Issue #2801: fix bug in float.is_integer where ValueError

could be incorrectly raised.  This is a backport of the
Py3k fix in r62939.  (Should really have been fixed
in the trunk first and svnmerged into py3k.)

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.6 beta 1?
 Core and Builtins
 -----------------
 
+- Issue #2801: fix bug in the float.is_integer method where a ValueError
+  was sometimes incorrectly raised.
+
 - Issue #2790: sys.flags was not properly exposing its bytes_warning attribute.
 
 Extension Modules

Objects/floatobject.c

@@ -1031,6 +1031,7 @@ float_is_integer(PyObject *v)
 		return NULL;
 	if (!Py_IS_FINITE(x))
 		Py_RETURN_FALSE;
+	errno = 0;
 	PyFPE_START_PROTECT("is_integer", return NULL)
 	o = (floor(x) == x) ? Py_True : Py_False;
 	PyFPE_END_PROTECT(x)