On 8/18/2011 6:49 AM, Antoine Latter wrote:
Hi Haskell,
I have a question about the Haskell FFI and creating FunPtrs to Haskell functions.
Does anyone have any recommendations for when I have a top-level function that I would like to pass to a C function as a function pointer (that is called via a foreign import)?
I know that the FFI provides the "wrapper" foreign import I can use to wrap Haskell functions, but then I would need to jump through hoops to manage the liefetime of of the FunPtr wrapper. If I were closing over interesting state I would want this - but the function (side-effectfully) operates only on its arguments (and the Haskell RTS, of course).
Is it "okay" to place an "unsafePerformIO $ mkWrapper myFunc" as a top-level declaration, or am I journeying into uncharted lands?
Is there something clever I can do with foreign exports and foreign imports, or is this just making things too complex?
Thanks, Antoine
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You can export and reimport the same function with no "wrapper" needed. For example: foreign export ccall foo :: ... foreign import ccall "& foo" fooptr :: FunPtr (...) Cheers, Kyra