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Simon Peyton Jones pushed to branch wip/T26989 at Glasgow Haskell Compiler / GHC

Commits:

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