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From: Markus Armbruster <armbru@redhat.com>
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Date: Mon, 27 Jul 2015 11:54:24 +0200
In-Reply-To: <55B0DFBE.1010403@redhat.com> (Eric Blake's message of "Thu, 23
	Jul 2015 06:36:14 -0600")
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Subject: Re: [Qemu-devel] [PATCH RFC v2 22/47] qapi: QAPISchema code
	generation helper methods
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To: Eric Blake <eblake@redhat.com>
Cc: kwolf@redhat.com, berto@igalia.com, qemu-devel@nongnu.org, mdroth@linux.vnet.ibm.com

Eric Blake <eblake@redhat.com> writes:

> On 07/01/2015 02:22 PM, Markus Armbruster wrote:
>> New methods c_name(), c_type(), c_null(), json_type(),
>> alternate_qtype().
>> 
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  scripts/qapi.py | 72
>> +++++++++++++++++++++++++++++++++++++++++++++++++++------
>>  1 file changed, 65 insertions(+), 7 deletions(-)
>> 
>
> I just noticed:
>
>> @@ -779,6 +811,12 @@ class QAPISchemaEnumType(QAPISchemaType):
>>          for v in values:
>>              assert isinstance(v, str)
>>          self.values = values
>> +    def c_type(self, is_param=False):
>> +        return c_name(self.name)
>> +    def c_null(self):
>> +        return c_enum_const(self.name, self.values[0])
>
> What does this return for an empty enum, as in { 'enum':'Empty',
> 'data':[] }?

I suspect self.values will be [] then, and self.values[0] will bomb.

Possible fixes:

* Outlaw empty enums

* Add the implicit MAX member to self.values[] (other code may have to
  skip it)

* Catch the special case here, and return the implicit MAX member.

>               Our testsuite proves we can do that, even if our normal
> .json code doesn't use it.

tests/qapi-schema/enum-empty.json:{ 'enum': 'MyEnum', 'data': [ ] }