[libcxx-commits] [libcxx] [libc++][NFC] Move attribute macros out of __config into a detail header (PR #176903)

Nikolas Klauser via libcxx-commits libcxx-commits at lists.llvm.org
Tue Jan 20 03:53:25 PST 2026


https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/176903

>From 13f3df33e083d3c8b5446736853764ca70fba88e Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Tue, 20 Jan 2026 12:33:11 +0100
Subject: [PATCH] [libc++][NFC] Move attribute macros out of __config into a
 detail header

---
 libcxx/include/CMakeLists.txt               |   1 +
 libcxx/include/__config                     | 441 +------------------
 libcxx/include/__configuration/attributes.h | 456 ++++++++++++++++++++
 libcxx/include/__configuration/language.h   |   6 +
 libcxx/include/module.modulemap.in          |   1 +
 5 files changed, 473 insertions(+), 432 deletions(-)
 create mode 100644 libcxx/include/__configuration/attributes.h

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 0811cd6bf9191..be222cffc27e5 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -329,6 +329,7 @@ set(files
   __condition_variable/condition_variable.h
   __config
   __configuration/abi.h
+  __configuration/attributes.h
   __configuration/availability.h
   __configuration/compiler.h
   __configuration/experimental.h
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 2a4abfd469d9e..c263ffe8698e5 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -11,13 +11,6 @@
 #define _LIBCPP___CONFIG
 
 #include <__config_site>
-#include <__configuration/abi.h>
-#include <__configuration/availability.h>
-#include <__configuration/compiler.h>
-#include <__configuration/experimental.h>
-#include <__configuration/hardening.h>
-#include <__configuration/language.h>
-#include <__configuration/platform.h>
 
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #  pragma GCC system_header
@@ -25,6 +18,15 @@
 
 #ifdef __cplusplus
 
+#  include <__configuration/abi.h>
+#  include <__configuration/attributes.h>
+#  include <__configuration/availability.h>
+#  include <__configuration/compiler.h>
+#  include <__configuration/experimental.h>
+#  include <__configuration/hardening.h>
+#  include <__configuration/language.h>
+#  include <__configuration/platform.h>
+
 // The attributes supported by clang are documented at https://clang.llvm.org/docs/AttributeReference.html
 
 // _LIBCPP_VERSION represents the version of libc++, which matches the version of LLVM.
@@ -184,80 +186,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_HAS_BLOCKS_RUNTIME 0
 #  endif
 
-#  define _LIBCPP_ALWAYS_INLINE __attribute__((__always_inline__))
-
-#  if defined(_LIBCPP_OBJECT_FORMAT_COFF)
-
-#    ifdef _DLL
-#      define _LIBCPP_CRT_FUNC __declspec(dllimport)
-#    else
-#      define _LIBCPP_CRT_FUNC
-#    endif
-
-#    if defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) || (defined(__MINGW32__) && !defined(_LIBCPP_BUILDING_LIBRARY))
-#      define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
-#      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
-#      define _LIBCPP_OVERRIDABLE_FUNC_VIS
-#      define _LIBCPP_EXPORTED_FROM_ABI
-#    elif defined(_LIBCPP_BUILDING_LIBRARY)
-#      if defined(__MINGW32__)
-#        define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllexport)
-#        define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
-#      else
-#        define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
-#        define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __declspec(dllexport)
-#      endif
-#      define _LIBCPP_OVERRIDABLE_FUNC_VIS __declspec(dllexport)
-#      define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllexport)
-#    else
-#      define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllimport)
-#      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
-#      define _LIBCPP_OVERRIDABLE_FUNC_VIS
-#      define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllimport)
-#    endif
-
-#    define _LIBCPP_HIDDEN
-#    define _LIBCPP_TEMPLATE_DATA_VIS
-#    define _LIBCPP_NAMESPACE_VISIBILITY
-
-#  else
-
-#    if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
-#      define _LIBCPP_VISIBILITY(vis) __attribute__((__visibility__(vis)))
-#    else
-#      define _LIBCPP_VISIBILITY(vis)
-#    endif
-
-#    define _LIBCPP_HIDDEN _LIBCPP_VISIBILITY("hidden")
-#    define _LIBCPP_TEMPLATE_DATA_VIS _LIBCPP_VISIBILITY("default")
-#    define _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_VISIBILITY("default")
-#    define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS _LIBCPP_VISIBILITY("default")
-#    define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
-
-// TODO: Make this a proper customization point or remove the option to override it.
-#    ifndef _LIBCPP_OVERRIDABLE_FUNC_VIS
-#      define _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_VISIBILITY("default")
-#    endif
-
-#    if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) && __has_attribute(__type_visibility__)
-#      define _LIBCPP_NAMESPACE_VISIBILITY __attribute__((__type_visibility__("default")))
-#    elif !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
-#      define _LIBCPP_NAMESPACE_VISIBILITY __attribute__((__visibility__("default")))
-#    else
-#      define _LIBCPP_NAMESPACE_VISIBILITY
-#    endif
-
-#  endif // defined(_LIBCPP_OBJECT_FORMAT_COFF)
-
-#  if __has_attribute(exclude_from_explicit_instantiation)
-#    define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION __attribute__((__exclude_from_explicit_instantiation__))
-#  else
-// Try to approximate the effect of exclude_from_explicit_instantiation
-// (which is that entities are not assumed to be provided by explicit
-// template instantiations in the dylib) by always inlining those entities.
-#    define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION _LIBCPP_ALWAYS_INLINE
-#  endif
-
 #  ifdef _LIBCPP_COMPILER_CLANG_BASED
 #    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
 #    define _LIBCPP_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
@@ -281,97 +209,6 @@ typedef __char32_t char32_t;
         _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wdeprecated-declarations")
 #  define _LIBCPP_SUPPRESS_DEPRECATED_POP _LIBCPP_DIAGNOSTIC_POP
 
