C++ Library - <atomic>


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Introduction

It is an objects of atomic types contain a value of a particular type (T) and 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.

Declaration

Following is the declaration for std::atomic.

template <class T> struct atomic;

Parameters

T − It is a type of the contained value.

Member functions

Sr.No. Member functions & Definition
1 (constructor)

It is a constructs an atomic object

2 operator=

It is stores a value into an atomic object

3 is_lock_free

It checks if the atomic object is lock-free

4 store

It atomically replaces the value of the atomic object with a non-atomic argument

5 load

It atomically obtains the value of the atomic object

6 operator T

It loads a value from an atomic object

7 exchange

It atomically replaces the value of the atomic object and obtains the value held previously

8 compare_exchange_weak & compare_exchange_strong

It atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not

Operations supported by certain specializations

Sr.No. Operations & Definition
1 fetch_add

It atomically adds the argument to the value stored in the atomic object and obtains the value held previously

2 fetch_sub

It atomically subtracts the argument from the value stored in the atomic object and obtains the value held previously

3 fetch_and

It atomically performs bitwise AND between the argument and the value of the atomic object and obtains the value held previously

4 fetch_or

It atomically performs bitwise OR between the argument and the value of the atomic object and obtains the value held previously

5 fetch_xor

It atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not

6 operator++

It increments the atomic value by one

7 operator--

It decrements the atomic value by one

atomic.htm
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