Question

I’d like to port some piece of code from Java to C++11 and I’m a bit confused with volatile keyword.

I’m not familiar with Java language and I don’t get what a volatile variable is. It guarantees that every thread has access to the up to date value of variable – it is the C++ volatile behaviour. But it is usually used to synchronize – are all actions performed on volatile variable atomic?

So I think thath the C++11 good replacement for Java volatile will be std::atomic. Or I’m totally wrong, cause I missed some additional Java volatile features?

Answer 1

Yes, they would be a good match, there is a good article on this at Dr Dobbs.

In a nutshell, ordered atomic variables are safe to read and write on
multiple threads at the same time without doing any explicit locking
because they provide two guarantees: their reads and writes are
guaranteed to be executed in the order they appear in your program’s
source code; and each read or write is guaranteed to be atomic,
all-or-nothing.

Java provides this type of variable as volatile, C++ as std::atomic.