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Issue #7406: Fix some occurrences of potential signed overflow in int 

arithmetic.
This commit is contained in:
Mark Dickinson 2009-12-02 17:33:41 +00:00
parent 5a73ff81f1
commit 34398184eb
2 changed files with 12 additions and 5 deletions
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9
Objects/intobject.c
View File

@ -461,7 +461,8 @@ int_add(PyIntObject *v, PyIntObject *w)
register long a, b, x;
CONVERT_TO_LONG(v, a);
CONVERT_TO_LONG(w, b);
x = a + b;
/* casts in the line below avoid undefined behaviour on overflow */
x = (long)((unsigned long)a + b);
if ((x^a) >= 0 || (x^b) >= 0)
return PyInt_FromLong(x);
return PyLong_Type.tp_as_number->nb_add((PyObject *)v, (PyObject *)w);
@ -473,7 +474,8 @@ int_sub(PyIntObject *v, PyIntObject *w)
register long a, b, x;
CONVERT_TO_LONG(v, a);
CONVERT_TO_LONG(w, b);
x = a - b;
/* casts in the line below avoid undefined behaviour on overflow */
x = (long)((unsigned long)a - b);
if ((x^a) >= 0 || (x^~b) >= 0)
return PyInt_FromLong(x);
return PyLong_Type.tp_as_number->nb_subtract((PyObject *)v,
@ -516,7 +518,8 @@ int_mul(PyObject *v, PyObject *w)
CONVERT_TO_LONG(v, a);
CONVERT_TO_LONG(w, b);
longprod = a * b;
/* casts in the next line avoid undefined behaviour on overflow */
longprod = (long)((unsigned long)a * b);
doubleprod = (double)a * (double)b;
doubled_longprod = (double)longprod;

8
Python/ceval.c
View File

@ -1321,7 +1321,9 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
register long a, b, i;
a = PyInt_AS_LONG(v);
b = PyInt_AS_LONG(w);
i = a + b;
/* cast to avoid undefined behaviour
on overflow */
i = (long)((unsigned long)a + b);
if ((i^a) < 0 && (i^b) < 0)
goto slow_add;
x = PyInt_FromLong(i);
@ -1351,7 +1353,9 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
register long a, b, i;
a = PyInt_AS_LONG(v);
b = PyInt_AS_LONG(w);
i = a - b;
/* cast to avoid undefined behaviour
on overflow */
i = (long)((unsigned long)a - b);
if ((i^a) < 0 && (i^~b) < 0)
goto slow_sub;
x = PyInt_FromLong(i);