GNU bug report logs - #1501
Emacs 22 loses undo buffer

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Message #80 received at 1501 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: emerick <at> gmail.com, 1501 <at> debbugs.gnu.org, cyd <at> stupidchicken.com,
 npostavs <at> gmail.com
Subject: Re: bug#1501: Emacs 22 loses undo buffer
Date: Wed, 20 Oct 2021 15:05:34 +0300

> From: Stefan Kangas <stefan <at> marxist.se>
> Date: Tue, 19 Oct 2021 18:01:43 -0700
> Cc: Emerick Rogul <emerick <at> gmail.com>, 1501 <at> debbugs.gnu.org,
>  Chong Yidong <cyd <at> stupidchicken.com>
> 
> +  /* Remove the `face' property to save space.  (Bug1501)  */
> +  if (!NILP (string))
> +    Fremove_list_of_text_properties (make_fixnum (0),
> +				     make_fixnum (SCHARS (string)),
> +				     CALLN (Flist, Qface),
> +				     string);

This modifies the text properties of STRING, which you don't own.

Also, it will do unnecessary non-trivial processing when undo is
turned off.

I definitely think that with the enlarged undo-limit we should leave
this obscure situation alone.  It isn't worth making such significant
low-level changes due to such obscure problems, which are arguably
cockpit errors.

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