Erik de Castro Lopo pushed to branch wip/fix-9809 at Glasgow Haskell Compiler / GHC Commits: cc533b66 by Sasha Bogicevic at 2026-10-31T09:18:15-04:00 Don't report -XStrict-generated bangs under -Wredundant-bang-patterns The -XStrict flag causes the desugarer to insert bang patterns. These are not user-written, so -Wredundant-bang-patterns must not report them. To achieve this, the desugarer now tracks whether it is desugaring compiler-generated code (similar to the typechecker's 'tcl_in_gen_code'). Bangs inserted by -XStrict are given generated spans, which suppresses the "redundant bang" warnings without otherwise affecting pattern-match warnings. Fixes #27323 - - - - - 13d38047 by Luite Stegeman at 2026-10-31T09:19:11-04:00 rts: tombstone Weak# copies that lose an evacuation race (#23160) Mark the losing copy of a Weak# during an evacuation race in parallel GC with stg_DEAD_WEAK_info. This ensures that the nonmoving GC doesn't follow dangling pointers, leading to crashes. Fixes #23160 - - - - - 63347328 by Zubin Duggal at 2026-10-31T09:19:52-04:00 ghci: Drop GHCi's exception context when rethrowing in ghc -e Fixes #27847. - - - - - a85fef3f by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context in modifyIOError Fixes #27851. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446 - - - - - 1d60b591 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context in mapException Fixes #27851. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446 - - - - - 3c029a1b by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in Handle reads Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - ab2b317a by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in hClose Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - f5abf277 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in Windows openFile Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - d842c672 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in executablePath Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - c5a8bb9f by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Simplify a tc-trace which could crash the compiler The trace formatted an error message, which prematurely read the ExpType in a FunResCtxt. Solution: don't put call the error message formatting when tc-tracing. - - - - - ab49b1d2 by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Tiny comment change to uniqAway - - - - - 6efe4ba3 by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Make niFixSubst idempotent I discovered (when fixing #27994) that `niFixSubst` didn't actually generate an idempotent subsitution despite its claims. It could return a substitution that mentions domain variables on in its range, when those variables are hidden inside the kind of a type variable occurrence. As a result it can generate ill-kinded types. Boo! The fix is simple, and uses deep substitution. See Note [Finding the substitution fixpoint] I don't think it actually /caused/ any bugs, so there is no regression test. - - - - - 3b60ae7e by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Fix a nasty bug in fundeps This MR fixes #27994, which turned out to be very tricky. See Note [Exploiting closed type famililes], especially (CF7). I was ending up with TyVars (not TcTyVars) in the solver, because the substitution computed in `getRelevantBranches` mixed the two. The code was just too clever. I ended up simplifying it quite a bit. For /closed/ families we no longer call `trimQtvs` (was `trim_qtvs`). Open families still do use `trimQtvs`. See Note [trimQTvs] This patch also fixes one other buglet in the same code. * Over-saturated type families were being mis-handled. See the new use of `saturatedFamApp_maybe`. - - - - - e4610f2d by Facundo Domínguez at 2026-10-31T09:21:24-04:00 Have haddock --incremental look for the module in -this-unit-id - - - - - bc6c0db6 by sheaf at 2026-10-31T09:22:20-04:00 mightBeFunTy: hotfix for #27979 ce01ccb6 refactored 'GHC.Types.RepType.mightBeFunTy' to look through unary classes. That change introduced the helper function 'unwrap_type' which was supposed to always return an unwrapped type, but its fallback equation mistakenly returned the original type. This caused the subsequent 'tyConAppTyCon_maybe' to fail in cases where it should succeed (e.g. looking through foralls). In this commit, we move all the unary class unwrapping logic into 'unwrapType' where it belonged from the start, and update the documentation of 'unwrapType' to better explain what it should be used for (#26695). Fixes #27979 #26695 ------------------------- Metric Increase: T5642 ------------------------- - - - - - 233cce46 by Alan Zimmerman at 2026-10-31T09:23:01-04:00 EPA: Tidy up ExactPrint.markAnnListA' It takes an action which can modify the AnnList, but this is never used. So remove it. - - - - - 3594a908 by Sylvain Henry at 2026-10-31T09:23:51-04:00 gitmodules: ignore dirty libffi-clib submodule (#26785) `./boot` runs autoreconf in libraries/libffi-clib, which leaves `configure~` behind and rewrites the tracked `aclocal.m4` whenever the local automake version differs from the one that generated it. Every checkout then looks dirty. Ignore working-tree changes in the submodule (`ignore = dirty`); a changed submodule commit is still reported. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> - - - - - 341223c0 by Rodrigo Mesquita at 2026-10-31T09:24:33-04:00 refactor: Keep the interactive Ids directly rather than Name Removes things like names <- map idName ids map (\i -> let id = find (\x -> i==idName x) names) idso and is more straightforward because there's less state going around (no more updating HscEnv as an output) It also kills `printTypeOfNames` completely, since now we just have the Ids. No longer `lookupName` names to get back the ids... ``` printTypeOfName :: GHC.GhcMonad m => Name -> m () printTypeOfName n = do maybe_tything <- GHC.lookupName n case maybe_tything of Nothing -> return () Just thing -> printTyThing thing ``` now is just `printTyThing . AnId` Also: ```diff - tythings <- catMaybes `liftM` mapM GHC.lookupName namesSorted - docs <- mapM pprTypeAndContents [i | AnId i <- tythings] + docs <- mapM pprTypeAndContents idsSorted ``` (and yes, in ExecBreaks there are only Ids, no TyThings, bc they are only constructed by the interpreter execution which can only bind ids. for TyThings use runDecls which doesn't return execBreaks.) There's some care to be had to make sure we use the "most refined" Ids, whereas when using `Name`s we'd always fetch the most refined Id from scratch. Fixes #28052 - - - - - c5daa74e by Erik de Castro Lopo at 2026-11-02T15:45:00+11:00 TimerManager: publish only evaluated timeout queues (#9809) The issue in #9809 was triggered by many threads registering timeouts at the same time and those timeouts being stored as unevaluated thunks in the shared list. When say 100,000 timeouts are registered at the same time, the program can be slowed down considerably and the memory usage grow unacceptably large. The commit that caused the problem was 2d5eccdf1c, a 2013 change that fixed #7653. The fix is to add a modifyTimeouts function which applies an edit to a copy of the list and fully evaluates the result before replacing the shared list with a CAS operation. Performance has improved for the threaded case and not regressed for the single thread case: Forked registrations of 100k timeouts (median of 5 runs): -N4: 0.577 s, 428 MB -> 0.078 s, 39 MB -N12: 1.227 s, 479 MB -> 0.127 s, 80 MB Forked registrations of 1M timeouts on -N1 (median of 3 and 10 runs): 5.21 s (range 0.67-9.47 s), 1613 MB -> 0.67 s, 250 MB Single-thread registrations are unchanged or slightly faster, and timer latency during registration storms improves (p99 lateness of a 1 ms threadDelay during 100k forked registrations on -N4: 302-394 ms -> 3.5-4.1 ms). The registration code still runs in constant stack, so #7653 stays fixed; T7653 and the concurrent, base and ghc-internal testsuites pass. modifyTimeouts is OPAQUE so that the optimiser cannot expose the edit function's inspection of the old queue next to the compare-and-swap and replace the expected pointer with the evaluated queue, which would make the compare-and-swap keep failing when the MutVar# holds a thunk or indirection. Regression test T9809.hs included. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - ad58ac74 by Moritz Angermann at 2026-11-02T15:45:02+11:00 testsuite: give pause_resume_via_safe_ffi_concurrent 60s on Darwin CI The 10s System.Timeout watchdog was a false deadlock: five serialized 1s pauses plus rts_pause waiting on threadDelay/timer-manager traffic overruns that budget on loaded Mac runners. Keep a watchdog so a real hang still fails. - - - - - 90 changed files: - .gitmodules - + changelog.d/T27323 - + changelog.d/T27847 - + changelog.d/T27979 - + changelog.d/T27994 - + changelog.d/T9809-timer-manager-contention - + changelog.d/clc-446 - + changelog.d/clc-447 - + changelog.d/fix-nonmoving-weak-evacuation-race-23160 - + changelog.d/ghc-api-interactive-ids - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Types.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Runtime/Context.hs - compiler/GHC/Runtime/Debugger.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Runtime/Eval/Types.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/RepType.hs - compiler/GHC/Types/Var/Env.hs - ghc/GHCi/UI.hs - ghc/GHCi/UI/Monad.hs - libraries/base/changelog.md - libraries/base/tests/.gitignore - + libraries/base/tests/T9809.hs - libraries/base/tests/all.T - libraries/ghc-internal/src/GHC/Internal/Control/Exception/Base.hs - libraries/ghc-internal/src/GHC/Internal/Event/TimerManager.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Internals.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Text.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Windows.hs - libraries/ghc-internal/src/GHC/Internal/System/Environment/ExecutablePath.hsc - libraries/ghc-internal/src/GHC/Internal/System/IO/Error.hs - rts/sm/Evac.c - + testsuite/tests/codeGen/should_compile/T27979.hs - + testsuite/tests/codeGen/should_compile/T27979.stderr - testsuite/tests/codeGen/should_compile/all.T - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/exceptions/T27851.hs - + testsuite/tests/exceptions/T27851.stderr - + testsuite/tests/exceptions/T27851b.hs - + testsuite/tests/exceptions/T27851b.stderr - + testsuite/tests/exceptions/T27851c.hs - + testsuite/tests/exceptions/T27851c.stdout - + testsuite/tests/exceptions/T27851d.hs - + testsuite/tests/exceptions/T27851d.stdout - + testsuite/tests/exceptions/T27851d.stdout-javascript-unknown-ghcjs - testsuite/tests/exceptions/all.T - testsuite/tests/ghc-e/should_fail/T18441fail7.stderr - testsuite/tests/ghc-e/should_run/ghc-e005.stderr - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.hs - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.script - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.stdout - testsuite/tests/ghci.debugger/scripts/all.T - + testsuite/tests/haddock/haddock_testsuite/IncrementalUnitId.hs - testsuite/tests/haddock/haddock_testsuite/Makefile - testsuite/tests/haddock/haddock_testsuite/all.T - + testsuite/tests/haddock/haddock_testsuite/haddockIncrementalUnitId.stdout - + testsuite/tests/pmcheck/should_compile/T27323.hs - + testsuite/tests/pmcheck/should_compile/T27323b.hs - testsuite/tests/pmcheck/should_compile/all.T - + testsuite/tests/rts/T23160.hs - + testsuite/tests/rts/T23160.stdout - testsuite/tests/rts/all.T - testsuite/tests/rts/pause-resume/all.T - testsuite/tests/rts/pause-resume/pause_resume_via_safe_ffi_concurrent.hs - + testsuite/tests/typecheck/should_compile/T27994.hs - + testsuite/tests/typecheck/should_compile/T27994a.hs - + testsuite/tests/typecheck/should_compile/T27994b.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/warnings/should_compile/Overflow.stderr-ws-32 - testsuite/tests/warnings/should_compile/Overflow.stderr-ws-64 - testsuite/tests/warnings/should_compile/T13256.stderr-ws-32 - testsuite/tests/warnings/should_compile/T13256.stderr-ws-64 - utils/check-exact/ExactPrint.hs - utils/haddock/CHANGES.md - utils/haddock/haddock-api/src/Haddock/Interface.hs The diff was not included because it is too large. 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