Function thread_enable_join

thread/thread.cpp:1524–1528

        return indirect_lock<thread>(ppt, nullptr);
    }
    join_handle* thread_enable_join(thread* th, bool flag)
    {
        th->set_joinable(flag);
        return (join_handle*)th;
    }

    void* thread_join(join_handle* jh) {
        auto th = (thread*)jh;