There is no guarantee that inline functions are actually inlined. They could even be inlined sometimes within a TU (hot code path) and sometimes call a function, which is shared between TUs. It could generally lead to hard-to-find bugs, if the function definitions would be different, depending on who calls the function.   -----Ursprüngliche Nachricht----- Von:sasho648 via Std-Proposals <std-proposals_at_[hidden]> Gesendet:Do 04.05.2023 19:12 Betreff:[std-proposals] Drop same sequence of tokens for inline An:std-proposals_at_[hidden]; CC:sasho648 <sasho648_at_[hidden]>; So why does inline functions need to have the same sequence of tokens in different TU - imagine in a TU there is a preprocessor define that changes the function definition - it would make sense this not to be UB.  In C inline functions have internal linkage - it would make the same sense for C++.  Like I don't see a reason requiring inline functions to have the same body - regardless of the statement above. -- Std-Proposals mailing list Std-Proposals_at_[hidden] https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals