Re: [Xen-devel] xen-unstable stubdom build-failure when debug=n

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 07/21/2014 01:43 PM, Olaf Hering wrote:
> On Mon, Jul 21, Ian Campbell wrote:
>
> > tpm_tis.c:618:71: error: array subscript is below array bounds 
> > [-Werror=array-bounds]
> >
> > Line 618 does appear to include the use of a signed variable as an array
> > offset, but I'm not sure how or why gcc is proving that it is negative.
> It can not prove that tpm->locality remains positive.
>
> Olaf
In that case, shouldn't the error be phrased less severely (something like 
"might be
below array bounds")?  Anyway, the actual value is checked by locality_enabled
prior to the array access, and that check is effectively (0x1F & (1 << 
locality)),
limiting the actual value to 0..4.  I can't reproduce the warning with my 
version
of GCC, so I'm only looking at the code, but it looks like GCC is being overly
conservative after not detecting the range limit and this is just a false 
positive.

--
Daniel De Graaf
National Security Agency

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