autoconf.texi

这是一个自动生成MAKEFILE的工具。在LINUX工程项目里是很好的帮手。希望对大家有点帮助。

The Autoconf macros are defined in several files.  Some of the files are
distributed with Autoconf; @code{autoconf} reads them first.  Then it
looks for the optional file @file{acsite.m4} in the directory that
contains the distributed Autoconf macro files, and for the optional file
@file{aclocal.m4} in the current directory.  Those files can contain
your site's or the package's own Autoconf macro definitions
(@pxref{Writing Macros}, for more information).  If a macro is defined
in more than one of the files that @code{autoconf} reads, the last
definition it reads overrides the earlier ones.

@code{autoconf} accepts the following options:

@table @code
@item --help
@itemx -h
Print a summary of the command line options and exit.

@item --localdir=@var{dir}
@itemx -l @var{dir}
Look for the package file @file{aclocal.m4} in directory @var{dir}
instead of in the current directory.

@item --macrodir=@var{dir}
@itemx -m @var{dir}
@evindex AC_MACRODIR
Look for the installed macro files in directory @var{dir}.  You can also
set the @code{AC_MACRODIR} environment variable to a directory; this
option overrides the environment variable.

@item --version
Print the version number of Autoconf and exit.
@end table

@node Invoking autoreconf,  , Invoking autoconf, Making configure Scripts
@section Using @code{autoreconf} to Update @code{configure} Scripts

If you have a lot of Autoconf-generated @code{configure} scripts, the
@code{autoreconf} program can save you some work.  It runs
@code{autoconf} (and @code{autoheader}, where appropriate) repeatedly to
remake the Autoconf @code{configure} scripts and configuration header
templates in the directory tree rooted at the current directory.  By
default, it only remakes those files that are older than their
@file{configure.in} or (if present) @file{aclocal.m4}.  Since
@code{autoheader} does not change the timestamp of its output file if
the file wouldn't be changing, this is not necessarily the minimum
amount of work.  If you install a new version of Autoconf, you can make
@code{autoreconf} remake @emph{all} of the files by giving it the
@samp{--force} option.

If you give @code{autoreconf} the @samp{--macrodir=@var{dir}} or
@samp{--localdir=@var{dir}} options, it passes them down to
@code{autoconf} and @code{autoheader} (with relative paths adjusted
properly).

@code{autoreconf} does not support having, in the same directory tree,
both directories that are parts of a larger package (sharing
@file{aclocal.m4} and @file{acconfig.h}), and directories that are
independent packages (each with their own @file{aclocal.m4} and
@file{acconfig.h}).  It assumes that they are all part of the same
package, if you use @samp{--localdir}, or that each directory is a
separate package, if you don't use it.  This restriction may be removed
in the future.

@xref{Automatic Remaking}, for @file{Makefile} rules to automatically
remake @code{configure} scripts when their source files change.  That
method handles the timestamps of configuration header templates
properly, but does not pass @samp{--macrodir=@var{dir}} or
@samp{--localdir=@var{dir}}.

@noindent
@code{autoreconf} accepts the following options:

@table @code
@item --help
@itemx -h
Print a summary of the command line options and exit.

@item --force
@itemx -f
Remake even @file{configure} scripts and configuration headers that are
newer than their input files (@file{configure.in} and, if present,
@file{aclocal.m4}).

@item --localdir=@var{dir}
@itemx -l @var{dir}
Have @code{autoconf} and @code{autoheader} look for the package files
@file{aclocal.m4} and (@code{autoheader} only) @file{acconfig.h} (but
not @file{@var{file}.top} and @file{@var{file}.bot}) in directory
@var{dir} instead of in the directory containing each @file{configure.in}.

@item --macrodir=@var{dir}
@itemx -m @var{dir}
@evindex AC_MACRODIR
Look for the Autoconf macro files in directory @var{dir} instead of the
default installation directory.
You can also set the @code{AC_MACRODIR}
environment variable to a directory; this option overrides the
environment variable.

@item --verbose
Print the name of each directory where @code{autoreconf} runs
@code{autoconf} (and @code{autoheader}, if appropriate).

@item --version
Print the version number of Autoconf and exit.
@end table

@node Setup, Existing Tests, Making configure Scripts, Top
@chapter Initialization and Output Files

Autoconf-generated @code{configure} scripts need some information about
how to initialize, such as how to find the package's source files; and
about the output files to produce.  The following sections describe
initialization and creating output files.

