Re: [Qemu-devel] [PATCH v2] numa: clarify error message when node index is out of range in -numa dist, ...

[Eric Blake]

On 05/16/2018 09:32 AM, Igor Mammedov wrote:
> > > Actually, error_setg() is documented as taking a single phrase (no '.'
> > > included), and that if you need a second sentence, it's better to use
> > > error_append_hint().
> well, using append_hint makes it less readable, before using it we get 
> following error:
>
> $ qemu-system-x86_64 -numa dist,src=128,dst=1,val=20
> qemu-system-x86_64: -numa dist,src=128,dst=1,val=20: Invalid node 128, The 
> valid node range is [0 - 127]
> $
>
> after using it we get:
>    
> $ qemu-system-x86_64 -numa dist,src=128,dst=1,val=20
> qemu-system-x86_64: -numa dist,src=128,dst=1,val=20: Invalid node value 128
> The valid node range is [0 - 127]$
>
> i.e. an extra newline in the middle of error message and looses automatic
> newline at the end so the shell prompt continues error message

Use of error_append_hint() requires you to provide a newline (unlike 
error_setg().  But as Markus pointed out, you don't need to use it:

> > Correct.  Providing help on valid values is exactly what
> > error_append_hint() is for.
> >
> > >                        Maybe Markus has an opinion on the best way to
> > > word this error message.
> >
> > Yes: "Parameter 'src' expects an integer between 0 and 127"

I like this wording better, which avoids the shortfalls that 
error_append_hint() would introduce.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org