[libcxx] [llvm] [libc++] Deprecate and remove meaningless `<cxxx>` headers (PR #111615)

[Louis Dionne via llvm-commits]

================
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// test <cstdalign> // deprecated in C++17, removed in C++20, but still provided by libc++ as an extension
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
+
+#include <cstdalign>
+
+#ifndef __alignas_is_defined
+#  error __alignas_is_defined not defined
+#endif
+
+#ifndef __alignof_is_defined
+#  error __alignof_is_defined not defined
+#endif
+
+#ifdef alignas
+#  error alignas should not be defined
+#endif
+
+#ifdef alignof
+#  error alignof should not be defined
+#endif
+
+int main(int, char**) { return 0; }
----------------
ldionne wrote:

I think this can be a `.compile.pass.cpp`?

https://github.com/llvm/llvm-project/pull/111615