This is doc/gcc.info, produced by makeinfo version 4.0 from
doc/gcc.texi.

INFO-DIR-SECTION Programming
START-INFO-DIR-ENTRY
* gcc: (gcc).                  The GNU Compiler Collection.
END-INFO-DIR-ENTRY
   This file documents the use and the internals of the GNU compiler.


   Published by the Free Software Foundation
59 Temple Place - Suite 330
Boston, MA 02111-1307 USA


   Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001 Free Software Foundation, Inc.


   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below).  A copy of the license is
included in the section entitled "GNU Free Documentation License".

   (a) The FSF's Front-Cover Text is:

   A GNU Manual

   (b) The FSF's Back-Cover Text is:

   You have freedom to copy and modify this GNU Manual, like GNU
software.  Copies published by the Free Software Foundation raise
funds for GNU development.


File: gcc.info,  Node: Code Gen Options,  Next: Environment Variables,  Prev: Submodel Options,  Up: Invoking GCC

Options for Code Generation Conventions
=======================================

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

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

`-fexceptions'
     Enable exception handling.  Generates extra code needed to
     propagate exceptions.  For some targets, this implies GCC will
     generate frame unwind information for all functions, which can
     produce significant data size overhead, although it does not
     affect execution.  If you do not specify this option, GCC will
     enable it by default for languages like C++ which normally require
     exception handling, and disable it for languages like C that do
     not normally require it.  However, you may need to enable this
     option when compiling C code that needs to interoperate properly
     with exception handlers written in C++.  You may also wish to
     disable this option if you are compiling older C++ programs that
     don't use exception handling.

`-fnon-call-exceptions'
     Generate code that allows trapping instructions to throw
     exceptions.  Note that this requires platform-specific runtime
     support that does not exist everywhere.  Moreover, it only allows
     _trapping_ instructions to throw exceptions, i.e. memory
     references or floating point instructions.  It does not allow
     exceptions to be thrown from arbitrary signal handlers such as
     `SIGALRM'.

`-funwind-tables'
     Similar to `-fexceptions', except that it will just generate any
     needed static data, but will not affect the generated code in any
     other way.  You will normally not enable this option; instead, a
     language processor that needs this handling would enable it on
     your behalf.

`-fpcc-struct-return'
     Return "short" `struct' and `union' values in memory like longer
     ones, rather than in registers.  This convention is less
     efficient, but it has the advantage of allowing intercallability
     between GCC-compiled files and files compiled with other compilers.

     The precise convention for returning structures in memory depends
     on the target configuration macros.

     Short structures and unions are those whose size and alignment
     match that of some integer type.

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

     If you specify neither `-fpcc-struct-return' nor its contrary
     `-freg-struct-return', GCC defaults to whichever convention is
     standard for the target.  If there is no standard convention, GCC
     defaults to `-fpcc-struct-return', except on targets where GCC is
     the principal compiler.  In those cases, we can choose the
     standard, and we chose the more efficient register return
     alternative.

`-fshort-enums'
     Allocate to an `enum' type only as many bytes as it needs for the
     declared range of possible values.  Specifically, the `enum' type
     will be equivalent to the smallest integer type which has enough
     room.

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

`-fshared-data'
     Requests that the data and non-`const' variables of this
     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'
     In C, allocate even uninitialized global variables in the data
     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++ constructors and
     destructors) in the form used by the GNU linker (on systems where
     the GNU linker is the standard method of handling them).  Use this
     option when you want to use a non-GNU linker, which also requires
     using the `collect2' program to make sure the system linker
     includes constructors and destructors.  (`collect2' is included in
     the GCC distribution.)  For systems which _must_ use `collect2',
     the compiler driver `gcc' is configured 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 locations far apart in memory.  This
     option is used when compiling `crtstuff.c'; you should not need to
     use it for anything else.

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

     `-fno-verbose-asm', the default, causes the extra information to
     be omitted and is useful when comparing two assembler files.

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

`-fvolatile-global'
     Consider all memory references to extern and global data items to
     be volatile.  GCC does not consider static data items to be
     volatile because of this switch.

`-fvolatile-static'
     Consider all memory references to static data to be volatile.

`-fpic'
     Generate position-independent code (PIC) suitable for use in a
     shared library, if supported for the target machine.  Such code
     accesses all constant addresses through a global offset table
     (GOT).  The dynamic loader resolves the GOT entries when the
     program starts (the dynamic loader is not part of GCC; it is part
     of the operating system).  If the GOT size for the linked
     executable exceeds a machine-specific maximum size, you get an
     error message from the linker indicating that `-fpic' does not
     work; in that case, recompile with `-fPIC' instead.  (These
     maximums are 16k on the m88k, 8k on the Sparc, and 32k on the m68k
     and RS/6000.  The 386 has no such limit.)

     Position-independent code requires special support, and therefore
     works only on certain machines.  For the 386, GCC supports PIC for
     System V but not for the Sun 386i.  Code generated for the IBM
     RS/6000 is always position-independent.

`-fPIC'
     If supported for the target machine, emit position-independent
     code, suitable for dynamic linking and avoiding any limit on the
     size of the global offset table.  This option makes a difference
     on the m68k, m88k, and the Sparc.

     Position-independent code requires special support, and therefore
     works only on certain machines.

`-ffixed-REG'
     Treat the register named REG as a fixed register; generated code
     should never refer to it (except perhaps as a stack pointer, frame
     pointer or in some other fixed role).

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

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

`-fcall-used-REG'
     Treat the register named REG as an allocable register that is
     clobbered by function calls.  It may be allocated for temporaries
     or variables that do not live across a call.  Functions compiled
     this way will not save and restore the register REG.

     It is an error to used this flag with the frame pointer or stack
     pointer.  Use of this flag for other registers that have fixed
     pervasive roles in the machine's execution model will produce
     disastrous results.

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

`-fcall-saved-REG'
     Treat the register named REG as an allocable register saved by
     functions.  It may be allocated even for temporaries or variables
     that live across a call.  Functions compiled this way will save
     and restore the register REG if they use it.

     It is an error to used this flag with the frame pointer or stack
     pointer.  Use of this flag for other registers that have fixed
     pervasive roles in the machine's execution model will produce
     disastrous results.

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

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

`-fpack-struct'
     Pack all structure members together without holes.  Usually you
     would not want to use this option, since it makes the code
     suboptimal, and the offsets of structure members won't agree with
     system libraries.

`-fcheck-memory-usage'
     Generate extra code to check each memory access.  GCC will generate
     code that is suitable for a detector of bad memory accesses such as
     `Checker'.

     Normally, you should compile all, or none, of your code with this
     option.

     If you do mix code compiled with and without this option, you must
     ensure that all code that has side effects and that is called by
     code compiled with this option is, itself, compiled with this
     option.  If you do not, you might get erroneous messages from the
     detector.

     If you use functions from a library that have side-effects (such as
     `read'), you might not be able to recompile the library and
     specify this option.  In that case, you can enable the
     `-fprefix-function-name' option, which requests GCC to encapsulate
     your code and make other functions look as if they were compiled
     with `-fcheck-memory-usage'.  This is done by calling "stubs",
     which are provided by the detector.  If you cannot find or build
     stubs for every function you call, you might have to specify
     `-fcheck-memory-usage' without `-fprefix-function-name'.

     If you specify this option, you can not use the `asm' or `__asm__'
     keywords in functions with memory checking enabled.  GCC cannot
     understand what the `asm' statement may do, and therefore cannot
     generate the appropriate code, so it will reject it.  However, if
     you specify the function attribute `no_check_memory_usage' (*note
     Function Attributes::), GCC will disable memory checking within a
     function; you may use `asm' statements inside such functions.  You
     may have an inline expansion of a non-checked function within a
     checked function; in that case GCC will not generate checks for
     the inlined function's memory accesses.

     If you move your `asm' statements to non-checked inline functions
     and they do access memory, you can add calls to the support code
     in your inline function, to indicate any reads, writes, or copies
     being done.  These calls would be similar to those done in the
     stubs described above.

`-fprefix-function-name'
     Request GCC to add a prefix to the symbols generated for function
     names.  GCC adds a prefix to the names of functions defined as
     well as functions called.  Code compiled with this option and code
     compiled without the option can't be linked together, unless stubs
     are used.

     If you compile the following code with `-fprefix-function-name'
          extern void bar (int);
          void
          foo (int a)
          {
            return bar (a + 5);
          }

     GCC will compile the code as if it was written:
          extern void prefix_bar (int);
          void
          prefix_foo (int a)
          {
            return prefix_bar (a + 5);
          }
     This option is designed to be used with `-fcheck-memory-usage'.

`-finstrument-functions'
     Generate instrumentation calls for entry and exit to functions.
     Just after function entry and just before function exit, the
     following profiling functions will be called with the address of
     the current function and its call site.  (On some platforms,
     `__builtin_return_address' does not work beyond the current
     function, so the call site information may not be available to the
     profiling functions otherwise.)

          void __cyg_profile_func_enter (void *this_fn,
                                         void *call_site);
          void __cyg_profile_func_exit  (void *this_fn,
                                         void *call_site);

     The first argument is the address of the start of the current
     function, which may be looked up exactly in the symbol table.

     This instrumentation is also done for functions expanded inline in
     other functions.  The profiling calls will indicate where,
     conceptually, the inline function is entered and exited.  This
     means that addressable versions of such functions must be
     available.  If all your uses of a function are expanded inline,
     this may mean an additional expansion of code size.  If you use
     `extern inline' in your C code, an addressable version of such
     functions must be provided.  (This is normally the case anyways,
     but if you get lucky and the optimizer always expands the
     functions inline, you might have gotten away without providing
     static copies.)

     A function may be given the attribute `no_instrument_function', in
     which case this instrumentation will not be done.  This can be
     used, for example, for the profiling functions listed above,
     high-priority interrupt routines, and any functions from which the
     profiling functions cannot safely be called (perhaps signal
     handlers, if the profiling routines generate output or allocate
     memory).

`-fstack-check'
     Generate code to verify that you do not go beyond the boundary of
     the stack.  You should specify this flag if you are running in an
     environment with multiple threads, but only rarely need to specify
     it in a single-threaded environment since stack overflow is
     automatically detected on nearly all systems if there is only one
     stack.

     Note that this switch does not actually cause checking to be done;
     the operating system must do that.  The switch causes generation
     of code to ensure that the operating system sees the stack being
     extended.

`-fstack-limit-register=REG'
`-fstack-limit-symbol=SYM'
`-fno-stack-limit'
     Generate code to ensure that the stack does not grow beyond a
     certain value, either the value of a register or the address of a
     symbol.  If the stack would grow beyond the value, a signal is
     raised.  For most targets, the signal is raised before the stack
     overruns the boundary, so it is possible to catch the signal
     without taking special precautions.

     For instance, if the stack starts at address `0x80000000' and grows
     downwards you can use the flags `-fstack-limit-symbol=__stack_limit
     -Wl,--defsym,__stack_limit=0x7ffe0000' which will enforce a stack
     limit of 128K.

`-fargument-alias'
`-fargument-noalias'
`-fargument-noalias-global'
     Specify the possible relationships among parameters and between
     parameters and global data.

     `-fargument-alias' specifies that arguments (parameters) may alias
     each other and may alias global storage.  `-fargument-noalias'
     specifies that arguments do not alias each other, but may alias
     global storage.  `-fargument-noalias-global' specifies that
     arguments do not alias each other and do not alias global storage.

     Each language will automatically use whatever option is required by
     the language standard.  You should not need to use these options
     yourself.

`-fleading-underscore'
     This option and its counterpart, `-fno-leading-underscore',
     forcibly change the way C symbols are represented in the object
     file.  One use is to help link with legacy assembly code.

     Be warned that you should know what you are doing when invoking
     this option, and that not all targets provide complete support for
     it.


File: gcc.info,  Node: Environment Variables,  Next: Running Protoize,  Prev: Code Gen Options,  Up: Invoking GCC

Environment Variables Affecting GCC
===================================

   This section describes several environment variables that affect how
GCC operates.  Some of them work by specifying directories or prefixes
to use when searching for various kinds of files.  Some are used to
specify other aspects of the compilation environment.

   Note that you can also specify places to search using options such as
`-B', `-I' and `-L' (*note Directory Options::).  These take precedence
over places specified using environment variables, which in turn take
precedence over those specified by the configuration of GCC.  *Note
Driver::.

`LANG'
`LC_CTYPE'
`LC_MESSAGES'
`LC_ALL'
     These environment variables control the way that GCC uses
     localization information that allow GCC to work with different
     national conventions.  GCC inspects the locale categories
     `LC_CTYPE' and `LC_MESSAGES' if it has been configured to do so.
     These locale categories can be set to any value supported by your
     installation.  A typical value is `en_UK' for English in the United
     Kingdom.

     The `LC_CTYPE' environment variable specifies character
     classification.  GCC uses it to determine the character boundaries
     in a string; this is needed for some multibyte encodings that
     contain quote and escape characters that would otherwise be
     interpreted as a string end or escape.

     The `LC_MESSAGES' environment variable specifies the language to
     use in diagnostic messages.

     If the `LC_ALL' environment variable is set, it overrides the value
     of `LC_CTYPE' and `LC_MESSAGES'; otherwise, `LC_CTYPE' and
     `LC_MESSAGES' default to the value of the `LANG' environment
     variable.  If none of these variables are set, GCC defaults to
     traditional C English behavior.

`TMPDIR'
     If `TMPDIR' is set, it specifies the directory to use for temporary
     files.  GCC uses temporary files to hold the output of one stage of
     compilation which is to be used as input to the next stage: for
     example, the output of the preprocessor, which is the input to the
     compiler proper.

`GCC_EXEC_PREFIX'
     If `GCC_EXEC_PREFIX' is set, it specifies a prefix to use in the
     names of the subprograms executed by the compiler.  No slash is
     added when this prefix is combined with the name of a subprogram,
     but you can specify a prefix that ends with a slash if you wish.

     If `GCC_EXEC_PREFIX' is not set, GCC will attempt to figure out an
     appropriate prefix to use based on the pathname it was invoked
     with.

     If GCC cannot find the subprogram using the specified prefix, it
     tries looking in the usual places for the subprogram.

     The default value of `GCC_EXEC_PREFIX' is `PREFIX/lib/gcc-lib/'
     where PREFIX is the value of `prefix' when you ran the `configure'
     script.

     Other prefixes specified with `-B' take precedence over this
     prefix.

     This prefix is also used for finding files such as `crt0.o' that
     are used for linking.

     In addition, the prefix is used in an unusual way in finding the
     directories to search for header files.  For each of the standard
     directories whose name normally begins with
     `/usr/local/lib/gcc-lib' (more precisely, with the value of
     `GCC_INCLUDE_DIR'), GCC tries replacing that beginning with the
     specified prefix to produce an alternate directory name.  Thus,
     with `-Bfoo/', GCC will search `foo/bar' where it would normally
     search `/usr/local/lib/bar'.  These alternate directories are
     searched first; the standard directories come next.

`COMPILER_PATH'
     The value of `COMPILER_PATH' is a colon-separated list of
     directories, much like `PATH'.  GCC tries the directories thus
     specified when searching for subprograms, if it can't find the
     subprograms using `GCC_EXEC_PREFIX'.

`LIBRARY_PATH'
     The value of `LIBRARY_PATH' is a colon-separated list of
     directories, much like `PATH'.  When configured as a native
     compiler, GCC tries the directories thus specified when searching
     for special linker files, if it can't find them using
     `GCC_EXEC_PREFIX'.  Linking using GCC also uses these directories
     when searching for ordinary libraries for the `-l' option (but
     directories specified with `-L' come first).

`C_INCLUDE_PATH'
`CPLUS_INCLUDE_PATH'
`OBJC_INCLUDE_PATH'
     These environment variables pertain to particular languages.  Each
     variable's value is a colon-separated list of directories, much
     like `PATH'.  When GCC searches for header files, it tries the
     directories listed in the variable for the language you are using,
     after the directories specified with `-I' but before the standard
     header file directories.

`DEPENDENCIES_OUTPUT'
     If this variable is set, its value specifies how to output
     dependencies for Make based on the header files processed by the
     compiler.  This output looks much like the output from the `-M'
     option (*note Preprocessor Options::), but it goes to a separate
     file, and is in addition to the usual results of compilation.

     The value of `DEPENDENCIES_OUTPUT' can be just a file name, in
     which case the Make rules are written to that file, guessing the
     target name from the source file name.  Or the value can have the
     form `FILE TARGET', in which case the rules are written to file
     FILE using TARGET as the target name.

`LANG'
     This variable is used to pass locale information to the compiler.
     One way in which this information is used is to determine the
     character set to be used when character literals, string literals
     and comments are parsed in C and C++.  When the compiler is
     configured to allow multibyte characters, the following values for
     `LANG' are recognized:

    `C-JIS'
          Recognize JIS characters.

    `C-SJIS'
          Recognize SJIS characters.

    `C-EUCJP'
          Recognize EUCJP characters.

     If `LANG' is not defined, or if it has some other value, then the
     compiler will use mblen and mbtowc as defined by the default
     locale to recognize and translate multibyte characters.


File: gcc.info,  Node: Running Protoize,  Prev: Environment Variables,  Up: Invoking GCC

Running Protoize
================

   The program `protoize' is an optional part of GCC.  You can use it
to add prototypes to a program, thus converting the program to ISO C in
one respect.  The companion program `unprotoize' does the reverse: it
removes argument types from any prototypes that are found.

   When you run these programs, you must specify a set of source files
as command line arguments.  The conversion programs start out by
compiling these files to see what functions they define.  The
information gathered about a file FOO is saved in a file named `FOO.X'.

   After scanning comes actual conversion.  The specified files are all
eligible to be converted; any files they include (whether sources or
just headers) are eligible as well.

   But not all the eligible files are converted.  By default,
`protoize' and `unprotoize' convert only source and header files in the
current directory.  You can specify additional directories whose files
should be converted with the `-d DIRECTORY' option.  You can also
specify particular files to exclude with the `-x FILE' option.  A file
is converted if it is eligible, its directory name matches one of the
specified directory names, and its name within the directory has not
been excluded.

   Basic conversion with `protoize' consists of rewriting most function
definitions and function declarations to specify the types of the
arguments.  The only ones not rewritten are those for varargs functions.

   `protoize' optionally inserts prototype declarations at the
beginning of the source file, to make them available for any calls that
precede the function's definition.  Or it can insert prototype
declarations with block scope in the blocks where undeclared functions
are called.

   Basic conversion with `unprotoize' consists of rewriting most
function declarations to remove any argument types, and rewriting
function definitions to the old-style pre-ISO form.

   Both conversion programs print a warning for any function
declaration or definition that they can't convert.  You can suppress
these warnings with `-q'.

   The output from `protoize' or `unprotoize' replaces the original
source file.  The original file is renamed to a name ending with
`.save' (for DOS, the saved filename ends in `.sav' without the
original `.c' suffix).  If the `.save' (`.sav' for DOS) file already
exists, then the source file is simply discarded.

   `protoize' and `unprotoize' both depend on GCC itself to scan the
program and collect information about the functions it uses.  So
neither of these programs will work until GCC is installed.

   Here is a table of the options you can use with `protoize' and
`unprotoize'.  Each option works with both programs unless otherwise
stated.

