qapi: Anonymous unions

The discriminator for anonymous unions is the data type. This allows to
have a union type that allows both of these:

    { 'file': 'my_existing_block_device_id' }
    { 'file': { 'filename': '/tmp/mydisk.qcow2', 'read-only': true } }

Unions like this are specified in the schema with an empty dict as
discriminator. For this example you could take:

    { 'union': 'BlockRef',
      'discriminator': {},
      'data': { 'definition': 'BlockOptions',
                'reference': 'str' } }
    { 'type': 'ExampleObject',
      'data: { 'file': 'BlockRef' } }

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 5c1297f430..f3fa420245 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -32,6 +32,8 @@ struct Visitor
 
     void (*type_enum)(Visitor *v, int *obj, const char *strings[],
                       const char *kind, const char *name, Error **errp);
+    void (*get_next_type)(Visitor *v, int *kind, const int *qobjects,
+                          const char *name, Error **errp);
 
     void (*type_int)(Visitor *v, int64_t *obj, const char *name, Error **errp);
     void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);