Re: [Qemu-block] [Qemu-devel] [RFC PATCH 04/56] char: Make ringbuf-read size unsigned in QAPI/QMP

[Marc-André Lureau]

Hi

On Tue, Aug 22, 2017 at 3:00 PM, Markus Armbruster <address@hidden> wrote:
> Marc-André Lureau <address@hidden> writes:
>
>> Hi
>>
>> On Mon, Aug 7, 2017 at 4:45 PM, Markus Armbruster <address@hidden> wrote:
>>> Sizes should use QAPI type 'size' (uint64_t).  ringbuf-read parameter
>>> @size is 'int' (int64_t).  qmp_ringbuf_read() rejects negative values,
>>> then implicitly converts to size_t.
>>>
>>> Change the parameter to 'size' and drop the check for negative values.
>>>
>>> ringbuf-read now accepts size values between 2^63 and 2^64-1.  It
>>> accepts negative values as before, because that's how the QObject
>>> input visitor works for backward compatibility.
>>>
>>
>> Negative values over json will be implicitly converted to positive
>> values with this change, right? Or are they rejected earlier?
>
> Yes.  For details, see my reply to Juan's review of PATCH 15.
>
>> If so that is a change of behaviour that I am not sure is worth doing
>> now (without explicit protocol break), but I don't mind.

So before this change:

(QEMU) ringbuf-read device=foo size=-1
{"error": {"class": "GenericError", "desc": "size must be greater than zero"}}

after:

(QEMU) ringbuf-read device=foo size=-1
{"return": ""}

Is this really what we want?

-- 
Marc-André Lureau