B19.1 select fails (NT4 SP3, IE5+perf enhancements)

malcolm malcolm@eml.co.uk
Sat Aug 22 14:38:00 GMT 1998

I don't think this is a Cygnus bug. Just a warning to other poor souls who
may see this problem.

First an apology for not having invetsigated more fully but time did not

Second the background. I have some fairly straighforward Unix network
application that I ported to NT using the Cygnus tools without any problems
(thankyou). I am also one of those people who has a machine with all the
latest (untested and less well tested) M$ pieces on it. This machine has
installed IE5 beta 2 (Version 5.00.0518.10 in M$ speak). All worked well.
Then I added the so called IP performance enhancements. And things broke.

Third the problem. Everything works OK if you do straight forward socket
operations until you use select() when you get an ACCVIO. I tried to find
out where in the select() code but got lost trying to build a debug version
of the Cygnus stuff but it is definitely internal.
Note: I investigated various combinations of the readfds, writefds,
exceptfds and timeval parameters, with and without NULL values, and the
value of the fdsize. All failed internally to select(). All tests I did were
for a UDP socket, I did not try TCP though I would not expect this is
relevant (but thats only a wild guess).

Fourth resolution. Removing the performance enhancements puts everything
back to working order again.

Fifth other stuff. I have found one other application that has a NULL
pointer exception with the performance enhancements and that is FTP explorer
by FTPx Corp. This may or may not be related.

Sixth. I think the problem is M$s rather than the applications. Clearly the
performance enhancements create problems! I would like to be able to pass a
bug report on to them, but I can't without being able to burrow down into
the select() call.


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