[libc++] Deprecated shared_ptr Atomic Access APIs as per P0718R2 & Implemented P2869R3: Remove Deprecated shared_ptr Atomic Access APIs from C++26

libcxx/docs/ReleaseNotes/19.rst

@@ -43,6 +43,7 @@ Implemented Papers
 - P2819R2 - Add ``tuple`` protocol to ``complex``
 - P2495R3 - Interfacing ``stringstream``\s with ``string_view``
 - P2867R2 - Remove Deprecated ``strstream``\s From C++26
+- P2869R4 - Remove Deprecated ``shared_ptr`` Atomic Access APIs from C++26
 - P2872R3 - Remove ``wstring_convert`` From C++26
 - P3142R0 - Printing Blank Lines with ``println`` (as DR against C++23)
 - P2302R4 - ``std::ranges::contains``
@@ -63,6 +64,9 @@ Improvements and New Features
 
 - The ``_LIBCPP_ENABLE_CXX26_REMOVED_STRSTREAM`` macro has been added to make the declarations in ``<strstream>`` available.
 
+- The ``_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS`` macro has been added to make the declarations in ``<memory>``
+  available.
+
 - The ``_LIBCPP_ENABLE_CXX26_REMOVED_WSTRING_CONVERT`` macro has been added to make the declarations in ``<locale>``
   available.
 

libcxx/docs/Status/Cxx20.rst

@@ -59,6 +59,8 @@ Paper Status
       * ``GPS clock`` not done
       * ``UTC clock`` not done
 
+   .. [#note-P0718] P0718: Implemented deprecation of ``shared_ptr`` atomic access APIs only.
+
 .. _issues-status-cxx20:
 
 Library Working Group Issues Status

libcxx/docs/Status/Cxx20Papers.csv

@@ -12,7 +12,7 @@
 "`P0600R1 <https://wg21.link/P0600R1>`__","LWG","nodiscard in the Library","Albuquerque","|Complete|","16.0"
 "`P0616R0 <https://wg21.link/P0616R0>`__","LWG","de-pessimize legacy <numeric> algorithms with std::move","Albuquerque","|Complete|","12.0"
 "`P0653R2 <https://wg21.link/P0653R2>`__","LWG","Utility to convert a pointer to a raw pointer","Albuquerque","|Complete|","6.0"
-"`P0718R2 <https://wg21.link/P0718R2>`__","LWG","Atomic shared_ptr","Albuquerque","",""
+"`P0718R2 <https://wg21.link/P0718R2>`__","LWG","Atomic shared_ptr","Albuquerque","|Partial| [#note-P0718]_",""
 "`P0767R1 <https://wg21.link/P0767R1>`__","CWG","Deprecate POD","Albuquerque","|Complete|","7.0"
 "`P0768R1 <https://wg21.link/P0768R1>`__","CWG","Library Support for the Spaceship (Comparison) Operator","Albuquerque","|Complete|",""
 "`P0777R1 <https://wg21.link/P0777R1>`__","LWG","Treating Unnecessary ``decay``\ ","Albuquerque","|Complete|","7.0"

libcxx/docs/Status/Cxx2cPapers.csv

@@ -48,7 +48,7 @@
 "","","","","","",""
 "`P2875R4 <https://wg21.link/P2875R4>`__","LWG","Undeprecate ``polymorphic_allocator::destroy`` for C++26","Tokyo March 2024","|Complete|","15.0",""
 "`P2867R2 <https://wg21.link/P2867R2>`__","LWG","Remove Deprecated ``strstreams`` From C++26","Tokyo March 2024","|Complete|","19.0",""
-"`P2869R4 <https://wg21.link/P2869R4>`__","LWG","Remove Deprecated ``shared_ptr`` Atomic Access APIs from C++26","Tokyo March 2024","","",""
+"`P2869R4 <https://wg21.link/P2869R4>`__","LWG","Remove Deprecated ``shared_ptr`` Atomic Access APIs from C++26","Tokyo March 2024","|Complete|","19.0",""
 "`P2872R3 <https://wg21.link/P2872R3>`__","LWG","Remove ``wstring_convert`` From C++26","Tokyo March 2024","|Complete|","19.0",""
 "`P3107R5 <https://wg21.link/P3107R5>`__","LWG","Permit an efficient implementation of ``std::print``","Tokyo March 2024","","","|format| |DR|"
 "`P3142R0 <https://wg21.link/P3142R0>`__","LWG","Printing Blank Lines with ``println``","Tokyo March 2024","|Complete|","19.0","|format|"

libcxx/docs/UsingLibcxx.rst

@@ -277,10 +277,14 @@ C++26 Specific Configuration Macros
 **_LIBCPP_ENABLE_CXX26_REMOVED_STRSTREAM**:
   This macro is used to re-enable all named declarations in ``<strstream>``.
 
