* class.c (rb_prepend_module): make T_ICLASS object shady because

this T_ICLASS object seems to share method table with other class
  objects. It was causes WB miss.
  TODO: need to know the data structure.
* test/ruby/test_module.rb: add a test for WB miss.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,12 @@
+Mon Aug 12 15:16:58 2013  Koichi Sasada  <ko1@atdot.net>
+
+	* class.c (rb_prepend_module): make T_ICLASS object shady because
+	  this T_ICLASS object seems to share method table with other class
+	  objects. It was causes WB miss.
+	  TODO: need to know the data structure.
+
+	* test/ruby/test_module.rb: add a test for WB miss.
+
 Mon Aug 12 13:47:54 2013  Zachary Scott  <e@zzak.io>
 
 	* process.c: [DOC] RDoc formatting of Process.clock_gettime

class.c

@@ -826,6 +826,7 @@ rb_prepend_module(VALUE klass, VALUE module)
     origin = RCLASS_ORIGIN(klass);
     if (origin == klass) {
 	origin = class_alloc(T_ICLASS, klass);
+	OBJ_WB_UNPROTECT(origin); /* TODO: conservertive shading. Need more survery. */
 	RCLASS_SET_SUPER(origin, RCLASS_SUPER(klass));
 	RCLASS_SET_SUPER(klass, origin);
 	RCLASS_ORIGIN(klass) = origin;

test/ruby/test_module.rb

@@ -1760,4 +1760,20 @@ class TestModule < Test::Unit::TestCase
       self.#{method}
     INPUT
   end
+
+  def test_prepend_gc
+    assert_separately [], %{
+      module Foo
+      end
+      class Object
+        prepend Foo
+      end
+      GC.start     # make created T_ICLASS old (or remembered shady)
+      class Object # add methods into T_ICLASS (need WB if it is old)
+        def foo; end
+        attr_reader :bar
+      end
+      1_000_000.times{''} # cause GC
+    }
+  end
 end