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[official-gcc.git] / libitm / local_atomic

// -*- C++ -*- header.

// Copyright (C) 2008-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

// ????????????????????????????????????????????????????????????????????
//
// This is a copy of the libstdc++ header, with the trivial modification
// of ignoring the c++config.h include.  If and when the top-level build is
// fixed so that target libraries can be built using the newly built, we can
// delete this file.
//
// ????????????????????????????????????????????????????????????????????

/** @file include/atomic
 *  This is a Standard C++ Library header.
 */

// Based on "C++ Atomic Types and Operations" by Hans Boehm and Lawrence Crowl.
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2427.html

#ifndef _GLIBCXX_ATOMIC
#define _GLIBCXX_ATOMIC 1

#define __libitm_always_inline __attribute__((always_inline))

// #pragma GCC system_header

// #ifndef __GXX_EXPERIMENTAL_CXX0X__
// # include <bits/c++0x_warning.h>
// #endif

// #include <bits/atomic_base.h>

namespace std // _GLIBCXX_VISIBILITY(default)
{
// _GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @defgroup atomics Atomics
   *
   * Components for performing atomic operations.
   * @{
   */

  /// Enumeration for memory_order
  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;

  inline __libitm_always_inline memory_order
  __calculate_memory_order(memory_order __m) noexcept
  {
    const bool __cond1 = __m == memory_order_release;
    const bool __cond2 = __m == memory_order_acq_rel;
    memory_order __mo1(__cond1 ? memory_order_relaxed : __m);
    memory_order __mo2(__cond2 ? memory_order_acquire : __mo1);
    return __mo2;
  }

  inline __libitm_always_inline void
  atomic_thread_fence(memory_order __m) noexcept
  {
    __atomic_thread_fence (__m);
  }

  inline __libitm_always_inline void
  atomic_signal_fence(memory_order __m) noexcept
  {
    __atomic_thread_fence (__m);
  }

  /// kill_dependency
  template<typename _Tp>
    inline _Tp
    kill_dependency(_Tp __y) noexcept
    {
      _Tp __ret(__y);
      return __ret;
    }

  /// Lock-free Property


#define ATOMIC_BOOL_LOCK_FREE           __GCC_ATOMIC_BOOL_LOCK_FREE
#define ATOMIC_CHAR_LOCK_FREE           __GCC_ATOMIC_CHAR_LOCK_FREE
#define ATOMIC_WCHAR_T_LOCK_FREE        __GCC_ATOMIC_WCHAR_T_LOCK_FREE
#define ATOMIC_CHAR16_T_LOCK_FREE       __GCC_ATOMIC_CHAR16_T_LOCK_FREE
#define ATOMIC_CHAR32_T_LOCK_FREE       __GCC_ATOMIC_CHAR32_T_LOCK_FREE
#define ATOMIC_SHORT_LOCK_FREE          __GCC_ATOMIC_SHORT_LOCK_FREE
#define ATOMIC_INT_LOCK_FREE            __GCC_ATOMIC_INT_LOCK_FREE
#define ATOMIC_LONG_LOCK_FREE           __GCC_ATOMIC_LONG_LOCK_FREE
#define ATOMIC_LLONG_LOCK_FREE          __GCC_ATOMIC_LLONG_LOCK_FREE
#define ATOMIC_POINTER_LOCK_FREE        __GCC_ATOMIC_POINTER_LOCK_FREE

  // Base types for atomics.
  template<typename _IntTp>
    struct __atomic_base;

  /// atomic_char
  typedef __atomic_base<char>                   atomic_char;

  /// atomic_schar
  typedef __atomic_base<signed char>            atomic_schar;

  /// atomic_uchar
  typedef __atomic_base<unsigned char>          atomic_uchar;

  /// atomic_short
  typedef __atomic_base<short>                  atomic_short;

  /// atomic_ushort
  typedef __atomic_base<unsigned short>         atomic_ushort;

  /// atomic_int
  typedef __atomic_base<int>                    atomic_int;

  /// atomic_uint
  typedef __atomic_base<unsigned int>           atomic_uint;

  /// atomic_long
  typedef __atomic_base<long>                   atomic_long;

  /// atomic_ulong
  typedef __atomic_base<unsigned long>          atomic_ulong;

  /// atomic_llong
  typedef __atomic_base<long long>              atomic_llong;

  /// atomic_ullong
  typedef __atomic_base<unsigned long long>     atomic_ullong;

  /// atomic_wchar_t
  typedef __atomic_base<wchar_t>                atomic_wchar_t;

  /// atomic_char16_t
  typedef __atomic_base<char16_t>               atomic_char16_t;

  /// atomic_char32_t
  typedef __atomic_base<char32_t>               atomic_char32_t;

  /// atomic_char32_t
  typedef __atomic_base<char32_t>               atomic_char32_t;


  /// atomic_int_least8_t
  typedef __atomic_base<int_least8_t>           atomic_int_least8_t;

  /// atomic_uint_least8_t
  typedef __atomic_base<uint_least8_t>          atomic_uint_least8_t;

  /// atomic_int_least16_t
  typedef __atomic_base<int_least16_t>          atomic_int_least16_t;

  /// atomic_uint_least16_t
  typedef __atomic_base<uint_least16_t>         atomic_uint_least16_t;

  /// atomic_int_least32_t
  typedef __atomic_base<int_least32_t>          atomic_int_least32_t;

  /// atomic_uint_least32_t
  typedef __atomic_base<uint_least32_t>         atomic_uint_least32_t;

  /// atomic_int_least64_t
  typedef __atomic_base<int_least64_t>          atomic_int_least64_t;

  /// atomic_uint_least64_t
  typedef __atomic_base<uint_least64_t>         atomic_uint_least64_t;


  /// atomic_int_fast8_t
  typedef __atomic_base<int_fast8_t>            atomic_int_fast8_t;

  /// atomic_uint_fast8_t
  typedef __atomic_base<uint_fast8_t>           atomic_uint_fast8_t;

  /// atomic_int_fast16_t
  typedef __atomic_base<int_fast16_t>           atomic_int_fast16_t;

  /// atomic_uint_fast16_t
  typedef __atomic_base<uint_fast16_t>          atomic_uint_fast16_t;

  /// atomic_int_fast32_t
  typedef __atomic_base<int_fast32_t>           atomic_int_fast32_t;

  /// atomic_uint_fast32_t
  typedef __atomic_base<uint_fast32_t>          atomic_uint_fast32_t;

  /// atomic_int_fast64_t
  typedef __atomic_base<int_fast64_t>           atomic_int_fast64_t;

  /// atomic_uint_fast64_t
  typedef __atomic_base<uint_fast64_t>          atomic_uint_fast64_t;


  /// atomic_intptr_t
  typedef __atomic_base<intptr_t>               atomic_intptr_t;

  /// atomic_uintptr_t
  typedef __atomic_base<uintptr_t>              atomic_uintptr_t;

  /// atomic_size_t
  typedef __atomic_base<size_t>                 atomic_size_t;

  /// atomic_intmax_t
  typedef __atomic_base<intmax_t>               atomic_intmax_t;

  /// atomic_uintmax_t
  typedef __atomic_base<uintmax_t>              atomic_uintmax_t;

  /// atomic_ptrdiff_t
  typedef __atomic_base<ptrdiff_t>              atomic_ptrdiff_t;


#define ATOMIC_VAR_INIT(_VI) { _VI }

  template<typename _Tp>
    struct atomic;

  template<typename _Tp>
    struct atomic<_Tp*>;


  /**
   *  @brief Base type for atomic_flag.
   *
   *  Base type is POD with data, allowing atomic_flag to derive from
   *  it and meet the standard layout type requirement. In addition to
   *  compatibilty with a C interface, this allows different
   *  implementations of atomic_flag to use the same atomic operation
   *  functions, via a standard conversion to the __atomic_flag_base
   *  argument.
  */
  // _GLIBCXX_BEGIN_EXTERN_C

  struct __atomic_flag_base
  {
    bool _M_i;
  };

  // _GLIBCXX_END_EXTERN_C

#define ATOMIC_FLAG_INIT { false }

  /// atomic_flag
  struct atomic_flag : public __atomic_flag_base
  {
    atomic_flag() noexcept = default;
    ~atomic_flag() noexcept = default;
    atomic_flag(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) volatile = delete;

    // Conversion to ATOMIC_FLAG_INIT.
    atomic_flag(bool __i) noexcept : __atomic_flag_base({ __i }) { }

    __libitm_always_inline bool
    test_and_set(memory_order __m = memory_order_seq_cst) noexcept
    {
      return __atomic_test_and_set (&_M_i, __m);
    }

    __libitm_always_inline bool
    test_and_set(memory_order __m = memory_order_seq_cst) volatile noexcept
    {
      return __atomic_test_and_set (&_M_i, __m);
    }

    __libitm_always_inline void
    clear(memory_order __m = memory_order_seq_cst) noexcept
    {
      // __glibcxx_assert(__m != memory_order_consume);
      // __glibcxx_assert(__m != memory_order_acquire);
      // __glibcxx_assert(__m != memory_order_acq_rel);

      __atomic_clear (&_M_i, __m);
    }

    __libitm_always_inline void
    clear(memory_order __m = memory_order_seq_cst) volatile noexcept
    {
      // __glibcxx_assert(__m != memory_order_consume);
      // __glibcxx_assert(__m != memory_order_acquire);
      // __glibcxx_assert(__m != memory_order_acq_rel);

      __atomic_clear (&_M_i, __m);
    }
  };


  /// Base class for atomic integrals.
  //
  // For each of the integral types, define atomic_[integral type] struct
  //
  // atomic_bool     bool
  // atomic_char     char
  // atomic_schar    signed char
  // atomic_uchar    unsigned char
  // atomic_short    short
  // atomic_ushort   unsigned short
  // atomic_int      int
  // atomic_uint     unsigned int
  // atomic_long     long
  // atomic_ulong    unsigned long
  // atomic_llong    long long
  // atomic_ullong   unsigned long long
  // atomic_char16_t char16_t
  // atomic_char32_t char32_t
  // atomic_wchar_t  wchar_t
  //
  // NB: Assuming _ITp is an integral scalar type that is 1, 2, 4, or
  // 8 bytes, since that is what GCC built-in functions for atomic
  // memory access expect.
  template<typename _ITp>
    struct __atomic_base
    {
    private:
      typedef _ITp      __int_type;

      __int_type        _M_i;

    public:
      __atomic_base() noexcept = default;
      ~__atomic_base() noexcept = default;
      __atomic_base(const __atomic_base&) = delete;
      __atomic_base& operator=(const __atomic_base&) = delete;
      __atomic_base& operator=(const __atomic_base&) volatile = delete;

