Revision: 12704
Author:   verwa...@chromium.org
Date:     Thu Oct 11 08:33:34 2012
Log:      Don't clear EnumLength but rather copy the enum cache. Added  
regression test for crashes from chromecrash.

Review URL: https://chromiumcodereview.appspot.com/11103036
http://code.google.com/p/v8/source/detail?r=12704

Added:
  /branches/bleeding_edge/test/mjsunit/regress/regress-convert-enum.js
Modified:
  /branches/bleeding_edge/src/objects.cc

=======================================
--- /dev/null
+++ /branches/bleeding_edge/test/mjsunit/regress/regress-convert-enum.js        
Thu Oct 11 08:33:34 2012
@@ -0,0 +1,60 @@
+// 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) { }
=======================================
--- /branches/bleeding_edge/src/objects.cc      Thu Oct 11 05:01:19 2012
+++ /branches/bleeding_edge/src/objects.cc      Thu Oct 11 08:33:34 2012
@@ -1806,6 +1806,9 @@
      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 @@
        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);