Add move support to BOOST_STRONG_TYPEDEF

doc/strong_typedef.html

@@ -70,17 +70,25 @@ <h3>Usage</h3>
 <code style="white-space: normal">typedef</code>.  So
 
 <pre><code>
-BOOST_STRONG_TYPEDEF(primitive type, name)
+BOOST_STRONG_TYPEDEF(type, name)
 </code></pre>
 
 will create a new type "name" which will be substitutable for the original
 type but still of distinct type.
+<p>
+The wrapped type need not be a primitive one.  It has to be default
+constructible, copyable and assignable, and to provide
+<code style="white-space: normal">==</code> and
+<code style="white-space: normal">&lt;</code>, from which the remaining
+comparisons are generated.
 
 <h3>Implemenation</h3>
 <code style="white-space: normal">BOOST_STRONG_TYPEDEF</code> is a macro
-which generates a class named "name" which wraps an instance of its
-primitive type and provides appropriate conversion operators in order
-to make the new type substitutable for the one that it wraps.
+which generates a class named "name" which wraps an instance of the
+type and provides appropriate conversion operators in order
+to make the new type substitutable for the one that it wraps.  The
+generated class copies and moves as the wrapped type does, so wrapping a
+type which is cheaper to move than to copy costs nothing.
 
 <hr>
 <p><i>&copy; Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004. 

include/boost/serialization/strong_typedef.hpp

@@ -28,6 +28,10 @@
 #include <boost/type_traits/has_nothrow_assign.hpp>
 #include <boost/type_traits/has_nothrow_constructor.hpp>
 #include <boost/type_traits/has_nothrow_copy.hpp>
+#include <boost/type_traits/is_nothrow_move_assignable.hpp>
+#include <boost/type_traits/is_nothrow_move_constructible.hpp>
+
+#include <utility>
 
 #define BOOST_STRONG_TYPEDEF(T, D)                                                                               \
 struct D                                                                                                         \
@@ -39,7 +43,10 @@ struct D
     explicit D(const T& t_) BOOST_NOEXCEPT_IF(boost::has_nothrow_copy_constructor<T>::value) : t(t_) {}          \
     D() BOOST_NOEXCEPT_IF(boost::has_nothrow_default_constructor<T>::value) : t() {}                             \
     D(const D & t_) BOOST_NOEXCEPT_IF(boost::has_nothrow_copy_constructor<T>::value) : t(t_.t) {}                \
+    D(D && t_) BOOST_NOEXCEPT_IF(boost::is_nothrow_move_constructible<T>::value) : t(std::move(t_.t)) {}         \
     D& operator=(const D& rhs) BOOST_NOEXCEPT_IF(boost::has_nothrow_assign<T>::value) {t = rhs.t; return *this;} \
+    D& operator=(D&& rhs) BOOST_NOEXCEPT_IF(boost::is_nothrow_move_assignable<T>::value)                         \
+        {t = std::move(rhs.t); return *this;}                                                                    \
     D& operator=(const T& rhs) BOOST_NOEXCEPT_IF(boost::has_nothrow_assign<T>::value) {t = rhs; return *this;}   \
     operator const T&() const {return t;}                                                                        \
     operator T&() {return t;}                                                                                    \

test/Jamfile.v2

@@ -159,6 +159,7 @@ if ! $(BOOST_ARCHIVE_LIST) {
         # [ test-bsl-run test_dll_plugin : : dll_derived2 : <link>static:<build>no <target-os>linux:<linkflags>-ldl ]
 
         [ test-bsl-run test_duplicate_type_registration ]
+        [ test-bsl-run test_strong_typedef_move ]
         [ test-bsl-run test_private_ctor ]
         [ test-bsl-run test_reset_object_address : A ]
         [ test-bsl-run test_void_cast ]

test/test_strong_typedef_move.cpp

@@ -0,0 +1,123 @@
+/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
+// test_strong_typedef_move.cpp
+
+// Copyright 2026 Gennaro Prota.
+// Distributed under 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 for updates, documentation, and revision history.
+
+// Declaring a copy constructor and a copy assignment operator stops the
+// compiler from declaring the move ones, so a strong typedef used to copy
+// the value it wraps where a move was asked for.  That was silent: the code
+// compiled and gave the right answer, only slowly, which is why it wants a
+// test that counts the operations rather than one that merely compiles.
+
+// Reported by bweed-mathworks in
+// https://github.com/boostorg/serialization/issues/341, with the two members
+// to add.  Thanks!
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/serialization/strong_typedef.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/type_traits/is_nothrow_move_assignable.hpp>
+#include <boost/type_traits/is_nothrow_move_constructible.hpp>
+
+#include <utility>
+
+// Says which of the two happened to it.  The counters are global so that a
+// check reads as "this many moves, no copies" without having to reason
+// about which object ended up holding the tally.
+struct counted {
+    static int copies;
+    static int moves;
+    counted(){}
+    counted(const counted &){
+        ++copies;
+    }
+    counted(counted &&){
+        ++moves;
+    }
+    counted & operator=(const counted &){
+        ++copies;
+        return *this;
+    }
+    counted & operator=(counted &&){
+        ++moves;
+        return *this;
+    }
+    bool operator==(const counted &) const {
+        return true;
+    }
+    bool operator<(const counted &) const {
+        return false;
+    }
+};
+
+int counted::copies = 0;
+int counted::moves = 0;
+
+BOOST_STRONG_TYPEDEF(counted, strong_counted)
+BOOST_STRONG_TYPEDEF(int, strong_int)
+
+static void reset(){
+    counted::copies = 0;
+    counted::moves = 0;
+}
+
+// A strong typedef of a type which can throw must not claim it cannot, and
+// one of a type which cannot must not throw away the guarantee.
+BOOST_STATIC_ASSERT(boost::is_nothrow_move_constructible<strong_int>::value);
+BOOST_STATIC_ASSERT(boost::is_nothrow_move_assignable<strong_int>::value);
+BOOST_STATIC_ASSERT(! boost::is_nothrow_move_constructible<strong_counted>::value);
+BOOST_STATIC_ASSERT(! boost::is_nothrow_move_assignable<strong_counted>::value);
+
+static void test_move_construction(){
+    reset();
+    strong_counted a;
+    strong_counted b(std::move(a));
+    (void) b;
+    BOOST_TEST_EQ(counted::moves, 1);
+    BOOST_TEST_EQ(counted::copies, 0);
+}
+
+static void test_move_assignment(){
+    reset();
+    strong_counted a;
+    strong_counted b;
+    b = std::move(a);
+    BOOST_TEST_EQ(counted::moves, 1);
+    BOOST_TEST_EQ(counted::copies, 0);
+}
+
+// Copying has to go on working, and go on being a copy.
+static void test_copy_still_copies(){
+    reset();
+    strong_counted a;
+    strong_counted b(a);
+    strong_counted c;
+    c = a;
+    BOOST_TEST_EQ(counted::copies, 2);
+    BOOST_TEST_EQ(counted::moves, 0);
+}
+
+// The value has to survive the move, not merely be moved.
+static void test_value_is_carried(){
+    strong_int a(42);
+    strong_int b(std::move(a));
+    BOOST_TEST_EQ(b.t, 42);
+
+    strong_int c;
+    c = std::move(b);
+    BOOST_TEST_EQ(c.t, 42);
+}
+
+int
+main(){
+    test_move_construction();
+    test_move_assignment();
+    test_copy_still_copies();
+    test_value_is_carried();
+    return boost::report_errors();
+}