From 2e19827ee060c820f10bd50162ca9a2b443401e8 Mon Sep 17 00:00:00 2001
From: YexuanXiao <bizwen@nykz.org>
Date: Sat, 26 Jul 2025 17:03:21 +0800
Subject: [PATCH 1/3] Guard headers and suppress Clang warnings

---
 .../tests/Dev11_0000000_null_forward_iterators/test.cpp   | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
index 94008bd066a..3da7864c61d 100644
--- a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
+++ b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
@@ -10,7 +10,9 @@
 #include <cstring>
 #include <deque>
 #include <experimental/filesystem>
+#if _HAS_CXX17
 #include <filesystem>
+#endif // _HAS_CXX17
 #include <forward_list>
 #include <iterator>
 #include <list>
@@ -18,13 +20,19 @@
 #include <new>
 #include <regex>
 #include <set>
+#if _HAS_CXX20
 #include <span>
+#endif // _HAS_CXX20
 #include <string>
 #include <type_traits>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wnontrivial-memcall"
+#endif // __clang__
+
 using namespace std;
 
 // N3797 24.2.5 [forward.iterators]/2:

From 79a6b3842ee747f6b5547fdf642a05f80b7add85 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Sat, 2 Aug 2025 02:30:37 -0700
Subject: [PATCH 2/3] Gather 17/20 headers at the end, add missing
 `<string_view>`.

---
 .../Dev11_0000000_null_forward_iterators/test.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
index 3da7864c61d..a0adcc533f2 100644
--- a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
+++ b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
@@ -10,9 +10,6 @@
 #include <cstring>
 #include <deque>
 #include <experimental/filesystem>
-#if _HAS_CXX17
-#include <filesystem>
-#endif // _HAS_CXX17
 #include <forward_list>
 #include <iterator>
 #include <list>
@@ -20,15 +17,21 @@
 #include <new>
 #include <regex>
 #include <set>
-#if _HAS_CXX20
-#include <span>
-#endif // _HAS_CXX20
 #include <string>
 #include <type_traits>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
+#if _HAS_CXX17
+#include <filesystem>
+#include <string_view>
+#endif // _HAS_CXX17
+
+#if _HAS_CXX20
+#include <span>
+#endif // _HAS_CXX20
+
 #ifdef __clang__
 #pragma clang diagnostic ignored "-Wnontrivial-memcall"
 #endif // __clang__

From af01c41cce1375485865d200de5c0473cef51a20 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Sat, 2 Aug 2025 02:35:53 -0700
Subject: [PATCH 3/3] Avoid aligned_union_t, avoid the warning.

---
 .../test.cpp                                    | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
index a0adcc533f2..b548e3d443d 100644
--- a/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
+++ b/tests/std/tests/Dev11_0000000_null_forward_iterators/test.cpp
@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#define _SILENCE_CXX23_ALIGNED_UNION_DEPRECATION_WARNING
 #define _SILENCE_EXPERIMENTAL_FILESYSTEM_DEPRECATION_WARNING
 #define _SILENCE_STDEXT_ARR_ITERS_DEPRECATION_WARNING
 
@@ -32,10 +31,6 @@
 #include <span>
 #endif // _HAS_CXX20
 
-#ifdef __clang__
-#pragma clang diagnostic ignored "-Wnontrivial-memcall"
-#endif // __clang__
-
 using namespace std;
 
 // N3797 24.2.5 [forward.iterators]/2:
@@ -102,14 +97,14 @@ void test_iterator() {
     }
 
     {
-        aligned_union_t<0, FwdIt> au3;
-        aligned_union_t<0, FwdIt> au4;
+        alignas(FwdIt) unsigned char buf3[sizeof(FwdIt)];
+        alignas(FwdIt) unsigned char buf4[sizeof(FwdIt)];
 
-        FwdIt* p3 = reinterpret_cast<FwdIt*>(&au3);
-        FwdIt* p4 = reinterpret_cast<FwdIt*>(&au4);
+        memset(buf3, 0xCC, sizeof(FwdIt));
+        memset(buf4, 0xDD, sizeof(FwdIt));
 
-        memset(p3, 0xCC, sizeof(FwdIt));
-        memset(p4, 0xDD, sizeof(FwdIt));
+        FwdIt* p3 = reinterpret_cast<FwdIt*>(buf3);
+        FwdIt* p4 = reinterpret_cast<FwdIt*>(buf4);
 
         new (p3) FwdIt{};
         new (p4) FwdIt{};