Fresh Fish 4/FreshFish_May-June1994.bin/bbs/gnu/gcc-2.5.8-bin.lha/man/cat1/gcc.0

Text File | 1994-02-08 | 121.5 KB | 3,499 lines

GCC(1)                      GNU Tools                      GCC(1)



NAME
     gcc, g++ - GNU project C and C++ Compiler (v2.4)

SYNOPSIS
     gcc [ _o_p_t_i_o_n | _f_i_l_e_n_a_m_e ]...
     g++ [ _o_p_t_i_o_n | _f_i_l_e_n_a_m_e ]...

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

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

     If we find that the things in this man page that are out  of
     date cause significant confusion or complaints, we will stop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

     For complete and current documentation, refer  to  the  Info
     file  `gcc' or the manual _U_s_i_n_g _a_n_d _P_o_r_t_i_n_g _G_N_U _C_C (_f_o_r _v_e_r_-
     _s_i_o_n _2._0).  Both are  made  from  the  Texinfo  source  file
     gcc.texinfo.

DESCRIPTION
     The C and C++ compilers are integrated.  Both process  input
     files  through  one  or  more of four stages: preprocessing,
     compilation, assembly, and linking.   Source  filename  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



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

     Most `-f' and `-W' options have two contrary  forms:  -f_n_a_m_e
     and  -fno-_n_a_m_e  (or  -W_n_a_m_e  and  -Wno-_n_a_m_e).  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 _f_i_l_e -pipe -v -x _l_a_n_g_u_a_g_e

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

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




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     Debugging Options
          -a -d_l_e_t_t_e_r_s -fpretend-float -g -g_l_e_v_e_l -gcoff -gxcoff
          -gxcoff+ -gdwarf -gdwarf+ -gstabs -gstabs+ -ggdb -p -pg
          -save-temps -print-libgcc-file-name

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

     Preprocessor Options
          -A_a_s_s_e_r_t_i_o_n -C -dD -dM -dN -D_m_a_c_r_o[=_d_e_f_n] -E -H
          -idirafter _d_i_r -include _f_i_l_e -imacros _f_i_l_e -iprefix
          _f_i_l_e -iwithprefix _d_i_r -M -MD -MM -MMD -nostdinc -P
          -U_m_a_c_r_o -undef

     Assembler Option
          -Wa,_o_p_t_i_o_n

     Linker Options
          -l_l_i_b_r_a_r_y -nostartfiles -nostdlib -static -shared
          -symbolic -Xlinker _o_p_t_i_o_n -Wl,_o_p_t_i_o_n -u _s_y_m_b_o_l

     Directory Options
          -B_p_r_e_f_i_x -I_d_i_r -I- -L_d_i_r

     Target Options
          -b  _m_a_c_h_i_n_e -V _v_e_r_s_i_o_n

     Configuration Dependent Options
          _M_6_8_0_x_0 _O_p_t_i_o_n_s
          -m68000 -m68020 -m68020-40 -m68030 -m68040 -m68881
          -mbitfield -mc68000 -mc68020 -mfpa -mnobitfield -mrtd
          -mshort -msoft-float

          _V_A_X _O_p_t_i_o_n_s
          -mg -mgnu -munix

          _S_P_A_R_C _O_p_t_i_o_n_s
          -mepilogue -mfpu -mhard-float -mno-fpu -mno-epilogue
          -msoft-float -msparclite -mv8

          _C_o_n_v_e_x _O_p_t_i_o_n_s
          -margcount -mc1 -mc2 -mnoargcount




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          _A_M_D_2_9_K _O_p_t_i_o_n_s
          -m29000 -m29050 -mbw -mdw -mkernel-registers -mlarge
          -mnbw -mnodw -msmall -mstack-check -muser-registers

          _M_8_8_K _O_p_t_i_o_n_s
          -m88000 -m88100 -m88110 -mbig-pic -mcheck-zero-division
          -mhandle-large-shift -midentify-revision
          -mno-check-zero-division -mno-ocs-debug-info
          -mno-ocs-frame-position -mno-optimize-arg-area
          -mno-seriazlize-volatile -mno-underscores
          -mocs-debug-info -mocs-frame-position
          -moptimize-arg-area -mserialize-volatile
          -mshort-data-_n_u_m -msvr3 -msvr4 -mtrap-large-shift
          -muse-div-instruction -mversion-03.00
          -mwarn-passed-structs

