chromium: cross compilation support

mkChromiumDerivation (base: rec {

  name = "chromium-browser";

  packageName = "chromium";

  buildTargets = [ "mksnapshot" "chrome_sandbox" "chrome" ];

  buildTargets = [ "run_mksnapshot_default" "chrome_sandbox" "chrome" ];

  outputs = ["out" "sandbox"];

, which

, llvmPackages_attrName

, rustc

, libuuid

, overrideCC

# postPatch:

, pkgsBuildHost

# configurePhase:

    inherit (upstream-info.deps.ungoogled-patches) rev sha256;

  };

  # There currently isn't a (much) more concise way to get a stdenv

  # that uses lld as its linker without bootstrapping pkgsLLVM; see

  # https://github.com/NixOS/nixpkgs/issues/142901

  buildPlatformLlvmStdenv =

    let

      llvmPackages = pkgsBuildBuild.${llvmPackages_attrName};

    in

      overrideCC llvmPackages.stdenv

        (llvmPackages.stdenv.cc.override {

          inherit (llvmPackages) bintools;

        });

  chromiumRosettaStone = {

    cpu = platform:

      let name = platform.parsed.cpu.name;

      in ({ "x86_64" = "x64";

            "i686" = "x86";

            "arm" = "arm";

            "aarch64" = "arm64";

          }.${platform.parsed.cpu.name}

        or (throw "no chromium Rosetta Stone entry for cpu: ${name}"));

    os = platform:

      if platform.isLinux

      then "linux"

      else throw "no chromium Rosetta Stone entry for os: ${platform.config}";

  };

  base = rec {

    pname = "${packageName}-unwrapped";

    inherit (upstream-info) version;

      bison gperf

    ];

    depsBuildBuild = [

      buildPlatformLlvmStdenv

      buildPlatformLlvmStdenv.cc

      pkg-config

      libuuid

      libpng # needed for "host/generate_colors_info"

    ]

    # When cross-compiling, chromium builds a huge proportion of its

    # components for both the `buildPlatform` (which it calls

    # `host`) as well as for the `hostPlatform` -- easily more than

    # half of the dependencies are needed here.  To avoid having to

    # maintain a separate list of buildPlatform-dependencies, we

    # simply throw in the kitchen sink.

    ++ buildInputs

    ;

    buildInputs = [

      (libpng.override { apngSupport = false; }) # https://bugs.chromium.org/p/chromium/issues/detail?id=752403

      bzip2 flac speex opusWithCustomModes

      ++ lib.optional pulseSupport libpulseaudio;

    patches = [

      ./cross-compile.patch

      # Optional patch to use SOURCE_DATE_EPOCH in compute_build_timestamp.py (should be upstreamed):

      ./patches/no-build-timestamps.patch

      # For bundling Widevine (DRM), might be replaceable via bundle_widevine_cdm=true in gnFlags:

      # weaken or disable security measures like sandboxing or ASLR):

      is_official_build = true;

      disable_fieldtrial_testing_config = true;

      # note: chromium calls buildPlatform "host" and calls hostPlatform "target"

      host_cpu      = chromiumRosettaStone.cpu stdenv.buildPlatform;

      host_os       = chromiumRosettaStone.os  stdenv.buildPlatform;

      target_cpu    = chromiumRosettaStone.cpu stdenv.hostPlatform;

      v8_target_cpu = chromiumRosettaStone.cpu stdenv.hostPlatform;

      target_os     = chromiumRosettaStone.os  stdenv.hostPlatform;

      # Build Chromium using the system toolchain (for Linux distributions):

      #

      # What you would expect to be caled "target_toolchain" is

      # actually called either "default_toolchain" or "custom_toolchain",

      # depending on which part of the codebase you are in; see:

      # https://github.com/chromium/chromium/blob/d36462cc9279464395aea5e65d0893d76444a296/build/config/BUILDCONFIG.gn#L17-L44

      custom_toolchain = "//build/toolchain/linux/unbundle:default";

      host_toolchain = "//build/toolchain/linux/unbundle:default";

      host_toolchain = "//build/toolchain/linux/unbundle:host";

      v8_snapshot_toolchain = "//build/toolchain/linux/unbundle:host";

      host_pkg_config = "${pkgsBuildBuild.pkg-config}/bin/pkg-config";

      pkg_config      = "${pkgsBuildHost.pkg-config}/bin/${stdenv.cc.targetPrefix}pkg-config";

      # Don't build against a sysroot image downloaded from Cloud Storage:

      use_sysroot = false;

      # Because we use a different toolchain / compiler version:

      # We do intentionally not set rustc_version as nixpkgs will never do incremental

      # rebuilds, thus leaving this empty is fine.

      rust_sysroot_absolute = "${rustc}";

    } // lib.optionalAttrs (!(stdenv.buildPlatform.canExecute stdenv.hostPlatform)) {

      # https://www.mail-archive.com/v8-users@googlegroups.com/msg14528.html

      arm_control_flow_integrity = "none";

    } // lib.optionalAttrs proprietaryCodecs {

      # enable support for the H.264 codec

      proprietary_codecs = true;

    # our Clang is always older than Chromium's and the build logs have a size

    # of approx. 25 MB without this option (and this saves e.g. 66 %).

    env.NIX_CFLAGS_COMPILE = "-Wno-unknown-warning-option";

    env.BUILD_CC = "$CC_FOR_BUILD";

    env.BUILD_CXX = "$CXX_FOR_BUILD";

    env.BUILD_AR = "$AR_FOR_BUILD";

    env.BUILD_NM = "$NM_FOR_BUILD";

    env.BUILD_READELF = "$READELF_FOR_BUILD";

    buildPhase = let

      buildCommand = target: ''

diff --git a/build/toolchain/linux/unbundle/BUILD.gn b/build/toolchain/linux/unbundle/BUILD.gn

index a091491236bb1..d36fd4e652fbf 100644

--- a/build/toolchain/linux/unbundle/BUILD.gn

+++ b/build/toolchain/linux/unbundle/BUILD.gn

@@ -9,6 +9,7 @@ gcc_toolchain("default") {

   cxx = getenv("CXX")

   ar = getenv("AR")

   nm = getenv("NM")

+  readelf = getenv("READELF")

   ld = cxx

   extra_cflags = getenv("CFLAGS")

@@ -27,6 +28,7 @@ gcc_toolchain("host") {

   cxx = getenv("BUILD_CXX")

   ar = getenv("BUILD_AR")

   nm = getenv("BUILD_NM")

+  readelf = getenv("BUILD_READELF")

   ld = cxx

   extra_cflags = getenv("BUILD_CFLAGS")

@@ -35,7 +37,8 @@ gcc_toolchain("host") {

   extra_ldflags = getenv("BUILD_LDFLAGS")

   toolchain_args = {

-    current_cpu = current_cpu

-    current_os = current_os

+    current_cpu = host_cpu

+    current_os = host_os

+    v8_current_cpu = target_cpu

   }

 }