I suppose it depends on the work the interviewer's company is doing, but when I last had a C++ job, knowing what a copy constructor was and the implications involved was important.
I agree that asking details related to syntax are not good questions. But copying objects is a very natural thing to do in most languages, and if you don't have some idea of the implications, that's a red flag.
Also: Some understanding on default copy constructors. I think it's OK not to know whether a default one is created for you or not, but just knowing that it might be is worthwhile to probe in an interview.
Of course, these concepts are due to a poor language design, but what can you do? If your team uses C++, you need to deal with the poor design, and need people who understand the poor design.
I agree that asking details related to syntax are not good questions. But copying objects is a very natural thing to do in most languages, and if you don't have some idea of the implications, that's a red flag.
Also: Some understanding on default copy constructors. I think it's OK not to know whether a default one is created for you or not, but just knowing that it might be is worthwhile to probe in an interview.
Of course, these concepts are due to a poor language design, but what can you do? If your team uses C++, you need to deal with the poor design, and need people who understand the poor design.