Show HN: Go Plan9 Memo

> Overall, pretty weird stuff. I am not sure why the Go team went down this route. Maybe it simplifies the compiler by having this bespoke assembly format?

Rob Pike spoke on the design of Go's assembler at a talk in 2016 [1][2]. I think it basically came down to the observation that most assembly language is roughly the same, so why not build a common assembly language that "lets you talk to the machine at the lowest level and yet not have to learn a new syntax." It also enables them to automatically generate a working assembler given an instruction manual PDF for a new architecture as input.

[1]: https://www.youtube.com/watch?v=KINIAgRpkDA [2]: https://go.dev/talks/2016/asm.slide#1

And it worked. Go established cross-compilation as table-stakes for new programming languages, at a time when very few were doing it well, if at all.

Go essentially copied the design from Plan9 compilers, which it was originally based on. It's one of the many things it inherited from Plan9 environment.

Yes, this is a great leap forward in my opinion. I had to do a project at a previous job where I wrote an agent that ran on x86, MIPS and ARM, and doing it in Go was a no-brainer. The other teams who had a bunch of C code that was a nightmare to cross-compile were so jealous they eventually moved a lot of things to Go.

I've been doing this for 35 years and cross compiling anything nontrivial was always a toolchain nightmare. Discovering a world where all I had to do was set GOARCH=mips64 (and possibly GOOS=darwin if I wanted mac binaries) before invoking the compiler is so magical I was extremely skeptical when I first read about it.

It's more "reused" because Plan9 compilers were designed / co-implemented by Pike / Thomson, 2 out of 3 original designers of Go.

For those interested, here's Thomson's paper about Plan9 C compilers: https://9p.io/sys/doc/compiler.html and https://doc.cat-v.org/bell_labs/new_c_compilers/

I would love to see a deep dive on what features / architectural paradigms the Golang runtime shares with Plan9. Has anything like that been written?

One that always sticks out to me personally is the use in Go of the term "dial" instead of "connect" for network connection establishment. This is, AFAICT, another Pike+Thompson-ism, as it can be seen previously in the form of the Plan9 dial(3) syscall — https://9fans.github.io/plan9port/man/man3/dial.html .

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A tangent: I have wondered before whether Pike and Thompson drafted the design for the language that would become Golang long before working at Google, initially to replace C specifically in the context of being the lingua-franca for systems programming on Plan 9. And that, therefore — at least in the designer's minds — Golang would have always had Plan9 as its secret "flagship target" that it should have a 1:1 zero-impedance abstraction mapping onto. Even if they never bothered to actually make a Plan9 Golang runtime.

You could test this hypothesis by implementing an actual Golang runtime for Plan9†, and then comparing it to the Golang runtimes for other OSes — if Plan9 were the "intended home" for Golang programs, then you'd expect the Golang runtime to be very "thin" on Plan9.

(To put that another way: imagine the Golang runtime as something like WINE — a virtualization layer that implements things that could be syscalls / OS library code, in the form of client-side runtime shim code. A "WINE implementation for Windows" would be an extremely thin shim, as every shim call would just point to a 1:1-API-matched piece of OS-provided code. My hypothesis here is that "Golang for Plan9" is the same kind of thing as "WINE for Windows.")

† I was saying this as a thought experiment, not thinking there would actually be a Plan9 implementation of the Golang runtime... but there is! (https://go.dev/wiki/Plan9) So someone can actually check this :)

> I would love to see a deep dive on what features / architectural paradigms the Golang runtime shares with Plan9. Has anything like that been written?

If it has, then it's most likely available on https://cat-v.org/. Even if it hasn't, cat-v.org is a great starting point.

Besides, close to your line of thought, and assuming you didn't knew about this already, Pike & al previously worked on Limbo[0], a "predecessor" of Go, used to wrote Inferno[1], a Plan9-like OS, which could be hosted on arbitrary OSes via a bespoke virtual machine called "Dis".

So there were indeed a few previous "drafts" for Go. I'd doubt that Go has been designed "for" Plan9 though.

[0]: https://en.wikipedia.org/wiki/Limbo_(programming_language)

[1]: https://en.wikipedia.org/wiki/Inferno_(operating_system)

As long as you don't have C libraries to cross compile / link against of course ;)

It sort of was and Rob blogged about it. It is based really on Newsqueak and plan9 C which is very different from Unix C

There’s also libthread[1] which implements concurrency model similar to goroutines (at least earlier, as they appear to be no longer just cooperatively scheduled?). That manual also mentions Alef and Newsqueak as influential predecessors.

