Re: [Qemu-devel] [PATCH V6 00/10] qapi script: support enum as discriminator and better enum name

[Eric Blake <eblake@redhat.com>]

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On 02/10/2014 02:48 PM, Wenchao Xia wrote:
> This series address two issues:
> 
> 1. support using enum as discriminator in union.
> For example, if we have following define in qapi schema:
> { 'enum': 'EnumOne',
>   'data': [ 'value1', 'value2', 'value3' ] }
> 
> { 'type': 'UserDefBase0',
>   'data': { 'base-string0': 'str', 'base-enum0': 'EnumOne' } }
> 
> Before this series, discriminator in union must be a string, and a
> hidden enum type as discriminator is generated. After this series,
> qapi schema can directly use predefined enum type:
> { 'union': 'UserDefEnumDiscriminatorUnion',
>   'base': 'UserDefBase0',
>   'discriminator' : 'base-enum0',
>   'data': { 'value1' : 'UserDefA',
>             'value2' : 'UserDefInherit',
>             'value3' : 'UserDefB' } }

See also:
https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg01663.html

There, I argued that even unions without a 'base':'TypeName' would
benefit from having a discriminator that calls out an enum type listing
the valid branches of the union.  I think that could be a followup to
this series.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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