Re: Multi-arch

[gshapovalov@gmail.com]

Ludovic Brenta wrote:
> I am following up on the questions raised here about running both
> 32-bit and 64-bit binary code on the same machine. This is called
> biarch. Currently, the gcc-4.1 source package in Debian supports biarch
[skipped]
> i586 and i686. The proposed design would solve the current problems
> with biarch, at the expense of rewriting dpkg almost from scratch.
>
> http://multiarch.alioth.debian.org/
>
> Thoughts?

Biarch, multiarch, khm, whatever :).
On the topic:
Yes, it can be done and is very well worth it. On Gentoo it is called
multilib and is supported distribution-wide, not only for x86 and
amd64, but ppc and sparc have theirs multilibs too IIRC (I think both
of them, but may be only sparc actually).  gcc is supported, as well
as Ada and most of the libs and apps (to the point where you can
have wine running 32-bit Windows code on otherwise
64bit-clean system - kernel and userspace).

This is regulated primarily via multilib and toolchain eclasses, which
is
basically the way to contain common controlling code. I recently put
Ada
on the same rails, so that now, on a multilib system, (that is for
users who
selected the multilib profile) two sets of rts libs are generated and
compiler can generate 64bit or 32bit code. Although, as there were no
requests so far, I haven't yet automatized switching between the
multilib
sub-profiles, only the usual niceties - like having FSF's 3.4.x, 4.1.x
based and AdaCore's gnat-gpl compilers installed side-by-side and
activated as necessary..

You can see the code here:
http://www.gentoo.org/cgi-bin/viewcvs.cgi/eclass/
You would be looking for the toolchain.eclass, multilib.eclass and
possibly
some other eclasses. And here:
http://www.gentoo.org/cgi-bin/viewcvs.cgi/dev-lang/gnat-gcc/
http://www.gentoo.org/cgi-bin/viewcvs.cgi/dev-lang/gnat-gpl/

The ebuilds and eclasses are mostly just a bash code, so should be
familiar, aside from a few vars that have special meaning. Some
Ada-specific implementation details and discussion can be found
in this bug:
https://bugs.gentoo.org/show_bug.cgi?id=111340
and you can catch me on irc,freenode.net in channels #gentoo and
#gentoo-dev if you would like to discuss this further (my nick there
is georges, email of course works too: george at gentoo.org), although
I suppose the way it will have to be done on Debian would be quite
different..

George