Returning compare_exchange_weak() result by reference?

I have the following code:

struct X{
    explicit X(int b) : a(b);
    int a;
}

struct Y{

    X& peek(X a){
        return X(g.load());
    }

    X& pop() const{
        int val = 0;
        return X(g.exchange(val));
    }

   X g;
}

and I am getting errors regarding invalid initialization of non-const reference of type X from an rvalue.

whilst I am trying to do:

Y something;
..
X& x = something.pop();

I would like to perform the compare and swap, but I want to return the resultant memory by reference, not making a copy?