[FFmpeg-devel] [PATCH] lavu/buffer: add release function

Lukasz Marek lukasz.m.luki at gmail.com
Sun Mar 2 17:48:11 CET 2014

On 02.03.2014 17:14, Reimar Döffinger wrote:
> On 28.02.2014, at 01:21, Lukasz Marek <lukasz.m.luki at gmail.com> wrote:
>>> Keep in mind that a buffer can come from a user application. There is
>>> no way you could free such a buffer correctly by destroying the buffer
>>> reference and just returning the raw data.
> This buffer might be allocated on some special hardware, and to allocate/lock or deallocate/unlock it you need to write some magic registers.
> What happens if you use this function on such a buffer?
> I can see only two things happen:
> 1) you call the custom free function, then all following code trying to use it will cause bus errors or worse

I'm not sure I understand but if user operates on data they released 
with free function its just their fault. free() is dangerous in the same 
I assumed user will not release buffer if don't know how to delete it.

> 2) you don't call it. Then the external hardware will forever stay in a locked state which essentialy might mean it will hang
> The only way I can even see this working is if you assume that the buffer was allocated with an ordinary memory managment function like malloc, but that is nothing you can assume in general.

If you mention such cases, I wonder what would happen when user ref 
buffer and make it writable and then second copy is freed with magic 
free function.

Revering patch attached.

Best Regards,
Lukasz Marek

Insanity: doing the same thing over and over again and expecting 
different results. - Albert Einstein
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