From bf623ae8843dc30b28c574bec8d29fc14be59d86 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 19 Apr 2017 20:03:52 +0300
Subject: bpo-30061: Check if
 PyObject_Size()/PySequence_Size()/PyMapping_Size() (#1096)

raised an error.

Replace them with using concrete types API that never fails if appropriate.
---
 Lib/test/test_io.py | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'Lib/test')

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 32f76a6c62..46c7833b5c 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -543,6 +543,22 @@ class IOTest(unittest.TestCase):
         with self.open(support.TESTFN, "r") as f:
             self.assertRaises(TypeError, f.readline, 5.3)
 
+    def test_readline_nonsizeable(self):
+        # Issue #30061
+        # Crash when readline() returns an object without __len__
+        class R(self.IOBase):
+            def readline(self):
+                return None
+        self.assertRaises((TypeError, StopIteration), next, R())
+
+    def test_next_nonsizeable(self):
+        # Issue #30061
+        # Crash when __next__() returns an object without __len__
+        class R(self.IOBase):
+            def __next__(self):
+                return None
+        self.assertRaises(TypeError, R().readlines, 1)
+
     def test_raw_bytes_io(self):
         f = self.BytesIO()
         self.write_ops(f)
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