*Update on the Mu computer's memory-safe language*

Progress has been slow over the holiday season because I've been working on a paper about Mu for 2020.programming-conference.or

But functions can now return outputs.

```
fn foo a: int -> result/eax: int {
result <- copy a
increment result
}
```

Project page: github.com/akkartik/mu#readme

Sources for the memory-safe language, now at 5kLoC: akkartik.github.io/mu/html/app

Caveats: no checking yet, only int types supported.

*Update on the Mu computer's memory-safe language*

Still no type-checking or memory-safety, but we can now write any programs with int variables.

There's still no 'var' keyword, so we can't define local variables yet. But that's not insurmountable; just pass in extra arguments for any space you want on the stack 😀

```
result <- factorial n 0 0 0
```

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*Update on the Mu computer's memory-safe language*

Basic language is done! Here's factorial. (Compare mastodon.social/@akkartik/1027.)

Still todo:
- user-defined types
- type checking and memory-safety

In other words, I'm about a third of the way there 😂 More detailed todo list: lobste.rs/s/pv8jpr/what_are_yo

(More details on the Mu project: akkartik.name/post/mu-2019-1. Repo: github.com/akkartik/mu)

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A brief timeline of the Mu computing stack

Jul 6, 2014: commit 0, tree-based interpreter for a statement-oriented language (github.com/akkartik/mu)

Jul 19, 2017: commit 3930, start of SubX machine code (akkartik.name/post/mu-2019-1)

Sep 20, 2018: started building SubX in SubX (mastodon.social/@akkartik/1007)

Jul 24, 2019: SubX in SubX done, commit 5461 (mastodon.social/@akkartik/1024)

Oct 2, 2019: started designing the Mu memory-safe language (akkartik.name/post/mu-2019-2)

Oct 29: started akkartik.github.io/mu/html/app

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I'll be in Porto, Portugal on Mar 24 to present a paper on Mu at the Convivial Computing Salon: 2020.programming-conference.or

Hoping for some great conversation and disagreements.

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*Update on the Mu computer's memory-safe language*

Mu just got its first couple of non-integer types: addresses and arrays. As a result, the factorial app can _finally_ run its tests based on command-line args.

akkartik.github.io/mu/html/app

Addresses are accessed using a '*' operator. Arrays are accessed using an 'index' instruction that takes an address (addr array T) and returns an address (addr T).

Literal indexes aren't supported yet.

Open q: indexing arrays of non-power-of-2 element sizes.

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*Update on the Mu computer's memory-safe language*

Still no type-checking or memory-safety, but we have partial support for arrays and product types. Still several sharp edges:

- can't index an array with a literal
- can't index an array with non-power-of-2-sized elements
- can allocate but not use arrays/records on the stack

My todo list is growing. But work per item is shrinking. Hopefully there's an asymptote.

(More details: akkartik.name/post/mu-2019-1. Repo: github.com/akkartik/mu)

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*Update on the Mu computer's memory-safe language*

Arrays and product types are now done. Any remaining rough edges are working as intended 😄 Only hex literals, for example.

What's left? Actually making it safe.

Complexity outlay so far: 16k lines of code, but only 6.5k if you exclude tests. Tests get _very_ repetitive in machine code. Hopefully we won't need another 15k LoC.

Example program: akkartik.github.io/mu/html/app

(More details: akkartik.name/post/mu-2019-2. Repo: github.com/akkartik/mu)

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The Mu compiler summarized in one page: akkartik.github.io/mu/html/mu_

More details: akkartik.name/akkartik-convivi

Repo: github.com/akkartik/mu

(Brief update since there isn't much to report: I'm working on safe heap allocations as described in the paper. But it's slow going because of life and the need to unwind some past decisions.)

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I'm back from a death march.

Mu is a safe language built in machine code, translating almost 1:1 to machine code. A key check is for use-after-free errors, using a second address type (akkartik.name/akkartik-convivi, section 4.4)

I spent the last 2 months switching all of Mu's implementation to this scheme. It was a tough time: lobste.rs/s/vcx5vu/what_are_yo. But now I know it works (with 10-15% slowdown), and Mu functions calling low-level libraries should behave unsurprisingly.

github.com/akkartik/mu

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I'm starting to build some simple apps in Mu, my memory-safe language that translates 1:1 to machine code.

Today I built a program to print a file to screen: akkartik.github.io/mu/html/app

Experience report: github.com/akkartik/mu/commit/

Also:
- I fixed a bug in the process: github.com/akkartik/mu/commit/
- I wished I already had clobbered-variable warnings.
- I wished I had type checks.

All in all, this language isn't ready for others yet. I'm constantly inspecting the code generated by the translator.

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@akkartik I'm interested in the note on syscalls. Is there a way you'd prefer to see them implemented? Mu still uses registers so I feel like I'm missing something there. Viewing syscalls a part of StdLib it seems fine for that to be subX or Mu so I think I'm missing something. :)

Think the program looks nice overall besides the noted orchestration. Things are getting pretty interesting! 👀

@kingcons Thanks!

You're right that putting wrappers around syscalls in the SubX layer is fine. Here I'm not sure of the right interface the wrapper should provide (which has the opportunity to be timeless, since Linux syscalls are anything but). So I wish I could put hacky layers 103-105 in the app. But my calling convention only supports pushing args to the stack.

I'd also like to change the syscall interface at some point (in the distant future). So this stuff is temporary, in my mind.

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