7. Release notes for version 8.10.5 — Glasgow Haskell Compiler 8.10.7 User's Guide

# Glasgow Haskell Compiler User's Guide

# 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