👀 Views: 73 💬 Answers: 1 📅 Created: 2025-06-27

c++11 multithreading std::array std::thread mutex C++

I'm trying to implement I'm encountering a data race issue when I try to use `std::array` in conjunction with `std::thread` and lambda captures in C++11. The goal is to initialize an array in one thread and read from it in another. However, I'm getting inconsistent results when running the program. Here's a simplified version of my code: ```cpp #include <iostream> #include <array> #include <thread> #include <chrono> std::array<int, 5> data; void writer() { for (int i = 0; i < 5; ++i) { data[i] = i * 2; std::this_thread::sleep_for(std::chrono::milliseconds(100)); } } void reader() { for (int i = 0; i < 5; ++i) { std::cout << "Data: " << data[i] << std::endl; std::this_thread::sleep_for(std::chrono::milliseconds(150)); } } int main() { std::thread t1(writer); std::thread t2(reader); t1.join(); t2.join(); return 0; } ``` When I run this code, the output sometimes shows uninitialized values or even crashes with a segmentation fault. I suspect it's a data race because both threads are accessing the `data` array concurrently without any synchronization mechanisms in place. I've tried using a mutex to protect access to the array, but I'm unsure how to properly implement it without introducing deadlock or additional complexity. Here’s the approach I attempted with a mutex: ```cpp #include <iostream> #include <array> #include <thread> #include <chrono> #include <mutex> std::array<int, 5> data; std::mutex dataMutex; void writer() { for (int i = 0; i < 5; ++i) { std::lock_guard<std::mutex> lock(dataMutex); data[i] = i * 2; std::this_thread::sleep_for(std::chrono::milliseconds(100)); } } void reader() { for (int i = 0; i < 5; ++i) { std::lock_guard<std::mutex> lock(dataMutex); std::cout << "Data: " << data[i] << std::endl; std::this_thread::sleep_for(std::chrono::milliseconds(150)); } } int main() { std::thread t1(writer); std::thread t2(reader); t1.join(); t2.join(); return 0; } ``` While this approach seems to work, I'm worried about the performance implications of locking for each access. Is there a better way to handle this without sacrificing data integrity or performance? Any insights on best practices for this kind of situation would be greatly appreciated. This issue appeared after updating to C++ latest.