Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.


// Minimal example of defining a predestructor for a class which
// uses boost::signals2::deconstruct as its factory function.
// Copyright Frank Mori Hess 2009.

// Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// For more information, see

#include <boost/shared_ptr.hpp>
#include <boost/signals2/deconstruct.hpp>
#include <iostream>

namespace bs2 = boost::signals2;

namespace mynamespace
  class X
      std::cout << "cruel world!" << std::endl;
    /* This adl_predestruct friend function will be found by
    via argument-dependent lookup when using boost::signals2::deconstruct. */
    friend void adl_predestruct(X *)
      std::cout << "Goodbye, ";
    /* boost::signals2::deconstruct always requires an adl_postconstruct function
    which can be found via argument-dependent, so we define one which does nothing. */
    template<typename T> friend
      void adl_postconstruct(const boost::shared_ptr<T> &, X *)
    friend class bs2::deconstruct_access;  // give boost::signals2::deconstruct access to private constructor
    // private constructor forces use of boost::signals2::deconstruct to create objects.

int main()
    boost::shared_ptr<mynamespace::X> x = bs2::deconstruct<mynamespace::X>();
  return 0;