[FFmpeg-devel] [PATCH v2 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Cai Fan]

Hi,

Thank you for the suggestion.

The tmp field in VideoMuxData is a fixed-size embedded array (char tmp[4][1024]), not a pointer. This makes using av_asprintf() not suitable.




typedef struct VideoMuxData {

    const AVClass *class;  /**< Class for private options. */

    int start_img_number;

    int img_number;

    int split_planes;       

    char tmp[4][1024];     // Fixed-size buffer within the struct

    char target[4][1024];

    int update;

    int use_strftime;

    int frame_pts;

    const char *muxer;

    int use_rename;

    AVDictionary *protocol_opts;

} VideoMuxData;

VideoMuxData *img = s->priv_data;





At 2025-08-04 06:57:00, "Michael Niedermayer" <michael at niedermayer.cc> wrote:
>On Thu, Jul 31, 2025 at 04:21:35PM +0800, Cai Fan wrote:
>> Signed-off-by: Cai Fan <caifan0425 at 163.com>
>> ---
>>  libavformat/img2enc.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>> 
>> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
>> index 41638d92b8..9a5718a8da 100644
>> --- a/libavformat/img2enc.c
>> +++ b/libavformat/img2enc.c
>> @@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>>      }
>>      for (i = 0; i < 4; i++) {
>>          av_dict_copy(&options, img->protocol_opts, 0);
>> -        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        if (len < 0 || len >= sizeof(img->tmp[i])) {
>> +            av_log(s, AV_LOG_ERROR, "filename '%s' exceeds buffer size %zu\n", filename, sizeof(img->tmp[i]));
>> +            ret = AVERROR(EINVAL);
>> +            goto fail;
>> +        }
>
>is there a reason this doesnt use av_asprintf() ?
>that is allocate as needed
>
>thx
>
>[...]
>-- 
>Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
>No great genius has ever existed without some touch of madness. -- Aristotle