      // Requires __int_type convertible to _M_i.
      constexpr __atomic_base(__int_type __i) noexcept : _M_i (__i) { }

      operator __int_type() const noexcept
      { return load(); }

      operator __int_type() const volatile noexcept
      { return load(); }

      __int_type
      operator=(__int_type __i) noexcept
      {
        store(__i);
        return __i;
      }

      __int_type
      operator=(__int_type __i) volatile noexcept
      {
        store(__i);
        return __i;
      }

      __int_type
      operator++(int) noexcept
      { return fetch_add(1); }

      __int_type
      operator++(int) volatile noexcept
      { return fetch_add(1); }

      __int_type
      operator--(int) noexcept
      { return fetch_sub(1); }

      __int_type
      operator--(int) volatile noexcept
      { return fetch_sub(1); }

      __int_type
      operator++() noexcept
      { return __atomic_add_fetch(&_M_i, 1, memory_order_seq_cst); }

      __int_type
      operator++() volatile noexcept
      { return __atomic_add_fetch(&_M_i, 1, memory_order_seq_cst); }

      __int_type
      operator--() noexcept
      { return __atomic_sub_fetch(&_M_i, 1, memory_order_seq_cst); }

      __int_type
      operator--() volatile noexcept
      { return __atomic_sub_fetch(&_M_i, 1, memory_order_seq_cst); }

      __int_type
      operator+=(__int_type __i) noexcept
      { return __atomic_add_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator+=(__int_type __i) volatile noexcept
      { return __atomic_add_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator-=(__int_type __i) noexcept
      { return __atomic_sub_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator-=(__int_type __i) volatile noexcept
      { return __atomic_sub_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator&=(__int_type __i) noexcept
      { return __atomic_and_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator&=(__int_type __i) volatile noexcept
      { return __atomic_and_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator|=(__int_type __i) noexcept
      { return __atomic_or_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator|=(__int_type __i) volatile noexcept
      { return __atomic_or_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator^=(__int_type __i) noexcept
      { return __atomic_xor_fetch(&_M_i, __i, memory_order_seq_cst); }

      __int_type
      operator^=(__int_type __i) volatile noexcept
      { return __atomic_xor_fetch(&_M_i, __i, memory_order_seq_cst); }

      bool
      is_lock_free() const noexcept
      { return __atomic_is_lock_free (sizeof (_M_i), &_M_i); }

      bool
      is_lock_free() const volatile noexcept
      { return __atomic_is_lock_free (sizeof (_M_i), &_M_i); }

      __libitm_always_inline void
      store(__int_type __i, memory_order __m = memory_order_seq_cst) noexcept
      {
        // __glibcxx_assert(__m != memory_order_acquire);
        // __glibcxx_assert(__m != memory_order_acq_rel);
        // __glibcxx_assert(__m != memory_order_consume);

        __atomic_store_n(&_M_i, __i, __m);
      }

      __libitm_always_inline void
      store(__int_type __i,
            memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        // __glibcxx_assert(__m != memory_order_acquire);
        // __glibcxx_assert(__m != memory_order_acq_rel);
        // __glibcxx_assert(__m != memory_order_consume);

        __atomic_store_n(&_M_i, __i, __m);
      }

      __libitm_always_inline __int_type
      load(memory_order __m = memory_order_seq_cst) const noexcept
      {
        // __glibcxx_assert(__m != memory_order_release);
        // __glibcxx_assert(__m != memory_order_acq_rel);

        return __atomic_load_n(&_M_i, __m);
      }

      __libitm_always_inline __int_type
      load(memory_order __m = memory_order_seq_cst) const volatile noexcept
      {
        // __glibcxx_assert(__m != memory_order_release);
        // __glibcxx_assert(__m != memory_order_acq_rel);

        return __atomic_load_n(&_M_i, __m);
      }

      __libitm_always_inline __int_type
      exchange(__int_type __i,
               memory_order __m = memory_order_seq_cst) noexcept
      {
        return __atomic_exchange_n(&_M_i, __i, __m);
      }

      __libitm_always_inline __int_type
      exchange(__int_type __i,
               memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return __atomic_exchange_n(&_M_i, __i, __m);
      }

      __libitm_always_inline bool
      compare_exchange_weak(__int_type& __i1, __int_type __i2,
                            memory_order __m1, memory_order __m2) noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 1, __m1, __m2);
      }

      __libitm_always_inline bool
      compare_exchange_weak(__int_type& __i1, __int_type __i2,
                            memory_order __m1,
                            memory_order __m2) volatile noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 1, __m1, __m2);
      }

      __libitm_always_inline bool
      compare_exchange_weak(__int_type& __i1, __int_type __i2,
                            memory_order __m = memory_order_seq_cst) noexcept
      {
        return compare_exchange_weak(__i1, __i2, __m,
                                     __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_weak(__int_type& __i1, __int_type __i2,
                   memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return compare_exchange_weak(__i1, __i2, __m,
                                     __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_strong(__int_type& __i1, __int_type __i2,
                              memory_order __m1, memory_order __m2) noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 0, __m1, __m2);
      }

      __libitm_always_inline bool
      compare_exchange_strong(__int_type& __i1, __int_type __i2,
                              memory_order __m1,
                              memory_order __m2) volatile noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 0, __m1, __m2);
      }

      __libitm_always_inline bool
      compare_exchange_strong(__int_type& __i1, __int_type __i2,
                              memory_order __m = memory_order_seq_cst) noexcept
      {
        return compare_exchange_strong(__i1, __i2, __m,
                                       __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_strong(__int_type& __i1, __int_type __i2,
                 memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return compare_exchange_strong(__i1, __i2, __m,
                                       __calculate_memory_order(__m));
      }

      __libitm_always_inline __int_type
      fetch_add(__int_type __i,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_add(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_add(__int_type __i,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_add(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_sub(__int_type __i,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_sub(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_sub(__int_type __i,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_sub(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_and(__int_type __i,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_and(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_and(__int_type __i,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_and(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_or(__int_type __i,
               memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_or(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_or(__int_type __i,
               memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_or(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_xor(__int_type __i,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_xor(&_M_i, __i, __m); }

