[GHC] #8834: 64-bit windows cabal.exe segfaults in GC

[GHC]

#8834: 64-bit windows cabal.exe segfaults in GC
---------------------------------+----------------------------------
        Reporter:  awson         |            Owner:
            Type:  bug           |           Status:  new
        Priority:  highest       |        Milestone:  7.8.1
       Component:  None          |          Version:  7.8.1-rc2
      Resolution:                |         Keywords:
Operating System:  Windows       |     Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |       Difficulty:  Unknown
       Test Case:                |       Blocked By:
        Blocking:                |  Related Tickets:
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Comment (by awson):

 1. I've reduced this case to the following:
 {{{
 import qualified Data.ByteString.Char8 as BSS

 main :: IO ()
 main = do
   cache <- BSS.readFile "00-index.cache"
   print (length $ BSS.lines cache)
 }}}

 `00-index.cache` is hackage packages cache file. Even truncated to 12000
 lines it gives segfault.

 2. After bisecting I've found the
 [https://github.com/ghc/ghc/commit/ad15c2b4bd37082ce989268b3d2f86a2cd34386a
 problematic commit]. I don't understand what is going here. I think I've
 made absolutely my best in this situation. Please, someone fix this! I
 feel myself completely alone fighting with numerous win64 bugs which
 nobody ever bother to look into.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8834#comment:2>
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