#7944: GHC goes into an apparently infinite loop at -O2 -------------------------------------+------------------------------------- Reporter: bos | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.9 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Compile-time | (amd64) crash | Test Case: Blocked By: | Blocking: Related Tickets: #5550 #8852 | Differential Revisions: -------------------------------------+------------------------------------- Comment (by amosrobinson): Hi, I had a go reducing this more. I only have ghc 7.8.3, so would someone be able to try this on head? {{{ #!haskell module T7944 where import GHC.Exts -- Force specialisation of "go" data SPEC = SPEC | SPEC2 {-# ANN type SPEC ForceSpecConstr #-} -- This is more or less just an ordinary fold go :: SPEC -> [a] -> IntMap a -> IntMap a go SPEC [] m = m go SPEC (_:xs) m = go SPEC xs -- This would be the "worker function" of the fold $ Unary m -- Both constructors are necessary, despite only one being used data IntMap a = Nil | Unary (IntMap a) }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7944#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler