Re: [Qemu-devel] [PATCH 06/21] qmp: Drop duplicated QMP command object checks

[Eric Blake]

On 02/23/2017 03:45 PM, Markus Armbruster wrote:
> qmp_check_input_obj() duplicates qmp_dispatch_check_obj(), except the
> latter screws up an error message.  handle_qmp_command() runs first
> the former, then the latter via qmp_dispatch(), masking the screwup.
> 
> qemu-ga also masks the screwup, because it also duplicates checks,
> just differently.

Cleaning up the duplication is a win in my book.

> 
> qmp_check_input_obj() exists because handle_qmp_command() needs to
> examine the command before dispatching it.  The previous commit got
> rid of this need, except for a tracepoint, and a bit of "id" code that
> relies on qdict not being null.
> 
> Fix up the error message in qmp_dispatch_check_obj(), drop
> qmp_check_input_obj() and the tracepoint.  Protect the "id" code with
> a conditional.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  monitor.c           | 74 
> +++++------------------------------------------------
>  qapi/qmp-dispatch.c |  3 +--
>  trace-events        |  1 -
>  3 files changed, 7 insertions(+), 71 deletions(-)
> 
> diff --git a/monitor.c b/monitor.c
> index dcf2de7..d83888d 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -3697,67 +3697,10 @@ static int monitor_can_read(void *opaque)
>      return (mon->suspend_cnt == 0) ? 1 : 0;
>  }
>  
> -/*
> - * Input object checking rules
> - *
> - * 1. Input object must be a dict
> - * 2. The "execute" key must exist
> - * 3. The "execute" key must be a string
> - * 4. If the "arguments" key exists, it must be a dict
> - * 5. If the "id" key exists, it can be anything (ie. json-value)
> - * 6. Any argument not listed above is considered invalid

You know, with just a little tweak, we could add something to the .json
file, and let generated code do all the checks of even the top-level
entities:

{ 'struct': 'WireCommand',
  'data': { 'execute': 'str', '*arguments': 'dict', '*id': 'any' } }

if we had a way to force 'dict' as a subset of 'any' but where it must
be a QDict.  (If we had a 'dict' recognized by the QAPI code generators,
we could probably also fix 'object-add' to use '*props':'dict' instead
of its current use of 'any')

But that sounds like a bit much to ask for in the 2.9 timeframe, so it
doesn't hold up this patch.

We lose a trace, but I don't think that's fatal.

Reviewed-by: Eric Blake <address@hidden>

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

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