cross-compiling to aarch64 fails: ld: src/topkg.a: error adding symbols

[lafleurdeboum]

Hello, thank you for the great overlay !

Following the suggestion in #620 and taking inspiration from doi2bib's flake and default.nix, I managed to build my current toy project to native (x86_64-linux-gnu) and musl targets.

Unfortunately, cross-compiling to aarch64-musl fails. I must admit I'm running nix over an Archlinux install, which of course complicates things a little. But since the x86_64 musl build succeeds, I hope I'm not too far from an expected setup. Here is the relevant error :

# nix build .#aarch64-musl
[...]
error: builder for '/nix/store/82gh18jj8i533w5rrghzx09bdgszd0cx-ocaml5.2.1-topkg-1.0.7.drv' failed with exit code 1;
       [...]
       > + ocamlfind ocamlopt -c -g -bin-annot -safe-string -I src -I test -I src-bin -I src-care -o src/topkg.cmx src/topkg.ml
       > + ocamlfind ocamlopt -a -I src src/topkg_string.cmx src/topkg_fpath.cmx src/topkg_cmd.cmx src/topkg_result.cmx src/topkg_log.cmx src/topkg_os.cmx src/topkg_codec.cmx src/topkg_vcs.cmx src/topkg_conf.cmx src/topkg_build.cmx src/topkg_opam.cmx src/topkg_distrib.cmx src/topkg_fexts.cmx src/topkg_test.cmx src/topkg_install.cmx src/topkg_publish.cmx src/topkg_pkg.cmx src/topkg_ipc.cmx src/topkg_main.cmx src/topkg.cmx -o src/topkg.cmxa
       > + ocamlfind ocamlopt -shared -linkall -I src src/topkg.cmxa -o src/topkg.cmxs
       > + ocamlfind ocamlopt -shared -linkall -I src src/topkg.cmxa -o src/topkg.cmxs
       > /nix/store/v63bxfiacw082c7ijshf60alvvrpfxsq-binutils-2.44/bin/ld: src/topkg.a: error adding symbols: archive has no index; run ranlib to add one
       > collect2: error: ld returned 1 exit status
       > File "caml_startup", line 1:
       > Error: Error during linking (exit code 1)
       > Command exited with code 2.
       > pkg.ml: [ERROR] cmd ['ocamlbuild' '-use-ocamlfind' '-classic-display' '-j' '4' '-tag' 'debug'
       >      '-build-dir' '_build' 'CHANGES.md' 'LICENSE.md' 'README.md' 'pkg/META'
       >      'topkg.opam' 'src/topkg.a' 'src/topkg.cmxs' 'src/topkg.cmxa'
       >      'src/topkg.cma' 'src/topkg_vcs.cmx' 'src/topkg_test.cmx'
       >      'src/topkg_string.cmx' 'src/topkg_result.cmx' 'src/topkg_publish.cmx'
       >      'src/topkg_pkg.cmx' 'src/topkg_os.cmx' 'src/topkg_opam.cmx'
       >      'src/topkg_main.cmx' 'src/topkg_log.cmx' 'src/topkg_ipc.cmx'
       >      'src/topkg_install.cmx' 'src/topkg_fpath.cmx' 'src/topkg_fexts.cmx'
       >      'src/topkg_distrib.cmx' 'src/topkg_conf.cmx' 'src/topkg_codec.cmx'
       >      'src/topkg_cmd.cmx' 'src/topkg_build.cmx' 'src/topkg.cmx'
       >      'src/topkg.cmi' 'src/topkg.mli' 'doc/index-topkg.mld']: exited with 10

I'm using the following setup :

flake.nix

{
  description = "liminar Nix Flake";

  nixConfig.extra-substituters = [
    "https://anmonteiro.nix-cache.workers.dev"
  ];

  inputs.nixpkgs.url = "github:nix-ocaml/nix-overlays";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages."${system}";
      in
      {
        packages = {
          native = pkgs.callPackage ./nix { };
          musl =
            let
              pkgs' = pkgs.pkgsCross.musl64;
            in
            pkgs'.lib.callPackageWith pkgs' ./nix {
              static = true;
            };
          aarch64-musl =
            let
              pkgs' = pkgs.pkgsCross.aarch64-multiplatform-musl;
            in
            pkgs'.lib.callPackageWith pkgs' ./nix {
              static = true;
              crossName = "aarch64";
            };

        };
      });
}

nix/default.nix

{
  pkgs,
  stdenv,
  lib,
  ocamlPackages,
  static ? false,
  crossName ? null,
}:

let
  html_of_jsx = ocamlPackages.buildDunePackage {
    pname = "html_of_jsx";
    version = "0.0.4";
    src = pkgs.fetchFromGitHub {
      owner = "davesnx";
      repo = "html_of_jsx";
      rev = "0.0.4";
      hash = "sha256-MOXV+yLlrzRaFVBuYyNhQoa1bw6/GPAY8vTvPCuv/2s=";
    };

    OCAMLFIND_TOOLCHAIN = crossName;
    buildInputs = with ocamlPackages; [
      ppxlib
    ];
    doCheck = false;
  };
in
ocamlPackages.buildDunePackage {
  pname = "liminar";
  version = "0.0.1";
  src = ./..;

  OCAMLFIND_TOOLCHAIN = crossName;
  nativeBuildInputs = with ocamlPackages; [
    mlx
  ];
  buildInputs = with ocamlPackages; [
    dream
    dream-pure
    jose
    oidc
    mlx
    cohttp-lwt-unix
    html_of_jsx
    uri
    yojson
    logs
    lwt_ppx
  ];
  buildPhase = ''
    pwd
    dune build bin/Liminar.exe --profile=${if static then "static" else "release"}
  '';
  installPhase = ''
    mkdir -p $out/bin
    mv _build/default/bin/Liminar.exe $out/bin/liminar
  '';

  meta = {
    homepage = "https://codeberg.org/lafleur/liminar";
    description = "companion webapp for the Laminar CI";
  };
}