From c761d1489d511358e7f8c9ebdfb1e6c0967528e1 Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34@live.cn>
Date: Tue, 26 Aug 2025 15:19:44 +0800
Subject: [PATCH 1/3] Add missing Mandates for `resize_and_overwrite`

---
 stl/inc/xstring                               |  8 +++--
 .../tests/P0980R1_constexpr_strings/test.cpp  | 32 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/stl/inc/xstring b/stl/inc/xstring
index b49bb137779..608b64e764e 100644
--- a/stl/inc/xstring
+++ b/stl/inc/xstring
@@ -2317,9 +2317,11 @@ public:
             _Mypair._Myval2._Mysize = _New_size;
         }
 
-        auto _Arg_ptr                   = _Mypair._Myval2._Myptr();
-        auto _Arg_size                  = _New_size;
-        const auto _Result_size         = _STD move(_Op)(_Arg_ptr, _Arg_size);
+        auto _Arg_ptr           = _Mypair._Myval2._Myptr();
+        auto _Arg_size          = _New_size;
+        const auto _Result_size = _STD move(_Op)(_Arg_ptr, _Arg_size);
+        static_assert(_Integer_like<decltype(_Result_size)>, "the return type of the operation must be integer-like");
+
         const auto _Result_as_size_type = static_cast<size_type>(_Result_size);
 #if _ITERATOR_DEBUG_LEVEL != 0
         _STL_VERIFY(_Result_size >= 0, "the returned size can't be smaller than 0");
diff --git a/tests/std/tests/P0980R1_constexpr_strings/test.cpp b/tests/std/tests/P0980R1_constexpr_strings/test.cpp
index 706ab1d0676..fd77a8eefeb 100644
--- a/tests/std/tests/P0980R1_constexpr_strings/test.cpp
+++ b/tests/std/tests/P0980R1_constexpr_strings/test.cpp
@@ -17,6 +17,10 @@
 #include <type_traits>
 #include <utility>
 
+#if _HAS_CXX20
+#include <ranges> // for integer-class types
+#endif // _HAS_CXX20
+
 using namespace std;
 
 constexpr auto literal_input     = "Hello fluffy kittens";
@@ -2226,15 +2230,41 @@ constexpr void test_all() {
 }
 
 #if _HAS_CXX23
+template <class I>
 void test_gh_2524() { // COMPILE-ONLY
     // GH-2524 resize_and_overwrite generates warning C4018 when Operation returns int
     string s;
     s.resize_and_overwrite(1, [](char* buffer, size_t) {
         *buffer = 'x';
-        int i   = 1;
+        I i     = 1;
         return i;
     });
 }
+
+void test_gh_2524_all() { // COMPILE-ONLY
+    test_gh_2524<signed char>();
+    test_gh_2524<short>();
+    test_gh_2524<int>();
+    test_gh_2524<long>();
+    test_gh_2524<long long>();
+
+    test_gh_2524<unsigned char>();
+    test_gh_2524<unsigned short>();
+    test_gh_2524<unsigned int>();
+    test_gh_2524<unsigned long>();
+    test_gh_2524<unsigned long long>();
+
+    test_gh_2524<char>();
+#ifdef __cpp_char8_t
+    test_gh_2524<char8_t>();
+#endif // defined(__cpp_char8_t)
+    test_gh_2524<char16_t>();
+    test_gh_2524<char32_t>();
+    test_gh_2524<wchar_t>();
+
+    test_gh_2524<_Signed128>();
+    test_gh_2524<_Unsigned128>();
+}
 #endif // _HAS_CXX23
 
 int main() {

From 5cfe9ae18301bec807c50a96e5214cd71a87fd18 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Sat, 6 Sep 2025 03:07:51 -0700
Subject: [PATCH 2/3] Cite the Standard (also pre-existing below).

---
 stl/inc/xstring | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/stl/inc/xstring b/stl/inc/xstring
index 608b64e764e..265ffc64a8e 100644
--- a/stl/inc/xstring
+++ b/stl/inc/xstring
@@ -2320,12 +2320,14 @@ public:
         auto _Arg_ptr           = _Mypair._Myval2._Myptr();
         auto _Arg_size          = _New_size;
         const auto _Result_size = _STD move(_Op)(_Arg_ptr, _Arg_size);
-        static_assert(_Integer_like<decltype(_Result_size)>, "the return type of the operation must be integer-like");
+        static_assert(_Integer_like<decltype(_Result_size)>,
+            "the return type of the operation must be integer-like, N5014 [string.capacity]/8");
 
         const auto _Result_as_size_type = static_cast<size_type>(_Result_size);
 #if _ITERATOR_DEBUG_LEVEL != 0
-        _STL_VERIFY(_Result_size >= 0, "the returned size can't be smaller than 0");
-        _STL_VERIFY(_Result_as_size_type <= _New_size, "the returned size can't be greater than the passed size");
+        _STL_VERIFY(_Result_size >= 0, "the returned size can't be smaller than 0, N5014 [string.capacity]/9.2");
+        _STL_VERIFY(_Result_as_size_type <= _New_size,
+            "the returned size can't be greater than the passed size, N5014 [string.capacity]/9.3");
 #endif // _ITERATOR_DEBUG_LEVEL != 0
         _Eos(_Result_as_size_type);
     }

From c4c9d81631f24b70719d7afbadd7b83ad881f8a7 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Sat, 6 Sep 2025 03:16:07 -0700
Subject: [PATCH 3/3] Include `<ranges>` only when necessary.

---
 tests/std/tests/P0980R1_constexpr_strings/test.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/std/tests/P0980R1_constexpr_strings/test.cpp b/tests/std/tests/P0980R1_constexpr_strings/test.cpp
index fd77a8eefeb..cc3004253ab 100644
--- a/tests/std/tests/P0980R1_constexpr_strings/test.cpp
+++ b/tests/std/tests/P0980R1_constexpr_strings/test.cpp
@@ -17,9 +17,9 @@
 #include <type_traits>
 #include <utility>
 
-#if _HAS_CXX20
-#include <ranges> // for integer-class types
-#endif // _HAS_CXX20
+#if _HAS_CXX23
+#include <ranges> // for integer-class types in test_gh_2524_all()
+#endif // _HAS_CXX23
 
 using namespace std;