diff --git a/CHANGES b/CHANGES
index 85b58a5180..d2ebe04cfb 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,5 @@
+4673.	[port]		Silence GCC 7 warnings. [RT #45592]
+
 4672.	[placeholder]
 
 4671.	[bug]		Fix a race condition that could cause the
diff --git a/bin/dig/dig.c b/bin/dig/dig.c
index 92e0438cc3..83bf649f8c 100644
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -325,7 +325,7 @@ static isc_result_t
 say_message(dns_rdata_t *rdata, dig_query_t *query, isc_buffer_t *buf) {
 	isc_result_t result;
 	isc_uint64_t diff;
-	char store[sizeof("12345678901234567890")];
+	char store[sizeof(" in 18446744073709551616 us.")];
 	unsigned int styleflags = 0;
 
 	if (query->lookup->trace || query->lookup->ns_search_only) {
@@ -348,13 +348,14 @@ say_message(dns_rdata_t *rdata, dig_query_t *query, isc_buffer_t *buf) {
 		return (result);
 	check_result(result, "dns_rdata_totext");
 	if (query->lookup->identify) {
+
 		diff = isc_time_microdiff(&query->time_recv, &query->time_sent);
 		ADD_STRING(buf, " from server ");
 		ADD_STRING(buf, query->servname);
 		if (query->lookup->use_usec)
-			snprintf(store, 19, " in %ld us.", (long) diff);
+			snprintf(store, sizeof(store), " in %" ISC_PLATFORM_QUADFORMAT "u us.", diff);
 		else
-			snprintf(store, 19, " in %ld ms.", (long) diff / 1000);
+			snprintf(store, sizeof(store), " in %" ISC_PLATFORM_QUADFORMAT "u ms.", diff / 1000);
 		ADD_STRING(buf, store);
 	}
 	ADD_STRING(buf, "\n");
diff --git a/bin/dnssec/dnssec-revoke.c b/bin/dnssec/dnssec-revoke.c
index 118d3dde25..b7ab5d7e03 100644
--- a/bin/dnssec/dnssec-revoke.c
+++ b/bin/dnssec/dnssec-revoke.c
@@ -140,7 +140,7 @@ main(int argc, char **argv) {
 			if (isc_commandline_option != '?')
 				fprintf(stderr, "%s: invalid argument -%c\n",
 					program, isc_commandline_option);
-			/* Falls into */
+			/* FALLTHROUGH */
 		    case 'h':
 			/* Does not return. */
 			usage();
diff --git a/bin/dnssec/dnssec-settime.c b/bin/dnssec/dnssec-settime.c
index f23be584a7..d26b8504af 100644
--- a/bin/dnssec/dnssec-settime.c
+++ b/bin/dnssec/dnssec-settime.c
@@ -348,7 +348,7 @@ main(int argc, char **argv) {
 			if (isc_commandline_option != '?')
 				fprintf(stderr, "%s: invalid argument -%c\n",
 					program, isc_commandline_option);
-			/* Falls into */
+			/* FALLTHROUGH */
 		case 'h':
 			/* Does not return. */
 			usage();
diff --git a/bin/dnssec/dnssectool.h b/bin/dnssec/dnssectool.h
index 97c7401462..da4caa59d8 100644
--- a/bin/dnssec/dnssectool.h
+++ b/bin/dnssec/dnssectool.h
@@ -36,8 +36,8 @@ check_result(isc_result_t result, const char *message);
 void
 vbprintf(int level, const char *fmt, ...) ISC_FORMAT_PRINTF(2, 3);
 
-void
-version(const char *program);
+ISC_PLATFORM_NORETURN_PRE void
+version(const char *program) ISC_PLATFORM_NORETURN_POST;
 
 void
 type_format(const dns_rdatatype_t type, char *cp, unsigned int size);
diff --git a/bin/named/query.c b/bin/named/query.c
index 5321a73c87..b55b21b13a 100644
--- a/bin/named/query.c
+++ b/bin/named/query.c
@@ -9283,7 +9283,7 @@ log_query(ns_client_t *client, unsigned int flags, unsigned int extflags) {
 	char classname[DNS_RDATACLASS_FORMATSIZE];
 	char onbuf[ISC_NETADDR_FORMATSIZE];
 	char ecsbuf[DNS_ECS_FORMATSIZE + sizeof(" [ECS ]") - 1] = { 0 };
-	char ednsbuf[sizeof("E(255)")] = { 0 };
+	char ednsbuf[sizeof("E(65535)")] = { 0 };
 	dns_rdataset_t *rdataset;
 	int level = ISC_LOG_INFO;
 
