2.6. Version 9.2.6

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

The LLVM backend of this release is to be used with LLVM 9, 10, 11, or 12.

2.6.1. 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 (#22425).
  • Fix a compiler panic in the simplifier due to a bad backport in GHC 9.2.5 (#22491).
  • Fix a compiler panic in the simplifier that manifests when compiling with optimisations (#19824,:ghc-ticket:22482).
  • Fix a compiler panic in the demand analyser due to a bug involving shadowing (#22718).
  • Fix a compiler panic during the “Float In” optimsation pass due to improper handling of shadowing (#22662).
  • Fix a compiler panic in the demand analyser (#22039).
  • Fix a shadowing related bug in the occurence analysis phase of the simplifier (#22623).
  • Fix a compiler bug where programs using Template Haskell involving Constant Applicative forms could be garbage collected too early (#22417).
  • Fix a regression in the typechecker where certain typeclass instances involving type and data familes would fail to resolve (#22647).
  • Fix the linker warning about chained fixups on Darwin platforms for programs compiled with GHC (#22429).
  • Fix a bug with the graph-colouring register allocater leading to compiler panics when compiling with -fregs-graph (#22798).
  • Fix a parser bug where certain keywords which could be used as variables were not allowed to be used with OverloadedRecordDot (#20723).
  • Fix the location of some Typeable definitions from GHC.Types which resulted in poor error messages (#22510).
  • Improve error messages involving non-exhaustive patterns when using ApplicativeDo (#22483).
  • Fix a driver bug where certain non-fatal Safe Haskell related warnings were being marked as fatal (#22728).
  • Fix a core lint error arises from incorrect scoping of type variables in specialise pragmas inside class instances (#22913).
  • Improve typchecker performance for modules with holes in type signatures (#14766).

2.6.2. Runtime system

  • Fix a GC bug where a race condition in the parallel GC could cause it to garbage collect live sparks (#22528).
  • Truncate eventlog events with a large payload (#20221).
  • A bug in the nonmoving garbage collector regarding the treatment of zero-length SmallArray#s has been fixed (#22264)
  • A number of bugs regarding the non-moving garbage collector’s treatment of Weak# pointers have been fixed (#22327)
  • A few race conditions between the non-moving collector and setNumCapabilities which could result in undefined behavior have been fixed (#22926, #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 (#22929).
  • Various bugs in the non-moving collector’s implementation of the selector optimisation have been fixed (#22930)

2.6.3. 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 (#22497, #22789).
  • Include haddock documentation in interface files for hadrian generated bindists, including darwin platforms (#22734).

2.6.4. Core libraries

  • Bump bytestring to 0.11.4.0.

2.6.5. 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 9.2.6 The compiler itself
Cabal 3.6.3.0 Dependency of ghc-pkg utility
Win32 2.12.0.1 Dependency of ghc library
array 0.5.4.0 Dependency of ghc library
base 4.16.4.0 Core library
binary 0.8.9.0 Dependency of ghc library
bytestring 0.11.4.0 Dependency of ghc library
containers 0.6.5.1 Dependency of ghc library
deepseq 1.4.6.1 Dependency of ghc library
directory 1.3.6.2 Dependency of ghc library
exceptions 0.10.4 Dependency of ghc and haskeline library
filepath 1.4.2.2 Dependency of ghc library
ghc-boot-th 9.2.6 Internal compiler library
ghc-boot 9.2.6 Internal compiler library
ghc-compact 0.1.0.0 Core library
ghc-heap 9.2.6 GHC heap-walking library
ghc-prim 0.8.0 Core library
ghci 9.2.6 The REPL interface
haskeline 0.8.2 Dependency of ghci executable
hpc 0.6.1.0 Dependency of hpc executable
integer-gmp 1.1 Core library
libiserv 9.2.6 Internal compiler library
mtl 2.2.2 Dependency of Cabal library
parsec 3.1.15.0 Dependency of Cabal library
pretty 1.1.3.6 Dependency of ghc library
process 1.6.16.0 Dependency of ghc library
stm 2.5.0.2 Dependency of haskeline library
template-haskell 2.18.0.0 Core library
terminfo 0.4.1.5 Dependency of haskeline library
text 1.2.5.0 Dependency of Cabal library
time 1.11.1.1 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