From 81c8b35752235aeb26058c0baadd0ea58046f640 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Thu, 3 Mar 2016 18:18:55 +0100
Subject: [PATCH] Append effective version to GUILE_LOAD[_COMPILED]_PATH
 elements.

* libguile/load.c (scm_path_append_effective_version): New function
  (scm_init_load_path): Use it.

* am/guilec (moddir,ccachedir): Use GUILE_EFFECTIVE_VERSION as prefix.
---
 am/guilec       |  4 ++--
 libguile/load.c | 27 ++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/am/guilec b/am/guilec
index 5ef07fa..fa2b5ba 100644
--- a/am/guilec
+++ b/am/guilec
@@ -3,9 +3,9 @@ GOBJECTS = $(SOURCES:%.scm=%.go) $(ELISP_SOURCES:%.el=%.go)
 
 GUILE_WARNINGS = -Wunbound-variable -Warity-mismatch -Wformat
 
-moddir = $(pkgdatadir)/$(GUILE_EFFECTIVE_VERSION)/$(modpath)
+moddir = $(pkgdatadir)/$(modpath)/$(GUILE_EFFECTIVE_VERSION)
 nobase_mod_DATA = $(SOURCES) $(ELISP_SOURCES) $(NOCOMP_SOURCES)
-ccachedir = $(pkglibdir)/$(GUILE_EFFECTIVE_VERSION)/ccache/$(modpath)
+ccachedir = $(pkglibdir)/ccache/$(GUILE_EFFECTIVE_VERSION)/$(modpath)
 nobase_ccache_DATA = $(GOBJECTS)
 EXTRA_DIST = $(SOURCES) $(ELISP_SOURCES) $(NOCOMP_SOURCES)
 ETAGS_ARGS = $(SOURCES) $(ELISP_SOURCES) $(NOCOMP_SOURCES)
diff --git a/libguile/load.c b/libguile/load.c
index d26f9fc..055f3c4 100644
--- a/libguile/load.c
+++ b/libguile/load.c
@@ -1,5 +1,6 @@
 /* Copyright (C) 1995, 1996, 1998, 1999, 2000, 2001, 2004, 2006, 2008,
- *   2009, 2010, 2011, 2012, 2013, 2014 Free Software Foundation, Inc.
+ *   2009, 2010, 2011, 2012, 2013, 2014, 2016 Free Software Foundation,
+ *   Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -312,6 +313,28 @@ scm_i_mirror_backslashes (char *path)
   return path;
 }
 
+/* Append effective_version to each element in PATH.  This allows using
+   one single heterogeneous path for different effective versions of
+   Guile, i.e., running different versions of guile alongside each other
+   from one shell, without juggling GUILE_LOAD_COMPILED_PATH.  */
+static SCM
+scm_path_append_effective_version (SCM path)
+{
+  SCM vpath = SCM_EOL;
+  SCM version = scm_effective_version ();
+  SCM slash = scm_from_utf8_string ("/");
+  for (path = scm_reverse (path); scm_is_pair (path);
+       path = SCM_CDR (path))
+    {
+      SCM dir = SCM_CAR (path);
+      SCM vdir = scm_string_append (scm_list_3 (dir, slash, version));
+      /* keep non-M.M suffixed dir as fallback for compatibility.  */
+      vpath = scm_cons (dir, vpath);
+      vpath = scm_cons (vdir, vpath);
+    }
+  return vpath;
+}
+
 /* Initialize the global variable %load-path, given the value of the
    SCM_SITE_DIR and SCM_LIBRARY_DIR preprocessor symbols and the
    GUILE_LOAD_PATH environment variable.  */
@@ -393,7 +416,9 @@ scm_init_load_path ()
   if (env)
     cpath = scm_parse_path_with_ellipsis (scm_from_locale_string (env), cpath);
 
+  path = scm_path_append_effective_version (path);
   *scm_loc_load_path = path;
+  cpath = scm_path_append_effective_version (cpath);
   *scm_loc_load_compiled_path = cpath;
 }
 
-- 
2.6.3