std::enable_shared_from_this<T>::shared_from_this (3) - Linux Manuals

std::enable_shared_from_this<T>::shared_from_this: std::enable_shared_from_this<T>::shared_from_this

NAME

std::enable_shared_from_this<T>::shared_from_this - std::enable_shared_from_this<T>::shared_from_this

Synopsis

shared_ptr<T> shared_from_this(); (1)
shared_ptr<T const> shared_from_this() const; (2)

Returns a std::shared_ptr<T> that shares ownership of *this with all existing std::shared_ptr that refer to *this.
Effectively executes std::shared_ptr<T>(weak_this), where weak_this is the private mutable std::weak_ptr<T> member of enable_shared_from_this.

Notes

It is permitted to call shared_from_this only on a previously shared object, i.e. on an object managed by std::shared_ptr (in particular, shared_from_this cannot be called during construction of *this).
Otherwise
the behavior is undefined
(until C++17)
std::bad_weak_ptr is thrown (by the shared_ptr constructor from a default-constructed weak_this)
(since C++17).

Return value

std::shared_ptr<T> that shares ownership of *this with pre-existing std::shared_ptrs

Example

// Run this code

  #include <iostream>
  #include <memory>

  struct Foo : public std::enable_shared_from_this<Foo> {
      Foo() { std::cout << "Foo::Foo\n"; }
      ~Foo() { std::cout << "Foo::~Foo\n"; }
      std::shared_ptr<Foo> getFoo() { return shared_from_this(); }
  };

  int main() {
      Foo *f = new Foo;
      std::shared_ptr<Foo> pf1;

      {
          std::shared_ptr<Foo> pf2(f);
          pf1 = pf2->getFoo(); // shares ownership of object with pf2
      }

      std::cout << "pf2 is gone\n";
  }

Output:

  Foo::Foo
  pf2 is gone
  Foo::~Foo