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

[Jonathan Wakely via llvm-commits]

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@@ -0,0 +1,42 @@
+// -*- C++ -*-
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jwakely wrote:

Yeah, GCC's `stdalign.h` only defines them for C11 and C17, but no versions of C++. I have a local patch fixing it which I'll propose. I don't think anybody has ever noticed before, because nobody cares about those macros in C++ (so much so that one of them was overlooked until earlier this year and nobody noticed or cared). The `__alignof_is_defined` macro isn't actually mentioned in any published C++ standard.

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