[haskell-updates] ghc: Backport compact unwind support

[roberth]

Motivation

• Allow to fix C++ exception handling in GHC-linked programs.

• Make sure inline-c-cpp actually works using its test suite

• Solve a problem with hercules-ci-agent on darwin (tbd in upcoming release)

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin (already tested previously, just not these exact commits)
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[sternenseemann]

Otherwise LGTM.

[sternenseemann]

I left a comment on the ghc MR w.r.t. documentation, given that it's a full rebuild to update it, can you take a look at that?

[roberth]

I've addressed that comment in an extra upstream commit, which is not part of the fetchpatch below, so no rebuild is required.

This technically leaves the feature undocumented in our build, but I don't expect any significant number of people to use the built documentation in the store, let alone a user who needs to use the feature.

[sternenseemann]

@roberth Did you check that ghcHEAD is new enough to support the flag? If not we should probably take the opportunity to update it to current upstream HEAD.

[roberth]

@sternenseemann I actually assumed that it'd be new enough or that it'd be okay because it'd be updated somewhat frequently. That appears to have been a little presumptuous.

I've tried to build an updated ghcHEAD, but it fails to build jailbreak-cabal because of changes to the cabal file parser.
It's been moved to a seprate package, but also the api has changed.

[1 of 2] Compiling Main             ( Main.hs, dist/build/jailbreak-cabal/jailbreak-cabal-tmp/Main.o )

Main.hs:13:41: error:
    Variable not in scope:
      readGenericPackageDescription
        :: Verbosity -> String -> IO GenericPackageDescription
    Suggested fix:
      Perhaps use one of these:
        data constructor ‘GenericPackageDescription’ (imported from Distribution.PackageDescription),
        ‘ppGenericPackageDescription’ (imported from Distribution.PackageDescription.PrettyPrint),
        ‘showGenericPackageDescription’ (imported from Distribution.PackageDescription.PrettyPrint)
   |
13 | main = getArgs >>= mapM_ (\cabalFile -> readGenericPackageDescription silent cabalFile >>= writeGenericPackageDescription cabalFile . stripVersionRestrictions)
   |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I've made a start https://github.com/NixOS/nixpkgs/compare/ghcHEAD-update?expand=1 but it's not something I can actually carry out now, so I don't think a PR should have my name on it :)

[sternenseemann]

Okay, so this is going to be a side quest where I have to make a new jailbreak-cabal release first, thanks for looking into it!