Use clearer notation for getnameinfo() return handling

Writing

    if (getnameinfo(...))
        handle_error();

reads quite strangely, so use something like

    if (getnameinfo(...) != 0)
        handle_error();

instead.

src/backend/libpq/hba.c

@@ -569,7 +569,7 @@ check_hostname(hbaPort *port, const char *hostname)
 		if (pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
 							   remote_hostname, sizeof(remote_hostname),
 							   NULL, 0,
-							   0))
+							   0) != 0)
 			return false;
 
 		port->remote_hostname = pstrdup(remote_hostname);

src/backend/postmaster/postmaster.c

@@ -3357,14 +3357,14 @@ BackendInitialize(Port *port)
 	if (pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
 						   remote_host, sizeof(remote_host),
 						   remote_port, sizeof(remote_port),
-					   (log_hostname ? 0 : NI_NUMERICHOST) | NI_NUMERICSERV))
+					   (log_hostname ? 0 : NI_NUMERICHOST) | NI_NUMERICSERV) != 0)
 	{
 		int			ret = pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
 											 remote_host, sizeof(remote_host),
 											 remote_port, sizeof(remote_port),
 											 NI_NUMERICHOST | NI_NUMERICSERV);
 
-		if (ret)
+		if (ret != 0)
 			ereport(WARNING,
 					(errmsg_internal("pg_getnameinfo_all() failed: %s",
 									 gai_strerror(ret))));

src/backend/utils/adt/network.c

@@ -1093,7 +1093,7 @@ inet_client_addr(PG_FUNCTION_ARGS)
 							 remote_host, sizeof(remote_host),
 							 NULL, 0,
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	clean_ipv6_addr(port->raddr.addr.ss_family, remote_host);
@@ -1132,7 +1132,7 @@ inet_client_port(PG_FUNCTION_ARGS)
 							 NULL, 0,
 							 remote_port, sizeof(remote_port),
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	PG_RETURN_DATUM(DirectFunctionCall1(int4in, CStringGetDatum(remote_port)));
@@ -1169,7 +1169,7 @@ inet_server_addr(PG_FUNCTION_ARGS)
 							 local_host, sizeof(local_host),
 							 NULL, 0,
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	clean_ipv6_addr(port->laddr.addr.ss_family, local_host);
@@ -1208,7 +1208,7 @@ inet_server_port(PG_FUNCTION_ARGS)
 							 NULL, 0,
 							 local_port, sizeof(local_port),
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	PG_RETURN_DATUM(DirectFunctionCall1(int4in, CStringGetDatum(local_port)));

src/backend/utils/adt/pgstatfuncs.c

@@ -682,13 +682,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 											 remote_host, sizeof(remote_host),
 											 remote_port, sizeof(remote_port),
 											 NI_NUMERICHOST | NI_NUMERICSERV);
-					if (ret)
-					{
-						nulls[9] = true;
-						nulls[10] = true;
-						nulls[11] = true;
-					}
-					else
+					if (ret == 0)
 					{
 						clean_ipv6_addr(beentry->st_clientaddr.addr.ss_family, remote_host);
 						values[9] = DirectFunctionCall1(inet_in,
@@ -699,6 +693,12 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 							nulls[10] = true;
 						values[11] = Int32GetDatum(atoi(remote_port));
 					}
+					else
+					{
+						nulls[9] = true;
+						nulls[10] = true;
+						nulls[11] = true;
+					}
 				}
 				else if (beentry->st_clientaddr.addr.ss_family == AF_UNIX)
 				{
@@ -939,7 +939,7 @@ pg_stat_get_backend_client_addr(PG_FUNCTION_ARGS)
 							 remote_host, sizeof(remote_host),
 							 NULL, 0,
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	clean_ipv6_addr(beentry->st_clientaddr.addr.ss_family, remote_host);
@@ -988,7 +988,7 @@ pg_stat_get_backend_client_port(PG_FUNCTION_ARGS)
 							 NULL, 0,
 							 remote_port, sizeof(remote_port),
 							 NI_NUMERICHOST | NI_NUMERICSERV);
-	if (ret)
+	if (ret != 0)
 		PG_RETURN_NULL();
 
 	PG_RETURN_DATUM(DirectFunctionCall1(int4in,