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

[Michael S. Tsirkin]

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...

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