Re: [libvirt] [PATCH python] override: Return NULL on python failure in getCPUModelNames

On 03/20/2014 11:58 AM, Cole Robinson wrote: ACK. We probably have other code not quite doing the right thing; maybe it's time to audit the code base. The rule of thumb (which took me some time to learn) is: If libvirt failed, we have a thread-local libvirt error set. Return a non-NULL sentinel value (-1 or None, depending on whether the interface normally returns an integer or a python struct) so that the wrapper code will then raise a libvirt exception class object. If python failed, we either encountered OOM, or there was some other problem with the user's input (perhaps the user passed in a python object that can't be converted to the type we expect), and we don't have any thread-local libvirt error set. Return NULL so that python will immediately raise a python exception class object without even getting to our wrapper. Returning NULL when there is no thread-local python exception ready to raise, or returning non-NULL when there is no thread-local libvirt error to convert to a libvirt exception object, or returning the wrong type of sentinel, results in broken code. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org