g++ allows to exist not inited reference in this case:

struct X
{
   int &x;
};

int main()
{
    X* p_x = new X; // now there is not inited reference (p_x->x)
    // now we can try to use p_x->x
    std::cout << p_x->x << std::endl; // segmentation fault
    return 0;
}

There are no errors or warnings. Compilation is successfull. 

I have tested on g++ (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu3).
Also it "works" on g++ 4.3.