Re: [RFC 3/5] convert code to object_new_dynamic() where appropriate

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

On Thu, Oct 31, 2024 at 03:21:17PM -0400, Peter Xu wrote:
> On Thu, Oct 31, 2024 at 03:53:48PM +0000, Daniel P. Berrangé wrote:
> > In cases where object_new() is not being passed a static, const
> > string, the caller cannot be sure what type they are instantiating.
> > There is a risk that instantiation could fail, if it is an abstract
> > type.
> > 
> > Convert such cases over to use object_new_dynamic() such that they
> > are forced to expect failure. In some cases failure can be easily
> > propagated, but in others using &error_abort maintainers existing
> > behaviour.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  chardev/char.c                   |  5 ++++-
> >  hw/core/bus.c                    |  2 +-
> >  hw/core/cpu-common.c             |  2 +-
> >  hw/core/qdev.c                   |  4 ++--
> >  hw/i386/x86-common.c             |  5 ++++-
> >  hw/i386/xen/xen-pvh.c            |  2 +-
> >  hw/vfio/common.c                 |  6 +++++-
> >  hw/vfio/container.c              |  6 +++++-
> >  qom/object_interfaces.c          |  7 ++-----
> >  qom/qom-qmp-cmds.c               | 15 +++++++++------
> >  tests/unit/check-qom-interface.c |  3 ++-
> >  tests/unit/test-smp-parse.c      | 20 ++++++++++----------
> >  12 files changed, 46 insertions(+), 31 deletions(-)
> 
> I think we could leave the test cases alone without _dynamic(), because
> they do test static types (even if they used "opaque"..), and they should
> really (and forever) assert on failures..
> 
> IMHO we should keep _dynamic() usages small if we'd like to introduce it,
> only in the paths where its failure will be properly handled.  Basically, I
> think we shouldn't use _dynamic() if we know it'll be error_abort.. because
> that's fundamentally identical to object_new().

For the sake of other readers, here's what you already figured out from
looking at patch 5...

The end of this series will enforce that the argument to object_new()
is a static, const string. It will become a compile error to pass a
variable to object_new(), and thus all such cases need switching to
object_new_dynamic(), even if they just end up passing in &error_abort
in some cases. 

With regards,
Daniel
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