[deliverable/binutils-gdb.git] / configure.texi

\input texinfo    @c -*-para-*-
@setfilename configure.info
@settitle Cygnus Configure

@node top, What Configure Does, (dir), (dir)

This file documents the configuration system used and distributed by
Cygnus Support.

@menu
* What Configure Does::		What Configure Does
* Invoking::			Invoking
* How It Does It::		How It Does It
* Canonical Triples And Config.Subr::  Canonical Triples And Config.Subr
* Native Ports::		Native Ports
* Adding Hosts Or Targets::	Adding Hosts Or Targets
* Adding Configure To Existing Programs::  Adding Configure To Existing Programs
* Makefile Support::		Makefile Support
* Known Bugs::			Known Bugs
@end menu

@node What Configure Does, Invoking, top, top
@chapter Invoking

The usual way to invoke @code{configure} is as follows:
@example
configure @var{host}
@end example
This asks @code{configure} to prepare the source to be compiled in a
@var{host} environment with programs and files to be installed in
@file{/usr/local}.

NOTE: support for multiple hosts is at least temporarily suspended.

If more than one host is specified on the command line, then
configurations are created for each and @code{-subdirs} is assumed.

@table @code

@item -datadir=@var{dir}
This option requests that the source be configured so that host
independent files will be installed in @var{dir}.

This option sets the @code{configure} variable @code{datadir}.  If
@code{datadir} is not empty, generated Makefiles will have their
@code{datadir} variables set to this value. (See @xref{Install Details}.)

@item -gas
Notifies @code{configure} that the @sc{GNU} assembler is available on
all specified hosts.

@item -help
Displays a quick summary of how to invoke @code{configure}.

@item -host=@var{host}
FIXME: I don't think this option should be documented.

@item -namesubdir=@var{name}
Asks that any subdirectories created by the @code{-subdirs} option be
named @var{name}.  Note that using multiple hosts with
@code{-namesubdir=} isn't terribly useful.

NOTE: support for this option is at least temporary suspended.

@item -nfp
Notifies @code{configure} that all of the specified hosts have @emph{no
floating point} units.

@item -norecursion
Asks @code{configure} to configure only this directory.  Any
subdirectories are ignored.  This is used by the executable shell script
@file{config.status} to reconfigure the current directory.
(@xref{FIXME:config.status}.

@item -objdir=@var{dir}
Asks @code{configure} to create the build tree in @var{dir}.  The
default is to use the source tree as the build tree.  The source
directory is assumed to be @file{.}.

NOTE: support for this option is at least temporary suspended.

@item -prefix=@var{dir}
This option requests that the source be configured so that programs and
files will be installed in @var{dir}.

This option sets the @code{configure} variable @code{prefix}.  If
@code{prefix} is not empty, generated Makefiles will have their
@code{prefix} variables set to this value. (See @xref{Install Details}.)

@item -recurring
This option is used internally by @code{configure} when recurring on
subdirectories.  It's sole purpose is to supress status output.  It can
be overriden with the @code{-verbose} option.

@item -rm
Asks @code{configure} to @emph{remove} a configuration rather than
create one.

@item -site=@var{site}
Asks that Makefiles be generated using site specific Makefiles for
@var{site}.  (@xref{FIXME: site specific Makefiles}.)

@item -srcdir=@var{_dir}
Tells @code{configure} that the sources are located in @var{dir}.  The
build directory is assumed to be @file{.}.

@item -subdirs
Asks that configurations be placed in subdirectories named
@file{H-@var{host}} of each build directory, for each host specified.
If this configuration is not native, (@var{host} is not @var{target}),
then he subdir will be named @file{X-@var{host}-@var{target}} instead.

NOTE: support for this option is at least temporary suspended.

@item -target=@var{target}
Requests that the sources be configured to target the @var{target}
machine.  If no targets are specified explicitly, the target is assumed
to be the same as the host.  If multiple targets are specified,
configurations for each are created and @code{-subdirs} is assumed.

NOTE: support for multiple targets is at least temporarily suspended.

@item -tmpdir=@var{tmpdir}
Sets the directory in which @code{configure} creates temporary files to
@var{tmpdir}.

@item -verbose
@item -v
Asks that @code{configure} print status lines for each directory
configured.  Normally, only the status lines for the current directory
are printed.

@item -x
Tells @code{configure} that @sc{MIT} style @sc{X11} header files and
libraries are available on this machine, even if they are not normally
available.

@end table

@node Using Configure, Canonical Triples And Config.Subr, Invoking, top
@chapter Using Configure

Configure prepares source directories in anticipation of building.
Source cannot be built until it has been configured.  The choices
and options available at configuration time generally have valid
defaults, but the defaults do not cover all cases.  The choices
available include:

@menu
* Install Locations::		Where to install things once they are built
* Build Directories::		Where to build object files
* Host::			Host
* Target::			Target
* Local Conventions::		Local Conventions
@end menu

@node Install Locations, Build Directories, What Configure Does, What Configure Does
@section Install Locations

@cindex Where to install

Using the default configuration, @code{make install} will create a
single tree of files, some of which are programs.  The location of this
tree is determined by the value of the variable @code{$(prefix)}.  The
default value of @code{$(prefix)} is @file{/usr/local}.  This is
probably correct for native tools installed on only one host.

@menu
* prefix::		Changing the default install directory
* datadir::		How to separate host independent files
			  from host dependent files when
			  installing for multiple hosts
* Install Details::	Full descriptions of all installation
			  subdirectories
@end menu

@node prefix, datadir, Install Locations, Install Locations
@subsection Changing the default install directory

@cindex Changing the default install directory
@cindex The prefix directory

In the default configuration, all files are installed in subdirectories
of @file{/usr/local}.  The actual location is determined by the value of
the @code{configure} variable @code{$@{prefix@}} which determines the
value of the Makefile variable @code{$(prefix)}.

You can also set the value of the Makefile variable @code{$(prefix)}
explicitly each time you invoke @code{make} if you are so inclined, but
because many programs have this location compiled in, you must specify
the @code{$(prefix)} value precisely on each invocation of @code{make}
or you will end up with a broken installation.

To make this easier, the value of the @code{configure} variable
@code{$@{prefix@}} can be set on the command line to @code{configure}
using the option @code{-prefix=}.  (See @xref{prefix}).


@node datadir, Install Details, prefix, Install Locations
@subsection Installing for multiple hosts

@cindex Configuring for multiple hosts
@cindex Sharing host independent files
@cindex The datadir directory
@cindex Installing host independent files

Host independent files are installed in subdirectories of
@file{/usr/local/lib}.  The actual location is determined by the value
of the @code{configure} variable @code{$@{datadir@}} which determines
the value of the Makefile variable @code{$(datadir)}.  By default, the
value of @code{$@{datadir@}} is @code{$@{prefix@}/lib}.  This makes
single host installs simple, and simplifies changing the default
location for the install tree, but doesn't allow for multiple hosts to
effectively share host independent files.

To configure so that multiple hosts can share common files, use
something like:

@example
configure @var{host1} -prefix=/usr/gnu/H-@var{host1} -datadir=/usr/gnu/H-independent
make all info install install-info clean
configure @var{host2} -prefix=/usr/gnu/H-@var{host2} -datadir=/usr/gnu/H-independent
make all info install install-info
@end example

The first line configures the source for @var{host1} in such a way that
host specific programs will be placed in subdirectories of
@file{/usr/gnu/H-@var{host1}} and host independent files will be placed
in @file{/usr/gnu/H-independent}.  (See @xref{datadir}.)

The second line builds and installs all programs for @var{host1},
including both host independent and host dependent files.

The third line reconfigures the source for @var{host2} in such a way
that host specific programs will be placed in subdirectories of
@file{/usr/gnu/H-@var{host2}} and host independent files will again be
placed in @file{/usr/gnu/H-independent}.

The fourth line builds and installs all programs for @var{host2}.  Host
dependent files will be installed in new directories but the host
independent files will be installed @emph{on top of} the host
independent files installed for @var{host1}.  This results in a single
copy of the host independent files suitable for use by both hosts.


@node Install Details,  , datadir, Install Locations
@subsection Full descriptions of all installation subdirectories

In any install, a number of standard directories are created.  Their
actual names are determined by Makefile variables.  Some of the
defaults for Makefile variables can be changed at configure time using
command line options to @code{configure}.  For more information on the
standard directories or the Makefile variables, please refer to
@cite{standards.text}.

Note that @code{configure} does not create @code{srcdir} at any time.
This is not an installation directory.  (@xref{}.)

All makefile variables can be overridden on the command line to
@code{make}.  (See @xref{Overriding, Overriding Variables, Overriding
Variables, make, Make}.)  If you do so, you will need to specify the
value precisely the same way for each invocation of @code{make} or you
risk ending up with a broken installation.  This is because many
programs have the locations of other programs or files compiled into
them.  If you find yourself overriding any of the variables frequently,
you should consider site depedent Makefile fragments.  (See @xref{}.)

During @code{make install}, the following standard directories will be
created and populated:

@vindex prefix
@defvr {Makefile and configure} prefix
By default, the value of this variable determines the root of the
installation tree.  It may be overridden with the @code{-srcdir=}
command line option to @code{configure}.  (@xref{Invoking}.)  The
default value for @code{prefix} is @file{/usr/local}.
@end defvr

@vindex bindir
@defvr Makefile bindir
The value of this variable names a directory intended to contain binary
programs that users can run.  The default value for @code{bindir}
depends on @code{prefix} so @code{bindir} is normally changed
only indirectly through @code{prefix}.  The default value for
@code{$(bindir)} is @code{prefix}@file{/bin}.
@end defvr

@vindex datadir
@defvr {Makefile and configure} datadir
The value of this variable names a directory intended to contain host
independent files.  The @code{configure} variable, which is used to set
the default value of the Makefile variable, can be set at configure time
using the @code{-datadir=} option to @code{configure}.
(@xref{Invoking}.)  The default value for @code{datadir} is
@code{prefix}@file{/lib}.
@end defvr

@vindex libdir
@defvr Makefile libdir
The value of this variable names a directory intended to hold libraries
and support programs.  The default value for @code{libdir}
depends on @code{prefix} so @code{libdir} is normally changed
only indirectly through @code{prefix}.  The default value for
@code{libdir} is @code{prefix}@file{/lib}.
@end defvr

@vindex mandir
@defvr Makefile mandir
The value of this variable names a directory intended to hold @emph{man}
format man pages.  The default value for @code{mandir}
depends on @code{prefix} so @code{mandir} is normally changed
only indirectly through @code{prefix}.  The default value for
@code{mandir} is @code{datadir}@file{/man}.
@end defvr

@vindex man@var{N}dir
@defvr Makefile man@var{N}dir
There are eight of these variables named @code{man1dir}, @code{man2dir},
etc.  They are intended to name the specific directories which hold the
man pages of their respective sections.  That is, @code{man1dir} holds
@file{emacs.1}, the man page for the emacs program while @code{man5dir}
holds the man page describing the @code{rcs} data file format, called
@file{rcsfile.5}.  The default value for @code{man@var{N}dir}
depends on @code{prefix} so @code{man@var{N}dir} is normally changed
only indirectly through @code{prefix}.  The default value for
@code{man@var{N}dir} is @code{mandir}@file{/man@var{N}}.
@end defvr

@vindex manext
@defvr Makefile manext
The makefile variable manext is not supported by the @code{configure}.
The @sc{gnu} coding standards do not call for @code{man1ext},
@code{man2ext}, so the intended use for @code{manext} is not clear.
(See also @xref{FIXME:extensions}.)
@end defvr

@vindex infodir
@defvr Makefile infodir
The value of this variable names a directory intended to hold
@emph{info} format documentation.  The default value for @code{infodir}
depends on @code{prefix} so @code{infodir} is normally changed
only indirectly through @code{prefix}.  The default value for
@code{infodir} is @code{datadir}@file{/info}.
@end defvr

@vindex docdir
@defvr Makefile docdir
The value of this variable names a directory intended to hold any
documentation that is in a format other than @emph{info} or @emph{man}.
The default value for @code{docdir} depends on @code{prefix} so
@code{docdir} is normally changed only indirectly through @code{prefix}.
The default value for @code{docdir} is @code{datadir}@file{/doc}.  Note
that this variable is an extension to the @sc{gnu} coding standards.
(See also @xref{FIXME:extensions}.)
@end defvr

@vindex includedir
@defvr Makefile includedir
The value of this variable names a directory intended to hold the
headers files that accompany the libraries installed in @code{libdir}.
The default value for @code{includedir} depends on @code{prefix} so
@code{includedir} is normally changed only indirectly through @code{prefix}.  The default value for
@code{includedir} is @code{prefix}@file{/include}.
@end defvr


@node Build Directories, Host, Install Locations, What Configure Does
@section Build Directories


@node Host, Target, Build Directories, What Configure Does
@section Host


@node Target, Local Conventions, Host, What Configure Does
@section Target


@node Local Conventions,  , Target, What Configure Does
@section Local Conventions


@node How It Does It, How It Does It, What Configure Does, top
@chapter How It Does It

When configure runs, it does the following things.

@itemize @bullet

@item Create Directories
When configure is run with either of the 

@itemize @minus
@item 		Parallels Source Tree (If -Srcdir)
@item 		Adds Subdirs (If -Subdir)
@end itemize

@item Generates Makefiles
@item Generates .Gdbinit
@item Makes Symlinks
@item Misc (Usually File Editting)
@item generates config.status
@end itemize

@node Canonical Triples And Config.Subr, Native Ports, How It Does It, top
@chapter Canonical Triples And Config.Subr


@menu
* Config.Subr Calling Convention::  Config.Subr Calling Convention
* Definition Of Canonical Triples::  Definition Of Canonical Triples
* Maps Aliases To Canonical Triples::  Maps Aliases To Canonical Triples
* Validates Canonical Triples::	 Validates Canonical Triples
@end menu

@node Config.Subr Calling Convention, Definition Of Canonical Triples, Canonical Triples And Config.Subr, Canonical Triples And Config.Subr
@section Config.Subr Calling Convention


@node Definition Of Canonical Triples, Maps Aliases To Canonical Triples, Config.Subr Calling Convention, Canonical Triples And Config.Subr
@section Definition Of Canonical Triples


@node Maps Aliases To Canonical Triples, Validates Canonical Triples, Definition Of Canonical Triples, Canonical Triples And Config.Subr
@section Maps Aliases To Canonical Triples


@node Validates Canonical Triples,  , Maps Aliases To Canonical Triples, Canonical Triples And Config.Subr
@section Validates Canonical Triples


@node Native Ports, Adding Hosts Or Targets, Canonical Triples And Config.Subr, top
@chapter Native Ports


@menu
* Add A Host::			Add A Host
* Port An Existing Target::	Port An Existing Target
* Add A Target::		Add A Target
* Build Host & Target::		Build Host & Target
* Build New Target On Some Other Host::	 Build New Target On Some Other Host
@end menu

@node Add A Host, Port An Existing Target, Native Ports, Native Ports
@section Add A Host


@node Port An Existing Target, Add A Target, Add A Host, Native Ports
@section Port An Existing Target


@node Add A Target, Build Host & Target, Port An Existing Target, Native Ports
@section Add A Target


@node Build Host & Target, Build New Target On Some Other Host, Add A Target, Native Ports
@section Build Host & Target


@node Build New Target On Some Other Host,  , Build Host & Target, Native Ports
@section Build New Target On Some Other Host


@node Adding Hosts Or Targets, Adding Configure To Existing Programs, Native Ports, top
@chapter Adding Hosts Or Targets


@menu
* Add Canonical Triple To Config.Subr (Cf Config.Subr)::	Add Canonical Triple To Config.Subr (Cf Config.Subr)
* (Optional) Add Alias (Cf Config.Subr)::  
* Monte Carlo - Configure ; Make::  Monte Carlo - Configure ; Make
* Remedies::			Remedies
@end menu

@node Add Canonical Triple To Config.Subr (Cf Config.Subr), (Optional) Add Alias (Cf Config.Subr), Adding Hosts Or Targets, Adding Hosts Or Targets
@section Add Canonical Triple To Config.Subr (Cf Config.Subr)


@node (Optional) Add Alias (Cf Config.Subr), Monte Carlo - Configure ; Make, Add Canonical Triple To Config.Subr (Cf Config.Subr), Adding Hosts Or Targets
@section (Optional) Add Alias (Cf Config.Subr)


@node Monte Carlo - Configure ; Make, Remedies, (Optional) Add Alias (Cf Config.Subr), Adding Hosts Or Targets
@section Monte Carlo - Configure ; Make


@node Remedies,  , Monte Carlo - Configure ; Make, Adding Hosts Or Targets
@section Remedies


@menu
* Automagic Config::		Automagic Config
* Symlinked Files::		Symlinked Files
* Makefile Fragments (Cf Configure.In)::  Makefile Fragments (Cf Configure.In)
@end menu

@node Automagic Config, Symlinked Files, Remedies, Remedies
@subsection Automagic Config


@node Symlinked Files, Makefile Fragments (Cf Configure.In), Automagic Config, Remedies
@subsection Symlinked Files


@node Makefile Fragments (Cf Configure.In),  , Symlinked Files, Remedies
@subsection Makefile Fragments (Cf Configure.In)

@node Adding Configure To Existing Programs, Known Bugs, Adding Hosts Or Targets, top
@chapter Adding Configure To Existing Programs


If you are writing a new program, don't worry about porting issues or
configure until it is running reasonably on some host.  Then refer
back to this section.

@menu
* Makefile Support::		Makefile Support
* Automagic Configuration::	Automagic Configuration
@end menu

@node Makefile Support, Automagic Configuration, Adding Configure To Existing Programs, Adding Configure To Existing Programs
@section Makefile Support


@menu
* Makefile Host Support - Move It To Host Fragments::  Makefile Host Support - Move It To Host Fragments
* Add Standard Macros (Template Follows)::  Add Standard Macros (Template Follows)
@end menu

@node Makefile Host Support - Move It To Host Fragments, Add Standard Macros (Template Follows), Makefile Support, Makefile Support
@subsection Makefile Host Support - Move It To Host Fragments


@node Add Standard Macros (Template Follows),  , Makefile Host Support - Move It To Host Fragments, Makefile Support
@subsection Add Standard Macros (Template Follows)

@itemize @bullet
@item as defined in standards.text
@item also add

@itemize @minus
@item includedir
This macro defines the directory in which to install any headers files that should be made available to users.
@item docdir
This macro defines where to install any documentation that is not either a man page or an info file.  For man pages, see mandir,
for info, see infodir.
@end itemize

@item template

@example

# Makefile for GNU tar program.

#
# Makefile
#   Copyright (C) 1990, 1991 Cygnus Support
#
# This file is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
#

srcdir = .

prefix = /usr/local

bindir = $(prefix)/bin
datadir = $(prefix)/lib
libdir = $(prefix)/lib
mandir = $(datadir)/man
man1dir = $(mandir)/man1
man2dir = $(mandir)/man2
man3dir = $(mandir)/man3
man4dir = $(mandir)/man4
man5dir = $(mandir)/man5
man6dir = $(mandir)/man6
man7dir = $(mandir)/man7
man8dir = $(mandir)/man8
man9dir = $(mandir)/man9
infodir = $(datadir)/info
includedir = $(prefix)/include
docdir = $(datadir)/doc

SHELL = /bin/sh

INSTALL = install -c
INSTALL_PROGRAM = $(INSTALL)
INSTALL_DATA = $(INSTALL)

