6.4 Using GNU autotools

6.4.1 Introduction

The various GNU autotools provide an abstraction mechanism for building a piece of software over a wide variety of operating systems and machine architectures. Within the Ports Collection, an individual port can make use of these tools via a simple construct:

USE_AUTOTOOLS= tool:version[:operation] ...

At the time of writing, tool can be one of libtool, libltdl, autoconf, autoheader, automake or aclocal.

version specifies the particular tool revision to be used (see devel/{automake,autoconf,libtool}[0-9]+ for valid versions).

operation is an optional extension to modify how the tool is used.

Multiple tools can be specified at once, either by including them all on a single line, or using the += Makefile construct.

Before proceeding any further, it cannot be stressed highly enough that the constructs discussed here are for use ONLY in building other ports. For cross-development work, the devel/gnu-{automake,autoconf,libtool} ports should be used, such as within an IDE. devel/anjuta and devel/kdevelop (GNOME and KDE respectively) are good examples of how to achieve this.

6.4.2 libtool

Shared libraries using the GNU building framework usually use libtool to adjust the compilation and installation of shared libraries to match the specifics of the underlying operating system. The usual practice is to use copy of libtool bundled with the application. In case you need to use external libtool, you can use the version provided by The Ports Collection:

USE_AUTOTOOLS= libtool:version[:env]

With no additional operations, libtool:version tells the building framework to patch the configure script with the system-installed copy of libtool. The GNU_CONFIGURE is implied. Further, a number of make and shell variables will be assigned for onward use by the port. See bsd.autotools.mk for details.

With the :env operation, only the environment will be set up.

Finally, LIBTOOLFLAGS and LIBTOOLFILES can be optionally set to override the most likely arguments to, and files patched by, libtool. Most ports are unlikely to need this. See bsd.autotools.mk for further details.

6.4.3 libltdl

Some ports make use of the libltdl library package, which is part of the libtool suite. Use of this library does not automatically necessitate the use of libtool itself, so a separate construct is provided.

USE_AUTOTOOLS= libltdl:version

Currently, all this does is to bring in a LIB_DEPENDS on the appropriate libltdl port, and is provided as a convenience function to help eliminate any dependencies on the autotools ports outside of the USE_AUTOTOOLS framework. There are no optional operations for this tool.

6.4.4 autoconf and autoheader

Some ports do not contain a configure script, but do contain an autoconf template in the configure.ac file. You can use the following assignments to let autoconf create the configure script, and also have autoheader create template headers for use by the configure script.

USE_AUTOTOOLS= autoconf:version[:env]

and

USE_AUTOTOOLS= autoheader:version

which also implies the use of autoconf:version.

Similarly to libtool, the inclusion of the optional :env operation simply sets up the environment for further use. Without it, patching and reconfiguration of the port is carried out.

The additional optional variables AUTOCONF_ARGS and AUTOHEADER_ARGS can be overridden by the port Makefile if specifically requested. As with the libtool equivalents, most ports are unlikely to need this.

6.4.5 automake and aclocal

Some packages only contain Makefile.am files. These have to be converted into Makefile.in files using automake, and the further processed by configure to generate an actual Makefile.

Similarly, packages occasionally do not ship with included aclocal.m4 files, again required to build the software. This can be achieved with aclocal, which scans configure.ac or configure.in.

aclocal has a similar relationship to automake as autoheader does to autoconf, described in the previous section. aclocal implies the use of automake, thus we have:

USE_AUTOTOOLS= automake:version[:env]

and

USE_AUTOTOOLS= aclocal:version

which also implies the use of automake:version.

Similarly to libtool and autoconf, the inclusion of the optional :env operation simply sets up the environment for further use. Without it, reconfiguration of the port is carried out.

As with autoconf and autoheader, both automake and aclocal have optional argument variables, AUTOMAKE_ARGS and ACLOCAL_ARGS respectively, which may be overriden by the port Makefile if required.