[New-bugs-announce] [issue1114] _curses issues on 64-bit big-endian (e.g, AIX)

Luke Mewburn report at bugs.python.org
Thu Sep 6 05:32:34 CEST 2007

New submission from Luke Mewburn:

Attempting to use curses attributes with python 2.3.5 on AIX (64bit
powerpc) doesn't work, and occasionally results in exceptions being raised.

_cursesmodule.c assumes that attr_t is a `long' and uses the "l"
decoding of PyArg_ParseTuple() to read values from python to C.  On
platforms where sizeof(int) == sizeof(long), this isn't a problem. 
However, on LP64, especially big-endian LP64, this results in the wrong
value being stored in the target address.

My solution is to use ParseTuple("l") into a variable with an explicit
type of 'long', and then assign that to the attr_t variable that the
underlying curses(3) functions are called with.

(I don't know if there's a different convention for dealing with reading
numbers from python into underlying C types where the C type size isn't
consistently an `int' or a `long', other that reading into an explicit
int/long and then assigning/casting to the final type)

The code in question doesn't appear to have changed much between python
2.3.5 and the svn trunk (as at 20070906), and my patch for the former
applied fairly cleanly to my checkout of the latter.  I've attached a
diff from the svn checkout.

components: Extension Modules
files: curses-attr_t-long.diff
messages: 55675
nosy: lukemewburn
severity: normal
status: open
title: _curses issues on 64-bit big-endian (e.g, AIX)
type: behavior
versions: Python 2.3

Tracker <report at bugs.python.org>
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