Re: [Qemu-arm] [Qemu-devel] [PATCH 1/3] qdev-properties.h: Explicitly set the default value for arraylen properties

[Markus Armbruster <armbru@redhat.com>]

Peter Maydell <peter.maydell@linaro.org> writes:

> In DEFINE_PROP_ARRAY, because we use a PropertyInfo (qdev_prop_arraylen)
> which has a .set_default_value member we will set the field to a default
> value. That default value will be zero, by the C rule that struct
> initialization sets unmentioned members to zero if at least one member
> is initialized. However it's clearer to state it explicitly.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> If my eyeball of the sources is correct, this is the only case we
> have of a Property struct that uses a PropertyInfo with a non-NULL
> .set_default_value but which doesn't explicitly set .defval.u.
> ---
>  include/hw/qdev-properties.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
> index 0604c33..36d040c 100644
> --- a/include/hw/qdev-properties.h
> +++ b/include/hw/qdev-properties.h
> @@ -110,6 +110,7 @@ extern PropertyInfo qdev_prop_arraylen;
>                            _arrayfield, _arrayprop, _arraytype) {        \
>          .name = (PROP_ARRAY_LEN_PREFIX _name),                          \
>          .info = &(qdev_prop_arraylen),                                  \
> +        .defval.u = 0,                                                  \
>          .offset = offsetof(_state, _field)                              \
>              + type_check(uint32_t, typeof_field(_state, _field)),       \
>          .arrayinfo = &(_arrayprop),                                     \

Hmm.

.info and .defval apply to the array *length*.
.info.set_default_value() is set_default_uint(), which uses .defval.u.
Setting it here is correct.

The array *elements* are described by .arrayinfo.  There is no
.arraydefval, but that's okay, because .arrayinfo.set_default_value()
doesn't get called.  Correct?