29 Atomic operations library [atomics]

29.6 Class template atomic_­ref [atomics.ref.generic]

29.6.2 Specializations for integral types [atomics.ref.int]

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There are specializations of the atomic_­ref class template for the integral types char, signed char, unsigned char, short, unsigned short, int, unsigned int, long, unsigned long, long long, unsigned long long, char16_­t, char32_­t, wchar_­t, and any other types needed by the typedefs in the header <cstdint>.
For each such type integral, the specialization atomic_­ref<integral> provides additional atomic operations appropriate to integral types.
[ Note
:
For the specialization atomic_­ref<bool>, see [atomics.ref.generic].
— end note
 ]
namespace std {
  template<> struct atomic_ref<integral> {
  private:
    integral* ptr;        // exposition only
  public:
    using value_type = integral;
    using difference_type = value_type;
    static constexpr bool is_always_lock_free = implementation-defined;
    static constexpr size_t required_alignment = implementation-defined;

    atomic_ref() = delete;
    atomic_ref& operator=(const atomic_ref&) = delete;

    explicit atomic_ref(integral&);
    atomic_ref(const atomic_ref&) noexcept;

    integral operator=(integral) const noexcept;
    operator integral() const noexcept;

    bool is_lock_free() const noexcept;
    void store(integral, memory_order = memory_order_seq_cst) const noexcept;
    integral load(memory_order = memory_order_seq_cst) const noexcept;
    integral exchange(integral,
                      memory_order = memory_order_seq_cst) const noexcept;
    bool compare_exchange_weak(integral&, integral,
                               memory_order, memory_order) const noexcept;
    bool compare_exchange_strong(integral&, integral,
                                 memory_order, memory_order) const noexcept;
    bool compare_exchange_weak(integral&, integral,
                               memory_order = memory_order_seq_cst) const noexcept;
    bool compare_exchange_strong(integral&, integral,
                                 memory_order = memory_order_seq_cst) const noexcept;

    integral fetch_add(integral,
                       memory_order = memory_order_seq_cst) const noexcept;
    integral fetch_sub(integral,
                       memory_order = memory_order_seq_cst) const noexcept;
    integral fetch_and(integral,
                       memory_order = memory_order_seq_cst) const noexcept;
    integral fetch_or(integral,
                      memory_order = memory_order_seq_cst) const noexcept;
    integral fetch_xor(integral,
                       memory_order = memory_order_seq_cst) const noexcept;

    integral operator++(int) const noexcept;
    integral operator--(int) const noexcept;
    integral operator++() const noexcept;
    integral operator--() const noexcept;
    integral operator+=(integral) const noexcept;
    integral operator-=(integral) const noexcept;
    integral operator&=(integral) const noexcept;
    integral operator|=(integral) const noexcept;
    integral operator^=(integral) const noexcept;
  };
}
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Descriptions are provided below only for members that differ from the primary template.
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The following operations perform arithmetic computations.
The key, operator, and computation correspondence is identified in Table 133.
🔗
integral fetch_key(integral operand, memory_order order = memory_order_seq_cst) const noexcept;
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Effects: Atomically replaces the value referenced by *ptr with the result of the computation applied to the value referenced by *ptr and the given operand.
Memory is affected according to the value of order.
These operations are atomic read-modify-write operations ([intro.races]).
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Returns: Atomically, the value referenced by *ptr immediately before the effects.
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Remarks: For signed integer types, arithmetic is defined to use two's complement representation.
There are no undefined results.
🔗
integral operator op=(integral operand) const noexcept;
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Effects: Equivalent to: return fetch_­key(operand) op operand;