libstdc++: Make ranges CPOs final and not addressable

This restricts the API of the CPOs and other function objects so they
cannot be misused by deriving from them or taking their addresses.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	* include/bits/ranges_base.h (ranges::begin, ranges::end)
	(ranges::cbegin, ranges::cend, ranges::rbeing, ranges::rend)
	(ranges::crbegin, ranges::crend, ranges::size, ranges::ssize)
	(ranges::empty, ranges::data, ranges::cdata): Make types final.
	Add deleted operator& overloads.
	(ranges::advance, ranges::distance, ranges::next, ranges::prev):
	Likewise.
	* testsuite/std/ranges/headers/ranges/synopsis.cc: Replace
	ill-formed & expressions with using-declarations. Add checks for
	other function objects.

diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index a63ef8e..e392c37 100644 (file)
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -91,7 +91,7 @@ namespace ranges
     using std::ranges::__detail::__maybe_borrowed_range;
     using std::__detail::__range_iter_t;
 
-    struct _Begin
+    struct _Begin final
     {
     private:
       template<typename _Tp>
@@ -106,6 +106,8 @@ namespace ranges
            return noexcept(__decay_copy(begin(std::declval<_Tp&>())));
        }
 
+      void operator&() const = delete;
+
     public:
       template<__maybe_borrowed_range _Tp>
        requires is_array_v<remove_reference_t<_Tp>> || __member_begin<_Tp>
@@ -142,7 +144,7 @@ namespace ranges
          { __decay_copy(end(__t)) } -> sentinel_for<__range_iter_t<_Tp>>;
        };
 
-    struct _End
+    struct _End final
     {
     private:
       template<typename _Tp>
@@ -157,6 +159,8 @@ namespace ranges
            return noexcept(__decay_copy(end(std::declval<_Tp&>())));
        }
 
+      void operator&() const = delete;
+
     public:
       template<__maybe_borrowed_range _Tp>
        requires is_bounded_array_v<remove_reference_t<_Tp>>
@@ -189,7 +193,7 @@ namespace ranges
          return static_cast<const _Tp&&>(__t);
       }
 
-    struct _CBegin
+    struct _CBegin final
     {
       template<typename _Tp>
        constexpr auto
@@ -199,9 +203,11 @@ namespace ranges
        {
          return _Begin{}(__cust_access::__as_const<_Tp>(__e));
        }
+
+      void operator&() const = delete;
     };
 
-    struct _CEnd
+    struct _CEnd final
     {
       template<typename _Tp>
        constexpr auto
@@ -211,6 +217,8 @@ namespace ranges
        {
          return _End{}(__cust_access::__as_const<_Tp>(__e));
        }
+
+      void operator&() const = delete;
     };
 
     template<typename _Tp>
@@ -236,7 +244,7 @@ namespace ranges
          { _End{}(__t) } -> same_as<decltype(_Begin{}(__t))>;
        };
 
-    struct _RBegin
+    struct _RBegin final
     {
     private:
       template<typename _Tp>
@@ -260,6 +268,8 @@ namespace ranges
            }
        }
 
+      void operator&() const = delete;
+
     public:
       template<__maybe_borrowed_range _Tp>
        requires __member_rbegin<_Tp> || __adl_rbegin<_Tp> || __reversable<_Tp>
@@ -294,7 +304,7 @@ namespace ranges
            -> sentinel_for<decltype(_RBegin{}(std::forward<_Tp>(__t)))>;
        };
 
-    struct _REnd
+    struct _REnd final
     {
     private:
       template<typename _Tp>
@@ -318,6 +328,8 @@ namespace ranges
            }
        }
 
+      void operator&() const = delete;
+
     public:
       template<__maybe_borrowed_range _Tp>
        requires __member_rend<_Tp> || __adl_rend<_Tp> || __reversable<_Tp>
@@ -334,7 +346,7 @@ namespace ranges
        }
     };
 
-    struct _CRBegin
+    struct _CRBegin final
     {
       template<typename _Tp>
        constexpr auto
@@ -344,9 +356,11 @@ namespace ranges
        {
          return _RBegin{}(__cust_access::__as_const<_Tp>(__e));
        }
+
+      void operator&() const = delete;
     };
 
-    struct _CREnd
+    struct _CREnd final
     {
       template<typename _Tp>
        constexpr auto
@@ -356,6 +370,8 @@ namespace ranges
        {
          return _REnd{}(__cust_access::__as_const<_Tp>(__e));
        }
+
+      void operator&() const = delete;
     };
 
     template<typename _Tp>
@@ -386,7 +402,7 @@ namespace ranges
          __detail::__to_unsigned_like(_End{}(__t) - _Begin{}(__t));
        };
 
-    struct _Size
+    struct _Size final
     {
     private:
       template<typename _Tp>
@@ -404,6 +420,8 @@ namespace ranges
                            - _Begin{}(std::declval<_Tp&>()));
        }
 
+      void operator&() const = delete;
+
     public:
       template<typename _Tp>
        requires is_bounded_array_v<remove_reference_t<_Tp>>
@@ -422,7 +440,7 @@ namespace ranges
        }
     };
 
-    struct _SSize
+    struct _SSize final
     {
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 3403. Domain of ranges::ssize(E) doesn't match ranges::size(E)
@@ -451,6 +469,8 @@ namespace ranges
          else // Must be one of __max_diff_type or __max_size_type.
            return __detail::__max_diff_type(__size);
        }
+
+      void operator&() const = delete;
     };
 
     template<typename _Tp>
@@ -467,7 +487,7 @@ namespace ranges
          bool(_Begin{}(__t) == _End{}(__t));
        };
 
-    struct _Empty
+    struct _Empty final
     {
     private:
       template<typename _Tp>
@@ -483,6 +503,8 @@ namespace ranges
                == _End{}(std::declval<_Tp&>())));
        }
 
+      void operator&() const = delete;
+
     public:
       template<typename _Tp>
        requires __member_empty<_Tp> || __size0_empty<_Tp>
@@ -512,7 +534,7 @@ namespace ranges
     template<typename _Tp>
       concept __begin_data = contiguous_iterator<__range_iter_t<_Tp>>;
 
-    struct _Data
+    struct _Data final
     {
     private:
       template<typename _Tp>
@@ -525,6 +547,8 @@ namespace ranges
            return noexcept(_Begin{}(std::declval<_Tp&>()));
        }
 
+      void operator&() const = delete;
+
     public:
       template<__maybe_borrowed_range _Tp>
        requires __member_data<_Tp> || __begin_data<_Tp>
@@ -538,7 +562,7 @@ namespace ranges
        }
     };
 
-    struct _CData
+    struct _CData final
     {
       template<typename _Tp>
        constexpr auto
@@ -548,6 +572,8 @@ namespace ranges
        {
          return _Data{}(__cust_access::__as_const<_Tp>(__e));
        }
+
+      void operator&() const = delete;
     };
 
   } // namespace __cust_access
@@ -669,7 +695,7 @@ namespace ranges
 
   // [range.iter.ops] range iterator operations
 
-  struct __advance_fn
+  struct __advance_fn final
   {
     template<input_or_output_iterator _It>
       constexpr void
@@ -774,11 +800,13 @@ namespace ranges
            return __n;
          }
       }
+
+    void operator&() const = delete;
   };
 
   inline constexpr __advance_fn advance{};
 
-  struct __distance_fn
+  struct __distance_fn final
   {
     template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
       constexpr iter_difference_t<_It>
@@ -807,11 +835,13 @@ namespace ranges
        else
          return (*this)(ranges::begin(__r), ranges::end(__r));
       }
+
+    void operator&() const = delete;
   };
 
   inline constexpr __distance_fn distance{};
 
-  struct __next_fn
+  struct __next_fn final
   {
     template<input_or_output_iterator _It>
       constexpr _It
@@ -844,11 +874,13 @@ namespace ranges
        ranges::advance(__x, __n, __bound);
        return __x;
       }
+
+    void operator&() const = delete;
   };
 
   inline constexpr __next_fn next{};
 
-  struct __prev_fn
+  struct __prev_fn final
   {
     template<bidirectional_iterator _It>
       constexpr _It
@@ -873,6 +905,8 @@ namespace ranges
        ranges::advance(__x, -__n, __bound);
        return __x;
       }
+
+    void operator&() const = delete;
   };
 
   inline constexpr __prev_fn prev{};

diff --git a/libstdc++-v3/testsuite/std/ranges/headers/ranges/synopsis.cc b/libstdc++-v3/testsuite/std/ranges/headers/ranges/synopsis.cc
index 115b157..ea26b50 100644 (file)
--- a/libstdc++-v3/testsuite/std/ranges/headers/ranges/synopsis.cc
+++ b/libstdc++-v3/testsuite/std/ranges/headers/ranges/synopsis.cc
@@ -33,12 +33,22 @@ namespace __gnu_test
 {
   constexpr const bool* disable_sized_range
     = &std::ranges::disable_sized_range<void>;
-  constexpr auto* begin = &std::ranges::begin;
-  constexpr auto* end = &std::ranges::end;
-  constexpr auto* cbegin = &std::ranges::cbegin;
-  constexpr auto* cend = &std::ranges::cend;
-  constexpr auto* rbegin = &std::ranges::rbegin;
-  constexpr auto* rend = &std::ranges::rend;
-  constexpr auto* crbegin = &std::ranges::crbegin;
-  constexpr auto* crend = &std::ranges::crend;
+  using std::ranges::begin;
+  using std::ranges::end;
+  using std::ranges::cbegin;
+  using std::ranges::cend;
+  using std::ranges::rbegin;
+  using std::ranges::rend;
+  using std::ranges::crbegin;
+  using std::ranges::crend;
+  using std::ranges::size;
+  using std::ranges::ssize;
+  using std::ranges::empty;
+  using std::ranges::data;
+  using std::ranges::cdata;
+
+  using std::ranges::advance;
+  using std::ranges::distance;
+  using std::ranges::next;
+  using std::ranges::prev;
 }