The use_count member
function returns the number of std::experimental::shared_ptr instances and std::experimental::atomic_shared_ptr instances
sharing ownership with *this. It is an instantaneous snapshot,
and in multithreaded systems the value may vary between consecutive calls
due to the actions of other threads.
long use_count() const noexcept;
The number of std::experimental::shared_ptr and std::experimental::atomic_shared_ptr instances
sharing ownership with *this at the point of the call.
Nothing
std::experimental::weak_ptr instances do
not count towards the value returned by use_count().
#include <experimental/atomic>