diff --git a/ChangeLog.txt b/ChangeLog.txt
index 275594ec..1701c5e4 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -9,6 +9,10 @@ Clients:
 - Set `receive-maximum` to not exceed the `-C` message count in mosquitto_sub
   and mosquitto_rr, to avoid potentially lost messages. Closes #2134.
 
+Build:
+- A variety of minor build related fixes, like functions not having previous
+  declarations.
+
 
 2.0.9 - 2021-03-11
 ==================
diff --git a/apps/db_dump/db_dump.c b/apps/db_dump/db_dump.c
index ad6d2f7b..5ae009f2 100644
--- a/apps/db_dump/db_dump.c
+++ b/apps/db_dump/db_dump.c
@@ -27,6 +27,7 @@ Contributors:
 #include <sys/stat.h>
 #include <time.h>
 
+#include "db_dump.h"
 #include <mosquitto_broker_internal.h>
 #include <memory_mosq.h>
 #include <persist.h>
diff --git a/apps/db_dump/print.c b/apps/db_dump/print.c
index 84ca2ef0..bc4eac3e 100644
--- a/apps/db_dump/print.c
+++ b/apps/db_dump/print.c
@@ -19,6 +19,7 @@ Contributors:
 #include <inttypes.h>
 #include <stdio.h>
 
+#include "db_dump.h"
 #include <mosquitto_broker_internal.h>
 #include <memory_mosq.h>
 #include <mqtt_protocol.h>
@@ -142,7 +143,7 @@ static void print__properties(mosquitto_property *properties)
 }
 
 
-void print__client(struct P_client *chunk, int length)
+void print__client(struct P_client *chunk, uint32_t length)
 {
 	printf("DB_CHUNK_CLIENT:\n");
 	printf("\tLength: %d\n", length);
@@ -159,7 +160,7 @@ void print__client(struct P_client *chunk, int length)
 }
 
 
-void print__client_msg(struct P_client_msg *chunk, int length)
+void print__client_msg(struct P_client_msg *chunk, uint32_t length)
 {
 	printf("DB_CHUNK_CLIENT_MSG:\n");
 	printf("\tLength: %d\n", length);
@@ -175,8 +176,10 @@ void print__client_msg(struct P_client_msg *chunk, int length)
 }
 
 
-void print__msg_store(struct P_msg_store *chunk, int length)
+void print__msg_store(struct P_msg_store *chunk, uint32_t length)
 {
+	uint8_t *payload;
+
 	printf("DB_CHUNK_MSG_STORE:\n");
 	printf("\tLength: %d\n", length);
 	printf("\tStore ID: %" PRIu64 "\n", chunk->F.store_id);
@@ -190,8 +193,6 @@ void print__msg_store(struct P_msg_store *chunk, int length)
 	printf("\tPayload Length: %d\n", chunk->F.payloadlen);
 	printf("\tExpiry Time: %" PRIu64 "\n", chunk->F.expiry_time);
 
-	uint8_t *payload;
-
 	payload = chunk->payload;
 	if(chunk->F.payloadlen < 256){
 		/* Print payloads with UTF-8 data below an arbitrary limit of 256 bytes */
diff --git a/apps/db_dump/stubs.c b/apps/db_dump/stubs.c
index af00f706..8e233871 100644
--- a/apps/db_dump/stubs.c
+++ b/apps/db_dump/stubs.c
@@ -1,8 +1,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "misc_mosq.h"
 #include "mosquitto_broker_internal.h"
 #include "mosquitto_internal.h"
+#include "util_mosq.h"
 
 struct mosquitto *context__init(mosq_sock_t sock)
 {
diff --git a/apps/mosquitto_ctrl/Makefile b/apps/mosquitto_ctrl/Makefile
index 286eb449..502f0dac 100644
--- a/apps/mosquitto_ctrl/Makefile
+++ b/apps/mosquitto_ctrl/Makefile
@@ -12,7 +12,7 @@ LIBMOSQ:=../../lib/libmosquitto.a
 endif
 endif
 
-LOCAL_CPPFLAGS:=-I../mosquitto_passwd
+LOCAL_CPPFLAGS:=-I../mosquitto_passwd -DWITH_CJSON
 
 OBJS=	mosquitto_ctrl.o \
 		client.o \
diff --git a/apps/mosquitto_ctrl/dynsec.c b/apps/mosquitto_ctrl/dynsec.c
index fae86f43..c906cb2c 100644
--- a/apps/mosquitto_ctrl/dynsec.c
+++ b/apps/mosquitto_ctrl/dynsec.c
@@ -689,7 +689,7 @@ static cJSON *init_create(const char *username, const char *password, const char
 }
 
 /* mosquitto_ctrl dynsec init <filename> <admin-user> <admin-password> [role-name] */
-int dynsec_init(int argc, char *argv[])
+static int dynsec_init(int argc, char *argv[])
 {
 	char *filename;
 	char *admin_user;
diff --git a/apps/mosquitto_ctrl/mosquitto_ctrl.c b/apps/mosquitto_ctrl/mosquitto_ctrl.c
index bda95902..b4433988 100644
--- a/apps/mosquitto_ctrl/mosquitto_ctrl.c
+++ b/apps/mosquitto_ctrl/mosquitto_ctrl.c
@@ -28,7 +28,7 @@ Contributors:
 #include "mosquitto.h"
 #include "mosquitto_ctrl.h"
 
-void print_version(void)
+static void print_version(void)
 {
 	int major, minor, revision;
 
@@ -36,7 +36,7 @@ void print_version(void)
 	printf("mosquitto_ctrl version %s running on libmosquitto %d.%d.%d.\n", VERSION, major, minor, revision);
 }
 
-void print_usage(void)
+static void print_usage(void)
 {
 	printf("mosquitto_ctrl is a tool for administering certain Mosquitto features.\n");
 	print_version();
@@ -51,7 +51,7 @@ int main(int argc, char *argv[])
 {
 	struct mosq_ctrl ctrl;
 	int rc = MOSQ_ERR_SUCCESS;
-	FUNC_ctrl_main ctrl_main = NULL;
+	FUNC_ctrl_main l_ctrl_main = NULL;
 	void *lib = NULL;
 	char lib_name[200];
 
@@ -76,22 +76,22 @@ int main(int argc, char *argv[])
  
 	/* In built modules */
 	if(!strcasecmp(argv[0], "dynsec")){
-		ctrl_main = dynsec__main;
+		l_ctrl_main = dynsec__main;
 	}else{
 		/* Attempt external module */
 		snprintf(lib_name, sizeof(lib_name), "mosquitto_ctrl_%s.so", argv[0]);
 		lib = LIB_LOAD(lib_name);
 		if(lib){
-			ctrl_main = (FUNC_ctrl_main)LIB_SYM(lib, "ctrl_main");
+			l_ctrl_main = (FUNC_ctrl_main)LIB_SYM(lib, "ctrl_main");
 		}
 	}
-	if(ctrl_main == NULL){
+	if(l_ctrl_main == NULL){
 		fprintf(stderr, "Error: Module '%s' not supported.\n", argv[0]);
 		rc = MOSQ_ERR_NOT_SUPPORTED;
 	}
 
-	if(ctrl_main){
-		rc = ctrl_main(argc-1, &argv[1], &ctrl);
+	if(l_ctrl_main){
+		rc = l_ctrl_main(argc-1, &argv[1], &ctrl);
 		if(rc < 0){
 			/* Usage print */
 			rc = 0;
diff --git a/apps/mosquitto_passwd/get_password.c b/apps/mosquitto_passwd/get_password.c
index a62a76cd..42842536 100644
--- a/apps/mosquitto_passwd/get_password.c
+++ b/apps/mosquitto_passwd/get_password.c
@@ -35,7 +35,9 @@ Contributors:
 #  include <sys/stat.h>
 #endif
 
-#define MAX_BUFFER_LEN 65536
+#include "get_password.h"
+
+#define MAX_BUFFER_LEN 65500
 #define SALT_LEN 12
 
 void get_password__reset_term(void)
diff --git a/apps/mosquitto_passwd/mosquitto_passwd.c b/apps/mosquitto_passwd/mosquitto_passwd.c
index 628bcc71..5a5a04f4 100644
--- a/apps/mosquitto_passwd/mosquitto_passwd.c
+++ b/apps/mosquitto_passwd/mosquitto_passwd.c
@@ -52,7 +52,7 @@ Contributors:
 #  include <sys/stat.h>
 #endif
 
-#define MAX_BUFFER_LEN 65536
+#define MAX_BUFFER_LEN 65500
 #define SALT_LEN 12
 
 #include "misc_mosq.h"
@@ -107,7 +107,7 @@ static FILE *mpw_tmpfile(void)
 #endif
 
 
-void print_usage(void)
+static void print_usage(void)
 {
 	printf("mosquitto_passwd is a tool for managing password files for mosquitto.\n\n");
 	printf("Usage: mosquitto_passwd [-H sha512 | -H sha512-pbkdf2] [-c | -D] passwordfile username\n");
@@ -122,7 +122,7 @@ void print_usage(void)
 	printf("\nSee https://mosquitto.org/ for more information.\n\n");
 }
 
-int output_new_password(FILE *fptr, const char *username, const char *password, int iterations)
+static int output_new_password(FILE *fptr, const char *username, const char *password, int iterations)
 {
 	int rc;
 	char *salt64 = NULL, *hash64 = NULL;
@@ -255,7 +255,7 @@ static int delete_pwuser_cb(FILE *fptr, FILE *ftmp, const char *username, const
 	return 0;
 }
 
-int delete_pwuser(FILE *fptr, FILE *ftmp, const char *username)
+static int delete_pwuser(FILE *fptr, FILE *ftmp, const char *username)
 {
 	struct cb_helper helper;
 	int rc;
@@ -288,7 +288,7 @@ static int update_file_cb(FILE *fptr, FILE *ftmp, const char *username, const ch
 	}
 }
 
-int update_file(FILE *fptr, FILE *ftmp)
+static int update_file(FILE *fptr, FILE *ftmp)
 {
 	return pwfile_iterate(fptr, ftmp, update_file_cb, NULL);
 }
@@ -315,7 +315,7 @@ static int update_pwuser_cb(FILE *fptr, FILE *ftmp, const char *username, const
 	return rc;
 }
 
-int update_pwuser(FILE *fptr, FILE *ftmp, const char *username, const char *password, int iterations)
+static int update_pwuser(FILE *fptr, FILE *ftmp, const char *username, const char *password, int iterations)
 {
 	struct cb_helper helper;
 	int rc;
@@ -334,7 +334,7 @@ int update_pwuser(FILE *fptr, FILE *ftmp, const char *username, const char *pass
 }
 
 
-int copy_contents(FILE *src, FILE *dest)
+static int copy_contents(FILE *src, FILE *dest)
 {
 	char buf[MAX_BUFFER_LEN];
 	size_t len;
@@ -361,7 +361,7 @@ int copy_contents(FILE *src, FILE *dest)
 	return 0;
 }
 
-int create_backup(const char *backup_file, FILE *fptr)
+static int create_backup(const char *backup_file, FILE *fptr)
 {
 	FILE *fbackup;
 
@@ -380,7 +380,7 @@ int create_backup(const char *backup_file, FILE *fptr)
 	return 0;
 }
 
-void handle_sigint(int signal)
+static void handle_sigint(int signal)
 {
 	get_password__reset_term();
 
diff --git a/client/client_shared.c b/client/client_shared.c
index 68a12b39..f60b98be 100644
--- a/client/client_shared.c
+++ b/client/client_shared.c
@@ -183,7 +183,7 @@ static int check_format(const char *str)
 }
 
 
-void init_config(struct mosq_config *cfg, int pub_or_sub)
+static void init_config(struct mosq_config *cfg, int pub_or_sub)
 {
 	memset(cfg, 0, sizeof(*cfg));
 	cfg->port = PORT_UNDEFINED;
@@ -485,7 +485,7 @@ int client_config_load(struct mosq_config *cfg, int pub_or_sub, int argc, char *
 	return MOSQ_ERR_SUCCESS;
 }
 
-int cfg_add_topic(struct mosq_config *cfg, int type, char *topic, const char *arg)
+static int cfg_add_topic(struct mosq_config *cfg, int type, char *topic, const char *arg)
 {
 	if(mosquitto_validate_utf8(topic, (int )strlen(topic))){
 		fprintf(stderr, "Error: Malformed UTF-8 in %s argument.\n\n", arg);
diff --git a/client/pub_client.c b/client/pub_client.c
index 8049de6e..e82d90e0 100644
--- a/client/pub_client.c
+++ b/client/pub_client.c
@@ -232,7 +232,7 @@ int pub_shared_init(void)
 }
 
 
-int pub_stdin_line_loop(struct mosquitto *mosq)
+static int pub_stdin_line_loop(struct mosquitto *mosq)
 {
 	char *buf2;
 	int buf_len_actual = 0;
@@ -334,7 +334,7 @@ int pub_stdin_line_loop(struct mosquitto *mosq)
 }
 
 
-int pub_other_loop(struct mosquitto *mosq)
+static int pub_other_loop(struct mosquitto *mosq)
 {
 	int rc;
 	int loop_delay = 1000;
@@ -387,7 +387,7 @@ void pub_shared_cleanup(void)
 }
 
 
-void print_version(void)
+static void print_version(void)
 {
 	int major, minor, revision;
 
@@ -395,7 +395,7 @@ void print_version(void)
 	printf("mosquitto_pub version %s running on libmosquitto %d.%d.%d.\n", VERSION, major, minor, revision);
 }
 
-void print_usage(void)
+static void print_usage(void)
 {
 	int major, minor, revision;
 
diff --git a/client/rr_client.c b/client/rr_client.c
index 2331a4ed..4b1edba4 100644
--- a/client/rr_client.c
+++ b/client/rr_client.c
@@ -50,8 +50,6 @@ enum rr__state {
 
 static enum rr__state client_state = rr_s_new;
 
-extern struct mosq_config cfg;
-
 bool process_messages = true;
 int msg_count = 0;
 struct mosquitto *g_mosq = NULL;
@@ -59,7 +57,7 @@ static bool timed_out = false;
 static int connack_result = 0;
 
 #ifndef WIN32
-void my_signal_handler(int signum)
+static void my_signal_handler(int signum)
 {
 	if(signum == SIGALRM){
 		process_messages = false;
@@ -80,7 +78,7 @@ int my_publish(struct mosquitto *mosq, int *mid, const char *topic, int payloadl
 }
 
 
-void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message, const mosquitto_property *properties)
+static void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message, const mosquitto_property *properties)
 {
 	UNUSED(mosq);
 	UNUSED(obj);
@@ -151,7 +149,7 @@ void my_connect_callback(struct mosquitto *mosq, void *obj, int result, int flag
 }
 
 
-void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
+static void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
 {
 	UNUSED(obj);
 	UNUSED(mid);
@@ -179,7 +177,7 @@ void my_publish_callback(struct mosquitto *mosq, void *obj, int mid, int reason_
 }
 
 
-void print_version(void)
+static void print_version(void)
 {
 	int major, minor, revision;
 
@@ -187,7 +185,7 @@ void print_version(void)
 	printf("mosquitto_rr version %s running on libmosquitto %d.%d.%d.\n", VERSION, major, minor, revision);
 }
 
-void print_usage(void)
+static void print_usage(void)
 {
 	int major, minor, revision;
 
diff --git a/client/sub_client.c b/client/sub_client.c
index e2cebcdc..72170ab2 100644
--- a/client/sub_client.c
+++ b/client/sub_client.c
@@ -48,7 +48,7 @@ static int connack_result = 0;
 bool connack_received = false;
 
 #ifndef WIN32
-void my_signal_handler(int signum)
+static void my_signal_handler(int signum)
 {
 	if(signum == SIGALRM || signum == SIGTERM || signum == SIGINT){
 		if(connack_received){
@@ -65,19 +65,7 @@ void my_signal_handler(int signum)
 #endif
 
 
-void my_publish_callback(struct mosquitto *mosq, void *obj, int mid, int reason_code, const mosquitto_property *properties)
-{
-	UNUSED(obj);
-	UNUSED(reason_code);
-	UNUSED(properties);
-
-	if(process_messages == false && (mid == last_mid || last_mid == 0)){
-		mosquitto_disconnect_v5(mosq, 0, cfg.disconnect_props);
-	}
-}
-
-
-void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message, const mosquitto_property *properties)
+static void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message, const mosquitto_property *properties)
 {
 	int i;
 	bool res;
@@ -120,7 +108,7 @@ void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquit
 	}
 }
 
-void my_connect_callback(struct mosquitto *mosq, void *obj, int result, int flags, const mosquitto_property *properties)
+static void my_connect_callback(struct mosquitto *mosq, void *obj, int result, int flags, const mosquitto_property *properties)
 {
 	int i;
 
@@ -153,7 +141,7 @@ void my_connect_callback(struct mosquitto *mosq, void *obj, int result, int flag
 	}
 }
 
-void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
+static void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
 {
 	int i;
 	bool some_sub_allowed = (granted_qos[0] < 128);
@@ -177,7 +165,7 @@ void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_c
 	}
 }
 
-void my_log_callback(struct mosquitto *mosq, void *obj, int level, const char *str)
+static void my_log_callback(struct mosquitto *mosq, void *obj, int level, const char *str)
 {
 	UNUSED(mosq);
 	UNUSED(obj);
@@ -186,7 +174,7 @@ void my_log_callback(struct mosquitto *mosq, void *obj, int level, const char *s
 	printf("%s\n", str);
 }
 
-void print_version(void)
+static void print_version(void)
 {
 	int major, minor, revision;
 
@@ -194,7 +182,7 @@ void print_version(void)
 	printf("mosquitto_sub version %s running on libmosquitto %d.%d.%d.\n", VERSION, major, minor, revision);
 }
 
-void print_usage(void)
+static void print_usage(void)
 {
 	int major, minor, revision;
 
diff --git a/config.mk b/config.mk
index d31b1160..d7b14b75 100644
--- a/config.mk
+++ b/config.mk
@@ -148,7 +148,7 @@ ifeq ($(UNAME),SunOS)
 		CFLAGS?=-Wall -ggdb -O2
 	endif
 else
-	CFLAGS?=-Wall -ggdb -O2 -Wconversion
+	CFLAGS?=-Wall -ggdb -O2 -Wconversion -Wextra
 endif
 
 STATIC_LIB_DEPS:=
diff --git a/lib/handle_auth.c b/lib/handle_auth.c
index e33d085d..61f3bb4f 100644
--- a/lib/handle_auth.c
+++ b/lib/handle_auth.c
@@ -26,6 +26,7 @@ Contributors:
 #include "mqtt_protocol.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "read_handle.h"
 
 
 int handle__auth(struct mosquitto *mosq)
diff --git a/lib/handle_disconnect.c b/lib/handle_disconnect.c
index a0a638db..28c51845 100644
--- a/lib/handle_disconnect.c
+++ b/lib/handle_disconnect.c
@@ -27,6 +27,7 @@ Contributors:
 #include "net_mosq.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "read_handle.h"
 #include "send_mosq.h"
 #include "util_mosq.h"
 
diff --git a/lib/handle_publish.c b/lib/handle_publish.c
index 40644ef3..3fec2d53 100644
--- a/lib/handle_publish.c
+++ b/lib/handle_publish.c
@@ -29,6 +29,7 @@ Contributors:
 #include "messages_mosq.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "read_handle.h"
 #include "send_mosq.h"
 #include "time_mosq.h"
 #include "util_mosq.h"
diff --git a/lib/handle_suback.c b/lib/handle_suback.c
index 91a40e26..770558be 100644
--- a/lib/handle_suback.c
+++ b/lib/handle_suback.c
@@ -31,6 +31,7 @@ Contributors:
 #include "mqtt_protocol.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "read_handle.h"
 #include "util_mosq.h"
 
 
diff --git a/lib/misc_mosq.c b/lib/misc_mosq.c
index e7bf0784..8f2f2d2a 100644
--- a/lib/misc_mosq.c
+++ b/lib/misc_mosq.c
@@ -36,6 +36,8 @@ Contributors:
 #  include <sys/stat.h>
 #endif
 
+#include "misc_mosq.h"
+
 
 FILE *mosquitto__fopen(const char *path, const char *mode, bool restrict_read)
 {
diff --git a/lib/misc_mosq.h b/lib/misc_mosq.h
index 233071e6..f86f5d76 100644
--- a/lib/misc_mosq.h
+++ b/lib/misc_mosq.h
@@ -19,6 +19,7 @@ Contributors:
 #define MISC_MOSQ_H
 
 #include <stdbool.h>
+#include <stdio.h>
 
 FILE *mosquitto__fopen(const char *path, const char *mode, bool restrict_read);
 char *misc__trimblanks(char *str);
diff --git a/lib/net_mosq_ocsp.c b/lib/net_mosq_ocsp.c
index 84b818c8..8c762373 100644
--- a/lib/net_mosq_ocsp.c
+++ b/lib/net_mosq_ocsp.c
@@ -64,10 +64,11 @@ int mosquitto__verify_ocsp_status_cb(SSL * ssl, void *arg)
 	OCSP_BASICRESP *br = NULL;
 	X509_STORE     *st = NULL;
 	STACK_OF(X509) *ch = NULL;
+	long len;
 
 	UNUSED(ssl);
 
-	long len = SSL_get_tlsext_status_ocsp_resp(mosq->ssl, &p);
+	len = SSL_get_tlsext_status_ocsp_resp(mosq->ssl, &p);
 	log__printf(mosq, MOSQ_LOG_DEBUG, "OCSP: SSL_get_tlsext_status_ocsp_resp returned %ld bytes", len);
 
 	/* the following functions expect a const pointer */
diff --git a/lib/property_mosq.c b/lib/property_mosq.c
index 8a77dbe6..0cfc9f9c 100644
--- a/lib/property_mosq.c
+++ b/lib/property_mosq.c
@@ -33,7 +33,7 @@ Contributors:
 #include "property_mosq.h"
 
 
-int property__read(struct mosquitto__packet *packet, uint32_t *len, mosquitto_property *property)
+static int property__read(struct mosquitto__packet *packet, uint32_t *len, mosquitto_property *property)
 {
 	int rc;
 	uint32_t property_identifier;
@@ -355,7 +355,7 @@ unsigned int property__get_remaining_length(const mosquitto_property *props)
 }
 
 
-int property__write(struct mosquitto__packet *packet, const mosquitto_property *property)
+static int property__write(struct mosquitto__packet *packet, const mosquitto_property *property)
 {
 	int rc;
 
@@ -975,7 +975,7 @@ int mosquitto_property_check_all(int command, const mosquitto_property *properti
 	return MOSQ_ERR_SUCCESS;
 }
 
-const mosquitto_property *property__get_property(const mosquitto_property *proplist, int identifier, bool skip_first)
+static const mosquitto_property *property__get_property(const mosquitto_property *proplist, int identifier, bool skip_first)
 {
 	const mosquitto_property *p;
 	bool is_first = true;
diff --git a/lib/send_connect.c b/lib/send_connect.c
index d35cd80e..d9a3257c 100644
--- a/lib/send_connect.c
+++ b/lib/send_connect.c
@@ -32,6 +32,7 @@ Contributors:
 #include "mqtt_protocol.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "send_mosq.h"
 
 int send__connect(struct mosquitto *mosq, uint16_t keepalive, bool clean_session, const mosquitto_property *properties)
 {
diff --git a/lib/send_subscribe.c b/lib/send_subscribe.c
index a8e77545..9217dc5b 100644
--- a/lib/send_subscribe.c
+++ b/lib/send_subscribe.c
@@ -32,10 +32,11 @@ Contributors:
 #include "mqtt_protocol.h"
 #include "packet_mosq.h"
 #include "property_mosq.h"
+#include "send_mosq.h"
 #include "util_mosq.h"
 
 
-int send__subscribe(struct mosquitto *mosq, int *mid, int topic_count, const char **topic, int topic_qos, const mosquitto_property *properties)
+int send__subscribe(struct mosquitto *mosq, int *mid, int topic_count, char *const *const topic, int topic_qos, const mosquitto_property *properties)
 {
 	struct mosquitto__packet *packet = NULL;
 	uint32_t packetlen;
diff --git a/lib/socks_mosq.c b/lib/socks_mosq.c
index a360d64b..ed8fe128 100644
--- a/lib/socks_mosq.c
+++ b/lib/socks_mosq.c
@@ -23,7 +23,7 @@ Contributors:
 #include <limits.h>
 #ifdef WIN32
 #  include <ws2tcpip.h>
-#elif __QNX__
+#elif defined(__QNX__)
 #  include <sys/socket.h>
 #  include <arpa/inet.h>
 #  include <netinet/in.h>
@@ -40,6 +40,7 @@ Contributors:
 #include "net_mosq.h"
 #include "packet_mosq.h"
 #include "send_mosq.h"
+#include "socks_mosq.h"
 #include "util_mosq.h"
 
 #define SOCKS_AUTH_NONE 0x00U
diff --git a/lib/tls_mosq.c b/lib/tls_mosq.c
index bddf2ec0..13d9aa22 100644
--- a/lib/tls_mosq.c
+++ b/lib/tls_mosq.c
@@ -84,7 +84,7 @@ int mosquitto__server_certificate_verify(int preverify_ok, X509_STORE_CTX *ctx)
 	}
 }
 
-int mosquitto__cmp_hostname_wildcard(char *certname, const char *hostname)
+static int mosquitto__cmp_hostname_wildcard(char *certname, const char *hostname)
 {
 	size_t i;
 	size_t len;
diff --git a/plugins/auth-by-ip/mosquitto_auth_by_ip.c b/plugins/auth-by-ip/mosquitto_auth_by_ip.c
index 6a6f6289..49cc0178 100644
--- a/plugins/auth-by-ip/mosquitto_auth_by_ip.c
+++ b/plugins/auth-by-ip/mosquitto_auth_by_ip.c
@@ -32,7 +32,7 @@ Contributors:
  *
  * Note that this only works on Mosquitto 2.0 or later.
  */
-
+#include "config.h"
 
 #include <stdio.h>
 #include <string.h>
@@ -49,6 +49,9 @@ static int basic_auth_callback(int event, void *event_data, void *userdata)
 	struct mosquitto_evt_basic_auth *ed = event_data;
 	const char *ip_address;
 
+	UNUSED(event);
+	UNUSED(userdata);
+
 	ip_address = mosquitto_client_address(ed->client);
 	if(!strcmp(ip_address, "127.0.0.1")){
 		/* Only allow connections from localhost */
@@ -72,11 +75,19 @@ int mosquitto_plugin_version(int supported_version_count, const int *supported_v
 
 int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
 {
+	UNUSED(user_data);
+	UNUSED(opts);
+	UNUSED(opt_count);
+
 	mosq_pid = identifier;
 	return mosquitto_callback_register(mosq_pid, MOSQ_EVT_BASIC_AUTH, basic_auth_callback, NULL, NULL);
 }
 
 int mosquitto_plugin_cleanup(void *user_data, struct mosquitto_opt *opts, int opt_count)
 {
+	UNUSED(user_data);
+	UNUSED(opts);
+	UNUSED(opt_count);
+
 	return mosquitto_callback_unregister(mosq_pid, MOSQ_EVT_BASIC_AUTH, basic_auth_callback, NULL);
 }
diff --git a/src/conf.c b/src/conf.c
index 33326c0c..bc4158ae 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -527,7 +527,7 @@ int config__parse_args(struct mosquitto__config *config, int argc, char *argv[])
 	return config__check(config);
 }
 
-void config__copy(struct mosquitto__config *src, struct mosquitto__config *dest)
+static void config__copy(struct mosquitto__config *src, struct mosquitto__config *dest)
 {
 	mosquitto__free(dest->security_options.acl_file);
 	dest->security_options.acl_file = src->security_options.acl_file;
@@ -721,7 +721,7 @@ int config__read(struct mosquitto__config *config, bool reload)
 }
 
 
-int config__read_file_core(struct mosquitto__config *config, bool reload, struct config_recurse *cr, int level, int *lineno, FILE *fptr, char **buf, int *buflen)
+static int config__read_file_core(struct mosquitto__config *config, bool reload, struct config_recurse *cr, int level, int *lineno, FILE *fptr, char **buf, int *buflen)
 {
 	int rc;
 	char *token;
diff --git a/src/conf_includedir.c b/src/conf_includedir.c
index 5dda0a1e..9673ca5f 100644
--- a/src/conf_includedir.c
+++ b/src/conf_includedir.c
@@ -50,7 +50,7 @@ Contributors:
 #include "mqtt_protocol.h"
 
 
-int scmp_p(const void *p1, const void *p2)
+static int scmp_p(const void *p1, const void *p2)
 {
 	const char *s1 = *(const char **)p1;
 	const char *s2 = *(const char **)p2;
diff --git a/src/database.c b/src/database.c
index 2ba131c5..88253c57 100644
--- a/src/database.c
+++ b/src/database.c
@@ -580,7 +580,7 @@ int db__message_update_outgoing(struct mosquitto *context, uint16_t mid, enum mo
 }
 
 
-void db__messages_delete_list(struct mosquitto_client_msg **head)
+static void db__messages_delete_list(struct mosquitto_client_msg **head)
 {
 	struct mosquitto_client_msg *tail, *tmp;
 
@@ -624,7 +624,7 @@ int db__messages_delete(struct mosquitto *context, bool force_free)
 int db__messages_easy_queue(struct mosquitto *context, const char *topic, uint8_t qos, uint32_t payloadlen, const void *payload, int retain, uint32_t message_expiry_interval, mosquitto_property **properties)
 {
 	struct mosquitto_msg_store *stored;
-	char *source_id;
+	const char *source_id;
 	enum mosquitto_msg_origin origin;
 
 	if(!topic) return MOSQ_ERR_INVAL;
@@ -752,7 +752,7 @@ int db__message_store_find(struct mosquitto *context, uint16_t mid, struct mosqu
 
 /* Called on reconnect to set outgoing messages to a sensible state and force a
  * retry, and to set incoming messages to expect an appropriate retry. */
-int db__message_reconnect_reset_outgoing(struct mosquitto *context)
+static int db__message_reconnect_reset_outgoing(struct mosquitto *context)
 {
 	struct mosquitto_client_msg *msg, *tmp;
 
@@ -821,7 +821,7 @@ int db__message_reconnect_reset_outgoing(struct mosquitto *context)
 
 
 /* Called on reconnect to set incoming messages to expect an appropriate retry. */
-int db__message_reconnect_reset_incoming(struct mosquitto *context)
+static int db__message_reconnect_reset_incoming(struct mosquitto *context)
 {
 	struct mosquitto_client_msg *msg, *tmp;
 
@@ -975,63 +975,6 @@ int db__message_release_incoming(struct mosquitto *context, uint16_t mid)
 	}
 }
 
-int db__message_write_inflight_in(struct mosquitto *context)
-{
-	struct mosquitto_client_msg *tail, *tmp;
-	int rc;
-
-	if(context->state != mosq_cs_active){
-		return MOSQ_ERR_SUCCESS;
-	}
-
-	DL_FOREACH_SAFE(context->msgs_in.inflight, tail, tmp){
-		if(tail->store->message_expiry_time){
-			if(db.now_real_s > tail->store->message_expiry_time){
-				/* Message is expired, must not send. */
-				db__message_remove(&context->msgs_in, tail);
-				if(tail->qos > 0){
-					util__increment_receive_quota(context);
-				}
-				continue;
-			}
-		}
-
-		switch(tail->state){
-			case mosq_ms_send_pubrec:
-				rc = send__pubrec(context, tail->mid, 0, NULL);
-				if(!rc){
-					tail->state = mosq_ms_wait_for_pubrel;
-				}else{
-					return rc;
-				}
-				break;
-
-			case mosq_ms_resend_pubcomp:
-				rc = send__pubcomp(context, tail->mid, NULL);
-				if(!rc){
-					tail->state = mosq_ms_wait_for_pubrel;
-				}else{
-					return rc;
-				}
-				break;
-
-			case mosq_ms_invalid:
-			case mosq_ms_publish_qos0:
-			case mosq_ms_publish_qos1:
-			case mosq_ms_publish_qos2:
-			case mosq_ms_resend_pubrel:
-			case mosq_ms_wait_for_puback:
-			case mosq_ms_wait_for_pubrec:
-			case mosq_ms_wait_for_pubrel:
-			case mosq_ms_wait_for_pubcomp:
-			case mosq_ms_queued:
-				break;
-		}
-	}
-	return MOSQ_ERR_SUCCESS;
-}
-
-
 static int db__message_write_inflight_out_single(struct mosquitto *context, struct mosquitto_client_msg *msg)
 {
 	mosquitto_property *cmsg_props = NULL, *store_props = NULL;
diff --git a/src/handle_connect.c b/src/handle_connect.c
index b4cefad5..b031d200 100644
--- a/src/handle_connect.c
+++ b/src/handle_connect.c
@@ -83,7 +83,7 @@ static char *client_id_gen(uint16_t *idlen, const char *auto_id_prefix, uint16_t
 
 /* Remove any queued messages that are no longer allowed through ACL,
  * assuming a possible change of username. */
-void connection_check_acl(struct mosquitto *context, struct mosquitto_client_msg **head)
+static void connection_check_acl(struct mosquitto *context, struct mosquitto_client_msg **head)
 {
 	struct mosquitto_client_msg *msg_tail, *tmp;
 
diff --git a/src/logging.c b/src/logging.c
index 915ede23..cfac6a20 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -187,7 +187,7 @@ DltLogLevelType get_dlt_level(unsigned int priority)
 }
 #endif
 
-int log__vprintf(unsigned int priority, const char *fmt, va_list va)
+static int log__vprintf(unsigned int priority, const char *fmt, va_list va)
 {
 	const char *topic;
 	int syslog_priority;
diff --git a/src/loop.c b/src/loop.c
index 5044e7c8..dbee55a0 100644
--- a/src/loop.c
+++ b/src/loop.c
@@ -133,7 +133,7 @@ static void read_message_expiry_interval(mosquitto_property **proplist, uint32_t
 	}
 }
 
-void queue_plugin_msgs(void)
+static void queue_plugin_msgs(void)
 {
 	struct mosquitto_message_v5 *msg, *tmp;
 	struct mosquitto *context;
@@ -279,7 +279,7 @@ int mosquitto_main_loop(struct mosquitto__listener_sock *listensock, int listens
 
 void do_disconnect(struct mosquitto *context, int reason)
 {
-	char *id;
+	const char *id;
 #ifdef WITH_WEBSOCKETS
 	bool is_duplicate = false;
 #endif
diff --git a/src/mosquitto.c b/src/mosquitto.c
index d3905ebe..1e5baec4 100644
--- a/src/mosquitto.c
+++ b/src/mosquitto.c
@@ -74,13 +74,6 @@ int allow_severity = LOG_INFO;
 int deny_severity = LOG_INFO;
 #endif
 
-void handle_sigint(int signal);
-void handle_sigusr1(int signal);
-void handle_sigusr2(int signal);
-#ifdef SIGHUP
-void handle_sighup(int signal);
-#endif
-
 /* mosquitto shouldn't run as root.
  * This function will attempt to change to an unprivileged user and group if
  * running as root. The user is given in config->user.
@@ -146,7 +139,7 @@ int drop_privileges(struct mosquitto__config *config)
 	return MOSQ_ERR_SUCCESS;
 }
 
-void mosquitto__daemonise(void)
+static void mosquitto__daemonise(void)
 {
 #ifndef WIN32
 	char *err;
@@ -208,7 +201,7 @@ void listeners__reload_all_certificates(void)
 }
 
 
-int listeners__start_single_mqtt(struct mosquitto__listener *listener)
+static int listeners__start_single_mqtt(struct mosquitto__listener *listener)
 {
 	int i;
 	struct mosquitto__listener_sock *listensock_new;
@@ -275,7 +268,7 @@ void listeners__add_websockets(struct lws_context *ws_context, mosq_sock_t fd)
 }
 #endif
 
-int listeners__add_local(const char *host, uint16_t port)
+static int listeners__add_local(const char *host, uint16_t port)
 {
 	struct mosquitto__listener *listeners;
 	listeners = db.config->listeners;
@@ -296,7 +289,7 @@ int listeners__add_local(const char *host, uint16_t port)
 	return MOSQ_ERR_SUCCESS;
 }
 
-int listeners__start_local_only(void)
+static int listeners__start_local_only(void)
 {
 	/* Attempt to open listeners bound to 127.0.0.1 and ::1 only */
 	int i;
@@ -336,7 +329,7 @@ int listeners__start_local_only(void)
 }
 
 
-int listeners__start(void)
+static int listeners__start(void)
 {
 	int i;
 
@@ -380,7 +373,7 @@ int listeners__start(void)
 }
 
 
-void listeners__stop(void)
+static void listeners__stop(void)
 {
 	int i;
 
@@ -407,7 +400,7 @@ void listeners__stop(void)
 }
 
 
-void signal__setup(void)
+static void signal__setup(void)
 {
 	signal(SIGINT, handle_sigint);
 	signal(SIGTERM, handle_sigint);
@@ -425,7 +418,7 @@ void signal__setup(void)
 }
 
