Add BOOST_CORE_ALIGNOF

include/boost/core/alignof.hpp

@@ -0,0 +1,57 @@
+#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>
+
+#if !defined(BOOST_NO_CXX11_ALIGNOF)
+
+#define BOOST_CORE_ALIGNOF alignof
+
+#elif defined(__GNUC__)
+
+#define BOOST_CORE_ALIGNOF __alignof__
+
+#elif defined(_MSC_VER)
+
+#define BOOST_CORE_ALIGNOF __alignof
+
+#else
+
+namespace boost
+{
+namespace core
+{
+namespace detail
+{
+
+template<class T> struct alignof_helper
+{
+    char x;
+    T t;
+};
+
+} // namespace detail
+} // namespace core
+} // namespace boost
+
+#if defined(__GNUC__)
+// ignoring -Wvariadic-macros with #pragma doesn't work under GCC
+# pragma GCC system_header
+#endif
+
+#define BOOST_CORE_ALIGNOF(...) offsetof( ::boost::core::detail::alignof_helper<__VA_ARGS__>, t );
+
+#endif
+
+#endif  // #ifndef BOOST_CORE_MAX_ALIGN_HPP_INCLUDED

test/Jamfile.v2

@@ -354,5 +354,7 @@ run-fail verbose_terminate_handler_fail.cpp : : : <exception-handling>off <rtti>
 
 run launder_test.cpp ;
 
+run alignof_test.cpp ;
+
 use-project /boost/core/swap : ./swap ;
 build-project ./swap ;

test/alignof_test.cpp

@@ -0,0 +1,88 @@
+// 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/core/lightweight_test.hpp>
+#include <boost/type_traits.hpp>
+#include <boost/config.hpp>
+#include <cstddef>
+
+template<class T> struct struct_of
+{
+    T t;
+};
+
+template<class T> union union_of
+{
+    T t;
+};
+
+template<class T> void test2()
+{
+    BOOST_TEST_EQ( BOOST_CORE_ALIGNOF(T), boost::alignment_of<T>::value );
+
+#if !defined(BOOST_NO_CXX11_ALIGNOF)
+
+    BOOST_TEST_EQ( BOOST_CORE_ALIGNOF(T), alignof(T) );
+
+#endif
+}
+
+template<class T> void test()
+{
+    test2<T>();
+    test2<T[2]>();
+    test2< struct_of<T> >();
+    test2< union_of<T> >();
+}
+
+struct X
+{
+};
+
+int main()
+{
+    test<char>();
+    test<short>();
+    test<int>();
+    test<long>();
+
+#if !defined(BOOST_NO_LONG_LONG)
+
+    test<boost::long_long_type>();
+
+#endif
+
+#if defined(BOOST_HAS_INT128)
+
+    test<boost::int128_type>();
+
+#endif
+
+    test<float>();
+    test<double>();
+    test<long double>();
+
+#if defined(BOOST_HAS_FLOAT128)
+
+    test<__float128>();
+
+#endif
+
+    test<void*>();
+    test<void(*)()>();
+
+#if !defined(_MSC_VER)
+
+    // under MSVC, alignof is 8, boost::alignment_of is 4
+    // under clang-cl, alignof is 4, boost::alignment_of is 8 (!)
+
+    test<int X::*>();
+
+#endif
+
+    test<void (X::*)()>();
+
+    return boost::report_errors();
+}