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 self_join_pshare_false (psh psh' : pshare) : ~sepalg.join psh psh psh'.