Re: [Qemu-devel] [RFC 00/14]: add printf-like human msg to error_set()

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jul 25, 2012 at 09:43:55PM -0500, Anthony Liguori wrote:
> Luiz Capitulino <lcapitulino@redhat.com> writes:
> 
> > Basically, this series changes a call like:
> >
> >  error_set(errp, QERR_DEVICE_NOT_FOUND, device);
> >
> > to:
> >
> >  error_set(errp, QERR_DEVICE_NOT_FOUND,
> >            "Device 'device=%s' not found", device);
> >
> > In the first call, QERR_DEVICE_NOT_FOUND is a string containing a json dict:
> >
> >     "{ 'class': 'DeviceNotFound', 'data': { 'device': %s } }"
> 
> This is the wrong direction.  Looking through the patch, this makes the
> code much more redundant overall.  You have dozens of calls that are
> duplicating the same error message.  This is not progress.

What we do in libvirt, is to define helper functions for
reporting the specific error codes. So, as well as having
the generic

  error_set(errp, QERR_CODE, "format string", args)

you would have

  error_set_device_not_found(errp, args)

which is just a #define

  #define error_set_device_not_found(errp, args) \
     error_set(errp, QERR_DEVICE_NOT_FOUND, "Device %s not found", args)

for the most part this should avoid the duplication you're concerned
about, while still letting use provided more detailed messsages.


Daniel
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