


 GCC(1)                           GNU Tools                           GCC(1)
 GNU Tools                                                         GNU Tools

                                 1997/12/03



 NAME
      gcc, g++ - GNU project C and C++ Compiler (v2.7)

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

 WARNING
      The information in this man page is an extract from the full
      documentation of the GNU C compiler, and is limited to the meaning of
      the options.

      This man page is not kept up to date except when volunteers want to
      maintain it.  If you find a discrepancy between the man page and the
      software, please check the Info file, which is the authoritative
      documentation.

      If we find that the things in this man page that are out of date cause
      significant confusion or complaints, we will stop distributing the man
      page.  The alternative, updating the man page when we update the Info
      file, is impossible because the rest of the work of maintaining GNU CC
      leaves us no time for that.  The GNU project regards man pages as
      obsolete and should not let them take time away from other things.

      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,
      assembly, and linking.  Source filename suffixes identify the source
      language, but which name you use for the compiler governs default
      assumptions:

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

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

      Suffixes of source file names indicate the language and kind of
      processing 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



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

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

      .o    Object file
      .a    Archive file

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

 OPTIONS
      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 -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



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           -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

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

      Assembler Option
           -Wa,option

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

      Directory Options
           -Bprefix -Idir -I- -Ldir

      Target Options
           -b  machine -V version

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

           VAX Options
           -mg -mgnu -munix

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

           Convex Options



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                                 1997/12/03



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

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

           i960 Options
           -mcpu-type -mnumerics -msoft-float -mleaf-procedures
           -mno-leaf-procedures -mtail-call -mno-tail-call -mcomplex-addr
           -mno-complex-addr -mcode-align -mno-code-align -mic-compat
           -mic2.0-compat -mic3.0-compat -masm-compat -mintel-asm
           -mstrict-align -mno-strict-align -mold-align -mno-old-align

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




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           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

 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', `objective-c',
           `c-header',     `c++',     `cpp-output',     `assembler',     and
           `assembler-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 input
           file specified.

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

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



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      -E   Stop after the preprocessing stage; do not run the compiler prop-
           er.  The output is preprocessed source code, which is sent to the
           standard output.

           GCC ignores input files which don't require preprocessing.

      -o file
           Place output in file file.  This applies regardless  to  whatever
           sort  of  output  GCC  is  producing, whether it be an executable
           file, an object file, an assembler file or preprocessed C code.

           Since only one output file can be specified,  it  does  not  make
           sense to use `-o' when compiling more than one input file, unless
           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 com-
           piler 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 identif-
           iers.

           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



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           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 reject-
           ed  gratuitously.   For that, `-pedantic' is required in addition
           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 mac-
           ros that the ANSI standard doesn't call for; this is to avoid in-
           terfering with any programs that might use these names for  other
           things.

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

      -fno-builtin
           Don't recognize built-in functions that do  not  begin  with  two
           leading  underscores.   Currently, the functions affected include
           _exit, abort, abs, alloca, cos, exit, fabs, labs, memcmp, memcpy,
           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



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           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 permitted.
           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++
           only).   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 implementation'
           (the definition) or `#pragma interface' (declarations).

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

      -fall-virtual
           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



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           calls are direct in any case.

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

      -fthis-is-variable
           Permit assignment to  this  (C++  only).   The  incorporation  of
           user-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
           machines 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.
           By default, such a bitfield  is  signed,  because  this  is  con-



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           sistent: the basic integer types such as int are signed types.

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

      -fwritable-strings
           Store string constants in the writable  data  segment  and  don't
           uniquize them.  This is for compatibility with old programs which
           assume they can write into string constants.  `-traditional' 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 in-
           put.  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  `-imac-
           ros'  options  are processed in the order in which they are writ-
           ten.

      -idirafter dir
           Add the directory dir to the second  include  path.   The  direc-
           tories 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-



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           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 speci-
           fied 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.

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

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

      -E   Run only the C preprocessor.  Preprocess all the C  source  files
           specified  and  output  the  results to standard output or to the
           specified output file.

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

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

      -M  [ -MG ]
           Tell the preprocessor to output a rule suitable for make describ-
           ing  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  pro-
           gram.

           `-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



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           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
           #question(answer)'.  `-A-' disables the standard assertions  that
           normally describe the target machine.

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

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

      -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.



