100 lines
4.5 KiB
Markdown
100 lines
4.5 KiB
Markdown
[depr.atomics]
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# Annex D (normative) Compatibility features [[depr]](./#depr)
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## D.23 Deprecated atomic operations [depr.atomics]
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### [D.23.1](#general) General [[depr.atomics.general]](depr.atomics.general)
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[1](#general-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L912)
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The header [<atomic>](atomics.syn#header:%3catomic%3e "32.5.2 Header <atomic> synopsis [atomics.syn]") has the following additions[.](#general-1.sentence-1)
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namespace std {template<class T>void atomic_init(volatile atomic<T>*, typename atomic<T>::value_type) noexcept; template<class T>void atomic_init(atomic<T>*, typename atomic<T>::value_type) noexcept; template<class T>constexpr T kill_dependency(T y) noexcept; // freestandinginline constexpr memory_order memory_order_consume = memory_order::consume; // freestanding#define ATOMIC_VAR_INIT(value) *see below*}
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### [D.23.2](#volatile) Volatile access [[depr.atomics.volatile]](depr.atomics.volatile)
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[1](#volatile-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L930)
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If an atomic ([[atomics.types.generic]](atomics.types.generic "32.5.8 Class template atomic")) specialization has one of the following overloads,
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then that overload participates in overload resolution
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even if atomic<T>::is_always_lock_free is false:void store(T desired, memory_order order = memory_order::seq_cst) volatile noexcept;
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T operator=(T desired) volatile noexcept;
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T load(memory_order order = memory_order::seq_cst) const volatile noexcept;operator T() const volatile noexcept;
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T exchange(T desired, memory_order order = memory_order::seq_cst) volatile noexcept;bool compare_exchange_weak(T& expected, T desired,
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memory_order success, memory_order failure) volatile noexcept;bool compare_exchange_strong(T& expected, T desired,
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memory_order success, memory_order failure) volatile noexcept;bool compare_exchange_weak(T& expected, T desired,
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memory_order order = memory_order::seq_cst) volatile noexcept;bool compare_exchange_strong(T& expected, T desired,
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memory_order order = memory_order::seq_cst) volatile noexcept;
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T fetch_*key*(T operand, memory_order order = memory_order::seq_cst) volatile noexcept;
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T operator *op*=(T operand) volatile noexcept;
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T* fetch_*key*(ptrdiff_t operand, memory_order order = memory_order::seq_cst) volatile noexcept;
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### [D.23.3](#nonmembers) Non-member functions [[depr.atomics.nonmembers]](depr.atomics.nonmembers)
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[ð](#lib:atomic_init)
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`template<class T>
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void atomic_init(volatile atomic<T>* object, typename atomic<T>::value_type desired) noexcept;
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template<class T>
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void atomic_init(atomic<T>* object, typename atomic<T>::value_type desired) noexcept;
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`
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[1](#nonmembers-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L964)
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*Effects*: Equivalent to: atomic_store_explicit(object, desired, memory_order::relaxed);
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### [D.23.4](#types.operations) Operations on atomic types [[depr.atomics.types.operations]](depr.atomics.types.operations)
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[ð](#lib:ATOMIC_VAR_INIT_)
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`#define ATOMIC_VAR_INIT(value) see below
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`
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[1](#types.operations-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L977)
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The macro expands to a token sequence suitable for constant initialization of
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an atomic variable with static storage duration of a type that
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is initialization-compatible with value[.](#types.operations-1.sentence-1)
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[*Note [1](#types.operations-note-1)*:
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This operation possibly needs to initialize locks[.](#types.operations-1.sentence-2)
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â *end note*]
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Concurrent access to the variable being initialized,
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even via an atomic operation,
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constitutes a data race[.](#types.operations-1.sentence-3)
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[*Example [1](#types.operations-example-1)*: atomic<int> v = ATOMIC_VAR_INIT(5); â *end example*]
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### [D.23.5](#order) memory_order::consume [[depr.atomics.order]](depr.atomics.order)
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[1](#order-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L998)
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The memory_order enumeration contains an additional enumerator:consume = 1
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The memory_order::consume enumerator is allowed wherevermemory_order::acquire is allowed, and it has the same meaning[.](#order-1.sentence-2)
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[ð](#order-itemdecl:1)
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`template<class T> constexpr T kill_dependency(T y) noexcept;
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`
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[2](#order-2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/future.tex#L1011)
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*Returns*: y[.](#order-2.sentence-1)
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