Add BOOST_HAS_BUILTIN_LAUNDER

doc/html/boost_config/boost_macro_reference.html

@@ -1576,6 +1576,26 @@ <h5>
                 </p>
               </td>
 </tr>
+<tr>
+    <td>
+        <p>
+            <code class="computeroutput"><span class="identifier">BOOST_HAS_BUILTIN_LAUNDER</span></code>
+        </p>
+    </td>
+    <td>
+        <p>
+            Compiler
+        </p>
+    </td>
+    <td>
+        <p>
+            The compiler implements the <code class="computeroutput">
+            <span class="identifier">__builtin_launder()</span></code>
+            compiler intrinsic that is needed to implement a constexpr
+            pointer laundering function like <code class="computeroutput">std::launder</code>.
+        </p>
+    </td>
+</tr>
 <tr>
 <td>
                 <p>

doc/macro_reference.qbk

@@ -405,6 +405,10 @@ standard. The macro is only defined if the feature is present.
 [[`BOOST_HAS_BETHREADS`][Platform][
 The platform supports BeOS style threads.
 ]]
+[[`BOOST_HAS_BUILTIN_LAUNDER`][Compiler][
+The compiler implements the `__builtin_launder()` compiler intrinsic that is needed
+to implement a constexpr pointer laundering function like `std::launder`.
+]]
 [[`BOOST_HAS_CLOCK_GETTIME`][Platform][
 The platform has the POSIX API `clock_gettime`.
 ]]

include/boost/config/compiler/gcc.hpp

@@ -353,6 +353,11 @@
 #define BOOST_DEPRECATED(msg) __attribute__((deprecated))
 #endif
 
+// __builtin_launder intrinsic
+#if BOOST_GCC_VERSION >= 70000
+#  define BOOST_HAS_BUILTIN_LAUNDER
+#endif
+
 #ifndef BOOST_COMPILER
 #  define BOOST_COMPILER "GNU C++ version " __VERSION__
 #endif

include/boost/config/compiler/visualc.hpp

@@ -115,6 +115,12 @@
 #define BOOST_DEPRECATED(msg) __declspec(deprecated)
 #endif
 
+// __builtin_launder intrinsic
+//The intrinsic is only available in C++17 or later mode
+#if (_MSC_VER >= 1910) && defined(_MSVC_LANG) && (_MSVC_LANG > 201402L)
+# define BOOST_HAS_BUILTIN_LAUNDER
+#endif
+
 //
 // TR1 features:
 //

include/boost/config/detail/suffix.hpp

@@ -1276,6 +1276,13 @@ namespace std{ using ::type_info; }
 #  define BOOST_NO_CXX17_DEDUCTION_GUIDES
 #endif
 
+// Generic __builtin_launder intrinsic in case it's not detected by the compiler file
+#if !defined(BOOST_HAS_BUILTIN_LAUNDER) && defined(__has_builtin)
+#  if __has_builtin(__builtin_launder)
+#    define BOOST_HAS_BUILTIN_LAUNDER
+#  endif
+#endif
+
 //
 // Define composite agregate macros:
 //

test/all/Jamfile.v2

@@ -28,6 +28,9 @@ test-suite "BOOST_HAS_TWO_ARG_USE_FACET" :
 test-suite "BOOST_HAS_BETHREADS" : 
 [ run ../has_bethreads_pass.cpp ]
 [ compile-fail ../has_bethreads_fail.cpp ] ;
+test-suite "BOOST_HAS_BUILTIN_LAUNDER" : 
+[ run ../has_builtin_launder_pass.cpp ]
+[ compile-fail ../has_builtin_launder_fail.cpp ] ;
 test-suite "BOOST_HAS_CLOCK_GETTIME" : 
 [ run ../has_clock_gettime_pass.cpp ]
 [ compile-fail ../has_clock_gettime_fail.cpp ] ;

test/boost_has_builtin_launder.ipp

@@ -0,0 +1,29 @@
+//  (C) Copyright Ion Gaztanaga 2022.
+//  Use, modification and distribution are subject to the 
+//  Boost Software License, Version 1.0. (See accompanying file 
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See http://www.boost.org/libs/config for most recent version.
+
+//  MACRO:         BOOST_HAS_BUILTIN_LAUNDER
+//  TITLE:         __builtin_launder
+//  DESCRIPTION:   The platform supports __builtin_launder.
+
+#include <new>
+
+namespace boost_has_builtin_launder {
+
+struct X
+{
+    const int const_int;
+};
+
+int test()
+{
+    X original{1};
+    new (&original) X{2}; //Overwrite X
+    return __builtin_launder(&original)->const_int == 2 ? 0 : -1; //After laundering, new value should be returned
+}
+
+}  //namespace boost_has_builtin_launder {
+

test/has_builtin_launder_fail.cpp

@@ -0,0 +1,32 @@
+//  This file was automatically generated on Fri Dec 03 18:03:59 2004
+//  by libs/config/tools/generate.cpp
+//  Copyright Ion Gaztanaga 2022.
+//  Use, modification and distribution are subject to the 
+//  Boost Software License, Version 1.0. (See accompanying file 
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See http://www.boost.org/libs/config for the most recent version.
+
+// Test file for macro BOOST_HAS_BUILTIN_LAUNDER
+// This file should not compile, if it does then
+// BOOST_HAS_BUILTIN_LAUNDER should be defined.
+// See file boost_has_builtin_launder.ipp for details
+
+// Must not have BOOST_ASSERT_CONFIG set; it defeats
+// the objective of this file:
+#ifdef BOOST_ASSERT_CONFIG
+#  undef BOOST_ASSERT_CONFIG
+#endif
+
+#include <boost/config.hpp>
+
+#ifndef BOOST_HAS_BUILTIN_LAUNDER
+#include "boost_has_builtin_launder.ipp"
+#else
+#error "this file should not compile"
+#endif
+
+int main( int, char *[] )
+{
+   return boost_has_builtin_launder::test();
+}

test/has_builtin_launder_pass.cpp

@@ -0,0 +1,34 @@
+//  This file was automatically generated on Fri Dec 03 18:03:59 2004
+//  by libs/config/tools/generate.cpp
+//  Copyright Ion Gaztanaga 2022.
+//  Use, modification and distribution are subject to the 
+//  Boost Software License, Version 1.0. (See accompanying file 
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+//  See http://www.boost.org/libs/config for the most recent version.
+
+// Test file for macro BOOST_HAS_BUILTIN_LAUNDER
+// This file should compile, if it does not then
+// BOOST_HAS_BUILTIN_LAUNDER should not be defined.
+// See file boost_has_builtin_launder.ipp for details
+
+// Must not have BOOST_ASSERT_CONFIG set; it defeats
+// the objective of this file:
+#ifdef BOOST_ASSERT_CONFIG
+#  undef BOOST_ASSERT_CONFIG
+#endif
+
+#include <boost/config.hpp>
+#include "test.hpp"
+
+#ifdef BOOST_HAS_BUILTIN_LAUNDER
+#include "boost_has_builtin_launder.ipp"
+#else
+namespace boost_has_builtin_launder = empty_boost;
+#endif
+
+int main( int, char *[] )
+{
+   return boost_has_builtin_launder::test();
+}
+