4.5.2 Configuring CFITSIO

The cfitsio component wraps the HEASARC FITS library of the same name, and installs from it the library itself, plus a few header files. Although we probably could adapt the library's distributed autoconf script, that script is sufficiently old, and there are sufficiently few components installed, that it is less trouble to simply wrap this configuration in another one.

The cfitsio component contains a cfitsio/ directory containing the distributed library source. Along with it are the usual component.xml.in file, copied from the template in `starconf --show buildsupportdata`, and Makefile.am and configure.ac files, which are too different from the template ones for them to be helpful.

The configure.ac looks like this:

dnl    Process this file with autoconf to produce a configure script
AC_REVISION($Revision: 1.116 $)
AC_INIT(cfitsio, 2.4-90, ussc@star.rl.ac.uk)

AC_PREREQ(2.50)
AM_INIT_AUTOMAKE(1.8.2-starlink)

AC_CONFIG_SRCDIR([cfitsio.news])

STAR_DEFAULTS

dnl    To configure CFITSIO proper we just run ./configure in the
dnl    cfitsio sub-directory. Do not invoke AC_CONFIG_SUBDIRS,
dnl    since that prompts autoreconf to try to reconfigure that directory, and
dnl    automake to assume it's allowed to play there, too.
(
    cd cfitsio
    ./configure --prefix=$prefix
)

dnl    Find required versions of the programs we need for configuration
AC_PROG_LIBTOOL
AC_PROG_MAKE_SET

STAR_LATEX_DOCUMENTATION(sun227)

AC_CONFIG_FILES([Makefile component.xml])
AC_OUTPUT

The Makefile.am looks like this:

## Process this file with automake to produce Makefile.in

dist_bin_SCRIPTS = cfitsio_link

lib_LIBRARIES = cfitsio/libcfitsio.a
# There are no sources for libcfits in this directory.
cfitsio_libcfitsio_a_SOURCES =

include_HEADERS = cfitsio/fitsio.h cfitsio/longnam.h \
    cfitsio/fitsio2.h cfitsio/drvrsmem.h

stardocs_DATA = @STAR_LATEX_DOCUMENTATION@

EXAMPLE_SOURCES = cfitsio/cookbook.c cfitsio/cookbook.f

# Put examples in dist_pkgdata
dist_pkgdata_DATA = $(EXAMPLE_SOURCES) \
    cfitsio_changes.txt CFITSIO_CONDITIONS Licence.txt cfitsio.news

# Headers and example sources are made within cfitsio
$(include_HEADERS) $(EXAMPLE_SOURCES):
	(cd cfitsio; unset CFLAGS; $(MAKE))

# Must be a separate target from above, otherwise automake doesn't notice,
# and adds its own, conflicting, target.
cfitsio/libcfitsio.a:
	(cd cfitsio; unset CFLAGS; $(MAKE))

...

This uses a number of useful automake features. First of all, the assignments which control what is installed -- the contents of the _LIBRARIES, _HEADERS and (via EXAMPLE_SOURCES) _DATA primaries -- refer to files within the cfitsio/ subdirectory. When these are installed, the path to them is stripped, so that libcfitsio.a, for example, ends up installed in .../lib/ and not in .../lib/cfitsio/, as you might possibly intuit. This is the useful behaviour which is turned off by the use of the nobase_ prefix, as described in item `Automake flattens paths when it installs things. Why?'.

Second, the presence of the lib_LIBRARIES line means that automake expects to find some library sources somewhere, and if it is not told where they are with a xxx_SOURCES variable, then it will assume a default based on the library name. In this case, of course, the sources are not in this directory, and we do not wish automake to generate rules to build them, so we have to pacify it by giving a value for the cfitsio_libcfitsio_a_SOURCES variable (note the canonicalisation of the library name).

Each of the cfitsio/ targets is built in the same way, by switching to the cfitsio/ directory and making `all' using that directory's own Makefile. The only remaining wrinkle is that it turns out we have to specify the cfitsio/libcfitsio.a target by itself, rather than as part of the previous compendium target. Due, probably, to a bug, automake does not appear to `notice' the library if it's mentioned in the compendium target, and instead generates its own conflicting target.