     START-INFO-DIR-ENTRY
     * configure: (configure).        Cygnus configure.
     END-INFO-DIR-ENTRY

This document describes the Cygnus Support version of configure.

Copyright (C) 1991, 1992, 1993 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.

Cygnus configure
****************

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

What configure does
*******************

This manual documents Cygnus configure, a program which helps to automate much of the setup activity associated with building large suites of programs, such the Cygnus Support Developer's Kit.  This manual is therefore geared toward readers who are likely to face the problem of configuring software in source form before compiling and installing it.  We assume you are an experienced programmer or system administrator. For further background on this topic, see Apologia Configure (On Configuring Development Tools), by K. Richard Pixley.

When configure runs, it does the following things:

* creates build directories
     When you run configure with the --srcdir option, it uses the current directory as the build directory, creating under it a directory tree that parallels the directory structure of the source directory.  If you don't specify a srcdir, configure first assumes that the source code you wish to configure is in your current directory; if it finds no configure.in input file there, it searches in the directory configure itself lies in.  (For details, see Build directories.)

* generates Makefile
     A Makefile template from the source directory, usually called Makefile.in, is copied to an output file in the build directory which is most often named Makefile.  configure places definitions for a number of standard Makefile macros at the beginning of the output file. If --prefix=DIR or --exec_prefix=DIR are specified on the 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.  (For details, see Makefile generation.)

* generates .gdbinit
     If the source directory contains a .gdbinit file and the build directory is not the same as the source directory, a .gdbinit file is created in the build directory.  This .gdbinit file contains commands which allow the source directory to be read when debugging with the GNU debugger, gdb.  (see Command Files (Debugging With GDB).)

* makes symbolic links
     Most build directories require that some symbolic links with generic names are built pointing to specific files in the source directory.  If the system where configure runs cannot support symbolic links, hard links are used instead.  (For details, see The configure.in input file.)

* generates config.status
     configure creates a shell script named config.status in the build directory.  This shell script, when run from the build directory (usually from within a Makefile), will reconfigure the build directory (but not its subdirectories).  This is most often used to have a Makefile update itself automatically if a new source directory is available.

* calls itself recursively
     If the source directory has subdirectories that should also be configured, configure is called for each.

Invoking configure
******************

Cygnus configure is a shell script which resides in a source tree.  The usual way to invoke configure is from the shell, as follows:

     eg$ ./configure HOST

This prepares the source in the current directory (.) to be compiled for a HOST environment.  It assumes that you wish to build programs and files in the default build directory (also the current directory, .). If you neglect to specify a value for HOST, Cygnus configure will attempt to discover this information by itself (see Determining system information).  For information on HOST environments, see Host.

All GNU software is packaged with one or more configure script(s) (see How Configuration Should Work (GNU Coding Standards)).  By using configure you prepare the source for your specific environment by selecting and using Makefile fragments and fragments of shell scripts, which are prepared in advance and stored with the source.

configure's command-line options also allow you to specify other aspects of the source configuration:

       configure HOST  [--target=TARGET] [--srcdir=DIR] [--rm]
                 [--site=SITE] [--prefix=DIR] [--exec_prefix=DIR]
                 [--program_prefix=STRING] [--tmpdir=DIR]
                 [--with-PACKAGE[=YES/NO]] [--norecursion]
                 [--nfp] [-s] [-v] [-V | --version] [--help]

--target=TARGET
     Requests that the sources be configured to target the TARGET machine.  If no target is specified explicitly, the target is assumed to be the same as the host (i.e., a native configuration).  See Host, and Target, for discussions of each.

--srcdir=DIR
     Direct each generated Makefile to use the sources located in directory DIR.  Use this option whenever you wish the object code to reside in a different place from the source code.  The build directory is always assumed to be the directory you call configure from.  See Build directories, for an example.  If the source directory is not specified, configure assumes that the source is in your current directory.  If configure finds no configure.in there, it searches in the same directory that the configure script itself lies in. Pathnames specified (Values for DIR) can be either absolute relative to the build directory.

--rm
     Remove the configuration specified by HOST and the other command-line options, rather than create it.

--site=SITE
     Generate the Makefile using site-specific Makefile fragments for SITE.  See Adding information about local conventions.

--prefix=DIR
     Configure the source to install programs and files under directory DIR.

     This option sets the variable prefix.  Each generated Makefile will have its prefix variables set to this value.  (see What configure really does.)

--exec_prefix=DIR
     Configure the source to install host dependent files in DIR.

     This option sets the variable exec_prefix.  Each generated Makefile will have its exec_prefix variables set to this value. (see What configure really does.)

--program_prefix=STRING
     Configure the source to install certain programs using STRING as a prefix.  This applies to programs which might be used for cross-compilation, such as the compiler and the binary utilities, and also to programs which have the same names as common Unix programs, such as make.

     This option sets the variable program_prefix.  Each generated Makefile will have its program_prefix variables set to this value.  (see What configure really does.)

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

--with-PACKAGE[=YES/NO]
     Set a flag for the compiler to recognize that PACKAGE is explicitly present, or not present, depending on YES/NO.  If YES/NO is nonexistent, its value is assumed to be yes.

     For example, if you wish to configure the program gcc for a Sun SPARCstation running SunOS 4.x, and you want to make sure gcc is built using the GNU linker ld, you can configure using

          eg$ configure --with-gnu-ld sun4

     See What configure really does, for details.  See the installation or release notes for your particular package for details on which other PACKAGE flags are useful.

--norecursion
     Configure only this directory; ignore any subdirectories.  This is used by the executable shell script config.status to reconfigure only the current directory; it is most often used non-interactively, when make is invoked.  (see config.status.)

--nfp
     Explicitly assume that the intended HOST has no floating point unit.

-s
     This option is used internally by configure when calling itself recursively in subdirectories.  Its sole purpose is to suppress status output. You can override this effect with the --verbose option.

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

--version
-V
     Print configure version number.

--help
     Display a quick summary of how to invoke configure.

Note: You may introduce options with a single dash, -, rather than two dashes, --.  However, you may not be able to truncate long option names when using a single dash.  When using two dashes, options may be abbreviated as long as each option can be uniquely identified.  For example,

     eg$ configure --s=/u/me/src myhost

is ambiguous, as --s could refer to either --site or --srcdir.  However,

     eg$ configure --src=/u/me/src myhost

is a perfectly legal abbreviation.  (Note that the above will probably not work unless there exists a valid host called myhost and you have source code in the directory /u/me/src that you wish to configure.)

Using configure
***************

configure prepares source directories for the process of building working programs.  ``Configuring'' is the process of preparing software to compile correctly on a given host, optionally for a given target. A program cannot be built until its source has been configured.

configure subsequently writes a configured Makefile from a pre-built template; configure uses variables that have been set in the configuring process to determine the values of some variables in the Makefile.  Because of this we will refer to both configure variables and Makefile variables.  This convention allows us to determine where the variable should be set initially, in either configure.in or Makefile.in.

What configure really does
==========================

Cygnus configure is a complex shell script you use to set up a certain environment in which your programs will compile correctly for your machine and operating system, and will install themselves in proper places. configure accomplishes this task in a variety of ways:

  * it generates a Makefile from a custom template called Makefile.in in each relevant source directory;

  * you set certain variables for configure, either on the command line or in the file configure.in, which subsequently sets variables in each generated Makefile to be used by make when actually building the software;

  * it establishes and populates build directories, places for your compiled code to reside before being installed;

  * it generates a .gdbinit in the build directory, if needed, to communicate information to gdb;

  * it generates a shell script called config.status which is used most often by the Makefile to reconfigure itself.

  * it recurs in subdirectories, setting up entire trees so that they build correctly; if configure finds another configure script further down in a given source tree, it knows to use this script and not recur.

