etl/include/etl/atomic/atomic_gcc_sync.h

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com

Copyright(c) 2017 John Wellbelove

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions :

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
******************************************************************************/

#ifndef ETL_ATOMIC_GCC_SYNC_INCLUDED
#define ETL_ATOMIC_GCC_SYNC_INCLUDED

#include "../platform.h"
#include "../char_traits.h"
#include "../mutex.h"
#include "../nullptr.h"
#include "../static_assert.h"
#include "../type_traits.h"

#include <stdint.h>
#include <string.h>

// Select the atomic builtins based on the ARM5 version of the GCC compiler.
#if defined(ETL_COMPILER_ARM5)
  #define ETL_USE_SYNC_BUILTINS
#endif

// Select the atomic builtins based on the ARM6 version of the GCC compiler.
#if defined(ETL_COMPILER_ARM6)
  #if ETL_COMPILER_FULL_VERSION >= 40700
    #define ETL_USE_ATOMIC_BUILTINS
  #else
    #define ETL_USE_SYNC_BUILTINS
  #endif
#endif

// Select the atomic builtins based on the version of the GCC compiler.
#if defined(ETL_COMPILER_GCC)
  #if ETL_COMPILER_FULL_VERSION >= 40700
    #define ETL_USE_ATOMIC_BUILTINS
  #else
    #define ETL_USE_SYNC_BUILTINS
  #endif
#endif

// Select the atomic builtins based on the version of the Clang compiler.
#if defined(ETL_COMPILER_CLANG)
  #if ETL_COMPILER_FULL_VERSION >= 50000
    #define ETL_USE_ATOMIC_BUILTINS
  #else
    #define ETL_USE_SYNC_BUILTINS
  #endif
#endif

namespace etl
{
#if defined(ETL_USE_ATOMIC_BUILTINS)

  #define ETL_BUILTIN_LOCK                                            \
    do {                                                              \
      while (__atomic_test_and_set(&flag, etl::memory_order_seq_cst)) \
      {                                                               \
      }                                                               \
    } while (0)
  #define ETL_BUILTIN_UNLOCK                            \
    do {                                                \
      __atomic_clear(&flag, etl::memory_order_seq_cst); \
    } while (0)

  //***************************************************************************
  // Atomic type for pre C++11 GCC compilers that support the builtin '__atomic'
  // functions. Only integral and pointer types are supported.
  //***************************************************************************

  typedef enum memory_order
  {
    memory_order_relaxed = __ATOMIC_RELAXED,
    memory_order_consume = __ATOMIC_CONSUME,
    memory_order_acquire = __ATOMIC_ACQUIRE,
    memory_order_release = __ATOMIC_RELEASE,
    memory_order_acq_rel = __ATOMIC_ACQ_REL,
    memory_order_seq_cst = __ATOMIC_SEQ_CST
  } memory_order;

  template <bool Is_Always_Lock_Free>
  struct atomic_traits
  {
    static ETL_CONSTANT bool is_always_lock_free = Is_Always_Lock_Free;
  };

  template <bool Is_Always_Lock_Free>
  ETL_CONSTANT bool atomic_traits<Is_Always_Lock_Free>::is_always_lock_free;

  //***************************************************************************
  /// For all types except bool, pointers and types that are always lock free.
  //***************************************************************************
  template <typename T, bool integral_type = etl::is_integral<T>::value>
  class atomic : public atomic_traits<integral_type>
  {
  public:

    atomic()
      : value(T())
    {
    }

    atomic(T v)
      : value(v)
    {
    }

    // Assignment
    T operator=(T v)
    {
      store(v);

      return v;
    }

    T operator=(T v) volatile
    {
      store(v);

      return v;
    }

    // Pre-increment
    T operator++()
    {
      return __atomic_add_fetch(&value, 1, etl::memory_order_seq_cst);
    }

    T operator++() volatile
    {
      return __atomic_add_fetch(&value, 1, etl::memory_order_seq_cst);
    }

    // Post-increment
    T operator++(int)
    {
      return __atomic_fetch_add(&value, 1, etl::memory_order_seq_cst);
    }

    T operator++(int) volatile
    {
      return __atomic_fetch_add(&value, 1, etl::memory_order_seq_cst);
    }

    // Pre-decrement
    T operator--()
    {
      return __atomic_sub_fetch(&value, 1, etl::memory_order_seq_cst);
    }

