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GCC(1)				   GNU Tools				GCC(1)

       gcc, g++	- GNU project C	and C++	Compiler

       gcc [ option | filename ]...
       g++ [ option | filename ]...

       The information in this man page	is an extract from the full documenta-
       tion of the GNU C compiler, and	is  limited  to	 the  meaning  of  the

       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 docu-

       If we find that the things in this man page that	are out	of date	 cause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 obso-
       lete and	should not let them take time away from	other things.

       For complete and	current	documentation, refer to	the Info file `gcc' or
       the manual Using	and Porting GNU	CC (for	version	2.0).  Both  are  made
       from the	Texinfo	source file gcc.texinfo.

       The  C  and  C++	 compilers  are	 integrated.  Both process input files
       through one or more of four stages: preprocessing, compilation,	assem-
       bly,  and  linking.   Source filename suffixes identify the source lan-
       guage, but which	name you use for the compiler governs default  assump-

       gcc    assumes  preprocessed (.i) files are C and assumes C style link-

       g++    assumes preprocessed (.i)	files are C++ and  assumes  C++	 style

       Suffixes	 of  source  file names	indicate the language and kind of pro-
       cessing to be done:

       .c    C source; preprocess, compile, assemble
       .C    C++ source; preprocess, compile, assemble
       .cc   C++ source; preprocess, compile, assemble
       .cxx  C++ source; preprocess, compile, assemble
       .m    Objective-C source; preprocess, compile, assemble
       .i    preprocessed C; compile, assemble
       .ii   preprocessed C++; compile,	assemble
       .s    Assembler source; assemble
       .S    Assembler source; preprocess, assemble
       .h    Preprocessor file;	not usually named on command line

       Files with other	suffixes are  passed  to  the  linker.	 Common	 cases

       .o    Object file
       .a    Archive file

       Linking	is  always the last stage unless you use one of	the -c,	-S, or
       -E options to avoid it (or unless compilation  errors  stop  the	 whole
       process).   For	the  link  stage, all .o files corresponding to	source
       files, -l libraries, unrecognized filenames (including named .o	object
       files  and .a archives) are passed to the linker	in command-line	order.

       Options must be separate: `-dr' is quite	different from `-d -r '.

       Most `-f'  and  `-W'  options  have  two	 contrary  forms:  -fname  and
       -fno-name  (or  -Wname  and -Wno-name).	Only the non-default forms are
       shown here.

       Here is a summary of all	the options, grouped  by  type.	  Explanations
       are in the following sections.

       Overall Options
	      -c -S -E -o file -pipe -v	-x language

       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

       Warning Options
	      -fsyntax-only -pedantic -pedantic-errors -w -W -Wall
	      -Waggregate-return -Wcast-align -Wcast-qual -Wchar-subscript
	      -Wcomment	-Wconversion -Wenum-clash -Werror -Wformat
	      -Wid-clash-len -Wimplicit	-Wimplicit-int
	      -Wimplicit-function-declaration -Winline -Wlong-long -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

       Debugging Options
	      -a -dletters -fpretend-float -g -glevel -gcoff -gxcoff -gxcoff+
	      -gdwarf -gdwarf+ -gstabs -gstabs+	-ggdb -p -pg -save-temps
	      -print-file-name=library -print-libgcc-file-name

       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 -O3 -O0

       Preprocessor Options
	      -Aassertion -C -dD -dM -dN -Dmacro[=defn]	-E -H -idirafter dir
	      -include file -imacros file -iprefix file	-iwithprefix dir -M
	      -MD -MM -MMD -nostdinc -P	-Umacro	-undef

       Assembler Option

       Linker Options
	      -llibrary	-nostartfiles -nostdlib	-static	-shared	-symbolic
	      -Xlinker option -Wl,option -u symbol

       Directory Options
	      -Bprefix -Idir -I- -Ldir

       Target Options
	      -b  machine -V version

       Configuration Dependent Options
	      M680x0 Options
	      -m68000 -m68020 -m68020-40 -m68030 -m68040 -m68881 -mbitfield
	      -mc68000 -mc68020	-mfpa -mnobitfield -mrtd -mshort -msoft-float

	      VAX Options
	      -mg -mgnu	-munix

	      SPARC Options
	      -mepilogue -mfpu -mhard-float -mno-fpu -mno-epilogue
	      -msoft-float -msparclite -mv8 -msupersparc -mcypress

	      Convex Options
	      -margcount -mc1 -mc2 -mnoargcount

	      AMD29K Options
	      -m29000 -m29050 -mbw -mdw	-mkernel-registers -mlarge -mnbw
	      -mnodw -msmall -mstack-check -muser-registers

	      M88K Options
	      -m88000 -m88100 -m88110 -mbig-pic	-mcheck-zero-division
	      -mhandle-large-shift -midentify-revision
	      -mno-check-zero-division -mno-ocs-debug-info
	      -mno-ocs-frame-position -mno-optimize-arg-area
	      -mno-serialize-volatile -mno-underscores -mocs-debug-info
	      -mocs-frame-position -moptimize-arg-area -mserialize-volatile
	      -mshort-data-num -msvr3 -msvr4 -mtrap-large-shift
	      -muse-div-instruction -mversion-03.00 -mwarn-passed-structs

	      RS6000 Options
	      -mfp-in-toc -mno-fop-in-toc

	      RT Options
	      -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

	      MIPS Options
	      -mcpu=cpu	type -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 num -nocpp

	      i386 Options
	      -m386 -m486 -mpentium -mpentiumpro -mno-486 -mcpu=cpu type
	      -march=cpu type -msoft-float -mrtd -mregparm -msvr3-shlib
	      -mno-ieee-fp -mno-fp-ret-in-387 -mfancy-math-387
	      -mno-wide-multiply -mdebug-addr -mno-move	-mprofiler-epilogue

	      HPPA Options
	      -mpa-risc-1-0 -mpa-risc-1-1 -mkernel -mshared-libs
	      -mno-shared-libs -mlong-calls -mdisable-fpregs
	      -mdisable-indexing -mtrailing-colon

	      i960 Options
	      -mcpu-type -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

	      DEC Alpha	Options
	      -mfp-regs	-mno-fp-regs -mno-soft-float -msoft-float

	      System V Options
	      -G -Qy -Qn -YP,paths -Ym,dir

       Code Generation Options
	      -fcall-saved-reg -fcall-used-reg -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

	      Link a user-threaded process against libc_r instead of libc.

       -x language
	      Specify  explicitly  the	language 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
	      `-x' option.  Possible  values  of  language  are	 `c',  `objec-
	      tive-c',	`c-header', `c++', `cpp-output', `assembler', and `as-

       -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 `-x' has not been used at all).

       If you want only	some of	the four stages	(preprocess,  compile,	assem-
       ble,  link),  you can use `-x' (or filename suffixes) to	tell gcc where
       to start, and one of the	options	`-c', `-S', or `-E' to say  where  gcc
       is  to  stop.  Note that	some combinations (for example,	`-x cpp-output
       -E') instruct gcc to do nothing at all.

       -c     Compile or assemble the source files, but	do not link.  The com-
	      piler  output  is	 an  object  file corresponding	to each	source

	      By default, GCC makes the	object file name for a source file  by
	      replacing	 the suffix `.c', `.i',	`.s', etc., with `.o'.	Use -o
	      to select	another	name.

	      GCC ignores any unrecognized input files (those that do not  re-
	      quire compilation	or assembly) with the -c option.

       -S     Stop  after  the	stage  of compilation proper; do not assemble.
	      The output is an assembler code file for each non-assembler  in-
	      put file specified.

	      By  default, GCC makes the assembler file	name for a source file
	      by replacing the suffix `.c', `.i', etc.,	with `.s'.  Use	-o  to
	      select another name.

	      GCC ignores any input files that don't require compilation.

       -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.

	      GCC ignores input	files which don't require preprocessing.

       -o file
	      Place  output in file file.  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.

	      Since only one output file can be	specified, it  does  not  make
	      sense  to	 use `-o' when compiling more than one input file, un-
	      less you are producing an	executable file	as output.

	      If you do	not specify `-o', the default is to put	an  executable
	      file   in	 `a.out',  the	object	file  for  `source.suffix'  in
	      `source.o', its assembler	file in	`source.s',  and  all  prepro-
	      cessed C source on standard output.

       -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

       -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.

       The  following  options	control	the dialect of C that the compiler ac-

       -ansi  Support all ANSI standard	C programs.

	      This turns off certain features of GNU C that  are  incompatible
	      with  ANSI  C,  such as the asm, inline and typeof keywords, and
	      predefined macros	such as	unix and vax that identify the type of
	      system  you  are	using.	 It  also  enables the undesirable and
	      rarely used ANSI trigraph	feature, and disallows `$' as part  of

	      The  alternate  keywords	__asm__, __extension__,	__inline__ and
	      __typeof__ continue to work despite `-ansi'.  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	`-ansi'.  Alternate predefined macros such as __unix__
	      and __vax__ are also available, with or without `-ansi'.

	      The `-ansi' option does not cause	non-ANSI programs  to  be  re-
	      jected gratuitously.  For	that, `-pedantic' is required in addi-
	      tion to `-ansi'.

	      The preprocessor predefines a macro __STRICT_ANSI__ when you use
	      the `-ansi' 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.

	      Do  not  recognize  asm,	inline	or typeof as a keyword.	 These
	      words may	then be	used as	identifiers.   You  can	 use  __asm__,
	      __inline__  and __typeof__ instead.  `-ansi' implies `-fno-asm'.

	      Don't recognize built-in functions that do not  begin  with  two
	      leading  underscores.  Currently,	the functions affected include
	      _exit, abort, abs, alloca, cos, exit, fabs, labs,	 memcmp,  mem-
	      cpy, sin,	sqrt, strcmp, strcpy, and strlen.

	      The  `-ansi' option prevents alloca and _exit from being builtin

	      Compile for a hosted environment;	this implies  the  `-fbuiltin'
	      option,  and implies that	suspicious declarations	of main	should
	      be warned	about.

	      Compile for a freestanding environment; this implies the	`-fno-
	      builtin'	option,	 and implies that main has no special require-

	      Treat a function declaration with	no arguments, such as `int foo
	      ();', as C would treat it--as saying nothing about the number of
	      arguments	or their types (C++ only).  Normally, such a  declara-
	      tion in C++ means	that the function foo takes no arguments.

	      Support  ANSI  C	trigraphs.   The `-ansi' option	implies	`-tri-

	      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.

	      But  one	note  about C++	programs only (not C).	`-traditional'
	      has one additional effect	for C++: assignment to this is permit-
	      ted.  This is the	same as	the effect of `-fthis-is-variable'.

	      Attempt  to support some aspects of traditional C	preprocessors.
	      This includes the	items that specifically	mention	the preproces-
	      sor above, but none of the other effects of `-traditional'.

	      Permit  the  use of `$' in identifiers (C++ only).  You can also
	      use `-fno-dollars-in-identifiers'	to explicitly prohibit use  of
	      `$'.   (GNU C++ allows `$' by default on some target systems but
	      not others.)

	      Permit implicit conversion of int	to enumeration types (C++  on-
	      ly).  Normally GNU C++ allows conversion of enum to int, but not
	      the other	way around.

	      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 `#pragma implementa-
	      tion' (the definition) or	`#pragma interface' (declarations).

	      When your	code is	compiled with `-fexternal-templates', all tem-
	      plate  instantiations  are  external.   You must arrange for all
	      necessary	instantiations to appear in the	 implementation	 file;
	      you  can	do this	with a typedef that references each instantia-
	      tion needed.  Conversely,	when you compile using the default op-
	      tion  `-fno-external-templates', all template instantiations are
	      explicitly internal.

	      Treat all	possible member	functions as virtual, implicitly.  All
	      member  functions	 (except  for constructor functions and	new or
	      delete member operators) are treated as virtual functions	of the
	      class where they appear.

	      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.

	      Allow  conditional expressions with mismatched types in the sec-
	      ond and third arguments.	The value of  such  an	expression  is

	      Permit  assignment to this (C++ only).  The incorporation	of us-
	      er-defined free store management into C++	has made assignment to
	      `this'  an  anachronism.	Therefore, by default it is invalid to
	      assign to	this within a class  member  function.	 However,  for
	      backwards	 compatibility,	you can	make it	valid with `-fthis-is-

	      Let the type char	be unsigned, like unsigned char.

	      Each kind	of machine has a default for what char should be.   It
	      is  either  like unsigned	char by	default	or like	signed char by

	      Ideally, a portable program should always	use signed char	or un-
	      signed char when it depends on the signedness of an object.  But
	      many programs have been written to use plain char	and expect  it
	      to  be signed, or	expect it to be	unsigned, depending on the ma-
	      chines they were written for.  This option, and its inverse, let
	      you make such a program work with	the opposite default.

	      The type char is always a	distinct type from each	of signed char
	      and unsigned char, even though its behavior is always just  like
	      one of those two.

	      Let the type char	be signed, like	signed char.

	      Note  that  this is equivalent to	`-fno-unsigned-char', which is
	      the   negative	form	of    `-funsigned-char'.     Likewise,
	      `-fno-signed-char' is equivalent to `-funsigned-char'.




	      These  options control whether a bitfield	is signed or unsigned,
	      when declared with no explicit `signed' or `unsigned' qualifier.
	      By  default,  such a bitfield is signed, because this is consis-
	      tent: the	basic integer types such as int	are signed types.

	      However, when you	specify	`-traditional',	bitfields are all  un-
	      signed no	matter what.

	      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.  `-tradition-
	      al' also has this	effect.

	      Writing into string constants is a very  bad  idea;  "constants"
	      should be	constant.

       These options control the C preprocessor, which is run on each C	source
       file before actual compilation.

       If you use the `-E' option,  GCC	 does  nothing	except	preprocessing.
       Some  of	 these options make sense only together	with `-E' because they
       cause the preprocessor output to	be unsuitable for actual  compilation.

       -include	file
	      Process  file as input before processing the regular input file.
	      In effect, the contents of file are compiled  first.   Any  `-D'
	      and `-U' options on the command line are always processed	before
	      `-include	file', regardless of the order in which	they are writ-
	      ten.  All	the `-include' and `-imacros' options are processed in
	      the order	in which they are written.

       -imacros	file
	      Process file as input, discarding	the resulting  output,	before
	      processing the regular input file.  Because the output generated
	      from file	is discarded, the only effect of `-imacros file' is to
	      make  the	 macros	 defined in file available for use in the main
	      input.  The preprocessor evaluates any `-D' and `-U' options  on
	      the command line before processing `-imacrosfile', regardless of
	      the order	in which they are written.   All  the  `-include'  and
	      `-imacros'  options are processed	in the order in	which they are

       -idirafter dir
	      Add the directory	dir to the second include path.	 The  directo-
	      ries  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 `-I' adds to).

       -iprefix	prefix
	      Specify  prefix  as the prefix for subsequent `-iwithprefix' op-

       -iwithprefix dir
	      Add a directory to the second  include  path.   The  directory's
	      name  is	made by	concatenating prefix and dir, where prefix was
	      specified	previously with	`-iprefix'.

	      Do not search the	standard system	directories for	header	files.
	      Only  the	 directories you have specified	with `-I' options (and
	      the current directory, if	appropriate) are searched.

	      By using both `-nostdinc'	and `-I-', you can limit the  include-
	      file search file to only those directories you specify explicit-

	      Do not search for	header files in	the C++-specific standard  di-
	      rectories,  but  do still	search the other standard directories.
	      (This option is used when	building `libg++'.)

       -undef Do not predefine any nonstandard macros.	 (Including  architec-
	      ture flags).

       -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.

       -C     Tell  the	 preprocessor  not to discard comments.	 Used with the
	      `-E' option.

       -P     Tell the preprocessor not	to generate  `#line'  commands.	  Used
	      with the `-E' option.

       -M  [ -MG ]
	      Tell  the	 preprocessor  to  output a rule suitable for make de-
	      scribing the dependencies	of each	object file.  For each	source
	      file, the	preprocessor outputs one make-rule whose target	is the
	      object file name for that	source file and	whose dependencies are
	      all the files `#include'd	in it.	This rule may be a single line
	      or may be	continued with `\'-newline if it is long.  The list of
	      rules  is	printed	on standard output instead of the preprocessed
	      C	program.

	      `-M' implies `-E'.

	      `-MG' says to treat missing header files as generated files  and
	      assume  they  live in the	same directory as the source file.  It
	      must be specified	in addition to `-M'.

       -MM  [ -MG ]
	      Like `-M'	but the	output mentions	only the user header files in-
	      cluded  with  `#include  "file"'.	  System header	files included
	      with `#include <file>' are omitted.

       -MD    Like `-M'	but the	dependency information	is  written  to	 files
	      with  names  made	 by replacing `.o' with	`.d' at	the end	of the
	      output file names.  This is in addition to compiling the file as
	      specified--`-MD'	does  not inhibit ordinary compilation the way
	      `-M' does.

	      The Mach utility `md' can	be used	to merge the `.d' files	into a
	      single  dependency  file suitable	for using with the `make' com-

       -MMD   Like `-MD' except	mention	only user  header  files,  not	system
	      header files.

       -H     Print  the  name	of each	header file used, in addition to other
	      normal activities.

	      Assert the answer	answer for question, in	case it	is tested with
	      a	 preprocessor  conditional  such  as  `#if #question(answer)'.
	      `-A-' disables the standard assertions  that  normally  describe
	      the target machine.

	      (answer)	Assert	the  answer answer for question, in case it is
	      tested with a  preprocessor  conditional	such  as  `#if	#ques-
	      tion(answer)'.  `-A-' disables the standard assertions that nor-
	      mally describe the target	machine.

	      Define macro macro with the string `1' as	its definition.

	      Define macro macro as defn.    All instances of `-D' on the com-
	      mand line	are processed before any `-U' options.

	      Undefine macro macro.  `-U' options are evaluated	after all `-D'
	      options, but before any `-include' and `-imacros'	options.

       -dM    Tell the preprocessor to output only a list of the macro defini-
	      tions that are in	effect at the end of preprocessing.  Used with
	      the `-E' option.

       -dD    Tell the preprocessor to pass all	 macro	definitions  into  the
	      output, in their proper sequence in the rest of the output.

       -dN    Like  `-dD'  except  that	 the  macro arguments and contents are
	      omitted.	Only `#define name' is included	in the output.

	      Pass option as an	option to the assembler.  If  option  contains
	      commas, it is split into multiple	options	at the commas.

       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.

	      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.

	      Use the library named library when linking.

	      The  linker  searches a standard list of directories for the li-
	      brary, which is actually a file named `liblibrary.a'.  The link-
	      er  then uses this file as if it had been	specified precisely by

	      The directories searched include several standard	system	direc-
	      tories plus any that you specify with `-L'.

	      Normally	the  files  found  this	way are	library	files--archive
	      files whose members are object files.  The linker	handles	an ar-
	      chive  file by scanning through it for members which define sym-
	      bols that	have so	far been referenced but	not defined.  However,
	      if  the  linker  finds an	ordinary object	file rather than a li-
	      brary, the object	file is	linked in the usual fashion.  The only
	      difference  between  using  an `-l' option and specifying	a file
	      name is that `-l'	surrounds library  with	 `lib'	and  `.a'  and
	      searches several directories.

       -lobjc You  need	this special case of the -l option in order to link an
	      Objective	C program.

	      Do not use the standard system startup files when	linking.   The
	      standard libraries are used normally.

	      Don't  use  the standard system libraries	and startup files when
	      linking.	Only the files you specify will	be passed to the link-

	      On  systems  that	support	dynamic	linking, this prevents linking
	      with the shared libraries.  On other systems, this option	has no

	      Produce  a shared	object which can then be linked	with other ob-
	      jects to form an executable.  Only a few	systems	 support  this

	      Bind references to global	symbols	when building a	shared object.
	      Warn about any unresolved	references (unless overridden  by  the
	      link  editor  option  `-Xlinker  -z -Xlinker defs').  Only a few
	      systems support this option.

       -Xlinker	option
	      Pass 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.

	      If you want to pass an option that takes an argument,  you  must
	      use `-Xlinker' twice, once for the option	and once for the argu-
	      ment.  For example, to  pass  `-assert  definitions',  you  must
	      write `-Xlinker -assert -Xlinker definitions'.  It does not work
	      to write `-Xlinker "-assert definitions"', because  this	passes
	      the  entire  string  as a	single argument, which is not what the
	      linker expects.

	      Pass option as an	option to the linker.  If option contains com-
	      mas, it is split into multiple options at	the commas.

       -u symbol
	      Pretend  the symbol symbol is undefined, to force	linking	of li-
	      brary modules to define it.  You can  use	 `-u'  multiple	 times
	      with  different  symbols	to force loading of additional library

       These options specify directories to search for header files,  for  li-
       braries and for parts of	the compiler:

       -Idir  Append directory dir to the list of directories searched for in-
	      clude files.

       -I-    Any directories you specify with `-I' options before  the	 `-I-'
	      option are searched only for the case of `#include "file"'; they
	      are not searched for `#include <file>'.

	      If additional directories	are specified with `-I'	options	 after
	      the `-I-', these directories are searched	for all	`#include' di-
	      rectives.	 (Ordinarily all `-I' directories are used this	 way.)

	      In  addition,  the  `-I-'	option inhibits	the use	of the current
	      directory	(where the current input file came from) as the	 first
	      search  directory	 for  `#include	 "file"'.   There is no	way to
	      override this effect of  `-I-'.	With  `-I.'  you  can  specify
	      searching	 the directory which was current when the compiler was
	      invoked.	That is	not exactly the	same as	what the  preprocessor
	      does by default, but it is often satisfactory.

	      `-I-'  does  not inhibit the use of the standard system directo-
	      ries for header files.  Thus, `-I-' and `-nostdinc' are indepen-

       -Ldir  Add  directory dir to the	list of	directories to be searched for

	      This option specifies where to find the  executables,  libraries
	      and data files of	the compiler itself.

	      The  compiler driver program runs	one or more of the subprograms
	      `cpp', `cc1' (or,	for C++, `cc1plus'), `as' and `ld'.  It	 tries
	      prefix  as  a prefix for each program it tries to	run, both with
	      and without `machine/version/'.

	      For each subprogram to be	run, the compiler driver  first	 tries
	      the  `-B'	prefix,	if any.	 If that name is not found, or if `-B'
	      was not specified, the driver tries two standard prefixes, which
	      are  `/usr/lib/gcc/'  and	`/usr/local/lib/gcc-lib/'.  If neither
	      of those results in a file name  that  is	 found,	 the  compiler
	      driver  searches	for the	unmodified program name, using the di-
	      rectories	specified in your `PATH' environment variable.

	      The run-time support file	`libgcc.a' is also searched for	 using
	      the  `-B'	 prefix, if needed.  If	it is not found	there, the two
	      standard prefixes	above are tried, and that is all.  The file is
	      left out of the link if it is not	found by those means.  Most of
	      the time,	on most	machines, `libgcc.a' is	 not  actually	neces-

	      You  can	get  a	similar	 result	 from the environment variable
	      GCC_EXEC_PREFIX; if it is	defined, its value is used as a	prefix
	      in  the same way.	 If both the `-B' option and the GCC_EXEC_PRE-
	      FIX variable are present,	the `-B' option	is used	first and  the
	      environment variable value second.

       Warnings	 are  diagnostic  messages that	report constructions which are
       not inherently erroneous	but which are risky or suggest there may  have
       been an error.

       These  options control the amount and kinds of warnings produced	by GNU

	      Check the	code for syntax	errors,	but don't emit any output.

       -w     Inhibit all warning messages.

	      Inhibit warning messages about the use of	#import.

	      Issue all	the warnings demanded by strict	ANSI standard  C;  re-
	      ject all programs	that use forbidden extensions.

	      Valid  ANSI  standard C programs should compile properly with or
	      without this option (though a rare few  will  require  `-ansi').
	      However,	without	this option, certain GNU extensions and	tradi-
	      tional C features	are supported as well.	With this option, they
	      are  rejected.  There is no reason to use	this option; it	exists
	      only to satisfy pedants.

	      `-pedantic' does not cause warning messages for use of  the  al-
	      ternate  keywords	whose names begin and end with `__'.  Pedantic
	      warnings are also	disabled in the	expression that	follows	 __ex-
	      tension__.   However,  only system header	files should use these
	      escape routes; application programs should avoid them.

	      Like `-pedantic',	except that errors are	produced  rather  than

       -W     Print extra warning messages for these events:

	  o   A	 nonvolatile  automatic	variable might be changed by a call to
	      longjmp.	These warnings are possible only in optimizing	compi-

	      The  compiler  sees  only	 the  calls to setjmp.	It cannot know
	      where longjmp will be called; in fact, a	signal	handler	 could
	      call  it	at  any	point in the code.  As a result, you may get a
	      warning even when	there is in fact no  problem  because  longjmp
	      cannot  in fact be called	at the place which would cause a prob-

	  o   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	 warn-

	      foo (a)
		if (a >	0)
		  return a;

	      Spurious warnings	can occur because GNU CC does not realize that
	      certain functions	(including abort and longjmp) will  never  re-

	  o   An expression-statement or the left-hand side of a comma expres-
	      sion contains no side effects.  To suppress  the	warning,  cast
	      the  unused expression to	void.  For example, an expression such
	      as `x[i,j]' will cause a warning,	but `x[(void)i,j]' will	not.

	  o   An unsigned value	is compared against zero with `>' or `<='.

	      Warn whenever a declaration does not specify a type.

	      Warn whenever a function is used before being declared.

	      Same as -Wimplicit-int and -Wimplicit-function-declaration.

       -Wmain Warn if the main function	is declared or defined with  a	suspi-
	      cious  type.  Typically, it is a function	with external linkage,
	      returning	int, and taking	zero or	two arguments.

	      Warn whenever a function is defined with a return-type that  de-
	      faults to	int.  Also warn	about any return statement with	no re-
	      turn-value in a function whose return-type is not	void.

	      Warn whenever a local variable is	unused aside from its declara-
	      tion,  whenever a	function is declared static but	never defined,
	      and whenever a statement computes	a result  that	is  explicitly
	      not used.

	      Warn  whenever  a	switch statement has an	index of enumeral type
	      and lacks	a case for one or more of the named codes of that enu-
	      meration.	  (The presence	of a default label prevents this warn-
	      ing.)  case labels outside the enumeration  range	 also  provoke
	      warnings when this option	is used.

	      Warn  whenever  a	 comment-start sequence	`/*' appears in	a com-

	      Warn if any trigraphs are	encountered  (assuming	they  are  en-

	      Check calls to printf and	scanf, etc., to	make sure that the ar-
	      guments supplied have types appropriate  to  the	format	string

	      Warn  if	an  array  subscript  has type char.  This is a	common
	      cause of error, as programmers often forget that	this  type  is
	      signed on	some machines.

	      An automatic variable is used without first being	initialized.

	      These  warnings are possible only	in optimizing compilation, be-
	      cause they require data flow information that is	computed  only
	      when  optimizing.	  If  you don't	specify	`-O', you simply won't
	      get these	warnings.

	      These warnings occur only	for variables that are candidates  for
	      register	allocation.   Therefore, they do not occur for a vari-
	      able that	is declared volatile, 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

	      Note  that there may be no warning about a variable that is used
	      only to compute a	value that itself is never used, because  such
	      computations  may	 be  deleted  by data flow analysis before the
	      warnings are printed.

	      These warnings are made optional because GNU  CC	is  not	 smart
	      enough  to see all the reasons why the code might	be correct de-
	      spite appearing to have an error.	 Here is one  example  of  how
	      this can happen:

		int x;
		switch (y)
		  case 1: x = 1;
		  case 2: x = 4;
		  case 3: x = 5;
		foo (x);

	      If the value of y	is always 1, 2 or 3, then x is always initial-
	      ized, but	GNU CC doesn't know  this.   Here  is  another	common

		int save_y;
		if (change_y) save_y = y, y = new_y;
		if (change_y) y	= save_y;

	      This has no bug because save_y is	used only if it	is set.

