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\input texinfo

\input texinfo

@c %**start of header

@c %**start of header

@setfilename configure.info

@setfilename configure.info

@settitle The GNU configure and build system

@settitle The GNU configure and build system

@setchapternewpage off

@setchapternewpage off

@c %**end of header

@c %**end of header

@dircategory GNU admin

@dircategory GNU admin

@direntry

@direntry

* configure: (configure).       The GNU configure and build system

* configure: (configure).       The GNU configure and build system

@end direntry

@end direntry

@ifnottex

@ifnottex

This file documents the GNU configure and build system.

This file documents the GNU configure and build system.

Copyright (C) 1998 Cygnus Solutions.

Copyright (C) 1998 Cygnus Solutions.

Permission is granted to make and distribute verbatim copies of

Permission is granted to make and distribute verbatim copies of

this manual provided the copyright notice and this permission notice

this manual provided the copyright notice and this permission notice

are preserved on all copies.

are preserved on all copies.

@ignore

@ignore

Permission is granted to process this file through TeX and print the

Permission is granted to process this file through TeX and print the

results, provided the printed document carries copying permission

results, provided the printed document carries copying permission

notice identical to this one except for the removal of this paragraph

notice identical to this one except for the removal of this paragraph

@end ignore

@end ignore

Permission is granted to copy and distribute modified versions of this

Permission is granted to copy and distribute modified versions of this

manual under the conditions for verbatim copying, provided that the entire

manual under the conditions for verbatim copying, provided that the entire

resulting derived work is distributed under the terms of a permission

resulting derived work is distributed under the terms of a permission

notice identical to this one.

notice identical to this one.

Permission is granted to copy and distribute translations of this manual

Permission is granted to copy and distribute translations of this manual

into another language, under the above conditions for modified versions,

into another language, under the above conditions for modified versions,

except that this permission notice may be stated in a translation approved

except that this permission notice may be stated in a translation approved

by the Foundation.

by the Foundation.

@end ifnottex

@end ifnottex

@titlepage

@titlepage

@title The GNU configure and build system

@title The GNU configure and build system

@author Ian Lance Taylor

@author Ian Lance Taylor

@page

@page

@vskip 0pt plus 1filll

@vskip 0pt plus 1filll

Copyright @copyright{} 1998 Cygnus Solutions

Copyright @copyright{} 1998 Cygnus Solutions

Permission is granted to make and distribute verbatim copies of

Permission is granted to make and distribute verbatim copies of

this manual provided the copyright notice and this permission notice

this manual provided the copyright notice and this permission notice

are preserved on all copies.

are preserved on all copies.

Permission is granted to copy and distribute modified versions of this

Permission is granted to copy and distribute modified versions of this

manual under the conditions for verbatim copying, provided that the entire

manual under the conditions for verbatim copying, provided that the entire

resulting derived work is distributed under the terms of a permission

resulting derived work is distributed under the terms of a permission

notice identical to this one.

notice identical to this one.

Permission is granted to copy and distribute translations of this manual

Permission is granted to copy and distribute translations of this manual

into another language, under the above conditions for modified versions,

into another language, under the above conditions for modified versions,

except that this permission notice may be stated in a translation

except that this permission notice may be stated in a translation

approved by the Free Software Foundation.

approved by the Free Software Foundation.

@end titlepage

@end titlepage

@ifnottex

@ifnottex

@node Top

@node Top

@top GNU configure and build system

@top GNU configure and build system

The GNU configure and build system.

The GNU configure and build system.

@menu

@menu

* Introduction::                Introduction.

* Introduction::                Introduction.

* Getting Started::             Getting Started.

* Getting Started::             Getting Started.

* Files::                       Files.

* Files::                       Files.

* Configuration Names::         Configuration Names.

* Configuration Names::         Configuration Names.

* Cross Compilation Tools::     Cross Compilation Tools.

* Cross Compilation Tools::     Cross Compilation Tools.

* Canadian Cross::              Canadian Cross.

* Canadian Cross::              Canadian Cross.

* Cygnus Configure::            Cygnus Configure.

* Cygnus Configure::            Cygnus Configure.

* Multilibs::                   Multilibs.

* Multilibs::                   Multilibs.

* FAQ::                         Frequently Asked Questions.

* FAQ::                         Frequently Asked Questions.

* Index::                       Index.

* Index::                       Index.

@end menu

@end menu

@end ifnottex

@end ifnottex

@node Introduction

@node Introduction

@chapter Introduction

@chapter Introduction

This document describes the GNU configure and build systems.  It

This document describes the GNU configure and build systems.  It

describes how autoconf, automake, libtool, and make fit together.  It

describes how autoconf, automake, libtool, and make fit together.  It

also includes a discussion of the older Cygnus configure system.

also includes a discussion of the older Cygnus configure system.

This document does not describe in detail how to use each of the tools;

This document does not describe in detail how to use each of the tools;

see the respective manuals for that.  Instead, it describes which files

see the respective manuals for that.  Instead, it describes which files

the developer must write, which files are machine generated and how they

the developer must write, which files are machine generated and how they

are generated, and where certain common problems should be addressed.

are generated, and where certain common problems should be addressed.

@ifnothtml

@ifnothtml

This document draws on several sources, including the autoconf manual by

This document draws on several sources, including the autoconf manual by

David MacKenzie (@pxref{Top, , autoconf overview, autoconf, Autoconf}),

David MacKenzie (@pxref{Top, , autoconf overview, autoconf, Autoconf}),

the automake manual by David MacKenzie and Tom Tromey (@pxref{Top, ,

the automake manual by David MacKenzie and Tom Tromey (@pxref{Top, ,

automake overview, automake, GNU Automake}), the libtool manual by

automake overview, automake, GNU Automake}), the libtool manual by

Gordon Matzigkeit (@pxref{Top, , libtool overview, libtool, GNU

Gordon Matzigkeit (@pxref{Top, , libtool overview, libtool, GNU

libtool}), and the Cygnus configure manual by K. Richard Pixley.

libtool}), and the Cygnus configure manual by K. Richard Pixley.

@end ifnothtml

@end ifnothtml

@ifhtml

@ifhtml

This document draws on several sources, including

This document draws on several sources, including

@uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_toc.html, the

@uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_toc.html, the

autoconf manual} by David MacKenzie,

autoconf manual} by David MacKenzie,

@uref{http://www.delorie.com/gnu/docs/automake/automake_toc.html, the

@uref{http://www.delorie.com/gnu/docs/automake/automake_toc.html, the

automake manual} by David MacKenzie and Tom Tromey,

automake manual} by David MacKenzie and Tom Tromey,

@uref{http://www.delorie.com/gnu/docs/libtool/libtool_toc.html, the

@uref{http://www.delorie.com/gnu/docs/libtool/libtool_toc.html, the

libtool manual} by Gordon Matzigkeit, and the Cygnus configure manual by

libtool manual} by Gordon Matzigkeit, and the Cygnus configure manual by

K. Richard Pixley.

K. Richard Pixley.

@end ifhtml

@end ifhtml

@menu

@menu

* Goals::                       Goals.

* Goals::                       Goals.

* Tools::                       The tools.

* Tools::                       The tools.

* History::                     History.

* History::                     History.

* Building::                    Building.

* Building::                    Building.

@end menu

@end menu

@node Goals

@node Goals

@section Goals

@section Goals

@cindex goals

@cindex goals

The GNU configure and build system has two main goals.

The GNU configure and build system has two main goals.