      __libitm_always_inline __int_type
      fetch_xor(__int_type __i,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_xor(&_M_i, __i, __m); }
    };


  /// Partial specialization for pointer types.
  template<typename _PTp>
    struct __atomic_base<_PTp*>
    {
    private:
      typedef _PTp*     __pointer_type;

      __pointer_type    _M_p;

    public:
      __atomic_base() noexcept = default;
      ~__atomic_base() noexcept = default;
      __atomic_base(const __atomic_base&) = delete;
      __atomic_base& operator=(const __atomic_base&) = delete;
      __atomic_base& operator=(const __atomic_base&) volatile = delete;

      // Requires __pointer_type convertible to _M_p.
      constexpr __atomic_base(__pointer_type __p) noexcept : _M_p (__p) { }

      operator __pointer_type() const noexcept
      { return load(); }

      operator __pointer_type() const volatile noexcept
      { return load(); }

      __pointer_type
      operator=(__pointer_type __p) noexcept
      {
        store(__p);
        return __p;
      }

      __pointer_type
      operator=(__pointer_type __p) volatile noexcept
      {
        store(__p);
        return __p;
      }

      __pointer_type
      operator++(int) noexcept
      { return fetch_add(1); }

      __pointer_type
      operator++(int) volatile noexcept
      { return fetch_add(1); }

      __pointer_type
      operator--(int) noexcept
      { return fetch_sub(1); }

      __pointer_type
      operator--(int) volatile noexcept
      { return fetch_sub(1); }

      __pointer_type
      operator++() noexcept
      { return __atomic_add_fetch(&_M_p, 1, memory_order_seq_cst); }

      __pointer_type
      operator++() volatile noexcept
      { return __atomic_add_fetch(&_M_p, 1, memory_order_seq_cst); }

      __pointer_type
      operator--() noexcept
      { return __atomic_sub_fetch(&_M_p, 1, memory_order_seq_cst); }

      __pointer_type
      operator--() volatile noexcept
      { return __atomic_sub_fetch(&_M_p, 1, memory_order_seq_cst); }

      __pointer_type
      operator+=(ptrdiff_t __d) noexcept
      { return __atomic_add_fetch(&_M_p, __d, memory_order_seq_cst); }

      __pointer_type
      operator+=(ptrdiff_t __d) volatile noexcept
      { return __atomic_add_fetch(&_M_p, __d, memory_order_seq_cst); }

      __pointer_type
      operator-=(ptrdiff_t __d) noexcept
      { return __atomic_sub_fetch(&_M_p, __d, memory_order_seq_cst); }

      __pointer_type
      operator-=(ptrdiff_t __d) volatile noexcept
      { return __atomic_sub_fetch(&_M_p, __d, memory_order_seq_cst); }

      bool
      is_lock_free() const noexcept
      { return __atomic_is_lock_free (sizeof (_M_p), &_M_p); }

      bool
      is_lock_free() const volatile noexcept
      { return __atomic_is_lock_free (sizeof (_M_p), &_M_p); }

      __libitm_always_inline void
      store(__pointer_type __p,
            memory_order __m = memory_order_seq_cst) noexcept
      {
        // __glibcxx_assert(__m != memory_order_acquire);
        // __glibcxx_assert(__m != memory_order_acq_rel);
        // __glibcxx_assert(__m != memory_order_consume);

        __atomic_store_n(&_M_p, __p, __m);
      }

      __libitm_always_inline void
      store(__pointer_type __p,
            memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        // __glibcxx_assert(__m != memory_order_acquire);
        // __glibcxx_assert(__m != memory_order_acq_rel);
        // __glibcxx_assert(__m != memory_order_consume);

        __atomic_store_n(&_M_p, __p, __m);
      }

      __libitm_always_inline __pointer_type
      load(memory_order __m = memory_order_seq_cst) const noexcept
      {
        // __glibcxx_assert(__m != memory_order_release);
        // __glibcxx_assert(__m != memory_order_acq_rel);

        return __atomic_load_n(&_M_p, __m);
      }

      __libitm_always_inline __pointer_type
      load(memory_order __m = memory_order_seq_cst) const volatile noexcept
      {
        // __glibcxx_assert(__m != memory_order_release);
        // __glibcxx_assert(__m != memory_order_acq_rel);

        return __atomic_load_n(&_M_p, __m);
      }

      __libitm_always_inline __pointer_type
      exchange(__pointer_type __p,
               memory_order __m = memory_order_seq_cst) noexcept
      {
        return __atomic_exchange_n(&_M_p, __p, __m);
      }

      __libitm_always_inline __pointer_type
      exchange(__pointer_type __p,
               memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return __atomic_exchange_n(&_M_p, __p, __m);
      }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                              memory_order __m1,
                              memory_order __m2) noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_p, &__p1, __p2, 0, __m1, __m2);
      }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                              memory_order __m1,
                              memory_order __m2) volatile noexcept
      {
        // __glibcxx_assert(__m2 != memory_order_release);
        // __glibcxx_assert(__m2 != memory_order_acq_rel);
        // __glibcxx_assert(__m2 <= __m1);

        return __atomic_compare_exchange_n(&_M_p, &__p1, __p2, 0, __m1, __m2);
      }

      __libitm_always_inline __pointer_type
      fetch_add(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_add(&_M_p, __d, __m); }

      __libitm_always_inline __pointer_type
      fetch_add(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_add(&_M_p, __d, __m); }

      __libitm_always_inline __pointer_type
      fetch_sub(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) noexcept
      { return __atomic_fetch_sub(&_M_p, __d, __m); }

