C++ for one - it has atomics with well defined memory barriers, and guarentees for what happens around them. The real answer is obviously Assembly - pick a ran

C++ for one - it has atomics with well defined memory barriers, and guarentees for what happens around them. The real answer is obviously Assembly - pick a random instruction from any random modern CPU and I'd wager there's a 95% chance it's something you can't express in C at all. If the goal is to model hardware (it's not), it's doing a terrible job.