text: #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_CLANG_HPP_INCLUDED
  #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_CLANG_HPP_INCLUDED
  
  // MS compatible compilers support #pragma once
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  # pragma once
  #endif
  
  //  detail/sp_counted_base_clang.hpp - __c11 clang intrinsics
  //
  //  Copyright (c) 2007, 2013, 2015 Peter Dimov
  //
  //  Distributed under the Boost Software License, Version 1.0.
  //  See accompanying file LICENSE_1_0.txt or copy at
  //  http://www.boost.org/LICENSE_1_0.txt
  
  #include <boost/detail/sp_typeinfo.hpp>
  #include <boost/cstdint.hpp>
  
  #error "how include me?"
  
  namespace boost
  {
  
  namespace detail
  {
  
  typedef _Atomic( boost::int_least32_t ) atomic_int_least32_t;
  
  inline void atomic_increment( atomic_int_least32_t * pw )
  {
      __c11_atomic_fetch_add( pw, 1, __ATOMIC_RELAXED );
  }
  
  inline boost::int_least32_t atomic_decrement( atomic_int_least32_t * pw )
  {
      return __c11_atomic_fetch_sub( pw, 1, __ATOMIC_ACQ_REL );
  }
  
  inline boost::int_least32_t atomic_conditional_increment( atomic_int_least32_t * pw )
  {
      // long r = *pw;
      // if( r != 0 ) ++*pw;
      // return r;
  
      boost::int_least32_t r = __c11_atomic_load( pw, __ATOMIC_RELAXED );
  
      for( ;; )
      {
          if( r == 0 )
          {
              return r;
          }
  
          if( __c11_atomic_compare_exchange_weak( pw, &r, r + 1, __ATOMIC_RELAXED, __ATOMIC_RELAXED ) )
          {
              return r;
          }
      }    
  }
  
  class sp_counted_base
  {
  private:
  
      sp_counted_base( sp_counted_base const & );
      sp_counted_base & operator= ( sp_counted_base const & );
  
      atomic_int_least32_t use_count_;	// #shared
      atomic_int_least32_t weak_count_;	// #weak + (#shared != 0)
  
  public:
  
      sp_counted_base()
      {
          __c11_atomic_init( &use_count_, 1 );
          __c11_atomic_init( &weak_count_, 1 );
      }
  
      virtual ~sp_counted_base() // nothrow
      {
      }
  
      // dispose() is called when use_count_ drops to zero, to release
      // the resources managed by *this.
  
      virtual void dispose() = 0; // nothrow
  
      // destroy() is called when weak_count_ drops to zero.
  
      virtual void destroy() // nothrow
      {
          delete this;
      }
  
      virtual void * get_deleter( sp_typeinfo const & ti ) = 0;
      virtual void * get_untyped_deleter() = 0;
  
      void add_ref_copy()
      {
          atomic_increment( &use_count_ );
      }
  
      bool add_ref_lock() // true on success
      {
          return atomic_conditional_increment( &use_count_ ) != 0;
      }
  
      void release() // nothrow
      {
          if( atomic_decrement( &use_count_ ) == 1 )
          {
              dispose();
              weak_release();
          }
      }
  
      void weak_add_ref() // nothrow
      {
          atomic_increment( &weak_count_ );
      }
  
      void weak_release() // nothrow
      {
          if( atomic_decrement( &weak_count_ ) == 1 )
          {
              destroy();
          }
      }
  
      long use_count() const // nothrow
      {
          return __c11_atomic_load( const_cast< atomic_int_least32_t* >( &use_count_ ), __ATOMIC_ACQUIRE );
      }
  };
  
  } // namespace detail
  
  } // namespace boost
  
  #endif  // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_CLANG_HPP_INCLUDED
  