nixpkgs/pkgs/test/rust-sysroot/default.nix

{ lib, rust, rustPlatform, fetchFromGitHub }:

let
  mkBlogOsTest = target: rustPlatform.buildRustPackage rec {
    name = "blog_os-sysroot-test";

    src = fetchFromGitHub {
        owner = "phil-opp";
        repo = "blog_os";
        rev = "4e38e7ddf8dd021c3cd7e4609dfa01afb827797b";
        sha256 = "0k9ipm9ddm1bad7bs7368wzzp6xwrhyfzfpckdax54l4ffqwljcg";
    };

    cargoSha256 = "1cbcplgz28yxshyrp2krp1jphbrcqdw6wxx3rry91p7hiqyibd30";

    inherit target;

    RUSTFLAGS = "-C link-arg=-nostartfiles";

    # Tests don't work for `no_std`. See https://os.phil-opp.com/testing/
    doCheck = false;

    meta = with lib; {
        description = "Test for using custom sysroots with buildRustPackage";
        maintainers = with maintainers; [ aaronjanse ];
        platforms = lib.platforms.x86_64;
    };
  };

  # The book uses rust-lld for linking, but rust-lld is not currently packaged for NixOS.
  # The justification in the book for using rust-lld suggests that gcc can still be used for testing:
  # > Instead of using the platform's default linker (which might not support Linux targets),
  # > we use the cross platform LLD linker that is shipped with Rust for linking our kernel.
  # https://github.com/phil-opp/blog_os/blame/7212ffaa8383122b1eb07fe1854814f99d2e1af4/blog/content/second-edition/posts/02-minimal-rust-kernel/index.md#L157
  targetContents = {
    "llvm-target" = "x86_64-unknown-none";
    "data-layout" = "e-m:e-i64:64-f80:128-n8:16:32:64-S128";
    "arch" = "x86_64";
    "target-endian" = "little";
    "target-pointer-width" = "64";
    "target-c-int-width" = "32";
    "os" = "none";
    "executables" = true;
    "linker-flavor" = "gcc";
    "panic-strategy" = "abort";
    "disable-redzone" = true;
    "features" = "-mmx,-sse,+soft-float";
  };

in {
  blogOS-targetByFile = mkBlogOsTest (builtins.toFile "x86_64-blog_os.json" (builtins.toJSON targetContents));
  blogOS-targetByNix = let
    plat = lib.systems.elaborate { config = "x86_64-none"; } // {
      rustc = {
        config = "x86_64-blog_os";
        platform = targetContents;
      };
    };
    in mkBlogOsTest (rust.toRustTargetSpec plat);
}