The standard currently does not discuss when library objects may be accessed, except in a non-normative note pertaining to synchronization in [res.on.objects], leaving it ambiguous whether single-threaded code can access a library object during its construction or destruction. For example, there is a reasonable question as to what happens if the deleter supplied to a unique_ptr transitively accesses the unique_ptr itself during unique_ptr's destruction; a straightforward reading suggests that this is permitted, and that the deleter will see the unique_ptr still holding the originally stored pointer, but consensus on the LWG reflector indicates this was not the intent (see discussion beginning with c++std-lib-33362).