[lld] [llvm] [clang] [libcxx] [flang] [libc++][streams] P1759R6: Native handles and file streams (PR #76632)

[Mark de Wever via cfe-commits]

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@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+// 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() {
+  HandleT native_handle{};
+  HandleT const_native_handle{};
+
+  {
+    std::basic_filebuf<CharT> f;
+    assert(!f.is_open());
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mordante wrote:

We don't need this assert, the second `is_open()` assert could be replaced by
`assert(f.open(p, std::ios_base::in) != nullptr);

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