ceph/src/boost/libs/optional/include/boost/optional/detail/optional_aligned_storage.hpp

   1 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
   2 // Copyright (C) 2016 Andrzej Krzemienski.
   3 //
   4 // Use, modification, and distribution is subject to the Boost Software
   5 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // See http://www.boost.org/libs/optional for documentation.
   9 //
  10 // You are welcome to contact the author at:
  11 //  fernando_cacciola@hotmail.com
  12 //  akrzemi1@gmail.com
  13
  14 #ifndef BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_ALIGNED_STORAGE_AJK_12FEB2016_HPP
  15 #define BOOST_OPTIONAL_OPTIONAL_DETAIL_OPTIONAL_ALIGNED_STORAGE_AJK_12FEB2016_HPP
  16
  17 namespace boost {
  18
  19 namespace optional_detail {
  20 // This local class is used instead of that in "aligned_storage.hpp"
  21 // because I've found the 'official' class to ICE BCB5.5
  22 // when some types are used with optional<>
  23 // (due to sizeof() passed down as a non-type template parameter)
  24 template <class T>
  25 class aligned_storage
  26 {
  27     // Borland ICEs if unnamed unions are used for this!
  28     union
  29     // This works around GCC warnings about breaking strict aliasing rules when casting storage address to T*
  30 #if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
  31     __attribute__((__may_alias__))
  32 #endif
  33     dummy_u
  34     {
  35         char data[ sizeof(T) ];
  36         BOOST_DEDUCED_TYPENAME type_with_alignment<
  37           ::boost::alignment_of<T>::value >::type aligner_;
  38     } dummy_ ;
  39
  40   public:
  41
  42 #if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
  43     void const* address() const { return &dummy_; }
  44     void      * address()       { return &dummy_; }
  45 #else
  46     void const* address() const { return dummy_.data; }
  47     void      * address()       { return dummy_.data; }
  48 #endif
  49
  50 #if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
  51         // This workaround is supposed to silence GCC warnings about broken strict aliasing rules
  52         T const* ptr_ref() const
  53         {
  54                 union { void const* ap_pvoid; T const* as_ptype; } caster = { address() };
  55                 return caster.as_ptype;
  56         }
  57         T *      ptr_ref()
  58         {
  59                 union { void* ap_pvoid; T* as_ptype; } caster = { address() };
  60                 return caster.as_ptype;
  61         }
  62 #else
  63         T const* ptr_ref() const { return static_cast<T const*>(address()); }
  64         T *      ptr_ref()       { return static_cast<T *>     (address()); }
  65 #endif
  66
  67         T const& ref() const { return *ptr_ref(); }
  68         T &      ref()       { return *ptr_ref(); }
  69
  70 } ;
  71
  72 } // namespace optional_detail
  73 } // namespace boost
  74
  75 #endif // header guard