[FFmpeg-devel] [PATCH] avcodec/mpegvideo: Fix all but one tsan warning in fate-vsynth1-mpeg4

[Ronald S. Bultje]

Hi,

On Sun, Jul 9, 2017 at 9:19 PM, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/mpegvideo.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
> index e29558b3a2..574b3854e0 100644
> --- a/libavcodec/mpegvideo.c
> +++ b/libavcodec/mpegvideo.c
> @@ -495,7 +495,20 @@ int ff_mpeg_update_thread_context(AVCodecContext
> *dst,
>      // in that case dst may need a reinit
>      if (!s->context_initialized) {
>          int err;
> -        memcpy(s, s1, sizeof(MpegEncContext));
> +#define COPY(x) s->x = s1->x;
>

Unused?


> +#define COPYR(a, b) memcpy(&s->a, &s1->a, ((uint8_t*)&s->b) -
> ((uint8_t*)&s->a))
> +        COPYR(h263_aic,                         qscale);
> +        COPYR(lambda,                           mv_dir);
> +        COPYR(no_rounding,                      dest);
> +        COPYR(mb_index2xy,                      resync_mb_x);
> +        COPYR(next_p_frame_damaged,             h263_aic_dir);
> +        COPYR(h263_slice_structured,            mcsel);
> +        COPYR(quant_precision,                  first_slice_line);
> +        COPYR(flipflop_rounding,                gb);
> +        COPYR(gop_picture_number,               picture_structure);
> +        COPYR(picture_structure,                pblocks);
> +        COPYR(decode_mb,                        er);
> +        COPYR(error_rate,                       noise_reduction);


This is very obscure... The obscure part is what happens when fields get
(through refactoring) reordered or new fields get inserted...

I also appear to remember that we used to use this same pattern for h264
also, but we don't anymore. Does anyone remember why?

Ronald