Don't clear EnumLength but rather copy the enum cache. Added regression test...

Don't clear EnumLength but rather copy the enum cache. Added regression test for crashes from chromecrash.

Review URL: https://chromiumcodereview.appspot.com/11103036

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12704 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -1806,6 +1806,9 @@ MaybeObject* JSObject::ConvertTransitionToMapTransition(
     Map* map;
     DescriptorArray* new_descriptors = new_map->instance_descriptors();
     DescriptorArray* old_descriptors = old_map->instance_descriptors();
+    if (old_descriptors->HasEnumCache()) {
+      new_descriptors->CopyEnumCacheFrom(old_descriptors);
+    }
     for (Object* current = old_map;
          !current->IsUndefined();
          current = map->GetBackPointer()) {
@@ -1813,8 +1816,6 @@ MaybeObject* JSObject::ConvertTransitionToMapTransition(
       if (!map->HasTransitionArray()) break;
       TransitionArray* transitions = map->transitions();
       if (transitions->descriptors() != old_descriptors) break;
-      // Invalidate the enum caches only if the map did not own its descriptors.
-      if (!owned_descriptors) map->SetEnumLength(Map::kInvalidEnumCache);
       transitions->set_descriptors(new_descriptors);
     }
     old_map->set_owns_descriptors(false);

test/mjsunit/regress/regress-convert-enum.js

+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --expose-gc
+
+// Create a transition tree A (no descriptors) -> B (descriptor for a) -> C
+// (descriptor for a and c), that all share the descriptor array [a,c]. C is the
+// owner of the descriptor array.
+var o = {};
+o.a = 1;
+o.c = 2;
+
+// Add a transition B -> D where D has its own descriptor array [a,b] where b is
+// a constant function.
+var o1 = {};
+o1.a = 1;
+
+// Install an enumeration cache in the descriptor array [a,c] at map B.
+for (var x in o1) { }
+o1.b = function() { return 1; };
+
+// Return ownership of the descriptor array [a,c] to B and trim it to [a].
+o = null;
+gc();
+
+// Convert the transition B -> D into a transition to B -> E so that E uses the
+// instance descriptors [a,b] with b being a field.
+var o2 = {};
+o2.a = 1;
+o2.b = 10;
+
+// Create an object with map B and iterate over it.
+var o3 = {};
+o3.a = 1;
+
+for (var y in o3) { }