	      Some spurious warnings can be avoided if you declare as volatile
	      all the functions	you use	that never return.

	      Warn if parentheses are omitted in certain contexts.

	      When using templates in a	C++ program, warn if debugging is  not
	      yet fully	available (C++ only).

       -Wall  All  of  the above `-W' options combined.	 These are all the op-
	      tions which pertain to usage that	we recommend avoiding and that
	      we believe is easy to avoid, even	in conjunction with macros.

       The  remaining  `-W...' options are not implied by `-Wall' because they
       warn about constructions	that we	consider reasonable to use,  on	 occa-
       sion, in	clean programs.

	      Warn  about certain constructs that behave differently in	tradi-
	      tional and ANSI C.

	  o   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.

	  o   A	function declared external in one block	and  then  used	 after
	      the end of the block.

	  o   A	switch statement has an	operand	of type	long.

	      Warn whenever a local variable shadows another local variable.

	      Warn  whenever  two  distinct identifiers	match in the first len
	      characters.  This	may help you prepare a program that will  com-
	      pile with	certain	obsolete, brain-damaged	compilers.

	      Warn  about  anything  that  depends on the "size	of" a function
	      type or of void.	GNU C assigns these types a  size  of  1,  for
	      convenience in calculations with void * pointers and pointers to

	      Warn whenever a pointer is cast so as to remove a	type qualifier
	      from  the	 target	 type.	For example, warn if a const char * is
	      cast to an ordinary char *.

	      Warn whenever a pointer is cast such that	the required alignment
	      of  the  target  is increased.  For example, warn	if a char * is
	      cast to an int * on machines where integers can only be accessed
	      at two- or four-byte boundaries.

	      Give  string constants the type const char[length] so that copy-
	      ing the address of one into a non-const 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 const in declarations and
	      prototypes.  Otherwise, it will just be a	nuisance; this is  why
	      we did not make `-Wall' request these warnings.

	      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

	      Warn if any functions that return	structures or unions  are  de-
	      fined  or	 called.  (In languages	where you can return an	array,
	      this also	elicits	a warning.)

	      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.)

	      Warn  if	a global function is defined without a previous	proto-
	      type declaration.	 This warning is issued	even if	the definition
	      itself  provides a prototype.  The aim is	to detect global func-
	      tions that fail to be declared in	header files.

	      Warn if a	global function	is defined without a previous declara-
	      tion.  Do	so even	if the definition itself provides a prototype.
	      Use this option to detect	global functions that are not declared
	      in header	files.

	      Warn  if	anything is declared more than once in the same	scope,
	      even in cases where multiple declaration is  valid  and  changes

	      Warn  if an extern declaration is	encountered within a function.

	      Warn about conversion between different enumeration  types  (C++

	      Warn  if	long  long type	is used.  This is default.  To inhibit
	      the  warning  messages,  use   flag   `-Wno-long-long'.	 Flags
	      `-W-long-long'  and `-Wno-long-long' are taken into account only
	      when flag	`-pedantic' is used.

	      (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 erro-
	      neous 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.

	      Warn  if	a  function  can not be	inlined, and either it was de-
	      clared as	inline,	or else	the -finline-functions option was giv-

	      Treat warnings as	errors;	abort compilation after	any warning.

       GNU  CC	has various special options that are used for debugging	either
       your program or GCC:

       -g     Produce debugging	information in the operating  system's	native
	      format  (stabs,  COFF, XCOFF, or DWARF).	GDB can	work with this
	      debugging	information.

	      On most systems that use stabs format, `-g' enables use of extra
	      debugging	information that only GDB can use; this	extra informa-
	      tion 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	infor-
	      mation,	use   `-gstabs+',  `-gstabs',  `-gxcoff+',  `-gxcoff',
	      `-gdwarf+', or `-gdwarf' (see below).

	      Unlike most other	C compilers, GNU CC allows  you	 to  use  `-g'
	      with  `-O'.  The shortcuts taken by optimized code may occasion-
	      ally produce surprising results: some variables you declared may
	      not exist	at all;	flow of	control	may briefly move where you did
	      not expect it; some statements may not be	executed because  they
	      compute  constant	 results or their values were already at hand;
	      some statements may execute in  different	 places	 because  they
	      were moved out of	loops.

	      Nevertheless it proves possible to debug optimized output.  This
	      makes it reasonable to use the optimizer for programs that might
	      have bugs.

       The  following options are useful when GNU CC is	generated with the ca-
       pability	for more than one debugging format.

       -ggdb  Produce debugging	information in the native format (if  that  is
	      supported), including GDB	extensions if at all possible.

	      Produce  debugging  information in stabs format (if that is sup-
	      ported), without GDB extensions.	This is	the format used	by DBX
	      on most BSD systems.

	      Produce  debugging  information in stabs format (if that is sup-
	      ported), using GNU extensions understood only by the GNU	debug-
	      ger  (GDB).  The use of these extensions is likely to make other
	      debuggers	crash or refuse	to read	the program.

       -gcoff Produce debugging	information in COFF format (if	that  is  sup-
	      ported).	 This  is the format used by SDB on most System	V sys-
	      tems prior to System V Release 4.

	      Produce debugging	information in XCOFF format (if	that  is  sup-
	      ported).	 This  is  the	format used by the DBX debugger	on IBM
	      RS/6000 systems.

	      Produce debugging	information in XCOFF format (if	that  is  sup-
	      ported),	using GNU extensions understood	only by	the GNU	debug-
	      ger (GDB).  The use of these extensions is likely	to make	 other
	      debuggers	crash or refuse	to read	the program.

	      Produce  debugging  information in DWARF format (if that is sup-
	      ported).	This is	the format used	by SDB on most	System	V  Re-
	      lease 4 systems.

	      Produce  debugging  information in DWARF format (if that is sup-
	      ported), using GNU extensions understood only by the GNU	debug-
	      ger  (GDB).  The use of these extensions is likely to make other
	      debuggers	crash or refuse	to read	the program.

       -gcofflevel -gxcofflevel

	      Request debugging	information and	also use level to specify  how
	      much information.	 The default level is 2.

	      Level  1	produces  minimal information, enough for making back-
	      traces in	parts of the program that you  don't  plan  to	debug.
	      This  includes descriptions of functions and external variables,
	      but no information about local variables and no line numbers.

	      Level 3 includes extra information, such as all the macro	 defi-
	      nitions  present	in  the	program.  Some debuggers support macro
	      expansion	when you use `-g3'.

       -p     Generate extra code to write profile  information	 suitable  for
	      the analysis program prof.

       -pg    Generate	extra  code  to	write profile information suitable for
	      the analysis program gprof.

       -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
	      tcov.   Note,  however,  that the	format of the data is not what
	      tcov expects.   Eventually  GNU  gprof  should  be  extended  to
	      process this data.

       -ax    Generate	extra  code  to	 read basic block profiling parameters
	      from file	`'	and write profiling results to file  `bb.out'.
	      `' contains a list of functions. Whenever a function	on the
	      list is entered, profiling is turned on. When the	outmost	 func-
	      tion  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	avail-
	      able  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.

	      Says  to make debugging dumps during compilation at times	speci-
	      fied by letters.	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.  `foo.c.rtl' or `foo.c.jump').

       -dM    Dump all macro definitions, at the  end  of  preprocessing,  and
	      write no output.

       -dN    Dump all macro names, at the end of preprocessing.

       -dD    Dump  all	macro definitions, at the end of preprocessing,	in ad-
	      dition to	normal output.

       -dy    Dump debugging information during	parsing, to standard error.

       -dr    Dump after RTL generation, to `file.rtl'.

       -dx    Just generate RTL	for a function instead of compiling it.	  Usu-
	      ally used	with `r'.

       -dj    Dump after first jump optimization, to `file.jump'.

       -ds    Dump  after  CSE (including the jump optimization	that sometimes
	      follows CSE), to `file.cse'.

       -dL    Dump after loop optimization, to `file.loop'.

       -dt    Dump after the second CSE	pass (including	the jump  optimization
	      that sometimes follows CSE), to `file.cse2'.

       -df    Dump after flow analysis,	to `file.flow'.

       -dc    Dump after instruction combination, to `file.combine'.

       -dS    Dump   after   the   first   instruction	 scheduling  pass,  to

       -dl    Dump after local register	allocation, to `file.lreg'.

       -dg    Dump after global	register allocation, to	`file.greg'.

       -dR    Dump  after  the	second	 instruction   scheduling   pass,   to

       -dJ    Dump after last jump optimization, to `file.jump2'.

       -dd    Dump after delayed branch	scheduling, to `file.dbr'.

       -dk    Dump  after conversion from registers to stack, to `file.stack'.

       -da    Produce all the dumps listed above.

       -dm    Print statistics on memory usage,	at the	end  of	 the  run,  to
	      standard error.

       -dp    Annotate	the  assembler	output with a comment indicating which
	      pattern and alternative was used.

	      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.

	      Store the	 usual	"temporary"  intermediate  files  permanently;
	      place  them  in the current directory and	name them based	on the
	      source file.  Thus,  compiling  `foo.c'  with  `-c  -save-temps'
	      would produce files `foo.cpp' and	`foo.s', as well as `foo.o'.

	      Print  the  full absolute	name of	the library file library  that
	      would be used when linking--and do not do	anything  else.	  With
	      this  option,  GNU CC does not compile or	link anything; it just
	      prints the file name.

	      Same as `-print-file-name=libgcc.a'.

	      Like `-print-file-name', but searches  for  a  program  such  as

       These options control various sorts of optimizations:


       -O1    Optimize.	  Optimizing compilation takes somewhat	more time, and
	      a	lot more memory	for a large function.

	      Without `-O', the	compiler's goal	is to reduce the cost of  com-
	      pilation	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.

	      Without `-O', only variables declared register are allocated  in
	      registers.   The	resulting compiled code	is a little worse than
	      produced by PCC without `-O'.

	      With `-O', the compiler tries to reduce code size	and  execution

	      When  you	 specify  `-O',	 the  two options `-fthread-jumps' and
	      `-fdefer-pop' are	turned on.  On machines	that have delay	slots,
	      the  `-fdelayed-branch' option is	turned on.  For	those machines
	      that can support debugging even without  a  frame	 pointer,  the
	      `-fomit-frame-pointer'  option  is  turned on.  On some machines
	      other flags may also be turned on.

       -O2    Optimize even more.  Nearly all supported	optimizations that  do
	      not  involve  a  space-speed  tradeoff  are performed.  Loop un-
	      rolling and function inlining are	not  done,  for	 example.   As
	      compared	to -O, this option increases both compilation time and
	      the performance of the generated code.

       -O3    Optimize yet more. This turns on everything -O2 does, along with
	      also turning on -finline-functions.

       -Os    Optimize	for  size.  This enables all -O2 optimizations that do
	      not typically increase code size.	 It also performs further  op-
	      timizations designed to reduce code size.

       -O0    Do not optimize.

	      If  you  use multiple -O options,	with or	without	level numbers,
	      the last such option is the one that is effective.

       Options of the form `-fflag' specify machine-independent	 flags.	  Most
       flags  have  both  positive  and	 negative  forms; the negative form of
       `-ffoo' would be	`-fno-foo'.  The following list	shows only one	form--
       the one which is	not the	default.  You can figure out the other form by
       either removing `no-' or	adding it.

	      Do not store floating point variables in registers.   This  pre-
	      vents undesirable	excess precision on machines such as the 68000
	      where the	floating registers (of the 68881) keep more  precision
	      than a double is supposed	to have.

	      For  most	 programs,  the	excess precision does only good, but a
	      few programs rely	on the precise	definition  of	IEEE  floating
	      point.  Use `-ffloat-store' for such programs.


	      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.

	      The  first time the compiler must	build a	call to	a member func-
	      tion (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

		cout <<	"This "	<< p <<	" has "	<< n <<	" legs.\n";

	      makes six	passes through all three steps.	 By using  a  software
	      cache,  a	"hit" significantly reduces this cost.	Unfortunately,
	      using the	cache introduces another  layer	 of  mechanisms	 which
	      must  be	implemented, and so incurs its own overhead.  `-fmemo-
	      ize-lookups' enables the software	cache.

	      Because access privileges	(visibility)  to  members  and	member
	      functions	 may differ from one function context to the next, g++
	      may need to flush	the cache.  With the `-fmemoize-lookups' flag,
	      the cache	is flushed after every function	that is	compiled.  The
	      `-fsave-memoized'	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 help-
	      ful 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	privi-
	      leges as every other, and	the cache need not be flushed.

	      Don't  make  member  functions  inline by	default	merely because
	      they are defined inside the class	scope (C++ only).

	      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

	      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	 hear-
	      ing about	the difference this makes.

	      Force  memory  address constants to be copied into registers be-
	      fore doing arithmetic on them.  This  may	 produce  better  code
	      just as `-fforce-mem' may.  I am interested in hearing about the
	      difference this makes.

	      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.  It also makes debugging impossible
	      on most machines.

	      On some machines,	such as	the Vax, this flag has no effect,  be-
	      cause  the  standard  calling sequence automatically handles the
	      frame pointer and	nothing	is saved by pretending it doesn't  ex-
	      ist.   The machine-description macro FRAME_POINTER_REQUIRED con-
	      trols whether a target machine supports this flag.

	      Integrate	all simple functions into their	callers.  The compiler
	      heuristically  decides  which  functions are simple enough to be
	      worth integrating	in this	way.

	      If all calls to a	given function are integrated, and  the	 func-
	      tion  is	declared static, then GCC normally does	not output the
	      function as assembler code in its	own right.

	      Enable values to be allocated in registers that  will  be	 clob-
	      bered  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 oth-
	      erwise be	produced.

	      This option is enabled by	default	on certain  machines,  usually
	      those which have no call-preserved registers to use instead.

	      Even  if	all  calls to a	given function are integrated, and the
	      function is declared static, nevertheless	output a separate run-
	      time callable version of the function.

	      Do  not  put function addresses in registers; make each instruc-
	      tion that	calls a	constant function contain the  function's  ad-
	      dress explicitly.

	      This  option  results  in	 less efficient	code, but some strange
	      hacks that alter the assembler output may	be confused by the op-
	      timizations performed when this option is	not used.

	      Disable any machine-specific peephole optimizations.

	      This option allows GCC to	violate	some ANSI or IEEE rules/speci-
	      fications	in the interest	of optimizing code for speed.  For ex-
	      ample,  it  allows  the compiler to assume arguments to the sqrt
	      function are non-negative	numbers.

	      This option should never be turned on by any `-O'	 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.

       The following options control specific optimizations.  The `-O2'	option
       turns on	all of these optimizations except `-funroll-loops' and	`-fun-

       The  `-O'  option  usually  turns  on  the  `-fthread-jumps' and	`-fde-
       layed-branch' options, but specific machines may	change the default op-

       You can use the following flags in the rare cases when "fine-tuning" of
       optimizations to	be performed is	desired.

	      Perform the optimizations	of loop	strength reduction and	elimi-
	      nation of	iteration variables.

	      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 des-
	      tination of the second branch or a point	immediately  following
	      it,  depending  on  whether the condition	is known to be true or

	      Perform the optimization of loop unrolling.  This	is  only  done
	      for  loops  whose	number of iterations can be determined at com-
	      pile time	or run time.

	      Perform the optimization of loop unrolling.  This	 is  done  for
	      all loops.  This usually makes programs run more slowly.

	      In  common subexpression elimination, scan through jump instruc-
	      tions when the target of the jump	is not reached	by  any	 other
	      path.   For example, when	CSE encounters an if statement with an
	      else clause, CSE will follow the jump when the condition	tested
	      is false.

	      This  is similar to `-fcse-follow-jumps',	but causes CSE to fol-
	      low jumps	which conditionally skip over blocks.	When  CSE  en-
	      counters	 a   simple   if   statement   with  no	 else  clause,
	      `-fcse-skip-blocks' causes CSE to	follow	the  jump  around  the
	      body of the if.

	      Re-run common subexpression elimination after loop optimizations
	      has been performed.

	      Elide constructors when this seems plausible (C++	 only).	  With
	      this  flag,  GNU C++ initializes y directly from the call	to foo
	      without going through a temporary	in the following code:

	      A	foo ();	A y = foo ();

	      Without this option, GNU C++ first initializes y by calling  the
	      appropriate  constructor	for type A; then assigns the result of
	      foo to a temporary; and, finally,	replaces the initial value  of
	      `y' with the temporary.

	      The default behavior (`-fno-elide-constructors') is specified by
	      the draft	ANSI C++ standard.   If	 your  program's  constructors
	      have  side  effects,  using `-felide-constructors' can make your
	      program act differently, since some  constructor	calls  may  be

	      Perform  a number	of minor optimizations that are	relatively ex-

	      If supported for the target machine, attempt to reorder instruc-
	      tions  to	 exploit  instruction  slots  available	 after delayed
	      branch instructions.

	      If supported for the target machine, attempt to reorder instruc-
	      tions  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  instruc-
	      tion is required.

	      Similar  to  `-fschedule-insns', but requests an additional pass
	      of instruction scheduling	after  register	 allocation  has  been
	      done.   This  is especially useful on machines with a relatively
	      small number of registers	and  where  memory  load  instructions
	      take more	than one cycle.

       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  in-
       stalled	side by	side.  Then you	specify	which one to use with the `-b'

       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.

       -b machine
	      The argument machine specifies the target	machine	 for  compila-
	      tion.  This is useful when you have installed GNU	CC as a	cross-

	      The value	to use for machine 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  `configure
	      i386v',  meaning	to compile for an 80386	running	System V, then
	      you would	specify	`-b i386v' to run that cross compiler.

	      When you do not specify `-b', it normally	means to  compile  for
	      the same type of machine that you	are using.

       -V version
	      The  argument  version specifies which version of	GNU CC to run.
	      This is useful when multiple versions are	installed.  For	 exam-
	      ple,  version might be `2.0', meaning to run GNU CC version 2.0.

	      The default version, when	you do not specify `-V', is controlled
	      by  the way GNU CC is installed.	Normally, it will be a version
	      that is recommended for general use.

       Each of the target machine types	can  have  its	own  special  options,
       starting	with `-m', to choose among various hardware models or configu-
       rations--for example, 68010 vs 68020, floating coprocessor or none.   A
       single  installed  version of the compiler can compile for any model or
       configuration, according	to the options specified.

       Some configurations of the compiler also	support	additional special op-
       tions,  usually	for command-line compatibility with other compilers on
       the same	platform.

