23 General utilities library [utilities]

23.11 Smart pointers [smartptr]

23.11.4 Class template weak_­ptr [util.smartptr.weak]

23.11.4.1 weak_­ptr constructors [util.smartptr.weak.const]

constexpr weak_ptr() noexcept;
Effects: Constructs an empty weak_­ptr object.
Postconditions: use_­count() == 0.
weak_ptr(const weak_ptr& r) noexcept; template<class Y> weak_ptr(const weak_ptr<Y>& r) noexcept; template<class Y> weak_ptr(const shared_ptr<Y>& r) noexcept;
Remarks: The second and third constructors shall not participate in overload resolution unless Y* is compatible with T*.
Effects: If r is empty, constructs an empty weak_­ptr object; otherwise, constructs a weak_­ptr object that shares ownership with r and stores a copy of the pointer stored in r.
Postconditions: use_­count() == r.use_­count().
weak_ptr(weak_ptr&& r) noexcept; template<class Y> weak_ptr(weak_ptr<Y>&& r) noexcept;
Remarks: The second constructor shall not participate in overload resolution unless Y* is compatible with T*.
Effects: Move constructs a weak_­ptr instance from r.
Postconditions: *this shall contain the old value of r.
r shall be empty.
r.use_­count() == 0.