I think it's also a bug that xmlrpclib just ignores unknown tags
(without even printing a warning).

and: wouldn't it be nice if we could also write back those integers?

>>> import xmlrpclib
>>> xmlrpclib.dumps((2**40,))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ralf/pydev/trunk/Lib/xmlrpclib.py", line 1126, in dumps
data = m.dumps(params)
  File "/home/ralf/pydev/trunk/Lib/xmlrpclib.py", line 671, in dumps
dump(v, write)
  File "/home/ralf/pydev/trunk/Lib/xmlrpclib.py", line 693, in __dump
f(self, value, write)
  File "/home/ralf/pydev/trunk/Lib/xmlrpclib.py", line 704, in dump_int
raise OverflowError, "int exceeds XML-RPC limits"
OverflowError: int exceeds XML-RPC limits

I asked about the implementations supporting this as this i8 tag does
not conform to the xmlrpc spec (but I would be happy if there was an de
facto standard for sending large integers and would also help implement it).