Re: [Qemu-devel] IDs in QOM

[Andreas Färber]

Am 02.10.2014 um 16:21 schrieb Markus Armbruster:
> Andreas Färber <address@hidden> writes:
> 
>> Am 02.10.2014 um 15:21 schrieb Stefan Hajnoczi:
>>> On Wed, Oct 01, 2014 at 02:33:47PM +0200, Markus Armbruster wrote:
>>>> Markus Armbruster <address@hidden> writes:
>>>
>>> This discussion seems orthogonal to your patch.  But I'm not applying it
>>> yet to give more time for discussion/review of the patch.
>>>
>>>> Is mangling array-ness into the name really a good idea?  Isn't this
>>>> type matter, not name matter?
>>>
>>> I agree.  It's nasty to hack the array selector into the name and will
>>> probably cause us pain down the line.
> 
> Andreas?

-> Paolo ;)

>>>> Backtracking a bit...  Unlike QMP object-add, -object ) and HMP
>>>> object-add use QemuOpts.  See object_create(), commit 68d98d3 "vl: add
>>>> -object option to create QOM objects from the command line", and
>>>> hmp_object_add(), commit cff8b2c "monitor: add object-add (QMP) and
>>>> object_add (HMP) command".  Parameter 'id' is the QemuOpts ID, thus
>>>> bound by its well-formedness rule.
>>>>
>>>> Therefore, -object and HMP object-add only support a subset of the
>>>> possible names.
>>>>
>>>> In particular, they do not permit "automatic arrayification".
>>>>
>>>> Should QOM names be (well-formed!) IDs?
>>>
>>> Yes, I think that is sane.
>>>
>>> Are there any invalid IDs used as QOM names today?
>>>
>>> Hopefully the answer is no and we can lock everything down using
>>> id_wellformed().
>>
>> On IRC I was arguing against that, preferring some more specific
>> object_property_name_wellformed() or so. This could be called from
>> object_property_add(), with invalid names returning an Error *.
>>
>> Only thing to check for would be '/'?
> 
> We obviously have to outlaw '/'.  However, unless we outlaw just like
> id_wellformed():
> 
>>> If not, is -object and HMP object-add restricting the names to
>>> well-formed IDs a bug?
> 
> Opinions?
> 
> My opinion is to stick to id_wellformed() and call it a day.

We cannot use id_wellformed() in object_property_add(), as I assume it
prohibits '.' as well, which we need for bus names.

This would be easier to discuss if you gave us the exact list of
outlawed characters for comparison. ',' is probably another?

If you just want to call id_wellformed() for -object / object-add, I
won't object to restricting it beyond the necessary, but it'll lead to
two places doing validity checks for QOM.

Regards,
Andreas

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