qapi: Add new visit_free() function

Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface.  Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.

The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it.  With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:

| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|-    QapiDeallocVisitor *qdv;
|     Visitor *v;
|
|     if (!obj) {
|         return;
|     }
|
|-    qdv = qapi_dealloc_visitor_new();
|-    v = qapi_dealloc_get_visitor(qdv);
|+    v = qapi_dealloc_visitor_new();
|     visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|-    qapi_dealloc_visitor_cleanup(qdv);
|+    visit_free(v);
|}

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 437cf6c8e3..5ace2cf065 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -150,17 +150,15 @@ def gen_type_cleanup(name):
 
 void qapi_free_%(c_name)s(%(c_name)s *obj)
 {
-    QapiDeallocVisitor *qdv;
     Visitor *v;
 
     if (!obj) {
         return;
     }
 
-    qdv = qapi_dealloc_visitor_new();
-    v = qapi_dealloc_get_visitor(qdv);
+    v = qapi_dealloc_visitor_new();
     visit_type_%(c_name)s(v, NULL, &obj, NULL);
-    qapi_dealloc_visitor_cleanup(qdv);
+    visit_free(v);
 }
 ''',
                 c_name=c_name(name))