Re: [Qemu-devel] [PATCH v0 00/21]: Monitor: improve handlers error handling

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/10/2010 07:49 PM, Luiz Capitulino wrote:
>   Hi there,
>
>   When I started converting handlers to the QObject style, I thought that
> returning an error code wouldn't be needed. That is, we have an error object
> already, so if the handler returns the error object it has failed, otherwise
> it has succeeded.
>
>   This was also very convenient, because handlers have never returned an error
> code, and thus it would be easier to add a call to qemu_error_new() in the
> right place instead of returning error codes.
>
>   Turns out we need both. Actually, I should not have abused the error object
> this way because (as Markus says) this is too fragile and we can end up
> reporting bogus errors to clients (among other problems).
>
>   The good news is that it's easy to fix.
>
>   All we have to do is to change cmd_new() (the handler callback) to return an
> error code and convert existing QObject handlers to it. This series does that
> and most of the patches are really straightforward conversions.
>
>   Additionally, Markus has designed an excellent debug mechanism for QMP, which
> is implemented by the last patches in this series, and will allow us to catch
> important QObject conversion and error handling bugs in handlers.
>    

Instead of returning -1, would it make more sense to return an error 
object?  If fact, why not drop ret_data as a passed in parameter, and 
just always return either the result or an error object.

Regards,

Anthony Liguori

>   Thanks.
>
>
>
>