Does the C spec actually specify it needs to be in that order? Been awhile since I messed that that sort of thing. I know in practice they typically just put

Does the C spec actually specify it needs to be in that order? Been awhile since I messed that that sort of thing. I know in practice they typically just put them in the same order and align on some sort of default packing depending on CPU. Usually to minimize on extra instructions. I have eeked out some extra perf on some CPUs and structs just by moving stuff around and making sure it fits into a cacheline. Sometimes the extra instructions are worth it to unpack some vars if you can get the data into a cacheline. But that depends on your data and usage.