ceph/src/boost/boost/atomic/detail/addressof.hpp

   1 /*
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * Copyright (c) 2018 Andrey Semashev
   7  */
   8 /*!
   9  * \file   atomic/detail/addressof.hpp
  10  *
  11  * This header defines \c addressof helper function. It is similar to \c boost::addressof but it is more
  12  * lightweight and also contains a workaround for some compiler warnings.
  13  */
  14
  15 #ifndef BOOST_ATOMIC_DETAIL_ADDRESSOF_HPP_INCLUDED_
  16 #define BOOST_ATOMIC_DETAIL_ADDRESSOF_HPP_INCLUDED_
  17
  18 #include <boost/atomic/detail/config.hpp>
  19 #include <boost/atomic/detail/header.hpp>
  20
  21 #ifdef BOOST_HAS_PRAGMA_ONCE
  22 #pragma once
  23 #endif
  24
  25 // Detection logic is based on boost/core/addressof.hpp
  26 #if defined(BOOST_MSVC_FULL_VER) && BOOST_MSVC_FULL_VER >= 190024215
  27 #define BOOST_ATOMIC_DETAIL_HAS_BUILTIN_ADDRESSOF
  28 #elif defined(BOOST_GCC) && BOOST_GCC >= 70000
  29 #define BOOST_ATOMIC_DETAIL_HAS_BUILTIN_ADDRESSOF
  30 #elif defined(__has_builtin)
  31 #if __has_builtin(__builtin_addressof)
  32 #define BOOST_ATOMIC_DETAIL_HAS_BUILTIN_ADDRESSOF
  33 #endif
  34 #endif
  35
  36 namespace boost {
  37 namespace atomics {
  38 namespace detail {
  39
  40 template< typename T >
  41 BOOST_FORCEINLINE T* addressof(T& value) BOOST_NOEXCEPT
  42 {
  43 #if defined(BOOST_ATOMIC_DETAIL_HAS_BUILTIN_ADDRESSOF)
  44     return __builtin_addressof(value);
  45 #else
  46     // Note: The point of using a local struct as the intermediate type instead of char is to avoid gcc warnings
  47     // if T is a const volatile char*:
  48     // warning: casting 'const volatile char* const' to 'const volatile char&' does not dereference pointer
  49     // The local struct makes sure T is not related to the cast target type.
  50     struct opaque_type;
  51     return reinterpret_cast< T* >(&const_cast< opaque_type& >(reinterpret_cast< const volatile opaque_type& >(value)));
  52 #endif
  53 }
  54
  55 } // namespace detail
  56 } // namespace atomics
  57 } // namespace boost
  58
  59 #include <boost/atomic/detail/footer.hpp>
  60
  61 #endif // BOOST_ATOMIC_DETAIL_ADDRESSOF_HPP_INCLUDED_