STL extension: Add a template argument to Prevent_deref for the value…

… type (#7410)

## Summary of Changes

Fix issue #7400

## Release Management

* Affected package(s):  Triangulation_2, Triangulation_3, STL_extension
* Issue(s) solved (if any): fix #7400 

* License and copyright ownership: unchanged

Arrangement_on_surface_2/include/CGAL/Arrangement_on_surface_2.h

@@ -1043,7 +1043,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a range over handles of the arrangement vertices .
+  returns a range over handles of the arrangement vertices.
   */
   Iterator_range<Prevent_deref<Vertex_iterator> >
   vertex_handles()
@@ -1068,7 +1068,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a const range (model of `ConstRange`) over handles of the arrangement vertices .
+  returns a const range (model of `ConstRange`) over handles of the arrangement vertices.
   */
   Iterator_range<Prevent_deref<Vertex_const_iterator> >
   vertex_handles() const
@@ -1098,7 +1098,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a range over handles of the arrangement halfedges .
+  returns a range over handles of the arrangement halfedges.
   */
   Iterator_range<Prevent_deref<Halfedge_iterator> >
   halfedge_handles()
@@ -1122,7 +1122,7 @@ class Arrangement_on_surface_2 {
                                     _Is_valid_halfedge(&m_topol_traits)));
   }
   /*!
-  returns a const range (model of `ConstRange`) over handles of the arrangement halfedges .
+  returns a const range (model of `ConstRange`) over handles of the arrangement halfedges.
   */
   Iterator_range<Prevent_deref<Halfedge_const_iterator> >
   halfedge_handles() const
@@ -1149,7 +1149,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a range over handles of the arrangement edges .
+  returns a range over handles of the arrangement edges.
   */
   Iterator_range<Prevent_deref<Edge_iterator> >
   edge_handles()
@@ -1172,7 +1172,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a const range (model of `ConstRange`) over handles of the arrangement edges .
+  returns a const range (model of `ConstRange`) over handles of the arrangement edges.
   */
   Iterator_range<Prevent_deref<Edge_const_iterator> >
   edge_handles() const
@@ -1199,7 +1199,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a range over handles of the arrangement faces .
+  returns a range over handles of the arrangement faces.
   */
   Iterator_range<Prevent_deref<Face_iterator> >
   face_handles()
@@ -1221,7 +1221,7 @@ class Arrangement_on_surface_2 {
   }
 
   /*!
-  returns a const range (model of `ConstRange`) over handles of the arrangement faces .
+  returns a const range (model of `ConstRange`) over handles of the arrangement faces.
   */
   Iterator_range<Prevent_deref<Face_const_iterator> >
   face_handles() const

SMDS_3/include/CGAL/Mesh_complex_3_in_triangulation_3.h

@@ -444,8 +444,8 @@ class Mesh_complex_3_in_triangulation_3
    */
   void remove_from_complex(const Vertex_handle& v)
   {
-    corners_.erase(v);
     v->set_dimension(-1);
+    corners_.erase(v);
   }
 
   /** sets the index of vertex \p vertex to \p index
@@ -983,7 +983,7 @@ class Mesh_complex_3_in_triangulation_3
     pointer operator->() const { return *(this->base()); }
     reference operator*() const { return **(this->base()); }
 
-    operator Vertex_handle() { return Vertex_handle(*(this->base())); }
+    operator const Vertex_handle&() const { return *(this->base()); }
   };
 
 public:
@@ -1048,13 +1048,13 @@ class Mesh_complex_3_in_triangulation_3
     Self operator++(int) { Self tmp(*this); ++(*this); return tmp; }
     Self operator--(int) { Self tmp(*this); --(*this); return tmp; }
 
-    operator Cell_handle() const { return Cell_handle(this->base()); }
+    operator const Cell_handle&() const { return this->base(); }
   }; // end class Cells_in_complex_iterator
 
-  typedef Iterator_range<Prevent_deref<Vertices_in_complex_iterator> > Vertices_in_complex;
-  typedef Iterator_range<Edges_in_complex_iterator>                    Edges_in_complex;
-  typedef Iterator_range<Facets_in_complex_iterator>                   Facets_in_complex;
-  typedef Iterator_range<Prevent_deref<Cells_in_complex_iterator> >    Cells_in_complex;
+  typedef Iterator_range<Prevent_deref<Vertices_in_complex_iterator, const Vertex_handle&>> Vertices_in_complex;
+  typedef Iterator_range<Edges_in_complex_iterator> Edges_in_complex;
+  typedef Iterator_range<Facets_in_complex_iterator> Facets_in_complex;
+  typedef Iterator_range<Prevent_deref<Cells_in_complex_iterator, const Cell_handle&>> Cells_in_complex;
 
 #endif
 
@@ -1162,8 +1162,7 @@ class Mesh_complex_3_in_triangulation_3
   */
   Vertices_in_complex vertices_in_complex() const
   {
-    return make_prevent_deref_range(vertices_in_complex_begin(),
-                                    vertices_in_complex_end());
+      return { vertices_in_complex_begin(), vertices_in_complex_end() };
   }
   /*!
     returns a range of iterators over the edges of the 1D complex,
@@ -1193,8 +1192,7 @@ class Mesh_complex_3_in_triangulation_3
   */
   Cells_in_complex cells_in_complex() const
   {
-    return make_prevent_deref_range(cells_in_complex_begin(),
-                                    cells_in_complex_end());
+    return { cells_in_complex_begin(), cells_in_complex_end() };
   }
 ///  @}
 

SMDS_3/test/SMDS_3/test_c3t3.cpp

@@ -49,6 +49,9 @@ struct Tester
   typedef typename C3t3::Facets_in_complex_iterator Facet_iterator;
   typedef typename C3t3::Vertex_handle Vertex_handle;
 
+  typedef typename C3t3::Vertices_in_complex Vertices_in_complex;
+  typedef typename C3t3::Cells_in_complex Cells_in_complex;
+
   typedef typename C3t3::Subdomain_index Subdomain_index;
   typedef typename C3t3::Surface_patch_index Surface_patch_index;
   typedef typename C3t3::Index Index;
@@ -120,6 +123,15 @@ struct Tester
     assert(c3t3.is_in_complex(ch));
     assert(c3t3.subdomain_index(ch) == subdomain_index);
 
+    // Test iterator range
+    {
+      Cell_handle ch = *c3t3.cells_in_complex().begin();
+      for (auto c : c3t3.cells_in_complex()) {
+        assert(c == ch);
+        break;
+      }
+    }
+
     //-------------------------------------------------------
     // Test move construction
     //-------------------------------------------------------

SMDS_3/test/SMDS_3/test_c3t3_with_features.cpp

@@ -218,6 +218,18 @@ struct Tester
            || ( v == vp4 && tr.point(vit) == p4 ) );
 
     assert ( tv1.in_dimension() == tv2.in_dimension() );
+
+
+    // Test iterator range
+    {
+      Vertex_handle vh =  *c3t3.vertices_in_complex().begin();
+      for (auto v : c3t3.vertices_in_complex()) {
+        assert(v == vh);
+        break;
+      }
+    }
+
+
     //-------------------------------------------------------
     // Check adjacencies
     //-------------------------------------------------------
@@ -335,8 +347,13 @@ struct Tester
     //-------------------------------------------------------
     std::cout << "Test vertex iterators\n";
     const Vertex_handle& vertex_to_modify = c3t3.vertices_in_complex_begin();
+    Vertex_handle vertex_to_modify_copy = vertex_to_modify;
+
     c3t3.remove_from_complex(vertex_to_modify);
-    c3t3.add_to_complex(vertex_to_modify,corner_index_bis);
+    // now `vertex_to_modify` is a dangling ref to a `Vertex_handle`
+
+    // use a copy of it: `vertex_to_modify_copy`
+    c3t3.add_to_complex(vertex_to_modify_copy,corner_index_bis);
 
     typename C3t3::Vertices_in_complex_iterator corner_vit =
       c3t3.vertices_in_complex_begin(corner_index);

STL_Extension/include/CGAL/iterator.h

@@ -25,6 +25,7 @@
 #include <CGAL/circulator.h>
 #include <CGAL/Iterator_range.h>
 #include <CGAL/tuple.h>
+#include <CGAL/type_traits.h>
 #include <CGAL/use.h>
 
 #include <variant>
@@ -37,28 +38,34 @@
 
 namespace CGAL {
 
-template<typename I>
+template<typename I, typename Reference_type = const I&>
 class Prevent_deref
   : public boost::iterator_adaptor<
-  Prevent_deref<I>
+    Prevent_deref<I, Reference_type>
   , I // base
-  , I // value
+  , CGAL::cpp20::remove_cvref_t<Reference_type> // value
+  , boost::use_default // category
+  , Reference_type // ref
   >
 {
 public:
-  typedef boost::iterator_adaptor<
-  Prevent_deref<I>
+  using Value_type = CGAL::cpp20::remove_cvref_t<Reference_type>;
+  using Base = boost::iterator_adaptor<
+    Prevent_deref<I, Reference_type>
   , I // base
-  , I // value
-  > Base;
-  typedef typename Base::reference reference;
+  , Value_type // value
+  , boost::use_default // category
+  , Reference_type // ref
+  >;
   typedef typename std::pair<I, I> range;
 
-  Prevent_deref() : Base() {}
+  Prevent_deref() = default;
   Prevent_deref(const I& i) : Base(i) {}
 private:
   friend class boost::iterator_core_access;
-  reference dereference() const { return const_cast<std::remove_reference_t<reference>&>(this->base_reference()); }
+  Reference_type dereference() const {
+    return this->base_reference();
+  }
 };
 
 template<typename I>
@@ -608,7 +615,7 @@ struct Filter_iterator {
   reference operator*() const { return *c_;  }
   pointer operator->() const  { return &*c_; }
   const Predicate& predicate() const { return p_; }
-  Iterator base() const { return c_; }
+  const Iterator& base() const { return c_; }
 
   Iterator end() const { return e_; }
   bool is_end() const { return (c_ == e_); }

STL_Extension/test/STL_Extension/CMakeLists.txt

@@ -12,6 +12,7 @@ if(NOT TARGET CGAL::TBB_support)
   message(STATUS "NOTICE: Tests are not using TBB.")
 endif()
 
+create_single_source_cgal_program("issue_7400.cpp")
 create_single_source_cgal_program("test_Boolean_tag.cpp")
 create_single_source_cgal_program("test_Cache.cpp")
 create_single_source_cgal_program("test_Compact_container.cpp")

STL_Extension/test/STL_Extension/issue_7400.cpp

@@ -0,0 +1,54 @@
+#include <type_traits>
+#include <iterator>
+#include <CGAL/type_traits.h>
+
+// Add C++20 utilities to C++14
+template <class Iterator>
+using iter_value_t = std::remove_reference_t<decltype(*std::declval<Iterator>())>;
+
+template<class Range>
+using range_value_t = iter_value_t<CGAL::cpp20::remove_cvref_t<decltype(std::begin(std::declval<Range>()))>>;
+
+template< class T, class U >
+constexpr bool is_same_v = std::is_same<T, U>::value;
+
+template< class T, class U >
+constexpr bool is_convertible_v = std::is_convertible<T, U>::value;
+
+
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Triangulation_3.h>
+
+using Triangulation = CGAL::Triangulation_3<CGAL::Exact_predicates_inexact_constructions_kernel>;
+
+using Vertex_handle =  Triangulation::Vertex_handle;
+
+Triangulation t;
+
+// Tds::vertex_handles() -> Vertex_handle
+static_assert(is_same_v<range_value_t<decltype(t.tds().vertex_handles())>, const Vertex_handle>);
+
+// Triangulation::all_vertex_handles() -> Vertex_handle
+static_assert(is_same_v<range_value_t<decltype(t.all_vertex_handles())>, const Vertex_handle>);
+
+// Triangulation::finite_vertex_handles() -> convertible to Vertex_handle
+static_assert(is_convertible_v<decltype(*std::begin(t.finite_vertex_handles())), Vertex_handle>);
+
+// But is it equal to Vertex_handle
+static_assert(is_same_v<range_value_t<decltype(t.finite_vertex_handles())>, const Vertex_handle>);
+
+int main()
+{
+  Vertex_handle v_inf = t.infinite_vertex();
+  for(auto v: t.finite_vertex_handles()) {
+    Vertex_handle v2 = v;
+    CGAL_USE(v2);
+    if(v == v_inf) return 1;
+  }
+  for (auto v : t.all_vertex_handles()) {
+      Vertex_handle v2 = v;
+      CGAL_USE(v2);
+      if (v == v_inf) std::cout << "found inf" << std::endl;
+  }
+  return 0;
+}

Stream_support/include/CGAL/IO/PLY/PLY_reader.h

@@ -17,7 +17,7 @@
 #include <CGAL/Kernel_traits.h>
 #include <CGAL/property_map.h>
 
-#include <boost/cstdint.hpp>
+#include <cstdint>
 #include <boost/range/value_type.hpp>
 
 #include <iostream>

TDS_2/include/CGAL/Triangulation_data_structure_2.h

@@ -183,7 +183,7 @@ class Triangulation_data_structure_2
   }
 
   Face_handles face_handles() const {
-    return make_prevent_deref_range(faces_begin(),faces_end());
+    return { faces_begin(), faces_end() };
   }
 
   Vertex_iterator vertices_begin() const  {
@@ -195,7 +195,7 @@ class Triangulation_data_structure_2
   }
 
   Vertex_handles vertex_handles() const {
-    return make_prevent_deref_range(vertices_begin(),vertices_end());
+    return { vertices_begin(), vertices_end() };
   }
 
   Edge_iterator edges_begin() const {

TDS_3/include/CGAL/Triangulation_data_structure_3.h

@@ -661,7 +661,7 @@ class Triangulation_data_structure_3
 
   Cell_handles cell_handles() const
   {
-    return make_prevent_deref_range(cells_begin(), cells_end());
+    return { cells_begin(), cells_end() };
   }
 
   Cell_iterator raw_cells_begin() const
@@ -720,7 +720,7 @@ class Triangulation_data_structure_3
 
   Vertex_handles vertex_handles() const
   {
-    return make_prevent_deref_range(vertices_begin(), vertices_end());
+    return { vertices_begin(), vertices_end() };
   }
 
   // CIRCULATOR METHODS