Johannes, I think Simon M who could help you with this is away, so I'll try and help you in the short term. This is most likely a bug in the generational garbage collector. I'm guessing you can't reproduce the problem very easily? If it happens say 7 in 10 times, I can have a look at it for you if you send the code over with instructions to cause failure. One thing you can try to prevent this is to use the semi-space collector instead of the generational: <snip from manual> Specifying 1 generation with +RTS -G1 gives you a simple 2-space collector, as you would expect. In a 2-space collector, the -A option (see above) specifies the minimum allocation area size, since the allocation area will grow with the amount of live data in the heap. In a multi-generational collector the allocation area is a fixed size (unless you use the -H option, see below). Hope that helps. Cheers Andy On Wed, 9 Jul 2003, Johannes Waldmann wrote:

I sometimes get this error:

...

internal error: scavenge_mutable_list: strange object? 3

( large program, running on debian linux on i368, compiled with ghc-6.0 -pgmc gcc-2.95 --make -O2 -fvia-C -funbox-strict-fields )

what can I do to a) work around this, b) help finding/fixing the reason? -- -- Johannes Waldmann ---- http://www.informatik.uni-leipzig.de/~joe/ -- -- joe@informatik.uni-leipzig.de -- phone/fax (+49) 341 9732 204/209 --

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********************************************************************* * Andrew Cheadle email: a.cheadle@doc.ic.ac.uk * * Department of Computing http://www.doc.ic.ac.uk/~amc4/ * * Imperial College * * University of London * *********************************************************************