Hi,

  I'm trying to compile some code using Cabal.  One of the files has a CPP directive

#include "undefined.h"

The file undefined.h is in the same directory as the file with the directive.

If I use the full path name, cabal can compile it.  However, if I use the relative path, 

it complains about not being able to find the file.   I tried adding it to 

extra-source-files, but that didn't help.  I see that Hackage packages like Agda use

this trick, so I know it's possible.  How can I get these paths worked out correctly?

There isn't much comment in the Cabal docs.

Thanks,

Sean