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

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 579 matching lines @@
     map->set_immutable_proto(true);
     object_function_prototype->set_map(*map);
 
     native_context()->set_initial_object_prototype(*object_function_prototype);
     // For bootstrapping set the array prototype to be the same as the object
     // prototype, otherwise the missing initial_array_prototype will cause
     // assertions during startup.
     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
   Handle<Code> code(isolate->builtins()->EmptyFunction());
   Handle<JSFunction> empty_function =
       factory->NewFunctionWithoutPrototype(factory->empty_string(), code);
 
   // Allocate the function map first and then patch the prototype later
   Handle<Map> empty_function_map =
       factory->CreateSloppyFunctionMap(FUNCTION_WITHOUT_PROTOTYPE);
@@ skipping 3433 matching lines @@
   native_context()->set_fast_template_instantiations_cache(
       *fast_template_instantiations_cache);
 
   auto slow_template_instantiations_cache = UnseededNumberDictionary::New(
       isolate(), ApiNatives::kInitialFunctionCacheSize);
   native_context()->set_slow_template_instantiations_cache(
       *slow_template_instantiations_cache);
 
   // 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.
   Handle<JSFunction> string_function(native_context()->string_function());
   JSObject* string_function_prototype =
       JSObject::cast(string_function->initial_map()->prototype());
   DCHECK(string_function_prototype->HasFastProperties());
   native_context()->set_string_function_prototype_map(
       string_function_prototype->map());
 
@@ skipping 1044 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8