Definition store_byte_list m b ofs lv :=
Mem.storebytes m b ofs (concat (map (encode_val Mint8unsigned) lv)).

Lemma change_has_ext : forall {Z} (a a' : Z) r H, app_pred (has_ext a) r ->
app_pred (has_ext a') (set_ghost r [Some (ext_ghost a', NoneP)] H).