[dragonfly.git] / contrib / gcc-3.4 / gcc / doc / g++.1

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.\" ========================================================================
.\"
.IX Title "GCC 1"
.TH GCC 1 "2006-03-06" "gcc-3.4.6" "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] \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 ``overall options'' allow you to stop this
process at an intermediate stage.  For example, the \fB\-c\fR option
says not to run the linker.  Then the output consists of object files
output by the assembler.
.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\-fforce\-mem\fR,
\&\fB\-fstrength\-reduce\fR, \fB\-Wformat\fR and so on.  Most of
these have both positive and negative forms; the negative form of
\&\fB\-ffoo\fR would be \fB\-fno\-foo\fR.  This manual documents
only one of these two forms, whichever one is not the default.
.SH "OPTIONS"
.IX Header "OPTIONS"
.Sh "Option Summary"
.IX Subsection "Option Summary"
Here is a summary of all the options, grouped by type.  Explanations are
in the following sections.
.IP "\fIOverall Options\fR" 4
.IX Item "Overall Options"
\&\fB\-c  \-S  \-E  \-o\fR \fIfile\fR  \fB\-pipe  \-pass\-exit\-codes  
\&\-x\fR \fIlanguage\fR  \fB\-v  \-###  \-\-help  \-\-target\-help  \-\-version\fR
.IP "\fIC Language Options\fR" 4
.IX Item "C Language Options"
\&\fB\-ansi  \-std=\fR\fIstandard\fR  \fB\-aux\-info\fR \fIfilename\fR 
\&\fB\-fno\-asm  \-fno\-builtin  \-fno\-builtin\-\fR\fIfunction\fR 
\&\fB\-fhosted  \-ffreestanding  \-fms\-extensions 
\&\-trigraphs  \-no\-integrated\-cpp  \-traditional  \-traditional\-cpp 
\&\-fallow\-single\-precision  \-fcond\-mismatch 
\&\-fsigned\-bitfields  \-fsigned\-char 
\&\-funsigned\-bitfields  \-funsigned\-char 
\&\-fwritable\-strings\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  \-fno\-const\-strings 
\&\-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\-fuse\-cxa\-atexit  \-fno\-weak  \-nostdinc++ 
\&\-fno\-default\-inline  \-Wabi  \-Wctor\-dtor\-privacy 
\&\-Wnon\-virtual\-dtor  \-Wreorder 
\&\-Weffc++  \-Wno\-deprecated 
\&\-Wno\-non\-template\-friend  \-Wold\-style\-cast 
\&\-Woverloaded\-virtual  \-Wno\-pmf\-conversions 
\&\-Wsign\-promo\fR
.IP "\fIObjective-C Language Options\fR" 4
.IX Item "Objective-C Language Options"
\&\fB\-fconstant\-string\-class=\fR\fIclass-name\fR 
\&\fB\-fgnu\-runtime  \-fnext\-runtime 
\&\-fno\-nil\-receivers 
\&\-fobjc\-exceptions 
\&\-freplace\-objc\-classes 
\&\-fzero\-link 
\&\-gen\-decls 
\&\-Wno\-protocol  \-Wselector \-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]
.IP "\fIWarning Options\fR" 4
.IX Item "Warning Options"
\&\fB\-fsyntax\-only  \-pedantic  \-pedantic\-errors 
\&\-w  \-Wextra  \-Wall  \-Waggregate\-return 
\&\-Wcast\-align  \-Wcast\-qual  \-Wchar\-subscripts  \-Wcomment 
\&\-Wconversion  \-Wno\-deprecated\-declarations 
\&\-Wdisabled\-optimization  \-Wno\-div\-by\-zero  \-Wendif\-labels 
\&\-Werror  \-Werror\-implicit\-function\-declaration 
\&\-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\-invalid\-offsetof  \-Winvalid\-pch 
\&\-Wlarger\-than\-\fR\fIlen\fR  \fB\-Wlong\-long 
\&\-Wmain  \-Wmissing\-braces 
\&\-Wmissing\-format\-attribute  \-Wmissing\-noreturn 
\&\-Wno\-multichar  \-Wnonnull  \-Wpacked  \-Wpadded 
\&\-Wparentheses  \-Wpointer\-arith  \-Wredundant\-decls 
\&\-Wreturn\-type  \-Wsequence\-point  \-Wshadow 
\&\-Wsign\-compare  \-Wstrict\-aliasing 
\&\-Wswitch  \-Wswitch\-default  \-Wswitch\-enum 
\&\-Wsystem\-headers  \-Wtrigraphs  \-Wundef  \-Wuninitialized 
\&\-Wunknown\-pragmas  \-Wunreachable\-code 
\&\-Wunused  \-Wunused\-function  \-Wunused\-label  \-Wunused\-parameter 
\&\-Wunused\-value  \-Wunused\-variable  \-Wwrite\-strings\fR
.IP "\fIC\-only Warning Options\fR" 4
.IX Item "C-only Warning Options"
\&\fB\-Wbad\-function\-cast  \-Wmissing\-declarations 
\&\-Wmissing\-prototypes  \-Wnested\-externs  \-Wold\-style\-definition 
\&\-Wstrict\-prototypes  \-Wtraditional 
\&\-Wdeclaration\-after\-statement\fR
.IP "\fIDebugging Options\fR" 4
.IX Item "Debugging Options"
\&\fB\-d\fR\fIletters\fR  \fB\-dumpspecs  \-dumpmachine  \-dumpversion 
\&\-fdump\-unnumbered  \-fdump\-translation\-unit\fR[\fB\-\fR\fIn\fR] 
\&\fB\-fdump\-class\-hierarchy\fR[\fB\-\fR\fIn\fR] 
\&\fB\-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\-feliminate\-dwarf2\-dups \-feliminate\-unused\-debug\-types 
\&\-feliminate\-unused\-debug\-symbols \-fmem\-report \-fprofile\-arcs 
\&\-frandom\-seed=\fR\fIstring\fR \fB\-fsched\-verbose=\fR\fIn\fR 
\&\fB\-ftest\-coverage  \-ftime\-report 
\&\-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\-fbranch\-probabilities \-fprofile\-values \-fvpt \-fbranch\-target\-load\-optimize 
\&\-fbranch\-target\-load\-optimize2 \-fcaller\-saves  \-fcprop\-registers 
\&\-fcse\-follow\-jumps  \-fcse\-skip\-blocks  \-fdata\-sections 
\&\-fdelayed\-branch  \-fdelete\-null\-pointer\-checks 
\&\-fexpensive\-optimizations  \-ffast\-math  \-ffloat\-store 
\&\-fforce\-addr  \-fforce\-mem  \-ffunction\-sections 
\&\-fgcse  \-fgcse\-lm  \-fgcse\-sm  \-fgcse\-las  \-floop\-optimize 
\&\-fcrossjumping  \-fif\-conversion  \-fif\-conversion2 
\&\-finline\-functions  \-finline\-limit=\fR\fIn\fR  \fB\-fkeep\-inline\-functions 
\&\-fkeep\-static\-consts  \-fmerge\-constants  \-fmerge\-all\-constants 
\&\-fmove\-all\-movables  \-fnew\-ra  \-fno\-branch\-count\-reg 
\&\-fno\-default\-inline  \-fno\-defer\-pop 
\&\-fno\-function\-cse  \-fno\-guess\-branch\-probability 
\&\-fno\-inline  \-fno\-math\-errno  \-fno\-peephole  \-fno\-peephole2 
\&\-funsafe\-math\-optimizations  \-ffinite\-math\-only 
\&\-fno\-trapping\-math  \-fno\-zero\-initialized\-in\-bss 
\&\-fomit\-frame\-pointer  \-foptimize\-register\-move 
\&\-foptimize\-sibling\-calls  \-fprefetch\-loop\-arrays 
\&\-fprofile\-generate \-fprofile\-use 
\&\-freduce\-all\-givs  \-fregmove  \-frename\-registers 
\&\-freorder\-blocks  \-freorder\-functions 
\&\-frerun\-cse\-after\-loop  \-frerun\-loop\-opt 
\&\-frounding\-math \-fschedule\-insns  \-fschedule\-insns2 
\&\-fno\-sched\-interblock  \-fno\-sched\-spec  \-fsched\-spec\-load 
\&\-fsched\-spec\-load\-dangerous  
\&\-fsched\-stalled\-insns=\fR\fIn\fR \fB\-sched\-stalled\-insns\-dep=\fR\fIn\fR 
\&\fB\-fsched2\-use\-superblocks 
\&\-fsched2\-use\-traces  \-fsignaling\-nans 
\&\-fsingle\-precision\-constant  
\&\-fstrength\-reduce  \-fstrict\-aliasing  \-ftracer  \-fthread\-jumps 
\&\-funroll\-all\-loops  \-funroll\-loops  \-fpeel\-loops 
\&\-funswitch\-loops  \-fold\-unroll\-loops  \-fold\-unroll\-all\-loops 
\&\-\-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\-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 
\&\-s  \-static  \-static\-libgcc  \-shared  \-shared\-libgcc  \-symbolic 
\&\-Wl,\fR\fIoption\fR  \fB\-Xlinker\fR \fIoption\fR 
\&\fB\-u\fR \fIsymbol\fR
.IP "\fIDirectory Options\fR" 4
.IX Item "Directory Options"
\&\fB\-B\fR\fIprefix\fR  \fB\-I\fR\fIdir\fR  \fB\-I\-  \-L\fR\fIdir\fR  \fB\-specs=\fR\fIfile\fR
.IP "\fITarget Options\fR" 4
.IX Item "Target Options"
\&\fB\-V\fR \fIversion\fR  \fB\-b\fR \fImachine\fR
.IP "\fIMachine Dependent Options\fR" 4
.IX Item "Machine Dependent Options"
\&\fIM680x0 Options\fR
\&\fB\-m68000  \-m68020  \-m68020\-40  \-m68020\-60  \-m68030  \-m68040 
\&\-m68060  \-mcpu32  \-m5200  \-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
\&\fI\s-1VAX\s0 Options\fR
\&\fB\-mg  \-mgnu  \-munix\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 
\&\-mflat  \-mno\-flat  \-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 
\&\-mcypress  \-mf930  \-mf934 
\&\-msparclite  \-msupersparc  \-mv8
\&\-threads \-pthreads\fR
.Sp
\&\fI\s-1ARM\s0 Options\fR
\&\fB\-mapcs\-frame  \-mno\-apcs\-frame 
\&\-mapcs\-26  \-mapcs\-32 
\&\-mapcs\-stack\-check  \-mno\-apcs\-stack\-check 
\&\-mapcs\-float  \-mno\-apcs\-float 
\&\-mapcs\-reentrant  \-mno\-apcs\-reentrant 
\&\-msched\-prolog  \-mno\-sched\-prolog 
\&\-mlittle\-endian  \-mbig\-endian  \-mwords\-little\-endian 
\&\-malignment\-traps  \-mno\-alignment\-traps 
\&\-msoft\-float  \-mhard\-float  \-mfpe 
\&\-mthumb\-interwork  \-mno\-thumb\-interwork 
\&\-mcpu=\fR\fIname\fR  \fB\-march=\fR\fIname\fR  \fB\-mfpe=\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\fR
.Sp
\&\fI\s-1MN10300\s0 Options\fR
\&\fB\-mmult\-bug  \-mno\-mult\-bug 
\&\-mam33  \-mno\-am33 
\&\-mam33\-2  \-mno\-am33\-2 
\&\-mno\-crt0  \-mrelax\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
\&\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 
\&\-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 
\&\-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=altivec  \-mabi=no\-altivec 
\&\-mabi=spe  \-mabi=no\-spe 
\&\-misel=yes  \-misel=no 
\&\-mspe=yes  \-mspe=no 
\&\-mfloat\-gprs=yes  \-mfloat\-gprs=no 
\&\-mprototype  \-mno\-prototype 
\&\-msim  \-mmvme  \-mads  \-myellowknife  \-memb  \-msdata 
\&\-msdata=\fR\fIopt\fR  \fB\-mvxworks  \-mwindiss  \-G\fR \fInum\fR  \fB\-pthread\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 
\&\-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  \-nofixprebinding \-nomultidefs  \-noprebind  \-noseglinkedit 
\&\-pagezero_size  \-prebind  \-prebind_all_twolevel_modules 
\&\-private_bundle  \-read_only_relocs  \-sectalign 
\&\-sectobjectsymbols  \-whyload  \-seg1addr 
\&\-sectcreate  \-sectobjectsymbols  \-sectorder 
\&\-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\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 
\&\-mxgot  \-mno\-xgot  \-membedded\-pic  \-mno\-embedded\-pic 
\&\-mgp32  \-mgp64  \-mfp32  \-mfp64  \-mhard\-float  \-msoft\-float 
\&\-msingle\-float  \-mdouble\-float  \-mint64  \-mlong64  \-mlong32 
\&\-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  
\&\-mrnames  \-mno\-rnames 
\&\-mcheck\-zero\-division  \-mno\-check\-zero\-division 
\&\-mmemcpy  \-mno\-memcpy  \-mlong\-calls  \-mno\-long\-calls 
\&\-mmad  \-mno\-mad  \-mfused\-madd  \-mno\-fused\-madd  \-nocpp 
\&\-mfix\-sb1  \-mno\-fix\-sb1  \-mflush\-func=\fR\fIfunc\fR 
\&\fB\-mno\-flush\-func  \-mbranch\-likely  \-mno\-branch\-likely\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\-momit\-leaf\-frame\-pointer 
\&\-mno\-red\-zone \-mno\-tls\-direct\-seg\-refs 
\&\-mcmodel=\fR\fIcode-model\fR 
\&\fB\-m32  \-m64\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 
\&\-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 
\&\-nolibdld  \-static  \-threads\fR
.Sp
\&\fIIntel 960 Options\fR
\&\fB\-m\fR\fIcpu-type\fR  \fB\-masm\-compat  \-mclean\-linkage 
\&\-mcode\-align  \-mcomplex\-addr  \-mleaf\-procedures 
\&\-mic\-compat  \-mic2.0\-compat  \-mic3.0\-compat 
