Re: undo in loaddefs.el buffer

[Richard Stallman]

    Right.  The same question is asked in auto-compression-mode during
    visiting large gzipped files.

I'm sure that can be fixed, if you tell me precisely where in the
code it occurs.  Would you please try making C and Lisp level backtraces
while Emacs is asking the question?

    And what is unusual for such yes-no prompts is that it can't be
    interrupted with C-g.  Typing C-g pops up an unwanted X popup menu.

C-g normally should quit out of this question.  Why not in this case?
This too may be fixable, but only with more precise information.

    Even better not to ask anything, but to display a message saying that
    to prevent discarding the undo info the user should change the value
    of undo-outer-limit.

That would not be an improvement.  That way, you could do a command
and be surprised that you can't undo it.