Re: [GHC] #11172: Turning on optimisations produces SEGFAULT or Impossible case alternative

#11172: Turning on optimisations produces SEGFAULT or Impossible case alternative -------------------------------------+------------------------------------- Reporter: nh2 | Owner: bgamari Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"514bac264cb60db26ff9da10c6b79c3f5bd6e96d/ghc" 514bac2/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="514bac264cb60db26ff9da10c6b79c3f5bd6e96d" Fix combineIdenticalAlts This long-standing bug in CoreUtils.combineIdenticalAlts was shown up by Trac #11172. The effect was that it returned a correct set of alternatives, but a bogus set of "impossible default constructors". That meant that we subsequently removed all the alternatives from a case, and hence ended up with a bogusly empty case that should not have been empty. See Note [Care with impossible-constructors when combining alternatives] in CoreUtils. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11172#comment:26 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler