#12571: GHC panic -------------------------------------+------------------------------------- Reporter: prsteele | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I received the following error message from GHC: {{{ <no location info>: ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): Simplifier ticks exhausted When trying UnfoldingDone $fStorableWord21 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: 8040 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} When I followed the suggestion of adding `-fsimpl-tick-factor=200` the compiler proceeds normally (finding a syntax error in a file). Removing this option, strangely, also causes the compiler to proceed normally. I can no longer reproduce this bug, although several compilations in a row (before adding the option) reproduced the bug. Although I cannot reproduce this bug, the syntax error that is present came from an error of the form: {{{#!hs f :: A -> M B f a = do x <- g a let c = h a in do ... }}} The actual file is attached. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12571 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler