[GHC] #7229: Detecting if a process was killed by a signal is impossible

[GHC]

#7229: Detecting if a process was killed by a signal is impossible
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        Reporter:  benmachine         |            Owner:
            Type:  bug                |           Status:  new
        Priority:  high               |        Milestone:  7.8.1
       Component:  libraries/process  |          Version:
      Resolution:                     |         Keywords:
Operating System:  Unknown/Multiple   |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown       |       Difficulty:  Unknown
       Test Case:                     |       Blocked By:
        Blocking:                     |  Related Tickets:
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Comment (by duncan):

 Here's my updated patch. '''Totally untested'''

 {{{#!diff
 diff --git a/GHC/TopHandler.lhs b/GHC/TopHandler.lhs
 index 9e4bc07..8953334 100644
 --- a/GHC/TopHandler.lhs
 +++ b/GHC/TopHandler.lhs
 @@ -180,7 +180,28 @@ flushStdHandles = do
  -- we have to use unsafeCoerce# to get the 'IO a' result type, since the
  -- compiler doesn't let us declare that as the result type of a foreign
 export.
  safeExit :: Int -> IO a
 +#ifdef mingw32_HOST_OS
  safeExit r = unsafeCoerce# (shutdownHaskellAndExit $ fromIntegral r)
 +#else
 +-- On Unix we use an encoding for the ExitCode:
 +--   Bits: 0-7  (mask 0x00ff)  normal exit code
 +--   Bits: 8-14 (mask 0x7f00)  exit by signal
 +--   Bits: 15   (mask 0x8000)  core dump (allowed with signal but
 ignored)
 +-- A normal exit, and exit by signal are mutually exclusive.
 +-- For any invalid encoding we just use a replacement (0xff).
 +safeExit r
 +  | sig /= 0 && code == 0 && other == 0 {-any cdump-}
 +  = unsafeCoerce# (shutdownHaskellAndSignal $ fromIntegral sig)
 +  | sig == 0 {-any code-} && other == 0 && cdump == 0
 +  = unsafeCoerce# (shutdownHaskellAndExit $ fromIntegral code)
 +  | otherwise
 +  = unsafeCoerce# (shutdownHaskellAndExit 0xff)
 +  where
 +    sig   = (r .&. 0x7f00) `shiftR` 8
 +    cdump =  r .&. 0x8000
 +    code  =  r .&. 0x00ff
 +    other =  r .&. (complement 0xffff)
 +#endif

  exitInterrupted :: IO a
  exitInterrupted =
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7229#comment:35>
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