[PATCH] D12747: Implement [depr.c.headers]

[Richard Smith via cfe-commits]

Next: factoring the definition of std::nullptr_t out into a separate file,
so that <cstddef> and <stddef.h> can both use it, without <stddef.h>
including <cstddef> and without <cstddef> providing a ::nullptr_t like
<stddef.h> does.

On Tue, Oct 6, 2015 at 3:02 PM, Eric Fiselier <eric at efcs.ca> wrote:

> LGTM.
>
> On Tue, Oct 6, 2015 at 3:58 PM, Richard Smith <richard at metafoo.co.uk>
> wrote:
> > On Mon, Oct 5, 2015 at 7:10 PM, Eric Fiselier <eric at efcs.ca> wrote:
> >>
> >> EricWF added a comment.
> >>
> >> I think thing change will help us close a number out outstanding bugs. I
> >> don't have any fundamental objections to this approach.  However the
> size of
> >> this patch scares me.  I understand the changes are mostly mechanical
> but
> >> their size can hide things. For example has anybody noticed that your
> >> internal changes to `<deque>` are in this patch? It would be nice to
> break
> >> this down into more digestible pieces that could be quickly spot
> checked.
> >
> >
> > OK. First such patch is attached. It just removes the macro-capturing
> > wrapper functions.
>
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Index: __nullptr
===================================================================
--- __nullptr	(revision 0)
+++ __nullptr	(working copy)
@@ -0,0 +1,66 @@
+// -*- C++ -*-
+//===--------------------------- __nullptr --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_NULLPTR
+#define _LIBCPP_NULLPTR
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#ifdef _LIBCPP_HAS_NO_NULLPTR
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct _LIBCPP_TYPE_VIS_ONLY nullptr_t
+{
+    void* __lx;
+
+    struct __nat {int __for_bool_;};
+
+    _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR nullptr_t() : __lx(0) {}
+    _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR nullptr_t(int __nat::*) : __lx(0) {}
+
+    _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR operator int __nat::*() const {return 0;}
+
+    template <class _Tp>
+        _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR
+        operator _Tp* () const {return 0;}
+
+    template <class _Tp, class _Up>
+        _LIBCPP_ALWAYS_INLINE
+        operator _Tp _Up::* () const {return 0;}
+
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator==(nullptr_t, nullptr_t) {return true;}
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator!=(nullptr_t, nullptr_t) {return false;}
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator<(nullptr_t, nullptr_t) {return false;}
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator<=(nullptr_t, nullptr_t) {return true;}
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator>(nullptr_t, nullptr_t) {return false;}
+    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator>=(nullptr_t, nullptr_t) {return true;}
+};
+
+inline _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR nullptr_t __get_nullptr_t() {return nullptr_t(0);}
+
+#define nullptr _VSTD::__get_nullptr_t()
+
+_LIBCPP_END_NAMESPACE_STD
+
+#else  // _LIBCPP_HAS_NO_NULLPTR
+
+namespace std
+{
+    typedef decltype(nullptr) nullptr_t;
+}
+
+#endif  // _LIBCPP_HAS_NO_NULLPTR
+
+#endif  // _LIBCPP_NULLPTR
Index: cstddef
===================================================================
--- cstddef	(revision 249368)
+++ cstddef	(working copy)
@@ -34,6 +34,7 @@
 */
 
 #include <__config>
+#include <__nullptr>
 
 #include <stddef.h>