-#  if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_FAST
-#    define _LIBCPP_HARDENING_SIG f
-#  elif _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_EXTENSIVE
-#    define _LIBCPP_HARDENING_SIG s
-#  elif _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
-#    define _LIBCPP_HARDENING_SIG d
-#  else
-#    define _LIBCPP_HARDENING_SIG n // "none"
-#  endif
-
-#  if _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_OBSERVE
-#    define _LIBCPP_ASSERTION_SEMANTIC_SIG o
-#  elif _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_QUICK_ENFORCE
-#    define _LIBCPP_ASSERTION_SEMANTIC_SIG q
-#  elif _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_ENFORCE
-#    define _LIBCPP_ASSERTION_SEMANTIC_SIG e
-#  else
-#    define _LIBCPP_ASSERTION_SEMANTIC_SIG i // `ignore`
-#  endif
-
-#  if !_LIBCPP_HAS_EXCEPTIONS
-#    define _LIBCPP_EXCEPTIONS_SIG n
-#  else
-#    define _LIBCPP_EXCEPTIONS_SIG e
-#  endif
-
-#  define _LIBCPP_ODR_SIGNATURE                                                                                        \
-    _LIBCPP_CONCAT(                                                                                                    \
-        _LIBCPP_CONCAT(_LIBCPP_CONCAT(_LIBCPP_HARDENING_SIG, _LIBCPP_ASSERTION_SEMANTIC_SIG), _LIBCPP_EXCEPTIONS_SIG), \
-        _LIBCPP_VERSION)
-
-// This macro marks a symbol as being hidden from libc++'s ABI. This is achieved
-// on two levels:
-// 1. The symbol is given hidden visibility, which ensures that users won't start exporting
-//    symbols from their dynamic library by means of using the libc++ headers. This ensures
-//    that those symbols stay private to the dynamic library in which it is defined.
-//
-// 2. The symbol is given an ABI tag that encodes the ODR-relevant properties of the library.
-//    This ensures that no ODR violation can arise from mixing two TUs compiled with different
-//    versions or configurations of libc++ (such as exceptions vs no-exceptions). Indeed, if the
-//    program contains two definitions of a function, the ODR requires them to be token-by-token
-//    equivalent, and the linker is allowed to pick either definition and discard the other one.
-//
-//    For example, if a program contains a copy of `vector::at()` compiled with exceptions enabled
-//    *and* a copy of `vector::at()` compiled with exceptions disabled (by means of having two TUs
-//    compiled with different settings), the two definitions are both visible by the linker and they
-//    have the same name, but they have a meaningfully different implementation (one throws an exception
-//    and the other aborts the program). This violates the ODR and makes the program ill-formed, and in
-//    practice what will happen is that the linker will pick one of the definitions at random and will
-//    discard the other one. This can quite clearly lead to incorrect program behavior.
-//
-//    A similar reasoning holds for many other properties that are ODR-affecting. Essentially any
-//    property that causes the code of a function to differ from the code in another configuration
-//    can be considered ODR-affecting. In practice, we don't encode all such properties in the ABI
-//    tag, but we encode the ones that we think are most important: library version, exceptions, and
-//    hardening mode.
-//
-//    Note that historically, solving this problem has been achieved in various ways, including
-//    force-inlining all functions or giving internal linkage to all functions. Both these previous
-//    solutions suffer from drawbacks that lead notably to code bloat.
-//
-// Note that we use _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION to ensure that we don't depend
-// on _LIBCPP_HIDE_FROM_ABI methods of classes explicitly instantiated in the dynamic library.
-//
-// Also note that the _LIBCPP_HIDE_FROM_ABI_VIRTUAL macro should be used on virtual functions
-// instead of _LIBCPP_HIDE_FROM_ABI. That macro does not use an ABI tag. Indeed, the mangled
-// name of a virtual function is part of its ABI, since some architectures like arm64e can sign
-// the virtual function pointer in the vtable based on the mangled name of the function. Since
-// we use an ABI tag that changes with each released version, the mangled name of the virtual
-// function would change, which is incorrect. Note that it doesn't make much sense to change
-// the implementation of a virtual function in an ABI-incompatible way in the first place,
-// since that would be an ABI break anyway. Hence, the lack of ABI tag should not be noticeable.
-//
-// The macro can be applied to record and enum types. When the tagged type is nested in
-// a record this "parent" record needs to have the macro too. Another use case for applying
-// this macro to records and unions is to apply an ABI tag to inline constexpr variables.
-// This can be useful for inline variables that are implementation details which are expected
-// to change in the future.
-//
-// TODO: We provide a escape hatch with _LIBCPP_NO_ABI_TAG for folks who want to avoid increasing
-//       the length of symbols with an ABI tag. In practice, we should remove the escape hatch and
-//       use compression mangling instead, see https://github.com/itanium-cxx-abi/cxx-abi/issues/70.
-#  ifndef _LIBCPP_NO_ABI_TAG
-#    define _LIBCPP_HIDE_FROM_ABI                                                                                      \
-      _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION                                                       \
-      __attribute__((__abi_tag__(_LIBCPP_TOSTRING(_LIBCPP_ODR_SIGNATURE))))
-#  else
-#    define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION
-#  endif
-#  define _LIBCPP_HIDE_FROM_ABI_VIRTUAL _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION
-
 // Clang modules take a significant compile time hit when pushing and popping diagnostics.
 // Since all the headers are marked as system headers unless _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER is defined, we can
 // simply disable this pushing and popping when _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER isn't defined.
@@ -433,10 +270,6 @@ typedef __char32_t char32_t;
 
 // clang-format on
 
-#  if __has_attribute(__enable_if__)
-#    define _LIBCPP_PREFERRED_OVERLOAD __attribute__((__enable_if__(true, "")))
-#  endif
-
 #  if !defined(__SIZEOF_INT128__) || defined(_MSC_VER)
 #    define _LIBCPP_HAS_INT128 0
 #  else
@@ -489,32 +322,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_WCTYPE_IS_MASK
 #  endif
 
-#  if _LIBCPP_STD_VER <= 17 || !defined(__cpp_char8_t)
-#    define _LIBCPP_HAS_CHAR8_T 0
-#  else
-#    define _LIBCPP_HAS_CHAR8_T 1
-#  endif
-
-// Deprecation macros.
-//
-// Deprecations warnings are always enabled, except when users explicitly opt-out
-// by defining _LIBCPP_DISABLE_DEPRECATION_WARNINGS.
-#  if !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
-#    if __has_attribute(__deprecated__)
-#      define _LIBCPP_DEPRECATED __attribute__((__deprecated__))
-#      define _LIBCPP_DEPRECATED_(m) __attribute__((__deprecated__(m)))
-#    elif _LIBCPP_STD_VER >= 14
-#      define _LIBCPP_DEPRECATED [[deprecated]]
-#      define _LIBCPP_DEPRECATED_(m) [[deprecated(m)]]
-#    else
-#      define _LIBCPP_DEPRECATED
-#      define _LIBCPP_DEPRECATED_(m)
-#    endif
-#  else
-#    define _LIBCPP_DEPRECATED
-#    define _LIBCPP_DEPRECATED_(m)
-#  endif
-
 // FIXME: using `#warning` causes diagnostics from system headers which include deprecated headers. This can only be
 // enabled again once https://github.com/llvm/llvm-project/pull/168041 (or a similar feature) has landed, since that
 // allows suppression in system headers.
@@ -524,50 +331,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_DIAGNOSE_DEPRECATED_HEADERS 0
 #  endif
 
-#  if !defined(_LIBCPP_CXX03_LANG)
-#    define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX11
-#  endif
-
-#  if _LIBCPP_STD_VER >= 14
-#    define _LIBCPP_DEPRECATED_IN_CXX14 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX14
-#  endif
-
-#  if _LIBCPP_STD_VER >= 17
-#    define _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX17
-#  endif
-
-#  if _LIBCPP_STD_VER >= 20
-#    define _LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX20
-#  endif
-
-#  if _LIBCPP_STD_VER >= 23
-#    define _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX23
-#  endif
-
-#  if _LIBCPP_STD_VER >= 26
-#    define _LIBCPP_DEPRECATED_IN_CXX26 _LIBCPP_DEPRECATED
-#    define _LIBCPP_DEPRECATED_IN_CXX26_(m) _LIBCPP_DEPRECATED_(m)
-#  else
-#    define _LIBCPP_DEPRECATED_IN_CXX26
-#    define _LIBCPP_DEPRECATED_IN_CXX26_(m)
-#  endif
-
-#  if _LIBCPP_HAS_CHAR8_T
-#    define _LIBCPP_DEPRECATED_WITH_CHAR8_T _LIBCPP_DEPRECATED
-#  else
-#    define _LIBCPP_DEPRECATED_WITH_CHAR8_T
-#  endif
-
 #  if _LIBCPP_STD_VER <= 11
 #    define _LIBCPP_EXPLICIT_SINCE_CXX14
 #  else
@@ -725,29 +488,6 @@ typedef __char32_t char32_t;
 #    endif
 #  endif
 
-#  if __has_cpp_attribute(_Clang::__no_thread_safety_analysis__)
-#    define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS [[_Clang::__no_thread_safety_analysis__]]
-#  else
-#    define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
-#  endif
-
-#  if defined(__CUDACC__) || defined(__CUDA_ARCH__) || defined(__CUDA_LIBDEVICE__)
-// The CUDA SDK contains an unfortunate definition for the __noinline__ macro,
-// which breaks the regular __attribute__((__noinline__)) syntax. Therefore,
-// when compiling for CUDA we use the non-underscored version of the noinline
-// attribute.
-//
-// This is a temporary workaround and we still expect the CUDA SDK team to solve
-// this issue properly in the SDK headers.
-//
-// See https://github.com/llvm/llvm-project/pull/73838 for more details.
-#    define _LIBCPP_NOINLINE __attribute__((noinline))
-#  elif __has_attribute(__noinline__)
-#    define _LIBCPP_NOINLINE __attribute__((__noinline__))
-#  else
-#    define _LIBCPP_NOINLINE
-#  endif
-
 // We often repeat things just for handling wide characters in the library.
 // When wide characters are disabled, it can be useful to have a quick way of
 // disabling it without having to resort to #if-#endif, which has a larger
@@ -784,16 +524,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_FOPEN_CLOEXEC_MODE
 #  endif
 
-#  if __has_cpp_attribute(msvc::no_unique_address)
-// MSVC implements [[no_unique_address]] as a silent no-op currently.
-// (If/when MSVC breaks its C++ ABI, it will be changed to work as intended.)
-// However, MSVC implements [[msvc::no_unique_address]] which does what
-// [[no_unique_address]] is supposed to do, in general.
-#    define _LIBCPP_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
-#  else
-#    define _LIBCPP_NO_UNIQUE_ADDRESS [[__no_unique_address__]]
-#  endif
-
 // c8rtomb() and mbrtoc8() were added in C++20 and C23. Support for these
 // functions is gradually being added to existing C libraries. The conditions
 // below check for known C library versions and conditions under which these
@@ -880,159 +610,6 @@ typedef __char32_t char32_t;
 
