ok, so that means message passing needs a runtime, and it can be assumed that pretty much every language that has a runtime uses message passing. more evidence that it is message passing that won out.

and the profound enlightenment ( https://news.ycombinator.com/item?id=42130432 ) is not specific to message passing but about a dynamic language runtime. being able to intercept messages/function calls is just one of the benefits of that.

Not sure if objc_msgSend is a runtime, but it does require malloc, so there are limits to how low level it can be.

> objc_msgSend [...] does require malloc,

Are you sure about that?

    ]pwd
    objc4/runtime/Messengers.subproj
    ]rg malloc
    ]

The two variants I implemented way back when also did not require malloc.

And of course NeXT used objc_msgSend() in the kernel, to good effect, so that's pretty low-level.