16. Running configure Scripts

Below are instructions on how to configure a package that uses a configure script, suitable for inclusion as an `INSTALL' file in the package. A plain-text version of `INSTALL' which you may use comes with Autoconf.

16.1 Basic Installation

Briefly, the shell commands `./configure; make; make install' should configure, build, and install this package. The following more-detailed instructions are generic; see the `README' file for instructions specific to this package. More recommendations for GNU packages can be found in (standards)Makefile Conventions section `Makefile Conventions' in GNU Coding Standards.

The configure shell script attempts to guess correct values for various system-dependent variables used during compilation. It uses those values to create a `Makefile' in each directory of the package. It may also create one or more `.h' files containing system-dependent definitions. Finally, it creates a shell script `config.status' that you can run in the future to recreate the current configuration, and a file `config.log' containing compiler output (useful mainly for debugging configure).

It can also use an optional file (typically called `config.cache' and enabled with `--cache-file=config.cache' or simply `-C') that saves the results of its tests to speed up reconfiguring. Caching is disabled by default to prevent problems with accidental use of stale cache files.

If you need to do unusual things to compile the package, please try to figure out how configure could check whether to do them, and mail diffs or instructions to the address given in the `README' so they can be considered for the next release. If you are using the cache, and at some point `config.cache' contains results you don't want to keep, you may remove or edit it.

The file `configure.ac' (or `configure.in') is used to create `configure' by a program called autoconf. You need `configure.ac' if you want to change it or regenerate `configure' using a newer version of autoconf.

The simplest way to compile this package is:

1. cd to the directory containing the package's source code and type `./configure' to configure the package for your system.

   Running configure might take a while. While running, it prints some messages telling which features it is checking for.

2. Type `make' to compile the package.
3. Optionally, type `make check' to run any self-tests that come with the package, generally using the just-built uninstalled binaries.
4. Type `make install' to install the programs and any data files and documentation. When installing into a prefix owned by root, it is recommended that the package be configured and built as a regular user, and only the `make install' phase executed with root privileges.
5. Optionally, type `make installcheck' to repeat any self-tests, but this time using the binaries in their final installed location. This target does not install anything. Running this target as a regular user, particularly if the prior `make install' required root privileges, verifies that the installation completed correctly.
6. You can remove the program binaries and object files from the source code directory by typing `make clean'. To also remove the files that configure created (so you can compile the package for a different kind of computer), type `make distclean'. There is also a `make maintainer-clean' target, but that is intended mainly for the package's developers. If you use it, you may have to get all sorts of other programs in order to regenerate files that came with the distribution.
7. Often, you can also type `make uninstall' to remove the installed files again. In practice, not all packages have tested that uninstallation works correctly, even though it is required by the GNU Coding Standards.
8. Some packages, particularly those that use Automake, provide `make distcheck', which can by used by developers to test that all other targets like `make install' and `make uninstall' work correctly. This target is generally not run by end users.

16.2 Compilers and Options

Some systems require unusual options for compilation or linking that the configure script does not know about. Run `./configure --help' for details on some of the pertinent environment variables.

You can give configure initial values for configuration parameters by setting variables in the command line or in the environment. Here is an example:

./configure CC=c99 CFLAGS=-g LIBS=-lposix

See section Defining Variables, for more details.

16.3 Compiling For Multiple Architectures

You can compile the package for more than one kind of computer at the same time, by placing the object files for each architecture in their own directory. To do this, you can use GNU make. cd to the directory where you want the object files and executables to go and run the configure script. configure automatically checks for the source code in the directory that configure is in and in `..'. This is known as a VPATH build.

With a non-GNU make, it is safer to compile the package for one architecture at a time in the source code directory. After you have installed the package for one architecture, use `make distclean' before reconfiguring for another architecture.

On MacOS X 10.5 and later systems, you can create libraries and executables that work on multiple system types--known as fat or universal binaries--by specifying multiple `-arch' options to the compiler but only a single `-arch' option to the preprocessor. Like this:

./configure CC="gcc -arch i386 -arch x86_64 -arch ppc -arch ppc64" \
            CXX="g++ -arch i386 -arch x86_64 -arch ppc -arch ppc64" \
            CPP="gcc -E" CXXCPP="g++ -E"

This is not guaranteed to produce working output in all cases, you may have to build one architecture at a time and combine the results using the lipo tool if you have problems.

16.4 Installation Names

By default, `make install' installs the package's commands under `/usr/local/bin', include files under `/usr/local/include', etc. You can specify an installation prefix other than `/usr/local' by giving configure the option `--prefix=prefix', where prefix must be an absolute file name.

You can specify separate installation prefixes for architecture-specific files and architecture-independent files. If you pass the option `--exec-prefix=prefix' to configure, the package uses prefix as the prefix for installing programs and libraries. Documentation and other data files still use the regular prefix.

In addition, if you use an unusual directory layout you can give options like `--bindir=dir' to specify different values for particular kinds of files. Run `configure --help' for a list of the directories you can set and what kinds of files go in them. In general, the default for these options is expressed in terms of `${prefix}', so that specifying just `--prefix' will affect all of the other directory specifications that were not explicitly provided.

The most portable way to affect installation locations is to pass the correct locations to configure; however, many packages provide one or both of the following shortcuts of passing variable assignments to the `make install' command line to change installation locations without having to reconfigure or recompile.

