Sockets don't have finalizers #4

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1. bos commented on Feb 2, 2011

   

   bos

   on Feb 2, 2011

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   I took a quick look at fixing this, and it's not completely trivial.

   The easiest thing, I thought, would be to use addMVarFinalizer to associate a finalizer with the MVar we already use to track the socket state. But the finalizer would want to know the state of the socket in order to close it safely, and if the finalizer has a reference to the MVar to read its state, I think that will unintentionally keep the MVar alive.

   We cannot simply unconditionally c_close the file descriptor, because by the time the finalizer is called on a closed Socket, the fd will probably refer to a different file entirely.

   So. Instead, I'm adding a finalizer to the 'Socket' itself, using 'System.Mem.Weak'.
2. lpeterse commented on May 18, 2015

   

   lpeterse

   on May 18, 2015

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   Hi Bryan,

   I'm currently trying to get an overview of the state of the network package.

   What is the state of this issue? I grepped the package for 'Weak' without result and therefore assume that whatever you did, did not make it into master.
3. lpeterse commented on Aug 11, 2016

   

   lpeterse

   on Aug 11, 2016

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   For anyone stumbling upon this issue: The finalization mechanism proposed by @bos does work when using mkWeakMVar (instead of now obsolete addMVarFinalizer). The considerations with the finalizer itself keeping the MVar alive do not apply.

   Here is a minimal example: lpeterse/haskell-socket#20
4. kazu-yamamoto

   self-assigned this

   on Dec 14, 2017
5. eborden

   closed this as completedin #269on Dec 15, 2017