Fix nullptr after listener consumer closed

lib/MultiTopicsConsumerImpl.cc

@@ -556,7 +556,9 @@ void MultiTopicsConsumerImpl::messageReceived(const Consumer& consumer, const Me
 
 void MultiTopicsConsumerImpl::internalListener(const Consumer& consumer) {
     Message m;
-    incomingMessages_.pop(m);
+    if (!incomingMessages_.pop(m)) {
+        return;
+    }
     try {
         Consumer self{get_shared_this_ptr()};
         messageProcessed(m);

tests/ConsumerTest.cc

@@ -1519,4 +1519,46 @@ TEST(ConsumerTest, testDuplicatedTopics) {
     }
 }
 
+TEST(ConsumerTest, testConsumerListenerShouldNotSegfaultAfterClose) {
+    Client client(lookupUrl);
+
+    const int MSG_COUNT = 100;
+    std::string topicName = "persistent://public/default/my-topic-" + std::to_string(time(nullptr));
+
+    // 1. Create producer send 100 msgs
+    Producer producer;
+    ProducerConfiguration producerConfig;
+    producerConfig.setBatchingEnabled(false);
+    ASSERT_EQ(ResultOk, client.createProducer(topicName, producerConfig, producer));
+    for (int i = 0; i < MSG_COUNT; ++i) {
+        std::string msg = "my-message-" + std::to_string(i);
+        Message message = MessageBuilder().setContent(msg).build();
+        ASSERT_EQ(ResultOk, producer.send(message));
+    }
+    ASSERT_EQ(ResultOk, producer.flush());
+
+    // 2. Create consumer with listener
+    Consumer consumer;
+    ConsumerConfiguration consumerConfig;
+    consumerConfig.setSubscriptionInitialPosition(InitialPositionEarliest);
+    Latch latchFirstReceiveMsg(1);
+    Latch latchAfterClosed(1);
+    consumerConfig.setMessageListener(
+        [&latchFirstReceiveMsg, &latchAfterClosed](Consumer consumer, const Message& msg) {
+            latchFirstReceiveMsg.countdown();
+            std::cout << "Consume message: " << msg.getDataAsString() << std::endl;
+            latchAfterClosed.wait();
+        });
+    auto result = client.subscribe(topicName, "test-sub", consumerConfig, consumer);
+    ASSERT_EQ(ResultOk, result);
+
+    // 3. wait first message consumed in listener and then close consumer.
+    latchFirstReceiveMsg.wait();
+    ASSERT_EQ(ResultOk, consumer.close());
+    latchAfterClosed.countdown();
+
+    ASSERT_EQ(ResultOk, producer.close());
+    ASSERT_EQ(ResultOk, client.close());
+}
+
 }  // namespace pulsar