 #  define _PSTL_USE_NONTEMPORAL_STORES_IF_ALLOWED
 
-// Optional attributes - these are useful for a better QoI, but not required to be available
-
-#  define _LIBCPP_NOALIAS __attribute__((__malloc__))
-#  define _LIBCPP_NODEBUG [[__gnu__::__nodebug__]]
-#  define _LIBCPP_NO_SANITIZE(...) __attribute__((__no_sanitize__(__VA_ARGS__)))
-#  define _LIBCPP_INIT_PRIORITY_MAX __attribute__((__init_priority__(100)))
-#  define _LIBCPP_ATTRIBUTE_FORMAT(archetype, format_string_index, first_format_arg_index)                             \
-    __attribute__((__format__(archetype, format_string_index, first_format_arg_index)))
-#  define _LIBCPP_PACKED __attribute__((__packed__))
-
-#  if __has_attribute(__no_sanitize__) && !defined(_LIBCPP_COMPILER_GCC)
-#    define _LIBCPP_NO_CFI __attribute__((__no_sanitize__("cfi")))
-#  else
-#    define _LIBCPP_NO_CFI
-#  endif
-
-#  if __has_attribute(__using_if_exists__)
-#    define _LIBCPP_USING_IF_EXISTS __attribute__((__using_if_exists__))
-#  else
-#    define _LIBCPP_USING_IF_EXISTS
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__no_destroy__)
-#    define _LIBCPP_NO_DESTROY [[_Clang::__no_destroy__]]
-#  else
-#    define _LIBCPP_NO_DESTROY
-#  endif
-
-#  if __has_attribute(__diagnose_if__)
-#    define _LIBCPP_DIAGNOSE_WARNING(...) __attribute__((__diagnose_if__(__VA_ARGS__, "warning")))
-#  else
-#    define _LIBCPP_DIAGNOSE_WARNING(...)
-#  endif
-
-#  if __has_attribute(__diagnose_if__) && !defined(_LIBCPP_APPLE_CLANG_VER) &&                                         \
-      (!defined(_LIBCPP_CLANG_VER) || _LIBCPP_CLANG_VER >= 2001)
-#    define _LIBCPP_DIAGNOSE_IF(...) __attribute__((__diagnose_if__(__VA_ARGS__)))
-#  else
-#    define _LIBCPP_DIAGNOSE_IF(...)
-#  endif
-
-#  define _LIBCPP_DIAGNOSE_NULLPTR_IF(condition, condition_description)                                                \
-    _LIBCPP_DIAGNOSE_IF(                                                                                               \
-        condition,                                                                                                     \
-        "null passed to callee that requires a non-null argument" condition_description,                               \
-        "warning",                                                                                                     \
-        "nonnull")
-
-#  if __has_cpp_attribute(_Clang::__lifetimebound__)
-#    define _LIBCPP_LIFETIMEBOUND [[_Clang::__lifetimebound__]]
-#  else
-#    define _LIBCPP_LIFETIMEBOUND
-#  endif
-
-// This is to work around https://llvm.org/PR156809
-#  ifndef _LIBCPP_CXX03_LANG
-#    define _LIBCPP_CTOR_LIFETIMEBOUND _LIBCPP_LIFETIMEBOUND
-#  else
-#    define _LIBCPP_CTOR_LIFETIMEBOUND
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__noescape__)
-#    define _LIBCPP_NOESCAPE [[_Clang::__noescape__]]
-#  else
-#    define _LIBCPP_NOESCAPE
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__no_specializations__)
-#    define _LIBCPP_NO_SPECIALIZATIONS                                                                                 \
-      [[_Clang::__no_specializations__("Users are not allowed to specialize this standard library entity")]]
-#  else
-#    define _LIBCPP_NO_SPECIALIZATIONS
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__preferred_name__)
-#    define _LIBCPP_PREFERRED_NAME(x) [[_Clang::__preferred_name__(x)]]
-#  else
-#    define _LIBCPP_PREFERRED_NAME(x)
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__scoped_lockable__)
-#    define _LIBCPP_SCOPED_LOCKABLE [[_Clang::__scoped_lockable__]]
-#  else
-#    define _LIBCPP_SCOPED_LOCKABLE
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__capability__)
-#    define _LIBCPP_CAPABILITY(...) [[_Clang::__capability__(__VA_ARGS__)]]
-#  else
-#    define _LIBCPP_CAPABILITY(...)
-#  endif
-
-#  if __has_attribute(__acquire_capability__)
-#    define _LIBCPP_ACQUIRE_CAPABILITY(...) __attribute__((__acquire_capability__(__VA_ARGS__)))
-#  else
-#    define _LIBCPP_ACQUIRE_CAPABILITY(...)
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__try_acquire_capability__)
-#    define _LIBCPP_TRY_ACQUIRE_CAPABILITY(...) [[_Clang::__try_acquire_capability__(__VA_ARGS__)]]
-#  else
-#    define _LIBCPP_TRY_ACQUIRE_CAPABILITY(...)
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__acquire_shared_capability__)
-#    define _LIBCPP_ACQUIRE_SHARED_CAPABILITY [[_Clang::__acquire_shared_capability__]]
-#  else
-#    define _LIBCPP_ACQUIRE_SHARED_CAPABILITY
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__try_acquire_shared_capability__)
-#    define _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(...) [[_Clang::__try_acquire_shared_capability__(__VA_ARGS__)]]
-#  else
-#    define _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(...)
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__release_capability__)
-#    define _LIBCPP_RELEASE_CAPABILITY [[_Clang::__release_capability__]]
-#  else
-#    define _LIBCPP_RELEASE_CAPABILITY
-#  endif
-
-#  if __has_cpp_attribute(_Clang::__release_shared_capability__)
-#    define _LIBCPP_RELEASE_SHARED_CAPABILITY [[_Clang::__release_shared_capability__]]
-#  else
-#    define _LIBCPP_RELEASE_SHARED_CAPABILITY
-#  endif
-
-#  if __has_attribute(__requires_capability__)
-#    define _LIBCPP_REQUIRES_CAPABILITY(...) __attribute__((__requires_capability__(__VA_ARGS__)))
-#  else
-#    define _LIBCPP_REQUIRES_CAPABILITY(...)
-#  endif
-
-#  if defined(_LIBCPP_ABI_MICROSOFT) && __has_declspec_attribute(empty_bases)
-#    define _LIBCPP_DECLSPEC_EMPTY_BASES __declspec(empty_bases)
-#  else
-#    define _LIBCPP_DECLSPEC_EMPTY_BASES
-#  endif
-
-// Allow for build-time disabling of unsigned integer sanitization
-#  if __has_attribute(no_sanitize) && !defined(_LIBCPP_COMPILER_GCC)
-#    define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK __attribute__((__no_sanitize__("unsigned-integer-overflow")))
-#  else
-#    define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
-#  endif
-
-#  if __has_feature(nullability)
-#    define _LIBCPP_DIAGNOSE_NULLPTR _Nonnull
-#  else
-#    define _LIBCPP_DIAGNOSE_NULLPTR
-#  endif
-
 #endif // __cplusplus
 
