[Bug c++/110367] [C++26] Add new built-in for std::is_within_lifetime

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110367

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Thanks, Hana. I expect we'll use the same name.