For the sake of safety (i.e., in order to prevent broken installations), the GNU coding standards call for software to be configured in such a way that an end user trying to build a given package will be able to do so by affecting a finite number of variables.  All GNU software comes with an executable configure shell script which sets up an environment within a build directory which will correctly compile your new package for your host (or, alternatively, whatever host you specify to configure). For further background on this topic, see Apologia Configure (On Configuring Development Tools), by K. Richard Pixley.

Use configure to effectively communicate with the build process:

  * correct terms for certain variables;

  * what host you wish to configure a given package for (see Host);

  * to tell the build tools where you want this package installed (by using prefix, exec_prefix and program_prefix; see Full descriptions of all installation directories);

  * optionally, what machine you wish to target this package's output to (see Target);

  * what other GNU packages are already installed and available to this particular build (by using the --with-PACKAGE option; see Invoking configure);

  * where to build temporary files (by using the --tmpdir=DIR option; see Invoking configure);

  * whether to recur in subdirectories (changeable through the --norecursion option; see Invoking configure).

configure uses a few other files to complete its tasks.  These are discussed in detail where noted.

configure.in
     Input file for configure.  Shell script fragments reside here. See The configure.in input file.

Makefile.in
     Template which configure uses to build a file called Makefile in the build directory.  See Makefile generation.

config.sub
     Shell script used by configure to expand referents to the HOST argument into a single specification of the form CPU-VENDOR-OS. For instance, on the command line you would specify

          eg$ ./configure sun4

     to configure for a Sun SPARCstation running SunOS 4.x.  configure consults config.sub to find that the three-part specification for this is

          sparc-sun-sunos4.1.1

     which notes the CPU as sparc, the MANUFACTURER as sun (Sun Microsystems), and the OS (operating system) as sunos4.1.1, the SunOS 4.1.1 release.  See Variables available to configure.

config.guess
     If you neglect to put the HOST argument on the command line, configure uses config.guess to make an analysis of your machine (and, incidentally, assumes that you wish to configure your software for the machine you happen to be running on).  The output of config.guess is the same three-part identifier as described above.

config.status
     The final step in configuring a directory is to create an executable shell script, config.status.  The main purpose of this file is to allow the Makefile for the current directory to rebuild itself, if necessary. See config.status.

config/*
     configure uses three types of Makefile fragments, which reside in the directory SRCDIR/config/.  See Adding information about local conventions.

Build variables
---------------

There are several variables in the build process which you can control through build programs such as make.  These include machine definitions, local conventions, installation locations, locations for temporary files, etc.  This data is accessible through certain variables which are configurable in the build process; we can refer to them as build variables.

For lists of build variables which you can affect by using configure, see Variables available to configure.in, and Full descriptions of all installation directories.

Generally, build variables, which are used by the Makefile to determine various aspects of the build and installation processes, are changeable by command-line options to configure.  The sense in this is especially seen when building large suites of programs, like the Cygnus Support Developer's Kit, whose individual programs reside in several subdirectories of a single source code ``tree''.  All of these subdirectories need to be configured with information relative to the build directory, which is not known until configure is run.  Unless specified otherwise, configure recursively configures every subdirectory in the source tree with correct information (i.e., supplied information that is correct, as well as correctly supplied information).

Build variables are passed from configure directly into the Makefile, and use the same names.  In other words, if you specify

     eg$ ./configure --prefix=/usr/gnu/local ... HOST

on the command line, configure sets an variable called prefix to /usr/gnu/local, and passes this into the Makefile in the same manner.  After this command, each Makefile generated by configure will contain a line that reads:

     prefix = /usr/gnu/local

For a list of the Makefile variables configure can change, and instructions on how to change them, see Variables available to configure.in, and Invoking configure.

Build directories
-----------------

By default, configure builds a Makefile and symbolic links in the same directory as the source files.  This default works for many cases, but it has limitations.  For instance, using this approach, you can only build object code for one host at a time.

We refer to each directory where configure builds a Makefile as a build directory.

