ctypes question

[News Wombat]

Hi everyone,

I've been experimenting with the ctypes module and think it's great.
I'm hitting a few snags though with seg faults.  I attached two links
that holds the code.  The line i'm having problems with is this,

sn=clibsmi.smiGetNextNode(pointer(sno),SMI_NODEKIND_ANY)

It will work one time, and if I call it again with the result of the
previous, even though the result (a c struct) looks ok, it will
segfault.  I think it's a problem with pointers or maybe the function
in the c library trying to change a string that python won't let it
change.  I'm stuck, any tips would be appreciated.  Thanks, and Merry
Christmas!

constants.py: http://pastebin.com/HvngjzZN
libsmi.py: http://pastebin.com/19C9kYEa