Make Failure inherit from MaybeObject instead of Object.

src/objects-inl.h

 // Copyright 2006-2008 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
@@ skipping 378 matching lines @@
 }
 
 
 bool Object::IsExternalFloatArray() {
   return Object::IsHeapObject() &&
       HeapObject::cast(this)->map()->instance_type() ==
       EXTERNAL_FLOAT_ARRAY_TYPE;
 }
 
 
-bool Object::IsFailure() {
+bool MaybeObject::IsFailure() {
   return HAS_FAILURE_TAG(this);
 }
 
 
-bool Object::IsRetryAfterGC() {
+bool MaybeObject::IsRetryAfterGC() {
   return HAS_FAILURE_TAG(this)
     && Failure::cast(this)->type() == Failure::RETRY_AFTER_GC;
 }
 
 
-bool Object::IsOutOfMemoryFailure() {
+bool MaybeObject::IsOutOfMemory() {
   return HAS_FAILURE_TAG(this)
     && Failure::cast(this)->IsOutOfMemoryException();
 }
 
 
-bool Object::IsException() {
+bool MaybeObject::IsException() {
   return this == Failure::Exception();
 }
 
 
+bool MaybeObject::IsTheHole() {
+  return this == Heap::the_hole_value();
+}
+
+
+Failure* Failure::cast(MaybeObject* obj) {
+  ASSERT(HAS_FAILURE_TAG(obj));
+  return reinterpret_cast<Failure*>(obj);
+}
+
+
 bool Object::IsJSObject() {
   return IsHeapObject()
     && HeapObject::cast(this)->map()->instance_type() >= FIRST_JS_OBJECT_TYPE;
 }
 
 
 bool Object::IsJSContextExtensionObject() {
   return IsHeapObject()
     && (HeapObject::cast(this)->map()->instance_type() ==
         JS_CONTEXT_EXTENSION_OBJECT_TYPE);
@@ skipping 239 matching lines @@
   }
   STRUCT_LIST(MAKE_STRUCT_PREDICATE)
 #undef MAKE_STRUCT_PREDICATE
 
 
 bool Object::IsUndefined() {
   return this == Heap::undefined_value();
 }
 
 
-bool Object::IsTheHole() {
-  return this == Heap::the_hole_value();
-}
-
-
 bool Object::IsNull() {
   return this == Heap::null_value();
 }
 
 
 bool Object::IsTrue() {
   return this == Heap::true_value();
 }
 
 
 bool Object::IsFalse() {
   return this == Heap::false_value();
 }
 
 
 double Object::Number() {
   ASSERT(IsNumber());
   return IsSmi()
     ? static_cast<double>(reinterpret_cast<Smi*>(this)->value())
     : reinterpret_cast<HeapNumber*>(this)->value();
 }
 
 
 
-Object* Object::ToSmi() {
+MaybeObject* Object::ToSmi() {
   if (IsSmi()) return this;
   if (IsHeapNumber()) {
     double value = HeapNumber::cast(this)->value();
     int int_value = FastD2I(value);
     if (value == FastI2D(int_value) && Smi::IsValid(int_value)) {
       return Smi::FromInt(int_value);
     }
   }
   return Failure::Exception();
 }
 
 
 bool Object::HasSpecificClassOf(String* name) {
   return this->IsJSObject() && (JSObject::cast(this)->class_name() == name);
 }
 
 
-Object* Object::GetElement(uint32_t index) {
+MaybeObject* Object::GetElement(uint32_t index) {
   return GetElementWithReceiver(this, index);
 }
 
 
-Object* Object::GetProperty(String* key) {
+Object* Object::GetElementNoExceptionThrown(uint32_t index) {
+  MaybeObject* maybe = GetElementWithReceiver(this, index);
+  ASSERT(!maybe->IsFailure());
+  Object* result = NULL;  // Initialization to please compiler.
+  maybe->ToObject(&result);
+  return result;
+}
+
+
+MaybeObject* Object::GetProperty(String* key) {
   PropertyAttributes attributes;
   return GetPropertyWithReceiver(this, key, &attributes);
 }
 
 
-Object* Object::GetProperty(String* key, PropertyAttributes* attributes) {
+MaybeObject* Object::GetProperty(String* key, PropertyAttributes* attributes) {
   return GetPropertyWithReceiver(this, key, attributes);
 }
 
