[FFmpeg-devel] [PATCH 1/2] libwebpenc_animencoder: zero initialize the WebPAnimEncoderOptions struct

[James Almer]

On 3/17/2016 1:20 PM, wm4 wrote:
> On Thu, 17 Mar 2016 13:15:23 -0300
> James Almer <jamrial at gmail.com> wrote:
> 
>> On 3/17/2016 1:02 PM, Michael Niedermayer wrote:
>>> On Thu, Mar 17, 2016 at 11:06:29AM -0300, James Almer wrote:  
>>>> On 3/17/2016 4:32 AM, wm4 wrote:  
>>>>> On Thu, 17 Mar 2016 01:03:49 -0300
>>>>> James Almer <jamrial at gmail.com> wrote:
>>>>>  
>>>>>> This zeroes the WebPAnimEncoderOptions.verbose field, silencing library info messages
>>>>>> printed to stderr.
>>>>>>
>>>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>>>> ---
>>>>>>  libavcodec/libwebpenc_animencoder.c | 2 +-
>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/libavcodec/libwebpenc_animencoder.c b/libavcodec/libwebpenc_animencoder.c
>>>>>> index d7437a9..35c456a 100644
>>>>>> --- a/libavcodec/libwebpenc_animencoder.c
>>>>>> +++ b/libavcodec/libwebpenc_animencoder.c
>>>>>> @@ -41,7 +41,7 @@ static av_cold int libwebp_anim_encode_init(AVCodecContext *avctx)
>>>>>>      int ret = ff_libwebp_encode_init_common(avctx);
>>>>>>      if (!ret) {
>>>>>>          LibWebPAnimContext *s = avctx->priv_data;
>>>>>> -        WebPAnimEncoderOptions enc_options;
>>>>>> +        WebPAnimEncoderOptions enc_options = { 0 };
>>>>>>          WebPAnimEncoderOptionsInit(&enc_options);
>>>>>>          // TODO(urvang): Expose some options on command-line perhaps.
>>>>>>          s->enc = WebPAnimEncoderNew(avctx->width, avctx->height, &enc_options);  
>>>>>
>>>>> Does this mean it was reading uninitialized values from the stack?  
>>>>
>>>> Apparently. Should i backport this?  
>>>
>>> please backport if older releases are affected  
>>
>> 2.7 and newer, yes.
>>
>>>
>>> also my gcc is not fully happy about this:
>>> libavcodec/libwebpenc_animencoder.c: In function ‘libwebp_anim_encode_init’:
>>> libavcodec/libwebpenc_animencoder.c:44:9: warning: missing braces around initializer [-Wmissing-braces]
>>> libavcodec/libwebpenc_animencoder.c:44:9: warning: (near initialization for ‘enc_options.anim_params’) [-Wmissing-braces]
>>>   
>>
>> Odd, GCC 5.3 doesn't complain, at least not when targeting mingw-w64.
>> anim_params is a WebPMuxAnimParams struct within the WebPAnimEncoderOptions struct,
>> and WebPAnimEncoderOptionsInit() initializes it to default values anyway, so probably
>> not an issue.
>>
>> In any case, would something like 
>>
>> WebPAnimEncoderOptions enc_options = { .anim_params = { 0 }, 0 };
>>
>> be better, or is it too ugly? Alternatively i could just memset the whole thing to 0.
> 
> You don't need that. Your original patch is perfectly valid C.

Ok, backported to 2.7, 2.8 and 3.0 branches. Thanks.