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