BewareMyPower commented on code in PR #16969:
URL: https://github.com/apache/pulsar/pull/16969#discussion_r950061016
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pulsar-client-cpp/lib/MultiTopicsConsumerImpl.cc:
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@@ -125,33 +144,37 @@ Future<Result, Consumer>
MultiTopicsConsumerImpl::subscribeOneTopicAsync(const s
}
// subscribe for each partition, when all partitions completed, complete
promise
-
lookupServicePtr_->getPartitionMetadataAsync(topicName).addListener(std::bind(
- &MultiTopicsConsumerImpl::subscribeTopicPartitions,
shared_from_this(), std::placeholders::_1,
- std::placeholders::_2, topicName, subscriptionName_, conf_,
topicPromise));
+ Lock lock(mutex_);
+ auto entry = topicsPartitions_.find(topic);
+ lock.unlock();
Review Comment:
You should not unlock here. `entry` is an iterator that references a node
from the map (`topicsPartitions_`). The iterator acts like a pointer, which
means the object which an iterator references could be modified.
For example,
```c++
std::map<int, int> m;
m[1] = 100;
const auto entry = m.find(1);
std::cout << entry->second << std::endl; // 100 as expected
m[1] = 200; // assume it happened in another thread
std::cout << entry->second << std::endl; // 200
```
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