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cc @serhiy-storchaka

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This change needs a test. test_non_continuous_buffer in Lib/test/pickletester.py can be an indirect test (it should be modified for this), but since this change does not use pickle.PickleBuffer, it needs more direct test that only uses memoryview.

I am not sure that this is a right solution, but the test will help us to decide.

This change needs a test. test_non_continuous_buffer in Lib/test/pickletester.py can be an indirect test (it should be modified for this), but since this change does not use pickle.PickleBuffer, it needs more direct test that only uses memoryview.

I am not sure that this is a right solution, but the test will help us to decide.

It's really hard to trigger the crash using just memoryview because we first need to construct an exported buffer that will clear the view. I tried, but I failed.
I'm consider adding following test in Lib/test/pickletester.py.

    def test_circular_reference_gc(self):
        mv = memoryview(b"foobar")
        error = None
        unraisable_exception = None
    
        def custom_unraisablehook(unraisable):
            nonlocal unraisable_exception
            unraisable_exception = unraisable

        def func():
            try:
                pb = pickle.PickleBuffer(mv)
                raise CustomError
            except CustomError as e:
                # Ensure `error` references the exception
                error = e
        func()
        del mv
        prev_unraisablehook = sys.unraisablehook
        sys.unraisablehook = custom_unraisablehook
        support.gc_collect()
        self.assertEqual(unraisable_exception.exc_type, BufferError)
        self.assertIsInstance(unraisable_exception.exc_value, BufferError)
        self.assertEqual(str(unraisable_exception.exc_value), 'memoryview has 1 exported buffer')
        sys.unraisablehook = prev_unraisablehook

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#123898 uses a different solution. Trying to break a reference loop is a normal situation, it should not produce error reports (the user cannot do anything about this in any case), so _memory_release() should not even be called if self->exports != 0. That PR also contains tests.