Grand Unified Python Object Layout

[encukou]

See: faster-cpython/ideas#553

Mark's proposal has several advantages, like:

• Supports multiple inheritance even if instances need C (“raw memory”) data storage
• The VM can generate correct tp_traverse and tp_clear automatically
• Core instance structs (PyObject, PyListObject, ...) no longer need to be exposed
• Focus on performance, especially for core types

[steve-s]

I think it would be useful to show how one would implement more complex layouts with that (if they are planned to be supported in this design?), like NumPy array.