Hannes Siebenhandl pushed to branch wip/fendor/T27202 at Glasgow Haskell Compiler / GHC Commits: 14bc71e4 by Sven Tennie at 2026-04-28T13:22:47-04:00 ghc: Distinguish between having an interpreter and having an internal one Actually, these are related but different things: - ghc can run an interpreter (either internal or external) - ghc is compiled with an internal interpreter Splitting the logic solves compiler warnings and expresses the intent better. - - - - - df691563 by Vladislav Zavialov at 2026-04-28T13:23:29-04:00 Refactor HsWildCardTy to use HoleKind (#27111) The payload of this patch is that the extension fields of HsWildCardTy and HsHole now match: type instance XWildCardTy Ghc{Ps,Rn} = HoleKind type instance XHole Ghc{Ps,Rn} = HoleKind This is progress towards unification of HsExpr and HsType. Test case: T25121_status In addition to that, exact-printing of infix holes is fixed. Test case: PprInfixHole - - - - - f3485446 by fendor at 2026-04-28T13:24:12-04:00 Expose startupHpc as an rts symbol - - - - - 28f07d70 by fendor at 2026-04-28T13:24:12-04:00 Make HPC work with bytecode interpreter Add support to generate .tix files from bytecode objects and the bytecode interpreter. Conceptually, we insert HPC ticks into the bytecode similar to how we insert breakpoints. HPC and breakpoints do not share the same tick array but we use a separate tick-array for hpc/breakpoint ticks during bytecode generation. We teach the bytecode interpreter to handle hpc ticks. The implementation is quite trivial, simply increment the counter in the global hpc_ticks array for the respective module. This hpc_ticks array is generated as part of the `CStub`, so we can rely on it existing. A tricky bit is "registering" a bytecode object for HPC instrumentation. In the compiled case, this is achieved via CStub and initializer/finalizers `.init` sections which are called when the executable is run. After the initializers have been invoked, which is before `hs_init_ghc`, we then call `startup_hpc` in `hs_init_ghc` iff any modules were "registered" for hpc instrumentation via `hs_hpc_module`. Since bytecode objects are loaded after starting up GHCi, this workflow doesn't work for supporting `hpc` and the `hpc` run-time is never started, even if a module is added for instrumentation. We fix this issue by employing the same technique as is for `SptEntry`s: * We introduce a new field to `CompiledByteCode`, called `ByteCodeHpcInfo` which contains enough information to call `hs_hpc_module`, allowing us to register the module for `hpc` instrumentation`. * After registering the module, we unconditionally call `startupHpc`, to make sure the .tix file is written. Calling `startupHpc` multiple times is safe. Calling `hs_hpc_module` multiple times for the same module is also safe. If we didn't register the hpc module in this way, evaluating a bytecode object instrumented with `-fhpc` without registering it in the `hpc` run-time will simply not generate any `.tix` files for this bytecode object. However, this shouldn't happen if everything is set up correctly. Closes #27036 - - - - - 950879f0 by Vladislav Zavialov at 2026-04-28T13:24:55-04:00 Move NamespaceSpecifier from x-fields into the AST proper (#26678) This refactoring moves NamespaceSpecifier out of extension fields and into the AST proper, as it is part of the user-written source, and is not pass-specific. Summary of changes: * Move NamespaceSpecifier from GHC/Hs/Basic.hs to Language/Haskell/Syntax/ImpExp.hs and parameterise it by the compiler pass, creating the necessary extension points * Move NamespaceSpecifier out of XFixitySig into FixitySig * Move NamespaceSpecifier out of XIEThingAll (IEThingAllExt) into IEThingAll * Move NamespaceSpecifier out of XIEWholeNamespace (IEWholeNamespaceExt) into IEWholeNamespace This is a pure refactoring with no change in behaviour. - - - - - 9797052b by Simon Peyton Jones at 2026-04-28T13:25:37-04:00 Fix assertion check in checkResultTy As #27210 shows, the assertion was a little bit too eager. I refactored a bit by moving some code from GHC.Tc.Gen.App to GHC.Tc.Utils.Unify; see the new function tcSubTypeApp, which replaces tcSubTypeDS - - - - - 9f85f034 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Make cmm 'import "package" name;' syntax use consistent label types There is a little-used syntactic form in cmm imports: import "package" foo; Which means to import foo from the given package (unit id, specified as a string). This syntax is somewhat reminiscent of GHC's package import extension. This syntax form is not used in the rts cmm code, nor any of the boot libraries. It may not be used at all. Unclear. Change the kind of CLabel this syntax generates to be consistent with the others. The other cmm imports use ForeignLabel with ForeignLabelInExternalPackage. For some reason this form was using CmmLabel. Change that to also be ForeignLabel but with ForeignLabelInPackage. This specifies a specific package, rather than an unnamed external package. - - - - - a811f68f by Duncan Coutts at 2026-04-30T04:52:42-04:00 Change default cmm import statements to be internal Previously a cmm statement like: import foo; meant to expect the symbol from a different shared library than the current one. Now it means to expect the symbol from the same shared library as the current one. We'll add explicit syntax to indicate that it's a foreign import. Most existing uses are in fact intenal (rts to rts), so few imports will need to be annotated foreign. Examples would include cmm code in libraries (other than the rts) that need to access RTS APIs. In practice, this makes no difference whatsoever at the moment on any platform other than windows (where building Haskell libs as shared libs does not fully work yet), since the 'labelDynamic' treats all such labels as foreign, irrespective of the foreign label source. - - - - - 17fe5d1d by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm import syntax 'import DATA foo;' as better name for CLOSURE The existing syntax is: import CLOSURE foo; The new syntax is import DATA foo; This means to interpret the symbol foo as refering to data (i.e. a global constant or variable) rather than to code (a function). The historical syntax for this uses CLOSURE, which is rather misleading. Presumably this was done to avoid introducing new reserved words. Be less squemish about new reserved words and add DATA and use that. Keep the existing CLOSURE syntax as an alias for compatibility. - - - - - 3a530d68 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm 'import extern name;' syntax Since the default for cmm imports is now for symbols within the same shared object, we need a way to indicate we want a symbol from an external shared object: import extern foo; -- for a function import extern DATA foo; -- for data This adds a new reserved word 'extern'. We don't expect to have to use this much. Most cmm imports are intra-DSO. This makes no difference currently on ELF and MachO platforms, but does make a difference to the linking conventions on PE (Windows). In future it's plausible we could take make distinctions on ELF or MachO, so it's worth trying to get it right. Windows can be the guinea pig. - - - - - 2b8e44c7 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm syntax 'import "package" DATA foo;' for completeness We already have: import DATA foo; -- for data imports import "package" foo; -- for imports from a given unitid There's no reason not to have both at once: import "package" DATA foo; So add that. - - - - - ee05e5cc by Duncan Coutts at 2026-04-30T04:52:42-04:00 Improve the commentary for the cmm import grammar. AFAIK, this is the only place where GHC-style Cmm syntax is documented. - - - - - b35946ad by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add a changelog.d entry for the .cmm import syntax changes - - - - - d59b7c71 by Wolfgang Jeltsch at 2026-04-30T04:53:25-04:00 Move code that uses `GHC.Internal.Text.Read` into `base` This contribution serves to remove all dependencies on `GHC.Internal.Text.Read` from within `ghc-internal`, so that the implementation of `Text.Read` and ultimately more reading-related code can be moved to `base` as well. The following things are moved from `ghc-internal` to `base`: * I/O-related `Read` instances * Most of the `Numeric` implementation * The instance `Read ByteOrder` * The `parseVersion` operation * The `readConstr` operation Metric Increase: LinkableUsage01 T9198 T12425 T13035 T13820 T18140 - - - - - 5bd6a964 by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 New rts Message to {set,unset} TSO flags This commit introduces stg_MSG_SET_TSO_FLAG_info and stg_MSG_UNSET_TSO_FLAG_info, which allows setting flags of a TSO other than yourself. This is especially useful/necessary to set breakpoints and toggle breakpoints of different threads, which is needed to safely implement features like pausing, toggling step-out, toggling step-in per thread, etc. Fixes #27131 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - ce97fd3e by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 test: Add test setting another TSO's flags Introduces a test that runs on two capabilities. The main thread running on Capability 0 sets the flags on a TSO running on Capability 1. The TSO from Capability 1 itself checks whether its flags were set and reports that back. This validates that the RTS messages for setting TSO flags work, even if it doesn't test a harsher scenario with race conditions to exercise why the message passing is necessary for safely setting another TSO's flags. Part of #27131 - - - - - a4ff6315 by David Eichmann at 2026-04-30T04:54:51-04:00 Hadrian: withResponseFile outputs response file when verbodity is Verbose At the Verbose verbosity, shake will display full commandlines. With the use of response files, the full command is hidden. That makes it hard to run the command manually. This commit outputs the contents of the response file so that that full command can be recreated and also hints at the use of the --keep-response-files hadrian flag. - - - - - cd732ee3 by Duncan Coutts at 2026-04-30T04:54:51-04:00 Use response files for hadrian linking with ghc (support long command lines) In future support for windows dynamic linking, we expect long command lines for linking dll files with ghc. Experiments with dynamic linking the ghc-internal library yielded a link command well over 32kb. We did not encounter this before for static libs, since we already use ar's @file feature (if available, which it is for the llvm toolchain). Co-authored-by: David Eichmann <davide@well-typed.com> - - - - - 3d41368f by Andreas Klebinger at 2026-04-30T04:55:32-04:00 Split GHC.Driver.Main.hs up into multiple components. This commit splits GHC.Driver.Main into four components: * GHC.Driver.Main.Compile * GHC.Driver.Main.Hsc * GHC.Driver.Main.Interactive * GHC.Driver.Main.Passes We might improve that separation further in the future but this should hopefully make it easier to reason about and work with this part of the code. - - - - - 2128ba85 by Cheng Shao at 2026-04-30T04:56:14-04:00 compiler: avoid unique OccNames for internal Names in bytecode objects This patch improves bytecode object serialization logic by avoiding the construction of unique `OccName`s when serializing/deserializing internal `Name`s. Closes #27213. ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - e16854c3 by Vladislav Zavialov at 2026-04-30T04:56:57-04:00 Replace GHC 9.16 references with GHC 10.0 - - - - - 39141343 by Alice Rixte at 2026-05-01T14:09:32+02:00 Add Bounded instances for Double, Float, CDouble and CFloat - - - - - 5c4c3bf4 by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: fix flaky foundation Divisible / mulIntMayOflo# tests (#27222) Since the LCG was widened to 64 bits and the seed randomised per CI run (commit 2d30f7d3400 "Vendor mini-QuickCheck for testsuite"), two latent bugs in the foundation test surface stochastically: * The Divisible property `(x `div` y) * y + (x `mod` y) == x` raises ArithException(Overflow) when (a, b) = (minBound, -1) for fixed-width signed Integral types. Split testNumber/testDivisible into Bounded and unbounded variants and skip just that one pair, gated by `(minBound :: a) < 0` so unsigned types lose no coverage. * The `mulIntMayOflo#` test compared raw Int# bit-for-bit, but the primop is only specified to return 0/non-zero -- the exact non-zero indicator legitimately differs between backends and inlining choices. Add a dedicated `testPrimopMayOflo` helper that only compares zero / non-zero. Also fix the long-standing typo "Dividible" -> "Divisible" in identifiers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> - - - - - e242ce4f by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: catch and display exceptions in MiniQuickCheck Exceptions raised while evaluating a property are now caught and reported as a normal failure (with arguments and seed), instead of aborting the test. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> - - - - - 3b75cccd by fendor at 2026-05-02T03:40:14-04:00 Fix name of Note [Structure of dep_boot_mods] - - - - - 9a9ae4df by Duncan Coutts at 2026-05-05T14:44:37-04:00 Use __attribute__((dllimport)) for external RTS symbol declarations This is needed to be hygenic about DLL symbol imports and exports. The attribute is ignored on platforms other than Windows. Use of the attribute however means that external data symbols do not have a compile-time constant address (they are loaded using an indirection). This means we have to adjust the rtsSyms initial linker table so that it is a local constant in a function, rather than a global constant. We now define it within a function that pre-populates the symbol table with the RTS symbols. - - - - - 2ad3e01e by Duncan Coutts at 