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

[Mateusz Kowalczyk]

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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-- 
Mateusz K.