One of the uses of problematic uses of PyUnicode_GetSize() is in Macintosh Gestalt interface:



/* Convert a 4-char string object argument to an OSType value */
static int
convert_to_OSType(PyObject *v, OSType *pr)
{
    uint32_t tmp;
    if (!PyUnicode_Check(v) || PyUnicode_GetSize(v) != 4) {
    PyErr_SetString(PyExc_TypeError,
                    "OSType arg must be string of 4 chars");
    return 0;
    }
    memcpy((char *)&tmp, _PyUnicode_AsString(v), 4);
    *pr = (OSType)ntohl(tmp);
    return 1;
}

(Modules/_gestalt.c:41)

This function seems to require a bytes, not str argument as interpreting 4 UTF-8 bytes as an int makes little sense.