logging: use stack allocated string buffer to constuct NM_LOG_DOMAINS fieldth/logging-syslog-facility

NM_LOG_DOMAINS is a comma-separated list of the selected logging domains.

As the number of all logging domains is fixed at compile-time, the maximum
length of the buffer is known.

  $ git grep $'^\t{ LOGD_' | sed 's/.*"\(.*\)" .*/\1/' | xargs | sed 's/  */,/g' | sed 's/^/NM_LOG_DOMAINS=/'
  NM_LOG_DOMAINS=PLATFORM,RFKILL,ETHER,WIFI,BT,MB,DHCP4,DHCP6,PPP,WIFI_SCAN,IP4,IP6,AUTOIP4,DNS,VPN,SHARING,SUPPLICANT,AGENTS,SETTINGS,SUSPEND,CORE,DEVICE,OLPC,INFINIBAND,FIREWALL,ADSL,BOND,VLAN,BRIDGE,DBUS_PROPS,TEAM,CONCHECK,DCB,DISPATCH,AUDIT,SYSTEMD,VPN_PLUGIN,PROXY

Note that the static buffer "_all_logging_domains_to_str" is known
to be large enough to contain these domain names (it's even longer,
as it also contains "ALL", "IP", and "DHCP" alises). We can use that
to define the array of suitable size.

1 files changed, 9 insertions, 20 deletions

diff --git a/src/nm-logging.c b/src/nm-logging.c
index b30c8815c7..ea1a6ccf31 100644
--- a/src/nm-logging.c
+++ b/src/nm-logging.c
@@ -775,7 +775,6 @@ _nm_log_impl (const char *file,
 			struct iovec *iov = iov_data;
 			char *iov_free_data[5];
 			char **iov_free = iov_free_data;
-			nm_auto_free_gstring GString *s_domain_all = NULL;
 
 			now = nm_utils_get_monotonic_timestamp_ns ();
 			boottime = nm_utils_monotonic_timestamp_as_boottime (now, 1);
@@ -786,32 +785,22 @@ _nm_log_impl (const char *file,
 			_iovec_set_format_a (iov++, 30, "SYSLOG_PID=%ld", (long) getpid ());
 			{
 				const LogDesc *diter;
-				const char *s_domain_1 = NULL;
 				NMLogDomain dom_all = domain;
+				char s_log_domains_buf[NM_STRLEN ("NM_LOG_DOMAINS=") + sizeof (_all_logging_domains_to_str)];
+				char *s_log_domains = s_log_domains_buf;
+				gsize l_log_domains = sizeof (s_log_domains_buf);
 
+				nm_utils_strbuf_append_str (&s_log_domains, &l_log_domains, "NM_LOG_DOMAINS=");
 				for (diter = &domain_desc[0]; dom_all != 0 && diter->name; diter++) {
 					if (!NM_FLAGS_ANY (dom_all, diter->num))
 						continue;
-
-					/* construct a list of all domains (not only the enabled ones).
-					 * Note that in by far most cases, there is only one domain present.
-					 * Hence, save the construction of the GString. */
+					if (dom_all != domain)
+						nm_utils_strbuf_append_c (&s_log_domains, &l_log_domains, ',');
+					nm_utils_strbuf_append_str (&s_log_domains, &l_log_domains, diter->name);
 					dom_all &= ~diter->num;
-					if (!s_domain_1)
-						s_domain_1 = diter->name;
-					else {
-						if (!s_domain_all) {
-							s_domain_all = g_string_new ("NM_LOG_DOMAINS=");
-							g_string_append (s_domain_all, s_domain_1);
-						}
-						g_string_append_c (s_domain_all, ',');
-						g_string_append (s_domain_all, diter->name);
-					}
 				}
-				if (s_domain_all)
-					_iovec_set (iov++, s_domain_all->str, s_domain_all->len);
-				else
-					_iovec_set_format_str_a (iov++, 30, "NM_LOG_DOMAINS=%s", s_domain_1);
+				nm_assert (l_log_domains > 0);
+				_iovec_set (iov++, s_log_domains_buf, s_log_domains - s_log_domains_buf);
 			}
 			G_STATIC_ASSERT_EXPR (LOG_FAC (LOG_DAEMON) == 3);
 			_iovec_set_string_literal (iov++, "SYSLOG_FACILITY=3");