build/config/BUILDCONFIG.gn

# Copyright 2018 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# =============================================================================
# WHAT IS THIS FILE?
# =============================================================================
#
# This is the master GN build configuration. This file is loaded after the
# build args (args.gn) for the build directory and after the toplevel ".gn"
# file (which points to this file as the build configuration).
#
# This file will be executed and the resulting context will be used to execute
# every other file in the build. So variables declared here (that don't start
# with an underscore) will be implicitly global.

# =============================================================================
# PLATFORM SELECTION
# =============================================================================
#
# There are two main things to set: "os" and "cpu". The "toolchain" is the name
# of the GN thing that encodes combinations of these things.
#
# Users typically only set the variables "target_os" and "target_cpu" in "gn
# args", the rest are set up by our build and internal to GN.
#
# There are three different types of each of these things: The "host"
# represents the computer doing the compile and never changes. The "target"
# represents the main thing we're trying to build. The "current" represents
# which configuration is currently being defined, which can be either the
# host, the target, or something completely different.

if (target_os == "") {
  target_os = host_os
}
if (target_cpu == "") {
  target_cpu = host_cpu
}
if (current_cpu == "") {
  current_cpu = target_cpu
}
if (current_os == "") {
  current_os = target_os
}

# =============================================================================
# BUILD FLAGS
# =============================================================================
#
# This block lists input arguments to the build, along with their default
# values.
#
# If a value is specified on the command line, it will overwrite the defaults
# given in a declare_args block, otherwise the default will be used.
#
# YOU SHOULD ALMOST NEVER NEED TO ADD FLAGS TO THIS FILE. GN allows any file in
# the build to declare build flags. If you need a flag for a single component,
# you can just declare it in the corresponding BUILD.gn file.

default_clang_base_path = "//third_party/llvm-build/Release+Asserts"

declare_args() {
  # Debug build.  Most global debug build flags are declared in
  # //build/config/BUILD.gn.
  is_debug = false

  # By default, we use the clang compiler on both Mac and Linux. To use the
  # gcc compiler on Linux instead, set is_gcc to true.
  is_gcc = false
  clang_base_path = default_clang_base_path

  # This would not normally be set as a build argument, but rather is used as a
  # default value during the first parse of this config.  All other toolchains
  # that cause this file to be re-parsed will already have this set.  For
  # further explanation, see
  # https://gn.googlesource.com/gn/+/refs/heads/master/docs/reference.md#toolchain-overview
  host_toolchain = ""

  # Must be enabled for fuzzing targets.
  use_libfuzzer = false
}

declare_args() {
  is_clang = !is_gcc
}

# ==============================================================================
# TOOLCHAIN SETUP
# ==============================================================================
#
# Here we set the host and default toolchains. Currently only Mac and POSIX are
# defined.
if (host_toolchain == "") {
  if (current_os == "chromeos" || current_os == "linux") {
    if (is_clang) {
      host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
    } else {
      host_toolchain = "//build/toolchain/linux:gcc_$host_cpu"
    }
  } else if (current_os == "mac") {
    host_toolchain = "//build/toolchain/mac:clang"
  } else {
    # TODO(miu): Windows, and others.
    assert(false, "Toolchain for current_os is not defined.")
  }
}

_default_toolchain = ""
if (target_os == "chromeos" || target_os == "linux") {
  if (is_clang) {
    _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
  } else {
    _default_toolchain = "//build/toolchain/linux:gcc_$target_cpu"
  }
} else if (target_os == "mac") {
  assert(host_os == "mac", "Cross-compiling on Mac is not supported.")
  _default_toolchain = "//build/toolchain/mac:clang"
} else {
  assert(false, "Toolchain for target_os is not defined.")
}
set_default_toolchain(_default_toolchain)

# =============================================================================
# OS DEFINITIONS
# =============================================================================
#
# We set these various is_FOO booleans for convenience in writing OS-based
# conditions.

if (current_os == "chromeos" || current_os == "linux") {
  is_linux = true
  is_mac = false
  is_posix = true
} else if (current_os == "mac") {
  is_linux = false
  is_mac = true
  is_posix = true
} else {
  # TODO(miu): Windows, and others.
  assert(false, "is_FOO booleans not defined for current_os.")
}

# =============================================================================
# TARGET DEFAULTS
# =============================================================================
#
# Set up the default configuration for every build target of the given type.
# The values configured here will be automatically set on the scope of the
# corresponding target. Target definitions can add or remove to the settings
# here as needed.

# All binary targets will get this list of configs by default.
_shared_binary_target_configs = [
  "//build/config:openscreen_code",
  "//build/config:no_exceptions",
  "//build/config:no_rtti",
  "//build/config:symbol_visibility_hidden",
  "//build/config:default_sanitizers",
  "//build/config:default_coverage",
  "//build/config:compiler_defaults",
  "//build/config:compiler_cpu_abi",
  "//build/config:default_optimization",
  "//build/config:sysroot_runtime_libraries",
  "//build/config:operating_system_defines",
]

# Apply that default list to the binary target types.
set_defaults("executable") {
  configs = _shared_binary_target_configs
}
set_defaults("static_library") {
  configs = _shared_binary_target_configs
}
set_defaults("shared_library") {
  configs = _shared_binary_target_configs
}
set_defaults("source_set") {
  configs = _shared_binary_target_configs
}