2.4. Version 9.6.4

The significant changes to the various parts of the compiler are listed below. See the migration guide on the GHC Wiki for specific guidance on migrating programs to this release.

The LLVM backend of this release is to be used with LLVM 11, 12, 13, 14 or 15.

2.4.1. Significant Changes

Issues fixed in this release include: Compiler

  • Fix a code generator bug on AArch64 platforms resulting in invalid conditional jumps (#23746).
  • Fix a simplifier bug that may cause segfaults and core lint failures due to incorrect handling of join points (#23952).
  • Ensure unconstrained instance dictionaries get IPE info (#24005).
  • Fix a bug where we could silently truncate 64 bit values to 32 bit on 32 bit architectures.
  • Fix a GHCi bug where a failure in the :add command would cause the process to exit (#24115).
  • Fix a bug causing suboptimal error messages for certain invalid cyclic module graphs with hs-boot files (#24196).
  • Fix a bug causing compiler panics with certain package databases involving unusable units and module reexports (#21097, #16996, #11050).
  • Fix some memory leaks in GHCi that manifest on reloads (#24107, #24118).
  • Fix a bug leading to some template haskell splices failing on being reloaded into GHCi due to not clearing the interactive context properly (#23405).
  • Fix a type checker crash on certain programs involving implicitly scoped type variables (#24083).
  • Fix a bug where certain warning flags were not recognised (#24071).
  • Fix an incorrect assertion in the simplifier (#23862).
  • Align objects in the data section properly when using the LLVM backend (#24163). Runtime system

  • Ensure concurrent thunk update is sound (#23185).
  • Ensure the listAllBlocks function takes the non-moving heap into account (#22627).
  • Ensure the non-moving GC is not running when pausing
  • Fix some non-moving loops and bugs on Windows and LLP64 platforms (#23003, #24042).
  • Fix a bug where certain programs could have incorrect async exception masking (#23513).
  • Ensure we respect maximum event length and don’t overflow into program memory (#24197). Build system and packaging

  • Ensure we use the right linker flags on AArch64 darwin (#21712, #24033).
  • Fix a bug where -DNOSMP wasn’t being passed to the C compiler even if the target doesn’t support SMP (#24082).
  • Ensure we use the right otool and install_name_tool on Darwin (#24211). Core libraries

  • Fix a bug in ghc-bignum where usage of bigNatIsPowerOf2 might result in out of bounds access (#24066).
  • Bump base to
  • base: Update to Unicode 15.1.0
  • Bump filepath to
  • Bump unix to
  • Bump haddock to 2.29.2
  • Bump bytestring to Included libraries

The package database provided with this distribution also contains a number of packages other than GHC itself. See the changelogs provided with these packages for further change information.