tree-wide: drop NULL sentinel from strjoin

This makes strjoin and strjoina more similar and avoids the useless final
argument.

spatch -I . -I ./src -I ./src/basic -I ./src/basic -I ./src/shared -I ./src/shared -I ./src/network -I ./src/locale -I ./src/login -I ./src/journal -I ./src/journal -I ./src/timedate -I ./src/timesync -I ./src/nspawn -I ./src/resolve -I ./src/resolve -I ./src/systemd -I ./src/core -I ./src/core -I ./src/libudev -I ./src/udev -I ./src/udev/net -I ./src/udev -I ./src/libsystemd/sd-bus -I ./src/libsystemd/sd-event -I ./src/libsystemd/sd-login -I ./src/libsystemd/sd-netlink -I ./src/libsystemd/sd-network -I ./src/libsystemd/sd-hwdb -I ./src/libsystemd/sd-device -I ./src/libsystemd/sd-id128 -I ./src/libsystemd-network --sp-file coccinelle/strjoin.cocci --in-place $(git ls-files src/*.c)

git grep -e '\bstrjoin\b.*NULL' -l|xargs sed -i -r 's/strjoin\((.*), NULL\)/strjoin(\1)/'

This might have missed a few cases (spatch has a really hard time dealing
with _cleanup_ macros), but that's no big issue, they can always be fixed
later.

88 files changed, 199 insertions, 194 deletions

diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
index 7c59f60d5f..c909b5bb51 100644
--- a/src/backlight/backlight.c
+++ b/src/backlight/backlight.c
@@ -357,9 +357,9 @@ int main(int argc, char *argv[]) {
                         return EXIT_FAILURE;
                 }
 
-                saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
+                saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname);
         } else
-                saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
+                saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname);
 
         if (!saved) {
                 log_oom();
diff --git a/src/basic/btrfs-util.c b/src/basic/btrfs-util.c
index 359d85f2e8..656bb13719 100644
--- a/src/basic/btrfs-util.c
+++ b/src/basic/btrfs-util.c
@@ -1642,7 +1642,7 @@ static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolum
                         if (old_child_fd < 0)
                                 return -errno;
 
-                        np = strjoin(subvolume, "/", ino_args.name, NULL);
+                        np = strjoin(subvolume, "/", ino_args.name);
                         if (!np)
                                 return -ENOMEM;
 
diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index cede835920..5fce32f769 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -345,7 +345,7 @@ int cg_kill_recursive(
         while ((r = cg_read_subgroup(d, &fn)) > 0) {
                 _cleanup_free_ char *p = NULL;
 
-                p = strjoin(path, "/", fn, NULL);
+                p = strjoin(path, "/", fn);
                 free(fn);
                 if (!p)
                         return -ENOMEM;
@@ -479,7 +479,7 @@ int cg_migrate_recursive(
         while ((r = cg_read_subgroup(d, &fn)) > 0) {
                 _cleanup_free_ char *p = NULL;
 
-                p = strjoin(pfrom, "/", fn, NULL);
+                p = strjoin(pfrom, "/", fn);
                 free(fn);
                 if (!p)
                         return -ENOMEM;
@@ -562,11 +562,11 @@ static int join_path_legacy(const char *controller, const char *path, const char
         if (isempty(path) && isempty(suffix))
                 t = strappend("/sys/fs/cgroup/", dn);
         else if (isempty(path))
-                t = strjoin("/sys/fs/cgroup/", dn, "/", suffix, NULL);
+                t = strjoin("/sys/fs/cgroup/", dn, "/", suffix);
         else if (isempty(suffix))
-                t = strjoin("/sys/fs/cgroup/", dn, "/", path, NULL);
+                t = strjoin("/sys/fs/cgroup/", dn, "/", path);
         else
-                t = strjoin("/sys/fs/cgroup/", dn, "/", path, "/", suffix, NULL);
+                t = strjoin("/sys/fs/cgroup/", dn, "/", path, "/", suffix);
         if (!t)
                 return -ENOMEM;
 
@@ -586,7 +586,7 @@ static int join_path_unified(const char *path, const char *suffix, char **fs) {
         else if (isempty(suffix))
                 t = strappend("/sys/fs/cgroup/", path);
         else
-                t = strjoin("/sys/fs/cgroup/", path, "/", suffix, NULL);
+                t = strjoin("/sys/fs/cgroup/", path, "/", suffix);
         if (!t)
                 return -ENOMEM;
 
@@ -613,7 +613,7 @@ int cg_get_path(const char *controller, const char *path, const char *suffix, ch
                 else if (!path)
                         t = strdup(suffix);
                 else
-                        t = strjoin(path, "/", suffix, NULL);
+                        t = strjoin(path, "/", suffix);
                 if (!t)
                         return -ENOMEM;
 
@@ -1145,7 +1145,7 @@ int cg_is_empty_recursive(const char *controller, const char *path) {
                 while ((r = cg_read_subgroup(d, &fn)) > 0) {
                         _cleanup_free_ char *p = NULL;
 
-                        p = strjoin(path, "/", fn, NULL);
+                        p = strjoin(path, "/", fn);
                         free(fn);
                         if (!p)
                                 return -ENOMEM;
diff --git a/src/basic/conf-files.c b/src/basic/conf-files.c
index c781610e14..c0c22610d7 100644
--- a/src/basic/conf-files.c
+++ b/src/basic/conf-files.c
@@ -60,7 +60,7 @@ static int files_add(Hashmap *h, const char *root, const char *path, const char
                 if (!dirent_is_file_with_suffix(de, suffix))
                         continue;
 
-                p = strjoin(dirpath, "/", de->d_name, NULL);
+                p = strjoin(dirpath, "/", de->d_name);
                 if (!p)
                         return -ENOMEM;
 
diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index 1cfb7a98f5..1615456659 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -676,7 +676,7 @@ static int load_env_file_push(
                 return -EINVAL;
         }
 
-        p = strjoin(key, "=", strempty(value), NULL);
+        p = strjoin(key, "=", strempty(value));
         if (!p)
                 return -ENOMEM;
 
@@ -963,9 +963,9 @@ static int search_and_fopen_internal(const char *path, const char *mode, const c
                 FILE *f;
 
                 if (root)
-                        p = strjoin(root, *i, "/", path, NULL);
+                        p = strjoin(root, *i, "/", path);
                 else
-                        p = strjoin(*i, "/", path, NULL);
+                        p = strjoin(*i, "/", path);
                 if (!p)
                         return -ENOMEM;
 
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index 48952a1c26..d2c322a0de 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -742,7 +742,7 @@ int chase_symlinks(const char *path, const char *_root, char **ret) {
                                 /* A relative destination. If so, this is what we'll prefix what's left to do with what
                                  * we just read, and start the loop again, but remain in the current directory. */
 
-                                joined = strjoin("/", destination, todo, NULL);
+                                joined = strjoin("/", destination, todo);
                                 if (!joined)
                                         return -ENOMEM;
 
diff --git a/src/basic/mount-util.c b/src/basic/mount-util.c
index 0ef00676ef..b221309a4d 100644
--- a/src/basic/mount-util.c
+++ b/src/basic/mount-util.c
@@ -641,7 +641,7 @@ static char* mount_flags_to_string(long unsigned flags) {
                     FLAG(MS_I_VERSION),
                     FLAG(MS_STRICTATIME),
                     FLAG(MS_LAZYTIME),
-                    y, NULL);
+                    y);
         if (!x)
                 return NULL;
         if (!y)
diff --git a/src/basic/path-util.c b/src/basic/path-util.c
index 0f5b20cf05..e438f27df5 100644
--- a/src/basic/path-util.c
+++ b/src/basic/path-util.c
@@ -83,7 +83,7 @@ char *path_make_absolute(const char *p, const char *prefix) {
         if (path_is_absolute(p) || !prefix)
                 return strdup(p);
 
-        return strjoin(prefix, "/", p, NULL);
+        return strjoin(prefix, "/", p);
 }
 
 int path_make_absolute_cwd(const char *p, char **ret) {
@@ -104,7 +104,7 @@ int path_make_absolute_cwd(const char *p, char **ret) {
                 if (!cwd)
                         return negative_errno();
 
-                c = strjoin(cwd, "/", p, NULL);
+                c = strjoin(cwd, "/", p);
         }
         if (!c)
                 return -ENOMEM;
@@ -444,13 +444,11 @@ char* path_join(const char *root, const char *path, const char *rest) {
                 return strjoin(root, endswith(root, "/") ? "" : "/",
                                path[0] == '/' ? path+1 : path,
                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
-                               rest && rest[0] == '/' ? rest+1 : rest,
-                               NULL);
+                               rest && rest[0] == '/' ? rest+1 : rest);
         else
                 return strjoin(path,
                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
-                               rest && rest[0] == '/' ? rest+1 : rest,
-                               NULL);
+                               rest && rest[0] == '/' ? rest+1 : rest);
 }
 
 int find_binary(const char *name, char **ret) {
@@ -494,7 +492,7 @@ int find_binary(const char *name, char **ret) {
                 if (!path_is_absolute(element))
                         continue;
 
-                j = strjoin(element, "/", name, NULL);
+                j = strjoin(element, "/", name);
                 if (!j)
                         return -ENOMEM;
 
diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index 54b644ad56..48a5c719af 100644
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -236,14 +236,14 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
                         return h;
 
                 if (max_length == 0)
-                        r = strjoin("[", t, "]", NULL);
+                        r = strjoin("[", t, "]");
                 else {
                         size_t l;
 
                         l = strlen(t);
 
                         if (l + 3 <= max_length)
-                                r = strjoin("[", t, "]", NULL);
+                                r = strjoin("[", t, "]");
                         else if (max_length <= 6) {
 
                                 r = new(char, max_length);
@@ -263,7 +263,7 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
                                         e--;
                                 *e = 0;
 
-                                r = strjoin("[", t, "...]", NULL);
+                                r = strjoin("[", t, "...]");
                         }
                 }
                 if (!r)
diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 6b06e643c9..2ba3604ba0 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -218,7 +218,7 @@ char *strappend(const char *s, const char *suffix) {
         return strnappend(s, suffix, suffix ? strlen(suffix) : 0);
 }
 
-char *strjoin(const char *x, ...) {
+char *strjoin_real(const char *x, ...) {
         va_list ap;
         size_t l;
         char *r, *p;
diff --git a/src/basic/string-util.h b/src/basic/string-util.h
index d029d538bd..0175803302 100644
--- a/src/basic/string-util.h
+++ b/src/basic/string-util.h
@@ -116,7 +116,8 @@ const char* split(const char **state, size_t *l, const char *separator, bool quo
 char *strappend(const char *s, const char *suffix);
 char *strnappend(const char *s, const char *suffix, size_t length);
 
-char *strjoin(const char *x, ...) _sentinel_;
+char *strjoin_real(const char *x, ...) _sentinel_;
+#define strjoin(a, ...) strjoin_real((a), __VA_ARGS__, NULL)
 
 #define strjoina(a, ...)                                                \
         ({                                                              \
diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c
index fe883b95c7..0a6efa449a 100644
--- a/src/basic/unit-name.c
+++ b/src/basic/unit-name.c
@@ -273,7 +273,7 @@ int unit_name_build(const char *prefix, const char *instance, const char *suffix
         if (!instance)
                 s = strappend(prefix, suffix);
         else
-                s = strjoin(prefix, "@", instance, suffix, NULL);
+                s = strjoin(prefix, "@", instance, suffix);
         if (!s)
                 return -ENOMEM;
 
@@ -554,7 +554,7 @@ int unit_name_from_path_instance(const char *prefix, const char *path, const cha
         if (r < 0)
                 return r;
 
-        s = strjoin(prefix, "@", p, suffix, NULL);
+        s = strjoin(prefix, "@", p, suffix);
         if (!s)
                 return -ENOMEM;
 
diff --git a/src/basic/util.c b/src/basic/util.c
index ec7939dc83..0f65e4839c 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -131,7 +131,7 @@ static int do_execute(char **directories, usec_t timeout, char *argv[]) {
                         if (r < 0)
                                 return log_oom();
 
-                        path = strjoin(*directory, "/", de->d_name, NULL);
+                        path = strjoin(*directory, "/", de->d_name);
                         if (!path)
                                 return log_oom();
 
diff --git a/src/cgls/cgls.c b/src/cgls/cgls.c
index adf488e8e1..b55aa86a40 100644
--- a/src/cgls/cgls.c
+++ b/src/cgls/cgls.c
@@ -223,7 +223,7 @@ int main(int argc, char *argv[]) {
 
                                 controller = c ?: SYSTEMD_CGROUP_CONTROLLER;
                                 if (p) {
-                                        j = strjoin(root, "/", p, NULL);
+                                        j = strjoin(root, "/", p);
                                         if (!j) {
                                                 r = log_oom();
                                                 goto finish;
diff --git a/src/cgtop/cgtop.c b/src/cgtop/cgtop.c
index aba17c9829..af5c3d8695 100644
--- a/src/cgtop/cgtop.c
+++ b/src/cgtop/cgtop.c
@@ -431,7 +431,7 @@ static int refresh_one(
                 if (r == 0)
                         break;
 
-                p = strjoin(path, "/", fn, NULL);
+                p = strjoin(path, "/", fn);
                 if (!p)
                         return -ENOMEM;
 
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 09bbe038e9..bd6248406f 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1201,9 +1201,10 @@ char *unit_default_cgroup_path(Unit *u) {
                 return NULL;
 
         if (slice)
-                return strjoin(u->manager->cgroup_root, "/", slice, "/", escaped, NULL);
+                return strjoin(u->manager->cgroup_root, "/", slice, "/",
+                               escaped);
         else
-                return strjoin(u->manager->cgroup_root, "/", escaped, NULL);
+                return strjoin(u->manager->cgroup_root, "/", escaped);
 }
 
 int unit_set_cgroup_path(Unit *u, const char *path) {
@@ -1643,7 +1644,7 @@ static int unit_watch_pids_in_path(Unit *u, const char *path) {
                 while ((r = cg_read_subgroup(d, &fn)) > 0) {
                         _cleanup_free_ char *p = NULL;
 
-                        p = strjoin(path, "/", fn, NULL);
+                        p = strjoin(path, "/", fn);
                         free(fn);
 
                         if (!p)
diff --git a/src/core/dbus-execute.c b/src/core/dbus-execute.c
index 1a7f770db1..03f23780c1 100644
--- a/src/core/dbus-execute.c
+++ b/src/core/dbus-execute.c
@@ -1368,7 +1368,7 @@ int bus_exec_context_set_transient_property(
                         if (mode != UNIT_CHECK) {
                                 char *buf = NULL;
 
-                                buf = strjoin(b ? "-" : "", path, NULL);
+                                buf = strjoin(b ? "-" : "", path);
                                 if (!buf)
                                         return -ENOMEM;
 
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 245912fc0f..6948daf682 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -484,7 +484,7 @@ int bus_unit_method_start_generic(
                 return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Job mode %s invalid", smode);
 
         if (reload_if_possible)
-                verb = strjoin("reload-or-", job_type_to_string(job_type), NULL);
+                verb = strjoin("reload-or-", job_type_to_string(job_type));
         else
                 verb = strdup(job_type_to_string(job_type));
         if (!verb)
@@ -986,7 +986,7 @@ static int append_cgroup(sd_bus_message *reply, const char *p, Set *pids) {
                 if (r == 0)
                         break;
 
-                j = strjoin(p, "/", g, NULL);
+                j = strjoin(p, "/", g);
                 if (!j)
                         return -ENOMEM;
 
@@ -1365,7 +1365,7 @@ static int bus_unit_set_transient_property(
                                 if (r < 0)
                                         return r;
 
-                                label = strjoin(name, "-", other, NULL);
+                                label = strjoin(name, "-", other);
                                 if (!label)
                                         return -ENOMEM;
 
diff --git a/src/core/device.c b/src/core/device.c
index 8a3e888e5e..bb10148223 100644
--- a/src/core/device.c
+++ b/src/core/device.c
@@ -239,7 +239,7 @@ static int device_update_description(Unit *u, struct udev_device *dev, const cha
                 if (label) {
                         _cleanup_free_ char *j;
 
-                        j = strjoin(model, " ", label, NULL);
+                        j = strjoin(model, " ", label);
                         if (j)
                                 r = unit_set_description(u, j);
                         else
diff --git a/src/core/execute.c b/src/core/execute.c
index 1b7b4a928d..23a702e93e 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -1630,7 +1630,7 @@ static int build_environment(
                 if (!joined)
                         return -ENOMEM;
 
-                x = strjoin("LISTEN_FDNAMES=", joined, NULL);
+                x = strjoin("LISTEN_FDNAMES=", joined);
                 if (!x)
                         return -ENOMEM;
                 our_env[n_env++] = x;
@@ -1737,7 +1737,7 @@ static int build_pass_environment(const ExecContext *c, char ***ret) {
                 v = getenv(*i);
                 if (!v)
                         continue;
-                x = strjoin(*i, "=", v, NULL);
+                x = strjoin(*i, "=", v);
                 if (!x)
                         return -ENOMEM;
                 if (!GREEDY_REALLOC(pass_env, n_bufsize, n_env + 2))
@@ -1951,7 +1951,7 @@ static int setup_runtime_directory(
         STRV_FOREACH(rt, context->runtime_directory) {
                 _cleanup_free_ char *p;
 
-                p = strjoin(params->runtime_prefix, "/", *rt, NULL);
+                p = strjoin(params->runtime_prefix, "/", *rt);
                 if (!p)
                         return -ENOMEM;
 
@@ -2027,7 +2027,7 @@ static int compile_read_write_paths(
         STRV_FOREACH(rt, context->runtime_directory) {
                 char *s;
 
-                s = strjoin(params->runtime_prefix, "/", *rt, NULL);
+                s = strjoin(params->runtime_prefix, "/", *rt);
                 if (!s)
                         return -ENOMEM;
 
@@ -3006,7 +3006,7 @@ int exec_context_destroy_runtime_directory(ExecContext *c, const char *runtime_p
         STRV_FOREACH(i, c->runtime_directory) {
                 _cleanup_free_ char *p;
 
-                p = strjoin(runtime_prefix, "/", *i, NULL);
+                p = strjoin(runtime_prefix, "/", *i);
                 if (!p)
                         return -ENOMEM;
 
diff --git a/src/core/locale-setup.c b/src/core/locale-setup.c
index ccf61d29fb..fdd847ee8b 100644
--- a/src/core/locale-setup.c
+++ b/src/core/locale-setup.c
@@ -87,7 +87,7 @@ int locale_setup(char ***environment) {
                 if (!variables[i])
                         continue;
 
-                s = strjoin(locale_variable_to_string(i), "=", variables[i], NULL);
+                s = strjoin(locale_variable_to_string(i), "=", variables[i]);
                 if (!s) {
                         r = -ENOMEM;
                         goto finish;
diff --git a/src/core/manager.c b/src/core/manager.c
index 0549f5ef1b..fa02389167 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -1196,7 +1196,7 @@ static void manager_build_unit_path_cache(Manager *m) {
                 FOREACH_DIRENT(de, d, r = -errno; goto fail) {
                         char *p;
 
-                        p = strjoin(streq(*i, "/") ? "" : *i, "/", de->d_name, NULL);
+                        p = strjoin(streq(*i, "/") ? "" : *i, "/", de->d_name);
                         if (!p) {
                                 r = -ENOMEM;
                                 goto fail;
diff --git a/src/core/namespace.c b/src/core/namespace.c
index 1195e9a854..db9a7aa5e7 100644
--- a/src/core/namespace.c
+++ b/src/core/namespace.c
@@ -909,7 +909,7 @@ static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
         if (r < 0)
                 return r;
 
-        x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX", NULL);
+        x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX");
         if (!x)
                 return -ENOMEM;
 
diff --git a/src/core/service.c b/src/core/service.c
index 53c26984ca..5a9b01dadb 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -3260,7 +3260,7 @@ int service_set_socket_fd(Service *s, int fd, Socket *sock, bool selinux_context
                 if (UNIT(s)->description) {
                         _cleanup_free_ char *a;
 
-                        a = strjoin(UNIT(s)->description, " (", peer, ")", NULL);
+                        a = strjoin(UNIT(s)->description, " (", peer, ")");
                         if (!a)
                                 return -ENOMEM;
 
diff --git a/src/core/timer.c b/src/core/timer.c
index 2469a517ea..c6b28dd9c5 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -147,7 +147,7 @@ static int timer_setup_persistent(Timer *t) {
 
                 e = getenv("XDG_DATA_HOME");
                 if (e)
-                        t->stamp_path = strjoin(e, "/systemd/timers/stamp-", UNIT(t)->id, NULL);
+                        t->stamp_path = strjoin(e, "/systemd/timers/stamp-", UNIT(t)->id);
                 else {
 
                         _cleanup_free_ char *h = NULL;
@@ -156,7 +156,7 @@ static int timer_setup_persistent(Timer *t) {
                         if (r < 0)
                                 return log_unit_error_errno(UNIT(t), r, "Failed to determine home directory: %m");
 
-                        t->stamp_path = strjoin(h, "/.local/share/systemd/timers/stamp-", UNIT(t)->id, NULL);
+                        t->stamp_path = strjoin(h, "/.local/share/systemd/timers/stamp-", UNIT(t)->id);
                 }
         }
 
diff --git a/src/core/unit.c b/src/core/unit.c
index 2fa397bd41..14e1d7d20d 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -2469,7 +2469,7 @@ int unit_set_default_slice(Unit *u) {
                         return -ENOMEM;
 
                 if (MANAGER_IS_SYSTEM(u->manager))
-                        b = strjoin("system-", escaped, ".slice", NULL);
+                        b = strjoin("system-", escaped, ".slice");
                 else
                         b = strappend(escaped, ".slice");
                 if (!b)
@@ -3629,7 +3629,7 @@ int unit_make_transient(Unit *u) {
         if (!UNIT_VTABLE(u)->can_transient)
                 return -EOPNOTSUPP;
 
-        path = strjoin(u->manager->lookup_paths.transient, "/", u->id, NULL);
+        path = strjoin(u->manager->lookup_paths.transient, "/", u->id);
         if (!path)
                 return -ENOMEM;
 
diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c
index a982c204be..6bd0e925eb 100644
--- a/src/coredump/coredump.c
+++ b/src/coredump/coredump.c
@@ -729,7 +729,10 @@ static int submit_coredump(
 
                 r = coredump_make_stack_trace(coredump_fd, context[CONTEXT_EXE], &stacktrace);
                 if (r >= 0)
-                        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID], " (", context[CONTEXT_COMM], ") of user ", context[CONTEXT_UID], " dumped core.\n\n", stacktrace, NULL);
+                        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
+                                               " (", context[CONTEXT_COMM], ") of user ",
+                                               context[CONTEXT_UID], " dumped core.\n\n",
+                                               stacktrace);
                 else if (r == -EINVAL)
                         log_warning("Failed to generate stack trace: %s", dwfl_errmsg(dwfl_errno()));
                 else
@@ -741,7 +744,9 @@ static int submit_coredump(
         if (!core_message)
 #endif
 log:
-        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID], " (", context[CONTEXT_COMM], ") of user ", context[CONTEXT_UID], " dumped core.", NULL);
+        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID], " (",
+                               context[CONTEXT_COMM], ") of user ",
+                               context[CONTEXT_UID], " dumped core.");
         if (core_message)
                 IOVEC_SET_STRING(iovec[n_iovec++], core_message);
 
diff --git a/src/coredump/coredumpctl.c b/src/coredump/coredumpctl.c
index 0e5351e621..877bbb34fc 100644
--- a/src/coredump/coredumpctl.c
+++ b/src/coredump/coredumpctl.c
@@ -108,7 +108,7 @@ static int add_match(Set *set, const char *match) {
         else
                 prefix = "COREDUMP_COMM=";
 
-        pattern = strjoin(prefix, match, NULL);
+        pattern = strjoin(prefix, match);
         if (!pattern) {
                 r = -ENOMEM;
                 goto fail;
@@ -667,7 +667,7 @@ static int save_core(sd_journal *j, FILE *file, char **path, bool *unlink_temp)
                 if (r < 0)
                         return log_error_errno(r, "Failed to acquire temporary directory path: %m");
 
-                temp = strjoin(vt, "/coredump-XXXXXX", NULL);
+                temp = strjoin(vt, "/coredump-XXXXXX");
                 if (!temp)
                         return log_oom();
 
diff --git a/src/cryptsetup/cryptsetup-generator.c b/src/cryptsetup/cryptsetup-generator.c
index e2dc4327fe..68029865a0 100644
--- a/src/cryptsetup/cryptsetup-generator.c
+++ b/src/cryptsetup/cryptsetup-generator.c
@@ -86,7 +86,7 @@ static int create_disk(
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        p = strjoin(arg_dest, "/", n, NULL);
+        p = strjoin(arg_dest, "/", n);
         if (!p)
                 return log_oom();
 
@@ -188,7 +188,7 @@ static int create_disk(
 
         if (!noauto) {
 
-                to = strjoin(arg_dest, "/", d, ".wants/", n, NULL);
+                to = strjoin(arg_dest, "/", d, ".wants/", n);
                 if (!to)
                         return log_oom();
 
@@ -198,9 +198,9 @@ static int create_disk(
 
                 free(to);
                 if (!nofail)
-                        to = strjoin(arg_dest, "/cryptsetup.target.requires/", n, NULL);
+                        to = strjoin(arg_dest, "/cryptsetup.target.requires/", n);
                 else
-                        to = strjoin(arg_dest, "/cryptsetup.target.wants/", n, NULL);
+                        to = strjoin(arg_dest, "/cryptsetup.target.wants/", n);
                 if (!to)
                         return log_oom();
 
@@ -210,7 +210,7 @@ static int create_disk(
         }
 
         free(to);
-        to = strjoin(arg_dest, "/dev-mapper-", e, ".device.requires/", n, NULL);
+        to = strjoin(arg_dest, "/dev-mapper-", e, ".device.requires/", n);
         if (!to)
                 return log_oom();
 
@@ -220,7 +220,7 @@ static int create_disk(
 
         if (!noauto && !nofail) {
                 _cleanup_free_ char *dmname;
-                dmname = strjoin("dev-mapper-", e, ".device", NULL);
+                dmname = strjoin("dev-mapper-", e, ".device");
                 if (!dmname)
                         return log_oom();
 
diff --git a/src/debug-generator/debug-generator.c b/src/debug-generator/debug-generator.c
index 7f11ec724d..1ee3471355 100644
--- a/src/debug-generator/debug-generator.c
+++ b/src/debug-generator/debug-generator.c
@@ -113,7 +113,7 @@ static int generate_mask_symlinks(void) {
         STRV_FOREACH(u, arg_mask) {
                 _cleanup_free_ char *p = NULL;
 
-                p = strjoin(arg_dest, "/", *u, NULL);
+                p = strjoin(arg_dest, "/", *u);
                 if (!p)
                         return log_oom();
 
@@ -136,7 +136,7 @@ static int generate_wants_symlinks(void) {
         STRV_FOREACH(u, arg_wants) {
                 _cleanup_free_ char *p = NULL, *f = NULL;
 
-                p = strjoin(arg_dest, "/", arg_default_unit, ".wants/", *u, NULL);
+                p = strjoin(arg_dest, "/", arg_default_unit, ".wants/", *u);
                 if (!p)
                         return log_oom();
 
diff --git a/src/delta/delta.c b/src/delta/delta.c
index f32744def2..6848662ccb 100644
--- a/src/delta/delta.c
+++ b/src/delta/delta.c
@@ -214,7 +214,7 @@ static int enumerate_dir_d(Hashmap *top, Hashmap *bottom, Hashmap *drops, const
 
         assert(!endswith(drop, "/"));
 
-        path = strjoin(toppath, "/", drop, NULL);
+        path = strjoin(toppath, "/", drop);
         if (!path)
                 return -ENOMEM;
 
@@ -242,7 +242,7 @@ static int enumerate_dir_d(Hashmap *top, Hashmap *bottom, Hashmap *drops, const
                 if (!endswith(*file, ".conf"))
                         continue;
 
-                p = strjoin(path, "/", *file, NULL);
+                p = strjoin(path, "/", *file);
                 if (!p)
                         return -ENOMEM;
                 d = p + strlen(toppath) + 1;
@@ -330,7 +330,7 @@ static int enumerate_dir(Hashmap *top, Hashmap *bottom, Hashmap *drops, const ch
                 if (!dirent_is_file(de))
                         continue;
 
-                p = strjoin(path, "/", de->d_name, NULL);
+                p = strjoin(path, "/", de->d_name);
                 if (!p)
                         return -ENOMEM;
 
@@ -383,7 +383,7 @@ static int process_suffix(const char *suffix, const char *onlyprefix) {
         NULSTR_FOREACH(p, prefixes) {
                 _cleanup_free_ char *t = NULL;
 
-                t = strjoin(p, "/", suffix, NULL);
+                t = strjoin(p, "/", suffix);
                 if (!t) {
                         r = -ENOMEM;
                         goto finish;
diff --git a/src/escape/escape.c b/src/escape/escape.c
index 9f39049577..af98c98e40 100644
--- a/src/escape/escape.c
+++ b/src/escape/escape.c
@@ -191,7 +191,7 @@ int main(int argc, char *argv[]) {
                         } else if (arg_suffix) {
                                 char *x;
 
-                                x = strjoin(e, ".", arg_suffix, NULL);
+                                x = strjoin(e, ".", arg_suffix);
                                 if (!x) {
                                         r = log_oom();
                                         goto finish;
diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index e77bd71a52..46507de937 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -80,7 +80,7 @@ static int add_swap(
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        unit = strjoin(arg_dest, "/", name, NULL);
+        unit = strjoin(arg_dest, "/", name);
         if (!unit)
                 return log_oom();
 
@@ -275,7 +275,7 @@ static int add_mount(
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        unit = strjoin(arg_dest, "/", name, NULL);
+        unit = strjoin(arg_dest, "/", name);
         if (!unit)
                 return log_oom();
 
@@ -335,7 +335,7 @@ static int add_mount(
                 return log_error_errno(r, "Failed to write unit file %s: %m", unit);
 
         if (!noauto && !automount) {
-                lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", name, NULL);
+                lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", name);
                 if (!lnk)
                         return log_oom();
 
@@ -349,7 +349,7 @@ static int add_mount(
                 if (r < 0)
                         return log_error_errno(r, "Failed to generate unit name: %m");
 
-                automount_unit = strjoin(arg_dest, "/", automount_name, NULL);
+                automount_unit = strjoin(arg_dest, "/", automount_name);
                 if (!automount_unit)
                         return log_oom();
 
@@ -391,7 +391,7 @@ static int add_mount(
                         return log_error_errno(r, "Failed to write unit file %s: %m", automount_unit);
 
                 free(lnk);
-                lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", automount_name, NULL);
+                lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", automount_name);
                 if (!lnk)
                         return log_oom();
 
@@ -619,7 +619,7 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
                 char *o;
 
                 o = arg_root_options ?
-                        strjoin(arg_root_options, ",", value, NULL) :
+                        strjoin(arg_root_options, ",", value) :
                         strdup(value);
                 if (!o)
                         return log_oom();
@@ -641,7 +641,7 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
                 char *o;
 
                 o = arg_usr_options ?
-                        strjoin(arg_usr_options, ",", value, NULL) :
+                        strjoin(arg_usr_options, ",", value) :
                         strdup(value);
                 if (!o)
                         return log_oom();
diff --git a/src/gpt-auto-generator/gpt-auto-generator.c b/src/gpt-auto-generator/gpt-auto-generator.c
index a098b27a8e..e64d5bb231 100644
--- a/src/gpt-auto-generator/gpt-auto-generator.c
+++ b/src/gpt-auto-generator/gpt-auto-generator.c
@@ -76,7 +76,7 @@ static int add_cryptsetup(const char *id, const char *what, bool rw, char **devi
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        p = strjoin(arg_dest, "/", n, NULL);
+        p = strjoin(arg_dest, "/", n);
         if (!p)
                 return log_oom();
 
@@ -111,7 +111,7 @@ static int add_cryptsetup(const char *id, const char *what, bool rw, char **devi
 
         from = strjoina("../", n);
 
-        to = strjoin(arg_dest, "/", d, ".wants/", n, NULL);
+        to = strjoin(arg_dest, "/", d, ".wants/", n);
         if (!to)
                 return log_oom();
 
@@ -120,7 +120,7 @@ static int add_cryptsetup(const char *id, const char *what, bool rw, char **devi
                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
 
         free(to);
-        to = strjoin(arg_dest, "/cryptsetup.target.requires/", n, NULL);
+        to = strjoin(arg_dest, "/cryptsetup.target.requires/", n);
         if (!to)
                 return log_oom();
 
@@ -129,7 +129,7 @@ static int add_cryptsetup(const char *id, const char *what, bool rw, char **devi
                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
 
         free(to);
-        to = strjoin(arg_dest, "/dev-mapper-", e, ".device.requires/", n, NULL);
+        to = strjoin(arg_dest, "/dev-mapper-", e, ".device.requires/", n);
         if (!to)
                 return log_oom();
 
@@ -138,7 +138,7 @@ static int add_cryptsetup(const char *id, const char *what, bool rw, char **devi
                 return log_error_errno(errno, "Failed to create symlink %s: %m", to);
 
         free(p);
-        p = strjoin(arg_dest, "/dev-mapper-", e, ".device.d/50-job-timeout-sec-0.conf", NULL);
+        p = strjoin(arg_dest, "/dev-mapper-", e, ".device.d/50-job-timeout-sec-0.conf");
         if (!p)
                 return log_oom();
 
@@ -194,7 +194,7 @@ static int add_mount(
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        p = strjoin(arg_dest, "/", unit, NULL);
+        p = strjoin(arg_dest, "/", unit);
         if (!p)
                 return log_oom();
 
@@ -236,7 +236,7 @@ static int add_mount(
                 return log_error_errno(r, "Failed to write unit file %s: %m", p);
 
         if (post) {
-                lnk = strjoin(arg_dest, "/", post, ".requires/", unit, NULL);
+                lnk = strjoin(arg_dest, "/", post, ".requires/", unit);
                 if (!lnk)
                         return log_oom();
 
@@ -340,7 +340,7 @@ static int add_swap(const char *path) {
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        unit = strjoin(arg_dest, "/", name, NULL);
+        unit = strjoin(arg_dest, "/", name);
         if (!unit)
                 return log_oom();
 
@@ -361,7 +361,7 @@ static int add_swap(const char *path) {
         if (r < 0)
                 return log_error_errno(r, "Failed to write unit file %s: %m", unit);
 
-        lnk = strjoin(arg_dest, "/" SPECIAL_SWAP_TARGET ".wants/", name, NULL);
+        lnk = strjoin(arg_dest, "/" SPECIAL_SWAP_TARGET ".wants/", name);
         if (!lnk)
                 return log_oom();
 
@@ -393,7 +393,7 @@ static int add_automount(
         assert(description);
 
         if (options)
-                opt = strjoin(options, ",noauto", NULL);
+                opt = strjoin(options, ",noauto");
         else
                 opt = strdup("noauto");
         if (!opt)
@@ -414,7 +414,7 @@ static int add_automount(
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        p = strjoin(arg_dest, "/", unit, NULL);
+        p = strjoin(arg_dest, "/", unit);
         if (!p)
                 return log_oom();
 
@@ -438,7 +438,7 @@ static int add_automount(
         if (r < 0)
                 return log_error_errno(r, "Failed to write unit file %s: %m", p);
 
-        lnk = strjoin(arg_dest, "/" SPECIAL_LOCAL_FS_TARGET ".wants/", unit, NULL);
+        lnk = strjoin(arg_dest, "/" SPECIAL_LOCAL_FS_TARGET ".wants/", unit);
         if (!lnk)
                 return log_oom();
         mkdir_parents_label(lnk, 0755);
diff --git a/src/hibernate-resume/hibernate-resume-generator.c b/src/hibernate-resume/hibernate-resume-generator.c
index 17e670604e..9f59c04b26 100644
--- a/src/hibernate-resume/hibernate-resume-generator.c
+++ b/src/hibernate-resume/hibernate-resume-generator.c
@@ -56,7 +56,7 @@ static int process_resume(void) {
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
 
-        lnk = strjoin(arg_dest, "/" SPECIAL_SYSINIT_TARGET ".wants/", name, NULL);
+        lnk = strjoin(arg_dest, "/" SPECIAL_SYSINIT_TARGET ".wants/", name);
         if (!lnk)
                 return log_oom();
 
diff --git a/src/hostname/hostnamed.c b/src/hostname/hostnamed.c
index 197f905b7d..74256e4444 100644
--- a/src/hostname/hostnamed.c
+++ b/src/hostname/hostnamed.c
@@ -335,7 +335,7 @@ static int context_write_data_machine_info(Context *c) {
                         continue;
                 }
 
-                t = strjoin(name[p], "=", c->data[p], NULL);
+                t = strjoin(name[p], "=", c->data[p]);
                 if (!t)
                         return -ENOMEM;
 
diff --git a/src/hwdb/hwdb.c b/src/hwdb/hwdb.c
index be4ef5f9e9..42e68e676a 100644
--- a/src/hwdb/hwdb.c
+++ b/src/hwdb/hwdb.c
@@ -669,7 +669,7 @@ static int hwdb_update(int argc, char *argv[], void *userdata) {
         log_debug("strings dedup'ed: %8zu bytes (%8zu)",
                   trie->strings->dedup_len, trie->strings->dedup_count);
 
-        hwdb_bin = strjoin(arg_root, "/", arg_hwdb_bin_dir, "/hwdb.bin", NULL);
+        hwdb_bin = strjoin(arg_root, "/", arg_hwdb_bin_dir, "/hwdb.bin");
         if (!hwdb_bin)
                 return -ENOMEM;
 
diff --git a/src/import/import-raw.c b/src/import/import-raw.c
index 29f3f896e5..808eae38f8 100644
--- a/src/import/import-raw.c
+++ b/src/import/import-raw.c
@@ -267,7 +267,7 @@ static int raw_import_open_disk(RawImport *i) {
         assert(!i->temp_path);
         assert(i->output_fd < 0);
 
-        i->final_path = strjoin(i->image_root, "/", i->local, ".raw", NULL);
+        i->final_path = strjoin(i->image_root, "/", i->local, ".raw");
         if (!i->final_path)
                 return log_oom();
 
diff --git a/src/import/import-tar.c b/src/import/import-tar.c
index 22f9b8c5ea..1c229ec82f 100644
--- a/src/import/import-tar.c
+++ b/src/import/import-tar.c
@@ -222,7 +222,7 @@ static int tar_import_fork_tar(TarImport *i) {
         assert(!i->temp_path);
         assert(i->tar_fd < 0);
 
-        i->final_path = strjoin(i->image_root, "/", i->local, NULL);
+        i->final_path = strjoin(i->image_root, "/", i->local);
         if (!i->final_path)
                 return log_oom();
 
diff --git a/src/journal-remote/journal-gatewayd.c b/src/journal-remote/journal-gatewayd.c
index 7325adee8f..f75a6f06d2 100644
--- a/src/journal-remote/journal-gatewayd.c
+++ b/src/journal-remote/journal-gatewayd.c
@@ -434,7 +434,7 @@ static int request_parse_arguments_iterator(
                 return MHD_YES;
         }
 
-        p = strjoin(key, "=", strempty(value), NULL);
+        p = strjoin(key, "=", strempty(value));
         if (!p) {
                 m->argument_parse_error = log_oom();
                 return MHD_NO;
diff --git a/src/journal-remote/journal-upload.c b/src/journal-remote/journal-upload.c
index 61190ff83c..42880cca76 100644
--- a/src/journal-remote/journal-upload.c
+++ b/src/journal-remote/journal-upload.c
@@ -438,7 +438,7 @@ static int setup_uploader(Uploader *u, const char *url, const char *state_file)
         }
 
         if (strchr(host, ':'))
-                u->url = strjoin(proto, url, "/upload", NULL);
+                u->url = strjoin(proto, url, "/upload");
         else {
                 char *t;
                 size_t x;
@@ -448,7 +448,7 @@ static int setup_uploader(Uploader *u, const char *url, const char *state_file)
                 while (x > 0 && t[x - 1] == '/')
                         t[x - 1] = '\0';
 
-                u->url = strjoin(proto, t, ":" STRINGIFY(DEFAULT_PORT), "/upload", NULL);
+                u->url = strjoin(proto, t, ":" STRINGIFY(DEFAULT_PORT), "/upload");
         }
         if (!u->url)
                 return log_oom();
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 7f997487b4..22cab67824 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -192,7 +192,7 @@ static int add_matches_for_device(sd_journal *j, const char *devpath) {
                         continue;
                 }
 
-                match = strjoin("_KERNEL_DEVICE=+", subsys, ":", sysname, NULL);
+                match = strjoin("_KERNEL_DEVICE=+", subsys, ":", sysname);
                 if (!match)
                         return log_oom();
 
diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
index 76c9baf6db..1ed223636c 100644
--- a/src/journal/journald-server.c
+++ b/src/journal/journald-server.c
@@ -733,7 +733,7 @@ static int get_invocation_id(const char *cgroup_root, const char *slice, const c
         if (!escaped)
                 return -ENOMEM;
 
-        p = strjoin(cgroup_root, "/", slice_path, "/", escaped, NULL);
+        p = strjoin(cgroup_root, "/", slice_path, "/", escaped);
         if (!p)
                 return -ENOMEM;
 
@@ -2053,8 +2053,8 @@ int server_init(Server *s) {
         s->runtime_storage.name = "Runtime journal";
         s->system_storage.name = "System journal";
 
-        s->runtime_storage.path = strjoin("/run/log/journal/", SERVER_MACHINE_ID(s), NULL);
-        s->system_storage.path  = strjoin("/var/log/journal/", SERVER_MACHINE_ID(s), NULL);
+        s->runtime_storage.path = strjoin("/run/log/journal/", SERVER_MACHINE_ID(s));
+        s->system_storage.path  = strjoin("/var/log/journal/", SERVER_MACHINE_ID(s));
         if (!s->runtime_storage.path || !s->system_storage.path)
                 return -ENOMEM;
 
diff --git a/src/journal/journald-wall.c b/src/journal/journald-wall.c
index 4d91fafffe..d857ff8d39 100644
--- a/src/journal/journald-wall.c
+++ b/src/journal/journald-wall.c
@@ -57,7 +57,7 @@ void server_forward_wall(
 
         } else if (identifier) {
 
-                l = l_buf = strjoin(identifier, ": ", message, NULL);
+                l = l_buf = strjoin(identifier, ": ", message);
                 if (!l_buf) {
                         log_oom();
                         return;
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index f2f8546086..47c77b1ba9 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -405,7 +405,7 @@ static char *match_make_string(Match *m) {
                         return mfree(p);
 
                 if (p) {
-                        k = strjoin(p, m->type == MATCH_OR_TERM ? " OR " : " AND ", t, NULL);
+                        k = strjoin(p, m->type == MATCH_OR_TERM ? " OR " : " AND ", t);
                         free(p);
                         free(t);
 
@@ -420,7 +420,7 @@ static char *match_make_string(Match *m) {
         }
 
         if (enclose) {
-                r = strjoin("(", p, ")", NULL);
+                r = strjoin("(", p, ")");
                 free(p);
                 return r;
         }
@@ -1416,7 +1416,7 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
          * and reenumerates directory contents */
 
         if (dirname)
-                path = strjoin(prefix, "/", dirname, NULL);
+                path = strjoin(prefix, "/", dirname);
         else
                 path = strdup(prefix);
         if (!path) {
diff --git a/src/libsystemd/sd-bus/bus-kernel.c b/src/libsystemd/sd-bus/bus-kernel.c
index 59398b841d..a3427ca33e 100644
--- a/src/libsystemd/sd-bus/bus-kernel.c
+++ b/src/libsystemd/sd-bus/bus-kernel.c
@@ -1649,7 +1649,7 @@ int bus_kernel_create_bus(const char *name, bool world, char **s) {
         if (s) {
                 char *p;
 
-                p = strjoin("/sys/fs/kdbus/", n->str, "/bus", NULL);
+                p = strjoin("/sys/fs/kdbus/", n->str, "/bus");
                 if (!p) {
                         safe_close(fd);
                         return -ENOMEM;
diff --git a/src/libsystemd/sd-bus/busctl-introspect.c b/src/libsystemd/sd-bus/busctl-introspect.c
index b09509f8e1..09cbd9ab44 100644
--- a/src/libsystemd/sd-bus/busctl-introspect.c
+++ b/src/libsystemd/sd-bus/busctl-introspect.c
@@ -285,7 +285,7 @@ static int parse_xml_node(Context *context, const char *prefix, unsigned n_depth
                                         if (endswith(prefix, "/"))
                                                 node_path = strappend(prefix, name);
                                         else
-                                                node_path = strjoin(prefix, "/", name, NULL);
+                                                node_path = strjoin(prefix, "/", name);
                                         if (!node_path)
                                                 return log_oom();
                                 }
diff --git a/src/libsystemd/sd-bus/busctl.c b/src/libsystemd/sd-bus/busctl.c
index 2c3f591053..9dd3828364 100644
--- a/src/libsystemd/sd-bus/busctl.c
+++ b/src/libsystemd/sd-bus/busctl.c
@@ -1102,7 +1102,7 @@ static int monitor(sd_bus *bus, char *argv[], int (*dump)(sd_bus_message *m, FIL
                         return -EINVAL;
                 }
 
-                m = strjoin("sender='", *i, "'", NULL);
+                m = strjoin("sender='", *i, "'");
                 if (!m)
                         return log_oom();
 
@@ -1111,7 +1111,7 @@ static int monitor(sd_bus *bus, char *argv[], int (*dump)(sd_bus_message *m, FIL
                         return bus_log_create_error(r);
 
                 free(m);
-                m = strjoin("destination='", *i, "'", NULL);
+                m = strjoin("destination='", *i, "'");
                 if (!m)
                         return log_oom();
 
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index d746348544..e809942278 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -1339,7 +1339,7 @@ int bus_set_address_system_remote(sd_bus *b, const char *host) {
                         return -ENOMEM;
         }
 
-        b->address = strjoin("unixexec:path=ssh,argv1=-xT,argv2=", e, ",argv3=systemd-stdio-bridge", c, NULL);
+        b->address = strjoin("unixexec:path=ssh,argv1=-xT,argv2=", e, ",argv3=systemd-stdio-bridge", c);
         if (!b->address)
                 return -ENOMEM;
 
@@ -1387,7 +1387,7 @@ int bus_set_address_system_machine(sd_bus *b, const char *machine) {
         if (!e)
                 return -ENOMEM;
 
-        b->address = strjoin("x-machine-kernel:machine=", e, ";x-machine-unix:machine=", e, NULL);
+        b->address = strjoin("x-machine-kernel:machine=", e, ";x-machine-unix:machine=", e);
         if (!b->address)
                 return -ENOMEM;
 
@@ -3470,7 +3470,7 @@ _public_ int sd_bus_path_encode(const char *prefix, const char *external_id, cha
         if (!e)
                 return -ENOMEM;
 
-        ret = strjoin(prefix, "/", e, NULL);
+        ret = strjoin(prefix, "/", e);
         if (!ret)
                 return -ENOMEM;
 
diff --git a/src/libsystemd/sd-bus/test-bus-objects.c b/src/libsystemd/sd-bus/test-bus-objects.c
index f11cafd888..233a21a523 100644
--- a/src/libsystemd/sd-bus/test-bus-objects.c
+++ b/src/libsystemd/sd-bus/test-bus-objects.c
@@ -49,7 +49,7 @@ static int something_handler(sd_bus_message *m, void *userdata, sd_bus_error *er
         r = sd_bus_message_read(m, "s", &s);
         assert_se(r > 0);
 
-        n = strjoin("<<<", s, ">>>", NULL);
+        n = strjoin("<<<", s, ">>>");
         assert_se(n);
 
         free(c->something);
diff --git a/src/libsystemd/sd-device/device-enumerator.c b/src/libsystemd/sd-device/device-enumerator.c
index 62d03ae00d..86f8935a14 100644
--- a/src/libsystemd/sd-device/device-enumerator.c
+++ b/src/libsystemd/sd-device/device-enumerator.c
@@ -773,7 +773,7 @@ static int parent_crawl_children(sd_device_enumerator *enumerator, const char *p
                 if (dent->d_type != DT_DIR)
                         continue;
 
-                child = strjoin(path, "/", dent->d_name, NULL);
+                child = strjoin(path, "/", dent->d_name);
                 if (!child)
                         return -ENOMEM;
 
diff --git a/src/libsystemd/sd-path/sd-path.c b/src/libsystemd/sd-path/sd-path.c
index b7aec1f20a..752c1ba56b 100644
--- a/src/libsystemd/sd-path/sd-path.c
+++ b/src/libsystemd/sd-path/sd-path.c
@@ -77,7 +77,7 @@ static int from_home_dir(const char *envname, const char *suffix, char **buffer,
         if (endswith(h, "/"))
                 cc = strappend(h, suffix);
         else
-                cc = strjoin(h, "/", suffix, NULL);
+                cc = strjoin(h, "/", suffix);
         if (!cc)
                 return -ENOMEM;
 
@@ -387,7 +387,7 @@ _public_ int sd_path_home(uint64_t type, const char *suffix, char **path) {
         if (endswith(ret, "/"))
                 cc = strappend(ret, suffix);
         else
-                cc = strjoin(ret, "/", suffix, NULL);
+                cc = strjoin(ret, "/", suffix);
 
         free(buffer);
 
@@ -455,7 +455,7 @@ static int search_from_environment(
                         if (endswith(e, "/"))
                                 h = strappend(e, home_suffix);
                         else
-                                h = strjoin(e, "/", home_suffix, NULL);
+                                h = strjoin(e, "/", home_suffix);
 
                         if (!h) {
                                 strv_free(l);
@@ -621,7 +621,7 @@ _public_ int sd_path_search(uint64_t type, const char *suffix, char ***paths) {
                 if (endswith(*i, "/"))
                         *j = strappend(*i, suffix);
                 else
-                        *j = strjoin(*i, "/", suffix, NULL);
+                        *j = strjoin(*i, "/", suffix);
 
                 if (!*j) {
                         strv_free(l);
diff --git a/src/locale/keymap-util.c b/src/locale/keymap-util.c
index a6bcd1ad54..da72bee4a9 100644
--- a/src/locale/keymap-util.c
+++ b/src/locale/keymap-util.c
@@ -519,7 +519,7 @@ int find_converted_keymap(const char *x11_layout, const char *x11_variant, char
         _cleanup_free_ char *n;
 
         if (x11_variant)
-                n = strjoin(x11_layout, "-", x11_variant, NULL);
+                n = strjoin(x11_layout, "-", x11_variant);
         else
                 n = strdup(x11_layout);
         if (!n)
@@ -529,8 +529,8 @@ int find_converted_keymap(const char *x11_layout, const char *x11_variant, char
                 _cleanup_free_ char *p = NULL, *pz = NULL;
                 bool uncompressed;
 
-                p = strjoin(dir, "xkb/", n, ".map", NULL);
-                pz = strjoin(dir, "xkb/", n, ".map.gz", NULL);
+                p = strjoin(dir, "xkb/", n, ".map");
+                pz = strjoin(dir, "xkb/", n, ".map.gz");
                 if (!p || !pz)
                         return -ENOMEM;
 
diff --git a/src/login/logind-inhibit.c b/src/login/logind-inhibit.c
index c93b24009b..a7e5c01ef3 100644
--- a/src/login/logind-inhibit.c
+++ b/src/login/logind-inhibit.c
@@ -294,7 +294,7 @@ int inhibitor_create_fifo(Inhibitor *i) {
                 if (r < 0)
                         return r;
 
-                i->fifo_path = strjoin("/run/systemd/inhibit/", i->id, ".ref", NULL);
+                i->fifo_path = strjoin("/run/systemd/inhibit/", i->id, ".ref");
                 if (!i->fifo_path)
                         return -ENOMEM;
 
diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index cbf035f706..e83c37a5ac 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -505,7 +505,7 @@ static int session_start_scope(Session *s) {
                 char *scope, *job = NULL;
                 const char *description;
 
-                scope = strjoin("session-", s->id, ".scope", NULL);
+                scope = strjoin("session-", s->id, ".scope");
                 if (!scope)
                         return log_oom();
 
diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
index 4f023640f6..b0f75b2a21 100644
--- a/src/login/pam_systemd.c
+++ b/src/login/pam_systemd.c
@@ -186,7 +186,7 @@ static int export_legacy_dbus_address(
          * daemons that spawn dbus-daemon, instead of forcing
          * DBUS_SESSION_BUS_ADDRESS= here. */
 
-        s = strjoin(runtime, "/bus", NULL);
+        s = strjoin(runtime, "/bus");
         if (!s)
                 goto error;
 
diff --git a/src/machine/machine.c b/src/machine/machine.c
index a02b9d7575..9e7b6cc03d 100644
--- a/src/machine/machine.c
+++ b/src/machine/machine.c
@@ -355,7 +355,7 @@ static int machine_start_scope(Machine *m, sd_bus_message *properties, sd_bus_er
                 if (!escaped)
                         return log_oom();
 
-                scope = strjoin("machine-", escaped, ".scope", NULL);
+                scope = strjoin("machine-", escaped, ".scope");
                 if (!scope)
                         return log_oom();
 
diff --git a/src/mount/mount-tool.c b/src/mount/mount-tool.c
index 80bba086e4..9d79e81918 100644
--- a/src/mount/mount-tool.c
+++ b/src/mount/mount-tool.c
@@ -697,7 +697,7 @@ static int acquire_mount_where(struct udev_device *d) {
                 if (!filename_is_valid(escaped))
                         return 0;
 
-                arg_mount_where = strjoin("/run/media/system/", escaped, NULL);
+                arg_mount_where = strjoin("/run/media/system/", escaped);
         } else
                 arg_mount_where = strdup(v);
 
@@ -721,7 +721,7 @@ static int acquire_description(struct udev_device *d) {
                 label = udev_device_get_property_value(d, "ID_PART_ENTRY_NUMBER");
 
         if (model && label)
-                arg_description = strjoin(model, " ", label, NULL);
+                arg_description = strjoin(model, " ", label);
         else if (label)
                 arg_description = strdup(label);
         else if (model)
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index 44dc9bfcf4..9a03f4b0bd 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -208,9 +208,9 @@ static int tmpfs_patch_options(
                 char *t;
 
                 if (options)
-                        t = strjoin(options, ",context=\"", selinux_apifs_context, "\"", NULL);
+                        t = strjoin(options, ",context=\"", selinux_apifs_context, "\"");
                 else
-                        t = strjoin("context=\"", selinux_apifs_context, "\"", NULL);
+                        t = strjoin("context=\"", selinux_apifs_context, "\"");
                 if (!t) {
                         free(buf);
                         return -ENOMEM;
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 2cbe563953..e013417cb4 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -2537,7 +2537,7 @@ static int determine_names(void) {
                  * search for a machine, but instead create a new one
                  * in /var/lib/machine. */
 
-                arg_directory = strjoin("/var/lib/machines/", arg_machine, NULL);
+                arg_directory = strjoin("/var/lib/machines/", arg_machine);
                 if (!arg_directory)
                         return log_oom();
         }
@@ -3380,7 +3380,7 @@ static int load_settings(void) {
         FOREACH_STRING(i, "/etc/systemd/nspawn", "/run/systemd/nspawn") {
                 _cleanup_free_ char *j = NULL;
 
-                j = strjoin(i, "/", fn, NULL);
+                j = strjoin(i, "/", fn);
                 if (!j)
                         return log_oom();
 
diff --git a/src/rc-local-generator/rc-local-generator.c b/src/rc-local-generator/rc-local-generator.c
index 618bbe428d..b704ca3b4b 100644
--- a/src/rc-local-generator/rc-local-generator.c
+++ b/src/rc-local-generator/rc-local-generator.c
@@ -45,11 +45,11 @@ static int add_symlink(const char *service, const char *where) {
         assert(service);
         assert(where);
 
-        from = strjoin(SYSTEM_DATA_UNIT_PATH, "/", service, NULL);
+        from = strjoin(SYSTEM_DATA_UNIT_PATH, "/", service);
         if (!from)
                 return log_oom();
 
-        to = strjoin(arg_dest, "/", where, ".wants/", service, NULL);
+        to = strjoin(arg_dest, "/", where, ".wants/", service);
         if (!to)
                 return log_oom();
 
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
index d4a267c89f..51327105d0 100644
--- a/src/resolve/resolved-dns-dnssec.c
+++ b/src/resolve/resolved-dns-dnssec.c
@@ -1303,7 +1303,7 @@ static int nsec3_hashed_domain_format(const uint8_t *hashed, size_t hashed_size,
         if (!l)
                 return -ENOMEM;
 
-        j = strjoin(l, ".", zone, NULL);
+        j = strjoin(l, ".", zone);
         if (!j)
                 return -ENOMEM;
 
diff --git a/src/resolve/resolved-dns-rr.c b/src/resolve/resolved-dns-rr.c
index 87e4abec6e..209d565033 100644
--- a/src/resolve/resolved-dns-rr.c
+++ b/src/resolve/resolved-dns-rr.c
@@ -792,7 +792,7 @@ static char *format_types(Bitmap *types) {
         if (!str)
                 return NULL;
 
-        return strjoin("( ", str, " )", NULL);
+        return strjoin("( ", str, " )");
 }
 
 static char *format_txt(DnsTxtItem *first) {
@@ -861,14 +861,14 @@ const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
         case DNS_TYPE_NS:
         case DNS_TYPE_CNAME:
         case DNS_TYPE_DNAME:
-                s = strjoin(k, " ", rr->ptr.name, NULL);
+                s = strjoin(k, " ", rr->ptr.name);
                 if (!s)
                         return NULL;
 
                 break;
 
         case DNS_TYPE_HINFO:
-                s = strjoin(k, " ", rr->hinfo.cpu, " ", rr->hinfo.os, NULL);
+                s = strjoin(k, " ", rr->hinfo.cpu, " ", rr->hinfo.os);
                 if (!s)
                         return NULL;
                 break;
@@ -879,7 +879,7 @@ const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
                 if (!t)
                         return NULL;
 
-                s = strjoin(k, " ", t, NULL);
+                s = strjoin(k, " ", t);
                 if (!s)
                         return NULL;
                 break;
@@ -891,7 +891,7 @@ const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
                 if (r < 0)
                         return NULL;
 
-                s = strjoin(k, " ", x, NULL);
+                s = strjoin(k, " ", x);
                 if (!s)
                         return NULL;
                 break;
@@ -902,7 +902,7 @@ const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
                 if (r < 0)
                         return NULL;
 
-                s = strjoin(k, " ", t, NULL);
+                s = strjoin(k, " ", t);
                 if (!s)
                         return NULL;
                 break;
@@ -942,7 +942,7 @@ const char *dns_resource_record_to_string(DnsResourceRecord *rr) {
                 if (!t)
                         return NULL;
 
-                s = strjoin(k, " ", t, NULL);
+                s = strjoin(k, " ", t);
                 if (!s)
                         return NULL;
                 break;
diff --git a/src/resolve/test-dnssec-complex.c b/src/resolve/test-dnssec-complex.c
index 58c089eb40..3d7074af11 100644
--- a/src/resolve/test-dnssec-complex.c
+++ b/src/resolve/test-dnssec-complex.c
@@ -42,7 +42,7 @@ static void prefix_random(const char *name, char **ret) {
                 char *x;
 
                 assert_se(asprintf(&b, "x%" PRIu64 "x", random_u64()));
-                x = strjoin(b, ".", name, NULL);
+                x = strjoin(b, ".", name);
                 assert_se(x);
 
                 free(m);
diff --git a/src/rfkill/rfkill.c b/src/rfkill/rfkill.c
index 0acdf229ed..c0f138b4f4 100644
--- a/src/rfkill/rfkill.c
+++ b/src/rfkill/rfkill.c
@@ -184,9 +184,9 @@ static int determine_state_file(
                 if (!escaped_path_id)
                         return log_oom();
 
-                state_file = strjoin("/var/lib/systemd/rfkill/", escaped_path_id, ":", type, NULL);
+                state_file = strjoin("/var/lib/systemd/rfkill/", escaped_path_id, ":", type);
         } else
-                state_file = strjoin("/var/lib/systemd/rfkill/", type, NULL);
+                state_file = strjoin("/var/lib/systemd/rfkill/", type);
 
         if (!state_file)
                 return log_oom();
diff --git a/src/run/run.c b/src/run/run.c
index 81b53fdfab..8f1cc9e2e3 100644
--- a/src/run/run.c
+++ b/src/run/run.c
@@ -747,7 +747,7 @@ static int make_unit_name(sd_bus *bus, UnitType t, char **ret) {
                 return -EINVAL;
         }
 
-        p = strjoin("run-u", id, ".", unit_type_to_string(t), NULL);
+        p = strjoin("run-u", id, ".", unit_type_to_string(t));
         if (!p)
                 return log_oom();
 
diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c
index 59a34a9d11..f1fbce9dca 100644
--- a/src/shared/base-filesystem.c
+++ b/src/shared/base-filesystem.c
@@ -82,7 +82,7 @@ int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
                                 if (table[i].exists) {
                                         _cleanup_free_ char *p = NULL;
 
-                                        p = strjoin(s, "/", table[i].exists, NULL);
+                                        p = strjoin(s, "/", table[i].exists);
                                         if (!p)
                                                 return log_oom();
 
diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index bb90c89cc2..3b8768b9a7 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -676,7 +676,7 @@ int bus_connect_user_systemd(sd_bus **_bus) {
         if (r < 0)
                 return r;
 
-        bus->address = strjoin("unix:path=", ee, "/systemd/private", NULL);
+        bus->address = strjoin("unix:path=", ee, "/systemd/private");
         if (!bus->address)
                 return -ENOMEM;
 
@@ -1460,7 +1460,7 @@ int bus_path_encode_unique(sd_bus *b, const char *prefix, const char *sender_id,
         if (!external_label)
                 return -ENOMEM;
 
-        p = strjoin(prefix, "/", sender_label, "/", external_label, NULL);
+        p = strjoin(prefix, "/", sender_label, "/", external_label);
         if (!p)
                 return -ENOMEM;
 
diff --git a/src/shared/cgroup-show.c b/src/shared/cgroup-show.c
index 3e451db715..4db6cefb6e 100644
--- a/src/shared/cgroup-show.c
+++ b/src/shared/cgroup-show.c
@@ -158,7 +158,7 @@ int show_cgroup_by_path(
         while ((r = cg_read_subgroup(d, &gn)) > 0) {
                 _cleanup_free_ char *k = NULL;
 
-                k = strjoin(fn, "/", gn, NULL);
+                k = strjoin(fn, "/", gn);
                 free(gn);
                 if (!k)
                         return -ENOMEM;
diff --git a/src/shared/conf-parser.c b/src/shared/conf-parser.c
index 2ec0155b71..19a371c865 100644
--- a/src/shared/conf-parser.c
+++ b/src/shared/conf-parser.c
@@ -101,7 +101,7 @@ int config_item_perf_lookup(
         else {
                 char *key;
 
-                key = strjoin(section, ".", lvalue, NULL);
+                key = strjoin(section, ".", lvalue);
                 if (!key)
                         return -ENOMEM;
 
diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 892f0aadf5..f9a6fd5f03 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -1076,7 +1076,7 @@ int dns_service_split(const char *joined, char **_name, char **_type, char **_do
                                 if (!name)
                                         return -ENOMEM;
 
-                                type = strjoin(b, ".", c, NULL);
+                                type = strjoin(b, ".", c);
                                 if (!type)
                                         return -ENOMEM;
 
@@ -1090,7 +1090,7 @@ int dns_service_split(const char *joined, char **_name, char **_type, char **_do
 
                         name = NULL;
 
-                        type = strjoin(a, ".", b, NULL);
+                        type = strjoin(a, ".", b);
                         if (!type)
                                 return -ENOMEM;
 
diff --git a/src/shared/dropin.c b/src/shared/dropin.c
index b9cd952ac8..2c1cd84df5 100644
--- a/src/shared/dropin.c
+++ b/src/shared/dropin.c
@@ -61,11 +61,11 @@ int drop_in_file(const char *dir, const char *unit, unsigned level,
         if (!filename_is_valid(b))
                 return -EINVAL;
 
-        p = strjoin(dir, "/", unit, ".d", NULL);
+        p = strjoin(dir, "/", unit, ".d");
         if (!p)
                 return -ENOMEM;
 
-        q = strjoin(p, "/", prefix, "-", b, ".conf", NULL);
+        q = strjoin(p, "/", prefix, "-", b, ".conf");
         if (!q) {
                 free(p);
                 return -ENOMEM;
@@ -163,7 +163,7 @@ static int iterate_dir(
                 if (hidden_or_backup_file(de->d_name))
                         continue;
 
-                f = strjoin(path, "/", de->d_name, NULL);
+                f = strjoin(path, "/", de->d_name);
                 if (!f)
                         return log_oom();
 
@@ -192,7 +192,7 @@ int unit_file_process_dir(
         assert(name);
         assert(suffix);
 
-        path = strjoin(unit_path, "/", name, suffix, NULL);
+        path = strjoin(unit_path, "/", name, suffix);
         if (!path)
                 return log_oom();
 
@@ -207,7 +207,7 @@ int unit_file_process_dir(
                 if (r < 0)
                         return log_error_errno(r, "Failed to generate template from unit name: %m");
 
-                p = strjoin(unit_path, "/", template, suffix, NULL);
+                p = strjoin(unit_path, "/", template, suffix);
                 if (!p)
                         return log_oom();
 
diff --git a/src/shared/fstab-util.c b/src/shared/fstab-util.c
index a4e0cd3267..f0bfb30bb5 100644
--- a/src/shared/fstab-util.c
+++ b/src/shared/fstab-util.c
@@ -241,7 +241,7 @@ static char *tag_to_udev_node(const char *tagvalue, const char *by) {
         if (encode_devnode_name(u, t, enc_len) < 0)
                 return NULL;
 
-        return strjoin("/dev/disk/by-", by, "/", t, NULL);
+        return strjoin("/dev/disk/by-", by, "/", t);
 }
 
 char *fstab_node_to_udev_node(const char *p) {
diff --git a/src/shared/install-printf.c b/src/shared/install-printf.c
index cbdf66827f..007c632f35 100644
--- a/src/shared/install-printf.c
+++ b/src/shared/install-printf.c
@@ -45,7 +45,7 @@ static int specifier_prefix_and_instance(char specifier, void *data, void *userd
         if (endswith(prefix, "@") && i->default_instance) {
                 char *ans;
 
-                ans = strjoin(prefix, i->default_instance, NULL);
+                ans = strjoin(prefix, i->default_instance);
                 if (!ans)
                         return -ENOMEM;
                 *ret = ans;
diff --git a/src/shared/install.c b/src/shared/install.c
index d33a658d0a..21cb57bc5a 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -1303,7 +1303,7 @@ static int unit_file_search(
         STRV_FOREACH(p, paths->search_path) {
                 _cleanup_free_ char *path = NULL;
 
-                path = strjoin(*p, "/", info->name, NULL);
+                path = strjoin(*p, "/", info->name);
                 if (!path)
                         return -ENOMEM;
 
@@ -1328,7 +1328,7 @@ static int unit_file_search(
                 STRV_FOREACH(p, paths->search_path) {
                         _cleanup_free_ char *path = NULL;
 
-                        path = strjoin(*p, "/", template, NULL);
+                        path = strjoin(*p, "/", template);
                         if (!path)
                                 return -ENOMEM;
 
@@ -1608,7 +1608,7 @@ static int install_info_symlink_wants(
                         continue;
                 }
 
-                path = strjoin(config_path, "/", dst, suffix, n, NULL);
+                path = strjoin(config_path, "/", dst, suffix, n);
                 if (!path)
                         return -ENOMEM;
 
@@ -1642,7 +1642,7 @@ static int install_info_symlink_link(
         if (r > 0)
                 return 0;
 
-        path = strjoin(config_path, "/", i->name, NULL);
+        path = strjoin(config_path, "/", i->name);
         if (!path)
                 return -ENOMEM;
 
@@ -2162,7 +2162,7 @@ int unit_file_revert(
                 STRV_FOREACH(j, fs) {
                         _cleanup_free_ char *t = NULL;
 
-                        t = strjoin(*i, "/", *j, NULL);
+                        t = strjoin(*i, "/", *j);
                         if (!t)
                                 return -ENOMEM;
 
diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c
index 060f8d50c7..6414ba5246 100644
--- a/src/shared/machine-image.c
+++ b/src/shared/machine-image.c
@@ -131,7 +131,7 @@ static int image_new(
                 return -ENOMEM;
 
         if (path)
-                i->path = strjoin(path, "/", filename, NULL);
+                i->path = strjoin(path, "/", filename);
         else
                 i->path = strdup(filename);
 
diff --git a/src/shared/path-lookup.c b/src/shared/path-lookup.c
index 862096ae7b..a23d09967e 100644
--- a/src/shared/path-lookup.c
+++ b/src/shared/path-lookup.c
@@ -70,7 +70,7 @@ static int user_config_dir(char **ret, const char *suffix) {
                 if (!home)
                         return -ENXIO;
 
-                j = strjoin(home, "/.config", suffix, NULL);
+                j = strjoin(home, "/.config", suffix);
         }
 
         if (!j)
@@ -102,7 +102,7 @@ static int user_data_dir(char **ret, const char *suffix) {
                         return -ENXIO;
 
 
-                j = strjoin(home, "/.local/share", suffix, NULL);
+                j = strjoin(home, "/.local/share", suffix);
         }
         if (!j)
                 return -ENOMEM;
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 129706d15f..2f20a250c2 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -518,7 +518,7 @@ static int output_units_list(const UnitInfo *unit_infos, unsigned c) {
                 }
 
                 if (u->machine) {
-                        j = strjoin(u->machine, ":", u->id, NULL);
+                        j = strjoin(u->machine, ":", u->id);
                         if (!j)
                                 return log_oom();
 
@@ -929,7 +929,7 @@ static int output_sockets_list(struct socket_info *socket_infos, unsigned cs) {
                         char **a;
 
                         if (s->machine) {
-                                j = strjoin(s->machine, ":", s->path, NULL);
+                                j = strjoin(s->machine, ":", s->path);
                                 if (!j)
                                         return log_oom();
                                 path = j;
@@ -1213,7 +1213,7 @@ static int output_timers_list(struct timer_info *timer_infos, unsigned n) {
                         format_timestamp_relative(trel2, sizeof(trel2), t->last_trigger);
 
                         if (t->machine) {
-                                j = strjoin(t->machine, ":", t->id, NULL);
+                                j = strjoin(t->machine, ":", t->id);
                                 if (!j)
                                         return log_oom();
                                 unit = j;
@@ -6418,12 +6418,12 @@ static int get_file_to_edit(
         assert(name);
         assert(ret_path);
 
-        path = strjoin(paths->persistent_config, "/", name, NULL);
+        path = strjoin(paths->persistent_config, "/", name);
         if (!path)
                 return log_oom();
 
         if (arg_runtime) {
-                run = strjoin(paths->runtime_config, "/", name, NULL);
+                run = strjoin(paths->runtime_config, "/", name);
                 if (!run)
                         return log_oom();
         }
diff --git a/src/sysv-generator/sysv-generator.c b/src/sysv-generator/sysv-generator.c
index c2c80175a2..921fd478d0 100644
--- a/src/sysv-generator/sysv-generator.c
+++ b/src/sysv-generator/sysv-generator.c
@@ -562,7 +562,7 @@ static int load_sysv(SysvStub *s) {
                                 char *d = NULL;
 
                                 if (chkconfig_description)
-                                        d = strjoin(chkconfig_description, " ", j, NULL);
+                                        d = strjoin(chkconfig_description, " ", j);
                                 else
                                         d = strdup(j);
                                 if (!d)
@@ -624,7 +624,7 @@ static int load_sysv(SysvStub *s) {
                                                 char *d = NULL;
 
                                                 if (long_description)
-                                                        d = strjoin(long_description, " ", t, NULL);
+                                                        d = strjoin(long_description, " ", t);
                                                 else
                                                         d = strdup(j);
                                                 if (!d)
@@ -803,7 +803,7 @@ static int enumerate_sysv(const LookupPaths *lp, Hashmap *all_services) {
                                 continue;
                         }
 
-                        fpath = strjoin(*path, "/", de->d_name, NULL);
+                        fpath = strjoin(*path, "/", de->d_name);
                         if (!fpath)
                                 return log_oom();
 
@@ -849,7 +849,7 @@ static int set_dependencies_from_rcnd(const LookupPaths *lp, Hashmap *all_servic
                         _cleanup_free_ char *path = NULL;
                         struct dirent *de;
 
-                        path = strjoin(*p, "/", rcnd_table[i].path, NULL);
+                        path = strjoin(*p, "/", rcnd_table[i].path);
                         if (!path) {
                                 r = log_oom();
                                 goto finish;
@@ -879,7 +879,7 @@ static int set_dependencies_from_rcnd(const LookupPaths *lp, Hashmap *all_servic
                                 if (a < 0 || b < 0)
                                         continue;
 
-                                fpath = strjoin(*p, "/", de->d_name, NULL);
+                                fpath = strjoin(*p, "/", de->d_name);
                                 if (!fpath) {
                                         r = log_oom();
                                         goto finish;
diff --git a/src/test/test-copy.c b/src/test/test-copy.c
index ed1ea51dbd..91e4e5b409 100644
--- a/src/test/test-copy.c
+++ b/src/test/test-copy.c
@@ -141,8 +141,8 @@ static void test_copy_tree(void) {
         STRV_FOREACH_PAIR(link, p, links) {
                 _cleanup_free_ char *target = NULL, *f, *l;
 
-                assert_se(f = strjoin(original_dir, *p, NULL));
-                assert_se(l = strjoin(copy_dir, *link, NULL));
+                assert_se(f = strjoin(original_dir, *p));
+                assert_se(l = strjoin(copy_dir, *link));
 
                 assert_se(readlink_and_canonicalize(l, &target) == 0);
                 assert_se(path_equal(f, target));
diff --git a/src/test/test-date.c b/src/test/test-date.c
index 7f497bb7d5..a8d3f1e083 100644
--- a/src/test/test-date.c
+++ b/src/test/test-date.c
@@ -60,7 +60,7 @@ static void test_one(const char *p) {
         _cleanup_free_ char *with_utc;
 
         log_info("Test: %s", p);
-        with_utc = strjoin(p, " UTC", NULL);
+        with_utc = strjoin(p, " UTC");
         test_should_pass(p);
         test_should_pass(with_utc);
 }
@@ -69,7 +69,7 @@ static void test_one_noutc(const char *p) {
         _cleanup_free_ char *with_utc;
 
         log_info("Test: %s", p);
-        with_utc = strjoin(p, " UTC", NULL);
+        with_utc = strjoin(p, " UTC");
         test_should_pass(p);
         test_should_fail(with_utc);
 }
diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c
index 92663ef66f..56316904a3 100644
--- a/src/test/test-fileio.c
+++ b/src/test/test-fileio.c
@@ -367,7 +367,7 @@ static void test_write_string_file_verify(void) {
         int r;
 
         assert_se(read_one_line_file("/proc/cmdline", &buf) >= 0);
-        assert_se((buf2 = strjoin(buf, "\n", NULL)));
+        assert_se((buf2 = strjoin(buf, "\n")));
 
         r = write_string_file("/proc/cmdline", buf, 0);
         assert_se(r == -EACCES || r == -EIO);
diff --git a/src/test/test-namespace.c b/src/test/test-namespace.c
index ff9f35cecd..de7be1f9cc 100644
--- a/src/test/test-namespace.c
+++ b/src/test/test-namespace.c
@@ -132,14 +132,14 @@ int main(int argc, char *argv[]) {
         assert_se(sd_id128_get_boot(&bid) >= 0);
         sd_id128_to_string(bid, boot_id);
 
-        x = strjoin("/tmp/systemd-private-", boot_id, "-abcd.service-", NULL);
-        y = strjoin("/var/tmp/systemd-private-", boot_id, "-abcd.service-", NULL);
+        x = strjoin("/tmp/systemd-private-", boot_id, "-abcd.service-");
+        y = strjoin("/var/tmp/systemd-private-", boot_id, "-abcd.service-");
         assert_se(x && y);
 
         test_tmpdir("abcd.service", x, y);
 
-        z = strjoin("/tmp/systemd-private-", boot_id, "-sys-devices-pci0000:00-0000:00:1a.0-usb3-3\\x2d1-3\\x2d1:1.0-bluetooth-hci0.device-", NULL);
-        zz = strjoin("/var/tmp/systemd-private-", boot_id, "-sys-devices-pci0000:00-0000:00:1a.0-usb3-3\\x2d1-3\\x2d1:1.0-bluetooth-hci0.device-", NULL);
+        z = strjoin("/tmp/systemd-private-", boot_id, "-sys-devices-pci0000:00-0000:00:1a.0-usb3-3\\x2d1-3\\x2d1:1.0-bluetooth-hci0.device-");
+        zz = strjoin("/var/tmp/systemd-private-", boot_id, "-sys-devices-pci0000:00-0000:00:1a.0-usb3-3\\x2d1-3\\x2d1:1.0-bluetooth-hci0.device-");
 
         assert_se(z && zz);
 
diff --git a/src/test/test-path.c b/src/test/test-path.c
index 4d3f0e9948..5e99d478ee 100644
--- a/src/test/test-path.c
+++ b/src/test/test-path.c
@@ -56,7 +56,7 @@ static int setup_test(Manager **m) {
         STRV_FOREACH(test_path, tests_path) {
                 _cleanup_free_ char *p = NULL;
 
-                p = strjoin("/tmp/test-path_", *test_path, NULL);
+                p = strjoin("/tmp/test-path_", *test_path);
                 assert_se(p);
 
                 (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL);
diff --git a/src/test/test-replace-var.c b/src/test/test-replace-var.c
index 297effce79..60e05d04c9 100644
--- a/src/test/test-replace-var.c
+++ b/src/test/test-replace-var.c
@@ -25,7 +25,7 @@
 #include "util.h"
 
 static char *lookup(const char *variable, void *userdata) {
-        return strjoin("<<<", variable, ">>>", NULL);
+        return strjoin("<<<", variable, ">>>");
 }
 
 int main(int argc, char *argv[]) {
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 954f4aa985..97a564d5a2 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -422,7 +422,7 @@ static int dir_cleanup(
                         continue;
                 }
 
-                sub_path = strjoin(p, "/", dent->d_name, NULL);
+                sub_path = strjoin(p, "/", dent->d_name);
                 if (!sub_path) {
                         r = log_oom();
                         goto finish;
@@ -1082,7 +1082,7 @@ static int item_do_children(Item *i, const char *path, action_t action) {
                 if (STR_IN_SET(de->d_name, ".", ".."))
                         continue;
 
-                p = strjoin(path, "/", de->d_name, NULL);
+                p = strjoin(path, "/", de->d_name);
                 if (!p)
                         return -ENOMEM;
 
diff --git a/src/udev/udev-builtin-hwdb.c b/src/udev/udev-builtin-hwdb.c
index f4a065a97d..acd1d1a6de 100644
--- a/src/udev/udev-builtin-hwdb.c
+++ b/src/udev/udev-builtin-hwdb.c
@@ -43,7 +43,7 @@ int udev_builtin_hwdb_lookup(struct udev_device *dev,
                 return -ENOENT;
 
         if (prefix) {
-                lookup = strjoin(prefix, modalias, NULL);
+                lookup = strjoin(prefix, modalias);
                 if (!lookup)
                         return -ENOMEM;
                 modalias = lookup;
diff --git a/src/udev/udevadm-hwdb.c b/src/udev/udevadm-hwdb.c
index 1bffe8e8ab..70a5fa4d7a 100644
--- a/src/udev/udevadm-hwdb.c
+++ b/src/udev/udevadm-hwdb.c
@@ -653,7 +653,7 @@ static int adm_hwdb(struct udev *udev, int argc, char *argv[]) {
                 log_debug("strings dedup'ed: %8zu bytes (%8zu)",
                           trie->strings->dedup_len, trie->strings->dedup_count);
 
-                hwdb_bin = strjoin(root, "/", hwdb_bin_dir, "/hwdb.bin", NULL);
+                hwdb_bin = strjoin(root, "/", hwdb_bin_dir, "/hwdb.bin");
                 if (!hwdb_bin) {
                         rc = EXIT_FAILURE;
                         goto out;