4. Release notes for version 8.10.2

The significant changes to the various parts of the compiler are listed in the following sections.

Like previous releases in the 8.10 series, the LLVM backend of this release is to be used with LLVM 9.

4.1. Highlights

  • A few important correctness fixes for the low-latency garbage collector. Users of --nonmoving-gc are strongly encouraged to upgrade promptly.

  • Fixes a bug in process creation on Windows (#17926).

  • Works around a Linux kernel bug in the implementation of timerfds (#18033).

  • Fixes a few specialiser regressions (#17810, #18120) and introduces a variety of miscellaneous specialiser improvements (#16473, #17930, #17966)

  • Fixes a potential loss of sharing due to left operator sections (#18151).

  • Fix bootstrapping of GHC with the LLVM backend on x86-64 (#17920).

4.2. Full details

4.2.1. Compiler

  • A simplifier panic manifesting when DWARF debug information is enabled has been fixed (#18162, #17619)

4.2.2. Runtime system

  • The RTS now supports a flag, --copying-gc, to counter-act the effect of --nonmoving-gc.

  • The RTS now allows the user to specify a minimum time between idle GCs with the -Iw ⟨seconds⟩ flag. 8.10.1 contained a user’s guide reference to this flag but did not include the associated implementation.

  • A memory leak in the cost-center profiler has been fixed (#18348)

  • A potential integer overflow in the compact normal form import logic has been fixed (#16992)

  • We now work around a Linux kernel bug in the implementation of timerfd which could previously result in program crashes (#18033)

  • The cost-center profiler’s JSON output backend now escapes backslashes correctly (#18438)

  • A variety of linker issues on ARM platforms have been fixed.

4.2.3. base library

  • Fix a precision issue in the implementation of log1mexp (#17125)

4.2.4. Build system

  • Fix a bug wherein GHC would link against the non-thread-safe unique supply implementation when bootstrapping with an unregisterised compiler (#18024)

4.3. Known issues

  • A long-standing bug (#16893) which can cause some applications of unsafeCoerce to segmentation fault is only partially fixed in this release. This release only avoids this issue in the uses of unsafeCoerce in Data.Typeable.Internal, which was the proximate cause of #16893.

    However, it is possible that this bug could manifest in user-code using unsafeCoerce to perform dynamic type checks. See the ticket for details.

    We expect that this issue will be fixed in the next major release of GHC.

4.4. 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

8.10.4

The compiler itself

Cabal

3.2.1.0

Dependency of ghc-pkg utility

Win32

2.6.1.0

Dependency of ghc library

array

0.5.4.0

Dependency of ghc library

base

4.14.1.0

Core library

binary

0.8.8.0

Dependency of ghc library

bytestring

0.10.12.0

Dependency of ghc library

containers

0.6.2.1

Dependency of ghc library

deepseq

1.4.4.0

Dependency of ghc library

directory

1.3.6.0

Dependency of ghc library

exceptions

0.10.4

Dependency of haskeline library

filepath

1.4.2.1

Dependency of ghc library

ghc-boot-th

8.10.4

Internal compiler library

ghc-boot

8.10.4

Internal compiler library

ghc-compact

0.1.0.0

Core library

ghc-heap

8.10.4

GHC heap-walking library

ghc-prim

0.6.1

Core library

ghci

8.10.4

The REPL interface

haskeline

0.8.0.1

Dependency of ghci executable

hpc

0.6.1.0

Dependency of hpc executable

integer-gmp

1.0.3.0

Core library

libiserv

8.10.4

Internal compiler library

mtl

2.2.2

Dependency of Cabal library

parsec

3.1.14.0

Dependency of Cabal library

pretty

1.1.3.6

Dependency of ghc library

process

1.6.9.0

Dependency of ghc library

stm

2.5.0.0

Dependency of haskeline library

template-haskell

2.16.0.0

Core library

terminfo

0.4.1.4

Dependency of haskeline library

text

1.2.4.1

Dependency of Cabal library

time

1.9.3

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