From: Martin v. Löwis <martin@v.loewis.de>
Date: Wed, 4 Oct 2006 05:47:47 +0000 (+0000)
Subject: Fix integer negation and absolute value to not rely
X-Git-Tag: v2.5.1c1~354
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=10525ad31383e33c6e2dcdfcc9180ada55fa3b50;p=python

Fix integer negation and absolute value to not rely
on undefined behaviour of the C compiler anymore.
---

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index ca7a8f38c0..f3bdbe29c4 100644
--- a/Lib/test/test_builtin.py
+++ b/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)
diff --git a/Misc/NEWS b/Misc/NEWS
index 61ccad6f34..e71be104e9 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 2.5.1c1?
 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.
 
diff --git a/Objects/intobject.c b/Objects/intobject.c
index b94e3e9887..28f7606710 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -760,10 +760,9 @@ 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);
@@ -772,7 +771,7 @@ int_neg(PyIntObject *v)
 		}
 		return NULL;
 	}
-	return PyInt_FromLong(x);
+	return PyInt_FromLong(-a);
 }
 
 static PyObject *