Enable failing tests

doc/array/changes.adoc

@@ -16,3 +16,6 @@ http://www.boost.org/LICENSE_1_0.txt
 * Added `noexcept` and `constexpr` as appropriate.
 * Marked obsolete functions as deprecated.
 * Removed obsolete compiler workarounds.
+* Changed `array<T, 0>::begin()`, `cbegin()`, `end()`, `cend()` to return `nullptr`, enabling `constexpr`.
+  This matches the behavior of `std::array`.
+* Removed local `hash_value` overload; `boost::hash` supports array-like types natively.

include/boost/array.hpp

@@ -195,6 +195,8 @@ namespace boost {
 
     template< class T >
     class array< T, 0 > {
+      public:
+        struct {} elems; // enables initialization with = {{}}
 
       public:
         // type definitions
@@ -207,13 +209,13 @@ namespace boost {
         typedef std::ptrdiff_t difference_type;
 
         // iterator support
-        iterator        begin()       BOOST_NOEXCEPT { return       iterator( reinterpret_cast<       T * >( this ) ); }
-        const_iterator  begin() const BOOST_NOEXCEPT { return const_iterator( reinterpret_cast< const T * >( this ) ); }
-        const_iterator cbegin() const BOOST_NOEXCEPT { return const_iterator( reinterpret_cast< const T * >( this ) ); }
+        BOOST_CXX14_CONSTEXPR iterator  begin()       BOOST_NOEXCEPT { return data(); }
+        BOOST_CONSTEXPR const_iterator  begin() const BOOST_NOEXCEPT { return data(); }
+        BOOST_CONSTEXPR const_iterator cbegin() const BOOST_NOEXCEPT { return data(); }
 
-        iterator        end()       BOOST_NOEXCEPT { return  begin(); }
-        const_iterator  end() const BOOST_NOEXCEPT { return  begin(); }
-        const_iterator cend() const BOOST_NOEXCEPT { return cbegin(); }
+        BOOST_CXX14_CONSTEXPR iterator  end()       BOOST_NOEXCEPT { return  begin(); }
+        BOOST_CONSTEXPR const_iterator  end() const BOOST_NOEXCEPT { return  begin(); }
+        BOOST_CONSTEXPR const_iterator cend() const BOOST_NOEXCEPT { return cbegin(); }
 
         // reverse iterator support
         typedef std::reverse_iterator<iterator> reverse_iterator;
@@ -395,14 +397,6 @@ namespace boost {
         return arg.elems;
     }
 
-    template <class It> std::size_t hash_range(It, It);
-
-    template<class T, std::size_t N>
-    std::size_t hash_value(const array<T,N>& arr)
-    {
-        return boost::hash_range(arr.begin(), arr.end());
-    }
-
    template <size_t Idx, typename T, size_t N>
    BOOST_CXX14_CONSTEXPR T &get(boost::array<T,N> &arr) BOOST_NOEXCEPT {
        BOOST_STATIC_ASSERT_MSG ( Idx < N, "boost::get<>(boost::array &) index out of range" );

test/array0.cpp

@@ -44,7 +44,12 @@ void    RunTests()
     BOOST_TEST ( const_test_case.begin() == const_test_case.end());
     BOOST_TEST ( const_test_case.cbegin() == const_test_case.cend());
 
-    BOOST_TEST ( test_case.begin() != const_test_case.begin() );
+    // BOOST_TEST ( test_case.begin() != const_test_case.begin() );
+    //
+    // TR1 specified that begin() must return a unique value for zero-sized
+    // arrays. However, this makes constexpr unimplementable, and all standard
+    // libraries have converged on using nullptr instead (see LWG issue 2157.)
+
     if( test_case.data() == const_test_case.data() ) {
     //  Value of data is unspecified in TR1, so no requirement this test pass or fail
     //  However, it must compile!

test/array_copy_test.cpp

@@ -44,11 +44,11 @@ template<class T> void test4()
 
 int main()
 {
-    // test1<int, 0>();
+    test1<int, 0>();
     test1<int, 1>();
     test1<int, 7>();
 
-    // test1<int const, 0>();
+    test1<int const, 0>();
     test1<int const, 1>();
     test1<int const, 7>();
 

test/array_init_test.cpp

@@ -46,11 +46,11 @@ template<class T> void test4()
 
 int main()
 {
-    // test1<int, 0>();
+    test1<int, 0>();
     test1<int, 1>();
     test1<int, 7>();
 
-    // test1<int const, 0>();
+    test1<int const, 0>();
     test1<int const, 1>();
     test1<int const, 7>();
 

test/array_init_test_cx.cpp

@@ -56,7 +56,8 @@ template<class T> void test4()
 
 template<class T> void test5()
 {
-    // constexpr boost::array<T, 0> a = {{}};
+    constexpr boost::array<T, 0> a = {{}};
+    (void)a;
 }
 
 template<class T> void test6()

test/array_iterator_test.cpp

@@ -94,11 +94,11 @@ template<class T> void test2()
 
 int main()
 {
-    // test<int, 0>();
+    test<int, 0>();
     test<int, 1>();
     test<int, 7>();
 
-    // test<int const, 0>();
+    test<int const, 0>();
     test<int const, 1>();
     test<int const, 7>();
 

test/array_iterator_test_cx.cpp

@@ -39,20 +39,17 @@ template<class T> void test2()
 {
     constexpr boost::array<T, 0> a = {};
 
-    // iterator access is not constexpr for boost::array<T, 0>
-    // it is for std::array<T, 0>, though, so we should change it
-
     STATIC_ASSERT( a.begin() == a.end() );
     STATIC_ASSERT( a.cbegin() == a.cend() );
 }
 
 int main()
 {
-    // test1<int, 0>();
+    test1<int, 0>();
     test1<int, 1>();
     test1<int, 7>();
 
-    // test2<int>();
+    test2<int>();
 }
 
 #endif

test/array_reverse_test.cpp

@@ -76,11 +76,11 @@ template<class T, std::size_t N> void test()
 
 int main()
 {
-    // test<int, 0>();
+    test<int, 0>();
     test<int, 1>();
     test<int, 7>();
 
-    // test<int const, 0>();
+    test<int const, 0>();
     test<int const, 1>();
     test<int const, 7>();
 

test/array_size_test.cpp

@@ -49,11 +49,11 @@ template<class T, std::size_t N> void test3()
 
 int main()
 {
-    // test1<int, 0>();
+    test1<int, 0>();
     test1<int, 1>();
     test1<int, 7>();
 
-    // test1<int const, 0>();
+    test1<int const, 0>();
     test1<int const, 1>();
     test1<int const, 7>();