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bug#57804: An infinite loop in a `fontify-region' function causes Emacs
From: |
Eli Zaretskii |
Subject: |
bug#57804: An infinite loop in a `fontify-region' function causes Emacs to hang indefinitely |
Date: |
Thu, 15 Sep 2022 09:27:14 +0300 |
> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, 57804@debbugs.gnu.org, Paul Pogonyshev
> <pogonyshev@gmail.com>
> Date: Thu, 15 Sep 2022 13:20:51 +0800
>
> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
> > Eli Zaretskii <eliz@gnu.org> writes:
> >
> >> This case is exactly one of those which I think we shouldn't try to
> >> fix, because it's the case of "buggy Lisp program", a.k.a. "don't do
> >> that". There's no reason for any useful Lisp program to have an
> >> infloop like this:
> >>
> >>> (while t
> >>> "whoopsie")
> >
> > You've never accidentally put an infloop into a font locking function?
> > Then you've been very lucky.
> >
> > We should definitely fix this is we can.
>
> Why isn't jit-lock-debug-mode an option?
It definitely is, for the particular use case of debugging font-lock.
So is running font-lock-fontify-buffer by hand.
So is attaching a debugger when such an infloop is bumped into
accidentally without expecting it.
There's also the recently-added backtrace-on-redisplay-error feature,
which could help with diagnosing such problems, perhaps combined with
debug-on-entry or somesuch.
IOW, I think we have already several useful tools available for the
particular problem of debugging loops in font-lock, if we want to
interpret this bug report in that narrow interpretation.
- bug#57804: An infinite loop in a `fontify-region' function causes Emacs to hang indefinitely, (continued)