`-B DIRECTORY'
     Look for the file `SYSCALLS.c.X' in DIRECTORY, instead of the
     usual directory (normally `/usr/local/lib').  This file contains
     prototype information about standard system functions.  This option
     applies only to `protoize'.

`-c COMPILATION-OPTIONS'
     Use  COMPILATION-OPTIONS as the options when running `gcc' to
     produce the `.X' files.  The special option `-aux-info' is always
     passed in addition, to tell `gcc' to write a `.X' file.

     Note that the compilation options must be given as a single
     argument to `protoize' or `unprotoize'.  If you want to specify
     several `gcc' options, you must quote the entire set of
     compilation options to make them a single word in the shell.

     There are certain `gcc' arguments that you cannot use, because they
     would produce the wrong kind of output.  These include `-g', `-O',
     `-c', `-S', and `-o' If you include these in the
     COMPILATION-OPTIONS, they are ignored.

`-C'
     Rename files to end in `.C' (`.cc' for DOS-based file systems)
     instead of `.c'.  This is convenient if you are converting a C
     program to C++.  This option applies only to `protoize'.

`-g'
     Add explicit global declarations.  This means inserting explicit
     declarations at the beginning of each source file for each function
     that is called in the file and was not declared.  These
     declarations precede the first function definition that contains a
     call to an undeclared function.  This option applies only to
     `protoize'.

`-i STRING'
     Indent old-style parameter declarations with the string STRING.
     This option applies only to `protoize'.

     `unprotoize' converts prototyped function definitions to old-style
     function definitions, where the arguments are declared between the
     argument list and the initial `{'.  By default, `unprotoize' uses
     five spaces as the indentation.  If you want to indent with just
     one space instead, use `-i " "'.

`-k'
     Keep the `.X' files.  Normally, they are deleted after conversion
     is finished.

`-l'
     Add explicit local declarations.  `protoize' with `-l' inserts a
     prototype declaration for each function in each block which calls
     the function without any declaration.  This option applies only to
     `protoize'.

`-n'
     Make no real changes.  This mode just prints information about the
     conversions that would have been done without `-n'.

`-N'
     Make no `.save' files.  The original files are simply deleted.
     Use this option with caution.

`-p PROGRAM'
     Use the program PROGRAM as the compiler.  Normally, the name `gcc'
     is used.

`-q'
     Work quietly.  Most warnings are suppressed.

`-v'
     Print the version number, just like `-v' for `gcc'.

   If you need special compiler options to compile one of your program's
source files, then you should generate that file's `.X' file specially,
by running `gcc' on that source file with the appropriate options and
the option `-aux-info'.  Then run `protoize' on the entire set of
files.  `protoize' will use the existing `.X' file because it is newer
than the source file.  For example:

     gcc -Dfoo=bar file1.c -aux-info file1.X
     protoize *.c

You need to include the special files along with the rest in the
`protoize' command, even though their `.X' files already exist, because
otherwise they won't get converted.

   *Note Protoize Caveats::, for more information on how to use
`protoize' successfully.


File: gcc.info,  Node: Installation,  Next: C Extensions,  Prev: Invoking GCC,  Up: Top

Installing GNU CC
*****************

   Note most of this information is out of date and superseded by the
new GCC install manual `gcc/doc/install.texi'.  It is provided for
historical reference only.

* Menu:

* Configuration Files::  Files created by running `configure'.
* Configurations::    Configurations Supported by GNU CC.
* Cross-Compiler::   Building and installing a cross-compiler.
* VMS Install::   See below for installation on VMS.
* Collect2::	  How `collect2' works; how it finds `ld'.
* Header Dirs::   Understanding the standard header file directories.

   Here is the procedure for installing GNU CC on a GNU or Unix system.
See *Note VMS Install::, for VMS systems.

  1. If you have chosen a configuration for GNU CC which requires other
     GNU tools (such as GAS or the GNU linker) instead of the standard
     system tools, install the required tools in the build directory
     under the names `as', `ld' or whatever is appropriate.  This will
     enable the compiler to find the proper tools for compilation of
     the program `enquire'.

     Alternatively, you can do subsequent compilation using a value of
     the `PATH' environment variable such that the necessary GNU tools
     come before the standard system tools.

  2. Specify the host, build and target machine configurations.  You do
     this when you run the `configure' script.

     The "build" machine is the system which you are using, the "host"
     machine is the system where you want to run the resulting compiler
     (normally the build machine), and the "target" machine is the
     system for which you want the compiler to generate code.

     If you are building a compiler to produce code for the machine it
     runs on (a native compiler), you normally do not need to specify
     any operands to `configure'; it will try to guess the type of
     machine you are on and use that as the build, host and target
     machines.  So you don't need to specify a configuration when
     building a native compiler unless `configure' cannot figure out
     what your configuration is or guesses wrong.

