Autoconf Support
****************

When Guile is installed, a set of autoconf macros is also installed as PREFIX/share/aclocal/guile.m4.  This chapter documents the macros provided in that file.  See The GNU Autoconf Manual (autoconf), for more info.

Autoconf Background
===================

As explained elsewhere (see The GNU Autoconf Manual (autoconf)), any package needs configuration at build-time.  If your package uses Guile (or uses a package that in turn uses Guile), you probably need to know what specific Guile features are available and details about them.

The way to do this is to write feature tests and arrange for their execution by the configure script, typically by adding the tests to configure.ac, and running autoconf to create configure. Users of your package then run configure in the normal way.

Macros are a way to make common feature tests easy to express.  Autoconf provides a wide range macros (see Existing Tests (autoconf)), and Guile installation provides Guile-specific tests in the areas of: program detection, compilation flags reporting, and Scheme module checks.

Autoconf Macros
===============

The macro names all begin with "GUILE_".

     [file autoconf-macros.texi not included]

Using Autoconf Macros
=====================

Using the autoconf macros is straightforward: Add the macro "calls" (actually instantiations) to configure.ac, run aclocal, and finally, run autoconf.  If your system doesn't have guile.m4 installed, place the desired macro definitions (AC_DEFUN forms) in acinclude.m4, and aclocal will do the right thing.

Some of the macros can be used inside normal shell constructs: if foo ; then GUILE_BAZ ; fi, but this is not guaranteed.  It's probably a good idea to instantiate macros at top-level.

We now include two examples, one simple and one complicated.

The first example is for a package that uses libguile, and thus needs to know how to compile and link against it.  So we use GUILE_FLAGS to set the vars GUILE_CFLAGS and GUILE_LDFLAGS, which are automatically substituted in the Makefile.

     In configure.ac:

       GUILE_FLAGS

     In Makefile.in:

       GUILE_CFLAGS  = @GUILE_CFLAGS@
       GUILE_LDFLAGS = @GUILE_LDFLAGS@

       myprog.o: myprog.c
               $(CC) -o $ $(GUILE_CFLAGS) $<
       myprog: myprog.o
               $(CC) -o $ $< $(GUILE_LDFLAGS)

The second example is for a package of Guile Scheme modules that uses an external program and other Guile Scheme modules (some might call this a "pure scheme" package).  So we use the GUILE_SITE_DIR macro, a regular AC_PATH_PROG macro, and the GUILE_MODULE_AVAILABLE macro.

     In configure.ac:

       GUILE_SITE_DIR

       probably_wont_work=""

       # pgtype pgtable
       GUILE_MODULE_AVAILABLE(have_guile_pg, (database postgres))
       test $have_guile_pg = no &&
           probably_wont_work="(my pgtype) (my pgtable) $probably_wont_work"

       # gpgutils
       AC_PATH_PROG(GNUPG,gpg)
       test x"$GNUPG" = x &&
           probably_wont_work="(my gpgutils) $probably_wont_work"

       if test ! "$probably_wont_work" = "" ; then
           p="         ***"
           echo
           echo "$p"
           echo "$p NOTE:"
           echo "$p The following modules probably won't work:"
           echo "$p   $probably_wont_work"
           echo "$p They can be installed anyway, and will work if their"
           echo "$p dependencies are installed later.  Please see README."
           echo "$p"
           echo
       fi

     In Makefile.in:

       instdir = @GUILE_SITE@/my

       install:
             $(INSTALL) my/*.scm $(instdir)