diff --git a/include/fast_io_core_impl/operations/writeimpl/basis.h b/include/fast_io_core_impl/operations/writeimpl/basis.h
index 7910442ae..bbf259c02 100644
--- a/include/fast_io_core_impl/operations/writeimpl/basis.h
+++ b/include/fast_io_core_impl/operations/writeimpl/basis.h
@@ -511,7 +511,7 @@ inline constexpr void write_all_impl(outstmtype outsm, typename outstmtype::outp
 		::std::ptrdiff_t bfddiff{ed - curr};
 		::std::ptrdiff_t itdiff{last - first};
 		if (itdiff < bfddiff)
-#if __has_cpp_attribute(__gnu__::__may_alias__)
+#if __has_cpp_attribute(likely)
 			[[likely]]
 #endif
 		{
@@ -542,7 +542,7 @@ inline constexpr ::std::byte const *write_some_bytes_impl(outstmtype outsm, ::st
 		::std::ptrdiff_t bfddiff{ed - curr};
 		::std::ptrdiff_t itdiff{last - first};
 		if (itdiff < bfddiff)
-#if __has_cpp_attribute(__gnu__::__may_alias__)
+#if __has_cpp_attribute(likely)
 			[[likely]]
 #endif
 		{
diff --git a/include/fast_io_unit/string_impl/msvc_stl.h b/include/fast_io_unit/string_impl/msvc_stl.h
index 45ac9144d..fc3f80db7 100644
--- a/include/fast_io_unit/string_impl/msvc_stl.h
+++ b/include/fast_io_unit/string_impl/msvc_stl.h
@@ -47,11 +47,95 @@ inline constexpr decltype(auto) hack_scary_val(::std::basic_string<elem, traits,
 										__builtin_offsetof(model_t, _Mypair) + __builtin_offsetof(compress_pair_type, _Myval2));
 }
 
+#ifdef _ACTIVATE_STRING_ANNOTATION
+/*
+https://github.com/microsoft/STL/blob/a357ff1750d3f6dffd54b10d537e93e0accfcc92/stl/inc/xstring#L617
+*/
+
+template <typename elem, typename traits, typename alloc>
+inline _CONSTEXPR20 void msvc_stl_xstring_Apply_annotation(::std::basic_string<elem, traits, alloc>::value_type const *const _First, 
+								::std::basic_string<elem, traits, alloc>::size_type const _Capacity,
+								::std::basic_string<elem, traits, alloc>::size_type const _Old_size,
+								::std::basic_string<elem, traits, alloc>::size_type const _New_size) noexcept
+{
+#if _HAS_CXX20
+	if (_STD is_constant_evaluated())
+	{
+		return;
+	}
+#endif // _HAS_CXX20
+	// Don't annotate small strings; only annotate on the heap.
+	if (_Capacity <= _Small_string_capacity || !_Asan_string_should_annotate)
+	{
+		return;
+	}
+
+	// Note that `_Capacity`, `_Old_size`, and `_New_size` do not include the null terminator
+	void const *const _End = _First + _Capacity + 1;
+	void const *const _Old_last = _First + _Old_size + 1;
+	void const *const _New_last = _First + _New_size + 1;
+
+	constexpr bool _Large_string_always_asan_aligned =
+		(_Container_allocation_minimum_asan_alignment<::std::basic_string<elem, traits, alloc>>) >= _Asan_granularity;
+
+	// for the non-aligned buffer options, the buffer must always have size >= 9 bytes,
+	// so it will always end at least one shadow memory section.
+
+	_Asan_aligned_pointers _Aligned;
+	if constexpr (_Large_string_always_asan_aligned)
+	{
+		_Aligned = {_First, _STD _Get_asan_aligned_after(_End)};
+	}
+	else
+	{
+		_Aligned = _STD _Get_asan_aligned_first_end(_First, _End);
+	}
+	void const *const _Old_fixed = _Aligned._Clamp_to_end(_Old_last);
+	void const *const _New_fixed = _Aligned._Clamp_to_end(_New_last);
+
+	// --- always aligned case ---
+	// old state:
+	//   [_First, _Old_last) valid
+	//   [_Old_last, asan_aligned_after(_End)) poison
+	// new state:
+	//   [_First, _New_last) valid
+	//   [_New_last, asan_aligned_after(_End)) poison
+
+	// --- sometimes non-aligned case ---
+	// old state:
+	//   [_Aligned._First, _Old_fixed) valid
+	//   [_Old_fixed, _Aligned._End) poison
+	//   [_Aligned._End, _End) valid
+	// new state:
+	//   [_Aligned._First, _New_fixed) valid
+	//   [_New_fixed, _Aligned._End) poison
+	//   [_Aligned._End, _End) valid
+	_CSTD __sanitizer_annotate_contiguous_container(_Aligned._First, _Aligned._End, _Old_fixed, _New_fixed);
+}
+
+template <typename elem, typename traits, typename alloc>
+inline _CONSTEXPR20 void msvc_stl_xstring_Modify_annotation(T &_My_data,
+	::std::basic_string<elem, traits, alloc>::size_type const _Old_size,
+	::std::basic_string<elem, traits, alloc>::size_type const _New_size) const noexcept
+{
+	if (_Old_size == _New_size)
+	{
+		return;
+	}
+
+	::fast_io::details::string_hack::msvc_stl_xstring_Apply_annotation(_My_data._Myptr(), _My_data._Myres, _Old_size, _New_size);
+}
+#endif
+
 template <typename T>
 inline constexpr void set_end_ptr(T &str, typename T::value_type *ptr) noexcept
 {
 	decltype(auto) scv{hack_scary_val(str)};
-	scv._Mysize = static_cast<::std::size_t>(ptr - str.data());
+	::std::size_t newsize{static_cast<::std::size_t>(ptr - str.data())};
+#ifdef _ACTIVATE_STRING_ANNOTATION
+	::fast_io::details::string_hack::sanitizer_annotate_contiguous_container(scv, scv._Mysize, newsize);
+#endif
+	scv._Mysize = newsize;
 }
 
 template <typename T>
diff --git a/tests/0034.string/CMakeLists.txt b/tests/0034.string/CMakeLists.txt
new file mode 100644
index 000000000..5418b934d
--- /dev/null
+++ b/tests/0034.string/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(stringtest stringtest.cc)
+add_test(stringtest stringtest)
diff --git a/tests/0034.string/stringtest.cc b/tests/0034.string/stringtest.cc
new file mode 100644
index 000000000..8ba44ccb1
--- /dev/null
+++ b/tests/0034.string/stringtest.cc
@@ -0,0 +1,8 @@
+#include <string>
+#include <fast_io.h>
+
+int main()
+{
+	::std::string str("asfasfjaspofjaspofajsfpoasfsaf");
+	::fast_io::details::string_hack::set_end_ptr(str, str.data() + 5); // resize to 5
+}
\ No newline at end of file
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 17f3d35a5..6057421fc 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -2,4 +2,5 @@ set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_EXTENSIONS off)
 add_subdirectory(tests/0002.printscan)
 add_subdirectory(tests/0026.container)
-add_subdirectory(tests/0033.legacy)
\ No newline at end of file
+add_subdirectory(tests/0033.legacy)
+add_subdirectory(tests/0034.string)
\ No newline at end of file