The build directory for any given build is always the directory from which you call configure, or . relative to your prompt.  The default source directory, the place configure looks to find source code, is also ..  For instance, if we have a directory /gnu-stuff/src/ that is the top branch of a tree of GNU source code we wish to configure, then the program we will use to configure this code is /gnu-stuff/src/configure, as follows.  (Assume for the sake of argument that our machine is a sun4.)

     eg$ cd /gnu-stuff/src
     eg$ ./configure sun4
     Created "Makefile" in /gnu-stuff/src
     eg$

We just configured the code in /gnu-stuff/src to run on a Sun SPARCstation using SunOS 4.x by creating a Makefile in /gnu-stuff/src.  By default, we also specified that when this code is built, the object code should reside in the same directory, /gnu-stuff/src.

However, if we wanted to build this code for more than one host, we would be in trouble, because the new configuration would write over the old one, destroying it in the process.  What we can do is to make a new build directory and configure from there.  Running configure from the new directory will place a correct Makefile and a config.status in this new file. That is all configure does; we must run make to generate any object code.

The new Makefile in /gnu-stuff/sun4-obj, created from the template file /gnu-stuff/src/Makefile.in, contains all the information needed to build the program.

     eg$ mkdir /gnu-stuff/sun4-obj
     eg$ cd /gnu-stuff/sun4-obj
     eg$ ../src/configure --srcdir=../src sun4
     Created "Makefile" in /gnu-stuff/sun4-obj
     eg$ ls
     Makefile       config.status
     eg$ make all info install install-info clean
     COMPILATION MESSAGES...
     eg$ mkdir /gnu-stuff/solaris2
     eg$ cd /gnu-stuff/solaris2
     eg$ ../src/configure --srcdir=../src sol2
     Created "Makefile" in /gnu-stuff/solaris2
     eg$ ls
     Makefile       config.status
     eg$ make all info install install-info clean
     COMPILATION MESSAGES...

We can repeat this for other configurations of the same software simply by making a new build directory and reconfiguring from inside it.  If you neglect to specify the host argument, configure will attempt to figure out what kind of machine and operating system you happen to be using. See Determining system information.  Of course, this may not always be the configuration you wish to build.

Caution: If you build more than one configuration for a single program, remember that you must also specify a different --prefix for each configuration at configure-time.  Otherwise, both configurations will be installed in the same default location (/usr/local); the configuration to be installed last would overwrite previously installed configurations.

Makefile generation
-------------------

Cygnus configure creates a file called Makefile in the build directory which can be used with make to automatically build a given program or package.  configure also builds a Makefile for each relevant subdirectory for a given program or package (irrelevant subdirectories would be those which contain no code which needs configuring, and which therefore have no configure input file configure.in and no Makefile template Makefile.in).  See How to Run make (GNU Make), for details on using make to compile your source code.

Each Makefile contains variables which have been configured for a specific build.  These build variables are determined when configure is run.  All build variables have defaults.  By default, configure generates a Makefile which specifies:

  * a native build, which is to occur

  * in the current directory, and which will be installed

  * in the default installation directory (/usr/local) when the code is compiled with make.

Variables are changeable through command-line options to configure (see Invoking configure).

If you are porting a new program and intend to use configure, see Porting with configure, as well as Writing Makefiles (GNU Make), and Makefile Conventions (GNU Coding Standards).

Determining system information
------------------------------

The shell script config.guess is called when you do not specify a HOST on the command line to configure.  config.guess acquires available system information from your local machine through the shell command uname.  It compares this information to a database and attempts to determine a usable three-part system identifier (known as a triple) to use as your HOST.  See What configure really does, to see how this information is used.

Note:  If you do not specify a HOST on the command line, configure will attempt to configure your software to run on the machine you happen to be using.  This may not be the configuration you desire.

config.status
-------------

The final step in configuring a directory is to create an executable shell script, config.status.  The main purpose of this file is to allow the Makefile for the current directory to rebuild itself, if necessary.  It is usually run from within the Makefile.  See Extensions to the GNU coding standards.

config.status also contains a record of the configure session which created it.

