[GHC] #13611: Segfault due to levity polymorphism of mkWeak#

[GHC]

#13611: Segfault due to levity polymorphism of mkWeak#
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 Neither do I.

 Though what guarantees do we provide when a user writes the `IO`
 constructor explicitly? This is tantamount to `unsafePerformIO`, is it
 not?

 While I conjecture that the segfault is possible without unsafe features,
 this test case isn't terribly convincing.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13611#comment:3>
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