text: // Protocol Buffers - Google's data interchange format
  // Copyright 2012 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
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  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  // This file is an internal atomic implementation, use atomicops.h instead.
  
  #ifndef GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_
  #define GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_
  
  #include <atomic>
  
  namespace google {
  namespace protobuf {
  namespace internal {
  
  // This implementation is transitional and maintains the original API for
  // atomicops.h. This requires casting memory locations to the atomic types, and
  // assumes that the API and the C++11 implementation are layout-compatible,
  // which isn't true for all implementations or hardware platforms. The static
  // assertion should detect this issue, were it to fire then this header
  // shouldn't be used.
  //
  // TODO(jfb) If this header manages to stay committed then the API should be
  //           modified, and all call sites updated.
  typedef volatile std::atomic<Atomic32>* AtomicLocation32;
  static_assert(sizeof(*(AtomicLocation32) nullptr) == sizeof(Atomic32),
                "incompatible 32-bit atomic layout");
  
  inline void MemoryBarrierInternal() {
  #if defined(__GLIBCXX__)
    // Work around libstdc++ bug 51038 where atomic_thread_fence was declared but
    // not defined, leading to the linker complaining about undefined references.
    __atomic_thread_fence(std::memory_order_seq_cst);
  #else
    std::atomic_thread_fence(std::memory_order_seq_cst);
  #endif
  }
  
  inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
                                           Atomic32 old_value,
                                           Atomic32 new_value) {
    ((AtomicLocation32)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_relaxed,
                                  std::memory_order_relaxed);
    return old_value;
  }
  
  inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
                                           Atomic32 new_value) {
    return ((AtomicLocation32)ptr)
        ->exchange(new_value, std::memory_order_relaxed);
  }
  
  inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
                                            Atomic32 increment) {
    return increment +
           ((AtomicLocation32)ptr)
               ->fetch_add(increment, std::memory_order_relaxed);
  }
  
  inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
                                          Atomic32 increment) {
    return increment + ((AtomicLocation32)ptr)->fetch_add(increment);
  }
  
  inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
                                         Atomic32 old_value,
                                         Atomic32 new_value) {
    ((AtomicLocation32)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_acquire,
                                  std::memory_order_acquire);
    return old_value;
  }
  
  inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
                                         Atomic32 old_value,
                                         Atomic32 new_value) {
    ((AtomicLocation32)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_release,
                                  std::memory_order_relaxed);
    return old_value;
  }
  
  inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
    ((AtomicLocation32)ptr)->store(value, std::memory_order_relaxed);
  }
  
  inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
    ((AtomicLocation32)ptr)->store(value, std::memory_order_relaxed);
    MemoryBarrierInternal();
  }
  
  inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
    ((AtomicLocation32)ptr)->store(value, std::memory_order_release);
  }
  
  inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
    return ((AtomicLocation32)ptr)->load(std::memory_order_relaxed);
  }
  
  inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
    return ((AtomicLocation32)ptr)->load(std::memory_order_acquire);
  }
  
  inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
    MemoryBarrierInternal();
    return ((AtomicLocation32)ptr)->load(std::memory_order_relaxed);
  }
  
  #if defined(GOOGLE_PROTOBUF_ARCH_64_BIT)
  
  typedef volatile std::atomic<Atomic64>* AtomicLocation64;
  static_assert(sizeof(*(AtomicLocation64) nullptr) == sizeof(Atomic64),
                "incompatible 64-bit atomic layout");
  
  inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
                                           Atomic64 old_value,
                                           Atomic64 new_value) {
    ((AtomicLocation64)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_relaxed,
                                  std::memory_order_relaxed);
    return old_value;
  }
  
  inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
                                           Atomic64 new_value) {
    return ((AtomicLocation64)ptr)
        ->exchange(new_value, std::memory_order_relaxed);
  }
  
  inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
                                            Atomic64 increment) {
    return increment +
           ((AtomicLocation64)ptr)
               ->fetch_add(increment, std::memory_order_relaxed);
  }
  
  inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
                                          Atomic64 increment) {
    return increment + ((AtomicLocation64)ptr)->fetch_add(increment);
  }
  
  inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
                                         Atomic64 old_value,
                                         Atomic64 new_value) {
    ((AtomicLocation64)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_acquire,
                                  std::memory_order_acquire);
    return old_value;
  }
  
  inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
                                         Atomic64 old_value,
                                         Atomic64 new_value) {
    ((AtomicLocation64)ptr)
        ->compare_exchange_strong(old_value,
                                  new_value,
                                  std::memory_order_release,
                                  std::memory_order_relaxed);
    return old_value;
  }
  
  inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
    ((AtomicLocation64)ptr)->store(value, std::memory_order_relaxed);
  }
  
  inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
    ((AtomicLocation64)ptr)->store(value, std::memory_order_relaxed);
    MemoryBarrierInternal();
  }
  
  inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
    ((AtomicLocation64)ptr)->store(value, std::memory_order_release);
  }
  
  inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
    return ((AtomicLocation64)ptr)->load(std::memory_order_relaxed);
  }
  
  inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
    return ((AtomicLocation64)ptr)->load(std::memory_order_acquire);
  }
  
  inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
    MemoryBarrierInternal();
    return ((AtomicLocation64)ptr)->load(std::memory_order_relaxed);
  }
  
  #endif  // defined(GOOGLE_PROTOBUF_ARCH_64_BIT)
  
  }  // namespace internal
  }  // namespace protobuf
  }  // namespace google
  
  #endif  // GOOGLE_PROTOBUF_ATOMICOPS_INTERNALS_GENERIC_C11_ATOMIC_H_
  