GitLab

Zubin pushed to branch wip/T27455 at Glasgow Haskell Compiler / GHC

Commits:

09326ca6

by Matthew Pickering at 2026-06-20T23:41:12+02:00

Add missing req_interp modifier to T18441fail3 and T18441fail19

These tests require the interpreter but they were failing in a different
way with the javascript backend because the interpreter was disabled and
stderr is ignored by the test.

521e55bf

by Matthew Pickering at 2026-06-20T23:41:13+02:00

hadrian: Fill in more of the default.host toolchain file

When you are building a cross compiler this file will be used to build
stage1 and it's libraries, so we need enough information here to work
accurately. There is still more work to be done (see for example, word
size is still fixed).

23c9b6c3

by Matthew Pickering at 2026-06-20T23:42:52+02:00

hadrian: Build stage 2 cross compilers

* Most of hadrian is abstracted over the stage in order to remove the
  assumption that the target of all stages is the same platform. This
  allows the RTS to be built for two different targets for example.
* Abstracts the bindist creation logic to allow building either normal
  or cross bindists. Normal bindists use stage 1 libraries and a stage 2
  compiler. Cross bindists use stage 2 libararies and a stage 2
  compiler.
* hadrian: Make binary-dist-dir the default build target. This allows us
  to have the logic in one place about which libraries/stages to build
  with cross compilers. Fixes #24192

New hadrian target:

* `binary-dist-dir-cross`: Build a cross compiler bindist (compiler =
  stage 1, libraries = stage 2)

This commit also contains various changes to make stage2 compilers
feasible.

-------------------------
Metric Decrease:
    LinkableUsage02
    ManyAlternatives
    ManyConstructors
    MultiComponentModulesRecomp
    MultiLayerModulesRecomp
    RecordUpdPerf
    T10421
    T12150
    T12227
    T12425
    T12707
    T13035
    T13379
    T13820
    T15703
    T16577
    T18140
    T18282
    T18698a
    T18698b
    T18923
    T1969
    T20049
    T21839c
    T3294
    T4801
    T5030
    T5321FD
    T5321Fun
    T5631
    T5642
    T6048
    T783
    T9020
    T9198
    T9233
    T9630
    T9872d
    T9961
    parsing001
    T3064

Metric Increase:
    T26989
    hard_hole_fits
-------------------------

Co-authored-by: Sven Tennie <sven.tennie@gmail.com>

26fed8ab

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Test cross bindists

We remove the special logic for testing in-tree cross
compilers and instead test cross compiler bindists, like we do for all
other platforms.

80c8910e

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Introduce CROSS_STAGE variable

In preparation for building and testing stage3 bindists we introduce the
CROSS_STAGE variable which is used by a CI job to determine what kind of
bindist the CI job should produce.

At the moment we are only using CROSS_STAGE=2 but in the future we will
have some jobs which set CROSS_STAGE=3 to produce native bindists for a
target, but produced by a cross compiler, which can be tested on by
another CI job on the native platform.

CROSS_STAGE=2: Build a normal cross compiler bindist
CROSS_STAGE=3: Build a stage 3 bindist, one which is a native compiler and library for the target

8215573d

by Sven Tennie at 2026-06-20T23:42:52+02:00

ci: Increase timeout for emulators

Test runs with emulators naturally take longer than on native machines.

Generate jobs.yml

5acb7dbc

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Javascript don't set CROSS_EMULATOR

There is no CROSS_EMULATOR needed to run javascript binaries, so we
don't set the CROSS_EMULATOR to some dummy value.

48345343

by Sven Tennie at 2026-06-20T23:42:52+02:00

Javascript skip T23697

See #22355 about how HSC2HS and the Javascript target don't play well
together.

5e44fd05

by Sven Tennie at 2026-06-20T23:42:52+02:00

Mark T24602 as fragile

It was skipped before (due to CROSS_EMULATOR being set, which changed
for JS), so we don't make things worse by marking it as fragile.

ab349ec2

by Sven Tennie at 2026-06-20T23:42:52+02:00

Fix T22744 for GHCJS

In fact, this test needs Template Haskell, not necessarily an
interpreter.

c73352d8

by Sven Tennie at 2026-06-20T23:42:52+02:00

haddock-test: fix GHCJS haddock test failures

Add --ghc-pkg-path flag support so haddock test runner can find
cross-prefixed ghc-pkg (e.g. javascript-unknown-ghcjs-ghc-pkg) which
is not on $PATH in cross install directories.

Skip haddockHtmlTest on GHCJS: Threaded.hs uses forkOS in a TH splice,
which GHCJS RTS doesn't support. Mark with js_skip in all.T.

5e814e76

by Andreas Klebinger at 2026-06-22T23:00:24-04:00

compiler: Deduplicate hscTidy

This function was accidentally duplicated during a refactor.

Fixes #27351

473b97eb

by sheaf at 2026-06-22T23:01:22-04:00

Avoid mkTick in Core Prep breaking ANF (part II)

Hotfix for 2f9579765f55b3920ceb2e04995ff41a9d0e2d4e fixing a small
oversight in the call to tickTickedExpr from mkTick, in which we
improperly recursively called mkTick without passing on the preserve_anf
flag.

Fixes #27386

9284a1f7

by Simon Hengel at 2026-06-23T05:55:33-04:00

Don't use global variables to address concurrency bugs! (fixes #27234)

This was originally introduce with
88f38b03025386f0f1e8f5861eed67d80495168a to address #17922.

In this specific case a better fix would have been to synchronize on
stderr:

    withHandle_ "stderrSupportsAnsiColors" stderr $ \ _ -> do
      ...

But apparently the dependency on `terminfo` was removed in
32ab07bf3d6ce45e8ea5b55e8095174a6b42a7f0, preventing #17922 in the first
place.

44309cd3

by Alan Zimmerman at 2026-06-23T05:56:20-04:00

EPA: remove LocatedL / SrcSpanAnnL and  LocatedLI / SrcSpanAnnLI

This is part of a refactor towards only having LocatedA / SrcSpanAnnA

It removes the stated items, but has to add back one for BooleanFormula,
LocatedBF / SrcSpanAnnBF

This commit also use the HsConDetails RecCon extension point to
capture the braces in a record constructor

2f6a5534

by Simon Jakobi at 2026-06-23T15:46:20+02:00

Add -dstable-core-dump-order for stable Core dump ordering (#27296)

The order of top-level bindings in Core dumps (-ddump-simpl etc.) is the
compiler's Unique-sensitive internal processing order, so an unrelated
upstream change can reorder them and defeat a textual diff of two dumps.

This adds an opt-in flag -dstable-core-dump-order that reorders the
top-level bindings of dumps routed through dumpPassResult into a stable,
Unique-independent order, so two dumps line up across rebuilds. See
Note [Stable Core dump order] in GHC.Core.Ppr for the sort key and its
rationale.

Adds tests T27296 (binders GHC emits in non-source order by default,
asserted to come out stably ordered under the flag) and T27296b (an
untidied -ddump-float-out dump pinning the ordering of the anonymous lvl
floats by literal value).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

141986e3

by mangoiv at 2026-06-24T15:51:14-04:00

compiler: refactor error reporting code for ExplicitLevelImports

Refactors error reporting code for ExplicitLevelImports to pass in a
RdrName and a GlobalReaderElt to be able to report errors that are
faithful to the source and to more precisely distinguish between names
that are in scope from different qualifications.

Fixes #27385 and #26616

aa7df6b6

by Simon Hengel at 2026-06-24T15:52:18-04:00

Set GHC_VERSION when calling custom pre-processors (see #25952)

(so that pre-processors can emit backwards compatible code)

a9e494f2

by Simon Hengel at 2026-06-24T15:54:08-04:00

Add a flag to control GHCi specific error hints (close #27409)

a805b2a2

by Simon Hengel at 2026-06-24T15:55:20-04:00

Reference correct package in error messages for reexported modules

(fixes #27417)

f235d183

by Simon Jakobi at 2026-06-25T05:51:18-04:00

Add explicit setBit/clearBit/complementBit for instance Bits Integer (#21176)

The default setBit, clearBit, and complementBit methods allocate
intermediate Integers per call. Define them explicitly via the new
integerSetBit[#], integerClearBit[#] and integerComplementBit[#], built
on the BigNat# primitives, which avoid those allocations. Allocation is not
eliminated entirely -- the negative (IN) cases would need in-place mutation,
which is left as future work.

