiler is using for optimization. This warning catches more cases than |
| \&\fB\-Wstrict\-aliasing\fR, but it will also give a warning for some ambiguous |
| cases that are safe. |
| .IP "\fB\-Wstrict\-overflow\fR" 4 |
| .IX Item "-Wstrict-overflow" |
| .PD 0 |
| .IP "\fB\-Wstrict\-overflow=\fR\fIn\fR" 4 |
| .IX Item "-Wstrict-overflow=n" |
| .PD |
| This option is only active when \fB\-fstrict\-overflow\fR is active. |
| It warns about cases where the compiler optimizes based on the |
| assumption that signed overflow does not occur. Note that it does not |
| warn about all cases where the code might overflow: it only warns |
| about cases where the compiler implements some optimization. Thus |
| this warning depends on the optimization level. |
| .Sp |
| An optimization which assumes that signed overflow does not occur is |
| perfectly safe if the values of the variables involved are such that |
| overflow never does, in fact, occur. Therefore this warning can |
| easily give a false positive: a warning about code which is not |
| actually a problem. To help focus on important issues, several |
| warning levels are defined. |
| .RS 4 |
| .IP "@option<\-Wstrict\-overflow=1>" 4 |
| .IX Item "@option<-Wstrict-overflow=1>" |
| Warn about cases which are both questionable and easy to avoid. For |
| example: \f(CW\*(C`x + 1 > x\*(C'\fR; with \fB\-fstrict\-overflow\fR, the |
| compiler will simplify this to \f(CW1\fR. This level of |
| \&\fB\-Wstrict\-overflow\fR is enabled by \fB\-Wall\fR; higher levels |
| are not, and must be explicitly requested. |
| .IP "@option<\-Wstrict\-overflow=2>" 4 |
| .IX Item "@option<-Wstrict-overflow=2>" |
| Also warn about other cases where a comparison is simplified to a |
| constant. For example: \f(CW\*(C`abs (x) >= 0\*(C'\fR. This can only be |
| simplified when \fB\-fstrict\-overflow\fR is in effect, because |
| \&\f(CW\*(C`abs (INT_MIN)\*(C'\fR overflows to \f(CW\*(C`INT_MIN\*(C'\fR, which is less than |
| zero. \fB\-Wstrict\-overflow\fR (with no level) is the same as |
| \&\fB\-Wstrict\-overflow=2\fR. |
| .IP "@option<\-Wstrict\-overflow=3>" 4 |
| .IX Item "@option<-Wstrict-overflow=3>" |
| Also warn about other cases where a comparison is simplified. For |
| example: \f(CW\*(C`x + 1 > 1\*(C'\fR will be simplified to \f(CW\*(C`x > 0\*(C'\fR. |
| .IP "@option<\-Wstrict\-overflow=4>" 4 |
| .IX Item "@option<-Wstrict-overflow=4>" |
| Also warn about other simplifications not covered by the above cases. |
| For example: \f(CW\*(C`(x * 10) / 5\*(C'\fR will be simplified to \f(CW\*(C`x * 2\*(C'\fR. |
| .IP "@option<\-Wstrict\-overflow=5>" 4 |
| .IX Item "@option<-Wstrict-overflow=5>" |
| Also warn about cases where the compiler reduces the magnitude of a |
| constant involved in a comparison. For example: \f(CW\*(C`x + 2 > y\*(C'\fR will |
| be simplified to \f(CW\*(C`x + 1 >= y\*(C'\fR. This is reported only at the |
| highest warning level because this simplification applies to many |
| comparisons, so this warning level will give a very large number of |
| false positives. |
| .RE |
| .RS 4 |
| .RE |
| .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. This also enables some language-specific |
| warnings described in \fB\*(C+ Dialect Options\fR and |
| \&\fBObjective-C and Objective\-\*(C+ Dialect Options\fR. |
| .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\-Wextra\fR" 4 |
| .IX Item "-Wextra" |
| (This option used to be called \fB\-W\fR. The older name is still |
| supported, but the newer name is more descriptive.) Print extra warning |
| messages for these events: |
| .RS 4 |
| .IP "*" 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 "*" 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 "*" 4 |
| An unsigned value is compared against zero with \fB<\fR or \fB>=\fR. |
| .IP "*" 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 "*" 4 |
| If \fB\-Wall\fR or \fB\-Wunused\fR is also specified, warn about unused |
| arguments. |
| .IP "*" 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 "*" 4 |
| An aggregate has an initializer which does not initialize all members. |
| This warning can be independently controlled by |
| \&\fB\-Wmissing\-field\-initializers\fR. |
| .IP "*" 4 |
| An initialized field without side effects is overridden when using |
| designated initializers. This warning can be independently controlled by |
| \&\fB\-Woverride\-init\fR. |
| .IP "*" 4 |
| A function parameter is declared without a type specifier in K&R\-style |
| functions: |
| .Sp |
| .Vb 1 |
| \& void foo(bar) { } |
| .Ve |
| .IP "*" 4 |
| An empty body occurs in an \fBif\fR or \fBelse\fR statement. |
| .IP "*" 4 |
| A pointer is compared against integer zero with \fB<\fR, \fB<=\fR, |
| \&\fB>\fR, or \fB>=\fR. |
| .IP "*" 4 |
| A variable might be changed by \fBlongjmp\fR or \fBvfork\fR. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| An enumerator and a non-enumerator both appear in a conditional expression. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| A non-static reference or non-static \fBconst\fR member appears in a |
| class without constructors. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| Ambiguous virtual bases. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| Subscripting an array which has been declared \fBregister\fR. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| Taking the address of a variable which has been declared \fBregister\fR. |
| .IP "*<(\*(C+ only)>" 4 |
| .IX Item "*<( only)>" |
| A base class is not initialized in a derived class' copy constructor. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-Wno\-div\-by\-zero\fR" 4 |
| .IX Item "-Wno-div-by-zero" |
| Do not warn about compile-time integer division by zero. Floating point |
| division by zero is not warned about, as it can be a legitimate way of |
| obtaining infinities and NaNs. |
| .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. |
| .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 analyzing the code, or in some other way) the maximum or |
| likely maximum error that the computation introduces, and allow for it |
| when performing comparisons (and when producing output, but that's a |
| different problem). In particular, instead of testing for equality, you |
| would check to see whether the two values have ranges that overlap; and |
| this is done with the relational operators, so equality comparisons are |
| probably mistaken. |
| .IP "\fB\-Wtraditional\fR (C only)" 4 |
| .IX Item "-Wtraditional (C only)" |
| Warn about certain constructs that behave differently in traditional and |
| \&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C |
| equivalent, and/or problematic constructs which should be avoided. |
| .RS 4 |
| .IP "*" 4 |
| Macro parameters that appear within string literals in the macro body. |
| In traditional C macro replacement takes place within string literals, |
| but does not in \s-1ISO\s0 C. |
| .IP "*" 4 |
| In traditional C, some preprocessor directives did not exist. |
| Traditional preprocessors would only consider a line to be a directive |
| if the \fB#\fR appeared in column 1 on the line. Therefore |
| \&\fB\-Wtraditional\fR warns about directives that traditional C |
| understands but would ignore because the \fB#\fR does not appear as the |
| first character on the line. It also suggests you hide directives like |
| \&\fB#pragma\fR not understood by traditional C by indenting them. Some |
| traditional implementations would not recognize \fB#elif\fR, so it |
| suggests avoiding it altogether. |
| .IP "*" 4 |
| A function-like macro that appears without arguments. |
| .IP "*" 4 |
| The unary plus operator. |
| .IP "*" 4 |
| The \fBU\fR integer constant suffix, or the \fBF\fR or \fBL\fR floating point |
| constant suffixes. (Traditional C does support the \fBL\fR suffix on integer |
| constants.) Note, these suffixes appear in macros defined in the system |
| headers of most modern systems, e.g. the \fB_MIN\fR/\fB_MAX\fR macros in \f(CW\*(C`<limits.h>\*(C'\fR. |
| Use of these macros in user code might normally lead to spurious |
| warnings, however \s-1GCC\s0's integrated preprocessor has enough context to |
| avoid warning in these cases. |
| .IP "*" 4 |
| A function declared external in one block and then used after the end of |
| the block. |
| .IP "*" 4 |
| A \f(CW\*(C`switch\*(C'\fR statement has an operand of type \f(CW\*(C`long\*(C'\fR. |
| .IP "*" 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 "*" 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 "*" 4 |
| Usage of \s-1ISO\s0 string concatenation is detected. |
| .IP "*" 4 |
| Initialization of automatic aggregates. |
| .IP "*" 4 |
| Identifier conflicts with labels. Traditional C lacks a separate |
| namespace for labels. |
| .IP "*" 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 "*" 4 |
| Conversions by prototypes between fixed/floating point values and vice |
| versa. The absence of these prototypes when compiling with traditional |
| C would cause serious problems. This is a subset of the possible |
| conversion warnings, for the full set use \fB\-Wconversion\fR. |
| .IP "*" 4 |
| Use of \s-1ISO\s0 C style function definitions. This warning intentionally is |
| \&\fInot\fR issued for prototype declarations or variadic functions |
| because these \s-1ISO\s0 C features will appear in your code when using |
| libiberty's traditional C compatibility macros, \f(CW\*(C`PARAMS\*(C'\fR and |
| \&\f(CW\*(C`VPARAMS\*(C'\fR. This warning is also bypassed for nested functions |
| because that feature is already a \s-1GCC\s0 extension and thus not relevant to |
| traditional C compatibility. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-Wdeclaration\-after\-statement\fR (C only)" 4 |
| .IX Item "-Wdeclaration-after-statement (C only)" |
| Warn when a declaration is found after a statement in a block. This |
| construct, known from \*(C+, was introduced with \s-1ISO\s0 C99 and is by default |
| allowed in \s-1GCC\s0. It is not supported by \s-1ISO\s0 C90 and was not supported by |
| \&\s-1GCC\s0 versions before \s-1GCC\s0 3.0. |
| .IP "\fB\-Wundef\fR" 4 |
| .IX Item "-Wundef" |
| Warn if an undefined identifier is evaluated in an \fB#if\fR directive. |
| .IP "\fB\-Wno\-endif\-labels\fR" 4 |
| .IX Item "-Wno-endif-labels" |
| Do not warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text. |
| .IP "\fB\-Wshadow\fR" 4 |
| .IX Item "-Wshadow" |
| Warn whenever a local variable shadows another local variable, parameter or |
| global variable or whenever a built-in function is shadowed. |
| .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\-Wunsafe\-loop\-optimizations\fR" 4 |
| .IX Item "-Wunsafe-loop-optimizations" |
| Warn if the loop cannot be optimized because the compiler could not |
| assume anything on the bounds of the loop indices. With |
| \&\fB\-funsafe\-loop\-optimizations\fR warn if the compiler made |
| such assumptions. |
| .IP "\fB\-Wpointer\-arith\fR" 4 |
| .IX Item "-Wpointer-arith" |
| Warn about anything that depends on the \*(L"size of\*(R" 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\fR (C only)" 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\-Wc++\-compat\fR" 4 |
| .IX Item "-Wc++-compat" |
| Warn about \s-1ISO\s0 C constructs that are outside of the common subset of |
| \&\s-1ISO\s0 C and \s-1ISO\s0 \*(C+, e.g. request for implicit conversion from |
| \&\f(CW\*(C`void *\*(C'\fR to a pointer to non\-\f(CW\*(C`void\*(C'\fR type. |
| .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" |
| When compiling C, 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; when compiling \*(C+, warn about the |
| deprecated conversion from string literals to \f(CW\*(C`char *\*(C'\fR. This |
| warning, by default, is enabled for \*(C+ programs. |
| These warnings will help you find at |
| compile time code that can try to write into a string constant, but |
| only if you have been very careful about using \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\-Wextra\fR; to get the other warnings |
| of \fB\-Wextra\fR without this warning, use \fB\-Wextra \-Wno\-sign\-compare\fR. |
| .IP "\fB\-Waddress\fR" 4 |
| .IX Item "-Waddress" |
| Warn about suspicious uses of memory addresses. These include using |
| the address of a function in a conditional expression, such as |
| \&\f(CW\*(C`void func(void); if (func)\*(C'\fR, and comparisons against the memory |
| address of a string literal, such as \f(CW\*(C`if (x == "abc")\*(C'\fR. Such |
| uses typically indicate a programmer error: the address of a function |
| always evaluates to true, so their use in a conditional usually |
| indicate that the programmer forgot the parentheses in a function |
| call; and comparisons against string literals result in unspecified |
| behavior and are not portable in C, so they usually indicate that the |
| programmer intended to use \f(CW\*(C`strcmp\*(C'\fR. This warning is enabled by |
| \&\fB\-Wall\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\-Wno\-attributes\fR" 4 |
| .IX Item "-Wno-attributes" |
| Do not warn if an unexpected \f(CW\*(C`_\|_attribute_\|_\*(C'\fR is used, such as |
| unrecognized attributes, function attributes applied to variables, |
| etc. This will not stop errors for incorrect use of supported |
| attributes. |
| .IP "\fB\-Wstrict\-prototypes\fR (C only)" 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\-Wold\-style\-definition\fR (C only)" 4 |
| .IX Item "-Wold-style-definition (C only)" |
| Warn if an old-style function definition is used. A warning is given |
| even if there is a previous prototype. |
| .IP "\fB\-Wmissing\-prototypes\fR (C only)" 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 (C only)" 4 |
| .IX Item "-Wmissing-declarations (C only)" |
| 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\-field\-initializers\fR" 4 |
| .IX Item "-Wmissing-field-initializers" |
| Warn if a structure's initializer has some fields missing. For |
| example, the following code would cause such a warning, because |
| \&\f(CW\*(C`x.h\*(C'\fR is implicitly zero: |
| .Sp |
| .Vb 2 |
| \& struct s { int f, g, h; }; |
| \& struct s x = { 3, 4 }; |
| .Ve |
| .Sp |
| This option does not warn about designated initializers, so the following |
| modification would not trigger a warning: |
| .Sp |
| .Vb 2 |
| \& struct s { int f, g, h; }; |
| \& struct s x = { .f = 3, .g = 4 }; |
| .Ve |
| .Sp |
| This warning is included in \fB\-Wextra\fR. To get other \fB\-Wextra\fR |
| warnings without this one, use \fB\-Wextra \-Wno\-missing\-field\-initializers\fR. |
| .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" |
| Warn about function pointers 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 function pointers with \f(CW\*(C`format\*(C'\fR attributes that |
| are used in assignment, initialization, parameter passing or return |
| statements should have a corresponding \f(CW\*(C`format\*(C'\fR attribute in the |
| resulting type. I.e. the left-hand side of the assignment or |
| initialization, the type of the parameter variable, or the return type |
| of the containing function respectively should also have a \f(CW\*(C`format\*(C'\fR |
| attribute to avoid the warning. |
| .Sp |
| \&\s-1GCC\s0 will also warn about function definitions which might be |
| candidates for \f(CW\*(C`format\*(C'\fR attributes. Again, these are only |
| possible candidates. \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. |
| .IP "\fB\-Wno\-multichar\fR" 4 |
| .IX Item "-Wno-multichar" |
| Do not 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\-Wnormalized=<none|id|nfc|nfkc>\fR" 4 |
| .IX Item "-Wnormalized=<none|id|nfc|nfkc>" |
| In \s-1ISO\s0 C and \s-1ISO\s0 \*(C+, two identifiers are different if they are |
| different sequences of characters. However, sometimes when characters |
| outside the basic \s-1ASCII\s0 character set are used, you can have two |
| different character sequences that look the same. To avoid confusion, |
| the \s-1ISO\s0 10646 standard sets out some \fInormalization rules\fR which |
| when applied ensure that two sequences that look the same are turned into |
| the same sequence. \s-1GCC\s0 can warn you if you are using identifiers which |
| have not been normalized; this option controls that warning. |
| .Sp |
| There are four levels of warning that \s-1GCC\s0 supports. The default is |
| \&\fB\-Wnormalized=nfc\fR, which warns about any identifier which is |
| not in the \s-1ISO\s0 10646 \*(L"C\*(R" normalized form, \fI\s-1NFC\s0\fR. \s-1NFC\s0 is the |
| recommended form for most uses. |
| .Sp |
| Unfortunately, there are some characters which \s-1ISO\s0 C and \s-1ISO\s0 \*(C+ allow |
| in identifiers that when turned into \s-1NFC\s0 aren't allowable as |
| identifiers. That is, there's no way to use these symbols in portable |
| \&\s-1ISO\s0 C or \*(C+ and have all your identifiers in \s-1NFC\s0. |
| \&\fB\-Wnormalized=id\fR suppresses the warning for these characters. |
| It is hoped that future versions of the standards involved will correct |
| this, which is why this option is not the default. |
| .Sp |
| You can switch the warning off for all characters by writing |
| \&\fB\-Wnormalized=none\fR. You would only want to do this if you |
| were using some other normalization scheme (like \*(L"D\*(R"), because |
| otherwise you can easily create bugs that are literally impossible to see. |
| .Sp |
| Some characters in \s-1ISO\s0 10646 have distinct meanings but look identical |
| in some fonts or display methodologies, especially once formatting has |
| been applied. For instance \f(CW\*(C`\eu207F\*(C'\fR, \*(L"\s-1SUPERSCRIPT\s0 \s-1LATIN\s0 \s-1SMALL\s0 |
| \&\s-1LETTER\s0 N\*(R", will display just like a regular \f(CW\*(C`n\*(C'\fR which has been |
| placed in a superscript. \s-1ISO\s0 10646 defines the \fI\s-1NFKC\s0\fR |
| normalization scheme to convert all these into a standard form as |
| well, and \s-1GCC\s0 will warn if your code is not in \s-1NFKC\s0 if you use |
| \&\fB\-Wnormalized=nfkc\fR. This warning is comparable to warning |
| about every identifier that contains the letter O because it might be |
| confused with the digit 0, and so is not the default, but may be |
| useful as a local coding convention if the programming environment is |
| unable to be fixed to display these characters distinctly. |
| .IP "\fB\-Wno\-deprecated\-declarations\fR" 4 |
| .IX Item "-Wno-deprecated-declarations" |
| Do not warn about uses of functions, |
| variables, and types marked as deprecated by using the \f(CW\*(C`deprecated\*(C'\fR |
| attribute. |
| .IP "\fB\-Wno\-overflow\fR" 4 |
| .IX Item "-Wno-overflow" |
| Do not warn about compile-time overflow in constant expressions. |
| .IP "\fB\-Woverride\-init\fR" 4 |
| .IX Item "-Woverride-init" |
| Warn if an initialized field without side effects is overridden when |
| using designated initializers. |
| .Sp |
| This warning is included in \fB\-Wextra\fR. To get other |
| \&\fB\-Wextra\fR warnings without this one, use \fB\-Wextra |
| \&\-Wno\-override\-init\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\fR (C only)" 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 behavior 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. |
| Even with this option, the compiler will not warn about failures to |
| inline functions declared in system headers. |
| .Sp |
| The compiler uses a variety of heuristics to determine whether or not |
| to inline a function. For example, the compiler takes into account |
| the size of the function being inlined and the amount of inlining |
| that has already been done in the current function. Therefore, |
| seemingly insignificant changes in the source program can cause the |
| warnings produced by \fB\-Winline\fR to appear or disappear. |
| .IP "\fB\-Wno\-invalid\-offsetof\fR (\*(C+ only)" 4 |
| .IX Item "-Wno-invalid-offsetof ( only)" |
| Suppress warnings from applying the \fBoffsetof\fR macro to a non-POD |
| type. According to the 1998 \s-1ISO\s0 \*(C+ standard, applying \fBoffsetof\fR |
| to a non-POD type is undefined. In existing \*(C+ implementations, |
| however, \fBoffsetof\fR typically gives meaningful results even when |
| applied to certain kinds of non-POD types. (Such as a simple |
| \&\fBstruct\fR that fails to be a \s-1POD\s0 type only by virtue of having a |
| constructor.) This flag is for users who are aware that they are |
| writing nonportable code and who have deliberately chosen to ignore the |
| warning about it. |
| .Sp |
| The restrictions on \fBoffsetof\fR may be relaxed in a future version |
| of the \*(C+ standard. |
| .IP "\fB\-Wno\-int\-to\-pointer\-cast\fR (C only)" 4 |
| .IX Item "-Wno-int-to-pointer-cast (C only)" |
| Suppress warnings from casts to pointer type of an integer of a |
| different size. |
| .IP "\fB\-Wno\-pointer\-to\-int\-cast\fR (C only)" 4 |
| .IX Item "-Wno-pointer-to-int-cast (C only)" |
| Suppress warnings from casts from a pointer to an integer type of a |
| different size. |
| .IP "\fB\-Winvalid\-pch\fR" 4 |
| .IX Item "-Winvalid-pch" |
| Warn if a precompiled header is found in |
| the search path but can't be used. |
| .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\-Wvariadic\-macros\fR" 4 |
| .IX Item "-Wvariadic-macros" |
| Warn if variadic macros are used in pedantic \s-1ISO\s0 C90 mode, or the \s-1GNU\s0 |
| alternate syntax when in pedantic \s-1ISO\s0 C99 mode. This is default. |
| To inhibit the warning messages, use \fB\-Wno\-variadic\-macros\fR. |
| .IP "\fB\-Wvolatile\-register\-var\fR" 4 |
| .IX Item "-Wvolatile-register-var" |
| Warn if a register variable is declared volatile. The volatile |
| modifier does not inhibit all optimizations that may eliminate reads |
| and/or writes to register variables. |
| .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\-Wpointer\-sign\fR" 4 |
| .IX Item "-Wpointer-sign" |
| Warn for pointer argument passing or assignment with different signedness. |
| This option is only supported for C and Objective\-C. It is implied by |
| \&\fB\-Wall\fR and by \fB\-pedantic\fR, which can be disabled with |
| \&\fB\-Wno\-pointer\-sign\fR. |
| .IP "\fB\-Werror\fR" 4 |
| .IX Item "-Werror" |
| Make all warnings into errors. |
| .IP "\fB\-Werror=\fR" 4 |
| .IX Item "-Werror=" |
| Make the specified warning into an errors. The specifier for a |
| warning is appended, for example \fB\-Werror=switch\fR turns the |
| warnings controlled by \fB\-Wswitch\fR into errors. This switch |
| takes a negative form, to be used to negate \fB\-Werror\fR for |
| specific warnings, for example \fB\-Wno\-error=switch\fR makes |
| \&\fB\-Wswitch\fR warnings not be errors, even when \fB\-Werror\fR |
| is in effect. You can use the \fB\-fdiagnostics\-show\-option\fR |
| option to have each controllable warning amended with the option which |
| controls it, to determine what to use with this option. |
| .Sp |
| Note that specifying \fB\-Werror=\fR\fIfoo\fR automatically implies |
| \&\fB\-W\fR\fIfoo\fR. However, \fB\-Wno\-error=\fR\fIfoo\fR does not |
| imply anything. |
| .IP "\fB\-Wstack\-protector\fR" 4 |
| .IX Item "-Wstack-protector" |
| This option is only active when \fB\-fstack\-protector\fR is active. It |
| warns about functions that will not be protected against stack smashing. |
| .IP "\fB\-Woverlength\-strings\fR" 4 |
| .IX Item "-Woverlength-strings" |
| Warn about string constants which are longer than the \*(L"minimum |
| maximum\*(R" length specified in the C standard. Modern compilers |
| generally allow string constants which are much longer than the |
| standard's minimum limit, but very portable programs should avoid |
| using longer strings. |
| .Sp |
| The limit applies \fIafter\fR string constant concatenation, and does |
| not count the trailing \s-1NUL\s0. In C89, the limit was 509 characters; in |
| C99, it was raised to 4095. \*(C+98 does not specify a normative |
| minimum maximum, so we do not diagnose overlength strings in \*(C+. |
| .Sp |
| This option is implied by \fB\-pedantic\fR, and can be disabled with |
| \&\fB\-Wno\-overlength\-strings\fR. |
| .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 2). \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, or \fB\-gvms\fR (see below). |
| .Sp |
| \&\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\-feliminate\-unused\-debug\-symbols\fR" 4 |
| .IX Item "-feliminate-unused-debug-symbols" |
| Produce debugging information in stabs format (if that is supported), |
| for only symbols that are actually used. |
| .IP "\fB\-femit\-class\-debug\-always\fR" 4 |
| .IX Item "-femit-class-debug-always" |
| Instead of emitting debugging information for a \*(C+ class in only one |
| object file, emit it in all object files using the class. This option |
| should be used only with debuggers that are unable to handle the way \s-1GCC\s0 |
| normally emits debugging information for classes because using this |
| option will increase the size of debugging information by as much as a |
| factor of two. |
| .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\-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. With this |
| option, \s-1GCC\s0 uses features of \s-1DWARF\s0 version 3 when they are useful; |
| version 3 is upward compatible with version 2, but may still cause |
| problems for older debuggers. |
| .IP "\fB\-gvms\fR" 4 |
| .IX Item "-gvms" |
| Produce debugging information in \s-1VMS\s0 debug format (if that is |
| supported). This is the format used by \s-1DEBUG\s0 on \s-1VMS\s0 systems. |
| .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\-gvms\fR\fIlevel\fR" 4 |
| .IX Item "-gvmslevel" |
| .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. |
| .Sp |
| \&\fB\-gdwarf\-2\fR does not accept a concatenated debug level, because |
| \&\s-1GCC\s0 used to support an option \fB\-gdwarf\fR that meant to generate |
| debug information in version 1 of the \s-1DWARF\s0 format (which is very |
| different from version 2), and it would have been too confusing. That |
| debug format is long obsolete, but the option cannot be changed now. |
| Instead use an additional \fB\-g\fR\fIlevel\fR option to change the |
| debug level for \s-1DWARF2\s0. |
| .IP "\fB\-feliminate\-dwarf2\-dups\fR" 4 |
| .IX Item "-feliminate-dwarf2-dups" |
| Compress \s-1DWARF2\s0 debugging information by eliminating duplicated |
| information about each symbol. This option only makes sense when |
| generating \s-1DWARF2\s0 debugging information with \fB\-gdwarf\-2\fR. |
| .IP "\fB\-p\fR" 4 |
| .IX Item "-p" |
| Generate extra code to write profile information suitable for the |
| analysis program \fBprof\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 \fBgprof\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\-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\-ftime\-report\fR" 4 |
| .IX Item "-ftime-report" |
| Makes the compiler print some statistics about the time consumed by each |
| pass when it finishes. |
| .IP "\fB\-fmem\-report\fR" 4 |
| .IX Item "-fmem-report" |
| Makes the compiler print some statistics about permanent memory |
| allocation when it finishes. |
| .IP "\fB\-fprofile\-arcs\fR" 4 |
| .IX Item "-fprofile-arcs" |
| Add code so that program flow \fIarcs\fR are instrumented. During |
| execution the program records how many times each branch and call is |
| executed and how many times it is taken or returns. When the compiled |
| program exits it saves this data to a file called |
| \&\fI\fIauxname\fI.gcda\fR for each source file. The data may be used for |
| profile-directed optimizations (\fB\-fbranch\-probabilities\fR), or for |
| test coverage analysis (\fB\-ftest\-coverage\fR). Each object file's |
| \&\fIauxname\fR is generated from the name of the output file, if |
| explicitly specified and it is not the final executable, otherwise it is |
| the basename of the source file. In both cases any suffix is removed |
| (e.g. \fIfoo.gcda\fR for input file \fIdir/foo.c\fR, or |
| \&\fIdir/foo.gcda\fR for output file specified as \fB\-o dir/foo.o\fR). |
| .IP "\fB\-\-coverage\fR" 4 |
| .IX Item "--coverage" |
| This option is used to compile and link code instrumented for coverage |
| analysis. The option is a synonym for \fB\-fprofile\-arcs\fR |
| \&\fB\-ftest\-coverage\fR (when compiling) and \fB\-lgcov\fR (when |
| linking). See the documentation for those options for more details. |
| .RS 4 |
| .IP "@bullet" 4 |
| .IX Item "@bullet" |
| Compile the source files with \fB\-fprofile\-arcs\fR plus optimization |
| and code generation options. For test coverage analysis, use the |
| additional \fB\-ftest\-coverage\fR option. You do not need to profile |
| every source file in a program. |
| .IP "@cvmmfu" 4 |
| .IX Item "@cvmmfu" |
| Link your object files with \fB\-lgcov\fR or \fB\-fprofile\-arcs\fR |
| (the latter implies the former). |
| .IP "@dwnngv" 4 |
| .IX Item "@dwnngv" |
| Run the program on a representative workload to generate the arc profile |
| information. This may be repeated any number of times. You can run |
| concurrent instances of your program, and provided that the file system |
| supports locking, the data files will be correctly updated. Also |
| \&\f(CW\*(C`fork\*(C'\fR calls are detected and correctly handled (double counting |
| will not happen). |
| .IP "@exoohw" 4 |
| .IX Item "@exoohw" |
| For profile-directed optimizations, compile the source files again with |
| the same optimization and code generation options plus |
| \&\fB\-fbranch\-probabilities\fR. |
| .IP "@fyppix" 4 |
| .IX Item "@fyppix" |
| For test coverage analysis, use \fBgcov\fR to produce human readable |
| information from the \fI.gcno\fR and \fI.gcda\fR files. Refer to the |
| \&\fBgcov\fR documentation for further information. |
| .RE |
| .RS 4 |
| .Sp |
| With \fB\-fprofile\-arcs\fR, 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. |
| .RE |
| .IP "\fB\-ftest\-coverage\fR" 4 |
| .IX Item "-ftest-coverage" |
| Produce a notes file that the \fBgcov\fR code-coverage utility can use to |
| show program coverage. Each source file's note file is called |
| \&\fI\fIauxname\fI.gcno\fR. Refer to the \fB\-fprofile\-arcs\fR option |
| above for a description of \fIauxname\fR and instructions on how to |
| generate test coverage data. Coverage data will match the source files |
| more closely, if you do not optimize. |
| .IP "\fB\-d\fR\fIletters\fR" 4 |
| .IX Item "-dletters" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-\fR\fIpass\fR" 4 |
| .IX Item "-fdump-rtl-pass" |
| .PD |
| Says to make debugging dumps during compilation at times specified by |
| \&\fIletters\fR. This is used for debugging the RTL-based passes of the |
| compiler. The file names for most of the dumps are made by appending a |
| pass number and a word to the \fIdumpname\fR. \fIdumpname\fR is generated |
| from the name of the output file, if explicitly specified and it is not |
| an executable, otherwise it is the basename of the source file. |
| .Sp |
| Most debug dumps can be enabled either passing a letter to the \fB\-d\fR |
| option, or with a long \fB\-fdump\-rtl\fR switch; here are the possible |
| letters for use in \fIletters\fR and \fIpass\fR, and their meanings: |
| .RS 4 |
| .IP "\fB\-dA\fR" 4 |
| .IX Item "-dA" |
| Annotate the assembler output with miscellaneous debugging information. |
| .IP "\fB\-dB\fR" 4 |
| .IX Item "-dB" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-bbro\fR" 4 |
| .IX Item "-fdump-rtl-bbro" |
| .PD |
| Dump after block reordering, to \fI\fIfile\fI.148r.bbro\fR. |
| .IP "\fB\-dc\fR" 4 |
| .IX Item "-dc" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-combine\fR" 4 |
| .IX Item "-fdump-rtl-combine" |
| .PD |
| Dump after instruction combination, to the file \fI\fIfile\fI.129r.combine\fR. |
| .IP "\fB\-dC\fR" 4 |
| .IX Item "-dC" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-ce1\fR" 4 |
| .IX Item "-fdump-rtl-ce1" |
| .IP "\fB\-fdump\-rtl\-ce2\fR" 4 |
| .IX Item "-fdump-rtl-ce2" |
| .PD |
| \&\fB\-dC\fR and \fB\-fdump\-rtl\-ce1\fR enable dumping after the |
| first if conversion, to the file \fI\fIfile\fI.117r.ce1\fR. \fB\-dC\fR |
| and \fB\-fdump\-rtl\-ce2\fR enable dumping after the second if |
| conversion, to the file \fI\fIfile\fI.130r.ce2\fR. |
| .IP "\fB\-dd\fR" 4 |
| .IX Item "-dd" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-btl\fR" 4 |
| .IX Item "-fdump-rtl-btl" |
| .IP "\fB\-fdump\-rtl\-dbr\fR" 4 |
| .IX Item "-fdump-rtl-dbr" |
| .PD |
| \&\fB\-dd\fR and \fB\-fdump\-rtl\-btl\fR enable dumping after branch |
| target load optimization, to \fI\fIfile\fI.31.btl\fR. \fB\-dd\fR |
| and \fB\-fdump\-rtl\-dbr\fR enable dumping after delayed branch |
| scheduling, to \fI\fIfile\fI.36.dbr\fR. |
| .IP "\fB\-dD\fR" 4 |
| .IX Item "-dD" |
| Dump all macro definitions, at the end of preprocessing, in addition to |
| normal output. |
| .IP "\fB\-dE\fR" 4 |
| .IX Item "-dE" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-ce3\fR" 4 |
| .IX Item "-fdump-rtl-ce3" |
| .PD |
| Dump after the third if conversion, to \fI\fIfile\fI.146r.ce3\fR. |
| .IP "\fB\-df\fR" 4 |
| .IX Item "-df" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-cfg\fR" 4 |
| .IX Item "-fdump-rtl-cfg" |
| .IP "\fB\-fdump\-rtl\-life\fR" 4 |
| .IX Item "-fdump-rtl-life" |
| .PD |
| \&\fB\-df\fR and \fB\-fdump\-rtl\-cfg\fR enable dumping after control |
| and data flow analysis, to \fI\fIfile\fI.116r.cfg\fR. \fB\-df\fR |
| and \fB\-fdump\-rtl\-cfg\fR enable dumping dump after life analysis, |
| to \fI\fIfile\fI.128r.life1\fR and \fI\fIfile\fI.135r.life2\fR. |
| .IP "\fB\-dg\fR" 4 |
| .IX Item "-dg" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-greg\fR" 4 |
| .IX Item "-fdump-rtl-greg" |
| .PD |
| Dump after global register allocation, to \fI\fIfile\fI.139r.greg\fR. |
| .IP "\fB\-dG\fR" 4 |
| .IX Item "-dG" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-gcse\fR" 4 |
| .IX Item "-fdump-rtl-gcse" |
| .IP "\fB\-fdump\-rtl\-bypass\fR" 4 |
| .IX Item "-fdump-rtl-bypass" |
| .PD |
| \&\fB\-dG\fR and \fB\-fdump\-rtl\-gcse\fR enable dumping after \s-1GCSE\s0, to |
| \&\fI\fIfile\fI.114r.gcse\fR. \fB\-dG\fR and \fB\-fdump\-rtl\-bypass\fR |
| enable dumping after jump bypassing and control flow optimizations, to |
| \&\fI\fIfile\fI.115r.bypass\fR. |
| .IP "\fB\-dh\fR" 4 |
| .IX Item "-dh" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-eh\fR" 4 |
| .IX Item "-fdump-rtl-eh" |
| .PD |
| Dump after finalization of \s-1EH\s0 handling code, to \fI\fIfile\fI.02.eh\fR. |
| .IP "\fB\-di\fR" 4 |
| .IX Item "-di" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-sibling\fR" 4 |
| .IX Item "-fdump-rtl-sibling" |
| .PD |
| Dump after sibling call optimizations, to \fI\fIfile\fI.106r.sibling\fR. |
| .IP "\fB\-dj\fR" 4 |
| .IX Item "-dj" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-jump\fR" 4 |
| .IX Item "-fdump-rtl-jump" |
| .PD |
| Dump after the first jump optimization, to \fI\fIfile\fI.112r.jump\fR. |
| .IP "\fB\-dk\fR" 4 |
| .IX Item "-dk" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-stack\fR" 4 |
| .IX Item "-fdump-rtl-stack" |
| .PD |
| Dump after conversion from registers to stack, to \fI\fIfile\fI.152r.stack\fR. |
| .IP "\fB\-dl\fR" 4 |
| .IX Item "-dl" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-lreg\fR" 4 |
| .IX Item "-fdump-rtl-lreg" |
| .PD |
| Dump after local register allocation, to \fI\fIfile\fI.138r.lreg\fR. |
| .IP "\fB\-dL\fR" 4 |
| .IX Item "-dL" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-loop2\fR" 4 |
| .IX Item "-fdump-rtl-loop2" |
| .PD |
| \&\fB\-dL\fR and \fB\-fdump\-rtl\-loop2\fR enable dumping after the |
| loop optimization pass, to \fI\fIfile\fI.119r.loop2\fR, |
| \&\fI\fIfile\fI.120r.loop2_init\fR, |
| \&\fI\fIfile\fI.121r.loop2_invariant\fR, and |
| \&\fI\fIfile\fI.125r.loop2_done\fR. |
| .IP "\fB\-dm\fR" 4 |
| .IX Item "-dm" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-sms\fR" 4 |
| .IX Item "-fdump-rtl-sms" |
| .PD |
| Dump after modulo scheduling, to \fI\fIfile\fI.136r.sms\fR. |
| .IP "\fB\-dM\fR" 4 |
| .IX Item "-dM" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-mach\fR" 4 |
| .IX Item "-fdump-rtl-mach" |
| .PD |
| Dump after performing the machine dependent reorganization pass, to |
| \&\fI\fIfile\fI.155r.mach\fR. |
| .IP "\fB\-dn\fR" 4 |
| .IX Item "-dn" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-rnreg\fR" 4 |
| .IX Item "-fdump-rtl-rnreg" |
| .PD |
| Dump after register renumbering, to \fI\fIfile\fI.147r.rnreg\fR. |
| .IP "\fB\-dN\fR" 4 |
| .IX Item "-dN" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-regmove\fR" 4 |
| .IX Item "-fdump-rtl-regmove" |
| .PD |
| Dump after the register move pass, to \fI\fIfile\fI.132r.regmove\fR. |
| .IP "\fB\-do\fR" 4 |
| .IX Item "-do" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-postreload\fR" 4 |
| .IX Item "-fdump-rtl-postreload" |
| .PD |
| Dump after post-reload optimizations, to \fI\fIfile\fI.24.postreload\fR. |
| .IP "\fB\-dr\fR" 4 |
| .IX Item "-dr" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-expand\fR" 4 |
| .IX Item "-fdump-rtl-expand" |
| .PD |
| Dump after \s-1RTL\s0 generation, to \fI\fIfile\fI.104r.expand\fR. |
| .IP "\fB\-dR\fR" 4 |
| .IX Item "-dR" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-sched2\fR" 4 |
| .IX Item "-fdump-rtl-sched2" |
| .PD |
| Dump after the second scheduling pass, to \fI\fIfile\fI.150r.sched2\fR. |
| .IP "\fB\-ds\fR" 4 |
| .IX Item "-ds" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-cse\fR" 4 |
| .IX Item "-fdump-rtl-cse" |
| .PD |
| Dump after \s-1CSE\s0 (including the jump optimization that sometimes follows |
| \&\s-1CSE\s0), to \fI\fIfile\fI.113r.cse\fR. |
| .IP "\fB\-dS\fR" 4 |
| .IX Item "-dS" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-sched\fR" 4 |
| .IX Item "-fdump-rtl-sched" |
| .PD |
| Dump after the first scheduling pass, to \fI\fIfile\fI.21.sched\fR. |
| .IP "\fB\-dt\fR" 4 |
| .IX Item "-dt" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-cse2\fR" 4 |
| .IX Item "-fdump-rtl-cse2" |
| .PD |
| Dump after the second \s-1CSE\s0 pass (including the jump optimization that |
| sometimes follows \s-1CSE\s0), to \fI\fIfile\fI.127r.cse2\fR. |
| .IP "\fB\-dT\fR" 4 |
| .IX Item "-dT" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-tracer\fR" 4 |
| .IX Item "-fdump-rtl-tracer" |
| .PD |
| Dump after running tracer, to \fI\fIfile\fI.118r.tracer\fR. |
| .IP "\fB\-dV\fR" 4 |
| .IX Item "-dV" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-vpt\fR" 4 |
| .IX Item "-fdump-rtl-vpt" |
| .IP "\fB\-fdump\-rtl\-vartrack\fR" 4 |
| .IX Item "-fdump-rtl-vartrack" |
| .PD |
| \&\fB\-dV\fR and \fB\-fdump\-rtl\-vpt\fR enable dumping after the value |
| profile transformations, to \fI\fIfile\fI.10.vpt\fR. \fB\-dV\fR |
| and \fB\-fdump\-rtl\-vartrack\fR enable dumping after variable tracking, |
| to \fI\fIfile\fI.154r.vartrack\fR. |
| .IP "\fB\-dw\fR" 4 |
| .IX Item "-dw" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-flow2\fR" 4 |
| .IX Item "-fdump-rtl-flow2" |
| .PD |
| Dump after the second flow pass, to \fI\fIfile\fI.142r.flow2\fR. |
| .IP "\fB\-dz\fR" 4 |
| .IX Item "-dz" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-peephole2\fR" 4 |
| .IX Item "-fdump-rtl-peephole2" |
| .PD |
| Dump after the peephole pass, to \fI\fIfile\fI.145r.peephole2\fR. |
| .IP "\fB\-dZ\fR" 4 |
| .IX Item "-dZ" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-web\fR" 4 |
| .IX Item "-fdump-rtl-web" |
| .PD |
| Dump after live range splitting, to \fI\fIfile\fI.126r.web\fR. |
| .IP "\fB\-da\fR" 4 |
| .IX Item "-da" |
| .PD 0 |
| .IP "\fB\-fdump\-rtl\-all\fR" 4 |
| .IX Item "-fdump-rtl-all" |
| .PD |
| Produce all the dumps listed above. |
| .IP "\fB\-dH\fR" 4 |
| .IX Item "-dH" |
| Produce a core dump whenever an error occurs. |
| .IP "\fB\-dm\fR" 4 |
| .IX Item "-dm" |
| Print statistics on memory usage, at the end of the run, to |
| standard error. |
| .IP "\fB\-dp\fR" 4 |
| .IX Item "-dp" |
| Annotate the assembler output with a comment indicating which |
| pattern and alternative was used. The length of each instruction is |
| also printed. |
| .IP "\fB\-dP\fR" 4 |
| .IX Item "-dP" |
| Dump the \s-1RTL\s0 in the assembler output as a comment before each instruction. |
| Also turns on \fB\-dp\fR annotation. |
| .IP "\fB\-dv\fR" 4 |
| .IX Item "-dv" |
| For each of the other indicated dump files (either with \fB\-d\fR or |
| \&\fB\-fdump\-rtl\-\fR\fIpass\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 "\fB\-dx\fR" 4 |
| .IX Item "-dx" |
| Just generate \s-1RTL\s0 for a function instead of compiling it. Usually used |
| with \fBr\fR (\fB\-fdump\-rtl\-expand\fR). |
| .IP "\fB\-dy\fR" 4 |
| .IX Item "-dy" |
| Dump debugging information during parsing, to standard error. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-fdump\-noaddr\fR" 4 |
| .IX Item "-fdump-noaddr" |
| When doing debugging dumps (see \fB\-d\fR option above), suppress |
| address output. This makes it more feasible to use diff on debugging |
| dumps for compiler invocations with different compiler binaries and/or |
| different text / bss / data / heap / stack / dso start locations. |
| .IP "\fB\-fdump\-unnumbered\fR" 4 |
| .IX Item "-fdump-unnumbered" |
| When doing debugging dumps (see \fB\-d\fR option above), suppress instruction |
| numbers, line number note and address output. This makes it more feasible to |
| use diff on debugging dumps for compiler invocations with different |
| options, in particular with and without \fB\-g\fR. |
| .IP "\fB\-fdump\-translation\-unit\fR (\*(C+ only)" 4 |
| .IX Item "-fdump-translation-unit ( only)" |
| .PD 0 |
| .IP "\fB\-fdump\-translation\-unit\-\fR\fIoptions\fR\fB \fR(\*(C+ only)" 4 |
| .IX Item "-fdump-translation-unit-options ( only)" |
| .PD |
| Dump a representation of the tree structure for the entire translation |
| unit to a file. The file name is made by appending \fI.tu\fR to the |
| source file name. If the \fB\-\fR\fIoptions\fR form is used, \fIoptions\fR |
| controls the details of the dump as described for the |
| \&\fB\-fdump\-tree\fR options. |
| .IP "\fB\-fdump\-class\-hierarchy\fR (\*(C+ only)" 4 |
| .IX Item "-fdump-class-hierarchy ( only)" |
| .PD 0 |
| .IP "\fB\-fdump\-class\-hierarchy\-\fR\fIoptions\fR\fB \fR(\*(C+ only)" 4 |
| .IX Item "-fdump-class-hierarchy-options ( only)" |
| .PD |
| Dump a representation of each class's hierarchy and virtual function |
| table layout to a file. The file name is made by appending \fI.class\fR |
| to the source file name. If the \fB\-\fR\fIoptions\fR form is used, |
| \&\fIoptions\fR controls the details of the dump as described for the |
| \&\fB\-fdump\-tree\fR options. |
| .IP "\fB\-fdump\-ipa\-\fR\fIswitch\fR" 4 |
| .IX Item "-fdump-ipa-switch" |
| Control the dumping at various stages of inter-procedural analysis |
| language tree to a file. The file name is generated by appending a switch |
| specific suffix to the source file name. The following dumps are possible: |
| .RS 4 |
| .IP "\fBall\fR" 4 |
| .IX Item "all" |
| Enables all inter-procedural analysis dumps; currently the only produced |
| dump is the \fBcgraph\fR dump. |
| .IP "\fBcgraph\fR" 4 |
| .IX Item "cgraph" |
| Dumps information about call-graph optimization, unused function removal, |
| and inlining decisions. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-fdump\-tree\-\fR\fIswitch\fR" 4 |
| .IX Item "-fdump-tree-switch" |
| .PD 0 |
| .IP "\fB\-fdump\-tree\-\fR\fIswitch\fR\fB\-\fR\fIoptions\fR" 4 |
| .IX Item "-fdump-tree-switch-options" |
| .PD |
| Control the dumping at various stages of processing the intermediate |
| language tree to a file. The file name is generated by appending a switch |
| specific suffix to the source file name. If the \fB\-\fR\fIoptions\fR |
| form is used, \fIoptions\fR is a list of \fB\-\fR separated options that |
| control the details of the dump. Not all options are applicable to all |
| dumps, those which are not meaningful will be ignored. The following |
| options are available |
| .RS 4 |
| .IP "\fBaddress\fR" 4 |
| .IX Item "address" |
| Print the address of each node. Usually this is not meaningful as it |
| changes according to the environment and source file. Its primary use |