The configure.in input file
===========================

A configure.in file for Cygnus configure consists of a per-invocation section, followed by a per-host section, followed by a per-target section, optionally followed by a post-target section. Each section is a shell script fragment, which is executed 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 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 $(srcdir)/ to the desired file name.

The beginning of the configure.in file begins the per-invocation section.

A line beginning with # per-host: begins the per-host section.

A line beginning with # per-target: begins the per-target section.

If it exists, the post-target section begins with # post-target:.

Variables available to configure.in
-----------------------------------

The following variables pass information between the standard parts of configure and the shell-script fragments in configure.in:

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 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.

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

configdirs
     Contains the names of any subdirectories in which configure should recurse.  You must usually set this in the per-invocation section of configure.in. If Makefile.in contains a line starting with SUBDIRS =, then it will be replaced with an assignment to SUBDIRS using the value of configdirs (if subdirs is empty).  This can be used to determine which directories to configure and build depending on the host and target configurations. Use configdirs (instead of the subdirs variable described below) if you want to be able to partition the subdirectories, or use independent Makefile fragments. Each subdirectory can be independent, and independently reconfigured.

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

host
     Contains the full configuration name for the host (generated by the script config.sub from the name that you entered).  This is a three-part name (commonly referred to as a triple) of the form CPU-VENDOR-OS.

     There are separate variables host_cpu, host_vendor, and 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.

host_cpu
     Contains the first element of the canonical triple representing the host as returned by 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.

host_vendor
     Contains the second element of the canonical triple representing the host as returned by config.sub.  This is usually used to distinguish among the numerous variations of common operating systems.

host_os
     Contains the the third element of the canonical triple representing the host as returned by config.sub.

target
     Contains the full configuration name (generated by the script config.sub from the name that you entered) for the target.  Like the host, this is a three-part name of the form CPU-VENDOR-OS.

     There are separate variables target_cpu, target_vendor, and 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.

target_cpu
     Contains the first element of the canonical triple representing the target as returned by config.sub.  This variable is used heavily by programs which are involved in building other programs, like the compiler, assembler, linker, etc.  Most programs will not need the 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.

target_vendor
     Contains the second element of the canonical triple representing the target as returned by config.sub.  This is usually used to distinguish among the numerous variations of common operating systems or object file formats.  It is sometimes used to switch between different flavors of user interfaces.

target_os
     Contains the the third element of the canonical triple representing the target as returned by 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.

floating_point
     Set to no if you invoked configure with the --nfp command-line option, otherwise it is empty.  This is a request to target machines with no floating point unit, even if the targets ordinarily have floating point units available.

gas
     Set to true if you invoked configure with the --with-gnu-as command line option, otherwise it is empty.  This is a request to assume that the specified HOST machine has GNU as available even if it ordinarily does not.

srcdir
     Set to the name of the directory containing the source for this program. This will be different from . if you have specified the --srcdir=DIR option.  srcdir can indicate either an absolute path or a path relative to the build directory.

package_makefile_frag
     If set in configure.in, this variable should be the name a file relative to srcdir to be included in the resulting Makefile.  If the named file does not exist, configure will print a warning message.  This variable is not set by configure.

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

target_makefile_frag
     If set in configure.in, this variable should be the name of a file, relative to srcdir, to be included in the resulting Makefile.  If the named file does not exist, configure will print a warning message. This variable is not set by configure.

site_makefile_frag
     Set to a file name representing to the default Makefile fragment for this host.  It may be set in configure.in to override this default. Normally site_makefile_frag is empty, but will have a value if you specify --site=SITE on the command line.

Makefile
     Set to the name of the generated Makefile.  Normally this value is precisely Makefile, but some programs may want something else.

removing
     Normally empty but will be set to some non-null value if you specified --rm on the command line.  That is, if removing is not empty, then configure is removing a configuration rather than creating one.

files
     If this variable is not empty following the per-target section, then each word in its value will be the target of a symbolic link named in the corresponding word from the links variable.

links
     If the files variable is not empty following the per-target section, then configure creates symbolic links 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.

