Re: [Qemu-devel] [PATCH RFC v2 07/47] qapi: Generate a nicer struct for flat unions

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> On 07/01/2015 02:21 PM, Markus Armbruster wrote:
>> The struct generated for a flat union is weird: the members of its
>> base are at the end, except for the union tag, which is renamed to
>> 'kind' and put at the beginning.
>
> The renaming to 'kind' was a bug waiting to happen.  Consider this
> example, which is broken before your series:
>
> diff --git i/tests/qapi-schema/qapi-schema-test.json
> w/tests/qapi-schema/qapi-schema-test.json
> index c7eaa86..12c09e3 100644
> --- i/tests/qapi-schema/qapi-schema-test.json
> +++ w/tests/qapi-schema/qapi-schema-test.json
> @@ -37,7 +37,7 @@
>    'data': { 'string1': 'str', 'string2': 'str' } }
>
>  { 'struct': 'UserDefUnionBase',
> -  'data': { 'string': 'str', 'enum1': 'EnumOne' } }
> +  'data': { 'kind': 'str', 'enum1': 'EnumOne' } }
>
>  { 'union': 'UserDefFlatUnion',
>    'base': 'UserDefUnionBase',
>
>
> leading to this compilation error during 'make check-unit':
>
> In file included from tests/test-qmp-output-visitor.c:17:0:
> tests/test-qapi-types.h:617:11: error: duplicate member ‘kind’
>      char *kind;
>            ^
> tests/test-qapi-types.h:631:11: error: duplicate member ‘kind’
>      char *kind;
>            ^
>
> Therefore, it might be worth mentioning that avoiding the rename to
> 'kind' is a bug fix, not just a nicer struct :)

Cool!  I'll work (a variation of) this test case into my series.