\&\-mintel\-asm  \-mno\-clean\-linkage  \-mno\-code\-align 
\&\-mno\-complex\-addr  \-mno\-leaf\-procedures 
\&\-mno\-old\-align  \-mno\-strict\-align  \-mno\-tail\-call 
\&\-mnumerics  \-mold\-align  \-msoft\-float  \-mstrict\-align 
\&\-mtail\-call\fR
.Sp
\&\fI\s-1DEC\s0 Alpha Options\fR
\&\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
\&\fIH8/300 Options\fR
\&\fB\-mrelax  \-mh  \-ms  \-mn  \-mint32  \-malign\-300\fR
.Sp
\&\fI\s-1SH\s0 Options\fR
\&\fB\-m1  \-m2  \-m2e  \-m3  \-m3e 
\&\-m4\-nofpu  \-m4\-single\-only  \-m4\-single  \-m4 
\&\-m5\-64media  \-m5\-64media\-nofpu 
\&\-m5\-32media  \-m5\-32media\-nofpu 
\&\-m5\-compact  \-m5\-compact\-nofpu 
\&\-mb  \-ml  \-mdalign  \-mrelax 
\&\-mbigtable  \-mfmovd  \-mhitachi  \-mnomacsave 
\&\-mieee  \-misize  \-mpadstruct  \-mspace 
\&\-mprefergot  \-musermode\fR
.Sp
\&\fISystem V Options\fR
\&\fB\-Qy  \-Qn  \-YP,\fR\fIpaths\fR  \fB\-Ym,\fR\fIdir\fR
.Sp
\&\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
\&\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-1NS32K\s0 Options\fR
\&\fB\-m32032  \-m32332  \-m32532  \-m32081  \-m32381 
\&\-mmult\-add  \-mnomult\-add  \-msoft\-float  \-mrtd  \-mnortd 
\&\-mregparam  \-mnoregparam  \-msb  \-mnosb 
\&\-mbitfield  \-mnobitfield  \-mhimem  \-mnohimem\fR
.Sp
\&\fI\s-1AVR\s0 Options\fR
\&\fB\-mmcu=\fR\fImcu\fR  \fB\-msize  \-minit\-stack=\fR\fIn\fR  \fB\-mno\-interrupts 
\&\-mcall\-prologues  \-mno\-tablejump  \-mtiny\-stack\fR
.Sp
\&\fIMCore Options\fR
\&\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-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-1IA\-64\s0 Options\fR
\&\fB\-mbig\-endian  \-mlittle\-endian  \-mgnu\-as  \-mgnu\-ld  \-mno\-pic 
\&\-mvolatile\-asm\-stop  \-mb\-step  \-mregister\-names  \-mno\-sdata 
\&\-mconstant\-gp  \-mauto\-pic  \-minline\-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\fR
.Sp
\&\fID30V Options\fR
\&\fB\-mextmem  \-mextmemory  \-monchip  \-mno\-asm\-optimize 
\&\-masm\-optimize  \-mbranch\-cost=\fR\fIn\fR  \fB\-mcond\-exec=\fR\fIn\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  \-mbackchain  \-mno\-backchain 
\&\-msmall\-exec  \-mno\-small\-exec  \-mmvcle \-mno\-mvcle 
\&\-m64  \-m31  \-mdebug  \-mno\-debug  \-mesa  \-mzarch  \-mfused\-madd  \-mno\-fused\-madd\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-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
\&\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
\&\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 
\&\-mlibrary\-pic  \-macc\-4 \-macc\-8 
\&\-mpack  \-mno\-pack  \-mno\-eflags  \-mcond\-move  \-mno\-cond\-move 
\&\-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 
\&\-mcpu=\fR\fIcpu\fR
.IP "\fICode Generation Options\fR" 4
.IX Item "Code Generation Options"
\&\fB\-fcall\-saved\-\fR\fIreg\fR  \fB\-fcall\-used\-\fR\fIreg\fR 
\&\fB\-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 
\&\-freg\-struct\-return  \-fshared\-data  \-fshort\-enums 
\&\-fshort\-double  \-fshort\-wchar 
\&\-fverbose\-asm  \-fpack\-struct  \-fstack\-check 
\&\-fstack\-limit\-register=\fR\fIreg\fR  \fB\-fstack\-limit\-symbol=\fR\fIsym\fR 
\&\fB\-fargument\-alias  \-fargument\-noalias 
\&\-fargument\-noalias\-global  \-fleading\-underscore 
\&\-ftls\-model=\fR\fImodel\fR 
\&\fB\-ftrapv  \-fwrapv  \-fbounds\-check\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 library
\&\fIlibobjc.a\fR to make an Objective-C program work.
.IP "\fIfile\fR\fB.mi\fR" 4
.IX Item "file.mi"
Objective-C source code which should not be preprocessed.