The default methods constant-folded on literal arguments via the
integerOr/integerAnd/integerXor rules, which fold literal Integers of any
size. The explicit functions have no such rule, so they (their Word-argument
wrappers, and the Bits Integer methods) are marked INLINE to expose the
underlying primops to the simplifier; see Note [INLINE for constant folding
of bit operations]. This restores folding only on the small-int (IS) path --
large literal Integers (IP/IN) are no longer constant-folded, a minor
regression for that case. T8832 covers the IS-path folding.

The new golden-output test T21176 checks all three operations against the
default implementations across the sign/size boundaries, recording each
result plus its integerCheck validity. The base and ghc-bignum interface-
stability export goldens gain the new functions.

The main changelog entry lives in changelog.d under a new ghc-internal
section (renamed from ghc-prim).

CLC proposal: https://github.com/haskell/core-libraries-committee/issues/423

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

202ed264

by Marc Scholten at 2026-06-25T05:52:21-04:00

haddock: use Text in documentation pipeline

This patch moves Haddock's documentation pipeline from String to Text
where the data is already textual. It avoids repeated conversions while
keeping the existing decoding behavior for invalid UTF-8 docstring
chunks.

The main changes are:

* Render and carry docstrings as Text in Haddock-facing paths.
* Use the Binary Text instance from GHC.Utils.Binary for Haddock
  interface files, and bump the Haddock binary interface version.
* Add a FastString HTML instance so XHTML rendering avoids
  intermediate String allocation.
* Keep HsDocStringChunk decoding lenient, matching the previous
  unpackHDSC behavior on invalid UTF-8 input.
* Update the xhtml submodule to 3000.4.1.0, which contains the
  apostrophe escaping fix used by the Haddock test output.

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Assisted-by: Codex <codex@openai.com>

a72ff58f

by mangoiv at 2026-06-25T05:53:07-04:00

compiler: rename ZonkAny to UnusedType and add pretty printing logic

ZonkAny is a hard to understand name for users who do not know how the
compiler works internally. Additionally, it is confusing that ZonkAny,
while being a concrete type *represents* a meta variable, espeically in
the compiler output.
This patch changes the name of ZonkAny to UnusedType which is closer to
its intended semantics and adds special pretty printing logic to display
this type in the same fashion the compiler displays meta variables in
other places, whenever they leak from the implementation to the user.
It also exports the type from ghc-internal:GHC.Internal.Types in order
to expose documentation.

Fixes #27390

Co-Authored-By: Sam Derbyshire <sam.derbyshire@gmail.com>

6813f002

by Simon Jakobi at 2026-06-26T04:51:47-04:00

Reg.Linear: drop Platform argument from most FR (FreeRegs) methods

The FR class has one instance per CPU architecture, so any
architecture-constant information its methods derived from the Platform
argument can instead be baked into the instance. This removes the now
needless Platform argument from frAllocateReg, frGetFreeRegs and
frReleaseReg.

frInitFreeRegs keeps its Platform argument: the initial allocatable set is
genuinely platform-dependent, see Note [Aarch64 Register x18 at Darwin and
Windows].

Fixes #26665

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

3b2a9409

by Zubin Duggal at 2026-06-26T04:52:39-04:00

testsuite: Report fragile failures as skipped in JUnit output

27463426

by Rodrigo Mesquita at 2026-06-26T20:54:58-04:00

perf: Share Module in Iface Symbol Table

This commit modifies the structure of the serialized `SymbolTable Name`
to then re-use and share the `Module` (both on disk and in memory) across
all `Name`s from the same module.

The new structure looks like:

  <total name count>
  $modules.size
  for (mod, names) in $modules:
    $mod
    $names.size
    for table_ix, occ in $names
      $table_ix
      $occ

i.e. we put the module just once, followed by all names in that module.
When deserializing, we deserialize the module just once, and all the
following `Name`s are constructed with a pointer to that same decoded
`Module`.

In `hoogle-test`, we must use `DNameEnv` rather than `Map Name`,
otherwise the output fixities order was susceptible to changes in the
uniques assigned to each Names, which is not stable.

Fixes #27401

-------------------------
Metric Decrease:
    InstanceMatching
    LinkableUsage01
    LinkableUsage02
    hard_hole_fits
-------------------------

412f1675

by Simon Hengel at 2026-06-26T20:55:41-04:00

Rename `MCDiagnostic` to `InternalMCDiagnostic`

`MCDiagnostic` is meant to be used for compiler diagnostics.

Any code that creates `MCDiagnostic` directly, without going through
`GHC.Driver.Errors.printMessage`, sidesteps `-fdiagnostics-as-json` (see
e.g. !14616, !14475, !14492 !14548).

To avoid this in the future, this change more narrowly controls who
creates `MCDiagnostic` (see #24113).

6f212121
by Facundo Domínguez at 2026-06-26T20:56:27-04:00
```
Encapsulate options of occurAnalysePgm in a record
```

adfbb179

by Facundo Domínguez at 2026-06-26T20:56:27-04:00

Allow to configure the occurrence analyser to retain some dead bindings

This is needed by plugins that are the only consumers of a binding which
is otherwise unused in the program.

See Note [Controlling elimination of dead bindings in occurrence analysis]
added in this commit, or
https://gitlab.haskell.org/ghc/ghc/-/issues/27240 for more discussion.

c745b11f
by Copilot at 2026-06-26T20:56:27-04:00
```
Address documentation feedback
```

2c2a4a2a

by Copilot at 2026-06-26T20:56:27-04:00

Keep the imp_rules parameter of occurPgmAnalysePgm and add occ_opts to OccEnv

e2262b0e

by Copilot at 2026-06-26T20:56:27-04:00

Strengthen T27240.hs with a binding that should be removed

5f9d9268

by Copilot at 2026-06-26T20:56:27-04:00

Move the reference #27240 to a related paragraph

d86d2644

by Simon Hengel at 2026-06-26T20:57:10-04:00

Remove deprecated flag `-ddump-json` (see #24113)

This was first deprecated in 9.10.1.

3b15ff03

by Simon Jakobi at 2026-06-27T18:48:34+02:00

Tweak mk_mod_usage_info

* Use O(log n) `elemModuleEnv` instead of O(n) `elem` to filter the
  direct imports.
* Use `nonDetModuleEnvKeys` to avoid sorting the ent_map keys twice.
* Prepend the presumably shorter list when creating all_mods with
  `(++)`. Actually this eliminates the `(++)` entirely, as it seems to
  fuse with the `filter` expression.

As a result there is a tiny speed-up when generating the .hi-files for
modules with many imports.

None of the changes affect compilation determinism as the module list
is explicitly sorted to ensure a canonical order.

2d0fd154

by Alan Zimmerman at 2026-06-29T11:44:00-04:00

EPA: Remove LocatedC / SrcSpanAnnC

This is part of a cleanup of the zoo of
SrcSpanAnnXXX types for exact print annotations.

This one removes SrcSpanAnnC used for storing exact print annotations
for contexts. It replaces it with an explicit `HsContext` data type
that carries the annotations and the context.

So, replace

  type HsContext pass = [LHsType pass]

with

  type HsContext pass = HsContextDetails pass (LHsType pass)

  data HsContextDetails pass arg
    = HsContext
      { hsc_ext  :: !(XHsContext pass)
      , hsc_ctxt :: [arg]
      }
    | XHsContextDetails !(XXHsContextDetails pass)

We need the parameterised HsContextDetails because it is used both for
HsQual carrying 'LHsExpr p' and "normal" contexts carrying 'LHsType p'.

cca0d589

by Luite Stegeman at 2026-06-30T13:33:40-04:00

rts: handle large AP closures in compacting GC

The function update_fwd_large in the compacting GC could run into
an unexpected object with the following error:

  internal error: update_fwd_large: unknown/strange object  24

Closure type 24 is the AP closure, which was not handled in
upd_fwd_large. This patch adds handling them.

fixes #27434

42935858

by Luite Stegeman at 2026-06-30T13:33:40-04:00

testsuite: use compacting_gc way instead of hardcoding +RTS -c

bf7b5ce6

by Alan Zimmerman at 2026-06-30T13:34:23-04:00

EPA: Remove LocatedLW from LStmtLR

HsDo already had its XDo extension point for an
AnnList, which also appeared in LocatedLW.
So we remove the redundant one and use the one inside HsDo
as originally intended.

Also delete LocatedLC/LocatedLS as they were unused

d7cfea49

by Recursion Ninja at 2026-06-30T21:37:12-04:00

Decoupling 'L.H.S' from 'GHC.Types.SourceText'

  * Migrated 'IntegralLit'   to 'L.H.S.Lit'.
  * Migrated 'FractionalLit' to 'L.H.S.Lit'.
  * Migrated 'StringLiteral' to 'L.H.S.Lit'.
  * Added TTG extension points to the types above.
  * Added nice export list to 'GHC.Hs.Lit'.
  * Added 'rnOverLitVal' and 'tcOverLitVal' functions to 'GHC.Hs.Lit'.
  * Added instance 'Anno (StringLiteral (GhcPass p)) = SrcSpanAnnN'
  * Moved [Notes] about 'SourceText' from 'L.H.S.*' to 'GHC.*'.
  * Removed all references to 'SourceText' from 'L.H.S'.
  * Removed the trailing comma record field from  'StringLiteral'
  * Renamed exported functions for nomenclature consistency.
  * Deprecated the renamed functions

Fixes #26953

a1f2558b

by Recursion Ninja at 2026-06-30T21:37:12-04:00

Monomorphising GHC pass parameters where appropriate

7bf9e3c5

by Teo Camarasu at 2026-06-30T21:38:03-04:00

Make Q abstract

This patch aims to clearly demarcate the internal and external interfaces
of Q.
In the past the `Quasi` typeclass was both part of the external,
public-facing interface, and was used to give the implementation of `Q`.

Now we separate out these two distinct roles. `Quasi` continues to exist
in the public interface, but we introduce a new `MetaHandlers` type,
which is equivalent to `Dict Quasi`.

`Q a` is now defined to be `MetaHandlers -> IO a`, and, crucially,
the constructor and the new `MetaHandlers` type are not exposed from the
public interface.

This gives us the ability to vary the interface on the GHC side without
forcing a breaking change on the `template-haskell` side.
Similarly `template-haskell` has more freedom to change the `Quasi`
typeclass without needing any changes in `lib:ghc`.

Implements https://github.com/ghc-proposals/ghc-proposals/pull/700

Resolves #27341

4262af36

by L0neGamer at 2026-06-30T21:38:56-04:00

generically defines mconcat in terms of internal type's Semigroup instance

add changelog entry

use simpler definition for mconcat

`nonEmpty` isn't available yet; inline branches in case

add test case

fixup generically defines mconcat in terms of internal type's Semigroup instance

add comment on Generically and deriving mishaps

swap mconcat to foldr version

add some strictness testing for mconcat

add to `base` changelog entry

e22ad997

by Cheng Shao at 2026-06-30T21:39:43-04:00

hadrian/rts: fix unregisterised build for gcc 15+

This patch fixes unregisterised build for gcc 15+:

- Pass -optc-Wno-error in hadrian when +werror enables -optc-Werror,
  see added comment for details.
- For RTS functions that the codegen would emit calls, ensure their
  real prototype is hidden when the header is included in .hc fies
  (IN_STG_CODE), and the dummy prototype is provided to match the EFF_
  convention.

In the future we should get rid of EFF_ (#14647) and remove these
hacks, but for now this patch makes unregisterised work again on newer
toolchains. Fixes #27404.

Co-authored-by: Codex <codex@openai.com>

3f00f234

by Cheng Shao at 2026-06-30T21:40:32-04:00

compiler: fix missing handling of CmmUnsafeForeignCall node in LayoutStack

This patch fixes missing handling of `CmmUnsafeForeignCall` middle
node in the `LayoutStack` pass.

Before proc-points splitting, this pass computes liveliness of local
registers, and spills those alive across a Cmm native call onto the
stack. It need to traverse all middle nodes in each block and check
whether a local register is an assignee, if so then the previous
mapping in `sm_regs` is invalidated and needs to be dropped. However,
it didn't handle `CmmUnsafeForeignCall` node which may also assign to
a local register. When proc-points splitting is enabled, this can
produce an invalid basic block that doesn't properly backup the
updated local register to the stack before doing a Cmm call, resulting
in completely invalid runtime behavior.

The patch also adds a `T27447` regression test. With no-TNTC or with
LLVM backend, without the fix the test case would output a stale
0x1111111111111111 value, instead of the expected 0x2222222222222222
output.

Fixes #27447.

Co-authored-by: Codex <codex@openai.com>

701088db

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Drop vestigial references to make build system

62d54a53

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Add support for running specifying a job's testsuite ways

7f97ac2c

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Run llvm testsuite ways in llvm jobs

Addresses #25762.

7ea75116

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Add normalise_ddump_deriv setup function

Some tests check the result of -ddump-deriv, which may contain INLINE pragmas depending on optimization flags.
With normalise_ddump_deriv setup function, INLINE pragmas are stripped off.

c7a8199f

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use -dsuppress-idinfo to make tests more robust

Previously, T18052a and T21755 were failing on 'optasm' and 'optllvm' ways because of visibility of unfoldings.

a12122e5

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use a trick to keep large objects alive

Previously, T17574 and T19381 were failing on 'optasm' and 'optllvm' ways because of compiler optimizations.
Change them to use NOINLINE to prevent unwanted optimizations.

1a95b327

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Only run T24224 in 'normal' way

This test is a frontend-only one and breaks if optimizations are enabled.

8abea737

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Ignore T18118's stderr

When optimizations are enabled, the compiler emits a warning (You cannot SPECIALISE ...).
The message is not important, so ignore it.

9453a722

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Mark T816 and tc216 broken with optimizations

These tests are about type checking, so we should not care too much if they are broken with optimizations.

See #26952

0aef9ec0

by Ben Gamari at 2026-07-01T10:34:03-04:00

testsuite: ds014 is not longer broken

It now appears to pass in the ways it was marked as broken in.

Closes #14901.

4692d1e4

by Ben Gamari at 2026-07-01T10:34:03-04:00

testsuite: Only run stack cloning tests in the normal way

These are too dependent upon code generation specifics to pass in most
other ways.

c154df26

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Update options_ghc_fbyte-code

The `-fbyte-code` option used to be overriden by `-fllvm` but it is no longer true since !14872 was merged.

I updated the test to accept the new behavior.

Closes #27049

5d8bb7b5

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Only run T22744 in 'normal' way

This test takes a long time on optimized ways.

d1e74c8e

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Disable tests that use -finfo-table-map on llvm ways

Currently, -finfo-table-map does not work with -fllvm. See #26435

3bf38c84

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Don't run T24726 on optimized ways

If optimizations are enabled, the rewrite rule just fires and -drule-check will report nothing.

e4eef116

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use -fno-unoptimized-core-for-interpreter when running LinkableUsage01/02

Optimizations for the bytecode interpreter are considered experimental, and need a flag to be enabled.

234a9872

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Suppress unwanted optimizations on T25284

99a2af2f

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Don't run stack_big_ret with optimizations

Stack layout may change with optimizations enabled.

04c836df

by ARATA Mizuki at 2026-07-01T10:34:04-04:00

testsuite: Mark memo001 broken on optimized ways

See #27396

1a8a24f4

by ARATA Mizuki at 2026-07-01T10:34:04-04:00

testsuite: Mark syn-perf broken on optimized ways

See #27398

40412093

by Duncan Coutts at 2026-07-01T10:34:50-04:00

Add a test for thread scheduler fairness

It also tests that the interval timer and context switching works.
We also test that fairness is lost when the context switching interval
is too coarse for the duration of the test.

We add this test before doing surgery on the interval timer, so we have
decent coverage.

3f34d557

by Duncan Coutts at 2026-07-01T10:34:50-04:00

Make exported stop/startTimer no-ops, and rename internal functions

Specifically, internally rename:
stop/startTimer to pause/unpauseTimer
stop/startTicker to pause/unpauseTicker

and keep stop/startTimer as exported functions, but now as no-ops.

In the past the stop/startTicker actions were used incorrectly as if
they were synchronous, which they are not. See issue #27105. We now
document pause/unpackTicker as being async and not to be used for the
purpose of concurrency safety.

The existing stop/startTimer (note Timer not Ticker, the Timer calls the
Ticker!) are also exported from the RTS as a public API. This was
historically because the ticker used signals and it was important to
suspend the timer signel over a process fork. So these functions were
exported to be used by the process and unix libraries.

We cannot just remove the RTS exports, but we now make them no-ops, and
they can be removed from the process and unix library later. This
was already documented in a changelog.d entry no-more-timer-signal but
due to changes during the MR process the change to make stop/startTicker
into no-ops didn't make it into the earlier MR.

02e84e5f

by Duncan Coutts at 2026-07-01T10:34:51-04:00

Make exitTicker/exitTimer unconditionally synchronous

We never use them asynchronously, and we should never need to do so.

And update some related comments.

13db6a72

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: update and improve comments on (un)pause and exit

Clarify what is async vs sync.

43d9a07d

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: split out ppoll/select helper functions

Move the #ifdefs out of the main code body by introducing local helper
functions and types, which themselves have two implementations (with a
common API) based on ppoll or select.

This helps improve clarity/readability.

a5491baa

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: improve the implementation

The existing implementation supported pausing and exiting, with the
implementation of pausing reling on a mutex and condition variable.
It needed to check the pause and stop shared variables on every
iteration. It relies on ppoll or select, to wait on the timeout and also
wait on an interrupt fd. The interrupt fd was only used for prompt
exit/shutdown, and not for pausing or other notification. The pause only
needed a lock and a memory operation, but the pause was not prompt. The
resume used a lock, and signaling a cond var.

The new implementation uses a somewhat more regular design: every
notification is done by setting a shared variable and
interrupting/notifying the ticker via the fd. The ticker thread does not
need to check any shared variables on normal timer expiry, only when it
recevies notification. This may be a micro-optimisation, but the tick
occurs 100 times a second by default so any improvements in the hot path
are amplified. When the ticker thread does receive notification it can
check the various shared variables and update its local state. The
blocking relies on using ppoll/select but without a timeout. This avoids
the condition var and also allows further notifications when paused
(also used for unpausing).

This design can be extended with further notification types if needed by
using and checking further shared vars (or making existing shared vars
an enum or counter). This may be used in future for additional
notifications to the ticker thread. This will likely be used to proxy
wakeUpRts from a single handler context for example. And this approach,
avoiding mutexes, is compatible with use from signal handlers.

So overall, it's:
 * slightly simpler / more regular;
 * easier to extend with additional notifications;
 * probably slightly more efficient (but a micro-optimisation);
 * and supports calling notification from signal handlers

5b20821e

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: further minor local renaming for code clarity

Improve the clarity with better choice of names for several local vars
and function.

1f3ec5e0
by Duncan Coutts at 2026-07-01T10:34:51-04:00
```
win32 ticker: split out local helper functions
```

596e7307

by Duncan Coutts at 2026-07-01T10:34:51-04:00

win32 ticker: provide guarantee about concurrency and idempotency

Use a lock to ensure pause/unpause can be used concurrently. Use a
paused variable, protected by the lock, to ensure that pause and unpause
are both idempotent. This is what the portable API expects.

1870edd7

by Duncan Coutts at 2026-07-01T10:34:51-04:00

win32 ticker: make the initial tick be after one wait interval

There is no need to tick immediately. This is consistent with the
posix implementation.

7c15ab5b

by Duncan Coutts at 2026-07-01T10:34:51-04:00

ticker: remove now-unnecessary layer of enable/disable

There was an atomic variable used to block *part* of the actions of the
tick handler. This still did not make stopTimer synchronous, even for
the part of the the handle_tick actions it covered. It also added a more
expensive (sequentuially consistent) atomic operation in the hot path
for the handle_tick action, whereas our new design requires no atomic
ops at all.

Now that we have eliminate the need for synchronous stop/startTicker,
we don't need this not-quite-working-anyway atomic protocol. The new
pause/unpauseTicker is explicitly asynchronous and idempotent.

8585f8cb

by Duncan Coutts at 2026-07-01T10:34:51-04:00

ticker: add TODOs about issue #27250: too much being done from handle_tick

The handle_tick should not perform I/O, block, perform long-running
operations or call arbitrary user code. Unfortunately, everything to
do with the eventlog (at the moment) falls into all those categories.

6e381626

by Duncan Coutts at 2026-07-01T22:29:55+01:00

Adjust releaseCapability_ precondition to allow cap->running_task == NULL

There are two use cases for releaseCapability_:

1. The current Task (cap->running_task) releases the Capability.
   The Capability is marked free, and if there is any work to do,
   an appropriate Task is woken up.

2. There is no current task (cap->task == NULL), and thus the
   Capability is idle, and we want to wake up an idle Task to animate
   the Capability. This case uses always_wakeup.

Currently, the precondition for releaseCapability_ is
  cap->running_task != NULL
and so the 2nd use cases have to set cap->running_task (which is then
immediately overwritten) just to satisfy the precondition. See the
use cases in sendMessage and prodCapability.

So we can relax the precondition to be:
  cap->running_task != NULL || always_wakeup
so that in the always_wakeup case, we say it is ok for the
cap->running_task to be NULL.

This lets us simplify sendMessage and prodCapability. In particular it
will allow prodCapability to not need a Task parameter.

The ulterior motive for all this is that I want to be able to call
prodCapability from an OS thread that is not itself a Task, in persuit
of issue #27086: disentangle I/O managers from wakeUpRts. The most
straightforward way to wake the RTS is using prodCapability, but the
context in which we will need to do that are threads that are not Tasks.

89404ebc

by Duncan Coutts at 2026-07-01T22:29:55+01:00

prodCapability no longer needs to take a Task param

Now that releaseCapability_ can accept cap->running_task == NULL then it
is no longer necessary for prodCapability to require a Task.

4e60c5f6

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Define prodOneCapability

There was an existing declaration for this in the header file, but no
definition.

Similarly, there is a declaration for prodAllCapabilities but no
definition, and we don't need it, so remove the declaration.

2527026f

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Add a wakeUpRtsViaTicker feature to the posix ticker

It proxies a call to wakeUpRts, but crucially, this can be called from
a signal handler context. It will be used for ctl-c handling.

aa5a03a5

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Change how wakeUpRts works

Previously it would call wakeupIOManager to get a capability to wake up
and run. This works but it entangles the I/O managers with unrelated
features: ctl-c handling and idle gc (the two features that use wakeUpRts).

The reason it used wakeupIOManager is that this action is safe to use
from a posix signal handler, since it just posts bytes to a pipe.
Otherwise the more direct approach (used e.g. by sendMessage when the
target capability is idle) is to use releaseCapability. But that uses
condition variables and mutexes, which are not safe to use from within a
signal handler.

So instead of entangling the (multiple) I/O managers with this, we make
wakeUpRts use the direct approach (using prodOneCapability). On win32
the ctl-c console handler can call wakeUpRts directly, since it is
called in a proper thread. On posix, to deal with the signal handler
problem, we make the signal handler ask the ticker thread to proxy the
call to wakeUpRts, since the ticker thread is also a proper thread.

This will allow the I/O managers to no longer be concerned with this.
This is good because there are many I/O managers (and they're
complicated), but there is (on posix) only one ticker implementation. So
this is an overall reduction in coupling and complexity.

Fixes issue #27086

c6d53c16

by sheaf at 2026-07-02T21:35:44-04:00

Test driver: normalise line numbers into libraries

When comparing the stdout of tests that print out callstacks, we can't
rely on the stability of exact line:column spans pointing into libraries
(e.g. ghc-internal), as any change (such as adding a comment) can change
them.

This commit addresses this by normalising away line:column in callstacks,
but only when those point into internal libraries. We don't do this in
general, as the exact span might be important to the test (e.g. for a
span within the test module itself).

Fixes #27387

81ee62e0

by Alan Zimmerman at 2026-07-02T21:36:33-04:00

EPA: Remove LocatedLW from MatchGroup

This is the last usage of LocatedLW / SrcSpanAnnLW

925959db

by Recursion Ninja at 2026-07-04T04:14:12-04:00

Decoupling 'L.H.S' from 'GHC.Hs.Doc'

  * Migrated 'GHC.Hs.Doc' and 'GHC.Hs.DocString' AST defintions from 'GHC.*' namespace,
    to new 'Language.Haskell.Syntax.Doc' module in the 'L.H.S' "namespace."
  * Updated 'HsDocString to be TTG-parameterised as 'HsDocString pass'.
  * Added 'GHC.Hs.Extension.Pass': splits 'GhcPass'/'Pass' and all 'HsDocString'
    TTG instances out of 'GHC.Hs.Extension', which re-exports it unchanged
    (this is backwards compatible and prevents the introduction of a boot file).
  * Deleted 'GHC.Hs.Doc.hs-boot'; removed all 'L.H.S.*' imports of 'GHC.Hs.Doc'.
  * Updated 'GHC.Hs.DocString' to be TTG pass-parameterised throughout; moved
    'mkHsDocStringChunk'/'unpackHDSC' here (require 'GHC.Utils.Encoding').
  * Split 'GHC.Rename.Doc.rnHsDoc' from 'rnHsDocIdentifiersOnly'.
  * Updated parser, renamer, typechecker, HIE, and exact-print for new types.
  * Added 'HsDocString' TTG instances for 'DocNameI' to 'Haddock.Types'.
  * Killed the last module loop between GHC.* and LHS.*.
        - Only edges from LHS.* to GHC.Data.FastString now!

Resolves #26971

b7e24044

by mangoiv at 2026-07-04T04:14:56-04:00

ci: retry fetching test metrics

Retry fetching test metrics to make the CI not fail if the services is
temporarily unavailable

4180af3f

by Zubin Duggal at 2026-07-04T04:15:38-04:00

Bump semaphore-compat submodule to 2.0.1

This versions includes some cruicial fixes for darwin

242d4317

by sheaf at 2026-07-04T04:16:19-04:00

Remove outdated comment in GHC.Data.ShortText

There was a long comment in GHC.Data.ShortText about a workaround that
was necessary when bootstrapping with GHC 9.2 and below. The actual
logic has since been dropped, but the comment remained. This commit
removes the vestigial comment.

9b714c4c

by Zubin Duggal at 2026-07-05T09:40:36+05:30

CorePrep: Don't speculatively evaluate bindings that we have already discovered to be absent

In #25924, we segfault because speculation forces a projection out of a RUBBISH dictionary
(which we generated because it absent).

Solution: Don't speculate on bindings we already know are absent.

Fixes 25924

4a59b3ee

by Zubin Duggal at 2026-07-05T09:40:36+05:30

Don't make absent fillers for terminating types

In #25924 we discovered that we could speculatively evaluate an absent filler
for a dictionary, and project a field (a superclass selector) out of it,
resulting in segfaults.

Solution: Never make an absent filler or rubbish literal for a terminating type
like a dictionary. mkAbsentFiller returns Nothing for isTerminatingType, so
worker/wrapper and the specialiser keep the real argument instead.

Some small metric decreases because we do a little less work in the
simplifier now.

Metric Decrease:
    T9872a
    T9872b
    T9872c
    TcPlugin_RewritePerf

383ddcd4

by Alan Zimmerman at 2026-07-06T07:08:16-04:00

EPA: Move the 'where' annotation for PatSynBind

This allows us to move it out of the MatchGroup exact print annotation
too

66d1a5d5

by fendor at 2026-07-07T16:57:56-04:00

Add 'backendInfoTableMapValidity' backend predicate

Check whether the backend supports the `-finfo-table-map` flag and
ignore it otherwise.

Improve by-design documentation of `backendCodeOutput`.

`Backend` is **abstract by design**. Make this clearer in
`backendCodeOutput` which is incorrectly being used as a proxy for
`Backend`.

Instead, define the desired property predicates in GHC.Driver.Backend
In the process, make `backendCodeOutput` total.

74f1071d

by fendor at 2026-07-07T16:57:56-04:00

Add failing test for `-finfo-table-map` and bytecode backend

If you compile a module using the bytecode backend, with
-finfo-table-map, then the info table map doesn't get populated for the
module.

This is because the -finfo-table-map code path is implemented mostly in
the StgToCmm phase which isn't run when creating bytecode.

Ticket #27039

28d63bca

by mangoiv at 2026-07-07T16:59:16-04:00

ci: don't fail nightly if there have been no changes that night

Fixes #27127

4ebfc478

by Rodrigo Mesquita at 2026-07-08T04:47:53-04:00

ttg: Using ShortText over FastString in the AST

To make the AST independent of GHC, this commit replaces usages of
`FastString` with `HText` in the AST, killing the last edge from
Language.Haskell.* to GHC.* modules.

Even though we /do/ want to use FastStrings in general -- critically in
Names or Ids -- there is no particular reason for the FastStrings that
occur in the AST proper to be FastStrings. Strings in the AST are
typically unique and don't benefit particularly from being interned
FastStrings with Uniques for fast comparison.

`HText` is a type synonym for `ShortText` which uses GHC's Modified
UTF-8 encoding exclusively.

Modified UTF-8 must be used to represent the Haskell AST because the
Haskell Report allows surrogate code points. `Data.Text.Text` functions
use Standard UTF-8 which replace surrogates with a placeholder value,
thus `Data.Text.Text` is unsuitable for AST strings. See the
`Language.Haskell.Syntax.Text` module header for more details.

Final progress towards #21592

Closes #21628

d910b353

by Simon Peyton Jones at 2026-07-08T04:48:36-04:00

Update equality-type documenation in GHC.Builtin.Types.Prim

Fix #27466

b2530542

by Simon Peyton Jones at 2026-07-08T04:48:36-04:00

Honour -dsuppress-coercions in GHC.Core.TyCo.pprCo

Fixes #27467

9a73179a

by Facundo Domínguez at 2026-07-08T04:49:26-04:00

Add item to MR checklist asking to squash fixup commits after approval

The checklist has an item that reads

    All commits are either individually buildable or squashed.

This item could be checked immediately after sending the merge request
though. If reviewers ask for amends later on, and the author amends
the merge request, there was no item that would remind the contributors
to squash the fixup commits before landing.

This commit adds a new item

    After all approvals and before landing: all fixup commits are squashed with their originating commits.

which should be harder to mark as done before approvals have been given.

ed09895d

by Andreas Klebinger at 2026-07-08T16:53:27-04:00

Fix a profiling race condition resulting in segfaults.

StgToCmm: Don't assume tagged FUN closures in closureCodeBody.
When entering a closure the self/node pointer might not be tagged in
some situations when a thunk is evaluated by multiple threads.
So we most AND away the tag bits rather than subtracting an expected tag.

Apply.cmm: Fix a race condition occuring when a thunk is mutated during GC.

In stg_ap_0_fast when might need to run GC before entering a thunk. If this happens
another thread or the GC itself might mutate the closure making entering it no longer
valid. We now check for this.

Add test and changelog for #27123 fixes.

67c03eb2

by Cheng Shao at 2026-07-08T16:54:09-04:00

ghc-heap: fix invalid srtlen returned by peekItbl when no-TNTC

This patch fixes the no-TNTC code path of `peekItbl` so that it looks
at the right memory address when reading the `srt` field from the
`StgInfoTable_` struct. Also adds a `T27465` regression test that
reproduces the bug on no-TNTC builds before the fix. Fixes #27465.

Co-authored-by: Codex <codex@openai.com>

2ecabb4f

by Zubin Duggal at 2026-07-09T09:23:25-04:00

hadrian: binary-dist-dir should not be the default target

Revert behaviour to pre 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2

In 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2, we applied the following behaviour change:

```
hadrian: Build stage 2 cross compilers
...
* hadrian: Make binary-dist-dir the default build target. This allows us
  to have the logic in one place about which libraries/stages to build
  with cross compilers. Fixes #24192
```

This is a major regression to development experience, a plain hadrian/build
--freeze1 now takes ages because we rebuild all docs (which need to go in the
binary dist dir).

`binary-dist-dir` is the wrong default target for regular GHC development work

Fixes #27445

e16388e3

by Zubin Duggal at 2026-07-09T09:23:25-04:00

.gitignore: Add the hadrian system.config introduced by commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2

Since

commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2
Author: Matthew Pickering <matthewtpickering@gmail.com>
Date:   Thu Dec 21 16:17:41 2023 +0000

    hadrian: Build stage 2 cross compilers

./configure produces /hadrian/cfg/system.config.{host,target}

Add these to .gitignore

7e8abf41

by Alan Zimmerman at 2026-07-09T09:24:12-04:00

EPA: Replace AnnListItem with simply [TrailingAnn]

Remove the unnecessary wrapper around a single field.

29032f17

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Keep real reason for fragile test failures

c34e03a7

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Fall back to the failure reason for empty JUnit bodies

409d40f0

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Show output diffs in JUnit output

Also refactor compare_outputs to return essentially a `Maybe Diff`
(`CompareOutput`) instead of a bool, but more pythonic. This
allows us to pass the diff through nice.

06fee1ab

by Zubin Duggal at 2026-07-09T09:24:58-04:00

perf notes: include stat deviation and acceptance window in notes so they show up in gitlab

57c0f32c

by mangoiv at 2026-07-10T11:08:38-04:00

driver: enable -finter-module-far-jumps by default

this fixes a compatibility bug with certain binutils/gcc versions where
we were seeing jump offset overflow errors.
This commit can probably reverted if we stop supporting the problematic
binutils/gcc verions (2.44 and 14.2, respectively)

Reolves #26994

4396a6f2
by Andrea Vezzosi at 2026-07-10T11:09:25-04:00
```
[Fix #27287] preserve ModBreaks in ModIface
```

ed261a7e

by Cheng Shao at 2026-07-14T17:59:38-04:00

hadrian: fix HLS support

This patch fixes hadrian's HLS support so one can rely on HLS when
working on the hadrian codebase. Fixes #27480.

Not building/linking shared libraries for hadrian is a severely
premature optimization; this top-level setting in `cabal.project` only
affects home packages while the dependencies in the cabal store are
built with vanilla/dynamic anyway, and even adding dynamic builds to
home packages would not be costly due to cabal's usage of
`-dynamic-too`.

eee8ec5b

by Cheng Shao at 2026-07-14T18:00:20-04:00

compiler: fix miscompiled %load_relaxed, add missing %store_relaxed

This patch fixes the %load_relaxed cmm primop compilation logic to
correctly use relaxed memory ordering, and adds the missing
%store_relaxed primop. Parsing logic of %load/%store with explicit
ordering is covered in the AtomicFetch test case. Fixes #27483.

Co-authored-by: Codex <codex@openai.com>

1718230f

by Alan Zimmerman at 2026-07-14T18:01:06-04:00

EPA: Keep binds and sigs together in HsValBindsLR

We combine them into a single list for GhcPs, wrapped in the
ValBind data type, which is the bind equivalent of ValD, having
constructors for binds and sigs.

This simplifies exact print processing, especially when using it to
update the contents of local binds, as we no longer need AnnSortKey
BindTag

6bd1ad2a

by Andreas Klebinger at 2026-07-14T18:01:49-04:00

Bump nofib submodule to account for MonoLocalBinds.

New versions of GHC enable MonoLocalBinds by default.
This breaks some of the benchmarks. I've fixed this and
this bump pulls in that fix.

7eb0f1c9

by Cheng Shao at 2026-07-14T18:02:31-04:00

testsuite: fix bytecodeIPE test under +ipe flavours

This patch fixes the bytecodeIPE test under +ipe flavours. It used to
fail under +ipe because the RTS is built with IPE info, then
stg_AP_info in RTS carries IPE info, so whereFrom wouldn't return
Nothing. Now the test checks IPE info of a datacon in the ghci-loaded
module which is not affected by whether the RTS is built with IPE info
or not. Fixes #27498.

Co-authored-by: Codex <codex@openai.com>

ef038aae

by cydparser at 2026-07-15T04:35:41-04:00

Reduce bytes allocated for `capabilities` in RTS (fixes #27487)

In rts/Capability.c, `capabilities` is an array of pointers, but it was allocated as if it were an
array of Capability's.

d377e83e

by Cheng Shao at 2026-07-15T04:36:27-04:00

rts: fix missing UNTAG in stg_readTVarIOzh

This patch fixes missing UNTAG on the current value closure read from
StgTVar. UNTAG is a no-op when it's stg_TREC_HEADER_info which is word
aligned; it may be a tagged closure, and reading info table from the
tagged address is an unaligned load which may cause issues on
platforms with strict alignment requirements.

Co-authored-by: Codex <codex@openai.com>

8ed03842

by Cheng Shao at 2026-07-15T04:36:27-04:00

rts: fix missing UNTAG in stg_control0zh_ll

This patch fixes missing UNTAG on the cont closure returned by
captureContinuationAndAbort. In case it's not NULL,
captureContinuationAndAbort returns a tagged StgContinuation closure,
in which case it must be untagged before accessing the
apply_mask_frame field.

In the past it worked out of luck: when apply_mask_frame was NULL then
mask_frame_offset is also 0 so the control flow didn't diverge to a
wrong path. Still, this is horribly wrong and will crash once
StgContinuation struct is refactored and fields are shuffled around.

Co-authored-by: Codex <codex@openai.com>

5aa7000a

by Cheng Shao at 2026-07-15T04:37:08-04:00

compiler: fix redundant AP thunk codegen when not using -ticky-ap-thunk

This patch fixes a double negation confusion in !7525 that results in
some redundant AP thunk code generation when not using
-ticky-ap-thunk. Now, we use `stgToCmmUseStdApThunk` to indicate
whether precomputed AP thunks in the RTS should be used, which
defaults to `True`, unless `-ticky-ap-thunk` is passed.
`-finfo-table-map` now also implies `-ticky-ap-thunk`, since when
doing IPE profiling we want the generated AP thunks to be unique.
Fixes #27502.

-------------------------
Metric Decrease:
    T3064
-------------------------

Co-authored-by: Codex <codex@openai.com>

d43a7b7a

by Brian McKenna at 2026-07-15T20:10:04+02:00

Strip ticks when desugaring bool guards

The special `considerAccessible` pattern was broken when compiling
with debug info. Compiling with debug info wraps expressions with
`SourceNote` ticks, which broke the internals of the
`desugarBoolGuard` function. Ticks are now ignored within this
function.

Fixes #27360

ede4b17b

by Ben Gamari at 2026-07-15T22:59:53-04:00

base: Display ExceptionContext in WhileHandling's textual description

As originally-implemented the implementation for
`WhileHandling(displayExceptionAnnotation)` would display the
`ExceptionContext` of the exception which it carries (as this was the
behavior of `displayException`, in terms of which
`displayExceptionAnnotation` was implemented).

However, in 284ffab3 the definition of `SomeException(displayException)`
was changed to exclude the `ExceptionContext`. This means that
`WhileHandling(displayExceptionAnnotation)` fails to describe the
provenance of the exception which it captures, greatly limiting its
utility.

Return the implementation to its originally-specified behavior by
implementing `WhileHandling(displayExceptionAnnotation)` in terms of
`displayExceptionWithInfo`.

Fixes #27456.

0f64f348

by Cheng Shao at 2026-07-16T15:41:08+00:00

ci: add missing docker permission workaround in abi-test job

660cb239

by Cheng Shao at 2026-07-16T19:37:48+00:00

bindist: Fix make install -j race condition on macos/freebsd

This patch fixes make install -j race condition on macos/freebsd. BSD
install fails with EEXIST when multiple install processes concurrently
create the same prefix directory. So we add an `install_dirs`
prerequisite job that sequentially creates the directories for
subsequent jobs to work with. Fixes #27499.

Co-authored-by: Codex <codex@openai.com>

08130257

by Cheng Shao at 2026-07-16T19:37:48+00:00

ci: run bindist make install with -j

This patch makes the ci scripts run `make install` with `-j` to reduce
wall clock time when installing the bindist, see related issue for
benchmark numbers. This only affects ghc ci logic, the user-facing
default is up to distributors and is still `-j1`. Closes #27029.

d5ae6906

by Adam Gundry at 2026-07-17T04:57:43-04:00

Mark various language extension flags as deprecated (see #27329)

The following language extensions are now deprecated:

 - AlternativeLayoutRule
 - AlternativeLayoutRuleTransitional
 - ParallelArrays
 - PolymorphicComponents
 - Rank2Types

In addition, the warning `-Walternative-layout-rule-transitional`
has been marked as deprecated, as it is emitted only under the
deprecated extension `XAlternativeLayoutRuleTransitional`.

fe3b059c

by Andrew Lelechenko at 2026-07-17T04:58:26-04:00

base: re-export GHC.Environment.getFullArgs from System.Environment

CLC proposal https://github.com/haskell/core-libraries-committee/issues/431

722236dd

by sheaf at 2026-07-18T08:48:31-04:00

Coercion optimisation: avoid double-Sym for InstCo

Ticket #27374 pointed out an issue with GHC.Core.Coercion.Opt.optCoercion's
handling of InstCo: it contravened (LC2) in Note [The LiftingContext in optCoercion]
because it applied the ambient 'sym' to a coercion that was then added
to the lifting context substitution.

Fixes #27374

Co-authored-by: Simon Jakobi <simon.jakobi@gmail.com>

ff70fc75

by sheaf at 2026-07-18T08:48:31-04:00

Coercion optimisation: avoid exponential behaviour

The change to coercion optimisation of 'InstCo' in the previous commit
introduces exponential behaviour to the coercion optimiser. To avoid
this, this commit provides a way to push in 'Sym' of an already-optimised
coercion: GHC.Core.Coercion.Opt.mkDeepSymCo.

See Note [Pushing Sym without re-optimising] in GHC.Core.Coercion.Opt.

dfef27f0

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Move THREADED_RTS-conditional struct members to end of Capability

Accessing members of the Capability struct from CMM code rely on
accessor macros. (The macros are generated by deriveConstants).

These macros have a single definition. This means that the offsets of
all struct members must *not* vary based on THREADED_RTS vs
!THREADED_RTS. This requires that any struct members that are
conditional on THREADED_RTS must occur after the unconditional struct
members. Hence we move all the ones that are conditional on
THREADED_RTS to the end.

Add a deriveConstants entry for the iomgr member of the Capability
struct, which was the motivation for this change.

Add warning messages to help our future selves. Debugging this took me
a couple hours in gdb!

c254e022

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Make the IOManager API use CapIOManager rather than Capability

This makes the API somewhat more self-contained and more consistent.
Now the IOManager API and each of the backends takes just the I/O
manager structure. Previously we had a bit of a mixture, depending on
whether the function needed access to the Capability or just the
CapIOManager.

We still need access to the cap, so we introduce a back reference to
reach the capability, via iomgr->cap.

Convert all uses in select and poll backends, but not win32 ones.
Convert callers in the scheduler and elsewhere.

Also convert the three CMM primops that call IOManager APIs. They just
need to use Capability_iomgr(MyCapability()).

4f3d8f31

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Split posix/MIO.c out of posix/Signals.c

The MIO I/O manager was secretly living inside the Signals file.

Now it gets its own file, like any other self-respecting I/O manager.

52ce04a9

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Rationalise some scheduler run queue utilities

Move them all to the same place in the file.

Make some static that were used only internally.

Also remove a redundant assignment after calling truncateRunQueue that
is already done within truncateRunQueue.

75bbdebc

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Rename initIOManager{AfterFork} to {re}startIOManager

These are more accurate names, since these actions happen after
initialisation and are really about starting (or restarting) background
threads.

724c0517

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Free per-cap I/O managers during shutdown and forkProcess

Historically this was not strictly necessary. The select and win32
legacy I/O managers did not maintain any dynamically allocated
resources. The new poll one does (an auxillary table), and so this
should be freed.

After forkProcess, all threads get deleted. This includes threads
waiting on I/O or timers. So as of this patch, resetting the I/O
manager is just about tidying things up. For example, for the poll
I/O manager this will reset the size of the AIOP table (which
otherwise grows but never shrinks).

In future however the re-initialising will become neeecessary for
functionality, since some I/O managers will need to re-initialise
wakeup fds that are set CLOEXEC.

c007d122

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add a TODO to the MIO I/O manager

The direction of travel is to make I/O managers per-capability and have
all their state live in the struct CapIOManager. The MIO I/O manager
however still has a number of global variables.

It's not obvious how handle these globals however.

b65ab7b3
by Duncan Coutts at 2026-07-18T08:49:12-04:00
```
Add a FIXME note in the Poll I/O manager
```

daf2bd6f

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add missing updateRemembSetPushClosure in poll I/O manager

For the non-moving GC.

e33ca830

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Minor doc improvement to struct StgAsyncIOOp member outcome

Mention the enumeration names, as well as their numeric values. The rest
of the code uses the enum names.

4edd2579

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Minor doc improvements for StgTSOBlockInfo

Clarify that certain union members are used only by certain legacy
I/O managers. Hopefully we will be able to remove these at some point.

536bedbb

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Avoid exporting various win32-specific rts symbols

The BeginPrivate.h / EndPrivate.h scheme works perfectly well on
Windows, but all of the rts/win32/*.h files were not using it.

8139b5ac

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Remove wakeupIOManager, ioManagerWakeup and setIOManagerWakeupFd

We no longer need wakeupIOManager for the threaded RTS case, so we can
remove it and the bits only needed to support it. This includes the
pipe/eventfd fd shared between the RTS and the in-library I/O manager
used for waking up the I/O manager thread. The pipe/eventfd still
exists, but it no longer has to be communicated to the RTS, since the
RTS no longer needs to use it.

So we remove the RTS API export setIOManagerWakeupFd, and remove uses of
it within the I/O managers in ghc-internal.

74fe7c66

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add a new interruptIOManager API for the I/O managers

It will be used to interrupt awaitCompletedTimeoutsOrIO. Also update the
return type and docs for awaitCompletedTimeoutsOrIO to have it return
false when it gets interrupted, and have no useful post condition in
that case.

38792843

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for select I/O manager

Uses the FdWakup mechanism.

2f3b00aa

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for poll I/O manager

Uses the FdWakup mechanism.

A quirk we have to cope with is that we now need to poll one more fd --
the wakeup_fd_r -- but this fd has no corresponding entry in the
aiop_table. This is awkward since we have set up our aiop_poll_table to
be an auxilliary table with matching indicies.

The solution this patch uses (and described in the comments) is to have
two tables: struct pollfd *aiop_poll_table, *full_poll_table;
and to have the aiop_poll_table alias the tail of the full_poll_table.
The head entry in the full_poll_table is the extra fd. So we poll the
full_poll_table, while the aiop_poll_table still has matching indicies
with the aiop_table.

Hurrah for C aliasing rules.

cee50131

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for win32 legacy I/O manager

And remove unused related helper resetAbandonRequestWait. It is not
called because the event is created in auto-reset mode, so never needs
to be reset manually.

cf453143

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Note lack of interruptIOManager support for WinIO I/O manager

Though there's a plausible design, we can't sanely test it at the moment
due to related WinIO bugs. Filed as issue #27403.

1b74a0ad

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Be more explicit about enum IOReadOrWrite values, and type within cmm

Belt and braces.

b388d093

by Brian McKenna at 2026-07-18T17:51:50-04:00

Ignore ticks in the pattern-match term oracle

The term-oracle in the pattern-match checker is keyed by a canonical
form of the scrutinee, computed by `makeDictsCoherent`. That canonical
form was tick-sensitive: two occurrences of an otherwise identical
expression that happened to carry different ticks were treated as
distinct values, breaking long-distance information.

This shows up in practice under `-finfo-table-map`, because the
desugarer wraps every record-selector use site in a `SourceNote`
carrying that site's span. For example:

     data Box = Box { unBox :: Maybe Int }
     f b = case unBox b of
       Nothing -> 0
       Just _  -> let Just x = unBox b in x

The two `unBox b` expressionss carry different SourceNote spans, the
pattern-match checker sees them as different, the long-distance
information from the outer `Just _` branch never reaches the
let-pattern, and `Just x = unBox b` is wrongly reported as
non-exhaustive.

We now strip all ticks in `makeDictsCoherent`.  This is documented as
Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap].

Fixes #27314

c23e1acb

by Mrjtjmn at 2026-07-18T17:52:45-04:00

Add explanations for unsolved Typeable constraints

This commit adds explanations for unsolved 'Typeable' constraints.

GHC will now provide additional explanations for an unsolved constraint
of the form 'Typeable ty', explain why GHC did not solve Typeable constraint.
e.g.:
 - 'ty' is a polymorphic type (e.g. forall a. a -> a)
 - 'ty' is a qualified type (e.g. Eq Int => Int)
 - 'ty' is an unboxed sum type
 - 'ty' is an unreduced type family application
 - 'ty' whose kind is not typeable

Fixes #26532

cbef021e
by Artem Pelenitsyn at 2026-07-19T07:49:55-04:00
```
ghc-internal: Lock.hs: fix typo and indentation
```

42918646

by Duncan Coutts at 2026-07-19T07:50:36-04:00

Fix failing test GcStaticPointers for non-moving GC

Minor mistake in asserting something before checking for that same
thing.

Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used
prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to
move the use of Bdescr after the guard.

Thanks to Simon Jakobi for identifying the problem.

c2f6dcd4

by Sasha Bogicevic at 2026-07-20T10:31:56+02:00

Improve error messages for invalid record wildcards

Record wildcard hints are now shown in more contexts and include
constructor arity; matching with `..` on a fieldless constructor
now produces a dedicated error message.

Fixes #21101

4c02e76b

by Duncan Coutts at 2026-07-21T10:37:21-04:00

Mark test T27105 as fragile, citing issue #27522

Scheduler fairness is fine, except when it isn't. And it isn't on CI
machines surprisingly often! See the issue for details.

43dd2b15

by Recursion Ninja at 2026-07-21T17:09:53-04:00

Resolving many TTG related orphan type-class instances

This is part a technical debt removal effort made possible now
that separating out the AST via TTG has come to a close.

As the AST in 'L.H.S' has been incrementally separated from the GHC internals,
there are many accumulated orphan instance of 'Binary', 'NFData', 'Outputable',
and 'Uniquable'. The orphan instance of data-types from within 'L.H.S' have had
their orphan instances moved to either:
  1. The module which defines the data-type
  2. The module which defines the type-class;
     i.e. moving an orphan 'Binary' instance to 'GHC.Utils.Binary'

Orphan instances resolved (37):

  | Data-type            | Resolved instance(s)       | Former orphan module(s)   |
  | -------------------- | -------------------------- | ------------------------- |
  | Role                 | Binary, NFData, Outputable | GHC.Core.Coercion.Axiom   |
  | SrcStrictness        | Binary, NFData, Outputable | GHC.Core.DataCon          |
  | SrcUnpackedness      | Binary, NFData, Outputable | GHC.Core.DataCon          |
  | Fixity               | Binary, Outputable         | GHC.Hs.Basic              |
  | FixityDirection      | Binary, Outputable         | GHC.Hs.Basic              |
  | LexicalFixity        | Outputable                 | GHC.Hs.Basic              |
  | CCallTarget          | NFData                     | GHC.Hs.Decls.Foreign      |
  | CType                | NFData                     | GHC.Hs.Decls.Foreign      |
  | Header               | NFData                     | GHC.Hs.Decls.Foreign      |
  | OverlapMode          | Binary, NFData             | GHC.Hs.Decls.Overlap      |
  | WithHsDocIdentifiers | NFData, Outputable         | GHC.Hs.Doc                |
  | HsDocString          | NFData                     | GHC.Hs.DocString          |
  | HsDocStringChunk     | Binary, Outputable         | GHC.Hs.DocString          |
  | HsDocStringDecorator | Binary, Outputable         | GHC.Hs.DocString          |
  | NamespaceSpecifier   | Outputable                 | GHC.Hs.ImpExp             |
  | ForAllTyFlag         | Binary, NFData, Outputable | GHC.Hs.Specificity        |
  | Specificity          | Binary, NFData             | GHC.Hs.Specificity        |
  | PromotionFlag        | Binary, Outputable         | GHC.Types.Basic           |
  | FieldLabelString     | Outputable, Uniquable      | GHC.Types.FieldLabel      |
  | InlinePragma         | Binary                     | GHC.Types.InlinePragma    |

-------------------------
Metric Decrease:
    hard_hole_fits
-------------------------

Closes #21262, #27469

ab9ab895

by Cheng Shao at 2026-07-21T17:10:53-04:00

rts: always use StgInt to represent cost center id

Currently cost center id is modeled as `Int` and it should be `StgInt`
uniformly in the RTS, hence this patch. Fixes #27524.

94d8f83b

by Cheng Shao at 2026-07-22T11:30:40-04:00

hadrian: clean up stale cabal package flags in the tree

This patch cleans up stale cabal package flags in the tree and related
hadrian/autoconf logic. Closes #27474.

Co-authored-by: Codex <codex@openai.com>

0bf1d8c9

by Sasha Bogicevic at 2026-07-22T11:31:21-04:00

parser: don't suggest ImportQualifiedPost when it is already enabled

-Wprepositive-qualified-module unconditionally attached a hint to
enable ImportQualifiedPost, even when the extension was already on
(as it is by default under GHC2021). Record the extension's state in
the PsWarnImportPreQualified diagnostic and drop the hint when it is
already enabled.

Fixes #27380

700a1dd1

by Simon Jakobi at 2026-07-23T11:21:20-04:00

ci: Reduce lint job setup costs

Avoid fetching unnecessary history and submodules for lightweight lint
jobs. Run changelog validation without Hadrian.

Because the lint-author job is now based on the .lint template directly,
we enhance it to allow Git to read from the runner-owned checkouts,
In the previously used .lint-params template, this permissions issue was
addressed via `chown`.

Closes #27521.

Assisted-by: gpt-5.6-sol via Codex CLI

26a44fb0

by ARATA Mizuki at 2026-07-23T11:22:10-04:00

testsuite: Fix memory issues of doublex2_* and simd010

doublex2_* had reads from uninitialized memory.

simd010 had out-of-bounds array access.

Fixes #27544

4d798b17