[1] http://man.9front.org/2/thread

I'd guess dial is probably a Bell Labs-ism

A fair enough assessment, it be that way, however I will note that a large reason that C exists in the first place was to have a machine independent language to write programs in.

sqlite is the only thing that makes me sad I have CGO_ENABLED=0.

mips64!? That's a blast from the past. It must be some kind of legacy hw that's getting current software updates in some kind of really niche use case. Or academia. :)

Like previous you, I have to admit I'm skeptical but would be happy to be wrong.

The idea isn't new, for example Amsterdam Compiler Kit from 1980's.

MIPS64 is still very much alive: https://store.ui.com/us/en/products/er-4

"EdgeOS" is based on Linux, and people run vanilla Linux distributions on those boxes, as well as OpenBSD and NetBSD.

I wonder how long Marvell will continue selling those Octeon MIPS64 chips, though. Marvell (then Cavium) switched to ARM nearly a decade ago (2016) for newer chips in the Octeon series. I think Loongson sells more modern MIPS64 (or at least MIPS64-like) chips, but they don't seem to be commercially available outside China.

For the UNIX authors, that was already possible a decade before.

> mips64 .. must be some kind of legacy hw that's getting current software updates

Hundreds of thousands of linux-based smartnic cards, actually. Fun stuff. Those particular ones were EOLd and have been replaced with ARM but the MIPS based ones will live on in the datacenters until they die, I'm sure.

> Like previous you, I have to admit I'm skeptical but would be happy to be wrong

Seriously, you are going to be delighted to be wrong. On your linux machine, go write a go program and write "GOOS=darwin GOARCH=arm64 go build ..." and you will have yourself an ARM mac binary. Or for going the other way, use GOOS=linux GOARCH=amd64. It really is that simple.

This is by far one of the best parts of Go. Its all around simple and painless to use. anyone designing a language should study what Go did well and what they didn't.

This non-cgo port might help - I started using it recently and it's fine but I'm not exactly a demanding user https://pkg.go.dev/modernc.org/sqlite

FWIW, that's also more or less what SpiderMonkey has been doing for ~25 years (and I presume other JavaScript VMs).

> however I will note that a large reason that C exists in the first place was to have a machine independent language to write programs in.

That's fair, but what we call a monstrosity by modern standards is much simpler than porting the assembly

There were cross plaform languages before C, but they never really took off for system development the wat C did (OSs, for example were commonly written in pure assembly)

Ohh...thats a name I haven't heard in a while... along with the purdue compiler construction kit

funny how CLang basically blew right by them in terms of option as a 'base' to build languages on.

It's still pretty slow, but overall correct. There's tricks, like reader connections and a single writer connection to reduce contention. There was a blog post on here detailing some speedups in general.

While good cross-compilation is one of Go's strengths... I don't really think a unified assembly language contributed to that? Any assembly code can't be shared across multiple architectures in general, so the only potential benefit would be the easiness of parser development, which doesn't sound like a big thing. Rob Pike himself even noted that it can be offputting to outsiders but considered it's a worthy trade-off nevertheless [1], the conclusion I don't really think justified.

[1] https://go.dev/talks/2016/asm.slide#32

It gets even more amazing than that. Look at this bit from my GitHub Actions: https://github.com/ncruces/go-sqlite3/blob/fefee692dbfad39f6...

I install QEMU (I have the same setup locally), then it's one line each to run unit tests for: Linux 386, arm64, riscv64, ppc64le and s390x.

With QEMU installed, all you have to do is:

    GOARCH=bla go test ./...

LLVM -- clang is the C language family front-end to LLVM.

It was basically dead by the time LLVM became a thing, in this industry we tend to reinvent a lot, pretending it is something utterly new.

Latest example, application servers in WebAssembly.

Cross-platform languages have existed for decades, no?

Wait is go test automatically running it under QEMU or what's going on here?

Ah I found this https://ctrl-c.us/posts/test-goarch I guess it's qemu-user-binfmt registering the alternate bin formats to automatically run under QEMU, that's pretty neat

Yep.

The Go build system runs under your current architecture, cross-compiling tests to your target architecture.

Then, the Go test runner also runs under your current architecture, orchestrating running your cross compiled test binaries.

Since you registered to run cross-compiled binaries under QEMU, those test binaries magically run through QEMU.

The Go test runner collects test results, and reports back to you.

The first run might be slowish, as the Go compiler needs to cross compile the standard library and all your dependencies to your target platform. But once that's done and cached, and if your tests are fast, the edit-test cycle becomes pretty quick.

They're not widely available in the west, but you can get a whole Loongarch workstation on aliexpress:

https://www.aliexpress.us/w/wholesale-loongson-3a6000.html

A side effect of C not having a price tag associated with it, anyone with UNIX source tapes got a C compiler for free, until commercial UNIX became a thing, and splitted into user/developer SKUs, and thus GCC largely ignored until then became a thing worth supporting.