As mentioned earlier in this chapter, Guile supports parallel
installation, and uses pkg-config to let the user choose which
version of Guile they are interested in. pkg-config has its own
set of Autoconf macros that are probably installed on most every
development system. The most useful of these macros is
PKG_CHECK_MODULES.
PKG_CHECK_MODULES([GUILE], [guile-3.0])
This example looks for Guile and sets the GUILE_CFLAGS and
GUILE_LIBS variables accordingly, or prints an error and exits if
Guile was not found.
Guile comes with additional Autoconf macros providing more information,
installed as prefix/share/aclocal/guile.m4. Their names
all begin with GUILE_.
This macro runs the pkg-config tool to find development files
for an available version of Guile.
By default, this macro will search for the latest stable version of Guile (e.g. 3.0), falling back to the previous stable version (e.g. 2.2) if it is available. If no guile-VERSION.pc file is found, an error is signaled. The found version is stored in GUILE_EFFECTIVE_VERSION.
If GUILE_PROGS was already invoked, this macro ensures that the
development files have the same effective version as the Guile
program.
GUILE_EFFECTIVE_VERSION is marked for substitution, as by
AC_SUBST.
This macro runs the pkg-config tool to find out how to compile
and link programs against Guile. It sets four variables:
GUILE_CFLAGS, GUILE_LDFLAGS, GUILE_LIBS, and
GUILE_LTLIBS.
GUILE_CFLAGS: flags to pass to a C or C++ compiler to build code that
uses Guile header files. This is almost always just one or more -I
flags.
GUILE_LDFLAGS: flags to pass to the compiler to link a program
against Guile. This includes -lguile-VERSION for the
Guile library itself, and may also include one or more -L flag
to tell the compiler where to find the libraries. But it does not
include flags that influence the program’s runtime search path for
libraries, and will therefore lead to a program that fails to start,
unless all necessary libraries are installed in a standard location
such as /usr/lib.
GUILE_LIBS and GUILE_LTLIBS: flags to pass to the compiler or to libtool, respectively, to link a program against Guile. It includes flags that augment the program’s runtime search path for libraries, so that shared libraries will be found at the location where they were during linking, even in non-standard locations. GUILE_LIBS is to be used when linking the program directly with the compiler, whereas GUILE_LTLIBS is to be used when linking the program is done through libtool.
The variables are marked for substitution, as by AC_SUBST.
This looks for Guile’s "site" directories. The variable GUILE_SITE will
be set to Guile’s "site" directory for Scheme source files (usually something
like PREFIX/share/guile/site). GUILE_SITE_CCACHE will be set to the
directory for compiled Scheme files also known as .go files
(usually something like
PREFIX/lib/guile/GUILE_EFFECTIVE_VERSION/site-ccache).
GUILE_EXTENSION will be set to the directory for compiled C extensions
(usually something like
PREFIX/lib/guile/GUILE_EFFECTIVE_VERSION/extensions). The latter two
are set to blank if the particular version of Guile does not support
them. Note that this macro will run the macros GUILE_PKG and
GUILE_PROGS if they have not already been run.
The variables are marked for substitution, as by AC_SUBST.
This macro looks for programs guile and guild, setting
variables GUILE and GUILD to their paths, respectively.
The macro will attempt to find guile with the suffix of
-X.Y, followed by looking for it with the suffix X.Y, and
then fall back to looking for guile with no suffix. If
guile is still not found, signal an error. The suffix, if any,
that was required to find guile will be used for guild
as well.
By default, this macro will search for the latest stable version of Guile (e.g. 3.0). x.y or x.y.z versions can be specified. If an older version is found, the macro will signal an error.
The effective version of the found guile is set to
GUILE_EFFECTIVE_VERSION. This macro ensures that the effective
version is compatible with the result of a previous invocation of
GUILE_FLAGS, if any.
As a legacy interface, it also looks for guile-config and
guile-tools, setting GUILE_CONFIG and GUILE_TOOLS.
The variables are marked for substitution, as by AC_SUBST.
var is a shell variable name to be set to the return value. check is a Guile Scheme expression, evaluated with "$GUILE -c", and returning either 0 or non-#f to indicate the check passed. Non-0 number or #f indicates failure. Avoid using the character "#" since that confuses autoconf.
var is a shell variable name to be set to "yes" or "no". module is a list of symbols, like: (ice-9 common-list). featuretest is an expression acceptable to GUILE_CHECK, q.v. description is a present-tense verb phrase (passed to AC_MSG_CHECKING).
var is a shell variable name to be set to "yes" or "no". module is a list of symbols, like: (ice-9 common-list).
symlist is a list of symbols, WITHOUT surrounding parens, like: ice-9 common-list.
var is a shell variable to be set to "yes" or "no". module is a list of symbols, like: (ice-9 common-list). modvar is the Guile Scheme variable to check.
module is a list of symbols, like: (ice-9 common-list). modvar is the Guile Scheme variable to check.