A minimal configure.in
----------------------

A minimal configure.in consists of four lines.

     srctrigger=foo.c
     srcname="source for the foo program"
     # per-host:
     # per-target:

The # per-host: and # per-target: lines divide the file into the three required sections.  The srctrigger line names a file. configure checks to see that this file exists in the source directory before configuring.  If the srctrigger file does not exist, configure uses the value of 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.

For each invocation
-------------------

configure invokes the entire shell script fragment from the start of configure.in up to a line beginning with # per-host: immediately after parsing command line arguments.  The variables srctrigger and srcname must be set here.

You might also want to set the variables configdirs and package_makefile_frag here.

Host-specific instructions
--------------------------

The per-host section of configure.in starts with the line that begins with # per-host: and ends before a line beginning with # per-target:.  configure invokes the commands in the per-host section when determining host-specific information.

This section usually contains a big case statement using the variable host to determine appropriate values for host_makefile_frag and files, although 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.

Target-specific instructions
----------------------------

The per-target section of configure.in starts with the line that begins with # per-target: and ends before the line that begins with # post-target:, if there is such a line.  Otherwise the per-target section extends to the end of the file.  configure invokes the commands in the per-target section when determining target-specific information, and before building any files, directories, or links.

This section usually contains a big case statement using the variable target to determine appropriate values for target_makefile_frag and files.  The last lines in the per-target section normally set the variables files and links.

Instructions to be executed after target info
---------------------------------------------

The post-target section is optional.  If it exists, the post-target section starts with a line beginning with # Post-target: and extends to the end of the file.  If it exists, configure invokes 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 configure.

An example configure.in
-----------------------

Here is a small example of a configure.in file.

     # 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}" in
     m88k-motorola-*)
             host_makefile_frag=config/mh-delta88
             ;;
     esac

     # per-target:
     files="bison_in.hairy"
     links="bison.hairy"

     # post-target:

Install locations
=================

Using the default configuration, 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 prefix.  The default value of prefix is /usr/local.  This is often correct for native tools installed on only one host.

Changing the default install directory
--------------------------------------

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

You can also set the value of the Makefile variable prefix explicitly each time you invoke make if you are so inclined.  However, because many programs have this location compiled in, you must specify the prefix value consistently on each invocation of make, or you will end up with a broken installation.

To make this easier, the value of the configure variable prefix can be set on the command line to configure using the option --prefix=.

Installing for multiple hosts
-----------------------------

By default, host dependent files are installed in subdirectories of $(exec_prefix).  The location is determined by the value of the configure variable exec_prefix, which determines the value of the Makefile variable exec_prefix.  This makes it easier to install for a single host, and simplifies changing the default location for the install tree.  The default doesn't allow for multiple hosts to effectively share host independent files, however.

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

     configure HOST1 -prefix=/usr/gnu -exec_prefix=/usr/gnu/H-host1
     make all info install install-info clean

     configure HOST2 -prefix=/usr/gnu -exec_prefix=/usr/gnu/H-host2
     make all info install install-info

The first line configures the source for HOST1 to place host-specific programs in subdirectories of /usr/gnu/H-HOST1.

The second line builds and installs all programs for HOST1, including both host-independent and host-specific files, as well as removing the host-specific object files from of the build directory.

The third line reconfigures the source for HOST2 to place host specific programs in subdirectories of /usr/gnu/H-HOST2.

The fourth line builds and installs all programs for HOST2.  Host specific files are installed in new directories, but the host independent files are installed on top of the host independent files installed for HOST1.  This results in a single copy of the host independent files, suitable for use by both hosts.

See Extensions to the GNU coding standards, for more information.

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 configuration time using command line options to configure.  For more information on the standard directories or the Makefile variables, please refer to Makefile Conventions (GNU Coding Standards).  See also Extensions to the GNU coding standards.

