https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92634
--- Comment #11 from Alan Modra <amodra at gmail dot com> --- Oh wow, so the line of reasoning relies on what the C standard *doesn't* say in 6.5.3.2. I also think the deductions are somewhat suspect. You say &p->f is the same as &((*p).f), which is from p->f being the same as (*p).f. While I agree that is generally true, it's relying on note 79 in the spec isn't it? 79) If &E is a valid pointer expression (where & is the ‘‘address-of’’ operator, which generates a pointer to its operand), the expression (&E)->MOS is the same as E.MOS. But if we don't have &E, which we don't when p is the null pointer (by 6.3.2.3/3), then how can you use note 79 to say p->f is the same as (*p).f when p is the null pointer? Quite likely I'm missing something. However, the fact that there is old C code around from many years ago that uses the offsetof macro as I wrote it, and the fact that no compiler on earth actually dereferences p in &p->f lends credence to the idea that there is no dereference here.
