Add options for conditional checking.

* gint.m4 (_GINT_OPTION_SWITCH): New macro.
* guile.m4 (GINT_CHECK_GUILE): Always declare substitution variables.
Generate --with-guile/--enable-guile options, if requested.
Don't do any checking if disabled by those options.
* README: Describe new features.

3 files changed, 202 insertions, 89 deletions

diff --git a/README b/README
index 2973837..9ca2c76 100644
--- a/README
+++ b/README
@@ -9,7 +9,7 @@ See end of file for copyright statement.
 GINT
 ====
 Sergey Poznyakoff <gray@gnu.org>
-1, April  5, 2010
+2, May 11, 2010
 
 NAME
 ----
@@ -273,21 +273,58 @@ Scheme counterpart.  By supplying the +snarf-doc-filter+ option, you instruct
 *GINT* to use Scheme implementation instead.  See the section
 <<doc-snarfing, Doc snarfing>> for a detailed discussion.
 
+[[option-generators]]
+By default, the generated +configure+ script always checks for Guile.  The
+following options modify this behavior:
+
+with-guile::
+Add a +--with-guile+ option to configure.  Do not check for Guile if
+configure was called with +--with-guile=no+ (or +--without-guile+).
+
+without-guile::
+Same as above, except that Guile checks are disabled by default.  I.e. the
+configure script checks for Guile only if invoked with the +--with-guile+
+option.
+
+enable-guile::
+Add a +--enable-guile+ option to configure.  Do not check for Guile if
+configure was called with +--enable-guile=no+ (or +--disable-guile+).
+
+disable-guile::
+Same as above, except that Guile checks are disabled by default.  I.e. the
+configure script checks for Guile only if invoked with the +--enable-guile+
+option.
+
+Only one of these four options may be given to a +GINT_INIT+ invocation.
+
 Here is a more complex example:
 
 
 .+GINT_INIT+ macro
 -------------------------------------------------------
-GINT_INIT([modules/gint], [1.8 std-site-dir],
+GINT_INIT([modules/gint], [1.8 with-guile std-site-dir],
           [use_guile=yes],
 	  [use_guile=no])
 -------------------------------------------------------
 
 This fragment initializes the +GINT+ module located in `modules/gint` and
-checks for Guile version 1.8 or newer.  The resulting script sets
-<<sitedir,sitedir>> to the standard Guile site directory.  The
-shell variable `use_guile` is set to `yes` or `no`, depending on
-whether Guile was found or not.
+checks for Guile version 1.8 or newer.  The resulting script understands
+the +--with-guile+ option and sets <<sitedir,sitedir>> to the standard Guile
+site directory.  The shell variable `use_guile` is set to `yes` or `no`,
+depending on whether Guile was found or not.
+
+Notice, that you may not use this macro within a shell conditional, or
+within any +Autoconf+ macro that generates such a conditional.  In particular,
+the following invocation is wrong:
+
+.*Wrong usage*
+-----------------------------------------
+AC_ARG_WITH([guile],
+            [GINT_INIT([modules/gint])])
+-----------------------------------------
+
+Instead, use one of the <<option-generators, option generating>> options,
+described above.
 
 [[gint-subst-vars]]
 Substitution Variables
@@ -295,10 +332,12 @@ Substitution Variables
 Upon successful return, +GINT_INIT+ sets the following Automake
 substitution variables:
 
+[[GUILE_VERSION]]
 GUILE_VERSION::
 The version of Guile, as a string, e.g. `1.9.9`.  Additionally,
 a _C_ preprocessor macro with the same name is defined.
 
+[[GUILE_VERSION_NUMBER]]
 GUILE_VERSION_NUMBER::
 The version of Guile packed into a decimal number using the following formula:
 +
@@ -330,6 +369,40 @@ The full pathname of the `guile-tools` binary.
 GUILE_SITE::
 The full pathname of the Guile site-wide module directory.
 
+[[gint-shell-vars]]
+Shell Variables
+---------------
+The +GINT_INIT+ macro sets the following shell variables:
+
+gint_enable_guile::
+By default, set to `yes`.  If an <<option-generators, option generating>>
+option was used, this variable is set to `no` if the *Guile* checks were
+disabled (either by default or by the user request) and to `yes` otherwise.
+
+gint_cv_guile::
+Set to `yes` if a sufficiently new version of *Guile* was found, and to
+`no` otherwise.
+
+[[gint_cv_guile_debug]]
+gint_cv_guile_debug::
+Set if guile supports the debugging macros (i.e. +SCM_DEVAL_P+,
++SCM_BACKTRACE_P+, +SCM_RECORD_POSITIONS_P+ and SCM_RESET_DEBUG_MODE).
+
+[[config.h defines]]
+Config.h Defines
+----------------
+GUILE_DEBUG_MACROS::
+Defined if guile supports the debugging macros (i.e. +SCM_DEVAL_P+,
++SCM_BACKTRACE_P+, +SCM_RECORD_POSITIONS_P+ and SCM_RESET_DEBUG_MODE).
+See also the <<gint_cv_guile_debug, +gint_cv_guile_debug+>> variable.
+
+GUILE_VERSION::
+Same as the <<GUILE_VERSION, +GUILE_VERSION+>> substitution variable.
+
+GUILE_VERSION_NUMBER::
+Same as the <<GUILE_VERSION_NUMBER, +GUILE_VERSION_NUMBER+>> substitution
+variable.
+
 [[doc-snarfing]]
 Doc Snarfing
 ~~~~~~~~~~~~
diff --git a/gint.m4 b/gint.m4
index 511d2c1..4f3ff48 100644
--- a/gint.m4
+++ b/gint.m4
@@ -38,6 +38,16 @@ AC_DEFUN([_GINT_SET_OPTION],
 AC_DEFUN([_GINT_IF_OPTION_SET],
 [m4_ifset(_GINT_MANGLE_OPTION([$1]),[$2],[$3])])
 
+# _GINT_OPTION_SWITCH(NAME1,IF-SET1,[NAME2,IF-SET2,[...]],[IF-NOT-SET])
+# ------------------------------------------------------------------------
+# If NAME1 is set, run IF-SET1.  Otherwise, if NAME2 is set, run IF-SET2.
+# Continue the process for all name-if-set pairs within [...].  If none
+# of the options is set, run IF-NOT-SET.
+AC_DEFUN([_GINT_OPTION_SWITCH],
+[m4_if([$4],,[_GINT_IF_OPTION_SET($@)],dnl
+[$3],,[_GINT_IF_OPTION_SET($@)],dnl
+[_GINT_IF_OPTION_SET([$1],[$2],[_GINT_OPTION_SWITCH(m4_shift(m4_shift($@)))])])])
+
 # _GINT_SET_OPTIONS(OPTIONS)
 # ----------------------------------
 # OPTIONS is a space-separated list of Gint options.
diff --git a/guile.m4 b/guile.m4
index 1d340b4..ccf9dc6 100644
--- a/guile.m4
+++ b/guile.m4
@@ -23,98 +23,128 @@ m4_define([_gint_mangle_version],[_gint_eval_version(m4_bpatsubst($1,\.,[,]))])
 
 m4_define([_gint_site_dir],[`guile -c '(write (%site-dir)) (newline)'`])
 
-dnl GINT_CHECK_GUILE(minversion, [act-if-found], [ac-if-not-found])
+dnl GINT_CHECK_GUILE(minversion, [act-if-found], [act-if-not-found])
 dnl                      $1            $2               $3
 AC_DEFUN([GINT_CHECK_GUILE],
 [
+  AC_SUBST(GUILE_INCLUDES)
+  AC_SUBST(GUILE_LIBS)
+  AC_SUBST(GUILE_VERSION)
+  AC_SUBST(GUILE_VERSION_NUMBER)
   AS_VAR_SET([gint_cv_guile], [no])
-  AC_PATH_PROG(GUILE_CONFIG, guile-config, no, $PATH)
-  if test "$GUILE_CONFIG" = no; then
-    m4_if([$3],,[AC_MSG_ERROR(cannot find Guile)], [$3])
-  else
-    AC_SUBST(GUILE_INCLUDES)
-    AC_SUBST(GUILE_LIBS)
-    AC_SUBST(GUILE_VERSION)
-    AC_SUBST(GUILE_VERSION_NUMBER)
-    AC_PATH_PROG(GUILE_SNARF, guile-snarf)
-    AC_PATH_PROG(GUILE_TOOLS, guile-tools)
-  
-    GUILE_INCLUDES=`$GUILE_CONFIG compile`
-    GUILE_LIBS=`$GUILE_CONFIG link`
-    GUILE_VERSION=`($GUILE_CONFIG --version 2>&1; echo '')|sed 's/guile-config [[^0-9]]* \([[0-9]][[0-9.]]*\)$/\1/'`
-    VEX=`echo $GUILE_VERSION | sed 's/\./ \\\\* 1000 + /;s/\./ \\\\* 100 + /'`
-    GUILE_VERSION_NUMBER=`eval expr "$VEX"`
 
-    m4_if([$1],,,[
-      if test $GUILE_VERSION_NUMBER -lt _gint_mangle_version($1); then
-        m4_if($3,,
-	        [AC_MSG_ERROR([Guile version too old; required is at least ]$1)],
