Use BOOST_CORE_ALIGNOF in boost/core/max_align.hpp

doc/changes.qbk

@@ -18,6 +18,8 @@
 * Marked `boost::swap` function with `noexcept`, depending on whether the type supports a non-throwing swap operation.
 * Added `boost::core::launder`, a portable implementation of `std::launder`.
 * Added `BOOST_CORE_ALIGNOF`, a portable implementation of `alignof`.
+* Added `boost::core::max_align_t`, a portable equivalent of `std::max_align_t`, and `boost::core::max_align`, the
+  alignment of `max_align_t`.
 
 [endsect]
 

doc/core.qbk

@@ -58,6 +58,7 @@ criteria for inclusion is that the utility component be:
 [include is_same.qbk]
 [include launder.qbk]
 [include lightweight_test.qbk]
+[include max_align.qbk]
 [include no_exceptions_support.qbk]
 [include noinit_adaptor.qbk]
 [include noncopyable.qbk]

doc/max_align.qbk

@@ -0,0 +1,42 @@
+[/
+  Copyright 2023 Peter Dimov
+  Distributed under the Boost Software License, Version 1.0.
+  https://boost.org/LICENSE_1_0.txt
+]
+
+[section:max_align max_align]
+
+[simplesect Authors]
+
+* Peter Dimov
+
+[endsimplesect]
+
+[section Header <boost/core/max_align.hpp>]
+
+The header `<boost/core/max_align.hpp>` defines the type
+`boost::core::max_align_t`, a portable equivalent of
+`std::max_align_t`, and the constant `boost::core::max_align`,
+the alignment of `max_align_t`.
+
+[section Synopsis]
+
+``
+namespace boost
+{
+namespace core
+{
+
+union max_align_t;
+
+constexpr max_align = alignof(max_align_t);
+
+} // namespace core
+} // namespace boost
+``
+
+[endsect]
+
+[endsect]
+
+[endsect]

include/boost/core/alignof.hpp

@@ -1,5 +1,5 @@
-#ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED
-#define BOOST_CORE_MAX_ALIGN_HPP_INCLUDED
+#ifndef BOOST_CORE_ALIGNOF_HPP_INCLUDED
+#define BOOST_CORE_ALIGNOF_HPP_INCLUDED
 
 // MS compatible compilers support #pragma once
 
@@ -54,4 +54,4 @@ template<class T> struct alignof_helper
 
 #endif
 
-#endif  // #ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED
+#endif  // #ifndef BOOST_CORE_ALIGNOF_HPP_INCLUDED

include/boost/core/max_align.hpp

@@ -0,0 +1,82 @@
+#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/core/alignof.hpp>
+#include <boost/config.hpp>
+#include <cstddef>
+
+// BOOST_CORE_HAS_FLOAT128
+
+#if defined(BOOST_HAS_FLOAT128)
+
+# define BOOST_CORE_HAS_FLOAT128
+
+#elif defined(__SIZEOF_FLOAT128__)
+
+# define BOOST_CORE_HAS_FLOAT128
+
+#elif defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 404) && defined(__i386__)
+
+# define BOOST_CORE_HAS_FLOAT128
+
+#endif
+
+// max_align_t, max_align
+
+namespace boost
+{
+namespace core
+{
+
+union max_align_t
+{
+    char c;
+    short s;
+    int i;
+    long l;
+
+#if !defined(BOOST_NO_LONG_LONG)
+
+    boost::long_long_type ll;
+
+#endif
+
+#if defined(BOOST_HAS_INT128)
+
+    boost::int128_type i128;
+
+#endif
+
+    float f;
+    double d;
+    long double ld;
+
+#if defined(BOOST_CORE_HAS_FLOAT128)
+
+    __float128 f128;
+
+#endif
+
+    void* p;
+    void (*pf) ();
+
+    int max_align_t::* pm;
+    void (max_align_t::*pmf)();
+};
+
+BOOST_CONSTEXPR_OR_CONST std::size_t max_align = BOOST_CORE_ALIGNOF( max_align_t );
+
+} // namespace core
+} // namespace boost
+
+#endif  // #ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED

test/Jamfile.v2

@@ -355,6 +355,7 @@ run-fail verbose_terminate_handler_fail.cpp : : : <exception-handling>off <rtti>
 run launder_test.cpp ;
 
 run alignof_test.cpp ;
+run max_align_test.cpp ;
 
 use-project /boost/core/swap : ./swap ;
 build-project ./swap ;

test/max_align_test.cpp

@@ -0,0 +1,70 @@
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/core/max_align.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/type_traits.hpp>
+#include <boost/config.hpp>
+#include <cstddef>
+
+#if defined(BOOST_LIBSTDCXX_VERSION) && BOOST_LIBSTDCXX_VERSION < 40900
+# define BOOST_NO_STD_MAX_ALIGN_T
+#endif
+
+struct X
+{
+};
+
+int main()
+{
+    BOOST_TEST_EQ( boost::core::max_align, boost::alignment_of<boost::core::max_align_t>::value );
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<char>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<short>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<int>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<long>::value );
+
+#if !defined(BOOST_NO_LONG_LONG)
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<boost::long_long_type>::value );
+
+#endif
+
+#if defined(BOOST_HAS_INT128)
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<boost::int128_type>::value );
+
+#endif
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<float>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<double>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<long double>::value );
+
+#if defined(BOOST_CORE_HAS_FLOAT128)
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<__float128>::value );
+
+#endif
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<void*>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<void(*)()>::value );
+
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<int X::*>::value );
+    BOOST_TEST_GE( boost::core::max_align, boost::alignment_of<void (X::*)()>::value );
+
+#if !defined(BOOST_NO_CXX11_ALIGNOF) && !defined(BOOST_NO_STD_MAX_ALIGN_T)
+# if defined(BOOST_LIBSTDCXX_VERSION) && BOOST_LIBSTDCXX_VERSION < 70000
+
+    // libstdc++ 7 adds __float128 to std::max_align_t, but we always have it
+    BOOST_TEST_GE( boost::core::max_align, alignof( std::max_align_t ) );
+
+# else
+
+    BOOST_TEST_EQ( boost::core::max_align, alignof( std::max_align_t ) );
+
+# endif
+#endif
+
+    return boost::report_errors();
+}