[Haskell-cafe] creating dll fails: missing references

[Phyx]

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 <K.Bleijenberg at lijbrandt.nl>
wrote:

> 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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