Re: [PATCH] qom: Allow object_property_add_child() to fail

[Auger Eric]

Hi Markus,

On 6/24/20 10:22 AM, Markus Armbruster wrote:
> Eric Auger <eric.auger@redhat.com> writes:
> 
>> object_property_add() does not allow object_property_try_add()
>> to gracefully fail as &error_abort is passed as an error handle.
>>
>> However such failure can easily be triggered from the QMP shell when,
>> for instance, one attempts to create an object with an id that already
>> exists:
>>
>> For instance, call twice:
>> object-add qom-type=memory-backend-ram id=mem1 props.size=1073741824
>> and QEMU aborts.
>>
>> This behavior is undesired as a user/management application mistake
>> in reusing a property ID shouldn't result in loss of the VM and live
>> data within.
>>
>> This patch introduces two new functions, object_property_add_err() and
>> object_property_add_child_err() whose prototype features an error handle.
>> object_property_add_child_err() now gets called from user_creatable_add_type.
>> This solution was chosen instead of changing the prototype of existing
>> functions because the number of existing callers is huge.
>>
>> The error now is returned gracefully to the QMP client.
>>
>> (QEMU) object-add qom-type=memory-backend-ram id=mem2  props.size=4294967296
>> {"return": {}}
>> (QEMU) object-add qom-type=memory-backend-ram id=mem2  props.size=4294967296
>> {"error": {"class": "GenericError", "desc": "attempt to add duplicate 
>> property
>> 'mem2' to object (type 'container')"}}
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> Recent regression, my fault.  Please point that out, and add
> 
>   Fixes: d2623129a7dec1d3041ad1221dda1ca49c667532
Thanks you for the reference. I will add the tag.

Eric
>