On 28/03/2024 13:15, tong1.wu-at-intel....@ffmpeg.org wrote:
From: Tong Wu <tong1...@intel.com>
HEVCHdrParams* receives a pointer which points to a dynamically
allocated memory block. It causes the memcmp always returning 1.
Add a function to do the comparision. A condition is also added to
avoid malloc(0).
Signed-off-by: Tong Wu <tong1...@intel.com>
---
libavcodec/hevc_ps.c | 20 ++++++++++++++++----
libavcodec/hevc_ps.h | 4 +++-
2 files changed, 19 insertions(+), 5 deletions(-)
It doesn't seem like this method works at all, even before the recent change
with the pointer.
Structs can contain arbitrary padding, and any write to the struct makes the
padding unspecified. memcmp() is therefore never valid as a method of
comparing after writing some fields, as done here. (It could only be valid if
the structs compared were made by memcpy() with no fields written directly.)
The problem is mostly harmless because the nondeterministic replacement of
structs which we were expecting to be equivalent doesn't actually change
anything, so why don't we just remove the comparison and always replace?
Thanks,
- Mark
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