Re: [Qemu-devel] chardev's and fd's in monitors

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

On Thu, Oct 20, 2016 at 12:01:08PM +0100, Dr. David Alan Gilbert wrote:
> * Markus Armbruster (armbru@redhat.com) wrote:
> > "Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:
> 
> > > The problem is that our way of propagating errors actively discourages 
> > > people from adding errors and you're left with lots of useless invented errno's.
> > > error_report makes it easy for people to scatter meaningful error messages
> > > in at any point.
> > >
> > > Make an easy, concise way of reporting an error that fits in with
> > > a propagation scheme and I'd consider converting stuff.
> > 
> > error_setg(errp, "This is as simple as it gets, I'm afraid")
> > 
> > Snark aside, I acknowledge the pain of converting call chains to
> > propagate Error objects, having converted "a few" myself.
> 
> If you can get it down to that line it would be great!
> 
> But unfortunately it isn't:
>   a) I have to make sure my cleanup path after that error_setg doesn't
>      cause any other errors because that breaks the rule
>      that I can't call error_setg twice.

>   b) I've got to put the whole local_err/error_propagate stuff all over.
> 
>   c) We insist on allowing the Err ** pointer to be NULL that
>      removes some potential simplifications.

This last point is one i really dislike - if we could mandate that
the error parameters was non-NULL, it will eliminate alot of the
need to use local_err/error_propagate, as you could just check
if (*errp), and so largely solve (b).


Regards,
Daniel
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