Atomics
Atomics are the base of the C++ memory model. By default, the strong version of the memory model is applied to the atomics; therefore, it makes much sense to understand the features of the strong memory model.
Strong versus Weak Memory Model
As you may already know from the subsection on Contract: The Challenges, with the strong memory model I refer to sequential consistency, and with the weak memory model I refer to relaxed semantic.
Strong Memory Model
Java 5.0 got its current memory model in 2004, C++ in 2011. Before that, Java had an erroneous memory model, and C++ had no memory model. Those who think this is the endpoint of a long process are entirely wrong. The foundations of multithreaded programming are 40 to 50 years old. Leslie Lamport defined the concept of sequential consistency in 1979.
Sequential consistency provides two guarantees:
- The instructions of a program are executed in the order written down.
- There is a global order of all operations on all...
