Re: [RFC 7/7] qom: improve error message for invalid ID values

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

On Wed, Jun 17, 2026 at 12:46:51PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > Include the actual ID that was validated, since this may not be
> > obvious in all contexts.
> >
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> 
> Reproducer?
> 
> I'm asking because:
> 
>     $ qemu-system-x86_64 -object id=@
>     qemu-system-x86_64: -object id=@: Parameter 'id' expects an identifier
>     Identifiers consist of letters, digits, '-', '.', '_', starting with a letter.
> 
> This is qemu_opts_create().
> 
> And:
> 
>     {"execute":"device_add","arguments":{"driver":"e1000", "id":"@"}}
>     {"error": {"class": "GenericError", "desc": "Invalid qdev ID '@'"}}
> 
> This is qdev_set_id().
> 
> Ah, found it:
> 
>     $ qemu-system-x86_64 -object '{"id": "@", "qom-type": "iothread"}'
>     qemu-system-x86_64: QOM ID value '@' is not valid
>     Identifiers consist of letters, digits, '-', '.', '_', starting with a letter.

Actually in this case it wasn't anything user controlled,
I was calling  object_new_with_props internally to create
child objects and it tripped over this due to a bug of
my own making. It was just rather confusing as to what I
had done wrong

> 
> > ---
> >  qom/object.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/qom/object.c b/qom/object.c
> > index 415d5c5291..9cd17e3bcc 100644
> > --- a/qom/object.c
> > +++ b/qom/object.c
> > @@ -774,7 +774,7 @@ object_new_with_props_helper(const char *typename,
> >             (id == NULL && parent == NULL));
> >  
> >      if (id != NULL && !id_wellformed(id)) {
> > -        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "id", "an identifier");
> > +        error_setg(errp, "QOM ID value '%s' is not valid", id);
> >          error_append_hint(errp, "Identifiers consist of letters, digits, "
> >                            "'-', '.', '_', starting with a letter.\n");
> >          return NULL;
> 
> Improvement, but what about other places reporting an error when
> id_wellformed() fails?
> 

With regards,
Daniel
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