Fix unexpected elements transition in JSON.parse

R=verwaest@chromium.org
BUG=241344

Review URL: https://chromiumcodereview.appspot.com/15739003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14746 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects-inl.h

@@ -1505,9 +1505,19 @@ MaybeObject* JSObject::ResetElements() {
 
 MaybeObject* JSObject::AllocateStorageForMap(Map* map) {
   ASSERT(this->map()->inobject_properties() == map->inobject_properties());
-  ElementsKind expected_kind = this->map()->elements_kind();
-  if (map->elements_kind() != expected_kind) {
-    MaybeObject* maybe_map = map->AsElementsKind(expected_kind);
+  ElementsKind obj_kind = this->map()->elements_kind();
+  ElementsKind map_kind = map->elements_kind();
+  if (map_kind != obj_kind) {
+    ElementsKind to_kind = map_kind;
+    if (IsMoreGeneralElementsKindTransition(map_kind, obj_kind) ||
+        IsDictionaryElementsKind(obj_kind)) {
+      to_kind = obj_kind;
+    }
+    MaybeObject* maybe_obj =
+        IsDictionaryElementsKind(to_kind) ? NormalizeElements()
+                                          : TransitionElementsKind(to_kind);
+    if (maybe_obj->IsFailure()) return maybe_obj;
+    MaybeObject* maybe_map = map->AsElementsKind(to_kind);
     if (!maybe_map->To(&map)) return maybe_map;
   }
   int total_size =

test/mjsunit/regress/regress-241344.js

+// Copyright 2013 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.
+
+// Create a JSON string for an object with indexed properties.
+// Parsing that string creates a sparse array that grows dense.
+
+var jsonstring = '{"0":0.1, "10000":0.4, ';
+for (var i = 1; i < 9999; i++) {
+  jsonstring += '"' + i + '":0.2, ';
+}
+jsonstring += '"9999":0.3}';
+
+var jsonobject = JSON.parse(jsonstring);
+for (var i = 1; i < 9999; i++) {
+  assertEquals(0.2, jsonobject[i]);
+}