- ghc-devs - Haskell.org

Missing Enum instance for IoSubSystem
by Adithya Kumar 04 Dec '24

04 Dec '24

Hi all, In ghc 9.12-alpha the Enum instance for IoSubSystem no longer exists. I don't see this change mentioned anywhere in the docs (release notes/changelog) here: https://downloads.haskell.org/ghc/9.12.1-alpha1/docs/users_guide/9.12.1-not… Was this change intended or was it a refactoring issue? The datatype itself was moved from GHC.Internal.RTS.Flags to GHC.Internal.IO.SubSystem. The enum instance was earlier defined in GHC.Internal.RTS.Flags but now isn't defined in either of the modules. Best, Adithya

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GHC 9.8.4 is now available
by Ben Gamari 02 Dec '24

02 Dec '24

The GHC developers are happy to announce the availability of GHC 9.8.4. Binary distributions, source distributions, and documentation are available on the [release] page. This release is a small release fixing a few issues noted in 9.8.3, including: * Update the `filepath` submodule to avoid a misbehavior of `splitFileName` under Windows. * Update the `unix` submodule to fix a compilation issue on `musl` platforms * Fix a potential source of miscompilation when building large projects on 32-bit platforms * Fix unsound optimisation of `prompt#` uses A full accounting of changes can be found in the [release notes]. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket] if you see anything amiss. Happy compiling! - Ben [release]: https://www.haskell.org/ghc/download_ghc_9_8_4.html [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.8.4/docs/users_guide/9.8.4-notes.html

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Beginning of GitLab maintenance
by Ben Gamari 02 Dec '24

02 Dec '24

Just a reminder that GitLab will be going down in just a moment. Cheers, - Ben

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GitLab downtime in 55 minutes
by Ben Gamari 02 Dec '24

02 Dec '24

Hi all, At 18:00 EST I will take GitLab down for a few minutes to complete a filesystem migration, hopefully at last freeing us from the disk space issue which has been plauguing us lately. I will sent notification when the migration is finished and things are back to normal. Cheers, - Ben

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Cannot get nightly builds of GHC
by Facundo Domínguez 02 Dec '24

02 Dec '24

Dear devs, Nightly builds of Liquid Haskell seem to be failing because https://ghc.gitlab.haskell.org gives 502 bad gateway. LH needs https://ghc.gitlab.haskell.org/ghcup-metadata/ghcup-nightlies-0.0.7.yaml Is there anyone I should tell about it? Thanks, Facundo -- All views and opinions expressed in this email message are the personal opinions of the author and do not represent those of the organization or its customers.

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[ANNOUNCE] GHC 9.12.1-rc1 is now available
by Zubin Duggal 29 Nov '24

29 Nov '24

The GHC developers are very pleased to announce the availability of the release candidate for GHC 9.12.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. We hope to have this release available via ghcup shortly. GHC 9.12 will bring a number of new features and improvements, including: * The new language extension [OrPatterns] allowing you to combine multiple pattern clauses into one. * The [MultilineStrings] language extension to allow you to more easily write strings spanning multiple lines in your source code. * Improvements to the OverloadedRecordDot extension, allowing the built-in `HasField` class to be used for records with fields of non lifted representations. * The [NamedDefaults] language extension has been introduced allowing you to define defaults for typeclasses other than `Num`. * More deterministic object code output, controlled by the `-fobject-determinism` flag, which improves determinism of builds a lot (though does not fully do so) at the cost of some compiler performance (1-2%). See #12935 for the details * GHC now accepts type syntax in expressions as part of [GHC Proposal #281]. * The WASM backend now has support for TemplateHaskell. * ... and many more A full accounting of changes can be found in the [release notes][]. As always, GHC's release status, including planned future releases, can be found on the GHC Wiki [status][]. We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. Cheers, Zubin [release notes]: https://downloads.haskell.org/ghc/9.12.1-rc1/docs/users_guide/9.12.1-notes.… [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.1-rc1 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [OrPatterns]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0522-o… [MultilineStrings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0569-m… [GHC Proposal #281]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0281-v… [NamedDefaults]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0409-e…

