Re: [PATCH-for-5.1 3/3] hw: Remove unnecessary DEVICE() cast

[Markus Armbruster <armbru@redhat.com>]

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

> The DEVICE() macro is defined as:
>
>   #define DEVICE(obj) OBJECT_CHECK(DeviceState, (obj), TYPE_DEVICE)
>
> Remove unnecessary DEVICE() casts.
>
> Patch created mechanically using spatch with this script:
>
>   @@
>   typedef DeviceState;
>   DeviceState *s;
>   @@
>   -   DEVICE(s)
>   +   s
>
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

DEVICE(obj) expands to

    OBJECT_CHECK(DeviceState, (obj), TYPE_DEVICE)

and then to

    ((DeviceState *)object_dynamic_cast_assert((Object *)(obj), (name),
                                               __FILE__, __LINE__, __func__))

object_dynamic_cast_assert() asserts @obj can be safely converted to the
type named by @name, and returns @obj.

Your patch drops the assertion.

The assertion can only fail when @obj points to something other than its
stated type, i.e. when we're in undefined behavior country.

Preferably with this argument worked into your commit message:
Reviewed-by: Markus Armbruster <armbru@redhat.com>

There are many similar macros.  Should they get the same treatment?