diff --git a/boost-math b/boost-math
index f395de082ec..c56f334348d 160000
--- a/boost-math
+++ b/boost-math
@@ -1 +1 @@
-Subproject commit f395de082eca6ee993a15f2bdb90277eda518295
+Subproject commit c56f334348d5476783fba996d604fc5c6ae980c3
diff --git a/docs/cgmanifest.json b/docs/cgmanifest.json
index a7d932b2729..d6f5dd7612f 100644
--- a/docs/cgmanifest.json
+++ b/docs/cgmanifest.json
@@ -6,7 +6,7 @@
                 "type": "git",
                 "git": {
                     "repositoryUrl": "https://github.com/boostorg/math",
-                    "commitHash": "f395de082eca6ee993a15f2bdb90277eda518295"
+                    "commitHash": "c56f334348d5476783fba996d604fc5c6ae980c3"
                 }
             }
         },
diff --git a/stl/CMakeLists.txt b/stl/CMakeLists.txt
index 64ee93e9055..6c2e456eedf 100644
--- a/stl/CMakeLists.txt
+++ b/stl/CMakeLists.txt
@@ -247,7 +247,6 @@ set(HEADERS
     ${CMAKE_CURRENT_LIST_DIR}/inc/xnode_handle.h
     ${CMAKE_CURRENT_LIST_DIR}/inc/xpolymorphic_allocator.h
     ${CMAKE_CURRENT_LIST_DIR}/inc/xsmf_control.h
-    ${CMAKE_CURRENT_LIST_DIR}/inc/xstddef
     ${CMAKE_CURRENT_LIST_DIR}/inc/xstring
     ${CMAKE_CURRENT_LIST_DIR}/inc/xthreads.h
     ${CMAKE_CURRENT_LIST_DIR}/inc/xtimec.h
diff --git a/stl/inc/header-units.json b/stl/inc/header-units.json
index 0d21964d524..345af8adf51 100644
--- a/stl/inc/header-units.json
+++ b/stl/inc/header-units.json
@@ -153,7 +153,6 @@
         "xnode_handle.h",
         "xpolymorphic_allocator.h",
         "xsmf_control.h",
-        "xstddef",
         "xstring",
         "xthreads.h",
         "xtimec.h",
diff --git a/stl/inc/limits b/stl/inc/limits
index cd4bbf056f9..b957442428a 100644
--- a/stl/inc/limits
+++ b/stl/inc/limits
@@ -36,7 +36,8 @@ _STL_DISABLE_CLANG_WARNINGS
 #undef new
 
 _STD_BEGIN
-_EXPORT_STD enum float_denorm_style { // constants for different IEEE float denormalization styles
+// constants for different IEEE float denormalization styles
+_EXPORT_STD enum _CXX23_DEPRECATE_DENORM float_denorm_style {
     denorm_indeterminate = -1,
     denorm_absent        = 0,
     denorm_present       = 1
@@ -51,8 +52,11 @@ _EXPORT_STD enum float_round_style { // constants for different IEEE rounding st
 };
 
 struct _Num_base { // base for all types, with common defaults
-    static constexpr float_denorm_style has_denorm = denorm_absent;
-    static constexpr bool has_denorm_loss          = false;
+    _STL_DISABLE_DEPRECATED_WARNING
+    _CXX23_DEPRECATE_DENORM static constexpr float_denorm_style has_denorm = denorm_absent;
+    _CXX23_DEPRECATE_DENORM static constexpr bool has_denorm_loss          = false;
+    _STL_RESTORE_DEPRECATED_WARNING
+
     static constexpr bool has_infinity             = false;
     static constexpr bool has_quiet_NaN            = false;
     static constexpr bool has_signaling_NaN        = false;
@@ -134,7 +138,10 @@ struct _Num_int_base : _Num_base { // base for integer types
 };
 
 struct _Num_float_base : _Num_base { // base for floating-point types
-    static constexpr float_denorm_style has_denorm = denorm_present;
+    _STL_DISABLE_DEPRECATED_WARNING
+    _CXX23_DEPRECATE_DENORM static constexpr float_denorm_style has_denorm = denorm_present;
+    _STL_RESTORE_DEPRECATED_WARNING
+
     static constexpr bool has_infinity             = true;
     static constexpr bool has_quiet_NaN            = true;
     static constexpr bool has_signaling_NaN        = true;
diff --git a/stl/inc/map b/stl/inc/map
index eaca60e2932..b7e1cb601c8 100644
--- a/stl/inc/map
+++ b/stl/inc/map
@@ -77,8 +77,6 @@ public:
         _MISMATCHED_ALLOCATOR_MESSAGE("map<Key, Value, Compare, Allocator>", "pair<const Key, Value>"));
     static_assert(is_object_v<_Kty>, "The C++ Standard forbids containers of non-object types "
                                      "because of [container.requirements].");
-    static_assert(is_object_v<_Ty>, "The C++ Standard forbids containers of non-object types "
-                                    "because of [container.requirements].");
 
     using _Mybase                = _Tree<_Tmap_traits<_Kty, _Ty, _Pr, _Alloc, false>>;
     using _Nodeptr               = typename _Mybase::_Nodeptr;
@@ -463,8 +461,6 @@ public:
         _MISMATCHED_ALLOCATOR_MESSAGE("multimap<Key, Value, Compare, Allocator>", "pair<const Key, Value>"));
     static_assert(is_object_v<_Kty>, "The C++ Standard forbids containers of non-object types "
                                      "because of [container.requirements].");
-    static_assert(is_object_v<_Ty>, "The C++ Standard forbids containers of non-object types "
-                                    "because of [container.requirements].");
 
     using _Mybase                = _Tree<_Tmap_traits<_Kty, _Ty, _Pr, _Alloc, true>>;
     using key_type               = _Kty;
diff --git a/stl/inc/type_traits b/stl/inc/type_traits
index c51ef667b26..3d26f56f401 100644
--- a/stl/inc/type_traits
+++ b/stl/inc/type_traits
@@ -8,8 +8,9 @@
 #define _TYPE_TRAITS_
 #include <yvals_core.h>
 #if _STL_COMPILER_PREPROCESSOR
+#include <cstddef>
 #include <cstdint>
-#include <xstddef>
+#include <xtr1common>
 
 #pragma pack(push, _CRT_PACKING)
 #pragma warning(push, _STL_WARNING_LEVEL)
@@ -19,6 +20,10 @@ _STL_DISABLE_CLANG_WARNINGS
 #undef new
 
 _STD_BEGIN
+template <class>
+// TRANSITION, CWG-2518: false value attached to a dependent name (for static_assert)
+_INLINE_VAR constexpr bool _Always_false = false;
+
 _EXPORT_STD template <class _Ty, _Ty... _Vals>
 struct integer_sequence { // sequence of integer parameters
     static_assert(is_integral_v<_Ty>, "integer_sequence<T, I...> requires T to be an integral type.");
diff --git a/stl/inc/unordered_map b/stl/inc/unordered_map
index 40561f6eb79..dee66749bfc 100644
--- a/stl/inc/unordered_map
+++ b/stl/inc/unordered_map
@@ -71,8 +71,6 @@ public:
         _MISMATCHED_ALLOCATOR_MESSAGE("unordered_map<Key, Value, Hasher, Eq, Allocator>", "pair<const Key, Value>"));
     static_assert(is_object_v<_Kty>, "The C++ Standard forbids containers of non-object types "
                                      "because of [container.requirements].");
-    static_assert(is_object_v<_Ty>, "The C++ Standard forbids containers of non-object types "
-                                    "because of [container.requirements].");
 
 private:
     using _Mytraits      = _Uhash_compare<_Kty, _Hasher, _Keyeq>;
@@ -563,8 +561,6 @@ public:
             "unordered_multimap<Key, Value, Hasher, Eq, Allocator>", "pair<const Key, Value>"));
     static_assert(is_object_v<_Kty>, "The C++ Standard forbids containers of non-object types "
                                      "because of [container.requirements].");
-    static_assert(is_object_v<_Ty>, "The C++ Standard forbids containers of non-object types "
-                                    "because of [container.requirements].");
 
 private:
     using _Mytraits      = _Uhash_compare<_Kty, _Hasher, _Keyeq>;
diff --git a/stl/inc/xstddef b/stl/inc/xstddef
deleted file mode 100644
index ffa37dfcc08..00000000000
--- a/stl/inc/xstddef
+++ /dev/null
@@ -1,32 +0,0 @@
-// xstddef internal header (core)
-
-// Copyright (c) Microsoft Corporation.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-#pragma once
-#ifndef _XSTDDEF_
-#define _XSTDDEF_
-#include <yvals_core.h>
-#if _STL_COMPILER_PREPROCESSOR
-#include <cstddef>
-#include <xtr1common>
-
-#pragma pack(push, _CRT_PACKING)
-#pragma warning(push, _STL_WARNING_LEVEL)
-#pragma warning(disable : _STL_DISABLED_WARNINGS)
-_STL_DISABLE_CLANG_WARNINGS
-#pragma push_macro("new")
-#undef new
-
-_STD_BEGIN
-template <class>
-// TRANSITION, CWG-2518: false value attached to a dependent name (for static_assert)
-_INLINE_VAR constexpr bool _Always_false = false;
-_STD_END
-
-#pragma pop_macro("new")
-_STL_RESTORE_CLANG_WARNINGS
-#pragma warning(pop)
-#pragma pack(pop)
-#endif // _STL_COMPILER_PREPROCESSOR
-#endif // _XSTDDEF_
diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
index b1fc9a6c944..02308dbbfab 100644
--- a/stl/inc/yvals_core.h
+++ b/stl/inc/yvals_core.h
@@ -365,6 +365,7 @@
 
 // _HAS_CXX23 and _SILENCE_ALL_CXX23_DEPRECATION_WARNINGS control:
 // P1413R3 Deprecate aligned_storage And aligned_union
+// P2614R2 Deprecating float_denorm_style, numeric_limits::has_denorm, numeric_limits::has_denorm_loss
 // Other C++23 deprecation warnings
 
 // Parallel Algorithms Notes
@@ -1431,7 +1432,18 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 #define _CXX23_DEPRECATE_UNIX_STREAMS
 #endif // ^^^ warning disabled ^^^
 
-// next warning number: STL4042
+#if _HAS_CXX23 && !defined(_SILENCE_CXX23_DENORM_DEPRECATION_WARNING) \
+    && !defined(_SILENCE_ALL_CXX23_DEPRECATION_WARNINGS)
+#define _CXX23_DEPRECATE_DENORM                                                                                        \
+    [[deprecated("warning STL4042: "                                                                                   \
+                 "std::float_denorm_style, std::numeric_limits::has_denorm, and std::numeric_limits::has_denorm_loss " \
+                 "are deprecated in C++23. You can define _SILENCE_CXX23_DENORM_DEPRECATION_WARNING or "               \
+                 "_SILENCE_ALL_CXX23_DEPRECATION_WARNINGS to suppress this warning.")]]
+#else // ^^^ warning enabled / warning disabled vvv
+#define _CXX23_DEPRECATE_DENORM
+#endif // ^^^ warning disabled ^^^
+
+// next warning number: STL4043
 
 // next error number: STL1006
 
diff --git a/tests/std/tests/Dev11_0437519_container_requirements/test.compile.pass.cpp b/tests/std/tests/Dev11_0437519_container_requirements/test.compile.pass.cpp
index 466a658ba69..296ca936c4a 100644
--- a/tests/std/tests/Dev11_0437519_container_requirements/test.compile.pass.cpp
+++ b/tests/std/tests/Dev11_0437519_container_requirements/test.compile.pass.cpp
@@ -3048,6 +3048,17 @@ void assert_container() {
     check_all_specific_requirements<Tag>();
 }
 
+// MapLike<K, V&> is squirrelly, but appears to be permitted.
+template <template <class...> class MapLike>
+void check_reference_as_mapped_type() {
+    double dbl = 3.14;
+
+    MapLike<int, double&> ml;
+    ml.emplace(10, dbl);
+
+    STATIC_ASSERT(std::is_same_v<decltype(ml.find(10)->second), double&>);
+}
+
 void assert_all() {
     assert_container<tag_deque>();
     assert_container<tag_forward_list>();
@@ -3063,4 +3074,9 @@ void assert_all() {
     assert_container<tag_unordered_multimap>();
     assert_container<tag_unordered_multiset>();
     assert_container<tag_unordered_set>();
+
+    check_reference_as_mapped_type<std::map>();
+    check_reference_as_mapped_type<std::multimap>();
+    check_reference_as_mapped_type<std::unordered_map>();
+    check_reference_as_mapped_type<std::unordered_multimap>();
 }
diff --git a/tests/std/tests/Dev11_1074023_constexpr/test.cpp b/tests/std/tests/Dev11_1074023_constexpr/test.cpp
index cdd745fd63c..58c32ebc3e2 100644
--- a/tests/std/tests/Dev11_1074023_constexpr/test.cpp
+++ b/tests/std/tests/Dev11_1074023_constexpr/test.cpp
@@ -6,6 +6,7 @@
 #define _SILENCE_CXX17_IS_LITERAL_TYPE_DEPRECATION_WARNING
 #define _SILENCE_CXX17_NEGATORS_DEPRECATION_WARNING
 #define _SILENCE_CXX20_IS_POD_DEPRECATION_WARNING
+#define _SILENCE_CXX23_DENORM_DEPRECATION_WARNING
 
 #include <algorithm>
 #include <array>
diff --git a/tests/std/tests/GH_001411_core_headers/test.cpp b/tests/std/tests/GH_001411_core_headers/test.cpp
index 0d5907989c5..ced205530ce 100644
--- a/tests/std/tests/GH_001411_core_headers/test.cpp
+++ b/tests/std/tests/GH_001411_core_headers/test.cpp
@@ -21,7 +21,6 @@
 
 // <__msvc_iter_core.hpp> is included by <tuple>
 // <xkeycheck.h> should not be included outside of <yvals_core.h>
-// <xstddef> is included by <type_traits>
 // <xtr1common> is included by <cstddef>
 // <yvals_core.h> is included by every public core header
 
diff --git a/tests/std/tests/VSO_0000000_instantiate_iterators_misc/test.compile.pass.cpp b/tests/std/tests/VSO_0000000_instantiate_iterators_misc/test.compile.pass.cpp
index e48746e4e1d..39008f01464 100644
--- a/tests/std/tests/VSO_0000000_instantiate_iterators_misc/test.compile.pass.cpp
+++ b/tests/std/tests/VSO_0000000_instantiate_iterators_misc/test.compile.pass.cpp
@@ -1624,7 +1624,7 @@ void typeindex_test() {
 
 template <typename FunctorArg, typename Arg>
 void functors_test_impl(Arg val) {
-    // Following from <xstddef>:
+    // Following from <type_traits> and <xutility>:
     (void) plus<FunctorArg>()(val, val);
     (void) minus<FunctorArg>()(val, val);
     (void) multiplies<FunctorArg>()(val, val);
diff --git a/tests/std/tests/VSO_0000000_instantiate_type_traits/test.compile.pass.cpp b/tests/std/tests/VSO_0000000_instantiate_type_traits/test.compile.pass.cpp
index 722f6ff98a4..7d2d946555f 100644
--- a/tests/std/tests/VSO_0000000_instantiate_type_traits/test.compile.pass.cpp
+++ b/tests/std/tests/VSO_0000000_instantiate_type_traits/test.compile.pass.cpp
@@ -124,7 +124,7 @@ void type_traits_test_impl() {
     TRAIT_V(is_null_pointer, T);
     TRAIT_V(is_union, T);
     TRAIT_V(is_class, T);
-    TRAIT_V(is_function, T); // from xstddef
+    TRAIT_V(is_function, T);
     TRAIT_V(is_fundamental, T);
     TRAIT_V(is_arithmetic, T); // from xtr1common
     TRAIT_V(is_object, T);
diff --git a/tests/tr1/tests/limits/test.cpp b/tests/tr1/tests/limits/test.cpp
index 96bdfa08d86..08e98d73468 100644
--- a/tests/tr1/tests/limits/test.cpp
+++ b/tests/tr1/tests/limits/test.cpp
@@ -4,6 +4,8 @@
 // test <limits>
 #define TEST_NAME "<limits>"
 
+#define _SILENCE_CXX23_DENORM_DEPRECATION_WARNING
+
 #include "tdefs.h"
 #include <float.h>
 #include <limits.h>