# 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
}

if (target_cpu == "") {
  if (target_os == "android") {
    # If we're building for Android, we should assume that we want to
    # build for ARM by default, not the host_cpu (which is likely x64).
    # This allows us to not have to specify both target_os and target_cpu
    # on the command line.
    target_cpu = "arm"
  } else {
    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. 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.

declare_args() {
  # How many symbols to include in the build. This affects the performance of
  # the build since the symbols are large and dealing with them is slow.
  #   2 means regular build with symbols.
  #   1 means minimal symbols, usually enough for backtraces only.
  #   0 means no symbols.
  #   -1 means auto-set (off in release, regular in debug).
  symbol_level = -1

  # Component build.
  is_component_build = false

  # Debug build.
  is_debug = true

  # Whether we're a traditional desktop unix.
  is_desktop_linux = current_os == "linux" && current_os != "chromeos"

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

  # 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

  if (current_os == "chromeos") {
    # Allows the target toolchain to be injected as arguments. This is needed
    # to support the CrOS build system which supports per-build-configuration
    # toolchains.
    cros_use_custom_toolchain = false
  }

  # DON'T ADD MORE FLAGS HERE. Read the comment above.
}

# =============================================================================
# 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" || current_os == "winrt_81" ||
    current_os == "winrt_81_phone" || current_os == "winrt_10") {
  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 == "chromeos") {
  is_android = false
  is_chromeos = true
  is_ios = false
  is_linux = true
  is_mac = false
  is_nacl = false
  is_posix = true
  is_win = false
} else if (current_os == "nacl") {
  # current_os == "nacl" will be passed by the nacl toolchain definition.
  # It is not set by default or on the command line. We treat is as a
  # Posix variant.
  is_android = false
  is_chromeos = false
  is_ios = false
  is_linux = false
  is_mac = false
  is_nacl = true
  is_posix = true
  is_win = false
} else if (current_os == "ios") {
  is_android = false
  is_chromeos = false
  is_ios = true
  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
}

# =============================================================================
# SOURCES FILTERS
# =============================================================================
#
# These patterns filter out platform-specific files when assigning to the
# sources variable. The magic variable |sources_assignment_filter| is applied
# to each assignment or appending to the sources variable and matches are
# automatcally removed.
#
# Note that the patterns are NOT regular expressions. Only "*" and "\b" (path
# boundary = end of string or slash) are supported, and the entire string
# muct match the pattern (so you need "*.cc" to match all .cc files, for
# example).

# DO NOT ADD MORE PATTERNS TO THIS LIST, see set_sources_assignment_filter call
# below.
sources_assignment_filter = []
if (!is_posix) {
  sources_assignment_filter += [
    "*_posix.h",
    "*_posix.cc",
    "*_posix_unittest.h",
    "*_posix_unittest.cc",
    "*\bposix/*",
  ]
}
if (!is_win) {
  sources_assignment_filter += [
    "*_win.cc",
    "*_win.h",
    "*_win_unittest.cc",
    "*\bwin/*",
    "*.def",
    "*.rc",
  ]
}
if (!is_mac) {
  sources_assignment_filter += [
    "*_mac.h",
    "*_mac.cc",
    "*_mac.mm",
    "*_mac_unittest.h",
    "*_mac_unittest.cc",
    "*_mac_unittest.mm",
    "*\bmac/*",
    "*_cocoa.h",
    "*_cocoa.cc",
    "*_cocoa.mm",
    "*_cocoa_unittest.h",
    "*_cocoa_unittest.cc",
    "*_cocoa_unittest.mm",
    "*\bcocoa/*",
  ]
}
if (!is_ios) {
  sources_assignment_filter += [
    "*_ios.h",
    "*_ios.cc",
    "*_ios.mm",
    "*_ios_unittest.h",
    "*_ios_unittest.cc",
    "*_ios_unittest.mm",
    "*\bios/*",
  ]
}
if (!is_mac && !is_ios) {
  sources_assignment_filter += [ "*.mm" ]
}
if (!is_linux) {
  sources_assignment_filter += [
    "*_linux.h",
    "*_linux.cc",
    "*_linux_unittest.h",
    "*_linux_unittest.cc",
    "*\blinux/*",
  ]
}
if (!is_android) {
  sources_assignment_filter += [
    "*_android.h",
    "*_android.cc",
    "*_android_unittest.h",
    "*_android_unittest.cc",
    "*\bandroid/*",
  ]
}
if (!is_chromeos) {
  sources_assignment_filter += [
    "*_chromeos.h",
    "*_chromeos.cc",
    "*_chromeos_unittest.h",
    "*_chromeos_unittest.cc",
    "*\bchromeos/*",
  ]
}

