bug#23871: 25.1.50; Undo unexpectedly leads to blank buffer

[Markus Triska]

phillip.lord@russet.org.uk (Phillip Lord) writes:

> This is probably not going to help. I'll probably need to rebuild emacs
> on the same machine.

First you need access to the machine, so if you need that please let me
know. You won't have to debug a ceiled root problem without root access!

> How complex is the interaction with prolog? If it's just calling it
> as a repl, then a shell script which dumps the same output should work.

OK, I have constructed a shell script that simulates SWI-Prolog for this
specific case, please download it from:

    https://www.metalevel.at/ei/simulans.sh

Place it in the current directory and change the invocation of Emacs to:

   emacs -Q ceiled.pl -fn "Bitstream Vera Sans Mono 15"   --eval \
        "(progn (load \"$PWD/ediprolog.el\") \
         (setq ediprolog-program \"$PWD/simulans.sh\"))"

Note the setting of ediprolog-program to simulans.sh. I can reproduce
the issue with this script. If it does not work for you, please try a
different window size, font, or running Emacs in the terminal.

Thank you and all the best!
Markus