tree-wide: return NULL from freeing functions

I started working on this because I wanted to change how
DEFINE_TRIVIAL_CLEANUP_FUNC is defined. Even independently of that change, it's
nice to make make things more consistent and predictable.

52 files changed, 154 insertions, 165 deletions

diff --git a/src/analyze/analyze.c b/src/analyze/analyze.c
index 5ab920f4df..7271adaf5b 100644
--- a/src/analyze/analyze.c
+++ b/src/analyze/analyze.c
@@ -213,10 +213,10 @@ static int compare_unit_start(const UnitTimes *a, const UnitTimes *b) {
         return CMP(a->activating, b->activating);
 }
 
-static void unit_times_free(UnitTimes *t) {
-        for (UnitTimes *p = t; p->has_data; p++)
+static UnitTimes* unit_times_free(UnitTimes *t) {
+        for (UnitTimes *p = t; p && p->has_data; p++)
                 free(p->name);
-        free(t);
+        return mfree(t);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(UnitTimes *, unit_times_free);
 
@@ -313,9 +313,9 @@ finish:
         return 0;
 }
 
-static void free_host_info(HostInfo *hi) {
+static HostInfo* free_host_info(HostInfo *hi) {
         if (!hi)
-                return;
+                return NULL;
 
         free(hi->hostname);
         free(hi->kernel_name);
@@ -324,7 +324,7 @@ static void free_host_info(HostInfo *hi) {
         free(hi->os_pretty_name);
         free(hi->virtualization);
         free(hi->architecture);
-        free(hi);
+        return mfree(hi);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(HostInfo *, free_host_info);
@@ -429,7 +429,7 @@ static int acquire_host_info(sd_bus *bus, HostInfo **hi) {
 
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *system_bus = NULL;
-        _cleanup_(free_host_infop) HostInfo *host;
+        _cleanup_(free_host_infop) HostInfo *host = NULL;
         int r;
 
         host = new0(HostInfo, 1);
diff --git a/src/basic/strbuf.c b/src/basic/strbuf.c
index aee6647e35..535ac58bed 100644
--- a/src/basic/strbuf.c
+++ b/src/basic/strbuf.c
@@ -26,7 +26,7 @@
  *   ...
  */
 
-struct strbuf *strbuf_new(void) {
+struct strbuf* strbuf_new(void) {
         struct strbuf *str;
 
         str = new(struct strbuf, 1);
@@ -65,13 +65,13 @@ void strbuf_complete(struct strbuf *str) {
 }
 
 /* clean up everything */
-void strbuf_cleanup(struct strbuf *str) {
+struct strbuf* strbuf_cleanup(struct strbuf *str) {
         if (!str)
-                return;
+                return NULL;
 
         strbuf_complete(str);
         free(str->buf);
-        free(str);
+        return mfree(str);
 }
 
 static int strbuf_children_cmp(const struct strbuf_child_entry *n1,
diff --git a/src/basic/strbuf.h b/src/basic/strbuf.h
index 82758d721b..9a21438d64 100644
--- a/src/basic/strbuf.h
+++ b/src/basic/strbuf.h
@@ -32,8 +32,8 @@ struct strbuf_child_entry {
         struct strbuf_node *child;
 };
 
-struct strbuf *strbuf_new(void);
+struct strbuf* strbuf_new(void);
 ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len);
 void strbuf_complete(struct strbuf *str);
-void strbuf_cleanup(struct strbuf *str);
+struct strbuf* strbuf_cleanup(struct strbuf *str);
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct strbuf*, strbuf_cleanup);
diff --git a/src/busctl/busctl.c b/src/busctl/busctl.c
index 142aba0b92..fde9240749 100644
--- a/src/busctl/busctl.c
+++ b/src/busctl/busctl.c
@@ -780,24 +780,22 @@ static int member_compare_funcp(Member * const *a, Member * const *b) {
         return member_compare_func(*a, *b);
 }
 
-static void member_free(Member *m) {
+static Member* member_free(Member *m) {
         if (!m)
-                return;
+                return NULL;
 
         free(m->interface);
         free(m->name);
         free(m->signature);
         free(m->result);
         free(m->value);
-        free(m);
+        return mfree(m);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(Member*, member_free);
 
-static void member_set_free(Set *s) {
-        set_free_with_destructor(s, member_free);
+static Set* member_set_free(Set *s) {
+        return set_free_with_destructor(s, member_free);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(Set*, member_set_free);
 
 static int on_interface(const char *interface, uint64_t flags, void *userdata) {
diff --git a/src/core/automount.c b/src/core/automount.c
index 5076b351f5..f0fa5c8ca9 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -48,13 +48,13 @@ struct expire_data {
         int ioctl_fd;
 };
 
-static void expire_data_free(struct expire_data *data) {
+static struct expire_data* expire_data_free(struct expire_data *data) {
         if (!data)
-                return;
+                return NULL;
 
         safe_close(data->dev_autofs_fd);
         safe_close(data->ioctl_fd);
-        free(data);
+        return mfree(data);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct expire_data*, expire_data_free);
diff --git a/src/core/namespace.h b/src/core/namespace.h
index a4287869f7..54d4985f80 100644
--- a/src/core/namespace.h
+++ b/src/core/namespace.h
@@ -137,11 +137,11 @@ int setup_namespace(
 
 #define RUN_SYSTEMD_EMPTY "/run/systemd/empty"
 
-static inline void namespace_cleanup_tmpdir(char *p) {
+static inline char* namespace_cleanup_tmpdir(char *p) {
         PROTECT_ERRNO;
         if (!streq_ptr(p, RUN_SYSTEMD_EMPTY))
                 (void) rmdir(p);
-        free(p);
+        return mfree(p);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, namespace_cleanup_tmpdir);
 
diff --git a/src/core/socket.c b/src/core/socket.c
index cb5316af3a..5631054cce 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -969,6 +969,8 @@ static void socket_close_fds(Socket *s) {
         if (s->remove_on_stop)
                 STRV_FOREACH(i, s->symlinks)
                         (void) unlink(*i);
+
+        /* Note that we don't return NULL here, since s has not been freed. */
 }
 
 static void socket_apply_socket_options(Socket *s, SocketPort *p, int fd) {
@@ -1611,8 +1613,8 @@ static int socket_address_listen_in_cgroup(
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Socket *, socket_close_fds);
 
-static int socket_open_fds(Socket *_s) {
-        _cleanup_(socket_close_fdsp) Socket *s = _s;
+static int socket_open_fds(Socket *orig_s) {
+        _cleanup_(socket_close_fdsp) Socket *s = orig_s;
         _cleanup_(mac_selinux_freep) char *label = NULL;
         bool know_label = false;
         SocketPort *p;
diff --git a/src/core/unit.c b/src/core/unit.c
index 3452712590..e9c22375dd 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -82,7 +82,7 @@ const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
 
 static void maybe_warn_about_dependency(Unit *u, const char *other, UnitDependency dependency);
 
-Unit *unit_new(Manager *m, size_t size) {
+Unit* unit_new(Manager *m, size_t size) {
         Unit *u;
 
         assert(m);
@@ -607,11 +607,11 @@ static void unit_done(Unit *u) {
                 cgroup_context_done(cc);
 }
 
-void unit_free(Unit *u) {
+Unit* unit_free(Unit *u) {
         char *t;
 
         if (!u)
-                return;
+                return NULL;
 
         u->transient_file = safe_fclose(u->transient_file);
 
@@ -741,7 +741,7 @@ void unit_free(Unit *u) {
         set_free_free(u->aliases);
         free(u->id);
 
-        free(u);
+        return mfree(u);
 }
 
 FreezerState unit_freezer_state(Unit *u) {
diff --git a/src/core/unit.h b/src/core/unit.h
index 7c13e50878..6d38e66680 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -674,8 +674,8 @@ static inline Unit* UNIT_TRIGGER(Unit *u) {
         return hashmap_first_key(u->dependencies[UNIT_TRIGGERS]);
 }
 
-Unit *unit_new(Manager *m, size_t size);
-void unit_free(Unit *u);
+Unit* unit_new(Manager *m, size_t size);
+Unit* unit_free(Unit *u);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Unit *, unit_free);
 
 int unit_new_for_name(Manager *m, size_t size, const char *name, Unit **ret);
diff --git a/src/coredump/coredump-vacuum.c b/src/coredump/coredump-vacuum.c
index 2b0a2e5250..d20df847e8 100644
--- a/src/coredump/coredump-vacuum.c
+++ b/src/coredump/coredump-vacuum.c
@@ -28,17 +28,17 @@ typedef struct VacuumCandidate {
         usec_t oldest_mtime;
 } VacuumCandidate;
 
-static void vacuum_candidate_free(VacuumCandidate *c) {
+static VacuumCandidate* vacuum_candidate_free(VacuumCandidate *c) {
         if (!c)
-                return;
+                return NULL;
 
         free(c->oldest_file);
-        free(c);
+        return mfree(c);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(VacuumCandidate*, vacuum_candidate_free);
 
-static void vacuum_candidate_hashmap_free(Hashmap *h) {
-        hashmap_free_with_destructor(h, vacuum_candidate_free);
+static Hashmap* vacuum_candidate_hashmap_free(Hashmap *h) {
+        return hashmap_free_with_destructor(h, vacuum_candidate_free);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Hashmap*, vacuum_candidate_hashmap_free);
diff --git a/src/initctl/initctl.c b/src/initctl/initctl.c
index d818f452f7..c48fef16ef 100644
--- a/src/initctl/initctl.c
+++ b/src/initctl/initctl.c
@@ -210,8 +210,9 @@ static int fifo_process(Fifo *f) {
         return 0;
 }
 
-static void fifo_free(Fifo *f) {
-        assert(f);
+static Fifo* fifo_free(Fifo *f) {
+        if (!f)
+                return NULL;
 
         if (f->server) {
                 assert(f->server->n_fifos > 0);
@@ -226,7 +227,7 @@ static void fifo_free(Fifo *f) {
                 safe_close(f->fd);
         }
 
-        free(f);
+        return mfree(f);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(Fifo*, fifo_free);
 
diff --git a/src/journal/journald-stream.c b/src/journal/journald-stream.c
index 1c3652bf5b..73b3240677 100644
--- a/src/journal/journald-stream.c
+++ b/src/journal/journald-stream.c
@@ -98,9 +98,9 @@ struct StdoutStream {
         char id_field[STRLEN("_STREAM_ID=") + SD_ID128_STRING_MAX];
 };
 
-void stdout_stream_free(StdoutStream *s) {
+StdoutStream* stdout_stream_free(StdoutStream *s) {
         if (!s)
-                return;
+                return NULL;
 
         if (s->server) {
 
@@ -129,7 +129,7 @@ void stdout_stream_free(StdoutStream *s) {
         free(s->state_file);
         free(s->buffer);
 
-        free(s);
+        return mfree(s);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(StdoutStream*, stdout_stream_free);
diff --git a/src/journal/journald-stream.h b/src/journal/journald-stream.h
index 0a033b4dce..7b756c05ec 100644
--- a/src/journal/journald-stream.h
+++ b/src/journal/journald-stream.h
@@ -9,7 +9,7 @@ typedef struct StdoutStream StdoutStream;
 int server_open_stdout_socket(Server *s, const char *stdout_socket);
 int server_restore_streams(Server *s, FDSet *fds);
 
-void stdout_stream_free(StdoutStream *s);
+StdoutStream* stdout_stream_free(StdoutStream *s);
 int stdout_stream_install(Server *s, int fd, StdoutStream **ret);
 void stdout_stream_destroy(StdoutStream *s);
 void stdout_stream_send_notify(StdoutStream *s);
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 80292befeb..bc50664dc7 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -649,12 +649,12 @@ static int parse_request(uint8_t code, uint8_t len, const void *option, void *us
         return 0;
 }
 
-static void dhcp_request_free(DHCPRequest *req) {
+static DHCPRequest* dhcp_request_free(DHCPRequest *req) {
         if (!req)
-                return;
+                return NULL;
 
         free(req->client_id.data);
-        free(req);
+        return mfree(req);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(DHCPRequest*, dhcp_request_free);
diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index 8abbefcf27..d9991cfe19 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -939,7 +939,7 @@ static void source_disconnect(sd_event_source *s) {
                 sd_event_unref(event);
 }
 
-static void source_free(sd_event_source *s) {
+static sd_event_source* source_free(sd_event_source *s) {
         assert(s);
 
         source_disconnect(s);
@@ -989,7 +989,7 @@ static void source_free(sd_event_source *s) {
                 s->destroy_callback(s->userdata);
 
         free(s->description);
-        free(s);
+        return mfree(s);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(sd_event_source*, source_free);
 
diff --git a/src/libsystemd/sd-hwdb/hwdb-util.c b/src/libsystemd/sd-hwdb/hwdb-util.c
index 4c94ba9c88..34be0e7fcc 100644
--- a/src/libsystemd/sd-hwdb/hwdb-util.c
+++ b/src/libsystemd/sd-hwdb/hwdb-util.c
@@ -115,13 +115,13 @@ static void trie_node_cleanup(struct trie_node *node) {
         free(node);
 }
 
-static void trie_free(struct trie *trie) {
+static struct trie* trie_free(struct trie *trie) {
         if (!trie)
-                return;
+                return NULL;
 
         trie_node_cleanup(trie->root);
         strbuf_cleanup(trie->strings);
-        free(trie);
+        return mfree(trie);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct trie*, trie_free);
diff --git a/src/login/logind-brightness.c b/src/login/logind-brightness.c
index f4306749ec..5eb3534f53 100644
--- a/src/login/logind-brightness.c
+++ b/src/login/logind-brightness.c
@@ -44,9 +44,9 @@ typedef struct BrightnessWriter {
         sd_event_source* child_event_source;
 } BrightnessWriter;
 
-static void brightness_writer_free(BrightnessWriter *w) {
+static BrightnessWriter* brightness_writer_free(BrightnessWriter *w) {
         if (!w)
-                return;
+                return NULL;
 
         if (w->manager && w->path)
                 (void) hashmap_remove_value(w->manager->brightness_writers, w->path, w);
@@ -59,7 +59,7 @@ static void brightness_writer_free(BrightnessWriter *w) {
 
         w->child_event_source = sd_event_source_unref(w->child_event_source);
 
-        free(w);
+        return mfree(w);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(BrightnessWriter*, brightness_writer_free);
diff --git a/src/network/netdev/l2tp-tunnel.c b/src/network/netdev/l2tp-tunnel.c
index e302a2cf3b..a909b15764 100644
--- a/src/network/netdev/l2tp-tunnel.c
+++ b/src/network/netdev/l2tp-tunnel.c
@@ -39,18 +39,16 @@ static const char* const l2tp_local_address_type_table[_NETDEV_L2TP_LOCAL_ADDRES
 
 DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING(l2tp_local_address_type, L2tpLocalAddressType);
 
-static void l2tp_session_free(L2tpSession *s) {
+static L2tpSession* l2tp_session_free(L2tpSession *s) {
         if (!s)
-                return;
+                return NULL;
 
         if (s->tunnel && s->section)
                 ordered_hashmap_remove(s->tunnel->sessions_by_section, s->section);
 
         network_config_section_free(s->section);
-
         free(s->name);
-
-        free(s);
+        return mfree(s);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(L2tpSession, l2tp_session_free);
diff --git a/src/network/netdev/macsec.c b/src/network/netdev/macsec.c
index bef5ba1c51..77c5f8c4e7 100644
--- a/src/network/netdev/macsec.c
+++ b/src/network/netdev/macsec.c
@@ -35,9 +35,9 @@ static void security_association_init(SecurityAssociation *sa) {
         sa->use_for_encoding = -1;
 }
 
-static void macsec_receive_association_free(ReceiveAssociation *c) {
+static ReceiveAssociation* macsec_receive_association_free(ReceiveAssociation *c) {
         if (!c)
-                return;
+                return NULL;
 
         if (c->macsec && c->section)
                 ordered_hashmap_remove(c->macsec->receive_associations_by_section, c->section);
@@ -45,7 +45,7 @@ static void macsec_receive_association_free(ReceiveAssociation *c) {
         network_config_section_free(c->section);
         security_association_clear(&c->sa);
 
-        free(c);
+        return mfree(c);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(ReceiveAssociation, macsec_receive_association_free);
@@ -90,9 +90,9 @@ static int macsec_receive_association_new_static(MACsec *s, const char *filename
         return 0;
 }
 
-static void macsec_receive_channel_free(ReceiveChannel *c) {
+static ReceiveChannel* macsec_receive_channel_free(ReceiveChannel *c) {
         if (!c)
-                return;
+                return NULL;
 
         if (c->macsec) {
                 if (c->sci.as_uint64 > 0)
@@ -104,7 +104,7 @@ static void macsec_receive_channel_free(ReceiveChannel *c) {
 
         network_config_section_free(c->section);
 
-        free(c);
+        return mfree(c);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(ReceiveChannel, macsec_receive_channel_free);
@@ -162,9 +162,9 @@ static int macsec_receive_channel_new_static(MACsec *s, const char *filename, un
         return 0;
 }
 
-static void macsec_transmit_association_free(TransmitAssociation *a) {
+static TransmitAssociation* macsec_transmit_association_free(TransmitAssociation *a) {
         if (!a)
-                return;
+                return NULL;
 
         if (a->macsec && a->section)
                 ordered_hashmap_remove(a->macsec->transmit_associations_by_section, a->section);
@@ -172,7 +172,7 @@ static void macsec_transmit_association_free(TransmitAssociation *a) {
         network_config_section_free(a->section);
         security_association_clear(&a->sa);
 
-        free(a);
+        return mfree(a);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(TransmitAssociation, macsec_transmit_association_free);
diff --git a/src/network/netdev/wireguard.c b/src/network/netdev/wireguard.c
index e442ecc266..75d6d376a5 100644
--- a/src/network/netdev/wireguard.c
+++ b/src/network/netdev/wireguard.c
@@ -26,11 +26,11 @@
 
 static void resolve_endpoints(NetDev *netdev);
 
-static void wireguard_peer_free(WireguardPeer *peer) {
+static WireguardPeer* wireguard_peer_free(WireguardPeer *peer) {
         WireguardIPmask *mask;
 
         if (!peer)
-                return;
+                return NULL;
 
         if (peer->wireguard) {
                 LIST_REMOVE(peers, peer->wireguard->peers, peer);
@@ -54,7 +54,7 @@ static void wireguard_peer_free(WireguardPeer *peer) {
         free(peer->preshared_key_file);
         explicit_bzero_safe(peer->preshared_key, WG_KEY_LEN);
 
-        free(peer);
+        return mfree(peer);
 }
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(WireguardPeer, wireguard_peer_free);
diff --git a/src/network/networkctl.c b/src/network/networkctl.c
index 4381f63a2d..1dd3438abd 100644
--- a/src/network/networkctl.c
+++ b/src/network/networkctl.c
@@ -230,7 +230,7 @@ static int link_info_compare(const LinkInfo *a, const LinkInfo *b) {
         return CMP(a->ifindex, b->ifindex);
 }
 
-static const LinkInfo* link_info_array_free(LinkInfo *array) {
+static LinkInfo* link_info_array_free(LinkInfo *array) {
         for (unsigned i = 0; array && array[i].needs_freeing; i++) {
                 sd_device_unref(array[i].sd_device);
                 free(array[i].ssid);
diff --git a/src/network/networkd-manager.c b/src/network/networkd-manager.c
index d7e0662453..debd9f1ecc 100644
--- a/src/network/networkd-manager.c
+++ b/src/network/networkd-manager.c
@@ -850,11 +850,11 @@ int manager_new(Manager **ret) {
         return 0;
 }
 
-void manager_free(Manager *m) {
+Manager* manager_free(Manager *m) {
         Link *link;
 
         if (!m)
-                return;
+                return NULL;
 
         free(m->state_file);
 
@@ -909,7 +909,7 @@ void manager_free(Manager *m) {
 
         m->fw_ctx = fw_ctx_free(m->fw_ctx);
 
-        free(m);
+        return mfree(m);
 }
 
 int manager_start(Manager *m) {
diff --git a/src/network/networkd-manager.h b/src/network/networkd-manager.h
index f553abcc54..8b5f8a9dc0 100644
--- a/src/network/networkd-manager.h
+++ b/src/network/networkd-manager.h
@@ -83,7 +83,7 @@ struct Manager {
 };
 
 int manager_new(Manager **ret);
-void manager_free(Manager *m);
+Manager* manager_free(Manager *m);
 
 int manager_connect_bus(Manager *m);
 int manager_start(Manager *m);
diff --git a/src/network/networkd-util.h b/src/network/networkd-util.h
index efeeb86eb0..1736e2b57b 100644
--- a/src/network/networkd-util.h
+++ b/src/network/networkd-util.h
@@ -47,8 +47,8 @@ sd_dhcp_lease_server_type dhcp_lease_server_type_from_string(const char *s) _pur
 
 int kernel_route_expiration_supported(void);
 
-static inline void network_config_section_free(NetworkConfigSection *cs) {
-        free(cs);
+static inline NetworkConfigSection* network_config_section_free(NetworkConfigSection *cs) {
+        return mfree(cs);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(NetworkConfigSection*, network_config_section_free);
 
@@ -66,13 +66,14 @@ static inline bool section_is_invalid(NetworkConfigSection *section) {
 }
 
 #define DEFINE_NETWORK_SECTION_FUNCTIONS(type, free_func)               \
-        static inline void free_func##_or_set_invalid(type *p) {        \
+        static inline type* free_func##_or_set_invalid(type *p) {       \
                 assert(p);                                              \
                                                                         \
                 if (p->section)                                         \
                         p->section->invalid = true;                     \
                 else                                                    \
                         free_func(p);                                   \
+                return NULL;                                            \
         }                                                               \
         DEFINE_TRIVIAL_CLEANUP_FUNC(type*, free_func);                  \
         DEFINE_TRIVIAL_CLEANUP_FUNC(type*, free_func##_or_set_invalid);
diff --git a/src/network/tc/qdisc.c b/src/network/tc/qdisc.c
index 7016dc1877..2e0f0a12eb 100644
--- a/src/network/tc/qdisc.c
+++ b/src/network/tc/qdisc.c
@@ -134,9 +134,9 @@ int qdisc_new_static(QDiscKind kind, Network *network, const char *filename, uns
         return 0;
 }
 
-void qdisc_free(QDisc *qdisc) {
+QDisc* qdisc_free(QDisc *qdisc) {
         if (!qdisc)
-                return;
+                return NULL;
 
         if (qdisc->network && qdisc->section)
                 ordered_hashmap_remove(qdisc->network->tc_by_section, qdisc->section);
@@ -144,7 +144,7 @@ void qdisc_free(QDisc *qdisc) {
         network_config_section_free(qdisc->section);
 
         free(qdisc->tca_kind);
-        free(qdisc);
+        return mfree(qdisc);
 }
 
 static int qdisc_handler(sd_netlink *rtnl, sd_netlink_message *m, Link *link) {
diff --git a/src/network/tc/qdisc.h b/src/network/tc/qdisc.h
index 2232189f4f..bf2df146a7 100644
--- a/src/network/tc/qdisc.h
+++ b/src/network/tc/qdisc.h
@@ -74,7 +74,7 @@ extern const QDiscVTable * const qdisc_vtable[_QDISC_KIND_MAX];
 /* For casting the various qdisc kinds into a qdisc */
 #define QDISC(q) (&(q)->meta)
 
-void qdisc_free(QDisc *qdisc);
+QDisc* qdisc_free(QDisc *qdisc);
 int qdisc_new_static(QDiscKind kind, Network *network, const char *filename, unsigned section_line, QDisc **ret);
 
 int qdisc_configure(Link *link, QDisc *qdisc);
diff --git a/src/network/tc/tclass.c b/src/network/tc/tclass.c
index 64bdfbb90b..d8145997f0 100644
--- a/src/network/tc/tclass.c
+++ b/src/network/tc/tclass.c
@@ -90,16 +90,16 @@ int tclass_new_static(TClassKind kind, Network *network, const char *filename, u
         return 0;
 }
 
-void tclass_free(TClass *tclass) {
+TClass* tclass_free(TClass *tclass) {
         if (!tclass)
-                return;
+                return NULL;
 
         if (tclass->network && tclass->section)
                 ordered_hashmap_remove(tclass->network->tc_by_section, tclass->section);
 
         network_config_section_free(tclass->section);
 
-        free(tclass);
+        return mfree(tclass);
 }
 
 static int tclass_handler(sd_netlink *rtnl, sd_netlink_message *m, Link *link) {
diff --git a/src/network/tc/tclass.h b/src/network/tc/tclass.h
index 8e5e52c401..fc91789f30 100644
--- a/src/network/tc/tclass.h
+++ b/src/network/tc/tclass.h
@@ -53,7 +53,7 @@ extern const TClassVTable * const tclass_vtable[_TCLASS_KIND_MAX];
 /* For casting the various tclass kinds into a tclass */
 #define TCLASS(t) (&(t)->meta)
 
-void tclass_free(TClass *tclass);
+TClass* tclass_free(TClass *tclass);
 int tclass_new_static(TClassKind kind, Network *network, const char *filename, unsigned section_line, TClass **ret);
 
 int tclass_configure(Link *link, TClass *tclass);
diff --git a/src/network/wait-online/manager.c b/src/network/wait-online/manager.c
index 8321395550..f6c8cf909f 100644
--- a/src/network/wait-online/manager.c
+++ b/src/network/wait-online/manager.c
@@ -347,21 +347,18 @@ int manager_new(Manager **ret, Hashmap *interfaces, char **ignore,
         return 0;
 }
 
-void manager_free(Manager *m) {
+Manager* manager_free(Manager *m) {
         if (!m)
-                return;
+                return NULL;
 
         hashmap_free_with_destructor(m->links, link_free);
         hashmap_free(m->links_by_name);
 
         sd_event_source_unref(m->network_monitor_event_source);
         sd_network_monitor_unref(m->network_monitor);
-
         sd_event_source_unref(m->rtnl_event_source);
         sd_netlink_unref(m->rtnl);
-
         sd_event_unref(m->event);
-        free(m);
 
-        return;
+        return mfree(m);
 }
diff --git a/src/network/wait-online/manager.h b/src/network/wait-online/manager.h
index f5e83532ae..9892a43dc9 100644
--- a/src/network/wait-online/manager.h
+++ b/src/network/wait-online/manager.h
@@ -32,7 +32,7 @@ struct Manager {
         sd_event *event;
 };
 
-void manager_free(Manager *m);
+Manager* manager_free(Manager *m);
 int manager_new(Manager **ret, Hashmap *interfaces, char **ignore,
                 LinkOperationalStateRange required_operstate,
                 bool any, usec_t timeout);
diff --git a/src/oom/oomd-manager.c b/src/oom/oomd-manager.c
index 94b17dd07b..bdf41807b2 100644
--- a/src/oom/oomd-manager.c
+++ b/src/oom/oomd-manager.c
@@ -397,7 +397,7 @@ static int monitor_cgroup_contexts(Manager *m) {
         return 0;
 }
 
-void manager_free(Manager *m) {
+Manager* manager_free(Manager *m) {
         assert(m);
 
         varlink_close_unref(m->varlink);
@@ -410,7 +410,7 @@ void manager_free(Manager *m) {
         hashmap_free(m->monitored_swap_cgroup_contexts);
         hashmap_free(m->monitored_mem_pressure_cgroup_contexts);
 
-        free(m);
+        return mfree(m);
 }
 
 int manager_new(Manager **ret) {
diff --git a/src/oom/oomd-manager.h b/src/oom/oomd-manager.h
index 521665e0a8..50f10021c7 100644
--- a/src/oom/oomd-manager.h
+++ b/src/oom/oomd-manager.h
@@ -51,7 +51,7 @@ struct Manager {
         Varlink *varlink;
 };
 
-void manager_free(Manager *m);
+Manager* manager_free(Manager *m);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
 
 int manager_new(Manager **ret);
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index cf0e221621..03da73c4ae 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -80,17 +80,16 @@ static const char *dns_cache_item_type_to_string(DnsCacheItem *item) {
         return NULL;
 }
 
-static void dns_cache_item_free(DnsCacheItem *i) {
+static DnsCacheItem* dns_cache_item_free(DnsCacheItem *i) {
         if (!i)
-                return;
+                return NULL;
 
         dns_resource_record_unref(i->rr);
         dns_resource_key_unref(i->key);
         dns_answer_unref(i->answer);
         dns_packet_unref(i->full_packet);
-        free(i);
+        return mfree(i);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsCacheItem*, dns_cache_item_free);
 
 static void dns_cache_item_unlink_and_free(DnsCache *c, DnsCacheItem *i) {
diff --git a/src/resolve/resolved-dns-zone.c b/src/resolve/resolved-dns-zone.c
index 4c5e1fe372..6f15c53953 100644
--- a/src/resolve/resolved-dns-zone.c
+++ b/src/resolve/resolved-dns-zone.c
@@ -26,16 +26,15 @@ void dns_zone_item_probe_stop(DnsZoneItem *i) {
         dns_transaction_gc(t);
 }
 
-static void dns_zone_item_free(DnsZoneItem *i) {
+static DnsZoneItem* dns_zone_item_free(DnsZoneItem *i) {
         if (!i)
-                return;
+                return NULL;
 
         dns_zone_item_probe_stop(i);
         dns_resource_record_unref(i->rr);
 
-        free(i);
+        return mfree(i);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsZoneItem*, dns_zone_item_free);
 
 static void dns_zone_item_remove_and_free(DnsZone *z, DnsZoneItem *i) {
diff --git a/src/shared/barrier.c b/src/shared/barrier.c
index 9c93d61a3c..271bba8cde 100644
--- a/src/shared/barrier.c
+++ b/src/shared/barrier.c
@@ -123,14 +123,15 @@ int barrier_create(Barrier *b) {
  *
  * If @b is NULL, this is a no-op.
  */
-void barrier_destroy(Barrier *b) {
+Barrier* barrier_destroy(Barrier *b) {
         if (!b)
-                return;
+                return NULL;
 
         b->me = safe_close(b->me);
         b->them = safe_close(b->them);
         safe_close_pair(b->pipe);
         b->barriers = 0;
+        return NULL;
 }
 
 /**
diff --git a/src/shared/barrier.h b/src/shared/barrier.h
index b11dce4fc0..b9fc92d752 100644
--- a/src/shared/barrier.h
+++ b/src/shared/barrier.h
@@ -37,7 +37,7 @@ struct Barrier {
 #define BARRIER_NULL {-1, -1, {-1, -1}, 0}
 
 int barrier_create(Barrier *obj);
-void barrier_destroy(Barrier *b);
+Barrier* barrier_destroy(Barrier *b);
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Barrier*, barrier_destroy);
 
diff --git a/src/shared/bitmap.c b/src/shared/bitmap.c
index 5d450c8832..33528388f0 100644
--- a/src/shared/bitmap.c
+++ b/src/shared/bitmap.c
@@ -24,11 +24,11 @@
 #define BITMAP_NUM_TO_REM(n)              ((n) % (sizeof(uint64_t) * 8))
 #define BITMAP_OFFSET_TO_NUM(offset, rem) ((offset) * sizeof(uint64_t) * 8 + (rem))
 
-Bitmap *bitmap_new(void) {
+Bitmap* bitmap_new(void) {
         return new0(Bitmap, 1);
 }
 
-Bitmap *bitmap_copy(Bitmap *b) {
+Bitmap* bitmap_copy(Bitmap *b) {
         Bitmap *ret;
 
         ret = bitmap_new();
@@ -43,12 +43,12 @@ Bitmap *bitmap_copy(Bitmap *b) {
         return ret;
 }
 
-void bitmap_free(Bitmap *b) {
+Bitmap* bitmap_free(Bitmap *b) {
         if (!b)
-                return;
+                return NULL;
 
         free(b->bitmaps);
-        free(b);
+        return mfree(b);
 }
 
 int bitmap_ensure_allocated(Bitmap **b) {
diff --git a/src/shared/bitmap.h b/src/shared/bitmap.h
index 1c305a2c41..5c7651c68d 100644
--- a/src/shared/bitmap.h
+++ b/src/shared/bitmap.h
@@ -12,10 +12,10 @@ typedef struct Bitmap {
         size_t bitmaps_allocated;
 } Bitmap;
 
-Bitmap *bitmap_new(void);
-Bitmap *bitmap_copy(Bitmap *b);
+Bitmap* bitmap_new(void);
+Bitmap* bitmap_copy(Bitmap *b);
 int bitmap_ensure_allocated(Bitmap **b);
-void bitmap_free(Bitmap *b);
+Bitmap* bitmap_free(Bitmap *b);
 
 int bitmap_set(Bitmap *b, unsigned n);
 void bitmap_unset(Bitmap *b, unsigned n);
diff --git a/src/shared/bus-wait-for-jobs.c b/src/shared/bus-wait-for-jobs.c
index 005294c33a..80f7785323 100644
--- a/src/shared/bus-wait-for-jobs.c
+++ b/src/shared/bus-wait-for-jobs.c
@@ -61,9 +61,9 @@ static int match_job_removed(sd_bus_message *m, void *userdata, sd_bus_error *er
         return 0;
 }
 
-void bus_wait_for_jobs_free(BusWaitForJobs *d) {
+BusWaitForJobs* bus_wait_for_jobs_free(BusWaitForJobs *d) {
         if (!d)
-                return;
+                return NULL;
 
         set_free(d->jobs);
 
@@ -75,7 +75,7 @@ void bus_wait_for_jobs_free(BusWaitForJobs *d) {
         free(d->name);
         free(d->result);
 
-        free(d);
+        return mfree(d);
 }
 
 int bus_wait_for_jobs_new(sd_bus *bus, BusWaitForJobs **ret) {
diff --git a/src/shared/bus-wait-for-jobs.h b/src/shared/bus-wait-for-jobs.h
index 0155887455..68c9d604ad 100644
--- a/src/shared/bus-wait-for-jobs.h
+++ b/src/shared/bus-wait-for-jobs.h
@@ -8,7 +8,7 @@
 typedef struct BusWaitForJobs BusWaitForJobs;
 
 int bus_wait_for_jobs_new(sd_bus *bus, BusWaitForJobs **ret);
-void bus_wait_for_jobs_free(BusWaitForJobs *d);
+BusWaitForJobs* bus_wait_for_jobs_free(BusWaitForJobs *d);
 int bus_wait_for_jobs_add(BusWaitForJobs *d, const char *path);
 int bus_wait_for_jobs(BusWaitForJobs *d, bool quiet, const char* const* extra_args);
 int bus_wait_for_jobs_one(BusWaitForJobs *d, const char *path, bool quiet);
diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c
index c23a91eeed..4f68a570b5 100644
--- a/src/shared/calendarspec.c
+++ b/src/shared/calendarspec.c
@@ -33,14 +33,13 @@
 /* Let's make sure that the microsecond component is safe to be stored in an 'int' */
 assert_cc(INT_MAX >= USEC_PER_SEC);
 
-static void chain_free(CalendarComponent *c) {
-        CalendarComponent *n;
-
+static CalendarComponent* chain_free(CalendarComponent *c) {
         while (c) {
-                n = c->next;
+                CalendarComponent *n = c->next;
                 free(c);
                 c = n;
         }
+        return NULL;
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(CalendarComponent*, chain_free);
diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index de94d3399c..62050daecd 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -1681,12 +1681,12 @@ static int verity_can_reuse(
         return 0;
 }
 
-static inline void dm_deferred_remove_clean(char *name) {
+static inline char* dm_deferred_remove_clean(char *name) {
         if (!name)
-                return;
+                return NULL;
 
         (void) sym_crypt_deactivate_by_name(NULL, name, CRYPT_DEACTIVATE_DEFERRED);
-        free(name);
+        return mfree(name);
 }
 DEFINE_TRIVIAL_CLEANUP_FUNC(char *, dm_deferred_remove_clean);
 
diff --git a/src/shared/install.c b/src/shared/install.c
index e70fa45022..77208582b7 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -3346,12 +3346,12 @@ int unit_file_preset_all(
         return execute_preset(scope, &plus, &minus, &paths, config_path, NULL, mode, !!(flags & UNIT_FILE_FORCE), changes, n_changes);
 }
 
-static void unit_file_list_free_one(UnitFileList *f) {
+static UnitFileList* unit_file_list_free_one(UnitFileList *f) {
         if (!f)
-                return;
+                return NULL;
 
         free(f->path);
-        free(f);
+        return mfree(f);
 }
 
 Hashmap* unit_file_list_free(Hashmap *h) {
diff --git a/src/systemctl/systemctl-show.c b/src/systemctl/systemctl-show.c
index 57e708095d..6f3b3566d7 100644
--- a/src/systemctl/systemctl-show.c
+++ b/src/systemctl/systemctl-show.c
@@ -147,15 +147,14 @@ typedef struct UnitCondition {
         LIST_FIELDS(struct UnitCondition, conditions);
 } UnitCondition;
 
-static void unit_condition_free(UnitCondition *c) {
+static UnitCondition* unit_condition_free(UnitCondition *c) {
         if (!c)
-                return;
+                return NULL;
 
         free(c->name);
         free(c->param);
-        free(c);
+        return mfree(c);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(UnitCondition*, unit_condition_free);
 
 typedef struct UnitStatusInfo {
diff --git a/src/sysv-generator/sysv-generator.c b/src/sysv-generator/sysv-generator.c
index 008a8250bb..8c7aef23c3 100644
--- a/src/sysv-generator/sysv-generator.c
+++ b/src/sysv-generator/sysv-generator.c
@@ -59,9 +59,9 @@ typedef struct SysvStub {
         bool loaded;
 } SysvStub;
 
-static void free_sysvstub(SysvStub *s) {
+static SysvStub* free_sysvstub(SysvStub *s) {
         if (!s)
-                return;
+                return NULL;
 
         free(s->name);
         free(s->path);
@@ -71,9 +71,8 @@ static void free_sysvstub(SysvStub *s) {
         strv_free(s->after);
         strv_free(s->wants);
         strv_free(s->wanted_by);
-        free(s);
+        return mfree(s);
 }
-
 DEFINE_TRIVIAL_CLEANUP_FUNC(SysvStub*, free_sysvstub);
 
 static void free_sysvstub_hashmapp(Hashmap **h) {
diff --git a/src/timesync/timesyncd-manager.c b/src/timesync/timesyncd-manager.c
index 07fee57391..8c2ee4cbec 100644
--- a/src/timesync/timesyncd-manager.c
+++ b/src/timesync/timesyncd-manager.c
@@ -915,9 +915,9 @@ void manager_flush_server_names(Manager  *m, ServerType t) {
                         server_name_free(m->fallback_servers);
 }
 
-void manager_free(Manager *m) {
+Manager* manager_free(Manager *m) {
         if (!m)
-                return;
+                return NULL;
 
         manager_disconnect(m);
         manager_flush_server_names(m, SERVER_SYSTEM);
@@ -934,7 +934,7 @@ void manager_free(Manager *m) {
 
         sd_bus_flush_close_unref(m->bus);
 
