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Blog post: working towards a more stable Template Haskell
by Teofil Camarasu 07 Jun '24

07 Jun '24

Hi folks, I’ve written up a blog post about our ongoing project to improve the stability of Template Haskell. The post lays out: - why users of Template Haskell often face broken code with each new version of the compiler. - some of our plans to make the interface more stable. - some groundwork we’ve lain to make these plans achievable - ways folks can get invovled Give it a read: https://informal.codes/posts/stabilising-th/ Cheers, Teo

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GitLab Approval
by Luke Tollefson 05 Jun '24

05 Jun '24

Hey! I'm looking to get my GitLab account approved for the ZuriHac workshop. Username: lukewtollefson Thanks! Luke

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RTS crashes
by Simon Peyton Jones 03 Jun '24

03 Jun '24

In my private build of !12492 I'm getting some assertion failures in CheckUnload (see below). This can't possibly be my fault! I don't know if CI perhaps has these assertion switched off, so only I am seeing them? I'd open a ticket but it may just be my bad, somehow Any ideas? Simon Stderr run ( MultiLayerModulesDefsGhci ): ghc: internal error: ASSERTION FAILED: file rts/CheckUnload.c, line 460 (GHC version 9.11.20240530 for x86_64_unknown_linux) Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug Aborted *** unexpected failure for MultiLayerModulesDefsGhci(ghci) ]0;MultiLayerModulesDefsGhciReload(ghci) 4776 of 10144 [0, 1, 0] ]0;InstanceMatching(normal) 4777 of 10144 [0, 1, 0] ]0;Running for 5m51s [35433/36451], predicted 1s (98%) Wrong exit code for MultiLayerModulesDefsGhciReload(ghci)(expected 0 , actual 134 ) Stderr run ( MultiLayerModulesDefsGhciReload ): ghc: internal error: ASSERTION FAILED: file rts/CheckUnload.c, line 460 (GHC version 9.11.20240530 for x86_64_unknown_linux) Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug Aborted *** unexpected failure for MultiLayerModulesDefsGhciReload(ghci) ]0;InstanceMatching1(normal) 4778 of 10144 [0, 2, 0] ]0;MultiLayerModulesNoCode(ghci) 4779 of 10144 [0, 2, 0] Wrong exit code for MultiLayerModulesNoCode(ghci)(expected 0 , actual 134 ) Stderr run ( MultiLayerModulesNoCode ): ghc: internal error: ASSERTION FAILED: file rts/CheckUnload.c, line 460 (GHC version 9.11.20240530 for x86_64_unknown_linux) Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug Aborted

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sempahore-compat-1.0.0 base bounds
by Shayne Fletcher 03 Jun '24

03 Jun '24

the bounds for semaphore-compat-1.0.0 do not include base-4.20. can this be fixed please? -- Shayne Fletcher

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Haddock test suite failure -- can anyone guide me?
by Simon Peyton Jones 01 Jun '24

01 Jun '24

Dear Haddock experts I'm getting a failure on !12492 <https://gitlab.haskell.org/ghc/ghc/-/merge_requests/12492> that I can't understand or debug. Can someone guide me? Failure is this: /builds/ghc/ghc/tmp/ghctest-2jo7oz8x/test spaces/testsuite/tests/haddock/haddock_testsuite/haddockHypsrcTest.run haddockHypsrcTest [bad exit code (2)] (normal) A snip of the log is at the end of this message. I want to - understand what it does - repro it locally. Trying the latter, I tried with my HEAD build and did bash$ cd testsuite/tests/haddock/haddock_testsuite bash$ make hypsrcTest but that failed on almost all the tests it does, even though HEAD is presumably OK. I'm stumped. Any ideas? The patch only changes the type checker! Thanks SImion This is the log from !12492 Wrong exit code for haddockHypsrcTest()(expected 0 , actual 2 ) Stdout ( haddockHypsrcTest ): [1 of 7] Compiling Test.Haddock.Process ( /builds/ghc/ghc/testsuite/../utils/haddock/haddock-test/src/Test/Haddock/Process.hs, Test/Haddock/Process.o ) [2 of 7] Compiling Test.Haddock.Utils ( /builds/ghc/ghc/testsuite/../utils/haddock/haddock-test/src/Test/Haddock/Utils.hs, Test/Haddock/Utils.o ) [3 of 7] Compiling Test.Haddock.Config ( /builds/ghc/ghc/testsuite/../utils/haddock/haddock-test/src/Test/Haddock/Config.hs, Test/Haddock/Config.o ) [4 of 7] Compiling Test.Haddock ( /builds/ghc/ghc/testsuite/../utils/haddock/haddock-test/src/Test/Haddock.hs, Test/Haddock.o ) [5 of 7] Compiling Test.Haddock.Xhtml ( /builds/ghc/ghc/testsuite/../utils/haddock/haddock-test/src/Test/Haddock/Xhtml.hs, Test/Haddock/Xhtml.o ) [6 of 7] Compiling Main ( /builds/ghc/ghc/testsuite/../utils/haddock/hypsrc-test/Main.hs, Main.o ) [7 of 7] Linking hypsrc-test Haddock version 2.30.0, (c) Simon Marlow 2006 Ported to use the GHC API by David Waern 2006-2008 9.11.20240530 Generating documentation... Testing output files... Checking "src/TemplateHaskellSplices.html"... PASS Checking "src/Bug1091.html"... PASS Checking "src/Polymorphism.html"... PASS Checking "src/UsingQuasiquotes.html"... PASS Checking "src/Records.html"... PASS Checking "src/Quasiquoter.html"... PASS Checking "src/CPP.html"... PASS Checking "src/Operators.html"... PASS Checking "src/Literals.html"... PASS Checking "src/LinkingIdentifiers.html"... PASS Checking "src/Classes.html"... FAIL Checking "src/PositionPragmas.html"... PASS Checking "src/Types.html"... PASS Checking "src/TemplateHaskellQuasiquotes.html"... PASS Checking "src/Constructors.html"... FAIL Checking "src/Identifiers.html"... FAIL Diffing failed cases... Diff for file "src/Classes.html": 1194c1194,1198 < > > >a -> b -> a > forall a b. a -> b -> a > > > >a -> b -> a > forall a b. a -> b -> a > > > >b -> a -> b > forall a b. a -> b -> a > > > >b -> a -> b > forall a b. a -> b -> a > > > >([Int] -> Int) -> (Norf -> [Int]) -> Norf -> Int > forall b c a. (b -> c) -> (a -> b) -> a -> c > > > >(String -> IO ()) -> (Int -> String) -> Int -> IO () > forall b c a. (b -> c) -> (a -> b) -> a -> c > ><a href="Identifiers.html#foo" < > > >Int -> Int -> Int > ><a href="Identifiers.html#foo" > > > >(String -> IO ()) -> (Int -> String) -> Int -> IO () > forall b c a. (b -> c) -> (a -> b) -> a -> c > ><a href="Identifiers.html#quux" < > > >Int -> Int > ><a href="Identifiers.html#quux" > > > >(String -> IO ()) -> (Int -> String) -> Int -> IO () > forall b c a. (b -> c) -> (a -> b) -> a -> c > ><a href="Identifiers.html#norf" < > > >Int -> Int -> Int -> Int > ><a href="Identifiers.html#norf" > ><span class="hs-identifier hs-var" Stderr run ( haddockHypsrcTest ): gmake: *** [Makefile:68: hypsrcTest] Error 1 *** unexpected failure for haddockHypsrcTest(normal)

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Documentation previews on Gitlab pipelines
by Teofil Camarasu 31 May '24

31 May '24

Hi folks, I just wanted to advertise that it is now possible to see rendered previews of documentation changes (haddocks/user guide/etc) on Gitlab pipelines. To access this you need to: 1. Wait for a pipeline to complete. 2. From the MR page, click on "Expand" under the pipeline widget, then "Documentation Preview" 3. This takes you to the job artefacts. Then open `docs/index.html`. 4. Gitlab will then redirect you to the hosted page. Alternatively instead of (2) you can open the "docs-tarball" job directly and click on "Browse" to go to the artefacts. I've also attached a screen recording to make it a bit clearer. I actually set this up a few weeks ago in !12415 <https://gitlab.haskell.org/ghc/ghc/-/merge_requests/12415>. But I forgot to advertise this more widely at the time. And Gitlab isn't super helpful in directing users to it. So, I realised most folks probably don't know it exists. Cheers, Teo

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GHC release series adoption rates
by Clinton Mead 29 May '24

29 May '24

Hi All The recent GHC blog post: https://www.haskell.org/ghc/blog/20240521-ghc-release-priorities.html states: *"9.6.5 seems to be a relatively stable release so far and we plan to prioritise fixes given the relatively higher adoption of this branch"* I was wondering where this information came from? Is this based on a number of downloads or some other metric? Number of companies that have adopted the version? How many stack/ghcup pulls? Or just a vibe/what people seem to be talking about? If there are hard numbers, are they public? The current project I'm working on is still on GHC 9.2.2, so I was considering an upgrade to GHC 9.4.8, but this blog post has made me lean towards the 9.6 series instead. This is just an upgrade for stability not features and so we don't get too far behind. But it would be good to have this popularity info generally instead of having to wait for a blog post. Cheers, Clinton

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Looking for recent works on STG
by Rodrigo Mesquita 26 May '24

26 May '24

Dear all, Do you know of any recent works on the STG? In particular, I am looking for a result connecting STG's execution and Core’s call-by-need semantics when written in structural operational semantics style. Nonetheless, I’m also interested in possibly more recent formulations of STG (e.g. a mechanized one?) beyond the original paper. Cheers Rodrigo Mesquita

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Question about -G RTS flag
by chessai 23 May '24

23 May '24

The docs for -G state: ``` ... Anything larger than about 4 is probably not a good idea unless your program runs for a *long* time, because the oldest generation will hardly ever get collected. ``` What is a "*long*" time?

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Priorities for upcoming GHC releases
by Zubin Duggal 21 May '24

21 May '24

Hi all, We detail our plans for upcoming GHC releases in a new blog post: https://www.haskell.org/ghc/blog/20240521-ghc-release-priorities.html The summary is that we will prioritise work on the 9.10, 9.6 and master branches over work on the 9.8 branch for the coming few months due to time and resource constraints. This does not mean that we are dropping support for GHC 9.8, but that releases in this series might be made at a slower pace than usual. Cheers, Zubin.

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