I am trying to use FFI to access some windows console functions via two simple C functions I created. Essentially my module looks like is this: {-# CFILES mouse.c #-} {-# LANGUAGE ForeignFunctionInterface #-} module Mouse where -- import Foreign import Foreign.C.Types foreign import ccall unsafe "mouse.h SetupConsole" c_setupConsole :: IO CInt foreign import ccall unsafe "mouse.h MouseEvent" c_mouseEvent :: IO CInt setupConsole :: IO Bool setupConsole = do c <- c_setupConsole return $ if c == 0 then True else False mouseEvent :: IO (Maybe (Int, Int)) mouseEvent = do c <- c_mouseEvent let d = toInteger c let e = (fromInteger d)::Int return $ if e < 0 then Nothing else Just (e `mod` 256, e `div` 256) It seems to compile fine. The problem comes when I need to link. Linking dist\build\BoardGames\BoardGames.exe ... dist\build\BoardGames\BoardGames-tmp\Mouse.o:fake:(.text+0x15): undefined reference to `SetupConsole' dist\build\BoardGames\BoardGames-tmp\Mouse.o:fake:(.text+0x11d): undefined reference to `MouseEvent' collect2: ld returned 1 exit status The problem seems obvious - it isn't compiling OR linking mouse.c which is this: #include <windows.h> int SetupConsole() { HANDLE hStdin; DWORD fdwMode, fdwSaveOldMode; int counter=0; hStdin = GetStdHandle(((DWORD)-10)); if (hStdin == ((HANDLE)(LONG_PTR)-1)) return -3; if (! GetConsoleMode(hStdin, &fdwSaveOldMode) ) return -2; fdwMode = 0x0010; if (! SetConsoleMode(hStdin, fdwMode) ) return -1; return 0; } int MouseEvent() { HANDLE hStdin; INPUT_RECORD irInBuf[128]; short x, y; unsigned i; DWORD cNumRead; static int ignoreNext = 0; hStdin = GetStdHandle(((DWORD)-10)); if (hStdin == ((HANDLE)(LONG_PTR)-1)) return -2; if (!ReadConsoleInputW( hStdin, irInBuf, 128, &cNumRead) ) return -1; for (i = 0; i < cNumRead; i++) { if (irInBuf[i].EventType == 0x0002 && irInBuf[i].Event.MouseEvent.dwEventFlags == 0) { if (ignoreNext == 1) { ignoreNext = 0; return -1; } x = irInBuf[i].Event.MouseEvent.dwMousePosition.X; y = irInBuf[i].Event.MouseEvent.dwMousePosition.Y; ignoreNext = 1; return x + (y << 8); } else { continue; } } return -1; } So far, I have only tested this with MSVC (it works), but not with haskell platform's mingw (which includes windows.h - so I would have to wait for this...) In my cabal file I have: c-sources: mouse.c So that basically sums up what I have, I just don't know how to do this. The cabal documentation says for this directive: c-sources: filename list A list of C source files to be compiled and linked with the Haskell files. Which is what I expected it to do - but to no avail. I should note that when I try to comment out with -- the c-sources line I get this: Linking dist\build\BoardGames\BoardGames.exe ... dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0x27d): undefined reference to `__stginit_Mouse_' dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xb4): undefined reference to `Mouse_a1_info' dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xcc): undefined reference to `Mouse_czusetupConsole_info' dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xf8): undefined reference to `Mouse_a1_info' dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0x17a): undefined reference to `Mouse_czusetupConsole_info' dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.data+0x14): undefined reference to `Mouse_a1_closure' collect2: ld returned 1 exit status Any help that can be offered would be appreciated. I would tell you where to find the project, but patch-tag is being unavailable for me at this time. It is the 'BoardGames' project, under iaefai. Thank you again, iaefai.