[libc++][memory] P2652R2: Disallow Specialization of `allocator_traits` #79978

H-G-Hristov · 2024-01-30T10:43:42Z

Implements P2652R2 https://wg21.link/P2652R2:

github-actions · 2024-01-30T10:46:02Z

✅ With the latest revision this PR passed the Python code formatter.

Implements P2652R2 <https://wg21.link/P2652R2>: - https://eel.is/c++draft/allocator.requirements.general - https://eel.is/c++draft/memory.syn - https://eel.is/c++draft/allocator.traits.general - https://eel.is/c++draft/allocator.traits.members - https://eel.is/c++draft/diff.cpp20.concepts - https://eel.is/c++draft/diff.cpp20.utilities

llvmbot · 2024-01-30T18:09:46Z

@llvm/pr-subscribers-libcxx

Author: Hristo Hristov (H-G-Hristov)

Changes

Implements P2652R2 <https://wg21.link/P2652R2>:

Patch is 26.95 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/79978.diff

23 Files Affected:

(modified) libcxx/docs/FeatureTestMacroTable.rst (+1-1)
(modified) libcxx/docs/ReleaseNotes/19.rst (+5-1)
(modified) libcxx/docs/Status/Cxx23Papers.csv (+1-1)
(modified) libcxx/docs/Status/Cxx2cIssues.csv (+1-1)
(modified) libcxx/include/CMakeLists.txt (+1)
(modified) libcxx/include/__format/buffer.h (+1)
(modified) libcxx/include/__memory/allocate_at_least.h (+9-6)
(added) libcxx/include/__memory/allocation_result.h (+45)
(modified) libcxx/include/__memory/allocator.h (+1)
(modified) libcxx/include/__memory/allocator_traits.h (+13)
(modified) libcxx/include/__split_buffer (+1)
(modified) libcxx/include/libcxx.imp (+1)
(modified) libcxx/include/memory (+8-4)
(modified) libcxx/include/module.modulemap.in (+1)
(modified) libcxx/include/string (+10-7)
(modified) libcxx/include/vector (+1)
(modified) libcxx/include/version (+2-2)
(modified) libcxx/modules/std/memory.inc (+2)
(modified) libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp (+5-5)
(modified) libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp (+5-5)
(modified) libcxx/test/std/utilities/memory/allocator.traits/allocate_at_least.pass.cpp (+3-3)
(added) libcxx/test/std/utilities/memory/allocator.traits/allocator.traits.members/allocate_at_least.pass.cpp (+70)
(modified) libcxx/utils/generate_feature_test_macro_components.py (+2-2)

diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index d0d057e6bbaf0..a5c6fa22cec06 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -304,7 +304,7 @@ Status
     ---------------------------------------------------------------------
     ``__cpp_lib_adaptor_iterator_pair_constructor``     ``202106L``
     --------------------------------------------------- -----------------
-    ``__cpp_lib_allocate_at_least``                     ``202106L``
+    ``__cpp_lib_allocate_at_least``                     ``202302L``
     --------------------------------------------------- -----------------
     ``__cpp_lib_associative_heterogeneous_erasure``     *unimplemented*
     --------------------------------------------------- -----------------
diff --git a/libcxx/docs/ReleaseNotes/19.rst b/libcxx/docs/ReleaseNotes/19.rst
index e96abc72c1648..dee9ebc8b8c33 100644
--- a/libcxx/docs/ReleaseNotes/19.rst
+++ b/libcxx/docs/ReleaseNotes/19.rst
@@ -37,12 +37,16 @@ What's New in Libc++ 19.0.0?
 
 Implemented Papers
 ------------------
+
 - P2637R3 - Member ``visit``
+- P2652R2 - Disallow User Specialization of ``allocator_traits``
 
 
 Improvements and New Features
 -----------------------------
-TODO
+
+- The ``_LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS`` macro has been added to re-enable user specialization
+  of `allocator_traits`, which was disabled by `P2652R2 <https://wg21.link/P2652R2>`_.
 
 
 Deprecations and Removals
diff --git a/libcxx/docs/Status/Cxx23Papers.csv b/libcxx/docs/Status/Cxx23Papers.csv
index ebab3ef735b61..eb415ed8c031f 100644
--- a/libcxx/docs/Status/Cxx23Papers.csv
+++ b/libcxx/docs/Status/Cxx23Papers.csv
@@ -115,7 +115,7 @@
 "`P2679R2 <https://wg21.link/P2679R2>`__","LWG", "Fixing ``std::start_lifetime_as`` for arrays","February 2023","","",""
 "`P2674R1 <https://wg21.link/P2674R1>`__","LWG", "A trait for implicit lifetime types","February 2023","","",""
 "`P2655R3 <https://wg21.link/P2655R3>`__","LWG", "``common_reference_t`` of ``reference_wrapper`` Should Be a Reference Type","February 2023","","",""
-"`P2652R2 <https://wg21.link/P2652R2>`__","LWG", "Disallow User Specialization of ``allocator_traits``","February 2023","","",""
+"`P2652R2 <https://wg21.link/P2652R2>`__","LWG", "Disallow User Specialization of ``allocator_traits``","February 2023","|Complete|","19.0",""
 "`P2787R1 <https://wg21.link/P2787R1>`__","LWG", "``pmr::generator`` - Promise Types are not Values","February 2023","","",""
 "`P2614R2 <https://wg21.link/P2614R2>`__","LWG", "Deprecate ``numeric_limits::has_denorm``","February 2023","|Complete|","18.0",""
 "`P2588R3 <https://wg21.link/P2588R3>`__","LWG", "``barrier``’s phase completion guarantees","February 2023","","",""
diff --git a/libcxx/docs/Status/Cxx2cIssues.csv b/libcxx/docs/Status/Cxx2cIssues.csv
index b69b094832541..58e995809777c 100644
--- a/libcxx/docs/Status/Cxx2cIssues.csv
+++ b/libcxx/docs/Status/Cxx2cIssues.csv
@@ -2,7 +2,7 @@
 "`2994 <https://wg21.link/LWG2994>`__","Needless UB for ``basic_string`` and ``basic_string_view``","Varna June 2023","|Complete|","5.0",""
 "`3884 <https://wg21.link/LWG3884>`__","``flat_foo`` is missing allocator-extended copy/move constructors","Varna June 2023","","","|flat_containers|"
 "`3885 <https://wg21.link/LWG3885>`__","``op`` should be in [zombie.names]","Varna June 2023","|Nothing To Do|","",""
-"`3887 <https://wg21.link/LWG3887>`__","Version macro for ``allocate_at_least``","Varna June 2023","","",""
+"`3887 <https://wg21.link/LWG3887>`__","Version macro for ``allocate_at_least``","Varna June 2023","|Complete|","19.0",""
 "`3893 <https://wg21.link/LWG3893>`__","LWG 3661 broke ``atomic<shared_ptr<T>> a; a = nullptr;``","Varna June 2023","","",""
 "`3894 <https://wg21.link/LWG3894>`__","``generator::promise_type::yield_value(ranges::elements_of<Rng, Alloc>)`` should not be ``noexcept``","Varna June 2023","","",""
 "`3903 <https://wg21.link/LWG3903>`__","span destructor is redundantly noexcept","Varna June 2023","|Complete|","7.0",""
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 0bb23710cae84..e2ca533510aa3 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -521,6 +521,7 @@ set(files
   __memory/aligned_alloc.h
   __memory/allocate_at_least.h
   __memory/allocation_guard.h
+  __memory/allocation_result.h
   __memory/allocator.h
   __memory/allocator_arg_t.h
   __memory/allocator_destructor.h
diff --git a/libcxx/include/__format/buffer.h b/libcxx/include/__format/buffer.h
index 8598f0a1c0395..9b18e01aea8bb 100644
--- a/libcxx/include/__format/buffer.h
+++ b/libcxx/include/__format/buffer.h
@@ -29,6 +29,7 @@
 #include <__iterator/wrap_iter.h>
 #include <__memory/addressof.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/construct_at.h>
 #include <__memory/ranges_construct_at.h>
diff --git a/libcxx/include/__memory/allocate_at_least.h b/libcxx/include/__memory/allocate_at_least.h
index 05cbdee828839..3aa99ae2a05a7 100644
--- a/libcxx/include/__memory/allocate_at_least.h
+++ b/libcxx/include/__memory/allocate_at_least.h
@@ -10,6 +10,7 @@
 #define _LIBCPP___MEMORY_ALLOCATE_AT_LEAST_H
 
