So it could be that an imaginary C++ implementation randomizes the order of members in non-standard layout types per type for security reasons?   -----Ursprüngliche Nachricht----- Von:Jason McKesson via Std-Proposals <std-proposals_at_[hidden]> Gesendet:Mi 18.06.2025 07:50 Betreff:Re: [std-proposals] I have a span but I need a container An:std-proposals_at_[hidden]; CC:Jason McKesson <jmckesson_at_[hidden]>; On Wed, Jun 18, 2025 at 12:57 AM Simon Schröder via Std-Proposals <std-proposals_at_[hidden]> wrote: > > There is one thing that the standard guarantees which is why in most (or even all) implementations this trick currently works: If member variables are defined in the same order in two different structs they are layout compatible. This is something that C specifies right from the beginning and C++ has taken over. It is why including a header in multiple translation units actually works. So, there is a guarantee for the layout. Note that this is only true for standard layout types... which `std::string` is not. No, the reason why this "works" is that implementations need to give subobjects *some* particular layout within a higher level object. Because that layout must be consistent across all uses of that type within that implementation, if you know what an object's layout is for your implementation, you can build something which mimics that layout. But it only works for that implementation. And it requires knowing very specific implementation details about an object which you are not generally privy to. -- Std-Proposals mailing list Std-Proposals_at_[hidden] https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals