On 04/18/2018 11:45 AM, Markus Armbruster wrote: >> Might also be worth mentioning that this explicitly guarantees that >> existing casts work correctly (even though we'd prefer to get rid of >> such casts in any location except the qobject.h macros); Markus pointed out: >> >>>> Uh, there's another reason: existing type casts from QObject * to >>>> subtypes. I just spotted one in tests/check-qdict.c: >>>> >>>> dst = (QDict *)qdict_crumple(src, &error_abort); > > As far as I'm concerned, that's the real reason. The simplification > plus the check to make it safe seems like a wash. > > The cast I spotted appears to be the only one, though: > > $ git-grep '(Q[A-Z][a-z]* \*)' > hmp.c: qmp_device_add((QDict *)qdict, NULL, &err); > include/qapi/qmp/qobject.h: return (QObject *)obj; > qobject/qobject.c:static void (*qdestroy[QTYPE__MAX])(QObject *) = { > tests/check-qdict.c: dst = (QDict *)qdict_crumple(src, &error_abort); > > The first two cast away const, the third isn't a type cast. The fourth > one should use qobject_to() instead, regardless of this patch. > > Do we want to force base to come first anyway? > > Where does PATCH 2 exploit "base first"?
It doesn't, but PATCH 4 does: > /** > * qobject_ref(): Increment QObject's reference count > + * > + * Returns: the same @obj. The type of @obj will be propagated to the > + * return type. > */ > -#define qobject_ref(obj) qobject_ref_impl(QOBJECT(obj)) > +#define qobject_ref(obj) ((typeof(obj)) qobject_ref_impl(QOBJECT(obj))) > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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