extended fancy pointer support for iterators

doc/reference/multi_index_container.html

@@ -552,8 +552,11 @@ <h4><a name="instantiation_types">Instantiation types</a></h4>
         <code>p</code> shall dereference to <code>*p</code>.
       </li>
     </ul>
+    <code>multi_index_container</code>s and all their iterators do not store references
+    to allocated elements other than through the allocator's pointer type.
   </li>
 </ol>
+
 Indices of a given <code>multi_index_container</code> instantiation cannot have
 duplicate <a href="indices.html#tags">tags</a>, either within a single
 index or in two different indices.
@@ -1069,9 +1072,9 @@ <h4><a name="serialization">Serialization</a></h4>
 
 <br>
 
-<p>Revised October 25th 2025</p>
+<p>Revised June 27th 2026</p>
 
-<p>&copy; Copyright 2003-2025 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
+<p>&copy; Copyright 2003-2026 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
 Distributed under the Boost Software 
 License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
 LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">

doc/release_notes.html

@@ -78,6 +78,11 @@ <h2><a name="boost_1_92">Boost 1.92 release</a></h2>
 
 <p>
 <ul>
+  <li>Fancy pointer support has been extended so that <code>multi_index_container</code>
+    iterators now store references to the elements through the allocator's pointer type.
+    In particular, this means that iterators can now be placed in shared memory using
+    <a href="../../interprocess/index.html">Boost.Interprocess</a> allocators.
+  </li>
   <li>Fixed a performance issue with hashed indices when rehashing at very large
     container sizes (<a href="https://github.com/boostorg/multi_index/pull/94">PR#94</a>).
     Contributed by Daniel Kr&aacute;l.
@@ -858,7 +863,7 @@ <h2><a name="boost_1_33">Boost 1.33 release</a></h2>
 
 <br>
 
-<p>Revised April 24th 2026</p>
+<p>Revised June 27th 2026</p>
 
 <p>&copy; Copyright 2003-2026 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
 Distributed under the Boost Software 

doc/tutorial/creation.html

@@ -201,7 +201,7 @@ <h2><a name="special_allocator">Special allocator support</a></h2>
 An important type of non-standard allocators supported are those provided by the
 <a href="../../../interprocess/index.html">Boost Interprocess Library</a>;
 this opens up the possibility of placing <code>multi_index_container</code>s
-in shared memory.
+and their iterators in shared memory.
 </p>
 
 <blockquote><pre>
@@ -340,9 +340,9 @@ <h2><a name="serialization">Serialization</a></h2>
 
 <br>
 
-<p>Revised July 17th 2007</p>
+<p>Revised June 27th 2026</p>
 
-<p>&copy; Copyright 2003-2007 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
+<p>&copy; Copyright 2003-2026 Joaqu&iacute;n M L&oacute;pez Mu&ntilde;oz.
 Distributed under the Boost Software 
 License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt">
 LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">

include/boost/multi_index/detail/bidir_node_iterator.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2023 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -14,6 +14,7 @@
 #endif
 
 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
+#include <boost/multi_index/detail/raw_ptr.hpp>
 #include <boost/operators.hpp>
 
 #if !defined(BOOST_MULTI_INDEX_DISABLE_SERIALIZATION)
@@ -77,7 +78,7 @@ class bidir_node_iterator:
   template<class Archive>
   void save(Archive& ar,const unsigned int)const
   {
-    node_base_type* bnode=node;
+    node_base_type* bnode=get_node();
     ar<<core::make_nvp("pointer",bnode);
   }
 
@@ -86,18 +87,18 @@ class bidir_node_iterator:
   {
     node_base_type* bnode;
     ar>>core::make_nvp("pointer",bnode);
-    node=static_cast<Node*>(bnode);
+    node=typename Node::pointer(static_cast<Node*>(bnode));
   }
 #endif
 
   /* get_node is not to be used by the user */
 
   typedef Node node_type;
 
-  Node* get_node()const{return node;}
+  Node* get_node()const{return raw_ptr<Node*>(node);}
 
 private:
-  Node* node;
+  typename Node::pointer node;
 };
 
 template<typename Node>

include/boost/multi_index/detail/hash_index_iterator.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2023 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -14,6 +14,7 @@
 #endif
 
 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
+#include <boost/multi_index/detail/raw_ptr.hpp>
 #include <boost/operators.hpp>
 
 #if !defined(BOOST_MULTI_INDEX_DISABLE_SERIALIZATION)
@@ -76,7 +77,7 @@ class hashed_index_iterator:
   template<class Archive>
   void save(Archive& ar,const unsigned int)const
   {
-    node_base_type* bnode=node;
+    node_base_type* bnode=get_node();
     ar<<core::make_nvp("pointer",bnode);
   }
 
@@ -92,7 +93,7 @@ class hashed_index_iterator:
   {
     node_base_type* bnode;
     ar>>core::make_nvp("pointer",bnode);
-    node=static_cast<Node*>(bnode);
+    node=typename Node::pointer(static_cast<Node*>(bnode));
     if(version<1){
       BucketArray* throw_away; /* consume unused ptr */
       ar>>core::make_nvp("pointer",throw_away);
@@ -105,13 +106,13 @@ class hashed_index_iterator:
   {
     node_base_type* bnode;
     ar>>core::make_nvp("pointer",bnode);
-    node=static_cast<Node*>(bnode);
+    node=typename Node::pointer(static_cast<Node*>(bnode));
     if(version<1){
       BucketArray* buckets;
       ar>>core::make_nvp("pointer",buckets);
-      if(buckets&&node&&node->impl()==buckets->end()->prior()){
+      if(buckets&&bnode&&node->impl()==buckets->end()->prior()){
         /* end local_iterators used to point to end node, now they are null */
-        node=0;
+        node=typename Node::pointer(0);
       }
     }
   }
@@ -121,7 +122,7 @@ class hashed_index_iterator:
 
   typedef Node node_type;
 
-  Node* get_node()const{return node;}
+  Node* get_node()const{return raw_ptr<Node*>(node);}
 
 private:
 
@@ -135,7 +136,7 @@ class hashed_index_iterator:
     Node::template increment_local<IndexCategory>(node);
   }
 
-  Node* node;
+  typename Node::pointer node;
 };
 
 template<

include/boost/multi_index/detail/hash_index_node.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2025 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -712,6 +712,13 @@ struct hashed_index_node:
   typedef typename trampoline::pointer            impl_pointer;
   typedef typename trampoline::const_pointer      const_impl_pointer;
   typedef typename trampoline::difference_type    difference_type;
+  typedef allocator_rebind_t<
+    typename trampoline::impl_allocator_type,
+    hashed_index_node>                            final_allocator_type;
+  typedef allocator_pointer_t<
+    final_allocator_type>                         pointer;
+  typedef allocator_const_pointer_t<
+    final_allocator_type>                         const_pointer;
 
   template<typename Category>
   struct node_alg{
@@ -754,15 +761,15 @@ struct hashed_index_node:
   /* interoperability with hashed_index_iterator */
 
   template<typename Category>
-  static void increment(hashed_index_node*& x)
+  static void increment(pointer& x)
   {
-    x=from_impl(node_alg<Category>::type::after(x->impl()));
+    x=pointer(from_impl(node_alg<Category>::type::after(x->impl())));
   }
 
   template<typename Category>
-  static void increment_local(hashed_index_node*& x)
+  static void increment_local(pointer& x)
   {
-    x=from_impl(node_alg<Category>::type::after_local(x->impl()));
+    x=pointer(from_impl(node_alg<Category>::type::after_local(x->impl())));
   }
 };
 

include/boost/multi_index/detail/ord_index_node.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2025 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -131,6 +131,7 @@ struct ordered_index_node_compressed_base
 {
   typedef ordered_index_node_traits<
     AugmentPolicy,Allocator>                    node_traits;
+  typedef typename node_traits::allocator       node_allocator;
   typedef ordered_index_node_impl<
     AugmentPolicy,Allocator>*                   pointer;
   typedef const ordered_index_node_impl<
@@ -608,6 +609,14 @@ struct ordered_index_node:
   typedef typename trampoline::const_pointer   const_impl_pointer;
   typedef typename trampoline::difference_type difference_type;
   typedef typename trampoline::size_type       size_type;
+  typedef allocator_rebind_t<
+    typename trampoline::node_allocator,
+    ordered_index_node>                        final_allocator_type;
+  typedef allocator_pointer_t<
+    final_allocator_type>                      pointer;
+  typedef allocator_const_pointer_t<
+    final_allocator_type>                      const_pointer;
+
 
   impl_color_ref      color(){return trampoline::color();}
   ordered_index_color color()const{return trampoline::color();}
@@ -646,20 +655,24 @@ struct ordered_index_node:
           raw_ptr<const impl_type*>(x)));
   }
 