| is for tying up a dump file with a debug environment. |
| .IP "\fBslim\fR" 4 |
| .IX Item "slim" |
| Inhibit dumping of members of a scope or body of a function merely |
| because that scope has been reached. Only dump such items when they |
| are directly reachable by some other path. When dumping pretty-printed |
| trees, this option inhibits dumping the bodies of control structures. |
| .IP "\fBraw\fR" 4 |
| .IX Item "raw" |
| Print a raw representation of the tree. By default, trees are |
| pretty-printed into a C\-like representation. |
| .IP "\fBdetails\fR" 4 |
| .IX Item "details" |
| Enable more detailed dumps (not honored by every dump option). |
| .IP "\fBstats\fR" 4 |
| .IX Item "stats" |
| Enable dumping various statistics about the pass (not honored by every dump |
| option). |
| .IP "\fBblocks\fR" 4 |
| .IX Item "blocks" |
| Enable showing basic block boundaries (disabled in raw dumps). |
| .IP "\fBvops\fR" 4 |
| .IX Item "vops" |
| Enable showing virtual operands for every statement. |
| .IP "\fBlineno\fR" 4 |
| .IX Item "lineno" |
| Enable showing line numbers for statements. |
| .IP "\fBuid\fR" 4 |
| .IX Item "uid" |
| Enable showing the unique \s-1ID\s0 (\f(CW\*(C`DECL_UID\*(C'\fR) for each variable. |
| .IP "\fBall\fR" 4 |
| .IX Item "all" |
| Turn on all options, except \fBraw\fR, \fBslim\fR and \fBlineno\fR. |
| .RE |
| .RS 4 |
| .Sp |
| The following tree dumps are possible: |
| .IP "\fBoriginal\fR" 4 |
| .IX Item "original" |
| Dump before any tree based optimization, to \fI\fIfile\fI.original\fR. |
| .IP "\fBoptimized\fR" 4 |
| .IX Item "optimized" |
| Dump after all tree based optimization, to \fI\fIfile\fI.optimized\fR. |
| .IP "\fBinlined\fR" 4 |
| .IX Item "inlined" |
| Dump after function inlining, to \fI\fIfile\fI.inlined\fR. |
| .IP "\fBgimple\fR" 4 |
| .IX Item "gimple" |
| Dump each function before and after the gimplification pass to a file. The |
| file name is made by appending \fI.gimple\fR to the source file name. |
| .IP "\fBcfg\fR" 4 |
| .IX Item "cfg" |
| Dump the control flow graph of each function to a file. The file name is |
| made by appending \fI.cfg\fR to the source file name. |
| .IP "\fBvcg\fR" 4 |
| .IX Item "vcg" |
| Dump the control flow graph of each function to a file in \s-1VCG\s0 format. The |
| file name is made by appending \fI.vcg\fR to the source file name. Note |
| that if the file contains more than one function, the generated file cannot |
| be used directly by \s-1VCG\s0. You will need to cut and paste each function's |
| graph into its own separate file first. |
| .IP "\fBch\fR" 4 |
| .IX Item "ch" |
| Dump each function after copying loop headers. The file name is made by |
| appending \fI.ch\fR to the source file name. |
| .IP "\fBssa\fR" 4 |
| .IX Item "ssa" |
| Dump \s-1SSA\s0 related information to a file. The file name is made by appending |
| \&\fI.ssa\fR to the source file name. |
| .IP "\fBsalias\fR" 4 |
| .IX Item "salias" |
| Dump structure aliasing variable information to a file. This file name |
| is made by appending \fI.salias\fR to the source file name. |
| .IP "\fBalias\fR" 4 |
| .IX Item "alias" |
| Dump aliasing information for each function. The file name is made by |
| appending \fI.alias\fR to the source file name. |
| .IP "\fBccp\fR" 4 |
| .IX Item "ccp" |
| Dump each function after \s-1CCP\s0. The file name is made by appending |
| \&\fI.ccp\fR to the source file name. |
| .IP "\fBstoreccp\fR" 4 |
| .IX Item "storeccp" |
| Dump each function after \s-1STORE\-CCP\s0. The file name is made by appending |
| \&\fI.storeccp\fR to the source file name. |
| .IP "\fBpre\fR" 4 |
| .IX Item "pre" |
| Dump trees after partial redundancy elimination. The file name is made |
| by appending \fI.pre\fR to the source file name. |
| .IP "\fBfre\fR" 4 |
| .IX Item "fre" |
| Dump trees after full redundancy elimination. The file name is made |
| by appending \fI.fre\fR to the source file name. |
| .IP "\fBcopyprop\fR" 4 |
| .IX Item "copyprop" |
| Dump trees after copy propagation. The file name is made |
| by appending \fI.copyprop\fR to the source file name. |
| .IP "\fBstore_copyprop\fR" 4 |
| .IX Item "store_copyprop" |
| Dump trees after store copy\-propagation. The file name is made |
| by appending \fI.store_copyprop\fR to the source file name. |
| .IP "\fBdce\fR" 4 |
| .IX Item "dce" |
| Dump each function after dead code elimination. The file name is made by |
| appending \fI.dce\fR to the source file name. |
| .IP "\fBmudflap\fR" 4 |
| .IX Item "mudflap" |
| Dump each function after adding mudflap instrumentation. The file name is |
| made by appending \fI.mudflap\fR to the source file name. |
| .IP "\fBsra\fR" 4 |
| .IX Item "sra" |
| Dump each function after performing scalar replacement of aggregates. The |
| file name is made by appending \fI.sra\fR to the source file name. |
| .IP "\fBsink\fR" 4 |
| .IX Item "sink" |
| Dump each function after performing code sinking. The file name is made |
| by appending \fI.sink\fR to the source file name. |
| .IP "\fBdom\fR" 4 |
| .IX Item "dom" |
| Dump each function after applying dominator tree optimizations. The file |
| name is made by appending \fI.dom\fR to the source file name. |
| .IP "\fBdse\fR" 4 |
| .IX Item "dse" |
| Dump each function after applying dead store elimination. The file |
| name is made by appending \fI.dse\fR to the source file name. |
| .IP "\fBphiopt\fR" 4 |
| .IX Item "phiopt" |
| Dump each function after optimizing \s-1PHI\s0 nodes into straightline code. The file |
| name is made by appending \fI.phiopt\fR to the source file name. |
| .IP "\fBforwprop\fR" 4 |
| .IX Item "forwprop" |
| Dump each function after forward propagating single use variables. The file |
| name is made by appending \fI.forwprop\fR to the source file name. |
| .IP "\fBcopyrename\fR" 4 |
| .IX Item "copyrename" |
| Dump each function after applying the copy rename optimization. The file |
| name is made by appending \fI.copyrename\fR to the source file name. |
| .IP "\fBnrv\fR" 4 |
| .IX Item "nrv" |
| Dump each function after applying the named return value optimization on |
| generic trees. The file name is made by appending \fI.nrv\fR to the source |
| file name. |
| .IP "\fBvect\fR" 4 |
| .IX Item "vect" |
| Dump each function after applying vectorization of loops. The file name is |
| made by appending \fI.vect\fR to the source file name. |
| .IP "\fBvrp\fR" 4 |
| .IX Item "vrp" |
| Dump each function after Value Range Propagation (\s-1VRP\s0). The file name |
| is made by appending \fI.vrp\fR to the source file name. |
| .IP "\fBall\fR" 4 |
| .IX Item "all" |
| Enable all the available tree dumps with the flags provided in this option. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-ftree\-vectorizer\-verbose=\fR\fIn\fR" 4 |
| .IX Item "-ftree-vectorizer-verbose=n" |
| This option controls the amount of debugging output the vectorizer prints. |
| This information is written to standard error, unless |
| \&\fB\-fdump\-tree\-all\fR or \fB\-fdump\-tree\-vect\fR is specified, |
| in which case it is output to the usual dump listing file, \fI.vect\fR. |
| For \fIn\fR=0 no diagnostic information is reported. |
| If \fIn\fR=1 the vectorizer reports each loop that got vectorized, |
| and the total number of loops that got vectorized. |
| If \fIn\fR=2 the vectorizer also reports non-vectorized loops that passed |
| the first analysis phase (vect_analyze_loop_form) \- i.e. countable, |
| inner\-most, single\-bb, single\-entry/exit loops. This is the same verbosity |
| level that \fB\-fdump\-tree\-vect\-stats\fR uses. |
| Higher verbosity levels mean either more information dumped for each |
| reported loop, or same amount of information reported for more loops: |
| If \fIn\fR=3, alignment related information is added to the reports. |
| If \fIn\fR=4, data-references related information (e.g. memory dependences, |
| memory access\-patterns) is added to the reports. |
| If \fIn\fR=5, the vectorizer reports also non-vectorized inner-most loops |
| that did not pass the first analysis phase (i.e. may not be countable, or |
| may have complicated control\-flow). |
| If \fIn\fR=6, the vectorizer reports also non-vectorized nested loops. |
| For \fIn\fR=7, all the information the vectorizer generates during its |
| analysis and transformation is reported. This is the same verbosity level |
| that \fB\-fdump\-tree\-vect\-details\fR uses. |
| .IP "\fB\-frandom\-seed=\fR\fIstring\fR" 4 |
| .IX Item "-frandom-seed=string" |
| This option provides a seed that \s-1GCC\s0 uses when it would otherwise use |
| random numbers. It is used to generate certain symbol names |
| that have to be different in every compiled file. It is also used to |
| place unique stamps in coverage data files and the object files that |
| produce them. You can use the \fB\-frandom\-seed\fR option to produce |
| reproducibly identical object files. |
| .Sp |
| The \fIstring\fR should be different for every file you compile. |
| .IP "\fB\-fsched\-verbose=\fR\fIn\fR" 4 |
| .IX Item "-fsched-verbose=n" |
| On targets that use instruction scheduling, this option controls the |
| amount of debugging output the scheduler prints. This information is |
| written to standard error, unless \fB\-dS\fR or \fB\-dR\fR is |
| specified, in which case it is output to the usual dump |
| listing file, \fI.sched\fR or \fI.sched2\fR respectively. However |
| for \fIn\fR greater than nine, the output is always printed to standard |
| error. |
| .Sp |
| For \fIn\fR greater than zero, \fB\-fsched\-verbose\fR outputs the |
| same information as \fB\-dRS\fR. For \fIn\fR greater than one, it |
| also output basic block probabilities, detailed ready list information |
| and unit/insn info. For \fIn\fR greater than two, it includes \s-1RTL\s0 |
| at abort point, control-flow and regions info. And for \fIn\fR over |
| four, \fB\-fsched\-verbose\fR also includes dependence info. |
| .IP "\fB\-save\-temps\fR" 4 |
| .IX Item "-save-temps" |
| Store the usual \*(L"temporary\*(R" 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. |
| .Sp |
| When used in combination with the \fB\-x\fR command line option, |
| \&\fB\-save\-temps\fR is sensible enough to avoid over writing an |
| input source file with the same extension as an intermediate file. |
| The corresponding intermediate file may be obtained by renaming the |
| source file before using \fB\-save\-temps\fR. |
| .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 |
| .Sp |
| The first number on each line is the \*(L"user time\*(R", that is time spent |
| executing the program itself. The second number is \*(L"system time\*(R", |
| time spent executing operating system routines on behalf of the program. |
| Both numbers are in seconds. |
| .IP "\fB\-fvar\-tracking\fR" 4 |
| .IX Item "-fvar-tracking" |
| Run variable tracking pass. It computes where variables are stored at each |
| position in code. Better debugging information is then generated |
| (if the debugging information format supports this information). |
| .Sp |
| It is enabled by default when compiling with optimization (\fB\-Os\fR, |
| \&\fB\-O\fR, \fB\-O2\fR, ...), debugging information (\fB\-g\fR) and |
| the debug info format supports it. |
| .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\-multi\-directory\fR" 4 |
| .IX Item "-print-multi-directory" |
| Print the directory name corresponding to the multilib selected by any |
| other switches present in the command line. This directory is supposed |
| to exist in \fB\s-1GCC_EXEC_PREFIX\s0\fR. |
| .IP "\fB\-print\-multi\-lib\fR" 4 |
| .IX Item "-print-multi-lib" |
| Print the mapping from multilib directory names to compiler switches |
| that enable them. The directory name is separated from the switches by |
| \&\fB;\fR, and each switch starts with an \fB@} instead of the |
| \&\f(CB@samp\fB{\-\fR, without spaces between multiple switches. This is supposed to |
| ease shell\-processing. |
| .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 <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 \fBgcc\fR will search\-\-\-and don't do anything else. |
| .Sp |
| This is useful when \fBgcc\fR 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 \fBgcc\fR 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 \fB/\fR. |
| .IP "\fB\-dumpmachine\fR" 4 |
| .IX Item "-dumpmachine" |
| Print the compiler's target machine (for example, |
| \&\fBi686\-pc\-linux\-gnu\fR)\-\-\-and don't do anything else. |
| .IP "\fB\-dumpversion\fR" 4 |
| .IX Item "-dumpversion" |
| Print the compiler version (for example, \fB3.0\fR)\-\-\-and don't do |
| anything else. |
| .IP "\fB\-dumpspecs\fR" 4 |
| .IX Item "-dumpspecs" |
| Print the compiler's built-in specs\-\-\-and don't do anything else. (This |
| is used when \s-1GCC\s0 itself is being built.) |
| .IP "\fB\-feliminate\-unused\-debug\-types\fR" 4 |
| .IX Item "-feliminate-unused-debug-types" |
| Normally, when producing \s-1DWARF2\s0 output, \s-1GCC\s0 will emit debugging |
| information for all types declared in a compilation |
| unit, regardless of whether or not they are actually used |
| in that compilation unit. Sometimes this is useful, such as |
| if, in the debugger, you want to cast a value to a type that is |
| not actually used in your program (but is declared). More often, |
| however, this results in a significant amount of wasted space. |
| With this option, \s-1GCC\s0 will avoid producing debug symbol output |
| for types that are nowhere used in the source file being compiled. |
| .Sh "Options That Control Optimization" |
| .IX Subsection "Options That Control Optimization" |
| These options control various sorts of optimizations. |
| .PP |
| Without any optimization option, the compiler's goal is to reduce the |
| cost of compilation and to make debugging produce the expected |
| results. Statements are independent: if you stop the program with a |
| breakpoint between statements, you can then assign a new value to any |
| variable or change the program counter to any other statement in the |
| function and get exactly the results you would expect from the source |
| code. |
| .PP |
| Turning on optimization flags makes the compiler attempt to improve |
| the performance and/or code size at the expense of compilation time |
| and possibly the ability to debug the program. |
| .PP |
| The compiler performs optimization based on the knowledge it has of |
| the program. Optimization levels \fB\-O\fR and above, in |
| particular, enable \fIunit-at-a-time\fR mode, which allows the |
| compiler to consider information gained from later functions in |
| the file when compiling a function. Compiling multiple files at |
| once to a single output file in \fIunit-at-a-time\fR mode allows |
| the compiler to use information gained from all of the files when |
| compiling each of them. |
| .PP |
| Not all optimizations are controlled directly by a flag. Only |
| optimizations that have a flag are listed. |
| .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 |
| With \fB\-O\fR, the compiler tries to reduce code size and execution |
| time, without performing any optimizations that take a great deal of |
| compilation time. |
| .Sp |
| \&\fB\-O\fR turns on the following optimization flags: |
| \&\fB\-fdefer\-pop |
| \&\-fdelayed\-branch |
| \&\-fguess\-branch\-probability |
| \&\-fcprop\-registers |
| \&\-fif\-conversion |
| \&\-fif\-conversion2 |
| \&\-ftree\-ccp |
| \&\-ftree\-dce |
| \&\-ftree\-dominator\-opts |
| \&\-ftree\-dse |
| \&\-ftree\-ter |
| \&\-ftree\-lrs |
| \&\-ftree\-sra |
| \&\-ftree\-copyrename |
| \&\-ftree\-fre |
| \&\-ftree\-ch |
| \&\-funit\-at\-a\-time |
| \&\-fmerge\-constants\fR |
| .Sp |
| \&\fB\-O\fR also turns on \fB\-fomit\-frame\-pointer\fR on machines |
| where doing so does not interfere with debugging. |
| .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 optimization flags specified by \fB\-O\fR. It |
| also turns on the following optimization flags: |
| \&\fB\-fthread\-jumps |
| \&\-fcrossjumping |
| \&\-foptimize\-sibling\-calls |
| \&\-fcse\-follow\-jumps \-fcse\-skip\-blocks |
| \&\-fgcse \-fgcse\-lm |
| \&\-fexpensive\-optimizations |
| \&\-frerun\-cse\-after\-loop |
| \&\-fcaller\-saves |
| \&\-fpeephole2 |
| \&\-fschedule\-insns \-fschedule\-insns2 |
| \&\-fsched\-interblock \-fsched\-spec |
| \&\-fregmove |
| \&\-fstrict\-aliasing \-fstrict\-overflow |
| \&\-fdelete\-null\-pointer\-checks |
| \&\-freorder\-blocks \-freorder\-functions |
| \&\-falign\-functions \-falign\-jumps |
| \&\-falign\-loops \-falign\-labels |
| \&\-ftree\-vrp |
| \&\-ftree\-pre\fR |
| .Sp |
| Please note the warning under \fB\-fgcse\fR about |
| invoking \fB\-O2\fR on programs that use computed gotos. |
| .Sp |
| \&\fB\-O2\fR doesn't turn on \fB\-ftree\-vrp\fR for the Ada compiler. |
| This option must be explicitly specified on the command line to be |
| enabled for the Ada compiler. |
| .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, |
| \&\fB\-funswitch\-loops\fR and \fB\-fgcse\-after\-reload\fR options. |
| .IP "\fB\-O0\fR" 4 |
| .IX Item "-O0" |
| Do not optimize. This is the default. |
| .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 |
| \&\fB\-Os\fR disables the following optimization flags: |
| \&\fB\-falign\-functions \-falign\-jumps \-falign\-loops |
| \&\-falign\-labels \-freorder\-blocks \-freorder\-blocks\-and\-partition |
| \&\-fprefetch\-loop\-arrays \-ftree\-vect\-loop\-version\fR |
| .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 you typically will |
| use. You can figure out the other form by either removing \fBno\-\fR |
| or adding it. |
| .PP |
| The following options control specific optimizations. They are either |
| activated by \fB\-O\fR options or are related to ones that are. You |
| can use the following flags in the rare cases when \*(L"fine\-tuning\*(R" of |
| optimizations to be performed is desired. |
| .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. |
| .Sp |
| Disabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. This option is now a nop and will be removed in 4.2. |
| .IP "\fB\-fforce\-addr\fR" 4 |
| .IX Item "-fforce-addr" |
| Force memory address constants to be copied into registers before |
| doing arithmetic on them. |
| .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 \s-1VAX\s0, 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. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-foptimize\-sibling\-calls\fR" 4 |
| .IX Item "-foptimize-sibling-calls" |
| Optimize sibling and tail recursive calls. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at level \fB\-O3\fR. |
| .IP "\fB\-finline\-functions\-called\-once\fR" 4 |
| .IX Item "-finline-functions-called-once" |
| Consider all \f(CW\*(C`static\*(C'\fR functions called once for inlining into their |
| caller even if they are not marked \f(CW\*(C`inline\*(C'\fR. If a call to a given |
| function is integrated, then the function is not output as assembler code |
| in its own right. |
| .Sp |
| Enabled if \fB\-funit\-at\-a\-time\fR is enabled. |
| .IP "\fB\-fearly\-inlining\fR" 4 |
| .IX Item "-fearly-inlining" |
| Inline functions marked by \f(CW\*(C`always_inline\*(C'\fR and functions whose body seems |
| smaller than the function call overhead early before doing |
| \&\fB\-fprofile\-generate\fR instrumentation and real inlining pass. Doing so |
| makes profiling significantly cheaper and usually inlining faster on programs |
| having large chains of nested wrapper functions. |
| .Sp |
| Enabled by default. |
| .IP "\fB\-finline\-limit=\fR\fIn\fR" 4 |
| .IX Item "-finline-limit=n" |
| By default, \s-1GCC\s0 limits the size of functions that can be inlined. This flag |
| allows the control of this limit for functions that are explicitly marked as |
| inline (i.e., marked with the inline keyword or defined within the class |
| definition in c++). \fIn\fR is the size of functions that can be inlined in |
| number of pseudo instructions (not counting parameter handling). The default |
| value of \fIn\fR is 600. |
| Increasing this value can result in more inlined code at |
| the cost of compilation time and memory consumption. Decreasing usually makes |
| the compilation faster and less code will be inlined (which presumably |
| means slower programs). This option is particularly useful for programs that |
| use inlining heavily such as those based on recursive templates with \*(C+. |
| .Sp |
| Inlining is actually controlled by a number of parameters, which may be |
| specified individually by using \fB\-\-param\fR \fIname\fR\fB=\fR\fIvalue\fR. |
| The \fB\-finline\-limit=\fR\fIn\fR option sets some of these parameters |
| as follows: |
| .RS 4 |
| .IP "\fBmax-inline-insns-single\fR" 4 |
| .IX Item "max-inline-insns-single" |
| .Vb 1 |
| \& is set to I<n>/2. |
| .Ve |
| .IP "\fBmax-inline-insns-auto\fR" 4 |
| .IX Item "max-inline-insns-auto" |
| .Vb 1 |
| \& is set to I<n>/2. |
| .Ve |
| .IP "\fBmin-inline-insns\fR" 4 |
| .IX Item "min-inline-insns" |
| .Vb 1 |
| \& is set to 130 or I<n>/4, whichever is smaller. |
| .Ve |
| .IP "\fBmax-inline-insns-rtl\fR" 4 |
| .IX Item "max-inline-insns-rtl" |
| .Vb 1 |
| \& is set to I<n>. |
| .Ve |
| .RE |
| .RS 4 |
| .Sp |
| See below for a documentation of the individual |
| parameters controlling inlining. |
| .Sp |
| \&\fINote:\fR pseudo instruction represents, in this particular context, an |
| abstract measurement of function's size. In no way does it represent a count |
| of assembly instructions and as such its exact meaning might change from one |
| release to an another. |
| .RE |
| .IP "\fB\-fkeep\-inline\-functions\fR" 4 |
| .IX Item "-fkeep-inline-functions" |
| In C, emit \f(CW\*(C`static\*(C'\fR functions that are declared \f(CW\*(C`inline\*(C'\fR |
| into the object file, even if the function has been inlined into all |
| of its callers. This switch does not affect functions using the |
| \&\f(CW\*(C`extern inline\*(C'\fR extension in \s-1GNU\s0 C. In \*(C+, emit any and all |
| inline functions into the object file. |
| .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\-fmerge\-constants\fR" 4 |
| .IX Item "-fmerge-constants" |
| Attempt to merge identical constants (string constants and floating point |
| constants) across compilation units. |
| .Sp |
| This option is the default for optimized compilation if the assembler and |
| linker support it. Use \fB\-fno\-merge\-constants\fR to inhibit this |
| behavior. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fmerge\-all\-constants\fR" 4 |
| .IX Item "-fmerge-all-constants" |
| Attempt to merge identical constants and identical variables. |
| .Sp |
| This option implies \fB\-fmerge\-constants\fR. In addition to |
| \&\fB\-fmerge\-constants\fR this considers e.g. even constant initialized |
| arrays or initialized constant variables with integral or floating point |
| types. Languages like C or \*(C+ require each non-automatic variable to |
| have distinct location, so using this option will result in non-conforming |
| behavior. |
| .IP "\fB\-fmodulo\-sched\fR" 4 |
| .IX Item "-fmodulo-sched" |
| Perform swing modulo scheduling immediately before the first scheduling |
| pass. This pass looks at innermost loops and reorders their |
| instructions by overlapping different iterations. |
| .IP "\fB\-fno\-branch\-count\-reg\fR" 4 |
| .IX Item "-fno-branch-count-reg" |
| Do not use \*(L"decrement and branch\*(R" instructions on a count register, |
| but instead generate a sequence of instructions that decrement a |
| register, compare it against zero, then branch based upon the result. |
| This option is only meaningful on architectures that support such |
| instructions, which include x86, PowerPC, \s-1IA\-64\s0 and S/390. |
| .Sp |
| The default is \fB\-fbranch\-count\-reg\fR. |
| .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. |
| .Sp |
| The default is \fB\-ffunction\-cse\fR |
| .IP "\fB\-fno\-zero\-initialized\-in\-bss\fR" 4 |
| .IX Item "-fno-zero-initialized-in-bss" |
| If the target supports a \s-1BSS\s0 section, \s-1GCC\s0 by default puts variables that |
| are initialized to zero into \s-1BSS\s0. This can save space in the resulting |
| code. |
| .Sp |
| This option turns off this behavior because some programs explicitly |
| rely on variables going to the data section. E.g., so that the |
| resulting executable can find the beginning of that section and/or make |
| assumptions based on that. |
| .Sp |
| The default is \fB\-fzero\-initialized\-in\-bss\fR. |
| .IP "\fB\-fbounds\-check\fR" 4 |
| .IX Item "-fbounds-check" |
| For front-ends that support it, generate additional code to check that |
| indices used to access arrays are within the declared range. This is |
| currently only supported by the Java and Fortran front\-ends, where |
| this option defaults to true and false respectively. |
| .IP "\fB\-fmudflap \-fmudflapth \-fmudflapir\fR" 4 |
| .IX Item "-fmudflap -fmudflapth -fmudflapir" |
| For front-ends that support it (C and \*(C+), instrument all risky |
| pointer/array dereferencing operations, some standard library |
| string/heap functions, and some other associated constructs with |
| range/validity tests. Modules so instrumented should be immune to |
| buffer overflows, invalid heap use, and some other classes of C/\*(C+ |
| programming errors. The instrumentation relies on a separate runtime |
| library (\fIlibmudflap\fR), which will be linked into a program if |
| \&\fB\-fmudflap\fR is given at link time. Run-time behavior of the |
| instrumented program is controlled by the \fB\s-1MUDFLAP_OPTIONS\s0\fR |
| environment variable. See \f(CW\*(C`env MUDFLAP_OPTIONS=\-help a.out\*(C'\fR |
| for its options. |
| .Sp |
| Use \fB\-fmudflapth\fR instead of \fB\-fmudflap\fR to compile and to |
| link if your program is multi\-threaded. Use \fB\-fmudflapir\fR, in |
| addition to \fB\-fmudflap\fR or \fB\-fmudflapth\fR, if |
| instrumentation should ignore pointer reads. This produces less |
| instrumentation (and therefore faster execution) and still provides |
| some protection against outright memory corrupting writes, but allows |
| erroneously read data to propagate within a program. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fgcse\fR" 4 |
| .IX Item "-fgcse" |
| Perform a global common subexpression elimination pass. |
| This pass also performs global constant and copy propagation. |
| .Sp |
| \&\fINote:\fR When compiling a program using computed gotos, a \s-1GCC\s0 |
| extension, you may get better runtime performance if you disable |
| the global common subexpression elimination pass by adding |
| \&\fB\-fno\-gcse\fR to the command line. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fgcse\-lm\fR" 4 |
| .IX Item "-fgcse-lm" |
| When \fB\-fgcse\-lm\fR is enabled, global common subexpression elimination will |
| attempt to move loads which are only killed by stores into themselves. This |
| allows a loop containing a load/store sequence to be changed to a load outside |
| the loop, and a copy/store within the loop. |
| .Sp |
| Enabled by default when gcse is enabled. |
| .IP "\fB\-fgcse\-sm\fR" 4 |
| .IX Item "-fgcse-sm" |
| When \fB\-fgcse\-sm\fR is enabled, a store motion pass is run after |
| global common subexpression elimination. This pass will attempt to move |
| stores out of loops. When used in conjunction with \fB\-fgcse\-lm\fR, |
| loops containing a load/store sequence can be changed to a load before |
| the loop and a store after the loop. |
| .Sp |
| Not enabled at any optimization level. |
| .IP "\fB\-fgcse\-las\fR" 4 |
| .IX Item "-fgcse-las" |
| When \fB\-fgcse\-las\fR is enabled, the global common subexpression |
| elimination pass eliminates redundant loads that come after stores to the |
| same memory location (both partial and full redundancies). |
| .Sp |
| Not enabled at any optimization level. |
| .IP "\fB\-fgcse\-after\-reload\fR" 4 |
| .IX Item "-fgcse-after-reload" |
| When \fB\-fgcse\-after\-reload\fR is enabled, a redundant load elimination |
| pass is performed after reload. The purpose of this pass is to cleanup |
| redundant spilling. |
| .IP "\fB\-funsafe\-loop\-optimizations\fR" 4 |
| .IX Item "-funsafe-loop-optimizations" |
| If given, the loop optimizer will assume that loop indices do not |
| overflow, and that the loops with nontrivial exit condition are not |
| infinite. This enables a wider range of loop optimizations even if |
| the loop optimizer itself cannot prove that these assumptions are valid. |
| Using \fB\-Wunsafe\-loop\-optimizations\fR, the compiler will warn you |
| if it finds this kind of loop. |
| .IP "\fB\-fcrossjumping\fR" 4 |
| .IX Item "-fcrossjumping" |
| Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The |
| resulting code may or may not perform better than without cross\-jumping. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fif\-conversion\fR" 4 |
| .IX Item "-fif-conversion" |
| Attempt to transform conditional jumps into branch-less equivalents. This |
| include use of conditional moves, min, max, set flags and abs instructions, and |
| some tricks doable by standard arithmetics. The use of conditional execution |
| on chips where it is available is controlled by \f(CW\*(C`if\-conversion2\*(C'\fR. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fif\-conversion2\fR" 4 |
| .IX Item "-fif-conversion2" |
| Use conditional execution (where available) to transform conditional jumps into |
| branch-less equivalents. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fdelete\-null\-pointer\-checks\fR" 4 |
| .IX Item "-fdelete-null-pointer-checks" |
| Use global dataflow analysis to identify and eliminate useless checks |
| for null pointers. The compiler assumes that dereferencing a null |
| pointer would have halted the program. If a pointer is checked after |
| it has already been dereferenced, it cannot be null. |
| .Sp |
| In some environments, this assumption is not true, and programs can |
| safely dereference null pointers. Use |
| \&\fB\-fno\-delete\-null\-pointer\-checks\fR to disable this optimization |
| for programs which depend on that behavior. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fexpensive\-optimizations\fR" 4 |
| .IX Item "-fexpensive-optimizations" |
| Perform a number of minor optimizations that are relatively expensive. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Note \fB\-fregmove\fR and \fB\-foptimize\-register\-move\fR are the same |
| optimization. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fno\-sched\-interblock\fR" 4 |
| .IX Item "-fno-sched-interblock" |
| Don't schedule instructions across basic blocks. This is normally |
| enabled by default when scheduling before register allocation, i.e. |
| with \fB\-fschedule\-insns\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fno\-sched\-spec\fR" 4 |
| .IX Item "-fno-sched-spec" |
| Don't allow speculative motion of non-load instructions. This is normally |
| enabled by default when scheduling before register allocation, i.e. |
| with \fB\-fschedule\-insns\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fsched\-spec\-load\fR" 4 |
| .IX Item "-fsched-spec-load" |
| Allow speculative motion of some load instructions. This only makes |
| sense when scheduling before register allocation, i.e. with |
| \&\fB\-fschedule\-insns\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fsched\-spec\-load\-dangerous\fR" 4 |
| .IX Item "-fsched-spec-load-dangerous" |
| Allow speculative motion of more load instructions. This only makes |
| sense when scheduling before register allocation, i.e. with |
| \&\fB\-fschedule\-insns\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fsched\-stalled\-insns=\fR\fIn\fR" 4 |
| .IX Item "-fsched-stalled-insns=n" |
| Define how many insns (if any) can be moved prematurely from the queue |
| of stalled insns into the ready list, during the second scheduling pass. |
| .IP "\fB\-fsched\-stalled\-insns\-dep=\fR\fIn\fR" 4 |
| .IX Item "-fsched-stalled-insns-dep=n" |
| Define how many insn groups (cycles) will be examined for a dependency |
| on a stalled insn that is candidate for premature removal from the queue |
| of stalled insns. Has an effect only during the second scheduling pass, |
| and only if \fB\-fsched\-stalled\-insns\fR is used and its value is not zero. |
| .IP "\fB\-fsched2\-use\-superblocks\fR" 4 |
| .IX Item "-fsched2-use-superblocks" |
| When scheduling after register allocation, do use superblock scheduling |
| algorithm. Superblock scheduling allows motion across basic block boundaries |
| resulting on faster schedules. This option is experimental, as not all machine |
| descriptions used by \s-1GCC\s0 model the \s-1CPU\s0 closely enough to avoid unreliable |
| results from the algorithm. |
| .Sp |
| This only makes sense when scheduling after register allocation, i.e. with |
| \&\fB\-fschedule\-insns2\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fsched2\-use\-traces\fR" 4 |
| .IX Item "-fsched2-use-traces" |
| Use \fB\-fsched2\-use\-superblocks\fR algorithm when scheduling after register |
| allocation and additionally perform code duplication in order to increase the |
| size of superblocks using tracer pass. See \fB\-ftracer\fR for details on |
| trace formation. |
| .Sp |
| This mode should produce faster but significantly longer programs. Also |
| without \fB\-fbranch\-probabilities\fR the traces constructed may not |
| match the reality and hurt the performance. This only makes |
| sense when scheduling after register allocation, i.e. with |
| \&\fB\-fschedule\-insns2\fR or at \fB\-O2\fR or higher. |
| .IP "\fB\-fsee\fR" 4 |
| .IX Item "-fsee" |
| Eliminates redundant extension instructions and move the non redundant |
| ones to optimal placement using \s-1LCM\s0. |
| .IP "\fB\-freschedule\-modulo\-scheduled\-loops\fR" 4 |
| .IX Item "-freschedule-modulo-scheduled-loops" |
| The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled |
| we may want to prevent the later scheduling passes from changing its schedule, we use this |
| option to control that. |
| .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 |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-ftree\-pre\fR" 4 |
| .IX Item "-ftree-pre" |
| Perform Partial Redundancy Elimination (\s-1PRE\s0) on trees. This flag is |
| enabled by default at \fB\-O2\fR and \fB\-O3\fR. |
| .IP "\fB\-ftree\-fre\fR" 4 |
| .IX Item "-ftree-fre" |
| Perform Full Redundancy Elimination (\s-1FRE\s0) on trees. The difference |
| between \s-1FRE\s0 and \s-1PRE\s0 is that \s-1FRE\s0 only considers expressions |
| that are computed on all paths leading to the redundant computation. |
| This analysis faster than \s-1PRE\s0, though it exposes fewer redundancies. |
| This flag is enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-copy\-prop\fR" 4 |
| .IX Item "-ftree-copy-prop" |
| Perform copy propagation on trees. This pass eliminates unnecessary |
| copy operations. This flag is enabled by default at \fB\-O\fR and |
| higher. |
| .IP "\fB\-ftree\-store\-copy\-prop\fR" 4 |
| .IX Item "-ftree-store-copy-prop" |
| Perform copy propagation of memory loads and stores. This pass |
| eliminates unnecessary copy operations in memory references |
| (structures, global variables, arrays, etc). This flag is enabled by |
| default at \fB\-O2\fR and higher. |
| .IP "\fB\-ftree\-salias\fR" 4 |
| .IX Item "-ftree-salias" |
| Perform structural alias analysis on trees. This flag |
| is enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-fipa\-pta\fR" 4 |
| .IX Item "-fipa-pta" |
| Perform interprocedural pointer analysis. |
| .IP "\fB\-ftree\-sink\fR" 4 |
| .IX Item "-ftree-sink" |
| Perform forward store motion on trees. This flag is |
| enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-ccp\fR" 4 |
| .IX Item "-ftree-ccp" |
| Perform sparse conditional constant propagation (\s-1CCP\s0) on trees. This |
| pass only operates on local scalar variables and is enabled by default |
| at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-store\-ccp\fR" 4 |
| .IX Item "-ftree-store-ccp" |
| Perform sparse conditional constant propagation (\s-1CCP\s0) on trees. This |
| pass operates on both local scalar variables and memory stores and |
| loads (global variables, structures, arrays, etc). This flag is |
| enabled by default at \fB\-O2\fR and higher. |
| .IP "\fB\-ftree\-dce\fR" 4 |
| .IX Item "-ftree-dce" |
| Perform dead code elimination (\s-1DCE\s0) on trees. This flag is enabled by |
| default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-dominator\-opts\fR" 4 |
| .IX Item "-ftree-dominator-opts" |
| Perform a variety of simple scalar cleanups (constant/copy |
| propagation, redundancy elimination, range propagation and expression |
| simplification) based on a dominator tree traversal. This also |
| performs jump threading (to reduce jumps to jumps). This flag is |
| enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-ch\fR" 4 |
| .IX Item "-ftree-ch" |
| Perform loop header copying on trees. This is beneficial since it increases |
| effectiveness of code motion optimizations. It also saves one jump. This flag |
| is enabled by default at \fB\-O\fR and higher. It is not enabled |
| for \fB\-Os\fR, since it usually increases code size. |
| .IP "\fB\-ftree\-loop\-optimize\fR" 4 |
| .IX Item "-ftree-loop-optimize" |
| Perform loop optimizations on trees. This flag is enabled by default |
| at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-loop\-linear\fR" 4 |
| .IX Item "-ftree-loop-linear" |
| Perform linear loop transformations on tree. This flag can improve cache |
| performance and allow further loop optimizations to take place. |
| .IP "\fB\-ftree\-loop\-im\fR" 4 |
| .IX Item "-ftree-loop-im" |
| Perform loop invariant motion on trees. This pass moves only invariants that |
| would be hard to handle at \s-1RTL\s0 level (function calls, operations that expand to |
| nontrivial sequences of insns). With \fB\-funswitch\-loops\fR it also moves |
| operands of conditions that are invariant out of the loop, so that we can use |
| just trivial invariantness analysis in loop unswitching. The pass also includes |
| store motion. |
| .IP "\fB\-ftree\-loop\-ivcanon\fR" 4 |
| .IX Item "-ftree-loop-ivcanon" |
| Create a canonical counter for number of iterations in the loop for that |
| determining number of iterations requires complicated analysis. Later |
| optimizations then may determine the number easily. Useful especially |
| in connection with unrolling. |
| .IP "\fB\-fivopts\fR" 4 |
| .IX Item "-fivopts" |
| Perform induction variable optimizations (strength reduction, induction |
| variable merging and induction variable elimination) on trees. |
| .IP "\fB\-ftree\-sra\fR" 4 |
| .IX Item "-ftree-sra" |
| Perform scalar replacement of aggregates. This pass replaces structure |
| references with scalars to prevent committing structures to memory too |
| early. This flag is enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-copyrename\fR" 4 |
| .IX Item "-ftree-copyrename" |
| Perform copy renaming on trees. This pass attempts to rename compiler |
| temporaries to other variables at copy locations, usually resulting in |
| variable names which more closely resemble the original variables. This flag |
| is enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-ter\fR" 4 |
| .IX Item "-ftree-ter" |
| Perform temporary expression replacement during the \s-1SSA\-\s0>normal phase. Single |
| use/single def temporaries are replaced at their use location with their |
| defining expression. This results in non-GIMPLE code, but gives the expanders |
| much more complex trees to work on resulting in better \s-1RTL\s0 generation. This is |
| enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-lrs\fR" 4 |
| .IX Item "-ftree-lrs" |
| Perform live range splitting during the \s-1SSA\-\s0>normal phase. Distinct live |
| ranges of a variable are split into unique variables, allowing for better |
| optimization later. This is enabled by default at \fB\-O\fR and higher. |
| .IP "\fB\-ftree\-vectorize\fR" 4 |
| .IX Item "-ftree-vectorize" |
| Perform loop vectorization on trees. |
| .IP "\fB\-ftree\-vect\-loop\-version\fR" 4 |
| .IX Item "-ftree-vect-loop-version" |
| Perform loop versioning when doing loop vectorization on trees. When a loop |
| appears to be vectorizable except that data alignment or data dependence cannot |
| be determined at compile time then vectorized and non-vectorized versions of |
| the loop are generated along with runtime checks for alignment or dependence |
| to control which version is executed. This option is enabled by default |
| except at level \fB\-Os\fR where it is disabled. |
| .IP "\fB\-ftree\-vrp\fR" 4 |
| .IX Item "-ftree-vrp" |
| Perform Value Range Propagation on trees. This is similar to the |
| constant propagation pass, but instead of values, ranges of values are |
| propagated. This allows the optimizers to remove unnecessary range |
| checks like array bound checks and null pointer checks. This is |
| enabled by default at \fB\-O2\fR and higher. Null pointer check |
| elimination is only done if \fB\-fdelete\-null\-pointer\-checks\fR is |
| enabled. |
| .IP "\fB\-ftracer\fR" 4 |
| .IX Item "-ftracer" |
| Perform tail duplication to enlarge superblock size. This transformation |
| simplifies the control flow of the function allowing other optimizations to do |
| better job. |
| .IP "\fB\-funroll\-loops\fR" 4 |
| .IX Item "-funroll-loops" |
| Unroll loops whose number of iterations can be determined at compile |
| time or upon entry to the loop. \fB\-funroll\-loops\fR implies |
| \&\fB\-frerun\-cse\-after\-loop\fR. This option makes code larger, |
| and may or may not make it run faster. |
| .IP "\fB\-funroll\-all\-loops\fR" 4 |
| .IX Item "-funroll-all-loops" |
| Unroll all loops, even if their number of iterations is uncertain when |
| the loop is entered. This usually makes programs run more slowly. |
| \&\fB\-funroll\-all\-loops\fR implies the same options as |
| \&\fB\-funroll\-loops\fR, |
| .IP "\fB\-fsplit\-ivs\-in\-unroller\fR" 4 |
| .IX Item "-fsplit-ivs-in-unroller" |
| Enables expressing of values of induction variables in later iterations |
| of the unrolled loop using the value in the first iteration. This breaks |
| long dependency chains, thus improving efficiency of the scheduling passes. |
| .Sp |
| Combination of \fB\-fweb\fR and \s-1CSE\s0 is often sufficient to obtain the |
| same effect. However in cases the loop body is more complicated than |
| a single basic block, this is not reliable. It also does not work at all |
| on some of the architectures due to restrictions in the \s-1CSE\s0 pass. |
| .Sp |
| This optimization is enabled by default. |
| .IP "\fB\-fvariable\-expansion\-in\-unroller\fR" 4 |
| .IX Item "-fvariable-expansion-in-unroller" |
| With this option, the compiler will create multiple copies of some |
| local variables when unrolling a loop which can result in superior code. |
| .IP "\fB\-fprefetch\-loop\-arrays\fR" 4 |
| .IX Item "-fprefetch-loop-arrays" |
| If supported by the target machine, generate instructions to prefetch |
| memory to improve the performance of loops that access large arrays. |
| .Sp |
| This option may generate better or worse code; results are highly |
| dependent on the structure of loops within the source code. |
| .Sp |
| Disabled at level \fB\-Os\fR. |
| .IP "\fB\-fno\-peephole\fR" 4 |
| .IX Item "-fno-peephole" |
| .PD 0 |
| .IP "\fB\-fno\-peephole2\fR" 4 |
| .IX Item "-fno-peephole2" |
| .PD |
| Disable any machine-specific peephole optimizations. The difference |
| between \fB\-fno\-peephole\fR and \fB\-fno\-peephole2\fR is in how they |
| are implemented in the compiler; some targets use one, some use the |
| other, a few use both. |
| .Sp |
| \&\fB\-fpeephole\fR is enabled by default. |
| \&\fB\-fpeephole2\fR enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fno\-guess\-branch\-probability\fR" 4 |
| .IX Item "-fno-guess-branch-probability" |
| Do not guess branch probabilities using heuristics. |
| .Sp |
