All, We've been using the cabal-install build reporting stuff to get more detailed info on build failures with ghc-6.10 vs 6.8. cabal-install generates these build-reports.log files and individual log files for each build. Below is a list of packages that worked with 6.8 and fail with 6.10. If your package is on this list then you might like to take a look at the actual failure. I've posted the logs here: http://haskell.org/~duncan/ghc/hackage-failures-ghc-6.10/ There's one set for ghc-6.8 and one for 6.10. We can get quite a bit of info from these build-reports.log files just using grep, sort, uniq etc. However we also have a parser for it so we can write more interesting queries. For example, we're interested in regressions: reports68 <- fmap parseList (readFile "ghc-6.8/build-reports.log") reports610 <- fmap parseList (readFile "ghc-6.10/build-reports.log") let merged = mergeBy (comparing package) (sortBy (comparing package) reports68) (sortBy (comparing package) reports610) worked InstallOk = True worked _ = False failed InstallOk = False failed (DependencyFailed _) = False failed _ = True regressions = [ new | InBoth old new <- merged , worked (installOutcome old) && failed (installOutcome new) ] print (length regressions) mapM_ (putStrLn . display . package) regressions There are 58 in this list. Though some have been since fixed and it doesn't count packages that fail due to dependencies failing. Here's our current list. I've pruned a couple that I know have been fixed. ArrayRef-0.1.2 CLASE-2008.9.23.2 EdisonCore-1.2.1.2 HPDF-1.4 HTF-0.1 HaLeX-1.1 Hashell-0.15 Hipmunk-0.2 MemoTrie-0.0 NewBinary-0.1.1 OpenAFP-1.1 PArrows-0.1 TypeCompose-0.5 Vec-0.9.2 WebBits-0.9.2 YamlReference-0.9.2 Yampa-0.9.2.2 arrows-0.4 bytestring-show-0.2 cabal-setup-1.2.1 chp-1.1.0 cmath-0.3 fixpoint-0.1 frag-1.1.1 harpy-0.4 hasim-0.1 hask-home-2007.12.6 heap-0.4.0 hetris-0.2 hexpat-0.2 hinstaller-2008.2.16 hint-0.2.4.1 hslackbuilder-0.0.1 hsx-0.4.4 hxt-8.1.0 iException-0.0.1 libGenI-0.16.1 list-extras-0.2.2 logfloat-0.9.1 mage-1.1.0 numeric-prelude-0.0.4 parameterized-data-0.1.3 plugins-1.3 quantum-arrow-0.0.4 regex-tdfa-0.94 stream-fusion-0.1.1 streamproc-1.1 stringtable-atom-0.0.4 time-1.1.2.1 typalyze-0.1.1 unicode-prelude-0.1 utf8-light-0.3 xmonad-contrib-0.8 xmonad-utils-0.1 yhccore-0.9 Duncan