The first is to simplify the development of portable programs.  The

The first is to simplify the development of portable programs.  The

system permits the developer to concentrate on writing the program,

system permits the developer to concentrate on writing the program,

simplifying many details of portability across Unix and even Windows

simplifying many details of portability across Unix and even Windows

systems, and permitting the developer to describe how to build the

systems, and permitting the developer to describe how to build the

program using simple rules rather than complex Makefiles.

program using simple rules rather than complex Makefiles.

The second is to simplify the building of programs distributed as source

The second is to simplify the building of programs distributed as source

code.  All programs are built using a simple, standardized, two step

code.  All programs are built using a simple, standardized, two step

process.  The program builder need not install any special tools in

process.  The program builder need not install any special tools in

order to build the program.

order to build the program.

@node Tools

@node Tools

@section Tools

@section Tools

The GNU configure and build system is comprised of several different

The GNU configure and build system is comprised of several different

tools.  Program developers must build and install all of these tools.

tools.  Program developers must build and install all of these tools.

People who just want to build programs from distributed sources normally

People who just want to build programs from distributed sources normally

do not need any special tools beyond a Unix shell, a make program, and a

do not need any special tools beyond a Unix shell, a make program, and a

C compiler.

C compiler.

@table @asis

@table @asis

@item autoconf

@item autoconf

provides a general portability framework, based on testing the features

provides a general portability framework, based on testing the features

of the host system at build time.

of the host system at build time.

@item automake

@item automake

a system for describing how to build a program, permitting the developer

a system for describing how to build a program, permitting the developer

to write a simplified @file{Makefile}.

to write a simplified @file{Makefile}.

@item libtool

@item libtool

a standardized approach to building shared libraries.

a standardized approach to building shared libraries.

@item gettext

@item gettext

provides a framework for translation of text messages into other

provides a framework for translation of text messages into other

languages; not really discussed in this document.

languages; not really discussed in this document.

@item m4

@item m4

autoconf requires the GNU version of m4; the standard Unix m4 does not

autoconf requires the GNU version of m4; the standard Unix m4 does not

suffice.

suffice.

@item perl

@item perl

automake requires perl.

automake requires perl.

@end table

@end table

@node History

@node History

@section History

@section History

@cindex history

@cindex history

This is a very brief and probably inaccurate history.

This is a very brief and probably inaccurate history.

As the number of Unix variants increased during the 1980s, it became

As the number of Unix variants increased during the 1980s, it became

harder to write programs which could run on all variants.  While it was

harder to write programs which could run on all variants.  While it was

often possible to use @code{#ifdef} to identify particular systems,

often possible to use @code{#ifdef} to identify particular systems,

developers frequently did not have access to every system, and the

developers frequently did not have access to every system, and the

characteristics of some systems changed from version to version.

characteristics of some systems changed from version to version.

By 1992, at least three different approaches had been developed:

By 1992, at least three different approaches had been developed:

@itemize @bullet

@itemize @bullet

@item

@item

The Metaconfig program, by Larry Wall, Harlan Stenn, and Raphael

The Metaconfig program, by Larry Wall, Harlan Stenn, and Raphael

Manfredi.

Manfredi.

@item

@item

The Cygnus configure script, by K. Richard Pixley, and the gcc configure

The Cygnus configure script, by K. Richard Pixley, and the gcc configure

script, by Richard Stallman.  These use essentially the same approach,

script, by Richard Stallman.  These use essentially the same approach,

and the developers communicated regularly.

and the developers communicated regularly.

@item

@item

The autoconf program, by David MacKenzie.

The autoconf program, by David MacKenzie.

@end itemize

@end itemize

The Metaconfig program is still used for Perl and a few other programs.

The Metaconfig program is still used for Perl and a few other programs.

It is part of the Dist package.  I do not know if it is being developed.

It is part of the Dist package.  I do not know if it is being developed.

In 1994, David MacKenzie and others modified autoconf to incorporate all

In 1994, David MacKenzie and others modified autoconf to incorporate all

the features of Cygnus configure.  Since then, there has been a slow but

the features of Cygnus configure.  Since then, there has been a slow but

steady conversion of GNU programs from Cygnus configure to autoconf. gcc

steady conversion of GNU programs from Cygnus configure to autoconf. gcc

has been converted, eliminating the gcc configure script.

has been converted, eliminating the gcc configure script.

GNU autoconf was regularly maintained until late 1996.  As of this

GNU autoconf was regularly maintained until late 1996.  As of this

writing in June, 1998, it has no public maintainer.

writing in June, 1998, it has no public maintainer.

Most programs are built using the make program, which requires the

Most programs are built using the make program, which requires the

developer to write Makefiles describing how to build the programs.

developer to write Makefiles describing how to build the programs.

Since most programs are built in pretty much the same way, this led to a

Since most programs are built in pretty much the same way, this led to a

lot of duplication.

lot of duplication.

The X Window system is built using the imake tool, which uses a database

The X Window system is built using the imake tool, which uses a database

of rules to eliminate the duplication.  However, building a tool which

of rules to eliminate the duplication.  However, building a tool which

was developed using imake requires that the builder have imake

was developed using imake requires that the builder have imake

installed, violating one of the goals of the GNU system.

installed, violating one of the goals of the GNU system.

The new BSD make provides a standard library of Makefile fragments,

The new BSD make provides a standard library of Makefile fragments,

which permits developers to write very simple Makefiles.  However, this

which permits developers to write very simple Makefiles.  However, this

requires that the builder install the new BSD make program.

requires that the builder install the new BSD make program.

In 1994, David MacKenzie wrote the first version of automake, which

In 1994, David MacKenzie wrote the first version of automake, which

permitted writing a simple build description which was converted into a

permitted writing a simple build description which was converted into a

Makefile which could be used by the standard make program.  In 1995, Tom

Makefile which could be used by the standard make program.  In 1995, Tom

Tromey completely rewrote automake in Perl, and he continues to enhance

Tromey completely rewrote automake in Perl, and he continues to enhance

it.

it.

Various free packages built libraries, and by around 1995 several

Various free packages built libraries, and by around 1995 several

included support to build shared libraries on various platforms.

included support to build shared libraries on various platforms.

However, there was no consistent approach.  In early 1996, Gordon

However, there was no consistent approach.  In early 1996, Gordon

Matzigkeit began working on libtool, which provided a standardized

Matzigkeit began working on libtool, which provided a standardized

approach to building shared libraries.  This was integrated into

approach to building shared libraries.  This was integrated into

automake from the start.

automake from the start.

The development of automake and libtool was driven by the GNITS project,

The development of automake and libtool was driven by the GNITS project,

a group of GNU maintainers who designed standardized tools to help meet

a group of GNU maintainers who designed standardized tools to help meet

the GNU coding standards.

the GNU coding standards.

@node Building

@node Building

@section Building

@section Building

Most readers of this document should already know how to build a tool by

Most readers of this document should already know how to build a tool by

running @samp{configure} and @samp{make}.  This section may serve as a

running @samp{configure} and @samp{make}.  This section may serve as a

quick introduction or reminder.

quick introduction or reminder.

Building a tool is normally as simple as running @samp{configure}

Building a tool is normally as simple as running @samp{configure}

followed by @samp{make}.  You should normally run @samp{configure} from

followed by @samp{make}.  You should normally run @samp{configure} from

an empty directory, using some path to refer to the @samp{configure}

an empty directory, using some path to refer to the @samp{configure}

script in the source directory.  The directory in which you run

script in the source directory.  The directory in which you run

@samp{configure} is called the @dfn{object directory}.

