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5.8.2 Autoconf Macros

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-2.2])

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_.

Autoconf Macro: GUILE_PKG [VERSIONS]

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. 2.0), falling back to the previous stable version (e.g. 1.8) if it is available. If no guile-VERSION.pc file is found, an error is signalled. 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.

Autoconf Macro: GUILE_FLAGS

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.

Autoconf Macro: GUILE_SITE_DIR

This looks for Guile’s "site" directory, usually something like PREFIX/share/guile/site, and sets var GUILE_SITE to the path. Note that the var name is different from the macro name.

The variable is marked for substitution, as by AC_SUBST.

Autoconf Macro: GUILE_PROGS [VERSION]

This macro looks for programs guile and guild, setting variables GUILE and GUILD to their paths, respectively. If guile is not found, signal an error.

By default, this macro will search for the latest stable version of Guile (e.g. 2.0). 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.

Autoconf Macro: GUILE_CHECK_RETVAL var check

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.

Autoconf Macro: GUILE_MODULE_CHECK var module featuretest description

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).

Autoconf Macro: GUILE_MODULE_AVAILABLE var module

var is a shell variable name to be set to "yes" or "no". module is a list of symbols, like: (ice-9 common-list).

Autoconf Macro: GUILE_MODULE_REQUIRED symlist

symlist is a list of symbols, WITHOUT surrounding parens, like: ice-9 common-list.

Autoconf Macro: GUILE_MODULE_EXPORTS var module modvar

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.

Autoconf Macro: GUILE_MODULE_REQUIRED_EXPORT module modvar

module is a list of symbols, like: (ice-9 common-list). modvar is the Guile Scheme variable to check.


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