Document how to safely override CFLAGS default.

[autoconf.git] / doc / install.texi

@c This file is included by autoconf.texi and is used to produce
@c the INSTALL file.

@ifclear autoconf
@firstparagraphindent insert

@unnumbered Installation Instructions

Copyright @copyright{} 1994, 1995, 1996, 1999, 2000, 2001, 2002, 2004,
2005, 2006, 2007, 2008, 2009, 2010 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.

@end ifclear

@node Basic Installation
@section Basic Installation

Briefly, the shell commands @samp{./configure; make; make install}
should configure, build, and install this package.  The following
more-detailed instructions are generic; see the @file{README} file for
instructions specific to this package.
@ifclear autoconf
Some packages provide this @file{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.
@end ifclear
More recommendations for @acronym{GNU} packages can be found in
@ref{Makefile Conventions, , Makefile Conventions, standards,
@acronym{GNU} Coding Standards}.

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

It can also use an optional file (typically called @file{config.cache}
and enabled with @option{--cache-file=config.cache} or simply
@option{-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 @command{configure} could check whether to do them, and
mail diffs or instructions to the address given in the @file{README} so
they can be considered for the next release.  If you are using the
cache, and at some point @file{config.cache} contains results you don't
want to keep, you may remove or edit it.

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

The simplest way to compile this package is:

@enumerate
@item
@command{cd} to the directory containing the package's source code and type
@samp{./configure} to configure the package for your system.

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

@item
Type @samp{make} to compile the package.

@item
Optionally, type @samp{make check} to run any self-tests that come with
the package, generally using the just-built uninstalled binaries.

@item
Type @samp{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 @samp{make install} phase executed with root privileges.

@item
Optionally, type @samp{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 @samp{make install} required root
privileges, verifies that the installation completed correctly.

@item
You can remove the program binaries and object files from the source
code directory by typing @samp{make clean}.  To also remove the files
that @command{configure} created (so you can compile the package for a
different kind of computer), type @samp{make distclean}.  There is also
a @samp{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.

@item
Often, you can also type @samp{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
@acronym{GNU} Coding Standards.

@item
Some packages, particularly those that use Automake, provide @samp{make
distcheck}, which can by used by developers to test that all other
targets like @samp{make install} and @samp{make uninstall} work
correctly.  This target is generally not run by end users.
@end enumerate

@node Compilers and Options
@section Compilers and Options

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

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

@example
./configure CC=c99 CFLAGS=-g LIBS=-lposix
@end example

@xref{Defining Variables}, for more details.


@node Multiple Architectures
@section 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 @acronym{GNU} @command{make}.
@command{cd} to the directory where you want the object files and
executables to go and run the @command{configure} script.
@command{configure} automatically checks for the source code in the
directory that @command{configure} is in and in @file{..}.  This is
known as a @dfn{VPATH} build.

With a non-@acronym{GNU} @command{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 @samp{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 @dfn{fat} or
@dfn{universal} binaries---by specifying multiple @option{-arch} options
to the compiler but only a single @option{-arch} option to the
preprocessor.  Like this:

@example
./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"
@end example

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 @command{lipo} tool if you have problems.

@node Installation Names
@section Installation Names

By default, @samp{make install} installs the package's commands under
@file{/usr/local/bin}, include files under @file{/usr/local/include}, etc.
You can specify an
installation prefix other than @file{/usr/local} by giving
@command{configure} the option @option{--prefix=@var{prefix}}, where
@var{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
@option{--exec-prefix=@var{prefix}} to @command{configure}, the
package uses @var{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 @option{--bindir=@var{dir}} to specify different values for
particular kinds of files.  Run @samp{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
@samp{$@{prefix@}}, so that specifying just @option{--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 @command{configure}; however, many packages provide
one or both of the following shortcuts of passing variable assignments
to the @samp{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, @samp{make install
prefix=/alternate/directory} will choose an alternate location for all
directory configuration variables that were expressed in terms of
@samp{$@{prefix@}}.  Any directories that were specified during
@command{configure}, but not in terms of @samp{$@{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 @acronym{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 @acronym{GNU} Libtool.

The second method involves providing the @samp{DESTDIR} variable.  For
example, @samp{make install DESTDIR=/alternate/directory} will prepend
@samp{/alternate/directory} before all installation names.  The approach
of @samp{DESTDIR} overrides is not required by the @acronym{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 @samp{$@{prefix@}} at @command{configure} time.

@node Optional Features
@section 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 @command{configure}
the option @option{--program-prefix=@var{PREFIX}} or
@option{--program-suffix=@var{SUFFIX}}.

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

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

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

@node Particular Systems
@section 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:

@example
./configure CC="cc -Ae -D_XOPEN_SOURCE=500"
@end example

@noindent
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 @code{<wchar.h>} header file.  The option @option{-nodtk} can be
used as a workaround.  If GNU CC is not installed, it is therefore
recommended to try

@example
./configure CC="cc"
@end example

@noindent
and if that doesn't work, try

@example
./configure CC="cc -nodtk"
@end example

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

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

@example
./configure --prefix=/boot/common
@end example

@node System Type
@section Specifying the System Type

There may be some features @command{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
@emph{same} architectures, @command{configure} can figure that out, but
if it prints a message saying it cannot guess the machine type, give it
the @option{--build=@var{type}} option.  @var{type} can either be a
short name for the system type, such as @samp{sun4}, or a canonical name
which has the form:

@example
@var{cpu}-@var{company}-@var{system}
@end example

@noindent
where @var{system} can have one of these forms:

@example
@var{os}
@var{kernel}-@var{os}
@end example

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

If you are @emph{building} compiler tools for cross-compiling, you
should use the option @option{--target=@var{type}} to select the type of
system they will produce code for.

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

@node Sharing Defaults
@section Sharing Defaults

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

@node Defining Variables
@section Defining Variables

Variables not defined in a site shell script can be set in the
environment passed to @command{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 @command{configure} command line, using @samp{VAR=value}.
For example:

@example
./configure CC=/usr/local2/bin/gcc
@end example

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

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

@example
CONFIG_SHELL=/bin/bash /bin/bash ./configure CONFIG_SHELL=/bin/bash
@end example

@node configure Invocation
@section @command{configure} Invocation

@command{configure} recognizes the following options to control how it
operates.

@table @option
@item --help
@itemx -h
Print a summary of all of the options to @command{configure}, and exit.

@item --help=short
@itemx --help=recursive
Print a summary of the options unique to this package's
@command{configure}, and exit.  The @code{short} variant lists options
used only in the top level, while the @code{recursive} variant lists
options also present in any nested packages.

@item --version
@itemx -V
Print the version of Autoconf used to generate the @command{configure}
script, and exit.

@item --cache-file=@var{file}
@cindex Cache, enabling
Enable the cache: use and save the results of the tests in @var{file},
traditionally @file{config.cache}.  @var{file} defaults to
@file{/dev/null} to disable caching.

@item --config-cache
@itemx -C
Alias for @option{--cache-file=config.cache}.

@item --quiet
@itemx --silent
@itemx -q
Do not print messages saying which checks are being made.  To suppress
all normal output, redirect it to @file{/dev/null} (any error messages
will still be shown).

@item --srcdir=@var{dir}
Look for the package's source code in directory @var{dir}.  Usually
@command{configure} can determine that directory automatically.

@item --prefix=@var{dir}
Use @var{dir} as the installation prefix.  @ref{Installation Names}
for more details, including other options available for fine-tuning
the installation locations.

@item --no-create
@itemx -n
Run the configure checks, but stop before creating any output files.
@end table

@noindent
@command{configure} also accepts some other, not widely useful, options.
Run @samp{configure --help} for more details.

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