#3872: New way to make the simplifier diverge -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.12.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #5400 #5448 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by sgraf): * related: => #5400 #5448 Comment: This doesn't loop infinitely anymore with GHC 8.2.1 and instead panics: {{{ ghc.exe: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-unknown-mingw32): Simplifier ticks exhausted When trying UnfoldingDone rir_s1bm To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 11721 Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler\utils\Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler\utils\Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler\simplCore\SimplMonad.hs:199:31 in ghc:SimplMonad }}} I think this should result in a warning rather than in a crash. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/3872#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler