> That doesn't sound like it lets me increment any stack address I want and store into the resulting pointer. Why not? > And are return values still on the sa

> That doesn't sound like it lets me increment any stack address I want and store into the resulting pointer. Why not? > And are return values still on the same stack? Other implementation-defined things might have addresses too, those things just aren't variables. I think you might be able to still allow inlining without UB if you make it implementation-defined per call-site what other things might get addresses.