unit: allocate bus name match string on the stack

Let's use strjoina() rather than strjoin() for construct dbus match
strings.

Also, while we are at it, fix parameter ordering, so that our functions
always put the object first, like it is customary for OO-like
programming.

3 files changed, 10 insertions, 13 deletions

diff --git a/src/core/dbus.c b/src/core/dbus.c
index 2d6a1ff836..d8891d49d8 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -777,7 +777,7 @@ static int bus_setup_api(Manager *m, sd_bus *bus) {
                 return r;
 
         HASHMAP_FOREACH_KEY(u, name, m->watch_bus, i) {
-                r = unit_install_bus_match(bus, u, name);
+                r = unit_install_bus_match(u, bus, name);
                 if (r < 0)
                         log_error_errno(r, "Failed to subscribe to NameOwnerChanged signal: %m");
         }
diff --git a/src/core/unit.c b/src/core/unit.c
index 39cd89f1e3..d8f0eb8111 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -2508,26 +2508,23 @@ static int signal_name_owner_changed(sd_bus_message *message, void *userdata, sd
         return 0;
 }
 
-int unit_install_bus_match(sd_bus *bus, Unit *u, const char *name) {
-        _cleanup_free_ char *match = NULL;
-        Manager *m = u->manager;
+int unit_install_bus_match(Unit *u, sd_bus *bus, const char *name) {
+        const char *match;
 
-        assert(m);
+        assert(u);
+        assert(bus);
+        assert(name);
 
         if (u->match_bus_slot)
                 return -EBUSY;
 
-        match = strjoin("type='signal',"
+        match = strjoina("type='signal',"
                         "sender='org.freedesktop.DBus',"
                         "path='/org/freedesktop/DBus',"
                         "interface='org.freedesktop.DBus',"
                         "member='NameOwnerChanged',"
-                        "arg0='",
-                        name,
-                        "'",
+                        "arg0='", name, "'",
                         NULL);
-        if (!match)
-                return -ENOMEM;
 
         return sd_bus_add_match(bus, &u->match_bus_slot, match, signal_name_owner_changed, u);
 }
@@ -2544,7 +2541,7 @@ int unit_watch_bus_name(Unit *u, const char *name) {
         if (u->manager->api_bus) {
                 /* If the bus is already available, install the match directly.
                  * Otherwise, just put the name in the list. bus_setup_api() will take care later. */
-                r = unit_install_bus_match(u->manager->api_bus, u, name);
+                r = unit_install_bus_match(u, u->manager->api_bus, name);
                 if (r < 0)
                         return log_warning_errno(r, "Failed to subscribe to NameOwnerChanged signal: %m");
         }
diff --git a/src/core/unit.h b/src/core/unit.h
index a4a1b011fc..9f8518c720 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -520,7 +520,7 @@ void unit_unwatch_all_pids(Unit *u);
 
 void unit_tidy_watch_pids(Unit *u, pid_t except1, pid_t except2);
 
-int unit_install_bus_match(sd_bus *bus, Unit *u, const char *name);
+int unit_install_bus_match(Unit *u, sd_bus *bus, const char *name);
 int unit_watch_bus_name(Unit *u, const char *name);
 void unit_unwatch_bus_name(Unit *u, const char *name);