2.3. Version 9.6.3¶
The significant changes to the various parts of the compiler are listed below. See the migration guide on the GHC Wiki for specific guidance on migrating programs to this release.
The LLVM backend
of this release is to be used with LLVM
11, 12, 13, 14 or 15.
2.3.1. Significant Changes¶
Issues fixed in this release include:
2.3.1.1. Compiler¶
- Disable Polymorphic Specialisation by default. It was discovered that Polymorphic
Specialisation as currently implemented in GHC can lead to hard to diagnose bugs
resulting in incorrect runtime results. Users wishing to use this optimisation
despite the caveats will now have to explicitly enable the new
-fpolymorphic-specialisation
flag. For more details see #23469 as well as #23109, #21229, #23445. - Fix a panic with the typechecker, reporting a type error instead of panicing on certain programs (#22707).
- Fix a bug preventing temporary directories created by GHC from being cleaned up after compilation (#22952).
- Fix the behaviour of the
-keep-tmp-files
when used in aOPTIONS_GHC
pragma (#23339). - Fix a bug with certain warnings being swallowed when
-fdefer-diagnostics
is enabled (#23305). - Fix a bug leading to incorrect “Redundant Constraint” warnings (#23323, #23143).
- Fix the behaviour of
-fsplit-sections
on Windows (#22834). - Fix some segfaults affecting users of
UnliftedDatatypes
(#23146, #23231). - Fix compiler panics with certain RULE pragmas (#23208, #22761).
- Fix a bug with
.hie
files containing spurious references to generated functions in files with partial field selectors (#23492). - Fix a specialiser bug leading to compiler panics (#23567).
- Fix a bug preventing using the command line to compile
.cmm
files to assembly (#23610). - Fix a compiler panic on certain programs with typed holes (#22684).
- Fix some simplifier panics due to incorrect scope tracking (#23630).
- Ensure array read operations have proper memory barriers (#23541).
- Make type equality
(~)
checks in the presence of quantified contrains more robust to argument ordering (#23333). - Fix a number of bugs having to do with default representation polymorphic type variables (#23153, #23154, #23176).
- Fix the behaviour of the
MulMayOflo
operation on x86 and aarch64 (#23721). - Make the recompilation check more robust when code generation flags are changed (#23369).
- With the aarch64 backend, fix a bug arising from lack of zero-extension for 8/16 bit add/sub with immediate (#23749).
- Fix a bug in the STG rewriter leading to excess allocations in certain circumstances (#23783).
- Fix a typechecker bug leading to incorrect multiplicity checking with
-XLinearTypes
and-XMultiWayIf
(#23814). - Improve zonking behavior for defaulting plugins (#23821).
- Fix a recompilation checking bug impacting the relinking step, where we failed to relink if transitive dependencies were changed (#23724).
- Fix a code generator panic with unboxed tuples (#23914).
- Fix a simplifier panic due to incorrect eta reduction of a join point (#23922).
- Fix a simplifer bug leading to
-dcore-lint
failures (#23938). - Add
-finfo-table-map-with-fallback
and-finfo-table-map-with-stack
flags for info table profiling (#23702). - Improve compile time and code generation performance when
-finfo-table-map
is enabled (#23103).
2.3.1.2. Runtime system¶
- Performance improvements for the ELF linker (#23464).
- Fix warnings with clang 14.0.3 (#23561).
- Prevent some segfaults by ensuring that pinned allocations respect block size (#23400).
- Prevent runtime crashes in statically linked GHCi sessions on AArch64 by providing some missing symbols from the RTS linker (#22012).
- Improve bounds checking with
-fcheck-prim-bounds
(#21054). - On Windows, ensure reliability of IO manager shutdown (#23691).
- Fix a bug with the GHC linker on windows (#22941).
- Properly escape characters when writing JSON profiles (
-pJ
) (#23924).
2.3.1.3. Build system and packaging¶
2.3.1.4. Core libraries¶
- Bump
base
to 4.18.1.0 - base: Restore``mingwex`` dependency on Windows (#23309).
- Bump
bytestring
to 0.11.5.2 - Bump
filepath
to 1.4.100.4 - Bump
haddock
to 2.29.1
2.3.1.5. 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.