Is “Explain the RAII idiom” a good C++ screening question?

Question

A company that I work with has asked me to do candidate phone screenings to make sure they aren't completely embarrassed when sending over someone to a potential client.

It turns out that a fair number of people were being placed for a C++ developer role. I don't spend much time in C++, but I have done a few trivial and non-trivial projects in the language. I figured that "Explain the RAII idiom" would be a nice softball question that most serious C++ developers could answer while half asleep, and would allow me to move on to more interesting questions about experience. But it turns out people who have 10+ years C++ experience don't recognize the term, even if I expand the acronym to "Resource Acquisition is Initialization." One candidate went so far as to say he felt it wasn't always practical to apply the technique in Windows development, which I thought was an odd sentiment, but I could see a couple of examples that arguably support that line of thought. (But really only arguably).

Even a couple of C++ developers I know well enough to judge their competence said they didn't recognize the term, but upon reading a summary of the technique, said "Oh, yeah, I didn't know that had a name. I just thought of those things as something you just have to do." I remember the term from the second edition of Stroustrup's book, even though the full impact didn't sink in at the time.

So, is "Can you explain the RAII idiom to me?" a fair screening question? Is it reasonable to expect all competent C++ developers to understand it? Is the term more esoteric than I would think? Assuming a candidate doesn't know the term, are there follow up questions that could help me tease out whether they have at least internalized the practices that make RAII work? Are there better alternative "weeder" questions that give the candidate some latitude in answering, and help the candidate demonstrate their understanding of C++ development?

Editing to add: To clarify, I'm not the sort of interviewer that disqualifies people because they don't know buzzwords and acronyms. However, I do think it's reasonable to expect that an experienced C++ programmer has internalized good practices for resource management. I also think that it's important to verify that a candidate understands some "basics" about the technology they claim expertise in before moving on to more interesting questions about design, problem solving, etc. I think what I'm looking for is a good way to ask an open-ended question, suitable for use in a short telephone screening, that I can use to judge a candidate's basic understanding of good resource management practices in C++, before I ask "hard" questions.

Answer 1

You seem to have found that C++ developers you know from experience are competent are unfamiliar with that acronym or even the full expression. That alone would seem to indicate that the question is not suitable as a screening question during a phone call.

On the other hand, you could get to the same point via a more roundabout way by posing a scenario. Something like: "You are implementing a Log class that will write logging information to a file. Obviously, you will need to have a member variable that is a file handle (std::FILE*). Where do you allocate and free this file handle?" If the candidate starts talking about creating an open() and a close() method rather than allocating the file handle in the constructor and deallocating the handle in the destructor, you can follow up by asking about things like how their class would behave if the calling code raised exceptions, etc.

Answer 2

I don't think it is a practical question as it is proposed. I think you will find a lot of developers will fall into the "oh, yeah, I didn't know that had a name" camp. I would suggest that you test the candidates on the concept and not the name of the concept. Give them a code example and ask why it is incomplete or have them demonstrate that they know the concept.

Answer 3

Well, I know that when I want to know if someone is competent, the first thing I do is check their knowledge of acronyms. Once that's established, I make sure they know the names of other technologies that I think sound cool. If they're still there after that, then I ask them for a list of their favorite colors.

I can't stand this sort of thing. I mean, on my end of the interview, this is sirens and warning bells. I don't want to be working in a place where it actually matters that I know bizarre mnemonics that my boss thinks are "fundamental". I can't be bothered to learn peoples names who I've dealt with for years, so I sure as hell don't waste brain space with cute acronyms that describe best practices.

Look at my code. Ask me how I'd do things. I'll doodle crap on a whiteboard until the cows come home. I'll code you an app. Don't give me bullshit trivia questions. Trivia is always hit or miss, and it's never fundamental.

Answer 4

I do think is a valid question. Although I don't know how popular is the RAII term (in my team, we do use the term RAII all the time) but the concept of resource handling is important especially if you want exception-safe and multi-threaded-safety as well.

Answer 5

If your purpose is to screen out total incompetents quickly, try something like this:

FizzBuzz Test

Then you can leave C++ concepts and practices to those in a better position to evaluate C++ expertise.