| \&\s-1GCC\s0 will use heuristics to guess branch probabilities if they are |
| not provided by profiling feedback (\fB\-fprofile\-arcs\fR). These |
| heuristics are based on the control flow graph. If some branch probabilities |
| are specified by \fB_\|_builtin_expect\fR, then the heuristics will be |
| used to guess branch probabilities for the rest of the control flow graph, |
| taking the \fB_\|_builtin_expect\fR info into account. The interactions |
| between the heuristics and \fB_\|_builtin_expect\fR can be complex, and in |
| some cases, it may be useful to disable the heuristics so that the effects |
| of \fB_\|_builtin_expect\fR are easier to understand. |
| .Sp |
| The default is \fB\-fguess\-branch\-probability\fR at levels |
| \&\fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-freorder\-blocks\fR" 4 |
| .IX Item "-freorder-blocks" |
| Reorder basic blocks in the compiled function in order to reduce number of |
| taken branches and improve code locality. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR. |
| .IP "\fB\-freorder\-blocks\-and\-partition\fR" 4 |
| .IX Item "-freorder-blocks-and-partition" |
| In addition to reordering basic blocks in the compiled function, in order |
| to reduce number of taken branches, partitions hot and cold basic blocks |
| into separate sections of the assembly and .o files, to improve |
| paging and cache locality performance. |
| .Sp |
| This optimization is automatically turned off in the presence of |
| exception handling, for linkonce sections, for functions with a user-defined |
| section attribute and on any architecture that does not support named |
| sections. |
| .IP "\fB\-freorder\-functions\fR" 4 |
| .IX Item "-freorder-functions" |
| Reorder functions in the object file in order to |
| improve code locality. This is implemented by using special |
| subsections \f(CW\*(C`.text.hot\*(C'\fR for most frequently executed functions and |
| \&\f(CW\*(C`.text.unlikely\*(C'\fR for unlikely executed functions. Reordering is done by |
| the linker so object file format must support named sections and linker must |
| place them in a reasonable way. |
| .Sp |
| Also profile feedback must be available in to make this option effective. See |
| \&\fB\-fprofile\-arcs\fR for details. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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 |
| .Sp |
| .Vb 5 |
| \& int f() { |
| \& a_union t; |
| \& t.d = 3.0; |
| \& return t.i; |
| \& } |
| .Ve |
| .Sp |
| The practice of reading from a different union member than the one most |
| recently written to (called \*(L"type\-punning\*(R") 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 |
| .Sp |
| Every language that wishes to perform language-specific alias analysis |
| should define a function that computes, given an \f(CW\*(C`tree\*(C'\fR |
| node, an alias set for the node. Nodes in different alias sets are not |
| allowed to alias. For an example, see the C front-end function |
| \&\f(CW\*(C`c_get_alias_set\*(C'\fR. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fstrict\-overflow\fR" 4 |
| .IX Item "-fstrict-overflow" |
| Allow the compiler to assume strict signed overflow rules, depending |
| on the language being compiled. For C (and \*(C+) this means that |
| overflow when doing arithmetic with signed numbers is undefined, which |
| means that the compiler may assume that it will not happen. This |
| permits various optimizations. For example, the compiler will assume |
| that an expression like \f(CW\*(C`i + 10 > i\*(C'\fR will always be true for |
| signed \f(CW\*(C`i\*(C'\fR. This assumption is only valid if signed overflow is |
| undefined, as the expression is false if \f(CW\*(C`i + 10\*(C'\fR overflows when |
| using twos complement arithmetic. When this option is in effect any |
| attempt to determine whether an operation on signed numbers will |
| overflow must be written carefully to not actually involve overflow. |
| .Sp |
| See also the \fB\-fwrapv\fR option. Using \fB\-fwrapv\fR means |
| that signed overflow is fully defined: it wraps. When |
| \&\fB\-fwrapv\fR is used, there is no difference between |
| \&\fB\-fstrict\-overflow\fR and \fB\-fno\-strict\-overflow\fR. With |
| \&\fB\-fwrapv\fR certain types of overflow are permitted. For |
| example, if the compiler gets an overflow when doing arithmetic on |
| constants, the overflowed value can still be used with |
| \&\fB\-fwrapv\fR, but not otherwise. |
| .Sp |
| The \fB\-fstrict\-overflow\fR option is enabled at levels |
| \&\fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .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 or is zero, use a machine-dependent default. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR. |
| .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 |
| \&\fB\-fno\-align\-labels\fR and \fB\-falign\-labels=1\fR are |
| equivalent and mean that labels will not be aligned. |
| .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 or is zero, use a machine-dependent default |
| which is very likely to be \fB1\fR, meaning no alignment. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR. |
| .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 |
| \&\fB\-fno\-align\-loops\fR and \fB\-falign\-loops=1\fR are |
| equivalent and mean that loops will not be aligned. |
| .Sp |
| If \fIn\fR is not specified or is zero, use a machine-dependent default. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR. |
| .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 |
| \&\fB\-fno\-align\-jumps\fR and \fB\-falign\-jumps=1\fR are |
| equivalent and mean that loops will not be aligned. |
| .Sp |
| If \fIn\fR is not specified or is zero, use a machine-dependent default. |
| .Sp |
| Enabled at levels \fB\-O2\fR, \fB\-O3\fR. |
| .IP "\fB\-funit\-at\-a\-time\fR" 4 |
| .IX Item "-funit-at-a-time" |
| Parse the whole compilation unit before starting to produce code. |
| This allows some extra optimizations to take place but consumes |
| more memory (in general). There are some compatibility issues |
| with \fIunit-at-a-time\fR mode: |
| .RS 4 |
| .IP "*" 4 |
| enabling \fIunit-at-a-time\fR mode may change the order |
| in which functions, variables, and top-level \f(CW\*(C`asm\*(C'\fR statements |
| are emitted, and will likely break code relying on some particular |
| ordering. The majority of such top-level \f(CW\*(C`asm\*(C'\fR statements, |
| though, can be replaced by \f(CW\*(C`section\*(C'\fR attributes. The |
| \&\fBfno-toplevel-reorder\fR option may be used to keep the ordering |
| used in the input file, at the cost of some optimizations. |
| .IP "*" 4 |
| \&\fIunit-at-a-time\fR mode removes unreferenced static variables |
| and functions. This may result in undefined references |
| when an \f(CW\*(C`asm\*(C'\fR statement refers directly to variables or functions |
| that are otherwise unused. In that case either the variable/function |
| shall be listed as an operand of the \f(CW\*(C`asm\*(C'\fR statement operand or, |
| in the case of top-level \f(CW\*(C`asm\*(C'\fR statements the attribute \f(CW\*(C`used\*(C'\fR |
| shall be used on the declaration. |
| .IP "*" 4 |
| Static functions now can use non-standard passing conventions that |
| may break \f(CW\*(C`asm\*(C'\fR statements calling functions directly. Again, |
| attribute \f(CW\*(C`used\*(C'\fR will prevent this behavior. |
| .RE |
| .RS 4 |
| .Sp |
| As a temporary workaround, \fB\-fno\-unit\-at\-a\-time\fR can be used, |
| but this scheme may not be supported by future releases of \s-1GCC\s0. |
| .Sp |
| Enabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .RE |
| .IP "\fB\-fno\-toplevel\-reorder\fR" 4 |
| .IX Item "-fno-toplevel-reorder" |
| Do not reorder top-level functions, variables, and \f(CW\*(C`asm\*(C'\fR |
| statements. Output them in the same order that they appear in the |
| input file. When this option is used, unreferenced static variables |
| will not be removed. This option is intended to support existing code |
| which relies on a particular ordering. For new code, it is better to |
| use attributes. |
| .IP "\fB\-fweb\fR" 4 |
| .IX Item "-fweb" |
| Constructs webs as commonly used for register allocation purposes and assign |
| each web individual pseudo register. This allows the register allocation pass |
| to operate on pseudos directly, but also strengthens several other optimization |
| passes, such as \s-1CSE\s0, loop optimizer and trivial dead code remover. It can, |
| however, make debugging impossible, since variables will no longer stay in a |
| \&\*(L"home register\*(R". |
| .Sp |
| Enabled by default with \fB\-funroll\-loops\fR. |
| .IP "\fB\-fwhole\-program\fR" 4 |
| .IX Item "-fwhole-program" |
| Assume that the current compilation unit represents whole program being |
| compiled. All public functions and variables with the exception of \f(CW\*(C`main\*(C'\fR |
| and those merged by attribute \f(CW\*(C`externally_visible\*(C'\fR become static functions |
| and in a affect gets more aggressively optimized by interprocedural optimizers. |
| While this option is equivalent to proper use of \f(CW\*(C`static\*(C'\fR keyword for |
| programs consisting of single file, in combination with option |
| \&\fB\-\-combine\fR this flag can be used to compile most of smaller scale C |
| programs since the functions and variables become local for the whole combined |
| compilation unit, not for the single source file itself. |
| .IP "\fB\-fno\-cprop\-registers\fR" 4 |
| .IX Item "-fno-cprop-registers" |
| After register allocation and post-register allocation instruction splitting, |
| we perform a copy-propagation pass to try to reduce scheduling dependencies |
| and occasionally eliminate the copy. |
| .Sp |
| Disabled at levels \fB\-O\fR, \fB\-O2\fR, \fB\-O3\fR, \fB\-Os\fR. |
| .IP "\fB\-fprofile\-generate\fR" 4 |
| .IX Item "-fprofile-generate" |
| Enable options usually used for instrumenting application to produce |
| profile useful for later recompilation with profile feedback based |
| optimization. You must use \fB\-fprofile\-generate\fR both when |
| compiling and when linking your program. |
| .Sp |
| The following options are enabled: \f(CW\*(C`\-fprofile\-arcs\*(C'\fR, \f(CW\*(C`\-fprofile\-values\*(C'\fR, \f(CW\*(C`\-fvpt\*(C'\fR. |
| .IP "\fB\-fprofile\-use\fR" 4 |
| .IX Item "-fprofile-use" |
| Enable profile feedback directed optimizations, and optimizations |
| generally profitable only with profile feedback available. |
| .Sp |
| The following options are enabled: \f(CW\*(C`\-fbranch\-probabilities\*(C'\fR, \f(CW\*(C`\-fvpt\*(C'\fR, |
| \&\f(CW\*(C`\-funroll\-loops\*(C'\fR, \f(CW\*(C`\-fpeel\-loops\*(C'\fR, \f(CW\*(C`\-ftracer\*(C'\fR |
| .PP |
| The following options control compiler behavior regarding floating |
| point arithmetic. These options trade off between speed and |
| correctness. All must be specifically enabled. |
| .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\-ffast\-math\fR" 4 |
| .IX Item "-ffast-math" |
| Sets \fB\-fno\-math\-errno\fR, \fB\-funsafe\-math\-optimizations\fR, \fB\-fno\-trapping\-math\fR, \fB\-ffinite\-math\-only\fR, |
| \&\fB\-fno\-rounding\-math\fR, \fB\-fno\-signaling\-nans\fR |
| and \fBfcx-limited-range\fR. |
| .Sp |
| This option causes the preprocessor macro \f(CW\*(C`_\|_FAST_MATH_\|_\*(C'\fR to be defined. |
| .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 |
| 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. |
| .Sp |
| The default is \fB\-fmath\-errno\fR. |
| .Sp |
| On Darwin systems, the math library never sets \f(CW\*(C`errno\*(C'\fR. There is therefore |
| no reason for the compiler to consider the possibility that it might, |
| and \fB\-fno\-math\-errno\fR is the default. |
| .IP "\fB\-funsafe\-math\-optimizations\fR" 4 |
| .IX Item "-funsafe-math-optimizations" |
| Allow optimizations for floating-point arithmetic that (a) assume |
| that arguments and results are valid and (b) may violate \s-1IEEE\s0 or |
| \&\s-1ANSI\s0 standards. When used at link\-time, it may include libraries |
| or startup files that change the default \s-1FPU\s0 control word or other |
| similar optimizations. |
| .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. |
| .Sp |
| The default is \fB\-fno\-unsafe\-math\-optimizations\fR. |
| .IP "\fB\-ffinite\-math\-only\fR" 4 |
| .IX Item "-ffinite-math-only" |
| Allow optimizations for floating-point arithmetic that assume |
| that arguments and results are not NaNs or +\-Infs. |
| .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. |
| .Sp |
| The default is \fB\-fno\-finite\-math\-only\fR. |
| .IP "\fB\-fno\-trapping\-math\fR" 4 |
| .IX Item "-fno-trapping-math" |
| Compile code assuming that floating-point operations cannot generate |
| user-visible traps. These traps include division by zero, overflow, |
| underflow, inexact result and invalid operation. This option implies |
| \&\fB\-fno\-signaling\-nans\fR. Setting this option may allow faster |
| code if one relies on \*(L"non\-stop\*(R" \s-1IEEE\s0 arithmetic, for example. |
| .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. |
| .Sp |
| The default is \fB\-ftrapping\-math\fR. |
| .IP "\fB\-frounding\-math\fR" 4 |
| .IX Item "-frounding-math" |
| Disable transformations and optimizations that assume default floating |
| point rounding behavior. This is round-to-zero for all floating point |
| to integer conversions, and round-to-nearest for all other arithmetic |
| truncations. This option should be specified for programs that change |
| the \s-1FP\s0 rounding mode dynamically, or that may be executed with a |
| non-default rounding mode. This option disables constant folding of |
| floating point expressions at compile-time (which may be affected by |
| rounding mode) and arithmetic transformations that are unsafe in the |
| presence of sign-dependent rounding modes. |
| .Sp |
| The default is \fB\-fno\-rounding\-math\fR. |
| .Sp |
| This option is experimental and does not currently guarantee to |
| disable all \s-1GCC\s0 optimizations that are affected by rounding mode. |
| Future versions of \s-1GCC\s0 may provide finer control of this setting |
| using C99's \f(CW\*(C`FENV_ACCESS\*(C'\fR pragma. This command line option |
| will be used to specify the default state for \f(CW\*(C`FENV_ACCESS\*(C'\fR. |
| .IP "\fB\-frtl\-abstract\-sequences\fR" 4 |
| .IX Item "-frtl-abstract-sequences" |
| It is a size optimization method. This option is to find identical |
| sequences of code, which can be turned into pseudo-procedures and |
| then replace all occurrences with calls to the newly created |
| subroutine. It is kind of an opposite of \fB\-finline\-functions\fR. |
| This optimization runs at \s-1RTL\s0 level. |
| .IP "\fB\-fsignaling\-nans\fR" 4 |
| .IX Item "-fsignaling-nans" |
| Compile code assuming that \s-1IEEE\s0 signaling NaNs may generate user-visible |
| traps during floating-point operations. Setting this option disables |
| optimizations that may change the number of exceptions visible with |
| signaling NaNs. This option implies \fB\-ftrapping\-math\fR. |
| .Sp |
| This option causes the preprocessor macro \f(CW\*(C`_\|_SUPPORT_SNAN_\|_\*(C'\fR to |
| be defined. |
| .Sp |
| The default is \fB\-fno\-signaling\-nans\fR. |
| .Sp |
| This option is experimental and does not currently guarantee to |
| disable all \s-1GCC\s0 optimizations that affect signaling NaN behavior. |
| .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\-fcx\-limited\-range\fR" 4 |
| .IX Item "-fcx-limited-range" |
| .PD 0 |
| .IP "\fB\-fno\-cx\-limited\-range\fR" 4 |
| .IX Item "-fno-cx-limited-range" |
| .PD |
| When enabled, this option states that a range reduction step is not |
| needed when performing complex division. The default is |
| \&\fB\-fno\-cx\-limited\-range\fR, but is enabled by \fB\-ffast\-math\fR. |
| .Sp |
| This option controls the default setting of the \s-1ISO\s0 C99 |
| \&\f(CW\*(C`CX_LIMITED_RANGE\*(C'\fR pragma. Nevertheless, the option applies to |
| all languages. |
| .PP |
| The following options control optimizations that may improve |
| performance, but are not enabled by any \fB\-O\fR options. This |
| section includes experimental options that may produce broken code. |
| .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 |
| the number of times each branch was taken. When the program |
| compiled with \fB\-fprofile\-arcs\fR exits it saves arc execution |
| counts to a file called \fI\fIsourcename\fI.gcda\fR for each source |
| file The information in this data file is very dependent on the |
| structure of the generated code, so you must use the same source code |
| and the same optimization options for both compilations. |
| .Sp |
| With \fB\-fbranch\-probabilities\fR, \s-1GCC\s0 puts a |
| \&\fB\s-1REG_BR_PROB\s0\fR note on each \fB\s-1JUMP_INSN\s0\fR and \fB\s-1CALL_INSN\s0\fR. |
| These can be used to improve optimization. Currently, they are only |
| used in one place: in \fIreorg.c\fR, instead of guessing which path a |
| branch is mostly to take, the \fB\s-1REG_BR_PROB\s0\fR values are used to |
| exactly determine which path is taken more often. |
| .IP "\fB\-fprofile\-values\fR" 4 |
| .IX Item "-fprofile-values" |
| If combined with \fB\-fprofile\-arcs\fR, it adds code so that some |
| data about values of expressions in the program is gathered. |
| .Sp |
| With \fB\-fbranch\-probabilities\fR, it reads back the data gathered |
| from profiling values of expressions and adds \fB\s-1REG_VALUE_PROFILE\s0\fR |
| notes to instructions for their later usage in optimizations. |
| .Sp |
| Enabled with \fB\-fprofile\-generate\fR and \fB\-fprofile\-use\fR. |
| .IP "\fB\-fvpt\fR" 4 |
| .IX Item "-fvpt" |
| If combined with \fB\-fprofile\-arcs\fR, it instructs the compiler to add |
| a code to gather information about values of expressions. |
| .Sp |
| With \fB\-fbranch\-probabilities\fR, it reads back the data gathered |
| and actually performs the optimizations based on them. |
| Currently the optimizations include specialization of division operation |
| using the knowledge about the value of the denominator. |
| .IP "\fB\-frename\-registers\fR" 4 |
| .IX Item "-frename-registers" |
| Attempt to avoid false dependencies in scheduled code by making use |
| of registers left over after register allocation. This optimization |
| will most benefit processors with lots of registers. Depending on the |
| debug information format adopted by the target, however, it can |
| make debugging impossible, since variables will no longer stay in |
| a \*(L"home register\*(R". |
| .Sp |
| Enabled by default with \fB\-funroll\-loops\fR. |
| .IP "\fB\-ftracer\fR" 4 |
| .IX Item "-ftracer" |
| Perform tail duplication to enlarge superblock size. This transformation |
| simplifies the control flow of the function allowing other optimizations to do |
| better job. |
| .Sp |
| Enabled with \fB\-fprofile\-use\fR. |
| .IP "\fB\-funroll\-loops\fR" 4 |
| .IX Item "-funroll-loops" |
| Unroll loops whose number of iterations can be determined at compile time or |
| upon entry to the loop. \fB\-funroll\-loops\fR implies |
| \&\fB\-frerun\-cse\-after\-loop\fR, \fB\-fweb\fR and \fB\-frename\-registers\fR. |
| It also turns on complete loop peeling (i.e. complete removal of loops with |
| small constant number of iterations). This option makes code larger, and may |
| or may not make it run faster. |
| .Sp |
| Enabled with \fB\-fprofile\-use\fR. |
| .IP "\fB\-funroll\-all\-loops\fR" 4 |
| .IX Item "-funroll-all-loops" |
| Unroll all loops, even if their number of iterations is uncertain when |
| the loop is entered. This usually makes programs run more slowly. |
| \&\fB\-funroll\-all\-loops\fR implies the same options as |
| \&\fB\-funroll\-loops\fR. |
| .IP "\fB\-fpeel\-loops\fR" 4 |
| .IX Item "-fpeel-loops" |
| Peels the loops for that there is enough information that they do not |
| roll much (from profile feedback). It also turns on complete loop peeling |
| (i.e. complete removal of loops with small constant number of iterations). |
| .Sp |
| Enabled with \fB\-fprofile\-use\fR. |
| .IP "\fB\-fmove\-loop\-invariants\fR" 4 |
| .IX Item "-fmove-loop-invariants" |
| Enables the loop invariant motion pass in the \s-1RTL\s0 loop optimizer. Enabled |
| at level \fB\-O1\fR |
| .IP "\fB\-funswitch\-loops\fR" 4 |
| .IX Item "-funswitch-loops" |
| Move branches with loop invariant conditions out of the loop, with duplicates |
| of the loop on both branches (modified according to result of the condition). |
| .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. Most systems |
| using the \s-1ELF\s0 object format and \s-1SPARC\s0 processors running Solaris 2 have |
| linkers with such optimizations. \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\-fbranch\-target\-load\-optimize\fR" 4 |
| .IX Item "-fbranch-target-load-optimize" |
| Perform branch target register load optimization before prologue / epilogue |
| threading. |
| The use of target registers can typically be exposed only during reload, |
| thus hoisting loads out of loops and doing inter-block scheduling needs |
| a separate optimization pass. |
| .IP "\fB\-fbranch\-target\-load\-optimize2\fR" 4 |
| .IX Item "-fbranch-target-load-optimize2" |
| Perform branch target register load optimization after prologue / epilogue |
| threading. |
| .IP "\fB\-fbtr\-bb\-exclusive\fR" 4 |
| .IX Item "-fbtr-bb-exclusive" |
| When performing branch target register load optimization, don't reuse |
| branch target registers in within any basic block. |
| .IP "\fB\-fstack\-protector\fR" 4 |
| .IX Item "-fstack-protector" |
| Emit extra code to check for buffer overflows, such as stack smashing |
| attacks. This is done by adding a guard variable to functions with |
| vulnerable objects. This includes functions that call alloca, and |
| functions with buffers larger than 8 bytes. The guards are initialized |
| when a function is entered and then checked when the function exits. |
| If a guard check fails, an error message is printed and the program exits. |
| .IP "\fB\-fstack\-protector\-all\fR" 4 |
| .IX Item "-fstack-protector-all" |
| Like \fB\-fstack\-protector\fR except that all functions are protected. |
| .IP "\fB\-fsection\-anchors\fR" 4 |
| .IX Item "-fsection-anchors" |
| Try to reduce the number of symbolic address calculations by using |
| shared \*(L"anchor\*(R" symbols to address nearby objects. This transformation |
| can help to reduce the number of \s-1GOT\s0 entries and \s-1GOT\s0 accesses on some |
| targets. |
| .Sp |
| For example, the implementation of the following function \f(CW\*(C`foo\*(C'\fR: |
| .Sp |
| .Vb 2 |
| \& static int a, b, c; |
| \& int foo (void) { return a + b + c; } |
| .Ve |
| .Sp |
| would usually calculate the addresses of all three variables, but if you |
| compile it with \fB\-fsection\-anchors\fR, it will access the variables |
| from a common anchor point instead. The effect is similar to the |
| following pseudocode (which isn't valid C): |
| .Sp |
| .Vb 5 |
| \& int foo (void) |
| \& { |
| \& register int *xr = &x; |
| \& return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; |
| \& } |
| .Ve |
| .Sp |
| Not all targets support this option. |
| .IP "\fB\-\-param\fR \fIname\fR\fB=\fR\fIvalue\fR" 4 |
| .IX Item "--param name=value" |
| In some places, \s-1GCC\s0 uses various constants to control the amount of |
| optimization that is done. For example, \s-1GCC\s0 will not inline functions |
| that contain more that a certain number of instructions. You can |
| control some of these constants on the command-line using the |
| \&\fB\-\-param\fR option. |
| .Sp |
| The names of specific parameters, and the meaning of the values, are |
| tied to the internals of the compiler, and are subject to change |
| without notice in future releases. |
| .Sp |
| In each case, the \fIvalue\fR is an integer. The allowable choices for |
| \&\fIname\fR are given in the following table: |
| .RS 4 |
| .IP "\fBsalias-max-implicit-fields\fR" 4 |
| .IX Item "salias-max-implicit-fields" |
| The maximum number of fields in a variable without direct |
| structure accesses for which structure aliasing will consider trying |
| to track each field. The default is 5 |
| .IP "\fBsalias-max-array-elements\fR" 4 |
| .IX Item "salias-max-array-elements" |
| The maximum number of elements an array can have and its elements |
| still be tracked individually by structure aliasing. The default is 4 |
| .IP "\fBsra-max-structure-size\fR" 4 |
| .IX Item "sra-max-structure-size" |
| The maximum structure size, in bytes, at which the scalar replacement |
| of aggregates (\s-1SRA\s0) optimization will perform block copies. The |
| default value, 0, implies that \s-1GCC\s0 will select the most appropriate |
| size itself. |
| .IP "\fBsra-field-structure-ratio\fR" 4 |
| .IX Item "sra-field-structure-ratio" |
| The threshold ratio (as a percentage) between instantiated fields and |
| the complete structure size. We say that if the ratio of the number |
| of bytes in instantiated fields to the number of bytes in the complete |
| structure exceeds this parameter, then block copies are not used. The |
| default is 75. |
| .IP "\fBmax-crossjump-edges\fR" 4 |
| .IX Item "max-crossjump-edges" |
| The maximum number of incoming edges to consider for crossjumping. |
| The algorithm used by \fB\-fcrossjumping\fR is O(N^2) in |
| the number of edges incoming to each block. Increasing values mean |
| more aggressive optimization, making the compile time increase with |
| probably small improvement in executable size. |
| .IP "\fBmin-crossjump-insns\fR" 4 |
| .IX Item "min-crossjump-insns" |
| The minimum number of instructions which must be matched at the end |
| of two blocks before crossjumping will be performed on them. This |
| value is ignored in the case where all instructions in the block being |
| crossjumped from are matched. The default value is 5. |
| .IP "\fBmax-grow-copy-bb-insns\fR" 4 |
| .IX Item "max-grow-copy-bb-insns" |
| The maximum code size expansion factor when copying basic blocks |
| instead of jumping. The expansion is relative to a jump instruction. |
| The default value is 8. |
| .IP "\fBmax-goto-duplication-insns\fR" 4 |
| .IX Item "max-goto-duplication-insns" |
| The maximum number of instructions to duplicate to a block that jumps |
| to a computed goto. To avoid O(N^2) behavior in a number of |
| passes, \s-1GCC\s0 factors computed gotos early in the compilation process, |
| and unfactors them as late as possible. Only computed jumps at the |
| end of a basic blocks with no more than max-goto-duplication-insns are |
| unfactored. The default value is 8. |
| .IP "\fBmax-delay-slot-insn-search\fR" 4 |
| .IX Item "max-delay-slot-insn-search" |
| The maximum number of instructions to consider when looking for an |
| instruction to fill a delay slot. If more than this arbitrary number of |
| instructions is searched, the time savings from filling the delay slot |
| will be minimal so stop searching. Increasing values mean more |
| aggressive optimization, making the compile time increase with probably |
| small improvement in executable run time. |
| .IP "\fBmax-delay-slot-live-search\fR" 4 |
| .IX Item "max-delay-slot-live-search" |
| When trying to fill delay slots, the maximum number of instructions to |
| consider when searching for a block with valid live register |
| information. Increasing this arbitrarily chosen value means more |
| aggressive optimization, increasing the compile time. This parameter |
| should be removed when the delay slot code is rewritten to maintain the |
| control-flow graph. |
| .IP "\fBmax-gcse-memory\fR" 4 |
| .IX Item "max-gcse-memory" |
| The approximate maximum amount of memory that will be allocated in |
| order to perform the global common subexpression elimination |
| optimization. If more memory than specified is required, the |
| optimization will not be done. |
| .IP "\fBmax-gcse-passes\fR" 4 |
| .IX Item "max-gcse-passes" |
| The maximum number of passes of \s-1GCSE\s0 to run. The default is 1. |
| .IP "\fBmax-pending-list-length\fR" 4 |
| .IX Item "max-pending-list-length" |
| The maximum number of pending dependencies scheduling will allow |
| before flushing the current state and starting over. Large functions |
| with few branches or calls can create excessively large lists which |
| needlessly consume memory and resources. |
| .IP "\fBmax-inline-insns-single\fR" 4 |
| .IX Item "max-inline-insns-single" |
| Several parameters control the tree inliner used in gcc. |
| This number sets the maximum number of instructions (counted in \s-1GCC\s0's |
| internal representation) in a single function that the tree inliner |
| will consider for inlining. This only affects functions declared |
| inline and methods implemented in a class declaration (\*(C+). |
| The default value is 450. |
| .IP "\fBmax-inline-insns-auto\fR" 4 |
| .IX Item "max-inline-insns-auto" |
| When you use \fB\-finline\-functions\fR (included in \fB\-O3\fR), |
| a lot of functions that would otherwise not be considered for inlining |
| by the compiler will be investigated. To those functions, a different |
| (more restrictive) limit compared to functions declared inline can |
| be applied. |
| The default value is 90. |
| .IP "\fBlarge-function-insns\fR" 4 |
| .IX Item "large-function-insns" |
| The limit specifying really large functions. For functions larger than this |
| limit after inlining inlining is constrained by |
| \&\fB\-\-param large-function-growth\fR. This parameter is useful primarily |
| to avoid extreme compilation time caused by non-linear algorithms used by the |
| backend. |
| This parameter is ignored when \fB\-funit\-at\-a\-time\fR is not used. |
| The default value is 2700. |
| .IP "\fBlarge-function-growth\fR" 4 |
| .IX Item "large-function-growth" |
| Specifies maximal growth of large function caused by inlining in percents. |
| This parameter is ignored when \fB\-funit\-at\-a\-time\fR is not used. |
| The default value is 100 which limits large function growth to 2.0 times |
| the original size. |
| .IP "\fBlarge-unit-insns\fR" 4 |
| .IX Item "large-unit-insns" |
| The limit specifying large translation unit. Growth caused by inlining of |
| units larger than this limit is limited by \fB\-\-param inline-unit-growth\fR. |
| For small units this might be too tight (consider unit consisting of function A |
| that is inline and B that just calls A three time. If B is small relative to |
| A, the growth of unit is 300\e% and yet such inlining is very sane. For very |
| large units consisting of small inlininable functions however the overall unit |
| growth limit is needed to avoid exponential explosion of code size. Thus for |
| smaller units, the size is increased to \fB\-\-param large-unit-insns\fR |
| before applying \fB\-\-param inline-unit-growth\fR. The default is 10000 |
| .IP "\fBinline-unit-growth\fR" 4 |
| .IX Item "inline-unit-growth" |
| Specifies maximal overall growth of the compilation unit caused by inlining. |
| This parameter is ignored when \fB\-funit\-at\-a\-time\fR is not used. |
| The default value is 50 which limits unit growth to 1.5 times the original |
| size. |
| .IP "\fBmax-inline-insns-recursive\fR" 4 |
| .IX Item "max-inline-insns-recursive" |
| .PD 0 |
| .IP "\fBmax-inline-insns-recursive-auto\fR" 4 |
| .IX Item "max-inline-insns-recursive-auto" |
| .PD |
| Specifies maximum number of instructions out-of-line copy of self recursive inline |
| function can grow into by performing recursive inlining. |
| .Sp |
| For functions declared inline \fB\-\-param max-inline-insns-recursive\fR is |
| taken into account. For function not declared inline, recursive inlining |
| happens only when \fB\-finline\-functions\fR (included in \fB\-O3\fR) is |
| enabled and \fB\-\-param max-inline-insns-recursive-auto\fR is used. The |
| default value is 450. |
| .IP "\fBmax-inline-recursive-depth\fR" 4 |
| .IX Item "max-inline-recursive-depth" |
| .PD 0 |
| .IP "\fBmax-inline-recursive-depth-auto\fR" 4 |
| .IX Item "max-inline-recursive-depth-auto" |
| .PD |
| Specifies maximum recursion depth used by the recursive inlining. |
| .Sp |
| For functions declared inline \fB\-\-param max-inline-recursive-depth\fR is |
| taken into account. For function not declared inline, recursive inlining |
| happens only when \fB\-finline\-functions\fR (included in \fB\-O3\fR) is |
| enabled and \fB\-\-param max-inline-recursive-depth-auto\fR is used. The |
| default value is 450. |
| .IP "\fBmin-inline-recursive-probability\fR" 4 |
| .IX Item "min-inline-recursive-probability" |
| Recursive inlining is profitable only for function having deep recursion |
| in average and can hurt for function having little recursion depth by |
| increasing the prologue size or complexity of function body to other |
| optimizers. |
| .Sp |
| When profile feedback is available (see \fB\-fprofile\-generate\fR) the actual |
| recursion depth can be guessed from probability that function will recurse via |
| given call expression. This parameter limits inlining only to call expression |
| whose probability exceeds given threshold (in percents). The default value is |
| 10. |
| .IP "\fBinline-call-cost\fR" 4 |
| .IX Item "inline-call-cost" |
| Specify cost of call instruction relative to simple arithmetics operations |
| (having cost of 1). Increasing this cost disqualifies inlining of non-leaf |
| functions and at the same time increases size of leaf function that is believed to |
| reduce function size by being inlined. In effect it increases amount of |
| inlining for code having large abstraction penalty (many functions that just |
| pass the arguments to other functions) and decrease inlining for code with low |
| abstraction penalty. The default value is 16. |
| .IP "\fBmax-unrolled-insns\fR" 4 |
| .IX Item "max-unrolled-insns" |
| The maximum number of instructions that a loop should have if that loop |
| is unrolled, and if the loop is unrolled, it determines how many times |
| the loop code is unrolled. |
| .IP "\fBmax-average-unrolled-insns\fR" 4 |
| .IX Item "max-average-unrolled-insns" |
| The maximum number of instructions biased by probabilities of their execution |
| that a loop should have if that loop is unrolled, and if the loop is unrolled, |
| it determines how many times the loop code is unrolled. |
| .IP "\fBmax-unroll-times\fR" 4 |
| .IX Item "max-unroll-times" |
| The maximum number of unrollings of a single loop. |
| .IP "\fBmax-peeled-insns\fR" 4 |
| .IX Item "max-peeled-insns" |
| The maximum number of instructions that a loop should have if that loop |
| is peeled, and if the loop is peeled, it determines how many times |
| the loop code is peeled. |
| .IP "\fBmax-peel-times\fR" 4 |
| .IX Item "max-peel-times" |
| The maximum number of peelings of a single loop. |
| .IP "\fBmax-completely-peeled-insns\fR" 4 |
| .IX Item "max-completely-peeled-insns" |
| The maximum number of insns of a completely peeled loop. |
| .IP "\fBmax-completely-peel-times\fR" 4 |
| .IX Item "max-completely-peel-times" |
| The maximum number of iterations of a loop to be suitable for complete peeling. |
| .IP "\fBmax-unswitch-insns\fR" 4 |
| .IX Item "max-unswitch-insns" |
| The maximum number of insns of an unswitched loop. |
| .IP "\fBmax-unswitch-level\fR" 4 |
| .IX Item "max-unswitch-level" |
| The maximum number of branches unswitched in a single loop. |
| .IP "\fBlim-expensive\fR" 4 |
| .IX Item "lim-expensive" |
| The minimum cost of an expensive expression in the loop invariant motion. |
| .IP "\fBiv-consider-all-candidates-bound\fR" 4 |
| .IX Item "iv-consider-all-candidates-bound" |
| Bound on number of candidates for induction variables below that |
| all candidates are considered for each use in induction variable |
| optimizations. Only the most relevant candidates are considered |
| if there are more candidates, to avoid quadratic time complexity. |
| .IP "\fBiv-max-considered-uses\fR" 4 |
| .IX Item "iv-max-considered-uses" |
| The induction variable optimizations give up on loops that contain more |
| induction variable uses. |
| .IP "\fBiv-always-prune-cand-set-bound\fR" 4 |
| .IX Item "iv-always-prune-cand-set-bound" |
| If number of candidates in the set is smaller than this value, |
| we always try to remove unnecessary ivs from the set during its |
| optimization when a new iv is added to the set. |
| .IP "\fBscev-max-expr-size\fR" 4 |
| .IX Item "scev-max-expr-size" |
| Bound on size of expressions used in the scalar evolutions analyzer. |
| Large expressions slow the analyzer. |
| .IP "\fBvect-max-version-checks\fR" 4 |
| .IX Item "vect-max-version-checks" |
| The maximum number of runtime checks that can be performed when doing |
| loop versioning in the vectorizer. See option ftree-vect-loop-version |
| for more information. |
| .IP "\fBmax-iterations-to-track\fR" 4 |
| .IX Item "max-iterations-to-track" |
| The maximum number of iterations of a loop the brute force algorithm |
| for analysis of # of iterations of the loop tries to evaluate. |
| .IP "\fBhot-bb-count-fraction\fR" 4 |
| .IX Item "hot-bb-count-fraction" |
| Select fraction of the maximal count of repetitions of basic block in program |
| given basic block needs to have to be considered hot. |
| .IP "\fBhot-bb-frequency-fraction\fR" 4 |
| .IX Item "hot-bb-frequency-fraction" |
| Select fraction of the maximal frequency of executions of basic block in |
| function given basic block needs to have to be considered hot |
| .IP "\fBmax-predicted-iterations\fR" 4 |
| .IX Item "max-predicted-iterations" |
| The maximum number of loop iterations we predict statically. This is useful |
| in cases where function contain single loop with known bound and other loop |
| with unknown. We predict the known number of iterations correctly, while |
| the unknown number of iterations average to roughly 10. This means that the |
| loop without bounds would appear artificially cold relative to the other one. |
| .IP "\fBtracer-dynamic-coverage\fR" 4 |
| .IX Item "tracer-dynamic-coverage" |
| .PD 0 |
| .IP "\fBtracer-dynamic-coverage-feedback\fR" 4 |
| .IX Item "tracer-dynamic-coverage-feedback" |
| .PD |
| This value is used to limit superblock formation once the given percentage of |
| executed instructions is covered. This limits unnecessary code size |
| expansion. |
| .Sp |
| The \fBtracer-dynamic-coverage-feedback\fR is used only when profile |
| feedback is available. The real profiles (as opposed to statically estimated |
| ones) are much less balanced allowing the threshold to be larger value. |
| .IP "\fBtracer-max-code-growth\fR" 4 |
| .IX Item "tracer-max-code-growth" |
| Stop tail duplication once code growth has reached given percentage. This is |
| rather hokey argument, as most of the duplicates will be eliminated later in |
| cross jumping, so it may be set to much higher values than is the desired code |
| growth. |
| .IP "\fBtracer-min-branch-ratio\fR" 4 |
| .IX Item "tracer-min-branch-ratio" |
| Stop reverse growth when the reverse probability of best edge is less than this |
| threshold (in percent). |
| .IP "\fBtracer-min-branch-ratio\fR" 4 |
| .IX Item "tracer-min-branch-ratio" |
| .PD 0 |
| .IP "\fBtracer-min-branch-ratio-feedback\fR" 4 |
| .IX Item "tracer-min-branch-ratio-feedback" |
| .PD |
| Stop forward growth if the best edge do have probability lower than this |
| threshold. |
| .Sp |
| Similarly to \fBtracer-dynamic-coverage\fR two values are present, one for |
| compilation for profile feedback and one for compilation without. The value |
| for compilation with profile feedback needs to be more conservative (higher) in |
| order to make tracer effective. |
| .IP "\fBmax-cse-path-length\fR" 4 |
| .IX Item "max-cse-path-length" |
| Maximum number of basic blocks on path that cse considers. The default is 10. |
| .IP "\fBmax-cse-insns\fR" 4 |
| .IX Item "max-cse-insns" |
| The maximum instructions \s-1CSE\s0 process before flushing. The default is 1000. |
| .IP "\fBglobal-var-threshold\fR" 4 |
| .IX Item "global-var-threshold" |
| Counts the number of function calls (\fIn\fR) and the number of |
| call-clobbered variables (\fIv\fR). If \fIn\fRx\fIv\fR is larger than this limit, a |
| single artificial variable will be created to represent all the |
| call-clobbered variables at function call sites. This artificial |
| variable will then be made to alias every call-clobbered variable. |
| (done as \f(CW\*(C`int * size_t\*(C'\fR on the host machine; beware overflow). |
| .IP "\fBmax-aliased-vops\fR" 4 |
| .IX Item "max-aliased-vops" |
| Maximum number of virtual operands allowed to represent aliases |
| before triggering the alias grouping heuristic. Alias grouping |
| reduces compile times and memory consumption needed for aliasing at |
| the expense of precision loss in alias information. |
| .IP "\fBggc-min-expand\fR" 4 |
| .IX Item "ggc-min-expand" |
| \&\s-1GCC\s0 uses a garbage collector to manage its own memory allocation. This |
| parameter specifies the minimum percentage by which the garbage |
| collector's heap should be allowed to expand between collections. |
| Tuning this may improve compilation speed; it has no effect on code |
| generation. |
| .Sp |
| The default is 30% + 70% * (\s-1RAM/1GB\s0) with an upper bound of 100% when |
| \&\s-1RAM\s0 >= 1GB. If \f(CW\*(C`getrlimit\*(C'\fR is available, the notion of \*(L"\s-1RAM\s0\*(R" is |
| the smallest of actual \s-1RAM\s0 and \f(CW\*(C`RLIMIT_DATA\*(C'\fR or \f(CW\*(C`RLIMIT_AS\*(C'\fR. If |
| \&\s-1GCC\s0 is not able to calculate \s-1RAM\s0 on a particular platform, the lower |
| bound of 30% is used. Setting this parameter and |
| \&\fBggc-min-heapsize\fR to zero causes a full collection to occur at |
| every opportunity. This is extremely slow, but can be useful for |
| debugging. |
| .IP "\fBggc-min-heapsize\fR" 4 |
| .IX Item "ggc-min-heapsize" |
| Minimum size of the garbage collector's heap before it begins bothering |
| to collect garbage. The first collection occurs after the heap expands |
| by \fBggc-min-expand\fR% beyond \fBggc-min-heapsize\fR. Again, |
| tuning this may improve compilation speed, and has no effect on code |
| generation. |
| .Sp |
| The default is the smaller of \s-1RAM/8\s0, \s-1RLIMIT_RSS\s0, or a limit which |
| tries to ensure that \s-1RLIMIT_DATA\s0 or \s-1RLIMIT_AS\s0 are not exceeded, but |
| with a lower bound of 4096 (four megabytes) and an upper bound of |
| 131072 (128 megabytes). If \s-1GCC\s0 is not able to calculate \s-1RAM\s0 on a |
| particular platform, the lower bound is used. Setting this parameter |
| very large effectively disables garbage collection. Setting this |
| parameter and \fBggc-min-expand\fR to zero causes a full collection |
| to occur at every opportunity. |
| .IP "\fBmax-reload-search-insns\fR" 4 |
| .IX Item "max-reload-search-insns" |
| The maximum number of instruction reload should look backward for equivalent |
| register. Increasing values mean more aggressive optimization, making the |
| compile time increase with probably slightly better performance. The default |
| value is 100. |
| .IP "\fBmax-cselib-memory-locations\fR" 4 |
| .IX Item "max-cselib-memory-locations" |
| The maximum number of memory locations cselib should take into account. |
| Increasing values mean more aggressive optimization, making the compile time |
| increase with probably slightly better performance. The default value is 500. |
| .IP "\fBmax-flow-memory-locations\fR" 4 |
| .IX Item "max-flow-memory-locations" |
| Similar as \fBmax-cselib-memory-locations\fR but for dataflow liveness. |
| The default value is 100. |
| .IP "\fBreorder-blocks-duplicate\fR" 4 |
| .IX Item "reorder-blocks-duplicate" |
| .PD 0 |
| .IP "\fBreorder-blocks-duplicate-feedback\fR" 4 |
| .IX Item "reorder-blocks-duplicate-feedback" |
| .PD |
| Used by basic block reordering pass to decide whether to use unconditional |
| branch or duplicate the code on its destination. Code is duplicated when its |
| estimated size is smaller than this value multiplied by the estimated size of |
| unconditional jump in the hot spots of the program. |
| .Sp |
| The \fBreorder-block-duplicate-feedback\fR is used only when profile |
| feedback is available and may be set to higher values than |
| \&\fBreorder-block-duplicate\fR since information about the hot spots is more |
| accurate. |
| .IP "\fBmax-sched-ready-insns\fR" 4 |
| .IX Item "max-sched-ready-insns" |
| The maximum number of instructions ready to be issued the scheduler should |
| consider at any given time during the first scheduling pass. Increasing |
| values mean more thorough searches, making the compilation time increase |
| with probably little benefit. The default value is 100. |
| .IP "\fBmax-sched-region-blocks\fR" 4 |
| .IX Item "max-sched-region-blocks" |
| The maximum number of blocks in a region to be considered for |
| interblock scheduling. The default value is 10. |
| .IP "\fBmax-sched-region-insns\fR" 4 |
| .IX Item "max-sched-region-insns" |
| The maximum number of insns in a region to be considered for |
| interblock scheduling. The default value is 100. |
| .IP "\fBmin-spec-prob\fR" 4 |
| .IX Item "min-spec-prob" |
| The minimum probability (in percents) of reaching a source block |
| for interblock speculative scheduling. The default value is 40. |
| .IP "\fBmax-sched-extend-regions-iters\fR" 4 |
| .IX Item "max-sched-extend-regions-iters" |
| The maximum number of iterations through \s-1CFG\s0 to extend regions. |
| 0 \- disable region extension, |
| N \- do at most N iterations. |
| The default value is 0. |
| .IP "\fBmax-sched-insn-conflict-delay\fR" 4 |
| .IX Item "max-sched-insn-conflict-delay" |
| The maximum conflict delay for an insn to be considered for speculative motion. |
| The default value is 3. |
| .IP "\fBsched-spec-prob-cutoff\fR" 4 |
| .IX Item "sched-spec-prob-cutoff" |
| The minimal probability of speculation success (in percents), so that |
| speculative insn will be scheduled. |
| The default value is 40. |
| .IP "\fBmax-last-value-rtl\fR" 4 |
| .IX Item "max-last-value-rtl" |
| The maximum size measured as number of RTLs that can be recorded in an expression |
| in combiner for a pseudo register as last known value of that register. The default |
| is 10000. |
| .IP "\fBinteger-share-limit\fR" 4 |
| .IX Item "integer-share-limit" |
| Small integer constants can use a shared data structure, reducing the |
| compiler's memory usage and increasing its speed. This sets the maximum |
| value of a shared integer constant's. The default value is 256. |
| .IP "\fBmin-virtual-mappings\fR" 4 |
| .IX Item "min-virtual-mappings" |
| Specifies the minimum number of virtual mappings in the incremental |
| \&\s-1SSA\s0 updater that should be registered to trigger the virtual mappings |
| heuristic defined by virtual\-mappings\-ratio. The default value is |
| 100. |
| .IP "\fBvirtual-mappings-ratio\fR" 4 |
| .IX Item "virtual-mappings-ratio" |
| If the number of virtual mappings is virtual-mappings-ratio bigger |
| than the number of virtual symbols to be updated, then the incremental |
| \&\s-1SSA\s0 updater switches to a full update for those symbols. The default |
| ratio is 3. |
| .IP "\fBssp-buffer-size\fR" 4 |
| .IX Item "ssp-buffer-size" |
| The minimum size of buffers (i.e. arrays) that will receive stack smashing |
| protection when \fB\-fstack\-protection\fR is used. |
| .IP "\fBmax-jump-thread-duplication-stmts\fR" 4 |
| .IX Item "max-jump-thread-duplication-stmts" |
| Maximum number of statements allowed in a block that needs to be |
| duplicated when threading jumps. |
| .IP "\fBmax-fields-for-field-sensitive\fR" 4 |
| .IX Item "max-fields-for-field-sensitive" |
| Maximum number of fields in a structure we will treat in |
| a field sensitive manner during pointer analysis. |
| .RE |
| .RS 4 |
| .RE |
| .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. |
| .Sp |
| .RS 4 |
| You can use \fB\-Wp,\fR\fIoption\fR to bypass the compiler driver |
| and pass \fIoption\fR directly through to the preprocessor. If |
| \&\fIoption\fR contains commas, it is split into multiple options at the |
| commas. However, many options are modified, translated or interpreted |
| by the compiler driver before being passed to the preprocessor, and |
| \&\fB\-Wp\fR forcibly bypasses this phase. The preprocessor's direct |
| interface is undocumented and subject to change, so whenever possible |
| you should avoid using \fB\-Wp\fR and let the driver handle the |
| options instead. |
| .RE |
| .IP "\fB\-Xpreprocessor\fR \fIoption\fR" 4 |
| .IX Item "-Xpreprocessor option" |
| Pass \fIoption\fR as an option to the preprocessor. You can use this to |
| supply system-specific preprocessor 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\-Xpreprocessor\fR twice, once for the option and once for the argument. |
| .IP "\fB\-D\fR \fIname\fR" 4 |
| .IX Item "-D name" |
| Predefine \fIname\fR as a macro, with definition \f(CW1\fR. |
| .IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4 |
| .IX Item "-D name=definition" |
| The contents of \fIdefinition\fR are tokenized and processed as if |
| they appeared during translation phase three in a \fB#define\fR |
| directive. In particular, the definition will be truncated by |
| embedded newline characters. |
| .Sp |
| If you are invoking the preprocessor from a shell or shell-like |
| program you may need to use the shell's quoting syntax to protect |
| characters such as spaces that have a meaning in the shell syntax. |
| .Sp |
| If you wish to define a function-like macro on the command line, write |
| its argument list with surrounding parentheses before the equals sign |
| (if any). Parentheses are meaningful to most shells, so you will need |
| to quote the option. With \fBsh\fR and \fBcsh\fR, |
| \&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works. |
| .Sp |
| \&\fB\-D\fR and \fB\-U\fR options are processed in the order they |
| are given on the command line. All \fB\-imacros\fR \fIfile\fR and |
| \&\fB\-include\fR \fIfile\fR options are processed after all |
| \&\fB\-D\fR and \fB\-U\fR options. |
| .IP "\fB\-U\fR \fIname\fR" 4 |
| .IX Item "-U name" |
| Cancel any previous definition of \fIname\fR, either built in or |
| provided with a \fB\-D\fR option. |
| .IP "\fB\-undef\fR" 4 |
| .IX Item "-undef" |
| Do not predefine any system-specific or GCC-specific macros. The |
| standard predefined macros remain defined. |
| .IP "\fB\-I\fR \fIdir\fR" 4 |
| .IX Item "-I dir" |
| Add the directory \fIdir\fR to the list of directories to be searched |
| for header files. |
| Directories named by \fB\-I\fR are searched before the standard |
| system include directories. If the directory \fIdir\fR is a standard |
| system include directory, the option is ignored to ensure that the |
| default search order for system directories and the special treatment |
| of system headers are not defeated |
| \&. |
| .IP "\fB\-o\fR \fIfile\fR" 4 |
| .IX Item "-o file" |
| Write output to \fIfile\fR. This is the same as specifying \fIfile\fR |
| as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a |
| different interpretation of a second non-option argument, so you must |
| use \fB\-o\fR to specify the output file. |
| .IP "\fB\-Wall\fR" 4 |
| .IX Item "-Wall" |
| Turns on all optional warnings which are desirable for normal code. |
| At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR, |
| \&\fB\-Wmultichar\fR and a warning about integer promotion causing a |
| change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the |
| preprocessor's warnings are on by default and have no options to |
| control them. |
| .IP "\fB\-Wcomment\fR" 4 |
| .IX Item "-Wcomment" |
| .PD 0 |
| .IP "\fB\-Wcomments\fR" 4 |
| .IX Item "-Wcomments" |
| .PD |
| 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. |
| (Both forms have the same effect.) |
| .IP "\fB\-Wtrigraphs\fR" 4 |
| .IX Item "-Wtrigraphs" |
| @anchor{Wtrigraphs} |
| Most trigraphs in comments cannot affect the meaning of the program. |
| However, a trigraph that would form an escaped newline (\fB??/\fR at |
| the end of a line) can, by changing where the comment begins or ends. |
| Therefore, only trigraphs that would form escaped newlines produce |
| warnings inside a comment. |
| .Sp |
| This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not |
| given, this option is still enabled unless trigraphs are enabled. To |
| get trigraph conversion without warnings, but get the other |
| \&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR. |
| .IP "\fB\-Wtraditional\fR" 4 |
| .IX Item "-Wtraditional" |
| Warn about certain constructs that behave differently in traditional and |
| \&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C |
| equivalent, and problematic constructs which should be avoided. |
| .IP "\fB\-Wimport\fR" 4 |
| .IX Item "-Wimport" |
| Warn the first time \fB#import\fR is used. |
| .IP "\fB\-Wundef\fR" 4 |
| .IX Item "-Wundef" |
| Warn whenever an identifier which is not a macro is encountered in an |
| \&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are |
| replaced with zero. |
| .IP "\fB\-Wunused\-macros\fR" 4 |
| .IX Item "-Wunused-macros" |
| Warn about macros defined in the main file that are unused. A macro |
| is \fIused\fR if it is expanded or tested for existence at least once. |
| The preprocessor will also warn if the macro has not been used at the |
| time it is redefined or undefined. |
| .Sp |
| Built-in macros, macros defined on the command line, and macros |
| defined in include files are not warned about. |
| .Sp |
| \&\fINote:\fR If a macro is actually used, but only used in skipped |
| conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the |
| warning in such a case, you might improve the scope of the macro's |
| definition by, for example, moving it into the first skipped block. |
| Alternatively, you could provide a dummy use with something like: |
| .Sp |
| .Vb 2 |
| \& #if defined the_macro_causing_the_warning |
| \& #endif |
| .Ve |
| .IP "\fB\-Wendif\-labels\fR" 4 |
| .IX Item "-Wendif-labels" |
| Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text. |
| This usually happens in code of the form |
| .Sp |
| .Vb 5 |
| \& #if FOO |
| \& ... |
| \& #else FOO |
| \& ... |
| \& #endif FOO |
| .Ve |
| .Sp |
| The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not |
| in older programs. This warning is on by default. |
| .IP "\fB\-Werror\fR" 4 |
| .IX Item "-Werror" |
| Make all warnings into hard errors. Source code which triggers warnings |
| will be rejected. |
| .IP "\fB\-Wsystem\-headers\fR" 4 |
| .IX Item "-Wsystem-headers" |
| Issue warnings for code in system headers. These are normally unhelpful |
| in finding bugs in your own code, therefore suppressed. If you are |
| responsible for the system library, you may want to see them. |
| .IP "\fB\-w\fR" 4 |
| .IX Item "-w" |
| Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default. |
| .IP "\fB\-pedantic\fR" 4 |
| .IX Item "-pedantic" |
| Issue all the mandatory diagnostics listed in the C standard. Some of |
| them are left out by default, since they trigger frequently on harmless |
| code. |
| .IP "\fB\-pedantic\-errors\fR" 4 |
| .IX Item "-pedantic-errors" |
| Issue all the mandatory diagnostics, and make all mandatory diagnostics |
| into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues |
| without \fB\-pedantic\fR but treats as warnings. |
| .IP "\fB\-M\fR" 4 |
| .IX Item "-M" |
| Instead of outputting the result of preprocessing, output a rule |
| suitable for \fBmake\fR describing the dependencies of the main |
| source file. The preprocessor outputs one \fBmake\fR rule containing |
| the object file name for that source file, a colon, and the names of all |
| the included files, including those coming from \fB\-include\fR or |
| \&\fB\-imacros\fR command line options. |
| .Sp |
| Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the |
| object file name consists of the basename of the source file with any |
| suffix replaced with object file suffix. If there are many included |
| files then the rule is split into several lines using \fB\e\fR\-newline. |
| The rule has no commands. |
| .Sp |
| This option does not suppress the preprocessor's debug output, such as |
| \&\fB\-dM\fR. To avoid mixing such debug output with the dependency |
| rules you should explicitly specify the dependency output file with |
| \&\fB\-MF\fR, or use an environment variable like |
| \&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output |
| will still be sent to the regular output stream as normal. |
| .Sp |
| Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses |
| warnings with an implicit \fB\-w\fR. |
| .IP "\fB\-MM\fR" 4 |
| .IX Item "-MM" |
| Like \fB\-M\fR but do not mention header files that are found in |
| system header directories, nor header files that are included, |
| directly or indirectly, from such a header. |
| .Sp |
| This implies that the choice of angle brackets or double quotes in an |
| \&\fB#include\fR directive does not in itself determine whether that |
| header will appear in \fB\-MM\fR dependency output. This is a |
| slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier. |
| .Sp |
| @anchor{dashMF} |
| .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. If no \fB\-MF\fR switch is given |
| the preprocessor sends the rules to the same place it would have sent |
| preprocessed output. |
| .Sp |
| When used with the driver options \fB\-MD\fR or \fB\-MMD\fR, |
| \&\fB\-MF\fR overrides the default dependency output file. |
| .IP "\fB\-MG\fR" 4 |
| .IX Item "-MG" |
| In conjunction with an option such as \fB\-M\fR requesting |
| dependency generation, \fB\-MG\fR assumes missing header files are |
| generated files and adds them to the dependency list without raising |
| an error. The dependency filename is taken directly from the |
| \&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR |
| also suppresses preprocessed output, as a missing header file renders |
| this useless. |
| .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 \fBmake\fR gives if you remove header |
| files without updating the \fIMakefile\fR to match. |
| .Sp |
| This is typical output: |
| .Sp |
| .Vb 1 |
| \& test.o: test.c test.h |
| .Ve |
| .Sp |
| .Vb 1 |
| \& test.h: |
| .Ve |
| .IP "\fB\-MT\fR \fItarget\fR" 4 |
| .IX Item "-MT target" |
| Change the target of the rule emitted by dependency generation. By |
| default \s-1CPP\s0 takes the name of the main input file, including any path, |
| deletes any file suffix such as \fB.c\fR, and appends the platform's |
| usual object suffix. The result is the target. |
| .Sp |
| An \fB\-MT\fR option will set the target to be exactly the string you |
| specify. 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 |
| For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give |
| .Sp |
| .Vb 1 |
| \& $(objpfx)foo.o: foo.c |
| .Ve |
| .IP "\fB\-MQ\fR \fItarget\fR" 4 |
| .IX Item "-MQ target" |
| Same as \fB\-MT\fR, but it quotes any characters which are special to |
| Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives |
| .Sp |
| .Vb 1 |
| \& $$(objpfx)foo.o: foo.c |
| .Ve |
| .Sp |
| The default target is automatically quoted, as if it were given with |
| \&\fB\-MQ\fR. |
| .IP "\fB\-MD\fR" 4 |
| .IX Item "-MD" |
| \&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that |
| \&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on |
| whether an \fB\-o\fR option is given. If it is, the driver uses its |
| argument but with a suffix of \fI.d\fR, otherwise it take the |
| basename of the input file and applies a \fI.d\fR suffix. |
| .Sp |
| If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any |
| \&\fB\-o\fR switch is understood to specify the dependency output file, but if used without \fB\-E\fR, each \fB\-o\fR |
| is understood to specify a target object file. |
| .Sp |
| Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate |
| a dependency output file as a side-effect of the compilation process. |
| .IP "\fB\-MMD\fR" 4 |
| .IX Item "-MMD" |
| Like \fB\-MD\fR except mention only user header files, not system |
| header files. |
| .IP "\fB\-fpch\-deps\fR" 4 |
| .IX Item "-fpch-deps" |
| When using precompiled headers, this flag |
| will cause the dependency-output flags to also list the files from the |
| precompiled header's dependencies. If not specified only the |
| precompiled header would be listed and not the files that were used to |
| create it because those files are not consulted when a precompiled |
| header is used. |
| .IP "\fB\-fpch\-preprocess\fR" 4 |
| .IX Item "-fpch-preprocess" |
| This option allows use of a precompiled header together with \fB\-E\fR. It inserts a special \f(CW\*(C`#pragma\*(C'\fR, |
| \&\f(CW\*(C`#pragma GCC pch_preprocess "<filename>"\*(C'\fR in the output to mark |
| the place where the precompiled header was found, and its filename. When |
| \&\fB\-fpreprocessed\fR is in use, \s-1GCC\s0 recognizes this \f(CW\*(C`#pragma\*(C'\fR and |
| loads the \s-1PCH\s0. |
| .Sp |
| This option is off by default, because the resulting preprocessed output |
| is only really suitable as input to \s-1GCC\s0. It is switched on by |
| \&\fB\-save\-temps\fR. |
| .Sp |
| You should not write this \f(CW\*(C`#pragma\*(C'\fR in your own code, but it is |
| safe to edit the filename if the \s-1PCH\s0 file is available in a different |
| location. The filename may be absolute or it may be relative to \s-1GCC\s0's |
| current directory. |
| .IP "\fB\-x c\fR" 4 |
| .IX Item "-x c" |
| .PD 0 |
| .IP "\fB\-x c++\fR" 4 |
| .IX Item "-x c++" |
| .IP "\fB\-x objective-c\fR" 4 |
| .IX Item "-x objective-c" |
| .IP "\fB\-x assembler-with-cpp\fR" 4 |
| .IX Item "-x assembler-with-cpp" |
| .PD |
| Specify the source language: C, \*(C+, Objective\-C, or assembly. This has |
| nothing to do with standards conformance or extensions; it merely |
| selects which base syntax to expect. If you give none of these options, |
| cpp will deduce the language from the extension of the source file: |
| \&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common |
| extensions for \*(C+ and assembly are also recognized. If cpp does not |
| recognize the extension, it will treat the file as C; this is the most |
| generic mode. |
| .Sp |
| \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option |
| which selected both the language and the standards conformance level. |
| This option has been removed, because it conflicts with the \fB\-l\fR |
| option. |
| .IP "\fB\-std=\fR\fIstandard\fR" 4 |
| .IX Item "-std=standard" |
| .PD 0 |
| .IP "\fB\-ansi\fR" 4 |
| .IX Item "-ansi" |
| .PD |
| Specify the standard to which the code should conform. Currently \s-1CPP\s0 |
| knows about C and \*(C+ standards; others may be added in the future. |
| .Sp |
| \&\fIstandard\fR |
| may be one of: |
| .RS 4 |
| .ie n .IP """iso9899:1990""" 4 |
| .el .IP "\f(CWiso9899:1990\fR" 4 |
| .IX Item "iso9899:1990" |
| .PD 0 |
| .ie n .IP """c89""" 4 |
| .el .IP "\f(CWc89\fR" 4 |
| .IX Item "c89" |
| .PD |
| The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for |
| this version of the standard. |
| .Sp |
| The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR. |
| .ie n .IP """iso9899:199409""" 4 |
| .el .IP "\f(CWiso9899:199409\fR" 4 |
| .IX Item "iso9899:199409" |
| The 1990 C standard, as amended in 1994. |
| .ie n .IP """iso9899:1999""" 4 |
| .el .IP "\f(CWiso9899:1999\fR" 4 |
| .IX Item "iso9899:1999" |
| .PD 0 |
| .ie n .IP """c99""" 4 |
| .el .IP "\f(CWc99\fR" 4 |
| .IX Item "c99" |
| .ie n .IP """iso9899:199x""" 4 |
| .el .IP "\f(CWiso9899:199x\fR" 4 |
| .IX Item "iso9899:199x" |
| .ie n .IP """c9x""" 4 |
| .el .IP "\f(CWc9x\fR" 4 |
| .IX Item "c9x" |
| .PD |
| The revised \s-1ISO\s0 C standard, published in December 1999. Before |
| publication, this was known as C9X. |
| .ie n .IP """gnu89""" 4 |
| .el .IP "\f(CWgnu89\fR" 4 |
| .IX Item "gnu89" |
| The 1990 C standard plus \s-1GNU\s0 extensions. This is the default. |
| .ie n .IP """gnu99""" 4 |
| .el .IP "\f(CWgnu99\fR" 4 |
| .IX Item "gnu99" |
| .PD 0 |
| .ie n .IP """gnu9x""" 4 |
| .el .IP "\f(CWgnu9x\fR" 4 |
| .IX Item "gnu9x" |
| .PD |
| The 1999 C standard plus \s-1GNU\s0 extensions. |
| .ie n .IP """c++98""" 4 |
| .el .IP "\f(CWc++98\fR" 4 |
| .IX Item "c++98" |
| The 1998 \s-1ISO\s0 \*(C+ standard plus amendments. |
| .ie n .IP """gnu++98""" 4 |
| .el .IP "\f(CWgnu++98\fR" 4 |
| .IX Item "gnu++98" |
| The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the |
| default for \*(C+ code. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-I\-\fR" 4 |
| .IX Item "-I-" |
| Split the include path. Any directories specified with \fB\-I\fR |
| options before \fB\-I\-\fR are searched only for headers requested with |
| \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for |
| \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are |
| specified with \fB\-I\fR options after the \fB\-I\-\fR, those |
| directories are searched for all \fB#include\fR directives. |
| .Sp |
| In addition, \fB\-I\-\fR inhibits the use of the directory of the current |
| file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR. |
| This option has been deprecated. |
| .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 directory of the current file, if appropriate) are searched. |
| .IP "\fB\-nostdinc++\fR" 4 |
| .IX Item "-nostdinc++" |
| Do not search for header files in the \*(C+\-specific standard directories, |
| but do still search the other standard directories. (This option is |
| used when building the \*(C+ library.) |
| .IP "\fB\-include\fR \fIfile\fR" 4 |
| .IX Item "-include file" |
| Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first |
| line of the primary source file. However, the first directory searched |
| for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR |
| the directory containing the main source file. If not found there, it |
| is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search |
| chain as normal. |
| .Sp |
| If multiple \fB\-include\fR options are given, the files are included |
| in the order they appear on the command line. |
| .IP "\fB\-imacros\fR \fIfile\fR" 4 |
| .IX Item "-imacros file" |
| Exactly like \fB\-include\fR, except that any output produced by |
| scanning \fIfile\fR is thrown away. Macros it defines remain defined. |
| This allows you to acquire all the macros from a header without also |
| processing its declarations. |
| .Sp |
| All files specified by \fB\-imacros\fR are processed before all files |
| specified by \fB\-include\fR. |
| .IP "\fB\-idirafter\fR \fIdir\fR" 4 |
| .IX Item "-idirafter dir" |
| Search \fIdir\fR for header files, but do it \fIafter\fR all |
| directories specified with \fB\-I\fR and the standard system directories |
| have been exhausted. \fIdir\fR is treated as a system include directory. |
| .IP "\fB\-iprefix\fR \fIprefix\fR" 4 |
| .IX Item "-iprefix prefix" |
| Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR |
| options. If the prefix represents a directory, you should include the |
| final \fB/\fR. |
| .IP "\fB\-iwithprefix\fR \fIdir\fR" 4 |
| .IX Item "-iwithprefix dir" |
| .PD 0 |
| .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4 |
| .IX Item "-iwithprefixbefore dir" |
| .PD |
| Append \fIdir\fR to the prefix specified previously with |
| \&\fB\-iprefix\fR, and add the resulting directory to the include search |
| path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR |
| would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would. |
| .IP "\fB\-isysroot\fR \fIdir\fR" 4 |
| .IX Item "-isysroot dir" |
| This option is like the \fB\-\-sysroot\fR option, but applies only to |
| header files. See the \fB\-\-sysroot\fR option for more information. |
| .IP "\fB\-imultilib\fR \fIdir\fR" 4 |
| .IX Item "-imultilib dir" |
| Use \fIdir\fR as a subdirectory of the directory containing |
| target-specific \*(C+ headers. |
| .IP "\fB\-isystem\fR \fIdir\fR" 4 |
| .IX Item "-isystem dir" |
| Search \fIdir\fR for header files, after all directories specified by |
| \&\fB\-I\fR but before the standard system directories. Mark it |
| as a system directory, so that it gets the same special treatment as |
| is applied to the standard system directories. |
| .IP "\fB\-iquote\fR \fIdir\fR" 4 |
| .IX Item "-iquote dir" |
| Search \fIdir\fR only for header files requested with |
| \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for |
| \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by |
| \&\fB\-I\fR and before the standard system directories. |
| .IP "\fB\-fdollars\-in\-identifiers\fR" 4 |
| .IX Item "-fdollars-in-identifiers" |
| @anchor{fdollars\-in\-identifiers} |
| Accept \fB$\fR in identifiers. |
| .IP "\fB\-fextended\-identifiers\fR" 4 |
| .IX Item "-fextended-identifiers" |
| Accept universal character names in identifiers. This option is |
| experimental; in a future version of \s-1GCC\s0, it will be enabled by |
| default for C99 and \*(C+. |
| .IP "\fB\-fpreprocessed\fR" 4 |
| .IX Item "-fpreprocessed" |
| Indicate to the preprocessor that the input file has already been |
| preprocessed. This suppresses things like macro expansion, trigraph |
| conversion, escaped newline splicing, and processing of most directives. |
| The preprocessor still recognizes and removes comments, so that you can |
| pass a file preprocessed with \fB\-C\fR to the compiler without |
| problems. In this mode the integrated preprocessor is little more than |
| a tokenizer for the front ends. |
| .Sp |
| \&\fB\-fpreprocessed\fR is implicit if the input file has one of the |
| extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the |
| extensions that \s-1GCC\s0 uses for preprocessed files created by |
| \&\fB\-save\-temps\fR. |
| .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4 |
| .IX Item "-ftabstop=width" |
| Set the distance between tab stops. This helps the preprocessor report |
| correct column numbers in warnings or errors, even if tabs appear on the |
| line. If the value is less than 1 or greater than 100, the option is |
| ignored. The default is 8. |
| .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4 |
| .IX Item "-fexec-charset=charset" |
| Set the execution character set, used for string and character |
| constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding |
| supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine. |
| .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4 |
| .IX Item "-fwide-exec-charset=charset" |
| Set the wide execution character set, used for wide string and |
| character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever |
| corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with |
| \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported |
| by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have |
| problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR. |
| .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4 |
| .IX Item "-finput-charset=charset" |
| Set the input character set, used for translation from the character |
| set of the input file to the source character set used by \s-1GCC\s0. If the |
| locale does not specify, or \s-1GCC\s0 cannot get this information from the |
| locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale |
| or this command line option. Currently the command line option takes |
| precedence if there's a conflict. \fIcharset\fR can be any encoding |
| supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine. |
| .IP "\fB\-fworking\-directory\fR" 4 |
| .IX Item "-fworking-directory" |
| Enable generation of linemarkers in the preprocessor output that will |
| let the compiler know the current working directory at the time of |
| preprocessing. When this option is enabled, the preprocessor will |
| emit, after the initial linemarker, a second linemarker with the |
| current working directory followed by two slashes. \s-1GCC\s0 will use this |
| directory, when it's present in the preprocessed input, as the |
| directory emitted as the current working directory in some debugging |
| information formats. This option is implicitly enabled if debugging |
| information is enabled, but this can be inhibited with the negated |
| form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is |
| present in the command line, this option has no effect, since no |
| \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever. |
| .IP "\fB\-fno\-show\-column\fR" 4 |
| .IX Item "-fno-show-column" |
| Do not print column numbers in diagnostics. This may be necessary if |
| diagnostics are being scanned by a program that does not understand the |
| column numbers, such as \fBdejagnu\fR. |
| .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4 |
| .IX Item "-A predicate=answer" |
| Make an assertion with the predicate \fIpredicate\fR and answer |
| \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR |
| \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because |
| it does not use shell special characters. |
| .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4 |
| .IX Item "-A -predicate=answer" |
| Cancel an assertion with the predicate \fIpredicate\fR and answer |
| \&\fIanswer\fR. |
| .IP "\fB\-dCHARS\fR" 4 |
| .IX Item "-dCHARS" |
| \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters, |
| and must not be preceded by a space. Other characters are interpreted |
| by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so |
| are silently ignored. If you specify characters whose behavior |
| conflicts, the result is undefined. |
| .RS 4 |
| .IP "\fBM\fR" 4 |
| .IX Item "M" |
| Instead of the normal output, generate a list of \fB#define\fR |
| directives for all the macros defined during the execution of the |
| preprocessor, including predefined macros. This gives you a way of |
| finding out what is predefined in your version of the preprocessor. |
| Assuming you have no file \fIfoo.h\fR, the command |
| .Sp |
| .Vb 1 |
| \& touch foo.h; cpp -dM foo.h |
| .Ve |
| .Sp |
| will show all the predefined macros. |
| .IP "\fBD\fR" 4 |
| .IX Item "D" |
| Like \fBM\fR except in two respects: it does \fInot\fR include the |
| predefined macros, and it outputs \fIboth\fR the \fB#define\fR |
| directives and the result of preprocessing. Both kinds of output go to |
| the standard output file. |
| .IP "\fBN\fR" 4 |
| .IX Item "N" |
| Like \fBD\fR, but emit only the macro names, not their expansions. |
| .IP "\fBI\fR" 4 |
| .IX Item "I" |
| Output \fB#include\fR directives in addition to the result of |
| preprocessing. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-P\fR" 4 |
| .IX Item "-P" |
| Inhibit generation of linemarkers in the output from the preprocessor. |
| This might be useful when running the preprocessor on something that is |
| not C code, and will be sent to a program which might be confused by the |
| linemarkers. |
| .IP "\fB\-C\fR" 4 |
| .IX Item "-C" |
| Do not discard comments. All comments are passed through to the output |
| file, except for comments in processed directives, which are deleted |
| along with the directive. |
| .Sp |
| You should be prepared for side effects when using \fB\-C\fR; it |
| causes the preprocessor to treat comments as tokens in their own right. |
| For example, comments appearing at the start of what would be a |
| directive line have the effect of turning that line into an ordinary |
| source line, since the first token on the line is no longer a \fB#\fR. |
| .IP "\fB\-CC\fR" 4 |
| .IX Item "-CC" |
| Do not discard comments, including during macro expansion. This is |
| like \fB\-C\fR, except that comments contained within macros are |
| also passed through to the output file where the macro is expanded. |
| .Sp |
| In addition to the side-effects of the \fB\-C\fR option, the |
| \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro |
| to be converted to C\-style comments. This is to prevent later use |
| of that macro from inadvertently commenting out the remainder of |
| the source line. |
| .Sp |
| The \fB\-CC\fR option is generally used to support lint comments. |
| .IP "\fB\-traditional\-cpp\fR" 4 |
| .IX Item "-traditional-cpp" |
| Try to imitate the behavior of old-fashioned C preprocessors, as |
| opposed to \s-1ISO\s0 C preprocessors. |
| .IP "\fB\-trigraphs\fR" 4 |
| .IX Item "-trigraphs" |
| Process 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 trigraphs and their replacements are |
| .Sp |
| .Vb 2 |
| \& Trigraph: ??( ??) ??< ??> ??= ??/ ??' ??! ??- |
| \& Replacement: [ ] { } # \e ^ | ~ |
| .Ve |
| .IP "\fB\-remap\fR" 4 |
| .IX Item "-remap" |
| Enable special code to work around file systems which only permit very |
| short file names, such as \s-1MS\-DOS\s0. |
| .IP "\fB\-\-help\fR" 4 |
| .IX Item "--help" |
| .PD 0 |
| .IP "\fB\-\-target\-help\fR" 4 |
| .IX Item "--target-help" |
| .PD |
| Print text describing all the command line options instead of |
| preprocessing anything. |
| .IP "\fB\-v\fR" 4 |
| .IX Item "-v" |
| Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of |
| execution, and report the final form of the include path. |
| .IP "\fB\-H\fR" 4 |
| .IX Item "-H" |
| Print the name of each header file used, in addition to other normal |
| activities. Each name is indented to show how deep in the |
| \&\fB#include\fR stack it is. Precompiled header files are also |
| printed, even if they are found to be invalid; an invalid precompiled |
| header file is printed with \fB...x\fR and a valid one with \fB...!\fR . |
| .IP "\fB\-version\fR" 4 |
| .IX Item "-version" |
| .PD 0 |
| .IP "\fB\-\-version\fR" 4 |
| .IX Item "--version" |
| .PD |
| Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to |
| preprocess as normal. With two dashes, exit immediately. |
| .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. |
| .IP "\fB\-Xassembler\fR \fIoption\fR" 4 |
| .IX Item "-Xassembler option" |
| Pass \fIoption\fR as an option to the assembler. You can use this to |
| supply system-specific assembler 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\-Xassembler\fR twice, once for the option and once for the argument. |
| .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" |
| .PD 0 |
| .IP "\fB\-l\fR \fIlibrary\fR" 4 |
| .IX Item "-l library" |
| .PD |
| Search the library named \fIlibrary\fR when linking. (The second |
| alternative with the library as a separate argument is only for |
| \&\s-1POSIX\s0 compliance and is not recommended.) |
| .Sp |
| It makes a difference where in the command you write this option; the |
| linker searches and processes libraries and object files in the order they |
| are specified. Thus, \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 or 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 \f(CW\*(C`memcmp\*(C'\fR, |
| \&\f(CW\*(C`memset\*(C'\fR, \f(CW\*(C`memcpy\*(C'\fR and \f(CW\*(C`memmove\*(C'\fR. |
| 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 \f(CW\*(C`memcmp\*(C'\fR, \f(CW\*(C`memset\*(C'\fR, |
| \&\f(CW\*(C`memcpy\*(C'\fR and \f(CW\*(C`memmove\*(C'\fR. |
| 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\-pie\fR" 4 |
| .IX Item "-pie" |
| Produce a position independent executable on targets which support it. |
| For predictable results, you must also specify the same set of options |
| that were used to generate code (\fB\-fpie\fR, \fB\-fPIE\fR, |
| or model suboptions) when you specify this option. |
| .IP "\fB\-rdynamic\fR" 4 |
| .IX Item "-rdynamic" |
| Pass the flag \fB\-export\-dynamic\fR to the \s-1ELF\s0 linker, on targets |
| that support it. This instructs the linker to add all symbols, not |
| only used ones, to the dynamic symbol table. This option is needed |
| for some uses of \f(CW\*(C`dlopen\*(C'\fR or to allow obtaining backtraces |
| from within a program. |
| .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 |
| Therefore, the G++ and \s-1GCJ\s0 drivers automatically add |
| \&\fB\-shared\-libgcc\fR whenever you build a shared library or a main |
| executable, because \*(C+ and Java programs typically use exceptions, so |
| this is the right thing to do. |
| .Sp |
| If, instead, you use the \s-1GCC\s0 driver to create shared libraries, you may |
| find that they will not always be linked with the shared \fIlibgcc\fR. |
| If \s-1GCC\s0 finds, at its configuration time, that you have a non-GNU linker |
| or a \s-1GNU\s0 linker that does not support option \fB\-\-eh\-frame\-hdr\fR, |
| it will link the shared version of \fIlibgcc\fR into shared libraries |
| by default. Otherwise, it will take advantage of the linker and optimize |
| away the linking with the shared version of \fIlibgcc\fR, linking with |
| the static version of libgcc by default. This allows exceptions to |
| propagate through such shared libraries, without incurring relocation |
| costs at library load time. |
| .Sp |
| However, if a library or main executable is supposed to throw or catch |
| exceptions, you must link it using the G++ or \s-1GCJ\s0 driver, as appropriate |
| for the languages used in the program, or using the option |
| \&\fB\-shared\-libgcc\fR, such that it is linked with the shared |
| \&\fIlibgcc\fR. |
| .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. However, you should |
| not use this option to add directories that contain vendor-supplied |
| system header files (use \fB\-isystem\fR for that). 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. |
| .Sp |
| If a standard system include directory, or a directory specified with |
| \&\fB\-isystem\fR, is also specified with \fB\-I\fR, the \fB\-I\fR |
| option will be ignored. The directory will still be searched but as a |
| system directory at its normal position in the system include chain. |
| This is to ensure that \s-1GCC\s0's procedure to fix buggy system headers and |
| the ordering for the include_next directive are not inadvertently changed. |
| If you really need to change the search order for system directories, |
| use the \fB\-nostdinc\fR and/or \fB\-isystem\fR options. |
| .IP "\fB\-iquote\fR\fIdir\fR" 4 |
| .IX Item "-iquotedir" |
| Add the directory \fIdir\fR to the head of the list of directories to |
| be searched for header files only for the case of \fB#include |
| "\fR\fIfile\fR\fB"\fR; they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR, |
| otherwise just like \fB\-I\fR. |
| .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/\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 |
| The compiler will check to see if the path provided by the \fB\-B\fR |
| refers to a directory, and if necessary it will add a directory |
| separator character at the end of the path. |
| .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. |
| .Sp |
| As a special kludge, if the path provided by \fB\-B\fR is |
| \&\fI[dir/]stage\fIN\fI/\fR, where \fIN\fR is a number in the range 0 to |
| 9, then it will be replaced by \fI[dir/]include\fR. This is to help |
| with boot-strapping the compiler. |
| .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. |
| .IP "\fB\-\-sysroot=\fR\fIdir\fR" 4 |
| .IX Item "--sysroot=dir" |
| Use \fIdir\fR as the logical root directory for headers and libraries. |
| For example, if the compiler would normally search for headers in |
| \&\fI/usr/include\fR and libraries in \fI/usr/lib\fR, it will instead |
| search \fI\fIdir\fI/usr/include\fR and \fI\fIdir\fI/usr/lib\fR. |
| .Sp |
| If you use both this option and the \fB\-isysroot\fR option, then |
| the \fB\-\-sysroot\fR option will apply to libraries, but the |
| \&\fB\-isysroot\fR option will apply to header files. |
| .Sp |
| The \s-1GNU\s0 linker (beginning with version 2.16) has the necessary support |
| for this option. If your linker does not support this option, the |
| header file aspect of \fB\-\-sysroot\fR will still work, but the |
| library aspect will not. |
| .IP "\fB\-I\-\fR" 4 |
| .IX Item "-I-" |
| This option has been deprecated. Please use \fB\-iquote\fR instead for |
| \&\fB\-I\fR directories before the \fB\-I\-\fR and remove the \fB\-I\-\fR. |
| 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. |
| .Sh "Specifying Target Machine and Compiler Version" |
| .IX Subsection "Specifying Target Machine and Compiler Version" |
| The usual way to run \s-1GCC\s0 is to run the executable called \fIgcc\fR, or |
| \&\fI<machine>\-gcc\fR when cross\-compiling, or |
| \&\fI<machine>\-gcc\-<version>\fR to run a version other than the one that |
| was installed last. Sometimes this is inconvenient, so \s-1GCC\s0 provides |
| options that will switch to another cross-compiler or version. |
| .IP "\fB\-b\fR \fImachine\fR" 4 |
| .IX Item "-b machine" |
| The argument \fImachine\fR specifies the target machine for compilation. |
| .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 |
| arm-elf\fR, meaning to compile for an arm processor with elf binaries, |
| then you would specify \fB\-b arm-elf\fR to run that cross compiler. |
| Because there are other options beginning with \fB\-b\fR, the |
| configuration must contain a hyphen. |
| .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 \fB4.0\fR, meaning to run \s-1GCC\s0 version 4.0. |
| .PP |
| The \fB\-V\fR and \fB\-b\fR options work by running the |
| \&\fI<machine>\-gcc\-<version>\fR executable, so there's no real reason to |
| use them if you can just run that directly. |
| .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 \s-1VAX\s0 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 |
| \fI\s-1ARC\s0 Options\fR |
| .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 |
| \fI\s-1ARM\s0 Options\fR |
| .IX Subsection "ARM Options" |
| .PP |
| These \fB\-m\fR options are defined for Advanced \s-1RISC\s0 Machines (\s-1ARM\s0) |
| architectures: |
| .IP "\fB\-mabi=\fR\fIname\fR" 4 |
| .IX Item "-mabi=name" |
| Generate code for the specified \s-1ABI\s0. Permissible values are: \fBapcs-gnu\fR, |
| \&\fBatpcs\fR, \fBaapcs\fR, \fBaapcs-linux\fR and \fBiwmmxt\fR. |
| .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\-mthumb\-interwork\fR" 4 |
| .IX Item "-mthumb-interwork" |
| Generate code which supports calling between the \s-1ARM\s0 and Thumb |
| 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\-mfloat\-abi=\fR\fIname\fR" 4 |
| .IX Item "-mfloat-abi=name" |
| Specifies which \s-1ABI\s0 to use for floating point values. Permissible values |
| are: \fBsoft\fR, \fBsoftfp\fR and \fBhard\fR. |
| .Sp |
| \&\fBsoft\fR and \fBhard\fR are equivalent to \fB\-msoft\-float\fR |
| and \fB\-mhard\-float\fR respectively. \fBsoftfp\fR allows the generation |
| of floating point instructions, but still uses the soft-float calling |
| conventions. |
| .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\-mcpu=\fR\fIname\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 emit when generating |
| assembly code. Permissible names are: \fBarm2\fR, \fBarm250\fR, |
| \&\fBarm3\fR, \fBarm6\fR, \fBarm60\fR, \fBarm600\fR, \fBarm610\fR, |
| \&\fBarm620\fR, \fBarm7\fR, \fBarm7m\fR, \fBarm7d\fR, \fBarm7dm\fR, |
| \&\fBarm7di\fR, \fBarm7dmi\fR, \fBarm70\fR, \fBarm700\fR, |
| \&\fBarm700i\fR, \fBarm710\fR, \fBarm710c\fR, \fBarm7100\fR, |
| \&\fBarm7500\fR, \fBarm7500fe\fR, \fBarm7tdmi\fR, \fBarm7tdmi\-s\fR, |
| \&\fBarm8\fR, \fBstrongarm\fR, \fBstrongarm110\fR, \fBstrongarm1100\fR, |
| \&\fBarm8\fR, \fBarm810\fR, \fBarm9\fR, \fBarm9e\fR, \fBarm920\fR, |
| \&\fBarm920t\fR, \fBarm922t\fR, \fBarm946e\-s\fR, \fBarm966e\-s\fR, |
| \&\fBarm968e\-s\fR, \fBarm926ej\-s\fR, \fBarm940t\fR, \fBarm9tdmi\fR, |
| \&\fBarm10tdmi\fR, \fBarm1020t\fR, \fBarm1026ej\-s\fR, |
| \&\fBarm10e\fR, \fBarm1020e\fR, \fBarm1022e\fR, |
| \&\fBarm1136j\-s\fR, \fBarm1136jf\-s\fR, \fBmpcore\fR, \fBmpcorenovfp\fR, |
| \&\fBarm1176jz\-s\fR, \fBarm1176jzf\-s\fR, \fBxscale\fR, \fBiwmmxt\fR, |
| \&\fBep9312\fR. |
| .IP "\fB\-mtune=\fR\fIname\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 \s-1ARM\s0 implementations better performance can be obtained by using |
| this option. |
| .IP "\fB\-march=\fR\fIname\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 emit when generating |
| assembly code. This option can be used in conjunction with or instead |
| of the \fB\-mcpu=\fR option. Permissible names are: \fBarmv2\fR, |
