std::thread not joining properly, causing unexpected behavior in C++11 application
I'm following best practices but I'm facing an issue with threads in my C++11 application where it seems that the threads are not joining properly, leading to unexpected behavior in my program. I have a simple function that processes some data in parallel using `std::thread`, but when I try to join the threads in the main function, it appears that the threads are not completing their tasks as expected. Here’s a simplified version of my code: ```cpp #include <iostream> #include <thread> #include <vector> #include <chrono> void process(int id) { std::this_thread::sleep_for(std::chrono::milliseconds(100 * id)); std::cout << "Thread " << id << " finished processing." << std::endl; } int main() { std::vector<std::thread> threads; for (int i = 0; i < 5; ++i) { threads.emplace_back(process, i); } // Intentionally trying to join threads before they are expected to finish for (auto& t : threads) { t.join(); } std::cout << "All threads joined." << std::endl; return 0; } ``` When I run this code, it does join all threads, but if I remove the `sleep_for` line in the `process` function, the output becomes unpredictable, even leading to some threads not completing before the main function exits. I initially thought that `std::thread` would ensure that all threads finish before `join()` returns, but it seems like the timing is causing issues. I've also tried adding a `std::mutex` to synchronize the outputs and protect shared resources, but the issue persists. The output is sometimes missing messages from certain threads, making me think they might be terminating prematurely. I'm compiling with GCC 11 under Ubuntu 20.04. Any insights or best practices to ensure that threads complete their execution reliably would be greatly appreciated. Any feedback is welcome!