happs on ghc 6.7 won't work because of dependency on Data.Binary, since everything that depends on Data.Binary is broken at present. This is for Data.Binary installed via cabal from darcs get --partial http://darcs.haskell.org/binary . Cabal installed without any errors, but perhaps there should have been one since it appears broke. So I think my project of using the ghc debugger to help understand happs is on ice until this gets resolved. Unless this has been fixed since August 16. (Anyone out there got a more recent version?) $ cat UseDataBinary.hs import Data.Binary main = putStrLn "hello world" $ /usr/local/bin/ghc-6.6.1 -e 'main' UseDataBinary.hs hello world $ /usr/local/bin/ghc-6.7.20070816 -e 'main' UseDataBinary.hs <interactive>: /usr/local/lib/binary-0.3/ghc-6.7.20070816/HSbinary-0.3.o: unknown symbol `stg_uncheckedShiftRL64' ghc-6.7.20070816: unable to load package `binary-0.3' $ /usr/local/bin/ghc-6.7.20070816 -e '' UseDataBinary.hs --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.