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diff --git a/gcc/gcc.1 b/gcc/gcc.1 new file mode 100644 index 00000000000..b09c8b741e8 --- /dev/null +++ b/gcc/gcc.1 @@ -0,0 +1,4167 @@ +.\" Copyright (c) 1991, 1992, 1993, 1994 Free Software Foundation -*-Text-*- +.\" See section COPYING for conditions for redistribution +.\" +.\" Set up \*(lq, \*(rq if -man hasn't already set it up. +.if @@\*(lq@ \{\ +. ds lq " +. if t .ds lq `` +. if !@@\(lq@ .ds lq "\(lq +.\} +.if @@\*(rq@ \{\ +. ds rq " +. if t .ds rq '' +. if !@@\(rq@ .ds rq "\(rq +.\} +.de Id +.ds Rv \\$3 +.ds Dt \\$4 +.. +.de Sp +.if n .sp +.if t .sp 0.4 +.. +.Id $Id: gcc.1,v 1.4 1993/10/13 23:19:12 pesch Exp $ +.TH GCC 1 "\*(Dt" "GNU Tools" "GNU Tools" +.SH NAME +gcc, g++ \- GNU project C and C++ Compiler (v2.7) +.SH SYNOPSIS +.B gcc +.RI "[ " option " | " filename " ].\|.\|." +.br +.B g++ +.RI "[ " option " | " filename " ].\|.\|." +.SH WARNING +The information in this man page is an extract from the full +documentation of the GNU C compiler, and is limited to the meaning of +the options. +.PP +This man page is not kept up to date except when volunteers want to +maintain it. If you find a discrepancy between the man page and the +software, please check the Info file, which is the authoritative +documentation. +.PP +If we find that the things in this man page that are out of date cause +significant confusion or complaints, we will stop distributing the man +page. The alternative, updating the man page when we update the Info +file, is impossible because the rest of the work of maintaining GNU CC +leaves us no time for that. The GNU project regards man pages as +obsolete and should not let them take time away from other things. +.PP +For complete and current documentation, refer to the Info file `\|\c +.B gcc\c +\&\|' or the manual +.I +Using and Porting GNU CC (for version 2.0)\c +\&. Both are made from the Texinfo source file +.BR gcc.texinfo . +.SH DESCRIPTION +The C and C++ compilers are integrated. Both process input files +through one or more of four stages: preprocessing, compilation, +assembly, and linking. Source filename suffixes identify the source +language, but which name you use for the compiler governs default +assumptions: +.TP +.B gcc +assumes preprocessed (\c +.B .i\c +\&) files are C and assumes C style linking. +.TP +.B g++ +assumes preprocessed (\c +.B .i\c +\&) files are C++ and assumes C++ style linking. +.PP +Suffixes of source file names indicate the language and kind of +processing to be done: +.Sp +.nf +.ta \w'\fB.cxx\fP 'u +\&\fB.c\fP C source; preprocess, compile, assemble +\&\fB.C\fP C++ source; preprocess, compile, assemble +\&\fB.cc\fP C++ source; preprocess, compile, assemble +\&\fB.cxx\fP C++ source; preprocess, compile, assemble +\&\fB.m\fP Objective-C source; preprocess, compile, assemble +\&\fB.i\fP preprocessed C; compile, assemble +\&\fB.ii\fP preprocessed C++; compile, assemble +\&\fB.s\fP Assembler source; assemble +\&\fB.S\fP Assembler source; preprocess, assemble +\&\fB.h\fP Preprocessor file; not usually named on command line +.Sp +.fi +Files with other suffixes are passed to the linker. Common cases include: +.Sp +.nf +\&\fB.o\fP Object file +\&\fB.a\fP Archive file +.br +.fi +.Sp +Linking is always the last stage unless you use one of the +.BR \-c , +.BR \-S , +or +.B \-E +options to avoid it (or unless compilation errors stop the whole +process). For the link stage, all +.B .o +files corresponding to source files, +.B \-l +libraries, unrecognized filenames (including named +.B .o +object files and +.B .a +archives) +are passed to the linker in command-line order. +.SH OPTIONS +Options must be separate: `\|\c +.B \-dr\c +\&\|' is quite different from `\|\c +.B \-d \-r +\&\|'. +.PP +Most `\|\c +.B \-f\c +\&\|' and `\|\c +.B \-W\c +\&\|' options have two contrary forms: +.BI \-f name +and +.BI \-fno\- name\c +\& (or +.BI \-W name +and +.BI \-Wno\- name\c +\&). Only the non-default forms are shown here. +.PP +Here is a summary of all the options, grouped by type. Explanations are +in the following sections. +.hy 0 +.na +.TP +.B Overall Options +.br +\-c +\-S +\-E +.RI "\-o " file +\-pipe +\-v +.RI "\-x " language +.TP +.B Language Options +\-ansi +\-fall\-virtual +\-fcond\-mismatch +\-fdollars\-in\-identifiers +\-fenum\-int\-equiv +\-fexternal\-templates +\-fno\-asm +\-fno\-builtin +\-fhosted +\-fno\-hosted +\-ffreestanding +\-fno\-freestanding +\-fno\-strict\-prototype +\-fsigned\-bitfields +\-fsigned\-char +\-fthis\-is\-variable +\-funsigned\-bitfields +\-funsigned\-char +\-fwritable\-strings +\-traditional +\-traditional\-cpp +\-trigraphs +.TP +.B Warning Options +\-fsyntax\-only +\-pedantic +\-pedantic\-errors +\-w +\-W +\-Wall +\-Waggregate\-return +\-Wcast\-align +\-Wcast\-qual +\-Wchar\-subscript +\-Wcomment +\-Wconversion +\-Wenum\-clash +\-Werror +\-Wformat +.RI \-Wid\-clash\- len +\-Wimplicit +\-Winline +\-Wmain +\-Wmissing\-prototypes +\-Wmissing\-declarations +\-Wnested\-externs +\-Wno\-import +\-Wparentheses +\-Wpointer\-arith +\-Wredundant\-decls +\-Wreturn\-type +\-Wshadow +\-Wstrict\-prototypes +\-Wswitch +\-Wtemplate\-debugging +\-Wtraditional +\-Wtrigraphs +\-Wuninitialized +\-Wunused +\-Wwrite\-strings +.TP +.B Debugging Options +\-a +.RI \-d letters +\-fpretend\-float +\-g +.RI \-g level +\-gcoff +\-gxcoff +\-gxcoff+ +\-gdwarf +\-gdwarf+ +\-gstabs +\-gstabs+ +\-ggdb +\-p +\-pg +\-save\-temps +.RI \-print\-file\-name= library +\-print\-libgcc\-file\-name +.RI \-print\-prog\-name= program +.TP +.B Optimization Options +\-fcaller\-saves +\-fcse\-follow\-jumps +\-fcse\-skip\-blocks +\-fdelayed\-branch +\-felide\-constructors +\-fexpensive\-optimizations +\-ffast\-math +\-ffloat\-store +\-fforce\-addr +\-fforce\-mem +\-finline\-functions +\-fkeep\-inline\-functions +\-fmemoize\-lookups +\-fno\-default\-inline +\-fno\-defer\-pop +\-fno\-function\-cse +\-fno\-inline +\-fno\-peephole +\-fomit\-frame\-pointer +\-frerun\-cse\-after\-loop +\-fschedule\-insns +\-fschedule\-insns2 +\-fstrength\-reduce +\-fthread\-jumps +\-funroll\-all\-loops +\-funroll\-loops +\-O +\-O2 +.TP +.B Preprocessor Options +.RI \-A assertion +\-C +\-dD +\-dM +\-dN +.RI \-D macro [\|= defn \|] +\-E +\-H +.RI "\-idirafter " dir +.RI "\-include " file +.RI "\-imacros " file +.RI "\-iprefix " file +.RI "\-iwithprefix " dir +\-M +\-MD +\-MM +\-MMD +\-nostdinc +\-P +.RI \-U macro +\-undef +.TP +.B Assembler Option +.RI \-Wa, option +.TP +.B Linker Options +.RI \-l library +\-nostartfiles +\-nostdlib +\-static +\-shared +\-symbolic +.RI "\-Xlinker\ " option +.RI \-Wl, option +.RI "\-u " symbol +.TP +.B Directory Options +.RI \-B prefix +.RI \-I dir +\-I\- +.RI \-L dir +.TP +.B Target Options +.RI "\-b " machine +.RI "\-V " version +.TP +.B Configuration Dependent Options +.I M680x0\ Options +.br +\-m68000 +\-m68020 +\-m68020\-40 +\-m68030 +\-m68040 +\-m68881 +\-mbitfield +\-mc68000 +\-mc68020 +\-mfpa +\-mnobitfield +\-mrtd +\-mshort +\-msoft\-float +.Sp +.I VAX Options +.br +\-mg +\-mgnu +\-munix +.Sp +.I SPARC Options +.br +\-mepilogue +\-mfpu +\-mhard\-float +\-mno\-fpu +\-mno\-epilogue +\-msoft\-float +\-msparclite +\-mv8 +\-msupersparc +\-mcypress +.Sp +.I Convex Options +.br +\-margcount +\-mc1 +\-mc2 +\-mnoargcount +.Sp +.I AMD29K Options +.br +\-m29000 +\-m29050 +\-mbw +\-mdw +\-mkernel\-registers +\-mlarge +\-mnbw +\-mnodw +\-msmall +\-mstack\-check +\-muser\-registers +.Sp +.I M88K Options +.br +\-m88000 +\-m88100 +\-m88110 +\-mbig\-pic +\-mcheck\-zero\-division +\-mhandle\-large\-shift +\-midentify\-revision +\-mno\-check\-zero\-division +\-mno\-ocs\-debug\-info +\-mno\-ocs\-frame\-position +\-mno\-optimize\-arg\-area +\-mno\-serialize\-volatile +\-mno\-underscores +\-mocs\-debug\-info +\-mocs\-frame\-position +\-moptimize\-arg\-area +\-mserialize\-volatile +.RI \-mshort\-data\- num +\-msvr3 +\-msvr4 +\-mtrap\-large\-shift +\-muse\-div\-instruction +\-mversion\-03.00 +\-mwarn\-passed\-structs +.Sp +.I RS6000 Options +.br +\-mfp\-in\-toc +\-mno\-fop\-in\-toc +.Sp +.I RT Options +.br +\-mcall\-lib\-mul +\-mfp\-arg\-in\-fpregs +\-mfp\-arg\-in\-gregs +\-mfull\-fp\-blocks +\-mhc\-struct\-return +\-min\-line\-mul +\-mminimum\-fp\-blocks +\-mnohc\-struct\-return +.Sp +.I MIPS Options +.br +\-mcpu=\fIcpu type\fP +\-mips2 +\-mips3 +\-mint64 +\-mlong64 +\-mlonglong128 +\-mmips\-as +\-mgas +\-mrnames +\-mno\-rnames +\-mgpopt +\-mno\-gpopt +\-mstats +\-mno\-stats +\-mmemcpy +\-mno\-memcpy +\-mno\-mips\-tfile +\-mmips\-tfile +\-msoft\-float +\-mhard\-float +\-mabicalls +\-mno\-abicalls +\-mhalf\-pic +\-mno\-half\-pic +\-G \fInum\fP +\-nocpp +.Sp +.I i386 Options +.br +\-m486 +\-mno\-486 +\-msoft\-float +\-mno\-fp\-ret\-in\-387 +.Sp +.I HPPA Options +.br +\-mpa\-risc\-1\-0 +\-mpa\-risc\-1\-1 +\-mkernel +\-mshared\-libs +\-mno\-shared\-libs +\-mlong\-calls +\-mdisable\-fpregs +\-mdisable\-indexing +\-mtrailing\-colon +.Sp +.I i960 Options +.br +\-m\fIcpu-type\fP +\-mnumerics +\-msoft\-float +\-mleaf\-procedures +\-mno\-leaf\-procedures +\-mtail\-call +\-mno\-tail\-call +\-mcomplex\-addr +\-mno\-complex\-addr +\-mcode\-align +\-mno\-code\-align +\-mic\-compat +\-mic2.0\-compat +\-mic3.0\-compat +\-masm\-compat +\-mintel\-asm +\-mstrict\-align +\-mno\-strict\-align +\-mold\-align +\-mno\-old\-align +.Sp +.I DEC Alpha Options +.br +\-mfp\-regs +\-mno\-fp\-regs +\-mno\-soft\-float +\-msoft\-float +.Sp +.I System V Options +.br +\-G +\-Qy +\-Qn +.RI \-YP, paths +.RI \-Ym, dir +.TP +.B Code Generation Options +.RI \-fcall\-saved\- reg +.RI \-fcall\-used\- reg +.RI \-ffixed\- reg +\-finhibit\-size\-directive +\-fnonnull\-objects +\-fno\-common +\-fno\-ident +\-fno\-gnu\-linker +\-fpcc\-struct\-return +\-fpic +\-fPIC +\-freg\-struct\-return +\-fshared\-data +\-fshort\-enums +\-fshort\-double +\-fvolatile +\-fvolatile\-global +\-fverbose\-asm +.ad b +.hy 1 +.SH OVERALL OPTIONS +.TP +.BI "\-x " "language" +Specify explicitly the +.I language\c +\& for the following input files (rather than choosing a default based +on the file name suffix) . This option applies to all following input +files until the next `\|\c +.B \-x\c +\&\|' option. Possible values of \c +.I language\c +\& are +`\|\c +.B c\c +\&\|', `\|\c +.B objective\-c\c +\&\|', `\|\c +.B c\-header\c +\&\|', `\|\c +.B c++\c +\&\|', +`\|\c +.B cpp\-output\c +\&\|', `\|\c +.B assembler\c +\&\|', and `\|\c +.B assembler\-with\-cpp\c +\&\|'. +.TP +.B \-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 `\|\c +.B \-x\c +\&\|' +has not been used at all). +.PP +If you want only some of the four stages (preprocess, compile, +assemble, link), you can use +`\|\c +.B \-x\c +\&\|' (or filename suffixes) to tell \c +.B gcc\c +\& where to start, and +one of the options `\|\c +.B \-c\c +\&\|', `\|\c +.B \-S\c +\&\|', or `\|\c +.B \-E\c +\&\|' to say where +.B gcc\c +\& is to stop. Note that some combinations (for example, +`\|\c +.B \-x cpp\-output \-E\c +\&\|') instruct \c +.B gcc\c +\& to do nothing at all. +.TP +.B \-c +Compile or assemble the source files, but do not link. The compiler +output is an object file corresponding to each source file. +.Sp +By default, GCC makes the object file name for a source file by replacing +the suffix `\|\c +.B .c\c +\&\|', `\|\c +.B .i\c +\&\|', `\|\c +.B .s\c +\&\|', etc., with `\|\c +.B .o\c +\&\|'. Use +.B \-o\c +\& to select another name. +.Sp +GCC ignores any unrecognized input files (those that do not require +compilation or assembly) with the +.B \-c +option. +.TP +.B \-S +Stop after the stage of compilation proper; do not assemble. The output +is an assembler code file for each non-assembler input +file specified. +.Sp +By default, GCC makes the assembler file name for a source file by +replacing the suffix `\|\c +.B .c\c +\&\|', `\|\c +.B .i\c +\&\|', etc., with `\|\c +.B .s\c +\&\|'. Use +.B \-o\c +\& to select another name. +.Sp +GCC ignores any input files that don't require compilation. +.TP +.B \-E +Stop after the preprocessing stage; do not run the compiler proper. The +output is preprocessed source code, which is sent to the +standard output. +.Sp +GCC ignores input files which don't require preprocessing. +.TP +.BI "\-o " file +Place output in file \c +.I file\c +\&. This applies regardless to whatever +sort of output GCC is producing, whether it be an executable file, +an object file, an assembler file or preprocessed C code. +.Sp +Since only one output file can be specified, it does not make sense to +use `\|\c +.B \-o\c +\&\|' when compiling more than one input file, unless you are +producing an executable file as output. +.Sp +If you do not specify `\|\c +.B \-o\c +\&\|', the default is to put an executable file +in `\|\c +.B a.out\c +\&\|', the object file for `\|\c +.I source\c +.B \&.\c +.I suffix\c +\&\c +\&\|' in +`\|\c +.I source\c +.B \&.o\c +\&\|', its assembler file in `\|\c +.I source\c +.B \&.s\c +\&\|', and +all preprocessed C source on standard output. +.TP +.B \-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. +.TP +.B \-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 cannot read from a pipe; but the GNU assembler has +no trouble. +.PP +.SH LANGUAGE OPTIONS +The following options control the dialect of C that the compiler +accepts: +.TP +.B \-ansi +Support all ANSI standard C programs. +.Sp +This turns off certain features of GNU C that are incompatible with +ANSI C, such as the \c +.B asm\c +\&, \c +.B inline\c +\& and \c +.B typeof +keywords, and predefined macros such as \c +.B unix\c +\& and \c +.B vax +that identify the type of system you are using. It also enables the +undesirable and rarely used ANSI trigraph feature, and disallows `\|\c +.B $\c +\&\|' as part of identifiers. +.Sp +The alternate keywords \c +.B _\|_asm_\|_\c +\&, \c +.B _\|_extension_\|_\c +\&, +.B _\|_inline_\|_\c +\& and \c +.B _\|_typeof_\|_\c +\& continue to work despite +`\|\c +.B \-ansi\c +\&\|'. You would not want to use them in an ANSI C program, of +course, but it is useful to put them in header files that might be included +in compilations done with `\|\c +.B \-ansi\c +\&\|'. Alternate predefined macros +such as \c +.B _\|_unix_\|_\c +\& and \c +.B _\|_vax_\|_\c +\& are also available, with or +without `\|\c +.B \-ansi\c +\&\|'. +.Sp +The `\|\c +.B \-ansi\c +\&\|' option does not cause non-ANSI programs to be +rejected gratuitously. For that, `\|\c +.B \-pedantic\c +\&\|' is required in +addition to `\|\c +.B \-ansi\c +\&\|'. +.Sp +The preprocessor predefines a macro \c +.B _\|_STRICT_ANSI_\|_\c +\& when you use the `\|\c +.B \-ansi\c +\&\|' +option. Some header files may notice this macro and refrain +from declaring certain functions or defining certain macros that the +ANSI standard doesn't call for; this is to avoid interfering with any +programs that might use these names for other things. +.TP +.B \-fno\-asm +Do not recognize \c +.B asm\c +\&, \c +.B inline\c +\& or \c +.B typeof\c +\& as a +keyword. These words may then be used as identifiers. You can +use \c +.B _\|_asm_\|_\c +\&, \c +.B _\|_inline_\|_\c +\& and \c +.B _\|_typeof_\|_\c +\& instead. +`\|\c +.B \-ansi\c +\&\|' implies `\|\c +.B \-fno\-asm\c +\&\|'. +.TP +.B \-fno\-builtin +Don't recognize built-in functions that do not begin with two leading +underscores. Currently, the functions affected include \c +.B _exit\c +\&, +.B abort\c +\&, \c +.B abs\c +\&, \c +.B alloca\c +\&, \c +.B cos\c +\&, \c +.B exit\c +\&, +.B fabs\c +\&, \c +.B labs\c +\&, \c +.B memcmp\c +\&, \c +.B memcpy\c +\&, \c +.B sin\c +\&, +.B sqrt\c +\&, \c +.B strcmp\c +\&, \c +.B strcpy\c +\&, and \c +.B strlen\c +\&. +.Sp +The `\|\c +.B \-ansi\c +\&\|' option prevents \c +.B alloca\c +\& and \c +.B _exit\c +\& from +being builtin functions. +.TP +.B \-fhosted +Compile for a hosted environment; this implies the `\|\c +.B \-fbuiltin\c +\&\|' option, and implies that suspicious declarations of +.B main\c +\& should be warned about. +.TP +.B \-ffreestanding +Compile for a freestanding environment; this implies the `\|\c +.B \-fno-builtin\c +\&\|' option, and implies that +.B main\c +\& has no special requirements. +.TP +.B \-fno\-strict\-prototype +Treat a function declaration with no arguments, such as `\|\c +.B int foo +();\c +\&\|', as C would treat it\(em\&as saying nothing about the number of +arguments or their types (C++ only). Normally, such a declaration in +C++ means that the function \c +.B foo\c +\& takes no arguments. +.TP +.B \-trigraphs +Support ANSI C trigraphs. The `\|\c +.B \-ansi\c +\&\|' option implies `\|\c +.B \-trigraphs\c +\&\|'. +.TP +.B \-traditional +Attempt to support some aspects of traditional C compilers. +For details, see the GNU C Manual; the duplicate list here +has been deleted so that we won't get complaints when it +is out of date. +.Sp +But one note about C++ programs only (not C). `\|\c +.B \-traditional\c +\&\|' has one additional effect for C++: assignment to +.B this +is permitted. This is the same as the effect of `\|\c +.B \-fthis\-is\-variable\c +\&\|'. +.TP +.B \-traditional\-cpp +Attempt to support some aspects of traditional C preprocessors. +This includes the items that specifically mention the preprocessor above, +but none of the other effects of `\|\c +.B \-traditional\c +\&\|'. +.TP +.B \-fdollars\-in\-identifiers +Permit the use of `\|\c +.B $\c +\&\|' in identifiers (C++ only). You can also use +`\|\c +.B \-fno\-dollars\-in\-identifiers\c +\&\|' to explicitly prohibit use of +`\|\c +.B $\c +\&\|'. (GNU C++ allows `\|\c +.B $\c +\&\|' by default on some target systems +but not others.) +.TP +.B \-fenum\-int\-equiv +Permit implicit conversion of \c +.B int\c +\& to enumeration types (C++ +only). Normally GNU C++ allows conversion of \c +.B enum\c +\& to \c +.B int\c +\&, +but not the other way around. +.TP +.B \-fexternal\-templates +Produce smaller code for template declarations, by generating only a +single copy of each template function where it is defined (C++ only). +To use this option successfully, you must also mark all files that +use templates with either `\|\c +.B #pragma implementation\c +\&\|' (the definition) or +`\|\c +.B #pragma interface\c +\&\|' (declarations). + +When your code is compiled with `\|\c +.B \-fexternal\-templates\c +\&\|', all +template instantiations are external. You must arrange for all +necessary instantiations to appear in the implementation file; you can +do this with a \c +.B typedef\c +\& that references each instantiation needed. +Conversely, when you compile using the default option +`\|\c +.B \-fno\-external\-templates\c +\&\|', all template instantiations are +explicitly internal. +.TP +.B \-fall\-virtual +Treat all possible member functions as virtual, implicitly. All +member functions (except for constructor functions and +.B new +or +.B delete +member operators) are treated as virtual functions of the class where +they appear. +.Sp +This does not mean that all calls to these member functions will be +made through the internal table of virtual functions. Under some +circumstances, the compiler can determine that a call to a given +virtual function can be made directly; in these cases the calls are +direct in any case. +.TP +.B \-fcond\-mismatch +Allow conditional expressions with mismatched types in the second and +third arguments. The value of such an expression is void. +.TP +.B \-fthis\-is\-variable +Permit assignment to \c +.B this\c +\& (C++ only). The incorporation of +user-defined free store management into C++ has made assignment to +`\|\c +.B this\c +\&\|' an anachronism. Therefore, by default it is invalid to +assign to \c +.B this\c +\& within a class member function. However, for +backwards compatibility, you can make it valid with +`\|\c +.B \-fthis-is-variable\c +\&\|'. +.TP +.B \-funsigned\-char +Let the type \c +.B char\c +\& be unsigned, like \c +.B unsigned char\c +\&. +.Sp +Each kind of machine has a default for what \c +.B char\c +\& should +be. It is either like \c +.B unsigned char\c +\& by default or like +.B signed char\c +\& by default. +.Sp +Ideally, a portable program should always use \c +.B signed char\c +\& or +.B unsigned char\c +\& when it depends on the signedness of an object. +But many programs have been written to use plain \c +.B char\c +\& 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 \c +.B char\c +\& is always a distinct type from each of +.B signed char\c +\& and \c +.B unsigned char\c +\&, even though its behavior +is always just like one of those two. +.TP +.B \-fsigned\-char +Let the type \c +.B char\c +\& be signed, like \c +.B signed char\c +\&. +.Sp +Note that this is equivalent to `\|\c +.B \-fno\-unsigned\-char\c +\&\|', which is +the negative form of `\|\c +.B \-funsigned\-char\c +\&\|'. Likewise, +`\|\c +.B \-fno\-signed\-char\c +\&\|' is equivalent to `\|\c +.B \-funsigned\-char\c +\&\|'. +.TP +.B \-fsigned\-bitfields +.TP +.B \-funsigned\-bitfields +.TP +.B \-fno\-signed\-bitfields +.TP +.B \-fno\-unsigned\-bitfields +These options control whether a bitfield is +signed or unsigned, when declared with no explicit `\|\c +.B signed\c +\&\|' or `\|\c +.B unsigned\c +\&\|' qualifier. By default, such a bitfield is +signed, because this is consistent: the basic integer types such as +.B int\c +\& are signed types. +.Sp +However, when you specify `\|\c +.B \-traditional\c +\&\|', bitfields are all unsigned +no matter what. +.TP +.B \-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. `\|\c +.B \-traditional\c +\&\|' also has this +effect. +.Sp +Writing into string constants is a very bad idea; \*(lqconstants\*(rq should +be constant. +.SH PREPROCESSOR OPTIONS +These options control the C preprocessor, which is run on each C source +file before actual compilation. +.PP +If you use the `\|\c +.B \-E\c +\&\|' option, GCC does nothing except preprocessing. +Some of these options make sense only together with `\|\c +.B \-E\c +\&\|' because +they cause the preprocessor output to be unsuitable for actual +compilation. +.TP +.BI "\-include " "file" +Process \c +.I file\c +\& as input before processing the regular input file. +In effect, the contents of \c +.I file\c +\& are compiled first. Any `\|\c +.B \-D\c +\&\|' +and `\|\c +.B \-U\c +\&\|' options on the command line are always processed before +`\|\c +.B \-include \c +.I file\c +\&\c +\&\|', regardless of the order in which they are +written. All the `\|\c +.B \-include\c +\&\|' and `\|\c +.B \-imacros\c +\&\|' options are +processed in the order in which they are written. +.TP +.BI "\-imacros " file +Process \c +.I file\c +\& as input, discarding the resulting output, before +processing the regular input file. Because the output generated from +.I file\c +\& is discarded, the only effect of `\|\c +.B \-imacros \c +.I file\c +\&\c +\&\|' is to +make the macros defined in \c +.I file\c +\& available for use in the main +input. The preprocessor evaluates any `\|\c +.B \-D\c +\&\|' and `\|\c +.B \-U\c +\&\|' options +on the command line before processing `\|\c +.B \-imacros\c +.I file\c +\&\|', regardless of the order in +which they are written. All the `\|\c +.B \-include\c +\&\|' and `\|\c +.B \-imacros\c +\&\|' +options are processed in the order in which they are written. +.TP +.BI "\-idirafter " "dir" +Add the directory \c +.I dir\c +\& to the second include path. The directories +on the second include path are searched when a header file is not found +in any of the directories in the main include path (the one that +`\|\c +.B \-I\c +\&\|' adds to). +.TP +.BI "\-iprefix " "prefix" +Specify \c +.I prefix\c +\& as the prefix for subsequent `\|\c +.B \-iwithprefix\c +\&\|' +options. +.TP +.BI "\-iwithprefix " "dir" +Add a directory to the second include path. The directory's name is +made by concatenating \c +.I prefix\c +\& and \c +.I dir\c +\&, where \c +.I prefix +was specified previously with `\|\c +.B \-iprefix\c +\&\|'. +.TP +.B \-nostdinc +Do not search the standard system directories for header files. Only +the directories you have specified with `\|\c +.B \-I\c +\&\|' options (and the +current directory, if appropriate) are searched. +.Sp +By using both `\|\c +.B \-nostdinc\c +\&\|' and `\|\c +.B \-I\-\c +\&\|', you can limit the include-file search file to only those +directories you specify explicitly. +.TP +.B \-nostdinc++ +Do not search for header files in the C++\-specific standard directories, +but do still search the other standard directories. +(This option is used when building `\|\c +.B libg++\c +\&\|'.) +.TP +.B \-undef +Do not predefine any nonstandard macros. (Including architecture flags). +.TP +.B \-E +Run only the C preprocessor. Preprocess all the C source files +specified and output the results to standard output or to the +specified output file. +.TP +.B \-C +Tell the preprocessor not to discard comments. Used with the +`\|\c +.B \-E\c +\&\|' option. +.TP +.B \-P +Tell the preprocessor not to generate `\|\c +.B #line\c +\&\|' commands. +Used with the `\|\c +.B \-E\c +\&\|' option. +.TP +.B \-M\ [ \-MG ] +Tell the preprocessor to output a rule suitable for \c +.B make +describing the dependencies of each object file. For each source file, +the preprocessor outputs one \c +.B make\c +\&-rule whose target is the object +file name for that source file and whose dependencies are all the files +`\|\c +.B #include\c +\&\|'d in it. This rule may be a single line or may be +continued with `\|\c +.B \e\c +\&\|'-newline if it is long. The list of rules is +printed on standard output instead of the preprocessed C program. +.Sp +`\|\c +.B \-M\c +\&\|' implies `\|\c +.B \-E\c +\&\|'. +.Sp +`\|\c +.B \-MG\c +\&\|' says to treat missing header files as generated files and assume \c +they live in the same directory as the source file. It must be specified \c +in addition to `\|\c +.B \-M\c +\&\|'. +.TP +.B \-MM\ [ \-MG ] +Like `\|\c +.B \-M\c +\&\|' but the output mentions only the user header files +included with `\|\c +.B #include "\c +.I file\c +\&"\c +\&\|'. System header files +included with `\|\c +.B #include <\c +.I file\c +\&>\c +\&\|' are omitted. +.TP +.B \-MD +Like `\|\c +.B \-M\c +\&\|' but the dependency information is written to files with +names made by replacing `\|\c +.B .o\c +\&\|' with `\|\c +.B .d\c +\&\|' at the end of the +output file names. This is in addition to compiling the file as +specified\(em\&`\|\c +.B \-MD\c +\&\|' does not inhibit ordinary compilation the way +`\|\c +.B \-M\c +\&\|' does. +.Sp +The Mach utility `\|\c +.B md\c +\&\|' can be used to merge the `\|\c +.B .d\c +\&\|' files +into a single dependency file suitable for using with the `\|\c +.B make\c +\&\|' +command. +.TP +.B \-MMD +Like `\|\c +.B \-MD\c +\&\|' except mention only user header files, not system +header files. +.TP +.B \-H +Print the name of each header file used, in addition to other normal +activities. +.TP +.BI "\-A" "question" ( answer ) +Assert the answer +.I answer +for +.I question\c +\&, in case it is tested +with a preprocessor conditional such as `\|\c +.BI "#if #" question ( answer )\c +\&\|'. `\|\c +.B \-A\-\c +\&\|' disables the standard +assertions that normally describe the target machine. +.TP +.BI "\-A" "question"\c +\&(\c +.I answer\c +\&) +Assert the answer \c +.I answer\c +\& for \c +.I question\c +\&, in case it is tested +with a preprocessor conditional such as `\|\c +.B #if +#\c +.I question\c +\&(\c +.I answer\c +\&)\c +\&\|'. `\|\c +.B \-A-\c +\&\|' disables the standard +assertions that normally describe the target machine. +.TP +.BI \-D macro +Define macro \c +.I macro\c +\& with the string `\|\c +.B 1\c +\&\|' as its definition. +.TP +.BI \-D macro = defn +Define macro \c +.I macro\c +\& as \c +.I defn\c +\&. All instances of `\|\c +.B \-D\c +\&\|' on +the command line are processed before any `\|\c +.B \-U\c +\&\|' options. +.TP +.BI \-U macro +Undefine macro \c +.I macro\c +\&. `\|\c +.B \-U\c +\&\|' options are evaluated after all `\|\c +.B \-D\c +\&\|' options, but before any `\|\c +.B \-include\c +\&\|' and `\|\c +.B \-imacros\c +\&\|' options. +.TP +.B \-dM +Tell the preprocessor to output only a list of the macro definitions +that are in effect at the end of preprocessing. Used with the `\|\c +.B \-E\c +\&\|' +option. +.TP +.B \-dD +Tell the preprocessor to pass all macro definitions into the output, in +their proper sequence in the rest of the output. +.TP +.B \-dN +Like `\|\c +.B \-dD\c +\&\|' except that the macro arguments and contents are omitted. +Only `\|\c +.B #define \c +.I name\c +\&\c +\&\|' is included in the output. +.SH ASSEMBLER OPTION +.TP +.BI "\-Wa," "option" +Pass \c +.I option\c +\& as an option to the assembler. If \c +.I option +contains commas, it is split into multiple options at the commas. +.SH LINKER OPTIONS +These options come into play when the compiler links object files into +an executable output file. They are meaningless if the compiler is +not doing a link step. +.TP +.I object-file-name +A file name that does not end in a special recognized suffix is +considered to name an object file or library. (Object files are +distinguished from libraries by the linker according to the file +contents.) If GCC does a link step, these object files are used as input +to the linker. +.TP +.BI \-l library +Use the library named \c +.I library\c +\& when linking. +.Sp +The linker searches a standard list of directories for the library, +which is actually a file named `\|\c +.B lib\c +.I library\c +\&.a\c +\&\|'. The linker +then uses this file as if it had been specified precisely by name. +.Sp +The directories searched include several standard system directories +plus any that you specify with `\|\c +.B \-L\c +\&\|'. +.Sp +Normally the files found this way are library files\(em\&archive files +whose members are object files. The linker handles an archive file by +scanning through it for members which define symbols that have so far +been referenced but not defined. However, if the linker finds an +ordinary object file rather than a library, the object file is linked +in the usual fashion. The only difference between using an `\|\c +.B \-l\c +\&\|' option and specifying a file +name is that `\|\c +.B \-l\c +\&\|' surrounds +.I library +with `\|\c +.B lib\c +\&\|' and `\|\c +.B .a\c +\&\|' and searches several directories. +.TP +.B \-lobjc +You need this special case of the +.B \-l +option in order to link an Objective C program. +.TP +.B \-nostartfiles +Do not use the standard system startup files when linking. +The standard libraries are used normally. +.TP +.B \-nostdlib +Don't use the standard system libraries and startup files when linking. +Only the files you specify will be passed to the linker. +.TP +.B \-static +On systems that support dynamic linking, this prevents linking with the shared +libraries. On other systems, this option has no effect. +.TP +.B \-shared +Produce a shared object which can then be linked with other objects to +form an executable. Only a few systems support this option. +.TP +.B \-symbolic +Bind references to global symbols when building a shared object. Warn +about any unresolved references (unless overridden by the link editor +option `\|\c +.B +\-Xlinker \-z \-Xlinker defs\c +\&\|'). Only a few systems support +this option. +.TP +.BI "\-Xlinker " "option" +Pass \c +.I option +as an option to the linker. You can use this to +supply system-specific linker options which GNU CC does not know how to +recognize. +.Sp +If you want to pass an option that takes an argument, you must use +`\|\c +.B \-Xlinker\c +\&\|' twice, once for the option and once for the argument. +For example, to pass `\|\c +.B +\-assert definitions\c +\&\|', you must write +`\|\c +.B +\-Xlinker \-assert \-Xlinker definitions\c +\&\|'. It does not work to write +`\|\c +.B +\-Xlinker "\-assert definitions"\c +\&\|', because this passes the entire +string as a single argument, which is not what the linker expects. +.TP +.BI "\-Wl," "option" +Pass \c +.I option\c +\& as an option to the linker. If \c +.I option\c +\& contains +commas, it is split into multiple options at the commas. +.TP +.BI "\-u " "symbol" +Pretend the symbol +.I symbol +is undefined, to force linking of +library modules to define it. You can use `\|\c +.B \-u\c +\&\|' multiple times with +different symbols to force loading of additional library modules. +.SH DIRECTORY OPTIONS +These options specify directories to search for header files, for +libraries and for parts of the compiler: +.TP +.BI "\-I" "dir" +Append directory \c +.I dir\c +\& to the list of directories searched for include files. +.TP +.B \-I\- +Any directories you specify with `\|\c +.B \-I\c +\&\|' options before the `\|\c +.B \-I\-\c +\&\|' +option are searched only for the case of `\|\c +.B +#include "\c +.I file\c +.B +\&"\c +\&\|'; +they are not searched for `\|\c +.B #include <\c +.I file\c +\&>\c +\&\|'. +.Sp +If additional directories are specified with `\|\c +.B \-I\c +\&\|' options after +the `\|\c +.B \-I\-\c +\&\|', these directories are searched for all `\|\c +.B #include\c +\&\|' +directives. (Ordinarily \c +.I all\c +\& `\|\c +.B \-I\c +\&\|' directories are used +this way.) +.Sp +In addition, the `\|\c +.B \-I\-\c +\&\|' option inhibits the use of the current +directory (where the current input file came from) as the first search +directory for `\|\c +.B +#include "\c +.I file\c +.B +\&"\c +\&\|'. There is no way to +override this effect of `\|\c +.B \-I\-\c +\&\|'. With `\|\c +.B \-I.\c +\&\|' you can specify +searching the directory which was current when the compiler was +invoked. That is not exactly the same as what the preprocessor does +by default, but it is often satisfactory. +.Sp +`\|\c +.B \-I\-\c +\&\|' does not inhibit the use of the standard system directories +for header files. Thus, `\|\c +.B \-I\-\c +\&\|' and `\|\c +.B \-nostdinc\c +\&\|' are +independent. +.TP +.BI "\-L" "dir" +Add directory \c +.I dir\c +\& to the list of directories to be searched +for `\|\c +.B \-l\c +\&\|'. +.TP +.BI "\-B" "prefix" +This option specifies where to find the executables, libraries and +data files of the compiler itself. +.Sp +The compiler driver program runs one or more of the subprograms +`\|\c +.B cpp\c +\&\|', `\|\c +.B cc1\c +\&\|' (or, for C++, `\|\c +.B cc1plus\c +\&\|'), `\|\c +.B as\c +\&\|' and `\|\c +.B ld\c +\&\|'. It tries +.I prefix\c +\& as a prefix for each program it tries to run, both with and +without `\|\c +.I machine\c +.B /\c +.I version\c +.B /\c +\&\|'. +.Sp +For each subprogram to be run, the compiler driver first tries the +`\|\c +.B \-B\c +\&\|' prefix, if any. If that name is not found, or if `\|\c +.B \-B\c +\&\|' +was not specified, the driver tries two standard prefixes, which are +`\|\c +.B /usr/lib/gcc/\c +\&\|' and `\|\c +.B /usr/local/lib/gcc-lib/\c +\&\|'. If neither of +those results in a file name that is found, the compiler driver +searches for the unmodified program +name, using the directories specified in your +`\|\c +.B PATH\c +\&\|' environment variable. +.Sp +The run-time support file `\|\c +.B libgcc.a\c +\&\|' is also searched for using the +`\|\c +.B \-B\c +\&\|' prefix, if needed. If it is not found there, the two +standard prefixes above are tried, and that is all. The file is left +out of the link if it is not found by those means. Most of the time, +on most machines, `\|\c +.B libgcc.a\c +\&\|' is not actually necessary. +.Sp +You can get a similar result from the environment variable +.B GCC_EXEC_PREFIX\c +\&; if it is defined, its value is used as a prefix +in the same way. If both the `\|\c +.B \-B\c +\&\|' option and the +.B GCC_EXEC_PREFIX\c +\& variable are present, the `\|\c +.B \-B\c +\&\|' option is +used first and the environment variable value second. +.SH WARNING OPTIONS +Warnings are diagnostic messages that report constructions which +are not inherently erroneous but which are risky or suggest there +may have been an error. +.Sp +These options control the amount and kinds of warnings produced by GNU +CC: +.TP +.B \-fsyntax\-only +Check the code for syntax errors, but don't emit any output. +.TP +.B \-w +Inhibit all warning messages. +.TP +.B \-Wno\-import +Inhibit warning messages about the use of +.BR #import . +.TP +.B \-pedantic +Issue all the warnings demanded by strict ANSI standard C; reject +all programs that use forbidden extensions. +.Sp +Valid ANSI standard C programs should compile properly with or without +this option (though a rare few will require `\|\c +.B \-ansi\c +\&\|'). However, +without this option, certain GNU extensions and traditional C features +are supported as well. With this option, they are rejected. There is +no reason to \c +.I use\c +\& this option; it exists only to satisfy pedants. +.Sp +`\|\c +.B \-pedantic\c +\&\|' does not cause warning messages for use of the +alternate keywords whose names begin and end with `\|\c +.B _\|_\c +\&\|'. Pedantic +warnings are also disabled in the expression that follows +.B _\|_extension_\|_\c +\&. However, only system header files should use +these escape routes; application programs should avoid them. +.TP +.B \-pedantic\-errors +Like `\|\c +.B \-pedantic\c +\&\|', except that errors are produced rather than +warnings. +.TP +.B \-W +Print extra warning messages for these events: +.TP +\ \ \ \(bu +A nonvolatile automatic variable might be changed by a call to +.B longjmp\c +\&. These warnings are possible only in +optimizing compilation. +.Sp +The compiler sees only the calls to \c +.B setjmp\c +\&. It cannot know +where \c +.B longjmp\c +\& 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 \c +.B longjmp\c +\& cannot +in fact be called at the place which would cause a problem. +.TP +\ \ \ \(bu +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 +.nf +foo (a) +{ + if (a > 0) + return a; +} +.Sp +.fi +Spurious warnings can occur because GNU CC does not realize that +certain functions (including \c +.B abort\c +\& and \c +.B longjmp\c +\&) +will never return. +.TP +\ \ \ \(bu +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 `\|\c +.B x[i,j]\c +\&\|' will cause a warning, +but `\|\c +.B x[(void)i,j]\c +\&\|' will not. +.TP +\ \ \ \(bu +An unsigned value is compared against zero with `\|\c +.B >\c +\&\|' or `\|\c +.B <=\c +\&\|'. +.PP +.TP +.B \-Wimplicit +Warn whenever a function or parameter is implicitly declared. +.TP +.B \-Wmain +Warn if the +.B main +function is declared or defined with a suspicious type. +Typically, it is a function with external linkage, returning +.B int\c +\&, and +taking zero or two arguments. + +.TP +.B \-Wreturn\-type +Warn whenever a function is defined with a return-type that defaults +to \c +.B int\c +\&. Also warn about any \c +.B return\c +\& statement with no +return-value in a function whose return-type is not \c +.B void\c +\&. +.TP +.B \-Wunused +Warn whenever a local variable is unused aside from its declaration, +whenever a function is declared static but never defined, and whenever +a statement computes a result that is explicitly not used. +.TP +.B \-Wswitch +Warn whenever a \c +.B switch\c +\& statement has an index of enumeral type +and lacks a \c +.B case\c +\& for one or more of the named codes of that +enumeration. (The presence of a \c +.B default\c +\& label prevents this +warning.) \c +.B case\c +\& labels outside the enumeration range also +provoke warnings when this option is used. +.TP +.B \-Wcomment +Warn whenever a comment-start sequence `\|\c +.B /\(**\c +\&\|' appears in a comment. +.TP +.B \-Wtrigraphs +Warn if any trigraphs are encountered (assuming they are enabled). +.TP +.B \-Wformat +Check calls to \c +.B printf\c +\& and \c +.B scanf\c +\&, etc., to make sure that +the arguments supplied have types appropriate to the format string +specified. +.TP +.B \-Wchar\-subscripts +Warn if an array subscript has type +.BR char . +This is a common cause of error, as programmers often forget that this +type is signed on some machines. +.TP +.B \-Wuninitialized +An automatic variable is used without first being initialized. +.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 `\|\c +.B \-O\c +\&\|', you simply won't +get these warnings. +.Sp +These warnings occur only for variables that are candidates for +register allocation. Therefore, they do not occur for a variable that +is declared \c +.B volatile\c +\&, 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 GNU CC 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 +.nf +{ + int x; + switch (y) + { + case 1: x = 1; + break; + case 2: x = 4; + break; + case 3: x = 5; + } + foo (x); +} +.Sp +.fi +If the value of \c +.B y\c +\& is always 1, 2 or 3, then \c +.B x\c +\& is +always initialized, but GNU CC doesn't know this. Here is +another common case: +.Sp +.nf +{ + int save_y; + if (change_y) save_y = y, y = new_y; + .\|.\|. + if (change_y) y = save_y; +} +.Sp +.fi +This has no bug because \c +.B save_y\c +\& is used only if it is set. +.Sp +Some spurious warnings can be avoided if you declare as +.B volatile\c +\& all the functions you use that never return. +.TP +.B \-Wparentheses +Warn if parentheses are omitted in certain contexts. +.TP +.B \-Wtemplate\-debugging +When using templates in a C++ program, warn if debugging is not yet +fully available (C++ only). +.TP +.B \-Wall +All of the above `\|\c +.B \-W\c +\&\|' options combined. These are all the +options which pertain to usage that we recommend avoiding and that we +believe is easy to avoid, even in conjunction with macros. +.PP +The remaining `\|\c +.B \-W.\|.\|.\c +\&\|' options are not implied by `\|\c +.B \-Wall\c +\&\|' +because they warn about constructions that we consider reasonable to +use, on occasion, in clean programs. +.TP +.B \-Wtraditional +Warn about certain constructs that behave differently in traditional and +ANSI C. +.TP +\ \ \ \(bu +Macro arguments occurring within string constants in the macro body. +These would substitute the argument in traditional C, but are part of +the constant in ANSI C. +.TP +\ \ \ \(bu +A function declared external in one block and then used after the end of +the block. +.TP +\ \ \ \(bu +A \c +.B switch\c +\& statement has an operand of type \c +.B long\c +\&. +.PP +.TP +.B \-Wshadow +Warn whenever a local variable shadows another local variable. +.TP +.BI "\-Wid\-clash\-" "len" +Warn whenever two distinct identifiers match in the first \c +.I len +characters. This may help you prepare a program that will compile +with certain obsolete, brain-damaged compilers. +.TP +.B \-Wpointer\-arith +Warn about anything that depends on the \*(lqsize of\*(rq a function type or +of \c +.B void\c +\&. GNU C assigns these types a size of 1, for +convenience in calculations with \c +.B void \(**\c +\& pointers and pointers +to functions. +.TP +.B \-Wcast\-qual +Warn whenever a pointer is cast so as to remove a type qualifier from +the target type. For example, warn if a \c +.B const char \(**\c +\& is cast +to an ordinary \c +.B char \(**\c +\&. +.TP +.B \-Wcast\-align +Warn whenever a pointer is cast such that the required alignment of the +target is increased. For example, warn if a \c +.B char \(**\c +\& is cast to +an \c +.B int \(**\c +\& on machines where integers can only be accessed at +two- or four-byte boundaries. +.TP +.B \-Wwrite\-strings +Give string constants the type \c +.B const char[\c +.I length\c +.B ]\c +\& so that +copying the address of one into a non-\c +.B const\c +\& \c +.B char \(** +pointer will get a warning. These warnings will help you find at +compile time code that can try to write into a string constant, but +only if you have been very careful about using \c +.B const\c +\& in +declarations and prototypes. Otherwise, it will just be a nuisance; +this is why we did not make `\|\c +.B \-Wall\c +\&\|' request these warnings. +.TP +.B \-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. +.TP +.B \-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.) +.TP +.B \-Wstrict\-prototypes +Warn if a function is declared or defined without specifying the +argument types. (An old-style function definition is permitted without +a warning if preceded by a declaration which specifies the argument +types.) +.TP +.B \-Wmissing\-prototypes +Warn if a global function is defined without a previous prototype +declaration. This warning is issued even if the definition itself +provides a prototype. The aim is to detect global functions that fail +to be declared in header files. +.TP +.B \-Wmissing\-declarations +Warn if a global function is defined without a previous declaration. +Do so even if the definition itself provides a prototype. +Use this option to detect global functions that are not declared in +header files. +.TP +.B \-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. +.TP +.B \-Wnested-externs +Warn if an \c +.B extern\c +\& declaration is encountered within an function. +.TP +.B \-Wenum\-clash +Warn about conversion between different enumeration types (C++ only). +.TP +.B \-Woverloaded\-virtual +(C++ only.) +In a derived class, the definitions of virtual functions must match +the type signature of a virtual function declared in the base class. +Use this option to request warnings when a derived class declares a +function that may be an erroneous attempt to define a virtual +function: that is, warn when a function with the same name as a +virtual function in the base class, but with a type signature that +doesn't match any virtual functions from the base class. +.TP +.B \-Winline +Warn if a function can not be inlined, and either it was declared as inline, +or else the +.B \-finline\-functions +option was given. +.TP +.B \-Werror +Treat warnings as errors; abort compilation after any warning. +.SH DEBUGGING OPTIONS +GNU CC has various special options that are used for debugging +either your program or GCC: +.TP +.B \-g +Produce debugging information in the operating system's native format +(stabs, COFF, XCOFF, or DWARF). GDB can work with this debugging +information. +.Sp +On most systems that use stabs format, `\|\c +.B \-g\c +\&\|' enables use of extra +debugging information that only GDB can use; this extra information +makes debugging work better in GDB but will probably make other debuggers +crash or +refuse to read the program. If you want to control for certain whether +to generate the extra information, use `\|\c +.B \-gstabs+\c +\&\|', `\|\c +.B \-gstabs\c +\&\|', +`\|\c +.B \-gxcoff+\c +\&\|', `\|\c +.B \-gxcoff\c +\&\|', `\|\c +.B \-gdwarf+\c +\&\|', or `\|\c +.B \-gdwarf\c +\&\|' +(see below). +.Sp +Unlike most other C compilers, GNU CC allows you to use `\|\c +.B \-g\c +\&\|' with +`\|\c +.B \-O\c +\&\|'. 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. +.PP +The following options are useful when GNU CC is generated with the +capability for more than one debugging format. +.TP +.B \-ggdb +Produce debugging information in the native format (if that is supported), +including GDB extensions if at all possible. +.TP +.B \-gstabs +Produce debugging information in stabs format (if that is supported), +without GDB extensions. This is the format used by DBX on most BSD +systems. +.TP +.B \-gstabs+ +Produce debugging information in stabs format (if that is supported), +using GNU extensions understood only by the GNU debugger (GDB). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program. +.TP +.B \-gcoff +Produce debugging information in COFF format (if that is supported). +This is the format used by SDB on most System V systems prior to +System V Release 4. +.TP +.B \-gxcoff +Produce debugging information in XCOFF format (if that is supported). +This is the format used by the DBX debugger on IBM RS/6000 systems. +.TP +.B \-gxcoff+ +Produce debugging information in XCOFF format (if that is supported), +using GNU extensions understood only by the GNU debugger (GDB). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program. +.TP +.B \-gdwarf +Produce debugging information in DWARF format (if that is supported). +This is the format used by SDB on most System V Release 4 systems. +.TP +.B \-gdwarf+ +Produce debugging information in DWARF format (if that is supported), +using GNU extensions understood only by the GNU debugger (GDB). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program. +.PP +.BI "\-g" "level" +.br +.BI "\-ggdb" "level" +.br +.BI "\-gstabs" "level" +.br +.BI "\-gcoff" "level" +.BI "\-gxcoff" "level" +.TP +.BI "\-gdwarf" "level" +Request debugging information and also use \c +.I level\c +\& to specify how +much information. The default level is 2. +.Sp +Level 1 produces minimal information, enough for making backtraces in +parts of the program that you don't plan to debug. This includes +descriptions of functions and external variables, but no information +about local variables and no line numbers. +.Sp +Level 3 includes extra information, such as all the macro definitions +present in the program. Some debuggers support macro expansion when +you use `\|\c +.B \-g3\c +\&\|'. +.TP +.B \-p +Generate extra code to write profile information suitable for the +analysis program \c +.B prof\c +\&. +.TP +.B \-pg +Generate extra code to write profile information suitable for the +analysis program \c +.B gprof\c +\&. +.TP +.B \-a +Generate extra code to write profile information for basic blocks, +which will record the number of times each basic block is executed. +This data could be analyzed by a program like \c +.B tcov\c +\&. Note, +however, that the format of the data is not what \c +.B tcov\c +\& expects. +Eventually GNU \c +.B gprof\c +\& should be extended to process this data. +.TP +.B \-ax +Generate extra code to read basic block profiling parameters from +file `bb.in' and write profiling results to file `bb.out'. +`bb.in' contains a list of functions. Whenever a function on the list +is entered, profiling is turned on. When the outmost function is left, +profiling is turned off. If a function name is prefixed with `-' +the function is excluded from profiling. If a function name is not +unique it can be disambiguated by writing +`/path/filename.d:functionname'. `bb.out' will list some available +filenames. +Four function names have a special meaning: +`__bb_jumps__' will cause jump frequencies to be written to `bb.out'. +`__bb_trace__' will cause the sequence of basic blocks to be piped +into `gzip' and written to file `bbtrace.gz'. +`__bb_hidecall__' will cause call instructions to be excluded from +the trace. +`__bb_showret__' will cause return instructions to be included in +the trace. +.TP +.BI "\-d" "letters" +Says to make debugging dumps during compilation at times specified by +.I letters\c +\&. This is used for debugging the compiler. The file names +for most of the dumps are made by appending a word to the source file +name (e.g. `\|\c +.B foo.c.rtl\c +\&\|' or `\|\c +.B foo.c.jump\c +\&\|'). +.TP +.B \-dM +Dump all macro definitions, at the end of preprocessing, and write no +output. +.TP +.B \-dN +Dump all macro names, at the end of preprocessing. +.TP +.B \-dD +Dump all macro definitions, at the end of preprocessing, in addition to +normal output. +.TP +.B \-dy +Dump debugging information during parsing, to standard error. +.TP +.B \-dr +Dump after RTL generation, to `\|\c +.I file\c +.B \&.rtl\c +\&\|'. +.TP +.B \-dx +Just generate RTL for a function instead of compiling it. Usually used +with `\|\c +.B r\c +\&\|'. +.TP +.B \-dj +Dump after first jump optimization, to `\|\c +.I file\c +.B \&.jump\c +\&\|'. +.TP +.B \-ds +Dump after CSE (including the jump optimization that sometimes +follows CSE), to `\|\c +.I file\c +.B \&.cse\c +\&\|'. +.TP +.B \-dL +Dump after loop optimization, to `\|\c +.I file\c +.B \&.loop\c +\&\|'. +.TP +.B \-dt +Dump after the second CSE pass (including the jump optimization that +sometimes follows CSE), to `\|\c +.I file\c +.B \&.cse2\c +\&\|'. +.TP +.B \-df +Dump after flow analysis, to `\|\c +.I file\c +.B \&.flow\c +\&\|'. +.TP +.B \-dc +Dump after instruction combination, to `\|\c +.I file\c +.B \&.combine\c +\&\|'. +.TP +.B \-dS +Dump after the first instruction scheduling pass, to +`\|\c +.I file\c +.B \&.sched\c +\&\|'. +.TP +.B \-dl +Dump after local register allocation, to `\|\c +.I file\c +.B \&.lreg\c +\&\|'. +.TP +.B \-dg +Dump after global register allocation, to `\|\c +.I file\c +.B \&.greg\c +\&\|'. +.TP +.B \-dR +Dump after the second instruction scheduling pass, to +`\|\c +.I file\c +.B \&.sched2\c +\&\|'. +.TP +.B \-dJ +Dump after last jump optimization, to `\|\c +.I file\c +.B \&.jump2\c +\&\|'. +.TP +.B \-dd +Dump after delayed branch scheduling, to `\|\c +.I file\c +.B \&.dbr\c +\&\|'. +.TP +.B \-dk +Dump after conversion from registers to stack, to `\|\c +.I file\c +.B \&.stack\c +\&\|'. +.TP +.B \-da +Produce all the dumps listed above. +.TP +.B \-dm +Print statistics on memory usage, at the end of the run, to +standard error. +.TP +.B \-dp +Annotate the assembler output with a comment indicating which +pattern and alternative was used. +.TP +.B \-fpretend\-float +When running a cross-compiler, pretend that the target machine uses the +same floating point format as the host machine. This causes incorrect +output of the actual floating constants, but the actual instruction +sequence will probably be the same as GNU CC would make when running on +the target machine. +.TP +.B \-save\-temps +Store the usual \*(lqtemporary\*(rq intermediate files permanently; place them +in the current directory and name them based on the source file. Thus, +compiling `\|\c +.B foo.c\c +\&\|' with `\|\c +.B \-c \-save\-temps\c +\&\|' would produce files +`\|\c +.B foo.cpp\c +\&\|' and `\|\c +.B foo.s\c +\&\|', as well as `\|\c +.B foo.o\c +\&\|'. +.TP +.BI "\-print\-file\-name=" "library" +Print the full absolute name of the library file \|\c +.nh +.I library +.hy +\&\| that +would be used when linking\(em\&and do not do anything else. With this +option, GNU CC does not compile or link anything; it just prints the +file name. +.TP +.B \-print\-libgcc\-file\-name +Same as `\|\c +.B \-print\-file\-name=libgcc.a\c +\&\|'. +.TP +.BI "\-print\-prog\-name=" "program" +Like `\|\c +.B \-print\-file\-name\c +\&\|', but searches for a program such as `\|\c +cpp\c +\&\|'. +.SH OPTIMIZATION OPTIONS +These options control various sorts of optimizations: +.TP +.B \-O +.TP +.B \-O1 +Optimize. Optimizing compilation takes somewhat more time, and a lot +more memory for a large function. +.Sp +Without `\|\c +.B \-O\c +\&\|', the compiler's goal is to reduce the cost of +compilation and to make debugging produce the expected results. +Statements are independent: if you stop the program with a breakpoint +between statements, you can then assign a new value to any