[Qemu-devel] [PATCH for-2.5 2/4] qapi: Fix command with named empty argument type

[Eric Blake <eblake@redhat.com>]

The generator special-cased
 { 'command':'foo', 'data': {} }
to avoid emitting a visitor variable, but failed to see that
 { 'struct':'NamedEmptyType, 'data': {} }
 { 'command':'foo', 'data':'NamedEmptyType' }
needs the same treatment.  Without a fix to the generator, the
change to qapi-schema-test.json fails to compile with:

tests/test-qmp-marshal.c: In function ‘qmp_marshal_user_def_cmd0’:
tests/test-qmp-marshal.c:264:14: error: variable ‘v’ set but not used [-Werror=unused-but-set-variable]
     Visitor *v;
              ^

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 scripts/qapi-commands.py                | 6 +++---
 tests/qapi-schema/qapi-schema-test.json | 2 ++
 tests/qapi-schema/qapi-schema-test.out  | 2 ++
 tests/test-qmp-commands.c               | 5 +++++
 4 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 561e47a..38cbffc 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -65,7 +65,7 @@ def gen_marshal_vars(arg_type, ret_type):
 ''',
                      c_type=ret_type.c_type())

-    if arg_type:
+    if arg_type and not arg_type.is_empty():
         ret += mcgen('''
     QmpInputVisitor *qiv = qmp_input_visitor_new_strict(QOBJECT(args));
     QapiDeallocVisitor *qdv;
@@ -97,7 +97,7 @@ def gen_marshal_vars(arg_type, ret_type):
 def gen_marshal_input_visit(arg_type, dealloc=False):
     ret = ''

-    if not arg_type:
+    if not arg_type or arg_type.is_empty():
         return ret

     if dealloc:
@@ -177,7 +177,7 @@ def gen_marshal(name, arg_type, ret_type):

     # 'goto out' produced by gen_marshal_input_visit->gen_visit_fields()
     # for each arg_type member, and by gen_call() for ret_type
-    if (arg_type and arg_type.members) or ret_type:
+    if (arg_type and not arg_type.is_empty()) or ret_type:
         ret += mcgen('''

 out:
diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index 44638da..2aa53fe 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -18,6 +18,8 @@
 { 'struct': 'Empty1', 'data': { } }
 { 'struct': 'Empty2', 'base': 'Empty1', 'data': { } }

+{ 'command': 'user_def_cmd0', 'data': 'Empty2', 'returns': 'Empty2' }
+
 # for testing override of default naming heuristic
 { 'enum': 'QEnumTwo',
   'prefix': 'QENUM_TWO',
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index e20a823..26cb094 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -201,6 +201,8 @@ command guest-sync :obj-guest-sync-arg -> any
    gen=True success_response=True
 command user_def_cmd None -> None
    gen=True success_response=True
+command user_def_cmd0 Empty2 -> Empty2
+   gen=True success_response=True
 command user_def_cmd1 :obj-user_def_cmd1-arg -> None
    gen=True success_response=True
 command user_def_cmd2 :obj-user_def_cmd2-arg -> UserDefTwo
diff --git a/tests/test-qmp-commands.c b/tests/test-qmp-commands.c
index 888fb5f..93bd7de 100644
--- a/tests/test-qmp-commands.c
+++ b/tests/test-qmp-commands.c
@@ -12,6 +12,11 @@ void qmp_user_def_cmd(Error **errp)
 {
 }

+Empty2 *qmp_user_def_cmd0(Error **errp)
+{
+    return g_new0(Empty2, 1);
+}
+
 void qmp_user_def_cmd1(UserDefOne * ud1, Error **errp)
 {
 }
-- 
2.4.3