From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Sun, 12 May 2019 09:37:15 +0000 (-0700)
Subject: bpo-36791: Safer detection of integer overflow in sum(). (GH-13080)
X-Git-Tag: v3.7.4rc1~165
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b7e483b6d07081d5f81860258e95785975a7cbf8;p=thirdparty%2FPython%2Fcpython.git

bpo-36791: Safer detection of integer overflow in sum(). (GH-13080)

(cherry picked from commit 29500737d45cbca9604d9ce845fb2acc3f531401)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
---

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 6306c3ac5641..8083ac961feb 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2374,9 +2374,11 @@ builtin_sum_impl(PyObject *module, PyObject *iterable, PyObject *start)
             }
             if (PyLong_CheckExact(item)) {
                 long b = PyLong_AsLongAndOverflow(item, &overflow);
-                long x = i_result + b;
-                if (overflow == 0 && ((x^i_result) >= 0 || (x^b) >= 0)) {
-                    i_result = x;
+                if (overflow == 0 &&
+                    (i_result >= 0 ? (b <= LONG_MAX - i_result)
+                                   : (b >= LONG_MIN - i_result)))
+                {
+                    i_result += b;
                     Py_DECREF(item);
                     continue;
                 }