-xc giving very little information

Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk
Mon Jan 5 11:35:37 EST 2004

Stefan Reich <doc at drjava.de> writes:

> A complex program of mine fails with this message:
> 	Fail: Maybe.fromJust: Nothing
> I tried to extract more information about the error by compiling with 
> -prof -auto-all and running the program with +RTS -xc, as advised on 
> http://www.haskell.org/hawiki/TipsAndTricks . This yielded exactly one 
> additional line:

This looks like the perfect situation in which to use program tracing
through Hat.  It will give you stack back-traces and much much more.


Unfortunately, Hat is currently limited to ghc version 5.04.3 (i.e. not
yet updated to cope with the 6.x series), but perhaps your program
is written in sufficiently standard Haskell for this to be no problem?
(Hat also works with nhc98.)


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