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

ChangeLog

@@ -1,3 +1,11 @@
+Tue Dec 22 22:15:53 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* 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.
+
 Tue Dec 22 22:15:08 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/io/console/io-console.gemspec: bump up to 0.4.4.

class.c

@@ -442,6 +442,19 @@ rb_singleton_class_attached(VALUE klass, VALUE obj)
  */
 #define META_CLASS_OF_CLASS_CLASS_P(k)  (METACLASS_OF(k) == (k))
 
+static int
+rb_singleton_class_has_metaclass_p(VALUE sklass)
+{
+    return rb_attr_get(METACLASS_OF(sklass), id_attached) == sklass;
+}
+
+int
+rb_singleton_class_internal_p(VALUE sklass)
+{
+    return (RB_TYPE_P(rb_attr_get(sklass, id_attached), T_CLASS) &&
+	    !rb_singleton_class_has_metaclass_p(sklass));
+}
+
 /*!
  * whether k has a metaclass
  * @retval 1 if \a k has a metaclass
@@ -449,7 +462,7 @@ rb_singleton_class_attached(VALUE klass, VALUE obj)
  */
 #define HAVE_METACLASS_P(k) \
     (FL_TEST(METACLASS_OF(k), FL_SINGLETON) && \
-     rb_ivar_get(METACLASS_OF(k), id_attached) == (k))
+     rb_singleton_class_has_metaclass_p(k))
 
 /*!
  * ensures \a klass belongs to its own eigenclass.

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;

internal.h

@@ -491,6 +491,7 @@ struct RClass {
 
 void rb_class_subclass_add(VALUE super, VALUE klass);
 void rb_class_remove_from_super_subclasses(VALUE);
+int rb_singleton_class_internal_p(VALUE sklass);
 
 #define RCLASS_EXT(c) (RCLASS(c)->ptr)
 #define RCLASS_IV_TBL(c) (RCLASS_EXT(c)->iv_tbl)

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

test/ruby/test_objectspace.rb

@@ -149,5 +149,12 @@ End
       }
       assert(exist, 'Bug #11360')
     End
+
+    klass = Class.new
+    instance = klass.new
+    sclass = instance.singleton_class
+    meta = klass.singleton_class
+    assert_kind_of(meta, sclass)
+    assert_include(ObjectSpace.each_object(meta).to_a, sclass)
   end
 end