GHC 9.6.2 is now available

Ben Gamari - 2023-05-23

The GHC developers are happy to announce the availability of GHC 9.6.2. Binary distributions, source distributions, and documentation are available at

This release is primarily a bugfix release addressing a few issues found in 9.6.2. These include:

  • a number of simplifier and specialisation issues (#22761, #22549)

  • A bug resulting in crashes of programs using the new listThreads# primop (#23071).

  • A compiler crash triggered by certain uses of quantified constraints (#23171)

  • Various bugs in the Javascript backend have been fixed (#23399, #23360, #23346)

  • A missing write barrier in the non-moving collector’s handling of selector thunks, resulting in undefined behavior (#22930).

  • The non-moving garbage collector’s treatment of weak pointers has been revamped which should allow more reliable finalization of Weak# closures (#22327)

  • The non-moving garbage collector now bounds the amount of marking it will do during the post-marking stop-the-world phase, greatly reducing tail latencies in some programs (#22929)

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