[FFmpeg-devel] [PATCH 1/5] avformat/aviobuf: set AVIOContext->error on bprint buffer ENOMEM

[Andreas Rheinhardt]

Marton Balint:
> This makes sure the error condition is kept in AVIOContext even if the user
> does not check the return value of avio_read_to_bprint or
> ff_read_line_to_bprint.
> 
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  libavformat/aviobuf.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
> index 29d4bd7510..6f8a822ee3 100644
> --- a/libavformat/aviobuf.c
> +++ b/libavformat/aviobuf.c
> @@ -875,8 +875,10 @@ static int64_t read_string_to_bprint_overwrite(AVIOContext *s, AVBPrint *bp,
>      if (ret < 0)
>          return ret;
>  
> -    if (!av_bprint_is_complete(bp))
> +    if (!av_bprint_is_complete(bp)) {
> +        s->error = AVERROR(ENOMEM);
>          return AVERROR(ENOMEM);
> +    }
>  
>      return bp->len;
>  }
> @@ -1351,8 +1353,10 @@ int avio_read_to_bprint(AVIOContext *h, AVBPrint *pb, size_t max_size)
>          if (ret <= 0)
>              return ret;
>          av_bprint_append_data(pb, buf, ret);
> -        if (!av_bprint_is_complete(pb))
> +        if (!av_bprint_is_complete(pb)) {
> +            h->error = AVERROR(ENOMEM);
>              return AVERROR(ENOMEM);
> +        }
>          max_size -= ret;
>      }
>      return 0;
> 

I don't really see the point of this: It is not a real read error that
should stick to the AVIOContext (which can still be used afterwards
without any issue). If the user does not check the errors, then the user
has no one to blame but himself for missing errors.

- Andreas

PS: If the AVBPrint API had a documented way of marking data as used,
one could avoid those stack buffers and use the AVBPrint buffer directly
with av_bprint_get_buffer(). (Marking data as used would be equivalent
to incrementing len and ensuring that the buffer stays zero-terminated.)
If this were done, no already read data would be lost in case of a later
allocation failure.