Function Watch

13-Multithreading/code/exception_ptr.cpp:26–34

}

void Watch()
{
    std::exception_ptr ptr;
    // join immediately.
    {std::jthread _{ Work, std::ref(ptr) }; }
    if (ptr)
        std::rethrow_exception(ptr);
    std::cout << "All students over.\n";
}

int main()
{