calc_addr
calc_addr(fcur, fcur->start_off),
calc_addr(fcur, fcur->end_off),
calc_addr(fcur, fcur->alt_start_off),
calc_addr(fcur, fcur->alt_end_off));
start = calc_addr(fcur, fcur->start_off);
end = calc_addr(fcur, fcur->end_off);
alt_start = calc_addr(fcur, fcur->alt_start_off);
alt_end = calc_addr(fcur, fcur->alt_end_off);