Re: [Qemu-devel] [PATCH 1/8] qapi: fix NULL pointer dereference

[Paolo Bonzini]

On 12/16/2011 04:05 PM, Anthony Liguori wrote:
> > > What are the uses of null in qdev string properties? I know you can't
> > > set a string to null since parse() doesn't have a null syntax. So we're
> > > really just talking about an uninitialized state, right?
> >
> > Yes. No ROM BAR is an example of a NULL string property.
>
> So it's really filenames and backend names, right?  Can we just treat
> empty strings like NULL?  I think all of the various bits handles both
> the same way.

The only case I can think of when it differs is serial numbers.  An 
empty serial number is different from no serial number (which means do 
not expose one at all).

However, DEFINE_PROP_STRING does not allow setting a default, and some 
device models rely on a NULL value as a default.  I see two ways out: 1) 
add nullable strings; 2) merge without this patch, knowing qom-get is 
kind-of broken, and proceed adding a default to all DEFINE_PROP_STRING; 
this would be a merge nightmare for you.  3) merge without this patch, 
knowing it's kind-of broken, and later decide what to do.

Let's do (3), and add nullable strings if the discussion stalls.

Paolo