+**_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS**:
+  This macro is used to re-enable all ``shared_ptr`` atomic access APIs in ``<memory>``.
+
 **_LIBCPP_ENABLE_CXX26_REMOVED_WSTRING_CONVERT**:
   This macro is used to re-enable the ``wstring_convert`` and ``wbuffer_convert``
   in ``<locale>``.
 
+
 Libc++ Extensions
 =================
 

libcxx/include/__memory/shared_ptr.h

@@ -1580,13 +1580,15 @@ class _LIBCPP_EXPORTED_FROM_ABI __sp_mut {
 
 _LIBCPP_EXPORTED_FROM_ABI __sp_mut& __get_sp_mut(const void*);
 
+#  if _LIBCPP_STD_VER < 26 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS)
+
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI bool atomic_is_lock_free(const shared_ptr<_Tp>*) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI bool atomic_is_lock_free(const shared_ptr<_Tp>*) {
   return false;
 }
 
 template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) {
   __sp_mut& __m = std::__get_sp_mut(__p);
   __m.lock();
   shared_ptr<_Tp> __q = *__p;
@@ -1595,25 +1597,28 @@ _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) {
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>
+atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order) {
   return std::atomic_load(__p);
 }
 
 template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
   __sp_mut& __m = std::__get_sp_mut(__p);
   __m.lock();
   __p->swap(__r);
   __m.unlock();
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI void atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI void
+atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) {
   std::atomic_store(__p, __r);
 }
 
 template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>
+atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
   __sp_mut& __m = std::__get_sp_mut(__p);
   __m.lock();
   __p->swap(__r);
@@ -1622,13 +1627,13 @@ _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_exchange(shared_ptr<_Tp>* __p, shar
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>
 atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) {
   return std::atomic_exchange(__p, __r);
 }
 
 template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI bool
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI bool
 atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) {
   shared_ptr<_Tp> __temp;
   __sp_mut& __m = std::__get_sp_mut(__p);
@@ -1646,23 +1651,25 @@ atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, share
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI bool
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI bool
 atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) {
   return std::atomic_compare_exchange_strong(__p, __v, __w);
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_strong_explicit(
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_strong_explicit(
     shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order, memory_order) {
   return std::atomic_compare_exchange_strong(__p, __v, __w);
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_weak_explicit(
+_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_weak_explicit(
     shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order, memory_order) {
   return std::atomic_compare_exchange_weak(__p, __v, __w);
 }
 
+#  endif // _LIBCPP_STD_VER < 26 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS)
+
 #endif // !defined(_LIBCPP_HAS_NO_THREADS)
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/memory

@@ -830,34 +830,34 @@ public:
 };
 
 template<class T>
-    bool atomic_is_lock_free(const shared_ptr<T>* p);
+    bool atomic_is_lock_free(const shared_ptr<T>* p);                                     // Deprecated in C++20, removed in C++26
 template<class T>
-    shared_ptr<T> atomic_load(const shared_ptr<T>* p);
+    shared_ptr<T> atomic_load(const shared_ptr<T>* p);                                    // Deprecated in C++20, removed in C++26
 template<class T>
-    shared_ptr<T> atomic_load_explicit(const shared_ptr<T>* p, memory_order mo);
+    shared_ptr<T> atomic_load_explicit(const shared_ptr<T>* p, memory_order mo);          // Deprecated in C++20, removed in C++26
 template<class T>
-    void atomic_store(shared_ptr<T>* p, shared_ptr<T> r);
+    void atomic_store(shared_ptr<T>* p, shared_ptr<T> r);                                 // Deprecated in C++20, removed in C++26
 template<class T>
-    void atomic_store_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
+    void atomic_store_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);       // Deprecated in C++20, removed in C++26
 template<class T>
-    shared_ptr<T> atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r);
+    shared_ptr<T> atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r);                     // Deprecated in C++20, removed in C++26
 template<class T>
     shared_ptr<T>
-    atomic_exchange_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
+    atomic_exchange_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);         // Deprecated in C++20, removed in C++26
 template<class T>
     bool
-    atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
+    atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);    // Deprecated in C++20, removed in C++26
 template<class T>
     bool
-    atomic_compare_exchange_strong( shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
+    atomic_compare_exchange_strong( shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w); // Deprecated in C++20, removed in C++26
 template<class T>
     bool
-    atomic_compare_exchange_weak_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
+    atomic_compare_exchange_weak_explicit(shared_ptr<T>* p, shared_ptr<T>* v,             // Deprecated in C++20, removed in C++26
                                           shared_ptr<T> w, memory_order success,
                                           memory_order failure);
 template<class T>
     bool
-    atomic_compare_exchange_strong_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
+    atomic_compare_exchange_strong_explicit(shared_ptr<T>* p, shared_ptr<T>* v,           // Deprecated in C++20, removed in C++26
                                             shared_ptr<T> w, memory_order success,
                                             memory_order failure);
 // Hash support

libcxx/modules/std/memory.inc

@@ -190,6 +190,9 @@ export namespace std {
   //  using std::inout_ptr;
 
