Subject: Re: [bug#54394] [PATCH core-updates 00/12] Remove old GNU utilities from early bootstrap

From: Jan Nieuwenhuizen <[email-masked]>
Date: Sun, 20 Mar 2022 12:38:50 +0100

Timothy Sample writes:

Hello!

> This is culmination of a lot of work, so I’m excited to be submitting
> it!  The main thrust of this series is to update Gash and Gash-Utils,
> and then remove most of the old GNU utilities we use during early
> bootstrap.  To elaborate, the current situation is that we climb a
> ladder through time: first we build Bash 2, then we build Bash 4, and
> finally we build Bash 5.  This is true for most GNU utilities: Sed,
> Gawk, Coreutils, etc.  The reason?  Until now, our Scheme
> implementations of those utilities (Gash and Gash-Utils) were very
> limited.  Bash 2 used to be a lot more useful then Gash, for example.
> Now, with recent releases of Gash and Gash-Utils, the Scheme utilities
> are, in general, capable of powering the builds of modern GNU software.

What an amazing piece of work.  Not only adding support for this in Gash
and Gash-Utils, also adding the "follow-up" for the Guix bootstrap.
Wow!

Not meaning to create more unwanted work for you, but I believe this
could do with a blog post.  I very much like your "climb a ladder
through time" description.

> To be clear, we still climb the time-ladder in a few cases.  The main
> ones are GCC, Glibc, and Binutils.  For example, we have to use GCC 2 to
> transition from TCC To GCC 4 (which is the last non-C++ GCC [1]).
> Fixing this would require quite a bit of TCC hacking

Yes, that needs work on MesCC, especially the Mes C Library, and TCC.
Possibly some work on mpz/gmp.  We definately want to jump from TCC to
GCC 4.6 (the last modular distribution) in the (near) future.

> We still use old versions of Gzip, Make, patch, and
> Gawk.  The fact that Gawk is still there disappoints me quite a bit, but
> ‘glibc-mesboot’ fails in a way that I just can’t figure out when
> building with Gash-Utils.

Yeah, I can imagine, especially after your (2nd?) rewrite of AWK.

> Gzip is not strictly necessary, but also pretty easy to replace.

and replacing possibly has quite a speed penalty.

> I’m not sure, but I think patch is only there
> to avoid using patches in ‘origin’ records during bootstrap.  We now
> have a way to do that, so it may no longer be necessary.

Yes, I believe patch is needed for the manual "apply-boot-patch" stages
to avoid adding a dependency on xz, created by adding patches to
"origin" records.

> Make will likely need to be rewritten in Scheme, but we have a head
> start: Potato Make [2].
>
> [2] https://github.com/spk121/potato-make

Interesting!

    POSIX Makefile Parser

     Recipes can contain the following parser function

     (parse ...) reads a standard Makefile and creates
     rules based on its contents.

Building glibc without GNU Make may be pretty difficult, though.

> Here’s some detailed info for reviewers.

> Ludovic Courtès writes:
> > The patches all LGTM!  I think you can push them to ‘core-updates’ if
> > there are no objections.

> Pushed!  (Maybe I didn’t leave enough time for objections – apologies if
> it ends up requiring a revert!  I’ll be around to work through any
> issues this might cause.)

Patches LGTM, and thanks for pushing.

> The rest hopefully speak for themselves.  Sadly, the last one is
> something of a jumble.  Originally I wanted to remove the utilities one
> at a time, but it turns out there are interference effects.  I can’t
> remember the exact details now, but to get an idea, removing both old
> Bash and old Grep might work, but removing one and then the other (in
> either order) might not.  Hence, many utilities get updated in one
> commit.

That's quite understandable, and certainly acceptable.  Much of this
time-ladder was created by me, it was an enormous effort to find old
(and some ancient) versions of the tools that worked well together.
There are undocumented build dependencies all around.  Some newer
packages cannot be used to build older versions of other packages, etc.

So, while this kludge was a necessary evil, I'm extremely happy we can
now do without it.  We should work towards a bootstrap that depends
mainly on current packages, and strive to keep current packages
bootstrappable.

To summarize what you removed:

    bzip2 (not an old version)
    sed-1.18
    sed-4.0.6
    binutils-2.14 (really great!)
    bash-2.05b
    bash-4.4
    gawk-3.0.0
    tar-1.22
    grep-2.0
    coreutils-5.0
    xz-5.0.0 (wow, that was difficult to build)

that's 11 old and ancient packages, if have counted correctly.

Greetings,
Janneke

-- 
Jan Nieuwenhuizen <[email-masked]> | GNU LilyPond http://lilypond.org
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