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Re: [libvirt] [PATCH 1/2] python: treat flags as default argument with value 0

On 03/21/2013 09:24 PM, Guannan Ren wrote:

>>> migrate(self, dconn, flags, dname, uri, bandwidth):
>>> migrate2(self, dconn, dxml, flags, dname, uri, bandwidth):
>>> migrateToURI(self, duri, flags, dname, bandwidth):
>>> migrateToURI2(self, dconnuri, miguri, dxml, flags, dname, bandwidth):
>> So how are they filtered? ...
>           If we add flags=0 to above four APIs, we have to move the
> flags arguments
>           to the last position in the arguments list because the rule
> "default arguments
>           have to come after positional arguments." Changing them will
> break the binding
>           APIs. so I didn't touch them.

Actually, we should probably use

migrate(self, dconn, flags=0, dname=None, uri=None, bandwidth=0)

with sane defaults for all arguments after the flags.  After all, the C
api states:

 * virDomainMigrate:
 * @domain: a domain object
 * @dconn: destination host (a connection object)
 * @flags: bitwise-OR of virDomainMigrateFlags
 * @dname: (optional) rename domain to this at destination
 * @uri: (optional) dest hostname/URI as seen from the source host
 * @bandwidth: (optional) specify migration bandwidth limit in Mbps

But I'm okay if you change the migrate* functions in a separate patch,
since it will be touching more than just flags.

>> ...As I see you write "flags=0" for all the automatically generated
>> APIs here? And is there any risk to have other APIs of which flags
>> doesn't default to 0? Except the ones you mentioned in commit log.
>        Yes,  I am not sure if the 0 is appropriatefor every APIs.
>        I need more advice here.
>        According to my test, they can accept the 0 value all.

flags == 0 should be sane for all APIs that we add.  In fact, for many
APIs, flags == 0 is the only value that we actually support, when we
haven't yet used any flags.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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