Add boost::core::max_align(_t)

include/boost/core/max_align.hpp

@@ -0,0 +1,84 @@
+#ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED
+#define BOOST_CORE_MAX_ALIGN_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//  Copyright 2023 Peter Dimov
+//  Distributed under the Boost Software License, Version 1.0.
+//  https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/config.hpp>
+#include <cstddef>
+
+namespace boost
+{
+namespace core
+{
+
+union max_align_t
+{
+    char c;
+    short s;
+    int i;
+    long l;
+
+#ifndef BOOST_NO_LONG_LONG
+    boost::long_long_type ll;
+#endif
+
+#ifdef BOOST_HAS_INT128
+    boost::int128_type i128;
+#endif
+
+    float f;
+    double d;
+    long double ld;
+
+#ifdef BOOST_HAS_FLOAT128
+    __float128 f128;
+#endif
+
+    void* p;
+    void (*pf) ();
+
+    int max_align_t::* pm;
+    void (max_align_t::*pmf)();
+};
+
+#if !defined(BOOST_NO_CXX11_ALIGNOF)
+
+BOOST_CONSTEXPR_OR_CONST std::size_t max_align = alignof( max_align_t );
+
+#elif defined(__GNUC__)
+
+BOOST_CONSTEXPR_OR_CONST std::size_t max_align = __alignof__( max_align_t );
+
+#elif defined(_MSC_VER)
+
+BOOST_CONSTEXPR_OR_CONST std::size_t max_align = __alignof( max_align_t );
+
+#else
+
+namespace detail
+{
+
+struct alignment_of_helper
+{
+    char x;
+    max_align_t a;
+};
+
+} // namespace detail
+
+BOOST_CONSTEXPR_OR_CONST std::size_t max_align = offsetof( core::detail::alignment_of_helper, a );
+
+#endif
+
+} // namespace core
+} // namespace boost
+
+#endif  // #ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED