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, 20 insertions, 0 deletions

diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb
index e60db37c15..81c11e6f88 100644
--- a/test/ruby/test_class.rb
+++ b/test/ruby/test_class.rb
@@ -556,4 +556,24 @@ class TestClass < Test::Unit::TestCase
       }
     end;
   end
+
+  def test_should_not_expose_singleton_class_without_metaclass
+    assert_normal_exit %q{
+      klass = Class.new(Array)
+      # The metaclass of +klass+ should handle #bla since it should inherit methods from meta:meta:Array
+      def (Array.singleton_class).bla; :bla; end
+      hidden = ObjectSpace.each_object(Class).find { |c| klass.is_a? c and c.inspect.include? klass.inspect }
+      raise unless hidden.nil?
+    }, '[Bug #11740]'
+
+    assert_normal_exit %q{
+      klass = Class.new(Array)
+      klass.singleton_class
+      # The metaclass of +klass+ should handle #bla since it should inherit methods from meta:meta:Array
+      def (Array.singleton_class).bla; :bla; end
+      hidden = ObjectSpace.each_object(Class).find { |c| klass.is_a? c and c.inspect.include? klass.inspect }
+      raise if hidden.nil?
+    }, '[Bug #11740]'
+
+  end
 end