Hello, Nowadays we have an official mechanism for third-party C extensions to be binary-compatible accross feature releases of Python: the stable ABI.
But, for non-stable ABI-using C extensions, there are also mechanisms in place to *try* and ensure binary compatibility. One of them is the way in which we add tp_ slots to the PyTypeObject structure. Typically, when adding a tp_XXX slot, you also need to add a Py_TPFLAGS_HAVE_XXX type flag to signal those static type structures that have been compiled against a recent enough PyTypeObject definition. This way, extensions compiled against Python N-1 are supposed to "still work": as they don't have Py_TPFLAGS_HAVE_XXX set, the core Python runtime won't try to access the (non-existing) tp_XXX member. However, beside internal code complication, it means you need to add a new Py_TPFLAGS_HAVE_XXX each time we add a slot. Since we have only 32 such bits available (many of them already taken), it is a very limited resource. Is it worth it? (*) Can an extension compiled against Python N-1 really claim to be compatible with Python N, despite other possible differences? (*) we can't extend the tp_flags field to 64 bits, precisely because of the binary compatibility problem... Regards Antoine. _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
