> A programmer needs to be aware This can be extrapolated to anything that causes UB. A programmer needs to be aware that what he does causes UB. You asked for

> A programmer needs to be aware This can be extrapolated to anything that causes UB. A programmer needs to be aware that what he does causes UB. You asked for a normal thing that is being done by a programmer that causes UB, and I think I gave a fair example. I don't want to aggressively argue a point, just wondering what exactly you want to prove here. It's not like programmers cause UB intentionally or when doing some weird stuff like code golfing. No, programmers code in C++ using standard techniques and fall victim to the UB. Another example of UB is accessing an array out of bounds. Again, you may say a programmer is expected to rationalize his code in this regard, and yet off-by-one is one of the most common categories of errors in practice.