Hi
On Tue, Mar 21, 2017 at 9:06 PM Eric Blake <[email protected]> wrote:
> On 03/21/2017 11:49 AM, Markus Armbruster wrote:
>
> >
> > QMP clients that work around the "large positive integers are rejected"
> > bugs by sending large negative ones instead may well exist. Fixing the
> > interface would break them. Depressing. Eric, could you have a peek at
> > libvirt?
>
> Yes, libvirt is such a client already. From
> util/virjson.c:virJSONValueObjectAddVArgs():
>
>
> * Adds the key-value pairs supplied as variable argument list to @obj.
> *
> * Keys look like s:name the first letter is a type code:
> ...
> * U: unsigned long integer value (see below for quirks)
> * P: unsigned long integer value, omitted if zero
> ...
> case 'P':
> case 'U': {
> /* qemu silently truncates numbers larger than LLONG_MAX,
> * so passing the full range of unsigned 64 bit integers
> * is not safe here. Pass them as signed 64 bit integers
> * instead.
> */
> long long val = va_arg(args, long long);
>
> if (!val && type == 'P')
> continue;
>
> rc = virJSONValueObjectAppendNumberLong(obj, key, val);
> } break;
>
> So if we "fix" QMP to reject negative values in place of large unsigned
> values, we'll need to also fix libvirt to have a way to introspect the
> difference and cope accordingly. (I'm thinking that we'll have to keep
> the negative parsing indefinitely, and can merely improve the parser to
> also parse large positive - but that we can still reject values <
> INT64_MIN that would have a weird wraparound).
>
Currently, parsing is done without expected type information. So if the
number fits in an int64, it should be a QINT, otherwise a QFLOAT (see
parse_literal). With this series, it will try QUINT before QFLOAT. But what
I was afraid though is that the int is sometime assigned back to a uint64.
And with my series, get_uint() will fail if the number is negative int, but
for compatibility reasons, I think it should cast it instead. We may want
to have a qmp capability bit to change this silent casting behaviour.
--
Marc-André Lureau