 #ifndef _LIBCPP_HAS_NO_THREADS
+
+#  if _LIBCPP_STD_VER < 26 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS)
+
   // [depr.util.smartptr.shared.atomic]
   using std::atomic_is_lock_free;
 
@@ -206,5 +209,8 @@ export namespace std {
   using std::atomic_compare_exchange_strong_explicit;
   using std::atomic_compare_exchange_weak;
   using std::atomic_compare_exchange_weak_explicit;
+
+#  endif // _LIBCPP_STD_VER < 26 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS)
+
 #endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std

libcxx/test/libcxx/depr/depr.util.smartptr.shared.atomic/atomic_compare_exchange_strong.depr_in_cxx20..verify.cpp

@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <memory>
+
+// shared_ptr
+
+// template <class T>
+// bool
+// atomic_compare_exchange_strong(shared_ptr<T>* p, shared_ptr<T>* v,
+//                                shared_ptr<T> w);                     // Deprecated in C++20, removed in C++26
+
+#include <atomic>
+#include <memory>
+#include <tuple>
+
+void test() {
+  std::shared_ptr<int> p(new int(4));
+  std::shared_ptr<int> v(new int(3));
+  std::shared_ptr<int> w(new int(2));
+  // expected-warning@+1 {{'atomic_compare_exchange_strong<int>' is deprecated}}
+  std::ignore = std::atomic_compare_exchange_strong(&p, &v, w);
+}

libcxx/test/libcxx/depr/depr.util.smartptr.shared.atomic/atomic_compare_exchange_strong_explicit.depr_in_cxx20.verify.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
+//
+//===----------------------------------------------------------------------===//
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <memory>
+
+// shared_ptr
+
+// template <class T>
+// bool
+// atomic_compare_exchange_strong_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
+//                                         shared_ptr<T> w, memory_order success,
+//                                         memory_order failure);                 // Deprecated in C++20, removed in C++26
+
+#include <atomic>
+#include <memory>
+#include <tuple>
+
+void test() {
+  std::shared_ptr<int> p(new int(4));
+  std::shared_ptr<int> v(new int(3));
+  std::shared_ptr<int> w(new int(2));
+  // expected-warning@+2 {{'atomic_compare_exchange_strong_explicit<int>' is deprecated}}
+  std::ignore =
+      std::atomic_compare_exchange_strong_explicit(&p, &v, w, std::memory_order_seq_cst, std::memory_order_seq_cst);
+}

libcxx/test/libcxx/depr/depr.util.smartptr.shared.atomic/atomic_compare_exchange_weak.depr_in_cxx20..verify.cpp

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <memory>
+
+// shared_ptr
+
+// template <class T>
+// bool
+// atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v,
+//                              shared_ptr<T> w);                    // Deprecated in C++20, removed in C++26
+
+#include <memory>
+#include <tuple>
+
+int main(int, char**) {
+  std::shared_ptr<int> p(new int(4));
+  std::shared_ptr<int> v(new int(3));
+  std::shared_ptr<int> w(new int(2));
+  // expected-warning@+1 {{'atomic_compare_exchange_weak<int>' is deprecated}}
+  std::ignore = std::atomic_compare_exchange_weak(&p, &v, w);
+}

libcxx/test/libcxx/depr/depr.util.smartptr.shared.atomic/atomic_compare_exchange_weak_explicit.depr_in_cxx20..verify.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
+//
+//===----------------------------------------------------------------------===//
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <memory>
+
+// shared_ptr
+
+// template <class T>
+// bool
+// atomic_compare_exchange_weak_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
+//                                       shared_ptr<T> w, memory_order success,
+//                                       memory_order failure);                 // Deprecated in C++20, removed in C++26
+
+#include <atomic>
+#include <memory>
+#include <tuple>
+
+void test() {
+  std::shared_ptr<int> p(new int(4));
+  std::shared_ptr<int> v(new int(3));
+  std::shared_ptr<int> w(new int(2));
+  // expected-warning@+2 {{'atomic_compare_exchange_weak_explicit<int>' is deprecated}}
+  std::ignore =
+      std::atomic_compare_exchange_weak_explicit(&p, &v, w, std::memory_order_seq_cst, std::memory_order_seq_cst);
+}

libcxx/test/libcxx/depr/depr.util.smartptr.shared.atomic/atomic_exchange.depr_in_cxx20..verify.cpp

@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX26_REMOVED_SHARED_PTR_ATOMICS
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <memory>
+
+// shared_ptr
+
+// template <class T>
+// shared_ptr<T>
+// atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r)   // Deprecated in C++20, removed in C++26
+
+#include <memory>
+#include <tuple>
+
+void test() {
+  std::shared_ptr<int> p(new int(4));
+  std::shared_ptr<int> r(new int(3));
+  // expected-warning@+1 {{'atomic_exchange<int>' is deprecated}}
+  std::ignore = std::atomic_exchange(&p, r);
+}