@samp{configure} is called the @dfn{object directory}.

In order to use a object directory which is different from the source

In order to use a object directory which is different from the source

directory, you must be using the GNU version of @samp{make}, which has

directory, you must be using the GNU version of @samp{make}, which has

the required @samp{VPATH} support.  Despite this restriction, using a

the required @samp{VPATH} support.  Despite this restriction, using a

different object directory is highly recommended:

different object directory is highly recommended:

@itemize @bullet

@itemize @bullet

@item

@item

It keeps the files generated during the build from cluttering up your

It keeps the files generated during the build from cluttering up your

sources.

sources.

@item

@item

It permits you to remove the built files by simply removing the entire

It permits you to remove the built files by simply removing the entire

build directory.

build directory.

@item

@item

It permits you to build from the same sources with several sets of

It permits you to build from the same sources with several sets of

configure options simultaneously.

configure options simultaneously.

@end itemize

@end itemize

If you don't have GNU @samp{make}, you will have to run @samp{configure}

If you don't have GNU @samp{make}, you will have to run @samp{configure}

in the source directory.  All GNU packages should support this; in

in the source directory.  All GNU packages should support this; in

particular, GNU packages should not assume the presence of GNU

particular, GNU packages should not assume the presence of GNU

@samp{make}.

@samp{make}.

After running @samp{configure}, you can build the tools by running

After running @samp{configure}, you can build the tools by running

@samp{make}.

@samp{make}.

To install the tools, run @samp{make install}.  Installing the tools

To install the tools, run @samp{make install}.  Installing the tools

will copy the programs and any required support files to the

will copy the programs and any required support files to the

@dfn{installation directory}.  The location of the installation

@dfn{installation directory}.  The location of the installation

directory is controlled by @samp{configure} options, as described below.

directory is controlled by @samp{configure} options, as described below.

In the Cygnus tree at present, the info files are built and installed as

In the Cygnus tree at present, the info files are built and installed as

a separate step.  To build them, run @samp{make info}.  To install them,

a separate step.  To build them, run @samp{make info}.  To install them,

run @samp{make install-info}. The equivalent html files are also built

run @samp{make install-info}. The equivalent html files are also built

and installed in a separate step. To build the html files, run

and installed in a separate step. To build the html files, run

@samp{make html}. To install the html files run @samp{make install-html}.

@samp{make html}. To install the html files run @samp{make install-html}.

All @samp{configure} scripts support a wide variety of options.  The

All @samp{configure} scripts support a wide variety of options.  The

most interesting ones are @samp{--with} and @samp{--enable} options

most interesting ones are @samp{--with} and @samp{--enable} options

which are generally specific to particular tools.  You can usually use

which are generally specific to particular tools.  You can usually use

the @samp{--help} option to get a list of interesting options for a

the @samp{--help} option to get a list of interesting options for a

particular configure script.

particular configure script.

The only generic options you are likely to use are the @samp{--prefix}

The only generic options you are likely to use are the @samp{--prefix}

and @samp{--exec-prefix} options.  These options are used to specify the

and @samp{--exec-prefix} options.  These options are used to specify the

installation directory.

installation directory.

The directory named by the @samp{--prefix} option will hold machine

The directory named by the @samp{--prefix} option will hold machine

independent files such as info files.

independent files such as info files.

The directory named by the @samp{--exec-prefix} option, which is

The directory named by the @samp{--exec-prefix} option, which is

normally a subdirectory of the @samp{--prefix} directory, will hold

normally a subdirectory of the @samp{--prefix} directory, will hold

machine dependent files such as executables.

machine dependent files such as executables.

The default for @samp{--prefix} is @file{/usr/local}.  The default for

The default for @samp{--prefix} is @file{/usr/local}.  The default for

@samp{--exec-prefix} is the value used for @samp{--prefix}.

@samp{--exec-prefix} is the value used for @samp{--prefix}.

The convention used in Cygnus releases is to use a @samp{--prefix}

The convention used in Cygnus releases is to use a @samp{--prefix}

option of @file{/usr/cygnus/@var{release}}, where @var{release} is the

option of @file{/usr/cygnus/@var{release}}, where @var{release} is the

name of the release, and to use a @samp{--exec-prefix} option of

name of the release, and to use a @samp{--exec-prefix} option of

@file{/usr/cygnus/@var{release}/H-@var{host}}, where @var{host} is the

@file{/usr/cygnus/@var{release}/H-@var{host}}, where @var{host} is the

configuration name of the host system (@pxref{Configuration Names}).

configuration name of the host system (@pxref{Configuration Names}).

Do not use either the source or the object directory as the installation

Do not use either the source or the object directory as the installation

directory.  That will just lead to confusion.

directory.  That will just lead to confusion.

@node Getting Started

@node Getting Started

@chapter Getting Started

@chapter Getting Started

To start using the GNU configure and build system with your software

To start using the GNU configure and build system with your software

package, you must write three files, and you must run some tools to

package, you must write three files, and you must run some tools to

manually generate additional files.

manually generate additional files.

@menu

@menu

* Write configure.in::          Write configure.in.

* Write configure.in::          Write configure.in.

* Write Makefile.am::           Write Makefile.am.

* Write Makefile.am::           Write Makefile.am.

* Write acconfig.h::            Write acconfig.h.

* Write acconfig.h::            Write acconfig.h.

* Generate files::              Generate files.

* Generate files::              Generate files.

* Getting Started Example::     Example.

* Getting Started Example::     Example.

@end menu

@end menu

@node Write configure.in

@node Write configure.in

@section Write configure.in

@section Write configure.in

@cindex @file{configure.in}, writing

@cindex @file{configure.in}, writing

You must first write the file @file{configure.in}.  This is an autoconf

You must first write the file @file{configure.in}.  This is an autoconf

input file, and the autoconf manual describes in detail what this file

input file, and the autoconf manual describes in detail what this file

should look like.

should look like.

You will write tests in your @file{configure.in} file to check for

You will write tests in your @file{configure.in} file to check for

conditions that may change from one system to another, such as the

conditions that may change from one system to another, such as the

presence of particular header files or functions.

presence of particular header files or functions.

For example, not all systems support the @samp{gettimeofday} function.

For example, not all systems support the @samp{gettimeofday} function.

If you want to use the @samp{gettimeofday} function when it is

If you want to use the @samp{gettimeofday} function when it is

available, and to use some other function when it is not, you would

available, and to use some other function when it is not, you would

check for this by putting @samp{AC_CHECK_FUNCS(gettimeofday)} in

check for this by putting @samp{AC_CHECK_FUNCS(gettimeofday)} in

@file{configure.in}.

@file{configure.in}.

When the configure script is run at build time, this will arrange to

When the configure script is run at build time, this will arrange to

define the preprocessor macro @samp{HAVE_GETTIMEOFDAY} to the value 1 if

define the preprocessor macro @samp{HAVE_GETTIMEOFDAY} to the value 1 if

the @samp{gettimeofday} function is available, and to not define the

the @samp{gettimeofday} function is available, and to not define the

macro at all if the function is not available.  Your code can then use

macro at all if the function is not available.  Your code can then use

@samp{#ifdef} to test whether it is safe to call @samp{gettimeofday}.

@samp{#ifdef} to test whether it is safe to call @samp{gettimeofday}.

If you have an existing body of code, the @samp{autoscan} program may

If you have an existing body of code, the @samp{autoscan} program may

help identify potential portability problems, and hence configure tests

help identify potential portability problems, and hence configure tests

that you will want to use.

that you will want to use.

@ifnothtml

@ifnothtml

@xref{Invoking autoscan, , , autoconf, the autoconf manual}.

@xref{Invoking autoscan, , , autoconf, the autoconf manual}.

@end ifnothtml

@end ifnothtml

@ifhtml

@ifhtml

See @uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_4.html, the

See @uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_4.html, the

autoscan documentation}.

autoscan documentation}.

@end ifhtml

@end ifhtml

Another handy tool for an existing body of code is @samp{ifnames}.  This

Another handy tool for an existing body of code is @samp{ifnames}.  This

will show you all the preprocessor conditionals that the code already

will show you all the preprocessor conditionals that the code already

uses.

uses.

@ifnothtml

@ifnothtml

@xref{Invoking ifnames, , , autoconf, the autoconf manual}.

@xref{Invoking ifnames, , , autoconf, the autoconf manual}.

@end ifnothtml

@end ifnothtml

@ifhtml

@ifhtml

See @uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_5.html, the

See @uref{http://www.delorie.com/gnu/docs/autoconf/autoconf_5.html, the

ifnames documentation}.

ifnames documentation}.

@end ifhtml

@end ifhtml

Besides the portability tests which are specific to your particular

Besides the portability tests which are specific to your particular

package, every @file{configure.in} file should contain the following

package, every @file{configure.in} file should contain the following

macros.

macros.

@table @samp

@table @samp

@item AC_INIT

@item AC_INIT

@cindex @samp{AC_INIT}

@cindex @samp{AC_INIT}

This macro takes a single argument, which is the name of a file in your

This macro takes a single argument, which is the name of a file in your

package.  For example, @samp{AC_INIT(foo.c)}.

package.  For example, @samp{AC_INIT(foo.c)}.

@item AC_PREREQ(@var{VERSION})

@item AC_PREREQ(@var{VERSION})

@cindex @samp{AC_PREREQ}

@cindex @samp{AC_PREREQ}

This macro is optional.  It may be used to indicate the version of

This macro is optional.  It may be used to indicate the version of

@samp{autoconf} that you are using.  This will prevent users from

@samp{autoconf} that you are using.  This will prevent users from

running an earlier version of @samp{autoconf} and perhaps getting an

running an earlier version of @samp{autoconf} and perhaps getting an

invalid @file{configure} script.  For example, @samp{AC_PREREQ(2.12)}.

invalid @file{configure} script.  For example, @samp{AC_PREREQ(2.12)}.

@item AM_INIT_AUTOMAKE

@item AM_INIT_AUTOMAKE

@cindex @samp{AM_INIT_AUTOMAKE}

@cindex @samp{AM_INIT_AUTOMAKE}

This macro takes two arguments: the name of the package, and a version

This macro takes two arguments: the name of the package, and a version

number.  For example, @samp{AM_INIT_AUTOMAKE(foo, 1.0)}.  (This macro is

number.  For example, @samp{AM_INIT_AUTOMAKE(foo, 1.0)}.  (This macro is

not needed if you are not using automake).

not needed if you are not using automake).

@item AM_CONFIG_HEADER

@item AM_CONFIG_HEADER

@cindex @samp{AM_CONFIG_HEADER}

@cindex @samp{AM_CONFIG_HEADER}

This macro names the header file which will hold the preprocessor macro

This macro names the header file which will hold the preprocessor macro

definitions at run time.  Normally this should be @file{config.h}.  Your

definitions at run time.  Normally this should be @file{config.h}.  Your

sources would then use @samp{#include "config.h"} to include it.

sources would then use @samp{#include "config.h"} to include it.

This macro may optionally name the input file for that header file; by

This macro may optionally name the input file for that header file; by

default, this is @file{config.h.in}, but that file name works poorly on

default, this is @file{config.h.in}, but that file name works poorly on

DOS filesystems.  Therefore, it is often better to name it explicitly as

DOS filesystems.  Therefore, it is often better to name it explicitly as

@file{config.in}.

@file{config.in}.

This is what you should normally put in @file{configure.in}:

This is what you should normally put in @file{configure.in}:

@example

@example

AM_CONFIG_HEADER(config.h:config.in)

AM_CONFIG_HEADER(config.h:config.in)

@end example

@end example

@cindex @samp{AC_CONFIG_HEADER}

@cindex @samp{AC_CONFIG_HEADER}

(If you are not using automake, use @samp{AC_CONFIG_HEADER} rather than

(If you are not using automake, use @samp{AC_CONFIG_HEADER} rather than

@samp{AM_CONFIG_HEADER}).

@samp{AM_CONFIG_HEADER}).

@item AM_MAINTAINER_MODE

@item AM_MAINTAINER_MODE

@cindex @samp{AM_MAINTAINER_MODE}

@cindex @samp{AM_MAINTAINER_MODE}

This macro always appears in Cygnus configure scripts.  Other programs

This macro always appears in Cygnus configure scripts.  Other programs

may or may not use it.

may or may not use it.

If this macro is used, the @samp{--enable-maintainer-mode} option is

If this macro is used, the @samp{--enable-maintainer-mode} option is

required to enable automatic rebuilding of generated files used by the

required to enable automatic rebuilding of generated files used by the

configure system.  This of course requires that developers be aware of,

configure system.  This of course requires that developers be aware of,

and use, that option.

and use, that option.

If this macro is not used, then the generated files will always be

If this macro is not used, then the generated files will always be

rebuilt automatically.  This will cause problems if the wrong versions

rebuilt automatically.  This will cause problems if the wrong versions

of autoconf, automake, or others are in the builder's @samp{PATH}.

of autoconf, automake, or others are in the builder's @samp{PATH}.

(If you are not using automake, you do not need to use this macro).

(If you are not using automake, you do not need to use this macro).

@item AC_EXEEXT

@item AC_EXEEXT

@cindex @samp{AC_EXEEXT}

@cindex @samp{AC_EXEEXT}

@cindex @samp{AM_EXEEXT}

@cindex @samp{AM_EXEEXT}

Either this macro or @samp{AM_EXEEXT} always appears in Cygnus configure

Either this macro or @samp{AM_EXEEXT} always appears in Cygnus configure

files.  Other programs may or may not use one of them.

files.  Other programs may or may not use one of them.

This macro looks for the executable suffix used on the host system.  On

This macro looks for the executable suffix used on the host system.  On

Unix systems, this is the empty string.  On Windows systems, this is

Unix systems, this is the empty string.  On Windows systems, this is

@samp{.exe}.  This macro directs automake to use the executable suffix

@samp{.exe}.  This macro directs automake to use the executable suffix

as appropriate when creating programs.  This macro does not take any

as appropriate when creating programs.  This macro does not take any

arguments.

arguments.

The @samp{AC_EXEEXT} form is new, and is part of a Cygnus patch to

The @samp{AC_EXEEXT} form is new, and is part of a Cygnus patch to

autoconf to support compiling with Visual C++.  Older programs use

autoconf to support compiling with Visual C++.  Older programs use

@samp{AM_EXEEXT} instead.

@samp{AM_EXEEXT} instead.

(Programs which do not use automake use neither @samp{AC_EXEEXT} nor

(Programs which do not use automake use neither @samp{AC_EXEEXT} nor

@samp{AM_EXEEXT}).

@samp{AM_EXEEXT}).

@item AC_PROG_CC

@item AC_PROG_CC

@cindex @samp{AC_PROG_CC}

@cindex @samp{AC_PROG_CC}

If you are writing C code, you will normally want to use this macro.  It

If you are writing C code, you will normally want to use this macro.  It

locates the C compiler to use.  It does not take any arguments.

locates the C compiler to use.  It does not take any arguments.

However, if this @file{configure.in} file is for a library which is to

However, if this @file{configure.in} file is for a library which is to

be compiled by a cross compiler which may not fully work, then you will

be compiled by a cross compiler which may not fully work, then you will

not want to use @samp{AC_PROG_CC}.  Instead, you will want to use a

not want to use @samp{AC_PROG_CC}.  Instead, you will want to use a

variant which does not call the macro @samp{AC_PROG_CC_WORKS}.  Examples

variant which does not call the macro @samp{AC_PROG_CC_WORKS}.  Examples

can be found in various @file{configure.in} files for libraries that are

can be found in various @file{configure.in} files for libraries that are

compiled with cross compilers, such as libiberty or libgloss.  This is

compiled with cross compilers, such as libiberty or libgloss.  This is

essentially a bug in autoconf, and there will probably be a better

essentially a bug in autoconf, and there will probably be a better

workaround at some point.

workaround at some point.

@item AC_PROG_CXX

@item AC_PROG_CXX

@cindex @samp{AC_PROG_CXX}

@cindex @samp{AC_PROG_CXX}

If you are writing C++ code, you will want to use this macro.  It

If you are writing C++ code, you will want to use this macro.  It

locates the C++ compiler to use.  It does not take any arguments.  The

locates the C++ compiler to use.  It does not take any arguments.  The

same cross compiler comments apply as for @samp{AC_PROG_CC}.

same cross compiler comments apply as for @samp{AC_PROG_CC}.

@item AM_PROG_LIBTOOL

@item AM_PROG_LIBTOOL

@cindex @samp{AM_PROG_LIBTOOL}

@cindex @samp{AM_PROG_LIBTOOL}

If you want to build libraries, and you want to permit them to be

If you want to build libraries, and you want to permit them to be

shared, or you want to link against libraries which were built using

shared, or you want to link against libraries which were built using

libtool, then you will need this macro.  This macro is required in order

libtool, then you will need this macro.  This macro is required in order

to use libtool.

to use libtool.

@cindex @samp{AM_DISABLE_SHARED}

@cindex @samp{AM_DISABLE_SHARED}

By default, this will cause all libraries to be built as shared

By default, this will cause all libraries to be built as shared

libraries.  To prevent this--to change the default--use

libraries.  To prevent this--to change the default--use

@samp{AM_DISABLE_SHARED} before @samp{AM_PROG_LIBTOOL}.  The configure

@samp{AM_DISABLE_SHARED} before @samp{AM_PROG_LIBTOOL}.  The configure

options @samp{--enable-shared} and @samp{--disable-shared} may be used

options @samp{--enable-shared} and @samp{--disable-shared} may be used

to override the default at build time.

to override the default at build time.

@item AC_DEFINE(_GNU_SOURCE)

@item AC_DEFINE(_GNU_SOURCE)

@cindex @samp{_GNU_SOURCE}

@cindex @samp{_GNU_SOURCE}

GNU packages should normally include this line before any other feature

GNU packages should normally include this line before any other feature

tests.  This defines the macro @samp{_GNU_SOURCE} when compiling, which

tests.  This defines the macro @samp{_GNU_SOURCE} when compiling, which

directs the libc header files to provide the standard GNU system

directs the libc header files to provide the standard GNU system

interfaces including all GNU extensions.  If this macro is not defined,

interfaces including all GNU extensions.  If this macro is not defined,

certain GNU extensions may not be available.

certain GNU extensions may not be available.

@item AC_OUTPUT

@item AC_OUTPUT

@cindex @samp{AC_OUTPUT}

@cindex @samp{AC_OUTPUT}

This macro takes a list of file names which the configure process should

This macro takes a list of file names which the configure process should

produce.  This is normally a list of one or more @file{Makefile} files

produce.  This is normally a list of one or more @file{Makefile} files

in different directories.  If your package lives entirely in a single

in different directories.  If your package lives entirely in a single

directory, you would use simply @samp{AC_OUTPUT(Makefile)}.  If you also

directory, you would use simply @samp{AC_OUTPUT(Makefile)}.  If you also

have, for example, a @file{lib} subdirectory, you would use

have, for example, a @file{lib} subdirectory, you would use

@samp{AC_OUTPUT(Makefile lib/Makefile)}.

@samp{AC_OUTPUT(Makefile lib/Makefile)}.

@end table

@end table

If you want to use locally defined macros in your @file{configure.in}

If you want to use locally defined macros in your @file{configure.in}

file, then you will need to write a @file{acinclude.m4} file which

file, then you will need to write a @file{acinclude.m4} file which

defines them (if not using automake, this file is called

defines them (if not using automake, this file is called

@file{aclocal.m4}).  Alternatively, you can put separate macros in an

@file{aclocal.m4}).  Alternatively, you can put separate macros in an

@file{m4} subdirectory, and put @samp{ACLOCAL_AMFLAGS = -I m4} in your

@file{m4} subdirectory, and put @samp{ACLOCAL_AMFLAGS = -I m4} in your

@file{Makefile.am} file so that the @samp{aclocal} program will be able

@file{Makefile.am} file so that the @samp{aclocal} program will be able

to find them.

to find them.

The different macro prefixes indicate which tool defines the macro.

The different macro prefixes indicate which tool defines the macro.

Macros which start with @samp{AC_} are part of autoconf.  Macros which

Macros which start with @samp{AC_} are part of autoconf.  Macros which

start with @samp{AM_} are provided by automake or libtool.

start with @samp{AM_} are provided by automake or libtool.

@node Write Makefile.am

@node Write Makefile.am

@section Write Makefile.am

@section Write Makefile.am

@cindex @file{Makefile.am}, writing

@cindex @file{Makefile.am}, writing

You must write the file @file{Makefile.am}.  This is an automake input

You must write the file @file{Makefile.am}.  This is an automake input

file, and the automake manual describes in detail what this file should

file, and the automake manual describes in detail what this file should

look like.

look like.

The automake commands in @file{Makefile.am} mostly look like variable

The automake commands in @file{Makefile.am} mostly look like variable

assignments in a @file{Makefile}.  automake recognizes special variable

assignments in a @file{Makefile}.  automake recognizes special variable

names, and automatically add make rules to the output as needed.

names, and automatically add make rules to the output as needed.

There will be one @file{Makefile.am} file for each directory in your

There will be one @file{Makefile.am} file for each directory in your

package.  For each directory with subdirectories, the @file{Makefile.am}

package.  For each directory with subdirectories, the @file{Makefile.am}

file should contain the line

file should contain the line

@smallexample

@smallexample

SUBDIRS = @var{dir} @var{dir} @dots{}

SUBDIRS = @var{dir} @var{dir} @dots{}

@end smallexample

@end smallexample

@noindent

@noindent

where each @var{dir} is the name of a subdirectory.

where each @var{dir} is the name of a subdirectory.

For each @file{Makefile.am}, there should be a corresponding

For each @file{Makefile.am}, there should be a corresponding

@file{Makefile} in the @samp{AC_OUTPUT} macro in @file{configure.in}.

@file{Makefile} in the @samp{AC_OUTPUT} macro in @file{configure.in}.

