[FFmpeg-devel] [RFC]lavu/timecode: Increase AV_TIMECODE_STR_SIZE.

[Carl Eugen Hoyos]

2017-05-05 3:29 GMT+02:00 Aaron Levinson <alevinsn at aracnet.com>:
> On 5/4/2017 4:27 PM, Carl Eugen Hoyos wrote:
>>
>> Hi!
>>
>> Attached patch is one possibility to fix the following warning with gcc 7:
>> libavutil/timecode.c: In function ‘av_timecode_make_string’:
>> libavutil/timecode.c:103:60: warning: ‘%02d’ directive output may be
>> truncated
>> writing between 2 and 10 bytes into a region of size between 0 and 7
>> [-Wformat-truncation=]
>>      snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%02d",
>>                                                             ^~~~
>> libavutil/timecode.c:103:41: note: directive argument in the range [0,
>> 2147483647]
>>      snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%02d",
>>                                          ^~~~~~~~~~~~~~~~~~~~~~~~
>> libavutil/timecode.c:103:5: note: ‘snprintf’ output between 12 and 32
>> bytes
>> into a destination of size 16
>>      snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%02d",
>>      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>               neg ? "-" : "",
>>               ~~~~~~~~~~~~~~~
>>               hh, mm, ss, drop ? ';' : ':', ff);
>>               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Several similar warnings are printed, an alternative is to disable the
>> warning.
>>
>> The warning seemed wrong on first sight but may actually be correct, we
>> accept invalid fps for timecode.
>
>
> Regarding the change in your patch:
>
> -#define AV_TIMECODE_STR_SIZE 16
> +#define AV_TIMECODE_STR_SIZE 23
>
> It seems like 23 characters wouldn't be sufficient based on the warning:
> "output between 12 and 32 bytes into a destination of size 16".  I would
> guess that you would need at least 32 characters and perhaps one more (?)
> for the terminating null character to avoid that warning.

How can I reproduce / test your findings?

Carl Eugen