[GHC] #9078: Segfault with makeStableName

[GHC]

#9078: Segfault with makeStableName
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       Reporter:  robertce          |             Owner:
           Type:  bug               |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.8.2
       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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 Calling `makeStableName` on the same object many times causes a segfault.
 The following triggers this behaviour on both OSX and Linux-x86_64,
 provided it is compiled (it doesn't seem to occur if the call to
 `makeStableName` is interpreted).

 {{{
 module Main where

 import Control.Monad
 import System.Mem.StableName

 main :: IO ()
 main = replicateM_ 100000 (makeStableName foo)

 foo :: Int
 foo = 1
 }}}

 It seems to happen largely at random. The 100000 calls to `makeStableName`
 in the above example essentially guarantee its occurrence, but I have
 observed it happen with far fewer.

 The reason this bug was discovered is it is causing frequent failures in
 Accelerate on 7.8.2. See
 [https://github.com/AccelerateHS/accelerate/issues/162]. In that case it
 seems to be causing more `strange closure type` errors than segfaults, but
 I assume it is the same root cause.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9078>
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