Re: The Case for Rust (in the base system)

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Konstantin Belousov writes:
> On Sat, Aug 03, 2024 at 11:36:52AM -0600, Warner Losh wrote:
> > [...]
> > These are the things to think about. We don't need to solve all of
> > them, but the Rust ecosystem is quite a bit different than the C ecosystem
> > in the details of a number of these points, so we have to address them
> > if we want to use Rust in base with the same traits as all the other bits
> > in base today (or we need to have a thoughtful discussion on paradigm
> > shift and settle on that). [...]
>
> [...]
>
> Instead of starting with integration into the build system, lets decide
> which useful things can we implement in Rust.  Lets ignore the problems
> of integrating (not yet written) code into the build, the problem of
> crates that should be vendored, etc.

Stop.

Just Stop!

Let me address kib@'s argument first:

Until we recognize the difference between "a programming language" and
"an ecosystem" these debates will lead nowhere.

If we continue ignore that crucial difference, we will be repeating
our prior mistakes instead of learning from them.

Back in the mists of time we imported Perl into the base system,
based on arguments /identical/ to what we hear now about Rust.

Importing Perl almost instantly turned into a disaster.

We had overlooked that Perl was not just a programming language,
it was an ecosystem of a language /and/ an rapidly exploding number
of Perl Modules from everybody and everywhere.

None of the lofty "We can (re)write all this stuff in Perl" promises
came to anything, once people realized that we only imported Perl
the programming language and not Perl the ecosystem (later known
as CPAN).

Having Perl in the tree was a net loss, and a big loss, because it
created a version gap between "real Perl" and "freebsd Perl", a gap
which kept growing larger over time as enthusiam for Perl in the
tree evaporated.

Adding Rust to FreeBSD will be the /exact/ same thing!

The many differences between the Perl and Rust languages does not
matter, the only thing which matters is that they are both ecosystems.

We can import only the Rust language, there is /no/ way we can
import the Rust ecosystem.

Any discussion and all promises about "useful things we can implement
in Rust" must therefore respect the following explicit restriction:

	You can only "use std::" and nothing else.
	(And probably not even all of std:: ?)


That then brings me to Warner's point:

Because we cannot import the ecosystem, we have two options:

A) FreeBSD-Rust is only intended for use in freebsd-src, where
   the Rust ecosystem will /never/ be available.

B) Make FreeBSD-Rust (seamlessly and continuously!) play nice with
   both Rust in ports and the Rust ecosystem outside ports.

I have no idea if B) is even possible or what it would take, but
without a design, implementation /and/ continuous maintenance of
B) we (eventually) get A).

In-tree-Perl was not (well-)integrated with ports, which I recall
not so much as caused by technical limitation as by the users wanting
the latest and greatest Perl, rather than the out-of-date FreeBSD-Perl.

I expect that outcome for /any/ programming language ecosystem[1].

Assuming B) is even possible, and attempted, it is almost guaranteed
to be a waste of our time and energy, and it will fizzle back to
A) in a couple of years.

The alternative to spending time on A) for a modest likely benefit,
is to work towards a pkg-based distribution of FreeBSD, where nobody
notices, or cares, that some of the pkg's are built out of src and
others are built out of ports, with the benefit of the Rust ecosystem.

... or built out of C++ modules.

... or written in Python.

... or ...

Poul-Henning

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.