Re: [FFmpeg-devel] [PATCH 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Zhao Zhili <quinkblack@foxmail.com>]

> On Jul 30, 2025, at 11:43, Cai Fan <caifan0425@163.com> wrote:
> 
> Signed-off-by: Cai Fan <caifan0425@163.com>
> ---
> libavformat/img2enc.c | 5 +++++
> 1 file changed, 5 insertions(+)
> 
> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
> index 41638d92b8..f7d983ec54 100644
> --- a/libavformat/img2enc.c
> +++ b/libavformat/img2enc.c
> @@ -180,6 +180,11 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>     }
>     for (i = 0; i < 4; i++) {
>         av_dict_copy(&options, img->protocol_opts, 0);
> +        if (strlen(filename) + 5 >= sizeof(img->tmp[i])) {
> +            av_log(s, AV_LOG_ERROR, "Filename too long: %s\n", filename);
> +            ret = AVERROR(EINVAL);
> +            goto fail;
> +        }
>         snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);

The return value of snprintf can be used to detect truncation. Use strlen before snprintf makes no sense.

>         av_strlcpy(img->target[i], filename, sizeof(img->target[i]));
>         if (s->io_open(s, &pb[i], img->use_rename ? img->tmp[i] : filename, AVIO_FLAG_WRITE, &options) < 0) {
> -- 
> 2.34.1
> 
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