-  /* interoperability with bidir_node_iterator */
+  /* Interoperability with bidir_node_iterator and index impl.
+   * Templated for raw-pointer/non-raw-pointer versions.
+   */
 
-  static void increment(ordered_index_node*& x)
+  template<typename NodePtr>
+  static void increment(NodePtr& x)
   {
     impl_pointer xi=x->impl();
     trampoline::increment(xi);
-    x=from_impl(xi);
+    x=NodePtr(from_impl(xi));
   }
 
-  static void decrement(ordered_index_node*& x)
+  template<typename NodePtr>
+  static void decrement(NodePtr& x)
   {
     impl_pointer xi=x->impl();
     trampoline::decrement(xi);
-    x=from_impl(xi);
+    x=NodePtr(from_impl(xi));
   }
 };
 

include/boost/multi_index/detail/rnd_index_node.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2025 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -215,11 +215,18 @@ struct random_access_index_node:
   typedef random_access_index_node_trampoline<Super> trampoline;
 
 public:
-  typedef typename trampoline::impl_type         impl_type;
-  typedef typename trampoline::pointer           impl_pointer;
-  typedef typename trampoline::const_pointer     const_impl_pointer;
-  typedef typename trampoline::difference_type   difference_type;
-  typedef typename trampoline::ptr_pointer       impl_ptr_pointer;
+  typedef typename trampoline::impl_type       impl_type;
+  typedef typename trampoline::pointer         impl_pointer;
+  typedef typename trampoline::const_pointer   const_impl_pointer;
+  typedef typename trampoline::difference_type difference_type;
+  typedef typename trampoline::ptr_pointer     impl_ptr_pointer;
+  typedef allocator_rebind_t<
+    typename trampoline::node_allocator,
+    random_access_index_node>                  final_allocator_type;
+  typedef allocator_pointer_t<
+    final_allocator_type>                      pointer;
+  typedef allocator_const_pointer_t<
+    final_allocator_type>                      const_pointer;
 
   impl_ptr_pointer& up(){return trampoline::up();}
   impl_ptr_pointer  up()const{return trampoline::up();}
@@ -254,25 +261,25 @@ struct random_access_index_node:
 
   /* interoperability with rnd_node_iterator */
 
-  static void increment(random_access_index_node*& x)
+  static void increment(pointer& x)
   {
     impl_pointer xi=x->impl();
     trampoline::increment(xi);
-    x=from_impl(xi);
+    x=pointer(from_impl(xi));
   }
 
-  static void decrement(random_access_index_node*& x)
+  static void decrement(pointer& x)
   {
     impl_pointer xi=x->impl();
     trampoline::decrement(xi);
-    x=from_impl(xi);
+    x=pointer(from_impl(xi));
   }
 
-  static void advance(random_access_index_node*& x,difference_type n)
+  static void advance(pointer& x,difference_type n)
   {
     impl_pointer xi=x->impl();
     trampoline::advance(xi,n);
-    x=from_impl(xi);
+    x=pointer(from_impl(xi));
   }
 
   static difference_type distance(

include/boost/multi_index/detail/rnd_node_iterator.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2023 Joaquin M Lopez Munoz.
+/* Copyright 2003-2026 Joaquin M Lopez Munoz.
  * 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)
@@ -14,6 +14,7 @@
 #endif
 
 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
+#include <boost/multi_index/detail/raw_ptr.hpp>
 #include <boost/operators.hpp>
 
 #if !defined(BOOST_MULTI_INDEX_DISABLE_SERIALIZATION)
@@ -87,7 +88,7 @@ class rnd_node_iterator:
   template<class Archive>
   void save(Archive& ar,const unsigned int)const
   {
-    node_base_type* bnode=node;
+    node_base_type* bnode=get_node();
     ar<<core::make_nvp("pointer",bnode);
   }
 
@@ -96,18 +97,18 @@ class rnd_node_iterator:
   {
     node_base_type* bnode;
     ar>>core::make_nvp("pointer",bnode);
-    node=static_cast<Node*>(bnode);
+    node=typename Node::pointer(static_cast<Node*>(bnode));
   }
 #endif
 
   /* get_node is not to be used by the user */
 
   typedef Node node_type;
 
-  Node* get_node()const{return node;}
+  Node* get_node()const{return raw_ptr<Node*>(node);}
 
 private:
-  Node* node;
+  typename Node::pointer node;
 };
 
 template<typename Node>