[notting@nostromo: ~]$ cat foo.c
#include <stdio.h>
#include <string.h>

int main() {
        char *foo = "..";
        printf("%d\n", strncmp(foo, ".",1));
        return 0;
}
[notting@nostromo: ~]$ gcc -Wall -o foo foo.c  -O2
foo.c: In function ‘main’:
foo.c:6: warning: offset ‘3’ outside bounds of constant string

Turning off optimization (or parens around strncmp) fixes the warning.

Version-Release number of selected component (if applicable):

gcc-4.4.0-0.30.x86_64
glibc-devel-2.9.90-11.x86_64

How reproducible:

100%