CppMem

Today, I'm happy to write about the probably most important C++ Core Guidelines for concurrency rule: Whenever feasible, use tools to validate your concurrent code. Not all, but many bugs can be detected with tools, and each fixed bug is a good bug. Here are two tools that gave me precious help in the last few years: ThreadSanitizer and CppMem.

With the relaxed semantics, we have no synchronizations and ordering constraints on atomic operations.

But we can improve and further improve the acquire-release semantics of the last post. Why should x be atomic? There is no reason. That was my first but incorrect assumption. See why?

With the acquire-release semantics, we break the sequential consistency. In the acquire-release semantics, synchronization occurs between atomic operations on the same atomic and not between threads.

With atomic data types, you can tailor your program to your needs and optimize it. But now we are in the domain of multithreading experts.

The easiest way to solve the undefined behaviour in the post Ongoing Optimization: Unsynchronized access is, to use a lock.

I described my challenge in the last post. Let's 's start with our process of ongoing optimization. To be sure, I verify my reasoning with CppMem. I once made a big mistake in my presentation at Meeting C++ 2014.

Now it's time to put the theory into practice. The job is relatively easy. A small program should undergo ongoing optimization.

CppMem is an interactive tool for exploring the behavior of small code snippets of the C++ memory model. No, it should have to be in the toolbox of each programmer who deals seriously with the memory model.