Segmentation Fault When Using std::map in a Multi-threaded C++ Application with C++17
I'm sure I'm missing something obvious here, but I'm working with a segmentation fault in my multi-threaded C++ application while trying to update a `std::map`. The application is built with C++17, and I'm using threads from the standard library. The question occurs when multiple threads attempt to read and write to the same `std::map` instance. I'm using a mutex to guard access to the map, but it seems that some threads are still working with segmentation faults. Here’s a simplified version of my code: ```cpp #include <iostream> #include <map> #include <thread> #include <mutex> std::map<int, int> myMap; std::mutex mapMutex; void updateMap(int key, int value) { std::lock_guard<std::mutex> lock(mapMutex); myMap[key] = value; } void printMap() { std::lock_guard<std::mutex> lock(mapMutex); for (const auto& pair : myMap) { std::cout << pair.first << " : " << pair.second << '\n'; } } int main() { std::thread t1(updateMap, 1, 10); std::thread t2(updateMap, 2, 20); std::thread t3(printMap); t1.join(); t2.join(); t3.join(); return 0; } ``` In this example, I'm updating the map from two threads while a third thread attempts to print the entire map. Even though I have a mutex in place, I still get a segmentation fault intermittently. In my debugging, I noticed that it only happens when the `printMap` function is called after `updateMap` threads have started, and sometimes even before `join()` is called. I also tried making all map accesses through a single function to avoid potential race conditions, but the scenario continues. I'm using GCC 9.3 on Ubuntu 20.04. Has anyone encountered similar issues with `std::map` and multithreading in C++17? Any insights on how to resolve this or best practices to ensure thread safety with `std::map` would be greatly appreciated. This is part of a larger CLI tool I'm building. I'd really appreciate any guidance on this.