C89cc.sh – standalone C89/ELF64 compiler in pure portable shell

https://gist.github.com/alganet/2b89c4368f8d23d033961d8a3deb5c19

by gaigalas • 4 months ago

201 48 4 months ago

gist.github.com

gaigalas15• 4 months ago

Single standalone file, no external tools used, PATH='' (empty), portable (bash, dash, ksh, zsh), produces x86 ELF executables, has mini-libc builtin.

Usage:

printf 'int main(){puts("hello");return 0;}' | sh c89cc.sh > hello

chmod +x hello

./hello

angry_octet• 4 months ago

I can't think of a reason to use c89cc.sh, but I salute this effort nonetheless.

gaigalas15• 4 months ago

The main show are the techniques for writing portable shell scripts, not the compiler.

If you want something one would actually use, try my project tuish:

http://github.com/alganet/tuish

jonahx• 4 months ago

gorgeous!

t-32• 4 months ago

Why not POSIX or some common external tools where it makes sense? Most of those big switch statements could be easily replaced with some standard programs that already exist everywhere.

gaigalas15• 4 months ago

One main reason is performance. Forking for other tools is very expensive.

That said, using larger sed or awk programs instead of ad-hoc calls for small snippets would perhaps be net-positive for performance and readability.

I'm currently working on very strict bootstrap scenarios in which sed and awk might not be available, but a shell might be (if I'm able to write it). It is possible that in such scenarios, the fist send and awk versions will be shell-written polyfills anyway.

Brian_K_White2• 4 months ago

Why not just use gcc which already exists everywhere?

When you answer that, same answer. If you can't imagine any answer for that, then the answer won't be convincing or make sense even if anyone tried to articulate it. Which is fine. Everyone doesn't have to find meaning in the same things.

dmitrygr• 4 months ago

Many parts of this are clearly autogenerated, but that in no way diminishes the sickening impressiveness of it!

phire• 4 months ago

It does make it a little hard to understand how the parser/ast_builder works.

But the rest seems easy enough to understand.

fuhsnn4• 4 months ago

It does make it a little hard to understand

Or much easier to backdoor...

gaigalas15• 4 months ago

This is a hand-written parser for the shell itself (portable shell parsing portable shell):

https://gist.github.com/alganet/23df53c567b8a0bf959ecbc7b689...

It's an incomplete idea from around a year ago. The approach taken here (aliases as macro-like evals, AST generation using shell variables) became the backbone for the BNF parser generator.

This one is much simpler to understand. Simpler grammars tend to produce parser code that looks more like this one.

userbinator• 4 months ago

It would be far more interesting to look at what this was "compiled" from; it looks like the output of a state-machine generator.

gaigalas15• 4 months ago

The source for BNF generator is here:

https://gist.github.com/alganet/4dfd501a3377a60f7825901114d6...

Roughly 70% of c89cc was generated from it (parser, emitter).

It can generate parsers for C, ES6 and XML for example (subsets but not missing a lot).

It's still a mess though and I have lots of work to do to a proper release.

gaigalas15• 4 months ago

Yes! The main parser and emitter come from a BNF parser generator, also written in portable shell (to be released though).

kelsey98765431• 4 months ago

Would be a lot better if it came with tests. Please do this justice and dont let it rot as a gist, make a real repo and add some docs and at least smoke tests or some kind. Thanks

fuhsnn4• 4 months ago

Don't understand why you were downvoted. An untested C compiler is simply worthless.

nananana9• 4 months ago

The 2026 brain simply cannot comprehend recreational programming.

gaigalas15• 4 months ago

You want to know what kinds of programs it can run, right?

Look at this one:

https://gist.github.com/alganet/1513d7b6abef5c1a53a324d897c3...

shell.c is a shell interpreter written for c89cc.sh. It can do the full self-hosting ouroboros:

- c89cc.sh can compile shell.c

- compiled shell.c via c89cc.sh can run c89cc.sh

It's not a full blown battle tested shell interpreter yet, but I'm working on it.

