20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.2 Shared-ownership pointers [util.sharedptr]

20.3.2.3 Class template weak_ptr [util.smartptr.weak]

20.3.2.3.6 Observers [util.smartptr.weak.obs]

long use_count() const noexcept;

Returns: 0 if *this is empty; otherwise, the number of shared_ptr instances that share ownership with *this.

🔗

bool expired() const noexcept;

Returns: use_count() == 0.

🔗

shared_ptr<T> lock() const noexcept;

Returns: expired() ? shared_ptr<T>() : shared_ptr<T>(*this), executed atomically.

🔗

template<class U> bool owner_before(const shared_ptr<U>& b) const noexcept;
template<class U> bool owner_before(const weak_ptr<U>& b) const noexcept;

Returns: An unspecified value such that

(4.1)
owner_before(b) defines a strict weak ordering as defined in [alg.sorting];
(4.2)
!owner_before(b) && !b.owner_before(*this) is true if and only if owner_equal(b) is true.

🔗

size_t owner_hash() const noexcept;

Returns: An unspecified value such that, for any object x where owner_equal(x) is true, owner_hash() == x.owner_hash() is true.

🔗

template<class U>
  bool owner_equal(const shared_ptr<U>& b) const noexcept;
template<class U>
  bool owner_equal(const weak_ptr<U>& b) const noexcept;

Returns: true if and only if *this and b share ownership or are both empty.

Otherwise returns false.

Remarks: owner_equal is an equivalence relation.