Re: [Qemu-devel] [RFC][PATCH 11/45] msi: Factor out delivery hook

[malc]

On Tue, 18 Oct 2011, Michael S. Tsirkin wrote:

> On Tue, Oct 18, 2011 at 02:23:29PM +0200, Jan Kiszka wrote:
> > On 2011-10-18 14:05, Michael S. Tsirkin wrote:
> > > On Mon, Oct 17, 2011 at 09:15:47PM +0200, Jan Kiszka wrote:
> > >> On 2011-10-17 15:43, Michael S. Tsirkin wrote:
> > >>> On Mon, Oct 17, 2011 at 11:27:45AM +0200, Jan Kiszka wrote:
> > >>>> diff --git a/hw/msi.c b/hw/msi.c
> > >>>> index 3c7ebc3..9055155 100644
> > >>>> --- a/hw/msi.c
> > >>>> +++ b/hw/msi.c
> > >>>> @@ -40,6 +40,14 @@
> > >>>>  /* Flag for interrupt controller to declare MSI/MSI-X support */
> > >>>>  bool msi_supported;
> > >>>>  
> > >>>> +static void msi_unsupported(MSIMessage *msg)
> > >>>> +{
> > >>>> +    /* If we get here, the board failed to register a delivery 
> > >>>> handler. */
> > >>>> +    abort();
> > >>>> +}
> > >>>> +
> > >>>> +void (*msi_deliver)(MSIMessage *msg) = msi_unsupported;
> > >>>> +
> > >>>
> > >>> How about we set this to NULL, and check it instead of the bool
> > >>> flag?
> > >>>
> > >>
> > >> Yeah. I will introduce
> > >>
> > >> bool msi_supported(void)
> > >> {
> > >>     return msi_deliver != msi_unsupported;
> > >> }
> > >>
> > >> OK?
> > >>
> > >> Jan
> > >>
> > > 
> > > Looks a bit weird ...
> > > NULL is a pretty standard value for an invalid pointer, isn't it?
> > 
> > Save us the runtime check and is equally expressive and readable IMHO.
> > 
> > Jan
> 
> Do we need to check?
> NULL dereference leads to a crash just as surely...
> 

Not universally (not on AIX for instance (read)).

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