TFD_CLOEXEC
nflags |= TFD_CLOEXEC;
if (flags & ~(TFD_CLOEXEC | TFD_NONBLOCK)) {
fd_set_exclose(l, fd, !!(flags & TFD_CLOEXEC));
~(TFD_CLOEXEC | TFD_NONBLOCK))) == -1);
TFD_NONBLOCK | TFD_CLOEXEC)) >= 0);