+typedef int freeuser_func_t(struct UserNode *user);
+int bind_freeuser(freeuser_func_t *func);
+void unbind_freeuser(freeuser_func_t *func);
+int event_freeuser(struct UserNode *user);
+
+typedef int freechan_func_t(struct ChanNode *chan);
+int bind_freechan(freechan_func_t *func);
+void unbind_freechan(freechan_func_t *func);
+int event_freechan(struct ChanNode *chan);