Build failure: zigbee2mqtt (buildNpmPackage cross compilation)

[kazikcz]

Steps To Reproduce

# default.nix:
let
        # Sun Nov 10 14:30:04 2024 +0000
        pkgs = import (fetchTarball https://github.com/nixos/nixpkgs/archive/d40ed47baac04ed2ba8d4b0d12e0bc7bd582eec9.tar.gz) {
                overlays = [
                        (final: prev: {
                                zigbee2mqtt = prev.zigbee2mqtt.overrideAttrs (attrs: {
                                        # Without this, -m64 is passed on x86_64 to an arm cross-gcc resulting in an error
                                        npmFlags = (attrs.npmFlags or []) ++ [ "--arch=arm" ];
                                });
                        })
                ];
        };
        z2m = pkgs.pkgsCross.raspberryPi.zigbee2mqtt;
        file = pkgs.file;
in
        # with npmFlags --arch=arm hack, this produces a script that refers to the buildPlatform nodejs (x86_64), instead of targetPlatform nodejs (arm)
        pkgs.runCommand "" {} ''eval ${file}/bin/file ''$(grep exec ${z2m}/bin/zigbee2mqtt | cut -d" " -f2)''

nix-build

Build log

Without the npmFlags hack:

npm error gyp info using node-gyp@10.1.0
npm error gyp info using node@20.18.0 | linux | x64
...
       > npm error gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
       > npm error armv6l-unknown-linux-gnueabihf-g++: error: unrecognized command-line option '-m64'
       > npm error make: *** [notify.target.mk:102: Release/obj.target/notify/notify.o] Error 1

With npmFlags hack, the package builds, but (as per runCommand) refers to the wrong nodejs and ends up being non-executable on ARM:

/nix/store/jz54v1m0ldqivx5i45q8i05pz5clf842-nodejs-20.18.0/bin/node: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), dynamically linked, interpreter /nix/store/3bvxjkkmwlymr0fssczhgi39c3aj1l7i-glibc-2.40-36/lib/ld-linux-x86-64.so.2, for GNU/Linux 3.10.0, not stripped

Additional context

I'm trying to build an sdImage for Raspberry Pi 0 (armv6l) on a x86_64 system. Wanted to include zigbee2mqtt.

I've found #327653 which fixed nodejs building itself. It looks like this alone may not be sufficient.

I've done some digging and it looks to me buildNpmPackage is not cross-compile aware/ready. It pulls in nodejs in both buildInputs and nativeBuildInputs. The npm used during setup is ofcourse the nativeBuildInputs one, so x86_64 specific (explains -m64 presence, wrong script exec wrapper). It seems the buildInputs one is not present in any way during the build.

Interestingly, when inspecting rootfs I found that both nodejs outputs (x86_64 and arm) are in /nix/store/, with zigbee2mqtt being the only one as "referer" (nix-store).

FWIW If I do this (+ npmFlags) to the zigbee2mqtt override I can get it actually start (didn't check beyond that) on the resulting rootfs, but it's a nasty hack:

 postInstall = ''sed -i "s@^exec.*node\"@exec ${prev.nodejs}/bin/node@" $out/bin/zigbee2mqtt'';

Plenty of files in the zigbee2mqtt output in store still refer to the wrong nodejs in shebangs.

Notify maintainers

@aduh95
@tie
@Cynerd
@sweber83

Metadata

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 6.11.6, NixOS, 24.11 (Vicuna), 24.11pre703931.4aa36568d413`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.24.10`
 - channels(root): `"nixos"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

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