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Date:	Tue, 16 Jan 2007 11:37:46 +0000
From:	Robin Walker <rdhw AT cam DOT ac DOT uk>
Reply-To:	Robin Walker <rdhw AT cam DOT ac DOT uk>
To:	cygwin AT cygwin DOT com
Subject:	Re: Cygwin Python/PIL TCL/TK fork rebase solution
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--On 15 January 2007 15:42 -0800 Ross Patterson wrote:

> But I'm also curious about rebase and to understand more about how one
> chooses what base address and offset to use.

My curiosity is deeper than that.  I would welcome some instruction or=20
elucidation on this issue.

My understanding (please correct me if I get this wrong) of normal Windows=
=20
DLLs is that, when they need to be loaded into memory (or mapped into an=20
address space), if their preferred base address and range is not free, then=
=20
Windows will slot them in elsewhere and automatically fix-up all the=20
embedded pointers in RAM to be consistent with the actual assigned run-time=
=20
DLL base.

So, usually, no-one need be too concerned about DLL base addresses: DLLs=20
just work, even if their preferred base is not available.  Things are more=
=20
efficient if the preferred base is free, but they still work, albeit slower=
=20
and less efficiently, if the preferred base is not free.

So, what is it about Cygwin DLLs that makes them apparently sensitive to=20
base address in a way that normal Windows DLLs are not?

What is it that Cygwin "rebase" does, that Windows dynamic run-time=20
rebasing cannot or does not do?

--=20
Robin Walker (Junior Bursar), Queens' College, Cambridge CB3 9ET, UK
rdhw AT cam DOT ac DOT uk  http://www.queens.cam.ac.uk/  Tel:+44 1223 335528
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