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GCC(1)				   GNU Tools				GCC(1)

       gcc, g++	- GNU project C	and C++	Compiler (v2.6)

       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       If we find that the things in this man page that	are out	of date	 cause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
	      -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	-Winline -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

       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

       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-seriazlize-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
	      -m486 -mno-486 -msoft-float -mno-fp-ret-in-387

	      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-returno -fshared-data -fshort-enums -fshort-double
	      -fvolatile -fvolatile-global -fverbose-asm

       -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

	      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 contains no side effects.

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

	      Warn whenever a function or parameter is implicitly declared.

	      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 an function.

	      Warn about conversion between different enumeration  types  (C++

	      (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.

	      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.

       -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 valyue 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 optimises code for
	      the Cypress CY7C602 chip,	as used	in the SparcStation/SparcSever
	      3xx  series.  This is also apropriate for	the older SparcStation
	      1, 2, IPX	etc.

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

       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 it's 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.

	      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.

       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 allocatable 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 allocatable 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).

       cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(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			   04:51:29				GCC(1)


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