gnulib poll() returns POLLERR on Win32 platform, breaking libvirt

[Daniel P. Berrange]

We're seeing a failure in libvirt on Win32 platforms whereby poll() often
returns POLLERR. I traced this down to the rpl_recv() function calling
FD_TO_SOCKET() and getting INVALID_SOCKET back. This is propagated back
to windows_compute_revents_socket() which sets POLLERR, because
WSAGetLastError() returns 0.

The windows_compute_revents_socket() is indeed passing a bad file descriptor
to recv, because it is actually passing in a SOCKET handle.

After bisecting gnulib, I found the root cause of this problem is this commit:

  commit 17f1e64f00011fb745019119e21b26e4aba65e4b
  Author: Paul Eggert <address@hidden>
  Date:   Tue Feb 24 16:16:19 2015 -0800

    poll: port to MSVC v18 on MS-Windows 8.1
    
    Problem reported by Gisle Vanem in:
    http://lists.gnu.org/archive/html/bug-gnulib/2015-02/msg00139.html
    * lib/poll.c: Always include <sys/select.h> and <sys/socket.h>.
    * modules/poll (Depends-on) [!HAVE_POLL || REPLACE_POLL]:
    Add sys_socket.


by unconditionally pulling in sys/select.c & sys/socket.c, we are causing
poll() to call gnulib's replacement rpl_recv() wrapper, rather than the
original bare Winsock recv() method.

Reverting that change fixes libvirt, but obviously that's not a valid
approach, since it'll re-break  MSVC v18 on Win8.1


So I tried the following change to make it pass in an FD into the rpl_recv
method instead of a HANDLE

@@ -571,7 +568,7 @@
           if (FD_ISSET ((SOCKET) h, &xfds))
             ev.lNetworkEvents |= FD_OOB;
 
-          happened = windows_compute_revents_socket (pfd[i].fd, pfd[i].events,
+          happened = windows_compute_revents_socket ((SOCKET) h, pfd[i].events,
                                                      ev.lNetworkEvents);
         }
       else


that makes the recv() work, but now poll() just gets into an infinite loop
calling select() over and over again, never reporting that the socket is
now read()able. So something else is now broken. I guess we're now calling
into gnulib's rpl_select() instead of the bare Winsock select() and so
triggering other badness - presumably more fd vs handle mixups ?

Regards,
Daniel
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