remove CGAL_CXX17 macro

... and no longer used macros

Combinatorial_map/include/CGAL/Combinatorial_map_storages.h

@@ -467,16 +467,6 @@ namespace CGAL {
     typename Helper::Attribute_containers mattribute_containers;
   };
 
-#ifndef CGAL_CXX17
-  template<unsigned int d_, class Items_, class Alloc_>
-  constexpr typename Combinatorial_map_storage_1<d_, Items_, Alloc_>::Null_descriptor_type
-  Combinatorial_map_storage_1<d_, Items_, Alloc_>::null_descriptor;
-
-  template<unsigned int d_, class Items_, class Alloc_>
-  constexpr typename Combinatorial_map_storage_1<d_, Items_, Alloc_>::Null_descriptor_type
-  Combinatorial_map_storage_1<d_, Items_, Alloc_>::null_handle;
-#endif
-
 } // namespace CGAL
 
 #if defined(BOOST_GCC)

Generalized_map/include/CGAL/Generalized_map_storages.h

@@ -457,17 +457,6 @@ namespace CGAL {
     /// Tuple of attributes containers
     typename Helper::Attribute_containers mattribute_containers;
   };
-
-#ifndef CGAL_CXX17
-  template<unsigned int d_, class Items_, class Alloc_>
-  constexpr typename Generalized_map_storage_1<d_, Items_, Alloc_>::Null_descriptor_type
-  Generalized_map_storage_1<d_, Items_, Alloc_>::null_descriptor;
-
-  template<unsigned int d_, class Items_, class Alloc_>
-  constexpr typename Generalized_map_storage_1<d_, Items_, Alloc_>::Null_descriptor_type
-  Generalized_map_storage_1<d_, Items_, Alloc_>::null_handle;
-#endif
-
 } // namespace CGAL
 
 #if defined(BOOST_GCC)

Installation/include/CGAL/config.h

@@ -36,11 +36,6 @@
 #  define WIN64
 #endif
 
-#ifdef _MSC_VER
-#define _SILENCE_CXX17_ALLOCATOR_VOID_DEPRECATION_WARNING 1
-#define _SILENCE_CXX17_OLD_ALLOCATOR_MEMBERS_DEPRECATION_WARNING 1
-#endif
-
 #ifdef CGAL_INCLUDE_WINDOWS_DOT_H
 // Mimic users including this file which defines min max macros
 // and other names leading to name clashes
@@ -147,8 +142,8 @@
 #endif
 
 // Same for C++17
-#if __cplusplus >= 201703L || _MSVC_LANG >= 201703L
+#if !(__cplusplus >= 201703L || _MSVC_LANG >= 201703L)
-#  define CGAL_CXX17 1
+#error "CGAL requires C++ 17"
 #endif
 // Same for C++20
 #if __cplusplus >= 202002L || _MSVC_LANG >= 202002L

Linear_cell_complex/include/CGAL/CMap_linear_cell_complex_storages.h

@@ -502,17 +502,6 @@ namespace CGAL {
     typename Helper::Attribute_containers mattribute_containers;
   };
 
-#ifndef CGAL_CXX17
-  template<unsigned int d_, unsigned int ambient_dim,
-           class Traits_, class Items_, class Alloc_>
-  constexpr typename CMap_linear_cell_complex_storage_1<d_,ambient_dim, Traits_, Items_, Alloc_>::Null_descriptor_type
-    CMap_linear_cell_complex_storage_1<d_,ambient_dim, Traits_, Items_, Alloc_>::null_descriptor;
-
-  template<unsigned int d_, unsigned int ambient_dim,
-           class Traits_, class Items_, class Alloc_>
-  constexpr typename CMap_linear_cell_complex_storage_1<d_,ambient_dim, Traits_, Items_, Alloc_>::Null_descriptor_type
-    CMap_linear_cell_complex_storage_1<d_,ambient_dim, Traits_, Items_, Alloc_>::null_handle;
-#endif
 } // namespace CGAL
 
 #if defined(BOOST_GCC)

Linear_cell_complex/include/CGAL/GMap_linear_cell_complex_storages.h

@@ -493,18 +493,6 @@ namespace CGAL {
     typename Helper::Attribute_containers mattribute_containers;
   };
 
-#ifndef CGAL_CXX17
-  template<unsigned int d_, unsigned int ambient_dim,
-           class Traits_, class Items_, class Alloc_>
-  constexpr typename GMap_linear_cell_complex_storage_1<d_, ambient_dim, Traits_, Items_, Alloc_>::Null_descriptor_type
-  GMap_linear_cell_complex_storage_1<d_, ambient_dim, Traits_, Items_, Alloc_>::null_descriptor;
-
-  template<unsigned int d_, unsigned int ambient_dim,
-           class Traits_, class Items_, class Alloc_>
-  constexpr typename GMap_linear_cell_complex_storage_1<d_, ambient_dim, Traits_, Items_, Alloc_>::Null_descriptor_type
-  GMap_linear_cell_complex_storage_1<d_, ambient_dim, Traits_, Items_, Alloc_>::null_handle;
-#endif
-
 } // namespace CGAL
 
 #if defined(BOOST_GCC)

Matrix_search/include/CGAL/Cartesian_matrix.h

@@ -28,11 +28,7 @@ template < class Operation,
 class Cartesian_matrix {
 public:
 
-#if CGAL_CXX17 && __has_cpp_attribute(nodiscard)
   typedef typename std::invoke_result<Operation, typename std::iterator_traits<RandomAccessIC_row>::value_type, typename std::iterator_traits<RandomAccessIC_column>::value_type>::type Value;
-#else
-  typedef typename Operation::result_type           Value;
-#endif
 
   Cartesian_matrix(RandomAccessIC_row r_f,
                    RandomAccessIC_row r_l,

Mesh_3/include/CGAL/Mesh_3/C3T3_helpers.h

@@ -1572,17 +1572,10 @@ private:
   Cell_vector c3t3_cells(const Cell_vector& cells) const
   {
     Cell_vector c3t3_cells;
-#ifdef CGAL_CXX17
     std::remove_copy_if(cells.begin(),
                         cells.end(),
                         std::back_inserter(c3t3_cells),
                         std::not_fn(Is_in_c3t3<Cell_handle>(c3t3_)));
-#else
-    std::remove_copy_if(cells.begin(),
-                        cells.end(),
-                        std::back_inserter(c3t3_cells),
-                        std::not1(Is_in_c3t3<Cell_handle>(c3t3_)) );
-#endif
     return c3t3_cells;
   }
 
@@ -3665,17 +3658,10 @@ incident_slivers(const Vertex_handle& v,
   std::vector<Cell_handle> incident_cells_;
   tr_.incident_cells(v, std::back_inserter(incident_cells_));
 
-#ifdef CGAL_CXX17
   std::remove_copy_if(incident_cells_.begin(),
                       incident_cells_.end(),
                       out,
                       std::not_fn(Is_sliver<Sc>(c3t3_, criterion, sliver_bound)));
-#else
-  std::remove_copy_if(incident_cells_.begin(),
-                      incident_cells_.end(),
-                      out,
-                      std::not1(Is_sliver<Sc>(c3t3_,criterion,sliver_bound)));
-#endif
 
   return out;
 }