Every @file{Makefile.am} written at Cygnus should contain the line

Every @file{Makefile.am} written at Cygnus should contain the line

@smallexample

@smallexample

AUTOMAKE_OPTIONS = cygnus

AUTOMAKE_OPTIONS = cygnus

@end smallexample

@end smallexample

@noindent

@noindent

This puts automake into Cygnus mode.  See the automake manual for

This puts automake into Cygnus mode.  See the automake manual for

details.

details.

You may to include the version number of @samp{automake} that you are

You may to include the version number of @samp{automake} that you are

using on the @samp{AUTOMAKE_OPTIONS} line.  For example,

using on the @samp{AUTOMAKE_OPTIONS} line.  For example,

@smallexample

@smallexample

AUTOMAKE_OPTIONS = cygnus 1.3

AUTOMAKE_OPTIONS = cygnus 1.3

@end smallexample

@end smallexample

@noindent

@noindent

This will prevent users from running an earlier version of

This will prevent users from running an earlier version of

@samp{automake} and perhaps getting an invalid @file{Makefile.in}.

@samp{automake} and perhaps getting an invalid @file{Makefile.in}.

If your package builds a program, then in the directory where that

If your package builds a program, then in the directory where that

program is built you will normally want a line like

program is built you will normally want a line like

@smallexample

@smallexample

bin_PROGRAMS = @var{program}

bin_PROGRAMS = @var{program}

@end smallexample

@end smallexample

@noindent

@noindent

where @var{program} is the name of the program.  You will then want a

where @var{program} is the name of the program.  You will then want a

line like

line like

@smallexample

@smallexample

@var{program}_SOURCES = @var{file} @var{file} @dots{}

@var{program}_SOURCES = @var{file} @var{file} @dots{}

@end smallexample

@end smallexample

@noindent

@noindent

where each @var{file} is the name of a source file to link into the

where each @var{file} is the name of a source file to link into the

program (e.g., @samp{foo.c}).

program (e.g., @samp{foo.c}).

If your package builds a library, and you do not want the library to

If your package builds a library, and you do not want the library to

ever be built as a shared library, then in the directory where that

ever be built as a shared library, then in the directory where that

library is built you will normally want a line like

library is built you will normally want a line like

@smallexample

@smallexample

lib_LIBRARIES = lib@var{name}.a

lib_LIBRARIES = lib@var{name}.a

@end smallexample

@end smallexample

@noindent

@noindent

where @samp{lib@var{name}.a} is the name of the library.  You will then

where @samp{lib@var{name}.a} is the name of the library.  You will then

want a line like

want a line like

@smallexample

@smallexample

lib@var{name}_a_SOURCES = @var{file} @var{file} @dots{}

lib@var{name}_a_SOURCES = @var{file} @var{file} @dots{}

@end smallexample

@end smallexample

@noindent

@noindent

where each @var{file} is the name of a source file to add to the

where each @var{file} is the name of a source file to add to the

library.

library.

If your package builds a library, and you want to permit building the

If your package builds a library, and you want to permit building the

library as a shared library, then in the directory where that library is

library as a shared library, then in the directory where that library is

built you will normally want a line like

built you will normally want a line like

@smallexample

@smallexample

lib_LTLIBRARIES = lib@var{name}.la

lib_LTLIBRARIES = lib@var{name}.la

@end smallexample

@end smallexample

The use of @samp{LTLIBRARIES}, and the @samp{.la} extension, indicate a

The use of @samp{LTLIBRARIES}, and the @samp{.la} extension, indicate a

library to be built using libtool.  As usual, you will then want a line

library to be built using libtool.  As usual, you will then want a line

like

like

@smallexample

@smallexample

lib@var{name}_la_SOURCES = @var{file} @var{file} @dots{}

lib@var{name}_la_SOURCES = @var{file} @var{file} @dots{}

@end smallexample

@end smallexample

The strings @samp{bin} and @samp{lib} that appear above in

The strings @samp{bin} and @samp{lib} that appear above in

@samp{bin_PROGRAMS} and @samp{lib_LIBRARIES} are not arbitrary.  They

@samp{bin_PROGRAMS} and @samp{lib_LIBRARIES} are not arbitrary.  They

refer to particular directories, which may be set by the @samp{--bindir}

refer to particular directories, which may be set by the @samp{--bindir}

and @samp{--libdir} options to @file{configure}.  If those options are

and @samp{--libdir} options to @file{configure}.  If those options are

not used, the default values are based on the @samp{--prefix} or

not used, the default values are based on the @samp{--prefix} or

@samp{--exec-prefix} options to @file{configure}.  It is possible to use

@samp{--exec-prefix} options to @file{configure}.  It is possible to use

other names if the program or library should be installed in some other

other names if the program or library should be installed in some other

directory.

directory.

The @file{Makefile.am} file may also contain almost anything that may

The @file{Makefile.am} file may also contain almost anything that may

appear in a normal @file{Makefile}.  automake also supports many other

appear in a normal @file{Makefile}.  automake also supports many other

special variables, as well as conditionals.

special variables, as well as conditionals.

See the automake manual for more information.

See the automake manual for more information.

@node Write acconfig.h

@node Write acconfig.h

@section Write acconfig.h

@section Write acconfig.h

@cindex @file{acconfig.h}, writing

@cindex @file{acconfig.h}, writing

If you are generating a portability header file, (i.e., you are using

If you are generating a portability header file, (i.e., you are using

@samp{AM_CONFIG_HEADER} in @file{configure.in}), then you will have to

@samp{AM_CONFIG_HEADER} in @file{configure.in}), then you will have to

write a @file{acconfig.h} file.  It will have to contain the following

write a @file{acconfig.h} file.  It will have to contain the following

lines.

lines.

@smallexample

@smallexample

/* Name of package.  */

/* Name of package.  */

#undef PACKAGE

#undef PACKAGE

/* Version of package.  */

/* Version of package.  */

#undef VERSION

#undef VERSION

@end smallexample

@end smallexample

This requirement is really a bug in the system, and the requirement may

This requirement is really a bug in the system, and the requirement may

be eliminated at some later date.

be eliminated at some later date.

The @file{acconfig.h} file will also similar comment and @samp{#undef}

The @file{acconfig.h} file will also similar comment and @samp{#undef}

lines for any unusual macros in the @file{configure.in} file, including

lines for any unusual macros in the @file{configure.in} file, including

any macro which appears in a @samp{AC_DEFINE} macro.

any macro which appears in a @samp{AC_DEFINE} macro.

In particular, if you are writing a GNU package and therefore include

In particular, if you are writing a GNU package and therefore include

@samp{AC_DEFINE(_GNU_SOURCE)} in @file{configure.in} as suggested above,

@samp{AC_DEFINE(_GNU_SOURCE)} in @file{configure.in} as suggested above,

you will need lines like this in @file{acconfig.h}:

you will need lines like this in @file{acconfig.h}:

@smallexample

@smallexample

/* Enable GNU extensions.  */

/* Enable GNU extensions.  */

#undef _GNU_SOURCE

#undef _GNU_SOURCE

@end smallexample

@end smallexample

Normally the @samp{autoheader} program will inform you of any such

Normally the @samp{autoheader} program will inform you of any such

requirements by printing an error message when it is run.  However, if

requirements by printing an error message when it is run.  However, if

you do anything particular odd in your @file{configure.in} file, you

you do anything particular odd in your @file{configure.in} file, you

will have to make sure that the right entries appear in

will have to make sure that the right entries appear in

@file{acconfig.h}, since otherwise the results of the tests may not be

@file{acconfig.h}, since otherwise the results of the tests may not be

available in the @file{config.h} file which your code will use.

available in the @file{config.h} file which your code will use.