       These are the `-m' options defined for the 68000	series:


	      Generate output for a 68000.  This is the	default	when the  com-
	      piler is configured for 68000-based systems.


	      Generate	output for a 68020 (rather than	a 68000).  This	is the
	      default when the compiler	is configured for 68020-based systems.

	      Generate	output	containing  68881  instructions	 for  floating
	      point.  This is the default for most 68020-based systems	unless
	      -nfp was specified when the compiler was configured.

	      Generate	output for a 68030.  This is the default when the com-
	      piler is configured for 68030-based systems.

	      Generate output for a 68040.  This is the	default	when the  com-
	      piler is configured for 68040-based systems.

	      Generate	output	for  a 68040, without using any	of the new in-
	      structions.  This	results	in code	which can run relatively effi-
	      ciently on either	a 68020/68881 or a 68030 or a 68040.

       -mfpa  Generate	output	containing  Sun	 FPA instructions for floating

	      Generate output containing library  calls	 for  floating	point.
	      WARNING:	the  requisite libraries are not part of GNU CC.  Nor-
	      mally 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.

	      Consider type int	to be 16 bits wide, like short int.

	      Do not use the bit-field instructions.  `-m68000'	implies	`-mno-

	      Do use the bit-field instructions.   `-m68020'  implies  `-mbit-
	      field'.	This is	the default if you use the unmodified sources.

       -mrtd  Use a different function-calling convention, in which  functions
	      that  take  a  fixed number of arguments return with the rtd in-
	      struction, which pops their  arguments  while  returning.	  This
	      saves  one  instruction  in the caller since there is no need to
	      pop the arguments	there.

	      This calling convention is incompatible with  the	 one  normally
	      used on Unix, so you cannot use it if you	need to	call libraries
	      compiled with the	Unix compiler.

	      Also, you	must provide function  prototypes  for	all  functions
	      that take	variable numbers of arguments (including printf); oth-
	      erwise incorrect code will be generated for calls	to those func-

	      In  addition, seriously incorrect	code will result if you	call a
	      function with too	many arguments.	  (Normally,  extra  arguments
	      are harmlessly ignored.)

	      The  rtd instruction is supported	by the 68010 and 68020 proces-
	      sors, but	not by the 68000.

       These `-m' options are defined for the Vax:

       -munix Do not output certain jump instructions (aobleq and so on)  that
	      the Unix assembler for the Vax cannot handle across long ranges.

       -mgnu  Do output	those jump instructions, on the	 assumption  that  you
	      will assemble with the GNU assembler.

       -mg    Output  code  for	 g-format floating point numbers instead of d-

       These `-m' switches are supported on the	SPARC:


	      Generate output containing floating point	instructions.  This is
	      the default.


	      Generate	output	containing  library  calls for floating	point.
	      Warning: there is	no GNU floating-point library for SPARC.  Nor-
	      mally 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.

	      -msoft-float changes the calling convention in the output	 file;
	      therefore,  it  is  only	useful if you compile all of a program
	      with this	option.


	      With -mepilogue (the default), the compiler  always  emits  code
	      for function exit	at the end of each function.  Any function ex-
	      it 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 func-

	      With -mno-epilogue, the compiler tries to	emit exit code	inline
	      at every function	exit.



	      These three options select variations on the SPARC architecture.

	      By default (unless specifically configured for the Fujitsu SPAR-
	      Clite),  GCC  generates code for the v7 variant of the SPARC ar-

	      -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.

	      -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.


	      These two	options	select the processor for which the code	is op-

	      With -mcypress (the default), the	compiler  optimizes  code  for
	      the Cypress CY7C602 chip,	as used	in the SparcStation/SparcServ-
	      er 3xx series. This is also appropriate for the older  SparcSta-
	      tion 1, 2, IPX etc.

	      With -msupersparc	the compiler optimizes code for	the SuperSparc
	      cpu, as used in the SparcStation 10, 1000	and 2000 series.  This
	      flag also	enables	use of the full	SPARC v8 instruction set.

       These `-m' options are defined for the Convex:

       -mc1   Generate output for a C1.	 This is the default when the compiler
	      is configured for	a C1.

       -mc2   Generate output for a C2.	 This is the default when the compiler
	      is configured for	a C2.

	      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  ta-

	      Omit  the	 argument  count word.	This is	the default if you use
	      the unmodified sources.

       These `-m' options are defined for the AMD Am29000:

       -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.

       -mnodw Generate code that assumes the DW	bit is not set.

       -mbw   Generate code that assumes the system supports byte and halfword
	      write operations.	 This is the default.

       -mnbw  Generate code that assumes the systems does not support byte and
	      halfword write operations.  This implies `-mnodw'.

	      Use a small memory model that assumes that all function address-
	      es  are  either within a single 256 KB segment or	at an absolute
	      address of less than 256K.  This allows the call instruction  to
	      be used instead of a const, consth, calli	sequence.

	      Do not assume that the call instruction can be used; this	is the

	      Generate code for	the Am29050.

	      Generate code for	the Am29000.  This is the default.

	      Generate	references   to	  registers   gr64-gr95	  instead   of
	      gr96-gr127.   This option	can be used when compiling kernel code
	      that wants a set of global registers disjoint from that used  by
	      user-mode	code.

	      Note that	when this option is used, register names in `-f' flags
	      must use the normal, user-mode, names.

	      Use the normal set of global registers, gr96-gr127.  This	is the

	      Insert  a	call to	__msp_check after each stack adjustment.  This
	      is often used for	kernel code.

       These `-m' options are defined for Motorola 88K architectures:

	      Generate code that works well on both the	m88100 and the m88110.

	      Generate code that works best for	the m88100, but	that also runs
	      on the m88110.

	      Generate code that works best for	the m88110, and	may not	run on
	      the m88100.

	      Include an ident directive in the	assembler output recording the
	      source file name,	compiler name and version, timestamp, and com-
	      pilation flags used.

	      In  assembler output, emit symbol	names without adding an	under-
	      score character at the beginning of each name.  The  default  is
	      to use an	underscore as prefix on	each name.


	      Early  models of the 88K architecture had	problems with division
	      by zero; in particular, many of them didn't trap.	 Use these op-
	      tions  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 `-mcheck-zero-division' by


	      Include (or omit)	additional debugging information (about	regis-
	      ters used	in each	stack frame) as	specified in the 88Open	Object
	      Compatibility Standard, "OCS".  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.


	      Force (or	do not require)	register values	to be stored in	a par-
	      ticular place in stack frames, as	specified in OCS.  The	DG/UX,
	      Delta88  SVr3.2,	and  BCS configurations	use `-mocs-frame-posi-
	      tion';   other   88k    configurations	have	the    default


	      Control how to store function arguments in stack frames.	`-mop-
	      timize-arg-area' saves space, but	may break some debuggers  (not
	      GDB).   `-mno-optimize-arg-area'	conforms  better to standards.
	      By default GCC does not optimize the argument area.

	      num Generate smaller data	references by making them relative  to
	      r0,  which  allows  loading  a  value using a single instruction
	      (rather than the usual two).  You	control	which data  references
	      are  affected  by	specifying num with this option.  For example,
	      if you specify `-mshort-data-512', then the data references  af-
	      fected are those involving displacements of less than 512	bytes.
	      `-mshort-data-num' is not	effective for num greater than 64K.


	      Do, or do	not, generate code to guarantee	sequential consistency
	      of volatile memory references.

	      GNU  CC  always  guarantees consistency by default, for the pre-
	      ferred processor submodel.  How this is done depends on the sub-

	      The  m88100  processor does not reorder memory references	and so
	      always provides sequential consistency.  If you  use  `-m88100',
	      GNU CC does not generate any special instructions	for sequential

	      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  be-
	      fore  a  preceding  store	instruction.  Such reordering violates
	      sequential consistency of	volatile memory	references, when there
	      are  multiple  processors.  When you use `-m88000' or `-m88110',
	      GNU CC generates special instructions when appropriate, to force
	      execution	in the proper order.

	      The extra	code generated to guarantee consistency	may affect the
	      performance of your application.	If you know that you can safe-
	      ly forgo this guarantee, you may use the option `-mno-serialize-

	      If you use the `-m88100' option but require  sequential  consis-
	      tency  when  running  on	the  m88110  processor,	you should use


       -msvr3 Turn on (`-msvr4') or off	(`-msvr3') compiler extensions related
	      to System	V release 4 (SVr4).  This controls the following:

	  o   Which variant of the assembler syntax to emit (which you can se-
	      lect independently using `-mversion-03.00').

	  o   `-msvr4' makes the C preprocessor	recognize `#pragma weak'

	  o   `-msvr4' makes GCC issue additional declaration directives  used
	      in SVr4.

       `-msvr3'	 is  the  default  for all m88K	configurations except the SVr4


	      Include code to detect bit-shifts	of more	than 31	bits;  respec-
	      tively,  trap  such shifts or emit code to handle	them properly.
	      By default GCC makes no special provision	for large bit  shifts.

	      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 instruc-

	      In the DG/UX configuration, there	are two	flavors	of SVr4.  This
	      option  modifies -msvr4 to select	whether	the hybrid-COFF	or re-
	      al-ELF flavor is used.  All other	configurations ignore this op-

	      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 prob-
	      lems.  By	default, GCC issues no such warning.

       These options are defined for the IBM RS6000:


	      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, `-mno-fp-in-toc' will reduce the size of
	      the TOC, which may avoid the overflow.

       These `-m' options are defined for the IBM RT PC:

	      Use an in-line code sequence for integer	multiplies.   This  is
	      the default.

