timersub
timersub(&eloop.timeout->time, &now, &tv);
#ifndef timersub
timersub(&SmEventQueue->ev_time, &now, &itime.it_value);
timersub(&SmEventQueue->ev_time, &now,
timersub(&SmEventQueue->ev_time, &now, &clr.it_value);
timersub(&now, &begin, &diff);
timersub(&slpv, &diff, &sm_io_to);
timersub(&sm_io_to_after, &sm_io_to_before, &sm_io_to_diff); \
timersub(&sm_io_to_after, &sm_io_to_before, &sm_io_to_diff); \
timersub((to), &sm_io_to_diff, (to)); \
timersub(&ep, &bp, &tp);
timersub(&now, start_time, &diff);
timersub(&now, start, &diff);