FreeBSD Man Pages

g++(1)

NAME

       gcc, g++ - GNU project C and C++ Compiler (gcc-3.2.1)

SYNOPSIS

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

WARNING

       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
       options.

       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-
       mentation.

       If we find that the things in this man page that are out of date  cause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

DESCRIPTION

       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-
       tions:

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

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

       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

       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

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

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

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

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

       Language Options
	      -ansi -fall-virtual -fcond-mismatch -fdollars-in-identifiers
	      -fenum-int-equiv -fexternal-templates -fno-asm -fno-builtin
	      -fhosted -fno-hosted -ffreestanding -fno-freestanding
	      -fno-strict-prototype -fsigned-bitfields -fsigned-char
	      -fthis-is-variable -funsigned-bitfields -funsigned-char
	      -fwritable-strings -traditional -traditional-cpp -trigraphs

       Warning Options
	      -fsyntax-only -pedantic -pedantic-errors -w -W -Wall
	      -Waggregate-return -Wcast-align -Wcast-qual -Wchar-subscript
	      -Wcomment -Wconversion -Wenum-clash -Werror -Wformat
	      -Wid-clash-len -Wimplicit -Wimplicit-int
	      -Wimplicit-function-declaration -Winline -Wlong-long -Wmain
	      -Wmissing-prototypes -Wmissing-declarations -Wnested-externs
	      -Wno-import -Wparentheses -Wpointer-arith -Wredundant-decls
	      -Wreturn-type -Wshadow -Wstrict-prototypes -Wswitch
	      -Wtemplate-debugging -Wtraditional -Wtrigraphs -Wuninitialized
	      -Wunused -Wwrite-strings

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

       Optimization Options
	      -fcaller-saves -fcse-follow-jumps -fcse-skip-blocks
	      -fdelayed-branch -felide-constructors -fexpensive-optimizations
	      -ffast-math -ffloat-store -fforce-addr -fforce-mem
	      -finline-functions -fkeep-inline-functions -fmemoize-lookups
	      -fno-default-inline -fno-defer-pop -fno-function-cse -fno-inline
	      -fno-peephole -fomit-frame-pointer -frerun-cse-after-loop
	      -fschedule-insns -fschedule-insns2 -fstrength-reduce
	      -fthread-jumps -funroll-all-loops -funroll-loops -O -O2 -O3 -O0
	      -Os

       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
       Directory Options
	      -Bprefix -Idir -I- -Ldir

       Target Options
	      -b  machine -V version

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

	      VAX Options
	      -mg -mgnu -munix

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

	      Convex Options
	      -margcount -mc1 -mc2 -mnoargcount

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

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

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

	      RT Options
	      -mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs
	      -mfull-fp-blocks -mhc-struct-return -min-line-mul
	      -mminimum-fp-blocks -mnohc-struct-return

	      MIPS Options
	      -mcpu=cpu type -mips2 -mips3 -mint64 -mlong64 -mlonglong128
	      -mmips-as -mgas -mrnames -mno-rnames -mgpopt -mno-gpopt -mstats
	      -mno-stats -mmemcpy -mno-memcpy -mno-mips-tfile -mmips-tfile
	      -msoft-float -mhard-float -mabicalls -mno-abicalls -mhalf-pic
	      -mno-half-pic -G num -nocpp

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

	      HPPA Options
	      -mic2.0-compat -mic3.0-compat -masm-compat -mintel-asm
	      -mstrict-align -mno-strict-align -mold-align -mno-old-align

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

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

       Code Generation Options
	      -fcall-saved-reg -fcall-used-reg -ffixed-reg
	      -finhibit-size-directive -fnonnull-objects -fno-common
	      -fno-ident -fno-gnu-linker -fpcc-struct-return -fpic -fPIC
	      -freg-struct-return -fshared-data -fshort-enums -fshort-double
	      -fvolatile -fvolatile-global -fverbose-asm

FreeBSD SPECIFIC OPTIONS

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

OVERALL OPTIONS

       -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-
	      sembler-with-cpp'.

       -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
	      file.

	      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.

       -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
	      proper.

       -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.

LANGUAGE OPTIONS

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

       -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
	      identifiers.

	      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.

       -fno-asm
	      cpy, sin, sqrt, strcmp, strcpy, and strlen.

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

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

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

       -fno-strict-prototype
	      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.

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

       -traditional
	      Attempt to support some aspects of traditional C compilers.  For
	      details,	see the GNU C Manual; the duplicate list here has been
	      deleted so that we won't get complaints when it is out of  date.