 
 #define FIELD_ADDR(p, offset) \
   (reinterpret_cast<byte*>(p) + offset - kHeapObjectTag)
 
 #define READ_FIELD(p, offset) \
   (*reinterpret_cast<Object**>(FIELD_ADDR(p, offset)))
 
@@ skipping 433 matching lines @@
 }
 
 
 void JSObject::initialize_elements() {
   ASSERT(map()->has_fast_elements());
   ASSERT(!Heap::InNewSpace(Heap::empty_fixed_array()));
   WRITE_FIELD(this, kElementsOffset, Heap::empty_fixed_array());
 }
 
 
-Object* JSObject::ResetElements() {
-  Object* obj = map()->GetFastElementsMap();
-  if (obj->IsFailure()) return obj;
+MaybeObject* JSObject::ResetElements() {
+  Object* obj;
+  { MaybeObject* maybe_obj = map()->GetFastElementsMap();
+    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  }
   set_map(Map::cast(obj));
   initialize_elements();
   return this;
 }
 
 
 ACCESSORS(Oddball, to_string, String, kToStringOffset)
 ACCESSORS(Oddball, to_number, Object, kToNumberOffset)
 
 
@@ skipping 469 matching lines @@
 CAST_ACCESSOR(String)
 CAST_ACCESSOR(SeqString)
 CAST_ACCESSOR(SeqAsciiString)
 CAST_ACCESSOR(SeqTwoByteString)
 CAST_ACCESSOR(ConsString)
 CAST_ACCESSOR(ExternalString)
 CAST_ACCESSOR(ExternalAsciiString)
 CAST_ACCESSOR(ExternalTwoByteString)
 CAST_ACCESSOR(JSObject)
 CAST_ACCESSOR(Smi)
-CAST_ACCESSOR(Failure)
 CAST_ACCESSOR(HeapObject)
 CAST_ACCESSOR(HeapNumber)
 CAST_ACCESSOR(Oddball)
 CAST_ACCESSOR(JSGlobalPropertyCell)
 CAST_ACCESSOR(SharedFunctionInfo)
 CAST_ACCESSOR(Map)
 CAST_ACCESSOR(JSFunction)
 CAST_ACCESSOR(GlobalObject)
 CAST_ACCESSOR(JSGlobalProxy)
 CAST_ACCESSOR(JSGlobalObject)
@@ skipping 52 matching lines @@
 
 bool String::Equals(String* other) {
   if (other == this) return true;
   if (StringShape(this).IsSymbol() && StringShape(other).IsSymbol()) {
     return false;
   }
   return SlowEquals(other);
 }
 
 
-Object* String::TryFlatten(PretenureFlag pretenure) {
+MaybeObject* String::TryFlatten(PretenureFlag pretenure) {
   if (!StringShape(this).IsCons()) return this;
   ConsString* cons = ConsString::cast(this);
   if (cons->second()->length() == 0) return cons->first();
   return SlowTryFlatten(pretenure);
 }
 
 
 String* String::TryFlattenGetString(PretenureFlag pretenure) {
-  Object* flat = TryFlatten(pretenure);
-  return flat->IsFailure() ? this : String::cast(flat);
+  MaybeObject* flat = TryFlatten(pretenure);
+  Object* successfully_flattened;
+  if (flat->ToObject(&successfully_flattened)) {
+    return String::cast(successfully_flattened);
+  }
+  return this;
 }
 
 
 uint16_t String::Get(int index) {
   ASSERT(index >= 0 && index < length());
   switch (StringShape(this).full_representation_tag()) {
     case kSeqStringTag | kAsciiStringTag:
       return SeqAsciiString::cast(this)->SeqAsciiStringGet(index);
     case kSeqStringTag | kTwoByteStringTag:
       return SeqTwoByteString::cast(this)->SeqTwoByteStringGet(index);
@@ skipping 690 matching lines @@
 }
 
 
 void Map::set_prototype(Object* value, WriteBarrierMode mode) {
   ASSERT(value->IsNull() || value->IsJSObject());
   WRITE_FIELD(this, kPrototypeOffset, value);
   CONDITIONAL_WRITE_BARRIER(this, kPrototypeOffset, mode);
 }
 
 
-Object* Map::GetFastElementsMap() {
+MaybeObject* Map::GetFastElementsMap() {
   if (has_fast_elements()) return this;
-  Object* obj = CopyDropTransitions();
-  if (obj->IsFailure()) return obj;
+  Object* obj;
+  { MaybeObject* maybe_obj = CopyDropTransitions();
+    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  }
   Map* new_map = Map::cast(obj);
   new_map->set_has_fast_elements(true);
   Counters::map_slow_to_fast_elements.Increment();
   return new_map;
 }
 
