[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v5 10/28] qapi: Segregate anonymous unions into

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH v5 10/28] qapi: Segregate anonymous unions into alternates in generator
Date: Thu, 26 Mar 2015 09:26:36 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

On 03/26/2015 08:47 AM, Markus Armbruster wrote:
> Eric Blake <address@hidden> writes:
>> Special-casing 'discriminator == {}' for handling anonymous unions
>> is getting awkward; since this particular type is not always a
>> dictionary on the wire, it is easier to treat it as a completely
>> different class of type, "alternate", so that if a type is listed
>> in the union_types array, we know it is not an anonymous union.
>> This patch just further segregates union handling, to make sure that
>> anonymous unions are not stored in union_types, and splitting up
>> check_union() into separate functions.  A future patch will change
>> the qapi grammar, and having the segregation already in place will
>> make it easier to deal with the distinct meta-type.
>> Signed-off-by: Eric Blake <address@hidden>
>> ---

>> @@ -535,7 +546,8 @@ def find_struct(name):
>>  def add_union(definition):
>>      global union_types
>> -    union_types.append(definition)
>> +    if definition.get('discriminator') != {}:
>> +        union_types.append(definition)
>>  def find_union(name):
>>      global union_types
> This is the only unobvious hunk.
> union_types is used only through find_union.  The hunk makes
> find_union(N) return None when N names an anonymous union.
> find_union() is used in two places:
> * find_alternate_member_qtype()
>   Patched further up.  It really wants only non-anonymous unions, and
>   this change to find_union() renders its check for anonymous unions
>   superfluous.  Good.
> * generate_visit_alternate()
>   Asserts that each member's type is either a built-in type, a complex
>   type, a union type, or an enum type.
>   The change relaxes the assertion not to trigger on anonymous union
>   types.  Why is that okay?

No, the change tightens the assertion so that it will now fail on an
anonymous union nested as a branch of another anonymous union (where
before it could silently pass the assertion), because the anonymous
union is no longer found by find_union().  And this is okay because the
earlier change to find_alternate_member_qtype means that we don't allow
nested anonymous unions, so making the assertion fail if an anonymous
union gets through anyway is correct.

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

Attachment: signature.asc
Description: OpenPGP digital signature

reply via email to

[Prev in Thread] Current Thread [Next in Thread]