The first method involves providing an override variable for each affected directory. For example, `make install prefix=/alternate/directory' will choose an alternate location for all directory configuration variables that were expressed in terms of `${prefix}'. Any directories that were specified during configure, but not in terms of `${prefix}', must each be overridden at install time for the entire installation to be relocated. The approach of makefile variable overrides for each directory variable is required by the GNU Coding Standards, and ideally causes no recompilation. However, some platforms have known limitations with the semantics of shared libraries that end up requiring recompilation when using this method, particularly noticeable in packages that use GNU Libtool.

The second method involves providing the `DESTDIR' variable. For example, `make install DESTDIR=/alternate/directory' will prepend `/alternate/directory' before all installation names. The approach of `DESTDIR' overrides is not required by the GNU Coding Standards, and does not work on platforms that have drive letters. On the other hand, it does better at avoiding recompilation issues, and works well even when some directory options were not specified in terms of `${prefix}' at configure time.

16.5 Optional Features

If the package supports it, you can cause programs to be installed with an extra prefix or suffix on their names by giving configure the option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Some packages pay attention to `--enable-feature' options to configure, where feature indicates an optional part of the package. They may also pay attention to `--with-package' options, where package is something like `gnu-as' or `x' (for the X Window System). The `README' should mention any `--enable-' and `--with-' options that the package recognizes.

For packages that use the X Window System, configure can usually find the X include and library files automatically, but if it doesn't, you can use the configure options `--x-includes=dir' and `--x-libraries=dir' to specify their locations.

Some packages offer the ability to configure how verbose the execution of make will be. For these packages, running `./configure --enable-silent-rules' sets the default to minimal output, which can be overridden with make V=1; while running `./configure --disable-silent-rules' sets the default to verbose, which can be overridden with make V=0.

16.6 Particular systems

On HP-UX, the default C compiler is not ANSI C compatible. If GNU CC is not installed, it is recommended to use the following options in order to use an ANSI C compiler:

./configure CC="cc -Ae -D_XOPEN_SOURCE=500"

and if that doesn't work, install pre-built binaries of GCC for HP-UX.

On OSF/1 a.k.a. Tru64, some versions of the default C compiler cannot parse its <wchar.h> header file. The option `-nodtk' can be used as a workaround. If GNU CC is not installed, it is therefore recommended to try

./configure CC="cc"

and if that doesn't work, try

./configure CC="cc -nodtk"

On Solaris, don't put /usr/ucb early in your PATH. This directory contains several dysfunctional programs; working variants of these programs are available in /usr/bin. So, if you need /usr/ucb in your PATH, put it after /usr/bin.

On Haiku, software installed for all users goes in `/boot/common', not `/usr/local'. It is recommended to use the following options:

./configure --prefix=/boot/common

16.7 Specifying the System Type

There may be some features configure cannot figure out automatically, but needs to determine by the type of machine the package will run on. Usually, assuming the package is built to be run on the same architectures, configure can figure that out, but if it prints a message saying it cannot guess the machine type, give it the `--build=type' option. type can either be a short name for the system type, such as `sun4', or a canonical name which has the form:

cpu-company-system

where system can have one of these forms:

os
kernel-os

See the file `config.sub' for the possible values of each field. If `config.sub' isn't included in this package, then this package doesn't need to know the machine type.

If you are building compiler tools for cross-compiling, you should use the option `--target=type' to select the type of system they will produce code for.

If you want to use a cross compiler, that generates code for a platform different from the build platform, you should specify the host platform (i.e., that on which the generated programs will eventually be run) with `--host=type'.

16.8 Sharing Defaults

If you want to set default values for configure scripts to share, you can create a site shell script called `config.site' that gives default values for variables like CC, cache_file, and prefix. configure looks for `prefix/share/config.site' if it exists, then `prefix/etc/config.site' if it exists. Or, you can set the CONFIG_SITE environment variable to the location of the site script. A warning: not all configure scripts look for a site script.

16.9 Defining Variables

Variables not defined in a site shell script can be set in the environment passed to configure. However, some packages may run configure again during the build, and the customized values of these variables may be lost. In order to avoid this problem, you should set them in the configure command line, using `VAR=value'. For example:

./configure CC=/usr/local2/bin/gcc

causes the specified gcc to be used as the C compiler (unless it is overridden in the site shell script).

Unfortunately, this technique does not work for CONFIG_SHELL due to an Autoconf bug. Until the bug is fixed you can use this workaround:

CONFIG_SHELL=/bin/bash /bin/bash ./configure CONFIG_SHELL=/bin/bash

16.10 configure Invocation

configure recognizes the following options to control how it operates.

`--help'

`-h'

Print a summary of all of the options to configure, and exit.

`--help=short'

`--help=recursive'

Print a summary of the options unique to this package's configure, and exit. The short variant lists options used only in the top level, while the recursive variant lists options also present in any nested packages.

`--version'

`-V'

Print the version of Autoconf used to generate the configure script, and exit.

`--cache-file=file'

Enable the cache: use and save the results of the tests in file, traditionally `config.cache'. file defaults to `/dev/null' to disable caching.

`--config-cache'

`-C'

Alias for `--cache-file=config.cache'.

`--quiet'

`--silent'

`-q'

Do not print messages saying which checks are being made. To suppress all normal output, redirect it to `/dev/null' (any error messages will still be shown).

`--srcdir=dir'

Look for the package's source code in directory dir. Usually configure can determine that directory automatically.

`--prefix=dir'

Use dir as the installation prefix. Installation Names for more details, including other options available for fine-tuning the installation locations.

`--no-create'

`-n'

Run the configure checks, but stop before creating any output files.

configure also accepts some other, not widely useful, options. Run `configure --help' for more details.

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