[GHC] #5902: Cannot tell from an exception handler whether the exception was asynchronous

[GHC]

#5902: Cannot tell from an exception handler whether the exception was
asynchronous
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    Reporter:  simonmar          |       Owner:  simonmar        
        Type:  bug               |      Status:  new             
    Priority:  high              |   Milestone:  7.8.1           
   Component:  Compiler          |     Version:  7.4.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Comment(by simonmar):

 Any time there's a catch/rethrow inside an `unsafePerformIO` we'll have
 this problem.  So in the specific case of the GHC API it would help to
 know where this is happening, and whether we can avoid it.

 One way I can think of that might help in general is to have a special
 kind of catch that doesn't catch asynchronous exceptions.  So in cases
 like your example, `catchIOError` would use the special sync-only catch
 internally, and would ignore the async exception.

 However, this unfortunately doesn't help with `bracket` and `finally`,
 which need to do some cleanup in the exception handler, and I suspect
 these are more common than `catch`.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5902#comment:6>
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