build: Compile and install '.go' files.

* configure.ac: Set and substitute 'mcronmoduledir'.  Check for 'guild'
which requires Guile >= 2.0.7.  Use 'AC_CANONICAL_HOST'.
* scm/mcron/makefile.am (.scm.go): New target.
(MODULES, GEN_MODULES, GOBJECTS, CLEANFILES, SUFFIXES)
(dist_mcronmodule_DATA, mcronmodule_DATA): New variables.
(pkgdata_DATA, EXTRA_DIST): Remove variables.
* .gitignore: Adjust accordingly.

.gitignore

@@ -1,9 +1,12 @@
 *~
+*.go
 .deps
 INSTALL
 aclocal.m4
 autom4te.cache
 /build-aux/compile
+/build-aux/config.guess
+/build-aux/config.sub
 /build-aux/depcomp
 /build-aux/install-sh
 /build-aux/mdate-sh

configure.ac

@@ -26,6 +26,8 @@ AC_INIT([GNU Mcron], [1.0.8], [bug-mcron@gnu.org])
 AC_CONFIG_AUX_DIR([build-aux])
 AM_INIT_AUTOMAKE
 
+mcronmoduledir="${datarootdir}/guile/site/2.0/mcron"
+AC_SUBST([mcronmoduledir])
 
 AC_MSG_CHECKING([whether debugging is requested])
 AC_ARG_ENABLE(debug,
@@ -45,12 +47,18 @@ AC_SUBST(CONFIG_DEBUG)
 # We have no interest (hence a no-op), but Debian wants this.
 AC_ARG_ENABLE(maintainer-mode)
 
-
+AC_CANONICAL_HOST
 AC_PROG_AWK
 AC_PROG_EGREP
 AM_PROG_CC_C_O
 
-PKG_CHECK_MODULES(GUILE, guile-2.0)
+PKG_CHECK_MODULES([GUILE], [guile-2.0 >= 2.0.7])
+AC_PATH_PROG([GUILE], [guile])
+
+# search guild
+AC_PATH_PROG([GUILD], [guild])
+AS_IF([test -z "$ac_cv_path_GUILD"],
+  [AC_MSG_ERROR(['guild' program cannot be found.])])
 
 # Checks for programs.
   

scm/mcron/main.scm

@@ -343,6 +343,8 @@ comes in on the above socket."
     (unless (option-ref options 'schedule #f)
       (with-output-to-file config-pid-file noop))
     (setenv "MAILTO" #f)
+    ;; XXX: At compile time, this yields a "possibly unbound variable"
+    ;; warning, but this is OK since it is bound in the C wrapper.
     (c-set-cron-signals))
 
   ;; Now we have the procedures in place for dealing with the contents of

scm/mcron/makefile.am

@@ -1,10 +1,48 @@
-EXTRA_DIST = main.scm mcron-core.scm vixie-specification.scm \
-             crontab.scm environment.scm job-specifier.scm redirect.scm \
+MODULES =				\
+  environment.scm			\
+  job-specifier.scm			\
+  main.scm				\
+  redirect.scm				\
+  vixie-specification.scm		\
   vixie-time.scm
 
-pkgdata_DATA = core.scm environment.scm job-specifier.scm redirect.scm \
-               vixie-time.scm vixie-specification.scm config.scm
+GEN_MODULES =				\
+  config.scm				\
+  core.scm
 
+GOBJECTS =				\
+  $(GEN_MODULES:%.scm=%.go)		\
+  $(MODULES:%.scm=%.go)
+
+mcronmodule_DATA =			\
+  $(GOBJECTS)				\
+  $(GEN_MODULES)
+
+dist_mcronmodule_DATA = 		\
+  $(MODULES)				\
+  crontab.scm				\
+  mcron-core.scm
+
+# Unset 'GUILE_LOAD_COMPILED_PATH' altogether while compiling.  Otherwise, if
+# $GUILE_LOAD_COMPILED_PATH contains $(mcronmoduledir), we may find .go files
+# in there that are newer than the local .scm files (for instance because the
+# user ran 'make install' recently).  When that happens, we end up loading
+# those previously-installed .go files, which may be stale, thereby breaking
+# the whole thing.
+#
+# XXX: Use the C locale for when Guile lacks
+# <http://git.sv.gnu.org/cgit/guile.git/commit/?h=stable-2.0&id=e2c6bf3866d1186c60bacfbd4fe5037087ee5e3f>.
+.scm.go:
+	unset GUILE_LOAD_COMPILED_PATH ;				\
+	LC_ALL=C							\
+	$(GUILD) compile						\
+	  --load-path="$(top_builddir)/scm"				\
+	  --load-path="$(top_srcdir)/scm"				\
+	  --warn=format --warn=unbound-variable --warn=arity-mismatch	\
+	  --target="$(host)" --output="$@" "$<"
+
+SUFFIXES = .go
+CLEANFILES = $(GOBJECTS)
 
 # If you're wondering, the configure script keeps deleting all files with a name
 # like core.*, so we have to keep re-making it (I lost a good day's work because