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

[GHC]

#8834: 64-bit windows cabal.exe segfaults in GC
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        Reporter:  awson          |            Owner:
            Type:  bug            |           Status:  patch
        Priority:  highest        |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.8.1-rc2
      Resolution:                 |         Keywords:
Operating System:  Windows        |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:                 |       Blocked By:
        Blocking:                 |  Related Tickets:
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Comment (by simonmar):

 I think the bad code is much more likely to be in a library somewhere, not
 in the code that calls `readFile`/`lines`, so we're not going to see
 anything bad in that file.

 @jstolarek - R1 is not caller-saves (on either Linux or Win64), so it is
 safe to leave it live across a foreign call.  Also, that code fragment is
 the standard `newCAF` call which appears everywhere, if this was broken
 then everything would be broken.

 I'm surprised that the change to `isTrivial` all by itself causes this
 failure.  That must mean that there was something wrong with the code
 before the "bad patch", because the change to `isTrivial` should be safe.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8834#comment:17>
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