linking buggy

example of runtime missing entry

import System.Exit ( exitWith, ExitCode(ExitSuccess) )
import Graphics.UI.GLUT
import Foreign.Marshal.Array

myInit :: IO ()
myInit = do
   clearColor $= Color4 0 0 0 0

display :: DisplayCallback
display = do
  clear [ ColorBuffer, DepthBuffer ]
  color (Color3 1.0 1.0 1.0 :: Color3 GLfloat)

  withNURBSObj () $ \nurbsObj -> do
    nurbsBeginEndCurve nurbsObj $
      withArrayLen knots $ \nKnots knots ->
        withArray controls $ \controls -> do
          nurbsCurve nurbsObj (fromIntegral nKnots) knots stride controls order

  flush

  where
    order = 3
    stride = 4 -- number of floats in Vertex
    controls = zipWith mkControl points weights
    mkControl (x, y) w = Vertex4 (x*w) (y*w) 0 w
    -- mkControl (x, y) w = Vertex4 x y 0 w
    knots = [0, 0, 0, 0.25, 0.25, 0.5, 0.5, 0.75, 0.75, 1, 1, 1]
    weights = let a = sqrt 0.5 in [1, a, 1, a, 1, a, 1, a, 1]
    points = [
      (x0, y1), (x0, y2), (x1, y2),
      (x2, y2), (x2, y1), (x2, y0),
      (x1, y0), (x0, y0), (x0, y1)
      ]

    y1 = (y0 + y2) / 2
    x1 = (x0 + x2) / 2
    (x0, x2) = (50, 450)
    (y0, y2) = (x0, x2)

reshape :: ReshapeCallback
reshape size@(Size w h) = do
   viewport $= (Position 0 0, size)
   matrixMode $= Projection
   loadIdentity
--   ortho2D 0 (fromIntegral w) 0 (fromIntegral h)
   -- the following line is not in the original example, but it's good style...
   matrixMode $= Modelview 0

keyboard :: KeyboardMouseCallback
keyboard (Char '\27') Down _ _ = exitWith ExitSuccess
keyboard _ _ _ _ = return ()

--  Request double buffer display mode.
--  Register mouse input callback functions
main :: IO ()
main = do
   (progName, _args) <- getArgsAndInitialize
   initialDisplayMode $= [ SingleBuffered, RGBMode ]
   initialWindowSize $= Size 500 500
   initialWindowPosition $= Position 100 100
   createWindow "Test"
   myInit
   displayCallback $= display
   reshapeCallback $= Just reshape
   keyboardMouseCallback $= Just keyboard
   mainLoop