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

[Carl Eugen Hoyos]

Am Mi., 22. Jan. 2020 um 16:21 Uhr schrieb Andreas Rheinhardt
<andreas.rheinhardt at gmail.com>:
>
> 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).

(on x86?)

Great!

Carl Eugen