	      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'.

       -traditional-cpp
	      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'.

       -fdollars-in-identifiers
	      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.)

       -fenum-int-equiv
	      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.

       -fexternal-templates
	      Produce smaller code for template  declarations,	by  generating
	      only a single copy of each template function where it is defined
	      (C++ only).  To use this option successfully, you must also mark
	      all  files  that	use templates with either `#pragma implementa-
	      tion' (the definition) or `#pragma interface' (declarations).

	      When your code is compiled with `-fexternal-templates', all tem-
	      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.

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

       -fthis-is-variable
	      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-
	      variable'.

       -funsigned-char
	      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
	      default.

	      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.

       -fsigned-char
	      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'.

       -fsigned-bitfields

       -funsigned-bitfields

       -fno-signed-bitfields

       -fno-unsigned-bitfields
	      These  options control whether a bitfield is signed or unsigned,
	      when declared with no explicit `signed' or `unsigned' qualifier.
	      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.

PREPROCESSOR OPTIONS

       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
	      written.

       -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-
	      tions.

       -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'.

       -nostdinc
	      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-
	      ly.

       -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-
	      mand.

       -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.

       -Aquestion(answer)
	      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.

       -Aquestion
	      (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.
       -Umacro
	      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.

ASSEMBLER OPTION

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

LINKER OPTIONS

       These  options come into play when the compiler links object files into
       an executable output file.  They are meaningless if the compiler is not
       doing a link step.

       object-file-name
	      A  file name that does not end in a special recognized suffix is
	      considered to name an object file or library.  (Object files are
	      distinguished from libraries by the linker according to the file
	      contents.)  If GCC does a link step, these object files are used
	      as input to the linker.

       -llibrary
	      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
	      name.

	      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.

       -nostartfiles
	      Do not use the standard system startup files when linking.   The
	      standard libraries are used normally.
	      with the shared libraries.  On other systems, this option has no
	      effect.

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

       -symbolic
	      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.

       -Wl,option
	      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
	      modules.

DIRECTORY OPTIONS

       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

       -Bprefix
	      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-
	      sary.

	      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.

WARNING OPTIONS

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

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

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

       -w     Inhibit all warning messages.

       -Wno-import
	      Inhibit warning messages about the use of #import.

       -pedantic
	      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.

	      warnings.

       -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-
	      lation.

	      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-
	      lem.

	  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-
	      ing:

	      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-
	      turn.

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

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

       -Wimplicit-int
	      Warn whenever a declaration does not specify a type.

       -Wimplicit-function-declaration
	      Warn whenever a function is used before being declared.

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

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

       -Wreturn-type
	      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.

       -Wunused
	      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.

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

       -Wtrigraphs
	      Warn if any trigraphs are encountered  (assuming	they  are  en-
	      abled).

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

       -Wchar-subscripts
	      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.

       -Wuninitialized
	      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
	      registers.

	      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;
		    break;
		  case 2: x = 4;
		    break;
		  case 3: x = 5;
		  }
		foo (x);
		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.

       -Wparentheses
	      Warn if parentheses are omitted in certain contexts.

       -Wtemplate-debugging
	      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.

       -Wtraditional
	      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.

       -Wshadow
	      Warn whenever a local variable shadows another local variable.

       -Wid-clash-len
	      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.

       -Wpointer-arith
	      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
	      functions.

       -Wcast-qual
	      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 *.

	      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.

       -Wconversion
	      Warn  if	a prototype causes a type conversion that is different
	      from what would happen to the same argument in the absence of  a
	      prototype.  This includes conversions of fixed point to floating
	      and vice versa, and conversions changing the width or signedness
	      of  a  fixed  point argument except when the same as the default
	      promotion.

       -Waggregate-return
	      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.)

       -Wstrict-prototypes
	      Warn if a function is declared or defined without specifying the
	      argument	types.	(An old-style function definition is permitted
	      without a warning if preceded by a declaration  which  specifies
	      the argument types.)

       -Wmissing-prototypes
	      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.

       -Wmissing-declarations
	      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.

       -Wredundant-decls
	      Warn  if	anything is declared more than once in the same scope,
	      even in cases where multiple declaration is  valid  and  changes
	      nothing.

       -Wnested-externs
	      Warn  if an extern declaration is encountered within a function.

       -Wenum-clash
	      Warn about conversion between different enumeration  types  (C++
	      only).