 #include <__config>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator_traits.h>
 #include <cstddef>
 
@@ -20,13 +21,8 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 23
-template <class _Pointer>
-struct allocation_result {
-  _Pointer ptr;
-  size_t count;
-};
-_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(allocation_result);
 
+#  ifdef _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
 template <class _Alloc>
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr allocation_result<typename allocator_traits<_Alloc>::pointer>
 allocate_at_least(_Alloc& __alloc, size_t __n) {
@@ -36,12 +32,19 @@ allocate_at_least(_Alloc& __alloc, size_t __n) {
     return {__alloc.allocate(__n), __n};
   }
 }
+#  endif // _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
 
 template <class _Alloc>
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto __allocate_at_least(_Alloc& __alloc, size_t __n) {
+#  ifndef _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
+  return std::allocator_traits<_Alloc>::allocate_at_least(__alloc, __n);
+#  else
   return std::allocate_at_least(__alloc, __n);
+#  endif
 }
+
 #else
+
 template <class _Pointer>
 struct __allocation_result {
   _Pointer ptr;
diff --git a/libcxx/include/__memory/allocation_result.h b/libcxx/include/__memory/allocation_result.h
new file mode 100644
index 0000000000000..c0e594bc34a14
--- /dev/null
+++ b/libcxx/include/__memory/allocation_result.h
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MEMORY_ALLOCATION_RESULT_H
+#define _LIBCPP___MEMORY_ALLOCATION_RESULT_H
+
+#include <__config>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+#  ifndef _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
+
+template <class _Pointer, class _SizeType = size_t>
+struct allocation_result {
+  _Pointer ptr;
+  _SizeType count;
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(allocation_result);
+
+#  else
+
+template <class _Pointer>
+struct allocation_result {
+  _Pointer ptr;
+  size_t count;
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(allocation_result);
+
+#  endif // _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
+#endif   // _LIBCPP_STD_VER
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___MEMORY_ALLOCATION_RESULT_H
diff --git a/libcxx/include/__memory/allocator.h b/libcxx/include/__memory/allocator.h
index 4e6303914c38a..b8cf33d4b1d46 100644
--- a/libcxx/include/__memory/allocator.h
+++ b/libcxx/include/__memory/allocator.h
@@ -13,6 +13,7 @@
 #include <__config>
 #include <__memory/addressof.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator_traits.h>
 #include <__type_traits/is_constant_evaluated.h>
 #include <__type_traits/is_same.h>
diff --git a/libcxx/include/__memory/allocator_traits.h b/libcxx/include/__memory/allocator_traits.h
index c4482872ea810..0cb699c2e7520 100644
--- a/libcxx/include/__memory/allocator_traits.h
+++ b/libcxx/include/__memory/allocator_traits.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___MEMORY_ALLOCATOR_TRAITS_H
 
 #include <__config>
+#include <__memory/allocation_result.h>
 #include <__memory/construct_at.h>
 #include <__memory/pointer_traits.h>
 #include <__type_traits/enable_if.h>
@@ -284,6 +285,18 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits {
     return __a.allocate(__n);
   }
 
+#if _LIBCPP_STD_VER >= 23 && !defined(_LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS)
+  template <class _Ap = _Alloc>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI static constexpr allocation_result<pointer, size_type>
+  allocate_at_least(_Ap& __alloc, size_type __n) {
+    if constexpr (requires { __alloc.allocate_at_least(__n); }) {
+      return __alloc.allocate_at_least(__n);
+    } else {
+      return {__alloc.allocate(__n), __n};
+    }
+  }
+#endif
+
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static void
   deallocate(allocator_type& __a, pointer __p, size_type __n) _NOEXCEPT {
     __a.deallocate(__p, __n);
diff --git a/libcxx/include/__split_buffer b/libcxx/include/__split_buffer
index aaf955685d2d3..c12272e57d857 100644
--- a/libcxx/include/__split_buffer
+++ b/libcxx/include/__split_buffer
@@ -18,6 +18,7 @@
 #include <__iterator/iterator_traits.h>
 #include <__iterator/move_iterator.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/compressed_pair.h>
diff --git a/libcxx/include/libcxx.imp b/libcxx/include/libcxx.imp
index 13c0dfeb2bc98..341c2c61f25cf 100644
--- a/libcxx/include/libcxx.imp
+++ b/libcxx/include/libcxx.imp
@@ -512,6 +512,7 @@
   { include: [ "<__memory/aligned_alloc.h>", "private", "<memory>", "public" ] },
   { include: [ "<__memory/allocate_at_least.h>", "private", "<memory>", "public" ] },
   { include: [ "<__memory/allocation_guard.h>", "private", "<memory>", "public" ] },
+  { include: [ "<__memory/allocation_result.h>", "private", "<memory>", "public" ] },
   { include: [ "<__memory/allocator.h>", "private", "<memory>", "public" ] },
   { include: [ "<__memory/allocator_arg_t.h>", "private", "<memory>", "public" ] },
   { include: [ "<__memory/allocator_destructor.h>", "private", "<memory>", "public" ] },
diff --git a/libcxx/include/memory b/libcxx/include/memory
index 19c11ee949872..c57f5dd9d3c7b 100644
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -88,6 +88,9 @@ struct allocator_traits
     static pointer allocate(allocator_type& a, size_type n);                          // constexpr and [[nodiscard]] in C++20
     static pointer allocate(allocator_type& a, size_type n, const_void_pointer hint); // constexpr and [[nodiscard]] in C++20
 
