If you read my post carefully the "thinks the result would be the same" was about compiler optimization case, not processors' out-of-order execution. Take this

If you read my post carefully the "thinks the result would be the same" was about compiler optimization case, not processors' out-of-order execution. Take this example: a = 5; b = sqrt(44); return a * b; If the optimizer is sure (and strict aliasing[0] also helps to be sure in many other not so obvious cases) that the sqrt function is not using the a variable then it can swap lines 1 and 2 in the generated machine code, and the result will be the same. In your example changing lines 2 and 3 will alter the result naturally so the optimizer won't touch it. [0] http://dbp-consulting.com/tutorials/StrictAliasing.html http://dbp-consulting.com/tutorials/StrictAliasing.html