How could I share "this" instance over my application in C++?

Question

Say I have :

class Foo
{
public:
    Foo(std::function< void(std::shared_ptr< Foo >) > callback);

    void shareMyFoo()
    {
        callback(std::make_shared< Foo >(this));
    }

    ....
};

When shareMyFoo() is invoked, someone will have a chance to copy the shared pointer. Unfortunately, as it will die --that is, its ref counter dropped to 0--, it will kill my Foo. I would like to prevent Foo from being suicided.

I thought of having a field std::shared_ptr< Foo > sharedSelf_ in Foo, that I would initialize in the constructor, but that's cheap as well.

More generally, imagine I instantiate and store a pointer to an object in a shared pointer, (auto foo = std::make_shared< Foo >() for instance), and later the instance wants to pass itself as a shared pointer. How can I update the ref counter globally ?

N.B. : I want/need to preserve my signatures/my shared_ptr arguments over my application.

Answer 1

You have to inherit from std::enable_shared_from_this (n3242 §20.7.2.4).

auto p = (new Foo) -> shared_from_this ();