      __libitm_always_inline __pointer_type
      fetch_sub(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return __atomic_fetch_sub(&_M_p, __d, __m); }
    };


  /**
   * @addtogroup atomics
   * @{
   */

  /// atomic_bool
  // NB: No operators or fetch-operations for this type.
  struct atomic_bool
  {
  private:
    __atomic_base<bool> _M_base;

  public:
    atomic_bool() noexcept = default;
    ~atomic_bool() noexcept = default;
    atomic_bool(const atomic_bool&) = delete;
    atomic_bool& operator=(const atomic_bool&) = delete;
    atomic_bool& operator=(const atomic_bool&) volatile = delete;

    constexpr atomic_bool(bool __i) noexcept : _M_base(__i) { }

    bool
    operator=(bool __i) noexcept
    { return _M_base.operator=(__i); }

    operator bool() const noexcept
    { return _M_base.load(); }

    operator bool() const volatile noexcept
    { return _M_base.load(); }

    bool
    is_lock_free() const noexcept { return _M_base.is_lock_free(); }

    bool
    is_lock_free() const volatile noexcept { return _M_base.is_lock_free(); }

    __libitm_always_inline void
    store(bool __i, memory_order __m = memory_order_seq_cst) noexcept
    { _M_base.store(__i, __m); }

    __libitm_always_inline void
    store(bool __i, memory_order __m = memory_order_seq_cst) volatile noexcept
    { _M_base.store(__i, __m); }

    __libitm_always_inline bool
    load(memory_order __m = memory_order_seq_cst) const noexcept
    { return _M_base.load(__m); }

    __libitm_always_inline bool
    load(memory_order __m = memory_order_seq_cst) const volatile noexcept
    { return _M_base.load(__m); }

    __libitm_always_inline bool
    exchange(bool __i, memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.exchange(__i, __m); }

    __libitm_always_inline bool
    exchange(bool __i,
             memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.exchange(__i, __m); }

    __libitm_always_inline bool
    compare_exchange_weak(bool& __i1, bool __i2, memory_order __m1,
                          memory_order __m2) noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m1, __m2); }

    __libitm_always_inline bool
    compare_exchange_weak(bool& __i1, bool __i2, memory_order __m1,
                          memory_order __m2) volatile noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m1, __m2); }

    __libitm_always_inline bool
    compare_exchange_weak(bool& __i1, bool __i2,
                          memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m); }

    __libitm_always_inline bool
    compare_exchange_weak(bool& __i1, bool __i2,
                     memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m); }

    __libitm_always_inline bool
    compare_exchange_strong(bool& __i1, bool __i2, memory_order __m1,
                            memory_order __m2) noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m1, __m2); }

    __libitm_always_inline bool
    compare_exchange_strong(bool& __i1, bool __i2, memory_order __m1,
                            memory_order __m2) volatile noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m1, __m2); }

    __libitm_always_inline bool
    compare_exchange_strong(bool& __i1, bool __i2,
                            memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m); }

    __libitm_always_inline bool
    compare_exchange_strong(bool& __i1, bool __i2,
                    memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m); }
  };


  /// atomic
  /// 29.4.3, Generic atomic type, primary class template.
  template<typename _Tp>
    struct atomic
    {
    private:
      _Tp _M_i;

    public:
      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(_Tp __i) noexcept : _M_i(__i) { }

      operator _Tp() const noexcept
      { return load(); }

      operator _Tp() const volatile noexcept
      { return load(); }

      _Tp
      operator=(_Tp __i) noexcept 
      { store(__i); return __i; }

      _Tp
      operator=(_Tp __i) volatile noexcept 
      { store(__i); return __i; }

      bool
      is_lock_free() const noexcept
      { return __atomic_is_lock_free(sizeof(_M_i), &_M_i); }

      bool
      is_lock_free() const volatile noexcept
      { return __atomic_is_lock_free(sizeof(_M_i), &_M_i); }

      void
      store(_Tp __i, memory_order _m = memory_order_seq_cst) noexcept
      { __atomic_store(&_M_i, &__i, _m); }

      __libitm_always_inline void
      store(_Tp __i, memory_order _m = memory_order_seq_cst) volatile noexcept
      { __atomic_store(&_M_i, &__i, _m); }

      __libitm_always_inline _Tp
      load(memory_order _m = memory_order_seq_cst) const noexcept
      { 
        _Tp tmp;
        __atomic_load(&_M_i, &tmp, _m); 
        return tmp;
      }

      __libitm_always_inline _Tp
      load(memory_order _m = memory_order_seq_cst) const volatile noexcept
      { 
        _Tp tmp;
        __atomic_load(&_M_i, &tmp, _m); 
        return tmp;
      }

      __libitm_always_inline _Tp
      exchange(_Tp __i, memory_order _m = memory_order_seq_cst) noexcept
      { 
        _Tp tmp;
        __atomic_exchange(&_M_i, &__i, &tmp, _m); 
        return tmp;
      }

      __libitm_always_inline _Tp
      exchange(_Tp __i, 
               memory_order _m = memory_order_seq_cst) volatile noexcept
      { 
        _Tp tmp;
        __atomic_exchange(&_M_i, &__i, &tmp, _m); 
        return tmp;
      }

      __libitm_always_inline bool
      compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s, 
                            memory_order __f) noexcept
      {
        return __atomic_compare_exchange(&_M_i, &__e, &__i, true, __s, __f); 
      }

      __libitm_always_inline bool
      compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s, 
                            memory_order __f) volatile noexcept
      {
        return __atomic_compare_exchange(&_M_i, &__e, &__i, true, __s, __f); 
      }

