Fix usage of Py_ssize_t type in Python/compile.c

[vstinner]

BPO	19617
Nosy	@vstinner, @benjaminp, @serhiy-storchaka
Files	compile_ssize_t.patch

^{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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GitHub fields:

assignee = None
closed_at = <Date 2013-11-19.21:24:37.918>
created_at = <Date 2013-11-15.23:08:07.747>
labels = []
title = 'Fix usage of Py_ssize_t type in Python/compile.c'
updated_at = <Date 2013-11-19.22:56:55.865>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2013-11-19.22:56:55.865>
actor = 'python-dev'
assignee = 'none'
closed = True
closed_date = <Date 2013-11-19.21:24:37.918>
closer = 'vstinner'
components = []
creation = <Date 2013-11-15.23:08:07.747>
creator = 'vstinner'
dependencies = []
files = ['32644']
hgrepos = []
issue_num = 19617
keywords = ['patch']
message_count = 8.0
messages = ['202976', '202982', '203263', '203292', '203425', '203427', '203433', '203441']
nosy_count = 4.0
nosy_names = ['vstinner', 'benjamin.peterson', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue19617'
versions = ['Python 3.4']

[vstinner]

On Windows 64-bit, Visual Studio generates a lot of warnings because Py_ssize_t values are downcasted to int.

Attached patch fixes all warnings and move the final downcast into compiler_addop_i(). This function uses an assertion to check that integer parameter fits into an C int type. I don't know if it's safe to "return 0" on overflow error.

The patch fixes also some indentation issues seen was I wrote the patch.

Nobody complained before, I don't know if the bugs can be seen in practice, so I prefer to not touch Python 2.7 nor 3.2.

[benjaminp]

You could use the Py_SAFE_DOWNCAST macro everywhere.

[vstinner]

You could use the Py_SAFE_DOWNCAST macro everywhere.

I prefer to store sizes in a size type (Py_ssize_t), and only downcast where it is really needed, in compiler_addop_i(). So in the future, if someone wants to support values larger than INT_MAX, only one function need to be changed.

[benjaminp]

I meant where you added casts, you could use it.

2013/11/18 STINNER Victor <report@bugs.python.org>:

STINNER Victor added the comment:

> You could use the Py_SAFE_DOWNCAST macro everywhere.

I prefer to store sizes in a size type (Py_ssize_t), and only downcast where it is really needed, in compiler_addop_i(). So in the future, if someone wants to support values larger than INT_MAX, only one function need to be changed.

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Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue19617\>

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[vstinner]

Oops, I forgot to mention this issue number in the commit:
---
changeset: 87277:68fd86a83ece
tag: tip
user: Victor Stinner <victor.stinner@gmail.com>
date: Tue Nov 19 22:23:20 2013 +0100
files: Python/compile.c
description:
Issue bpo-9566: compile.c uses Py_ssize_t instead of int to store sizes to fix
compiler warnings on Windows 64-bit. Use Py_SAFE_DOWNCAST() where the final
downcast is needed.

The bytecode doesn't support integer parameters larger than 32-bit yet.
---

I added some more Py_SAFE_DOWNCAST() in the final commit.

[python-dev]

New changeset 8d3e85dfa46f by Victor Stinner in branch 'default':
Issue bpo-9566, bpo-19617: Fix compilation on Windows
http://hg.python.org/cpython/rev/8d3e85dfa46f

[python-dev]

New changeset ee4da7291211 by Victor Stinner in branch 'default':
Issue bpo-9566, bpo-19617: New try to fix compilation on Windows
http://hg.python.org/cpython/rev/ee4da7291211

[python-dev]

New changeset 116bd550e309 by Victor Stinner in branch 'default':
Issue bpo-9566, bpo-19617: Fix more compiler warnings in compile.c on Windows 64-bit
http://hg.python.org/cpython/rev/116bd550e309