sd-bus: standarize on NULL for empty signature in method calls

We would use sometimes "" and sometimes NULL. They are equivalent, so let's use
NULL everywhere, except for a two places in tests.

3 files changed, 47 insertions, 48 deletions

diff --git a/src/analyze/analyze.c b/src/analyze/analyze.c
index c25d11e0de..72ebd25525 100644
--- a/src/analyze/analyze.c
+++ b/src/analyze/analyze.c
@@ -1277,7 +1277,7 @@ static int dot(int argc, char *argv[], void *userdata) {
         if (r < 0)
                 return r;
 
-        r = bus_call_method(bus, bus_systemd_mgr, "ListUnits", &error, &reply, "");
+        r = bus_call_method(bus, bus_systemd_mgr, "ListUnits", &error, &reply, NULL);
         if (r < 0)
                 log_error_errno(r, "Failed to list units: %s", bus_error_message(&error, r));
 
diff --git a/src/busctl/busctl.c b/src/busctl/busctl.c
index 7774aeac7c..c577ac2bab 100644
--- a/src/busctl/busctl.c
+++ b/src/busctl/busctl.c
@@ -442,7 +442,7 @@ static int find_nodes(sd_bus *bus, const char *service, const char *path, Set *p
 
         r = sd_bus_call_method(bus, service, path,
                                "org.freedesktop.DBus.Introspectable", "Introspect",
-                               &error, &reply, "");
+                               &error, &reply, NULL);
         if (r < 0) {
                 printf("%sFailed to introspect object %s of service %s: %s%s\n",
                        ansi_highlight_red(),
@@ -981,7 +981,7 @@ static int introspect(int argc, char **argv, void *userdata) {
 
         r = sd_bus_call_method(bus, argv[1], argv[2],
                                "org.freedesktop.DBus.Introspectable", "Introspect",
-                               &error, &reply_xml, "");
+                               &error, &reply_xml, NULL);
         if (r < 0)
                 return log_error_errno(r, "Failed to introspect object %s of service %s: %s",
                                        argv[2], argv[1], bus_error_message(&error, r));
diff --git a/src/libsystemd/sd-bus/test-bus-objects.c b/src/libsystemd/sd-bus/test-bus-objects.c
index 80d2a5d98b..5ef3f30c70 100644
--- a/src/libsystemd/sd-bus/test-bus-objects.c
+++ b/src/libsystemd/sd-bus/test-bus-objects.c
@@ -297,8 +297,7 @@ static int client(struct context *c) {
         assert_se(r >= 0);
         assert_se(streq(s, "<<<hallo>>>"));
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
         r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Doesntexist", &error, &reply, "");
         assert_se(r < 0);
@@ -306,6 +305,12 @@ static int client(struct context *c) {
 
         sd_bus_error_free(&error);
 
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Doesntexist", &error, &reply, NULL); /* NULL and "" are equivalent */
+        assert_se(r < 0);
+        assert_se(sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD));
+
+        sd_bus_error_free(&error);
+
         r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "AlterSomething", &error, &reply, "as", 1, "hallo");
         assert_se(r < 0);
         assert_se(sd_bus_error_has_name(&error, SD_BUS_ERROR_INVALID_ARGS));
@@ -319,8 +324,7 @@ static int client(struct context *c) {
         assert_se(r >= 0);
         assert_se(streq(s, "<<<hallo>>>"));
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
         r = sd_bus_set_property(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Something", &error, "s", "test");
         assert_se(r >= 0);
@@ -332,8 +336,7 @@ static int client(struct context *c) {
         assert_se(r >= 0);
         assert_se(streq(s, "test"));
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
         r = sd_bus_set_property(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "AutomaticIntegerProperty", &error, "u", 815);
         assert_se(r >= 0);
@@ -352,8 +355,16 @@ static int client(struct context *c) {
         assert_se(r >= 0);
         fputs(s, stdout);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
+
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, NULL); /* NULL and "" are equivalent */
+        assert_se(r >= 0);
+
+        r = sd_bus_message_read(reply, "s", &s);
+        assert_se(r >= 0);
+        fputs(s, stdout);
+
+        reply = sd_bus_message_unref(reply);
 
         r = sd_bus_get_property(bus, "org.freedesktop.systemd.test", "/value/xuzz", "org.freedesktop.systemd.ValueTest", "Value", &error, &reply, "s");
         assert_se(r >= 0);
@@ -362,66 +373,60 @@ static int client(struct context *c) {
         assert_se(r >= 0);
         log_info("read %s", s);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_message_read(reply, "s", &s);
         assert_se(r >= 0);
         fputs(s, stdout);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_message_read(reply, "s", &s);
         assert_se(r >= 0);
         fputs(s, stdout);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.DBus.Introspectable", "Introspect", &error, &reply, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_message_read(reply, "s", &s);
         assert_se(r >= 0);
         fputs(s, stdout);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.DBus.Properties", "GetAll", &error, &reply, "s", "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.DBus.Properties", "GetAll", &error, &reply, "s", NULL);
         assert_se(r >= 0);
 
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
         r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.DBus.Properties", "GetAll", &error, &reply, "s", "org.freedesktop.systemd.ValueTest2");
         assert_se(r < 0);
         assert_se(sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_INTERFACE));
         sd_bus_error_free(&error);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.DBus.ObjectManager", "GetManagedObjects", &error, &reply, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.DBus.ObjectManager", "GetManagedObjects", &error, &reply, NULL);
         assert_se(r < 0);
         assert_se(sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD));
         sd_bus_error_free(&error);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value", "org.freedesktop.DBus.ObjectManager", "GetManagedObjects", &error, &reply, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value", "org.freedesktop.DBus.ObjectManager", "GetManagedObjects", &error, &reply, NULL);
         assert_se(r >= 0);
 
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.systemd.ValueTest", "NotifyTest", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.systemd.ValueTest", "NotifyTest", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -430,10 +435,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.Properties", "PropertiesChanged"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.systemd.ValueTest", "NotifyTest2", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/value/a", "org.freedesktop.systemd.ValueTest", "NotifyTest2", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -442,10 +446,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.Properties", "PropertiesChanged"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitInterfacesAdded", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitInterfacesAdded", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -454,10 +457,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesAdded"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitInterfacesRemoved", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitInterfacesRemoved", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -466,10 +468,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesRemoved"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectAdded", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectAdded", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -478,10 +479,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesAdded"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectRemoved", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectRemoved", &error, NULL, NULL);
         assert_se(r >= 0);
 
         r = sd_bus_process(bus, &reply);
@@ -490,10 +490,9 @@ static int client(struct context *c) {
         assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesRemoved"));
         sd_bus_message_dump(reply, stdout, SD_BUS_MESSAGE_DUMP_WITH_HEADER);
 
-        sd_bus_message_unref(reply);
-        reply = NULL;
+        reply = sd_bus_message_unref(reply);
 
-        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Exit", &error, NULL, "");
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Exit", &error, NULL, NULL);
         assert_se(r >= 0);
 
         sd_bus_flush(bus);