re PR libstdc++/65352 (array<T,0>::begin()/end() etc. forms a null reference and…

re PR libstdc++/65352 (array<T,0>::begin()/end() etc. forms a null reference and breaks on clang+ubsan)

	PR libstdc++/65352
	* include/std/array (__array_traits::_S_ptr): New function.
	(array::data): Use _S_ptr to avoid creating invalid reference.
	* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
	dg-error line numbers.
	* testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc:
	likewise.

From-SVN: r223806

libstdc++-v3/ChangeLog

+2015-05-28  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/65352
+	* include/std/array (__array_traits::_S_ptr): New function.
+	(array::data): Use _S_ptr to avoid creating invalid reference.
+	* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
+	dg-error line numbers.
+	* testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc:
+	likewise.
+
 2015-05-27  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/stl_tree.h (_Rb_tree::_M_end()): Return _Base_ptr

libstdc++-v3/include/std/array

@@ -51,6 +51,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       static constexpr _Tp&
       _S_ref(const _Type& __t, std::size_t __n) noexcept
       { return const_cast<_Tp&>(__t[__n]); }
+
+      static constexpr _Tp*
+      _S_ptr(const _Type& __t) noexcept
+      { return const_cast<_Tp*>(__t); }
     };
 
  template<typename _Tp>
@@ -61,6 +65,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
      static constexpr _Tp&
      _S_ref(const _Type&, std::size_t) noexcept
      { return *static_cast<_Tp*>(nullptr); }
+
+     static constexpr _Tp*
+     _S_ptr(const _Type&) noexcept
+     { return nullptr; }
    };
 
   /**
@@ -219,11 +227,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
       pointer
       data() noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
 
       const_pointer
       data() const noexcept
-      { return std::__addressof(_AT_Type::_S_ref(_M_elems, 0)); }
+      { return _AT_Type::_S_ptr(_M_elems); }
     };
 
   // Array comparisons.

libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc

@@ -28,6 +28,6 @@ int n1 = std::get<1>(a);
 int n2 = std::get<1>(std::move(a));
 int n3 = std::get<1>(ca);
 
-// { dg-error "static assertion failed" "" { target *-*-* } 274 }
-// { dg-error "static assertion failed" "" { target *-*-* } 283 }
+// { dg-error "static assertion failed" "" { target *-*-* } 282 }
 // { dg-error "static assertion failed" "" { target *-*-* } 291 }
+// { dg-error "static assertion failed" "" { target *-*-* } 299 }

libstdc++-v3/testsuite/23_containers/array/tuple_interface/tuple_element_neg.cc

@@ -23,4 +23,4 @@
 
 typedef std::tuple_element<1, std::array<int, 1>>::type type;
 
-// { dg-error "static assertion failed" "" { target *-*-* } 322 }
+// { dg-error "static assertion failed" "" { target *-*-* } 330 }