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@setfilename configure.info
@settitle Cygnus Configure
@c %**end of header
@synindex ky cp
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@ifinfo
@format
START-INFO-DIR-ENTRY
* configure: (configure).		Cygnus configure.
END-INFO-DIR-ENTRY
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@ifinfo
This document attempts to describe the Cygnus Support version of
@code{configure}.

Copyright (C) 1991, 1992 Cygnus Support
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by Cygnus Support.
@end ifinfo

@titlepage
@sp 10
@title{Cygnus Configure}
@subtitle @manvers, for Cygnus Configure version 1.84
@author{K. Richard Pixley, @code{rich@@cygnus.com}}
@author{Cygnus Support}
@page

@vskip 0pt plus 1filll
Copyright @copyright{} 1991, 1992 Cygnus Support

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by Cygnus Support.
@end titlepage

@ifinfo

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

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

@menu
* What Configure Does::		What Configure Does
* Invoking::			Invoking
* Using Configure::		Using Configure
* Porting::			Porting with Configure
* Reference::			Gory details described
* Known Bugs::			Known Bugs
* Variables Index::		Variable Index
* Concept Index::		Concept Index

 --- The Detailed Node Listing ---

Using Configure

* Install Locations::		Where to install things once they are built
* Build Directories::		Where to build object files
* Host::			Telling @code{configure} what will source will
			  be built
* Target::			Telling @code{configure} what the source will
			  target
* Local Conventions::		Adding information about local conventions

Install Locations

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

Porting with Configure

* Programs::			Adding configure to new programs
* Hosts and Targets::		Adding hosts and targets
* Sites::			Adding site info

Gory details described

* Makefile Extensions::		Extensions to the @sc{gnu} coding standards
* configure.in::		The format of the configure.in file
* config.status::		config.status
* Makefile Fragments::		Makefile Fragments

The format of the @file{configure.in} file

* Minimal::			A minimal configure.in
* Configure Variables::		Variables available to configure.in
* Declarations::		For each invocation
* Per-host::			For each host
* Per-target::			For each target
* Post-target::			After each target
* Example::			An example configure.in
@end menu

@end ifinfo

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

@code{configure} prepares source directories for building working
programs.  A program cannot be built until its source has been
configured.  When configure runs, it does the following things.

@table @emph
@item Create build directories
(see @ref{Build Directories}).  When you run @code{configure} with the
@code{-srcdir=} option, it uses the current directory as build
directory, creating under it a directory tree that parallels the
directory structure under the source directory.  (See @ref{Invoking}).

@item Generate makefiles
A makefile template from the source directory, usually called
@file{Makefile.in}, is copied to an output file in the build directory.
The output file is usually named @file{Makefile}.  @code{configure}
places definitions for a number of standard makefile macros at the
beginning of the output file.  If @code{-prefix=} or @code{-exec_prefix}
were specified on the @code{configure} command line, corresponding
makefile variables are set accordingly.  If host, target, or site
specific makefile fragments exist, these are inserted into the output
file.  (See @ref{Makefiles, , , make, Makefiles}.)

@item Generate @file{.gdbinit} If the source directory contains a
@file{.gdbinit} file and the build directory is not the same as the
source directory, a @file{.gdbinit} file is created in the build
directory.  This @file{.gdbinit} file contains @code{dir} commands and
a @code{source} command, which will cause the @file{.gdbinit} file from
the source directory to be read by GDB, and will allow GDB to find
source files in either the source directory or the build directory.
(see @ref{Command Files, , , gdb, Command Files}.)

@item Make symbolic links
Most directories have some symbolic links with generic names built
pointing to specific files in the source directory.  If the system where
@code{configure} runs cannot support symbolic links, hard links are used
instead.

@item Miscellaneous
If the source directory has special needs, they are handled by shell
script fragments stored with the source.  Usually there are no special
needs, but sometimes they involve changes to the output makefile.

@item Generate @file{config.status}
@code{configure} creates a shell script named @file{config.status} in
the build directory.  This shell script, when run from the build
directory, will reconfigure the build directory (but not its
subdirectories).  This is most often used to have a @code{Makefile} update
itself automatically if a new source directory is available.

@item Recursion
If the source directory has subdirectories that should also be
configured, @code{configure} is called for each.
@end table

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

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

@code{configure} prepares the source as you specify by selecting and
using script and Makefile fragments prepared in advance, and stored with
the source.  @code{configure}'s command line options also allow you to
specify other aspects of the source configuration:

@table @code
@item -exec_prefix=@var{dir}
Configure the source to install host dependent files in @var{dir}.

This option sets the @code{configure} variable @code{exec_prefix}.
Generated Makefiles will have their @code{exec_prefix} variables set to
this value. (See @ref{Install Details}.)

@item -gas
Configure to use the @sc{GNU} assembler.

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

@item -host=@var{host}
FIXME-soon: I don't think this option should be documented.
@c Then why does it exist?  /Pesch 7jan92

@item -nfp
@emph{No floating point} unit available on the target; configure to
avoid dependencies on hardware floating point.

@item -norecursion
Configure only this directory; ignore any subdirectories.  This is used
by the executable shell script @file{config.status} to reconfigure the
current directory.  (see @ref{config.status}).

@item -prefix=@var{dir}
Configure the source to install programs and files under directory
@file{@var{dir}}.

This option sets the @code{configure} variable @code{prefix}.  Generated
Makefiles will have their @code{prefix} variables set to this value.
(See @ref{Install Details}.)

@item -recurring
@c Wouldn't it make more sense to call this "-quiet"? (FIXME).
This option is used internally by @code{configure} when recurring on
subdirectories.  Its sole purpose is to suppress status output.  You can
override this effect with the @code{-verbose} option.

@item -rm
@emph{Remove} the configuration specified by @var{host} and the other
command-line options, rather than creating it.

@item -site=@var{site}
Generate Makefiles using site specific Makefile fragments for
@var{site}.  See also @ref{Sites}.

@item -srcdir=@var{_dir}
Build Makefiles to use the sources located in directory @file{@var{dir}}.  The
build directory is assumed to be @file{.}.

@item -target=@var{target}
Requests that the sources be configured to target the @var{target}
machine.  If no target is specified explicitly, the target is assumed
to be the same as the host.  

@item -tmpdir=@var{tmpdir}
Use the directory @var{tmpdir} for @code{configure}'s temporary files.
The default is the value of the environment variable TMPDIR, or
@file{/tmp} if the environment variable is not set.

@item -verbose
@itemx -v
Print status lines for each directory configured.  Normally, only the
status lines for the initial working directory are printed.

@item -x
Use @sc{MIT} style @sc{X11} header files and libraries on the host, even
if they are not normally available.
@end table

@node Using Configure, Porting, Invoking, top
@chapter Using Configure

The choices and options available at configuration time
generally have valid defaults, but the defaults do not cover all cases.
The choices available include install locations, build directories,
host, target, and local conventions.

@menu
* Install Locations::		Where to install things once they are built
* Build Directories::		Where to build object files
* Host::			Telling @code{configure} what will source will
			  be built
* Target::			Telling @code{configure} what the source will
			  target
* Local Conventions::		Adding information about local conventions
@end menu

@node Install Locations, Build Directories, Using Configure, Using Configure
@section Install Locations
@cindex Where to install

Using the default configuration, @code{make install} creates 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
often correct for native tools installed on only one host.

@menu
* prefix::		Changing the default install directory
* exec_prefix::		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, exec_prefix, Install Locations, Install Locations
@subsection Changing the default install directory
@cindex Changing the default install directory
@cindex Prefix directory

In the default configuration, all files are installed in subdirectories
of @file{/usr/local}.  The location is determined by the value of
the @code{configure} variable @code{prefix}; in turn, this determines the
value of the Makefile variable of the same name (@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 consistently 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=}.  


@node exec_prefix, Install Details, prefix, Install Locations
@subsection Installing for multiple hosts
@cindex Configuring for multiple hosts
@cindex Sharing host independent files
@cindex The @file{exec_prefix} directory
@cindex Installing host independent files

By default, host dependent files are installed in subdirectories of
@file{@var{exec_prefix}}.  The location is determined by the value of the
@code{configure} variable @code{exec_prefix}, which determines the value of
the Makefile variable @code{exec_prefix}.  This makes it simpler to install
for a single host, and simplifies changing the default location for the
install tree; but the default 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 -exec_prefix=/usr/gnu/H-host1
make all info install install-info clean

configure @var{host2} -prefix=/usr/gnu -exec_prefix=/usr/gnu/H-host2
make all info install install-info
@end example

The first line configures the source for @var{host1} to place host
specific programs in subdirectories of @file{/usr/gnu/H-@var{host1}}.  

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

The third line reconfigures the source for @var{host2} to place host
specific programs in subdirectories of @file{/usr/gnu/H-@var{host2}}.

