inc_unless_negative

 1cat <<EOF
 2	${int} c = raw_${atomic}_read(v);
 3
 4	do {
 5		if (unlikely(c < 0))
 6			return false;
 7	} while (!raw_${atomic}_try_cmpxchg(v, &c, c + 1));
 8
 9	return true;
10EOF