A lot of C++ code depends on deallocation order for correctness. Like a destructor may want to say bye-bye to a pointed-to-object, and if you reverse order of deallocation, that pointer may be dangling.

Consider this code

    {
        Window a;
        ClickHandler* b = new ClickHandler(&a);
        delete b;
    }

Let's say b tries to deregister itself when it's deleted. This code will work as written. But if you defer the deletion of b, then stack allocated Window a may already be gone.