[GHC] #11760: runST with lazy blackholing breaks referential transparency

[GHC]

#11760: runST with lazy blackholing breaks referential transparency
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        Reporter:  Yuras             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by NeilMitchell):

 It turns out the widely used zlib library suffers from exactly this issue,
 and can segfault when executed in parallel. See
 https://github.com/haskell/zlib/issues/7#issuecomment-253028108 for more
 details.

 It seems like adding {{{noDuplicate}}} to {{{runST}}} and adding
 {{{unsafeRunST}}} is a reasonable compromise. There may be a performance
 impact on {{{runST}}}, but having segfaults/value-changes should require
 typing something with the word {{{unsafe}}} in it at some point.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11760#comment:6>
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