 #endif // _LIBCPP___CONFIG
diff --git a/libcxx/include/__configuration/attributes.h b/libcxx/include/__configuration/attributes.h
new file mode 100644
index 0000000000000..f208f6725dff5
--- /dev/null
+++ b/libcxx/include/__configuration/attributes.h
@@ -0,0 +1,456 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___CONFIGURATION_ATTRIBUTES_H
+#define _LIBCPP___CONFIGURATION_ATTRIBUTES_H
+
+#include <__config_site>
+#include <__configuration/hardening.h>
+#include <__configuration/language.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+// Attributes relevant for layout ABI
+// ----------------------------------
+
+#if __has_cpp_attribute(msvc::no_unique_address)
+// MSVC implements [[no_unique_address]] as a silent no-op currently.
+// (If/when MSVC breaks its C++ ABI, it will be changed to work as intended.)
+// However, MSVC implements [[msvc::no_unique_address]] which does what
+// [[no_unique_address]] is supposed to do, in general.
+#  define _LIBCPP_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#else
+#  define _LIBCPP_NO_UNIQUE_ADDRESS [[__no_unique_address__]]
+#endif
+
+#define _LIBCPP_PACKED __attribute__((__packed__))
+
+// Attributes affecting overload resolution
+// ----------------------------------------
+
+#if __has_attribute(__enable_if__)
+#  define _LIBCPP_PREFERRED_OVERLOAD __attribute__((__enable_if__(true, "")))
+#endif
+
+// Visibility attributes
+// ---------------------
+
+#if defined(_LIBCPP_OBJECT_FORMAT_COFF)
+
+#  ifdef _DLL
+#    define _LIBCPP_CRT_FUNC __declspec(dllimport)
+#  else
+#    define _LIBCPP_CRT_FUNC
+#  endif
+
+#  if defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) || (defined(__MINGW32__) && !defined(_LIBCPP_BUILDING_LIBRARY))
+#    define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
+#    define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+#    define _LIBCPP_OVERRIDABLE_FUNC_VIS
+#    define _LIBCPP_EXPORTED_FROM_ABI
+#  elif defined(_LIBCPP_BUILDING_LIBRARY)
+#    if defined(__MINGW32__)
+#      define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllexport)
+#      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+#    else
+#      define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS
+#      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __declspec(dllexport)
+#    endif
+#    define _LIBCPP_OVERRIDABLE_FUNC_VIS __declspec(dllexport)
+#    define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllexport)
+#  else
+#    define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllimport)
+#    define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+#    define _LIBCPP_OVERRIDABLE_FUNC_VIS
+#    define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllimport)
+#  endif
+
+#  define _LIBCPP_HIDDEN
+#  define _LIBCPP_TEMPLATE_DATA_VIS
+#  define _LIBCPP_NAMESPACE_VISIBILITY
+
+#else
+
+#  if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
+#    define _LIBCPP_VISIBILITY(vis) __attribute__((__visibility__(vis)))
+#  else
+#    define _LIBCPP_VISIBILITY(vis)
+#  endif
+
+#  define _LIBCPP_HIDDEN _LIBCPP_VISIBILITY("hidden")
+#  define _LIBCPP_TEMPLATE_DATA_VIS _LIBCPP_VISIBILITY("default")
+#  define _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_VISIBILITY("default")
+#  define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS _LIBCPP_VISIBILITY("default")
+#  define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+
+// TODO: Make this a proper customization point or remove the option to override it.
+#  ifndef _LIBCPP_OVERRIDABLE_FUNC_VIS
+#    define _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_VISIBILITY("default")
+#  endif
+
+#  if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) && __has_attribute(__type_visibility__)
+#    define _LIBCPP_NAMESPACE_VISIBILITY __attribute__((__type_visibility__("default")))
+#  elif !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
+#    define _LIBCPP_NAMESPACE_VISIBILITY __attribute__((__visibility__("default")))
+#  else
+#    define _LIBCPP_NAMESPACE_VISIBILITY
+#  endif
+
+#endif // defined(_LIBCPP_OBJECT_FORMAT_COFF)
+
+// hide_from_abi
+// -------------
+
+#define _LIBCPP_ALWAYS_INLINE __attribute__((__always_inline__))
+
+#if __has_attribute(exclude_from_explicit_instantiation)
+#  define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION __attribute__((__exclude_from_explicit_instantiation__))
+#else
+// Try to approximate the effect of exclude_from_explicit_instantiation
+// (which is that entities are not assumed to be provided by explicit
+// template instantiations in the dylib) by always inlining those entities.
+#  define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION _LIBCPP_ALWAYS_INLINE
+#endif
+
+#if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_FAST
+#  define _LIBCPP_HARDENING_SIG f
+#elif _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_EXTENSIVE
+#  define _LIBCPP_HARDENING_SIG s
+#elif _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
+#  define _LIBCPP_HARDENING_SIG d
+#else
+#  define _LIBCPP_HARDENING_SIG n // "none"
+#endif
+
+#if _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_OBSERVE
+#  define _LIBCPP_ASSERTION_SEMANTIC_SIG o
+#elif _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_QUICK_ENFORCE
+#  define _LIBCPP_ASSERTION_SEMANTIC_SIG q
+#elif _LIBCPP_ASSERTION_SEMANTIC == _LIBCPP_ASSERTION_SEMANTIC_ENFORCE
+#  define _LIBCPP_ASSERTION_SEMANTIC_SIG e
+#else
+#  define _LIBCPP_ASSERTION_SEMANTIC_SIG i // `ignore`
+#endif
+
+#if !_LIBCPP_HAS_EXCEPTIONS
+#  define _LIBCPP_EXCEPTIONS_SIG n
+#else
+#  define _LIBCPP_EXCEPTIONS_SIG e
+#endif
+
+#define _LIBCPP_ODR_SIGNATURE                                                                                          \
+  _LIBCPP_CONCAT(                                                                                                      \
+      _LIBCPP_CONCAT(_LIBCPP_CONCAT(_LIBCPP_HARDENING_SIG, _LIBCPP_ASSERTION_SEMANTIC_SIG), _LIBCPP_EXCEPTIONS_SIG),   \
+      _LIBCPP_VERSION)
+
+// This macro marks a symbol as being hidden from libc++'s ABI. This is achieved
+// on two levels:
+// 1. The symbol is given hidden visibility, which ensures that users won't start exporting
+//    symbols from their dynamic library by means of using the libc++ headers. This ensures
+//    that those symbols stay private to the dynamic library in which it is defined.
+//
+// 2. The symbol is given an ABI tag that encodes the ODR-relevant properties of the library.
+//    This ensures that no ODR violation can arise from mixing two TUs compiled with different
+//    versions or configurations of libc++ (such as exceptions vs no-exceptions). Indeed, if the
+//    program contains two definitions of a function, the ODR requires them to be token-by-token
+//    equivalent, and the linker is allowed to pick either definition and discard the other one.
+//
+//    For example, if a program contains a copy of `vector::at()` compiled with exceptions enabled
+//    *and* a copy of `vector::at()` compiled with exceptions disabled (by means of having two TUs
+//    compiled with different settings), the two definitions are both visible by the linker and they
+//    have the same name, but they have a meaningfully different implementation (one throws an exception
+//    and the other aborts the program). This violates the ODR and makes the program ill-formed, and in
+//    practice what will happen is that the linker will pick one of the definitions at random and will
+//    discard the other one. This can quite clearly lead to incorrect program behavior.
+//
+//    A similar reasoning holds for many other properties that are ODR-affecting. Essentially any
+//    property that causes the code of a function to differ from the code in another configuration
+//    can be considered ODR-affecting. In practice, we don't encode all such properties in the ABI
+//    tag, but we encode the ones that we think are most important: library version, exceptions, and
+//    hardening mode.
+//
+//    Note that historically, solving this problem has been achieved in various ways, including
+//    force-inlining all functions or giving internal linkage to all functions. Both these previous
+//    solutions suffer from drawbacks that lead notably to code bloat.
+//
+// Note that we use _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION to ensure that we don't depend
+// on _LIBCPP_HIDE_FROM_ABI methods of classes explicitly instantiated in the dynamic library.
+//
+// Also note that the _LIBCPP_HIDE_FROM_ABI_VIRTUAL macro should be used on virtual functions
+// instead of _LIBCPP_HIDE_FROM_ABI. That macro does not use an ABI tag. Indeed, the mangled
+// name of a virtual function is part of its ABI, since some architectures like arm64e can sign
+// the virtual function pointer in the vtable based on the mangled name of the function. Since
+// we use an ABI tag that changes with each released version, the mangled name of the virtual
+// function would change, which is incorrect. Note that it doesn't make much sense to change
+// the implementation of a virtual function in an ABI-incompatible way in the first place,
+// since that would be an ABI break anyway. Hence, the lack of ABI tag should not be noticeable.
+//
+// The macro can be applied to record and enum types. When the tagged type is nested in
+// a record this "parent" record needs to have the macro too. Another use case for applying
+// this macro to records and unions is to apply an ABI tag to inline constexpr variables.
+// This can be useful for inline variables that are implementation details which are expected
+// to change in the future.
+//
+// TODO: We provide a escape hatch with _LIBCPP_NO_ABI_TAG for folks who want to avoid increasing
+//       the length of symbols with an ABI tag. In practice, we should remove the escape hatch and
+//       use compression mangling instead, see https://github.com/itanium-cxx-abi/cxx-abi/issues/70.
+#ifndef _LIBCPP_NO_ABI_TAG
+#  define _LIBCPP_HIDE_FROM_ABI                                                                                        \
+    _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION                                                         \
+    __attribute__((__abi_tag__(_LIBCPP_TOSTRING(_LIBCPP_ODR_SIGNATURE))))
+#else
+#  define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION
+#endif
+#define _LIBCPP_HIDE_FROM_ABI_VIRTUAL _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION
+
+// Optional attributes
+// -------------------
+
+// these are useful for a better QoI, but not required to be available
+
+#define _LIBCPP_NOALIAS __attribute__((__malloc__))
+#define _LIBCPP_NODEBUG [[__gnu__::__nodebug__]]
+#define _LIBCPP_NO_SANITIZE(...) __attribute__((__no_sanitize__(__VA_ARGS__)))
+#define _LIBCPP_INIT_PRIORITY_MAX __attribute__((__init_priority__(100)))
+#define _LIBCPP_ATTRIBUTE_FORMAT(archetype, format_string_index, first_format_arg_index)                               \
+  __attribute__((__format__(archetype, format_string_index, first_format_arg_index)))
+
+#if __has_attribute(__no_sanitize__) && !defined(_LIBCPP_COMPILER_GCC)
+#  define _LIBCPP_NO_CFI __attribute__((__no_sanitize__("cfi")))
+#else
+#  define _LIBCPP_NO_CFI
+#endif
+
+#if __has_attribute(__using_if_exists__)
+#  define _LIBCPP_USING_IF_EXISTS __attribute__((__using_if_exists__))
+#else
+#  define _LIBCPP_USING_IF_EXISTS
+#endif
+
+#if __has_cpp_attribute(_Clang::__no_destroy__)
+#  define _LIBCPP_NO_DESTROY [[_Clang::__no_destroy__]]
+#else
+#  define _LIBCPP_NO_DESTROY
+#endif
+
+#if __has_attribute(__diagnose_if__)
+#  define _LIBCPP_DIAGNOSE_WARNING(...) __attribute__((__diagnose_if__(__VA_ARGS__, "warning")))
+#else
+#  define _LIBCPP_DIAGNOSE_WARNING(...)
+#endif
+
+#if __has_attribute(__diagnose_if__) && !defined(_LIBCPP_APPLE_CLANG_VER) &&                                           \
+    (!defined(_LIBCPP_CLANG_VER) || _LIBCPP_CLANG_VER >= 2001)
+#  define _LIBCPP_DIAGNOSE_IF(...) __attribute__((__diagnose_if__(__VA_ARGS__)))
+#else
+#  define _LIBCPP_DIAGNOSE_IF(...)
+#endif
+
+#define _LIBCPP_DIAGNOSE_NULLPTR_IF(condition, condition_description)                                                  \
+  _LIBCPP_DIAGNOSE_IF(                                                                                                 \
+      condition,                                                                                                       \
+      "null passed to callee that requires a non-null argument" condition_description,                                 \
+      "warning",                                                                                                       \
+      "nonnull")
+
+#if __has_cpp_attribute(_Clang::__lifetimebound__)
+#  define _LIBCPP_LIFETIMEBOUND [[_Clang::__lifetimebound__]]
+#else
+#  define _LIBCPP_LIFETIMEBOUND
+#endif
+
+// This is to work around https://llvm.org/PR156809
+#ifndef _LIBCPP_CXX03_LANG
+#  define _LIBCPP_CTOR_LIFETIMEBOUND _LIBCPP_LIFETIMEBOUND
+#else
+#  define _LIBCPP_CTOR_LIFETIMEBOUND
+#endif
+
+#if __has_cpp_attribute(_Clang::__noescape__)
+#  define _LIBCPP_NOESCAPE [[_Clang::__noescape__]]
+#else
+#  define _LIBCPP_NOESCAPE
+#endif
+
+#if __has_cpp_attribute(_Clang::__no_specializations__)
+#  define _LIBCPP_NO_SPECIALIZATIONS                                                                                   \
+    [[_Clang::__no_specializations__("Users are not allowed to specialize this standard library entity")]]
+#else
+#  define _LIBCPP_NO_SPECIALIZATIONS
+#endif
+
+#if __has_cpp_attribute(_Clang::__preferred_name__)
+#  define _LIBCPP_PREFERRED_NAME(x) [[_Clang::__preferred_name__(x)]]
+#else
+#  define _LIBCPP_PREFERRED_NAME(x)
+#endif
+
+#if __has_cpp_attribute(_Clang::__scoped_lockable__)
+#  define _LIBCPP_SCOPED_LOCKABLE [[_Clang::__scoped_lockable__]]
+#else
+#  define _LIBCPP_SCOPED_LOCKABLE
+#endif
+
+#if __has_cpp_attribute(_Clang::__capability__)
+#  define _LIBCPP_CAPABILITY(...) [[_Clang::__capability__(__VA_ARGS__)]]
+#else
+#  define _LIBCPP_CAPABILITY(...)
+#endif
+
+#if __has_attribute(__acquire_capability__)
+#  define _LIBCPP_ACQUIRE_CAPABILITY(...) __attribute__((__acquire_capability__(__VA_ARGS__)))
+#else
+#  define _LIBCPP_ACQUIRE_CAPABILITY(...)
+#endif
+
+#if __has_cpp_attribute(_Clang::__try_acquire_capability__)
+#  define _LIBCPP_TRY_ACQUIRE_CAPABILITY(...) [[_Clang::__try_acquire_capability__(__VA_ARGS__)]]
+#else
+#  define _LIBCPP_TRY_ACQUIRE_CAPABILITY(...)
+#endif
+
+#if __has_cpp_attribute(_Clang::__acquire_shared_capability__)
+#  define _LIBCPP_ACQUIRE_SHARED_CAPABILITY [[_Clang::__acquire_shared_capability__]]
+#else
+#  define _LIBCPP_ACQUIRE_SHARED_CAPABILITY
+#endif
+
+#if __has_cpp_attribute(_Clang::__try_acquire_shared_capability__)
+#  define _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(...) [[_Clang::__try_acquire_shared_capability__(__VA_ARGS__)]]
+#else
+#  define _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(...)
+#endif
+
+#if __has_cpp_attribute(_Clang::__release_capability__)