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

       -Woverloaded-virtual
	      (C++ only.)  In a derived  class,  the  definitions  of  virtual
       -Winline
	      Warn  if	a  function  can not be inlined, and either it was de-
	      clared as inline, or else the -finline-functions option was giv-
	      en.

       -Werror
	      Treat warnings as errors; abort compilation after any warning.

DEBUGGING OPTIONS

       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.

       -gstabs
	      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.

       -gstabs+
	      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.

	      ger (GDB).  The use of these extensions is likely to make  other
	      debuggers crash or refuse to read the program.

       -gdwarf
	      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.

       -gdwarf+
	      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.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel -gxcofflevel

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

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

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

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

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

       -a     Generate extra code  to  write  profile  information  for  basic
	      blocks,  which  will record the number of times each basic block
	      is executed.  This data could be	analyzed  by  a  program  like
	      tcov.   Note,  however,  that the format of the data is not what
	      tcov expects.   Eventually  GNU  gprof  should  be  extended  to
	      process this data.

       -ax    Generate	extra  code  to  read basic block profiling parameters
	      from file `bb.in' and write profiling results to file  `bb.out'.
	      `bb.in' contains a list of functions. Whenever a function on the
	      list is entered, profiling is turned on. When the outmost  func-
	      tion  is	left,  profiling  is turned off. If a function name is
	      prefixed with `-' the function is excluded from profiling. If  a
	      function	name  is not unique it can be disambiguated by writing
	      `/path/filename.d:functionname'. `bb.out' will list some	avail-
	      able  filenames.	 Four  function  names have a special meaning:
	      `__bb_jumps__' will cause jump  frequencies  to  be  written  to
	      `bb.out'.   `__bb_trace__'  will	cause  the  sequence  of basic
	      blocks to be piped into `gzip' and written to file `bbtrace.gz'.
	      `__bb_hidecall__'  will  cause  call instructions to be excluded

       -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
	      `file.sched'.

       -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
	      `file.sched2'.

       -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.

       -fpretend-float
	      When running a cross-compiler, pretend that the  target  machine
	      uses  the  same floating point format as the host machine.  This
	      causes incorrect output of the actual  floating  constants,  but

       -print-file-name=library
	      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.

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

       -print-prog-name=program
	      Like `-print-file-name', but searches  for  a  program  such  as
	      `cpp'.

OPTIMIZATION OPTIONS

       These options control various sorts of optimizations:

       -O

       -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
	      time.

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

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

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

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

       -O0    Do not optimize.
       either removing `no-' or adding it.

       -ffloat-store
	      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.

       -fmemoize-lookups

       -fsave-memoized
	      Use  heuristics  to compile faster (C++ only).  These heuristics
	      are not enabled by default, since they are  only	effective  for
	      certain input files.  Other input files compile more slowly.

	      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.

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

       -fno-defer-pop
	      Always pop the arguments to each function call as soon  as  that
	      function returns.  For machines which must pop arguments after a
	      are  not	common	subexpressions, instruction combination should
	      eliminate the separate register-load.  I am interested in  hear-
	      ing about the difference this makes.

       -fforce-addr
	      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.

       -fomit-frame-pointer
	      Don't keep the frame pointer in a register  for  functions  that
	      don't  need  one.   This avoids the instructions to save, set up
	      and restore frame pointers; it  also  makes  an  extra  register
	      available in many functions.  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.

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

	      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.

       -fcaller-saves
	      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.

       -fkeep-inline-functions
	      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.

       -fno-function-cse
	      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.

       -fno-peephole
	      Disable any machine-specific peephole optimizations.
	      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-
       roll-all-loops'.

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

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

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

       -fthread-jumps
	      Perform  optimizations  where we check to see if a jump branches
	      to a location where another comparison subsumed by the first  is
	      found.  If so, the first branch is redirected to either the des-
	      tination of the second branch or a point	immediately  following
	      it,  depending  on  whether the condition is known to be true or
	      false.

       -funroll-loops
	      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.

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

       -fcse-follow-jumps
	      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.

       -fcse-skip-blocks
	      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.

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

       -felide-constructors
	      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:
	      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
	      omitted.

       -fexpensive-optimizations
	      Perform  a number of minor optimizations that are relatively ex-
	      pensive.

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

       -fschedule-insns
	      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.

       -fschedule-insns2
	      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.

TARGET OPTIONS

       By  default, GNU CC compiles code for the same type of machine that you
       are using.  However, it can also be installed as a  cross-compiler,  to
       compile	for  some  other  type of machine.  In fact, several different
       configurations of GNU CC, for different target  machines,  can  be  in-
       stalled	side by side.  Then you specify which one to use with the `-b'
       option.

