Each GNU distribution should come with a shell script named
configure. This script is given arguments which describe the
kind of machine and system you want to compile the program for.
configure script must record the configuration options so
that they affect compilation.
The description here is the specification of the interface for the
configure script in GNU packages. Many packages implement it
using GNU Autoconf (see Introduction in Autoconf)
and/or GNU Automake (see Introduction in Automake),
but you do not have to use these tools. You can implement it any way
you like; for instance, by making
configure be a wrapper around
a completely different configuration system.
Another way for the
configure script to operate is to make a
link from a standard name such as config.h to the proper
configuration file for the chosen system. If you use this technique,
the distribution should not contain a file named
config.h. This is so that people won’t be able to build the
program without configuring it first.
Another thing that
configure can do is to edit the Makefile. If
you do this, the distribution should not contain a file named
Makefile. Instead, it should include a file Makefile.in which
contains the input used for editing. Once again, this is so that people
won’t be able to build the program without configuring it first.
configure does write the Makefile, then Makefile
should have a target named Makefile which causes
to be rerun, setting up the same configuration that was set up last
time. The files that
configure reads should be listed as
dependencies of Makefile.
All the files which are output from the
configure script should
have comments at the beginning explaining that they were generated
configure. This is so that users won’t think
of trying to edit them by hand.
configure script should write a file named config.status
which describes which configuration options were specified when the
program was last configured. This file should be a shell script which,
if run, will recreate the same configuration.
configure script should accept an option of the form
‘--srcdir=dirname’ to specify the directory where sources are found
(if it is not the current directory). This makes it possible to build
the program in a separate directory, so that the actual source directory
is not modified.
If the user does not specify ‘--srcdir’, then
check both . and .. to see if it can find the sources. If
it finds the sources in one of these places, it should use them from
there. Otherwise, it should report that it cannot find the sources, and
should exit with nonzero status.
Usually the easy way to support ‘--srcdir’ is by editing a
VPATH into the Makefile. Some rules may need to
refer explicitly to the specified source directory. To make this
configure can add to the Makefile a variable named
srcdir whose value is precisely the specified directory.
In addition, the ‘configure’ script should take options corresponding to most of the standard directory variables (see Directory Variables). Here is the list:
--prefix --exec-prefix --bindir --sbindir --libexecdir --sysconfdir --sharedstatedir --localstatedir --libdir --includedir --oldincludedir --datarootdir --datadir --infodir --localedir --mandir --docdir --htmldir --dvidir --pdfdir --psdir
configure script should also take an argument which specifies the
type of system to build the program for. This argument should look like
For example, an Athlon-based GNU/Linux system might be ‘i686-pc-linux-gnu’.
configure script needs to be able to decode all plausible
alternatives for how to describe a machine. Thus,
‘athlon-pc-gnu/linux’ would be a valid alias. There is a shell
config.sub that you can use as a subroutine to validate system
types and canonicalize aliases.
configure script should also take the option
--build=buildtype, which should be equivalent to a
plain buildtype argument. For example, ‘configure
--build=i686-pc-linux-gnu’ is equivalent to ‘configure
i686-pc-linux-gnu’. When the build type is not specified by an option
or argument, the
configure script should normally guess it using
the shell script
Other options are permitted to specify in more detail the software or hardware present on the machine, to include or exclude optional parts of the package, or to adjust the name of some tools or arguments to them:
Configure the package to build and install an optional user-level facility called feature. This allows users to choose which optional features to include. Giving an optional parameter of ‘no’ should omit feature, if it is built by default.
No ‘--enable’ option should ever cause one feature to replace another. No ‘--enable’ option should ever substitute one useful behavior for another useful behavior. The only proper use for ‘--enable’ is for questions of whether to build part of the program or exclude it.
The package package will be installed, so configure this package to work with package.
Possible values of package include ‘gnu-as’ (or ‘gas’), ‘gnu-ld’, ‘gnu-libc’, ‘gdb’, ‘x’, and ‘x-toolkit’.
Do not use a ‘--with’ option to specify the file name to use to find certain files. That is outside the scope of what ‘--with’ options are for.
Set the value of the variable variable to value. This is used to override the default values of commands or arguments in the build process. For example, the user could issue ‘configure CFLAGS=-g CXXFLAGS=-g’ to build with debugging information and without the default optimization.
Specifying variables as arguments to
configure, like this:
is preferable to setting them in environment variables:
as it helps to recreate the same configuration later with config.status. However, both methods should be supported.
configure scripts should accept all of the “detail”
options and the variable settings, whether or not they make any
difference to the particular package at hand. In particular, they
should accept any option that starts with ‘--with-’ or
‘--enable-’. This is so users will be able to configure an
entire GNU source tree at once with a single set of options.
You will note that the categories ‘--with-’ and ‘--enable-’ are narrow: they do not provide a place for any sort of option you might think of. That is deliberate. We want to limit the possible configuration options in GNU software. We do not want GNU programs to have idiosyncratic configuration options.
Packages that perform part of the compilation process may support cross-compilation. In such a case, the host and target machines for the program may be different.
configure script should normally treat the specified type of
system as both the host and the target, thus producing a program which
works for the same type of machine that it runs on.
To compile a program to run on a host type that differs from the build type, use the configure option --host=hosttype, where hosttype uses the same syntax as buildtype. The host type normally defaults to the build type.
To configure a cross-compiler, cross-assembler, or what have you, you should specify a target different from the host, using the configure option ‘--target=targettype’. The syntax for targettype is the same as for the host type. So the command would look like this:
./configure --host=hosttype --target=targettype
The target type normally defaults to the host type. Programs for which cross-operation is not meaningful need not accept the ‘--target’ option, because configuring an entire operating system for cross-operation is not a meaningful operation.
Some programs have ways of configuring themselves automatically. If
your program is set up to do this, your
configure script can simply
ignore most of its arguments.