> If the compiler happened to map [the first member of a struct] c to the last byte of a machine word, the next byte (the first of p) would be the first byte of

> If the compiler happened to map [the first member of a struct] c to the last byte of a machine word, the next byte (the first of p) would be the first byte of the next one and properly pointer-aligned. No, a compiler can't do this. You have to assume that the first member of a struct will be machine word aligned. I'm sure there are many reasons, but the one I can think of now is that structs can be dynamically allocated. That means it has to be possible to take the return value of malloc() and assign it to a pointer, and there is no way to get malloc() to return a memory block with that wired alignment (starting on the last byte of a machine word).