September 2025 - ghc-devs

GitLab maintenance window tonight
by Ben Gamari 30 Sep '25

30 Sep '25

Hi all, Tonight (around 19:00 ET) I will be carrying out a GitLab upgrade and a bit of work to mitigate crawler traffic. As usual, I hope this will be less than ten minutes of downtime. Cheers, - Ben

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GHC Developer retreat 2026
by Magnus Viernickel 30 Sep '25

30 Sep '25

Dear GHC developers and contributors, Teo Camarasu and I, Magnus Viernickel are planning a GHC Developer retreat for people interested in cabal, HLS and GHC hacking in Hathersage, UK. The main goal is to create an informal and productive atmosphere for focused GHC hacking, just like the Nix ecosystem does with their "sprints" and like Andreas Klebinger and Matthew Pickering planned with their GHC Week 5 years ago before the pandemic cancelled their plans. For more information, please have a look at: https://ghc-dev-retreat.mangoiv.com/ If that makes you interested, please fill in our interest check form at: https://forms.gle/JTD9mgG24ejM4ybe6 Mind that we currently do not know - if the venue is fixed (we might need to switch to a bigger one if there are a lot more people interested than the current capacity of 14 people) - the concrete costs (this will depend on how many people are interested, the Sladenlodge is not that expensive in the off-season though and I think it will be very manageable, esp. when it's fully booked) If you have any ideas or questions, please feel free to reach out. Best Teo and Magnus

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mistakenly deleted lables "bug" and "needs triage" from a new bug, can somebody add them ?
by George Colpitts 25 Sep '25

25 Sep '25

Hello I created a new bug, #26441, but mistakenly deleted /label ~bug /label ~"needs triage" from the description and when I add them it doesn't seem to do anything. Can somebody with the appropriate permissions add them now. Thanks George

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GHC 9.12.3-rc1 is now available
by Zubin Duggal 22 Sep '25

22 Sep '25

The GHC developers are very pleased to announce the availability of the release candidate for GHC 9.12.3. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][] and via [GHCup](https://www.haskell.org/ghcup/). GHC 9.12.3 is a bug-fix release fixing several issues of a variety of severities and scopes. A full accounting of these fixes 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][]. This release candidate will have a two-week testing period. If all goes well the final release will be available the week of 2 October 2025. We would like to thank Well-Typed, Tweag I/O, Juspay, QBayLogic, Channable, Serokell, 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://gitlab.haskell.org/ghc/ghc/-/blob/ghc-9.12/docs/users_guide/9.12.3-… [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.3-rc1 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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CStub in inline-java
by Facundo Domínguez 18 Sep '25

18 Sep '25

Dear devs, I upgraded inline-java [1] to use GHC 9.10.2 recently. inline-java has a GHC plugin responsible for embedding JVM bytecode in Haskell modules. This message is to consult on the most appropriate way to do it. The byte code is placed in a C literal array of bytes, and the C code is added in mg_foreign together with C constructor functions that run when loading the module to add the bytecode to a global bytecode table [2]. The global bytecode table is then fed to the JVM when initializing inline-java. The GHC API in 9.10.2 requires creating a CStub which does have a field to indicate constructor functions [3], but I wouldn't know how to create the CLabels it needs. So instead, I just put the constructor functions in the getCStub field, and set getInitializers to an empty list. The constructor functions seem to run at initialization just the same. Should inline-java do this differently? Thanks in advance! Facundo [1] https://github.com/tweag/inline-java [2] https://github.com/tweag/inline-java/blob/c6b590c29ef9190164dec3a235b8e386c… [3] https://gitlab.haskell.org/ghc/ghc/-/blob/3c37d30b07fc85fe09452f4ce250aec42… data CStub = CStub { getCStub :: SDoc , getInitializers :: [CLabel] -- ^ Initializers to be run at startup -- See Note [Initializers and finalizers in Cmm] in -- "GHC.Cmm.InitFini". , getFinalizers :: [CLabel] -- ^ Finalizers to be run at shutdown } -- 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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GHC 9.14.1-alpha2 is now available
by Ben Gamari 15 Sep '25

