Hello, reading the documentation for enable_shared_from_this,
I can't understand why this kind of base class is needed. In
the example code in the documentation, we have:

class Y: public enable_shared_from_this<Y>

{
public:

    shared_ptr<Y> f()
    {
        return shared_from_this();
    }
}

int main()
{
    shared_ptr<Y> p(new Y);
    shared_ptr<Y> q = p->f();
    assert(p == q);

    assert(!(p < q || q < p)); // p and q must share ownership
}

Isn't this piece of code equivalent (since the two pointers share ownership):

class Y
{
};

int main(int argc, char * argv[])
{
shared_ptr<Y> p(new Y);
shared_ptr<Y> q(p);
...

}