The fourth line builds and installs all programs for @var{host2}.  Host
specific files are installed in new directories, but the host
independent files are 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,  , exec_prefix, Install Locations
@subsection Full descriptions of all installation subdirectories

During any install, a number of standard directories are created.  Their
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 the directory @code{srcdir}
at any time.  @code{srcdir} is not an installation directory.

You can override all makefile variables on the command line to
@code{make}.  (See @ref{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 dependent Makefile fragments.  See also
@ref{Sites}.

During @code{make install}, a number of standard directories are
created and populated.  The following Makefile variables define them.
Those whose defaults are set by corresponding @code{configure} variables
are marked ``Makefile and configure''.

@vindex prefix
@defvr {Makefile and configure} prefix
The root of the installation tree.  You can set
its Makefile default with the @code{-prefix=} command line option to
@code{configure}.  (@ref{Invoking}.)  The default value for
@code{prefix} is @file{/usr/local}.
@end defvr

@vindex bindir
@defvr Makefile bindir
A directory for binary programs that users can run.
The default value for @code{bindir} depends on @code{prefix};
@code{bindir} is normally changed only indirectly through @code{prefix}.
The default value for @code{bindir} is @file{$(prefix)/bin}.
@end defvr

@vindex exec_prefix
@defvr {Makefile and configure} exec_prefix
A directory for host dependent files.  You can specify the Makefile
default value by using the @code{-exec_prefix=} option to @code{configure}.
(See also @ref{Invoking}.)  The default value for @code{exec_prefix} is
@file{$(prefix)}.
@end defvr

@vindex libdir
@defvr Makefile libdir
A directory for libraries and support programs.  The default value for
@code{libdir} depends on @code{prefix}; @code{libdir} is normally
changed only indirectly through @code{prefix}.  The default value for
@code{libdir} is @file{$(prefix)/lib}.
@end defvr

@vindex mandir
@defvr Makefile mandir
A directory for @code{man} format documentation (``man pages'').  The
default value for @code{mandir} depends on @code{prefix};
@code{mandir} is normally changed only indirectly through @code{prefix}.
The default value for @code{mandir} is @file{$(prefix)/man}.
@end defvr

@vindex man@var{N}dir
@defvr Makefile man@var{N}dir
There are eight variables named @code{man1dir}, @code{man2dir}, etc.
They name the specific directories for each man page section.  For
example, @code{man1dir} holds @file{emacs.1} (the man page for the emacs
program), while @code{man5dir} holds @file{rcsfile.5} (the man page
describing the @code{rcs} data file format).  The default value for any
of the @code{man@var{N}dir} variables depends indirectly on
@code{prefix}, and is normally changed only through @code{prefix}.  The
default value for @code{man@var{N}dir} is
@file{$(mandir)/man@var{N}}.
@end defvr

@vindex manext
@defvr Makefile manext
@emph{Not supported by @code{configure}}.  The @sc{gnu} coding standards
do not call for @code{man1ext}, @code{man2ext}, so the intended use for
@code{manext} is apparently not parallel to @code{mandir}.  Its use is
not clear.  (See also @ref{Makefile Extensions}.)
@end defvr

@vindex infodir
@defvr Makefile infodir
A directory for @emph{info} format documentation.  The default value for
@code{infodir} depends indirectly on @code{prefix}; @code{infodir} is
normally changed only through @code{prefix}.  The default value for
@code{infodir} is @file{$(prefix)/info}.
@end defvr

@vindex docdir
@defvr Makefile docdir
A directory for any documentation that is in a format other than those
used by @code{info} or @code{man}.  The default value for @code{docdir}
depends indirectly on @code{prefix}; @code{docdir} is normally changed only
through @code{prefix}.  The default value for @code{docdir}
is @file{$(datadir)/doc}.  @emph{This variable is an extension to
the @sc{gnu} coding standards}.  (See also @ref{Makefile Extensions}.)
@end defvr

@vindex includedir
@defvr Makefile includedir
A directory for the header files accompanying the libraries installed in
@code{libdir}.  The default value for @code{includedir} depends on
@code{prefix}; @code{includedir} is normally changed only indirectly
through @code{prefix}.  The default value for @code{includedir} is
@file{$(prefix)/include}.
@end defvr

@node Build Directories, Host, Install Locations, Using Configure
@section Build Directories
@cindex Build directories
@kindex objdir
@cindex Object directories
@kindex subdirs
@cindex Building for multiple hosts
@cindex Building for multiple targets

Normally, @code{configure} builds a @file{Makefile} and symbolic links
in the same directory as the source files.  This is the typical
@sc{un*x} way to build programs, but it has limitations.  For instance,
using this approach, you can only build for one host at a time.

