Flag warnings show intermediate hscpp filenames on SmartOS

On SmartOS GHC flag warnings show up like this: /tmp/ghc72341_0/ghc_1.hscpp:7:16: Warning: -fffi is deprecated: use -XForeignFunctionInterface or pragma {-# LANGUAGE ForeignFunctionInterface #-} instead It appears that this line in DriverPipeline leads to the correct filename in warnings on Ubuntu, but not on SmartOS: src_opts <- liftIO $ getOptionsFromFile dflags0 output_fn https://github.com/ghc/ghc/blob/bb7f2e33197e667eb694bd1243f125c722a0a868/com... How does the intermediate hscpp filename get restored to a correct filename if warnings are generated during a re-read of the pragmas after having preprocessed the file? Full investigation notes are here (rambling and unedited): https://gist.github.com/AlainODea/98141991849093285c52