[atomics.ref.float] (original) (raw)

There are specializations of the atomic_­ref class template for the floating-point typesfloat,double, andlong double.

For each such type floating-point, the specialization atomic_­ref<floating-point> provides additional atomic operations appropriate to floating-point types.

namespace std { template<> struct atomic_ref { private: floating-point* ptr;
public: using value_type = floating-point; 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(floating-point&);
atomic_ref(const atomic_ref&) noexcept;
atomic_ref& operator=(const atomic_ref&) = delete;

void store(floating-point, memory_order = memory_order::seq_cst) const noexcept;
floating-point operator=(floating-point) const noexcept;
floating-point load(memory_order = memory_order::seq_cst) const noexcept;
operator floating-point() const noexcept;

floating-point exchange(floating-point,
                        memory_order = memory_order::seq_cst) const noexcept;
bool compare_exchange_weak(floating-point&, floating-point,
                           memory_order, memory_order) const noexcept;
bool compare_exchange_strong(floating-point&, floating-point,
                             memory_order, memory_order) const noexcept;
bool compare_exchange_weak(floating-point&, floating-point,
                           memory_order = memory_order::seq_cst) const noexcept;
bool compare_exchange_strong(floating-point&, floating-point,
                             memory_order = memory_order::seq_cst) const noexcept;

floating-point fetch_add(floating-point,
                         memory_order = memory_order::seq_cst) const noexcept;
floating-point fetch_sub(floating-point,
                         memory_order = memory_order::seq_cst) const noexcept;

floating-point operator+=(floating-point) const noexcept;
floating-point operator-=(floating-point) const noexcept;

void wait(floating-point, memory_order = memory_order::seq_cst) const noexcept;
void notify_one() const noexcept;
void notify_all() const noexcept;

}; }

Descriptions are provided below only for members that differ from the primary template.

The following operations perform arithmetic computations.

The key, operator, and computation correspondence are identified in Table 144.

Effects:Atomically replaces the value referenced by *ptr with the result of the computation applied to the value referenced by *ptrand the given operand.

Memory is affected according to the value of order.

These operations are atomic read-modify-write operations ([intro.races]).

Returns:Atomically, the value referenced by *ptrimmediately before the effects.

Remarks:If the result is not a representable value for its type ([expr.pre]), the result is unspecified, but the operations otherwise have no undefined behavior.

Atomic arithmetic operations on floating-point should conform to the std​::​numeric_­limits<floating-point> traits associated with the floating-point type ([limits.syn]).

The floating-point environment ([cfenv]) for atomic arithmetic operations on floating-pointmay be different than the calling thread's floating-point environment.