Stream: compiler development

Topic: zig compiler - musl and binary dependencies

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:17):

we've discussed before wanting to build roc with musl libc on Linux, so that it works across distros

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:17):

also we still need to bundle llvm and it's looking like also we'll want to bundle lld

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:18):

both of which are part of the same project, but we'd need to compile them with musl and use those binaries as dependencies that end up in our final zig output

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:18):

(that is, in our final binary produced by Zig)

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:20):

I know the zig compiler itself already builds llvm from source with musl, so presumably we can reuse the same process - and seems likely it could be adapted to work with lld too, since lld is also part of the llvm project

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:21):

I think it would be great if we could be building on Linux with musl and full static linking as early as possible, and verify it with ci (like, fail ci if any dynamic dependencies are detected in the final output executable)

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:23):

and I'd like to similarly verify that our only dynamic dep on macOS is libSystem, and on windows that it's whatever the equivalent of libSystem is there. (I think I remember Windows having some dependency you're always expected to link dynamically bc they don't guarantee syscall stability the way Linux does.)

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:24):

this would mean we'd never accidentally introduce dynamic deps when introducing third party packages or anything like that

view this post on Zulip Richard Feldman (Feb 02 2025 at 19:25):

and we could be confident that roc can (finally!) be downloaded and used immediately on any freshly installed OS, with nothing else needing to be installed

view this post on Zulip Brendan Hansknecht (Feb 02 2025 at 19:43):

I think it would be great if we could be building on Linux with musl and full static linking as early as possible, and verify it with ci (like, fail ci if any dynamic dependencies are detected in the final output executable)

Yes please!

view this post on Zulip Luke Boswell (Feb 02 2025 at 22:14):

I'd like to have a crack at setting up our build pipeline, or make a start on the roc cli in zig.

Specifically bundling lld and compiling an app (using a stubbed app.o) for Linux, Windows, macOS.

view this post on Zulip Richard Feldman (Feb 02 2025 at 22:20):

love it! :heart_eyes:

view this post on Zulip Richard Feldman (Feb 02 2025 at 22:20):

I'd ask Andrew about bundling lld

view this post on Zulip Richard Feldman (Feb 02 2025 at 22:21):

with musl specifically

view this post on Zulip Richard Feldman (Feb 02 2025 at 22:21):

he definitely knows the best way to do that in Zig

view this post on Zulip Luke Boswell (Feb 02 2025 at 22:25):

@Andrew Kelley -- what's the best way to ask you about this? :smiley:

My plan was to dig around and explore a little to scope it out.

view this post on Zulip Luke Boswell (Feb 02 2025 at 23:27):

I wonder if we could use zig ld or something like @Jakub Konka 's bold? these are all written in zig.

view this post on Zulip Richard Feldman (Feb 02 2025 at 23:52):

oh yeah also we should look into bundling libunwind too for backtracing

view this post on Zulip Richard Feldman (Feb 02 2025 at 23:54):

https://github.com/libunwind/libunwind

view this post on Zulip Andrew Kelley (Feb 03 2025 at 22:54):

Luke Boswell said:

Andrew Kelley -- what's the best way to ask you about this? :smiley:

My plan was to dig around and explore a little to scope it out.

I don't mind the occasional ping here, I'm happy to help. If it gets too much I'll turn notifications off

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 17:20):

Just double checking this, musl is only a linux thing, right?

So for mac and windows, there is no change.

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 17:20):

If so, my gut feel is we should just make our ci script at a minimum build the compiler for the N different targets we want to support.

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 17:21):

I guess we could also default to musl on linux, but that doesn't specifically feel necessary.

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 17:22):

To do so would just require modifying the build script to detect when it is being built on linux and then pick the right version of musl based on the architecture. I don't think that has any specific gains over building for the musl target we care about in CI.

view this post on Zulip Anton (Feb 04 2025 at 18:05):

I'll get started on setting up the CI for the new compiler tomorrow

view this post on Zulip Anton (Feb 04 2025 at 18:08):

Hmm, I'll probably do the folder move first

view this post on Zulip Jasper Woudenberg (Feb 04 2025 at 19:07):

Maybe I misunderstand, but musl is Zig's default ABI for Linux, so it might be the easiest option:
https://ziglang.org/documentation/0.13.0/std/#std.Target.Abi.default

view this post on Zulip Richard Feldman (Feb 04 2025 at 19:26):

I'd honestly like to only ever build with musl on Linux

view this post on Zulip Richard Feldman (Feb 04 2025 at 19:27):

just never deal with libc differences across distros ever again

view this post on Zulip Luke Boswell (Feb 04 2025 at 19:45):

Anton said:

I'll get started on setting up the CI for the new compiler tomorrow

Can we also include WASM as a build target. So we dont forget about 32-bit arch's.

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 19:50):

Jasper Woudenberg said:

Maybe I misunderstand, but musl is Zig's default ABI for Linux, so it might be the easiest option:
https://ziglang.org/documentation/0.13.0/std/#std.Target.Abi.default

Oh, missed that....cool. no work. Also, I guess we don't even link libc currently, so no dependency at all even on musl.

view this post on Zulip Brendan Hansknecht (Feb 04 2025 at 19:51):

Anton said:

I'll get started on setting up the CI for the new compiler tomorrow

Many thanks :folded_hands:. You do the hard work that carries us all.

view this post on Zulip Andrew Kelley (Feb 04 2025 at 23:07):

Jasper Woudenberg said:

Maybe I misunderstand, but musl is Zig's default ABI for Linux, so it might be the easiest option:
https://ziglang.org/documentation/0.13.0/std/#std.Target.Abi.default

to be clear, the default is to match the host. If you do not specify a target, and you link libc, it will link against your system libc, whichever one you are running the compiler on. However, if you specify, for example, -target x86_64-linux then you are cross-compiling, and in this case it picks musl as a default (as well as defaulting to the "baseline" CPU), and a conservative OS version range.

view this post on Zulip Anton (Feb 05 2025 at 17:01):

I think it would be great if we could be building on Linux with musl and full static linking as early as possible, and verify it with ci (like, fail ci if any dynamic dependencies are detected in the final output executable)

and I'd like to similarly verify that our only dynamic dep on macOS is libSystem, and on windows that it's whatever the equivalent of libSystem is there. (I think I remember Windows having some dependency you're always expected to link dynamically bc they don't guarantee syscall stability the way Linux does.)

I've got this working on all targets :) PR#7582
Now I just need to integrate this nicely with the current ci-manager workflow

view this post on Zulip Jakub Konka (Feb 06 2025 at 19:01):

Luke Boswell said:

I wonder if we could use zig ld or something like Jakub Konka 's bold? these are all written in zig.

Just to clarify, bold is a drop-in replacement for Apple's ld only and missing features :-) https://github.com/kubkon/bold/issues/170

Last updated: Jul 06 2025 at 12:14 UTC