Ensure slow properties for simple {__proto__:null} literals.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index f76aa35bbea0674adbc27d5b3da24a21c7fae67d..9c60a0b24a60588789827b48c8f20e033f2dc60a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -597,6 +597,15 @@ Handle<JSFunction> Genesis::CreateEmptyFunction(Isolate* isolate) {
     native_context()->set_initial_array_prototype(*object_function_prototype);
     Accessors::FunctionSetPrototype(object_fun, object_function_prototype)
         .Assert();
+
+    // Set up the map for Object.create(null) instances.
+    Handle<Map> slow_object_with_null_prototype_map =
+        Map::CopyInitialMap(handle(object_fun->initial_map(), isolate));
+    slow_object_with_null_prototype_map->set_dictionary_map(true);
+    Map::SetPrototype(slow_object_with_null_prototype_map,
+                      isolate->factory()->null_value());
+    native_context()->set_slow_object_with_null_prototype_map(
+        *slow_object_with_null_prototype_map);

[Toon Verwaest, 2017/03/14 13:27:47]

This already exists?

[Camillo Bruni, 2017/03/17 16:40:55]

just moved to here, so it's available earlier in the bootstrapping for the
unscopable Array properties.

   }
 
   // Allocate the empty function as the prototype for function - ES6 19.2.3
@@ -4050,20 +4059,13 @@ bool Genesis::InstallNatives(GlobalContextType context_type) {
 
   // Store the map for the %ObjectPrototype% after the natives has been compiled
   // and the Object function has been set up.
-  Handle<JSFunction> object_function(native_context()->object_function());
-  DCHECK(JSObject::cast(object_function->initial_map()->prototype())
-             ->HasFastProperties());
-  native_context()->set_object_function_prototype_map(
-      HeapObject::cast(object_function->initial_map()->prototype())->map());
-
-  // Set up the map for Object.create(null) instances.
-  Handle<Map> slow_object_with_null_prototype_map =
-      Map::CopyInitialMap(handle(object_function->initial_map(), isolate()));
-  slow_object_with_null_prototype_map->set_dictionary_map(true);
-  Map::SetPrototype(slow_object_with_null_prototype_map,
-                    isolate()->factory()->null_value());
-  native_context()->set_slow_object_with_null_prototype_map(
-      *slow_object_with_null_prototype_map);
+  {
+    Handle<JSFunction> object_function(native_context()->object_function());
+    DCHECK(JSObject::cast(object_function->initial_map()->prototype())
+               ->HasFastProperties());
+    native_context()->set_object_function_prototype_map(
+        HeapObject::cast(object_function->initial_map()->prototype())->map());
+  }
 
   // Store the map for the %StringPrototype% after the natives has been compiled
   // and the String function has been set up.