33 Concurrency support library [thread]

33.5 Atomic operations [atomics]

33.5.7 Class template atomic_ref [atomics.ref.generic]

33.5.7.3 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, char8_t, char16_t, char32_t, wchar_t, and any other types needed by the typedefs in the header <cstdint>.
For each such type integral-type, the specialization atomic_ref<integral-type> provides additional atomic operations appropriate to integral types.
[Note 1: 
The specialization atomic_ref<bool> uses the primary template ([atomics.ref.generic]).
— end note]
namespace std { template<> struct atomic_ref<integral-type> { private: integral-type* ptr; // exposition only public: using value_type = integral-type; using difference_type = value_type; static constexpr size_t required_alignment = implementation-defined; static constexpr bool is_always_lock_free = implementation-defined; bool is_lock_free() const noexcept; explicit atomic_ref(integral-type&); atomic_ref(const atomic_ref&) noexcept; atomic_ref& operator=(const atomic_ref&) = delete; void store(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type operator=(integral-type) const noexcept; integral-type load(memory_order = memory_order::seq_cst) const noexcept; operator integral-type() const noexcept; integral-type exchange(integral-type, memory_order = memory_order::seq_cst) const noexcept; bool compare_exchange_weak(integral-type&, integral-type, memory_order, memory_order) const noexcept; bool compare_exchange_strong(integral-type&, integral-type, memory_order, memory_order) const noexcept; bool compare_exchange_weak(integral-type&, integral-type, memory_order = memory_order::seq_cst) const noexcept; bool compare_exchange_strong(integral-type&, integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type fetch_add(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type fetch_sub(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type fetch_and(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type fetch_or(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type fetch_xor(integral-type, memory_order = memory_order::seq_cst) const noexcept; integral-type operator++(int) const noexcept; integral-type operator--(int) const noexcept; integral-type operator++() const noexcept; integral-type operator--() const noexcept; integral-type operator+=(integral-type) const noexcept; integral-type operator-=(integral-type) const noexcept; integral-type operator&=(integral-type) const noexcept; integral-type operator|=(integral-type) const noexcept; integral-type operator^=(integral-type) const noexcept; void wait(integral-type, memory_order = memory_order::seq_cst) const noexcept; void notify_one() const noexcept; void notify_all() 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 correspondence among key, operator, and computation is specified in Table 145.
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integral-type fetch_key(integral-type 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, the result is as if the object value and parameters were converted to their corresponding unsigned types, the computation performed on those types, and the result converted back to the signed type.
[Note 2: 
There are no undefined results arising from the computation.
— end note]
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integral-type operator op=(integral-type operand) const noexcept;
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Effects: Equivalent to: return fetch_key(operand) op operand;