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 mem_wd_alloc_global: forall  {F V} (ge: Genv.t F V) a m0 m1
(GA: Genv.alloc_global ge m0 a = Some m1),
mem_wd m0 -> valid_genv ge m0 -> mem_wd m1.