From the article: """ Here be dragons, though, since we must always remember to: * Update tag whenever assigning a new value. * Only retrieve the correct ty

From the article: """ Here be dragons, though, since we must always remember to: * Update tag whenever assigning a new value. * Only retrieve the correct type from the union (according to tag). * Call constructors and destructors at appropriate times for all non-trivial types. (string is the only one here, but you could imagine similar scenarios with others.) """ ...the last paragraph is the part that will almost surely trip a C++ newcomer up if they tried this out. The first to are (valid in my experience) complaints about maintenance mistakes that result in compiling programs but runtime errors.