(Thee @samp{PACKAGE} and @samp{VERSION} lines are not required if you

(Thee @samp{PACKAGE} and @samp{VERSION} lines are not required if you

are not using automake, and in that case you may not need a

are not using automake, and in that case you may not need a

@file{acconfig.h} file at all).

@file{acconfig.h} file at all).

@node Generate files

@node Generate files

@section Generate files

@section Generate files

Once you have written @file{configure.in}, @file{Makefile.am},

Once you have written @file{configure.in}, @file{Makefile.am},

@file{acconfig.h}, and possibly @file{acinclude.m4}, you must use

@file{acconfig.h}, and possibly @file{acinclude.m4}, you must use

autoconf and automake programs to produce the first versions of the

autoconf and automake programs to produce the first versions of the

generated files.  This is done by executing the following sequence of

generated files.  This is done by executing the following sequence of

commands.

commands.

@smallexample

@smallexample

aclocal

aclocal

autoconf

autoconf

autoheader

autoheader

automake

automake

@end smallexample

@end smallexample

The @samp{aclocal} and @samp{automake} commands are part of the automake

The @samp{aclocal} and @samp{automake} commands are part of the automake

package, and the @samp{autoconf} and @samp{autoheader} commands are part

package, and the @samp{autoconf} and @samp{autoheader} commands are part

of the autoconf package.

of the autoconf package.

If you are using a @file{m4} subdirectory for your macros, you will need

If you are using a @file{m4} subdirectory for your macros, you will need

to use the @samp{-I m4} option when you run @samp{aclocal}.

to use the @samp{-I m4} option when you run @samp{aclocal}.

If you are not using the Cygnus tree, use the @samp{-a} option when

If you are not using the Cygnus tree, use the @samp{-a} option when

running @samp{automake} command in order to copy the required support

running @samp{automake} command in order to copy the required support

files into your source directory.

files into your source directory.

If you are using libtool, you must build and install the libtool package

If you are using libtool, you must build and install the libtool package

with the same @samp{--prefix} and @samp{--exec-prefix} options as you

with the same @samp{--prefix} and @samp{--exec-prefix} options as you

used with the autoconf and automake packages.  You must do this before

used with the autoconf and automake packages.  You must do this before

running any of the above commands.  If you are not using the Cygnus

running any of the above commands.  If you are not using the Cygnus

tree, you will need to run the @samp{libtoolize} program to copy the

tree, you will need to run the @samp{libtoolize} program to copy the

libtool support files into your directory.

libtool support files into your directory.

Once you have managed to run these commands without getting any errors,

Once you have managed to run these commands without getting any errors,

you should create a new empty directory, and run the @samp{configure}

you should create a new empty directory, and run the @samp{configure}

script which will have been created by @samp{autoconf} with the

script which will have been created by @samp{autoconf} with the

@samp{--enable-maintainer-mode} option.  This will give you a set of

@samp{--enable-maintainer-mode} option.  This will give you a set of

Makefiles which will include rules to automatically rebuild all the

Makefiles which will include rules to automatically rebuild all the

generated files.

generated files.

After doing that, whenever you have changed some of the input files and

After doing that, whenever you have changed some of the input files and

want to regenerated the other files, go to your object directory and run

want to regenerated the other files, go to your object directory and run

@samp{make}.  Doing this is more reliable than trying to rebuild the

@samp{make}.  Doing this is more reliable than trying to rebuild the

files manually, because there are complex order dependencies and it is

files manually, because there are complex order dependencies and it is

easy to forget something.

easy to forget something.

@node Getting Started Example

@node Getting Started Example

@section Example

@section Example

Let's consider a trivial example.

Let's consider a trivial example.

Suppose we want to write a simple version of @samp{touch}.  Our program,

Suppose we want to write a simple version of @samp{touch}.  Our program,

which we will call @samp{poke}, will take a single file name argument,

which we will call @samp{poke}, will take a single file name argument,

and use the @samp{utime} system call to set the modification and access

and use the @samp{utime} system call to set the modification and access

times of the file to the current time.  We want this program to be

times of the file to the current time.  We want this program to be

highly portable.

highly portable.

We'll first see what this looks like without using autoconf and

We'll first see what this looks like without using autoconf and

automake, and then see what it looks like with them.

automake, and then see what it looks like with them.

@menu

@menu

* Getting Started Example 1::           First Try.

* Getting Started Example 1::           First Try.

* Getting Started Example 2::           Second Try.

* Getting Started Example 2::           Second Try.

* Getting Started Example 3::           Third Try.

* Getting Started Example 3::           Third Try.

* Generate Files in Example::           Generate Files.

* Generate Files in Example::           Generate Files.

@end menu

@end menu

@node Getting Started Example 1

@node Getting Started Example 1

@subsection First Try

@subsection First Try

Here is our first try at @samp{poke.c}.  Note that we've written it

Here is our first try at @samp{poke.c}.  Note that we've written it

without ANSI/ISO C prototypes, since we want it to be highly portable.

without ANSI/ISO C prototypes, since we want it to be highly portable.

@example

@example

#include <stdio.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/types.h>

#include <utime.h>

#include <utime.h>

int

int

main (argc, argv)

main (argc, argv)

     int argc;

     int argc;

     char **argv;

     char **argv;

@{

@{

  if (argc != 2)

  if (argc != 2)

    @{

    @{

      fprintf (stderr, "Usage: poke file\n");

      fprintf (stderr, "Usage: poke file\n");

      exit (1);

      exit (1);

    @}

    @}

  if (utime (argv[1], NULL) < 0)

  if (utime (argv[1], NULL) < 0)

    @{

    @{

      perror ("utime");

      perror ("utime");

      exit (1);

      exit (1);

    @}

    @}

  exit (0);

  exit (0);

@}

@}

@end example

@end example

We also write a simple @file{Makefile}.

We also write a simple @file{Makefile}.

@example

@example

CC = gcc

CC = gcc

CFLAGS = -g -O2

CFLAGS = -g -O2

all: poke

all: poke

poke: poke.o

poke: poke.o

        $(CC) -o poke $(CFLAGS) $(LDFLAGS) poke.o

        $(CC) -o poke $(CFLAGS) $(LDFLAGS) poke.o

@end example

@end example

So far, so good.

So far, so good.

Unfortunately, there are a few problems.

Unfortunately, there are a few problems.

On older Unix systems derived from BSD 4.3, the @samp{utime} system call

On older Unix systems derived from BSD 4.3, the @samp{utime} system call

does not accept a second argument of @samp{NULL}.  On those systems, we

does not accept a second argument of @samp{NULL}.  On those systems, we

need to pass a pointer to @samp{struct utimbuf} structure.

need to pass a pointer to @samp{struct utimbuf} structure.

Unfortunately, even older systems don't define that structure; on those

Unfortunately, even older systems don't define that structure; on those

systems, we need to pass an array of two @samp{long} values.

systems, we need to pass an array of two @samp{long} values.

The header file @file{stdlib.h} was invented by ANSI C, and older

The header file @file{stdlib.h} was invented by ANSI C, and older

systems don't have a copy.  We included it above to get a declaration of

systems don't have a copy.  We included it above to get a declaration of

@samp{exit}.

@samp{exit}.

We can find some of these portability problems by running

We can find some of these portability problems by running

@samp{autoscan}, which will create a @file{configure.scan} file which we

@samp{autoscan}, which will create a @file{configure.scan} file which we

can use as a prototype for our @file{configure.in} file.  I won't show

can use as a prototype for our @file{configure.in} file.  I won't show

the output, but it will notice the potential problems with @samp{utime}

the output, but it will notice the potential problems with @samp{utime}

and @file{stdlib.h}.

and @file{stdlib.h}.

In our @file{Makefile}, we don't provide any way to install the program.

In our @file{Makefile}, we don't provide any way to install the program.

This doesn't matter much for such a simple example, but a real program

This doesn't matter much for such a simple example, but a real program

will need an @samp{install} target.  For that matter, we will also want

will need an @samp{install} target.  For that matter, we will also want

a @samp{clean} target.

a @samp{clean} target.

@node Getting Started Example 2

@node Getting Started Example 2

@subsection Second Try

@subsection Second Try

Here is our second try at this program.

Here is our second try at this program.

We modify @file{poke.c} to use preprocessor macros to control what

We modify @file{poke.c} to use preprocessor macros to control what

features are available.  (I've cheated a bit by using the same macro

features are available.  (I've cheated a bit by using the same macro

names which autoconf will use).

names which autoconf will use).

@example

@example

#include <stdio.h>

#include <stdio.h>

#ifdef STDC_HEADERS

#ifdef STDC_HEADERS

#include <stdlib.h>

#include <stdlib.h>

#endif

#endif

#include <sys/types.h>

#include <sys/types.h>

#ifdef HAVE_UTIME_H

#ifdef HAVE_UTIME_H

#include <utime.h>

#include <utime.h>

#endif

#endif

#ifndef HAVE_UTIME_NULL

#ifndef HAVE_UTIME_NULL

#include <time.h>

#include <time.h>

#ifndef HAVE_STRUCT_UTIMBUF

#ifndef HAVE_STRUCT_UTIMBUF

struct utimbuf

struct utimbuf

@{

@{

  long actime;

  long actime;

  long modtime;

  long modtime;

@};

@};

#endif

#endif

static int

static int

utime_now (file)

utime_now (file)

     char *file;

     char *file;

@{

@{

  struct utimbuf now;

  struct utimbuf now;

  now.actime = now.modtime = time (NULL);

  now.actime = now.modtime = time (NULL);

  return utime (file, &now);

  return utime (file, &now);

@}

@}

#define utime(f, p) utime_now (f)

#define utime(f, p) utime_now (f)

#endif /* HAVE_UTIME_NULL  */

#endif /* HAVE_UTIME_NULL  */

int

int

main (argc, argv)

main (argc, argv)

     int argc;

     int argc;

     char **argv;

     char **argv;

@{

@{

  if (argc != 2)

  if (argc != 2)

    @{

    @{

      fprintf (stderr, "Usage: poke file\n");

      fprintf (stderr, "Usage: poke file\n");

      exit (1);

      exit (1);

    @}

    @}

  if (utime (argv[1], NULL) < 0)

  if (utime (argv[1], NULL) < 0)

    @{

    @{

      perror ("utime");

      perror ("utime");

      exit (1);

      exit (1);

    @}

    @}

  exit (0);

  exit (0);

@}

@}

@end example

@end example

Here is the associated @file{Makefile}.  We've added support for the

Here is the associated @file{Makefile}.  We've added support for the

preprocessor flags we use.  We've also added @samp{install} and

preprocessor flags we use.  We've also added @samp{install} and

@samp{clean} targets.

@samp{clean} targets.

@example

@example

# Set this to your installation directory.

# Set this to your installation directory.

bindir = /usr/local/bin

bindir = /usr/local/bin

# Uncomment this if you have the standard ANSI/ISO C header files.

# Uncomment this if you have the standard ANSI/ISO C header files.

# STDC_HDRS = -DSTDC_HEADERS

# STDC_HDRS = -DSTDC_HEADERS

# Uncomment this if you have utime.h.

# Uncomment this if you have utime.h.

# UTIME_H = -DHAVE_UTIME_H

# UTIME_H = -DHAVE_UTIME_H

# Uncomment this if utime (FILE, NULL) works on your system.

# Uncomment this if utime (FILE, NULL) works on your system.

# UTIME_NULL = -DHAVE_UTIME_NULL

# UTIME_NULL = -DHAVE_UTIME_NULL

# Uncomment this if struct utimbuf is defined in utime.h.

# Uncomment this if struct utimbuf is defined in utime.h.

# UTIMBUF = -DHAVE_STRUCT_UTIMBUF

# UTIMBUF = -DHAVE_STRUCT_UTIMBUF

CC = gcc

CC = gcc

CFLAGS = -g -O2

CFLAGS = -g -O2

ALL_CFLAGS = $(STDC_HDRS) $(UTIME_H) $(UTIME_NULL) $(UTIMBUF) $(CFLAGS)

ALL_CFLAGS = $(STDC_HDRS) $(UTIME_H) $(UTIME_NULL) $(UTIMBUF) $(CFLAGS)

all: poke

all: poke

poke: poke.o

poke: poke.o

        $(CC) -o poke $(ALL_CFLAGS) $(LDFLAGS) poke.o

        $(CC) -o poke $(ALL_CFLAGS) $(LDFLAGS) poke.o

.c.o:

.c.o:

        $(CC) -c $(ALL_CFLAGS) poke.c

        $(CC) -c $(ALL_CFLAGS) poke.c

install: poke

install: poke

        cp poke $(bindir)/poke

        cp poke $(bindir)/poke

clean:

clean:

        rm poke poke.o

        rm poke poke.o

@end example

@end example

Some problems with this approach should be clear.

Some problems with this approach should be clear.

Users who want to compile poke will have to know how @samp{utime} works

Users who want to compile poke will have to know how @samp{utime} works

on their systems, so that they can uncomment the @file{Makefile}

on their systems, so that they can uncomment the @file{Makefile}

correctly.

correctly.

The installation is done using @samp{cp}, but many systems have an

The installation is done using @samp{cp}, but many systems have an

@samp{install} program which may be used, and which supports optional

@samp{install} program which may be used, and which supports optional

features such as stripping debugging information out of the installed

features such as stripping debugging information out of the installed

binary.

binary.

The use of @file{Makefile} variables like @samp{CC}, @samp{CFLAGS} and

The use of @file{Makefile} variables like @samp{CC}, @samp{CFLAGS} and

@samp{LDFLAGS} follows the requirements of the GNU standards.  This is

@samp{LDFLAGS} follows the requirements of the GNU standards.  This is

convenient for all packages, since it reduces surprises for users.

convenient for all packages, since it reduces surprises for users.

However, it is easy to get the details wrong, and wind up with a

However, it is easy to get the details wrong, and wind up with a

slightly nonstandard distribution.

slightly nonstandard distribution.

@node Getting Started Example 3

@node Getting Started Example 3

@subsection Third Try

@subsection Third Try

For our third try at this program, we will write a @file{configure.in}

For our third try at this program, we will write a @file{configure.in}

script to discover the configuration features on the host system, rather

script to discover the configuration features on the host system, rather

than requiring the user to edit the @file{Makefile}.  We will also write

than requiring the user to edit the @file{Makefile}.  We will also write

a @file{Makefile.am} rather than a @file{Makefile}.

a @file{Makefile.am} rather than a @file{Makefile}.

The only change to @file{poke.c} is to add a line at the start of the

The only change to @file{poke.c} is to add a line at the start of the

file:

file:

@smallexample

@smallexample

#include "config.h"

#include "config.h"

@end smallexample

@end smallexample

The new @file{configure.in} file is as follows.

The new @file{configure.in} file is as follows.

@example

@example