September 2026 - ghc-commits

[Git][ghc/ghc][wip/io-manager-deadlock-detection] 36 commits: Improvements to type/data family handling
by Duncan Coutts (＠dcoutts) 24 Sep '26

24 Sep '26

Duncan Coutts pushed to branch wip/io-manager-deadlock-detection at Glasgow Haskell Compiler / GHC Commits: 1b4a622f by sheaf at 2026-09-17T02:39:13-04:00 Improvements to type/data family handling This commit makes several improvements to the treatment of type and data families in GHC: - We consistently use "type family" instead of "type synonym family" to avoid a confusion with type synonyms. For example: - OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon - ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon - Various functions that were specific to data families have been renamed to make this clear. For example: - tyConFamInst_maybe ==> tyConDataFamInst_maybe - isFamInstTyCon ==> isDataFamInstTyCon - 'FamTyConFlav' has been refactored so that all closed type families share a single 'ClosedTypeFamilyTyCon' constructor. The corresponding 'IfaceFamTyConFlav' type was updated similarly. This is then used to tidy up the implementation of GHC.Core.FamInstEnv.reduceTyFamApp_maybe. - - - - - c5aa9098 by sheaf at 2026-09-17T02:39:13-04:00 Small refactor of lookupFamInstEnv This commit reworks the code for looking up family instances in GHC.Core.FamInstEnv, reducing duplication a little bit. No change in behaviour. - - - - - a3ad4588 by sheaf at 2026-09-17T02:39:14-04:00 Use a type family for boxing unboxed types This commit overhauls the way in which unboxed types are boxed, as per the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box. The main change is to allow boxing to be parametrised by representation, e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box' using a closed type family: newtype Box (a :: TYPE r) = Box (BoxTF r) type BoxTF :: RuntimeRep -> Type type family BoxTF r where BoxTF IntRep = BoxInt BoxTF Int8Rep = BoxInt8 BoxTF WordRep = BoxWord BoxTF LiftedRep = Any @Type BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2) ... BoxTF (SumRep rs) = BoxSum rs This new design solves the following problems: - It allows boxing a type whose 'RuntimeRep' has not yet been determined (e.g. because we only learn the 'RuntimeRep' after constraint solving). That is, 'Box @r a' is a perfectly valid type even if 'r' is an unfilled metavariable. This is a requirement to fix #25065 (in which we need to box a type whose 'RuntimeRep' is only filled in during constraint solving). - It handles boxing of unboxed tuples and unboxed sums, via recursive boxing. See Note [Boxing TupleRep and SumRep] in GHC.Builtin.WiredIn.Types.Box. 'Box', 'BoxTF' and all of the boxing data constructors are defined in a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains nothing but wired-in declarations, and GHC never loads its interface on account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule); see Note [Loading instances for wired-in things] in GHC.Iface.Load. The individual boxing data constructors are deliberately left as an internal implementation detail, and not exported. The intended API is via the two new magic 'Id's: box :: forall {r} (a :: TYPE r). a -> Box a unbox :: forall {r} (a :: TYPE r). Box a -> a exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer exported from base (CLC proposal #421). We use this new design to consistently desugar: - parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt}) - then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt}) - recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo) - arrows (GHC.HsToCore.Arrows) by consistently using 'box'/'unbox' to deal with unboxed types being put into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}' to create fresh /representation-polymorphic/ type variables for the binders that we are going to put into a big tuple (previously, GHC only allowed lifted types in that position). These desugaring of box and unbox is explained in Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking, the desugaring looks like: box @r @ty e ==> K e unbox @r @ty e ==> case e of K x -> x where 'K' is the boxing data constructor at RuntimeRep 'r'. It's slightly more complicated than that in practice: we first need to insert a cast (see Note [The canonical type of a RuntimeRep]) using the new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need recursive logic explained in Note [box/unbox for unboxed tuples and sums], including a specific 'BoxSum' datatypes for unboxed sum (which also needed a wired-in type-level list indexing type family (!!)). The desugaring happens in two ways: - Occurrences of 'box'/'unbox' emitted by the typechecker are eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr. - Other code that needs to box/unbox emits the appropriate code inline. This includes the big tuple machinery of GHC.Core.Make used by the desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as the float-out pass (GHC.Core.Opt.SetLevels). Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring. On the way, we overhaul the litany of big tuple functions by introducing data BigTupleLayout = BoxedElements | BareElements to distinguish the two kinds of "big tuples" that GHC routinely deals with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'. All of this code is moved to the new module GHC.Core.Make.BigTuple. Fixes #20864 #22336 #22473 #25065 #27331 ------------------------- Metric Decrease: T9872a ------------------------- - - - - - 4cf7628a by Evgeny Malyshev at 2026-09-17T02:39:56-04:00 Fix the CompactionFailed documentation link to compact The old Haddock reference links into base instead of ghc-compact. Use an explicit URL because ghc-compact depends on base, not vice versa. Fixes #27558 Assisted-By: OpenAI Codex - - - - - 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - 545fd4fb by ARATA Mizuki at 2026-09-22T15:03:24-04:00 Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types bitReverse{16,32}# and byteSwap{16,32}# have the type Word# -> Word#, but their C correspondents took and returned StgWord{16,32}. The mismatch on bitReverse16# led to the problem reported in #27299. Although no similar issue is reported for bitReverse32# and byteSwap{16,32}#, it seemed wise to change them proactively. This commit fixes the mismatch by changing the C type. Fixes #27299 - - - - - bf17f289 by fendor at 2026-09-22T15:04:05-04:00 Don't lose instances from shadowed imported modules with the same name When we look for instances below the current module, we need to check the unit id as well when we check for whether the module is the current module, otherwise we ignore modules we import that have the same name as the import module. Adds regression test. - - - - - be627893 by Duncan Coutts at 2026-09-23T17:58:07+01:00 Move idle GC tracking to its own file, step 1 of 2 Add a new IdleGC.{c,h} module. Move the RecentActivity type, recent_activity variable and {get,set}RecentActivity wrappers. - - - - - eab757f2 by Duncan Coutts at 2026-09-23T17:58:07+01:00 Move idle GC functionality to its own file, step 2 of 2 We can now fully encapsulate the recent_activity state, exposing just three hooks, and one query used in the scheduler and timer tick. This is a prelude to making changes to the implementation of tracking when to perform an idle gc. - - - - - 8b24b2a3 by Duncan Coutts at 2026-09-23T17:58:07+01:00 Correct comments in idle GC code The comments still referred to stopTimer/startTimer. These were replaced recently by pauseTimer/unpauseTimer, but the comment was not updated. - - - - - 14f26d65 by Duncan Coutts at 2026-09-23T17:58:07+01:00 Make signal handling be a responsibility of the I/O manager(s) Previously it was scattered between I/O managers and the scheduler, and especially the scheduler's deadlock detection. Previously the scheduler would poll for pending signals each iteration of the scheduler loop. The scheduler also had some hairy signal functionality in the deadlock detection: in the non-threaded RTS (only) if there were still no threads running after deadlock detection then it would block waiting for signals. But signals can and (in my opinion) should be thought of as just a funny kind of I/O, and thus should be a responsibility of the I/O manager. So now we have the I/O managers poll for signals when they are polling for I/O completion (and removing the separate poll in the scheduler). And when I/O managers block waiting for I/O then they now also start signal handlers if they get interrupted by a signal. Crucially, if there is no pending I/O or timers, the awaitCompletedTimeoutsOrIO will still block waiting for signals. This patch puts us into an intermediate state: it temporarily breaks deadlock detection in the non-threaded RTS. The waiting on I/O currently happens before deadlock detection. This means we'll now wait forever on signals before doing deadlock detection. We need to move waiting after deadlock detection. We'll do that in a later patch. - - - - - a60625a6 by Duncan Coutts at 2026-09-24T13:47:34+01:00 Clean up the RTS internal signal handling API Now that the I/O manager is responsible for signals, we can simplify the API we present for signal handling. We now just need startPendingSignalHandlers, which is called from the I/O managers. We can get rid of awaitUserSignals. We also don't need RtsSignals.h to re-export the platform-specific posix/Signals.h or win32/ConsoleHandler.h We can also hide more of the implementation of signals. Less has to be exposed in posix/Signals.h or win32/ConsoleHandler.h. Indeed, posix/Signals.h becomes empty and we remove it. Partly this is because we don't need inline functions (or macros) in the interface. Also remove signal_handlers from RTS ABI exported symbols list. It does not appear to have any users in the core libs, and its really an internal implementation detail. It should not be exposed unless it's really necessary. - - - - - 886eceef by Duncan Coutts at 2026-09-24T13:48:16+01:00 In the scheduler, move I/O blocking after deadlock detection To make deadlock detection effective in the non-threaded RTS when there are deadlocked threads and other unrelated threads waiting on I/O, we need to arrange to do deadlock detection before we block in scheduler to wait on I/O. The solution is to: 1. adjust scheduleFindWork, which runs before deadlock detection, to only poll for I/O and not block; and 2. add a step after deadlock detection to wait on I/O if there are still no threads to run (and there's any I/O or timeouts outstanding) The scheduleCheckBlockedThreads is now so simple that it made more sense to inline it into scheduleFindWork. - - - - - d4e365ef by Duncan Coutts at 2026-09-24T13:48:16+01:00 Remove bogus anyPendingTimeoutsOrIO guard from scheduleDetectDeadlock The deadlock detection was only invoked if both of these conditions hold: 1. the run queue is empty 2. there is no pending I/O or timeouts The second condition is unnecessary. The deadlock detection mechanism can find deadlocks even if there are other threads waiting on I/O or timers. Having this extra condition means that we fail to detect blocked threads if there are any threads waiting on I/O or timers. Part of fixing issue #26408 - - - - - ca8ef4a1 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Don't consider pending I/O for early context switch optimisation Context switches are normally initiated by the timer signal. If however the user specifies "context switch as often as possible", with +RTS -C0 then the scheduler arranges for an early context switch (when it's just about to run a Haskell thread). Context switching very often is expensive, so as an optimisation there cases where we do not arrange an early context switch: 1. if there's no other threads to run 2. if there is no pending I/O or timers This patch eliminates case 2, leaving only case 1. The rationale is as follows. The use of this was inconsistent across platforms and threaded/non-threaded RTS ways. It only worked on the non-threaded RTS and on Windows only worked for the win32-legacy I/O manager. On all other combinations anyPendingTimeoutsOrIO would always return false. The fact that nobody noticed and complained about this inconsistency suggests that the feature is not relied upon. If however it turns out that applications do rely on this, then the proper thing to do is not to restore this check, but to add a new I/O manager hint function that returns if there is any pending events that are likely to happen *soon*: for example timeouts expiring within one timeslice, or I/O waits on things likely to complete soon like disk I/O, but not for example socket/pipe I/O. The motivation to avoid this use of anyPendingTimeoutsOrIO is to allow us to eliminate anyPendingTimeoutsOrIO entirely. All other uses of this are just guards on {await,poll}CompletedTimeoutsOrIO and the guards can safely be folded into those functions. This will better cope with some I/O managers having no proper implementation of anyPendingTimeoutsOrIO. Ultimately this will let us simplify the scheduler which currently has to have special #ifdef mingw32_HOST_OS cases to cope with the lack of a working anyPendingTimeoutsOrIO for some Windows I/O managers - - - - - 6adafed8 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Remove anyPendingTimeoutsOrIO guarding {poll,await}CompletedTimeoutsOrIO Previously the API of the I/O manager used a two step process: check anyPendingTimeoutsOrIO and then call {poll,await}CompletedTimeoutsOrIO. This was primarily there as a performance thing, to cheaply check if we need to do anything. And then because anyPendingTimeoutsOrIO existed, it was used for other things too. We have now eliminated the other uses, and are just left with the performance pattern. But this was problematic because not all I/O managers correctly implement anyPendingTimeoutsOrIO (specifically the win32 ones), and now that we also make I/O managers responsible for signals then we need to poll/await even if there is no pending I/O or timeouts. If there is no pending I/O or timeouts then await needs to degenerate to just waiting forever for any signals. - - - - - efe6f98a by Duncan Coutts at 2026-09-24T13:48:16+01:00 Remove anyPendingTimeoutsOrIO, it is no longer used And this avoids the problems arising from the win32 I/O managers having had a bogus implementation. - - - - - 47c98c09 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Remove second scheduler call to awaitCompletedTimeoutsOrIO Previously awaitCompletedTimeoutsOrIO was called both before and after deadlock detection in the scheduler. The reason for that was that the win32 I/O managers had a bogus implementation of anyPendingTimeoutsOrIO and this was used to guard the call of awaitCompletedTimeoutsOrIO prior to deadlock detection. This meant the first call site was never actually called when using the win32 I/O managers. This was the reason for the second call: the first one was never used. What a mess. So now we have a simple design in the scheduler: 1. poll for completed I/O, timers or signals 2. if no runnable threads: do deadlock detection 3. if still no runnable threads: block waiting for I/O, timers or signals. - - - - - 35d8dff3 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Lift emptyRunQueue guard out of scheduleDetectDeadlock this improved the clarity of the logic when reading the scheduler code. And improve the comment about scheduleDoGC that was rather unclear. - - - - - 96ec61c4 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Make interruptIOManager work for WinIO (non-threaded) Fixes #27403 The idle GC scheme now fundamentally relies on interruptIOManager working, so it's no longer acceptable for it to be missing for WinIO. Not having it would cause lock ups. - - - - - 21f55291 by Duncan Coutts at 2026-09-24T13:48:16+01:00 Make non-threaded deadlock detection also rely on idle GC Only do deadlock detection GC when idle GC kicks in. This also relies on using wakeUpRts, so now do this unconditionally. Previously wakeUpRts was for the threaded rts only. - - - - - 96bab74b by Duncan Coutts at 2026-09-24T13:48:16+01:00 Enable idle GC by default on non-threaded RTS The behaviour is now uniform between the threaded and non-threaded RTS ways. The deadlock detection now relies on idle GC for both threaded and non-threaded ways. Previously deadlock detection did not rely on idle GC for the non-threaded way. Also tweak test T7275 to account for idle GC. This test's output is sensitive to the number of major GCs run. Since this commit enables idle GC for the non-threaded RTS, for this test that increases the number of major GCs, since the test program is frequently idle for more than 300ms. - - - - - 2c5a537f by Duncan Coutts at 2026-09-24T13:48:16+01:00 Fix state of idle GC control vars with +RTS -V0 Currently when the user uses +RTS -I0, then doIdleGC is set to false. But if the master tick interval -V is set to 0 then the idleGCDelayTime was being set to 0 but doIdleGC was not being set to false, which is inconsistent, and almost certainly buggy. - - - - - 4c6089bd by Duncan Coutts at 2026-09-24T15:54:49+01:00 Add a long Note [Deadlock detection] It describes the historical and modern designs and their trade-offs. The point is we've now unified the code for deadlock detection between the threaded and non-threaded ways, by changing the non-threaded to follow the same design as the threaded. - - - - - 71e1e1ce by Duncan Coutts at 2026-09-25T00:27:21+01:00 fixup Add a long Note [Deadlock detection] - - - - - b387895d by Duncan Coutts at 2026-09-25T00:27:23+01:00 Refactor the utils providing the I/O timeout for different system APIs We have to provide a timeout in three different time formats (int milliseconds, struct timeval *, and struct timespec *). These are for platform APIs including poll, select, ppoll, pselect, epoll_wait, epoll_wait2 and in future kevent and io_uring. Previously we had one util for each format that both worked out what the timeout should be and converted it into the particular format. This duplicates some logic and it also makes it awkward to modify the timeout value (since there's no common format). Modifying the timeout value is exactly what we want to do, in a subsequent commit, where we want to adjust the timeout to take account of idle GC. - - - - - e414c31f by Duncan Coutts at 2026-09-25T00:27:23+01:00 Update the old select I/O manager to use the new timeout utils This will make it much easier to adjust the timeout to take account of idle GC. - - - - - b3c1c686 by Duncan Coutts at 2026-09-25T00:27:53+01:00 Add opportunistic deadlock detection without idle GC Our general design is now that comprehensive deadlock detection relies on idle GC. This allows us to detect partial deadlocks that are not system deadlocks. But it's not prompt. It's a nice to have feature to be able to promptly detect the cases that are system deadlocks. There's no hope to do this in the threaded RTS with -N > 1, but it can be done for the non-threaded RTS and _could_ be done for the threaded RTS with -N1. We can integrate this feature into the general design without too many contortions. We just need the I/O managers to check before sleeping if they would be about to sleep indefinately with no I/O and no registered signal handlers. If so, they can notify the idle GC that we're deadlocked and we schedule and idle GC. - - - - - 5637c825 by Duncan Coutts at 2026-09-25T00:28:26+01:00 Add idle GC mode for !HAVE_PREEMPTION We have to do idle GC (and thus deadlock detection) differently when we do not have the ticker and the ability to interrupt the I/O manager when it's blocking. - - - - - 3432949d by Duncan Coutts at 2026-09-25T00:28:28+01:00 Add and use USED_IF_PREEMPTION to avoid warnings - - - - - 1fff75a7 by Duncan Coutts at 2026-09-25T00:28:28+01:00 Add performDeadlockDetection and export via ghc-experimental When documenting the idle GC and deadlock detection behaviour in the user guide, it becomes obiovus that in some cases one would want manual control over deadlock detection. In particular, for applications that disable idle GC, for debugging or robustness, they may want to invoke deadlock detecting GC manually. Bind it in ghc-internal GHC.Internal.System.Mem and re-export via ghc-experimental in System.Mem.Experimental. It is clearly implementation specific behaviour, especially since in GHC the deadlock detection is tied to doing a major GC. - - - - - 383d6455 by Duncan Coutts at 2026-09-25T00:28:28+01:00 Add tests for deadlock detection, issue #26408 We have three tests: T26408a: make sure that we can detect a /partial deadlock/ that is not also a /system deadlock/ T26408b: make sure that we can detect a /system deadlock/ promptly without relying on idle GC T26408c: make sure that we do not falsely detect a deadlock when there is nothing to do except wait on signals - - - - - c20f42b2 by Duncan Coutts at 2026-09-25T00:28:28+01:00 Update the user guide with the revised idle GC behaviour It's now not just for the threaded RTS, but general. Add a new section in the RTS chapter: Idle GC and deadlock detection. Provide general documentation on both topics. In particular, document the behaviour of deadlock detection and how it depends on idle GC. Move the existing entries for -I and -Iw to this section. Add a changelog entry. - - - - - 182 changed files: - + changelog.d/25763-cmdline-opt - + changelog.d/26610 - + changelog.d/boxing-family - + changelog.d/clc-421 - + changelog.d/idle-gc-and-deadlock-detection - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/Builtin/Uniques.hs - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/WiredIn/TypeLits.hs - compiler/GHC/Builtin/WiredIn/Types.hs - + compiler/GHC/Builtin/WiredIn/Types/Box.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - + compiler/GHC/Core/Make/BigTuple.hs - + compiler/GHC/Core/Make/Box.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/ListComp.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Rename.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/StgToJS/CodeGen.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Match.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Instance/Typeable.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Types/CompleteMatch.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/TyThing.hs - compiler/GHC/Types/TyThing/Ppr.hs - compiler/GHC/Types/Unique.hs - compiler/ghc.cabal.in - docs/users_guide/profiling.rst - docs/users_guide/runtime_control.rst - ghc/GHC/Driver/Session/Mode.hs - libraries/base/src/GHC/Base.hs - libraries/base/src/GHC/Exts.hs - libraries/ghc-experimental/src/System/Mem/Experimental.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/RtsIfaceSymbols.h - + libraries/ghc-internal/src/GHC/Internal/Box.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/System/Mem.hs - libraries/ghc-internal/src/GHC/Internal/TypeNats.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - linters/lint-codes/LintCodes/Static.hs - rts/Capability.c - rts/IOManager.c - rts/IOManager.h - + rts/IdleGC.c - + rts/IdleGC.h - rts/Linker.c - rts/Prelude.h - rts/RtsFlags.c - rts/RtsSignals.h - rts/RtsStartup.c - rts/RtsSymbols.c - rts/Schedule.c - rts/Schedule.h - rts/Timer.c - rts/include/rts/OSThreads.h - rts/include/rts/RtsToHsIface.h - rts/include/rts/storage/GC.h - rts/include/stg/Prim.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - rts/posix/SelectBis.c - rts/posix/SelectBis.h - rts/posix/Signals.c - − rts/posix/Signals.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/prim/bitrev.c - rts/prim/bswap.c - rts/rts.cabal - rts/sm/Evac.c - rts/win32/AsyncMIO.c - rts/win32/AsyncMIO.h - rts/win32/AsyncWinIO.c - rts/win32/AsyncWinIO.h - rts/win32/AwaitEvent.c - rts/win32/ConsoleHandler.c - rts/win32/ConsoleHandler.h - testsuite/tests/MiniQuickCheck.hs - testsuite/tests/arrows/should_run/all.T - + testsuite/tests/arrows/should_run/arrowrun005.hs - + testsuite/tests/arrows/should_run/arrowrun005.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_compile/T25065a.hs - testsuite/tests/deSugar/should_compile/all.T - + testsuite/tests/deSugar/should_run/T20864.hs - + testsuite/tests/deSugar/should_run/T20864.stdout - + testsuite/tests/deSugar/should_run/T25065b.hs - + testsuite/tests/deSugar/should_run/T25065b.stdout - testsuite/tests/deSugar/should_run/all.T - testsuite/tests/driver/all.T - + testsuite/tests/driver/stringtrie.hs - + testsuite/tests/driver/stringtrie.stdout - + testsuite/tests/ghci/prog-mhu008/Makefile - + testsuite/tests/ghci/prog-mhu008/a/M.hs - + testsuite/tests/ghci/prog-mhu008/all.T - + testsuite/tests/ghci/prog-mhu008/b/M.hs - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.script - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout - + testsuite/tests/ghci/prog-mhu008/unitA - + testsuite/tests/ghci/prog-mhu008/unitB - + testsuite/tests/indexed-types/should_run/T27331.hs - + testsuite/tests/indexed-types/should_run/T27331.stdout - + testsuite/tests/indexed-types/should_run/T27331b.hs - + testsuite/tests/indexed-types/should_run/T27331b.stdout - + testsuite/tests/indexed-types/should_run/T27331b_Plugin.hs - testsuite/tests/indexed-types/should_run/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/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32 - testsuite/tests/interface-stability/ghc-prim-exports.stdout - testsuite/tests/interface-stability/ghc-prim-exports.stdout-mingw32 - testsuite/tests/linters/notes.stdout - + testsuite/tests/perf/compiler/T25763.stderr - testsuite/tests/perf/compiler/all.T - + testsuite/tests/primops/should_run/T27299.hs - + testsuite/tests/primops/should_run/T27299.stdout - testsuite/tests/primops/should_run/all.T - testsuite/tests/profiling/should_run/Makefile - testsuite/tests/rts/Makefile - + testsuite/tests/rts/T26408a.hs - + testsuite/tests/rts/T26408a.stderr - + testsuite/tests/rts/T26408b.hs - + testsuite/tests/rts/T26408b.stderr - + testsuite/tests/rts/T26408c.hs - + testsuite/tests/rts/T26408c.stdout - testsuite/tests/rts/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/haddock/haddock-api/src/Haddock/Convert.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/cd4aaf05d6ab5b299b8b00c2631d5f… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/cd4aaf05d6ab5b299b8b00c2631d5f… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/sjakobi/T27847-ghci-rethrow-backtrace] ghc -e: Print uncaught exceptions without their context
by Simon Jakobi (＠sjakobi) 24 Sep '26

24 Sep '26

Simon Jakobi pushed to branch wip/sjakobi/T27847-ghci-rethrow-backtrace at Glasgow Haskell Compiler / GHC Commits: b5957144 by Simon Jakobi at 2026-09-25T01:11:21+02:00 ghc -e: Print uncaught exceptions without their context Since 2ab02c579a9, exceptions rethrown inside GHCi keep collecting backtraces and WhileHandling annotations, so a failing `ghc -e` or runghc script printed extra "HasCallStack backtrace" blocks pointing into GHC's own sources (#27847). By the time an exception reaches the top-level handler, its context only describes GHC-internal frames: the user program's own context is already part of the message text. So drop the context before printing. This also removes the WhileHandling noise from prettyPrintGhcErrors that predates 2ab02c579a9. Fixes #27847. Assisted-by: Claude Opus 5.5 - - - - - 5 changed files: - compiler/GHC/Utils/Exception.hs - ghc/GHCi/UI.hs - libraries/ghci/GHCi/Message.hs - testsuite/tests/ghc-e/should_fail/T18441fail7.stderr - testsuite/tests/ghc-e/should_run/ghc-e005.stderr Changes: ===================================== compiler/GHC/Utils/Exception.hs ===================================== @@ -11,6 +11,7 @@ import GHC.Prelude.Basic import GHC.IO (catchException) import Control.Exception as CE hiding (assert) +import Control.Exception.Context (emptyExceptionContext) import Control.Monad.IO.Class import Control.Monad.Catch @@ -24,4 +25,8 @@ handleIO = flip catchIO tryIO :: IO a -> IO (Either IOException a) tryIO = CE.try +-- | Remove the context, such as backtraces and annotations, from an exception. +dropExceptionContext :: SomeException -> SomeException +dropExceptionContext e = toException (ExceptionWithContext emptyExceptionContext e) + type ExceptionMonad m = (MonadCatch m, MonadThrow m, MonadMask m, MonadIO m) ===================================== ghc/GHCi/UI.hs ===================================== @@ -1079,8 +1079,12 @@ runGHCi paths maybe_exprs = do -- current progname in the exception text: -- <progname>: <exception> liftIO $ withProgName (progname st) - $ topHandler e -- this used to be topHandlerFastExit, see #2228 + $ topHandler + -- The program's own context is already part of the + -- message (see toSerializableException). The rest + -- comes from GHC itself (#27847). + $ dropExceptionContext e runInputTWithPrefs defaultPrefs defaultSettings $ do -- make `ghc -e` exit nonzero on failure, see #7962, #9916, #17560, #18441 _ <- runCommands' hdle ===================================== libraries/ghci/GHCi/Message.hs ===================================== @@ -466,8 +466,7 @@ data LoadedDLL -- * UserInterrupt has a special meaning -- * In ghc -e, exitWith should exit with the appropriate exit code -- --- So all we need to do is distinguish UserInterrupt and ExitCode, and --- all other exceptions can be represented by their 'show' string. +-- So all we need to do is distinguish UserInterrupt and ExitCode. -- data SerializableException = EUserInterrupt ===================================== testsuite/tests/ghc-e/should_fail/T18441fail7.stderr ===================================== @@ -1,16 +1,4 @@ <interactive>: Uncaught exception ghc-10.1-inplace:GHC.Utils.Panic.GhcException: IO error: "Abcde" does not exist - -While handling ghc-10.1-inplace:GHC.Utils.Panic.GhcException: - | - | IO error: "Abcde" does not exist - | - | HasCallStack backtrace: - | throw, called at compiler/GHC/Utils/Panic.hs:180:21 in ghc-10.1-inplace:GHC.Utils.Panic - | throwGhcException, called at ghc/GHCi/UI.hs:2851:21 in ghc-bin-10.1.20260801-inplace:GHCi.UI - -HasCallStack backtrace: - throwIO, called at compiler/GHC/Utils/Error.hs:513:19 in ghc-10.1-inplace:GHC.Utils.Error - 1 ===================================== testsuite/tests/ghc-e/should_run/ghc-e005.stderr ===================================== @@ -4,8 +4,3 @@ foo HasCallStack backtrace: error, called at ghc-e005.hs:12:10 in main:Main - - -HasCallStack backtrace: - throwIO, called at ghc\GHCi\UI.hs:1655:31 in ghc-bin-10.1.20260629-inplace:GHCi.UI - View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b595714474d516f621143a1f8b4459e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b595714474d516f621143a1f8b4459e… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/T27828] Wibbles
by Simon Peyton Jones (＠simonpj) 24 Sep '26

24 Sep '26

Simon Peyton Jones pushed to branch wip/T27828 at Glasgow Haskell Compiler / GHC Commits: 75745004 by Simon Peyton Jones at 2026-09-24T23:43:34+01:00 Wibbles - - - - - 4 changed files: - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/IfaceToCore.hs Changes: ===================================== compiler/GHC/Core/FamInstEnv.hs ===================================== @@ -610,12 +610,14 @@ compareBranches b1@(CoAxBranch { cab_lhs = lhs1, cab_rhs = rhs1 }) -- Here we need the cab_tvs of the two branches to be disinct. -- See Note [CoAxBranch type variables] in GHC.Core.Coercion.Axiom. SurelyApart -> BC_Apart - MaybeApart {} -> pprPanic "compareBranches" (ppr b1 $$ ppr b2) Unifiable subst | Type.substTyAddInScope subst rhs1 `eqType` Type.substTyAddInScope subst rhs2 -> BC_Compat | otherwise -> BC_Incompat + MaybeApart {} -> BC_Incompat + -- An occurs check yields MaybeApart; + -- see Note [Infinitary substitutions] in GHC.Core.Unify where (commonlhs1, commonlhs2) = zipAndUnzip lhs1 lhs2 -- See Note [Compatibility of eta-reduced axioms] ===================================== compiler/GHC/Iface/Decl.hs ===================================== @@ -112,7 +112,7 @@ coAxBranchToIfaceBranch tc lhs_s , ifaxbRoles = roles , ifaxbRHS = toIfaceType rhs , ifaxbIncomps = iface_incomps } - where + where iface_incomps = map (expectJust . flip findIndex lhs_s . eqTypes ===================================== compiler/GHC/Iface/Syntax.hs ===================================== @@ -338,7 +338,12 @@ data IfaceAxBranch = IfaceAxBranch { ifaxbTyVars :: [IfaceTvBndr] , ifaxbRoles :: [Role] , ifaxbRHS :: IfaceType , ifaxbIncomps :: [BranchIndex] } - -- See Note [Storing compatibility] in GHC.Core.Coercion.Axiom + -- We store the incompatibilities in IfaceAxBranch + -- just for (perhaps unnecessary) display purposes: + -- see Note [Displaying axiom incompatibilities] + -- When we construct a real CoAxBranch we compute cab_incomps directly + -- from the equations, ignoring the ifaxbIncomps. + -- We could consider getting rid of ifaxbIncomps altogether. data IfaceConDecls = IfAbstractTyCon -- c.f TyCon.AbstractTyCon ===================================== compiler/GHC/IfaceToCore.hs ===================================== @@ -1111,15 +1111,14 @@ tc_fd (tvs1, tvs2) = do { tvs1' <- mapM tcIfaceTyVar tvs1 ; return (tvs1', tvs2') } tc_ax_branches :: [IfaceAxBranch] -> IfL [CoAxBranch] -tc_ax_branches if_branches = foldlM tc_ax_branch [] if_branches +tc_ax_branches if_branches = mapM tc_ax_branch if_branches -tc_ax_branch :: [CoAxBranch] -> IfaceAxBranch -> IfL [CoAxBranch] -tc_ax_branch prev_branches - (IfaceAxBranch { ifaxbTyVars = tv_bndrs +tc_ax_branch :: IfaceAxBranch -> IfL CoAxBranch +tc_ax_branch (IfaceAxBranch { ifaxbTyVars = tv_bndrs , ifaxbEtaTyVars = eta_tv_bndrs , ifaxbCoVars = cv_bndrs , ifaxbLHS = lhs, ifaxbRHS = rhs - , ifaxbRoles = roles, ifaxbIncomps = _incomps }) + , ifaxbRoles = roles }) = bindIfaceTyConBinders_AT (map (\b -> Bndr (IfaceTvBndr b) (NamedTCB Inferred)) tv_bndrs) $ \ tvs -> -- The _AT variant is needed here; see Note [CoAxBranch type variables] in GHC.Core.Coercion.Axiom @@ -1130,16 +1129,15 @@ tc_ax_branch prev_branches ; this_mod <- getIfModule ; let loc = mkGeneralSrcSpan (fsLit "module " `appendFS` moduleNameFS (moduleName this_mod)) - br = CoAxBranch { cab_loc = loc - , cab_tvs = binderVars tvs - , cab_eta_tvs = eta_tvs - , cab_cvs = cvs - , cab_lhs = tc_lhs - , cab_roles = roles - , cab_rhs = tc_rhs - , cab_overlaps = placeHolderOverlaps - , cab_incomps = placeHolderIncomps } - ; return (prev_branches ++ [br]) } + ; return (CoAxBranch { cab_loc = loc + , cab_tvs = binderVars tvs + , cab_eta_tvs = eta_tvs + , cab_cvs = cvs + , cab_lhs = tc_lhs + , cab_roles = roles + , cab_rhs = tc_rhs + , cab_overlaps = placeHolderOverlaps + , cab_incomps = placeHolderIncomps }) } tcIfaceDataCons :: Name -> TyCon -> IfaceConDecls -> IfL AlgTyConRhs tcIfaceDataCons tycon_name tycon if_cons View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/75745004ef3f28f18a532b015cfe729… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/75745004ef3f28f18a532b015cfe729… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/apk/fix-timeout
by Andreas Klebinger (＠AndreasK) 24 Sep '26

24 Sep '26

Andreas Klebinger pushed new branch wip/apk/fix-timeout at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/apk/fix-timeout You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/T27847-ghci-rethrow-backtrace
by Simon Jakobi (＠sjakobi) 24 Sep '26

24 Sep '26

Simon Jakobi pushed new branch wip/sjakobi/T27847-ghci-rethrow-backtrace at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/T27847-ghci-rethrow-b… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 2 commits: Correct the documentation of `explicitUnits`
by Marge Bot (＠marge-bot) 24 Sep '26

