[FFmpeg-devel] [PATCH] doc/APIchanges: document the lavu/lavf field moves

[Michael Niedermayer]

On Thu, Jun 30, 2016 at 04:21:03PM -0300, James Almer wrote:
> On 6/30/2016 1:53 PM, James Almer wrote:
> > On 6/30/2016 1:15 PM, Michael Niedermayer wrote:
> >> The text is copied from the lavfi case. Not sure this matches
> >> exactly private / public ABI wise, better text welcome!
> >>
> >> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >> ---
> >>  doc/APIchanges |   16 ++++++++++++++++
> >>  1 file changed, 16 insertions(+)
> >>
> >> diff --git a/doc/APIchanges b/doc/APIchanges
> >> index 47106c2..fd649d6 100644
> >> --- a/doc/APIchanges
> >> +++ b/doc/APIchanges
> >> @@ -15,6 +15,22 @@ libavutil:     2015-08-28
> >>  
> >>  API changes, most recent first:
> >>  
> >> +2016-06-30 - c1c7e0ab - lavf 57.41.100 - avformat.h
> >> +  Fix accidental ABI breakage in AVFrame.
> >> +  ABI was broken in 6f69f7a8, lavf 57.32.100 and released as ffmpeg 3.1.
> > 
> > AVStream, and again, there was *no* breakage in 3,1. A public field
> > was added above private fields.
> > The breakage is what we're now introducing in 3.1.1 to keep people
> > misusing the API happy.
> > 
> > if we add a line here, it should mention how we're in breaking the
> > 3.1 ABI to make 3.1.1 compatible at runtime with API-violating
> > applications built against 3.0
> 

> How about something like
> 
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 47106c2..c80606a 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -15,6 +15,30 @@ libavutil:     2015-08-28
> 
>  API changes, most recent first:
> 
> +2016-06-30 - c1c7e0ab - lavf 57.41.100 - avformat.h
> +  Moved codecpar field from AVFilterContext to the end of the struct.
> +  This is an intentional ABI breakage as it's been informed to us that
> +  several downstream projects wrongly accessed fields marked as private
> +  which were below the newly added public field.

i think this is a confusing to someone who hasnt followed the
discussions, it sounds a bit like "we break ABI to break apps"
when the goal is to match (private) ABI toward the widly used 3.0
as many applications used it and would otherwise break

[...]

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