| \&\fBarmv2a\fR, \fBarmv3\fR, \fBarmv3m\fR, \fBarmv4\fR, \fBarmv4t\fR, |
| \&\fBarmv5\fR, \fBarmv5t\fR, \fBarmv5te\fR, \fBarmv6\fR, \fBarmv6j\fR, |
| \&\fBiwmmxt\fR, \fBep9312\fR. |
| .IP "\fB\-mfpu=\fR\fIname\fR" 4 |
| .IX Item "-mfpu=name" |
| .PD 0 |
| .IP "\fB\-mfpe=\fR\fInumber\fR" 4 |
| .IX Item "-mfpe=number" |
| .IP "\fB\-mfp=\fR\fInumber\fR" 4 |
| .IX Item "-mfp=number" |
| .PD |
| This specifies what floating point hardware (or hardware emulation) is |
| available on the target. Permissible names are: \fBfpa\fR, \fBfpe2\fR, |
| \&\fBfpe3\fR, \fBmaverick\fR, \fBvfp\fR. \fB\-mfp\fR and \fB\-mfpe\fR |
| are synonyms for \fB\-mfpu\fR=\fBfpe\fR\fInumber\fR, for compatibility |
| with older versions of \s-1GCC\s0. |
| .Sp |
| If \fB\-msoft\-float\fR is specified this specifies the format of |
| floating point values. |
| .IP "\fB\-mstructure\-size\-boundary=\fR\fIn\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, 32 |
| and 64. The default value varies for different toolchains. For the \s-1COFF\s0 |
| targeted toolchain the default value is 8. A value of 64 is only allowed |
| if the underlying \s-1ABI\s0 supports it. |
| .Sp |
| Specifying the larger number can produce faster, more efficient code, but |
| can also increase the size of the program. Different values are potentially |
| incompatible. Code compiled with one value cannot necessarily expect to |
| work with code or libraries compiled with another value, if they exchange |
| information using structures or unions. |
| .IP "\fB\-mabort\-on\-noreturn\fR" 4 |
| .IX Item "-mabort-on-noreturn" |
| Generate a call to the function \f(CW\*(C`abort\*(C'\fR at the end of a |
| \&\f(CW\*(C`noreturn\*(C'\fR 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\-mno\-long\-calls\fR will restore the default behavior, 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 support for the \f(CW\*(C`dllimport\*(C'\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 initializing this register with an appropriate value |
| before execution begins. |
| .IP "\fB\-mpic\-register=\fR\fIreg\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. |
| .IP "\fB\-mcirrus\-fix\-invalid\-insns\fR" 4 |
| .IX Item "-mcirrus-fix-invalid-insns" |
| Insert NOPs into the instruction stream to in order to work around |
| problems with invalid Maverick instruction combinations. This option |
| is only valid if the \fB\-mcpu=ep9312\fR option has been used to |
| enable generation of instructions for the Cirrus Maverick floating |
| point co\-processor. This option is not enabled by default, since the |
| problem is only present in older Maverick implementations. The default |
| can be re-enabled by use of the \fB\-mno\-cirrus\-fix\-invalid\-insns\fR |
| switch. |
| .IP "\fB\-mpoke\-function\-name\fR" 4 |
| .IX Item "-mpoke-function-name" |
| Write the name of each function into the text section, directly |
| preceding the function prologue. The generated code is similar to this: |
| .Sp |
| .Vb 9 |
| \& t0 |
| \& .ascii "arm_poke_function_name", 0 |
| \& .align |
| \& t1 |
| \& .word 0xff000000 + (t1 - t0) |
| \& arm_poke_function_name |
| \& mov ip, sp |
| \& stmfd sp!, {fp, ip, lr, pc} |
| \& sub fp, ip, #4 |
| .Ve |
| .Sp |
| When performing a stack backtrace, code can inspect the value of |
| \&\f(CW\*(C`pc\*(C'\fR stored at \f(CW\*(C`fp + 0\*(C'\fR. If the trace function then looks at |
| location \f(CW\*(C`pc \- 12\*(C'\fR and the top 8 bits are set, then we know that |
| there is a function name embedded immediately preceding this location |
| and has length \f(CW\*(C`((pc[\-3]) & 0xff000000)\*(C'\fR. |
| .IP "\fB\-mthumb\fR" 4 |
| .IX Item "-mthumb" |
| Generate code for the 16\-bit Thumb instruction set. The default is to |
| use the 32\-bit \s-1ARM\s0 instruction set. |
| .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\-tpcs\-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\-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\-mtp=\fR\fIname\fR" 4 |
| .IX Item "-mtp=name" |
| Specify the access model for the thread local storage pointer. The valid |
| models are \fBsoft\fR, which generates calls to \f(CW\*(C`_\|_aeabi_read_tp\*(C'\fR, |
| \&\fBcp15\fR, which fetches the thread pointer from \f(CW\*(C`cp15\*(C'\fR directly |
| (supported in the arm6k architecture), and \fBauto\fR, which uses the |
| best available method for the selected processor. The default setting is |
| \&\fBauto\fR. |
| .PP |
| \fI\s-1AVR\s0 Options\fR |
| .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, at43usb320, at76c711). |
| .Sp |
| Instruction set avr4 is for the enhanced \s-1AVR\s0 core with up to 8K program |
| memory space (\s-1MCU\s0 types: atmega8, 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: atmega16, atmega161, atmega163, atmega32, atmega323, |
| atmega64, atmega128, at43usb355, 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, |
| \&\fB_\|_stack\fR 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. |
| .IP "\fB\-mint8\fR" 4 |
| .IX Item "-mint8" |
| Assume int to be 8 bit integer. This affects the sizes of all types: A |
| char will be 1 byte, an int will be 1 byte, an long will be 2 bytes |
| and long long will be 4 bytes. Please note that this option does not |
| comply to the C standards, but it will provide you with smaller code |
| size. |
| .PP |
| \fIBlackfin Options\fR |
| .IX Subsection "Blackfin Options" |
| .IP "\fB\-momit\-leaf\-frame\-pointer\fR" 4 |
| .IX Item "-momit-leaf-frame-pointer" |
| Don't keep the frame pointer in a register for leaf functions. This |
| avoids the instructions to save, set up and restore frame pointers and |
| makes an extra register available in leaf functions. The option |
| \&\fB\-fomit\-frame\-pointer\fR removes the frame pointer for all functions |
| which might make debugging harder. |
| .IP "\fB\-mspecld\-anomaly\fR" 4 |
| .IX Item "-mspecld-anomaly" |
| When enabled, the compiler will ensure that the generated code does not |
| contain speculative loads after jump instructions. This option is enabled |
| by default. |
| .IP "\fB\-mno\-specld\-anomaly\fR" 4 |
| .IX Item "-mno-specld-anomaly" |
| Don't generate extra code to prevent speculative loads from occurring. |
| .IP "\fB\-mcsync\-anomaly\fR" 4 |
| .IX Item "-mcsync-anomaly" |
| When enabled, the compiler will ensure that the generated code does not |
| contain \s-1CSYNC\s0 or \s-1SSYNC\s0 instructions too soon after conditional branches. |
| This option is enabled by default. |
| .IP "\fB\-mno\-csync\-anomaly\fR" 4 |
| .IX Item "-mno-csync-anomaly" |
| Don't generate extra code to prevent \s-1CSYNC\s0 or \s-1SSYNC\s0 instructions from |
| occurring too soon after a conditional branch. |
| .IP "\fB\-mlow\-64k\fR" 4 |
| .IX Item "-mlow-64k" |
| When enabled, the compiler is free to take advantage of the knowledge that |
| the entire program fits into the low 64k of memory. |
| .IP "\fB\-mno\-low\-64k\fR" 4 |
| .IX Item "-mno-low-64k" |
| Assume that the program is arbitrarily large. This is the default. |
| .IP "\fB\-mid\-shared\-library\fR" 4 |
| .IX Item "-mid-shared-library" |
| Generate code that supports shared libraries via the library \s-1ID\s0 method. |
| This allows for execute in place and shared libraries in an environment |
| without virtual memory management. This option implies \fB\-fPIC\fR. |
| .IP "\fB\-mno\-id\-shared\-library\fR" 4 |
| .IX Item "-mno-id-shared-library" |
| Generate code that doesn't assume \s-1ID\s0 based shared libraries are being used. |
| This is the default. |
| .IP "\fB\-mshared\-library\-id=n\fR" 4 |
| .IX Item "-mshared-library-id=n" |
| Specified the identification number of the \s-1ID\s0 based shared library being |
| compiled. Specifying a value of 0 will generate more compact code, specifying |
| other values will force the allocation of that number to the current |
| library but is no more space or time efficient than omitting this option. |
| .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 24 bit addressing range of the offset based |
| version of subroutine call instruction. |
| .Sp |
| This feature is not enabled by default. Specifying |
| \&\fB\-mno\-long\-calls\fR will restore the default behavior. Note these |
| switches have no effect on how the compiler generates code to handle |
| function calls via function pointers. |
| .PP |
| \fI\s-1CRIS\s0 Options\fR |
| .IX Subsection "CRIS Options" |
| .PP |
| These options are defined specifically for the \s-1CRIS\s0 ports. |
| .IP "\fB\-march=\fR\fIarchitecture-type\fR" 4 |
| .IX Item "-march=architecture-type" |
| .PD 0 |
| .IP "\fB\-mcpu=\fR\fIarchitecture-type\fR" 4 |
| .IX Item "-mcpu=architecture-type" |
| .PD |
| Generate code for the specified architecture. The choices for |
| \&\fIarchitecture-type\fR are \fBv3\fR, \fBv8\fR and \fBv10\fR for |
| respectively \s-1ETRAX\s0\ 4, \s-1ETRAX\s0\ 100, and \s-1ETRAX\s0\ 100\ \s-1LX\s0. |
| Default is \fBv0\fR except for cris\-axis\-linux\-gnu, where the default is |
| \&\fBv10\fR. |
| .IP "\fB\-mtune=\fR\fIarchitecture-type\fR" 4 |
| .IX Item "-mtune=architecture-type" |
| Tune to \fIarchitecture-type\fR everything applicable about the generated |
| code, except for the \s-1ABI\s0 and the set of available instructions. The |
| choices for \fIarchitecture-type\fR are the same as for |
| \&\fB\-march=\fR\fIarchitecture-type\fR. |
| .IP "\fB\-mmax\-stack\-frame=\fR\fIn\fR" 4 |
| .IX Item "-mmax-stack-frame=n" |
| Warn when the stack frame of a function exceeds \fIn\fR bytes. |
| .IP "\fB\-melinux\-stacksize=\fR\fIn\fR" 4 |
| .IX Item "-melinux-stacksize=n" |
| Only available with the \fBcris-axis-aout\fR target. Arranges for |
| indications in the program to the kernel loader that the stack of the |
| program should be set to \fIn\fR bytes. |
| .IP "\fB\-metrax4\fR" 4 |
| .IX Item "-metrax4" |
| .PD 0 |
| .IP "\fB\-metrax100\fR" 4 |
| .IX Item "-metrax100" |
| .PD |
| The options \fB\-metrax4\fR and \fB\-metrax100\fR are synonyms for |
| \&\fB\-march=v3\fR and \fB\-march=v8\fR respectively. |
| .IP "\fB\-mmul\-bug\-workaround\fR" 4 |
| .IX Item "-mmul-bug-workaround" |
| .PD 0 |
| .IP "\fB\-mno\-mul\-bug\-workaround\fR" 4 |
| .IX Item "-mno-mul-bug-workaround" |
| .PD |
| Work around a bug in the \f(CW\*(C`muls\*(C'\fR and \f(CW\*(C`mulu\*(C'\fR instructions for \s-1CPU\s0 |
| models where it applies. This option is active by default. |
| .IP "\fB\-mpdebug\fR" 4 |
| .IX Item "-mpdebug" |
| Enable CRIS-specific verbose debug-related information in the assembly |
| code. This option also has the effect to turn off the \fB#NO_APP\fR |
| formatted-code indicator to the assembler at the beginning of the |
| assembly file. |
| .IP "\fB\-mcc\-init\fR" 4 |
| .IX Item "-mcc-init" |
| Do not use condition-code results from previous instruction; always emit |
| compare and test instructions before use of condition codes. |
| .IP "\fB\-mno\-side\-effects\fR" 4 |
| .IX Item "-mno-side-effects" |
| Do not emit instructions with side-effects in addressing modes other than |
| post\-increment. |
| .IP "\fB\-mstack\-align\fR" 4 |
| .IX Item "-mstack-align" |
| .PD 0 |
| .IP "\fB\-mno\-stack\-align\fR" 4 |
| .IX Item "-mno-stack-align" |
| .IP "\fB\-mdata\-align\fR" 4 |
| .IX Item "-mdata-align" |
| .IP "\fB\-mno\-data\-align\fR" 4 |
| .IX Item "-mno-data-align" |
| .IP "\fB\-mconst\-align\fR" 4 |
| .IX Item "-mconst-align" |
| .IP "\fB\-mno\-const\-align\fR" 4 |
| .IX Item "-mno-const-align" |
| .PD |
| These options (no\-options) arranges (eliminate arrangements) for the |
| stack\-frame, individual data and constants to be aligned for the maximum |
| single data access size for the chosen \s-1CPU\s0 model. The default is to |
| arrange for 32\-bit alignment. \s-1ABI\s0 details such as structure layout are |
| not affected by these options. |
| .IP "\fB\-m32\-bit\fR" 4 |
| .IX Item "-m32-bit" |
| .PD 0 |
| .IP "\fB\-m16\-bit\fR" 4 |
| .IX Item "-m16-bit" |
| .IP "\fB\-m8\-bit\fR" 4 |
| .IX Item "-m8-bit" |
| .PD |
| Similar to the stack\- data\- and const-align options above, these options |
| arrange for stack\-frame, writable data and constants to all be 32\-bit, |
| 16\-bit or 8\-bit aligned. The default is 32\-bit alignment. |
| .IP "\fB\-mno\-prologue\-epilogue\fR" 4 |
| .IX Item "-mno-prologue-epilogue" |
| .PD 0 |
| .IP "\fB\-mprologue\-epilogue\fR" 4 |
| .IX Item "-mprologue-epilogue" |
| .PD |
| With \fB\-mno\-prologue\-epilogue\fR, the normal function prologue and |
| epilogue that sets up the stack-frame are omitted and no return |
| instructions or return sequences are generated in the code. Use this |
| option only together with visual inspection of the compiled code: no |
| warnings or errors are generated when call-saved registers must be saved, |
| or storage for local variable needs to be allocated. |
| .IP "\fB\-mno\-gotplt\fR" 4 |
| .IX Item "-mno-gotplt" |
| .PD 0 |
| .IP "\fB\-mgotplt\fR" 4 |
| .IX Item "-mgotplt" |
| .PD |
| With \fB\-fpic\fR and \fB\-fPIC\fR, don't generate (do generate) |
| instruction sequences that load addresses for functions from the \s-1PLT\s0 part |
| of the \s-1GOT\s0 rather than (traditional on other architectures) calls to the |
| \&\s-1PLT\s0. The default is \fB\-mgotplt\fR. |
| .IP "\fB\-maout\fR" 4 |
| .IX Item "-maout" |
| Legacy no-op option only recognized with the cris-axis-aout target. |
| .IP "\fB\-melf\fR" 4 |
| .IX Item "-melf" |
| Legacy no-op option only recognized with the cris-axis-elf and |
| cris-axis-linux-gnu targets. |
| .IP "\fB\-melinux\fR" 4 |
| .IX Item "-melinux" |
| Only recognized with the cris-axis-aout target, where it selects a |
| GNU/linux\-like multilib, include files and instruction set for |
| \&\fB\-march=v8\fR. |
| .IP "\fB\-mlinux\fR" 4 |
| .IX Item "-mlinux" |
| Legacy no-op option only recognized with the cris-axis-linux-gnu target. |
| .IP "\fB\-sim\fR" 4 |
| .IX Item "-sim" |
| This option, recognized for the cris-axis-aout and cris-axis-elf arranges |
| to link with input-output functions from a simulator library. Code, |
| initialized data and zero-initialized data are allocated consecutively. |
| .IP "\fB\-sim2\fR" 4 |
| .IX Item "-sim2" |
| Like \fB\-sim\fR, but pass linker options to locate initialized data at |
| 0x40000000 and zero-initialized data at 0x80000000. |
| .PP |
| \fI\s-1CRX\s0 Options\fR |
| .IX Subsection "CRX Options" |
| .PP |
| These options are defined specifically for the \s-1CRX\s0 ports. |
| .IP "\fB\-mmac\fR" 4 |
| .IX Item "-mmac" |
| Enable the use of multiply-accumulate instructions. Disabled by default. |
| .IP "\fB\-mpush\-args\fR" 4 |
| .IX Item "-mpush-args" |
| Push instructions will be used to pass outgoing arguments when functions |
| are called. Enabled by default. |
| .PP |
| \fIDarwin Options\fR |
| .IX Subsection "Darwin Options" |
| .PP |
| These options are defined for all architectures running the Darwin operating |
| system. |
| .PP |
| \&\s-1FSF\s0 \s-1GCC\s0 on Darwin does not create \*(L"fat\*(R" object files; it will create |
| an object file for the single architecture that it was built to |
| target. Apple's \s-1GCC\s0 on Darwin does create \*(L"fat\*(R" files if multiple |
| \&\fB\-arch\fR options are used; it does so by running the compiler or |
| linker multiple times and joining the results together with |
| \&\fIlipo\fR. |
| .PP |
| The subtype of the file created (like \fBppc7400\fR or \fBppc970\fR or |
| \&\fBi686\fR) is determined by the flags that specify the \s-1ISA\s0 |
| that \s-1GCC\s0 is targetting, like \fB\-mcpu\fR or \fB\-march\fR. The |
| \&\fB\-force_cpusubtype_ALL\fR option can be used to override this. |
| .PP |
| The Darwin tools vary in their behavior when presented with an \s-1ISA\s0 |
| mismatch. The assembler, \fIas\fR, will only permit instructions to |
| be used that are valid for the subtype of the file it is generating, |
| so you cannot put 64\-bit instructions in an \fBppc750\fR object file. |
| The linker for shared libraries, \fI/usr/bin/libtool\fR, will fail |
| and print an error if asked to create a shared library with a less |
| restrictive subtype than its input files (for instance, trying to put |
| a \fBppc970\fR object file in a \fBppc7400\fR library). The linker |
| for executables, \fIld\fR, will quietly give the executable the most |
| restrictive subtype of any of its input files. |
| .IP "\fB\-F\fR\fIdir\fR" 4 |
| .IX Item "-Fdir" |
| Add the framework directory \fIdir\fR to the head of the list of |
| directories to be searched for header files. These directories are |
| interleaved with those specified by \fB\-I\fR options and are |
| scanned in a left-to-right order. |
| .Sp |
| A framework directory is a directory with frameworks in it. A |
| framework is a directory with a \fB\*(L"Headers\*(R"\fR and/or |
| \&\fB\*(L"PrivateHeaders\*(R"\fR directory contained directly in it that ends |
| in \fB\*(L".framework\*(R"\fR. The name of a framework is the name of this |
| directory excluding the \fB\*(L".framework\*(R"\fR. Headers associated with |
| the framework are found in one of those two directories, with |
| \&\fB\*(L"Headers\*(R"\fR being searched first. A subframework is a framework |
| directory that is in a framework's \fB\*(L"Frameworks\*(R"\fR directory. |
| Includes of subframework headers can only appear in a header of a |
| framework that contains the subframework, or in a sibling subframework |
| header. Two subframeworks are siblings if they occur in the same |
| framework. A subframework should not have the same name as a |
| framework, a warning will be issued if this is violated. Currently a |
| subframework cannot have subframeworks, in the future, the mechanism |
| may be extended to support this. The standard frameworks can be found |
| in \fB\*(L"/System/Library/Frameworks\*(R"\fR and |
| \&\fB\*(L"/Library/Frameworks\*(R"\fR. An example include looks like |
| \&\f(CW\*(C`#include <Framework/header.h>\*(C'\fR, where \fBFramework\fR denotes |
| the name of the framework and header.h is found in the |
| \&\fB\*(L"PrivateHeaders\*(R"\fR or \fB\*(L"Headers\*(R"\fR directory. |
| .IP "\fB\-gused\fR" 4 |
| .IX Item "-gused" |
| Emit debugging information for symbols that are used. For \s-1STABS\s0 |
| debugging format, this enables \fB\-feliminate\-unused\-debug\-symbols\fR. |
| This is by default \s-1ON\s0. |
| .IP "\fB\-gfull\fR" 4 |
| .IX Item "-gfull" |
| Emit debugging information for all symbols and types. |
| .IP "\fB\-mmacosx\-version\-min=\fR\fIversion\fR" 4 |
| .IX Item "-mmacosx-version-min=version" |
| The earliest version of MacOS X that this executable will run on |
| is \fIversion\fR. Typical values of \fIversion\fR include \f(CW10.1\fR, |
| \&\f(CW10.2\fR, and \f(CW10.3.9\fR. |
| .Sp |
| The default for this option is to make choices that seem to be most |
| useful. |
| .IP "\fB\-mkernel\fR" 4 |
| .IX Item "-mkernel" |
| Enable kernel development mode. The \fB\-mkernel\fR option sets |
| \&\fB\-static\fR, \fB\-fno\-common\fR, \fB\-fno\-cxa\-atexit\fR, |
| \&\fB\-fno\-exceptions\fR, \fB\-fno\-non\-call\-exceptions\fR, |
| \&\fB\-fapple\-kext\fR, \fB\-fno\-weak\fR and \fB\-fno\-rtti\fR where |
| applicable. This mode also sets \fB\-mno\-altivec\fR, |
| \&\fB\-msoft\-float\fR, \fB\-fno\-builtin\fR and |
| \&\fB\-mlong\-branch\fR for PowerPC targets. |
| .IP "\fB\-mone\-byte\-bool\fR" 4 |
| .IX Item "-mone-byte-bool" |
| Override the defaults for \fBbool\fR so that \fBsizeof(bool)==1\fR. |
| By default \fBsizeof(bool)\fR is \fB4\fR when compiling for |
| Darwin/PowerPC and \fB1\fR when compiling for Darwin/x86, so this |
| option has no effect on x86. |
| .Sp |
| \&\fBWarning:\fR The \fB\-mone\-byte\-bool\fR switch causes \s-1GCC\s0 |
| to generate code that is not binary compatible with code generated |
| without that switch. Using this switch may require recompiling all |
| other modules in a program, including system libraries. Use this |
| switch to conform to a non-default data model. |
| .IP "\fB\-mfix\-and\-continue\fR" 4 |
| .IX Item "-mfix-and-continue" |
| .PD 0 |
| .IP "\fB\-ffix\-and\-continue\fR" 4 |
| .IX Item "-ffix-and-continue" |
| .IP "\fB\-findirect\-data\fR" 4 |
| .IX Item "-findirect-data" |
| .PD |
| Generate code suitable for fast turn around development. Needed to |
| enable gdb to dynamically load \f(CW\*(C`.o\*(C'\fR files into already running |
| programs. \fB\-findirect\-data\fR and \fB\-ffix\-and\-continue\fR |
| are provided for backwards compatibility. |
| .IP "\fB\-all_load\fR" 4 |
| .IX Item "-all_load" |
| Loads all members of static archive libraries. |
| See man \fIld\fR\|(1) for more information. |
| .IP "\fB\-arch_errors_fatal\fR" 4 |
| .IX Item "-arch_errors_fatal" |
| Cause the errors having to do with files that have the wrong architecture |
| to be fatal. |
| .IP "\fB\-bind_at_load\fR" 4 |
| .IX Item "-bind_at_load" |
| Causes the output file to be marked such that the dynamic linker will |
| bind all undefined references when the file is loaded or launched. |
| .IP "\fB\-bundle\fR" 4 |
| .IX Item "-bundle" |
| Produce a Mach-o bundle format file. |
| See man \fIld\fR\|(1) for more information. |
| .IP "\fB\-bundle_loader\fR \fIexecutable\fR" 4 |
| .IX Item "-bundle_loader executable" |
| This option specifies the \fIexecutable\fR that will be loading the build |
| output file being linked. See man \fIld\fR\|(1) for more information. |
| .IP "\fB\-dynamiclib\fR" 4 |
| .IX Item "-dynamiclib" |
| When passed this option, \s-1GCC\s0 will produce a dynamic library instead of |
| an executable when linking, using the Darwin \fIlibtool\fR command. |
| .IP "\fB\-force_cpusubtype_ALL\fR" 4 |
| .IX Item "-force_cpusubtype_ALL" |
| This causes \s-1GCC\s0's output file to have the \fI\s-1ALL\s0\fR subtype, instead of |
| one controlled by the \fB\-mcpu\fR or \fB\-march\fR option. |
| .IP "\fB\-allowable_client\fR \fIclient_name\fR" 4 |
| .IX Item "-allowable_client client_name" |
| .PD 0 |
| .IP "\fB\-client_name\fR" 4 |
| .IX Item "-client_name" |
| .IP "\fB\-compatibility_version\fR" 4 |
| .IX Item "-compatibility_version" |
| .IP "\fB\-current_version\fR" 4 |
| .IX Item "-current_version" |
| .IP "\fB\-dead_strip\fR" 4 |
| .IX Item "-dead_strip" |
| .IP "\fB\-dependency\-file\fR" 4 |
| .IX Item "-dependency-file" |
| .IP "\fB\-dylib_file\fR" 4 |
| .IX Item "-dylib_file" |
| .IP "\fB\-dylinker_install_name\fR" 4 |
| .IX Item "-dylinker_install_name" |
| .IP "\fB\-dynamic\fR" 4 |
| .IX Item "-dynamic" |
| .IP "\fB\-exported_symbols_list\fR" 4 |
| .IX Item "-exported_symbols_list" |
| .IP "\fB\-filelist\fR" 4 |
| .IX Item "-filelist" |
| .IP "\fB\-flat_namespace\fR" 4 |
| .IX Item "-flat_namespace" |
| .IP "\fB\-force_flat_namespace\fR" 4 |
| .IX Item "-force_flat_namespace" |
| .IP "\fB\-headerpad_max_install_names\fR" 4 |
| .IX Item "-headerpad_max_install_names" |
| .IP "\fB\-image_base\fR" 4 |
| .IX Item "-image_base" |
| .IP "\fB\-init\fR" 4 |
| .IX Item "-init" |
| .IP "\fB\-install_name\fR" 4 |
| .IX Item "-install_name" |
| .IP "\fB\-keep_private_externs\fR" 4 |
| .IX Item "-keep_private_externs" |
| .IP "\fB\-multi_module\fR" 4 |
| .IX Item "-multi_module" |
| .IP "\fB\-multiply_defined\fR" 4 |
| .IX Item "-multiply_defined" |
| .IP "\fB\-multiply_defined_unused\fR" 4 |
| .IX Item "-multiply_defined_unused" |
| .IP "\fB\-noall_load\fR" 4 |
| .IX Item "-noall_load" |
| .IP "\fB\-no_dead_strip_inits_and_terms\fR" 4 |
| .IX Item "-no_dead_strip_inits_and_terms" |
| .IP "\fB\-nofixprebinding\fR" 4 |
| .IX Item "-nofixprebinding" |
| .IP "\fB\-nomultidefs\fR" 4 |
| .IX Item "-nomultidefs" |
| .IP "\fB\-noprebind\fR" 4 |
| .IX Item "-noprebind" |
| .IP "\fB\-noseglinkedit\fR" 4 |
| .IX Item "-noseglinkedit" |
| .IP "\fB\-pagezero_size\fR" 4 |
| .IX Item "-pagezero_size" |
| .IP "\fB\-prebind\fR" 4 |
| .IX Item "-prebind" |
| .IP "\fB\-prebind_all_twolevel_modules\fR" 4 |
| .IX Item "-prebind_all_twolevel_modules" |
| .IP "\fB\-private_bundle\fR" 4 |
| .IX Item "-private_bundle" |
| .IP "\fB\-read_only_relocs\fR" 4 |
| .IX Item "-read_only_relocs" |
| .IP "\fB\-sectalign\fR" 4 |
| .IX Item "-sectalign" |
| .IP "\fB\-sectobjectsymbols\fR" 4 |
| .IX Item "-sectobjectsymbols" |
| .IP "\fB\-whyload\fR" 4 |
| .IX Item "-whyload" |
| .IP "\fB\-seg1addr\fR" 4 |
| .IX Item "-seg1addr" |
| .IP "\fB\-sectcreate\fR" 4 |
| .IX Item "-sectcreate" |
| .IP "\fB\-sectobjectsymbols\fR" 4 |
| .IX Item "-sectobjectsymbols" |
| .IP "\fB\-sectorder\fR" 4 |
| .IX Item "-sectorder" |
| .IP "\fB\-segaddr\fR" 4 |
| .IX Item "-segaddr" |
| .IP "\fB\-segs_read_only_addr\fR" 4 |
| .IX Item "-segs_read_only_addr" |
| .IP "\fB\-segs_read_write_addr\fR" 4 |
| .IX Item "-segs_read_write_addr" |
| .IP "\fB\-seg_addr_table\fR" 4 |
| .IX Item "-seg_addr_table" |
| .IP "\fB\-seg_addr_table_filename\fR" 4 |
| .IX Item "-seg_addr_table_filename" |
| .IP "\fB\-seglinkedit\fR" 4 |
| .IX Item "-seglinkedit" |
| .IP "\fB\-segprot\fR" 4 |
| .IX Item "-segprot" |
| .IP "\fB\-segs_read_only_addr\fR" 4 |
| .IX Item "-segs_read_only_addr" |
| .IP "\fB\-segs_read_write_addr\fR" 4 |
| .IX Item "-segs_read_write_addr" |
| .IP "\fB\-single_module\fR" 4 |
| .IX Item "-single_module" |
| .IP "\fB\-static\fR" 4 |
| .IX Item "-static" |
| .IP "\fB\-sub_library\fR" 4 |
| .IX Item "-sub_library" |
| .IP "\fB\-sub_umbrella\fR" 4 |
| .IX Item "-sub_umbrella" |
| .IP "\fB\-twolevel_namespace\fR" 4 |
| .IX Item "-twolevel_namespace" |
| .IP "\fB\-umbrella\fR" 4 |
| .IX Item "-umbrella" |
| .IP "\fB\-undefined\fR" 4 |
| .IX Item "-undefined" |
| .IP "\fB\-unexported_symbols_list\fR" 4 |
| .IX Item "-unexported_symbols_list" |
| .IP "\fB\-weak_reference_mismatches\fR" 4 |
| .IX Item "-weak_reference_mismatches" |
| .IP "\fB\-whatsloaded\fR" 4 |
| .IX Item "-whatsloaded" |
| .PD |
| These options are passed to the Darwin linker. The Darwin linker man page |
| describes them in detail. |
| .PP |
| \fI\s-1DEC\s0 Alpha Options\fR |
| .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 \fIlibgcc.a\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 preprocessor macro \f(CW\*(C`_IEEE_FP\*(C'\fR is |
| defined during compilation. 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. In addition to |
| \&\f(CW\*(C`_IEEE_FP\*(C'\fR, \f(CW\*(C`_IEEE_FP_EXACT\*(C'\fR is defined as a preprocessor |
| macro. On some Alpha implementations the resulting code may execute |
| significantly slower than the code generated by default. Since there is |
| very little code that depends on the \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 \fBu\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\-mfix\fR" 4 |
| .IX Item "-mfix" |
| .IP "\fB\-mno\-fix\fR" 4 |
| .IX Item "-mno-fix" |
| .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, \s-1FIX\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\-mfloat\-vax\fR" 4 |
| .IX Item "-mfloat-vax" |
| .PD 0 |
| .IP "\fB\-mfloat\-ieee\fR" 4 |
| .IX Item "-mfloat-ieee" |
| .PD |
| Generate code that uses (does not use) \s-1VAX\s0 F and G floating point |
| arithmetic instead of \s-1IEEE\s0 single and double precision. |
| .IP "\fB\-mexplicit\-relocs\fR" 4 |
| .IX Item "-mexplicit-relocs" |
| .PD 0 |
| .IP "\fB\-mno\-explicit\-relocs\fR" 4 |
| .IX Item "-mno-explicit-relocs" |
| .PD |
| Older Alpha assemblers provided no way to generate symbol relocations |
| except via assembler macros. Use of these macros does not allow |
| optimal instruction scheduling. \s-1GNU\s0 binutils as of version 2.12 |
| supports a new syntax that allows the compiler to explicitly mark |
| which relocations should apply to which instructions. This option |
| is mostly useful for debugging, as \s-1GCC\s0 detects the capabilities of |
| the assembler when it is built and sets the default accordingly. |
| .IP "\fB\-msmall\-data\fR" 4 |
| .IX Item "-msmall-data" |
| .PD 0 |
| .IP "\fB\-mlarge\-data\fR" 4 |
| .IX Item "-mlarge-data" |
| .PD |
| When \fB\-mexplicit\-relocs\fR is in effect, static data is |
| accessed via \fIgp-relative\fR relocations. When \fB\-msmall\-data\fR |
| is used, objects 8 bytes long or smaller are placed in a \fIsmall data area\fR |
| (the \f(CW\*(C`.sdata\*(C'\fR and \f(CW\*(C`.sbss\*(C'\fR sections) and are accessed via |
| 16\-bit relocations off of the \f(CW$gp\fR register. This limits the |
| size of the small data area to 64KB, but allows the variables to be |
| directly accessed via a single instruction. |
| .Sp |
| The default is \fB\-mlarge\-data\fR. With this option the data area |
| is limited to just below 2GB. Programs that require more than 2GB of |
| data must use \f(CW\*(C`malloc\*(C'\fR or \f(CW\*(C`mmap\*(C'\fR to allocate the data in the |
| heap instead of in the program's data segment. |
| .Sp |
| When generating code for shared libraries, \fB\-fpic\fR implies |
| \&\fB\-msmall\-data\fR and \fB\-fPIC\fR implies \fB\-mlarge\-data\fR. |
| .IP "\fB\-msmall\-text\fR" 4 |
| .IX Item "-msmall-text" |
| .PD 0 |
| .IP "\fB\-mlarge\-text\fR" 4 |
| .IX Item "-mlarge-text" |
| .PD |
| When \fB\-msmall\-text\fR is used, the compiler assumes that the |
| code of the entire program (or shared library) fits in 4MB, and is |
| thus reachable with a branch instruction. When \fB\-msmall\-data\fR |
| is used, the compiler can assume that all local symbols share the |
| same \f(CW$gp\fR value, and thus reduce the number of instructions |
| required for a function call from 4 to 1. |
| .Sp |
| The default is \fB\-mlarge\-text\fR. |
| .IP "\fB\-mcpu=\fR\fIcpu_type\fR" 4 |
| .IX Item "-mcpu=cpu_type" |
| Set the instruction 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, \s-1EV5\s0 and \s-1EV6\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 "\fBev45\fR" 4 |
| .IX Item "ev45" |
| .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-1EV6\s0 and supports the \s-1BWX\s0, \s-1FIX\s0, and \s-1MAX\s0 extensions. |
| .IP "\fBev67\fR" 4 |
| .IX Item "ev67" |
| .PD 0 |
| .IP "\fB21264a\fR" 4 |
| .IX Item "21264a" |
| .PD |
| Schedules as an \s-1EV6\s0 and supports the \s-1BWX\s0, \s-1CIX\s0, \s-1FIX\s0, and \s-1MAX\s0 extensions. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-mtune=\fR\fIcpu_type\fR" 4 |
| .IX Item "-mtune=cpu_type" |
| Set only the instruction scheduling parameters for machine type |
| \&\fIcpu_type\fR. The instruction set is not changed. |
| .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 |
| \&\*(L"typical\*(R" \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 |
| \fI\s-1DEC\s0 Alpha/VMS Options\fR |
| .IX Subsection "DEC Alpha/VMS Options" |
| .PP |
| These \fB\-m\fR options are defined for the \s-1DEC\s0 Alpha/VMS implementations: |
| .IP "\fB\-mvms\-return\-codes\fR" 4 |
| .IX Item "-mvms-return-codes" |
| Return \s-1VMS\s0 condition codes from main. The default is to return \s-1POSIX\s0 |
| style condition (e.g. error) codes. |
| .PP |
| \fI\s-1FRV\s0 Options\fR |
| .IX Subsection "FRV Options" |
| .IP "\fB\-mgpr\-32\fR" 4 |
| .IX Item "-mgpr-32" |
| Only use the first 32 general purpose registers. |
| .IP "\fB\-mgpr\-64\fR" 4 |
| .IX Item "-mgpr-64" |
| Use all 64 general purpose registers. |
| .IP "\fB\-mfpr\-32\fR" 4 |
| .IX Item "-mfpr-32" |
| Use only the first 32 floating point registers. |
| .IP "\fB\-mfpr\-64\fR" 4 |
| .IX Item "-mfpr-64" |
| Use all 64 floating point registers |
| .IP "\fB\-mhard\-float\fR" 4 |
| .IX Item "-mhard-float" |
| Use hardware instructions for floating point operations. |
| .IP "\fB\-msoft\-float\fR" 4 |
| .IX Item "-msoft-float" |
| Use library routines for floating point operations. |
| .IP "\fB\-malloc\-cc\fR" 4 |
| .IX Item "-malloc-cc" |
| Dynamically allocate condition code registers. |
| .IP "\fB\-mfixed\-cc\fR" 4 |
| .IX Item "-mfixed-cc" |
| Do not try to dynamically allocate condition code registers, only |
| use \f(CW\*(C`icc0\*(C'\fR and \f(CW\*(C`fcc0\*(C'\fR. |
| .IP "\fB\-mdword\fR" 4 |
| .IX Item "-mdword" |
| Change \s-1ABI\s0 to use double word insns. |
| .IP "\fB\-mno\-dword\fR" 4 |
| .IX Item "-mno-dword" |
| Do not use double word instructions. |
| .IP "\fB\-mdouble\fR" 4 |
| .IX Item "-mdouble" |
| Use floating point double instructions. |
| .IP "\fB\-mno\-double\fR" 4 |
| .IX Item "-mno-double" |
| Do not use floating point double instructions. |
| .IP "\fB\-mmedia\fR" 4 |
| .IX Item "-mmedia" |
| Use media instructions. |
| .IP "\fB\-mno\-media\fR" 4 |
| .IX Item "-mno-media" |
| Do not use media instructions. |
| .IP "\fB\-mmuladd\fR" 4 |
| .IX Item "-mmuladd" |
| Use multiply and add/subtract instructions. |
| .IP "\fB\-mno\-muladd\fR" 4 |
| .IX Item "-mno-muladd" |
| Do not use multiply and add/subtract instructions. |
| .IP "\fB\-mfdpic\fR" 4 |
| .IX Item "-mfdpic" |
| Select the \s-1FDPIC\s0 \s-1ABI\s0, that uses function descriptors to represent |
| pointers to functions. Without any PIC/PIE\-related options, it |
| implies \fB\-fPIE\fR. With \fB\-fpic\fR or \fB\-fpie\fR, it |
| assumes \s-1GOT\s0 entries and small data are within a 12\-bit range from the |
| \&\s-1GOT\s0 base address; with \fB\-fPIC\fR or \fB\-fPIE\fR, \s-1GOT\s0 offsets |
| are computed with 32 bits. |
| .IP "\fB\-minline\-plt\fR" 4 |
| .IX Item "-minline-plt" |
| Enable inlining of \s-1PLT\s0 entries in function calls to functions that are |
| not known to bind locally. It has no effect without \fB\-mfdpic\fR. |
| It's enabled by default if optimizing for speed and compiling for |
| shared libraries (i.e., \fB\-fPIC\fR or \fB\-fpic\fR), or when an |
| optimization option such as \fB\-O3\fR or above is present in the |
| command line. |
| .IP "\fB\-mTLS\fR" 4 |
| .IX Item "-mTLS" |
| Assume a large \s-1TLS\s0 segment when generating thread-local code. |
| .IP "\fB\-mtls\fR" 4 |
| .IX Item "-mtls" |
| Do not assume a large \s-1TLS\s0 segment when generating thread-local code. |
| .IP "\fB\-mgprel\-ro\fR" 4 |
| .IX Item "-mgprel-ro" |
| Enable the use of \f(CW\*(C`GPREL\*(C'\fR relocations in the \s-1FDPIC\s0 \s-1ABI\s0 for data |
| that is known to be in read-only sections. It's enabled by default, |
| except for \fB\-fpic\fR or \fB\-fpie\fR: even though it may help |
| make the global offset table smaller, it trades 1 instruction for 4. |
| With \fB\-fPIC\fR or \fB\-fPIE\fR, it trades 3 instructions for 4, |
| one of which may be shared by multiple symbols, and it avoids the need |
| for a \s-1GOT\s0 entry for the referenced symbol, so it's more likely to be a |
| win. If it is not, \fB\-mno\-gprel\-ro\fR can be used to disable it. |
| .IP "\fB\-multilib\-library\-pic\fR" 4 |
| .IX Item "-multilib-library-pic" |
| Link with the (library, not \s-1FD\s0) pic libraries. It's implied by |
| \&\fB\-mlibrary\-pic\fR, as well as by \fB\-fPIC\fR and |
| \&\fB\-fpic\fR without \fB\-mfdpic\fR. You should never have to use |
| it explicitly. |
| .IP "\fB\-mlinked\-fp\fR" 4 |
| .IX Item "-mlinked-fp" |
| Follow the \s-1EABI\s0 requirement of always creating a frame pointer whenever |
| a stack frame is allocated. This option is enabled by default and can |
| be disabled with \fB\-mno\-linked\-fp\fR. |
| .IP "\fB\-mlong\-calls\fR" 4 |
| .IX Item "-mlong-calls" |
| Use indirect addressing to call functions outside the current |
| compilation unit. This allows the functions to be placed anywhere |
| within the 32\-bit address space. |
| .IP "\fB\-malign\-labels\fR" 4 |
| .IX Item "-malign-labels" |
| Try to align labels to an 8\-byte boundary by inserting nops into the |
| previous packet. This option only has an effect when \s-1VLIW\s0 packing |
| is enabled. It doesn't create new packets; it merely adds nops to |
| existing ones. |
| .IP "\fB\-mlibrary\-pic\fR" 4 |
| .IX Item "-mlibrary-pic" |
| Generate position-independent \s-1EABI\s0 code. |
| .IP "\fB\-macc\-4\fR" 4 |
| .IX Item "-macc-4" |
| Use only the first four media accumulator registers. |
| .IP "\fB\-macc\-8\fR" 4 |
| .IX Item "-macc-8" |
| Use all eight media accumulator registers. |
| .IP "\fB\-mpack\fR" 4 |
| .IX Item "-mpack" |
| Pack \s-1VLIW\s0 instructions. |
| .IP "\fB\-mno\-pack\fR" 4 |
| .IX Item "-mno-pack" |
| Do not pack \s-1VLIW\s0 instructions. |
| .IP "\fB\-mno\-eflags\fR" 4 |
| .IX Item "-mno-eflags" |
| Do not mark \s-1ABI\s0 switches in e_flags. |
| .IP "\fB\-mcond\-move\fR" 4 |
| .IX Item "-mcond-move" |
| Enable the use of conditional-move instructions (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-cond\-move\fR" 4 |
| .IX Item "-mno-cond-move" |
| Disable the use of conditional-move instructions. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mscc\fR" 4 |
| .IX Item "-mscc" |
| Enable the use of conditional set instructions (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-scc\fR" 4 |
| .IX Item "-mno-scc" |
| Disable the use of conditional set instructions. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mcond\-exec\fR" 4 |
| .IX Item "-mcond-exec" |
| Enable the use of conditional execution (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-cond\-exec\fR" 4 |
| .IX Item "-mno-cond-exec" |
| Disable the use of conditional execution. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mvliw\-branch\fR" 4 |
| .IX Item "-mvliw-branch" |
| Run a pass to pack branches into \s-1VLIW\s0 instructions (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-vliw\-branch\fR" 4 |
| .IX Item "-mno-vliw-branch" |
| Do not run a pass to pack branches into \s-1VLIW\s0 instructions. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mmulti\-cond\-exec\fR" 4 |
| .IX Item "-mmulti-cond-exec" |
| Enable optimization of \f(CW\*(C`&&\*(C'\fR and \f(CW\*(C`||\*(C'\fR in conditional execution |
| (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-multi\-cond\-exec\fR" 4 |
| .IX Item "-mno-multi-cond-exec" |
| Disable optimization of \f(CW\*(C`&&\*(C'\fR and \f(CW\*(C`||\*(C'\fR in conditional execution. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mnested\-cond\-exec\fR" 4 |
| .IX Item "-mnested-cond-exec" |
| Enable nested conditional execution optimizations (default). |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-mno\-nested\-cond\-exec\fR" 4 |
| .IX Item "-mno-nested-cond-exec" |
| Disable nested conditional execution optimizations. |
| .Sp |
| This switch is mainly for debugging the compiler and will likely be removed |
| in a future version. |
| .IP "\fB\-moptimize\-membar\fR" 4 |
| .IX Item "-moptimize-membar" |
| This switch removes redundant \f(CW\*(C`membar\*(C'\fR instructions from the |
| compiler generated code. It is enabled by default. |
| .IP "\fB\-mno\-optimize\-membar\fR" 4 |
| .IX Item "-mno-optimize-membar" |
| This switch disables the automatic removal of redundant \f(CW\*(C`membar\*(C'\fR |
| instructions from the generated code. |
| .IP "\fB\-mtomcat\-stats\fR" 4 |
| .IX Item "-mtomcat-stats" |
| Cause gas to print out tomcat statistics. |
| .IP "\fB\-mcpu=\fR\fIcpu\fR" 4 |
| .IX Item "-mcpu=cpu" |
| Select the processor type for which to generate code. Possible values are |
| \&\fBfrv\fR, \fBfr550\fR, \fBtomcat\fR, \fBfr500\fR, \fBfr450\fR, |
| \&\fBfr405\fR, \fBfr400\fR, \fBfr300\fR and \fBsimple\fR. |
| .PP |
| \fIGNU/Linux Options\fR |
| .IX Subsection "GNU/Linux Options" |
| .PP |
| These \fB\-m\fR options are defined for GNU/Linux targets: |
| .IP "\fB\-mglibc\fR" 4 |
| .IX Item "-mglibc" |
| Use the \s-1GNU\s0 C library instead of uClibc. This is the default except |
| on \fB*\-*\-linux\-*uclibc*\fR targets. |
| .IP "\fB\-muclibc\fR" 4 |
| .IX Item "-muclibc" |
| Use uClibc instead of the \s-1GNU\s0 C library. This is the default on |
| \&\fB*\-*\-linux\-*uclibc*\fR targets. |
| .PP |
| \fIH8/300 Options\fR |
| .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 H8S. |
| .IP "\fB\-mn\fR" 4 |
| .IX Item "-mn" |
| Generate code for the H8S and H8/300H in the normal mode. This switch |
| must be used either with \fB\-mh\fR or \fB\-ms\fR. |
| .IP "\fB\-ms2600\fR" 4 |
| .IX Item "-ms2600" |
| Generate code for the H8S/2600. This switch must be used with \fB\-ms\fR. |
| .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 H8S, use the same alignment rules as for the H8/300. |
| The default for the H8/300H and H8S is to align longs and floats on 4 |
| byte boundaries. |
| \&\fB\-malign\-300\fR causes them to be aligned on 2 byte boundaries. |
| This option has no effect on the H8/300. |
| .PP |
| \fI\s-1HPPA\s0 Options\fR |
| .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 HP-UX system to determine the proper |
| architecture option for your machine. Code compiled for lower numbered |
| architectures will run on higher numbered architectures, but not the |
| other way around. |
| .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 \fB\-march=1.0\fR, \fB\-march=1.1\fR, and \fB\-march=2.0\fR 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\-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. |
| .IP "\fB\-mlong\-load\-store\fR" 4 |
| .IX Item "-mlong-load-store" |
| Generate 3\-instruction load and store sequences as sometimes required by |
| the HP-UX 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, \fB7300\fR and \fB8000\fR. Refer |
| to \fI/usr/lib/sched.models\fR on an HP-UX system to determine the |
| proper scheduling option for your machine. The default scheduling is |
| \&\fB8000\fR. |
| .IP "\fB\-mlinker\-opt\fR" 4 |
| .IX Item "-mlinker-opt" |
| Enable the optimization pass in the HP-UX linker. Note this makes symbolic |
| debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9 |
| linkers in which they give bogus error messages when linking some programs. |
| .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. |
| .IP "\fB\-msio\fR" 4 |
| .IX Item "-msio" |
| Generate the predefine, \f(CW\*(C`_SIO\*(C'\fR, for server \s-1IO\s0. The default is |
| \&\fB\-mwsio\fR. This generates the predefines, \f(CW\*(C`_\|_hp9000s700\*(C'\fR, |
| \&\f(CW\*(C`_\|_hp9000s700_\|_\*(C'\fR and \f(CW\*(C`_WSIO\*(C'\fR, for workstation \s-1IO\s0. These |
| options are available under HP-UX and \s-1HI\-UX\s0. |
| .IP "\fB\-mgnu\-ld\fR" 4 |
| .IX Item "-mgnu-ld" |
| Use \s-1GNU\s0 ld specific options. This passes \fB\-shared\fR to ld when |
| building a shared library. It is the default when \s-1GCC\s0 is configured, |
| explicitly or implicitly, with the \s-1GNU\s0 linker. This option does not |
| have any affect on which ld is called, it only changes what parameters |
| are passed to that ld. The ld that is called is determined by the |
| \&\fB\-\-with\-ld\fR configure option, \s-1GCC\s0's program search path, and |
| finally by the user's \fB\s-1PATH\s0\fR. The linker used by \s-1GCC\s0 can be printed |
| using \fBwhich `gcc \-print\-prog\-name=ld`\fR. This option is only available |
| on the 64 bit HP-UX \s-1GCC\s0, i.e. configured with \fBhppa*64*\-*\-hpux*\fR. |
| .IP "\fB\-mhp\-ld\fR" 4 |
| .IX Item "-mhp-ld" |
| Use \s-1HP\s0 ld specific options. This passes \fB\-b\fR to ld when building |
| a shared library and passes \fB+Accept TypeMismatch\fR to ld on all |
| links. It is the default when \s-1GCC\s0 is configured, explicitly or |
| implicitly, with the \s-1HP\s0 linker. This option does not have any affect on |
| which ld is called, it only changes what parameters are passed to that |
| ld. The ld that is called is determined by the \fB\-\-with\-ld\fR |
| configure option, \s-1GCC\s0's program search path, and finally by the user's |
| \&\fB\s-1PATH\s0\fR. The linker used by \s-1GCC\s0 can be printed using \fBwhich |
| `gcc \-print\-prog\-name=ld`\fR. This option is only available on the 64 bit |
| HP-UX \s-1GCC\s0, i.e. configured with \fBhppa*64*\-*\-hpux*\fR. |
| .IP "\fB\-mlong\-calls\fR" 4 |
| .IX Item "-mlong-calls" |
| Generate code that uses long call sequences. This ensures that a call |
| is always able to reach linker generated stubs. The default is to generate |
| long calls only when the distance from the call site to the beginning |
| of the function or translation unit, as the case may be, exceeds a |
| predefined limit set by the branch type being used. The limits for |
| normal calls are 7,600,000 and 240,000 bytes, respectively for the |
| \&\s-1PA\s0 2.0 and \s-1PA\s0 1.X architectures. Sibcalls are always limited at |
| 240,000 bytes. |
| .Sp |
| Distances are measured from the beginning of functions when using the |
