std::thread causes program to abort

Question

I have the following code snippet:

#include <thread>
int main(){
    std::thread trial([](){ return 2;});
    //trial.join()
    return 0;
}

From this I get the following output:

terminate called without an active exception
[1]    17963 abort (core dumped)  ./a.out

Now, this doesn't happen when I call .join() after I create the thread. As far as I know, .join() waits until the execution of the thread ends. However, it also seems to prevent abort from happening. Could somebody explain what's going on?

Answer 1

Could somebody explain what's going on?

From the documentation of the destructor of std::thread:

If *this has an associated thread (joinable() == true), std::terminate() is called.

In the example, you failed to join the thread, therefore it is joinable when it is destroyed, therefore the process std::terminate() is called. By default std::terminate() calls std::abort.

If you do join, then after the join, the thread will not be joinable. Therefore std::terminate() will not be called upon the destruction.