On 01/22/2016 12:24 PM, Markus Armbruster wrote: > Eric Blake <ebl...@redhat.com> writes: > >> When reporting that an unvisited member remains at the end of an >> input visit for a struct, we were using g_hash_table_find() >> coupled with a callback function that always returns true, to >> locate an arbitrary member of the hash table. But if all we >> need is an arbitrary entry, we can get that from a single-use >> iterator, without needing a tautological callback function. > > Good idea. > >> Suggested-by: Markus Armbruster <arm...@redhat.com> > > Whoops, it's even mine! I forgot... %-) > >> Signed-off-by: Eric Blake <ebl...@redhat.com> >> Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com> >> >> ---
>> GQueue *any;
>>
>> if (--ov->depth > 0) {
>> @@ -174,8 +168,8 @@ opts_end_struct(Visitor *v, Error **errp)
>> }
>>
>> /* we should have processed all (distinct) QemuOpt instances */
>> - any = g_hash_table_find(ov->unprocessed_opts, &ghr_true, NULL);
>> - if (any) {
>> + g_hash_table_iter_init(&iter, ov->unprocessed_opts);
>> + if (g_hash_table_iter_next(&iter, NULL, (void **)&any)) {
>
> Is this cast kosher?
You may have a point that it violates some corner of C99, but I'm not
the first such user:
hw/i386/intel_iommu.c: while (g_hash_table_iter_next (&bus_it, NULL,
(void**)&vtd_bus)) {
qom/object.c: while (g_hash_table_iter_next(&iter, NULL, (gpointer
*)&prop)) {
Conceptually, it seems fine - void* can be assigned to any pointer, and
'any' qualifies as such a pointer. We are then taking the address of
that (or void**) to pass by reference.
I suppose a stricter version would be:
void *wrap;
GQueue *any;
if (g_hash_table_iter_next(&iter, NULL, &wrap)) {
any = wrap;
...
but is it worth the bother? Put another way, will a compiler ever do
the wrong thing to us because C99 might have some corner case? Laszlo,
what's your take?
>> if (top_ht) {
>> - if (g_hash_table_size(top_ht)) {
>> - const char *key;
>> - g_hash_table_find(top_ht, always_true, &key);
>> + GHashTableIter iter;
>> + const char *key;
>> +
>> + g_hash_table_iter_init(&iter, top_ht);
>> + if (g_hash_table_iter_next(&iter, (void **)&key, NULL)) {
>
> Is this cast kosher?
Here, in addition to the above argument, we also needed to cast away const.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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