Re: [PATCH-for-5.2 v4] hw/core/qdev: Increase qdev_realize() kindness

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <f4bug@amsat.org> writes:

> Since commit 510ef98dca5, qdev_realize() aborts if bus-less
> device is realized on a bus. While commits 514db7710b..007d1dbf72
> took care of converting all mainstream uses, QEMU forks weren't
> converted.
>
> These forks are usually maintained by hobbyist with interest in
> following mainstream development, but with limited time, so usually
> rebase from time to time. To avoid them to spend time on debugging
> and reading git-log history, display a kind hint about what is wrong.
>
> Before:
>
>   qemu-system-mipsel: hw/core/qdev.c:376: qdev_realize: Assertion `!DEVICE_GET_CLASS(dev)->bus_type' failed.
>   Aborted (core dumped)
>
> After:
>
>   Unexpected error in qdev_realize() at hw/core/qdev.c:376:
>   qemu-system-mipsel: Unexpected bus 'System' for bus-less device 'unimplemented-device'
>   Aborted (core dumped)
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/core/qdev.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 2131c7f951..a16f1270f1 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -392,8 +392,11 @@ bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp)
>  
>      if (bus) {
>          qdev_set_parent_bus(dev, bus);
> -    } else {
> -        assert(!DEVICE_GET_CLASS(dev)->bus_type);
> +    } else if (DEVICE_GET_CLASS(dev)->bus_type) {
> +        error_setg(errp, "Unexpected bus '%s' for bus-less device '%s'",
> +                   DEVICE_GET_CLASS(dev)->bus_type,
> +                   object_get_typename(OBJECT(dev)));
> +        return false;
>      }
>  
>      object_property_set_bool(OBJECT(dev), true, "realized", &err);

Objection.  This turns an abort into something else unless the caller
passes &error_abort.  The caller in your commit message's example does,
others don't.

Keep the unconditional abort, please.  Feel free to print something kind
right before.  I doubt it's all that useful, as I believe whoever gets
to fix the bug will have to figure out the code anyway, but I could be
wrong.