title: The uses of std::osyncstream?
body: <p>What are the uses of the new C++20 <code>std::osyncstream</code> (<a href="http://en.cppreference.com/w/cpp/io/basic_osyncstream" rel="nofollow noreferrer">http://en.cppreference.com/w/cpp/io/basic_osyncstream</a>)? Isn't the <code>std::ostream</code> already thread-safe?</p>