Installation Instructions
*************************

Basic Installation
==================

The following shell commands:

     test -f configure || ./bootstrap
     ./configure
     make
     make install

should configure, build, and install this package. The first line, which bootstraps, is intended for developers; when building from distribution tarballs it does nothing and can be skipped.

The following more-detailed instructions are generic; see the README file for instructions specific to this package. Some packages provide this INSTALL file but do not implement all of the features documented below.  The lack of an optional feature in a given package is not necessarily a bug. More recommendations for GNU packages can be found in the GNU Coding Standards.

Many packages have scripts meant for developers instead of ordinary builders, as they may use developer tools that are less commonly installed, or they may access the network, which has privacy implications. If the bootstrap shell script exists, it attempts to build the configure shell script and related files, possibly using developer tools or the network.  Because the output of bootstrap is system-independent, it is normally run by a package developer so that its output can be put into the distribution tarball and ordinary builders and users need not run bootstrap. Some packages have commands like ./autopull.sh and ./autogen.sh that you can run instead of ./bootstrap, for more fine-grained control over bootstrapping.

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 output useful 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 autoconf program generates configure from the file configure.ac.  Normally you should edit configure.ac instead of editing configure directly.

The simplest way to compile this package is:

 1. cd to the directory containing the package's source code.

 2. If this is a developer checkout and file configure does not yet exist, type ./bootstrap to create it. You may need special developer tools and network access to bootstrap, and the network access may have privacy implications.

 3. Type ./configure to configure the package for your system. This might take a while.  While running, configure prints messages telling which features it is checking for.

 4. Type make to compile the package.

 5. Optionally, type make check to run any self-tests that come with the package, generally using the just-built uninstalled binaries.

 6. 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.

 7. 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.

 8. 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 bootstrap again.

 9. If the package follows the GNU Coding Standards, you can type make uninstall to remove the installed files.

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=gcc CFLAGS=-g LIBS=-lposix

See ``Defining Variables'' for more details.

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 system 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 system at a time in the source code directory.  After you have installed the package for one system, use make distclean before reconfiguring for another system.

Some platforms, notably macOS, support ``fat'' or ``universal'' binaries, where a single binary can execute on different architectures. On these platforms you can configure and compile just once, with options specific to that platform.

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.

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 and --disable-FEATURE options to configure, where FEATURE indicates an optional part of the package.  They may also pay attention to --with-PACKAGE and --without-PACKAGE options, where PACKAGE is something like gnu-ld. ./configure --help should mention the --enable-... and --with-... options that the package recognizes.

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.

Specifying a System Type
========================

By default configure builds for the current system. To create binaries that can run on a different system type, specify a --host=TYPE option along with compiler variables that specify how to generate object code for TYPE. For example, to create binaries intended to run on a 64-bit ARM processor:

     ./configure --host=aarch64-linux-gnu \
        CC=aarch64-linux-gnu-gcc \
        CXX=aarch64-linux-gnu-g++

If done on a machine that can execute these binaries (e.g., via qemu-aarch64, $QEMU_LD_PREFIX, and Linux's binfmt_misc capability), the build behaves like a native build. Otherwise it is a cross-build: configure will make cross-compilation guesses instead of running test programs, and make check will not work.

A system type can either be a short name like mingw64, or a canonical name like x86_64-pc-linux-gnu. Canonical names have the form CPU-COMPANY-SYSTEM where SYSTEM is either OS or KERNEL-OS. To canonicalize and validate a system type, you can run the command config.sub, which is often squirreled away in a subdirectory like build-aux. For example:

     $ build-aux/config.sub arm64-linux
     aarch64-unknown-linux-gnu
     $ build-aux/config.sub riscv-lnx
     Invalid configuration 'riscv-lnx': OS 'lnx' not recognized

You can look at the config.sub file to see which types are recognized. If the file is absent, this package does not need the system type.

If configure fails with the diagnostic ``cannot guess build type''. config.sub did not recognize your system's type. In this case, first fetch the newest versions of these files from the GNU config package (https://savannah.gnu.org/projects/config). If that fixes things, please report it to the maintainers of the package containing configure. Otherwise, you can try the configure option --build=TYPE where TYPE comes close to your system type; also, please report the problem to config-patches@gnu.org.

For more details about configuring system types, see the Autoconf documentation.

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.

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 limitation.  Until the limitation is lifted, you can use this workaround:

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

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.

--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. See ``Installation Names'' for more details, including other options available for fine-tuning the installation locations.

--host=TYPE
     Build binaries for system TYPE. See ``Specifying a System Type''.

--enable-FEATURE
--disable-FEATURE
     Enable or disable the optional FEATURE. See ``Optional Features''.

--with-PACKAGE
--without-PACKAGE
     Use or omit PACKAGE when building. See ``Optional Features''.

--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).

--no-create
-n
     Run the configure checks, but stop before creating any output files.

configure also recognizes several environment variables, and accepts some other, less widely useful, options. Run configure --help for more details.

Copyright notice
================

Copyright © 1994--1996, 1999--2002, 2004--2017, 2020--2024 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.  This file is offered as-is, without warranty of any kind.