Re: Merge of opam-overlays and mirage-opam-overlays

[Virgile Robles <virgile@xxxxxxxxxxx>]

Hi Anil,
> Is the redirect actually necessary, as keeping
> the mirage overlay empty should be fine I think?

It's not strictly necessary, but it would have been a good use case of
redirects.

> I'm also curious (as an aside) what the differences between the mirage/dune
> Zarith and the opam-overlay dunified Zarith packages is. If it's just the
> cross-compilation glue, it's worth retiring the dunified Zarith as the
> Mirage one should be strictly better.

They are very similar, but indeed the mirage port (done and maintained
by Dinosaure and Hannes) seems strictly better and cleaner at
discovering its environment both for cross-compilation or not.

Best,
Virgile

> best,
> Anil
> 
> /--
> Anil Madhavapeddy, Professor of Planetary Computing (https://
> anil.recoil.org)
> Computer Laboratory, University of Cambridge (https://cst.cam.ac.uk)/
> 
>> On 13 Jul 2026, at 13:29, Virgile Robles <virgile@xxxxxxxxxxx> wrote:
>>
>> Hi Kate,
>>
>> Thanks for the report. Locally I never encountered any exceptions,
>> however I realize that my tests never checked that the redirection
>> worked (I tested having only opam-overlays or
>> opam-overlays+mirage-opam-overlays), since I expected any user of
>> mirage-opam-overlays to have opam-overlays added as well.
>>
>> And indeed opam doesn't seem to follow the redirect and I couldn't find
>> a way to make it work.
>>
>> For now I've re-added the packages to mirage-opam-overlays, which is the
>> safer option (they are still in opam-overlays, and mirage-opam-overlays
>> is still deprecated).
>>
>> Does that solve the issue you were seeing?
>>
>> Cheers,
>> Virgile
>>
>> Le 11/07/2026 à 19:58, Kate a écrit :
>>> Hi,
>>>
>>> Locally, the first time i called opam update, this repository failed
>>> with some uncaught exception and even after non-failed subsequent
>>> updates the resulting repository wasn't the one it's supposed to be
>>> redirected to, thus leaving us with the empty repository.
>>>
>>> Could you confirm the redirection worked for you locally when you tested
>>> this?
>>>
>>>
>>> Cheers,
>>> Kate
>>>
>>> On 7/8/26 17:18, Virgile Robles wrote:
>>>> Dear all,
>>>>
>>>> Today our build infrastructure based on opam-monorepo is relying on
>>>> all unikernel dependencies building with dune. To that end, we have
>>>> two opam overlay repositories containing ports of packages that do not
>>>> use dune upstream:
>>>>
>>>>   * opam-overlays <https://github.com/dune-universe/opam-overlays>:
>>>>     historically decoupled from Mirage, containing almost all ports
>>>>     guaranteed to build with dune but not necessarily cross-compilable
>>>>   * mirage-opam-overlays <https://github.com/dune-universe/mirage-opam-
>>>>     overlays>: for ports that need further or different adaptations to
>>>>     be cross-compilable, since we need it for Mirage.
>>>>
>>>> The second one actually only contains the zarith package, for which we
>>>> have two different ports.
>>>>
>>>> Following some discussions we had some time ago observing there is
>>>> some seemingly unnecessary complexity in having two separate
>>>> repositories for one single package, and that opam-monorepo is (to my
>>>> knowledge) only used by Mirage, I have merged mirage-opam-overlays
>>>> into opam-overlays and propose that going forward only opam-overlays
>>>> be used (and requires that all ports are cross-compilable).
>>>>
>>>> mirage-opam-overlays is now empty and redirecting to opam-overlays, so
>>>> no unikernels should be affected, but I'm ready to revert if this
>>>> change broke someone's workflow (Mirage-related or not), so please let
>>>> me know if this is the case or if you have a use for the non-mirage
>>>> zarith port!
>>>>
>>>> After some time in the absence of issues I'll submit a PR to mirage/
>>>> mirage to produce Makefiles without mirage-opam-overlays.
>>>>
>>>> Have a great day,
>>>>
>>>> Virgile
>>>>
>>>
>>>
>>
>>
>