 
-Object* Map::GetSlowElementsMap() {
+MaybeObject* Map::GetSlowElementsMap() {
   if (!has_fast_elements()) return this;
-  Object* obj = CopyDropTransitions();
-  if (obj->IsFailure()) return obj;
+  Object* obj;
+  { MaybeObject* maybe_obj = CopyDropTransitions();
+    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  }
   Map* new_map = Map::cast(obj);
   new_map->set_has_fast_elements(false);
   Counters::map_fast_to_slow_elements.Increment();
   return new_map;
 }
 
 
 ACCESSORS(Map, instance_descriptors, DescriptorArray,
           kInstanceDescriptorsOffset)
 ACCESSORS(Map, code_cache, Object, kCodeCacheOffset)
@@ skipping 679 matching lines @@
 }
 
 
 bool JSObject::AllowsSetElementsLength() {
   bool result = elements()->IsFixedArray();
   ASSERT(result == (!HasPixelElements() && !HasExternalArrayElements()));
   return result;
 }
 
 
-Object* JSObject::EnsureWritableFastElements() {
+MaybeObject* JSObject::EnsureWritableFastElements() {
   ASSERT(HasFastElements());
   FixedArray* elems = FixedArray::cast(elements());
   if (elems->map() != Heap::fixed_cow_array_map()) return elems;
-  Object* writable_elems = Heap::CopyFixedArrayWithMap(elems,
-                                                       Heap::fixed_array_map());
-  if (writable_elems->IsFailure()) return writable_elems;
+  Object* writable_elems;
+  { MaybeObject* maybe_writable_elems =
+        Heap::CopyFixedArrayWithMap(elems, Heap::fixed_array_map());
+    if (!maybe_writable_elems->ToObject(&writable_elems)) {
+      return maybe_writable_elems;
+    }
+  }
   set_elements(FixedArray::cast(writable_elems));
   Counters::cow_arrays_converted.Increment();
   return writable_elems;
 }
 
 
 StringDictionary* JSObject::property_dictionary() {
   ASSERT(!HasFastProperties());
   return StringDictionary::cast(properties());
 }
@@ skipping 124 matching lines @@
   ASSERT(!IsJSGlobalProxy());
   return GetPropertyAttributePostInterceptor(this,
                                              Heap::hidden_symbol(),
                                              false) != ABSENT;
 }
 
 
 Object* JSObject::GetHiddenPropertiesObject() {
   ASSERT(!IsJSGlobalProxy());
   PropertyAttributes attributes;
-  return GetLocalPropertyPostInterceptor(this,
-                                         Heap::hidden_symbol(),
-                                         &attributes);
+  // You can't install a getter on a property indexed by the hidden symbol,
+  // so we can be sure that GetLocalPropertyPostInterceptor returns a real
+  // object.
+  Object* result =
+      GetLocalPropertyPostInterceptor(this,
+                                      Heap::hidden_symbol(),
+                                      &attributes)->ToObjectUnchecked();
+  return result;
 }
 
 
-Object* JSObject::SetHiddenPropertiesObject(Object* hidden_obj) {
+MaybeObject* JSObject::SetHiddenPropertiesObject(Object* hidden_obj) {
   ASSERT(!IsJSGlobalProxy());
   return SetPropertyPostInterceptor(Heap::hidden_symbol(),
                                     hidden_obj,
                                     DONT_ENUM);
 }
 
 
 bool JSObject::HasElement(uint32_t index) {
   return HasElementWithReceiver(this, index);
 }
@@ skipping 86 matching lines @@
   set_length(static_cast<Object*>(length), SKIP_WRITE_BARRIER);
 }
 
 
 void JSArray::SetContent(FixedArray* storage) {
   set_length(Smi::FromInt(storage->length()));
   set_elements(storage);
 }
 
 
-Object* FixedArray::Copy() {
+MaybeObject* FixedArray::Copy() {
   if (length() == 0) return this;
   return Heap::CopyFixedArray(this);
 }
 
 
 int JSObject::BodyDescriptor::SizeOf(Map* map, HeapObject* object) {
   return map->instance_size();
 }
 
 
@@ skipping 77 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_