.. _release-9-8-2:

Version 9.8.2
==============

The significant changes to the various parts of the compiler are listed below.
See the `migration guide
<https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.8>`_ on the GHC Wiki
for specific guidance on migrating programs to this release.

The :ghc-flag:`LLVM backend <-fllvm>` of this release is to be used with LLVM
11, 12, 13, 14 or 15.

Significant Changes
~~~~~~~~~~~~~~~~~~~~

Issues fixed in this release include:

Compiler
--------

- Fix a recompilation checking bug impacting the relinking step, where we failed to
  relink if transitive dependencies were changed (:ghc-ticket:`23724`).
- Fix a renamer bug where certain styles of import lists for associated type
  families would not be processed correctly (:ghc-ticket:`24084`).
- Fix a typechecker bug that could lead to non-termination in certain situations
  (:ghc-ticket:`24134`).
- Support code points greater than 2^16 in ``toJSString`` when using the JS
  backend (:ghc-ticket:`23628`).
- Fix a code generation bug on the JS backend involving tuple constructors
  (:ghc-ticket:`23659`).
- Fix a code generator panic when compiling code using FMA primops
  (:ghc-ticket:`24160`).
- Fix a bug causing suboptimal error messages for certain invalid cyclic
  module graphs with hs-boot files (:ghc-ticket:`24196`, :ghc-ticket:`24275`).
- Fix an incorrect assertion in the simplifier (:ghc-ticket:`23862`).
- Fix a bug causing compiler panics with certain package databases involving
  unusable units and module reexports (:ghc-ticket:`21097`, :ghc-ticket:`16996`,
  :ghc-ticket:`11050`).
- Fix some memory leaks in GHCi that manifest on reloads (:ghc-ticket:`24107`,
  :ghc-ticket:`24118`).
- Fix a GHCi bug where a failure in the ``:add`` command would cause the
  process to exit (:ghc-ticket:`24115`).
- Align objects in the data section properly when using the LLVM backend
  (:ghc-ticket:`24163`).
- Fix a simplifier panic when simplifying certain unfoldings
  (:ghc-ticket:`24242`).
- Fix a typechecker bug where ``TYPE`` and ``CONSTRAINT`` were treated as apart
  (:ghc-ticket:`24279`).
- Allow template haskell code to look up record fields (:ghc-ticket:`24293`).
- Add ``-finfo-table-map-with-fallback`` and ``-finfo-table-map-with-stack`` flags
  for info table profiling (:ghc-ticket:`23702`).
- Improve compile time and code generation performance when ``-finfo-table-map``
  is enabled (:ghc-ticket:`23103`).
- Fix a bug in the check for unused type variables in type class instances
  (:ghc-ticket:`23768`).
- Fix a panic when typechecking GADT data family instances with unused variables
  (:ghc-ticket:`23784`).
- Improve error message for unused variables in RHS of data family instance
  (:ghc-ticket:`23778`).
- Fix a compiler panic due to mismatches between ``.hs`` and ``.hs-boot`` files
  (:ghc-ticket:`16127`).
- Improve error message for unused variables type family instances
  (:ghc-ticket:`23734`).
- Fix a type checker crash on certain programs involving implicitly scoped type
  variables (:ghc-ticket:`24083`).
- Fix a bug where certain warning flags were not recognised (:ghc-ticket:`24071`).
- Fix a bug involving the miscompilation of certain loops (:ghc-ticket:`24295`).
- Produce FMA instructions even if `-mfma` is not set on AArch64
  (:ghc-ticket:`24311`).
- Fix a bug leading to some template haskell splices failing on being reloaded
  into GHCi due to not clearing the interactive context properly
  (:ghc-ticket:`23405`).
- Fix a bug where we could silently truncate 64 bit values to 32 bit on
  32 bit architectures.
- Don't produce invalid opcode for FMA instruction on LLVM (:ghc-ticket:`24223`).
- Fix a warning about non-existent ``+fma`` flag on LLVM (:ghc-ticket:`24379`).
- Ensure we give nested documentation comments accurate source spans
  (:ghc-ticket:`24378`).
- Ensure we don't emit shadowing warnings for ``NoFieldSelector`` fields
  (:ghc-ticket:`24381`).
- Fix several bugs involving free variables in breakpoints (:ghc-ticket:`23612`,
  :ghc-ticket:`23607`, :ghc-ticket:`23998`, :ghc-ticket:`23666`).
- Fix a bug preventing some specialisations from firing (:ghc-ticket:`24370`).
- On x86, Don't require ``-mavx2`` when using 256-bit floating-point SIMD
  primitives (:ghc-ticket:`24222`).
- Fix a bug preventing haddock from computing the correct links
  (:ghc-ticket:`24294`).

Runtime system
--------------

- Ensure we respect maximum event length and don't overflow into program
  memory (:ghc-ticket:`24197`, :ghc-ticket:`24287`).
- Ensure concurrent thunk update is sound (:ghc-ticket:`23185`).

Build system and packaging
--------------------------

- Ensure we use the right ``otool`` and ``install_name_tool`` on Darwin
  (:ghc-ticket:`24211`).
- Ensure we use the correct bindist name for the test artifact when generating
  release ghcup metadata (:ghc-ticket:`24268`).
- Ensure we handle CXX and CC flags involving standard flags correctly with
  new autotools versions (:ghc-ticket:`24324`). 
- Ensure we correctly set ``--target`` when configuring the linker
  (:ghc-ticket:`24414`).
- Suppress duplicate library warnings on new macOS linker (:ghc-ticket:`24167`,
  :ghc-ticket:`24168`).
- Fix a bug where ``-DNOSMP`` wasn't being passed to the C compiler even if the
  target doesn't support SMP (:ghc-ticket:`24082`).
- Don't assume the locale is ``*.UTF-8`` in hadrian.

Core libraries
--------------

- Fix a bug in ghc-bignum where usage of `bigNatIsPowerOf2` might result in
  out of bounds access (:ghc-ticket:`24066`).
- Bump ``base`` to 4.19.1.0
- Bump ``filepath`` to 1.4.200.1
- Bump ``unix`` to 2.8.4.0
- Bump ``bytestring`` to 0.12.1.0
- Bump ``text`` to 2.1.1
