I've been working with the new parser entry points - they have been very useful. Ostensibly the new parser entry points are pure functions but they require a copy of DynFlags. As far as I can work out there's no pure way to reliably construct DynFlags but it also seems that the Parser doesn't use any of the impure mutable parts of it. This makes it tricky to write pure functions such as "parseExprFromString :: String -> LHsExpr RdrName" which would use some sort of dummy configuration. So far I've tried using "unsafeGlobalDynFlags" which (expectedly) fails occasionally. I've found a more reliable method to be the following which relies on unsafePerformIO. getDynFlags = unsafePerformIO $ GHC.defaultErrorHandler GHC.defaultFatalMessager GHC.defaultFlushOut $ GHC.runGhc (Just libdir) GHC.getSessionDynFlags The question is - is this use of unsafePerformIO safe? Is there a better way to purely initialise a copy of DynFlags? Thanks, Matt