Re: Using DeepSeq for exception ordering

And the important observation is: all of them throw A if interpreted in ghci or compiled without -O, right? On Thu, Nov 8, 2012 at 11:24 AM, Albert Y. C. Lai wrote:

On 12-11-08 07:12 AM, Simon Hengel wrote:

...

I was just going to say that I can give at least one counterexample where this does not hold:

evaluate (('a' : undefined) `deepseq` return () :: IO ()) throwIO exceptionB

But then I realized that here exceptionA is optimized away altogether. For me this smells like a bug. Is this related to [1]?

[1] http://hackage.haskell.org/**trac/ghc/ticket/2273http://hackage.haskell.org/trac/ghc/ticket/2273

Interesting. A few more tests (all GHC 7.4.2, linux, x86 32-bit, use "ghc -O" to compile):

The following cases throw A:

import Control.DeepSeq import Control.Exception

main = do evaluate (('a' : error "A") `deepseq` return () :: Maybe ()) throwIO (userError "B")

main = do evaluate (('a' : error "A") `deepseq` ()) throwIO (userError "B")

main = do evaluate (('a' : error "A") `deepseq` True) throwIO (userError "B")

main = do x <- evaluate (('a' : error "A") `deepseq` putStrLn "hi") x throwIO (userError "B")

The following cases throw B:

main = do evaluate (('a' : error "A") `deepseq` return () :: IO ()) throwIO (userError "B")

main = do evaluate (('a' : error "A") `deepseq` putStrLn "hi") throwIO (userError "B")

main = do evaluate (('a' : error "A") `deepseq` getLine) throwIO (userError "B")

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