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gcc (1)
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  • Ключ gcc обнаружен в базе ключевых слов.
         gcc, g++ - GNU project C and C++ Compiler (gcc-2.95)
         gcc [ option | filename ]...
         g++ [ option | filename ]...
         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         If we find that the things in this man page that are out  of
         date cause significant confusion or complaints, we will stop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 ver-
         sion 2.0).  Both are  made  from  the  Texinfo  source  file
         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  suf-
         fixes  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
         .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, unrecog-
         nized filenames (including named  .o  object  files  and  .a
         archives) are passed to the linker in command-line order.
         Options must be separate: `-dr' is quite different from  `-d
         -r '.
         Most `-f' and `-W' options have two contrary forms:   -fname
         and  -fno-name  (or  -Wname  and  -Wno-name).  Only the non-
         default forms are shown here.
         Here is a summary of  all  the  options,  grouped  by  type.
         Explanations are in the following sections.
         Overall Options
              -c -S -E -o file -pipe -v -x language
         Language Options
              -ansi -fall-virtual -fcond-mismatch
              -fdollars-in-identifiers -fenum-int-equiv
              -fexternal-templates -fno-asm -fno-builtin -fhosted
              -fno-hosted -ffreestanding -fno-freestanding
              -fno-strict-prototype -fsigned-bitfields -fsigned-char
              -fthis-is-variable -funsigned-bitfields -funsigned-char
              -fwritable-strings -traditional -traditional-cpp
         Warning Options
              -fsyntax-only -pedantic -pedantic-errors -w -W -Wall
              -Waggregate-return -Wcast-align -Wcast-qual
              -Wchar-subscript -Wcomment -Wconversion -Wenum-clash
              -Werror -Wformat -Wid-clash-len -Wimplicit
              -Wimplicit-int -Wimplicit-function-declaration -Winline
              -Wlong-long -Wmain -Wmissing-prototypes
              -Wmissing-declarations -Wnested-externs -Wno-import
              -Wparentheses -Wpointer-arith -Wredundant-decls
              -Wreturn-type -Wshadow -Wstrict-prototypes -Wswitch
              -Wtemplate-debugging -Wtraditional -Wtrigraphs
              -Wuninitialized -Wunused -Wwrite-strings
         Debugging Options
              -a -dletters -fpretend-float -g -glevel -gcoff -gxcoff
              -gxcoff+ -gdwarf -gdwarf+ -gstabs -gstabs+ -ggdb -p -pg
              -save-temps -print-file-name=library
              -print-libgcc-file-name -print-prog-name=program
         Optimization Options
              -fcaller-saves -fcse-follow-jumps -fcse-skip-blocks
              -fdelayed-branch -felide-constructors
              -fexpensive-optimizations -ffast-math -ffloat-store
              -fforce-addr -fforce-mem -finline-functions
              -fkeep-inline-functions -fmemoize-lookups
              -fno-default-inline -fno-defer-pop -fno-function-cse
              -fno-inline -fno-peephole -fomit-frame-pointer
              -frerun-cse-after-loop -fschedule-insns
              -fschedule-insns2 -fstrength-reduce -fthread-jumps
              -funroll-all-loops -funroll-loops -O -O2 -O3
         Preprocessor Options
              -Aassertion -C -dD -dM -dN -Dmacro[=defn] -E -H
              -idirafter dir -include file -imacros file -iprefix
              file -iwithprefix dir -M -MD -MM -MMD -nostdinc -P
              -Umacro -undef
         Assembler Option
         Linker Options
              -llibrary -nostartfiles -nostdlib -static -shared
              -symbolic -Xlinker option -Wl,option -u symbol
         Directory Options
              -Bprefix -Idir -I- -Ldir
         Target Options
              -b  machine -V version
         Configuration Dependent Options
              M680x0 Options
              -m68000 -m68020 -m68020-40 -m68030 -m68040 -m68881
              -mbitfield -mc68000 -mc68020 -mfpa -mnobitfield -mrtd
              -mshort -msoft-float
              VAX Options
              -mg -mgnu -munix
              SPARC Options
              -mepilogue -mfpu -mhard-float -mno-fpu -mno-epilogue
              -msoft-float -msparclite -mv8 -msupersparc -mcypress
              Convex Options
              -margcount -mc1 -mc2 -mnoargcount
              AMD29K Options
              -m29000 -m29050 -mbw -mdw -mkernel-registers -mlarge
              -mnbw -mnodw -msmall -mstack-check -muser-registers
              M88K Options
              -m88000 -m88100 -m88110 -mbig-pic -mcheck-zero-division
              -mhandle-large-shift -midentify-revision
              -mno-check-zero-division -mno-ocs-debug-info
              -mno-ocs-frame-position -mno-optimize-arg-area
              -mno-serialize-volatile -mno-underscores
              -mocs-debug-info -mocs-frame-position
              -moptimize-arg-area -mserialize-volatile
              -mshort-data-num -msvr3 -msvr4 -mtrap-large-shift
              -muse-div-instruction -mversion-03.00
              RS6000 Options
              -mfp-in-toc -mno-fop-in-toc
              RT Options
              -mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs
              -mfull-fp-blocks -mhc-struct-return -min-line-mul
              -mminimum-fp-blocks -mnohc-struct-return
              MIPS Options
              -mcpu=cpu type -mips2 -mips3 -mint64 -mlong64
              -mlonglong128 -mmips-as -mgas -mrnames -mno-rnames
              -mgpopt -mno-gpopt -mstats -mno-stats -mmemcpy
              -mno-memcpy -mno-mips-tfile -mmips-tfile -msoft-float
              -mhard-float -mabicalls -mno-abicalls -mhalf-pic
              -mno-half-pic -G num -nocpp
              i386 Options
              -m486 -mno-486 -msoft-float -mno-fp-ret-in-387
              HPPA Options
              -mpa-risc-1-0 -mpa-risc-1-1 -mkernel -mshared-libs
              -mno-shared-libs -mlong-calls -mdisable-fpregs
              -mdisable-indexing -mtrailing-colon
              i960 Options
              -mcpu-type -mnumerics -msoft-float -mleaf-procedures
              -mno-leaf-procedures -mtail-call -mno-tail-call
              -mcomplex-addr -mno-complex-addr -mcode-align
              -mno-code-align -mic-compat -mic2.0-compat
              -mic3.0-compat -masm-compat -mintel-asm -mstrict-align
              -mno-strict-align -mold-align -mno-old-align
              DEC Alpha Options
              -mfp-regs -mno-fp-regs -mno-soft-float -msoft-float
              System V Options
              -G -Qy -Qn -YP,paths -Ym,dir
         Code Generation Options
              -fcall-saved-reg -fcall-used-reg -ffixed-reg
              -finhibit-size-directive -fnonnull-objects -fno-common
              -fno-ident -fno-gnu-linker -fpcc-struct-return -fpic
              -fPIC -freg-struct-return -fshared-data -fshort-enums
              -fshort-double -fvolatile -fvolatile-global
         -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
         -x none
              Turn off any specification of a language, so that  sub-
              sequent  files are handled according to their file name
              suffixes (as they are if `-x'  has  not  been  used  at
         If you want only some of the four stages  (preprocess,  com-
         pile,  assemble,  link),  you can use `-x' (or filename suf-
         fixes) 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  compiler 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  require  compilation  or assembly) with the -c op-
         -S   Stop after the stage of compilation proper; do not  as-
              semble.   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 compila-
         -E   Stop after the preprocessing stage; do not run the com-
              piler  proper.  The output is preprocessed source code,
              which is sent to the standard output.
              GCC ignores input files which don't require preprocess-
         -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 preprocessed C source on standard
         -v   Print (on standard error output) the commands  executed
              to  run the stages of compilation.  Also print the ver-
              sion number of the compiler driver program and  of  the
              preprocessor and the compiler proper.
              Use pipes rather than temporary files for communication
              between  the various stages of compilation.  This fails
              to work on some systems where the assembler cannot read
              from a pipe; but the GNU assembler has no trouble.
         The following options control the dialect of C that the com-
         piler accepts:
              Support all ANSI standard C programs.
              This turns off certain features of GNU C that  are  in-
              compatible  with  ANSI  C,  such as the asm, inline and
              typeof keywords, and predefined macros such as unix and
              that identify the type of system  you  are  using.   It
              also  enables the undesirable and rarely used ANSI tri-
              graph feature, and disallows `$' as  part  of  identif-
              The alternate keywords  __asm__,  __extension__,  __in-
              line__ and __typeof__ continue to work despite `-ansi'.
              You would not want to use them in an ANSI C program, of
              course,  but  it  is useful to put them in header files
              that  might  be  included  in  compilations  done  with
              `-ansi'.   Alternate predefined macros such as __unix__
              and  __vax__  are  also  available,  with  or   without
              The `-ansi' option does not cause non-ANSI programs  to
              be rejected gratuitously.  For that, `-pedantic' is re-
              quired 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  macros  that the ANSI
              standard doesn't call for; this is to avoid interfering
              with  any programs that might use these names for other
              Do not recognize asm, inline or typeof  as  a  keyword.
              These  words  may then be used as identifiers.  You can
              use  __asm__,  __inline__   and   __typeof__   instead.
              `-ansi' implies `-fno-asm'.
              Don't recognize built-in functions that  do  not  begin
              with two leading underscores.  Currently, the functions
              affected include _exit, abort, abs, alloca, cos,  exit,
              fabs,  labs, memcmp, memcpy, sin, sqrt, strcmp, strcpy,
              and strlen.
              The `-ansi' option prevents alloca and _exit from being
              builtin functions.
              Compile for a  hosted  environment;  this  implies  the
              `-fbuiltin'  option,  and  implies  that suspicious de-
              clarations of main should be warned about.
              Compile for a freestanding  environment;  this  implies
              the `-fno-builtin' option, and implies that main has no
              special requirements.
              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 declaration in C++ means that
              the function foo takes no arguments.
              Support ANSI C trigraphs.  The `-ansi'  option  implies
              Attempt to support some aspects of traditional  C  com-
              pilers.   For details, see the GNU C Manual; the dupli-
              cate 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).  `-tradi-
              tional'  has  one additional effect for C++: assignment
              to this is permitted.  This is the same as  the  effect
              of `-fthis-is-variable'.
              Attempt  to  support  some  aspects  of  traditional  C
              preprocessors.   This  includes the items that specifi-
              cally mention the preprocessor above, but none  of  the
              other effects of `-traditional'.
              Permit the use of `$' in identifiers (C++  only).   You
              can also use `-fno-dollars-in-identifiers' to explicit-
              ly prohibit use of `$'.  (GNU C++ allows `$' by default
              on some target systems but not others.)
              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.
              Produce smaller code for template declarations, by gen-
              erating  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 de-
              finition) or `#pragma interface' (declarations).
              When your code is compiled with `-fexternal-templates',
              all template instantiations are external.  You must ar-
              range 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 explicitly internal.
              Treat all possible member functions as virtual,  impli-
              citly.   All  member  functions (except for constructor
              functions and  new  or  delete  member  operators)  are
              treated  as  virtual  functions of the class where they
              This does not mean that all calls to these member func-
              tions will be made through the internal table of virtu-
              al functions.  Under some circumstances,  the  compiler
              can  determine  that a call to a given virtual function
              can be made directly; in  these  cases  the  calls  are
              direct in any case.
              Allow conditional expressions with mismatched types  in
              the  second  and third arguments.  The value of such an
              expression is void.
              Permit assignment to this (C++ only).   The  incorpora-
              tion 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 compati-
              bility,   you   can  make  it  valid  with  `-fthis-is-
              Let the type char be unsigned, like unsigned char.
              Each kind of machine has a default for what char should
              be.  It is either like unsigned char by default or like
              signed char by default.
              Ideally, a portable program should  always  use  signed
              char or unsigned 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.
              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'.  Like-
              wise,    `-fno-signed-char'    is     equivalent     to
              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 consistent: the basic integer
              types such as int are signed types.
              However, when you specify `-traditional', bitfields are
              all unsigned no matter what.
              Store string constants in the writable data segment and
              don't  uniquize  them.   This is for compatibility with
              old programs which assume they can  write  into  string
              constants.  `-traditional' also has this effect.
              Writing into string constants is a very bad idea; "con-
              stants" should be constant.
         These options control the C preprocessor, which  is  run  on
         each C source file before actual compilation.
         If you use the `-E' option, GCC does nothing except  prepro-
         cessing.   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 in-
              put 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 written.  All the  `-in-
              clude' and `-imacros' options are processed in the ord-
              er 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  ef-
              fect  of  `-imacros file' is to make the macros defined
              in file available for  use  in  the  main  input.   The
              preprocessor evaluates any `-D' and `-U' options on the
              command line before processing `-imacrosfile',  regard-
              less  of  the order in which they are written.  All the
              `-include' and `-imacros' options are processed in  the
              order in which they are written.
         -idirafter dir
              Add the directory dir to the second include path.   The
              directories  on  the  second  include path are searched
              when a header file is not found in any  of  the  direc-
              tories in the main include path (the one that `-I' adds
         -iprefix prefix
              Specify prefix as the prefix for subsequent `-iwithpre-
              fix' options.
         -iwithprefix dir
              Add a  directory  to  the  second  include  path.   The
              directory's  name  is  made by concatenating prefix and
              dir, where prefix was specified previously with `-ipre-
              Do not  search  the  standard  system  directories  for
              header  files.  Only the directories you have specified
              with `-I' options (and the current  directory,  if  ap-
              propriate) are searched.
              By using both `-nostdinc' and `-I-', you can limit  the
              include-file  search file to only those directories you
              specify explicitly.
              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 build-
              ing `libg++'.)
              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 stan-
              dard 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  describing  the dependencies of each object file.
              For each source  file,  the  preprocessor  outputs  one
              make-rule whose target is the object file name for that
              source file and whose dependencies are  all  the  files
              `#include'd  in  it.  This rule may be a single line or
              may be continued with `\'-newline if it is  long.   The
              list  of rules is printed on standard output instead of
              the preprocessed C program.
              `-M' implies `-E'.
              `-MG' says to treat missing header files  as  generated
              files and assume they live in the same directory as the
              source file.  It must be specified in addition to `-M'.
         -MM  [ -MG ]
              Like `-M' but the output mentions only the user  header
              files  included  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 inhi-
              bit 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' command.
         -MMD Like `-MD' except mention only user header  files,  not
              system header files.
         -H   Print the name of each header file used, in addition to
              other normal activities.
              Assert the answer answer for question, in  case  it  is
              tested  with  a  preprocessor  conditional such as `#if
              #question(answer)'.  `-A-' disables the standard asser-
              tions that normally describe the target machine.
              (answer) Assert the answer answer for question, in case
              it  is  tested  with a preprocessor conditional such as
              `#if #question(answer)'.  `-A-' disables  the  standard
              assertions that normally describe the target machine.
              Define macro macro with the string `1' as  its  defini-
              Define macro macro as defn.    All instances of `-D' on
              the command line are processed before any `-U' options.
              Undefine macro macro.  `-U' options are evaluated after
              all `-D' options, but before any `-include' and `-imac-
              ros' options.
         -dM  Tell the preprocessor to output only a list of the mac-
              ro definitions that are in effect at the end of prepro-
              cessing.  Used with the `-E' option.
         -dD  Tell the preprocessor to  pass  all  macro  definitions
              into  the  output, in their proper sequence in the rest
              of the output.
         -dN  Like `-dD' except that the macro arguments and contents
              are  omitted.   Only  `#define name' is included in the
              Pass option as an option to the assembler.   If  option
              contains  commas,  it is split into multiple options at
              the commas.
         These options come into play when the compiler links  object
         files  into an executable output file.  They are meaningless
         if the compiler is not doing a link step.
              A file name that does not end in a  special  recognized
              suffix is considered to name an object file or library.
              (Object files are distinguished from libraries  by  the
              linker  according to the file contents.)  If GCC does a
              link step, these object files are used as input to  the
              Use the library named library when linking.
              The linker searches a standard list of directories  for
              the   library,   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  sys-
              tem directories 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 speci-
              fying a file name is that `-l' surrounds  library  with
              `lib' and `.a' and searches several directories.
              You need this special case of the -l option in order to
              link an Objective C program.
              Do not use the standard system startup files when link-
              ing.  The standard libraries are used normally.
              Don't use the standard  system  libraries  and  startup
              files when linking.  Only the files you specify will be
              passed to the linker.
              On systems that support dynamic linking, this  prevents
              linking  with  the shared libraries.  On other systems,
              this option has no effect.
              Produce a shared object which can then be  linked  with
              other  objects  to form an executable.  Only a few sys-
              tems support this option.
              Bind references  to  global  symbols  when  building  a
              shared  object.   Warn  about any unresolved references
              (unless overridden by the link editor option  `-Xlinker
              -z  -Xlinker  defs').   Only a few systems support this
         -Xlinker option
              Pass option as an option to the linker.   You  can  use
              this to supply system-specific linker options which GNU
              CC does not know how to recognize.
              If you want to pass an option that takes  an  argument,
              you  must use `-Xlinker' twice, once for the option and
              once for the argument.  For example, to  pass  `-assert
              definitions', you must write `-Xlinker -assert -Xlinker
              definitions'.  It does  not  work  to  write  `-Xlinker
              "-assert  definitions"', because this passes the entire
              string as a single argument,  which  is  not  what  the
              linker expects.
              Pass option as an option to the linker.  If option con-
              tains  commas, it is split into multiple options at the
         -u symbol
              Pretend the symbol symbol is undefined, to force  link-
              ing  of library modules to define it.  You can use `-u'
              multiple times with different symbols to force  loading
              of additional library modules.
         These options  specify  directories  to  search  for  header
         files, for libraries and for parts of the compiler:
              Append  directory  dir  to  the  list  of   directories
              searched for include 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
              If additional directories are specified with  `-I'  op-
              tions  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 override this effect of
              `-I-'.  With `-I.' you can specify searching the direc-
              tory  which  was current when the compiler was invoked.
              That is not exactly the same as what  the  preprocessor
              does by default, but it is often satisfactory.
              `-I-' does not inhibit the use of the  standard  system
              directories  for header files.  Thus, `-I-' and `-nost-
              dinc' are independent.
              Add directory dir to the  list  of  directories  to  be
              searched for `-l'.
              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
              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
              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.
              You can get a similar result from the environment vari-
              able  GCC_EXEC_PREFIX;  if  it is defined, its value is
              used as a prefix in the same way.  If both the `-B' op-
              tion  and the GCC_EXEC_PREFIX variable are present, the
              `-B' option is used first and the environment  variable
              value second.
         Warnings are diagnostic messages that  report  constructions
         which  are  not  inherently erroneous but which are risky or
         suggest there may have been an error.
         These options control the amount and kinds of warnings  pro-
         duced by GNU CC:
              Check the code for syntax errors, but  don't  emit  any
         -w   Inhibit all warning messages.
              Inhibit warning messages about the use of #import.
              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 re-
              quire `-ansi').  However, without this option,  certain
              GNU extensions and traditional C features are supported
              as well.  With this option, they are  rejected.   There
              is  no  reason  to  use  this option; it exists only to
              satisfy pedants.
              `-pedantic' does not cause warning messages for use  of
              the  alternate  keywords whose names begin and end with
              `__'.  Pedantic warnings are also disabled in  the  ex-
              pression  that  follows  __extension__.   However, only
              system header files should use these escape routes; ap-
              plication programs should avoid them.
              Like `-pedantic', except that errors are produced rath-
              er than warnings.
         -W   Print extra warning messages for these events:
            o A nonvolatile automatic variable might be changed by  a
              call  to  longjmp.  These warnings are possible only in
              optimizing compilation.
              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.
            o A function can return either with or without  a  value.
              (Falling off the end of the function body is considered
              returning without a value.)  For example, this function
              would evoke such a 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 return.
            o An expression-statement or the left-hand side of a com-
              ma expression contains no side effects. To suppress the
              warning, cast the unused expression to void.  For exam-
              ple,  an expression such as `x[i,j]' will cause a warn-
              ing, but `x[(void)i,j]' will not.
            o An unsigned value is compared against zero with `>'  or
              Warn whenever a declaration does not specify a type.
              Warn whenever a function is used before being declared.
              Same   as   -Wimplicit-int   and   -Wimplicit-function-
              Warn if the main function is declared or defined with a
              suspicious  type.   Typically,  it  is  a function with
              external linkage, returning int, and taking zero or two
              Warn whenever a function is defined with a  return-type
              that  defaults  to  int.   Also  warn  about any return
              statement with no  return-value  in  a  function  whose
              return-type is not void.
              Warn whenever a local variable is unused aside from its
              declaration, whenever a function is declared static but
              never defined, and  whenever  a  statement  computes  a
              result that is explicitly not used.
              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 out-
              side the enumeration range also provoke  warnings  when
              this option is used.
              Warn whenever a comment-start sequence `/*' appears  in
              a comment.
              Warn if any trigraphs are  encountered  (assuming  they
              are enabled).
              Check calls to printf and scanf,  etc.,  to  make  sure
              that  the  arguments supplied have types appropriate to
              the format string specified.
              Warn if an array subscript has type char.   This  is  a
              common cause of error, as programmers often forget that
              this type is signed on some machines.
              An automatic variable is used without first being  ini-
              These warnings are possible only in optimizing compila-
              tion,  because  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 candi-
              dates  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  struc-
              tures,  unions  or arrays, even when they are in regis-
              Note that there may be no warning about a variable that
              is  used  only  to compute a value that itself is never
              used, because such computations may be deleted by  data
              flow analysis before the warnings are printed.
              These warnings are made optional because GNU CC is  not
              smart  enough to see all the reasons why the code might
              be correct despite appearing to have an error.  Here is
              one example of how this can happen:
                int x;
                switch (y)
                  case 1: x = 1;
                  case 2: x = 4;
                  case 3: x = 5;
                foo (x);
              If the value of y is always 1, 2 or 3, then x is always
              initialized,  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
              Some spurious warnings can be avoided if you declare as
              volatile all the functions you use that never return.
              Warn if parentheses are omitted in certain contexts.
              When using templates in a C++ program, warn  if  debug-
              ging is not yet fully available (C++ only).
              All of the above `-W' options combined.  These are  all
              the  options  which  pertain to usage that we recommend
              avoiding and that we believe is easy to avoid, even  in
              conjunction with macros.
         The remaining `-W...' options are not implied by `-Wall' be-
         cause they warn about constructions that we consider reason-
         able to use, on occasion, in clean programs.
              Warn about certain constructs that  behave  differently
              in traditional and ANSI C.
            o Macro arguments occurring within  string  constants  in
              the macro body.  These would substitute the argument in
              traditional C, but are part of the constant in ANSI C.
            o A function declared external in one block and then used
              after the end of the block.
            o A switch statement has an operand of type long.
              Warn whenever a local variable  shadows  another  local
              Warn whenever two distinct  identifiers  match  in  the
              first len characters.  This may help you prepare a pro-
              gram that will compile with  certain  obsolete,  brain-
              damaged compilers.
              Warn about anything that depends on  the  "size  of"  a
              function  type or of void.  GNU C assigns these types a
              size of 1, for convenience in calculations with void  *
              pointers and pointers to functions.
              Warn whenever a pointer is cast so as to remove a  type
              qualifier from the target type.  For example, warn if a
              const char * is cast to an ordinary char *.
              Warn whenever a pointer is cast such that the  required
              alignment  of  the  target  is increased.  For example,
              warn if a char * is cast to an int * on machines  where
              integers  can  only  be  accessed  at two- or four-byte
              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 proto-
              types.  Otherwise, it will just be a nuisance; this  is
              why we did not make `-Wall' request these warnings.
              Warn if a prototype causes a type  conversion  that  is
              different  from  what would happen to the same argument
              in the absence of a prototype.  This  includes  conver-
              sions  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 pro-
              Warn if any functions that return structures or  unions
              are defined or called.  (In languages where you can re-
              turn an array, this also elicits a warning.)
              Warn if a  function  is  declared  or  defined  without
              specifying  the argument types.  (An old-style function
              definition is permitted without a warning  if  preceded
              by a declaration which specifies the argument types.)
              Warn if a global function is defined without a previous
              prototype  declaration.  This warning is issued even if
              the definition itself provides a prototype.  The aim is
              to  detect global functions that fail to be declared in
              header files.
              Warn if a global function is defined without a previous
              declaration.   Do so even if the definition itself pro-
              vides a prototype.  Use this option  to  detect  global
              functions that are not declared in header files.
              Warn if anything is declared more than once in the same
              scope,  even  in  cases  where  multiple declaration is
              valid and changes nothing.
              Warn if an extern declaration is encountered within  an
              Warn about  conversion  between  different  enumeration
              types (C++ only).
              Warn if long long type is used.  This is  default.   To
              inhibit     the     warning    messages,    use    flag
              `-Wno-long-long'.      Flags     `-W-long-long'     and
              `-Wno-long-long'  are taken into account only when flag
              `-pedantic' is used.
              (C++ only.)  In a derived  class,  the  definitions  of
              virtual  functions  must  match the type signature of a
              virtual function declared in the base class.  Use  this
              option  to  request  warnings  when a derived class de-
              clares 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 functions from the base class.
              Warn if a function can not be inlined,  and  either  it
              was  declared as inline, or else the -finline-functions
              option was given.
              Treat warnings as errors; abort compilation  after  any
         GNU CC has various special options that are used for  debug-
         ging 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 information makes debugging work  better  in
              GDB but will probably make other debuggers crash or re-
              fuse 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 vari-
              ables  you  declared may not exist at all; flow of con-
              trol may briefly move where you did not expect it; some
              statements  may  not  be  executed because they compute
              constant results or their values were already at  hand;
              some statements may execute in different places because
              they were moved out of loops.
              Nevertheless it proves possible to debug optimized out-
              put.  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 capability for more than one debugging format.
              Produce debugging information in the native format  (if
              that  is supported), including GDB extensions if at all
              Produce debugging information in stabs format (if  that
              is  supported),  without  GDB  extensions.  This is the
              format used by DBX on most BSD systems.
              Produce debugging information in stabs format (if  that
              is  supported), using GNU extensions understood only by
              the GNU debugger (GDB).  The use of these extensions is
              likely  to make other debuggers crash or refuse to read
              the program.
              Produce debugging information in COFF format  (if  that
              is  supported).  This is the format used by SDB on most
              System V systems prior to System V Release 4.
              Produce debugging information in XCOFF format (if  that
              is  supported).  This is the format used by the DBX de-
              bugger on IBM RS/6000 systems.
              Produce debugging information in XCOFF format (if  that
              is  supported), using GNU extensions understood only by
              the GNU debugger (GDB).  The use of these extensions is
              likely  to make other debuggers crash or refuse to read
              the program.
              Produce debugging information in DWARF format (if  that
              is  supported).  This is the format used by SDB on most
              System V Release 4 systems.
              Produce debugging information in DWARF format (if  that
              is  supported), using GNU extensions understood only by
              the GNU debugger (GDB).  The use of these extensions is
              likely  to make other debuggers crash or refuse to read
              the program.
         -gcofflevel -gxcofflevel
              Request debugging information and  also  use  level  to
              specify how much information.  The default level is 2.
              Level 1 produces minimal information, enough for making
              backtraces  in parts of the program that you don't plan
              to debug.  This includes descriptions of functions  and
              external  variables,  but  no  information  about local
              variables and no line numbers.
              Level 3 includes extra information,  such  as  all  the
              macro  definitions  present  in  the program.  Some de-
              buggers support macro expansion when you use `-g3'.
         -p   Generate extra code to write profile information  suit-
              able for the analysis program prof.
         -pg  Generate extra code to write profile information  suit-
              able for the analysis program gprof.
         -a   Generate extra code to write  profile  information  for
              basic  blocks,  which  will  record the number of times
              each basic block  is  executed.   This  data  could  be
              analyzed  by  a program like tcov.  Note, however, that
              the format of the data is not what tcov expects.  Even-
              tually  GNU  gprof  should  be extended to process this
         -ax  Generate extra  code  to  read  basic  block  profiling
              parameters   from  file  `'  and  write  profiling
              results to file `bb.out'.  `' contains a  list  of
              functions.  Whenever a function on the list is entered,
              profiling is turned on. When the  outmost  function  is
              left,  profiling  is  turned off. If a function name is
              prefixed with `-' the function is excluded from profil-
              ing.  If a function name is not unique it can be disam-
              biguated  by  writing  `/path/filename.d:functionname'.
              `bb.out'  will  list  some  available  filenames.  Four
              function names have a special meaning:   `__bb_jumps__'
              will  cause jump frequencies to be written to `bb.out'.
              `__bb_trace__' will cause the sequence of basic  blocks
              to   be   piped   into   `gzip'  and  written  to  file
              `bbtrace.gz'.  `__bb_hidecall__' will  cause  call  in-
              structions    to    be   excluded   from   the   trace.
              `__bb_showret__' will cause return instructions  to  be
              included in the trace.
              Says to make  debugging  dumps  during  compilation  at
              times specified 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  preprocess-
              ing, and write no output.
         -dN  Dump all macro names, at the end of preprocessing.
         -dD  Dump all macro definitions, at the end  of  preprocess-
              ing, in addition to normal output.
         -dy  Dump debugging information during parsing, to  standard
         -dr  Dump after RTL generation, to `file.rtl'.
         -dx  Just generate RTL for a function instead  of  compiling
              it.  Usually used with `r'.
         -dj  Dump after first jump optimization, to `file.jump'.
         -ds  Dump after CSE (including the  jump  optimization  that
              sometimes follows CSE), to `file.cse'.
         -dL  Dump after loop optimization, to `file.loop'.
         -dt  Dump after the second CSE pass (including the jump  op-
              timization that sometimes follows CSE), to `file.cse2'.
         -df  Dump after flow analysis, to `file.flow'.
         -dc  Dump after instruction combination, to `file.combine'.
         -dS  Dump after the first instruction  scheduling  pass,  to
         -dl  Dump after local register allocation, to `file.lreg'.
         -dg  Dump after global register allocation, to `file.greg'.
         -dR  Dump after the second instruction scheduling  pass,  to
         -dJ  Dump after last jump optimization, to `file.jump2'.
         -dd  Dump after delayed branch scheduling, to `file.dbr'.
         -dk  Dump after  conversion  from  registers  to  stack,  to
         -da  Produce all the dumps listed above.
         -dm  Print statistics on memory usage, at  the  end  of  the
              run, to standard error.
         -dp  Annotate the assembler output with a comment indicating
              which pattern and alternative was used.
              When running a cross-compiler, pretend that the  target
              machine uses the same floating point format as the host
              machine.  This causes incorrect output  of  the  actual
              floating constants, but the actual instruction sequence
              will probably be the same as GNU  CC  would  make  when
              running on the target machine.
              Store the usual  "temporary"  intermediate  files  per-
              manently;  place them in the current directory and name
              them based on the source file.  Thus, compiling `foo.c'
              with `-c -save-temps' would produce files `foo.cpp' and
              `foo.s', as well as `foo.o'.
              Print the  full  absolute  name  of  the  library  file
              library   that would be used when linking-and do not do
              anything else.  With this option, GNU CC does not  com-
              pile or link anything; it just prints the file name.
              Same as `-print-file-name=libgcc.a'.
              Like `-print-file-name', but  searches  for  a  program
              such as `cpp'.
         These options control various sorts of optimizations:
         -O1  Optimize.  Optimizing compilation takes  somewhat  more
              time, and a lot more memory for a large function.
              Without `-O', the compiler's goal is to reduce the cost
              of  compilation  and  to make debugging produce the ex-
              pected results.  Statements  are  independent:  if  you
              stop  the program with a breakpoint between statements,
              you can then assign a new  value  to  any  variable  or
              change  the  program  counter to any other statement in
              the function and get exactly the results you would  ex-
              pect from the source code.
              Without `-O', only variables declared register are  al-
              located 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' op-
              tion  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 per-
              formed.  Loop unrolling and function inlining  are  not
              done,  for example.  As compared to -O, this option in-
              creases both compilation time and  the  performance  of
              the generated code.
         -O3  Optimize yet more. This turns on everything  -O2  does,
              along with also turning on -finline-functions.
         -O0  Do not optimize.
              If you use multiple -O options, with or  without  level
              numbers, the last such option is the one that is effec-
         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  fol-
         lowing list shows only one form-the one which is not the de-
         fault.  You can figure out the other form by either removing
         `no-' or adding it.
              Do not store floating  point  variables  in  registers.
              This  prevents undesirable excess precision on machines
              such as the 68000 where the floating registers (of  the
              68881) keep more precision than a double is supposed to
              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 pro-
              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  function  (or  reference  to a data member), it
              must (1) determine whether the class implements  member
              functions  of that name; (2) resolve which member func-
              tion 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
                cout << "This " << p << " has " << n << " legs.\n";
              makes six passes through all three steps.  By  using  a
              software  cache,  a  "hit"  significantly  reduces this
              cost.  Unfortunately, using the cache introduces anoth-
              er  layer  of mechanisms which must be implemented, and
              so incurs its own  overhead.   `-fmemoize-lookups'  en-
              ables 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 com-
              piler determines that the context of the last  function
              compiled  would yield the same access privileges of the
              next function to compile, it preserves the cache.  This
              is most helpful when defining many member functions for
              the same class: with the exception of member  functions
              which  are  friends of other classes, each member func-
              tion has exactly the same access  privileges  as  every
              other, and the cache need not be flushed.
              Don't make member functions inline  by  default  merely
              because  they  are  defined inside the class scope (C++
              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.
              Force memory operands to be copied into  registers  be-
              fore doing arithmetic on them.  This may produce better
              code by making all memory references  potential  common
              subexpressions.   When  they  are not common subexpres-
              sions, instruction  combination  should  eliminate  the
              separate  register-load.   I  am  interested in hearing
              about the difference this makes.
              Force memory address constants to be copied into regis-
              ters before doing arithmetic on them.  This may produce
              better code just as `-fforce-mem' may.  I am interested
              in hearing about the difference this makes.
              Don't keep the frame pointer in a  register  for  func-
              tions  that  don't  need one.  This avoids the instruc-
              tions to save, set up and restore  frame  pointers;  it
              also  makes  an  extra register available in many func-
              tions.  It also makes debugging impossible on .
              On some machines, such as the Vax, this flag has no ef-
              fect,  because  the standard calling sequence automati-
              cally handles the frame pointer and nothing is saved by
              pretending  it  doesn't exist.  The machine-description
              macro FRAME_POINTER_REQUIRED controls whether a  target
              machine supports this flag.
              Integrate all simple functions into their callers.  The
              compiler heuristically decides which functions are sim-
              ple 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 function as assembler code  in  its  own
              Enable values to be allocated in registers that will be
              clobbered by function calls, by emitting extra instruc-
              tions to save and restore  the  registers  around  such
              calls.   Such  allocation is done only when it seems to
              result in better code than would otherwise be produced.
              This option is enabled by default on certain  machines,
              usually those which have no call-preserved registers to
              use instead.
              Even if all calls to a given function  are  integrated,
              and  the function is declared static, nevertheless out-
              put a separate run-time callable version of  the  func-
              Do not put function addresses in registers;  make  each
              instruction  that calls a constant function contain the
              function's address explicitly.
              This option results in less efficient  code,  but  some
              strange  hacks  that  alter the assembler output may be
              confused by the optimizations performed when  this  op-
              tion is not used.
              Disable any machine-specific peephole optimizations.
              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  as-
              sume  arguments  to  the sqrt function are non-negative
              This option should never be turned on by any  `-O'  op-
              tion  since  it can result in incorrect output for pro-
              grams which depend on an exact implementation  of  IEEE
              or ANSI rules/specifications for math functions.
         The following options control specific  optimizations.   The
         `-O2'  option  turns  on  all  of these optimizations except
         `-funroll-loops' and `-funroll-all-loops'.
         The `-O' option usually turns on  the  `-fthread-jumps'  and
         `-fdelayed-branch' options, but specific machines may change
         the default optimizations.
         You can use the following  flags  in  the  rare  cases  when
         "fine-tuning" of optimizations to be performed is desired.
              Perform the optimizations of  loop  strength  reduction
              and elimination of iteration variables.
              Perform optimizations where we check to see if  a  jump
              branches  to  a  location where another comparison sub-
              sumed by the first is found.  If so, the  first  branch
              is  redirected  to either the destination of the second
              branch or a point immediately following  it,  depending
              on whether the condition is known to be true or false.
              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.
              Perform the optimization of loop  unrolling.   This  is
              done  for  all  loops.  This usually makes programs run
              more slowly.
              In common subexpression elimination, scan through  jump
              instructions when the target of the jump is not reached
              by any other path.  For example, when CSE encounters an
              if  statement  with an else clause, CSE will follow the
              jump when the condition tested is false.
              This is similar to `-fcse-follow-jumps', but causes CSE
              to  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.
              Re-run common subexpression elimination after loop  op-
              timizations has been performed.
              Elide  constructors  when  this  seems  plausible  (C++
              only).   With this flag, GNU C++ initializes y directly
              from the call to foo without going through a  temporary
              in the following code:
              A foo (); A y = foo ();
              Without this option, GNU C++  first  initializes  y  by
              calling  the  appropriate  constructor for type A; then
              assigns the result of foo to a temporary; and, finally,
              replaces the initial value of `y' with the temporary.
              The  default  behavior  (`-fno-elide-constructors')  is
              specified  by  the  draft  ANSI  C++ standard.  If your
              program's  constructors  have   side   effects,   using
              `-felide-constructors'  can  make your program act dif-
              ferently, since some constructor calls may be omitted.
              Perform a number of minor optimizations that are  rela-
              tively expensive.
              If supported for the target machine, attempt to reorder
              instructions  to  exploit  instruction  slots available
              after delayed branch instructions.
              If supported for the target machine, attempt to reorder
              instructions  to  eliminate execution stalls due to re-
              quired data being  unavailable.   This  helps  machines
              that  have  slow floating point or memory load instruc-
              tions by allowing other instructions to be issued until
              the result of the load or floating point instruction is
              Similar to `-fschedule-insns', but  requests  an  addi-
              tional  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
         By default, GNU CC  compiles  code  for  the  same  type  of
         machine  that  you  are  using.  However, it can also be in-
         stalled as a cross-compiler, to compile for some other  type
         of  machine.   In  fact, several different configurations of
         GNU CC, for different target machines, can be installed side
         by  side.   Then  you specify which one to use with the `-b'
         In addition, older and newer versions of GNU CC can  be  in-
         stalled  side  by  side.   One of them (probably the newest)
         will be the default, but  you  may  sometimes  wish  to  use
         -b machine
              The argument machine specifies the target  machine  for
              compilation.   This  is  useful when you have installed
              GNU CC as a cross-compiler.
              The value to use for machine is the same as was  speci-
              fied  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 com-
              pile 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 in-
              stalled.  For example, 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
         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  confi-
         guration, 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:
              Generate output for a 68000.  This is the default  when
              the compiler is configured for 68000-based systems.
              Generate output for a  68020  (rather  than  a  68000).
              This is the default when the compiler is configured for
              68020-based systems.
              Generate  output  containing  68881  instructions   for
              floating  point.   This  is the default for most 68020-
              based systems unless -nfp was specified when  the  com-
              piler was configured.
              Generate output for a 68030.  This is the default  when
              the compiler is configured for 68030-based systems.
              Generate output for a 68040.  This is the default  when
              the compiler is configured for 68040-based systems.
              Generate output for a 68040, without using any  of  the
              new  instructions.   This results in code which can run
              relatively efficiently on either  a  68020/68881  or  a
              68030 or a 68040.
              Generate output containing  Sun  FPA  instructions  for
              floating point.
              Generate output containing library calls  for  floating
              point.   WARNING:  the requisite libraries are not part
              of GNU CC.  Normally the facilities  of  the  machine's
              usual  C  compiler  are  used,  but  this can't be done
              directly in cross-compilation.  You must make your  own
              arrangements  to provide suitable library functions for
              Consider type int to be 16 bits wide, like short int.
              Do not use the bit-field instructions.   `-m68000'  im-
              plies `-mnobitfield'.
              Do use the bit-field instructions.   `-m68020'  implies
              `-mbitfield'.  This is the default if you use the unmo-
              dified sources.
              Use a different function-calling convention,  in  which
              functions  that take a fixed number of arguments return
              with the rtd instruction, which  pops  their  arguments
              while  returning.   This  saves  one instruction in the
              caller since there is no  need  to  pop  the  arguments
              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 (in-
              cluding printf); otherwise incorrect code will be  gen-
              erated for calls to those functions.
              In addition, seriously incorrect code  will  result  if
              you  call a function with too many arguments.  (Normal-
              ly, extra arguments are harmlessly ignored.)
              The rtd instruction is supported by the 68010 and 68020
              processors, but not by the 68000.
         These `-m' options are defined for the Vax:
              Do not output certain jump instructions (aobleq and  so
              on)  that  the Unix assembler for the Vax cannot handle
              across long ranges.
              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:
              Generate output containing floating point instructions.
              This is the default.
              Generate output containing library calls  for  floating
              point.  Warning: there is no GNU floating-point library
              for SPARC.  Normally the facilities  of  the  machine's
              usual  C  compiler  are  used,  but this cannot be done
              directly in cross-compilation.  You must make your  own
              arrangements  to provide suitable library functions for
              -msoft-float changes the calling convention in the out-
              put  file;  therefore, it is only useful if you compile
              all of a program with this option.
              With -mepilogue (the default), the compiler always  em-
              its 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.
              These three options select variations on the SPARC  ar-
              By default  (unless  specifically  configured  for  the
              Fujitsu SPARClite), GCC generates code for the v7 vari-
              ant of the SPARC architecture.
              -mv8 will give you SPARC v8 code.  The only  difference
              from  v7  code  is  that the compiler emits the integer
              multiply and integer divide instructions which exist in
              SPARC v8 but not in SPARC v7.
              -msparclite will give you SPARClite  code.   This  adds
              the  integer  multiply,  integer  divide  step and scan
              (ffs) instructions which exist in SPARClite but not  in
              SPARC v7.
              These two options select the processor  for  which  the
              code is optimised.
              With -mcypress (the default),  the  compiler  optimises
              code  for  the  Cypress  CY7C602  chip,  as used in the
              SparcStation/SparcServer 3xx series. This is  also  ap-
              propriate for the older SparcStation 1, 2, IPX etc.
              With -msupersparc the compiler optimises code  for  the
              SuperSparc  cpu,  as  used in the SparcStation 10, 1000
              and 2000 series. This flag also enables use of the full
              SPARC v8 instruction set.
         These `-m' options are defined for the Convex:
         -mc1 Generate output for a C1.  This is the default when the
              compiler is configured for a C1.
         -mc2 Generate output for a C2.  This is the default when the
              compiler is configured for a C2.
              Generate code which puts an argument count in the  word
              preceding  each argument list.  Some nonportable Convex
              and Vax programs need this word.  (Debuggers don't, ex-
              cept for functions with variable-length argument lists;
              this info is in the symbol table.)
              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 support-
              ed by the hardware.  This is the default.
              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.
              Generate code that assumes the systems does not support
              byte  and  halfword  write  operations.   This  implies
              Use a small memory model that assumes that all function
              addresses  are either within a single 256 KB segment or
              at an absolute address of less than 256K.  This  allows
              the  call  instruction  to  be used instead of a const,
              consth, calli sequence.
              Do not assume that the call instruction  can  be  used;
              this is the default.
              Generate code for the Am29050.
              Generate code for the Am29000.  This is the default.
              Generate references to registers gr64-gr95  instead  of
              gr96-gr127.   This  option  can  be used when compiling
              kernel code that wants a set of global  registers  dis-
              joint from that used by user-mode code.
              Note that when this option is used, register  names  in
              `-f' flags must use the normal, user-mode, names.
              Use the normal set  of  global  registers,  gr96-gr127.
              This is the default.
              Insert a call to __msp_check after each  stack  adjust-
              ment.  This is often used for kernel code.
         These `-m' options are defined for  Motorola  88K  architec-
              Generate code that works well on both  the  m88100  and
              the m88110.
              Generate code that works best for the m88100, but  that
              also runs on the m88110.
              Generate code that works best for the m88110,  and  may
              not run on the m88100.
              Include an ident  directive  in  the  assembler  output
              recording  the source file name, compiler name and ver-
              sion, timestamp, and compilation flags used.
              In assembler output, emit symbol names  without  adding
              an  underscore character at the beginning of each name.
              The default is to use an underscore as prefix  on  each
              Early models of the 88K architecture had problems  with
              division  by  zero;  in particular, many of them didn't
              trap.  Use these options to avoid including (or to  in-
              clude explicitly) additional code to detect division by
              zero and signal an exception.  All  GCC  configurations
              for the 88K use `-mcheck-zero-division' by default.
              Include  (or  omit)  additional  debugging  information
              (about registers used in each stack frame) as specified
              in the 88Open  Object  Compatibility  Standard,  "OCS".
              This  extra  information is not needed by GDB.  The de-
              fault for DG/UX, SVr4, and Delta 88 SVr3.2  is  to  in-
              clude  this  information; other 88k configurations omit
              this information by default.
              Force (or do not require) register values to be  stored
              in  a particular place in stack frames, as specified in
              OCS.  The DG/UX, Delta88 SVr3.2, and BCS configurations
              use  `-mocs-frame-position';  other  88k configurations
              have the default `-mno-ocs-frame-position'.
              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 standards.
              By default GCC does not optimize the argument area.
              num Generate smaller data references by making them re-
              lative to r0, which allows loading a value using a sin-
              gle instruction (rather than the usual two).  You  con-
              trol  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.
              Do, or do not, generate code  to  guarantee  sequential
              consistency of volatile memory references.
              GNU CC always guarantees consistency  by  default,  for
              the  preferred  processor  submodel.   How this is done
              depends on the submodel.
              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 in-
              structions for sequential consistency.
              The order of memory references made by the m88110  pro-
              cessor  does not always match the order of the instruc-
              tions requesting those references.   In  particular,  a
              load  instruction  may execute before a preceding store
              instruction.  Such reordering violates sequential  con-
              sistency  of volatile memory references, when there are
              multiple  processors.   When  you  use   `-m88000'   or
              `-m88110',  GNU  CC generates special instructions when
              appropriate, to force execution in the proper order.
              The extra code generated to guarantee  consistency  may
              affect  the  performance  of  your application.  If you
              know that you can safely forgo this guarantee, you  may
              use the option `-mno-serialize-volatile'.
              If you use the `-m88100' option but require  sequential
              consistency  when  running on the m88110 processor, you
              should use `-mserialize-volatile'.
              Turn on (`-msvr4') or off  (`-msvr3')  compiler  exten-
              sions  related to System V release 4 (SVr4).  This con-
              trols the following:
            o Which variant of the assembler syntax  to  emit  (which
              you can select independently using `-mversion-03.00').
            o `-msvr4' makes the C  preprocessor  recognize  `#pragma
            o `-msvr4' makes GCC issue additional declaration  direc-
              tives used in SVr4.
         `-msvr3' is the default for all m88K  configurations  except
         the SVr4 configuration.
              Include code to detect bit-shifts of more than 31 bits;
              respectively,  trap  such shifts or emit code to handle
              them properly.  By default GCC makes no special  provi-
              sion for large bit shifts.
              Very early models of the 88K architecture didn't have a
              divide  instruction,  so GCC avoids that instruction by
              default.  Use this option to specify that it's safe  to
              use the divide instruction.
              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.
              Warn when a function passes a struct as an argument  or
              result.   Structure-passing  conventions  have  changed
              during the evolution of the C language, and  are  often
              the  source  of  portability problems.  By default, GCC
              issues no such warning.
         These options are defined for the IBM RS6000:
              Control whether or not floating-point constants  go  in
              the  Table  of  Contents  (TOC),  a table of all global
              variable and function addresses.  By default  GCC  puts
              floating-point  constants  there; if the TOC overflows,
              `-mno-fp-in-toc' will reduce the size of the TOC, which
              may avoid the overflow.
         These `-m' options are defined for the IBM RT PC:
              Use an in-line code sequence  for  integer  multiplies.
              This is the default.
              Call lmul$$ for integer multiples.
              Generate full-size floating point data blocks,  includ-
              ing  the minimum amount of scratch space recommended by
              IBM.  This is the default.
              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 dynam-
              Use a calling sequence incompatible with the  IBM  cal-
              ling  convention  in which floating point arguments are
              passed  in  floating  point   registers.    Note   that
              varargs.h  and  stdargs.h  will  not work with floating
              point operands if this option is specified.
              Use the normal calling convention  for  floating  point
              arguments.  This is the default.
              Return structures of more  than  one  word  in  memory,
              rather than in a register.  This provides compatibility
              with   the   MetaWare   HighC   (hc)   compiler.    Use
              `-fpcc-struct-return'  for compatibility with the Port-
              able C Compiler (pcc).
              Return some structures of more than one word in  regis-
              ters,  when convenient.  This is the default.  For com-
              patibility with the IBM-supplied compilers, use  either
              `-fpcc-struct-return' or `-mhc-struct-return'.
         These `-m' options are defined for the MIPS family  of  com-
              Assume the defaults for the machine type cpu-type  when
              scheduling  instructions.   The default cpu-type is de-
              fault, 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 gen-
              erate any code that does not meet level 1 of  the  MIPS
              ISA  (instruction  set architecture) without the -mips2
              or -mips3 switches being used.
              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
              Issue instructions from level 3 of the MIPS ISA (64 bit
              instructions).   The -mcpu=r4000 switch must be used in
              conjunction with -mips2.
              These options don't work at present.
              Generate  code  for  the  MIPS  assembler,  and  invoke
              mips-tfile  to  add  normal debug information.  This is
              the default for all  platforms  except  for  the  OSF/1
              reference  platform,  using the OSF/rose object format.
              If any of the -ggdb, -gstabs, or -gstabs+ switches  are
              used, the mips-tfile program will encapsulate the stabs
              within MIPS ECOFF.
              Generate code for the GNU assembler.  This is  the  de-
              fault  on  the  OSF/1  reference  platform,  using  the
              OSF/rose object format.
              The -mrnames switch says to output code using the  MIPS
              software  names  for  the  registers,  instead  of  the
              hardware names (ie, a0 instead of $4).  The GNU  assem-
              bler does not support the -mrnames switch, and the MIPS
              assembler will be instructed to run the MIPS C  prepro-
              cessor over the source file.  The -mno-rnames switch is
              The -mgpopt switch says to write all of  the  data  de-
              clarations before the instructions in the text section,
              to all the MIPS assembler to generate one  word  memory
              references  instead of using two words for short global
              or static data items.  This is on by default if optimi-
              zation is selected.
              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  pro-
              gram (number of registers saved, stack size, etc.).
              The -mmemcpy switch makes all block moves call the  ap-
              propriate  string function (memcpy or bcopy) instead of
              possibly generating inline code.
              The -mno-mips-tfile  switch  causes  the  compiler  not
              postprocess  the  object  file with the mips-tfile pro-
              gram, after the MIPS assembler has generated it to  add
              debug support.  If mips-tfile is not run, then no local
              variables will be available to the debugger.  In  addi-
              tion, 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
              Generate output containing library calls  for  floating
              point.   WARNING:  the requisite libraries are not part
              of GNU CC.  Normally the facilities  of  the  machine's
              usual  C  compiler  are  used,  but  this can't be done
              directly in cross-compilation.  You must make your  own
              arrangements  to provide suitable library functions for
              Generate output containing floating point instructions.
              This is the default if you use the unmodified sources.
              Assume that the FR bit in the status word  is  on,  and
              that  there are 32 64-bit floating point registers, in-
              stead of 32 32-bit floating point registers.  You  must
              also specify the -mcpu=r4000 and -mips3 switches.
              Assume that there are 32 32-bit floating  point  regis-
              ters.  This is the default.
              Emit (or do  not  emit)  the  .abicalls,  .cpload,  and
              .cprestore pseudo operations that some System V.4 ports
              use for position independent code.
              The -mhalf-pic switch says to put  pointers  to  extern
              references  into  the  data  section  and load them up,
              rather than put the 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 normal
              data or bss section.  This allows the assembler to emit
              one  word  memory  reference  instructions based on the
              global pointer (gp or $28), instead of the  normal  two
              words  used.  By default, num is 8 when the MIPS assem-
              bler is used, and 0 when the  GNU  assembler  is  used.
              The  -Gnum  switch  is also passed to the assembler and
              linker.  All modules should be compiled with  the  same
              -Gnum value.
              Tell the MIPS assembler to  not  run  its  preprocessor
              over user assembler files (with a `.s' suffix) when as-
              sembling them.
         These `-m' options are defined for the Intel 80386 family of
         computers:  -m486
              Control whether or not code is optimized for a 486  in-
              stead  of an 386.  Code generated for a 486 will run on
              a 386 and vice versa.
              Generate output containing library calls  for  floating
              point.   Warning:  the requisite libraries are not part
              of GNU CC.  Normally the facilities  of  the  machine's
              usual  C  compiler  are  used,  but  this can't be done
              directly in cross-compilation.  You must make your  own
              arrangements  to provide suitable library functions for
              On machines where a  function  returns  floating  point
              results  in  the  80387  register  stack, some floating
              point opcodes may be emitted even if `-msoft-float'  is
              Do not use the FPU registers for return values of func-
              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  operat-
              ing 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  com-
              Generate code for a PA 1.0 processor.
              Generate code for a PA 1.1 processor.
              Generate code which is suitable  for  use  in  kernels.
              Specifically,  avoid  add  instructions in which one of
              the arguments is the DP register;  generate  addil  in-
              structions  instead.   This avoids a rather serious bug
              in the HP-UX linker.
              Generate code that can be linked against  HP-UX  shared
              libraries.   This option is not fully function yet, and
              is not on by default for any PA target.  Using this op-
              tion  can  cause  incorrect code to be generated by the
              Don't generate code that will be linked against  shared
              libraries.  This is the default for all PA targets.
              Generate code which allows calls to  functions  greater
              than 256K away from the caller when the caller and cal-
              lee are in the same source file.  Do not turn this  op-
              tion on unless code refuses to link with "branch out of
              range errors from the linker.
              Prevent floating point registers from being used in any
              manner.   This is necessary for compiling kernels which
              perform lazy context switching of floating point regis-
              ters.   If  you  use this option and attempt to perform
              floating point operations, the compiler will abort.
              Prevent the compiler from using indexing address modes.
              This avoids some rather obscure problems when compiling
              MIG generated code under MACH.
              Add a colon to the end of label  definitions  (for  ELF
         These `-m' options are defined for the Intel 80960 family of
              Assume the defaults for the machine type  cpu-type  for
              instruction and addressing-mode availability and align-
              ment.  The default cpu-type is kb;  other  choices  are
              ka, mc, ca, cf, sa, and sb.
              The -mnumerics option indicates that the processor does
              support  floating-point instructions.  The -msoft-float
              option indicates that floating-point support should not
              be assumed.
              Do (or do not) attempt to alter leaf procedures  to  be
              callable  with  the  bal  instruction  as well as call.
              This will result in more efficient  code  for  explicit
              calls  when  the  bal instruction can be substituted by
              the assembler or linker, but  less  efficient  code  in
              other  cases,  such  as calls via function pointers, or
              using a linker that doesn't support this optimization.
              Do (or do not) make additional attempts  (beyond  those
              of the machine-independent portions of the compiler) to
              optimize tail-recursive calls into branches.   You  may
              not  want  to  do  this  because the detection of cases
              where this is not valid is not totally  complete.   The
              default is -mno-tail-call.
              Assume (or do not assume) that the use of a complex ad-
              dressing  mode  is  a win on this implementation of the
              i960.  Complex addressing modes may not  be  worthwhile
              on  the  K-series,  but  they  definitely are on the C-
              series.  The default is  currently  -mcomplex-addr  for
              all processors except the CB and CC.
              Align code to 8-byte boundaries for faster fetching (or
              don't  bother).   Currently turned on by default for C-
              series implementations only.
              Enable compatibility with iC960 v2.0 or v3.0.
              Enable compatibility with the iC960 assembler.
              Do not permit (do permit) unaligned accesses.
              Enable structure-alignment compatibility  with  Intel's
              gcc release 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 implementa-
              Use (do not use) the hardware  floating-point  instruc-
              tions for floating-point operations.  When -msoft-float
              is specified, functions in `libgcc1.c' will be used  to
              perform floating-point operations.  Unless they are re-
              placed by  routines  that  emulate  the  floating-point
              operations,  or  compiled in such a way as to call such
              emulations  routines,   these   routines   will   issue
              floating-point  operations.    If you are compiling for
              an Alpha without floating-point  operations,  you  must
              ensure  that  the  library  is  built so as not to call
              Note that Alpha implementations without  floating-point
              operations  are  required to have floating-point regis-
              Generate code that uses (does not  use)  the  floating-
              point register set.  -mno-fp-regs implies -msoft-float.
              If the floating-point register set is not used,  float-
              ing  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 registers.
         These additional options are available on System V Release 4
         for compatibility with other compilers on those systems:
         -G   On SVr4 systems,  gcc  accepts  the  option  `-G'  (and
              passes it to the system linker), for compatibility with
              other compilers.  However, we suggest you use `-symbol-
              ic'  or  `-shared' as appropriate, instead of supplying
              linker options on the gcc command line.
         -Qy  Identify the versions of each tool  used  by  the  com-
              piler, in a .ident assembler directive in the output.
         -Qn  Refrain from adding .ident  directives  to  the  output
              file (this is the default).
              Search the directories dirs, and  no  others,  for  li-
              braries specified with `-l'.  You can separate directo-
              ry entries in dirs from one another with colons.
              Look in the directory dir to find the M4  preprocessor.
              The assembler uses this option.
         These machine-independent options control the interface con-
         ventions used in code generation.
         Most of them begin with `-f'.  These options have both posi-
         tive  and negative forms; the negative form of `-ffoo' would
         be `-fno-foo'.  In the table below, only one of the forms is
         listed-the one which is not the default.  You can figure out
         the other form by either removing `no-' or adding it.
              Assume that objects reached through references are  not
              null (C++ 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
              obj &a = g (); a.f (2);
              Checking that references of  this  sort  have  non-null
              values requires extra code, however, and it is unneces-
              sary  for  many  programs.   You  can  use  `-fnonnull-
              objects'  to  omit the checks for null, if your program
              doesn't require checking.
              Use the same convention for returning struct and  union
              values  that  is  used  by the usual C compiler on your
              system.  This convention is less  efficient  for  small
              structures,  and  on many machines it fails to be reen-
              trant; but it has the advantage of allowing intercalla-
              bility between GCC-compiled code and PCC-compiled code.
              Use the convention that struct and union values are re-
              turned  in registers when possible.  This is more effi-
              cient for small structures than -fpcc-struct-return.
              If  you   specify   neither   -fpcc-struct-return   nor
              -freg-struct-return,  GNU CC defaults to whichever con-
              vention is standard for the target.   If  there  is  no
              standard     convention,    GNU    CC    defaults    to
              Allocate to an enum type only as many bytes as it needs
              for the declared range of possible values.  Specifical-
              ly, the enum type will be equivalent  to  the  smallest
              integer type which has enough room.
              Use the same size for double as for float .
              Requests that the data and non-const variables of  this
              compilation  be  shared  data rather than private data.
              The distinction makes sense only on  certain  operating
              systems,  where shared data is shared between processes
              running the same program, while private data exists  in
              one copy per process.
              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  systems
              which always work this way.
              Ignore the `#ident' directive.
              Do not output global initializations (such as C++  con-
              structors  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 linker in-
              cludes constructors and destructors.  (collect2 is  in-
              cluded  in the GNU CC distribution.)  For systems which
              must use collect2, the compiler driver gcc  is  config-
              ured to do this automatically.
              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  loca-
              tions  far  apart  in memory.  This option is used when
              compiling `crtstuff.c'; you should not need to  use  it
              for anything else.
              Put extra commentary information in the  generated  as-
              sembly  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 debug-
              ging the compiler itself).
              Consider all memory references through pointers  to  be
              Consider all memory references  to  extern  and  global
              data items to be volatile.
              If  supported  for  the   target   machines,   generate
              position-independent code, suitable for use in a shared
              If supported for the  target  machine,  emit  position-
              independent code, suitable for dynamic linking, even if
              branches need large displacements.
              Treat the register named reg as a fixed register;  gen-
              erated code should never refer to it (except perhaps as
              a stack pointer, frame pointer or in some  other  fixed
              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
              This flag does not have a  negative  form,  because  it
              specifies a three-way choice.
              Treat the register named reg as an  allocable  register
              that  is  clobbered by function calls.  It may be allo-
              cated 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  per-
              vasive  role  in the machine's execution model, such as
              the stack pointer or frame pointer, will produce disas-
              trous results.
              This flag does not have a  negative  form,  because  it
              specifies a three-way choice.
              Treat the register named reg as an  allocable  register
              saved  by functions.  It may be allocated even for tem-
              poraries or variables that live across a  call.   Func-
              tions  compiled  this way will save and restore the re-
              gister reg if they use it.
              Use of this flag for a register that has a  fixed  per-
              vasive  role  in the machine's execution model, such as
              the stack pointer or frame pointer, will produce disas-
              trous results.
              A different sort of disaster will result from  the  use
              of  this  flag  for a register in which function values
              may be returned.
              This flag does not have a  negative  form,  because  it
              specifies a three-way choice.
         Two `#pragma' directives are supported for GNU C++, to  per-
         mit using the same header file for two purposes: as a defin-
         ition 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 ob-
              ject files that use  those  classes.   Normally,  local
              copies  of certain information (backup copies of inline
              member functions, debugging information, and the inter-
              nal  tables  that  implement virtual functions) must be
              kept in each object file that  includes  class  defini-
              tions.   You can use this pragma to avoid such duplica-
              tion.  When a header file  containing  `#pragma  inter-
              face'  is included in a compilation, this auxiliary in-
              formation will not be generated (unless the main  input
              source file itself uses `#pragma implementation').  In-
              stead, 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 in-
              formation,  and  the  internal tables used to implement
              virtual functions are all generated  in  implementation
              If you use `#pragma implementation' with  no  argument,
              it applies to an include file with the same basename as
              your  source  file;  for  example,  in   `',
              `#pragma  implementation'  by  itself  is equivalent to
              `#pragma implementation "allclass.h"'.  Use the  string
              argument  if  you  want a single implementation file to
              include code from multiple header files.
              There is no way to split up the contents  of  a  single
              header file into multiple implementation files.
         file.c             C source file
         file.h             C header (preprocessor) file
         file.i             preprocessed C source file
         file.C             C++ source file            C++ source file
         file.cxx           C++ source file
         file.m             Objective-C source file
         file.s             assembly language file
         file.o             object file
         a.out              link edited output
         TMPDIR/cc*         temporary files
         LIBDIR/cpp         preprocessor
         LIBDIR/cc1         compiler for C
         LIBDIR/cc1plus     compiler for C++
         LIBDIR/collect     linker front end needed on some machines
         LIBDIR/libgcc.a    GCC subroutine library
         /lib/crt[01n].o    start-up routine
         LIBDIR/ccrt0       additional start-up routine for C++
         /lib/libc.a        standard C library, see
         /usr/include       standard directory for #include files
         LIBDIR/include     standard gcc directory for #include files
         LIBDIR/g++-include additional g++ directory for #include
         LIBDIR is usually /usr/local/lib/machine/version.
         TMPDIR comes from the environment variable  TMPDIR  (default
         /usr/tmp if available, else /tmp).
         cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1).
         `gcc', `cpp', `as', `ld', and `gdb' entries in info.
         Using and Porting GNU  CC  (for  version  2.0),  Richard  M.
         Stallman; The C Preprocessor, Richard M. Stallman; Debugging
         with GDB: the GNU Source-Level Debugger, Richard M. Stallman
         and  Roland H. Pesch; Using as: the GNU Assembler, Dean Els-
         ner, Jay Fenlason & friends; ld: the GNU linker, Steve Cham-
         berlain and Roland Pesch.
         For instructions on reporting bugs, see the GCC manual.
         Copyright 1991, 1992, 1993 Free Software Foundation, Inc.
         Permission is granted to make and distribute verbatim copies
         of  this  manual provided the copyright notice and this per-
         mission notice are preserved on all copies.
         Permission is granted to copy and distribute  modified  ver-
         sions of this manual under the conditions for verbatim copy-
         ing, provided that the entire resulting derived work is dis-
         tributed under the terms of a permission notice identical to
         this one.
         Permission is granted to copy and distribute translations of
         this  manual  into  another language, under the above condi-
         tions for modified versions, except that this permission no-
         tice  may  be  included in translations approved by the Free
         Software Foundation instead of in the original English.
         See the GNU CC Manual for the contributors to GNU CC.

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