We refer to the directories where @code{configure} builds a
Makefile as the @emph{build directories} or sometimes as
@emph{objdir} because these are the directories in which @code{make}
will build object files, among other things.

The default build directory is the same as the source directory.
You can use a different build directory with a sequence like the following:

@example
mkdir @var{builddir}
cd @var{builddir}
configure @var{host} -srcdir=@var{sourcedirectory}
@end example

@noindent
where @var{builddir} is the directory where you wish to build,
@var{host} is the host for which you want to build, and
@var{sourcedirectory} is the directory containing the source files.

If you were to do this twice with different values for @var{builddir}
and @var{host}, then you could @code{make} for both at the same time.

@node Host, Target, Build Directories, Using Configure
@section Host

The arguments to @code{configure} are @emph{hosts}.  By @emph{host} we
mean the environment in which the source will be compiled.  This need
not necessarily be the same as the  physical machine involved,
although it usually is.

For example, if some obscure machine running an operating system other
than @sc{un*x}  had the @sc{gnu} @sc{posix} emulation libraries
available, it would be possible to configure most @sc{gnu} source for a
@sc{posix} system and build it on the obscure host.

For more on this topic, see @ref{Host Environments, , Host Environments,
cfg-paper, On Configuring Development Tools}.

@node Target, Local Conventions, Host, Using Configure
@section Target

For building native development tools, or most of the other @sc{gnu}
tools, you need not worry about the target.  The @emph{target} of a
configuration defaults to the same as the @emph{host}.

For building cross development tools, please see @ref{Building
Development Environments, , Building Development Environments,
cfg-paper, On Configuring Development Tools}.

@node Local Conventions,  , Target, Using Configure
@section Local Conventions

If you find that a tool does not get configured to your liking, or if
@code{configure}'s conventions differ from your local conventions, you
should probably consider site specific Makefile fragments.  See also
@ref{Sites}.

These are probably not the right choice for options that can be set from
the @code{configure} command line or for differences that are host or
target dependent.

@node Porting, Reference, Using Configure, top
@chapter Porting with Configure
@cindex Porting

This section explains how to add programs, host and target configuration
names, and site-specific information to Cygnus configure.

@menu
* Programs::			Adding configure to new programs
* Hosts and Targets::		Adding hosts and targets
* Sites::			Adding site info
@end menu


@node Programs, Hosts and Targets, Porting, Porting
@section Adding Configure To New Programs

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

If the program in question currently has a configure script that meets
the criteria set out by @cite{standards.text}, please do not add Cygnus
configure.  It should be possible to add this program without change to
a Cygnus configure style source tree.

If the program is not target dependent, please consider using
@code{autoconf} instead of Cygnus configure.  @code{autoconf} will
be available soon from the @sc{fsf}.

To add Cygnus configure to an existing program, do the following:

@table @asis
@item Make sure the Makefile conforms to @sc{gnu} standard
The coding standard for @sc{gnu} Makefiles is described in
@cite{standards.text}.

@item Add Cygnus extensions to the Makefile
These are described in @ref{Makefile Extensions}.

@item Move host support from Makefile to fragments
This usually involves finding sections of the Makefile that say things
like ``uncomment these lines for host foo'' and moving them to a new
file called @file{./config/mh-foo}. For more information, see @ref{Hosts
and Targets}.

@item Choose defaults
If the program has compile time options that determine the way the
program should behave, chose reasonable defaults and make these Makefile
variables.  Be sure the variables are assigned their default values
before the @code{####} line so that site specific Makefile fragments can
override them (@pxref{Makefile Extensions,,Extensions to the @sc{gnu}
coding standards}).

@item Locate configuration files
If there is configuration information in header files or source files,
separate it in such a way that the files have a generic name.  Then move
the specific instances of those files into the @file{./config}
directory.

@item Separate host and target information
Some programs already have this information separated.  If yours does
not, you will need to separate these two kinds of configuration
information.  @dfn{Host specific} information is the information needed to
compile the program.  @dfn{Target specific} information is information on the
format of data files that the program will read or write.  This
information should live in separate files in the @file{./config}
directory with names that reflect the configuration for which they are
intended.

At this point you might skip this step and simply move on.  If you do,
you should end up with a program that can be configured only to build
native tools, that is, tools for which the host system is also the
target system.  Later, you could attempt to build a cross tool and
separate out the target specific information by figuring out what went
wrong.  This is often simpler than combing through all of the source
code.

@item Write @code{configure.in}
Usually this involves writing shell script fragments to map from
canonical configuration names into the names of the configuration files.
These files will then be linked at configure time from the specific
instances of those files in @file{./config} to file in the build
directory with more generic names.  (see also @ref{Build Directories}).
The format of configure.in is described in @ref{configure.in}.

@item Rename @file{Makefile} to @file{Makefile.in}
@end table

At this point you should have a program that can be configured using
Cygnus @code{configure}.

@node Hosts and Targets, Sites, Programs, Porting
@section Adding hosts and targets

To add a host or target to a program that already uses Cygnus
configure, do the following.

@itemize @bullet

@item
Make sure the new configuration name is represented in
@file{config.sub}.  If not, add it.  For more details, see the comments
in the shell script @file{config.sub}.

@item
If you are adding a host configuration, look in @file{configure.in}, in
the per-host section.  Make sure that your configuration name is
represented in the mapping from host configuration names to
configuration files.  If not, add it.  Also see @ref{configure.in}.

@item
If you are adding a target configuration, look in @file{configure.in},
in the per-target section.  Make sure that your configuration name is
represented in the mapping from target configuration names to
configuration files.  If not, add it.  Also see @ref{configure.in}.

@item
Look in @file{configure.in} for the variables @samp{files},
@samp{links}, @samp{host_makefile_frag}, and
@samp{target_makefile_frag}.  The values assigned to these variables are
the names of the configuration files, relative to @code{srcdir} that the
program uses.  Make sure that copies of the files exist for your host.
If not, create them.  See also @ref{Configure Variables}.
@end itemize

This should be enough to configure for a new host or target
configuration name.  Getting the program to compile and run properly
remains the hard work of the port.

@node Sites,  , Hosts and Targets, Porting
@section Adding site info

If some of the Makefile defaults are not right for your site, you can
build site specific Makefile fragments.  To do this, do the following.

@itemize @bullet

@item
Choose a name for your site.  It must be less than eleven characters for
now.

@item
If the program source does not have a @file{./config} directory, create it.

@item
Create a file called @file{./config/ms-@var{site}} where @var{site} is
the name of your site.  In it, set whatever Makefile variables you need
to override to match your site's conventions.

@item
Configure the program with:

@example
configure @dots{} +site=@var{site}
@end example

@end itemize

@node Reference, Known Bugs, Porting, top
@chapter Gory details described

@cindex Backends
Here we describe the backend support.

@menu
* Makefile Extensions::		Extensions to the @sc{gnu} coding standards
* configure.in::		The format of the configure.in file
* config.status::		config.status
* Makefile Fragments::		Makefile Fragments
@end menu

@node Makefile Extensions, configure.in, Reference, Reference
@section Extensions to the @sc{gnu} coding standards

@cindex Makefile extensions
@cindex Cygnus extensions

The following additions to the @sc{gnu} coding standards are required
for Cygnus configure to work properly.

@itemize @bullet
@item
The Makefile must contain exactly one line starting with @code{####}.
This line should follow any default macro definitions but precede any
rules.  Host, target, and site specific Makefile fragments will be
inserted immediately after this line.  If the line is missing, the
fragments will not be inserted.
@end itemize

Cygnus adds the following targets to our Makefiles.  Their existence is
not required for Cygnus configure, but they are documented here for
completeness.

@table @code
@kindex info
@item info
Build all info files from texinfo source.

@kindex install-info
@item install-info
Install all info files.

@kindex clean-info
@item clean-info
Remove all info files and any intermediate files that can be generated
from texinfo source.

@kindex stage1
@item stage1
@kindex stage2
@itemx stage2
@kindex stage3
@itemx stage3
@kindex stage4
@itemx stage4
@kindex de-stage1
@itemx de-stage1
@kindex de-stage2
@itemx de-stage2
@kindex de-stage3
@itemx de-stage3
@kindex de-stage4
@itemx de-stage4
@kindex bootstrap
@itemx bootstrap
@kindex comparison
@itemx comparison
@kindex Makefile
@itemx Makefile
These targets are in transition and may be removed shortly.
@end table

In addition, the following Makefile targets have revised semantics:

@table @code
@kindex install
@item install
Should @emph{not} depend on the target @code{all}.  If the program is
not already built, @code{make install} should fail.  This allows you
to install programs even when @code{make} would otherwise determine
them to be out of date.  This can happen when the result of a @code{make
all} is transported via tape to another machine for installation as
well as in a number of other cases.