     In those cases, specify the build machine's "configuration name"
     with the `--host' option; the host and target will default to be
     the same as the host machine.  (If you are building a
     cross-compiler, see *Note Cross-Compiler::.)

     Here is an example:

          ./configure --host=sparc-sun-sunos4.1

     A configuration name may be canonical or it may be more or less
     abbreviated.

     A canonical configuration name has three parts, separated by
     dashes.  It looks like this: `CPU-COMPANY-SYSTEM'.  (The three
     parts may themselves contain dashes; `configure' can figure out
     which dashes serve which purpose.)  For example,
     `m68k-sun-sunos4.1' specifies a Sun 3.

     You can also replace parts of the configuration by nicknames or
     aliases.  For example, `sun3' stands for `m68k-sun', so
     `sun3-sunos4.1' is another way to specify a Sun 3.

     You can specify a version number after any of the system types,
     and some of the CPU types.  In most cases, the version is
     irrelevant, and will be ignored.  So you might as well specify the
     version if you know it.

     See *Note Configurations::, for a list of supported configuration
     names and notes on many of the configurations.  You should check
     the notes in that section before proceeding any further with the
     installation of GNU CC.



File: gcc.info,  Node: Configuration Files,  Next: Configurations,  Up: Installation

Files Created by `configure'
============================

   Here we spell out what files will be set up by `configure'.  Normally
you need not be concerned with these files.

   * A file named `config.h' is created that contains a `#include' of
     the top-level config file for the machine you will run the compiler
     on (*note Config::).  This file is responsible for defining
     information about the host machine.  It includes `tm.h'.

     The top-level config file is located in the subdirectory `config'.
     Its name is always `xm-SOMETHING.h'; usually `xm-MACHINE.h', but
     there are some exceptions.

     If your system does not support symbolic links, you might want to
     set up `config.h' to contain a `#include' command which refers to
     the appropriate file.

   * A file named `tconfig.h' is created which includes the top-level
     config file for your target machine.  This is used for compiling
     certain programs to run on that machine.

   * A file named `tm.h' is created which includes the
     machine-description macro file for your target machine.  It should
     be in the subdirectory `config' and its name is often `MACHINE.h'.

   * The command file `configure' also constructs the file `Makefile'
     by adding some text to the template file `Makefile.in'.  The
     additional text comes from files in the `config' directory, named
     `t-TARGET' and `x-HOST'.  If these files do not exist, it means
     nothing needs to be added for a given target or host.


File: gcc.info,  Node: Configurations,  Next: Cross-Compiler,  Prev: Configuration Files,  Up: Installation

Configurations Supported by GNU CC
==================================

   Here are the possible CPU types:

     1750a, a29k, alpha, arm, avr, cN, clipper, dsp16xx, elxsi, fr30,
     h8300, hppa1.0, hppa1.1, i370, i386, i486, i586, i686, i786, i860,
     i960, m32r, m68000, m68k, m6811, m6812, m88k, mcore, mips, mipsel,
     mips64, mips64el, mn10200, mn10300, ns32k, pdp11, powerpc,
     powerpcle, romp, rs6000, sh, sparc, sparclite, sparc64, v850, vax,
     we32k.

   Here are the recognized company names.  As you can see, customary
abbreviations are used rather than the longer official names.

     acorn, alliant, altos, apollo, apple, att, bull, cbm, convergent,
     convex, crds, dec, dg, dolphin, elxsi, encore, harris, hitachi,
     hp, ibm, intergraph, isi, mips, motorola, ncr, next, ns, omron,
     plexus, sequent, sgi, sony, sun, tti, unicom, wrs.

   The company name is meaningful only to disambiguate when the rest of
the information supplied is insufficient.  You can omit it, writing
just `CPU-SYSTEM', if it is not needed.  For example, `vax-ultrix4.2'
is equivalent to `vax-dec-ultrix4.2'.

   Here is a list of system types:

     386bsd, aix, acis, amigaos, aos, aout, aux, bosx, bsd, clix, coff,
     ctix, cxux, dgux, dynix, ebmon, ecoff, elf, esix, freebsd, hms,
     genix, gnu, linux, linux-gnu, hiux, hpux, iris, irix, isc, luna,
     lynxos, mach, minix, msdos, mvs, netbsd, newsos, nindy, ns, osf,
     osfrose, ptx, riscix, riscos, rtu, sco, sim, solaris, sunos, sym,
     sysv, udi, ultrix, unicos, uniplus, unos, vms, vsta, vxworks,
     winnt, xenix.

You can omit the system type; then `configure' guesses the operating
system from the CPU and company.

   You can add a version number to the system type; this may or may not
make a difference.  For example, you can write `bsd4.3' or `bsd4.4' to
distinguish versions of BSD.  In practice, the version number is most
needed for `sysv3' and `sysv4', which are often treated differently.

   `linux-gnu' is the canonical name for the GNU/Linux target; however
GNU CC will also accept `linux'.  The version of the kernel in use is
not relevant on these systems.  A suffix such as `libc1' or `aout'
distinguishes major versions of the C library; all of the suffixed
versions are obsolete.

