qapi: Disallow qmp_marshal_FOO(NULL, ...)

For QMP commands without arguments, gen_marshal() laboriously
generates a qmp_marshal_FOO() that copes with null @args.  Turns
there's just one caller that passes null instead of an empty QDict.
Adjust that caller, and simplify gen_marshal().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200424084338.26803-15-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 2 insertions, 24 deletions

diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index bc30876c88..f545903567 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -104,6 +104,7 @@ def gen_marshal(name, arg_type, boxed, ret_type):
 %(proto)s
 {
     Error *err = NULL;
+    Visitor *v;
 ''',
                 proto=build_marshal_proto(name))
 
@@ -117,21 +118,14 @@ def gen_marshal(name, arg_type, boxed, ret_type):
         visit_members = ('visit_type_%s_members(v, &arg, &err);'
                          % arg_type.c_name())
         ret += mcgen('''
-    Visitor *v;
     %(c_name)s arg = {0};
-
 ''',
                      c_name=arg_type.c_name())
     else:
         visit_members = ''
-        ret += mcgen('''
-    Visitor *v = NULL;
-
-    if (args) {
-''')
-        push_indent()
 
     ret += mcgen('''
+
     v = qobject_input_visitor_new(QOBJECT(args));
     visit_start_struct(v, NULL, NULL, 0, &err);
     if (err) {
@@ -148,12 +142,6 @@ def gen_marshal(name, arg_type, boxed, ret_type):
 ''',
                  visit_members=visit_members)
 
-    if not have_args:
-        pop_indent()
-        ret += mcgen('''
-    }
-''')
-
     ret += gen_call(name, arg_type, boxed, ret_type)
 
     ret += mcgen('''
@@ -168,10 +156,6 @@ out:
                          % arg_type.c_name())
     else:
         visit_members = ''
-        ret += mcgen('''
-    if (args) {
-''')
-        push_indent()
 
     ret += mcgen('''
     v = qapi_dealloc_visitor_new();
@@ -182,12 +166,6 @@ out:
 ''',
                  visit_members=visit_members)
 
-    if not have_args:
-        pop_indent()
-        ret += mcgen('''
-    }
-''')
-
     ret += mcgen('''
 }
 ''')