@kindex clean
@item clean
Should remove any file that can be regenerated by the Makefile,
excepting only the Makefile itself, and any links created by configure.
That is, @code{make all clean} should return all directories to their
original condition.  If this is not done, then:

@example
configure @var{host1} ; make all clean ; configure @var{host2} ; make all
@end example

@noindent
will fail because of intermediate files intended for @var{host1}.
@end table

Cygnus adds the following macros to all @file{Makefile.in} files, but
you are not required to use them to run Cygnus configure.

@table @code
@kindex docdir
@item docdir
The directory in which to install any documentation that is not either a
man page or an info file.  For man pages, see mandir, for info, see
infodir.

@kindex includedir
@item includedir
The directory in which to install any headers files that should be made
available to users.  This is distinct from the @code{gcc} include
directory which is intended for @code{gcc} only.  Files in
@code{includedir} may be used by @code{cc} as well.
@end table

In addition, the following macros have revised semantics.  Most of them
describe installation directories; see also @ref{Install Details,,Full
description of all installation subdirectories}.

@table @code

@kindex manext
@item manext
is not used.  The intended usage is not clear.  For example, if you have a
@file{foo.man} and a @file{bar.man}, and @file{foo.man} is destined for
@file{/usr/local/lib/man/man1/foo.1} while @file{bar.man} is destined
for @file{/usr/local/lib/man/man5/bar.5}, then what is the desired value
of @code{manext}?

@kindex datadir
@item datadir
is used for host independent data files.

@kindex mandir
@item mandir
The default path for @code{mandir} depends on @code{prefix}.

@kindex infodir
@item infodir
The default path for @code{infodir} depends on @code{prefix}.

@kindex BISON
@item BISON
is assumed to have a @code{yacc} calling convention.  To  use
@code{bison}, use @code{BISON=bison -y}.
@end table

Cygnus Makefiles also conform to one additional restriction:

@itemize @bullet
@item
When libraries are installed, the line containing the call to
@code{INSTALL_DATA} should always be followed by a line containing a
call to @code{RANLIB} on the installed library.  This is to accomodate
systems that use @code{ranlib}.  Systems that do not use @code{ranlib}
can set @code{RANLIB} to @code{echo} in a host specific Makefile
fragment.
@end itemize

@node configure.in, config.status, Makefile Extensions, Reference
@section The format of the @file{configure.in} file
@kindex configure.in

A @file{configure.in} file for Cygnus configure consists of a
@dfn{per-invocation} section, followed by a @dfn{per-host} section,
followed by a @dfn{per-target} section, optionally followed by a
@dfn{post-target} section.  Each section is a shell script fragment,
which is sourced by the configure shell script at an appropriate time.
Values are passed among configure and the shell fragments through a
set of shell variables.  When each section is being interpreted
(sourced) by the shell, the shell's current directory is the build
directory, and any files created by the section (or referred to by the
section) will be relative to the build directory.  To reference files
in other places (such as the source directory), prepend a shell
variable such as @code{srcdir} to the desired file name.

@cindex Per-invocation section
The beginning of the @file{configure.in} file begins the per-invocation
section.

@cindex Per-host section
A line beginning with @code{# Per-host:} begins the per-host section.

@cindex Per-target section
A line beginning with @code{# Per-target:} begins the per-target
section.

@cindex Post-target section
If it exists, the post-target section begins with @code{# Per-target:}.

@menu
* Minimal::			A minimal configure.in
* Configure Variables::		Variables available to configure.in
* Declarations::		For each invocation
* Per-host::			For each host
* Per-target::			For each target
* Post-target::			After each target
* Example::			An example configure.in
@end menu

@node Minimal, Configure Variables, configure.in, configure.in
@subsection A minimal @file{configure.in}

@cindex Minimal @file{configure.in} example
A minimal @file{configure.in} consists of four lines.

@example
srctrigger=foo.c
srcname="source for the foo program"
# Per-host:
# Per-target:
@end example

The @samp{Per-host} and @samp{Per-target} lines divide the file into the
three required sections.  The @samp{srctrigger} line names a file.
@code{configure} checks to see that this file exists in the source
directory before configuring.  If the @samp{srctrigger} file does not
exist, @code{configure} uses the value of @samp{srcname} to print an
error message about not finding the source.

This particular example uses no links, and only the default host,
target, and site specific Makefile fragments if they exist.

@node Configure Variables, Declarations, Minimal, configure.in
@subsection Variables available to configure.in

@cindex @file{configure.in} interface

The following variables pass information between the standard parts of
@code{configure} and the shell-script fragments in @file{configure.in}:

@defvar{srctrigger}
Contains the name of a source file that is expected to live in the
source directory.  You must usually set this in the per-invocation
section of @file{configure.in}.  Configure tests to see that this file
exists.  If the file does not exist, configure prints an error message.
This is used as a sanity check that configure.in matches the source
directory.
@end defvar

@defvar{srcname}
Contains the name of the source collection contained in the source
directory.  You must usually set this in the per-invocation section of
@file{configure.in}.  If the file named in @code{srctrigger} does not
exist, configure uses the value of this variable when it prints the
error message.
@end defvar

@defvar{configdirs}
Contains the names of any subdirectories where @code{configure} should
recur.  You must usually set this in the per-invocation section of
@file{configure.in}.
If @file{Makefile.in} contains a line starting with @code{SUBDIRS =},
then it will be replaced with an assignment to @code{SUBDIRS} using
the value of @code{configdirs} (if @code{subdirs} is empty).  This can
be used to determine which directories to configure and build depending
on the host and target configurations.
@c Most other matching makefile/config vars use the same name.  Why not
@c this? (FIXME).
@c Can we get rid of SUBDIRS-substitution?  It doesn't work well with subdirs.
Use @code{configdirs} (instead of the @code{subdirs} variable
described below) if you want to be able to partition the
sub-directories, or use independent Makefile fragments.
Each sub-directory can be independent, and independently re-configured.
@end defvar

@defvar{subdirs}
Contains the names of any subdirectories where @code{configure} should
create a @code{Makefile} (in addition to the current directory),
@emph{without} recursively running @code{configure}.
Use @code{subdirs} (instead of the @code{configdirs} variable
described above) if you want to configure all of the directories
as a unit.  Since there is a single invocation of @code{configure}
that configures many directories, all the directories can use the
same Makefile fragments, and the same @code{configure.in}.
@end defvar

@defvar{host}
Contains the full configuration name (generated by the script
@file{config.sub} from the name that the user entered) for the host.
This is a three-part name of the form 

@example
@var{cpu}-@var{vendor}-@var{os}
@end example

@noindent
There are separate variables @code{host_cpu}, @code{host_vendor}, and
@code{host_os} that you can use to test each of the three parts; this
variable is useful, however, for error messages, and for testing
combinations of the three components.
@end defvar

@defvar{host_cpu}
Contains the first element of the canonical triple representing the host
as returned by @file{config.sub}.  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.sub}.  This is usually used to
distinguish betwen the numerous variations between @emph{common}
operating systems.
@c "@emph{common} OS" doesn't convey much to me.  Is this meant to cover 
@c cases like Unix, widespread but with many variations?
@end defvar

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

@defvar{target}
Contains the full configuration name (generated by the script
@file{config.sub} from the name that the user entered) for the target.
This is a three-part name of the form 

@example
@var{cpu}-@var{vendor}-@var{os}
@end example

@noindent
There are separate variables @code{target_cpu}, @code{target_vendor}, and
@code{target_os} that you can use to test each of the three parts; this
variable is useful, however, for error messages, and for testing
combinations of the three components.
@end defvar

@defvar{target_cpu}
Contains the first element of the canonical triple representing the
target as returned by @file{config.sub}.  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 differ from the system where 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.sub}.  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 user interfaces.
@c above query re "@emph{common} OS" applies here too
@end defvar

@defvar{target_os}
Contains the the third element of the canonical triple representing the
target as returned by @file{config.sub}.  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{floating_point}
Is set to @code{no} if the user invoked configure with the @code{-nfp}
command line option, otherwise it is empty.  This is a request to target
machines with @emph{no floating point} unit, even if the targets
ordinarily have floating point units 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 all target machines have @sc{gas} available even if they ordinarily do
not.  The converse option @samp{-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
on all hosts, regardless of what is normally available on them.
@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
the @code{-srcdir=} option.  Note that @code{srcdir} is not necessarily
an absolute path.
@end defvar

@defvar{host_makefile_frag}
If set by @file{configure.in}, this variable should be the name a file,
relative to @code{srcdir} to be included in the resulting Makefile.  If
the named file does not exist, @code{configure} will print a warning
message.  This variable is not set by @code{configure}.
@end defvar

@defvar{target_makefile_frag}
If set by @file{configure.in}, this variable should be the name of a
file, relative to @code{srcdir}, to be included in the resulting
Makefile.  If the named file does not exist, @code{configure} will print
a warning message.  This variable is not set by @code{configure}.
@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 override this
default.  Normally @code{site_makefile_frag} is empty, but will have a
value if the user specified @code{-site=} on the command line.  It is
probably not a good idea to override this variable from
@file{configure.in}, since that may defeat the @code{configure} user's
intentions. 
@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 its value will be the target of a symbolic link named
in the corresponding word from the @code{links} variable.
@end defvar

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

@node Declarations, Per-host, Configure Variables, configure.in
@subsection For each invocation

@cindex Declarations section

@code{configure} sources the entire shell script fragment from the start
of @file{configure.in} up to a line beginning with @samp{# Per-host:}
immediately after parsing command line arguments.  The variables
@code{srctrigger} and @code{srcname} @emph{must} be set here.

You might also want to set the variable @code{configdirs} here.

@node Per-host, Per-target, Declarations, configure.in
@subsection For each host
@cindex per-host section
@cindex host shell-script fragment

The per-host section of @file{configure.in} starts with the line that begins
with @samp{# Per-host:} and ends before a line beginning with 
@samp{# Per-target:}.  @code{configure} sources the per-host section once for
each host.

This section usually contains a big case statement using the variables
@samp{host_cpu}, @samp{host_vendor}, and @samp{host_os} to determine
appropriate values for @samp{host_makefile_frag} and @samp{files},
although @samp{files} is not usually set here.  Usually, it is set
at the end of the per-target section after determining the names of the
target specific configuration files.

@node Per-target, Post-target, Per-host, configure.in
@subsection For each target
@cindex per-target section
@cindex target shell-script fragment

The per-target section of @file{configure.in} starts with the line that
begins with @samp{# Per-target:} and ends before the line that begins
with @samp{# Post-target:}, if there is such a line.  Otherwise the
per-target section extends to the end of the file.  @code{configure} sources
the per-target section once for each target before building any files,
directories, or links.

This section usually contains a big case statement using the variables called
@samp{target_cpu}, @samp{target_vendor}, and @samp{target_os} to determine
appropriate values for @samp{target_makefile_frag} and @samp{files}.
The last lines in the per-target section normally set the variables
@code{files} and @code{links}.

@node Post-target, Example, Per-target, configure.in
@subsection After each target

The post-target section is optional.  If it exists, the post-target
section starts with a line beginning with @code{# Post-target:} and
extends to the end of the file.  If it exists, @code{configure} sources this
section once for each target after building all files, directories, or
links.

This section is seldom needed, but you can use it to edit the Makefile
generated by @code{configure}.

@node Example,  , Post-target, configure.in
@subsection An example @file{configure.in}
@cindex example @file{configure.in}
@cindex sample @file{configure.in}
@cindex Bison @file{configure.in}

Here is a small example of a @file{configure.in} file.

@example
# This file is a collection of shell script fragments used to tailor
# a template configure script as appropriate for this directory.  
# For more information, see configure.texi.

configdirs=
srctrigger=warshall.c
srcname="bison"

# per-host:
case "$@{host_os@}" in
m88kbcs)
	host_makefile_frag=config/mh-delta88
	;;
esac

# per-target:

files="bison_in.hairy"
links="bison.hairy"

# post-target:
@end example

@node config.status, Makefile Fragments, configure.in, Reference
@section @code{config.status}

@kindex config.status

The final step in configuring a directory is to create an executable
shell script, @file{config.status}.  The main purpose of this file
is to allow the Makefile for the current directory to rebuild itself, if
necessary.  For this reason, @file{config.status} uses the
@samp{-norecursion} option to @code{configure}, and is therefore
probably inappropriate for reconfiguring a tree of source code.

@node Makefile Fragments,  , config.status, Reference
@section Makefile Fragments

@cindex Makefile fragments

Cygnus @code{configure} uses three types of Makefile fragments.  In a
generated Makefile they appear in the order target fragment, host
fragment, and site fragment.  This allows host fragments to override
target fragments, and site fragments to override both.

Host specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form
@file{mh-@var{host}}.  They are used for hosts that require
odd options to the standard compiler and for compile time options based
on the host configuration.

Target specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form @file{mt-@var{target}}.
They are used for target dependent compile time options.

Site specific Makefile fragments conventionally reside in the
@file{./config} directory with names of the form @file{ms-@var{site}}.
They are used to override host and target independent compile time
options.  Note that you can also override these options on the
@code{make} invocation line.

@node Known Bugs, Variables Index, Reference, top
@chapter Known Bugs

@cindex bugs

We know of the following bugs:

@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

@page
@node Variables Index, Concept Index, Known Bugs, top
@appendix Variable Index

@printindex vr

@page
@node     Concept Index,  , Variables Index, top
@appendix Concept Index

@printindex cp
@contents
@bye

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