1. That's a rare use case
2. There are ways of measuring that without hampering readability. I mean, are programmers supposed to add all the variables' sizes up in their head??
i = get_thing();
j = do_stuff(i);
j = do_stuff(get_thing());Actually, not even that helps, you would also have to know how much stack a function call takes (might be non-trivial in the presence of stack alignment rules), and which functions get inlined. Edit: if you declare all your locals at the start of a function, chances are the compiler will check whether it can make some of them share memory, so you’d have to take that into account, too.
If you’re concerned about stack overflows in your threading code, it is tooling is what you need, not manually counting stack usage.
And that's ignoring registers. Not every local ever needs to reside in memory.