class template

std::atomic

template <class T> struct atomic;

Atomic

Objects of atomic types contain a value of a particular type (T).

The main characteristic of atomic objects is that access to this contained value from different threads cannot cause data races (i.e., doing that is well-defined behavior, with accesses properly sequenced). Generally, for all other objects, the possibility of causing a data race for accessing the same object concurrently qualifies the operation as undefined behavior.

Additionally, atomic objects have the ability to synchronize access to other non-atomic objects in their threads by specifying different memory orders.

Template parameters

T: Type of the contained value.
This shall be a trivially copyable type.

Member functions

(constructor): Construct atomic (public member function)

operator=: Assign contained value (public member function)

General atomic operations

is_lock_free: Is lock-free (public member function)

store: Modify contained value (public member function)

load: Read contained value (public member function)

operator T: Access contained value (public member function)

exchange: Access and modify contained value (public member function)

compare_exchange_weak: Compare and exchange contained value (weak) (public member function)

compare_exchange_strong: Compare and exchange contained value (strong) (public member function)

Operations supported by certain specializations (integral and/or pointer, see below)

fetch_add: Add to contained value (public member function)

fetch_sub: Subtract from contained value (public member function)

fetch_and: Apply bitwise AND to contained value (public member function)

fetch_or: Apply bitwise OR to contained value (public member function)

fetch_xor: Apply bitwise XOR to contained value (public member function)

operator++: Increment container value (public member function)

operator--: Decrement container value (public member function)

atomic::operator (comp. assign.): Compound assignments (public member function)

Template specializations

The atomic class template is fully specialized for all fundamental integral types (except bool), and any extended integral types needed for the typedefs in <cstdint>. These specializations have the following additional member functions:

specializations	additional member functions
`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` extended integral types (if any)	`atomic::fetch_add` `atomic::fetch_sub` `atomic::fetch_and` `atomic::fetch_or` `atomic::fetch_xor` `atomic::operator++` `atomic::operator--` `operator (comp. assign.)`

For bool instantiations, only the general atomic operations are supported.
Note that most of the C-style atomic types are aliases of these specializations (or aliases of a base class inherited by these specializations).

atomic is also partially specialized for all pointer types, with the following additional member functions:

specializations	additional member functions
`U` (for any type `U`)*	`atomic::fetch_add` `atomic::fetch_sub` `atomic::operator++` `atomic::operator--` `operator (comp. assign.)`

classes

enum types

functions

initialization macros

functions (C-style atomics)