| \&\fB\-ffunction\-sections\fR option, or when using the \fB\-mgas\fR |
| and \fB\-mno\-portable\-runtime\fR options together under HP-UX with |
| the \s-1SOM\s0 linker. |
| .Sp |
| It is normally not desirable to use this option as it will degrade |
| performance. However, it may be useful in large applications, |
| particularly when partial linking is used to build the application. |
| .Sp |
| The types of long calls used depends on the capabilities of the |
| assembler and linker, and the type of code being generated. The |
| impact on systems that support long absolute calls, and long pic |
| symbol-difference or pc-relative calls should be relatively small. |
| However, an indirect call is used on 32\-bit \s-1ELF\s0 systems in pic code |
| and it is quite long. |
| .IP "\fB\-munix=\fR\fIunix-std\fR" 4 |
| .IX Item "-munix=unix-std" |
| Generate compiler predefines and select a startfile for the specified |
| \&\s-1UNIX\s0 standard. The choices for \fIunix-std\fR are \fB93\fR, \fB95\fR |
| and \fB98\fR. \fB93\fR is supported on all HP-UX versions. \fB95\fR |
| is available on HP-UX 10.10 and later. \fB98\fR is available on HP-UX |
| 11.11 and later. The default values are \fB93\fR for HP-UX 10.00, |
| \&\fB95\fR for HP-UX 10.10 though to 11.00, and \fB98\fR for HP-UX 11.11 |
| and later. |
| .Sp |
| \&\fB\-munix=93\fR provides the same predefines as \s-1GCC\s0 3.3 and 3.4. |
| \&\fB\-munix=95\fR provides additional predefines for \f(CW\*(C`XOPEN_UNIX\*(C'\fR |
| and \f(CW\*(C`_XOPEN_SOURCE_EXTENDED\*(C'\fR, and the startfile \fIunix95.o\fR. |
| \&\fB\-munix=98\fR provides additional predefines for \f(CW\*(C`_XOPEN_UNIX\*(C'\fR, |
| \&\f(CW\*(C`_XOPEN_SOURCE_EXTENDED\*(C'\fR, \f(CW\*(C`_INCLUDE_\|_STDC_A1_SOURCE\*(C'\fR and |
| \&\f(CW\*(C`_INCLUDE_XOPEN_SOURCE_500\*(C'\fR, and the startfile \fIunix98.o\fR. |
| .Sp |
| It is \fIimportant\fR to note that this option changes the interfaces |
| for various library routines. It also affects the operational behavior |
| of the C library. Thus, \fIextreme\fR care is needed in using this |
| option. |
| .Sp |
| Library code that is intended to operate with more than one \s-1UNIX\s0 |
| standard must test, set and restore the variable \fI_\|_xpg4_extended_mask\fR |
| as appropriate. Most \s-1GNU\s0 software doesn't provide this capability. |
| .IP "\fB\-nolibdld\fR" 4 |
| .IX Item "-nolibdld" |
| Suppress the generation of link options to search libdld.sl when the |
| \&\fB\-static\fR option is specified on HP-UX 10 and later. |
| .IP "\fB\-static\fR" 4 |
| .IX Item "-static" |
| The HP-UX implementation of setlocale in libc has a dependency on |
| libdld.sl. There isn't an archive version of libdld.sl. Thus, |
| when the \fB\-static\fR option is specified, special link options |
| are needed to resolve this dependency. |
| .Sp |
| On HP-UX 10 and later, the \s-1GCC\s0 driver adds the necessary options to |
| link with libdld.sl when the \fB\-static\fR option is specified. |
| This causes the resulting binary to be dynamic. On the 64\-bit port, |
| the linkers generate dynamic binaries by default in any case. The |
| \&\fB\-nolibdld\fR option can be used to prevent the \s-1GCC\s0 driver from |
| adding these link options. |
| .IP "\fB\-threads\fR" 4 |
| .IX Item "-threads" |
| Add support for multithreading with the \fIdce thread\fR library |
| under \s-1HP\-UX\s0. This option sets flags for both the preprocessor and |
| linker. |
| .PP |
| \fIIntel 386 and \s-1AMD\s0 x86\-64 Options\fR |
| .IX Subsection "Intel 386 and AMD x86-64 Options" |
| .PP |
| These \fB\-m\fR options are defined for the i386 and x86\-64 family of |
| computers: |
| .IP "\fB\-mtune=\fR\fIcpu-type\fR" 4 |
| .IX Item "-mtune=cpu-type" |
| Tune to \fIcpu-type\fR everything applicable about the generated code, except |
| for the \s-1ABI\s0 and the set of available instructions. The choices for |
| \&\fIcpu-type\fR are: |
| .RS 4 |
| .IP "\fIgeneric\fR" 4 |
| .IX Item "generic" |
| Produce code optimized for the most common \s-1IA32/AMD64/EM64T\s0 processors. |
| If you know the \s-1CPU\s0 on which your code will run, then you should use |
| the corresponding \fB\-mtune\fR option instead of |
| \&\fB\-mtune=generic\fR. But, if you do not know exactly what \s-1CPU\s0 users |
| of your application will have, then you should use this option. |
| .Sp |
| As new processors are deployed in the marketplace, the behavior of this |
| option will change. Therefore, if you upgrade to a newer version of |
| \&\s-1GCC\s0, the code generated option will change to reflect the processors |
| that were most common when that version of \s-1GCC\s0 was released. |
| .Sp |
| There is no \fB\-march=generic\fR option because \fB\-march\fR |
| indicates the instruction set the compiler can use, and there is no |
| generic instruction set applicable to all processors. In contrast, |
| \&\fB\-mtune\fR indicates the processor (or, in this case, collection of |
| processors) for which the code is optimized. |
| .IP "\fInative\fR" 4 |
| .IX Item "native" |
| This selects the \s-1CPU\s0 to tune for at compilation time by determining |
| the processor type of the compiling machine. Using \fB\-mtune=native\fR |
| will produce code optimized for the local machine under the constraints |
| of the selected instruction set. Using \fB\-march=native\fR will |
| enable all instruction subsets supported by the local machine (hence |
| the result might not run on different machines). |
| .IP "\fIi386\fR" 4 |
| .IX Item "i386" |
| Original Intel's i386 \s-1CPU\s0. |
| .IP "\fIi486\fR" 4 |
| .IX Item "i486" |
| Intel's i486 \s-1CPU\s0. (No scheduling is implemented for this chip.) |
| .IP "\fIi586, pentium\fR" 4 |
| .IX Item "i586, pentium" |
| Intel Pentium \s-1CPU\s0 with no \s-1MMX\s0 support. |
| .IP "\fIpentium-mmx\fR" 4 |
| .IX Item "pentium-mmx" |
| Intel PentiumMMX \s-1CPU\s0 based on Pentium core with \s-1MMX\s0 instruction set support. |
| .IP "\fIpentiumpro\fR" 4 |
| .IX Item "pentiumpro" |
| Intel PentiumPro \s-1CPU\s0. |
| .IP "\fIi686\fR" 4 |
| .IX Item "i686" |
| Same as \f(CW\*(C`generic\*(C'\fR, but when used as \f(CW\*(C`march\*(C'\fR option, PentiumPro |
| instruction set will be used, so the code will run on all i686 family chips. |
| .IP "\fIpentium2\fR" 4 |
| .IX Item "pentium2" |
| Intel Pentium2 \s-1CPU\s0 based on PentiumPro core with \s-1MMX\s0 instruction set support. |
| .IP "\fIpentium3, pentium3m\fR" 4 |
| .IX Item "pentium3, pentium3m" |
| Intel Pentium3 \s-1CPU\s0 based on PentiumPro core with \s-1MMX\s0 and \s-1SSE\s0 instruction set |
| support. |
| .IP "\fIpentium-m\fR" 4 |
| .IX Item "pentium-m" |
| Low power version of Intel Pentium3 \s-1CPU\s0 with \s-1MMX\s0, \s-1SSE\s0 and \s-1SSE2\s0 instruction set |
| support. Used by Centrino notebooks. |
| .IP "\fIpentium4, pentium4m\fR" 4 |
| .IX Item "pentium4, pentium4m" |
| Intel Pentium4 \s-1CPU\s0 with \s-1MMX\s0, \s-1SSE\s0 and \s-1SSE2\s0 instruction set support. |
| .IP "\fIprescott\fR" 4 |
| .IX Item "prescott" |
| Improved version of Intel Pentium4 \s-1CPU\s0 with \s-1MMX\s0, \s-1SSE\s0, \s-1SSE2\s0 and \s-1SSE3\s0 instruction |
| set support. |
| .IP "\fInocona\fR" 4 |
| .IX Item "nocona" |
| Improved version of Intel Pentium4 \s-1CPU\s0 with 64\-bit extensions, \s-1MMX\s0, \s-1SSE\s0, |
| \&\s-1SSE2\s0 and \s-1SSE3\s0 instruction set support. |
| .IP "\fIk6\fR" 4 |
| .IX Item "k6" |
| \&\s-1AMD\s0 K6 \s-1CPU\s0 with \s-1MMX\s0 instruction set support. |
| .IP "\fIk6\-2, k6\-3\fR" 4 |
| .IX Item "k6-2, k6-3" |
| Improved versions of \s-1AMD\s0 K6 \s-1CPU\s0 with \s-1MMX\s0 and 3dNOW! instruction set support. |
| .IP "\fIathlon, athlon-tbird\fR" 4 |
| .IX Item "athlon, athlon-tbird" |
| \&\s-1AMD\s0 Athlon \s-1CPU\s0 with \s-1MMX\s0, 3dNOW!, enhanced 3dNOW! and \s-1SSE\s0 prefetch instructions |
| support. |
| .IP "\fIathlon\-4, athlon\-xp, athlon-mp\fR" 4 |
| .IX Item "athlon-4, athlon-xp, athlon-mp" |
| Improved \s-1AMD\s0 Athlon \s-1CPU\s0 with \s-1MMX\s0, 3dNOW!, enhanced 3dNOW! and full \s-1SSE\s0 |
| instruction set support. |
| .IP "\fIk8, opteron, athlon64, athlon-fx\fR" 4 |
| .IX Item "k8, opteron, athlon64, athlon-fx" |
| \&\s-1AMD\s0 K8 core based CPUs with x86\-64 instruction set support. (This supersets |
| \&\s-1MMX\s0, \s-1SSE\s0, \s-1SSE2\s0, 3dNOW!, enhanced 3dNOW! and 64\-bit instruction set extensions.) |
| .IP "\fIwinchip\-c6\fR" 4 |
| .IX Item "winchip-c6" |
| \&\s-1IDT\s0 Winchip C6 \s-1CPU\s0, dealt in same way as i486 with additional \s-1MMX\s0 instruction |
| set support. |
| .IP "\fIwinchip2\fR" 4 |
| .IX Item "winchip2" |
| \&\s-1IDT\s0 Winchip2 \s-1CPU\s0, dealt in same way as i486 with additional \s-1MMX\s0 and 3dNOW! |
| instruction set support. |
| .IP "\fIc3\fR" 4 |
| .IX Item "c3" |
| Via C3 \s-1CPU\s0 with \s-1MMX\s0 and 3dNOW! instruction set support. (No scheduling is |
| implemented for this chip.) |
| .IP "\fIc3\-2\fR" 4 |
| .IX Item "c3-2" |
| Via C3\-2 \s-1CPU\s0 with \s-1MMX\s0 and \s-1SSE\s0 instruction set support. (No scheduling is |
| implemented for this chip.) |
| .RE |
| .RS 4 |
| .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. |
| .RE |
| .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\-mtune\fR. Moreover, |
| specifying \fB\-march=\fR\fIcpu-type\fR implies \fB\-mtune=\fR\fIcpu-type\fR. |
| .IP "\fB\-mcpu=\fR\fIcpu-type\fR" 4 |
| .IX Item "-mcpu=cpu-type" |
| A deprecated synonym for \fB\-mtune\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 |
| These options are synonyms for \fB\-mtune=i386\fR, \fB\-mtune=i486\fR, |
| \&\fB\-mtune=pentium\fR, and \fB\-mtune=pentiumpro\fR respectively. |
| These synonyms are deprecated. |
| .IP "\fB\-mfpmath=\fR\fIunit\fR" 4 |
| .IX Item "-mfpmath=unit" |
| Generate floating point arithmetics for selected unit \fIunit\fR. The choices |
| for \fIunit\fR are: |
| .RS 4 |
| .IP "\fB387\fR" 4 |
| .IX Item "387" |
| Use the standard 387 floating point coprocessor present majority of chips and |
| emulated otherwise. Code compiled with this option will run almost everywhere. |
| The temporary results are computed in 80bit precision instead of precision |
| specified by the type resulting in slightly different results compared to most |
| of other chips. See \fB\-ffloat\-store\fR for more detailed description. |
| .Sp |
| This is the default choice for i386 compiler. |
| .IP "\fBsse\fR" 4 |
| .IX Item "sse" |
| Use scalar floating point instructions present in the \s-1SSE\s0 instruction set. |
| This instruction set is supported by Pentium3 and newer chips, in the \s-1AMD\s0 line |
| by Athlon\-4, Athlon-xp and Athlon-mp chips. The earlier version of \s-1SSE\s0 |
| instruction set supports only single precision arithmetics, thus the double and |
| extended precision arithmetics is still done using 387. Later version, present |
| only in Pentium4 and the future \s-1AMD\s0 x86\-64 chips supports double precision |
| arithmetics too. |
| .Sp |
| For the i386 compiler, you need to use \fB\-march=\fR\fIcpu-type\fR, \fB\-msse\fR |
| or \fB\-msse2\fR switches to enable \s-1SSE\s0 extensions and make this option |
| effective. For the x86\-64 compiler, these extensions are enabled by default. |
| .Sp |
| The resulting code should be considerably faster in the majority of cases and avoid |
| the numerical instability problems of 387 code, but may break some existing |
| code that expects temporaries to be 80bit. |
| .Sp |
| This is the default choice for the x86\-64 compiler. |
| .IP "\fBsse,387\fR" 4 |
| .IX Item "sse,387" |
| Attempt to utilize both instruction sets at once. This effectively double the |
| amount of available registers and on chips with separate execution units for |
| 387 and \s-1SSE\s0 the execution resources too. Use this option with care, as it is |
| still experimental, because the \s-1GCC\s0 register allocator does not model separate |
| functional units well resulting in instable performance. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-masm=\fR\fIdialect\fR" 4 |
| .IX Item "-masm=dialect" |
| Output asm instructions using selected \fIdialect\fR. Supported |
| choices are \fBintel\fR or \fBatt\fR (the default one). Darwin does |
| not support \fBintel\fR. |
| .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, |
| OpenBSD and NetBSD. This option is overridden when \fB\-march\fR |
| indicates that the target cpu will always have an \s-1FPU\s0 and so the |
| instruction will not need emulation. As of revision 2.6.1, these |
| instructions are not generated unless you also use the |
| \&\fB\-funsafe\-math\-optimizations\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. |
| .Sp |
| On x86\-64, \fB\-malign\-double\fR is enabled by default. |
| .Sp |
| \&\fBWarning:\fR if you use the \fB\-malign\-double\fR switch, |
| structures containing the above types will be aligned differently than |
| the published application binary interface specifications for the 386 |
| and will not be binary compatible with structures in code compiled |
| without that switch. |
| .IP "\fB\-m96bit\-long\-double\fR" 4 |
| .IX Item "-m96bit-long-double" |
| .PD 0 |
| .IP "\fB\-m128bit\-long\-double\fR" 4 |
| .IX Item "-m128bit-long-double" |
| .PD |
| These switches control the size of \f(CW\*(C`long double\*(C'\fR type. The i386 |
| application binary interface specifies the size to be 96 bits, |
| so \fB\-m96bit\-long\-double\fR is the default in 32 bit mode. |
| .Sp |
| Modern architectures (Pentium and newer) would prefer \f(CW\*(C`long double\*(C'\fR |
| to be aligned to an 8 or 16 byte boundary. In arrays or structures |
| conforming to the \s-1ABI\s0, this would not be possible. So specifying a |
| \&\fB\-m128bit\-long\-double\fR will align \f(CW\*(C`long double\*(C'\fR |
| to a 16 byte boundary by padding the \f(CW\*(C`long double\*(C'\fR with an additional |
| 32 bit zero. |
| .Sp |
| In the x86\-64 compiler, \fB\-m128bit\-long\-double\fR is the default choice as |
| its \s-1ABI\s0 specifies that \f(CW\*(C`long double\*(C'\fR is to be aligned on 16 byte boundary. |
| .Sp |
| Notice that neither of these options enable any extra precision over the x87 |
| standard of 80 bits for a \f(CW\*(C`long double\*(C'\fR. |
| .Sp |
| \&\fBWarning:\fR if you override the default value for your target \s-1ABI\s0, the |
| structures and arrays containing \f(CW\*(C`long double\*(C'\fR variables will change |
| their size as well as function calling convention for function taking |
| \&\f(CW\*(C`long double\*(C'\fR will be modified. Hence they will not be binary |
| compatible with arrays or structures in code compiled without that switch. |
| .IP "\fB\-mmlarge\-data\-threshold=\fR\fInumber\fR" 4 |
| .IX Item "-mmlarge-data-threshold=number" |
| When \fB\-mcmodel=medium\fR is specified, the data greater than |
| \&\fIthreshold\fR are placed in large data section. This value must be the |
| same across all object linked into the binary and defaults to 65535. |
| .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 local variables into the |
| \&\f(CW\*(C`bss\*(C'\fR or \f(CW\*(C`data\*(C'\fR segments. \fB\-msvr3\-shlib\fR places them |
| into \f(CW\*(C`bss\*(C'\fR. These options are meaningful only on System V Release 3. |
| .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\-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\-msseregparm\fR" 4 |
| .IX Item "-msseregparm" |
| Use \s-1SSE\s0 register passing conventions for float and double arguments |
| and return values. You can control this behavior for a specific |
| function by using the function attribute \fBsseregparm\fR. |
| .Sp |
| \&\fBWarning:\fR if you use this switch then you must build all |
| modules with the same value, including any libraries. This includes |
| the system libraries and startup modules. |
| .IP "\fB\-mstackrealign\fR" 4 |
| .IX Item "-mstackrealign" |
| Realign the stack at entry. On the Intel x86, the |
| \&\fB\-mstackrealign\fR option will generate an alternate prologue and |
| epilogue that realigns the runtime stack. This supports mixing legacy |
| codes that keep a 4\-byte aligned stack with modern codes that keep a |
| 16\-byte stack for \s-1SSE\s0 compatibility. The alternate prologue and |
| epilogue are slower and bigger than the regular ones, and the |
| alternate prologue requires an extra scratch register; this lowers the |
| number of registers available if used in conjunction with the |
| \&\f(CW\*(C`regparm\*(C'\fR attribute. The \fB\-mstackrealign\fR option is |
| incompatible with the nested function prologue; this is considered a |
| hard error. See also the attribute \f(CW\*(C`force_align_arg_pointer\*(C'\fR, |
| applicable to individual functions. |
| .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 |
| 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 may not work |
| properly 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, and generally |
| increases code size. Code that is sensitive to stack space usage, such |
| as embedded systems and operating system kernels, may want to reduce the |
| preferred alignment to \fB\-mpreferred\-stack\-boundary=2\fR. |
| .IP "\fB\-mmmx\fR" 4 |
| .IX Item "-mmmx" |
| .PD 0 |
| .IP "\fB\-mno\-mmx\fR" 4 |
| .IX Item "-mno-mmx" |
| .IP "\fB\-msse\fR" 4 |
| .IX Item "-msse" |
| .IP "\fB\-mno\-sse\fR" 4 |
| .IX Item "-mno-sse" |
| .IP "\fB\-msse2\fR" 4 |
| .IX Item "-msse2" |
| .IP "\fB\-mno\-sse2\fR" 4 |
| .IX Item "-mno-sse2" |
| .IP "\fB\-msse3\fR" 4 |
| .IX Item "-msse3" |
| .IP "\fB\-mno\-sse3\fR" 4 |
| .IX Item "-mno-sse3" |
| .IP "\fB\-m3dnow\fR" 4 |
| .IX Item "-m3dnow" |
| .IP "\fB\-mno\-3dnow\fR" 4 |
| .IX Item "-mno-3dnow" |
| .PD |
| These switches enable or disable the use of instructions in the \s-1MMX\s0, |
| \&\s-1SSE\s0, \s-1SSE2\s0 or 3DNow! extended instruction sets. These extensions are |
| also available as built-in functions: see \fBX86 Built-in Functions\fR, |
| for details of the functions enabled and disabled by these switches. |
| .Sp |
| To have \s-1SSE/SSE2\s0 instructions generated automatically from floating-point |
| code (as opposed to 387 instructions), see \fB\-mfpmath=sse\fR. |
| .Sp |
| These options will enable \s-1GCC\s0 to use these extended instructions in |
| generated code, even without \fB\-mfpmath=sse\fR. Applications which |
| perform runtime \s-1CPU\s0 detection must compile separate files for each |
| supported architecture, using the appropriate flags. In particular, |
| the file containing the \s-1CPU\s0 detection code should be compiled without |
| these options. |
| .IP "\fB\-mpush\-args\fR" 4 |
| .IX Item "-mpush-args" |
| .PD 0 |
| .IP "\fB\-mno\-push\-args\fR" 4 |
| .IX Item "-mno-push-args" |
| .PD |
| 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 is faster on most modern CPUs |
| because of reduced dependencies, improved scheduling and reduced stack usage |
| when preferred stack boundary is not equal to 2. The drawback is a notable |
| increase in code size. This switch implies \fB\-mno\-push\-args\fR. |
| .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 \s-1GCC\s0 doesn'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. |
| .IP "\fB\-momit\-leaf\-frame\-pointer\fR" 4 |
| .IX Item "-momit-leaf-frame-pointer" |
| Don't keep the frame pointer in a register for leaf functions. This |
| avoids the instructions to save, set up and restore frame pointers and |
| makes an extra register available in leaf functions. The option |
| \&\fB\-fomit\-frame\-pointer\fR removes the frame pointer for all functions |
| which might make debugging harder. |
| .IP "\fB\-mtls\-direct\-seg\-refs\fR" 4 |
| .IX Item "-mtls-direct-seg-refs" |
| .PD 0 |
| .IP "\fB\-mno\-tls\-direct\-seg\-refs\fR" 4 |
| .IX Item "-mno-tls-direct-seg-refs" |
| .PD |
| Controls whether \s-1TLS\s0 variables may be accessed with offsets from the |
| \&\s-1TLS\s0 segment register (\f(CW%gs\fR for 32\-bit, \f(CW%fs\fR for 64\-bit), |
| or whether the thread base pointer must be added. Whether or not this |
| is legal depends on the operating system, and whether it maps the |
| segment to cover the entire \s-1TLS\s0 area. |
| .Sp |
| For systems that use \s-1GNU\s0 libc, the default is on. |
| .PP |
| These \fB\-m\fR switches are supported in addition to the above |
| on \s-1AMD\s0 x86\-64 processors in 64\-bit environments. |
| .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 and |
| generates code that runs on any i386 system. |
| The 64\-bit environment sets int to 32 bits and long and pointer |
| to 64 bits and generates code for \s-1AMD\s0's x86\-64 architecture. |
| .IP "\fB\-mno\-red\-zone\fR" 4 |
| .IX Item "-mno-red-zone" |
| Do not use a so called red zone for x86\-64 code. The red zone is mandated |
| by the x86\-64 \s-1ABI\s0, it is a 128\-byte area beyond the location of the |
| stack pointer that will not be modified by signal or interrupt handlers |
| and therefore can be used for temporary data without adjusting the stack |
| pointer. The flag \fB\-mno\-red\-zone\fR disables this red zone. |
| .IP "\fB\-mcmodel=small\fR" 4 |
| .IX Item "-mcmodel=small" |
| Generate code for the small code model: the program and its symbols must |
| be linked in the lower 2 \s-1GB\s0 of the address space. Pointers are 64 bits. |
| Programs can be statically or dynamically linked. This is the default |
| code model. |
| .IP "\fB\-mcmodel=kernel\fR" 4 |
| .IX Item "-mcmodel=kernel" |
| Generate code for the kernel code model. The kernel runs in the |
| negative 2 \s-1GB\s0 of the address space. |
| This model has to be used for Linux kernel code. |
| .IP "\fB\-mcmodel=medium\fR" 4 |
| .IX Item "-mcmodel=medium" |
| Generate code for the medium model: The program is linked in the lower 2 |
| \&\s-1GB\s0 of the address space but symbols can be located anywhere in the |
| address space. Programs can be statically or dynamically linked, but |
| building of shared libraries are not supported with the medium model. |
| .IP "\fB\-mcmodel=large\fR" 4 |
| .IX Item "-mcmodel=large" |
| Generate code for the large model: This model makes no assumptions |
| about addresses and sizes of sections. Currently \s-1GCC\s0 does not implement |
| this model. |
| .PP |
| \fI\s-1IA\-64\s0 Options\fR |
| .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-1HP\-UX\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 GNU/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\-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\-float\-divide\-min\-latency\fR" 4 |
| .IX Item "-minline-float-divide-min-latency" |
| Generate code for inline divides of floating point values |
| using the minimum latency algorithm. |
| .IP "\fB\-minline\-float\-divide\-max\-throughput\fR" 4 |
| .IX Item "-minline-float-divide-max-throughput" |
| Generate code for inline divides of floating point values |
| using the maximum throughput algorithm. |
| .IP "\fB\-minline\-int\-divide\-min\-latency\fR" 4 |
| .IX Item "-minline-int-divide-min-latency" |
| Generate code for inline divides of integer values |
| using the minimum latency algorithm. |
| .IP "\fB\-minline\-int\-divide\-max\-throughput\fR" 4 |
| .IX Item "-minline-int-divide-max-throughput" |
| Generate code for inline divides of integer values |
| using the maximum throughput algorithm. |
| .IP "\fB\-minline\-sqrt\-min\-latency\fR" 4 |
| .IX Item "-minline-sqrt-min-latency" |
| Generate code for inline square roots |
| using the minimum latency algorithm. |
| .IP "\fB\-minline\-sqrt\-max\-throughput\fR" 4 |
| .IX Item "-minline-sqrt-max-throughput" |
| Generate code for inline square roots |
| 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\-mearly\-stop\-bits\fR" 4 |
| .IX Item "-mearly-stop-bits" |
| .PD 0 |
| .IP "\fB\-mno\-early\-stop\-bits\fR" 4 |
| .IX Item "-mno-early-stop-bits" |
| .PD |
| Allow stop bits to be placed earlier than immediately preceding the |
| instruction that triggered the stop bit. This can improve instruction |
| scheduling, but does not always do so. |
| .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. |
| .IP "\fB\-mtls\-size=\fR\fItls-size\fR" 4 |
| .IX Item "-mtls-size=tls-size" |
| Specify bit size of immediate \s-1TLS\s0 offsets. Valid values are 14, 22, and |
| 64. |
| .IP "\fB\-mtune=\fR\fIcpu-type\fR" 4 |
| .IX Item "-mtune=cpu-type" |
| Tune the instruction scheduling for a particular \s-1CPU\s0, Valid values are |
| itanium, itanium1, merced, itanium2, and mckinley. |
| .IP "\fB\-mt\fR" 4 |
| .IX Item "-mt" |
| .PD 0 |
| .IP "\fB\-pthread\fR" 4 |
| .IX Item "-pthread" |
| .PD |
| Add support for multithreading using the \s-1POSIX\s0 threads library. This |
| option sets flags for both the preprocessor and linker. It does |
| not affect the thread safety of object code produced by the compiler or |
| that of libraries supplied with it. These are HP-UX specific flags. |
| .IP "\fB\-milp32\fR" 4 |
| .IX Item "-milp32" |
| .PD 0 |
| .IP "\fB\-mlp64\fR" 4 |
| .IX Item "-mlp64" |
| .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. These are HP-UX specific flags. |
| .IP "\fB\-mno\-sched\-br\-data\-spec\fR" 4 |
| .IX Item "-mno-sched-br-data-spec" |
| .PD 0 |
| .IP "\fB\-msched\-br\-data\-spec\fR" 4 |
| .IX Item "-msched-br-data-spec" |
| .PD |
| (Dis/En)able data speculative scheduling before reload. |
| This will result in generation of the ld.a instructions and |
| the corresponding check instructions (ld.c / chk.a). |
| The default is 'disable'. |
| .IP "\fB\-msched\-ar\-data\-spec\fR" 4 |
| .IX Item "-msched-ar-data-spec" |
| .PD 0 |
| .IP "\fB\-mno\-sched\-ar\-data\-spec\fR" 4 |
| .IX Item "-mno-sched-ar-data-spec" |
| .PD |
| (En/Dis)able data speculative scheduling after reload. |
| This will result in generation of the ld.a instructions and |
| the corresponding check instructions (ld.c / chk.a). |
| The default is 'enable'. |
| .IP "\fB\-mno\-sched\-control\-spec\fR" 4 |
| .IX Item "-mno-sched-control-spec" |
| .PD 0 |
| .IP "\fB\-msched\-control\-spec\fR" 4 |
| .IX Item "-msched-control-spec" |
| .PD |
| (Dis/En)able control speculative scheduling. This feature is |
| available only during region scheduling (i.e. before reload). |
| This will result in generation of the ld.s instructions and |
| the corresponding check instructions chk.s . |
| The default is 'disable'. |
| .IP "\fB\-msched\-br\-in\-data\-spec\fR" 4 |
| .IX Item "-msched-br-in-data-spec" |
| .PD 0 |
| .IP "\fB\-mno\-sched\-br\-in\-data\-spec\fR" 4 |
| .IX Item "-mno-sched-br-in-data-spec" |
| .PD |
| (En/Dis)able speculative scheduling of the instructions that |
| are dependent on the data speculative loads before reload. |
| This is effective only with \fB\-msched\-br\-data\-spec\fR enabled. |
| The default is 'enable'. |
| .IP "\fB\-msched\-ar\-in\-data\-spec\fR" 4 |
| .IX Item "-msched-ar-in-data-spec" |
| .PD 0 |
| .IP "\fB\-mno\-sched\-ar\-in\-data\-spec\fR" 4 |
| .IX Item "-mno-sched-ar-in-data-spec" |
| .PD |
| (En/Dis)able speculative scheduling of the instructions that |
| are dependent on the data speculative loads after reload. |
| This is effective only with \fB\-msched\-ar\-data\-spec\fR enabled. |
| The default is 'enable'. |
| .IP "\fB\-msched\-in\-control\-spec\fR" 4 |
| .IX Item "-msched-in-control-spec" |
| .PD 0 |
| .IP "\fB\-mno\-sched\-in\-control\-spec\fR" 4 |
| .IX Item "-mno-sched-in-control-spec" |
| .PD |
| (En/Dis)able speculative scheduling of the instructions that |
| are dependent on the control speculative loads. |
| This is effective only with \fB\-msched\-control\-spec\fR enabled. |
| The default is 'enable'. |
| .IP "\fB\-msched\-ldc\fR" 4 |
| .IX Item "-msched-ldc" |
| .PD 0 |
| .IP "\fB\-mno\-sched\-ldc\fR" 4 |
| .IX Item "-mno-sched-ldc" |
| .PD |
| (En/Dis)able use of simple data speculation checks ld.c . |
| If disabled, only chk.a instructions will be emitted to check |
| data speculative loads. |
| The default is 'enable'. |
| .IP "\fB\-mno\-sched\-control\-ldc\fR" 4 |
| .IX Item "-mno-sched-control-ldc" |
| .PD 0 |
| .IP "\fB\-msched\-control\-ldc\fR" 4 |
| .IX Item "-msched-control-ldc" |
| .PD |
| (Dis/En)able use of ld.c instructions to check control speculative loads. |
| If enabled, in case of control speculative load with no speculatively |
| scheduled dependent instructions this load will be emitted as ld.sa and |
| ld.c will be used to check it. |
| The default is 'disable'. |
| .IP "\fB\-mno\-sched\-spec\-verbose\fR" 4 |
| .IX Item "-mno-sched-spec-verbose" |
| .PD 0 |
| .IP "\fB\-msched\-spec\-verbose\fR" 4 |
| .IX Item "-msched-spec-verbose" |
| .PD |
| (Dis/En)able printing of the information about speculative motions. |
| .IP "\fB\-mno\-sched\-prefer\-non\-data\-spec\-insns\fR" 4 |
| .IX Item "-mno-sched-prefer-non-data-spec-insns" |
| .PD 0 |
| .IP "\fB\-msched\-prefer\-non\-data\-spec\-insns\fR" 4 |
| .IX Item "-msched-prefer-non-data-spec-insns" |
| .PD |
| If enabled, data speculative instructions will be chosen for schedule |
| only if there are no other choices at the moment. This will make |
| the use of the data speculation much more conservative. |
| The default is 'disable'. |
| .IP "\fB\-mno\-sched\-prefer\-non\-control\-spec\-insns\fR" 4 |
| .IX Item "-mno-sched-prefer-non-control-spec-insns" |
| .PD 0 |
| .IP "\fB\-msched\-prefer\-non\-control\-spec\-insns\fR" 4 |
| .IX Item "-msched-prefer-non-control-spec-insns" |
| .PD |
| If enabled, control speculative instructions will be chosen for schedule |
| only if there are no other choices at the moment. This will make |
| the use of the control speculation much more conservative. |
| The default is 'disable'. |
| .IP "\fB\-mno\-sched\-count\-spec\-in\-critical\-path\fR" 4 |
| .IX Item "-mno-sched-count-spec-in-critical-path" |
| .PD 0 |
| .IP "\fB\-msched\-count\-spec\-in\-critical\-path\fR" 4 |
| .IX Item "-msched-count-spec-in-critical-path" |
| .PD |
| If enabled, speculative dependencies will be considered during |
| computation of the instructions priorities. This will make the use of the |
| speculation a bit more conservative. |
| The default is 'disable'. |
| .PP |
| \fIM32C Options\fR |
| .IX Subsection "M32C Options" |
| .IP "\fB\-mcpu=\fR\fIname\fR" 4 |
| .IX Item "-mcpu=name" |
| Select the \s-1CPU\s0 for which code is generated. \fIname\fR may be one of |
| \&\fBr8c\fR for the R8C/Tiny series, \fBm16c\fR for the M16C (up to |
| /60) series, \fBm32cm\fR for the M16C/80 series, or \fBm32c\fR for |
| the M32C/80 series. |
| .IP "\fB\-msim\fR" 4 |
| .IX Item "-msim" |
| Specifies that the program will be run on the simulator. This causes |
| an alternate runtime library to be linked in which supports, for |
| example, file I/O. You must not use this option when generating |
| programs that will run on real hardware; you must provide your own |
| runtime library for whatever I/O functions are needed. |
| .IP "\fB\-memregs=\fR\fInumber\fR" 4 |
| .IX Item "-memregs=number" |
| Specifies the number of memory-based pseudo-registers \s-1GCC\s0 will use |
| during code generation. These pseudo-registers will be used like real |
| registers, so there is a tradeoff between \s-1GCC\s0's ability to fit the |
| code into available registers, and the performance penalty of using |
| memory instead of registers. Note that all modules in a program must |
| be compiled with the same value for this option. Because of that, you |
| must not use this option with the default runtime libraries gcc |
| builds. |
| .PP |
| \fIM32R/D Options\fR |
| .IX Subsection "M32R/D Options" |
| .PP |
| These \fB\-m\fR options are defined for Renesas M32R/D architectures: |
| .IP "\fB\-m32r2\fR" 4 |
| .IX Item "-m32r2" |
| Generate code for the M32R/2. |
| .IP "\fB\-m32rx\fR" 4 |
| .IX Item "-m32rx" |
| Generate code for the M32R/X. |
| .IP "\fB\-m32r\fR" 4 |
| .IX Item "-m32r" |
| Generate code for the M32R. This is the default. |
| .IP "\fB\-mmodel=small\fR" 4 |
| .IX Item "-mmodel=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\-mmodel=medium\fR" 4 |
| .IX Item "-mmodel=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\-mmodel=large\fR" 4 |
| .IX Item "-mmodel=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. |
| .IP "\fB\-mdebug\fR" 4 |
| .IX Item "-mdebug" |
| Makes the M32R specific code in the compiler display some statistics |
| that might help in debugging programs. |
| .IP "\fB\-malign\-loops\fR" 4 |
| .IX Item "-malign-loops" |
| Align all loops to a 32\-byte boundary. |
| .IP "\fB\-mno\-align\-loops\fR" 4 |
| .IX Item "-mno-align-loops" |
| Do not enforce a 32\-byte alignment for loops. This is the default. |
| .IP "\fB\-missue\-rate=\fR\fInumber\fR" 4 |
| .IX Item "-missue-rate=number" |
| Issue \fInumber\fR instructions per cycle. \fInumber\fR can only be 1 |
| or 2. |
| .IP "\fB\-mbranch\-cost=\fR\fInumber\fR" 4 |
| .IX Item "-mbranch-cost=number" |
| \&\fInumber\fR can only be 1 or 2. If it is 1 then branches will be |
| preferred over conditional code, if it is 2, then the opposite will |
| apply. |
| .IP "\fB\-mflush\-trap=\fR\fInumber\fR" 4 |
| .IX Item "-mflush-trap=number" |
| Specifies the trap number to use to flush the cache. The default is |
| 12. Valid numbers are between 0 and 15 inclusive. |
| .IP "\fB\-mno\-flush\-trap\fR" 4 |
| .IX Item "-mno-flush-trap" |
| Specifies that the cache cannot be flushed by using a trap. |
| .IP "\fB\-mflush\-func=\fR\fIname\fR" 4 |
| .IX Item "-mflush-func=name" |
| Specifies the name of the operating system function to call to flush |
| the cache. The default is \fI_flush_cache\fR, but a function call |
| will only be used if a trap is not available. |
| .IP "\fB\-mno\-flush\-func\fR" 4 |
| .IX Item "-mno-flush-func" |
| Indicates that there is no \s-1OS\s0 function for flushing the cache. |
| .PP |
| \fIM680x0 Options\fR |
| .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\-mcfv4e\fR" 4 |
| .IX Item "-mcfv4e" |
| Generate output for a ColdFire V4e family cpu (e.g. 547x/548x). |
| This includes use of hardware floating point instructions. |
| .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\-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. |
| Additionally, parameters passed on the stack are also aligned to a |
| 16\-bit boundary even on targets whose \s-1API\s0 mandates promotion to 32\-bit. |
| .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 \fB\-fpic\fR, |
| allowing at most a 16\-bit offset for pc-relative addressing. \fB\-fPIC\fR is |
| not presently supported with \fB\-mpcrel\fR, 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. |
| .IP "\fB\-msep\-data\fR" 4 |
| .IX Item "-msep-data" |
| Generate code that allows the data segment to be located in a different |
| area of memory from the text segment. This allows for execute in place in |
| an environment without virtual memory management. This option implies |
| \&\fB\-fPIC\fR. |
| .IP "\fB\-mno\-sep\-data\fR" 4 |
| .IX Item "-mno-sep-data" |
| Generate code that assumes that the data segment follows the text segment. |
| This is the default. |
| .IP "\fB\-mid\-shared\-library\fR" 4 |
| .IX Item "-mid-shared-library" |
| Generate code that supports shared libraries via the library \s-1ID\s0 method. |
| This allows for execute in place and shared libraries in an environment |
| without virtual memory management. This option implies \fB\-fPIC\fR. |
| .IP "\fB\-mno\-id\-shared\-library\fR" 4 |
| .IX Item "-mno-id-shared-library" |
| Generate code that doesn't assume \s-1ID\s0 based shared libraries are being used. |
| This is the default. |
| .IP "\fB\-mshared\-library\-id=n\fR" 4 |
| .IX Item "-mshared-library-id=n" |
| Specified the identification number of the \s-1ID\s0 based shared library being |
| compiled. Specifying a value of 0 will generate more compact code, specifying |
| other values will force the allocation of that number to the current |
| library but is no more space or time efficient than omitting this option. |
| .PP |
| \fIM68hc1x Options\fR |
| .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\-m68S12\fR" 4 |
| .IX Item "-m68S12" |
| .PD 0 |
| .IP "\fB\-m68hcs12\fR" 4 |
| .IX Item "-m68hcs12" |
| .PD |
| Generate output for a 68HCS12. |
| .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\-minmax\fR" 4 |
| .IX Item "-minmax" |
| .PD 0 |
| .IP "\fB\-nominmax\fR" 4 |
| .IX Item "-nominmax" |
| .PD |
| Enable the use of 68HC12 min and max instructions. |
| .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 use the \f(CW\*(C`call\*(C'\fR instruction to |
| call a function and the \f(CW\*(C`rtc\*(C'\fR instruction for returning. |
| .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 |
| \fIMCore Options\fR |
| .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\-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\-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\-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\-mno\-wide\-bitfields\fR" 4 |
| .IX Item "-mno-wide-bitfields" |
| .PD |
| Always treat bit-fields as int\-sized. |
| .IP "\fB\-m4byte\-functions\fR" 4 |
| .IX Item "-m4byte-functions" |
| .PD 0 |
| .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\-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\-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\-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\-m340\fR" 4 |
| .IX Item "-m340" |
| .PD |
| Generate code for the 210 processor. |
| .PP |
| \fI\s-1MIPS\s0 Options\fR |
| .IX Subsection "MIPS Options" |
| .IP "\fB\-EB\fR" 4 |
| .IX Item "-EB" |
| Generate big-endian code. |
| .IP "\fB\-EL\fR" 4 |
| .IX Item "-EL" |
| Generate little-endian code. This is the default for \fBmips*el\-*\-*\fR |
| configurations. |
| .IP "\fB\-march=\fR\fIarch\fR" 4 |
| .IX Item "-march=arch" |
| Generate code that will run on \fIarch\fR, which can be the name of a |
| generic \s-1MIPS\s0 \s-1ISA\s0, or the name of a particular processor. |
| The \s-1ISA\s0 names are: |
| \&\fBmips1\fR, \fBmips2\fR, \fBmips3\fR, \fBmips4\fR, |
| \&\fBmips32\fR, \fBmips32r2\fR, and \fBmips64\fR. |
| The processor names are: |
| \&\fB4kc\fR, \fB4km\fR, \fB4kp\fR, |
| \&\fB5kc\fR, \fB5kf\fR, |
| \&\fB20kc\fR, |
| \&\fB24k\fR, \fB24kc\fR, \fB24kf\fR, \fB24kx\fR, |
| \&\fBm4k\fR, |
| \&\fBorion\fR, |
| \&\fBr2000\fR, \fBr3000\fR, \fBr3900\fR, \fBr4000\fR, \fBr4400\fR, |
| \&\fBr4600\fR, \fBr4650\fR, \fBr6000\fR, \fBr8000\fR, |
| \&\fBrm7000\fR, \fBrm9000\fR, |
| \&\fBsb1\fR, |
| \&\fBsr71000\fR, |
| \&\fBvr4100\fR, \fBvr4111\fR, \fBvr4120\fR, \fBvr4130\fR, \fBvr4300\fR, |
| \&\fBvr5000\fR, \fBvr5400\fR and \fBvr5500\fR. |
| The special value \fBfrom-abi\fR selects the |
| most compatible architecture for the selected \s-1ABI\s0 (that is, |
| \&\fBmips1\fR for 32\-bit ABIs and \fBmips3\fR for 64\-bit ABIs). |
| .Sp |
| In processor names, a final \fB000\fR can be abbreviated as \fBk\fR |
| (for example, \fB\-march=r2k\fR). Prefixes are optional, and |
| \&\fBvr\fR may be written \fBr\fR. |
| .Sp |
| \&\s-1GCC\s0 defines two macros based on the value of this option. The first |
| is \fB_MIPS_ARCH\fR, which gives the name of target architecture, as |
| a string. The second has the form \fB_MIPS_ARCH_\fR\fIfoo\fR, |
| where \fIfoo\fR is the capitalized value of \fB_MIPS_ARCH\fR. |
| For example, \fB\-march=r2000\fR will set \fB_MIPS_ARCH\fR |
| to \fB\*(L"r2000\*(R"\fR and define the macro \fB_MIPS_ARCH_R2000\fR. |
| .Sp |
| Note that the \fB_MIPS_ARCH\fR macro uses the processor names given |
| above. In other words, it will have the full prefix and will not |
| abbreviate \fB000\fR as \fBk\fR. In the case of \fBfrom-abi\fR, |
| the macro names the resolved architecture (either \fB\*(L"mips1\*(R"\fR or |
| \&\fB\*(L"mips3\*(R"\fR). It names the default architecture when no |
| \&\fB\-march\fR option is given. |
| .IP "\fB\-mtune=\fR\fIarch\fR" 4 |
| .IX Item "-mtune=arch" |
| Optimize for \fIarch\fR. Among other things, this option controls |
| the way instructions are scheduled, and the perceived cost of arithmetic |
| operations. The list of \fIarch\fR values is the same as for |
| \&\fB\-march\fR. |
| .Sp |
| When this option is not used, \s-1GCC\s0 will optimize for the processor |
| specified by \fB\-march\fR. By using \fB\-march\fR and |
| \&\fB\-mtune\fR together, it is possible to generate code that will |
| run on a family of processors, but optimize the code for one |
| particular member of that family. |
| .Sp |
| \&\fB\-mtune\fR defines the macros \fB_MIPS_TUNE\fR and |
| \&\fB_MIPS_TUNE_\fR\fIfoo\fR, which work in the same way as the |
| \&\fB\-march\fR ones described above. |
| .IP "\fB\-mips1\fR" 4 |
| .IX Item "-mips1" |
| Equivalent to \fB\-march=mips1\fR. |
| .IP "\fB\-mips2\fR" 4 |
| .IX Item "-mips2" |
| Equivalent to \fB\-march=mips2\fR. |
| .IP "\fB\-mips3\fR" 4 |
| .IX Item "-mips3" |
| Equivalent to \fB\-march=mips3\fR. |
| .IP "\fB\-mips4\fR" 4 |
| .IX Item "-mips4" |
| Equivalent to \fB\-march=mips4\fR. |
| .IP "\fB\-mips32\fR" 4 |
| .IX Item "-mips32" |
| Equivalent to \fB\-march=mips32\fR. |
| .IP "\fB\-mips32r2\fR" 4 |
| .IX Item "-mips32r2" |
| Equivalent to \fB\-march=mips32r2\fR. |
| .IP "\fB\-mips64\fR" 4 |
| .IX Item "-mips64" |
| Equivalent to \fB\-march=mips64\fR. |
| .IP "\fB\-mips16\fR" 4 |
| .IX Item "-mips16" |
| .PD 0 |
| .IP "\fB\-mno\-mips16\fR" 4 |
| .IX Item "-mno-mips16" |
| .PD |
| Generate (do not generate) \s-1MIPS16\s0 code. If \s-1GCC\s0 is targetting a |
| \&\s-1MIPS32\s0 or \s-1MIPS64\s0 architecture, it will make use of the MIPS16e \s-1ASE\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 given \s-1ABI\s0. |
| .Sp |
| Note that the \s-1EABI\s0 has a 32\-bit and a 64\-bit variant. \s-1GCC\s0 normally |
| generates 64\-bit code when you select a 64\-bit architecture, but you |
| can use \fB\-mgp32\fR to get 32\-bit code instead. |
| .Sp |
| For information about the O64 \s-1ABI\s0, see |
| <\fBhttp://gcc.gnu.org/projects/mipso64\-abi.html\fR>. |
| .IP "\fB\-mabicalls\fR" 4 |
| .IX Item "-mabicalls" |
| .PD 0 |
| .IP "\fB\-mno\-abicalls\fR" 4 |
| .IX Item "-mno-abicalls" |
| .PD |
| Generate (do not generate) code that is suitable for SVR4\-style |
| dynamic objects. \fB\-mabicalls\fR is the default for SVR4\-based |
| systems. |
| .IP "\fB\-mshared\fR" 4 |
| .IX Item "-mshared" |
| .PD 0 |
| .IP "\fB\-mno\-shared\fR" 4 |
| .IX Item "-mno-shared" |
| .PD |
| Generate (do not generate) code that is fully position\-independent, |
| and that can therefore be linked into shared libraries. This option |
| only affects \fB\-mabicalls\fR. |
| .Sp |
| All \fB\-mabicalls\fR code has traditionally been position\-independent, |
| regardless of options like \fB\-fPIC\fR and \fB\-fpic\fR. However, |
| as an extension, the \s-1GNU\s0 toolchain allows executables to use absolute |
| accesses for locally-binding symbols. It can also use shorter \s-1GP\s0 |
| initialization sequences and generate direct calls to locally-defined |
| functions. This mode is selected by \fB\-mno\-shared\fR. |
| .Sp |
| \&\fB\-mno\-shared\fR depends on binutils 2.16 or higher and generates |
| objects that can only be linked by the \s-1GNU\s0 linker. However, the option |
| does not affect the \s-1ABI\s0 of the final executable; it only affects the \s-1ABI\s0 |
| of relocatable objects. Using \fB\-mno\-shared\fR will generally make |
| executables both smaller and quicker. |
| .Sp |
| \&\fB\-mshared\fR is the default. |
| .IP "\fB\-mxgot\fR" 4 |
| .IX Item "-mxgot" |
| .PD 0 |
| .IP "\fB\-mno\-xgot\fR" 4 |
| .IX Item "-mno-xgot" |
| .PD |
| Lift (do not lift) the usual restrictions on the size of the global |
| offset table. |
| .Sp |
| \&\s-1GCC\s0 normally uses a single instruction to load values from the \s-1GOT\s0. |
| While this is relatively efficient, it will only work if the \s-1GOT\s0 |
| is smaller than about 64k. Anything larger will cause the linker |
| to report an error such as: |
| .Sp |
| .Vb 1 |
| \& relocation truncated to fit: R_MIPS_GOT16 foobar |
| .Ve |
| .Sp |
| If this happens, you should recompile your code with \fB\-mxgot\fR. |
| It should then work with very large GOTs, although it will also be |
| less efficient, since it will take three instructions to fetch the |
| value of a global symbol. |
| .Sp |
| Note that some linkers can create multiple GOTs. If you have such a |
| linker, you should only need to use \fB\-mxgot\fR when a single object |
