I recently switched to ghc 6.0.1 running on a debian linux box.

When compiling a program using ghc --make -O or ghc --make -O2 I get lots of errors while linking. The linker concerns about undefined references to Data.FiniteMap, which I frequently use. For example, the linker says:

../Options.o(.text+0xc0d): In function `s4m5T_ret': : undefined reference to `DataziFiniteMap_lvl4_closure'

Without optimizing my code, doing a plain ghc --make everything goes fine. Similarly, compiling the same program with the older ghc 6.0 I do not get any linking errors, whether I optimize or not.

Any ideas, how I can get rid of the linking errors, except for switching back to ghc 6.0?

It could be a problem with your build of ghc-6.0.1. Where did it come from? Cheers, Simon