Looks like the wchar_t* array returned by Py_GetArgcArgv() on OSX suffers by double encoding. This can affect sys.argv, sys.executable and C code relying on the above function of course.

On Linux:

$ python3
Python 3.0rc1+ (py3k, Oct 28 2008, 09:22:29) 
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os, sys
>>> snowman = '\u2603'
>>> os.system(sys.executable + " -c 'import sys; [print(a.encode(\"utf8\")) for a in sys.argv]' foo bar " + snowman)
b'-c'
b'foo'
b'bar'
b'\xe2\x98\x83'
0

On OSX (uname -a is Darwin comicbookguy.local 10.4.0 Darwin Kernel Version 10.4.0: Fri Apr 23 18:28:53 PDT 2010; root:xnu-1504.7.4~1/RELEASE_I386 i386)

$ python3
Python 3.1.2 (r312:79147, Jul  5 2010, 11:57:14) 
[GCC 4.2.1 (Apple Inc. build 5659)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import os, sys
>>> snowman = '\u2603'
>>> os.system(sys.executable + " -c 'import sys; [print(a.encode(\"utf8\")) for a in sys.argv]' foo bar " + snowman)
b'-c'
b'foo'
b'bar'
b'\xc3\xa2\xc2\x98\xc2\x83'
0

Is this a known limitation of the platform? I don't know much about OSX, just found it testing for regressions in setproctitle <http://code.google.com/p/py-setproctitle/>

Reported correctly working on Windows.