#11555: catch under unsafePerformIO breaks on -O1 -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): It is fallout from #11222, but it's not a bug. There's no guarantee that the ''pure value'' passed to `catch` will be evaluated at any particular time. `catch` catches exceptions that arise from the ''execution'' of its IO argument action. Correct versions of this program would include changing `abort` to `abort :: Stack -> IO a; abort x = throwIO $ ...` or changing `C.catch (abort "fail")` to `C.catch (evaluate (abort "fail"))`. But I'm not sure that there is any way currently to, given an (unevaluated) IO action, evaulate it and execute it, catching exceptions raised by either step. A possible attempt would be `catch (do { a <- evaluate action; a })`, but would GHC see through this? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11555#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler