You&#x27;re welcome. The underscore thing is mentioned in 17.6.4.3.2 Global names, however it&#x27;s more complex than what I said initially (this is C++ after all):<p>* double underscore or underscore + capital letter is reserved in any scope<p>* underscore is reserved in global scope<p>Your code is allowed in fact, sorry. My personal rule is that I never start an identifier with an underscore anywhere.