1# Copyright 2018 The Chromium Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5# =============================================================================
6# WHAT IS THIS FILE?
7# =============================================================================
8#
9# This is the master GN build configuration. This file is loaded after the
10# build args (args.gn) for the build directory and after the toplevel ".gn"
11# file (which points to this file as the build configuration).
12#
13# This file will be executed and the resulting context will be used to execute
14# every other file in the build. So variables declared here (that don't start
15# with an underscore) will be implicitly global.
16
17# =============================================================================
18# PLATFORM SELECTION
19# =============================================================================
20#
21# There are two main things to set: "os" and "cpu". The "toolchain" is the name
22# of the GN thing that encodes combinations of these things.
23#
24# Users typically only set the variables "target_os" and "target_cpu" in "gn
25# args", the rest are set up by our build and internal to GN.
26#
27# There are three different types of each of these things: The "host"
28# represents the computer doing the compile and never changes. The "target"
29# represents the main thing we're trying to build. The "current" represents
30# which configuration is currently being defined, which can be either the
31# host, the target, or something completely different.
32
33if (target_os == "") {
34  target_os = host_os
35}
36if (target_cpu == "") {
37  target_cpu = host_cpu
38}
39if (current_cpu == "") {
40  current_cpu = target_cpu
41}
42if (current_os == "") {
43  current_os = target_os
44}
45
46# =============================================================================
47# BUILD FLAGS
48# =============================================================================
49#
50# This block lists input arguments to the build, along with their default
51# values.
52#
53# If a value is specified on the command line, it will overwrite the defaults
54# given in a declare_args block, otherwise the default will be used.
55#
56# YOU SHOULD ALMOST NEVER NEED TO ADD FLAGS TO THIS FILE. GN allows any file in
57# the build to declare build flags. If you need a flag for a single component,
58# you can just declare it in the corresponding BUILD.gn file.
59
60default_clang_base_path = "//third_party/llvm-build/Release+Asserts"
61
62declare_args() {
63  # Debug build.  Most global debug build flags are declared in
64  # //build/config/BUILD.gn.
65  is_debug = false
66
67  # By default, we use the clang compiler on both Mac and Linux. To use the
68  # gcc compiler on Linux instead, set is_gcc to true.
69  is_gcc = false
70  clang_base_path = default_clang_base_path
71
72  # This would not normally be set as a build argument, but rather is used as a
73  # default value during the first parse of this config.  All other toolchains
74  # that cause this file to be re-parsed will already have this set.  For
75  # further explanation, see
76  # https://gn.googlesource.com/gn/+/refs/heads/master/docs/reference.md#toolchain-overview
77  host_toolchain = ""
78}
79
80declare_args() {
81  is_clang = !is_gcc
82}
83
84# ==============================================================================
85# TOOLCHAIN SETUP
86# ==============================================================================
87#
88# Here we set the host and default toolchains. Currently only Mac and POSIX are
89# defined.
90if (host_toolchain == "") {
91  if (current_os == "chromeos" || current_os == "linux") {
92    if (is_clang) {
93      host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
94    } else {
95      host_toolchain = "//build/toolchain/linux:gcc_$host_cpu"
96    }
97  } else if (current_os == "mac") {
98    host_toolchain = "//build/toolchain/mac:clang"
99  } else {
100    # TODO(miu): Windows, and others.
101    assert(false, "Toolchain for current_os is not defined.")
102  }
103}
104
105_default_toolchain = ""
106if (target_os == "chromeos" || target_os == "linux") {
107  if (is_clang) {
108    _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
109  } else {
110    _default_toolchain = "//build/toolchain/linux:gcc_$target_cpu"
111  }
112} else if (target_os == "mac") {
113  assert(host_os == "mac", "Cross-compiling on Mac is not supported.")
114  _default_toolchain = "//build/toolchain/mac:clang"
115} else {
116  assert(false, "Toolchain for target_os is not defined.")
117}
118set_default_toolchain(_default_toolchain)
119
120# =============================================================================
121# OS DEFINITIONS
122# =============================================================================
123#
124# We set these various is_FOO booleans for convenience in writing OS-based
125# conditions.
126
127if (current_os == "chromeos" || current_os == "linux") {
128  is_linux = true
129  is_mac = false
130  is_posix = true
131} else if (current_os == "mac") {
132  is_linux = false
133  is_mac = true
134  is_posix = true
135} else {
136  # TODO(miu): Windows, and others.
137  assert(false, "is_FOO booleans not defined for current_os.")
138}
139
140# =============================================================================
141# TARGET DEFAULTS
142# =============================================================================
143#
144# Set up the default configuration for every build target of the given type.
145# The values configured here will be automatically set on the scope of the
146# corresponding target. Target definitions can add or remove to the settings
147# here as needed.
148
149# All binary targets will get this list of configs by default.
150_shared_binary_target_configs = [
151  "//build/config:openscreen_code",
152  "//build/config:no_exceptions",
153  "//build/config:no_rtti",
154  "//build/config:symbol_visibility_hidden",
155  "//build/config:default_sanitizers",
156  "//build/config:default_coverage",
157  "//build/config:compiler_defaults",
158  "//build/config:compiler_cpu_abi",
159  "//build/config:default_optimization",
160  "//build/config:sysroot_runtime_libraries",
161]
162
163# Apply that default list to the binary target types.
164set_defaults("executable") {
165  configs = _shared_binary_target_configs
166}
167set_defaults("static_library") {
168  configs = _shared_binary_target_configs
169}
170set_defaults("shared_library") {
171  configs = _shared_binary_target_configs
172}
173set_defaults("source_set") {
174  configs = _shared_binary_target_configs
175}
176