(* This file is developed by Qinxiang Cao, Aquinas Hobor and Shengyi Wang in 2015. *)
Definition pointer_range_overlap p n p' n' :=
exists l l', val2adr p l /\ val2adr p' l' /\ range_overlap l n l' n'.

Lemma pointer_range_overlap_comm: forall p1 n1 p2 n2,
pointer_range_overlap p1 n1 p2 n2 <->
pointer_range_overlap p2 n2 p1 n1.