Definition StoreEffect (tv:val)(vl : list memval) (b:Values.block) (z:Z):bool :=
  match tv with Vptr bb ofs => eq_block bb b &&
             zle (Ptrofs.unsigned ofs) z && zlt z (Ptrofs.unsigned ofs + Z.of_nat (length vl))
         | _ => false
  end.

Lemma freelist_curWR l: forall m m' (FR: Mem.free_list m l = Some m') b z (EFF : FreelistEffect m l b z = true), Mem.perm m b z Cur Writable.