Well, that's a copout. Of course, if you take absolutely any computer architecture, you can't assume simple things like sizeof(int) or data structure alignment.

Well, that's a copout. Of course, if you take absolutely any computer architecture, you can't assume simple things like sizeof(int) or data structure alignment. But if sizeof(int) is at 4 and data needs to be aligned by its own size - like on any real architecture relevant today - many of these questions have a deterministic answer. In practice, compiler bugs are a much bigger issue than architecture assumptions.