Haskell Plugins and cabal sandbox

Question

So, I'm trying to use the Plugins package to dynamically load a haskell function from a source file. The source file depends on a package foo with module Foo.Bar. I'm running my project in a Cabal sandbox, where I have foo installed. Both my main program, and the module I'm loading with plugins, depend on foo. I always get one of the following two errors:

When I have foo installed in ~/.cabal, I get the error:

GHCi runtime linker: fatal error: I found a duplicate definition for symbol
  aizmvszmaizmlibzm0zi1_FooziBar_zdfTypeableBazzuds2_closure
whilst processing object file
  /home/joey/.cabal/lib/foo-0.1/ghc-7.6.3/HSfoo-0.1.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.

When I don't have it installed in ~/.cabal, I get a standard "module not found" error. And when I don't have it installed in my sandbox, I get the same module not found error trying to compile my main program code.

The plugins documentation is scarce at best. Any thoughts on how to solve this?

Answer 1

I got this working by using System.Plugins.Make to actually do the compliation, instead of relying on pre-existing object files. Not a complete solution, doesn't explain the problem, but it works for me for now.