cancelling std::thread using native_handle() + pthread_cancel()
c++, c++11, gcc, pthreads, stdthread
Solution
No, I don't think that you will not have additional problems than:
- not being portable
- having to program _very_very_ carefully that all objects of the cancelled thread are destroyed...
For example, the Standard says that when a thread ends variables will be destroyed. If you cancel a thread this will be much harder for the compiler, if not impossible.
I would, therefore recommend not to cancel a thread if you can somehow avoid it. Write a standard polling-loop, use a condition variable, listen on a signal to interrupt reads and so on -- and end the thread regularly.
Problem
I am converting a previous thread wrapper around pthreads to std::thread. However c++11 does not have any way to cancel the thread. I REQUIRE, nonetheless, to cancel threads since they may be performing a very lengthy task inside an external library. I was considering using the native_handle that gives me pthread_id in my platform. I'm using gcc 4.7 in Linux (Ubuntu 12.10). The idea would be: ``` #include <iostream> #include <thread> #include <chrono> using namespace std; int main(int argc, char **argv) { cout << "Hello, world!" << endl; auto lambda = []() { cout << "ID: "<<pthread_self() <<endl; while (true) { cout << "Hello" << endl; this_thread::sleep_for(chrono::seconds(2)); } }; pthread_t id; { std::thread th(lambda); this_thread::sleep_for(chrono::seconds(1)); id = th.native_handle(); cout << id << endl; th.detach(); } cout << "cancelling ID: "<< id << endl; pthread_cancel(id); cout << "cancelled: "<< id << endl; return 0; } ``` The thread is canceled by an exception thrown by pthreads. My question is: Will there be any problem with this approach (besides not being portable)?