    T operator--() volatile
    {
      return __atomic_sub_fetch(&value, 1, etl::memory_order_seq_cst);
    }

    // Post-decrement
    T operator--(int)
    {
      return __atomic_fetch_sub(&value, 1, etl::memory_order_seq_cst);
    }

    T operator--(int) volatile
    {
      return __atomic_fetch_sub(&value, 1, etl::memory_order_seq_cst);
    }

    // Add
    T operator+=(T v)
    {
      return __atomic_fetch_add(&value, v, etl::memory_order_seq_cst);
    }

    T operator+=(T v) volatile
    {
      return __atomic_fetch_add(&value, v, etl::memory_order_seq_cst);
    }

    // Subtract
    T operator-=(T v)
    {
      return __atomic_fetch_sub(&value, v, etl::memory_order_seq_cst);
    }

    T operator-=(T v) volatile
    {
      return __atomic_fetch_sub(&value, v, etl::memory_order_seq_cst);
    }

    // And
    T operator&=(T v)
    {
      return __atomic_fetch_and(&value, v, etl::memory_order_seq_cst);
    }

    T operator&=(T v) volatile
    {
      return __atomic_fetch_and(&value, v, etl::memory_order_seq_cst);
    }

    // Or
    T operator|=(T v)
    {
      return __atomic_fetch_or(&value, v, etl::memory_order_seq_cst);
    }

    T operator|=(T v) volatile
    {
      return __atomic_fetch_or(&value, v, etl::memory_order_seq_cst);
    }

    // Exclusive or
    T operator^=(T v)
    {
      return __atomic_fetch_xor(&value, v, etl::memory_order_seq_cst);
    }

    T operator^=(T v) volatile
    {
      return __atomic_fetch_xor(&value, v, etl::memory_order_seq_cst);
    }

    // Conversion operator
    operator T() const
    {
      return __atomic_fetch_add(&value, 0, etl::memory_order_seq_cst);
    }

    operator T() volatile const
    {
      return __atomic_fetch_add(&value, 0, etl::memory_order_seq_cst);
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      __atomic_store_n(&value, v, order);
    }

    void store(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      __atomic_store_n(&value, v, order);
    }

    // Load
    T load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      return __atomic_load_n(&value, order);
    }

    T load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      return __atomic_load_n(&value, order);
    }

    // Fetch add
    T fetch_add(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_fetch_add(&value, v, order);
    }

    T fetch_add(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_fetch_add(&value, v, order);
    }

    // Fetch subtract
    T fetch_sub(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_fetch_sub(&value, v, order);
    }

    T fetch_sub(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_fetch_sub(&value, v, order);
    }

    // Fetch or
    T fetch_or(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_fetch_or(&value, v, order);
    }

    T fetch_or(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_fetch_or(&value, v, order);
    }

    // Fetch and
    T fetch_and(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_fetch_and(&value, v, order);
    }

    T fetch_and(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_fetch_and(&value, v, order);
    }

    // Fetch exclusive or
    T fetch_xor(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_fetch_xor(&value, v, order);
    }

    T fetch_xor(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_fetch_xor(&value, v, order);
    }

    // Fetch max
    T fetch_max(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      T old = load(order);

      while (v > old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    T fetch_max(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      T old = load(order);

      while (v > old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    // Fetch min
    T fetch_min(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      T old = load(order);

      while (v < old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    T fetch_min(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      T old = load(order);

      while (v < old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    // Exchange
    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_exchange_n(&value, v, order);
    }

    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_exchange_n(&value, v, order);
    }

    // Compare exchange weak
    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, true, order, order);
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, true, order, order);
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, true, success, failure);
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, true, success, failure);
    }

    // Compare exchange strong
    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, false, order, order);
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, false, order, order);
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, false, success, failure);
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      return __atomic_compare_exchange_n(&value, &expected, desired, false, success, failure);
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable T value;
  };

  //***************************************************************************
  /// Specialisation for pointers
  //***************************************************************************
  template <typename T>
  class atomic<T*, false> : public atomic_traits<true>
  {
  public:

    atomic()
      : value(0U)
    {
    }

    atomic(T* v)
      : value(uintptr_t(v))
    {
    }

    // Assignment
    T* operator=(T* v)
    {
      store(v);

      return v;
    }

    T* operator=(T* v) volatile
    {
      store(v);

      return v;
    }

    // Pre-increment
    T* operator++()
    {
      return reinterpret_cast<T*>(__atomic_add_fetch(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    T* operator++() volatile
    {
      return reinterpret_cast<T*>(__atomic_add_fetch(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    // Post-increment
    T* operator++(int)
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    T* operator++(int) volatile
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    // Pre-decrement
    T* operator--()
    {
      return reinterpret_cast<T*>(__atomic_sub_fetch(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    T* operator--() volatile
    {
      return reinterpret_cast<T*>(__atomic_sub_fetch(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    // Post-decrement
    T* operator--(int)
    {
      return reinterpret_cast<T*>(__atomic_fetch_sub(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    T* operator--(int) volatile
    {
      return reinterpret_cast<T*>(__atomic_fetch_sub(&value, sizeof(T), etl::memory_order_seq_cst));
    }

    // Add
    T* operator+=(ptrdiff_t v)
    {
      return reinterpret_cast<T*>(
        __atomic_fetch_add(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), etl::memory_order_seq_cst));
    }

    T* operator+=(ptrdiff_t v) volatile
    {
      return reinterpret_cast<T*>(
        __atomic_fetch_add(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), etl::memory_order_seq_cst));
    }

    // Subtract
    T* operator-=(ptrdiff_t v)
    {
      return reinterpret_cast<T*>(
        __atomic_fetch_sub(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), etl::memory_order_seq_cst));
    }

    T* operator-=(ptrdiff_t v) volatile
    {
      return reinterpret_cast<T*>(
        __atomic_fetch_sub(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), etl::memory_order_seq_cst));
    }

    // Conversion operator
    operator T*() const
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, 0, etl::memory_order_seq_cst));
    }

    operator T*() volatile const
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, 0, etl::memory_order_seq_cst));
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(T* v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      __atomic_store_n(&value, uintptr_t(v), order);
    }

    void store(T* v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      __atomic_store_n(&value, uintptr_t(v), order);
    }

    // Load
    T* load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      return reinterpret_cast<T*>(__atomic_load_n(&value, order));
    }

    T* load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      return reinterpret_cast<T*>(__atomic_load_n(&value, order));
    }

    // Fetch add
    T* fetch_add(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), order));
    }

    T* fetch_add(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__atomic_fetch_add(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), order));
    }

    // Fetch subtract
    T* fetch_sub(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__atomic_fetch_sub(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), order));
    }

    T* fetch_sub(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__atomic_fetch_sub(&value, static_cast<uintptr_t>(v * static_cast<ptrdiff_t>(sizeof(T))), order));
    }

    // Exchange
    T* exchange(T* v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__atomic_exchange_n(&value, uintptr_t(v), order));
    }

    T* exchange(T* v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__atomic_exchange_n(&value, uintptr_t(v), order));
    }

    // Compare exchange weak
    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), true, order, order);
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), true, order, order);
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure)
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), true, success, failure);
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), true, success, failure);
    }

    // Compare exchange strong
    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), false, order, order);
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), false, order, order);
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure)
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), false, success, failure);
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      uintptr_t expected_v = uintptr_t(expected);

      return __atomic_compare_exchange_n(&value, &expected_v, uintptr_t(desired), false, success, failure);
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable uintptr_t value;
  };

  //***************************************************************************
  /// Specialisation for bool
  //***************************************************************************
  template <>
  class atomic<bool, true> : public atomic_traits<true>
  {
  public:

    atomic()
      : value(0U)
    {
    }

    atomic(bool v)
      : value(char(v))
    {
    }

    // Assignment
    bool operator=(bool v)
    {
      store(v);

      return v;
    }

    bool operator=(bool v) volatile
    {
      store(v);

      return v;
    }

    // Conversion operator
    operator bool() const
    {
      return static_cast<bool>(__atomic_fetch_add(&value, 0, etl::memory_order_seq_cst));
    }

    operator bool() volatile const
    {
      return static_cast<bool>(__atomic_fetch_add(&value, 0, etl::memory_order_seq_cst));
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(bool v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      __atomic_store_n(&value, char(v), order);
    }

    void store(bool v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      __atomic_store_n(&value, char(v), order);
    }

    // Load
    bool load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      return static_cast<bool>(__atomic_load_n(&value, order));
    }

    bool load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      return static_cast<bool>(__atomic_load_n(&value, order));
    }

    // Exchange
    bool exchange(bool v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return static_cast<bool>(__atomic_exchange_n(&value, char(v), order));
    }

    bool exchange(bool v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return static_cast<bool>(__atomic_exchange_n(&value, char(v), order));
    }

    // Compare exchange weak
    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, true, order, order);
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, true, order, order);
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure)
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, true, success, failure);
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, true, success, failure);
    }

    // Compare exchange strong
    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, false, order, order);
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, false, order, order);
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure)
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, false, success, failure);
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      char expected_v = char(expected);
      char desired_v  = char(desired);

      return __atomic_compare_exchange_n(&value, &expected_v, desired_v, false, success, failure);
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable char value;
  };

  //***************************************************************************
  /// Specialisation for type that are not integral, pointer or bool.
  /// Uses a mutex to control access.
  //***************************************************************************
  template <typename T>
  class atomic<T, false> : public atomic_traits<false>
  {
  public:

    ETL_STATIC_ASSERT((etl::is_trivially_copyable<T>::value), "atomic<T> requires that T is trivially copyable");
    ETL_STATIC_ASSERT((etl::is_copy_constructible<T>::value), "atomic<T> requires that T is copy constructible");
    ETL_STATIC_ASSERT((etl::is_copy_assignable<T>::value), "atomic<T> requires that T is copy assignable");
    ETL_STATIC_ASSERT((etl::is_move_constructible<T>::value), "atomic<T> requires that T is move constructible");
    ETL_STATIC_ASSERT((etl::is_move_assignable<T>::value), "atomic<T> requires that T is move assignable");
    ETL_STATIC_ASSERT((etl::is_same<T, typename etl::remove_cv<T>::type>::value), "atomic<T> requires that T is not const or volatile");

    atomic()
      : flag(0)
      , value(T())
    {
    }

    atomic(T v)
      : flag(0)
      , value(v)
    {
    }

    // Assignment
    T operator=(T v)
    {
      store(v);

      return v;
    }

    // Conversion operator
    operator T() const
    {
      ETL_BUILTIN_LOCK;
      T result = value;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return false;
    }

    // Store
    void store(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      ETL_BUILTIN_LOCK;
      value = v;
      ETL_BUILTIN_UNLOCK;
    }

    // Load
    T load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      (void)order;
      ETL_BUILTIN_LOCK;
      T result = value;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Exchange
    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      ETL_BUILTIN_LOCK;
      T result = value;
      value    = v;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Compare exchange weak
    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      bool result;

      (void)order;
      ETL_BUILTIN_LOCK;
      if (memcmp(&value, &expected, sizeof(T)) == 0)
      {
        value  = desired;
        result = true;
      }
      else
      {
        result = false;
      }
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      (void)success;
      (void)failure;
      return compare_exchange_weak(expected, desired);
    }

    // Compare exchange strong
    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return compare_exchange_weak(expected, desired);
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      (void)success;
      (void)failure;
      return compare_exchange_weak(expected, desired);
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable char flag;
    mutable T    value;
  };

  #undef ETL_BUILTIN_LOCK
  #undef ETL_BUILTIN_UNLOCK

#endif

#if defined(ETL_USE_SYNC_BUILTINS)

  #define ETL_BUILTIN_LOCK                        \
    do {                                          \
      while (__sync_lock_test_and_set(&flag, 1U)) \
      {                                           \
      }                                           \
    } while (0)
  #define ETL_BUILTIN_UNLOCK      \
    do {                          \
      __sync_lock_release(&flag); \
    } while (0)

  //***************************************************************************
  // Atomic type for pre C++11 GCC compilers that support the builtin '__sync'
  // functions. Only integral and pointer types are supported.
  //***************************************************************************

  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;

  template <bool Is_Always_Lock_Free>
  struct atomic_traits
  {
    static ETL_CONSTANT bool is_always_lock_free = Is_Always_Lock_Free;
  };

  template <bool Is_Always_Lock_Free>
  ETL_CONSTANT bool atomic_traits<Is_Always_Lock_Free>::is_always_lock_free;

  //***************************************************************************
  /// For all types except bool and pointers
  //***************************************************************************
  template <typename T, bool integral_type = etl::is_integral<T>::value>
  class atomic : public atomic_traits<integral_type>
  {
  public:

