Re: [Qemu-devel] [PATCH v1 00/14]: Initial QObject conversion

[Gerd Hoffmann <kraxel@redhat.com>]

On 10/02/09 15:47, Luiz Capitulino wrote:
> On Fri, 02 Oct 2009 14:47:02 +0200
> Gerd Hoffmann<kraxel@redhat.com>  wrote:
>
>>     Hi,
>>
>>>    Some people have suggested that we should have a better error handling
>>> in the Monitor, in the meaning that error information should be correctly
>>> propagated and handled in order to be used by the Monitor Protocol and
>>> the existing user protocol.
>>
>> A bunch of code paths can be called from both monitor and non-monitor
>> contexts (network configuration, device hotplug).  Right now there are
>> the qemu_error*() functions to make sure the error messages appear on
>> the correct place (monitor or stderr) without having to pass through a
>> Monitor pointer all the way down.
>>
>> How do you plan to handle this in the new world of monitor error reporting?
>
>   Good question.
>
>   The first thing to bear in mind is that MonitorError is not just about
> error reporting, but more importantly, it makes errors have a common
> structure so that they can be emitted by the Monitor Protocol.

So maybe they shouldn't be named MonitorError in the first place?
And make sure the design works for non-monitor contexts too?
Having the user_error callback in struct mon_cmd_t doesn't make sense 
from that point of view for example.

Why user_error is needed in the first place btw?  To maintain 
backward-compatible error message formating?

>   One way to solve the problem could be to move the MonitorError pointer
> to the Monitor struct.

I think that is a good idea nevertheless.

> This way, when there's a ERR_SINK_MONITOR
> qemu_error() would fill MonitorError instead of calling monitor_vprintf().
>
>   The bad news though, is that we would have to change all qemu_error()
> calls to have "structured" errors instead of pretty printing, that is,
> create macros, define its errors data and write functions to do
> pretty printing....

Or add a qemu_error_structed() variant for smooth switchover and have 
qemu_error() use a generic error code, so you don't have to switch over 
all at once.  There are not *that* many qemu_error users though, so just 
converting them all in one go might not be too hard.

cheers,
   Gerd