I'm a fairly new user of this site but I have been using other Stack Exchange sites for quite some time. Yesterday, I've answered a question that looked (and still looks) fine to me. However, it was closed as off-topic several hours after I've answered. I'm generally trying to be careful to only answer good questions so I would like to understand what was wrong about this one.
Re-reading the “on-topic” page, I couldn't identify any obvious problem. As far as I can tell, the question was about a common confusion about integer overflow in C and C++ which can be a vector of attack. The only thing I can think of is that it might be too programming-specific. But then again, it is a conceptual question and not asking for advice in writing or debugging code. I've seen plenty of questions regarding PHP or Java Script code. Are the rules for C different? There even is a C and C++ tag (which were applied to the question in question) so I assume those technologies are not off-topic per se.
So, what is wrong with this question?