In C is “i+=1;” atomic?

Question

In C, is i+=1; atomic?

Answer 1

Whether the expression is atomic or not depends only on the machine code that the compiler generates, and the CPU architectre that it will run on. Unless the addition can be achieved in one machine instruction, its unlikely to be atomic.

If you are using Windows then you can use the InterlockedIncrement() API function to do a guaranteed atomic increment. There are similar functions for decrement, etc.