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Haskell in Nixpkgs/NixOS

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For discussions and questions about Haskell with Nix, cabal2nix and haskellPackages in nixpkgs | Current Docs: https://haskell4nix.readthedocs.io/ | More Nix: #community:nixos.org | More Haskell: #haskell-space:matrix.org143 Servers

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16 Jul 2025
@sternenseemann:systemli.orgsterni (he/him)https://www.haskell.org/ghc/blog/20250702-ghc-release-schedules.html22:38:21
@maralorn:maralorn.demaralornYeah. I am wondering what that’s gonna mean for stackage LTS.23:08:20
17 Jul 2025
@kubitess:matrix.orgkubitess joined the room.11:57:34
18 Jul 2025
@dmjio:matrix.org@dmjio:matrix.org set a profile picture.00:21:22
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19 Jul 2025
@prsteele:matrix.orgPatrick Steele Indeed, cabal run --enable-profiling myprog -- +RTS -p worked 21:07:44
@prsteele:matrix.orgPatrick Steele without modification to the cabal file, i.e. no -prof 21:08:05
20 Jul 2025
@profpatsch:augsburg.oneProfpatsch gonna switch to 9.14 and never update again13:11:26
@maralorn:maralorn.demaralorn
In reply to @profpatsch:augsburg.one
gonna switch to 9.14 and never update again
I feel like I am missing context. 🤣
22:09:55
21 Jul 2025
@profpatsch:augsburg.oneProfpatsch LTS00:09:46
@magic_rb:matrix.redalder.orgmagic_rb im benchmarking a thing i wrote and im making a nix package out of a cabal file using cabal2nix, however if i change the source cabal file and remove -fllvm, -O2, or -fexpose-all-unfoldings the performance measurements dont seem to change even though im positive they should. Is nixpkgs overwriting my flags somehow? 09:41:41
@magic_rb:matrix.redalder.orgmagic_rbim now trying the same bench but build outside of nixpkgs09:45:07
@maralorn:maralorn.demaralorn magic_rb: None of those should be overriden, I think. 10:02:32
@magic_rb:matrix.redalder.orgmagic_rbhm10:02:39
@magic_rb:matrix.redalder.orgmagic_rbokay10:02:41
@magic_rb:matrix.redalder.orgmagic_rbthan my thing is weird, il running the benches on an interactively compiled version10:02:59
@magic_rb:matrix.redalder.orgmagic_rbyeah same result10:03:15
@maralorn:maralorn.demaralornMaybe the even appear somewhere in the build log, e.g. in the configureFlags, although I am not sure about that.10:03:23
@magic_rb:matrix.redalder.orgmagic_rbhm, i could swear it made a difference when i was developing this thing, idk why the performance difference vanished, now it doesnt really matter what flags i use10:03:47
@magic_rb:matrix.redalder.orgmagic_rbfun, my thesis is gonna be "well, these did something when i was writing this, now they seemingly dont anymore. IDFK why, future work"10:05:12
@maralorn:maralorn.demaralornDid you maybe apply expose-all-unfoldings to dependencies as well? That might make a difference.10:07:42
@magic_rb:matrix.redalder.orgmagic_rbnot that im aware of10:08:10
@magic_rb:matrix.redalder.orgmagic_rb
    ghc-options: -Wall -threaded -O2 -fllvm -Wno-unrecognised-pragmas -fspecialise-aggressively -fexpose-all-unfoldings

on my library and executables

10:08:23
@magic_rb:matrix.redalder.orgmagic_rb but not in cabal.project 10:08:29
@magic_rb:matrix.redalder.orgmagic_rband when i was profiling this back then, most of the slowness was in my code because of my custom monad transformer10:09:04
@magic_rb:matrix.redalder.orgmagic_rb im gonna remove the inline pragmas, those didnt seem to be enough last time i tried, which is why i enabled -fexpose-all-unfoldings 10:10:29
@magic_rb:matrix.redalder.orgmagic_rbbut ill try to removing them again and see if some difference shows up10:10:42
@magic_rb:matrix.redalder.orgmagic_rbokay, same result, im completely confused and have no clue what is going on10:19:40
@maralorn:maralorn.demaralornI mean, is it a different ghc version than when you added those flags?10:20:28
@magic_rb:matrix.redalder.orgmagic_rbi think i found it10:21:36

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