So the overall to-do list here is sounding like:

1. Document "Py_buffer->obj" appropriately in both the C API documentation and in PEP 3118

2. Ensure GetBuffer/ReleaseBuffer are used as the moral equivalent of INCREF/DECREF for Py_buffer objects.

3. Check builtin types correctly manage the lifecycle of all elements of their exported Py_buffer structs

4. Check return values and throw exceptions as noted in the original post