From 35d2fcfc8e2462bccf0b078c457c052138dbc4ed Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 22 Jun 2011 22:17:44 +0000
Subject: [PATCH] Teach libc++ about the addressof() overloads it needs to work
 with Objective-C Automatic Reference Counting, where Objective-C object
 pointers can have several different qualifiers (__strong, __weak,
 __autoreleasing, __unsafe_unretained). These addressof() overloads are only
 provided in ARC mode, and the __weak variant is conditionalized on having
 weak-reference support in the ARC runtime.

For historical reasons, Clang provides these definitions itself, and
defines the macro _LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF to note when
it as done so. The code belongs here, and this redundancy will be
eliminated in the future.

Addresses <rdar://problem/9658274>.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@133656 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/__config |  9 +++++++++
 include/memory   | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/__config b/include/__config
index fea7a96b..a9432749 100644
--- a/include/__config
+++ b/include/__config
@@ -157,6 +157,15 @@ typedef __char32_t char32_t;
 #define _LIBCPP_HAS_NO_TRAILING_RETURN
 #endif
 
+// Objective-C++ features (opt-in)
+#if __has_feature(objc_arc)
+#define _LIBCPP_HAS_OBJC_ARC
+#endif
+
+#if __has_feature(objc_arc_weak)
+#define _LIBCPP_HAS_OBJC_ARC_WEAK
+#endif
+
 // Inline namespaces are available in Clang regardless of C++ dialect.
 #define _LIBCPP_BEGIN_NAMESPACE_STD namespace std {inline namespace _LIBCPP_NAMESPACE {
 #define _LIBCPP_END_NAMESPACE_STD  } }
diff --git a/include/memory b/include/memory
index 6f6a8ce3..479077fb 100644
--- a/include/memory
+++ b/include/memory
@@ -619,6 +619,46 @@ addressof(_Tp& __x) _NOEXCEPT
     return (_Tp*)&(char&)__x;
 }
 
+#if defined(_LIBCPP_HAS_OBJC_ARC) && !defined(_LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF)
+// Objective-C++ Automatic Reference Counting uses qualified pointers
+// that require special addressof() signatures. When
+// _LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF is defined, the compiler
+// itself is providing these definitions. Otherwise, we provide them.
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__strong _Tp*
+addressof(__strong _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+
+#ifdef _LIBCPP_HAS_OBJC_ARC_WEAK
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__weak _Tp*
+addressof(__weak _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+#endif
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__autoreleasing _Tp*
+addressof(__autoreleasing _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__unsafe_unretained _Tp*
+addressof(__unsafe_unretained _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+#endif
+
 template <class _Tp> class allocator;
 
 template <>