20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.2 Shared-ownership pointers [util.sharedptr]

20.3.2.5 Class template enable_shared_from_this [util.smartptr.enab]

A class T can inherit from enable_shared_from_this<T> to inherit the shared_from_this member functions that obtain a shared_ptr instance pointing to *this.
[Example 1: struct X: public enable_shared_from_this<X> { }; int main() { shared_ptr<X> p(new X); shared_ptr<X> q = p->shared_from_this(); assert(p == q); assert(!p.owner_before(q) && !q.owner_before(p)); // p and q share ownership } — end example]
namespace std { template<class T> class enable_shared_from_this { protected: constexpr enable_shared_from_this() noexcept; enable_shared_from_this(const enable_shared_from_this&) noexcept; enable_shared_from_this& operator=(const enable_shared_from_this&) noexcept; ~enable_shared_from_this(); public: shared_ptr<T> shared_from_this(); shared_ptr<T const> shared_from_this() const; weak_ptr<T> weak_from_this() noexcept; weak_ptr<T const> weak_from_this() const noexcept; private: mutable weak_ptr<T> weak_this; // exposition only }; }
The template parameter T of enable_shared_from_this may be an incomplete type.
constexpr enable_shared_from_this() noexcept; enable_shared_from_this(const enable_shared_from_this<T>&) noexcept;
Effects: Value-initializes weak_this.
enable_shared_from_this<T>& operator=(const enable_shared_from_this<T>&) noexcept;
Returns: *this.
[Note 1: 
weak_this is not changed.
— end note]
shared_ptr<T> shared_from_this(); shared_ptr<T const> shared_from_this() const;
Returns: shared_ptr<T>(weak_this).
weak_ptr<T> weak_from_this() noexcept; weak_ptr<T const> weak_from_this() const noexcept;
Returns: weak_this.