Re: [FFmpeg-devel] [PATCH] avcodec/motion_est: don't add offsets to NULL pointers

[James Almer <jamrial@gmail.com>]

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On 7/18/2025 8:01 PM, Michael Niedermayer wrote:
> On Tue, Jul 15, 2025 at 10:33:10AM -0300, James Almer wrote:
>> Fixes: libavcodec/motion_est.c:94:31: runtime error: applying zero offset to null pointer
>> Signed-off-by: James Almer <jamrial@gmail.com>
>> ---
>>   libavcodec/motion_est.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavcodec/motion_est.c b/libavcodec/motion_est.c
>> index 93be712cc0..3273451f9a 100644
>> --- a/libavcodec/motion_est.c
>> +++ b/libavcodec/motion_est.c
>> @@ -91,12 +91,12 @@ static inline void init_ref(MotionEstContext *c, uint8_t *const src[3],
>>       };
>>       int i;
>>       for(i=0; i<3; i++){
>> -        c->src[0][i]= src [i] + offset[i];
>> -        c->ref[0][i]= ref [i] + offset[i];
>> +        c->src[0][i]= src[i] ? FF_PTR_ADD(src[i], offset[i]) : NULL;
>> +        c->ref[0][i]= ref[i] ? FF_PTR_ADD(ref[i], offset[i]) : NULL;
> 
> why does this need FF_PTR_ADD() when the pointer is not NULL ?

FF_PTR_ADD() checks the offset, not the pointer. I don't know if it can 
be 0 or not here, so better safe than sorry.

If you can confirm offset[i] is never 0, then i'll remove it.

> 
> patch is ok except that
> 
> thx
> 
> [...]
> 
> 
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