Truncate strings synchronized.

src/objects-inl.h

 // 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 4313 matching lines @@
 int HeapObject::SizeFromMap(Map* map) {
   int instance_size = map->instance_size();
   if (instance_size != kVariableSizeSentinel) return instance_size;
   // Only inline the most frequent cases.
   InstanceType instance_type = map->instance_type();
   if (instance_type == FIXED_ARRAY_TYPE) {
     return FixedArray::BodyDescriptor::SizeOf(map, this);
   }
   if (instance_type == ONE_BYTE_STRING_TYPE ||
       instance_type == ONE_BYTE_INTERNALIZED_STRING_TYPE) {
+    // Strings may get concurrently truncated, hence we have to access its
+    // length synchronized.
     return SeqOneByteString::SizeFor(
-        reinterpret_cast<SeqOneByteString*>(this)->length());
+        reinterpret_cast<SeqOneByteString*>(this)->synchronized_length());
   }
   if (instance_type == BYTE_ARRAY_TYPE) {
     return reinterpret_cast<ByteArray*>(this)->ByteArraySize();
   }
   if (instance_type == FREE_SPACE_TYPE) {
     return reinterpret_cast<FreeSpace*>(this)->nobarrier_size();
   }
   if (instance_type == STRING_TYPE ||
       instance_type == INTERNALIZED_STRING_TYPE) {
+    // Strings may get concurrently truncated, hence we have to access its
+    // length synchronized.
     return SeqTwoByteString::SizeFor(
-        reinterpret_cast<SeqTwoByteString*>(this)->length());
+        reinterpret_cast<SeqTwoByteString*>(this)->synchronized_length());
   }
   if (instance_type == FIXED_DOUBLE_ARRAY_TYPE) {
     return FixedDoubleArray::SizeFor(
         reinterpret_cast<FixedDoubleArray*>(this)->length());
   }
   if (instance_type == CONSTANT_POOL_ARRAY_TYPE) {
     return reinterpret_cast<ConstantPoolArray*>(this)->size();
   }
   if (instance_type >= FIRST_FIXED_TYPED_ARRAY_TYPE &&
       instance_type <= LAST_FIXED_TYPED_ARRAY_TYPE) {
@@ skipping 2959 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_