using fenix to suply cargo and rust to a makeRustPlatform results in "error: linker cc not found"

[wucke13]

I tried both "CARGO_TARGET_${ shoutTarget }_LINKER" ="${p.stdenv.cc.targetPrefix}cc"; and RUSTFLAGS = "-C linker=dasdsa${p.stdenv.cc.targetPrefix}cc"; in the call to buildRustPackage, but nonetheless cargo tries to call cc.
Roughly speaking, this is my derivation:

{
my-package = let
  p = pkgs.pkgsStatic;

  # the rust target of `p`
  target = p.rust.toRustTargetSpec p.targetPlatform;

  # the rust target in shout case
  shoutTarget = builtins.replaceStrings ["-"] ["_"] (pkgs.lib.toUpper target);

  # suitable Rust toolchain
  toolchain = with inputs.fenix.packages.${system}; combine [
    stable.cargo
    stable.rustc
    targets.${target}.stable.rust-std
  ];
  customRustPlatform = p.makeRustPlatform {
    cargo = toolchain;
    rustc = toolchain;
  };
 in  customRustPlatform.buildRustPackage {
    # ....
  };
}

[figsoda]

It seems to have something to do with using makeRustPlatform from pkgsStatic, I was able to build this with naersk using CARGO_BUILD_TARGET using the flake below, the same thing should also be possible with crane, but I'm not sure about vanilla makeRustPlatform since it has --target baked in

{
  inputs = {
    fenix = {
      url = "github:nix-community/fenix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    flake-utils.url = "github:numtide/flake-utils";
    naersk = {
      url = "github:nix-community/naersk";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    nixpkgs.url = "nixpkgs/nixos-unstable";
  };

  outputs = { self, fenix, flake-utils, naersk, nixpkgs }:
    flake-utils.lib.eachDefaultSystem (system: {
      packages.default =
        let
          inherit (nixpkgs) lib;
          pkgs = nixpkgs.legacyPackages.${system}.pkgsStatic;
          target = pkgs.rust.toRustTargetSpec pkgs.stdenv.targetPlatform;
          toolchain = with fenix.packages.${system}; combine [
            stable.cargo
            stable.rustc
            targets.${target}.stable.rust-std
          ];
          shoutTarget = builtins.replaceStrings [ "-" ] [ "_" ] (lib.toUpper target);
        in

        (naersk.lib.${system}.override {
          cargo = toolchain;
          rustc = toolchain;
        }).buildPackage {
          src = self;
          nativeBuildInputs = [ pkgs.stdenv.cc ];
          CARGO_BUILD_TARGET = target;
          "CARGO_TARGET_${shoutTarget}_LINKER" = "${pkgs.stdenv.cc.targetPrefix}cc";
        };
    });
}

[figsoda]

I think cargo was just trying to run cc regardless, I was able to build it with makeRustPlatform by adding p.buildPackages.stdenv.cc to nativeBuildInputs (without needing to set the linker manually)

[wucke13]

@figsoda The issue is, that sometimes cc is not named cc but has the targetPrefix, but cargo still tries to call cc. I have a suspicion though: maybe cc is used when compiing all derive macros (as they are not cross compiled), and only then later CARGO_TARGET_..._LINKER is used for the final build?
Edit: yes, this seems to be the case.

[figsoda]

proc macros does sound like a reason to use build platform cc, does using buildPackages.stdenv.cc fix the issue for you?

[wucke13]

Yeah, with it I get further but still no complete build. Again a cc error, but this time for the final linkage:

       >   = note: /nix/store/pnajkjw1fz03z1x27ski1qbx9n3hd4df-binutils-2.39/bin/ld: /nix/store/s652h8znmysdbxcmwlzzcwrj6bb1xyln-gcc-11.3.0/lib/gcc/x86_64-unknown-linux-gnu/11.3.0/crtbeginT.o: relocation R_X86_64_32 against hidden symbol `__TMC_END__' can not be used when making a shared object
       >           /nix/store/pnajkjw1fz03z1x27ski1qbx9n3hd4df-binutils-2.39/bin/ld: failed to set dynamic section sizes: bad value
       >           collect2: error: ld returned 1 exit status

I believe this again is a musl libc mixed with glibc gcc problem.

[figsoda]

Can I see the nix expression you are working with?

[wucke13]

@figsoda Sure! Here, take a look at the rosenpass-static output of https://github.com/rosenpass/rosenpass/blob/dev/wucke13/flake.nix#L89