January 2023 - Glasgow-haskell-users

[ANNOUNCE] GHC 9.6.1-alpha2 is now available
by Ben Gamari 30 Jan '23

30 Jan '23

The GHC team is very pleased to announce the availability of GHC 9.6.1-alpha2. As usual, binaries and source distributions are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.6.1-alpha2/ Beginning with GHC 9.6.1, GHC can be built as a cross-compiler to WebAssembly and JavaScript. This is an important step towards robust support for compiling Haskell to the Web, but there are a few caveats to be aware of in the 9.6 series: - Both the Javascript and WebAssembly backends are still at an early stage of development and are present in this release as a technology preview - Using GHC as a cross-compiler is not as easy as we would like it to be; in particular, there are challenges related to Template Haskell. - GHC is not yet run-time retargetable; a given GHC binary targets exactly one platform, and both WebAssembly and JavaScript are considered platforms for this purpose. Cross-compilers must be built from source by their users We hope to lift all of these limitations in future releases. Additionally, 9.6.1 will include: - Significant latency improvements in the non-moving garbage collector - Efficient runtime support for delimited continuations - Improvements in compiler error messages - Numerous improvements in the compiler's memory usage See the [release notes] for a comprehensive accounting of changes in this release. As always, one can find a [migration guide] to aid in transitioning from older releases on the GHC Wiki. We have also recently started extending our release process to cover a wider set of Linux distributions. In particular, we now offer Rocky 8 and Ubuntu 20.04 binary distributions which cover RedHat-derivative and distributions using older `glibc` releases (namely 2.27), respectively. Please do give this release a try and open a [ticket] if you see anything amiss. Cheers, - Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/issues/ [migration-guide]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.6 [release notes]: https://downloads.haskell.org/ghc/9.6.1-alpha2/docs/users_guide/9.6.1-notes…

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How to fool the divergence checker in ghc 9
by Michael Sperber 20 Jan '23

20 Jan '23

I'm trying to port Conal Elliott's ConCat plugin from ghc 8 to 9, and the divergence checker foils me. Background: The plugin works by transforming calls to a pseudo-function toCcc' defined like so: -- | Pseudo function to trigger rewriting to TOCCC form. toCcc' :: forall k a b. (a -> b) -> (a `k` b) toCcc' _ = oops "toCcc' called" {-# NOINLINE toCcc' #-} For ghc 8, oops was defined like so: module ConCat.Misc where -- | Pseudo function to fool GHC's divergence checker. oops :: String -> b oops str = errorWithStackTrace ("Oops: "++str) {-# NOINLINE oops #-} ... but unfortunately, ghc 9 is not so easily fooled and reports <A>x for toCcc'. Is there any way to prevent this that works for ghc 9? Help would be much appreciated! -- Regards, Mike

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[ANNOUNCE] GHC 9.6.1-alpha1 is now available
by Ben Gamari 16 Jan '23

16 Jan '23

The GHC team is very pleased to announce the availability of GHC 9.6.1-alpha1. As usual, binaries and source distributions are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.6.1-alpha1/ This is the first alpha release in the 9.6 series which will bring a number of exciting features: * A new Javascript code generation backend * A new WebAssembly code generation backend, * Significant latency improvements in the non-moving garbage collector * Support for loading of multiple components in GHCi * Efficient support for delimited continuations * Improvements in error messages * Numerous improvements in compiler-residency Note that both the Javascript and WebAssembly backends are still in a state of infancy and are present in this release as a technology preview; we hope that they will mature considerably before the final 9.6.1 release. Please give this release a try and open a [ticket] if you see anything amiss. Cheers, - Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/issues/

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