zircon/public/gn/toolchain/clang.gni

# Copyright 2019 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() {
  # If $clang_tool_dir is "", then this controls how the Clang toolchain
  # binaries are found.  If true, then the standard prebuilt is used.
  # Otherwise the tools are just expected to be found by the shell via `PATH`.
  use_prebuilt_clang = true

  # Directory where the Clang toolchain binaries ("clang", "llvm-nm", etc.) are
  # found.  If this is "", then the behavior depends on $use_prebuilt_clang.
  # This toolchain is expected to support both Fuchsia targets and the host.
  clang_tool_dir = ""
}

# This is a string identifying the particular toolchain version in use.  Its
# only purpose is to be unique enough that it changes when switching to a new
# toolchain, so that recompilations with the new compiler can be triggered.
#
# When using the prebuilt, the CIPD instance ID of the prebuilt is perfect.
# When not using the prebuilt, there isn't a quick way to extract the compiler
# version.  But at least changing the setting to a different compiler will
# change the string.
clang_version_string = clang_tool_dir
if (clang_tool_dir == "" && use_prebuilt_clang) {
  _prebuilt_dir = "$zx/prebuilt/downloads/clang"
  clang_tool_dir = "$_prebuilt_dir/bin"
  _prebuilt_cipd_version =
      read_file("$_prebuilt_dir/.versions/clang.cipd_version", "json")
  clang_version_string = _prebuilt_cipd_version.instance_id
}