Notices by _L4NyrlfL1I0 (yrlf@graz.social)

@shafik @regehr I think the main reason it is like this is that there is no easy and concise way to do type punning like this in C. In C++ we have std::bit_cast now, which works (as long as your floats are IEEE754), but in C the alternative is uglier (either unions or manual memcpy, though I don't know if the union trick is even legal).

@thephd can we please have _Bit_cast() in C26/C29? This would solve so many things.

@drewdevault how exactly does async I/O differ from I/O multiplexing in your understanding?

I/O multiplexing is IIUC having a single thread of execution and using poll() / epoll() / select() / ... to periodically check which I/O is ready and then handling that (either directly or via callbacks). Most nontrivial programs that do that do it via callbacks and an event loop.

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@miki

@cuddle @drewdevault @miki

Even in Async I/O you don't have infinite work to do. At some point you will run out of useful work to do while waiting and you will need to block on I/O (otherwise you will needlessly spin the CPU)

With I/O multiplexing it's the same: you will repeatedly call poll() / epoll() / select() on your file descriptors, and as long as you still have useful work to do while waiting you can pass the timeout as 0 and it will not block if no fd is ready at this point.

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@cuddle @drewdevault @miki

On POSIX/Linux, AFAIK the only "real" low-level async I/O API that exists is IO uring (you put work in the ring and it completes at some point in the future). All other APIs are basically variations on the I/O multiplexing model (poll() / epoll() / select()).

There is O_NONBLOCK, but all that does IIUC (correct me if I'm wrong) is to make sure that I/O calls return EAGAIN when too much work is posted at once to do it without blocking, and you need to poll() it again

@cuddle @drewdevault @miki

Disclaimer: I'm mostly extrapolating from code I've read, articles I've read, a few personal projects that attempt to not needlessly block, and a few experiments with the various APIs.

It might very well be that my understanding of this is incomplete, lacking, or wrong. If anyone here has more experience, feel free to correct me as I'd like to know more about this as well.