Construct a new std::experimental::weak_ptr object that shares
ownership the supplied std::experimental::weak_ptr instance.
template<class Target> explicit weak_ptr(weak_ptr<Target> const& p) noexcept;
Target*
is implicitly convertible to T*.
Construct a new std::experimental::weak_ptr instance that
shares ownership with p
this->use_count()==p.use_count()
and !this->owner_before(p). !p.owner_before(*this).
p.use_count()
is unchanged.
Nothing.
#include <experimental/atomic>