Am 01.06.2012 13:18, schrieb Markus Armbruster: > Andreas Färber <afaer...@suse.de> writes: > >> Am 31.05.2012 13:17, schrieb Igor Mammedov: >>> On 05/31/2012 12:16 PM, Paolo Bonzini wrote: >>>> Il 31/05/2012 10:30, Markus Armbruster ha scritto: >>>>>>> Makes much sense, but maybe it should be done in OBJECT() cast? Assert >>>>>>> when we do OBJECT(NULL). >>>>> In my opinion, OBJECT(p) where p is a null pointer is perfectly valid >>>>> and should yield a null pointer. >>>> >>>> Perhaps object_dynamic_cast and object_dynamic_cast_assert should do the >>>> same? >>>> >>> >>> or better object_dynamic_cast should return NULL if obj is NULL, >>> after all it's expected that it may return NULL >> >> That's what I was suggesting: I think that we should define "NULL is not >> of type TYPE_FOO" and thus have the ..._is_... functions return false, >> and have the ..._cast_assert assert. > > Is it?
See http://www.mail-archive.com/qemu-devel@nongnu.org/msg113922.html > Igor: object_dynamic_cast should return NULL if obj is NULL, > > You: have the ..._cast_assert assert [on null argument, I presume] > > Doesn't sound like the same suggestion to me :) I'll let you to your opinion. :) However, my opinion is that object_dynamic_cast_assert() should assert (its name should be program), not segfault, and that object_dynamic_cast()/object_is_type()/type_is_ancestor() should not assert but return false / NULL. So as to the effects and usability that pretty much aligns with Igor M., no? > If I understood you correctly: what do such assertions buy us other than > silliness like > > p ? some_cast(p) : NULL > > ? Nack. The point is that currently deployed MY_TYPE(x) should assert (because nobody expects it to return NULL) and he who does want to handle NULL can use object_dynamic_cast(p). There's no real change to what we have except that an error case that was unhandled now is handled. >> So I still think this patch is correct. It could be accompanied by >> further patches adding error handling in the remaining functions. > > I'm not convinced. Shed any light? Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
