in ruby I can bind a method to a receiver (instance):

class TEST
  def meth
  end
end
bound_method = TEST.new.method(:meth)

Question: How I can get the reveiver from a bound method back?

possible solution, found in docs:

/*
 *  call-seq:
 *     binding.receiver    -> object
 *
 *  Returns the bound receiver of the binding object.
 */
static VALUE
bind_receiver(VALUE bindval)
{
    const rb_binding_t *bind;
    GetBindingPtr(bindval, bind);
    return vm_block_self(&bind->block);
}