This file is part of the bootstrapping setup I'm working on for very early (pre tinyc) bootstrap from source in x64 machines and it is by far the most complicated program c89cc.sh can compile.

gaigalas15• 4 months ago

This gist is a concatenation of several shell script modules which form a comprehensive parser library for the portable shell.

The main parser and emitter are BFN-generated (that's why they look so mechanical). The BNF parser generator is also written in portable shell (I posted another gist with a preview of it in another thread).

All modules have comprehensive tests, but it is still lacking documentation and not ready for prime time!

akavel• 4 months ago

In the classic FLOSS tradition, it would be cool if you might still consider publishing such a "not-ready" repository - some people may (or may not!) be still interested, and also (sorry!) there's the bus factor... But on the other hand, in the classic FLOSS tradition, it's also 100% your decision and you have the full right to do any way you like!

jey• 4 months ago

It targets x86-64/ELF? I thought it would target `sh` to be portable?

gaigalas15• 4 months ago

That sounds like pnut:

https://github.com/udem-dlteam/pnut

saagarjha• 4 months ago

SuperH is not that portable.

_ache_• 4 months ago

I'm tempted to execute it, but it may as well be shellcode I couldn't tell.

self_awareness2• 4 months ago

"Claude please generate me a C compiler in bash"

I mean, today it's possible to generate it in Tcl, Elisp, Windows BAT, Powershell.

The effort is just 1 prompt.

The WHY question is much more important today -- "because I can" no longer makes sense, because we all can do much, much more with minimum effort today than before LLMs.

gaigalas15• 4 months ago

Here's a prototype parser from 10 months ago, when this was not possible yet:

https://gist.github.com/alganet/23df53c567b8a0bf959ecbc7b689...

Here is me 10 years ago experimenting on parsing stuff with sed:

https://gist.github.com/alganet/542f46865420529c9bd2

---

Yes, c89cc.sh was definitely AI-assisted. However, I do carry extensive knowledge of the portable shell that was essential for the AI to complete it.

You'll find tricks inside c89cc.sh that don't exist anywhere, except in other code from me (like the ksh93 fix for local dynamic scoping or the alias/macro read -n1 polyfill).

The WHY is pretty obvious: I want to show that the portable shell is not a toy.

self_awareness2• 4 months ago

I didn't mean to imply that you're not capable doing it without LLM. I believe you.

The point I'm trying to make is that the rest of us that don't know bash that well is capable of doing it as well.

This is the new reality we all need to adapt to.

fkoep• 4 months ago

The WHY is pretty obvious: I want to show that the portable shell is not a toy.

What does that mean? You sat down with the goal of showing that a decades old scripting environment can be used for large projects in production, with all its obscure hacks? I'd say it's more a novelty project made for the fun of it - and that's fine, it's a cool project.

It would be pretty interesting to read a blog post about the making-of: How to write a compiler in portable shell, what parts could be automated and where LLM-coding fell short, what rare tricks were applied, etc...

anthk2• 4 months ago

LLM's can barely generate valid Subleq code.

uecker• 4 months ago

I am tempted to click the "report abuse" link ;-)

dmead• 4 months ago

This is vibe coded right?

gaigalas15• 4 months ago

It is AI assisted, but way less than one might think.

All the portability tricks are authored by me (I have previous repos from before the AI era that feature them).

The parsing structure is also authored by me (also have pre-AI proof).

What AI did here was the boring, mechanical work.

Just prompt it, all AI as of 2026 is clueless about wide portability shell scripts.

wengo314• 4 months ago

if one could boostrap tcc with it, then it might be a viable tool.

cestith• 4 months ago

I love this as a novelty, and it could be useful for bootstrapping a system that’s had a shell cross-compiled to it.

Thinking about this in the context of a job I used to do, security on shared hosting environments, it gives me a bit of a shiver. There are reasons compilers aren’t available to normal users on those.

C89cc.sh – standalone C89/ELF64 compiler in pure portable shell

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