[tyler569]

And that ABI specific stack manipulation would be UB, so the optimizer can assume it doesn't happen. With no UB, that's not true.

[Dylan16807]

You assume a langue without UB would allow stack manipulation. But then it would have to be defined. How would you possibly define it fully?

[remexre]

There's an area of memory into which variables with automatic storage duration are allocated at implementation-defined addrs, at any point exactly those variables have addresses.