diff --git a/stl/inc/algorithm b/stl/inc/algorithm
index cb6147d51fa..8bff4dfa87b 100644
--- a/stl/inc/algorithm
+++ b/stl/inc/algorithm
@@ -41,7 +41,7 @@ _STD_BEGIN
 _INLINE_VAR constexpr int _ISORT_MAX = 32; // maximum size for insertion sort
 
 template <class _It>
-_INLINE_VAR constexpr auto _Isort_max = _Iter_diff_t<_It>{_ISORT_MAX};
+_INLINE_VAR constexpr _Iter_diff_t<_It> _Isort_max{_ISORT_MAX};
 
 template <class _Diff>
 constexpr ptrdiff_t _Temporary_buffer_size(const _Diff _Value) noexcept {
diff --git a/stl/inc/cvt/wbuffer b/stl/inc/cvt/wbuffer
index cea11d042be..150bc758ff2 100644
--- a/stl/inc/cvt/wbuffer
+++ b/stl/inc/cvt/wbuffer
@@ -252,7 +252,7 @@ namespace stdext {
                 if (_Mystrbuf && _Status != _Wrote) {
                     // got buffer, haven't written, try to compose an element
                     if (_Status != _Eof) {
-                        if (_Str.size() == 0) {
+                        if (_Str.empty()) {
                             _Status = _Need;
                         } else {
                             _Status = _Got;
diff --git a/stl/inc/exception b/stl/inc/exception
index 483e71ff5c1..0643e0be91a 100644
--- a/stl/inc/exception
+++ b/stl/inc/exception
@@ -264,25 +264,27 @@ public:
         return __ExceptionPtrCompare(&_Lhs, &_Rhs);
     }
 
-    _NODISCARD friend bool operator==(nullptr_t, const exception_ptr& _Rhs) noexcept {
-        return !_Rhs;
-    }
-
     _NODISCARD friend bool operator==(const exception_ptr& _Lhs, nullptr_t) noexcept {
         return !_Lhs;
     }
 
+#if !_HAS_CXX20
+    _NODISCARD friend bool operator==(nullptr_t, const exception_ptr& _Rhs) noexcept {
+        return !_Rhs;
+    }
+
     _NODISCARD friend bool operator!=(const exception_ptr& _Lhs, const exception_ptr& _Rhs) noexcept {
         return !(_Lhs == _Rhs);
     }
 
-    _NODISCARD friend bool operator!=(nullptr_t _Lhs, const exception_ptr& _Rhs) noexcept {
+    _NODISCARD friend bool operator!=(const exception_ptr& _Lhs, nullptr_t _Rhs) noexcept {
         return !(_Lhs == _Rhs);
     }
 
-    _NODISCARD friend bool operator!=(const exception_ptr& _Lhs, nullptr_t _Rhs) noexcept {
+    _NODISCARD friend bool operator!=(nullptr_t _Lhs, const exception_ptr& _Rhs) noexcept {
         return !(_Lhs == _Rhs);
     }
+#endif // !_HAS_CXX20
 
 private:
 #ifdef __clang__
diff --git a/stl/inc/experimental/coroutine b/stl/inc/experimental/coroutine
index ed2b37665a6..0508a76808d 100644
--- a/stl/inc/experimental/coroutine
+++ b/stl/inc/experimental/coroutine
@@ -88,8 +88,9 @@ namespace experimental {
             return _Ptr;
         }
 
-        __declspec(
-            deprecated("is deprecated. Use coroutine_handle::address() instead")) void* to_address() const noexcept {
+        [[deprecated("coroutine_handle::to_address() is deprecated. "
+                     "Use coroutine_handle::address() instead.")]] void*
+            to_address() const noexcept {
             return _Ptr;
         }
 
@@ -131,8 +132,9 @@ namespace experimental {
     struct coroutine_handle : coroutine_handle<> { // general form
         using coroutine_handle<>::coroutine_handle;
 
-        __declspec(deprecated("with pointer parameter is deprecated. Use coroutine_handle::from_promise(T&) "
-                              "instead")) static coroutine_handle from_promise(_PromiseT* _Prom) noexcept {
+        [[deprecated("coroutine_handle::from_promise(T*) with pointer parameter is deprecated. "
+                     "Use coroutine_handle::from_promise(T&) instead.")]] static coroutine_handle
+            from_promise(_PromiseT* _Prom) noexcept {
             return from_promise(*_Prom);
         }
 
diff --git a/stl/inc/future b/stl/inc/future
index c7568af6df4..1eed675290f 100644
--- a/stl/inc/future
+++ b/stl/inc/future
@@ -1157,7 +1157,7 @@ public:
     }
 
     _NODISCARD future<_Ty> get_future() {
-        return future<_Ty>(_MyPromise._Get_state_for_future(), _Nil());
+        return future<_Ty>(_MyPromise._Get_state_for_future(), _Nil{});
     }
 
     void set_value(const _Ty& _Val) {
@@ -1219,7 +1219,7 @@ public:
     }
 
     _NODISCARD future<_Ty&> get_future() {
-        return future<_Ty&>(_MyPromise._Get_state_for_future(), _Nil());
+        return future<_Ty&>(_MyPromise._Get_state_for_future(), _Nil{});
     }
 
     void set_value(_Ty& _Val) {
@@ -1273,7 +1273,7 @@ public:
     }
 
     _NODISCARD future<void> get_future() {
-        return future<void>(_MyPromise._Get_state_for_future(), _Nil());
+        return future<void>(_MyPromise._Get_state_for_future(), _Nil{});
     }
 
     void set_value() {
@@ -1365,7 +1365,7 @@ public:
     }
 
     _NODISCARD future<_Ret> get_future() {
-        return future<_Ret>(_MyPromise._Get_state_for_future(), _Nil());
+        return future<_Ret>(_MyPromise._Get_state_for_future(), _Nil{});
     }
 
     void operator()(_ArgTypes... _Args) {
@@ -1494,7 +1494,7 @@ _NODISCARD future<_Invoke_result_t<decay_t<_Fty>, decay_t<_ArgTypes>...>> async(
         _Get_associated_state<_Ret>(_Policy, _Fake_no_copy_callable_adapter<_Fty, _ArgTypes...>(
                                                  _STD forward<_Fty>(_Fnarg), _STD forward<_ArgTypes>(_Args)...)));
 
-    return future<_Ret>(_Pr._Get_state_for_future(), _Nil());
+    return future<_Ret>(_Pr._Get_state_for_future(), _Nil{});
 }
 
 template <class _Fty, class... _ArgTypes>
diff --git a/stl/inc/random b/stl/inc/random
index b0155d67a6d..2ed8c68bb06 100644
--- a/stl/inc/random
+++ b/stl/inc/random
@@ -3011,7 +3011,7 @@ private:
                 _LogSx = _STD log(_Sx) + static_cast<_Ty>(_ExpMax) * (_Ln2 * 2);
             }
 
-            const auto _Fx = _Ty{_STD sqrt(_Ty{-2} * _LogSx / _Sx)};
+            const _Ty _Fx{_STD sqrt(_Ty{-2} * _LogSx / _Sx)};
             if (_Keep) { // save second value for next call
                 _Xx2   = _Fx * _Vx2;
                 _Valid = true;
diff --git a/stl/inc/stdatomic.h b/stl/inc/stdatomic.h
index 462759021bf..b36f35c5e34 100644
--- a/stl/inc/stdatomic.h
+++ b/stl/inc/stdatomic.h
@@ -9,6 +9,10 @@
 #include <yvals.h>
 #if _STL_COMPILER_PREPROCESSOR
 
+#ifndef __cplusplus
+#error <stdatomic.h> is not yet supported when compiling as C, but this is planned for a future release.
+#endif // __cplusplus
+
 #ifdef _M_CEE_PURE
 #error <stdatomic.h> is not supported when compiling with /clr:pure.
 #endif // _M_CEE_PURE
diff --git a/stl/inc/string b/stl/inc/string
index 41cb4877fd4..10d08c88f53 100644
--- a/stl/inc/string
+++ b/stl/inc/string
@@ -95,7 +95,7 @@ _NODISCARD inline int stoi(const string& _Str, size_t* _Idx = nullptr, int _Base
         _Xinvalid_argument("invalid stoi argument");
     }
 
-    if (_Errno_ref == ERANGE || _Ans < INT_MIN || INT_MAX < _Ans) {
+    if (_Errno_ref == ERANGE) {
         _Xout_of_range("stoi argument out of range");
     }
 
@@ -276,7 +276,7 @@ _NODISCARD inline int stoi(const wstring& _Str, size_t* _Idx = nullptr, int _Bas
         _Xinvalid_argument("invalid stoi argument");
     }
 
-    if (_Errno_ref == ERANGE || _Ans < INT_MIN || INT_MAX < _Ans) {
+    if (_Errno_ref == ERANGE) {
         _Xout_of_range("stoi argument out of range");
     }
 
diff --git a/stl/inc/tuple b/stl/inc/tuple
index 8fae9205b56..180de03fbfd 100644
--- a/stl/inc/tuple
+++ b/stl/inc/tuple
@@ -963,7 +963,7 @@ constexpr _Ret _Tuple_cat(index_sequence<_Kx...>, index_sequence<_Ix...>, _Ty&&
 template <class... _Tuples>
 _NODISCARD constexpr typename _Tuple_cat1<_Tuples...>::type tuple_cat(_Tuples&&... _Tpls) { // concatenate tuples
     using _Cat1 = _Tuple_cat1<_Tuples...>;
-    return _Tuple_cat<typename _Cat1::type>(typename _Cat1::_Kx_arg_seq(), typename _Cat1::_Ix_arg_seq(),
+    return _Tuple_cat<typename _Cat1::type>(typename _Cat1::_Kx_arg_seq{}, typename _Cat1::_Ix_arg_seq{},
         _STD forward_as_tuple(_STD forward<_Tuples>(_Tpls)...));
 }
 
diff --git a/stl/inc/xcharconv_ryu.h b/stl/inc/xcharconv_ryu.h
index 282e18dc1bf..d4f7ca635d1 100644
--- a/stl/inc/xcharconv_ryu.h
+++ b/stl/inc/xcharconv_ryu.h
@@ -134,7 +134,6 @@ _NODISCARD inline uint64_t __double_to_bits(const double __d) {
 // vvvvvvvvvv DERIVED FROM d2s.h vvvvvvvvvv
 
 inline constexpr int __DOUBLE_MANTISSA_BITS = 52;
-inline constexpr int __DOUBLE_EXPONENT_BITS = 11;
 inline constexpr int __DOUBLE_BIAS = 1023;
 
 inline constexpr int __DOUBLE_POW5_INV_BITCOUNT = 122;
@@ -950,7 +949,6 @@ _NODISCARD inline to_chars_result __d2exp_buffered_n(char* _First, char* const _
 // vvvvvvvvvv DERIVED FROM f2s.c vvvvvvvvvv
 
 inline constexpr int __FLOAT_MANTISSA_BITS = 23;
-inline constexpr int __FLOAT_EXPONENT_BITS = 8;
 inline constexpr int __FLOAT_BIAS = 127;
 
 // This table is generated by PrintFloatLookupTable.
diff --git a/stl/inc/xlocmon b/stl/inc/xlocmon
index 3452c969eab..914e94bf305 100644
--- a/stl/inc/xlocmon
+++ b/stl/inc/xlocmon
@@ -360,7 +360,7 @@ protected:
             _State |= ios_base::eofbit;
         }
 
-        if (_Str.size() == 0) {
+        if (_Str.empty()) {
             _State |= ios_base::failbit; // _Getmfld failed
         } else { // convert to long double
             const char* _Eb = _Str.c_str();
@@ -476,7 +476,7 @@ private:
                     int _Fracdigseen        = 0;
                     int _Fracdigits         = _Ppunct_fac->frac_digits();
                     const string _Grouping  = _Ppunct_fac->grouping();
-                    const _Elem _Kseparator = _Grouping.size() == 0 ? _Elem{} : _Ppunct_fac->thousands_sep();
+                    const _Elem _Kseparator = _Grouping.empty() ? _Elem{} : _Ppunct_fac->thousands_sep();
 
                     if (_Kseparator == _Elem{} || CHAR_MAX <= static_cast<unsigned char>(*_Grouping.c_str())) {
                         for (; _First != _Last && (_Idx = _Find_elem(_Atoms, *_First)) < 10; ++_First) {
@@ -540,7 +540,7 @@ private:
                         }
                     }
 
-                    if (_Val.size() == 0) {
+                    if (_Val.empty()) {
                         _Bad = true; // fail if no elements parsed
                     } else {
                         for (; _Fracdigseen < _Fracdigits; ++_Fracdigseen) {
diff --git a/stl/inc/xlocnum b/stl/inc/xlocnum
index 549b02ae8f5..498ad09a300 100644
--- a/stl/inc/xlocnum
+++ b/stl/inc/xlocnum
@@ -656,7 +656,7 @@ private:
         const locale& _Loc) const { // get integer field from [_First, _Last) into _Ac
         const auto& _Punct_fac  = _STD use_facet<numpunct<_Elem>>(_Loc);
         const string _Grouping  = _Punct_fac.grouping();
-        const _Elem _Kseparator = _Grouping.size() == 0 ? _Elem{} : _Punct_fac.thousands_sep();
+        const _Elem _Kseparator = _Grouping.empty() ? _Elem{} : _Punct_fac.thousands_sep();
 
         constexpr int _Numget_signoff = 22;
         constexpr int _Numget_xoff    = 24;
@@ -812,7 +812,7 @@ private:
                 }
             }
         } else { // grouping specified, gather digits and group sizes
-            const _Elem _Kseparator = _Grouping.size() == 0 ? _Elem{} : _Punct_fac.thousands_sep();
+            const _Elem _Kseparator = _Grouping.empty() ? _Elem{} : _Punct_fac.thousands_sep();
             string _Groups(1, '\0');
             size_t _Group = 0;
 
@@ -1003,7 +1003,7 @@ private:
                 }
             }
         } else { // grouping specified, gather digits and group sizes
-            const _Elem _Kseparator = _Grouping.size() == 0 ? _Elem{} : _Punct_fac.thousands_sep();
+            const _Elem _Kseparator = _Grouping.empty() ? _Elem{} : _Punct_fac.thousands_sep();
             string _Groups(1, '\0');
             size_t _Group = 0;
 
diff --git a/stl/inc/xthreads.h b/stl/inc/xthreads.h
index c8c88800575..a1b8ee2bfec 100644
--- a/stl/inc/xthreads.h
+++ b/stl/inc/xthreads.h
@@ -28,27 +28,27 @@ struct _Thrd_t { // thread identifier for Win32
 // Size and alignment for _Mtx_internal_imp_t and _Cnd_internal_imp_t
 #ifdef _CRT_WINDOWS
 #ifdef _WIN64
-#define _Mtx_internal_imp_size      32
-#define _Mtx_internal_imp_alignment 8
-#define _Cnd_internal_imp_size      16
-#define _Cnd_internal_imp_alignment 8
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_size      = 32;
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_alignment = 8;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_size      = 16;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_alignment = 8;
 #else // _WIN64
-#define _Mtx_internal_imp_size      20
-#define _Mtx_internal_imp_alignment 4
-#define _Cnd_internal_imp_size      8
-#define _Cnd_internal_imp_alignment 4
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_size      = 20;
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_alignment = 4;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_size      = 8;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_alignment = 4;
 #endif // _WIN64
 #else // _CRT_WINDOWS
 #ifdef _WIN64
-#define _Mtx_internal_imp_size      80
-#define _Mtx_internal_imp_alignment 8
-#define _Cnd_internal_imp_size      72
-#define _Cnd_internal_imp_alignment 8
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_size      = 80;
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_alignment = 8;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_size      = 72;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_alignment = 8;
 #else // _WIN64
-#define _Mtx_internal_imp_size      48
-#define _Mtx_internal_imp_alignment 4
-#define _Cnd_internal_imp_size      40
-#define _Cnd_internal_imp_alignment 4
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_size      = 48;
+_INLINE_VAR constexpr size_t _Mtx_internal_imp_alignment = 4;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_size      = 40;
+_INLINE_VAR constexpr size_t _Cnd_internal_imp_alignment = 4;
 #endif // _WIN64
 #endif // _CRT_WINDOWS
 
diff --git a/stl/inc/xutility b/stl/inc/xutility
index dc3f747c32a..7da65d0906e 100644
--- a/stl/inc/xutility
+++ b/stl/inc/xutility
@@ -1280,10 +1280,10 @@ struct _Distance_unknown {
 };
 
 template <class _Diff>
-_INLINE_VAR constexpr auto _Max_possible_v = _Diff{static_cast<make_unsigned_t<_Diff>>(-1) >> 1};
+_INLINE_VAR constexpr _Diff _Max_possible_v{static_cast<make_unsigned_t<_Diff>>(-1) >> 1};
 
 template <class _Diff>
-_INLINE_VAR constexpr auto _Min_possible_v = _Diff{-_Max_possible_v<_Diff> - 1};
+_INLINE_VAR constexpr _Diff _Min_possible_v{-_Max_possible_v<_Diff> - 1};
 
 template <class _Iter, class = void>
 _INLINE_VAR constexpr bool _Offset_verifiable_v = false;
diff --git a/stl/src/cthread.cpp b/stl/src/cthread.cpp
index 9a032bb05d9..d5923f5312b 100644
--- a/stl/src/cthread.cpp
+++ b/stl/src/cthread.cpp
@@ -33,7 +33,7 @@ namespace {
         *b.started = 1;
         _Cnd_signal(*b.cond);
         _Mtx_unlock(*b.mtx);
-        const unsigned int res = (b.func) (b.data);
+        const unsigned int res = b.func(b.data);
         _Cnd_do_broadcast_at_thread_exit();
         return res;
     }
diff --git a/stl/src/fiopen.cpp b/stl/src/fiopen.cpp
index da9b5363207..d304f37e08b 100644
--- a/stl/src/fiopen.cpp
+++ b/stl/src/fiopen.cpp
@@ -23,7 +23,7 @@ FILE* _Xfsopen(_In_z_ const wchar_t* filename, _In_ int mode, _In_ int prot) {
     return _wfsopen(filename, mods[mode], prot);
 }
 
-template <typename CharT>
+template <class CharT>
 FILE* _Xfiopen(const CharT* filename, ios_base::openmode mode, int prot) {
     static const int valid[] = {
         // valid combinations of open flags
diff --git a/tests/libcxx/expected_results.txt b/tests/libcxx/expected_results.txt
index 39350ca0d9f..e22989a7664 100644
--- a/tests/libcxx/expected_results.txt
+++ b/tests/libcxx/expected_results.txt
@@ -275,16 +275,7 @@ std/utilities/memory/default.allocator/allocator.members/allocate.verify.cpp SKI
 
 
 # *** MISSING STL FEATURES ***
-# C++23 P1048R1 "is_scoped_enum"
-std/utilities/meta/meta.unary/meta.unary.prop/is_scoped_enum.pass.cpp FAIL
-
-# C++23 P1679R3 "contains() For basic_string/basic_string_view"
-std/strings/basic.string/string.contains/contains.char.pass.cpp FAIL
-std/strings/basic.string/string.contains/contains.ptr.pass.cpp FAIL
-std/strings/basic.string/string.contains/contains.string_view.pass.cpp FAIL
-std/strings/string.view/string.view.template/contains.char.pass.cpp FAIL
-std/strings/string.view/string.view.template/contains.ptr.pass.cpp FAIL
-std/strings/string.view/string.view.template/contains.string_view.pass.cpp FAIL
+# Nothing here! :-)
 
 
 # *** MISSING COMPILER FEATURES ***
diff --git a/tests/libcxx/skipped_tests.txt b/tests/libcxx/skipped_tests.txt
index 3390cb1e8e9..e0424d97bfc 100644
--- a/tests/libcxx/skipped_tests.txt
+++ b/tests/libcxx/skipped_tests.txt
@@ -275,16 +275,7 @@ utilities\memory\default.allocator\allocator.members\allocate.verify.cpp
 
 
 # *** MISSING STL FEATURES ***
-# C++23 P1048R1 "is_scoped_enum"
-utilities\meta\meta.unary\meta.unary.prop\is_scoped_enum.pass.cpp
-
-# C++23 P1679R3 "contains() For basic_string/basic_string_view"
-strings\basic.string\string.contains\contains.char.pass.cpp
-strings\basic.string\string.contains\contains.ptr.pass.cpp
-strings\basic.string\string.contains\contains.string_view.pass.cpp
-strings\string.view\string.view.template\contains.char.pass.cpp
-strings\string.view\string.view.template\contains.ptr.pass.cpp
-strings\string.view\string.view.template\contains.string_view.pass.cpp
+# Nothing here! :-)
 
 
 # *** MISSING COMPILER FEATURES ***
diff --git a/tests/std/include/test_death.hpp b/tests/std/include/test_death.hpp
index 296a0f69012..521945a24b1 100644
--- a/tests/std/include/test_death.hpp
+++ b/tests/std/include/test_death.hpp
@@ -9,7 +9,7 @@
 #include <string>
 #include <vector>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 namespace std_testing {
     constexpr int internal_failure = 103;
diff --git a/tests/std/include/test_thread_support.hpp b/tests/std/include/test_thread_support.hpp
index 322612a93bf..3f51384ddd1 100644
--- a/tests/std/include/test_thread_support.hpp
+++ b/tests/std/include/test_thread_support.hpp
@@ -10,7 +10,7 @@
 #include <stdlib.h>
 #include <thread>
 #ifdef _MSC_EXTENSIONS
-#include <test_windows.hpp>
+#include <Windows.h>
 #endif // _MSC_EXTENSIONS
 
 class one_shot {
diff --git a/tests/std/include/test_windows.hpp b/tests/std/include/test_windows.hpp
deleted file mode 100644
index aecb1ac36b4..00000000000
--- a/tests/std/include/test_windows.hpp
+++ /dev/null
@@ -1,6 +0,0 @@
-// Copyright (c) Microsoft Corporation.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-#pragma once
-struct IUnknown; // windows.h drags in a template that uses IUnknown before it has been declared.
-#include <windows.h>
diff --git a/tests/std/tests/Dev08_563686_ostream/test.cpp b/tests/std/tests/Dev08_563686_ostream/test.cpp
index ffaf75ef30e..1b5d8b4bd46 100644
--- a/tests/std/tests/Dev08_563686_ostream/test.cpp
+++ b/tests/std/tests/Dev08_563686_ostream/test.cpp
@@ -29,7 +29,7 @@
 #include <sstream>
 #include <stdlib.h>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 int main() {
     // Track CRT blocks
diff --git a/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp b/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
index d34c7618fef..b495ef5fd1d 100644
--- a/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
+++ b/tests/std/tests/Dev09_056375_locale_cleanup/test.cpp
@@ -5,7 +5,7 @@
 #include <locale>
 #include <stdio.h>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 using namespace std;
 
diff --git a/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp b/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
index 93ecade7061..c0301b3020e 100644
--- a/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
+++ b/tests/std/tests/Dev09_056375_locale_cleanup/testdll.cpp
@@ -4,7 +4,7 @@
 #include <assert.h>
 #include <locale>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 using namespace std;
 
diff --git a/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp b/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
index 99712972256..5d219e233d6 100644
--- a/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
+++ b/tests/std/tests/Dev11_0493504_error_category_lifetime/test.cpp
@@ -10,7 +10,7 @@
 #include <future>
 #endif // _M_CEE
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 using namespace std;
 
diff --git a/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp b/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
index f6878463eb0..0e1e96bb23c 100644
--- a/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
+++ b/tests/std/tests/VSO_0121275_filesystem_canonical_should_handle_many_double_dots/test.cpp
@@ -12,7 +12,7 @@
 #include <system_error>
 #include <wctype.h>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 using namespace std;
 namespace fs = std::experimental::filesystem;
diff --git a/tests/std/tests/VSO_0226079_mutex/test.cpp b/tests/std/tests/VSO_0226079_mutex/test.cpp
index cb071ec84f3..c23eace4605 100644
--- a/tests/std/tests/VSO_0226079_mutex/test.cpp
+++ b/tests/std/tests/VSO_0226079_mutex/test.cpp
@@ -13,7 +13,7 @@
 #include <thread>
 #include <utility>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 using namespace std;
 using namespace std::chrono;
@@ -339,10 +339,10 @@ struct mutex_test_fixture {
     }
 
     // nonstandard xtime type
-    template <class rep, class period>
-    xtime to_xtime(const chrono::duration<rep, period>& rel_time) { // convert duration to xtime
+    template <class Rep, class Period>
+    xtime to_xtime(const chrono::duration<Rep, Period>& rel_time) { // convert duration to xtime
         xtime xt;
-        if (rel_time <= chrono::duration<rep, period>::zero()) { // negative or zero relative time, return zero
+        if (rel_time <= chrono::duration<Rep, Period>::zero()) { // negative or zero relative time, return zero
             xt.sec  = 0;
             xt.nsec = 0;
         } else { // positive relative time, convert
diff --git a/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp b/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
index 4e633d77536..352e6a7fc64 100644
--- a/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
+++ b/tests/std/tests/VSO_0744055_atomic_load_8_bytes_readonly/test.cpp
@@ -5,7 +5,7 @@
 #include <atomic>
 #include <stdio.h>
 
-#include <test_windows.hpp>
+#include <Windows.h>
 
 int main() {
     // A customer wanted to read a std::atomic from a read-only memory-mapped file.