    ETL_STATIC_ASSERT(etl::is_integral<T>::value, "Only integral types are supported");

    atomic()
      : value(0)
    {
    }

    atomic(T v)
      : value(v)
    {
    }

    // Assignment
    T operator=(T v)
    {
      store(v);

      return v;
    }

    T operator=(T v) volatile
    {
      store(v);

      return v;
    }

    // Pre-increment
    T operator++()
    {
      return __sync_add_and_fetch(&value, 1);
    }

    T operator++() volatile
    {
      return __sync_add_and_fetch(&value, 1);
    }

    // Post-increment
    T operator++(int)
    {
      return __sync_fetch_and_add(&value, 1);
    }

    T operator++(int) volatile
    {
      return __sync_fetch_and_add(&value, 1);
    }

    // Pre-decrement
    T operator--()
    {
      return __sync_sub_and_fetch(&value, 1);
    }

    T operator--() volatile
    {
      return __sync_sub_and_fetch(&value, 1);
    }

    // Post-decrement
    T operator--(int)
    {
      return __sync_fetch_and_sub(&value, 1);
    }

    T operator--(int) volatile
    {
      return __sync_fetch_and_sub(&value, 1);
    }

    // Add
    T operator+=(T v)
    {
      return __sync_fetch_and_add(&value, v);
    }

    T operator+=(T v) volatile
    {
      return __sync_fetch_and_add(&value, v);
    }

    // Subtract
    T operator-=(T v)
    {
      return __sync_fetch_and_sub(&value, v);
    }

    T operator-=(T v) volatile
    {
      return __sync_fetch_and_sub(&value, v);
    }

    // And
    T operator&=(T v)
    {
      return __sync_fetch_and_and(&value, v);
    }

    T operator&=(T v) volatile
    {
      return __sync_fetch_and_and(&value, v);
    }

    // Or
    T operator|=(T v)
    {
      return __sync_fetch_and_or(&value, v);
    }

    T operator|=(T v) volatile
    {
      return __sync_fetch_and_or(&value, v);
    }

    // Exclusive or
    T operator^=(T v)
    {
      return __sync_fetch_and_xor(&value, v);
    }

    T operator^=(T v) volatile
    {
      return __sync_fetch_and_xor(&value, v);
    }

    // Conversion operator
    operator T() const
    {
      return __sync_fetch_and_add(&value, 0);
    }

    operator T() volatile const
    {
      return __sync_fetch_and_add(&value, 0);
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      (void)__sync_lock_test_and_set(&value, v);
    }

    void store(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      (void)__sync_lock_test_and_set(&value, v);
    }

    // Load
    T load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      (void)order;
      return __sync_fetch_and_add(&value, 0);
    }

    T load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      (void)order;
      return __sync_fetch_and_add(&value, 0);
    }

    // Fetch add
    T fetch_add(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_fetch_and_add(&value, v);
    }

    T fetch_add(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_fetch_and_add(&value, v);
    }

    // Fetch subtract
    T fetch_sub(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_fetch_and_sub(&value, v);
    }

    T fetch_sub(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_fetch_and_sub(&value, v);
    }

    // Fetch or
    T fetch_or(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_fetch_and_or(&value, v);
    }

    T fetch_or(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_fetch_and_or(&value, v);
    }

    // Fetch and
    T fetch_and(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_fetch_and_and(&value, v);
    }

    T fetch_and(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_fetch_and_and(&value, v);
    }

    // Fetch exclusive or
    T fetch_xor(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_fetch_and_xor(&value, v);
    }

    T fetch_xor(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_fetch_and_xor(&value, v);
    }

    // Fetch max
    T fetch_max(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      T old = load(order);

      while (v > old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    T fetch_max(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      T old = load(order);

      while (v > old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    // Fetch min
    T fetch_min(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      T old = load(order);

      while (v < old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    T fetch_min(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      T old = load(order);

      while (v < old)
      {
        if (compare_exchange_weak(old, v, order))
        {
          break;
        }
      }

      return old;
    }

    // Exchange
    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      return __sync_lock_test_and_set(&value, v);
    }

    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      return __sync_lock_test_and_set(&value, v);
    }

    // Compare exchange weak
    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      T old = __sync_val_compare_and_swap(&value, expected, desired);

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      T old = __sync_val_compare_and_swap(&value, expected, desired);

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      (void)success;
      (void)failure;
      T old = __sync_val_compare_and_swap(&value, expected, desired);

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      (void)success;
      (void)failure;
      T old = __sync_val_compare_and_swap(&value, expected, desired);

