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From: "Jiangning Liu" <jiangning.liu@arm.com>
To: "Jiangning Liu" <Jiangning.Liu@arm.com>,	<gcc@gcc.gnu.org>
Cc: <jakub@gcc.gnu.org>,	<mueller@gcc.gnu.org>,	<rguenth@gcc.gnu.org>,	"Matthew Gretton-Dann" <Matthew.Gretton-Dann@arm.com>
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Subject: RE: A question about detecting array bounds for case Warray-bounds-3.c
Date: Mon, 26 Sep 2011 08:32:00 -0000
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PING...

> -----Original Message-----
> From: Jiangning Liu [mailto:jiangning.liu@arm.com]
> Sent: Thursday, September 22, 2011 10:19 AM
> To: gcc@gcc.gnu.org
> Cc: 'jakub@gcc.gnu.org'; 'mueller@gcc.gnu.org'; 'rguenth@gcc.gnu.org';
> Matthew Gretton-Dann
> Subject: A question about detecting array bounds for case Warray-
> bounds-3.c
>=20
> Hi,
>=20
> For case gcc/testsuite/gcc.dg/Warray-bounds-3.c, obviously it is an
> invalid C program, because the last iterations of all the loops cause
> the access of arrays is beyond the max size of corresponding array
> declarations. The condition of checking upper bound should be "<"
> rather than "<=3D".
>=20
> Right now, GCC compiler doesn't report any warning messages for this
> case, should it be a bug in both test case and compiler?
>=20
> But looking at http://gcc.gnu.org/PR31227 , it seems this test case is
> designed to be like this on purpose. Anybody can explain about this?
>=20
> The case is like below,
>=20
> /* { dg-do compile } */
> /* { dg-options "-O2 -Warray-bounds" } */
> /* based on PR 31227 */
>=20
> struct S
> {
>   const char *abday[7];
>   const char *day[7];
>   const char *abmon[12];
>   const char *mon[12];
>   const char *am_pm[2];
> };
>=20
> ...
>=20
>   for (cnt =3D 0; cnt <=3D 7; ++cnt)
>     {
>       iov[2 + cnt].iov_base =3D (void *) (time->abday[cnt] ?: "");
>       iov[2 + cnt].iov_len =3D strlen (iov[2 + cnt].iov_base) + 1;
>     }
>=20
>   for (; cnt <=3D 14; ++cnt)
>     {
>       iov[2 + cnt].iov_base =3D (void *) (time->day[cnt - 7] ?: "");
>       iov[2 + cnt].iov_len =3D strlen (iov[2 + cnt].iov_base) + 1;
>     }
>=20
>   for (; cnt <=3D 26; ++cnt)
>     {
>       iov[2 + cnt].iov_base =3D (void *) (time->abmon[cnt - 14] ?: "");
>       iov[2 + cnt].iov_len =3D strlen (iov[2 + cnt].iov_base) + 1;
>     }
>=20
>   for (; cnt <=3D 38; ++cnt)
>     {
>       iov[2 + cnt].iov_base =3D (void *) (time->mon[cnt - 26] ?: "");
>       iov[2 + cnt].iov_len =3D strlen (iov[2 + cnt].iov_base) + 1;
>     }
>=20
>   for (; cnt <=3D 40; ++cnt)
>     {
>       iov[2 + cnt].iov_base =3D  (void *) (time->am_pm[cnt - 38] ?: "");
>       iov[2 + cnt].iov_len =3D strlen (iov[2 + cnt].iov_base) + 1;
>     }
>=20
> Thanks,
> -Jiangning