       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-
	      compiler.

	      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.
       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:

       -m68000

       -mc68000
	      Generate output for a 68000.  This is the default when the  com-
	      piler is configured for 68000-based systems.

       -m68020

       -mc68020
	      Generate	output for a 68020 (rather than a 68000).  This is the
	      default when the compiler is configured for 68020-based systems.

       -m68881
	      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.

       -m68030
	      Generate	output for a 68030.  This is the default when the com-
	      piler is configured for 68030-based systems.

       -m68040
	      Generate output for a 68040.  This is the default when the  com-
	      piler is configured for 68040-based systems.

       -m68020-40
	      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
	      point.

       -msoft-float
	      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.

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

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

	      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-
	      format.

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

       -mfpu

       -mhard-float
	      Generate output containing floating point instructions.  This is
	      the default.

       -mno-fpu

       -msoft-float
	      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.

       -mno-epilogue

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

       -mv8

       -msparclite
	      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-
	      chitecture.

	      -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.

       -mcypress

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

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

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

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

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

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

       -margcount
	      Generate code which puts an argument count in the word preceding
	      each argument list.  Some nonportable Convex  and  Vax  programs
	      need  this  word.   (Debuggers  don't, except for functions with
	      variable-length argument lists; this info is in the  symbol  ta-
	      ble.)

       -mnoargcount
	      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.

       -msmall
	      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.

       -mlarge
	      Do not assume that the call instruction can be used; this is the
	      default.

       -m29050
	      Generate code for the Am29050.

       -m29000
	      Generate code for the Am29000.  This is the default.

       -mkernel-registers
	      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.

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

       -mstack-check
	      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:

       -m88000
	      Generate code that works well on both the m88100 and the m88110.

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

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

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

       -mno-underscores
	      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.

       -mno-check-zero-division

       -mocs-debug-info

       -mno-ocs-debug-info
	      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.

       -mocs-frame-position

       -mno-ocs-frame-position
	      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
	      `-mno-ocs-frame-position'.

       -moptimize-arg-area

       -mno-optimize-arg-area
	      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.

       -mshort-data-num
	      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.

       -mserialize-volatile

       -mno-serialize-volatile
	      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-
	      model.

	      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
	      consistency.

	      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
	      tency  when  running  on	the  m88110  processor, you should use
	      `-mserialize-volatile'.

       -msvr4

       -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
       configuration.

       -mtrap-large-shift

       -mhandle-large-shift
	      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.

       -muse-div-instruction
	      Very  early  models of the 88K architecture didn't have a divide
	      instruction, so GCC avoids that  instruction  by	default.   Use
	      this option to specify that it's safe to use the divide instruc-
	      tion.

       -mversion-03.00
	      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-
	      tion.

       -mwarn-passed-structs
	      Warn  when  a function passes a struct as an argument or result.
	      Structure-passing conventions have changed during the  evolution
	      of the C language, and are often the source of portability prob-
	      lems.  By default, GCC issues no such warning.

       These options are defined for the IBM RS6000:

       -mfp-in-toc

       -mno-fp-in-toc
	      Control whether or not floating-point constants go in the  Table
	      of  Contents  (TOC), a table of all global variable and function
	      addresses.  By default GCC puts floating-point constants	there;
	      if  the  TOC overflows, `-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:

       -min-line-mul
	      minimum amount of scratch space recommended by IBM.  This is the
	      default.

       -mminimum-fp-blocks
	      Do  not  include	extra  scratch	space  in  floating point data
	      blocks.  This results in smaller	code,  but  slower  execution,
	      since scratch space must be allocated dynamically.

       -mfp-arg-in-fpregs
	      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.

       -mfp-arg-in-gregs
	      Use the normal calling convention for floating point  arguments.
	      This is the default.

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

       -mnohc-struct-return
	      Return some structures of more than one word in registers,  when
	      convenient.   This  is  the default.  For compatibility with the
	      IBM-supplied  compilers,	use  either  `-fpcc-struct-return'  or
	      `-mhc-struct-return'.

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

       -mcpu=cpu-type
	      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
	      -mips2.

       -mint64

       -mlong64

       -mlonglong128
	      These options don't work at present.

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

       -mrnames

       -mno-rnames
	      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.

       -mgpopt

       -mno-gpopt
	      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.

       -mstats

       -mno-stats
	      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.).

       -mmemcpy

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

       -mmips-tfile

       -mno-mips-tfile
	      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.

