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

"Martin v. Löwis" martin at v.loewis.de
Wed Feb 11 12:52:16 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.

The MS Win64 compiler (Itanium) is pretty good at finding size_t/int conversions, as size_t 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.

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 ob_size should be a signed type, so it should be ssize_t where available. The tricky part is finding an appropriate type on systems where ssize_t is not available.

(size_t)(-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 (size_t)(-1).

Regards, Martin

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