Re: [Xen-devel] [PATCH v3 2/4] GlobalProperty: Display warning about unused -global

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 04/19/14 16:54, Paolo Bonzini wrote:
> Il 18/04/2014 11:21, Andreas Färber ha scritto:
> > Improving this is greatly appreciated, thanks.
> >
> > Now, I can see two ways things can go wrong: a) Mistyping or later
> > refactoring devices, or b) user typos or thinkos.
> > And four ways to set globals: -global, config file (I hope?), legacy
> > command line options (vl.c) and machine .compat_props.
> >
> > If a property does not exist on the instance of an existing type,
> > object_property_parse() will raise an Error and we will abort in
> > device_post_init().
> >
> > What we are silently missing is if a type is misspelled; for that we can
> > probably add an Error **errp to the two qdev_prop_register_global*()
> > functions - assuming QOM types are already registered at that point.
> > qom-test would help us catch any such mistake by instantiating each machine.
> Even then, I suspect sooner or later machines other than PC and Q35 will be 
> versioned.  At that point we'll probably want QEMU-global compat_props that 
> automatically apply to all machines, even if a type is not missing.  I think we 
> should already approximate this behavior by allowing machine .compat_props 
> where the type doesn't exist.
If I am reading this correctly, this is asking that .compat_props to not
be reported.  This currently happens because of not_used being false
in all C99 struct initializations.

And that Andreas Färber would like me to extend qom-test to check
that at least 1 instance of each machine does use each .compat_props
so that a typo there gets "checked".

   -Don Slutz

> Paolo
>
> > I note that your proposed check is not failing, but still, with hot-add
> > of e.g. PCI devices we might well get a global property default for a
> > type that is not instantiated immediately but possibly used later on.

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