Problem z linkerem GHCi podczas wykonywania deklaracji FFI

Question

May 18, 2012, 08:44 PM

Problem z linkerem GHCi podczas wykonywania deklaracji FFI

Mam problem z FFI w Haskell i interaktywnym trybie GHCjeszcze raz.

RozważaćFFISo.hs:

{-# LANGUAGE OverloadedStrings #-}
module Main where

import qualified Data.ByteString.Char8 as B

import FFIFun.Foo

main :: IO ()
main = do
  B.putStrLn "main"
  callMeFromC
  callMeFromHaskell
  return ()

c.c:

#include <stdio.h>

void callMeFromC(void);

void callMeFromHaskell(void)
{
    printf("callMeFromHaskell\n");
    callMeFromC();
}

FFIFun/Foo.hs:

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ForeignFunctionInterface #-}
module FFIFun.Foo where

import qualified Data.ByteString.Char8 as B

foreign import ccall "callMeFromHaskell"
  callMeFromHaskell :: IO ()

foreign export ccall callMeFromC :: IO ()
callMeFromC :: IO ()
callMeFromC = B.putStrLn "callMeFromC"

i aMakefile:

SHELL := bash

GHC_OPT := -Wall -O2 -fno-warn-unused-do-bind


all: ffiso

test: ffiso
    ./$<

ffiso: FFISo.hs c.c
    ghc --make $(GHC_OPT) $^ -o $@

clean:
    rm -rf *{.hi,o,_stub.*} ffiso FFIFun/*{.hi,.o,_stub.*}

ghci: ffiso
    ghci -package bytestring FFIFun/Foo.o c.o FFISo.hs

ty też to znajdziesztutaj jako istota.

Więc mój problem:

$ make ghci
[...]
Ok, modules loaded: Main, FFIFun.Foo.
Prelude Main> -- fine, it's loading.
Prelude Main> :t callMeFromC

<interactive>:1:1: Not in scope: `callMeFromC'
Prelude Main> -- uhm, why?
Prelude Main> :t main
main :: IO ()
Prelude Main> main


GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   FFIFunziFoo_callMeFromC_info
whilst processing object file
   ./FFIFun/Foo.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

Hrmpf, co tu jest nie tak? Co ciekawe, mam inny błądi686 (powyżej, to jestx86_64 system, ale oba GHC 7.4.1):

GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   __stginit_FFIFunziFoo
whilst processing object file
   ./FFIFun/Foo.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

Czy jest też jakaś dokumentacja na ten temat? Czuję, że jestem jedynym, który ma ciężkie czasy z FFI i GHCi.

edytuj: zauważ, żemake test działa w porządku:

$ ghc --make -Wall -O2 -fno-warn-unused-do-bind FFISo.hs c.c -o ffiso
[1 of 2] Compiling FFIFun.Foo       ( FFIFun/Foo.hs, FFIFun/Foo.o )
[2 of 2] Compiling Main             ( FFISo.hs, FFISo.o )
Linking ffiso ...
./ffiso
main
callMeFromC
callMeFromHaskell
callMeFromC

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