diff --git a/coreutils/logname.c b/coreutils/logname.c
index 3400c30d9..7983d1704 100644
--- a/coreutils/logname.c
+++ b/coreutils/logname.c
@@ -27,7 +27,7 @@
 int logname_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int logname_main(int argc, char **argv UNUSED_PARAM)
 {
-	char buf[128];
+	char buf[64];
 
 	if (argc > 1) {
 		bb_show_usage();
diff --git a/editors/awk.c b/editors/awk.c
index 30f09cbaf..cb98a67b6 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -114,7 +114,7 @@ typedef struct nvblock_s {
 	var *pos;
 	struct nvblock_s *prev;
 	struct nvblock_s *next;
-	var nv[0];
+	var nv[];
 } nvblock;
 
 typedef struct tsplitter_s {
diff --git a/loginutils/su.c b/loginutils/su.c
index a8b852b09..a3f7ed8a0 100644
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -40,11 +40,24 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 
 	if (ENABLE_FEATURE_SU_SYSLOG) {
 		/* The utmp entry (via getlogin) is probably the best way to identify
-		the user, especially if someone su's from a su-shell.
-		But getlogin can fail -- usually due to lack of utmp entry.
-		in this case resort to getpwuid.  */
-		old_user = xstrdup(IF_FEATURE_UTMP(getlogin() ? : ) (pw = getpwuid(cur_uid)) ? pw->pw_name : "");
-		tty = xmalloc_ttyname(2) ? : "none";
+		 * the user, especially if someone su's from a su-shell.
+		 * But getlogin can fail -- usually due to lack of utmp entry.
+		 * in this case resort to getpwuid.  */
+		const char *user;
+#if ENABLE_FEATURE_UTMP
+		char user_buf[64];
+		user = user_buf;
+		if (getlogin_r(user_buf, sizeof(user_buf)) != 0)
+#endif
+		{
+			pw = getpwuid(cur_uid);
+			user = pw ? pw->pw_name : "";
+		}
+		old_user = xstrdup(user);
+		tty = xmalloc_ttyname(2);
+		if (!tty) {
+			tty = "none";
+		}
 		openlog(applet_name, 0, LOG_AUTH);
 	}