FFI: "capi" calling convention doesn't work

[guest]

According to http://www.haskell.org/ghc/docs/7.6.1/html/users_guide/ffi.html#ffi-capi there is a capi calling convention, but ghc disagrees:

% cat capi.hs 
{-# LANGUAGE ForeignFunctionInterface #-}

import Foreign.C

foreign import capi "math.h value M_PI" mPI :: CDouble

main :: IO ()
main = print mPI

% ghc capi.hs
[1 of 1] Compiling Main             ( capi.hs, capi.o )

capi.hs:5:16: parse error on input `capi'

Is the documentation wrong?

[simonmar]

You need to add CAPI to your LANGUAGE pragma.

[guest]

I did but ghc doesn't accept it:

% cat capi.hs
{-# LANGUAGE ForeignFunctionInterface, CAPI #-}

import Foreign.C

foreign import capi "math.h value M_PI" mPI :: CDouble

main :: IO ()
main = print mPI

% ghc capi.hs

capi.hs:1:40: Unsupported extension: CAPI

[thoughtpolice]

The docs are wrong. The extension is actually called CApiFFI, and your example works if you use that instead of CAPI.

This should be fixed in the users manual and merged into 7.6.2 I think. I'll fix it in HEAD with this bug as the ticket.

[thoughtpolice]

Nevermind; this was already fixed a while back:

Author: shelarcy <shelarcy@gmail.com>
Date:   Tue Oct 2 17:10:13 2012 +0900

    Fix typo in the documentation of CApiFFI
    
    Signed-off-by: Gabor Greif <ggreif@gmail.com>