hs-plugins -- simple example fails

[Peter Collingbourne]

Hello,

I'm having problems trying to use hs-plugins (the darcs version, as I
am on a 64-bit machine).  The test suite mostly works without problems,
but I can't get my own code to work.  I put together a simple example
which illustrates my problem:

Main.hs

====================
module Main (Tree(..), Interface(..), main) where

import Ptr
import System.Plugins

data Tree = Tree (Ptr Tree)

data Interface = Interface {
        processTree :: Ptr Tree -> IO (Ptr Tree)
}

main = load "XYZuse.o" ["."] [] "resource" >>= (\(LoadSuccess _ v) -> (processTree v nullPtr))
====================

XYZuse.hs

====================
module XYZuse (resource) where

import Main

resource = Interface {
        processTree = return
}
====================

This is the output I get:

====================
$ ghc -c -o Main.o Main.hs
$ ghc -c -o XYZuse.o XYZuse.hs
$ ghci
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Prelude> :l Main
Ok, modules loaded: Main.
Prelude Main> main
Loading package Cabal-1.1.6 ... linking ... done.
Loading package haskell98 ... linking ... done.
Loading package haskell-src-1.0 ... linking ... done.
Loading package plugins-1.0 ... linking ... done.


GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   Main_processTree_closure
whilst processing object file
   ./Main.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.
====================

Thanks,
-- 
Peter
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