default logger name only if argument is not given at all, distinguish from 'undefined' given as argument

src/duk_bi_logger.c

@@ -17,17 +17,21 @@ static const duk_uint8_t duk__log_level_strings[] = {
 /* Constructor */
 duk_ret_t duk_bi_logger_constructor(duk_context *ctx) {
 	duk_hthread *thr = (duk_hthread *) ctx;
+	duk_int_t nargs;  /* FIXME: type */
 
 	/* Calling as a non-constructor is not meaningful. */
 	if (!duk_is_constructor_call(ctx)) {
 		return DUK_RET_TYPE_ERROR;
 	}
 
+	nargs = duk_get_top(ctx);
+	duk_set_top(ctx, 1);
+
 	duk_push_this(ctx);
 
 	/* [ name this ] */
 
-	if (duk_is_undefined(ctx, 0)) {
+	if (nargs == 0) {
 		/* Automatic defaulting of logger name from caller. */
 		if (thr->callstack_top >= 2) {
 			duk_activation *act_caller = thr->callstack + thr->callstack_top - 2;

src/genbuiltins.py

@@ -1213,6 +1213,7 @@ bi_logger_constructor = {
 	'name': 'Logger',
 
 	'length': 1,
+	'varargs': True,
 	'native': 'duk_bi_logger_constructor',
 	'callable': True,
 	'constructable': True,