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.
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index ca7a8f3..f3bdbe2 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -116,6 +116,7 @@
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 0001f9f..2fb0793 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
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 cbca495..4e1f04f 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -754,10 +754,9 @@
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 @@
}
return NULL;
}
- return PyInt_FromLong(x);
+ return PyInt_FromLong(-a);
}
static PyObject *