.IP "\fIfile\fR\fB.h\fR" 4
.IX Item "file.h"
C or \*(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.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
Fortran source code which should not be preprocessed.
.IP "\fIfile\fR\fB.F\fR" 4
.IX Item "file.F"
.PD 0
.IP "\fIfile\fR\fB.fpp\fR" 4
.IX Item "file.fpp"
.IP "\fIfile\fR\fB.FPP\fR" 4
.IX Item "file.FPP"
.PD
Fortran source code which must be preprocessed (with the traditional
preprocessor).
.IP "\fIfile\fR\fB.r\fR" 4
.IX Item "file.r"
Fortran source code which must be preprocessed with a \s-1RATFOR\s0
preprocessor (not included with \s-1GCC\s0).
.IP "\fIfile\fR\fB.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 8
\&        c  c-header  cpp-output
\&        c++  c++-header  c++-cpp-output
\&        objective-c  objective-c-header  objc-cpp-output
\&        assembler  assembler-with-cpp
\&        ada
\&        f77  f77-cpp-input  ratfor
\&        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.
.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 you specify \fB\-o\fR when compiling more than one input file, or
you are producing an executable file as output, all the source files
on the command line will be compiled at once.
.Sp
If \fB\-o\fR is not specified, the default is to put an executable file
in \fIa.out\fR, the object file for \fI\fIsource\fI.\fIsuffix\fI\fR in
\&\fI\fIsource\fI.o\fR, its assembler file in \fI\fIsource\fI.s\fR, and
all preprocessed C source on standard output.
.IP "\fB\-v\fR" 4
.IX Item "-v"
Print (on standard error output) the commands executed to run the stages
of compilation.  Also print the version number of the compiler driver
program and of the preprocessor and the compiler proper.
.IP "\fB\-###\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\-\-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.
.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, \*(C+ programs often require class libraries as well as a
compiler that understands the \*(C+ language\-\-\-and under some
circumstances, you might want to compile programs or header files from
standard input, or otherwise without a suffix that flags them as \*(C+
programs.  You might also like to precompile a C header file with a
\&\fB.h\fR extension to be used in \*(C+ compilations.  \fBg++\fR is a
program that calls \s-1GCC\s0 with the default language set to \*(C+, and
automatically specifies linking against the \*(C+ library.  On many
systems, \fBg++\fR is also installed with the name \fBc++\fR.
.PP
When you compile \*(C+ programs, you may specify many of the same
command-line options that you use for compiling programs in any
language; or command-line options meaningful for C and related
languages; or options that are meaningful only for \*(C+ programs.
.Sh "Options Controlling C Dialect"
.IX Subsection "Options Controlling C Dialect"
The following options control the dialect of C (or languages derived
from C, such as \*(C+ and Objective\-C) that the compiler accepts:
.IP "\fB\-ansi\fR" 4
.IX Item "-ansi"
In C mode, support all \s-1ISO\s0 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\-3.4/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\-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.
.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\-fms\-extensions\fR" 4
.IX Item "-fms-extensions"
Accept some non-standard constructs used in Microsoft header files.
.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.
.IP "\fB\-fwritable\-strings\fR" 4
.IX Item "-fwritable-strings"
Store string constants in the writable data segment and don't uniquize
them.  This is for compatibility with old programs which assume they can
write into string constants.
.Sp
Writing into string constants is a very bad idea; ``constants'' should
be constant.
.Sp
This option is deprecated.
.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\-fno\-const\-strings\fR" 4
.IX Item "-fno-const-strings"
Give string constants type \f(CW\*(C`char *\*(C'\fR instead of type \f(CW\*(C`const
char *\*(C'\fR.  By default, G++ uses type \f(CW\*(C`const char *\*(C'\fR as required by
the standard.  Even if you use \fB\-fno\-const\-strings\fR, you cannot
actually modify the value of a string constant, unless you also use
\&\fB\-fwritable\-strings\fR.
.Sp
This option might be removed in a future release of G++.  For maximum
portability, you should structure your code so that it works with
string constants that have type \f(CW\*(C`const char *\*(C'\fR.
.IP "\fB\-fno\-elide\-constructors\fR" 4
.IX Item "-fno-elide-constructors"
The \*(C+ standard allows an implementation to omit creating a temporary
which is only used to initialize another object of the same type.
Specifying this option disables that optimization, and forces G++ to
call the copy constructor in all cases.
.IP "\fB\-fno\-enforce\-eh\-specs\fR" 4
.IX Item "-fno-enforce-eh-specs"
Don't check for violation of exception specifications at runtime.  This
option violates the \*(C+ standard, but may be useful for reducing code
size in production builds, much like defining \fB\s-1NDEBUG\s0\fR.  The compiler
will still optimize based on the exception specifications.
.IP "\fB\-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.
.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\-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\-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 enabled by \fB\-Wall\fR.
.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\-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 (\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 Dialect"
.IX Subsection "Options Controlling Objective-C Dialect"
(\s-1NOTE:\s0 This manual does not describe the Objective-C language itself.  See
<\fBhttp://gcc.gnu.org/readings.html\fR> for references.)
.PP
This section describes the command-line options that are only meaningful
for Objective-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`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 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 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\-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.  Currently, this option is only
available in conjunction with the NeXT runtime on Mac \s-1OS\s0 X 10.3 and later.
.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\-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\-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 \f(CW\*(C`\-Wno\-protocol\*(C'\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 \f(CW\*(C`\-fsyntax\-only\*(C'\fR option is
being used.
.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 \f(CW\*(C`\-Wselector\*(C'\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.
.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 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.
.IP "\fB\-Wcomment\fR" 4
.IX Item "-Wcomment"
Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
comment, or whenever a Backslash-Newline appears in a \fB//\fR comment.
.IP "\fB\-Wformat\fR" 4
.IX Item "-Wformat"
Check calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR, etc., to make sure that
the arguments supplied have types appropriate to the format string
specified, and that the conversions specified in the format string make
sense.  This includes standard functions, and others specified by format
attributes, in the \f(CW\*(C`printf\*(C'\fR,
\&\f(CW\*(C`scanf\*(C'\fR, \f(CW\*(C`strftime\*(C'\fR and \f(CW\*(C`strfmon\*(C'\fR (an X/Open extension,
not in the C standard) families.
.Sp
The formats are checked against the format features supported by \s-1GNU\s0
libc version 2.2.  These include all \s-1ISO\s0 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+, and Objective-C only)" 4
.IX Item "-Winit-self (C, , and Objective-C 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.
.IP "\fB\-Wimplicit\-function\-declaration\fR" 4
.IX Item "-Wimplicit-function-declaration"
.PD 0
.IP "\fB\-Werror\-implicit\-function\-declaration\fR" 4
.IX Item "-Werror-implicit-function-declaration"
.PD
Give a warning (or error) whenever a function is used before being
declared.
.IP "\fB\-Wimplicit\fR" 4
.IX Item "-Wimplicit"
Same as \fB\-Wimplicit\-int\fR and \fB\-Wimplicit\-function\-declaration\fR.
.IP "\fB\-Wmain\fR" 4
.IX Item "-Wmain"
Warn if the type of \fBmain\fR is suspicious.  \fBmain\fR should be a
function with external linkage, returning int, taking either zero
arguments, two, or three arguments of appropriate types.
.IP "\fB\-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
.IP "\fB\-Wparentheses\fR" 4
.IX Item "-Wparentheses"
Warn if parentheses are omitted in certain contexts, such
as when there is an assignment in a context where a truth value
is expected, or when operators are nested whose precedence people
often get confused about.
.Sp
Also warn about constructions where there may be confusion to which
\&\f(CW\*(C`if\*(C'\fR statement an \f(CW\*(C`else\*(C'\fR branch belongs.  Here is an example of
such a case:
.Sp
.Vb 7
\&        {
\&          if (a)
\&            if (b)
\&              foo ();
\&          else
\&            bar ();
\&        }
.Ve
.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
.IP "\fB\-Wsequence\-point\fR" 4
.IX Item "-Wsequence-point"
Warn about code that may have undefined semantics because of violations
of sequence point rules in the C standard.
.Sp
The C standard defines the order in which expressions in a C program are
evaluated in terms of \fIsequence points\fR, which represent a partial
ordering between the execution of parts of the program: those executed
before the sequence point, and those executed after it.  These occur
after the evaluation of a full expression (one which is not part of a
larger expression), after the evaluation of the first operand of a
\&\f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, \f(CW\*(C`? :\*(C'\fR or \f(CW\*(C`,\*(C'\fR (comma) operator, before a
function is called (but after the evaluation of its arguments and the
expression denoting the called function), and in certain other places.
Other than as expressed by the sequence point rules, the order of
evaluation of subexpressions of an expression is not specified.  All
these rules describe only a partial order rather than a total order,
since, for example, if two functions are called within one expression
with no sequence point between them, the order in which the functions
are called is not specified.  However, the standards committee have
ruled that function calls do not overlap.
.Sp
It is not specified when between sequence points modifications to the
values of objects take effect.  Programs whose behavior depends on this
have undefined behavior; the C standard specifies that ``Between the
previous and next sequence point an object shall have its stored value
modified at most once by the evaluation of an expression.  Furthermore,
the prior value shall be read only to determine the value to be
stored.''.  If a program breaks these rules, the results on any
particular implementation are entirely unpredictable.
.Sp
Examples of code with undefined behavior are \f(CW\*(C`a = a++;\*(C'\fR, \f(CW\*(C`a[n]
= b[n++]\*(C'\fR and \f(CW\*(C`a[i++] = i;\*(C'\fR.  Some more complicated cases are not
diagnosed by this option, and it may give an occasional false positive
result, but in general it has been found fairly effective at detecting
this sort of problem in programs.
.Sp
The present implementation of this option only works for C programs.  A
future implementation may also work for \*(C+ programs.
.Sp
The C 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>.
.IP "\fB\-Wreturn\-type\fR" 4
.IX Item "-Wreturn-type"
Warn whenever a function is defined with a return-type that defaults to
\&\f(CW\*(C`int\*(C'\fR.  Also warn about any \f(CW\*(C`return\*(C'\fR statement with no
return-value in a function whose return-type is not \f(CW\*(C`void\*(C'\fR.
.Sp
For \*(C+, a function without return type always produces a diagnostic
message, even when \fB\-Wno\-return\-type\fR is specified.  The only
exceptions are \fBmain\fR and functions defined in system headers.
.IP "\fB\-Wswitch\fR" 4
.IX Item "-Wswitch"
Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of 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.
.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).
.IP "\fB\-Wunused\-function\fR" 4
.IX Item "-Wunused-function"
Warn whenever a static function is declared but not defined or a
non\e\-inline static function is unused.
.IP "\fB\-Wunused\-label\fR" 4
.IX Item "-Wunused-label"
Warn whenever a label is declared but not used.
.Sp
To suppress this warning use the \fBunused\fR attribute.
.IP "\fB\-Wunused\-parameter\fR" 4
.IX Item "-Wunused-parameter"
Warn whenever a function parameter is unused aside from its declaration.
.Sp
To suppress this warning use the \fBunused\fR attribute.
.IP "\fB\-Wunused\-variable\fR" 4
.IX Item "-Wunused-variable"
Warn whenever a local variable or non-constant static variable is unused
aside from its declaration
.Sp
To suppress this warning use the \fBunused\fR attribute.
.IP "\fB\-Wunused\-value\fR" 4
.IX Item "-Wunused-value"
Warn whenever a statement computes a result that is explicitly not used.
.Sp
To suppress this warning cast the expression to \fBvoid\fR.
.IP "\fB\-Wunused\fR" 4
.IX Item "-Wunused"
All 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 don't specify \fB\-O\fR, you simply won't
get these warnings.
.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 only for variables that are candidates for
register allocation.  Therefore, they do not occur for a variable that
is declared \f(CW\*(C`volatile\*(C'\fR, or whose address is taken, or whose size
is other than 1, 2, 4 or 8 bytes.  Also, they do not occur for
structures, unions or arrays, even when they are in registers.
.Sp
Note that there may be no warning about a variable that is used only
to compute a value that itself is never used, because such
computations may be deleted by data flow analysis before the warnings
are printed.
.Sp
These warnings are made optional because \s-1GCC\s0 is not smart
enough to see all the reasons why the code might be correct
despite appearing to have an error.  Here is one example of how
this can happen:
.Sp
.Vb 12
\&        {
\&          int x;
\&          switch (y)
\&            {
\&            case 1: x = 1;
\&              break;
\&            case 2: x = 4;
\&              break;
\&            case 3: x = 5;
\&            }
\&          foo (x);
\&        }
.Ve
.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.  
.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\-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\-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 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
A comparison like \fBx<=y<=z\fR appears; this is equivalent to
\&\fB(x<=y ? 1 : 0) <= z\fR, which is a different interpretation from
that of ordinary mathematical notation.
.IP "*" 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
The return type of a function has a type qualifier such as \f(CW\*(C`const\*(C'\fR.
Such a type qualifier has no effect, since the value returned by a
function is not an lvalue.  (But don't warn about the \s-1GNU\s0 extension of
\&\f(CW\*(C`volatile void\*(C'\fR return types.  That extension will be warned about
if \fB\-pedantic\fR is specified.)
.IP "*" 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.
For example, the following code would cause such a warning, because
\&\f(CW\*(C`x.h\*(C'\fR would be implicitly initialized to zero:
.Sp
.Vb 2
\&        struct s { int f, g, h; };
\&        struct s x = { 3, 4 };
.Ve
.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 "*" 4
Any of several floating-point events that often indicate errors, such as
overflow, underflow, loss of precision, etc.
.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\-Wendif\-labels\fR" 4
.IX Item "-Wendif-labels"
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\-Wpointer\-arith\fR" 4
.IX Item "-Wpointer-arith"
Warn about anything that depends on the ``size of'' a function type or
of \f(CW\*(C`void\*(C'\fR.  \s-1GNU\s0 C assigns these types a size of 1, for
convenience in calculations with \f(CW\*(C`void *\*(C'\fR pointers and pointers
to functions.
.IP "\fB\-Wbad\-function\-cast\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\-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 constants to \f(CW\*(C`char *\*(C'\fR.
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\-Waggregate\-return\fR" 4
.IX Item "-Waggregate-return"
Warn if any functions that return structures or unions are defined or
called.  (In languages where you can return an array, this also elicits
a warning.)
.IP "\fB\-Wstrict\-prototypes\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\-noreturn\fR" 4
.IX Item "-Wmissing-noreturn"
Warn about functions which might be candidates for attribute \f(CW\*(C`noreturn\*(C'\fR.
Note these are only possible candidates, not absolute ones.  Care should
be taken to manually verify functions actually do not ever return before
adding the \f(CW\*(C`noreturn\*(C'\fR attribute, otherwise subtle code generation
bugs could be introduced.  You will not get a warning for \f(CW\*(C`main\*(C'\fR in
hosted C environments.
.IP "\fB\-Wmissing\-format\-attribute\fR" 4
.IX Item "-Wmissing-format-attribute"
If \fB\-Wformat\fR is enabled, also warn about functions which might be
candidates for \f(CW\*(C`format\*(C'\fR attributes.  Note these are only possible
candidates, not absolute ones.  \s-1GCC\s0 will guess that \f(CW\*(C`format\*(C'\fR
attributes might be appropriate for any function that calls a function
like \f(CW\*(C`vprintf\*(C'\fR or \f(CW\*(C`vscanf\*(C'\fR, but this might not always be the
case, and some functions for which \f(CW\*(C`format\*(C'\fR attributes are
appropriate may not be detected.  This option has no effect unless
\&\fB\-Wformat\fR is enabled (possibly by \fB\-Wall\fR).
.IP "\fB\-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\-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.
(@pxref{Function Attributes}, \f(CW@pxref\fR{Variable Attributes},
\&\f(CW@pxref\fR{Type Attributes}.)
.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 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\-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\-Wdisabled\-optimization\fR" 4
.IX Item "-Wdisabled-optimization"
Warn if a requested optimization pass is disabled.  This warning does
not generally indicate that there is anything wrong with your code; it
merely indicates that \s-1GCC\s0's optimizers were unable to handle the code
effectively.  Often, the problem is that your code is too big or too
complex; \s-1GCC\s0 will refuse to optimize programs when the optimization
itself is likely to take inordinate amounts of time.
.IP "\fB\-Werror\fR" 4
.IX Item "-Werror"
Make all warnings into errors.
.Sh "Options for Debugging Your Program or \s-1GCC\s0"
.IX Subsection "Options for Debugging Your Program or GCC"
\&\s-1GCC\s0 has various special options that are used for debugging
either your program or \s-1GCC:\s0
.IP "\fB\-g\fR" 4
.IX Item "-g"
Produce debugging information in the operating system's native format
(stabs, \s-1COFF\s0, \s-1XCOFF\s0, or \s-1DWARF\s0).  \s-1GDB\s0 can work with this debugging
information.
.Sp
On most systems that use stabs format, \fB\-g\fR enables use of extra
debugging information that only \s-1GDB\s0 can use; this extra information
makes debugging work better in \s-1GDB\s0 but will probably make other debuggers
crash or
refuse to read the program.  If you want to control for certain whether
to generate the extra information, use \fB\-gstabs+\fR, \fB\-gstabs\fR,
\&\fB\-gxcoff+\fR, \fB\-gxcoff\fR, or \fB\-gvms\fR (see below).
.Sp
Unlike most other C compilers, \s-1GCC\s0 allows you to use \fB\-g\fR with
\&\fB\-O\fR.  The shortcuts taken by optimized code may occasionally
produce surprising results: some variables you declared may not exist
at all; flow of control may briefly move where you did not expect it;
some statements may not be executed because they compute constant
results or their values were already at hand; some statements may
execute in different places because they were moved out of loops.
.Sp
Nevertheless it proves possible to debug optimized output.  This makes
it reasonable to use the optimizer for programs that might have bugs.
.Sp
The following options are useful when \s-1GCC\s0 is generated with the
capability for more than one debugging format.
.IP "\fB\-ggdb\fR" 4
.IX Item "-ggdb"
Produce debugging information for use by \s-1GDB\s0.  This means to use the
most expressive format available (\s-1DWARF\s0 2, stabs, or the native format
if neither of those are supported), including \s-1GDB\s0 extensions if at all
possible.
.IP "\fB\-gstabs\fR" 4
.IX Item "-gstabs"
Produce debugging information in stabs format (if that is supported),
without \s-1GDB\s0 extensions.  This is the format used by \s-1DBX\s0 on most \s-1BSD\s0
systems.  On \s-1MIPS\s0, Alpha and System V Release 4 systems this option
produces stabs debugging output which is not understood by \s-1DBX\s0 or \s-1SDB\s0.
On System V Release 4 systems this option requires the \s-1GNU\s0 assembler.
.IP "\fB\-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\-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.