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

James Almer jamrial at gmail.com
Thu Mar 17 17:15:23 CET 2016


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.

> [...]
> 
> 
> 
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