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: unassig...@gcc.gnu.org
ReportedBy: dim...@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?
