Hi, i am working on a project where I just updated from nix 22.11 to 24.11. this project uses a haskell library that does ffi stuff. since the update I am getting the following error when trying to compile something that uses the ffi haskell library:

       > <no location info>: error:
       >     /nix/store/ig69mqspa9a7gmkib1p05rndsfmp5qjl-mypackage-0.1.0/lib/ghc-9.6.6/lib/x86_64-linux-ghc-9.6.6/mypackage-0.1.0-GG7CxsqkGDRPE7u83aSVw-ghc9.6.6.so: undefined symbol: my_function

Anyone has a clue what broke or how to debug this? Did anything change in the way nix/ghc handles ffi things since nix 22.11?

Cabal 3.14.1.1 breaks GHC 9.12 bootstrap and it's kind of interesting how this happened

1. So to begin with GHC 9.12 arbitrarily requests Cabal 3.14 for hadrian because they need it for some feature. Since no previous GHC actually ships this version of Cabal, you can't use the core package.
2. Cabal 3.14.1.1 newly introduces a constraint on unix that is supposed to prevent building it with a buggy version of unix (a bug that apparently only affects 32bit platforms). I must say that these is a questionable decision and seems like abusing the constraint system. It's also strange that even though the bug only affects certain platforms, the constraint isn't conditional. (https://github.com/haskell/unix/pull/318)
3. Since GHC 9.10 which we use for bootstrapping ships an affected version of Unix we get a violated constraint.

Which goes to show that making your bootstrapping process more complex, things will go wrong as soon as someone steps just a tiny bit away from the CI tested bootstrap plans that pin every dependency.

The question is whether we even need it

On that platform (as well as any other glibc/musl platform), however, CTimeVal isn't used for anything at all because there are #ifdefs that prefer using utimensat which takes CTimeSpec instead. This fix is therefore quite theoretical, as it is unknown whether there are any platforms actually affected.