       -msoft-float
	      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.

       -mhard-float
	      Generate output containing floating point instructions.  This is
	      is the default.

       -mabicalls

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

       -mhalf-pic

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

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

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

       -m486

       -mno-486
	      Control whether or not code is optimized for a 486 instead of an
	      386.  Code generated for a 486 will run on a 386 and vice versa.

       -mpentium
	      Synonym for -mcpu=pentium

       -mpentiumpro
	      Synonym for -mcpu=pentiumpro

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

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

       -msoft-float
	      Generate	output	containing  library  calls for floating point.
	      emitted even if `-msoft-float' is used.

       -mno-fp-ret-in-387
	      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
	      FPU.

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

       -mprofiler-epilogue

       -mno-profiler-epilogue
	      Generate extra code to write profile  information  for  function
	      exits.

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

       -mpa-risc-1-0
	      Generate code for a PA 1.0 processor.

       -mpa-risc-1-1
	      Generate code for a PA 1.1 processor.

       -mkernel
	      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.

       -mshared-libs
	      Generate code that can be linked against HP-UX shared libraries.
	      This  option is not fully function yet, and is not on by default
	      for any PA target.  Using this option can cause  incorrect  code
	      to be generated by the compiler.

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

       -mlong-calls
	      Generate code which allows calls to functions greater than  256K
	      away  from the caller when the caller and callee are in the same
	      source file.  Do not turn this option on unless code refuses  to
	      link with "branch out of range errors from the linker.

       -mdisable-fpregs
	      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.

       -mdisable-indexing
	      Prevent  the  compiler  from using indexing address modes.  This

       -mcpu-type
	      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
	      sb.

       -mnumerics

       -msoft-float
	      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.

       -mleaf-procedures

       -mno-leaf-procedures
	      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.

       -mtail-call

       -mno-tail-call
	      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.

       -mcomplex-addr

       -mno-complex-addr
	      Assume  (or  do not assume) that the use of a complex addressing
	      mode is a win on this implementation of the i960.   Complex  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.

       -mcode-align

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

       -mic-compat

       -mic2.0-compat

       -mic3.0-compat
	      Enable compatibility with iC960 v2.0 or v3.0.

       -masm-compat

       -mold-align
	      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:

       -mno-soft-float

       -msoft-float
	      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.

       -mfp-reg

       -mno-fp-regs
	      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
	      registers.

       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
	      line.

       -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).

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

       -fnonnull-objects
	      Assume that objects reached through references are not null (C++
	      only).

	      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.

       -fpcc-struct-return
	      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.

       -freg-struct-return
	      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.

       -fshort-enums
	      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
	      room.

       -fshort-double
	      Use the same size for double as for float .

       -fshared-data
	      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.

       -fno-common
       -fno-ident
	      Ignore the `#ident' directive.

       -fno-gnu-linker
	      Do not output global initializations (such as  C++  constructors
	      and  destructors) in the form used by the GNU linker (on systems
	      where the GNU linker is the standard method of  handling	them).
	      Use this option when you want to use a non-GNU linker, which 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-
	      matically.

       -finhibit-size-directive
	      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.

       -fverbose-asm
	      Put extra commentary information in the generated assembly  code
	      to  make it more readable.  This option is generally only of use
	      to those who actually need to read the generated	assembly  code
	      (perhaps while debugging the compiler itself).

       -fvolatile
	      Consider	all memory references through pointers to be volatile.

       -fvolatile-global
	      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
	      displacements.

       -ffixed-reg
	      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.

       -fcall-used-reg
	      Treat  the  register  named reg as an allocable register that is
	      clobbered by function calls.  It may  be	allocated  for	tempo-
	      raries  or  variables that do not live across a call.  Functions
	      compiled this way will not save and restore the register reg.
       -fcall-saved-reg
	      Treat  the  register named reg as an allocable register saved by
	      functions.  It may be allocated even for	temporaries  or  vari-
	      ables that live across a call.  Functions compiled this way will
	      save and restore the register reg if they use it.

	      Use of this flag for a register that has a fixed pervasive  role
	      in  the  machine's execution model, such as the stack pointer or
	      frame pointer, will produce disastrous results.

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

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

PRAGMAS

       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
	      files.

	      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 `allclass.cc', `#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.

FILES

       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
       intro(3)
       /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).

SEE ALSO

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

BUGS

       For instructions on reporting bugs, see the GCC manual.

COPYING

       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.

AUTHORS

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

GNU Tools			  1998/12/16				GCC(1)

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