| file accesses more than 64k's worth of \s-1GOT\s0 entries. Very few do. |
| .Sp |
| These options have no effect unless \s-1GCC\s0 is generating position |
| independent code. |
| .IP "\fB\-mgp32\fR" 4 |
| .IX Item "-mgp32" |
| Assume that general-purpose registers are 32 bits wide. |
| .IP "\fB\-mgp64\fR" 4 |
| .IX Item "-mgp64" |
| Assume that general-purpose registers are 64 bits wide. |
| .IP "\fB\-mfp32\fR" 4 |
| .IX Item "-mfp32" |
| Assume that floating-point registers are 32 bits wide. |
| .IP "\fB\-mfp64\fR" 4 |
| .IX Item "-mfp64" |
| Assume that floating-point registers are 64 bits wide. |
| .IP "\fB\-mhard\-float\fR" 4 |
| .IX Item "-mhard-float" |
| Use floating-point coprocessor instructions. |
| .IP "\fB\-msoft\-float\fR" 4 |
| .IX Item "-msoft-float" |
| Do not use floating-point coprocessor instructions. Implement |
| floating-point calculations using library calls instead. |
| .IP "\fB\-msingle\-float\fR" 4 |
| .IX Item "-msingle-float" |
| Assume that the floating-point coprocessor only supports single-precision |
| operations. |
| .IP "\fB\-mdouble\-float\fR" 4 |
| .IX Item "-mdouble-float" |
| Assume that the floating-point coprocessor supports double-precision |
| operations. This is the default. |
| .IP "\fB\-mdsp\fR" 4 |
| .IX Item "-mdsp" |
| .PD 0 |
| .IP "\fB\-mno\-dsp\fR" 4 |
| .IX Item "-mno-dsp" |
| .PD |
| Use (do not use) the \s-1MIPS\s0 \s-1DSP\s0 \s-1ASE\s0. |
| .IP "\fB\-mpaired\-single\fR" 4 |
| .IX Item "-mpaired-single" |
| .PD 0 |
| .IP "\fB\-mno\-paired\-single\fR" 4 |
| .IX Item "-mno-paired-single" |
| .PD |
| Use (do not use) paired-single floating-point instructions. |
| This option can only be used |
| when generating 64\-bit code and requires hardware floating-point |
| support to be enabled. |
| .IP "\fB\-mips3d\fR" 4 |
| .IX Item "-mips3d" |
| .PD 0 |
| .IP "\fB\-mno\-mips3d\fR" 4 |
| .IX Item "-mno-mips3d" |
| .PD |
| Use (do not use) the \s-1MIPS\-3D\s0 \s-1ASE\s0. |
| The option \fB\-mips3d\fR implies \fB\-mpaired\-single\fR. |
| .IP "\fB\-mlong64\fR" 4 |
| .IX Item "-mlong64" |
| Force \f(CW\*(C`long\*(C'\fR types to be 64 bits wide. See \fB\-mlong32\fR for |
| an explanation of the default and the way that the pointer size is |
| determined. |
| .IP "\fB\-mlong32\fR" 4 |
| .IX Item "-mlong32" |
| Force \f(CW\*(C`long\*(C'\fR, \f(CW\*(C`int\*(C'\fR, and pointer types to be 32 bits wide. |
| .Sp |
| The default size of \f(CW\*(C`int\*(C'\fRs, \f(CW\*(C`long\*(C'\fRs and pointers depends on |
| the \s-1ABI\s0. All the supported ABIs use 32\-bit \f(CW\*(C`int\*(C'\fRs. The n64 \s-1ABI\s0 |
| uses 64\-bit \f(CW\*(C`long\*(C'\fRs, as does the 64\-bit \s-1EABI\s0; the others use |
| 32\-bit \f(CW\*(C`long\*(C'\fRs. Pointers are the same size as \f(CW\*(C`long\*(C'\fRs, |
| or the same size as integer registers, whichever is smaller. |
| .IP "\fB\-msym32\fR" 4 |
| .IX Item "-msym32" |
| .PD 0 |
| .IP "\fB\-mno\-sym32\fR" 4 |
| .IX Item "-mno-sym32" |
| .PD |
| Assume (do not assume) that all symbols have 32\-bit values, regardless |
| of the selected \s-1ABI\s0. This option is useful in combination with |
| \&\fB\-mabi=64\fR and \fB\-mno\-abicalls\fR because it allows \s-1GCC\s0 |
| to generate shorter and faster references to symbolic addresses. |
| .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 section instead of the normal data or bss section. |
| This allows the data to be accessed using a single instruction. |
| .Sp |
| All modules should be compiled with the same \fB\-G\fR \fInum\fR |
| value. |
| .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 |
| Put uninitialized \f(CW\*(C`const\*(C'\fR variables in the read-only data section. |
| This option is only meaningful in conjunction with \fB\-membedded\-data\fR. |
| .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 |
| Enable (disable) use of the \f(CW\*(C`%hi()\*(C'\fR and \f(CW\*(C`%lo()\*(C'\fR assembler |
| relocation operators. This option has been superseded by |
| \&\fB\-mexplicit\-relocs\fR but is retained for backwards compatibility. |
| .IP "\fB\-mexplicit\-relocs\fR" 4 |
| .IX Item "-mexplicit-relocs" |
| .PD 0 |
| .IP "\fB\-mno\-explicit\-relocs\fR" 4 |
| .IX Item "-mno-explicit-relocs" |
| .PD |
| Use (do not use) assembler relocation operators when dealing with symbolic |
| addresses. The alternative, selected by \fB\-mno\-explicit\-relocs\fR, |
| is to use assembler macros instead. |
| .Sp |
| \&\fB\-mexplicit\-relocs\fR is the default if \s-1GCC\s0 was configured |
| to use an assembler that supports relocation operators. |
| .IP "\fB\-mcheck\-zero\-division\fR" 4 |
| .IX Item "-mcheck-zero-division" |
| .PD 0 |
| .IP "\fB\-mno\-check\-zero\-division\fR" 4 |
| .IX Item "-mno-check-zero-division" |
| .PD |
| Trap (do not trap) on integer division by zero. The default is |
| \&\fB\-mcheck\-zero\-division\fR. |
| .IP "\fB\-mdivide\-traps\fR" 4 |
| .IX Item "-mdivide-traps" |
| .PD 0 |
| .IP "\fB\-mdivide\-breaks\fR" 4 |
| .IX Item "-mdivide-breaks" |
| .PD |
| \&\s-1MIPS\s0 systems check for division by zero by generating either a |
| conditional trap or a break instruction. Using traps results in |
| smaller code, but is only supported on \s-1MIPS\s0 \s-1II\s0 and later. Also, some |
| versions of the Linux kernel have a bug that prevents trap from |
| generating the proper signal (\f(CW\*(C`SIGFPE\*(C'\fR). Use \fB\-mdivide\-traps\fR to |
| allow conditional traps on architectures that support them and |
| \&\fB\-mdivide\-breaks\fR to force the use of breaks. |
| .Sp |
| The default is usually \fB\-mdivide\-traps\fR, but this can be |
| overridden at configure time using \fB\-\-with\-divide=breaks\fR. |
| Divide-by-zero checks can be completely disabled using |
| \&\fB\-mno\-check\-zero\-division\fR. |
| .IP "\fB\-mmemcpy\fR" 4 |
| .IX Item "-mmemcpy" |
| .PD 0 |
| .IP "\fB\-mno\-memcpy\fR" 4 |
| .IX Item "-mno-memcpy" |
| .PD |
| Force (do not force) the use of \f(CW\*(C`memcpy()\*(C'\fR for non-trivial block |
| moves. The default is \fB\-mno\-memcpy\fR, which allows \s-1GCC\s0 to inline |
| most constant-sized copies. |
| .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 |
| Disable (do not disable) use of the \f(CW\*(C`jal\*(C'\fR instruction. Calling |
| functions using \f(CW\*(C`jal\*(C'\fR is more efficient but requires the caller |
| and callee to be in the same 256 megabyte segment. |
| .Sp |
| This option has no effect on abicalls code. The default is |
| \&\fB\-mno\-long\-calls\fR. |
| .IP "\fB\-mmad\fR" 4 |
| .IX Item "-mmad" |
| .PD 0 |
| .IP "\fB\-mno\-mad\fR" 4 |
| .IX Item "-mno-mad" |
| .PD |
| Enable (disable) use of the \f(CW\*(C`mad\*(C'\fR, \f(CW\*(C`madu\*(C'\fR and \f(CW\*(C`mul\*(C'\fR |
| instructions, as provided by the R4650 \s-1ISA\s0. |
| .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 |
| Enable (disable) use of the floating point multiply-accumulate |
| instructions, when they are available. The default is |
| \&\fB\-mfused\-madd\fR. |
| .Sp |
| When multiply-accumulate instructions are used, the intermediate |
| product is calculated to infinite precision and is not subject to |
| the \s-1FCSR\s0 Flush to Zero bit. This may be undesirable in some |
| circumstances. |
| .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\-mfix\-r4000\fR" 4 |
| .IX Item "-mfix-r4000" |
| .PD 0 |
| .IP "\fB\-mno\-fix\-r4000\fR" 4 |
| .IX Item "-mno-fix-r4000" |
| .PD |
| Work around certain R4000 \s-1CPU\s0 errata: |
| .RS 4 |
| .IP "\-" 4 |
| A double-word or a variable shift may give an incorrect result if executed |
| immediately after starting an integer division. |
| .IP "\-" 4 |
| A double-word or a variable shift may give an incorrect result if executed |
| while an integer multiplication is in progress. |
| .IP "\-" 4 |
| An integer division may give an incorrect result if started in a delay slot |
| of a taken branch or a jump. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-mfix\-r4400\fR" 4 |
| .IX Item "-mfix-r4400" |
| .PD 0 |
| .IP "\fB\-mno\-fix\-r4400\fR" 4 |
| .IX Item "-mno-fix-r4400" |
| .PD |
| Work around certain R4400 \s-1CPU\s0 errata: |
| .RS 4 |
| .IP "\-" 4 |
| A double-word or a variable shift may give an incorrect result if executed |
| immediately after starting an integer division. |
| .RE |
| .RS 4 |
| .RE |
| .IP "\fB\-mfix\-vr4120\fR" 4 |
| .IX Item "-mfix-vr4120" |
| .PD 0 |
| .IP "\fB\-mno\-fix\-vr4120\fR" 4 |
| .IX Item "-mno-fix-vr4120" |
| .PD |
| Work around certain \s-1VR4120\s0 errata: |
| .RS 4 |
| .IP "\-" 4 |
| \&\f(CW\*(C`dmultu\*(C'\fR does not always produce the correct result. |
| .IP "\-" 4 |
| \&\f(CW\*(C`div\*(C'\fR and \f(CW\*(C`ddiv\*(C'\fR do not always produce the correct result if one |
| of the operands is negative. |
| .RE |
| .RS 4 |
| .Sp |
| The workarounds for the division errata rely on special functions in |
| \&\fIlibgcc.a\fR. At present, these functions are only provided by |
| the \f(CW\*(C`mips64vr*\-elf\*(C'\fR configurations. |
| .Sp |
| Other \s-1VR4120\s0 errata require a nop to be inserted between certain pairs of |
| instructions. These errata are handled by the assembler, not by \s-1GCC\s0 itself. |
| .RE |
| .IP "\fB\-mfix\-vr4130\fR" 4 |
| .IX Item "-mfix-vr4130" |
| Work around the \s-1VR4130\s0 \f(CW\*(C`mflo\*(C'\fR/\f(CW\*(C`mfhi\*(C'\fR errata. The |
| workarounds are implemented by the assembler rather than by \s-1GCC\s0, |
| although \s-1GCC\s0 will avoid using \f(CW\*(C`mflo\*(C'\fR and \f(CW\*(C`mfhi\*(C'\fR if the |
| \&\s-1VR4130\s0 \f(CW\*(C`macc\*(C'\fR, \f(CW\*(C`macchi\*(C'\fR, \f(CW\*(C`dmacc\*(C'\fR and \f(CW\*(C`dmacchi\*(C'\fR |
| instructions are available instead. |
| .IP "\fB\-mfix\-sb1\fR" 4 |
| .IX Item "-mfix-sb1" |
| .PD 0 |
| .IP "\fB\-mno\-fix\-sb1\fR" 4 |
| .IX Item "-mno-fix-sb1" |
| .PD |
| Work around certain \s-1SB\-1\s0 \s-1CPU\s0 core errata. |
| (This flag currently works around the \s-1SB\-1\s0 revision 2 |
| \&\*(L"F1\*(R" and \*(L"F2\*(R" floating point errata.) |
| .IP "\fB\-mflush\-func=\fR\fIfunc\fR" 4 |
| .IX Item "-mflush-func=func" |
| .PD 0 |
| .IP "\fB\-mno\-flush\-func\fR" 4 |
| .IX Item "-mno-flush-func" |
| .PD |
| Specifies the function to call to flush the I and D caches, or to not |
| call any such function. If called, the function must take the same |
| arguments as the common \f(CW\*(C`_flush_func()\*(C'\fR, that is, the address of the |
| memory range for which the cache is being flushed, the size of the |
| memory range, and the number 3 (to flush both caches). The default |
| depends on the target \s-1GCC\s0 was configured for, but commonly is either |
| \&\fB_flush_func\fR or \fB_\|_cpu_flush\fR. |
| .IP "\fB\-mbranch\-likely\fR" 4 |
| .IX Item "-mbranch-likely" |
| .PD 0 |
| .IP "\fB\-mno\-branch\-likely\fR" 4 |
| .IX Item "-mno-branch-likely" |
| .PD |
| Enable or disable use of Branch Likely instructions, regardless of the |
| default for the selected architecture. By default, Branch Likely |
| instructions may be generated if they are supported by the selected |
| architecture. An exception is for the \s-1MIPS32\s0 and \s-1MIPS64\s0 architectures |
| and processors which implement those architectures; for those, Branch |
| Likely instructions will not be generated by default because the \s-1MIPS32\s0 |
| and \s-1MIPS64\s0 architectures specifically deprecate their use. |
| .IP "\fB\-mfp\-exceptions\fR" 4 |
| .IX Item "-mfp-exceptions" |
| .PD 0 |
| .IP "\fB\-mno\-fp\-exceptions\fR" 4 |
| .IX Item "-mno-fp-exceptions" |
| .PD |
| Specifies whether \s-1FP\s0 exceptions are enabled. This affects how we schedule |
| \&\s-1FP\s0 instructions for some processors. The default is that \s-1FP\s0 exceptions are |
| enabled. |
| .Sp |
| For instance, on the \s-1SB\-1\s0, if \s-1FP\s0 exceptions are disabled, and we are emitting |
| 64\-bit code, then we can use both \s-1FP\s0 pipes. Otherwise, we can only use one |
| \&\s-1FP\s0 pipe. |
| .IP "\fB\-mvr4130\-align\fR" 4 |
| .IX Item "-mvr4130-align" |
| .PD 0 |
| .IP "\fB\-mno\-vr4130\-align\fR" 4 |
| .IX Item "-mno-vr4130-align" |
| .PD |
| The \s-1VR4130\s0 pipeline is two-way superscalar, but can only issue two |
| instructions together if the first one is 8\-byte aligned. When this |
| option is enabled, \s-1GCC\s0 will align pairs of instructions that it |
| thinks should execute in parallel. |
| .Sp |
| This option only has an effect when optimizing for the \s-1VR4130\s0. |
| It normally makes code faster, but at the expense of making it bigger. |
| It is enabled by default at optimization level \fB\-O3\fR. |
| .PP |
| \fI\s-1MMIX\s0 Options\fR |
| .IX Subsection "MMIX Options" |
| .PP |
| These options are defined for the \s-1MMIX:\s0 |
| .IP "\fB\-mlibfuncs\fR" 4 |
| .IX Item "-mlibfuncs" |
| .PD 0 |
| .IP "\fB\-mno\-libfuncs\fR" 4 |
| .IX Item "-mno-libfuncs" |
| .PD |
| Specify that intrinsic library functions are being compiled, passing all |
| values in registers, no matter the size. |
| .IP "\fB\-mepsilon\fR" 4 |
| .IX Item "-mepsilon" |
| .PD 0 |
| .IP "\fB\-mno\-epsilon\fR" 4 |
| .IX Item "-mno-epsilon" |
| .PD |
| Generate floating-point comparison instructions that compare with respect |
| to the \f(CW\*(C`rE\*(C'\fR epsilon register. |
| .IP "\fB\-mabi=mmixware\fR" 4 |
| .IX Item "-mabi=mmixware" |
| .PD 0 |
| .IP "\fB\-mabi=gnu\fR" 4 |
| .IX Item "-mabi=gnu" |
| .PD |
| Generate code that passes function parameters and return values that (in |
| the called function) are seen as registers \f(CW$0\fR and up, as opposed to |
| the \s-1GNU\s0 \s-1ABI\s0 which uses global registers \f(CW$231\fR and up. |
| .IP "\fB\-mzero\-extend\fR" 4 |
| .IX Item "-mzero-extend" |
| .PD 0 |
| .IP "\fB\-mno\-zero\-extend\fR" 4 |
| .IX Item "-mno-zero-extend" |
| .PD |
| When reading data from memory in sizes shorter than 64 bits, use (do not |
| use) zero-extending load instructions by default, rather than |
| sign-extending ones. |
| .IP "\fB\-mknuthdiv\fR" 4 |
| .IX Item "-mknuthdiv" |
| .PD 0 |
| .IP "\fB\-mno\-knuthdiv\fR" 4 |
| .IX Item "-mno-knuthdiv" |
| .PD |
| Make the result of a division yielding a remainder have the same sign as |
| the divisor. With the default, \fB\-mno\-knuthdiv\fR, the sign of the |
| remainder follows the sign of the dividend. Both methods are |
| arithmetically valid, the latter being almost exclusively used. |
| .IP "\fB\-mtoplevel\-symbols\fR" 4 |
| .IX Item "-mtoplevel-symbols" |
| .PD 0 |
| .IP "\fB\-mno\-toplevel\-symbols\fR" 4 |
| .IX Item "-mno-toplevel-symbols" |
| .PD |
| Prepend (do not prepend) a \fB:\fR to all global symbols, so the assembly |
| code can be used with the \f(CW\*(C`PREFIX\*(C'\fR assembly directive. |
| .IP "\fB\-melf\fR" 4 |
| .IX Item "-melf" |
| Generate an executable in the \s-1ELF\s0 format, rather than the default |
| \&\fBmmo\fR format used by the \fBmmix\fR simulator. |
| .IP "\fB\-mbranch\-predict\fR" 4 |
| .IX Item "-mbranch-predict" |
| .PD 0 |
| .IP "\fB\-mno\-branch\-predict\fR" 4 |
| .IX Item "-mno-branch-predict" |
| .PD |
| Use (do not use) the probable-branch instructions, when static branch |
| prediction indicates a probable branch. |
| .IP "\fB\-mbase\-addresses\fR" 4 |
| .IX Item "-mbase-addresses" |
| .PD 0 |
| .IP "\fB\-mno\-base\-addresses\fR" 4 |
| .IX Item "-mno-base-addresses" |
| .PD |
| Generate (do not generate) code that uses \fIbase addresses\fR. Using a |
| base address automatically generates a request (handled by the assembler |
| and the linker) for a constant to be set up in a global register. The |
| register is used for one or more base address requests within the range 0 |
| to 255 from the value held in the register. The generally leads to short |
| and fast code, but the number of different data items that can be |
| addressed is limited. This means that a program that uses lots of static |
| data may require \fB\-mno\-base\-addresses\fR. |
| .IP "\fB\-msingle\-exit\fR" 4 |
| .IX Item "-msingle-exit" |
| .PD 0 |
| .IP "\fB\-mno\-single\-exit\fR" 4 |
| .IX Item "-mno-single-exit" |
| .PD |
| Force (do not force) generated code to have a single exit point in each |
| function. |
| .PP |
| \fI\s-1MN10300\s0 Options\fR |
| .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\-mreturn\-pointer\-on\-d0\fR" 4 |
| .IX Item "-mreturn-pointer-on-d0" |
| When generating a function which returns a pointer, return the pointer |
| in both \f(CW\*(C`a0\*(C'\fR and \f(CW\*(C`d0\*(C'\fR. Otherwise, the pointer is returned |
| only in a0, and attempts to call such functions without a prototype |
| would result in errors. Note that this option is on by default; use |
| \&\fB\-mno\-return\-pointer\-on\-d0\fR to disable it. |
| .IP "\fB\-mno\-crt0\fR" 4 |
| .IX Item "-mno-crt0" |
| Do not link in the C run-time initialization object file. |
| .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 |
| \fI\s-1MT\s0 Options\fR |
| .IX Subsection "MT Options" |
| .PP |
| These \fB\-m\fR options are defined for Morpho \s-1MT\s0 architectures: |
| .IP "\fB\-march=\fR\fIcpu-type\fR" 4 |
| .IX Item "-march=cpu-type" |
| Generate code that will run on \fIcpu-type\fR, which is the name of a system |
| representing a certain processor type. Possible values for |
| \&\fIcpu-type\fR are \fBms1\-64\-001\fR, \fBms1\-16\-002\fR, |
| \&\fBms1\-16\-003\fR and \fBms2\fR. |
| .Sp |
| When this option is not used, the default is \fB\-march=ms1\-16\-002\fR. |
| .IP "\fB\-mbacc\fR" 4 |
| .IX Item "-mbacc" |
| Use byte loads and stores when generating code. |
| .IP "\fB\-mno\-bacc\fR" 4 |
| .IX Item "-mno-bacc" |
| Do not use byte loads and stores when generating code. |
| .IP "\fB\-msim\fR" 4 |
| .IX Item "-msim" |
| Use simulator runtime |
| .IP "\fB\-mno\-crt0\fR" 4 |
| .IX Item "-mno-crt0" |
| Do not link in the C run-time initialization object file |
| \&\fIcrti.o\fR. Other run-time initialization and termination files |
| such as \fIstartup.o\fR and \fIexit.o\fR are still included on the |
| linker command line. |
| .PP |
| \fI\s-1PDP\-11\s0 Options\fR |
| .IX Subsection "PDP-11 Options" |
| .PP |
| These options are defined for the \s-1PDP\-11:\s0 |
| .IP "\fB\-mfpu\fR" 4 |
| .IX Item "-mfpu" |
| Use hardware \s-1FPP\s0 floating point. This is the default. (\s-1FIS\s0 floating |
| point on the \s-1PDP\-11/40\s0 is not supported.) |
| .IP "\fB\-msoft\-float\fR" 4 |
| .IX Item "-msoft-float" |
| Do not use hardware floating point. |
| .IP "\fB\-mac0\fR" 4 |
| .IX Item "-mac0" |
| Return floating-point results in ac0 (fr0 in Unix assembler syntax). |
| .IP "\fB\-mno\-ac0\fR" 4 |
| .IX Item "-mno-ac0" |
| Return floating-point results in memory. This is the default. |
| .IP "\fB\-m40\fR" 4 |
| .IX Item "-m40" |
| Generate code for a \s-1PDP\-11/40\s0. |
| .IP "\fB\-m45\fR" 4 |
| .IX Item "-m45" |
| Generate code for a \s-1PDP\-11/45\s0. This is the default. |
| .IP "\fB\-m10\fR" 4 |
| .IX Item "-m10" |
| Generate code for a \s-1PDP\-11/10\s0. |
| .IP "\fB\-mbcopy\-builtin\fR" 4 |
| .IX Item "-mbcopy-builtin" |
| Use inline \f(CW\*(C`movmemhi\*(C'\fR patterns for copying memory. This is the |
| default. |
| .IP "\fB\-mbcopy\fR" 4 |
| .IX Item "-mbcopy" |
| Do not use inline \f(CW\*(C`movmemhi\*(C'\fR patterns for copying memory. |
| .IP "\fB\-mint16\fR" 4 |
| .IX Item "-mint16" |
| .PD 0 |
| .IP "\fB\-mno\-int32\fR" 4 |
| .IX Item "-mno-int32" |
| .PD |
| Use 16\-bit \f(CW\*(C`int\*(C'\fR. This is the default. |
| .IP "\fB\-mint32\fR" 4 |
| .IX Item "-mint32" |
| .PD 0 |
| .IP "\fB\-mno\-int16\fR" 4 |
| .IX Item "-mno-int16" |
| .PD |
| Use 32\-bit \f(CW\*(C`int\*(C'\fR. |
| .IP "\fB\-mfloat64\fR" 4 |
| .IX Item "-mfloat64" |
| .PD 0 |
| .IP "\fB\-mno\-float32\fR" 4 |
| .IX Item "-mno-float32" |
| .PD |
| Use 64\-bit \f(CW\*(C`float\*(C'\fR. This is the default. |
| .IP "\fB\-mfloat32\fR" 4 |
| .IX Item "-mfloat32" |
| .PD 0 |
| .IP "\fB\-mno\-float64\fR" 4 |
| .IX Item "-mno-float64" |
| .PD |
| Use 32\-bit \f(CW\*(C`float\*(C'\fR. |
| .IP "\fB\-mabshi\fR" 4 |
| .IX Item "-mabshi" |
| Use \f(CW\*(C`abshi2\*(C'\fR pattern. This is the default. |
| .IP "\fB\-mno\-abshi\fR" 4 |
| .IX Item "-mno-abshi" |
| Do not use \f(CW\*(C`abshi2\*(C'\fR pattern. |
| .IP "\fB\-mbranch\-expensive\fR" 4 |
| .IX Item "-mbranch-expensive" |
| Pretend that branches are expensive. This is for experimenting with |
| code generation only. |
| .IP "\fB\-mbranch\-cheap\fR" 4 |
| .IX Item "-mbranch-cheap" |
| Do not pretend that branches are expensive. This is the default. |
| .IP "\fB\-msplit\fR" 4 |
| .IX Item "-msplit" |
| Generate code for a system with split I&D. |
| .IP "\fB\-mno\-split\fR" 4 |
| .IX Item "-mno-split" |
| Generate code for a system without split I&D. This is the default. |
| .IP "\fB\-munix\-asm\fR" 4 |
| .IX Item "-munix-asm" |
| Use Unix assembler syntax. This is the default when configured for |
| \&\fBpdp11\-*\-bsd\fR. |
| .IP "\fB\-mdec\-asm\fR" 4 |
| .IX Item "-mdec-asm" |
| Use \s-1DEC\s0 assembler syntax. This is the default when configured for any |
| \&\s-1PDP\-11\s0 target other than \fBpdp11\-*\-bsd\fR. |
| .PP |
| \fIPowerPC Options\fR |
| .IX Subsection "PowerPC Options" |
| .PP |
| These are listed under |
| .PP |
| \fI\s-1IBM\s0 \s-1RS/6000\s0 and PowerPC Options\fR |
| .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" |
| .IP "\fB\-mmfcrf\fR" 4 |
| .IX Item "-mmfcrf" |
| .IP "\fB\-mno\-mfcrf\fR" 4 |
| .IX Item "-mno-mfcrf" |
| .IP "\fB\-mpopcntb\fR" 4 |
| .IX Item "-mpopcntb" |
| .IP "\fB\-mno\-popcntb\fR" 4 |
| .IX Item "-mno-popcntb" |
| .IP "\fB\-mfprnd\fR" 4 |
| .IX Item "-mfprnd" |
| .IP "\fB\-mno\-fprnd\fR" 4 |
| .IX Item "-mno-fprnd" |
| .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 Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and |
| the \s-1IBM\s0 4xx, 6xx, and follow-on 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\-mmfcrf\fR option allows \s-1GCC\s0 to generate the move from |
| condition register field instruction implemented on the \s-1POWER4\s0 |
| processor and other processors that support the PowerPC V2.01 |
| architecture. |
| The \fB\-mpopcntb\fR option allows \s-1GCC\s0 to generate the popcount and |
| double precision \s-1FP\s0 reciprocal estimate instruction implemented on the |
| \&\s-1POWER5\s0 processor and other processors that support the PowerPC V2.02 |
| architecture. |
| The \fB\-mfprnd\fR option allows \s-1GCC\s0 to generate the \s-1FP\s0 round to |
| integer instructions implemented on the \s-1POWER5+\s0 processor and other |
| processors that support the PowerPC V2.03 architecture. |
| .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. With |
| \&\fB\-mnew\-mnemonics\fR, \s-1GCC\s0 uses the assembler mnemonics defined for |
| the PowerPC architecture. With \fB\-mold\-mnemonics\fR it uses 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 \fB401\fR, \fB403\fR, |
| \&\fB405\fR, \fB405fp\fR, \fB440\fR, \fB440fp\fR, \fB505\fR, |
| \&\fB601\fR, \fB602\fR, \fB603\fR, \fB603e\fR, \fB604\fR, |
| \&\fB604e\fR, \fB620\fR, \fB630\fR, \fB740\fR, \fB7400\fR, |
| \&\fB7450\fR, \fB750\fR, \fB801\fR, \fB821\fR, \fB823\fR, |
| \&\fB860\fR, \fB970\fR, \fB8540\fR, \fBec603e\fR, \fBG3\fR, |
| \&\fBG4\fR, \fBG5\fR, \fBpower\fR, \fBpower2\fR, \fBpower3\fR, |
| \&\fBpower4\fR, \fBpower5\fR, \fBpower5+\fR, \fBpower6\fR, |
| \&\fBcommon\fR, \fBpowerpc\fR, \fBpowerpc64\fR, |
| \&\fBrios\fR, \fBrios1\fR, \fBrios2\fR, \fBrsc\fR, and \fBrs64\fR. |
| .Sp |
| \&\fB\-mcpu=common\fR selects a completely generic processor. Code |
| generated under this option will run on any \s-1POWER\s0 or PowerPC processor. |
| \&\s-1GCC\s0 will use only the instructions in the common subset of both |
| architectures, and will not use the \s-1MQ\s0 register. \s-1GCC\s0 assumes a generic |
| processor model for scheduling purposes. |
| .Sp |
| \&\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 |
| The other options specify a specific processor. Code generated under |
| those options will run best on that processor, and may not run at all on |
| others. |
| .Sp |
| The \fB\-mcpu\fR options automatically enable or disable the |
| following options: \fB\-maltivec\fR, \fB\-mfprnd\fR, |
| \&\fB\-mhard\-float\fR, \fB\-mmfcrf\fR, \fB\-mmultiple\fR, |
| \&\fB\-mnew\-mnemonics\fR, \fB\-mpopcntb\fR, \fB\-mpower\fR, |
| \&\fB\-mpower2\fR, \fB\-mpowerpc64\fR, \fB\-mpowerpc\-gpopt\fR, |
| \&\fB\-mpowerpc\-gfxopt\fR, \fB\-mstring\fR, \fB\-mmulhw\fR, \fB\-mdlmzb\fR. |
| The particular options |
| set for any particular \s-1CPU\s0 will vary between compiler versions, |
| depending on what setting seems to produce optimal code for that \s-1CPU\s0; |
| it doesn't necessarily reflect the actual hardware's capabilities. If |
| you wish to set an individual option to a particular value, you may |
| specify it after the \fB\-mcpu\fR option, like \fB\-mcpu=970 |
| \&\-mno\-altivec\fR. |
| .Sp |
| On \s-1AIX\s0, the \fB\-maltivec\fR and \fB\-mpowerpc64\fR options are |
| not enabled or disabled by the \fB\-mcpu\fR option at present because |
| \&\s-1AIX\s0 does not have full support for these options. You may still |
| enable or disable them individually if you're sure it'll work in your |
| environment. |
| .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, or |
| choice of mnemonics, as \fB\-mcpu=\fR\fIcpu_type\fR would. The same |
| values for \fIcpu_type\fR are used for \fB\-mtune\fR as for |
| \&\fB\-mcpu\fR. If both are specified, the code generated will use the |
| architecture, registers, and mnemonics set by \fB\-mcpu\fR, but the |
| scheduling parameters set by \fB\-mtune\fR. |
| .IP "\fB\-mswdiv\fR" 4 |
| .IX Item "-mswdiv" |
| .PD 0 |
| .IP "\fB\-mno\-swdiv\fR" 4 |
| .IX Item "-mno-swdiv" |
| .PD |
| Generate code to compute division as reciprocal estimate and iterative |
| refinement, creating opportunities for increased throughput. This |
| feature requires: optional PowerPC Graphics instruction set for single |
| precision and \s-1FRE\s0 instruction for double precision, assuming divides |
| cannot generate user-visible traps, and the domain values not include |
| Infinities, denormals or zero denominator. |
| .IP "\fB\-maltivec\fR" 4 |
| .IX Item "-maltivec" |
| .PD 0 |
| .IP "\fB\-mno\-altivec\fR" 4 |
| .IX Item "-mno-altivec" |
| .PD |
| Generate code that uses (does not use) AltiVec instructions, and also |
| enable the use of built-in functions that allow more direct access to |
| the AltiVec instruction set. You may also need to set |
| \&\fB\-mabi=altivec\fR to adjust the current \s-1ABI\s0 with AltiVec \s-1ABI\s0 |
| enhancements. |
| .IP "\fB\-mvrsave\fR" 4 |
| .IX Item "-mvrsave" |
| .PD 0 |
| .IP "\fB\-mno\-vrsave\fR" 4 |
| .IX Item "-mno-vrsave" |
| .PD |
| Generate \s-1VRSAVE\s0 instructions when generating AltiVec code. |
| .IP "\fB\-msecure\-plt\fR" 4 |
| .IX Item "-msecure-plt" |
| Generate code that allows ld and ld.so to build executables and shared |
| libraries with non-exec .plt and .got sections. This is a PowerPC |
| 32\-bit \s-1SYSV\s0 \s-1ABI\s0 option. |
| .IP "\fB\-mbss\-plt\fR" 4 |
| .IX Item "-mbss-plt" |
| Generate code that uses a \s-1BSS\s0 .plt section that ld.so fills in, and |
| requires .plt and .got sections that are both writable and executable. |
| This is a PowerPC 32\-bit \s-1SYSV\s0 \s-1ABI\s0 option. |
| .IP "\fB\-misel\fR" 4 |
| .IX Item "-misel" |
| .PD 0 |
| .IP "\fB\-mno\-isel\fR" 4 |
| .IX Item "-mno-isel" |
| .PD |
| This switch enables or disables the generation of \s-1ISEL\s0 instructions. |
| .IP "\fB\-misel=\fR\fIyes/no\fR" 4 |
| .IX Item "-misel=yes/no" |
| This switch has been deprecated. Use \fB\-misel\fR and |
| \&\fB\-mno\-isel\fR instead. |
| .IP "\fB\-mspe\fR" 4 |
| .IX Item "-mspe" |
| .PD 0 |
| .IP "\fB\-mno\-spe\fR" 4 |
| .IX Item "-mno-spe" |
| .PD |
| This switch enables or disables the generation of \s-1SPE\s0 simd |
| instructions. |
| .IP "\fB\-mspe=\fR\fIyes/no\fR" 4 |
| .IX Item "-mspe=yes/no" |
| This option has been deprecated. Use \fB\-mspe\fR and |
| \&\fB\-mno\-spe\fR instead. |
| .IP "\fB\-mfloat\-gprs=\fR\fIyes/single/double/no\fR" 4 |
| .IX Item "-mfloat-gprs=yes/single/double/no" |
| .PD 0 |
| .IP "\fB\-mfloat\-gprs\fR" 4 |
| .IX Item "-mfloat-gprs" |
| .PD |
| This switch enables or disables the generation of floating point |
| operations on the general purpose registers for architectures that |
| support it. |
| .Sp |
| The argument \fIyes\fR or \fIsingle\fR enables the use of |
| single-precision floating point operations. |
| .Sp |
| The argument \fIdouble\fR enables the use of single and |
| double-precision floating point operations. |
| .Sp |
| The argument \fIno\fR disables floating point operations on the |
| general purpose registers. |
| .Sp |
| This option is currently only available on the MPC854x. |
| .IP "\fB\-m32\fR" 4 |
| .IX Item "-m32" |
| .PD 0 |
| .IP "\fB\-m64\fR" 4 |
| .IX Item "-m64" |
| .PD |
| Generate code for 32\-bit or 64\-bit environments of Darwin and \s-1SVR4\s0 |
| targets (including GNU/Linux). The 32\-bit environment sets int, long |
| and pointer to 32 bits and generates code that runs on any PowerPC |
| variant. The 64\-bit environment sets int to 32 bits and long and |
| pointer to 64 bits, and generates code for PowerPC64, as for |
| \&\fB\-mpowerpc64\fR. |
| .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\-compat\fR" 4 |
| .IX Item "-mxl-compat" |
| .PD 0 |
| .IP "\fB\-mno\-xl\-compat\fR" 4 |
| .IX Item "-mno-xl-compat" |
| .PD |
| Produce code that conforms more closely to \s-1IBM\s0 \s-1XL\s0 compiler semantics |
| when using AIX-compatible \s-1ABI\s0. Pass floating-point arguments to |
| prototyped functions beyond the register save area (\s-1RSA\s0) on the stack |
| in addition to argument FPRs. Do not assume that most significant |
| double in 128\-bit long double value is properly rounded when comparing |
| values and converting to double. Use \s-1XL\s0 symbol names for long double |
| support routines. |
| .Sp |
| 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-1IBM\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-1IBM\s0 |
| \&\s-1XL\s0 compilers without optimization. |
| .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\-pthread\fR |
| option are incompatible. |
| .IP "\fB\-malign\-natural\fR" 4 |
| .IX Item "-malign-natural" |
| .PD 0 |
| .IP "\fB\-malign\-power\fR" 4 |
| .IX Item "-malign-power" |
| .PD |
| On \s-1AIX\s0, 32\-bit Darwin, and 64\-bit PowerPC GNU/Linux, the option |
| \&\fB\-malign\-natural\fR overrides the ABI-defined alignment of larger |
| types, such as floating-point doubles, on their natural size-based boundary. |
| The option \fB\-malign\-power\fR instructs \s-1GCC\s0 to follow the ABI-specified |
| alignment rules. \s-1GCC\s0 defaults to the standard alignment defined in the \s-1ABI\s0. |
| .Sp |
| On 64\-bit Darwin, natural alignment is the default, and \fB\-malign\-power\fR |
| is not supported. |
| .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\-mmulhw\fR" 4 |
| .IX Item "-mmulhw" |
| .PD 0 |
| .IP "\fB\-mno\-mulhw\fR" 4 |
| .IX Item "-mno-mulhw" |
| .PD |
| Generate code that uses (does not use) the half-word multiply and |
| multiply-accumulate instructions on the \s-1IBM\s0 405 and 440 processors. |
| These instructions are generated by default when targetting those |
| processors. |
| .IP "\fB\-mdlmzb\fR" 4 |
| .IX Item "-mdlmzb" |
| .PD 0 |
| .IP "\fB\-mno\-dlmzb\fR" 4 |
| .IX Item "-mno-dlmzb" |
| .PD |
| Generate code that uses (does not use) the string-search \fBdlmzb\fR |
| instruction on the \s-1IBM\s0 405 and 440 processors. This instruction is |
| generated by default when targetting those processors. |
| .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 bit-fields 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\-mdynamic\-no\-pic\fR" 4 |
| .IX Item "-mdynamic-no-pic" |
| On Darwin and Mac \s-1OS\s0 X systems, compile code so that it is not |
| relocatable, but that its external references are relocatable. The |
| resulting code is suitable for applications, but not shared |
| libraries. |
| .IP "\fB\-mprioritize\-restricted\-insns=\fR\fIpriority\fR" 4 |
| .IX Item "-mprioritize-restricted-insns=priority" |
| This option controls the priority that is assigned to |
| dispatch-slot restricted instructions during the second scheduling |
| pass. The argument \fIpriority\fR takes the value \fI0/1/2\fR to assign |
| \&\fIno/highest/second\-highest\fR priority to dispatch slot restricted |
| instructions. |
| .IP "\fB\-msched\-costly\-dep=\fR\fIdependence_type\fR" 4 |
| .IX Item "-msched-costly-dep=dependence_type" |
| This option controls which dependences are considered costly |
| by the target during instruction scheduling. The argument |
| \&\fIdependence_type\fR takes one of the following values: |
| \&\fIno\fR: no dependence is costly, |
| \&\fIall\fR: all dependences are costly, |
| \&\fItrue_store_to_load\fR: a true dependence from store to load is costly, |
| \&\fIstore_to_load\fR: any dependence from store to load is costly, |
| \&\fInumber\fR: any dependence which latency >= \fInumber\fR is costly. |
| .IP "\fB\-minsert\-sched\-nops=\fR\fIscheme\fR" 4 |
| .IX Item "-minsert-sched-nops=scheme" |
| This option controls which nop insertion scheme will be used during |
| the second scheduling pass. The argument \fIscheme\fR takes one of the |
| following values: |
| \&\fIno\fR: Don't insert nops. |
| \&\fIpad\fR: Pad with nops any dispatch group which has vacant issue slots, |
| according to the scheduler's grouping. |
| \&\fIregroup_exact\fR: Insert nops to force costly dependent insns into |
| separate groups. Insert exactly as many nops as needed to force an insn |
| to a new group, according to the estimated processor grouping. |
| \&\fInumber\fR: Insert nops to force costly dependent insns into |
| separate groups. Insert \fInumber\fR nops to force an insn to a new group. |
| .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\-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\-mcall\-gnu\fR" 4 |
| .IX Item "-mcall-gnu" |
| On System V.4 and embedded PowerPC systems compile code for the |
| Hurd-based \s-1GNU\s0 system. |
| .IP "\fB\-mcall\-netbsd\fR" 4 |
| .IX Item "-mcall-netbsd" |
| On System V.4 and embedded PowerPC systems compile code for the |
| NetBSD operating system. |
| .IP "\fB\-maix\-struct\-return\fR" 4 |
| .IX Item "-maix-struct-return" |
| Return all structures in memory (as specified by the \s-1AIX\s0 \s-1ABI\s0). |
| .IP "\fB\-msvr4\-struct\-return\fR" 4 |
| .IX Item "-msvr4-struct-return" |
| Return structures smaller than 8 bytes in registers (as specified by the |
| \&\s-1SVR4\s0 \s-1ABI\s0). |
| .IP "\fB\-mabi=\fR\fIabi-type\fR" 4 |
| .IX Item "-mabi=abi-type" |
| Extend the current \s-1ABI\s0 with a particular extension, or remove such extension. |
| Valid values are \fIaltivec\fR, \fIno-altivec\fR, \fIspe\fR, |
| \&\fIno-spe\fR, \fIibmlongdouble\fR, \fIieeelongdouble\fR. |
| .IP "\fB\-mabi=spe\fR" 4 |
| .IX Item "-mabi=spe" |
| Extend the current \s-1ABI\s0 with \s-1SPE\s0 \s-1ABI\s0 extensions. This does not change |
| the default \s-1ABI\s0, instead it adds the \s-1SPE\s0 \s-1ABI\s0 extensions to the current |
| \&\s-1ABI\s0. |
| .IP "\fB\-mabi=no\-spe\fR" 4 |
| .IX Item "-mabi=no-spe" |
| Disable Booke \s-1SPE\s0 \s-1ABI\s0 extensions for the current \s-1ABI\s0. |
| .IP "\fB\-mabi=ibmlongdouble\fR" 4 |
| .IX Item "-mabi=ibmlongdouble" |
| Change the current \s-1ABI\s0 to use \s-1IBM\s0 extended precision long double. |
| This is a PowerPC 32\-bit \s-1SYSV\s0 \s-1ABI\s0 option. |
| .IP "\fB\-mabi=ieeelongdouble\fR" 4 |
| .IX Item "-mabi=ieeelongdouble" |
| Change the current \s-1ABI\s0 to use \s-1IEEE\s0 extended precision long double. |
| This is a PowerPC 32\-bit Linux \s-1ABI\s0 option. |
| .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\-mwindiss\fR" 4 |
| .IX Item "-mwindiss" |
| Specify that you are compiling for the WindISS simulation environment. |
| .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 |
| data in the \fB.sdata\fR section. Put small uninitialized global |
| 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. |
| .IP "\fB\-mlongcall\fR" 4 |
| .IX Item "-mlongcall" |
| .PD 0 |
| .IP "\fB\-mno\-longcall\fR" 4 |
| .IX Item "-mno-longcall" |
| .PD |
| By default assume that all calls are far away so that a longer more |
| expensive calling sequence is required. This is required for calls |
| further than 32 megabytes (33,554,432 bytes) from the current location. |
| A short call will be generated if the compiler knows |
| the call cannot be that far away. This setting can be overridden by |
| the \f(CW\*(C`shortcall\*(C'\fR function attribute, or by \f(CW\*(C`#pragma |
| longcall(0)\*(C'\fR. |
| .Sp |
| Some linkers are capable of detecting out-of-range calls and generating |
| glue code on the fly. On these systems, long calls are unnecessary and |
| generate slower code. As of this writing, the \s-1AIX\s0 linker can do this, |
| as can the \s-1GNU\s0 linker for PowerPC/64. It is planned to add this feature |
| to the \s-1GNU\s0 linker for 32\-bit PowerPC systems as well. |
| .Sp |
| On Darwin/PPC systems, \f(CW\*(C`#pragma longcall\*(C'\fR will generate \*(L"jbsr |
| callee, L42\*(R", plus a \*(L"branch island\*(R" (glue code). The two target |
| addresses represent the callee and the \*(L"branch island\*(R". The |
| Darwin/PPC linker will prefer the first address and generate a \*(L"bl |
| callee\*(R" if the \s-1PPC\s0 \*(L"bl\*(R" instruction will reach the callee directly; |
| otherwise, the linker will generate \*(L"bl L42\*(R" to call the \*(L"branch |
| island\*(R". The \*(L"branch island\*(R" is appended to the body of the |
| calling function; it computes the full 32\-bit address of the callee |
| and jumps to it. |
| .Sp |
| On Mach-O (Darwin) systems, this option directs the compiler emit to |
| the glue for every direct call, and the Darwin linker decides whether |
| to use or discard it. |
| .Sp |
| In the future, we may cause \s-1GCC\s0 to ignore all longcall specifications |
| when the linker is known to generate glue. |
| .IP "\fB\-pthread\fR" 4 |
| .IX Item "-pthread" |
| Adds support for multithreading with the \fIpthreads\fR library. |
| This option sets flags for both the preprocessor and linker. |
| .PP |
| \fIS/390 and zSeries Options\fR |
| .IX Subsection "S/390 and zSeries Options" |
| .PP |
| These are the \fB\-m\fR options defined for the S/390 and zSeries architecture. |
| .IP "\fB\-mhard\-float\fR" 4 |
| .IX Item "-mhard-float" |
| .PD 0 |
| .IP "\fB\-msoft\-float\fR" 4 |
| .IX Item "-msoft-float" |
| .PD |
| Use (do not use) the hardware floating-point instructions and registers |
| for floating-point operations. When \fB\-msoft\-float\fR is specified, |
| functions in \fIlibgcc.a\fR will be used to perform floating-point |
| operations. When \fB\-mhard\-float\fR is specified, the compiler |
| generates \s-1IEEE\s0 floating-point instructions. This is the default. |
| .IP "\fB\-mlong\-double\-64\fR" 4 |
| .IX Item "-mlong-double-64" |
| .PD 0 |
| .IP "\fB\-mlong\-double\-128\fR" 4 |
| .IX Item "-mlong-double-128" |
| .PD |
| These switches control the size of \f(CW\*(C`long double\*(C'\fR type. A size |
| of 64bit makes the \f(CW\*(C`long double\*(C'\fR type equivalent to the \f(CW\*(C`double\*(C'\fR |
| type. This is the default. |
| .IP "\fB\-mbackchain\fR" 4 |
| .IX Item "-mbackchain" |
| .PD 0 |
| .IP "\fB\-mno\-backchain\fR" 4 |
| .IX Item "-mno-backchain" |
| .PD |
| Store (do not store) the address of the caller's frame as backchain pointer |
| into the callee's stack frame. |
| A backchain may be needed to allow debugging using tools that do not understand |
| \&\s-1DWARF\-2\s0 call frame information. |
| When \fB\-mno\-packed\-stack\fR is in effect, the backchain pointer is stored |
| at the bottom of the stack frame; when \fB\-mpacked\-stack\fR is in effect, |
| the backchain is placed into the topmost word of the 96/160 byte register |
| save area. |
| .Sp |
| In general, code compiled with \fB\-mbackchain\fR is call-compatible with |
| code compiled with \fB\-mmo\-backchain\fR; however, use of the backchain |
| for debugging purposes usually requires that the whole binary is built with |
| \&\fB\-mbackchain\fR. Note that the combination of \fB\-mbackchain\fR, |
| \&\fB\-mpacked\-stack\fR and \fB\-mhard\-float\fR is not supported. In order |
| to build a linux kernel use \fB\-msoft\-float\fR. |
| .Sp |
| The default is to not maintain the backchain. |
| .IP "\fB\-mpacked\-stack\fR" 4 |
| .IX Item "-mpacked-stack" |
| .PD 0 |
| .IP "\fB\-mno\-packed\-stack\fR" 4 |
| .IX Item "-mno-packed-stack" |
| .PD |
| Use (do not use) the packed stack layout. When \fB\-mno\-packed\-stack\fR is |
| specified, the compiler uses the all fields of the 96/160 byte register save |
| area only for their default purpose; unused fields still take up stack space. |
| When \fB\-mpacked\-stack\fR is specified, register save slots are densely |
| packed at the top of the register save area; unused space is reused for other |
| purposes, allowing for more efficient use of the available stack space. |
| However, when \fB\-mbackchain\fR is also in effect, the topmost word of |
| the save area is always used to store the backchain, and the return address |
| register is always saved two words below the backchain. |
| .Sp |
| As long as the stack frame backchain is not used, code generated with |
| \&\fB\-mpacked\-stack\fR is call-compatible with code generated with |
| \&\fB\-mno\-packed\-stack\fR. Note that some non-FSF releases of \s-1GCC\s0 2.95 for |
| S/390 or zSeries generated code that uses the stack frame backchain at run |
| time, not just for debugging purposes. Such code is not call-compatible |
| with code compiled with \fB\-mpacked\-stack\fR. Also, note that the |
| combination of \fB\-mbackchain\fR, |
| \&\fB\-mpacked\-stack\fR and \fB\-mhard\-float\fR is not supported. In order |
| to build a linux kernel use \fB\-msoft\-float\fR. |
| .Sp |
| The default is to not use the packed stack layout. |
| .IP "\fB\-msmall\-exec\fR" 4 |
| .IX Item "-msmall-exec" |
| .PD 0 |
| .IP "\fB\-mno\-small\-exec\fR" 4 |
| .IX Item "-mno-small-exec" |
| .PD |
| Generate (or do not generate) code using the \f(CW\*(C`bras\*(C'\fR instruction |
| to do subroutine calls. |
| This only works reliably if the total executable size does not |
| exceed 64k. The default is to use the \f(CW\*(C`basr\*(C'\fR instruction instead, |
| which does not have this limitation. |
| .IP "\fB\-m64\fR" 4 |
| .IX Item "-m64" |
| .PD 0 |
| .IP "\fB\-m31\fR" 4 |
| .IX Item "-m31" |
| .PD |
| When \fB\-m31\fR is specified, generate code compliant to the |
| GNU/Linux for S/390 \s-1ABI\s0. When \fB\-m64\fR is specified, generate |
| code compliant to the GNU/Linux for zSeries \s-1ABI\s0. This allows \s-1GCC\s0 in |
| particular to generate 64\-bit instructions. For the \fBs390\fR |
| targets, the default is \fB\-m31\fR, while the \fBs390x\fR |
| targets default to \fB\-m64\fR. |
| .IP "\fB\-mzarch\fR" 4 |
| .IX Item "-mzarch" |
| .PD 0 |
| .IP "\fB\-mesa\fR" 4 |
| .IX Item "-mesa" |
| .PD |
| When \fB\-mzarch\fR is specified, generate code using the |
| instructions available on z/Architecture. |
| When \fB\-mesa\fR is specified, generate code using the |
| instructions available on \s-1ESA/390\s0. Note that \fB\-mesa\fR is |
| not possible with \fB\-m64\fR. |
| When generating code compliant to the GNU/Linux for S/390 \s-1ABI\s0, |
| the default is \fB\-mesa\fR. When generating code compliant |
| to the GNU/Linux for zSeries \s-1ABI\s0, the default is \fB\-mzarch\fR. |
| .IP "\fB\-mmvcle\fR" 4 |
| .IX Item "-mmvcle" |
| .PD 0 |
| .IP "\fB\-mno\-mvcle\fR" 4 |
| .IX Item "-mno-mvcle" |
| .PD |
| Generate (or do not generate) code using the \f(CW\*(C`mvcle\*(C'\fR instruction |
| to perform block moves. When \fB\-mno\-mvcle\fR is specified, |
| use a \f(CW\*(C`mvc\*(C'\fR loop instead. This is the default unless optimizing for |
| size. |
| .IP "\fB\-mdebug\fR" 4 |
| .IX Item "-mdebug" |
| .PD 0 |
| .IP "\fB\-mno\-debug\fR" 4 |
| .IX Item "-mno-debug" |
| .PD |
| Print (or do not print) additional debug information when compiling. |
| The default is to not print debug information. |
| .IP "\fB\-march=\fR\fIcpu-type\fR" 4 |
| .IX Item "-march=cpu-type" |
