[bug#46865] [PATCH] gnu: racket: update to 8.0.

[Philip McGrath]

Hi!

On 3/5/21 6:49 AM, Ludovic Courtès wrote:
> I applied it and tweak the commit log to mention the fields that were
> changed.  The new synopsis and description LGTM!

That's great!

> Did you try unbundling Chez?  It would be great if we could do that.
> (In Guix we unbundle software as much as possible, notably for security
> reasons.)

The Racket fork of Chez Scheme has diverged significantly from upstream.
Racket regularly syncs with upstream Chez and contributes patches back, 
but they are likely to coexist as two different "flavors" of Chez for 
the foreseeable future. There's a detailed (though almost two-year-old) 
review of the differences in their ICFP report[1]. In essence, some of 
Racket's "changes to Chez Scheme are either controversial or heavyweight 
compared to the expected benefit for applications other than Racket". 
You can see how one controversial pull request[2] became a Flatt and 
Dybvig 2020 PLDI paper.[3] At this point, for example, Racket's Chez has 
gained an Aarch64 backend, floating-point unboxing, and a 
type-reconstruction compiler pass.

So, no, I don't think there's a prospect of unbundling Chez.

On the other hand, since sending this patch, I saw that much of the work 
Guix and Nix had to do with around absolute paths could be better 
addressed upstream. Racket has merged my fixes for most of them[4] (and 
Matthew solved another in C [5]), which means we can greatly simplify 
the package definition. I hope to get those fixes into upstream Chez, too.

I do think I should be able to unbundle Nanopass, as the Chez Guix 
package does.

Just now I've been working on bootstrapping. Chez has the usual problem 
that you need the old version of Chez (specifically "bootfiles") to 
compile the new version. Racket's fork added an architecture-independent 
backend: those bootfiles are in the source distribution, which are how 
the Guix package is building now. But Racket is also able to simulate 
enough of Chez to (slowly) compile the Chez compiler, providing a path 
to Chez from just a C compiler. Racket does its whole bootstrapping 
process regularly in CI, and I'm working on getting the Guix package to 
do likewise.

(I knew from previous discussions that Racket on Guix could benefit from 
some attention, so I'm hoping to use it as an opportunity to learn more 
about Guix.)

-Philip

[1]: https://www.cs.utah.edu/plt/publications/icfp19-fddkmstz.pdf
[2]: https://github.com/cisco/ChezScheme/pull/336
[3]: https://www.cs.utah.edu/plt/publications/pldi20-fd.pdf
[4]: https://github.com/racket/racket/pull/3710
[5]: 
https://github.com/mflatt/racket/commit/7319a22ed605fb3110b98f6c9aa1e8ed3aa03794