-        free(m);
+        return mfree(m);
 }
 
 static int manager_network_read_link_servers(Manager *m) {
diff --git a/src/timesync/timesyncd-manager.h b/src/timesync/timesyncd-manager.h
index 37cf406190..af218a5f63 100644
--- a/src/timesync/timesyncd-manager.h
+++ b/src/timesync/timesyncd-manager.h
@@ -103,7 +103,7 @@ struct Manager {
 };
 
 int manager_new(Manager **ret);
-void manager_free(Manager *m);
+Manager* manager_free(Manager *m);
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
 
diff --git a/src/udev/net/link-config.c b/src/udev/net/link-config.c
index 9209f8f4b4..f2ca1bb561 100644
--- a/src/udev/net/link-config.c
+++ b/src/udev/net/link-config.c
@@ -45,9 +45,9 @@ struct link_config_ctx {
         usec_t network_dirs_ts_usec;
 };
 
-static void link_config_free(link_config *link) {
+static link_config* link_config_free(link_config *link) {
         if (!link)
-                return;
+                return NULL;
 
         free(link->filename);
 
@@ -62,7 +62,7 @@ static void link_config_free(link_config *link) {
         free(link->alternative_names_policy);
         free(link->alias);
 
-        free(link);
+        return mfree(link);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(link_config*, link_config_free);
@@ -77,19 +77,14 @@ static void link_configs_free(link_config_ctx *ctx) {
                 link_config_free(link);
 }
 
-void link_config_ctx_free(link_config_ctx *ctx) {
+link_config_ctx* link_config_ctx_free(link_config_ctx *ctx) {
         if (!ctx)
-                return;
+                return NULL;
 
         safe_close(ctx->ethtool_fd);
-
         sd_netlink_unref(ctx->rtnl);
-
         link_configs_free(ctx);
-
-        free(ctx);
-
-        return;
+        return mfree(ctx);
 }
 
 int link_config_ctx_new(link_config_ctx **ret) {
diff --git a/src/udev/net/link-config.h b/src/udev/net/link-config.h
index 3f899e9879..71f8983fb7 100644
--- a/src/udev/net/link-config.h
+++ b/src/udev/net/link-config.h
@@ -69,7 +69,7 @@ struct link_config {
 };
 
 int link_config_ctx_new(link_config_ctx **ret);
-void link_config_ctx_free(link_config_ctx *ctx);
+link_config_ctx* link_config_ctx_free(link_config_ctx *ctx);
 DEFINE_TRIVIAL_CLEANUP_FUNC(link_config_ctx*, link_config_ctx_free);
 
 int link_load_one(link_config_ctx *ctx, const char *filename);
diff --git a/src/udev/udev-ctrl.c b/src/udev/udev-ctrl.c
index c65f8772ea..61090a6e4a 100644
--- a/src/udev/udev-ctrl.c
+++ b/src/udev/udev-ctrl.c
@@ -164,6 +164,7 @@ static void udev_ctrl_disconnect_and_listen_again(struct udev_ctrl *uctrl) {
         udev_ctrl_disconnect(uctrl);
         udev_ctrl_unref(uctrl);
         (void) sd_event_source_set_enabled(uctrl->event_source, SD_EVENT_ON);
+        /* We don't return NULL here because uctrl is not freed */
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct udev_ctrl *, udev_ctrl_disconnect_and_listen_again);
diff --git a/src/udev/udev-rules.c b/src/udev/udev-rules.c
index fb4de17a5c..78184b4136 100644
--- a/src/udev/udev-rules.c
+++ b/src/udev/udev-rules.c
@@ -264,9 +264,9 @@ static void udev_rule_line_clear_tokens(UdevRuleLine *rule_line) {
         rule_line->tokens = NULL;
 }
 
-static void udev_rule_line_free(UdevRuleLine *rule_line) {
+static UdevRuleLine* udev_rule_line_free(UdevRuleLine *rule_line) {
         if (!rule_line)
-                return;
+                return NULL;
 
         udev_rule_line_clear_tokens(rule_line);
 
@@ -278,7 +278,7 @@ static void udev_rule_line_free(UdevRuleLine *rule_line) {
         }
 
         free(rule_line->line);
-        free(rule_line);
+        return mfree(rule_line);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(UdevRuleLine*, udev_rule_line_free);
diff --git a/src/udev/udevd.c b/src/udev/udevd.c
index 0134f78b4b..9772246aeb 100644
--- a/src/udev/udevd.c
+++ b/src/udev/udevd.c
@@ -173,9 +173,9 @@ static void event_free(struct event *event) {
         free(event);
 }
 
-static void worker_free(struct worker *worker) {
+static struct worker* worker_free(struct worker *worker) {
         if (!worker)
-                return;
+                return NULL;
 
         assert(worker->manager);
 
@@ -183,7 +183,7 @@ static void worker_free(struct worker *worker) {
         sd_device_monitor_unref(worker->monitor);
         event_free(worker->event);
 
-        free(worker);
+        return mfree(worker);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct worker *, worker_free);
@@ -287,9 +287,9 @@ static void manager_clear_for_worker(Manager *manager) {
         manager->worker_watch[READ_END] = safe_close(manager->worker_watch[READ_END]);
 }
 
-static void manager_free(Manager *manager) {
+static Manager* manager_free(Manager *manager) {
         if (!manager)
-                return;
+                return NULL;
 
         udev_builtin_exit();
 
@@ -306,7 +306,7 @@ static void manager_free(Manager *manager) {
         safe_close(manager->fd_inotify);
         safe_close_pair(manager->worker_watch);
 
-        free(manager);
+        return mfree(manager);
 }
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);