[webkit-dev] Reference count leak with InBandTextTracks?

Benjamin Dupont (bedupont) bedupont at cisco.com
Tue Oct 1 02:48:59 PDT 2013

Hi all,

I am currently working on the InbandTextTracks in webkit and I am trying to understand how the memory is released.

When we launch the track-in-band.html layout test, two in-band text tracks have been created and added, the corresponding RefPtr has a refCount equals to three.
1. Why are there 3 owners for each in-band text track? Is there an hidden cache mechanism?

After this test, if we load another page, the player is destroyed and the clearTextTracks method is called.
In my understanding, the player should be the only owner of in-band text tracks and thus after the clearTextTracks method is called, the ref count should be decreased to 0 and the in-band text track object should be deleted.
In fact, after the clearTextTracks method the ref count isn't equals to 0 thus the in-band text track object isn't deleted.
This text track object is deleted when the clear memory cache is called.

2. Is it a normal behavior? If yes, what is the interest to use smart pointer?

3. How does the clear memory cache know that this ref pointer (with a ref count != 0) can be released?

Thanks in advance for your explanations,

            Benjamin Dupont.

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