bug#22789: 25.1.50; In last master build https connections stop working

[Alain Schneble]

Alain Schneble <a.s@realize.ch> writes:

>                (I'll try to search the wisock documentation tomorrow to
> find some hints that lead in this direction, or maybe you know?)

IIUC, this could be the reason why it fails:

- The reader_thread in w32proc.c calls _sys_wait_connect which in turn
  does a WSAEventSelect.

- The documentation says:
  
https://msdn.microsoft.com/en-us/library/windows/desktop/ms738573(v=vs.85).aspx

  The WSAAsyncSelect and WSAEventSelect functions automatically set a
  socket to nonblocking mode.  If WSAAsyncSelect or WSAEventSelect has
  been issued on a socket, then any attempt to use ioctlsocket to set
  the socket back to blocking mode will fail with WSAEINVAL.

- So there /is/ a dependency between these calls.  Unfortunately, I
  couldn't see that ioctlsocket returns with WSAEINVAL in the scenarios
  I tried.  Could it be a multi-threading issue then?  Multiple threads
  accessing the same socket...  I don't see how both threads are
  synchronized.  The patch I sent would synchronize them through the
  FILE_CONNECT flag, I think.  Did I miss something?