sprintf function's buffer overflow?

{     
    char buf[8];
    sprintf(buf,"AAAA%3s","XXXXXXXX");
    printf("%s\n",buf);
}

what will happen?

The buffer have 8 characters space and only 3 free characters left, however, "XXXXXXXX" is 8 characters long.

I take a test with Visual Studion 2008 on Windows 7. As a result, the program printed:AAAXXXXXXX, and a run-time error happened.