#13380: raiseIO# result looks wrong -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Full test case: {{{#!hs import Control.Exception {-# NOINLINE f #-} f :: Int -> Int -> IO Int f x y | x>0 = throwIO (userError "What") | y>0 = return 1 | otherwise = return 2 main = f 2 undefined >>= print }}} I would expect this to throw the "What" exception, but when it's compiled with optimization I get the "undefined" exception. If I had written `throw (userError "What")`, that would be acceptable, because we don't make any guarantees about which imprecise exception in the imprecise exception set we actually throw. But here we are re-ordering evaluation in such a fashion as to throw an imprecise exception instead of a precise one, and I don't think that's legit. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13380#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler