RFC: Cygwin 64 bit?

Corinna Vinschen corinna-cygwin@cygwin.com
Wed Jun 29 13:42:00 GMT 2011

On Jun 29 09:22, Ryan Johnson wrote:
> On 29/06/2011 3:30 AM, Corinna Vinschen wrote:
> >On Jun 28 17:05, Ryan Johnson wrote:
> >>One last thought, a question, actually: given that LONG is 32 bits
> >>in 64-bit windows, and only the low 32-bits of handles are
> >>meaningful****
> >>****how does that impact dll loading, BTW?
> >No.  Should it?  Do you have an example to show what you're concerned
> >about?
> I just remember (somewhere in this now-enormous thread) somebody
> mentioned that only the low 32 bits of handles are meaningful in
> order to allow sharing of handles between 64- and 32-bit processes.
> It seems that this would force dlls to load in the low 2/4GB of
> memory so that their handles are shareable. Perhaps (hopefully) the
> sharing thing only applies to HANDLE and not to HMODULE?

The idea of having HANDLEs with only 32 significant bit is to allow
handle sharing between 64 and 32 bit processes.  The actual meaning of
the handles is something we don't care about.  They are opaque values,
just like file descriptors.

HMODULE is an address value.  Given that you don't share 64 bit DLLs
with 32 bit processes, they are a non-issue.  And HMODULE values are not
usefully shareable anyway since they only make sense in the VM of the
given process.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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