[U-Boot] fdt performance

[Michael Pratt]

Hi Wolfgang,

On Mon, Oct 21, 2013 at 3:55 PM, Wolfgang Denk <wd at denx.de> wrote:
>
> Dear Michael,
>
> In message <CAPx6ZwHLn-VABzQOyAMF+T2VyQEc3MZDi1E_kdTVZG8OkJmBYA at mail.gmail.com> you wrote:
> >
> > > > it's possible that these checks could be simply optimised away. The
> > >
> > > This is not hwat happens.
> >
> > Actually, it is my understanding that the "if (p + len < p)" can be
> > optimized away.  This exact case is discussed in the LWN article "GCC and
> > pointer overflows"[1].
>
> No, this does not apply here.  You miss a key point.  We are not doing
> any pointer arithmetics here.  We have:
>
>         int offset;
>         unsigned int len;
>
> and then do:
>
>         if (((offset + len) < offset) ...)

We seem to have a misunderstanding, I did not mean to imply that the
"offset + len"
expression was undefined.  I agree that it is fine.  I was referring
to this statement from
Aaron's original email:

        if (p + len < p)

Which is following:

        const char *p;
        unsigned int len;

That is the statement which is utilizing pointer overflow.
.
>
> > --001a1133769056575204e93035f1
> > Content-Type: text/html; charset=UTF-8
> > Content-Transfer-Encoding: quoted-printable
>
> Can you please stop posting HTML?  Thanks!

Sorry about that!  Hopefully this message is correct.

Regards,
Michael Pratt