[GHC] #11627: Segmentation fault for space_leak_001 with profiling (-hc)

[GHC]

#11627: Segmentation fault for space_leak_001 with profiling (-hc)
-------------------------------------+-------------------------------------
        Reporter:  thomie            |                Owner:  jme
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Profiling         |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
                                     |  perf/space_leaks/space_leak_001
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by jme):

 * owner:   => jme


Comment:

 The segfault occurs because `shrinkMutableByteArray#` and
 `resizeMutableByteArray#`
 introduce slop at the ends of the `large_object` `MutableByteArray#`s
 holding the `Integer`s.
 Since the arrays are large, they are not copied during GC, so this slop
 is still present when the heap census is run (after GC).  But when
 `heapCensusChain`
 encounters a shrunken `MutableByteArray#`, it thinks the slop following
 the array is
 another closure, and chaos quickly ensues.

 The fix should be straightforward.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11627#comment:1>
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