[GHC] #11972: Weak pointers can cause segfault

[GHC]

#11972: Weak pointers can cause segfault
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        Reporter:  ryantrinkle       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1-rc3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by niteria):

 It also reproduces on HEAD. I've run it in gdb with a breakpoint on the
 address it's complaining about: https://phabricator.haskell.org/P107

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11972#comment:1>
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