2026-05-05T14:44:37-04:00 Fix the rts linker declarations for a few data symbols and ensure that the (windows only) rts_IOManagerIsWin32Native data symbol is marked as externally visible. - - - - - 8ff4fdb5 by David Eichmann at 2026-05-05T14:44:37-04:00 Hadrian: Disable runtime pseudo relocations for RTS on windows hosts - - - - - 96974723 by Teo Camarasu at 2026-05-05T14:45:20-04:00 ghci/TH: refactor to use IORef QState This is a pure refactor and shouldn't modify semantics at all - - - - - eff6bfaf by Teo Camarasu at 2026-05-05T14:45:20-04:00 iserv: recover/getQ/putQ should behave same as internal interpreter The internal and external interpreter should behave the same when handling `recover`, the exeception recovery method of Q. In practice, they diverge. In case of failure, the internal interpreter only restores error message state to before the computation, wheras the external interperter restores error message state *and* the state of putQ/getQ. As far as I can tell this is a simple mistake in the implementation. Note [TH recover with -fexternal-interpreter] describes the correct behaviour but the implementation doesn't mirror this. This change restores the correct behaviour by keeping the effects of putQ in the erroring computation. This is a breaking change since it modifies the behaviour of programs that rely on recover ignoring putQ from failling computations when used with the external interpreter. Although I highly doubt anyone relies on this behaviour. This divergence was first introduced in d00c308633fe7d216d31a1087e00e63532d87d6d. As far as I can tell this was unintentional and tha commit was trying to solve a different bug. Resolves #27022 - - - - - 1cb1d672 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add dynamic trace flags API This commit adds an API to the RTS (exposed via Rts.h) that allows users to dynamically change the trace flags. Prior to this commit, users were able to stop and start the profiling and heap profiling timers (via startProfTimer/stopProfTimer and startHeapProfTimer/stopHeapProfTimer). This extends that functionality to also cover the core event types. The getTraceFlag/setTraceFlag functions read and write the values of the trace flag cache, which is allocated by Trace.c, rather than modifying the members of RtsFlags.TraceFlags. This is done under the assumption that the members of RtsFlags should not be modified after RTS initialisation. Consequently, if the user modifies the trace flags using setTraceFlag, the object returned by getTraceFlags (from base) will not reflect these changes. The trace flags are not protected by locks of any sort. Hence, these functions are not thread-safe. However, the trace flags are not modified by the RTS after initialisation, only read, so the race conditions introduced by one user modifying them are most likely benign. This PR also puts the trace flag cache in a single global struct, as opposed to a collection of global variables, and changes the types of the individual flags from uint8_t to bool, as these have the same size on both Clang and GCC and are a better semantic match. Prior to the change to uint8_t, they had type int, see 42c47cd6. Even with its deprecation in C23, I don't think there should be any issue depending on stdbool.h. The TRACE_X macros are redefined to access the global struct, with values cast to const bool to ensure they are read-only. - - - - - 9d54dc94 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Ensure TRACE_X values are used in place of RtsFlags.TraceFlags.X - - - - - 418d737b by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Fix nonmoving-GC tracing The current nonmoving-GC tracing functions were written in a different style from the other tracing functions. They were directly implemented as, e.g., a traceConcMarkEnd function that called postConcMarkEnd. The other tracing functions are implemented as, e.g., traceThreadLabel_, a function that posts the thread label event, and traceThreadLabel, a macro that checks whether TRACE_scheduler is set. This commit fixes that implementation, and ensures that the nonmoving-GC tracing functions only emit events if nonmoving-GC tracing is enabled. - - - - - 99f4afa4 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for get/setTraceFlag - - - - - 7e9eb8b9 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for start/endEventLogging - - - - - 3a3045fb by Wen Kokke at 2026-05-06T09:53:41-04:00 rts: Add changelog entry - - - - - a3b339a4 by Teo Camarasu at 2026-05-06T09:54:25-04:00 interface-stability/base: don't distinguish ws-32 The interface of base is identical when the Word size is 32bits. Therefore, there is no need to have another file for this case. So, we delete it. Step towards: #26752 - - - - - eb922183 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add a rts posix FdWakup utility module This will be used to implement wakeupIOManager for in-RTS I/O managers. It provides a notification/wakeup mechanism using FDs, suitable for situations when a thread is blocked on a set of fds anyway. It uses the classic self-pipe trick, or equivalently eventfd on supported platforms. This will initially be used to implement prompt interrupt or shutdown of the posix ticker thread. - - - - - 01b0e233 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add prompt shutdown to the pthread ticker implementation. The Linux timerfd ticker monitors a pipe which is used by exitTicker to ensure a prompt wakeup and shutdown. The pthread ticker lacked this and so would only exit at the next ticker wakeup (10ms by default). This patch adds the same mechanism to the pthread ticker. This changes the pthread ticker from waiting by using nanosleep() to waiting using either ppoll() or select(), so that it can wait on both a time and a file descriptor. On Linux at least, a test program to compare the timing jitter of these APIs shows that using nanpsleep, ppoll or select makes no statistical difference to the maximum or average jitter. This is a step towards unifying the posix ticker implementations, so that we can have just one portable one (albeit with some limited cpp). It is also a step towards using the ticker as part of a more general implementation of wakeUpRts, since this will require a method to wake the rts from a signal handler context (ctl-c handler). - - - - - bc41d646 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Update ticker header commentary It was antique and didn't apply even to the previous implementation, and certainly not to the updated one. - - - - - 4ed9a386 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Remove the timerfd-based ticker implementation There does not appear to be any remaining advantage on Linux to using the timerfd ticker implementation over the portable one (using ppoll on Linux for precise timing). The eventfd implementation was originally added at a time when Linux was still using a signal based implementation. So it made sense at the time. See (closed) issue #10840. - - - - - 97504fa6 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Consolidate to a single posix ticker implementation Previously we had four implementations, two using signals and two using threads. Having just one should make behaviour more consistent between platforms, and should make maintenance easier. - - - - - 1e60023b by Facundo Domínguez at 2026-05-07T18:01:16-04:00 Generalize so_inline to specify which bindings should be preserved This commit generalizes the so_inline option of the simple optimizer so we can indicate with a predicate the specific bindings that should be kept. This feature is important for the LiquidHaskell plugin, which relies on the simple optimizer to make core programs easier to read, but needs to preserve bindings that are relevant for verification. See https://gitlab.haskell.org/ghc/ghc/-/issues/24386 for the full discussion. - - - - - 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - 5fab2238 by Wolfgang Jeltsch at 2026-05-12T21:24:27+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com> Co-authored-by: Fendor <fendor@posteo.de> - - - - - 38b76b2f by Cheng Shao at 2026-05-13T17:48:48-04:00 testsuite: mark T22159 as fragile This patch marks T22159 as fragile on Windows for issue described in #27248. Before we get to the bottom of those failures, this unblocks newer Windows runners. - - - - - 16001ae8 by fendor at 2026-05-15T09:46:57+02:00 Fix regression T27202: `:load` and `:add` work in GHCi To fix the regression there are conceptually two major things that we fix: * We don't remove the `importDirs` from `interactive-session` * When `:add`ing a module, we don't try to find them via PackageImports * The PackageImport is wrong as we can't know the package-name at this stage in ghc/UI.hs What does it mean to not remove the `importDirs` from `interactive-session`? It means that, given some initial `DynFlags`, we will use those `importDirs` in `interactive-session`. The initial `DynFlags`, however, depend on how you initialise the GHC session. For a simple session, initialised by ghc -isrc -this-unit-id main It is simple, just use the `DynFlags` given on the cli. Thus, `main` and `interactive-session` will have the same `DynFlags`, except for the `homeUnitId` and `interactive-session` depends on `main` by construction of the GHCi session. What about a multiple home unit session, though? ghc -unit @unit1 -unit @unit2 What are the `DynFlags` in this cli invocation? It shouldn't be either `@unti1` nor `@unit2`, as the order shouldn't matter or any other implicit condition. For consistency, we decide that the initial `DynFlags` are the top `DynFlags` on the cli, ignoring `-unit` flags. Thus, in this example, there are no `importsDirs` regardless of what we might find in `@unit1` and `@unit2`. But in this invocation: ghc -isrc -unit @unit1 -unit @unit2 The `interactive-session` will have the `importsDirs` `src`. Note, `-isrc` will be inherited in `@unit1` and `@unit2`, so you need to explicitly use `-i` to clear the `importsDirs`, in order to avoid accidentally adding `src` as an import directory to all other home units. This fix has been made possible by the improvements introduced in !15888, which avoids ambiguity when a home unit shares the `importsDirs` with the `interactive-session`, on top of being much faster for multiple home units. Adds regression tests for T27202 for `:load`ing and `:add`ing modules that are located in import directories. - - - - - 35d402c2 by fendor at 2026-05-15T09:46:57+02:00 Use home unit package db stacks in GHCi prompt and session unit In order to import modules from home unit dependencies (e.g., `Data.Map`), the ghci prompt unit needs to populate its `UnitState`. This is tricky to handle correctly, which `PackageDBFlag`s should we use to populate the `UnitState`? We decide, the most intuitive solution for users is to depend on all `PackageDBFlag`s, so that any dependency can be imported in GHCi. This assumes consistency in the `PackageDBFlag`s, so no two home units specify `PackageDBFlag`s that are inconsistent with each other. We could simply concat all the `PackageDBFlag`s of the existing home units, but later `PackageDBFlag`s shadow earlier ones, leading to the last processed home units' `PackageDBFlag`s to shadow the earlier ones. This is hard to fix, we need to give users the capability to provide ghc options for the ghci prompt home unit. However, as this is considerably more work, we decided on an approximation that should work out most of the time. Package Db stacks in cabal and stack follow a certain structure: -no-user-package-db > -package-db $cabal-store > -package-db $local-db The first two arguments are always the same, namely the `-no-user-package-db` and `-package-db`. We compute the longest common prefix over all home units, and use that as the start of the package db stack. Then, over the rest of the `PackageDBFlag`s, we simply take the union and append them to our initial stack. We assume, that this rest of package dbs only defines very few, "local" units that are usually not shadowing each other. This allows us to get a relatively consistent package database stack for the ghci prompt home unit. Similar reasoning applies to the session unit in order to add modules to the session and have dependencies available in the module. We do something similar for `-package` flags, to make sure only the correct units are actually visible in the ghci session. This time, we simply take the union of all `PackageFlag`s, allowing us to import modules from the home unit dependencies. In the future, it would be beneficial to allow the user to provide the exact ghc options to control the visibilities. For now, this will have to do. - - - - - 308 changed files: - + changelog.d/T19174.md - + changelog.d/T27022 - + changelog.d/T27131 - + changelog.d/T27202 - + changelog.d/bytecode-interpreter-hpc-support - + changelog.d/cmm-import-syntax-changes - + changelog.d/dynamic-trace-flags - + changelog.d/ghc-api-epa-parens - + changelog.d/ghc-api-holes-ast-27111 - + changelog.d/ghc-api-namespace-specifier-26678 - + changelog.d/more-efficient-home-unit-imports-finding - + changelog.d/so_inline_is_a_predicate - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Binary.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/Cmm/Lexer.x - compiler/GHC/Cmm/Parser.y - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Driver/Backend.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/CodeOutput.hs - compiler/GHC/Driver/Config.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Env/Types.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Main.hs - + compiler/GHC/Driver/Main/Compile.hs - 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utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. 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