Scm_UnknownClass  105 src/class.c    SCM_DEFINE_BUILTIN_CLASS_SIMPLE(Scm_UnknownClass, NULL);
Scm_UnknownClass  584 src/gauche.h   SCM_CLASS_DECL(Scm_UnknownClass);
Scm_UnknownClass  597 src/gauche.h   #define SCM_CLASS_UNKNOWN          (&Scm_UnknownClass)