Fix #143: memory leak from not freeing per-message callback pointer

[felixmulder]

No description provided.

[AlexeyRaga]

Would bracket be better in this situation?
Or it doesn't matter in this case?

[felixmulder]

It would be nice, but I don't think it's possible. The pointer is created in Kafka.Producer and when the per-message callback is invoked it ends up here. So there's not really a good way to tie those two together that I can think of...

[AlexeyRaga]

I thought of bracket (castPtrToStablePtr cbPtr) freeStablePtr $ \stablePrt -> do ..., not the actual pointer...

[felixmulder]

We'd have to do:

else bracket (pure $ castPtrToStablePtr cbPtr) freeStablePtr $ \stablePtr -> do
  msgCb <- deRefStablePtr @(DeliveryReport -> IO ()) stablePtr
  -- Here we fork the callback since it might be a longer action and
  -- blocking here would block librdkafka from continuing its execution
  void . forkIO $ msgCb rep

I can change it to that if ya like :)

[felixmulder]

Done

[AlexeyRaga]

Thank you very much!