 
-int pid__write(void)
+static int pid__write(void)
 {
 	FILE *pid;
 
diff --git a/src/mosquitto_broker_internal.h b/src/mosquitto_broker_internal.h
index 6f6d48d2..c66126c8 100644
--- a/src/mosquitto_broker_internal.h
+++ b/src/mosquitto_broker_internal.h
@@ -819,6 +819,16 @@ void session_expiry__remove_all(void);
 void session_expiry__check(void);
 void session_expiry__send_all(void);
 
+/* ============================================================
+ * Signals
+ * ============================================================ */
+void handle_sigint(int signal);
+void handle_sigusr1(int signal);
+void handle_sigusr2(int signal);
+#ifdef SIGHUP
+void handle_sighup(int signal);
+#endif
+
 /* ============================================================
  * Window service and signal related functions
  * ============================================================ */
@@ -855,4 +865,3 @@ void xtreport(void);
 #endif
 
 #endif
-
diff --git a/src/mux_epoll.c b/src/mux_epoll.c
index 6b1b2e89..dd81b7d9 100644
--- a/src/mux_epoll.c
+++ b/src/mux_epoll.c
@@ -106,12 +106,6 @@ int mux_epoll__init(struct mosquitto__listener_sock *listensock, int listensock_
 	return MOSQ_ERR_SUCCESS;
 }
 
-int mux_epoll__loop_setup(void)
-{
-	return MOSQ_ERR_SUCCESS;
-}
-
-
 int mux_epoll__add_out(struct mosquitto *context)
 {
 	struct epoll_event ev;
diff --git a/src/net.c b/src/net.c
index bbdb2708..cbcfc677 100644
--- a/src/net.c
+++ b/src/net.c
@@ -427,7 +427,7 @@ int net__tls_server_ctx(struct mosquitto__listener *listener)
 #endif
 
 
-int net__load_crl_file(struct mosquitto__listener *listener)
+static int net__load_crl_file(struct mosquitto__listener *listener)
 {
 #ifdef WITH_TLS
 	X509_STORE *store;
diff --git a/src/persist.h b/src/persist.h
index 21c0e679..35081770 100644
--- a/src/persist.h
+++ b/src/persist.h
@@ -19,6 +19,8 @@ Contributors:
 #ifndef PERSIST_H
 #define PERSIST_H
 
+#include "mosquitto_broker_internal.h"
+
 #define MOSQ_DB_VERSION 6
 
 /* DB read/write */
diff --git a/src/security.c b/src/security.c
index 839ec31e..98b4d962 100644
--- a/src/security.c
+++ b/src/security.c
@@ -47,7 +47,7 @@ void LIB_ERROR(void)
 }
 
 
-int security__load_v2(struct mosquitto__auth_plugin *plugin, struct mosquitto_auth_opt *auth_options, int auth_option_count, void *lib)
+static int security__load_v2(struct mosquitto__auth_plugin *plugin, struct mosquitto_auth_opt *auth_options, int auth_option_count, void *lib)
 {
 	int rc;
 
@@ -121,7 +121,7 @@ int security__load_v2(struct mosquitto__auth_plugin *plugin, struct mosquitto_au
 }
 
 
-int security__load_v3(struct mosquitto__auth_plugin *plugin, struct mosquitto_opt *auth_options, int auth_option_count, void *lib)
+static int security__load_v3(struct mosquitto__auth_plugin *plugin, struct mosquitto_opt *auth_options, int auth_option_count, void *lib)
 {
 	int rc;
 
@@ -194,7 +194,7 @@ int security__load_v3(struct mosquitto__auth_plugin *plugin, struct mosquitto_op
 }
 
 
-int security__load_v4(struct mosquitto__auth_plugin *plugin, struct mosquitto_opt *auth_options, int auth_option_count, void *lib)
+static int security__load_v4(struct mosquitto__auth_plugin *plugin, struct mosquitto_opt *auth_options, int auth_option_count, void *lib)
 {
 	int rc;
 
diff --git a/src/security_default.c b/src/security_default.c
index ec96e319..e659e7bf 100644
--- a/src/security_default.c
+++ b/src/security_default.c
@@ -202,7 +202,7 @@ int mosquitto_security_cleanup_default(bool reload)
 }
 
 
-int add__acl(struct mosquitto__security_options *security_opts, const char *user, const char *topic, int access)
+static int add__acl(struct mosquitto__security_options *security_opts, const char *user, const char *topic, int access)
 {
 	struct mosquitto__acl_user *acl_user=NULL, *user_tail;
 	struct mosquitto__acl *acl, *acl_tail;
@@ -298,7 +298,7 @@ int add__acl(struct mosquitto__security_options *security_opts, const char *user
 	return MOSQ_ERR_SUCCESS;
 }
 
-int add__acl_pattern(struct mosquitto__security_options *security_opts, const char *topic, int access)
+static int add__acl_pattern(struct mosquitto__security_options *security_opts, const char *topic, int access)
 {
 	struct mosquitto__acl *acl, *acl_tail;
 	char *local_topic;
diff --git a/src/signals.c b/src/signals.c
index 9938996f..82d911be 100644
--- a/src/signals.c
+++ b/src/signals.c
@@ -29,6 +29,8 @@ Contributors:
 #include <stdbool.h>
 #include <signal.h>
 
+#include "mosquitto_broker_internal.h"
+
 #ifdef WITH_PERSISTENCE
 extern bool flag_db_backup;
 #endif