# Copyright (c) 2013 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.

# =============================================================================
# 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 (like nacl). GN will
# run the same build file multiple times for the different required
# configuration in the same build.
#
# This gives the following variables:
#  - host_os, host_cpu, host_toolchain
#  - target_os, target_cpu, default_toolchain
#  - current_os, current_cpu, current_toolchain.
#
# Note the default_toolchain isn't symmetrical (you would expect
# target_toolchain). This is because the "default" toolchain is a GN built-in
# concept, and "target" is something our build sets up that's symmetrical with
# its GYP counterpart. Potentially the built-in default_toolchain variable
# could be renamed in the future.
#
# When writing build files, to do something only for the host:
#   if (current_toolchain == host_toolchain) { ...

if (target_os == "") {
  target_os = host_os
}

assert(host_cpu != "")
assert(target_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. If you need a
# flag in multiple components, there are a few options:
#
# - If your feature is a single target, say //components/foo, and the targets
#   depending on foo need to have some define set if foo is enabled: (1) Write
#   a declare_args block in foo's BUILD.gn file listing your enable_foo build
#   flag. (2) Write a config in that file listing the define, and list that
#   config in foo's public_configs. This will propagate that define to all the
#   targets depending on foo. (3) When foo is not enabled, just make it expand
#   to an empty group (or whatever's appropriate for the "off" state of your
#   feature.
#
# - If a semi-random set of targets need to know about a define: (1) In the
#   lowest level of the build that knows about this feature, add a declare_args
#   block in the build file for your enable flag. (2) Write a config that adds
#   a define conditionally based on that build flags. (3) Manually add that
#   config to the "configs" applying to the targets that need the define.
#
# - If a semi-random set of targets need to know about the build flag (to do
#   file inclusion or exclusion, more than just defines): (1) Write a .gni file
#   in the lowest-level directory that knows about the feature. (2) Put the
#   declare_args block with your build flag in that .gni file. (3) Import that
#   .gni file from the BUILD.gn files that need the flag.
#
# Other advice:
#
# - Use boolean values when possible. If you need a default value that expands
#   to some complex thing in the default case (like the location of the
#   compiler which would be computed by a script), use a default value of -1 or
#   the empty string. Outside of the declare_args block, conditionally expand
#   the default value as necessary.
#
# - Use a name like "use_foo" or "is_foo" (whatever is more appropriate for
#   your feature) rather than just "foo".
#
# - Write good comments directly above the declaration with no blank line.
#   These comments will appear as documentation in "gn args --list".
#
# - Don't call exec_script inside declare_args. This will execute the script
#   even if the value is overridden, which is wasteful. See first bullet.

# There is no component build for the Dart VM, but build files in some
# dependencies check this.
is_component_build = false

declare_args() {
  # Debug build.
  is_debug = true

  # Release build.
  is_release = false

  # Product build.
  is_product = false

  # Set to true when compiling with the Clang compiler. Typically this is used
  # to configure warnings.
  is_clang = current_os == "mac" || current_os == "linux"

  # Compile for Address Sanitizer to find memory bugs.
  is_asan = false

  # Compile for Leak Sanitizer to find leaks.
  is_lsan = false

  # Compile for Memory Sanitizer to find uninitialized reads.
  is_msan = false

  # Compile for Thread Sanitizer to find threading bugs.
  is_tsan = false
}

# =============================================================================
# OS DEFINITIONS
# =============================================================================
#
# We set these various is_FOO booleans for convenience in writing OS-based
# conditions.
#
# - is_android, is_chromeos, is_ios, and is_win should be obvious.
# - is_mac is set only for desktop Mac. It is not set on iOS.
# - is_posix is true for mac and any Unix-like system (basically everything
#   except Windows).
# - is_linux is true for desktop Linux and ChromeOS, but not Android (which is
#   generally too different despite being based on the Linux kernel).
#
# Do not add more is_* variants here for random lesser-used Unix systems like
# aix or one of the BSDs. If you need to check these, just check the
# current_os value directly.

if (current_os == "win") {
  is_android = false
  is_chromeos = false
  is_ios = false
  is_linux = false
  is_mac = false
  is_nacl = false
  is_posix = false
  is_win = true
} else if (current_os == "mac") {
  is_android = false
  is_chromeos = false
  is_ios = false
  is_linux = false
  is_mac = true
  is_nacl = false
  is_posix = true
  is_win = false
} else if (current_os == "android") {
  is_android = true
  is_chromeos = false
  is_ios = false
  is_linux = false
  is_mac = false
  is_nacl = false
  is_posix = true
  is_win = false
} else if (current_os == "linux") {
  is_android = false
  is_chromeos = false
  is_ios = false
  is_linux = true
  is_mac = false
  is_nacl = false
  is_posix = true
  is_win = false
}

# =============================================================================
# BUILD OPTIONS
# =============================================================================

# These Sanitizers all imply using the Clang compiler. On Windows they either
# don't work or work differently.
if (!is_clang && (is_asan || is_lsan || is_tsan || is_msan)) {
  is_clang = true
}

# =============================================================================
# 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.

# Holds all configs used for making native executables and libraries, to avoid
# duplication in each target below.
_native_compiler_configs = [
  "//build/config/compiler:compiler",
  "//build/config/compiler:compiler_arm_fpu",
  "//build/config/compiler:chromium_code",
  "//build/config/compiler:default_include_dirs",
  "//build/config/compiler:no_rtti",
  "//build/config/compiler:runtime_library",
]
if (is_win) {
  _native_compiler_configs += [
    "//build/config/win:lean_and_mean",
    "//build/config/win:nominmax",
    "//build/config/win:sdk",
    "//build/config/win:unicode",
    "//build/config/win:winver",
  ]
}
if (is_posix) {
  _native_compiler_configs += [
    "//build/config/gcc:no_exceptions",
  ]
}

if (is_linux) {
  _native_compiler_configs += [ "//build/config/linux:sdk" ]
} else if (is_mac) {
  _native_compiler_configs += [ "//build/config/mac:sdk" ]
} else if (is_android) {
  _native_compiler_configs += [ "//build/config/android:sdk" ]
}

if (is_clang) {
  _native_compiler_configs += [
    "//build/config/clang:find_bad_constructs",
    "//build/config/clang:extra_warnings",
  ]
}

# Optimizations and debug checking.
if (is_debug) {
  _native_compiler_configs += [ "//build/config:debug" ]
  _default_optimization_config = "//build/config/compiler:no_optimize"
} else if (is_release) {
  _native_compiler_configs += [ "//build/config:release" ]
  _default_optimization_config = "//build/config/compiler:optimize"
} else {
  assert(is_product)
  _native_compiler_configs += [ "//build/config:product" ]
  _default_optimization_config = "//build/config/compiler:optimize"
}
_native_compiler_configs += [ _default_optimization_config ]

# Symbol setup.
_default_symbols_config = "//build/config/compiler:symbols"
_native_compiler_configs += [ _default_symbols_config ]

# Windows linker setup for EXEs and DLLs.
if (is_win) {
  _windows_linker_configs = [
    "//build/config/win:default_incremental_linking",
    "//build/config/win:sdk_link",
    "//build/config/win:common_linker_setup",

    # Default to console-mode apps. Most of our targets are tests and such
    # that shouldn't use the windows subsystem.
    "//build/config/win:console",
  ]
}

# Executable defaults.
_executable_configs = _native_compiler_configs
if (is_win) {
  _executable_configs += _windows_linker_configs
} else if (is_mac) {
  _executable_configs += [
    "//build/config/mac:mac_dynamic_flags",
    "//build/config/mac:mac_executable_flags",
  ]
} else if (is_linux || is_android) {
  _executable_configs += [ "//build/config/gcc:executable_ldconfig" ]
  if (is_android) {
    _executable_configs += [ "//build/config/android:executable_config" ]
  }
}
set_defaults("executable") {
  configs = _executable_configs
}

# Static library defaults.
set_defaults("static_library") {
  configs = _native_compiler_configs
}

# Shared library defaults (also for components in component mode).
_shared_library_configs = _native_compiler_configs
if (is_win) {
  _shared_library_configs += _windows_linker_configs
} else if (is_mac) {
  _shared_library_configs += [ "//build/config/mac:mac_dynamic_flags" ]
}
set_defaults("shared_library") {
  configs = _shared_library_configs
}

# Source set defaults (also for components in non-component mode).
set_defaults("source_set") {
  configs = _native_compiler_configs
}
set_defaults("component") {
  configs = _native_compiler_configs
}

