GNU bug report logs -
#21730
25.0.50; Random errors in redisplay--pre-redisplay-functions
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Reported by: Michael Welsh Duggan <mwd <at> md5i.com>
Date: Thu, 22 Oct 2015 04:05:02 UTC
Severity: normal
Found in version 25.0.50
Done: Eli Zaretskii <eliz <at> gnu.org>
Bug is archived. No further changes may be made.
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Michael Welsh Duggan <mwd <at> md5i.com> writes:
> Eli Zaretskii <eliz <at> gnu.org> writes:
>
>> From the backtrace it is obvious that the immediate reason for the
>> problem is the call to 'get-char-property' with an invalid 1st argument
>> of zero (it's a buffer position, so should be at least 1).
>>
>> Looking at 'cursor-sensor--detect', I see this:
>>
>> (defun cursor-sensor--detect (window)
>> (unless cursor-sensor-inhibit
>> (let* ((point (window-point window))
>> ;; It's often desirable to make the cursor-sensor-functions property
>> ;; non-sticky on both ends, but that means get-pos-property might
>> ;; never see it.
>> (new (or (get-char-property point 'cursor-sensor-functions)
>> (unless (bobp)
>> (get-char-property (1- point) 'cursor-sensor-functions))))
>>
>> So my guess is that the value of 'point' (the variable, not the
>> function) is 1, i.e. beginning of buffer, and subtracting 1 from it
>> produces that zero. Then the second call to 'get-char-property' barfs
>> as expected.
>>
>> The code tries to protect itself against such a calamity by calling
>> 'bobp', but that function looks at the buffer's value of point, which
>> might be different from what 'window-point' returns.
>>
>> So my advice would be to replace the call to 'bobp' with an explicit
>> test of the value of the local variable 'point', and see if that fixes
>> the problem.
>
> I've changed the (bobp) to (= point 1). I'll run it for a couple of
> weeks and report back.
This change seems to have done the trick. I have not encountered the
error in several days.
--
Michael Welsh Duggan
(md5i <at> md5i.com)
This bug report was last modified 7 years and 358 days ago.
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