diff --git a/tools/bifcl/builtin-func.l b/tools/bifcl/builtin-func.l
index 8f0468ceab..6d31f9613a 100644
--- a/tools/bifcl/builtin-func.l
+++ b/tools/bifcl/builtin-func.l
@@ -255,7 +255,7 @@ void init_alternative_mode()
 
 	static char name[1024];
 	strncpy(name, input_filename, sizeof(name) - 1);
-	name[sizeof(name) - 1] = 0;
+	name[sizeof(name) - 1] = '\0';
 	char* dot = strchr(name, '.');
 	if ( dot )
 		*dot = '\0';
@@ -264,7 +264,7 @@ void init_alternative_mode()
 		{
 		static char plugin_canon[1024];
 		strncpy(plugin_canon, plugin, sizeof(plugin_canon) - 1);
-		plugin_canon[sizeof(plugin_canon) - 1] = 0;
+		plugin_canon[sizeof(plugin_canon) - 1] = '\0';
 		char* colon = strstr(plugin_canon, "::");
 
 		if ( colon ) {
@@ -355,10 +355,9 @@ int main(int argc, char* argv[])
 	for ( int i = optind; i < argc; i++ )
 		{
 		FILE* fp_input;
-		char* slash;
 
 		input_filename = input_filename_with_path = argv[i];
-		slash = strrchr(input_filename, '/');
+		char* slash = strrchr(input_filename, '/');
 
 		if ( (fp_input = fopen(input_filename, "r")) == NULL )
 			{
diff --git a/tools/bifcl/builtin-func.y b/tools/bifcl/builtin-func.y
index 365ff15bd3..66ef357d05 100644
--- a/tools/bifcl/builtin-func.y
+++ b/tools/bifcl/builtin-func.y
@@ -4,8 +4,6 @@
 #include <string>
 #include <cstring>
 
-using namespace std;
-
 #include <stdio.h>
 #include <stdlib.h>
 
diff --git a/tools/bifcl/include/bif_arg.h b/tools/bifcl/include/bif_arg.h
index 4ca9de0d21..588f1d60d2 100644
--- a/tools/bifcl/include/bif_arg.h
+++ b/tools/bifcl/include/bif_arg.h
@@ -13,7 +13,7 @@ enum builtin_func_arg_type
 
 extern const char* builtin_func_arg_type_bro_name[];
 
-class BuiltinFuncArg
+class BuiltinFuncArg final
 	{
 public:
 	BuiltinFuncArg(const char* arg_name, int arg_type);
@@ -29,7 +29,7 @@ public:
 	void PrintCArg(FILE* fp, int n);
 	void PrintValConstructor(FILE* fp);
 
-protected:
+private:
 	const char* name;
 	int type;
 	const char* type_str;