Protect the emptiness of Array prototype elements with a PropertyCell.

src/isolate.cc

 // Copyright 2012 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 <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/v8.h"
@@ skipping 2357 matching lines @@
 
 
 bool Isolate::use_crankshaft() const {
   return FLAG_crankshaft &&
          !serializer_enabled_ &&
          CpuFeatures::SupportsCrankshaft();
 }
 
 
 bool Isolate::IsFastArrayConstructorPrototypeChainIntact() {
+  Handle<PropertyCell> no_elements_cell =
+      handle(heap()->array_protector(), this);
+  bool cell_reports_intact = no_elements_cell->value()->IsSmi() &&
+                             Smi::cast(no_elements_cell->value())->value() == 1;
+
+#ifdef DEBUG
   Map* root_array_map =
       get_initial_js_array_map(GetInitialFastElementsKind());
-  DCHECK(root_array_map != NULL);
   JSObject* initial_array_proto = JSObject::cast(*initial_array_prototype());
+  JSObject* initial_object_proto = JSObject::cast(*initial_object_prototype());
+
+  if (root_array_map == NULL || initial_array_proto == initial_object_proto) {
+    // We are in the bootstrapping process, and the entire check sequence
+    // shouldn't be performed.
+    return cell_reports_intact;
+  }
 
   // Check that the array prototype hasn't been altered WRT empty elements.
-  if (root_array_map->prototype() != initial_array_proto) return false;
+  if (root_array_map->prototype() != initial_array_proto) {
+    DCHECK_EQ(false, cell_reports_intact);
+    return cell_reports_intact;
+  }
+
   if (initial_array_proto->elements() != heap()->empty_fixed_array()) {
-    return false;
+    DCHECK_EQ(false, cell_reports_intact);
+    return cell_reports_intact;
   }
 
   // Check that the object prototype hasn't been altered WRT empty elements.
-  JSObject* initial_object_proto = JSObject::cast(*initial_object_prototype());
   PrototypeIterator iter(this, initial_array_proto);
   if (iter.IsAtEnd() || iter.GetCurrent() != initial_object_proto) {
-    return false;
+    DCHECK_EQ(false, cell_reports_intact);
+    return cell_reports_intact;
   }
   if (initial_object_proto->elements() != heap()->empty_fixed_array()) {
-    return false;
+    DCHECK_EQ(false, cell_reports_intact);
+    return cell_reports_intact;
   }
 
   iter.Advance();
-  return iter.IsAtEnd();
+  if (!iter.IsAtEnd()) {
+    DCHECK_EQ(false, cell_reports_intact);
+    return cell_reports_intact;
+  }
+
+#endif
+
+  return cell_reports_intact;
 }
 
 
+void Isolate::UpdateArrayProtectorOnSetElement(Handle<JSObject> object) {
+  Handle<PropertyCell> array_protector = factory()->array_protector();
+  if (IsFastArrayConstructorPrototypeChainIntact() &&
+      object->map()->is_prototype_map()) {
+    Object* context = heap()->native_contexts_list();
+    while (!context->IsUndefined()) {
+      Context* current_context = Context::cast(context);
+      if (current_context->get(Context::INITIAL_OBJECT_PROTOTYPE_INDEX) ==
+              *object ||
+          current_context->get(Context::INITIAL_ARRAY_PROTOTYPE_INDEX) ==
+              *object) {
+        PrintF("INVALIDATING YOU!!!\n");

[Jakob Kummerow, 2015/04/22 08:02:20]

yeah...

[mvstanton, 2015/04/22 09:39:07]

I've discovered a bit of drama livens up the workday.

+        PropertyCell::SetValueWithInvalidation(array_protector,
+                                               handle(Smi::FromInt(0), this));
+        break;
+      }
+      context = current_context->get(Context::NEXT_CONTEXT_LINK);
+    }
+  }
+}
+
+
+bool Isolate::IsAnyInitialArrayPrototype(Handle<JSArray> array) {
+  if (array->map()->is_prototype_map()) {
+    Object* context = heap()->native_contexts_list();
+    while (!context->IsUndefined()) {
+      Context* current_context = Context::cast(context);
+      if (current_context->get(Context::INITIAL_ARRAY_PROTOTYPE_INDEX) ==
+          *array) {
+        return true;
+      }
+      context = current_context->get(Context::NEXT_CONTEXT_LINK);
+    }
+  }
+  return false;
+}
+
+
 CallInterfaceDescriptorData* Isolate::call_descriptor_data(int index) {
   DCHECK(0 <= index && index < CallDescriptors::NUMBER_OF_DESCRIPTORS);
   return &call_descriptor_data_[index];
 }
 
 
 Object* Isolate::FindCodeObject(Address a) {
   return inner_pointer_to_code_cache()->GcSafeFindCodeForInnerPointer(a);
 }
 
@@ skipping 252 matching lines @@
   if (prev_ && prev_->Intercept(flag)) return true;
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 } }  // namespace v8::internal