# ==============================================================================
# TOOLCHAIN SETUP
# ==============================================================================
#
# Here we set the default toolchain, as well as the variable host_toolchain
# which will identify the toolchain corresponding to the local system when
# doing cross-compiles. When not cross-compiling, this will be the same as the
# default toolchain.

if (is_win) {
  # On windows we use the same toolchain for host and target by default.
  host_toolchain = "//build/toolchain/win:$current_cpu"
  set_default_toolchain("$host_toolchain")
} else if (is_android) {
  if (host_os == "linux") {
    if (host_cpu == "x86" || host_cpu == "x64") {
      host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
    } else {
      host_toolchain = "//build/toolchain/linux:$host_cpu"
    }
  } else if (host_os == "mac") {
    host_toolchain = "//build/toolchain/mac:clang_$host_cpu"
  } else {
    assert(false, "Unknown host for android cross compile")
  }
  if (is_clang) {
    set_default_toolchain("//build/toolchain/android:clang_$current_cpu")
  } else {
    set_default_toolchain("//build/toolchain/android:$current_cpu")
  }
} else if (is_linux) {
  if (is_clang) {
    host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
    set_default_toolchain("//build/toolchain/linux:clang_$current_cpu")
  } else {
    host_toolchain = "//build/toolchain/linux:$host_cpu"
    set_default_toolchain("//build/toolchain/linux:$current_cpu")
  }
} else if (is_mac) {
  host_toolchain = "//build/toolchain/mac:clang_x64"
  set_default_toolchain(host_toolchain)
}

# ==============================================================================
# COMPONENT SETUP
# ==============================================================================

# Don't try to do component builds for the standalone Dart VM.
assert(!is_component_build)
component_mode = "source_set"

template("component") {
  source_set(target_name) {
    # See above.
    configs = []  # Prevent list overwriting warning.
    configs = invoker.configs

    # See above call.
    set_sources_assignment_filter([])

    if (defined(invoker.all_dependent_configs)) {
      all_dependent_configs = invoker.all_dependent_configs
    }
    if (defined(invoker.allow_circular_includes_from)) {
      allow_circular_includes_from = invoker.allow_circular_includes_from
    }
    if (defined(invoker.cflags)) {
      cflags = invoker.cflags
    }
    if (defined(invoker.cflags_c)) {
      cflags_c = invoker.cflags_c
    }
    if (defined(invoker.cflags_cc)) {
      cflags_cc = invoker.cflags_cc
    }
    if (defined(invoker.cflags_objc)) {
      cflags_objc = invoker.cflags_objc
    }
    if (defined(invoker.cflags_objcc)) {
      cflags_objcc = invoker.cflags_objcc
    }
    if (defined(invoker.check_includes)) {
      check_includes = invoker.check_includes
    }
    if (defined(invoker.data)) {
      data = invoker.data
    }
    if (defined(invoker.data_deps)) {
      data_deps = invoker.data_deps
    }
    if (defined(invoker.datadeps)) {
      datadeps = invoker.datadeps
    }
    if (defined(invoker.defines)) {
      defines = invoker.defines
    }
    if (defined(invoker.deps)) {
      deps = invoker.deps
    }
    if (defined(invoker.direct_dependent_configs)) {
      direct_dependent_configs = invoker.direct_dependent_configs
    }
    if (defined(invoker.forward_dependent_configs_from)) {
      forward_dependent_configs_from = invoker.forward_dependent_configs_from
    }
    if (defined(invoker.include_dirs)) {
      include_dirs = invoker.include_dirs
    }
    if (defined(invoker.ldflags)) {
      ldflags = invoker.ldflags
    }
    if (defined(invoker.lib_dirs)) {
      lib_dirs = invoker.lib_dirs
    }
    if (defined(invoker.libs)) {
      libs = invoker.libs
    }
    if (defined(invoker.output_extension)) {
      output_extension = invoker.output_extension
    }
    if (defined(invoker.output_name)) {
      output_name = invoker.output_name
    }
    if (defined(invoker.public)) {
      public = invoker.public
    }
    if (defined(invoker.public_configs)) {
      public_configs = invoker.public_configs
    }
    if (defined(invoker.public_deps)) {
      public_deps = invoker.public_deps
    }
    if (defined(invoker.sources)) {
      sources = invoker.sources
    }
    if (defined(invoker.testonly)) {
      testonly = invoker.testonly
    }
    if (defined(invoker.visibility)) {
      visibility = invoker.visibility
    }
  }
}