@menu
* Input::                       Where Autoconf should find files.
* Output::                      Creating output files.
* Makefile Substitutions::      Using output variables in @file{Makefile}s.
* Configuration Headers::       Creating a configuration header file.
* Subdirectories::              Configuring independent packages together.
* Default Prefix::              Changing the default installation prefix.
* Versions::                    Version numbers in @code{configure}.
@end menu

@node Input, Output, Setup, Setup
@section Finding @code{configure} Input

Every @code{configure} script must call @code{AC_INIT} before doing
anything else.  The only other required macro is @code{AC_OUTPUT}
(@pxref{Output}).

@defmac AC_INIT (@var{unique-file-in-source-dir})
@maindex INIT
Process any command-line arguments and find the source code directory.
@var{unique-file-in-source-dir} is some file that is in the package's
source directory; @code{configure} checks for this file's existence to
make sure that the directory that it is told contains the source code in
fact does.  Occasionally people accidentally specify the wrong directory
with @samp{--srcdir}; this is a safety check.  @xref{Invoking configure},
for more information.
@end defmac

Packages that do manual configuration or use the @code{install} program
might need to tell @code{configure} where to find some other shell
scripts by calling @code{AC_CONFIG_AUX_DIR}, though the default places
it looks are correct for most cases.

@defmac AC_CONFIG_AUX_DIR(@var{dir})
@maindex CONFIG_AUX_DIR
Use the @file{install-sh}, @file{config.sub}, @file{config.guess}, and
Cygnus @code{configure} scripts that are in directory @var{dir}.  These
are auxiliary files used in configuration.  @var{dir} can be either
absolute or relative to @file{@var{srcdir}}.  The default is
@file{@var{srcdir}} or @file{@var{srcdir}/..} or
@file{@var{srcdir}/../..}, whichever is the first that contains
@file{install-sh}.  The other files are not checked for, so that using
@code{AC_PROG_INSTALL} does not automatically require distributing the
other auxiliary files.  It checks for @file{install.sh} also, but that
name is obsolete because some @code{make} programs have a rule that
creates @file{install} from it if there is no @file{Makefile}.
@end defmac

@node Output, Makefile Substitutions, Input, Setup
@section Creating Output Files

Every Autoconf-generated @code{configure} script must finish by calling
@code{AC_OUTPUT}.  It is the macro that creates the @file{Makefile}s and
optional other files resulting from configuration.  The only other
required macro is @code{AC_INIT} (@pxref{Input}).

@defmac AC_OUTPUT (@r{[}@var{file}@dots{} @r{[}, @var{extra-cmds} @r{[}, @var{init-cmds}@r{]]]})
@maindex OUTPUT
Create output files.  Call this macro once, at the end of @file{configure.in}.
The @var{file}@dots{} argument is a
whitespace-separated list of output files; it may be empty.  This macro
creates each file @file{@var{file}} by copying an input file (by default
named @file{@var{file}.in}), substituting the output variable values.
@c If the file would be unchanged, it is left untouched, to preserve its timestamp.
@xref{Makefile Substitutions}, for more information on using output variables.
@xref{Setting Output Variables}, for more information on creating them.  This
macro creates the directory that the file is in if it doesn't exist (but
not the parents of that directory).  Usually, @file{Makefile}s are
created this way, but other files, such as @file{.gdbinit}, can be
specified as well.

If @code{AC_CONFIG_HEADER}, @code{AC_LINK_FILES}, or
@code{AC_CONFIG_SUBDIRS} has been called, this macro also creates the
files named as their arguments.

A typical call to @code{AC_OUTPUT} looks like this:
@example
AC_OUTPUT(Makefile src/Makefile man/Makefile X/Imakefile)
@end example

You can override an input file name by appending to @var{file} a
colon-separated list of input files.  Examples:
@example
AC_OUTPUT(Makefile:templates/top.mk lib/Makefile:templates/lib.mk)
AC_OUTPUT(Makefile:templates/vars.mk:Makefile.in:templates/rules.mk)
@end example
Doing this allows you to keep your file names acceptable to MS-DOS, or
to prepend and/or append boilerplate to the file.