Note that configure does not create the directory indicated by the variable srcdir at any time.  $(srcdir) is not an installation directory.

You can override all Makefile variables on the command line to make.  (see Overriding Variables (GNU Make).)  If you do so, you will need to specify the value precisely the same way for each invocation of 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 Adding site info.

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

prefix (Makefile and configure)
     The root of the installation tree.  You can set its Makefile default with the --prefix= command line option to configure (see Invoking configure).  The default value for prefix is /usr/local.

bindir
     A directory for binary programs that users can run.  The default value for bindir depends on prefix; bindir is normally changed only indirectly through prefix.  The default value for bindir is $(prefix)/bin.

exec_prefix (Makefile and configure)
     A directory for host dependent files.  You can specify the Makefile default value by using the --exec_prefix= option to configure. (see Invoking configure.)  The default value for exec_prefix is $(prefix).

libdir
     A directory for libraries and support programs.  The default value for libdir depends on prefix; libdir is normally changed only indirectly through prefix.  The default value for libdir is $(prefix)/lib.

mandir
     A directory for man format documentation (``man pages'').  The default value for mandir depends on prefix; mandir is normally changed only indirectly through prefix.  The default value for mandir is $(prefix)/man.

manNdir
     These are eight variables named man1dir, man2dir, etc.  They name the specific directories for each man page section.  For example, man1dir by default holds the filename $(mandir)/man1; this directory contains emacs.1 (the man page for GNU Emacs). Similarly, man5dir contains the value $(mandir)/man5, indicating the directory which holds rcsfile.5 (the man page describing the rcs data file format).  The default value for any of the manNdir variables depends indirectly on prefix, and is normally changed only through prefix.  The default value for manNdir is $(mandir)/manN.

manNext
     Not supported by Cygnus configure.  The GNU Coding Standards do not call for man1ext, man2ext, so the intended use for manext is apparently not parallel to mandir.  Its use is not clear.  (See also Extensions to the GNU coding standards.)

infodir
     A directory for info format documentation.  The default value for infodir depends indirectly on prefix; infodir is normally changed only through prefix.  The default value for infodir is $(prefix)/info.

docdir
     A directory for any documentation that is in a format other than those used by info or man.  The default value for docdir depends indirectly on prefix; docdir is normally changed only through prefix.  The default value for docdir is $(datadir)/doc. This variable is an extension to the GNU coding standards.  (See also Extensions to the GNU coding standards.)

includedir
     A directory for the header files accompanying the libraries installed in libdir.  The default value for includedir depends on prefix; includedir is normally changed only indirectly through prefix.  The default value for includedir is $(prefix)/include.

Host
====

The arguments to configure are hosts.  By 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 had the GNU POSIX emulation libraries available, it would be possible to configure most GNU source for a POSIX system and build it on the obscure host.

For more on this topic, see Host Environments (On Configuring Development Tools).

Target
======

For building native development tools, or most of the other GNU tools, you need not worry about the target.  The target of a configuration defaults to the same as the host.

For building cross development tools, please see Building Development Environments (On Configuring Development Tools).

Adding information about local conventions
==========================================

If you find that a tool does not get configured to your liking, or if configure's conventions differ from your local conventions, you should probably consider site-specific Makefile fragments.  See also Adding site info.

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

Cygnus 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 ./config/ subdirectory with names of the form mh-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 ./config/ subdirectory with names of the form mt-TARGET. They are used for target dependent compile time options.

Site specific Makefile fragments conventionally reside in the ./config/ subdirectory with names of the form ms-SITE. They are used to override host- and target-independent compile time options. Note that you can also override these options on the make invocation line.

Extensions to the GNU coding standards
======================================

The following additions to the GNU coding standards are required for Cygnus configure to work properly.

  * The Makefile must contain exactly one line starting with ####. 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.

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

     info
          Build all info files from texinfo source.

     install-info
          Install all info files.

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

     Makefile
          Calls ./config.status to rebuild the Makefile in this directory.