                                   - 12 -            Formatted:  May 4, 1999






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                                 1997/12/03



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

      -dN  Like `-dD' except that the macro arguments and contents are omit-
           ted.  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 linker
           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 archive
           file by scanning through it for members which define symbols that
           have  so  far  been  referenced but not defined.  However, if the
           linker finds an ordinary object file rather than a  library,  the
           object  file is linked in the usual fashion.  The only difference
           between using an `-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



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                                 1997/12/03



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

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

      -static
           On systems that support dynamic linking,  this  prevents  linking
           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 op-
           tion.

      -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 sys-
           tems support this option.

      -Xlinker option
           Pass option as an option to the linker.  You can use this to sup-
           ply 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:



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                                 1997/12/03



      -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'
           directives.  (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 over-
           ride  this effect of `-I-'.  With `-I.' you can specify searching
           the directory which was current when the  compiler  was  invoked.
           That is not exactly the same as what the preprocessor does by de-
           fault, but it is often satisfactory.

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

      -Ldir
           Add directory dir to the list of directories to be  searched  for
           `-l'.

      -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 directories
           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 necessary.



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                                 1997/12/03



           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_PREFIX
           variable  are  present, the `-B' option is used first and the en-
           vironment 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; reject
           all programs that use forbidden extensions.

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

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

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

      -W   Print extra warning messages for these events:

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




                                   - 16 -            Formatted:  May 4, 1999






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                                 1997/12/03



           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 problem.

         + A function can return either with or without a  value.   (Falling
           off  the end of the function body is considered returning without
           a value.)  For example, this function would evoke such a warning:

           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.

         + 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.

         + 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
           return-value in a function whose return-type is not void.

      -Wunused
           Warn whenever a local variable is unused aside from its  declara-



                                   - 17 -            Formatted:  May 4, 1999






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                                 1997/12/03



           tion,  whenever  a function is declared static but never defined,
           and whenever a statement computes a result that is explicitly not
           used.

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

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

      -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 variable
           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  regis-
           ters.

           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



                                   - 18 -            Formatted:  May 4, 1999






 GCC(1)                           GNU Tools                           GCC(1)
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                                 1997/12/03



           enough  to  see  all  the  reasons  why the code might be correct
           despite appearing to have an error.  Here is one example  of  how
           this can happen:

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

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

           {
             int save_y;
             if (change_y) save_y = y, y = new_y;
             ...
             if (change_y) y = save_y;
           }

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

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

      -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



                                   - 19 -            Formatted:  May 4, 1999






 GCC(1)                           GNU Tools                           GCC(1)
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                                 1997/12/03



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

         + 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.

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

         + 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 conveni-
           ence in calculations with void * pointers and pointers  to  func-
           tions.

      -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 *.

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

      -Wwrite-strings
           Give string constants the type const char[length] so that copying
           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 pro-
           totypes.   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



                                   - 20 -            Formatted:  May 4, 1999






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                                 1997/12/03



           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 prototype
           declaration.   This  warning is issued even if the definition it-
           self provides a prototype.  The aim is to detect global functions
           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 an function.

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

      -Woverloaded-virtual
           (C++ only.) In a derived class, the definitions of virtual  func-
           tions  must  match  the  type signature of a virtual function de-
           clared in the base class.  Use this option  to  request  warnings
           when a derived class declares a function that may be an erroneous
           attempt to define a virtual function: that is, warn when a  func-
           tion  with the same name as a virtual function in the base class,
           but with a type signature that doesn't match  any  virtual  func-
           tions from the base class.



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                                 1997/12/03



      -Winline
           Warn if a function can not be inlined, and either it was declared
           as inline, or else the -finline-functions option was given.

      -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 information,
           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 occasionally
           produce surprising results: some variables you declared  may  not
           exist  at all; flow of control may briefly move where you did not
           expect it; some statements may not be executed because they  com-
           pute  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+



                                   - 22 -            Formatted:  May 4, 1999






 GCC(1)                           GNU Tools                           GCC(1)
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                                 1997/12/03



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

      -gcoff
           Produce debugging information in COFF format (if that is support-
           ed).   This  is  the  format used by SDB on most System V systems
           prior to System V Release 4.

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

      -gxcoff+
           Produce debugging information in XCOFF format (if  that  is  sup-
           ported), using GNU extensions understood only by the GNU debugger
           (GDB).  The use of these extensions is likely to make  other  de-
           buggers 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 Release
           4 systems.

      -gdwarf+
           Produce debugging information in DWARF format (if  that  is  sup-
           ported), using GNU extensions understood only by the GNU debugger
           (GDB).  The use of these extensions is likely to make  other  de-
           buggers 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 defini-
           tions  present  in the program.  Some debuggers support macro ex-
           pansion when you use `-g3'.



                                   - 23 -            Formatted:  May 4, 1999






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                                 1997/12/03



      -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 ex-
           pects.  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 pre-
           fixed  with  `-'  the  function  is excluded from profiling. If a
           function name is not unique it can be  disambiguated  by  writing
           `/path/filename.d:functionname'.  `bb.out'  will list some avail-
           able filenames.  Four function  names  have  a  special  meaning:
           `__bb_jumps__'  will  cause  jump  frequencies  to  be written to
           `bb.out'.  `__bb_trace__' will cause the sequence of basic blocks
           to  be  piped  into  `gzip'  and  written  to  file `bbtrace.gz'.
           `__bb_hidecall__' will cause call  instructions  to  be  excluded
           from  the trace.  `__bb_showret__' will cause return instructions
           to be included in the trace.

      -dletters
           Says to make debugging dumps during compilation at  times  speci-
           fied  by  letters.  This is used for debugging the compiler.  The
           file names for most of the dumps are made by appending a word  to
           the source file name (e.g.  `foo.c.rtl' or `foo.c.jump').

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

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

      -dD  Dump all macro definitions, at the end of preprocessing, in addi-
           tion 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.  Usual-
           ly used with `r'.



                                   - 24 -            Formatted:  May 4, 1999






 GCC(1)                           GNU Tools                           GCC(1)
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                                 1997/12/03



      -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 stan-
           dard 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 the
           actual  instruction  sequence will probably be the same as GNU CC
           would make when running on the target machine.

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



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           duce files `foo.cpp' and `foo.s', as well as `foo.o'.

      -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 compi-
           lation  and  to  make  debugging  produce  the  expected results.
           Statements are independent: if you stop the program with a break-
           point  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 unrolling
           and function inlining are not done, for example.  As compared  to
           -O,  this  option increases both compilation time and the perfor-



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           mance of the generated code.

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

      -O0  Do not optimize.

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

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

      -ffloat-store
           Do  not  store  floating  point  variables  in  registers.   This
           prevents  undesirable  excess  precision  on machines such as the
           68000 where the floating registers (of the 68881) keep more  pre-
           cision 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, us-
           ing the cache introduces another layer of mechanisms  which  must



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           be    implemented,    and    so    incurs   its   own   overhead.
           `-fmemoize-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 func-
           tion  to  compile,  it preserves the cache.  This is most helpful
           when defining many member functions for the same class: with  the
           exception of member functions which are friends of other classes,
           each member function has exactly the same  access  privileges  as
           every other, and the cache need not be flushed.

      -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
           function call, the compiler normally lets arguments accumulate on
           the stack for several function calls and pops them all at once.

      -fforce-mem
           Force memory operands to be copied into  registers  before  doing
           arithmetic  on  them.  This may produce better code by making all
           memory references potential common subexpressions.  When they are
           not  common  subexpressions, instruction combination should elim-
           inate the separate register-load.  I  am  interested  in  hearing
           about the difference this makes.

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

           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-



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           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 function
           is  declared  static, then GCC normally does not output the func-
           tion as assembler code in its own right.

      -fcaller-saves
           Enable values to be allocated in registers that will be clobbered
           by function calls, by emitting extra instructions to save and re-
           store the registers around such calls.  Such allocation  is  done
           only  when it seems to result in better code than would otherwise
           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 instruction
           that calls a constant function contain the function's address ex-
           plicitly.

           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.

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

           This option should never be turned on by any `-O' option since it
           can  result  in  incorrect output for programs which depend on an
           exact implementation of IEEE  or  ANSI  rules/specifications  for
           math functions.



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

      The  `-O'  option  usually   turns   on   the   `-fthread-jumps'   and
      `-fdelayed-branch'  options,  but specific machines may change the de-
      fault optimizations.

      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 elimina-
           tion 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 compile
           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 follow
           jumps  which conditionally skip over blocks.  When CSE encounters
           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.




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      -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:

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

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

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




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

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

 MACHINE DEPENDENT OPTIONS
      Each of the target machine types can have  its  own  special  options,
      starting  with  `-m',  to  choose  among  various  hardware  models or
      configurations-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
      options,  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



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           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.  Normal-
           ly 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-
           bitfield'.

