subprocess returncode is masked

[Emmanuel]

I'm using Python 2.6 and the new subprocess module to get the exit value 
of an external executable. It appears the return value given by wait() 
or poll() operations is masked under Unix: I only get the lower 8 bits. 
So an exit value of 0x0402 in the C program will be seen as 0x02 in 
Python. And this does not happen on Windows...
Any idea why that is ?
Emmanuel