Share Flags and Values with std::atomic

Learn to share flags and values with std::atomic.

The std::atomic class encapsulates a single object and guarantees it to be atomic. Writing to the atomic object is controlled by memory-order policies and reads may occur simultaneously. It's typically used to synchronize access among different threads.

std::atomic defines an atomic type from its template type. The type must be trivial. A type is trivialIn programming, trivial refers to a construct or operation that is straightforward, simple, or requires minimal effort or complexity to implement or understand. if it occupies contiguous memory, has no user-defined constructor, and has no virtual member functions. All primitive types are trivial. While it is possible to construct a trivial type, std::atomic is most often used with simple primitive types, such as bool, int, long, float, and double.

How to do it

This recipe uses a simple function that loops over a counter to demonstrate sharing atomic objects. We will spawn a swarm of these loops as threads that share atomic values:

  • Atomic objects are often placed in a global namespace. They must be accessible to all the threads that need to share its value:

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