  * The following Makefile targets have revised semantics:

     install
          Should not depend on the target all.  If the program is not already built, make install should fail.  This allows you to install programs even when make would otherwise determine them to be out of date.  This can happen, for example, when the result of a make all is transported via tape to another machine for installation.

     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, make all clean should return all directories to their original condition.  If this is not done, then the command sequence

               configure HOST1 ; make all install clean ;
               configure HOST2 ; make all install

          will fail because of intermediate files intended for HOST1.

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

     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.

     includedir
          The directory in which to install any header files that should be made available to users.  This is distinct from the gcc include directory, which is intended for gcc only.  Files in includedir may be used by cc as well.

  * The following macros have revised semantics.  Most of them describe installation directories; see also Full description of all installation subdirectories.

     datadir
          is used for host independent data files.

     mandir
          The default path for mandir depends on prefix.

     infodir
          The default path for infodir depends on prefix.

     BISON
          is assumed to have a yacc calling convention.  To use GNU bison, use BISON=bison -y.

  * Each Cygnus Makefile also conforms to one additional restriction:

     When libraries are installed, the line containing the call to INSTALL_DATA should always be followed by a line containing a call to RANLIB on the installed library.  This is to accommodate systems that use ranlib.  Systems that do not use ranlib can set RANLIB to ``echo'' in a host specific Makefile fragment.

Porting with configure
**********************

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

Adding configure to new programs
================================

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

If your program currently has a configure script that meets the GNU standards (see How Configuration Should Work (GNU Coding Standards), 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 autoconf instead of Cygnus configure.  autoconf is available from the Free Software Foundation; it is a program which generates an executable shell script called configure by automatically finding information on the system to be configured on and embedding this information in the shell script. configure scripts generated by autoconf require no arguments, and accept the same options as Cygnus configure.  For detailed instructions on using autoconf, see How to organize and produce Autoconf scripts (Autoconf).

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

Make sure the Makefile conforms to the GNU standard
     The coding standard for writing a GNU Makefile is described in Makefile Conventions (GNU Coding Standards).  For technical information on writing a Makefile, see Writing Makefiles (GNU Make).

Add Cygnus extensions to the Makefile
     These are described in Extensions to the GNU coding standards.

Collect package specific definitions in a single file
     Many packages are best configured using a common Makefile fragment which is included by all of the makefiles in the different directories of the package.  In order to accomplish this, set the variable package_makefile_fragment to the name of the file.  It will be inserted into the final Makefile before the target-specific fragment.

Move host support from Makefile to fragments
     This usually involves finding sections of the Makefile that say things like ``uncomment these lines for host HOST'' and moving them to a new file called ./config/mh-HOST. For more information, see Adding hosts and targets.

Choose defaults
     If the program has compile-time options that determine the way the program should behave, choose reasonable defaults and make these Makefile variables.  Be sure the variables are assigned their default values before the #### line so that site-specific Makefile fragments can override them (see Extensions to the GNU coding standards).

Locate configuration files
     If there is configuration information in header files or source files, separate it in such a way that the files have generic names.  Then move the specific instances of those files into the ./config/ subdirectory.

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.  Host specific information is the information needed to compile the program. 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 ./config/ subdirectory 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.

Write 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 ./config to files in the build directory with more generic names.  (See also Build directories.)  The format of configure.in is described in The configure.in input file.

Rename Makefile to Makefile.in

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

Adding hosts and targets
========================

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

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

  * If you are adding a host configuration, look in 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 The configure.in input file.

  * If you are adding a target configuration, look in 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 The configure.in input file.

  * Look in configure.in for the variables files, links, host_makefile_frag, and target_makefile_frag.  The values assigned to these variables are the names of the configuration files, (relative to srcdir) that the program uses.  Make sure that copies of the files exist for your host.  If not, create them.  See also Variables available to configure.in.

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

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.

  * Choose a name for your site.  It must currently be less than eleven characters.

  * If the program source does not have a ./config/ subdirectory, create it.

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

  * Configure the program with:

          configure ... --site=SITE