👀 Views: 24 💬 Answers: 1 📅 Created: 2025-06-07

c++ multithreading smart-pointers cpp

I'm integrating two systems and I'm experiencing an issue with `std::shared_ptr` in a multi-threaded application where the reference count seems to not update correctly... I have a class that manages a resource via a `std::shared_ptr`, and I'm using multiple threads to access this resource. Here's a simplified version of my code: ```cpp #include <iostream> #include <memory> #include <thread> #include <vector> class Resource { public: Resource() { std::cout << "Resource Created" << std::endl; } ~Resource() { std::cout << "Resource Destroyed" << std::endl; } }; class Manager { public: std::shared_ptr<Resource> resource; Manager() : resource(std::make_shared<Resource>()) {} }; void accessResource(std::shared_ptr<Resource> res) { std::cout << "Accessing resource" << std::endl; } int main() { Manager manager; std::vector<std::thread> threads; for (int i = 0; i < 5; ++i) { threads.emplace_back(accessResource, manager.resource); } for (auto& thread : threads) { thread.join(); } std::cout << "Main thread exiting" << std::endl; return 0; } ``` When I run this code, I sometimes get unexpected results. Occasionally, I see "Resource Destroyed" being printed, even while threads are still accessing the resource. This indicates that the reference count may not be incrementing correctly when accessed from multiple threads. I've tried using mutex locks around the access function, but it hasn't resolved the issue. I suspect there might be a race condition with the reference count management, but I'm unsure how to properly synchronize access to the `std::shared_ptr`. What’s the best practice for handling `std::shared_ptr` in a multi-threaded context? Is there a specific pattern I should follow? Any guidance would be appreciated! This is my first time working with Cpp 3.9. Any ideas how to fix this?