build/host.gni

# Copyright 2017 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

declare_args() {
  # This is the directory where host tools intended for manual use by
  # developers get installed.  It's something a developer might put
  # into their shell's $PATH.  Host tools that are just needed as part
  # of the build do not get copied here.  This directory is only for
  # things that are generally useful for testing or debugging or
  # whatnot outside of the GN build itself.  These are only installed
  # by an explicit install_host_tools() rule (see //build/host.gni).
  host_tools_dir = "$root_build_dir/host-tools"

  # Set this to the path of a directory containing prebuilt binaries for
  # the host tools generated by compiled_action(). This is useful when
  # performing sub-builds (e.g. when generating the IDK which requires
  # rebuilding SDK collections for different API levels and CPU architectures)
  # to avoid rebuilding the host tools every time.
  #
  host_tools_base_path_override = ""
}

# This declares that a host tool (a target built in host_toolchain)
# should be installed in host_tools_dir.  This target can be used in
# any toolchain, and it will forward to host_toolchain.
#
# Parameters
#
#   outputs (required)
#     [files list] Simple file name of each tool, should be the
#     same as the output_name in the executable() or similar rule
#     (which is usually just that target's name).
#
#   deps (recommended)
#     [label list] Should list each target that actually builds each output.
#     It does not need to use explicit toolchain suffixes; the only target
#     using the deps will be instantiated only in host_toolchain.
#
#   allow_previously_built_tools (optional)
#     [boolean] Set to false to prevent the use of previously built host tools
#     when performing IDK sub-builds.
#
#   testonly (optional)
#   visibility (optional)
#     Standard GN meaning.
#
# Example of usage:
#
#   executable("frob") { ... }
#   install_host_tools("fiddlers") {
#     deps = [ ":frob", "//some/other/dir:twiddle" ]
#     outputs = [ "frob", "twiddle" ]
#   }
template("install_host_tools") {
  assert(defined(invoker.outputs), "install_host_tools() must define outputs")

  # There is more than one host_toolchain when variants are involved, or when
  # building tools for multiple host environments, so we only want to do this
  # copy in "our" host toolchain (ie, `host_toolchain).
  #
  # When variants are involved, they copy their executables to the base
  # host_toolchain's output dir (which toolchain_variant.base points to in every
  # host_toolchain).
  if (current_toolchain == host_toolchain &&
      current_toolchain == toolchain_variant.base) {
    copy(target_name) {
      forward_variables_from(invoker,
                             [
                               "testonly",
                               "visibility",
                             ])
      if (defined(visibility)) {
        visibility += [ ":$target_name" ]
      }
      outputs = [ "$host_tools_dir/{{source_file_part}}" ]
      sources = []
      _allow_previously_built_tools =
          !defined(invoker.allow_previously_built_tools) ||
          invoker.allow_previously_built_tools
      if (_allow_previously_built_tools &&
          host_tools_base_path_override != "") {
        not_needed(invoker, [ "deps" ])
        foreach(output_name, invoker.outputs) {
          # Compute location of prebuilt host binary, relative to the current
          # build directory first, then compute its GN unrebased path to list
          # it as a proper input.
          source_rebased =
              "${host_tools_base_path_override}/" +
              rebase_path("$root_out_dir/$output_name", root_build_dir)
          sources +=
              [ "//" + rebase_path(source_rebased, "//", root_build_dir) ]
        }
      } else {
        forward_variables_from(invoker, [ "deps" ])
        foreach(output_name, invoker.outputs) {
          sources += [ "$root_out_dir/$output_name" ]
        }
      }
    }
  } else {
    # Redirect to the base host_toolchain, where the copy rule above is.
    # In a variant host_toolchain context, toolchain_variant.base points
    # there, while host_toolchain always matches current_toolchain.
    group(target_name) {
      if (current_toolchain == host_toolchain) {
        toolchain = toolchain_variant.base
      } else {
        toolchain = host_toolchain
      }
      public_deps = [ ":$target_name($toolchain)" ]

      forward_variables_from(invoker,
                             [
                               "testonly",
                               "visibility",
                             ])
      not_needed(invoker,
                 [
                   "deps",
                   "outputs",
                 ])
    }
  }
}