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.

Lib/test/test_builtin.py

@@ -116,6 +116,7 @@ class BuiltinTest(unittest.TestCase):
         self.assertEqual(abs(0), 0)
         self.assertEqual(abs(1234), 1234)
         self.assertEqual(abs(-1234), 1234)
+        self.assertTrue(abs(-sys.maxint-1) > 0)
         # float
         self.assertEqual(abs(0.0), 0.0)
         self.assertEqual(abs(3.14), 3.14)

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.6 alpha 1?
 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
   number of arguments, as was the case in Python 2.4.
 

Objects/intobject.c

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