Closest you can realistically get in current compilers is adding some no-op asm statement "modifying" some subexpression as an "optimization barrier". e.g.

Closest you can realistically get in current compilers is adding some no-op asm statement "modifying" some subexpression as an "optimization barrier". e.g. __asm__("" : "=r"(x) : "0"(x)); to make the optimizer unable to preserve known properties of "x" from before to after this line. Though this requires knowing the assembly register constraint to use ("r" here for a GPR), and can inhibit some other optimizations. (do note that this still allows dead code elimination and common subexpression elimination; "asm volatile" prevents these too)