[Python-Dev] [Python-checkins] r43041 - python/trunk/Modules/_ctypes/cfield.c (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sat Mar 18 23🔞50 CET 2006

Fernando Perez wrote:

So I think M.A. is right on the money here with his statement. Unless you consider the Linux/64bit camp insignificant. But if that is the case, it might be worth putting a big statement in the 2.5 release notes indicating "there is a good chance, if you use third party extensions and a 64 bit OS, that this won't work for you". Which will mean that a fraction of the scientific userbase (a big, enthusiastic and growing community of python users) will have to stick to 2.4.

It's more intricate than that. If certain extensions are of interest to the scientific community, I certainly expect the authors of them to fix them.

However, to "fix" the extension can still be done in different levels: you can easily fix it to not crash, by just honoring all compiler warnings that gcc produces. That doesn't mean you fully support Py_ssize_t, since you might not support collections with more than 2**31 elements. In these cases, the extension will not crash, but it will compute incorrect results if you ever encounter such a collection. Even on all these AMD64 Linux machines, this is still fairly unlikely, since you need considerably more than 16GiB main memory to do something useful on such collections - very few machines have that much memory today. Again, people that have such machines and need to run Python programs with that many data need to make sure that the extensions work for them. Sticking with 2.4 is no option for these people, since 2.4 doesn't support such large collections, anyway.

To really fix such extensions, I recommend building with either Microsoft C or Intel C. The Microsoft compiler is available free of charge, but runs on Windows only. It gives good warnings, and if you fix them all (in a careful way), your code should fully support 64 bits. Likewise for the Intel compiler: it is available for free only for a month, but it runs on Linux as well.

OTOH, I'm still doubtful how many extensions will be really affected by the change in the first place. Your code breaks with the change only if you implement the sequence or buffer protocols. I'm doubtful that this is an issue for most applications, since many extensions (I believe) work without implementing these protocols.

Regards, Martin

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