Compute next field offset correctly.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 29769)
+++ runtime/vm/object.cc	(working copy)
@@ -480,7 +480,7 @@
     cls.raw_ = class_class_;
     cls.set_handle_vtable(fake.vtable());
     cls.set_instance_size(Class::InstanceSize());
-    cls.set_next_field_offset(Class::InstanceSize());
+    cls.set_next_field_offset(Class::NextFieldOffset());
     cls.set_id(Class::kClassId);
     cls.set_state_bits(0);
     cls.set_is_finalized();
@@ -1662,7 +1662,7 @@
   FakeObject fake;
   result.set_handle_vtable(fake.vtable());
   result.set_instance_size(FakeObject::InstanceSize());
-  result.set_next_field_offset(FakeObject::InstanceSize());
+  result.set_next_field_offset(FakeObject::NextFieldOffset());
   ASSERT((FakeObject::kClassId != kInstanceCid));
   result.set_id(FakeObject::kClassId);
   result.set_state_bits(0);
@@ -2032,7 +2032,7 @@
   intptr_t offset = 0;
   intptr_t type_args_field_offset = kNoTypeArguments;
   if (super.IsNull()) {
-    offset = sizeof(RawObject);
+    offset = Instance::NextFieldOffset();
   } else {
     ASSERT(super.is_finalized() || super.is_prefinalized());
     type_args_field_offset = super.type_arguments_field_offset();
@@ -2394,7 +2394,7 @@
   ASSERT(fake.IsInstance());
   result.set_handle_vtable(fake.vtable());
   result.set_instance_size(FakeInstance::InstanceSize());
-  result.set_next_field_offset(FakeInstance::InstanceSize());
+  result.set_next_field_offset(FakeInstance::NextFieldOffset());
   result.set_id(index);
   result.set_state_bits(0);
   result.set_type_arguments_field_offset_in_words(kNoTypeArguments);
@@ -2426,7 +2426,7 @@
   const Class& result = Class::Handle(New(name, script, token_pos));
   // Instances of a signature class can only be closures.
   result.set_instance_size(Closure::InstanceSize());
-  result.set_next_field_offset(Closure::InstanceSize());
+  result.set_next_field_offset(Closure::NextFieldOffset());
   // Signature classes extend the _FunctionImpl class.
   result.set_super_type(Type::Handle(
       Isolate::Current()->object_store()->function_impl_type()));
@@ -2498,7 +2498,7 @@
     cls.set_super_type(Type::Handle(Type::ObjectType()));
     // Compute instance size. First word contains a pointer to a properly
     // sized typed array once the first native field has been set.
-    intptr_t instance_size = sizeof(RawObject) + kWordSize;
+    intptr_t instance_size = sizeof(RawInstance) + kWordSize;
     cls.set_instance_size(RoundedAllocationSize(instance_size));
     cls.set_next_field_offset(instance_size);
     cls.set_num_native_fields(field_count);
@@ -2514,19 +2514,24 @@
 
 RawClass* Class::NewStringClass(intptr_t class_id) {
   intptr_t instance_size;
+  intptr_t next_field_offset;
   if (class_id == kOneByteStringCid) {
+    next_field_offset = OneByteString::NextFieldOffset();
     instance_size = OneByteString::InstanceSize();
   } else if (class_id == kTwoByteStringCid) {
+    next_field_offset = TwoByteString::NextFieldOffset();
     instance_size = TwoByteString::InstanceSize();
   } else if (class_id == kExternalOneByteStringCid) {
+    next_field_offset = ExternalOneByteString::NextFieldOffset();
     instance_size = ExternalOneByteString::InstanceSize();
   } else {
     ASSERT(class_id == kExternalTwoByteStringCid);
+    next_field_offset = ExternalTwoByteString::NextFieldOffset();
     instance_size = ExternalTwoByteString::InstanceSize();
   }
   Class& result = Class::Handle(New<String>(class_id));
   result.set_instance_size(instance_size);
-  result.set_next_field_offset(instance_size);
+  result.set_next_field_offset(next_field_offset);
   result.set_is_prefinalized();
   return result.raw();
 }
@@ -2537,7 +2542,7 @@
   intptr_t instance_size = TypedData::InstanceSize();
   Class& result = Class::Handle(New<TypedData>(class_id));
   result.set_instance_size(instance_size);
-  result.set_next_field_offset(instance_size);
+  result.set_next_field_offset(TypedData::NextFieldOffset());
   result.set_is_prefinalized();
   return result.raw();
 }
@@ -2547,7 +2552,7 @@
   ASSERT(RawObject::IsTypedDataViewClassId(class_id));
   Class& result = Class::Handle(New<Instance>(class_id));
   result.set_instance_size(0);
-  result.set_next_field_offset(0);
+  result.set_next_field_offset(-1);
   return result.raw();
 }
 
@@ -2557,7 +2562,7 @@
   intptr_t instance_size = ExternalTypedData::InstanceSize();
   Class& result = Class::Handle(New<ExternalTypedData>(class_id));
   result.set_instance_size(instance_size);
-  result.set_next_field_offset(instance_size);
+  result.set_next_field_offset(ExternalTypedData::NextFieldOffset());
   result.set_is_prefinalized();
   return result.raw();
 }
@@ -10814,7 +10819,7 @@
     ASSERT(instance_size != 0);
     uword this_addr = reinterpret_cast<uword>(this->raw_ptr());
     uword other_addr = reinterpret_cast<uword>(other.raw_ptr());
-    for (intptr_t offset = sizeof(RawObject);
+    for (intptr_t offset = Instance::NextFieldOffset();
          offset < instance_size;
          offset += kWordSize) {
       if ((*reinterpret_cast<RawObject**>(this_addr + offset)) !=