[Libvir] Python bindings, errors & exceptions

Richard W.M. Jones rjones at redhat.com
Fri Mar 23 13:28:36 UTC 2007

Daniel P. Berrange wrote:
> Actually looks like it is the generated code actually. The generator.py
> appears to only add in the 'raise libvirtError' stuff if the return value
> is a virConnectPtr/virDomainPtr/virNeworkPtr  object - any other function
> with a non-object return value gives back None upon error. 

The generator.py code as it stands doesn't deal with the case where a 
function is prototyped (in C) as returning 'int'.

If I were to modify generator.py so that it adds the check for functions 
returning int, then it doesn't work because there is not enough 
information from just the C return type to tell what the Python return 
type will be.

As an example:

	C returns int
	Python returns int
	Current bindings fail to check for ret < 0 and
	  raise an exception.

	C returns int
	Python returns list of networks, or None
	Current bindings fail to check for ret == None and
	  raise an exception.

We could do some run-time type magic in the generated wrapper, although 
that seems evil.

I think the above are examples of the only two possible cases.


Emerging Technologies, Red Hat  http://et.redhat.com/~rjones/
64 Baker Street, London, W1U 7DF     Mobile: +44 7866 314 421
  "[Negative numbers] darken the very whole doctrines of the equations
  and make dark of the things which are in their nature excessively
  obvious and simple" (Francis Maseres FRS, mathematician, 1759)
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