Add workaround for redefinition of __proto__ property.

This is a temporary workaround when the __proto__ property is being
redefined (e.g. by Object.freeze()) to not loose the foreign callback.
Once the __proto__ property is a real JavaScript accessor this hack is
no longer necessary. This change also makes __proto__ configurable.

R=rossberg@chromium.org
BUG=v8:2565
TEST=mjsunit/regress/regress-2565

Review URL: https://codereview.chromium.org/12398010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13817 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/bootstrapper.cc

@@ -493,8 +493,7 @@ Handle<JSFunction> Genesis::CreateEmptyFunction(Isolate* isolate) {
 
     Handle<Foreign> object_prototype(
         factory->NewForeign(&Accessors::ObjectPrototype));
-    PropertyAttributes attribs = static_cast<PropertyAttributes>(
-        DONT_ENUM | DONT_DELETE);
+    PropertyAttributes attribs = static_cast<PropertyAttributes>(DONT_ENUM);
     object_prototype_map->set_instance_descriptors(*prototype_descriptors);
 
     {  // Add __proto__.

src/runtime.cc

@@ -4099,6 +4099,14 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_DefineOrRedefineDataProperty) {
     if (callback->IsAccessorInfo()) {
       return isolate->heap()->undefined_value();
     }
+    // TODO(mstarzinger): The __proto__ property should actually be a real
+    // JavaScript accessor instead of a foreign callback. But for now we just
+    // avoid changing the writability and configurability attribute of this
+    // property.
+    Handle<Name> proto_string = isolate->factory()->proto_string();
+    if (callback->IsForeign() && proto_string->Equals(*name)) {
+      attr = static_cast<PropertyAttributes>(attr & ~(READ_ONLY | DONT_DELETE));
+    }
     // Avoid redefining foreign callback as data property, just use the stored
     // setter to update the value instead.
     // TODO(mstarzinger): So far this only works if property attributes don't

test/mjsunit/regress/regress-2565.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.
+
+Object.freeze(Object.prototype);
+var p = {};
+var o = Object.create(p);
+assertSame(p, o.__proto__);
+assertSame(p, Object.getPrototypeOf(o));