Ltac dsepcon :=
match goal with
  [ H : sepcon _ _ _ |- _ ] =>
  let s1 := fresh "s" in
    let s2 := fresh "s" in
      let JOIN := fresh "JOIN" in
        let H1 := fresh "H" in
          let H2 := fresh "H" in
      destruct H as [s1 [s2 [JOIN [H1 H2]]]]
end.

Lemma next_next_join_False : forall s0 s0' s1 s2 x z1 z2, rawnext x z1 s0 -> join_sub s0 s0' -> rawnext x z2 s2 -> join_sub s2 s1 -> joins s0' s1 -> False.