Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -476,6 +476,7 @@
 - Implemented `P2128R6: Multidimensional subscript operator <https://wg21.link/P2128R6>`_.
 - Implemented `P0849R8: auto(x): decay-copy in the language <https://wg21.link/P0849R8>`_.
 - Implemented `P2242R3: Non-literal variables (and labels and gotos) in constexpr functions	<https://wg21.link/P2242R3>`_.
+- Implemented `LWG3659: Consider ATOMIC_FLAG_INIT undeprecation <https://wg21.link/LWG3659>`_.
 
 CUDA/HIP Language Changes in Clang
 ----------------------------------
Index: clang/lib/Headers/stdatomic.h
===================================================================
--- clang/lib/Headers/stdatomic.h
+++ clang/lib/Headers/stdatomic.h
@@ -158,10 +158,6 @@
 typedef struct atomic_flag { atomic_bool _Value; } atomic_flag;
 
 #define ATOMIC_FLAG_INIT { 0 }
-#if __cplusplus >= 202002L && !defined(_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS)
-/* ATOMIC_FLAG_INIT was deprecated in C++20 but is not deprecated in C. */
-#pragma clang deprecated(ATOMIC_FLAG_INIT)
-#endif
 
 /* These should be provided by the libc implementation. */
 #ifdef __cplusplus
Index: clang/test/Headers/stdatomic-deprecations.c
===================================================================
--- clang/test/Headers/stdatomic-deprecations.c
+++ clang/test/Headers/stdatomic-deprecations.c
@@ -12,7 +12,6 @@
 void func(void) {
   _Atomic int i = ATOMIC_VAR_INIT(12); // expected-warning {{macro 'ATOMIC_VAR_INIT' has been marked as deprecated}} \
                                        // expected-note@stdatomic.h:* {{macro marked 'deprecated' here}}
-  #if defined(ATOMIC_FLAG_INIT) // cxx-warning {{macro 'ATOMIC_FLAG_INIT' has been marked as deprecated}} \
-                                // cxx-note@stdatomic.h:* {{macro marked 'deprecated' here}}
+  #if defined(ATOMIC_FLAG_INIT) // Ok, deprecated in C++20, undeprecated in C++23 via LWG4659.
   #endif
 }