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rts_getThreadId: fix return type on newer GHCs by amesgen · Pull Request #263 · haskell-unordered-containers/hashable · GitHub
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rts_getThreadId: fix return type on newer GHCs #263

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phadej merged 1 commit into from
Jan 4, 2023
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rts_getThreadId: fix return type on newer GHCs #263

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14 changes: 14 additions & 0 deletions src/Data/Hashable/Class.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -126,7 +126,13 @@ import Data.Typeable.Internal (Typeable, TypeRep (..))
import GHC.Fingerprint.Type(Fingerprint(..))
#endif

#if __GLASGOW_HASKELL__ >= 904
import Foreign.C.Types (CULLong(..))
#elif __GLASGOW_HASKELL__ >= 900
import Foreign.C.Types (CLong(..))
#else
import Foreign.C.Types (CInt(..))
#endif

#if !(MIN_VERSION_base(4,8,0))
import Data.Word (Word)
Expand Down Expand Up @@ -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

@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).

@phadej phadej Jan 4, 2023

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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

@amesgen amesgen Jan 4, 2023

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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

hashable/src/Data/Hashable/Class.hs

Line 764 in 18138a1

-- this cannot be capi, as GHC panics.

you added in #213.

#if __GLASGOW_HASKELL__ >= 904
-- https://gitlab.haskell.org/ghc/ghc/-/merge_requests/6163
:: ThreadId# -> CULLong
#elif __GLASGOW_HASKELL__ >= 900
-- https://gitlab.haskell.org/ghc/ghc/-/merge_requests/1254
:: ThreadId# -> CLong
#else
:: ThreadId# -> CInt
#endif

instance Hashable ThreadId where
hash = hashThreadId
Expand Down