remove virtual

include/ustring.h

@@ -3,6 +3,10 @@
 // Copyright (c) 2005 by Mike Sharov <msharov@users.sourceforge.net>
 // This file is free software, distributed under the MIT License.
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #pragma once
 #include "memblock.h"
 #include "utf8.h"
@@ -306,3 +310,7 @@ inline hashvalue_t hash_value (const char* v)
 //----------------------------------------------------------------------
 
 } // namespace ustl
+
+#ifdef __cplusplus
+}
+#endif