diff --git a/src/basic/calendarspec.c b/src/basic/calendarspec.c
index be7328af40..1fc9e9b154 100644
--- a/src/basic/calendarspec.c
+++ b/src/basic/calendarspec.c
@@ -421,11 +421,7 @@ static int parse_weekdays(const char **p, CalendarSpec *c) {
 
                         skip = strlen(day_nr[i].name);
 
-                        if ((*p)[skip] != '-' &&
-                            (*p)[skip] != '.' &&
-                            (*p)[skip] != ',' &&
-                            (*p)[skip] != ' ' &&
-                            (*p)[skip] != 0)
+                        if (!IN_SET((*p)[skip], 0, '-', '.', ',', ' '))
                                 return -EINVAL;
 
                         c->weekdays_bits |= 1 << day_nr[i].nr;
@@ -484,7 +480,7 @@ static int parse_weekdays(const char **p, CalendarSpec *c) {
                 }
 
                 /* Allow a trailing comma but not an open range */
-                if (**p == 0 || **p == ' ') {
+                if (IN_SET(**p, 0, ' ')) {
                         *p += strspn(*p, " ");
                         return l < 0 ? 0 : -EINVAL;
                 }
@@ -644,7 +640,7 @@ static int prepend_component(const char **p, bool usec, CalendarComponent **c) {
                         return -ERANGE;
         }
 
-        if (*e != 0 && *e != ' ' && *e != ',' && *e != '-' && *e != '~' && *e != ':')
+        if (!IN_SET(*e, 0, ' ', ',', '-', '~', ':'))
                 return -EINVAL;
 
         cc = new0(CalendarComponent, 1);
@@ -741,7 +737,7 @@ static int parse_date(const char **p, CalendarSpec *c) {
                 return r;
 
         /* Already the end? A ':' as separator? In that case this was a time, not a date */
-        if (*t == 0 || *t == ':') {
+        if (IN_SET(*t, 0, ':')) {
                 free_chain(first);
                 return 0;
         }
@@ -761,7 +757,7 @@ static int parse_date(const char **p, CalendarSpec *c) {
         }
 
         /* Got two parts, hence it's month and day */
-        if (*t == ' ' || *t == 0) {
+        if (IN_SET(*t, 0, ' ')) {
                 *p = t + strspn(t, " ");
                 c->month = first;
                 c->day = second;
@@ -789,7 +785,7 @@ static int parse_date(const char **p, CalendarSpec *c) {
         }
 
         /* Got three parts, hence it is year, month and day */
-        if (*t == ' ' || *t == 0) {
+        if (IN_SET(*t, 0, ' ')) {
                 *p = t + strspn(t, " ");
                 c->year = first;
                 c->month = second;
diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index f3f6a21576..d51c3efd22 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -374,7 +374,7 @@ int cg_kill_recursive(
 
         if (flags & CGROUP_REMOVE) {
                 r = cg_rmdir(controller, path);
-                if (r < 0 && ret >= 0 && r != -ENOENT && r != -EBUSY)
+                if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
                         return r;
         }
 
@@ -509,7 +509,7 @@ int cg_migrate_recursive(
 
         if (flags & CGROUP_REMOVE) {
                 r = cg_rmdir(cfrom, pfrom);
-                if (r < 0 && ret >= 0 && r != -ENOENT && r != -EBUSY)
+                if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
                         return r;
         }
 
@@ -1883,9 +1883,7 @@ char *cg_escape(const char *p) {
         /* The return value of this function (unlike cg_unescape())
          * needs free()! */
 
-        if (p[0] == 0 ||
-            p[0] == '_' ||
-            p[0] == '.' ||
+        if (IN_SET(p[0], 0, '_', '.') ||
             streq(p, "notify_on_release") ||
             streq(p, "release_agent") ||
             streq(p, "tasks") ||
@@ -1951,7 +1949,7 @@ bool cg_controller_is_valid(const char *p) {
         if (s)
                 p = s;
 
-        if (*p == 0 || *p == '_')
+        if (IN_SET(*p, 0, '_'))
                 return false;
 
         for (t = p; *t; t++)
@@ -2003,7 +2001,7 @@ int cg_slice_to_path(const char *unit, char **ret) {
                 char n[dash - p + sizeof(".slice")];
 
                 /* Don't allow trailing or double dashes */
-                if (dash[1] == 0 || dash[1] == '-')
+                if (IN_SET(dash[1], 0, '-'))
                         return -EINVAL;
 
                 strcpy(stpncpy(n, p, dash - p), ".slice");
diff --git a/src/basic/env-util.c b/src/basic/env-util.c
index d72940acb3..fa42edfa96 100644
--- a/src/basic/env-util.c
+++ b/src/basic/env-util.c
@@ -707,7 +707,7 @@ char **replace_env_argv(char **argv, char **env) {
         STRV_FOREACH(i, argv) {
 
                 /* If $FOO appears as single word, replace it by the split up variable */
-                if ((*i)[0] == '$' && (*i)[1] != '{' && (*i)[1] != '$') {
+                if ((*i)[0] == '$' && !IN_SET((*i)[1], '{', '$')) {
                         char *e;
                         char **w, **m = NULL;
                         unsigned q;
diff --git a/src/basic/escape.c b/src/basic/escape.c
index 22b8b04156..0a6122c64a 100644
--- a/src/basic/escape.c
+++ b/src/basic/escape.c
@@ -426,7 +426,7 @@ char *octescape(const char *s, size_t len) {
 
         for (f = s, t = r; f < s + len; f++) {
 
-                if (*f < ' ' || *f >= 127 || *f == '\\' || *f == '"') {
+                if (*f < ' ' || *f >= 127 || IN_SET(*f, '\\', '"')) {
                         *(t++) = '\\';
                         *(t++) = '0' + (*f >> 6);
                         *(t++) = '0' + ((*f >> 3) & 8);
diff --git a/src/basic/extract-word.c b/src/basic/extract-word.c
index 804f14c44c..f4ac526eb1 100644
--- a/src/basic/extract-word.c
+++ b/src/basic/extract-word.c
@@ -152,7 +152,7 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
                         for (;; (*p)++, c = **p) {
                                 if (c == 0)
                                         goto finish_force_terminate;
-                                else if ((c == '\'' || c == '"') && (flags & EXTRACT_QUOTES)) {
+                                else if (IN_SET(c, '\'', '"') && (flags & EXTRACT_QUOTES)) {
                                         quote = c;
                                         break;
                                 } else if (c == '\\' && !(flags & EXTRACT_RETAIN_ESCAPE)) {
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index af63171041..b90f343ed3 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -324,7 +324,7 @@ int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gi
                 mkdir_parents(path, 0755);
 
         fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY,
-                        (mode == 0 || mode == MODE_INVALID) ? 0644 : mode);
+                  IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
         if (fd < 0)
                 return -errno;
 
diff --git a/src/basic/hashmap.c b/src/basic/hashmap.c
index 6ef1b0ba35..a5ab4570fa 100644
--- a/src/basic/hashmap.c
+++ b/src/basic/hashmap.c
@@ -508,7 +508,7 @@ static void base_remove_entry(HashmapBase *h, unsigned idx) {
         /* Find the stop bucket ("right"). It is either free or has DIB == 0. */
         for (right = next_idx(h, left); ; right = next_idx(h, right)) {
                 raw_dib = dibs[right];
-                if (raw_dib == 0 || raw_dib == DIB_RAW_FREE)
+                if (IN_SET(raw_dib, 0, DIB_RAW_FREE))
                         break;
 
                 /* The buckets are not supposed to be all occupied and with DIB > 0.
diff --git a/src/basic/hostname-util.c b/src/basic/hostname-util.c
index b511a36301..ea9e77087f 100644
--- a/src/basic/hostname-util.c
+++ b/src/basic/hostname-util.c
@@ -90,9 +90,7 @@ static bool hostname_valid_char(char c) {
                 (c >= 'a' && c <= 'z') ||
                 (c >= 'A' && c <= 'Z') ||
                 (c >= '0' && c <= '9') ||
-                c == '-' ||
-                c == '_' ||
-                c == '.';
+                IN_SET(c, '-', '_', '.');
 }
 
 /**
@@ -235,7 +233,7 @@ int read_hostname_config(const char *path, char **hostname) {
         /* may have comments, ignore them */
         FOREACH_LINE(l, f, return -errno) {
                 truncate_nl(l);
-                if (l[0] != '\0' && l[0] != '#') {
+                if (!IN_SET(l[0], '\0', '#')) {
                         /* found line with value */
                         name = hostname_cleanup(l);
                         name = strdup(name);
diff --git a/src/basic/mount-util.c b/src/basic/mount-util.c
index 8c1d2bc9c9..65b488351e 100644
--- a/src/basic/mount-util.c
+++ b/src/basic/mount-util.c
@@ -472,14 +472,14 @@ int bind_remount_recursive_with_mountinfo(const char *prefix, bool ro, char **bl
                 while ((x = set_steal_first(todo))) {
 
                         r = set_consume(done, x);
-                        if (r == -EEXIST || r == 0)
+                        if (IN_SET(r, 0, -EEXIST))
                                 continue;
                         if (r < 0)
                                 return r;
 
                         /* Deal with mount points that are obstructed by a later mount */
                         r = path_is_mount_point(x, NULL, 0);
-                        if (r == -ENOENT || r == 0)
+                        if (IN_SET(r, 0, -ENOENT))
                                 continue;
                         if (r < 0)
                                 return r;
diff --git a/src/basic/parse-util.c b/src/basic/parse-util.c
index 89bb667c5f..4ae07b0a8e 100644
--- a/src/basic/parse-util.c
+++ b/src/basic/parse-util.c
@@ -152,7 +152,7 @@ int parse_size(const char *t, uint64_t base, uint64_t *size) {
         unsigned n_entries, start_pos = 0;
 
         assert(t);
-        assert(base == 1000 || base == 1024);
+        assert(IN_SET(base, 1000, 1024));
         assert(size);
 
         if (base == 1000) {
diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index ab661a8f16..a1b50b6c79 100644
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -392,7 +392,7 @@ int is_kernel_thread(pid_t pid) {
         bool eof;
         FILE *f;
 
-        if (pid == 0 || pid == 1 || pid == getpid_cached()) /* pid 1, and we ourselves certainly aren't a kernel thread */
+        if (IN_SET(pid, 0, 1) || pid == getpid_cached()) /* pid 1, and we ourselves certainly aren't a kernel thread */
                 return 0;
 
         assert(pid > 1);
@@ -817,7 +817,7 @@ bool pid_is_alive(pid_t pid) {
                 return true;
 
         r = get_process_state(pid);
-        if (r == -ESRCH || r == 'Z')
+        if (IN_SET(r, -ESRCH, 'Z'))
                 return false;
 
         return true;
diff --git a/src/basic/rm-rf.c b/src/basic/rm-rf.c
index 77fe88e42c..0bbafb4cd7 100644
--- a/src/basic/rm-rf.c
+++ b/src/basic/rm-rf.c
@@ -132,7 +132,7 @@ int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev) {
 
                                 r = btrfs_subvol_remove_fd(fd, de->d_name, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA);
                                 if (r < 0) {
-                                        if (r != -ENOTTY && r != -EINVAL) {
+                                        if (!IN_SET(r, -ENOTTY, -EINVAL)) {
                                                 if (ret == 0)
                                                         ret = r;
 
@@ -193,7 +193,7 @@ int rm_rf(const char *path, RemoveFlags flags) {
                 if (r >= 0)
                         return r;
 
-                if (r != -ENOTTY && r != -EINVAL && r != -ENOTDIR)
+                if (!IN_SET(r, -ENOTTY, -EINVAL, -ENOTDIR))
                         return r;
 
                 /* Not btrfs or not a subvolume */
diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index e8d39674cc..5942b2df9b 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -892,7 +892,7 @@ bool ifname_valid(const char *p) {
                 if ((unsigned char) *p <= 32U)
                         return false;
 
-                if (*p == ':' || *p == '/')
+                if (IN_SET(*p, ':', '/'))
                         return false;
 
                 numeric = numeric && (*p >= '0' && *p <= '9');
diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 5808b1280e..2eed99d9c0 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -673,7 +673,7 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz) {
                 case STATE_BRACKET:
 
                         if (i >= *ibuf + isz || /* EOT */
-                            (!(*i >= '0' && *i <= '9') && *i != ';' && *i != 'm')) {
+                            (!(*i >= '0' && *i <= '9') && !IN_SET(*i, ';', 'm'))) {
                                 fputc_unlocked('\x1B', f);
                                 fputc_unlocked('[', f);
                                 state = STATE_OTHER;
diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index f67467c5bd..46ec722989 100644
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -1308,7 +1308,7 @@ bool timezone_is_valid(const char *name) {
                 if (!(*p >= '0' && *p <= '9') &&
                     !(*p >= 'a' && *p <= 'z') &&
                     !(*p >= 'A' && *p <= 'Z') &&
-                    !(*p == '-' || *p == '_' || *p == '+' || *p == '/'))
+                    !IN_SET(*p, '-', '_', '+', '/'))
                         return false;
 
                 if (*p == '/') {
diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c
index 5e3f307dcd..f9c034c94b 100644
--- a/src/basic/unit-name.c
+++ b/src/basic/unit-name.c
@@ -305,7 +305,7 @@ static char *do_escape(const char *f, char *t) {
         for (; *f; f++) {
                 if (*f == '/')
                         *(t++) = '-';
-                else if (*f == '-' || *f == '\\' || !strchr(VALID_CHARS, *f))
+                else if (IN_SET(*f, '-', '\\') || !strchr(VALID_CHARS, *f))
                         t = do_escape_char(*f, t);
                 else
                         *(t++) = *f;
diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index c619dad527..a691a0d3fc 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -543,8 +543,7 @@ bool valid_user_group_name(const char *u) {
                 if (!(*i >= 'a' && *i <= 'z') &&
                     !(*i >= 'A' && *i <= 'Z') &&
                     !(*i >= '0' && *i <= '9') &&
-                    *i != '_' &&
-                    *i != '-')
+                    !IN_SET(*i, '_', '-'))
                         return false;
         }
 
diff --git a/src/basic/utf8.c b/src/basic/utf8.c
index 6eae2b983d..7a52fac621 100644
--- a/src/basic/utf8.c
+++ b/src/basic/utf8.c
@@ -73,7 +73,7 @@ static bool unichar_is_control(char32_t ch) {
           '\t' is in C0 range, but more or less harmless and commonly used.
         */
 
-        return (ch < ' ' && ch != '\t' && ch != '\n') ||
+        return (ch < ' ' && !IN_SET(ch, '\t', '\n')) ||
                 (0x7F <= ch && ch <= 0x9F);
 }
 
diff --git a/src/basic/xattr-util.c b/src/basic/xattr-util.c
index 8256899eda..e086376d7c 100644
--- a/src/basic/xattr-util.c
+++ b/src/basic/xattr-util.c
@@ -129,7 +129,7 @@ static int parse_crtime(le64_t le, usec_t *usec) {
         assert(usec);
 
         u = le64toh(le);
-        if (u == 0 || u == (uint64_t) -1)
+        if (IN_SET(u, 0, (uint64_t) -1))
                 return -EIO;
 
         *usec = (usec_t) u;
diff --git a/src/basic/xml.c b/src/basic/xml.c
index 1dbeac7324..a4337f4865 100644
--- a/src/basic/xml.c
+++ b/src/basic/xml.c
@@ -208,7 +208,7 @@ int xml_tokenize(const char **p, char **name, void **state, unsigned *line) {
                         if (*c == '=') {
                                 c++;
 
-                                if (*c == '\'' || *c == '\"') {
+                                if (IN_SET(*c, '\'', '\"')) {
                                         /* Tag with a quoted value */
 
                                         e = strchr(c+1, *c);
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 85f549c4c4..e9f9447118 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -355,7 +355,7 @@ static int whitelist_major(const char *path, const char *name, char type, const
 
         assert(path);
         assert(acc);
-        assert(type == 'b' || type == 'c');
+        assert(IN_SET(type, 'b', 'c'));
 
         f = fopen("/proc/devices", "re");
         if (!f)
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 791649e5b5..a9a68826b4 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -917,7 +917,7 @@ static int append_process(sd_bus_message *reply, const char *p, pid_t pid, Set *
         assert(pid > 0);
 
         r = set_put(pids, PID_TO_PTR(pid));
-        if (r == -EEXIST || r == 0)
+        if (IN_SET(r, 0, -EEXIST))
                 return 0;
         if (r < 0)
                 return r;
diff --git a/src/core/execute.c b/src/core/execute.c
index e1c2a57cc6..3e264d1dd4 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -2062,7 +2062,7 @@ static int setup_smack(
                 _cleanup_free_ char *exec_label = NULL;
 
                 r = mac_smack_read(command->path, SMACK_ATTR_EXEC, &exec_label);
-                if (r < 0 && r != -ENODATA && r != -EOPNOTSUPP)
+                if (r < 0 && !IN_SET(r, -ENODATA, -EOPNOTSUPP))
                         return r;
 
                 r = mac_smack_apply_pid(0, exec_label ? : SMACK_DEFAULT_PROCESS_LABEL);
diff --git a/src/core/job.c b/src/core/job.c
index f962881a12..fb57f193fd 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -681,7 +681,7 @@ _pure_ static const char *job_get_status_message_format(Unit *u, JobType t, JobR
         /* Return generic strings */
         if (t == JOB_START)
                 return generic_finished_start_job[result];
-        else if (t == JOB_STOP || t == JOB_RESTART)
+        else if (IN_SET(t, JOB_STOP, JOB_RESTART))
                 return generic_finished_stop_job[result];
         else if (t == JOB_RELOAD)
                 return generic_finished_reload_job[result];
diff --git a/src/core/main.c b/src/core/main.c
index 2dfd48005b..962ee28ae5 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1672,7 +1672,7 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
-        if (arg_action == ACTION_TEST || arg_action == ACTION_HELP) {
+        if (IN_SET(arg_action, ACTION_TEST, ACTION_HELP)) {
                 pager_open(arg_no_pager, false);
                 skip_setup = true;
         }
@@ -1696,7 +1696,7 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
-        assert_se(arg_action == ACTION_RUN || arg_action == ACTION_TEST);
+        assert_se(IN_SET(arg_action, ACTION_RUN, ACTION_TEST));
 
         /* Close logging fds, in order not to confuse fdset below */
         log_close();
@@ -1892,7 +1892,7 @@ int main(int argc, char *argv[]) {
                 r = manager_load_unit(m, arg_default_unit, NULL, &error, &target);
                 if (r < 0)
                         log_error("Failed to load default target: %s", bus_error_message(&error, r));
-                else if (target->load_state == UNIT_ERROR || target->load_state == UNIT_NOT_FOUND)
+                else if (IN_SET(target->load_state, UNIT_ERROR, UNIT_NOT_FOUND))
                         log_error_errno(target->load_error, "Failed to load default target: %m");
                 else if (target->load_state == UNIT_MASKED)
                         log_error("Default target masked.");
@@ -1905,7 +1905,7 @@ int main(int argc, char *argv[]) {
                                 log_emergency("Failed to load rescue target: %s", bus_error_message(&error, r));
                                 error_message = "Failed to load rescue target";
                                 goto finish;
-                        } else if (target->load_state == UNIT_ERROR || target->load_state == UNIT_NOT_FOUND) {
+                        } else if (IN_SET(target->load_state, UNIT_ERROR, UNIT_NOT_FOUND)) {
                                 log_emergency_errno(target->load_error, "Failed to load rescue target: %m");
                                 error_message = "Failed to load rescue target";
                                 goto finish;
diff --git a/src/core/manager.c b/src/core/manager.c
index 5c127e0848..02bc8065d8 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -396,7 +396,7 @@ static int enable_special_signals(Manager *m) {
         /* Enable that we get SIGINT on control-alt-del. In containers
          * this will fail with EPERM (older) or EINVAL (newer), so
          * ignore that. */
-        if (reboot(RB_DISABLE_CAD) < 0 && errno != EPERM && errno != EINVAL)
+        if (reboot(RB_DISABLE_CAD) < 0 && !IN_SET(errno, EPERM, EINVAL))
                 log_warning_errno(errno, "Failed to enable ctrl-alt-del handling: %m");
 
         fd = open_terminal("/dev/tty0", O_RDWR|O_NOCTTY|O_CLOEXEC);
@@ -985,10 +985,8 @@ static void unit_gc_sweep(Unit *u, unsigned gc_marker) {
 
         assert(u);
 
-        if (u->gc_marker == gc_marker + GC_OFFSET_GOOD ||
-            u->gc_marker == gc_marker + GC_OFFSET_BAD ||
-            u->gc_marker == gc_marker + GC_OFFSET_UNSURE ||
-            u->gc_marker == gc_marker + GC_OFFSET_IN_PATH)
+        if (IN_SET(u->gc_marker - gc_marker,
+                   GC_OFFSET_GOOD, GC_OFFSET_BAD, GC_OFFSET_UNSURE, GC_OFFSET_IN_PATH))
                 return;
 
         if (u->in_cleanup_queue)
@@ -1055,8 +1053,8 @@ static unsigned manager_dispatch_gc_unit_queue(Manager *m) {
 
                 n++;
 
-                if (u->gc_marker == gc_marker + GC_OFFSET_BAD ||
-                    u->gc_marker == gc_marker + GC_OFFSET_UNSURE) {
+                if (IN_SET(u->gc_marker - gc_marker,
+                           GC_OFFSET_BAD, GC_OFFSET_UNSURE)) {
                         if (u->id)
                                 log_unit_debug(u, "Collecting.");
                         u->gc_marker = gc_marker + GC_OFFSET_BAD;
@@ -3747,7 +3745,7 @@ int manager_dispatch_user_lookup_fd(sd_event_source *source, int fd, uint32_t re
 
         l = recv(fd, &buffer, sizeof(buffer), MSG_DONTWAIT);
         if (l < 0) {
-                if (errno == EINTR || errno == EAGAIN)
+                if (IN_SET(errno, EINTR, EAGAIN))
                         return 0;
 
                 return log_error_errno(errno, "Failed to read from user lookup fd: %m");
diff --git a/src/core/service.c b/src/core/service.c
index e990d47797..915943aff3 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -218,7 +218,7 @@ static void service_start_watchdog(Service *s) {
         assert(s);
 
         watchdog_usec = service_get_watchdog_usec(s);
-        if (watchdog_usec == 0 || watchdog_usec == USEC_INFINITY)
+        if (IN_SET(watchdog_usec, 0, USEC_INFINITY))
                 return;
 
         if (s->watchdog_event_source) {
diff --git a/src/core/socket.c b/src/core/socket.c
index 06ceb46eca..c0f4030302 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1444,7 +1444,7 @@ static int socket_determine_selinux_label(Socket *s, char **ret) {
                         goto no_label;
 
                 r = mac_selinux_get_create_label_from_exe(c->path, ret);
-                if (r == -EPERM || r == -EOPNOTSUPP)
+                if (IN_SET(r, -EPERM, -EOPNOTSUPP))
                         goto no_label;
         }
 
diff --git a/src/core/unit.c b/src/core/unit.c
index 2b7c7738fe..357306dce8 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3647,7 +3647,7 @@ int unit_kill_common(
                         return -ENOMEM;
 
                 q = cg_kill_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, signo, 0, pid_set, NULL, NULL);
-                if (q < 0 && q != -EAGAIN && q != -ESRCH && q != -ENOENT)
+                if (q < 0 && !IN_SET(q, -EAGAIN, -ESRCH, -ENOENT))
                         r = q;
                 else
                         killed = true;
@@ -4179,7 +4179,7 @@ int unit_kill_context(
                                       pid_set,
                                       log_func, u);
                 if (r < 0) {
-                        if (r != -EAGAIN && r != -ESRCH && r != -ENOENT)
+                        if (!IN_SET(r, -EAGAIN, -ESRCH, -ENOENT))
                                 log_unit_warning_errno(u, r, "Failed to kill control group %s, ignoring: %m", u->cgroup_path);
 
                 } else if (r > 0) {
diff --git a/src/cryptsetup/cryptsetup-generator.c b/src/cryptsetup/cryptsetup-generator.c
index f882a4f80e..3752ca2ef2 100644
--- a/src/cryptsetup/cryptsetup-generator.c
+++ b/src/cryptsetup/cryptsetup-generator.c
@@ -378,7 +378,7 @@ static int add_crypttab_devices(void) {
                 crypttab_line++;
 
                 l = strstrip(line);
-                if (*l == '#' || *l == 0)
+                if (IN_SET(*l, 0, '#'))
                         continue;
 
                 k = sscanf(l, "%ms %ms %ms %ms", &name, &device, &keyfile, &options);
diff --git a/src/fsck/fsck.c b/src/fsck/fsck.c
index 434321f806..bcb07fe976 100644
--- a/src/fsck/fsck.c
+++ b/src/fsck/fsck.c
@@ -462,7 +462,7 @@ int main(int argc, char *argv[]) {
 
         if (status.si_code != CLD_EXITED || (status.si_status & ~1)) {
 
-                if (status.si_code == CLD_KILLED || status.si_code == CLD_DUMPED)
+                if (IN_SET(status.si_code, CLD_KILLED, CLD_DUMPED))
                         log_error("fsck terminated by signal %s.", signal_to_string(status.si_status));
                 else if (status.si_code == CLD_EXITED)
                         log_error("fsck failed with error code %i.", status.si_status);
diff --git a/src/import/import-common.c b/src/import/import-common.c
index 81209cdaf6..ae71682988 100644
--- a/src/import/import-common.c
+++ b/src/import/import-common.c
@@ -37,7 +37,7 @@ int import_make_read_only_fd(int fd) {
         /* First, let's make this a read-only subvolume if it refers
          * to a subvolume */
         r = btrfs_subvol_set_read_only_fd(fd, true);
-        if (r == -ENOTTY || r == -ENOTDIR || r == -EINVAL) {
+        if (IN_SET(r, -ENOTTY, -ENOTDIR, -EINVAL)) {
                 struct stat st;
 
                 /* This doesn't refer to a subvolume, or the file
diff --git a/src/import/importd.c b/src/import/importd.c
index e20aca0d9e..9b3fd06b52 100644
--- a/src/import/importd.c
+++ b/src/import/importd.c
@@ -250,7 +250,7 @@ static void transfer_send_logs(Transfer *t, bool flush) {
                 n = strndup(t->log_message, e - t->log_message);
 
                 /* Skip over NUL and newlines */
-                while ((e < t->log_message + t->log_message_size) && (*e == 0 || *e == '\n'))
+                while ((e < t->log_message + t->log_message_size) && IN_SET(*e, 0, '\n'))
                         e++;
 
                 memmove(t->log_message, e, t->log_message + sizeof(t->log_message) - e);
diff --git a/src/import/pull-job.c b/src/import/pull-job.c
index 3e20905d79..995a652ec3 100644
--- a/src/import/pull-job.c
+++ b/src/import/pull-job.c
@@ -108,7 +108,7 @@ void pull_job_curl_on_finished(CurlGlue *g, CURL *curl, CURLcode result) {
         if (curl_easy_getinfo(curl, CURLINFO_PRIVATE, (char **)&j) != CURLE_OK)
                 return;
 
-        if (!j || j->state == PULL_JOB_DONE || j->state == PULL_JOB_FAILED)
+        if (!j || IN_SET(j->state, PULL_JOB_DONE, PULL_JOB_FAILED))
                 return;
 
         if (result != CURLE_OK) {
diff --git a/src/import/qcow2-util.c b/src/import/qcow2-util.c
index ee2121cc36..00734865b2 100644
--- a/src/import/qcow2-util.c
+++ b/src/import/qcow2-util.c
@@ -213,8 +213,7 @@ static int verify_header(const Header *header) {
         if (HEADER_MAGIC(header) != QCOW2_MAGIC)
                 return -EBADMSG;
 
-        if (HEADER_VERSION(header) != 2 &&
-            HEADER_VERSION(header) != 3)
+        if (!IN_SET(HEADER_VERSION(header), 2, 3))
                 return -EOPNOTSUPP;
 
         if (HEADER_CRYPT_METHOD(header) != 0)
diff --git a/src/journal/catalog.c b/src/journal/catalog.c
index f42be0adf9..bf92da9f90 100644
--- a/src/journal/catalog.c
+++ b/src/journal/catalog.c
@@ -216,7 +216,7 @@ int catalog_file_lang(const char* filename, char **lang) {
                 return 0;
 
         beg = end - 1;
-        while (beg > filename && *beg != '.' && *beg != '/' && end - beg < 32)
+        while (beg > filename && !IN_SET(*beg, '.', '/') && end - beg < 32)
                 beg--;
 
         if (*beg != '.' || end <= beg + 1)
@@ -312,7 +312,7 @@ int catalog_import_file(Hashmap *h, const char *path) {
                     line[0] == '-' &&
                     line[1] == '-' &&
                     line[2] == ' ' &&
-                    (line[2+1+32] == ' ' || line[2+1+32] == '\0')) {
+                    IN_SET(line[2+1+32], ' ', '\0')) {
 
                         bool with_language;
                         sd_id128_t jd;
diff --git a/src/journal/compress.c b/src/journal/compress.c
index 818a720ba8..7ad7dd519d 100644
--- a/src/journal/compress.c
+++ b/src/journal/compress.c
@@ -280,7 +280,7 @@ int decompress_startswith_xz(const void *src, uint64_t src_size,
         for (;;) {
                 ret = lzma_code(&s, LZMA_FINISH);
 
-                if (ret != LZMA_STREAM_END && ret != LZMA_OK)
+                if (!IN_SET(ret, LZMA_OK, LZMA_STREAM_END))
                         return -EBADMSG;
 
                 if (*buffer_size - s.avail_out >= prefix_len + 1)
@@ -417,7 +417,7 @@ int compress_stream_xz(int fdf, int fdt, uint64_t max_bytes) {
                 }
 
                 ret = lzma_code(&s, action);
-                if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
+                if (!IN_SET(ret, LZMA_OK, LZMA_STREAM_END)) {
                         log_error("Compression failed: code %u", ret);
                         return -EBADMSG;
                 }
@@ -579,7 +579,7 @@ int decompress_stream_xz(int fdf, int fdt, uint64_t max_bytes) {
                 }
 
                 ret = lzma_code(&s, action);
-                if (ret != LZMA_OK && ret != LZMA_STREAM_END) {
+                if (!IN_SET(ret, LZMA_OK, LZMA_STREAM_END)) {
                         log_debug("Decompression failed: code %u", ret);
                         return -EBADMSG;
                 }
diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 3dcfb0e97a..641b9afa34 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -248,7 +248,7 @@ static int parse_boot_descriptor(const char *x, sd_id128_t *boot_id, int *offset
                 if (r >= 0)
                         x += 32;
 
