[flang] [lld] [lldb] [openmp] [compiler-rt] [libc] [mlir] [clang] [clang-tools-extra] [llvm] [libcxx] [libc++][streams] P1759R6: Native handles and file streams (PR #76632)

[Hristo Hristov via llvm-commits]

================
@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+#include <cassert>
+#include <concepts>
+#include <cstdio>
+#include <fstream>
+#include <filesystem>
+#include <type_traits>
+#include <utility>
+
+#if defined(_WIN32)
+#  include <io.h>
+#  include <windows.h>
+#else
+#  include <fcntl.h>
+#endif
+
+#include "platform_support.h"
+#include "test_macros.h"
+#include "types.h"
+
+#if TEST_STD_VER >= 26
+
+#  include "check_assertion.h"
+
+inline bool is_handle_valid(NativeHandleT handle) {
+#  if defined(_WIN32)
+  BY_HANDLE_FILE_INFORMATION fileInformation;
+  return GetFileInformationByHandle(handle, &fileInformation));
+#  elif __has_include(<unistd.h>) // POSIX
+  return fcntl(handle, F_GETFL) != -1 || errno != EBADF;
+#  else
+#    error "Provide a native file handle!"
+#  endif
+}
+
+template <typename CharT, typename StreamT>
+inline 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;
+  std::filesystem::path p = get_temp_file_name();
+
+  // non-const
+  {
+    f.open(p);
+    std::same_as<NativeHandleT> decltype(auto) handle = f.native_handle();
+    assert(is_handle_valid(handle));
+    assert(f.rdbuf()->native_handle() == handle);
+    assert(std::as_const(f).rdbuf()->native_handle() == handle);
+    f.close();
+    assert(!is_handle_valid(handle));
+    static_assert(noexcept(f.native_handle()));
+  }
+  // const
+  {
+    f.open(p);
+    std::same_as<NativeHandleT> decltype(auto) const_handle = std::as_const(f).native_handle();
+    assert(is_handle_valid(const_handle));
+    assert(f.rdbuf()->native_handle() == const_handle);
+    assert(std::as_const(f).rdbuf()->native_handle() == const_handle);
+    f.close();
+    assert(!is_handle_valid(const_handle));
+    static_assert(noexcept(std::as_const(f).native_handle()));
+  }
+}
+
+template <typename StreamT>
+inline void test_native_handle_assertion() {
+  StreamT f;
+
+  // non-const
+  { TEST_LIBCPP_ASSERT_FAILURE(f.native_handle(), "File must be opened"); }
+  // const
+  { TEST_LIBCPP_ASSERT_FAILURE(std::as_const(f).native_handle(), "File must be opened"); }
----------------
Zingam wrote:

```suggestion
  // non-const
  TEST_LIBCPP_ASSERT_FAILURE(f.native_handle(), "File must be opened");
  // const
  TEST_LIBCPP_ASSERT_FAILURE(std::as_const(f).native_handle(), "File must be opened");
```

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