I've been in an interviewing mindset for awhile and I've come to realize something important about C++ in particular. C++ is a "two peak" language. That is to say C++ is the only language I know of where two very different sets of programmers consider themselves well versed in the language. Let me show you in fake graph form:
Programmers (especially those coming from C) can very quickly get up to speed in C++ and feel quite proficient. These programmers will tell you that they know C++. They are lying. As a programmer continues in C++, he goes through this valley of frustration where he fully comes to terms with the full complexity of the language. The good news is that it's really easy to tell the difference between C++ programmers pre- and post- valley (in an interview, in this case). Just mention that C++ is an extremely large and complex language, and the post-valley people will give you 127 different tiny frustrations they have with the language. The pre-valley people will say "Yea, I guess. I mean, it's just C with classes.".