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From: Pip Cet <pipcet@gmail.com>
To: Stefan Kangas <stefan@marxist.se>
Cc: 41520@debbugs.gnu.org
Subject: bug#41520: 28.0.50; Crash in character.h due to assertion error
Date: Mon, 25 May 2020 07:28:23 +0000	[thread overview]
Message-ID: <CAOqdjBe5CG5A7MGQ0hY7BZDi+EAwFczJ0MYxTPcxmVjxS_=J8Q@mail.gmail.com> (raw)
In-Reply-To: <CADwFkm=znFOKpwW-suS2Oc_5tQn0QzAwZEz8Xc-TNO5x27vKzA@mail.gmail.com>

On Mon, May 25, 2020 at 7:06 AM Stefan Kangas <stefan@marxist.se> wrote:
> When editing an org-mode document, I saw a crash due to this assertion
> error:

It's a bug in this code in xdisp.c:

  else if (it->bidi_it.charpos == bob
       || (!string_p
           && (FETCH_CHAR (it->bidi_it.bytepos - 1) == '\n'
           || FETCH_CHAR (it->bidi_it.bytepos) == '\n')))

The first FETCH_CHAR should be a FETCH_BYTE to avoid the assertion error.

There's at least one other place that has the same error, so I'll grep
some more before sending a patch.

My suggestion is to drop the "eassume" on emacs-27, and fix FETCH_CHAR
to FETCH_BYTE on master.

(I'd like to reiterate my proposal to use a pos_t for bytepos/charpos
pairs, which would catch or silently fix (which happened in this case
on my pos_t branch) such bugs. The code on my branch reads:

  else if (POS_CHAR_EQUAL (it->bidi_it.pos, bob)
       || (!string_p
           && (FETCH_CHAR (dec_pos (it->bidi_it.pos)) == '\n'
           || FETCH_CHAR (it->bidi_it.pos) == '\n')))

which, while minimally slower, doesn't throw assertion errors.)





  reply	other threads:[~2020-05-25  7:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-25  7:05 bug#41520: 28.0.50; Crash in character.h due to assertion error Stefan Kangas
2020-05-25  7:28 ` Pip Cet [this message]
2020-05-25  7:41   ` Pip Cet
2020-05-25 14:18   ` Eli Zaretskii
2020-05-25 14:30     ` Pip Cet
2020-05-25 15:07       ` Eli Zaretskii
2020-05-25 15:16         ` Pip Cet
2020-05-25 16:09           ` Eli Zaretskii
2020-05-25 17:54             ` Pip Cet
2020-05-25 19:30               ` Eli Zaretskii
2020-05-25 20:39                 ` Pip Cet
2020-05-26 16:17                   ` Eli Zaretskii
2020-09-27 14:36         ` Lars Ingebrigtsen
2020-09-27 15:15           ` Eli Zaretskii
2020-09-27 15:42             ` Lars Ingebrigtsen
2020-09-27 16:00               ` Eli Zaretskii

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