Re: [FFmpeg-devel] [PATCH] avcodec/avcodec: don't free AVOption settable fields in avcodec_close()

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

James Almer:
> It can uninitialize fields that may still be used after the context was closed,
> so do it instead in avcodec_free_context().
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
>  libavcodec/avcodec.c | 1 -
>  libavcodec/options.c | 2 +-
>  2 files changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/libavcodec/avcodec.c b/libavcodec/avcodec.c
> index 38bdaad4fa..122d09b63a 100644
> --- a/libavcodec/avcodec.c
> +++ b/libavcodec/avcodec.c
> @@ -524,7 +524,6 @@ av_cold int avcodec_close(AVCodecContext *avctx)
>  
>      if (avctx->priv_data && avctx->codec && avctx->codec->priv_class)
>          av_opt_free(avctx->priv_data);
> -    av_opt_free(avctx);
>      av_freep(&avctx->priv_data);
>      if (av_codec_is_encoder(avctx->codec)) {
>          av_freep(&avctx->extradata);
> diff --git a/libavcodec/options.c b/libavcodec/options.c
> index 33f11480a7..91335415c1 100644
> --- a/libavcodec/options.c
> +++ b/libavcodec/options.c
> @@ -172,7 +172,7 @@ void avcodec_free_context(AVCodecContext **pavctx)
>      av_freep(&avctx->intra_matrix);
>      av_freep(&avctx->inter_matrix);
>      av_freep(&avctx->rc_override);
> -    av_channel_layout_uninit(&avctx->ch_layout);
> +    av_opt_free(avctx);
>  
>      av_freep(pavctx);
>  }

This will lead to memleaks for users that use avcodec_close(avctx) +
av_free(avctx) to free an AVCodecContext (e.g. our frame-threaded
encoders do this). Notice that avcodec_free_context() violates the
documentation of AVCodecContext.extradata (documented to not be freed
for decoders) and AVCodecContext.subtitle_header and
AVCodecContext.rc_override (documented to not be freed by lavc for
encoders), so there is a reason for using it instead of
avcodec_free_context() (even when not reusing the context).

- Andreas
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