"3.4.3 undefined behavior behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard impose

"3.4.3 undefined behavior behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements" It is _very_ explicit. The following note is (as all notes are) not normative. So even if the note would cast any doubt (it really doesn't), it can safely be ignored.