      __libitm_always_inline bool
      compare_exchange_weak(_Tp& __e, _Tp __i,
                            memory_order __m = memory_order_seq_cst) noexcept
      { return compare_exchange_weak(__e, __i, __m, __m); }

      __libitm_always_inline bool
      compare_exchange_weak(_Tp& __e, _Tp __i,
                     memory_order __m = memory_order_seq_cst) volatile noexcept
      { return compare_exchange_weak(__e, __i, __m, __m); }

      __libitm_always_inline bool
      compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s, 
                              memory_order __f) noexcept
      {
        return __atomic_compare_exchange(&_M_i, &__e, &__i, false, __s, __f); 
      }

      __libitm_always_inline bool
      compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s, 
                              memory_order __f) volatile noexcept
      {
        return __atomic_compare_exchange(&_M_i, &__e, &__i, false, __s, __f); 
      }

      __libitm_always_inline bool
      compare_exchange_strong(_Tp& __e, _Tp __i,
                               memory_order __m = memory_order_seq_cst) noexcept
      { return compare_exchange_strong(__e, __i, __m, __m); }

      __libitm_always_inline bool
      compare_exchange_strong(_Tp& __e, _Tp __i,
                     memory_order __m = memory_order_seq_cst) volatile noexcept
      { return compare_exchange_strong(__e, __i, __m, __m); }
    };


  /// Partial specialization for pointer types.
  template<typename _Tp>
    struct atomic<_Tp*>
    {
      typedef _Tp*                      __pointer_type;
      typedef __atomic_base<_Tp*>       __base_type;
      __base_type                       _M_b;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__pointer_type __p) noexcept : _M_b(__p) { }

      operator __pointer_type() const noexcept
      { return __pointer_type(_M_b); }

      operator __pointer_type() const volatile noexcept
      { return __pointer_type(_M_b); }

      __pointer_type
      operator=(__pointer_type __p) noexcept
      { return _M_b.operator=(__p); }

      __pointer_type
      operator=(__pointer_type __p) volatile noexcept
      { return _M_b.operator=(__p); }

      __pointer_type
      operator++(int) noexcept
      { return _M_b++; }

      __pointer_type
      operator++(int) volatile noexcept
      { return _M_b++; }

      __pointer_type
      operator--(int) noexcept
      { return _M_b--; }

      __pointer_type
      operator--(int) volatile noexcept
      { return _M_b--; }

      __pointer_type
      operator++() noexcept
      { return ++_M_b; }

      __pointer_type
      operator++() volatile noexcept
      { return ++_M_b; }

      __pointer_type
      operator--() noexcept
      { return --_M_b; }

      __pointer_type
      operator--() volatile noexcept
      { return --_M_b; }

      __pointer_type
      operator+=(ptrdiff_t __d) noexcept
      { return _M_b.operator+=(__d); }

      __pointer_type
      operator+=(ptrdiff_t __d) volatile noexcept
      { return _M_b.operator+=(__d); }

      __pointer_type
      operator-=(ptrdiff_t __d) noexcept
      { return _M_b.operator-=(__d); }

      __pointer_type
      operator-=(ptrdiff_t __d) volatile noexcept
      { return _M_b.operator-=(__d); }

      bool
      is_lock_free() const noexcept
      { return _M_b.is_lock_free(); }

      bool
      is_lock_free() const volatile noexcept
      { return _M_b.is_lock_free(); }

      __libitm_always_inline void
      store(__pointer_type __p,
            memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.store(__p, __m); }

      __libitm_always_inline void
      store(__pointer_type __p,
            memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.store(__p, __m); }

      __libitm_always_inline __pointer_type
      load(memory_order __m = memory_order_seq_cst) const noexcept
      { return _M_b.load(__m); }

      __libitm_always_inline __pointer_type
      load(memory_order __m = memory_order_seq_cst) const volatile noexcept
      { return _M_b.load(__m); }

      __libitm_always_inline __pointer_type
      exchange(__pointer_type __p,
               memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.exchange(__p, __m); }

      __libitm_always_inline __pointer_type
      exchange(__pointer_type __p,
               memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.exchange(__p, __m); }

      __libitm_always_inline bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
                            memory_order __m1, memory_order __m2) noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

      __libitm_always_inline bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
                            memory_order __m1,
                            memory_order __m2) volatile noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

      __libitm_always_inline bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
                            memory_order __m = memory_order_seq_cst) noexcept
      {
        return compare_exchange_weak(__p1, __p2, __m,
                                     __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
                    memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return compare_exchange_weak(__p1, __p2, __m,
                                     __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                              memory_order __m1, memory_order __m2) noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                              memory_order __m1,
                              memory_order __m2) volatile noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                              memory_order __m = memory_order_seq_cst) noexcept
      {
        return _M_b.compare_exchange_strong(__p1, __p2, __m,
                                            __calculate_memory_order(__m));
      }

      __libitm_always_inline bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
                    memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        return _M_b.compare_exchange_strong(__p1, __p2, __m,
                                            __calculate_memory_order(__m));
      }

      __libitm_always_inline __pointer_type
      fetch_add(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.fetch_add(__d, __m); }

      __libitm_always_inline __pointer_type
      fetch_add(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.fetch_add(__d, __m); }

      __libitm_always_inline __pointer_type
      fetch_sub(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.fetch_sub(__d, __m); }

      __libitm_always_inline __pointer_type
      fetch_sub(ptrdiff_t __d,
                memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.fetch_sub(__d, __m); }
    };


