[Haskell-beginners] Compiling shared (dll) library

5 Dec 2011

      Hi, Haskellers.

I'm trying to compile following program (where Regex.Genex is a package
what I need to produce all possible expresions by the given pattern and
`adder' is just FFI sample):

-- genexlib.hs
{-# LANGUAGE BangPatterns, ForeignFunctionInterface #-}

module GenexLib where

import Regex.Genex
import System.IO
import System.Environment

adder :: Int -> Int -> IO Int  -- gratuitous use of IO
adder x y = return (x+y)
foreign export stdcall adder :: Int -> Int -> IO Int
-- genexlib.hs end

// start.c
#include <Rts.h>

void HsStart()
{
   int argc = 1;
   char* argv[] = {"ghcDll", NULL}; // argv must end with NULL

   // Initialize Haskell runtime
   char** args = argv;
   hs_init(&argc, &args);
}

void HsEnd()
{
   hs_exit();
}
// start.c end

I'm using ghc
...
ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.0.2
compiling:
...
ghc -c genexlib.hs
ghc -c start.c
ghc -shared -o genexlib.dll genexlib.o genexlib_stub.o start.o
genexlib.o:fake:(.text+0xd1): undefined reference to
`__stginit_regexzmgenexzm0zi3zi2_RegexziGenex_'
Creating library file: genexlib.dll.a
collect2: ld returned 1 exit status
and get undefined reference.

But If I try to compile the executable from similar code:

-- genexlib.hs
{-# LANGUAGE BangPatterns, ForeignFunctionInterface #-}

-- module GenexLib where

import Regex.Genex
import System.IO
import System.Environment

defaultRegex :: String
defaultRegex = "a(b|c)d{2,3}e*"

main :: IO ()
main = do
    hSetBuffering stdout NoBuffering
    args <- getArgs
    case args of
        [] -> do
            prog <- getProgName
            if prog == "<interactive>" then run [defaultRegex] else do
                fail $ "Usage: " ++ prog ++ " regex [regex...]"
        rx -> run rx

run :: [String] -> IO ()
run regex = do
  let s = genexPure regex
  mapM_ print s
-- genexlib.hs end
...
ghc --make genexlib.hs -O2
it's ok, no errors, and you can see in GHCi:
*Main> :main
"abdd"
"acdd"
"abddd"
"acddd"
"abddeee"
"acddeee"
"abdddeee"
"acdddeee"
"abddee"
"acddee"
"abdddee"
"acdddee"
"abdde"
"acdde"
"abddde"
"acddde"

Where is my mistake? What am I doing wrong?
In first case, when compiling shared dll, I tried to link libraries what
I've found in `cabal' directory (like `libHSregex-genex-0.3.2.a') to work
around errors but all in vain.

--
Alexander Popov

[Haskell-beginners] Compiling shared (dll) library

Alexander.Vladislav.Popov