[libc++] [P0325] Implement to_array from LFTS with updates.

mkurdej · mkurdej · commit 86aae78268f3 · 2020-01-30T13:38:37.000+01:00
Summary: This patch implements https://wg21.link/P0325. Please mind that at it is my first contribution to libc++, so I may have forgotten to abide to some conventions. Reviewers: EricWF, mclow.lists, ldionne, lichray Reviewed By: ldionne, lichray Subscribers: lichray, dexonsmith, zoecarver, christof, ldionne, libcxx-commits Tags: #libc Differential Revision: https://reviews.llvm.org/D69882
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
@@ -199,6 +199,8 @@ Status
     ``__cpp_lib_ranges``                              *unimplemented*  
     ------------------------------------------------- -----------------
     ``__cpp_lib_three_way_comparison``                *unimplemented*  
+    ------------------------------------------------- -----------------
+    ``__cpp_lib_to_array``                            ``201907L``      
     ================================================= =================
 
 
diff --git a/libcxx/include/array b/libcxx/include/array
@@ -479,6 +479,47 @@ get(const array<_Tp, _Size>&& __a) _NOEXCEPT
 
 #endif  // !_LIBCPP_CXX03_LANG
 
+#if _LIBCPP_STD_VER > 17
+
+template <typename _Tp, size_t _Size, size_t... _Index>
+_LIBCPP_INLINE_VISIBILITY constexpr array<remove_cv_t<_Tp>, _Size>
+__to_array_lvalue_impl(_Tp (&__arr)[_Size], index_sequence<_Index...>) {
+  return {{__arr[_Index]...}};
+}
+
+template <typename _Tp, size_t _Size, size_t... _Index>
+_LIBCPP_INLINE_VISIBILITY constexpr array<remove_cv_t<_Tp>, _Size>
+__to_array_rvalue_impl(_Tp(&&__arr)[_Size], index_sequence<_Index...>) {
+  return {{_VSTD::move(__arr[_Index])...}};
+}
+
+template <typename _Tp, size_t _Size>
+_LIBCPP_INLINE_VISIBILITY constexpr array<remove_cv_t<_Tp>, _Size>
+to_array(_Tp (&__arr)[_Size]) noexcept(is_nothrow_constructible_v<_Tp, _Tp&>) {
+  static_assert(
+      !is_array_v<_Tp>,
+      "[array.creation]/1: to_array does not accept multidimensional arrays.");
+  static_assert(
+      is_constructible_v<_Tp, _Tp&>,
+      "[array.creation]/1: to_array requires copy constructible elements.");
+  return __to_array_lvalue_impl(__arr, make_index_sequence<_Size>());
+}
+
+template <typename _Tp, size_t _Size>
+_LIBCPP_INLINE_VISIBILITY constexpr array<remove_cv_t<_Tp>, _Size>
+to_array(_Tp(&&__arr)[_Size]) noexcept(is_nothrow_move_constructible_v<_Tp>) {
+  static_assert(
+      !is_array_v<_Tp>,
+      "[array.creation]/4: to_array does not accept multidimensional arrays.");
+  static_assert(
+      is_move_constructible_v<_Tp>,
+      "[array.creation]/4: to_array requires move constructible elements.");
+  return __to_array_rvalue_impl(_VSTD::move(__arr),
+                                make_index_sequence<_Size>());
+}
+
+#endif // _LIBCPP_STD_VER > 17
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_ARRAY
diff --git a/libcxx/include/version b/libcxx/include/version
@@ -101,6 +101,7 @@ __cpp_lib_shared_timed_mutex                            201402L <shared_mutex>
 __cpp_lib_string_udls                                   201304L <string>
 __cpp_lib_string_view                                   201606L <string> <string_view>
 __cpp_lib_three_way_comparison                          201711L <compare>
+__cpp_lib_to_array                                      201907L <array>
 __cpp_lib_to_chars                                      201611L <utility>
 __cpp_lib_transformation_trait_aliases                  201304L <type_traits>
 __cpp_lib_transparent_operators                         201510L <functional>
@@ -233,6 +234,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # endif
 // # define __cpp_lib_list_remove_return_type              201806L
 // # define __cpp_lib_ranges                               201811L
+# define __cpp_lib_to_array                                201907L
 // # define __cpp_lib_three_way_comparison                 201711L
 #endif
 
diff --git a/libcxx/test/std/containers/sequences/array/array.creation/to_array.fail.cpp b/libcxx/test/std/containers/sequences/array/array.creation/to_array.fail.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <array>
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+#include <array>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+
+int main(int, char**) {
+  {
+    char source[3][6] = {"hi", "world"};
+    std::to_array(source); // expected-error {{here}}
+  }
+
+  {
+    MoveOnly mo[] = {MoveOnly{3}};
+    std::to_array(mo); // expected-error {{here}}
+  }
+
+  {
+    const MoveOnly cmo[] = {MoveOnly{3}};
+    std::to_array(std::move(cmo)); // expected-error {{here}}
+  }
+
+  return 0;
+}
diff --git a/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp b/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp
@@ -0,0 +1,122 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <array>
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// template <typename T, size_t Size>
+// constexpr auto to_array(T (&arr)[Size])
+//    -> array<remove_cv_t<T>, Size>;
+
+// template <typename T, size_t Size>
+// constexpr auto to_array(T (&&arr)[Size])
+//    -> array<remove_cv_t<T>, Size>;
+
+#include <array>
+#include <cassert>
+
+#include "test_macros.h"
+#include "MoveOnly.h"
+
+int main(int, char**) {
+  //  Test deduced type.
+  {
+    auto arr = std::to_array({1, 2, 3});
+    ASSERT_SAME_TYPE(decltype(arr), std::array<int, 3>);
+    assert(arr[0] == 1);
+    assert(arr[1] == 2);
+    assert(arr[2] == 3);
+  }
+
+  {
+    const long l1 = 42;
+    auto arr = std::to_array({1L, 4L, 9L, l1});
+    ASSERT_SAME_TYPE(decltype(arr)::value_type, long);
+    static_assert(arr.size() == 4, "");
+    assert(arr[0] == 1);
+    assert(arr[1] == 4);
+    assert(arr[2] == 9);
+    assert(arr[3] == l1);
+  }
+
+  {
+    auto arr = std::to_array("meow");
+    ASSERT_SAME_TYPE(decltype(arr), std::array<char, 5>);
+    assert(arr[0] == 'm');
+    assert(arr[1] == 'e');
+    assert(arr[2] == 'o');
+    assert(arr[3] == 'w');
+    assert(arr[4] == '\0');
+  }
+
+  {
+    double source[3] = {4.0, 5.0, 6.0};
+    auto arr = std::to_array(source);
+    ASSERT_SAME_TYPE(decltype(arr), std::array<double, 3>);
+    assert(arr[0] == 4.0);
+    assert(arr[1] == 5.0);
+    assert(arr[2] == 6.0);
+  }
+
+  {
+    double source[3] = {4.0, 5.0, 6.0};
+    auto arr = std::to_array(std::move(source));
+    ASSERT_SAME_TYPE(decltype(arr), std::array<double, 3>);
+    assert(arr[0] == 4.0);
+    assert(arr[1] == 5.0);
+    assert(arr[2] == 6.0);
+  }
+
+  {
+    MoveOnly source[] = {MoveOnly{0}, MoveOnly{1}, MoveOnly{2}};
+
+    auto arr = std::to_array(std::move(source));
+    ASSERT_SAME_TYPE(decltype(arr), std::array<MoveOnly, 3>);
+    for (int i = 0; i < 3; ++i)
+      assert(arr[i].get() == i && source[i].get() == 0);
+  }
+
+  // Test C99 compound literal.
+  {
+    auto arr = std::to_array((int[]){3, 4});
+    ASSERT_SAME_TYPE(decltype(arr), std::array<int, 2>);
+    assert(arr[0] == 3);
+    assert(arr[1] == 4);
+  }
+
+  //  Test explicit type.
+  {
+    auto arr = std::to_array<long>({1, 2, 3});
+    ASSERT_SAME_TYPE(decltype(arr), std::array<long, 3>);
+    assert(arr[0] == 1);
+    assert(arr[1] == 2);
+    assert(arr[2] == 3);
+  }
+
+  {
+    struct A {
+      int a;
+      double b;
+    };
+
+    auto arr = std::to_array<A>({{3, .1}});
+    ASSERT_SAME_TYPE(decltype(arr), std::array<A, 1>);
+    assert(arr[0].a == 3);
+    assert(arr[0].b == .1);
+  }
+
+  // Test constexpr.
+  {
+    constexpr std::array<int, 3> arr = std::to_array({1, 2, 3});
+    static_assert(arr[0] == 1);
+    static_assert(arr[1] == 2);
+    static_assert(arr[2] == 3);
+  }
+
+  return 0;
+}
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp
@@ -17,6 +17,7 @@
     __cpp_lib_array_constexpr               201603L [C++17]
     __cpp_lib_constexpr_misc                201811L [C++2a]
     __cpp_lib_nonmember_container_access    201411L [C++17]
+    __cpp_lib_to_array                      201907L [C++2a]
 */
 
 #include <array>
@@ -36,6 +37,10 @@
 #   error "__cpp_lib_nonmember_container_access should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 #elif TEST_STD_VER == 14
 
 # ifdef __cpp_lib_array_constexpr
@@ -50,6 +55,10 @@
 #   error "__cpp_lib_nonmember_container_access should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 #elif TEST_STD_VER == 17
 
 # ifndef __cpp_lib_array_constexpr
@@ -70,6 +79,10 @@
 #   error "__cpp_lib_nonmember_container_access should have the value 201411L in c++17"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 #elif TEST_STD_VER > 17
 
 # ifndef __cpp_lib_array_constexpr
@@ -99,6 +112,13 @@
 #   error "__cpp_lib_nonmember_container_access should have the value 201411L in c++2a"
 # endif
 
+# ifndef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should be defined in c++2a"
+# endif
+# if __cpp_lib_to_array != 201907L
+#   error "__cpp_lib_to_array should have the value 201907L in c++2a"
+# endif
+
 #endif // TEST_STD_VER > 17
 
 int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
@@ -88,6 +88,7 @@
     __cpp_lib_string_udls                          201304L [C++14]
     __cpp_lib_string_view                          201606L [C++17]
     __cpp_lib_three_way_comparison                 201711L [C++2a]
+    __cpp_lib_to_array                             201907L [C++2a]
     __cpp_lib_to_chars                             201611L [C++17]
     __cpp_lib_transformation_trait_aliases         201304L [C++14]
     __cpp_lib_transparent_operators                201210L [C++14]
@@ -402,6 +403,10 @@
 #   error "__cpp_lib_three_way_comparison should not be defined before c++2a"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 # ifdef __cpp_lib_to_chars
 #   error "__cpp_lib_to_chars should not be defined before c++17"
 # endif
@@ -794,6 +799,10 @@
 #   error "__cpp_lib_three_way_comparison should not be defined before c++2a"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 # ifdef __cpp_lib_to_chars
 #   error "__cpp_lib_to_chars should not be defined before c++17"
 # endif
@@ -1390,6 +1399,10 @@
 #   error "__cpp_lib_three_way_comparison should not be defined before c++2a"
 # endif
 
+# ifdef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should not be defined before c++2a"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_to_chars
 #     error "__cpp_lib_to_chars should be defined in c++17"
@@ -2136,6 +2149,13 @@
 #   endif
 # endif
 
+# ifndef __cpp_lib_to_array
+#   error "__cpp_lib_to_array should be defined in c++2a"
+# endif
+# if __cpp_lib_to_array != 201907L
+#   error "__cpp_lib_to_array should have the value 201907L in c++2a"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_to_chars
 #     error "__cpp_lib_to_chars should be defined in c++2a"
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
@@ -586,6 +586,12 @@ def add_version_header(tc):
    },
    "headers": ["bit"],
    },
+  {"name": "__cpp_lib_to_array",
+   "values": {
+     "c++2a": 201907L,
+   },
+   "headers": ["array"],
+   },
 ]], key=lambda tc: tc["name"])
 
 def get_std_dialects():
diff --git a/libcxx/www/cxx2a_status.html b/libcxx/www/cxx2a_status.html
@@ -157,7 +157,7 @@ <h3>Paper Status</h3>
 	<tr><td><a href="https://wg21.link/P1464R1">P1464R1</a></td><td>LWG</td><td>Mandating the Standard Library: Clause 22 - Iterators library</td><td>Kona</td><td>Complete</td><td>9.0</td></tr>
 
  	<tr><td></td><td></td><td></td><td></td><td></td><td></td></tr>
-	<tr><td><a href="https://wg21.link/P0325">P0325</a></td><td>LWG</td><td>to_array from LFTS with updates</td><td>Cologne</td><td></td><td></td></tr>
+	<tr><td><a href="https://wg21.link/P0325">P0325</a></td><td>LWG</td><td>to_array from LFTS with updates</td><td>Cologne</td><td>Complete</td><td>10.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0408">P0408</a></td><td>LWG</td><td>Efficient Access to basic_stringbuf ’s Buffer</td><td>Cologne</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0466">P0466</a></td><td>LWG</td><td>Layout-compatibility and Pointer-interconvertibility Traits</td><td>Cologne</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0553">P0553</a></td><td>LWG</td><td>Bit operations</td><td>Cologne</td><td>Complete</td><td>9.0</td></tr>
