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Date: Sun, 10 Jan 2010 09:36:50 -0800
From: Steven Monai <steve+cygwin AT monai DOT ca>
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Subject: Re: Update problems
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On 2010/01/09 2:09 AM, Corinna Vinschen wrote:
> On Jan  8 17:28, Steven Monai wrote:
>> Not to beat a dead hippo here, but if Cygwin allows in-use files to be
>> replaced, then what is 'setup.exe' needed for? (Aside from the initial
>> bootstrap of Cygwin, of course.) Shouldn't it be possible to have proper
>> package management---like dpkg, apt, rpm, yum, etc---from within Cygwin now?
> 
> The most pressing problem is the replacement of the cygwin DLL itself.
> It's like installing a new kernel in Linux.  However, in Linux you have
> to reboot to use the new kernel, while Cygwin is just a DLL.  After the
> rename and replace operation, existing processes will use the old DLL
> while new processes will use the new DLL.  This is bound to break and
> there's no clean way to do it, except to replace the Cygwin DLL while no
> other Cygwin process is running.

Could a Cygwin-specific package manager treat the cygwin DLL as a
special case? Instead of immediately replacing the cygwin DLL file (as
it would normally do for any other DLL), the package manager could use
the Windows "schedule-a-delete/rename-on-reboot" facility to arrange for
the DLL's replacement at the next reboot. Thus there would never be more
than one version of the cygwin DLL loaded at any given time.

-SM
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