function static variable destructor and thread

Question

I have the a simple program.

int main() 
{
    std::atomic<bool> b = true;
    ConcurrentQueue<std::string> queue;

    std::thread thread( [&]{
        while ( b ) {
            auto str = queue.wait_and_pop();
            std::cout << *str;
        }
    });

    b = false;
    queue.push( "end" );
    thread.join();
}

ConcurrentQueue<T> is my own implementation of thread safe queue, wait_and_pop is a blocking operation that use std::condition_variable.

this program successfully prints "end" and exits, no problem here. ( there is a bug that b is false when thread started which cause it to exit immediately but that is not relevant here )

But if I wrap all these in a class

class object {
public:
    object() {
        b = true;

        thread = std::thread( [this]{
            while ( b ) {
                auto str = queue.wait_and_pop();
                std::cout << *str;
            }
        });
    }

    ~object() {
        b = false;
        queue.push( "end" );
        thread.join();
    }

private:
    std::atomic<bool> b;
    std::thread thread;
    ConcurrentQueue<std::string> queue;
};

and have a function static variable like

object & func() {
  static object o;
  return o;
}

and main

int main() {
    object & o = func();
}

now the program prints "end" then stuck at destructor of o at line thread.join().

I have tested this with clang and no problem. This seem to only happen in VC11. Why is that?

Answer 1

There recently was a thread with the same problem, but I can't find it anymore.

Basically, there's a deadlock in VS's runtime library when you have a static lifetime object that tries to end a thread in its destructor.