On Thu, Nov 30, 2023 at 4:33 PM Frederick Virchanza Gotham via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
On Thu, Nov 30, 2023 at 8:36 PM Arthur O'Dwyer wrote:
>
> This is the `__datasizeof` builtin. In chronological order:
> https://orodu.net/2023/01/15/trivially-relocatable.html (Ctrl+F data_size_of)
> https://quuxplusone.github.io/blog/2023/02/24/trivial-swap-x-prize/#if-stdswap-cant-memcpy-then-how-do-we-trivially-swap
> https://clang.llvm.org/docs/LanguageExtensions.html#implementation-defined-keywords

Okay then so we need __datasizeof in C++26, right?

No. Let's see it get into more than one compiler, first; and also get some usage experience in practice.
So far, as far as practical uses are concerned, I'm only aware of the std::copy/std::move/std::swap_ranges family; and the current debacle with std::expected in libc++. And the latter shouldn't count as we never should have got into that situation to begin with.

–Arthur