std::shared_ptr causing double deletion in multi-threaded C++ application with custom deleter
I've encountered a strange issue with I've been struggling with this for a few days now and could really use some help. I'm working with an scenario in my multi-threaded C++ application where I'm using `std::shared_ptr` with a custom deleter... The application occasionally crashes with a segmentation fault due to double deletion of the same resource. I have tried ensuring that the shared pointer instances are properly managed across threads, but I'm still running into issues. Here's a simplified version of my code: ```cpp #include <iostream> #include <memory> #include <thread> #include <vector> class Resource { public: Resource() { std::cout << "Resource acquired" << std::endl; } ~Resource() { std::cout << "Resource destroyed" << std::endl; } }; void threadFunction(std::shared_ptr<Resource> res) { std::this_thread::sleep_for(std::chrono::milliseconds(100)); } int main() { auto deleter = [](Resource* r) { std::cout << "Custom deleter called" << std::endl; delete r; }; std::shared_ptr<Resource> res(new Resource(), deleter); std::vector<std::thread> threads; for (int i = 0; i < 5; ++i) { threads.emplace_back(threadFunction, res); } for (auto& t : threads) { t.join(); } return 0; } ``` In this setup, I create a shared pointer that is passed to multiple threads. However, I suspect that the question arises from the fact that I'm not synchronizing access to the shared pointer. I've read that shared pointers are thread-safe for reading, but I'm worried that the custom deleter might not be handled correctly when multiple threads are accessing it concurrently. Here’s the behavior I get sometimes: ``` *** glibc detected *** ./my_app: double free or corruption (fast): 0x0000000001b0d1e0 *** ``` Is there a recommended approach to safely use `std::shared_ptr` in a multi-threaded context with custom deleters? Should I use `std::atomic<std::shared_ptr<Resource>>` or is there a different pattern I should follow? My development environment is Linux. For context: I'm using C++ on Ubuntu. Any ideas what could be causing this? I recently upgraded to C++ 3.9. What's the best practice here?