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- # 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.
- # =============================================================================
- # 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 (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 your feature is a single target, say //components/foo, you can put
- # a declare_args() block in //components/foo/BUILD.gn and use it there.
- # Nobody else in the build needs to see the flag.
- #
- # - Defines based on build variables should be implemented via the generated
- # build flag header system. See //build/buildflag_header.gni. You can put
- # the buildflag_header target in the same file as the build flag itself. You
- # should almost never set "defines" directly.
- #
- # - If your flag toggles a target on and off or toggles between different
- # versions of similar things, write a "group" target that forwards to the
- # right target (or no target) depending on the value of the build flag. This
- # group can be in the same BUILD.gn file as the build flag, and targets can
- # depend unconditionally on the group rather than duplicating flag checks
- # across many targets.
- #
- # - If a semi-random set of build files REALLY needs to know about a define and
- # the above pattern for isolating the build logic in a forwarding group
- # doesn't work, you can put the argument in a .gni file. This should be put
- # in the lowest level of the build that knows about this feature (which should
- # almost always be outside of the //build directory!).
- #
- # Other flag 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() {
- # Set to enable the official build level of optimization. This has nothing
- # to do with branding, but enables an additional level of optimization above
- # release (!is_debug). This might be better expressed as a tri-state
- # (debug, release, official) but for historical reasons there are two
- # separate flags.
- #
- # IMPORTANT NOTE: (!is_debug) is *not* sufficient to get satisfying
- # performance. In particular, DCHECK()s are still enabled for release builds,
- # which can halve overall performance, and do increase memory usage. Always
- # set "is_official_build" to true for any build intended to ship to end-users.
- is_official_build = false
- # Set to true when compiling with the Clang compiler.
- is_clang = current_os != "linux" ||
- (current_cpu != "s390x" && current_cpu != "s390" &&
- current_cpu != "ppc64" && current_cpu != "ppc" &&
- current_cpu != "mips" && current_cpu != "mips64" &&
- current_cpu != "riscv64")
- # Allows the path to a custom target toolchain to be injected as a single
- # argument, and set as the default toolchain.
- custom_toolchain = ""
- # This should not normally be set as a build argument. It's here so that
- # every toolchain can pass through the "global" value via toolchain_args().
- host_toolchain = ""
- # DON'T ADD MORE FLAGS HERE. Read the comment above.
- }
- declare_args() {
- # Debug build. Enabling official builds automatically sets is_debug to false.
- is_debug = !is_official_build
- }
- declare_args() {
- # Component build. Setting to true compiles targets declared as "components"
- # as shared libraries loaded dynamically. This speeds up development time.
- # When false, components will be linked statically.
- #
- # For more information see
- # https://chromium.googlesource.com/chromium/src/+/main/docs/component_build.md
- is_component_build = is_debug && current_os != "ios"
- }
- assert(!(is_debug && is_official_build), "Can't do official debug builds")
- assert(!(current_os == "ios" && is_component_build),
- "Can't use component build on iOS")
- # ==============================================================================
- # 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.
- #
- # We do this before anything else to make sure we complain about any
- # unsupported os/cpu combinations as early as possible.
- if (host_toolchain == "") {
- # This should only happen in the top-level context.
- # In a specific toolchain context, the toolchain_args()
- # block should have propagated a value down.
- # TODO(dpranke): Add some sort of assert here that verifies that
- # no toolchain omitted host_toolchain from its toolchain_args().
- if (host_os == "linux") {
- if (target_os != "linux") {
- host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
- } else if (is_clang) {
- host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
- } else {
- host_toolchain = "//build/toolchain/linux:$host_cpu"
- }
- } else if (host_os == "mac") {
- host_toolchain = "//build/toolchain/mac:clang_$host_cpu"
- } else if (host_os == "win") {
- # On Windows always use the target CPU for host builds for x86/x64. On the
- # configurations we support this will always work and it saves build steps.
- # Windows ARM64 targets require an x64 host for cross build.
- if (target_cpu == "x86" || target_cpu == "x64") {
- if (is_clang) {
- host_toolchain = "//build/toolchain/win:win_clang_$target_cpu"
- } else {
- host_toolchain = "//build/toolchain/win:$target_cpu"
- }
- } else if (is_clang) {
- host_toolchain = "//build/toolchain/win:win_clang_$host_cpu"
- } else {
- host_toolchain = "//build/toolchain/win:$host_cpu"
- }
- } else if (host_os == "aix") {
- host_toolchain = "//build/toolchain/aix:$host_cpu"
- } else if (host_os == "zos") {
- host_toolchain = "//build/toolchain/zos:$host_cpu"
- } else {
- assert(false, "Unsupported host_os: $host_os")
- }
- }
- _default_toolchain = ""
- if (target_os == "android") {
- assert(host_os == "linux" || host_os == "mac",
- "Android builds are only supported on Linux and Mac hosts.")
- _default_toolchain = "//build/toolchain/android:android_clang_$target_cpu"
- } else if (target_os == "chromeos" || target_os == "linux") {
- # See comments in build/toolchain/cros/BUILD.gn about board compiles.
- if (is_clang) {
- _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
- } else {
- _default_toolchain = "//build/toolchain/linux:$target_cpu"
- }
- } else if (target_os == "fuchsia") {
- _default_toolchain = "//build/toolchain/fuchsia:$target_cpu"
- } else if (target_os == "ios") {
- _default_toolchain = "//build/toolchain/ios:ios_clang_$target_cpu"
- } else if (target_os == "mac") {
- assert(host_os == "mac" || host_os == "linux",
- "Mac cross-compiles are unsupported.")
- _default_toolchain = "//build/toolchain/mac:clang_$target_cpu"
- } else if (target_os == "win") {
- # On Windows, we use the same toolchain for host and target by default.
- # Beware, win cross builds have some caveats, see docs/win_cross.md
- if (is_clang) {
- _default_toolchain = "//build/toolchain/win:win_clang_$target_cpu"
- } else {
- _default_toolchain = "//build/toolchain/win:$target_cpu"
- }
- } else if (target_os == "winuwp") {
- # Only target WinUWP on for a Windows store application and only
- # x86, x64 and arm are supported target CPUs.
- assert(target_cpu == "x86" || target_cpu == "x64" || target_cpu == "arm" ||
- target_cpu == "arm64")
- _default_toolchain = "//build/toolchain/win:uwp_$target_cpu"
- } else if (target_os == "aix") {
- _default_toolchain = "//build/toolchain/aix:$target_cpu"
- } else if (target_os == "zos") {
- _default_toolchain = "//build/toolchain/zos:$target_cpu"
- } else {
- assert(false, "Unsupported target_os: $target_os")
- }
- # If a custom toolchain has been set in the args, set it as default. Otherwise,
- # set the default toolchain for the platform (if any).
- if (custom_toolchain != "") {
- set_default_toolchain(custom_toolchain)
- } else if (_default_toolchain != "") {
- set_default_toolchain(_default_toolchain)
- }
- # =============================================================================
- # 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 Fuchsia and Windows).
- # - is_linux is true for desktop Linux, but not for ChromeOS nor 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.
- is_android = current_os == "android"
- is_chromeos = current_os == "chromeos"
- is_fuchsia = current_os == "fuchsia"
- is_ios = current_os == "ios"
- is_linux = current_os == "linux"
- is_mac = current_os == "mac"
- is_nacl = current_os == "nacl"
- is_win = current_os == "win" || current_os == "winuwp"
- is_apple = is_ios || is_mac
- is_posix = !is_win && !is_fuchsia
- # =============================================================================
- # 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.
- #
- # WHAT GOES HERE?
- #
- # Other than the main compiler and linker configs, the only reason for a config
- # to be in this list is if some targets need to explicitly override that config
- # by removing it. This is how targets opt-out of flags. If you don't have that
- # requirement and just need to add a config everywhere, reference it as a
- # sub-config of an existing one, most commonly the main "compiler" one.
- # Holds all configs used for running the compiler.
- default_compiler_configs = [
- "//build/config:feature_flags",
- "//build/config/compiler:afdo",
- "//build/config/compiler:afdo_optimize_size",
- "//build/config/compiler:cet_shadow_stack",
- "//build/config/compiler:chromium_code",
- "//build/config/compiler:compiler",
- "//build/config/compiler:compiler_arm_fpu",
- "//build/config/compiler:compiler_arm_thumb",
- "//build/config/compiler:default_include_dirs",
- "//build/config/compiler:default_init_stack_vars",
- "//build/config/compiler:default_optimization",
- "//build/config/compiler:default_stack_frames",
- "//build/config/compiler:default_symbols",
- "//build/config/compiler:export_dynamic",
- "//build/config/compiler:no_exceptions",
- "//build/config/compiler:no_rtti",
- "//build/config/compiler:no_unresolved_symbols",
- "//build/config/compiler:runtime_library",
- "//build/config/compiler:thin_archive",
- "//build/config/compiler:thinlto_optimize_default",
- "//build/config/compiler/pgo:default_pgo_flags",
- "//build/config/coverage:default_coverage",
- "//build/config/sanitizers:default_sanitizer_flags",
- ]
- if (is_win) {
- default_compiler_configs += [
- "//build/config/win:default_cfg_compiler",
- "//build/config/win:default_crt",
- "//build/config/win:lean_and_mean",
- "//build/config/win:nominmax",
- "//build/config/win:unicode",
- "//build/config/win:winver",
- ]
- }
- if (is_posix) {
- if (current_os != "aix") {
- default_compiler_configs +=
- [ "//build/config/gcc:symbol_visibility_hidden" ]
- }
- }
- if (is_fuchsia) {
- default_compiler_configs += [ "//build/config/gcc:symbol_visibility_hidden" ]
- }
- if (is_android) {
- default_compiler_configs +=
- [ "//build/config/android:default_orderfile_instrumentation" ]
- }
- if (is_clang && !is_nacl) {
- default_compiler_configs += [
- "//build/config/clang:find_bad_constructs",
- "//build/config/clang:extra_warnings",
- ]
- }
- # Debug/release-related defines.
- if (is_debug) {
- default_compiler_configs += [ "//build/config:debug" ]
- } else {
- default_compiler_configs += [ "//build/config:release" ]
- }
- # Static libraries and source sets use only the compiler ones.
- set_defaults("static_library") {
- configs = default_compiler_configs
- }
- set_defaults("source_set") {
- configs = default_compiler_configs
- }
- set_defaults("rust_library") {
- configs = default_compiler_configs
- }
- set_defaults("rust_proc_macro") {
- configs = default_compiler_configs
- }
- # Compute the set of configs common to all linked targets (shared libraries,
- # loadable modules, executables) to avoid duplication below.
- if (is_win) {
- # Many targets remove these configs, so they are not contained within
- # //build/config:executable_config for easy removal.
- _linker_configs = [
- "//build/config/win:default_incremental_linking",
- # Default to console-mode apps. Most of our targets are tests and such
- # that shouldn't use the windows subsystem.
- "//build/config/win:console",
- ]
- } else if (is_mac) {
- _linker_configs = [ "//build/config/mac:strip_all" ]
- } else {
- _linker_configs = []
- }
- # Executable defaults.
- default_executable_configs = default_compiler_configs + [
- "//build/config:default_libs",
- "//build/config:executable_config",
- ] + _linker_configs
- if (is_win) {
- # Turn on linker CFI for executables, and position it so it can be removed
- # if needed.
- default_executable_configs += [ "//build/config/win:cfi_linker" ]
- }
- set_defaults("executable") {
- configs = default_executable_configs
- }
- # Shared library and loadable module defaults (also for components in component
- # mode).
- default_shared_library_configs = default_compiler_configs + [
- "//build/config:default_libs",
- "//build/config:shared_library_config",
- ] + _linker_configs
- if (is_win) {
- # Turn on linker CFI for DLLs, and position it so it can be removed if needed.
- default_shared_library_configs += [ "//build/config/win:cfi_linker" ]
- }
- if (is_android) {
- # Strip native JNI exports from shared libraries by default. Binaries that
- # want this can remove this config.
- default_shared_library_configs +=
- [ "//build/config/android:hide_all_but_jni_onload" ]
- }
- set_defaults("shared_library") {
- configs = default_shared_library_configs
- }
- set_defaults("loadable_module") {
- configs = default_shared_library_configs
- # loadable_modules are generally used by other libs, not just via JNI.
- if (is_android) {
- configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
- }
- }
- # A helper for forwarding testonly and visibility.
- # Forwarding "*" does not include variables from outer scopes (to avoid copying
- # all globals into each template invocation), so it will not pick up
- # file-scoped or outer-template-scoped variables. Normally this behavior is
- # desired, but "visibility" and "testonly" are commonly defined in outer scopes.
- # Explicitly forwarding them in forward_variables_from() works around this
- # nuance. See //build/docs/writing_gn_templates.md#using-forward_variables_from
- TESTONLY_AND_VISIBILITY = [
- "testonly",
- "visibility",
- ]
- # Sets default dependencies for executable and shared_library targets.
- #
- # Variables
- # no_default_deps: If true, no standard dependencies will be added.
- # Targets that set this usually also want to remove
- # "//build/config/compiler:runtime_library" from configs (to remove
- # its subconfig "//build/config/c++:runtime_library").
- foreach(_target_type,
- [
- "executable",
- "loadable_module",
- "shared_library",
- ]) {
- template(_target_type) {
- # Alias "target_name" because it is clobbered by forward_variables_from().
- _target_name = target_name
- target(_target_type, _target_name) {
- forward_variables_from(invoker,
- "*",
- TESTONLY_AND_VISIBILITY + [ "no_default_deps" ])
- forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
- if (!defined(deps)) {
- deps = []
- }
- if (!defined(invoker.no_default_deps) || !invoker.no_default_deps) {
- # This pulls in one of:
- # //build/config:executable_deps
- # //build/config:loadable_module_deps
- # //build/config:shared_library_deps
- # (This explicit list is so that grepping for these configs finds where
- # they are used.)
- deps += [ "//build/config:${_target_type}_deps" ]
- }
- # On Android, write shared library output file to metadata. We will use
- # this information to, for instance, collect all shared libraries that
- # should be packaged into an APK.
- if (!defined(invoker.metadata) && is_android &&
- (_target_type == "shared_library" ||
- _target_type == "loadable_module")) {
- _output_name = _target_name
- if (defined(invoker.output_name)) {
- _output_name = invoker.output_name
- }
- # Remove 'lib' prefix from output name if it exists.
- _magic_prefix = "$0x01$0x01"
- _output_name = string_replace("${_magic_prefix}${_output_name}",
- "${_magic_prefix}lib",
- _magic_prefix,
- 1)
- _output_name = string_replace(_output_name, _magic_prefix, "", 1)
- if (defined(output_extension)) {
- _shlib_extension = ".$output_extension"
- } else if (is_component_build && _target_type != "loadable_module") {
- _shlib_extension = ".cr.so"
- } else {
- _shlib_extension = ".so"
- }
- metadata = {
- shared_libraries =
- [ "$root_out_dir/lib${_output_name}${_shlib_extension}" ]
- }
- }
- }
- }
- }
- # ==============================================================================
- # COMPONENT SETUP
- # ==============================================================================
- # Defines a component, which equates to a shared_library when
- # is_component_build == true and a static_library otherwise.
- #
- # Use static libraries for the static build rather than source sets because
- # many of of our test binaries link many large dependencies but often don't
- # use large portions of them. The static libraries are much more efficient to
- # link in this situation since only the necessary object files are linked.
- #
- # The invoker can override the type of the target in the non-component-build
- # case by setting static_component_type to either "source_set" or
- # "static_library". If unset, the default will be used.
- template("component") {
- if (is_component_build) {
- _component_mode = "shared_library"
- } else if (defined(invoker.static_component_type)) {
- assert(invoker.static_component_type == "static_library" ||
- invoker.static_component_type == "source_set")
- _component_mode = invoker.static_component_type
- } else if (!defined(invoker.sources) || invoker.sources == []) {
- # When there are no sources defined, use a source set to avoid creating
- # an empty static library (which generally don't work).
- _component_mode = "source_set"
- } else {
- _component_mode = "static_library"
- }
- target(_component_mode, target_name) {
- forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
- forward_variables_from(invoker, "*", TESTONLY_AND_VISIBILITY)
- }
- }
- # Component defaults
- # Set a variable since we also want to make this available
- # to mixed_component.gni
- if (is_component_build) {
- default_component_configs = default_shared_library_configs
- if (is_android) {
- default_component_configs -=
- [ "//build/config/android:hide_all_but_jni_onload" ]
- }
- } else {
- default_component_configs = default_compiler_configs
- }
- set_defaults("component") {
- configs = default_component_configs
- }
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