Machine-checked object layout for C++ multiple inheritance with empty-base optimization

We also adopt the following additional notations: • rst is a function de ned on non-empty lists, such that rst(a :: l′) def. a for all a, l′. • last is a function de ned on non-empty lists, computing their last elements: last(a :: nil) def. a and last(a :: b :: l′) def. last(b :: l′) for all a, b, l′. • length(l) is the length of a list l: length(nil) def. 0 and length(a :: l′) def. 1 + length(l′) • For any sets A and S ⊆ A× Z, and any ω ∈ Z: ω + S def. {(A,ω + o) | (A, o) ∈ S}