There is a different bug in Microsoft C++, that is too difficult for us to reverse engineer. The warning about improper ## usage helps us diagnose when that other problem occurs. Without our warning, the situation is very difficult for us to diagnose. We have found this problem to be common in code written for Microsoft C++, so the warning saves us a lot of time. I did not want to complicate the issue with this bug report because I was not expecting any resistance. The ## usage in stringize.hpp is wrong, and there is no disadvantage to fixing it. But if you want all the details, see www.bullseye.com/help/trouble_microsoftPaste.html. The problem in stringize.hpp is described in CAUSE #1. The real reason we need to issue the warning is CAUSE #2.