gc.c: do not expose internal singleton class

* gc.c (internal_object_p): should not expose singleton classes
  without a metaclass.  based on patches by ko1 and shugo.
  [Bug #11740]
* class.c (rb_singleton_class_object_p): added.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53243 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 6 insertions, 0 deletions

diff --git a/gc.c b/gc.c
index 12be1eac11..24e746e798 100644
--- a/gc.c
+++ b/gc.c
@@ -2400,6 +2400,12 @@ internal_object_p(VALUE obj)
 	  case T_NODE:
 	  case T_ZOMBIE:
 	    break;
+	  case T_CLASS:
+	    if (!p->as.basic.klass) break;
+	    if (FL_TEST(obj, FL_SINGLETON)) {
+		return rb_singleton_class_internal_p(obj);
+	    }
+	    return 0;
 	  default:
 	    if (!p->as.basic.klass) break;
 	    return 0;