get: int A::a = 1
get: int B::b = 2
derived from "B": int B::b = 2
derived from "B::b": int B::b = 2
get: int C::c = 3
derived from "B": int C::c = 3
get: int D::d = 4
derived from "B": int D::d = 4
get: int D::b = 5
derived from "B": int D::b = 5
derived from "B::b": int D::b = 5