How do I provide stable iteration order with std::map in multithreaded code?

In C++, using std::map provides a stable iteration order since it is a sorted associative container. However, in multithreaded applications, concurrent modifications may lead to unpredictable behavior. To maintain stability while iterating over a std::map, it's crucial to implement proper synchronization mechanisms.

Here’s an example illustrating how to safely iterate over a std::map in a multithreaded environment using mutex locks:


        #include <iostream>
        #include <map>
        #include <thread>
        #include <mutex>
        #include <chrono>

        std::map<int, std::string> myMap;
        std::mutex mapMutex;

        void addToMap(int key, const std::string &value) {
            std::lock_guard<std::mutex> lock(mapMutex);
            myMap[key] = value;
        }

        void iterateMap() {
            std::lock_guard<std::mutex> lock(mapMutex);
            for (const auto &pair : myMap) {
                std::cout << pair.first << ": " << pair.second << std::endl;
            }
        }

        int main() {
            std::thread t1(addToMap, 1, "One");
            std::thread t2(addToMap, 2, "Two");

            t1.join();
            t2.join();

            std::this_thread::sleep_for(std::chrono::milliseconds(100)); // Ensure the map is populated
            
            iterateMap();
            return 0;
        }

How do I provide stable iteration order with std::map in multithreaded code?

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How do I provide stable iteration order with std::map in multithreaded code?

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