[GHC] #4820: "Invalid object in isRetainer" when doing retainer profiling in GHC 7 branch

[GHC]

#4820: "Invalid object in isRetainer" when doing retainer profiling in GHC 7
branch
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    Reporter:  dleuschner      |        Owner:               
        Type:  bug             |       Status:  new          
    Priority:  high            |    Milestone:  7.0.2        
   Component:  Profiling       |      Version:  7.0.1        
    Keywords:                  |     Testcase:               
   Blockedby:                  |   Difficulty:               
          Os:  Linux           |     Blocking:               
Architecture:  x86_64 (amd64)  |      Failure:  Runtime crash
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Comment(by dleuschner):

 Does anybody have an idea what could be causing this behavior?  Could it
 have something to do with networking?  Or FFI?  Or any specific type-
 system/language feature?  Is there anything we should pay attention to?
 Could the numbers after "isRetainer()" tell us anything?  Although we
 cannot open source our application code at the moment, we of course could
 send it to you, Simon, so that you could, in principle, reproduce the
 problem.  But unfortunately it's still an awful lot of code and libraries.
 I would try to write a simple test case but I have no idea what I should
 include?

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4820#comment:2>
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