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8d49ed42
by Kazu Yamamoto at 2026-10-06T19:37:25-04:00
Do not leave standard file descriptors free at startup (#24450)
A process may be started with stdout closed -- `prog >&-` from a shell does
exactly that. Nothing then reserves descriptor 1, and open(), pipe() and
socket() hand out the lowest free descriptor, so the next descriptor the
runtime creates for itself takes it: the ticker's pipe, or a capability's IO
manager control pipe.
'GHC.Internal.IO.StdHandles.stdout' is a CAF, built the first time the program
writes to stdout, which is long after that has happened. It builds a 'Handle'
over descriptor 1, which now belongs to the runtime, and nothing reports an
error because the descriptor is perfectly good. The program then writes its
output into the runtime's own plumbing.
What that looks like from the outside is a hang. The descriptor the Handle has
taken over is the read end of a pipe, so poll() for POLLOUT on it never says
yes and epoll_ctl() accepts a registration for it; the thread waiting to write
blocks for ever. Closing the Handle at exit closes the runtime's descriptor,
which is worse: the ticker then fails on every tick.
'hs_init_ghc' now opens /dev/null onto whichever of descriptors 0, 1 and 2 are
closed, before the runtime creates any descriptor of its own. Each is opened
for the access that descriptor would normally have, read-only for 0 and
write-only for 1 and 2, so that writing to 'stdin' or reading from 'stdout'
still fails rather than quietly succeeding against /dev/null. See
Note [Standard file descriptors must be open].
Moving only the descriptors the runtime opens would not do: the first file the
program itself opened would land on the free number instead. The fix has to
leave no free number. A program run this way therefore finds stdout connected
to /dev/null rather than failing with EBADF on the first write, which is what
such a program would get from most other language runtimes.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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65bcf9e9
by Simon Jakobi at 2026-10-06T19:38:09-04:00
changelog: Repair the sentence describing #27477
The description read "programs using could crash", the object of
"using" having been lost. The synopsis already says which programs are
affected, so drop the dangling word.
Assisted-by: Claude Fable 5.1
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15ece296
by mangoiv at 2026-10-08T15:14:56-04:00
ci: move hadrian/ghci into the lint category so it can be picked up by more runners
Fixes #27817
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c0823135
by mangoiv at 2026-10-08T15:14:56-04:00
ci: make lint-adjacent jobs into platform independent
- move lint jobs into lint-anyarch tag
- unify lint jobs under the same platform independent container
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f76464cf
by Zubin Duggal at 2026-10-08T15:15:39-04:00
DmdAnal: Make AbsDmd neutral in maxDmd
fixes #27845
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ffa56ae4
by sheaf at 2026-10-09T17:15:59+02:00
Preserve sign of zero when parsing -0.0#
This commit leverages the recently added GHC.Types.Literal.Floating
module in order to preserve the sign of negative zero from
source-written floating-point literals.
Fixes #27545
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d538cac9
by Facundo Domínguez at 2026-10-09T20:26:38-04:00
Propagate annotations to simple interfaces
This allows annotations to be visible to plugins when run by
haddock. The LiquidHaskell plugin needs the annotations, in particular.
Fixes #26761
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32c4f4ab
by meooow25 at 2026-10-09T20:27:28-04:00
Bump containers submodule to 0.8.1
And fix affected tests.
* T4086a: containers depends on template-haskell-lift now instead of
template-haskell.
* T22611: Updated to be less dependent on containers internals.
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c786065e
by sheaf at 2026-10-09T20:28:20-04:00
Use an explicit pattern match in toIfaceIdDetails
The old wildcard pattern let this code bit rot: it did not properly account
for recently added 'IdDetails' such as 'RepPolyId', which resulted in
spurious 'pprTrace' messages that could even pollute HLS sessions.
Fixes #23785
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e7cacf59
by sheaf at 2026-10-09T20:29:09-04:00
Take into account ifKind in freeNamesIfDecl
Commit 3c2f4bb4 added the 'ifKind' field to various constructors
of 'IfaceDecl', which preserves the original kind (before type synonym
expansion) for better error messages.
However, that commit forgot to update 'freeNamesIfDecl' correspondingly.
This could result in a "urk! lookup local fingerpring" crash when e.g.
a type's kind uses a type synonym defined later, as we failed to add a
dependency on the type synonym during dependency analysis.
Fixes #27916
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41e80f41
by Simon Peyton Jones at 2026-10-11T14:38:51-04:00
Simplify the error-suppression mechanism in GHC.Tc.Errors
In `GHC.Tc.Errors.reportWanteds` we suppress some errors in favour of
others. But the mechanism had grown crufty, and #27331 exposed a bug.
This MR makes it simpler and more uniform, by doing everything via
the `ei_suppress` field of the ErrorItem.
Claude then found another closely-related bug (see the review linked
on !16564). That bug is immortalised in new test T18851d.
I'm still not happy with `ignoreConstraint` but we can worry about
that another day; I have not touched it.
Main changes
* Instead of /predicting/ when an error will be reported, we set
`cec_error_reported` when an error is /actually/ reported. (I renamed
it from `cec_suppress` to reflect this change.)
Now errors are suppressed only when a preceding error has actually been
reported. Simpler and more robust.
See `Note [cec_error_reported: suppressing less-serious errors]`
The big changes are in `reportWanteds` which looks very different.
* New `Note [ei_suppress: suppressing confusing errors]` describes the
(quite separate) `ei_suppress` mechanism for suppressing confusing
errors, mainly arising from non-empty rewriter sets
* In `tryTypeClassDefaulting`, instead of switching off type-class defaulting
if there is an insoluble /anywhere/, we just switch it off locally when
we find an insoluble sub-tree. See Note [When to do type-class defaulting]
and (W5) in Note [ApproximateWC]
* Greatly simplify `insolubleWantedCt`.
* I made type-class-defaulting be a bit more eager, only switched off when
a peer or ancestor (but not child) constraint is insoluble. See
Note [When to do type-class defaulting].
Small refactorings
* Rename `askNoErrs` to `askErrsFound` and flip its polarity
* The code for "check if ei_suppress is true of all items" code is
moved to `mkErrorItems` rather than in the large `reportWanteds`.
* Code for `has_gadt_match` moves to `mkGivenErrorReporter`, rather than
polluting the large `reportWanteds`.
* Many tests with `-fdefer-type-errors` get more warnings, especially
about ambiguous (Num a) constraints. This is by-design: see
Note [Always warn with -fdefer-type-errors]. Previously GHC was not
honouring this Note but now it is, hence the extra errors.
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f217fc31
by Cheng Shao at 2026-10-11T14:39:33-04:00
compiler: ensure cross ghc --info output target unit ids
Previously, for cross ghcs, the base/ghc/ghc-internal unit ids in
--info output do not match the target unit ids reported by ghc-pkg,
breaking cross ghc release builds with hash-unit-ids when being used
with cabal 3.18. This patch fixes it by making --info output target
unit ids. Fixes #27919.
Co-authored-by: Codex <codex@openai.com>
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fe0825de
by Andrea Vezzosi at 2026-10-13T15:45:14+02:00
add runGhcWithSignalHandlers and remove handling from runGhc[T]
it only ever makes sense to call `withSignalHandlers` from `main`, otherwise
signals can be too easily swallowed without notification to the rest of your
process.
This commit takes withSignalHandlers out of `runGhc/runGhcT` and provides
`runGhcWithSignalHandlers` for the old behaviour.