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GHC 9.12.1 updates and rc1 status
by Zubin Duggal 27 Nov '24

27 Nov '24

Hi all, We had planned to release 9.12.1-rc1 today. Unfortunately, we discovered a few regressions and bugs which need to be fixed before we can publish a release candidate, including #25382, #25375 and !13633. I am currently waiting for some of these fixes to land in master before backporting them to the release branch. I will try to have the release candidate out on Monday the 25th. The final release is currently scheduled for December 6th. We will inform you if there are any changes to this schedule. Cheers, Zubin.

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labeling MVar and STM data structures
by Kazu Yamamoto 21 Nov '24

21 Nov '24

Hello, I'm seeking of the source of the bug that my server based on Warp gets not-responding. "listThreads" shows that IOManager is blocked on a MVar permanently: 2 IOManager on cap 0: ThreadBlocked BlockedOnForeignCall 3 IOManager on cap 1: ThreadBlocked BlockedOnMVar 4 TimerManager: ThreadBlocked BlockedOnForeignCall IOManager should have the BlockedOnForeignCall reason since it's calling epoll_wait(). It's quit hard to debug this bug since I don't understand which MVar blocks IOManager of 3. Users can register MVar operations to IOManager while IOManager itself is using MVars internally. To make this kind of debugging easier, I would like ask GHC developers to extend MVar to hold its label and provide "labelMVar" like "labelThread". The same mechanism should be provided for STM as well. "BlockReason" should contain the target label. What do you think? Background: https://github.com/haskell/network/issues/590 --Kazu

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[ANNOUNCE] GHC 9.12.1-alpha3 is now available
by Zubin Duggal 15 Nov '24

15 Nov '24

The GHC developers are very pleased to announce the availability of the third alpha release of GHC 9.12.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. We hope to have this release available via ghcup shortly. GHC 9.12 will bring a number of new features and improvements, including: * The new language extension [OrPatterns] allowing you to combine multiple pattern clauses into one. * The [MultilineStrings] language extension to allow you to more easily write strings spanning multiple lines in your source code. * Improvements to the OverloadedRecordDot extension, allowing the built-in `HasField` class to be used for records with fields of non lifted representations. * The [NamedDefaults] language extension has been introduced allowing you to define defaults for typeclasses other than `Num`. * More deterministic object code output, controlled by the `-fobject-determinism` flag, which improves determinism of builds a lot (though does not fully do so) at the cost of some compiler performance (1-2%). See #12935 for the details * GHC now accepts type syntax in expressions as part of [GHC Proposal #281]. * The WASM backend now has support for TemplateHaskell. * ... and many more A full accounting of changes can be found in the [release notes][]. As always, GHC's release status, including planned future releases, can be found on the GHC Wiki [status][]. We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. [release notes]: https://downloads.haskell.org/ghc/9.12.1-alpha3/docs/users_guide/9.12.1-not… [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.1-alpha3 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [OrPatterns]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0522-o… [MultilineStrings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0569-m… [GHC Proposal #281]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0281-v… [NamedDefaults]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0409-e… Cheers, Zubin

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Under which circumstances are the elements of a linked list laid next to each-other in memory?
by Hécate 13 Nov '24

13 Nov '24

Hi everyone, I was asked at work today why I went for Vector instead plain old List in order to store an API result that is quite small. While writing my reasons (pointer indirection, conversion to Aeson's internal representation of a JSON array using Vector), I remember that I heard that in some cases, GHC would be able to lay down in memory the elements of a linked list next to each other. I don't think this gets rid of the pointer-chasing, but I'm interested to know more about the circumstances in which linked lists are optimised. Does anyone know if there is a wiki page or something that I could read on the topic of linked list optimisation **other than fusion**? Cheers, Hécate -- Hécate ✨ 🐦: @TechnoEmpress IRC: Hecate WWW: https://glitchbra.in RUN: BSD

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