+#  define _LIBCPP_RELEASE_CAPABILITY [[_Clang::__release_capability__]]
+#else
+#  define _LIBCPP_RELEASE_CAPABILITY
+#endif
+
+#if __has_cpp_attribute(_Clang::__release_shared_capability__)
+#  define _LIBCPP_RELEASE_SHARED_CAPABILITY [[_Clang::__release_shared_capability__]]
+#else
+#  define _LIBCPP_RELEASE_SHARED_CAPABILITY
+#endif
+
+#if __has_attribute(__requires_capability__)
+#  define _LIBCPP_REQUIRES_CAPABILITY(...) __attribute__((__requires_capability__(__VA_ARGS__)))
+#else
+#  define _LIBCPP_REQUIRES_CAPABILITY(...)
+#endif
+
+#if __has_cpp_attribute(_Clang::__no_thread_safety_analysis__)
+#  define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS [[_Clang::__no_thread_safety_analysis__]]
+#else
+#  define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+#endif
+
+#if defined(_LIBCPP_ABI_MICROSOFT) && __has_declspec_attribute(empty_bases)
+#  define _LIBCPP_DECLSPEC_EMPTY_BASES __declspec(empty_bases)
+#else
+#  define _LIBCPP_DECLSPEC_EMPTY_BASES
+#endif
+
+// Allow for build-time disabling of unsigned integer sanitization
+#if __has_attribute(no_sanitize) && !defined(_LIBCPP_COMPILER_GCC)
+#  define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK __attribute__((__no_sanitize__("unsigned-integer-overflow")))
+#else
+#  define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+#endif
+
+#if __has_feature(nullability)
+#  define _LIBCPP_DIAGNOSE_NULLPTR _Nonnull
+#else
+#  define _LIBCPP_DIAGNOSE_NULLPTR
+#endif
+
+#if defined(__CUDACC__) || defined(__CUDA_ARCH__) || defined(__CUDA_LIBDEVICE__)
+// The CUDA SDK contains an unfortunate definition for the __noinline__ macro,
+// which breaks the regular __attribute__((__noinline__)) syntax. Therefore,
+// when compiling for CUDA we use the non-underscored version of the noinline
+// attribute.
+//
+// This is a temporary workaround and we still expect the CUDA SDK team to solve
+// this issue properly in the SDK headers.
+//
+// See https://github.com/llvm/llvm-project/pull/73838 for more details.
+#  define _LIBCPP_NOINLINE __attribute__((noinline))
+#elif __has_attribute(__noinline__)
+#  define _LIBCPP_NOINLINE __attribute__((__noinline__))
+#else
+#  define _LIBCPP_NOINLINE
+#endif
+
+// Deprecation macros
+// ------------------
+
+// Deprecations warnings are always enabled, except when users explicitly opt-out
+// by defining _LIBCPP_DISABLE_DEPRECATION_WARNINGS.
+#if !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
+#  if __has_attribute(__deprecated__)
+#    define _LIBCPP_DEPRECATED __attribute__((__deprecated__))
+#    define _LIBCPP_DEPRECATED_(m) __attribute__((__deprecated__(m)))
+#  elif _LIBCPP_STD_VER >= 14
+#    define _LIBCPP_DEPRECATED [[deprecated]]
+#    define _LIBCPP_DEPRECATED_(m) [[deprecated(m)]]
+#  else
+#    define _LIBCPP_DEPRECATED
+#    define _LIBCPP_DEPRECATED_(m)
+#  endif
+#else
+#  define _LIBCPP_DEPRECATED
+#  define _LIBCPP_DEPRECATED_(m)
+#endif
+
+#if !defined(_LIBCPP_CXX03_LANG)
+#  define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX11
+#endif
+
+#if _LIBCPP_STD_VER >= 14
+#  define _LIBCPP_DEPRECATED_IN_CXX14 _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX14
+#endif
+
+#if _LIBCPP_STD_VER >= 17
+#  define _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX17
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+#  define _LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX20
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+#  define _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX23
+#endif
+
+#if _LIBCPP_STD_VER >= 26
+#  define _LIBCPP_DEPRECATED_IN_CXX26 _LIBCPP_DEPRECATED
+#  define _LIBCPP_DEPRECATED_IN_CXX26_(m) _LIBCPP_DEPRECATED_(m)
+#else
+#  define _LIBCPP_DEPRECATED_IN_CXX26
+#  define _LIBCPP_DEPRECATED_IN_CXX26_(m)
+#endif
+
+#if _LIBCPP_HAS_CHAR8_T
+#  define _LIBCPP_DEPRECATED_WITH_CHAR8_T _LIBCPP_DEPRECATED
+#else
+#  define _LIBCPP_DEPRECATED_WITH_CHAR8_T
+#endif
+
+#endif // _LIBCPP___CONFIGURATION_ATTRIBUTES_H
diff --git a/libcxx/include/__configuration/language.h b/libcxx/include/__configuration/language.h
index 26e87f87afd87..3137ba2ea27ef 100644
--- a/libcxx/include/__configuration/language.h
+++ b/libcxx/include/__configuration/language.h
@@ -50,4 +50,10 @@
 #  define _LIBCPP_HAS_EXCEPTIONS 0
 #endif
 
+#if _LIBCPP_STD_VER <= 17 || !defined(__cpp_char8_t)
+#  define _LIBCPP_HAS_CHAR8_T 0
+#else
+#  define _LIBCPP_HAS_CHAR8_T 1
+#endif
+
 #endif // _LIBCPP___CONFIGURATION_LANGUAGE_H
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 1d7af6d00e13b..4cccfdf9d0a1a 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -4,6 +4,7 @@ module std_config [system] {
   @LIBCXX_CONFIG_SITE_MODULE_ENTRY@ // generated via CMake
   textual header "__config"
   textual header "__configuration/abi.h"
+  textual header "__configuration/attributes.h"
   textual header "__configuration/availability.h"
   textual header "__configuration/compiler.h"
   textual header "__configuration/experimental.h"



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