“defensive check - one typically performed at runtime (e.g., using a C-style assert macro) to verify some condition that is impossible to occur in a correct program. A common use case is to verify, for a given function, that there has not been a contract violation — i.e., a precondition or postcondition violation — yet is entirely superfluous in a correctly implemented program. Generalized PODs ’11 (468), Rvalue References (744)” (EMCppSfe 2021)