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Date:	Wed, 19 Jun 2013 13:45:14 -0400
From:	Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Adding MSYS functionality to Cygwin
Message-ID:	<20130619174514.GA6071@ednor.casa.cgf.cx>
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On Wed, Jun 19, 2013 at 11:30:11AM -0600, Warren Young wrote:
>On 6/18/2013 20:02, Christopher Faylor wrote:
>> On Tue, Jun 18, 2013 at 04:04:06PM -0600, Warren Young wrote:
>>> It would be possible, though somewhat evil, for Cygwin's exec()
>>> implementation to peek at the DLL dependency list of a program before
>>> starting it, and from that infer whether it should automatically
>>> translate paths.
>>
>> Cygwin already does this.  It detects whether the program it is about
>> to run uses the Cygwin DLL and, if not, makes decisions on how to
>> handle exec.  It would be relatively easy to extend this.
>
>Well, given that we're already paying the "peek" cost, I don't have any 
>objection to making exec() take longer for the native Windows case only.
>
>Do you know how you want to cope with my contrived "xcopy /bin a b" 
>example?  The point of the example, of course, is that "/bin" looks like 
>a real, existing POSIX path, but isn't.

I don't think people are getting this:

*How this is implemented doesn't matter*.

I'm talking about providing hooks so that an add-on MSYS dll could
modify the windows command-line.  Then we wouldn't care what MSYS does
with the command-line since it isn't a Cygwin DLL decision.  The goal is
to allow a small DLL to hook into Cygwin and do whatever MSYS wants to
do.

Something like:

callout (CO_EXEC, &command_line);

Where it is expected that the command line could be modified.

The "check-for-windows" code is already there.  Calling out would be
close to a no-op in the non-MSYS cost.  Otherwise, I really don't care
what it costs.

I understand the objections to the way that MSYS does things.  I really
do.  I don't like what it does, either (and I've voiced the same
objections in the past) but we're willing to selectively modify Cygwin
to allow it to be used as the engine that drives future MSYS
development.  The goal would be to collapse the fork back into Cygwin
with minimal cost to the Cygwin DLL.

cgf

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