And outstreams where not that bad, aswell. Sure, the operator overloading looks a bit rough. But that's IMHO a pragmatic choice if you want to offer customisation points and didn't have variadic functions yet. They where introduced only in c++11.
Do you mean this feature [0]? I'm not aware of any differences in c and c++ about this. Can you get a type of a argument in C? How? At compile time, or at runtime? Both sound very un-C-like to me. cppreference is usually excellent documentation but it doesn't mention something like this.
I don't considers this to be "proper" variadic arguments, because a functions argument has to have a type. and these, as far as I'm aware of don't have one. This is about a powerfull as passing a void**. This is essentially memcopying multiple differently typed into a char* buffer and then passing that buffer. You can than correctly copies them back you have pretty much the same behaviour. Both methodss obviously lacks important aspects of the language abstraction of a function parameter and i don't what that feature can bring to the table that the previous techniques don't.
Sorry my bad. Yes, it works for proper function arguments. Does this work for variadic arguments? Parent seems to suggest, but i'm not aware of any mechanism for this.