Unacceptable result type in FFI

[David Waern]

2008/11/17 Neal Alexander <wqeqweuqy at hotmail.com>:
> Graphics/Rendering/OGL/GL/FlushFinish.hs:39:0:
>    Unacceptable result type in foreign declaration: GL ()
>    When checking declaration:
>        foreign import ccall unsafe "static  &glFlush" flush :: GL ()
>
> Graphics/Rendering/OGL/GL/FlushFinish.hs:47:0:
>    Unacceptable result type in foreign declaration: GL ()
>    When checking declaration:
>        foreign import ccall unsafe "static  &glFinish" finish :: GL ()
> haddock: Failed to check module: Graphics.Rendering.OGL.GL.FlushFinish
>
> -------------
>
> The error message is the same as what GHC would give without
> -XGeneralizedNewtypeDeriving.

Hm, if you don't turn on GeneralizedNewtypeDeriving with GHC,
shouldn't it fail earlier on the definition of the newtype that you
are deriving things for?

> full log here:
>
> http://hackage.haskell.org/packages/archive/OGL/0.0.0/logs/failure/ghc-6.10
>
> David Waern wrote:
>>
>> 2008/11/16 Neal Alexander <wqeqweuqy at hotmail.com>:
>>>
>>> How do you get Haddock 2.4 to handle the return type of an FFI function
>>> that
>>> isnt "IO". It works automatically in the haddock version that ships with
>>> ghc
>>> 6.8.1.
>>>
>>> I tried:
>>>
>>> haddock --haddock-options=--optghc=-XGeneralizedNewtypeDe
>>> riving

You should not pass --haddock-options to haddock itself. It's used to
tell Cabal which options to give to Haddock. So the right line would
be:

> haddock --optghc=-XGeneralizedNewtypeDeriving

David