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Date: Sun, 15 Dec 2013 09:51:15 +1000
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From: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
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Subject: Re: [Qemu-devel] a QOM Coding Conventions question
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>, =?ISO-8859-1?Q?Andreas_F=E4rber?= <afaerber@suse.de>, Antony Pavlov <antonynpavlov@gmail.com>

On Sun, Dec 15, 2013 at 9:42 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 14 December 2013 23:06, Peter Crosthwaite
> <peter.crosthwaite@xilinx.com> wrote:
>> On Sat, Dec 14, 2013 at 6:26 AM, Antony Pavlov <antonynpavlov@gmail.com> wrote:
>>> What do the "< private >" and "< public >" comments exactly mean here?
>>
>> Private means inaccessible to everybody, including the implementation
>> of class being instantiated. No one should ever dereference a private
>> variable, they should be managed by QOM indirectly via casts if
>> needed. Public means that at least someone can access it. Note that
>> public does not declare a free-for-all. QOM class variables may be
>> "public" in the sense that the class implementation may access them.
>> Container devices however still can not, and they are private from
>> that point of view.
>
> I'm not sure I find this a terribly convincing explanation. Last time
> I asked this IIRC the answer was just "they need to be there for the
> output of the documentation generator".
>
> The usual definition of 'public' vs 'private' is "what can a user of the
> object rather than the implementor safely access?". That would be
> actually interesting to document IMHO. (I should resurrect my patch
> for marking those fields up with __private so we enforce it...)
>

Yes, that means we really have three levels of access, but only tags
for two. Hence the confusion over public.

Regards,
Peter

> thanks
> -- PMM
>