[FFmpeg-devel] [PATCH 01/18] mpeg4videodec: do not copy a range of fields at once

[Paul B Mahol]

On 3/14/20, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> Am Fr., 13. März 2020 um 11:30 Uhr schrieb Anton Khirnov
> <anton at khirnov.net>:
>>
>> This is extremely fragile against reordering and hides what is actually
>> being copied. Copy all the fields manually instead.
>> ---
>>  libavcodec/mpeg4videodec.c | 27 ++++++++++++++++++++++++++-
>>  1 file changed, 26 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
>> index cc03486646..a51985d51b 100644
>> --- a/libavcodec/mpeg4videodec.c
>> +++ b/libavcodec/mpeg4videodec.c
>> @@ -3460,7 +3460,32 @@ static int
>> mpeg4_update_thread_context(AVCodecContext *dst,
>>      if (ret < 0)
>>          return ret;
>>
>> -    memcpy(((uint8_t*)s) + sizeof(MpegEncContext), ((uint8_t*)s1) +
>> sizeof(MpegEncContext), sizeof(Mpeg4DecContext) - sizeof(MpegEncContext));
>> +    s->time_increment_bits       = s1->time_increment_bits;
>> +    s->shape                     = s1->shape;
>> +    s->vol_sprite_usage          = s1->vol_sprite_usage;
>> +    s->sprite_brightness_change  = s1->sprite_brightness_change;
>> +    s->num_sprite_warping_points = s1->num_sprite_warping_points;
>> +    s->rvlc                      = s1->rvlc;
>> +    s->resync_marker             = s1->resync_marker;
>> +    s->t_frame                   = s1->t_frame;
>> +    s->new_pred                  = s1->new_pred;
>> +    s->enhancement_type          = s1->enhancement_type;
>> +    s->scalability               = s1->scalability;
>> +    s->use_intra_dc_vlc          = s1->use_intra_dc_vlc;
>> +    s->intra_dc_threshold        = s1->intra_dc_threshold;
>> +    s->divx_version              = s1->divx_version;
>> +    s->divx_build                = s1->divx_build;
>> +    s->xvid_build                = s1->xvid_build;
>> +    s->lavc_build                = s1->lavc_build;
>> +    s->showed_packed_warning     = s1->showed_packed_warning;
>> +    s->vol_control_parameters    = s1->vol_control_parameters;
>> +    s->cplx_estimation_trash_i   = s1->cplx_estimation_trash_i;
>> +    s->cplx_estimation_trash_p   = s1->cplx_estimation_trash_p;
>> +    s->cplx_estimation_trash_b   = s1->cplx_estimation_trash_b;
>> +    s->rgb                       = s1->rgb;
>> +
>> +    memcpy(s->sprite_shift, s1->sprite_shift, sizeof(s1->sprite_shift));
>> +    memcpy(s->sprite_traj,  s1->sprite_traj,  sizeof(s1->sprite_traj));
>
> Am I really the only one who finds the code more "fragile" after this
> change?

Elaborate how it is "fragile"?

>
> Carl Eugen
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".