7. Release notes for version 8.10.5

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.

7.1. General bug fixes

  • First-class support for Apple M1 hardware using GHC’s LLVM ARM backend

  • Fix a bug where code may be unloaded prematurely when using the parallel garbage collector (see #19417)

  • Fix a bug where the linker may during shutdown unload code before libraries’ atexit handlers have a chance to run (#19297).

  • Improve code layout by distiguishing conditional and unconditional branches (#18053).

  • Add hs-boot file support for -ddump-minimal-imports (#18497).

  • Ensure hs-boot files are built before source files in GHCs -M mode (#14482)

  • Fix a long standing GHC API bug affecting clients like HLS where async exceptions used to cancel threads during typechecking would be caught by the Template Haskell evaluator and reported as compile errors (#19410).

  • Improve error messages when looking up packages fails (#19370).

  • Fix a number of quirks in GC accounting (#19147)

  • Fix a code generation bug which could result in entry of unlifted objects in some programs using unboxed sums (#19645).

  • Ensure that POSIX signals are not delivered to the ticker thread when using the pthread itimer implementation.

  • Fix a specialiser bug which could result in the construction of recursive dictionaries in some programs (#17151).

  • Bump containers to 0.6.4.1

  • Do not treat -Winferred-safe-imports warnings as errors.

  • Fix a bug where typechecker plugins could be run with an inconsistent typechecker environment (#19191).

  • Fix a simplifier bug which lead to an exponential blow up and excessive memory usage in certain cases (#18923, #18140, #10421, #18282, #13253)

7.2. Portability fixes

  • Fix a number of linking portability issues affecting Apple’s macOS Big Sur.

  • Use the pthread-based itimer implemention under FreeBSD by default

  • Enable large-file support in base’s the OFD file locking implementation, avoiding #17950.

  • Ensure that Darwin binary distributions do not depend upon utimensat (#17895).

  • Remove a number of older autoconf idioms from the configure script, improving support in newer environments.

7.3. 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.

  • A long-standing bug (#17760) where some uses of the touch# primop can be dropped by the simplifier is present in this release. This bug will be fixed in GHC 9.0.1. In the meantime, see the ticket for mitigations.

7.4. 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

 8.10.7

The compiler itself

Cabal

 3.2.1.0

Dependency of ghc-pkg utility

Win32

 2.6.2.1

Dependency of ghc library

array

 0.5.4.0

Dependency of ghc library

base

 4.14.3.0

Core library

binary

 0.8.8.0

Dependency of ghc library

bytestring

 0.10.12.0

Dependency of ghc library

containers

 0.6.5.1

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

 8.10.7

Internal compiler library

ghc-boot

 8.10.7

Internal compiler library

ghc-compact

 0.1.0.0

Core library

ghc-heap

 8.10.7

GHC heap-walking library

ghc-prim

 0.6.1

Core library

ghci

 8.10.7

The REPL interface

haskeline

 0.8.2

Dependency of ghci executable

hpc

 0.6.1.0

Dependency of hpc executable

integer-gmp

 1.0.3.0

Core library

libiserv

 8.10.7

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

 1.6.13.2

Dependency of ghc library

stm

 2.5.0.1

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