On Fri, Mar 3, 2023 at 4:53 AM Andrey Semashev via Std-Proposals
<std-proposals_at_[hidden]> wrote:
> or if `import std` is more expensive than `#include <cstddef>` (or pick any
> other lightweight header)

We already have an answer to this. There's evidence, from the compiler
that supports a standard library import, that it is close to an order
of magnitude faster to `import std;` than to include even one header.
The evidence is listed in P2412.

I know there are a lot of questions about modules out there. But
people keep reraising these questions as if there aren't already
answers to at least some of them.