[GHC] #14931: Segfault compiling file that uses Template Haskell with -prof (was: Segfault compiling files with -prof)

[GHC]

#14931: Segfault compiling file that uses Template Haskell with -prof
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Profiling         |              Version:  8.4.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I forgot that `mtl` is bundled with GHC now, so you can reproduce this
 with a single file:

 {{{#!hs
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TemplateHaskell #-}
 module Bug where

 import Prelude (Int, IO, Bool(..), Num(..), Monad(..), not, print)
 import qualified Language.Haskell.TH.Syntax as TH
 import Control.Monad.State

 wat :: IO ()
 wat = print $(let playGame []     = do
                       (_, score) <- get
                       return score
                   playGame (x:xs) = do
                       (on, score) <- get
                       case x of
                            'a' | on -> put (on, score + 1)
                            'b' | on -> put (on, score - 1)
                            'c'      -> put (not on, score)
                            _        -> put (on, score)
                       playGame xs

                   startState :: (Bool, Int)
                   startState = (False, 0)
               in TH.lift (evalState (playGame "abcaaacbbcabbab")
 startState) )
 }}}

 {{{
 $ ~/Software/ghc-8.4.1/bin/ghc -O -prof -osuf p_o -hisuf p_hi Bug.hs
 [1 of 1] Compiling Bug              ( Bug.hs, Bug.p_o )
 Segmentation fault (core dumped)
 }}}

 Also, Template Haskell appears to be a key ingredient here, since removing
 it makes the issue go away.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14931#comment:4>
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