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) 2020 Andrey Semashev
7  */
8 /*!
9  * \file   atomic/detail/aligned_variable.hpp
10  *
11  * This header defines a convenience macro for declaring aligned variables
12  */
13 
14 #ifndef BOOST_ATOMIC_DETAIL_ALIGNED_VARIABLE_HPP_INCLUDED_
15 #define BOOST_ATOMIC_DETAIL_ALIGNED_VARIABLE_HPP_INCLUDED_
16 
17 #include <boost/atomic/detail/config.hpp>
18 #if defined(BOOST_ATOMIC_DETAIL_NO_CXX11_ALIGNAS)
19 #include <boost/config/helper_macros.hpp>
20 #include <boost/type_traits/type_with_alignment.hpp>
21 #endif
22 #include <boost/atomic/detail/header.hpp>
23 
24 #ifdef BOOST_HAS_PRAGMA_ONCE
25 #pragma once
26 #endif
27 
28 #if !defined(BOOST_ATOMIC_DETAIL_NO_CXX11_ALIGNAS)
29 
30 #define BOOST_ATOMIC_DETAIL_ALIGNED_VAR(var_alignment, var_type, var_name) \
31     alignas(var_alignment) var_type var_name
32 
33 #define BOOST_ATOMIC_DETAIL_ALIGNED_VAR_TPL(var_alignment, var_type, var_name) \
34     alignas(var_alignment) var_type var_name
35 
36 #else // !defined(BOOST_ATOMIC_DETAIL_NO_CXX11_ALIGNAS)
37 
38 // Note: Some compilers cannot use constant expressions in alignment attributes or alignas, so we have to use the union trick
39 #define BOOST_ATOMIC_DETAIL_ALIGNED_VAR(var_alignment, var_type, var_name) \
40     union \
41     { \
42         var_type var_name; \
43         boost::type_with_alignment< var_alignment >::type BOOST_JOIN(var_name, _aligner); \
44     }
45 
46 #define BOOST_ATOMIC_DETAIL_ALIGNED_VAR_TPL(var_alignment, var_type, var_name) \
47     union \
48     { \
49         var_type var_name; \
50         typename boost::type_with_alignment< var_alignment >::type BOOST_JOIN(var_name, _aligner); \
51     }
52 
53 #endif // !defined(BOOST_ATOMIC_DETAIL_NO_CXX11_ALIGNAS)
54 
55 #include <boost/atomic/detail/footer.hpp>
56 
57 #endif // BOOST_ATOMIC_DETAIL_ALIGNED_VARIABLE_HPP_INCLUDED_
58