GHC 9.6.3 is now available

Bryan Richter - 2023-09-25

The GHC developers are happy to announce the availability of GHC 9.6.3. Binary distributions, source distributions, and documentation are available on the release page.

This release is primarily a bugfix release addressing a few issues found in the 9.6 series. These include:

  • Disable Polymorphic Specialisation (a performance optimisation) by default. It was discovered that Polymorphic Specialisation as currently implemented in GHC can lead to hard to diagnose bugs resulting in incorrect runtime results. Users wishing to use this optimisation despite the caveats will now have to explicitly enable the new -fpolymorphic-specialisation flag. For more details see #23469 as well as #23109, #21229, #23445.

  • Improve compile time and code generation performance when -finfo-table-map is enabled (#23103).

  • Make the recompilation check more robust when code generation flags are changed (#23369).

  • Addition of memory barriers that improve soundness on platforms with weak memory ordering.

  • And dozens of other fixes.

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.