Definition full_hist h v := exists l, hist_list h l /\ apply_hist (vint 0) l = Some (vint v).
Definition full_hist' h v := exists l, hist_list' h l /\ apply_hist (vint 0) l = Some v.

Lemma full_hist'_drop : forall h h' v (Hh : full_hist' h v)
(Hh' : incl h' h) (HNoDup : NoDup (map fst h'))
(Hdiff : forall t e, In (t, e) h -> ~In (t, e) h' -> forall v, ~writes e v),
full_hist' h' v.