I don't know. Since CInt is just a newtype wrapper around Int32, at the moment it seems limited to that. I'm not sure about the actual data structure that's being read from though. Int64 (or Word64) seems more appropriate since it's certainly possible to fork more than 4 billion threads in the lifetime of one haskell application. But my guess is that it's currently just backed by Int32.

On Wed, Nov 1, 2017 at 1:04 PM, David Feuer <david.feuer@gmail.com> wrote:

If there some concern a ThreadId could be bigger than an Int somewhere/somewhen? Should it be Int64? Or could it be variable size, suggesting whatever it is that backs SmallByteString?

On Nov 1, 2017 10:54 AM, "Andrew Martin" <andrew.thaddeus@gmail.com> wrote:
ThreadId has a Show instance that makes uses the FFI to turn a ThreadId to a CInt:

instance Show ThreadId where
showsPrec d t =
showString "ThreadId " .
showsPrec d (getThreadId (id2TSO t))

foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> CInt

Can getThreadId be exported? This would make it possible to write a Hashable instance for ThreadId, and it would make it possible to use a ThreadId to index into an array (with modulus of course).

-Andrew Thaddeus Martin

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-Andrew Thaddeus Martin