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Fix integer negation and absolute value to not rely 

on undefined behaviour of the C compiler anymore.
Will backport to 2.5 and 2.4.
This commit is contained in:
Martin v. Löwis 2006-10-04 05:47:34 +00:00
parent 82271f13e7
commit 820d6ac9d7
3 changed files with 7 additions and 4 deletions
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1
Lib/test/test_builtin.py
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@ -116,6 +116,7 @@ class BuiltinTest(unittest.TestCase):
self.assertEqual(abs(0), 0) self.assertEqual(abs(0), 0)
self.assertEqual(abs(1234), 1234) self.assertEqual(abs(1234), 1234)
self.assertEqual(abs(-1234), 1234) self.assertEqual(abs(-1234), 1234)
self.assertTrue(abs(-sys.maxint-1) > 0)
# float # float
self.assertEqual(abs(0.0), 0.0) self.assertEqual(abs(0.0), 0.0)
self.assertEqual(abs(3.14), 3.14) self.assertEqual(abs(3.14), 3.14)

3
Misc/NEWS
View File

@ -12,6 +12,9 @@ What's New in Python 2.6 alpha 1?
Core and builtins Core and builtins
----------------- -----------------
- Integer negation and absolute value were fixed to not rely
on undefined behaviour of the C compiler anymore.
- Bug #1566800: make sure that EnvironmentError can be called with any - Bug #1566800: make sure that EnvironmentError can be called with any
number of arguments, as was the case in Python 2.4. number of arguments, as was the case in Python 2.4.

7
Objects/intobject.c
View File

@ -754,10 +754,9 @@ int_pow(PyIntObject *v, PyIntObject *w, PyIntObject *z)
static PyObject * static PyObject *
int_neg(PyIntObject *v) int_neg(PyIntObject *v)
{ {
register long a, x; register long a;
a = v->ob_ival; a = v->ob_ival;
x = -a; if (a < 0 && (unsigned long)a == 0-(unsigned long)a) {
if (a < 0 && x < 0) {
PyObject *o = PyLong_FromLong(a); PyObject *o = PyLong_FromLong(a);
if (o != NULL) { if (o != NULL) {
PyObject *result = PyNumber_Negative(o); PyObject *result = PyNumber_Negative(o);
@ -766,7 +765,7 @@ int_neg(PyIntObject *v)
} }
return NULL; return NULL;
} }
return PyInt_FromLong(x); return PyInt_FromLong(-a);
} }
static PyObject * static PyObject *