#12168: panic! (the 'impossible' happened) with gi-gtk 3.0.4 -------------------------------------+------------------------------------- Reporter: drb226 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): I'm not up to reproducing using docker etc (but perhaps someone else may be?). But here are some pointers. * After this: {{{ [599 of 654] Compiling GI.Gtk.Objects.Widget ( GI/Gtk/Objects/Widget.hs, .stack-work/dist/x86_64-linux/Cabal-1.24.0.0/build/GI/Gtk/Objects/Widget.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): urk! lookup local fingerprint $fAttrInfoWidgetMarginTopPropertyInfo4 }}} if you compile just that one module `GI.Gtk.Objects.Widget` all by itself (use `-v` to see the command line that stack is using, I guess), does the error repeat? I hope so! * Add `-ddump-simpl` to the command line, which should show the Core that `MkIface` stumbles on. Beyond that I think we may need to start add debug-prints to `MkIface` to get more data. I'm guessing that the strongly-connected component analysis in `MkIface.addFingerprints` is somehow missing an edge. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12168#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler