+ int i;
+
+ /* FreeBSD 8.2 has a bug: it does not always detect invalid fds. */
+ if (nfds < 0 || nfds > FD_SETSIZE)
+ {
+ errno = EINVAL;
+ return -1;
+ }
+ for (i = 0; i < nfds; i++)
+ {
+ if (((rfds && FD_ISSET (i, rfds))
+ || (wfds && FD_ISSET (i, wfds))
+ || (xfds && FD_ISSET (i, xfds)))
+ && dup2 (i, i) != i)
+ return -1;
+ }
+