Re: [FFmpeg-devel] [PATCH 2/8] lavfi/vf_vpp_qsv: handle NULL pointer when evaluating an expression

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

Xiang, Haihao:
> From: Haihao Xiang <haihao.xiang@intel.com>
> 
> This patch provides default value if the expression is NULL.
> 
> This is in preparation for reusing the code for other QSV filters.
> 
> Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>
> ---
>  libavfilter/vf_vpp_qsv.c | 36 ++++++++++++++++++++----------------
>  1 file changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/libavfilter/vf_vpp_qsv.c b/libavfilter/vf_vpp_qsv.c
> index 8d4227f841..3a0a395732 100644
> --- a/libavfilter/vf_vpp_qsv.c
> +++ b/libavfilter/vf_vpp_qsv.c
> @@ -172,14 +172,19 @@ enum var_name {
>  static int eval_expr(AVFilterContext *ctx)
>  {
>  #define PASS_EXPR(e, s) {\
> -    ret = av_expr_parse(&e, s, var_names, NULL, NULL, NULL, NULL, 0, ctx); \
> -    if (ret < 0) {\
> -        av_log(ctx, AV_LOG_ERROR, "Error when passing '%s'.\n", s);\
> -        goto release;\
> +    if (s) {\
> +        ret = av_expr_parse(&e, s, var_names, NULL, NULL, NULL, NULL, 0, ctx); \
> +        if (ret < 0) {                                                  \
> +            av_log(ctx, AV_LOG_ERROR, "Error when passing '%s'.\n", s); \
> +            goto release;                                               \
> +        }                                                               \
>      }\
>  }
> -#define CALC_EXPR(e, v, i) {\
> -    i = v = av_expr_eval(e, var_values, NULL); \
> +#define CALC_EXPR(e, v, i, d) {\
> +    if (e)\
> +        i = v = av_expr_eval(e, var_values, NULL);      \
> +    else\
> +        i = v = d;\
>  }
>      VPPContext *vpp = ctx->priv;
>      double  var_values[VAR_VARS_NB] = { NAN };
> @@ -209,30 +214,29 @@ static int eval_expr(AVFilterContext *ctx)
>      var_values[VAR_DAR] = var_values[VAR_A] * var_values[VAR_SAR];
>  
>      /* crop params */
> -    CALC_EXPR(cw_expr, var_values[VAR_CW], vpp->crop_w);
> -    CALC_EXPR(ch_expr, var_values[VAR_CH], vpp->crop_h);
> +    CALC_EXPR(cw_expr, var_values[VAR_CW], vpp->crop_w, var_values[VAR_IW]);
> +    CALC_EXPR(ch_expr, var_values[VAR_CH], vpp->crop_h, var_values[VAR_IH]);
>  
>      /* calc again in case cw is relative to ch */
> -    CALC_EXPR(cw_expr, var_values[VAR_CW], vpp->crop_w);
> +    CALC_EXPR(cw_expr, var_values[VAR_CW], vpp->crop_w, var_values[VAR_IW]);
>  
>      CALC_EXPR(w_expr,
>              var_values[VAR_OUT_W] = var_values[VAR_OW] = var_values[VAR_W],
> -            vpp->out_width);
> +            vpp->out_width, var_values[VAR_CW]);
>      CALC_EXPR(h_expr,
>              var_values[VAR_OUT_H] = var_values[VAR_OH] = var_values[VAR_H],
> -            vpp->out_height);
> +            vpp->out_height, var_values[VAR_CH]);
>  
>      /* calc again in case ow is relative to oh */
>      CALC_EXPR(w_expr,
>              var_values[VAR_OUT_W] = var_values[VAR_OW] = var_values[VAR_W],
> -            vpp->out_width);
> +            vpp->out_width, var_values[VAR_CW]);
>  
> -
> -    CALC_EXPR(cx_expr, var_values[VAR_CX], vpp->crop_x);
> -    CALC_EXPR(cy_expr, var_values[VAR_CY], vpp->crop_y);
> +    CALC_EXPR(cx_expr, var_values[VAR_CX], vpp->crop_x, (var_values[VAR_IW] - var_values[VAR_OW]) / 2);
> +    CALC_EXPR(cy_expr, var_values[VAR_CY], vpp->crop_y, (var_values[VAR_IH] - var_values[VAR_OH]) / 2);
>  
>      /* calc again in case cx is relative to cy */
> -    CALC_EXPR(cx_expr, var_values[VAR_CX], vpp->crop_x);
> +    CALC_EXPR(cx_expr, var_values[VAR_CX], vpp->crop_x, (var_values[VAR_IW] - var_values[VAR_OW]) / 2);
>  
>      if ((vpp->crop_w != var_values[VAR_IW]) || (vpp->crop_h != var_values[VAR_IH]))
>          vpp->use_crop = 1;

Does this add runtime checks to cases where there are not necessary?

- Andreas

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