15 Sep '25

The GHC developers are very pleased to announce the availability of the second alpha prerelease of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org] GHC 9.14 will bring a number of new features and improvements, including: * Significant improvements in specialisation: * The `SPECIALISE` pragma now allows use of type application syntax * The `SPECIALISE` pragma can be used to specialise for expression arguments as well as type arguments. * Specialisation is now considerably more reliable in the presence of `newtype`s * Significant improvements in the GHCi debugger * Record fields can be defined to be non-linear when `LinearTypes` is enabled. * `RequiredTypeArgments` can now be used in more contexts * SSE/AVX2 support in the x86 native code generator backend * A major update of the Windows toolchain * ... and many more A full accounting of changes can be found in the [release notes]. Given the many specialisation improvements and their potential for regression, we would very much appreciate testing and performance characterisation on downstream workloads. Observant readers of these prerelease announcements will note that polymorphic specialisation has been dropped from alpha 2. This measure was taken out of an abundance of caution after finding a miscompilation during testing of alpha 1. While this bug will be fixed in the next alpha, we expect to keep polymorphic specialisation disabled by default in the final release. Users needing more aggressive specialisation can explicitly enable this feature with the `-fpolymorphic-specialisation` flag. Depending upon our experience with 9.14.1, we may enable this feature by default in a later minor release. This is the second of three expected alpha prereleases. We expect the next (third) alpha will come 23 Sept. 2025, with the release candidate coming 7 Oct. 2025. We would like to thank the Zw3rk stake pool, Well-Typed, Mercury, Channable, Tweag I/O, Serokell, 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 have made the Haskell ecosystem what it is today. As always, do give this release a try and open a [ticket] if you see anything amiss. [downloads.haskell.org] https://downloads.haskell.org/ghc/9.14.1-alpha2 [release notes]: https://downloads.haskell.org/ghc/9.14.1-alpha2/docs/users_guide/9.14.1-not… [ticket]: https://gitlab.haskell.org/ghc/homepage/-/issues/new

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Haskell Symposium 2025 Last Call for Talks (deadline Sept 15th)
by Ningning Xie 14 Sep '25

14 Sep '25

======================================================== Haskell Symposium 2025 Call for Talks Thu 16 - Fri 17 Oct 2025, Singapore https://conf.researchr.org/home/icfp-splash-2025/haskellsymp-2025 ======================================================== The ACM SIGPLAN Haskell Symposium 2025 will be co-located with the 2025 International Conference on Functional Programming (ICFP) and the 2025 International Conference on Systems, Programming, Languages and Applications: Software for Humanity (SPLASH). The Haskell Symposium presents original research on Haskell, discusses practical experience and future development of the language, and promotes other forms of declarative programming. We invite proposals from potential speakers for talks. Talk proposals should report work in progress relevant to Haskell language design, theory, tools, or applications. Talks are proposed by submitting an abstract. Please submit a talk title and abstract of no more than 300 words. There will be no published proceedings. Papers should be submitted through HotCRP at: https://haskell25.hotcrp.com/ Submission deadline: 15 September 2025 (Mon) Deadlines are valid anywhere on Earth. Talk proposals will go through a lightweight reviewing process, evaluated by the PC for relevance to the Haskell community, but are not expected to include finished results. Talk proposals will not be distributed to attendees, but authors of talk proposals may provide links to materials to be included on the program. Topics of interest include: * Language design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, such as formal semantics of the present language or future extensions, type systems, effects, metatheory, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management, as well as foreign function and component interfaces; * Libraries, that demonstrate new ideas or techniques for functional programming in Haskell; * Tools, such as profilers, tracers, debuggers, preprocessors, and testing tools; * Applications, to scientific and symbolic computing, databases, multimedia, telecommunication, the web, and so forth; * Experience Reports, to document general practice and experience in education, industry, or other contexts; * System Demonstrations, based on running software rather than novel research results.

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AArch64/Linux CI runners
by Ben Gamari 11 Sep '25

11 Sep '25

Hi all, Last night we brought up the new AArch64/Linux runners in their temporary home. They are now serving jobs, seemingly successfully. If you observe any suspicious failures do let us know. At some point in the near future we will need to bring the runners back down for a day or so to move them to their final home at OpenCape. We will communicate plans for this as they are formed. Cheers, - Ben

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GHC 9.10.3 is now available
by Zubin Duggal 11 Sep '25

11 Sep '25

The GHC developers are very pleased to announce the availability of the final release for GHC 9.10.3. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. GHC 9.10.3 is a bug-fix release fixing many issues of a variety of severities and scopes, including: * Fix a number of crashes in the compiler frontend (#25960, #25004, #25056) * Fix incorrect results in the NCG (#25601, #26061) * Support for far jumps in the AArch64 NCG (#24648) * A fix for a segfault in the RTS when running certain code involving STM (#26205) * And many more! A full accounting of these fixes 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 Well-Typed, Tweag I/O, Juspay, QBayLogic, Channable, Serokell, 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/9.10.3/docs/users_guide/9.10.3-notes.html [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.10.3 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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gitlab.haskell.org is now behind Cloudflare
by Ben Gamari 07 Sep '25

07 Sep '25

Hi all, In response to reports of Anubis breaking some page loads and the LLM crawling load, I have put gitlab.haskell.org behind Cloudflare proxying. My hope is that this allows us to both mitigate some of the spam problem, avoid the crawling load, and avoid the issues with Anubis. Naturally, let me know if you observe anything amiss. Cheers, - Ben

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