// The value 'current_base' (libevent 1) or
// 'event_global_current_base_' (libevent 2) is filled in by event_set(),
// allowing examination of its value without an explicit reference here.
- // If ev.ev_base is NULL, then event_init() must be called, otherwise
+ // If ev.ev_base is nullptr, then event_init() must be called, otherwise
// call event_base_new().
event_set(&ev, 0, 0, nullptr, nullptr);
if (!ev.ev_base) {