From 490cf75094167556289716c49ad43ad827f1d0dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Wed, 5 Nov 2008 18:50:23 +0100
Subject: [PATCH] Work around unintentional retention of modules by the GC.

This reverts par of "Document the failure of `gc.test' wrt. unused modules."
(commit 328efeb9a66dddcf78a24fad96d3db58e9c3375d.)

* ice-9/boot-9.scm (set-module-eval-closure!): Don't set the `module' property
  on CLOSURE.

* libguile/modules.c (scm_lookup_closure_module): Call `abort ()' to make it
  clear that code that uses the `module' property no longer works.  That code
  is unused anyway.
---
 ice-9/boot-9.scm         | 16 ++++++++++++----
 libguile/modules.c       |  8 +++++++-
 test-suite/tests/gc.test |  3 ---
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/ice-9/boot-9.scm b/ice-9/boot-9.scm
index 5a74f945f..1a0283da1 100644
--- a/ice-9/boot-9.scm
+++ b/ice-9/boot-9.scm
@@ -1,6 +1,6 @@
 ;;; installed-scm-file
 
-;;;; Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007
+;;;; Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008
 ;;;; Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
@@ -1223,8 +1223,6 @@
 	  ;; We can't pass this as an argument to module-constructor,
 	  ;; because we need it to close over a pointer to the module
 	  ;; itself.
-          ;; FIXME: This creates a circular reference between MODULE and its
-          ;; standard eval closure which precludes them from being collected.
 	  (set-module-eval-closure! module (standard-eval-closure module))
 
 	  module))))
@@ -1264,7 +1262,17 @@
       ;; Make it possible to lookup the module from the environment.
       ;; This implementation is correct since an eval closure can belong
       ;; to maximally one module.
-      (set-procedure-property! closure 'module module))))
+
+      ;; XXX: The following line introduces a circular reference that
+      ;; precludes garbage collection of modules with the current weak hash
+      ;; table semantics (see
+      ;; http://thread.gmane.org/gmane.comp.programming.garbage-collection.boehmgc/2465
+      ;; for details).  Since it doesn't appear to be used (only in
+      ;; `scm_lookup_closure_module ()', which has 1 caller), we just comment
+      ;; it out.
+
+      ;(set-procedure-property! closure 'module module)
+      )))
 
 
 
diff --git a/libguile/modules.c b/libguile/modules.c
index d59428c8d..04527a529 100644
--- a/libguile/modules.c
+++ b/libguile/modules.c
@@ -255,7 +255,13 @@ scm_lookup_closure_module (SCM proc)
     return SCM_PACK (SCM_SMOB_DATA (proc));
   else
     {
-      SCM mod = scm_procedure_property (proc, sym_module);
+      SCM mod;
+
+      /* FIXME: The `module' property is no longer set.  See
+	 `set-module-eval-closure!' in `boot-9.scm'.  */
+      abort ();
+
+      mod = scm_procedure_property (proc, sym_module);
       if (scm_is_false (mod))
 	mod = the_root_module ();
       return mod;
diff --git a/test-suite/tests/gc.test b/test-suite/tests/gc.test
index 0fdfaaf6d..407c4a286 100644
--- a/test-suite/tests/gc.test
+++ b/test-suite/tests/gc.test
@@ -59,9 +59,6 @@
 
 (with-test-prefix "gc"
   (pass-if "Unused modules are removed"
-           ;; FIXME: This test fails because of the circular reference
-           ;; created by `make-module' between the module itself and its
-           ;; standard eval closure.
 	   (let* ((guard (make-guardian))
                   (total 1000))