Cygwin Python/PIL TCL/TK fork rebase solution

Robin Walker
Tue Jan 16 11:38:00 GMT 2007

--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 
elucidation on this issue.

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

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

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

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

Robin Walker (Junior Bursar), Queens' College, Cambridge CB3 9ET, UK  Tel:+44 1223 335528
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