Re: [Qemu-devel] [RFC PATCH 09/11] Implement qdict_flatten()

[Kevin Wolf]

Am 11.07.2013 um 22:25 hat Eric Blake geschrieben:
> On 07/09/2013 03:53 AM, Kevin Wolf wrote:
> 
> Worth repeating this comment from the code into the commit message?
> 
> > + * qdict_flatten(): For each nested QDict with key x, all fields with
> key y
> > + * are moved to this QDict and their key is renamed to "x.y".
> 
> Otherwise, I had to read nearly the entire patch to learn what I was
> supposed to be reviewing.

Okay, will do that.

> > +static void qdict_do_flatten(QDict *qdict, QDict *target, const char 
> > *prefix)
> > +{
> > +    QObject *value;
> > +    const QDictEntry *entry, *next;
> > +    const char *new_key;
> > +    bool delete;
> > +
> > +    entry = qdict_first(qdict);
> > +
> > +    while (entry != NULL) {
> > +
> > +        next = qdict_next(qdict, entry);
> > +        value = qdict_entry_value(entry);
> > +        new_key = NULL;
> > +        delete = false;
> > +
> > +        if (prefix) {
> > +            qobject_incref(value);
> > +            new_key = g_strdup_printf("%s.%s", prefix, entry->key);
> > +            qdict_put_obj(target, new_key, value);
> 
> You are calling this function with the same parameter for both qdict and
> target.  Doesn't that mean you are modifying qdict while iterating it?
> Is that safe?  [/me re-reads] - oh, you recursively call this function,
> and this modification of target happens _only_ if prefix is non-null,
> which happens only:
> 
> > +            delete = true;
> > +        }
> > +
> > +        if (qobject_type(value) == QTYPE_QDICT) {
> > +            qdict_do_flatten(qobject_to_qdict(value), target,
> > +                             new_key ? new_key : entry->key);
> 
> when passing two different dicts into the function.  Maybe add an
> assert(!prefix || qdict != target).

Your point still stands: The recursively called function modifies target
(which is qdict on the top level) by adding new keys. I guess when it
returns I need to restart the loop from the beginning in order to be
safe.

Kevin

> > +            delete = true;
> > +        }
> > +
> > +        if (delete) {
> > +            qdict_del(qdict, entry->key);
> > +        }
> > +
> > +        entry = next;
> > +    }
> > +}
> > +
> > +/**
> > + * qdict_flatten(): For each nested QDict with key x, all fields with key y
> > + * are moved to this QDict and their key is renamed to "x.y".
> > + */
> > +void qdict_flatten(QObject *obj)
> > +{
> > +    QDict *qdict = qobject_to_qdict(obj);
> > +    qdict_do_flatten(qdict, qdict, NULL);
> > +}
> > 
> 
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>