P0784R7 Library Support For More constexpr Containers (#1369)

Co-authored-by: Adam Bucior <35536269+AdamBucior@users.noreply.github.com> Co-authored-by: Curtis Jacques Bezault <curtbezault@gmail.com> Co-authored-by: Michael Schellenberger Costa <mschellenbergercosta@gmail.com> Co-authored-by: mnatsuhara <46756417+mnatsuhara@users.noreply.github.com> Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>
microsoft · Jan 8, 2021 · 2561974 · 2561974
1 parent 54cce5e
commit 2561974
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Showing 8 changed files with 472 additions and 118 deletions.
diff --git a/stl/inc/memory b/stl/inc/memory
@@ -496,22 +496,7 @@ namespace ranges {
     };
 
     inline constexpr _Uninitialized_fill_n_fn uninitialized_fill_n{_Not_quite_object::_Construct_tag{}};
-} // namespace ranges
-#endif // __cpp_lib_concepts
-
-// FUNCTION TEMPLATE construct_at
-#if _HAS_CXX20
-template <class _Ty, class... _Types>
-_CONSTEXPR20_DYNALLOC auto construct_at(_Ty* const _Location, _Types&&... _Args) noexcept(
-    noexcept(::new (const_cast<void*>(static_cast<const volatile void*>(_Location)))
-            _Ty(_STD forward<_Types>(_Args)...))) // strengthened
-    -> decltype(
-        ::new (const_cast<void*>(static_cast<const volatile void*>(_Location))) _Ty(_STD forward<_Types>(_Args)...)) {
-    return ::new (const_cast<void*>(static_cast<const volatile void*>(_Location))) _Ty(_STD forward<_Types>(_Args)...);
-}
 
-#ifdef __cpp_lib_concepts
-namespace ranges {
     // VARIABLE ranges::construct_at
     class _Construct_at_fn : private _Not_quite_object {
     public:
@@ -532,26 +517,7 @@ namespace ranges {
     };
 
     inline constexpr _Construct_at_fn construct_at{_Not_quite_object::_Construct_tag{}};
-} // namespace ranges
-#endif // __cpp_lib_concepts
-#endif // _HAS_CXX20
 
-#if _HAS_CXX17
-// FUNCTION TEMPLATE destroy_at
-template <class _Ty>
-_CONSTEXPR20_DYNALLOC void destroy_at(_Ty* const _Location) noexcept /* strengthened */ {
-#if _HAS_CXX20
-    if constexpr (is_array_v<_Ty>) {
-        _Destroy_range(_STD begin(*_Location), _STD end(*_Location));
-    } else
-#endif // _HAS_CXX20
-    {
-        _Location->~_Ty();
-    }
-}
-
-#ifdef __cpp_lib_concepts
-namespace ranges {
     // VARIABLE ranges::destroy_at
     // clang-format off
     template <_No_throw_input_iterator _It, _No_throw_sentinel_for<_It> _Se>
@@ -577,9 +543,11 @@ namespace ranges {
 } // namespace ranges
 #endif // __cpp_lib_concepts
 
+#if _HAS_CXX17
 // FUNCTION TEMPLATE destroy
 template <class _NoThrowFwdIt>
-void destroy(const _NoThrowFwdIt _First, const _NoThrowFwdIt _Last) { // destroy all elements in [_First, _Last)
+_CONSTEXPR20_DYNALLOC void destroy(const _NoThrowFwdIt _First, const _NoThrowFwdIt _Last) {
+    // destroy all elements in [_First, _Last)
     _Adl_verify_range(_First, _Last);
     _Destroy_range(_Get_unwrapped(_First), _Get_unwrapped(_Last));
 }
@@ -606,7 +574,7 @@ namespace ranges {
         // clang-format off
         template <_No_throw_input_iterator _It, _No_throw_sentinel_for<_It> _Se>
             requires destructible<iter_value_t<_It>>
-        /* _CONSTEXPR20_DYNALLOC */ _It operator()(_It _First, _Se _Last) const noexcept {
+        _CONSTEXPR20_DYNALLOC _It operator()(_It _First, _Se _Last) const noexcept {
             // clang-format on
             _Adl_verify_range(_First, _Last);
             _Seek_wrapped(_First,
@@ -617,7 +585,7 @@ namespace ranges {
         // clang-format off
         template <_No_throw_input_range _Rng>
             requires destructible<range_value_t<_Rng>>
-        /* _CONSTEXPR20_DYNALLOC */ borrowed_iterator_t<_Rng> operator()(_Rng&& _Range) const noexcept {
+        _CONSTEXPR20_DYNALLOC borrowed_iterator_t<_Rng> operator()(_Rng&& _Range) const noexcept {
             // clang-format on
             auto _First = _RANGES begin(_Range);
             _Seek_wrapped(_First, _RANGES _Destroy_unchecked(_Get_unwrapped(_STD move(_First)), _Uend(_Range)));
@@ -631,7 +599,7 @@ namespace ranges {
 
 // FUNCTION TEMPLATE destroy_n
 template <class _NoThrowFwdIt, class _Diff>
-_NoThrowFwdIt destroy_n(_NoThrowFwdIt _First, const _Diff _Count_raw) {
+_CONSTEXPR20_DYNALLOC _NoThrowFwdIt destroy_n(_NoThrowFwdIt _First, const _Diff _Count_raw) {
     // destroy all elements in [_First, _First + _Count)
     _Algorithm_int_t<_Diff> _Count = _Count_raw;
     if (_Count <= 0) {
@@ -661,8 +629,9 @@ namespace ranges {
         // clang-format off
         template <_No_throw_input_iterator _It>
             requires destructible<iter_value_t<_It>>
-        /* _CONSTEXPR20_DYNALLOC */ _It operator()(_It _First, const iter_difference_t<_It> _Count) const noexcept {
+        _CONSTEXPR20_DYNALLOC _It operator()(_It _First, const iter_difference_t<_It> _Count_raw) const noexcept {
             // clang-format on
+            _Algorithm_int_t<iter_difference_t<_It>> _Count = _Count_raw;
             if (_Count <= 0) {
                 return _First;
             }