[libcxx-commits] [libcxx] [libc++] stddef.h needs to #include_next for the new clang __need_ macros (PR #86252)

[Louis Dionne via libcxx-commits]

================
@@ -7,16 +7,27 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if defined(__need_ptrdiff_t) || defined(__need_size_t) || defined(__need_wchar_t) || defined(__need_NULL) ||          \
-    defined(__need_wint_t)
+#if defined(__need_ptrdiff_t) || defined(__need_size_t) || defined(__need_rsize_t) || defined(__need_wchar_t) ||       \
----------------
ldionne wrote:

I would actually suggest that we change the whole header to this:

```c++
// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

/*
    stddef.h synopsis

Macros:

    offsetof(type,member-designator)
    NULL

Types:

    ptrdiff_t
    size_t
    max_align_t // C++11
    nullptr_t

*/

#include <__config>

// Note: This include is outside of header guards because we sometimes get included multiple times
//       with different defines and the underlying <stddef.h> will know how to deal with that.
#include_next <stddef.h>

#ifndef _LIBCPP_STDDEF_H
#  define _LIBCPP_STDDEF_H

#  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#    pragma GCC system_header
#  endif

#  ifdef __cplusplus
typedef decltype(nullptr) nullptr_t;
#  endif

#endif // _LIBCPP_STDDEF_H
```

WDYT?

https://github.com/llvm/llvm-project/pull/86252