all library components that use backpack should be compiled with -j1

[chessai]

GHC cannot perform typechecking on "backpackified" code in parallel. All components affected must be built with -j1. Cabal seems smart enough to infer this and does the right thing (inserts -j1), but both haskell.nix and nixpkgs pass the same number to -j (i think $NIX_BUILD_CORES?), which causes a build-time failure (GHC sees -jN where N > 1 and aborts with an error message).

Backpack typechecking not supported with -j

[chessai]

Of course, users can override this pretty easily on a per-package basis, but it would be nice if they didn't have to; especially since this would affect pre-built caches of hackage due to avoidable build failures.

[angerman]

I completely missed this issue. Let's try to fix it with #244 together.

[chessai]

Thank you!

[Ericson2314]

I wrote https://gitlab.haskell.org/ghc/ghc/merge_requests/1823 which allows -j with backpack. I have 8.8 and 8.6 backports already. An 8.10 backport should be no problem either.

[chessai]

@Ericson2314 I'll have to try that out! That's great!

[Ericson2314]

Knock on wood, but I think https://gitlab.haskell.org/ghc/ghc/merge_requests/1823 will finally be merged soon.

[stale]

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