Revert "[libc++] Fix PR35491 - std::array of zero-size doesn't work with non-default constructible types."

Revert "Fix initialization of array<const T, 0> with GCC."
Revert "Make array<const T, 0> non-CopyAssignable and make swap and fill ill-formed."

This reverts commit r324182, r324185, and r324194 which were causing issues with zero-length std::arrays.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@324309 91177308-0d34-0410-b5e6-96231b3b80d8

include/array

@@ -117,57 +117,6 @@ template <size_t I, class T, size_t N> const T&& get(const array<T, N>&&) noexce
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp, size_t _Size>
-struct __array_traits {
-  typedef _Tp _StorageT[_Size];
-
-  _LIBCPP_INLINE_VISIBILITY
-  static _LIBCPP_CONSTEXPR_AFTER_CXX14 typename remove_const<_Tp>::type*
-  __data(typename remove_const<_StorageT>::type& __store) {
-    return __store;
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static _LIBCPP_CONSTEXPR_AFTER_CXX14 _Tp const* __data(const _StorageT& __store) {
-    return __store;
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static void __swap(_StorageT& __lhs, _StorageT& __rhs) {
-    std::swap_ranges(__lhs, __lhs + _Size, __rhs);
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static void __fill(_StorageT& __arr, _Tp const& __val) {
-    _VSTD::fill_n(__arr, _Size, __val);
-  }
-};
-
-template <class _Tp>
-struct __array_traits<_Tp, 0> {
-  typedef typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
-      _NonConstStorageT[1];
-  typedef typename conditional<is_const<_Tp>::value, const _NonConstStorageT,
-                               _NonConstStorageT>::type _StorageT;
-  typedef typename remove_const<_Tp>::type _NonConstTp;
-
-  _LIBCPP_INLINE_VISIBILITY
-  static _NonConstTp* __data(_NonConstStorageT &__store) {
-    return reinterpret_cast<_NonConstTp*>(__store);
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static const _Tp* __data(const _StorageT &__store) {
-    return reinterpret_cast<const _Tp*>(__store);
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static void __swap(_StorageT&, _StorageT&) {}
-
-  _LIBCPP_INLINE_VISIBILITY
-  static void __fill(_StorageT&, _Tp const&) {}
-};
-
 template <class _Tp, size_t _Size>
 struct _LIBCPP_TEMPLATE_VIS array
 {
@@ -185,33 +134,31 @@ struct _LIBCPP_TEMPLATE_VIS array
     typedef std::reverse_iterator<iterator>       reverse_iterator;
     typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 
-    typedef __array_traits<_Tp, _Size> _Traits;
+    value_type __elems_[_Size > 0 ? _Size : 1];
-    typename _Traits::_StorageT __elems_;
 
     // No explicit construct/copy/destroy for aggregate type
-    _LIBCPP_INLINE_VISIBILITY void fill(const value_type& __u) {
+    _LIBCPP_INLINE_VISIBILITY void fill(const value_type& __u)
-      static_assert(_Size != 0 || !is_const<_Tp>::value,
+        {_VSTD::fill_n(__elems_, _Size, __u);}
-                    "cannot fill zero-sized array of type 'const T'");
+    _LIBCPP_INLINE_VISIBILITY
-      _Traits::__fill(__elems_, __u);
+    void swap(array& __a) _NOEXCEPT_(_Size == 0 || __is_nothrow_swappable<_Tp>::value)
-    }
+        { __swap_dispatch((std::integral_constant<bool, _Size == 0>()), __a); }
 
     _LIBCPP_INLINE_VISIBILITY
-    void swap(array& __a)
+    void __swap_dispatch(std::true_type, array&) {}
-        _NOEXCEPT_(_Size == 0 || __is_nothrow_swappable<_Tp>::value) {
+
-      static_assert(_Size != 0 || !is_const<_Tp>::value,
+    _LIBCPP_INLINE_VISIBILITY
-                    "cannot swap zero-sized array of type 'const T'");
+    void __swap_dispatch(std::false_type, array& __a)
-      _Traits::__swap(__elems_, __a.__elems_);
+        { _VSTD::swap_ranges(__elems_, __elems_ + _Size, __a.__elems_);}
-    }
 
     // iterators:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    iterator begin() _NOEXCEPT {return iterator(data());}
+    iterator begin() _NOEXCEPT {return iterator(__elems_);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    const_iterator begin() const _NOEXCEPT {return const_iterator(data());}
+    const_iterator begin() const _NOEXCEPT {return const_iterator(__elems_);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    iterator end() _NOEXCEPT {return iterator(data() + _Size);}
+    iterator end() _NOEXCEPT {return iterator(__elems_ + _Size);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    const_iterator end() const _NOEXCEPT {return const_iterator(data() + _Size);}
+    const_iterator end() const _NOEXCEPT {return const_iterator(__elems_ + _Size);}
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     reverse_iterator rbegin() _NOEXCEPT {return reverse_iterator(end());}
@@ -254,9 +201,9 @@ struct _LIBCPP_TEMPLATE_VIS array
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference back() const  {return __elems_[_Size > 0 ? _Size-1 : 0];}
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    value_type* data() _NOEXCEPT {return _Traits::__data(__elems_);}
+    value_type* data() _NOEXCEPT {return __elems_;}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-    const value_type* data() const _NOEXCEPT {return _Traits::__data(__elems_);}
+    const value_type* data() const _NOEXCEPT {return __elems_;}
 };
 
 template <class _Tp, size_t _Size>

test/std/containers/sequences/array/array.cons/default.pass.cpp

@@ -14,14 +14,6 @@
 #include <array>
 #include <cassert>
 
-// std::array is explicitly allowed to be initialized with A a = { init-list };.
-// Disable the missing braces warning for this reason.
-#include "disable_missing_braces_warning.h"
-
-struct NoDefault {
-  NoDefault(int) {}
-};
-
 int main()
 {
     {
@@ -36,13 +28,4 @@ int main()
         C c;
         assert(c.size() == 0);
     }
-    {
-      typedef std::array<NoDefault, 0> C;
-      C c;
-      assert(c.size() == 0);
-      C c1 = {};
-      assert(c1.size() == 0);
-      C c2 = {{}};
-      assert(c2.size() == 0);
-    }
 }

test/std/containers/sequences/array/array.cons/implicit_copy.pass.cpp

@@ -1,93 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// <array>
-
-// implicitly generated array constructors / assignment operators
-
-#include <array>
-#include <type_traits>
-#include <cassert>
-#include "test_macros.h"
-
-// std::array is explicitly allowed to be initialized with A a = { init-list };.
-// Disable the missing braces warning for this reason.
-#include "disable_missing_braces_warning.h"
-
-// In C++03 the copy assignment operator is not deleted when the implicitly
-// generated operator would be ill-formed; like in the case of a struct with a
-// const member.
-#if TEST_STD_VER < 11
-#define TEST_NOT_COPY_ASSIGNABLE(T) ((void)0)
-#else
-#define TEST_NOT_COPY_ASSIGNABLE(T) static_assert(!std::is_copy_assignable<T>::value, "")
-#endif
-
-struct NoDefault {
-  NoDefault(int) {}
-};
-
-int main() {
-  {
-    typedef double T;
-    typedef std::array<T, 3> C;
-    C c = {1.1, 2.2, 3.3};
-    C c2 = c;
-    c2 = c;
-    static_assert(std::is_copy_constructible<C>::value, "");
-    static_assert(std::is_copy_assignable<C>::value, "");
-  }
-  {
-    typedef double T;
-    typedef std::array<const T, 3> C;
-    C c = {1.1, 2.2, 3.3};
-    C c2 = c;
-    ((void)c2);
-    static_assert(std::is_copy_constructible<C>::value, "");
-    TEST_NOT_COPY_ASSIGNABLE(C);
-  }
-  {
-    typedef double T;
-    typedef std::array<T, 0> C;
-    C c = {};
-    C c2 = c;
-    c2 = c;
-    static_assert(std::is_copy_constructible<C>::value, "");
-    static_assert(std::is_copy_assignable<C>::value, "");
-  }
-  {
-    // const arrays of size 0 should disable the implicit copy assignment operator.
-    typedef double T;
-    typedef std::array<const T, 0> C;
-    C c = {};
-    C c2 = c;
-    ((void)c2);
-    static_assert(std::is_copy_constructible<C>::value, "");
-    TEST_NOT_COPY_ASSIGNABLE(C);
-  }
-  {
-    typedef NoDefault T;
-    typedef std::array<T, 0> C;
-    C c = {};
-    C c2 = c;
-    c2 = c;
-    static_assert(std::is_copy_constructible<C>::value, "");
-    static_assert(std::is_copy_assignable<C>::value, "");
-  }
-  {
-    typedef NoDefault T;
-    typedef std::array<const T, 0> C;
-    C c = {};
-    C c2 = c;
-    ((void)c2);
-    static_assert(std::is_copy_constructible<C>::value, "");
-    TEST_NOT_COPY_ASSIGNABLE(C);
-  }
-
-}

test/std/containers/sequences/array/array.data/data.pass.cpp

@@ -36,22 +36,4 @@ int main()
         T* p = c.data();
         (void)p; // to placate scan-build
     }
-    {
-      typedef double T;
-      typedef std::array<const T, 0> C;
-      C c = {};
-      const T* p = c.data();
-      static_assert((std::is_same<decltype(c.data()), const T*>::value), "");
-      (void)p; // to placate scan-build
-    }
-    {
-      struct NoDefault {
-        NoDefault(int) {}
-      };
-      typedef NoDefault T;
-      typedef std::array<T, 0> C;
-      C c = {};
-      T* p = c.data();
-      assert(p != nullptr);
-    }
 }

test/std/containers/sequences/array/array.data/data_const.pass.cpp

@@ -38,16 +38,6 @@ int main()
         const T* p = c.data();
         (void)p; // to placate scan-build
     }
-    {
-      struct NoDefault {
-        NoDefault(int) {}
-      };
-      typedef NoDefault T;
-      typedef std::array<T, 0> C;
-      const C c = {};
-      const T* p = c.data();
-      assert(p != nullptr);
-    }
 #if TEST_STD_VER > 14
     {
         typedef std::array<int, 5> C;

test/std/containers/sequences/array/array.fill/fill.fail.cpp

@@ -1,29 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// <array>
-
-// void fill(const T& u);
-
-#include <array>
-#include <cassert>
-
-// std::array is explicitly allowed to be initialized with A a = { init-list };.
-// Disable the missing braces warning for this reason.
-#include "disable_missing_braces_warning.h"
-
-int main() {
-  {
-    typedef double T;
-    typedef std::array<const T, 0> C;
-    C c = {};
-    // expected-error@array:* {{static_assert failed "cannot fill zero-sized array of type 'const T'"}}
-    c.fill(5.5); // expected-note {{requested here}}
-  }
-}

test/std/containers/sequences/array/array.swap/swap.fail.cpp

@@ -1,30 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// <array>
-
-// void swap(array& a);
-
-#include <array>
-#include <cassert>
-
-// std::array is explicitly allowed to be initialized with A a = { init-list };.
-// Disable the missing braces warning for this reason.
-#include "disable_missing_braces_warning.h"
-
-int main() {
-  {
-    typedef double T;
-    typedef std::array<const T, 0> C;
-    C c = {};
-    C c2 = {};
-    // expected-error@array:* {{static_assert failed "cannot swap zero-sized array of type 'const T'"}}
-    c.swap(c2); // expected-note {{requested here}}
-  }
-}

test/std/containers/sequences/array/begin.pass.cpp

@@ -31,13 +31,4 @@ int main()
         *i = 5.5;
         assert(c[0] == 5.5);
     }
-    {
-      struct NoDefault {
-        NoDefault(int) {}
-      };
-      typedef NoDefault T;
-      typedef std::array<T, 0> C;
-      C c = {};
-      assert(c.begin() == c.end());
-    }
 }