Re: [Qemu-devel] [RFC v2 3/5] vmstate: add VMS_MUST_EXIST

[Dr. David Alan Gilbert]

* Michael S. Tsirkin (address@hidden) wrote:
> On Mon, Mar 24, 2014 at 05:11:16PM +0000, Dr. David Alan Gilbert wrote:

<snip>

> > I think your intent here is just to misuse the field_exist function pointer 
> > as a call for a different reason as a hook for a validator; is it really 
> > worth
> > misusing it like that or is something more explicit worth it?
> > Perhaps something passed an Error** so it could pass back what was wrong?
> 
> 
> Well adding a required field seems valuable by itself, does it not?

Maybe; however most fields are always-present, unless they have a test
function or minimum version, so it's a little weird to add a 'required'
when that's the default.

> And there's no way to pass in Error** since none of the callers
> has Error**: all of migration still uses stderr to pass
> errors.
> 
> So we could add an API but it doesn't seem too valuable.
> 
> Since all callers will use this through a wrapper like VMSTATE_TEST,
> it will be easy to change our mind later.

Yep, that's fine - was just an idea.

Dave
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK