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Subject: Re: WPS playlist viewer exposes a bug in either plaback/buffering or playlist. I'm stumped!

Re: WPS playlist viewer exposes a bug in either plaback/buffering or playlist. I'm stumped!

From: Magnus Holmgren <magnushol_at_gmail.com>
Date: Sat, 17 Apr 2010 13:16:03 +0200

On 2010-04-16 09:07, Jonathan Gordon wrote:

> Well I'm stumped on this bug
> (http://www.rockbox.org/tracker/task/11175 ). Basically what happens
> is if you use a wps with the playlist viewer (attached should work on
> every target) the playlist will load in the wrong order and Wierd Shit
> (TM) happens when jumping around tracks. If you use a theme without it
> (or even I assume the same theme with it disabled (i.e in a
> conditional viewport)) the playlist would work fine.
>
> The code for the playlist viewer is draw_playlist_viewer_list() in
> apps/gui/skin_engine/skin_display.c starting around line 182. I'm
> pretty certain the problem is either in audio_peek_track() being
> called or playlist_peek(). Nothing else there touchees anything
> outside of the drawing/skln code.
>
> I dont know playlist/buffering/playback anywhere near enough to figure
> out what's going on, so if someone who does could have a look, that
> would be great.

I had a quick look at it, and I noticed two things:

* It uses quite a bit of stack (about 2700 bytes, on ARM at least).
Probably not a problem, but checking stack usage could perhaps be an idea.

* Looks like "buf" (in draw_playlist_viewer_list) can overflow. Consider
what happens if "buf_used" goes larger than "sizeof(buf)"... Suggestion:
use strlcat instead. Protects against overflow and simplifies the code.
Don't know if that's what causing the problems though.

-- 
   Magnus
Received on 2010-04-17

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