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Re: [Qemu-devel] [PATCH 3/4] qobject: Parse non-finite numbers, as an ex

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH 3/4] qobject: Parse non-finite numbers, as an extension
Date: Thu, 16 Jun 2016 21:00:32 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

On 06/16/2016 10:25 AM, Markus Armbruster wrote:
> I think this commit mixes up parsing of non-finite numbers, which we may
> or may not want, with general test improvements, which we'll want
> regardless.  Please split the patch.
> On the parsing of non-finite numbers: the code looks good to me, but as
> long as we're not ready to extend QMP to include non-finite numbers both
> ways, I doubt we need to parse them.

Even if we want to guarantee that we will never generate a non-finite
number as the result of a QMP command, we DO have to worry about the
'id' field.  With all this series applied:

$  ./x86_64-softmmu/qemu-system-x86_64 -nodefaults -nographic -qmp
stdio{"QMP": {"version": {"qemu": {"micro": 50, "minor": 6, "major": 2},
"package": " (v2.6.0-1151-g1bb9f5e)"}, "capabilities": []}}
{'execute':'qmp_capabilities', 'id':[nan,inf,-Infinity]}
{"return": {}, "id": ["nan", "inf", "-inf"]}

and with just 1-3 applied:

$ ./x86_64-softmmu/qemu-system-x86_64 -nodefaults -nographic -qmp
stdio{"QMP": {"version": {"qemu": {"micro": 50, "minor": 6, "major": 2},
"package": " (v2.6.0-1151-g1bb9f5e)"}, "capabilities": []}}
{'execute':'qmp_capabilities', 'id':[nan,inf,-Infinity]}
{"return": {}, "id": [nan, inf, -inf]}

[okay, I cheated, as evidenced by the new git stuff appended in the
version output being the same between the two lines, but you get the idea].

I'm comfortable with a compromise that asserts that QMP commands will
never output a non-finite number anywhere that introspection lists
'number', but that QMP itself understands the extension of parsing a
bare inf anywhere, and if a bare inf appears under 'id', then the replay
of 'id' will also include a bare inf (if your JSON library allows you to
send non-JSON, it should also allow you to parse non-JSON).

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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