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From: Markus Armbruster <armbru@redhat.com>
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Date: Thu, 21 Jan 2016 07:22:29 +0100
In-Reply-To: <569FAED2.3060609@redhat.com> (Eric Blake's message of "Wed, 20
	Jan 2016 08:59:14 -0700")
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Subject: Re: [Qemu-devel] [PATCH v9 02/37] qapi: Avoid use of misnamed
	DO_UPCAST()
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To: Eric Blake <eblake@redhat.com>
Cc: marcandre.lureau@redhat.com, qemu-devel@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>

Eric Blake <eblake@redhat.com> writes:

> On 01/20/2016 03:04 AM, Markus Armbruster wrote:
>> Eric Blake <eblake@redhat.com> writes:
>>=20
>>> The macro DO_UPCAST() is incorrectly named: it converts from a
>>> parent class to a derived class (which is a downcast).  Better,
>>> and more consistent with some of the other qapi visitors, is
>>> to use the container_of() macro through a to_FOO() helper.
>>>
>>> Our current definition of container_of() is weaker than
>>> DO_UPCAST(), in that it does not require the derived class to
>>> have Visitor as its first member, but this does not hurt our
>>> usage patterns in qapi visitors.
>>>
>>> Signed-off-by: Eric Blake <eblake@redhat.com>
>>> Reviewed-by: Marc-Andr=C3=A9 Lureau <marcandre.lureau@redhat.com>
>>>
>
>>>
>>> +static OptsVisitor *to_ov(Visitor *v)
>>> +{
>>> +    return container_of(v, OptsVisitor, visitor);
>>> +}
>>> +
>>> +
>>=20
>> The name to_ov() is rather laconic even for my taste.  Tolerable, since
>> it's static.
>
> And matches existing practice pre-patch:
>
> qapi/qapi-dealloc-visitor.c:static QapiDeallocVisitor *to_qov(Visitor *v)
> qapi/qmp-input-visitor.c:static QmpInputVisitor *to_qiv(Visitor *v)
> qapi/qmp-output-visitor.c:static QmpOutputVisitor *to_qov(Visitor *v)
>
>
>>=20
>> Patch gets rid of all DO_UPCAST() in qapi/.  PATCH 33 brings one back;
>> it should use to_ov() instead.
>
> D'oh. You can tell what order I wrote the patches in :)
>
> If I need to respin, I'll fix it; otherwise, I assume you can handle it.

Yes.