Definition compat_pointer_chunks (chunk1 chunk2: memory_chunk) : Prop :=
  match chunk1, chunk2 with
  | (Mint32 | Many32), (Mint32 | Many32) => True
  | (Mint64 | Many64), (Mint64 | Many64) => True
  | _, _ => False
  end.

Theorem valid_access_alloc_other: forall chunk b' ofs p, valid_access m1 chunk b' ofs p -> valid_access m2 chunk b' ofs p.