# DO NOT ADD MORE PATTERNS TO THIS LIST, see set_sources_assignment_filter call
# below.

# Actually save this list.
#
# These patterns are executed for every file in the source tree of every run.
# Therefore, adding more patterns slows down the build for everybody. We should
# only add automatic patterns for configurations affecting hundreds of files
# across many projects in the tree.
#
# Therefore, we only add rules to this list corresponding to platforms on the
# Chromium waterfall.  This is not for non-officially-supported platforms
# (FreeBSD, etc.) toolkits, (X11, GTK, etc.), or features. For these cases,
# write a conditional in the target to remove the file(s) from the list when
# your platform/toolkit/feature doesn't apply.
set_sources_assignment_filter(sources_assignment_filter)

# =============================================================================
# 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:feature_flags",
  "//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 (current_os == "winrt_81" || current_os == "winrt_81_phone" ||
    current_os == "winrt_10") {
  _native_compiler_configs += [ "//build/config/win:target_winrt" ]
}
if (is_posix) {
  _native_compiler_configs += [
    "//build/config/gcc:no_exceptions",
    "//build/config/gcc:symbol_visibility_hidden",
  ]
}

if (is_linux) {
  _native_compiler_configs += [ "//build/config/linux:sdk" ]
} else if (is_mac) {
  _native_compiler_configs += [ "//build/config/mac:sdk" ]
} else if (is_ios) {
  _native_compiler_configs += [ "//build/config/ios: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 {
  _native_compiler_configs += [ "//build/config:release" ]
  _default_optimization_config = "//build/config/compiler:optimize"
}
_native_compiler_configs += [ _default_optimization_config ]

# If it wasn't manually set, set to an appropriate default.
if (symbol_level == -1) {
  # Linux is slowed by having symbols as part of the target binary, whereas
  # Mac and Windows have them separate, so in Release Linux, default them off.
  if (is_debug || !is_linux) {
    symbol_level = 2
  } else if (is_asan || is_lsan || is_tsan || is_msan) {
    # Sanitizers require symbols for filename suppressions to work.
    symbol_level = 1
  } else {
    symbol_level = 0
  }
}

# Symbol setup.
if (symbol_level == 2) {
  _default_symbols_config = "//build/config/compiler:symbols"
} else if (symbol_level == 1) {
  _default_symbols_config = "//build/config/compiler:minimal_symbols"
} else if (symbol_level == 0) {
  _default_symbols_config = "//build/config/compiler:no_symbols"
} else {
  assert(false, "Bad value for symbol_level.")
}
_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 + [ "//build/config:default_libs" ]
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 + [ "//build/config:default_libs" ]
if (is_win) {
  _shared_library_configs += _windows_linker_configs
} else if (is_mac) {
  _shared_library_configs += [ "//build/config/mac:mac_dynamic_flags" ]
} else if (is_android) {
  # Strip native JNI exports from shared libraries by default. Binaries that
  # want this can remove this config.
  _shared_library_configs +=
      [ "//build/config/android:hide_native_jni_exports" ]
}
set_defaults("shared_library") {
  configs = _shared_library_configs
}
if (is_component_build) {
  set_defaults("component") {
    configs = _shared_library_configs
  }
}

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

# Test defaults.
set_defaults("test") {
  if (is_android) {
    configs = _shared_library_configs
  } else {
    configs = _executable_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.
  if (is_clang) {
    host_toolchain = "//build/toolchain/win:clang_$current_cpu"
  } else {
    host_toolchain = "//build/toolchain/win:$current_cpu"
  }

  if (current_os == "win") {
    set_default_toolchain("$host_toolchain")
  } else if (current_cpu == "x64") {  # WinRT x64
    set_default_toolchain("//build/toolchain/win:winrt_x64")
  } else if (current_cpu == "x86") {  # WinRT x86
    set_default_toolchain("//build/toolchain/win:winrt_x86")
  }
} else if (is_android) {
  if (host_os == "linux") {
    # Use clang for the x86/64 Linux host builds.
    if (host_cpu == "x86" || host_cpu == "x64") {
      host_toolchain = "//build/toolchain/linux:clang_$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")
  }
  if (is_chromeos && cros_use_custom_toolchain) {
    set_default_toolchain("//build/toolchain/cros:target")
  }
} else if (is_mac) {
  host_toolchain = "//build/toolchain/mac:clang_x64"
  set_default_toolchain(host_toolchain)
} else if (is_ios) {
  host_toolchain = "//build/toolchain/mac:clang_x64"
  set_default_toolchain("//build/toolchain/mac:ios_clang_arm")
} else if (is_nacl) {
  # TODO(GYP): This will need to change when we get NaCl working
  # on multiple platforms, but this whole block of code (how we define
  # host_toolchain) needs to be reworked regardless to key off of host_os
  # and host_cpu rather than the is_* variables.
  host_toolchain = "//build/toolchain/linux:clang_x64"
}

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

if (is_component_build) {
  _component_mode = "shared_library"
} else {
  _component_mode = "source_set"
}
template("component") {
  target(_component_mode, target_name) {
    forward_variables_from(invoker, "*")

    # All shared libraries must have the sanitizer deps to properly link in
    # asan mode (this target will be empty in other cases).
    if (!defined(deps)) {
      deps = []
    }
    deps += [ "//build/config/sanitizers:deps" ]
  }
}