-	        [$3])
-      fi])
+  _GINT_OPTION_SWITCH(
+    [with-guile],
+     [AC_ARG_WITH([guile],
+	[AC_HELP_STRING([--with-guile],
+	                [compile with Guile support (default)])],
+	[gint_enable_guile=$withval],
+	[gint_enable_guile=yes])],
+    [without-guile],
+     [AC_ARG_WITH([guile],
+	[AC_HELP_STRING([--with-guile],
+	                [compile with Guile support])],
+	[gint_enable_guile=$withval],
+	[gint_enable_guile=no])],
+    [enable-guile],
+     [AC_ARG_ENABLE([guile],
+	[AC_HELP_STRING([--enable-guile],
+	                [enable Guile support (default)])],
+	[gint_enable_guile=$enableval],
+	[gint_enable_guile=yes])],
+    [disable-guile],
+     [AC_ARG_ENABLE([guile],
+	[AC_HELP_STRING([--enable-guile],
+	                [enable Guile support])],
+	[gint_enable_guile=$enableval],
+	[gint_enable_guile=no])],
+    [gint_enable_guile=yes])
 
-    save_LIBS=$LIBS
-    save_CFLAGS=$CFLAGS
-    LIBS="$LIBS $GUILE_LIBS"
-    CFLAGS="$CFLAGS $GUILE_INCLUDES"
-    AC_TRY_LINK([#include <libguile.h>],
-                 m4_if([$1], , scm_shell(0, NULL);, [$1]),
-                [AS_VAR_SET([gint_cv_guile], $GUILE_VERSION)])
-    LIBS=$save_LIBS
-    CFLAGS=$save_CFLAGS
-  fi
+  if test "$gint_enable_guile" = yes; then
+    AC_PATH_PROG(GUILE_CONFIG, guile-config, no, $PATH)
+    if test "$GUILE_CONFIG" = no; then
+      m4_if([$3],,[AC_MSG_ERROR(cannot find Guile)], [$3])
+    else
+      AC_PATH_PROG(GUILE_SNARF, guile-snarf)
+      AC_PATH_PROG(GUILE_TOOLS, guile-tools)
+  
+      GUILE_INCLUDES=`$GUILE_CONFIG compile`
+      GUILE_LIBS=`$GUILE_CONFIG link`
+      GUILE_VERSION=`($GUILE_CONFIG --version 2>&1; echo '')|sed 's/guile-config [[^0-9]]* \([[0-9]][[0-9.]]*\)$/\1/'`
+      VEX=`echo $GUILE_VERSION | sed 's/\./ \\\\* 1000 + /;s/\./ \\\\* 100 + /'`
+      GUILE_VERSION_NUMBER=`eval expr "$VEX"`
 
-  if test $gint_cv_guile = no; then
-    GUILE_INCLUDES=
-    GUILE_LIBS=
-    GUILE_VERSION=
-    GUILE_VERSION_NUMBER=
-    m4_if([$3],,[AC_MSG_ERROR(required library libguile not found)], [$3])
-  else
-    save_LIBS=$LIBS
-    save_CFLAGS=$CFLAGS
-    LIBS="$LIBS $GUILE_LIBS"
-    CFLAGS="$CFLAGS $GUILE_INCLUDES"
-    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <libguile.h>]],
-                      [SCM_DEVAL_P = 1;
-                       SCM_BACKTRACE_P = 1;
-                       SCM_RECORD_POSITIONS_P = 1;
-                       SCM_RESET_DEBUG_MODE;])],
-                      [gint_cv_guile_debug=yes],
-                      [gint_cv_guile_debug=no])
-    if test $gint_cv_guile_debug = yes; then
-      AC_DEFINE_UNQUOTED(GUILE_DEBUG_MACROS, 1,
-                         [Define to 1 if SCM_DEVAL_P, SCM_BACKTRACE_P, SCM_RECORD_POSITIONS_P and SCM_RESET_DEBUG_MODE are defined])
+      m4_if([$1],,,[
+        if test $GUILE_VERSION_NUMBER -lt _gint_mangle_version($1); then
+          m4_if($3,,
+	          [AC_MSG_ERROR([Guile version too old; required is at least ]$1)],
+	          [$3])
+        fi])
+
+      save_LIBS=$LIBS
+      save_CFLAGS=$CFLAGS
+      LIBS="$LIBS $GUILE_LIBS"
+      CFLAGS="$CFLAGS $GUILE_INCLUDES"
+      AC_TRY_LINK([#include <libguile.h>],
+                   m4_if([$1], , scm_shell(0, NULL);, [$1]),
+                  [AS_VAR_SET([gint_cv_guile], $GUILE_VERSION)])
+      LIBS=$save_LIBS
+      CFLAGS=$save_CFLAGS
     fi
-    AC_CHECK_TYPES([scm_t_off],[],[],[#include <libguile.h>])
-    LIBS=$save_LIBS
-    CFLAGS=$save_CFLAGS
+
+    if test $gint_cv_guile = no; then
+      GUILE_INCLUDES=
+      GUILE_LIBS=
+      GUILE_VERSION=
+      GUILE_VERSION_NUMBER=
