That worked because you were on an OS that supported it, using a device with simple enough behavior that things like timing or extra/elided writes didn't matter. It's great when that works, but there are very many environments and devices for which that option won't exist.

> That worked because you were on an OS that supported it

I mean... yeah? I'd be surprised if most operating systems didn't have a facility for directly accessing memory mapped devices in some capacity. Even Windows does I think. Have any examples of an OS that doesn't support banging directly on memory?

> using a device with simple enough behavior that things like timing or extra/elided writes didn't matter

Yeah, but that's less of a function of the language like GP was referring to and more a property of using a non-RTOS that doesn't play nice with timing sensitive things from user-space. The language itself is not really the issue there, which was my point.

>I mmaped a `/dev/uio` from Python this morning.

You might want to go and have a look at the implementation of 'mmap' in CPython. Here's a clue: it's in the name 'CPython'.

As it is for an OS written in C, sure it does have some helper C wrappers.

It is still “syscall”s at the end of the day, and many programming languages can output assembly just fine.

There's nothing special about C that makes it possible to use mmap. Just because CPython happens to be implemented in C doesn't mean anything in this context. I could do the same thing in Go or Hare, neither of which have any C in them and be able to do the same thing.