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

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



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           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); otherwise
           incorrect code will be generated for calls to those functions.

           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;



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           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 exit in
           the middle of the function (such as a return statement in C) will
           generate a jump to the exit code at the end of the function.

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

      -mno-v8

      -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 archi-
           tecture.

           -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-
           timised.

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

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

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



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      -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
           table.)

      -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.

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

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

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

      -msmall
           Use a small memory model that assumes that all function addresses
           are  either  within a single 256 KB segment or at an absolute ad-
           dress 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.




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      -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

      -mcheck-zero-division
           Early models of the 88K architecture had problems  with  division
           by  zero; in particular, many of them didn't trap.  Use these op-
           tions to avoid including (or to  include  explicitly)  additional
           code to detect division by zero and signal an exception.  All GCC
           configurations for the 88K  use  `-mcheck-zero-division'  by  de-
           fault.



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      -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 need-
           ed  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-position'; 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.
           `-moptimize-arg-area'  saves  space, but may break some debuggers
           (not GDB).  `-mno-optimize-arg-area'  conforms  better  to  stan-
           dards.   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 affected
           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



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           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 before
           a  preceding store instruction.  Such reordering violates sequen-
           tial 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  execu-
           tion in the proper order.

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

           If you use the `-m88100' option but require sequential consisten-
           cy   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:

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

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

         + `-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 instruction.




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      -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
           real-ELF flavor is used.  All other  configurations  ignore  this
           option.

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

      -mcall-lib-mul
           Call lmul$$ for integer multiples.

      -mfull-fp-blocks
           Generate full-size floating  point  data  blocks,  including  the
           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



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           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 compatibility  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 scheduling
           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 architec-
           ture) 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.

      -mmips-as
           Generate code for the MIPS assembler, and  invoke  mips-tfile  to
           add  normal debug information.  This is the default for all plat-
           forms except for the OSF/1 reference platform, using the OSF/rose



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           object  format.   If  any  of  the  -ggdb,  -gstabs,  or -gstabs+
           switches are used, the mips-tfile program  will  encapsulate  the
           stabs within MIPS ECOFF.

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

      -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 be-
           fore the instructions in the text section, to all the MIPS assem-
           bler to generate one word memory references instead of using  two
           words  for  short global or static data items.  This is on by de-
           fault if optimization is selected.

      -mstats

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

      -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 de-



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           bugger.  In addition, stage2 and stage3  objects  will  have  the
           temporary  file names passed to the assembler embedded in the ob-
           ject 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.  Normal-
           ly 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
           the default if you use the unmodified sources.

      -mfp64
           Assume that the FR bit in the status word is on, and  that  there
           are  32  64-bit  floating  point  registers, instead of 32 32-bit
           floating point registers.  You must also specify the  -mcpu=r4000
           and -mips3 switches.

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

      -mabicalls

      -mno-abicalls
           Emit (or do not emit)  the  .abicalls,  .cpload,  and  .cprestore
           pseudo operations that some System V.4 ports use for position in-
           dependent 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
           references 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 nor-
           mal  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  as-
           sembler  is  used.  The -Gnum switch is also passed to the assem-
           bler and linker.  All modules should be compiled  with  the  same
           -Gnum value.




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

      These `-m' options are defined for the Intel 80386 family  of  comput-
      ers: -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.

      -msoft-float
           Generate output containing  library  calls  for  floating  point.
           Warning: the requisite libraries are not part of GNU CC.  Normal-
           ly the facilities of the machine's usual C compiler are used, but
           this  can't be done directly in cross-compilation.  You must make
           your own arrangements to provide suitable library  functions  for
           cross-compilation.

           On machines where a function returns floating  point  results  in
           the  80387 register stack, some floating point opcodes may be em-
           itted 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 returned
           in ordinary CPU registers instead.

      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.



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           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 libraries.
           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
           avoids  some rather obscure problems when compiling MIG generated
           code under MACH.

      -mtrailing-colon
           Add a colon to the end of label definitions (for ELF assemblers).

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

      -mcpu-type
           Assume the defaults for the machine type cpu-type for instruction
           and  addressing-mode  availability  and  alignment.   The default
           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



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           more efficient code for explicit calls when the  bal  instruction
           can be substituted by the assembler or linker, but less efficient
           code in other cases, such as calls via function pointers, or  us-
           ing a linker that doesn't support this optimization.

