I am trying to make this succeed:
nix-build --arg crossSystem '(import <nixpkgs/lib>).systems.examples.musl64' -A netbsd.compat

Is that the right way to use Musl?

@dtzWill had me testing with this:

nix-build --arg localSystem '{config="x86_64-unknown-linux-musl";}' -A netbsd.compat

Which hopefully still works.

Either way your changes look good. No need to build install for musl if it's already available in buildPackages.

crossSystem vs localSystem: "build musl-native or cross-compile to musl using glibc tools".

I'm shocked that coreutils isn't building--looks like something indeed is rather wrong with cross wrapper and indeed the compiler isn't finding anything it should (and used to!). Will look into this...

Works on staging, "phew". Looks like it's this: #41429

I broke cross on staging a few weeks ago. 645f03b fixes it on staging yesterday. Maybe we should get that to master sooner?

Haha @dtzWill beat me.

re:this PR, as-is I think the coreutils used might not run on the builder at all--consider cross-compiling to aarch64? I'm not sure best way to express these things re:strings, I think this should work though.

UPDATE: Yep, here's cross-compiling to aarch64: https://gist.github.com/dtzWill/6b5db001e14e714563a696ede76bfd62
(nix build -f . --arg crossSystem '(import <nixpkgs/lib>).systems.examples.aarch64-multiplatform' netbsd.compat)

I'm not sure best way to express these things re:strings, I think this should work though.

I think @orivej are the best way. AFAICT Nixpkgs splicing will rewrite "native" build inputs to buildPackages automatically. If you're referencing it outside of the inputs, buildPackages will accomplish the same thing for you.

On staging I'm getting this: https://gist.github.com/dtzWill/f3a12fc18d2c16a9616f1ceb448003bc

Which looks like we need to specify/provide a host-native compiler... depsBuildBuild = [ buildPackages.stdenv.cc ] ?

Yeah I am still a noob on cross compiling - but that looks like it might work.

Note that the zlib thing is an issue with dropbear as well:

https://hydra.nixos.org/build/75406713/nixlog/1

dropbear seems to work on staging for me, both local and cross. Is that perhaps an old job (without the fix mentioned earlier in this thread)?

@Ericson2314 hmm, yes this would be nice to fix on master. Can you look into that? Is it just picking that commit?

I think we'll have to wait for it to work through staging. It's a true mass rebuild - every single hash will change.

FWIW I think we need to add some cross-compilation tests to release.nix to prevent this from happening again. The channel should block on some cross compilation things that we know should work.

Merging for now because this is a step in the right direction. More PRs on this stuff are definitely welcome though.