The GHC developers are very pleased to announce the availability of the second alpha prerelease of GHC 10.0.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][] and via [GHCup](https://www.haskell.org/ghcup/). See also the [previous announcement of 10.0.1-alpha1][alpha1]. The changes since the first alpha are: * Fixes for miscompilations involving strict fields (#27831, #27845). * Fixes for runtime system crashes and deadlocks (#23160, #27272, #24450). * Fixes for several compiler panics and crashes (#27368, #27828, #27916, #27994, #28081). * A fix for instances being dropped during instance resolution (#26610), and fixes for the shared unit database cache (#27834, #27835, #27836). * A fix for a segfault when interface files generated with `-fbyte-code-and-object-code` are reused with `-fprefer-byte-code` (#27842). * Exception context is now preserved when rethrowing in more places in `base` ([CLC #446][clc446], [CLC #447][clc447]), and a WinIO fix for misreported I/O results (#27971). * Fixes for Quick Look under `ImpredicativeTypes` (#26543), GHCi's `:add` (#27641), and a performance regression when evaluating polymorphic thunks (#27979). * Hadrian and build system fixes (#25850, #27404, #27499, #27786, #27823, #28053), and an update to `containers` 0.8.1. GHC 10.0 will bring a number of new features and improvements, including: * The default language edition is now `GHC2024` ([GHC Proposal #632][ghc2024], #26039). * `Type` and `Constraint` are now completely distinct types, just as much as `Int` and `Bool` (#24279). * The new [QualifiedStrings][] language extension ([GHC Proposal #723][qualified-strings]) allows string literals to be qualified using module qualification syntax, so that `M."my string"` desugars to`M.fromString "my string"`. * The treatment of static forms has been simplified, implementing [GHC Proposal #732][static-forms] (#26556). The free term variables of `(static e)` must now be bound at top level. * `-fpolymorphic-specialisation` is now (re)enabled by default (#23559), * Bytecode can now be written to disk with `-fwrite-byte-code` and packaged into bytecode libraries with `-bytecodelib`, which the interpreter can use to satisfy package dependencies (#26298). * Executables can now be properly statically linked with the new `-fully-static` and `-static-external` flags (#26434). * SIMD support in the AArch64 native code generator (#26536). * A new `poll` I/O manager, which is now the default in the single-threaded RTS on all POSIX platforms except macOS (!9677). * Version 2 of the [GHC Jobserver Protocol][jsem] for GHC's `-jsem` jobserver on Linux and other POSIX platforms (#25087, #27253). This is sadly a necessary breaking change. `-jsem` requires cabal-install 3.18 or later, and is otherwise ignored with a warning, falling back to sequential compilation. * Changes to `base`: * `GHC.Num.{BigNat,Integer,Natural}` are no longer exposed ([CLC #359][clc-359]) and GHC internals in `GHC.Num` are deprecated ([CLC #360][clc-360]). * `Data.List.init` and `Data.List.last` now carry an `x-partial` warning ([CLC #292][clc-292]). * The minimum bootstrap compiler is now GHC 9.10, LLVM versions up to 23 are supported (#26813, #27764), and the Debian 9, Debian 10, Ubuntu 18.04 and Ubuntu 20.04 bindists have been dropped in favour of a new Debian 13 bindist (#25876). * ... and many more A full accounting of changes can be found in the [release notes][]. See the [migration guide][] for guidance on migrating programs to this release. As always, GHC's release status, including planned future releases, can be found on the GHC Wiki [status][]. Given the many changes in this major release, we would very much appreciate testing on downstream workloads. GHC development is sponsored by: * [Juspay](https://juspay.com/) * [QBayLogic](https://qbaylogic.com/) * [Channable](https://www.channable.com/) * [Haskell Foundation](https://haskell.foundation/) * [Serokell](https://serokell.io/) * [Well-Typed](https://well-typed.com/) * [Tweag](https://www.tweag.io/) * [Dotcom-Monitor](https://www.dotcom-monitor.com/) * [LoadView](https://www.loadview-testing.com/) * [Web Hosting Buddy](https://webhostingbuddy.com/) * [Find My Electric](https://www.findmyelectric.com/) * [Standard Chartered](https://www.sc.com) * [UpCloud](https://upcloud.com) * [Mercury](https://mercury.com) We would like to thank these sponsors 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. [downloads.haskell.org]: https://downloads.haskell.org/ghc/10.0.1-alpha2 [release notes]: https://downloads.haskell.org/ghc/10.0.1-alpha2/docs/users_guide/10.0.1-note... [migration guide]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/10.0 [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [alpha1]: https://www.haskell.org/ghc/blog/20260918-ghc-10.0.1-alpha1-released.html [ghc2024]: https://github.com/ghc-proposals/ghc-proposals/pull/632 [static-forms]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0732-si... [QualifiedStrings]: https://downloads.haskell.org/ghc/10.0.1-alpha2/docs/users_guide/exts/qualif... [qualified-strings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0723-qu... [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-js... [clc-292]: https://github.com/haskell/core-libraries-committee/issues/292 [clc-359]: https://github.com/haskell/core-libraries-committee/issues/359 [clc-360]: https://github.com/haskell/core-libraries-committee/issues/360 [clc446]: https://github.com/haskell/core-libraries-committee/issues/446 [clc447]: https://github.com/haskell/core-libraries-committee/issues/447