[libcxx-commits] [libcxx] [libc++][streams] P1759R6: Native handles and file streams (PR #76632)

via libcxx-commits libcxx-commits at lists.llvm.org
Sun Dec 31 09:59:24 PST 2023


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Hristo Hristov (H-G-Hristov)

<details>
<summary>Changes</summary>

Implements: `P1759R6` https://wg21.link/P1759R6

- https://eel.is/c++draft/filebuf
- https://eel.is/c++draft/ifstream
- https://eel.is/c++draft/ofstream
- https://eel.is/c++draft/fstream

---

Patch is 22.30 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/76632.diff


15 Files Affected:

- (modified) libcxx/docs/FeatureTestMacroTable.rst (+1-1) 
- (modified) libcxx/docs/ReleaseNotes/18.rst (+1) 
- (modified) libcxx/docs/Status/Cxx2cPapers.csv (+1-1) 
- (modified) libcxx/include/fstream (+60) 
- (modified) libcxx/include/version (+1-1) 
- (modified) libcxx/src/CMakeLists.txt (+1) 
- (added) libcxx/src/fstream.cpp (+33) 
- (added) libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/native_handle.pass.cpp (+45) 
- (added) libcxx/test/std/input.output/file.streams/fstreams/fstream.members/native_handle.pass.cpp (+27) 
- (added) libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/native_handle.pass.cpp (+27) 
- (added) libcxx/test/std/input.output/file.streams/fstreams/ofstream.members/native_handle.pass.cpp (+27) 
- (added) libcxx/test/std/input.output/file.streams/fstreams/test_helpers.h (+60) 
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/fstream.version.compile.pass.cpp (+5-11) 
- (modified) libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp (+5-11) 
- (modified) libcxx/utils/generate_feature_test_macro_components.py (-1) 


``````````diff
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index ad12b109023154..0427615a9636fd 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -418,7 +418,7 @@ Status
     --------------------------------------------------- -----------------
     ``__cpp_lib_freestanding_variant``                  *unimplemented*
     --------------------------------------------------- -----------------
-    ``__cpp_lib_fstream_native_handle``                 *unimplemented*
+    ``__cpp_lib_fstream_native_handle``                 ``202306L``
     --------------------------------------------------- -----------------
     ``__cpp_lib_function_ref``                          *unimplemented*
     --------------------------------------------------- -----------------
diff --git a/libcxx/docs/ReleaseNotes/18.rst b/libcxx/docs/ReleaseNotes/18.rst
index fa60a581652d6a..e6f1adf4d5529b 100644
--- a/libcxx/docs/ReleaseNotes/18.rst
+++ b/libcxx/docs/ReleaseNotes/18.rst
@@ -58,6 +58,7 @@ Implemented Papers
 - P2870R3 - Remove basic_string::reserve()
 - P2909R4 - Fix formatting of code units as integers (Dude, where’s my ``char``?)
 - P0521R0 - Proposed Resolution for CA 14 (shared_ptr use_count/unique)
+- P1759R6 - Native handles and file streams
 
 
 Improvements and New Features
diff --git a/libcxx/docs/Status/Cxx2cPapers.csv b/libcxx/docs/Status/Cxx2cPapers.csv
index ff83648aa76830..1d7807a4291a99 100644
--- a/libcxx/docs/Status/Cxx2cPapers.csv
+++ b/libcxx/docs/Status/Cxx2cPapers.csv
@@ -19,7 +19,7 @@
 "`P2757R3 <https://wg21.link/P2757R3>`__","LWG","Type-checking format args","Varna June 2023","","","|format|"
 "`P2637R3 <https://wg21.link/P2637R3>`__","LWG","Member ``visit``","Varna June 2023","","","|format|"
 "`P2641R4 <https://wg21.link/P2641R4>`__","CWG, LWG","Checking if a ``union`` alternative is active","Varna June 2023","","",""
-"`P1759R6 <https://wg21.link/P1759R6>`__","LWG","Native handles and file streams","Varna June 2023","","",""
+"`P1759R6 <https://wg21.link/P1759R6>`__","LWG","Native handles and file streams","Varna June 2023","|Complete|","18.0",""
 "`P2697R1 <https://wg21.link/P2697R1>`__","LWG","Interfacing ``bitset`` with ``string_view``","Varna June 2023","|Complete|","18.0",""
 "`P1383R2 <https://wg21.link/P1383R2>`__","LWG","More ``constexpr`` for ``<cmath>`` and ``<complex>``","Varna June 2023","","",""
 "`P2734R0 <https://wg21.link/P2734R0>`__","LWG","Adding the new SI prefixes","Varna June 2023","|Complete|","17.0",""
diff --git a/libcxx/include/fstream b/libcxx/include/fstream
index 7a4e15b55d56fe..ab854cf534e7fb 100644
--- a/libcxx/include/fstream
+++ b/libcxx/include/fstream
@@ -73,6 +73,7 @@ public:
     typedef typename traits_type::int_type int_type;
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
+    using native_handle_type = typename basic_filebuf<charT, traits>::native_handle_type; // Since C++26
 
     basic_ifstream();
     explicit basic_ifstream(const char* s, ios_base::openmode mode = ios_base::in);
@@ -85,6 +86,7 @@ public:
     void swap(basic_ifstream& rhs);
 
     basic_filebuf<char_type, traits_type>* rdbuf() const;
+    native_handle_type native_handle() const noexcept; // Since C++26
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in);
     void open(const string& s, ios_base::openmode mode = ios_base::in);
@@ -110,6 +112,7 @@ public:
     typedef typename traits_type::int_type int_type;
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
+    using native_handle_type = typename basic_filebuf<charT, traits>::native_handle_type; // Since C++26
 
     basic_ofstream();
     explicit basic_ofstream(const char* s, ios_base::openmode mode = ios_base::out);
@@ -122,6 +125,8 @@ public:
     void swap(basic_ofstream& rhs);
 
     basic_filebuf<char_type, traits_type>* rdbuf() const;
+    native_handle_type native_handle() const noexcept; // Since C++26
+
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::out);
     void open(const string& s, ios_base::openmode mode = ios_base::out);
@@ -148,6 +153,7 @@ public:
     typedef typename traits_type::int_type int_type;
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
+    using native_handle_type = typename basic_filebuf<charT, traits>::native_handle_type; // Since C++26
 
     basic_fstream();
     explicit basic_fstream(const char* s, ios_base::openmode mode = ios_base::in|ios_base::out);
@@ -160,6 +166,7 @@ public:
     void swap(basic_fstream& rhs);
 
     basic_filebuf<char_type, traits_type>* rdbuf() const;
+    native_handle_type native_handle() const noexcept; // Since C++26
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in|ios_base::out);
     void open(const string& s, ios_base::openmode mode = ios_base::in|ios_base::out);
@@ -208,8 +215,34 @@ _LIBCPP_PUSH_MACROS
 
 #if !defined(_LIBCPP_HAS_NO_FILESYSTEM)
 
+#  if defined(_LIBCPP_WIN32API)
+#    define WIN32_LEAN_AND_MEAN
+#    define NOMINMAX
+#    include <io.h>
+#    include <windows.h>
+#  endif
+
+// #  include <fcntl.h>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#  if _LIBCPP_STD_VER >= 26
+#    if defined(_LIBCPP_WIN32API)
+using __filebuf_native_handle_type = HANDLE;
+_LIBCPP_EXPORTED_FROM_ABI __filebuf_native_handle_type __filebuf_windows_native_handle(FILE* __file);
+#    else // POSIX
+using __filebuf_native_handle_type = int; // File descriptor
+#    endif
+
+_LIBCPP_HIDE_FROM_ABI inline __filebuf_native_handle_type __filebuf_native_handle(FILE* __file) noexcept {
+#    if defined(_LIBCPP_WIN32API)
+  return __filebuf_windows_native_handle(__file);
+#    else
+  return ::fileno(__file);
+#    endif
+}
+#  endif
+
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS basic_filebuf : public basic_streambuf<_CharT, _Traits> {
 public:
@@ -219,6 +252,9 @@ public:
   typedef typename traits_type::pos_type pos_type;
   typedef typename traits_type::off_type off_type;
   typedef typename traits_type::state_type state_type;
+#  if _LIBCPP_STD_VER >= 26
+  using native_handle_type = __filebuf_native_handle_type;
+#  endif
 
   // 27.9.1.2 Constructors/destructor:
   basic_filebuf();
@@ -245,6 +281,12 @@ public:
 #  endif
   _LIBCPP_HIDE_FROM_ABI basic_filebuf* __open(int __fd, ios_base::openmode __mode);
   basic_filebuf* close();
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() const noexcept {
+    _LIBCPP_ASSERT_UNCATEGORIZED(this->is_open(), "File must be opened");
+    return std::__filebuf_native_handle(__file_);
+  }
+#  endif
 
   _LIBCPP_HIDE_FROM_ABI inline static const char* __make_mdstring(ios_base::openmode __mode) _NOEXCEPT;
 
@@ -1024,6 +1066,9 @@ public:
   typedef typename traits_type::int_type int_type;
   typedef typename traits_type::pos_type pos_type;
   typedef typename traits_type::off_type off_type;
+#  if _LIBCPP_STD_VER >= 26
+  using native_handle_type = typename basic_filebuf<_CharT, _Traits>::native_handle_type;
+#  endif
 
   _LIBCPP_HIDE_FROM_ABI basic_ifstream();
   _LIBCPP_HIDE_FROM_ABI explicit basic_ifstream(const char* __s, ios_base::openmode __mode = ios_base::in);
@@ -1041,6 +1086,9 @@ public:
   _LIBCPP_HIDE_FROM_ABI void swap(basic_ifstream& __rhs);
 
   _LIBCPP_HIDE_FROM_ABI basic_filebuf<char_type, traits_type>* rdbuf() const;
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() const noexcept { return rdbuf()->native_handle(); }
+#  endif
   _LIBCPP_HIDE_FROM_ABI bool is_open() const;
   void open(const char* __s, ios_base::openmode __mode = ios_base::in);
 #  ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
@@ -1171,6 +1219,9 @@ public:
   typedef typename traits_type::int_type int_type;
   typedef typename traits_type::pos_type pos_type;
   typedef typename traits_type::off_type off_type;
+#  if _LIBCPP_STD_VER >= 26
+  using native_handle_type = typename basic_filebuf<_CharT, _Traits>::native_handle_type;
+#  endif
 
   _LIBCPP_HIDE_FROM_ABI basic_ofstream();
   _LIBCPP_HIDE_FROM_ABI explicit basic_ofstream(const char* __s, ios_base::openmode __mode = ios_base::out);
@@ -1190,6 +1241,9 @@ public:
   _LIBCPP_HIDE_FROM_ABI void swap(basic_ofstream& __rhs);
 
   _LIBCPP_HIDE_FROM_ABI basic_filebuf<char_type, traits_type>* rdbuf() const;
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() const noexcept { return rdbuf()->native_handle(); }
+#  endif
   _LIBCPP_HIDE_FROM_ABI bool is_open() const;
   void open(const char* __s, ios_base::openmode __mode = ios_base::out);
 #  ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
@@ -1321,6 +1375,9 @@ public:
   typedef typename traits_type::int_type int_type;
   typedef typename traits_type::pos_type pos_type;
   typedef typename traits_type::off_type off_type;
+#  if _LIBCPP_STD_VER >= 26
+  using native_handle_type = typename basic_filebuf<_CharT, _Traits>::native_handle_type;
+#  endif
 
   _LIBCPP_HIDE_FROM_ABI basic_fstream();
   _LIBCPP_HIDE_FROM_ABI explicit basic_fstream(const char* __s,
@@ -1345,6 +1402,9 @@ public:
   _LIBCPP_HIDE_FROM_ABI void swap(basic_fstream& __rhs);
 
   _LIBCPP_HIDE_FROM_ABI basic_filebuf<char_type, traits_type>* rdbuf() const;
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() const noexcept { return rdbuf()->native_handle(); }
+#  endif
   _LIBCPP_HIDE_FROM_ABI bool is_open() const;
   _LIBCPP_HIDE_FROM_ABI void open(const char* __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
 #  ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
diff --git a/libcxx/include/version b/libcxx/include/version
index 768710ef5c84aa..a2bb11b62a44d3 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -495,7 +495,7 @@ __cpp_lib_within_lifetime                               202306L <type_traits>
 // # define __cpp_lib_freestanding_optional                202311L
 // # define __cpp_lib_freestanding_string_view             202311L
 // # define __cpp_lib_freestanding_variant                 202311L
-// # define __cpp_lib_fstream_native_handle                202306L
+# define __cpp_lib_fstream_native_handle                202306L
 // # define __cpp_lib_function_ref                         202306L
 // # define __cpp_lib_hazard_pointer                       202306L
 // # define __cpp_lib_linalg                               202311L
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 329964a001363b..b931460ec76297 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -14,6 +14,7 @@ set(LIBCXX_SOURCES
   filesystem/filesystem_error.cpp
   filesystem/path_parser.h
   filesystem/path.cpp
+  fstream.cpp
   functional.cpp
   hash.cpp
   include/apple_availability.h
diff --git a/libcxx/src/fstream.cpp b/libcxx/src/fstream.cpp
new file mode 100644
index 00000000000000..814d912e7d22b3
--- /dev/null
+++ b/libcxx/src/fstream.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <cstdio>
+#include <fstream>
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <io.h>
+#  include <windows.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 26
+#  if defined(_LIBCPP_WIN32API)
+_LIBCPP_EXPORTED_FROM_ABI __filebuf_native_handle_type __filebuf_windows_native_handle(FILE* __file) noexcept {
+  // https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle?view=msvc-170
+  intptr_t __handle = _get_osfhandle(::fileno(__file));
+  if (__handle == -1)
+    return nullptr;
+  return reinterpret_cast<__filebuf_native_handle_type>(__handle);
+#  endif
+#endif
+
+  _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/native_handle.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/native_handle.pass.cpp
new file mode 100644
index 00000000000000..790cc91effc822
--- /dev/null
+++ b/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/native_handle.pass.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <fstream>
+
+// class basic_filebuf;
+
+// native_handle_type native_handle() const noexcept;
+
+#include <cassert>
+#include <fstream>
+#include <filesystem>
+#include <utility>
+
+#include "platform_support.h"
+#include "test_macros.h"
+#include "../test_helpers.h"
+
+template <typename CharT>
+void test() {
+  std::basic_filebuf<CharT> f;
+  assert(!f.is_open());
+  std::filesystem::path p = get_temp_file_name();
+  f.open(p, std::ios_base::in);
+  assert(f.is_open());
+  assert(is_handle_valid(f.native_handle()));
+  assert(is_handle_valid(std::as_const(f).native_handle()));
+  static_assert(noexcept(f.native_handle()));
+}
+
+int main(int, char**) {
+  test<char>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test<wchar_t>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/fstream.members/native_handle.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/fstream.members/native_handle.pass.cpp
new file mode 100644
index 00000000000000..900475069a1c9b
--- /dev/null
+++ b/libcxx/test/std/input.output/file.streams/fstreams/fstream.members/native_handle.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <fstream>
+
+// class basic_fstream;
+
+// native_handle_type native_handle() const noexcept;
+
+#include "test_macros.h"
+#include "../test_helpers.h"
+
+int main(int, char**) {
+  test_native_handle<char, std::basic_fstream<char>>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test_native_handle<wchar_t, std::basic_fstream<wchar_t>>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/native_handle.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/native_handle.pass.cpp
new file mode 100644
index 00000000000000..95a95cb69560b7
--- /dev/null
+++ b/libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/native_handle.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <fstream>
+
+// class basic_ifstream;
+
+// native_handle_type native_handle() const noexcept;
+
+#include "test_macros.h"
+#include "../test_helpers.h"
+
+int main(int, char**) {
+  test_native_handle<char, std::basic_ifstream<char>>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test_native_handle<wchar_t, std::basic_ifstream<wchar_t>>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/ofstream.members/native_handle.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/ofstream.members/native_handle.pass.cpp
new file mode 100644
index 00000000000000..45f0841dad18cb
--- /dev/null
+++ b/libcxx/test/std/input.output/file.streams/fstreams/ofstream.members/native_handle.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <fstream>
+
+// class basic_ofstream;
+
+// native_handle_type native_handle() const noexcept;
+
+#include "test_macros.h"
+#include "../test_helpers.h"
+
+int main(int, char**) {
+  test_native_handle<char, std::basic_ofstream<char>>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test_native_handle<wchar_t, std::basic_ofstream<wchar_t>>();
+#endif
+
+  return 0;
+}
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/test_helpers.h b/libcxx/test/std/input.output/file.streams/fstreams/test_helpers.h
new file mode 100644
index 00000000000000..a3069549315611
--- /dev/null
+++ b/libcxx/test/std/input.output/file.streams/fstreams/test_helpers.h
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TEST_STD_INPUT_OUTPUT_FILE_STREAMS_FSTREAMS_TEST_HELPERS_H
+#define TEST_STD_INPUT_OUTPUT_FILE_STREAMS_FSTREAMS_TEST_HELPERS_H
+
+#if _LIBCPP_STD_VER >= 26
+
+#  include <cassert>
+#  include <cstdio>
+#  include <fstream>
+#  include <filesystem>
+#  include <utility>
+
+#  if defined(_LIBCPP_WIN32API)
+#    define WIN32_LEAN_AND_MEAN
+#    define NOMINMAX
+#    include <io.h>
+#    include <windows.h>
+#  else
+#    include <fcntl.h>
+#  endif
+
+#  include "platform_support.h"
+
+#  if defined(_LIBCPP_WIN32API)
+auto is_handle_valid([[maybe_unused]] HANDLE handle) {
+  // TODO: Maybe test HANDLE with GetFileInformationByHandle??
+  return true;
+};
+#  else
+// POSIX
+auto is_handle_valid(int fd) { return fcntl(fd, F_GETFL) != -1 || errno != EBADF; };
+#  endif
+
+template <typename CharT, typename StreamT>
+void test_native_handle() {
+  static_assert(
+      std::is_same_v<typename std::basic_filebuf<CharT>::native_handle_type, typename StreamT::native_handle_type>);
+
+  StreamT f;
+  static_assert(noexcept(f.native_handle()));
+  assert(!f.is_open());
+  std::filesystem::path p = get_temp_file_name();
+  f.open(p);
+  assert(f.is_open());
+  assert(f.native_handle() == f.rdbuf()->native_handle());
+  assert(is_handle_valid(f.native_handle()));
+  assert(is_handle_valid(std::as_const(f).native_handle()));
+  static_assert(noexcept(f.native_handle()));
+}
+
+#endif // _LIBCPP_STD_VER >= 26
+
+#endif // TEST_STD_INPUT_OUTPUT_FILE_STREAMS_FSTREAMS_TEST_HELPERS_H
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/fstream.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/fstream.version.compile.pass.cpp
index 981f5420ff7e0f..eab0313b2c1ef7 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/fstream.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/fstream.version.compile.pass.cpp
@@ -56,17 +56,11 @@
 
 #elif TEST_STD_VER > 23
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_fstream_native_handle
-#     error "__cpp_lib_fstream_native_handle should be defined in c++26"
-#   endif
-#   if __cpp_lib_fstream_native_handle != 202306L
-#     error "__cpp_lib_fstream_native_handle should have the value 202306L in c++26"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_fstream_native_handle
-#     error "...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/76632


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