[cesarb]

> Why would humans care about how much scratch space is needed?

In some contexts, it's important. For instance, each thread within the Linux kernel has a very limited fixed-size stack space (used to be 4K bytes, IIRC it's been increased to 8K and then 16K), which resides in physical memory (cannot be swapped out or lazily allocated). Avoiding large stack frames is necessary.

[atilaneves]

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??

[MaxBarraclough]

That wouldn't work anyway. You could rewrite code to use fewer variables without changing the resulting assembly.

    i = get_thing();
    j = do_stuff(i);

vs

    j = do_stuff(get_thing());

[Someone]

Also, unless your thread has only a single function that has local variables or arguments and that function doesn’t contain sub blocks that declare variables (say inside a while block), All variable declarations at top of block doesn’t help much in gauging stack space usage of a thread.

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.

[MaxBarraclough]

> 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.

And that's ignoring registers. Not every local ever needs to reside in memory.