+    [[nodiscard]] static constexpr allocation_result<pointer, size_type>
+      allocate_at_least(Alloc& a, size_type n); // Since C++23
+
     static void deallocate(allocator_type& a, pointer p, size_type n) noexcept; // constexpr in C++20
 
     template <class T, class... Args>
@@ -100,15 +103,15 @@ struct allocator_traits
     static allocator_type select_on_container_copy_construction(const allocator_type& a); // constexpr in C++20
 };
 
-template<class Pointer>
+template<class Pointer, class SizeType = size_t>
 struct allocation_result {
     Pointer ptr;
-    size_t count;
-}; // since C++23
+    SizeType count;
+}; // since C++23, modified C++23
 
 template<class Allocator>
 [[nodiscard]] constexpr allocation_result<typename allocator_traits<Allocator>::pointer>
-    allocate_at_least(Allocator& a, size_t n); // since C++23
+    allocate_at_least(Allocator& a, size_t n); // Since C++23, removed C++23
 
 template <>
 class allocator<void> // removed in C++20
@@ -924,6 +927,7 @@ template<size_t N, class T>
 #include <__memory/align.h>
 #include <__memory/allocate_at_least.h>
 #include <__memory/allocation_guard.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator.h>
 #include <__memory/allocator_arg_t.h>
 #include <__memory/allocator_traits.h>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 207b44b6444bf..ceb576b662612 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1499,6 +1499,7 @@ module std_private_memory_align                           [system] { header "__m
 module std_private_memory_aligned_alloc                   [system] { header "__memory/aligned_alloc.h" }
 module std_private_memory_allocate_at_least               [system] { header "__memory/allocate_at_least.h" }
 module std_private_memory_allocation_guard                [system] { header "__memory/allocation_guard.h" }
+module std_private_memory_allocation_result               [system] { header "__memory/allocation_result.h" }
 module std_private_memory_allocator                       [system] { header "__memory/allocator.h" }
 module std_private_memory_allocator_arg_t                 [system] { header "__memory/allocator_arg_t.h" }
 module std_private_memory_allocator_destructor            [system] { header "__memory/allocator_destructor.h" }
diff --git a/libcxx/include/string b/libcxx/include/string
index efdff3dd42da0..a8a8469751c7e 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -585,6 +585,7 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
 #include <__iterator/wrap_iter.h>
 #include <__memory/addressof.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/compressed_pair.h>
@@ -922,7 +923,11 @@ public:
       // Turning off ASan instrumentation for variable initialization with _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS
       // does not work consistently during initialization of __r_, so we instead unpoison __str's memory manually first.
       // __str's memory needs to be unpoisoned only in the case where it's a short string.
-      : __r_([](basic_string &__s) -> decltype(__s.__r_)&& { if(!__s.__is_long()) __s.__annotate_delete(); return std::move(__s.__r_); }(__str)) {
+      : __r_([](basic_string& __s) -> decltype(__s.__r_)&& {
+          if (!__s.__is_long())
+            __s.__annotate_delete();
+          return std::move(__s.__r_);
+        }(__str)) {
     __str.__r_.first() = __rep();
     __str.__annotate_new(0);
     if (!__is_long())
@@ -1902,7 +1907,7 @@ private:
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __annotate_new(size_type __current_size) const _NOEXCEPT {
-    (void) __current_size;
+    (void)__current_size;
 #if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
     if (!__libcpp_is_constant_evaluated() && (__asan_short_string_is_annotated() || __is_long()))
       __annotate_contiguous_container(data() + capacity() + 1, data() + __current_size + 1);
@@ -1917,7 +1922,7 @@ private:
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __annotate_increase(size_type __n) const _NOEXCEPT {
-    (void) __n;
+    (void)__n;
 #if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
     if (!__libcpp_is_constant_evaluated() && (__asan_short_string_is_annotated() || __is_long()))
       __annotate_contiguous_container(data() + size() + 1, data() + size() + 1 + __n);
@@ -1925,7 +1930,7 @@ private:
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __annotate_shrink(size_type __old_size) const _NOEXCEPT {
-    (void) __old_size;
+    (void)__old_size;
 #if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
     if (!__libcpp_is_constant_evaluated() && (__asan_short_string_is_annotated() || __is_long()))
       __annotate_contiguous_container(data() + __old_size + 1, data() + size() + 1);
@@ -1936,9 +1941,7 @@ private:
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 size_type __align_it(size_type __s) _NOEXCEPT {
     return (__s + (__a - 1)) & ~(__a - 1);
   }
-  enum {
-    __alignment = 8
-  };
+  enum { __alignment = 8 };
   static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 size_type __recommend(size_type __s) _NOEXCEPT {
     if (__s < __min_cap) {
       return static_cast<size_type>(__min_cap) - 1;
diff --git a/libcxx/include/vector b/libcxx/include/vector
index f24d2c4b9c6ac..66aa25a70ce0b 100644
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -332,6 +332,7 @@ template<class T, class charT> requires is-vector-bool-reference<T> // Since C++
 #include <__iterator/wrap_iter.h>
 #include <__memory/addressof.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/allocation_result.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/pointer_traits.h>
 #include <__memory/swap_allocator.h>
diff --git a/libcxx/include/version b/libcxx/include/version
index 9e26da8c1b242..e4dbb7bdd5fc2 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -16,7 +16,7 @@
 Macro name                                              Value   Headers
 __cpp_lib_adaptor_iterator_pair_constructor             202106L <queue> <stack>
 __cpp_lib_addressof_constexpr                           201603L <memory>
-__cpp_lib_allocate_at_least                             202106L <memory>
+__cpp_lib_allocate_at_least                             202302L <memory>
 __cpp_lib_allocator_traits_is_always_equal              201411L <deque> <forward_list> <list>
                                                                 <map> <memory> <scoped_allocator>
                                                                 <set> <string> <unordered_map>
@@ -433,7 +433,7 @@ __cpp_lib_within_lifetime                               202306L <type_traits>
 
 #if _LIBCPP_STD_VER >= 23
 # define __cpp_lib_adaptor_iterator_pair_constructor    202106L
-# define __cpp_lib_allocate_at_least                    202106L
+# define __cpp_lib_allocate_at_least                    202302L
 // # define __cpp_lib_associative_heterogeneous_erasure    202110L
 // # define __cpp_lib_bind_back                            202202L
 # define __cpp_lib_byteswap                             202110L
diff --git a/libcxx/modules/std/memory.inc b/libcxx/modules/std/memory.inc
index ef89845457fbb..a930119462cdc 100644
--- a/libcxx/modules/std/memory.inc
+++ b/libcxx/modules/std/memory.inc
@@ -44,7 +44,9 @@ export namespace std {
 #if _LIBCPP_STD_VER >= 23
   using std::allocation_result;
 
+#  ifdef _LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF_ALLOCATOR_TRAITS
   using std::allocate_at_least;
+#  endif
 #endif
 
   // [default.allocator], the default allocator
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
index b1f6c76d84739..45d9271faa578 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
@@ -17,7 +17,7 @@
 
 /*  Constant                                      Value
     __cpp_lib_addressof_constexpr                 201603L [C++17]
-    __cpp_lib_allocate_at_least                   202106L [C++23]
+    __cpp_lib_allocate_at_least                   202302L [C++23]
     __cpp_lib_allocator_traits_is_always_equal    201411L [C++17]
     __cpp_lib_assume_aligned                      201811L [C++20]
     __cpp_lib_atomic_value_initialization         201911L [C++20]
@@ -432,8 +432,8 @@
 # ifndef __cpp_lib_allocate_at_least
 #   error "__cpp_lib_allocate_at_least should be defined in c++23"
 # endif
-# if __cpp_lib_allocate_at_lea...
[truncated]

philnik777

Other than removing the flag this looks pretty good.

libcxx/docs/ReleaseNotes/19.rst

…_ALLOCATOR_TRAITS` Since this features was introduced in C++23 there is no need for a re-enable flag and the redundant code was removed.