   If you specify an impossible combination such as `i860-dg-vms', then
you may get an error message from `configure', or it may ignore part of
the information and do the best it can with the rest.  `configure'
always prints the canonical name for the alternative that it used.  GNU
CC does not support all possible alternatives.

   Often a particular model of machine has a name.  Many machine names
are recognized as aliases for CPU/company combinations.  Thus, the
machine name `sun3', mentioned above, is an alias for `m68k-sun'.
Sometimes we accept a company name as a machine name, when the name is
popularly used for a particular machine.  Here is a table of the known
machine names:

     3300, 3b1, 3bN, 7300, altos3068, altos, apollo68, att-7300,
     balance, convex-cN, crds, decstation-3100, decstation, delta,
     encore, fx2800, gmicro, hp7NN, hp8NN, hp9k2NN, hp9k3NN, hp9k7NN,
     hp9k8NN, iris4d, iris, isi68, m3230, magnum, merlin, miniframe,
     mmax, news-3600, news800, news, next, pbd, pc532, pmax, powerpc,
     powerpcle, ps2, risc-news, rtpc, sun2, sun386i, sun386, sun3,
     sun4, symmetry, tower-32, tower.

Remember that a machine name specifies both the cpu type and the company
name.  If you want to install your own homemade configuration files,
you can use `local' as the company name to access them.  If you use
configuration `CPU-local', the configuration name without the cpu prefix
is used to form the configuration file names.

   Thus, if you specify `m68k-local', configuration uses files
`m68k.md', `local.h', `m68k.c', `xm-local.h', `t-local', and `x-local',
all in the directory `config/m68k'.

   Here is a list of configurations that have special treatment or
special things you must know:

`vax-dec-vms'
     See *Note VMS Install::, for details on how to install GNU CC on
     VMS.


File: gcc.info,  Node: Cross-Compiler,  Next: VMS Install,  Prev: Configurations,  Up: Installation

Building and Installing a Cross-Compiler
========================================

   GNU CC can function as a cross-compiler for many machines, but not
all.

   * Cross-compilers for the Mips as target using the Mips assembler
     currently do not work, because the auxiliary programs
     `mips-tdump.c' and `mips-tfile.c' can't be compiled on anything
     but a Mips.  It does work to cross compile for a Mips if you use
     the GNU assembler and linker.

   * Cross-compilers between machines with different floating point
     formats have not all been made to work.  GNU CC now has a floating
     point emulator with which these can work, but each target machine
     description needs to be updated to take advantage of it.

   * Cross-compilation between machines of different word sizes is
     somewhat problematic and sometimes does not work.

   Since GNU CC generates assembler code, you probably need a
cross-assembler that GNU CC can run, in order to produce object files.
If you want to link on other than the target machine, you need a
cross-linker as well.  You also need header files and libraries suitable
for the target machine that you can install on the host machine.

* Menu:

* Steps of Cross::      Using a cross-compiler involves several steps
                          that may be carried out on different machines.
* Configure Cross::     Configuring a cross-compiler.
* Tools and Libraries:: Where to put the linker and assembler, and the C library.
* Cross Headers::       Finding and installing header files
                          for a cross-compiler.
* Build Cross::         Actually compiling the cross-compiler.


File: gcc.info,  Node: Steps of Cross,  Next: Configure Cross,  Up: Cross-Compiler

Steps of Cross-Compilation
--------------------------

   To compile and run a program using a cross-compiler involves several
steps:

   * Run the cross-compiler on the host machine to produce assembler
     files for the target machine.  This requires header files for the
     target machine.

   * Assemble the files produced by the cross-compiler.  You can do this
     either with an assembler on the target machine, or with a
     cross-assembler on the host machine.

   * Link those files to make an executable.  You can do this either
     with a linker on the target machine, or with a cross-linker on the
     host machine.  Whichever machine you use, you need libraries and
     certain startup files (typically `crt....o') for the target
     machine.

   It is most convenient to do all of these steps on the same host
machine, since then you can do it all with a single invocation of GNU
CC.  This requires a suitable cross-assembler and cross-linker.  For
some targets, the GNU assembler and linker are available.


File: gcc.info,  Node: Configure Cross,  Next: Tools and Libraries,  Prev: Steps of Cross,  Up: Cross-Compiler

Configuring a Cross-Compiler
----------------------------

   To build GNU CC as a cross-compiler, you start out by running
`configure'.  Use the `--target=TARGET' to specify the target type.  If
`configure' was unable to correctly identify the system you are running
on, also specify the `--build=BUILD' option.  For example, here is how
to configure for a cross-compiler that produces code for an HP 68030
system running BSD on a system that `configure' can correctly identify:

     ./configure --target=m68k-hp-bsd4.3


File: gcc.info,  Node: Tools and Libraries,  Next: Cross Headers,  Prev: Configure Cross,  Up: Cross-Compiler

Tools and Libraries for a Cross-Compiler
----------------------------------------

   If you have a cross-assembler and cross-linker available, you should
install them now.  Put them in the directory `/usr/local/TARGET/bin'.
Here is a table of the tools you should put in this directory:

`as'
     This should be the cross-assembler.

`ld'
     This should be the cross-linker.

`ar'
     This should be the cross-archiver: a program which can manipulate
     archive files (linker libraries) in the target machine's format.

`ranlib'
     This should be a program to construct a symbol table in an archive
     file.

   The installation of GNU CC will find these programs in that
directory, and copy or link them to the proper place to for the
cross-compiler to find them when run later.

   The easiest way to provide these files is to build the Binutils
package and GAS.  Configure them with the same `--host' and `--target'
options that you use for configuring GNU CC, then build and install
them.  They install their executables automatically into the proper
directory.  Alas, they do not support all the targets that GNU CC
supports.

   If you want to install libraries to use with the cross-compiler,
such as a standard C library, put them in the directory
`/usr/local/TARGET/lib'; installation of GNU CC copies all the files in
that subdirectory into the proper place for GNU CC to find them and
link with them.  Here's an example of copying some libraries from a
target machine:

     ftp TARGET-MACHINE
     lcd /usr/local/TARGET/lib
     cd /lib
     get libc.a
     cd /usr/lib
     get libg.a
     get libm.a
     quit

The precise set of libraries you'll need, and their locations on the
target machine, vary depending on its operating system.

   Many targets require "start files" such as `crt0.o' and `crtn.o'
which are linked into each executable; these too should be placed in
`/usr/local/TARGET/lib'.  There may be several alternatives for
`crt0.o', for use with profiling or other compilation options.  Check
your target's definition of `STARTFILE_SPEC' to find out what start
files it uses.  Here's an example of copying these files from a target
machine:

     ftp TARGET-MACHINE
     lcd /usr/local/TARGET/lib
     prompt
     cd /lib
     mget *crt*.o
     cd /usr/lib
     mget *crt*.o
     quit


File: gcc.info,  Node: Cross Headers,  Next: Build Cross,  Prev: Tools and Libraries,  Up: Cross-Compiler

Cross-Compilers and Header Files
--------------------------------

   If you are cross-compiling a standalone program or a program for an
embedded system, then you may not need any header files except the few
that are part of GNU CC (and those of your program).  However, if you
intend to link your program with a standard C library such as `libc.a',
then you probably need to compile with the header files that go with
the library you use.

   The GNU C compiler does not come with these files, because (1) they
are system-specific, and (2) they belong in a C library, not in a
compiler.

   If the GNU C library supports your target machine, then you can get
the header files from there (assuming you actually use the GNU library
when you link your program).

   If your target machine comes with a C compiler, it probably comes
with suitable header files also.  If you make these files accessible
from the host machine, the cross-compiler can use them also.

   Otherwise, you're on your own in finding header files to use when
cross-compiling.

   When you have found suitable header files, put them in the directory
`/usr/local/TARGET/include', before building the cross compiler.  Then
installation will run fixincludes properly and install the corrected
versions of the header files where the compiler will use them.

   Provide the header files before you build the cross-compiler, because
the build stage actually runs the cross-compiler to produce parts of
`libgcc.a'.  (These are the parts that _can_ be compiled with GNU CC.)
Some of them need suitable header files.

   Here's an example showing how to copy the header files from a target
machine.  On the target machine, do this:

     (cd /usr/include; tar cf - .) > tarfile

   Then, on the host machine, do this:

     ftp TARGET-MACHINE
     lcd /usr/local/TARGET/include
     get tarfile
     quit
     tar xf tarfile


File: gcc.info,  Node: Build Cross,  Prev: Cross Headers,  Up: Cross-Compiler

Actually Building the Cross-Compiler
------------------------------------

   Now you can proceed just as for compiling a single-machine compiler
through the step of building stage 1.

   If your target is exotic, you may need to provide the header file
`float.h'.One way to do this is to compile `enquire' and run it on your
target machine.  The job of `enquire' is to run on the target machine
and figure out by experiment the nature of its floating point
representation.  `enquire' records its findings in the header file
`float.h'.  If you can't produce this file by running `enquire' on the
target machine, then you will need to come up with a suitable `float.h'
in some other way (or else, avoid using it in your programs).

   Do not try to build stage 2 for a cross-compiler.  It doesn't work to
rebuild GNU CC as a cross-compiler using the cross-compiler, because
that would produce a program that runs on the target machine, not on the
host.  For example, if you compile a 386-to-68030 cross-compiler with
itself, the result will not be right either for the 386 (because it was
compiled into 68030 code) or for the 68030 (because it was configured
for a 386 as the host).  If you want to compile GNU CC into 68030 code,
whether you compile it on a 68030 or with a cross-compiler on a 386, you
must specify a 68030 as the host when you configure it.

   To install the cross-compiler, use `make install', as usual.

