Re: Should undefined behavior be encouraged in Emacs?

[Richard Stallman]

    My impression is that Emacs built-ins are generally supposed to
    have defined behavior, so that Emacs is easier to use reliably.

What is the meaning of "defined" or "undefined", here?
Is it a matter of whether the documentation says what happens in that case?

In simple cases such as (goto-char -5), users tend to see what the
behavior is, and are likely to write code that depends on it, even if
it isn't documented.  Thus, leaving it undocumented doesn't mean that
we can change it and nobody will notice.

Meanwhile, even if something is documented, we CAN change it.
It just means somewhat more annoyance will occur.

-- 
Dr Richard Stallman
President, Free Software Foundation
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