variable or +change the program counter to any other statement in the function and +get exactly the results you would expect from the source code. +.Sp +Without `\|\c +.B \-O\c +\&\|', only variables declared \c +.B register\c +\& are +allocated in registers. The resulting compiled code is a little worse +than produced by PCC without `\|\c +.B \-O\c +\&\|'. +.Sp +With `\|\c +.B \-O\c +\&\|', the compiler tries to reduce code size and execution +time. +.Sp +When you specify `\|\c +.B \-O\c +\&\|', the two options `\|\c +.B \-fthread\-jumps\c +\&\|' and `\|\c +.B \-fdefer\-pop\c +\&\|' are turned on. On machines that have delay slots, the `\|\c +.B \-fdelayed\-branch\c +\&\|' option is turned on. For those machines that can support debugging even +without a frame pointer, the `\|\c +.B \-fomit\-frame\-pointer\c +\&\|' option is turned on. On some machines other flags may also be turned on. +.TP +.B \-O2 +Optimize even more. Nearly all supported optimizations that do not +involve a space-speed tradeoff are performed. Loop unrolling and function +inlining are not done, for example. As compared to +.B \-O\c +\&, +this option increases both compilation time and the performance of the +generated code. +.TP +.B \-O3 +Optimize yet more. This turns on everything +.B \-O2 +does, along with also turning on +.B \-finline\-functions. +.TP +.B \-O0 +Do not optimize. +.Sp +If you use multiple +.B \-O +options, with or without level numbers, the last such option is the +one that is effective. +.PP +Options of the form `\|\c +.B \-f\c +.I flag\c +\&\c +\&\|' specify machine-independent +flags. Most flags have both positive and negative forms; the negative +form of `\|\c +.B \-ffoo\c +\&\|' would be `\|\c +.B \-fno\-foo\c +\&\|'. The following list shows +only one form\(em\&the one which is not the default. +You can figure out the other form by either removing `\|\c +.B no\-\c +\&\|' or +adding it. +.TP +.B \-ffloat\-store +Do not store floating point variables in registers. This +prevents undesirable excess precision on machines such as the +68000 where the floating registers (of the 68881) keep more +precision than a \c +.B double\c +\& is supposed to have. +.Sp +For most programs, the excess precision does only good, but a few +programs rely on the precise definition of IEEE floating point. +Use `\|\c +.B \-ffloat\-store\c +\&\|' for such programs. +.TP +.B \-fmemoize\-lookups +.TP +.B \-fsave\-memoized +Use heuristics to compile faster (C++ only). These heuristics are not +enabled by default, since they are only effective for certain input +files. Other input files compile more slowly. +.Sp +The first time the compiler must build a call to a member function (or +reference to a data member), it must (1) determine whether the class +implements member functions of that name; (2) resolve which member +function to call (which involves figuring out what sorts of type +conversions need to be made); and (3) check the visibility of the member +function to the caller. All of this adds up to slower compilation. +Normally, the second time a call is made to that member function (or +reference to that data member), it must go through the same lengthy +process again. This means that code like this +.Sp +\& cout << "This " << p << " has " << n << " legs.\en"; +.Sp +makes six passes through all three steps. By using a software cache, +a \*(lqhit\*(rq significantly reduces this cost. Unfortunately, using the +cache introduces another layer of mechanisms which must be implemented, +and so incurs its own overhead. `\|\c +.B \-fmemoize\-lookups\c +\&\|' enables +the software cache. +.Sp +Because access privileges (visibility) to members and member functions +may differ from one function context to the next, +.B g++ +may need to flush the cache. With the `\|\c +.B \-fmemoize\-lookups\c +\&\|' flag, the cache is flushed after every +function that is compiled. The `\|\c +\-fsave\-memoized\c +\&\|' flag enables the same software cache, but when the compiler +determines that the context of the last function compiled would yield +the same access privileges of the next function to compile, it +preserves the cache. +This is most helpful when defining many member functions for the same +class: with the exception of member functions which are friends of +other classes, each member function has exactly the same access +privileges as every other, and the cache need not be flushed. +.TP +.B \-fno\-default\-inline +Don't make member functions inline by default merely because they are +defined inside the class scope (C++ only). +.TP +.B \-fno\-defer\-pop +Always pop the arguments to each function call as soon as that +function returns. For machines which must pop arguments after a +function call, the compiler normally lets arguments accumulate on the +stack for several function calls and pops them all at once. +.TP +.B \-fforce\-mem +Force memory operands to be copied into registers before doing +arithmetic on them. This may produce better code by making all +memory references potential common subexpressions. When they are +not common subexpressions, instruction combination should +eliminate the separate register-load. I am interested in hearing +about the difference this makes. +.TP +.B \-fforce\-addr +Force memory address constants to be copied into registers before +doing arithmetic on them. This may produce better code just as +`\|\c +.B \-fforce\-mem\c +\&\|' may. I am interested in hearing about the +difference this makes. +.TP +.B \-fomit\-frame\-pointer +Don't keep the frame pointer in a register for functions that +don't need one. This avoids the instructions to save, set up and +restore frame pointers; it also makes an extra register available +in many functions. \c +.I It also makes debugging impossible on most machines\c +\&. +.Sp +On some machines, such as the Vax, this flag has no effect, because +the standard calling sequence automatically handles the frame pointer +and nothing is saved by pretending it doesn't exist. The +machine-description macro \c +.B FRAME_POINTER_REQUIRED\c +\& controls +whether a target machine supports this flag. +.TP +.B \-finline\-functions +Integrate all simple functions into their callers. The compiler +heuristically decides which functions are simple enough to be worth +integrating in this way. +.Sp +If all calls to a given function are integrated, and the function is +declared \c +.B static\c +\&, then GCC normally does not output the function as +assembler code in its own right. +.TP +.B \-fcaller\-saves +Enable values to be allocated in registers that will be clobbered by +function calls, by emitting extra instructions to save and restore the +registers around such calls. Such allocation is done only when it +seems to result in better code than would otherwise be produced. +.Sp +This option is enabled by default on certain machines, usually those +which have no call-preserved registers to use instead. +.TP +.B \-fkeep\-inline\-functions +Even if all calls to a given function are integrated, and the function +is declared \c +.B static\c +\&, nevertheless output a separate run-time +callable version of the function. +.TP +.B \-fno\-function\-cse +Do not put function addresses in registers; make each instruction that +calls a constant function contain the function's address explicitly. +.Sp +This option results in less efficient code, but some strange hacks +that alter the assembler output may be confused by the optimizations +performed when this option is not used. +.TP +.B \-fno\-peephole +Disable any machine-specific peephole optimizations. +.TP +.B \-ffast-math +This option allows GCC to violate some ANSI or IEEE rules/specifications +in the interest of optimizing code for speed. For example, it allows +the compiler to assume arguments to the \c +.B sqrt\c +\& function are +non-negative numbers. +.Sp +This option should never be turned on by any `\|\c +.B \-O\c +\&\|' option since +it can result in incorrect output for programs which depend on +an exact implementation of IEEE or ANSI rules/specifications for +math functions. +.PP +The following options control specific optimizations. The `\|\c +.B \-O2\c +\&\|' +option turns on all of these optimizations except `\|\c +.B \-funroll\-loops\c +\&\|' +and `\|\c +.B \-funroll\-all\-loops\c +\&\|'. +.PP +The `\|\c +.B \-O\c +\&\|' option usually turns on +the `\|\c +.B \-fthread\-jumps\c +\&\|' and `\|\c +.B \-fdelayed\-branch\c +\&\|' options, but +specific machines may change the default optimizations. +.PP +You can use the following flags in the rare cases when \*(lqfine-tuning\*(rq +of optimizations to be performed is desired. +.TP +.B \-fstrength\-reduce +Perform the optimizations of loop strength reduction and +elimination of iteration variables. +.TP +.B \-fthread\-jumps +Perform optimizations where we check to see if a jump branches to a +location where another comparison subsumed by the first is found. If +so, the first branch is redirected to either the destination of the +second branch or a point immediately following it, depending on whether +the condition is known to be true or false. +.TP +.B \-funroll\-loops +Perform the optimization of loop unrolling. This is only done for loops +whose number of iterations can be determined at compile time or run time. +.TP +.B \-funroll\-all\-loops +Perform the optimization of loop unrolling. This is done for all loops. +This usually makes programs run more slowly. +.TP +.B \-fcse\-follow\-jumps +In common subexpression elimination, scan through jump instructions +when the target of the jump is not reached by any other path. For +example, when CSE encounters an \c +.B if\c +\& statement with an +.B else\c +\& clause, CSE will follow the jump when the condition +tested is false. +.TP +.B \-fcse\-skip\-blocks +This is similar to `\|\c +.B \-fcse\-follow\-jumps\c +\&\|', but causes CSE to +follow jumps which conditionally skip over blocks. When CSE +encounters a simple \c +.B if\c +\& statement with no else clause, +`\|\c +.B \-fcse\-skip\-blocks\c +\&\|' causes CSE to follow the jump around the +body of the \c +.B if\c +\&. +.TP +.B \-frerun\-cse\-after\-loop +Re-run common subexpression elimination after loop optimizations has been +performed. +.TP +.B \-felide\-constructors +Elide constructors when this seems plausible (C++ only). With this +flag, GNU C++ initializes \c +.B y\c +\& directly from the call to \c +.B foo +without going through a temporary in the following code: +.Sp +A foo (); +A y = foo (); +.Sp +Without this option, GNU C++ first initializes \c +.B y\c +\& by calling the +appropriate constructor for type \c +.B A\c +\&; then assigns the result of +.B foo\c +\& to a temporary; and, finally, replaces the initial value of +`\|\c +.B y\c +\&\|' with the temporary. +.Sp +The default behavior (`\|\c +.B \-fno\-elide\-constructors\c +\&\|') is specified by +the draft ANSI C++ standard. If your program's constructors have side +effects, using `\|\c +.B \-felide-constructors\c +\&\|' can make your program act +differently, since some constructor calls may be omitted. +.TP +.B \-fexpensive\-optimizations +Perform a number of minor optimizations that are relatively expensive. +.TP +.B \-fdelayed\-branch +If supported for the target machine, attempt to reorder instructions +to exploit instruction slots available after delayed branch +instructions. +.TP +.B \-fschedule\-insns +If supported for the target machine, attempt to reorder instructions to +eliminate execution stalls due to required data being unavailable. This +helps machines that have slow floating point or memory load instructions +by allowing other instructions to be issued until the result of the load +or floating point instruction is required. +.TP +.B \-fschedule\-insns2 +Similar to `\|\c +.B \-fschedule\-insns\c +\&\|', but requests an additional pass of +instruction scheduling after register allocation has been done. This is +especially useful on machines with a relatively small number of +registers and where memory load instructions take more than one cycle. +.SH TARGET OPTIONS +By default, GNU CC compiles code for the same type of machine that you +are using. However, it can also be installed as a cross-compiler, to +compile for some other type of machine. In fact, several different +configurations of GNU CC, for different target machines, can be +installed side by side. Then you specify which one to use with the +`\|\c +.B \-b\c +\&\|' option. +.PP +In addition, older and newer versions of GNU CC can be installed side +by side. One of them (probably the newest) will be the default, but +you may sometimes wish to use another. +.TP +.BI "\-b " "machine" +The argument \c +.I machine\c +\& specifies the target machine for compilation. +This is useful when you have installed GNU CC as a cross-compiler. +.Sp +The value to use for \c +.I machine\c +\& is the same as was specified as the +machine type when configuring GNU CC as a cross-compiler. For +example, if a cross-compiler was configured with `\|\c +.B configure +i386v\c +\&\|', meaning to compile for an 80386 running System V, then you +would specify `\|\c +.B \-b i386v\c +\&\|' to run that cross compiler. +.Sp +When you do not specify `\|\c +.B \-b\c +\&\|', it normally means to compile for +the same type of machine that you are using. +.TP +.BI "\-V " "version" +The argument \c +.I version\c +\& specifies which version of GNU CC to run. +This is useful when multiple versions are installed. For example, +.I version\c +\& might be `\|\c +.B 2.0\c +\&\|', meaning to run GNU CC version 2.0. +.Sp +The default version, when you do not specify `\|\c +.B \-V\c +\&\|', is