add support for strings in foreign export

backendC/CleanCompilerSources/instructions.c

@@ -3679,6 +3679,14 @@ static void print_foreign_export_type (TypeNode type)
 		} else if (symbol_p->symb_kind==real_type){
 			FPrintF (OutFile,"R");
 			return;
+		} else if (symbol_p->symb_kind==unboxed_array_type){
+			TypeNode type_node_p;
+
+			type_node_p=type->type_node_arguments->type_arg_node;
+			if (!type_node_p->type_node_is_var && type_node_p->type_node_symbol->symb_kind==char_type){
+				FPrintF (OutFile,"S");
+				return;
+			}
 		} else if (symbol_p->symb_kind==tuple_type){
 			TypeArgs type_arg_p;