class SizeTracker

SizeTracker is a partially specialized internal class used to track (or

explicitly to not track) the size of Lists in the fbl:: containers. Its

behavior and size depends on the SizeOrder template parameter passed to it.

Please note that to use this class the [[no_unique_address]] tag should be

be used to ensure the SizeOrder::N version of the tracker, which is nominally

of 0 size, does not have any storage allocated.

static_assert tests for this exist in the non-sized doubly and singly linked

list tests.