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Comment by nixosbestos | Hacker News Reader

You can't build modern Rust without a rustc binary... Does that mean it "can't be built from source"?

I mean.. that is absolutely something the bootstrap/reproducibility folks would flag as a problem. Heck, https://guix.gnu.org/en/blog/2023/the-full-source-bootstrap-... went to great extremes to bootstrap a C compiler through the all-important gcc 4.9 (which comes up constantly in these efforts because it was the last gcc that builds without a C++ compiler).

It does provide a neat way to hide a supply line attack. C.f. http://wiki.c2.com/?TheKenThompsonHack

I would be shocked if the rust documentation didn't explain very clearly how to bootstrap rustc starting from gcc

Prepare yourself for a shock then; bootstrapping rustc starts from an already-built version of rustc[1]:

> the only way to build a modern version of rustc is a slightly less modern version.

(There is, at least theoretically, a non-circular bootstrap chain starting with a very old rustc written in OCaml, but the more practical alternative is probably to use mrustc[2] instead.)

[1] https://rustc-dev-guide.rust-lang.org/building/bootstrapping...

[2] https://guix.gnu.org/en/blog/2018/bootstrapping-rust/

Ocaml has a bytecode blob in the sources (even checked into Git). It uses that to resolve its own bootstrap problem. If you aim for a source-only starting point, your journey won't stop at Ocaml.

Then you need to build GCC without GCC.

That is possible too:

https://guix.gnu.org/en/blog/2023/the-full-source-bootstrap-... https://bootstrappable.org/ https://lwn.net/Articles/983340/

The GCC project wants it to be possible to build GCC with a C++11 compiler that is not GCC.

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