ghc8102: bootstrap with ghc8102BinaryMinimal on aarch32

[Fuseteam]

ghc refuses to evaluate on armhf even tho ghc does provide binaries for the arch
hi @sorki as discussed i have now proposed the change

Motivation for this change

compilation on armv7 fails because ghc fails to evaluate

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[maralorn]

I don‘t feel really to qualified to judge this PR, but maybe you could be slightly more verbose in your commit message? e.g. which ghc version does not evaluate? (I know that it is derivable from the context, but I think it would make it easier to see what's going on at a glimpse.

Also "evaluate" in nix context normally means, that the nix code does not produce a valid nix-derivation. Is that what you mean? If yes could maybe give a link to what fails? Or is the problem building the derivation?

[Fuseteam]

hi @maralorn the issue is that i cannot build any packages on armv7 i always run into this error:

error: Package ‘ghc-8.8.4’ in /nix/store/6qa9pjalsk76va40b5amagwii3gcxyqj-source/pkgs/development/compilers/ghc/8.8.4.nix:251 is not supported
on ‘armv7l-linux’, refusing to evaluate.

a) To temporarily allow packages that are unsupported for this system, you can use an environment variable
   for a single invocation of the nix tools.

     $ export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1

b) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

(use '--show-trace' to show detailed location information)

it should be noted that ghc does provide armv binaries
....huh weird why is it pulling ghc 8.8.4

[maralorn]

I have no idea.

otoh hand after some consideration activating a fix that is used for arm 64bit also for arm32bit seems very sane to me.

Have you actually tested that this solves your problem? (Just a bit suspicious because your branch name looks like this change happened in github ui.)

I have no way to test this and ofBorg does not seem to be a lot of help …

[Fuseteam]

@maralorn your suspicion is right i have a low end device so i haven't been able to test it yet, do you have any tips on how i should test it? i do have a setup using github actions that does reproduce the error without the 'fix'

[maralorn]

No, not really, sorry. I guess we'll need someone with a system like that, to jump in. I’ll try to ask around.

[sorki]

I was able to do this on my arvm7l system but using packages.ghc8102Binary not Minimal variant which should work I guess.

Like you can just use packages.ghc8102Binary as your haskellPackages but it's nice to be able to bootstrap on armv7l as well and not having to carry overrides around.

I can re-test later to make sure it's still the case and that it works with Minimal as well.

This needs a more descriptive commit message tho, something like ghc8102: bootstrap with ghc8102BinaryMinimal on aarch32

[Fuseteam]

@maralorn no problem
@sorki thanks, i'll look forward to your findings then;
i don't think i can edit the commit message can i?

[maralorn]

@Fuseteam You can run "git commit --amend" on the branch and then force push.

[Fuseteam]

alright will do

[Fuseteam]

welp i figured i would do it with a git clone but dang is it big 😂 only 25% and 300MB and counting 😂

[Fuseteam]

I'll be honest, looking at the error again I'm growing skeptical if this will actually solve it........., for some reason the error message seems to refer to ghc 8.8.4, but if i'm reading this right i modified ghc-8.10.2

[sorki]

It depends on nixpkgs commit which you are using. A week ago pkgs.haskellPackages were pointing to pkgs.haskell.packages.ghc884, now it's

pkgs/top-level/all-packages.nix:  haskellPackages = dontRecurseIntoAttrs haskell.packages.ghc8102;

[Fuseteam]

oh yeah lemme try the latest commit

[Fuseteam]

ah cool it changed the rev to newer version and indeed pulls the 8.10.2 thanks for the reassurance

[Fuseteam]

i have now verified with github actions that it no longer runs into the same issue with this change. the job obviously fails due to not actually being set up for cross compilation but that's outside the scope of this issue i think

[maralorn]

@sorki You said you also wanted to test run this. Can you can confirm, that it works for you, too?

[sorki]

I've used similar approach like a month ago so it should be good. I'm unable to test this right now as I can't really update my system due to unrelated coreutils build failure.

[sorki]

LGTM

[maralorn]

thx

[Fuseteam]

awesome