I think it's more acceptable to require matching versions now than it was 10 years ago -- people are much more likely to use installer tools like pip and conda that can check version compatibility.
I think I'd be okay with dropping the flag-based mechanism you describe if we were to introduce a clear mechanism that always rejected a dynamically loaded module if it was compiled for a different Python version. This should happen without any cooperation from the module. Perhaps in Python.h we can introduce a reference to a variable whose name varies by version (major.minor, I think) and which is defined only by the interpreter itself. Or perhaps the version should be based on a separate ABI version. On Sat, Dec 16, 2017 at 5:22 AM, Antoine Pitrou <solip...@pitrou.net> wrote: > > 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/ > guido%40python.org > -- --Guido van Rossum (python.org/~guido)
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