-                if (*x != '-' && *x != '+' && *x != 0)
+                if (!IN_SET(*x, 0, '-', '+'))
                         return -EINVAL;
 
                 if (*x != 0) {
@@ -1572,7 +1572,7 @@ static int setup_keys(void) {
         struct stat st;
 
         r = stat("/var/log/journal", &st);
-        if (r < 0 && errno != ENOENT && errno != ENOTDIR)
+        if (r < 0 && !IN_SET(errno, ENOENT, ENOTDIR))
                 return log_error_errno(errno, "stat(\"%s\") failed: %m", "/var/log/journal");
 
         if (r < 0 || !S_ISDIR(st.st_mode)) {
diff --git a/src/journal/journald-audit.c b/src/journal/journald-audit.c
index b20e7ab129..3334418f33 100644
--- a/src/journal/journald-audit.c
+++ b/src/journal/journald-audit.c
@@ -49,7 +49,7 @@ static int map_simple_field(const char *field, const char **p, struct iovec **io
                 return -ENOMEM;
 
         memcpy(c, field, l);
-        for (e = *p; *e != ' ' && *e != 0; e++) {
+        for (e = *p; !IN_SET(*e, 0, ' '); e++) {
                 if (!GREEDY_REALLOC(c, allocated, l+2))
                         return -ENOMEM;
 
@@ -110,7 +110,7 @@ static int map_string_field_internal(const char *field, const char **p, struct i
                         return -ENOMEM;
 
                 memcpy(c, field, l);
-                for (e = *p; *e != ' ' && *e != 0; e += 2) {
+                for (e = *p; !IN_SET(*e, 0, ' '); e += 2) {
                         int a, b;
                         uint8_t x;
 
@@ -167,7 +167,7 @@ static int map_generic_field(const char *prefix, const char **p, struct iovec **
 
         for (e = *p; e < *p + 16; e++) {
 
-                if (*e == 0 || *e == ' ')
+                if (IN_SET(*e, 0, ' '))
                         return 0;
 
                 if (*e == '=')
@@ -176,7 +176,7 @@ static int map_generic_field(const char *prefix, const char **p, struct iovec **
                 if (!((*e >= 'a' && *e <= 'z') ||
                       (*e >= 'A' && *e <= 'Z') ||
                       (*e >= '0' && *e <= '9') ||
-                      *e == '_' || *e == '-'))
+                      IN_SET(*e, '_', '-')))
                         return 0;
         }
 
diff --git a/src/journal/journald-native.c b/src/journal/journald-native.c
index 554f91460d..8a2962335c 100644
--- a/src/journal/journald-native.c
+++ b/src/journal/journald-native.c
@@ -183,7 +183,7 @@ static int server_process_entry(
                         break;
                 }
 
-                if (*p == '.' || *p == '#') {
+                if (IN_SET(*p, '.', '#')) {
                         /* Ignore control commands for now, and
                          * comments too. */
                         *remaining -= (e - p) + 1;
diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
index de643c9149..463a8dd97c 100644
--- a/src/journal/journald-server.c
+++ b/src/journal/journald-server.c
@@ -317,7 +317,7 @@ static int system_journal_open(Server *s, bool flush_requested) {
                         (void) cache_space_refresh(s, &s->system_storage);
                         patch_min_use(&s->system_storage);
                 } else if (r < 0) {
-                        if (r != -ENOENT && r != -EROFS)
+                        if (!IN_SET(r, -ENOENT, -EROFS))
                                 log_warning_errno(r, "Failed to open system journal: %m");
 
                         r = 0;
@@ -1620,7 +1620,7 @@ static int server_connect_notify(Server *s) {
         if (!e)
                 return 0;
 
-        if ((e[0] != '@' && e[0] != '/') || e[1] == 0) {
+        if (!IN_SET(e[0], '@', '/') || e[1] == 0) {
                 log_error("NOTIFY_SOCKET set to an invalid value: %s", e);
                 return -EINVAL;
         }
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index fb7269e510..a47bd122b9 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -450,7 +450,7 @@ _pure_ static int compare_with_location(JournalFile *f, Location *l) {
         assert(f);
         assert(l);
         assert(f->location_type == LOCATION_SEEK);
-        assert(l->type == LOCATION_DISCRETE || l->type == LOCATION_SEEK);
+        assert(IN_SET(l->type, LOCATION_DISCRETE, LOCATION_SEEK));
 
         if (l->monotonic_set &&
             sd_id128_equal(f->current_boot_id, l->boot_id) &&
diff --git a/src/journal/test-compress.c b/src/journal/test-compress.c
index 92108a84b3..bd0ffaffbf 100644
--- a/src/journal/test-compress.c
+++ b/src/journal/test-compress.c
@@ -194,7 +194,7 @@ static void test_compress_stream(int compression,
 
         assert_se(lseek(dst, 1, SEEK_SET) == 1);
         r = decompress(dst, dst2, st.st_size);
-        assert_se(r == -EBADMSG || r == 0);
+        assert_se(IN_SET(r, 0, -EBADMSG));
 
         assert_se(lseek(dst, 0, SEEK_SET) == 0);
         assert_se(lseek(dst2, 0, SEEK_SET) == 0);
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index d0ce7989d8..29b22eed45 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -528,7 +528,7 @@ static int client_message_init(
         assert(ret);
         assert(_optlen);
         assert(_optoffset);
-        assert(type == DHCP_DISCOVER || type == DHCP_REQUEST);
+        assert(IN_SET(type, DHCP_DISCOVER, DHCP_REQUEST));
 
         optlen = DHCP_MIN_OPTIONS_SIZE;
         size = sizeof(DHCPPacket) + optlen;
@@ -707,8 +707,7 @@ static int client_send_discover(sd_dhcp_client *client) {
         int r;
 
         assert(client);
-        assert(client->state == DHCP_STATE_INIT ||
-               client->state == DHCP_STATE_SELECTING);
+        assert(IN_SET(client->state, DHCP_STATE_INIT, DHCP_STATE_SELECTING));
 
         r = client_message_init(client, &discover, DHCP_DISCOVER,
                                 &optlen, &optoffset);
@@ -1688,7 +1687,7 @@ static int client_receive_message_udp(
 
         len = recv(fd, message, buflen, 0);
         if (len < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return log_dhcp_client_errno(client, errno,
@@ -1782,7 +1781,7 @@ static int client_receive_message_raw(
 
         len = recvmsg(fd, &msg, 0);
         if (len < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return log_dhcp_client_errno(client, errno,
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 727cc16ab5..663fd0e41d 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -993,7 +993,7 @@ static int server_receive_message(sd_event_source *s, int fd,
 
         len = recvmsg(fd, &msg, 0);
         if (len < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return -errno;
diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
index 6444b0ce94..eba0c8bcbb 100644
--- a/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -940,7 +940,7 @@ static int client_receive_message(
 
         len = recv(fd, message, buflen, 0);
         if (len < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return log_dhcp6_client_errno(client, errno, "Could not receive message from UDP socket: %m");
diff --git a/src/libsystemd-network/sd-lldp.c b/src/libsystemd-network/sd-lldp.c
index 39ddb2461a..0f591a8011 100644
--- a/src/libsystemd-network/sd-lldp.c
+++ b/src/libsystemd-network/sd-lldp.c
@@ -218,7 +218,7 @@ static int lldp_receive_datagram(sd_event_source *s, int fd, uint32_t revents, v
 
         length = recv(fd, LLDP_NEIGHBOR_RAW(n), n->raw_size, MSG_DONTWAIT);
         if (length < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return log_lldp_errno(errno, "Failed to read LLDP datagram: %m");
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
index 5c3ae170ed..1942199294 100644
--- a/src/libsystemd-network/test-dhcp-client.c
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -294,7 +294,7 @@ static void test_discover_message(sd_event *e) {
 
         res = sd_dhcp_client_start(client);
 
-        assert_se(res == 0 || res == -EINPROGRESS);
+        assert_se(IN_SET(res, 0, -EINPROGRESS));
 
         sd_event_run(e, (uint64_t) -1);
 
@@ -513,7 +513,7 @@ static void test_addr_acq(sd_event *e) {
                                     test_dhcp_hangcheck, NULL) >= 0);
 
         res = sd_dhcp_client_start(client);
-        assert_se(res == 0 || res == -EINPROGRESS);
+        assert_se(IN_SET(res, 0, -EINPROGRESS));
 
         assert_se(sd_event_loop(e) >= 0);
 
diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 2a509c7d1a..3fc447df3f 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -4219,8 +4219,7 @@ _public_ int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char
                 return 1;
         }
 
-        if (c->signature[c->index] == SD_BUS_TYPE_STRUCT_BEGIN ||
-            c->signature[c->index] == SD_BUS_TYPE_DICT_ENTRY_BEGIN) {
+        if (IN_SET(c->signature[c->index], SD_BUS_TYPE_STRUCT_BEGIN, SD_BUS_TYPE_DICT_ENTRY_BEGIN)) {
 
                 if (contents) {
                         size_t l;
diff --git a/src/locale/keymap-util.c b/src/locale/keymap-util.c
index 7068603f0f..b71091f706 100644
--- a/src/locale/keymap-util.c
+++ b/src/locale/keymap-util.c
@@ -39,7 +39,7 @@ static bool startswith_comma(const char *s, const char *prefix) {
         if (!s)
                 return false;
 
-        return *s == ',' || *s == '\0';
+        return IN_SET(*s, ',', '\0');
 }
 
 static const char* strnulldash(const char *s) {
@@ -177,7 +177,7 @@ static int x11_read_data(Context *c) {
                 char_array_0(line);
                 l = strstrip(line);
 
-                if (l[0] == 0 || l[0] == '#')
+                if (IN_SET(l[0], 0, '#'))
                         continue;
 
                 if (in_section && first_word(l, "Option")) {
@@ -425,7 +425,7 @@ static int read_next_mapping(const char* filename,
                 (*n)++;
 
                 l = strstrip(line);
-                if (l[0] == 0 || l[0] == '#')
+                if (IN_SET(l[0], 0, '#'))
                         continue;
 
                 r = strv_split_extract(&b, l, WHITESPACE, EXTRACT_QUOTES);
diff --git a/src/login/loginctl.c b/src/login/loginctl.c
index 1862e8983c..a63174c093 100644
--- a/src/login/loginctl.c
+++ b/src/login/loginctl.c
@@ -407,7 +407,7 @@ static int prop_map_first_of_struct(sd_bus *bus, const char *member, sd_bus_mess
         if (r < 0)
                 return r;
 
-        if (contents[0] == 's' || contents[0] == 'o') {
+        if (IN_SET(contents[0], 's', 'o')) {
                 const char *s;
                 char **p = (char **) userdata;
 
diff --git a/src/login/logind-seat.c b/src/login/logind-seat.c
index 85258737c3..64a622307e 100644
--- a/src/login/logind-seat.c
+++ b/src/login/logind-seat.c
@@ -663,8 +663,7 @@ static bool seat_name_valid_char(char c) {
                 (c >= 'a' && c <= 'z') ||
                 (c >= 'A' && c <= 'Z') ||
                 (c >= '0' && c <= '9') ||
-                c == '-' ||
-                c == '_';
+                IN_SET(c, '-', '_');
 }
 
 bool seat_name_is_valid(const char *name) {
diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index d2e5c74fab..068bc455b5 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -547,7 +547,7 @@ static int user_remove_runtime_path(User *u) {
          * quite possible, if we lacked the permissions to mount
          * something */
         r = umount2(u->runtime_path, MNT_DETACH);
-        if (r < 0 && errno != EINVAL && errno != ENOENT)
+        if (r < 0 && !IN_SET(errno, EINVAL, ENOENT))
                 log_error_errno(errno, "Failed to unmount user runtime directory %s: %m", u->runtime_path);
 
         r = rm_rf(u->runtime_path, REMOVE_ROOT);
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index a385e6819b..2447e734a2 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -1458,8 +1458,7 @@ static int login_machine(int argc, char *argv[], void *userdata) {
                 return -EINVAL;
         }
 
-        if (arg_transport != BUS_TRANSPORT_LOCAL &&
-            arg_transport != BUS_TRANSPORT_MACHINE) {
+        if (!IN_SET(arg_transport, BUS_TRANSPORT_LOCAL, BUS_TRANSPORT_MACHINE)) {
                 log_error("Login only supported on local machines.");
                 return -EOPNOTSUPP;
         }
@@ -1521,8 +1520,7 @@ static int shell_machine(int argc, char *argv[], void *userdata) {
 
         assert(bus);
 
-        if (arg_transport != BUS_TRANSPORT_LOCAL &&
-            arg_transport != BUS_TRANSPORT_MACHINE) {
+        if (!IN_SET(arg_transport, BUS_TRANSPORT_LOCAL, BUS_TRANSPORT_MACHINE)) {
                 log_error("Shell only supported on local machines.");
                 return -EOPNOTSUPP;
         }
diff --git a/src/network/networkctl.c b/src/network/networkctl.c
index 54d54c8fd5..e4b95e4195 100644
--- a/src/network/networkctl.c
+++ b/src/network/networkctl.c
@@ -383,7 +383,7 @@ static int get_gateway_description(
 
         assert(rtnl);
         assert(ifindex >= 0);
-        assert(family == AF_INET || family == AF_INET6);
+        assert(IN_SET(family, AF_INET, AF_INET6));
         assert(gateway);
         assert(gateway_description);
 
diff --git a/src/network/networkd-address.c b/src/network/networkd-address.c
index 8f625975fb..214192ffe8 100644
--- a/src/network/networkd-address.c
+++ b/src/network/networkd-address.c
@@ -453,7 +453,7 @@ int address_remove(
         int r;
 
         assert(address);
-        assert(address->family == AF_INET || address->family == AF_INET6);
+        assert(IN_SET(address->family, AF_INET, AF_INET6));
         assert(link);
         assert(link->ifindex > 0);
         assert(link->manager);
@@ -553,7 +553,7 @@ int address_configure(
         int r;
 
         assert(address);
-        assert(address->family == AF_INET || address->family == AF_INET6);
+        assert(IN_SET(address->family, AF_INET, AF_INET6));
         assert(link);
         assert(link->ifindex > 0);
         assert(link->manager);
diff --git a/src/network/networkd-conf.c b/src/network/networkd-conf.c
index e28e018116..025662437b 100644
--- a/src/network/networkd-conf.c
+++ b/src/network/networkd-conf.c
@@ -87,7 +87,7 @@ int config_parse_duid_rawdata(
                 }
 
                 len = strlen(cbyte);
-                if (len != 1 && len != 2) {
+                if (!IN_SET(len, 1, 2)) {
                         log_syntax(unit, LOG_ERR, filename, line, 0, "Invalid length - DUID byte: %s, ignoring assignment: %s.", cbyte, rvalue);
                         return 0;
                 }
diff --git a/src/network/networkd-route.c b/src/network/networkd-route.c
index 5b4874795a..cf42037915 100644
--- a/src/network/networkd-route.c
+++ b/src/network/networkd-route.c
@@ -401,7 +401,7 @@ int route_remove(Route *route, Link *link,
         assert(link->manager);
         assert(link->manager->rtnl);
         assert(link->ifindex > 0);
-        assert(route->family == AF_INET || route->family == AF_INET6);
+        assert(IN_SET(route->family, AF_INET, AF_INET6));
 
         r = sd_rtnl_message_new_route(link->manager->rtnl, &req,
                                       RTM_DELROUTE, route->family,
@@ -528,7 +528,7 @@ int route_configure(
         assert(link->manager);
         assert(link->manager->rtnl);
         assert(link->ifindex > 0);
-        assert(route->family == AF_INET || route->family == AF_INET6);
+        assert(IN_SET(route->family, AF_INET, AF_INET6));
 
         if (route_get(link, route->family, &route->dst, route->dst_prefixlen, route->tos, route->priority, route->table, NULL) <= 0 &&
             set_size(link->routes) >= routes_max())
diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index ec059d9586..17d125c821 100644
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -307,7 +307,7 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         if (af == AF_UNSPEC)
                 af = AF_INET;
 
-        if (af != AF_INET && af != AF_INET6) {
+        if (!IN_SET(af, AF_INET, AF_INET6)) {
                 r = -EAFNOSUPPORT;
                 goto fail;
         }
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
index eddab58a81..651c660e96 100644
--- a/src/resolve/resolved-dns-dnssec.c
+++ b/src/resolve/resolved-dns-dnssec.c
@@ -1247,10 +1247,10 @@ static int nsec3_is_good(DnsResourceRecord *rr, DnsResourceRecord *nsec3) {
 
         /* Ignore NSEC3 RRs generated from wildcards. If these NSEC3 RRs weren't correctly signed we can't make this
          * check (since rr->n_skip_labels_source is -1), but that's OK, as we won't trust them anyway in that case. */
-        if (rr->n_skip_labels_source != 0 && rr->n_skip_labels_source != (unsigned) -1)
+        if (!IN_SET(rr->n_skip_labels_source, 0, (unsigned) -1))
                 return 0;
         /* Ignore NSEC3 RRs that are located anywhere else than one label below the zone */
-        if (rr->n_skip_labels_signer != 1 && rr->n_skip_labels_signer != (unsigned) -1)
+        if (!IN_SET(rr->n_skip_labels_signer, 1, (unsigned) -1))
                 return 0;
 
         if (!nsec3)
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index ffaefbe3f2..b01ee6c9cc 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -904,7 +904,7 @@ int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
          * messages, not all of them. That should be enough to
          * indicate where there might be a conflict */
         r = ordered_hashmap_put(scope->conflict_queue, rr->key, rr);
-        if (r == -EEXIST || r == 0)
+        if (IN_SET(r, 0, -EEXIST))
                 return 0;
         if (r < 0)
                 return log_debug_errno(r, "Failed to queue conflicting RR: %m");
diff --git a/src/resolve/resolved-dns-synthesize.c b/src/resolve/resolved-dns-synthesize.c
index ad38c6a561..e8592a60d8 100644
--- a/src/resolve/resolved-dns-synthesize.c
+++ b/src/resolve/resolved-dns-synthesize.c
@@ -383,8 +383,7 @@ int dns_synthesize_answer(
                 const char *name;
                 int af;
 
-                if (key->class != DNS_CLASS_IN &&
-                    key->class != DNS_CLASS_ANY)
+                if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY))
                         continue;
 
                 name = dns_resource_key_name(key);
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 8b23132339..3cda429c3c 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -190,7 +190,7 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key)
                 return -EOPNOTSUPP;
 
         /* We only support the IN class */
-        if (key->class != DNS_CLASS_IN && key->class != DNS_CLASS_ANY)
+        if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY))
                 return -EOPNOTSUPP;
 
         if (hashmap_size(s->manager->dns_transactions) >= TRANSACTIONS_MAX)
@@ -1593,7 +1593,7 @@ int dns_transaction_go(DnsTransaction *t) {
                         log_debug("Sending query via TCP since it is too large.");
                 else if (r == -EAGAIN)
                         log_debug("Sending query via TCP since server doesn't support UDP.");
-                if (r == -EMSGSIZE || r == -EAGAIN)
+                if (IN_SET(r, -EMSGSIZE, -EAGAIN))
                         r = dns_transaction_open_tcp(t);
         }
 
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index b6620875ea..efdf7e5aaa 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -741,7 +741,7 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) {
         if (l == 0)
                 return 0;
         if (l < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return -errno;
diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c
index f4e071ebaa..2af77b3407 100644
--- a/src/resolve/resolved-resolv-conf.c
+++ b/src/resolve/resolved-resolv-conf.c
@@ -87,7 +87,7 @@ int manager_read_resolv_conf(Manager *m) {
                 char *l;
 
                 l = strstrip(line);
-                if (*l == '#' || *l == ';')
+                if (IN_SET(*l, '#', ';'))
                         continue;
 
                 a = first_word(l, "nameserver");
diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index de3847adfd..e33d8b11cf 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -337,7 +337,7 @@ int ask_password_tty(
                                 backspace_chars(ttyfd, p);
                         p = 0;
 
-                } else if (c == '\b' || c == 127) {
+                } else if (IN_SET(c, '\b', 127)) {
 
                         if (p > 0) {
 
diff --git a/src/shared/condition.c b/src/shared/condition.c
index 103f8d2e39..74d5e854e1 100644
--- a/src/shared/condition.c
+++ b/src/shared/condition.c
@@ -131,7 +131,7 @@ static int condition_test_kernel_command_line(Condition *c) {
                         const char *f;
 
                         f = startswith(word, c->parameter);
-                        found = f && (*f == '=' || *f == 0);
+                        found = f && IN_SET(*f, 0, '=');
                 }
 
                 if (found)
diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index 243a46f2e3..b782b05f88 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -57,7 +57,7 @@ _unused_ static int probe_filesystem(const char *node, char **ret_fstype) {
 
         errno = 0;
         r = blkid_do_safeprobe(b);
-        if (r == -2 || r == 1) {
+        if (IN_SET(r, -2, 1)) {
                 log_debug("Failed to identify any partition type on partition %s", node);
                 goto not_found;
         }
@@ -156,7 +156,7 @@ int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectI
 
         errno = 0;
         r = blkid_do_safeprobe(b);
-        if (r == -2 || r == 1) {
+        if (IN_SET(r, -2, 1)) {
                 log_debug("Failed to identify any partition table.");
                 return -ENOPKG;
         }
diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 139d286af8..d75abd8121 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -76,7 +76,7 @@ int dns_label_unescape(const char **name, char *dest, size_t sz) {
                                 /* Ending NUL */
                                 return -EINVAL;
 
-                        else if (*n == '\\' || *n == '.') {
+                        else if (IN_SET(*n, '\\', '.')) {
                                 /* Escaped backslash or dot */
 
                                 if (d)
@@ -164,7 +164,7 @@ int dns_label_unescape_suffix(const char *name, const char **label_terminal, cha
         }
 
         terminal = *label_terminal;
-        assert(*terminal == '.' || *terminal == 0);
+        assert(IN_SET(*terminal, 0, '.'));
 
         /* Skip current terminal character (and accept domain names ending it ".") */
         if (*terminal == 0)
@@ -228,7 +228,7 @@ int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
         q = dest;
         while (l > 0) {
 
-                if (*p == '.' || *p == '\\') {
+                if (IN_SET(*p, '.', '\\')) {
 
                         /* Dot or backslash */
 
@@ -240,8 +240,7 @@ int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
 
                         sz -= 2;
 
-                } else if (*p == '_' ||
-                           *p == '-' ||
+                } else if (IN_SET(*p, '_', '-') ||
                            (*p >= '0' && *p <= '9') ||
                            (*p >= 'a' && *p <= 'z') ||
                            (*p >= 'A' && *p <= 'Z')) {
diff --git a/src/shared/firewall-util.c b/src/shared/firewall-util.c
index 3a6e987ee1..6d295ea65b 100644
--- a/src/shared/firewall-util.c
+++ b/src/shared/firewall-util.c
@@ -110,7 +110,7 @@ int fw_add_masquerade(
         if (af != AF_INET)
                 return -EOPNOTSUPP;
 
-        if (protocol != 0 && protocol != IPPROTO_TCP && protocol != IPPROTO_UDP)
+        if (!IN_SET(protocol, 0, IPPROTO_TCP, IPPROTO_UDP))
                 return -EOPNOTSUPP;
 
         h = iptc_init("nat");
@@ -194,7 +194,7 @@ int fw_add_local_dnat(
         if (af != AF_INET)
                 return -EOPNOTSUPP;
 
-        if (protocol != IPPROTO_TCP && protocol != IPPROTO_UDP)
+        if (!IN_SET(protocol, IPPROTO_TCP, IPPROTO_UDP))
                 return -EOPNOTSUPP;
 
         if (local_port <= 0)
diff --git a/src/shared/logs-show.c b/src/shared/logs-show.c
index 54516cfb96..0626d80b19 100644
--- a/src/shared/logs-show.c
+++ b/src/shared/logs-show.c
@@ -683,7 +683,7 @@ void json_escape(
                 fputc('\"', f);
 
                 while (l > 0) {
-                        if (*p == '"' || *p == '\\') {
+                        if (IN_SET(*p, '"', '\\')) {
                                 fputc('\\', f);
                                 fputc(*p, f);
                         } else if (*p == '\n')
diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c
index 32a4c67590..859e5ffc1a 100644
--- a/src/shared/machine-image.c
+++ b/src/shared/machine-image.c
@@ -313,7 +313,7 @@ int image_find(const char *name, Image **ret) {
                 }
 
                 r = image_make(NULL, dirfd(d), path, name, ret);
-                if (r == 0 || r == -ENOENT) {
+                if (IN_SET(r, 0, -ENOENT)) {
                         _cleanup_free_ char *raw = NULL;
 
                         raw = strappend(name, ".raw");
@@ -321,7 +321,7 @@ int image_find(const char *name, Image **ret) {
                                 return -ENOMEM;
 
                         r = image_make(NULL, dirfd(d), path, raw, ret);
-                        if (r == 0 || r == -ENOENT)
+                        if (IN_SET(r, 0, -ENOENT))
                                 continue;
                 }
                 if (r < 0)
@@ -364,7 +364,7 @@ int image_discover(Hashmap *h) {
                                 continue;
 
                         r = image_make(NULL, dirfd(d), path, de->d_name, &image);
-                        if (r == 0 || r == -ENOENT)
+                        if (IN_SET(r, 0, -ENOENT))
                                 continue;
                         if (r < 0)
                                 return r;
diff --git a/src/shared/path-lookup.c b/src/shared/path-lookup.c
index bf10acda94..e7a878ab50 100644
--- a/src/shared/path-lookup.c
+++ b/src/shared/path-lookup.c
@@ -514,13 +514,13 @@ int lookup_paths_init(
                 /* Note: if XDG_RUNTIME_DIR is not set, this will fail completely with ENXIO */
                 r = acquire_generator_dirs(scope, tempdir,
                                            &generator, &generator_early, &generator_late);
-                if (r < 0 && r != -EOPNOTSUPP && r != -ENXIO)
+                if (r < 0 && !IN_SET(r, -EOPNOTSUPP, -ENXIO))
                         return r;
         }
 
         /* Note: if XDG_RUNTIME_DIR is not set, this will fail completely with ENXIO */
         r = acquire_transient_dir(scope, tempdir, &transient);
-        if (r < 0 && r != -EOPNOTSUPP && r != -ENXIO)
+        if (r < 0 && !IN_SET(r, -EOPNOTSUPP, -ENXIO))
                 return r;
 
         /* Note: when XDG_RUNTIME_DIR is not set this will not return -ENXIO, but simply set runtime_control to NULL */
diff --git a/src/socket-proxy/socket-proxyd.c b/src/socket-proxy/socket-proxyd.c
index bf8c2f86a3..34c938438c 100644
--- a/src/socket-proxy/socket-proxyd.c
+++ b/src/socket-proxy/socket-proxyd.c
@@ -164,7 +164,7 @@ static int connection_shovel(
                         if (z > 0) {
                                 *full += z;
                                 shoveled = true;
-                        } else if (z == 0 || errno == EPIPE || errno == ECONNRESET) {
+                        } else if (z == 0 || IN_SET(errno, EPIPE, ECONNRESET)) {
                                 *from_source = sd_event_source_unref(*from_source);
                                 *from = safe_close(*from);
                         } else if (!IN_SET(errno, EAGAIN, EINTR))
@@ -176,7 +176,7 @@ static int connection_shovel(
                         if (z > 0) {
                                 *full -= z;
                                 shoveled = true;
-                        } else if (z == 0 || errno == EPIPE || errno == ECONNRESET) {
+                        } else if (z == 0 || IN_SET(errno, EPIPE, ECONNRESET)) {
                                 *to_source = sd_event_source_unref(*to_source);
                                 *to = safe_close(*to);
                         } else if (!IN_SET(errno, EAGAIN, EINTR))
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 897fc48b98..782924d95a 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -7815,7 +7815,7 @@ static int halt_parse_argv(int argc, char *argv[]) {
         assert(argv);
 
         if (utmp_get_runlevel(&runlevel, NULL) >= 0)
-                if (runlevel == '0' || runlevel == '6')
+                if (IN_SET(runlevel, '0', '6'))
                         arg_force = 2;
 
         while ((c = getopt_long(argc, argv, "pfwdnih", options, NULL)) >= 0)
diff --git a/src/sysusers/sysusers.c b/src/sysusers/sysusers.c
index e9e6dae10c..50fce6b29f 100644
--- a/src/sysusers/sysusers.c
+++ b/src/sysusers/sysusers.c
@@ -1669,7 +1669,7 @@ static int read_config_file(const char *fn, bool ignore_enoent) {
                 v++;
 
                 l = strstrip(line);
-                if (*l == '#' || *l == 0)
+                if (IN_SET(*l, 0, '#'))
                         continue;
 
                 k = parse_line(fn, v, l);
diff --git a/src/test/test-architecture.c b/src/test/test-architecture.c
index f41e488d99..68975b790a 100644
--- a/src/test/test-architecture.c
+++ b/src/test/test-architecture.c
@@ -26,7 +26,7 @@ int main(int argc, char *argv[]) {
         int a, v;
 
         v = detect_virtualization();
-        if (v == -EPERM || v == -EACCES)
+        if (IN_SET(v, -EPERM, -EACCES))
                 return EXIT_TEST_SKIP;
 
         assert_se(v >= 0);
diff --git a/src/test/test-cgroup-mask.c b/src/test/test-cgroup-mask.c
index 15d76bddda..02aae84152 100644
--- a/src/test/test-cgroup-mask.c
+++ b/src/test/test-cgroup-mask.c
@@ -40,7 +40,7 @@ static int test_cgroup_mask(void) {
         assert_se(set_unit_path(get_testdata_dir("")) >= 0);
         assert_se(runtime_dir = setup_fake_runtime_dir());
         r = manager_new(UNIT_FILE_USER, MANAGER_TEST_RUN_MINIMAL, &m);
-        if (r == -EPERM || r == -EACCES) {
+        if (IN_SET(r, -EPERM, -EACCES)) {
                 puts("manager_new: Permission denied. Skipping test.");
                 return EXIT_TEST_SKIP;
         }
diff --git a/src/test/test-clock.c b/src/test/test-clock.c
index f246ae8385..94f8b50f41 100644
--- a/src/test/test-clock.c
+++ b/src/test/test-clock.c
@@ -82,7 +82,7 @@ static void test_clock_is_localtime_system(void) {
                 log_info("/etc/adjtime exists, clock_is_localtime() == %i", r);
                 /* if /etc/adjtime exists we expect some answer, no error or
                  * crash */
-                assert_se(r == 0 || r == 1);
+                assert_se(IN_SET(r, 0, 1));
         } else
                 /* default is UTC if there is no /etc/adjtime */
                 assert_se(r == 0);
diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c
index b5b6391cdd..27495fa5be 100644
--- a/src/test/test-fileio.c
+++ b/src/test/test-fileio.c
@@ -393,7 +393,7 @@ static void test_capeff(void) {
                 r = get_process_capeff(0, &capeff);
                 log_info("capeff: '%s' (r=%d)", capeff, r);
 
-                if (r == -ENOENT || r == -EPERM)
+                if (IN_SET(r, -ENOENT, -EPERM))
                         return;
 
                 assert_se(r == 0);
@@ -479,15 +479,15 @@ static void test_write_string_file_verify(void) {
         assert_se((buf2 = strjoin(buf, "\n")));
 
         r = write_string_file("/proc/cmdline", buf, 0);
-        assert_se(r == -EACCES || r == -EIO);
+        assert_se(IN_SET(r, -EACCES, -EIO));
         r = write_string_file("/proc/cmdline", buf2, 0);
-        assert_se(r == -EACCES || r == -EIO);
+        assert_se(IN_SET(r, -EACCES, -EIO));
 
         assert_se(write_string_file("/proc/cmdline", buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE) == 0);
         assert_se(write_string_file("/proc/cmdline", buf2, WRITE_STRING_FILE_VERIFY_ON_FAILURE) == 0);
 
         r = write_string_file("/proc/cmdline", buf, WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_AVOID_NEWLINE);
-        assert_se(r == -EACCES || r == -EIO);
+        assert_se(IN_SET(r, -EACCES, -EIO));
         assert_se(write_string_file("/proc/cmdline", buf2, WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_AVOID_NEWLINE) == 0);
 }
 
diff --git a/src/test/test-nss.c b/src/test/test-nss.c
index 44570caa6c..be8b9d71ba 100644
--- a/src/test/test-nss.c
+++ b/src/test/test-nss.c
@@ -97,7 +97,7 @@ static int print_gaih_addrtuples(const struct gaih_addrtuple *tuples) {
 
                 memcpy(&u, it->addr, 16);
                 r = in_addr_to_string(it->family, &u, &a);
-                assert_se(r == 0 || r == -EAFNOSUPPORT);
+                assert_se(IN_SET(r, 0, -EAFNOSUPPORT));
                 if (r == -EAFNOSUPPORT)
                         assert_se((a = hexmem(it->addr, 16)));
 
diff --git a/src/test/test-unit-file.c b/src/test/test-unit-file.c
index 578e09447f..07f21d0d3d 100644
--- a/src/test/test-unit-file.c
+++ b/src/test/test-unit-file.c
@@ -55,7 +55,7 @@ static int test_unit_file_get_set(void) {
 
         r = unit_file_get_list(UNIT_FILE_SYSTEM, NULL, h, NULL, NULL);
 
-        if (r == -EPERM || r == -EACCES) {
+        if (IN_SET(r, -EPERM, -EACCES)) {
                 log_notice_errno(r, "Skipping test: unit_file_get_list: %m");
                 return EXIT_TEST_SKIP;
         }
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 3f5c1e62ee..17fce93328 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -333,7 +333,7 @@ static int dir_is_mount_point(DIR *d, const char *subdir) {
 
         /* got only one handle; assume different mount points if one
          * of both queries was not supported by the filesystem */
-        if (r_p == -ENOSYS || r_p == -EOPNOTSUPP || r == -ENOSYS || r == -EOPNOTSUPP)
+        if (IN_SET(r_p, -ENOSYS, -EOPNOTSUPP) || IN_SET(r, -ENOSYS, -EOPNOTSUPP))
                 return true;
 
         /* return error */
@@ -501,7 +501,7 @@ static int dir_cleanup(
 
                         log_debug("Removing directory \"%s\".", sub_path);
                         if (unlinkat(dirfd(d), dent->d_name, AT_REMOVEDIR) < 0)
-                                if (errno != ENOENT && errno != ENOTEMPTY) {
+                                if (!IN_SET(errno, ENOENT, ENOTEMPTY)) {
                                         log_error_errno(errno, "rmdir(%s): %m", sub_path);
                                         r = -errno;
                                 }
@@ -984,7 +984,7 @@ static int path_set_attribute(Item *item, const char *path) {
 
         r = chattr_fd(fd, f, item->attribute_mask);
         if (r < 0)
-                log_full_errno(r == -ENOTTY || r == -EOPNOTSUPP ? LOG_DEBUG : LOG_WARNING,
+                log_full_errno(IN_SET(r, -ENOTTY, -EOPNOTSUPP) ? LOG_DEBUG : LOG_WARNING,
                                r,
                                "Cannot set file attribute for '%s', value=0x%08x, mask=0x%08x: %m",
                                path, item->attribute_value, item->attribute_mask);
@@ -1075,7 +1075,7 @@ static int item_do_children(Item *i, const char *path, action_t action) {
 
         d = opendir_nomod(path);
         if (!d)
-                return errno == ENOENT || errno == ENOTDIR ? 0 : -errno;
+                return IN_SET(errno, ENOENT, ENOTDIR) ? 0 : -errno;
 
         FOREACH_DIRENT_ALL(de, d, r = -errno) {
                 _cleanup_free_ char *p = NULL;
@@ -1253,7 +1253,7 @@ static int create_item(Item *i) {
                 if (r < 0) {
                         int k;
 
-                        if (r != -EEXIST && r != -EROFS)
+                        if (!IN_SET(r, -EEXIST, -EROFS))
                                 return log_error_errno(r, "Failed to create directory or subvolume \"%s\": %m", i->path);
 
                         k = is_dir(i->path, false);
@@ -2215,7 +2215,7 @@ static int read_config_file(const char *fn, bool ignore_enoent) {
                 v++;
 
                 l = strstrip(line);
-                if (*l == '#' || *l == 0)
+                if (IN_SET(*l, 0, '#'))
                         continue;
 
                 k = parse_line(fn, v, l);
diff --git a/src/tty-ask-password-agent/tty-ask-password-agent.c b/src/tty-ask-password-agent/tty-ask-password-agent.c
index 3ea8dae7a9..495ae464b4 100644
--- a/src/tty-ask-password-agent/tty-ask-password-agent.c
+++ b/src/tty-ask-password-agent/tty-ask-password-agent.c
@@ -206,7 +206,7 @@ static int ask_password_plymouth(
                         r = -ENOENT;
                         goto finish;
 
-                } else if (buffer[0] == 2 || buffer[0] == 9) {
+                } else if (IN_SET(buffer[0], 2, 9)) {
                         uint32_t size;
                         char **l;
 
diff --git a/src/udev/ata_id/ata_id.c b/src/udev/ata_id/ata_id.c
index ad152b9d31..1dc62b69d5 100644
--- a/src/udev/ata_id/ata_id.c
+++ b/src/udev/ata_id/ata_id.c
@@ -617,7 +617,7 @@ int main(int argc, char *argv[])
                  */
 
                 word = identify.wyde[76];
-                if (word != 0x0000 && word != 0xffff) {
+                if (!IN_SET(word, 0x0000, 0xffff)) {
                         printf("ID_ATA_SATA=1\n");
                         /*
                          * If bit 2 of word 76 is set to one, then the device supports the Gen2
@@ -661,8 +661,7 @@ int main(int argc, char *argv[])
                 }
 
                 /* from Linux's include/linux/ata.h */
-                if (identify.wyde[0] == 0x848a ||
-                    identify.wyde[0] == 0x844a ||
+                if (IN_SET(identify.wyde[0], 0x848a, 0x844a) ||
                     (identify.wyde[83] & 0xc004) == 0x4004)
                         printf("ID_ATA_CFA=1\n");
         } else {
diff --git a/src/udev/cdrom_id/cdrom_id.c b/src/udev/cdrom_id/cdrom_id.c
index 1f906a8525..b9cf3bdf68 100644
--- a/src/udev/cdrom_id/cdrom_id.c
+++ b/src/udev/cdrom_id/cdrom_id.c
@@ -544,7 +544,7 @@ static int cd_profiles(struct udev *udev, int fd)
         if ((err != 0)) {
                 info_scsi_cmd_err(udev, "GET CONFIGURATION", err);
                 /* handle pre-MMC2 drives which do not support GET CONFIGURATION */
-                if (SK(err) == 0x5 && (ASC(err) == 0x20 || ASC(err) == 0x24)) {
+                if (SK(err) == 0x5 && IN_SET(ASC(err), 0x20, 0x24)) {
                         log_debug("drive is pre-MMC2 and does not support 46h get configuration command");
                         log_debug("trying to work around the problem");
                         ret = cd_profiles_old_mmc(udev, fd);
diff --git a/src/udev/scsi_id/scsi_serial.c b/src/udev/scsi_id/scsi_serial.c
index f007cc6001..b56a541f78 100644
--- a/src/udev/scsi_id/scsi_serial.c
+++ b/src/udev/scsi_id/scsi_serial.c
@@ -115,9 +115,8 @@ static int sg_err_category_new(struct udev *udev,
         if (!scsi_status && !host_status && !driver_status)
                 return SG_ERR_CAT_CLEAN;
 
-        if ((scsi_status == SCSI_CHECK_CONDITION) ||
-            (scsi_status == SCSI_COMMAND_TERMINATED) ||
-            ((driver_status & 0xf) == DRIVER_SENSE)) {
+        if (IN_SET(scsi_status, SCSI_CHECK_CONDITION, SCSI_COMMAND_TERMINATED) ||
+            (driver_status & 0xf) == DRIVER_SENSE) {
                 if (sense_buffer && (sb_len > 2)) {
                         int sense_key;
                         unsigned char asc;
@@ -143,9 +142,7 @@ static int sg_err_category_new(struct udev *udev,
                 return SG_ERR_CAT_SENSE;
         }
         if (host_status) {
-                if ((host_status == DID_NO_CONNECT) ||
-                    (host_status == DID_BUS_BUSY) ||
-                    (host_status == DID_TIME_OUT))
+                if (IN_SET(host_status, DID_NO_CONNECT, DID_BUS_BUSY, DID_TIME_OUT))
                         return SG_ERR_CAT_TIMEOUT;
         }
         if (driver_status) {
@@ -215,7 +212,7 @@ static int scsi_dump_sense(struct udev *udev,
                                   dev_scsi->kernel, sb_len, s - sb_len);
                         return -1;
                 }
-                if ((code == 0x0) || (code == 0x1)) {
+                if (IN_SET(code, 0x0, 0x1)) {
                         sense_key = sense_buffer[2] & 0xf;
                         if (s < 14) {
                                 /*
@@ -227,7 +224,7 @@ static int scsi_dump_sense(struct udev *udev,
                         }
                         asc = sense_buffer[12];
                         ascq = sense_buffer[13];
-                } else if ((code == 0x2) || (code == 0x3)) {
+                } else if (IN_SET(code, 0x2, 0x3)) {
                         sense_key = sense_buffer[1] & 0xf;
                         asc = sense_buffer[2];
                         ascq = sense_buffer[3];
diff --git a/src/udev/udev-builtin-uaccess.c b/src/udev/udev-builtin-uaccess.c
index 3ebe36f043..d92a10e1c5 100644
--- a/src/udev/udev-builtin-uaccess.c
+++ b/src/udev/udev-builtin-uaccess.c
@@ -47,7 +47,7 @@ static int builtin_uaccess(struct udev_device *dev, int argc, char *argv[], bool
                 seat = "seat0";
 
         r = sd_seat_get_active(seat, NULL, &uid);
-        if (r == -ENXIO || r == -ENODATA) {
+        if (IN_SET(r, -ENXIO, -ENODATA)) {
                 /* No active session on this seat */
                 r = 0;
                 goto finish;
diff --git a/src/udev/udev-builtin-usb_id.c b/src/udev/udev-builtin-usb_id.c
index 587649eff0..3ce075f079 100644
--- a/src/udev/udev-builtin-usb_id.c
+++ b/src/udev/udev-builtin-usb_id.c
@@ -307,7 +307,7 @@ static int builtin_usb_id(struct udev_device *dev, int argc, char *argv[], bool
         dev_if_packed_info(dev_usb, packed_if_str, sizeof(packed_if_str));
 
         /* mass storage : SCSI or ATAPI */
-        if (protocol == 6 || protocol == 2) {
+        if (IN_SET(protocol, 6, 2)) {
                 struct udev_device *dev_scsi;
                 const char *scsi_model, *scsi_vendor, *scsi_type, *scsi_rev;
                 int host, bus, target, lun;
diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c
index 53cfd9c053..01e56cac36 100644
--- a/src/udev/udev-node.c
+++ b/src/udev/udev-node.c
@@ -87,7 +87,7 @@ static int node_symlink(struct udev_device *dev, const char *node, const char *s
                 log_debug("creating symlink '%s' to '%s'", slink, target);
                 do {
                         err = mkdir_parents_label(slink, 0755);
-                        if (err != 0 && err != -ENOENT)
+                        if (!IN_SET(err, 0, -ENOENT))
                                 break;
                         mac_selinux_create_file_prepare(slink, S_IFLNK);
                         err = symlink(target, slink);
@@ -104,7 +104,7 @@ static int node_symlink(struct udev_device *dev, const char *node, const char *s
         unlink(slink_tmp);
         do {
                 err = mkdir_parents_label(slink_tmp, 0755);
-                if (err != 0 && err != -ENOENT)
+                if (!IN_SET(err, 0, -ENOENT))
                         break;
                 mac_selinux_create_file_prepare(slink_tmp, S_IFLNK);
                 err = symlink(target, slink_tmp);
@@ -209,7 +209,7 @@ static void link_update(struct udev_device *dev, const char *slink, bool add) {
                         int fd;
 
                         err = mkdir_parents(filename, 0755);
-                        if (err != 0 && err != -ENOENT)
+                        if (!IN_SET(err, 0, -ENOENT))
                                 break;
                         fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
                         if (fd >= 0)
diff --git a/src/udev/udev-rules.c b/src/udev/udev-rules.c
index 5ab697e399..9aaec72baf 100644
--- a/src/udev/udev-rules.c
+++ b/src/udev/udev-rules.c
@@ -579,7 +579,7 @@ static int import_property_from_string(struct udev_device *dev, char *line) {
                 key++;
 
         /* comment or empty line */
-        if (key[0] == '#' || key[0] == '\0')
+        if (IN_SET(key[0], '#', '\0'))
                 return -1;
 
         /* split key/value */
@@ -613,7 +613,7 @@ static int import_property_from_string(struct udev_device *dev, char *line) {
                 return -1;
 
         /* unquote */
-        if (val[0] == '"' || val[0] == '\'') {
+        if (IN_SET(val[0], '"', '\'')) {
                 if (len == 1 || val[len-1] != val[0]) {
                         log_debug("inconsistent quoting: '%s', skip", line);
                         return -1;
@@ -741,7 +741,7 @@ static int get_key(struct udev *udev, char **line, char **key, enum operation_ty
                         break;
                 if (linepos[0] == '=')
                         break;
-                if ((linepos[0] == '+') || (linepos[0] == '-') || (linepos[0] == '!') || (linepos[0] == ':'))
+                if (IN_SET(linepos[0], '+', '-', '!', ':'))
                         if (linepos[1] == '=')
                                 break;
         }
@@ -1968,7 +1968,7 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                                 int count;
 
                                 util_remove_trailing_chars(result, '\n');
-                                if (esc == ESCAPE_UNSET || esc == ESCAPE_REPLACE) {
+                                if (IN_SET(esc, ESCAPE_UNSET, ESCAPE_REPLACE)) {
                                         count = util_replace_chars(result, UDEV_ALLOWED_CHARS_INPUT);
                                         if (count > 0)
                                                 log_debug("%i character(s) replaced" , count);
@@ -2219,7 +2219,7 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                         else
                                 label = rules_str(rules, cur->key.value_off);
 
-                        if (cur->key.op == OP_ASSIGN || cur->key.op == OP_ASSIGN_FINAL)
+                        if (IN_SET(cur->key.op, OP_ASSIGN, OP_ASSIGN_FINAL))
                                 udev_list_cleanup(&event->seclabel_list);
                         udev_list_entry_add(&event->seclabel_list, name, label);
                         log_debug("SECLABEL{%s}='%s' %s:%u",
@@ -2260,13 +2260,13 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                         const char *p;
 
                         udev_event_apply_format(event, rules_str(rules, cur->key.value_off), tag, sizeof(tag), false);
-                        if (cur->key.op == OP_ASSIGN || cur->key.op == OP_ASSIGN_FINAL)
+                        if (IN_SET(cur->key.op, OP_ASSIGN, OP_ASSIGN_FINAL))
                                 udev_device_cleanup_tags_list(event->dev);
                         for (p = tag; *p != '\0'; p++) {
                                 if ((*p >= 'a' && *p <= 'z') ||
                                     (*p >= 'A' && *p <= 'Z') ||
                                     (*p >= '0' && *p <= '9') ||
-                                    *p == '-' || *p == '_')
+                                    IN_SET(*p, '-', '_'))
                                         continue;
                                 log_error("ignoring invalid tag name '%s'", tag);
                                 break;
@@ -2288,7 +2288,7 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                         if (cur->key.op == OP_ASSIGN_FINAL)
                                 event->name_final = true;
                         udev_event_apply_format(event, name, name_str, sizeof(name_str), false);
-                        if (esc == ESCAPE_UNSET || esc == ESCAPE_REPLACE) {
+                        if (IN_SET(esc, ESCAPE_UNSET, ESCAPE_REPLACE)) {
                                 count = util_replace_chars(name_str, "/");
                                 if (count > 0)
                                         log_debug("%i character(s) replaced", count);
@@ -2323,7 +2323,7 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                                 break;
                         if (cur->key.op == OP_ASSIGN_FINAL)
                                 event->devlink_final = true;
-                        if (cur->key.op == OP_ASSIGN || cur->key.op == OP_ASSIGN_FINAL)
+                        if (IN_SET(cur->key.op, OP_ASSIGN, OP_ASSIGN_FINAL))
                                 udev_device_cleanup_devlinks_list(event->dev);
 
                         /* allow  multiple symlinks separated by spaces */
@@ -2396,7 +2396,7 @@ void udev_rules_apply_to_event(struct udev_rules *rules,
                 case TK_A_RUN_PROGRAM: {
                         struct udev_list_entry *entry;
 
-                        if (cur->key.op == OP_ASSIGN || cur->key.op == OP_ASSIGN_FINAL)
+                        if (IN_SET(cur->key.op, OP_ASSIGN, OP_ASSIGN_FINAL))
                                 udev_list_cleanup(&event->run_list);
                         log_debug("RUN '%s' %s:%u",
                                   rules_str(rules, cur->key.value_off),
diff --git a/src/update-utmp/update-utmp.c b/src/update-utmp/update-utmp.c
index f68d60a134..679471e217 100644
--- a/src/update-utmp/update-utmp.c
+++ b/src/update-utmp/update-utmp.c
@@ -183,7 +183,7 @@ static int on_runlevel(Context *c) {
         q = utmp_get_runlevel(&previous, NULL);
 
         if (q < 0) {
-                if (q != -ESRCH && q != -ENOENT)
+                if (!IN_SET(q, -ESRCH, -ENOENT))
                         return log_error_errno(q, "Failed to get current runlevel: %m");
 
                 previous = 0;
@@ -213,7 +213,7 @@ static int on_runlevel(Context *c) {
 #endif
 
         q = utmp_put_runlevel(runlevel, previous);
-        if (q < 0 && q != -ESRCH && q != -ENOENT) {
+        if (q < 0 && !IN_SET(q, -ESRCH, -ENOENT)) {
                 log_error_errno(q, "Failed to write utmp record: %m");
                 r = q;
         }
@@ -249,7 +249,7 @@ int main(int argc, char *argv[]) {
         /* If the kernel lacks netlink or audit support,
          * don't worry about it. */
         c.audit_fd = audit_open();
-        if (c.audit_fd < 0 && errno != EAFNOSUPPORT && errno != EPROTONOSUPPORT)
+        if (c.audit_fd < 0 && !IN_SET(errno, EAFNOSUPPORT, EPROTONOSUPPORT))
                 log_error_errno(errno, "Failed to connect to audit log: %m");
 #endif
         r = bus_connect_system_systemd(&c.bus);