Inductive valid_genv {F V:Type} (ge:Genv.t F V) (m:mem) : Type :=
  mk_valid_genv :
    (forall b, isGlobalBlock ge b=true -> val_valid (Vptr b Ptrofs.zero) m) ->
    (forall b f, Genv.find_funct_ptr ge b = Some f -> val_valid (Vptr b Ptrofs.zero) m) ->
    valid_genv ge m.Inductive valid_genv {F V:Type} (ge:Genv.t F V) (m:mem) : Type :=
  mk_valid_genv :
    (forall b, isGlobalBlock ge b=true -> val_valid (Vptr b Ptrofs.zero) m) ->
    (forall b f, Genv.find_funct_ptr ge b = Some f -> val_valid (Vptr b Ptrofs.zero) m) ->
    valid_genv ge m.

Lemma getN_range: forall n ofs M bytes1 v bytes2, Mem.getN n ofs M = bytes1 ++ v::bytes2 -> (length bytes1 < n)%nat.