| Generate code that will run on \fIcpu-type\fR, which is the name of a system |
| representing a certain processor type. Possible values for |
| \&\fIcpu-type\fR are \fBg5\fR, \fBg6\fR, \fBz900\fR, and \fBz990\fR. |
| When generating code using the instructions available on z/Architecture, |
| the default is \fB\-march=z900\fR. Otherwise, the default is |
| \&\fB\-march=g5\fR. |
| .IP "\fB\-mtune=\fR\fIcpu-type\fR" 4 |
| .IX Item "-mtune=cpu-type" |
| Tune to \fIcpu-type\fR everything applicable about the generated code, |
| except for the \s-1ABI\s0 and the set of available instructions. |
| The list of \fIcpu-type\fR values is the same as for \fB\-march\fR. |
| The default is the value used for \fB\-march\fR. |
| .IP "\fB\-mtpf\-trace\fR" 4 |
| .IX Item "-mtpf-trace" |
| .PD 0 |
| .IP "\fB\-mno\-tpf\-trace\fR" 4 |
| .IX Item "-mno-tpf-trace" |
| .PD |
| Generate code that adds (does not add) in \s-1TPF\s0 \s-1OS\s0 specific branches to trace |
| routines in the operating system. This option is off by default, even |
| when compiling for the \s-1TPF\s0 \s-1OS\s0. |
| .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 point is used. |
| .IP "\fB\-mwarn\-framesize=\fR\fIframesize\fR" 4 |
| .IX Item "-mwarn-framesize=framesize" |
| Emit a warning if the current function exceeds the given frame size. Because |
| this is a compile time check it doesn't need to be a real problem when the program |
| runs. It is intended to identify functions which most probably cause |
| a stack overflow. It is useful to be used in an environment with limited stack |
| size e.g. the linux kernel. |
| .IP "\fB\-mwarn\-dynamicstack\fR" 4 |
| .IX Item "-mwarn-dynamicstack" |
| Emit a warning if the function calls alloca or uses dynamically |
| sized arrays. This is generally a bad idea with a limited stack size. |
| .IP "\fB\-mstack\-guard=\fR\fIstack-guard\fR" 4 |
| .IX Item "-mstack-guard=stack-guard" |
| .PD 0 |
| .IP "\fB\-mstack\-size=\fR\fIstack-size\fR" 4 |
| .IX Item "-mstack-size=stack-size" |
| .PD |
| These arguments always have to be used in conjunction. If they are present the s390 |
| back end emits additional instructions in the function prologue which trigger a trap |
| if the stack size is \fIstack-guard\fR bytes above the \fIstack-size\fR |
| (remember that the stack on s390 grows downward). These options are intended to |
| be used to help debugging stack overflow problems. The additionally emitted code |
| causes only little overhead and hence can also be used in production like systems |
| without greater performance degradation. The given values have to be exact |
| powers of 2 and \fIstack-size\fR has to be greater than \fIstack-guard\fR without |
| exceeding 64k. |
| In order to be efficient the extra code makes the assumption that the stack starts |
| at an address aligned to the value given by \fIstack-size\fR. |
| .PP |
| \fIScore Options\fR |
| .IX Subsection "Score Options" |
| .PP |
| These options are defined for Score implementations: |
| .IP "\fB\-mel\fR" 4 |
| .IX Item "-mel" |
| Compile code for little endian mode. |
| .IP "\fB\-meb\fR" 4 |
| .IX Item "-meb" |
| Compile code for big endian mode. This is the default. |
| .IP "\fB\-mmac\fR" 4 |
| .IX Item "-mmac" |
| Enable the use of multiply-accumulate instructions. Disabled by default. |
| .IP "\fB\-mscore5u\fR" 4 |
| .IX Item "-mscore5u" |
| Specify the \s-1SCORE5U\s0 of the target architecture. |
| .IP "\fB\-mscore7\fR" 4 |
| .IX Item "-mscore7" |
| Specify the \s-1SCORE7\s0 of the target architecture. This is the default. |
| .PP |
| \fI\s-1SH\s0 Options\fR |
| .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\-m2e\fR" 4 |
| .IX Item "-m2e" |
| Generate code for the SH2e. |
| .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 arithmetic. |
| .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\-m4a\-nofpu\fR" 4 |
| .IX Item "-m4a-nofpu" |
| Generate code for the SH4al\-dsp, or for a SH4a in such a way that the |
| floating-point unit is not used. |
| .IP "\fB\-m4a\-single\-only\fR" 4 |
| .IX Item "-m4a-single-only" |
| Generate code for the SH4a, in such a way that no double-precision |
| floating point operations are used. |
| .IP "\fB\-m4a\-single\fR" 4 |
| .IX Item "-m4a-single" |
| Generate code for the SH4a assuming the floating-point unit is in |
| single-precision mode by default. |
| .IP "\fB\-m4a\fR" 4 |
| .IX Item "-m4a" |
| Generate code for the SH4a. |
| .IP "\fB\-m4al\fR" 4 |
| .IX Item "-m4al" |
| Same as \fB\-m4a\-nofpu\fR, except that it implicitly passes |
| \&\fB\-dsp\fR to the assembler. \s-1GCC\s0 doesn't generate any \s-1DSP\s0 |
| instructions at the moment. |
| .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 \fB\-mdalign\fR. |
| .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 Renesas. |
| .IP "\fB\-mrenesas\fR" 4 |
| .IX Item "-mrenesas" |
| Comply with the calling conventions defined by Renesas. |
| .IP "\fB\-mno\-renesas\fR" 4 |
| .IX Item "-mno-renesas" |
| Comply with the calling conventions defined for \s-1GCC\s0 before the Renesas |
| conventions were available. This option is the default for all |
| targets of the \s-1SH\s0 toolchain except for \fBsh-symbianelf\fR. |
| .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\-mieee\fR" 4 |
| .IX Item "-mieee" |
| Increase IEEE-compliance of floating-point code. |
| At the moment, this is equivalent to \fB\-fno\-finite\-math\-only\fR. |
| When generating 16 bit \s-1SH\s0 opcodes, getting IEEE-conforming results for |
| comparisons of NANs / infinities incurs extra overhead in every |
| floating point comparison, therefore the default is set to |
| \&\fB\-ffinite\-math\-only\fR. |
| .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. |
| .IP "\fB\-multcost=\fR\fInumber\fR" 4 |
| .IX Item "-multcost=number" |
| Set the cost to assume for a multiply insn. |
| .IP "\fB\-mdiv=\fR\fIstrategy\fR" 4 |
| .IX Item "-mdiv=strategy" |
| Set the division strategy to use for SHmedia code. \fIstrategy\fR must be |
| one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call, |
| inv:call2, inv:fp . |
| \&\*(L"fp\*(R" performs the operation in floating point. This has a very high latency, |
| but needs only a few instructions, so it might be a good choice if |
| your code has enough easily exploitable \s-1ILP\s0 to allow the compiler to |
| schedule the floating point instructions together with other instructions. |
| Division by zero causes a floating point exception. |
| \&\*(L"inv\*(R" uses integer operations to calculate the inverse of the divisor, |
| and then multiplies the dividend with the inverse. This strategy allows |
| cse and hoisting of the inverse calculation. Division by zero calculates |
| an unspecified result, but does not trap. |
| \&\*(L"inv:minlat\*(R" is a variant of \*(L"inv\*(R" where if no cse / hoisting opportunities |
| have been found, or if the entire operation has been hoisted to the same |
| place, the last stages of the inverse calculation are intertwined with the |
| final multiply to reduce the overall latency, at the expense of using a few |
| more instructions, and thus offering fewer scheduling opportunities with |
| other code. |
| \&\*(L"call\*(R" calls a library function that usually implements the inv:minlat |
| strategy. |
| This gives high code density for m5\-*media\-nofpu compilations. |
| \&\*(L"call2\*(R" uses a different entry point of the same library function, where it |
| assumes that a pointer to a lookup table has already been set up, which |
| exposes the pointer load to cse / code hoisting optimizations. |
| \&\*(L"inv:call\*(R", \*(L"inv:call2\*(R" and \*(L"inv:fp\*(R" all use the \*(L"inv\*(R" algorithm for initial |
| code generation, but if the code stays unoptimized, revert to the \*(L"call\*(R", |
| \&\*(L"call2\*(R", or \*(L"fp\*(R" strategies, respectively. Note that the |
| potentially-trapping side effect of division by zero is carried by a |
| separate instruction, so it is possible that all the integer instructions |
| are hoisted out, but the marker for the side effect stays where it is. |
| A recombination to fp operations or a call is not possible in that case. |
| \&\*(L"inv20u\*(R" and \*(L"inv20l\*(R" are variants of the \*(L"inv:minlat\*(R" strategy. In the case |
| that the inverse calculation was nor separated from the multiply, they speed |
| up division where the dividend fits into 20 bits (plus sign where applicable), |
| by inserting a test to skip a number of operations in this case; this test |
| slows down the case of larger dividends. inv20u assumes the case of a such |
| a small dividend to be unlikely, and inv20l assumes it to be likely. |
| .IP "\fB\-mdivsi3_libfunc=\fR\fIname\fR" 4 |
| .IX Item "-mdivsi3_libfunc=name" |
| Set the name of the library function used for 32 bit signed division to |
| \&\fIname\fR. This only affect the name used in the call and inv:call |
| division strategies, and the compiler will still expect the same |
| sets of input/output/clobbered registers as if this option was not present. |
| .IP "\fB\-madjust\-unroll\fR" 4 |
| .IX Item "-madjust-unroll" |
| Throttle unrolling to avoid thrashing target registers. |
| This option only has an effect if the gcc code base supports the |
| \&\s-1TARGET_ADJUST_UNROLL_MAX\s0 target hook. |
| .IP "\fB\-mindexed\-addressing\fR" 4 |
| .IX Item "-mindexed-addressing" |
| Enable the use of the indexed addressing mode for SHmedia32/SHcompact. |
| This is only safe if the hardware and/or \s-1OS\s0 implement 32 bit wrap-around |
| semantics for the indexed addressing mode. The architecture allows the |
| implementation of processors with 64 bit \s-1MMU\s0, which the \s-1OS\s0 could use to |
| get 32 bit addressing, but since no current hardware implementation supports |
| this or any other way to make the indexed addressing mode safe to use in |
| the 32 bit \s-1ABI\s0, the default is \-mno\-indexed\-addressing. |
| .IP "\fB\-mgettrcost=\fR\fInumber\fR" 4 |
| .IX Item "-mgettrcost=number" |
| Set the cost assumed for the gettr instruction to \fInumber\fR. |
| The default is 2 if \fB\-mpt\-fixed\fR is in effect, 100 otherwise. |
| .IP "\fB\-mpt\-fixed\fR" 4 |
| .IX Item "-mpt-fixed" |
| Assume pt* instructions won't trap. This will generally generate better |
| scheduled code, but is unsafe on current hardware. The current architecture |
| definition says that ptabs and ptrel trap when the target anded with 3 is 3. |
| This has the unintentional effect of making it unsafe to schedule ptabs / |
| ptrel before a branch, or hoist it out of a loop. For example, |
| _\|_do_global_ctors, a part of libgcc that runs constructors at program |
| startup, calls functions in a list which is delimited by \-1. With the |
| \&\-mpt\-fixed option, the ptabs will be done before testing against \-1. |
| That means that all the constructors will be run a bit quicker, but when |
| the loop comes to the end of the list, the program crashes because ptabs |
| loads \-1 into a target register. Since this option is unsafe for any |
| hardware implementing the current architecture specification, the default |
| is \-mno\-pt\-fixed. Unless the user specifies a specific cost with |
| \&\fB\-mgettrcost\fR, \-mno\-pt\-fixed also implies \fB\-mgettrcost=100\fR; |
| this deters register allocation using target registers for storing |
| ordinary integers. |
| .IP "\fB\-minvalid\-symbols\fR" 4 |
| .IX Item "-minvalid-symbols" |
| Assume symbols might be invalid. Ordinary function symbols generated by |
| the compiler will always be valid to load with movi/shori/ptabs or |
| movi/shori/ptrel, but with assembler and/or linker tricks it is possible |
| to generate symbols that will cause ptabs / ptrel to trap. |
| This option is only meaningful when \fB\-mno\-pt\-fixed\fR is in effect. |
| It will then prevent cross-basic-block cse, hoisting and most scheduling |
| of symbol loads. The default is \fB\-mno\-invalid\-symbols\fR. |
| .PP |
| \fI\s-1SPARC\s0 Options\fR |
| .IX Subsection "SPARC Options" |
| .PP |
| These \fB\-m\fR options 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 \s-1SPARC\s0 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\-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 \s-1SPARC\s0 |
| \&\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\-mimpure\-text\fR" 4 |
| .IX Item "-mimpure-text" |
| \&\fB\-mimpure\-text\fR, used in addition to \fB\-shared\fR, tells |
| the compiler to not pass \fB\-z text\fR to the linker when linking a |
| shared object. Using this option, you can link position-dependent |
| code into a shared object. |
| .Sp |
| \&\fB\-mimpure\-text\fR suppresses the \*(L"relocations remain against |
| allocatable but non-writable sections\*(R" linker error message. |
| However, the necessary relocations will trigger copy\-on\-write, and the |
| shared object is not actually shared across processes. Instead of |
| using \fB\-mimpure\-text\fR, you should compile all source code with |
| \&\fB\-fpic\fR or \fB\-fPIC\fR. |
| .Sp |
| This option is only available on SunOS and Solaris. |
| .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, |
| \&\fBf930\fR, \fBf934\fR, \fBhypersparc\fR, \fBsparclite86x\fR, |
| \&\fBsparclet\fR, \fBtsc701\fR, \fBv9\fR, \fBultrasparc\fR, |
| \&\fBultrasparc3\fR, and \fBniagara\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, ultrasparc3, niagara |
| .Ve |
| .Sp |
| By default (unless configured otherwise), \s-1GCC\s0 generates code for the V7 |
| variant of the \s-1SPARC\s0 architecture. With \fB\-mcpu=cypress\fR, the compiler |
| additionally optimizes it 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\-mcpu=v8\fR, \s-1GCC\s0 generates code for the V8 variant of the \s-1SPARC\s0 |
| architecture. The only difference from V7 code is that the compiler emits |
| the integer multiply and integer divide instructions which exist in \s-1SPARC\-V8\s0 |
| but not in \s-1SPARC\-V7\s0. With \fB\-mcpu=supersparc\fR, the compiler additionally |
| optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and |
| 2000 series. |
| .Sp |
| With \fB\-mcpu=sparclite\fR, \s-1GCC\s0 generates code for the SPARClite variant of |
| the \s-1SPARC\s0 architecture. 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\-V7\s0. |
| With \fB\-mcpu=f930\fR, the compiler additionally optimizes it for the |
| Fujitsu \s-1MB86930\s0 chip, which is the original SPARClite, with no \s-1FPU\s0. With |
| \&\fB\-mcpu=f934\fR, the compiler additionally optimizes it for the Fujitsu |
| \&\s-1MB86934\s0 chip, which is the more recent SPARClite with \s-1FPU\s0. |
| .Sp |
| With \fB\-mcpu=sparclet\fR, \s-1GCC\s0 generates code for the SPARClet variant of |
| the \s-1SPARC\s0 architecture. This adds the integer multiply, multiply/accumulate, |
| integer divide step and scan (\f(CW\*(C`ffs\*(C'\fR) instructions which exist in SPARClet |
| but not in \s-1SPARC\-V7\s0. With \fB\-mcpu=tsc701\fR, the compiler additionally |
| optimizes it for the \s-1TEMIC\s0 SPARClet chip. |
| .Sp |
| With \fB\-mcpu=v9\fR, \s-1GCC\s0 generates code for the V9 variant of the \s-1SPARC\s0 |
| architecture. This adds 64\-bit integer and floating-point move instructions, |
| 3 additional floating-point condition code registers and conditional move |
| instructions. With \fB\-mcpu=ultrasparc\fR, the compiler additionally |
| optimizes it for the Sun UltraSPARC I/II/IIi chips. With |
| \&\fB\-mcpu=ultrasparc3\fR, the compiler additionally optimizes it for the |
| Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With |
| \&\fB\-mcpu=niagara\fR, the compiler additionally optimizes it for |
| Sun UltraSPARC T1 chips. |
| .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 can be used for |
| \&\fB\-mtune=\fR\fIcpu_type\fR, but the only useful values are those |
| that select a particular cpu implementation. Those are \fBcypress\fR, |
| \&\fBsupersparc\fR, \fBhypersparc\fR, \fBf930\fR, \fBf934\fR, |
| \&\fBsparclite86x\fR, \fBtsc701\fR, \fBultrasparc\fR, |
| \&\fBultrasparc3\fR, and \fBniagara\fR. |
| .IP "\fB\-mv8plus\fR" 4 |
| .IX Item "-mv8plus" |
| .PD 0 |
| .IP "\fB\-mno\-v8plus\fR" 4 |
| .IX Item "-mno-v8plus" |
| .PD |
| With \fB\-mv8plus\fR, \s-1GCC\s0 generates code for the \s-1SPARC\-V8+\s0 \s-1ABI\s0. The |
| difference from the V8 \s-1ABI\s0 is that the global and out registers are |
| considered 64\-bit wide. This is enabled by default on Solaris in 32\-bit |
| mode for all \s-1SPARC\-V9\s0 processors. |
| .IP "\fB\-mvis\fR" 4 |
| .IX Item "-mvis" |
| .PD 0 |
| .IP "\fB\-mno\-vis\fR" 4 |
| .IX Item "-mno-vis" |
| .PD |
| With \fB\-mvis\fR, \s-1GCC\s0 generates code that takes advantage of the UltraSPARC |
| Visual Instruction Set extensions. The default is \fB\-mno\-vis\fR. |
| .PP |
| These \fB\-m\fR options are supported in addition to the above |
| on \s-1SPARC\-V9\s0 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. It is only |
| available for a few configurations and most notably not on Solaris and Linux. |
| .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: 64\-bit addresses, programs |
| must be linked in the low 32 bits of memory. 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: 64\-bit addresses, programs |
| must be linked in the low 44 bits of memory, the text and data segments must |
| be less than 2GB in size and the data segment must be located within 2GB of |
| the text segment. |
| .IP "\fB\-mcmodel=medany\fR" 4 |
| .IX Item "-mcmodel=medany" |
| Generate code for the Medium/Anywhere code model: 64\-bit addresses, programs |
| may be linked anywhere in memory, the text and data segments must be less |
| than 2GB in size and the data segment must be located within 2GB of the |
| text segment. |
| .IP "\fB\-mcmodel=embmedany\fR" 4 |
| .IX Item "-mcmodel=embmedany" |
| Generate code for the Medium/Anywhere code model for embedded systems: |
| 64\-bit addresses, the text and data segments must be less than 2GB in |
| size, both starting anywhere in memory (determined at link time). The |
| global register \f(CW%g4\fR points to the base of the data segment. Programs |
| are statically linked and \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. This is the default in 64\-bit mode. |
| Otherwise, assume no such offset is present. |
| .PP |
| These switches are supported in addition to the above on Solaris: |
| .IP "\fB\-threads\fR" 4 |
| .IX Item "-threads" |
| Add support for multithreading using the Solaris threads library. This |
| option sets flags for both the preprocessor and linker. This option does |
| not affect the thread safety of object code produced by the compiler or |
| that of libraries supplied with it. |
| .IP "\fB\-pthreads\fR" 4 |
| .IX Item "-pthreads" |
| Add support for multithreading using the \s-1POSIX\s0 threads library. This |
| option sets flags for both the preprocessor and linker. This option does |
| not affect the thread safety of object code produced by the compiler or |
| that of libraries supplied with it. |
| .IP "\fB\-pthread\fR" 4 |
| .IX Item "-pthread" |
| This is a synonym for \fB\-pthreads\fR. |
| .PP |
| \fIOptions for System V\fR |
| .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 |
| \fITMS320C3x/C4x Options\fR |
| .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, |
| DBcond(D), instructions. This is enabled by default for the C4x. To be |
| on the safe side, this is disabled for the C3x, since the maximum |
| iteration count on the C3x is 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 utilize the decrement and branch instruction, but will give |
| up if there is more than one memory reference in the loop. Thus a loop |
| where the loop counter is decremented can generate slightly more |
| efficient code, in cases where the \s-1RPTB\s0 instruction cannot be utilized. |
| .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 \fB\-mmpyi\fR 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 \fB\-O2\fR. |
| .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 \fB\-O2\fR. |
| .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 \fB\-mparallel\-insns\fR is also specified. These instructions have |
| tight register constraints which can pessimize the code generation |
| of large functions. |
| .PP |
| \fIV850 Options\fR |
| .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 prologue and epilogue of a function. The external functions |
| are slower, but use less code space if more than one function saves |
| the same number of registers. The \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. |
| .IP "\fB\-mapp\-regs\fR" 4 |
| .IX Item "-mapp-regs" |
| This option will cause r2 and r5 to be used in the code generated by |
| the compiler. This setting is the default. |
| .IP "\fB\-mno\-app\-regs\fR" 4 |
| .IX Item "-mno-app-regs" |
| This option will cause r2 and r5 to be treated as fixed registers. |
| .IP "\fB\-mv850e1\fR" 4 |
| .IX Item "-mv850e1" |
| Specify that the target processor is the V850E1. The preprocessor |
| constants \fB_\|_v850e1_\|_\fR and \fB_\|_v850e_\|_\fR will be defined if |
| this option is used. |
| .IP "\fB\-mv850e\fR" 4 |
| .IX Item "-mv850e" |
| Specify that the target processor is the V850E. The preprocessor |
| constant \fB_\|_v850e_\|_\fR will be defined if this option is used. |
| .Sp |
| If neither \fB\-mv850\fR nor \fB\-mv850e\fR nor \fB\-mv850e1\fR |
| are defined then a default target processor will be chosen and the |
| relevant \fB_\|_v850*_\|_\fR preprocessor constant will be defined. |
| .Sp |
| The preprocessor constants \fB_\|_v850\fR and \fB_\|_v851_\|_\fR are always |
| defined, regardless of which processor variant is the target. |
| .IP "\fB\-mdisable\-callt\fR" 4 |
| .IX Item "-mdisable-callt" |
| This option will suppress generation of the \s-1CALLT\s0 instruction for the |
| v850e and v850e1 flavors of the v850 architecture. The default is |
| \&\fB\-mno\-disable\-callt\fR which allows the \s-1CALLT\s0 instruction to be used. |
| .PP |
| \fI\s-1VAX\s0 Options\fR |
| .IX Subsection "VAX Options" |
| .PP |
| These \fB\-m\fR options are defined for the \s-1VAX:\s0 |
| .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 \s-1VAX\s0 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 |
| \fIx86\-64 Options\fR |
| .IX Subsection "x86-64 Options" |
| .PP |
| These are listed under |
| .PP |
| \fIXstormy16 Options\fR |
| .IX Subsection "Xstormy16 Options" |
| .PP |
| These options are defined for Xstormy16: |
| .IP "\fB\-msim\fR" 4 |
| .IX Item "-msim" |
| Choose startup files and linker script suitable for the simulator. |
| .PP |
| \fIXtensa Options\fR |
| .IX Subsection "Xtensa Options" |
| .PP |
| These options are supported for Xtensa targets: |
| .IP "\fB\-mconst16\fR" 4 |
| .IX Item "-mconst16" |
| .PD 0 |
| .IP "\fB\-mno\-const16\fR" 4 |
| .IX Item "-mno-const16" |
| .PD |
| Enable or disable use of \f(CW\*(C`CONST16\*(C'\fR instructions for loading |
| constant values. The \f(CW\*(C`CONST16\*(C'\fR instruction is currently not a |
| standard option from Tensilica. When enabled, \f(CW\*(C`CONST16\*(C'\fR |
| instructions are always used in place of the standard \f(CW\*(C`L32R\*(C'\fR |
| instructions. The use of \f(CW\*(C`CONST16\*(C'\fR is enabled by default only if |
| the \f(CW\*(C`L32R\*(C'\fR instruction is not available. |
| .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 |
| Enable or disable use of fused multiply/add and multiply/subtract |
| instructions in the floating-point option. This has no effect if the |
| floating-point option is not also enabled. Disabling fused multiply/add |
| and multiply/subtract instructions forces the compiler to use separate |
| instructions for the multiply and add/subtract operations. This may be |
| desirable in some cases where strict \s-1IEEE\s0 754\-compliant results are |
| required: the fused multiply add/subtract instructions do not round the |
| intermediate result, thereby producing results with \fImore\fR bits of |
| precision than specified by the \s-1IEEE\s0 standard. Disabling fused multiply |
| add/subtract instructions also ensures that the program output is not |
| sensitive to the compiler's ability to combine multiply and add/subtract |
| operations. |
| .IP "\fB\-mtext\-section\-literals\fR" 4 |
| .IX Item "-mtext-section-literals" |
| .PD 0 |
| .IP "\fB\-mno\-text\-section\-literals\fR" 4 |
| .IX Item "-mno-text-section-literals" |
| .PD |
| Control the treatment of literal pools. The default is |
| \&\fB\-mno\-text\-section\-literals\fR, which places literals in a separate |
| section in the output file. This allows the literal pool to be placed |
| in a data \s-1RAM/ROM\s0, and it also allows the linker to combine literal |
| pools from separate object files to remove redundant literals and |
| improve code size. With \fB\-mtext\-section\-literals\fR, the literals |
| are interspersed in the text section in order to keep them as close as |
| possible to their references. This may be necessary for large assembly |
| files. |
| .IP "\fB\-mtarget\-align\fR" 4 |
| .IX Item "-mtarget-align" |
| .PD 0 |
| .IP "\fB\-mno\-target\-align\fR" 4 |
| .IX Item "-mno-target-align" |
| .PD |
| When this option is enabled, \s-1GCC\s0 instructs the assembler to |
| automatically align instructions to reduce branch penalties at the |
| expense of some code density. The assembler attempts to widen density |
| instructions to align branch targets and the instructions following call |
| instructions. If there are not enough preceding safe density |
| instructions to align a target, no widening will be performed. The |
| default is \fB\-mtarget\-align\fR. These options do not affect the |
| treatment of auto-aligned instructions like \f(CW\*(C`LOOP\*(C'\fR, which the |
| assembler will always align, either by widening density instructions or |
| by inserting no-op instructions. |
| .IP "\fB\-mlongcalls\fR" 4 |
| .IX Item "-mlongcalls" |
| .PD 0 |
| .IP "\fB\-mno\-longcalls\fR" 4 |
| .IX Item "-mno-longcalls" |
| .PD |
| When this option is enabled, \s-1GCC\s0 instructs the assembler to translate |
| direct calls to indirect calls unless it can determine that the target |
| of a direct call is in the range allowed by the call instruction. This |
| translation typically occurs for calls to functions in other source |
| files. Specifically, the assembler translates a direct \f(CW\*(C`CALL\*(C'\fR |
| instruction into an \f(CW\*(C`L32R\*(C'\fR followed by a \f(CW\*(C`CALLX\*(C'\fR instruction. |
| The default is \fB\-mno\-longcalls\fR. This option should be used in |
| programs where the call target can potentially be out of range. This |
| option is implemented in the assembler, not the compiler, so the |
| assembly code generated by \s-1GCC\s0 will still show direct call |
| instructions\-\-\-look at the disassembled object code to see the actual |
| instructions. Note that the assembler will use an indirect call for |
| every cross-file call, not just those that really will be out of range. |
| .PP |
| \fIzSeries Options\fR |
| .IX Subsection "zSeries Options" |
| .PP |
| These are listed under |
| .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\-fbounds\-check\fR" 4 |
| .IX Item "-fbounds-check" |
| For front-ends that support it, generate additional code to check that |
| indices used to access arrays are within the declared range. This is |
| currently only supported by the Java and Fortran front\-ends, where |
| this option defaults to true and false respectively. |
| .IP "\fB\-ftrapv\fR" 4 |
| .IX Item "-ftrapv" |
| This option generates traps for signed overflow on addition, subtraction, |
| multiplication operations. |
| .IP "\fB\-fwrapv\fR" 4 |
| .IX Item "-fwrapv" |
| This option instructs the compiler to assume that signed arithmetic |
| overflow of addition, subtraction and multiplication wraps around |
| using twos-complement representation. This flag enables some optimizations |
| and disables others. This option is enabled by default for the Java |
| front\-end, as required by the Java language specification. |
| .IP "\fB\-fexceptions\fR" 4 |
| .IX Item "-fexceptions" |
| Enable exception handling. Generates extra code needed to propagate |
| exceptions. For some targets, this implies \s-1GCC\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-1GCC\s0 will enable it by default for languages like |
| \&\*(C+ which normally require exception handling, and disable it for |
| languages like C that do not normally require it. However, you may need |
| to enable this option when compiling C code that needs to interoperate |
| properly with exception handlers written in \*(C+. You may also wish to |
| disable this option if you are compiling older \*(C+ programs that don't |
| use exception handling. |
| .IP "\fB\-fnon\-call\-exceptions\fR" 4 |
| .IX Item "-fnon-call-exceptions" |
| Generate code that allows trapping instructions to throw exceptions. |
| Note that this requires platform-specific runtime support that does |
| not exist everywhere. Moreover, it only allows \fItrapping\fR |
| instructions to throw exceptions, i.e. memory references or floating |
| point instructions. It does not allow exceptions to be thrown from |
| arbitrary signal handlers such as \f(CW\*(C`SIGALRM\*(C'\fR. |
| .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\-fasynchronous\-unwind\-tables\fR" 4 |
| .IX Item "-fasynchronous-unwind-tables" |
| Generate unwind table in dwarf2 format, if supported by target machine. The |
| table is exact at each instruction boundary, so it can be used for stack |
| unwinding from asynchronous events (such as debugger or garbage collector). |
| .IP "\fB\-fpcc\-struct\-return\fR" 4 |
| .IX Item "-fpcc-struct-return" |
| Return \*(L"short\*(R" \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, particularly |
| the Portable C Compiler (pcc). |
| .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. |
| .Sp |
| \&\fBWarning:\fR code compiled with the \fB\-fpcc\-struct\-return\fR |
| switch is not binary compatible with code compiled with the |
| \&\fB\-freg\-struct\-return\fR switch. |
| Use it to conform to a non-default application binary interface. |
| .IP "\fB\-freg\-struct\-return\fR" 4 |
| .IX Item "-freg-struct-return" |
| Return \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values 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 |
| \&\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. |
| .Sp |
| \&\fBWarning:\fR code compiled with the \fB\-freg\-struct\-return\fR |
| switch is not binary compatible with code compiled with the |
| \&\fB\-fpcc\-struct\-return\fR switch. |
| Use it to conform to a non-default application binary interface. |
| .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. |
| .Sp |
| \&\fBWarning:\fR the \fB\-fshort\-enums\fR switch causes \s-1GCC\s0 to generate |
| code that is not binary compatible with code generated without that switch. |
| Use it to conform to a non-default application binary interface. |
| .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. |
| .Sp |
| \&\fBWarning:\fR the \fB\-fshort\-double\fR switch causes \s-1GCC\s0 to generate |
| code that is not binary compatible with code generated without that switch. |
| Use it to conform to a non-default application binary interface. |
| .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. |
| .Sp |
| \&\fBWarning:\fR the \fB\-fshort\-wchar\fR switch causes \s-1GCC\s0 to generate |
| code that is not binary compatible with code generated without that switch. |
| Use it to conform to a non-default application binary interface. |
| .IP "\fB\-fno\-common\fR" 4 |
| .IX Item "-fno-common" |
| In C, allocate even uninitialized global variables in the data section of the |
| object file, rather than generating them as common blocks. This has the |
| effect that if the same variable is declared (without \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\-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\-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 8k on the \s-1SPARC\s0 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. |
| .Sp |
| When this flag is set, the macros \f(CW\*(C`_\|_pic_\|_\*(C'\fR and \f(CW\*(C`_\|_PIC_\|_\*(C'\fR |
| are defined to 1. |
| .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, |
| PowerPC and \s-1SPARC\s0. |
| .Sp |
| Position-independent code requires special support, and therefore works |
| only on certain machines. |
| .Sp |
| When this flag is set, the macros \f(CW\*(C`_\|_pic_\|_\*(C'\fR and \f(CW\*(C`_\|_PIC_\|_\*(C'\fR |
| are defined to 2. |
| .IP "\fB\-fpie\fR" 4 |
| .IX Item "-fpie" |
| .PD 0 |
| .IP "\fB\-fPIE\fR" 4 |
| .IX Item "-fPIE" |
| .PD |
| These options are similar to \fB\-fpic\fR and \fB\-fPIC\fR, but |
| generated position independent code can be only linked into executables. |
| Usually these options are used when \fB\-pie\fR \s-1GCC\s0 option will be |
| used during linking. |
| .IP "\fB\-fno\-jump\-tables\fR" 4 |
| .IX Item "-fno-jump-tables" |
| Do not use jump tables for switch statements even where it would be |
| more efficient than other code generation strategies. This option is |
| of use in conjunction with \fB\-fpic\fR or \fB\-fPIC\fR for |
| building code which forms part of a dynamic linker and cannot |
| reference the address of a jump table. On some targets, jump tables |
| do not require a \s-1GOT\s0 and this option is not needed. |
| .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\fIn\fR\fB]\fR" 4 |
| .IX Item "-fpack-struct[=n]" |
| Without a value specified, pack all structure members together without |
| holes. When a value is specified (which must be a small power of two), pack |
| structure members according to this value, representing the maximum |
| alignment (that is, objects with default alignment requirements larger than |
| this will be output potentially unaligned at the next fitting location. |
| .Sp |
| \&\fBWarning:\fR the \fB\-fpack\-struct\fR switch causes \s-1GCC\s0 to generate |
| code that is not binary compatible with code generated without that switch. |
| Additionally, it makes the code suboptimal. |
| Use it to conform to a non-default application binary interface. |
| .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 4 |
| \& void __cyg_profile_func_enter (void *this_fn, |
| \& void *call_site); |
| \& void __cyg_profile_func_exit (void *this_fn, |
| \& void *call_site); |
| .Ve |
| .Sp |
| 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 absolute address \fB0x80000000\fR |
| and grows downwards, you can use the flags |
| \&\fB\-fstack\-limit\-symbol=_\|_stack_limit\fR and |
| \&\fB\-Wl,\-\-defsym,_\|_stack_limit=0x7ffe0000\fR to enforce a stack limit |
| of 128KB. Note that this may only work with the \s-1GNU\s0 linker. |
| .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" |
| .IP "\fB\-fargument\-noalias\-anything\fR" 4 |
| .IX Item "-fargument-noalias-anything" |
| .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. |
| \&\fB\-fargument\-noalias\-anything\fR specifies that arguments do not |
| alias any other 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, \fB\-fno\-leading\-underscore\fR, forcibly |
| change the way C symbols are represented in the object file. One use |
| is to help link with legacy assembly code. |
| .Sp |
| \&\fBWarning:\fR the \fB\-fleading\-underscore\fR switch causes \s-1GCC\s0 to |
| generate code that is not binary compatible with code generated without that |
| switch. Use it to conform to a non-default application binary interface. |
| Not all targets provide complete support for this switch. |
| .IP "\fB\-ftls\-model=\fR\fImodel\fR" 4 |
| .IX Item "-ftls-model=model" |
| Alter the thread-local storage model to be used. |
| The \fImodel\fR argument should be one of \f(CW\*(C`global\-dynamic\*(C'\fR, |
| \&\f(CW\*(C`local\-dynamic\*(C'\fR, \f(CW\*(C`initial\-exec\*(C'\fR or \f(CW\*(C`local\-exec\*(C'\fR. |
| .Sp |
| The default without \fB\-fpic\fR is \f(CW\*(C`initial\-exec\*(C'\fR; with |
| \&\fB\-fpic\fR the default is \f(CW\*(C`global\-dynamic\*(C'\fR. |
| .IP "\fB\-fvisibility=\fR\fIdefault|internal|hidden|protected\fR" 4 |
| .IX Item "-fvisibility=default|internal|hidden|protected" |
| Set the default \s-1ELF\s0 image symbol visibility to the specified option\-\-\-all |
| symbols will be marked with this unless overridden within the code. |
| Using this feature can very substantially improve linking and |
| load times of shared object libraries, produce more optimized |
| code, provide near-perfect \s-1API\s0 export and prevent symbol clashes. |
| It is \fBstrongly\fR recommended that you use this in any shared objects |
| you distribute. |
| .Sp |
| Despite the nomenclature, \f(CW\*(C`default\*(C'\fR always means public ie; |
| available to be linked against from outside the shared object. |
| \&\f(CW\*(C`protected\*(C'\fR and \f(CW\*(C`internal\*(C'\fR are pretty useless in real-world |
| usage so the only other commonly used option will be \f(CW\*(C`hidden\*(C'\fR. |
| The default if \fB\-fvisibility\fR isn't specified is |
| \&\f(CW\*(C`default\*(C'\fR, i.e., make every |
| symbol public\-\-\-this causes the same behavior as previous versions of |
| \&\s-1GCC\s0. |
| .Sp |
| A good explanation of the benefits offered by ensuring \s-1ELF\s0 |
| symbols have the correct visibility is given by \*(L"How To Write |
| Shared Libraries\*(R" by Ulrich Drepper (which can be found at |
| <\fBhttp://people.redhat.com/~drepper/\fR>)\-\-\-however a superior |
| solution made possible by this option to marking things hidden when |
| the default is public is to make the default hidden and mark things |
| public. This is the norm with \s-1DLL\s0's on Windows and with \fB\-fvisibility=hidden\fR |
| and \f(CW\*(C`_\|_attribute_\|_ ((visibility("default")))\*(C'\fR instead of |
| \&\f(CW\*(C`_\|_declspec(dllexport)\*(C'\fR you get almost identical semantics with |
| identical syntax. This is a great boon to those working with |
| cross-platform projects. |
| .Sp |
| For those adding visibility support to existing code, you may find |
| \&\fB#pragma \s-1GCC\s0 visibility\fR of use. This works by you enclosing |
| the declarations you wish to set visibility for with (for example) |
| \&\fB#pragma \s-1GCC\s0 visibility push(hidden)\fR and |
| \&\fB#pragma \s-1GCC\s0 visibility pop\fR. |
| Bear in mind that symbol visibility should be viewed \fBas |
| part of the \s-1API\s0 interface contract\fR and thus all new code should |
| always specify visibility when it is not the default ie; declarations |
| only for use within the local \s-1DSO\s0 should \fBalways\fR be marked explicitly |
| as hidden as so to avoid \s-1PLT\s0 indirection overheads\-\-\-making this |
| abundantly clear also aids readability and self-documentation of the code. |
| Note that due to \s-1ISO\s0 \*(C+ specification requirements, operator new and |
| operator delete must always be of default visibility. |
| .Sp |
| Be aware that headers from outside your project, in particular system |
| headers and headers from any other library you use, may not be |
| expecting to be compiled with visibility other than the default. You |
| may need to explicitly say \fB#pragma \s-1GCC\s0 visibility push(default)\fR |
| before including any such headers. |
| .Sp |
| \&\fBextern\fR declarations are not affected by \fB\-fvisibility\fR, so |
| a lot of code can be recompiled with \fB\-fvisibility=hidden\fR with |
| no modifications. However, this means that calls to \fBextern\fR |
| functions with no explicit visibility will use the \s-1PLT\s0, so it is more |
| effective to use \fB_\|_attribute ((visibility))\fR and/or |
| \&\fB#pragma \s-1GCC\s0 visibility\fR to tell the compiler which \fBextern\fR |
| declarations should be treated as hidden. |
| .Sp |
| Note that \fB\-fvisibility\fR does affect \*(C+ vague linkage |
| entities. This means that, for instance, an exception class that will |
| be thrown between DSOs must be explicitly marked with default |
| visibility so that the \fBtype_info\fR nodes will be unified between |
| the DSOs. |
| .Sp |
| An overview of these techniques, their benefits and how to use them |
| is at <\fBhttp://gcc.gnu.org/wiki/Visibility\fR>. |
| .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_GB.UTF\-8\fR for English in the United |
| Kingdom encoded in \s-1UTF\-8\s0. |
| .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-1GCC\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/\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\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 "\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 |
| .PP |
| Some additional environments variables affect the behavior of the |
| preprocessor. |
| .IP "\fB\s-1CPATH\s0\fR" 4 |
| .IX Item "CPATH" |
| .PD 0 |
| .IP "\fBC_INCLUDE_PATH\fR" 4 |
| .IX Item "C_INCLUDE_PATH" |
| .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 |
| Each variable's value is a list of directories separated by a special |
| character, much like \fB\s-1PATH\s0\fR, in which to look for header files. |
| The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and |
| determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a |
| semicolon, and for almost all other targets it is a colon. |
| .Sp |
| \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if |
| specified with \fB\-I\fR, but after any paths given with \fB\-I\fR |
| options on the command line. This environment variable is used |
| regardless of which language is being preprocessed. |
| .Sp |
| The remaining environment variables apply only when preprocessing the |
| particular language indicated. Each specifies a list of directories |
| to be searched as if specified with \fB\-isystem\fR, but after any |
| paths given with \fB\-isystem\fR options on the command line. |
| .Sp |
| In all these variables, an empty element instructs the compiler to |
| search its current working directory. Empty elements can appear at the |
| beginning or end of a path. For instance, if the value of |
| \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same |
| effect as \fB\-I.\ \-I/special/include\fR. |
| .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 non-system header files processed |
| by the compiler. System header files are ignored in the dependency |
| output. |
| .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. |
| .Sp |
| In other words, this environment variable is equivalent to combining |
| the options \fB\-MM\fR and \fB\-MF\fR, |
| with an optional \fB\-MT\fR switch too. |
| .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4 |
| .IX Item "SUNPRO_DEPENDENCIES" |
| This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above), |
| except that system header files are not ignored, so it implies |
| \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the |
| main input file is omitted. |
| .SH "BUGS" |
| .IX Header "BUGS" |
| For instructions on reporting bugs, see |
| <\fBhttp://gcc.gnu.org/bugs.html\fR>. |
| .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" |
| \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), |
| \&\fIcpp\fR\|(1), \fIgcov\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, \fIas\fR, |
| \&\fIld\fR, \fIbinutils\fR and \fIgdb\fR. |
| .SH "AUTHOR" |
| .IX Header "AUTHOR" |
| See the Info entry for \fBgcc\fR, or |
| <\fBhttp://gcc.gnu.org/onlinedocs/gcc/Contributors.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, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc. |
| .PP |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being \*(L"\s-1GNU\s0 General Public License\*(R" and \*(L"Funding |
| Free Software\*(R", the Front-Cover texts being (a) (see below), and with |
| the Back-Cover Texts being (b) (see below). A copy of the license is |
| included in the \fIgfdl\fR\|(7) man page. |
| .PP |
| (a) The \s-1FSF\s0's Front-Cover Text is: |
| .PP |
| .Vb 1 |
| \& A GNU Manual |
| .Ve |
| .PP |
| (b) The \s-1FSF\s0's Back-Cover Text is: |
| .PP |
| .Vb 3 |
| \& You have freedom to copy and modify this GNU Manual, like GNU |
| \& software. Copies published by the Free Software Foundation raise |
| \& funds for GNU development. |
| .Ve |
