Issue #23099: Closing io.BytesIO with exported buffer is rejected now to

prevent corrupting exported buffer.

Lib/_pyio.py

@@ -833,8 +833,14 @@ class BytesIO(BufferedIOBase):
     def getbuffer(self):
         """Return a readable and writable view of the buffer.
         """
+        if self.closed:
+            raise ValueError("getbuffer on closed file")
         return memoryview(self._buffer)
 
+    def close(self):
+        self._buffer.clear()
+        super().close()
+
     def read(self, size=None):
         if self.closed:
             raise ValueError("read from closed file")

Lib/test/test_memoryio.py

@@ -398,14 +398,19 @@ class BytesIOMixin:
         # raises a BufferError.
         self.assertRaises(BufferError, memio.write, b'x' * 100)
         self.assertRaises(BufferError, memio.truncate)
+        self.assertRaises(BufferError, memio.close)
+        self.assertFalse(memio.closed)
         # Mutating the buffer updates the BytesIO
         buf[3:6] = b"abc"
         self.assertEqual(bytes(buf), b"123abc7890")
         self.assertEqual(memio.getvalue(), b"123abc7890")
-        # After the buffer gets released, we can resize the BytesIO again
+        # After the buffer gets released, we can resize and close the BytesIO
+        # again
         del buf
         support.gc_collect()
         memio.truncate()
+        memio.close()
+        self.assertRaises(ValueError, memio.getbuffer)
 
 
 class PyBytesIOTest(MemoryTestMixin, MemorySeekTestMixin,