24 Sep '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: db9c95ac by Wolfgang Jeltsch at 2026-09-24T15:51:34-04:00 Correct the documentation of `explicitUnits` Resolves #27787. - - - - - a6b642b6 by Simon Jakobi at 2026-09-24T15:51:35-04:00 Remove stale specHeader bullet from Note [Don't make fillers for constraint types] The Note said that Specialise.specHeader also calls mkAbsentFiller. abfc224a27c removed that call: the specialiser no longer drops dead arguments at all, see Note [Do not drop dead args from specialisations] in GHC.Core.Opt.Specialise. Assisted-by: Claude Fable 5.1 - - - - - 2 changed files: - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Unit/State.hs Changes: ===================================== compiler/GHC/Core/Opt/WorkWrap/Utils.hs ===================================== @@ -1367,13 +1367,8 @@ It's surprisingly subtle. application; see test `T27627f`. TL;DR: we play safe: we never make an absent filler for any /constraint-kinded/ type, -using `isPredTy` to decide. - - * `mkAbsentFiller` returns `Nothing` for any constraint type, so worker/wrapper - keeps the real argument. - - * `Specialise.specHeader` calls `mkAbsentFiller` too, so it likewise keeps the - dead dictionary argument rather than dropping it for a filler. +using `isPredTy` to decide: `mkAbsentFiller` returns `Nothing` for any constraint +type, so worker/wrapper keeps the real argument. Prior failed approaches ===================================== compiler/GHC/Unit/State.hs ===================================== @@ -369,10 +369,15 @@ data UnitState = UnitState { -- is always mentioned before the units it depends on. preloadUnits :: [UnitId], - -- | Units which we explicitly depend on (from a command line flag). - -- We'll use this to generate version macros and the unused packages warning. The - -- original flag which was used to bring the unit into scope is recorded for the - -- -Wunused-packages warning. + -- | The units that can be used by the respective home unit. Despite the + -- identifier, this does not just cover units that are enabled explicitly + -- using flags but also units from the package database that are enabled + -- implicitly in case @-hide-all-packages@ is absent. The former are paired + -- with 'Just' applied to the respective flags, the latter are paired with + -- 'Nothing'. + -- + -- This field is used for generating version macros and “unused packages” + -- warnings. explicitUnits :: [(Unit, Maybe PackageArg)], homeUnitDepends :: Set UnitId, @@ -907,7 +912,7 @@ mkUnitState logger unit_index cfg = do let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p) | p <- pkgs2 ] - -- The explicitUnits accurately reflects the set of units we have turned + -- The explicitUnits accurately reflects the set of units that are turned -- on; as such, it also is the only way one can come up with requirements. -- The requirement context is directly based off of this: we simply -- look for nested unit IDs that are directly fed holes: the requirements View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/f08bae90b4359fde91eb2493f9bd49… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/f08bae90b4359fde91eb2493f9bd49… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/az/exactprint-annotation-rationalisation] 33 commits: MOVE: Exactprint layout scope plan. Do not commit
by Alan Zimmerman (＠alanz) 24 Sep '26

24 Sep '26

Alan Zimmerman pushed to branch wip/az/exactprint-annotation-rationalisation at Glasgow Haskell Compiler / GHC Commits: 0ff41c0e by Alan Zimmerman at 2026-09-24T11:02:40+01:00 MOVE: Exactprint layout scope plan. Do not commit - - - - - 97be233b by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: tidy up a bit. Combine somewhere else - - - - - ab12bb37 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Introduce LayoutFrame stacks in ExactPrint state - - - - - 751058a9 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 Align with ghc-exactprint - - - - - e917fb51 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Fix AnnList leading semis when layout When there is layout, anything printed triggers it, including leading semis. Add some test case examples too - - - - - 70714290 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 Exactprint: tidy up layout capturing - - - - - 290d1948 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: add makeDelta test for Test20297 The original #20297 related to comment placement for exact printing after running ExactPrint.makeDelta on ParsedSource. Add an additional test that explicitly tests this. - - - - - 69a5f176 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make ValBinds LocatedA in HsLocalBindsLR If we have items with an AnnList Annotation, as part of another, which has different content, it must be LocatedA. This is a technical requirement due to the way comment allocation happens during the makeDelta processing. Comments are queued for printing, and as soon as any non-comment is to be printed, the pending comments before that position are printed, and in makeDelta processing these attached as preceding comments to the thing just printed. The means they end up captured inside the layout region of the AnnList item. So for foo = x where -- comment x = 3 the comment ends up as a preceding comment of `x = 3`, inside the layout, and prints as foo = x where -- comment x = 3 - - - - - dc1510c9 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make IPBinds LocatedA - - - - - 0e1d283d by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make ClsInstDecl decls LocatedA - - - - - 4d0574c8 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make ClassDecls decls LocatedA - - - - - acb08ef2 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make ClosedTypeFamily equations Located For FamilyDecl/ClosedTypeFamily - - - - - b77f1c3e by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make dd_cons located - - - - - 1a6c9c54 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make HsMultiIf options located - - - - - 4b960994 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make DecBrl contents LocatedA - - - - - 90532ca0 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Located do statements - - - - - 40f055d7 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Print RecStmt located - - - - - 7d93f2ee by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: HsCmdDo Located - - - - - 8341dcd4 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 Extend Test20297 for additional occurrences - - - - - fce8043f by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Tweak PatSynBind location for comments - - - - - 7d05fed9 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: WIP, add test for where ;; ValBinds - - - - - 2495cef1 by Alan Zimmerman at 2026-09-24T11:02:49+01:00 EPA: Make EpVirtualBraces noSpanAnchor if no contents Otherwise the vocurly is emitted at the start of the next item parsed Check: is this needed, or just a check for empty contents? - - - - - 9cb8b9b9 by Alan Zimmerman at 2026-09-24T17:51:46+01:00 EPA: Use EpNoLayout in AnnList with empty contents and no explicit braces - - - - - 602cd545 by Alan Zimmerman at 2026-09-24T18:49:55+01:00 TODO: XClassDecl: remove additional EpLayout - - - - - 6170ccb1 by Alan Zimmerman at 2026-09-24T18:49:55+01:00 WIP: turn off exactprint debug printing - - - - - caa62748 by Alan Zimmerman at 2026-09-24T18:49:55+01:00 EPA: Remove CanUpdateAnchorOnly - - - - - 534c3e18 by Alan Zimmerman at 2026-09-24T18:49:55+01:00 Plan update DO NOT COMMIT - - - - - fb713865 by Alan Zimmerman at 2026-09-24T20:33:12+01:00 EPA: First pass implementation of HsList, for ClassDecls Just as a straight list replacement to start with, no payload. This shows the scope and invasiveness of the initial change - - - - - 0036bee3 by Alan Zimmerman at 2026-09-24T20:33:12+01:00 EPA: HsList attempt WIP - - - - - 823d41ac by Alan Zimmerman at 2026-09-24T20:33:12+01:00 Enable ppr test for Haddock1. It currently fails - - - - - 73458c58 by Alan Zimmerman at 2026-09-24T20:33:12+01:00 WIP on removing NoEpAnn. Likely abandon - - - - - f6c262d0 by Alan Zimmerman at 2026-09-24T20:33:12+01:00 EPA: Add an overview doc for exact printing - - - - - 88562119 by Simon Peyton Jones at 2026-09-24T20:33:12+01:00 Added an intro section - - - - - 80 changed files: - ANNLIST-LAYOUT-PLAN.md - + ExactPrint.md - + LAYOUT-SCOPE-PLAN.md - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Main/Interactive.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/DocString.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Stats.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Rename/Bind.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Gen/Bind.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/ThToHs.hs - compiler/Language/Haskell/Syntax.hs - compiler/Language/Haskell/Syntax/Basic.hs - compiler/Language/Haskell/Syntax/Binds.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Expr.hs - ghc/GHCi/UI.hs - testsuite/tests/ghc-api/exactprint/Test20239.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544_kw.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T24221.stderr - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/DumpSemis.hs - testsuite/tests/parser/should_compile/DumpSemis.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/parser/should_compile/T15323.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/perf/compiler/hard_hole_fits.stderr - testsuite/tests/printer/Makefile - testsuite/tests/printer/Ppr003.hs - testsuite/tests/printer/T18791.stderr - + testsuite/tests/printer/Test20297.expected.hs - testsuite/tests/printer/Test20297.hs - testsuite/tests/printer/Test20297.stdout - + testsuite/tests/printer/Test20297MD.stdout - testsuite/tests/printer/Test24533.stdout - testsuite/tests/printer/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Parsers.hs - utils/check-exact/Transform.hs - utils/check-exact/Utils.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/8ebd722dffe09368c05d69ad201f9f… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/8ebd722dffe09368c05d69ad201f9f… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 4 commits: Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types
by Marge Bot (＠marge-bot) 24 Sep '26

24 Sep '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 545fd4fb by ARATA Mizuki at 2026-09-22T15:03:24-04:00 Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types bitReverse{16,32}# and byteSwap{16,32}# have the type Word# -> Word#, but their C correspondents took and returned StgWord{16,32}. The mismatch on bitReverse16# led to the problem reported in #27299. Although no similar issue is reported for bitReverse32# and byteSwap{16,32}#, it seemed wise to change them proactively. This commit fixes the mismatch by changing the C type. Fixes #27299 - - - - - bf17f289 by fendor at 2026-09-22T15:04:05-04:00 Don't lose instances from shadowed imported modules with the same name When we look for instances below the current module, we need to check the unit id as well when we check for whether the module is the current module, otherwise we ignore modules we import that have the same name as the import module. Adds regression test. - - - - - 9169b4fa by Wolfgang Jeltsch at 2026-09-24T15:02:15-04:00 Correct the documentation of `explicitUnits` Resolves #27787. - - - - - f08bae90 by Simon Jakobi at 2026-09-24T15:02:16-04:00 Remove stale specHeader bullet from Note [Don't make fillers for constraint types] The Note said that Specialise.specHeader also calls mkAbsentFiller. abfc224a27c removed that call: the specialiser no longer drops dead arguments at all, see Note [Do not drop dead args from specialisations] in GHC.Core.Opt.Specialise. Assisted-by: Claude Fable 5.1 - - - - - 18 changed files: - + changelog.d/26610 - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Unit/State.hs - rts/include/stg/Prim.h - rts/prim/bitrev.c - rts/prim/bswap.c - + testsuite/tests/ghci/prog-mhu008/Makefile - + testsuite/tests/ghci/prog-mhu008/a/M.hs - + testsuite/tests/ghci/prog-mhu008/all.T - + testsuite/tests/ghci/prog-mhu008/b/M.hs - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.script - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout - + testsuite/tests/ghci/prog-mhu008/unitA - + testsuite/tests/ghci/prog-mhu008/unitB - + testsuite/tests/primops/should_run/T27299.hs - + testsuite/tests/primops/should_run/T27299.stdout - testsuite/tests/primops/should_run/all.T Changes: ===================================== changelog.d/26610 ===================================== @@ -0,0 +1,7 @@ +section: compiler +synopsis: Fix instance resolution for shadowed modules +description: + Instances imported from modules with the same module name as the importing module + were dropped accidentally since we didn't account for the unit id of the imported module. +mrs: !16648 +issues: #26610 ===================================== compiler/GHC/Core/Opt/WorkWrap/Utils.hs ===================================== @@ -1367,13 +1367,8 @@ It's surprisingly subtle. application; see test `T27627f`. TL;DR: we play safe: we never make an absent filler for any /constraint-kinded/ type, -using `isPredTy` to decide. - - * `mkAbsentFiller` returns `Nothing` for any constraint type, so worker/wrapper - keeps the real argument. - - * `Specialise.specHeader` calls `mkAbsentFiller` too, so it likewise keeps the - dead dictionary argument rather than dropping it for a filler. +using `isPredTy` to decide: `mkAbsentFiller` returns `Nothing` for any constraint +type, so worker/wrapper keeps the real argument. Prior failed approaches ===================================== compiler/GHC/Driver/Env.hs ===================================== @@ -263,13 +263,13 @@ hugCompleteSigsBelow hsc uid mn = foldr (++) [] <$> -- | Find instances visible from the given set of imports hugInstancesBelow :: HscEnv -> UnitId -> ModuleNameWithIsBoot -> IO (InstEnv, [FamInst]) hugInstancesBelow hsc_env uid mnwib = do - let mn = gwib_mod mnwib + let mn = mkModule uid (gwib_mod mnwib) (insts, famInsts) <- unzip . concat <$> hugSomeThingsBelowUs (\mod_info -> let details = hm_details mod_info -- Don't include instances for the current module - in if moduleName (mi_module (hm_iface mod_info)) == mn + in if fmap toUnitId (mi_module (hm_iface mod_info)) == mn then [] else [(md_insts details, md_fam_insts details)]) True -- Include -hi-boot ===================================== compiler/GHC/Unit/State.hs ===================================== @@ -369,10 +369,15 @@ data UnitState = UnitState { -- is always mentioned before the units it depends on. preloadUnits :: [UnitId], - -- | Units which we explicitly depend on (from a command line flag). - -- We'll use this to generate version macros and the unused packages warning. The - -- original flag which was used to bring the unit into scope is recorded for the - -- -Wunused-packages warning. + -- | The units that can be used by the respective home unit. Despite the + -- identifier, this does not just cover units that are enabled explicitly + -- using flags but also units from the package database that are enabled + -- implicitly in case @-hide-all-packages@ is absent. The former are paired + -- with 'Just' applied to the respective flags, the latter are paired with + -- 'Nothing'. + -- + -- This field is used for generating version macros and “unused packages” + -- warnings. explicitUnits :: [(Unit, Maybe PackageArg)], homeUnitDepends :: Set UnitId, @@ -907,7 +912,7 @@ mkUnitState logger unit_index cfg = do let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p) | p <- pkgs2 ] - -- The explicitUnits accurately reflects the set of units we have turned + -- The explicitUnits accurately reflects the set of units that are turned -- on; as such, it also is the only way one can come up with requirements. -- The requirement context is directly based off of this: we simply -- look for nested unit IDs that are directly fed holes: the requirements ===================================== rts/include/stg/Prim.h ===================================== @@ -59,16 +59,16 @@ StgWord hs_xchg32(StgWord x, StgWord val); StgWord64 hs_xchg64(StgWord x, StgWord64 val); /* rts/prim/bswap.c */ -StgWord16 hs_bswap16(StgWord16 x); -StgWord32 hs_bswap32(StgWord32 x); +StgWord hs_bswap16(StgWord x); +StgWord hs_bswap32(StgWord x); StgWord64 hs_bswap64(StgWord64 x); /* rts/prim/bitrev.c This was done as part of issue #16164. See Note [Bit reversal primop] for more details about the implementation.*/ StgWord hs_bitrev8(StgWord x); -StgWord16 hs_bitrev16(StgWord16 x); -StgWord32 hs_bitrev32(StgWord32 x); +StgWord hs_bitrev16(StgWord x); +StgWord hs_bitrev32(StgWord x); StgWord64 hs_bitrev64(StgWord64 x); /* rts/prim/longlong.c */ ===================================== rts/prim/bitrev.c ===================================== @@ -36,8 +36,8 @@ hs_bitrev8(StgWord x) return x; } -StgWord16 -hs_bitrev16(StgWord16 x) +StgWord +hs_bitrev16(StgWord x) { x = ((x >> 1) & 0x5555) | ((x & 0x5555) << 1 ); x = ((x >> 2) & 0x3333) | ((x & 0x3333) << 2 ); @@ -46,14 +46,14 @@ hs_bitrev16(StgWord16 x) return x; } -StgWord32 -hs_bitrev32(StgWord32 x) +StgWord +hs_bitrev32(StgWord x) { - x = ((x >> 1) & 0x55555555) | ((x & 0x55555555) << 1 ); - x = ((x >> 2) & 0x33333333) | ((x & 0x33333333) << 2 ); - x = ((x >> 4) & 0x0F0F0F0F) | ((x & 0x0F0F0F0F) << 4 ); - x = ((x >> 8) & 0x00FF00FF) | ((x & 0x00FF00FF) << 8 ); - x = ( x >> 16 ) | ( x << 16 ); + x = ((x >> 1) & 0x55555555) | ((x & 0x55555555) << 1 ); + x = ((x >> 2) & 0x33333333) | ((x & 0x33333333) << 2 ); + x = ((x >> 4) & 0x0F0F0F0F) | ((x & 0x0F0F0F0F) << 4 ); + x = ((x >> 8) & 0x00FF00FF) | ((x & 0x00FF00FF) << 8 ); + x = ((x >> 16) & 0x0000FFFF) | ((x & 0x0000FFFF) << 16); return x; } ===================================== rts/prim/bswap.c ===================================== @@ -1,16 +1,18 @@ #include "Rts.h" -StgWord16 -hs_bswap16(StgWord16 x) +StgWord +hs_bswap16(StgWord x) { - return ((x >> 8) | (x << 8)); + x = (StgWord16)x; + return (StgWord16)((x >> 8) | (x << 8)); } -StgWord32 -hs_bswap32(StgWord32 x) +StgWord +hs_bswap32(StgWord x) { - return ((x >> 24) | ((x >> 8) & 0xff00) | - (x << 24) | ((x & 0xff00) << 8)); + x = (StgWord32)x; + return (StgWord32)((x >> 24) | ((x >> 8) & 0xff00) | + (x << 24) | ((x & 0xff00) << 8)); } StgWord64 ===================================== testsuite/tests/ghci/prog-mhu008/Makefile ===================================== @@ -0,0 +1,3 @@ +TOP=../../.. +include $(TOP)/mk/boilerplate.mk +include $(TOP)/mk/test.mk ===================================== testsuite/tests/ghci/prog-mhu008/a/M.hs ===================================== @@ -0,0 +1,4 @@ +module M (T (..)) where + +newtype T = MkT Int + deriving (Eq, Ord) ===================================== testsuite/tests/ghci/prog-mhu008/all.T ===================================== @@ -0,0 +1,5 @@ +test('prog-mhu008', + [extra_files(['a/', 'b/', 'unitA', 'unitB']), + cmd_prefix('ghciWayFlags=' + config.ghci_way_flags), + req_interp], + ghci_multiunit_script, [['unitA', 'unitB'], 'prog-mhu008.script']) ===================================== testsuite/tests/ghci/prog-mhu008/b/M.hs ===================================== @@ -0,0 +1,11 @@ +{-# LANGUAGE PackageImports #-} + +module M + ( module Export + , cmp + ) where + +import "a" M as Export + +cmp :: T -> T -> Bool +cmp x y = x <= y ===================================== testsuite/tests/ghci/prog-mhu008/prog-mhu008.script ===================================== @@ -0,0 +1,5 @@ +:set -XPackageImports +import "a" M qualified as MA +import "b" M qualified as MB + +MB.cmp (MA.MkT 1) (MA.MkT 2) ===================================== testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout ===================================== @@ -0,0 +1 @@ +True ===================================== testsuite/tests/ghci/prog-mhu008/unitA ===================================== @@ -0,0 +1,5 @@ +-this-unit-id a-0-inplace +-this-package-name a +-i +-ia +M ===================================== testsuite/tests/ghci/prog-mhu008/unitB ===================================== @@ -0,0 +1,6 @@ +-this-unit-id b-0-inplace +-this-package-name b +-package-id a-0-inplace +-i +-ib +M ===================================== testsuite/tests/primops/should_run/T27299.hs ===================================== @@ -0,0 +1,23 @@ +{-# LANGUAGE MagicHash #-} +import GHC.Exts +import GHC.Word +import Numeric + +main :: IO () +main = do + putStrLn $ showHex (W# (bitReverse8# 0x55##)) "" + putStrLn $ showHex (W# (bitReverse8# 0xAA##)) "" + putStrLn $ showHex (W# (bitReverse16# 0x5555##)) "" + putStrLn $ showHex (W# (bitReverse16# 0xAAAA##)) "" + putStrLn $ showHex (W# (bitReverse32# 0x5555_5555##)) "" + putStrLn $ showHex (W# (bitReverse32# 0xAAAA_AAAA##)) "" + putStrLn $ showHex (W# (byteSwap16# 0xABCD##)) "" + putStrLn $ showHex (W# (byteSwap32# 0xABCD_EF12##)) "" + putStrLn $ showHex (W# (noinline bitReverse8# 0x55##)) "" + putStrLn $ showHex (W# (noinline bitReverse8# 0xAA##)) "" + putStrLn $ showHex (W# (noinline bitReverse16# 0x5555##)) "" + putStrLn $ showHex (W# (noinline bitReverse16# 0xAAAA##)) "" + putStrLn $ showHex (W# (noinline bitReverse32# 0x5555_5555##)) "" + putStrLn $ showHex (W# (noinline bitReverse32# 0xAAAA_AAAA##)) "" + putStrLn $ showHex (W# (noinline byteSwap16# 0xABCD##)) "" + putStrLn $ showHex (W# (noinline byteSwap32# 0xABCD_EF12##)) "" ===================================== testsuite/tests/primops/should_run/T27299.stdout ===================================== @@ -0,0 +1,16 @@ +aa +55 +aaaa +5555 +aaaaaaaa +55555555 +cdab +12efcdab +aa +55 +aaaa +5555 +aaaaaaaa +55555555 +cdab +12efcdab ===================================== testsuite/tests/primops/should_run/all.T ===================================== @@ -91,3 +91,4 @@ test('T24496' ] , compile_and_run, ['-O']) test('T6026', normal, compile_and_run, ['']) +test('T27299', normal, compile_and_run, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/43ddbbbafab824cd34325d6c1fab27… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/43ddbbbafab824cd34325d6c1fab27… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc] Pushed new branch wip/T27844
by Simon Peyton Jones (＠simonpj) 24 Sep '26

24 Sep '26

Simon Peyton Jones pushed new branch wip/T27844 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/T27844 You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/T27477-changelog
by Simon Jakobi (＠sjakobi) 24 Sep '26

24 Sep '26

Simon Jakobi pushed new branch wip/sjakobi/T27477-changelog at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/T27477-changelog You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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