tests: Add check-qnull

Add a new test, for checking reference counting of qnull(). As
part of the new file, move a previous reference counting change
added in commit a861564 to a more logical place.

Note that while most of the check-q*.c leave visitor stuff to
the test-qmp-*-visitor.c, in this case we actually want the
visitor tests in our new file because we are validating the
reference count of qnull_, which is an internal detail that
test-qmp-*-visitor should not be peeking into (or put another
way, qnull() is the only special case where we don't have
independent allocation of a QObject, so none of the other
visitor tests require the layering violation present in this
test).

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-14-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

tests/.gitignore

@@ -3,6 +3,7 @@ check-qfloat
 check-qint
 check-qjson
 check-qlist
+check-qnull
 check-qstring
 check-qom-interface
 check-qom-proplist

tests/Makefile

@@ -16,6 +16,8 @@ check-unit-y += tests/check-qstring$(EXESUF)
 gcov-files-check-qstring-y = qobject/qstring.c
 check-unit-y += tests/check-qlist$(EXESUF)
 gcov-files-check-qlist-y = qobject/qlist.c
+check-unit-y += tests/check-qnull$(EXESUF)
+gcov-files-check-qnull-y = qobject/qnull.c
 check-unit-y += tests/check-qjson$(EXESUF)
 gcov-files-check-qjson-y = qobject/qjson.c
 check-unit-y += tests/test-qmp-output-visitor$(EXESUF)
@@ -382,7 +384,8 @@ GENERATED_HEADERS += tests/test-qapi-types.h tests/test-qapi-visit.h \
 	tests/test-qmp-introspect.h
 
 test-obj-y = tests/check-qint.o tests/check-qstring.o tests/check-qdict.o \
-	tests/check-qlist.o tests/check-qfloat.o tests/check-qjson.o \
+	tests/check-qlist.o tests/check-qfloat.o tests/check-qnull.o \
+	tests/check-qjson.o \
 	tests/test-coroutine.o tests/test-string-output-visitor.o \
 	tests/test-string-input-visitor.o tests/test-qmp-output-visitor.o \
 	tests/test-qmp-input-visitor.o tests/test-qmp-input-strict.o \
@@ -410,6 +413,7 @@ tests/check-qstring$(EXESUF): tests/check-qstring.o $(test-util-obj-y)
 tests/check-qdict$(EXESUF): tests/check-qdict.o $(test-util-obj-y)
 tests/check-qlist$(EXESUF): tests/check-qlist.o $(test-util-obj-y)
 tests/check-qfloat$(EXESUF): tests/check-qfloat.o $(test-util-obj-y)
+tests/check-qnull$(EXESUF): tests/check-qnull.o $(test-util-obj-y)
 tests/check-qjson$(EXESUF): tests/check-qjson.o $(test-util-obj-y)
 tests/check-qom-interface$(EXESUF): tests/check-qom-interface.o $(test-qom-obj-y)
 tests/check-qom-proplist$(EXESUF): tests/check-qom-proplist.o $(test-qom-obj-y)

tests/check-qnull.c

@@ -0,0 +1,66 @@
+/*
+ * QNull unit-tests.
+ *
+ * Copyright (C) 2016 Red Hat Inc.
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include <glib.h>
+
+#include "qapi/qmp/qobject.h"
+#include "qemu-common.h"
+#include "qapi/qmp-output-visitor.h"
+
+/*
+ * Public Interface test-cases
+ *
+ * (with some violations to access 'private' data)
+ */
+
+static void qnull_ref_test(void)
+{
+    QObject *obj;
+
+    g_assert(qnull_.refcnt == 1);
+    obj = qnull();
+    g_assert(obj);
+    g_assert(obj == &qnull_);
+    g_assert(qnull_.refcnt == 2);
+    g_assert(qobject_type(obj) == QTYPE_QNULL);
+    qobject_decref(obj);
+    g_assert(qnull_.refcnt == 1);
+}
+
+static void qnull_visit_test(void)
+{
+    QObject *obj;
+    QmpOutputVisitor *qov;
+
+    /*
+     * Most tests of interactions between QObject and visitors are in
+     * test-qmp-*-visitor; but these tests live here because they
+     * depend on layering violations to check qnull_ refcnt.
+     */
+
+    g_assert(qnull_.refcnt == 1);
+    qov = qmp_output_visitor_new();
+    /* FIXME: Empty visits are ugly, we should have a visit_type_null(). */
+    obj = qmp_output_get_qobject(qov);
+    g_assert(obj == &qnull_);
+    qobject_decref(obj);
+
+    qmp_output_visitor_cleanup(qov);
+    g_assert(qnull_.refcnt == 1);
+}
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+
+    g_test_add_func("/public/qnull_ref", qnull_ref_test);
+    g_test_add_func("/public/qnull_visit", qnull_visit_test);
+
+    return g_test_run();
+}

tests/test-qmp-output-visitor.c

@@ -484,8 +484,6 @@ static void test_visitor_out_empty(TestOutputVisitorData *data,
 
     arg = qmp_output_get_qobject(data->qov);
     g_assert(qobject_type(arg) == QTYPE_QNULL);
-    /* Check that qnull reference counting is sane */
-    g_assert(arg->refcnt == 2);
     qobject_decref(arg);
 }