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

[Phillip Lord]

Markus Triska <triska@metalevel.at> writes:

> phillip.lord@russet.org.uk (Phillip Lord) writes:
>
>> I haven't started to look at 23871 yet, only 21722; I would rather deal
>> with the simple case first. Can you tell me whether it fixes this
>> case?
>
> The patch fixes the concrete case reported in #21722 but leads to a new
> problem with undo that is not there without this patch.

And is it there in Emacs-24.5?

> I cannot regard this as a good fix for #21722. If you want to close
> #21722 after applying your patch, I can file a new report for the new
> problem.
>
> Please note that #23871 is the main problem for me and has been present
> in Emacs for about a decade. The other issues I filed are only my
> attempts to make the issue more easily reproducible, and may in fact
> even be unrelated issues that I find while trying to find the root cause
> of #23871. I first filed #1095, then adapted this to #21722, and now
> also filed #23871 because redisplay may also be involved.
>
> I have tolerated the problems described in #1095 and #21722 for about a
> decade and see no reason to delay Emacs 25: Neither Emacs 23 nor 24 were
> delayed because of them although these issues were already reported!
> #23871 was also present during this time but not yet reported.


I've tried to reproduce #23871, but unfortunately, swiprolog crashes as
shown below.

The packaged version of swiprolog on my machine is 6.6.4, rather than >
7.2. I'm not keen on trying to update to 7.2. Is there a reproduction
that will work on 6.6.4?

Phil



% 1
% 2
% 3
% 4 almost empty lines; next line is: line 15
%?- time(ceiled_square_root(2^10000, R)).
%@ [Thread 1] pl-arith.c:1669: ar_pow: Assertion failed: 0
%@ C-stack trace labeled "crash":
%@   [0] __assert_fail+0x41
%@   [1] PL_license+0x584a
%@   [2] PL_license+0x3755
%@   [3] PL_license+0x3be0
%@   [4] PL_next_solution+0x5c3e
%@   [5] pl_skip_list3_va+0x1629
%@   [6] pl_skip_list3_va+0x1da0
%@   [7] PL_toplevel+0x1d
%@   [8] main+0x2d
%@   [9] __libc_start_main+0xf5