@@ -9298,7 +9298,7 @@ log_query(ns_client_t *client, unsigned int flags, unsigned int extflags) {
 	isc_netaddr_format(&client->destaddr, onbuf, sizeof(onbuf));
 
 	if (client->ednsversion >= 0)
-		snprintf(ednsbuf, sizeof(ednsbuf), "E(%d)",
+		snprintf(ednsbuf, sizeof(ednsbuf), "E(%hd)",
 			 client->ednsversion);
 
 	if (HAVEECS(client)) {
diff --git a/bin/tools/named-rrchecker.c b/bin/tools/named-rrchecker.c
index 98993e0e43..fbf435bb9f 100644
--- a/bin/tools/named-rrchecker.c
+++ b/bin/tools/named-rrchecker.c
@@ -30,6 +30,9 @@ static isc_lex_t *lex;
 
 static isc_lexspecials_t specials;
 
+ISC_PLATFORM_NORETURN_PRE static void
+usage(void) ISC_PLATFORM_NORETURN_POST;
+
 static void
 usage(void) {
 	fprintf(stderr, "usage: named-rrchecker [-o origin] [-hpCPTu]\n");
diff --git a/lib/bind9/getaddresses.c b/lib/bind9/getaddresses.c
index 7a4fb8c0b9..2928911582 100644
--- a/lib/bind9/getaddresses.c
+++ b/lib/bind9/getaddresses.c
@@ -154,6 +154,7 @@ bind9_getaddresses(const char *hostname, in_port_t port,
 			goto again;
 		}
 #endif
+		/* FALLTHROUGH */
 	default:
 		return (ISC_R_FAILURE);
 	}
diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index 8d3df4ecc7..4de12f487c 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -7042,6 +7042,7 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
 	case dns_rcode_formerr:
 		if (fctx->rmessage->counts[DNS_SECTION_QUESTION] == 0)
 			break;
+		/* FALLTHROUGH */
 	case dns_rcode_nxrrset:	/* Not expected. */
 	case dns_rcode_badcookie:
 	case dns_rcode_noerror:
diff --git a/lib/dns/rootns.c b/lib/dns/rootns.c
index ea77acf492..d86d0172d1 100644
--- a/lib/dns/rootns.c
+++ b/lib/dns/rootns.c
@@ -122,7 +122,7 @@ check_node(dns_rdataset_t *rootns, dns_name_t *name,
 		case dns_rdatatype_ns:
 			if (dns_name_compare(name, dns_rootname) == 0)
 				break;
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 		default:
 			result = ISC_R_FAILURE;
 			goto cleanup;
diff --git a/lib/dns/time.c b/lib/dns/time.c
index f1c365dc90..b2a3c7c06f 100644
--- a/lib/dns/time.c
+++ b/lib/dns/time.c
@@ -31,7 +31,7 @@ static const int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
 isc_result_t
 dns_time64_totext(isc_int64_t t, isc_buffer_t *target) {
 	struct tm tm;
-	char buf[sizeof("YYYYMMDDHHMMSS")];
+	char buf[sizeof("!!!!!!YYYY!!!!!!!!MM!!!!!!!!DD!!!!!!!!HH!!!!!!!!MM!!!!!!!!SS")];
 	int secs;
 	unsigned int l;
 	isc_region_t region;
diff --git a/lib/dns/update.c b/lib/dns/update.c
index 5df6c582b0..4b5d8a7d5f 100644
--- a/lib/dns/update.c
+++ b/lib/dns/update.c
@@ -1539,7 +1539,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 
 		update_log(log, zone, ISC_LOG_DEBUG(3),
 			   "updated data signatures");
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case remove_orphaned:
 		state->state = remove_orphaned;
 
@@ -1572,7 +1572,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 		update_log(log, zone, ISC_LOG_DEBUG(3),
 			   "rebuilding NSEC chain");
 
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case build_chain:
 		state->state = build_chain;
 		/*
@@ -1660,7 +1660,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 
 		CHECK(uniqify_name_list(&state->affected));
 
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case process_nsec:
 		state->state = process_nsec;
 
@@ -1777,7 +1777,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 		update_log(log, zone, ISC_LOG_DEBUG(3),
 			   "signing rebuilt NSEC chain");
 
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case sign_nsec:
 		state->state = sign_nsec;
 		/* Update RRSIG NSECs. */
@@ -1807,7 +1807,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 		}
 		ISC_LIST_APPENDLIST(state->nsec_mindiff.tuples,
 				    state->work.tuples, link);
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case update_nsec3:
 		state->state = update_nsec3;
 
@@ -1895,7 +1895,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 				t = ISC_LIST_NEXT(t, link);
 		}
 
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case process_nsec3:
 		state->state = process_nsec3;
 		while ((t = ISC_LIST_HEAD(state->affected.tuples)) != NULL) {
@@ -1950,7 +1950,7 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 		update_log(log, zone, ISC_LOG_DEBUG(3),
 			   "signing rebuilt NSEC3 chain");
 
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case sign_nsec3:
 		state->state = sign_nsec3;
 		/* Update RRSIG NSEC3s. */
diff --git a/lib/dns/xfrin.c b/lib/dns/xfrin.c
index f691336cdc..13c8c6a777 100644
--- a/lib/dns/xfrin.c
+++ b/lib/dns/xfrin.c
@@ -615,6 +615,7 @@ xfr_rr(dns_xfrin_ctx_t *xfr, dns_name_t *name, isc_uint32_t ttl,
 	case XFRST_IXFR_END:
 		FAIL(DNS_R_EXTRADATA);
 		/* NOTREACHED */
+		/* FALLTHROUGH */
 	default:
 		INSIST(0);
 		break;
diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index 247b77641d..871f6e8efd 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -9570,6 +9570,7 @@ zone_maintenance(dns_zone_t *zone) {
 	case dns_zone_redirect:
 		if (zone->masters == NULL)
 			break;
+		/* FALLTHROUGH */
 	case dns_zone_slave:
 	case dns_zone_stub:
 		LOCK_ZONE(zone);
@@ -9591,6 +9592,7 @@ zone_maintenance(dns_zone_t *zone) {
 	case dns_zone_redirect:
 		if (zone->masters == NULL)
 			break;
+		/* FALLTHROUGH */
 	case dns_zone_slave:
 	case dns_zone_stub:
 		if (!DNS_ZONE_FLAG(zone, DNS_ZONEFLG_DIALREFRESH) &&
@@ -14780,7 +14782,7 @@ zone_xfrdone(dns_zone_t *zone, isc_result_t result) {
 	switch (xfrresult) {
 	case ISC_R_SUCCESS:
 		DNS_ZONE_SETFLAG(zone, DNS_ZONEFLG_NEEDNOTIFY);
-		/*FALLTHROUGH*/
+		/* FALLTHROUGH */
 	case DNS_R_UPTODATE:
 		DNS_ZONE_CLRFLAG(zone, DNS_ZONEFLG_FORCEXFER);
 		/*
diff --git a/lib/isc/entropy.c b/lib/isc/entropy.c
index 0d0983d88f..a45f0aa28a 100644
--- a/lib/isc/entropy.c
+++ b/lib/isc/entropy.c
@@ -325,9 +325,11 @@ entropypool_adddata(isc_entropy_t *ent, void *p, unsigned int len,
 		case 3:
 			val = *buf++;
 			len--;
+			/* FALLTHROUGH */
 		case 2:
 			val = val << 8 | *buf++;
 			len--;
+			/* FALLTHROUGH */
 		case 1:
 			val = val << 8 | *buf++;
 			len--;
@@ -348,8 +350,10 @@ entropypool_adddata(isc_entropy_t *ent, void *p, unsigned int len,
 		switch (len) {
 		case 3:
 			val = *buf++;
+			/* FALLTHROUGH */
 		case 2:
 			val = val << 8 | *buf++;
+			/* FALLTHROUGH */
 		case 1:
 			val = val << 8 | *buf++;
 		}
diff --git a/lib/isc/print.c b/lib/isc/print.c
index a6eb668d24..97bef07413 100644
--- a/lib/isc/print.c
+++ b/lib/isc/print.c
@@ -630,7 +630,7 @@ isc__print_printf(void (*emit)(char, void *), void *arg,
 #else
 			assert("long doubles are not supported" == NULL);
 #endif
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 		case 'e':
 		case 'E':
 		case 'f':
diff --git a/lib/isc/unix/entropy.c b/lib/isc/unix/entropy.c
index 2d52acd5d0..e3e8eff154 100644
--- a/lib/isc/unix/entropy.c
+++ b/lib/isc/unix/entropy.c
@@ -151,7 +151,7 @@ get_from_usocketsource(isc_entropysource_t *source, isc_uint32_t desired) {
 			INSIST(n == 2);
 			source->sources.usocket.status =
 						isc_usocketsource_wrote;
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 
 		case isc_usocketsource_wrote:
 			if (recvfrom(fd, buf, 1, 0, NULL, NULL) != 1) {
@@ -189,7 +189,7 @@ get_from_usocketsource(isc_entropysource_t *source, isc_uint32_t desired) {
 			source->sources.usocket.sz_to_recv = sz_to_recv;
 			if (sz_to_recv > sizeof(buf))
 				goto err;
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 
 		case isc_usocketsource_reading:
 			if (sz_to_recv != 0U) {
diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 2d16779da3..c096414f54 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -5220,6 +5220,8 @@ socket_send(isc__socket_t *sock, isc_socketevent_t *dev, isc_task_t *task,
 			break;
 		}
 
+		/* FALLTHROUGH */
+
 	case DOIO_HARD:
 	case DOIO_SUCCESS:
 		if ((flags & ISC_SOCKFLAG_IMMEDIATE) == 0)
diff --git a/lib/isccfg/aclconf.c b/lib/isccfg/aclconf.c
index 93d6480e61..1fe1ce44f8 100644
--- a/lib/isccfg/aclconf.c
+++ b/lib/isccfg/aclconf.c
@@ -412,23 +412,27 @@ geoip_can_answer(dns_aclelement_t *elt, cfg_aclconfctx_t *ctx) {
 		    ctx->geoip->country_v6 != NULL ||
 		    ctx->geoip->region != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_region:
 	case dns_geoip_regionname:
 		if (ctx->geoip->city_v4 != NULL ||
 		    ctx->geoip->city_v6 != NULL ||
 		    ctx->geoip->region != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_country_code:
 	case dns_geoip_country_code3:
 	case dns_geoip_country_name:
 		if (ctx->geoip->country_v4 != NULL ||
 		    ctx->geoip->country_v6 != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_region_countrycode:
 	case dns_geoip_region_code:
 	case dns_geoip_region_name:
 		if (ctx->geoip->region != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_city_countrycode:
 	case dns_geoip_city_countrycode3:
 	case dns_geoip_city_countryname:
@@ -443,18 +447,23 @@ geoip_can_answer(dns_aclelement_t *elt, cfg_aclconfctx_t *ctx) {
 		if (ctx->geoip->city_v4 != NULL ||
 		    ctx->geoip->city_v6 != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_isp_name:
 		if (ctx->geoip->isp != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_org_name:
 		if (ctx->geoip->org != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_as_asnum:
 		if (ctx->geoip->as != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_domain_name:
 		if (ctx->geoip->domain != NULL)
 			return (ISC_TRUE);
+		/* FALLTHROUGH */
 	case dns_geoip_netspeed_id:
 		if (ctx->geoip->netspeed != NULL)
 			return (ISC_TRUE);
diff --git a/lib/lwres/print.c b/lib/lwres/print.c
index 58f7dfd55b..797b27085e 100644
--- a/lib/lwres/print.c
+++ b/lib/lwres/print.c
@@ -497,7 +497,7 @@ lwres__print_vsnprintf(char *str, size_t size, const char *format, va_list ap) {
 #else
 			INSIST("long doubles are not supported" == NULL);
 #endif
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 		case 'e':
 		case 'E':
 		case 'f':