If you pass @var{extra-cmds}, those commands will be inserted into
@file{config.status} to be run after all its other processing.  If
@var{init-cmds} are given, they are inserted just before
@var{extra-cmds}, with shell variable, command, and backslash
substitutions performed on them in @code{configure}.  You can use
@var{init-cmds} to pass variables from @code{configure} to the
@var{extra-cmds}.  If @code{AC_OUTPUT_COMMANDS} has been called, the
commands given to it are run just before the commands passed to this macro.
@end defmac

@defmac AC_OUTPUT_COMMANDS (@var{extra-cmds} @r{[}, @var{init-cmds}@r{]})
Specify additional shell commands to run at the end of
@file{config.status}, and shell commands to initialize any variables
from @code{configure}.  This macro may be called multiple times.
Here is an unrealistic example:

@example
fubar=27
AC_OUTPUT_COMMANDS([echo this is extra $fubar, and so on.], fubar=$fubar)
AC_OUTPUT_COMMANDS([echo this is another, extra, bit], [echo init bit])
@end example
@end defmac

If you run @code{make} on subdirectories, you should run it using the
@code{make} variable @code{MAKE}.  Most versions of @code{make} set
@code{MAKE} to the name of the @code{make} program plus any options it
was given.  (But many do not include in it the values of any variables
set on the command line, so those are not passed on automatically.)
Some old versions of @code{make} do not set this variable.  The
following macro allows you to use it even with those versions.

@defmac AC_PROG_MAKE_SET
@maindex PROG_MAKE_SET
@ovindex SET_MAKE
If @code{make} predefines the variable @code{MAKE}, define output
variable @code{SET_MAKE} to be empty.  Otherwise, define @code{SET_MAKE}
to contain @samp{MAKE=make}.  Calls @code{AC_SUBST} for @code{SET_MAKE}.
@end defmac

To use this macro, place a line like this in each @file{Makefile.in}
that runs @code{MAKE} on other directories:

@example
@@SET_MAKE@@
@end example

@node Makefile Substitutions, Configuration Headers, Output, Setup
@section Substitutions in Makefiles

Each subdirectory in a distribution that contains something to be
compiled or installed should come with a file @file{Makefile.in}, from
which @code{configure} will create a @file{Makefile} in that directory.
To create a @file{Makefile}, @code{configure} performs a simple variable
substitution, replacing occurrences of @samp{@@@var{variable}@@} in
@file{Makefile.in} with the value that @code{configure} has determined
for that variable.  Variables that are substituted into output files in
this way are called @dfn{output variables}.  They are ordinary shell
variables that are set in @code{configure}.  To make @code{configure}
substitute a particular variable into the output files, the macro
@code{AC_SUBST} must be called with that variable name as an argument.
Any occurrences of @samp{@@@var{variable}@@} for other variables are
left unchanged.  @xref{Setting Output Variables}, for more information on
creating output variables with @code{AC_SUBST}.

A software package that uses a @code{configure} script should be
distributed with a file @file{Makefile.in}, but no @file{Makefile}; that
way, the user has to properly configure the package for the local system
before compiling it.

@xref{Makefile Conventions, , Makefile Conventions, standards, The
GNU Coding Standards}, for more information on what to put in
@file{Makefile}s.

@menu
* Preset Output Variables::     Output variables that are always set.
* Build Directories::           Supporting multiple concurrent compiles.
* Automatic Remaking::          Makefile rules for configuring.
@end menu

@node Preset Output Variables, Build Directories, Makefile Substitutions, Makefile Substitutions
@subsection Preset Output Variables

Some output variables are preset by the Autoconf macros.  Some of the
Autoconf macros set additional output variables, which are mentioned in
the descriptions for those macros.  @xref{Output Variable Index}, for a
complete list of output variables.  Here is what each of the preset ones
contains.  @xref{Directory Variables, , Variables for Installation Directories,
standards, The GNU Coding Standards}, for more information about
the variables with names that end in @samp{dir}.

@defvar bindir
@ovindex bindir
The directory for installing executables that users run.
@end defvar

@defvar configure_input
@ovindex configure_input
A comment saying that the file was generated automatically by
@code{configure} and giving the name of the input file.
@code{AC_OUTPUT} adds a comment line containing this variable to the top
of every @file{Makefile} it creates.  For other files, you should
reference this variable in a comment at the top of each input file.  For
example, an input shell script should begin like this:

@example
#! /bin/sh
# @@configure_input@@
@end example

@noindent
The presence of that line also reminds people editing the file that it