…ion-of-allocator_traits

github-actions · 2024-01-31T07:05:36Z

✅ With the latest revision this PR passed the C/C++ code formatter.

…ion-of-allocator_traits

philnik777 · 2024-01-31T10:29:29Z

libcxx/include/__memory/allocation_result.h

+
+#if _LIBCPP_STD_VER >= 23
+
+template <class _Pointer, class _SizeType = size_t>


Why did you move this to it's own header?

Originally to unbreak a circular dependency.

I guess this can be folded into allocator_traits.h now.

libcxx/utils/generate_feature_test_macro_components.py

…ion-of-allocator_traits

philnik777

Thanks! LGTM.

…s` (llvm#79978) Implements P2652R2 <https://wg21.link/P2652R2>: - https://eel.is/c++draft/allocator.requirements.general - https://eel.is/c++draft/memory.syn - https://eel.is/c++draft/allocator.traits.general - https://eel.is/c++draft/allocator.traits.members - https://eel.is/c++draft/diff.cpp20.concepts - https://eel.is/c++draft/diff.cpp20.utilities --------- Co-authored-by: Zingam <[email protected]>

H-G-Hristov force-pushed the hgh/libcxx/P2652R2-Disallow-User-Specialization-of-allocator_traits branch 4 times, most recently from ba7820d to ce6a3f5 Compare January 30, 2024 13:16

H-G-Hristov changed the title ~~[libc++][memory] P2652R2 - Disallow Specialization of allocator_traits~~ [libc++][memory] P2652R2: Disallow Specialization of allocator_traits Jan 30, 2024

H-G-Hristov force-pushed the hgh/libcxx/P2652R2-Disallow-User-Specialization-of-allocator_traits branch 3 times, most recently from 64b9d9c to 945eb13 Compare January 30, 2024 14:13

H-G-Hristov force-pushed the hgh/libcxx/P2652R2-Disallow-User-Specialization-of-allocator_traits branch from 945eb13 to c2b9a24 Compare January 30, 2024 14:14

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H-G-Hristov added 2 commits January 31, 2024 08:59

Removed redundant fllag: `_LIBCPP_ENABLE_CXX23_USER_SPECIALIZATION_OF…

252f67b

…_ALLOCATOR_TRAITS` Since this features was introduced in C++23 there is no need for a re-enable flag and the redundant code was removed.

Merge branch 'main' into hgh/libcxx/P2652R2-Disallow-User-Specializat…

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…ion-of-allocator_traits

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Fixed formatting

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Merge branch 'main' into hgh/libcxx/P2652R2-Disallow-User-Specializat…

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…ion-of-allocator_traits

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Update libcxx/utils/generate_feature_test_macro_components.py

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…ion-of-allocator_traits

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…ion-of-allocator_traits

H-G-Hristov requested a review from philnik777 January 31, 2024 18:50

H-G-Hristov added 4 commits January 31, 2024 20:54

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Merge branch 'main' into hgh/libcxx/P2652R2-Disallow-User-Specializat…

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…ion-of-allocator_traits

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[libc++][memory] P2652R2: Disallow Specialization of `allocator_traits` #79978

[libc++][memory] P2652R2: Disallow Specialization of `allocator_traits` #79978

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		#if _LIBCPP_STD_VER >= 23

		template <class _Pointer, class _SizeType = size_t>

[libc++][memory] P2652R2: Disallow Specialization of allocator_traits #79978

[libc++][memory] P2652R2: Disallow Specialization of allocator_traits #79978

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[libc++][memory] P2652R2: Disallow Specialization of `allocator_traits` #79978

[libc++][memory] P2652R2: Disallow Specialization of `allocator_traits` #79978

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