.. _release-8-6-4:

Release notes for version 8.6.4
===============================

GHC 8.6.4 is a bug-fix release, fixing a few regressions found in 8.6.3.


Highlights
----------

The highlights, since the 8.6.3 release, are:

- Inconsistencies between the versions of ``transformers`` and ``process``
  shipped with the compiler and those present on Hackage have been resolved
  (:ghc-ticket:`16199`).
- A patch fixing a set of linker failures on Windows has been reverted as it unfortunately caused 
  (:ghc-ticket:`15105`, :ghc-ticket:`15894`, :ghc-ticket:`15934`)
- A bug wherein changes in default method definitions would fail to trigger
  recompilation has been fixed (:ghc-ticket:`15970`).
- A bug wherein plugins would fail to lookup names not in scope in the module
  being compiled has been fixed (:ghc-ticket:`16104`)
- A bug resulting in hangs during RTS shutdown on Darwin has been resolved
  (:ghc-ticket:`16150`)
- A bug where some programs involving :extension:`StaticData` would be rejected
  with either a typechecking error or internal compiler error has been fixed
  (:ghc-ticket:`16141`)
- A bug where compilation on Windows can fail with linker errors referring to
  ``__chkstk_ms`` has been fixed (:ghc-ticket:`16166`)

Known issues
------------

Note that the LLVM code generator (:ghc-flag:`-fllvm`) in GHC 8.6, as well as
all earlier releases, are affected by :ghc-ticket:`14251`, which can result in
miscompilation of some programs calling functions with unboxed floating-point
arguments. While originally scheduled to be fixed for this release, the fix
ended up being more difficult than anticipated and, given that issue is not a
strict regression from 8.4, we decided to proceed with the release.

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.

.. ghc-package-list::

    libraries/array/array.cabal:             Dependency of ``ghc`` library
    libraries/base/base.cabal:               Core library
    libraries/binary/binary.cabal:           Dependency of ``ghc`` library
    libraries/bytestring/bytestring.cabal:   Deppendency of ``ghc`` library
    libraries/Cabal/Cabal/Cabal.cabal:       Dependency of ``ghc-pkg`` utility
    libraries/containers/containers.cabal:   Dependency of ``ghc`` library
    libraries/deepseq/deepseq.cabal:         Dependency of ``ghc`` library
    libraries/directory/directory.cabal:     Dependency of ``ghc`` library
    libraries/filepath/filepath.cabal:       Dependency of ``ghc`` library
    compiler/ghc.cabal:                      The compiler itself
    libraries/ghci/ghci.cabal:               The REPL interface
    libraries/ghc-boot/ghc-boot.cabal:       Internal compiler library
    libraries/ghc-compact/ghc-compact.cabal: Core library
    libraries/ghc-prim/ghc-prim.cabal:       Core library
    libraries/haskeline/haskeline.cabal:     Dependency of ``ghci`` executable
    libraries/hpc/hpc.cabal:                 Dependency of ``hpc`` executable
    libraries/integer-gmp/integer-gmp.cabal: Core library
    libraries/mtl/mtl.cabal:                 Dependency of ``Cabal`` library
    libraries/parsec/parsec.cabal:           Dependency of ``Cabal`` library
    libraries/process/process.cabal:         Dependency of ``ghc`` library
    libraries/template-haskell/template-haskell.cabal:     Core library
    libraries/text/text.cabal:               Dependency of ``Cabal`` library
    libraries/time/time.cabal:               Dependency of ``ghc`` library
    libraries/transformers/transformers.cabal: Dependency of ``ghc`` library
    libraries/unix/unix.cabal:               Dependency of ``ghc`` library
    libraries/Win32/Win32.cabal:             Dependency of ``ghc`` library
    libraries/xhtml/xhtml.cabal:             Dependency of ``haddock`` executable