Re: [Qemu-devel] [PATCH qom-next] qom: make object cast assert if NULL object is passed as argument

[Igor Mammedov]

On 05/31/2012 11:34 AM, Igor Mitsyanko wrote:
> On 05/31/2012 12:11 PM, Igor Mammedov wrote:
> > On 05/30/2012 07:05 PM, Igor Mitsyanko wrote:
> > > On 05/30/2012 08:19 PM, Igor Mammedov wrote:
> > > > without assert it will crash at following point:
> > > > OBJECT_CHECK(type, obj, name) \
> > > > ((type *)object_dynamic_cast_assert(OBJECT(obj), (name)))
> > > > => object_dynamic_cast(obj, typename)
> > > > => object_is_type(obj, target_type)
> > > > => type_is_ancestor(obj->class->type, target_type);
> > > > ^^^
> > > > so abort earlier and print nice message instead of SIGSEGV
> > > >
> > > > Signed-off-by: Igor Mammedov<address@hidden>
> > > > ---
> > > > qom/object.c | 2 ++
> > > > 1 files changed, 2 insertions(+), 0 deletions(-)
> > > >
> > > > diff --git a/qom/object.c b/qom/object.c
> > > > index 00bb3b0..444e2fc 100644
> > > > --- a/qom/object.c
> > > > +++ b/qom/object.c
> > > > @@ -481,6 +481,8 @@ Object *object_dynamic_cast_assert(Object *obj,
> > > > const char *typename)
> > > > {
> > > > Object *inst;
> > > >
> > > > + g_assert(obj != NULL);
> > > > +
> > > > inst = object_dynamic_cast(obj, typename);
> > > >
> > > > if (!inst) {
> > > Makes much sense, but maybe it should be done in OBJECT() cast? Assert
> > > when we do OBJECT(NULL).
> > sort grep shows that no one is casting NULLs to anything, what's the point?
> No one passing NULL to OBJECT_CHECK() either, what I'm talking about is cases 
> when we cast some variable foo to Object * with OBJECT(foo) when foo ==
> NULL. But Markus thinks that its OK to do that, perhaps he's right, asserting 
> will impose unnecessary restrictions on developers.

Ah I see, I've got confused, sorry.

--
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 Igor