+      m4_if([$3],,[AC_MSG_ERROR(required library libguile not found)], [$3])
+    else
+      save_LIBS=$LIBS
+      save_CFLAGS=$CFLAGS
+      LIBS="$LIBS $GUILE_LIBS"
+      CFLAGS="$CFLAGS $GUILE_INCLUDES"
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <libguile.h>]],
+                        [SCM_DEVAL_P = 1;
+                         SCM_BACKTRACE_P = 1;
+                         SCM_RECORD_POSITIONS_P = 1;
+                         SCM_RESET_DEBUG_MODE;])],
+                        [gint_cv_guile_debug=yes],
+                        [gint_cv_guile_debug=no])
+      if test $gint_cv_guile_debug = yes; then
+        AC_DEFINE_UNQUOTED(GUILE_DEBUG_MACROS, 1,
+         [Define to 1 if SCM_DEVAL_P, SCM_BACKTRACE_P, SCM_RECORD_POSITIONS_P and SCM_RESET_DEBUG_MODE are defined])
+      fi
+      AC_CHECK_TYPES([scm_t_off],[],[],[#include <libguile.h>])
+      LIBS=$save_LIBS
+      CFLAGS=$save_CFLAGS
     
-    AC_SUBST(GUILE_SITE)
-    _GINT_IF_OPTION_SET([std-site-dir],
-       [GUILE_SITE=_gint_site_dir],
-       [AC_ARG_WITH([guile-site-dir],
-                AC_HELP_STRING([--with-guile-site-dir=DIR],
-                               [specify directory to install guile modules to]),
-                [case $withval in
-                 /*) GUILE_SITE=$withval;;
-                 yes) GUILE_SITE=_gint_site_dir;;
-                 *)  AC_MSG_ERROR([Argument to --with-guile-site-dir must be an absolute directory name]);;
-                 esac],
-                [GUILE_SITE=_gint_site_dir
-                 pfx=$prefix 
-                 test "x$pfx" = xNONE && pfx=$ac_default_prefix
-                 case $GUILE_SITE in
-                 $pfx/*) ;; # OK
-	         *) AC_MSG_WARN([guile site directory "$GUILE_SITE" lies outside your current prefix ($pfx).])
-                    GUILE_SITE='$(datadir)/guile/site'
-                    AC_MSG_WARN([Falling back to ${GUILE_SITE} instead. Use --with-guile-site-dir to force using site directory.])
-                    ;;
-                 esac])])
-    AC_DEFINE_UNQUOTED(GUILE_VERSION, "$GUILE_VERSION",
-                       [Guile version number])
-    AC_DEFINE_UNQUOTED(GUILE_VERSION_NUMBER, $GUILE_VERSION_NUMBER,
-                       [Guile version number: MAX*10 + MIN])
-    m4_if([$2],,,[$2])
+      AC_SUBST(GUILE_SITE)
+      _GINT_IF_OPTION_SET([std-site-dir],
+         [GUILE_SITE=_gint_site_dir],
+         [AC_ARG_WITH([guile-site-dir],
+            [AC_HELP_STRING([--with-guile-site-dir=DIR],
+                            [specify directory to install guile modules to])],
+            [case $withval in
+             /*) GUILE_SITE=$withval;;
+             yes) GUILE_SITE=_gint_site_dir;;
+             *)  AC_MSG_ERROR([Argument to --with-guile-site-dir must be an absolute directory name]);;
+             esac],
+            [GUILE_SITE=_gint_site_dir
+             pfx=$prefix 
+             test "x$pfx" = xNONE && pfx=$ac_default_prefix
+             case $GUILE_SITE in
+             $pfx/*) ;; # OK
+	     *) AC_MSG_WARN([guile site directory "$GUILE_SITE" lies outside your current prefix ($pfx).])
+             GUILE_SITE='$(datadir)/guile/site'
+             AC_MSG_WARN([Falling back to ${GUILE_SITE} instead. Use --with-guile-site-dir to force using site directory.])
+             ;;
+             esac])])
+      AC_DEFINE_UNQUOTED(GUILE_VERSION, "$GUILE_VERSION",
+                         [Guile version number])
+      AC_DEFINE_UNQUOTED(GUILE_VERSION_NUMBER, $GUILE_VERSION_NUMBER,
+                         [Guile version number: MAX*10 + MIN])
+      m4_if([$2],,,[$2])
+    fi
   fi
 ])