controlled +by the way GNU CC is installed. Normally, it will be a version that +is recommended for general use. +.SH MACHINE DEPENDENT OPTIONS +Each of the target machine types can have its own special options, +starting with `\|\c +.B \-m\c +\&\|', to choose among various hardware models or +configurations\(em\&for example, 68010 vs 68020, floating coprocessor or +none. A single installed version of the compiler can compile for any +model or configuration, according to the options specified. +.PP +Some configurations of the compiler also support additional special +options, usually for command-line compatibility with other compilers on +the same platform. +.PP +These are the `\|\c +.B \-m\c +\&\|' options defined for the 68000 series: +.TP +.B \-m68000 +.TP +.B \-mc68000 +Generate output for a 68000. This is the default when the compiler is +configured for 68000-based systems. +.TP +.B \-m68020 +.TP +.B \-mc68020 +Generate output for a 68020 (rather than a 68000). This is the +default when the compiler is configured for 68020-based systems. +.TP +.B \-m68881 +Generate output containing 68881 instructions for floating point. +This is the default for most 68020-based systems unless +.B \-nfp +was specified when the compiler was configured. +.TP +.B \-m68030 +Generate output for a 68030. This is the default when the compiler is +configured for 68030-based systems. +.TP +.B \-m68040 +Generate output for a 68040. This is the default when the compiler is +configured for 68040-based systems. +.TP +.B \-m68020\-40 +Generate output for a 68040, without using any of the new instructions. +This results in code which can run relatively efficiently on either a +68020/68881 or a 68030 or a 68040. +.TP +.B \-mfpa +Generate output containing Sun FPA instructions for floating point. +.TP +.B \-msoft\-float +Generate output containing library calls for floating point. +.I +WARNING: +the requisite libraries are not part of GNU CC. Normally the +facilities of the machine's usual C compiler are used, but this can't +be done directly in cross-compilation. You must make your own +arrangements to provide suitable library functions for cross-compilation. +.TP +.B \-mshort +Consider type \c +.B int\c +\& to be 16 bits wide, like \c +.B short int\c +\&. +.TP +.B \-mnobitfield +Do not use the bit-field instructions. `\|\c +.B \-m68000\c +\&\|' implies +`\|\c +.B \-mnobitfield\c +\&\|'. +.TP +.B \-mbitfield +Do use the bit-field instructions. `\|\c +.B \-m68020\c +\&\|' implies +`\|\c +.B \-mbitfield\c +\&\|'. This is the default if you use the unmodified +sources. +.TP +.B \-mrtd +Use a different function-calling convention, in which functions +that take a fixed number of arguments return with the \c +.B rtd +instruction, which pops their arguments while returning. This +saves one instruction in the caller since there is no need to pop +the arguments there. +.Sp +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. +.Sp +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including \c +.B printf\c +\&); +otherwise incorrect code will be generated for calls to those +functions. +.Sp +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) +.Sp +The \c +.B rtd\c +\& instruction is supported by the 68010 and 68020 +processors, but not by the 68000. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the Vax: +.TP +.B \-munix +Do not output certain jump instructions (\c +.B aobleq\c +\& and so on) +that the Unix assembler for the Vax cannot handle across long +ranges. +.TP +.B \-mgnu +Do output those jump instructions, on the assumption that you +will assemble with the GNU assembler. +.TP +.B \-mg +Output code for g-format floating point numbers instead of d-format. +.PP +These `\|\c +.B \-m\c +\&\|' switches are supported on the SPARC: +.PP +.B \-mfpu +.TP +.B \-mhard\-float +Generate output containing floating point instructions. This is the +default. +.PP +.B \-mno\-fpu +.TP +.B \-msoft\-float +Generate output containing library calls for floating point. +.I Warning: +there is no GNU floating-point library for SPARC. +Normally the facilities of the machine's usual C compiler are used, but +this cannot be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. +.Sp +.B \-msoft\-float +changes the calling convention in the output file; +therefore, it is only useful if you compile +.I all +of a program with this option. +.PP +.B \-mno\-epilogue +.TP +.B \-mepilogue +With +.B \-mepilogue +(the default), the compiler always emits code for +function exit at the end of each function. Any function exit in +the middle of the function (such as a return statement in C) will +generate a jump to the exit code at the end of the function. +.Sp +With +.BR \-mno\-epilogue , +the compiler tries to emit exit code inline at every function exit. +.PP +.B \-mno\-v8 +.TP +.B \-mv8 +.TP +.B \-msparclite +These three options select variations on the SPARC architecture. +.Sp +By default (unless specifically configured for the Fujitsu SPARClite), +GCC generates code for the v7 variant of the SPARC architecture. +.Sp +.B \-mv8 +will give you SPARC v8 code. The only difference from v7 +code is that the compiler emits the integer multiply and integer +divide instructions which exist in SPARC v8 but not in SPARC v7. +.Sp +.B \-msparclite +will give you SPARClite code. This adds the integer +multiply, integer divide step and scan (ffs) instructions which +exist in SPARClite but not in SPARC v7. +.PP +.B \-mcypress +.TP +.B \-msupersparc +These two options select the processor for which the code is optimised. +.Sp +With +.B \-mcypress +(the default), the compiler optimises code for the Cypress CY7C602 chip, as +used in the SparcStation/SparcServer 3xx series. This is also appropriate for +the older SparcStation 1, 2, IPX etc. +.Sp +With +.B \-msupersparc +the compiler optimises code for the SuperSparc cpu, as used in the SparcStation +10, 1000 and 2000 series. This flag also enables use of the full SPARC v8 +instruction set. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the Convex: +.TP +.B \-mc1 +Generate output for a C1. This is the default when the compiler is +configured for a C1. +.TP +.B \-mc2 +Generate output for a C2. This is the default when the compiler is +configured for a C2. +.TP +.B \-margcount +Generate code which puts an argument count in the word preceding each +argument list. Some nonportable Convex and Vax programs need this word. +(Debuggers don't, except for functions with variable-length argument +lists; this info is in the symbol table.) +.TP +.B \-mnoargcount +Omit the argument count word. This is the default if you use the +unmodified sources. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the AMD Am29000: +.TP +.B \-mdw +Generate code that assumes the DW bit is set, i.e., that byte and +halfword operations are directly supported by the hardware. This is the +default. +.TP +.B \-mnodw +Generate code that assumes the DW bit is not set. +.TP +.B \-mbw +Generate code that assumes the system supports byte and halfword write +operations. This is the default. +.TP +.B \-mnbw +Generate code that assumes the systems does not support byte and +halfword write operations. This implies `\|\c +.B \-mnodw\c +\&\|'. +.TP +.B \-msmall +Use a small memory model that assumes that all function addresses are +either within a single 256 KB segment or at an absolute address of less +than 256K. This allows the \c +.B call\c +\& instruction to be used instead +of a \c +.B const\c +\&, \c +.B consth\c +\&, \c +.B calli\c +\& sequence. +.TP +.B \-mlarge +Do not assume that the \c +.B call\c +\& instruction can be used; this is the +default. +.TP +.B \-m29050 +Generate code for the Am29050. +.TP +.B \-m29000 +Generate code for the Am29000. This is the default. +.TP +.B \-mkernel\-registers +Generate references to registers \c +.B gr64-gr95\c +\& instead of +.B gr96-gr127\c +\&. This option can be used when compiling kernel code +that wants a set of global registers disjoint from that used by +user-mode code. +.Sp +Note that when this option is used, register names in `\|\c +.B \-f\c +\&\|' flags +must use the normal, user-mode, names. +.TP +.B \-muser\-registers +Use the normal set of global registers, \c +.B gr96-gr127\c +\&. This is the +default. +.TP +.B \-mstack\-check +Insert a call to \c +.B _\|_msp_check\c +\& after each stack adjustment. This +is often used for kernel code. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for Motorola 88K architectures: +.TP +.B \-m88000 +Generate code that works well on both the m88100 and the +m88110. +.TP +.B \-m88100 +Generate code that works best for the m88100, but that also +runs on the m88110. +.TP +.B \-m88110 +Generate code that works best for the m88110, and may not run +on the m88100. +.TP +.B \-midentify\-revision +Include an \c +.B ident\c +\& directive in the assembler output recording the +source file name, compiler name and version, timestamp, and compilation +flags used. +.TP +.B \-mno\-underscores +In assembler output, emit symbol names without adding an underscore +character at the beginning of each name. The default is to use an +underscore as prefix on each name. +.TP +.B \-mno\-check\-zero\-division +.TP +.B \-mcheck\-zero\-division +Early models of the 88K architecture had problems with division by zero; +in particular, many of them didn't trap. Use these options to avoid +including (or to include explicitly) additional code to detect division +by zero and signal an exception. All GCC configurations for the 88K use +`\|\c +.B \-mcheck\-zero\-division\c +\&\|' by default. +.TP +.B \-mocs\-debug\-info +.TP +.B \-mno\-ocs\-debug\-info +Include (or omit) additional debugging information (about +registers used in each stack frame) as specified in the 88Open Object +Compatibility Standard, \*(lqOCS\*(rq. This extra information is not needed +by GDB. The default for DG/UX, SVr4, and Delta 88 SVr3.2 is to +include this information; other 88k configurations omit this information +by default. +.TP +.B \-mocs\-frame\-position +.TP +.B \-mno\-ocs\-frame\-position +Force (or do not require) register values to be stored in a particular +place in stack frames, as specified in OCS. The DG/UX, Delta88 SVr3.2, +and BCS configurations use `\|\c +.B \-mocs\-frame\-position\c +\&\|'; other 88k +configurations have the default `\|\c +.B \-mno\-ocs\-frame\-position\c +\&\|'. +.TP +.B \-moptimize\-arg\-area +.TP +.B \-mno\-optimize\-arg\-area +Control how to store function arguments in stack frames. +`\|\c +.B \-moptimize\-arg\-area\c +\&\|' saves space, but may break some +debuggers (not GDB). `\|\c +.B \-mno\-optimize\-arg\-area\c +\&\|' conforms better to +standards. By default GCC does not optimize the argument area. +.TP +.BI "\-mshort\-data\-" "num" +.I num +Generate smaller data references by making them relative to \c +.B r0\c +\&, +which allows loading a value using a single instruction (rather than the +usual two). You control which data references are affected by +specifying \c +.I num\c +\& with this option. For example, if you specify +`\|\c +.B \-mshort\-data\-512\c +\&\|', then the data references affected are those +involving displacements of less than 512 bytes. +`\|\c +.B \-mshort\-data\-\c +.I num\c +\&\c +\&\|' is not effective for \c +.I num\c +\& greater +than 64K. +.PP +.B \-mserialize-volatile +.TP +.B \-mno-serialize-volatile +Do, or do not, generate code to guarantee sequential consistency of +volatile memory references. +.Sp +GNU CC always guarantees consistency by default, for the preferred +processor submodel. How this is done depends on the submodel. +.Sp +The m88100 processor does not reorder memory references and so always +provides sequential consistency. If you use `\|\c +.B \-m88100\c +\&\|', GNU CC does +not generate any special instructions for sequential consistency. +.Sp +The order of memory references made by the m88110 processor does not +always match the order of the instructions requesting those references. +In particular, a load instruction may execute before a preceding store +instruction. Such reordering violates sequential consistency of +volatile memory references, when there are multiple processors. When +you use `\|\c +.B \-m88000\c +\&\|' or `\|\c +.B \-m88110\c +\&\|', GNU CC generates special +instructions when appropriate, to force execution in the proper order. +.Sp +The extra code generated to guarantee consistency may affect the +performance of your application. If you know that you can safely forgo +this guarantee, you may use the option `\|\c +.B \-mno-serialize-volatile\c +\&\|'. +.Sp +If you use the `\|\c +.B \-m88100\c +\&\|' option but require sequential consistency +when running on the m88110 processor, you should use +`\|\c +.B \-mserialize-volatile\c +\&\|'. +.PP +.B \-msvr4 +.TP +.B \-msvr3 +Turn on (`\|\c +.B \-msvr4\c +\&\|') or off (`\|\c +.B \-msvr3\c +\&\|') compiler extensions +related to System V release 4 (SVr4). This controls the following: +.TP +\ \ \ \(bu +Which variant of the assembler syntax to emit (which you can select +independently using `\|\c +.B \-mversion\-03.00\c +\&\|'). +.TP +\ \ \ \(bu +`\|\c +.B \-msvr4\c +\&\|' makes the C preprocessor recognize `\|\c +.B #pragma weak\c +\&\|' +.TP +\ \ \ \(bu +`\|\c +.B \-msvr4\c +\&\|' makes GCC issue additional declaration directives used in +SVr4. +.PP +`\|\c +.B \-msvr3\c +\&\|' is the default for all m88K configurations except +the SVr4 configuration. +.TP +.B \-mtrap\-large\-shift +.TP +.B \-mhandle\-large\-shift +Include code to detect bit-shifts of more than 31 bits; respectively, +trap such shifts or emit code to handle them properly. By default GCC +makes no special provision for large bit shifts. +.TP +.B \-muse\-div\-instruction +Very early models of the 88K architecture didn't have a divide +instruction, so GCC avoids that instruction by default. Use this option +to specify that it's safe to use the divide instruction. +.TP +.B \-mversion\-03.00 +In the DG/UX configuration, there are two flavors of SVr4. This option +modifies +.B \-msvr4 +to select whether the hybrid-COFF or real-ELF +flavor is used. All other configurations ignore this option. +.TP +.B \-mwarn\-passed\-structs +Warn when a function passes a struct as an argument or result. +Structure-passing conventions have changed during the evolution of the C +language, and are often the source of portability problems. By default, +GCC issues no such warning. +.PP +These options are defined for the IBM RS6000: +.PP +.B \-mfp\-in\-toc +.TP +.B \-mno\-fp\-in\-toc +Control whether or not floating-point constants go in the Table of +Contents (TOC), a table of all global variable and function addresses. By +default GCC puts floating-point constants there; if the TOC overflows, +`\|\c +.B \-mno\-fp\-in\-toc\c +\&\|' will reduce the size of the TOC, which may avoid +the overflow. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the IBM RT PC: +.TP +.B \-min\-line\-mul +Use an in-line code sequence for integer multiplies. This is the +default. +.TP +.B \-mcall\-lib\-mul +Call \c +.B lmul$$\c +\& for integer multiples. +.TP +.B \-mfull\-fp\-blocks +Generate full-size floating point data blocks, including the minimum +amount of scratch space recommended by IBM. This is the default. +.TP +.B \-mminimum\-fp\-blocks +Do not include extra scratch space in floating point data blocks. This +results in smaller code, but slower execution, since scratch space must +be allocated dynamically. +.TP +.B \-mfp\-arg\-in\-fpregs +Use a calling sequence incompatible with the IBM calling convention in +which floating point arguments are passed in floating point registers. +Note that \c +.B varargs.h\c +\& and \c +.B stdargs.h\c +\& will not work with +floating point operands if this option is specified. +.TP +.B \-mfp\-arg\-in\-gregs +Use the normal calling convention for floating point arguments. This is +the default. +.TP +.B \-mhc\-struct\-return +Return structures of more than one word in memory, rather than in a +register. This provides compatibility with the MetaWare HighC (hc) +compiler. Use `\|\c +.B \-fpcc\-struct\-return\c +\&\|' for compatibility with the +Portable C Compiler (pcc). +.TP +.B \-mnohc\-struct\-return +Return some structures of more than one word in registers, when +convenient. This is the default. For compatibility with the +IBM-supplied compilers, use either `\|\c +.B \-fpcc\-struct\-return\c +\&\|' or +`\|\c +.B \-mhc\-struct\-return\c +\&\|'. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the MIPS family of computers: +.TP +.BI "\-mcpu=" "cpu-type" +Assume the defaults for the machine type +.I cpu-type +when +scheduling instructions. The default +.I cpu-type +is +.BR default , +which picks the longest cycles times for any of the machines, in order +that the code run at reasonable rates on all MIPS cpu's. Other +choices for +.I cpu-type +are +.BR r2000 , +.BR r3000 , +.BR r4000 , +and +.BR r6000 . +While picking a specific +.I cpu-type +will schedule things appropriately for that particular chip, the +compiler will not generate any code that does not meet level 1 of the +MIPS ISA (instruction set architecture) without the +.B \-mips2 +or +.B \-mips3 +switches being used. +.TP +.B \-mips2 +Issue instructions from level 2 of the MIPS ISA (branch likely, square +root instructions). The +.B \-mcpu=r4000 +or +.B \-mcpu=r6000 +switch must be used in conjunction with +.BR \-mips2 . +.TP +.B \-mips3 +Issue instructions from level 3 of the MIPS ISA (64 bit instructions). +The +.B \-mcpu=r4000 +switch must be used in conjunction with +.BR \-mips2 . +.TP +.B \-mint64 +.TP +.B \-mlong64 +.TP +.B \-mlonglong128 +These options don't work at present. +.TP +.B \-mmips\-as +Generate code for the MIPS assembler, and invoke +.B mips\-tfile +to add normal debug information. This is the default for all +platforms except for the OSF/1 reference platform, using the OSF/rose +object format. If any of the +.BR \-ggdb , +.BR \-gstabs , +or +.B \-gstabs+ +switches are used, the +.B mips\-tfile +program will encapsulate the stabs within MIPS ECOFF. +.TP +.B \-mgas +Generate code for the GNU assembler. This is the default on the OSF/1 +reference platform, using the OSF/rose object format. +.TP +.B \-mrnames +.TP +.B \-mno\-rnames +The +.B \-mrnames +switch says to output code using the MIPS software names for the +registers, instead of the hardware names (ie, +.B a0 +instead of +.BR $4 ). +The GNU assembler does not support the +.B \-mrnames +switch, and the MIPS assembler will be instructed to run the MIPS C +preprocessor over the source file. The +.B \-mno\-rnames +switch is default. +.TP +.B \-mgpopt +.TP +.B \-mno\-gpopt +The +.B \-mgpopt +switch says to write all of the data declarations before the +instructions in the text section, to all the MIPS assembler to +generate one word memory references instead of using two words for +short global or static data items. This is on by default if +optimization is selected. +.TP +.B \-mstats +.TP +.B \-mno\-stats +For each non-inline function processed, the +.B \-mstats +switch causes the compiler to emit one line to the standard error file +to print statistics about the program (number of registers saved, +stack size, etc.). +.TP +.B \-mmemcpy +.TP +.B \-mno\-memcpy +The +.B \-mmemcpy +switch makes all block moves call the appropriate string function +.RB ( memcpy +or +.BR bcopy ) +instead of possibly generating inline code. +.TP +.B \-mmips\-tfile +.TP +.B \-mno\-mips\-tfile +The +.B \-mno\-mips\-tfile +switch causes the compiler not postprocess the object file with the +.B mips\-tfile +program, after the MIPS assembler has generated it to add debug +support. If +.B mips\-tfile +is not run, then no local variables will be available to the debugger. +In addition, +.B stage2 +and +.B stage3 +objects will have the temporary file names passed to the assembler +embedded in the object file, which means the objects will not compare +the same. +.TP +.B \-msoft\-float +Generate output containing library calls for floating point. +.I +WARNING: +the requisite libraries are not part of GNU CC. Normally the +facilities of the machine's usual C compiler are used, but this can't +be done directly in cross-compilation. You must make your own +arrangements to provide suitable library functions for cross-compilation. +.TP +.B \-mhard\-float +Generate output containing floating point instructions. This is the +default if you use the unmodified sources. +.TP +.B \-mfp64 +Assume that the +.B FR +bit in the status word is on, and that there are 32 64-bit floating +point registers, instead of 32 32-bit floating point registers. You +must also specify the +.B \-mcpu=r4000 +and +.B \-mips3 +switches. +.TP +.B \-mfp32 +Assume that there are 32 32-bit floating point registers. This is the +default. +.PP +.B \-mabicalls +.TP +.B \-mno\-abicalls +Emit (or do not emit) the +.BR \&.abicalls , +.BR \&.cpload , +and +.B \&.cprestore +pseudo operations that some System V.4 ports use for position +independent code. +.TP +.B \-mhalf\-pic +.TP +.B \-mno\-half\-pic +The +.B \-mhalf\-pic +switch says to put pointers to extern references into the data section +and load them up, rather than put the references in the text section. +This option does not work at present. +.B +.BI \-G num +Put global and static items less than or equal to +.I num +bytes into the small data or bss sections instead of the normal data +or bss section. This allows the assembler to emit one word memory +reference instructions based on the global pointer +.RB ( gp +or +.BR $28 ), +instead of the normal two words used. By default, +.I num +is 8 when the MIPS assembler is used, and 0 when the GNU +assembler is used. The +.BI \-G num +switch is also passed to the assembler and linker. All modules should +be compiled with the same +.BI \-G num +value. +.TP +.B \-nocpp +Tell the MIPS assembler to not run it's preprocessor over user +assembler files (with a `\|\c +.B .s\c +\&\|' suffix) when assembling them. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the Intel 80386 family of computers: +.B \-m486 +.TP +.B \-mno\-486 +Control whether or not code is optimized for a 486 instead of an +386. Code generated for a 486 will run on a 386 and vice versa. +.TP +.B \-msoft\-float +Generate output containing library calls for floating point. +.I Warning: +the requisite libraries are not part of GNU CC. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. +.Sp +On machines where a function returns floating point results in the 80387 +register stack, some floating point opcodes may be emitted even if +`\|\c +.B \-msoft-float\c +\&\|' is used. +.TP +.B \-mno-fp-ret-in-387 +Do not use the FPU registers for return values of functions. +.Sp +The usual calling convention has functions return values of types +.B float\c +\& and \c +.B double\c +\& in an FPU register, even if there +is no FPU. The idea is that the operating system should emulate +an FPU. +.Sp +The option `\|\c +.B \-mno-fp-ret-in-387\c +\&\|' causes such values to be returned +in ordinary CPU registers instead. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the HPPA family of computers: +.TP +.B \-mpa-risc-1-0 +Generate code for a PA 1.0 processor. +.TP +.B \-mpa-risc-1-1 +Generate code for a PA 1.1 processor. +.TP +.B \-mkernel +Generate code which is suitable for use in kernels. Specifically, avoid +.B add\c +\& instructions in which one of the arguments is the DP register; +generate \c +.B addil\c +\& instructions instead. This avoids a rather serious +bug in the HP-UX linker. +.TP +.B \-mshared-libs +Generate code that can be linked against HP-UX shared libraries. This option +is not fully function yet, and is not on by default for any PA target. Using +this option can cause incorrect code to be generated by the compiler. +.TP +.B \-mno-shared-libs +Don't generate code that will be linked against shared libraries. This is +the default for all PA targets. +.TP +.B \-mlong-calls +Generate code which allows calls to functions greater than 256K away from +the caller when the caller and callee are in the same source file. Do +not turn this option on unless code refuses to link with \*(lqbranch out of +range errors\*('' from the linker. +.TP +.B \-mdisable-fpregs +Prevent floating point registers from being used in any manner. This is +necessary for compiling kernels which perform lazy context switching of +floating point registers. If you use this option and attempt to perform +floating point operations, the compiler will abort. +.TP +.B \-mdisable-indexing +Prevent the compiler from using indexing address modes. This avoids some +rather obscure problems when compiling MIG generated code under MACH. +.TP +.B \-mtrailing-colon +Add a colon to the end of label definitions (for ELF assemblers). +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the Intel 80960 family of computers: +.TP +.BI "\-m" "cpu-type" +Assume the defaults for the machine type +.I cpu-type +for instruction and addressing-mode availability and alignment. +The default +.I cpu-type +is +.BR kb ; +other choices are +.BR ka , +.BR mc , +.BR ca , +.BR cf , +.BR sa , +and +.BR sb . +.TP +.B \-mnumerics +.TP +.B \-msoft\-float +The +.B \-mnumerics +option indicates that the processor does support +floating-point instructions. The +.B \-msoft\-float +option indicates +that floating-point support should not be assumed. +.TP +.B \-mleaf\-procedures +.TP +.B \-mno\-leaf\-procedures +Do (or do not) attempt to alter leaf procedures to be callable with the +.I bal +instruction as well as +.IR call . +This will result in more +efficient code for explicit calls when the +.I bal +instruction can be +substituted by the assembler or linker, but less efficient code in other +cases, such as calls via function pointers, or using a linker that doesn't +support this optimization. +.TP +.B \-mtail\-call +.TP +.B \-mno\-tail\-call +Do (or do not) make additional attempts (beyond those of the +machine-independent portions of the compiler) to optimize tail-recursive +calls into branches. You may not want to do this because the detection of +cases where this is not valid is not totally complete. The default is +.BR \-mno\-tail\-call . +.TP +.B \-mcomplex\-addr +.TP +.B \-mno\-complex\-addr +Assume (or do not assume) that the use of a complex addressing mode is a +win on this implementation of the i960. Complex addressing modes may not +be worthwhile on the K-series, but they definitely are on the C-series. +The default is currently +.B \-mcomplex\-addr +for all processors except +the CB and CC. +.TP +.B \-mcode\-align +.TP +.B \-mno\-code\-align +Align code to 8-byte boundaries for faster fetching (or don't bother). +Currently turned on by default for C-series implementations only. +.TP +.B \-mic\-compat +.TP +.B \-mic2.0\-compat +.TP +.B \-mic3.0\-compat +Enable compatibility with iC960 v2.0 or v3.0. +.TP +.B \-masm\-compat +.TP +.B \-mintel\-asm +Enable compatibility with the iC960 assembler. +.TP +.B \-mstrict\-align +.TP +.B \-mno\-strict\-align +Do not permit (do permit) unaligned accesses. +.TP +.B \-mold\-align +Enable structure-alignment compatibility with Intel's gcc release version +1.3 (based on gcc 1.37). Currently this is buggy in that +.B #pragma align 1 +is always assumed as well, and cannot be turned