It would be a valid implementation of C. But if you want to <i>depend</i> on the new behavior, which was previously undefined, then you would have to reference this new specification. That effectively makes it a new language, because you would no longer reference the C specification, but this new one.<p>(And if you <i>don&#x27;t</i> want to depend on the new behavior, which was previously undefined, then there&#x27;s not much point in using this particular implementation.)