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Simon Peyton Jones pushed to branch wip/T26548 at Glasgow Haskell Compiler / GHC

Commits:

5cdcfaed

by Ben Gamari at 2025-11-06T09:01:36-05:00

compiler: Exclude units with no exposed modules from unused package check

Such packages cannot be "used" in the Haskell sense of the word yet
are nevertheless necessary as they may provide, e.g., C object code or
link flags.

Fixes #24120.

74b8397a
by Brandon Chinn at 2025-11-06T09:02:19-05:00
```
Replace deprecated argparse.FileType
```
36ddf988
by Ben Gamari at 2025-11-06T09:03:01-05:00
```
Bump unix submodule to 2.8.8.0

Closes #26474.
```

c32b3a29

by fendor at 2025-11-06T09:03:43-05:00

Fix assertion in `postStringLen` to account for \0 byte

We fix the assertion to handle trailing \0 bytes in `postStringLen`.
Before this change, the assertion looked like this:

    ASSERT(eb->begin + eb->size > eb->pos + len + 1);

Let's assume some values to see why this is actually off by one:

    eb->begin = 0
    eb->size  = 1
    eb->pos   = 0

    len       = 1

then the assertion would trigger correctly:

    0 + 1 > 0 + 1 + 1 => 1 > 2 => false

as there is not enough space for the \0 byte (which is the trailing +1).
However, if we change `eb->size = 2`, then we do have enough space for a
string of length 1, but the assertion still fails:

    0 + 2 > 0 + 1 + 1 => 2 > 2 => false

Which causes the assertion to fail if there is exactly enough space for
the string with a trailing \0 byte.

Clearly, the assertion should be `>=`!
If we switch around the operand, it should become more obvious that `<=`
is the correct comparison:

    ASSERT(eb->pos + len + 1 <= eb->begin + eb->size);

This is expresses more naturally that the current position plus the
length of the string (and the null byte) must be smaller or equal to the
overall size of the buffer.

This change also is in line with the implementation in
`hasRoomForEvent` and `hasRoomForVariableEvent`:

  ```
  StgBool hasRoomForEvent(EventsBuf *eb, EventTypeNum eNum)
  {
    uint32_t size = ...;
    if (eb->pos + size > eb->begin + eb->size)
    ...
  ```

the check `eb->pos + size > eb->begin + eb->size` is identical to
`eb->pos + size <= eb->begin + eb->size` plus a negation.

3034a6f2
by Ben Gamari at 2025-11-06T09:04:24-05:00
```
Bump os-string submodule to 2.0.8
```

39567e85

by Cheng Shao at 2025-11-06T09:05:06-05:00

rts: use computed goto for instruction dispatch in the bytecode interpreter

This patch uses computed goto for instruction dispatch in the bytecode
interpreter. Previously instruction dispatch is done by a classic
switch loop, so executing the next instruction requires two jumps: one
to the start of the switch loop and another to the case block based on
the instruction tag. By using computed goto, we can build a jump table
consisted of code addresses indexed by the instruction tags
themselves, so executing the next instruction requires only one jump,
to the destination directly fetched from the jump table.

Closes #12953.

93fc7265

by sheaf at 2025-11-06T21:33:24-05:00

Correct hasFixedRuntimeRep in matchExpectedFunTys

This commit fixes a bug in the representation-polymormorphism check in
GHC.Tc.Utils.Unify.matchExpectedFunTys. The problem was that we put
the coercion resulting from hasFixedRuntimeRep in the wrong place,
leading to the Core Lint error reported in #26528.

The change is that we have to be careful when using 'mkWpFun': it
expects **both** the expected and actual argument types to have a
syntactically fixed RuntimeRep, as explained in Note [WpFun-FRR-INVARIANT]
in GHC.Tc.Types.Evidence.

On the way, this patch improves some of the commentary relating to
other usages of 'mkWpFun' in the compiler, in particular in the view
pattern case of 'tc_pat'. No functional changes, but some stylistic
changes to make the code more readable, and make it easier to understand
how we are upholding the WpFun-FRR-INVARIANT.

Fixes #26528

c052c724

by Simon Peyton Jones at 2025-11-06T21:34:06-05:00

Fix a horrible shadowing bug in implicit parameters

Fixes #26451.  The change is in GHC.Tc.Solver.Monad.updInertDicts
where we now do /not/ delete /Wanted/ implicit-parameeter constraints.

This bug has been in GHC since 9.8!  But it's quite hard to provoke;
I contructed a tests in T26451, but it was hard to do so.

b253013e

by Georgios Karachalias at 2025-11-07T17:21:57-05:00

Remove the `CoreBindings` constructor from `LinkablePart`

Adjust HscRecompStatus to disallow unhydrated WholeCoreBindings
from being passed as input to getLinkDeps (which would previously
panic in this case).

Fixes #26497

ac7b737e

by Sylvain Henry at 2025-11-07T17:22:51-05:00

Testsuite: pass ext-interp test way (#26552)

Note that some tests are still marked as broken with the ext-interp way
(see #26552 and #14335)

3c2f4bb4