off. +.PP +These `\|\c +.B \-m\c +\&\|' options are defined for the DEC Alpha implementations: +.TP +.B \-mno-soft-float +.TP +.B \-msoft-float +Use (do not use) the hardware floating-point instructions for +floating-point operations. When \c +.B \-msoft-float\c +\& is specified, +functions in `\|\c +.B libgcc1.c\c +\&\|' will be used to perform floating-point +operations. Unless they are replaced by routines that emulate the +floating-point operations, or compiled in such a way as to call such +emulations routines, these routines will issue floating-point +operations. If you are compiling for an Alpha without floating-point +operations, you must ensure that the library is built so as not to call +them. +.Sp +Note that Alpha implementations without floating-point operations are +required to have floating-point registers. +.TP +.B \-mfp-reg +.TP +.B \-mno-fp-regs +Generate code that uses (does not use) the floating-point register set. +.B \-mno-fp-regs\c +\& implies \c +.B \-msoft-float\c +\&. If the floating-point +register set is not used, floating point operands are passed in integer +registers as if they were integers and floating-point results are passed +in $0 instead of $f0. This is a non-standard calling sequence, so any +function with a floating-point argument or return value called by code +compiled with \c +.B \-mno-fp-regs\c +\& must also be compiled with that +option. +.Sp +A typical use of this option is building a kernel that does not use, +and hence need not save and restore, any floating-point registers. +.PP +These additional options are available on System V Release 4 for +compatibility with other compilers on those systems: +.TP +.B \-G +On SVr4 systems, \c +.B gcc\c +\& accepts the option `\|\c +.B \-G\c +\&\|' (and passes +it to the system linker), for compatibility with other compilers. +However, we suggest you use `\|\c +.B \-symbolic\c +\&\|' or `\|\c +.B \-shared\c +\&\|' as +appropriate, instead of supplying linker options on the \c +.B gcc +command line. +.TP +.B \-Qy +Identify the versions of each tool used by the compiler, in a +.B .ident\c +\& assembler directive in the output. +.TP +.B \-Qn +Refrain from adding \c +.B .ident\c +\& directives to the output file (this is +the default). +.TP +.BI "\-YP," "dirs" +Search the directories \c +.I dirs\c +\&, and no others, for libraries +specified with `\|\c +.B \-l\c +\&\|'. You can separate directory entries in +.I dirs\c +\& from one another with colons. +.TP +.BI "\-Ym," "dir" +Look in the directory \c +.I dir\c +\& to find the M4 preprocessor. +The assembler uses this option. +.SH CODE GENERATION OPTIONS +These machine-independent options control the interface conventions +used in code generation. +.PP +Most of them begin with `\|\c +\-f\c +\&\|'. These options have both positive and negative forms; the negative form +of `\|\c +.B \-ffoo\c +\&\|' would be `\|\c +.B \-fno\-foo\c +\&\|'. In the table below, only +one of the forms is listed\(em\&the one which is not the default. You +can figure out the other form by either removing `\|\c +.B no\-\c +\&\|' or adding +it. +.TP +.B \-fnonnull\-objects +Assume that objects reached through references are not null +(C++ only). +.Sp +Normally, GNU C++ makes conservative assumptions about objects reached +through references. For example, the compiler must check that \c +.B a +is not null in code like the following: +.Sp +obj &a = g (); +a.f (2); +.Sp +Checking that references of this sort have non-null values requires +extra code, however, and it is unnecessary for many programs. You can +use `\|\c +.B \-fnonnull-objects\c +\&\|' to omit the checks for null, if your +program doesn't require checking. +.TP +.B \-fpcc\-struct\-return +Use the same convention for returning \c +.B struct\c +\& and \c +.B union +values that is used by the usual C compiler on your system. This +convention is less efficient for small structures, and on many +machines it fails to be reentrant; but it has the advantage of +allowing intercallability between GCC-compiled code and PCC-compiled +code. +.TP +.B \-freg\-struct\-return +Use the convention that +.B struct +and +.B union +values are returned in registers when possible. This is more +efficient for small structures than +.BR \-fpcc\-struct\-return . +.Sp +If you specify neither +.B \-fpcc\-struct\-return +nor +.BR \-freg\-struct\-return , +GNU CC defaults to whichever convention is standard for the target. +If there is no standard convention, GNU CC defaults to +.BR \-fpcc\-struct\-return . +.TP +.B \-fshort\-enums +Allocate to an \c +.B enum\c +\& type only as many bytes as it needs for the +declared range of possible values. Specifically, the \c +.B enum\c +\& type +will be equivalent to the smallest integer type which has enough room. +.TP +.B \-fshort\-double +Use the same size for +.B double +as for +.B float +\&. +.TP +.B \-fshared\-data +Requests that the data and non-\c +.B const\c +\& variables of this +compilation be shared data rather than private data. The distinction +makes sense only on certain operating systems, where shared data is +shared between processes running the same program, while private data +exists in one copy per process. +.TP +.B \-fno\-common +Allocate even uninitialized global variables in the bss section of the +object file, rather than generating them as common blocks. This has the +effect that if the same variable is declared (without \c +.B extern\c +\&) in +two different compilations, you will get an error when you link them. +The only reason this might be useful is if you wish to verify that the +program will work on other systems which always work this way. +.TP +.B \-fno\-ident +Ignore the `\|\c +.B #ident\c +\&\|' directive. +.TP +.B \-fno\-gnu\-linker +Do not output global initializations (such as C++ constructors and +destructors) in the form used by the GNU linker (on systems where the GNU +linker is the standard method of handling them). Use this option when +you want to use a non-GNU linker, which also requires using the +.B collect2\c +\& program to make sure the system linker includes +constructors and destructors. (\c +.B collect2\c +\& is included in the GNU CC +distribution.) For systems which \c +.I must\c +\& use \c +.B collect2\c +\&, the +compiler driver \c +.B gcc\c +\& is configured to do this automatically. +.TP +.B \-finhibit-size-directive +Don't output a \c +.B .size\c +\& assembler directive, or anything else that +would cause trouble if the function is split in the middle, and the +two halves are placed at locations far apart in memory. This option is +used when compiling `\|\c +.B crtstuff.c\c +\&\|'; you should not need to use it +for anything else. +.TP +.B \-fverbose-asm +Put extra commentary information in the generated assembly code to +make it more readable. This option is generally only of use to those +who actually need to read the generated assembly code (perhaps while +debugging the compiler itself). +.TP +.B \-fvolatile +Consider all memory references through pointers to be volatile. +.TP +.B \-fvolatile\-global +Consider all memory references to extern and global data items to +be volatile. +.TP +.B \-fpic +If supported for the target machines, generate position-independent code, +suitable for use in a shared library. +.TP +.B \-fPIC +If supported for the target machine, emit position-independent code, +suitable for dynamic linking, even if branches need large displacements. +.TP +.BI "\-ffixed\-" "reg" +Treat the register named \c +.I reg\c +\& as a fixed register; generated code +should never refer to it (except perhaps as a stack pointer, frame +pointer or in some other fixed role). +.Sp +.I reg\c +\& must be the name of a register. The register names accepted +are machine-specific and are defined in the \c +.B REGISTER_NAMES +macro in the machine description macro file. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.TP +.BI "\-fcall\-used\-" "reg" +Treat the register named \c +.I reg\c +\& as an allocatable register that is +clobbered by function calls. It may be allocated for temporaries or +variables that do not live across a call. Functions compiled this way +will not save and restore the register \c +.I reg\c +\&. +.Sp +Use of this flag for a register that has a fixed pervasive role in the +machine's execution model, such as the stack pointer or frame pointer, +will produce disastrous results. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.TP +.BI "\-fcall\-saved\-" "reg" +Treat the register named \c +.I reg\c +\& as an allocatable register saved by +functions. It may be allocated even for temporaries or variables that +live across a call. Functions compiled this way will save and restore +the register \c +.I reg\c +\& if they use it. +.Sp +Use of this flag for a register that has a fixed pervasive role in the +machine's execution model, such as the stack pointer or frame pointer, +will produce disastrous results. +.Sp +A different sort of disaster will result from the use of this flag for +a register in which function values may be returned. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.SH PRAGMAS +Two `\|\c +.B #pragma\c +\&\|' directives are supported for GNU C++, to permit using the same +header file for two purposes: as a definition of interfaces to a given +object class, and as the full definition of the contents of that object class. +.TP +.B #pragma interface +(C++ only.) +Use this directive in header files that define object classes, to save +space in most of the object files that use those classes. Normally, +local copies of certain information (backup copies of inline member +functions, debugging information, and the internal tables that +implement virtual functions) must be kept in each object file that +includes class definitions. You can use this pragma to avoid such +duplication. When a header file containing `\|\c +.B #pragma interface\c +\&\|' is included in a compilation, this auxiliary information +will not be generated (unless the main input source file itself uses +`\|\c +.B #pragma implementation\c +\&\|'). Instead, the object files will contain references to be +resolved at link time. +.TP +.B #pragma implementation +.TP +\fB#pragma implementation "\fP\fIobjects\fP\fB.h"\fP +(C++ only.) +Use this pragma in a main input file, when you want full output from +included header files to be generated (and made globally visible). +The included header file, in turn, should use `\|\c +.B #pragma interface\c +\&\|'. +Backup copies of inline member functions, debugging information, and +the internal tables used to implement virtual functions are all +generated in implementation files. +.Sp +If you use `\|\c +.B #pragma implementation\c +\&\|' with no argument, it applies to an include file with the same +basename as your source file; for example, in `\|\c +.B allclass.cc\c +\&\|', `\|\c +.B #pragma implementation\c +\&\|' by itself is equivalent to `\|\c +.B +#pragma implementation "allclass.h"\c +\&\|'. Use the string argument if you want a single implementation +file to include code from multiple header files. +.Sp +There is no way to split up the contents of a single header file into +multiple implementation files. +.SH FILES +.nf +.ta \w'LIBDIR/g++\-include 'u +file.c C source file +file.h C header (preprocessor) file +file.i preprocessed C source file +file.C C++ source file +file.cc C++ source file +file.cxx C++ source file +file.m Objective-C source file +file.s assembly language file +file.o object file +a.out link edited output +\fITMPDIR\fR/cc\(** temporary files +\fILIBDIR\fR/cpp preprocessor +\fILIBDIR\fR/cc1 compiler for C +\fILIBDIR\fR/cc1plus compiler for C++ +\fILIBDIR\fR/collect linker front end needed on some machines +\fILIBDIR\fR/libgcc.a GCC subroutine library +/lib/crt[01n].o start-up routine +\fILIBDIR\fR/ccrt0 additional start-up routine for C++ +/lib/libc.a standard C library, see +.IR intro (3) +/usr/include standard directory for \fB#include\fP files +\fILIBDIR\fR/include standard gcc directory for \fB#include\fP files +\fILIBDIR\fR/g++\-include additional g++ directory for \fB#include\fP +.Sp +.fi +.I LIBDIR +is usually +.B /usr/local/lib/\c +.IR machine / version . +.br +.I TMPDIR +comes from the environment variable +.B TMPDIR +(default +.B /usr/tmp +if available, else +.B /tmp\c +\&). +.SH "SEE ALSO" +cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1). +.br +.RB "`\|" gcc "\|', `\|" cpp \|', +.RB "`\|" as "\|', `\|" ld \|', +and +.RB `\| gdb \|' +entries in +.B info\c +\&. +.br +.I +Using and Porting GNU CC (for version 2.0)\c +, Richard M. Stallman; +.I +The C Preprocessor\c +, Richard M. Stallman; +.I +Debugging with GDB: the GNU Source-Level Debugger\c +, Richard M. Stallman and Roland H. Pesch; +.I +Using as: the GNU Assembler\c +, Dean Elsner, Jay Fenlason & friends; +.I +ld: the GNU linker\c +, Steve Chamberlain and Roland Pesch. +.SH BUGS +For instructions on reporting bugs, see the GCC manual. +.SH COPYING +Copyright +.if t \(co +1991, 1992, 1993 Free Software Foundation, Inc. +.PP +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. +.PP +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided that the +entire resulting derived work is distributed under the terms of a +permission notice identical to this one. +.PP +Permission is granted to copy and distribute translations of this +manual into another language, under the above conditions for modified +versions, except that this permission notice may be included in +translations approved by the Free Software Foundation instead of in +the original English. +.SH AUTHORS +See the GNU CC Manual for the contributors to GNU CC. |