	      Call lmul$$ for integer multiples.

	      Generate	full-size  floating  point  data blocks, including the
	      minimum amount of	scratch	space recommended by IBM.  This	is the

	      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.

	      Use a calling sequence incompatible with the IBM calling conven-
	      tion in which floating point arguments are  passed  in  floating
	      point  registers.	  Note	that  varargs.h	and stdargs.h will not
	      work with	floating point operands	if this	option is specified.

	      Use the normal calling convention	for floating point  arguments.
	      This is the default.

	      Return  structures  of more than one word	in memory, rather than
	      in a register.  This provides compatibility  with	 the  MetaWare
	      HighC (hc) compiler.  Use	`-fpcc-struct-return' for compatibili-
	      ty with the Portable C Compiler (pcc).

	      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  `-fpcc-struct-return'  or

       These `-m' options are defined for the MIPS family of computers:

	      Assume  the defaults for the machine type	cpu-type when schedul-
	      ing instructions.	 The default cpu-type is 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 cpu-type are	r2000, r3000, r4000, and r6000.	 While
	      picking a	specific 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 -mips2	or -mips3 switches being used.

       -mips2 Issue instructions from level 2 of the MIPS ISA (branch  likely,
	      square  root  instructions).   The  -mcpu=r4000  or  -mcpu=r6000
	      switch must be used in conjunction with -mips2.

       -mips3 Issue instructions from level 3 of the MIPS ISA (64 bit instruc-
	      tions).  The -mcpu=r4000 switch must be used in conjunction with



	      These options don't work at present.

	      Generate code for	the MIPS assembler, and	invoke	mips-tfile  to
	      add normal debug information.  This is the default for all plat-
	      forms  except  for  the  OSF/1  reference	 platform,  using  the
	      OSF/rose	object	format.	  If  any  of  the  -ggdb, -gstabs, or
	      -gstabs+ switches	are used, the mips-tfile program will encapsu-
	      late the stabs within MIPS ECOFF.

       -mgas  Generate code for	the GNU	assembler.  This is the	default	on the
	      OSF/1 reference platform,	using the OSF/rose object format.


	      The -mrnames switch says to output code using the	MIPS  software
	      names  for  the registers, instead of the	hardware names (ie, a0
	      instead of $4).  The GNU assembler does not support the -mrnames
	      switch,  and  the	 MIPS  assembler will be instructed to run the
	      MIPS C preprocessor  over	 the  source  file.   The  -mno-rnames
	      switch is	default.


	      The  -mgpopt  switch  says to write all of the data declarations
	      before the instructions in the text section, to all the MIPS as-
	      sembler  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.


	      For each non-inline function processed, the -mstats switch caus-
	      es the compiler to emit one line to the standard error  file  to
	      print  statistics	 about the program (number of registers	saved,
	      stack size, etc.).


	      The -mmemcpy switch makes	all block moves	call  the  appropriate
	      string function (memcpy or bcopy)	instead	of possibly generating
	      inline code.


	      The -mno-mips-tfile switch causes	the compiler  not  postprocess
	      the  object file with the	mips-tfile program, after the MIPS as-
	      sembler has generated it to add debug support.  If mips-tfile is
	      not run, then no local variables will be available to the	debug-
	      ger.  In addition, stage2	and stage3 objects will	have the  tem-
	      porary file names	passed to the assembler	embedded in the	object
	      file, which means	the objects will not compare the same.

	      Generate output containing library  calls	 for  floating	point.
	      WARNING:	the  requisite libraries are not part of GNU CC.  Nor-
	      mally 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.

	      Generate output containing floating point	instructions.  This is
	      the default if you use the unmodified sources.

       -mfp64 Assume that the 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 -mcpu=r4000
	      and -mips3 switches.

       -mfp32 Assume  that there are 32	32-bit floating	point registers.  This
	      is the default.


	      Emit (or do not emit) the	 .abicalls,  .cpload,  and  .cprestore
	      pseudo  operations  that	some System V.4	ports use for position
	      independent code.


	      The -mhalf-pic switch says to put	pointers to extern  references
	      into the data section and	load them up, rather than put the ref-
	      erences in the text section.   This  option  does	 not  work  at
	      present.	 -Gnum	Put global and static items less than or equal
	      to 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  (gp  or $28), instead of	the normal two words used.  By
	      default, num is 8	when the MIPS assembler	is used,  and  0  when
	      the  GNU	assembler is used.  The	-Gnum switch is	also passed to
	      the assembler and	linker.	 All modules should be	compiled  with
	      the same -Gnum value.

       -nocpp Tell  the	 MIPS  assembler to not	run its	preprocessor over user
	      assembler	files (with a `.s' suffix) when	assembling them.

       These `-m' options are defined for the Intel 80386 family of computers:


	      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.

	      Synonym for -mcpu=pentium

	      Synonym for -mcpu=pentiumpro

       -mcpu=cpu type
	      Assume  the defaults for the machine type	CPU TYPE when schedul-
	      ing instructions.	 The choices for CPU  TYPE  are:  i386,	 i486,
	      i586  (pentium),	pentium,  i686	(pentiumpro),  and pentiumpro.
	      While picking a specific CPU TYPE	will schedule things appropri-
	      ately  for  that particular chip,	the compiler will not generate
	      any code that does not run on the	i386  without  the  -march=cpu
	      type option being	used.

       -march=cpu type
	      Generate instructions for	the machine type CPU TYPE.  The	choic-
	      es for CPU TYPE are: i386, i486, pentium,	and pentiumpro.	 Spec-
	      ifying -march=cpu	type implies -mcpu=cpu type.

	      Generate	output	containing  library  calls for floating	point.
	      Warning: the requisite libraries are not part of GNU  CC.	  Nor-
	      mally the	facilities of the machine's usual C compiler are used,
	      but this can't be	done directly in cross-compilation.  You  must
	      make your	own arrangements to provide suitable library functions
	      for cross-compilation.

	      On machines where	a function returns floating point  results  in
	      the  80387  register  stack,  some floating point	opcodes	may be
	      emitted even if `-msoft-float' is	used.

	      Do not use the FPU registers for return values of	functions.

	      The usual	calling	convention  has	 functions  return  values  of
	      types  float  and	double in an FPU register, even	if there is no
	      FPU.  The	idea is	that the operating system  should  emulate  an

	      The  option  `-mno-fp-ret-in-387'	 causes	 such values to	be re-
	      turned in	ordinary CPU registers instead.


	      Generate extra code to write profile  information	 for  function

       These `-m' options are defined for the HPPA family of computers:

	      Generate code for	a PA 1.0 processor.

	      Generate code for	a PA 1.1 processor.

	      Generate code which is suitable for use in kernels.  Specifical-
	      ly, avoid	add instructions in which one of the arguments is  the
	      DP register; generate addil instructions instead.	 This avoids a
	      rather serious bug in the	HP-UX linker.

	      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.

	      Don't  generate  code  that  will	 be  linked against shared li-
	      braries.	This is	the default for	all PA targets.

	      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	"branch	out of range errors from the linker.

	      Prevent  floating	point registers	from being used	in any manner.
	      This is necessary	for compiling kernels which perform lazy  con-
	      text switching of	floating point registers.  If you use this op-
	      tion and attempt to perform floating point operations, the  com-
	      piler will abort.

	      Prevent  the  compiler  from using indexing address modes.  This
	      avoids some rather obscure problems when compiling MIG generated
	      code under MACH.

	      Add  a  colon  to	 the  end of label definitions (for ELF	assem-

       These `-m' options are defined for the Intel 80960 family of computers:

	      Assume  the  defaults for	the machine type cpu-type for instruc-
	      tion and addressing-mode availability and	 alignment.   The  de-
	      fault  cpu-type is kb; other choices are ka, mc, ca, cf, sa, and


	      The -mnumerics option indicates that the processor does  support
	      floating-point  instructions.  The -msoft-float option indicates
	      that floating-point support should not be	assumed.


	      Do (or do	not) attempt to	alter leaf procedures to  be  callable
	      with  the	 bal instruction as well as call.  This	will result in
	      more efficient code for explicit calls when the bal  instruction
	      can  be  substituted  by the assembler or	linker,	but less effi-
	      cient code in other cases, such as calls via function  pointers,
	      or using a linker	that doesn't support this optimization.


	      Do (or do	not) make additional attempts (beyond those of the ma-
	      chine-independent	portions of the	compiler) to optimize tail-re-
	      cursive  calls  into  branches.  You may not want	to do this be-
	      cause the	detection of cases where this is not valid is not  to-
	      tally complete.  The default is -mno-tail-call.


	      Assume  (or  do not assume) that the use of a complex addressing
	      mode is a	win on this implementation of the i960.	  Complex  ad-
	      dressing	modes  may not be worthwhile on	the K-series, but they
	      definitely are on	the C-series.  The default is currently	-mcom-
	      plex-addr	for all	processors except the CB and CC.


	      Align  code  to  8-byte boundaries for faster fetching (or don't
	      bother).	Currently turned on by default for C-series  implemen-
	      tations only.



	      Enable compatibility with	iC960 v2.0 or v3.0.


	      Enable compatibility with	the iC960 assembler.


	      Do not permit (do	permit)	unaligned accesses.

	      Enable  structure-alignment  compatibility  with Intel's gcc re-
	      lease version 1.3	(based on gcc 1.37).  Currently	this is	 buggy
	      in that #pragma align 1 is always	assumed	as well, and cannot be
	      turned off.

