Subject: Re: bug#18558: 24.4.50; Debugger slow with long strings

From: Marcin Borkowski <[email-masked]>
Date: Fri, 19 Feb 2016 09:41:01 +0100

On 2014-09-25, at 12:16, Helmut Eller <[email-masked]> wrote:

> Moving the cursor in the debugger window is very slow in the following
> example:
>
> shell> cat test.el
> (progn
>   (defun foo (n string)
>     (cond ((= n 0) (debug))
>           (t (foo (1- n) string))))
>   (foo 30 (make-string 500000 ?\\)))
>
> shell> emacs -Q -nw -l test.el
>
> Now move the cursor around to see the slowness.
>
> Maybe the debugger should truncate long strings as it does with long
> lists.

Confirmed on GNU Emacs 25.1.50.2 (commit 4ccd268).

I would guess that the problem is not in long string /per se/, but with
lon lines in the *Backtrace* buffer, i.e. probably something connected
with the display engine.  I guess this bug should either be closed or
merged with some other one (one of the other ones, perhaps) dealing with
efficiency problems with long lines.

Best,

-- 
mbork