AR = ar
AR_FLAGS = qv
BISON = bison
MAKEINFO = makeinfo
RANLIB = ranlib

# In order to disable remote-tape support, add -DNO_REMOTE to the
# appropriate DEFS line, and remove rtape_lib.* from LOCAL_@{SRC,OBJ@}
# For Ultrix 3.1, you will have to compile rtape_lib.c with -DUSG.
# Add -DUSE_REXEC to use rexec for remote tape operations
# instead of forking rsh or remsh.
#
# If tar fails to properly print error msgs, or core-dumps doing same,
# you may need to change which version of msg...() you are using.
# To do so, add one of the following to your DEFS= line
# -DSTDC_MSG		If you are using an ANSI compiler, and have vfprintf().
# -DVARARGS_MSG		If you have varargs.h and vfprintf()
# -DDOPRNT_MSG		If you have _doprnt(), and no useful varargs support
# -DLOSING_MSG		If nothing else works.
#
# Some non-BSD systems may have to add -DNEED_TZSET in order to have getdate.y
# compile correctly.
#
# If you have a system V system which defines size_t, add -DHAVE_SIZE_T.
# If you have a system which defines strstr, add -DHAVE_STRSTR.
#
# If you can't use remote tar with the rmt library, you can still get
# some stuff to work right by adding -DUSE_REXEC.
#
# Some people's systems define a prototype for signal handlers which
# require them to be declared as void.  If you get such problems in
# rtape_lib, function command, then define -DSIGNAL_VOID.  
#
# getdate.y has 8 shift/reduce conflicts.
#
# In addition to setting DEFS appropriately for your system, you might
# have to hand edit the #defines and #undefs in port.c.
#

## GNU version
DEFS = -DBSD42
LOCAL_SRC = 
LOCAL_OBJ = 
LDFLAGS =
LIBS =  -lutils
LINT = lint
LINTFLAGS = -abchx
DEF_AR_FILE = \"-\"
DEFBLOCKING = 20
O = o
@end example

#### Host, target, and site specific Makefile fragments come in here.
###

@itemize @bullet
@item 		Identify Nonstandard Macros
@itemize @minus
@item 				Put Defaults Before The Fragment Hook (Cf)
@item 				Move Non-Defaults To Makefile Fragments (Cf)
@item 				Map To Those Fragments In Configure.In (Cf)
@end itemize

@item 		Fragment Hook

@itemize @minus
@item 				Should Follow Standard And Non-Standard Macros
@item 				Should Preceed All Targets
@item 				Looks Like
#### Host, target, and site specific Makefile fragments come in here.
###

The line beginning with four hashes is the important part.  The comment and the line beginning with three hashes are only
a conventional convenience.
@end itemize

@item 		Makefile Fragments
@item 				Host
@item 				Target
@item 				Site
@item Mv Makefile Makefile.In
@item 		Standard Targets
@item 				All (Should Be The Default)
@item 				Install
@item 				Clean
@item 				Info
@item 				Install-Info
@item 				Clean-Info
@item The Config Subdirectory
@item Configure.In
@item 		Declarations
@item 				Srctrigger
@item 				Srcname
@item 				Configdirs
@item 				Target_Dependent
@item 		Per-Host
@item 		Per-Target
@item 		Post-Target
@item 		Available Variables

@defvar{host}
Contains the actual name that the user entered for the host.  Since many
things that the user could enter would map to the same canonical triple,
this variable is innappropriate to use for picking available
configurations.  For that, use @code{host_cpu}, @code{host_vendor},
and/or @code{host_os}.  This variable is useful, however, for error
messages.
@end defvar

@defvar{host_cpu}
Contains the first element of the canonical triple representing the host
as returned by @file{config.subr}.  This is occasionally used to
distinguish between minor variations of a particular vendor's operating
system and sometimes to determine variations in binary format between
the host and the target.
@end defvar

@defvar{host_vendor}
Contains the second element of the canonical triple representing the
host as returned by @file{config.subr}.  This is usually used to
distinguish betwen the numerous variations between @emph{common}
operating systems.
@end defvar

@defvar{host_os}
Contains the the third element of the canonical triple representing the
host as returned by @file{config.subr}.
@end defvar

@defvar{target}
Contains the actual name that the user entered for the target.  Since many
things that the user could enter would map to the same canonical triple,
this variable is innappropriate to use for picking available
configurations.  For that, use @code{target_cpu}, @code{target_vendor},
and/or @code{target_os}.  This variable is useful, however, for error
messages.
@end defvar

@defvar{target_cpu}
Contains the first element of the canonical triple representing the
target as returned by @file{config.subr}.  This is used heavily by
programs involved in building programs, like the compiler, assembler,
linker, etc.  Most programs will not need the @code{target} variables at
all, but this one could conceivably be used to build a program, for
instance, that operated on binary data files whose byte order or
alignment are other than that of the system on which the program is
running.
@end defvar

@defvar{target_vendor}
Contains the second element of the canonical triple representing the
target as returned by @file{config.subr}.  This is usually used to
distinguish betwen the numerous variations between @emph{common}
operating systems or object file formats.  Sometimes it is used to
switch between different flavors of users interfaces.
@end defvar

@defvar{target_os}
Contains the the third element of the canonical triple representing the
target as returned by @file{config.subr}.  This variable is used by
development tools to distinguish between subtle variations in object
file formats that some vendors use across operating system releases.  It
might also be use to decide which libraries to build or what user
interface the tool should provide.
@end defvar

@defvar{nfp}
Is set to @code{true} if the user invoked configure with the @code{-nfp}
command line option, otherwise it is empty.  This is a request to target
a machine with @emph{no floating point} unit, even if the machine ordinarily
has a floating point unit available.  This option has no negation.
@end defvar

@defvar{gas}
Is set to @code{true} if the user invoked configure with the @code{-gas}
command line option, otherwise it is empty.  This is a request to assume
that the target machine has gas available even if it ordinarily does
not.  The converse option, @code{-no-gas} is not available.
@end defvar

@defvar{x}
Is set to @code{true} if the user invoked configure with the @code{-x}
command line option, otherwise it is empty.  This is a request to assume
that @sc{mit x11} compatible headers files and libraries are available,
regardless of what is normally available on this host.
@end defvar

@defvar{srcdir}
Is set to the name of the directory containing the source for this
program.  This will be different from @file{.} if the user has
specified either the @code{-srcdir=} or the @code{-subdirs} options.
Note that @code{srcdir} is not necessarily an absolute path.
@end defvar

@defvar{host_makefile_frag}
Is set to a file name representing to the default Makefile fragment for
this host.  It may be set in @file{configure.in} to overide this
default.
@end defvar

@defvar{target_makefile_frag}
Is set to a file name representing to the default Makefile fragment for
this target.  It may be set in @file{configure.in} to overide this
default.
@end defvar

@defvar{site_makefile_frag}
Is set to a file name representing to the default Makefile fragment for
this host.  It may be set in @file{configure.in} to overide this
default.  Normally @code{site_makefile_frag} is empty, but will have a
value if the user specified @code{-site=} on the command line.  This
variable should probably not be overridden.
@end defvar

@defvar{Makefile}
Is set to the name of the generated @file{Makefile}.  Normally this
value is precisely @file{Makefile} but some programs may want something
else.
@end defvar

@defvar{removing}
Is normally empty but will be set to some non-empty value if the user
specified @code{-rm} on the command line.  That is, if @code{removing}
is non-empty, then configure is @emph{removing} a configuration rather
than creating one.
@end defvar

@defvar{files}
If this variable is non-empty following the @code{per-target:} section,
then each word in it's value will be the target of a symbolic link
named in the @code{links} variable.
@end defvar

@defvar{links}
If the @code{files} variable is non-empty following the
@code{per-target:} section, then symbolic links will be created with the
first word of links pointing to the first word of files, the second word of
links pointing to the second word of files, and so on.
@end defvar

@end itemize
@end itemize

@node Automagic Configuration,  , Makefile Support, Adding Configure To Existing Programs
@section Automagic Configuration


@menu
* Should Be Used If Prep'D Files Don'T Exist::	Should Be Used If Prep'D Files Don'T Exist
@end menu

@node Should Be Used If Prep'D Files Don'T Exist,  , Automagic Configuration, Automagic Configuration
@subsection Should Be Used If Prep'D Files Don'T Exist


@node Known Bugs, Variables Index, Adding Configure To Existing Programs, top
@chapter Known Bugs

The following bugs are known to exist.

@itemize @bullet

@item
There is no way to query about known hosts, known targets, or the
porting or testing status of any configuration.

@item
The negations to the options @code{-gas}, @code{-x}, and @code{-nfp} are
not available.

@end itemize

@node Variables Index, Concept Index, Known Bugs, top
@unnumbered Variable Index

@printindex vr

@node     Concept Index,  , Variables Index, top
@unnumbered Concept Index

@printindex cp

@summarycontents
@contents
@bye

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