  /// Explicit specialization for bool.
  template<>
    struct atomic<bool> : public atomic_bool
    {
      typedef bool                      __integral_type;
      typedef atomic_bool               __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for char.
  template<>
    struct atomic<char> : public atomic_char
    {
      typedef char                      __integral_type;
      typedef atomic_char               __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for signed char.
  template<>
    struct atomic<signed char> : public atomic_schar
    {
      typedef signed char               __integral_type;
      typedef atomic_schar              __base_type;

      atomic() noexcept= default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for unsigned char.
  template<>
    struct atomic<unsigned char> : public atomic_uchar
    {
      typedef unsigned char             __integral_type;
      typedef atomic_uchar              __base_type;

      atomic() noexcept= default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for short.
  template<>
    struct atomic<short> : public atomic_short
    {
      typedef short                     __integral_type;
      typedef atomic_short              __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for unsigned short.
  template<>
    struct atomic<unsigned short> : public atomic_ushort
    {
      typedef unsigned short            __integral_type;
      typedef atomic_ushort             __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for int.
  template<>
    struct atomic<int> : atomic_int
    {
      typedef int                       __integral_type;
      typedef atomic_int                __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for unsigned int.
  template<>
    struct atomic<unsigned int> : public atomic_uint
    {
      typedef unsigned int              __integral_type;
      typedef atomic_uint               __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for long.
  template<>
    struct atomic<long> : public atomic_long
    {
      typedef long                      __integral_type;
      typedef atomic_long               __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for unsigned long.
  template<>
    struct atomic<unsigned long> : public atomic_ulong
    {
      typedef unsigned long             __integral_type;
      typedef atomic_ulong              __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for long long.
  template<>
    struct atomic<long long> : public atomic_llong
    {
      typedef long long                 __integral_type;
      typedef atomic_llong              __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for unsigned long long.
  template<>
    struct atomic<unsigned long long> : public atomic_ullong
    {
      typedef unsigned long long        __integral_type;
      typedef atomic_ullong             __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for wchar_t.
  template<>
    struct atomic<wchar_t> : public atomic_wchar_t
    {
      typedef wchar_t                   __integral_type;
      typedef atomic_wchar_t            __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for char16_t.
  template<>
    struct atomic<char16_t> : public atomic_char16_t
    {
      typedef char16_t                  __integral_type;
      typedef atomic_char16_t           __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };

  /// Explicit specialization for char32_t.
  template<>
    struct atomic<char32_t> : public atomic_char32_t
    {
      typedef char32_t                  __integral_type;
      typedef atomic_char32_t           __base_type;

      atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

      constexpr atomic(__integral_type __i) noexcept : __base_type(__i) { }

      using __base_type::operator __integral_type;
      using __base_type::operator=;
    };


  // Function definitions, atomic_flag operations.
  inline __libitm_always_inline bool
  atomic_flag_test_and_set_explicit(atomic_flag* __a,
                                    memory_order __m) noexcept
  { return __a->test_and_set(__m); }

  inline __libitm_always_inline bool
  atomic_flag_test_and_set_explicit(volatile atomic_flag* __a,
                                    memory_order __m) noexcept
  { return __a->test_and_set(__m); }

  inline __libitm_always_inline void
  atomic_flag_clear_explicit(atomic_flag* __a, memory_order __m) noexcept
  { __a->clear(__m); }

  inline __libitm_always_inline void
  atomic_flag_clear_explicit(volatile atomic_flag* __a,
                             memory_order __m) noexcept
  { __a->clear(__m); }

  inline __libitm_always_inline bool
  atomic_flag_test_and_set(atomic_flag* __a) noexcept
  { return atomic_flag_test_and_set_explicit(__a, memory_order_seq_cst); }

  inline __libitm_always_inline bool
  atomic_flag_test_and_set(volatile atomic_flag* __a) noexcept
  { return atomic_flag_test_and_set_explicit(__a, memory_order_seq_cst); }

  inline __libitm_always_inline void
  atomic_flag_clear(atomic_flag* __a) noexcept
  { atomic_flag_clear_explicit(__a, memory_order_seq_cst); }

  inline __libitm_always_inline void
  atomic_flag_clear(volatile atomic_flag* __a) noexcept
  { atomic_flag_clear_explicit(__a, memory_order_seq_cst); }


  // Function templates generally applicable to atomic types.
  template<typename _ITp>
    __libitm_always_inline bool
    atomic_is_lock_free(const atomic<_ITp>* __a) noexcept
    { return __a->is_lock_free(); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_is_lock_free(const volatile atomic<_ITp>* __a) noexcept
    { return __a->is_lock_free(); }

  template<typename _ITp>
    __libitm_always_inline void
    atomic_init(atomic<_ITp>* __a, _ITp __i) noexcept;

  template<typename _ITp>
    __libitm_always_inline void
    atomic_init(volatile atomic<_ITp>* __a, _ITp __i) noexcept;

  template<typename _ITp>
    __libitm_always_inline void
    atomic_store_explicit(atomic<_ITp>* __a, _ITp __i,
                          memory_order __m) noexcept
    { __a->store(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline void
    atomic_store_explicit(volatile atomic<_ITp>* __a, _ITp __i,
                          memory_order __m) noexcept
    { __a->store(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_load_explicit(const atomic<_ITp>* __a, memory_order __m) noexcept
    { return __a->load(__m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_load_explicit(const volatile atomic<_ITp>* __a,
                         memory_order __m) noexcept
    { return __a->load(__m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_exchange_explicit(atomic<_ITp>* __a, _ITp __i,
                             memory_order __m) noexcept
    { return __a->exchange(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_exchange_explicit(volatile atomic<_ITp>* __a, _ITp __i,
                             memory_order __m) noexcept
    { return __a->exchange(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_weak_explicit(atomic<_ITp>* __a,
                                          _ITp* __i1, _ITp __i2,
                                          memory_order __m1,
                                          memory_order __m2) noexcept
    { return __a->compare_exchange_weak(*__i1, __i2, __m1, __m2); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_weak_explicit(volatile atomic<_ITp>* __a,
                                          _ITp* __i1, _ITp __i2,
                                          memory_order __m1,
                                          memory_order __m2) noexcept
    { return __a->compare_exchange_weak(*__i1, __i2, __m1, __m2); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_strong_explicit(atomic<_ITp>* __a,
                                            _ITp* __i1, _ITp __i2,
                                            memory_order __m1,
                                            memory_order __m2) noexcept
    { return __a->compare_exchange_strong(*__i1, __i2, __m1, __m2); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_strong_explicit(volatile atomic<_ITp>* __a,
                                            _ITp* __i1, _ITp __i2,
                                            memory_order __m1,
                                            memory_order __m2) noexcept
    { return __a->compare_exchange_strong(*__i1, __i2, __m1, __m2); }


