Subject: bug#41669: Cross-compiled powerpc64-linux bootstrap-tarballs not reproducible

From: Ludovic Courtès <[email-masked]>
Date: Mon, 14 Dec 2020 09:36:09 +0100

Hi Chris,

Chris Marusich <[email-masked]> skribis:

> It's been almost half a year now, and we're not really any closer to
> figuring out why the cross-built GCC bootstrap binary is
> non-reproducible.  It seems counter-productive to obsess about making
> this specific binary reproducible, although I wish it could be so.
>
> What do you think about using the bootstrap binaries we built half a
> year ago, and proceed with bootstrapping efforts?  To be totally honest,
> I'm feeling pretty exhausted by this bug, since I have spent so many
> days trying to unravel it, and I haven't made any significant progress.
> With no clear end in sight, I would really prefer to move on instead of
> blocking the entire bootstrapping effort on this reproducibility bug.
> The reproducibility of the bootstrap binaries is important, but simply
> having any bootstrap binaries at all is also important.  I think I have
> done my due diligence to try making them reproducible.  Most of them
> are, but I just can't figure out why GCC isn't.  I think it would be
> best to proceed with the binaries we have.

I didn’t follow the whole discussion nor did I try to investigate
myself, but thanks a lot for going to great lengths trying to identify
the issue; this is an impressive amount of work, and I can only share
your disappointment.

Given this effort, I agree that it may be best at this point to move on
and start with these non-reproducible binaries.  At least, the problem
is now documented.

> At this point, it might even make more sense to try bootstrapping for
> powerpc64le instead of powerpc64, since the rest of the world seems to
> be gravitating toward the little-endian variant on POWER9 hardware, and
> thus various programs out there are more likely to be better tested on
> powerpc64le than powerpc64.

Yes, my understanding is that other people, in particular Tobias Platen
and dftxbs3e, were looking at powerpc64le, so perhaps it’s a good idea
to concentrate on that one?

Anyhow, please let me know if/when bootstrap binaries should be uploaded
to ftp.gnu.org (with a signed message).  When updating bootstrap.scm to
refer to them, please include the commit ID used to build them in the
commit message.

Thanks,
Ludo’.