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    // Compare exchange strong
    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      (void)order;
      T old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      (void)order;
      T old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      (void)success;
      (void)failure;
      T old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      (void)success;
      (void)failure;
      T old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable volatile T value;
  };

  //***************************************************************************
  /// Specialisation for pointers
  //***************************************************************************
  template <typename T>
  class atomic<T*, false> : public atomic_traits<true>
  {
  public:

    atomic()
      : value(0U)
    {
    }

    atomic(T* v)
      : value(uintptr_t(v))
    {
    }

    // Assignment
    T* operator=(T* v)
    {
      store(v);

      return v;
    }

    T* operator=(T* v) volatile
    {
      store(v);

      return v;
    }

    // Pre-increment
    T* operator++()
    {
      return reinterpret_cast<T*>(__sync_add_and_fetch(&value, sizeof(T)));
    }

    T* operator++() volatile
    {
      return reinterpret_cast<T*>(__sync_add_and_fetch(&value, sizeof(T)));
    }

    // Post-increment
    T* operator++(int)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, sizeof(T)));
    }

    T* operator++(int) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, sizeof(T)));
    }

    // Pre-decrement
    T* operator--()
    {
      return reinterpret_cast<T*>(__sync_sub_and_fetch(&value, sizeof(T)));
    }

    T* operator--() volatile
    {
      return reinterpret_cast<T*>(__sync_sub_and_fetch(&value, sizeof(T)));
    }

    // Post-decrement
    T* operator--(int)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, sizeof(T)));
    }

    T* operator--(int) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, sizeof(T)));
    }

    // Add
    T* operator+=(ptrdiff_t v)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, v * sizeof(T)));
    }

    T* operator+=(ptrdiff_t v) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, v * sizeof(T)));
    }

    // Subtract
    T* operator-=(ptrdiff_t v)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, v * sizeof(T)));
    }

    T* operator-=(ptrdiff_t v) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, v * sizeof(T)));
    }

    // Conversion operator
    operator T*() const
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, 0));
    }

    operator T*() volatile const
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, 0));
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(T* v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      __sync_lock_test_and_set(&value, uintptr_t(v));
    }

    void store(T* v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      __sync_lock_test_and_set(&value, uintptr_t(v));
    }

    // Load
    T* load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, 0));
    }

    T* load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, 0));
    }

    // Fetch add
    T* fetch_add(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, v));
    }

    T* fetch_add(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_add(&value, v));
    }

    // Fetch subtract
    T* fetch_sub(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, v));
    }

    T* fetch_sub(ptrdiff_t v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__sync_fetch_and_sub(&value, v));
    }

    // Exchange
    T* exchange(T* v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return reinterpret_cast<T*>(__sync_lock_test_and_set(&value, uintptr_t(v)));
    }

    T* exchange(T* v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return reinterpret_cast<T*>(__sync_lock_test_and_set(&value, uintptr_t(v)));
    }

    // Compare exchange weak
    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      T* old = reinterpret_cast<T*>(__sync_val_compare_and_swap(&value, uintptr_t(expected), uintptr_t(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      T* old = reinterpret_cast<T*>(__sync_val_compare_and_swap(&value, uintptr_t(expected), uintptr_t(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure)
    {
      T* old = reinterpret_cast<T*>(__sync_val_compare_and_swap(&value, uintptr_t(expected), uintptr_t(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      T* old = reinterpret_cast<T*>(__sync_val_compare_and_swap(&value, uintptr_t(expected), uintptr_t(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    // Compare exchange strong
    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      T* old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T*)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      T* old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T*)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure)
    {
      T* old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T*)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(T*& expected, T* desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      T* old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(T*)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable uintptr_t value;
  };

  //***************************************************************************
  /// Specialisation for bool
  //***************************************************************************
  template <>
  class atomic<bool, true> : public atomic_traits<true>
  {
  public:

    atomic()
      : value(0U)
    {
    }

    atomic(bool v)
      : value(char(v))
    {
    }

    // Assignment
    bool operator=(bool v)
    {
      store(v);

      return v;
    }

    bool operator=(bool v) volatile
    {
      store(v);

      return v;
    }

    // Conversion operator
    operator bool() const
    {
      return static_cast<bool>(__sync_fetch_and_add(&value, 0));
    }

    operator bool() volatile const
    {
      return static_cast<bool>(__sync_fetch_and_add(&value, 0));
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return true;
    }

    bool is_lock_free() const volatile
    {
      return true;
    }

    // Store
    void store(bool v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      __sync_lock_test_and_set(&value, char(v));
    }

    void store(bool v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      __sync_lock_test_and_set(&value, char(v));
    }