  template<typename _ITp>
    __libitm_always_inline void
    atomic_store(atomic<_ITp>* __a, _ITp __i) noexcept
    { atomic_store_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline void
    atomic_store(volatile atomic<_ITp>* __a, _ITp __i) noexcept
    { atomic_store_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_load(const atomic<_ITp>* __a) noexcept
    { return atomic_load_explicit(__a, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_load(const volatile atomic<_ITp>* __a) noexcept
    { return atomic_load_explicit(__a, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_exchange(atomic<_ITp>* __a, _ITp __i) noexcept
    { return atomic_exchange_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_exchange(volatile atomic<_ITp>* __a, _ITp __i) noexcept
    { return atomic_exchange_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_weak(atomic<_ITp>* __a,
                                 _ITp* __i1, _ITp __i2) noexcept
    {
      return atomic_compare_exchange_weak_explicit(__a, __i1, __i2,
                                                   memory_order_seq_cst,
                                                   memory_order_seq_cst);
    }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_weak(volatile atomic<_ITp>* __a,
                                 _ITp* __i1, _ITp __i2) noexcept
    {
      return atomic_compare_exchange_weak_explicit(__a, __i1, __i2,
                                                   memory_order_seq_cst,
                                                   memory_order_seq_cst);
    }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_strong(atomic<_ITp>* __a,
                                   _ITp* __i1, _ITp __i2) noexcept
    {
      return atomic_compare_exchange_strong_explicit(__a, __i1, __i2,
                                                     memory_order_seq_cst,
                                                     memory_order_seq_cst);
    }

  template<typename _ITp>
    __libitm_always_inline bool
    atomic_compare_exchange_strong(volatile atomic<_ITp>* __a,
                                   _ITp* __i1, _ITp __i2) noexcept
    {
      return atomic_compare_exchange_strong_explicit(__a, __i1, __i2,
                                                     memory_order_seq_cst,
                                                     memory_order_seq_cst);
    }

  // Function templates for atomic_integral operations only, using
  // __atomic_base. Template argument should be constricted to
  // intergral types as specified in the standard, excluding address
  // types.
  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_add_explicit(__atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_add(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_add_explicit(volatile __atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_add(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_sub_explicit(__atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_sub(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_sub_explicit(volatile __atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_sub(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_and_explicit(__atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_and(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_and_explicit(volatile __atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_and(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_or_explicit(__atomic_base<_ITp>* __a, _ITp __i,
                             memory_order __m) noexcept
    { return __a->fetch_or(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_or_explicit(volatile __atomic_base<_ITp>* __a, _ITp __i,
                             memory_order __m) noexcept
    { return __a->fetch_or(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_xor_explicit(__atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_xor(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_xor_explicit(volatile __atomic_base<_ITp>* __a, _ITp __i,
                              memory_order __m) noexcept
    { return __a->fetch_xor(__i, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_add(__atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_add_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_add(volatile __atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_add_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_sub(__atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_sub_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_sub(volatile __atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_sub_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_and(__atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_and_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_and(volatile __atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_and_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_or(__atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_or_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_or(volatile __atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_or_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_xor(__atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_xor_explicit(__a, __i, memory_order_seq_cst); }

  template<typename _ITp>
    __libitm_always_inline _ITp
    atomic_fetch_xor(volatile __atomic_base<_ITp>* __a, _ITp __i) noexcept
    { return atomic_fetch_xor_explicit(__a, __i, memory_order_seq_cst); }


  // Partial specializations for pointers.
  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_add_explicit(atomic<_ITp*>* __a, ptrdiff_t __d,
                              memory_order __m) noexcept
    { return __a->fetch_add(__d, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_add_explicit(volatile atomic<_ITp*>* __a, ptrdiff_t __d,
                              memory_order __m) noexcept
    { return __a->fetch_add(__d, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_add(volatile atomic<_ITp*>* __a, ptrdiff_t __d) noexcept
    { return __a->fetch_add(__d); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_add(atomic<_ITp*>* __a, ptrdiff_t __d) noexcept
    { return __a->fetch_add(__d); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_sub_explicit(volatile atomic<_ITp*>* __a,
                              ptrdiff_t __d, memory_order __m) noexcept
    { return __a->fetch_sub(__d, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_sub_explicit(atomic<_ITp*>* __a, ptrdiff_t __d,
                              memory_order __m) noexcept
    { return __a->fetch_sub(__d, __m); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_sub(volatile atomic<_ITp*>* __a, ptrdiff_t __d) noexcept
    { return __a->fetch_sub(__d); }

  template<typename _ITp>
    __libitm_always_inline _ITp*
    atomic_fetch_sub(atomic<_ITp*>* __a, ptrdiff_t __d) noexcept
    { return __a->fetch_sub(__d); }
  // @} group atomics

// _GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif