4. Release notes for version 8.6.2

GHC 8.6.2 is a bug-fix release, fixing a few regressions found in 8.6.1.

4.1. Highlights

The highlights, since the 8.6.1 release, are:

• A long-standing bug exposed in GHC 8.6.1, Trac #15696, has been fixed. This issue resulted in undefined runtime behavior with some uses of the dataToTag# primop. Note that this issue, while less likely to manifest, has existed in some form in all GHC releases prior to this release and may result in silent, incorrect evaluation. For this reason, users are strongly encouraged to upgrade to 8.6.2.
• A long-standing bug in the LLVM code generator (Trac #14251), resulting in incorrect floating point evaluation, has been fixed.
• Several compiler panics observed in GHC 8.6.1 have been fixed (Trac #15499, Trac #15053, Trac #15692, Trac #15695)
• GHC now runs without complaining when installed to a read-only location on Windows (Trac #15667)
• An integer overflow, resulting in some encodeFloat uses returning incorrect results, has been fixed (Trac #15271)

4.2. 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.

4.3. 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