      -mtail-call

      -mno-tail-call
           Do (or do not) make additional  attempts  (beyond  those  of  the
           machine-independent  portions  of the compiler) to optimize tail-
           recursive calls into branches.  You may not want to do  this  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
           -mcomplex-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 implementa-
           tions only.

      -mic-compat

      -mic2.0-compat

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

      -masm-compat

      -mintel-asm
           Enable compatibility with the iC960 assembler.

      -mstrict-align

      -mno-strict-align
           Do not permit (do permit) unaligned accesses.

      -mold-align
           Enable structure-alignment compatibility with Intel's gcc release



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           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, func-
           tions 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
           floating-point operations.   If you are compiling  for  an  Alpha
           without  floating-point  operations, you must ensure that the li-
           brary is built so as not to call them.

           Note that Alpha implementations without floating-point operations
           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
           floating-point results are passed in $0 instead of $f0.  This  is
           a   non-standard   calling  sequence,  so  any  function  with  a
           floating-point argument or return value called by  code  compiled
           with -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 re-
           gisters.

      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.  How-
           ever, we suggest you use `-symbolic' or `-shared' as appropriate,
           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.




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      -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
           one another with colons.

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

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

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

      -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
           machines  it  fails  to be reentrant; but it has the advantage of
           allowing intercallability  between  GCC-compiled  code  and  PCC-
           compiled code.

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



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           If    you     specify     neither     -fpcc-struct-return     nor
           -freg-struct-return,  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
           private data exists in one copy per process.

      -fno-common
           Allocate even uninitialized global variables in the  bss  section
           of the object file, rather than generating them as common blocks.
           This has the  effect  that  if  the  same  variable  is  declared
           (without  extern)  in two different compilations, you will get an
           error when you link them.  The only reason this might  be  useful
           is if you wish to verify that the program will work on other sys-
           tems which always work this way.

      -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 also
           requires using the collect2 program to make sure the system link-
           er  includes constructors and destructors.  (collect2 is included
           in the GNU CC distribution.)  For systems  which  must  use  col-
           lect2, the compiler driver gcc is configured to do this automati-
           cally.

      -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



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           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-
           independent 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 temporaries
           or variables that do not live across a call.  Functions  compiled
           this way will not save and restore the register reg.

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

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




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      -fcall-saved-reg
           Treat the register named reg as an allocable  register  saved  by
           functions.  It may be allocated even for temporaries or variables
           that live across a call.  Functions compiled this way  will  save
           and restore the register 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 object
           classes, to save space in most of the object files that use those
           classes.  Normally, local copies of certain  information  (backup
           copies of inline member functions, debugging information, and the
           internal tables that implement virtual functions) must be kept in
           each  object  file  that includes class definitions.  You can use
           this pragma to avoid such duplication.  When a header  file  con-
           taining  `#pragma  interface'  is included in a compilation, this
           auxiliary information will not be generated (unless the main  in-
           put  source file itself uses `#pragma implementation').  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 functions,
           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 itself



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           is  equivalent to `#pragma implementation "allclass.h"'.  Use the
           string argument if you want a single implementation file  to  in-
           clude 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.c             C source file
      file.h             C header (preprocessor) file
      file.i             preprocessed C source file
      file.C             C++ source file
      file.cc            C++ source file
      file.cxx           C++ source file
      file.m             Objective-C source file
      file.s             assembly language file
      file.o             object file
      a.out              link edited output
      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
      cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1).
      `gcc', `cpp', `as', `ld', and `gdb' entries in info.
      Using and Porting GNU CC (for version 2.0), Richard M. Stallman; The C
      Preprocessor ,  Richard  M.  Stallman;  Debugging  with  GDB:  the GNU
      Source-Level Debugger, Richard M. Stallman and Roland H. Pesch;  Using
      as:  the  GNU  Assembler, Dean Elsner, Jay Fenlason & friends; ld: the
      GNU linker, Steve Chamberlain and Roland Pesch.

 BUGS
      For instructions on reporting bugs, see the GCC manual.

 COPYING



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                                 1997/12/03



      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
      entire resulting derived work is distributed under the terms of a per-
      mission notice identical to this one.

      Permission is granted to copy  and  distribute  translations  of  this
      manual  into another language, under the above conditions for modified
      versions, except that this permission notice may be included in trans-
      lations  approved  by  the  Free Software Foundation instead of in the
      original English.

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

































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