I'd even argue that, with an LTO-optimizing compiler (e.g. clang -flto), writing functions inline is basically obsolete. In my case clang/llvm is very much able

I'd even argue that, with an LTO-optimizing compiler (e.g. clang -flto), writing functions inline is basically obsolete. In my case clang/llvm is very much able to inline code across object file boundaries, even capable of analyzing function-pointer assigments and inline the respective functions.