Cheng Shao pushed to branch wip/ubsan at Glasgow Haskell Compiler / GHC

Commits:

• 682bf979
  by Mike Pilgrem at 2025-11-16T16:44:14+00:00

  Fix #26293 Valid stack.yaml for hadrian
  

• acc70c3a
  by Simon Peyton Jones at 2025-11-18T16:21:20-05:00

  Fix a bug in defaulting
  
  Addresses #26582
  
  Defaulting was doing some unification but then failing to
  iterate. Silly.
  
  I discovered that the main solver was unnecessarily iterating even
  if there was a unification for an /outer/ unification variable, so
  I fixed that too.
  

• c12fa73e
  by Simon Peyton Jones at 2025-11-19T02:55:01-05:00

  Make PmLit be in Ord, and use it in Map
  
  This MR addresses #26514, by changing from
  
      data PmAltConSet = PACS !(UniqDSet ConLike) ![PmLit]
    to
      data PmAltConSet = PACS !(UniqDSet ConLike) !(Map PmLit PmLit)
  
  This matters when doing pattern-match overlap checking, when there
  is a very large set of patterns.  For most programs it makes
  no difference at all.
  
  For the N=5000 case of the repro case in #26514, compiler
  mutator time (with `-fno-code`) goes from 1.9s to 0.43s.
  
  All for the price for an Ord instance for PmLit
  

• 41b84f40
  by sheaf at 2025-11-19T02:55:52-05:00

  Add passing tests for #26311 and #26072
  
  This commit adds two tests cases that now pass since landing the changes
  to typechecking of data constructors in b33284c7.
  
  Fixes #26072 #26311
  

• 1faa758a
  by sheaf at 2025-11-19T02:55:52-05:00

  mkCast: weaken bad cast warning for multiplicity
  
  This commit weakens the warning message emitted when constructing a bad
  cast in mkCast to ignore multiplicity.
  
  Justification: since b33284c7, GHC uses sub-multiplicity coercions to
  typecheck data constructors. The coercion optimiser is free to discard
  these coercions, both for performance reasons, and because GHC's Core
  simplifier does not (yet) preserve linearity.
  We thus weaken 'mkCast' to use 'eqTypeIgnoringMultiplicity' instead of
  'eqType', to avoid getting many spurious warnings about mismatched
  multiplicities.
  

• 55eab80d
  by Sylvain Henry at 2025-11-20T17:33:13-05:00

  Build external interpreter program on demand (#24731)
  
  This patch teaches GHC how to build the external interpreter program
  when it is missing. As long as we have the `ghci` library, doing this is
  trivial so most of this patch is refactoring for doing it sanely.
  

• 08bbc028
  by Rodrigo Mesquita at 2025-11-20T17:33:54-05:00

  Add tests for #23973 and #26565
  
  These were fixed by 4af4f0f070f83f948e49ad5d7835fd91b8d3f0e6 in !10417
  

• 6b42232c
  by sheaf at 2025-11-20T17:34:35-05:00

  Mark T26410_ffi as fragile on Windows
  
  As seen in #26595, this test intermittently fails on Windows.
  This commit marks it as fragile, until we get around to fixing it.
  

• b7b7c049
  by Andrew Lelechenko at 2025-11-21T21:04:01+00:00

  Add nubOrd / nubOrdBy to Data.List and Data.List.NonEmpty
  
  As per https://github.com/haskell/core-libraries-committee/issues/336
  

• 352d5462
  by Marc Scholten at 2025-11-22T10:33:03-05:00

  Fix haddock test runner to handle UTF-8 output
  
  xhtml 3000.4.0.0 now produces UTF-8 output instead of escaping non-ASCII characters.
  
  When using --test-accept it previously wrote files in the wrong encoding
  because they have not been decoded properly when reading the files.
  

• 167e1d8e
  by Cheng Shao at 2025-11-24T12:29:09+01:00

  hadrian: add support for building with UndefinedBehaviorSanitizer
  
  This patch adds a +ubsan flavour transformer to hadrian to build all
  stage1+ C/C++ code with UndefinedBehaviorSanitizer. This is
  particularly useful to catch potential undefined behavior in the RTS
  codebase.
  

• 05734099
  by Cheng Shao at 2025-11-24T12:29:13+01:00

  configure: bump LlvmMaxVersion to 22
  
  This commit bumps LlvmMaxVersion to 22; 21.x releases have been
  available since Aug 26th, 2025 and there's no regressions with 21.x so
  far. This bump is also required for updating fedora image to 43.
  

• 243832d8
  by Cheng Shao at 2025-11-24T12:29:13+01:00

  ci: add x86_64-linux-fedora43-validate+ubsan job
  
  This patch updates fedora image to 43, and adds a
  `x86_64-linux-fedora43-validate+ubsan` job that's run in
  validate/nightly pipelines to catch undefined behavior in the RTS
  codebase.
  

• 5263c337
  by Cheng Shao at 2025-11-24T12:29:13+01:00

  rts: fix zero-length VLA undefined behavior in interpretBCO
  
  This commit fixes a zero-length VLA undefined behavior in interpretBCO, caught by UBSan:
  
  ```
  +rts/Interpreter.c:3133:19: runtime variable length array bound evaluates to non-positive value 0
  ```
  

• a54904f2
  by Cheng Shao at 2025-11-24T12:29:13+01:00

  rts: fix unaligned ReadSpB in interpretBCO
  
  This commit fixes unaligned ReadSpB in interpretBCO, caught by UBSan:
  
  ```
  +rts/Interpreter.c:2174:64: runtime load of misaligned address 0x004202059dd1 for type 'StgWord', which requires 8 byte alignment
  ```
  
  To perform proper unaligned read, we define StgUnalignedWord as a type
  alias of StgWord with aligned(1) attribute, and load StgUnalignedWord
  instead of StgWord in ReadSpB, so the C compiler is aware that we're
  not loading with natural alignment.
  

• 39853771
  by Cheng Shao at 2025-11-24T12:29:13+01:00

  rts: fix signed integer overflow in subword arithmetic in interpretBCO
  

70 changed files:

• .gitlab-ci.yml
• .gitlab/generate-ci/gen_ci.hs
• .gitlab/jobs.yaml
• .gitlab/rel_eng/fetch-gitlab-artifacts/fetch_gitlab.py
• .gitlab/rel_eng/mk-ghcup-metadata/mk_ghcup_metadata.py
• compiler/GHC.hs
• compiler/GHC/Core/Utils.hs
• + compiler/GHC/Driver/Config/Interpreter.hs
• compiler/GHC/Driver/Config/Linker.hs
• compiler/GHC/Driver/DynFlags.hs
• compiler/GHC/Driver/Pipeline.hs
• compiler/GHC/Driver/Pipeline/Execute.hs
• compiler/GHC/HsToCore/Pmc/Solver/Types.hs
• compiler/GHC/Linker/Config.hs
• compiler/GHC/Linker/Dynamic.hs
• + compiler/GHC/Linker/Executable.hs
• − compiler/GHC/Linker/ExtraObj.hs
• compiler/GHC/Linker/Loader.hs
• compiler/GHC/Linker/MacOS.hs
• compiler/GHC/Linker/Static.hs
• compiler/GHC/Linker/Windows.hs
• + compiler/GHC/Runtime/Interpreter/C.hs
• + compiler/GHC/Runtime/Interpreter/Init.hs
• compiler/GHC/SysTools/Tasks.hs
• compiler/GHC/Tc/Solver/Default.hs
• compiler/GHC/Tc/Solver/Monad.hs
• compiler/GHC/Tc/Solver/Solve.hs
• compiler/GHC/Tc/Utils/TcType.hs
• compiler/GHC/Types/SourceText.hs
• compiler/ghc.cabal.in
• configure.ac
• hadrian/doc/flavours.md
• hadrian/src/Flavour.hs
• hadrian/stack.yaml
• hadrian/stack.yaml.lock
• libraries/base/base.cabal.in
• libraries/base/changelog.md
• libraries/base/src/Data/List.hs
• libraries/base/src/Data/List/NonEmpty.hs
• + libraries/base/src/Data/List/NubOrdSet.hs
• libraries/ghc-internal/src/GHC/Internal/Data/OldList.hs
• rts/Interpreter.c
• rts/include/stg/Types.h
• rts/rts.cabal
• testsuite/driver/testglobals.py
• testsuite/driver/testlib.py
• + testsuite/tests/bytecode/T23973.hs
• + testsuite/tests/bytecode/T23973.script
• + testsuite/tests/bytecode/T23973.stdout
• + testsuite/tests/bytecode/T26565.hs
• + testsuite/tests/bytecode/T26565.script
• + testsuite/tests/bytecode/T26565.stdout
• testsuite/tests/bytecode/all.T
• + testsuite/tests/driver/T24731.hs
• testsuite/tests/driver/all.T
• testsuite/tests/interface-stability/base-exports.stdout
• testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs
• testsuite/tests/interface-stability/base-exports.stdout-mingw32
• testsuite/tests/interface-stability/base-exports.stdout-ws-32
• + testsuite/tests/linear/should_run/T26311.hs
• + testsuite/tests/linear/should_run/T26311.stdout
• testsuite/tests/linear/should_run/all.T
• testsuite/tests/pmcheck/should_compile/pmcOrPats.stderr
• + testsuite/tests/rep-poly/T26072b.hs
• testsuite/tests/rep-poly/all.T
• testsuite/tests/simd/should_run/all.T
• + testsuite/tests/typecheck/should_compile/T26582.hs
• testsuite/tests/typecheck/should_compile/all.T
• utils/haddock/haddock-test/src/Test/Haddock.hs
• utils/iserv/iserv.cabal.in

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