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From: =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= <f4bug@amsat.org>
Date: Fri, 5 Jan 2018 18:28:51 -0300
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Subject: Re: [Qemu-devel] [PATCH v2 1/4] sdbus: add a QMP command to access
 a SDBus
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To: Eric Blake <eblake@redhat.com>
Cc: Alistair Francis <alistair.francis@xilinx.com>, Peter Maydell <peter.maydell@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Eduardo Habkost <ehabkost@redhat.com>, "Daniel P . Berrange" <berrange@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>, "Edgar E . Iglesias" <edgar.iglesias@xilinx.com>, Markus Armbruster <armbru@redhat.com>, Thomas Huth <thuth@redhat.com>, =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= <marcandre.lureau@redhat.com>

Hi Eric,

On Fri, Jan 5, 2018 at 12:29 PM, Eric Blake <eblake@redhat.com> wrote:
> On 01/03/2018 03:49 PM, Philippe Mathieu-Daud=C3=A9 wrote:
[...]
>> +        if (ambiguous) {
>> +            error_setg(errp, "Path '%s' is ambiguous", qom_path);
>> +        } else {
>> +            error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
>> +                      "Device '%s' not found", qom_path);
>> +        }
>> +        return NULL;
>> +    }
>> +    sdbus =3D (SDBus *)object_dynamic_cast(obj, TYPE_SD_BUS);
>
> Is the cast still necessary, or does object_dynamic_cast() return void*
> so that you can omit the cast?

Apparently the cast is necessary, since the object_dynamic_cast()
returns an Object pointer,
and the SD_BUS() macro uses object_dynamic_cast_assert() which
generates a runtime assert.

without casting:
hw/sd/sdbus-qmp.c:37:11: error: assignment from incompatible pointer
type [-Werror=3Dincompatible-pointer-types]
     sdbus =3D object_dynamic_cast(obj, TYPE_SD_BUS);
           ^

>
>> +    if (sdbus =3D=3D NULL) {
>> +        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
>> +                  "Device '%s' not a sd-bus", qom_path);
>> +        return NULL;
>> +    }