FLOW_CHECK
if (async_flowcontrol_sw_input(asy, FLOW_CHECK, IN_FLOW_NULL))
if (async_flowcontrol_sw_input(asy, FLOW_CHECK, IN_FLOW_NULL))
if (async_flowcontrol_sw_input(asy, FLOW_CHECK, IN_FLOW_NULL))
(void) xcasync_flowcontrol_sw_input(xcp, FLOW_CHECK, IN_FLOW_NULL);