At a former job, I had a set of simple, if contrived examples, that I asked. Programs were short, less than 20 lines; candidates were instructed that the source would compile unless indicated otherwise, in which case they were given the entire compiler output. I would ask fairly simple questions that would expose a lot about the candidates knowledge. Such as:

if (~false == true) std::cout << "true"; else std::cout << "false";

In C++, what does this print? And if they answered correctly, I'd ask them to explain how/why. This question wasn't a deal breaker, but did immediately given an insight into their depth of knowledge of the language.