Simon Peyton Jones pushed to branch wip/T27724 at Glasgow Haskell Compiler / GHC Commits: 06eee015 by Luite Stegeman at 2026-09-08T06:03:06+02:00 rts: Fix missing memory barrier in eval_thunk_selector (#27477) unchain_thunk_selectors() was missing an ACQUIRE_LOAD for the indirectee, leading to segfaults and corruption during GC on weakly-ordered architectures. Fixes #27477 - - - - - f8b2bd8f by Alan Zimmerman at 2026-09-08T09:39:12-04:00 EPA Fix HsCmdDo exact print with comments Exact printing of HsCmdDo was ignoring the location for the do statements, and this is an annotation that can have comments in it. Update it so we print the statements as a unit, including any comments. Also add the result of auditing that we capture comments in all needed places, noting that the remaining Anno SrcSpan instances are benign. - - - - - 430967ab by Duncan Coutts at 2026-09-09T11:07:01+01:00 Reorder cmm decls in HeapStackCheck for a better logical grouping And put more section headers in to deliniate the groups. We're about to add more here, so better to organise it first. - - - - - 344080fd by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add raisePrimIOException and add it to RTS<->ghc-internal API The raisePrimIOException is a new helper function that I/O primops will use to help them report I/O errors. This is implemented in Haskell (since that's a lot easier), but has a calling convention that is easy(ish) to use from Cmm in the I/O primops. So we add it to the RTS API struct, and since we'll use it from Cmm we also need a field accessor macro for cmm (in deriveConstants). See the Note about how we cannot have nice things due to async exceptions and thunks preventing us from using catch. - - - - - cfdb3399 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add new blocking functions for I/O primops See the Note [Thread blocking for new I/O primops], and the Note [Calling convention for raisePrimIOException]. The point is, it will allow us to report synchronous exceptions from I/O primops, and do so much more flexibly. Previously the I/O managers could only report async exceptions and only nullary exceptions. This was OK historically, but no good as we add more I/O managers and expand the range of I/O operations we support. - - - - - f09c09d8 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Change the encoding of results from the I/O manager to I/O primops Previously we just had async continue or heap overflow. We now extend what we can report with synchronous success, and synchronous failure with an errno. See Note [Encoding of result of I/O manager operations] We don't use these two new cases yet, but we will. In particular an epoll I/O manager needs to be able to report synchronous success or failure for waitRead#/waitWrite#. - - - - - 30f074d9 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch waitRead/Write# to use new blocking return frames and update the I/O managers to set the result before resuming the blocked threads. This makes it possible for I/O managers to report synchronous exceptions from the I/O primops, but that will be done in a subsequent commit. - - - - - a8786ced by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch Poll and Select I/O managers to report sync exceptions rather than using raiseAsync with blockedOnBadFD_closure. This uses the new mechanism in the blocking frame return code to report synchronous exceptions. - - - - - 7a9df79a by Duncan Coutts at 2026-09-09T11:07:01+01:00 Remove now-unused blockedOnBadFD It was previously thrown by the select and poll I/O managers, but now they use raisePrimIOException (with an EBADF errno). - - - - - 6b0424e3 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Improve the docs for delay# waitRead# and waitWrite# Document that the waitRead/Write# can throw exceptions (this was true before too), and that all of them are async exception cancellation points. - - - - - afeb2c30 by Duncan Coutts at 2026-09-09T20:08:58-04:00 Enable printf warnings for trace functions and fix resulting warnings Most of the existing printf-style functions are annotated with attributes to enable gcc/clang warnings for the printf format string, but several trace functions in Trace.h were missing this annotation. Enable them, and fix the resulting warnings. - - - - - 9a442c93 by Alan Zimmerman at 2026-09-09T20:09:36-04:00 EPA: Exact print ConDeclGADT without custom enterAnn !16321 brought in explicit capture of parens in a ConDeclGADT. The ExactPrint update introduced a modification of the fundamental function in exact printing, `enterAnn`, by splitting it into a version allowing injection of functionality normally handled by the ExactPrint class methods. This commit refactors that code, to restore the prior `enterAnn` version, by following the convention in ExactPrint of introducing a helper data structure with its own `ExactPrint` instance to achieve the same effect. - - - - - 4e9297ea by Simon Jakobi at 2026-09-11T08:32:45-04:00 ci: Actually pass --ignore-perf-failures to the testsuite driver 684c0018d9 changed the IGNORE_PERF_FAILURES handling to append to RUNTEST_ARGS with bash array syntax, but the three use sites still expand RUNTEST_ARGS as a scalar, which yields only the first array element. The appended flag was therefore dropped in every job, so perf improvements kept failing Marge Bot batches and master pipelines, contrary to #19562. Append as a string instead, matching the existing --force-colors append in test_hadrian. Fixes #27563. Assisted-by: Claude Fable 5.1 - - - - - 4f78dfdf by Simon Jakobi at 2026-09-11T08:33:24-04:00 testsuite: Give T26537 a 1.5x compile timeout Its -fregs-graph compile step tends to time out in unoptimized builds (#27188, #27776). Assisted-by: Claude Fable 5.1 - - - - - 130286e3 by Alan Zimmerman at 2026-09-11T08:34:08-04:00 EPA: Remove ListBanana / ListParens from AnnListBrackets This is a step towards making AnnList only represent lists of items which can have either braces or layout. - - - - - a9827d13 by Simon Jakobi at 2026-09-11T18:53:32-04:00 Reject ~, UNPACK and multiplicity annotations on type data fields Only `!` was rejected so far. `~`, UNPACK and multiplicity annotations were silently accepted. None of them make sense at the type level, so restriction (R3) of Note [Type data declarations] now covers all of them. Fixes #27732. Assisted-by: Claude Fable 5.1 - - - - - c71d5e23 by Alan Zimmerman at 2026-09-11T18:54:11-04:00 EPA: Add a Note for the exact print main loop - - - - - 7a108e43 by Simon Jakobi at 2026-09-12T18:35:59-04:00 FastString: Drop mkFastStringWith's constructor callback All three callers passed the same callback, a partial application of mkNewFastStringShortByteString to the string being interned. That partial application is allocated as a closure before the table lookup, on the common hit path too, although the callback is needed only after a miss. Drop the parameter and call mkNewFastStringShortByteString directly after a miss. Since nothing is passed "with" anymore, rename the function to internSB. Suggested by Simon PJ in #27528: https://gitlab.haskell.org/ghc/ghc/-/work_items/27528#note_687031 Assisted-by: Claude Fable 5 - - - - - 82c73b22 by Alan Zimmerman at 2026-09-12T18:36:38-04:00 EPA: More targeted HsDo exact print annotation HsDo is multi-purpose, as encoded in its HsDoFlavour field. Some of these are in a layout context (DoExpr, MDoExpr), others are not (ListComp, MonadComp). We are moving towards using AnnList only in layout contexts, so we switch the HsDo TTG annotation from holding an AnnList for this, to holding Either (EpToken "[", EpToken "]") AnnList This also allows us to trim down AnnListBrackets to only have braces or None, thereby opening the door for unification with the existing layout context data type EpLayout. - - - - - 6ce1e2d0 by Simon Peyton Jones at 2026-09-15T11:16:53+01:00 Redesign the noinline magic Main idea: * When simplifying `noinline (f e1 e2)`, switch off inlining when simplifying `f` * Mechanism: see `simplOutId`, the `noinlineIdKey` case * If we see `noinline (f e1) e2`, the simplifier moves the `e2` inside; see the `splitContArgs` call. This is important so you can write `noinliine f e1 e2` and have it mean the same as `noinline (f e1 e2)`. * Now `f` sees all its arguments, henc: * Fixes #27724 * Fixes #23911 See Note [noinlineId magic] for lots of specifics. It's surprisingly tricky! - - - - - 102 changed files: - .gitlab/ci.sh - + changelog.d/27732 - + changelog.d/T27724 - + changelog.d/fix-parallel-gc-selector-race-27477 - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/primops.txt.pp - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/Type.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/FastString.hs - compiler/GHC/Driver/Config/Core/Opt/Simplify.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Extension/Pass.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/Types/Origin.hs - docs/users_guide/exts/type_data.rst - libraries/ghc-internal/include/RtsIfaceSymbols.h - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Thread.hs - libraries/ghc-internal/src/GHC/Internal/Magic.hs - rts/Capability.c - rts/HeapStackCheck.cmm - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/Messages.c - rts/Prelude.h - rts/PrimOps.cmm - rts/Printer.c - rts/STM.c - rts/Schedule.c - rts/Sparks.c - rts/StableName.c - rts/ThreadPaused.c - rts/Threads.c - rts/Trace.h - rts/include/rts/RtsToHsIface.h - rts/include/stg/MiscClosures.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - rts/posix/Timeout.c - rts/sm/Compact.c - rts/sm/Evac.c - rts/sm/GC.c - rts/sm/GCUtils.c - rts/sm/MBlock.c - rts/sm/NonMoving.c - rts/sm/NonMovingMark.c - rts/sm/Storage.c - rts/sm/Sweep.c - testsuite/tests/codeGen/should_run/all.T - testsuite/tests/corelint/LintEtaExpand.hs - + testsuite/tests/dmdanal/should_compile/T23911.hs - testsuite/tests/dmdanal/should_compile/all.T - testsuite/tests/ghc-api/T25121_status.stdout - testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr - testsuite/tests/parser/should_compile/DumpSemis.stderr - testsuite/tests/printer/Test20297.stdout - + testsuite/tests/rts/T27477.hs - + testsuite/tests/rts/T27477.stdout - testsuite/tests/rts/all.T - + testsuite/tests/simplCore/should_compile/T27724a.hs - + testsuite/tests/simplCore/should_compile/T27724a.stderr - + testsuite/tests/simplCore/should_compile/T27803.hs - + testsuite/tests/simplCore/should_compile/T27803.stderr - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/type-data/should_fail/T27732a.hs - + testsuite/tests/type-data/should_fail/T27732a.stderr - + testsuite/tests/type-data/should_fail/T27732b.hs - + testsuite/tests/type-data/should_fail/T27732b.stderr - + testsuite/tests/type-data/should_fail/T27732c.hs - + testsuite/tests/type-data/should_fail/T27732c.stderr - + testsuite/tests/type-data/should_fail/T27732d.hs - + testsuite/tests/type-data/should_fail/T27732d.stderr - + testsuite/tests/type-data/should_fail/T27732e.hs - + testsuite/tests/type-data/should_fail/T27732e.stderr - + testsuite/tests/type-data/should_fail/T27732f.hs - + testsuite/tests/type-data/should_fail/T27732f.stderr - testsuite/tests/type-data/should_fail/TDStrictnessGADT.stderr - testsuite/tests/type-data/should_fail/TDStrictnessH98.stderr - testsuite/tests/type-data/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Utils.hs - utils/deriveConstants/Main.hs - utils/genprimopcode/Main.hs The diff was not included because it is too large. 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