> That just requires that your packing algorithm be deterministic and there's no reason for it not to be. The packing algorithm would also need to be static, s

> That just requires that your packing algorithm be deterministic and there's no reason for it not to be. The packing algorithm would also need to be static, since object code produced by different compilers, or by different compiler settings (eg. -O2 or -O3) is still expected to link together correctly without error. Some kind of attribute declaration in the struct definition itself could manage this, assuming that the algorithm it specifies is deterministic. But it can't be completely automatic, since that would differ from the current (deterministic) algorithm.