[Bug middle-end/34843] New: Missing overflow diagnostic for Python 2.5's unicodeobject.c

["ismail at pardus dot org dot tr" <gcc-bugzilla at gcc dot gnu dot org>]

unicodeobject.c from Python 2.5 assumes signed integer overflow in the
following code in unicode_expandtabs function :

i and j are signed integers (defined as ssize_t) :

[...]
        else {
            j++;
            if (*p == '\n' || *p == '\r') {
                i += j;  <=== Possible overflow
                old_j = j = 0;
                if (i < 0) {  <== Code won't work due to undefined overflow
                    PyErr_SetString(PyExc_OverflowError,
                                    "new string is too long");
                    return NULL;
                }
            }
        }
[...]

Now if I compile this file with -O3 -Wstrict-overflow=3 I got no warning
although undefined overflow occurs and code is miscompiled unless -fwrapv is
specified. I think gcc should be warning us here about undefined overflow.


-- 
           Summary: Missing overflow diagnostic for Python 2.5's
                    unicodeobject.c
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ismail at pardus dot org dot tr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34843