-#define evio_set(ev,fd_,events_) do { (ev)->fd = (fd_); (ev)->events = (events_); } while (0)
-#define evtimer_set_rel(ev,after_,repeat_) do { (ev)->at = (after_); (ev)->repeat = (repeat_); (ev)->is_abs = 0; } while (0)
-#define evtimer_set_abs(ev,at_,repeat_) do { (ev)->at = (at_); (ev)->repeat = (repeat_); (ev)->is_abs = 1; } while (0)
-#define evsignal_set(ev,signum_) do { (ev)->signum = (signum_); } while (0)
+/* these may evaluate ev multiple times, and the other arguments at most once */
+/* either use ev_watcher_init + ev_TYPE_set, or the ev_TYPE_init macro, below, to first initialise a watcher */
+#define ev_watcher_init(ev,cb_) do { (ev)->active = 0; (ev)->pending = 0; (ev)->cb = (cb_); } while (0)
+
+#define ev_io_set(ev,fd_,events_) do { (ev)->fd = (fd_); (ev)->events = (events_); } while (0)
+#define ev_timer_set(ev,after_,repeat_) do { (ev)->at = (after_); (ev)->repeat = (repeat_); } while (0)
+#define ev_periodic_set(ev,at_,interval_) do { (ev)->at = (at_); (ev)->interval = (interval_); } while (0)
+#define ev_signal_set(ev,signum_) do { (ev)->signum = (signum_); } while (0)
+#define ev_idle_set(ev) /* nop, yes, this is a serious in-joke */
+#define ev_prepare_set(ev) /* nop, yes, this is a serious in-joke */
+#define ev_check_set(ev) /* nop, yes, this is a serious in-joke */
+#define ev_child_set(ev,pid_) do { (ev)->pid = (pid_); } while (0)
+
+#define ev_io_init(ev,cb,fd,events) do { ev_watcher_init ((ev), (cb)); ev_io_set ((ev),(fd),(events)); } while (0)
+#define ev_timer_init(ev,cb,after,repeat) do { ev_watcher_init ((ev), (cb)); ev_timer_set ((ev),(after),(repeat)); } while (0)
+#define ev_periodic_init(ev,cb,at,interval) do { ev_watcher_init ((ev), (cb)); ev_periodic_set ((ev),(at),(interval)); } while (0)
+#define ev_signal_init(ev,cb,signum) do { ev_watcher_init ((ev), (cb)); ev_signal_set ((ev), (signum)); } while (0)
+#define ev_idle_init(ev,cb) do { ev_watcher_init ((ev), (cb)); ev_idle_set ((ev)); } while (0)
+#define ev_prepare_init(ev,cb) do { ev_watcher_init ((ev), (cb)); ev_prepare_set ((ev)); } while (0)
+#define ev_check_init(ev,cb) do { ev_watcher_init ((ev), (cb)); ev_check_set ((ev)); } while (0)
+#define ev_child_init(ev,cb,pid) do { ev_watcher_init ((ev), (cb)); ev_child_set ((ev),(pid)); } while (0)