20 General utilities library [utilities]

20.11 Smart pointers [smartptr]

20.11.2 Shared-ownership pointers [util.sharedptr]

20.11.2.2 Class template shared_­ptr [util.smartptr.shared]

20.11.2.2.4 Assignment [util.smartptr.shared.assign]

shared_ptr& operator=(const shared_ptr& r) noexcept; template<class Y> shared_ptr& operator=(const shared_ptr<Y>& r) noexcept;
Effects: Equivalent to shared_­ptr(r).swap(*this).
Returns: *this.
[Note 1:
The use count updates caused by the temporary object construction and destruction are not observable side effects, so the implementation can meet the effects (and the implied guarantees) via different means, without creating a temporary.
In particular, in the example: shared_ptr<int> p(new int); shared_ptr<void> q(p); p = p; q = p; both assignments can be no-ops.
— end note]
shared_ptr& operator=(shared_ptr&& r) noexcept; template<class Y> shared_ptr& operator=(shared_ptr<Y>&& r) noexcept;
Effects: Equivalent to shared_­ptr(std​::​move(r)).swap(*this).
Returns: *this.
template<class Y, class D> shared_ptr& operator=(unique_ptr<Y, D>&& r);
Effects: Equivalent to shared_­ptr(std​::​move(r)).swap(*this).
Returns: *this.