20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.1 Unique-ownership pointers [unique.ptr]

20.3.1.3 unique_ptr for single objects [unique.ptr.single]

20.3.1.3.4 Assignment [unique.ptr.single.asgn]

constexpr unique_ptr& operator=(unique_ptr&& u) noexcept;
Constraints: is_move_assignable_v<D> is true.
Preconditions: If D is not a reference type, D meets the Cpp17MoveAssignable requirements (Table 33) and assignment of the deleter from an rvalue of type D does not throw an exception.
Otherwise, D is a reference type; remove_reference_t<D> meets the Cpp17CopyAssignable requirements and assignment of the deleter from an lvalue of type D does not throw an exception.
Effects: Calls reset(u.release()) followed by get_deleter() = std​::​forward<D>(u.get_deleter()).
Postconditions: If this != addressof(u), u.get() == nullptr, otherwise u.get() is unchanged.
Returns: *this.
template<class U, class E> constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;
Constraints:
  • unique_ptr<U, E>​::​pointer is implicitly convertible to pointer, and
  • U is not an array type, and
  • is_assignable_v<D&, E&&> is true.
Preconditions: If E is not a reference type, assignment of the deleter from an rvalue of type E is well-formed and does not throw an exception.
Otherwise, E is a reference type and assignment of the deleter from an lvalue of type E is well-formed and does not throw an exception.
Effects: Calls reset(u.release()) followed by get_deleter() = std​::​forward<E>(u.get_deleter()).
Postconditions: u.get() == nullptr.
Returns: *this.
constexpr unique_ptr& operator=(nullptr_t) noexcept;
Effects: As if by reset().
Postconditions: get() == nullptr.
Returns: *this.