- Do not visit length and hash of string objects. They are guaranteed to be Smi.

runtime/vm/raw_object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/raw_object.h"
 
 #include "vm/class_table.h"
 #include "vm/freelist.h"
 #include "vm/isolate.h"
 #include "vm/object.h"
@@ skipping 653 matching lines @@
 intptr_t RawString::VisitStringPointers(RawString* raw_obj,
                                         ObjectPointerVisitor* visitor) {
   // String is an abstract class.
   UNREACHABLE();
   return 0;
 }
 
 
 intptr_t RawOneByteString::VisitOneByteStringPointers(
     RawOneByteString* raw_obj, ObjectPointerVisitor* visitor) {
+  ASSERT(!raw_obj->ptr()->length_->IsHeapObject());
+  ASSERT(!raw_obj->ptr()->hash_->IsHeapObject());
   intptr_t length = Smi::Value(raw_obj->ptr()->length_);
-  visitor->VisitPointers(raw_obj->from(), raw_obj->to());
   return OneByteString::InstanceSize(length);
 }
 
 
 intptr_t RawTwoByteString::VisitTwoByteStringPointers(
     RawTwoByteString* raw_obj, ObjectPointerVisitor* visitor) {
+  ASSERT(!raw_obj->ptr()->length_->IsHeapObject());
+  ASSERT(!raw_obj->ptr()->hash_->IsHeapObject());
   intptr_t length = Smi::Value(raw_obj->ptr()->length_);
-  visitor->VisitPointers(raw_obj->from(), raw_obj->to());
   return TwoByteString::InstanceSize(length);
 }
 
 
 intptr_t RawExternalOneByteString::VisitExternalOneByteStringPointers(
     RawExternalOneByteString* raw_obj, ObjectPointerVisitor* visitor) {
   // Make sure that we got here with the tagged pointer as this.
   ASSERT(raw_obj->IsHeapObject());
   visitor->VisitPointers(raw_obj->from(), raw_obj->to());
   return ExternalOneByteString::InstanceSize();
@@ skipping 265 matching lines @@
 
 intptr_t RawWeakProperty::VisitWeakPropertyPointers(
     RawWeakProperty* raw_obj, ObjectPointerVisitor* visitor) {
   // Make sure that we got here with the tagged pointer as this.
   ASSERT(raw_obj->IsHeapObject());
   visitor->VisitPointers(raw_obj->from(), raw_obj->to());
   return WeakProperty::InstanceSize();
 }
 
 }  // namespace dart