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FFmpeg/libavutil/video_enc_params.c
Martin Storsjö 01f58f3646 lavu/video_enc_params: Avoid relying on an undefined C construct
The construct of using offsetof on a (potentially anonymous) struct
defined within the offsetof expression, while supported by all
current compilers, has been declared explicitly undefined by the
C standards committee [1].

Clang recently got a change to identify this as an issue [2];
initially it was treated as a hard error, but it was soon after
softened into a warning under the -Wgnu-offsetof-extensions option
(not enabled automatically as part of -Wall though).

Nevertheless - in this particular case, it's trivial to fix the
code not to rely on the construct that the standards committee has
explicitly called out as undefined.

[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm
[2] https://reviews.llvm.org/D133574

Signed-off-by: Martin Storsjö <martin@martin.st>
2023-01-31 14:22:54 +02:00

81 lines
2.3 KiB
C

/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stddef.h>
#include <stdint.h>
#include "buffer.h"
#include "frame.h"
#include "mem.h"
#include "video_enc_params.h"
AVVideoEncParams *av_video_enc_params_alloc(enum AVVideoEncParamsType type,
unsigned int nb_blocks, size_t *out_size)
{
struct TestStruct {
AVVideoEncParams p;
AVVideoBlockParams b;
};
const size_t blocks_offset = offsetof(struct TestStruct, b);
size_t size = blocks_offset;
AVVideoEncParams *par;
if (nb_blocks > (SIZE_MAX - size) / sizeof(AVVideoBlockParams))
return NULL;
size += sizeof(AVVideoBlockParams) * nb_blocks;
par = av_mallocz(size);
if (!par)
return NULL;
par->type = type;
par->nb_blocks = nb_blocks;
par->block_size = sizeof(AVVideoBlockParams);
par->blocks_offset = blocks_offset;
if (out_size)
*out_size = size;
return par;
}
AVVideoEncParams*
av_video_enc_params_create_side_data(AVFrame *frame, enum AVVideoEncParamsType type,
unsigned int nb_blocks)
{
AVBufferRef *buf;
AVVideoEncParams *par;
size_t size;
par = av_video_enc_params_alloc(type, nb_blocks, &size);
if (!par)
return NULL;
buf = av_buffer_create((uint8_t *)par, size, NULL, NULL, 0);
if (!buf) {
av_freep(&par);
return NULL;
}
if (!av_frame_new_side_data_from_buf(frame, AV_FRAME_DATA_VIDEO_ENC_PARAMS, buf)) {
av_buffer_unref(&buf);
return NULL;
}
return par;
}