std::atomic<bool> not behaving as expected in multi-threaded C++ application
I'm sure I'm missing something obvious here, but I've been struggling with this for a few days now and could really use some help... I'm working on a project and hit a roadblock. I've searched everywhere and can't find a clear answer. I'm experiencing unexpected behavior when using `std::atomic<bool>` in my multi-threaded C++ application. I have a scenario where multiple threads are changing the state of an atomic boolean, but the changes seem to not propagate as expected. Here is a simplified version of my code: ```cpp #include <iostream> #include <atomic> #include <thread> #include <chrono> std::atomic<bool> flag(false); void toggleFlag() { for (int i = 0; i < 10; ++i) { flag.store(!flag.load()); std::this_thread::sleep_for(std::chrono::milliseconds(100)); } } void printFlag() { while (flag.load() == false) { std::this_thread::sleep_for(std::chrono::milliseconds(50)); } std::cout << "Flag is now true!" << std::endl; } int main() { std::thread t1(toggleFlag); std::thread t2(printFlag); t1.join(); t2.join(); return 0; } ``` When I run this code, I expect that `printFlag` will eventually output "Flag is now true!", but often it seems to hang indefinitely. I have tried adding more logging to see the value of `flag`, and it shows that the flag is indeed being toggled, but `printFlag` is not catching it. I’ve also considered memory visibility issues, but since I'm using `std::atomic`, I thought this would handle that for me. My compiler is GCC 11.2 and I’m compiling with `-std=c++17`. What could I be missing here? Is there something about the way I handle the atomic that could lead to this behavior? Any insights or suggestions would be greatly appreciated! This is part of a larger application I'm building. What am I doing wrong? I'm working on a API that needs to handle this. This is part of a larger API I'm building. Thanks in advance! This issue appeared after updating to C++ 3.9. What's the correct way to implement this? Has anyone dealt with something similar?