Add test for out-of-bounds read after resize

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/test_memoryview.py

@@ -3,6 +3,8 @@
 #
 # Licensed under the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
 
+import sys
+import pytest
 
 def test_subscript():
     v = memoryview(b'abcefg')
@@ -162,3 +164,21 @@ def test_pack():
     assert b == b'\x01'
     memoryview(b).cast('?')[0] = False
     assert b == b'\x00'
+
+def test_read_after_resize():
+    if sys.implementation.name != "graalpython":
+        return
+    # CPython prevents resizing of acquired buffers at all to avoid a segfault
+    # We don't want to impose locking on managed objects because we cannot automatically
+    # release the lock by reference counting. Check that we don't hard crash when
+    # does an out-of-bound read on a resized buffer
+    b = bytearray(b'12341251452134523463456435643')
+    m = memoryview(b)
+    assert m[1] == ord('2')
+    b.clear()
+    with pytest.raises(IndexError):
+        print(m[1])
+    with pytest.raises(IndexError):
+        m[1] = 3
+    with pytest.raises(IndexError):
+        print(m.tobytes())