[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:  normal            |        Milestone:  7.8.1
       Component:  Compiler          |          Version:  7.4.1
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by simonmar):

 Now I think about it, this isn't such a bad idea.  Unfortunately we can't
 implement `newCatch`, because the async exception might have been re-
 thrown (say by a `finally`) inside the io.  So the best you can do is
 recognise an async exception by its type - i.e. if it is an child of
 `AsyncException` then it's async, otherwise not.  But that's good, because
 it means we don't have to change the RTS or primops.

 Then there's the question of whether restarting the io is safe.  It
 probably is; as Simon pointed out, the io inside `unsafePerformIO` is
 supposed to be a benign side-effect, so we ought to be able to repeat it.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5902#comment:14>
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