          _R_S_6_0_0_0 _O_p_t_i_o_n_s
          -mfp-in-toc -mno-fop-in-toc

          _R_T _O_p_t_i_o_n_s
          -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

          _M_I_P_S _O_p_t_i_o_n_s
          -mcpu=_c_p_u _t_y_p_e -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 _n_u_m -nocpp

          _i_3_8_6 _O_p_t_i_o_n_s
          -m486 -mno-486 -msoft-float -mno-fp-ret-in-387

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

          _i_9_6_0 _O_p_t_i_o_n_s
          -m_c_p_u-_t_y_p_e -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

          _D_E_C _A_l_p_h_a _O_p_t_i_o_n_s
          -mfp-regs -mno-fp-regs -mno-soft-float -msoft-float

          _S_y_s_t_e_m _V _O_p_t_i_o_n_s



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GCC(1)                      GNU Tools                      GCC(1)



          -G -Qy -Qn -YP,_p_a_t_h_s -Ym,_d_i_r

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

OVERALL OPTIONS
     -x _l_a_n_g_u_a_g_e
          Specify explicitly the _l_a_n_g_u_a_g_e 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 _l_a_n_g_u_a_g_e are `c', `objective-c',  `c-header',
          `c++',       `cpp-output',       `assembler',       and
          `assembler-with-cpp'.

     -x none
          Turn off any specification of a language, so that  sub-
          sequent  files are handled according to their file name
          suffixes (as they are if `-x'  has  not  been  used  at
          all).

     If you want only some of the four stages  (preprocess,  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-
          tion.

     -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.



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          GCC ignores any input files that don't require compila-
          tion.

     -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-
          ing.

     -o _f_i_l_e
          Place output in file _f_i_l_e.  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
          `_s_o_u_r_c_e._s_u_f_f_i_x' in `_s_o_u_r_c_e.o', its  assembler  file  in
          `_s_o_u_r_c_e.s',  and  all preprocessed C source on standard
          output.

     -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.

     -pipe
          Use pipes rather than temporary files for communication
          between  the various stages of compilation.  This fails
          to work on some systems where the assembler cannot read
          from a pipe; but the GNU assembler has no trouble.

LANGUAGE OPTIONS
     The following options control the dialect of C that the com-
     piler accepts:

     -ansi
          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
          vax 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-
          iers.



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          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
          `-ansi'.

          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
          things.

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

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

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

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

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

     -traditional
          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



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          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'.

     -traditional-cpp
          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'.

     -fdollars-in-identifiers
          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.)

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

     -fexternal-templates
          Produce smaller code for template declarations, by 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.

     -fall-virtual
          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
          appear.

          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



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          can be made directly; in  these  cases  the  calls  are
          direct in any case.

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

     -fthis-is-variable
          Permit assignment to this (C++ only).   The  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-
          variable'.

     -funsigned-char
          Let the type char be unsigned, like unsigned char.

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

          Ideally, a portable program should  always  use  signed
          char or 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.

     -fsigned-char
          Let the type char be signed, like signed char.

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

     -fsigned-bitfields

     -funsigned-bitfields

     -fno-signed-bitfields

     -fno-unsigned-bitfields
          These options control whether a bitfield is  signed  or



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          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.

     -fwritable-strings
          Store string constants in the writable data segment and
          don't  uniquize  them.   This is for compatibility with
          old programs which assume they can  write  into  string
          constants.  `-traditional' also has this effect.

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

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

     If you use the `-E' option, GCC does nothing except  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 _f_i_l_e
          Process _f_i_l_e as input before processing the regular in-
          put file.  In effect, the contents of _f_i_l_e are compiled
          first.  Any `-D' and `-U' options on the  command  line
          are always processed before `-include _f_i_l_e', 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 _f_i_l_e
          Process _f_i_l_e as input, discarding the resulting output,
          before  processing the regular input file.  Because the
          output generated from _f_i_l_e is discarded, the  only  ef-
          fect  of  `-imacros _f_i_l_e' is to make the macros defined
          in _f_i_l_e available for  use  in  the  main  input.   The
          preprocessor evaluates any `-D' and `-U' options on the
          command line before processing `-imacros_f_i_l_e',  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 _d_i_r
          Add the directory _d_i_r 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



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          to).

     -iprefix _p_r_e_f_i_x
          Specify _p_r_e_f_i_x as the prefix for subsequent `-iwithpre-
          fix' options.

     -iwithprefix _d_i_r
          Add a  directory  to  the  second  include  path.   The
          directory's  name  is  made by concatenating _p_r_e_f_i_x and
          _d_i_r, where _p_r_e_f_i_x was specified previously with `-ipre-
          fix'.

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

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

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

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




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          `-M' implies `-E'.

     -MM  Like `-M' but the output mentions only the user  header
          files  included  with  `#include _f_i_l_e"'.  System header
          files included with `#include <_f_i_l_e>' 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.

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

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

     -D_m_a_c_r_o
          Define macro _m_a_c_r_o with the string `1' as  its  defini-
          tion.

     -D_m_a_c_r_o=_d_e_f_n
          Define macro _m_a_c_r_o as _d_e_f_n.    All instances of `-D' on
          the command line are processed before any `-U' options.

     -U_m_a_c_r_o
          Undefine macro _m_a_c_r_o.  `-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



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          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 _n_a_m_e' is included in the
          output.

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

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

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

     -l_l_i_b_r_a_r_y
          Use the library named _l_i_b_r_a_r_y when linking.

          The linker searches a standard list of directories  for
          the   library,   which   is   actually   a  file  named
          `lib_l_i_b_r_a_r_y.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  _l_i_b_r_a_r_y  with
          `lib' and `.a' and searches several directories.

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




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     -nostartfiles
          Do not use the standard system startup files when link-
          ing.  The standard libraries are used normally.

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

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

     -shared
          Produce a shared object which can then be  linked  with
          other  objects  to form an executable.  Only a few sys-
          tems support this option.

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

     -Xlinker _o_p_t_i_o_n
          Pass _o_p_t_i_o_n 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.

     -Wl,_o_p_t_i_o_n
          Pass _o_p_t_i_o_n as an option to the linker.  If _o_p_t_i_o_n con-
          tains  commas, it is split into multiple options at the
          commas.

     -u _s_y_m_b_o_l
          Pretend the symbol _s_y_m_b_o_l 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.





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DIRECTORY OPTIONS
     These options  specify  directories  to  search  for  header
     files, for libraries and for parts of the compiler:

     -I_d_i_r
          Append  directory  _d_i_r  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 "_f_i_l_e"'; they are not searched for  `#include
          <_f_i_l_e>'.

          If additional directories are specified with  `-I'  op-
          tions  after  the `-I-', these directories are searched
          for all `#include' directives.   (Ordinarily  _a_l_l  `-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
          "_f_i_l_e"'.   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.

     -L_d_i_r
          Add directory _d_i_r to the  list  of  directories  to  be
          searched for `-l'.

     -B_p_r_e_f_i_x
          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 _p_r_e_f_i_x as a prefix for each program
          it    tries    to    run,   both   with   and   without
          `_m_a_c_h_i_n_e/_v_e_r_s_i_o_n/'.

          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



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          the  directories  specified  in your `PATH' environment
          variable.

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

          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.

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

     These options control the amount and kinds of warnings  pro-
     duced by GNU CC:

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

     -w   Inhibit all warning messages.

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

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

          Valid ANSI standard C programs should compile  properly
          with or without this option (though a rare few will 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  _u_s_e  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.



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     -pedantic-errors
          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 contains no side effects.

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

     -Wimplicit
          Warn whenever a function or parameter is implicitly de-
          clared.

     -Wreturn-type
          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.

     -Wunused
          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.



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

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

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

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

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

     -Wuninitialized
          An automatic variable is used without first being  ini-
          tialized.

          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-
          ters.

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

          These warnings are made optional because GNU CC is  not
          smart  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:



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

          If the value of y is always 1, 2 or 3, then x is always
          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
          set.

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

     -Wparentheses
          Warn if parentheses are omitted in certain contexts.

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

     -Wall
          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.

     -Wtraditional
          Warn about certain constructs that  behave  differently
          in traditional and ANSI C.

        o+ Macro arguments occurring within  string  constants  in



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          the macro body.  These would substitute the argument in
          traditional C, but are part of the constant in ANSI C.

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

        o+ A switch statement has an operand of type long.

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

     -Wid-clash-_l_e_n
          Warn whenever two distinct  identifiers  match  in  the
          first _l_e_n characters.  This may help you prepare a pro-
          gram that will compile with  certain  obsolete,  brain-
          damaged compilers.

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

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

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

     -Wwrite-strings
          Give string constants the type  const  char[_l_e_n_g_t_h]  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.

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



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          point argument except when the same as the default pro-
          motion.

     -Waggregate-return
          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.)

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

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

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

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

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

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

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

     -Werror
          Treat warnings as errors; abort compilation  after  any



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          warning.

DEBUGGING OPTIONS
     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.

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

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

     -gstabs+
          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.



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     -gcoff
          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.

     -gxcoff
          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.

     -gxcoff+
          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.

     -gdwarf
          Produce debugging information in DWARF format (if  that
          is  supported).  This is the format used by SDB on most
          System V Release 4 systems.

     -gdwarf+
          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.

     -g_l_e_v_e_l
     -ggdb_l_e_v_e_l
     -gstabs_l_e_v_e_l
     -gcoff_l_e_v_e_l -gxcoff_l_e_v_e_l

     -gdwarf_l_e_v_e_l
          Request debugging information and  also  use  _l_e_v_e_l  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-



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          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
          data.

     -d_l_e_t_t_e_r_s
          Says to make  debugging  dumps  during  compilation  at
          times specified by _l_e_t_t_e_r_s.  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
          error.

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

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

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

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

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

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

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

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

     -dS  Dump after the first instruction  scheduling  pass,  to
          `_f_i_l_e.sched'.

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




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

     -dR  Dump after the second instruction scheduling  pass,  to
          `_f_i_l_e.sched2'.

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

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

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

     -da  Produce all the dumps listed above.

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

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

     -fpretend-float
          When running a cross-compiler, pretend that the  target
          machine uses the same floating point format as the host
          machine.  This causes incorrect output  of  the  actual
          floating constants, but the actual instruction sequence
          will probably be the same as GNU  CC  would  make  when
          running on the target machine.

     -save-temps
          Store the usual  "temporary"  intermediate  files  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-libgcc-file-name
          Print the  full  absolute  name  of  the  library  file
          `libgcc.a'  that  would be used when linking-and do not
          do anything else.  With this option, GNU  CC  does  not
          compile or link anything; it just prints the file name.

OPTIMIZATION OPTIONS
     These options control various sorts of optimizations:

     -O

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

          Without `-O', the compiler's goal is to reduce the cost
          of  compilation  and  to make debugging produce the ex-
          pected results.  Statements  are  independent:  if  you



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          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',    `-fthread-jumps'    and
          `-fdelayed-branch'  are  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.  As compared to -O, this option increases  both
          compilation  time  and the performance of the generated
          code.

          -O2 turns on all -f_f_l_a_g options that enable more optim-
          ization,  except for -funroll-loops, -funroll-all-loops
          and -fomit-frame-pointer.

     -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-
          tive.

     Options of the  form  `-f_f_l_a_g'  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.

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

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




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     -fmemoize-lookups

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

          The first time the compiler must  build  a  call  to  a
          member  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
          this

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

          makes six passes through all three steps.  By  using  a
          software  cache,  a  "hit"  significantly  reduces this
          cost.  Unfortunately, using the cache introduces 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.

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

     -fno-defer-pop
          Always pop the arguments to each function call as  soon



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          as  that function returns.  For machines which must pop
          arguments after a function call, the compiler  normally
          lets  arguments  accumulate  on  the  stack for several
          function calls and pops them all at once.

     -fforce-mem
          Force memory operands to be copied into  registers  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.

     -fforce-addr
          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.

     -fomit-frame-pointer
          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.  _I_t _a_l_s_o  _m_a_k_e_s  _d_e_b_u_g_g_i_n_g  _i_m_p_o_s_s_i_b_l_e  _o_n  most
          machines.

          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.

     -finline-functions
          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
          right.

     -fcaller-saves
          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.




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

     -fkeep-inline-functions
          Even if all calls to a given function  are  integrated,
          and  the function is declared static, nevertheless out-
          put a separate run-time callable version of  the  func-
          tion.

     -fno-function-cse
          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.

     -fno-peephole
          Disable any machine-specific peephole optimizations.

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

          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.

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

     -fthread-jumps
          Perform optimizations where we check to see if  a  jump



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          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.

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

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

     -fcse-follow-jumps
          In common subexpression elimination, scan through  jump
          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.

