Avoiding stack buffer clear being optimised out

[Jonathan Wakely]

On Tue, 24 Jan 2023 at 13:52, Jonny Grant <jg@jguk.org> wrote:
>
> Probably other functions be "compiled out" like memset() is, would memcpy() be compiled out?

The compiler can do anything which does not change the observable side
effects of a valid program.

https://en.cppreference.com/w/cpp/language/as_if

So yes, the compiler can omit a memcpy that doesn't do anything. Or
any other function call that doesn't do anything.