qapi: Normalize marshalling's visitor initialization and cleanup

Input and output marshalling functions do it differently.  Change them
to work the same: initialize the I/O visitor, use it, clean it up,
initialize the dealloc visitor, use it, clean it up.

This delays dealloc visitor initialization in output marshalling
functions, and input visitor cleanup in input marshalling functions.
No functional change, but the latter will be convenient when I change
the error handling.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

docs/qapi-code-gen.txt

@@ -434,8 +434,8 @@ Example:
 
     static void qmp_marshal_output_my_command(UserDefOne * ret_in, QObject **ret_out, Error **errp)
     {
-        QapiDeallocVisitor *md = qapi_dealloc_visitor_new();
         QmpOutputVisitor *mo = qmp_output_visitor_new();
+        QapiDeallocVisitor *md;
         Visitor *v;
 
         v = qmp_output_get_visitor(mo);
@@ -444,6 +444,7 @@ Example:
             *ret_out = qmp_output_get_qobject(mo);
         }
         qmp_output_visitor_cleanup(mo);
+        md = qapi_dealloc_visitor_new();
         v = qapi_dealloc_get_visitor(md);
         visit_type_UserDefOne(v, &ret_in, "unused", NULL);
         qapi_dealloc_visitor_cleanup(md);
@@ -452,15 +453,13 @@ Example:
     static void qmp_marshal_input_my_command(QDict *args, QObject **ret, Error **errp)
     {
         UserDefOne * retval = NULL;
-        QmpInputVisitor *mi;
+        QmpInputVisitor *mi = qmp_input_visitor_new_strict(QOBJECT(args));
         QapiDeallocVisitor *md;
         Visitor *v;
         UserDefOne * arg1 = NULL;
 
-        mi = qmp_input_visitor_new_strict(QOBJECT(args));
         v = qmp_input_get_visitor(mi);
         visit_type_UserDefOne(v, &arg1, "arg1", errp);
-        qmp_input_visitor_cleanup(mi);
 
         if (error_is_set(errp)) {
             goto out;
@@ -471,6 +470,7 @@ Example:
         }
 
     out:
+        qmp_input_visitor_cleanup(mi);
         md = qapi_dealloc_visitor_new();
         v = qapi_dealloc_get_visitor(md);
         visit_type_UserDefOne(v, &arg1, "arg1", NULL);

scripts/qapi-commands.py

@@ -69,16 +69,17 @@ def gen_marshal_output_call(name, ret_type):
         return ""
     return "qmp_marshal_output_%s(retval, ret, errp);" % c_fun(name)
 
-def gen_visitor_input_containers_decl(args):
+def gen_visitor_input_containers_decl(args, obj):
     ret = ""
 
     push_indent()
     if len(args) > 0:
         ret += mcgen('''
-QmpInputVisitor *mi;
+QmpInputVisitor *mi = qmp_input_visitor_new_strict(%(obj)s);
 QapiDeallocVisitor *md;
 Visitor *v;
-''')
+''',
+                     obj=obj)
     pop_indent()
 
     return ret.rstrip()
@@ -106,7 +107,7 @@ bool has_%(argname)s = false;
     pop_indent()
     return ret.rstrip()
 
-def gen_visitor_input_block(args, obj, dealloc=False):
+def gen_visitor_input_block(args, dealloc=False):
     ret = ""
     errparg = 'errp'
 
@@ -118,15 +119,14 @@ def gen_visitor_input_block(args, obj, dealloc=False):
     if dealloc:
         errparg = 'NULL'
         ret += mcgen('''
+qmp_input_visitor_cleanup(mi);
 md = qapi_dealloc_visitor_new();
 v = qapi_dealloc_get_visitor(md);
 ''')
     else:
         ret += mcgen('''
-mi = qmp_input_visitor_new_strict(%(obj)s);
 v = qmp_input_get_visitor(mi);
-''',
-                     obj=obj)
+''')
 
     for argname, argtype, optional, structured in parse_args(args):
         if optional:
@@ -151,10 +151,6 @@ visit_end_optional(v, %(errp)s);
     if dealloc:
         ret += mcgen('''
 qapi_dealloc_visitor_cleanup(md);
-''')
-    else:
-        ret += mcgen('''
-qmp_input_visitor_cleanup(mi);
 ''')
     pop_indent()
     return ret.rstrip()
@@ -166,8 +162,8 @@ def gen_marshal_output(name, args, ret_type, middle_mode):
     ret = mcgen('''
 static void qmp_marshal_output_%(c_name)s(%(c_ret_type)s ret_in, QObject **ret_out, Error **errp)
 {
-    QapiDeallocVisitor *md = qapi_dealloc_visitor_new();
     QmpOutputVisitor *mo = qmp_output_visitor_new();
+    QapiDeallocVisitor *md;
     Visitor *v;
 
     v = qmp_output_get_visitor(mo);
@@ -176,6 +172,7 @@ static void qmp_marshal_output_%(c_name)s(%(c_ret_type)s ret_in, QObject **ret_o
         *ret_out = qmp_output_get_qobject(mo);
     }
     qmp_output_visitor_cleanup(mo);
+    md = qapi_dealloc_visitor_new();
     v = qapi_dealloc_get_visitor(md);
     %(visitor)s(v, &ret_in, "unused", NULL);
     qapi_dealloc_visitor_cleanup(md);
@@ -228,9 +225,9 @@ def gen_marshal_input(name, args, ret_type, middle_mode):
 %(visitor_input_block)s
 
 ''',
-                     visitor_input_containers_decl=gen_visitor_input_containers_decl(args),
+                     visitor_input_containers_decl=gen_visitor_input_containers_decl(args, "QOBJECT(args)"),
                      visitor_input_vars_decl=gen_visitor_input_vars_decl(args),
-                     visitor_input_block=gen_visitor_input_block(args, "QOBJECT(args)"))
+                     visitor_input_block=gen_visitor_input_block(args))
     else:
         ret += mcgen('''
     (void)args;
@@ -250,7 +247,7 @@ out:
     ret += mcgen('''
 %(visitor_input_block_cleanup)s
 ''',
-                 visitor_input_block_cleanup=gen_visitor_input_block(args, None,
+                 visitor_input_block_cleanup=gen_visitor_input_block(args,
                                                                      dealloc=True))
 
     if middle_mode: