bug#34690: 26.1; Emacs gets stuck when replacing text

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 01 Mar 2019 11:37:10 -0300
> From: Daniel Hernandez <daniel@degu.cl>
> Cc: "34690" <34690@debbugs.gnu.org>
> 
>  > Does this happen with any text in any buffer, and with any search and 
>  > replacement strings? or just with some? 
>  
> It happens with any buffer; even with an empty one.
> This problem occurs also when I only have that lines in
> the ".emacs" file.
>   
>  > > The lines added by Custom are the following: 
>  > >  
>  > > (custom-set-faces 
>  > >  ;; custom-set-faces was added by Custom. 
>  > >  ;; If you edit it by hand, you could mess it up, so be careful. 
>  > >  ;; Your init file should contain only one such instance. 
>  > >  ;; If there is more than one, they won't work right. 
>  > >  '(default ((t (:family "Inconsolata" :foundry "unknown" :slant 
>  > >  normal :weight normal :height 128 :width normal))))) 
>  >  
>  > Only with this particular font, or with any font? 
>  
> I noticed that it occurs with some font and it does not occur
> with other. For instance, it does not occur with DejaVu Sans
> Mono. That is, it does not occur with the following lines:
> 
> (custom-set-faces
>  ;; custom-set-faces was added by Custom.
>  ;; If you edit it by hand, you could mess it up, so be careful.
>  ;; Your init file should contain only one such instance.
>  ;; If there is more than one, they won't work right.
>  '(default ((t (:family "DejaVu Sans Mono" :foundry "unknown"
>  :slant normal :weight normal :height 98 :width normal)))))

Can you try the latest pretest of Emacs 26.2?  Maybe this problem is
already fixed.

If Emacs 26.2 also has this problem, the next step is to attach GDB to
Emacs when this happens and use the technique described in etc/DEBUG
to find out where it loops.

> Another detail. When it occurs the text "Query replace:" is
> not showed.

This is consistent with redisplay looping.