[FFmpeg-devel] [PATCH 1/4] avcodec/startcode: Use AV_RN due to UBSan warning about unaligned access

[Andreas Rheinhardt]

On Wed, Jan 22, 2020 at 4:06 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:

> Am Mi., 22. Jan. 2020 um 15:57 Uhr schrieb Andreas Rheinhardt
> <andreas.rheinhardt at gmail.com>:
> >
> > when directly accessing a buffer via a pointer to uint8_t cast to a
> > pointer to uint64_t/uint32_t. This happened only if HAVE_FAST_UNALIGNED
> > was set, so it was ok, but UBSan nevertheless complained about unaligned
> > accesses. So simply use AV_RNxx to read the buffer; this also improves
> > readability.
>
> Is there a speed impact?
>
> The assembly produced by both Clang as well as GCC was completely
unchanged (for non-UBSan builds).

- Andreas