Hi Gašper, > #pragma once is unimplementable. That may be the case, nevertheless "all" compilers offer it. Why not make the notion, whether a file is the same implementation-defined.   Everybody deeply involved in large build systems and farms and the ones doing the company C++ Coding Guidelines knows about the pitfalls with hard links and can judge, whether it should be allowed; everybody else would perhaps use #pragma once even now without standardization.   What risks would you see due to standardization for which user group?   Sebastian   -----Ursprüngliche Nachricht----- Von:Gašper Ažman via Std-Proposals <std-proposals_at_[hidden]> Gesendet:Di 27.08.2024 17:34 Betreff:Re: [std-proposals] Revising #pragma once An:std-proposals_at_[hidden]; CC:Gašper Ažman <gasper.azman_at_[hidden]>; #pragma once is unimplementable.  That's because it doesn't mean "don't include a file with the same bytes", it means "don't include the same file". And the second you have the same file accessible through two separate fuse mountpoints, no amount of stat() will help you identify it's the same file.  We hit this in our build-farms all the time, I had to write tooling to kill it.  Don't make me explain this in-committee, again.