January 2020 - ghc-devs

lots of spam repos on gitlab
by Carter Schonwald 21 Jan '20

21 Jan '20

theres a lot of spam repos on the gitlab :( 11:07 AM <carter> https://gitlab.haskell.org/wandaibson/oberton-paris <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=keto&sort=l… lots of keto 11:10 AM <carter> two CBD 11:10 AM <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=CBD&sort=la… 11:11 AM <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=pep&sort=la… 11:13 AM <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=pill&sort=l… 11:17 AM <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=vitality&so… 11:17 AM <carter> alp: ? 11:23 AM ⇐ zeta_0 quit (~zeta(a)h78.48.155.207.dynamic.ip.windstream.net) Quit: doing a rebuild switch 11:24 AM <carter> https://gitlab.haskell.org/explore/projects?utf8=%E2%9C%93&name=suppl&sort=…

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submodule instructions?
by Richard Eisenberg 21 Jan '20

21 Jan '20

Hi devs, Are there up-to-date instructions on how to deal with submodules in GHC? https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/git/submodules <https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/git/submodules> does give nice information. It refers to https://gitlab.haskell.org/ghc/ghc/wikis/repositories <https://gitlab.haskell.org/ghc/ghc/wikis/repositories> to learn about specific repositories. But is that second page correct? It refers to e.g. GitHub as the upstream for Haddock. Will our new GitLab-based CI pull from GitHub's Haddock? And what if a contributor doesn't have commit access? Maybe it's all there, but I don't quite see how a contributor can ensure that CI has access to patches on submodules. Thanks, Richard

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GitLab restart
by Ben Gamari 20 Jan '20

20 Jan '20

Hi everyone, In around 30 minutes I'll be migrating some data on gitlab.haskell.org to a larger storage volume. This will take around 10 minutes, during which time GitLab will down. I'll sent another email before I begin the migration. Cheers, - Ben

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Unboxed Tuple in a single STG variable
by Csaba Hruska 20 Jan '20

20 Jan '20

Hello, Can an STG variable (Id) store a whole unboxed tuple value? Or is it required to decompose a returned unboxed value immediately by using an StgCase expression? If so, then is it correct that the STG variables can store values only from the following types: Addr, Float, Double, Int, Word, Ptr (for boxed values)? (and no multi-value values) Thanks, Csaba

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is Unlifted Type == Primitive Type?
by Csaba Hruska 20 Jan '20

20 Jan '20

Hello, According to GHC Wiki <https://gitlab.haskell.org/ghc/ghc/wikis/commentary/compiler/type-type#Clas…> it seems that only primitive types can be unlifted. Is this true in general? (i.e. no user type can be unlifted) [image: image.png] Does the Stg to Cmm codegen support compilation for a variable of user defined ADT as unlifted? i.e. some analysis proved that it is always a constructor and never a thunk. Thanks, Csaba

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Github mirror
by Phyx 20 Jan '20

20 Jan '20

Hi Ben, It looks like the github mirror for ghc hasn't updated in a month. Kind regards, Tamar Sent from my Mobile

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Fixing type synonyms to Uniq(D)FM newtypes
by Ömer Sinan Ağacan 17 Jan '20

17 Jan '20

Hi, UniqFM and UniqDFM types are basically maps from Uniques to other stuff. Most of the time we don't actually map Uniques but instead map things like Vars or Names. For those we have types like VarEnv, NameEnv, FastStringEnv, ... which are defined as type synonyms to UniqFM or UniqDFM, and operations are defined like extendFsEnv = addToUFM extendNameEnv = addToUFM extendVarEnv = addToUFM This causes problems when I have multiple Uniquables in scope and use the wrong one to update an environment because the program type checks and does the wrong thing in runtime. An example is #17667 where I did delVarEnv env name where `name :: Name`. I shouldn't be able to remove a Name from a Var env but this currently type checks. Two solutions proposed: - Make these env types newtypes instead of type synonyms. - Add a phantom type parameter to UniqFM/UniqDFM. If you could share your opinion on how to fix this I'd like to fix this soon. Personally I prefer (1) because it looks simpler but I'd be happy with (2) as well. Ömer

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Windows testsuite failures
by Ben Gamari 17 Jan '20

17 Jan '20

Hi all, Currently Windows CI is a bit flaky due to some unfortunately rather elusive testsuite driver bugs. Progress in resolving this has been a bit slow due to travel over the last week but I will be back home tomorrow and should be able to resolve the issue soon thereafter. Cheers, - Ben

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Find constraints over type
by Alejandro Serrano Mena 17 Jan '20

17 Jan '20

Dear GHC devs, I am trying to figure out a way to obtain the constraints that hold over a type. Let me give you an example: suppose that I write the following function: f :: Eq a => [a] -> Bool f xs = xs == [] If I ask for the type of the Var ' xs', I get back '[a]'. This is correct, but I am missing the crucial information that '[a]' must be Eq. Is there an easy way to get it? It seems that 'varType' doesn't give me enough information. Regards, Alejandro

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Linking stage 2 compiler with non-threaded RTS using Make?
by Ömer Sinan Ağacan 15 Jan '20

15 Jan '20

Anyone know how to link stage 2 with non-threaded RTS using Make build system? There's a variable GhcThreaded, but setting it "NO" makes no difference, stage 2 compiler is still threaded. So far the only way I could find is to redirect build system output to a file, find the step that linked ghc-stage2, repeat that command but without -threaded. It's really painful as I have to repeat this step after every rebuild. Any tips? Thanks, Ömer

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