[GHC] #9169: Add mkWeakTMVar to Control.Concurrent.STM.TMVar

[GHC]

#9169: Add mkWeakTMVar to Control.Concurrent.STM.TMVar
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       Reporter:  basvandijk         |             Owner:
           Type:  feature request    |            Status:  new
       Priority:  normal             |         Milestone:
      Component:  libraries (other)  |           Version:  7.8.2
       Keywords:  stm                |  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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 I just needed a Weak pointer to a TMVar:

 {{{
 -- | Make a 'Weak' pointer to a 'TMVar', using the second argument as
 -- a finalizer to run when 'TMVar' is garbage-collected.
 mkWeakTMVar :: TMVar a -> IO () -> IO (Weak (TMVar a))
 mkWeakTMVar tmv@(TMVar (TVar t#)) f = IO $ \s ->
     case mkWeak# t# tmv f s of (# s1, w #) -> (# s1, Weak w #)
 }}}

 It might make sense to add a similar function for TSem as well.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9169>
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