The idea is that you implement a simple, ASCII-based VM for your platform and that's enough to bootstrap a number of different assemblers, to a basic C compiler, to a full-fledged C compiler and (very minimal) POSIX environment.
The goal is twofold: a base for trusted compilation like this one, and a way to guarantee long-term executability of various archiving programs (ie: guarantee that you can unrar a file in 20 years with minimal work).
EDIT: very rough repo is here - https://github.com/mmastrac/bootstrap
https://gitlab.com/giomasce/asmc
My philosophy is of having a very simple and custom language (which I called G) for which it is easier to write a compiler in (x86) Assembly, then write a C compiler in G that is good enough to compile tcc. Then tcc is known to be able to compile gcc 4.7.4 (the last version which does not require a C++ compiler).
My C compiler is starting to have a shape, and in theory (if I find the time to work on it) it should not be far from supporting all that tcc needs.
The README in the linked page contains more information.
I'll look at your code too!
Does this take into account a potential change in the predominant architecture? I.e., we move from x86 to fooarch? Presumably there's more work than "implement the VM in fooarch instructions"? You'd have to write a fooarch assembler as well, right? As well as fooarch C compiler backends?
You can also choose to write the VM in raw assembly. While this isn't ideal, the VM itself is mainly just straightforward register operations and should map trivially to any hardware that has bit operations and hardware 32-bit multiply/divide.
If it comes down to it, you can implement the VM itself on bare metal, but you'll need to do some work implementing things like a filesystem (not terribly hard to get a basic, non-scalable one up-and-running).
I suppose there's an assumption that the platform provides 32-bit integers, but I _think_ that's a safe assumption.
Since Reflections on Trusting Trust has been linked already, I'm going to offer something else. Today's nightmare: https://www.teamten.com/lawrence/writings/coding-machines/
That being said, it's not professional fiction. It's possibly the first work of the writer, and works because of talent (probably) and a good premise (definitely), but it's sorely lacking in polish and editing. I wouldn't look too closely at the cracks. :)
The now-defunct Aboriginal Linux project was doing a similar sort of bootstrapping, and the build dependencies for GCC was a big issue:
http://landley.net/aboriginal/
To work around this, it never used anything later than gcc-4.2.1 from 2007, while we're now on GCC 8.2.
http://gcc.gnu.org/releases.html
EDIT: Yes, it appears GCC uses C++: https://lwn.net/Articles/542457/
So literally once that step is done, we would have a full path...
Recursive descent seems to be the go-to parsing technique for compilers both big and small now. I like how all the repetitive functions for each level have been refactored into a "general_recursion" function, but if you want to make it even simpler and yet more extendable, table-driven precedence climbing would be ideal:
I think the fact that everyone just writes recursive descent parers tells us in practice that there isn't sufficient value in using more techniques like table-driven variants and they don't make anything practically simpler.
From http://git.savannah.nongnu.org/cgit/stage0.git/tree/README (which also declares GPL3):
> This is a set of manually created hex programs in a Cthulhu Path to madness fashion. Which only have the goal of creating a bootstrapping path to a C compiler capable of Compiling GCC, with only the explicit requirement of a single 1 KByte binary or less.
> Additionally, all code must be able to be understood by 70% of the population of programmers. If the code can not be understood by that volume, it needs to be altered until it satifies the above requirement.
From https://savannah.nongnu.org/projects/stage0/:
> A class of minimal bootstrap binaries that has a reproducible build on all platforms. Providing a verifiable base for defeating the trusting trust attack.
Cooooooool.
And was written using the bare metal text editor found here: http://git.savannah.nongnu.org/cgit/stage0.git/tree/stage1/S...
http://git.savannah.nongnu.org/cgit/stage0.git/tree/vm_instr...
Why would it be more useful than just cross compiling?
Some context is this: https://bootstrapping.miraheze.org/wiki/Stage0
That should do the full bootstrap in about 1 minute
I wished I had time today to put this through its paces.
I am phantasizing about a sort of ceremony in which the whole bootstrap process is done live in front of an audience starting with a discrete computer (using e.g. this board as a CPU https://monster6502.com), absolutely no electronic non-volatile memory and the first programs read into the computer from punch cards or punch tape. This would be used to create later stages for more powerful hardware and the end result (after maybe one or two hardware switches) is hopefully a minimal C compiler or similar that can be used to bootstrap production compilers like GCC. Ideally, this binary is shown to be completely identical to a binary built by a typical build process.
Even if such a ceremony is ultimately not very useful, it could still be seen as a kind of artistic performance.
Initially the project was written in Java, after enough features were working the bootstrap phase could start.
[0] https://web.archive.org/web/20120712111627/http://www.rano.o... [1] https://github.com/certik/bcompiler (Fork in GitHub)
Also worth check - https://www.t3x.org/t3x/book.html :-)
