(** * Abstracting read-only global variables *)

Definition romem := PTree.t ablock.

Lemma romatch_ext: forall m rm m', romatch m rm -> (forall b id ofs n bytes, bc b = BCglob id -> Mem.loadbytes m' b ofs n = Some bytes -> Mem.loadbytes m b ofs n = Some bytes) -> (forall b id ofs p, bc b = BCglob id -> Mem.perm m' b ofs Max p -> Mem.perm m b ofs Max p) -> romatch m' rm.