[Python-Dev] Optimization of the Year (original) (raw)

Guido van Rossum guido at python.org
Wed Feb 11 12:58:26 EST 2004

Guido van Rossum wrote: > I'm all for this. I imagine there are many subtleties though -- I > know I consciously chose 'int' for this purpose in Python 0, and the > assumption that it fits in an int is everywhere. I would trust a > decent compiler to find most cases, but not all.

[MvL]

The MS Win64 compiler (Itanium) is pretty good at finding sizet/int conversions, as sizet is wider even than long on the system. I have patches sitting on my disk to change all function signatures, but not the structure layouts. They are (unfortunately) still incomplete, and it is doubtful whether I can complete them before PyCon.

Maybe it can be a sprint topic?

> Also, occasionally (sizet)(-1) may be used to indicate an error > (e.g. PySequenceSize()).

This is the tricky part that I want to defer in the first round of patches: I believe obsize should be a signed type, so it should be ssizet where available. The tricky part is finding an appropriate type on systems where ssizet is not available.

Why not simply use Py_intptr_t then?

(sizet)(-1) is not a problem per se; this is well-defined on all ISO C compilers. However, some code may expect that the error marker is smaller than any other value, which would not be the case for (sizet)(-1).

Right, that's what I meant.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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