[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 awson):

 Replying to [comment:24 jstolarek]:
 > It would be great if we had a test case that does not depend on any
 library code. This way we could eyeball the problem by looking at Cmm. Do
 you think you would be able to create such a test case.

 I think, this code should be enough:
 {{{
 module BugIso (lines1) where

 import Prelude hiding (null, take, drop)
 import Data.ByteString hiding (elemIndex)
 import Data.ByteString.Internal
 import Data.Word

 import Foreign

 elemIndex1 :: Word8 -> ByteString -> Maybe Int
 elemIndex1 c (PS x s l) = inlinePerformIO $ withForeignPtr x $ \p -> do
     let p' = p `plusPtr` s
     q <- memchr p' c (fromIntegral l)
     return $! if q == nullPtr then Nothing else Just $! q `minusPtr` p'
 {-# INLINE elemIndex1 #-}

 elemIndex :: Char -> ByteString -> Maybe Int
 elemIndex = elemIndex1 . c2w
 {-# INLINE elemIndex #-}

 lines1 :: ByteString -> [ByteString]
 lines1 ps
     | null ps = []
     | otherwise = case search ps of
              Nothing -> [ps]
              Just n  -> take n ps : lines1 (drop (n+1) ps)
     where search = elemIndex '\n'
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8834#comment:27>
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