    // Load
    bool load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      return static_cast<bool>(__sync_fetch_and_add(&value, 0));
    }

    bool load(etl::memory_order order = etl::memory_order_seq_cst) const volatile
    {
      return static_cast<bool>(__sync_fetch_and_add(&value, 0));
    }

    // Exchange
    bool exchange(bool v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return static_cast<bool>(__sync_lock_test_and_set(&value, char(v)));
    }

    bool exchange(bool v, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      return static_cast<bool>(__sync_lock_test_and_set(&value, char(v)));
    }

    // Compare exchange weak
    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      bool old = static_cast<bool>(__sync_val_compare_and_swap(&value, char(expected), char(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      bool old = static_cast<bool>(__sync_val_compare_and_swap(&value, char(expected), char(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure)
    {
      bool old = static_cast<bool>(__sync_val_compare_and_swap(&value, char(expected), char(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    bool compare_exchange_weak(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      bool old = static_cast<bool>(__sync_val_compare_and_swap(&value, char(expected), char(desired)));

      if (old == expected)
      {
        return true;
      }
      else
      {
        expected = old;
        return false;
      }
    }

    // Compare exchange strong
    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      bool old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(bool)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order order = etl::memory_order_seq_cst) volatile
    {
      bool old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(bool)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure)
    {
      bool old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(bool)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

    bool compare_exchange_strong(bool& expected, bool desired, etl::memory_order success, etl::memory_order failure) volatile
    {
      bool old = expected;

      while (!compare_exchange_weak(old, desired))
      {
        if (memcmp(&old, &expected, sizeof(bool)))
        {
          expected = old;
          return false;
        }
      }

      return true;
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable char value;
  };

  //***************************************************************************
  /// Specialisation for type that are not integral, pointer or bool.
  /// Uses a mutex to control access.
  //***************************************************************************
  template <typename T>
  class atomic<T, false> : public atomic_traits<false>
  {
  public:

    ETL_STATIC_ASSERT((etl::is_trivially_copyable<T>::value), "atomic<T> requires that T is trivially copyable");
    ETL_STATIC_ASSERT((etl::is_copy_constructible<T>::value), "atomic<T> requires that T is copy constructible");
    ETL_STATIC_ASSERT((etl::is_copy_assignable<T>::value), "atomic<T> requires that T is copy assignable");
    ETL_STATIC_ASSERT((etl::is_move_constructible<T>::value), "atomic<T> requires that T is move constructible");
    ETL_STATIC_ASSERT((etl::is_move_assignable<T>::value), "atomic<T> requires that T is move assignable");
    ETL_STATIC_ASSERT((etl::is_same<T, typename etl::remove_cv<T>::type>::value), "atomic<T> requires that T is not const or volatile");

    atomic()
      : flag(0)
      , value(T())
    {
    }

    atomic(T v)
      : flag(0)
      , value(v)
    {
    }

    // Assignment
    T operator=(T v)
    {
      store(v);

      return v;
    }

    // Conversion operator
    operator T() const
    {
      ETL_BUILTIN_LOCK;
      T result = value;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Is lock free?
    bool is_lock_free() const
    {
      return false;
    }

    // Store
    void store(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      ETL_BUILTIN_LOCK;
      value = v;
      ETL_BUILTIN_UNLOCK;
    }

    // Load
    T load(etl::memory_order order = etl::memory_order_seq_cst) const
    {
      ETL_BUILTIN_LOCK;
      T result = value;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Exchange
    T exchange(T v, etl::memory_order order = etl::memory_order_seq_cst)
    {
      ETL_BUILTIN_LOCK;
      T result = value;
      value    = v;
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    // Compare exchange weak
    bool compare_exchange_weak(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      bool result;

      ETL_BUILTIN_LOCK;
      if (memcmp(&value, &expected, sizeof(T)) == 0)
      {
        value  = desired;
        result = true;
      }
      else
      {
        result = false;
      }
      ETL_BUILTIN_UNLOCK;

      return result;
    }

    bool compare_exchange_weak(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      return compare_exchange_weak(expected, desired);
    }

