diff --git a/include/osmocom/bsc/assignment_fsm.h b/include/osmocom/bsc/assignment_fsm.h
index 98bec420e..3dffaf212 100644
--- a/include/osmocom/bsc/assignment_fsm.h
+++ b/include/osmocom/bsc/assignment_fsm.h
@@ -40,7 +40,7 @@ enum assignment_fsm_event {
 	ASSIGNMENT_EV_CONN_RELEASING,
 };
 
-void assignment_fsm_init();
+void assignment_fsm_init(void);
 
 int reassignment_request_to_lchan(enum assign_for assign_for, struct gsm_lchan *lchan, struct gsm_lchan *to_lchan,
 				  int tsc_set, int tsc);
diff --git a/include/osmocom/bsc/bsc_stats.h b/include/osmocom/bsc/bsc_stats.h
index e8837aa1e..eae97509c 100644
--- a/include/osmocom/bsc/bsc_stats.h
+++ b/include/osmocom/bsc/bsc_stats.h
@@ -113,4 +113,4 @@ extern const struct osmo_stat_item_group_desc bsc_statg_desc;
 void bsc_update_connection_stats(struct gsm_network *net);
 
 void all_allocated_update_bts(struct gsm_bts *bts);
-void all_allocated_update_bsc();
+void all_allocated_update_bsc(void);
diff --git a/include/osmocom/bsc/bsc_subscr_conn_fsm.h b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
index 0ab484372..b358da656 100644
--- a/include/osmocom/bsc/bsc_subscr_conn_fsm.h
+++ b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
@@ -57,7 +57,7 @@ struct osmo_mgcpc_ep_ci;
 struct assignment_request;
 struct gsm_lchan;
 
-void bsc_subscr_conn_fsm_init();
+void bsc_subscr_conn_fsm_init(void);
 
 /* Allocate a subscriber connection and its associated FSM */
 struct gsm_subscriber_connection *bsc_subscr_con_allocate(struct gsm_network *net);
diff --git a/include/osmocom/bsc/chan_counts.h b/include/osmocom/bsc/chan_counts.h
index c11473e71..a830e8745 100644
--- a/include/osmocom/bsc/chan_counts.h
+++ b/include/osmocom/bsc/chan_counts.h
@@ -6,11 +6,11 @@ struct gsm_bts_trx;
 struct gsm_bts_trx_ts;
 struct gsm_lchan;
 
-void chan_counts_sig_init();
+void chan_counts_sig_init(void);
 void chan_counts_ts_update(struct gsm_bts_trx_ts *ts);
 void chan_counts_ts_clear(struct gsm_bts_trx_ts *ts);
 void chan_counts_trx_update(struct gsm_bts_trx *trx);
-void chan_counts_bsc_verify();
+void chan_counts_bsc_verify(void);
 
 /* First array index to chan_counts.val. */
 enum chan_counts_dim1 {
diff --git a/include/osmocom/bsc/handover_fsm.h b/include/osmocom/bsc/handover_fsm.h
index 052e09d79..faec73fcc 100644
--- a/include/osmocom/bsc/handover_fsm.h
+++ b/include/osmocom/bsc/handover_fsm.h
@@ -55,7 +55,7 @@ struct handover_rr_detect_data {
 	const uint8_t *access_delay;
 };
 
-void handover_fsm_init();
+void handover_fsm_init(void);
 
 int handover_request(struct handover_out_req *req);
 void handover_start(struct handover_out_req *req);
diff --git a/include/osmocom/bsc/handover_vty.h b/include/osmocom/bsc/handover_vty.h
index 6ad5276e2..1dd8bf08a 100644
--- a/include/osmocom/bsc/handover_vty.h
+++ b/include/osmocom/bsc/handover_vty.h
@@ -3,6 +3,6 @@
 #include <osmocom/vty/vty.h>
 #include <osmocom/bsc/handover_cfg.h>
 
-void ho_vty_init();
+void ho_vty_init(void);
 void ho_vty_write_net(struct vty *vty, struct gsm_network *net);
 void ho_vty_write_bts(struct vty *vty, struct gsm_bts *bts);
diff --git a/include/osmocom/bsc/lb.h b/include/osmocom/bsc/lb.h
index dbea0b0e1..08206d4d8 100644
--- a/include/osmocom/bsc/lb.h
+++ b/include/osmocom/bsc/lb.h
@@ -57,7 +57,7 @@ struct smlc_config {
 extern const struct rate_ctr_desc smlc_ctr_description[];
 extern const struct rate_ctr_group_desc smlc_ctrg_desc;
 
-int lb_init();
-int lb_start_or_stop();
+int lb_init(void);
+int lb_start_or_stop(void);
 int lb_send(struct gsm_subscriber_connection *conn, const struct bssap_le_pdu *bssap_le);
 void lb_close_conn(struct gsm_subscriber_connection *conn);
diff --git a/include/osmocom/bsc/lchan_fsm.h b/include/osmocom/bsc/lchan_fsm.h
index b9ffb2243..cc231dcf4 100644
--- a/include/osmocom/bsc/lchan_fsm.h
+++ b/include/osmocom/bsc/lchan_fsm.h
@@ -56,7 +56,7 @@ enum lchan_fsm_event {
 	LCHAN_EV_REQUEST_MODE_MODIFY,
 };
 
-void lchan_fsm_init();
+void lchan_fsm_init(void);
 
 void lchan_fsm_alloc(struct gsm_lchan *lchan);
 void lchan_release(struct gsm_lchan *lchan, bool do_rr_release,
diff --git a/include/osmocom/bsc/neighbor_ident.h b/include/osmocom/bsc/neighbor_ident.h
index c6a2c4237..bd14bd409 100644
--- a/include/osmocom/bsc/neighbor_ident.h
+++ b/include/osmocom/bsc/neighbor_ident.h
@@ -73,7 +73,7 @@ void bts_cell_ab(struct cell_ab *arfcn_bsic, const struct gsm_bts *bts);
 int resolve_neighbors(struct gsm_bts **local_neighbor_p, struct gsm0808_cell_id_list2 *remote_neighbors,
 		      struct gsm_bts *from_bts, const struct cell_ab *target_ab, bool log_errors);
 
-void neighbor_ident_vty_init();
+void neighbor_ident_vty_init(void);
 void neighbor_ident_vty_write_bts(struct vty *vty, const char *indent, struct gsm_bts *bts);
 void neighbor_ident_vty_write_network(struct vty *vty, const char *indent);
 
@@ -81,7 +81,7 @@ int neighbor_ident_add_neighbor(struct vty *vty, struct gsm_bts *bts, struct nei
 int neighbor_ident_del_neighbor(struct vty *vty, struct gsm_bts *bts, struct neighbor *n);
 int neighbor_ident_ctrl_init(void);
 
-int neighbors_check_cfg();
+int neighbors_check_cfg(void);
 
 #define CELL_AB_VTY_PARAMS "arfcn <0-1023> bsic (<0-63>|any)"
 #define CELL_AB_VTY_DOC \
diff --git a/include/osmocom/bsc/osmo_bsc.h b/include/osmocom/bsc/osmo_bsc.h
index 13ccdd7b2..ee8cc1312 100644
--- a/include/osmocom/bsc/osmo_bsc.h
+++ b/include/osmocom/bsc/osmo_bsc.h
@@ -17,7 +17,7 @@ struct gsm_audio_support;
 struct gsm_subscriber_connection;
 struct gsm_bts;
 
-struct bsc_api *osmo_bsc_api();
+struct bsc_api *osmo_bsc_api(void);
 
 int bsc_scan_bts_msg(struct gsm_subscriber_connection *conn, struct msgb *msg);
 int bsc_scan_msc_msg(struct gsm_subscriber_connection *conn, struct msgb *msg);
@@ -25,7 +25,8 @@ int bsc_scan_msc_msg(struct gsm_subscriber_connection *conn, struct msgb *msg);
 int bsc_handle_udt(struct bsc_msc_data *msc, struct msgb *msg, unsigned int length);
 int bsc_handle_dt(struct gsm_subscriber_connection *conn, struct msgb *msg, unsigned int len);
 
-int bsc_ctrl_cmds_install();
+struct gsm_network;
+int bsc_ctrl_cmds_install(struct gsm_network *net);
 
 void bsc_gen_location_state_trap(struct gsm_bts *bts);
 
diff --git a/src/ipaccess/abisip-find.c b/src/ipaccess/abisip-find.c
index 4bba8a315..a26bb55d7 100644
--- a/src/ipaccess/abisip-find.c
+++ b/src/ipaccess/abisip-find.c
@@ -53,7 +53,7 @@ static struct {
 	.format_json = false,
 };
 
-static void print_help()
+static void print_help(void)
 {
 	printf("\n");
 	printf("Usage: abisip-find [-l] [<interface-name>]\n");
@@ -265,7 +265,7 @@ LLIST_HEAD(base_stations);
 
 void *ctx = NULL;
 
-void print_timestamp()
+void print_timestamp(void)
 {
 	time_t now = time(NULL);
 	printf("\n\n----- %s\n", ctime(&now));
@@ -304,7 +304,7 @@ bool base_stations_add(struct base_station *new_bs)
 	return true;
 }
 
-bool base_stations_timeout()
+bool base_stations_timeout(void)
 {
 	struct base_station *bs, *next_bs;
 	time_t now = time(NULL);
@@ -323,7 +323,7 @@ bool base_stations_timeout()
 	return changed;
 }
 
-void base_stations_print()
+void base_stations_print(void)
 {
 	struct base_station *bs;
 	int count = 0;
diff --git a/src/osmo-bsc/assignment_fsm.c b/src/osmo-bsc/assignment_fsm.c
index 7ca17c6a1..fff7e59eb 100644
--- a/src/osmo-bsc/assignment_fsm.c
+++ b/src/osmo-bsc/assignment_fsm.c
@@ -364,7 +364,7 @@ static bool lchan_type_compat_with_mode(enum gsm_chan_t type, const struct chann
 	}
 }
 
-void assignment_fsm_init()
+void assignment_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&assignment_fsm) == 0);
 }
diff --git a/src/osmo-bsc/bsc_stats.c b/src/osmo-bsc/bsc_stats.c
index e8c39bece..ce307207c 100644
--- a/src/osmo-bsc/bsc_stats.c
+++ b/src/osmo-bsc/bsc_stats.c
@@ -229,7 +229,7 @@ void all_allocated_update_bts(struct gsm_bts *bts)
 	all_allocated_update(&bts->all_allocated, &bts->chan_counts);
 }
 
-void all_allocated_update_bsc()
+void all_allocated_update_bsc(void)
 {
 	struct gsm_network *net = bsc_gsmnet;
 	all_allocated_update(&net->all_allocated, &net->chan_counts);
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index baa54e0a0..a19be0c33 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -1202,7 +1202,7 @@ static struct osmo_fsm gscon_fsm = {
 	.event_names = gscon_fsm_event_names,
 };
 
-void bsc_subscr_conn_fsm_init()
+void bsc_subscr_conn_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&gscon_fsm) == 0);
 	OSMO_ASSERT(osmo_fsm_register(&lcls_fsm) == 0);
diff --git a/src/osmo-bsc/bssmap_reset.c b/src/osmo-bsc/bssmap_reset.c
index 30fc02e91..fa6684d2f 100644
--- a/src/osmo-bsc/bssmap_reset.c
+++ b/src/osmo-bsc/bssmap_reset.c
@@ -251,7 +251,7 @@ void bssmap_reset_resend_reset(struct bssmap_reset *bssmap_reset)
 	osmo_fsm_inst_state_chg_ms(bssmap_reset->fi, BSSMAP_RESET_ST_DISC, 1, 0);
 }
 
-static __attribute__((constructor)) void bssmap_reset_fsm_init()
+static __attribute__((constructor)) void bssmap_reset_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&bssmap_reset_fsm) == 0);
 }
diff --git a/src/osmo-bsc/chan_counts.c b/src/osmo-bsc/chan_counts.c
index a8631784e..bf863688d 100644
--- a/src/osmo-bsc/chan_counts.c
+++ b/src/osmo-bsc/chan_counts.c
@@ -248,7 +248,7 @@ void chan_counts_sig_init(void)
 	osmo_signal_register_handler(SS_NM, chan_counts_sig_cb, NULL);
 }
 
-void chan_counts_bsc_verify()
+void chan_counts_bsc_verify(void)
 {
 	struct gsm_bts *bts;
 	struct chan_counts bsc_counts = {0};
diff --git a/src/osmo-bsc/handover_fsm.c b/src/osmo-bsc/handover_fsm.c
index 92e8c6e5a..0d888e024 100644
--- a/src/osmo-bsc/handover_fsm.c
+++ b/src/osmo-bsc/handover_fsm.c
@@ -293,7 +293,7 @@ static void handover_reset(struct gsm_subscriber_connection *conn)
 	};
 }
 
-void handover_fsm_init()
+void handover_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&ho_fsm) == 0);
 }
diff --git a/src/osmo-bsc/handover_vty.c b/src/osmo-bsc/handover_vty.c
index e5435f53d..afc12d9d1 100644
--- a/src/osmo-bsc/handover_vty.c
+++ b/src/osmo-bsc/handover_vty.c
@@ -170,7 +170,7 @@ HODEC1_CFG_ALL_MEMBERS
 #undef HO_CFG_ONE_MEMBER
 }
 
-void ho_vty_init()
+void ho_vty_init(void)
 {
 	ho_vty_init_cmds(GSMNET_NODE);
 	install_element(GSMNET_NODE, &cfg_net_ho_congestion_check_interval_cmd);
diff --git a/src/osmo-bsc/lb.c b/src/osmo-bsc/lb.c
index 276b0a197..6f3cfac7c 100644
--- a/src/osmo-bsc/lb.c
+++ b/src/osmo-bsc/lb.c
@@ -46,7 +46,7 @@ static struct gsm_subscriber_connection *get_bsc_conn_by_lb_conn_id(int conn_id)
 }
 
 /* Send reset to SMLC */
-int bssmap_le_tx_reset()
+int bssmap_le_tx_reset(void)
 {
 	struct osmo_ss7_instance *ss7;
 	struct msgb *msg;
@@ -74,7 +74,7 @@ int bssmap_le_tx_reset()
 }
 
 /* Send reset-ack to SMLC */
-int bssmap_le_tx_reset_ack()
+int bssmap_le_tx_reset_ack(void)
 {
 	struct osmo_ss7_instance *ss7;
 	struct msgb *msg;
@@ -352,7 +352,7 @@ count_tx:
 #define DEFAULT_ASP_LOCAL_IP "localhost"
 #define DEFAULT_ASP_REMOTE_IP "localhost"
 
-void lb_cancel_all()
+void lb_cancel_all(void)
 {
 	struct gsm_subscriber_connection *conn;
 	llist_for_each_entry(conn, &bsc_gsmnet->subscr_conns, entry)
@@ -384,7 +384,7 @@ void lb_reset_tx_reset_ack(void *data)
 	bssmap_le_tx_reset_ack();
 }
 
-static void lb_start_reset_fsm()
+static void lb_start_reset_fsm(void)
 {
 	struct bssmap_reset_cfg cfg = {
 		.conn_cfm_failure_threshold = 3,
@@ -404,13 +404,13 @@ static void lb_start_reset_fsm()
 	bsc_gsmnet->smlc->bssmap_reset = bssmap_reset_alloc(bsc_gsmnet, "Lb", &cfg);
 }
 
-static void lb_stop_reset_fsm()
+static void lb_stop_reset_fsm(void)
 {
 	bssmap_reset_term_and_free(bsc_gsmnet->smlc->bssmap_reset);
 	bsc_gsmnet->smlc->bssmap_reset = NULL;
 }
 
-static int lb_start()
+static int lb_start(void)
 {
 	uint32_t default_pc;
 	struct osmo_ss7_instance *cs7_inst = NULL;
@@ -484,7 +484,7 @@ static int lb_start()
 	return 0;
 }
 
-static int lb_stop()
+static int lb_stop(void)
 {
 	/* Not set up? */
 	if (!bsc_gsmnet->smlc->sccp_user)
@@ -499,7 +499,7 @@ static int lb_stop()
 	return 0;
 }
 
-int lb_start_or_stop()
+int lb_start_or_stop(void)
 {
 	int rc;
 	if (bsc_gsmnet->smlc->enable) {
@@ -534,7 +534,7 @@ int lb_start_or_stop()
 
 static void smlc_vty_init(void);
 
-int lb_init()
+int lb_init(void)
 {
 	OSMO_ASSERT(!bsc_gsmnet->smlc);
 	bsc_gsmnet->smlc = talloc_zero(bsc_gsmnet, struct smlc_config);
diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c
index 21e145bdd..b1cef5d03 100644
--- a/src/osmo-bsc/lchan_fsm.c
+++ b/src/osmo-bsc/lchan_fsm.c
@@ -463,7 +463,7 @@ void lchan_fsm_update_id(struct gsm_lchan *lchan)
 
 extern void lchan_rtp_fsm_init();
 
-void lchan_fsm_init()
+void lchan_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&lchan_fsm) == 0);
 	lchan_rtp_fsm_init();
diff --git a/src/osmo-bsc/lchan_rtp_fsm.c b/src/osmo-bsc/lchan_rtp_fsm.c
index 466b1681d..0791619f4 100644
--- a/src/osmo-bsc/lchan_rtp_fsm.c
+++ b/src/osmo-bsc/lchan_rtp_fsm.c
@@ -70,7 +70,7 @@ struct osmo_tdef_state_timeout lchan_rtp_fsm_timeouts[32] = {
 	} while (0)
 
 /* Called from lchan_fsm_init(), does not need to be visible in lchan_rtp_fsm.h */
-void lchan_rtp_fsm_init()
+void lchan_rtp_fsm_init(void)
 {
 	OSMO_ASSERT(osmo_fsm_register(&lchan_rtp_fsm) == 0);
 }
diff --git a/src/osmo-bsc/neighbor_ident.c b/src/osmo-bsc/neighbor_ident.c
index 44b0b4381..e41a4b2ed 100644
--- a/src/osmo-bsc/neighbor_ident.c
+++ b/src/osmo-bsc/neighbor_ident.c
@@ -293,7 +293,7 @@ bool cell_ab_valid(const struct cell_ab *cell)
 	return true;
 }
 
-int neighbors_check_cfg()
+int neighbors_check_cfg(void)
 {
 	/* A local neighbor can be configured by BTS number, or by a cell ID. A local neighbor can omit the ARFCN+BSIC,
 	 * in which case those are taken from that local BTS config. If a local neighbor has ARFCN+BSIC configured, it
diff --git a/src/osmo-bsc/neighbor_ident_vty.c b/src/osmo-bsc/neighbor_ident_vty.c
index 86adbf23c..7e58e3799 100644
--- a/src/osmo-bsc/neighbor_ident_vty.c
+++ b/src/osmo-bsc/neighbor_ident_vty.c
@@ -628,7 +628,7 @@ DEFUN(show_bts_neighbor, show_bts_neighbor_cmd,
 	return CMD_SUCCESS;
 }
 
-void neighbor_ident_vty_init()
+void neighbor_ident_vty_init(void)
 {
 	install_element(GSMNET_NODE, &cfg_neighbor_bind_cmd);
 
diff --git a/src/osmo-bsc/osmo_bsc_main.c b/src/osmo-bsc/osmo_bsc_main.c
index dd8e69609..c85f1c46a 100644
--- a/src/osmo-bsc/osmo_bsc_main.c
+++ b/src/osmo-bsc/osmo_bsc_main.c
@@ -91,12 +91,12 @@ static const char *config_file = "osmo-bsc.cfg";
 static const char *rf_ctrl = NULL;
 static int daemonize = 0;
 
-static void print_usage()
+static void print_usage(void)
 {
 	printf("Usage: osmo-bsc\n");
 }
 
-static void print_help()
+static void print_help(void)
 {
 	printf("Some useful options:\n");
 	printf("  -h --help 			This text.\n");