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Re: bootstrap integration strategies

From: Ludovic Courtès
Subject: Re: bootstrap integration strategies
Date: Thu, 12 Jul 2018 18:15:11 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)

Hello OriansJ,

"Orians, Jeremiah (DTMB)" <address@hidden> skribis:

>> I think that's the main difficulty.  I think we'd rather not have
>> separate bootstrap paths for Intel GNU/Linux on one hand, and everything
>> else on the other hand.
> Well, due to the design of mescc-tools; the bootstrap paths only have to be 
> divergent up to the M1-macro level.
> After that, we could simply use flags make the source work on different 
> platforms

Sounds nice.  I wonder if Jan was referring to something else then?

There’s still the question of GNU/Hurd, though, which requires a vastly
different libc.

>> Yet, we know that porting what you already did on x86-linux-gnu to
>> GNU/Hurd and ARMv7 and AArch64 etc. is going to be a lot of non-trivial
>> work (especially since historical versions of the GNU toolchain did not
>> support AArch64, for instance.)
> Nor RISC-V but that is likely to be a much bigger issue in terms of 
> bootstrapping

So far the initial ports of Guix to non-x86 were done through
cross-compilation (info "(guix) Porting").  So in a way, the binary
seeds for these platforms were built from source; we just “cut” the
source-to-binary connection by making those binaries the root of the
dependency graph on these platforms.

Maybe that’s something we’ll have to live with on new architectures.

>> Waiting for this to be "solved" (and we don't even know how) would
>> equate to a status quo.  But obviously, it'd be sad to have all this
>> work already done on Intel and not be able to benefit from it.
> Actually the work for the stage0 bootstrap steps have already been done on 
> non-x86 hardware (Knight platform to be precise)
> And the engineering decisions involved where explicitly selected to minimize 
> porting and cross-platform bootstrapping effort.
> M1-macro and hex2-linker only need flags to be set to build for all of the 
> different supported platforms

So, problem solved?  Or am I missing something? :-)

I think the ‘wip-bootstrap’ branch does not use M1 at this point, does


>> There's also another option you didn't mention: ditching the 2.0
>> bootstrap Guile in favor of Mes.  That can be done in several steps:
>>  1. Replace the guile-2.0.*.xz binary tarballs with Mes, and add a step
>>      that builds Guile 2.x using our big bootstrap GCC binary.
> Slow but possible
>>   2. Same, but build Guile 2.x, libgc, etc. using MesCC.
> MesCC can't directly build Guile yet but I do enjoy that ambition ;-)

I wonder what it would take to fix that.  After all, compiling libguile
must not be much harder than compiling tcc, no?

> At this point, we effectively have a rope bridge to full bootstrappability
> But we still have a lot of details to hammer out, like getting basic ARM 
> support and having the ARM and x86 binaries verify each other's bootstrap;
> Finding 6502, z80, 8051, 68K, VAX, pdp11, Alpha, MIPS, SPARC and 
> PowerPC/Power Developer(s) to do stage0 work for their platforms and perform 
> the cross verify steps.
> Hammer out cross-platform build details for MesCC and M2-Planet

One thing at a time.  :-)

IMO what matters most at this point is to come up with a plan that allow
us to incrementally reduce the size of our binary seeds.  A port of
M1/stage0 to Z80 can wait.  ;-)  So we really need a list of actionable
items in the short term to start taking advantage of all the work that’s
been done on Mes, MesCC, M1, stage0, Gash, etc.

Thanks for your feedback!


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