[libc++] Change memory_order to an enum class

This implements P0439R0.

Thanks to Zoe Carver for the patch.
Differential Revision: https://reviews.llvm.org/D58201

llvm-svn: 355403

libcxx/include/atomic

@@ -20,17 +20,24 @@ namespace std
 
 #define __cpp_lib_atomic_is_always_lock_free // as specified by SG10
 
-// order and consistency
+ // order and consistency
 
-typedef enum memory_order
+ enum memory_order: unspecified // enum class in C++20
-{
+ {
-    memory_order_relaxed,
+    relaxed,
-    memory_order_consume,  // load-consume
+    consume, // load-consume
-    memory_order_acquire,  // load-acquire
+    acquire, // load-acquire
-    memory_order_release,  // store-release
+    release, // store-release
-    memory_order_acq_rel,  // store-release load-acquire
+    acq_rel, // store-release load-acquire
-    memory_order_seq_cst   // store-release load-acquire
+    seq_cst // store-release load-acquire
-} memory_order;
+ };
+
+ inline constexpr auto memory_order_relaxed = memory_order::relaxed;
+ inline constexpr auto memory_order_consume = memory_order::consume;
+ inline constexpr auto memory_order_acquire = memory_order::acquire;
+ inline constexpr auto memory_order_release = memory_order::release;
+ inline constexpr auto memory_order_acq_rel = memory_order::acq_rel;
+ inline constexpr auto memory_order_seq_cst = memory_order::seq_cst;
 
 template <class T> T kill_dependency(T y) noexcept;
 
@@ -577,14 +584,39 @@ void atomic_signal_fence(memory_order m) noexcept;
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-typedef enum memory_order
+#if _LIBCPP_STD_VER > 17
-{
+
-    memory_order_relaxed, memory_order_consume, memory_order_acquire,
+enum class memory_order: unsigned {
-    memory_order_release, memory_order_acq_rel, memory_order_seq_cst
+  relaxed, consume, acquire, release, acq_rel, seq_cst
+};
+
+inline constexpr auto memory_order_relaxed = memory_order::relaxed;
+inline constexpr auto memory_order_consume = memory_order::consume;
+inline constexpr auto memory_order_acquire = memory_order::acquire;
+inline constexpr auto memory_order_release = memory_order::release;
+inline constexpr auto memory_order_acq_rel = memory_order::acq_rel;
+inline constexpr auto memory_order_seq_cst = memory_order::seq_cst;
+
+static_assert((is_same<underlying_type<memory_order>::type,
+			   unsigned>::value), "Underlying type differs from unsigned unexpectedly");
+
+#else
+
+typedef enum memory_order {
+  memory_order_relaxed, memory_order_consume, memory_order_acquire,
+  memory_order_release, memory_order_acq_rel, memory_order_seq_cst
 } memory_order;
 
+static_assert((is_same<underlying_type<memory_order>::type,
+			   unsigned>::value), "Underlying type differs from unsigned unexpectedly");
+
+#endif // _LIBCPP_STD_VER > 17
+
+typedef underlying_type<memory_order>::type __memory_order_underlying_t; // unsigned
+
+
 #if defined(_LIBCPP_HAS_GCC_ATOMIC_IMP) || \
-    defined(_LIBCPP_ATOMIC_ONLY_USE_BUILTINS)
+	defined(_LIBCPP_ATOMIC_ONLY_USE_BUILTINS)
 
 // [atomics.types.generic]p1 guarantees _Tp is trivially copyable. Because
 // the default operator= in an object is not volatile, a byte-by-byte copy
@@ -1423,65 +1455,65 @@ struct __atomic_base  // false
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
       _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
-        {__cxx_atomic_store(&__a_, __d, __m);}
+        {__cxx_atomic_store(&__a_, __d, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
       _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
-        {__cxx_atomic_store(&__a_, __d, __m);}
+        {__cxx_atomic_store(&__a_, __d, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
       _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
-        {return __cxx_atomic_load(&__a_, __m);}
+        {return __cxx_atomic_load(&__a_, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const _NOEXCEPT
       _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
-        {return __cxx_atomic_load(&__a_, __m);}
+        {return __cxx_atomic_load(&__a_, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     operator _Tp() const volatile _NOEXCEPT {return load();}
     _LIBCPP_INLINE_VISIBILITY
     operator _Tp() const _NOEXCEPT          {return load();}
     _LIBCPP_INLINE_VISIBILITY
     _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_exchange(&__a_, __d, __m);}
+        {return __cxx_atomic_exchange(&__a_, __d, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_exchange(&__a_, __d, __m);}
+        {return __cxx_atomic_exchange(&__a_, __d, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) volatile _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__s), static_cast<__memory_order_underlying_t>(__f));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__s), static_cast<__memory_order_underlying_t>(__f));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) volatile _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__s), static_cast<__memory_order_underlying_t>(__f));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) _NOEXCEPT
       _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
-        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__s), static_cast<__memory_order_underlying_t>(__f));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                               memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__m), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__m), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                               memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__m), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
+        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, static_cast<__memory_order_underlying_t>(__m), static_cast<__memory_order_underlying_t>(__m));}
 
