I while I ago I sent an email regarding hs-plugins not working on windows. I now tried to directly use GHC API, but I also failed. The following program (which might be buggy, I copy/pasted from various sources) import DynFlags import GHC main = defaultErrorHandler defaultDynFlags $ do session <- newSession (Just "d:/app/ghc-6.8.2") flags <- getSessionDynFlags session (flags, _) <- parseDynamicFlags flags [] GHC.defaultCleanupHandler flags $ do setSessionDynFlags session flags{ hscTarget=HscInterpreted } prelude <- findModule session (mkModuleName "Prelude") Nothing setContext session [] [prelude] runStmt session "let n = 2 + 2" RunToCompletion -- n is bound runStmt session "n" RunToCompletion -- 4 is printed (note "it" is bound) gives the following error when run from GHCi *Main> :load "l:/test.hs" [1 of 1] Compiling Main ( l:/test.hs, interpreted ) Ok, modules loaded: Main. *Main> main GHCi runtime linker: fatal error: I found a duplicate definition for symbol _forkOS_entry whilst processing object file d:/app/ghc-6.8.2/lib\base-3.0.1.0/HSbase-3.0.1.0.o This could be caused by: * Loading two different object files which export the same symbol * Specifying the same object file twice on the GHCi command line * An incorrect `package.conf' entry, causing some object to be loaded twice. GHCi cannot safely continue in this situation. Exiting now. Sorry. Process haskell finished Is my code incorrect, or is this a (known?) bug in GHC 6.8.2 on Windows? I haven't tried the Linux version yet. NOTE: The program *does* run fine when compiling via GHC --make. Thanks, Peter