Re: unexpected reproducibility of reproducible blog post?

[zimoun <zimon.toutoune@gmail.com>]

On Wed, 29 Apr 2020 at 18:00, Konrad Hinsen <konrad.hinsen@fastmail.net> wrote:

> I have also opened an issue for this:
>
>   https://github.com/khinsen/reproducibility-with-guix/issues/2

I will add something overthere for tracking reproduciblity infos in the future.


> > Grafts or maybe Guile 2 -> 3?
>
> With time-machine, you run the full Guix from back then, so you run
> Guile 2 if that's what it takes. What I am not so sure about is how the
> old Guix release is built. If the build uses the equivalent of "guix
> environment guix", it would start using Guile 3.

From [1] and assuming that the commit was the same, i.e.,
769b96b62e8c09b078f73adc09fb860505920f8f, there is also a mismatch
about the resulting binary.

Expected:
1be3c1b5d1e065017e4c56f725b1a692

Now:
2805a33e2e48f648307c6b913b69e41c

--8<---------------cut here---------------start------------->8---
guix describe # f03e5ca
guix time-machine \
     --commit=769b96b62e8c09b078f73adc09fb860505920f8f \
     -- environment --container --ad-hoc gcc-toolchain \
     -- gcc pi.c -o pi-guix
--8<---------------cut here---------------end--------------->8---

[1] https://lists.gnu.org/archive/html/guix-devel/2020-01/msg00192.html

From f03e5ca, the time machine downloads the substitute:
   https://ci.guix.gnu.org/nar/lzip/ij38zh495f81xpzmp4qzqz4fprczwck2-gcc-toolchain-9.2.0


> Time travelling is not as simple as it looks, but then we should have
> expected that!

I agree but it is annoying.
Because `in fine` the computations are not more reproducible than say
Debian if 3 months later we are not able to reproduce them bit-to-bit.
I do not know. Maybe it is about 'time-machine', maybe about the exact
commit used (most probable! :-)), maybe about the Guix build toolchain
(seed) used to travel back and restore the previous build toolchain.
Who knows? :-)

Well, I will try later with my desktop machine when I will be back at
the office; hoping that I did not garbage collected. :-)


Cheers,
simon