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From: "dimhen at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/55079] New: [4.8 regeression] false positive -Warray-bounds
Date: Fri, 26 Oct 2012 09:56:00 -0000 [thread overview]
Message-ID: <bug-55079-4@http.gcc.gnu.org/bugzilla/> (raw)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55079
Bug #: 55079
Summary: [4.8 regeression] false positive -Warray-bounds
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: dimhen@gmail.com
$ cat tst.c
int f(unsigned len, int buflen)
{
unsigned taillen;
unsigned slen;
unsigned i;
int b[17]; /* needed <= 17 to trigger Warning */
int j = 0; /* needed to trigger Warning */
b[0] = 0;
taillen= buflen & 7; /* taillen [0..7] */
if(taillen) { /* taillen [1..7] */
slen= 8 - taillen; /* slen [7..1] */
if (len<slen) /* needed to trigger Warning */
slen=len; /* slen' < slen */
for(i=0; i<slen; i++) {
j = b[taillen]; /* taillen + slen = [1..7] + [7..1] = 8 */
taillen++;
}
}
return j;
}
$ gcc -Warray-bounds -c -O3 tst.c
tst.c: In function 'f':
tst.c:17:9: warning: array subscript is above array bounds [-Warray-bounds]
j = b[taillen]; /* taillen + slen = [1..7] + [7..1] = 8 */
^
gcc version 4.8.0 20121026 (experimental) [trunk revision 192837] (GCC)
- if i remove some code then warning disappeared
- why '18' is safe array top-bound?
next reply other threads:[~2012-10-26 9:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 9:56 dimhen at gmail dot com [this message]
2012-10-26 10:09 ` [Bug tree-optimization/55079] " rguenth at gcc dot gnu.org
2012-10-30 9:34 ` [Bug tree-optimization/55079] [4.8 regression] " rguenth at gcc dot gnu.org
2012-10-30 9:35 ` rguenth at gcc dot gnu.org
2012-11-02 16:35 ` hubicka at gcc dot gnu.org
2012-11-02 16:47 ` hubicka at gcc dot gnu.org
2012-11-02 18:45 ` hubicka at gcc dot gnu.org
2012-11-02 20:51 ` hubicka at gcc dot gnu.org
2012-11-14 19:31 ` [Bug tree-optimization/55079] [4.8 regression] false positive -Warray-bounds (also seen at -O3 bootstrap) hubicka at gcc dot gnu.org
2012-11-15 1:01 ` hubicka at gcc dot gnu.org
2012-12-07 12:55 ` rguenth at gcc dot gnu.org
2012-12-10 13:23 ` rguenth at gcc dot gnu.org
2012-12-10 13:50 ` rguenth at gcc dot gnu.org
2012-12-10 14:14 ` rguenth at gcc dot gnu.org
2012-12-10 16:27 ` hubicka at ucw dot cz
2012-12-11 10:06 ` rguenth at gcc dot gnu.org
2012-12-11 10:08 ` rguenth at gcc dot gnu.org
2012-12-12 9:33 ` schwab at gcc dot gnu.org
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