Definition same_except_cur (m m' : Mem.mem) :=
  Mem.mem_contents m = Mem.mem_contents m' /\
  max_access_at m = max_access_at m' /\
  Mem.nextblock m = Mem.nextblock m'.

Lemma weak_exclusive_joins_false R phi phi1 phi2 : level phi = level phi1 -> app_pred (weak_exclusive_mpred R) phi -> app_pred R phi1 -> app_pred R phi2 -> joins phi1 phi2 -> False.