Fiddle::Handle.sym_defined?

static VALUE
rb_fiddle_handle_s_sym_defined(VALUE self, VALUE sym)
{
    fiddle_void_func func;

    func = fiddle_handle_find_func(RTLD_NEXT, sym);

    if( func ) {
        return PTR2NUM(func);
    }
    else {
        return Qnil;
    }
}