6. 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.

6.1. 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 (Trac #16199).
• A patch fixing a set of linker failures on Windows has been reverted as it unfortunately caused (Trac #15105, Trac #15894, Trac #15934)
• A bug wherein changes in default method definitions would fail to trigger recompilation has been fixed (Trac #15970).
• A bug wherein plugins would fail to lookup names not in scope in the module being compiled has been fixed (Trac #16104)
• A bug resulting in hangs during RTS shutdown on Darwin has been resolved (Trac #16150)
• A bug where some programs involving StaticData would be rejected with either a typechecking error or internal compiler error has been fixed (Trac #16141)
• A bug where compilation on Windows can fail with linker errors referring to __chkstk_ms has been fixed (Trac #16166)

6.2. Known issues

Note that the LLVM code generator (-fllvm) in GHC 8.6, as well as all earlier releases, are affected by Trac #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.

6.3. 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.

Package	Version	Reason for inclusion
ghc	8.6.4	The compiler itself
Cabal	2.4.0.1	Dependency of ghc-pkg utility
Win32	2.6.1.0	Dependency of ghc library
array	0.5.3.0	Dependency of ghc library
base	4.12.0.0	Core library
binary	0.8.6.0	Dependency of ghc library
bytestring	0.10.8.2	Deppendency of ghc library
containers	0.6.0.1	Dependency of ghc library
deepseq	1.4.4.0	Dependency of ghc library
directory	1.3.3.0	Dependency of ghc library
filepath	1.4.2.1	Dependency of ghc library
ghc-boot	8.6.4	Internal compiler library
ghc-compact	0.1.0.0	Core library
ghc-prim	0.5.3	Core library
ghci	8.6.4	The REPL interface
haskeline	0.7.4.3	Dependency of ghci executable
hpc	0.6.0.3	Dependency of hpc executable
integer-gmp	1.0.2.0	Core library
mtl	2.2.2	Dependency of Cabal library
parsec	3.1.13.0	Dependency of Cabal library
process	1.6.5.0	Dependency of ghc library
template-haskell	2.14.0.0	Core library
text	1.2.3.1	Dependency of Cabal library
time	1.8.0.2	Dependency of ghc library
transformers	0.5.6.2	Dependency of ghc library
unix	2.7.2.2	Dependency of ghc library
xhtml	3000.2.2.1	Dependency of haddock executable