[Nix-dev] Use GHC 7.10.1 as default Haskell compiler in nixpkgs

[Austin Seipp]

Hello *,

I figured I'd chime in as the GHC release manager right quick - moving
to 7.10.1 soon sounds OK to me. I speculate we will probably ship
7.10.2 soon enough though, probably within a few weeks, because we've
found some bugs (including a codegen bug and an unsafeCoerce). So it
might be best to wait, which will also give Hackage a few weeks to
catch up as well.

Peter, if the switch is going to happen within 3-4 weeks, it may be
best to hold on a little longer, I'm not sure. I can keep you in the
loop as we go forward.

On Fri, Apr 3, 2015 at 11:37 AM, Mateusz Kowalczyk
<fuuzetsu at fuuzetsu.co.uk> wrote:
> On 04/03/2015 04:31 PM, Mateusz Kowalczyk wrote:
>> On 04/02/2015 11:21 PM, Peter Simons wrote:
>>> Hi guys,
>>>
>>> I believe that we should switch our default compiler to GHC 7.10.1
>>> within the next three or four weeks -- assuming that no major bug is
>>> discovered in that compiler. It is true that this update will break some
>>> packages, but GHC versions prior to 7.10.x are a disaster for
>>> distributions like us because they generate non-deterministic library
>>> IDs. This means that two builds running in identical environments can
>>> produce outputs that differ and that break binary compatibility when
>>> linked by other libraries. This is a nightmare for systems like Hydra,
>>> and I've just had to rebuild all our Haskell packages [1] for the
>>> umpteenth time because of that bug. GHC 7.10.1 is supposed to fix that
>>> issue, so I'd say let's go for it.
>>
>> If not fix, it should be much better at least. If someone hits the
>> problem with 7.10, let me know.
>>
>>> Those of you who don't want to update can stick to GHC 7.8.4, of course,
>>> it's just that Hydra will no longer provide binaries for that version
>>> after the switch.
>>>
>>> Also, I'd like to remove all code related to the old Haskell package set
>>> from Nixpkgs shortly after the switch, to make sure that obsolete code
>>> won't make it into the next release branch. If you haven't migrated to
>>> Haskell NG yet ... now would be a good time to do it. (I'm looking at
>>> you, Agda.)
>>
>> I can update the Agda stuff today.
>>
>>> How do you guys feels about that approach? Any concerns? Other
>>> suggestions?
>>>
>>> Best regards,
>>> Peter
>>>
>>>
>>> [1] https://github.com/NixOS/nixpkgs/commit/945269a48fa8b91024e18a72b485797eeca308ee
>>>
>>> _______________________________________________
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>>> nix-dev at lists.science.uu.nl
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>>>
>>
>>
>
> …or, well, I would have but the Hackage-available Agda version has the
> cpphs version issue but from what I can tell, here are the steps to
> migrate Agda over to haskell-ng:
>
> in all-packages.nix change inherits and references to haskellngPackages
> (AgdaStdlib package). For the ‘agda’ builder, just change the Agda arg
> to use haskellngPackages.Agda.
>
> Then for cleanup, move out the expression for AgdaStdlib to libraries/agda.
>
> --
> Mateusz K.
> _______________________________________________
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> nix-dev at lists.science.uu.nl
> http://lists.science.uu.nl/mailman/listinfo/nix-dev



-- 
Regards,
Austin - PGP: 4096R/0x91384671