Resurrect discussion: Mixing 32 and 64 bit distro

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

Hi guys,


I slept a bit bad tonight.

As you may or may not remember, we had a discussion about how to go
forward with a 64 bit distro in 2011.

In this discussion I held vehemently to the view that we have to create
the 64 bit distro in a way which allows to mix Cygwin 64 and 32 bit
applications freely.  My main point was that it may take a long time
until we get all the Cygwin 32 bit packages built for 64 bit, and
therefore have to provide a mix so that users can adopt the 64 bit
distro early without having to drop the tools they are using.

But is that really so?  I'm not so sure anymore.  Maybe that problem
is exaggerated or overvalued.

The communication between 32 and 64 bit processes is rather complicated.
While carefully maintained shared mem regions are not much of a problem,
the dll shared section is, since it's not shared anymore.  Also, parts
of the information given to a process at spawn/execve time has to be
serialized, mainly the stuff from cygheap which needs to be inherited by
the child.  Information easily available in /proc isn't that easily
available anymore when you have to share it between 342 and 64 bit
processes.

setup will also get pretty complicated, because you have to differ
between 64/32 bit apps and 64/32 bit libs and setup has to know all the
time which version it installs and to make sure to pull in the right
libs.  This is easy enough with rpm, but, AFAIK, nothing of that sort is
available in setup or upset yet.

Another, more development oriented downside is the fact that we have to
introduce the cyg64 DLL prefix, which, as far as I remember from the
discussion in 2011, breaks libtool and potentially configury and/or
Makefiles of a couple of packages.

So, I'm inclined to resurrect this discussion.  I'd like to hear your
point of view and why you're rating one over the other (separate
distro vs. mixed distro).  Personally I'm really not sure what is
more important, a full distro right from the start, or a clean
separation.


Thanks in advance,
Corinna

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