[handles] Sanitize Handle and friends.

src/handles.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 "src/v8.h"
 
 #include "src/handles.h"
 
 namespace v8 {
 namespace internal {
 
+#ifdef DEBUG
+bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {
+  DCHECK_NOT_NULL(location_);
+  Object* object = *location_;
+  if (object->IsSmi()) return true;
+  HeapObject* heap_object = HeapObject::cast(object);
+  Heap* heap = heap_object->GetHeap();
+  Object** roots_array_start = heap->roots_array_start();
+  if (roots_array_start <= location_ &&
+      location_ < roots_array_start + Heap::kStrongRootListLength &&
+      heap->RootCanBeTreatedAsConstant(
+          static_cast<Heap::RootListIndex>(location_ - roots_array_start))) {
+    return true;
+  }
+  if (!AllowHandleDereference::IsAllowed()) return false;
+  if (mode == INCLUDE_DEFERRED_CHECK &&
+      !AllowDeferredHandleDereference::IsAllowed()) {
+    // Accessing cells, maps and internalized strings is safe.
+    if (heap_object->IsCell()) return true;
+    if (heap_object->IsMap()) return true;
+    if (heap_object->IsInternalizedString()) return true;
+    return !heap->isolate()->IsDeferredHandle(location_);
+  }
+  return true;
+}
+#endif
+
+
 int HandleScope::NumberOfHandles(Isolate* isolate) {
   HandleScopeImplementer* impl = isolate->handle_scope_implementer();
   int n = impl->blocks()->length();
   if (n == 0) return 0;
   return ((n - 1) * kHandleBlockSize) + static_cast<int>(
       (isolate->handle_scope_data()->next - impl->blocks()->last()));
 }
 
 
 Object** HandleScope::Extend(Isolate* isolate) {
@@ skipping 38 matching lines @@
 void HandleScope::DeleteExtensions(Isolate* isolate) {
   HandleScopeData* current = isolate->handle_scope_data();
   isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
 }
 
 
 #ifdef ENABLE_HANDLE_ZAPPING
 void HandleScope::ZapRange(Object** start, Object** end) {
   DCHECK(end - start <= kHandleBlockSize);
   for (Object** p = start; p != end; p++) {
-    *reinterpret_cast<Address*>(p) = v8::internal::kHandleZapValue;
+    *reinterpret_cast<Address*>(p) = kHandleZapValue;
   }
 }
 #endif
 
 
 Address HandleScope::current_level_address(Isolate* isolate) {
   return reinterpret_cast<Address>(&isolate->handle_scope_data()->level);
 }
 
 
@@ skipping 40 matching lines @@
   data->next = prev_next_;
   data->limit = prev_limit_;
 #ifdef DEBUG
   handles_detached_ = true;
 #endif
   return deferred;
 }
 
 }  // namespace internal
 }  // namespace v8