[FFmpeg-devel] [RFC] avcodec/avcodec.h: Add encryption info side data

[Derek Buitenhuis]

On 12/6/2017 12:36 AM, Jacob Trimble wrote:
> Would a 0-length array work?  Otherwise I would need to have it be a
> 1-length array and have to account for that when calculating the size
> to allocate; it would also require a comment to ignore the size of the
> array.

Aren't 0-length arrays a GNU extensions? If so, I would gather that it
probably is not OK in a public header, either.

> The reason I want it to be an array is because I want a variable
> number of elements, but I want the data contained in the struct.
> Since this will be extra data, AFAIK it will only be free()'d, so I
> can't use pointers or it will leak.
> 
> Another alternative would be to still malloc more than needed and have
> the memory past the struct be the array.  That seems like a hack, but
> would allow a simple free().  For example:

I'm not entirely sure what way we prefer nowadays, but you can see
we've had side data with variable length members before with e.g.
AV_PKT_DATA_QUALITY_STATS, but that doesn't have a struct associated
with it. I'm hoping someone more up to date with the side data stuff
can chime in with a suggestion on what our current best practices
are for it.

- Derek