Return a theoretical upper bound on this set's size.
Declared in <bslstl_unorderedset.h>
unordered_set<KEY, HASH, EQUAL, ALLOCATOR>::size_type
max_size() const noexcept;
Return a theoretical upper bound on the largest number of elements that this set could possibly hold. Note that there is no guarantee that the set can successfully grow to the returned size, or even close to that size without running out of resources.
theoretical maximum number of elements