[libc++] Implement std::experimental::observer_ptr

This patch adds std::experimental::observer_ptr (n4282) and also fixes LWG2516. Co-Authored-By: Louis Dionne <ldionne.2@gmail.com> Differential Revision: https://reviews.llvm.org/D63230
llvm · Nov 6, 2023 · 7a62bee · 7a62bee
1 parent cf7d4f5
commit 7a62bee
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diff --git a/libcxx/docs/Status/Cxx17Issues.csv b/libcxx/docs/Status/Cxx17Issues.csv
@@ -143,7 +143,7 @@
 "`2441 <https://wg21.link/LWG2441>`__","Exact-width atomic typedefs should be provided","Oulu","|Complete|",""
 "`2451 <https://wg21.link/LWG2451>`__","[fund.ts.v2] optional should 'forward' T's implicit conversions","Oulu","|Nothing To Do|",""
 "`2509 <https://wg21.link/LWG2509>`__","[fund.ts.v2] any_cast doesn't work with rvalue reference targets and cannot move with a value target","Oulu","|Complete|",""
-"`2516 <https://wg21.link/LWG2516>`__","[fund.ts.v2] Public ""exposition only"" members in observer_ptr","Oulu","",""
+"`2516 <https://wg21.link/LWG2516>`__","[fund.ts.v2] Public ""exposition only"" members in observer_ptr","Oulu","|Complete|","18.0"
 "`2542 <https://wg21.link/LWG2542>`__","Missing const requirements for associative containers","Oulu","",""
 "`2549 <https://wg21.link/LWG2549>`__","Tuple EXPLICIT constructor templates that take tuple parameters end up taking references to temporaries and will create dangling references","Oulu","|Complete|",""
 "`2550 <https://wg21.link/LWG2550>`__","Wording of unordered container's clear() method complexity","Oulu","|Complete|",""

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
@@ -925,6 +925,7 @@ set(files
   experimental/iterator
   experimental/list
   experimental/map
+  experimental/memory
   experimental/memory_resource
   experimental/propagate_const
   experimental/regex

diff --git a/libcxx/include/__std_clang_module b/libcxx/include/__std_clang_module
@@ -91,6 +91,7 @@
 #include <experimental/iterator>
 #include <experimental/list>
 #include <experimental/map>
+#include <experimental/memory>
 #include <experimental/memory_resource>
 #include <experimental/propagate_const>
 #if !defined(_LIBCPP_HAS_NO_LOCALIZATION)

diff --git a/libcxx/include/experimental/memory b/libcxx/include/experimental/memory
@@ -0,0 +1,194 @@
+// -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_MEMORY
+#define _LIBCPP_EXPERIMENTAL_MEMORY
+
+/*
+    experimental/memory synopsis
+
+namespace std::experimental::inline fundamentals_v2  {
+
+template <class W> class observer_ptr {
+public:
+    using element_type = W;
+    using pointer = add_pointer_t<W>; // exposition-only
+    using reference = add_lvalue_reference_t<W>; // exposition-only
+
+    // default ctor
+    constexpr observer_ptr() noexcept;
+
+    // pointer-accepting ctors
+    constexpr observer_ptr(nullptr_t) noexcept;
+    constexpr explicit observer_ptr(pointer) noexcept;
+
+    // copying ctors (in addition to compiler-generated copy ctor)
+    template <class W2> constexpr observer_ptr(observer_ptr<W2>) noexcept;
+
+    // observers
+    constexpr pointer get() const noexcept;
+    constexpr reference operator*() const;
+    constexpr pointer operator->() const noexcept;
+    constexpr explicit operator bool() const noexcept;
+
+    // conversions
+    constexpr explicit operator pointer() const noexcept;
+
+    // modifiers
+    constexpr pointer release() noexcept;
+    constexpr void reset(pointer = nullptr) noexcept;
+    constexpr void swap(observer_ptr&) noexcept;
+};
+
+}
+*/
+
+#include <__functional/hash.h>
+#include <__functional/operations.h>
+#include <__type_traits/add_lvalue_reference.h>
+#include <__type_traits/add_pointer.h>
+#include <__type_traits/common_type.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_convertible.h>
+#include <cstddef>
+#include <experimental/__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
+
+_LIBCPP_BEGIN_NAMESPACE_LFTS_V2
+
+#  if _LIBCPP_STD_VER >= 17
+
+template <class _Wp>
+class observer_ptr {
+public:
+  using element_type = _Wp;
+
+  // constructors
+  _LIBCPP_HIDE_FROM_ABI constexpr observer_ptr() noexcept : __ptr_(nullptr) {}
+  _LIBCPP_HIDE_FROM_ABI constexpr observer_ptr(nullptr_t) noexcept : __ptr_(nullptr) {}
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit observer_ptr(element_type* __p) noexcept : __ptr_(__p) {}
+
+  template <class _W2, class = __enable_if_t<is_convertible<_W2*, _Wp*>::value>>
+  _LIBCPP_HIDE_FROM_ABI constexpr observer_ptr(observer_ptr<_W2> __other) noexcept : __ptr_(__other.get()) {}
+
+  // observers
+  _LIBCPP_HIDE_FROM_ABI constexpr element_type* get() const noexcept { return __ptr_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr add_lvalue_reference_t<_Wp> operator*() const { return *__ptr_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr element_type* operator->() const noexcept { return __ptr_; }
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return __ptr_ != nullptr; }
+
+  // conversions
+  _LIBCPP_HIDE_FROM_ABI constexpr explicit operator element_type*() const noexcept { return __ptr_; }
+
+  // modifiers
+  _LIBCPP_HIDE_FROM_ABI constexpr void reset(element_type* __p = nullptr) noexcept { __ptr_ = __p; }
+  _LIBCPP_HIDE_FROM_ABI constexpr void swap(observer_ptr& __other) noexcept {
+    observer_ptr __tmp = __other;
+    __other            = *this;
+    *this              = __tmp;
+  }
+  _LIBCPP_HIDE_FROM_ABI constexpr element_type* release() noexcept {
+    observer_ptr __p;
+    __p.swap(*this);
+    return __p.get();
+  }
+
+private:
+  element_type* __ptr_;
+};
+
+// specializations
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI constexpr void swap(observer_ptr<_Wp>& __a, observer_ptr<_Wp>& __b) noexcept {
+  __a.swap(__b);
+}
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI observer_ptr<_Wp> make_observer(_Wp* __ptr) noexcept {
+  return observer_ptr<_Wp>{__ptr};
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator==(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return __a.get() == __b.get();
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator!=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return !(__a == __b);
+}
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI bool operator==(observer_ptr<_Wp> __p, nullptr_t) {
+  return !__p;
+}
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI bool operator==(nullptr_t, observer_ptr<_Wp> __p) {
+  return !__p;
+}
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI bool operator!=(observer_ptr<_Wp> __p, nullptr_t) {
+  return (bool)__p;
+}
+
+template <class _Wp>
+_LIBCPP_HIDE_FROM_ABI bool operator!=(nullptr_t, observer_ptr<_Wp> __p) {
+  return (bool)__p;
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator<(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return std::less<typename std::common_type<_W1*, _W2*>::type>()(__a.get(), __b.get());
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator>(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return __b < __a;
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator<=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return !(__a > __b);
+}
+
+template <class _W1, class _W2>
+_LIBCPP_HIDE_FROM_ABI bool operator>=(observer_ptr<_W1> __a, observer_ptr<_W2> __b) {
+  return !(__a < __b);
+}
+
+#  endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_LFTS_V2
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// hash
+
+#  if _LIBCPP_STD_VER >= 17
+template <class _Tp>
+struct hash<experimental::observer_ptr<_Tp>> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const experimental::observer_ptr<_Tp>& __ptr) const noexcept {
+    return hash<_Tp*>()(__ptr.get());
+  }
+};
+#  endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_ENABLE_EXPERIMENTAL
+
+#endif /* _LIBCPP_EXPERIMENTAL_MEMORY */
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
@@ -533,6 +533,10 @@ module std_experimental [system] {
     header "experimental/map"
     export *
   }
+  module memory {
+    header "experimental/memory"
+    export *
+  }
   module memory_resource {
     header "experimental/memory_resource"
     export *

diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -241,6 +241,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource atomic
 experimental/memory_resource climits
 experimental/memory_resource concepts

diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -242,6 +242,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource atomic
 experimental/memory_resource climits
 experimental/memory_resource concepts

diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -242,6 +242,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource atomic
 experimental/memory_resource climits
 experimental/memory_resource concepts

diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -242,6 +242,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource atomic
 experimental/memory_resource climits
 experimental/memory_resource concepts

diff --git a/libcxx/test/libcxx/transitive_includes/cxx20.csv b/libcxx/test/libcxx/transitive_includes/cxx20.csv
@@ -248,6 +248,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource atomic
 experimental/memory_resource climits
 experimental/memory_resource concepts

diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -170,6 +170,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource cstddef
 experimental/memory_resource experimental/utility
 experimental/memory_resource limits

diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -170,6 +170,10 @@ experimental/list experimental/memory_resource
 experimental/list list
 experimental/map experimental/memory_resource
 experimental/map map
+experimental/memory cstddef
+experimental/memory cstdint
+experimental/memory cstring
+experimental/memory limits
 experimental/memory_resource cstddef
 experimental/memory_resource experimental/utility
 experimental/memory_resource limits