How to diagnose exception <<loop>> ?

[Simon Marlow]

> I'm using GHC 5.04.2 on Windows.
> 
> I made some changes which broke my application, in that 
> certain input now causes
> *** Exception: <<loop>>
> 
> I can't work out what I did to introduce an infinite loop.
> Is there something I can do to extract more information to 
> narrow this down?
> 
> Any pointers appreciated

You can try compiling the program with -prof -auto-all, and running it with +RTS -xc.  This is a primitive debugging tool for
diagnosing the location of exceptions.  See:

http://www.haskell.org/ghc/docs/latest/html/users_guide/runtime-control.html#RTS-OPTIONS-DEBUGGING

Cheers,
	Simon