gnu: chez-scheme: Bootstrap from source.

* gnu/packages/chez.scm (chez-scheme)[source]<snippet>: Also unbundle
pre-built boot files.
(chez-scheme-bootstrap-bootfiles): Stop inheriting from 'chez-scheme'.
[native-inputs]: Add 'zuo', 'chez-nanopass-bootstrap', and either
'chez-scheme-for-racket' or, for cross builds, 'chez-scheme'.
[build-system]: Change to gnu-build-system.
[arguments]: Change to run 'configure' and then bootstrap via
`make re.boot` or, for cross builds, `make cross.boot`
[synopsis, description]: Update accordingly.
(chez-scheme-for-racket-bootstrap-bootfiles)[synopsis]: Write "boot
files" as two words in prose.
[description]: Likewise.
* gnu/packages/racket.scm: Update comments.

Change-Id: I55d9b57090ecaca0aa2ab19c2c3ebae2243a9173
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 16 insertions, 8 deletions

diff --git a/gnu/packages/racket.scm b/gnu/packages/racket.scm
index f50f6f3eab..2b20353159 100644
--- a/gnu/packages/racket.scm
+++ b/gnu/packages/racket.scm
@@ -72,6 +72,7 @@
 ;;             ├── bc/
 ;;             ├── cs/
 ;;             ├── ChezScheme/
+;;             ├── rktboot/
 ;;             ├── zuo/
 ;;             └── ...
 ;;
@@ -149,14 +150,12 @@
 ;;   - Racket BC [3M] needs an existing Racket to run "xform",
 ;;     which transforms its own C source code to add additional annotations
 ;;     for the precise garbage collector.
-;;   - Racket CS needs (bootfiles for) Racket's fork of Chez Scheme.
-;;     It also needs an existing Racket to compile Racket-implemented
+;;   - Racket CS needs (boot files for) the corresponding version of Chez
+;;     Scheme. It also needs an existing Racket to compile Racket-implemented
 ;;     parts of the runtime system to R6RS libraries.
-;;   - Chez Scheme also needs bootfiles for itself, but Racket can simulate
-;;     enough of Chez Scheme to load Racket's fork of the Chez Scheme compiler
-;;     purely from source into Racket and apply the compiler to itself,
-;;     producing the needed bootfiles (albeit very slowly).
-;;     Any variant of Racket since version 7.1 can run the simulation.
+;;   - Chez Scheme also needs boot files for itself, but Racket BC can
+;;     bootstrap these using the code in "racket/src/rktboot/".
+;;     See the commentary in "chez.scm" for further details
 ;;
 ;; So, we build CGC to build 3M to build bootfiles and CS.
 ;;
@@ -164,6 +163,14 @@
 ;; often use "BC" to mean "3M", consistent with `(banner)` and the
 ;; suffixes used on executables when more than one variant co-exists.)
 ;;
+;; Since the pre-releases for Chez Scheme 10.0.0, all of Racket's changes have
+;; been merged upstream, and development will be kept in sync going
+;; forward. However, there is no plan to align the Chez Scheme and Racket
+;; release cycles. For the near fulture, a given released version of Racket
+;; will continue to depend on a specific pre-release version of Chez Scheme as
+;; part of Racket CS's "ABI". See upstream discussion at
+;; <https://racket.discourse.group/t/2739/3>.
+;;
 ;; One remaining bootstrapping limitation is that Racket's reader, module
 ;; system, and macro expander are implemented in Racket. For Racket CS,
 ;; they are compiled to R6RS libraries as discussed above. This note from the
@@ -189,7 +196,8 @@
 ;; Zuo is notably *not* a problem for bootstrapping. The implementation is a
 ;; single hand-written C file designed to build with just `cc -o zuo zuo.c`,
 ;; even with very old or limited compilers. (We use the Autoconf support for
-;; convienience.)
+;; convienience.) As of Zuo 1.8, Zuo has tagged releases in its own repository
+;; independent of the Racket release cycle.
 ;;
 ;; CODE: