bug#25156: 26.0.50; `describe-text-properties' hangs with 100% cpu usage when property is a char-table

[Peter Wang]

A simplest test case is like:

(describe-property-list (list 'syntax-table lisp-mode-syntax-table))

evaluating this Elisp _expression_ will hang with 100% CPU usage.

On Sat, Dec 10, 2016 at 10:22 PM, Eli Zaretskii <eliz@gnu.org> wrote:

> From: Peter Wang <ptr.wang@gmail.com>
> Date: Sat, 10 Dec 2016 21:59:32 +0800
>
> I came across the problem when I was using `C-u C-x =' on a SLIME
> presentation. After some debugging, I found out the cause of the
> problem. Here is it:
>
> In a slime REPL buffer, when the evaluation result is rendered, SLIME
> adds text properties using `slime-add-presentation-properties'. One
> of the text properties is a syntax-table `slime-presentation-syntax-table'.
>
> `C-u C-x =' calls `(describe-char (point))', which in turn calls
> `describe-text-properties', which hangs with 100% cpu usage.
>
> I think a possible fix could be done in `describe-property-list', adding
> a case in cond to handle the type of syntax-table, something like:

Thanks.  Could you perhaps prepare a small test case for this problem?
It would help understanding the underlying problem, and possibly also
serve as a beginning of a test for our test suite.