.. _release-9-2-6:
Version 9.2.6
==============
The significant changes to the various parts of the compiler are listed in the
following sections.
The :ghc-flag:`LLVM backend <-fllvm>` of this release is to be used with LLVM
9, 10, 11, or 12.
Compiler
--------
- Fix a regression in the simplifier due to a bad backport in GHC 9.2.5 that
could seriously impact runtime performance when compiling with optimisations
due to duplication of expensive work (:ghc-ticket:`22425`).
- Fix a compiler panic in the simplifier due to a bad backport in GHC 9.2.5
(:ghc-ticket:`22491`).
- Fix a compiler panic in the simplifier that manifests when compiling with
optimisations (:ghc-ticket:`19824`, :ghc-ticket:`22482`).
- Fix a compiler panic in the demand analyser due to a bug involving shadowing
(:ghc-ticket:`22718`).
- Fix a compiler panic during the "Float In" optimsation pass due to improper
handling of shadowing (:ghc-ticket:`22662`).
- Fix a compiler panic in the demand analyser (:ghc-ticket:`22039`).
- Fix a shadowing related bug in the occurence analysis phase of the simplifier
(:ghc-ticket:`22623`).
- Fix a compiler bug where programs using Template Haskell involving Constant
Applicative forms could be garbage collected too early (:ghc-ticket:`22417`).
- Fix a regression in the typechecker where certain typeclass instances
involving type and data familes would fail to resolve (:ghc-ticket:`22647`).
- Fix the linker warning about chained fixups on Darwin platforms for programs
compiled with GHC (:ghc-ticket:`22429`).
- Fix a bug with the graph-colouring register allocater leading to compiler
panics when compiling with ``-fregs-graph`` (:ghc-ticket:`22798`).
- Fix a parser bug where certain keywords which could be used as variables
were not allowed to be used with :extension:`OverloadedRecordDot`
(:ghc-ticket:`20723`).
- Fix the location of some ``Typeable`` definitions from ``GHC.Types`` which
resulted in poor error messages (:ghc-ticket:`22510`).
- Improve error messages involving non-exhaustive patterns when using
:extension:`ApplicativeDo` (:ghc-ticket:`22483`).
- Fix a driver bug where certain non-fatal Safe Haskell related warnings were
being marked as fatal (:ghc-ticket:`22728`).
- Fix a core lint error arises from incorrect scoping of type variables in
specialise pragmas inside class instances (:ghc-ticket:`22913`).
- Improve typchecker performance for modules with holes in type signatures
(:ghc-ticket:`14766`).
Runtime system
--------------
- Fix a GC bug where a race condition in the parallel GC could cause it to
garbage collect live sparks (:ghc-ticket:`22528`).
- Truncate eventlog events with a large payload (:ghc-ticket:`20221`).
- A bug in the nonmoving garbage collector regarding the treatment of
zero-length ``SmallArray#``\ s has been fixed (:ghc-ticket:`22264`)
- A number of bugs regarding the non-moving garbage collector's treatment of
``Weak#`` pointers have been fixed (:ghc-ticket:`22327`)
- A few race conditions between the non-moving collector and
``setNumCapabilities`` which could result in undefined behavior have been
fixed (:ghc-ticket:`22926`, :ghc-ticket:`22927`)
- The non-moving collector is now able to better schedule marking work during
the post-mark synchronization phase of collection, significantly reducing
pause times in some workloads (:ghc-ticket:`22929`).
- Various bugs in the non-moving collector's implementation of the selector
optimisation have been fixed (:ghc-ticket:`22930`)
Build system and packaging
--------------------------
- Bump ``gmp-tarballs`` to a version which doesn't use the reserved ``x18``
register on AArch64/Darwin systems, and also has fixes for CVE-2021-43618
(:ghc-ticket:`22497`, :ghc-ticket:`22789`).
- Include haddock documentation in interface files for hadrian generated
bindists, including darwin platforms (:ghc-ticket:`22734`).
Core libraries
--------------
- Bump ``bytestring`` to 0.11.4.0.
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.
.. ghc-package-list::
libraries/array/array.cabal: Dependency of ``ghc`` library
libraries/base/base.cabal: Core library
libraries/binary/binary.cabal: Dependency of ``ghc`` library
libraries/bytestring/bytestring.cabal: Dependency of ``ghc`` library
libraries/Cabal/Cabal/Cabal.cabal: Dependency of ``ghc-pkg`` utility
libraries/containers/containers/containers.cabal: Dependency of ``ghc`` library
libraries/deepseq/deepseq.cabal: Dependency of ``ghc`` library
libraries/directory/directory.cabal: Dependency of ``ghc`` library
libraries/exceptions/exceptions.cabal: Dependency of ``ghc`` and ``haskeline`` library
libraries/filepath/filepath.cabal: Dependency of ``ghc`` library
compiler/ghc.cabal: The compiler itself
libraries/ghci/ghci.cabal: The REPL interface
libraries/ghc-boot/ghc-boot.cabal: Internal compiler library
libraries/ghc-boot-th/ghc-boot-th.cabal: Internal compiler library
libraries/ghc-compact/ghc-compact.cabal: Core library
libraries/ghc-heap/ghc-heap.cabal: GHC heap-walking library
libraries/ghc-prim/ghc-prim.cabal: Core library
libraries/haskeline/haskeline.cabal: Dependency of ``ghci`` executable
libraries/hpc/hpc.cabal: Dependency of ``hpc`` executable
libraries/integer-gmp/integer-gmp.cabal: Core library
libraries/libiserv/libiserv.cabal: Internal compiler library
libraries/mtl/mtl.cabal: Dependency of ``Cabal`` library
libraries/parsec/parsec.cabal: Dependency of ``Cabal`` library
libraries/pretty/pretty.cabal: Dependency of ``ghc`` library
libraries/process/process.cabal: Dependency of ``ghc`` library
libraries/stm/stm.cabal: Dependency of ``haskeline`` library
libraries/template-haskell/template-haskell.cabal: Core library
libraries/terminfo/terminfo.cabal: Dependency of ``haskeline`` library
libraries/text/text.cabal: Dependency of ``Cabal`` library
libraries/time/time.cabal: Dependency of ``ghc`` library
libraries/transformers/transformers.cabal: Dependency of ``ghc`` library
libraries/unix/unix.cabal: Dependency of ``ghc`` library
libraries/Win32/Win32.cabal: Dependency of ``ghc`` library
libraries/xhtml/xhtml.cabal: Dependency of ``haddock`` executable