     _LIBCPP_INLINE_VISIBILITY
     __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT
@@ -1520,34 +1552,34 @@ struct __atomic_base<_Tp, true>
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_and(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_and(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_or(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_or(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_xor(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_xor(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp operator++(int) volatile _NOEXCEPT      {return fetch_add(_Tp(1));}
@@ -1629,17 +1661,17 @@ struct atomic<_Tp*>
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst)
                                                                         volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_add(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst)
                                                                         volatile _NOEXCEPT
-        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
+        {return __cxx_atomic_fetch_sub(&this->__a_, __op, static_cast<__memory_order_underlying_t>(__m));}
 
     _LIBCPP_INLINE_VISIBILITY
     _Tp* operator++(int) volatile _NOEXCEPT            {return fetch_add(1);}
@@ -2232,16 +2264,16 @@ typedef struct atomic_flag
 
     _LIBCPP_INLINE_VISIBILITY
     bool test_and_set(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);}
+        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     bool test_and_set(memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);}
+        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     void clear(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
-        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);}
+        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), static_cast<__memory_order_underlying_t>(__m));}
     _LIBCPP_INLINE_VISIBILITY
     void clear(memory_order __m = memory_order_seq_cst) _NOEXCEPT
-        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);}
+        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), static_cast<__memory_order_underlying_t>(__m));}
 
     _LIBCPP_INLINE_VISIBILITY
     atomic_flag() _NOEXCEPT _LIBCPP_DEFAULT
@@ -2323,14 +2355,14 @@ inline _LIBCPP_INLINE_VISIBILITY
 void
 atomic_thread_fence(memory_order __m) _NOEXCEPT
 {
-    __cxx_atomic_thread_fence(__m);
+    __cxx_atomic_thread_fence(static_cast<__memory_order_underlying_t>(__m));
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
 void
 atomic_signal_fence(memory_order __m) _NOEXCEPT
 {
-    __cxx_atomic_signal_fence(__m);
+    __cxx_atomic_signal_fence(static_cast<__memory_order_underlying_t>(__m));
 }
 
 // Atomics for standard typedef types

libcxx/test/std/atomics/atomics.order/memory_order.pass.cpp

@@ -21,14 +21,15 @@
 
 int main(int, char**)
 {
-    assert(std::memory_order_relaxed == 0);
+    assert(static_cast<int>(std::memory_order_relaxed) == 0);
-    assert(std::memory_order_consume == 1);
+    assert(static_cast<int>(std::memory_order_consume) == 1);
-    assert(std::memory_order_acquire == 2);
+    assert(static_cast<int>(std::memory_order_acquire) == 2);
-    assert(std::memory_order_release == 3);
+    assert(static_cast<int>(std::memory_order_release) == 3);
-    assert(std::memory_order_acq_rel == 4);
+    assert(static_cast<int>(std::memory_order_acq_rel) == 4);
-    assert(std::memory_order_seq_cst == 5);
+    assert(static_cast<int>(std::memory_order_seq_cst) == 5);
-    std::memory_order o = std::memory_order_seq_cst;
-    assert(o == 5);
 
-  return 0;
+    std::memory_order o = std::memory_order_seq_cst;
+    assert(static_cast<int>(o) == 5);
+
+    return 0;
 }

libcxx/test/std/atomics/atomics.order/memory_order_new.pass.cpp

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads, c++98, c++03, c++11, c++14, c++17
+
+#include <atomic>
+
+int main(int, char**)
+{
+    static_assert(std::memory_order_relaxed == std::memory_order::relaxed);
+    static_assert(std::memory_order_consume == std::memory_order::consume);
+    static_assert(std::memory_order_acquire == std::memory_order::acquire);
+    static_assert(std::memory_order_release == std::memory_order::release);
+    static_assert(std::memory_order_acq_rel == std::memory_order::acq_rel);
+    static_assert(std::memory_order_seq_cst == std::memory_order::seq_cst);
+
+    return 0;
+}

libcxx/www/cxx2a_status.html

@@ -61,7 +61,7 @@
 	<tr><td><a href="https://wg21.link/P0053R7">P0053R7</a></td><td>LWG</td><td>C++ Synchronized Buffered Ostream</td><td>Albuquerque</td><td></td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0202R3">P0202R3</a></td><td>LWG</td><td>Add constexpr modifiers to functions in &lt;algorithm&gt; and &lt;utility&gt; Headers</td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0415R1">P0415R1</a></td><td>LWG</td><td>Constexpr for <tt>std::complex</tt></td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>
-	<tr><td><a href="https://wg21.link/P0439R0">P0439R0</a></td><td>LWG</td><td>Make <tt>std::memory_order</tt> a scoped enumeration</td><td>Albuquerque</td><td></td><td></td></tr>
+	<tr><td><a href="https://wg21.link/P0439R0">P0439R0</a></td><td>LWG</td><td>Make <tt>std::memory_order</tt> a scoped enumeration</td><td>Albuquerque</td><td>Complete</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/P0457R2">P0457R2</a></td><td>LWG</td><td>String Prefix and Suffix Checking</td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0550R2">P0550R2</a></td><td>LWG</td><td>Transformation Trait <tt>remove_cvref</tt></td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
 	<tr><td><a href="https://wg21.link/P0600R1">P0600R1</a></td><td>LWG</td><td>nodiscard in the Library</td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>