build: Support VPATH builds.

This allows using 'mcron' before it is installed without hardcoding the
local build environment in the executable.

* build-aux/pre-inst-env.in: New script.
* configure.ac (AC_CONFIG_FILES): Create it.
(AC_CONFIG_HEADER): Add 'config.h'.
(moduledir): New variable.
(PACKAGE_LOAD_PATH): new C preprocessor macro.
* mcron.c: Include "config.h".
(main): Don't overwrite Guile load paths.
(inner_main): Prepend Mcron modules load paths.
* Makefile.am (.scm.go, doc/mcron.1): Use 'pre-inst-env'.
(mcron_CFLAGS): Remove GUILE_LOAD_PATH macro.
(noinst_SCRIPTS): New variable.
* .gitignore: Update.

1 files changed, 9 insertions, 1 deletions

diff --git a/mcron.c b/mcron.c
index 0c62ec8..92e1a37 100644
--- a/mcron.c
+++ b/mcron.c
@@ -22,6 +22,7 @@
    is needed because the crontab personality requires SUID which is not
    permitted for executable scripts.  */
 
+#include "config.h"
 #include <libguile.h>
 #include <signal.h>
 #include <stdlib.h>
@@ -35,7 +36,6 @@ static SCM set_cron_signals (void);
 int
 main (int argc, char **argv)
 {
-  setenv ("GUILE_LOAD_PATH", GUILE_LOAD_PATH, 1);
   scm_boot_guile (argc, argv, inner_main, 0);
 
   return EXIT_SUCCESS;
@@ -45,6 +45,14 @@ main (int argc, char **argv)
 static void
 inner_main (void *closure, int argc, char **argv)
 {
+  /* Set Guile load paths to ensure that Mcron modules will be found.  */
+  if (getenv ("MCRON_UNINSTALLED") == NULL)
+    {
+      scm_c_eval_string ("(set! %load-path (cons \""
+                         PACKAGE_LOAD_PATH "\" %load-path))");
+      scm_c_eval_string ("(set! %load-compiled-path (cons \""
+                         PACKAGE_LOAD_PATH "\" %load-compiled-path))");
+    }
   scm_set_current_module (scm_c_resolve_module ("mcron main"));
   /* Register set_cron_signals to be called from Guile.  */
   scm_c_define_gsubr ("c-set-cron-signals", 0, 0, 0, set_cron_signals);