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

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

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

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

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

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



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     -fexpensive-optimizations
          Perform a number of minor optimizations that are  rela-
          tively expensive.

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

     -fschedule-insns
          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
          required.

     -fschedule-insns2
          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
          cycle.

TARGET OPTIONS
     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'
     option.

     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
     another.

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

          The value to use for _m_a_c_h_i_n_e 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.




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

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

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

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

     -m68000

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

     -m68020

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

     -m68881
          Generate  output  containing  68881  instructions   for
          floating  point.   This  is the default for most 68020-
          based systems unless -nfp was specified when  the  com-
          piler was configured.

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

     -m68040



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

     -m68020-40
          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.

     -mfpa
          Generate output containing  Sun  FPA  instructions  for
          floating point.

     -msoft-float
          Generate output containing library calls  for  floating
          point.   _W_A_R_N_I_N_G:  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
          cross-compilation.

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

     -mnobitfield
          Do not use the bit-field instructions.   `-m68000'  im-
          plies `-mnobitfield'.

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

     -mrtd
          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
          there.

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

          Also, you must  provide  function  prototypes  for  all
          functions  that take variable numbers of arguments (in-
          cluding printf); otherwise incorrect code will be  gen-
          erated for calls to those functions.

          In addition, seriously incorrect code  will  result  if



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          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:

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

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

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

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

     -mfpu

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

     -mno-fpu

     -msoft-float
          Generate output containing library calls  for  floating
          point.  _W_a_r_n_i_n_g: 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
          cross-compilation.

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

     -mno-epilogue

     -mepilogue
          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.




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

     -mv8

     -msparclite
          These two options select variations on the SPARC archi-
          tecture.

          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 `-m' options are defined for the Convex:

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

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

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

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

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

     -mdw Generate code that assumes the DW  bit  is  set,  i.e.,
          that byte and halfword operations are directly support-
          ed by the hardware.  This is the default.

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

     -mbw Generate code that assumes the system supports byte and



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          halfword write operations.  This is the default.

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

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

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

     -m29050
          Generate code for the Am29050.

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

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

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

     -mstack-check
          Insert a call to __msp_check after each  stack  adjust-
          ment.  This is often used for kernel code.

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

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

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




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

     -midentify-revision
          Include an ident  directive  in  the  assembler  output
          recording  the source file name, compiler name and ver-
          sion, timestamp, and compilation flags used.

     -mno-underscores
          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
          name.

     -mno-check-zero-division

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

     -mocs-debug-info

     -mno-ocs-debug-info
          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.

     -mocs-frame-position

     -mno-ocs-frame-position
          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'.

     -moptimize-arg-area

     -mno-optimize-arg-area
          Control  how  to  store  function  arguments  in  stack
          frames.   `-moptimize-arg-area'  saves  space,  but may
          break       some       debuggers       (not       GDB).
          `-mno-optimize-arg-area'  conforms better to standards.



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          By default GCC does not optimize the argument area.

     -mshort-data-_n_u_m
          _n_u_m 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
          _n_u_m 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-_n_u_m'  is  not  effective for _n_u_m
          greater than 64K.

     -mserialize-volatile

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

          GNU CC always guarantees consistency  by  default,  for
          the  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'.

     -msvr4

     -msvr3
          Turn on (`-msvr4') or off  (`-msvr3')  compiler  exten-
          sions  related to System V release 4 (SVr4).  This con-



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          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
          weak'

        o+ `-msvr4' makes GCC issue additional declaration  direc-
          tives used in SVr4.

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

     -mtrap-large-shift

     -mhandle-large-shift
          Include code to detect bit-shifts of more than 31 bits;
          respectively,  trap  such shifts or emit code to handle
          them properly.  By default GCC makes no special  provi-
          sion for large bit shifts.

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

     -mversion-03.00
          In the DG/UX configuration, there are  two  flavors  of
          SVr4.   This  option  modifies -msvr4 to select whether
          the hybrid-COFF or real-ELF flavor is used.  All  other
          configurations ignore this option.

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

     These options are defined for the IBM RS6000:

     -mfp-in-toc

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



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

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

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

     -mfull-fp-blocks
          Generate full-size floating point data blocks,  includ-
          ing  the minimum amount of scratch space recommended by
          IBM.  This is the default.

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

     -mfp-arg-in-fpregs
          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.

