Using size_t where appropriate

[loewis]

BPO	1166195
Nosy	@loewis
Files	size_t.diff ssize_t.diff.gz: Version 2 (PyCon)

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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assignee = None
closed_at = <Date 2006-04-15.07:15:32.000>
created_at = <Date 2005-03-18.19:59:12.000>
labels = []
title = 'Using size_t where appropriate'
updated_at = <Date 2006-04-15.07:15:32.000>
user = 'https://github.com/loewis'

bugs.python.org fields:

activity = <Date 2006-04-15.07:15:32.000>
actor = 'loewis'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['None']
creation = <Date 2005-03-18.19:59:12.000>
creator = 'loewis'
dependencies = []
files = ['6550', '6551']
hgrepos = []
issue_num = 1166195
keywords = ['patch']
message_count = 4.0
messages = ['47994', '47995', '47996', '47997']
nosy_count = 1.0
nosy_names = ['loewis']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1166195'
versions = []

[loewis]

This patch is (a first draft of) an attempt to make
Python properly use size_t where necessary. This work
is triggered by compilation on Win64 (where the
compiler warns about potential truncation errors a
lot). The rationale for the patch is that size_t might
be larger than int, in particular on 64-bit platforms,
and that the size of a memory chunk cannot reliably be
measured with an int.

It turns out that using size_t is not enough, since
values can sometimes also be negative. For these cases,
a "signed" size_t is used, which is called Py_ssize_t
and is a define for ssize_t if the compiler supports
the latter.

The guideline for converting int to size_t used in this
patch is this:

• if the variable is meant to store the number of
  bytes, and is always guaranteed to be positive, and
  could get arbitrarily large, use size_t
• if the value could be negative also, use ssize_t
• if the value is meant to store a number of "things",
  but this directly translates into size_t (e.g. number
  of pointers, number of characters), also use size_t/ssize_t
• if the value is in a range limited to 32-bit int
  (e.g. the number of characters in a path name), convert
  the size_t to int, after asserting that the value
  really is in the range.

This version is work in progress, and needs review. I
hope to work on it during the sprints at PyConDC.

[loewis]

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Second version of the patch attached (PyCon version). It turns out that
changing everything from signed to unsigned breaks too many things, so
this version of the patch uses Py_ssize_t in nearly all places.

[loewis]

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This patch is now maintained in

http://svn.python.org/projects/python/branches/ssize_t/

[loewis]

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And now it is part of the trunk.