From de5f9f4f70c6527c49d482e3b0bb0aad2851d34c Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 7 Sep 2015 22:51:56 +0300
Subject: [PATCH] Raise more correct exception on overflow in setting
 buffer_size attribute of expat parser.

---
 Lib/test/test_pyexpat.py |  3 +++
 Modules/pyexpat.c        | 13 +++++++------
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py
index 7548924e0f8..216a46b903e 100644
--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
@@ -3,6 +3,7 @@
 
 from io import BytesIO
 import os
+import sys
 import sysconfig
 import unittest
 import traceback
@@ -543,6 +544,8 @@ class ChardataBufferTest(unittest.TestCase):
             parser.buffer_size = -1
         with self.assertRaises(ValueError):
             parser.buffer_size = 0
+        with self.assertRaises((ValueError, OverflowError)):
+            parser.buffer_size = sys.maxsize + 1
         with self.assertRaises(TypeError):
             parser.buffer_size = 512.0
 
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index c4fdaafb860..6a901f756ca 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1403,17 +1403,18 @@ xmlparse_setattro(xmlparseobject *self, PyObject *name, PyObject *v)
         return -1;
       }
 
-      new_buffer_size=PyLong_AS_LONG(v);
+      new_buffer_size = PyLong_AsLong(v);
+      if (new_buffer_size <= 0) {
+        if (!PyErr_Occurred())
+          PyErr_SetString(PyExc_ValueError, "buffer_size must be greater than zero");
+        return -1;
+      }
+
       /* trivial case -- no change */
       if (new_buffer_size == self->buffer_size) {
         return 0;
       }
 
-      if (new_buffer_size <= 0) {
-        PyErr_SetString(PyExc_ValueError, "buffer_size must be greater than zero");
-        return -1;
-      }
-
       /* check maximum */
       if (new_buffer_size > INT_MAX) {
         char errmsg[100];