       These `-m' options are defined for the DEC Alpha	implementations:


	      Use (do not use) the hardware  floating-point  instructions  for
	      floating-point  operations.   When  -msoft-float	is  specified,
	      functions	in `libgcc1.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	float-
	      ing-point	operations.   If you are compiling for an Alpha	 with-
	      out  floating-point operations, you must ensure that the library
	      is built so as not to call them.

	      Note that	Alpha implementations  without	floating-point	opera-
	      tions are	required to have floating-point	registers.


	      Generate code that uses (does not	use) the floating-point	regis-
	      ter set.	-mno-fp-regs implies -msoft-float.  If	the  floating-
	      point  register  set  is	not  used, floating point operands are
	      passed in	integer	registers as if	they were integers and	float-
	      ing-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
	      -mno-fp-regs must	also be	compiled with that option.

	      A	typical	use of this option is building a kernel	that does  not
	      use,  and	 hence	need  not save and restore, any	floating-point

       These additional	options	are available on System	V Release 4  for  com-
       patibility with other compilers on those	systems:

       -G     On  SVr4	systems, gcc accepts the option	`-G' (and passes it to
	      the system linker),  for	compatibility  with  other  compilers.
	      However,	we  suggest you	use `-symbolic'	or `-shared' as	appro-
	      priate, instead of supplying linker options on the  gcc  command

       -Qy    Identify	the  versions  of each tool used by the	compiler, in a
	      .ident assembler directive in the	output.

       -Qn    Refrain from adding .ident directives to the output  file	 (this
	      is the default).

	      Search the directories dirs, and no others, for libraries	speci-
	      fied with	`-l'.  You can separate	directory entries in dirs from
	      one another with colons.

	      Look  in the directory dir to find the M4	preprocessor.  The as-
	      sembler uses this	option.

       These machine-independent options  control  the	interface  conventions
       used in code generation.

       Most  of	 them  begin  with `-f'.  These	options	have both positive and
       negative	forms; the negative form of `-ffoo' would be  `-fno-foo'.   In
       the  table below, only one of the forms is listed--the one which	is not
       the default.  You can figure out	the  other  form  by  either  removing
       `no-' or	adding it.

	      Assume that objects reached through references are not null (C++

	      Normally,	GNU C++	makes conservative assumptions	about  objects
	      reached  through	references.   For  example,  the compiler must
	      check that a is not null in code like the	following:

	      obj &a = g (); a.f (2);

	      Checking that references of this sort have non-null  values  re-
	      quires  extra code, however, and it is unnecessary for many pro-
	      grams.  You can use `-fnonnull-objects' to omit the  checks  for
	      null, if your program doesn't require checking.

	      Use  the	same  convention for returning struct and union	values
	      that is used by the usual	C compiler on your system.  This  con-
	      vention  is less efficient for small structures, and on many ma-
	      chines it	fails to be reentrant; but it has the advantage	of al-
	      lowing  intercallability	between	GCC-compiled code and PCC-com-
	      piled code.

	      Use the convention that struct and union values are returned  in
	      registers	 when  possible.   This	 is  more  efficient for small
	      structures than -fpcc-struct-return.

	      If you specify neither -fpcc-struct-return nor  -freg-struct-re-
	      turn,  GNU  CC  defaults to whichever convention is standard for
	      the target.  If there is no standard convention, GNU CC defaults
	      to -fpcc-struct-return.

	      Allocate	to an enum type	only as	many bytes as it needs for the
	      declared range of	possible values.  Specifically,	the enum  type
	      will be equivalent to the	smallest integer type which has	enough

	      Use the same size	for double as for float	.

	      Requests that the	data and non-const variables of	this  compila-
	      tion  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 pri-
	      vate data	exists in one copy per process.

	      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  de-
	      clared  (without extern) in two different	compilations, you will
	      get an error when	you link them.	The only reason	this might  be
	      useful  is  if  you wish to verify that the program will work on
	      other systems which always work this way.

	      Ignore the `#ident' directive.

	      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 al-
	      so requires using	the collect2 program to	make sure  the	system
	      linker  includes constructors and	destructors.  (collect2	is in-
	      cluded in	the GNU	CC distribution.)  For systems which must  use
	      collect2,	the compiler driver gcc	is configured to do this auto-

	      Don't output a .size assembler directive,	or anything else  that
	      would  cause trouble if the function is split in the middle, and
	      the two halves are placed	at  locations  far  apart  in  memory.
	      This  option is used when	compiling `crtstuff.c';	you should not
	      need to use it for anything else.

	      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).

	      Consider	all memory references through pointers to be volatile.

	      Consider all memory references to	extern and global  data	 items
	      to be volatile.

       -fpic  If supported for the target machines, generate position-indepen-
	      dent code, suitable for use in a shared library.

       -fPIC  If supported for the target machine,  emit  position-independent
	      code,  suitable for dynamic linking, even	if branches need large

	      Treat the	register named reg as a	fixed register;	generated code
	      should  never  refer  to	it (except perhaps as a	stack pointer,
	      frame pointer or in some other fixed role).

	      reg must be the name of a	register.  The register	names accepted
	      are machine-specific and are defined in the REGISTER_NAMES macro
	      in the machine description macro file.

	      This flag	does not have a	negative form, because it specifies  a
	      three-way	choice.

	      Treat  the  register  named reg as an allocable register that is
	      clobbered	by function calls.  It may  be	allocated  for	tempo-
	      raries  or  variables that do not	live across a call.  Functions
	      compiled this way	will not save and restore the register reg.

	      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.

	      This flag	does not have a	negative form, because it specifies  a
	      three-way	choice.

	      Treat  the  register named reg as	an allocable register saved by
	      functions.  It may be allocated even for	temporaries  or	 vari-
	      ables that live across a call.  Functions	compiled this way will
	      save and restore the register reg	if they	use it.

	      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.

	      A	different sort of disaster will	result from the	 use  of  this
	      flag for a register in which function values may be returned.

	      This  flag does not have a negative form,	because	it specifies a
	      three-way	choice.

       Two `#pragma' 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.

       #pragma interface
	      (C++  only.)  Use	this directive in header files that define ob-
	      ject 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  informa-
	      tion,  and the internal tables that implement virtual functions)
	      must be kept in each object file	that  includes	class  defini-
	      tions.  You can use this pragma to avoid such duplication.  When
	      a	header file containing `#pragma	interface' is  included	 in  a
	      compilation,  this  auxiliary  information will not be generated
	      (unless the main input source file itself	uses  `#pragma	imple-
	      mentation').   Instead, the object files will contain references
	      to be resolved at	link time.

       #pragma implementation

       #pragma implementation "objects.h"
	      (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  `#pragma  interface'.  Backup copies	of inline member func-
	      tions, debugging information, and	the internal  tables  used  to
	      implement	 virtual functions are all generated in	implementation

	      If you use `#pragma implementation' with no argument, it applies
	      to  an  include file with	the same basename as your source file;
	      for example, in `', `#pragma implementation'  by  it-
	      self  is	equivalent  to	`#pragma implementation	"allclass.h"'.
	      Use the string argument if you want a single implementation file
	      to include code from multiple header files.

	      There is no way to split up the contents of a single header file
	      into multiple implementation files.

       file.c		  C source file
       file.h		  C header (preprocessor) file
       file.i		  preprocessed C source	file
       file.C		  C++ source file		  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
       TMPDIR/cc*	  temporary files
       LIBDIR/cpp	  preprocessor
       LIBDIR/cc1	  compiler for C
       LIBDIR/cc1plus	  compiler for C++
       LIBDIR/collect	  linker front end needed on some machines
       LIBDIR/libgcc.a	  GCC subroutine library
       /lib/crt[01n].o	  start-up routine
       LIBDIR/ccrt0	  additional start-up routine for C++
       /lib/libc.a	  standard C library, see
       /usr/include	  standard directory for #include files
       LIBDIR/include	  standard gcc directory for #include files
       LIBDIR/g++-include additional g++ directory for #include

       LIBDIR is usually /usr/local/lib/machine/version.
       TMPDIR comes from the environment variable TMPDIR (default /usr/tmp  if
       available, else /tmp).

       as(1), cpp(1), gdb(1), ld(1)
       `gcc', `cpp', `as', `ld', and `gdb' entries in info.
       Using  and Porting GNU CC (for version 2.0), Richard M. Stallman; The C
       Preprocessor, Richard M.	Stallman; Debugging with GDB: the GNU  Source-
       Level  Debugger,	Richard	M. Stallman and	Roland H. Pesch; Using as: the
       GNU Assembler, Dean Elsner, Jay Fenlason	& friends; ld: the GNU linker,
       Steve Chamberlain and Roland Pesch.

       For instructions	on reporting bugs, see the GCC manual.

       Copyright 1991, 1992, 1993 Free Software	Foundation, Inc.

       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.

       Permission  is granted to copy and distribute modified versions of this
       manual under the	conditions for verbatim	copying, provided that the en-
       tire resulting derived work is distributed under	the terms of a permis-
       sion notice identical to	this one.

       Permission is granted to	copy and distribute translations of this manu-
       al  into	another	language, under	the above conditions for modified ver-
       sions, except that this permission notice may be	included  in  transla-
       tions approved by the Free Software Foundation instead of in the	origi-
       nal English.

       See the GNU CC Manual for the contributors to GNU CC.

GNU Tools			  1998/12/16				GCC(1)


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