When querying a XML-RPC server that returns a 64 bit integer, the python
interface always returns an empty tuple.

When running with verbose=True the response is still intact, the library
just can't parse the result between the <i8></i8> tags.

Example response:
body: '<?xml version="1.0"
encoding="UTF-8"?>\r\n<methodResponse>\r\n<params>\r\n<param><value><i8>1157</i8></value></param>\r\n</params>\r\n</methodResponse>\r\n'

I attached a patch that seems to fix the problem, needs proper testing
though.

which implementations do support those 64 bit integers?

I ran into 64bit integer responses with rtorrent's XML-RPC API.

Thanks, fixed in r63782.

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).

The I8 tag is an extension by xmlrpc-c:
http://xmlrpc-c.sourceforge.net/doc/libxmlrpc.html#extensiontype
(XMLRPC_TYPE_I8)

As long as long integers aren't in the official spec, the current status
is fine - liberal in accepting, and strict in sending.