The spec says: > For signed integers, the operations +, -, , /, and << may legally overflow and the resulting value exists and is deterministically defined by

The spec says: > For signed integers, the operations +, -, , /, and << may legally overflow and the resulting value exists and is deterministically defined by …* It does not go on to define the overflow values; that gets to be implementation defined. This is in contrast to unsigned integers, which the spec does precisely define overflow for.