From 36dcaab7fde5d2e54cdeff5b705b5adcb27726dd Mon Sep 17 00:00:00 2001
From: Zackery Spytz <zspytz@gmail.com>
Date: Sat, 1 Jun 2019 15:07:46 -0600
Subject: [PATCH] Fix the error handling in bytesio_sizeof(). (GH-10459)

bytesio_sizeof() must check if an error has occurred in _PySys_GetSizeOf().
---
 Modules/_io/bytesio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index 32427e44de5..19e1ed8441e 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -943,8 +943,13 @@ bytesio_sizeof(bytesio *self, void *unused)
     Py_ssize_t res;
 
     res = _PyObject_SIZE(Py_TYPE(self));
-    if (self->buf && !SHARED_BUF(self))
-        res += _PySys_GetSizeOf(self->buf);
+    if (self->buf && !SHARED_BUF(self)) {
+        Py_ssize_t s = _PySys_GetSizeOf(self->buf);
+        if (s == -1) {
+            return NULL;
+        }
+        res += s;
+    }
     return PyLong_FromSsize_t(res);
 }