    // Compare exchange strong
    bool compare_exchange_strong(T& expected, T desired, etl::memory_order order = etl::memory_order_seq_cst)
    {
      return compare_exchange_weak(expected, desired);
    }

    bool compare_exchange_strong(T& expected, T desired, etl::memory_order success, etl::memory_order failure)
    {
      return compare_exchange_weak(expected, desired);
    }

  private:

    atomic& operator=(const atomic&) ETL_DELETE;
    atomic& operator=(const atomic&) volatile ETL_DELETE;

    mutable char flag;
    mutable T    value;
  };

  #undef ETL_SYNC_BUILTIN_LOCK
  #undef ETL_SYNC_BUILTIN_UNLOCK

#endif

  typedef etl::atomic<bool>               atomic_bool;
  typedef etl::atomic<char>               atomic_char;
  typedef etl::atomic<signed char>        atomic_schar;
  typedef etl::atomic<unsigned char>      atomic_uchar;
  typedef etl::atomic<short>              atomic_short;
  typedef etl::atomic<unsigned short>     atomic_ushort;
  typedef etl::atomic<int>                atomic_int;
  typedef etl::atomic<unsigned int>       atomic_uint;
  typedef etl::atomic<long>               atomic_long;
  typedef etl::atomic<unsigned long>      atomic_ulong;
  typedef etl::atomic<long long>          atomic_llong;
  typedef etl::atomic<unsigned long long> atomic_ullong;
  typedef etl::atomic<wchar_t>            atomic_wchar_t;
#if ETL_HAS_NATIVE_CHAR8_T
  typedef etl::atomic<char8_t> atomic_char8_t;
#endif
#if ETL_HAS_NATIVE_CHAR16_T
  typedef etl::atomic<char16_t> atomic_char16_t;
#endif
#if ETL_HAS_NATIVE_CHAR32_T
  typedef etl::atomic<char32_t> atomic_char32_t;
#endif
#if ETL_USING_8BIT_TYPES
  typedef etl::atomic<uint8_t> atomic_uint8_t;
  typedef etl::atomic<int8_t>  atomic_int8_t;
#endif
  typedef etl::atomic<uint16_t> atomic_uint16_t;
  typedef etl::atomic<int16_t>  atomic_int16_t;
  typedef etl::atomic<uint32_t> atomic_uint32_t;
  typedef etl::atomic<int32_t>  atomic_int32_t;
#if ETL_USING_64BIT_TYPES
  typedef etl::atomic<uint64_t> atomic_uint64_t;
  typedef etl::atomic<int64_t>  atomic_int64_t;
#endif
  typedef etl::atomic<int_least8_t>   atomic_int_least8_t;
  typedef etl::atomic<uint_least8_t>  atomic_uint_least8_t;
  typedef etl::atomic<int_least16_t>  atomic_int_least16_t;
  typedef etl::atomic<uint_least16_t> atomic_uint_least16_t;
  typedef etl::atomic<int_least32_t>  atomic_int_least32_t;
  typedef etl::atomic<uint_least32_t> atomic_uint_least32_t;
#if ETL_USING_64BIT_TYPES
  typedef etl::atomic<int_least64_t>  atomic_int_least64_t;
  typedef etl::atomic<uint_least64_t> atomic_uint_least64_t;
#endif
  typedef etl::atomic<int_fast8_t>   atomic_int_fast8_t;
  typedef etl::atomic<uint_fast8_t>  atomic_uint_fast8_t;
  typedef etl::atomic<int_fast16_t>  atomic_int_fast16_t;
  typedef etl::atomic<uint_fast16_t> atomic_uint_fast16_t;
  typedef etl::atomic<int_fast32_t>  atomic_int_fast32_t;
  typedef etl::atomic<uint_fast32_t> atomic_uint_fast32_t;
#if ETL_USING_64BIT_TYPES
  typedef etl::atomic<int_fast64_t>  atomic_int_fast64_t;
  typedef etl::atomic<uint_fast64_t> atomic_uint_fast64_t;
#endif
  typedef etl::atomic<intptr_t>  atomic_intptr_t;
  typedef etl::atomic<uintptr_t> atomic_uintptr_t;
  typedef etl::atomic<size_t>    atomic_size_t;
  typedef etl::atomic<ptrdiff_t> atomic_ptrdiff_t;
  typedef etl::atomic<intmax_t>  atomic_intmax_t;
  typedef etl::atomic<uintmax_t> atomic_uintmax_t;
} // namespace etl

#endif