Atomically replaces the current value with
desired. Memory is affected according to the value of
|desired||-|| the |
|order||-||memory order constraints to enforce|
 Return value
All changes to the
atomic_weak_ptr object itself, and all associated use_count increments, are guaranteed to be performed atomically. Associated
use_count decrements take place after the atomic operation, but are not required to be part of it. Any associated destruction or deallocation operations take place after the atomic operation and are not part of it.