Ltac memval_lessdef_tac :=
match goal with
 | H: memval_lessdef ?a ?b |- _ => destruct a,b; inv H
 | H: list_forall2 _ ?a ?b |- _ => destruct a,b; inv H
 | H: proj_bytes ?a = Some _ |- _ => match a with context [nil] => inv H end
end;
 try discriminate;
 try solve [unfold decode_val; simpl; auto] .

Lemma weak_valid_pointer_lessalloc {m m2} (M:mem_lessalloc m m2): Mem.weak_valid_pointer m = Mem.weak_valid_pointer m2.