BewareMyPower opened a new pull request, #168:
URL: https://github.com/apache/pulsar-client-cpp/pull/168

   Fixes https://github.com/apache/pulsar-client-cpp/issues/167
   
   ### Motivation
   
   Here are some debugging info when the segfault happened in 
`testCloseClient`. The outputs have been trimmed to make them clear.
   
   An example crash at `async_write`:
   
   ```
   #12 0x00007ffff7496dad in basic_stream_socket<...>::boost::asio::async_write 
/usr/include/boost/asio/impl/write.hpp:512
   #13 0x00007ffff748e003 in ClientConnection::asyncWrite 
lib/ClientConnection.h:245
   #14 0x00007ffff746e0b6 in ClientConnection::handleHandshake 
(this=0x555555e689d0) lib/ClientConnection.cc:502
   ```
   
   Another example crash at `async_receive`:
   
   ```
   #6  0x00007ffff7497247 in basic_stream_socket<...>::async_receive 
/usr/include/boost/asio/basic_stream_socket.hpp:677
   #7  0x00007ffff748e647 in ClientConnection::asyncReceive 
lib/ClientConnection.h:258
   #8  0x00007ffff746fa5d in ClientConnection::readNextCommand 
lib/ClientConnection.cc:606
   ```
   
   The frame where it crashed:
   
   ```
   245       if (descriptor_data->shutdown_)
   (gdb) p descriptor_data
   $2 = (boost::asio::detail::epoll_reactor::per_descriptor_data &) 
@0x555555e4a780: 0x0
   ```
   
   We can see the socket descriptor is `nullptr`. The root cause is when 
`async_receive` or `async_write` is called, the `io_service` object might be 
closed. This case happened when `createProducerAsync` is called, the actual 
producer creation continues in another thread, while the `client.close()` 
happens in the current thread.
   
   ### Modifications
   
   Check if the `ClientConnection` is closed before `async_receive` or 
`async_write`. To avoid the use of lock, changing the `state_` field to atomic.
   
   ### Verifications
   
   ```bash
   ./tests/pulsar-tests --gtest_filter='ClientTest.testCloseClient' 
--gtest_repeat=20
   ```
   
   It never crashed after applying this patch.


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