Note the 's' on implementations.

That's typically labelled as implementation defined. Which is not the same as undefined behaviour.

Care to differentiate between them?

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In the absence of evidence, opinion is indistinguishable from prejudice.
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In reply to Re^4: The behavior is [sic] undefined by BrowserUk
in thread The behavior is [sic] undefined by John M. Dlugosz

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