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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.lang.c
Subject: Re: Python recompile
Date: Mon, 10 Mar 2025 21:36:49 -0000 (UTC)
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On Mon, 10 Mar 2025 15:20:00 +0200, Michael S wrote:

> Similar to poll(), yes. Not so similar to super-ugly select(). I
> hope that Unix people stopped using select in new programs two or
> more decades ago.

Seems like WaitForMultipleObjects is more similar to select() than
poll(), though: it has a fixed limit (MAXIMUM_WAIT_OBJECTS) on the
number of objects you can wait on at once.

> But WaitForMultipleObjects can do things that poll can not, like
> waiting on semaphore or on event or on thread (for completion, which
> POSIX people, in their eternal fondness for idiotic names call
> 'join').

There are actually some straightforward techniques to handle that.

<https://manpages.debian.org/eventfd(2)>
<https://manpages.debian.org/signalfd(2)>

There are slightly more roundabout ways to do it within vanilla POSIX,
too. There’s an old technique -- I think invented by Daniel Bernstein
-- where worker threads can report their termination back to the main
thread by writing to a pipe. I use that technique here (look! actual C
code for a change!) <https://gitlab.com/ldo/slow_dbus_server>.

> As to "the one way", you yourself mentioned substantially different way
> in your post here several weeks ago - stackless co-routines. Even if
> ends up the same under the hood, it appears quite different from
> perspective of application programmer.

It is still built on the exact same underlying poll/select calls --
that’s the whole point. It allows for interoperability, too. Yes, it
does make a lot of things easier -- that, too, is part of the point.

Interesting to see how trying to implement such event loops on Windows
is far from straightforward. Python has to offer a choice of 2
different implementations, neither of which quite covers all the bases
<https://docs.python.org/3/library/asyncio-eventloop.html#event-loop-implementations>.

> I don't know where was a catch. As a matter of fact, cygwin people
> found solution, so the problem was soluble.

But not, it seems, by Microsoft ...