Object#clone && Object#dup

VALUE
rb_obj_clone(obj)
    VALUE obj;
{
    VALUE clone;

    if (rb_special_const_p(obj)) {
        rb_raise(rb_eTypeError, "can't clone %s", rb_obj_classname(obj));
    }
    clone = rb_obj_alloc(rb_obj_class(obj));
    RBASIC(clone)->klass = rb_singleton_class_clone(obj);
    RBASIC(clone)->flags = (RBASIC(obj)->flags | FL_TEST(clone, FL_TAINT)) & ~(FL_FREEZE|FL_FINALIZE);
    init_copy(clone, obj);
    RBASIC(clone)->flags |= RBASIC(obj)->flags & FL_FREEZE;

    return clone;
}

VALUE
rb_obj_dup(obj)
    VALUE obj;
{
    VALUE dup;

    if (rb_special_const_p(obj)) {
        rb_raise(rb_eTypeError, "can't dup %s", rb_obj_classname(obj));
    }
    dup = rb_obj_alloc(rb_obj_class(obj));
    init_copy(dup, obj);

    return dup;
}

special constants

static inline int
#if defined(HAVE_PROTOTYPES)
rb_type(VALUE obj)
#else
rb_type(obj)
   VALUE obj;
#endif
{
    if (FIXNUM_P(obj)) return T_FIXNUM;
    if (obj == Qnil) return T_NIL;
    if (obj == Qfalse) return T_FALSE;
    if (obj == Qtrue) return T_TRUE;
    if (obj == Qundef) return T_UNDEF;
    if (SYMBOL_P(obj)) return T_SYMBOL;
    return BUILTIN_TYPE(obj);
}

static inline int
#if defined(HAVE_PROTOTYPES)
rb_special_const_p(VALUE obj)
#else
rb_special_const_p(obj)
    VALUE obj;
#endif
{
    if (SPECIAL_CONST_P(obj)) return Qtrue;
    return Qfalse;
}