* this heap never changes.
*/
protected void walk(ObjectVisitor visitor, boolean locking, Word flagsMask, Word flagsValue) {
// Go through the heap and mark all objects in the allocation bitmap.
final Word headerSize = Word.fromIntZeroExtend(this.headerSize);
final Offset sizeOffset = this.sizeOffset;
final Word size = Word.fromIntZeroExtend(getSize());
Word offset = headerSize;
while (offset.LT(size)) {
final Address ptr = start.add(offset);
final Object object = ptr.toObjectReference().toObject();