RE: Converting an Integer into Human Readable String

[Drew Adams]

> > (format-mode-line "%I" 4060) -> "4.6k"
> 
> Beware: this has side effects.  It doesn't just return a string.

What side effects?  Where are they documented?
Or is there a doc bug wrt this missing info?

In any case, what I wrote was incorrect.  AFAICT there is no way to pass the
number that is to be interpreted as the buffer size by "%I", except by passing
an actual BUFFER of the given size as arg.  This will do it, I guess, but it
seems a bit silly:

(with-temp-buffer
 (insert (make-string 4060 ?*))
 (format-mode-line "%I" nil nil (current-buffer)))