[FFmpeg-devel] [PATCH] lavu/video_enc_params: make sure blocks are properly aligned

[Anton Khirnov]

Quoting Andreas Rheinhardt (2021-04-08 11:41:41)
> Anton Khirnov:
> > ---
> >  libavutil/video_enc_params.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/libavutil/video_enc_params.c b/libavutil/video_enc_params.c
> > index 635176ab91..1779a8799a 100644
> > --- a/libavutil/video_enc_params.c
> > +++ b/libavutil/video_enc_params.c
> > @@ -30,9 +30,9 @@ AVVideoEncParams *av_video_enc_params_alloc(enum AVVideoEncParamsType type,
> >                                              unsigned int nb_blocks, size_t *out_size)
> >  {
> >      AVVideoEncParams *par;
> > -    size_t size;
> > +    size_t blocks_offset = FFALIGN(sizeof(*par), 8);
> > +    size_t size          = blocks_offset;
> >  
> > -    size = sizeof(*par);
> >      if (nb_blocks > (SIZE_MAX - size) / sizeof(AVVideoBlockParams))
> >          return NULL;
> >      size += sizeof(AVVideoBlockParams) * nb_blocks;
> > @@ -44,7 +44,7 @@ AVVideoEncParams *av_video_enc_params_alloc(enum AVVideoEncParamsType type,
> >      par->type          = type;
> >      par->nb_blocks     = nb_blocks;
> >      par->block_size    = sizeof(AVVideoBlockParams);
> > -    par->blocks_offset = sizeof(*par);
> > +    par->blocks_offset = blocks_offset;
> >  
> >      if (out_size)
> >          *out_size = size;
> > 
> Wouldn't it be safer to just define a struct { AVVideoEncParams header;
> AVVideoBlockParams blocks[1]; } and use the offset of blocks in that?

I don't see how it would be safer and it prevents you from adding new
fields to AVVideoEncParams

-- 
Anton Khirnov