Add a frozenness check to Enumerator#initialize.

* enumerator.c (enumerator_init): Add a frozenness check to
  prevent a frozen Enumerator object from being reinitialized with
  a different enumerable object.  This is the least we should do,
  and more fixes will follow. [Fixes GH-368] Patch by Kenichi
  Kamiya.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42233 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Mon Jul 29 20:53:24 2013  Akinori MUSHA  <knu@iDaemons.org>
+
+	* enumerator.c (enumerator_init): Add a frozenness check to
+	  prevent a frozen Enumerator object from being reinitialized with
+	  a different enumerable object.  This is the least we should do,
+	  and more fixes will follow. [Fixes GH-368] Patch by Kenichi
+	  Kamiya.
+
 Mon Jul 29 20:14:24 2013  Masaki Matsushita  <glass.saga@gmail.com>
 
 	* hash.c (rb_hash_assoc): revert r42224. table->type->compare is

enumerator.c

@@ -270,6 +270,7 @@ enumerator_init(VALUE enum_obj, VALUE obj, VALUE meth, int argc, VALUE *argv, rb
 {
     struct enumerator *ptr;
 
+    rb_check_frozen(enum_obj);
     TypedData_Get_Struct(enum_obj, struct enumerator, &enumerator_data_type, ptr);
 
     if (!ptr) {

test/ruby/test_enumerator.rb

@@ -67,6 +67,16 @@ class TestEnumerator < Test::Unit::TestCase
     assert_match 'Enumerator.new without a block is deprecated', err
     assert_equal([1, 2, 3], Enumerator.new { |y| i = 0; loop { y << (i += 1) } }.take(3))
     assert_raise(ArgumentError) { Enumerator.new }
+
+    enum = @obj.to_enum
+    assert_raise(NoMethodError) { enum.each {} }
+    enum.freeze
+    assert_raise(RuntimeError) {
+      capture_io do
+        # warning: Enumerator.new without a block is deprecated; use Object#to_enum
+        enum.__send__(:initialize, @obj, :foo)
+      end
+    }
   end
 
   def test_initialize_copy