A question about detecting array bounds for case Warray-bounds-3.c

["Jiangning Liu" <jiangning dot liu at arm dot com>]

Hi,

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 "<=". 

Right now, GCC compiler doesn't report any warning messages for this case,
should it be a bug in both test case and compiler?

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?

The case is like below,

/* { dg-do compile } */
/* { dg-options "-O2 -Warray-bounds" } */
/* based on PR 31227 */

struct S
{
  const char *abday[7];
  const char *day[7];
  const char *abmon[12];
  const char *mon[12];
  const char *am_pm[2];
};

...

  for (cnt = 0; cnt <= 7; ++cnt)
    {
      iov[2 + cnt].iov_base = (void *) (time->abday[cnt] ?: "");
      iov[2 + cnt].iov_len = strlen (iov[2 + cnt].iov_base) + 1;
    }

  for (; cnt <= 14; ++cnt)
    {
      iov[2 + cnt].iov_base = (void *) (time->day[cnt - 7] ?: "");
      iov[2 + cnt].iov_len = strlen (iov[2 + cnt].iov_base) + 1;
    }

  for (; cnt <= 26; ++cnt)
    {
      iov[2 + cnt].iov_base = (void *) (time->abmon[cnt - 14] ?: "");
      iov[2 + cnt].iov_len = strlen (iov[2 + cnt].iov_base) + 1;
    }

  for (; cnt <= 38; ++cnt)
    {
      iov[2 + cnt].iov_base = (void *) (time->mon[cnt - 26] ?: "");
      iov[2 + cnt].iov_len = strlen (iov[2 + cnt].iov_base) + 1;
    }

  for (; cnt <= 40; ++cnt)
    {
      iov[2 + cnt].iov_base =  (void *) (time->am_pm[cnt - 38] ?: "");
      iov[2 + cnt].iov_len = strlen (iov[2 + cnt].iov_base) + 1;
    }

Thanks,
-Jiangning