Definition size_chunk_nat (chunk: memory_chunk) : nat :=
nat_of_Z(size_chunk chunk).

Lemma size_chunk_Mptr: size_chunk Mptr = if Archi.ptr64 then 8 else 4.
Definition align_chunk (chunk: memory_chunk) : Z :=
match chunk with
| Mint8signed => 1
| Mint8unsigned => 1
| Mint16signed => 2
| Mint16unsigned => 2
| Mint32 => 4
| Mint64 => 8
| Mfloat32 => 4
| Mfloat64 => 4
| Many32 => 4
| Many64 => 4
end.