Lemma weak_valid_pointer_dry:
forall b ofs m, app_pred (weak_valid_pointer (Vptr b ofs)) (m_phi m) ->
(Mem.valid_pointer (m_dry m) b (Ptrofs.unsigned ofs)
|| Mem.valid_pointer (m_dry m) b (Ptrofs.unsigned ofs - 1))%bool = true.