Re: [Qemu-devel] [PATCH v9 30/37] qapi: Canonicalize missing object to :empty

[Markus Armbruster]

Markus Armbruster <address@hidden> writes:

> Markus Armbruster <address@hidden> writes:
>
>> Eric Blake <address@hidden> writes:
>>
>>> Now that we elide unnecessary visits of empty types, we can
>>> start using the special ':empty' type in more places.  By using
>>> the empty type as the base class of every explicit struct or
>>> union, and as the default data for any command or event, we can
>>> simplify later logic in qapi-{visit,commands,event} by merely
>>> checking whether the type is empty, without also having to worry
>>> whether a type was even supplied.

You rewrite a command's arg_type from None to ':empty', bit not its
ret_type.  Deepens the assymmetry between the two.

>>> Note that gen_object() in qapi-types still has to check for a
>>> base, because it is also called for alternates (which have no
>>> base).
>>
>> What about the one in gen_visit_struct()?
>>
>>         if (base and not base.is_empty()) or members:
>>             ret += mcgen('''
>>         visit_type_%(c_name)s_fields(v, obj, &err);
>>     ''',
>>                          c_name=c_name(name))
>>
>>> No change to generated code.
>>>
>>> Signed-off-by: Eric Blake <address@hidden>
>>>
>>> ---
>>> v9: squash in more related changes
>>> v8: rebase to earlier changes
>>> v7: rebase to earlier changes
>>> v6: new patch
>>> ---
>>>  scripts/qapi-commands.py                | 17 +++++++------
>>>  scripts/qapi-event.py                   |  5 ++--
>>>  scripts/qapi-types.py                   |  4 +--
>>>  scripts/qapi-visit.py                   | 12 +++++----
>>>  scripts/qapi.py                         | 25 +++++++++---------
>>>  tests/qapi-schema/event-case.out        |  2 +-
>>>  tests/qapi-schema/flat-union-empty.out  |  1 +
>>>  tests/qapi-schema/ident-with-escape.out |  1 +
>>>  tests/qapi-schema/indented-expr.out     |  4 +--
>>>  tests/qapi-schema/qapi-schema-test.out  | 45 
>>> ++++++++++++++++++++++++++++++---
>>>  tests/qapi-schema/union-clash-data.out  |  2 ++
>>>  tests/qapi-schema/union-empty.out       |  1 +
>>>  12 files changed, 83 insertions(+), 36 deletions(-)
>
> Missing: update to qapi-introspect.py.  At least the expressions like
>
>     arg_type or self._schema.the_empty_object_type
>
> need updating.

But so far not the ret_type or self._schema.the_empty_object_type.

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