[Python-Dev] New PEP: Using ssize_t as the index type (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Tue Jan 10 21:28:43 CET 2006

M.-A. Lemburg wrote:

I don't see a good solution for these other than introducing a set of new APIs (and maybe doing some macro magic as Martin did for PyArgParseTuple()). Due to the fact that changes in the types of output parameters require changes in the extension variable type layout itself, they introduce a large number of type changes in the extension and make writing backwards compatible extensions harder than necessary.

That's not true. It is very easy to write extensions that receive such values and are still backwards-compatible.

Suppose you had

int pos; PyObject *k, *v;

PyDict_Next(dict, &pos, &k, &v);

You just change this to

/* beginning of file */ #ifdef Py_HEX_VERSION < 2.5 typedef int Py_ssize_t; #endif

/* later */ Py_ssize_t pos; PyObject *k, *v;

PyDict_Next(dict, &pos, &k, &v);

That's it!

Furthermore, all extensions for Python 2.4 would have to be ported to the new Python API and porting is not going to be a simple recompile, but will require C skills.

Not all extensions. Only those that call functions that expect int* output parameters - which is fairly uncommon.

Martin, please add the above points to the PEP. I'd also like to see it published, because it's hard to track a PEP in the mailing

It's very difficult to get a PEP number assigned. I wrote peps at python.org with no response.

Regards, Martin

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