A Fil-C userland for finix

finixModules.filc-userland (finix/userland.nix) builds a finix system's whole userland with Fil-C. finix modules take their packages from pkgs, which is just config.nixpkgs.pkgs; the module sets that to a Fil-C package set, so finit, busybox, bash, coreutils, util-linux, OpenSSH, sudo, Linux-PAM, D-Bus, dhcpcd, mdevd, sysklogd, Python, Perl, git and the rest become Fil-C builds without a per-service override.

nixosConfigurations.host = finix.lib.finixSystem {
  inherit (nixpkgs) lib;
  modules = [
    filnix.finixModules.filc-userland
    {
      filc.userland = {
        enable = true;
        system = "aarch64-linux";
        # Your own Nixpkgs: native packages come from its binary cache.
        nativePackages = import nixpkgs { system = "aarch64-linux"; };
        native = [ "tailscale" ];
      };
    }
    ./configuration.nix
  ];
};

What stays native

A process is either all Fil-C or all native: a Fil-C program cannot load a native library, nor the other way round. So exceptions are whole packages, listed by top-level attribute in filc.userland.native and taken from filc.userland.nativePackages. The module always adds:

Attribute	Why
`linuxKernel`, `linuxPackages*`	Fil-C cannot build the kernel
`limine`, `sbctl`, `efibootmgr`	the bootloader and its install hook
`userborn`	finix creates users with it during activation; Rust
`pkgsStatic`	the setuid wrappers are static; Fil-C does not link statically
`glibc`	only the wrappers use it, for a header from its source
`nix`	unless `nativeNix = false`: the Fil-C Nix cannot sandbox builds

Everything else is Fil-C, and nothing Rust or Go can slip in unnoticed: mkPkgsFilc { blockRustGo = true; } (lib/block-rust-go.nix) gives every derivation built with rustc, cargo or go a broken problem, so evaluation stops with

error: Refusing to evaluate package 'ripgrep-15.1.0' … because it has problems:
- filc (kind "broken"): Rust has no Fil-C target. Use the native build instead (filc.userland.native in finix), or leave it out.

The adapter only touches meta, so derivations hash the same as in the plain pkgsFilc. Haskell (cachix, pandoc) and Zig (ghostty) are not detected; name them in native too.

Checking the result

finix/filc-audit.sh classifies every ELF file in a closure by whether it uses the Fil-C loader or libpizlo:

finix/filc-audit.sh ./result

It also finds packages built by the Fil-C stdenv that came out native. filcc has no target prefix, so a build that runs plain cc or gcc can pick up the build platform's compiler from depsBuildBuild. busybox did, until its port named the compiler; any Fil-C-named package in the "native" list deserves a look.

Nixpkgs revisions

nativePackages defaults to pkgsFilc.pkgsBuildBuild, the fully native stage of filnix's own Nixpkgs. Not buildPackages: its target platform is Fil-C, which matters for any package that is itself a compiler (Emacs' native compilation pulled in a Fil-C-targeted libgccjit that way). Passing your own Nixpkgs, as above, keeps the kernel and the other native packages identical to the rest of your machines.