Definition permission_block (sh: Share.t)  (v: val) (t: type) : mpred :=
    match access_mode t with
         | By_value ch =>
            match v with
            | Vptr b ofs =>
                 nonlock_permission_bytes sh (b, Ptrofs.unsigned ofs)
                       (size_chunk ch)
            | _ => FF
            end
         | _ => FF
         end.Definition mapsto_ sh t v1 := mapsto sh t v1 Vundef.Fixpoint writable_blocks (bl : list (ident*Z)) : assert :=
 match bl with
  | nil =>  fun rho => emp
  | (b,n)::bl' =>  fun rho => writable_block b n rho * writable_blocks bl' rho
 end.Fixpoint address_mapsto_zeros (sh: share) (n: nat) (adr: address) : mpred :=
 match n with
 | O => emp
 | S n' => address_mapsto Mint8unsigned (Vint Int.zero) sh adr 
               * address_mapsto_zeros sh n' (fst adr, Z.succ (snd adr))
end.Definition address_mapsto_zeros' (n: Z) : spec :=
     fun (sh: Share.t) (l: address) =>
          allp (jam (adr_range_dec l (Z.max n 0))
                                  (fun l' => yesat NoneP (VAL (Byte Byte.zero)) sh l')
                                  noat) && noghost.

Lemma address_mapsto_zeros_eq: forall sh n, address_mapsto_zeros sh n = address_mapsto_zeros' (Z_of_nat n) sh.