public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug tree-optimization/31227]  New: [4.3 Regression] -Warray-bounds doesn't play together with loop optimizations
@ 2007-03-16 18:14 jakub at gcc dot gnu dot org
  2007-03-16 19:17 ` [Bug tree-optimization/31227] " jakub at gcc dot gnu dot org
                   ` (8 more replies)
  0 siblings, 9 replies; 10+ messages in thread
From: jakub at gcc dot gnu dot org @ 2007-03-16 18:14 UTC (permalink / raw)
  To: gcc-bugs

typedef __SIZE_TYPE__ size_t;

extern size_t strlen (const char *);

struct iovec
{
  void *iov_base;
  size_t iov_len;
};

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

extern void foo (size_t, struct iovec *);

void
bar (struct S *time)
{
  struct iovec iov[43];
  size_t cnt;
  iov[0].iov_base = (void *) "abc";
  iov[0].iov_len = 3;

  iov[1].iov_base = (void *) "def";
  iov[1].iov_len = 3;

  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;
    }

  foo (2 + cnt, iov);
}

issues at -O2 -Wall bogus warnings:
/tmp/w.c:24: warning: array subscript is above array bounds
/tmp/w.c:24: warning: array subscript is above array bounds

Apparently tree loop optimizations decide to use &time->abmon[14] and
&time->mon[30] pointers (which are outside of the range of the arrays) and then
dereferences that pointer - 112B (96B is the size of abmon array and 16B are
extra 2 pointers because the other array is biased by 2).

The testcase is extracted from glibc.


-- 
           Summary: [4.3 Regression] -Warray-bounds doesn't play together
                    with loop optimizations
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31227


^ permalink raw reply	[flat|nested] 10+ messages in thread
end of thread, other threads:[~2007-04-18 20:10 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-03-16 18:14 [Bug tree-optimization/31227] New: [4.3 Regression] -Warray-bounds doesn't play together with loop optimizations jakub at gcc dot gnu dot org
2007-03-16 19:17 ` [Bug tree-optimization/31227] " jakub at gcc dot gnu dot org
2007-03-16 21:45 ` rguenth at gcc dot gnu dot org
2007-03-16 21:47 ` pinskia at gcc dot gnu dot org
2007-03-21  9:05 ` mueller at gcc dot gnu dot org
2007-03-21 14:16 ` mueller at gcc dot gnu dot org
2007-03-21 14:17 ` mueller at gcc dot gnu dot org
2007-03-21 14:53 ` jakub at gcc dot gnu dot org
2007-04-18 20:09 ` mueller at gcc dot gnu dot org
2007-04-18 20:10 ` mueller at gcc dot gnu dot org

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).