[Python-Dev] Type of range object members (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Tue Aug 15 09:25:35 CEST 2006

Alexander Belopolsky wrote:

Since on most platforms ssizet is the same as long, the choice between the two is just a matter of self-documenting code.

No, it would be an actual change: on Win64, sizeof(Py_ssize_t)>sizeof(long).

Speaking of which, I find it unfortunate that the name Pyssizet was selected for the typedef. I would prefer Pyindext. The first time I saw Pyssizet, I did not notice the double 's' and thought it was an unsigned type.

Hmm. That you fail to read it correctly can hardly be an argument against it.

On the second look, I've realized that it is signed and started wondering why not ptrdifft. I understand that ssizet is defined by POSIX as the return type of functions such as "read" that can return either size or -1 for error. I don't think POSIX mandates sizeof(sizet) == sizeof(ssizet), but I may be wrong.

In the rationale (XRAT) they say

"This is intended to be a signed analog of size_t."

They don't mandate it to have the same size, but it is the expectation that implementations typically will.

I would agree that ptrdifft, although standard C, is not a very intuitive name, but ssizet is even less clear.

In the discussion, ptrdiff_t was never brought up as an alternative (intptr_t was; see the PEP for why it is unsuitable). ssize_t seemed most natural to me since size_t is the C "number of bytes" type, and we need a signed version of it.

Regards, Martin

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