[issue7406] int arithmetic relies on C signed overflow behaviour

[Zooko O'Whielacronx]

Zooko O'Whielacronx <zo...@zooko.com> added the comment:

Here is a way to test for overflow which is correct for any C implementation:

static PyObject *
int_add(PyIntObject *v, PyIntObject *w)
{
        register long a, b;
        CONVERT_TO_LONG(v, a);
        CONVERT_TO_LONG(w, b);
        if (((a>0)&&(b>0)&&((LONG_MAX-a)<b))
                ||((a<0)&&(b<0)&&((LONG_MIN-a)>b))) {
                /* would overflow the long type */
            return PyLong_Type.tp_as_number->nb_add((PyObject *)v, (PyObject 
*)w);
        }
        
        return PyInt_FromLong(a+b);
}

----------
nosy: +zooko

_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue7406>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe: 
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com