std::map iterator invalidation on concurrent modifications with C++17
I've been struggling with this for a few days now and could really use some help... I'm facing an issue with iterating over a `std::map` while concurrently modifying it in a multi-threaded environment using C++17. I have a producer thread that adds elements to the map and a consumer thread that iterates over the map to read values. Despite using `std::mutex` to protect the map, I'm getting unexpected behavior. Sometimes the consumer gets an invalid iterator or accesses uninitialized memory, which leads to segmentation faults. Here's a simplified version of my code: ```cpp #include <iostream> #include <map> #include <thread> #include <mutex> #include <chrono> std::map<int, std::string> myMap; std::mutex mapMutex; void producer() { for (int i = 0; i < 10; ++i) { std::lock_guard<std::mutex> lock(mapMutex); myMap[i] = "Value " + std::to_string(i); std::this_thread::sleep_for(std::chrono::milliseconds(100)); } } void consumer() { while (true) { std::lock_guard<std::mutex> lock(mapMutex); for (const auto &pair : myMap) { std::cout << "Key: " << pair.first << ", Value: " << pair.second << '\n'; } std::this_thread::sleep_for(std::chrono::milliseconds(150)); } } int main() { std::thread prod(producer); std::thread cons(consumer); prod.join(); cons.detach(); // This may cause issues if the consumer runs indefinitely return 0; } ``` I've tried using `std::lock_guard` to ensure mutual exclusion while accessing the map, but I still encounter crashes. It seems like the consumer sometimes tries to access elements that are in the process of being modified. Am I missing something regarding the lock scope or maybe there’s a better way to handle this? Should I be using `std::shared_mutex` for read-write access? Any insights would be greatly appreciated! I'm working on a web app that needs to handle this. Any help would be greatly appreciated! I'd love to hear your thoughts on this.