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Use a better check for overflow from a<<b.

This commit is contained in:
Guido van Rossum 2002-08-11 14:04:13 +00:00
parent cc8764ca9d
commit 643d59cbd6
1 changed files with 4 additions and 2 deletions
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6
Objects/intobject.c
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@ -675,13 +675,15 @@ int_lshift(PyIntObject *v, PyIntObject *w)
return NULL; return NULL;
return PyInt_FromLong(0L); return PyInt_FromLong(0L);
} }
c = (long)((unsigned long)a << b); c = a < 0 ? ~a : a;
if ((c >> b) != a || (c < 0 && a > 0)) { c >>= LONG_BIT - 1 - b;
if (c) {
if (PyErr_Warn(PyExc_DeprecationWarning, if (PyErr_Warn(PyExc_DeprecationWarning,
"x<<y losing bits or changing sign " "x<<y losing bits or changing sign "
"will return a long in Python 2.4 and up") < 0) "will return a long in Python 2.4 and up") < 0)
return NULL; return NULL;
} }
c = (long)((unsigned long)a << b);
return PyInt_FromLong(c); return PyInt_FromLong(c);
} }