You're calling gcc my hand, which means you have to tell it which packages
your source need.
Pass it "-package directory" and it should work.
Tamar
Sent from my Mobile
On Tue, Jun 11, 2019, 11:57 Kees Bleijenberg
HI all,
I try to create a dll with ghc (ver 8.6.5) on Windows 7 64 bits. I ‘am using the dll with loadLibrary in a cpp program in Visual Studio. I create the dll with:
ghc Vogels.hs
ghc -c StartEnd.c
ghc --make -static -shared -fPIC Vogels.o StartEnd.o -o Vogels.dll
StartEnd.o defines HsStart and HsEnd to initialize and close the Haskell runtime.
This works. I can create the dll and use the dll in VS.
But, if I replace in Vogels.hs the line b=True with b <- doesFileExist vogelsFn, creating the dll fails with error message:
Vogels.o:fake:(.text+0x35c): undefined reference to `directoryzm1zi3zi3zi2zmB9tglvOQ6L9Cf7zzVEJ1S6t_SystemziDirectory_doesFileExist_closure'
Vogels.o:fake:(.text+0x37d): undefined reference to `directoryzm1zi3zi3zi2zmB9tglvOQ6L9Cf7zzVEJ1S6t_SystemziDirectory_doesFileExist_closure'
Vogels.o:fake:(.data+0xd0): undefined reference to `directoryzm1zi3zi3zi2zmB9tglvOQ6L9Cf7zzVEJ1S6t_SystemziDirectory_doesFileExist_closure'
It looks like GHC can’t find the Directory package. I’ve installed this package. What can I do about it and how can I find out the dependencies in a *.hs or *.o file? Almost all documentation about dll’s is about Linux or about using dll’s in Haskell.
Kees
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE ForeignFunctionInterface #-}
module Vogels (
loadVogels
) where
import System.Directory
import Foreign.Ptr
import Foreign.Storable
import Foreign.C.String
loadVogels :: String -> IO (Either String String)
loadVogels vogelsFn = do
-- b <- doesFileExist vogelsFn
let b=True
if b
then return $ Left $ "Can\'t find " ++ vogelsFn
else do
txt <- readFile vogelsFn
return $ Right txt
loadVogelsFFI :: Ptr Int -> CString -> IO CString
loadVogelsFFI messageKind vogelsFnFFI = do
vogelsFn <- peekCString vogelsFnFFI
eitherRes <- loadVogels vogelsFn
case eitherRes of
Left errMsg -> do
poke messageKind 1
newCString errMsg
Right txt -> do
poke messageKind 0
newCString txt
foreign export ccall loadVogelsFFI :: Ptr Int -> CString -> IO CString
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