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added chapter: The GNU build system
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Steven G. Johnson
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@ -132,7 +132,7 @@ package. This is edition @value{EDITION}, for Autoconf version
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@menu
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* Introduction:: Autoconf's purpose, strengths, and weaknesses
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* The GNU build system::
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* The GNU build system:: A set of tools for portable software packages
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* Making configure Scripts:: How to organize and produce Autoconf scripts
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* Setup:: Initialization and output
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* Existing Tests:: Macros that check for particular features
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@ -155,6 +155,12 @@ package. This is edition @value{EDITION}, for Autoconf version
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@detailmenu
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--- The Detailed Node Listing ---
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The GNU build system
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* Automake::
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* Libtool::
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* Pointers::
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Making @code{configure} Scripts
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* Writing configure.ac:: What to put in an Autoconf input file
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@ -431,13 +437,12 @@ inconvenient when configuring large source trees. Unlike Metaconfig
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scripts, Autoconf scripts can support cross-compiling, if some care is
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taken in writing them.
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@c FIXME: Tom, your cue is here.
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There are several jobs related to making portable software packages that
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Autoconf currently does not do. Among these are automatically creating
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@file{Makefile} files with all of the standard targets, and supplying
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replacements for standard library functions and header files on systems
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that lack them. Work is in progress to add those features in the
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future.
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Autoconf does not solve all problems related to making portable software
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packages---for a more complete solution, it should be used in concert
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with other GNU build tools like Automake and Libtool. These other tools
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take on jobs like the creation of a portable, recursive @file{Makefile}
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with all of the standard targets, linking of shared libraries, and so
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on. @xref{The GNU build system}, for more information.
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Autoconf imposes some restrictions on the names of macros used with
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@code{#if} in C programs (@pxref{Preprocessor Symbol Index}).
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@ -452,7 +457,7 @@ do not have. You must use version 1.4 or later of @sc{gnu} M4.
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See the @href{http://www.gnu.org/software/autoconf/autoconf.html,
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Autoconf web page} for up to date information, details on the mailing
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Autoconf web page} for up-to-date information, details on the mailing
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lists, pointers to a list of known bugs, etc.
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Mail suggestions to @email{autoconf@@gnu.org, the Autoconf mailing
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@ -466,19 +471,18 @@ not already solved in current development versions, and that it has not
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been reported yet. Be sure to include all the needed information and a
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short @file{configure.ac} that demonstrates the problem.
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Autoconf's development tree is accessible via @sc{cvs}, see the Autoconf
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Autoconf's development tree is accessible via @sc{cvs}; see the Autoconf
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web page for details. There is also a
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@href{http://subversions.gnu.org/cgi-bin/cvsweb/autoconf/, @sc{cvs}web
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interface to the Autoconf development tree}.
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interface to the Autoconf development tree}. Patches relative to the
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current @sc{cvs} version can be sent for review to the
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@email{autoconf-patches@@gnu.org, Autoconf Patches mailing list}.
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Patches relative to the current @sc{cvs} version can be sent for review to
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the @email{autoconf-patches@@gnu.org, Autoconf Patches mailing list}.
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Because of its mission, Autoconf includes only a set of highly used
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Because of its mission, Autoconf includes only a set of often-used
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macros that have already demonstrated their usefulness. Nevertheless,
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if you wish to share your macros, or find existing ones, see the
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@href{http://research.cys.de/autoconf-archive/, Autoconf Macro
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Repository}, which is kindly run by @email{simons@@research.cys.de,
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@href{http://cryp.to/autoconf-archive/, Autoconf Macro
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Repository}, which is kindly run by @email{simons@@computer.org,
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Peter Simons}.
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@ -487,27 +491,143 @@ Peter Simons}.
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@node The GNU build system, Making configure Scripts, Introduction, Top
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@chapter The GNU build system
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@emph{This chapter is still under construction. It will hopefully be ready
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for the release.}
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Autoconf solves an important problem---reliable discovery of
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system-specific build and runtime information---but this is only one
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piece of the puzzle for the development of portable software. To this
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end, the GNU project has developed a suite of integrated utilities to
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finish the job Autoconf started: the GNU build system, whose most
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important components are Autoconf, Automake, and Libtool. In this
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chapter, we introduce you to those tools, point you to sources of more
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information, and try to convince you to use the entire GNU build system
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for your software.
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I'm unsure about the title.
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@menu
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* Automake:: Escaping Makefile hell
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* Libtool:: Portable shared libraries
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* Pointers:: More info on the GNU build system
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@end menu
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Move the dissertation `A shell script compiler' here. The text above,
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probably starting at `There are several jobs...', should be moved here.
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Hm?
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@node Automake, Libtool, The GNU build system, The GNU build system
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@section Automake
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Talk about Automake, Libtool.
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The ubiquity of @code{make} means that a @code{Makefile} is almost the
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only viable way to distribute automatic build rules for software, but
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one quickly runs into @code{make}'s numerous limitations. Its lack of
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support for automatic dependency tracking, recursive builds in
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subdirectories, reliable timestamps (e.g. for network filesystems), and
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so on, mean that developers must painfully (and often incorrectly)
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reinvent the wheel for each project. Portability is non-trivial, thanks
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to the quirks of @code{make} on many systems. On top of all this is the
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manual labor required to implement the many standard targets that users
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have come to expect (@code{make install}, @code{make distclean},
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@code{make uninstall}, etc.). Since you are, of course, using Autoconf,
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you also have to insert repetitive code in your @code{Makefile.in} to
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recognize @code{@@CC@@}, @code{@@CFLAGS@@}, and other substitutions
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provided by @code{configure}. Into this mess steps @dfn{Automake}.
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@cindex Automake
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Explain the concept of system.h.
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Automake allows you to specify your build needs in a @code{Makefile.am}
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file with a vastly simpler and more powerful syntax than that of a plain
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@code{Makefile}, and then generates a portable @code{Makefile.in} for
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use with Autoconf. For example, the @code{Makefile.am} to build and
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install a simple ``Hello world'' program might look like:
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Promote Bison, Flex and other GNU tools.
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@example
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bin_PROGRAMS = hello
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hello_SOURCES = hello.c
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@end example
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Provide pointers to the various documentations and tutorials (books, web
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etc.).
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@noindent
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The resulting @code{Makefile.in} (~400 lines) automatically supports all
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the standard targets, the substitutions provided by Autoconf, automatic
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dependency tracking, @code{VPATH} building, and so on. @code{make} will
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build the @code{hello} program, and @code{make install} will install it
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in @file{/usr/local/bin} (or whatever prefix was given to
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@code{configure}, if not @file{/usr/local}).
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Explain that learning is painful, agreed, but getting inspiration is the
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way out. Fetish, libit, liberty.
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Automake may require that additional tools be present on the
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@emph{developer's} machine. For example, the @code{Makefile.in} that
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the developer works with may not be portable (e.g. it might use special
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features of your compiler to automatically generate dependency
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information). Running @code{make dist}, however, produces a
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@file{hello-1.0.tar.gz} package (or whatever the program/version is)
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with a @code{Makefile.in} that will work on any system.
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The benefits of Automake increase for larger packages (especially ones
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with subdirectories), but even for small programs the added convenience
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and portability can be substantial. And that's not all@dots{}
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@node Libtool, Pointers, Automake, The GNU build system
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@section Libtool
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Very often, one wants to build not only programs, but libraries, so that
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other programs can benefit from the fruits of your labor. Ideally, one
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would like to produce @emph{shared} (dynamically-linked) libraries,
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which can be used by multiple programs without duplication on disk or in
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memory and can be updated independently of the linked programs.
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Producing shared libraries portably, however, is the stuff of
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nightmares---each system has its own incompatible tools, compiler flags,
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and magic incantations. Fortunately, GNU provides a solution:
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@dfn{Libtool}.
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@cindex Libtool
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Libtool handles all the requirements of building shared libraries for
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you, and at this time seems to be the @emph{only} way to do so with any
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portability. It also handles many other headaches, such as: the
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interaction of @code{Makefile} rules with the variable suffixes of
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shared libraries, linking reliably to shared libraries before they are
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installed by the superuser, and supplying a consistent versioning system
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(so that different versions of a library can be installed or upgraded
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without breaking binary compatibility). Although Libtool, like
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Autoconf, can be used on its own, it is most simply utilized in
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conjunction with Automake---there, Libtool is used automatically
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whenever shared libraries are needed, and you need not know its syntax.
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@node Pointers, , Libtool, The GNU build system
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@section Pointers
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Developers who are used to the simplicity of @code{make} for small
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projects on a single system might be daunted at the prospect of learning
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to use Automake and Autoconf. As your software is distributed to more
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and more users, however, you will otherwise quickly find yourself
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putting lots of effort into reinventing the services that the GNU build
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tools provide, and making the same mistakes that they once made and
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overcame. (Besides, since you're already learning Autoconf, Automake
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will be a piece of cake.)
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There are a number of places that you can go to for more information on
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the GNU build tools.
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@itemize @minus
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@item Web
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The home pages for
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@uref{http://www.gnu.org/software/autoconf/,Autoconf},
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@uref{http://www.gnu.org/software/automake/,Automake}, and
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@uref{http://www.gnu.org/software/libtool/,Libtool}.
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@item Automake Manual (TeXinfo)
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@xref{Top,,Automake,automake,GNU Automake}, for more
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information on Automake.
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@item Books
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The book @cite{GNU Autoconf, Automake and Libtool}, by G. V. Vaughan,
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B. Elliston, T. Tromey, and I. L. Taylor (New Riders, 2000) (ISBN
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1578701902) describes the complete GNU build environment. You can also
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find the entire book on-line at
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@uref{http://sources.redhat.com/autobook/,``The Goat Book'' home page}.
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@item Tutorials and Examples
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The @uref{http://sources.redhat.com/autoconf/,Autoconf Developer Page}
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maintains links to a number of Autoconf/Automake tutorials online, and
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also links to the @uref{http://cryp.to/autoconf-archive/,Autoconf Macro
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Archive}.
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@end itemize
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@c ================================================= Making configure Scripts.
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