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rts_getThreadId: fix return type on newer GHCs #263

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amesgen
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@amesgen amesgen commented Jan 4, 2023

Found via the GHC WASM backend: https://gitlab.haskell.org/ghc/ghc/-/issues/22617#note_470653

Also see https://hackage-search.serokell.io/?q=rts_getThreadId for other packages doing the same thing.

@@ -763,7 +769,15 @@ hashThreadId (ThreadId t) = hash (fromIntegral (getThreadId t) :: Int)

-- this cannot be capi, as GHC panics.
foreign import ccall unsafe "rts_getThreadId" getThreadId
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@phadej phadej Jan 4, 2023

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is rts_getThreadId exported from some header? Could you change that to ccall to capi (with CApiFFI).

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Ah, crap. It cannot be capi as GHC panics, but does even GHC-9.4 panic still? It does :( https://gitlab.haskell.org/ghc/ghc/-/issues/22705

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If I change it to capi, I get

ghc: panic! (the 'impossible' happened)
  (GHC version 9.2.4:
	toCType
  ThreadId#
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/GHC/Utils/Panic.hs:181:37 in ghc:GHC.Utils.Panic
        pprPanic, called at compiler/GHC/HsToCore/Foreign/Decl.hs:763:17 in ghc:GHC.HsToCore.Foreign.Decl

which seems to be consistent with the comment

-- this cannot be capi, as GHC panics.

you added in #213.

@phadej phadej merged commit ee10c3d into haskell-unordered-containers:master Jan 4, 2023
@amesgen amesgen deleted the fix-rts_getThreadId-return-type branch January 4, 2023 17:11
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 25, 2023
Version 1.4.2.0
* Fix the foreign signature of getThreadId
  haskell-unordered-containers/hashable#263
* Drop support for GHCs prior GHC-8.2 The recent unordered-containers
  releases support only GHC-8.2+
* Add instance for OsString, PosixString, WindowsString from
  filepath-1.4.100.1
* Add Hashable ByteArray instance using data-array-byte compat package
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2 participants