Hello, what do I have to do to use a locally compiled GHC on my own projects? Background: I'm working on this [1]. I've managed to compile GHC following the instructions given on https://ghc.dev, also here [2]. I can run $ ./_build/stage1/bin/ghc --interactive GHCi, version 9.15.20251202: https://www.haskell.org/ghc/ :? for help with the expected result. However, the locally built compiler (master branch, without any modifications) fails with all but the most primitive of my own projects. I try to do this by adding a line with-compiler: /home/sk/prg/ghc/master/_build/stage1/bin/ghc to the `cabal.project` file of a project. Then, success depends on the dependencies of a project. Here is one using `criterion`: $ cabal build Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.12.1.0 supports 'ghc' version < 9.12): /home/sk/prg/ghc/third/_build/stage1/bin/ghc is version 9.15.20251202 Resolving dependencies... Error: [Cabal-7107] Could not resolve dependencies: [__0] next goal: foo (user goal) [__0] rejecting: foo-1.0 (constraint from user target requires ==0.0.1) [__0] trying: foo-0.0.1 [__1] trying: criterion-1.6.4.1 (dependency of foo) [__2] trying: vector-algorithms-0.9.1.0 (dependency of criterion) [__3] trying: primitive-0.9.1.0 (dependency of vector-algorithms) [__4] next goal: base (dependency of foo) [__4] rejecting: base-4.22.0.0/installed-inplace (conflict: primitive => base>=4.10 && <4.22) [__4] rejecting: base; 4.21.0.0, 4.20.2.0, 4.20.1.0, 4.20.0.1, 4.20.0.0, 4.19.2.0, 4.19.1.0, 4.19.0.0, 4.18.3.0, 4.18.2.1, 4.18.2.0, 4.18.1.0, 4.18.0.0, 4.17.2.1, 4.17.2.0, 4.17.1.0, 4.17.0.0, 4.16.4.0, 4.16.3.0, 4.16.2.0, 4.16.1.0, 4.16.0.0, 4.15.1.0, 4.15.0.0, 4.14.3.0, 4.14.2.0, 4.14.1.0, 4.14.0.0, 4.13.0.0, 4.12.0.0, 4.11.1.0, 4.11.0.0, 4.10.1.0, 4.10.0.0, 4.9.1.0, 4.9.0.0, 4.8.2.0, 4.8.1.0, 4.8.0.0, 4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (constraint from non-reinstallable package requires installed instance) [__4] fail (backjumping, conflict set: base, foo, primitive) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, primitive, vector-algorithms, criterion, uvector, foo Try running with --minimize-conflict-set to improve the error message. And similar problems occur when depending on `unliftio` or `attoparsec`. How should I approach this? And I expect to run into similar questions in the near future, i.e., related to bulding, testing, using, but not necessarily related to [1]. Where should I ask? Kind regards Stefan [1]: https://github.com/haskell/core-libraries-committee/issues/367 [2]: https://gitlab.haskell.org/ghc/ghc/-/wikis/contributing -- Stefan Klinger, Ph.D. -- computer scientist o/X http://stefan-klinger.de /\/ https://github.com/s5k6 \ I prefer receiving plain text messages, not exceeding 32kB.