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Date: Fri, 23 Jan 2009 11:17:57 +0100
From: Spiro Trikaliotis <an-cygwin AT spiro DOT trikaliotis DOT net>
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Subject: Re: Problem using select() with com0com virtual serial ports
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Hello,

* On Thu, Jan 22, 2009 at 10:55:22AM -0500 Christopher Faylor wrote:
> On Thu, Jan 22, 2009 at 10:25:32AM -0500, Paul Ingemi wrote:
[...] 
> It is a simple enough hack that I don't mind adding it, if it fixes your
> problem but I am not convinced that your driver is operating correctly.

As I had added serial port access to the Windows version of VICE one or
two months ago, I can tell that the com0com driver is indeed buggy. One
of my testers always claimed that the serial support just did not work.
After some debugging with him, we found out that it is com0com that is
"problematic", to say it positively.

Taking into account the opinion at various MS related newsgroups, which
states that the serial port driver of Windows is most probably one of
the most complicated drivers in the Windows driver world (neglecting the
filesystem drivers), this is not very surprising. Additionally, the
driver sources are very complicated, giving much room for BSODs if
something is not done correctly. I also have not seen any USB to serial
adapter yet where its drivers could not bluescreen the whole machine if
"the right steps were taken". The drivers for the Prolific PL2312 chip
is one of the worser variants, just pressing Ctrl+C in the right moment
in your console application will create a BSOD. I think this shows
enough that it is indeed very hard to get it right.

IMHO, the better solution is to fix com0com, and not to apply some
hotfixes to other software (cygwin, VICE, whatever). That's the approach
I followed, too, ignoring com0com completely. If I might have some time,
I might want to debug com0com myself, but don't hold your breath on it.

Best regards,
Spiro.

-- 
Spiro R. Trikaliotis                              http://opencbm.sf.net/
http://www.trikaliotis.net/                     http://www.viceteam.org/

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