Re: [Qemu-devel] [PATCH v9 12/37] qapi: Don't cast Enum* to int*

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> On 01/20/2016 11:08 AM, Markus Armbruster wrote:
>> Eric Blake <eblake@redhat.com> writes:
>> 
>>> C compilers are allowed to represent enums as a smaller type
>>> than int, if all enum values fit in the smaller type.  There
>>> are even compiler flags that force the use of this smaller
>>> representation, and using them changes the ABI of a binary.
>> 
>> Suggest "although using them".
>> 
>
> Okay.
>
>
>>> with generated code changing as:
>>>
>>> | void visit_type_GuestDiskBusType(Visitor *v, GuestDiskBusType
>>> | *obj, const char *name, Error **errp)
>>> | {
>>> |-    visit_type_enum(v, (int *)obj, GuestDiskBusType_lookup, "GuestDiskBusType", name, errp);
>>> |+    int tmp = *obj;
>>> |+    visit_type_enum(v, &tmp, GuestDiskBusType_lookup, "GuestDiskBusType", name, errp);
>>> |+    *obj = tmp;
>>> | }
>> 
>> Long lines.  Do we have an example with a shorter enum name handy?
>
> Shortest is QType; runner-ups RxState and TpmType.

QType comes out okay:

| void visit_type_QType(Visitor *v, QType *obj, const char *name, Error **errp)
| {
|-    visit_type_enum(v, (int *)obj, QType_lookup, "QType", name, errp);
|+    int tmp = *obj;
|+     visit_type_enum(v, &tmp, QType_lookup, "QType", name, errp);
|+    *obj = tmp;
| }

Let's use it.

>>>  void visit_type_%(c_name)s(Visitor *v, %(c_name)s *obj, const char *name, Error **errp)
>>>  {
>>> -    visit_type_enum(v, (int *)obj, %(c_name)s_lookup, "%(name)s", name, errp);
>>> +    int tmp = *obj;
>>> +    visit_type_enum(v, &tmp, %(c_name)s_lookup, "%(name)s", name, errp);
>>> +    *obj = tmp;
>>>  }
>>>  ''',
>>>                   c_name=c_name(name), name=name)
>> 
>> Same pattern in qapi-visit-core.c, except we name the variable @value
>> there.  Your choice.
>
> 'value' sounds consistent. An easy swap on a respin.

Okay.