Re: [GHC] #13080: Memory leak caused by nested monadic loops

4 Sep 2018

      #13080: Memory leak caused by nested monadic loops
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        Reporter:  Feuerbach         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by saurabhnanda):

 I ''think'' I have been hit by this bug. Is the following going to leak
 memory due to this bug:

 {{{
 worker :: (AppMonad m) => TChan MyType -> m ()
 worker chan = do
   mItem <- tryReadTChanIO chan
   case mItem of
     Just item -> do
        processItem item
        worker chan
     Nothing -> pure ()

 }}}

 Can it be fixed by using {{{whileJust_}}} from
 http://hackage.haskell.org/package/monad-loops-0.4.3/docs/src/Control-
 Monad-Loops.html#whileJust_ ?
 {{{
 worker :: (AppMonad m) => TChan MyType -> m ()
 worker chan = whileJust_ (tryReadTChanIO chan) processItem
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13080#comment:25
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