replacement poll does not return POLLIN if `accept' is possible on Mac OS X

[Paolo Bonzini]

The attached patch fixes poll to return POLLIN if an accept is possible.

A much better fix would have been to use SO_ACCEPTCONN, but due to a bug 
in the kernel it is not possible to read this option from user mode.

Will apply if nobody complains in a couple of days.

Paolo

2006-11-29  Paolo Bonzini  <address@hidden>

        * lib/poll.c (poll): Define as rpl_poll.  On Darwin, fall back to
        Apple's broken poll if no data is available.

Index: poll.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/poll.c,v
retrieving revision 1.5
diff -u -r1.5 poll.c
--- poll.c      28 Sep 2006 19:58:33 -0000      1.5
+++ poll.c      29 Nov 2006 08:21:56 -0000
@@ -55,8 +55,10 @@
 #define EOVERFLOW EINVAL
 #endif
 
+#undef poll
+
 int
-poll (pfd, nfd, timeout)
+rpl_poll (pfd, nfd, timeout)
      struct pollfd *pfd;
      nfds_t nfd;
      int timeout;
@@ -172,6 +174,19 @@
              while (r == -1 && (errno == EAGAIN || errno == EINTR));
              if (avail < 0)
                avail = 0;
+
+             if (avail == 0)
+               {
+                 /* The above fails for listening sockets; of course, BSD
+                    derivatives have a bug and don't expose SO_ACCEPTCONN to
+                    user programs!  So we rely on Apple's broken poll(2) in
+                    this case.  It can't be worse than what we did so far.  */
+                 struct pollfd pfd_for_apple_poll = pfd[0];
+                 extern int poll (struct pollfd *, nfds_t, int);
+                 r = poll (&pfd_for_apple_poll, 1, 0);
+                 if (r != -1 && (pfd_for_apple_poll.revents & POLLHUP) == 0)
+                   avail = 1;
+               }
 #else
              char data[64];
              r = recv (pfd[i].fd, data, 64, MSG_PEEK);