So...you had to make your own version of unique_ptr to make it zero-cost? Doesn't that just confirm the original statement you were disagreeing with, that unique_ptr has a small runtime cost? Or was there some other reason you thought the creator of the video you shared has "no idea" what unique_ptr is?

I also don't understand why the standard library can't use the trivial-abi attribute. Different implementations of the standard library aren't required to be interoperable, are they?

I still don't understand what you think is "apples-to-oranges" here. If you change the Rust code to require the C ABI, there's no difference in the generated code: https://godbolt.org/z/1xf9qG3n8