Re: [PATCH] libcpp: Optimize AArch64 search_line_fast

On Wed, 12 Aug 2026, Alexander Monakov wrote:

> > +  const uchar *limit = (const uchar*) ((uintptr_t)end & ~15);
> 
> This is not safe in absence of padding: when 's' itself is not aligned,
> and 'end' is close to it, this may move 'limit' to before 's', and then
> the load from *limit will pick up bytes prior to 's'.
> 
> Now, libcpp provides sufficient tail padding (at least 16 bytes, with '\n'
> at the beginning of padding area) so in context this is safe, but then
> the final aligned load should never be reached, and computing 'limit' is
> pointless.

Correction: search_line_fast is called with 'end' pointing to the beginning
of the padding area, not the end, so this is just unsafe (aligning 'end'
can move it to before 's').

Alexander