31 Atomic operations library [atomics]

31.8 Class template atomic [atomics.types.generic]

31.8.1 General [atomics.types.generic.general]

namespace std { template<class T> struct atomic { using value_type = T; static constexpr bool is_always_lock_free = implementation-defined; bool is_lock_free() const volatile noexcept; bool is_lock_free() const noexcept; // [atomics.types.operations], operations on atomic types constexpr atomic() noexcept(is_nothrow_default_constructible_v<T>); constexpr atomic(T) noexcept; atomic(const atomic&) = delete; atomic& operator=(const atomic&) = delete; atomic& operator=(const atomic&) volatile = delete; T load(memory_order = memory_order::seq_cst) const volatile noexcept; T load(memory_order = memory_order::seq_cst) const noexcept; operator T() const volatile noexcept; operator T() const noexcept; void store(T, memory_order = memory_order::seq_cst) volatile noexcept; void store(T, memory_order = memory_order::seq_cst) noexcept; T operator=(T) volatile noexcept; T operator=(T) noexcept; T exchange(T, memory_order = memory_order::seq_cst) volatile noexcept; T exchange(T, memory_order = memory_order::seq_cst) noexcept; bool compare_exchange_weak(T&, T, memory_order, memory_order) volatile noexcept; bool compare_exchange_weak(T&, T, memory_order, memory_order) noexcept; bool compare_exchange_strong(T&, T, memory_order, memory_order) volatile noexcept; bool compare_exchange_strong(T&, T, memory_order, memory_order) noexcept; bool compare_exchange_weak(T&, T, memory_order = memory_order::seq_cst) volatile noexcept; bool compare_exchange_weak(T&, T, memory_order = memory_order::seq_cst) noexcept; bool compare_exchange_strong(T&, T, memory_order = memory_order::seq_cst) volatile noexcept; bool compare_exchange_strong(T&, T, memory_order = memory_order::seq_cst) noexcept; void wait(T, memory_order = memory_order::seq_cst) const volatile noexcept; void wait(T, memory_order = memory_order::seq_cst) const noexcept; void notify_one() volatile noexcept; void notify_one() noexcept; void notify_all() volatile noexcept; void notify_all() noexcept; }; }
The template argument for T shall meet the Cpp17CopyConstructible and Cpp17CopyAssignable requirements.
The program is ill-formed if any of
  • is_­trivially_­copyable_­v<T>,
  • is_­copy_­constructible_­v<T>,
  • is_­move_­constructible_­v<T>,
  • is_­copy_­assignable_­v<T>, or
  • is_­move_­assignable_­v<T>
is false.
[Note 1:
Type arguments that are not also statically initializable can be difficult to use.
— end note]
The specialization atomic<bool> is a standard-layout struct.
[Note 2:
The representation of an atomic specialization need not have the same size and alignment requirement as its corresponding argument type.
— end note]