[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#21730: 25.0.50; Random errors in redisplay--pre-redisplay-functions
From: |
Michael Welsh Duggan |
Subject: |
bug#21730: 25.0.50; Random errors in redisplay--pre-redisplay-functions |
Date: |
Tue, 27 Oct 2015 00:19:13 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
>> From: Michael Welsh Duggan <mwd@md5i.com>
>> Date: Thu, 22 Oct 2015 00:04:06 -0400
>>
>> I don't have a recipe for this. Every now again I get the following in
>> my *Messages* buffer:
>>
>> redisplay--pre-redisplay-functions: (args-out-of-range 0)
>>
>> I turned on debug-on-error, and got the following backtrace:
>>
>> Debugger entered--Lisp error: (args-out-of-range 0)
>> get-char-property(0 cursor-sensor-functions)
>> cursor-sensor--detect(#<window 224 on *Group*>)
>> run-hook-with-args(cursor-sensor--detect #<window 224 on *Group*>)
>> redisplay--pre-redisplay-functions(t)
>> apply(redisplay--pre-redisplay-functions t)
>> #[128 "\300\301\"\210\300\302\"\207" [apply
>> redisplay--pre-redisplay-functions ignore nil] 4 nil nil](t)
>> redisplay_internal\ \(C\ function\)()
>>
>> This happens infrequently, about a couple of times a day. I cannot make
>> this happen on demand, but I can add debugging code if led in the
>> correct direction.
>
> Thanks for reporting this. I'll try to help, although Stefan might
> have better ideas.
>
> 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.
--
Michael Welsh Duggan
(md5i@md5i.com)