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