Re: [Qemu-block] [PATCH 09/13] qdict: Make qdict_flatten() shallow-clone-friendly

[Eric Blake]

On 05/09/2018 11:55 AM, Max Reitz wrote:
> In its current form, qdict_flatten() removes all entries from nested
> QDicts that are moved to the root QDict.  It is completely sufficient to
> remove all old entries from the root QDict, however.  If the nested
> dicts have a refcount of 1, this will automatically delete them, too.
> And if they have a greater refcount, we probably do not want to modify
> them in the first place.
>
> The latter observation means that it was currently (in general)
> impossible to qdict_flatten() a shallowly cloned dict because that would
> empty nested QDicts in the original dict as well.  This patch changes
> this, so you can now use qdict_flatten(qdict_shallow_clone(dict)) to get
> a flattened copy without disturbing the original.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
>   qobject/qdict.c | 23 ++++++++++++++++-------
>   1 file changed, 16 insertions(+), 7 deletions(-)

>   
>           g_free(new_key);
>   
> -        if (delete) {
> +        if (copied_value && qdict == target) {
> +            /* If we have copied a value, and if we are on the root
> +             * level, we need to remove the old entry.  Otherwise, we
> +             * do not, because by removing these entries on the root
> +             * level, the reference counts of nested dicts and listed

s/listed/lists/

> +             * will be reduced automatically.  In fact, we probably do
> +             * not want to modify nested dicts and lists with
> +             * refcounts greater than 1 anyway. */
>               qdict_del(qdict, entry->key);
>   
> -            /* Restart loop after modifying the iterated QDict */
> +            /* Restart loop after modifying the iterated QDict.  We
> +             * only need to do this if qdict == target, because
> +             * otherwise copying the value did not affect qdict. */
>               entry = qdict_first(qdict);
>               continue;
>           }

With the typo fix,
Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org