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

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

     -mnohc-struct-return
          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-
     puters:

     -mcpu=_c_p_u-_t_y_p_e
          Assume the defaults for the machine type _c_p_u-_t_y_p_e  when
          scheduling  instructions.   The default _c_p_u-_t_y_p_e is de-
          fault, which picks the longest cycles times for any  of
          the  machines, in order that the code run at reasonable



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          rates on all MIPS cpu's.  Other  choices  for  _c_p_u-_t_y_p_e
          are  r2000,  r3000,  r4000, and r6000.  While picking a
          specific _c_p_u-_t_y_p_e 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.

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

     -mips3
          Issue instructions from level 3 of the MIPS ISA (64 bit
          instructions).   The -mcpu=r4000 switch must be used in
          conjunction with -mips2.

     -mint64

     -mlong64

     -mlonglong128
          These options don't work at present.

     -mmips-as
          Generate  code  for  the  MIPS  assembler,  and  invoke
          mips-tfile  to  add  normal debug information.  This is
          the default for all  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.

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

     -mrnames

     -mno-rnames
          The -mrnames switch says to output code using the  MIPS
          software  names  for  the  registers,  instead  of  the
          hardware names (ie, a0 instead of $4).  The GNU  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
          default.

     -mgpopt



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     -mno-gpopt
          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.

     -mstats

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

     -mmemcpy

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

     -mmips-tfile

     -mno-mips-tfile
          The -mno-mips-tfile  switch  causes  the  compiler  not
          postprocess  the  object  file with the mips-tfile 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
          same.

     -msoft-float
          Generate output containing library calls  for  floating
          point.   _W_A_R_N_I_N_G:  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
          cross-compilation.

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

     -mfp64
          Assume that the FR bit in the status word  is  on,  and
          that  there are 32 64-bit floating point registers, in-



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          stead of 32 32-bit floating point registers.  You  must
          also specify the -mcpu=r4000 and -mips3 switches.

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

     -mabicalls

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

     -mhalf-pic

     -mno-half-pic
          The -mhalf-pic switch says to put  pointers  to  extern
          references  into  the  data  section  and load them up,
          rather than put the references  in  the  text  section.
          This option does not work at present.  -G_n_u_m Put global
          and static items less than or equal to _n_u_m  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, _n_u_m is 8 when the MIPS assem-
          bler is used, and 0 when the  GNU  assembler  is  used.
          The  -G_n_u_m  switch  is also passed to the assembler and
          linker.  All modules should be compiled with  the  same
          -G_n_u_m value.

     -nocpp
          Tell the MIPS assembler to not  run  it's  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

     -mno-486
          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.

     -msoft-float
          Generate output containing library calls  for  floating
          point.   _W_a_r_n_i_n_g:  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



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          cross-compilation.

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

     -mno-fp-ret-in-387
          Do not use the FPU registers for return values of func-
          tions.

          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-
     puters:

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

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

     -mkernel
          Generate code which is suitable  for  use  in  kernels.
          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.

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

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

     -mlong-calls
          Generate code which allows calls to  functions  greater
          than 256K away from the caller when the caller and 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.



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     -mdisable-fpregs
          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.

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

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

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

     -m_c_p_u-_t_y_p_e
          Assume the defaults for the machine type  _c_p_u-_t_y_p_e  for
          instruction and addressing-mode availability and align-
          ment.  The default _c_p_u-_t_y_p_e is kb;  other  choices  are
          ka, mc, ca, cf, sa, and sb.

     -mnumerics

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

     -mleaf-procedures

     -mno-leaf-procedures
          Do (or do not) attempt to alter leaf procedures  to  be
          callable  with  the  _b_a_l  instruction  as well as _c_a_l_l.
          This will result in more efficient  code  for  explicit
          calls  when  the  _b_a_l 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.

     -mtail-call

     -mno-tail-call
          Do (or do not) make additional attempts  (beyond  those
          of the machine-independent portions of the compiler) to
          optimize tail-recursive calls into branches.   You  may
          not  want  to  do  this  because the detection of cases
          where this is not valid is not totally  complete.   The



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          default is -mno-tail-call.

     -mcomplex-addr

     -mno-complex-addr
          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.

     -mcode-align

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

     -mic-compat

     -mic2.0-compat

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

     -masm-compat

     -mintel-asm
          Enable compatibility with the iC960 assembler.

     -mstrict-align

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

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

     -mno-soft-float

     -msoft-float
          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-



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          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
          them.

          Note that Alpha implementations without  floating-point
          operations  are  required to have floating-point regis-
          ters.

     -mfp-reg

     -mno-fp-regs
          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).

     -YP,_d_i_r_s
          Search the directories _d_i_r_s, and  no  others,  for  li-
          braries specified with `-l'.  You can separate directo-
          ry entries in _d_i_r_s from one another with colons.

     -Ym,_d_i_r
          Look in the directory _d_i_r to find the M4  preprocessor.
          The assembler uses this option.



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CODE GENERATION OPTIONS
     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.

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

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

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

          Checking that references of  this  sort  have  non-null
          values 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.

     -fpcc-struct-return
          Use the same convention for returning struct and  union
          values  that  is  used  by the usual C compiler on your
          system.  This 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.

     -freg-struct-return
          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
          -fpcc-struct-return.

     -fshort-enums
          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.




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

     -fshared-data
          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.

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

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

     -fno-gnu-linker
          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
          _m_u_s_t use collect2, the compiler driver gcc  is  config-
          ured to do this automatically.

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

     -fverbose-asm
          Put extra commentary information in the  generated  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).

     -fvolatile



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          Consider all memory references through pointers  to  be
          volatile.

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

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

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

     -ffixed-_r_e_g
          Treat the register named _r_e_g 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
          role).

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

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

     -fcall-used-_r_e_g
          Treat the register named _r_e_g as an allocatable 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 _r_e_g.

          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.

     -fcall-saved-_r_e_g
          Treat the register named _r_e_g as an allocatable 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-
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          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.

PRAGMAS
     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 de-
          fine  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 "_o_b_j_e_c_t_s.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
          files.

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



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          include code from multiple header files.

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

FILES
     file.c             C source file
     file.h             C header (preprocessor) file
     file.i             preprocessed C source file
     file.C             C++ source file
     file.cc            C++ source file
     file.cxx           C++ source file
     file.m             Objective-C source file
     file.s             assembly language file
     file.o             object file
     a.out              link edited output
     _T_M_P_D_I_R/cc*         temporary files
     _L_I_B_D_I_R/cpp         preprocessor
     _L_I_B_D_I_R/cc1         compiler for C
     _L_I_B_D_I_R/cc1plus     compiler for C++
     _L_I_B_D_I_R/collect     linker front end needed on some machines
     _L_I_B_D_I_R/libgcc.a    GCC subroutine library
     /lib/crt[01n].o    start-up routine
     _L_I_B_D_I_R/ccrt0       additional start-up routine for C++
     /lib/libc.a        standard C library, see
     _i_n_t_r_o(3)
     /usr/include       standard directory for #include files
     _L_I_B_D_I_R/include     standard gcc directory for #include files
     _L_I_B_D_I_R/g++-include additional g++ directory for #include

     _L_I_B_D_I_R is usually /usr/local/lib/_m_a_c_h_i_n_e/_v_e_r_s_i_o_n.
     _T_M_P_D_I_R comes from the environment variable  TMPDIR  (default
     /usr/tmp if available, else /tmp).

SEE ALSO
     cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1).
     `gcc', `cpp', `as', `ld', and `gdb' entries in info.
     _U_s_i_n_g _a_n_d _P_o_r_t_i_n_g _G_N_U  _C_C  (_f_o_r  _v_e_r_s_i_o_n  _2._0),  Richard  M.
     Stallman; _T_h_e _C _P_r_e_p_r_o_c_e_s_s_o_r, Richard M. Stallman; _D_e_b_u_g_g_i_n_g
     _w_i_t_h _G_D_B: _t_h_e _G_N_U _S_o_u_r_c_e-_L_e_v_e_l _D_e_b_u_g_g_e_r, Richard M. Stallman
     and  Roland H. Pesch; _U_s_i_n_g _a_s: _t_h_e _G_N_U _A_s_s_e_m_b_l_e_r, Dean Els-
     ner, Jay Fenlason & friends; _l_d: _t_h_e _G_N_U _l_i_n_k_e_r, Steve Cham-
     berlain and Roland Pesch.

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

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

     Permission is granted to make and distribute verbatim copies
     of  this  manual provided the copyright notice and this per-



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     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.

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







































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